NO811257L - FLUIDUM PRESSURE DEVICE. - Google Patents

Description

The present invention relates to power releases, in particular devices where fluid pressure moves a drive member to a position which can be easily changed with the help of externally controlled members, preferably a magnetic field.

The invention is particularly applicable when hydraulic pressure is used as a trigger operating force and shall be described with special reference to this, although the invention has wider and other application possibilities and can be used in connection with high-pressure gases, and the movement of the drive member can be used to control mechanical devices of all type, such as valves, motors and/or pumps that require considerable mechanical force for release or control and where the electrical control signal is relatively weak.

There are many cases in industry where a force trigger must be remotely controlled to exert sufficient mechanical force to move an object over short distances to a fixed point and then hold the object at that point, regardless of variations in the object's reactive force on the trigger.

The object can of course be any variable weight or force, a motor or pump control, a valve control or the like, and the term "object" is used here in a very broad sense.

Electric motors, electric solenoids and hydraulic pressure driven devices have been used for this purpose with varying degrees of success.

Electric motors and solenoid triggers have hitherto constituted the simplest type of remote control, because electrical wiring is all that is required between the trigger and the controls, which latter can be either manual or automatic.

Electric motors must work via reduction gears and are consequently bulky, complicated, expensive and have a very long reaction time. Otherwise, they are desirable because the reduction gear is usually self-locking to keep the object in a desired set position regardless of variations in the object's force effect on the trigger. But because they are self-locking, there is no automatic mechanism to return the object to its original position in the event of a power failure. Triggers powered by an electric motor are usually activated with electrical power pulses that must be precisely timed to determine the distance the object is to be moved. Such time management devices are complicated, expensive and thus not desirable.

Electric solenoids have limited power capacity for

a given physical size and a relatively low power/electrical energy ratio, where the energy must be supplied continuously in the form of an analogue electrical signal. While solenoids respond quickly at a fixed actuation current, they are unable to hold the object in a fixed position when the object's effect on the trigger varies. To achieve the latter effect, a complicated feedback circuit arrangement is required.

Triggers operated by hydraulic pressure are ideal for the purpose. They are capable of exerting very strong physical forces at a minimal size. They easily hold an object in a desired set position, even if the object's force on the trigger varies. But remote control of such a trigger has always been a problem. Electric motors or solenoid-operated valves have been used, but with the above-mentioned difficulties. In addition, the trigger had to include a control rod that extends through packing glands in its housing, where the rod moves a member inside the housing to exert the final control of the drive member. Normally, the inside of the housing is under high hydraulic pressure. In such a device, the packing gland exerts considerable friction against the control rod, so that considerable mechanical forces are required to move the rod. Furthermore, this friction, especially in the case of a solenoid release, creates a hysteresis loop in the response curve. The gland must also be constructed so that it resists the overall hydraulic pressure and leaks often develop which require maintenance work. The leaks are also always associated with spills.

In the case of hydraulic releases, it is therefore common to direct the high-pressure hydraulic fluid through a pipe from a pump to a control point, through manually or automatically operated valves and then back to the hydraulic release.

With such a device, the distance that the hydraulic fluid must travel can be considerable. The pipe arrangement is expensive. Installation of pipes with many bends is expensive. Fittings or hoses are often required to enable articulation of the triggered device in relation to its support. When there are a large number of controls, a large number of pipelines are required. The cross-sectional area of all these pipes or wires can be very extensive. Leaks develop both in cables, fittings and controls. Such leaks are expensive to repair and cause a lot of mess, which is particularly troublesome when leaks occur in the controls that are normally located in a cab.

Remotely controlled linear servo motors have long been known.

They usually comprise a drive member mounted in a housing and a drive shaft extending through the housing. A zero-type servo valve is mounted in the actuator and connects either the pressure or suction chamber to a third chamber with variable pressure.

The control element for the servo valve has a shaft which projects from the housing and which is positioned by various power means which are activated from the outside. As one end of the shaft is at atmospheric pressure, the other end must have the same diameter and be vented against atmospheric pressure. This requires careful sealing devices and entails great difficulty in keeping many ports absolutely concentrically aligned, especially when they are significantly spaced apart. Alignment is never perfect and this leads to additional friction in connection with the servo valve control element. The careful sealing also causes extra friction when the element is moved. This leads to severe hysteresis in servo valves. The higher the hysteresis, the higher the force characteristics of the actuation means must be, as the total positioning accuracy can only be as accurate as the total hysteresis force divided by the actuation force. This invention overcomes these problems and provides guidance on various additional ways of reducing hysteresis friction.

US Patents 2,930,360 and 3,131,608 describe electrically controlled servo motors. According to the latter patent document, an electromagnet, which is arranged in the pressure control chamber, moves a cylindrical control element, so that this opens pressure inlet and outlet ports (in the housing) towards the control pressure chamber and varies the pressure there. This control element is operationally connected to the working piston via a tension spring, which moves the control element substantially back to its initial position to restore the pressure balance. Such a device has proven impractical for various reasons, e.g. the electrical winding is immersed in the operating fluid and its insulation breaks down in modern hydraulic fluids, while at the same time it is difficult to replace. Furthermore, it only works with spring return and the spring must have a sufficiently low spring rate. For high fluid pressures where strong forces can develop, physically large springs are required. There is also a significant hysteresis problem due to friction between the element and the housing.

The present invention overcomes all the aforementioned difficulties and a device is provided where a fluid pressure release or servo motor can be accurately controlled remotely by means of a conventional electrical wiring device and an analog electrical signal instead of a timed pulse, and the electrical signal can have a relatively small electrical strength compared to the actual force emitted by the trigger.

According to the invention, a trigger or servo motor is also provided which has such little hysteresis and is so precise in its displacement at a given value that an electrical signal or other external force influences that it can be used for precise control of fluid valves, e.g. flow, pressure or directional valves, and can also be used to control fluid pumps and/or motors, both in terms of speed and/or direction of rotation. In other words, the object of the invention can be used not only as a remote-controlled fluid pressure release, but can also be used as an integral part of a remote-controlled valve, where the fluid pressure for activating the release comes from the pressure in the fluids affected by the valve.

The present invention is particularly applicable for controlling the relief pressures for the pressure relief valves of the type that have different areas. Such valves have generally included a piston which acts on a valve body and is displaceable in a cylindrical chamber with a low-pressure outlet passage in an axial chamber end and a high-pressure inlet passage through the chamber side. The piston is provided at the end with a valve closing member which rests against a valve seat which surrounds the outlet passage and has a larger cross-sectional area than the area of the valve seat. High inlet pressure against this larger area when the differential forces developed by the pressures are such that they exceed internal spring forces, moves the valve piston and valve body away from the valve seat to allow fluid flow through the valve.

In such valves, the piston diameter is necessarily larger than the diameter of the valve seat, so that forces can be developed that move the piston to the valve-opening position. As such, the sliding seal for the piston, which is usually in the form of an O-ring, has a significant circumference in contact with the wall of the piston chamber and thus forms significant friction against it. In addition, the inlet pressures will compress such an O-ring in a direction away from the inlet port, and at very high fluid pressures these tend to extrude parts of the O-ring into the clearance between the piston and its chamber wall. With such a device, the O-ring's friction is increased even more, especially when the piston is moved from the valve's open to its closed position. All this results in a hysteresis loop in the pressure versus the flow curve and in the valve tending to bleed too much at pressures that are somewhat lower than the set pressure. This is undesirable.

Another problem with such valves has been that when the valve body moves away from the piston seat, the fluid flow past the valve seat exerts a jet effect in the opposite direction to the opening movement, with the result that the fluid flow opposes the opening movement of the valve seat so that a sloping or curved pressure occurs opposite the flow curve.

A further principle difficulty with such valves has been that the relief pressure is usually varied by varying the compression of an internal spring by means of means such as a guide shaft, which extends through the housing wall and is moved locally and manually or "remotely actuated by means of a gear motor which receives a electrical pulse of variable length.

Such gear motors take up space and have a long reaction time.

The invention can also be used in particular for control

of fluid flow valves of the type where the piston has a differential area, where fluid under high pressure is received and released with a controlled pressure to a fluid-activated engine piston or similar, regardless of variations in the applied pressure or the engine load. As such, the valve must respond continuously, opening and closing quickly to any changes. This valve should also be easily controlled remotely. Electric motors and solenoids are undesirable for this purpose for reasons discussed above.

Another problem with such valves, when the fluid is an oil, is that the flow or outlet pressure varies with the temperature and/or viscosity of the fluid, necessitating a complicated feedback circuit for recording such changes and correcting in dependence on them. Until now, expensive devices have been installed for heating or cooling the fluid so that its temperature is kept constant.

The invention is also particularly applicable for controlling two- or four-way directional control valves. Until now, remote control valves of this type required either two pilot valves, one at each end, or a large solenoid capable of exerting a greater force than the pressure forces developed on the valve side by the pressures being controlled. In addition, such valves to date have always required one or more shafts that extend through the high-pressure seals to release the valve armature on the inside.

The invention can also be used to operate a fluid pressure amplifier that must be remotely controlled.

To the applicant's knowledge, no one has yet been able to successfully (commercially speaking) control the position of the actuating member of a fluid actuator or the opening, closing or flow through a fluid valve electrically, without a mechanical control rod extending through a high pressure seal and/ or use of an analogue signal with relatively low power, e.g. less than two watts and often less than five watts. As far as the applicant knows, no one has so far used a gate-equipped rod which is surrounded by a sleeve as a control element in a linear servomotor.

The present invention relates to a new and improved device for controlling the position of the output member for a fluid pressure-activated device, where all the above-mentioned difficulties are avoided and a simple remote control of said position is made possible by means of low-power electrical signals, especially analogue electrical signals. The device can be incorporated into a variety of fluid pressure-activated devices that require a controlled mechanical force, such as fluid valves and other fluid-driven devices.

According to the broadest aspect of the invention, a fluid pressure-activated trigger or servo motor is provided which in combination comprises: a housing with a generally closed control pressure chamber and a drive member chamber, a drive member in its chamber with a surface exposed to the pressure in the control chamber and movable in the drive member chamber, inlet and outlet passages adapted to put the control pressure chamber in communication with high and low pressure respectively, where at least one of the passages is movable together with the drive member, a control element which is completely occupied in the control pressure chamber and is affected when the drive member moves the one passage in relation to the element to open or close one passage in relation to the other, where the control element is at least partially made of such a material that it can be moved by a magnetic field and a controllable magnetic means for moving the control element to controlled, fixed positions in relation to the housing.

The magnet body is normally external to and/or incorporated as part of the housing and can be a permanent magnet, an alternating current and/or direct current magnetized electromagnet or multiphase alternating current electromagnets. In the case of one or more permanent magnets, they must be arranged outside and movable relative to the housing, and the housing must consist of a magnetic, non-permeable material to allow flux passage through it. The control element will normally be a permanent magnet.

Normally, the control element will be biased to a fixed position in the housing by means of a biasing spring based on the housing, and the control element is moved against the spring bias a distance that is directly proportional to the strength and location of the magnetic field induced by an electrical signal of analog type.

The control element which is completely occupied in the control pressure chamber has balanced pressure forces towards its ends and is inherently fluid in relation to such pressures. The control element, which is made of a material that makes it possible to move the element by means of an electric field, can be placed in relation to the drive element by means of a magnetic field that is either created externally or in the chamber and can thus move the control element without the need for a mechanical element , which is connected to the control element and extends through sealing glands on the side of the housing.

In another main aspect of the invention, at least part of the drive member has the form of a cylindrical piston which is displaceable in a sealed relationship to the walls of its chamber.

One end of the piston forms one of the faces that limit the pressure chamber. This end has an elongated, port-provided rod which extends axially into the control chamber and comprises the inlet (and/or outlet) port(s) which open radially into the chamber from one or more internal passages. This rod with its ports moves with the piston in response to external force variations in a partially sealed relationship to the control element for variable mutual narrowing of the passages.

The gate-provided rod can be made in one with, but is preferably attached to the drive member in such a way that it is slightly radially movable in relation to it. This prevents jamming or strong friction in the type of device where all clearances are reduced to a minimum, tolerances are very small, and/or exact alignment of all sliding surfaces in line with each other is extremely difficult to achieve. The attachment method is further such that the gate-equipped rod has a high-pressure surface that faces in one direction and has half the area of a control pressure surface that faces in the other direction, so that the rod is in a pressure-balanced relationship.

To achieve radial pressure equalization on the control element according to the invention, the ports are grooves in the circumferential direction in the side surface of the port-equipped element, and the control element is a sleeve that surrounds the port-equipped element with its inner surface in the at least partially sealed relationship with the other surface of the element.

The end of the sleeve may be open or restrict a port in the ported element or a groove may be provided in its inner surface in communication with the outer surface to restrict one of the ports relative to the others and to connect the resulting pressure in the groove to the control pressure chamber when the two are moved in relation to each other.

It is believed that the combination of a sleeve surrounding the ported element in a fluid pressure servo mechanism is in itself novel, has improved operating characteristics and is an invention regardless of how it is placed in the pressure chamber. Conventional devices can thus be used which extend to the outside of the housing for adjusting the position of the sleeve in the chamber. Such conventional means include a push/pull rod, a tension member, toothed rack with gears or a threaded engagement between the sleeve and its housing, where the housing of the control pressure chamber is rotatable in relation to the housing of the drive member.

In a somewhat narrower but important aspect of the invention, a fluid pressure servomechanism is thus provided, where the control element is a sleeve that surrounds a gate-equipped rod rather than a coil with a groove that is movable in close relation to the drive member or housing of a known type. The sleeve is moved in any way, e.g. of a magnetic field or an external mechanical connection.

The port-equipped element according to the invention has a relatively small diameter (e.g. 6.35 mm) in relation to the diameter of the associated piston. With the same clearance between the sleeve and the gate-equipped element, the zero leakage is reduced and significantly smaller than with previously known servomotors where a coil or cylinder is used as a control element, and where the diameter of the gates necessarily had to be much larger and thus with a given clearance had a much larger area for zero leakage.

During operation and in both cases, the drive member will move its passage or gate in relation to the control element, regardless of its position, so that the pressures in the pressure chamber which exert a force on the drive member will correspond exactly to each other even when external forces are exerted. If the others, e.g. external forces are increased or decreased, the drive member and its passage will move in relation to the control element for opening and closing the two passages. The pressure in the pressure chamber will automatically change to compensate for such changes in the external forces. Insofar as the pressure change between the pressure chamber and the passage affected by the control element can vary within relatively wide limits with extremely small relative movements, the result is that large variations in external forces on the drive element will lead to large variations in the chamber pressure with extremely small relative movements of the two parts.

If the governing body is subsequently moved to a new position

in the chamber, the drive member will quickly move to restore the balance between the external forces and the chamber pressures on the member.

In reality, the drive member exactly follows the control member when this is moved in relation to the housing.

According to the invention, the control element and the passage can be arranged so that relative movement means that one of the passages opens or closes independently of the others, or the outlet passage can be limited in relation to the inlet passage and the control element only opens or closes the inlet passage or the control element opens a passage while closing it second. In the latter situation, the drive member can be moved equally quickly in one of the directions. In the two former situations, the drive member can be moved faster in one direction than in the other.

In both cases, according to the invention, the gate for the passage controlled by the control element will open in a direction perpendicular to the direction of movement of the control element, so that the control element is at all times in a pressure equalized situation, not only in directions parallel to its line of movement, but also in directions perpendicular to its line of motion. This is achieved by the controlled gate being open in at least two opposite directions, perpendicular to the control element's line of motion.

Apart from gravity, friction and/or bias spring, the control element is thus in a fluid state in the chamber and can thus be easily moved with minimal friction by any externally controlled body.

The movement of the drive member can be suitably utilized to exert a mechanical force against an object or control a valve, operate a switch, control another fluid pressure device, such as a pump or motor, bias the spring for another mechanical device and/or operate a pump.

In a further main aspect of the invention, means are arranged for biasing the piston against the control chamber in the form of a piston of the differential area type, where its end facing away from the control chamber limits a surface including a first surface which is exposed to low pressure and a second surface with less area (preferably half) than the area facing the control chamber, exposed to high pressure. The piston will move in one direction or the other determined by the differences in the pressure forces created by the different pressures on each end of the piston affecting different areas. When microscopic changes in the restriction of one port relative to the other cause large changes in the pressure drop through the restriction, extremely accurate adjustment of the piston relative to the control means results.

In another aspect of the invention, the outlet passage is permanently restricted relative to the inlet passage by a ratio in excess of 1000:1, and the valve element restricts the outlet port of the inlet passage such that the piston moves the outlet port relative to the control element to a location where the flow through the restriction exactly corresponds to the flow through the restricted outlet passage.

In another aspect of the invention, the narrowed outlet passage consists of a plurality of circumferential grooves in the cylindrical surface of the piston and a single longitudinal groove from the control pressure surface to the low pressure surface from a plurality of sharp-edged openings between the chamber and the low pressure. The pressure drop through each orifice is generally viscosity insensitive and the flow is proportional to the square root of the pressure differential. By using a plurality of such openings, the longitudinal track can be wider for the same volume of fluid flow, and thus there is less danger of it being clogged by accompanying dirt particles in the fluid. In this way, extremely low flow rates can be achieved with a relatively wide longitudinal passage and the production of a plurality of openings is greatly simplified.

The housing for the control pressure chamber consists of two (or more) spaced parts of magnetically permeable material and intermediate part(s) of magnetically non-permeable material, where the magnetically permeable parts form the magnet poles for one (or more) electric coil or solenoid which surrounds the magnetically non-permeable part(s). A sleeve of magnetically permeable material surrounds the coil and ends butt-in-butt with the spaced portions to form a closed flux path except for the intermediate portions, where the path is partially completed by the magnetically permeable control element located in the chamber.

If only one coil is used, the magnetic polarity of the coil is not important. If two coils are used, the electrical connections to the coils are such that the adjacent ends of the two coils have the same magnetic polarity.

According to the invention, the inlet to the pressure chamber's inlet passage is placed near the base of a bowl of magnetized material, so that the fluid flowing into the inlet is moved through a tortuous path past the bowl and any suspended particles in the fluid are attracted by the bowl and prevented from passing into the pressure chamber. The bowl's edges preferably form a valve seat and the flow into the bowl is close to and in the direction of the seat, so that any particles that are collected will be close to the seat and flushed away when the valve is opened.

According to the invention, the control element is a sleeve that is biased by a spring (preferably a coil spring) towards a first position near a magnetically permeable part when the coil is not magnetized and is pulled against the spring's bias past a magnetically non-permeable part towards another magnetically permeable part when the coil is magnetized, where the leading edge of the sleeve tapers to limit the smallest magnetic air gap as the control element approaches the second magnetically permeable partic and creates a generally constant force displacement curve on the sleeve at a given coil magnetizing current over the range of motion. As a coil spring has a sloping force-displacement curve, the two curves will intersect at a certain point, so that the actual displacement of the sleeve against the spring bias becomes highly sensitive to variations in the magnetizing current.

According to the invention, the control element has an outer diameter that provides a fixed minimum clearance against the magnetically permeable walls of the control pressure chamber, and the outer surface of the control element has a layer or coating of magnetically non-permeable material with a thickness that is at least twice the minimum clearance, so that even if eccentric magnetic forces pull the control element radially, the ratio between the maximum magnetic air grip and the minimum air gap between the outer magnetically permeable surface of the control element will usually be less than 2:1.

It is known that the attractive forces rise asymptotically to a maximum at zero as the magnetic air gap approaches zero. By keeping the air gap ratio above 2:1, the adverse effects of an air gap of zero are limited. Thus, the walls of the control pressure chamber can act in such a way that they physically control the control element without the development of too strong side forces and static friction which is always higher than moving friction with the same pressure forces between the parts. According to the invention, the outer surface of the control element is made of magnetically non-permeable material Teflon or a similar material.

In a hydraulic flow control valve, the piston end opposite the pressure chamber of the invention has a tapered valve seat which contacts a surface which receives high pressure through the valve seat area, and a solenoid coil comprising multiple turns of electrical wire is arranged to move the control element to positions, wherein the valve is opened to controlled amounts in combination with means to maintain the solenoid coil at substantially the same temperature as the hydraulic fluid. This leads to a temperature compensated flow control valve. Such devices may include thermal insulation or an enclosed air space surrounding the coil.

At a given opening of the valve, the flow-through volume will thus increase as the fluid's temperature increases and its viscosity decreases. At a given or fixed magnetizing voltage on the coil, its resistance and thus the current passing through it will simultaneously decrease with an increase in temperature, so that the control element is moved a shorter distance and the valve thus opens less, but maintains the same flow-through volume due to the oil's lower viscosity . By suitably measuring the resistance of the coil at ambient temperature or using wire material that has a suitable temperature coefficient for the resistance, complete temperature compensation for the valve can be achieved, so to speak, especially with small valve openings, where the problem in connection with flow temperature variations is most conspicuous.

According to the invention, the tapered nose of the flow control valve is further concave to create a decreasing variation in the valve opening in the face of increasing linear displacement of the surface that contacts the valve seat, away from this seat. The degree of concavity is proportional to known leaks in a fluid engine to which fluid is directed as compensation for the leaks. Such leaks have a major effect on the engine at low fluid flow rates and low rotational speeds. The exact value of the concavity must be designed in relation to the engine's leakage characteristics.

Furthermore, according to the invention, in a pressure equalization valve, a valve piston is arranged with a valve seat contact surface which is adapted to be exposed to high pressure through the valve seat area. The valve piston is variably biased towards the valve's closed position by variable compression of a spring between the valve piston and the control pressure operated piston as a result of suitable positioning of the control element.

According to the invention, the valve piston for a pressure equalization valve has a rod with a smaller diameter than the diameter of the valve seat with a gasket on the outer surface in displaceable, sealed relation to a suitable cylinder in the control pressure chamber piston. The friction of such a gasket, which is pressed against the valve seat by the high pressure it seals against, is thus reduced when the valve piston closes, so that the valve's hysteresis curve is reduced.

In a directional control valve, the drive element according to the invention is assigned to one end of the guide slide, where the guide slide has a piston at the opposite end which is exposed to the inlet pressure and an internal passage that feeds the high inlet pressure to the piston pressure chamber and the drive element's control pressure chamber.

With such a device, the slide valve can easily be moved from a neutral or middle position to one of its other positions without a mechanical organ extending through the sides of the slide valve housing, either with or without pressure seals.

According to the invention, the surface of this pressure equalization valve, which contracts with the valve seat, is further curved and the valve seat is conical, so that a uniform fluid flow occurs when the surface is moved away from the valve seat.

According to the invention, the output means operates a piston

in a chamber that has a smaller diameter than the output member's chamber, which piston then acts as a pressure booster for the device's release pressure.

Fluid pressure-operated servo mechanisms are of course well known, but as far as is known, the control element has always had the form of a coil with grooves that are movable in relation to inlet and outlet ports in the walls of the house, and where the coil has a drive shaft that is made in one with the coil and extends through the housing to a location where external steering forces can be exerted against the axle.

It is now, according to the invention, provided a fluid pressure-operated servo mechanism where the control element is completely occupied in and pressure suspended in a control pressure chamber and can be displaced in the chamber by means of a magnetic field, without having an external mechanical connection.

"High pressure" in this text is used for any fluid pressure that is higher than atmospheric pressure, up to and above 120 bar, which may occur in the lines from a pressure source

to a device representing the invention.

"Low pressure" means any pressure below high pressure, including atmospheric pressure, which may occur in a line from the device, e.g. to a sump or to pressure-driven equipment that the device according to the invention controls.

"Control chamber pressure" means any pressure between high pressure

and low pressure that can occur in the control pressure chamber and forms the force on the piston that performs the device's output work.

"Relatively unobstructed passage" means a passage with

a cross-sectional area through which fluid under pressure can flow freely, e.g. at a pressure differential of 140,614 kp/cm 2 at a speed of at least 3.8 l/min. Apart from this, even a relatively limited passage will limit the fluid flow in accordance with known principles and formulas.

"Relatively restricted passage" means a passage with a cross-sectional area (or an opening or openings in an unobstructed passage) that is small enough that the free flow through of fluid is inhibited. Normally, the limitation will be such that the flow at a pressure differential of 140.614 kp/

cm 2 will lie between 4.1 and 819 cm 3/min. although it may be larger.

The degree of restriction of the restricted passage will control the rate of return of the piston to a retracted position and may vary over wider limits than those indicated as long as it is always more than the restriction value in the relatively unobstructed passage when the control element has maximum opening of the unobstructed passage, outlet port to the pressure chamber.

During operation, the control element naturally limits the outlet of one passage in relation to the other to induce a pressure in the control pressure chamber, so that the flow rate is exactly the same in both passages. When the control element is moved in relation to a passage when the piston is moved in relation to the housing and the control element can be moved to fixed positions in the chamber, it will be seen that the piston at all times moves in relation to the position of the control element so that these flow conditions exist.

If the outlet opening and the control element have sharp, i.e., right-angled, opposing corners forming the restriction, there will only be an exact distance between the corners that gives exactly equal flow rates. The piston and its associated outlet port will precisely follow the control element which is in a fully balanced position as far as both radial and axial thrust forces against it are concerned, and which has been moved to a position where the magnetic and bias spring forces are balanced. Reduced sensitivity can be achieved by rounding the corners or by allowing the sealing rafts near the corners to taper.

"Magnetically permeable material" means a material which has a greater magnetic permeability than air, i.e. greater than 1. Such materials are usually alloys of iron, e.g. steel and some of the stainless steel types. They can have a permeability of 150-20,000 or more. Such materials are attracted by a magnetic field.

"Magnetic non-permeable material" means a material that has the same magnetic permeability as air and includes some stainless steel types, aluminum, copper, plastic, hydraulic fluid and the like. Such materials are unaffected by the presence of a magnetic flux.

"Magnetic air gap" means a gap in a magnetic circuit or loop that is filled with a magnetically non-permeable material.

"Control element" in the present text means an organ or a set of organs which are capable of relative restriction, e.g. opening or closing, of the communication between one passage to the chamber in relation to the other. Except for brief moments, the communication between the passages will never close or open completely.

"Actuator" means a piston, disc, diaphragm or other mechanical member which moves in whole or in part in response to control chamber pressure variations against it.

"Magnetically sensitive material" means either a magnetically permeable material or a magnetically non-permeable material that can be permanently magnetized, such as barium or strontium ferrites and the like, which has a magnetic permea-

bility of approx. 1, but can be magnetized and in the magnetized state will be attracted or repelled by a magnetic field or an electrically conducting body in the presence of a moving, e.g. multiphase magnetic field. It is important that the control element is at least affected by a magnetic field.

"Completely occupied in the chamber" means that no part of the control element or anything firmly connected to it extends through a pressure chamber wall to expose it to different pressure influences. The element is thus exposed to pressure in the control chamber on all sides and actually floats in the fluid.

"Pressure valves" include all fluid valves where force is used to determine a pressure. Usually the force is exerted by a spring. These include relief valves, sequence valves, pressure reduction valves, balancing valves and over-center valves. A special embodiment of this type of valve is a flow dividing valve which controls flow, but does so by sensing pressure drop through an opening and reacts via bias springs. Although it controls flow, this is actually a pressure type valve.

"Directional control valves" include two-way on-off valves, two-position three-way valves, two-position four-way valves with one-sided spring loading and three-position four-way valves. All these valves can have metering coils or non-metering coils and can be easily designed so that one, none or all ports can be opened or blocked in a given position.

All of the above designations are commonly used within the fluid power industry today. For the sake of brevity, only one valve of each type will be described below, but those skilled in the art will easily be able to apply the invention to all of the above-mentioned valves.

The mechanisms described here in connection with their operation mainly include the use of a relatively incompressible fluid (oil). Professionals will, however, be able to operate these devices with a compressible medium (air) without difficulty with minor changes.

The main purpose of the present invention is to provide a new and improved fluid pressure-activated release device which can be easily controlled by an analogue low-power signal and where no part of the moving parts of the release, apart from the output shaft, extends through to the release housing's exterior.

Such a device must be simply constructed and induce an essentially linear movement of the drive member in relation to an analogue electrical control signal.

Furthermore, a new and improved electrically controlled fluid pressure release device is to be provided where the ratio between the output force and the electrical control force is relatively high.

A new and improved fluid pressure release device is to be provided which does not require fluid pressure lines from the release to a remote control point.

The new and improved fluid pressure release device must accurately position the release drive element at a given electrical actuation current.

A new and improved fluid pressure release is to be provided which is controlled by an analogue electrical control signal with minimal hysteresis.

The invention is to provide a new and improved servomotor of the type described, where there is reduced zero leakage at the same clearance between the control element and associated parts. Furthermore, a new and improved device of the mentioned type must be provided where the gate-equipped element is attached to the piston in such a way that jamming is not caused in the housings when the clearances are very small.

A new and improved servo motor is to be provided, where the control element has the form of a sleeve that surrounds an organ, where there is a port that connects pressure with the control pressure chamber.

The new servo motor must have minimal hysteresis.

In the new servo motor, the control element must be able to be moved to any position with the application of minimal force against it.

The new servomotor's control element does not need a regulating shaft which can be moved through a sealed opening in the housing.

A new and improved electrically controlled servomotor is to be provided, where the motor's control element is spring biased in such a way in its control pressure chamber that a fine movement of the electric controls is required before the element starts to move.

According to the invention, an electrically controlled fluid flow valve is to be provided which enables variable control of relatively large fluid volumes with relatively small amounts of electrical power.

The invention further aims to provide a new and improved electrically controlled servomotor, where the electrical controls are arranged so that the control element is pressed against its centering or neutral spring by a force which is somewhat less than the spring's original biasing force, so that a sensitive control of the device is achieved.

The invention is to provide a new and improved fluid pressure release device with means for capturing magnetic particles which have to be carried with the fluid to the control pressure chamber.

A new and improved electrically controlled fluid valve is to be provided which can be easily installed in a conduit block to control the flow.

A further purpose of the invention is the provision of a way to attach and pressure seal a gate-equipped element to its drive piston, where the element is in a pressure equalized relationship and can be easily moved in relation to the piston.

Another object of the invention is to provide a new and improved fluid pressure actuation device, where the pilot control element is completely enclosed in a pressure chamber and has equalizing fluid pressure forces directed against it, so that only a minimal force, magnetic or otherwise, is required to move that from one position to another.

According to the invention, a new and improved servo motor is to be provided which has reduced zero leakage.

A new and improved fluid pressure release device or servo motor of the type mentioned must also be provided, where at least one of the fluid ports of the control pressure chamber is located in the side of a rod with a small diameter and where the control element that opens and closes this port is a sleeve that tightly surrounds the rod .

A new and improved fluid pressure-triggered servo motor is to be provided which is physically small for a given power output and can be produced economically.

A new and improved servo motor will also be provided which can easily be used to control fluid valves, motors and pumps.

The invention further aims at providing a new and improved servo motor, where at least one of the passages establishes communication between the control chamber and external pressure via and movable with the operating member.

The invention aims to provide a fluid pressure-activated servomotor, where the control element is moved by remotely arranged, variable electric resistance controls, where the spring bias of the control element towards the neutral position is such that the feeling of the manual operation of the electric controls will be similar to the feeling of the previously known manual fluid controls.

A new and better device is to be provided for creating a plurality of sharp-edged openings for narrowing the fluid flow, with simple and reasonable construction.

A new and improved plunger is to be provided which can be moved in a solenoid coil and is arranged and constructed so that the unbalanced radial magnetic forces on it and thus excessive friction with an outer surface are limited.

A new plunger is to be provided for use in a solenoid coil where the ends of the plunger are designed to limit the minimum magnetic air gap and provide a generally constant force displacement curve on the member, where the force displacement curve for a bias spring will intersect said curve at a sharply defined point.

According to the invention, a new and improved fluid flow control valve is to be provided, where the valve seat and the surface that abuts the valve seat are designed so that a uniform fluid flow past the valve is achieved when it is opened.

A new and improved fluid flow control valve must also be provided where the gasket that sealed the body that abuts against the valve seat is compressed by the controlled pressure, in such a direction that the friction of the gasket is reduced when the body is moved to the closed valve position.

The invention also seeks to provide a new and improved electrically controlled, hydraulic flow control valve which automatically compensates for the reduction in viscosity of the passing fluid as the fluid temperature increases.

In a new and improved hydraulic flow control valve, the shape of the surface that abuts against the valve seat is such that temperature compensation is created for the increased leakage in a hydraulic motor that is controlled by the valve as a result of increased temperature of the fluid and resulting lower fluid viscosity.

A new and improved construction of a control chamber for an electrically operated control device is to be provided, where the surfaces of the chamber are formed by parts of magnetically permeable material at a distance from each other, separated by a magnetically non-permeable part so that a minimal air gap is created where a magnetic permeable organ is movable in the chamber.

A directional control valve must also be provided which does not have an external control member which extends through a pressure seal into the housing and which can be remotely controlled by an analogue electrical signal.

According to the invention, an electrically remote controllable trigger or valve shall be provided which returns to a certain safe position in the event of a power failure.

Other and more special purposes of the invention will become apparent from the present description.

The invention can take physical form in individual parts and arrangements of parts, preferred embodiments of which will be discussed in detail and which are illustrated in the drawing, where

fig. 1 is a cross-sectional, partial view of a magnetically controlled unidirectional fluid pressure release device illustrating a preferred embodiment of the invention,

fig. 2 is a partial reproduction on a larger scale of fig. 1, taken approximately along line 2-2 in fig. 1,

fig. 3 is a partial reproduction on a larger scale of fig. 2, taken approximately along line 3-3 therein,

fig. 4 is a connection core of a simplified electrical circuit device for controlling the device's magnetic field,

fig. 5 is a representation similar to fig. 1, but shows a double-acting fluid pressure release device where a pair of solenoid coils are used to create a magnetic field,

fig. 5A is a connection core of an electric control circuit for the double solenoid device according to fig. 5,

fig. 5 is a rendering quite similar to fig. 1, which shows an alternative embodiment of the invention, where the outlet passage is built into the surface of the control pressure piston and the trigger controls a slide valve,

fig. 7 shows a further embodiment of the invention where the trigger controls a pressure relief valve,

fig. 7A is a partial reproduction on a larger scale of FIG. 7 and shows the relationship between the pressure traces without fluid pressure in a solid line and with fluid pressure in a dashed line,

fig. 8 shows a further embodiment of the invention, where the trigger controls a flow control valve.,

fig. 8A is a partial reproduction of FIG. 8 on a larger scale and shows the relationship for the pressure traces, and

fig. 9 shows yet another embodiment of the invention, where the trigger is a cartridge valve that is mounted in connection with a housing that has inlet and outlet passages.

In the drawings, some examples of execution are shown which are intended exclusively as illustrations of preferred embodiments of the invention without thereby limiting it. Fig. 1 shows a magnetically controlled fluid pressure release comprising: a housing generally designed in two parts, namely a control piston housing H

and a control element housing M, a differential area piston consisting of a control pressure piston P and a high pressure piston Q, ;^ which is slidably supported in the housing H and has an output shaft a ported element E, which is movable in the piston P, a control element C which is displaceably supported in the housing M in an at least partially sealed relationship with element E, and a solenoid coil S adapted to create a magnetic field for movement of the control element C to relatively fixed positions in the housing M, depending on the magnetization of the solenoid S.

The piston housing H, which forms part of the housing in this embodiment of the invention, generally has the shape of a block or cylinder of metal with a cylindrical cavity,

which is formed on the inside and limited by cylindrical side walls 10, as well as a second adjacent cavity which is axially aligned with the first cylindrical cavity but has a smaller diameter and is limited by cylindrical side walls 11. The side walls are coaxial and the different diameters lead to form a shoulder 12, which acts as a left stop for the piston P.

The high-pressure piston Q has an outer surface 13 which is slidingly movable in relation to the walls 11 and divides the cavity into a low-pressure chamber 15 on its right side and a high-pressure chamber 16 on its left side. The output shaft 0 extends displaceably through a seal 14 in a sleeve nut 17, which is screwed into the left end of the pressure chamber 16 and sealed by an O-ring 18. A high-pressure inlet port 19 is threaded at its outer end, as at 20, to accommodate a hydraulic fitting, not shown, and communicates with the high pressure chamber 16 at its left end.

Similarly, the control pressure piston P has an outer surface 21 in a displaceable, sealed relationship with the surface 10 and divides the cavity in a control pressure chamber 22 at its right end, while the left end 23 faces the low pressure chamber 15.

Low pressure, e.g. a sump, is allowed to communicate with the low-pressure chamber 15 via an outlet port 24, which is threaded at the outer end, as at 25, to accommodate a hydraulic fitting, not shown.

The control pressure piston P is the driving element in this design

and has a relatively conventional construction, where the outer surface 21 is provided with a plurality of pressure equalization grooves 26

in a conventional way. The right end 28 of the piston P forms a pressure surface which faces the control pressure chamber 20, while the left surface 23 forms a surface which faces the low pressure chamber. One or a plurality of radial grooves 29 are taken out in the surface 23.

The pressure piston Q functions as a device that biases the piston P against the control pressure chamber. It has a relatively conventional construction and has one or a plurality of pressure equalization grooves 32 in its outer surface 13 and comprises a high-pressure surface 33 facing the chamber 16 and a low-pressure surface 34

which faces the low-pressure chamber 15 in a conventional manner. The piston Q is either integral with or attached to the control piston P. The shaft 0 may be integral with or attached to the piston Q. Its outer end, not shown, may be designed to cooperate with the object to be controlled. The cross-sectional area of the piston Q minus the cross-sectional area of the shaft 0 amounts to approx. 50% of the cross-sectional area of the stamp P.

The control chamber housing M is the second part of the housing in this embodiment and generally comprises a pair of magnetically permeable parts 40, 41, which are axially spaced apart and are separated by a magnetically non-permeable part 42 which butts at its axial ends against the parts 40, 41 in a pressure sealed condition. This can be achieved in a number of different ways, e.g. when using 0-rings, but in the version shown, the parts are folded as shown, and butt-soldered together. The parts 40, 41, 42 have a continuous cylindrical passage 45, which is limited by a cylindrical surface 46. The passage 45 in reality forms an extension of and limits part of the control chamber 22 in the piston housing H.

The magnetically permeable portion 40 is screwed into the piston housing H, as shown at 48, and pressure-sealed against it with an O-ring 49. Its left face 46 forms a right stop for the piston P, so that the maximum stroke s is the opening between the faces 12 and 4 6 minus the axial length of the piston P. In addition, the portion 40 has a flange 50 near its left end. The flange 50 extends radially into the passage 45 and forms a left stop

51 for the control element C. The right end of the passage 45 is closed with a bowl-shaped plug 60 which is screwed into the part 40 and sealed with an O-ring 61. The plug 60 can consist

of magnetically permeable or non-permeable material.

House M and the part of house H that is on the right

for the surface 27 of the piston P contains the control pressure chamber.

The part 40 has a radially projecting flange 52 and the magnetically permeable part 41 has a magnetically permeable ring 53 which butts against and extends radially out at a distance from the flange 52. The solenoid coil S is arranged between these radially projecting parts. A sleeve 55 of magnetically permeable material surrounds the solenoid coil S with its ends in an overlapping relationship with the radially extending flanges 52, 53. According to the invention, the control pressure chamber housing M forms a closed magnetic loop around the solenoid S, apart from the magnetic air gap which results from portion 42 is magnetically impermeable. It is assumed that the house's M construction is new and unique.

The gated element E is in the form of an elongated rod of magnetically non-permeable material, which extends axially to the right from the face 24 of the control pressure piston P, which has a cylindrical outer surface 65. The element E may extend integrally with the piston P or it may be designed separately and attached to the piston P (see e.g. fig. 5). The outer diameter of element E is approx. 6.35 mm and less than the inner surface of the flange 50 to allow free fluid flow when the piston P and member E are moved as a unit in the housings.

According to the invention, means are provided which bring the high pressure in chamber 16 into communication with the control pressure chamber 22. In this embodiment, these means comprise an axial passage 70 which extends from a location near the right end of the element E, through the piston P and the piston Q , where it is in connection with a radial passage 71, which leads to the high-pressure chamber 16. The passage 70, which is normally drilled from the right end 72 in the element E, is closed with a plug 73. In a similar way, according to the invention, provision is made for means that connect the control pressure chamber 22 with low pressure. In the embodiment shown, these members comprise an axial passage 74, which extends from a place near the right end of the element E, through the control piston P, where it connects with a radial passage 76, which opens into the low pressure chamber 15. Similarly, this passage drilled out from the right end of the control element E and the right end is closed with a plug 78.

On its outer surface, the element E has a pair of circumferential grooves 80, 81 at an axial distance from each other, separated by a land 82 with an axial width approximately equal to the stroke P of the piston. The groove 80 is connected to the high-pressure passage 70 via a radial passage 84, while the groove 81 is connected to the low-pressure passage 75 via a radial passage 86. The groove 80 is limited by left and right radially extending side walls 80', 80", where the latter cuts the outer surface 65 of the port-equipped element E with a sharp corner 87. The groove 81 has right and left radially extending side walls 81', 81", where the former cuts the outer surface 65 with a sharp corner 88.

The control pressure chamber 22 is, apart from the variable effect of the control element C which will be discussed in more detail, in connection with high and low pressure via essentially identical grooves at an axial distance from each other in the gate-equipped element E, via essentially identical, axially extending passages in the element E and the pistons P and Q. The piston P and the element E are movable in a line of motion which runs parallel to the axis of the piston P, while the pores 80, 81 form inlet and outlet ports to and from the chamber facing in a perpendicular direction in relation to the control element's C movement line. It is believed that this arrangement of the piston P and the ported element E is new and unique.

According to the invention, the control element C is displaceably supported by the surface 46 and must at the same time limit the fluid flow out of the inlet port slot 80 and open fluid flow to the outlet port slot 81 or vice versa, outlet and inlet in this connection being used to indicate the direction of the fluid flow into or out of the control pressure chamber 22.

In the embodiment shown, the control element C has the shape of a sleeve with an inner surface with a diameter which forms a small clearance f against the outer surface of the gate-equipped element E. This inner surface is generally provided in the middle of the sleeve with a groove 90 which is in connection with the outer surface of the sleeve via a pair of diametrically opposed radial passages 91, which in turn are connected to the axial ends of the sleeve via longitudinal grooves 93.

The groove 90 preferably has a width that at least corresponds to the total stroke length s of the piston P. For a stroke of 15.875 mm, this width should be at least 19.05 mm. The wall 90' has a distance from the left end of element C

which corresponds at least to the maximum movement of the element C to the right, which range of movement corresponds at least to the maximum movements of the piston P.

Track 90 has left and right radial sidewalls 90', 90" spaced slightly less than (e.g., 0.051 mm to 0.102 mm) the width of land 82 and intersects the inner surface of member E with sharp corners 94,96, which facing the corners 87 and 88 respectively, to form fluid openings 97,98, the width of which varies in an inverse relationship to the movements of the control element C in relation to the gate-equipped element E.

The control element C is biased to the left with a small force, e.g. 0.9 kg, of a spiral spring 95 which at one end is supported against the bottom of the bowl for stopper 60 and at the other end is supported against the right axial end of the control element C. The left end of the control element C butts against a ring 99 of magnetic, non-permeable material, which in turn butts against the right surface 51 of the flange 50. The ring 99 forms a magnetic air gap between the flange 50 and the control element C. One or more radial grooves 99' in the surface that abuts the flange establish a connection between the pressure in chamber 45 and chamber 22.

The grooves 80, 81 are spaced from the piston P, so that the land 82 is in line with the groove 90 when the control element C is in the neutral position shown. There is a limited overlap of the corners and a limited fluid leakage through the clearance f from the high-pressure chamber through the passage 70 to the groove 90 and then out through the low-pressure passage 75 to the low-pressure chamber 15. The groove 90 and thus the chamber 22 will be approximately midway between high and low Print. As such, the pistons P and Q are exposed to equalizing pressure forces.

According to the invention, the right end of the control element C is tapered towards the end, as at 100, for reasons that will be discussed in more detail.

The control element C has a construction clearance c of 0.0127 mm between its outer surface 103 and the inner surface 46 of the chamber 45, so that the control element C can be easily moved in the control pressure chamber without undue friction. As shown in fig. 3, the control element C consists of a magnetically permeable part with an external diameter d and an external layer 105 of a magnetically non-permeable material with a thickness t, which according to the invention is at least twice as large as the constructive clearance c, e.g. 0.051 mm. The material 105 can be any known metallic non-permeable material, such as copper, brass, stainless steel or the like, but in the preferred embodiment consists of "Teflon", which is known for its low friction characteristics.

The radial magnetic forces on the control element C will almost always be somewhat eccentric, which results in the element being pulled radially over a distance corresponding to the element's constructive clearance, until a point or a line of the outer surface physically comes into contact with the wall 46. It is known that when two magnetically permeable surfaces are drawn towards each other by a magnetic field, the magnetic forces will increase to a maximum with an asymptotic curve, as the magnetic air gap approaches zero. When using the magnetically non-permeable layer or coating of the specified thickness, the ratio between the maximum air gap between the surfaces of magnetically permeable material and the minimum air gap will never exceed 2:1. Radial forces between the outer surface of the control element C and the inner surfaces of the magnetically permeable parts 40 or 41 will thus be limited. The clearance f between the inner surface of the element C and the outer surface 65 of the element E is preferably at least as large as the clearance c in order to prevent these radial forces pulling the element C into frictional pressure against the element E.

When the control element C in the embodiment shown is biased to the left against the spacer 99 and the stopper 50,

both grooves 80 and 81 are normally in equally constricted connection with groove 90. The axial width of groove 90 is preferably at least as large as its own and the full stroke distance of the piston P, so that it always communicates with groove 81, even if the control element C is in the right position and the piston P in the left position.

Significant pressure drops occur through the openings 97, 98, and even in zero position there will be a continuous fluid flow, which is directly proportional to the areas of the two openings. The area of each opening is equal to the clearance f multiplied by the circumference of element E. The diameter of element E is as small as possible to still allow passage to form or exist. 6.35 mm is preferred, which with the same clearances results in an opening area that is smaller than has hitherto been thought possible in linear servomotors which have always included the use of a track-equipped coil which is movable in a gate-equipped piston. Less zero leakage results. The elements can also be more easily created in precise and small tolerances and exact concentricity.

The passages 70, 75 are shown as parallel bores. They can of course be formed by concentric tubes at a distance from each other, where the interior is determined for one pressure and the distance between them for the other pressure.

The solenoid S may have one of many different forms, which are not part of the present invention, but will normally comprise a plurality of layers of copper wire suitably enclosed in an insulating medium, and it will comprise a pair of connecting wires 110, 111 extending out through the insulators in the shell 55.

The solenoid S can be made electrically current-carrying in the desired way from an optional electrical power source which supplies the desired current in relation to the number of turns in the winding. In some cases, it is desirable that the power source for the solenoid S is an alternating current source or alternatively a combination of an alternating current and a direct current source. The weak pulsation of the resulting flux will have a weak vibrational effect on the control element C, which contributes to overcoming the static frictional effects and eliminates hysteresis that would have to be induced by such friction. Fig. 4 shows a connection core which comprises a power source 115, which can be an alternating current source, alternating current in addition to direct current or a direct current source and a potentiometer 116, which has one of its outer connections 117 connected via wire 118 to a source connection. The second external connection 119 is via the wire 120, the variable resistance 121 and the wire 111 connected to the second source connection. The solenoid S is connected via the wire 110 to the potentiometer arm 126 and the other connection 127 goes to wire 111. When the potentiometer arm 126 is varied, the current in the coil S can be varied from a minimum, determined by the resistance 121, to a maximum, determined by the resistance in the coil S and the voltage of the power source. Alternatively, the source may be a computer or other source of analog electrical signals directly coupled to coil S.

The current through the solenoid S generates a magnetic flux that flows through the magnetically permeable portion 40 to the magnetically permeable portion of the control element C, which is opposite the magnetic air gap in the form of the layer 105 to the magnetically permeable portion 41, then through the element C and above it magnetic air gap to part 41. When the magnetic flux increases, the control element C is pulled to the right against the bias of the spring 95 to close this magnetic air gap.

The variable resistor 121 maintains a weak bias current in the solenoid S, when the arm 126 is in the minimum energy position shown, i.e. in contact with the connection 119, so that the control element C is biased to the right by a value that is slightly less than the minimum biasing force of the spring 95.

By tapering the front end of a control element C, the magnetic forces that pull the element to the right for any given magnetizing current can be made essentially constant over the entire movement range of the control element. In other words, there is a relatively flat force-versus-displacement curve. Provided that a coil spring such as the spring 95 has a substantially sloping force-versus-displacement curve, the two curves will intersect at a sharply defined point. This enables the control element C

at all times to return to a sharply limited point in the chamber at a given magnetizing current in the solenoid S.

When the operation of the device is to be described, it is appropriate to consider the interaction between the control element C and the gate-equipped element E when they are moved in relation to each other, then the movement of the pistons P.Q,

as a result of the compressive forces affecting them and then the movements of the two control elements in relation to each other, as caused by the pistons P.Q. motion.

When the control element C is moved in relation to the gate-equipped element E, the degree of communication between track 80 and track 90 is thus increased or reduced in relation to the size of the relative movement, while the communication between track 90 and track 81 decreases or increases vice versa. The communication stage can be considered as a pair of variable valves or openings in series between high and low pressure, where slot 90 is the connecting passage and at an intermediate or control pressure. The flow through an orifice is directly proportional to the orifice area and the square root of the pressure drop across the orifice. Insofar as the flows through two openings must be exactly the same, the pressure in the connecting passage, i.e. the groove 90 between the two valves must be inherently adjusted or vary up and down to a pressure which maintains this equal flow through both openings. The pressure in the groove 90 is fully communicated to the control chamber 22 through the groove 90', where it exerts a force to the left equal to the pressure times the area of the piston P.

The piston Q also has a higher pressure on the flat 33

which has a smaller, i.e. 50%, area than piston P and this pressure exerts a force on the pistons to the right. If these forces plus or minus any external forces against the drive shaft 0 are not equal, the pistons will move in the direction of the higher force and will seek to do so, even though they are in contact with the shoulder 12 or the face 65, until the forces are exact equally and oppositely directed.

In the mechanical connection of the port-equipped element E with the pistons, any movement of the pistons will vary the communication between the two valves or openings, until the pressure in the control pressure chamber exceeds a force to the left on the surface 27 which exactly corresponds to the high pressure against piston Q and the external force against the drive shaft 0.

Very small relative expansions and narrowings of the valves or openings cause rather large changes in the pressure in groove 90 and thus in the control pressure chamber. Thus, the pistons will at all times almost exactly follow the control element C when this is moved to the right or left by variations in the magnetization of the solenoid S. Large changes in the external forces on the shaft 0, i.e. either compressive or tensile forces, can result in large changes in the pressure in the control pressure chamber with only a very small movement, e.g. 0.025 mm of the piston.

Fig. 1 shows the release device at maximum fluid pressure and almost zero magnetizing current. In this state, track 80 has high pressure and track 81 low pressure. Tracks 80 and 81 are in an equally narrowed connection with track 90. There is thus an equal pressure drop from track 80 to track 90 and from track 90 to track 81. Track 90 and chamber 22 are thus located halfway between the difference between high and low pressure. Provided that the area of the surface 27, which includes the cross-sectional area of the gate-equipped element E, is twice the area of the surface 33, the pressure forces are equalized and the pistons P,Q and the element E are completely out in the left position.

If the solenoid S is now magnetized by the arm 126

of the potentiometer 116 is moved to the left, i.e. towards connect-

iron 117, more current will flow in the solenoid S and generate more magnetic flux in the magnetically permeable parts 40, 41. This flux causes the control element C to be moved to the right against the bias of the spring 95. When this happens, track 90 is moved away from track 80 and towards track 81. There will then tend to be an increasing pressure drop between tracks 80 and 90 and a decreasing pressure drop between tracks 90 and 81. This increasing pressure drop between tracks 80 and 90 tends to reduce the pressure in the control chamber 4 5 and thus the pressure forces on the piston P to the left. The pressure forces to the right on the piston Q remain the same. The pistons P,Q and the element E are moved to the right, until the pressure forces on the three elements are again exactly balanced. If the control element C is still moved to the right, the pressure will tend to fall further in the groove 90 and the chamber 22 and the pistons P.Q. and element E will be moved further to the right to maintain the compressive forces on the pistons P,Q and the gate equipped element E exactly balanced.

In the absence of external forces on the drive shaft O,

the control chamber pressure will remain constant at a constant high pressure. The only thing that changes it is the position of the pistons, element E and shaft 0 when they follow the guide element C.

Extremely small relative movements of the tracks 80, 81 in relation to track 90 can cause large pressure changes. The pressures in chamber 22 can vary from almost high pressure to almost low pressure with a very small movement, e.g. of 0.025 mm, of the pistons P and Q to counteract the effect of any external forces on the shaft 0.

In the event of a failure in the power supply, the control element C will be moved to the left by the spring 95, and the pistons P.Q will then automatically be moved to the left position shown in fig. 1.

Fig. 5 shows a double-acting fluid pressure-activated release device which is generally similar to the embodiment shown in fig. 1. Only the differences between the two devices will be discussed. Identical parts, but of different shape, are denoted by the same reference number, marked '.

In fig. 1, the gate-equipped element E is shown in an embodiment in one with the stamp P. In fig. 5, the element E' is attached to the piston P, so that it is radially movable in relation to the piston. A misalignment of the axes for the two houses is thus taken up.

The left end 108 of the gate-equipped element E' thus extends relatively loosely into a bore 107

at the right end of the piston P' and is sealed by an elastic pressure seal 110. The element E<1> has a flange 121 at a distance from the end 108 with an elastic pressure seal 111 in the outer surface which seals against a recess surface. The left end 108 between these seals is equipped with a circumferential groove 113, which via a radial passage 114 communicates with the left end of the passage 75'. This slot is connected to the low-pressure chamber or cavity 115 via a passage 116 which runs diagonally through the piston P' through the pressure surface 12 3. The left end 108 is closed inside the bore 107 by means of a disc 120 which is in contact with a right-facing shoulder of a flange 121 on the element E' and a slotted locking ring 124 which fits into a slot at the open end of the bore.

According to the invention, the flange 121 has an area twice as large as the end 108 and will be in pressure force balance in relation to the piston P'.

The same or a similar radially movable pressure-balanced construction can be used in all embodiments mentioned here.

In fig. 1, there is only one solenoid. In the embodiment shown in fig. 5, a pair of right and left solenoid coils S.S<1> are arranged with an axial mutual distance. Furthermore, a pair of magnetically non-permeable parts 42, 42' are present in these coils at an axial distance with a magnetically permeable part 43 between them. The part 43 comprises a radially extending part 43', which extends out between the adjacent ends of the coils S, S'.

In this way, both solenoid coils S, S<1> have a closed magnetic loop except for the non-permeable parts 42, 42', and the loop is closed via the control element C.

The control element C' is generally identical to the construction of element C in fig. 1, except that the left end tapers off as at 100', identical to the right end 100 in the embodiment according to fig. 1, and for the same reason.

Magnetically permeable parts 40, 41 are provided with recesses with a diameter of 0.254 mm to form left- and right-facing shoulders with a mutual distance of preferably 0.254 mm more than the axial length of the control element C'. A slotted locking ring 128 is slotted into a groove in this countersunk surface to form a stop for a stainless steel ring 129 on the right side of the ring. The locking ring 128 is arranged so that the right surface 130 of the ring, taking into account the thickness of the ring 129, will have the same distance from the shoulder as the base of the bowl 60 from the right-facing shoulder. A pair of rings 132, 133 are arranged in each recess with such a diameter that they are axially movable in the recess and butt against the shoulders. Spiral springs 95 and 95', one at each end of the control element C, bias the rings 132, 133 against the shoulders. The springs 95, 95' preferably have identical construction and are under light compression, e.g. of approx. 0.9 kg. With this device, the springs 95, 95' must not be completely identical in order to center the groove 90 in the control element C' in relation to the grooves 80, 81. When a control works in the direction of gradual magnetization of the coil, there will be a weak dead center in the control element movement before the magnetization of the coil is sufficient to overcome this compression force and move the control element C.

Fig. 5A is a connection core for controlling the magnetization of the coils S,S'. A potentiometer has a resistance element 142 with external contacts connected via wires 150, 151 to the respective contacts for a battery 14 6 and a contact

for the coils S, S'. The potentiometer arm 144 is connected to both other contacts for the coils S,S' via the wire 14 5. The arm 144 is biased towards the center position by springs not shown, as is usual in the area. In this position, both coils are the same, but

minimally magnetized with opposite magnetic polarity, and each exerts an equal force to the right or left of the control element

C. This thus remains in the neutral or middle position.

The operation of the solenoids S, S' in connection with the control element C is generally the same as that discussed in connection with fig. 1. If the solenoid S becomes more magnetized than the solenoid S', the control element will move to the right and the gate equipped element E<1> and the piston P<1> will move to the right in the same way as discussed in connection with fig. 1. If the left solenoid S<1> is more magnetized than the solenoid S, the control element C will move to the left and the gated element E' and the piston P' will also move to the left. In case

of power failure, the control element C will be returned to its neutral or center position by the springs 95, 95', as shown.

Because the springs 95, 95' are under output compression, the arm 144 must be moved in a small arc in one of the directions before the magnetic force on the element C overcomes this output compression and begins to move the element C'. This gives a small zero or dead center in the steering.

It will thus appear that a single-acting and a double-acting electrically controlled fluid pressure-activated trigger are discussed, where the only element that protrudes from a pressure chamber is the output shaft 0. The position of this output shaft can also be easily controlled by an analog electric current in a one or the other of the solenoids. These solenoids created a magnetic flux which causes a control element, which is fully enclosed in the actuator housing, to move relative to inlet and outlet passages connecting a high and low pressure control pressure chamber, respectively. By moving the control element in relation to the inlet and outlet passages, the pressure drop between these passages and the pressure chamber will vary. The differential area pistons in the trigger move under differential pressure forces exerted against them and thus precisely follow the position of the control element determined by the magnetic forces. The pistons are then held in substantially accurate positions relative to the control element, regardless of variations in the external forces on the output shaft of the trigger.

Fig. 6 shows the trigger according to fig. 5 incorporated in a directional valve of the remote-controlled type. In this embodiment, the valve comprises a combined valve and piston housing A, a control pressure housing B, a control pressure piston N which acts on the valve's coil D, a high pressure piston L, a gate equipped element K, a control element F and a pair of solenoid coils S, S' for selective movement of the control element F to the right or left and to bring the control pressure piston N to move the coil D to the right or left, as it follows the movement of the control element F.

The housing A is generally conventionally constructed and comprises an elongated cylindrical chamber 610 with a cylindrical side wall 611, in which the piston N is slidably supported and a plurality of port chambers separated by sealing lands, which from right to left comprise a low pressure chamber 613, a narrow land 614 , an outlet/inlet chamber 615, a wide land 618, an inlet/outlet chamber 619, a narrow land 620 and a low pressure chamber 621. The chambers all have the same axial width and the wide lands are twice as wide as the narrow lands.

In the vicinity of and in communication with the low-pressure chamber 621, according to the invention, a cylindrical cavity 625 is arranged with a smaller diameter than the diameter of the various lands and the chamber 610. The left end of the chamber 625 is closed with a plug 628 which is screwed into the housing A and sealed by an O-ring seal 629. An internal passage 633 connects the low pressure chambers 621 and 613. The chamber 613 has a port 634

which is threaded at the outer end to receive a conduit fitting (not shown), which port 634 is normally associated with low pressure, such as a sump or the like.

The chamber 615 has a port 640 which at the outer end is

threaded to receive a conduit fitting that communicates with a port on a fluid pressure device to be operated. The inlet pressure chamber 617 has an inlet port 642 which is threaded at its outer end to receive a conduit fitting and is adapted to connect to a source of a constant volume high pressure fluid. The chamber 619 has a port 644 which is threaded at the outer end to receive a fitting which is adapted to connect to the other port of the fluid pressure device.

The coil D comprises a pair of cylindrical coils 650, 651 with a mutual axial distance corresponding to the distance between the two inlet/outlet pressure chambers and a length corresponding to the width of the chambers plus the width of a wide land. Coil 650 has a surface adapted for alternating contact with lands 614 or 616 and coil 651 has a surface adapted for alternating contact with lands 618 or 620.

These surfaces are each provided with a pair of constricted passages 654, 655, one at each end, which have increased depth towards the axial ends of the coils to conventionally maintain a continuous inlet pressure and allow a restricted fluid flow, e.g. 113.56 l/min. through the valve. This inlet pressure naturally varies within wide limits with the variation of the load on the device being controlled. The tracks 654, 655 are shown in cross-section on the coil 650 and in elevation on the coil 651 to give a clearer picture of the device.

Depending on which countries are in sealing contact, fluid will be directed through the valve from the inlet port to one of the outlet ports in a conventional manner.

The high-pressure piston L runs together with the left end

of the coil D and is displaceable in a sealing relationship with the walls of the cavity 625 to form a high pressure chamber 661 with the right face of the plug 628.

The coil also has a reduced diameter lot 662,

which restricts a passage for connecting the inlet/outlet chamber 619 with low pressure when the coil D is moved to the right.

Similarly, the coil D has a portion 665 of reduced diameter which limits a passage 666 in connection with the cavity 610, and when the coil D is moved to the left, the inlet/outlet chamber 615 is brought into communication with low pressure in the chamber 616.

The coil has a part 657 of reduced diameter and continuous with the coils 650, 651, which part has a transverse passage 656 which connects the inlet pressure in chamber 617 with an axially continuous passage 658 which extends through the entire length of the coil D and connects the high pressure in the inlet chamber 617 with the right end of the coil D and the pressure chamber 661.

The piston N is preferably made in one with the coil D and has, in a conventional manner, a plurality of pressure equalization grooves 670, which run axially apart around the surface of the piston. According to the invention, the piston N also has an axially extending groove 671, which connects the left axial surface 672 and the right axial surface 673. The groove 671 intersects the circumferential grooves 670 and forms a plurality of sharp-edged openings to create a constricted passage from the control pressure chamber to the low pressure in the same way as generally discussed in connection with fig. 7 and 8.

The manner in which the gate-equipped element K is attached

to the pressure piston N is shown in and described in connection with fig. 5 and will not be discussed further. In the shown embodiment of the invention, due to the narrowed passage formed by the groove 671 from the control pressure chamber to low pressure, it is only necessary that a single high-pressure inlet passage 675 be arranged in the port-equipped element K. This passage extends axially through element K to plug 676 at the right end. A groove 678 in the outer flare 679 of the element K connects with the passage 675 via cross-drilled openings 680. This groove is limited by left and right radially extending side walls 678', 678".

The control element F is generally identical to the construction of the control element C which is discussed in connection with fig. 5 and will not be discussed further, except that it should be mentioned that it has a circumferential groove 681 in its inner surface which is connected to a longitudinal groove 682 via cross-drilled passages 683, so that high pressure in the inlet chamber 617 can be connected to the control pressure chamber via the cross-drilled openings 656, the axial passage 658, the axial passage 675, the radial passage 680, the groove 678, the groove 681, the radial passage 683 and the groove 682.

In this embodiment of the invention, the groove 678 is arranged so that the right wall of the groove 678 and the left wall of the groove 681 overlap somewhat when the control element F is in the middle position shown when the solenoids S, S' are not magnetized. The size of the overlap depends on the constrictions in the outlet groove 671 and the clearance f. In any case, the piston N will move the grooves in relation to each other, so that the flow between them will correspond to the flow through the groove or passage 671.

In the embodiment shown, the high pressure is also connected from passage 658 to chamber 661 and this pressure exerts a force to the right on the surface 660. The variable pressures in the pressure control chamber exert a force to the left on the piston N. The piston N moves the groove 678 in relation to the groove 681 for

to open and close the inlet passage from high pressure in relation to the outlet passage to low pressure, until the pressure forces are equalized on piston N and piston L for coil D.

If the solenoid S is magnetized, the control element F is moved to the right, and the pressures in the pressure control chamber tend to be reduced. The piston N and the slide D follow the control element F to keep this pressure constant. This movement of slide D directs fluid flow to port 640. If solenoid S' is activated, control element F is moved to the left and piston N will also move to the left to move slide D to the left, causing fluid flow to port 640 Variations in the pressure in the inlet port 642 induce proportional pressure changes in the high and low pressure chambers and do not adversely affect the force balance on the piston N and coil D.

Should the current fail, the control element F will return to its neutral or middle position as shown in fig. 6 and the slide D will automatically return to the neutral position.

In this embodiment of the invention, the springs 95, 95' are designed so that their free, unloaded length is greater than their length when installed in the device. The springs thus exert their own output voltage against the discs which are in contact with the ends of the control element F. With this device, the potentiometer arms according to fig. 5A is moved in a slight arc to energize one of the solenoids sufficiently to move more than the other before the control element F begins to move toward the spring output bias. In this way, the operator has a weak dead center in his hand control lever before further movement of the hand lever begins to move the control element F and the coil D for controlling the motor or piston which the device is to control.

It will thus be seen that a two-way directional valve has been provided which can be controlled remotely by means of an analog electric current and which will be accurate in its location of the lands on the slide D in relation to the lands of the housing, and will provide accurate control of the device such as coil - the valve controls.

Fig. 7 shows the release incorporated as part of a pressure relief valve of the differential area piston type. This valve generally comprises a control piston housing T, a control pressure chamber housing U, a valve actuation piston V, a control pressure piston W, a ported element X, a magnetically actuated control element Y in the form of a sleeve, and a solenoid S, which is adapted to be connected to a variable electric power source and which, depending on its magnetisation, brings the control element to a desired position in the housing U.

The housing T generally takes the form of a block of steel, aluminum or another high-strength material. An elongated cylindrical chamber 710 is formed in the block and the control piston W is displaceably mounted in the chamber and in turn supports the valve piston V displaceably.

House U is constructed in the same way as house B in fig.l and needs no further explanation. Suffice it to say that it has a chamber 717 which is coaxial and communicates with the chamber 710, and it is limited by cylindrical side walls 718. Otherwise like parts will be designated by like reference signs .. Left side of the magnetically permeable part

740 has a surface 716, which acts as a stop to the rightward movement of the piston W, as further discussed below. The left end of the chamber 710 is provided with a recess as at 720, which forms a right-facing shoulder or stop 721 for left end of the stem spot W. The axial length of the stem W is smaller than the distance between these two stops by a value d.

The left end of the housing T has an inlet opening 724 on the axis of the chamber 710, where a valve seat forming member 725 is placed. The member 725 has a cylindrical portion 726 in the opening and is sealed with an O-ring 727. The opening 724 is internally threaded to receive a suitable fluid line fitting, not shown. The right end of the valve seat forming member 725 has a conical valve seat surface 731 surrounding an inlet port 732. The surface 731 is adapted to engage an arcuate valve seat engagement surface 734, which is formed on the left end of the valve actuating piston V, generally as shown. This surface 734 engages tangentially with the conical surface 731 on a circle 735, which has a diameter a, determined by the arc radius of the surface 734 and the angle which the conical surface 731 encloses. These dimensions are chosen so that the diameter a is at least greater than the diameter of the opposite end of the piston V, which is exposed to high pressure and the diameter of the part 726 of the part 725.

The circle 735 limits an area against which fluid pressure in the inlet port exerts a force to the right, which is equal to the pressure times the left-facing area.

Generally close to but just to the left of organ 725

forming the valve seat is an outlet port 740, which is threaded to receive a fluid line fitting, not shown, and communicates with the chamber formed by the recess 720. Normally, this port will be at zero pressure, and when the valve piston V is moved to the right, it moves the surface 734 which is in contact with the valve seat away from the valve seat surface 731. Fluid can then flow from the inlet port, past the valve seat 731 and out through the outlet port 740.

The control piston W has an outside diameter such that it is displaceable in sealing engagement with the chamber 710 surface, and is provided with a plurality of generally rectangular oiti circuit grooves 750 for pressure equalization, as is customary in the field. However, according to the invention, the outer surface is also provided with an axially extending, rectangular groove 752 which intersects each circumferential groove 750 and at the right end communicates with chamber 717 and at the left end communicates with chamber 710, which chamber is in connection with the outlet port 740. The intersections between the grooves 750 and groove 752 forms a narrowed passage from housing B interior 717 to outlet port 740, which consists of several sharp-edged openings, so that any fluid flowing through will flow at a velocity insensitive to viscosity and will have a pressure drop proportional to -tionally with the square root of the pressure difference between the pressure in chamber 717 and the outlet port 74 0, as discussed in more detail below. The groove's 752 dimensions are preferably such that the leakage rate will be in the order of 4.09-16.387 cm 3 -min, at maximum design pressure inlet to the valve. In practice, the circumferential grooves 750 will have dimensions of approximately 0.508 mm width and 0.508 mm depth. The leakage track 752 has a width of approx. 0.762 mm and a depth of 0.508 mm. These dimensions can of course be varied to achieve the desired flow rates and the desired pressure balance.

The piston W has an internal cylindrical chamber 765, where the right end 766 of the piston V is displaceably supported. An O-ring 767 in a groove in the outer surface of this right end

766 seals the opposing surfaces displaceably. The left end of the piston V has a radial flange 769 with a diameter which enables displaceable abutment against the surface of a recess 720 in the chamber 710. The flange 769 is provided with an axially extending groove 771 which allows fluid passage.

The left end of the control piston W has a recess which forms a shoulder 772 and a space 773 for a spring 774, one end of which rests against the shoulder 772 and the other end of which abuts against the left side of the flange 769. This spring 774 is the main means of pressure control and biases the pistons V and W towards the left and right, respectively, and the surface 734 for sealing against the valve seat surface 731.

The piston V has an axial passage 779, which connects the high pressure in the inlet port 729 with the right end of the piston V and the chamber 765. The pressure is connected via the clearance between the piston part 766 and the wall of the chamber 765 to affect the left side of the O-ring 767. The chamber 765 is the piston V pressure chamber and this pressure pushes the piston V to the left and to the closed valve position. This pressure also tends to compress the O-ring 767 in the direction to the left, i.e. towards the valve seat 731. It is important that the cross-sectional area of the part 766 according to the invention is smaller than the area of the circle 735, the net area being such that pressure in the inlet port 729

will tend to push the piston V to the right. These forces are counteracted by the bias from the compression spring 774 which is variably compressed by the piston W.

According to the invention, means are provided which vary the compression of the spring 774 via a remotely controlled electrical analogue signal. According to the invention, a gate-equipped element X thus extends from the piston W, coaxially into chamber 717, and the control piston W and the gate-equipped element X have an axial passage 870, which at the left end communicates with the chamber 765 and at the right end communicates with a transverse passage 782. The passage 782 communicates with a cylindrical groove 783 in the element X surface 784. These passages 782,

780 and 779 will, in the absence of the control element Y, form an unobstructed passage which brings the inner 717 of the housing U into contact with the inlet pressure. The pressure chamber 717 exerts a force to the left on the piston W, which is equal to the cross-sectional area of the piston W minus the area of the chamber 765.

The control element Y is generally identical to the control element C in fig. 1, and will not be further discussed, except that its inner surface has an elongated circumferential groove 790 which communicates with a longitudinal groove 791 in the outer surface via a transversely drilled passage 792. As shown in fig. 7A has track 790

a left side wall 793 which has a distance from the left end of the element Y which is at least equal to the element's maximum range of movement towards the right, and such a length that it will overlap the groove 782 significantly when there is zero fluid pressure and the piston W is in the right position , as shown, to overlap the track 783 by a small value, e.g. 0.127 mm,

when the piston W has moved in a complete stroke d to the left under the influence of high pressure in the chamber 717.

While most other devices discussed here have a ratio of net control piston pressure area to net high-pressure piston pressure area (differential pressure area ratio) of

about. 2:1, spring pressure-controlled valves, such as relief-pressure-

reduction sequence valves, etc. have a spring force that is set well in advance of activation. In fig. 7, the net control pressure area is thus 7.5 times the net area of the control piston which is exposed to the system pressure, instead of the 2:1 ratio in the other mentioned devices. The spring control devices are completely opposite to the other devices, where an increase in magnetic flux will reduce the spring force, and it is only necessary to increase the force in one direction.

The control element Y is constantly biased to the left by the spring 795. There is thus normally a partially restricted flow of fluid into chamber 717 and a completely constricted flow of fluid out of chamber 717.

During operation, high pressure in the inlet port 724 will exert

a force to the right on the area that is limited by the circle 735 on the member 733 that abuts the valve seat. The high pressure goes via the passage 779 and exerts a leftward force on the right end 796 of the piston V. Since the area of the right end 796 is smaller than the area of the circle 735, these forces would normally move the piston V to the right. When the spring 774 biases the valve piston V to the left with a force equal to the spring characteristic of the spring and the compression. When the differential pressure forces on the piston V exceed the force of the spring, the piston V will move to the right and thus create a limited connection between the inlet port 724 and the outlet port 740.

The inlet pressure is also connected to the control piston's pressure chamber 717 via the passages 779, 780, 782, the grooves 783, 790, the passage 792 and the groove 791. This pressure is then vented towards the outlet via the groove 771 which forms a narrowed passage for the fluid flow. When the inlet pressure increases, the pressure in chamber 717 also increases. The control piston W is moved to the left by the pressure on the right end of the piston. When the control piston W is moved to the left, it compresses the spring 774 and thus increases the inlet pressure, so that the valve piston V is moved to the open valve position. The shoulder 721 limits the movement of the control piston W to the left and thus the maximum compression of the spring 774. Depending on the characteristic of the spring 774, the valve's maximum relief pressure is thus determined.

When the solenoid S is magnetized, the magnetic flux will cause the control element Y to move to the right against the spring 795 bias, and the element Y will remain in any position determined by the magnetization of the solenoid S. When the control element Y is moved to the right, it limits the fluid flow out of the groove 783 to a degree where the amount of fluid flowing into the pressure chamber 717 begins to be less than the amount of fluid flowing out of the pressure chamber 717 through the passages 752, 771. At this point the control piston W will move to the right as a result of the spring 774 Power. The degree of compression of the spring 774 is reduced and the pressure at which the differential pressure on the valve piston V will move the valve to the open position is thus reduced.

It will be apparent that a valve is discussed here, where the pressure at which the valve opens can be controlled by means of an analogue electrical signal, which can be generated anywhere, remote from the valve and sent to the valve via normal electrical lines.

By suitable positioning of the control element Y, the compression of the spring 774 can be controlled within certain limits and the opening pressure of the valve can thus be controlled within the maximum design opening pressure and a lower value, depending on the relationship of the spring 774 and the maximum range of movement of the piston W.

In addition to this feature, the present invention has other advantages. It should thus be noted that the diameter of the O-ring 767 is smaller than the diameter of the circle 735 in contrast to what is the case with known differential pressure valves, where the diameter of the O-ring is always larger than the diameter of the valve's seat. With the arrangement shown, the 0-ring has significantly less area in contact with its sealing surface and thus less friction against it. The valve member V can react more easily to pressure variations.

It should also be noted that the high pressure on the O-ring 767 always acts in the direction of the valve seat, in contrast to what is the case with known technology in the area, where the pressure on the O-ring is always away from the valve seat. This pressure, especially if it is very high, will tend to push parts of the O-ring into the clearance between the opposing surfaces. When the O-ring is pressed into the clearance between the surfaces in a direction away from the valve seat, this will further increase the friction against closing movement of the valve piston and give a hysteresis in the pressure-versus-valve position curve when opening and closing. In the illustrated device according to the invention, the closing movement of the valve piston will tend to push the O-ring 767 from its extruded position and enable the valve piston to close with far less friction against the piston movement. The valve will thus not tend to leak as much as with the known valves at pressures that are somewhat lower than the set relief pressure and will be able to return to the closed seat after pressure relief with a much smaller pressure difference from the set pressure.

Another advantage of the present invention is that when the valve piston V is moved to the open valve position, the fluid flow through the inlet port exerts a jet effect on the valve piston, which promotes rapid opening and helps to create an extremely flat pressure-versus-flow curve for the valve.

The groove 752 which intersects the grooves 750 to form a plurality of sharp-edged openings is the preferred means for creating the constricted passage from the pressure chamber of the control piston D to the outlet. Other types of constricted passages may be used, but are not considered advantageous, provided that the flow through a regular passage of uniform diameter is proportional to the pressure difference between the inlet and outlet ends of the passage. With the sharp-edged openings, as stated above, the flow becomes directly proportional to the square root of the pressure and generally independent of the viscosity.

The valve is basically safe against failure, i.e. if a power failure occurs, the spring 795 will move the control element Y to the left. This will cause the control piston W to move and the spring 774 to be compressed. But the left end of the control piston W rests against the shoulder 721 which limits the maximum compression 774. With this arrangement, in the event of a power failure, the valve will go to maximum relief pressure, but never further. The important factor is that the valve's relief pressure does not drop to a minimum in the event of a power failure, which in some cases could be dangerous.

The curved surface 734 combined with a conical valve seat provides improved flow characteristics through the valve. This combination is such that the effect of eddy currents when the valve opens is completely eliminated, leading to a much flatter pressure-versus-flow curve. It can be explained by the fact that eddy currents when the valve opens and allows the flow of hydraulic fluid both occur at a smaller diameter than the diameter of the circle 735 (ie the diameter of the actual valve seat) and at a larger diameter. Eddy currents within the actual seat result in an area of the piston that is at less pressure than the incoming pressure. Unless counteracted, this would result in a rising flow-against-pressure characteristic. As areas are important, having an area available at a larger diameter than the actual valve seat diameter, on which eddies occur dynamically and not on a static seal, will make it possible to produce a flat pressure-flow curve.

It will thus appear that an embodiment of the invention is discussed here, which provides a pressure relief valve of the differential pressure type which has greatly improved operating characteristics and where the relief pressure can be easily varied from distant locations by means of an appropriate electrical signal.

The invention is also particularly applicable for controlling valves for flow control, where the output pressure must be maintained at a controlled value. Fig. 8 shows a flow control valve of the differential area piston type, which generally comprises a piston and valve housing R, a pressure chamber control housing G, a valve piston I, a gate equipped element J, a magnetically movable control element K and a solenoid S which in the magnetized state can move the control element K to different positions in the housing G.

The housing R is again generally in the form of a block of steel, aluminum or other high strength material, having an elongated cylindrical chamber 810, in which the piston I is displaceably mounted. The chamber 810 has a recess and threads at the right end for receiving a threaded end 811 on the left end of the steering housing G. The left end of the chamber 810 has a recess as at 812 to form what may be called an exit pressure chamber r and has a recess, as at 813, for creating an inlet passage for the valve which is threaded at 814 to receive a suitable conduit fitting, not shown. A valve seat 814, which is sealed by an O-ring 815, is provided in the recess 813 and has a locating flange 816, which extends into the recess 812. An O-ring 817 which is fitted into a groove in the recess 813 wall locks the valve seat 814 in place.

The valve seat 814 has the general shape of a right-facing bowl, the outer edges of which form a circular valve seat 820. A plurality of passages 821 extend from the left surface of the valve body 814 to the inside of the bowl which is designed so as to form inlet passages from the high pressure in the recess 813. According to the invention, the body 814 consists of a magnetically permeable material, so that it attracts any magnetic particles in the fluid.

Just to the right of the valve body 814 which forms the valve seat, the countersink 812 has an outlet port 830 in connection with the countersink and threaded to receive a conduit fitting not shown. Normally, the cavity limited by the recess 812 will be at low pressure, and this low pressure is what is determined by the valve itself, as discussed in more detail below.

The control pressure housing G has an identical construction to the housing M in fig. 1 and needs no further explanation. However, it should be noted that the left-facing surface 835 forms a right-hand stop for the piston I.

The piston I consists of a cylindrical body with a diameter which allows the piston to slide against the surfaces of the cavity 810. Conventionally, the piston I is provided with a plurality of pressure equalization grooves 841, which extend in a circumferential direction at an axial distance from each other. The left end I has a valve seat-forming part 844, on which there is a contact surface 845 for the valve seat, which in the embodiment shown and for reasons discussed below, tapers towards the left end to a progressively decreasing degree, so that the valve seat contact surface can be said to be concave conical. With this arrangement, it follows that when the valve seat installation surface 845 is moved to the right from the valve seat 820, the rate of change of the opening area in relation to the linear movement of the valve seat will decrease in a non-linear manner. As will be seen, the shape of the valve seat installation surface 845 can be designed for use with a device operated with a special fluid to compensate for variations in the leakage in the device, particularly at low speed, the viscosity of the fluid affected by the valve decreasing with increased fluid temperature .

It is important that the diameter of the valve seat 820 is smaller than the diameter of the piston. Fluid forces towards the left end of the piston I will exert biasing forces towards the right of the piston, which forces are equal to the area of the valve seat 820 multiplied by the pressure.

The gated element J is in the form of a cylindrical rod extending to the right from the right surface 851. The rod has an outer cylindrical surface 853 with a circumferential groove 855 spaced from the surface 851, as shown.

In this design example, the control element K is generally identical to the construction of the control element C in fig. 1,

both as regards the pressure chamber walls and the surfaces of the port-equipped element and needs no further explanation. The groove 855 and the groove 890 in the control element K are arranged axially on

such a way that when the control element K is biased to the left, as shown, and the valve seat contact surface 845 is in contact with the valve seat 820, the grooves will overlap by a small amount, e.g. 0.127 mm.

The piston I and the element J have an axial, through passage 880, which at the left end communicates with the inlet port 813 and at the right end communicates with a transverse passage 882, which in turn communicates with the groove 855.

The passages 880, 882, the groove 855, the groove 890 and the other mentioned passages connect the high inlet pressure in the recess or the inlet port 813 in a limited way with the control pressure chamber. This pressure affecting the right end of the element J and the surface 851 (the area of both is greater than the area of the valve seat 820), creates a force to the left, which biases the piston I into contact with the valve seat 820 against the fluid pressure force against the valve seat forming part 844 of the piston I.

The piston I body 840 is arranged to form a narrowed passage from the control pressure chamber to the outlet or low pressure cavity 812. In the embodiment shown, this device comprises a longitudinal groove 850 in the piston I surface, which groove 850 intersects each of the circumferential grooves 841 to form a plurality sharp-edged openings connecting the right end of the portion 840 with the left end and the cavity 812. The advantages and operation of this longitudinal groove 850 are discussed in connection with fig. 6.

When the solenoid S is magnetized during operation, the magnetic flux will move the control element K to the right towards the bias of the spring 895 and at the same time narrow the communication between track 855 and track 890 in the control element K, so that a pressure drop follows in the control pressure chamber 810. When this pressure drop reaches a value such that the pressure forces to the left on the piston I are less than the pressure forces to the right on the valve seat installation surface 845, the piston I will move to the right and move the valve seat installation surface 845 away from the valve seat 820. High-pressure fluid can now flow through the opening thus created and towards the outlet port 830, from which it may flow to another pressure activated device (not shown).

For a given opening or distance between the valve seat installation surface and the valve seat, the fluid flow and thus the pressure drop will vary with the viscosity of the fluid flowing through the opening. In the case of certain media, especially oil, the viscosity can vary over fairly wide areas with the temperature variations. The present invention automatically compensates such viscosity changes, e.g. at ambient temperatures between 21.11 and 82.22°C, which is a conventional oil operating temperature.

According to the invention, the solenoid S and its magnetic circuit are thus arranged and constructed so that the control element K can be moved using relatively low electric currents, e.g. less than 6 watts. The heat generated by these currents is minimal. Means are provided to keep the solenoid S at substantially the same temperature as the fluid controlled by the valve. In the embodiment shown, such means include means for conducting the heat of the fluid to the coil and heat insulation surrounding the solenoid S to prevent cooling of the coil. The insulation can be an air gap or a layer of non-metallic insulation 89 0. When the temperature of the fluid in the inlet port 813 varies, these temperature changes will thus be conducted through the metal in the piston housing R and the metal in the control pressure housing G to the solenoid S. The temperature of the solenoid S becomes significantly more affected by the temperature of the fluid than internal heating from the magnetizing current.

The solenoid S comprises 14,000 turns of copper wire and the copper wire has a resistance of approx. 24 ohms at 21.11°C. The resistance will increase with temperature. With a fixed magnetizing voltage to the solenoid S, the current in the solenoid and thus the magnetic flux formed will decrease when the temperature of the solenoid S rises. The consequence is that the control element K will move to the left, which in turn tends to close the opening between the valve seat 820 and the valve seat installation surface 845. When the solenoid S receives sufficiently greater amounts of heat from the fluid than is generated internally by the I 2R heat, it can then be achieved that is to say complete temperature compensation of the variations in the temperature of a hydraulic fluid that is affected. Greater or lesser compensation can be achieved by choosing metals for the wire with a different resistance temperature coefficient.

The valve According to fig. 8 can be considered fail-safe. Should the electric current be interrupted for some reason, the control element K will move to the left as a result of the spring 895 bias, which will increase the pressure on the right end of the piston I to the same value as the inlet pressure and the differential areas will cause the piston I to move to valve closing position.

Fig. 9 shows a valve cartridge adapted for sale as a unit and insertion into a conduit housing having a high-pressure inlet passage and an outlet passage to which fluid flow is to be directed. Such a conduit housing is shown in dashed lines and comprises a block of metal with a cylindrical passage 910, which is bounded by a cylindrical surface 911 extending from a side surface 912 of the housing to a remote point adapted for connection to a source of high pressure fluid. A cylindrical outlet passage 914 is also formed in the housing and intersects the passage 910 at a point remote from the face 912. The passage 910 is threaded, as at 916, to receive the valve cartridge, as further discussed below.

The valve cartridge generally comprises a piston housing AA, a control pressure chamber housing BB, a valve drive piston CC, a valve seat DD, a gate equipped element FF, a control element GG and a solenoid SS, which in the mangetized state moves the control element GG to the right, so that pressure occurs in the cartridge, which moves the valve piston CC to the right and opens the valve.

The housing AA is generally formed from a block of one magnetically permeable metal of high strength and comprises an elongate cylindrical chamber bounded by cylindrical side walls 920, which are threaded midway along their length for screw connection with the threads 916 of the lead housing and sealed by an O-ring seal 912. The left end of the housing AA is adapted for insertion into the passage 910 at a point to the left of the outlet passage 914 and is sealed with an O-ring 922. The housing between the seals 921 and 922 has radial openings 924 which connects the left end of chamber 919 with the outlet passage 914.

The valve seat DD is a sleeve-like body of magnetically permeable material and has a valve seat 932 which is sealingly arranged at the left end of chamber 919. A locking ring 934 prevents accidental removal.

The control chamber housing BB is generally similar to that described in connection with the other design examples and comprises a pair of magnetically permeable parts 970, 971 which are placed axially apart and separated by a magnetic, non-permeable part 972. These parts are folded and brazed together to form a pressure-tight housing. The parts have an axial passage which is limited by a cylindrical surface 975. The right end of the passage is closed by a bowl-shaped plug 976 which is screwed into the magnetically permeable part 970 and sealed with an O-ring 977. This plug 876 is made of magnetically permeable material. The solenoid coil SS surrounds the portions 976, 970, 972 and 971 and is surrounded by an outer shell 980 of magnetically permeable material, which extends from a location butt-in-butt with the outer surface of the plug 876 to a location butt-in-butt with the main body of the housing which also consists of magnetically permeable material.

The piston CC has a diameter which allows it to be displaced in sealing contact with the surface 920 and conventionally has a plurality of pressure compensating grooves 940 extending axially apart around the circumference of the outer surface of the piston. The left end of the piston CC is provided with a valve seat installation surface 941 with a smaller diameter than the diameter of the piston CC.

In the embodiment shown, the control piston has CC

a longitudinal passage 964, extending throughout from the right face 942 of the piston, to the left face 965 to connect the control pressure chamber with the outlet or low pressure. The left end of the passage 964 has a constricted diameter, as at 966, to form an opening and a constricted fluid flow through the passage 964.

From the right surface 942 of the piston CC, the gate equipped element FF extends to the right and the surface 942, together with the right surface 943 of the element FF, forms the pressure surface for movement of the piston CC to the left. The outer surface 944 of the element FF has a circumferential groove 945, which is connected via a radial cross-bored passage 946 to an internal axial passage 947 which extends from a place near the end surface 94 3, through the left end 948 of the piston CC. Pressure relief grooves 953 extending in the circumferential direction with mutual axial distance are also provided

in flat 944.

A plug 950 of magnetically impermeable material extends into the left end of the passage 947 and has an axial passage 951 in communication with cross-bored passages 952, which connects the high pressure passage 910 with the passage 947, which in turn conducts high pressure to the slot 945. The plug 950

has a left-facing surface 948 which is chamfered at the outer edges to form a means that divides and diverts steady flow of fluid towards the valve seat 932 when the valve seat installation surface 941

is at a distance.

The control element GG generally has the shape of a bowl with

a bottom 955 and side walls 956 and with an internal diameter which allows it to make sliding and sealing contact with the surface 944 of the gate equipped element FF. In this design example, the control element GG is displaceably supported on the port-equipped element FF, rather than by the walls of the control pressure chamber.

The outer surface 958 of the control element GG has a smaller diameter than the diameter of the surface 920, so that there is a clearance that creates a passage for the pressure in the groove 945 to be connected to the surface 942 and the stamp CC. The bowl's walls are provided with cross-drilled openings 9 60, which connect the outside of the control element GG with the groove 945. In the embodiment shown, the openings 960 overlap the right end of the groove 945 by approx. half the diameter.

A spacer 9 62 of magnetically non-permeable material is arranged between the left end of the control element GG and the CC surface 942 of the piston.

The control element GG is biased to the left by a spring 982 which rests with its right end against the bottom of the cup for the plug 976 and with its left end rests against the bottom 984 of a bore 985 in the right end of the control element GG. A small opening 986 extends from the bottom 984, through the bottom 955 and in reality forms a vibration damper for stabilizing the movement of the control element GG in relation to the gate-equipped element FF.

When the solenoid SS is magnetized via the circuit according to fig.

4 during operation of the device, there is a weak current in the coil which creates a small amount of flux, which is insufficient to move element GG towards the spring 982 output bias. In passage 910 there is high pressure. This high pressure is led via passages 952, 951, 947, 946, tracks 945 and 960 to the right end of the piston CC. Provided that the right-facing area of the piston CC is greater than the area of the valve seat 932, the piston CC is biased to the left. At all times, there is a limited fluid flow through these passages to the control chamber and thus through the passage 964 and the opening 966 to the outlet passage 914. The fluid volume is primarily controlled by the size of the opening 966.

When the solenoid SS is magnetized more strongly, the control element GG will move to the right and limit the communication between the track 945 and the passage 960. When this happens, the pressure in the control chamber will drop as a result of the fact that the chamber continuously leaks to the outlet through the opening 966, and when the pressure forces towards left on the piston CC becomes less than the pressure forces of the high pressure on the left end of the piston CC, limited by the valve seat 930, the piston CC will move to the right and thus open the valve and allow fluid flow through.

If fluid is supplied from the outlet passage 914 to the hydraulic device, pressure will develop in the passage 914. The valve will then maintain a constant pressure differential between the inlet passage 910 and the outlet passage 914. If it is desired to increase or decrease this pressure differential, the solenoid SS is either magnetized or demagnetized, which means that the control element GG is moved to the right or left and the valve seat installation surface is moved further away from or closer to the valve seat 932.

The valve seat DD and housings AA and BB consist of magnetically permeable material and the magnetizing current in the solenoid SS is sufficient to create a magnetic field around and near the valve seat mounting surface 941. This field will, near the seat 941, attract and capture any entrained magnetic particles in the confined fluid flow which enters the passage 952. When there is sufficient fluid flow

through the valve, these particles are flushed away.

In all mentioned embodiments, a housing in reality comprises two parts, namely a drive member housing with a high-pressure cavity and a control housing that limits a generally closed pressure chamber. These housings can either be made in one or separately and joined together with a pressure-tight seal. A drive member has a surface that is exposed to pressure in the control chamber and is movable in its housing against opposing forces under the influence of such pressure to positions that are, so to speak, precisely determined by a magnetically positioned or magnetically movable control element. This actuator may then move an output shaft extending from the housing, compress or release a spring associated with a fluid valve, operate a slide valve, operate a valve seat forming a continuous or separate part of the member, move the piston of a pump back and forth , or perform another operation that requires a card, e.g. less than 50.8 mm long, but strong impact in one direction.

In fig. 1, 7 and 8 where the two housings are manufactured separately and assembled together, it may be difficult to achieve exact axial alignment of the two chambers. The drive member is displaceably supported in a housing. The control member is displaceably supported in the second housing and surrounds the gate-equipped element quite closely. If alignment problems arise, you can use the method for attaching the door-equipped element and its drive element which is illustrated in fig. 5 and 6.

Electromagnetically controlled needle valves are already known. However, due to the hydraulic forces on the valve fittings, large amounts of electrical power are required to control the flow so that even small amounts of fluid, in a known device e.g. 12 watts for a maximum of 1.8927 l/min at 210,921 kp/cm 2, a ratio of 6.34 w/l. Moreover, such valves are either fully open or fully closed.

In addition, the maximum flow rate is so small that the valve can normally only be used to control a pressure-operated main valve, which then takes care of the larger fluid volumes required by the fluid-driven devices to be controlled. In the present invention, it is assumed that the valve can control sufficiently large flow volumes and that the flow can be used directly to operate the fluid-driven device without an intermediate valve.

It is assumed that the present invention requires a maximum of 6 watts for variable control of over 113,560 l/min,

(a ratio of less than about 0.05 watt/liter), with an infinitely variable scale from 40.967 cm 2 /min. to a maximum of more than 113,560 l/min.

As a trigger or servo motor, it is assumed that the device using 210.921 kp/cm 2 and a driver with a diameter of 50.8 mm can easily control in excess of 4082.328 kg of force at 6 watts, a ratio of 680.124 kg/watt. When using larger diameters, even larger ratios can be expected.

When using the trigger devices according to fig. 1 and 5, it is further possible to make the drive member (or piston) move back and forth by continuously changing the magnetic force on the control element C, respectively C. This can be done by oscillation of the potentiometer control arm(s) or oscillation of a permanent magnet that surrounds the control chamber or by switching the current on and off to the solenoid in fig. 1, or by connecting the current from one solenoid to the other in fig. 5.

The back and forth movement of the piston can be used to operate a piston pump.

Alternatively and as a pressure amplifier, the device can be used without the passage 71. High pressure can communicate with the passage 70 in another known way and chamber 16 can be provided with an inlet port which is connected to high pressure via a non-return valve and an outlet port which, via a non-return valve, is connected to a device that requires enhanced pressures above high pressures.

Magnetic means are preferred for controlling the position of the control element in the control chamber. Such a device is simple, requires little electrical power and can easily be controlled remotely using simple electrical wiring and electrical control. If permanent magnets are used outside the house, the control element should preferably be a permanent magnet and

Claims (31)

the housing surrounding the element must consist of a magnetically non-permeable material, such as austenitic stainless steel. Alternatively, it is assumed that the control element in the form of a sleeve which surrounds an element with ports, where one of the passages to the control pressure chamber is arranged, is a new and useful device. There is patentable novelty in the combination of a sleeve-shaped control element that surrounds a gate-equipped rod and other known mechanical setting means such as a push/pull means, a rack and pinion arrangement, where the rack and pinion is mechanically connected to the control element and the pinion is turned by a shaft extending through the housing of the control pressure chamber, or the housing of the control pressure chamber can be rotated relative to the drive member housing with threads that are movable with the housing and in engagement with threads that are assigned to the sleeve control element. The invention is described in detail in connection with preferred embodiments. Modifications and changes will appear obvious to professionals on the basis of this description, and such modifications and changes fall within the scope of the invention provided they fall within the scope of the following claims. Patent claims. 1. Magnetically controlled fluid pressure device which in combination includes: (a) a housing comprising an actuator housing with a cavity at high pressure and a control housing confining a control pressure chamber, (b) an actuator which has a surface exposed to pressure in the pressure chamber and is movable in the housing of the actuator, (c) separate inlet and outlet passages connecting both high pressure and low pressure to the control pressure chamber, (d) a control element which is fully occupied in the control chamber and is movable in relation to at least one of the said passages for opening or closing the communication of that passage and the chamber to the communication of the other passage and the chamber, characterized in that (e) said at least one of the passages is movable together with said body, (f) the control member is made of a material that can be moved to controlled positions in the control chamber by means of a magnetic field and (g) controllable magnetic means for positioning the control element in the control pressure chamber. 2. Device as specified in claim 1, characterized in that it includes means for exerting a force on the drive member, which is oppositely directed in relation to the force of the control chamber pressure. 3. Device as specified in claims 1 and 2, characterized in that the member comprises an opposing surface on the drive member with a smaller area than the control pressure surface and exposed to high pressure in said cavity. 4. Device as stated in claims 1-3, characterized in that the area of the drive member which is exposed to high pressure in the cavity constitutes half of the area of the drive member which is exposed to the pressure in the control pressure chamber. 5. Device as specified in claims 1-4, characterized in that the drive means includes a shaft that extends out of the housing. 6. Device as specified in claims 1-4, characterized in that the drive means includes the coil for a coil valve. 7. Device as stated in claims 1-4, characterized in that the drive means includes a valve seat installation surface. 8. Device as specified in claims 1-4, characterized in that the drive means varies the compression of a spring in a spring pressure controlled valve. 9. Device as specified in claims 1-4, characterized in that the drive member is operationally assigned to a valve seat installation surface. 10. Device as specified in claims 1-9, characterized in that the drive element comprises an element that extends into the control pressure chamber, one of the passages has a port in a side surface of said element and that said control element is a sleeve that surrounds the element and is movable in relation to that. 11. Device as stated in claims 1-10, characterized in that the outlet passage has the form of a plurality of sharp-edged openings formed by a plurality of circumferential grooves that are cut by a longitudinal groove in the surface of the drive member, where the drive member is movable in sliding, sealing contact against surfaces in the drive body housing. 12. Device as specified in claims 1-11, characterized in that the drive means comprises a cylindrical element that extends into the control chamber, and that one of the passages has a port in one side of said element towards said chamber, where the port has the shape of a cylindrical groove. 13. Device as stated in claims 1-11, characterized in that the drive element comprises a cylindrical element that extends into the control chamber and that one of the passages has an outlet port in one side of said element, where the control element has the shape of a sleeve that has a groove in its inner surface, adapted for communication with said port and passage connecting the control element's groove with the pressure chamber. 14. Device as set forth in claims 1-11, characterized in that the drive member comprises a cylindrical member that extends into the control pressure chamber, that the inlet and outlet passages have ports at an axial distance from each other on the side of the element, that the control element has the shape of a sleeve with a inner surface which at least has a close distance relationship to the surface of the port-equipped element, that the inner surface of the sleeve has a circumferential groove with side walls at a certain mutual distance which is approximately equal to the distance between adjacent side walls of said inlet and outlet ports. 15. Device as set forth in claims 1-14, characterized in that the drive member comprises an element that extends into the control pressure chamber, and that at least one of the passages extends from near one end of said element, through the drive member. 16. Device as stated in claims 1-15, characterized in that the controllable magnetic body comprises a solenoid which surrounds the control pressure chamber and that a spring biases the control element towards a fixed position in the chamber. 17. Device as stated in claims 1-16, characterized in that the drive element comprises an element that extends into the control chamber, that at least one of the passages has a gate in a side surface of said element and that the control element surrounds the gate-equipped element, that there is means comprising a spring at each end of the control element which biases the control element towards a central position in the chamber. 18. Device as set forth in claim 17, characterized in that it comprises stoppers that have a somewhat greater mutual distance than the length of the control element, that said biasing means engages with the stoppers to keep them at a distance from the end of the control element, and that the controllable magnetic means comprise a pair of solenoid coils which are located axially in line with each other, and which surround the control pressure chamber, while the coils are symmetrically arranged in relation to the center position of the control element. 19. Device as stated in claims 1-18, characterized in that the control element has the shape of a sleeve of magnetically permeable material and has an external coating of a magnetically non-permeable material. 20. Device as stated in claims 1-19, characterized in that the control element is displaceably supported in the control chamber and has a fixed clearance to it, and that the magnetically non-permeable coating has a thickness of at least twice the size of the fixed clearance. 21. Device as set forth in claims 1-20, characterized in that the drive means includes a valve seat installation surface and the controllable magnetic means include a solenoid coil, as well as means that surround the solenoid coil and prevent the radiation of heat from it, as well as means that conduct the heat from the fluid that is affected by the valve to the coil, where the heat conducted from the fluid is significantly greater than the heat generated by the magnetizing currents in the solenoid coil, and that the drive means comprises a valve seat installation surface having a conical concave tapering portion that increases in a direction away from the valve seat. 22. Device as specified in claims 1-21, characterized in that it comprises a valve seat in the cavity, where the drive means comprises a tapered valve seat installation surface that extends past the valve seat, that the inlet passage extends through the part of the valve seat installation surface that extends past the valve seat, and that the valve seat consists of a magnetically permeable material. 23. Device as specified in claims 1-21, characterized in that the valve seat surrounds a generally closed recess and that parts of the valve seat installation surface extend into said recess, and that passages in the wall of the recess connect the cavity with the inside of the bowl near the valve seat. 24. Device as stated in claims 1-21, incorporated in a directional valve for fluid flow, characterized in that it comprises (a) a housing with an elongated, generally closed cylindrical chamber, (b) a portion of reduced diameter at one end of said chamber, (c) a control piston which is displaceable in the chamber near the opposite end and forms a control pressure chamber, (d) high pressure and inlet/outlet ports and a low pressure port communicating with said chamber between the control piston and the reduced diameter end; (e) a valve spool in the chamber, movable to selectively connect the inlet port with one of the other inlet/outlet ports and the other low pressure inlet/outlet port, (f) a pressure piston associated with and displaceable in sealed relation to the walls of the reduced diameter chamber; (g) an operational mapping of the control piston with the spool, (h) a ported element associated with the control piston and extending into the control pressure chamber and having at least one radially opening port, (i) passages in the coil, the pressure piston and the control piston and the port equipped element for connection of inlet pressure with said port, (j) an outlet passage connecting the control pressure chamber with the low pressure; (k) a control element in the control pressure chamber which is movable in relation to said port to limit the communication between the inlet passage and the control chamber in relation to the communication between the outlet passage and the control chamber, and (1) magnetic means for moving the control element to fixed positions in the chamber. 25. Device as stated in claims 1-21 in the form of a fluid pressure release, characterized in that it comprises in combination a housing with a generally closed, elongated, cylindrical chamber, where one end of the chamber has a smaller diameter than the diameter of a nearby part, a differential area piston having a high-pressure part displaceable in the small-diameter chamber to form a high-pressure chamber and a larger-diameter part displaceable in the larger-diameter chamber part, dividing the latter part into a low-pressure chamber near the high-pressure piston, and a control pressure chamber on the side of the differential area piston remote from the small diameter chamber, a member provided with ports extending from the control piston into the control pressure chamber, an inlet passage connecting the high pressure chamber to a side surface of the ported member, an outlet passage connecting the control pressure chamber to low pressure, a control element which is movable in the chamber and surrounds the port equipped element and can be moved relative to the gated element to limit the communication between one of said passages and the chamber relative to the other passage's communication, wherein the control element at least partially consists of a magnetically permeable material, and a solenoid coil that surrounds the control pressure chamber and by magnetization can move the control element to fixed positions in the chamber. 26. Device as specified in claims 1-21 in the form of an electrically controlled cartridge valve, characterized in that it comprises in combination an elongated housing with a generally elongated, cylindrical chamber in the housing, closed at one end, external threads on the housing in the middle its length for screwing into a fluid line, a valve seat forming member surrounding the chamber at the open end, sealing means on the outer surface of the housing near the valve seat, an outlet port in the housing between the valve seat and the threads, a valve piston displaceable in the chamber and having a valve seat fitting surface adapted to for abutment against the valve seat, wherein the diameter of the piston is greater than the diameter of the valve seat, wherein the piston divides the chamber into a control pressure chamber near the closed end and a low pressure chamber near the outlet port, a ported member extending from the piston into the control pressure chamber, a port in the surface of the gate equipped element, a passage connecting the gate with the valve seat installation surface, so that high pressure k munitions with the gate, a narrowed passage adjacent to the piston connecting the control pressure chamber with the low pressure chamber, and a control element which is displaceable in said chamber and can be moved to limit said gate, springs which bias the control element to a specific position in the chamber, where the control element in the the smallest part consists of magnetically permeable material and magnetic means outside the housing for movement of the control element against the spring bias to fixed positions in the control pressure chamber. 27. Device as set forth in claims 1-21, which operates a pressure relief valve, characterized in that it comprises a housing with a pressure chamber which is closed at one end, a high pressure inlet port which is surrounded by a valve seat of a fixed diameter at the other end , and a low pressure outlet port near the valve seat, a valve body movable within the chamber and having a valve seat contact surface at one end, a spring operatively associated with the valve body to bias the valve seat contact surface into contact with the valve seat, a drive member which is movable in and divides the chamber into a control pressure chamber and a low pressure chamber" with a pressure surface at one end which is exposed to the pressures of a control chamber at the other end of the housing, a second surface of smaller area which is exposed to pressure in the inlet port and a third surface which is exposed to low pressure, where the actuator cooperates with the spring when it is moved as a result of pressure in the control chamber to change the bias of said spring on the valve body, a first passage in the actuator connecting inlet pressure to the control chamber, a second passage connecting the low pressure control chamber and a magnetically actuated member movable to fixed positions in the housing and operable to restrict the connection from one passage to the control chamber relative to the other when the actuating member is moved relative thereto by pressure in its pressure chamber and thus controls the preload of the spring. 28. Valve as specified in claim 27, characterized in that the piston of the valve body is displaceable in the actuator cylinder with a smaller area than the area of the valve seat, and a groove in the outer surface and an O-ring in the groove which has a sealing contact against a surface of the cylinder. 29. Valve as specified in claim 27, characterized in that the valve seat installation surface is exposed to inlet pressure, that the valve seat has a cone shape and that the valve seat installation surface is curved and at the other end, where the arc radius of the curved surface and the angle of expansion of the cone are such that the diameter of the two surfaces' contact line is larger than the diameter of the valve body's pressure surface. 30. Valve as specified in claims 27-29, characterized in that the cavity is located at one end of the housing and is surrounded by a valve seat with a fixed diameter, that the outlet port is adjacent to the valve seat and extends through a side wall of the housing, that the valve body piston is movable in the cylinder and has a pressure surface exposed to inlet pressure, that an O-ring seal is arranged between the opposite surfaces of the valve body piston and the cylinder, that the piston pressure surface and the O-ring have a smaller diameter than the diameter of the valve seat and that the pressure spring is a pressure spring that biases the valve seat contact surface to contact the valve seat. 31. Device as stated in claims 1-21 which controls a fluid flow control valve, characterized in that it comprises a housing with a pressure chamber in the housing, a first port on the axis of the chamber, a valve seat of fixed diameter, which surrounds the port, a second port up to the first port, a valve piston which is movable in the chamber and can be driven to move a valve seat installation surface to and from contact with the valve seat, that the piston has a pressure surface which is exposed to an opposite end of the chamber, that the pressures at this end bias the valve piston in direction of closed valve position, a first passage adjacent to the valve piston and movable with the valve piston to connect high pressure fluid with the pressure chamber, a second passage connecting the pressure chamber with low pressure, a magnetically sensitive member in the housing which is movable by means of an external magnetic field to fixed positions in the housing, and which can be operated to limit the connection of one passage in relation to the other passage, when the piston is moved relative to it due to the pressure against the pressure surface of the piston.