DE29713293U1 - Solenoid operated drain valve - Google Patents

Description

GRÜNEECKER,

LAW FIRM

LAW FIRM MAXIMILIANSTRASSE 58 D-80538 MUNICH GERMANY

Applicant:

HEILMEIER & WElNLEin FABRIK F. OEL-HYDRAULIK GMBH & CO. KG STREITFELDSTRASSE 25
81673 MUNICH

LAWYERS

DR. HERMANN SCHWANHÄUSSER
DR. HELMUT EICHMANN
GERHARD BARTH
DR. ULRICH 8LUMENRÖDER, LL M.
CHRISTA NIKLAS-FALTER

YOUR REF.

OUR REF.

G 3678-25/Sü PATENT ATTORNEYS

EUROPEAN PATENT ATTORNEYS

AUGUST GRÜNEECKER

DR. HERMANN KINKELDEY

DR. WILFRIED STOCKMAIR (-1996)

DR. KLAUS SCHUMANN

PETER H, JACOB

DR. GUNTER BEZOLD

WOLFHARD MEISTER

HANS HILGERS

DR. HENNING MEYER-PLATH

ANNELIE EHNOLD

THOMAS SCHUSTER

DR. WALTER LANGHOFF

DR. KLARA GOLDBACH

MARTIN AUFENANGER

GOTTFRIED KLITSCH

DR. HEIKE VOGELSANG-WENKE

REINHARD KNAUER

DIETMAR KUHL

DR. FRANZ-JOSEF ZIMMER

BETTINA K. REICHELT

DR. ANTON K. PFAU

DATE

16.07.97

Solenoid operated drain valve

TEL 089 / 21 23 SO · FAX (GR 4) 089 / 21 86 92 93 · FAX (GR 3) 089 / 22 02 87 · http://www.grunecker.de ■ e-mail: postmaster@grunecker.de ■ TELEX 529 380 MONA D MAXIMILIANSTRASSE 58 ■ D-80538 MUNICH DEUTSCHE BANK MUNICH, NO. 17 51734, BLZ 700 700 10

Solenoid operated drain valve

The invention relates to a solenoid-operated drain valve according to the preamble of claim 1.

From data sheet D 7490/1 from Heilmeier & Weinlein, March 1996, solenoid seat valves of the types EM 11 to 31 are known, which are leak-free in the closed position. These drain valves are inexpensive and reliable, but as pure black/white valves they are not able to generate a noticeable ramp function, i.e. to regulate the flow rate depending on the stroke and independent of the pressure. A ramp function is required in particular in lifting modules for forklift trucks, which is achieved with considerable effort when using these known drain valves, for example electronically, in order to avoid the need for an expensive and complex two-way flow regulator that is not leak-proof.

In order to achieve a ramp function with this inexpensive and compact seat valve type without any significant change in the design principle, it is known from DE-U-29 61 7922 to design the spring provided between the pilot valve and the magnet as a hard spring with a steep characteristic curve, to provide a stroke-dependent quantity adjustment device between the seat closing element and the main valve seat, and to modify the pilot valve. With these structural measures, a ramp function can be achieved hydraulically because, among other things, the seat valve then responds much more slowly than the black/white seat valve mentioned at the beginning, and because the quantity adjustment device is specifically used for the ramp function. However, the ramp function is not independent of the load pressure.

From DE-A-42 39 321 it is known to design a drain valve in a lifting module for forklift trucks as a two-way flow regulator in order to be able to run a ramp function independent of the load pressure. However, this involves a high level of hydraulic components, which is not justifiable for simple forklift trucks, and has the disadvantage that the lifting module is only "tight against the forklift truck" in the closed position, i.e. leakage oil can flow out to a small but undesirable extent.

The invention is based on the object of improving a structurally simple, small-sized solenoid-operated drain valve of the design known from DE-U-29 61 7922 in such a way that the ramp function is independent of the load pressure.

The stated object is achieved according to the invention with the features of claim 1.

The structurally simple combination of the drain valve based on a black/white valve with the pressure compensator leads to the desired pressure independence, so that a real two-way flow regulator is created that is small and inexpensive. The seat valve function provided in the pressure compensator, in combination with the seat valve function in the main valve and the pilot valve, ensures that the drain valve is absolutely leak-free in the closed position of the main valve. This is because the load pressure is already shut off in the main valve and the pilot valve without leaking oil, and additionally also in the pressure compensator, which is rendered inoperative by the seat valve function, in which the load pressure is used during normal control play to carry out the quantity adjustment "independently of pressure". The seat valve function is then eliminated during the control play of the pressure compensator, but this is irrelevant in this operating state. In a forklift truck, the drain valve has the advantage of being able to control the ramp function independently of the load pressure, either with a proportional magnet or even with a conventional magnet whose characteristic curve is adapted to the hard spring characteristic curve. In the closed position of the drain valve S, the load pressure is supported without leakage, so that even during a long break in operation, a lifted load or a component of the forklift truck under load is held. The trick used in accordance with DE-U-29 61 7922 of making a black/white drain valve have a ramp function by using a hard spring and a special design of the main valve is profitably supplemented by the pressure compensator in order to become independent of the load pressure in the ramp function or quantity control, and to prevent leakage in the pressure compensator in the closed position through the seat valve function. This can be achieved with little structural effort and simple components, leads to a small size and avoids, for example, the otherwise

required control engineering and electronic effort to generate the ramp function.

The pressure compensator according to claim 2 is expediently arranged downstream of the main valve seat.

According to claim 3, only a modification that only has an insignificant effect on the black/white valve concept is required to integrate the pressure compensator. The pressure set downstream of the main valve is tapped off on one side of the pressure compensator, while the load pressure is brought to the other side of the pressure compensator, where the seat valve function is also provided, which is used by the load pressure to shut off without leaking oil. The drain valve can be accommodated in the same installation space as a conventional black/white drain valve.

According to claim 4, the orifice piston is designed as a slide part with an integrated conical sealing surface, which is simple to manufacture.

According to claim 5, the orifice piston works with its control end in a slide-tight manner with the discharge opening except for a throttle opening or a control notch. The throttle opening or the control notch ensures, among other things, the proper closing of the main valve and can be used for quantity control.

According to claim 6, the impact surfaces on both sides of the orifice piston are the same size.

According to claim 7, a positive overlap is present in the shut-off position of the piston, but this only needs to be slide-tight.

In a structurally simple manner, the piston is arranged in direct extension of the main valve seat according to claim 8.

According to claim 9, the sleeve intended for the main valve seat is extended in order to provide the bore for the piston and the valve seat for the additional

sealing function. The connecting channel that brings the load pressure to the pressure compensator can be provided in the sleeve. However, it is also conceivable to guide the load pressure into the pressure compensator in another way.

According to claim 10, the sleeve also contains the main valve seat and the throttle, via which the pilot valve controls the opening and closing movements of the main valve. This throttle is expediently smaller than or at most as large as the passage of the pilot valve, whereby the passage of the pilot valve should expediently have at most the size of a bore with a diameter of 0.6 mm.

According to claims 11 and 12, the spring of the piston of the pressure compensator can alternatively surround the outside of the piston or be housed inside the piston, in the latter case to reduce the size.

According to claim 13, the pilot valve is also leak-tight (seat valve), where the spring is a hard spring with a steep characteristic curve in order to achieve the ramp function with appropriate tuning of the magnet.

It is further expedient according to claim 14 to design the main valve with a quantity adjustment device which makes the black/white valve similar to a control valve which works with the pressure compensator independently of the load pressure.

As is usual with such drain valves in black/white design, a connection is selected according to claims 15 or 16 in which the main valve is either closed or open when the magnet is de-energized. In the closed position of the main valve, leak-free tightness is guaranteed.

Embodiments of the subject matter of the invention are explained using the drawing. They show:

Fig. 1 shows a longitudinal section through a drain valve which provides a leak-free seal when the magnet is de-energized,

Fig. 2 shows another embodiment of a drain valve which, when the power is off,

Magnets seal off corners,

Fig. 3 shows a further embodiment of a drain valve in a longitudinal section, where the drain valve is freely passable when the magnet is de-energized and is only leak-tight in the closed position,

Fig. 4 + 5 schematic block diagrams of the embodiments of the drain valve of Fig. 1 and 3, and

Fig. 6 is a diagram (current or pressure versus quantity) showing the response behavior of the drain valve.

A drain valve A in Fig. 1 is designed as a two-way flow regulator Z and has a main valve H designed as a seat valve between a line 2, which carries the pressure P to be controlled or a quantity to be regulated, and a drain line 3 leading to a tank. In a housing 4 designed as a screw-in insert, a magnet M, expediently a proportional magnet or a simple switching magnet with a modified characteristic curve, is arranged for a pilot valve V arranged in the main valve H, with which the main valve H is actuated. Furthermore, a pressure compensator W is provided, expediently downstream of the main valve H.

The magnet M contains a stationary part 6 and a magnet armature 7 that can be moved upwards when a magnetic coil 8 is energized. A hard spring 9 with a steep characteristic curve supported on part 6 acts on a tappet 10, the end of which, for example, is conical and forms a closing element 11 for the pilot valve V and works together with a valve seat of a passage 14 in a seat closing element 13 of the main valve H. The pilot valve V is a seat valve that is leak-tight in its closed position. The pilot valve V monitors the connection between a control chamber 12 that can be pressurized with a control pressure and the discharge line 3. A throttle D is provided between the control chamber 12 and the line 2. The seat closing element 13 of the main valve H has a

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conical or spherical sealing surface 15, which cooperates with a main valve seat 17, which, like the throttle D, is arranged in a sleeve 5 inserted into the line 3. The sleeve 5 is screwed to the housing 4.

The area of action of the seat closing element 13 in the control chamber 12 is larger than the cross-section of the main valve seat 17 of the main valve H. Downstream of the main valve seat 17, a bore section 18 is provided, which forms a quantity adjustment device with an annular flange 16 of the seat closing element 13. The ring flange 16 is provided in connection with the sealing surface 15 of the seat closing element 13, such that when the main valve H is closed, the annular flange 16 dips into the bore section 18. In the closed position, the main valve H is leak-tight.

The bore section 18 is extended in Fig. 1 by a bore 19, from which lateral outflow openings 20 (in the form of orifice slots or orifice bores) lead to line 3. A piston K of the pressure compensator B is guided in the bore 19 in the type of a slide valve. This has a control end 21 facing the main valve H and a conical or spherical sealing surface 23 facing away from the main valve H, which interacts with a seat 22 in the sleeve 5 with a seat valve function (leak-free tight) when the piston K of the pressure compensator W is in the shut-off position shown in Fig. 1, in which its control end 21 interacts with the outflow openings 20, e.g. with a positive overlap U, and shuts them off. The seat valve function of the piston K of the pressure compensator W is indicated with S. A lower end 24 of the piston K is located in a chamber 28, which is connected to the line 2 via a channel 27. The end 24 is urged downwards by a spring 25 in Fig. 1, whereby the spring 25 is supported in the sleeve 5. The spring 25 surrounds the piston K on the outside.

A weak closing spring 29 for the seat closing element 13 can be provided in the control chamber 12. A control notch or bevel F can be provided at the control end 21, which leaves a predetermined, small outflow cross-section to the outflow opening 20 open even in the shut-off position of the piston K.

Since the spring 9 in the pilot valve V is closed when the magnet M is de-energized and the area of action of the seat closing element 13 in the control chamber 12 is larger than the cross-sectional area of the main valve seat 17, the main valve H is kept closed when the magnet is de-energized. Since the pilot valve V and the main valve H are leak-tight in their closing positions, the piston K of the pressure compensator W is also held in its shut-off position and the sealing surface 23 rests on the seat 22, so that the pressure medium in the chamber 28 is also shut off leak-tight. In the closed position (in Fig. 1 with the magnet de-energized), the drain valve is thus leak-tight.

If the coil 8 of the magnet M is supplied with current of a certain current intensity, then the magnet armature 7 pulls the tappet 10 upwards against the force of the spring 9. The pilot valve V is opened. The control pressure in the control chamber 12 changes in a predetermined manner via the passage 14. The pressure in the line 2 lifts the seat closing element 13 from the main valve seat H when the control pressure drops accordingly, whereby due to a slow response behavior and the quantity adjustment device in the main valve H, the pressure P in the line 2 is not suddenly relieved, but with a predetermined ramp function. However, the quantity would vary without the pressure compensator W depending on the level of the pressure P. However, in order to achieve pressure-independent control, the piston K of the pressure compensator works in a pressure-compensating and orifice-like manner with the outflow openings 20, whereby it gives up its shut-off position as soon as the pressure downstream of the main valve seat has increased to a value that corresponds to the pressure P prevailing in the chamber 28 less the force of the spring 25. Thanks to the pressure compensator W, the quantity is then regulated independently of the pressure, whereby the seat valve function S between the sealing surface 23 and the sealing seat 22 is cancelled out when the piston K controls the play. The pressure compensator keeps the pressure difference constant in accordance with the current strength. It is expedient for the spring 9 to be a hard spring with a steep characteristic curve, for the quantity adjustment device to be present in the main valve H, and for the passage 14 of the pilot valve to be relatively small, for example no larger than a bore with a diameter of 0.6 mm. The throttle D is matched to the cross-section of the passage 14 in such a way that it is at most equal in size.

If the current supply to the coil 8 is reduced again, the pilot valve V increases the control pressure in the control chamber 12 again, so that the main valve H reduces the passage by regulating the quantity, while the pressure compensator W continues to ensure that the pressure is independent.

If the current supply to the coil 8 is completely removed, the spring 9 closes the pilot valve V. The control pressure in the control chamber 12 presses the seat closing element 13 onto the main valve seat H. The pressure P in the chamber 28 pushes the piston K into its shut-off position. The pilot valve, the main valve H and the sealing surface 23 sitting on the sealing seat 22 create the desired leak-free tightness. The pressure P is maintained without leakage as long as the drain valve A is in the closed position.

The drain valve A is used, for example, in a lifting module of a forklift truck (or for a tipper) in which a consumer that can be pressurized with pressure P works against a load in order to move it at a predetermined speed set by energizing the magnet M and to hold it in the closed position. The drain valve A is located in such a lifting module between the consumer's supply line and the tank (see DE-A-42 39 321) and can be used for raising and lowering control or just for lowering control. If the drain valve A is closed when the magnet M is de-energized, it can be used, for example, for lowering control in order to lower a load independently of the pressure that was previously raised, for example by controlling the supply pump. For lowering, when the consumer pump is disconnected, the speed of the lowering movement is controlled by the amount flowing out via the drain valve A, in this case independently of the prevailing pressure P.

In Fig. 2, the drain valve A with the same function as in Fig. 1 (two-way flow regulator Z) is modified with respect to the pressure compensator W compared to Fig. 1. The piston K is designed as a pot piston and the spring 25, which acts on the piston K, is arranged inside the pot piston in such a way that it is supported with its lower end on the piston K and with its upper end on a stop 32 which is on

a pin 31 is arranged, which can be moved in the piston K. The stop 32 can be supported in the bore 19 at a transition to the smaller diameter bore section 18 in the upward pressure direction. The piston K therefore has, for example, a larger contact surface than the cross-section of the main valve seat 17. Instead of the control notch F of Fig. 1, at least one throttle opening F' to the discharge opening 20 is provided in the piston K of Fig. 2. The spring chamber of the piston K is indicated by 30.

In Fig. 3, the drain valve A, which works as a two-way flow regulator and is similar in structure to the embodiment in Fig. 1, is designed so that when the magnet M is de-energized, the connection between the line 2 and the discharge line 3 is continuous. For this purpose, the stationary part 6 of the magnet M is arranged below the armature 7, which can be moved downwards. The hard spring 9 with a steep characteristic curve is supported at the bottom of part 6 and pushes the tappet 10 and thus the armature 7 upwards, so that when the magnet M is de-energized, the pilot valve V is opened and the seat closing element 13 of the main valve H is lifted off the main valve seat 17. When the main valve H is open, the piston K of the pressure compensator is moved downwards from the shut-off position shown in order to clear the flow path.

In a lifting truck, the drain valve A in Fig. 3 can be used, for example, to control the lifting and lowering. When the pump is switched on, the pressure medium flows out via the open drain valve A. As the current to the magnet M increases, the main valve H is closed and the pressure P and the quantity for the consumer are increased in accordance with the current, with the pressure compensator W ensuring that the quantity control is independent of the pressure. When the current is fully applied and the main valve H is closed, the entire available quantity is fed to the consumer. If the load is to be stopped, the supply pump is switched off and the load pressure is kept leak-free. The lowering control then takes place by reducing the current to the magnet M by regulating the quantity that flows out to the tank T, thanks to the pressure compensator W, independently of the load pressure. In Fig. 3, the spring 25 of the piston K could be arranged inside the piston as in Fig. 2. In addition, the piston K is designed without a chamfer or notch.

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Fig. 4 shows a symbolic representation of the drain valve A as a two-way flow regulator in the design according to Figs. 1 and 2, i.e. closed without energizing the magnet M. The pilot valve V is not shown in Fig. 4 for the sake of simplicity. Thanks to the seat valve function in the main valve H and the seat valve function S of the pressure compensator A in the shut-off position of the piston K, the pressure P is kept leak-free tight, although the pressure compensator W only needs to be slide-tight.

In Fig. 5, the drain valve A is symbolically shown as a two-way flow regulator Z corresponding to the embodiment of Fig. 3, i.e., open without current. The seat valve function in the main valve H is then not present, as is the seat valve function S of the pressure compensator P (the sealing surface 23 is lifted off the seat 22). On the other hand, when the magnet M is fully energized, there is leak-free tightness in the main valve H and in the pressure compensator W, since the main valve H seals off the pressure without leakage and the seat valve function S of the pressure compensator W also comes into play.

Fig. 6 shows a diagram of the current intensity I over the quantity Q with the solid curve P, which shows how the quantity Q is regulated independently of the pressure P only by the current intensity i, namely either the quantity that flows to the consumer or the quantity that flows out of the consumer. The dashed curves P ¹ and P" indicate how the drain valve A could only adjust the quantity Q depending on the pressure without the pressure compensator directly assigned to the main valve and arranged downstream of the main valve. This means that for a certain current intensity 1, the quantity Q would be smaller at a lower pressure P ¹ than at the same current intensity I and higher pressure P", and also that different speeds would occur despite the same current intensity. The solid curve P, on the other hand, shows that the quantity Q and thus the speed of the consumer is adjusted independently of the pressure with the current intensity 1.

In essence, a leak-proof black/white valve concept with minor modifications and a pressure compensator with seat valve function is used to create a fully functional two-way flow regulator that is cost-effective and compact.

Claims (16)

l sayings 1. Solenoid-operated drain valve (A) between a load pressure connection (P) and a drain connection (T) ₁ , in particular for a lifting module of a forklift truck, with a seat closing element (13) assigned to a main valve seat (17), which can be acted upon in the closing direction by a variable difference between the drain pressure and a control pressure derived from the load pressure, and with a pilot valve (V) for the control pressure that can be actuated by the magnet (M), characterized in that the main valve (H) formed by the main valve seat (17) and the seat closing element (13) is assigned a pressure compensator (W) with a seat valve sealing function (S), which forms a load pressure-independent two-way flow regulator (Z) with the main valve (H) which is leak-tight under the load pressure and in the closed position of the main valve. 2. Solenoid-operated drain valve according to claim 1, characterized in that the pressure compensator (W) is arranged downstream of the main valve seat (17). 3. Solenoid-operated drain valve according to at least one of claims 1 or 2, characterized in that a piston (K) is provided in the pressure compensator (W), which can be displaced in a slide-like manner in a bore (19) from a blocking position closing at least one lateral discharge opening (20) to the drain connection (T) until the discharge opening (20) is released and is acted upon in the direction of the blocking position by the load pressure (P) ₁ in the opposite direction by a spring (25) and a pressure downstream of the main valve seat (17) and the pilot valve (V), and that the piston (K) has a sealing surface (23) for securing the load pressure in the blocking position, which can be placed on a stationary auxiliary valve seat (22). 4. Solenoid-operated drain valve according to claim 3, characterized in that the piston (K) has a slide part with a control end (21) and no conical sealing surface (23). 5. Solenoid-operated drain valve according to claim 4, characterized in that the piston (K) has at least one throttle opening (F ¹ ) or one control notch (F ¹ ) which, in the shut-off position, forms a throttled connection from the pilot valve (V) to the discharge opening (20). 6. Solenoid-operated drain valve according to claim 4, characterized in that the two-sided loading surfaces of the piston (K) for the load pressure (P) and the pressure downstream of the main valve (H) are of equal size. 7. Solenoid operated drain valve according to claim 4, characterized in that the piston (K) in the shut-off position covers the discharge opening (20) with positive overlap (U). 8. Solenoid-operated drain valve according to claim 4, characterized in that the piston (K) is arranged in direct reduction of the main valve seat (17) and with its control end (21) points towards the main valve seat (17). 9. Solenoid-operated drain valve according to at least one of claims 4 to 8, characterized in that the bore (19) for the piston (K) is formed in a sleeve (5) in which the outflow opening (20), a pressure chamber (28) delimited by the piston (K), a connecting channel (27) from the load pressure connection (2) to the pressure chamber (28) and the auxiliary valve seat (22) between the pressure chamber (28) and the bore (19) are arranged. 10. Solenoid-operated drain valve according to claim 9, characterized in that a throttle (D) is provided in the sleeve (5) of the main valve seat (17) and is operatively arranged between the load pressure connection (2) and the pilot valve (V). 11. Solenoid-operated drain valve according to claim 3, characterized in that the spring (25) of the piston (K) is arranged in the pressure chamber (28) between an abutment in the sleeve (5) and a stop on the piston (K) and surrounds the piston (K) on the outside. 12. Solenoid-operated drain valve according to claim 3, characterized in that the spring (25) of the piston (K) is arranged inside the piston (K) between a stop of the piston and an abutment (32) supported on the sleeve (5). 13. Solenoid operated drain valve according to claim 1, characterized in that the pilot valve (V) is a seat valve with a closing element (10) adjustable by the magnet (M) against the force of a spring (9) and a passage (14) in the seat-closing element (13), and that the spring (9) is a hard spring with a steep characteristic curve. 14. Solenoid-operated drain valve according to at least one of the preceding claims, characterized in that the seat closing element (13) is formed at its end projecting through the main valve seat (17) in the closed position with an annular flange (16) which forms a stroke-dependent quantity adjustment device with a bore section (18) downstream of the main valve seat (17). 15. Solenoid-operated drain valve according to at least one of the preceding claims, characterized in that the seat closing element (13) closes the main valve seat (17) under the force of the spring (9) when the magnet (M) is de-energized, and that the piston (K) is held in the blocking position by the load pressure. 16. Solenoid-operated drain valve according to at least one of claims 1 to 14, characterized in that the seat-closing element (13) is de-energized when the magnet (M) is lifted from the main valve seat (17) by the spring (9), and that the piston (K) is moved out of the locking position by the spring (25).