US3489063A - Electrical control device for a hydraulic circuit - Google Patents

Description

J. PIRET 3,489,063

ELECTRICAL CONTROL DEVICE FOR A HYDRAULIC CIRCUIT Jan. 13, 1970 Filed NOV; 24, 1967 Q1 \B oo llo Fm w Illa F United States Patent 5 05 Int. Cl. F01] 25/08:- Fb 13/16, 13/04 US. Cl. 91275 4 Claims ABSTRACT OF THE DISCLOSURE A device for controlling a hydraulic circuit which comprises a source of pressurized fluid, a pressure regulator controlling the maximum pressure of the source of pressurized fluid, a cylinder having a double-acting reciproeating piston, a distributor selectively connecting the source of pressurized fluid to the cylinder and a return conduit, a pair of electromagnets mounted at each end of the distributor, control circuit means for the electromagnets including a pair of end of travel switches and a change of direction switch, the end of travel switches and the change of direction switch being controlled by the piston, a second pair of switches each of which has at least two sets of contacts, the second pair of switches being operated by the movement of the corresponding electromagnet by the intermediary of a mechanical transmission cooperating with the distributor, one of each of the two sets of contacts of the second pair of switches is placed in the supply circuit of each of the electromagnets so that only one of the electromagnets can be energized at a time.

The present invention relates to an electric control device for hydraulically controlling a double-acting piston, and particularly to devices of this type in which the hydraulic piston is actuated by a fluid which controls a machine-tool.

It is well known that in order to achieve the alternating displacement of a mechanical element such as a tool holder, a pressure plate, or a mechanical shovel, a hydraulic circuit which acts alternately on the doubleacting piston of a cylinder, may be used. The piston being rigidly connected to the element to be displaced.

The simplest hydraulic circuits usually associated with double-acting cylinders having two chambers are in general constituted by a source of hydraulic fluid under pres sure such as a pump which draws fluid from a reservoir, a pressure regulator in the delivery line of the pump and a distributor mounted in the delivery line downstream of the pressure regulator and upstream of the cylinder. This distributor being adjustable into three positions so as to establish the following connections: in a first end position of the distributor, the left chamber of the cylinder is connected with the delivery conduit of the pump and the right chamber of the cylinder is connected with a reservoir return conduit; in a second or intermediate position of the distributor, the two chambers of the cylinder are connected with the delivery conduit and the reservoir return conduit; and in the other end position, the right chamber of the cylinder is connected with the pump delivery conduit and the left chamber is connected with the reservoir return conduit.

An electric control for this type of a hydraulic circuit normally comprises: two electromagnets one of which is connected to each side of the distributor. These electromagnets act on the distributor in a direction opposite to each other so as to urge the distributor from the intermediate position into one of its end positions. The electric control also includes an electrical circuit for controlling these electromagnets and includes two end of travel switches and one travel reversing switch. The three switches are controlled by a cam carried by the rod of the piston mounted in the cylinder. The electric circuit further includes two relay connected to the electromagnets by a delay switch utilized to delay the excitation of the second electromagnet until after the de-excitation of the first electromagnet.

The known electrical devices are normally placed in a protective housing provided beside the machine-tool and always require connecting electric cables or wires for the different electrical elements contained in the housing. In this type of an installation the electromagnets must be provided with cables which can handle the excitation current thereof, which is much higher than the intensity of the circuit current utilized by the relays and the switches. Furthermore, the relays are usually fairly expensive which adds considerably to the cost of the installation. Also, since the excitation and de-excitation of the electromagnets is not only a function of the position of the piston in the cylinder by means of the cam and the switches at the finish of a stroke, but also of the delay switch, the operation of the device is not exact.

The present invention eliminates all of these inconveniences by providing an electrical control means for a hydraulic circuit of the type mentioned above which does away with all relays and the requirements for a separate protective housing and which controls the feeding of the electromagnets as a function of the position of the distributor.

In this way, it is possible to eliminate the relays and the large protective housing and to control the feeding of the electromagnets as a function of the position of the slide valve in the distributor, thus assuring a highly exact control of the hydraulic circuit.

These and other objects of the present invention will become more readily understood from the following description of an embodiment of the invention, given only by way of example, together with the attached drawing in which:

FIG. 1 is a schematic representation of a hydraulic operating circuit for a piston and an electrical control device for this hydraulic circuit; and

FIG. 2 is a schematic representation of an electrical control device in accordance with this invention.

Referring now to FIG. 1, there is shown a cylinder 1, for use with a machine tool sealingly carrying a piston 2 therein. A piston rod 3 is integrally formed at one end with the piston 2 and carries at its free end a earn 4. Two chambers 5 and 6 are formed on either side of the piston 2 in the cylinder 1. A principal distributor 9 is connected to chamber 5 by a conduit 7 and to chamber 6 by a conduit 8. This distributor 9 is constituted by a slide valve which is movable into three positions 9a, 9b and 9c as schematically shown in FIG. 1. In these three positions the chambers 5 and 6 of the cylinder are selectively connected to a hydraulic delivery circuit 10 of a pump P and/or a return conduit 11 which feeds fluid into a pump reservoir 12. e

In the intermediate or normal position 91), the distributor 9 connects the hydraulic delivery line 10 with the chambers 5 and 6 and the chambers 5 and 6 with the return conduit 11. In other words, the conduits 10 and 11, and the chambers 5 and 6 all communicate with each other and there is practically no pressure in all of the elements.

In the end position 9a, shown at the left in FIG. 1 of the drawing, the distributor 9 connects the hydraulic delivery conduit 10 with the chamber 5 and the return conduit 11 with the chamber 6.

In the other end position 9c, shown at the right in FIG. 1 of the drawing, the distributor 9 connects the delivery conduit 10 with the chamber 6 and the return conduit 11 with the chamber 5.

A pressure regulator 13 is mounted in parallel with the delivery conduit 10 and permits the maximum pressure in this conduit to be accurately governed.

Two springs 14 and 15 of equal force act against opposite ends of the distributor 9 to normally maintain this distributor in the intermediate position 9b.

Transmission rods 16 and 17 are attached to each end of the distributor 9 and cooperate with movable armatures 18 and 19, respectively, of a corresponding electromagnet A or B. The free ends of the armatures 18 and 19 are provided with push rods 20 and 21, respectively. The push rod 20 cooperates with one end of a hinged arm 22 which is capable of acting on a switch having two sets of contacts B and B: through the other end of the arm. The push rod 21 cooperates with a hinged arm 23 to operate the contacts A A in the same manner. That is, the double throw switch A A is operated by the movement of the armature 18 of the electromagnet A by means of a unidirectional mechanical transmission which comprises the slide valve of the distributor 9, the rod 17, the movable armature 19 of the electromagnet B, the push rod 21 and the hinged lever 23. The movable armature 18 acts an the unidirectional mechanical transmission, only when the electromagnet A is energized.

The operation of the switch containing the contacts B B is effected in an analogous manner by the movable armature 19 of the electromagnet B by means of the slide valve in the distributor 9, the rod 16, push rod 20 and hinged lever 22.

Each of a pair of switches containing the two sets of contacts A A and B B are subjected to the action of springs 24 and 25, respectively, which springs are disposed in association with the respective levers 23 and 22, in such a manner that in the intermediate position 9b of the distributor 9, the contacts A and B are closed and the contacts A and B are open. Each of the pair of switches is housed within a fluid tight housing 27, 28, respectively, mounted on the distributor 9.

The cam 4 cooperates with two end of travel switches F and P and a change of direction switch F These switches are disposed in such a manner that in the starting position of the piston 2, the cam 4 cooperates with the switch F and in the end position of the piston shown to the right in FIG. 1, this cam cooperates with the switches F and Peg.

When the control rod of the switch F is contacted by the cam 4, it is biased into the open position and when the common control rod of the switches P and P is contacted by the cam 4, the switch F is opened and the switch F is closed. The end of travel switch F is opened when the front inclined ramps portion of the cam 4 first comes in contact with its push rod, while the opened change of direction switch remains in the opened position, until the push rod arrives on the flat top portion of the cam 4.

The electrical control device is supplied from a source of alternating current (not shown) via lines and 31, and comprises two electrical units U and U each of which is, respectively, provided with an operating coil, for the electromagnets A and B.

The different switches represented in FIG. 2 are of two types. All of the switches which are found on the left hand side of an electric line taken in the direction of the arrow F are closed and the switches indicated as being to the right of this line are opened when they are not activated by their corresponding control elements.

The first electric unit U comprises the end of travel switch F connected in series with a parallel assembly containing the set of contacts A a manual starting switch Ma, and an automatic cycling switch Ca. Once operated the automatic cycling switch Ca remains in the position in which it has been placed. The parallel assembly is in turn connected in series with the contact B which is connected in series with the coil of the electromagnet A.

The second electric unit U includes a parallel assembly constituted by the change of direction switch F and the end of travel switch F connected in series with the set of contacts B The parallel assembly of unit 2 is connected in series with the set of contacts A which is in turn connected in series with the coil of the electromagnet B.

The operation of the device is as follows: as shown in FIGS. 1 and 2, the device rests in its normal or rest position with the electromagnets A and B being in an unexcited position. The piston 2 is in its extreme left position, the end of travel switch F is open, the end of travel switch P is closed, the change of direction switch P is open, the distributor 9 is in the intermediate position, the contacts A and B are closed and the contacts A and B are open.

To control the displacement of the slide valve contained in the distributor 9 and thereby displace the piston 2 from the left to the right, the starting switch Ma is closed thereby causing the excitation of the electromagnet A. The movable armature 18 moves from left to right thereby moving the distributor 9 into its end position 9a. At the same time, this movement is transmitted, by the intermediary of the rod 16 of the distributor 9 to the rod 17 and thus to the movable armature 19 of the electromagnet B, thereby moving the push rod 21 causing the lever 23 to turn on its fulcrum first opening the contacts A and, then, closing the contacts A The further excitation of the elcctromagnet is now assured by the closed contacts F A and B and the manual switch Ma may be released.

In this end position 9a of the distributor 9, the chamber 5 of the cylinder 1 is connected to the delivery conduit 10, and the chamber 6 is connected to the return conduit 11. The piston 2 is thus moved from the left towards the right under the action of the fluid entering the chamber 5. At the beginning of the movement of the piston 2, the cam 4 releases the push rod of switch F allowing the switch to move to the closed position, but this closing has no instantaneous effect on the device. When the piston 2 arrives at the extreme right position of the cylinder 1, the inclined ramp portion of the cam 4 opens the end of travel switch F thereby cutting-off the fiow of current to the electromagnet A and when the push rod reaches the top portion of the cam, the switch P is closed.

When the current supply to the electromagnet A is cutoh, the springs 14 and 15 bias the slide valve of the distributor into the intermediate position 9b in which the contacts A are closed therefore allowing the coil of the electromagnet B to be excited through the intermediary of the switch Fcg.

The excitation of the electromagnet B causes the displacement of the movable armature 19 of distributor 9 and of the movable armature 18 of electromagnet A. This movement causes the lever 22 to first open the contacts B, and then close the contacts B when the slide valve of the distributor 9 has been moved to the position 9c. In this position, the chamber 5 is connected to the return conduit 11 and the chamber 6 is connected to the delivery conduit 10.

The closing of the contact B connected in parallel with the switch F assures feeding of the coil of the electromagnet B. There is therefore no de-excitation of the electromagnet B when the piston 2 is moved from right to left and the cam 4 releases the push rod of the switch F to reopen it.

The closing of the switch F does not excite the electromagnet A since the contacts B remain open. When the piston 2 arrives at the extreme left end position in the cylinder 1, the cam 4 opens the switch F which cutsoff the flow of current to the electromagnet B and the springs 14 and 15 bias the distributor into its intermediate position 9b. In this position the contacts A and B are again closed and the contacts A and B are open.

However, the excitation of one of the electromagnets takes place only after the feeding current has been cut-off to the other electromagnet since the cut-off signal will only be observed after the slide valve of the distributor has started its movement towards the center. It is therefore impossible to provoke an accidental excitation of one of the electromagnets, The contacts A A B and B; will not supply current to an electromagnet until after a delay caused by the time required to cut olf the other electromagnet and a predetermined movement of the distributor slide valve. In this manner, these contacts control the end of one sequence of operation of the distributor before they allow the commencement of another sequence.

If, during a first reciprocating stroke of the piston 2, the automatic cycling switch Cu is closed, the feeding of the coil of the electromagnet A is automatically assured by the intermediary of the switch Ca and the contacts B which are now closed and a new cycle commences. In the opposite case, such as shown in FIG. 2, the piston 2 rests in its extreme left position.

This invention is particularly adapted to be used with switch control systems which are operated by a distributor or the movable armature of an electromagnet associated with the distributor. But, the invention also may be applied to control systems which require the operation of a pneumatic distributor having a slide valve, check valves or a rotary valve and for all other modes of distribution.

Also, the number of sets of contacts operating the electromagnets do not have to be limited to two, but, if considered desired, four or more sets of contacts may be used to assure the automatic operation of a more complex cycle.

What is claimed is:

1. A device for the electric control of a hydraulic circuit; said hydraulic circuit comprising: a source of pressurized fluid; a delivery conduit for said pressurized fluid; a distributor in said delivery conduit having a body and two ends; a cylinder having a double acting piston connected to said distributor; electrical control means for said device including: an electromagnet mounted at each end of said distributor and a control circuit for said electromagnets; said control circuit having two end of travel switches and a change of travel switch; said switches being controlled by said piston; a second pair of switches each of which contains two sets of contacts; each of said second pair of switches capable of being operated by a corresponding electromagnet through the intermediary of the distributor; one of the two sets of contacts of one of said second pair of switches being placed in a supply circuit of one of the electromagnets and the other set of contacts being placed in a supply circuit of the other electromagnet.

2. A device for controlling a hydraulic circuit as recited in claim 1 including a starting switch and a recycling switch in parallel, said switches being in the supply circuit of one of said electromagnets.

3. A device for controlling a hydraulic circuit as recited in claim 1 wherein each of said end of travel switches are in series circuit arrangement with the contact in the supply circuit of one of said electromagnets.

4. A device for controlling a hydraulic circuit as recited in claim 1, wherein each of said second pair of switches is housed within a fluid tight housing mounted on said distributor.

References Cited UNITED STATES PATENTS 2,735,405 2/1956 Hipple 91-275 2,736,296 2/1956 Romine et a1. 91-275 2,991,760 7/1961 Rhine 91--275 3,060,466 10/1962 Kozacka 91275 3,225,541 12/1965 Piret 91-275 FOREIGN PATENTS 551,765 11/ 1956 Italy.

PAUL E. MASLOUSKY, Primary Examiner US. Cl. X.R. 91361, 466

Images