GB2084702A

GB2084702A - Hydraulic control for a tracked vehicle

Info

Publication number: GB2084702A
Application number: GB8128489A
Authority: GB
Original assignee: STENIUCK FRERES
Current assignee: STENIUCK FRERES
Priority date: 1980-09-22
Filing date: 1981-09-21
Publication date: 1982-04-15
Also published as: ES8206322A1; ES505655A0; BE890437A; DE3137711A1; FR2490571A1; IT8168230A0

Abstract

The present invention relates to a hydraulic control device for driving and steering a tracked vehicle, comprising two motors (1, 2) and two hydraulic brakes each corresponding to a track. The two motors (1, 2) are connected in parallel to one and the same closed power circuit (3) which is fed, in one or other direction by a reversible pump (4). Separate gate valves (5, 6) are provided for controlling the supply of fluid to the two motors independently of one another, and the valves (5, 6) and brakes are controlled by a pilot circuit (9) including respective distributors (10, 20). <IMAGE>

Description

SPECIFICATION Hydraulic control for a tracked vehicle The object of the invention is a hydraulic control for driving and steering a tracked vehicle.

Some public works' equipment, particularly drilling machines or boring machines, is arranged on a chassis which is displaceable on tracks so as to be capable of moving over any ground.

To determine the changes of direction of a tracked vehicle, it is conventional to control the drive of the tracks at different speeds and even to stop or drive in reverse the track towards which it is intended to turn.

For this purpose, it is convenient to be able to control the drive or stopping of the drive means of the two tracks independently of one another.

Consequently, in the case where the drive of the two tracks is controlled by hydraulic means, it is customary to use two pumps, each connected to the drive means of one of the tracks by an independent circuit. This results in an increase in the complexity and cost of the hydraulic circuits and, consequently, of the machine. It is also necessary to duplicate the control and safety devices and provide a means for the mechanical coupling of the two pumps in order to ensure that the vehicle advances in a straight line.

On the other hand, in the case of drilling machines, since drilling can take place only when the vehicle is stopped, the custom has been to use one of the pumps for controlling the displacement of the vehicle to control the drive means for rotating the drill, when the vehicle has stopped. The result of this is that this pump operates for a longer time than the other pump, the only function of which is to control the drive of the other track, and it is therefore subjected to more rapid wear. In course of time, this greater wear of one of the pumps results in a tendency of the vehicle not to move in a straight line.

According to the invention there is provided a hydraulic control device for driving and steering a tracked vehicle including two motors and two hydraulic brakes each corresponding to a track, comprising, for the two motors, one and the same closed power circuit which is fed, in one or other direction, by a reversible pump and to which the two motors are connected in parallel by means of two circuit branches, and separate means for controlling the stopping of the two motors independently of one another.

Advantageously the means for controlling the stopping of the two motors comprise two hydraulically controlled gate valves which are located one on each of the circuit branches and which are at rest in a position cutting off the supply to the corresponding motor. An auxiliary pilot circuit is provided comprising two branches for controlling the opening of each of these two valves, each branch being provided with a distributor having two positions respectively for opening and closing said branch.

In a preferred embodiment, the two brakes are clamped at rest, and each branch of the pilot circuit is connected by a shunt to the corresponding brake for controlling release of the brake simultaneously with the opening of the gate valve of the motor.

In a particular embodiment, the power circuit is connected to a booster circuit fed by an auxiliary pump and the pilot circuit is shunted to the booster circuit.

The invention will now be described with referpence to an embodiment thereof, given by way of example only, with reference to the accompanying drawing of which the single Figure is a diagram of an embodiment of a hydraulic circuit according to the invention for controlling the drive motors and the rotation motor of a tracked vehicle, such as a drilling machine.

The Figure does not include illustration of the tracked vehicle, which can be of any known type, but only, diagrammatically, the two drive means or motors 1 and 2 for driving the tracks of the vehicle.

The motors 1,2 are connected in parallel to one and the same closed power circuit 3 which is fed, in one or the other direction, by a reversible variabledelivery pump 4 driven by a motor (M). The power circuit 3 is represented by solid lines in the Figure.

A gate valve, 5 and 6 respectively, is placed on each of branches 31, 32 respectively connecting the motors 1 and 2 to the power circuit 3.

As shown in the Figure, the two gate valves 5 and 6 are distributors each having an open and a closed position and which are biassed to their closed positions by, for example, a spring, to place the respective circuit 31 or 32 in a closed condition.

Depending on the direction in which the circuit 3 is fed with fluid, each gate valve is located either upstream or downstream of the corresponding motor, but in both cases, in the position of rest, the circuit is broken and the motor is stopped.

It will consequently be understood that by actuating the gate valves 5 and 6 separately, it is possible to operate one or other of the motors 1 and 2, and, as a result, to cause the vehicle to turn in one direction or the other.

On the other hand, when the valves 5 and 6 are placed in the open position, the two motors 1 and 2 are fed by the circuit at the same delivery rate and drive the vehicle in a straight line.

However, to control the change of direction of the vehicle, it may not be sufficient to cut athe supply to the corresponding motor. A brake, 7, 8 respectively, is, therefore, associated with each motor in a conventional way. The brake is, most often, a disc brake acting on the shaft connected to the motor, but has been shown only symbolically in the Figure.

The two brakes 7 and 8 are designed so that, at rest, they brake the corresponding motors 1 and 2, and they are released as a result of a positive action, in the same way as the gate valves 5 and 6 are opened.

To ensure that the release of the brake and the supply to the corresponding motor take place simultaneously, the hydraulic circuits for controlling the brake and the gate valve are shunted to two branches 91, 92 of a pilot circuit 9 shown by dot-and-dash lines in the Figure.

The supply to each of the branches 91, 92 of the pilot circuit is provided with a distributor, 10 and 20 respectively, each having two positions for opening and closing the corresponding branch.

As is shown in the Figure, in the position of rest, the two distributors 10 and 20 close the corresponding circuits 91 and 92. A positive action on one or other of the distributors causes opening of the corresponding branch of the pilot circuit and, consequently, to supply of fluid to the corresponding motor and the release of the corresponding brake.

In practice, the two distributors 10 and 20 will be controlled by the driver of the vehicle, either by hand or preferably by foot, by means of two pedals each corresponding to a track, the driver controlling by hand the delivery rate of the pump 4 and, consequently, the speed of the tracks.

In the position of rest, the distributors 10 and 20 put the corresponding circuits 91 and 92 in communication with a circuit 93 for return to the tank, so as to enable the brakes 7 and 8 to return immediately to the clamping position and the valves 5 and 6 to the closed position.

In a conventional way, the main pump 4 is associated with an auxiliary pump 40 which feeds a circuit 41 for boosting the power circuit. This booster circuit 41, also shown by dot-and-dash lines, is kept permanently under a set pressure by a valve 42, and it is therefore appropriate to shunt the pilot circuit 9 to the booster circuit 41. In fact, in this way, the pilot circuit 9 will always be under pressure, the quantity of oil needed for controlling the brakes and the gate valves being provided by a hydraulic accumulator 94.

It will be seen that the use of one and the same closed power circuit for feeding the two motors 1 and 2 makes it possible to simplify the hydraulic circuits considerably and in particular, to use a single block 33 of safety valves which is shunted to the closed circuit 3. Since this safety block can be of any known type, it has not been shown in detail in the Figure.

The pump 4, which, as described above, supplies the two drive motors 1 and 2 also, in a very simple way, feeds a rotation motor 1 1,when the vehicle is stopped. For this purpose, the two feed and return branches of the circuit 3 are provided with reversing valves 12 and 13which are controlled simultaneous- ly and which enable the pump 4 to communicate either with the two drive motors 1, 2 of the tracks or with the rotation motor 11. In the position for driving the tracks, the pump 4 is subject to a manual control of the delivery rate, with an automatic return to zero.

In this way, the driver can regulate the speed of movement of the machine. On the other hand, in the drilling position, the control of the pump is indexed, thus making it possible to maintain a delivery rate previously selected by the driver, without any other intervention by the latter.

Apart from its simplicity, the control circuit which has just been described has the advantage of great reliability.

In fact, as has been indicated, in the absence of positive controls on the distributors 10 and 20, the brakes 7 and 8 are clamped and the valves 5 and 6 are closed. The return circuit 93 permits the immediate connection of the brakes 7 and 8 to the tank and, consequently, a very rapid clamping.

In this way, in the absence of a driver or in the drilling position in which the pump communicates with the rotation motor, the machine is still blocked.

To cause it to advance, it is necessary not only to actuate the reversing valves 12 and 13, but also to activate the distributors 10 and 20. During movement, if the driver were to fall in the machine for any reason,the latter would be immediately immobilised, since the tracks would be automatically braked and the supply to their drive motors cut off.

At the same time, the delivery of the pump would cease because of the automatic return to zero of the manual control, which further adds to the safety of the machine.

Advantageously, the main pump 4 is provided with a flushing circuit 43, illustrated by dashed lines in the Figure, which permanently ensures the circulation of warm oil in the motors 1 and 2 when these are stopped. In this way, cooling of the motors is avoided when the machine is in the drilling position in which only the rotation motor 11 is fed for a period which can last for several days. Thus, the motors for driving the tracks are ready to operate without delay by means of a simple reversal of the valves 12 and 13.

The invention is not, of course, intended to be limited to the details of the circuit which has just been described; other circuits can be conceived to obtain similar results, just as it would be possible to use devices equivalent to those which have been described for controlling the drive and orientation of the vehicle.

Claims

1. A hydraulic control device for driving and steering a tracked vehicle including two motors and two hydraulic brakes each corresponding to a track, comprising, for the two motors, one and the same closed power circuit which is fed, in one or other direction, by a reversible pump and to which the two motors are connected in parallel by means of two circuit branches, and separate means for controlling the stopping of the motors independently of one another.

2. A control device according to claim 1, wherein the means for controlling the stopping of the two motors comprise two hydraulically controlled gate valves which are located one in each of the circuit branches and which are at rest in a position cutting off the supply to the corresponding motor, an auxliary pilot circuit being provided comprising two branches for controlling the opening of each of the valves, each branch being provided with a distributor having two positions respectively for opening and closing the corresponding branch of the pilot circuit.

3. A control device according to claim 2, wherein the brakes of the two tracks are clamped at rest, and each branch of the pilot circuit is connected by a shunt to the corresponding brake for controlling release of the brake simultaneously with the opening of the gate valve of the motor.

4. A control device according to either claim 2 or claim 3, wherein the power circuit is connected to a booster circuit fed by an auxiliary pump, the pilot circuit being shunted to the booster circuit.

5. A control device according to any one of claims 2 to 4, wherein the two distributors of the pilot circuit are controlled separately by the driver of the vehicie, the distributors being in their closing positions at rest.

6. A control device according to any one of claims 2 to 5, wherein the two branches of the pilot circuit are connected by means of the respective distributors, in the position of rest of the distributors, to a circuit for return to the tank.

7. A control device according to any one of the preceding claims, wherein the vehicle carries a machine driven by a motor, and the power circuit is provided upstream and downstream of the reversi ble pump with two reversing valves permitting closed-circuit supply to the motor of the machine carried by the vehicle.

8. A control device according to claim 7, including a circuit for flushing the pump, the circuit being adapted to ensure permanently a circulation of oil in the drive motors when the vehicle is stopped.

9. A control device according to any one of claims 2 to 8, including a manual control of the delivery rate of the reversible pump and two foot pedals for controlling the two distributors of the pilot circuit.

10. A hydraulic control device for a tracked vehicle substantially as herein described with reference to the accompanying drawing.

11. A tracked vehicle and a hydraulic control therefor as claimed in any one of the preceding claims.