GB2048438A

GB2048438A - A device for mechanically actuating the adjusting member of variable-capacity hydraulic pumps or variable-capacity hydraulic motors

Info

Publication number: GB2048438A
Application number: GB8007746A
Authority: GB
Original assignee: Wacker Werke GmbH and Co KG
Current assignee: Wacker Werke GmbH and Co KG
Priority date: 1979-03-09
Filing date: 1980-03-07
Publication date: 1980-12-10
Also published as: DE2909262A1; SE8001742L

Abstract

In order to give non linear displacement of an adjusting member 4 the connection between the actuating element (14) and the adjusting member (4) comprises a driving lever (1) connected to the actuating lever and pivotable about a first fixed pivot (7) and a driven lever (3) connected to the adjusting member and pivotable about a second fixed pivot (9) parallel to and spaced from the first fixed pivot. The free end of the driven lever has a pin (2) which is received in a slot (1c) in an arm (1a) of the driving lever. <IMAGE>

Description

SPECIFICATION A device for mechanically actuating the adjusting member of variable-capacity hydraulic pumps or variable-capacity hydraulic motors This invention concerns a device having a manually operable actuating element for mechanically actuating the displaceable adjusting member of a variable-capacity hydraulic pump or variable-capacity hydraulic motor in an hydraulically driven vehicle.

Hydraulically driven vehicles, particularly rollers and construction vehicles, should be able to move in the forward and reverse directions in a smooth, slow and sensitive manner. With the known devices of simple construction, in which the adjusting travel of the actuating element is approximately linearly proportional to the adjusting travel of the adjusting member, this can only be achieved, if at all, by taking great care when operating the actuating element, so that it is quite possible that the moving-off operation will be jerky if the operator does not always give his full attention to the actuating operation.

An object of the invention is to provide a device which, whilst retaining structural simplicity, is designed such that a desired smooth, slow and sensitive moving-off operation can be achieved without great care on the part of the operator, and a jerky moving-off operation can be avoided.

According to the present invention there is provided a device for mechanically actuating the capacity-adjusting member of a variablecapacity hydraulic pump or variable-capacity hydraulic motor in an hydraulically driven vehicle, in which a manually operable actuating element is connected to a driving lever which is pivotable about a first fixed pivot, and a driven lever, is connected to the capacity adjusting member and is pivotable about a second fixed pivot which is parallel to and spaced from the first fixed pivot, one end of the driven lever, and one of which levers carries in the vicinity of its free end a stud which engages a slotted hole provided in a free end of the other lever and extending along the same, such that, when the device is in its neutral position, the stud is located in the vicinity of that end of the slotted hole which is adjacent to the first fixed pivot for the driving lever and moves away from this end of the slotted hole during pivoting of the driven lever from its rest position under progressive pivoting of the driving lever.

In accordance with these features, upon actuation of the actuating element in a direction forwardly or backwardly from its neutral position, the adjusting travel of the adjusting member progressively increases relative to the increasing adjusting travel of the actuating element, so that, in the vicinity of the zero position of the actuating element, relatively large actuating travels of the actuating element result in only relatively small actuating travels of the adjusting member, whilst, at the end regions of the adjusting travel of the actuating element, corresponding displacement of the same causes substantially larger displacement of the adjusting member.Thus, the operator is not compelled to perform only small control movements during the movingoff operation, whilst, on the other hand, he can readily accelerate and decelerate the moving vehicle without the total range of adjustment of actuating element exceeding a convenient length. Furthermore, it is also particularly advantageous that, at the maximum velocity of the vehicle, particularly a roller, the velocity can be reduced very rapidly by a small backward movement of the actuating element.

A preferred embodiment of the invention has the advantage that too rapid a change in the direction of travel can be prevented and maximum security against unintentional moving off can be achieved by arranging for the actuating element to be guided along slotted portions which are parallel to one another and offset. The invention will now be further described hereinafter, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side view of one embodiment of the device according to the invention, Figure 2 is a longitudinal section through the device of Fig. 1, taken on the line ll-ll of Fig. 1, Figure 3 is a partial plan view relating to Fig. 2, and Figure 4 is a graph showing the dependence of the travel of the receiving lever upon the travel of the driving lever.

Referring now to Figs. 1 to 3 there is shown a device for mechanically actuating the adjusting member of a variable-capacity hydraulic pump or variable-capacity hydraulic motor for use in a hydraulic transmission for the vehicle, the adjusting element charging the displacement of the pump or motor.

The device has a carrier 8 which is secured to the vehicle and in which a first fixed pivot 7 and a second fixed pivot 9 are secured parallel to one another and spaced part one above the other. A two-arm driving lever 1 is pivotally mounted on the first fixed pivot 7 so as to be pivotable in the direction of the arrows in Fig. 1 and carries a spherical handle 14 acting as an actuating element. The second fixed pivot 9 carries a pivotable one-arm driven lever 3. The latter lever and that arm 1 a of the driving lever which faces the driven lever extend parallel to one another and, when the device is in its neutral position, are located one behind the other in the direction of their axes of rotation as viewed in Fig. 1. In the embodiment under consideration the two arms are straight, although this characteristic is not essential in connection with the invention.

That arm 1 a of the driving lever 1 which faces the driven lever 3 is provided with an axially extending slotted hole 1 cwhich is engaged by a stud 2 secured to the driven lever in the vicinity of the free end thereof, such that, when the device is in its neutral position shown in the drawing, the stud is located in the vicinity of that end of the slotted hole adjacent to the fixed pivot 7.

The driving lever is of bifurcated construction directly above its fixed pivot 7 and the second arm 1 b of the driving lever which extends upwardly to the actuating element 14 is mounted in this fork by a pin 1 2 located at right angles to the pivot 7 so as to be laterally pivotable about the pin 1 2. A spring 10 seeks to maintain the laterally pivotable arm 1 b of the driving lever in a position in which it is parallel to the other arm 1 C of the driving lever.

The arm 1 b of the driving lever is guided below the actuating element 1 4 in a slotted guideway 13 which is fixedly mounted on the vehicle and which, when viewed from the side, is of arcuate configuration with the fixed pivot 7 as a centre point. The shape of the slot in the slotted guideway 1 3 is shown in Fig. 3. The slot 1 3 comprises straight portions 1 3a and 1 3b which are substantially parallel to one another and which are laterally offset relative to one another with respect to the pivoting direction of the driving lever 1, the adjacent ends of which portions merge into one another by way of a connection slot 1 3c at right angles thereto at the normal position of the driving lever 1.The pivotability of the upper arm 1 b of the driving lever about the pin 1 2 renders it possible to urge the arm 1 b of the driving lever, held in the connection slot 13e by the spring 10 in the position shown in Fig. 3, against the force of the spring either in alignment with the slot portion 1 3a or in alignment with the slot portion 1 3b, and then to move it along the relevant portion of the slot. During the return of arm 1 b of the driving lever into its normal position, undesired entry of this arm into the other portion of the slotted guideway 1 3 is prevented by the lateral offset of these portions of the slot.

Namely, the arm 1 b is moved in the first instance by the force of the spring only into its central position in the slot portion 1 3c from which it first has to be brought into alignment against with the portion of the slot against the force of the spring in order to be moved into the latter portion of the slot.

Owing to the engagement of the stud 2 in the slotted hole 1 c, any pivoting 'of the driving lever 1 results in pivoting of the driven lever 3. This pivoting of the driven lever is accompanied by movement of an adjusting member 4 which is secured to the driven lever in the vicinity of the fixed pivot 9 and which leads to an adjusting element of the hydraulic unit to be controlled.

The relationship between the pivoting or angular adjustment of the driving lever 1 plotted on the abscissa and the pivoting or angular adjustment of the driven lever 3 plotted on the ordinate is shown in Fig. 4. The neutral position is represented by the intersection of the two axses. It wll be seen from the graph of Fig. 4 that, when the device is in the vicinity of its neutral position, a predetermined angular adjustment of the driving lever results in only a relatively small angular adjustment of the driven lever and thus also in a correspondingly small displacement of the adjusting member 4, whilst the same angular adjustment of the driving lever in the end regions of the path of adjustment results in a far greater angular adjustment of the driven lever with the adjusting member 4 connected thereto. The characteristic of this progressivity can be influenced in a variety of ways by utilising configurations other than the straight configuration of the slotted hole shown in Fig. 1, and by changing the distance ratios of the fixed pivots 7 and 9 from the stud 2.

Claims

1. A device for mechanically actuating the capacity adjusting member of a variable-capacity hydraulic pump or variable-capacity hydraulic motor in an hydraulically driven vehicle, in which a manually operable actuating element is connected to a driving lever which is pivotable about a fixed pivot, and a driven lever is connected to the capacity adjusting member and is pivotable about a second fixed pivot which is parallel to and spaced from the first fixed pivot, one end of the driven lever, and one of which levers carries in the vicinity of its free end a stud which engages a slotted hole provided in a free end of the other lever and extending along the same, such that, when the device is in its neutral position, the stud is located in the vicinity of that end of the slotted hole which is adjacent to the first fixed pivot for the driving lever and moves away from this end of the slotted hole during pivoting of the driven lever from its rest position under progressive pivoting of the driving lever.

2. A device as claimed in claim 1, in which the driving lever has an actuating arm which is movable laterally to a limited extent relative to its pivot axis and runs in a slotted guideway which comprises straight slotted portions which are substantially parallel to one another and are offset relative to one another relative to the direction of pivoting and their adjacent ends merge into one another by way of a connection slot disposed at right angles thereto and located at the normal position of the driving lever.

3. A device constructed and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.