GB2024375A - Valve device - Google Patents

Abstract

The invention relates to a valve device (1) having a cam-operated valve body (7) which can be moved by the action of the cam (20) into an operating position of the valve device (1), seated against a valve seat (9:10). A pressure spring element (17) is arranged between the cam (20) and the valve body (7) so as to ensure an adequate seating force exists to seat the valve body (7) fully in said valve operating position. Valve devices of this kind are intended, for example, for use in reversing hydraulic drives. <IMAGE>

Description

SPECIFICATION Valve device The invention relates to a valve device having a cam-operated valve body which can be moved by the action of the cam into an operating position of the valve device, seated against a valve seat.

Particularly in the case of several valve bodies actuated by a common cam shaft, it can happen by unavoidable manufacturing tolerances that one or even several valve bodies are not seated, or at least not with sufficient force, against their valve seats, in one or more operating positions of the valve devices. Because of such effects, one or more of the valve devices may not close satisfactorily or open with a sufficiently large throughflow cross-section. In order to avoid such deviations from the intended operation, adjusting elements are usually provided, the manual displacement of which makes possible suitable adjustment. However, the provision of such adjustment facilities is expensive. It may be necessary from time to time to repeat the adjustment, as the adjusting elements can become displaced because of unavoidable phenomena of wear.

According to the invention there is provided a valve device having a cam-operated valve body which can be moved by the action of the cam into an operating position of the valve device, seated against a valve seat, wherein a pressure spring element is arranged between the cam and the valve body so as to ensure an adequate seating force exists to seat the valve body fully in said valve operating position.

The pressure spring element convenientiy comprises a spiral spring. Spiral springs can be produced economically for all required spring forces: In a preferred construction a plunger guided in the valve body is arranged to convey the action of the cam to the pressure spring element. Then the cam does not act against the pressure spring element directly but by way of the plunger. In this way the force expended by the cam can be transferred more uniformly onto the pressure spring element. This applies particularly when spiral springs are used.

The valve device to be operated can be one in which only one path is to be blocked by closing the valve device. Opening of the valve device takes place for example by way of a pressure spring arranged between valve body and valve seat, this pressure spring removing the valve body from the valve seat when the closing force of the cam is absent.

Alternatively, the valve device can be a reversing valve (three-way valve) which, for example, serves the purpose of reversing a pistoncylinder arrangement of a hydraulic drive.

Particularly with such a valve device in mind, in a further development the cam extends into a recess in the valve body and different operating portions of the cam can be brought selectively into operative connection with respective pressure spring elements so as to ensure adequate seating forces exist in all of the operating positions of the valve device. Thus it is possible for example in the case of a three-way valve to cause the valve body to engage with the one or the other valve seat by altering the direction of rotation of the cam and thereby to block one path respectively and simultaneously clear the other path. The necessary seating fcrce for each direction of rotation of the cam shaft is ensured by way of the two pressure spring elements.

For a better understanding of the invention and to show the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing in which Figures 1 and 2 diagrammatically show one embodiment of the invention in two different operating positions.

Figure 1 shows an arrangement of two valve devices each in the form of a reversing valve 1.

Each valve has an inlet 3, an exhaust 2, and an outlet 4. As the exhaust 2 is connected to a low pressure chamber 5, while inlet 3 is connected to a pressure reservoir 6, either low or high pressure is present in the outlet 4 of valve 1, depending on the position of the valve body 7. A piston-cylinder arrangement (not shown) of a hydraulic drive, which is connected to the outlet 4, can be reversed by the varying pressure in the outlet 4. In the region of each inlet 3 and each exhaust 2 of each valve 1, the latter is provided with valve seats 8 and 9, against which correspondingly conically shaped surfaces 10 and 11 of the valve bodies 7 can seat in different operating positions of each valve.Furthermore, the valve body 7 is formed with a recess 1 5 and, on both sides of this recess along the longitudinal axis of the valve body, further recesses 1 6 for receiving in each case a pressure spring 17 and a plunger 1 8. Cams 20 on a common cam shaft 21 engage in the recesses 1 5 with operating portions on the cams 20 which can selectively be brought into operative contact with the plunger 1 8.

In the Figure 1 embodiment, the cam shaft is rotated in a clockwise direction, so that the conical surface 10 of the valve body 7 is seated against the valve seat 8. The inlet 2 of valve 1 is accordingly closed. As can be seen in the Figure by way of example, the depressed plunger of the valve at the top of the Figure is pressed further into the recess 1 6 than the corresponding plunger 18 of the lower valve in the Figure. This can be due for example to the fact that the two cams 20 are somewhat distorted in relation to each other.

Without the pressure springs 17 which balance this difference in tolerance, only the upper valve 1 would close fully in a case such as this. As further rotation of the fixed cam shaft would not be possible, the lower valve 1 would still remain open slightly. However, the pressure springs provide adequate seating forces to guarantee that both valve bodies are seated fully against their respective seats.

Figure 2 shows the same valve arrangement and so the same parts are given the same reference numbers. As opposed to Figure 1, however, the cam shaft is rotated in an anticlockwise direction. Thus, the cams 20 press on the left-hand plungers 18 in the Figure.

Correspondingly, the valve bodies 7 are displaced to the left until the conical surfaces 11 of the valve bodies 7 are seated against the valve seats 9 and consequently the inlets 3 of the valves 1 are fully closed. Simultaneously, the exhaust 2 of the valves are opened. Once again the case is shown of the plungers 18 pressed by differing amount into the recesses 1 6. However, for the same reasons as explained in connection with the Figure 1 embodiment, the tolerance equilibrium is guaranteed here also by way of the pressure springs, so that both valve inlets 3 are closed securely.

Therefore, the described valve arrangement avoids the need for manually operated adjusting elements for adjusting tolerances between the cams and the valve bodies and serves to create a reliable tolerance balance. The pressure spring elements ensure that the valves close securely by means of spring tension. Therefore adjustment between cam and valve body is unnecessary.

Variations in manufacturing tolerances between the cams and the valve bodies are balanced out automatically.

Claims (6)

1. A valve device having a cam-operated valve body which can be moved by the action of the cam into an operating position of the valve device, seated against a valve seat, wherein a pressure spring element is arranged between the cam and the valve body, so as to ensure an adequate seating force exists to seat the valve body fully in said valve operating position.

2. A valve device according to claim 1, wherein the pressure spring element comprises a spiral spring.

3. A valve device according to claim 1 or 2, wherein a plunger, guided in the valve body, is arranged to convey the action of the cam to the pressure spring element.

4. A valve device according to any one 1 claims 1 to 3 having different valve seats against which the valve body is seated in the various operating positions of the valve device, wherein the cam extends into a recess in the valve body and different operating portions of the cam can be brought selectively into operative connection with respective pressure spring elements so as to ensure adequate seating forces exist in all of the operating positions of the valve device.

5. A valve device substantially as hereinbefore described with reference to the accompanying drawing.

6. An arrangement of a plurality of valve devices in accordance with any one of the preceding claims, wherein a common operating element is provided for operating the several cams.