GB2073854A

GB2073854A - Control Valve Assembly for a Pneumatic Spring

Info

Publication number: GB2073854A
Application number: GB8106852A
Authority: GB
Original assignee: Wabco Fahrzeugbremsen GmbH
Current assignee: Wabco Fahrzeugbremsen GmbH
Priority date: 1980-03-04
Filing date: 1981-03-04
Publication date: 1981-10-21
Also published as: DE3008150A1; FR2483337B1; GB2073854B; FR2483337A1; DE3008150C2

Abstract

A valve assembly for controlling the flow of air to or from a pneumatic spring employs, as the inlet and disk valves 5, 6 which are acted on directly by cam surfaces (13, 14) Fig i (not shown) of an operating member 12 which is rotated by a lever 11 in dependence on the load on the spring. A throttle member (16) throttles the flow of air through the valves during small movements of the lever, to prevent undue oscillation of the spring, but allows unthrottled flow for larger movements. A dampening arrangement, comprising both a mechanical damping assembly (30, 31, 32) Fig 8 (not shown) and an hydraulic damping assembly 34, 35, 39, 40 is arranged between the lever 11 and the valve operating member 12 to allow only a delayed (if any) flow of air through the valves in the case of small changes in the load on the spring. <IMAGE>

Description

SPECIFICATION Control Valve Assembly for a Pneumatic Spring The invention relates to a control valve assembly for the load-dependent regulation of a pneumatic spring.

A known control valve assembly for a pneumatic spring includes an inlet valve controlling the connection of air supply to the pneumatic spring, an outlet valve for venting the spring to atmosphere, and mechanical transmission means for the load-dependent regulation of the spring. This mechanical transmission means includes a verticallyadjustable push rod for controlling the valves and, as a result, the dimensions of the assembly when installed, especially its height, are relatively large, so that, when there is little space available, for example in pneumatically-sprung driving seats, the accommodation of the valve assembly can present problems.

Pneumatic springs are generally subject to a continuously-changing continuous load and, since the mechanical transmission of force is effected, in the above-mentioned known assembly, by way of a plurality of mechanical connections between operating levers, an eccentric device and the valve push rod, failure may occur as a result of this continuous load.

The problem with which the present invention is concerned is the provision of a control valve assembly which can be manufactured, comparatively inexpensively, with a compact construction having comparatively low height when installed and capable of withstanding extreme continuous loads.

The present invention provides a control valve assembly for the load-dependent regulation of a pneumatic spring, the assembly including an inlet valve and an outlet valve operable to connect to pneumatic spring connection to, respectively, an air supply connection and an outlet opening, the valves being disk valves each including a valve disk resiliently-biased into a closed position, and being operable in dependence on the load on the pneumatic spring by a valve operating member comprising a cam element which directly operates the valve disks.

An embodiment of the invention includes a throttle member operable by the valve operating member with a pre-determined amount of play whereby, over an initial control range only of the operating member, the throttle member throttles the flow of air to and/or from the pneumatic spring connection. Preferably, the throttle member is restrained against movement with the operating member during the said pre-determined amount of play. In this embodiment, the throttle member includes a throttle surface which, over an initial range of positions of the throttle member throttles a passage for the flow of air to and/or from the pneumatic spring connection and, adjacent the throttle surface, at least one recess which, in subsequent positions of the throttle member, unblocks the passage.

The valve assembly may include a damping arrangement operable to delay movement of the valve operating member and the operation of the inlet or outlet valve in response to a change in the load on the pneumatic spring. The damping arrangement may consist of a mechanical damping assembly and a hydraulic damping assembly.

An embodiment of the invention is described in greater detail below, with reference to the accompanying drawings, in which: Fig. 1 shows, in cross section, a control valve assembly for a pneumatic spring, in accordance with the present invention; Fig. 2 shows a throttle device forming part of the assembly and indicated by a dotted line in Fig.

1; Fig. 3 is another view of the assembly of Fig. 1, showing a damping arrangement and Fig. 4 shows a section A-A through the damping arrangement of Fig. 3 together with a section B-B through the valves of Fig. 3.

The valve assembly shown in Figure 1 consists of a housing 1 having an air supply connection 2, a pneumatic spring connection 3 and an outlet opening 4 leading to the atmosphere. Two valve disks 5 and 6 are arranged horizontally in a chamber 1 a of the housing 1 and form, respectively, with their sealing surfaces 5a and 6a and with bores 7 and 8, an inlet valve 5, 7 and an outlet valve 6, 8. The inlet valve controls the connection of the pneumatic spring port 3, via the bore 7, to the supply connection 2 and the outlet valve 6, 8 controls the connection of port 3, via the bore 8, to the outlet opening 4. Valve springs 9 and 10 arranged above the valve disks 5 and 6, respectively, hold the two valves 5, 7 and 6, 8 in the closed position.

A valve operating member 12, constructed as a cam member and connected to an actuating lever 11 in a torsionally resistant manner, is so arranged between the two valves 5, 7 and 6, 8 that a first cam surface 13 is engageable with one end of the valve disk 5 and a second cam surface 1 4 is engageable with one end of the valve disk 6.

The valve disks 5, 6 are each mounted at their other ends so as to be rotatable about those ends so that, when the lever 11 initiates a rotating movement of the valve operating member 12 in one direction, the cam surface 13 opens the inlet valve 5, 7 and, when the valve operating member 1 2 rotates in the other direction, the second cam surface 14 opens the outlet valve 6, 8.

A floating throttle 1 6 which, as described below, can rotate relative to the valve operating member 12 is arranged, in the bore 15, adjacent the end of the valve operating member 12. This throttle, shown in Figure 2 and indicated by a dotted line in Figure 1, and forms, with its external circumference 17 a throttle gap with the bore 15: more particularly, the throttle gap is formed by a given surface area 18, defined by two throttle edges 1 9 and 20, at the external circumference 17 of the floating throttle 16 which, when the throttle is in the position shown (Figs. 1 and 2), covers a bore 3a leading from the recess 1 5 to the pneumatic spring connection 3.

Recesses 21 and 22 in the floating throttle 16, which define the throttle edges 1 9 and 20, can be brought into registration with the bore 3a, to uncover the iatter, by appropriate rotation of the throttle. A driving element 23 in the form of a pin fastened to the valve operating member 12 projects into the recess 22 which also receives a spring 24 arranged in the centre of the floating throttle 16. The throttle 16 is formed of a resilient material and recess 22, as seen in Fig. 2, effectively defines two spring arms therein which are biased apart by the spring 24 to press the outer surface 1 7 of the floating throttle 16 against the surface of bore 1 5.As a result of this pressing action, when the valve operating member 1 2 rotates, the throttle 1 6 remains in its position during a certain range of that rotational movement, and only when the driving element 23 comes to rest against one of the faces of the recess 22 is the rotational movement of the valve operating member 12 transmitted to the floating throttle 16.

The play between the floating throttle 16 and the valve operating member 12 is so calculated that for small excursions (rotation) of the valve operating member 12, the throttle continues to throttle with its surface 18 the flow of air to and from the pneumatic spring connection 3 but, for large excursions, allows an unthrottled flow via recess 21 or 22.

The operation of the valve assembly is as follows: When the load on the pneumatic spring increases, the lever 11 moves downwards as seen in Fig. 1 and, as a result of the rotational movement transmitted to the valve operating member 12, the inlet valve 5, 7 is opened by the cam surface 13 engaging the valve disk 5, so that a compressed air connection is produced between the supply connection 2 and the pneumatic spring connection 3. Air is admitted via this connection to the pneumatic spring until pressure equalisation corresponding to the weight of the load has occurred and the lever 11 returns to its normal position whereupon the inlet valve 5, 7 closes again.

If, on the other hand, the load on the pneumatic spring decreases, the lever 11 moves upwards as seen in Fig. 1 and the rotational movement of the valve operating member 12 results in the cam surface 14 engaging the valve disk 6 so that the outlet valve 6, 8 is opened and a compressed air connection is produced between the pneumatic spring connection 3 and the atmosphere via the opening 4. Air is released from the pneumatic spring via this connection until the lever 11 returns to its normal position whereupon the outlet valve 6, 8 closes again.

In the operation of the valve assembly described thus far, the accompanying operation of the floating throttle 1 6 has not been considered.

This operation will now be described.

Assuming, for example, that the valve assembly is used in a pneumatically-sprung driving seat, then the position of the floating throttle 1 6 shown in Figures 1 and 2 corresponds to the driver being seated. The bore 3a leading to the pneumatic spring connection 3 is covered by the throttle surface 18 and, while this situation is maintained, any flow of air to and from the connection 3 as a result of operation of the inlet or outlet valve 5, 7, 6, 8 will be throttle.If, as a result of unevenness of the road, the driver bounces upwards, then, once the play has been exceeded, the floating throttle 1 6 follows the rotational movement of the valve operating member 12 by means of the driving element 23 and surface 25, but the rapid release of compressed air from the pneumatic spring into the atmosphere via the opening outlet valve 6, 8 does not occur because the throttle surface 1 8 is so dimensioned that in the case of normal oscillations of the seat during a journey the throttle edge 20 of the throttle surface 1 8 is not passed.

Only when a predetermined travel of the seat has been exceeded, for example when the driver leaves his seat, is the movement of the valve operating member 12 so great that the throttle edge 20 of the throttle surface 1 8 passes over the bore 3a of the pneumatic spring connection 3 and the pneumatic spring is rapidly vented to the atmosphere, via the (then) unthrottled bore of the pneumatic spring connection 3 and open outlet valve 6, 8.

If the driver sits on the seat again, the seat sinks as far as a stop and the throttle edge 19, after passing over the bore 3a, allows the rapid admission of air to the pneumatic spring.

The seat adopts its normal position again and the driver then has a seat which, as a result of the throttle device, does not oscillate greatly but, owing to the throttled admission and release of air which is still possible, still provides the normal comfort afforded by springs.

Some further details of the valve assembly will now be described, with reference to Figures 3 and 4, which illustrate a damping arrangement connected between the lever 1 1 and the valve operating member 12.

Reference numerals used in Figure 1 are used also in Figures 3 and 4 to denote the same components having the same function.

When the load on the pneumatic spring decreases, the lever 11 (indicated in broken lines in Figs. 3 and 4) moves upwards as already described, this movement being upwards out of the plane of the paper in the case of Fig. 3. A spring housing 30, connected to the lever 11, moves therewith but a flattened operating shaft 31 coupled to the spring housing 30 does not immediately follow the movement due to the action of a piston 33 which is mounted in the housing 30 and is under the force of a spring 32.

This piston 33, which has a graded end, is moved by the spring housing 30 and the graded end of the piston presses against one edge 31 a of the flattened operating shaft 31 until, when the spring 32 is sufficiently compressed, a turning moment acts on the operating shaft 31 and hence on the remainder of the damping arrangement described below.

The operating shaft 31 is connected in a torsionally resistant manner to the valve operatinc member 12 and also exerts a force on a hydraulic piston 35, arranged in a housing 34, by way of a driving pin 36 and pins 37 and 38. The piston 35 resists this force, however, because damping chambers 39, 40 behind the piston 35 are filled with fluid which the piston, in order to move, has to force through a gap between itself and the housing 34 from one damping chamber to the other.

The movement of the piston 35 and the transmission of the damped rotational movement of the operating shaft 31 to the valve operating member 12 lifts the valve disk 6 and compressed air flows from the pneumatic spring connection 3 through the open outlet valve 6, 8 into the atmosphere as already described. The throttle device 1 6 will also function as already described, but has not been shown in Figs. 3 and 4.

When the load on the pneumatic spring is increased, the described process takes place in the same manner but with the piston 35 moving in the opposite direction. In this case, air is admitted to the pneumatic spring via the supply connection 2, the open inlet valve 5, 7 and the connection 3.

When the piston 35 is about to return from its particular end position into the middle position, one of the control edges 41 or 42 of the piston is located in the region of one of the two damping chambers 39 or 40. In this case, the fluid is able to flow back rapidly from one damping chamber to the other via a large gap 35a or 35b and a valve tongue 43 or 44 which can then open: the piston 35 thus follows rapidly the return movement of the lever 11.

The effect of the described hydraulic damping arrangement, in the case of a pneumaticallysprung driving seat, is to allow only a delayed, if any, flow of air to or from the pneumatic spring in the case of small oscillations of the seat.

As a modification of the arrangement shown in the drawings, the described throttle device 1 6 may be arranged upstream of the inlet valve 5, 7 and/or downstream of the outlet valve 6, 8 so that its function is exerted only on the inlet or outlet valve: in either case, it is possible to arrange the device either inside or outside the valve housing 1.

The gap between the cam surfaces 13, 14 and the valve disks 5, 6 determines the response of the disk valves 5, 7 and 6, 8 and must be maintained within definite tolerances. In order that this response does not achieve impermissible tolerances, which would be the case if the valve could tilt in an undefined manner, the valves have a defined rest position in which they are supported on raised portions 50 of the housing (Fig. 1). To ensure that the valves rest firmly, the point of application of the force of the springs 9, 10 lies between the valve bores 7, 8 and the supports 50: as a result, the valves are unable to tilt in an undefined manner and the tolerances of the response do not increase to an impermissible extent.

As a result of using disk valve 5, 7 arranged side-by-side, the valve assembly is comparatively compact and inexpensive to produce. Further, the assembly requires comparatively small operating forces owing to the more favourable transmissioii of force, and is suitable for extreme continuous loads.

The arrangement of the disk valves 5, 7 makes possible the lateral arrangement of the projecting lever 11 at right angles to the direction of closure of the valves and the use of a rotatable cam shaft 1 2 for operating the disk valves, and these features further contribute to the compactness of the construction.

Claims

1. A control valve assembly for the loaddependent regulation of a pneumatic spring, the assembly including an inlet valve and an outlet valve operable to connect a pneumatic spring connection to, respectively, an air supply connection and an outlet opening, the valves being disk valves each including a valve disk resiliently-biased into a closed position, and being operable in dependence on the load on the pneumatic spring by a valve operating member comprising a cam element which directly operates the valve disks.

2. A valve assembly according to claim 1, in which the valve disks are arranged side-by-side and parallel to each other in a common housing chamber.

3. A valve assembly according to claim 1 or claim 2, including a throttle member operable by the valve operating member with a predetermined amount of play whereby, over an initial control range only of the operating member, the throttle member throttles the flow of air to and/or from the pneumatic spring connection.

4. A valve assembly according to claim 3, in which the throttle member is restrained against movement with the operating member during the said pre-determined amount of play.

5. A valve assembly according to claim 3 or claim 4, in which the throttle member includes a throttle surface which, over an initial range of positions of the throttle member throttles a passage for the flow of air to and/or from the pneumatic spring connection and, adjacent the throttle surface, at least one recess which, in subsequent positions of the throttle member, unblocks the passage.

6. A valve assembly according to claim 5, in which a driving element, fastened to the valve operating member, projects into the recess in such a manner that, when the driving element rests against a face of the recess, the throttle member is movable with the valve operating member.

7. A valve assembly according to claim 5 or claim 6, in which the throttle member is sprung into frictional engagement with a surrounding housing to restrain the throttle against movement during the said pre-determined amount of play.

8. A valve assembly according to any one of the preceding claims including a damping arrangement operable to delay movement of the valve operating member and the operation of the inlet or outlet valve in response to a change in the load on the pneumatic spring.

9. A valve assembly according to claim 8, in which the damping arrangement consists of a mechanical damping assembly and a hydraulic damping assembly.

1 0. A valve assembly according to claim 9, in which the mechanical damping assembly comprises a resiiiently-biased piston arranged in a housing which is movable in dependence on the load on the pneumatic spring, the piston engaging an operating shaft in such a manner that only when the resilient biasing means has been compressed is movement of the piston housing converted into movement of the operating shaft, the shaft being connected to the valve operating member.

11. A valve assembly according to claim 10, in which the hydraulic damping arrangement comprises a piston connected to the operating shaft and arranged in a housing with two damping chambers filled with fluid which oppose the movement of the piston in both directions; the piston and the housing being shaped to provide a gap therebetween through which fluid can be forced from one damping chamber to the other by the piston in a throttled manner, valve means being provided to allow the fluid to flow rapidly from one damping chamber into the other damping chamber during return movement of the piston.

12. A valve assembly according to claim 3, in which the throttle member is arranged between on one side the pneumatic spring connection and, on the other side, the inlet and outlet valves.

13. A valve assembly according to claim 3, in which the throttle member is so arranged that its throttling function acts only on the inlet valve or only on the outlet valve.

14. A valve assembly according to claim 3, in which the throttle member is housed separately from the inlet and outlet valves.

1 5. A valve assembly according to any one of the preceding claims, in which each disk valve includes a valve bore over which the valve disk lies loosely, held merely by the bias of a spring.

16. A valve assembly according to claim 15, in which the valve disk is mounted so as to rotate about one end and lies, in the rest position, on a stop, the point of application of the bias of the said spring lying between the stop and the valve bore.

17. A valve assembly according to any one of the preceding claims, in which the valve operating member is movable by an angularly-adjustable lever.

1 8. A valve assembly according to claim 17, when appendant to claim 10, in which the angularly adjustable lever is connected to the piston housing.

1 9. A control valve assembly for the loaddependent regulation of a pneumatic spring, the assembly being substantially as described herein with reference to, and as shown in, Figs. 1 and 2 or Figs. 3 and 4 of the accompanying drawings.