GB2253885A

GB2253885A - A wheel cylinder valve linkage

Info

Publication number: GB2253885A
Application number: GB9105978A
Authority: GB
Inventors: William Ernest Haines
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1991-03-21
Filing date: 1991-03-21
Publication date: 1992-09-23
Anticipated expiration: 2011-03-21
Also published as: GB9105978D0; GB2253885B

Abstract

A wheel cylinder valve 10 which varies the brake pressure as the wheel moves relative to the suspended part of a vehicle has a valve stem 16 which is acted on by a lever 40 pivoting about a nut 38. The lever is acted on by an actuation member 18 via a resilient connection comprising a helical spring 50 and a coaxial link 54. The spring 50 has one end 56 resting on the lever 40 and the link 54 which may be attached to the other end of the spring 50 passes through the spring 50 and a hole 46 in the lever and is coupled to the actuating member 18. <IMAGE>

Description

A WHEEL CYLINDER VALVE LINKAGE The present invention relates to linkages Cor wheel cylinder valves.

Wheel cylinder valves are known which are arranged in vehicle hydraulic brake systems near the wheel cylinder of, for example, a drum brake. The valves operate to vary the hydraulic pressure applied to a wheel cylinder as the wheel alcoves relative tc the vehicle on the sllspension system. An examole of such c valve and associated linkage is described in WO 90/06871.

That document shcws a wheel. cylinder valve which is integral with the wheel cylinder and which has a valve stem ich is acted on by a helical spring under compression. The helical spring is compressed between a cap mounted on the valve stem and one end of a lever, the other end of.the lever being connected via a rod or cable to a vehicle subframe.

That arrangement has two main disadvantages. Firstly the helical spring ic not restricted from bowing out sideways as the angle of force applied to it by thn lever changes. Also the force which ras to be transmitted through the spring to operate the valv is quite high so a stiff so ring is required which CE n make the system hard to calibrate and adjust accuratel . Another disadvantage of the arrangement described is that the lever has to protrude a long way beyond the back c f the brake drum.

The present invention provides a control linkage for a wheel cylinder valve having a movable valve control member, the linkage comprisir g an actuation member connectol to a fixed part of a vehicle, a lever and resilient connecting means connecting the actuation member to the lever, the lever being arranged tt transmit force from the actuation member to the valve control member.

Preferred embodirents of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Fig 1 is a view, partly in suction, of a wheel cylinder valve linkage according to the invention, and Fig 2 shows a mocification of the linkage of Fig 1.

A wheel cylinder 10 having an integral wheel cylinder valve 12 is mounted on a brake drum backplate 14. A valve stem 16 protrudes from the wheel cylinder valve 12 and is slideable in the valve 12.

An actuation memker in the form of an Th - shaped actuation lever 18 has one arm 24 connected via a rod 2(3 to the vehicle sub frame 22, and its heel rotatably coupled to a bracket 26 mounted on the hankplate 14. another arm 28 of the lever 18 extends in a direction substantiallv parallel to the backolate 14 and has a notch 30 at its free end 32.

The actuation leper 18 is arranged such that the free end 32 of the lever arm 28 is close to the valve 12 on one side thereof. On the other side of the valve 12 is a pivot means in the form of a bolt 34 which passes through the backplate 14 such that its threaded shank 3G extends from the backplate 14 further than the valve rtem 1t, a nut 38 being mounted thereon. A lever 48 having a U-shaped cross section has a hole 44,46 therethrough near each end.In the centre of the lever is en indentation 42 which rests against the valve stem 16. rihe bolt 34 passes through the hole 44 at one end of the lever 88 which rest against the nut 38. A resilient connecting means 5(3 comprises a resilient member in the form oE a helical spring 52 and a link member in the form of a rod 54 formed as an extension of one end of the helical spring 5 so that the rod and spring are formed from a single length cf wire.On end 56 of the helical spring 52 rests against the lover 40, the end coil 58 being located around the hole 46 hy locating means formed by the rim 60 of the hole 46 being turned un. The ro;3 54 is joined to the other end of the helical spring 52 52 and extends along the axis thereof and through the hole 46 in the lever 4g. The end of the rod ic turned over to form a hook 62 which fits into the notch 30 in the lever arm 28, the lever arm 28 extending betwer the lever 4(3 and the hackplate 14.

When the rod 20 s put under tension, due to movement of the vehicle subframe 22 relative to the backplate 14, the actuation lever 18 pivots on the bracket 2, pulling the rod 54 towards the btckplate 14. This compresses the spring 52 against the lever 48 which pivots about an axis passing through the bolt 34 depressing the valve steal 16. The force applied to the valve stem 16 is greater than that applied to the liver 4(3 by the spring 52 beaus of the lever arrangement. The valve stem 16 is biased outwards due to hydraulic pre sure against the lever 4(3 so that relaxing of the tension ir the rod 20 allows the valve steal 16 to move outwards.

In the embodiment: shown in Fig 2, the resilient connecting means comprises c helical spring 12, a cap 153 which fits over the end of t:he helical spring 152 and has a hole 155 in its centre and a rod 154 which extends through th hole 155 and hooks over a pin 156 which holds the end of the rod 154 in the hole 155.

Claims

1. A control linkage for a wheel cylinder salve having a movable valre control member, the linkage omprising an actuation mcmber connected to a fixed part of a vehicle, a lever, and resilient connecting means connecting the actuation member to the lever the lever being arranced to transmit force from the actuation member to the valve control member.

2. A control linkage according to Claim 1 wherein the lever is arranged to amplify force transmiteed from the actuation member to the valve control member.

3. A control linkage according to olaigl 2 wherein the lever is pi'.'otable about 3 pivot axis and the valve control member is acted on by a part of the lever between the pivot axis and the resilient connecting means.

4. A control linkage according to any foregoing claim wherein the resilient connecting means comprises a resilient member and a link member arranged coaxially with the resilient member.

5. A control linkage according to Claim 4 wherein the resilient connecting means arranged such that force transmitted between the actuation meniher and the lever compresses the resilient member.

6. A control linkage according to Claim 4 or Claim 5 wherein the link member extends through the resilient member.

7. A control linkage according to any foregoing claim wherein the actuation member comprises a second lever.

8. A control linkage according to Claim 7 when appendant on anv one cf claims 4 to 6 wherein the resilient means is on one side of one of the levers and the link member is connector to the other of the levers on the other side of the said one of the levers.