GB2193547A

GB2193547A - Dual circuit air brake valve

Info

Publication number: GB2193547A
Application number: GB08718795A
Authority: GB
Inventors: Stephen Walter Fogg
Original assignee: Bendix Ltd
Current assignee: Honeywell UK Ltd
Priority date: 1986-08-09
Filing date: 1987-08-07
Publication date: 1988-02-10
Anticipated expiration: 2007-08-07
Also published as: EP0260805A3; EP0260805A2; GB8718795D0; GB2193547B; EP0260805B1; ES2021364B3; DE3769253D1; GB8619490D0

Abstract

A dual circuit foot-operable compressed air pressure control valve has an input plunger (7) which acts through springs (12, 13) on a pressure responsive member (14) for operating a lappable double valve (21, 22, 23) to connect an output port (30) to a supply port (29) or a vent (4), pressure at the output port acting on the member in a sense tending to oppose the springs (12, 13) and vent the output port, the member (14) having a resiliently deflectable stop means (41) such that the member is displaceable beyond its normal stop position during venting to temporarily increase the vent opening through the valve. <IMAGE>

Description

1 GB2193547A 1 SPECIFICATION way of example with reference to the accom

panying drawing of which:

Improvement relating to fluid pressure con- Fig. 1 illustrates a dual circuit compressed trol valves air brake pressure control valve device and, 70 Fig. 2 illustrates a resilient deflectable stop This invention relates to fluid pressure control member employed in the valve device of Fig.

valves and relates especially but not exclu- ' 1.

sively to dual pressure control valves for Referring to Fig. 1 the valve device shown vehicle compressed air braking systems. therein comprises an housing formed of four In vehicle compressed air braking systems it 75 parts 1, 2, 3 and 4 joined together by suit- is usual to provide two independent service able bolts or other means. The upper end of brake control circuits for brakes on the same the housing is provided with the first part de or different axles on a vehicle. These indepen- noted by reference 1, beneath which the dent circuits are fed from separate comgenerally cylindrical part 2 has a machined pressed air reservoirs via pneumatically sepa- 80 bore 5 to receive a pressure repsonsive mem rate portions of a dual pressure control valve ber 14. Beneath part 2 the third part 3 has a operable by a driver's brake pedal. A typical machined bore 6 to receive a further pressure such valve comprises a pedal operated plunger responsive member 24 and the lower end is which acts through a spring on one side of a closed by the fourth part 4 which comprises a piston the other side of which piston is sub- 85 vent cap. An input plunger denoted by refer ject to air pressure delivered to a first comence 7 has a socket 8 for receiving an actuat pressed air brake circuit via a self-lapping ing stud or other member of a driver's foot valve which is controlled by the piston. The pedal mechanism (not shown). The plunger 7 delivered pressure typically also acts on one is sealingly moveable in the housing by virtue side of a further piston which controls a fur- 90 of a flexible annular diaphragm 9, located be ther self-lapping valve for supplying fluid pres- tween a peripheral groove 10 of the plunger sure to a second brake circuit. In order to and an annular upstand 11 of the housing part meet progressively more exacting performance 1.

requirements for compressed air braking sys- Input forces applied to the plunger 7 by the tems it has been found that there are often 95 foot pedal are transmitted via one or both of conflicting requirements imposed upon the a pair of springs 12 and 13 to one side of compressed air control valve. For example, on the pressure responsive member 14 which the one hand a large amount of free move- comprises a piston responsive member 14 ment of the plunger, before the first men- which comprises a piston slideable in the bore tioned self-lapping valve closes its exhaust 100 5. The plunger 7 has a downwardly extending valve and opens its inlet valve, is unaccep- stem 15 which is freely slideable in a central table whereas on the other hand substantial axial bore 16 of the piston 14. The. lower end exhaust seat openings are nevertheless desir- of 15 carries a stop 17 retained by a central able to minimise air venting restrtiction for enscrew 18. A further spring 19 acts between suring rapid response to driver pedal pressure 105 housing part 2 and a shoulder 20 of the pis variations. ton 14 in a direction to support the piston 14 The present invention has an object to over- against the springs 12 and 13. The piston 14 come or reduce the conflict between require- carries a lappable double valve assembly hav ments such as the foregoing. ing a valve member 21 engageable with an According to the present invention there is 110 inlet valve seat 22 carried by the piston itself provided a fluid pressure control valve corn- and co-operable with an exhaust valve seat 23 prising a body housing a pressure responsive carried by an upward projection 25 of the fur member sealingly moveable therein for operat- ther pressure responsive member 24, in the ing a lappable double valve arrangement, alter form of a second piston. Piston 24 has a natively displaceable from a lap position for 115 further downward projection 26 which carries connecting an output port to a supply port or a similar exhaust valve seat 27 of a further a vent port, said pressure responsive member double valve assembly having a valve member being subject on one side to fluid pressure at 28 and an inlet valve seat 29 located in the the output port acting in a sense to vent said body part 3.

pressure and to urge said member towards a 120 The body part 2 is provided with a first stop position and being subject to an input fluid pressure supply port 29 and a first pres force acting in an opposing sense to tend to sure delivery port 30 whereas the lower body connect the output port to the supply port part 3 is provided with a second pressure and said member being resiliently deflectable supply port 31 and second pressure delivery beyond said stop position following removal 125 port 32.

of the input force thereby temporarily to in- The general consturction of the viave as- crease the vent opening through said valve. semblies comprising valve members 21 and In order that the present invention may be 28 is conventional and need not be described more clearly understoodand readily carried into in detail but it will be appreciated that pres effect, the same will be further described by 130 sure balancing for the valve members in the in 2 GB2193547A 2 lap positions is provided by small fluid pres- and 29 then acts in the manner of a relay sure passages 33 and 3.4 communicating with valve to supply air under pressure from port the respective fluid pressure output ports 30 31 to port 32. After the pressure accumulated and 34, the valve members being suitably bi- on the underside of piston 14 has attained a assed towards their respective inlet valve 70 balancing value the first double valve assembly seats 18 and 29 by light springs 35 and 36 moves into a lapping condition in relation to respectively. A common vent passage for the seat 23, accompanied by similar lapping both valve assemblies is provided through the of the further valve assembly. In the lapping centre of the assembly to communicate with a condition the respective double valve is in a common vent port 37 in the vent cap 4. 75 stable state with both its inlet and exhaust Clamped between the member part 1 and passages closed by the respective valve mem- the body part 2 there is provided a generally ber. The pressures at which the valve assem annular member 40 which carries, as illus- blies lap depend, of course, on the force ap trated in Fig. 2, four inward projections such plied via springs 12 and 13. Upon release as 41 which provide a step against which the 80 following a reduction of the brake pedal force, piston 14 rests in the unoperated or vented venting commences by virtue initially of up condition of the valve assemblies as shown. ward movement of piston 14. In the event of The member 40 is formed of a spring sheet a complete release of pedal force on plunger material such as phosphor-bronze the thick- 7 the piston 14 moves towards its stop posi ness of which is chosen together with the 85 tion against the projections 41 of member 40.

dimensions of projection 41 to provide appro- Under the influence of the pressure acting un priate resilience and thereby permit a pre- der piston 14, the projections 41 and there scribed amount of upward deflection of 14 fore the piston 14 are resiliently temporarily beyond a normal stop or rest position during upwardly deflected beyond the normal stop venting. 90 position. The venting clearance between the In use of the valve assembly, the ports 29 valve member 21 and the vent valve seat 23 and 31 are connected to separate charged is thus temporarily increased to reduce the re compressed air reservoirs of a vehicle braking striction which otherwise results from other system and the ports 30 and 32 are conconstraints imposed upon this clearance. After nected to separate brake circuits of the 95 release of the air pressure from the delivery vehicle. In the position shown the piston 14 port 30 via the upper valve, the downward rests in its stop position against the projec- force of resilience projections 41 is such as to tions 41 of the member 40 and the plunger 7 return the piston 14 to the stop position is located in relation thereto by its stop 17 shown. A prescribed clearance in thus re under the influence of spring 12. A prescribed 100 stored between valve member 21 and seat socket clearance is, therefore, established be- 23.

tween the socket 8 and the stud or other In an alternative embodiment of the present means (not shown) by which the plunger 7 is invention a precise upper stop may be pro operated by the brake pedal mechanism. Due vided for the plunger such as 7 of Fig. 1 to the action of return springs 39 and 19, 105 whereas the annular member such as 38 may exhaust valve seats 21 and 27 will be at a be ommitted leaving a clearance above piston rest position in which they are fixed distances 14 in its normal position. The position of the from the respective valve members 18 and upper stop for the plunger 7 is then so cho 28. The output ports 30 and 32 are thereby sen that a prescribed clearance between the vented through these clearances to atmos- 110 piston 14 and the first part of the body in Fig.

phere, via the vent port 27. Initially the piston 1 exists in the fully vented condition. During 12, therefore, rests in the position shown venting the piston 14 will then again be resili against projection 41. Upon operation of the ently delfectable from its stop position due to driver's brake pedal mechanism by more than the action of the air pressure being vented the socket clearancei the plunger 7 is moved 115 and the clearance between the first vlave downwards to exert a downward force via member 22 and its vent valve seat 23 will spring 12 and then 13 upon the piston 14 then again be temporarily increased as before.

which, after closing the valve member 18

Claims

against the vent valve seat 23, causes down- CLAIMS ward movement of

piston 24 to tend to close 120 1. A fluid pressure control valve assembly vent valve seat 27 against valve member 28. comprising a body housing a pressure respon Further downward movement results in un- sive member for operating a lappable double seating of the valve member 21 from inlet valve arrangement, alternatively displaceable valve seat 21 and unseating of valve member from a lap position for connecting an output 28 from inlet valve seat 29. Fluid pressure is 125 port to a supply port or a vent port, said then applied above the piston 24 from the pressure responsive member being subject on supply port 29, such pressure appearing at one side to fluid pressure at the output port the delivery port 30 and also urging piston 24 and acting in a sense to tend to vent said downwards. The piston 24 and the valve as- pressure and urge said member towards a sembly comprising member 28 and seats 27 130 normal stop position and being subject to an 3 GB2193547A 3 input force acting in an opposite sense to tend to connect the output port to the supply port and said member being resiliently deflec table beyond said normal stop position follow ing removal of the input force thereby tempo rarily to increase the vent opening through said valve.
2. A fluid pressure control valve assembly as claimed in claim 1 including a plunger and spring means via which said input force may be applied to said member and said plunger being provided with resiliently deflectable stop means.
3. A fluid pressure control valve assembly as claimed in claim 2 said housing including a first part and a second part within which the member is slideable and wherein said resili ence stop means comprises a resilient annular member retained between said first and sec ond parts and having an inwardly projection with which said member is engageable in the normal stop position thereof.
4. A fluid pressure control valve as claimed in claim 1 including a plunger and spring means via which said input force may be ap plied to said member said plunger having a stop and said member being deflectable be yond said normal stop position against the spring means temporarily to increase the vent opening through said valve.
5. A fluid pressure control valve substan- tially as described herein with reference to Fig.

1 of the accompanying drawing.

Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WC 1 R 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent 8115 3RD.

Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.