GB2243671A

GB2243671A - A pressure-limiting valve

Info

Publication number: GB2243671A
Application number: GB9108317A
Authority: GB
Inventors: Ulrich Muhr
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1990-04-20
Filing date: 1991-04-19
Publication date: 1991-11-06
Anticipated expiration: 2011-04-19
Also published as: ITMI910973A0; HU911308D0; DE4012576A1; GB2243671B; GB9108317D0; ITMI910973A1; HU207388B; IT1245715B; HUT57879A

Abstract

A safety valve (30), which is disposed in a hollow piston (22) of a pressure-limiting valve (10), has a valve closure member (31), which cooperates with a bore (32) in the base (27) of the hollow piston (22). The valve closure member is accommodated in a guide member (33), which forms discharge passages (43). The guide member (33) is provided with baffle surfaces (44), which restrict the cross section of the discharge passages (43) and are formed by webs. When the safety valve (30) becomes effective, pressure medium strikes the baffle surfaces (44) and generates a force which aids the lifting of the valve closure member (31) from the base (27) of the hollow piston (22). This enables the opening cross section of the safety valve (30) to be enlarged. The pressure-limiting valve can be used in compressed-air braking systems of motor vehicles. <IMAGE>

Description

If 11

-1DESCRIPTION

A PRESSURE-LIMITING VALVE The invention relates to a pressure-limiting valve for limiting the pressure of a fluid coming from a source and intended for a destination, and more particularly to a pressure-limiting valve provided with a safety valve.

In a commercially available pressure-limiting valve having a safety valve which is intended for use in a compressed-air braking system for a motor vehicle, the flow quantity is increased when the safety valve becomes operative. Attempts to increase the flow quantity by enlarging the bore in the base of the hollow piston failed because of mechanical faults in the safety valve.

The present invention resides in a pressurelimiting valve for limiting the fluid pressure supplied to a receiver from a source to a predeterimed level, comprising a hollow piston whose base is subjected to the pressure on the receiver side, and a safety valve which is disposed in the hollow piston and has a valve closure member which cooperates with a bore in the base of the hollow piston, a guide member which is longitudinally guided in the hollow piston and carries the valve closure member, and a closure spring which acts on the guide member on the side thereof remote from the base of the hollow piston, wherein discharge passages are provided along the guide member for the pressure medium, and the guide member is provided with baffle surfaces for the pressure medium, which restrict the cross section of the discharge passages.

This has the advantage that a considerable increase in the flow quantity through the safety valve is achieved by an opening stroke of the valve closure member which is increased with respect to the known valve, because, due to the baffle surfaces on the guide member, a force becomes effective which aids the raising of the valve closure member. At the same time, this solution is characterised by a relatively small outlay.

The invention is further described, by way of example, with reference to the accompanying drawings, in which:- Fig. 1 is a longitudinal section through a pressure-limiting valve having a safety valve, whose closure member is accommodated in a guide member having baffle surfaces for the pressure medium; Fig. 2 is a view of the guide member to a scale different to that in Fig 1; and i 1 Fig. 3 is a plan view of the guide member to a scale corresponding to that of Fig. 2.

A pressure-limiting valve 10 shown in Fig. 1 of the drawings has a housing 11 having two lateral threaded ports 12 and 13. A compressed-air line 14, leads to the port 12 from a source 15 which in the illustrated application of the invention, is an operating brake valve of a motor vehicle braking system (not shown). The threaded port 13 is connected to a compressed-air line 16, which leads to a receiver 17. which is a compressed-air cylinder of the braking system. The pressure-limiting valve 10, which is disposed between the source 15 and the receiver 17, limits the pressure, which is introduced by the source and intended for the receiver, to a predetermined level.

The housing 11 of the pressure-limiting valve 10 has a blind bore 21, which is closed off by a lid-20 of disc shape. A hollow piston 22 is longitudinally guided in the bore 21. The hollow piston 22 has a peripheral outer collar which forms a closure member 23 of the pressurelimiting valve 10. The closure member 23 cooperates with a sealing ring 24, which is accommodated in the housing 11. In the hollow piston 22, there is a sleeve 25, which is supported on the 1 hollow piston base 27 under the action of a compression spring 26. To adjust the maximum effective pressure derived from the source 17 and acting on the receiver 17, the initial stress in the compression spring 26 can be adjusted using an adjusting screw 28, which is guided in the housing 11.

When the arrangement is unpressurized, the hollow piston 22 of the pressure-limiting valve 10 takes up its position as shown, in which the passage between the closure member 23 and the sealing ring 24 is open. When the source 15 is activated, compressed air flows into the housing 11 of the pressure-limiting valve 10 and to the receiver 17. The pressure on the source side acts on the base 27 of the hollow piston 22 and moves the latter against the force of the compression spring 26 once the set limiting pressure has been reached. The closure member 23 of the hollow piston 22 then abuts the sealing ring 24 and prevents a further rise in pressure in the receiver 17.

When the pressure at the source 15 is reduced, compressed air flows from the port 13, under the sealing ring 24 and to the port 12, such that the force of the air on the base 27 of the hollow piston 22 is reduced and the latter is moved, due to the effect of the compression spring 26, into a position 1 in which it opens the pressure-limiting valve 10. The pressure in the receiver 17 can then be reduced through the open cross section between the closure member 23 of the hollow piston 22 and the sealing ring 24.

The pressure-limiting valve 10 is additionally provided with a safety valve 30, which is disposed in the hollow piston 22. This safety valve has a resilient rubber valve closure member 31, which cooperates with a bore 32 in the base 27 of the hollow piston 22. The valve closure member 31 is accommodated in a guide member 32. is longitudinally guided in the sleeve 25 against the force of a closure spring 34.

The guide member 33, which is shown to a larger scale in Figs. 2 and 3, has a hollow-cylindrical core 38 for accommodating the valve closure member 31. Four uniformly distributed, radially extending guide ribs 39 issue from the core 38. They extend from the end face 40 of the guide member 33 facing the base 27 of the hollow piston 22 for about half the length of the core 38. Webs 41 are disposed on the ends of the guide ribs 39 remote from the end face 40, and extend transversely to the longitudinal axis of the guide member 33. They are of a circular arc shape and This auide ember extend at a distance from the cylindrical core 38 of the guide member 33. The webs 41 form an annular disc 42, which is secured on the guide ribs 39.

The webs 41 have baffle surfaces 44 for compressed air, which restrict the cross section of discharge passages 43 extending between the cylindrical core 38 and the guide ribs 39 of the guide member 33 and of the sleeve 25. The compressed air strikes the baffle surfaces 44 when the safety valve 30 becomes effective due to an inadmissibly large pressure increase in the receiver 17, and the valve closure member 31 rising from the base 27 of the hollow piston 22 opens the bore 32. The compressed air striking the baffle surfaces 44 of the webs 41 on the guide member 33 causes a force which acts against the closure spring 34 and which increases the opening cross section between the valve closure member 31 and the bore 32 of the hollow piston base 27. As a re-sult of the relatively large flow quantity of the safety valve 30 which is achieved thereby. the inadmissibly high pressure in the receiver 17 is reduced very rapidly. The compressed air, which has flowed into" the hollow piston 22 by way of the safety valve 30, can escape through a vent 46 in the housing 11 of the pressure-limiting valve 10 to the atmosphere. Given 1 sufficient pressure reduction in the receiver 17, the valve closure member 31 of the safety valve 30 returns to its closed position.

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Claims

1. A pressure-limiting valve for limiting the fluid pressure supplied to a receiver from a source to a predetermined level, comprising a hollow piston whose base is subjected to the pressure on the receiver side, and a safety valve, which is disposed in the hollow piston and has a valve closure member which cooperates with a bore in the base of the hollow piston, a guide member which is longitudinally guided in the hollow piston and carries the valve closure member, and a closure spring which acts on the guide member on the side thereof remote from the base of the hollow piston, wherein discharge passages are provided along the guide member for the pressure medium, and the guide member is provided with baffle surfaces for the pressure medium, which restrict the cross section of the discharge passages.

2. A pressure-limiting valve as claimed in claim 1, in which the guide member has a cylindrical core and longitudinally extending guide ribs, between which webs are disposed which extend transversely to the longitudinal axis of the guide member.

3. A pressure-limiting valve as claimed in claim 2, in which the webs are of a circular are shape and extend around the guide member at a distance from the 4 1 -9cylindrical core thereof.

4. A pressure-limiting valve as claimed in claim 3, in which the webs.are formed by an annular disc, which is secured to the guide ribs.

5. A pressure limiting valve constructed and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.

Published 1991 at The Patent OffIce, Concept House, Cardiff Road, Newport. Gwent NP9 1RH. Further copies may be obtained from Sales Branch, Unit 6, Nine Mile Point. Cwmfelinfach, Cross Keys, Newport, NP I 7HZ. Printed by Multiplex techniques ltd, St Mary Cray, Kent.