GB2027174A - Multi-circuit vehicle brake safety valve assembly - Google Patents

Abstract

The assembly comprises a housing including a plurality of overflow valves 1, 2, 3, 4, each overflow valve having a movable valve body 10, the effective area of which is sub-divided into areas 18, 19 by the corresponding valve seat 13 so that it can be opened by fluid pressure on the inner or outer sides of the valve seat, at least one of the overflow valves being associated with a stop valve 26 which is upstream of said one overflow valve and follows the movement of the associated overflow valve to limit the maximum pressure admitted to a reservoir 31 connected to the outlet of the associated valve. The overflow and stop valves may be formed by a single member (Fig. 4, not shown). <IMAGE>

Description

SPECIFICATION Multi-circuit vehicle brake safety valve The invention relates to a multi-circuit safety valve assembly for a brake arrangement of a motor vehicle of the type comprising overflow valves each of which is provided with a movable valve body the effective area of which, acted on by fluid pressure, is sub-divided by the corresponding valve seat, so that it can be operated by fluid pressures on the inner or outer sides of the valve seat.

Multi-circuit safety valve assemblies of this type are widely known (German Auslegeschrift 2,143,733). In order to have available pressures of different magnitudes in the individual circuits of a dual-line and dual-circuit brake arrangement for motor vehicles, it is also known from German Offenlegungsschrift 2,452,188 to connect together a brake arrangement composed of a multi-circuit safety valve assembly separate pressure-relief valves plus air reservoirs. The outlets of the first two circuits of the multi-circuit safety valve assemblies are each connected to a compressed air reservoir from each of which a line returns to the multi-circuit safety valve assembly, a pressurerelief valve being arranged in each line. In this way a third circuit controlled by the multi-circuit safety valve assembly is supplied with a lower pressure.

The constructional expenditure of this arrangement is considerable. It is not possible to achieve a reduction in pressure in the first two circuits of the multi-circuit safety valve assembly with the known system.

According to the invention, there is provided a multi-circuit safety valve assembly for the brake arrangement of a motor vehicle, the assembly comprising a housing including a plurality of overflow valves, each overflow valve having a movable valve body, the effective area of which is sub-divided by the corresponding valve seat so that it can be opened by fluid pressure on the inner or outer sides of the valve seat, at least one of the overflow valves being associated with a stop valve to define a pressure relief valve, the stop valve being upstream of said one overflow valve, the effective area of the movable valve body of said one overflow valve being effective also to operate the stop valve. With this arrangement there is great constructional freedom in the selection of the individual pressure stages.For example, the pressure-relief valve can be arranged in the area of the inlet which is fed from a source of compressed gas, for example after the compressed gas has been stored in a high-pressure air reservoir. It is also possible to connect secondary users which can be connected as an unprotected circuit. The invention is based on the concept of integrating the pressure-relief valve into the multi-circuit safety valve. In a further development, the stroke of the valve body of the overflow valve is then utilised to actuate a closing element of the stop valve. This provides the stroke of the overlfow valve, apart from its opening phase, with meaningful significance within the multi-circuit safety valve. In addition, the further advantage is obtained that no stop is needed for limiting the stroke of the valve body of the overflow valve in the opening phase.Every time the pressure is used in the connected circuit the valve body of the overflow valve is moved.

The stop valve can be provided with a drawn-in housing rim and a resiliently supported closure member, either the valve body of the overflow valve of the closure member of the stop valve being provided with an extension which in the opening position of the stop valve abuts the respective other part. It is also possible that the closure member of the stop valve is connected to the valve body of the overflow valve so that a spring for the resilient support of the valve body of the stop valve can be omitted.

In order to form a variable throttle, the extension can be provided with a cross-section which varies over its length.

In another group of embodiments the valve body of the overflow valve simultaneously forms the closure member of the stop valve. In this way both valves, that is the stop valve and the overflow valve, are united structurally to a very large extent.

The valve body of the overflow valve can be provided with a cavity into which a hollow tubular stub projects which accommodates the incident flow, the stop valve being formed between a seal arranged in the cavity and the stub. This represents a structurally simple variant In this arrangement the seal of the stop valve can be constructed as an overflow collar if for purposes of pressure equalisation a return flow between the individual reservoirs is required.

Between the stop valve and the overflow valve a line connection for a dircuit not protected by an overflow valve can be provided.

Reference is now made to the accompanying drawings wherein:-- Figure 1 is a diagrammatic sectional view through a first embodiment of a multi-circuit safety valve assembly according to the invention; Figure 2 is a diagrammatic sectional view through a second embodiment of a multi-circuit safety valve assembly according to the invention; Figure 3 is a diagrammatic sectional view through a third embodiment of a rnulti-circuit safety valve according to the invention; Figure 4 is a detail of an overflow valve with an integrated pressure-relief valve; and Figure 5 is a section through a fourth embodiment of a multi-circuit safety valve assembly according to the invention.

The muiti-circuit safety valve assembly shown in Figure 1 has a housing 5 in which overflow valves 1 , 2, 3 and 4 are arranged. The housing 5 has an inlet connection 6 connected to a line 7 which comes from a compressor 8 via a pressure regulator 9 and supplies compressed air to the valve assembly.

The overflow valves 1 and 2 have no pressurerelief feature. Each has a valve body 10 slidably and sealingly guided in the housing and acted on by a spring 1 the force of which can be adjusted.

At the inlet side, the valve body 10 has an extension 12 which extends with play through a throttle plate 1 3. The throttle plate 1 3 is interposed between a housing rim 1 4 and a seat 15 provided on the valve body 10, the housing rim 14 and the seat 15 having the same internal diameter so that there is the air pressures on opposite sides of the throttle plate 13 are balanced. A spring 1 6 is interposed between the throttle plate 13 and the valve body 10. In this manner two gate valves 13, 15 and 13, 14 are formed.Between the extension 12 and the throttle plate 13 a throttle 1 7 is formed which, in the example of the overflow valve 2 has a constant throttle, and in the example of valve 1 has a variable throttle by virtue of the extension 1 2 having a cross-section varying over its length. The seat 15 causes the effective area of the valve body 10 of each overflow valve to be- sub-divided into area 1 8 which is loaded on the side of the incident flow, and an annular area 19 loaded on the exit side. On the exit side of the overflow valves 1 and 2 connections 20 are provided from which a line 21 leads to the compressed air reservoirs 22 of the first and second circuits I and II. From each reservoir a line 23 leads back to the housing 5 of the multi-circuit safety valve assembly and, via a check valve, 24 into a common flow chamber 25.

The external lines 21 and 23 shown can also be arranged in the housing 5, however, between the secondary circuits Ill; IV and the primary circuits I; II.

The flow chamber 25 is connected to the two overflow valves 3 and 4 each of which is constructed as an integrated pressure-relief valve.

The construction of the overflow valves 3 and 4 is similar to that of the overflow valves 1 and 2 so that here the identical reference designations are used. In addition, a closure member 26 is provided, however, which is arranged either directiy on the extention 12 or connected to this as shown with relation to overflow valve 3, or consists of a separate closing body 26 which is supported via a spring 27 and is held merely to rest against the extension 1 2 as shown in relation to overflow valve 4.In each case the closure member 26 co-operates with a drawn-in housing rim 28, thus forming stop valves 26, 28. The fluidpressure area 18 of the valve body 1 O of each overflow valve 3 and 4 simultaneously represent the fluid-pressure areas of the stop valve 11, 18, 26, 28. The springs 11, also simultaneously form a component of the overflow valves 3, 4 and of the stop valves.

On the overflow valves 3 and 4, also, the exit side is provided with the connections 29 from each of which a line 30 leads to compressed air reservoirs 31 which are associated with the two circuits Ill and IV. Between the stop valves 26, 28 and the overflow valves 3 and 4, respectively, lines 32 branch off to line connections 33 which can be associated with the circuits V and VI. In this arrangement these circuits V and VI are not directly protected by an overflow valve. According to Figure 1, of course, the circuits V, VI are associated with protection by these two overflow valves 1 and 2 preceding them. These circuits V and VI, however, do not posses their own overflow valves.

The operation of the multi-circuit safety valve assembly according to Figure 1 is as follows. Let the compressor 8 be adapted for a high pressure of, for example, 10 bars. The force of the springs 11 is set to adjust the overflow valves 1 and 2 to this high pressure. If compressed air is supplied from the compressor 8 to the multi-circuit safety valve assembly, the overflow valves 1 and 2 will open when the set pressure has been reached. The amount of compressed air, depending on engine revolutions, determines which of the gate valves will open. With a low rate of air flow, air will flow through the throttle 17 with the gate valve 13, 1 5 opening and gate valve 13, 14 remaining closed.

The reservoirs 22 are filled up correspondingly. If there is a high flow rate of compressed air which is supplied for a period, for example at a high speed of the compressor 8, the gate valve 13, 14 will open while the gate valve 13, 1 5 will remain closed initially. The gate valve 13, 14 will close only in the course of the filling process of the reservoirs 22 and of the remaining system components following it, while the gate valve 13, 1 5 will open. When the reservoirs 22 are filled up the overflow valves 1 and 2 will remain open.

During this filling process compressed air also already flows through the two lines 23 and the two check valves 24 into the flow chamber 25 and there, when the opening pressure of the overflow valves 3 and 4 has been reached, via the open stop valves 26, 28 via the lines 30 into the reservoirs 31 of the circuits Ill and IV. In this arrangement the force of the springs 11 of the overflow valves 3 and 4 can be set in such a manner that the overflow valves 3 and 4 represent an opening pressure of approximately 6 bars and simultaneously a limit pressure of approximately 7.5 bars for the two circuits Ill and IV. Thus here the gate valves 13, 1 5 and 13, 1 4, respectively, will also open in dependence on flow, but with an opening pressure of approximately 6 bars.On the other hand, the compression of the springs 11 of the overflow valves 3 and 4 increases their force so that the stop valves 26, 28 will close at approximately 7.5 bars, whereby this pressure is not exceeded in the reservoirs 31. The circuits V and Vl, also, can also be provided at the most with a pressure corresponding to that in the reservoirs 31, for example 7.5 bars.

In the illustrative embodiment of Figure 2 a multi-circuit safety valve assembly is represented which initially has two overflow valves 1 and 2 associated with the circuits I and 11, the construction being analogous to that according to Figure 1. Here, also, an overflow valve 3 is provided which has a valve body 10 with only a single gate valve 14, 1 5, i.e., the throttle plate 1 3 is missing. The extensions 12 is here arranged on the closure member 26. In addition, the closure member 26 is provided with a drilling 34 so that in the space containing the spring 27 the same pressure exists as in the flow chamber 25.

The operation of the embodiment of the multicircuit safety valve assembly of Figure 2 is analogous to that according to Figure 1.

In the embodiment of the multi-circuit safety valve assembly according to Figure 3 again four overflow valves 1, 2, 3, and 4 are provided which are associated with the individual circuits l,.ll, Ill and IV. There is pressure limiting in each of these circuits, i.e., each overflow valve 1; 2; 3; 4 is an integrated pressure-relief valve. In addition, a high-pressure reservoir 35 is arranged in the line 7, that is it precedes the multi-circuit safety valve assembly. From the line 7 also a line 36 can lead to a secondary user while is, therefore, operated at an even higher pressure than that corresponding to the circuits I to IV.The overflow vavles 1 and 2 are constructed in such a manner that a separate stop for limiting the opening stroke of the valve body 10 can be omitted on the housing side since the associated closure member 26 of the stop valves 26, 28 simultaneously take over the function of this stop.

Figure 3 shows a single overflow valve, for example, the overflow valve 3, with integrated pressure limiting. In principle, the overflow valve can be arranged at any place in the multi-circuit safety valve, i.e., associated with any circuit. Here, also, the overflow valve is provided with a valve body 10 supported by a spring 11. In order to limit the stroke of the valve body 10, a stop 37 is provided. The valve body 10 has a cavity 38 into which a stub 39, having a peripheral valve seat, projects. Through the stub 39 a passage 40 passes admitting free flow to the overflow valve.

In the cavity 38 a seal 41 is arranged surrounding the stub for engagement with the seat on the stub.

In this arrangement there is a particularly close integration between the overflow valve and the stop valve. The valve body 10 of the overflow valve also forms the closure member 26 of the stop valve.

The embodiment of the multi-circuit safety valve according to Figure 5 is designed for three circuits if the high-pressure reservoir 35 preceding it is not counted separately. In this arrangement overflow valves 1,2 and 3 are provided. Onlv the overflow valve 1 is an integrated pressure-relief valve, the closure body 26 being arranged in the housing 5 in such a manner that the pressure limiting affects all three overflow valves 1,2 and 3 and the circuits connected to them.

Claims (10)

1. A multi-circuit safety valve assembly for the brake arrangement of a motor vehicle, the assembly comprising a housing including a plurality of overflow valves, each overflow valve having a movable valve body, the effective area of.

which is sub-divided by the corresponding valve seat so that it can be opened by fluid pressure on the inner or outer sides of the valve seat, at least one of the overflow valves being associated with a stop valve to define a pressure relief valve, the stop valve being upstream of said one overflow valve, the effective area of the movable valve body of said one overflow valve being effective also to operate the stop valve.

2. A safety valve assembly according to claim 1 wherein the stop valve has a valve seat enclosing an area smaller than said effective area and a valve closure member which is resiliently urged to the closed position and is opened by an extension of said valve body acting on said valve closure member, or by an extension of said valve closure member being acted on by said valve body.

3. A safety valve assembly according to claim 2, wherein said extension varies in cross-section and extends through a gap to define a variable throttle.

4. A safety valve assembly according to claim 1 wherein said valve closure member is secured to said valve body.

5. A safety valve assembly according to claim 4 wherein said valve body has a cavity into which a projection extends, the projection incorporating an inlet passage for fluid, the stop valve being defined' by a seat on the periphery of the projection and a seal on the valve body within said cavity, or by a seat on the valve body within a said cavity and a seal on the periphery of the projection.

6. A safety valve assembly according to claim 5, wherein the seal is a collar around the projection and mounted on the valve body.

7. A safety valve assembly according to any preceding claim, wherein a passage communicates with the pressure relief valve between the stop valve seat and the overflow valve seat, the passage communicating with a fluid line, which is not protected by an overflow valve.

8. A multi-circuit safety valve assembly constructed substanttally as herein described with reference to Figure 1; figure 2 or Figure 3 of the accompanying drawings.

9. A multi-circuit safety valve assembly constructed substantially as herein described with reference to Figure 4 of the accompanying drawings.

10. A multi-circuit safety valve assembly constructed substantially as herein described with reference to Figure 5 of the accompanying drawings.