GB1573199A

GB1573199A - Fluid pressure control valve

Info

Publication number: GB1573199A
Application number: GB5424476A
Authority: GB
Original assignee: Wabco Westinghouse SA
Current assignee: Wabco Westinghouse SA
Priority date: 1975-12-30
Filing date: 1976-12-29
Publication date: 1980-08-20
Also published as: IT1072303B; FR2384662A1; FR2384662B1; BE849932A; DE2658206A1

Description

(54) FLUID PRESSURE CONTROL VALVE (71) We, WABCO WESTINGHOUSE, a French Corporation of 2, Boulevard Westinghouse, 93270 Sevran, France, do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This inventon relates to a fluid pressure control valve and relates especially but not exclusively to a pressure control valve for fluid operable brake systems for motor vehicles.

According to the present invention there is provided a fluid pressure control valve including a body, a fluid pressure input port and a fluid pressure output port, a manually operable control member acting against one side of a resilient double piston arrangement, the other side of which acts to operate a self-lapping valve controlling connection between the output port and the input port or an exhaust port the pressure of the output port acting on both sides of the double piston arrangement the lapping of the arrangement being permitted by the resilience of the double piston arrangement.

A "resilient double piston arrangement" comprises one piston slidable within another and containing means whereby forces are resiliently transmissible between one piston and the other.

The invention further optionally provides such a control valve provided with an additional cut-off valve to enable a cutting off of the output from the control valve to brake actuators at a predetermined position of the control member.

The invention further optionally provides a tractor vehicle braking system employing a control valve provided with a said additional cut-off valve to operate tractor vehicle spring brakes and to provide an inverse control pressure input to a relay valve for supplying a tractor service brake line.

The invention further optionally provides such a control valve provided with two additional cut-off valves, arranged to be operable respectively upon movements in opposite directions of the control member away from a predetermined position.

The invention further optionally provides a vehicle braking system provided with a control valve having said two additional cut-off valves one said cut-off valve being connected to cut off an over-riding supply of hold off pressure to vehicle main spring brakes but to remove said supply upon movement of the control member in one direction to cause the control valve to gradually apply the spring brakes and the other said cut-off valve being connected to connect a source of fluid control pressure to brake cylinders of the vehicle for a hold brake application upon movement of the control member in a direction opposite to said one direction.

In order that the invention may be more clearly understood and readily carried into effect, the same will be further described by way of example with reference to the accompanying drawings in which: Fig. 1 is a diagrammatical representation of a spring brake control valve employing the invention, Fig. 2 illustrates a modification of such a valve to include an additional cut-off valve, Figs. 3 and 4 illustrate vehicle braking systems employing a control valve according to the invention, Figs. 5a and b illustrate valve gates and pressure curves for the system of Fig. 3 and Figs. 6a and 6b illustrate a gate and pressure curves for the system of Fig. 4.

Referring to Fig. 1 the control valve comprises a main body 1 and a manually operable control lever 2 pivotally movable between two positions A and B. The control member 2 is attached to a cam 3 operable to position a projection 4 separated from a spring R2 by a resilient double piston arrangement 5. A further resilient spring R1 is contained within the double piston arrangement to provide the resiliency thereof and this is adjustable by means of an internal screw within the stem 5b of the inner piston. The stem 5b is slidable within the housing and itself forms part of a self-lapping valve which seats on a surface J3 of a movable member 6a to close off the exhaust passage via a bore C4 communicating with a vent port 6.The member 6a is resiliently urged by a spring R3 against a further seat at an annular seating region J4 outside the surface 53 referred to above.

In operation of the arrangement, the valve has a supply port 12 for connection to a reservoir denoted by reference 13 and an output port 10 for connection to utilisation means such as a spring brake actuator denoted by reference 11. The output port 10 communicates with a region C2 underneath the resilient double piston arrangement and the region C2 communicates via a passage 20 with a region C3 above the double piston arrangement which is sealed off from atmosphere by virtue of an annular seal ii. Furthermore, the inner piston is sealingly slidable by virtue of an annular seal 52 within the outer piston arrangement 5a and therefore the region C5 within the resilient double piston arrangement communicates with atmosphere via a passage 32 as shown.A projection 21 is slidable in a groove 30 to provide relative location against rotation of the two pistons one within another.

In operation of the control valve, the man ually operable handle 2 is effective to rotate the cam 3 and thereby depress the resilient double piston arrangement to close off the exhaust passage C4. Further such movement unseats the member 6a at 54 to provide a path from the input port 12 to the chamber C2 and to the output port 10. When the pressure in the port 10 reaches a value dependent upon the movement of the cam, the resilient double piston spring Ri allows the double piston to compress to permit the valve to lap off at a specific controlled pressure. On return of the handle or on subsequent increase of pressure at 10, the inner piston moves upwards slightly to unseat the valve at J3 and allow exhausting of air from the chamber C2 until the control lever of pressure is regained.

Although not shown, the handle 2 is assumed to be provided with a torque spring which tends to return the handle from the position A to the position B and means may be provided to lock the lever 2 in position A if required. Assuming that the control valve is arranged as an emergency or secondary brake control valve on a vehicle fitted with fluid pressure operable spring brakes, the reservoir 13 is assumed charged and the lever 2 is held in the position B corresponding to the normal road operating position. In this position, it will be understood from the foregoing that the spring brakes are connected through the valve to the reservoir 13 to hold them in the fully released position.The pressure from reservoir 13 acts against the double piston arrangement in an upward direction and this in fact is applied to the portion 5b over an area which corresponds to the difference between the surface areas enclosed by the seals J2 and 53. At the same time, a downward thrust is exerted on part Sa which is proportional to the area enclosed by the seal 52 less the area enclosed by the seal J1. The result of this is that the resilient double piston arrangement is so balanced as to be able to operate at quite high pressures whilst nevertheless presenting minimal reaction via the lever 2 despite the presence of a substantial spring R1.

When the vehicle driver wishes to apply a secondary or emergency brake, he moves the lever 2 to a position possibly intermediate between B and A and the force which the driver has to exert is largely independent of the fluid pressure in the system and is predominantly dependent only on the compression of springs R1 and R2 and the handle torque spring which always acts towards the position B.

Whilst the brake control valve is shown with an axis which is transverse to the general axis vertical of the valve assembly, it will be appreciated that the cam 3 could be arranged so that the movement of the handle would be in a generally horizontal plane.

From the foregoing, it will also be appreciated that the valve assembly may be readily dismantlable by access from the lower side after removal of a lower assembly including the spring R3 and the sliding member 6a.

In the description, whilst specific reference is made to a so-called manually controlled valve, it is to be understood that the term manually i to be taken in a broad sense in that the invention can also be applied to a foot operated control valve.

Referring to Fig. 2, this shows a control valve assembly which, apart from the cam profile, is generally similar to that of Fig. 1 with the main distinguishing feature being that an additional cut-off valve arrangement.

denoted generally by reference 31 is provided on the side of the assembly. The modified arrangement as shown in Fig. 2 is intended for use in a tractor vehicle braking system for a tractor and trailer combination in which it is required to be able to establish that after release of the trailer brakes when parking, a demonstrated full operation of the tractor spring brakes can be demonstrated.

Reference to the operation of the modified valve of Fig. 2 can best be taken with a discussion of the system illustrated diagrammatically in Fig. 3 and with reference also to Figs.

5a, 5b.

Referring to Fig. 3 the secondary braking circuit for an articulated tractor/trailor arrangement contains a manual control valve, the construction of which is as referred to above with reference to Fig. 2. This is provided with a reservoir 32 chargeable in the normal way from the vehicle compression air supply and the control valve provides by means of a manual control portion VP a pressure for application to a line x connected to the inverse port of a + + - trailer relay valve 4 which controls the supply of pressure to a trailer brake control line for coupling at 35 to the braking circuit on the trailer which is not shown.The same outlet 36 as provides the supply to the control port 33 of the multi-circuit relay valve 34, is also connected to a so-called cut-off valve Vi. This is a two position valve, is provided with three ports and is operable in a movement of the control handle of the main valve away from a position B to interrupt connection between the main valve and spring brakes 39 of the vehicle. In order to achieve this, as shown in Fig.

3, the cut-off valve 31 is actuable in a certain position of the handle by a push rod denoted generally by the.reference 37. It will be seen moreover that the modified control valve of Fig. 2 is provived with dual cam profiles 3a and 3b. In the position B, these profiles lie to either side of the operating plunger 4 and the effect of movement from position A through position B to position C is illustrated by the curves of Fig. Sb corresponding to the pressures on the lines x andy of Fig. 3 when the main control handle is moved through positions A, B and C of a gate arrangement such as shown in Fig. 5a.Thus movement from fully released position A wherein full reservoir pressure is applied to the spring brakes and zero pressure is applied to the trailer line coupling 35 via multi-relay valve 34, graduable application of the tractor spring brakes 39 and the trailer brakes is effected by a reduction of the pressure in line x towards the position B in which the brakes are fully applied. In order to test the validity of the tractor spring brakes, the driver can then move the handle further towards position C resulting in a recovery of pressure on the line x to release the trailer brakes but owing to the operation of the cut-off valve, the line y remains vented thereby demonstrating the tractor spring brakes independently of any trailer brakes.

A further modification of the valve of Fig.

1 is illustrated by way of the system exemplified by Fig. 4 and the gate illustration and pressure curve illustrations of Figs. 6a and 6b respectively.

For the purposes of understanding Fig. 4, it is to be assumed that the valve of Fig. 1 is modified similarly to Fig. 2 but with the addition of a further cut-off valve operable on movement of the handle in the opposite direction towards position A. In this modified arrangement, the cam profile is assumed to be a profile somewhat similar to that of Fig. 1 but such as to produce a steady pressure to the spring brakes on the line x ' on movement from a position G through a position H and to then graduably reduce the spring brake pressure to a position I of the gate of Fig. 6a.The two cut-off valves operate on movement respectively in one direction or the other from the position H the cut-off valve Vil is included between a reservoir 44 which is extra to the main supply reservoir 41 of the control valve VP and supplies a double check valve 43 which permits whichever is the greater of the pressures x' and y' to be applied to the vehicle spring brakes. In this case, the vehicle is assumed to be a bus which is required to make frequent short stops and the normal pressure operable actuators of the front brakes are denoted by reference 47 being fed from the main supply reservoir 41 for the secondary brake valve VP via the second cut-off valve Vi2. This feed is via one side of a double check valve the other side of which is fed from a service circuit.

In operation of the system of Fig. 4, the gate arrangement of Fig. 6a has a so-called hold position G, a position H which is the normal road running position and a position I for parking. In the position H, the spring brake cylinders 42 of the bus are fed from the line y wherein the pressure is considerably greater than the pressure in the line x as shown in Fig. 6b . As soon as the driver moves the control valve handle from H towards I, the valve Vil changes over and connects the line y directly to atmosphere. Beyond a certain angle of rotation of the handle, the pressure in the line x progressively reduces as a function of the angle of rotation to produce a variable emergency or secondary braking effect.In the eventual position I, the spring operated brake cylinders 42 no longer receive pressure and assuming that no service brake application is being made, the vehicle is parked purely by mechanical means, namely the spring brakes 42. In the position G, the full pressure of the reservoir 44 is applied via the cut-off valve Vil to the spring brakes 42 in order to fully release them but the cut-off valve Vi2 is opened by the mechanical linkage denoted by reference 50 in Fig. 4 to apply fluid pressure via the check valve 48 to the front service brake actuators 47 of the vehicle. This corresponds to the pressure on the line z indicated in Fig. 4 and Fig. 6b.Accordingly, after making a normal service application to stop the vehicle, the driver can provide a temporary hold of the vehicle by moving the handle through a small angle from H to G thereby applying air pressure to the front service brakes for a tempor ary stop to permit boarding or alighting of passengers, for example. The consumption of air for this purpose can be appreciably less than required for full secondary (or emergency) operation of the spring brakes for temporary stops.

WHAT WE CLAIM IS: 1. A fluid pressure control valve including a body, a fluid pressure input port and a fluid pressure output port, a manually operable control member acting against one side of a resilient double piston arrangement, the other side of which acts to operate a selflapping valve controlling connection between the output port and the input port or an exhaust port the pressure of the ouput port acting on both sides of the double piston arrangement the lapping of the arrangement being permitted by the resilience of the double piston arrangement.

2. A fluid pressure control valve as claimed in Claim 1, wherein the double piston comprises one piston sealingly slidable within the other and the volume between said pistons being provided with a passage to atmosphere.

3. A fluid pressure control valve as claimed in Claim 1 or 2 the double piston arrangement being provided with a screw adjustment means whereby resilient means between them is adjustable.

4. A fluid pressure control valve as claimed in Claims 1, 2 or 3 the manually operable control member comprising a cam profile affording mechanical coupling with the double piston via means sealingly slidable in the body.

5. A fluid pressure control valve as claimed in Claims 1, 2, 3 or 4 having a cut-off valve in a path between the double piston and the output port operable in a certain position of the manually operable control means to close off said path and vent the output port.

6. A fluid pressure control valve substantially as described herein with reference to Fig. 1 of the accompanying drawings.

7. A tractor vehicle fluid pressure operable braking system employing a control valve as claimed in Claim 5 or 6, being connected to enable operation of tractor vehicle spring brakes and to provide an inverse control pressure input to a relay valve for supplying a trailer service brake line.

8. A fluid pressure control valve as claimed in Claim 1, 2, 3 or 4 provided with two additional cut-off valves, arranged to be operable respectively upon movements in opposite directions of the control member away from a predetermined position.

9. A vehicle fluid pressure operable braking system having a control valve as claimed in Claim 1 2, 3, or 4 and said control valve having two additional cut-off valves arranged to be operable respectively upon movements in opposite directions of the control member away from a predetermined position, one said cut-off valve being connected to cut off an over-riding supply of hold off pressure to vehicle main spring brakes but to remove said supply upon movement of the control member in one direction to cause the control valve to graduably apply the spring brakes and the other said cut-off valve being connected to connect a source of fluid pressure to brake cylinders of the vehicle for a hold brake application upon movement of the control member in a direction opposite to said one direction.

10. A fluid pressure control valve substantially described herein with reference to Fig. 2 of the accompanying drawings.

11. A fluid pressure operable braking system substantially as described herein with reference to Fig. 3 employing a valve as claimed in any of Claims 1-7.

12. A fluid pressure operable braking system as described herein with reference to Fig. 4 and employing a valve as claimed in any of Claims 1-6. ~ ~ ~~

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. ary stop to permit boarding or alighting of passengers, for example. The consumption of air for this purpose can be appreciably less than required for full secondary (or emergency) operation of the spring brakes for temporary stops. WHAT WE CLAIM IS:

1. A fluid pressure control valve including a body, a fluid pressure input port and a fluid pressure output port, a manually operable control member acting against one side of a resilient double piston arrangement, the other side of which acts to operate a selflapping valve controlling connection between the output port and the input port or an exhaust port the pressure of the ouput port acting on both sides of the double piston arrangement the lapping of the arrangement being permitted by the resilience of the double piston arrangement.