GB1601089A - Control valve assemblies for hydraulic braking systems - Google Patents

Description

(54) IMPROVEMENTS IN CONTROL VALVE ASSEMBLIES FOR HYDRAULIC BRAKING SYSTEMS (71) We, GIRLING LIMITED, a British Company of Kings Road, Tyseley, Birmingham 11, 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 invention relates to improvements in control valve assemblies for vehicle dual hydraulic braking systems of the kind commonly used on agricultural tractors and like vehicles in which separate brake-applying valves are operable independently or simultaneously to cause hydraulic fluid from a distributor chamber to be supplied to one or both of a pair of outlets respectively for connection to brakes or wheels on opposite sides of a vehicle.

The brake-applying valves can be operated simultaneously for retarding the vehicle or separately for steering.

In known control valve assemblies of the kind set forth the chamber is supplied with fluid from an inlet for connection to a pressure source, conveniently a pump, and difficulty is experienced in maintaining a brake-applying force upon failure of the source during a brake application.

According to our invention a control valve assembly of the kind set forth incorporates a pressure control valve operable to supply fluid under pressure to the distributor chamber from an inlet for connection to a pressure source, irrespective of whether one or both brake-applying valve are to be operated, a one-way valve located on the upstream side of the pressure control valve to prevent flow from the distributor chamber in a reverse direction, a back-up piston working in a bore in communication with the distributor chamber, and an exhaust valve which controls communication between the distributor chamber and an exhaust port for connection to a reservoir for fluid and which closes before the control valve can open, the exhaust valve comprising an exhaust valve member guided to slide in a bore in the back-up piston and providing communication between the distributor chamber and the exhaust port, through an opening surrounded by an annular seal which is engageable with a seating to isolate the distributor chamber from the exhaust port, and -the back-up piston acts to pressurise fluid in the distributor chamber after the exhaust valve has closed.

Thus in the event of failure of the pressure source, fluid trapped in the distributor chamber by one-way valve can be pressurised by the back-up piston to continue that brake application, after the exhaust valve has closed.

In one construction the brake-applying valves, the one-way valve, the pressure control valve and the exhaust valve are incorporated in a common housing having a longitudinal bore in which the back-up piston works and the brake-applying valve and the back-up piston are operated through a common mechanism which is conventiently actuated by one or both of a pair of pedals. The exhaust valve is adapted to be closed by the mechanism before the pressure control valve opens.

Conveniently, the seating is provided by a part of a valve member of which another part is engageable with a fixed seating to define the pressure control valve.

One embodiment of our invention is illustrated in the single Figure of the accompanying drawings, which is a longitudinal section through a control valve assembly for a vehicle dual hydraulic braking system.

The control valve assembly illustrated in the drawing comprises a housing 1 comprising an annular body part 2 which is clamped between a valve block 3 and a cup-shaped cylinder 4.

A pair of brake applying valves 5 and 6 are mounted in the valve block 3, and each valve 5, 6 comprises a spool 7 which works in a bore 8 and projects at its outer end from the block 3. Each spool 7 carries a radial seal 9 which seals with a portion of the bore on the axially outer side of a radial oudet passage 10 for connecting brakes on one side of the vehicle, and the spool 7 has an inner inclined end carrying a seal 11 for engagement with a seating 12 defined by a completmentary face at the inner end of the bore 8. The inner end of each spool 7 carries an axial extension 13 which projects into a distribution chamber 14, defined between the body part 2 and the block 3, through a passage 15 of a diameter greater than that of the extension 13. The free end of the extension 13 carries an enlarged head 16 forming a stop to limit movement of the spool 7 in an outward direction.

The body part 2 includes a radial inlet passage 17 which connects a bore 18 at the centre of the body part 2 with a union 19 for connection to a high pressure pump through a one-way valve 20 which is housed in the inner end of the union 19.

Communication between the inlet passage 17 and the distributor chamber 14 is controlled by a pressure control valve 21. The control valve 21 comprises a hollow plunger 22 which is guided to slide in the bore 18 and has an enlarged valve head 23 which is located in the chamber 14 and which is normally urged into a closed position in engagement with a complementary seating 24 in the body part 2 by means of a compression spring 61 in abutment with a step on an operating rod 36 to isolate the inlet passage 17, and in consequence the source from the chamber 14.

An annular back-up piston 26 of substantial diameter works in the cylindrical bore 27 of the cylinder 4 and movement of the piston 26 away from the body part 2 is limited by a radial stop face 28 in the housing. The bore 27 is in permanent communication with the distributor chamber 14 through at least one passage 55 in the body part 2.

A valve member 29 comprises with the hollow plunger 22 an exahust valve for controlling communication between the bore 27 and the distributor chamber 14, and an exhaust port 30 in the end wall of the cylinder 4 for connection to a reservoir for fluid for the pump. The valve member 29 has a central opening 58 round which is located an annular seal 57, which is held in position by a retainer 60. The end of the hollow plunger 22 remote from the head 23 forms a seating 56 for engagement with the seal 57 to cut-off communication between the bore 27 and the exhaust port 30. The valve member 29 slides in a central bore 31 in the piston 26, and is urged away from the seating 56 by a compression spring 35 in abutment with the body part 2.

The valve member 29 is mounted on one end of an operating rod 36 which extends through a bore 37 in the valve block 3, an axial clearance bore 38 in the valve plunger 22, and with a clearance 59 through the retainer 60. The rod 36 carries a seal 54 which works in the bore 38. The opposite outer end of the rod 36 is pivotally connected to substantially the mid-point in the length of a rocking lever 39 of which each opposite end is pivotally connected through a suitable linkage to one of a pair of pedals which can be operated separately or simultaneously conveniently by latching the pedals together. The inner face of the lever 39 adjacent to the valve block 3 is provided with arcuate abutment portions 40 and 41 which are normally urged inwardly into engagement with the outer ends of the spools 7 of the valve 5 and 6 to hold the valves in the closed position with the seals 11 engaging with the seatings 12. The abutments 40 and 41 are urged inwardly by the force in the spring 35 which is transmitted through the rod 36 and the force in a pair of opposed Belleville or like spring washers 42 acting between the valve member 29 and an abutment 43 at the free inner end of the rod 36.

In the inoperative position shown in which the brake applying valves 5 and 6, and the pressure control valve 21 are closed, the exhaust valve is open so that both the cylinder 27 and distributor chamber 14 are in communication with the reservoir through the exhaust port 30.

When the brakes on opposite sides of the vehicle are to be applied simultaneously for vehicle retardation, both pedals are operated simultaneously and the lever 39 is moved away from the valve block 3 with the rod 36 withdrawn therefrom initially to cause the seal 57 on the valve member 29 to engage with the seating 56 on the plunger 22. This closes the exhaust valve to isolate the cylinder 27 and the distributor chamber 14 from the exhaust port 30. Further movement of the rod 36 in the same direction advances the valve member 29 and the plunger 22 to urge the head 23 away from the seating 24. High pressure fluid is then admitted to the chamber 14 through the inlet passage 17. The fluid flows into the cylinder 27 through the passage 55 and also flows to the brakes through the outlet ports 10 after the pressure has moved the spools 7 away from the seatings 12. Further movement of the rod 36 causes the valve member 29 to engage with the piston 26 to advance it in the bore 27.

By providing a common chamber 14 the pressure supplied to both sets of brakes is equalised to prevent differential wear of the linings. When the brakes on the wheels on one side of the vehicle are to be applied for steering, say those supplied by the valve 6, only one pedal is operated. The rod 36 is still withdrawn to operate the exhaust valve and the control valve 21 as described above but with the lever 39 pivoting about its connection with the rod to urge the abutment 40 into engagement with the spool 7 of the valve 5 to maintain that valve closed and prevent the brakes on opposite sides of the vehicle from being applied.

The distributor chamber 14, and the cylinder 27 on both sides of the piston 26 are normally filled with fluid at atmospheric pressure in the inoperative position.

Since the one-way valve 20 prevents a reverse flow of fluid to the pump, should the pump fail, the brakes can still be applied by pressurisation at the valve of fluid trapped in the cylinder 27 after the exhaust valve has closed and further movement of the valve member 29 moves the piston 26 towards the body part 2. In such an event there is reverse flow of fluid through the passage 55.

WHAT WE CLAIM IS: 1. A control valve assembly of the kind set forth incorporating a pressure control valve operable to supply fluid under pressure to the distributor chamber from an inlet for connection to a pressure source, irrespective of whether one or both brake-applying valves are to be operated, a one-way valve located on the upstream side of the pressure control valve to prevent flow from the distributor chamber in a reverse direction, a back-up piston working in a bore in communication with the distributor chamber and an exhaust valve which controls communication between the distributor chamber and an exhaust port for connection to a reservoir for fluid and which closes before the control valve can open, the exhaust valve comprising an exhaust valve member guided to slide in a bore in the back-up piston and providing communication between the distributor chamber and the exhaust port through an opening sur rounded by an annular seal, which is engageable with a seating to isolate the distributor chamber from the exhaust port, and the back-up piston acts to pressurise fluid in the distributor chamber after the exhaust valve has closed.

2. A control valve assembly as claimed in claim 1, in which the brake-applying valves, the one-way valve, the pressure control valve and the exhaust valve are incorporated in a common housing having a longitudinal bore in which the back-up piston works.

3. A control valve assembly as claimed in claim 1 or claim 2, in which the brakeapplying valves and the back-up piston are operated through a common mechanism which is actuated by one or both of a pair of pedals.

4. A control valve assembly as claimed in claim 3, in which the exhaust valve is adapted to be closed by the mechanism before the pressure control valve opens.

5. A control valve assembfy as claimed in any preceding claim, in which the seating is provided by a part of a valve member of which another part is engageable with a fixed seating to define the pressure control valve.

6. A control valve assembly substantially as herein described with reference to and as illustrated in the accompanying drawing.

Reference has been directed in pursuance of Section 9, Subsection (1) of the Patents Act 1949, to Patent No. 1,483,069.

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

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. and the control valve 21 as described above but with the lever 39 pivoting about its connection with the rod to urge the abutment 40 into engagement with the spool 7 of the valve 5 to maintain that valve closed and prevent the brakes on opposite sides of the vehicle from being applied. The distributor chamber 14, and the cylinder 27 on both sides of the piston 26 are normally filled with fluid at atmospheric pressure in the inoperative position. Since the one-way valve 20 prevents a reverse flow of fluid to the pump, should the pump fail, the brakes can still be applied by pressurisation at the valve of fluid trapped in the cylinder 27 after the exhaust valve has closed and further movement of the valve member 29 moves the piston 26 towards the body part 2. In such an event there is reverse flow of fluid through the passage 55. WHAT WE CLAIM IS:

1. A control valve assembly of the kind set forth incorporating a pressure control valve operable to supply fluid under pressure to the distributor chamber from an inlet for connection to a pressure source, irrespective of whether one or both brake-applying valves are to be operated, a one-way valve located on the upstream side of the pressure control valve to prevent flow from the distributor chamber in a reverse direction, a back-up piston working in a bore in communication with the distributor chamber and an exhaust valve which controls communication between the distributor chamber and an exhaust port for connection to a reservoir for fluid and which closes before the control valve can open, the exhaust valve comprising an exhaust valve member guided to slide in a bore in the back-up piston and providing communication between the distributor chamber and the exhaust port through an opening sur rounded by an annular seal, which is engageable with a seating to isolate the distributor chamber from the exhaust port, and the back-up piston acts to pressurise fluid in the distributor chamber after the exhaust valve has closed.

2. A control valve assembly as claimed in claim 1, in which the brake-applying valves, the one-way valve, the pressure control valve and the exhaust valve are incorporated in a common housing having a longitudinal bore in which the back-up piston works.

3. A control valve assembly as claimed in claim 1 or claim 2, in which the brakeapplying valves and the back-up piston are operated through a common mechanism which is actuated by one or both of a pair of pedals.

4. A control valve assembly as claimed in claim 3, in which the exhaust valve is adapted to be closed by the mechanism before the pressure control valve opens.

5. A control valve assembfy as claimed in any preceding claim, in which the seating is provided by a part of a valve member of which another part is engageable with a fixed seating to define the pressure control valve.

6. A control valve assembly substantially as herein described with reference to and as illustrated in the accompanying drawing.

Reference has been directed in pursuance of Section 9, Subsection (1) of the Patents Act 1949, to Patent No. 1,483,069.