A hydraulic system for applying brakes on opposite sides of a vehicle either independently or simultaneously

Claim 2

An hydraulic braking system for a vehicle in which brakes on wheels'on opposite sides of the vehicle can be applied independently for steering or simultaneously for retarding the progress of the vehicle by means of a single pedal-operated hydraulic master cylinder (1) for supplying hydraulic fluid to the brakes, and a selector valve assembly (2) for controlling the supply of fluid to the brakes on either side, or on both sides of the vehicle, characterised in that a brake-torque regulating means (20) is incorporated which operates in conjunction with the selector valve assembly (2) so that, for a given pedal force, an output torque from the brake on either side of the vehicle is greater when that brake is applied independently of the brake on the opposite side than when the brakes on both sides are applied simultaneously.

Claim 3

A braking system according to Claim 1, characterised in that the torque regulating means (20) acts to intensify the pressure applied to an applied brake when that brake is operated independently of the brake on the opposite side of the vehicle

Claim 4

A braking system according to Claim 1, characterised in that the effective area of an actuator (10, 12) is increased when the brake which it operates is applied independently of the brake on the opposite side of the vehicle.

Claim 5

A braking system according to any preceding claim, characterised in that the selector valve assembly (2) comprises a distribution chamber (4), a pair of normally open diverter valves (6, 7), each diverter valve (6, 7) controlling communication between the distribution chamber (4) and an outlet port (8, 9) for connection to a respective brake actuator (10, 12), and valve control means (31) for simultaneously closing either one of the diverter valves (6 or 7) and operating the torque regulating means (20).

Claim 6

A braking system according to Claim 4, characterised in that the torque regulating means comprises a double acting valve (20) which controls communication between the distribution chamber (4) of the selector valve assembly and a fluid port (21), and between said fluid port and a connection (23) to a reservoir (24) for the master cylinder (1).

Claim 7

A braking system according to Claim 5, characterised in that the double acting valve (20) is combined with the selector valve assembly (2) within. a common housing (3) and the valve control means comprises a lever (31) pivotally mounted for rocking movement about a pivot (32) in the housing, the double acting valve comprising a valve member (25) having a first valve head (27) for engagement with a first valve seating (29) between the distribution chamber (4) and the fluid port (21) and a second valve head (29a) for engagement with a second valve seating (30) between the fluid port (21) and the connection (23) to the reservoir (24), the valve member (25) being normally urged by a spring (30a) into a first position in which the second valve head (29a) engages with the second valve seating (30) and the first valve head (27) is spaced from the first valve seating (29) and movement of the lever (31) about the pivot (32) in one direction being operative to close a corresponding one of the diverter valves (6 or 7) and at the same time to urge the valve member (25) of the double acting valve into a second position in which the first valve head (27) engages with the first valve seating (29) and the second valve head (29a) is spaced from the second valve seating (30).

Claim 8

A braking system according to Claim 5 or Claim 6, as appended to Claim 3, characterised in that the fluid port of the double acting valve comprises an outlet port (21) which is connected to the brake actuators (10, 12) on both sides of the vehicle through a common connection (22), each actuator (10, 12) comprising a housing (35), a stepped bore (36) in the housing and a differential piston (37) for applying the brake.

Claim 9

A braking system according to Claim 5 or Claim 6, as appended to Claim 3, characterised in that the fluid port (21) of the double acting valve comprises an inlet port (21) which is connected to a pressure intensifier (1) comprising primary and secondary pressure spaces (40 and 41 respectively) in a housing and a differential piston (42) working in a stepped bore (43) in the housing, the primary pressure space (40) being defined between corresponding portions of the piston (42) and the bore (43) which are of different areas and being connected to the fluid port (21) of the double acting valve, and the secondary pressure space (41) being defined between the end of the piston (42) which is of smaller area and the closed end of the bore (43) and being connected to the distribution chamber (4) of the selector valve assembly.

Claim 10

A braking system according to Claim 8, characterised in that the pedal-operated hydraulic master cylinder (1) constitutes the pressure intensifier.

Claim 11

A braking system according to Claim 5 or Claim 6, characterised in that a pressure intensifying valve (50) is interposed between the master cylinder (1) and the distribution chamber (4) of the selector valve assembly and the fluid port (21) of the double acting valve, the pressure intensifying valve (50) comprising a differential piston (51) working in a stepped bore (52) in a housing (53), an annular chamber (57) defined between corresponding portions of the piston and the bore which are of different areas, a pressure space (58) defined between the end of the piston which is of smaller area and the adjacent end of the bore, and a one-way valve (55), the annular chamber (57) being connected to the fluid port (21), the pressure space (59) being connected to the distribution chamber (4), and the one-way valve (55) allowing communication between the said pressure space (58) and the end of the piston (51) of greater area which is connected to the master cylinder (1).