Abstract: An hydraulic anti-skid system incorporates a pump having a piston assembly. The piston assembly comprises a pump plunger which is reciprocable in a bore of a drive mechanism, a signal piston coupled to the pump plunger, and a spring for urging the pump plunger out of engagement with the drive mechanism. The signal piston has a first area which is exposed to the pressure from a master cylinder or the brake when the brake is applied to urge the signal piston in a direction such that the pump plunger can engage with the drive mechanism. A dump valve is provided for controlling fluid in a stop chamber to which the piston assembly is exposed at least after the brake has been applied.

Abstract: A flywheel mechanism incorporates a pivotally-mounted lever for operating a pressure control valve when relative angular movement between a thrust member and a flywheel rotatable with a shaft attains a predetermined value. The lever is urged in one direction by a spring and in the opposite direction by axial movement of the thrust member with respect to the flywheel. The effective strength of the spring is responsive to the pressure in a brake line applied to the spring through a connection so that this, in turn, reflects the optimum braking pressure for a particular road surface.

Abstract: An hydraulic anti-skid braking system for vehicles is disclosed in which a supply of operating fluid from a master cylinder to a vehicle brake is modulated by a modulator assembly in accordance with signals from a skid sensing device. The modulator assembly incorporates an expansion chamber and an hydraulic pump has a working chamber which is connected to the expansion chamber. A dump valve disposed between the expansion chamber and a reservoir for fluid is operable by the sensing device to regulate the pressure in the expansion chamber in accordance with the deceleration of the wheel braked by the brake. The pump is operable only to repressurize the expansion chamber following correction of a skid.

Abstract: A tandem master cylinder is disclosed having primary and secondary pistons which are freely movable apart, the pistons defining one wall of respective pressure chambers connected to primary and secondary braking circuits. The ratio of the effective areas of the piston are selected to lie in the range 0.2 to 0.8 resulting in the availability of the full effective area of the primary piston upon failure of the secondary system, with substantially decreased pedal travel over that required in prior systems where the pistons are freely movable apart but are of equal effective area.

Abstract: In an hydraulic system an unloader valve is located in a line between a pump and an hydraulic accumulator. The unloader valve is operative to prevent the accumulator from being overcharged and to allow the pump to re-charge the accumulator should the pressure stored therein fall below a desired minimum value. The unloader valve incorporates a control valve comprising a spool and a pressure responsive slave which is operated by fluid pressure under the control of the control valve. A single spring acts to bias the spool into a first position against pressure in a control chamber into which fluid is pumped through a first one-way inlet valve. A second one-way exhaust valve located between the first one-way valve and an exhaust port can be opened by the slave to unload the pump.

Abstract: In a servo-motor assembly for a vehicle braking system a valve controlling the servo pressure is operated by an operating assembly comprising an angularly movable rotary operating member, an axially movable transmission member for applying an operating force to the rotary member, and a camming mechanism for translating axial movement of the transmission member into angular movement of the rotary member.

Abstract: A control valve assembly for a vehicle braking system comprises an inlet, an outlet, a valve having a pressure operated relay member movable to open and close the valve to control communication between the inlet and the outlet, and an inertia-responsive device, preferably a pendulum, responsive to deceleration of the vehicle and operable to reduce the pressure at the outlet after the valve has closed. The inertia-responsive device supplies a signal in dependence upon deceleration, and a servo system applies a force in opposition to the force on the relay member in response to the signal to move the relay member in a direction to reduce the outlet pressure.

Abstract: An hydraulic booster in which a control chamber is defined between an input piston and a second piston relative to which the input piston is movable, and recuperation valve for controlling communication between the control chamber and a reservoir is located in the control chamber. The recuperation valve closes upon relative movement of the input piston towards the second piston, further movement of the input piston in the same direction causing pressurization of fluid trapped in the control chamber.

Abstract: A disc brake (1) comprises a cylinder (5) slidably mounted on a carrier member (2) for movement parallel to the axis of rotation of the disc. The cylinder (5) is closed at the end adjacent the disc. A bridge member (10) of integral structure, for example forged steel, connects the piston (7) to the outboard brake pad (15). In use, when hydraulic fluid is supplied to the cylinder (5) the cylinder slides on the carrier to apply the inboard brake pad (14) to the disc, and the piston applies a force to the outboard pad (15) via the bridge member (10). The seals (8,9) between the piston (7) and cylinder (5) are isolated from the heat produced by the brake pads, and the bridge member (10) does not require accurate machining and can be designed to provide the maximum strength.

Abstract: A master cylinder assembly for a vehicle braking system having two pressure circuits, comprises a master cylinder having two separate pressure chambers associated with respective pistons one chamber being arranged for connection to one of the pressure circuits, generally the circuit to the front wheel brakes, and a control valve arrangement fast with the master cylinder. The control valve arrangement has an inlet for connection to the other of the chambers and an outlet for connection to the other of the pressure circuits, usually the rear wheel brake circuit, a normally-open valve for controlling communication between the inlet and the outlet, and an auxiliary piston assembly movable to open and close the valve to control the pressure applied to the rear wheel brakes as compared to full braking pressure applied to the front wheel brakes.

Abstract: A control valve assembly for a dual circuit braking system has two valves controlling the pressure in the respective circuits. In order to ensure substantially equal braking pressures in the circuits, a pressure equalizing piston is provided which is free floating in a bore interconnecting outlets of the valve assembly. The braking pressure can thus be equalized even after closure of the valves. One valve is preferably inertia-responsive.

Abstract: A pump assembly for an hydraulic braking system comprises a housing having an inlet for connection to a tank for liquid, an outlet for connection to an hydraulic accumulator, and a piston reciprocably mounted in a bore in the housing to draw liquid into a working chamber during an induction stroke and to force it to the outlet during a power stroke. A drive mechanism is provided for moving the piston in one direction during the induction stroke, and the piston is moved in the opposite direction during the power stroke by subjecting the piston to pressure at the outlet.

Abstract: A fluid-pressure operated servo-motor assembly transmits an effort from a pedal to a master cylinder for wheel brakes. The assembly includes in a housing, a pedal-operated input member, an output member acting on the master cylinder and a movable wall for transmitting the effort between them. The effort is augmented by fluid pressure in a boost chamber acting on the movable wall. The boost pressure is controlled by a valve in a stationary part of the housing. An operating assembly controls operation of the valve, and comprises a non-rotatable operating member, and a rotatable actuating member co-operating with the valve.To ensure positive operation of the valve, a helical engagement provided between the operating and actuating members, and the co-operation of the valve with the actuating member are arranged so that relative axial movement between the members causes rotation of the actuating member to operate the valve.

Abstract: A control valve assembly for a vehicle braking system comprises an inlet, an outlet, a proportioning valve having a control valve member movable to open and close the valve to control communication between the inlet and the outlet, and an inertia-responsive device, preferably a pendulum, responsive to deceleration of the vehicle and operable to reduce the pressure at the outlet after the valve has closed. The inertia-responsive device supplies a signal in dependence upon deceleration, and a servo system applies a force to the control valve member in response to the signal to move the control valve member in a direction to reduce the outlet pressure.

Abstract: In a servo-motor assembly for a vehicle braking system a valve controlling the servo pressure is operated by an operating assembly including a rotary valve actuator positioned between a pedal-operated input member and an abutment member. The valve actuator is axially movable through a limited distance and a camming mechanism translates axial movement of the actuator into angular movement which operates the valve.

Abstract: Servo boosters for vehicle hydraulic braking systems are described which incorporate a novel arrangement for providing an increasing reaction force on the input member in response to an increasing output force. In the novel arrangement a first thrust assembly is interposed between the input member and the output member, and a second thrust assembly is interposed between the movable wall of the booster, which may be a diaphragm or a piston, and the output member. The thrust assemblies each generally consist of rotatable parallel plates having inclined ramp surfaces on opposed faces co-operating with balls or rollers located between the plates. Some of the plates of the two thrust assemblies are keyed together. Axial forces between the members generate torques in the thrust assemblies and since the torques must balance each other as a result of the connections between the plates a fixed relationship is maintained between the input and output forces and the force exerted by the movable wall.

Abstract: A vehicle load-sensing assembly for use with a vehicle fluid-pressure braking system comprises an input member subjected to a force in a road spring and a valve which has a movable valve member for controlling the flow of fluid through the valve. A thrust transmitting mechanism is located between the input member and the valve member. The thrust transmitting mechanism comprises relatively movable parts, and a camming device is disposed between the parts to transmit movement between the parts to control operation of the valve member.

Abstract: In an hydraulic power system for operating a vehicle levelling system and braking system, an accumulator supplies both the levelling system and the braking system. The accumulator is connected indirectly to the braking system through a pressure limiting device, which disconnects the braking system from the accumulator when a predetermined pressure is reached.

Abstract: In an hydraulic system an unloader valve is located in a line between a pump and an hydraulic accumulator. The unloader valve is operative to prevent the accumulator from being overcharged and to allow the pump to re-charge the accumulator should the pressure stored therein fall below a desired minimum value. The unloader valve incorporates a control valve comprising a spool, and a pressure responsive slave which is operated by fluid pressure under the control of the control valve. Two springs bias the spool into a first position in which pump pressure can be supplied to the accumulator, and the second spring is inoperative when the spool is moved into a second position in which fluid pressure from the accumulator can act on the sleeve to reduce the pump pressure to that of the tank for the pump.

Abstract: In a disc brake of the slidable reaction type in which an hydraulic actuator is located in a stationary member, a clamp member is guided for movement relative to the stationary member in a direction substantially parallel to the axis of the disc by means of a pin which is connected to one of the members and is slidably mounted in the other member.