Abstract: A booster operated master cylinder piston for use in an anti-skid braking system includes a modulator piston located between the master cylinder piston and the booster valve assembly. In the event of a skid the pressure of booster fluid acting on the modulator piston is equalized across the modulator piston.

Abstract: An hydraulic control valve assembly for a vehicle anti-skid braking system incorporates a modulating piston for modulating the supply of hydraulic fluid between communicating ports in a housing, and a compression spring normally urges the modulator piston into an inoperative position. The housing is provided with an additional outlet port for connection to a reservoir for fluid and an anti-skid control valve assembly normally places opposite faces of the modulator piston in communication with the additional outlet port. In response to a skid control signal the anti-skid control valve assembly is operative to isolate the opposite faces of the modulator piston from each other and subsequently place the one face opposite the compression spring in communication with a first inlet port in the housing.

Abstract: A master cylinder assembly for a vehicle hydraulic braking system comprises a pedal-operated valve assembly for controlling a supply of fluid under pressure to a power chamber in a housing on the opposite side of a piston to a pressure space which has an outlet for connection to a wheel brake, and a second piston is adapted to be applied by the pedal to generate fluid pressure in said pressure space.

Abstract: A fluid pressure operated vehicle braking system includes a control valve assembly comprising an inlet and outlet, a normally-open valve having a valve member movable in response to a predetermined inlet pressure to control the flow of pressure fluid between the inlet and the outlet, and a stepped piston subjected to a biasing force dependent upon the vehicle loading and operable in response to both the inlet pressure and the biasing force to reduce the outlet pressure after the predetermined inlet pressure is attained.

Abstract: A disc or drum brake fluid pressure actuator incorporates a lock actuator strut acting on an inner part of a telescopic piston assembly, of which the inner and outer parts are normally rendered effectively unitary by pre-stressed spring which can, however, deflect under excess pressure to permit extension of the lock actuator strut when it is desired to operate the strut for parking purposes. An hydraulic control system for operating the actuator is also described and illustrated.

Abstract: A disc brake includes a friction element which has a portion of increased axial thickness defining an initial friction surface, the center of pressure of this surface being radially offset from the center of pressure of the whole friction surface of the element so that a relatively large braking torque can be developed while the element is bedding in.

Abstract: A diaphragm valve has a relatively long seating formed by a plurality of ribs which engage with one air operated diaphragm. An annular valve is provided by slotting the outer surface of an annular seating member which engages an endless diaphragm, alternate slots communicating with the inlet or outlet of the valve. A pneumatic actuator for a vehicle braking system is provided with internal valve means for controlling the flow of air through the movable wall carrying the actuating member. An anti-skid braking system employs such a pneumatic brake actuator, the internal valve means being operated by skid sensing means.

Abstract: A piston and seal assembly is adapted to work in a cylinder, particularly a master cylinder of a vehicle braking system, the seal having a lip which sealingly engages the cylinder bore on the pressure stroke, an inner portion mounted on the piston, and an interconnecting portion between the lip and the inner portion. A retaining member holds the seal on the piston and engages the interconnecting portion during the return stroke of the piston so that the seal flexes about the line of engagement between the retaining member and the interconnecting portion to provide a recuperation flow path between the lip and the cylinder bore.

Abstract: A booster operated master cylinder piston for use in an anti-skid braking system includes a modulator piston located between the master cylinder piston and the booster valve assembly. In the event of a skid the pressure of booster fluid acting on the modulator piston is relieved.

Abstract: An internal shoe-drum brake in which arcuate shoes carrying friction linings for engagement with a rotatable drum are mounted on a stationary back-plate and the shoes are separated at one end to bring them into engagement with the drum by a service actuator for normal service braking and at the other end by a mechanical parking actuator. Abutments are provided at or adjacent to the mechanical parking actuator to take the braking loads when the brake is applied by the service actuator, and means are provided in or adjacent to the service actuator for transmitting servo braking forces from one shoe to the other when the brake is applied by the mechanical parking actuator. An actuating member is operative to actuate the parking actuator to release energy stored therein thereby applying continuously to the shoes a force to urge them into engagement with the drum irrespective of the initial position of the shoes when the actuating member is operated.

Abstract: A pressure control valve for a braking system having separate pressure circuits comprises a control member movable to control communication between an inlet and an outlet for connection in one of the circuits and spring biased to a valve open position. The control member has an extension which passes sealingly into a space between and sealed from the two circuits and which engages a piston subject to the pressure in the other circuit. The piston is separate from the control member and is operable under the pressure in that other circuit to overcome the spring bias and close the valve by displacing the control member.

Abstract: In an hydraulic actuating assembly for a vehicle shoe-drum brake comprising first and second relatively slidable members, the first member is provided with a longitudinally extending bore which is closed at one end and in which works a portion of the second member, and a sealed hydraulic chamber is defined within the bore between the closed end of the first member and the second member. One of the members incorporates an inlet port for the chamber and a vent port is located in a portion of the wall of that member to provide an indication, by external leakage of hydraulic fluid, of failure of the sealing of the chamber.

Abstract: In a power-operated hydraulic booster for a vehicle braking system pressurization of a power chamber in a housing on one side of a boost piston is controlled by an assembly of at least two separate spool parts which work in bores in the boost piston and the housing, and a boost chamber is defined in the housing between the power chamber and an output piston having an effective area less than that of the boost piston.

Abstract: A pressure control valve for a braking system having two separate pressure circuits comprises two valves for connection in the respective circuits. Each valve has a valve closure member, the members being axially aligned and coupled together for movement in unison for simultaneous opening and closing of the valves.

Abstract: A brake actuating assembly for actuating a master cylinder having a power assistor comprises a brake pedal pivotable about a pivot point at one end and connected at a point intermediate its ends to an actuating member of the master cylinder, movement of the actuator member also actuating the power assistor, the pivot point being connected to a piston of a fluid motor operable in response to the operating pressure of the power assistor the arrangement being such that in normal operation the pressure of the power assistor actuates the piston to hold the pivot point in a fixed position but upon failure of the power assisting means the pivot point is moved to vary the pedal ratio, to permit the master cylinder to be operated without power assistance.

Abstract: A disc brake comprises a fluid pressure-operated actuator for urging two pressure plates carrying friction pads to opposite faces of a disc. In the actuator a piston movable in a housing is detachably engaged with a draw-bar which acts on one of the pressure plates, the housing acting directly on the second pressure plate. A seal between the housing and the draw-bar contacts an enlarged portion of the draw-bar. A screw-driver slot is provided to prevent the draw-bar from rotating.

Abstract: A vehicle brake comprises a plurality of elongated friction members for engagement with the brake rotor, the friction members being laterally supported close to their rotor-engaging ends, and an actuating mechanism having an elongated thrust-transmitting member substantially co-extensive with the friction members and an abutment member carried by the thrust-transmitting member and engageable with the friction members.

Abstract: A drag-taking member for a disc brake of the sliding caliper reaction type comprises a pair of circumferentially spaced arms which form drag-taking guide means for a directly actuated friction pad assembly. The radially innermost ends of the arms are separate from each other, and the arms are interconnected by an integral bar disposed at one axial end of the member.

Abstract: An automatic adjuster comprises a mechanism of adjustable length operative between a hydraulic brake piston and either a cylinder or an opposed piston. A cam journalled in the cylinder or the opposed piston serves to apply the brake mechanically (hand brake) and act as a stop for the mechanism. The adjustable length mechanism comprises two members, one of which may be the first mentioned piston in interengagement with one another through a non-reversible screw-thread connection. A reversible screw-thread connection or a reversible face cam is provided for turning one member of the mechanism relatively to the other responsively to excessive piston travel to effect adjustment.

Abstract: In an actuator assembly for an hydraulic braking system the effective volume of a chamber through which hydraulic fluid under pressure is supplied to a wheel brake is adapted to be varied between a minimum and a maximum value by movement of a piston assembly working in a bore in communication with the chamber. An actuator piston having first and second different faces of different areas normally holds the piston assembly in a position in which the effective volume of the chamber is at a minimum until equal hydraulic pressures are applied to the areas of the actuator piston to cause the actuator piston to retract and permit the piston assembly to be withdrawn whereby the effective volume of the chamber is increased.