Abstract: An air compressor having a piston driven via a crankshaft from an input shaft by means of a multi-plate clutch which is normally held in engaged condition by a spring device. The clutch and spring device are contained within a housing which includes a retainer placed, after the spring device has been pre-loaded to a desired extent, in a position determined by said pre-loading and secured in that position to maintain the spring device in pre-loaded state. The crankshaft is housed within a crankcase and passages interconnect the interiors of the crankcase and clutch housing, with the casing ends of the passages at a higher level than a predetermined permissible oil level for the crankcase. This permits crankcase pressure during operation to expel oil from the crankcase along the passage into the clutch casing, while limiting the height to which oil may accumulate in the crank case when the piston is stationary.

Abstract: In an hydraulic booster a load applied to a master cylinder assembly through the booster is fed back to a pedal-operated input piston through a reducer mechanism. This provides, when a booster chamber for operating a boost piston is pressurized by boost pressure, a reaction of "feel" at the pedal which is unaffected by the magnitude of the boost pressure.

Abstract: A pedal-operated booster incorporates a valve mechanism for controlling pressurization of a boost chamber. The valve mechanism comprises a pedal-operated piston and a pressure-responsive valve spool which is coupled to the piston for limited relative movement in a longitudinal direction within a working chamber in the piston. The spool is movable with the piston in an initial brake-applying direction in which the spool is operative to isolate the boost chamber from an exhaust port and the piston is operative to place an inlet port in communication with the working chamber. This causes the spool to move relatively away from the piston in response to pressure fluid in the working chamber which is admitted to the boost chamber.

Abstract: In a power braking system for a vehicle a supply of fluid from a power source is utilized to augment the output pressure to be supplied to a brake from a pedal-operated brake control valve assembly. The power source comprises a source of hydraulic fluid of a type different from that which is supplied to the brake from the control valve assembly, and the fluid under pressure from the pressure source is supplied to at least one pressure converter which is adapted to pressurize hydraulic fluid in a sub-system to augment the output pressure from the control valve assembly. The sub-system is provided with hydraulic fluid of a type different from that of the power source, and an hydraulic accumulator is incorporated in a line between the pressure converter and the control valve assembly.

Abstract: In an hydraulic anti-skid braking system a pump having a liquid throughput which is adapted to increase with the rotational speed of the wheel is arranged to control operation of a modulator valve assembly for relieving the pressure supplied to the brake when the deceleration of a wheel exceeds a predetermined value. A sensing device for sensing the deceleration of wheel operates a control valve assembly which is provided to control the supply of operating fluid from the pump output to the modulator valve assembly.

Abstract: A fluid pressure braking system is disclosed which includes an hydraulic actuator connected to a vehicle brake and a pressure actuator for operating the hydraulic actuator and which is connected to a fluid pressure reservoir via a brake control valve. An auxiliary valve having an inlet connected to a fluid pressure source, which may be the reservoir, is responsive to a deceleration responsive inertia device which, when deceleration exceeds a predetermined value operates the valve to connect pressure from the source to a pressure operable member which operates on the actuators in opposition to the pressure at the inlet of the pressure actuator thereby effecting a pressure reduction at the outlet of the hydraulic actuator in dependence on deceleration. The auxiliary valve includes a metering feature whereby when it is opened, outlet pressure operates against a pressure area of the valve to effect metering of pressure to the pressure operable member.

Abstract: A drum brake is disclosed in which at least two, and preferably four, friction pad assemblies are symmetrically arranged with respect to the drum. The pad assemblies are slidably guided for movement towards and away from the drum in a substantially radial direction on drag-taking abutments in a relatively stationary drag-taking member, and the pad assemblies are applied to the drum by levers upon which actuators act.

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 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 comprises a rigid caliper which straddles the peripheral edge of a rotatable disc, and friction pads for engagement with the disc are located in the caliper. One pad is applied directly to the disc by an actuator which is provided in adjacent limb of the caliper, and the other pad is applied to the disc by the reaction on the caliper which causes the caliper to move with respect to the disc and a relatively stationary drag-taking part from which the caliper is carried by a drag-transmitting arm. The arm is connected at one end to the stationary part by a single pivot pin which pivots the arm for movement about an axis normal to the axis of the disc, and the arm is coupled to the caliper by of a spherical joint.

Abstract: A helical thrust bearing (14) is arranged between two rotatable cam components (12 and 13) of a brake actuator. The cam component (13) is turned first while the brake slack is being taken up and the brake-applying force is relatively low, the reaction to such force being transmitted to the body (10) at a plain axial thrust bearing (17,18). Only the cam component (12) is turned when the brake is actually being applied with the relatively high brake force which is transmitted to a thrust member (15) at a roller axial thrust bearing (16). This enables the pneumatic force motor or the prime mover to be used more efficiently. Also a greater angular displacement at the helical thrust bearing (14) is obtained for a given angular displacement of the cam components (12 and 13) relative to the body (10).In a modification, the plain thrust bearing (17,18) is replaced by another helical thrust bearing.

Abstract: An arrangement for varying a pre-load on a control valve of a vehicle braking system in dependence upon vehicle loading includes a low frequency vibration sensor or an accelerometer for sensing the oscillation frequency of a sprung part of the vehicle and providing an output signal, preferably an electrical signal, indicative of the frequency, a signal processing circuit for processing the signal, the circuit including a filter which filters components of the signal which are not indicative of a frequency within the normal oscillation frequency range, and an arrangement for altering the pre-load in dependence upon the processed signal.

Abstract: A vehicle brake system in which an output member is axially displaceable by the application of differential fluid pressure, under the control of a valve operable by an input member, across a movable internal wall which divides a housing of the booster into a pair of fluid chambers. Displacement of the movable wall is communicated to the output member via a lever mechanism providing a mechanical advantage between said movable wall and the output member. The lever mechanism comprises first and second levers. The second lever is pivotable relative to the input and output members at respective pivot points.

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: An hydro-pneumatic suspension device comprises a pressure chamber and a working chamber which are separated from each other by a first diaphragm. The pressure chamber contains a trapped volume of gas under pressure for supporting the load on a wheel or axle, the working chamber contains a volume of liquid under pressure which is trapped between the first diaphragm, and oppositely acting one-way valves or restrictors are provided for damping liquid flow in the working chamber. The side of the second diaphragm remote from the working chamber is subjected to a supply of liquid of which the pressure can be altered to compensate for changes in pressure in the pressure chamber due to changes in the loading on a vehicle.

Abstract: Anti-skid brake control systems are described in which anti-skid brake control modules associated with the braked axles are each provided with a failsafe circuit and these failsafe circuits are connected in cascade fashion to form a chain so that an input signal applied to a first failsafe circuit will propagate through the chain of failsafe circuits to the output of the last failsafe circuit only if the wiring connecting the modules is correct, the failsafe circuits are themselves operating correctly and electrical power is being supplied to each module, a warning being given to the driver of the vehicle if the output signal from the last failsafe circuit fails. In a previously proposed system the warning given is only produced in the event of a fault, and there is no positive indication of correct operation of the system at switch on.

Abstract: In a fluid pressure-operated anti-skid braking system for rail and other vehicles operating fluid from a supply for actuating a wheel brake is supplied to the brake through a fluid-flow control valve interposed in the line between the supply and the brake. Deceleration responsive sensors responsive to a skid signal are incorporated for operating the valve to relieve the brake pressure of the fluid supplied to the brake when the deceleration of the wheel is excessive and exceeds a predetermined value. The valve incorporates a fluid pressure memory chamber for sensing the skid pressure, and the memory chamber provides a datum or changeover point between first and second successive stages of brake re-application following a skid.

Abstract: In a vehicle disc brake of the single sided sliding reaction caliper type the drag on the friction pad assemblies is taken by a drag-taking member. The caliper is slidably mounted for movement relative to the disc on a guide in the form of a single pin which is located on the same side of the disc as that on which an actuator for the brake is located.