Abstract: In an hydraulic anti-skid braking system for a vehicle of the four wheel type in which an anti-skid modulator is adapted to control the brake on a rear wheel, an apportioning valve is incorporated in a line between each modulator and the brake, and a pressure-responsive control valve assembly is also incorporated in the line. The valve assembly comprises a pressure-responsive member, for example a piston working in a bore, and operable when subjected to a differential pressure in excess of a predetermined value, to restrict the effective area of passage through which fluid is dumped from the brake. This reduces the rate at which the pressure is released from the rear brake, thereby enabling this brake to do more work. Hence the stopping distance for the vehicle can be shortened.

Abstract: In a vehicle anti-skid hydraulic braking system of the pump/re-apply type the pump plunger is of differential outline and works in a stepped bore. An annular chamber and a full pump chamber are defined in the bore on opposite sides of the head of the piston. The annular chamber is pressurized by fluid at a pressure dependent on the difference in pressure between the master cylinder and the brake, and the chamber is subjected to the pressure in the annular chamber in one direction and the pressure in the master cylinder in the opposite direction. The system is therefore provided with a pump which forces fluid back to the master cylinder but with torque levels similar to a pump which acts against brake pressure.

Abstract: In an hydraulic anti-skid braking system in which a modulator is fitted to each front wheel brake with which it forms a separate braking circuit, a valve assembly is connected between the circuits on the downstream of the modulators, between the modulators and the front wheel brakes. The valve assembly is responsive to differential pressures applied to both front wheel brakes and is operative to restrict the rate of pressure increase applied to the front wheel brake which is at the higher pressure.

Abstract: A vehicle suspension strut 1 comprising a telescopic hydraulic damper 2 and coaxial main suspension spring 3 is fitted with a brake pressure control valve 23. The control member 22 of the valve is acted on by a lever 20 pivotally mounted on a bracket 18 fast with the damper body. The lever 20 supports the end of a tubular support 7 which is movable axially of the damper body and which carries the support plate 9 for the main suspension spring. A compensating spring 12 acts between a ring 13 supported on bracket 18 and an adjustable collar 14 mounted on the tubular element. The compensating spring 12 reacts part of the main suspension spring load onto the damper body, and the remaining suspension spring load is transferred to the body via the lever 20 which distributes the force equally between the bracket 18 and the control member 22.

Abstract: A servo-assisted master cylinder assembly for a vehicle hydraulic braking system has a tandem master cylinder with primary and secondary pistons operative to pressurise primary and secondary pressure spaces for primary and secondary brake circuits. A servo chamber is defined behind the primary piston, and pressurisation of the servo chamber from a source of pressure fluid is controlled by a valve in response to an input force applied to the primary piston. The valve comprises a spool operated solely by pressure in the primary space and a bias force from servo pressure in a bias chamber and a spring. The secondary piston has a smaller effective area than the primary piston, so that the pistons are in abutment in their retracted positions. To reduce pedal travel, one of the brakes of the primary circuit can be supplied from the servo chamber instead of the primary pressure space.

Abstract: A flywheel mechanism acts on a dump valve through a lever assembly. The lever assembly comprises a lever which carries an arm at an intermediate point in its length and the arm projects through a seal into a chamber in a casing to co-operate with a valve member of the dump valve which is engageable with a seating. The arm is pivotally connected to the casing by a pivot pin of which the axis is offset from the main axis of the arm in a direction towards the flywheel mechanism. Brake pressure acts on the arm to move it angularly about the pin in a direction to enhance the closing force of the dump valve. Offsetting the pin ensures that the flywheel mechanism has to generate a relatively higher torque on good surfaces when relatively high brake pressures are present before the dump valve will open, than on poor surfaces when the brake pressures are relatively low.

Abstract: In an anti-skid braking system a modulator for modulating the supply of hydraulic fluid from a master cylinder to a brake incorporates a flow-control regulator valve and an exhaust valve which is responsive to signals from a sensor. When the exhaust valve is closed the regulator valve is in a first position to permit unrestricted direct flow through it and when the exhaust valve is open a variable orifice in the regulator valve provides a restricted flow through it. The exhaust valve and the valve are only connected hydraulically and a conventional inlet valve normally operated directly by the sensor is omitted. The construction is therefore simplified since relative position tolerances are otherwise eliminated.

Abstract: In a modulator assembly of the kind including a dump valve operable by skid sensor to cause closure of a valve to isolate a master cylinder from a brake and initiate operation of a pump, the modulator assembly incorporates a time-delay piston of differential outline working in a stepped bore in a housing. The piston is exposed a its end of smaller area to pressure in the master cylinder which is applied to the brake through a flow-control regulator valve and at its end of greater area to pressure in an expansion chamber through fixed outline . Equalization of the pressures acting on the piston causes the piston to move in a direction to open the regulator valve whereby to ensure that fluid from the master cylinder can flow to the brake at a rate faster than the rate at which it is returned from the brake by the pump.

Abstract: A load conscious brake pressure reducing valve assembly comprises a piston (2A) mounted on a piston rod (2) and movable to control a valve (6) for controlling the connection between an inlet (4) and outlet (3). The valve body (1) is mounted on a sprung part (7) of a vehicle and the piston rod (2) is coupled to an unsprung part (9) by a position sensing lever (10) and springs (32,20) nominal separation of the sprung and unsprung parts the sensing device (8) exerts no force on the piston rod. For greater spacings of the sprung and unsprung parts the spring (20) exert a force on the piston rod which opposes the force of an internal spring (5), and for lesser spacings the spring (32) exert a force on the piston rod which enhances the force of the internal spring. As a result the net spring force acting on the piston always decreases as the separation of the sprung and unsprung parts increases.

Abstract: A short hydraulic master cylinder includes a secondary pressure chamber recuperation valve assembly which is mounted in the side of the master cylinder body and incorporates a center valve operable by a lever which engages the rear surface of the front seal support flange of the secondary piston. Thus, the portion of the secondary chamber defined by the master cylinder bore is devoid of all valve and operating linkage components. Recuperation flow to the primary chamber is via a center valve assembly connected by bores to the space between the seals of the secondary piston, and the passage through which the lever extends.

Abstract: A vehicle comprising sprung and unsprung parts is provided with a brake pressure reducing valve (10) controlled by a position sensing spring which applies to the control piston (12) a force (S) determined by the relative position of the sprung and unsprung parts. The sensing spring force (S) tends to move the control piston (12) in the direction to open the valve, and is opposed by an internal bias spring (18) which tends to close the valve. By suitable choice of piston areas A.sub.1 and A.sub.2 and spring forces increase (above cut-in pressure) in input pressure (P.sub.1) will always produce an increase in output pressure (P.sub.2) despite the reduction in sensing spring force (S) which will occur due to weight transfer.

Abstract: In a flywheel mechanism of the axially expanding type a clutch plate which is rotatable with a shaft and from which the mechanism is driven, is provided on pitch circles of greater and smaller diameters with outer and inner clutch faces with which complementary clutch faces on the mechanism are alternately engageable. This defines first and second clutch engagements of higher and lower torque settings which are operative, respectively, when the flywheel mechanism is in an inoperative brake-applying position and when the flywheel mechanism is in an operative brake-applying expanded position.

Abstract: In an anti-skid braking system of the de-boost and pump to re-apply type, a solenoid-operated cut-off valve is disposed between an expander piston and a brake, and the cut-off valve is operable independently of and separately from the expander piston. The cut-off valve co-operates with a one-way valve disposed between a master cylinder and the brake to hold the one-way valve in an open position when the cut-off valve is in a closed position with the solenoid de-energized. This ensures that the one-way valve can close only as a result of movement of the cut-off valve into an open position which can occur only when the solenoid is energized in response to a skid signal.

Abstract: A rotary flywheel mechanism comprising a flywheel driven from a wheel driven shaft through a thrust member and angularly spaced balls located in complementary recesses in adjacent faces of the flywheel and the thrust member is disclosed. A locking mechanism is incorporated to prevent operation of the flywheel mechanism until the vehicle has attained a predetermined minimum road speed. The locking mechanism comprises a centrifugally-operable weight carried by the flywheel and which is normally urged inwardly by a spring and into engagement with the thrust member to lock the flywheel and the thrust member against relative movement. The centrifugal force generated at speeds above the minimum speed urges the weight outwardly to unlock the flywheel and the thrust member. The weight may comprise a plunger guided for radial movement in a radial bore in the flywheel, or the weight may comprise a mass carried by a lever which is angularly movable about a pivot parallel to the axis of the shaft.

Abstract: An anti-skid hydraulic braking system incorporates a modulator assembly for modulating the supply of fluid from a master cylinder to a brake in accordance with skid signals. The modulator assembly comprises a de-boost piston located in a bore in a housing, an expander chamber connected to the brake, a first valve between the master cylinder and the chamber, and a second valve for controlling the application of the de-boost piston of a fluid sustained-support force. The modulator assembly incorporates a safety piston which prevents the first valve from closing unless a device, suitably an hydraulic accumulator or pump, and which provides the fluid sustained-support force, is operative.

Abstract: In a fluid-pressure operated braking system for vehicles operating fluid from a supply for actuating a wheel brake is supplied to the brake through a skid control unit interposed in the line between the supply and the brake, and a skid responsive device responsive to a skid signal is incorporated for operating a valve assembly to relieve the pressure of the fluid supplied to the brake at a skid point. The unit incorporates a memory chamber for controlling the rate of brake re-application following correction of a skid, and the memory chamber is charged with air only when the skid signal is received. When separate control units are provided for the brakes of wheels at opposite ends of an axle, the memory chambers are interconnected by a pneumatic connection incorporating a restrictor.

Abstract: A load conscious brake pressure reduction valve is mounted between the suspension arm (1) and the suspension spring (5) of a vehicle. The control piston (8) of the valve is directly loaded with a force equal to the suspension spring load less the force of a compensating spring (12). To enable the valve to close against this load the area (A) of the control piston is made large. The movement required to effect valve closing is made small by careful control of the projection of the valve opening pin (26) and of the length of the valve seat member (20).

Abstract: An hydraulic booster has a boost piston which works in a bore and is subjected to boost pressure in a boost chamber to actuate a master cylinder assembly, and a control valve assembly controls pressurization of the boost chamber in response to an input load applied to a pedal-operated input member. The input member works in a bore in the boost piston and in operation, a reaction load from the master cylinder is fed back through the booster to the input member through a reducer mechanism to provide a reaction at the pedal which is not affected by the boost pressure, and the reducer mechanism is received within a recess in the boost piston, which is defined between two relatively movable parts of the boost piston.

Abstract: In an hydraulic anti-skid braking systems for vehicles, for example motor cycles or light passenger cars, a supply of operating fluid from a supply to a vehicle brake is modulated in accordance with skid signals from a skid sensing devices suitably an opto-sensor, which are electrical in nature, and an hydraulic pump incorporating at least one plunger working in a bore has a working chamber to control brake re-application following skid correction. The supply of fluid from the supply to the brake is modulated by a solenoid-operated valve assembly which is responsive to the skid signals, the valve assembly incorporating a normally-open isolating valve disposed between the source and the brake, and a normally closed dump valve disposed between the brake and a reservoir for fluid.

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.