Abstract: A brake servo booster capable of operating in a traction control mode has a housing (100) containing a diaphragm assembly (500) which divides the housing into two chambers A and B. Supply of air to the diaphragm assembly is controlled by a valve mechanism which includes a reciprocable valve member (7) operatively connected to a force input member (5) actuated by a driver-operated control. The force input member includes two parts (11,12) connected respectively to the valve element and driver-operated control. The arrangement is such that operating force applied to the control is transmitted through both of the first and second input member parts (11,12) whilst a traction control operative mode is permitted by the second part (11) moving relative to the first part (12).

Abstract: A solenoid-operated fluid-flow control valve comprises a housing (10) incorporating a solenoid coil (14), a single armature (15) responsive to energization of the coil to determine a pressure differential across a pressure-sensitive member (28, 18) and to open an exhaust port (45), in combination with a valve assembly (13) comprising a hollow valve body (16), and a valve head (19), the valve body being axially movable with respect to the housing in response to the pressure differential acting on the pressure-sensitive member. The valve body and the valve head are relatively movable axially with the valve head being movable with respect to a seating (47) in the housing and a seating (23) on the valve body, whereby to provide selective communication between an inlet port (46), an outlet port (47) and the exhaust port (45).

Abstract: In a hydraulic system for traction control, a pump is adapted to withdraw fluid from a reservoir through a master cylinder assembly under the control of a solenoid-controlled valve responsive to signals from an electronic control module, and a pressure-sensitive valve. The system is also provided with a solenoid-controlled flow control valve also responsive to signals from an electronic control module, a switch is responsive to movement of the throttle of the engine of a vehicle, and from which signals are transmitted to the control module. Thus, when the signal from the switch changes as the foot is released from the throttle pedal, the control module recognizes the change in signal and re-sets the modulator means, for example the solenoid-operated flow control valve.

Abstract: A solenoid-operated fluid-flow control valve comprising a single solenoid coil, the energization of which controls the movement of first and second armatures which in turn control first and second respective valve members. The armatures are biased away from the solenoid by respective springs, one of which is weaker than the other. When the solenoid is energized by a constant current the armature with the weaker spring is attracted to the end of the solenoid and forms part of a magnetic circuit. This increases the magnetic flux at the other end of the solenoid, allowing the second armature to be drawn to the solenoid sequentially after, and subsequent to, the drawing-in the of the first armature. Particular anti-lock brake systems incorporating the valve are disclosed.

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: An actuator assembly incorporates a strut assembly of which the effective length is adjustable to compensate for wear of a friction lining and through which a brake-applying force is transmitted to a braking member, and an adjuster mechanism arranged in parallel with the strut assembly. The adjuster mechanism is arranged in parallel with the strut assembly and incorporates a spring in which energy is adapted to be stored. The mechanism is adapted to receive a signal dependent upon movement of the strut assembly in a brake-applying direction, and is also adapted to apply an adjusting force to the strut assembly in response to energy released from the spring when the brake is itself released.

Abstract: A tread brake for braking a wheel (2) of a railway vehicle which is sprung relative to a frame (4) of the vehicle, comprises an actuator (5) suspended from the frame (4) by a swing arm (6), and a rigid link arm (7) fixed to the actuator (5) and connected through a pivot (8) parallel to the wheel axis to a bracket (9) fixedly mounted to a bearing in which the wheel axle is journalled. The link arm (7) adjusts the position of the actuator (5) in response to any movement of the wheel (2) relative to the frame (4) so that the braking element (11) is always applied substantially radially to the wheel, which allows the element to take the form of an elongate rod of friction material. A new handbrake structure is also described.

Abstract: A vehicle wheel brake, particularly for a railway vehicle, has an elongate friction pad for engagement with a braking surface. In order to provide for adjustment of the pad without excessive length of the brake, the friction pad is hollow and an elongate adjuster member is located within the friction pad. Relative rotation of the pad and adjuster member, which occurs when there is excessive wear of the friction material, causes axial movement of the friction material to compensate for the wear.

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 friction pad assembly for a rail vehicle brake comprises a pad of friction material carried by a rigid backing plate, and the backing plate is detachably mounted on a shoe. A part-circular notch at one end of the shoe receives the stem of a headed stud which acts as an abutment for that end of the backing plate, and the backing plate is urged into engagement with the stud by means of a keeper which acts on the opposite end of the backing plate. The keeper comprises a stop member in combination with a relatively movable resilient abutment comprising a strip of metal which is bent into a loop and of which a forward terminal projection of part-circular outline is received in a notch of complementary outline in the other end of the backing plate.

Abstract: A vehicle braking system employs a fluid pressure operated device for engaging the brakes. Flow of liquid under pressure to this device is controlled by a solenoid inlet valve and escape of fluid is controlled by a solenoid outlet valve both of which are normally closed. A demand signal and a feedback signal representing the degree to which brake operation has been achieved are fed to a comparator circuit and the valves are energized in accordance with the sign of the error signal. Operation of the respective means for controlling the operation of the respective valves is obtained by a pulse train generator, and a pair of pulse width modulating means, connected to the respective valves for modifying the mark-space ratio of the pulse train.

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 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.