Abstract: In an hydraulic anti-skid braking system (FIG. 1), a valve controlling the flow of braking fluid to a brake actuator is actuated by a pulse-driven stepper motor in response to signals emanating from a skid sensor. In a practical arrangement (FIG. 3), a motor under the control of a microprocessor actuates a pressure dump valve via an eccentric mechanism upon the appearance of a skid signal at the sensor, in order to de-pressurize the actuator, and also drives a pump which assists in re-pressurizing the system when the skid signal ceases.

Abstract: A control valve for controlling the distribution of pumped hydrodynamic fluid to the trailer brakes of a tractor and trailer combination in response to hydrostatic pressure applied from the tractor braking system has an inlet for pumped fluid, a spool valve operable in response to a control piston to control the flow of pumped fluid to a first working trailer braking circuit through an outlet and to a tank, or reservoir, through an outlet, a flow control valve which provides a passageway communicating with a first flow path for pumped fluid to the spool valve and which is operable in response to pumped fluid pressure to control the flow of pumped fluid to a second working implement circuit through an outlet, and a second flow path for pumped fluid extending between the inlet and spool valve independent from and parallel with the first flow path, so that the spool valve controls the flow of pumped fluid through the second flow path to the fluid outlet leading to the trailer braking circuit.

Abstract: A fluid flow control valve assembly has a housing with first and second ports, and a valve mechanism for controlling fluid flow by closing either port or permitting fluid flow between them. The valve mechanism comprises two relatively movable members, a first member for controlling flow through the first port in response to a first spring, a solenoid, and the pressure differential across the first member; and a second member for controlling flow through the second port in response to the first member, the pressure differential across the second member and a second spring.

Abstract: In a high pressure hydraulic system a slave unit is supplied with fluid from a source through a control valve assembly. The assembly has a valve mechanism to control flow between ports communicating with the source and slave unit. The valve mechanism has two members, a first member controlling flow through the first port in response to a spring, a solenoid, and the pressure differential, the solenoid being unable to move the member against a significant pressure differential, and a second member controlling flow through the second port in dependence on the first member, the pressure differential and a spring. The first port has an elastomeric seal preventing leakage when the port is closed. The system has particular advantages when it is used as a vehicle suspension levelling system, in which an electronic control system controls the supply of fluid from an accumulator through a manifold and control valve assemblies to hydraulic suspension struts in accordance with ride height signals.

Abstract: In a master cylinder assembly the pressure spaces in advance of pedal-operated pistons of two separate master cylinders are interconnected by a transfer passage, and each master cylinder incorporates a boost chamber to which hydraulic fluid from a pressure source is admitted to act on the piston and augment the force applied to the piston by the pedal when the master cylinder is operated. Each master cylinder incorporates a control valve having a valve spool which is normally urged by a spring into a retracted position to close a transfer port providing communication between the pressure space and the transfer passage and to close an inlet port to cut-off communication between the pressure source and the boost chamber.

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.