Abstract: In an hydraulic anti-lock braking system a flow control valve operates with a single-acting solenoid-operated valve (35), and the flow control valve incorporates a spool (17) working in a bore (8) in a housing (7) with the flow directed thorough a passage (20) passing substantially through the centre of the spool (17). A fixed orifice (21) is located at the one end of the spool which defines a chamber (19) for a control spring (18), and a variable orifice is defined between a port (33) in the housing (7) and a metering edge on the input side of an annular groove (24) in the spool (17) and which communicates with the passage (20) in the spool (17).

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.