Anti-skid vehicle braking systems

A fluid-pressure operated anti-skid system for vehicles comprising a wheel brake, a supply of operating fluid for actuating said wheel brake, fluid-flow control valve means through which operating fluid from said supply is supplied to said wheel brake, means responsive to a skid signal for operating said valve means to relieve pressure of said operating fluid at a skid point, means defining a memory chamber for storing a memory pressure dependent upon said pressure of said operating fluid at said skid point to provide a first changeover point between first and second stages of brake re-application, said first stage comprising the re-application of said operating fluid from said supply until an intermediate pressure less than the pressure at said skid point is attained at said first changeover point, and said second stage comprising the continued re-application of said supply of operating fluid at a reduced rate of pressure increase, means defining an application chamber for operating said fluid-flow control means, a supply of application pressure for said application chamber of which said pressure is reduced at said skid point by said means responsive to said skid signal, an inlet port from which said application pressure is supplied to said application chamber, a first one-way valve providing communication between said application chamber and said memory chamber, a first restrictor providing communication between said application chamber and said memory chamber in both directions, a latch valve disposed between said inlet port and said application chamber, said latch valve comprising a valve member dividing a space into first and second compartments, and a seating with which said valve member is adapted to co-operate to cut-off communication from said inlet port to said first compartment, a first connection between said application chamber and said first compartment, a second connection between one of said chambers and said second compartment to urge said valve member into engagement with said seating thereby urging said latch valve into a closed position and holding said latch valve in said closed position upon a reduction at said skid point of pressure in said first compartment which is responsive to a decrease in pressure in said application chamber caused by said means responsive to said skid signal whereby said first and second successive stages of brake re-application depend upon said pressure in the application chamber being increased other than through said latch valve until that pressure attains a predetermined value at a second changeover point, and means responsive to pressure in said application chamber at said second changeover point to cause the pressure in said first compartment to increase and overcome that in said second compartment whereby said valve member can move away from said seating whereafter said application pressure at said inlet port can again be supplied to said application chamber through said latch valve to enable the pressure in said application chamber to be increased at an increased rate whereby brake re-application continues in a third stage continuous with said second but at a higher rate of pressure increase.