Fluid-pressure operated anti-skid braking systems for vehicles

A fluid-pressure operated anti-skid braking system including a wheel brake, an actuator for said wheel brake, a supply of brake-applying fluid, a brake-pressure control valve assembly through which fluid from said supply is supplied to said actuator, and control pressure means for operating said control valve assembly, wherein said control valve assembly incorporates a brake-applying chamber connected to said actuator, a fluid-flow control relay valve interposed between said supply and said brake for controlling pressurisation of said brake-applying chamber by fluid from said supply, an application chamber subjected to said control pressure means to control operation of said relay valve, means responsive to a skid signal for operating said relay valve at a skid point determined by said skid signal to relieve the pressure of the fluid supplied to said actuator from said brake-applying chamber, a memory chamber for storing a memory pressure dependant upon the brake pressure occurring at said skid point to provide a datum or changeover point between first and second successive stages of brake re-application, said first stage comprising the re-application to said brake of the supply fluid from said supply until a pressure less than the pressure at said skid point is attained at said changeover point, and said second stage comprising the continued re-application to said brake of said supply fluid but at a reduced rate of pressure increase, and means connecting said memory chamber to said brake-applying chamber for feeding said memory chamber with fluid from said supply upon initial brake application in a common braking cycle.