Fluid-pressure operated anti-skid braking systems for vehicles

Abstract

Brakes (1,2; 3,4) on the wheels (5,6; 7,8) at opposite ends of a common axle are each controlled by a separate skid control unti and a single latch valve (21) common to both units closes at the first skid point to be sensed by a sensor (9,10; 11,12) on either wheel. A control module (13) responsive to signals from at least one of the sensors is operative to operate the latch valve and the skid control unit for the respective wheel. When a skid-signal is detected from a sensor on only one wheel the latch valve closes and the brake on the skidding wheel is released and re-applied when the skid signal terminates. The brake is re-applied in a fast first stage, due to pressure from an associated memory chanber and thereafter in a slower second stage due to the latch valve restricting the increase of braking pressure when it is closed. The rate of increase of brake pressure of the non-skidding wheel is restricted to that of the slow stage from the time that the latch valve is closed due to the other wheel skidding. The pressure in the memory chamber can decoy during a skid to compensate for pressure build up elsewhere in the system and so ensure that the pressure to which the brakes are applied in the first stage of brake re-application is not more than that at which the skid occurred.