Pneumatic antiskid braking system

Claim 1

A pneumatic antiskid vehicle braking system comprising a normally open inlet valve adapted to control the fluid connection between a variable pneumatic braking pressure source and the variable volume motor chamber of a brake actuator controlling the braking operation of at least one of the vehicle wheels, a normally open outlet valve adapted to control the fluid connection between the variable volume exhaust chamber of said brake actuator opposite to said motor chamber and a relatively low fluid pressure reservoir, a first normally closed exhaust valve adapted to control the fluid connection between said motor and exhaust chambers of said brake actuators, which inlet, outlet and first exhaust valves are operatively connected to and actuated by an antiskid control unit responsive to the angular displacement of said braked vehicle wheel so as to modulate the differential pressure between said motor and exhaust chambers of said brake motors according to predetermined skidding conditions of said braked wheel, and a second normally closed exhaust valve adapted to control the fluid connection between said motor chamber and said reservoir, said second exhaust valve being operatively connected to and actuated by a piston responsive to said differential pressure between said motor and exhaust chambers so as to connect said motor chamber to said reservoir whenever the pressure level in said exhaust chamber exceeds the pressure level in said motor chamber by a predetermined value, characterized in that said exhaust valve is further operatively connected to control means actuated by said antiskid control unit so as to be maintained in its normally closed position whenever said inlet, outlet and first exhaust valves are not actuated away from their respective normal positions.