Control valve for anti-skid air braking system

Claim 1

In an air braking system comprising a brake for a wheel of a vehicle, an actuator including a high pressure chamber and a low pressure chamber on opposite sides of a movable wall for applying said brake, a supply of air under pressure, a pedal-operated valve controlling the flow of air from said supply to said high pressure chamber of said actuator, skid sensing means for supplying a signal when the deceleration of said braked wheel exceeds a predetermined value, and skid control means for reducing the differential pressure across said movable wall in response to said signal; a control valve assembly comprising a housing having an inlet connected to said air supply, a first outlet connected to said high pressure chamber, and a second outlet connected to said low pressure chamber, a first valve seat located in said housing between said inlet and said first outlet, a first valve controlling communication through said first valve seat, a spring acting on said first valve so that said first valve is normally closed, a second valve seat located in said housing between said first and second outlets, a second valve controlling communication through said second valve seat, a pressure responsive member controlling said valves, said pressure responsive member having first and second opposed areas and arranged to open said first valve and close said second valve in response to increased fluid pressure acting on said first area, said first area being acted upon by fluid pressure under the control of said skid control means which is arranged to reduce said pressure acting on said first area in the event of a skid signal to close said first valve and open said second valve, and said second area of said pressure responsive member being exposed to pressure in said first outlet to oppose re-opening of said first valve on cessation of said skid signal.