Continuous quick service valves for braking systems

Claim 1

Apparatus for improved quick service operation in a fluid pressure operable vehicle braking system which operates to make brake applications in response to reductions of fluid pressure in a brake pipe, the apparatus including a quick service valve having a brake pipe pressure input port and a port connected to atmosphere, a pressure difference sensing device responsive to a reduction of fluid pressure in the brake pipe in relation to the fluid pressure at a reference pressure input port to open a further valve to apply fluid pressure from a source distinct from the brake pipe via a first restriction to a pulsating device, the pulsating device comprising a volume receiving the fluid pressure applied to the pulsating device, a pressure responsive member having a first side exposed continuously to atmospheric pressure and a second side having a first area subject to the pressure in said volume and a second area connected via a further restriction to atmosphere, said member being displaceable in response to accumulated pressure in said volume applied to said first area to, on the one hand, open said quick service valve and, on the other hand, to inter-connect said areas to permit reduction of pressure in said volume via said further restriction with resulting reclosure of the quick service valve and repetitive action during continued reduction of fluid pressure in the brake pipe.