Brake control valve including failsafe means for manually pumping brakes of a vehicle

Claim 1

In a brake valve comprising in combination; a housing defining a bore closed at one end by an end-wall, a shaft slideably disposed through said end-wall having a first end for accepting an operator''s force input and a second end in said bore, a moveable-wall which is moveable by said second end of said shaft including an annular piston slideably disposed in said bore and a reaction piston, said pistons defining between themselves a circumferential variable orifice adapted to narrow and thereby become restrictive in response to said force input, a collapsible chamber defined by said bore, by said end-wall and by said moveable-wall, said chamber having a fluid inlet including a check valve means and a pressure output port, and a flow passage through said brake valve starting at said inlet, passing into said chamber and exiting said chamber through said annular piston and said variable orifice, so that during power-on operation said force input causes the narrowing of said variable orifice and a restriction of flow through the flow passage which in turn generates pressure at the pressure output port, and during power-off operation said force input causes a closing of said variable orifice and a movement of said moveable-wall toward said end-wall thereby decreasIng the volume of said chamber and manually pumping pressurized fluid through said output port.