Hydraulic pressure control valve

Claim 1

A pressure control valve comprising a housing having therein a bore having a passage extending therefrom for communicating with a source of hydraulic fluid, a control pressure chamber connected to said bore and having a passage extending therefrom for communicating with pressure actuating means, and an exhaust chamber connected to said control pressure chamber and having a passage extending therefrom for communicating with a reservoir of hydraulic fluid, a piston slidably disposed in said bore and a fixed abutment in said bore and elastic means in said bore acting on one end of said piston for urging said piston against said fixed abutment, said piston having a supply pressure space therewithin and a radial opening communicating with said passage to said source of hydraulic fluid, a member in said housing defining an axial opening connecting said supply pressure space to the control pressure chamber, an elongated valve member extending axially of the housing within said supply pressure space and said chambers and having an axial bore extending therethrough and a valve portion on the outer circumference thereof and cooperating with the inner end of said member defining the axial opening from the supply pressure space into the control pressure chamber to form a supply valve, one end of the piston having a blind bore therein in which one end of said valve member is slidably supported, said valve member having an aperture therein opening into said axial bore from said control pressure chamber through which the hydraulic pressure in the control pressure chamber is supplied into the blind bore through the axial bore, and the other end of the valve member being slidable into the exhaust chamber, and a manually operable push rod extending into the exhaust chamber and cooperating with the other end of the valve member to form an exhaust valve between the axial bore and the passage extending from the exhaust chamber to the reservoir for hydraulic fluid.