Flow control and accumulator charging valve

Claim 1

A valve device comprising; a pressure port connected to a pump; a first user port in communication with a pressure accumulator and a first user component, said first user port connected to said pressure port through a first conduit having a first throttle and a first check valve disposed therein; a second user port in communication with a second user component and connected with said pressure port through a by-pass valve including a by-pass piston having a first effective surface adjacent said pressure port subjected to pressure at said pressure port in the opening direction of said by-pass valve and a second effective surface spaced from said first effective surface subjected to pressure from said pressure port in the closing direction of said by-pass valve; said second effective surface being disposed in a control chamber, said control chamber connected to said pressure port through said first throttle and an accumulator-pressure-responsive pilot valve when the pressure of said accumulator is below a predetermined limit and to a return line when the pressure of said accumulator reaches said predetermined limit; a third user port in communication with a third user component requiring a large amount of pressure transmitting fluid and connected with said pressure port through a control valve, said control valve including an operating piston spring loaded in the closing direction of said control valve and having a third effective surface subjected to the pressure at said first user port in the opening direction of said control valve and a fourth effective surface subjected to the pressure at said third user port in the closing direction of said control valve, said third user port connected to said first user port through a second throttle, said operating piston is axially slidable in a cylindrical bore and subdivides said cylindrical bore into first and second chambers, said first chamber connected to said first user port and said second chamber connected to said third user port, the end surface of said operating piston adjacent said first chamber is said third effective surface and the end surface of said operating piston adjacent said second chamber is said fourth effective surface, said operating piston is a hollow piston including an axial bore therethrough having a portion thereof dimensioned to provide said second throttle; the axial stroke of said operating piston is limited by spaced stops provided in said cylindrical bore; and a second conduit connected to said pressure port opens radially into said cylindrical bore, said second conduit being open in one end position of said operating piston and being closed by the circumferential surface of said operating piston in the other end position of said operating piston.