Improvements in relief valve mechanisms for fluid pressure operated systems

摘要

960,533. Valves. HYDRAULIC UNIT SPECIALTIES CO. Aug. 16, 1962 [April 12, 1962], No. 31451/62. Heading F2V. A relief valve arrangement for relieving abnormally high and low pressures in a system having high pressure supply and low pressure return lines 8, 9 respectively which are communicable with one another through an annular valve seat 13 or 40, comprises a body 16 or 41 providing a cylinder 18 which is open at its front and closed at its rear, a piston 29 slidable in the cylinder, and poppet valve mechanism carried by the piston and guided thereby for movement toward and from a normally closed forward operating position in which the poppet mechanism blocks communication between the supply and return lines 8, 9. This poppet mechanism comprises a hollow low pressure outer poppet valve 19 or 22 which is fast with the piston and projects from the front thereof and having a system port 24 opening through its front for communication with the line 8 and an annular portion surrounding this port for engagement with the seat 13 or 40, an annular rearwardly facing valve seat 27 on its front portion through which the system port 12 or 45 opens to the hollow interior of the poppet, a reservoir port 26 opening through the side of the outer poppet to communicate the system port 12 or 45 with the return line 9 when the valve seat on the outer poppet is in open position. A spring 35 urges the outer poppet toward closed position, and a forwardly facing shoulder 38 on the poppet surrounding a front portion thereof, provides a surface upon which fluid in the return line 9 can act to unseat the outer poppet when pressure at the port 12 drops to a predetermining low relief valve below the pressure at the reservoir port 9. The poppet mechanism further comprises an inner high pressure poppet 32 supported from the piston to control communication between the ports 12, 9, this inner poppet engaging the seat on the outer poppet in a forward operating position and presenting a forwardly facing surface upon which fluid at the port 12 can act to unseat the inner poppet when the pressure reaches an abnormally high valve. A spring 34 maintains the inner poppet in its forward position as long as pressure at the port 12 remains below a predetermined high relief value, and a duct 36 that extends axially through the piston and the inner poppet, has one end in communication with the port 12 and its other end opening into the closed rear portion of the cylinder, so that fluid at normally high system port pressure will be maintained in the cylinder to bias the outer poppet, the duct 36 also allowing fluid to be exhausted from the cylinder to allow the outer poppet to open. In a modification, the inner poppet slides on a tubular extension of the piston.