US 5,381,823 AGranted

Hydraulic pressure control valve

AssigneeSun Hydraulics, LLC

InventorErnest A. DiBartolo

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Abstract

A hydraulic pressure control valve, such as a pilot-operated relief valve and such as a direct-acting differential piston relief valve, having a spring chamber pressurized with fluid from a passage though a movable relief piston. The fluid within the spring chamber may be at the same pressure as that at the inlet valve closing pressure to assist a coil spring acting against the inner face of the relief piston. Inlet pressure in the valve working on an area difference between the faces of the relief piston produces the hydraulic force which is opposed by the spring to open the valve. At its other end, the spring transmits force against a movable biasing piston immediately adjacent a closed end of the spring chamber. The biasing piston provides automatic linearly increasing adjustment of the set pressure in response to inlet pressure acting over a greater net area than that of the relief piston. Inlet pressure fluid flowing into the valve moves the biasing piston toward a stop within the spring chamber to compress the spring and, in doing so, serves to buffer otherwise abrupt pressure spikes as the system is activated. Various types of pressure relief and pressure control valves in hydraulic systems are provided.

A differential piston relief valve comprising:

a body having a longitudinally extending bore therein;
said bore having first and second ends, said first end being closed and first and second piston cylinders adjacent one another, said first piston cylinder being larger in diameter than said second piston cylinder to define a first net area, said first piston cylinder being positioned adjacent said closed first end;
a biasing piston slidably supported in said bore for movement between said first end of said bore and a stop means in said bore;
said biasing piston having a first outside diameter forming an interface with said first piston cylinder and a second outside diameter forming an interface with said second piston cylinder;
a body extension secured to said body at said second end of said bore;
a valve seat secured to said body extension;
said valve seat defining a valve inlet port;
a radially extending passage through said body extension adjacent to said valve seat defining a valve outlet port;
a spring chamber in said body defined by said bore, said first end of said bore and said body extension;
said body extension having a longitudinal bore therethrough forming a third piston cylinder;
a relief piston slidably supported in said third piston cylinder forming an interface therewith;
said relief piston having a head extending radially outwardly from said relief piston, whereby said relief piston has a smaller outside diameter than said piston head to define a second net area;
said piston head having a longitudinally extending annular extension thereon;
an inner edge on said piston head annular extension;
said inner edge forming a seal with said valve seat when said inner edge abuts said valve seat;
a spring guide in said spring chamber abutting said relief piston;
a coil spring axially supported in said spring chamber for transmitting spring force against spring guide and said biasing piston, whereby said spring tends to close said valve;
a passage extending through said relief piston between said spring chamber and said inlet port;
said biasing piston having an orifice therethrough extending from said spring chamber to said first end of said bore, said first net area being greater than said second net area, whereby said differential piston moves toward said stop means as inlet pressure increases.

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Abstract

Claims11