Combination accumulator charging, flow control and relief valve assembly

Claim 1

A control valve for a system including a First source of hydraulic fluid under pressure, an open center circuit, a second source of hydraulic fluid under pressure in communication with said open center circuit, and a circuit including a fluid accumulator comprising: a valve body; a valve spool reciprocally arranged in the valve body, the spool including a first chamber, a second chamber and a restrictive orifice therebetween; means communicating the first source with the first chamber; means for communicating the second chamber with the accumulator circuit and delivering fluid directly to the accumulator circuit at a rate at least partially determined by the orifice; means for communicating the first chamber with the open center circuit and delivering excess fluid thereinto; pilot means associated with the accumulator circuit and in communication through another more restrictive orifice in the valve spool with the second chamber of said valve spool, the pilot means being responsive to maximum accumulator pressure for providing fluid pressure relief for the valve spool downstream of its restrictive orifice and causing the spool to divert fluid flow from the source to the open center circuit, the pilot means being responsive to substantial reduction of accumulator pressure from its maximum value for terminating fluid relief for the valve spool; passage means communicating the valve spool downstream of its more restrictive orifice to a fluid drain, the pilot means comprising a spool; and spring means for urging said pilot spool into blocking relation with the passage, piston means of smaller cross section than the pilot spool, the piston means in coaxial alignment with the pilot spool and in communication with the accumulator circuit, the piston means responsive to maximum accumulator pressure for urging the pilot spool toward unblocking relation with the passage and means for communicating an end surface of the pilot spool with the accumulator circuit when the pilot spool is shifted by the piston means.