Patent ID: 6681794
Filing Date: 2004-01-27
Classification: F04B,Y10T

Abstract:
An unloading valve (30) comprising:a valve body (31) having a first pressure chamber (34), a second pressure chamber (35) and a spool bore (32); a spool (33) having a spool body (44) inserted in said spool bore such that one end of said spool is positioned in said first pressure chamber and the other end of said spool is positioned in said second-pressure chamber; a flange (39) provided at the end of said spool on the side of said second pressure chamber and coming into contact with an abutment surface (51) formed on the side of said valve body, thereby properly positioning said spool body in a neutral state; and a spring (52) disposed in said second pressure chamber and biasing said spool such that said flange contacts said abutment surface on the side of said valve body, said spool being moved toward the side of said second pressure chamber when a pressure in said first pressure chamber rises above a pressure in said second pressure chamber in excess of a setting value of said spring, thereby releasing the pressure in said first pressure chamber to a reservoir (15), wherein at least one of said valve body (31) and said spool body (44) includes hydraulic pressure guiding means (60, 61) for introducing a hydraulic fluid under the same pressure as that in said second pressure chamber (35) to an interface between said flange (39) and said abutment surface (51) on the side of said valve body.