Patent ID: 8276919
Filing Date: 2012-10-02
Classification: F15B,F16J

Abstract:
1. A hydraulic cylinder comprising: a cylinder having a shaft hole; a piston inserted into the shaft hole; and a seal member mounted in an annular mounting groove formed in an inner periphery of the shaft hole to seal an annular clearance between the inner periphery of the shaft hole and the piston, the seal member including a main body and a lip formed integral with and extending in an axial direction from said main body to slide against the piston, and a portion of the annular clearance on a side of a tip end of the lip between the inner circumferential face of the shaft hole and the piston being made up of a minute clearance formed directly in the inner periphery of the shaft hole of the cylinder in order to suppress protrusion of the lip, an annular clearance area formed directly in the inner periphery of the shaft hole of the cylinder for suppressing occurrence of cavitation and for shortening an axial distance of the annular clearance portion made up of the minute clearance, said annular clearance area is formed on an opposite side of said minute clearance from the seal member, said annular clearance area having a smaller inner diameter than said annular mounting groove and a larger inner diameter than said minute clearance.