| 摘要 |
PURPOSE:To prevent an accumulation of a working fluid in a circuit so as to prevent a local temperature rise of the fluid by providing an actuator with a discharge valve switched by the working fluid pressure in an apparatus for reciprocating the actuator in short stroke. CONSTITUTION:A working fluid from a fluid pressure pump 20 is introduced to a rotary direction-changing valve 21 through a flow path 54, and introduced to through holes 31, 32 alternately by rotation of a rotary vlave 22 of the valve 21. When the fluid is introduced to the through hole 31, a piston 25 is pushed down by fluid supplied to a piston upper chamber 26 through a flow path 28. At this time, the fluid in the chamber 26 is also introduced to a liquid chamber 34 through a through hole 36, and an upper valve seat 62 is blocked up by lowering of a spool 38 so that a piston lower chamber 27 is opened to a tank 42. Thus, each chamber 26, 27 is always supplied with new fluid to prevent an accumulation of a fluid in a circuit. |
