| 摘要 |
PURPOSE:To reduce sliding resistance by providing a pocket which is communicated with one oil chamber and a drain groove which is communicated with a tank through a drain passage in a piston rod on a piston outer circumference and thereby generating back pressure in the oil chamber at the discharge time from the oil chamber to a tank. CONSTITUTION:Inside of a cylinder tube 1 is divided by a piston 2 into two oil chambers A and B, while on an outer circumference of the piston 2 a pocket 9 which is communicated with a circular passage 10 on a central part through an oriffice 11 and a drain groove 13 which is communicated with a circular passage 15 through a through hole 14 are provided. The circular passage 10 is communicated with the oil chamber A through an introducing hole 12, and the circular passage 15 is communicated with a drain passage 16 of a piston rod 3. When resistance applied to a valve 8 between the oil chamber A and a tank 7 is small, the oriffice is provided. Friction between the piston 2 and the cylinder tube 1 owing to presence of actuation oil is reduced, so that the structure is simplified and mulfunction is prevented. |
