| 摘要 |
A fluid pressure operated motor for producing reciprocating motion in which each of a pair of spool working chambers is respectively in communication with one of a pair of piston chambers by way of a non-return valve which opens communication between its associated spool working chamber and piston chamber when fluid pressure in the spool working chamber exceeds that in the associated piston chamber and closes communication between its associated spool working chamber and piston chamber when fluid pressure in the piston chamber exceeds that in the associated spool working chamber; each piston chamber has an exhaust port which is so located that, during axial movement of the piston, the one of such exhaust ports through which the contracting piston chamber is exhausting is closed by the piston towards its end of stroke; and wherein a valve element is provided which is responsive to axial movement of the piston, the valve element being adapted to open communication between the contracting piston chamber and the spool working chamber associated therewith so that fluid displaced from the contracting piston chamber acts at least partly to reverse the spool when the exhaust port associated with the contracting piston chamber is closed, and subsequently to close communication between the contracting piston chamber and the spool working chamber associated therewith prior to the piston reaching its end of stroke so that, with the non-return valve associated with the contracting piston chamber closed and the valve element closed, the fluid in the piston chamber is trapped to provide a dashpot arrangement for arresting the piston at its end of stroke. |
