| 摘要 |
This invention relates to a cyclic hydraulic actuator, and more particularly to an actuator for a rock drill and includes: a housing; at least two chambers in the housing; a fluid passage between a first of the chambers and the outside of the housing for feeding a liquid at supply pressure to the chamber during operation of the actuator; a fluid passage between a second of the chambers and the outside of the housing for exhausting liquid from the second chamber during operation of the actuator; a piston reciprocable on an axis in at least the first and second chambers with the piston including an exposed piston area in each of the two chambers for causing, with the liquid at supply pressure, reciprocation of the piston; an inlet valve for opening and closing the second chamber to liquid at supply pressure in the first chamber; an exhaust valve for opening and closing the exhaust passage; the inlet and exhaust valves, chambers and exposed piston areas being so arranged that during cyclic operation of the actuator, when the inlet valve is closed and the exhaust valve is open, the piston is accelerated in one direction, and when the inlet valve is open and the exhaust valve is closed the piston is accelerated in the opposite direction; means on the piston for opening the inlet valve after closing the exhaust valve, means for closing the inlet valve independently of the exhaust valve, and means biasing the exhaust valve from a position in which it closes the exhaust passage to a position in which the exhaust passage is at least partially open once the inlet valve is closed irrespective of the position of the piston in the remainder of its first direction of acceleration, during the cyclic operation of the actuator. |
