| 摘要 |
In a hydraulic percussive machine with a shuttle valve 19 to control the flow of fluid to and from a drive chamber 14 there are no timing lands on the piston 11 and a seal 25 between the drive and return chambers. This is made possible as a result of a restrictive orifice 24 connected to the shuttle valve of conventional design and a port 22 in the return chamber 15 which is covered and uncovered by the piston 11. When the port 22 is uncovered the shuttle valve 19 moves over under pressure. When the port is covered, pressure leaks through the orifice 24 to that the shuttle valve moves back again. |
