| 摘要 |
A reverse percussion device (30) for use with hydraulic percussive drills is provided. The reverse percussion device (30) includes a cycling piston (34), valve (36) and anvil (38). The piston (34) and valve (36) move in opposing directions between low and high pressure passages automatically until a lodged drill bit (18) is freed, ther eby facilitating removal of the drill bit (18) from the drilled hole and eliminating alternate loosening and tightening of drill string threads ( 14). The reverse percussion device (30) preferably inclu des an automatic disabling feature which causes the reverse percussion operation to cease when the bit is free to retract normally.
|
