| 摘要 |
Hydraulic percussive apparatus has a body 104 in which a unitary piston/striker 101 with piston portion 102 and striker portion 103 is reciprocable, for impact with a tool T releasably retained in the forward end of the body 104. The body 104 contains a forward pressure chamber 105 and a return pressure chamber 106. The forward pressure chamber 105 is controlled by a valve V which in a cyclic manner alternately connects the chamber 105 to supply pressure P and to exhaust Ex with fluid pressure in this chamber acting on the piston portion 102 to produce forward strokes of the piston/striker 101 so that the striker portion 103 impacts the tool T. The return pressure chamber 106 is connected to the supply pressure P to provide a continuous return force acting on the piston/striker 101. A channel 113 is closed off during normal reciprocation of the piston/striker 101 but in the event of an overstroke of the latter in the forward direction interconnects the two chambers 105 and 106. The resultant hydraulic flow through the channel 113 pressurises the chamber 105 sufficiently to apply a forward fluid pressure force bias to the piston/striker 101.This holds the piston/striker 101 in the forward position so that reciprocation thereof ceases. <IMAGE> |
