| 摘要 |
<p>In representative embodiments, a backhead for a drill assembly comprises an elongate member having a proximal end connectible to a source of pressurized fluid, a side wall defining an axial bore and an open distal end. A portion of the bore extending proximally from the distal end has an inner surface defining a cylinder portion shaped to receive an axially movable piston. The axial bore also comprises a check valve receiving area shaped to receive a check valve and to separate, during normal operation when a check valve is received in the check valve receiving area, an inlet area extending proximally to the proximal end from the cylinder portion extending distally to the distal end. Various improvements in retaining the distributor and increasing flow efficiency are described.</p> |
