| 摘要 |
A percussion drill bit includes a drill body having a fluid passage formed therein for conducting flushing fluid to a front drilling face of the drill bit. The fluid passage includes a main portion extending from a rear end of the bit and terminating short of the drilling face, and a plurality of branch lines extending from a front end of the main portion to the drilling face. Front and rear axially spaced seats are disposed in the main portion of the fluid passage. A check valve in the form of a ball is freely movable within the main portion of the fluid passage between contact with the front and rear seats. When the drill bit is oriented upwardly and no flushing fluid is supplied, the ball gravitates rearwardly into sealing contact with the rear seat so that no fluid can flow rearwardly past the rear seat. When flushing fluid is conducted, the flushing fluid pushes the ball forwardly, into non-sealing contact with the front seat and travels past the ball into the branch lines. During downwards drilling, if the density of the ball is less than that of backflowing fluid, the ball will float upwardly upon the back-flowing fluid and into sealing contact with the rear seat. |
