| 摘要 |
A reversible, pneumatic ground piercing tool has a tail assembly with exhaust passages therethrough. At least a potion of each exhaust passage angles radially inwardly and ends in discharge ports that communicate with a central hole at the rear end of the tail assembly, whereby exhaust escapes through the central hole. A tail cone has a radially inwardly extending flange on the inner periphery of the central hole, which flange is rearwardly spaced from and covers the discharge ports. |
