| 摘要 |
A method of the invention uses a pneumatic ground piercing tool having a reversing mechanism with a supplemental air line capable of supplying compressed air for reverse operation to a radial port in the air distributing mechanism. This radial port is located between a pair of bearing surfaces on the step of the air inlet conduit, and when pressurized by the supplemental air line, causes the front pressure chamber to receive compressed air earlier than normal, shifting the stroke of the striker rearwardly so that the tool operates in reverse. Such a method includes the steps of operating the tool in forward mode by supplying compressed air to the first air hose, and operating the tool in reverse mode by supplying compressed air to the second air hose while permitting partial venting of the front pressure chamber through the first air hose.
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