| 摘要 |
<p>An improved ground piercing tool includes a reciprocating striker (6) having, on its posterior end, a resilient sealing bearing (151) preferably made of a long-wearing, high-lubricity material such as oil-filled nylon and, on its anterior end, two or more spot bearings (101) of relatively small surface area and made of a long-wearing, resilient, high-lubricity material such as oil-filled nylon. A tubular air inlet air valve (208) of this invention may include a sleeve (201) constructed of a flexible, high-lubricity plastic material which sleeve (201) is connected to a metal air inlet pipe (7).</p> |
