| 摘要 |
A percussion drill apparatus is provided which isolates the surfaces that pound on one another from borehole cuttings, while also sealing in grease, all in a compact assembly. The percussion sub which holds the drill bit and which has an anvil surface which can be repeatedly struck, includes a cylindrical outer surface extending down from the anvil surface. The outer barrel, which has a hammer surface that hammers the anvil surface, carries a cage which surrounds the cylindrical surface, and which holds a seal assembly which seals to the cylindrical surface. Thus, percussion occurs in a sealed area.
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