| 摘要 |
An impact drilling tool for rotary drilling which includes a reciprocating hammer inside a casing for striking the top of an anvil. A drilling bit is connected to the opposite end of the anvil for cutting into the earth's formations. The casing is connected in a string of drilling pipe through which a high pressure fluid flows for operating the hammer and removing cuttings. A feeder means extends through the hammer for alternately directing the high pressure fluid above and below the hammer which high pressure fluid causes the reciprocating motion of the hammer. A shuttle valve located around the feeder maintains communication of the high pressure fluid above the hammer for increased effective stroke to insure a harder driving action of the hammer against the anvil. Also the shuttle valve insures a more complete exhaust above the hammer which reduces the force needed to raise the hammer. In alternative embodiments, the shuttle may control only one of the exhaust or pressurization functions.
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