| 摘要 |
A jar for use in imparting jarring blows to an object lodged in the bore of a well. The jar includes a mandrel member and outer telescopically related tubular member, the mandrel member and said tubular member being telescopically movable between an extended and a collapsed position of the jar. One of the members is connected to a drill string while the other of the members is connected to the object to be jarred. Telescopically overlapping portions of the members provide an annular chamber for confining an operating fluid. A sleeve and a cylinder extend into the chamber and into an essentially fluid tight fit with each other for a selected portion of the telescopic travel between the extended and collapsed positions. An operating fluid bypass is provided in the first one of the members, the bypass being in fluid communication with the operating fluid above and below the sleeve, the bypass including a channel. An orifice is disposed in the channel. A filter, distinct from said orifice, is provided by controlling the clearances between the sleeve and the first one of the members.
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