| 摘要 |
A mechanical-hydraulic double-acting drilling jar includes an inner tubular mandrel telescopingly supported inside an outer tubular housing. The mandrel and the housing each consist of a plurality of tubular segments joined together, preferably by threaded inner connections. Upper and lower pressure pistons are slidably disposed within the housing, respectively closing upper and lower substantially sealed hydraulic chambers. Longitudinal movement of the mandrel engages the collet, which in turn, translates either the upper piston or the lower piston, depending on the direction of mandrel movement. As one of the pistons is moved, fluid pressure builds in the associated hydraulic chamber, retarding further movement of the mandrel, enabling potential energy to build in the drill string. The collet is restricted from expanding until the mandrel reaches a particular point in the housing, at which time the collet expands, releasing the mandrel to rapidly collide a hammer surface thereon with an anvil surface in the housing. |
