| 摘要 |
An overshot adapted to engage and disengage a fishing neck in a well bore. The apparatus comprises an overshot body, a set of collet fingers which deflect radially and have a surface to grasp a fish in a well bore, a tapered surface abutting the collet fingers which deflect inwardly and outwardly to engage and disengage the fish, and a cam and cam follower mechanism. The cam preferably includes a set of inwardly projecting pins which engage grooves formed on a cam body. The grooves cause the cam body to move upwardly and downwardly with respect to the overshot body. The cam body reciprocates, moving the fingers relative to the tapered surface, thereby providing the engagement and disengagement movement. The cam body causes repetitive movement lengthwise of the cam body relative to the pins which serve as a cam. The groove enables movement toward one end of the body and then toward the other. A spring forces the cam body in one direction while it is forced in the other direction by contact with the fish. Movement in the two directions is typically achieved by jarring to set the tool and jarring to release the tool. A wash pipe through the tool is optionally included.
|
