Patent GB-850210-A (GB)
Title: Straight pull jar well tool and spring means therefor
Inventor: BROWN ORA ALEX
IPC: E21B31/107
Filed: 1959-06-22
Abstract: 850,210. Drilling oil-wells. JOY MANUFACTURING CO. June 22,1959, No. 21286/59. Class 85. A well tool for dislodging a piece of drilling equipment lodged in a well-hole by imparting an upwardly directed force thereto, comprises a hollow body 16 connected to a drill string and having an upwardly directed hammer face 29, a mandrel 18 connected to the fish and having a downwardly directed anvil face 43, and a spring assembly 45 positioned between the body 16 and the mandrel 18 and compressible by upward strain imposed on the body 16 by the drill string, the spring assembly being clutchable to the body 16 by fingers which are released when predetermined compression of the spring assembly is attained, whereby the body 16 and its hammer face 29 snap upwardly to impart an upward jar on the anvil 43 and on the fish. Figs. 1, 1a, 1b joined end to end show the tool with the compressed spring assembly 45 clutched, by the engagement of protuberances and grooves 62, 63 on fingers 60 with a corresponding formation on a collar 81 secured against axial movement relatively to the body 16 by a channel section split ring 82. The fingers 60 are arranged around the mandrel 18 and have enlarged heads 57 which are notched to receive a circular retaining member 56. In use the drill string and the body 16 are forced down from the position shown in Fig. 2, the fingers 60 which bear against the bottom of the assembly, being prevented from moving down beyond the limit imposed by a flange 70 on the mandrel. The body 16 moves down until the formations 62, 63 snap into the corresponding formations on the collar 81, this being effected by a weak spring 77 urging a latching sleeve 66 upwardly so that cam faces 61, 67 on the fingers and the sleeve force the fingers outwardly. The sleeve 66 is then further forced behind the fingers to latch them securely to the collar 81 as shown in Fig. 1a. The spring assembly 45 is then compressed by raising the drill string and the body 16, during which movement the lower parts of the fingers 60 slide up the latching sleeve until the cam faces 61, 67 come into line at the same time as the cam action of the formations 62, 63 force the fingers inwardly to push the sleeve 66 downwardly against the action of the spring 77. The body 16, being suddenly released, snaps upwardly to strike the hammer face 29 on the anvil face 43. This action is repeated by again depressing the body 16 and re-latching the fingers 60 before again compressing the assembly 45 by pulling up the drill pipe until the latches are released. The force of the impact is determined by the initial setting of the compression of the springs 45, this being effected by rotating a nut 48 threaded on the mandrel. The nut has a friction brake arrangement 90 to prevent. inadvertent movement of the nut; and adjustments are made in steps by moving the body 16 through the small angle permitted by a spline system 31, 32 on the body 16 and the mandrel 18. This system makes it imperative, when splines 31, 32 prevent further rotation, to lift the body 16, and turn it back when one set of splines cam ride over the other, and drop it again. This axial movement of the body 16 enables splines 107 on the body to disengage and re-engage, in angularly displaced position, splines 106 on a sleeve 103 which has projections 102 engaging castellations on a nut member 97 screwed on the nut 48 but locked in an adjusted position thereon by a keeper 100 retained by a ring 101. The nut 48 can, by repeated lifting, lowering and restricted turning of the body 16, be adjusted in any position, the limit being when the projection 102 substantially leave the castellations when further increase of compression is prevented by the cam faces 102a, 99a riding over one another.