| 摘要 |
An upstroke wireline jar having a hammer 12 at the bottom end of an operating rod 3 which is axially slidable in a casing 2 having an anvil 13 at its upper end. This casing also includes a releasable coupling means which is biased downwards by a spring 5 to a rest position, said coupling means comprising a sleeve 4 which receives the rod 3 into its upper end and a plurality of arcuate segments 9 which are contained in apertures in the sleeve and engage in a circumferential groove 10 in the rod. Circumferential recesses 11 and 17 in the interior wall of the casing 2 are adapted to partially receive the segments when the sleeve is in appropriate registration therewith thereby facilitating disconnection and subsequent re-engagement of the operating rod with the sleeve. The spring 5 is mounted below the hammer so as to allow free travel of the latter along a substantial portion of the casing. The spring is provided with an upper abutment 6 mounted on a rod 7 the axial position of which is adjustable from outside the jar. At its bottom end the spring 5 abuts a flanged bush 15 which depends from the sleeve 4. A second spring 6 assists in biasing the sleeve to its rest position. |
