| 摘要 |
PCT No. PCT/GB92/02198 Sec. 371 Date Jul. 18, 1994 Sec. 102(e) Date Jul. 18, 1994 PCT Filed Nov. 27, 1992 PCT Pub. No. WO93/11336 PCT Pub. Date Jun. 19, 1993.A check valve for connection with the top end of a drillstring as a mud saver comprises a tubular valve member (18) which is axially shiftable within a tubular body (10) through a sleeve seal (19) which is mounted in the body (10) and which cooperates with ports in the wall of the tubular valve member (18) and which is disposed adjacent a downstream end of the tubular valve member. A compression spring (20) urges the tubular valve member (18) in the upstream direction into abutment with an upstream stop (15). The downstream end of the tubular valve member is closed by means of a frangible glass disc (21). The sleeve seal (19) is also axially shiftable in the body (10) in an upstream direction away from a downstream stop (17) and the compression spring (20) urges the sleeve seal (19) in the downstream direction. In a compact arrangement, the tubular valve member (18) is housed within an upstream hollow pin (30) of a saver sub particularly suited to a top drive arrangement.
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