| 摘要 |
<p>4 Drill tube provided with a check valve and comprising a tube (1) and two end pie ces (2,3). One of the end pieces comprises a first contact surface (4) for limitting the mo vement of a valve body (5) when the check valve is open and a second contact surface (6) aga inst which a valve seat (7) rests. The valve seat is held in place by a lock ring (8) which preferably has circular cross section. The cooperating surfaces (12,11) on the valve body and v alve seat are plane.</p> |
