| 摘要 |
The air lift contains an annular chamber (3), which is formed around a drilling pipe (1) and is connected by conduits to the cavity of the latter and, via a non-return valve (4) to a pipe (2) for feeding in compressed air. The non-return valve (4) has a housing (7) and a plunger (12) which is arranged in the latter, is spring-loaded upwards and forms chambers (16, 17) of variable volume in the housing (7). These chambers (16, 17) are connected to the pipe (2) for feeding in the compressed air and, via axial passages (20) in the plunger (12), to one another. The inner surface of the housing (7) and the outer surface of the plunger (12) are designed in such a way that they form an annular space (21) of adjustable volume which is connected to the annular space for the purpose of downward movement of the plunger (12). The annular chamber (3) is formed by the inner surface of the plunger (12) and an annular channel (23) in the wall of the cooling pipe (1), which channel is connected to the cavity of the cooling pipe (1) and communicates with the chamber (16) of adjustable volume arranged above the plunger (12) during the downward movement of the latter. <IMAGE>
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