| 摘要 |
<p>A valve assembly in a bailer for liquid sampling comprises a support 26 located in the lower part of the bailer, and a valve member 20 having a stem 22 passing through a bore in the support and a hemispherical, frusto-conical, or tapered closure surface covered by a layer 19 of cushion material. When the bailer is lowered into a liquid the valve member is displaced upwardly to allow liquid to enter, and, on subsequent lifting of the bailer, the valve member engages seat 21 to trap a sample of the liquid. The cushion material prevents leakage by sealing around any particulate material trapped between the closure surface and the seat and/or by compensating for imperfect manufacture. The flexible plastic guide means 40 is optional, and, if not present, the cushion material extends along the bottom of the valve member.</p> |
