| 摘要 |
<p>The vessel cover has an outer section which engages over a coaxial inner section of the bottom part of the vessel. The outer section has radial bores each of which contains a blocking member in the form of a ball while the inner section has recessed abutment surfaces for each ball. A closure ring surrounds the outer section and when in a locked position, the ring presses the balls against the abutment surfaces whereas in a released position, the balls are allowed to move outwards from the abutment surfaces. The inner surface of the ring pressing the balls against the abutment surfaces is formed by the end surfaces of set screws which are threadably inserted in the ring so that pressure can be exactly adjusted for each ball.</p> |
