| 摘要 |
A piston (2) displaces in a cylinder (1) between two positions. The cylinder is connected at one end to pipework (3,4,6) comprising a first section (3) whose interior volume is greater than the cylinder swept volume. Second (4) and third (6) sections are connected at the end of the first section. The second pipework section (4) ends in a storage reservoir (5) containing the product to be pumped and the third section (6) ends in a return reservoir (7). The second section (4) has a non return valve (8) which prevents the product returning to the storage reservoir (5) and the third section (6) has a non return valve (9) preventing the returned product coming back into the pipework. The cylinder and the part of the pipework not containing any product are filled with a neutral gas if oxygen in the air is not compatible with the product.
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