Bellows type oil filled pump - has valve on rod inside bellows to prevent accumulation of air bubbles in oil inside bellows

摘要

The pump has a plunger (11) on the end of a bellows (5). A reciprocating rod (8) moves the plunger in a chamber (4) between inlet and discharge non-return valves (2, 3). The vol. (12) inside the bellows and the space (7) round the rod (8) are filled with oil which is admitted through a non-return valve (14). There is an air relief pipe (19) from the space. The section (9) of the rod running through the inside of the bellows has a valve disc (10). When the bellows is compressed the disc seats on a face (18) in the pump casing to shut the vol. inside the bellows from the space round the rod.