| 摘要 |
A valve-less twin-cylinder pump having a tube switch comprises a pump casing (8) which is closed by a cover (17) so as to produce a suction chamber (7). The medium to be pumped reaches the suction chamber (7) via a connection piece (20). A switch tube (10) can be swivelled with the aid of a swing mechanism (16) upstream of either port (5, 6) of one of the two pump cylinders. A shut-off plate (13) at the pivotable end of the switch tube (10) covers, in its central positions, the ports (5, 6) of the pump cylinders in order to prevent the medium to be pumped from dropping back into the suction chamber (7). Small pressure surges are compensated by means of a bellows cylinder (18) which, via a top up valve (19), communicates with ambient air. <IMAGE>
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