| 摘要 |
<p>An electromagnetic pump comprising a housing (12) having a fluid receiving chamber (14) in communication with an inlet (20), a pair of fluid chambers (16, 18) connected by a fluid bypass passage to accommodate bubbles, one chamber (16) in communication with the fluid receiving chamber (14) and the other chamber (18) in communication with an outlet (22), an electromagnet (80) carried by the housing (12) located external to the fluid chambers (14, 16, 18) thereof, and a barrier in the form of a thin diaphragm (90) of fluid impermeable material which hermetically isolates the electromagnet (80) from the fluid chambers (14, 16, 18). An armature (120) in the housing (12) is movable within a body (100) of magnetically permeable material which contains the bypass passage (110), has a pole portion (124) located for magnetic attraction by the electromagnet, and has a piston portion (150), preferably of smaller cross-section than the pole portion (124), for forcing fluid from the fluid chambers and through the outlet (22). The armature (120) is moved from a rest position through a forward pumping stroke when attracted by the electromagnet (80) and is moved by a biasing spring (160) in an opposite direction through a return stroke back to the rest position. A main check valve (170) is movably carried by the armature (120) and located in the fluid receiving chamber (14) for closing the pump inlet (20) when the armature (120) is in the rest position and allowing opening the inlet (20) after the armature (120) beings the forward pumping stroke. The structure and arrangement of the main check valve (170) minimises the volume of the fluid receiving chamber (14) to limit the maximum size of a bubble contained therein. A bypass passage (180) containing a check valve (186) which opens during the armature return stroke provides a path for bubbles around the piston (150) to the fluid receiving chamber (14).</p> |
