Low power electromagnetic pump

Abstract

An electromagnetic pump comprising a housing having a fluid receiving chamber in communication with an inlet, a pair of fluid chambers connected by a fluid bypass passage to accommodate bubbles, one in communication with the fluid receiving chamber and the other in communication with an outlet, an electromagnet carried by the housing located external to the fluid chambers thereof, and a barrier in the form of a thin diaphragm of fluid impermeable material which hermetically isolates the electromagnet from the fluid chambers. An armature in the housing is movable within a body of magnetically permeable material which contains the bypass, has a pole portion located for magnetic attraction by the electromagnet, and has a piston portion, preferably of smaller cross-section than the pole portion, for forcing fluid from the fluid chambers and through the outlet. The armature is moved from a rest position through a forward pumping stroke when attracted by the electromagnet and is moved by a biasing spring in an opposite direction through a return stroke back to the rest position. A main valve is movably carried by the armature and located in the fluid receiving chamber for closing the pump inlet when the armature is in the rest position and allowing opening the inlet after the armature begins the forward pumping stroke. The structure and arrangement of the check valve minimizes the volume of the fluid receiving chamber to limit the maximum size of a bubble contained therein. A bypass passage containing a check valve which opens during the armature return stroke provides a path for bubbles around the piston to the fluid receiving chamber.