Low power electromagnetic pump

An electromagnetic pump comprising:

• a) a housing having an interior fluid containing region including a fluid receiving chamber and a fluid pumping chamber in fluid communication therewith, an inlet in fluid communication with said receiving chamber and an outlet in fluid communication with said pumping chamber;
• b) check valve means operatively associated with said fluid containing region for allowing fluid flow in a direction from said inlet through said outlet and blocking fluid flow in a direction from said outlet through said inlet;
• c) electromagnet means carried by said housing and located external to said fluid containing region,
• d) an armature positioned in said fluid containing region of said housing having a pole portion located for magnetic attraction by said electromagnet means and having a piston portion operatively associated with said fluid receiving and pumping chambers for forcing fluid from said receiving chamber through said outlet, said armature being movably supported in said housing for movement from a rest position through a forward pumping stroke when attracted by said electromagnet means to force fluid from said receiving chamber through said outlet and for movement in an opposite direction through a return stroke back to said rest position, said armature piston portion being located between a plunger portion and said pump inlet and movable within said housing, there being a relatively small clearance between said armature piston portion and said housing;
• e) means defining a magnetic circuit including said electromagnet means and said armature and a gap between said pole portion of said armature and said electromagnet means for moving said armature toward said electromagnet means to close said gap in response to electrical energization of said electromagnet means;
• f) controlled means for providing a bypass path for bubbles in the fluid around said armature piston portion between said fluid pumping chamber and said fluid receiving chamber only during said return stroke of said armature;
• and
• g) said check valve means and said inlet being arranged so that the pump displacement can be reduced without reducing the bubble pumping capability of the pump.