Patent ID: 7094041

Claim:
An electromagnetically driven plunger pump, comprising: a cylindrical body defining a passage for a liquid; a plunger, having a passage extending therethrough, reciprocally disposed in said passage defined by said cylindrical body and having intimate contact therewith, said plunger being free to reciprocate within a specific range; a feeding spring for exerting an urging force against said plunger in a first direction; a first check valve for opening and closing said passage extending through said plunger; a chamber on a downstream side of said first check valve; a second check valve on a downstream side of said chamber; a first spring for exerting an urging force against said second check valve for preventing flow of the fluid from said chamber; a second spring, surrounding said feeding spring, for exerting an urging force against said plunger in a second direction opposite the first direction; and a magnetic circuit including a solenoid coil for applying a thrust to said plunger so as to move said plunger in the second direction, such that (i) when said magnetic circuit is activated, said plunger moves in the second direction so as to draw liquid into said chamber through said passage extending through said plunger and so as to accumulate energy in said feeding spring, and (ii) when said magnetic circuit is de-activated, accumulated energy in said feeding spring is released so as to move said plunger in the first direction and thereby discharge the liquid from said chamber.