Automatic air venting device for electromagnetic plunger pump

Claim 1

An automatic venting device for an electromagnetic plunger pump including an electromagnetic coil, and an electromagnetic plunger mounted in sliding reciprocatory movement in a guide case extending through the electromagnetic coil on its center axis, the sliding reciprocatory movement of the electromagnetic plunger being caused by an intermittent magnetic attracting force produced by energization of the electromagnetic coil with a pulse current and the biasing force of a return spring, so as to enable a pumping action to be performed with the cooperation of a suction valve and a discharge valve actuated simultaneously as energization of the electromagnetic coil, wherein said automatic venting device is arranged with a shut-off valve mechanism in a passage at the pressure side between the discharge valve of the pump and a discharge port of the pump, said automatic air venting device comprising: a venting cylinder which is at its one end flow-connected to said passage at the pressure side of the pump and at the other end flow-connected to a return port; a valved plunger fitted in the venting cylinder for sliding reciprocatory movement and formed at one end portion with a leak passage for gas communicating said passage at the pressure side of the pump with said return port; a valve mounted at the other end of the valved cylinder facing said return port; a valve seat arranged on said return port adapted to be brought into and out of engagement with the valve; a spring mounted between the valved plunger and the return port for urging the valve to be brought out of engagement with the valve seat to open the valve; and a return passage provided outside a pump body separately from an intake passage; said spring and said leak passage being set such that when the internal pressure of the pump rises above a predetermined pressure during operation of the pump, said leak passage is blocked by the liquid so that said valve is operative to be closed as it is brought into engagement with the valve seat, and that only when the pressure and flow rate of the liquid at the pressure side of the pump drops below the predetermined valve due to entrainment of the gas in the liquid, said lead passage allows gas or liquid containing gas to glow therethrough and the valve is brought out of engagement with the valve seat by the biasing force of the spring to thereby cause the gas or the liquid containing gas to flow through the return port and the return passage to be vented out of a pump body.