Pressure switch for a sump pump

Claim 1

A control switch mechanism for controlling a sump pump, particularly a submersible pump, having no integrally associated control mechanism, comprising a housing structure having electrical plug-in contacts extending therefrom for insertion in an electrical power outlet, an electrical outlet socket in said housing structure into which the electrical connecting cord of a sump pump to be controlled is to be inserted, a pressure responsive switch disposed in said housing structure and electrically connected intermediate said plug-in contacts and said socket to selectively complete an electrical connection therebetween, said housing having an air chamber therein and an adjacent water chamber therein, said chambers being separated by an expandable bellows, whereby the division of the total combined volume of said chambers may be varied, resilient means acting on said bellows operative to urge the latter in a direction to expand said air chamber to maximum volume and contract the water chamber to minimum volume, said housing structure having an air supply port therein and an actuating-air port therein, which ports communicate with said air chamber, and further having a water supply port communicating with said water chamber, said pressure switch having the actuating pressure side thereof operatively communicating with said air chamber, a low pressure check valve normally closing said air supply port, tubing means operatively connected to said actuating-air port, the open end of which is adapted to be so disposed with respect to the liquid to be pumped by said sump pump that such liquid will exert a pressure on the air in said tube, whereby the air pressure at a predetermined liquid level will effect actuation of said pressure responsive switch, and tubing means operatively connected to said water supply port adapted to be connected to such a sump pump at the discharge side thereof whereby said water chamber may be supplied with liquid at the pump discharge pressure, said resilient means being so calibrated that the action thereof on said bellows is less than the liquid discharge pressure thereon whereby, during operation of the sump pump, said bellows will be collapsed with the volume of said liquid chamber at a maximum and that of said air chamber at a minimum, said resilient means being operable, upon deenergization of such a pump, to expand said air chamber to maximum volume with air being supplied thereto through said air supply port.