Patent ID: 7855345

Claim:
In a pneumatic pressure operated electrical switch construction for a sump pump assembly comprising a housing, a pressure responsive actuator carried by the housing, an electrical switch having a pair of electrical contacts, one movable and one stationary carried by the housing and being operatively associated with the actuator so that the actuator will operate the switch from an on to off position depending upon the sensed pneumatic pressure reaching a predetermined pressure, and reset means carried by the housing for a constant resetting of the switch from its on position to its off position, the improvement comprising a first spring attached to portions of a spring plate having the one movable electrical contact to create a snap over action of the spring plate against the other stationary electrical contact affixed to the housing, a pillar connected to the actuator and engaging the spring plate, a second concentric spring engaging the pillar and having a spring holder thereover, a third spring concentric with the second spring and wound around the spring holder, a knob mounted over the third spring and partially disposed within the housing, a thumbscrew affixed to the housing and having a distal end axially aligned and adjustable in height above the knob for moving the knob either up or down along its vertical axis to adjust the compression of the second and third springs to set the trip point of the switch, wherein the pneumatic pressure against the actuator reaches a predetermined trip point causing the spring plate to move and snap over the movable electrical contact against the stationary contact on the housing to close the switch contacts to the on position, the pressure switch trip point differential being adjustable by the vertical movement of the thumbscrew distal end against the top of the knob and the first spring biasing the snap over motion to provide a constant reset point for the switch as the pressure against the actuator decreases to the predetermined level no matter what the trip point setting happens to be by adjusting the thumbscrew, the thumbscrew is rotatably mounted to the housing and axially aligned with the axis of the knob for adjusting the position of the knob within the housing to set the compression of the second and third springs, which sets the differential trip point and controls the snap over action of the first control spring in the closure of the electrical contacts to energize the sump pump assembly, wherein the thumbscrew is axially movable relative to the housing to set the trip point of the pressure switch, wherein the actuator is axially movable relative to the housing in opposing directions for the constant reset and the differential trip points for the pressure switch, and wherein the knob includes scale readings on its external surface for setting the trip point of the pressure switch by manual screwing the thumbscrew to raise or lower the height of the knob extending above the housing to correspond to a predetermined set point.