Fluid pressure switch having a belleville washer

Abstract

A resilient diaphragm operated pressure switch has a Belleville spring washer with a dished spring disc nested in the center and supported on the inner periphery of the washer resisting movement of the diaphragm. An actuator member is spring biased against the disc and has one end of a toggle spring registered thereon with the other end connected to a movable switch contact blade initially in an open-circuit condition. Upon the diaphragm initially experiencing increasing pressure to a first level, the actuator of the dished disc reverses curvature and moves the actuator to effect movement of the contact blade to a closed circuit condition. Upon further pressure increase to a second level, the Belleville washer snaps over-center and causes further movement of the actuator in the same direction and causes the toggle spring to snap over-center and return the contact blade member to the open-circuit condition. Upon decreasing pressure to a third level between the first and second levels, the Belleville washer again snaps over-center and retracts the actuator and causes the toggle spring to go over-center and move the contact blade again to closed circuit condition. Upon further pressure decrease to a fourth level less than the first level, the dished disc snaps back and retracts the actuator sufficiently to cause the toggle spring to allow the control blade to return to the initial open-circuit condition.