Three-function pressure switch

Abstract

A pressure switch for controlling the pressure of a refrigerant has a first switch normally open biased, which first switch is used for a condenser, and a second switch normally closed biased, which second switch is used for a compressor. The three-function pressure switch has a pressure chamber partitioned by a diaphragm. First to third movable elements urged toward the diaphragm are displaced in response to the pressure applied via the diaphragm. Displacement of the first and second movable elements is restricted by a stepped portion of the housing. An actuating projection provided on the third movable element presses upward a second leaf spring of the second switch at a lower limit pressure value so as to open the second switch. When the pressure reaches a normal maximum value, a first snap disc mounted on the first movable element actuates the first switch via a push rod. First snap disc and the push rod are restored at a minimum pressure value. In case the pressure abnormally rises above an upper limit value, a second snap disc mounted on the second movable element is altered in shape, so that a cylindrical member connected to the second disc presses downward the second leaf spring. Because the second leaf spring is pivoted about the actuating projection, a movable contact mounted on one end of the second leaf spring is set apart from a stationary contact, so that the second switch is opened again.