Pressure switch with laminated diaphragm

Abstract

A pressure switch includes a housing, the inner space of which is divided into a pressurized fluid operating chamber and a switch mechanism chamber by a flexible diaphragm. The operating chamber communicates with a pressurized fluid inlet hole, and the mechanism chamber houses a switch mechanism. The diaphragm is hermetically fixed to the inner surface of the housing by an elastic seal member. The switch mechanism has a spring for urging the diaphragm toward the operating chamber. The switch mechanism is turned on or off as the diaphragm is transformed against the urging force of the spring by the pressure of a fluid introduced through the inlet hole into the operating chamber. The diaphragm is constructed by stacking a metal film and a flexible plastic film in layers so that the films are independent of each other. The diaphragm, whose peripheral edge is fixed to the inner surface of the inner space is so located that the metal film faces the operating chamber and the plastic film faces the mechanism chamber. The respective thicknesses of the metal film and the plastic film are so set that stress produced in the metal film when the metal film is elastically transformed by the transformation of the diaphragm is smaller than stress produced in the plastic film when the plastic film is elastically transformed by the transformation of the diaphragm.