Pressure sensing switch with conductive deflectable diaphragm

Claim 1

A pressure sensing switch comprising; a diaphragm having a ring-shaped peripheral portion, a frustoconical side wall portion being continuous to a radially inner edge of said peripheral portion and extending upward therefrom, and a deflectable portion constituting a portion of sphere and being continuous to a radially inner edge of said side wall portion and deflectable between one dead point and the other dead point in response to a pressure change within a predetermined pressure range; and a movable contact member positioned to face said diaphragm in such a way that a contact point of said contact member to be contacted with said deflectable portion of said diaphragm is positioned intermediate said one dead point and said other dead point of said deflectable portion; said diaphragm being made of a material having a Young's modulus E of 1.0×10 4 -2.1×10 4 kg/mm 2 , Poisson's ratio V of 0.3 and a thickness t of 0.02-0.2 mm, a diameter d measured at the radially inner edge of said side wall portion being 5-10 mm, a radius of curvature R of said deflectable portion being 18-44 mm, a ratio of the radius of curvature R of said deflectable portion to the diameter d measured at the radially inner edge of said side wall portion being 2.5-5, and a maximum deflection Dmax as expressed by a general formula of ##EQU3## where P is a pressure (kg/cm 2 ) acting on said diaphragm, being 0.2-0.4 mm.