Thermostatic switch with improved heater assembly and method of assembling same

Claim 1

An electric switch comprising: an open ended cup-shaped housing composed of electrical insulating material, the housing having a bottom wall and sidewalls depending therefrom, a ledge formed in the sidewalls and a disc seated on the ledge, the disc provided with a bore therethrough; a cap closing the open of the housing, a heat responsive thermostatic member mounted between the cap and the disc, a stationary contact and a movable contact means mounted in the housing between the bottom wall and the disc, the movable contact means movable into and out of engagement with the stationary contact, a motion transfer pin slidably located in the bore of the disc transferring motion from the thermostatic element to the movable contact means, a first recessed portion formed in the disc on the side thereof closest to the thermostatic element, a heater assembly mounted in the recessed portion, the heater assembly including a ceramic substrate, a resistive coating on the face of the substrate remote from the thermostatic element, first and second spaced conductive contact layers on the resistive coatings, a second and third recessed portion formed in the disc in alignment with the first and second conductive contact layer and in communication with the first recessed portion, an aperture extending from each of the second and third recessed portions through the disc, four terminal members mounted on the bottom wall, one of the terminal members connected to the stationary contact, the second of the terminal members connected to the movable contact means, the third and fourth terminal members connected respectively to the first and second conductive contact layer, the connection of the latter two terminal members to the conductive contact layers each being effected by a stiff spring element having an elongated distal end portion, the element extending from the respective terminal member through a respective aperture provided in the sidewall, through the respective aperture in the disc into the respective second and third recessed portion, the spring element biased into approximately a normal directioN to that portion of the element extending through the disc aperture with the distal end portion of the element lying flat against the conductive contact layer and in firm electrical connection therewith and the heater assembly cemented into fixed relationship with the disc.