by means of illustration and are not considered limiting a second bimetallic disc 122 is coaxially disposed within a recess 124 defined by flange 14 and is supported thereby from displacement in one axial direction by a shoulder 126 formed in flange 14 the material forming flange 14 adjacent the circumferential edge of bimetallic disc 122 is swedged or otherwise deformed to prevent displacement of disc 122 in the other axial direction of travel a ceramic heating element 128 is likewise disposed coaxially within recess 124 adjacent bimetallic disc 122 heating element 128 operates to heat the surrounding area including bimetallic disc 122 upon electrical excitation via a pair of insulated electrical leads one lead 130 passes radially outwardly through a passageway 132 in flange 14 exiting at the circumferential surface of still another reduced intermediate portion 134 of driving shaft 12 a steel race 136 is pressed over portion 134 for support thereon through an intermediate insulating gasket 138 lead 130 passes through a registering aperture 140 in gasket 138 and is electrically connected to race 136 the remaining lead not illustrated is electrically connected to flange 14 and thus ground race 136 is thus mechanically supported by driving shaft 12 for rotation therewith but is electrically insulated therefrom race 136 and gasket 138 coact to support a bronze slip ring 142 from axial displacement while allowing it to rotate freely thereabout slip ring 142 is locally connected to an elongated tether 144 constructed of electrically conductive material.