GB956577A - A snap-action electric switch device - Google Patents

Abstract

956,577. Thermal switches. J. W. WELSH. Oct. 14, 1960 [Oct. 20, 1959], No. 35291/60. Heading H2B. A snap-action thermal flasher has a thermallyexpansible ribbon attached to a snap-acting vane which is normally curved so as to have a convex front face and concave back face, the ribbon flattening the vane at its sides and buckling it about a different axis, and the ribbon carrying a contact co-operating with a fixed contact. As shown, the vane 40 is initially curved along its longitudinal axis, Fig. 8, but is deformed therefrom to bend about a central lateral axis, Fig. 9, by the ribbon 50 which is fixed to the ends of the vane. The latter is mounted slightly below its horizontal centre line on a leg 28 of a terminal 25 and the contact 55 on the ribbon co-operates with a contact 56 on a terminal 26. The contact 55 is slightly below the centre line of the ribbon so as to tilt and wipe on contact 56. As the ribbon expands on heating, a depression 45 at the centre of the vane flattens out, and the vane eventually snaps over to its initiallycurved state, thereby opening the contacts, which reclose when the ribbon recools. The comers 53, 54 of the vane are bent rearwardly to assist in holding the ribbon.