GB135672A - - Google Patents

Abstract

135,672. Fagerlund, E. A. Dec. 23, 1918. Thermal switches. -A short-time thermal switch for staircase lighting &c. comprises a thermal element made up of a flat coil of wire a held at its ends and connected at its middle to the contact-member f which co-operates with two pivoted contact-arms h<1>, h<2> loaded by the weights k<1>, k<2> so that their lower ends tend to take up a position against the adjustable stops l', l<2>. When the staircase button m is depressed, the thermal element is connected to the mains through the contact-member f and the contact-arm h<2>. The resulting expansion of the thermal element causes a movement of the contact-member to the left under the action of the spring d. If the button m is held depressed, the heating-circuit remains completed until the contact-arm h<2> is held up by the stop P. The contact-arm continues its movement and, by engagement with the arm h<1>, completes the lamp circuit, which is again broken only after the thermal element, which is now deenergized, has contracted sufficiently to take the contact-member past the held-up position of the contact-arm h<1>. By adjusting the positions of the stops l<1>, l<2>, the time during which the lamps are illuminated may be varied. The thermal element may consist of a flat coil p, Fig. 3, wound on insulation o, and enveloped by insulating- material q. Further to conserve the heat, a conductor s in series or parallel with the heating- conductor p may be wound round the flat body.