GB652067A - Improvements in or relating to electric heaters for typesetting and composing machines and the like - Google Patents

Abstract

652,067. Automatic temperature control systems. BADER, K. E. July 19, 1948, No. 19279. [Class 38 (iv)] [Also in Group XXXVII] An electric apparatus for type-setting and composing machines comprises two individual thermostatically-controlled heating circuits located inside the melting pot for the type metal, a manually-controlled heating circuit for the mouthpiece of the melting pot, and a bi-range thermostat. The temperatures at which each of the heating circuits are operated may be individually varied. One of the heater circuits carries a heavier load than the other and is adapted to be cut-out at a temperature about 10‹ F. lower than the second circuit. After the initial heating of the pot complete control is assumed by the second circuit, but in tha event of failure of the second circuit the first circuit serves to prevent the metal from solidifying and the pot is not put out of action during repair of the second circuit. The circuits may be operated by two mercury switches attached to thermosprings or by a thermostat as shown in Fig. 2, comprising a rod 2 of negligible co-efficient of expansion and a tube 1 of high co-efficient of expansion. Upon heating, a nut 14 on rod 2 is pulled down upon the ear of two levers 9 pivoted at 8 so that at predetermined temperatures pins 10 of a pair of limit switches 4, 5 are depressed so as to switch off the heating circuits. The temperatures at which the heating circuits are individually operated may be varied by adjustment of screws 12, 13, whilst the working temperature to be maintained may be. adjusted by turning the nut 14.