GB356110A - Improvements in or relating to thermal cut-out switches - Google Patents

Abstract

356,110. Thermostats. AKTIEBOLAGET BIRKA REGULATOR, 48, Surbrunnsgatan, Stockholm. May 22, 1930, No. 15841. Convention date, May 25, 1929. [Class 64 (ii).] A thermal cutout switch 1, adapted to open by the expansion of a solid member 5 in a sealed glass vessel 1, upon overheating or overload, is held open by means of a heating winding 6 connected across its contacts. The member 5 may, as shown, take the form of a frame attached to two rod contacts 4. To reclose the switch the circuit must be temporarily opened elsewhere. Fig. 3 shows a form in which the switch is caused to open by means of a heating winding 7 which is energized when an auxiliary switch 9 in thermal communication with an electric heater 2 is closed. Opening of the contacts 4 puts the winding 6 into circuit and the contacts 4 therefore remain open even when the switch 9 opens. Fig. 6 shows a modification in which a second auxiliary switch 11, adapted to close at a lower temperature than the switch 9, is used. When the temperature falls owing to the opening of the contacts 4, the switch 9 will first open but current will still flow through the switch 11 and winding 6. At a lower temperature, the switch 11 opens, breaking this circuit so that the switch 1 then automatically recloses. Several switches 11 in parallel may be used situated at different places to ensure that the temperature is sufficiently low everywhere before the switch 1 can close.