GB287453A - Improvements in or relating to thermostatic switches - Google Patents

Abstract

287,453. Aktiebolaget Birka Regulator. March 19, 1927, [Convention date]. Thermal switches; contacts; thermostats - In thermal switches in which the contacts are enclosed in an evacuated or gas-filled receptacle, the thermal element is arranged in effective heat-conducting connection with the walls of the receptacle, so that it responds readily to changes of temperature outside the receptacle, whether these changes are atmospheric or produced by a heating coil wound round the receptacle. According to the construction shown in Fig. 1, a bimetallic strip 11, which opens contacts 6, 7 upon an increase of temperature, is mounted on a split copper tube 1 fitting closely to the walls of a glass receptacle 2. In a modification. Fig. 2, rise of temperature causes the expansion of a metal tube 13 and thereby the separation of two contacts 16, 16<1> mounted on non-expanding rods 15, 15<1>, made e.g. of invar. Heat-absorbing copper tubes may surround the rods 15, 15<1> to cool the contacts. The tube 13 is provided with an aperture 18 for observing the contacts. In another modification, the rods 15, 15<1> of Fig. 2 are made hook-shaped so that expansion of the tube 13 opens the contacts 16, 16<1>. When an external heating coil is wound round the receptacle, the coil can be protected by surrounding it with an insulating cylinder. The Specification as open to inspection under Sect. 91 (3) (a) describes also a modification in which the metal tubes 1 or 13 themselves form the body of the receptacle and are provided with end pieces of glasses. This subject-matter does not appear in the Specification as accepted.