GB318574A - Improvements in or relating to electrical heating apparatus particularly for use with incubators - Google Patents

Abstract

318,574. Church, G. T. June 6, 1928. Supplying consuming devices. - Relates to apparatus employing a heating resistance A tapped at different points which are connected to contact studs B co-operating with an arm C connected to one of the supply leads and consists in the provision of a make and break device D' operated by a temperature responsive element to control a part of the heating resistance. The apparatus is particularly intended for use in incubators. In Fig. 3 a second contact arm C<2> is provided, the arm C<2> being mechanically connected to the arm C but electrically insulated from it. The arm C<2> is connected to the supply lead when the switch D<1> closes. An extra heating resistance A<3> may be connected at one end to a knife contact A<4> which engages with an extension C‹ on the arm C when the latter is moved to reduce the main resistance to a minimum. Additional dummy contact studs B<x> are provided so that the arm C<2> can be moved on to the stud appertaining to the maximum resistance. In a modification the resistance A constitutes an auxiliary element in parallel with a main heating element which is permanently in circuit. In a further modification there are three contact arms and two make and break devices. In Fig. 6 there are two make-and-break devices D, D<1> operated by a common rod D<2> and connected to contacts E, E<1>, and to the positive supply lead. The contacts E, E<1> are arranged on either side of a pivoted armature E<2> carrying contact-blades E<3>, E<4>, connected to electromagnets E<6>, E<5> which are also connected to the negative supply lead. The pivot of the armature E<2> carries a weighted lever E' having prongs E<9> dipping in mercury cups E<10> connected to the contact arms C, C<2>.