GB733684A - Electric heating devices - Google Patents

Abstract

733,684. Heating liquids electrically. SCHMIDT, G. Nov. 29, 1951 [Nov. 30, 1950], No. 27983/51. Class 39 (3). [Also in Group XXXVII] A cup-shaped vessel 4 containing water for heating a feeding bottle 14 or like liquid container immersed therein has an exterior layer of insulating material and a heating resistance wire 6 wound on and partly embedded in the insulation on the lateral wall, controlled by a thermostatic switch 10 in contact with the underside of the vessel 4, which is so constructed as to conduct such a quantity of heat to the switch 10 as to compensate for the delay of operation of the switch which would occur if the operation depended solely on heat transference from the liquid in the bottle. The switch and the contents of the bottle are thus brought simultaneously to the required temperature. The vessel 4 may be of glass or a metal of low heat conductivity, e.g. iron or steel or may be of artificial resin preferably with particles of copper or aluminium therein to give the desired heat conductivity. If the vessel 4 is of copper, a further layer of insulation is applied to the base. A small auxiliary resistance strip in parallel with the heater 6 may be placed below the thermal switch 10 to effect a more rapid actuation. The switch 10 comprises a folded bimetallic strip 16 soldered at the fold to a copper gauge strip 17 providing good heat conductivity and connected by a lead 9 to the heater 6. The switch contacts comprise a nickel strip 23 soldered on one arm 22 of the bimetal strip, and two tungsten rods 20 are supported on insulation 19 on the other arm 18 of the bimetal strip. The auxiliary resistance may be placed between the arms of the bimetal. The vessel 4 is supported on a rubber ring 5 in a container 1, which is attached by a bayonet joint 2 to a base 3 carrying a supply cable 8 and a pilot lamp 12 in series with the switch 10. Specification 668,148 is referred to.