GB683029A - Multiple coil tubular electric heating element - Google Patents

Abstract

683,029. Tubular electric resistance heaters. BACKER, C. B. Nov. 2, 1949 [Nov. 18, 1948], No. 28071/49. Class 39(iii) A tubular heating element e.g. for hotplates, room heaters or immersion heaters comprises a closed tube 39 with its ends adjacent containing two separate heating coils 6, 7, one coil 6 having a section extending from one end of tube to an intermediate point 9 where it is bent back to have a return section to the same end 18 of the tube, while the other coil 7 has a section extending from the other end 18<SP>1</SP> of the tube to a point 11 adjacent the point 9, where it is bent back to have a section returning to said end 18<SP>1</SP>, so that the coils 6, 7 may be separately energized to heat different parts of the tube. The coils are embedded in solid insulation in the tube, and the return section of each coil may be stretched out uncoiled to liberate less heat. A third coil 19 of low load e.g. for simmering may run the full length of the tube with a terminal 20 at each end and may be stretched out in one part. The sections of the coil lie alongside one another and may be stretched out near the ends of the tube, which may be longitudinally indented so as to follow the contour of the coils through more than 60 per cent of the circumference of each coil. The coils may be arranged to give a hot centre in a hotplate. The tube may contain four coils. In Fig. 8 one coil 25 has two return sections 26, 27 and the tube contains a low temperature coil 28. The tube is preferably convolute, with its adjacent ends at the edge or in the centre of the hot-plate. The adjacent return bends of the coils may lie at an outer edge of the hot plate, which may comprise a coiled narrow tube in which the coils lie in a vertical plane, the vessel to be heated resting on the edge of the tube. The ends of the tube carry pin terminals. When the adjacent ends of a tubular hot-plate are arranged centrally, the outer part of the tube is bent down and radially inwards at 48 and has a part 49 bent up at the centre and then down to carry a plug terminal 41. The coils may be connected separately, in series or in parallel. The Specification as open to inspection under Sect. 91, comprises also a heating tube with three heating coils extending from end to end of the tube with terminals at opposite ends, two coils being stretched out at opposite ends to give major heating at different parts of the tube, the third coil heating the tube uniformly. This subject-matter does not appear in the Specification as accepted.