GB1013825A - A method of making a flexible electric heating device - Google Patents

Abstract

1,013,825. Flexible electric heaters. ELECTROTHERMAL ENGINEERING Ltd. March 1, 1963 [March 5, 1962], No. 8485/62. Heading H5H. A flexible electric heating device, e.g. a flat sheet or strip, or a cup-shaped mantle, is produced by forming a first bond of interlocking loops of insulating material, subsequently making a second bond which includes a plurality of individual length of looped insulating material interlocking together, and simultaneously both incorporating in the second band an elongate electric heating element in a non- interlocked manner, and interlocking some of the loops of the second band with loops of the first band, whereby the bands are joined together, side-by-side. A resistance element 1, Fig. 3, formed from a resistance wire wound on a core of, and covered by, glass fibre, is fed into a four-needle overlook machine, which forms three glass fibre yarns into interlocking loops around the element, which is bent back spirally upon itself so that the fourth yarn 14 can simultaneously be formed into loops interlocking with those of the adjacent section of element. The tension of the element 1 fed into the machine may be varied such that, upon release, the disc-shaped heater is distorted into a cup form (Fig. 4, not shown). Rectangular strips or sheets may be formed from a plurality of separate, sequentially formed bands (Figs. 6 to 8, not shown), some of which may lack resistance elements, thereby acting as spacers to adjust the temperature distributions; the latter may also be achieved by a non-uniform diameter of heating element or spacer, or by varying the tension of the yarns on the rate of feed of the heating elements or spacers to the interlock machine.