Patent GB-1102859-A (GB)
Title: Electrical heating element
IPC: H05B3/56
Filed: 1966-08-23
Abstract: A flexible electrical heating element is characterised by a flexible heat stable electrically insulating strand interlaced with a strand of wire having an electrical resistivity less than about 120 ohm-circular mils per foot, a deflection weight of less than about 4 ounces and a heat stable flexible electrical p  insulation coating. "Deflection weight" is defined as the weight necessary to produce a deflection of one centimeter in a ten centimeter span of a bar supported at the span ends.  A formula is given for calculating this from the material and gauge of the wire.  The wire may be copper, aluminium, tin, tungsten, zinc, brass, silver, nickel, chromium, carbon, steels.  The coating may be aromatic polyimides, aromatic polyamides, aromatic polyamide-imides, polybenzimidazoles, polyoxydiazoles.  The insulating strand may be glass fibre, asbestos, aromatic polyimides, aromatic polyamides, poly (m-phenylene isophthalamide), Examples of heating elements are given.  One is woven using 60 warp threads per inch glass yarn and 20 woof threads per inch of polyimide coated No. 32 B. and S. gauge copper wire, the glass yarn being made from continuous filament strands 0.29 mils diameter and a strand count of 225 by first twisting two single strands into a ply and then twisting two plies with 4.4 turns per inch in an S twist to form the yarn, the woven element is coated with polyimide by dipping, draining, removing excess solution by pulling glass rods over the surface and baking 10 minutes at 105 DEG C, 20 minutes at 150 DEG C and 1 minute at 400 DEG C, details of the preparation of the solution being given.  The second example is as the first but the element is woven using uncoated wire.  The third is a linear heating element prepared by mixing 25 parts by weight staple fibres of heat stable poly (m-phenylene isophthalamide) with 75 parts by weight of short lengths (6-8 inches) B. and S. gauge uncoated copper wire, carding, forming into a yarn and coating as in the first example. The fourth is a linear heating element prepared by twisting a continuous yarn of 32 B. and S. gauge copper wire with a continuous yarn of heat stable poly (m-phenylene isophthalamide) fibres then coating as in the first example.ALSO:A flexible electrical heating element is characterised by a flexible heat stable electrically insulating strand interlaced with a strand of wire having an electrical resistivity less than about 120 ohm-circular mils per foot, a deflection weight of less than about 4 ounces and a heat stable flexible electrical insulation coating "Deflection weight" is defined as the weight necessary to produce a deflection of one centimetre in a ten centimetre span of a bar supported at the span ends.  A formula is given for calculating this from the material and gauge of the wire.  The wire may be copper, aluminium, tin, tungsten, zinc, brass, silver, nickel, chromium, carbon steels.  The coating may be aromatic polyimides, aromatic polyamides, aromatic polyamide-imides, polybenzimidazoles, polyoxydiazoles.  The insulating strand may be glass fibre, asbestos, aromatic polyimides, aromatic polyamides, poly (m-phenylene isophthalamide).  Examples of heating elements are given.  One is woven using 60 warp threads per inch glass yarn and 20 weft threads per inch of polyimide coated No. 32 B. and S. gauge copper wire.  The woven element is coated with polyimide by dipping, draining, removing excess solution by pulling glass rods over the surface and baking 10 minutes at 105 DEG C, 20 minutes at 150 DEG C and 1 minute at 400 DEG C, details of the preparation of the solution being given.  The second example is as the first but the element is woven using uncoated wire.  The third is a linear heating element prepared by mixing 25 parts by weight staple fibres of heat stable poly (m-pherylene isophthalamide) with 75 parts by weight of short lengths (6-8 inches) 32 B. and S. gauge uncoated copper wire, cording, forming into a yarn and coating as in the first example. The fourth is a linear heating element prepared by twisting a continuous yarn of 32 B. and S. gauge copper wire with a continuous yarn of heat stable poly (m-phenylene isophthalamide) fibres then coating as in the first example.