GB708542A - Improvements in and relating to electric heating elements - Google Patents

Abstract

708,542. Eleotric heating resistances. HOBOURN AERO COMPONENTS, Ltd. Sept. 24, 1951 [May 30, 1951], No. 12759/51. Class 39 (3) A flexible electric heater is made as a cord or flat ribbon by braiding together several strands 1 of heatinsulating material such as fibre glass with one or more resistance wires 2 so that portions of the wire are exposed at the surface. The wire may be interlaced into the material during braiding of the fibre glass strands. The wires may be of nickel chromium and extend in tortuous or straight parallel paths through the insulating strands. The wire is held against short-circuiting self contact by the material and is free to expand and contract in relation to the glass strands. Two wires may be brought up respectively through the centre of the second horn gear from each edge, and in order to expose the wires on opposite sides of a braided ribbon, several bobbins are omitted at equal intervals in the braiding machine, whereby the wires are laid parallel in the ribbon, which is an open plait allowing air to pass through the braid. Alternatively a bobbin of resistance wire replaces a bobbin for the fibre glass, which gives the wire a zigzag path. The braid may be made on a cord or round machine, and by including alternate bobbins of wire and fibre glass, spirals of wire are insulated by the fibre glass. The heaters are mounted on formers, give black heat and may be used as convection heaters or for drying.