GB725125A - Improvements in or relating to electrically heated protective coverings - Google Patents

Abstract

725,125. Electric heating resistances. GOODRICH CO., B. F. Nov. 17, 1953, [Nov. 26, 1952], No. 31839/53. Class 39 (3). [Also in Group XXII] An electrically heated flexible covering especially for de-icing aeroplanes comprises rectangular or trapezoidal sheets 41-43, 45 of natural or synthetic rubber or neoprene or the like superposed to enclose resistance wires 64 extending in parallel in groups to opposite margins where they are connected to flexible conductors 62, 63 so arranged that the heating elements consist of wires in parallel in groups, and the groups are connected in series to give equal heat in each unit. The resistance wires 64 are placed between woven glass sheets 59, 60 with a rubber sheet 61 and are covered by a woven or knitted textile fabric 44 of cotton, silk or glass fibres and embedded in the covering, which is cemented together and to the aeroplane. Thus a wing is protected by several electric heaters 46-48 insulated from one another, the leading edge section 47 being rectangular and preferably heated more than the outer sections 46, 48 which are tapered. In order to ensure unbroken heating at the meeting surfaces of the sections, the outer edges of the heaters are folded downwards and inwards at 54, 55 as in Figs. 3, 16, the dielectric sheets 42, 43 being of such size as to allow space for the inwardly turned parts with their braided supply conductors 62, 63. To make the heaters, a glass fabric sheet 59 is held by tabs 83 on a rotatable drum 75 and the conductors 62, 63 are laid in pairs on strips 85 of Holland cloth thereon (Fig. 7). The resistance wire 64 is then wound on helically from a spool and soldered to the conductors 62, 63. The wires are severed between each pair of conductors 62, 63 along the line 90. A second layer 60 of glass fabric is cemented over the wires to the glass cloth 59, and the layers 59, 60 are severed also between each pair of conductors 62, 63. The heaters may be of tapered form and are then removed from the drum. The ends of the wires 64 are trimmed, the edge of the top sheet 60 being folded back as a flap 60b (Fig. 14). The lower sheet 59 is cut back as shown and a layer 61 of neoprene is adhered thereto. A woven tape 66 is secured at the lower edge of the layer 61 adjacent a polythene strip 95. The conductors 62, 63 are severed and rendered discontinuous by fillers 96 of neoprene between the severed ends, so that groups of parallel wires 64 are connected in series. The tape 66 is then bent forward to the conductor 63 and the flap 60b of the sheet 60 is folded over and cemented to the conductor 63 and tape 66. The polythene strip 95 is removed and the edge of the heater is folded back over itself as shown in Figs. 3, 16. The heaters are then vulcanized to dielectric sheets 41-43 and 45.