Patent GB-644565-A (GB)
Title: Improvements relating to the production of patterns, for use as conductors in electric circuits and apparatus
IPC: H02K3/26
Filed: 1945-08-31
Abstract: 644,565. Inductances and transformers; dynamo-electric machines. STRONG, H. V., and EISLER, P. Aug. 31, 1945, Nos. 22485/45 and 13376/46. [Classes 35 and 38 (ii)] [Also in Group XXXVI] An electric winding for an inductance, transformer or dynamo-electric machine is produced by bringing a blank of conductive material into the final form together with sufficient bridgepieces to enable it to be handled as a unit, securing it to an insulating support and then removing the bridge-pieces. The process may be carried out in more than two stages by subdividing the production of the complete pattern into stages and securing it to insulation between each stage. The conductive material may be bonded to the insulation over its whole area or only over a sufficient area to enable it to be handled, or it may be sandwiched between two layers of insulation which are then bonded together. The bridge pieces may be, removed by punching through them and the insulation. Figs. 1 and 3 show two stages in the formation of a coil made from a metal blank 1. Slots 3 are first punched in the blank at certain places only as shown in Fig. 1 to leave a pattern which is stiff enough to be handled and which is then cemented or otherwise attached to an insulating sheet 4 as shown in Fig. 3. A second series of slots is then punched in the unpunched portions left after the first operation to complete the coil. Fig. 7 shows an alternative method of construction in which a metal blank 11 is first formed with a spiral corrugation and then embedded in insulating material 12 which is cast or moulded round the blank. The structure so produced is then ground or placed on one or both sides to remove the crests of the corrugations. If both sides are planed two separate coils 13, 14 are formed as shown in Fig. 7, which can be used as a transformer. A single spiral coil is formed by planing only one side. In a further modification an incomplete pattern having bridge-pieces left intact is sandwiched between two layers of insulation which may consist of paper packs, woven glass, or textile material impregnated with synthetic resin. The whole is pressed and cured to force the insulation through the openings in the metal pattern and lock the parts in position and bond together the insulation on both sides of the pattern. The insulating layers may be larger than the metal pattern which thus becomes completely embedded on all sides. Terminal tags may be brought out through openings in the insulation. The bridge pieces are removed by punching through the insulation. Fig. 9 shows a metal pattern 27 enclosed between two insulating packs of paper sheets 26 impregnated with polystyrene and outer packs 28 impregnated with phenol formaldehyde resin for giving strength to the assembly. Openings are provided in the inner packs and pattern 27 to enable the outer packs to be pressed inwards till they become bonded together. The bridgepieces left in the pattern can be removed by punching before or after the packs 28 have been applied. If the thickness of the assembly is too great to allow the layers 28 to be bonded together directly through the openings in the layers 26 the latter openings may be filled with plastic powder 30. Fig. 10 shows a modification in which two patterns 31 are embedded in polystyrene impregnated paper 32 with outer layers of paper 33 impregnated with phenol formaldehyde resin. A connection between the two patterns is shown at 34 and a plastic powder filling at 35 to bond the layers 33. Specifications 639,111, 639,178 and 639,179, [Group XXXVI], are referred to.