GB823725A - Improvements in or relating to the manufacture of transformers - Google Patents

Abstract

823,725. Transformers. GENERAL ELEC. TRIC CO. Ltd. Jan. 8, 1958 [Oct. 8, 1956], No. 30646/56. Class 38 (2). A transformer having at least two windings and one electrostatic screen is made by laying these elements in turn on surfaces, the first of which is on a plastic or other bobbin and the others are on plastic material in which each of the elements are embedded in turn. A bobbin 7 having flanges 12, 13 is machined on a lathe from a cylinder of epoxy resin. Two start helical grooves are cut in the surface of the bobbin and wires 27, 28 are wound in them. The wire ends are soldered in hollow nickel terminal pins 22, 23, 24, 25 which pass through holes in the flanges, the wires subsequently being connected in series to form a single winding. Epoxy resin is then cast round the wound bobbin in a mould and the bobbin is again turned to form a bobbin 37 with a single flange 39, Fig. 8. On this is sprung a curved strip of beryllium copper forming a gapped electrostatic screen 41 with a projecting terminal 42. The application and machining of another layer of epoxy resin is followed by the superposition of a second screen, the casting of another resin layer and machining to a two flanged surface. A layer of enamelled wire is wound over the bobbin with cotton thread separating the turns, one end being secured to a further nickel pin held in the flange and the other being connected to the terminal of the second screen. Plastic material is then moulded over the coil and then over the terminals at 53. Finally, the coil structure is clamped between two ferrite pot-core parts 54, 55 from which segments have been removed to leave planar surfaces 57.