Patent GB-752373-A (GB)
Abstract: 752,373. Capacitors. BOSCH GES., R. March 24, 1954 [March 25, 1953], No. 8539/54. Class 37. A roll-type capacitor comprises two spirallywound main electrodes arranged side-by-side and, placed between the turns of the main electrode winding, a floating-electrode structure having identical dielectric layers on each side of it. Owing to the symmetrical disposition of the floating-electrode structure with respect to the turns of the main electrodes, equal dielectric stressing is obtained to both sides thereof. The floating electrode structure comprises two floating electrodes or " blind plates " and these may be adjacent or may be disposed on opposite sides of an insulating layer. The thickness of the floating electrodes is made so small that the capacitor is self-sealing in the event of breakdown between the main and floating electrodes. Fig. 1 shows the main aluminium electrodes 11, 12 with an adjacent turn 111, 121 thereof. Disposed between the turns of the main elecf trodes are dielectric layers 13, 15 consisting opaper sheets which are coated at their adjacent surfaces with self-sealing metal layers 14, 16 having thicknesses of about 0.02-0.2 Á. In the arrangement shown in Fig. 2, the floating electrodes comprise layers 24, 25 on a paper strip 26 while dielectric layers 23, 27 are made of polystyrene. Fig. 3 (not shown) illustrates an arrangement similar to that of Fig. 1 with the single dielectric layers replaced by double layers of polystyrene and paper. In Fig. 4 (not shown), a capacitor as in Fig. 2 is provided with additional vapour-deposited metal layers between the main electrodes and the dielectric (i.e. on the dielectric but in contact with the main electrodes) while Fig. 5 (not shown) shows the corresponding modification of the embodiment of Fig. 1. In the arrangement shown in Fig. 6, which is similar to that of Fig. 1, the main electrodes comprise vapour-deposited metal coatings 61, 62 about 0.02-0.2 Á thick deposited on one side of an insulating strip 60 which is then folded to the shape shown. The main electrode construction may be similarly modified in the embodiments of Figs. 2 and 3. In Fig. 7 (not shown) is shown an alternative form of mainelectrode construction in which the main electrodes comprise metal coatings on both sides of a single paper strip. Figs. 8, 9 and 10 illustrate arrangements employing a lacquer as the dielectric. In Fig. 8 the main conductors 81, 82 are coated over their faces and one edge with lacquer layers 83, 84 between 0.1 and 1 Á thick. The floating electrodes 85, 86 comprise vapourdeposited metal coatings approximately 0.01- 0.10 Á thick upon an insulating strip 87. In Fig. 9 (not shown) the lacquer layers are applied directly over the floating electrodes which are again in the form of metal coatings on an insulating base. In Fig. 10, the main electrodes comprise vapour-deposited metal layers on a paper-strip base 100 and the floating electrodes comprise metal layers upon an insulating strip 107. The lacquer dielectric 105, 109 completely encloses the floating electrodes, thus preventing any danger of short-circuiting the electrodes when the metal connections are attached at the ends of the rolled capacitor.