GB807617A - Improvements in or relating to electric capacitors - Google Patents

Abstract

807,617. Capacitors. GENERAL ELECTRIC CO. Ltd., and FARNSWORTH, J. Jan. 14, 1957 [Jan. 13, 1956], No. 1263/56. Class 37. A capacitor comprises electrodes 1, 1 formed by metal layers completely embedded in a thermoplastic dielectric 2, 3, 4 which has been stretched and returned to its original size by heat treatment; a strip capacitor is thus formed which is folded or rolled to provide the finished capacitor. As described, aluminium strips 1, 1 form the electrodes which are interleaved with dielectric strips 2, 3, 4 of prestretched polystyrene to form a composite strip which, together with a paper backing strip 5, is wound upon a mandrel 6. The resulting roll is heated for two hours at 100‹ to 110‹ C. thus causing the dielectric strips 2, 3, 4 to contract and bond together completely embedding the electrode strips. The roll may comprise sufficient composite strip for several capacitors in which case each electrode strip comprises several separate lengths placed end to end (see Fig. 2). Connecting tabs, 7, 8 are inserted in the composite strip; the subsequent heat treatment causes these to be sealed firmly in position. After heating, the roll is unwound and the bonded composite strip cut into the appropriate lengths for the individual capacitors which are formed by rolling into spiral or folding into zig-zag shape; in the latter case, the bonded strip is heated to avoid fracture during the folding. Polyethylene terephthalate may be used instead of paper for the backing strip 5.