Patent GB-759613-A (GB)
Title: Improvements in the manufacture of electric capacitors
Inventor: SHEN TZU EN
IPC: H01G13/00
Filed: 1953-08-24
Abstract: 759,613. Capacitors. BRITISH DIELECTRIC RESEARCH, Ltd. Aug. 24, 1954 [Aug. 24, 1953], No. 23327/53. Class 37. In the manufacture of a stacktype capacitor a plurality of metallized flexible dielectric strips provided with uniformly-spaced transverse gaps in the metallizing are assembled in a superimposed and laterally staggered fashion, with the non-metallized portions in coincidence, and the assembly is then passed through a sealing stage wherein the strips are sealed together by the application of heat and pressure at the non-metallized places followed by a severing stage wherein the assembly is divided into short lengths by cutting through the strips at the regions of sealing. A plurality of strips 2 comprising polystyrene foil 2a and a metal coating 2b are fed from rolls 1 which are alternately staggered laterally to produce the deposition shown in section in Fig. 2. Alternatively, the polystyrene foil may be replaced by paper strips coated with polystyrene. The strips are drawn forward intermittently by the driven rollers 6 so that the strips are periodically stationary during which time the demetallizing wheels 8, 9 make contact with the strips in the manner described in Specification 742,056. The wheels 8 and 9 move transversely across the strips during the stationary periods, the wheel 8 applying solvent contained in a bath 51 to the strip to soften the metallizing thereon and the wheel 9 wiping the metal from the portion of the strip engaged by the wheel 8 during the previous stationary period. The strips subsequently pass through edge-turning devices 11 which turn over the edges of the strips so that after passing between the rollers 3 together with thicker unmetallized strips 4 from the rollers 5, the assembly appears in section as in Fig. 4. The strip assembly issuing from rollers 3 passes between heated sealing bars 12 which come together each time the assembly is stationary and are so spaced from the wheels 8 and 9 that they apply heat and pressure to the unmetallized portions of the strips to seal the assembly at these points. Simultaneously, pressure plates 13 come together and metal is sprayed on to the exposed edges of the assembly to unite the exposed metallizing 52 (Fig. 4). The assembly subsequently passes between rollers 6 and guides 14 to cutters 15 which also operate when the assembly is stationary and are so positioned as to sever the assembly at successive sealed portions, thus producing a succession of small capacitor units. Terminals or leads are subsequently attached to the sprayed metal coatings and a casing or coating provided. In the arrangement illustrated, roller electrodes 10 connected to a source of high potential are provided to clear any electrically weak spots in the strips 2 and additional unmetallized strips may be interposed between the strips 2 to increase the thickness of dielectric. In modifications of this arrangement, the pressure plates 13 may be dispensed with, a plurality of the capacitor units issuing from the apparatus being piled together and held as a group between plates, the edges of the group then being sprayed with metal. Also the demetallization process may be omitted, and the metallized strips prepared by offering pieces of metal foil at intervals along a dielectric strip as described in Specification 759,614. The strips 2 and 4 may be drawn continuously through the apparatus in which case the members 8, 9, 12, 13 and 15 are arranged to move with the strips when they are in engagement therewith.