Patent GB-703618-A (GB)
Abstract: 703,618. Removing metal by spark discharge. DUBILIER, W. June 1, 1951 [June 2, 1950], No. 13812/50. Class 83 (4). [Also in Group XXXVI] Relates to rolled condensers comprising a dielectric strip having on one face a metallic coating which is removed along a sinuous or zig-zag track so as to form successive separate metallic areas which register when the strip is rolled. According to the invention, the removal of metal is performed by a plurality of branding units, each of which produces a part only of the pattern and is rendered operative repeatedly, one unit extending transversely of the strip to produce the complete transverse track each time it is operated, the longitudinal spacing between successive transverse tracks being varied progressively throughout the length of the strip. In Fig. 1 metallized dielectric strip 5 is led from a spool 6 by driven roller 9 and wound upon spool 14 driven from motor 12 by a slipping clutch so that the strip passes below a metalremoving roller 1 at constant speed ; the roller 1 has a raised surface 2 as shown in Figs. 2, 3 and is driven through the variable speed gear - of Fig. 4 so that the pattern formed increases in size as the strip is wound on spool 14 .as shown in Fig. 5. The variable speed gear comprises a coned pulley 17 driven by motor 12 and coupled by endless band 19 to the inversely coned pulley 18 driving the roller 1; a fork 20 progressively shifts -the band 19 under the action of screw 21 driven from motor 12. The roller may have metal removing ridges as shown in Fig. 7 to produce the pattern of Fig. 9 or as shown in Fig. 8 to produce the pattern of Fig. 10 which latter, when wound, provides two thicknesses of dielectric material between the foils. The roller 9 may be omitted and the spool 14 driven without slip, the pitch of the screw 21, Fig. 4, of the variable speed being correspondingly adjusted, Fig. 11 (not shown). The variable speed gear may be replaced by a separate driving motor for the roller 1, the speed of this motor being varied by a theostat controlled by motor 12, Fig. 13 (not shown). In Fig. 14 the condenser is wound on former 60 which is driven at constant speed by motor 12 which also drives the roller 1 at constant speed. In Fig. 16 the metal removing roller is replaced by three electrodes 62, 63, 64 intermittently brought into contact with the metallized strip 5 by cams 67, 68, 59, driven through a variable speed gear 16. Cam 69 actuates electrode 64 to produce a transverse strip 65, Fig. 17, while cams 67, 68 actuate electrodes 62, 63 to produce the longitudinal strips of Figs. 5, 9. By increasing the time of contact of electrode 64, the pattern of Fig. 10 or Fig. 19 may be produced, Fig. 18 (not shown). With a strip as in Fig. 19, the wound condenser has three thicknesses of dielectric between the plates. In Fig. 20, the de-metallizing electrodes 62, 63, 64 are maintained in contact with the metallized strip 5 and are connected into circuit by commutators 93, 94;' 95 driven by the motor 12 winding the condenser 82. The electrodes may be continuously vibrated to maintain an arc discharge. Instead of three commutators, an endless band 107, Fig. 21, may be apertured to connect the electrodes in circuit as required. If the strip 5 is driven at constant speed, the band,107 may have its apertures progressively spaced. The band 107 need not be endless but may be wound from one spool to another, Fig. 23 (not shown). It may actuate solenoids to press the electrodes into contact with the strip 5, Fig. 25 (not shown); these two latter arrangements allow the bands to be changed according to the type of condenser required. Instead of perforations in the bands, the patterns may be printed and photo-electric control used. In Fig. 26, the de-metallizing means comprise three 'rollers 140, 147, 141, the middle one producing the horizontal lines 145, Fig. 27, and the outer ones producing the transverse lines ; the rollers are appropriately driven and are put into circuit as required by such means as the band of Fig. 21. A wide strip 5 may be patterned in three rows and cut longitudinally to provide three wound condensers, Figs, 28 and 29 (Hot shown). A pattern such as shown in Fig. 30 will provide a wound condenser in which each turn will comprise two plates connected together and extending each over half a turn, the turns being separated by one thickness of dielectric. A pattern such as shown in Fig. 31 will provide a wound condenser in which each turn comprises two plates of opposite polarity, each extending over half a turn, the turns being separated by two thicknesses of dielectric material. To maintain a constant width of the demetallized transverse strip, the electrode forming the transverse strip is put into circuit by switch arm 204, Fig. 35, contacting 205 under the control of cam 201 driven with the mandrel 202 on which the condenser is wound; a bell crank lever 207, 206 progressively shifts the contact 205 as the rolled condenser increase in size to progressively reduce the period during which the switch 205 is closed by the cam 201 The strip 5 may be of paper metallized with zinc, cadmium or aluminium and coated with lacquer. It may be subjected to a bum-out test by passing between metal cylinders at appropriate potentials. Specification 647,573, [Group XXXVI], is referred to.