GB558834A - Improvements in and relating to the electrical perforation of sheet material - Google Patents

Abstract

558,834. Perforating non-metallic materials. MEAKER, J. W. Sept. 11, 1942, No. 12863. [Class 31 (i)] [Also in Group XL] To perforate, non-metallic materials such as fabrics, leather, or paper to be made into bags over a wide area with perforations arranged close together longitudinally and transversely, a web of the imaterial is led through a plurality of spark gaps between pairs of oppositely spaced electrodes arranged transversely to the web, the electric discharges taking place simultaneously and at a frequency which may be twice that of a 60 cycle alternating current which produces the discharge with the aid of transformers, condensers. or Tesla coils. As shown in Figs. 1 and 4 the web is passed through a number of rows of electrodes 12, 12' the pairs of electrodes in the rows being staggered with respect to those in adjacent rows. The electrodes in each row are arranged in series and one pair of mains 14, 15 supplies current to the primary coils 16 of transformers T. the secondaries of which are earthed and also connected to the electrodes 12. If a wide web is being treated each gang of electrodes may be energized by a pair of similar transformers. As shown in Figs. 6, 8 the electrodes are constructed so as to rotate in order to avoid erosion, and are mounted on shafts 27, 27<SP>1</SP> formed of an insulating material and rotated by pulleys 28 and a belt 29. The electrodes 31, 31<SP>1</SP> are arranged between alternating metal sleeves 34, 34<SP>1</SP>, and sleeves 35, 35' of non conducting material. The current is supplied by a brush 37 to the left hand sleeve 34 and passes through the discs to a brush 38 and conductor 39. The upper sets of electrodes may be mounted in a frame pivoted about a side hinge which permits the electrodes to be moved aside to permit of the insertion of a new web which is led over guide rollers before the perforating operation commences. In a further modification, Fig. 10, the electrodes consist of metal plates 40, 40<SP>1</SP> provided with ears 41 having rounded under surfaces 42. The plates are slotted, at 43 to receive screws 44 for attaching the plates to non-conducting mounting boards 45.