GB1361835A - Method of and apparatus for removing static charge from webs of material - Google Patents

Abstract

1361835 Discharging static electricity from webs of material KALLE AG 7 Sept 1971 [10 Sept 1970] 41661/71 Heading H1X A statically charged web of material is uniformly discharged to the extent of at least 99% of the original charge by bombardment, over the entire width of the web, under conditions having no deleterious effect on the said material, with charge carriers (i.e. gas ions and electrons) which are produced by a highfrequency A.C. voltage of 1 to 1000 Kcs/sec. and having a current intensity of between a few Á amp and several hundred Á amp/cm. of web width. Apparatus for performing the method in. cludes at least one corona wire having a thickness of less than 100 Á. Alternative wire arrangements described comprise:- a single wire mounted adjacent an earthed counter-electrode (Fig. 1, not shown); a plurality of wires secured by tensioning springs to a rectangular frame (Fig. 2, not shown) with additional transverse supporting strips, if necessary (Fig. 4, not shown) and an optional protective grid (Fig. 6, not shown); a single wire wound zig-zag around supports on a frame and tensioned by a single spring (Fig. 3, not shown); a plurality of tensioned wires staggered in relation to each other to enable the width of the web to be covered by shorter wires (Fig. 5, not shown). The wires may be mounted in channels of rectangular or semicircular cross-section in a protective member (Figs. 7 and 8, not shown) which may form a counter-electrode, a lining of synthetic film being fitted between the corona wires and the interior of the protective elements. In the arrangement shown the web 7 is passed over a roll consisting of rods 18 enclosing corona wires 5 which preferably rotate with the roll but may alternatively be stationary in which case they need only be provided along the looping arc of the web 7 (Fig. 10, not shown). A curved counter-electrode consists of a protective element 14 with a number of corona wires 5. An arrangement for discharging both sides of the web comprises four rolls with curved counterelectrodes arranged alternately on opposite sides (Fig. 11, not shown). The charge carriers are normally produced in air, but may be produced in an inert gas which may be heated.