GB1176605A - Method and apparatus for rolling a flat strip of material laterally into a tubular member. - Google Patents

Abstract

1,176,605. Making tubes. STANDARD TELEPHONES & CABLES Ltd. 7 March, 1968, No. 11049/68. Addition to 1,128,529. Heading F2P. [Also in Division B8] In order to reduce friction between layers during the convolute wrapping of a strip, e.g. of paper, into tubular form having a spiral cross-section and an outer layer which overlaps an inner layer by at least 360 degrees, a skeleton die is formed from a number of elements which are well-spaced along an axis 9 and which each have an aperture 10 through which the axis 9 passes, the apertures in a first group 2-5 of adjacent elements being profiled so that they lie on the boundary of a first imaginary tapering passageway 9, and a slot 14 in communication with the passageway along one side thereof which slots are longitudinally aligned, and the apertures in a second group 6-8 of adjacent elements being profiled so that they lie on the boundary of a second imaginary tapering passageway 12 whose larger end is adjacent the smaller end of the first passageway. The arrangement is such that when a strip of material is drawn through the elements along the axis 9, the first group of elements 2-5 wrap the inner layer of the tubular member leaving at least half the width of the strip outside the first passageway and projecting into the slot, and the second group, 6-8, wraps the remaining uniformed width of the strip around the inner layer to form the outer layer, tension being maintained in the strip as it passes into the apparatus so that the portions of the strip projecting into the slots 14 are prevented from entering the first passageway. The elements 2-8 correspond with the equivalent crosssections of the solid die described in the parent Specification. In order to reduce friction a maximum amount of material may be removed from the plate portion which would otherwise contact the strip, e.g. plate 5 ; alternatively, the plates 2-8 may be replaced by thick wire bent to the shapes of the apertures and secured to the base 1. The plates 2-8 are advantageously made of tungsten carbide. To insulate a wire conductor the inside of the edge which is to become the end of the outer layer is coated with an adhesive and the wire is drawn through the apparatus at the same time as the strip, radial pressure being applied to the overlapping edge as the insulated wire is wound upon a capstan. In order to locate the wire centrally within the insulation the portion of the width of the strip which forms the inner layer may be longitudinally corrugated, Fig. 4 (not shown).