GB2242447A - S-Z Twisting of cable elements - Google Patents

Abstract

To provide S-Z twisted elements H, of non-circular cross-section, for assembly into an S-Z twisted cable, the elements are simultaneously passed through shaped orifices in respective gears C which are oscillated, to give the required S-Z twist, by gear ring F rotatable on stationary plate S. Each gear orifice can have free-running or driven rollers guiding the elements. A stationary plate (A) with an orifice array is located upstream of plate S (Figure 1). <IMAGE>

Description

MECHANISM FOR THE BI-DIRECTIONAL TWISTING OF MULTIPLE NON-CIRCULAR LONGITUDINAL ELEMENTS This invention relates to the bi-directional twisting of multiple non-circular longitudinal elements.

Longitudinal elements such as, for example, conductors for multi-core electric cables are often shaped in cross-section other than circular. Usually the shape is in the form of a segment of a circle so that when the cable cores are assembled the assembly is made compact and less material is used overall. These shaped conductors are often pre-spiralled before the insulation is applied.

This pre-spiralling avoids undue twisting of the insulation during assemblage. Care is needed during conventional uni-directional twisting assemblage to ensure that the pre-spiralling matches the twisting together of the cores.

It is an advantage to bi-directionally twist cable cores and similar longitudinal elements during assemblage so that an in-line manufacturing unit is feasible combining pre-assemblage, assemblage and post assemblage operations.

One method of assemblage is to twist the longitudinal elements to be assembled one half twist in one direction followed by an equal twist in the opposite direction.

This process of oscillation is continued along the length of the assemblage. The pre-oscillation of shaped cross-section elements by twisting 180 degrees in one direction followed by 180 degrees in the reverse direction along the length of the element provides the advantages for bi-directional assemblage that pre-spiralling provides for conventionally uni-directionally assembled elements.

An in-line production unit would be improved if all of the longitudinal elements were pre-oscillated at the same time and fed into the next manufacturing operation such that they are identical in the length of the oscillation cycle, have the same degree of twist and are in phase with one another. This present invention enables this to be achieved.

According to the present invention there is provided a fixed disc with orifices suitably spaced and shaped to allow a number of longitudinal elements to pass through without undue slackness between longitudinal elements and the orifices. Spaced from this fixed disc is a fixed circular plate upon which are mounted equally spaced gear wheels with similar orifices in their centres to those on the fixed disc.

These orifice gears rotate about their centres on bearings and they protrude beyond the outer edge of circular plate to mesh with the inside of a gear rim which forms part of a drive wheel. This drive wheel is caused to rotate in either direction by a suitable drive mechanism such as, for example a drive gear meshing with the gear rim. The orificed gears are mechanically connected together by an equal number of idler gears which are free to rotate in bearings attached to the circular plate. This arrangement provides rigidity and a smooth operation for the mechanism. The gear rim is caused to rotate in one direction followed by an equal movement in the opposite direction so as to cause a 180 degree, or greater if required, alternate twisting of the orifice gears and the longitudinal elements passing through them.The speed of rotation and counter rotation is directly related to the linear speed of the longitudinal elements by mechanical, electrical or similar means so that the cycle of twisting represents a constant length of longitudinal element. In the present invention all longitudinal elements are subject to an identical degree of twisting, are completely in phase relative to one another and the length of each cycle of twisting is identical. Each orifice can be provided with free running or driven rollers to reduce friction or to convey the elements through the mechanism.

The longitudinal elements will normally be hauled through the mechanism by driven rollers, caterpillar drives or suitable haul off wheels. The proposed method of pre-oscillation of longitudinal elements would enable an in-line production unit of longitudinal element preparation, assemblage and final finishing to form a combined manufacturing plant.

A specific embodiment of the invention will now be described by way of example for the pre-oscillation by bi-directional twisting of four segmentally shaped conductors of an electric cable with reference to the accompanying drawing in which : Figure 1 shows in plan the fixed disc and bi-directional twisting mechanism.

Figure 2 shows in elevation the bi-directional twisting mechanism.

Referring to the drawing the four segmentally shaped conductors H pass through the orifices in the fixed disc A and then through the orifice gears C attached via bearings to the circular fixed plate S within the bi-directional twisting mechanism B. These four orifice gears mesh with the four idler gears D with bearings on the circular plate S and also with the driving rim F. As the cable conductors are drawn through the mechanism by means of driven rollers, caterpillars or haul off wheels the rim F which is part of the twisting mechanism B is driven by the drive gear N to rotate in one direction followed by an equal rotation in the opposite direction. This alternate rotation continues as the conductors move through the mechanism. As the rim F rotates each of the orifice gears rotates about its own axis and causes the conductors H to be twisted by 180 degrees, or such other amount as may be required, in one direction followed by an equal amount in the opposite direction. The drive for the rim F is directly related to the linear speed of the conductors through the mechanism and is easily achieved by means of a cam or crank linked to the drive for the conductor haul off equipment operating the drive gear N.

Each orifice shown can incorporate free running or driven rollers to improve the movement of the conductors through the mechanism.

The conductors H passing through the mechanism will be twisted alternately to provide pre-oscillated conductors suitable for in-line extrusion of conductor insulation, bi-directional assemblage and final outer sheath extrusion to form a complete in-line production unit.

Claims (4)

1 A mechanism which twists a number of non-circular cross-section longitudinal elements in one direction and then equally in the opposite direction about the axis of the elements to provide a pre-oscillation of the elements for subsequent combination into a multi-element assemblage.

2 A mechanism as claimed in claim 1 which bi-directionally twists a number of non-circular longitudinal elements so that each of the elements is twisted exactly as the other elements to ensure all the elements are in phase, receive the same degree of twist and length of oscillation to provide a satisfactory subsequent bi-directional assemblage of the elements.

3 A Mechanism as claimed in claim 1 or claim 2 which is capable of incorporation with other equipment to form an in-line manufacturing unit capable of complete manufacture from longitudinal elements to their bi-directional assemblage and final finishing.

4 A mechanism substantially as described herein with reference to figures 1 and 2 of the accompanying drawing.