GB2242446A - Positioning pre-twisted cable elements - Google Patents

Abstract

Running elements H, of non-circular cross-section, have a preparatory S-Z twist, and are to be positioned for incorporation into an S-Z twist cable. Each element passes through a rotatable sensor S in a rotatable disc BC. The twist in an element H rotates a sensor S, and the movement of sensor pointer E is sensed (e.g. by electrical, mechanical or optical means) to control rotation of disc BC. Such rotation bends element H until pointer E is centralised. An apex of element H always points towards the axis of disc BC. A number of discs BC may be used in sequence, and the sensors may be on a disc separate from disc BC (Figure 2). For circular elements H, a computer may replace the sensors to obtain required element bending. <IMAGE>

Description

MECHANISM FOR THE BI-DIRECTIONALLY TWISTED ASSEMBLAGE OF LONGITUDINAL ELEMENTS This invention relates to a mechanism, a number of which form the basis of a machine for the assemblage by twisting in alternate directions of longitudinal elements. The mehanism applies particularly to longitudinal elements having a non-circular shape in cross-section, these are hereinafter referred to as shaped elements to distinguish them from circular cross-section elements. Whilst the mechanism is particularly suited to shaped elements it can be adapted with advantage for the bi-directionally twisted assemblage of circular cross-section logitudinal elements.

Longitudinal elements such as electric cable cores for power or communication purposes, optical fibres, hydraulic or pneumatic tubes or the like often need to be put together to form a multi-element assemblage. Typically a multi-core electric cable is formed by the rotation of bobbins containing the cores. These cores are led off from the bobbins and twisted together to form a multi-core cable. Sometimes longitudinal elements are assembled by twisting a number of times in one direction followed by a number of twists in the opposite direction. This process cotinues along the length of the assemblage. This latter process increases manufacturing output and allows in-line production units to be combined into one operation.A further improvement is to have an assemblage formed by by one full twist of 360 degrees or preferably one-half twist of 180 degrees of the longitudinal elements in one direction followed by an equal amount of reverse twist, this cycle of events being repeated along the length of the assemblage. This form of assemblage retains the benefits of in-line production but will be likely to need a longitudinal tension unit incorporated within the assemblage or outside it to avoid unravelling of the individual elements. The benefits from such an assemblage are that spare core length is available at T-joints for services from distribution network cables and that the cable will be extensible without damage from earthquake, subsidence and the like.

Conventionally assembled cables often incorporate shaped conductors in the form of a segment of a circle to form a more compact assemblage and a saving in the use of materials. To avoid twisting insulated cores during assemblage, with the possibility of damage to the insulation, shaped conductors are often pre-spiralled before applying the insulation. The assemblage of insulated pre-spiralled conductors in a conventional uni-directional manner needs careful control to ensure pre-spiralling coincides with the twisting together of the cores during assemblage. The degree of control necessary for bi-directional assemblage is greater than for conventional uni-directional assemblage and the present invention provides this control when using insulated pre-oscillated conductors or other longitudinal non-circular pre-oscillated elements required to be bi-directionally assembled.In this context pre-oscillated conductors or elements refer to shaped elements which have been twisted about their axis with one whole twist or one-half twist followed by a similar degree of twist in the opposite direction and so on along the length of the element.

A number of the mechanisms described herein will normally be necessary. These will be arranged in sequence to ensure that the pre-oscillated elements are held along a path prior to final assemblage which avoids any tendancy for untwisting and also causes bi-directional twisting to take place with a smooth and correct final assemblage.

According to the present invention the orientation of the pre-oscillated shaped element in cross-section is identified by a sensor whilst passing through an orifice in a centrally pivoted wheel. Other longitudinal elements to be assembled pass through orifices spaced around the wheel. All these pre-oscillated elements are arranged to be in phase with one another according to their ultimate location in the assemblage. If the sensor detects that the initiating element is incorrectly orientated in cross-section with regard to the wheel centre then the output from the sensor causes a motor to to rotate the wheel until the initiating element is correctly positioned. The sensor may be placed on a separate disc from the driven wheel device or combined with it according to the convenience of the total machine.

A separate sensor disc can give an earlier indication of change of orientation or can be used to accurately locate the orientation of elements just before final assemblage.

A combination of a number of mechanisms of driven wheels and sensors ensures that the longitudinal elements are rotated about the axis of the wheels so that the orientation of the elements for final assemblage is correct at all times.

Whilst the mechanism described requires a longitudinal shaped pre-oscillated element to initiate the subsequent operations the assemblage of circular cross-section longitudinal elements can also be achieved by the use of a phantom initiating pre-oscillated element. The same mechanism is used but in this case the output from the sensing device is replaced by the output from a computer to give an output identical to that which would have been given by the sensor when a pre-oscillated shaped element was passing through it, the computer acting as a phantom pre-oscillated shaped element. The outputs from the computer, corresponding to those from the sensors of the mechanisms in sequence, are supplied to the individual drive motors of the separate mechanisms and the circular cross-section longitudinal elements are caused to take the format of a bi-directionally twisted assemblage.The longitudinal speed of the final assemblage through the machine is measured and supplied as electrical or optical information to the input of the computer. This forms the time base for the correct output representation of a chosen type of shaped pre-oscill-ated longitudinal element.

This flexible arrangement allows one bi-directional assemblage machine to be used for shaped pre-oscillated elements with the sensors operative or for circular cross-section elements with the computer replacing the role of the sensors. In the latter case multi-element assemblages can be produced in several layers with smaller wheel mechanisms operating to form the inner layer and progressively larger wheel devices forming outer layers.

Different lengths of oscillation cycle of the assemblage can be produced by the computer for any layer or changed at any time during manufacture.

In either case of shaped or circular elements the mechanisms at the beginning of the passage of the elements through the assemblage machine can be arranged to over-bend the elements beyond that necessary for correct orientation by extending the period of time for which the motor drives operate. This over-bending can be used to overcome residual forces in elements prior to final assemblage.

A specific embodiment of the invention will now be described by way of example for the assemblage of a 4-core shaped 180 degree pre-oscillated insulated conductor electric cable with reference to the accompanying drawing in which : Figure 1 shows diagrammatically in elevation the mechanisms of sensor discs, wheel devices and combined sensor and driven wheel devices incorporated in one machine for the bi-directionally twisted assemblage of the cable cores.

Figure 2 shows the same assemblage machine as shown in figure 1 but in perspective.

Figure 3 shows in elevation the mechanism of a combined sensor and driven wheel which is the subject of this present invention. An enlarged view of the sensing device is also provided in this figure.

Referring to the drawing the mechanism of a combined driven wheel device BC and sensor S is shown in figure 3.

The mechanism comprises a centrally pivoted wheel with a means for causing this to be rotated about its axis in either direction. In the case shown the outside rim of the wheel has gear teeth which mesh with a smaller gear which is mechanically connected to a motor N shown in figures 1 and 2. The wheel in the case shown has four shaped equally spaced orifices through which the shaped cores H pass. Rollers G may be incorporated at each of the orifice positions as shown in the specific case of the initiating core passing through the sensor device S.

This device is shown in figure 3 and comprises a central plate upon which three or more rollers G are arranged to follow the orientation of the initiating shaped core H.

This central plate is mounted in a bearing F so that the plate will rotate corresponding to any radial movement of the shaped core H . As the pre-oscillated core passes through the sensing device S the rollers G will follow the radial movement of the core and cause the central plate to rotate within the bearing F. This rotation will cause the pointer E to move relative to the drive wheel and by means of electrical contacts, magnetic, optical or other similar means initiate the operation of the corresponding drive motor shown as N (figures 1 and 2 ) to turn the drive wheel about its axis in the same direction (clockwise or anti-clockwise) as the radial movement of the shaped core H. This rotation of the driven wheel continues until the pointer E returns to its central, neutral position.In this way the shaped cores are caused to be bent along their length so that the apex of the shaped core segment is always pointing towards the axis of the driven wheel which is the orientation required for the final assemblage of the four cores in a bi-directionally twisted form.

Figures 1 and 2 show a number of these mechanisms in sequence to form a complete assemblage machine. The number of actual mechanisms required will vary according to the size of the cable cores and the length over which the 180 degree oscillation is completed. In the example shown there are two combined sensor and drive wheel mechanisms B and C and two mechanisms where the sensor discs X and Y are separate from their driven wheels A and D. In figures 1 and 2 the shaped pre-oscillated cores enter from the left hand side and the orientation of the core in cross-section is detected early by the sensor S on the disc X. The output from the sensing device causes the motor N driving the wheel A to operate and to cause the wheel to rotate and bend the core into its correct position.Sensor and wheel combination mechanisms B and C with their sensors S and motors N carry out similar functions as the pitch circle for the cable cores is reduced. The driven wheel mechanism D and its motor N is controlled from the sensor disc Y with its sensor S which is located as close as possible to the final assemblage to ensure correct orientation of the cores at the final point of closure. Driven horizontal rollers P and vertical rollers T haul the core assemblage and individual cores through the machine in this case but other means such as caterpillars or haul off capstans could be used if required. A longitudinal tape or helically lapped tape can be applied immediately after assemblage to hold the cores in position prior to the next manufacturing operation such as the extrusion of a sheath overall.

It can be seen from the drawing figures 1 and 2 that the proposed mechanisms can be incorporated into a machine which can form part of an in-line manufacturing unit with the formation of conductors and their electrical insulating, for example, by extrusion of plastic material before assemblage and the extrusion of a sheath for overall protection and longitudinal tensile strength after assemblage.

The same machine as shown in the drawing with additional orifices in the wheels would be used, for example, for the bi-directional assemblage of multi-core circular cross-section cable cores with computer control in place of the sensor initiators as previously described herein.

The diameter of individual driven wheels in the mechanisms need not be very great, their size being determined largely by the mechanical force necessary to bend the cores into the correct formation. The driven wheels will normally be designed for the smallest acceptable diameter and mass so as to reduce the inertia during oscillation of the wheels during assemblage. Care must-also be taken to have each core reasonably in phase with other cores with respect to pre-oscillation although the driven wheels are designed to hold all cores in the correct orientation with respect to the initiating core passing through the sensor.

Claims (9)

1 A mechanism consisting of a driven wheel and sensor which with similar devices in sequence will identify the orientation in cross-section of a pre-oscillated longitudinal non-circular cross-section element and to bend this element and similar elements along their length so that they are in the correct location to form a bi-directionally twisted assemblage.

2 A mechanism as claimed in claim 1 which with similar devices and replacement of sensors by computer output to correctly locate circular cross-section longitudinal elements to form a bi-directionally twisted assemblage.

3 A mechanism as claimed in claims 1 or 2 which with similar devices in sequence will correcly locate longitudinal elements to form a multi-layer bi-directionally twisted assemblage.

4 A mechanism as claimed in claim 1 or 2 or 3 which with similar devices in sequence will prevent the untwisting of longitudinal elements during the formation of a bi-directionally twisted assemblage.

5 A mechanism as claimed in claim 1 or 2 or 3 or 4 which with similar devices in sequence provides a means of assemblage which can form part of an in-line manufacturing plant with pre-asemblage manufacture and post assemblage manufacture combined in one unit to provide greater output without inter-manufacture transportation.

6 A mechanism of a driven wheel and sensor capable of combination in one mechanism or of separation into a driven wheel and separate sensor disc to give exact orientation of elements just prior to final assemblage.

7 A mechanism of a driven wheel and sensor capable of over-bending longitudinal elements beyond the ideal for final bi-directionally twisted assembage in order to overcome any residual forces in longitudinal elements to provide a more mechanically stable bi-directionally twisted assemblage.

8 A mechanism of a driven wheel and sensor capable of adaption by the replacement of the sensor output by computer output to enable a number of circular cross-section longitudinal elements to be assembled in bi-directional twisted form in one or more layers with the length of each bi-directional oscillation capable of alteration during the formation of the assemblage.

9 A mechanism of a driven wheel and sensor substantially as described herein with reference to figures 1, 2 and 3 of the accompanying drawing.