GB2160555A - Twisting apparatus - Google Patents

Abstract

Apparatus for the twisting together of two or more strands (1, Figure 1) comprises two vessels (4), (9) rotated in opposite directions, input capstan (3) for feeding the strands to the first of the vessels (4), and an output capstan (10) for withdrawing the strands from the second of the vessels (9), the input and output capstans operating at substantially the same speed. A transfer unit (8) feeds the strands from the first to the second vessel at a speed alternating between a rate below that of the capstans and a rate above that of the capstans. The transfer unit (8) comprises a steadily rotating cone-shaped member (19, Figure 3) and a pulley wheel (22) engaging the surface thereof. The pulley wheel (22) is movable between two positions (27), (28) on the surface of the cone-shaped member (19), to vary the speed of a pulley (30) which, bearing against a further pulley (31), drives the strands (1), to produce the alternating strand feed speeds. <IMAGE>

Description

SPECIFICATION Twisting apparatus This invention relates to apparatus for twisting together two or more electric conductors or other flexible elongate members (hereinafter for convenience referred to as "strands"). This invention has particular, though not exclusive, use in the manufacture of electric cables.

In order to produce an electric cable comprising two or more electric conductors, and which has the required flexibility for everyday use, it is well known to twist the strands of each conductor together before applying insulation around each conductor and/or to twist the conductors together before applying an outer sheath around the conductors. In order to apply the necessary twist however, a known technique requires passing the conductors through a die to a pay-off stand which is rotated to apply the necessary twist. This known technique has the disadvantages that it requires the rotation of a large piece of machinery, and that the twisted conductors cannot be fed directly to an extruder or other apparatus.

It is an object of this invention to overcome these disadvantages.

According to the present invention, apparatus for twisting together two or more strands comprises two vessels, each vessel being rotatable about an axis, the vessels being rotatable in opposite directions to one another and each vessel having an aperture at the axis of rotation through which the strands pass; input means for feeding the strands to a first one of the vessels at a predetermined speed; output means for feeding the strands from a second one of the vessels at substantially the same predetermined speed; and transfer means for feeding the strands from the first vessel to the second vessel, the transfer means comprising a cone-shaped member rotatable about its longitudinal axis, and a rotatable pulley member which engages the outer surface of the cone-shaped member, such that it is rotated by rotation of the cone-shaped member, rotation of the pulley member driving the strands, the pulley member being movable substantially instantaneously between two positions on the outer surface of the coneshaped member such that the strands are fed at a speed which alternates between a rate below the predetermined speed for a first predetermined time and a rate above the predetermined speed for a second predetermined time.

The cone-shaped member is preferably rotated by a direct drive arrangement. The pulley member is preferably moved between its two positions by a pneumatically actuated piston.

In this arrangement, as the strands pass into a vessel, which is rotating, through the aperture in the vessel, the centrifugal forces involved push the strands against the walls of the vessel and twist the strands together. As the vessels rotate in opposite directions, if the strands passed from the first vessel to the second vessel at the predetermined speed, the second vessel would simply undo the twist put in the strands by the first vessel.

By varying the speed of transfer of the strands between the two vessels between two values, one above the predetermined speed, the other below the predetermined speed, and by changing from one value to the other substantially instantaneously, the problem of untwisting is overcome.

The strands leaving the output means have an S-Z twist, and can be fed directly to another machine (for example, if the strands are electric conductors, the twisted strands can be fed directly to an extruder for applying an insulating sheath around the twisted conductors).

The input and output means are preferably beltdriven capstans.

The first and second vessels are preferably belt driven. Preferably each vessel comprises a base and a surrounding wall, the cross-section of each vessel being substantially U-shaped.

From the predetermined speed of the input and output of the strands, the rotational speed of the vessels, the upper and lower values of the transfer speed, and the predetermined times of these transfer speeds, the number of twists per unit length of the strands can be calculated and set. For example, for a predetermined speed of 300m/min a rotational speed of 12000rpm for the vessels, and transfer speeds of 200m/min for 30 sec and 600m/ min for 10 secs, a net twist of 440 twists and +40 twists/m are produced in the strands.

This invention also includes a method of twisting together two or more strands as herein described.

This invention is further illustrated by way of example, by the accompanying drawings in which: Figure 1 is a diagrammatic view of apparatus in accordance with the invention; Figure 2 is a more detailed side view of the apparatus; Figure 3 is a cross-sectional view of the transfer means; and Figure 4 is a graph of change in speed with time produced by the transfer means.

Referring to Figure 1, strands 1, typically of copper wire, are fed from their individual reels 2 by means of an input capstan 3 to first vessel shown generally at 4. The vessel 4 comprises a base 5 and a circumferential side wall 6, the base 5 having at its centre an aperture 7 through which the strands 1 pass.

The vessel 4 is rotated about a central axis such that the centrifugal forces involved push the incoming strands 1 against the side wall 6 and twist the strands together with a right hand lay. The twisted strands exit the vessel 4 and pass through a transfer unit 8 before being fed to a second vessel 9 which is rotated in an opposite direction to that of the vessel 4. In the vessel 9 therefore, the strands are twisted in a similar manner but with a left hand lay. The strands are drawn out from the vessel 9 by an output capstan 10, running at an identical speed to that of the input capstan 3.

The transfer unit 8 runs for part of a cycle at a speed below that of the input and output capstans 3 and 10. During this part of the cycle the strands will spend more time in vessel 4 than in vessel 9.

Consequently the strands will reach the output capstan 10 with a net right hand lay. This is the area shown at 11 in Figure 4, in which the speed of the transfer unit is shown at 12 compared with the speed of the input and output capstans, which is shown at 13.

For the remainder of the cycle the transfer unit 8 runs at a speed greater than that of the input and output capstans 3 and 10. The strands will therefore spend more time in the vessel than in vessel 4 and will reach the output capstan 10 with a net left hand lay. This is the area shown at 14 in the Figure 4.

The strands leaving the output capstan over a period of time will therefore have an alternating right and left hand lay, producing the required S-Z twist in the strands. If the transfer unit 8 is programmed to switch such that the areas 11 and 14 are equal, there will be no build up of strands in either vessel.

Figure 2 shows a practical embodiment of the apparatus. Input and output capstans 3 and 10 are driven by belt drives 15 and 16 respectively. Similarly the first and second vessels 4 and 9 are driven by belt drives 17 and 18. The transfer unit 8 includes a cone-shaped member 19 rotated about its central axis 20 by a direct belt drive 21. The transfer unit 8 is shown in more detail in Figure 3.

Rotation of the cone-shaped member 19 causes rotation of a pulley wheel 22 which is in frictional contact with its surface. The pulley wheel 22 is mounted on an axle 23 which extends parallel to the surface of the cone-shaped member 13. The axle is rotatably mounted within a frame 24, the pulley wheel 22 forming part of a carriage 25 which is slidably mounted within the frame. The pulley wheel is mounted so as to be rotatable with respect to the carriage 25 such that its rotation causes corresponding rotation of the axle 23. In addition the pulley wheel may be slidably moved along the axle 23 by the operation of a pneumatic cylinder 26 acting on the carriage 25. To facilitate longitudinal movement of the pulley wheel 22 along the axle 23, whilst maintaining the transfer of rotation from the wheel to the axle, the axle 23 is provided with longitudinally extending ribs (not shown).

Mounted on the axle 23, external to the frame 24, is a transfer wheel 30 around which the strands 1 are constrained to pass. A second pressure wheel 31 ensures a minimum of slippage between the strands and the transfer wheel 30. Rotation of the cone-shaped member 19, rotates the pulley wheel 22, causing corresponding rotation of the axle 23 and hence the transfer wheel 30 to drive the strands.

The pneumatic cylinder 26 moves the carriage 25 within the frame 24 between two positions, a first position 27 in which the pulley wheel 22 is located towards the nose of the cone-shaped member 19, and a second position 28 in which it is towards the base thereof. Due to the difference in circumferences of the cone shaped member 19 at the two positions, the speed at which the pulley 22 is driven is greater in the second position 28 than when it is in the first position 29.

Hence the movement of the carriage between the two positions 27 and 28 produces the change in the speed of the transfer unit 8 between the lower and higher levels as depicted in Figure 4.

Provided a swift movement of the carriage 25 is achieved, the change in speed of the transfer unit is substantially instantaneous.

Claims (8)

1. Apparatus for twisting together two or more strands comprising two vessels, each vessel being rotatable about an axis, the vessels being rotatable in opposite directions one to another and each vessel having an aperture at the axis of rotation through which the strands pass; input means for feeding the strands to a first one of the vessels at a predetermined speed; output means for feeding the strands from a second one of the vessels at substantially the same predetermined speed; and transfer means for feeding the strands from the first vessel to the second vessel, the transfer means comprising a cone-shaped member rotatable about its longitudinal axis and a rotatable pul ley member which engages the outer surface of the cone-shaped member, such that is is rotated by rotation of the cone-shaped member, rotation of the pulley member driving the strands, the pulley member being movable substantially instantaneously between two positions on the outer surface of the cone-shaped member such that the strands are fed at a speed which alternates between a rate below the predetermined speed for a first predetermined time and a rate above the predetermined speed for a second predetermined time.

2. Apparatus according to Claim 1 wherein the cone shaped member is rotated by a direct drive arrangement.

3. Apparatus according to Claim 1 or Claim 2 wherein the pulley member is moved between its two positions by a pneumatically operated piston.

4. Apparatus according to any of Claims 1 to 3 wherein each vessel comprises a base and a surrounding wall, the cross-section of each vessel being substantially U-shaped.

5. Apparatus according to any of Claims 1 to 4 wherein the vessels are belt driven.

6. Apparatus according to any preceding Claim wherein the input and output means are belt driven capstans.

7. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.

8. A method of twisting together two or more strands incorporating apparatus as claimed in any of Claims 1 to 7.