Textiles: spinning – twisting – and twining – Apparatus and processes – Alternate twist
Patent
1994-10-03
1996-08-20
Stryjewski, William
Textiles: spinning, twisting, and twining
Apparatus and processes
Alternate twist
57314, 57361, D01H 500, D01H 746
Patent
active
055467415
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method in connection with reverse stranding, wherein conductors for a cable to be produced, such as wires, groups or blocks, are drawn from supply reels or the like through a divider means, torsion tubes peripherally surrounding a central element and periodically rotatable in opposite directions about the central element, and a twisting head rotatable in opposite directions, into a nozzle or the like.
In traditional reverse stranding, i.e. SZ stranding, conductors are drawn by a suitable drawing apparatus through a stationary divider means and a twisting means rotating periodically in opposite directions into a nozzle, thereafter the conductor is immediately bonded in a bonding device into a reversely stranded product, such as a cable. After the drawing apparatus, the cable is reeled, or the stranded cable is passed to the next production stage. In a traditional reverse stranding apparatus of this type, it is usual to position a tubular intermediate element rotating with the twisting means between the stationary divider means and the rotating twisting means. The intermediate element is attached centrally to the twisting means and mounted at one end rotatably with respect to the stationary divider means.
This traditional arrangement, however, has the disadvantage that the rotation rate of the intermediate element between the divider means and the twisting means is constant, and therefore the twist in the conductors tends to accumulate at the end close to the twisting means. The pitch angle of the conductors thereby gets greater, and the angle deviation of the conductors in the twisting means increases. As a consequence, a greater force is required to draw the conductors, and so the stranded conductors tend to untwist.
Several different solutions have been suggested to the above problem. FI Patent Specification 78576, corresponding to U.S. Pat. No. 4,974,408, for instance, discloses one prior art solution.
The solution disclosed in FI Patent Specification 78576 works well in practice although it has certain disadvantages. A problem with the SZ twisting is that the friction increases with the twisting angle of the oscillating divider plate, and so the tension caused in the wires, conductors, groups or blocks varies. As a result, the pitch length varies, and locking at the direction reversion point becomes more difficult to carry out. This is significant particularly with telecommunication cables as the interference tolerance of the group increases with the degree of symmetry of the pair or quad. Such interferences include cross-talk, external interferences, etc. Wires are subjected to jerks already when they are unwound from the supply reels. Each bending over the idler wheels increases the tension of the wires. The tension of the wires varies within a wide range especially when unreeling "over the flange". Before the grouping or stranding means, the tension of each wire is different, and it cannot be levelled out by the brakes provided at the inlet end. The friction increases with the twisting angle in the tube packet of the SZ torsion tube stranding means, and at the same time the tube packet gets shorter. In addition to the variation in tension, there occurs variation in the speed of the wires. For locking the stranding, a pitch shorter than the nominal pitch is used on both sides of the reversion point. This is called edge acceleration. The shortness of the locking pitch and the number of turns used, i.e. the effective length, determine the magnitude of the speed variations acting on the wires between the twisting head and the supply reels. This factor is particularly apparent after the stranding point. At the direction reversion point, i.e. at the edge acceleration stage, an extra wire length is instantaneously needed at the stranding point. Extra length is obtained from the supply side as well as from the side of the finished group. The attempt to obtain extra wire length after the stranding point results in the occurrence of slipping on the capsta
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Nokia-Maillefer Oy
Stryjewski William
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