Textiles: spinning – twisting – and twining – Apparatus and processes – Twist setting
Patent
1996-04-26
1998-03-10
Stryjewski, William
Textiles: spinning, twisting, and twining
Apparatus and processes
Twist setting
57264, 57284, 57289, 57333, D01H 746, D01H 792
Patent
active
057248028
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to false twist texturing of yarns.
BACKGROUND OF THE INVENTION
Conventionally, yarns are textured by the false twisting process in a false twist zone which extends from a twist trap that defines the upstream limit of false twist, and contains a heater that raises the temperature of the false twisted yarn, a cooling zone in which the false twisted yarn is cooled, a false twisting device and an output roller arrangement that hauls the yarn through the false twist zone. The yarn may optionally then be wound up as stretch yarn without further processing, though with some relaxation in an overfeed zone to control the wind-up tension, or, with further heat processing in a relaxation zone, to produce a set textured yarn.
The supply yarn may be fully drawn or oriented yarn, or more usually nowadays, partially oriented yarn produced by high speed extrusion from the spinneret, in which case the false twist texturing may involve sequential drawing, in which the yarn is drawn in an in-line operation before passing into the false twist zone or, more usually, simultaneous drawing in which the partially oriented yarn is drawn in the false twist zone itself.
As false twist devices have been developed which operate at higher and higher twisting speeds, the rate at which yarn can be processed--which is limited by the false twisting speed, since false twist texturing requires high rates of twist per unit length--has increased correspondingly. The threadline of a false twisting machine as described is necessarily straight or substantially so--a gently curved heater track can be tolerated--between twist trap and false twist device--and because the twisted yarn must remain in contact with the heater for a certain time in order to reach an effective temperature, the heater has become very long and much ingenuity has been put into the design of false twist texturing machines to cope with the long heaters--which can be several metres in length. Eventually, limitations on practical heater length have limited processing rates. For example, 167 dtex yarn could be false twisted at a speed corresponding to a throughput speed of 1500 metres/minute, but is rarely processed at speeds in excess of 900 metres/minute because of heater limitations.
SUMMARY OF THE INVENTION
The present invention provides a false twist texturing method that avoids such problems.
The invention comprises false twist texturing comprising supplying a yarn hot to a twist trap upstream of a false twist device instead of supplying heat to the yarn intermediate the twist trap and the false twist device.
The yarn may be cooled between the twist trap and the false twist device.
The yarn may pass through a heating zone as an untwisted yarn prior to the twist trap. The heating zone may comprise a Jet heater, which may be supplied with steam and/or hot air. The yarn may be heated in a plug. Jet heaters can operate on untwisted yarn at speeds in excess of 6000 metres/minute.
A feed back control arrangement may be used to control the texturing. The feed back control may comprise a bulk measurement after the false twisting device and which may be effected in a relaxation zone, as by measuring yarn speed or yarn tension in the relaxation zone.
The feed back control may act on a yarn heater, which may be a supplementary yarn heater--that is to say a readily controllable heater that is additional to a primary, uncontrolled heater. The feed back control may, however, act on a yarn hauling device, which may be the output roller of the false twist zone or a false twisting device.
The yarn may be draw-textured. The supply yarn may be taken from a spinneret over a twist trap into a false twisting zone, the heat remaining in the yarn from the spinning operation being sufficient to avoid the need for a separate heating arrangement.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of false twist texturing apparatus and methods according to the invention will now be described with reference to the accompanying drawings, in which:
FIG. 1 is a d
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Stryjewski William
University of Manchester Institute of Science and Technology
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