Textiles: weaving – Weft manipulation – Weaving with stationary weft supply
Reexamination Certificate
2000-09-06
2001-06-05
Calvert, John J. (Department: 3741)
Textiles: weaving
Weft manipulation
Weaving with stationary weft supply
C139S011000, C139S116100, C057S293000
Reexamination Certificate
active
06240977
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an improved apparatus and method for manufacturing woven products utilizing alternating twist (or net zero twist) yarn. There are a number of methods for producing yarn and fabrics that have a net zero twist.
One method for producing alternating twist yarn is by using reversible motors, which can be used to alternately cause a yarn to be twisted one way and then the other. Such motors, however, are relatively expensive and complex. These motors are also subject to mechanical breakdown. Another means of producing net zero twist yarn is by utilizing a pair of airjets, with the first jet capable of twisting the yarn in the opposite direction to that of the second, and periodically alternating the flow of actuating air from one jet to the other. However, it is found that polymer particles, trimer, loose dyestuff, and other debris can become lodged in the air jet when it is not actuated, preventing subsequent normal operation. This problem is significant since it can destroy the commercial viability of this process.
The use of twisted yarns in woven products is well known in the art. Traditionally, the yarn is passed through a mechanism for applying the twist, and is then rolled back onto a spool or bobbin. The bobbin is then transported to a loom to provide yarn for the weaving process. Thus, using twisted yarns has heretofore been a two-step process.
Thus, it would be desirable to provide an apparatus and method for alternately twisting yarn that allows the yarn to be twisted and woven in a single continuous, streaming step. Another desirable feature would be to provide an in-line air-jet yarn twisting apparatus that significantly reduces or eliminates the problem of debris becoming lodged in the air jet when it is not actuated. One effort to solve a few of these problems is described in U.S. patent application Ser. No. 08/725,647, filed Oct. 1, 1996, which is hereby incorporated herein by specific reference in its entirety.
SUMMARY OF THE INVENTION
This invention relates to an improved assembly for imparting alternating twist to yarn in continuous motion by utilizing a pair of air jets into which compressed air is alternately supplied producing a vortex that causes the yarn passing therethrough to experience a torque about the yarn's longitudinal axis. This assembly is attached to a loom in a manner so that initially untwisted yarn passes therethrough immediately before being inserted into the weft of the woven product.
The two air jets are arranged in-line so that the torque direction induced by one is opposite to that induced by the other. Air pressure is alternately applied at a desired cycling frequency to each jet to produce the alternate “s” and “z” twist in the yarn. There is a bias or backing air pressure that is applied on whichever jet is not being activated. This backing air pressure is typically a fraction of the air pressure utilized on the activated jet. This is extremely useful in preventing polymer particles, trimer, loose dyestuff, and other debris from becoming lodged in the unused air jet, preventing its subsequent normal operation. The cycling frequency may be coordinated with the weaving process in such a way that switching from the “s” twist to the “z” twist, and vice versa (reversing the twist), occurs prior to each successive weft insertion. When yarn is woven in this manner, the regions of zero twist commonly found in yarns of this type are eliminated from the woven product, because they occur during the time when no filling is being inserted, and they occur spatially outside the boundaries of the woven cloth. Furthermore, when the yarn is woven in this manner, alternating weft yarns possess alternating twist directions, and the woven product has a balanced torque. Woven products having a balanced torque have no tendency to roll or curl.
An advantage of the present invention is that the twisting process can be performed inline with the weaving process while the yarn is in continuous motion, thereby combining two steps into a single, more efficient step. Yet another advantage of the present invention is the ability to produce woven products having a balanced torque, having a net twist of zero, without including individual yarns having areas of zero twist within the weave. It is another advantage to create unique fabrics having varying amounts of twist. Another advantage of this invention is to eliminate impurities from clogging an air jet, and thereby thwarting its operation.
Fabrics produced by this process are torque balanced, meaning that there are equal numbers of fill yarns having “s” twist as there are having “z” twist. This feature is important, particularly where the fabric is to be subjected to subsequent processes or where the tendency for the fabric to roll up or twist would be detrimental. Heretofore, the only way to arrange the fill yarns in this way was to prepare, off-line, two yarns where one has an “s” twist and the other has a “z” twist, and then to insert them alternately within the weave to create the fabric in a twist balanced or zero torque manner. The present apparatus and method achieves this balance without the necessity of pre-twisting the yarns using a conventional and expensive twisting process.
Fabrics produced by this process are particularly useful in such applications as conveyor belts, tire reinforcement belts, drive belts, etc.
REFERENCES:
patent: 5295516 (1994-03-01), Tanaka et al.
patent: 5937915 (1999-08-01), Wahhoud
Calvert John J.
Milliken & Company
Moses Thomas L.
Moyer Terry T.
Muromoto Jr. Robert H.
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