Textiles: manufacturing – Thread finishing – Surface modification of running length
Reexamination Certificate
2000-02-01
2001-10-23
Vanatta, Amy B. (Department: 3765)
Textiles: manufacturing
Thread finishing
Surface modification of running length
C028S250000, C028S255000, C028S263000
Reexamination Certificate
active
06305059
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of stuffer box crimping a multifilament yarn, as well as an apparatus for carrying out the method.
To produce a crimped yarn, it is known to compress a freshly spun yarn consisting of a plurality of filaments to a yarn plug by means of a crimping device. To this end, the crimping device is designed and constructed, for example, as a texturing nozzle. This texturing nozzle comprises a yarn channel, in which a hot medium, preferably air advances the yarn. The yarn channel terminates in a stuffer chamber. The yarn plug is formed inside the stuffer chamber. In this process, the yarn deposits in loops on the surface of the yarn plug and is compressed by the conveying medium, which is allowed to escape from the stuffer chamber through slots above the yarn plug. Subsequently, the yarn plug is removed from the stuffer chamber and cooled by means of a downstream cooling device. After cooling, the yarn plug is unraveled to the crimped yarn.
In this process, the crimp of the yarn is decisively influenced in its intensity and stability by the plug formation and by the thermal treatment of the yarn plug. Thus, besides the temperature and the pressure of the conveying medium, the dwelling time of the yarn plug during the thermal treatment also constitutes a parameter that has a decisive influence on the crimping result.
For example, it has been known for a long time to control the feed and/or the withdrawal speed of the yarn such that a uniform formation of the yarn plug is maintained during the process. An apparatus and a method of this kind are disclosed, for example, in DE 1 236 126. There, for purposes of monitoring the yarn plug, the position of the unraveling point at the end of the yarn plug is determined and adjusted to a predetermined level by changing the withdrawal speed of the yarn.
The known method is suitable only to a limited extent to produce a yarn with a uniform crimp, since it does not enable a direct intervention in the formation of the yarn plug. Thus, for example, fluctuations in the temperature or the pressure of the conveying medium may lead to considerable differences in the crimp of the yarn.
To be able to intervene in the thermal treatment of the yarn directly, DE 23 24 827 proposes a method and an apparatus, wherein the heat supply to the yarn plug is adjusted as a function of the position of the unraveling point of the yarn plug.
Furthermore, it is known from DE 42 24 454 and related U.S. Pat. No. 5,088,168 to adjust the heat supply to the yarn plug as a function of a yarn tension necessary to unravel the yarn plug.
The known methods, wherein the heat supply is adjusted to realize a uniform crimp in the yarn, are unsuitable in processes operating at high yarn speeds of more than 3,000 m/min. The intervention in the yarn plug formation is too sluggish to prevent the yarn plugs from shifting, which leads to an unsteady behavior of the process in the extreme case.
It is therefore an object of the invention to provide a method of stuffer box crimping a multifilament yarn of the initially described kind, as well as an apparatus for carrying out the method, wherein a yarn is produced with a uniform crimp in particular at high yarn speeds of more than 3,000 m/min.
SUMMARY OF THE INVENTION
The above and other objects and advantages of the invention are achieved by the provision of a method and apparatus wherein the yarn is fed into a crimping device to form a yarn plug, and then cooling the yarn plug within a cooling zone. The yarn is withdrawn from an unraveling point of the yarn plug adjacent the end of the cooling zone, and the position of the unraveling point is adjusted by changing the withdrawal speed. Upon a change of the withdrawal speed, a signal is generated for controlling at least one of the parameters of the crimping device so as to influence the formation of the yarn plug.
The invention distinguishes itself in particular by a stable process control with a controlled and regulated plug formation. In this process, the change in the withdrawal speed is used both for adjusting the length of the yarn plug and for controlling the formation of the yarn plug. The inventive combination between the position adjustment of the unraveling point of the yarn plug and the control of the yarn plug formation has the advantage that the fluctuations in the parameter adjustment of the crimping device are constantly compensated irrespective of the wear of the crimping device. The position of the yarn plug remains unaffected by such fluctuations and leads to a stable course of the process. A continuous control of the parameters of the crimping devices ensures a uniform quality of the crimp in the yarn. To this end, a signal is generated for controlling at least one parameter of the crimping device, which influences the formation of the yarn plug, when the withdrawal speed changes. In the case of a texturing nozzle, the parameters that are controlled are in particular the temperature and pressure of the conveying medium. Further parameters that may be made controllable are, for example, the speed of the entering yarn or the speed of the yarn plug leaving the crimping device.
An especially preferred further development of the method has the advantage that the effects of the control for forming the yarn plug are controllable. To this end, the change in the withdrawal speed is repeatedly determined at predetermined time intervals by a comparison between a desired value and an actual value of the withdrawal speed. The desired value of the withdrawal speed may correspond to a stored, optimal adjustment, to which corresponding parameter adjustments of the crimping devices are associated.
Should it be found in the comparison that the desired value of the withdrawal speed is equal to the actual value of the withdrawal speed, no signal will be generated for the control. In this instance, the adjusted parameters and withdrawal speeds will lead to an optimally crimped yarn. However, if a deviation is found between the desired value of the withdrawal speed and the actual value of the withdrawal speed, a signal will be generated accordingly for controlling at least one of the parameters of the crimping device, which influences the formation of the yarn plug.
To obtain a correction of the adjusted values as quickly as possible and, thus, small deviations from a predetermined crimp quality, the variant of the method as follows is especially advantageous. Specifically, it is generally known that a loose yarn plug occupies a greater length. To keep in this instance the yarn plug at a constant length, the adjustment will effect an increase in the withdrawal speed. If it is found in the comparison between the desired value and the actual value of the withdrawal speed that the actual speed is greater than the desired speed, the signal will cause a parameter change, which leads to an increase in the packing density of the yarn plug. This can occur, for example, in that the temperature of the conveying medium is increased. As a result of the greater packing density, the yarn plug becomes shorter. In the case that the desired value is greater than the actual value of the withdrawal speed, the signal will cause a parameter change, which leads to a reduction of the packing density of the yarn plug. Thus, the yarn plug would lengthen without an adjustment.
The especially preferred variant for carrying out the method of the present invention distinguishes itself in that direct use is made of the unraveling point and, thus, the controlled value for controlling the parameter of the crimping device. To this end, the withdrawal speed is repeatedly adjusted at predetermined time intervals to a predetermined desired value. At the same time, the position of the unraveling point of the yarn plug is determined. If a change occurs in the position of the unraveling point, a corresponding signal will be generated for controlling the parameter of the crimping device.
In this connection, corresponding parameter changes will be generated from the kind
Alston & Bird LLP
Barmag AG
Vanatta Amy B.
LandOfFree
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