Method and apparatus for winding a continuously advancing yarn

Winding – tensioning – or guiding – Helical or random winding of material – Distributing material along the package

Reexamination Certificate

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C242S477300, C242S477600

Reexamination Certificate

active

06283401

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for winding a continuously advancing yarn to a package, and of the general type disclosed in EP 0 235 557 and corresponding U.S. Pat. No. 4,913,363.
When winding a yarn to a cross-wound package, the yarn is deposited at a crossing angle on the package surface within the package width at a substantially constant circumferential speed of the package. To this end, the yarn is reciprocated by a traversing yarn guide within a traverse stroke, before it contacts the package surface. To obtain a uniform mass distribution of the yarn, in particular in the edge regions of the package, it is known to shorten and lengthen the traverse stroke cyclically during the winding. This shortening and lengthening of the traverse stroke is named a so-called stroke modification. The stroke modification prevents a high edge buildup (saddle formation) of the packages.
In the method known from the above cited prior patents, the stroke modification occurs in predetermined modified stroke cycles. A modified stroke cycle is defined by the period of time, which is required for reaching again the length of the traverse stroke that has been adjusted before the stroke modification. Thus, a modified stroke cycle is formed by a plurality of modified strokes, which define one reciprocal movement of the traversing yarn guide at a modified length of the traverse stroke length. Thus, when passing through a modified stroke cycle, the yarn is deposited on the package surface in many modified strokes. The beginning of the modified stroke cycle may thus be removed from the end of the modified stroke cycle by a plurality of yarn layers. In this connection, there exists the problem that the yarns deposited at the outer edge of the package, i.e. at a maximum traverse stroke, are deposited before and after the modified stroke cycle in the same place on the circumference of the package, which leads to undesired double layers.
It is therefore an object of the invention to provide a method of the initially described kind as well as an apparatus for carrying out the method, which makes it possible to wind a cross-wound package with substantially evenly distributed yarn reversal points in the end regions of the cross-wound package.
SUMMARY OF THE INVENTION
The above and other objects and advantages of the present invention are achieved by the provision of a method and apparatus wherein the modified stroke cycle proceeds such that before and after the modified stroke cycle, the yarn reversal points are arranged offset on the circumference of the package. To this end, the speed of the traversing yarn guide or the traverse stroke of the traversing yarn guide is controlled in such a manner that after completing the modified stroke cycle, the yarn is deposited in a reversal point on the outer edge of the cross-wound package (end point). On the circumference of the package, this end reversal point is offset relative to the starting reversal point. The starting reversal point is the yarn reversal point at the edge of the package before the start of the modified stroke cycle. The special advantage of the invention lies in that the front faces of the packages exhibit a very straight-line configuration. Beadlike configurations as are caused by yarn layers overlying one another, are totally prevented. A uniform edge buildup of the package is produced.
In a particularly advantageous further development of the invention, the yarn reversal points are determined or calculated with respect to their position. To this end, one determines the instantaneous actual position of the starting point at the beginning of the modified stroke cycle. Proceeding from the instantaneous values, the complete modified stroke cycle is calculated with reference to a predetermined time for the modified stroke cycle as well as with regard to the actual position of the starting point, and a desired position of the end point is determined. By a comparison between the actual position of the starting point and the calculated desired position of the end point, it is possible to generate corresponding control signals.
In this connection, it will be especially advantageous, when the traversing speed is varied in the case that the actual position of the starting point coincides with the desired position of the end point on the circumference of the package, so that at the end of the modified stroke cycle, the yarn is deposited in an actual position of the end point that differs from the desired position. The variation of the traversing speed may occur such that, for example, a minimum distance is ensured between the starting point and the end point.
It will likewise be advantageous to modify the traverse stroke, when the actual position of the starting point and desired position of the end point coincide on the circumference of the package. The change of the traverse stroke will occur preferably by shortening or lengthening the modified stroke cycle. However, it is also possible to vary the maximum length or the minimum length of the traverse stroke for determining a modified stroke cycle.
Both the change of the traverse stroke and the variation of the traverse speed may be performed parallel. In all cases, the duration of the modified stroke cycle is changed. In this instance, the changes may shorten or lengthen the time of the modified stroke cycle.
To determine the actual position of the starting reversal point, it is proposed to determine the instantaneous angular position of the package and the instantaneous diameter of the package. This defines the starting point of the yarn reversal at the beginning of the modified stroke cycle. The determination of the diameter of the package has in this instance the special advantage that the diameter increase can be taken into account in the determination of the desired position of the end point. As the package diameter increases, and the time of the modified stroke cycle remains constant, a shorter distance is covered on the circumference of the package between the starting points and the end points.
In a particularly advantageous variant of the method, a control device performs the determination and adjustment of the yarn reversal points, as well as the control of the traversing yarn guide. The control device connects to the drive of the traversing yarn guide. The drive influences the traversing motion and traverse stroke of the traversing yarn guide.
To obtain an as precise package buildup as possible, the actual diameter of the package and the angular position may be continuously determined, so that the drive is controlled by the control device as a function of the comparison between the position of the starting reversal point and the position of the end reversal point.
The method of the present invention is independent of the type of wind. The types of wind include random wind, precision wind, or stepped precision wind. In the case of the random wind, the mean value of the traversing speed remains substantially constant during the winding cycle. In this instance, the winding ratio (spindle speed/traversing speed) will constantly change during the winding cycle. In the case of a precision wind, the winding ratio is kept constant. In the case of a stepped precision wind, however, the winding ratio is varied in steps by a predetermined program.
Likewise, it is especially advantageous to combine the method of the present invention with the known ribbon breaking methods. With that, it is possible to produce cross-wound packages with a large diameter and great package density, which ensure a troublefree overhead unwinding of the yarn at high withdrawal speeds of 1,000 m/min and greater.
The method of the present invention may be used both for producing cylindrical cross-wound packages with substantially rectangular front. faces, and for winding biconical packages with oblique front faces.
The apparatus of the present invention for carrying out the method distinguishes itself by its great flexibility in the production of packages. With the use of the

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