Winding – tensioning – or guiding – Helical or random winding of material – Distributing material along the package
Reexamination Certificate
1999-12-15
2001-02-13
Mansen, Michael R. (Department: 3653)
Winding, tensioning, or guiding
Helical or random winding of material
Distributing material along the package
C242S477500, C242S481400, C242S481600
Reexamination Certificate
active
06186435
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for winding a continuously advancing yarn into a package.
When winding a yarn into a package, it is always attempted to obtain a stable package build, a uniform packing density, as well as satisfactory unwinding characteristics during a later further processing stage. In this connection, the end faces of such packages may extend in a normal plane, so that cylindrical packages are obtained, or they may be inclined relative to this normal plane, so that a biconical package is formed. In the winding of packages, the problem arises that the yarn reversal causes a mass accumulation at the package edges, which leads to hard package edges or a bulgy package edge.
It is known both from U.S. Pat. No. 4,659,027 and from EP 0 235 557 that for purposes of avoiding the bulges at the package ends, the traverse stroke may be changed by modifying the stroke, i.e., by periodically shortening and lengthening the traverse stroke in the end region of the package edges, thereby displacing the reversal point at the package edge. However, the yarn deposit in each of the reversal points is the same, so that the yarns are distributed at the package ends as a function of the stroke modification frequency. This procedure has shown that at a small stroke modification frequency the end faces of the package are softer in comparison with a package that is wound at a high stroke modification frequency.
In an effort of avoiding excessively high package edges, a further disadvantage is found in that the traverse stroke must be shortened by as much as 20 mm during the stroke modification. While this shortening prevents a buildup of edges, the yarn is deposited irregularly and, thus, an irregular packing density is incurred in the edge region, which leads likewise to soft end faces of the package. Depending on the kind of further processing, this is undesirable, since soft packages are more susceptible to damage than hard packages.
Furthermore, the alternate shortening or lengthening of the traverse stroke has the disadvantage that the yarn guide reciprocating the yarn is urged to cover alternatingly a long and a short traverse distance.
It is accordingly an object of the present invention to provide a method and apparatus for winding an advancing yarn into a package, which corrects the yarn deposit in the edge region irrespective of a stroke modification and irrespective of the length of the traverse stroke.
SUMMARY OF THE INVENTION
The above and other objects and advantages of the present invention are achieved by the provision of a yarn winding method and apparatus which include guiding the advancing yarn onto a rotating core by a traversing yarn guide which moves within a traverse stroke. Also, during each traverse stroke the traversing yarn guide is accelerated by a predetermined acceleration to a guiding speed within a reversal length at one end of the traverse stroke, and decelerated from the guiding speed by a predetermined deceleration within a second reversal length at the opposite end of the traverse stroke. The traverse stroke has a length which is shorter than the wound length of the package, and the traverse stroke is alternately displaced flush with the package ends without changing the length of the traverse stroke.
The yarn traversing mechanism for reciprocating the yarn preferably comprises a belt drive system which is controlled by a programmable control device so as to effect the alternate displacement of the traverse stroke as described above.
The invention will be seen to be distinct from EP 0 453 622 which discloses a method in which the position of the yarn guide is dependent on the position of the rotor of an electric motor. The known method describes a solution to operating an apparatus, which facilitates movement of the yarn guide in the reversal region at very high accelerations and decelerations. In this apparatus, the movement of the electric motor is controlled by means of a control unit as a function of normal laws of winding, thus giving rise to the aforesaid problems with the package edges.
While being traversed, the yarn is deposited by a speed function of the traversing yarn guide. This speed function is characterized by three stages. Initially, it is necessary to accelerate the yarn guide from the reversal point to a guiding speed. The distance, which is covered by the yarn until it reaches the desired guiding speed, is defined as the reversal length. Subsequently, the yarn is moved at the guiding speed until it reaches the opposite end of the traverse stroke, with the covered distance being described herein as the linear length. At the opposite end, the yarn guide is decelerated from the guiding speed such that its speed is zero at the reversal point. The distance covered during the deceleration phase is likewise referred to as the reversal length. Thus, the traverse stroke as defined by the reversal points results from adding these three partial lengths. The reversal length of the yarn guide is determined substantially by the adjusted acceleration or deceleration of the yarn guide. The method of the present invention now uses in particular the acceleration or deceleration of the yarn guide, so as to influence the deposit of the yarn. To this end, the accelerations and decelerations may be controlled so as to change the extent of the reversal length, thus initiating the start of the yarn reversal at an earlier or later point toward the end of the traverse stroke. As a result, the yarn is deposited at different angles toward the end face of the package, thus facilitating a uniform distribution of the yarn directly after the reversal point.
The reversal function of the acceleration and deceleration may be determined by a microprocessor, such that it is possible to realize any desired reversal functions of the yarn guide. It is also possible, however, to move the yarn guide by a stepping motor.
The reversal function may be made symmetric, so that deceleration and acceleration of the yarn guide are identical. This realization is suitable in particular for making the yarn deposit uniform in the edge region.
It is also possible to predetermine an asymmetric reversal function. Such a control is advantageous to prevent yarn from sloughing off at the package end. To this end, the yarn is guided with a slight deceleration toward the package end and, thereafter, moved away therefrom at a very high acceleration. The change of the reversal length makes it possible to realize, without additional measures, an acceptable package build with relatively flat edges and straight end faces or smooth slope surfaces.
In the above cases, the control of the deceleration and acceleration of the yarn guide may be effected by a predetermined chronological program sequence. This allows any desired time function to be realized. Thus, while breaking a ribbon, it would be possible to follow the change of the reversal length proportionately after switching to a higher traversing speed.
In a further, advantageous modification, the deceleration and/or acceleration of the yarn guide are controlled as a function of the guiding speed. Thus, it becomes possible to produce within a double stroke a different yarn deposit in each single stroke. Furthermore, it is possible to realize an advantageous interconnection with a ribbon breaking method. A ribbon is described as a phenomenon of the package, in which undirected yarn lengths come to lie more or less exactly on top of one another in successively wound layers of the yarn. Normally, the symptoms of such ribbons are avoided by constantly decreasing or increasing, for example, between an upper and a lower limit, the guiding or traversing speed, which is expressed as number of reciprocal movements (double strokes) of the traversing yarn guide per unit time. The cooperation of change in the reversal length and a ribbon breaking makes it possible to realize a further improved binding of the yarn layers in the edge region of the package. In this connection, it is also possible to change
Lenz Friedhelm
Mayer Manfred
Alston & Bird LLP
Barmag AG
Mansen Michael R.
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