Winding – tensioning – or guiding – Helical or random winding of material – Distributing material along the package
Reexamination Certificate
2001-03-30
2002-11-26
Mansen, Michael R. (Department: 3653)
Winding, tensioning, or guiding
Helical or random winding of material
Distributing material along the package
C242S477500
Reexamination Certificate
active
06484962
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for the stepwise precision winding of yarn into the form of a package commonly referred to as a cheese. More particularly, the present invention relates to such a method wherein a staple fiber yarn is fed at a constant yarn speed from a feeder mechanism of an open-end spinning system to a winding apparatus which rotates the cheese at a constant circumferential winding speed and, over the course of the progressive building of the cheese by the winding operation, the winding ratio is reduced in stages by graduations of decreasing size as the cheese diameter increases.
BACKGROUND OF THE INVENTION
When a cross-wound bobbin, also known as a cheese, is produced with a random winding, the speed of yarn traversing and the circumferential speed of the cheese over the course of building the bobbin, i.e., from the beginning to the end of the winding process, are in a fixed ratio to one another. As a result, the yarn crossing angle remains constant, while the winding ratio decreases as the bobbin diameter increases. The winding ratio indicates the number of bobbin revolutions per double yarn traversing stroke. A cheese produced with random winding has a stable yarn package and a largely uniform density. For instance, when integral values of the winding ratio are followed, so-called winding ribbons or mirror windings occur. To avoid their disadvantageous consequences, so-called ribbon breaking methods are employed, but such methods do not break up the ribbons completely.
The term “cheese” used here also applies to the bobbin package that builds up during the winding of the cheese. In producing a cheese with precision winding, it is not the yarn crossing angle but the winding ratio that is kept constant over the entire bobbin travel. The yarn crossing angle decreases as the cheese diameter increases. As the crossing angle decreases, the winding density increases outwardly. As a result, the pressure on the relatively soft bobbin core accordingly increases to an undesirable and disadvantageous extent. Problems can result in unwinding the cheese resulting from uneven yarn tension and increasingly frequent yarn breakage as well as uneven penetration of dye through the yarn package. In principle, the advantages of precision winding reside in the possibility of a high payout speed, high package density, and thus greater running length for the same bobbin volume, compared to a cheese with random winding. However, as the cheese diameter increases, the decreasing crossing angle limits the diameter in the production of precision bobbins made of staple fiber yarns due to the defects that occur at the package edges since staple fiber yarns in particular cannot be wound with arbitrarily small crossing angles. For this reason, in open- end spinning, crossing angles of less than 28 degrees should be avoided. As a result, precision winding with staple fiber yarns can be used only with severe limitations.
Graduated precision winding represents a combination of random winding and precision winding, in which the advantages of both types of winding are intended to be achieved and the disadvantages are intended to be decreased. Along with random winding and precision winding, graduated precision winding is a conventional term in textile technology, which is discussed at length for example in German Patent DE 42 23 271 C1 and German Patent Disclosure DE 39 20 374.
In graduated precision winding, as the term already expresses, a precision winding is produced in stages or steps. For example, a maximum permissible crossing angle is set and, as each stage progresses, the crossing angle gradually becomes smaller while the winding ratio remains constant. Once the crossing angle reaches the smallest permissible value, the crossing angle is abruptly restored to the initial value. The winding ratio thus drops to a smaller value. As a result, a cheese with a virtually constant crossing angle is obtained in which the winding ratio has been reduced in stages.
With graduated precision winding produced in this manner, however, the above-described density problems and problems of stability of the bobbin edge are merely lessened. Along with the density problems with the above-described causes and an increasing pressure on the internal yarn layers, still another problem arises. With the reduction in the crossing angle, the wound length per unit of time also drops. This is especially disadvantageous in open-end spinning machines. Since the yarn produced on open-end spinning machines is always fed at a constant yarn speed, the yarn tension between the cheese and the draw-off rolls, for instance, is reduced by the decreasing windup length per unit of time. By the time the cheese has been nearly fully wound, there can be differences in the tension distortion of about 3.5%. This leads to marked differences in density and impairs the reeling-off (i.e., unwinding) properties of the cheese considerably. Depending on the graduation in the graduated precision winding, it can happen that the winding ratio or winding number will randomly drop to one of the aforementioned mirror values or to the critical vicinity of such a value.
From the extensive prior art mentioned above, which addresses the problems that occur in graduated precision winding, several selected references warrant comment. In German Patent 42 23 271 C1, a method for winding a yarn by means of graduated precision winding is described, in which the traversing frequency is increased abruptly within a range that is determined by a minimum winding angle and a maximum lay angle. The traversing frequency is decreased within a stage from an initial frequency to a final frequency in proportion to the bobbin speed (rpm) and is then increased abruptly to the initial frequency of the next stage. This initial frequency in each stage is at most equal to a fixed maximum frequency. The final frequency in each stage is at least equal to a fixed minimum frequency. Because winding is performed in all stages with winding numbers near a mirroring value, the intent is to provide the bobbin with a uniformly high packing density.
In German Patent Disclosure DE 41 12 768 A1, a method for producing stepwise precision winding is described, in which the switchover to the next winding stage in each case takes place when a diameter value stored in memory is reached. The intent is for instance not to have to input certain individual yarn-specific parameters of the yarn to be wound into the computer, or to make additional measurements. According to this reference, the procedure for producing graduated precision windings is expediently accomplished by selecting a crossing angle &agr;, or a crossing angle tolerance range &agr;1 to &agr;2, on the basis of which characteristic variables of the winding stages are calculated. In this German Patent Disclosure DE 41 12 768 A1, it is recommended that the method be performed such that the tolerance range &agr;1 to &agr;2 of the selected crossing angle a is between ±4°.
Along with the above-described method in which the beginning of a new stage is initiated when the values of predetermined threshold crossing angles are exceeded, it is also possible to designate graduations in respect to the winding ratio, for example as a function of threshold values formed of cheese diameters. The graduations in the winding ratio can then be of constant size, for instance.
European Patent Disclosure EP 0 055 849 B1, which defines the basic type of graduated precision winding method to which the present invention relates, defines a method for graduated precision winding of yarns by means of a winding apparatus wherein the yarns are delivered continuously at constant speed. This method seeks to avert excessive differences in the winding speed, and the disadvantageous effects of such differences on the quality of the yarns and on the bobbin construction, by keeping the change in the winding ratio from one stage of the precision winding to the next so slight that the attendant change in winding speed of the yarn do
Kennedy Covington Lobdell & Hickman LLP
Mansen Michael R.
Pham Minh-Chau
W. Schlafhorst AG & Co.
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