Winding – tensioning – or guiding – Helical or random winding of material – Distributing material along the package
Reexamination Certificate
1999-10-14
2001-10-30
Mansen, Michael R. (Department: 3653)
Winding, tensioning, or guiding
Helical or random winding of material
Distributing material along the package
C242S481400
Reexamination Certificate
active
06308907
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for winding a continuously advancing yarn to form a yarn package.
When winding the yarn to form a package, it is desirable to achieve a stable package build, a uniform packing density, as well as satisfactory unwinding properties in a subsequent further processing. In this connection, the end faces of such packages may extend in a normal plane, so that cylindrical packages result, or they may be inclined relative to this normal plane, so that a biconical package is wound. During the winding of the packages, the problem arises that the yarn reversal at the package edges causes a mass accumulation which leads to hard package edges or a bead-type package edge.
EP 0 453 622 discloses a method and an apparatus, wherein a traversing yarn guide performs a relatively high deceleration and acceleration in the reversal region. This results in an undefined yarn deposit in the reversal region. In the case of too high decelerations and accelerations, layers of yarn slip in the package edge region, which lead to an undefined buildup of the package edges. However, if the decelerations and accelerations of the traversing yarn guide are performed too slowly, a relatively large mass accumulates on the package edges.
It is accordingly an object of the invention to provide a method and an apparatus for winding a yarn to a package, wherein the yarn is deposited in the edge region with a minimal mass accumulation.
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 advancing yarn is guided onto a rotating core by a traversing yarn guide so that during each traverse stroke the traversing yarn guide is accelerated by a predetermined acceleration to a guiding speed within a reversal range at one end of the traverse stroke, and decelerated from the guiding speed by a predetermined deceleration within a second reversal range at the opposite end of the traverse stroke. Also, the acceleration and the deceleration of the yarn guide are controlled such that the reversal ranges of the traverse strokes become greater in length as the diameter of the package increases.
During the traversing, the yarn deposit occurs by a speed function of the traversing yarn guide. This speed function is characterized by three stages. First, starting from a reversal point, the yarn guide must be accelerated to a guiding speed. The distance covered by the yarn guide, until it reaches the desired guiding speed, is defined as the reversal range. Subsequently, the yarn guide moves at the guiding speed to the opposite end of the traverse stroke. The distance covered in this case is referred to as the linear length. At the opposite end, the yarn guide is decelerated from the guiding speed such that its speed is zero in the opposite reversal point. The distance covered during the deceleration phase is likewise defined as a reversal range. Thus, the two reversal points result in the defined length of the traverse stroke by adding these three stages. The reversal range of the yarn guide is defined essentially by the controlled acceleration or deceleration of the yarn guide. The method of the present invention therefore uses precisely the acceleration or deceleration of the yarn guide to influence the yarn deposit. To this end, the acceleration and deceleration are controlled such that the lengths of the reversal ranges continuously increase, as the diameter of the package becomes larger. With that, it is accomplished that with an increasing package diameter, the mass accumulation becomes less in the edge region, and that thus prevents the formation of bead-type package edges. The mass accumulation in the yarn reversal develops from the fact that the varied speed of the traversing yarn guide makes it necessary to deposit on the package surface a larger mass of yarn per unit time. The shorter the reversal range, the smaller is the accumulation of masses. The yarn deposit within the reversal range, however, remains stable, since the surface of a cylinder with a larger diameter requires a yarn reversal with a larger radius.
In a particularly advantageous further development of the invention, a minimum length of the reversal range is determined for each package diameter that ensures a stable yarn layer on the package surface. Thus, it is possible to minimize mass accumulation in the reversal ranges during the entire winding cycle. This variant of the method is based on the knowledge that it is possible to deposit the yarn within the reversal range on the package surface at a minimal radius without the yarn dislodging on the package surface.
Since the minimum length of the reversal range depends essentially on the minimal radius of curvature of the yarn deposit and the respective angle of crossing, a variant of the method is especially advantageous wherein a continuous determination of the minimum length of the reversal range is made such that the yarn layer is prevented from slipping on the package surface. In this instance, it is possible to compute the minimal radius of curvature from the quotient of the package diameter and twice a coefficient of friction of the package surface. The coefficient of friction of the package surface is for textile yarns in a range from 0.2 to 0.6. This would result, for example, with a package diameter of 200 mm in a minimal radius of curvature of the yarn deposit within the reversal length from 167 mm to 500 mm.
To attain a high flexibility during the winding of the yarn, the minimum length of the reversal range is continuously computed by means of a control device and converted into control signals for controlling the acceleration and deceleration of the traversing yarn guide.
In this connection, it will be especially advantageous, when the package diameter is continuously determined and input to the control unit for computing the minimum length of the reversal range. Since the coefficient of friction of the package surface depends essentially on the yarn type and the traversing program, it is possible to store same as a value in the control unit. Likewise known from the traversing program and stored in the control unit is the wound angle of crossing of the yarn. Thus, the control unit that is formed, for example, by a microprocessor, continuously computes the minimum length of the reversal range. The computed value is then converted directly into control signals to control a drive of the traversing yarn guide accordingly.
The method of the present invention can be used for winding the yarn both in a random wind with a constant angle of crossing and in a precision wind with varied crossing angles.
In a further advantageous modification, the guiding speed of the traversing yarn guide is variable. Thus, it is possible to produce within a double stroke a different yarn deposit in each single stroke. Furthermore, it is possible to realize an advantageous combination with a ribbon breaking method. A ribbon is defined as a phenomenon of the package, wherein unidirectional yarn lengths overlie more or less in successively wound layers of the yarn. The symptoms of such ribbons are normally prevented in that the guiding speed or the traversing speed that is expressed as a number of reciprocating movements (double strokes) of the traversing yarn guide per unit time, is decreased and increased constantly, for example, between an upper and a lower limit. As a result of coordinating variations in the reversal ranges and a ribbon breaking, it is possible to realize a still better stabilization of the yarn layers in the edge region of the package.
In a further, preferred variant of the method, the length of the traverse stroke is variable. With that, it is possible to avoid a buildup of high edges even in the case of adjustments to slow accelerations and decelerations. In this connection, any kind of stroke modification in combination is possible for varying the reversal stroke. A further advantage lies in that it is possible to co
Alston & Bird LLP
Barmag AG
Mansen Michael R.
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