EP0578966B1 - Method for winding a yarn with stepped precision winding - Google Patents

Abstract

The stepwise high precision winding method includes winding the yarn on the bobbin with a reciprocating yarn changing guide in a series of steps so that an outer circumferential speed of the yarn-bobbin package is constant; reducing the yarn guide reciprocation frequency in each step from a starting frequency value to a final frequency value while keeping a winding number constant during each step so that the final frequency value is proportional to a bobbin rotation frequency in each step, and then increasing the yarn guide reciprocation frequency discontinuously to another starting frequency value and beginning a following step with the yarn guide reciprocation frequency equal to the other starting frequency value; setting the starting frequency value in each step to not more than a fixed maximum frequency; setting the final frequency value in each step to not less than a certain fixed minimum frequency; and setting the winding number in the Sth step equal to either iS-iSx/(MS+x) or iS+iSx/(MS-x), wherein x=a/2H; iS is a mirror value for the Sth step, MS is the order of the mirror value for the Sth step, a=the lay spacing between windings of a Kth lay and a (K+MS)th lay and H is a total height of the yarn-bobbin package.

Description

The invention relates to a method for winding a continuously fed thread according to the preamble of patent claim 1.

When winding continuously fed threads on bobbins that are driven at a constant peripheral speed, a distinction is made between three different methods:
Wild winding
Precision winding
graduated precision winding

The traversing frequency is constant in the wild winding. This results in a constant thread laying angle. However, since the speed decreases with increasing coil diameter, the number of turns i, ie the ratio of speed / traversing frequency, decreases continuously with increasing diameter. If the number of turns becomes an integer or assumes a value that differs from an integer by a simple fraction, such as 1 1/2 (2nd order), 2 2/3 (3rd order), 5 3/4 (4th . Order), so-called mirror windings arise. For the sake of brevity, the numbers in which mirror windings arise, ie the whole and the mixed numbers, are referred to below as "mirror values".

The characteristic feature of a mirror winding is that turns are placed exactly on turns previously laid.

For integer turns, i.e. with 1st order mirror values, the turns of successive layers lie on top of each other. In general, the M-order mirror value means that the turns of the (K + M) -th layer lie exactly on the turns of the K-th layer.

The "layer" is the piece of thread that is placed on the spool during a double stroke, i.e. while the traversing thread guide moves from one end of the bobbin to the other and back. The "thread" is the piece of thread that is put on during one revolution. The number of turns i is the number of turns per layer.

As is well known, mirror windings can cause a number of disadvantages, in particular an unstable spool structure, difficulties in unwinding the affected spool and unevenness in a subsequent coloring.

In the precision winding, the traversing frequency is in a fixed ratio to the speed of the coil; the number of turns therefore remains constant. According to the coil speed, the traversing frequency also becomes smaller and smaller as the coil diameter increases. The result is that the thread-laying angle also becomes smaller and smaller. It is essentially proportional to the traversing frequency. As the angle of deposit decreases, the coherence of the coil deteriorates. This method can therefore only be used to a limited extent. However, it has the advantage that one can avoid mirror formation by choosing the number of turns.

bleibt also in jeder Stufe konstant. Sie wird bei bekannten Verfahren grundsätzlich so gewählt, daß zu Beginn einer jeden Stufe mit der maximal zulässigen Changierfrequenz, d.h. mit dem maximal zulässigen Ablegewinkel gearbeitet wird, der bei einem bestimmten Durchmesser annähernd proportional zur Windungszahl ist. Der Übergang zur nächstfolgenden Stufe erfolgt bei bekannten Verfahren in der Regel dann, wenn der Ablegewinkel das kleinste noch zulässige Maß erreicht hat. Beim Übergang in die neue Stufe wird die Changierfrequenz sprunghaft erhöht, so daß sich wieder die maximale Changierfrequenz und der maximale Ablegewinkel einstellen. Dementsprechend springt die Windungszahl auf einen neuen, kleineren Wert. Dabei kann es vorkommen, daß die Windungszahl zufällig auf einen Spiegelwert oder in dessen kritische Nähe fällt.With the stepped precision winding, the winding is built up in several stages. In each individual stage, the traversing frequency f decreases proportionally with the coil speed n. The number of turns $\text{i = n / f}$

therefore remains constant in each stage. In the case of known methods, it is basically chosen so that at the beginning of each stage the maximum permissible traversing frequency, ie the maximum permissible depositing angle, which is approximately proportional to the number of turns for a certain diameter, is used. In known methods, the transition to the next stage usually takes place when the placement angle has reached the smallest dimension that is still permissible. At the transition to the new stage, the traversing frequency is increased suddenly, so that the maximum traversing frequency and the maximum placement angle are set again. Accordingly, the number of turns jumps to a new, smaller value. It can happen that the number of turns accidentally falls on a mirror value or in its critical proximity.

According to DE-OS 40 37 278, which corresponds to EP-A-0 486 896 on which the invention is based, a computer determines the number of turns from stage to stage and compares them with the dangerous mirror values. If the calculated number of turns does not fall within the critical range of a mirror value, this number of turns is used. However, if it is in the critical range of a mirror value, a slightly increased number of turns is used. This lies at a precisely defined short distance from the dangerous mirror value, which depends in particular on the size and the atomic number of the mirror value. It is thereby achieved that the turns of the (K + M) -th layer are not placed exactly on the turns of the K-th layer, but at a predetermined constant laying distance a next to the turns of the K-th layer. The laying distance a is measured from the middle of the thread to the middle of the thread and is therefore in any case greater than the width of an overlying thread. It is recommended to make it as small as possible, if possible not larger than twice the thread width.

According to the cited document, the aim is to keep the number of corrective interventions as small as possible. Therefore, winding is only carried out with a corrected number of turns in those stages in which this is essential to avoid a mirror winding. In the other stages, the number of turns is obtained, which is obtained by choosing the maximum permissible traversing frequency as the starting frequency. With these numbers of turns, the distances between the turns of corresponding layers are random and therefore uneven.

The invention has for its object to improve the method according to the preamble of claim 1 so that the coil receives a uniformly high packing density with little edge increase.

in dem zweiten Fall $${\text{Δi}}_{\text{s}}\text{= +}\frac{{\text{i}}_{\text{s}}\text{· x}}{{\text{M}}_{\text{s}}\text{-x}}$$

This object is achieved by the feature specified in the characterizing part of claim 1. A "number of turns close to the mirror" in the sense of the invention is by no means a mirror value and also not a number that comes anywhere near a mirror value, but rather a number of turns that differs from a mirror value i _s by a defined difference. Each mirror value corresponds to two numbers of turns close to the mirror, one of which is a little smaller, the other a little larger than the mirror value. In the first case, the difference is $${\text{Δi}}_{\text{s}}\text{= -}\frac{{\text{i}}_{\text{s}}\text{· X}}{{\text{M}}_{\text{s}}\text{+ x}}$$

in the second case $${\text{Δi}}_{\text{s}}\text{= +}\frac{{\text{i}}_{\text{s}}\text{· X}}{{\text{M}}_{\text{s}}\text{-x}}$$

The characters have the following meaning:

M _s is the order of the mirror value i _s . $$\text{x =}\frac{\hfill \text{a}}{\hfill \text{2H}}$$

H is the traverse stroke, i. H. the length of the winding.

a is the laying distance between the turns of the K th layer and the (K + M) th layer, measured from the middle of the thread to the middle of the thread; it is at least equal to the width and at most equal to 3 times the width of the thread lying thereon, preferably not greater than twice the width.

Since in practice the size X is usually negligibly small compared to the atomic number M _s , the two difference terms are almost identical. It is characteristic that they are proportional to the number of turns and essentially inversely proportional to the atomic number. So they vary in size from level to level.

The sizes marked with the index s differ individually for the individual levels. In contrast, the sizes a and H and thus the derived size x are the same size for all levels.

In other words, the characterizing part of claim 1 means that in each individual stage a number of turns is selected in which the turns of the (K + M) th position are deposited at a fixed distance a next to the turns of the K th position.

Various exemplary embodiments of the invention, which have advantages depending on the boundary conditions of the individual case, are specified in the subclaims.

Figures 1-6 illustrate various embodiments.

The selection of the number of turns close to the mirror for the individual stages is expediently carried out with the aid of an i-D diagram in which the hyperbolic limit curves for the minimum and the maximum depositing angle as well as the start and end diameter of the coil are entered. In such a diagram, the coil travel with a stepped precision winding is generally symbolized by a staircase curve that lies between the two limit curves. It is characteristic of the invention that all steps parallel to the abscissa correspond to the number of turns close to the mirror.

In the example according to FIG. 1, the number of turns close to the mirror has been selected such that they lie at defined positive distances from first order mirror values. The mirror values are the whole numbers from 8 to 2 in continuous descending order. As is well known, since the mirror values of the higher order are least densely arranged on the number scale in the vicinity of the integer mirror values, the restriction to the number of turns near the mirror in the vicinity of integer mirror values has the advantage that collisions with mirror values of a higher order are easy to avoid. It is characteristic of the example of FIG. 1 that the transition to the next stage - i.e. the sudden increase in the traversing frequency - always occurs exactly when the traversing frequency and thus also the lay-off angle has reached the lowest permissible value. As a result, the upper corner points of the staircase curve are all on the hyperbola, which is assigned to the minimum laying angle. The lower corner points lie in the space between this hyperbola and the hyperbola, which is assigned to the maximum placement angle.

A typical example is from practice the diameter of the coil sleeve Do = 0.1 m the traverse stroke H = 0.17 m the width of the thread b = 1.7 mm the laying distance a = 3.4 mm the surface speed of the coil v = 5,500 mmin ^-1 the minimum lay angle α _min = 6 ° the maximum lay angle α _max = 9 °

As FIG. 1 shows, the coil journey begins with that number of turns close to the mirror which is a little larger than 8. The exact value results from the given formula: $${\text{i}}_{\text{1}}\text{= 8.08}$$

die anfängliche Changierfrequenz zu $${\text{f}}_{\text{1}}{\text{= 2.166 min}}^{\text{-1}}$$

der anfängliche Ablegewinkel zu $${\text{α}}_{\text{1}}\text{= 7,63°}$$

The initial speed of the coil is calculated $${\text{<figure-callout id="1" label="n" filenames="imgf0001.png,imgf0002.png" state="{{state}}">n</figure-callout>}}_{\text{1}}{\text{= 17,507 min}}^{\text{-1}}$$

the initial traversing frequency too $${\text{<figure-callout id="1" label="f" filenames="imgf0001.png,imgf0002.png" state="{{state}}">f</figure-callout>}}_{\text{1}}{\text{= 2,166 min}}^{\text{-1}}$$

the initial drop angle to $${\text{α}}_{\text{1}}\text{= 7.63 °}$$

The diameter reached at the end of the first stage is $${\text{<figure-callout id="1" label="D" filenames="imgf0001.png,imgf0002.png" state="{{state}}">D</figure-callout>}}_{\text{1}}\text{= 0.127 m}$$

die Changierfrequenz auf $${\text{f}}_{\text{min}}{\text{= 1.700 min}}^{\text{-1}}$$

As a result of the increase in the diameter, the speed of the coil has dropped to at this time $${\text{n}}_{\text{2nd}}{\text{= 13,739 min}}^{\text{-1}}$$

the traversing frequency $${\text{f}}_{\text{min}}{\text{= 1,700 min}}^{\text{-1}}$$

ergibt sich für die zweite Stufe eine anfängliche Changierfrequenz von $${\text{f}}_{\text{2}}{\text{= 1.943 min}}^{\text{-1}}$$

This is the minimum frequency that corresponds to the minimum placement angle of 6 °. The frequency is now increased by leaps and bounds. From the speed and the number of turns close to the mirror calculated for the second stage $${\text{i}}_{\text{2nd}}\text{= 7.07}$$

for the second stage there is an initial traversing frequency of $${\text{f}}_{\text{2nd}}{\text{= 1,943 min}}^{\text{-1}}$$

gewickelt, die von dem zugehörigen Spiegelwert 2 nur noch um 0,02 abweicht. Der Durchmesser ist am Ende der letzten Stufe angewachsen auf $${\text{D}}_{\text{max}}\text{= 0,429 m}$$

The same procedure is followed in the further stages. The corner point of the staircase curve, which marks the beginning of the last step, happens to be almost exactly on the hyperbolic boundary curve, which is assigned to the maximum angle 9 °. In the last stage, the number of turns close to the mirror $${\text{i}}_{}$$$${}_{\text{7}}\text{= 2.02}$$

wound, which only deviates from the associated mirror value 2 by 0.02. The diameter increased to at the end of the last stage $${\text{D}}_{\text{Max}}\text{= 0.429 m}$$

The example shown in FIG. 2 initially differs from the example in FIG. 1 in that the maximum placement angle is only 8 °. The maximum traversing frequency is therefore correspondingly lower than in the first example. The stair curve, which symbolizes the coil travel, must be accommodated in the space between the two hyperbolic limit curves, which is narrowed in comparison with FIG. 1. This is made possible by the fact that those turns numbers close to the mirror which are adjacent to the 2nd order mirror values, ie the half-numbered mirror values, are also used. These number of turns close to the mirror are briefly referred to below as "2nd order turn numbers close to the mirror". The distances between the associated mirror values are all the same, namely 0.5. The distances between the number of turns close to the mirror differ slightly, however, since the difference between the mirror value and the corresponding number of turns close to the mirror also depends on the ordinal number, which in this example alternately takes on the values 1 or 2. The limitation to a reduced frequency range has the advantage that the frequency jumps occurring at the transitions between the individual stages are smaller. This improves the coil structure.

In the example which is illustrated in FIG. 3, the critical angles are likewise 6 or 8 °. At the beginning of the coil journey, the number of turns close to the mirror is used, which are adjacent to the integer mirror values 8, 7, 6, 5, 4, i.e. with 1st order turns numbers close to the mirror. If, however, analogous to FIG. 1, one jumps directly from the number of turns 4.04 close to the mirror to the next following number of turns of the 1st order, namely to 3.03 and 2.02, the initial depositing angles in the corresponding stages would exceed the predetermined maximum limit. Therefore, both the first-order number of turns close to the mirror and the second-order number of turns close to the mirror are used in the end section of the coil travel. In comparison to FIG. 2, the total number of switching operations required during the coil trip is reduced. The layers corresponding to the steps are correspondingly thicker in the area near the sleeve.

Figure 4 illustrates an embodiment in which the placement angle is limited to the extremely narrow range between 7 and 8 °. This severely limits the selection of the number of turns close to the mirror for the individual stages. In the first half of the coil trip we work with 1st and 2nd order number of turns close to the mirror. In contrast to the examples discussed so far, the number of turns close to the mirror is used, which is smaller than the corresponding mirror values, namely at mirror values 7.5; 7; 5.5; 5; 4, 5 and 4. This makes it easier to fit the stair curve into the narrow space between the two limit curves. In the second half of the coil trip, the gradation is further refined by using 3rd order number of turns close to the mirror, the distances of the number of turns close to the mirror from the associated mirror values being irregular in part, partly positive, partly negative.

The exemplary embodiment of FIG. 5 largely corresponds to that of FIG. 2. The difference is that the lower corner points of the stair curve lie on the hyperbola, which corresponds to the maximum placement angle. This means that after each stage, the frequency increase is carried out at the moment when the coil speed has dropped just enough that the maximum frequency results as the starting frequency for the following stage.

The example illustrated in FIG. 6 differs from all previous exemplary embodiments in particular in that the transition to the next stage takes place whenever the diameter has increased by a certain amount, which is the same for all stages. The first and second order number of turns close to the mirror are used in full sequence, starting with 8.08 and ending with 2.513. It can be seen that in the beginning and end phase of the coil travel, the placement angles come close to the maximum placement angle. In the middle phase, the discard angle approaches the lower limit. The uniform thickness of the layers wound in the individual stages ensures that the shoulders which appear on the end faces of the coils lie at uniform intervals. This can have advantages when the thread is pulled off during further processing. Even if there is a relatively large space between the minimum and maximum placement angles, a fine gradation is required.

Claims (9)

1. A method of winding a continuously supplied thread onto a bobbin rotating at a constant peripheral speed with a stepped precision winding, with the following features:

   a) the traversing frequency is reduced at each stage from an initial frequency to a final frequency proportional to the rotational speed of the bobbin and is then abruptly increased to the initial frequency of the following stage;

   b) in each stage the initial frequency is at most equal to a fixed maximum frequency;

   c) in each stage the final frequency is at least equal to a fixed minimum frequency;

   characterized in that
   in each stage s the operation is performed with a winding number which differs from a mirror value i _s by a difference of $${\text{Δi}}_{\text{s}}\text{= -}\frac{{\text{i}}_{\text{s}}\text{· x}}{{\text{M}}_{\text{s}}\text{+ x}}{\text{or Δi}}_{\text{s}}\text{= +}\frac{{\text{i}}_{\text{s}}\text{· x}}{{\text{M}}_{\text{s}}\text{- x}}$$

   

   in which case the symbols have the following meanings:
   M _s is the ordinal number of the mirror value i _s ;
   x = a / 2H;
   H is the traversing stroke, and
   a is the positioning distance between the windings of the layer No. K and the layer No. (K+M), measured from thread centre to thread centre; a is at least equal to the width and at most equal to three times the width of the positioned thread.
2. A method according to Claim 1, characterized in that the positioning distance a is at most equal to double the width of the positioned thread.
3. A method according to Claim 1 or 2, characterized in that the abrupt increase in frequency after each stage occurs at the moment at which the traversing frequency has reached the minimum frequency.
4. A method according to Claim 1 or 2, characterized in that the abrupt increase in frequency after each stage occurs at the moment at which the rotational speed of the bobbin has dropped so far that the maximum traversing frequency occurs as the initial frequency for the following stage.
5. A method according to Claim 1 or 2, characterized in that the abrupt increase in frequency after each stage occurs at the moment at which the bobbin diameter has reached a pre-determined increment.
6. A method according to one of Claims 1 to 5, characterized in that in all the stages winding takes place with winding numbers which are close to the mirror value and which are associated with mirror values of the first order.
7. A method according to one of Claims 1 to 5, characterized in that in all the stages winding takes place with winding numbers which are close to the mirror value and which are associated with mirror values of the first or second order.
8. A method according to one of Claims 1 to 7, characterized by equally large intervals of the mirror values, with which the winding numbers of the individual stages close to the mirror value are associated.
9. A method according to one of Claims 1 to 4 or according to Claim 7, characterized in that, as the travel of the bobbins continues, winding takes place to an increasing extent with winding numbers which are close to the mirror value and which are associated with mirror values of a higher order.

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