EP0488939B1 - Method and apparatus for the disentangling of a yarn plug after texturising - Google Patents

Description

The invention is in the field of textile technology and relates to a method and a device according to the preambles of the independent process and the independent device claim known from CH-A-618 561, with which the plug formed from thermoplastic yarns during texturing is dissolved and a spoolable therefrom Yarn is produced.

Thermoplastic yarns, which usually consist of several fibrils, are subjected to heat treatment using known texturing methods and are driven through texturing nozzles or pressed in stuffer boxes. At the exit of the texturing nozzle or stuffer box there is a still warm but mechanically but relatively stable plug, which in the next process step usually has to be cooled and, above all, dissolved before the textured (crimped) yarn can be wound up.

According to the prior art, the yarn plug obtained from the texturing is cooled while it is, for example, in a vertical position Pipe moved up. In the upper part of the tube, the yarn is accelerated by a draw-off device, so that the plug dissolves into a more or less crimped yarn. This yarn is passed over a mechanical brake, for example an arrangement of brake rods, and then wound up. The take-off and winding device is operated at a constant speed (take-off speed), the mechanical brake brings about a constant thread tension during winding and prevents an increase in the thread tension in the cooling tube, which would lead to an early and uncontrolled plug release. Measuring the height of the plug in the cooling tube or measuring its speed, both of which depend on the texturing conditions, can be used as measuring elements for regulating the texturing conditions. Such a method and a corresponding device are described, for example, in European Patent No. 0 021 573.

A further method of dissolving the plug after texturing thermoplastic yarns is that the plug is guided from the texturing nozzle onto a sieve drum or perforated roller rotating at a constant speed, on which it is held by air sucked into the drum or roller and cooled at the same time. The yarn is accelerated on the drum and the plug is released. The yarn is also drawn off and wound up by a mechanical brake from the screening drum. Fluctuations in plug length caused by fluctuations in texturing conditions are prevented by the constant speed of the drum. Fluctuations in the length of the plugs due to the pulling-off process are automatically regulated by automatically changing the friction of the drawn-off yarn on the drum. A corresponding method and a corresponding device are described, for example, in Swiss Patent No. 618,561.

In both of the methods mentioned, the plug is converted into a spoolable yarn in two steps. First, the plug is released into a more or less crimped but oriented in a main direction. This happens between the end of the graft and the mechanical brake. The yarn is then brought to the desired thread tension between the mechanical brake and the take-off spool, so that it has the desired, effective or possibly only latent crimp in the wound state.

In both parts of the stretching process, forces have to act on the yarn, namely acceleration forces in the direction of the yarn movement, by means of which the yarn is accelerated against the take-off spool, and tension forces, which are of equal magnitude in both directions of the yarn and by which the yarn is stretched, rsp . the stopper is released. The acceleration and tension forces in the direction of yarn movement are applied by the take-off spool. The tension force in the opposite direction in the second part of the process (stretching the crimped yarn) is the braking force of the mechanical brake, due to the mechanical friction of the yarn on the brake elements. The same force in the first part of the process (dissolving the plug) is the weight and the resistance of the plug in the tube for the first described process, and the braking force for the second described process is caused by the friction of the plug and the drawn-off yarn on the sieve drum. It is necessary to split the process in two by using the mechanical brake, since the plug dissolution only takes place in an orderly and controlled manner when only minimal tension forces act, but on the other hand are far from sufficient to stretch the yarn in the desired mass.

However, it has now been shown that the use of mechanical yarn brakes on a crimped yarn is not optimal at the yarn speeds required today in the region of 4000 m / min, since they result in a reduction in the yarn quality due to increased fibril breaks.

It is an object of the invention to provide a method and a corresponding device which use means other than mechanical friction on the crimped yarns to generate the desired yarn tension. The process is said to provide a spoolable yarn with intact fibrils. It is intended to allow the yarn tension between the end of the graft and the take-off spool to be increased successively, so that in one process step the graft can be released with low yarn tension and wound up with increased yarn tension. The method is intended to be self-regulating in that it not only compensates for fluctuations in the plug properties due to fluctuations in the texturing conditions, but also, if possible, for fluctuations in the yarn entering the texturing by appropriate stretching of the crimped yarn.

This object is achieved by the method and the device according to the invention, which are mentioned in the characterizing parts of the independent claims and are described in detail below.

The basic principle of the method according to the invention is based on the fact that instead of the mechanical friction which is used in the methods according to the prior art as a tension force against the direction of yarn movement, the yarn is accelerated and freely deflected. This creates forces that are opposite to the yarn movement, that is, the thread brake. According to the invention, these forces can be increased by appropriate use of gravity, aerodynamic or hydrodynamic frictional forces. Both the deflection forces and the dynamic frictional forces can be successively increased between the end of the plug and the take-off spool, so that there is no need to divide the process into stopper and yarn stretching.

Fig. 1:

ein Schema zur physikalischen Grundlage der Kräfte, die bei der freien Umlenkung wirken,

Fig. 2:

ein allgemeines Verfahrensschema,

Fig. 3:

zwei verschiedene Ausführungsformen der erfindungsgemässen Vorrichtung mit Kühltrommel

Fig. 4:

zwei verschiedene Ausführungsformen der erfindungsgemässen Vorrichtung ohne Kühltrommel,

Fig. 5:

ein Beispiel für die Integration der erfindungsgemässen Vorrichtung zur Pfropfenauflösung in einer vollständigen Anordnung zur Herstellung texturierter Garne im Vergleich mit einer entsprechenden Anordnung gemäss dem Stande der Technik.

The following figures serve as an aid to the description. They show:

Fig. 1:

a diagram of the physical basis of the forces that act in free deflection,

Fig. 2:

a general procedure,

Fig. 3:

two different embodiments of the device according to the invention with a cooling drum

Fig. 4:

two different embodiments of the device according to the invention without a cooling drum,

Fig. 5:

an example of the integration of the device according to the invention for plug removal in a complete arrangement for producing textured yarns in comparison with a corresponding arrangement according to the prior art.

wobei m/l die Masse des Garnes pro Längeneinheit, v die Garngeschwindigkeit bedeutet. FIG. 1 illustrates the forces that act when a yarn 1 is deflected. In order for the yarn to move around the deflection radius r, each piece of yarn, for example the piece of yarn between points A and B, must be included the mass m and the length l, a corresponding centripetal force K _{Z are} applied. This centripetal force can be broken down into the two force components K _SV and K _SR , which act in opposite directions in the yarn movement direction and the yarn movement direction, which act from the adjacent yarn pieces on the yarn piece under consideration and tension the yarn piece. From the physical conditions for the centripetal force it follows:

${\text{| K}}_{\text{SV}}{\text{| = | K}}_{\text{SR}}\text{| = (m / l) x v²}$

where m / l is the mass of the yarn per unit length, v is the yarn speed.

If the forces K _SV and K _{SR are} large enough to make the yarn stiff, the deflection becomes stable without mechanical guide elements. Such stable deflections are known in the case of long belts which are carried by dancers and which move stably through the air on complicated tracks without further mechanical assistance. If the tension forces are greater than the force required for a dissolution of the stopper rsp: for an extension of the yarn, the stopper is released, rsp. the yarn stretched.

It can be seen from the equation that the tension forces are not dependent on the deflection radius, but rather on the yarn thickness and its speed. For a thinner yarn with a smaller m / l, smaller forces act at the same speed than for a thicker one. With increased speed, the forces increase with the same yarn thickness. If these forces are used to loosen the plug and to stretch the yarn, these two facts have an advantageous effect, because higher tension forces cause the yarn to have the same elastic properties, which means that a thicker irregularity of the yarn in one the same deflection is stretched more than the normal thick yarn and that as the yarn speed increases between the end of the plug and the take-off spool, the drawing forces gradually increase, as was postulated in the task.

Figure 2 shows the inventive method schematically. The yarn plug 1.1 is pushed at the constant speed v 1 in the direction indicated by the arrow v 1, the yarn 1.2 is drawn off in a different direction at the constant speed v 2, which is greater than v 1. The change in direction necessitates a deflection which is stable under the conditions specified in connection with FIG. 1 without mechanical guidance. The in this redirection to plug 1.1, rsp. Forces 1.2 acting forces also have a dissolving and stretching effect. The speeds v₁ and v₂ must be set so that the deflection is stable and that the forces are sufficient to dissolve the plug and stretch the yarn to the desired extent. The deflection radius will be set depending on the selected speeds, the available free yarn length and the arrangement of the system components. The balance is mainly dependent on the elastic and plastic properties of plug 1.1 and yarn 1.2, the two speeds v₁ and v₂ and the system-related deflection angle β. A certain curve shape of the plug-yarn loop will correspond to each balance. In the state of equilibrium, the plug-yarn loop is so stable that it does not require any mechanical backdrop to support it.

The braking force on the yarn can be increased rsp. are weakened by any forces which additionally act on the yarn in such a way that they can be broken down into components in such a way that a component counteracts the direction of the yarn movement, that is to say acts as a braking force, rsp. acts in the direction of yarn movement, thus weakening the braking effect. For example, gravity or the frictional force on a flowing or standing medium can be used in this way.

Figure 3a shows an embodiment of the device according to the invention. The plug 1.1, which emerges from any texturing device 4, be it a texturing nozzle or a stuffer box, is applied in points C to a sieve drum or perforated roller 2 rotating at a constant surface speed v 1. Air is sucked into the screening drum 2, which simultaneously holds and cools the plug 1.1 on the drum surface. The plug 1.1 moves with the surface of the drum and, when it reaches the point D 1 rsp. D₂ has reached, by a corresponding chicane or by closing the perforation so that it is no longer held by the negative pressure in the drum, detached from the drum surface. The yarn 1.2 is drawn off from the take-off spool 3 at the speed v 2. By varying the point D (D₁ rsp. D₂), the cooling angle τ (τ₁ rsp. Τ₂) changes. This changes above all the deflection angle β (β₁ rsp. Β₂), which affects the braking effect of the arrangement and thus the yarn tension in front of the take-off spool. In addition, such a change also changes the cooling time of the plug, which will have an impact due to the changed elastic and plastic properties of the plug and the yarn. Obviously, the cooling angle τ is well suited as a variation parameter for the stretching process. The cooling angle τ can be varied by displacing the baffle which releases the plug from the drum or by displacing the means which are provided for closing the perforation in the interior of the drum.

The arrangement shown in FIG. 3a for the plug release according to the invention can be changed by changing the relative positions of the screening drum 2 of the take-off spool 3 are changed in such a way that gravity is increasingly included in the braking process during the deflection. Such an arrangement is shown in FIG. 3b. The plug 1.1 is pushed upward by appropriate arrangement of the detachment point D₃ by its kinetic energy and changes its direction towards the bottom in a point E, which is dependent on the plug speed, the plug weight and the weight of the downward hanging plug piece. From this movement, it is deflected upwards again by the correspondingly arranged take-off spool in the area of point F. The upward deflection, as described in connection with the method according to the invention, has a braking effect on the stopper. In addition to the tension forces caused by the deflection, the gravity at the deflection point F also has a braking effect and increases the braking effect, which results in a higher yarn tension.

Variants of the two devices according to the invention shown in FIGS. 3a and 3b consist in that additional means are attached with which, for example, air is blown against the deflection point, specifically from its concave side in order to increase the braking force, from the convex side to reduce the braking effect. In these cases it may be advantageous to surround the deflection point with a suitably designed housing with corresponding air inlet openings and outlet openings.

FIGS. 4a and 4b show exemplary embodiments of the device according to the invention, in which no rotating sieve drum is used to cool the yarn plug. The plug 1.1 is conveyed in both cases through an inlet opening 40 into a channel-shaped, ventilated housing 41, in which it is driven downward by gravity emotional. In this housing, it is deflected by the force and withdrawal direction of the take-off spool 3 and is withdrawn accelerated through the outlet opening 42.

FIG. 4a shows a corresponding housing 41a into which the plug 1.1 is inserted via the inclined guide groove 43a provided with holes. The guide groove 43a is followed by a deflection space 44a with a horizontal bottom, also provided with holes, in which the plug 1.1 is pulled off towards the top and against the direction of its insertion and is simultaneously released. The exit opening 42a is located just above the entry opening 40a. An exhaust air duct 45a adjoins the deflection space 44a on the side opposite the inlet and outlet opening and is connected to the deflection space 44a by holes. Air is actively sucked out of the housing 41a through the exhaust air duct 44a and outside air is sucked in through the holes in the guide trough 43a and the deflection space 44a and through the inlet and outlet openings (40a / 42a). The resulting air flow in the housing 41a (indicated by arrows in the figure) runs in the inlet opening 40a in the yarn transport direction, in the outlet opening 42a against the yarn movement direction, so that it acts as a brake on the yarn 1.2. In the deflection space 44a, depending on the position of the deflection loop, the air flow has a more or less braking effect on the plug and yarn.

Figure 4b shows a device similar to Figure 4a. The housing 41b has a much steeper guide groove 43b, so that the deflection loop has a hanging position. In this case, gravity acts as a brake, but the exhaust air duct 45b is arranged between the inlet opening 40b and the outlet opening 42b in such a way that the air flow through the housing 41b counteracts the braking.

Variants are conceivable for all of the described embodiments of the device according to the invention, in which the take-off spool is preceded by a pneumatic detangling nozzle, which serves as an additional brake for detangling and stretching the yarn. The air flow required for braking in this nozzle can also be guided in such a way that the force it exerts on the yarn does not act exactly in the direction opposite to the direction of yarn movement and thus at the same time causes the fibrils to swirl to stretch the yarn. A separate device for swirling is then unnecessary. A corresponding “combined” nozzle 46 is shown in FIG. 4b.

FIG. 5 shows how any of the embodiments of the device for plug dissolution according to the invention can be integrated into a complete arrangement for producing textured yarns. The arrangement is shown in FIG. 5a, while FIG. 5b shows a corresponding arrangement according to the prior art and is used for comparison. The arrangement comprises an entry zone between points P and Q, in which the fibrils emerging from the spinnerets are combined to form a yarn and the yarn is pre-stretched. The texturing zone follows between points Q and R, in which the yarn is textured and the plug formed during texturing is dissolved. This is followed by the draw-off zone between points R and T, in which the yarn is stretched, swirled and wound up. The point R between the texturing zone and the draw-off zone is not shown in FIG. 5a, because the use of a pneumatic detangling and swirling nozzle 50 fuses the two zones. It can be seen from the comparison of the two drawings 5a and 5b that the use of the device according to the invention for plug removal, especially together with the combined pneumatic nozzle, greatly simplifies the arrangement.

Claims (10)

1. A method for the disentangling of a yarn plug and for drawing a crimp yarn after texturising, characterized in that after the cooling of the yarn plug the yarn is deflected freely without mechanical friction to disentangle the yarn plug and is drawn off and stretched with a speed which is larger than the speed of the yarn plug and that thereby a plug-yarn loop is formed which does not require any mechanical crank for its support.
2. A method as claimed in claim 1, characterized in that in addition to the forces produced by the deflection, respective components of gravity and/or of dynamic frictional forces are used for the disentangling of the yarn plug and the subsequent stretching of the yarn.
3. A method as claimed in one of the claims 1 or 2, characterized in that it is varied with respect to material by variation of the cooling angle τ changing the cooling time of the yarn plug and/or the deflection angle β acting on the yarn tension before the draw-off bobbin.
4. An apparatus for texturising a moved thermoplastic yarn (1.2) with a texturing apparatus (4) for forming a plug (1.1), a cooling part (2, 43a, 43b) for cooling the plug and a draw-off part (3) for drawing off the plug from the cooling part and for stretching the yarn, characterized in that the draw-off part (3) is arranged relative to the cooling part (2, 43a, 43b) in such a way that from a first direction of movement a mechanically unguided free deflection of the plug and the yarn arises in a second direction of movement and that the draw-off part is arranged in such a way that the yarn is accelerated from a plug speed (v1) to a yarn speed (v2) which is sufficient so as to disentangle the plug.
5. An apparatus as claimed in claim 4, characterized in that the cooling part comprises a screening drum (2) or perforated roller in which a pressure below atmospheric is produced by way of respective means and detaching means which are variable in their relative position to the centre point of the drum, with the help of which the plug is detached from the drum.
6. An apparatus as claimed in claim 5, characterized in that the detaching means consist of a mechanical baffle plate positioned at the desired detaching position (D₁, D₂, D₃) above the drum surface or of a cover means attached in the interior of the drum, with which the air bores in the drum surface are closed at the desired detaching position.
7. An apparatus as claimed in one of the claims 4 to 6, characterized in that a ventilated casing (41a, 41b) in which the deflection loop extends is attached between the output of the cooling part (2, 43a, 43b) and the draw-off part (3).
8. An apparatus as claimed in claim 7, characterized in that the cooling part (43a, 43b) is integrated in the casing (41a, 41b) and consists of an inclining guide groove (43a, 43b) with air bores.
9. An apparatus as claimed in claim 8, characterized in that the angle of inclination of the guide groove is so large that the deflection loop hangs in the casing and that by respective arrangement of the ventilation by means of a deflection space (44a, 44b) it is prevented that the plug is disentangled by its own gravity.
10. An apparatus as claimed in one of the claims 4 to 9, characterized in that a pneumatic nozzle (46) is arranged in front of the draw-off part in the direction of movement of the yarn, in which an air stream is produced with ventilation means which brake the yarn and simultaneously intermingle it.

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