WO2008101658A1

WO2008101658A1 - Method and device for temporarily storing a thread

Info

Publication number: WO2008101658A1
Application number: PCT/EP2008/001269
Authority: WO
Inventors: Volker Rossner
Original assignee: Ontec Elektro- Und Steuerungstechnik Gmbh
Priority date: 2007-02-19
Filing date: 2008-02-19
Publication date: 2008-08-28
Also published as: DE102007008150B3

Abstract

The invention relates to a method for temporarily storing, in a twist-free manner, the free end (1a) of a thread (1) in a thread storage space to which a predefined magnetic field is applied, said thread (1) being tangentially unwound from a support roll (2) at a substantially constant speed. In said method, a current flow is applied to the electrically conducting thread (1) between two contact skids (4, 7) in such a way that the magnetic field generated around the thread (1) causes the yarn to slacken (10) in the predefined external magnetic field in order to temporarily store the thread.

Description

Method and apparatus for thread caching

The present invention relates to a method for thread clogging, in particular in connection with the provision of weft threads in weaving operations, and an apparatus for performing the method according to the invention.

In a variety of applications in the processing of a thread to be unwound from a spool (carrier roll), it is necessary to provide an extremely high feed rate of the thread to be processed at its free end to a finishing tool. In particular, when the yarn to be processed is to be supplied as a weft thread in the production of a fabric, it may be necessary to use typical feed rates (delivery speeds) of the order of magnitude of up to 500 m / min.

While such delivery speeds could be readily achieved by "over-the-head removal, from a quiescent spool, i. be achieved by unwinding of the yarn substantially in the direction of the longitudinal axis of the spool. However, such a "pull-over head has the consequence that the thread with each drawn from the quiescent thread roll wrap once twisted around itself, so is gradually twisted about its longitudinal axis, which in turn is undesirable in a variety of applications. For example, e.g. It is known that the use of a twisted weft yarn during weaving can lead to undesirable loss of quality of the fabric.

In order to avoid this, usually a Tangentialabwicklung of the yarn to be processed is selected by the carrier role, ie the thread is withdrawn from the substantially cylindrical outer surface of the rotating about its longitudinal axis support roller in the tangential direction. In a variety of applications, however, aggravating added that no continuous supply of the yarn to be processed is desired, but a discontinuous processing in which phases in which the yarn to be processed at very high speeds to be supplied to the actual processing tool, with such Alternate phases in which the thread to be processed is supplied only at low speed, or even temporarily temporarily completely resting. This typically occurs, for example, when the thread to be processed is incorporated as a weft thread into a fabric. In this case, the thread to be processed is introduced at high speed as a weft thread transversely into the open during weaving fan of the warp threads and then cut when reaching the opposite end of the fabric, whereupon a new weft thread taken from the spool and when shooting into the open compartments of the warp threads accelerated again abruptly. This results in a permanent change of acceleration and deceleration processes in the supplied yarn.

If you were to subtract tangentially the thread to be supplied directly from the carrier roll, so the carrier role would be accelerated and decelerated again and again about its longitudinal axis according to the required acceleration and deceleration processes in the supplied thread.

This procedure is undesirable, especially in the case of large and high-mass carrier rolls, since a constant change of extremely high counterrotating torques on the carrier roll would have to occur, which could lead to undesirable dynamic loads in the suspension and in the drive of the carrier roll, and in particular also to inertial forces that could lead to such high tensile stresses in tangentially unwinding thread in opposite movements of the massive carrier roll that the unwound thread could be damaged.

In order to avoid this, it is known in particular in weaving machines in the prior art to provide tangential unwinding of a weft thread from a carrier roll with mechanical compensating devices in the form of auxiliary rolls and / or auxiliary rolls (so-called "dancers" or "feeders") over which the unwound Thread is guided to allow the carrier roll side end of the unwinding thread a substantially constant feed rate and thus a substantially constant tension in the unwound thread, while in the unwinding behind this Auxiliary rollers and / or auxiliary rollers located "free" thread end extreme acceleration or deceleration operations can be suspended.

Such a system of dancers and a feeder is e.g. disclosed in DE 10 2005 010 534 Al.

However, such mechanical systems to compensate for abrupt tensile stresses at the free end of the thread require very high precision in the manufacture and adjustment of precision mechanical components.

Furthermore, it is also known in the prior art to effect a twist-free intermediate storage of a "free" thread end in an approximately U-shaped free loop of a thread section which is in a strong air flow No. 774 774 A. High acceleration forces occurring at the free end of the thread are compensated for by shortening the thread section stored in the air stream, without there being any appreciable increase in the tensile stress in the thread substantially continuously unwound therefrom.

GB 1 240 462 A further discloses a weft yarn storage device in which a thread portion hanging through a thread storage section is provided with a weight in the form of a piston in a guide cylinder, whereby the piston can be deflected by a negative pressure together with the thread section attached thereto.

With a large number of thread materials, mechanical damage can often occur in such an air flow, in particular as a result of splitting of the thread. Furthermore, reliable regulation and control of such airflow, as ultimately required by e.g. in an application such as the caching of a weft thread during weaving operations is necessary, also a very high and therefore costly effort in providing a control pneumatics.

The object of the present invention is therefore to provide an alternative method and an alternative device for temporarily storing the free end of a thread tangentially and substantially continuously unwound from a carrier roll. This object is achieved by the measures of the independent claims.

The dependent claims relate to advantageous embodiments of the present invention.

The advantages and features of the present invention will become apparent from the following embodiments in conjunction with the drawings.

Show it:

Figure 1 is a schematic representation of a first embodiment of a device according to the invention for non-twisting caching of the free end of a substantially continuously unwound from a carrier roll electrically conductive thread.

Fig. 2 is a schematic representation of a second embodiment of a device according to the invention, showing a modification of the device shown in Fig. 1;

Fig. 3 is a schematic representation of a third embodiment of a device according to the invention, which represents a modification of the device shown in Fig. 2.

Fig. 1 shows a schematic representation of a first embodiment of a device according to the invention for non-twist caching of the free end of an electrically conductive thread 1, which is unwound from a carrier roll (spool) 2 substantially continuously.

In this case, "substantially continuously unwound" should mean that at each point in the process of tangential unwinding of the thread 1 from the carrier roll 2, it is ensured that the carrier roll experiences only those accelerations in which the tensile stresses in the thread remain sufficiently low under thread material-related threshold values. so that no unwanted permanent thread stretches or thread breaks may occur. Optionally, the unwound from the support roller 2 thread 1 via a drive and balance roller 3 ("dancer") are guided, which is freely movably mounted in the space that they the tension and feed rate in the unwound thread 1 by compensating movements in space within a A dancer-controlled bobbin drive unwinds the yarn at a medium speed from the bobbin 2. The dancer 3 controls this by a compensating movement directed upwards or downwards in Fig. 1 which, during unwinding of the yarn, is accompanied by the associated change in diameter of the yarn Coil resulting speed change of the supplied yarn.

Of the dancer 3 optionally shown in Fig. 1, the yarn is passed over a first electrically conductive contact pad 4 to at least one, but preferably a pair of conveyor rollers 5 and from the conveyor rollers 5 to a guide roller 6. Behind the guide roller 6, the thread passed over a second electrically conductive contact pad 7.

Behind the second electrically conductive contact skid 7, a withdrawal of the free end of the thread can take place under application of very high acceleration forces towards a finishing tool (not shown). For example, can take place behind the contact blade 7 a deduction of the free end of the thread 1 to a weft device of a loom, where the thread is further processed as weft.

The contact skids 4 and 7 can each be in the form of a relatively closely spaced pair of runners 4a, 4b and 7a, 7b, so that a reliable mechanical guidance is predetermined for the thread 1 to be passed therebetween, which ensures safe passage of the thread through the thread respective skids pair allows.

The contact skids 4 and 7 or 4a, 4b and 7a, 7b are connected to the poles of a DC voltage source 8.

When an electrical voltage is applied between the skids thus serving as voltage terminals, an electric current thus flows through the filament 1 when it is electrically conductive. A current flow through the running between the contact skids 4 and 7 thread is known to be accompanied by a magnetic field surrounding the thread. This magnetic field is referred to below as the "first" magnetic field.

In Fig. 1 below the skids 4, 7 are arranged one or more preferably also a plurality of magnets 9. These magnets 9 may be permanent magnets. In principle, however, it may also be current-carrying coils which are in turn surrounded by a magnetic field because of the current flowing through them. This further magnetic field is referred to below as the "second" magnetic field.

It does not matter if the magnets 9 are permanent magnets or current-carrying coils, in each case the orientation of their magnetic field (of the "second" magnetic field) is to be matched to the polarity of the electrical DC voltage applied between the contact skids 4, 7, that surrounding the current-carrying thread 1 "First" magnetic field and the "second" magnetic field generated by the magnets 9 ensure that the current-carrying thread 1 is attracted to the magnet 9.

As a result of this attractive force between the current-carrying thread 1 and the magnets 9, an approximately U-shaped deflection toward the magnets 9 results in FIG. 1 for the thread section guided between the runners 4, 7. As a result, the area between the contact runners 4 and 7 and the magnet 9 effectively acts as a thread store, in which a more or less long yarn sag 10 can be temporarily stored.

If there is an abrupt acceleration of the thread at the free end 1a of the thread, then the tensile stress occurring in the thread can be compensated by shortening the thread sag 10.

This means that an abrupt draw request at the free end 1 a of the thread can be answered by a thread slackness that can be operated from the yarn slack. Since only a relatively small inertial forces in the thread occur at the free end because of the low mass of the thread section located in the Garndurchhang, it can be ensured that these inertial forces remain well under material damage or even demolition limits. By controlling the electrical voltage applied to the runners 4, 7, the flow of current through the yarn sag 10 can be regulated and thus the strength of the first magnetic field and thus ultimately both the force with which the yarn sag is drawn to the magnets 9 and its effective "Immersion depth" in the range of the magnets 9 (distance "h" in Fig. 1, ie the deviation from the lower point of sag of the Garndurchhangs 10 to the tangential surface E to the rollers 5, 6). In other words, by regulating the tension applied to the runners 4, 7, it is ultimately also possible to regulate the thread length and amount of thread stored in the "thread store" between the runners 4, 7.

Fig. 2 shows a second embodiment of a device according to the invention for the intermediate storage of a thread.

Components which correspond to the components shown in FIG. 1 are denoted by identical reference symbols as in FIG. 1 and will not be explained again below.

In addition to the components shown in FIG. 1, in this second embodiment there are also light barriers I Ia-Hd, which in FIG. 2 enclose the yarn slack 10 on the left and on the right. A sagging between a light barrier thread section blocks light that otherwise passes through the photocell. As the yarn sag increases, more and more light barriers are blocked downwards, so that a measure of the immersion depth of the yarn sag can be determined in each case from the signals picked up by the respective light barriers.

Depending on the optically determined actual immersion depth, it is then again possible to determine a manipulated variable for the DC voltage to be applied between the contact skids 4, 7 in dependence on the unwinding speed of the carrier roll and the thread accumulator in the event of an abrupt yarn requirement on the finishing tool nachzuliefernden amount of thread is necessary to reach a desired target immersion depth again as quickly as possible.

Alternatively to the optical measurement of the immersion depth with the aid of light barriers, the following procedure can also be used: The current flow through the contact skids 4, 7 is determined by means of a measuring device 13. For a given source voltage of Voltage source 8 can be determined from the resistance of located between the contact skids thread section and known thread cross-section and known resistivity of the thread and its length, which in turn can then provide a measure of the immersion depth in the yarn store.

Fig. 3 shows a third preferred embodiment of a device according to the invention. Components which correspond to the components shown in FIGS. 1 and 2 are denoted by identical reference symbols as in FIGS. 1 and 2 and will not be explained again below.

In the apparatus shown in Fig. 3, a pair of closely spaced side plates 12a, 12b surround the yarn sag, thereby resisting lateral forces such as e.g. a draft or even mechanical external impact is protected.

The use of the apparatus shown in FIGS. 1 to 3 has proved to be particularly advantageous in practice in the processing of ribbon-shaped yarn material made of carbon fibers as weft thread material in weaving machines. Carbon fibers are used particularly in so-called high performance fabrics, e.g. then be impregnated with thermosetting plastic to form parts. Such moldings are used wherever extremely lightweight yet extremely durable components are needed, such as e.g. in the construction of fuselage parts, certain car body parts, etc. However, in order to be able to ensure the optimum mechanical resistance in the fabric for future purposes, it is essential that an untwisted inlet of serving as a weft carbon yarn is ensured in a loom. This eliminates - as already discussed - the dynamic per se favorable overhead deduction of a carbon thread from standing coils. However, the use of feeders in carbon fibers also leads to irregularities in the weave pattern and damage to the delicate fibers. In the case of a slack control assisted by an air flow in a yarn store in front of the loom, it is also found in practice that the air flow damages the sensitive carbon band.

However, since carbon fibers show good electrical conductivity, they are predestined for use with the filament-storing method of the present invention. Experiments have led to very good results, since the application of current-carrying carbon fibers in one with an attractive Provided magnetic field provided thread storage to a satisfactory and gentle intermediate storage of carbon fibers before feeding as a weft thread in a loom.

If a carbon fiber is woven in a weaving machine (not shown) connected behind the thread store, then the pair of rolls 5 pulls the thread out of the dancer and guides it into the thread store. The drive of the rollers 5 then applies in a controller as a master. Thus, the yarn can be withdrawn from the spool both at the average speed and with a weaving machine approximated but smoothed dynamic. The thread withdrawal from the memory then takes place through the loom (not shown). This works as a slave. When released, the memory function starts and only when sufficient yarn length is available in the thread store, the loom can start. The yarn guide in the yarn storage takes place through the two side plates 12a, 12b in the memory. The query of the memory filling is carried out by light barriers 1 Ia - 1 Id.

* * *

LIST OF REFERENCE NUMBERS

1 thread

1 a free thread end

2 spool (carrier roller) dancer (4a, 4b) first contact pad (pair) conveyor roller (s) guide roller (7a, 7b) second contact pad (n pair) DC source magnet (s) 0 yarn sag 1 a - 1 1 d Photocells 2a, 12b Side plates 3 Ammeters

Claims

claims

1. A method for intermediate storage of the free end (1 a) of a carrier roll (2) at a substantially constant speed tangentially unwound electrically conductive thread (1) acted upon in a predetermined magnetic field yarn storage space, wherein the thread (1) so with a Current flow is applied, that thereby causes the yarn (1) generated magnetic field in the given magnetic field Garndurchhang for thread storage.

2. The method of claim 1, wherein the external magnetic field is predetermined by permanent magnets.

3. The method of claim 2, wherein the external magnetic field is predetermined by current-carrying coil.

4. The method according to any one of claims 1 to 3, wherein the thread is a carbon-containing thread.

5. A device for carrying out a method according to one of claims 1 to 4, which comprises:

- At least one conveyor roller (5) for tangentially unwinding an electrically conductive thread (1) from a support roller (2);

- A deflection roller (6) for deflecting the thread towards a finishing tool;

- A DC voltage source (8) by means of a DC electrical voltage between a first and a second contact blade (4, 7) is placed; at least one magnet (9) for providing an external magnetic field in order to attract the current-carrying thread (1) guided via the contact skids (4, 7).

6. The device according to claim 5, wherein between the support roller (2) and the at least one conveying roller (5) is provided in a space movable dancer roller (3) to take place during unwinding of the thread (1) from the support roller (2) decrease to compensate for the diameter of the carrier roll.

7. Apparatus according to claim 5 or 6, wherein the contact runners (4, 7) are each formed as contact pad pairs (4a, 4b and 7a, 7b), through which the thread (1) is guided in each case.

8. Device according to one of claims 5 to 7, wherein the current flow between the contact runners (4, 7) is measured to the length of the current between the contact runners thread section and thus the immersion depth (h) of the thread in the yarn storage space between the at least one conveyor roller (5) and the deflection roller (6) and the at least one magnet (9) to determine.

9. Device according to one of claims 5 to 8, wherein between the region of the conveying roller (5) and the deflection roller (6) on the one hand and the region of the at least one magnet (9) photoelectric barriers (1 Ia - 1 Id) are mounted, with which the Immersion depth (h) of the thread in the yarn storage space between the conveyor roller (5) and the deflection roller (6) and the at least one magnet (9) can be determined.

10. Device according to one of claims 5 to 9, wherein a yarn storage space between the conveying roller (5) and the deflection roller (6) on the one hand and the region of the at least one magnet (9) by a pair of side plates (12a, 12b) is enclosed, by the side of the thread is protected.

1 1. loom, in which the supply of the weft thread by means of a device according to one of claims 5 to 10 takes place.