Description Plastic weaving element

The invention relates to a weaving element for guiding warp threads in a weaving device, wherein the weaving element is formed at least partially out of plastic. The invention further relates to a method for manufacturing a weaving element.

Weaving elements are used in a weaving device for example as heddles to move warp threads for forming a shed. The heddles are generally pin- like, strip-like or needle-like and have for example guide elements at both ends by which they can be fastened to an associated heddle frame. The heddles furthermore have in their center an eye, also referred to as heddle eye, through which a warp thread is passed in use. Other weaving elements for guidance of warp threads are reed dents or lamellas for weaving reeds or warp thread detectors, wherein in the context of the invention every type of contact is referred to as guidance of the warp thread, without the warp thread having to be moved by the weaving ele- ment to do so.

Weaving elements are in use moved for example by the heddle frames at a high speed and are hence subjected to high forces. It is generally desirable to design such weaving elements in such a way that they only have a low weight. Therefore it is known, to manufacture heddles of thin plate. It is further known to manufacture heddles of plastic. Heddles of plastic have the drawback, however, that the commercially available plastics are not suitable to withstand in the long term the high forces generated during weaving. A further drawback of weaving elements made of plastic in contact with warp threads is a possible electrostatic charging arising from contact with the warp threads. In addition, plastic weaving elements are in many cases insufficiently wear-resistant.

Various tests were therefore conducted to embed reinforcing material in a plastic in order to thereby permit the use of a plastic when manufacturing heddles. For example, carbon fibres were embedded in a plastic in order to provide in this way a carbon-fibre-reinforced plastic of high strength. To achieve a reinforcement of the plastic necessary for weaving, however, a large percentage proportion of carbon fibres is needed. Due to the high carbon fibre content, a relatively rough surface is created that can damage the warp threads guided inside the eye and/or adjacent warp threads in use. In addition, there is a risk that the heddle is too brittle.

The object underlying the present invention is therefore to provide a plastic weaving element which has sufficient strength and which does not damage warp threads or if so only in an insubstantial way.

This object is solved by a weaving element for guiding warp threads of a weaving device, wherein the weaving element is formed at least partially of plastic, reinforcing material is embedded in the plastic in at least one part of a body of the weaving element, and the reinforcing material is embedded in the form of nanotubes.

Nanotubes are tubes whose diameter is less than 100 nm. The extent in the longitudinal direction of a nanotube is here usually larger than its diameter. In one embodiment the nanotubes are single-walled. The nano- tubes are however preferably multi-walled. The use of nanotubes permits a very fine distribution of the reinforcing material, so that sufficient strength for a weaving element can already be achieved with a low percentage by mass or mass fraction of the reinforcing material. Surprisingly, it has been shown that a plastic strengthened with embedded nanotubes behaves in a manner "friendly" to fibres and moved threads, so that the risk of damage to the warp threads is relatively small. The

mass of a component relative to the total mass of the substance mixture is referred to as the percentage by mass or mass fraction.

In an embodiment of the invention, carbon nanotubes are embedded in the plastic as reinforcing material. Carbon nanotubes (CNTs) are microscopically small and tubular structures of carbon. The walls of the tubes comprise carbon, with the carbon atoms assuming an approximately honeycombed structure with hexagons and usually three bonding partners. The embedding of carbon nanotubes makes the weaving element electrically conductive, so that electrostatic charging is prevented. The electrical conductivity depends for example on a structure of the carbon nanotubes.

In a further embodiment of the invention, the nanotubes are filled. By filling the nanotubes with suitable materials, properties such as electrical conductivity and strength can be altered.

The nanotubes preferably have a diameter of approx. 1 nm to 50 nm, in particular from 1 nm to 30 nm, and preferably 5 nm to 15 nm. Nanotubes with a small diameter can be easily embedded in the plastic.

Advantageously, the nanotubes have a length of approx. 1 μm to 15 μm, in particular 1 μm to 10 μm, and preferably 1 μm to 5 μm. The short length permits good distribution. In other variants, however, a greater length can be advantageous.

In a further embodiment of the invention, the weaving element is formed from polyoxymethylene (POM) homo- or copolymer. POM, also referred to as acetal or polyacetal, is a highly crystalline technical high- performance polymer having a wide spectrum of properties, in particular a low friction coefficient, high wear resistance, high reversed bending fatigue strength, good creep resistance, high modulus of elasticity, resis-

tance to repeated impacts and shocks, and resistance to numerous solvents. It should however be noted that the wear resistance and the resistance to impacts and shocks of the currently available POM are, without reinforcing material, not sufficient to withstand the high stresses to which a weaving element such as a heddle on a heddle frame is subjected in use.

In a development of the invention, the percentage by mass of the embedded nanotubes is approx. 1 to 8%, in particular approx. 1 to 6%, and preferably 3 to 4%. With a percentage by mass of this type, good reinforcement can be achieved. The electrical conductivity of a plastic with embedded carbon nanotubes increases greatly up to about 4% percentage by mass, with any further addition of carbon nanotubes only insub- stantially influencing the conductivity.

In an embodiment of the invention, the weaving element is a heddle with at least one guide and/or fastening element, in particular an eyelet, preferably with two guide elements for connection with one heddle frame. The heddles are arranged by means of the guide or fastening elements on the heddle frame, with the arrangement usually being floating, i.e. the heddles are mounted on the heddle frame in a movable manner relative to the latter. Eyelets, also referred to as eyes or loops, are usually suspended in a profiled rod of a heddle frame. The guide elements can be provided during forming of the heddle body or subsequently integrated into the heddle body. When forming the heddle body by means of injection moulding or similar, almost any required design of the guide elements is possible. It is conceivable here that the two guide elements of the heddles are designed differently. The guide elements are however preferably designed identical in order to permit attachment to the heddle frame regardless of the alignment of the heddle.

Advantageously, the guide elements of the heddle are eyelets in an O, J, C, U or V shape. Thanks to these basic shapes, almost all variants for fastening on a heddle frame are possible.

In a further embodiment of the invention, the weaving element has at least one eye for a warp thread. Usually, only one warp thread is guided per weaving element, in particular per heddle. The eye, also referred to as heddle eye, is for example arranged approximately in the middle of a heddle.

In a development of the invention, the at least one eye is closed. The warp thread is threaded into the eye and then guided safely through the weaving element.

In a further development of the invention, the eye has at least one slit. It is possible with this slit to introduce the warp thread into the eye in a simple manner.

The slit is advantageously provided in such a way that it is at an angle to a tendential warp thread direction. This prevents the warp thread from leaving the eye in an unwelcome way during use.

In a further embodiment of the invention, the weaving element has in the area of the eye a twisted portion for better guidance of a picked up warp thread. Thanks to the twisted portion, the weaving element can be adapted to the introduced warp thread in order to stretch the warp thread, preventing aperture edges of the eye from rubbing against the warp thread.

In other advantageous embodiments of the invention, the weaving element is a lamella of a warp thread detector, a weaving reed or a reed dent of a weaving reed, a weaving heddle and/or a half-heddle and/or a

lifting heddle of a cross or leno weaving device, a needle of a leno weaving harness or the like.

These weaving elements all have in common the fact that during use they contact the warp threads at least part of the time and are subjected to high forces. For weaving elements of this type, the use of a plastic with embedded nanotubes has proved particularly advantageous. The use of nanotubes permits an electrically conductive plastic weaving element to be provided that has a surface of low roughness, so that the warp threads are not damaged by contact with the weaving element.

The object is further solved by a method for manufacturing a weaving element, wherein a body of the weaving element is formed from a plastic with embedded nanotubes, in particular carbon nanotubes.

In an advantageous embodiment of the invention, the body of the weaving element is formed by casting, injection moulding, press shaping, extrusion and/or cutting. The production method can be selected based on its suitability for the required form of the weaving element. Injection moulding of the reinforced plastic permits almost any required forms of weaving elements to be designed that are adaptable to specific weaving and/or thread types. The weaving elements are for example formed as heddles, lamellas, weaving reed dents, half-heddles, lifting heddles, needles etc.

Further advantages of the invention are clear from the following description of embodiments of the invention shown schematically in the drawings. Consistent reference numbers are used in the drawings for identical or similar components. All features and/or advantages shown in the claims, the description or the drawings, including method steps, design details and spatial arrangements, can be fundamental to the invention both per se and in the various combinations. Features described or illus-

trated as part of an embodiment can also be used in another embodiment to obtain a further embodiment of the invention.

The drawings show, in

Fig. 1 a schematic view of a heddle frame with attached heddles;

Fig. 2 a schematic view of a heddle in accordance with a first embodiment;

Fig. 3 a schematic view of a heddle in accordance with a second embodiment;

Fig. 4 a schematic and partially cutaway view of a heddle in accor- dance with a third embodiment;

Fig. 5 a schematic and partially cutaway view of a heddle in accordance with a fourth embodiment;

Fig. 6 a schematic and partially cutaway perspective view of a heddle in accordance with a fifth embodiment;

Fig. 7 a schematic and partially cutaway sectional side view of a heddle in accordance with a sixth embodiment;

Fig. 8 - a schematic view of a heddle in accordance with a seventh embodiment;

Fig. 9 a schematic view of a heddle in accordance with an eighth em- bodiment;

Fig. 10 a schematic view of a half-heddle of a leno weaving device;

Fig. 11 a schematic view of a lifting heddle of a leno weaving device;

Fig. 12 a schematic view of a lamella of a warp thread detector and

Fig. 13 a schematic view of a weaving reed dent.

Fig. 1 shows schematically a heddle frame 1 which is formed by a frame of two side struts 10 and two cross struts 11. The cross struts 11 have in the area of their facing sides profiled rails 12 used to receive lamella-like heddles 2. The profiled rails 12 are, in the embodiment shown, fastened by means of holders 13 to the cross struts 11. The heddles 2 each have in their centre an eye 20 for receiving a warp thread, not shown. The heddles 2 have at their ends guide elements 21 guided on the profiled rails 12. In the embodiment shown in Fig. 1 , the guide elements 21 are designed as eyelets. To prevent the heddles 2 from slipping off the profiled rails 12, the profiled rails 12 have end stops 14 at their ends.

The guide elements or eyelets 21 shown are dimensioned such that the profiled rails 12 guide the heddles 2 in the transverse direction, i.e. in the direction of the cross struts 11 , but have no carrying function when the heddle frame 1 is raised or lowered, i.e. during movement in the direction of the side struts 10. For carrying the heddles 2 during raising or lowering, stops 15 are provided in the embodiment shown that can have damping properties. In other embodiments, however, it is alternatively or additionally possible for the heddles 2 to be carried by the profiled rails 12, wherein the rails 12 usually carry the heddles 2 by pulling.

The heddles 2 should if possible have a low weight. In addition, the heddles 2 in use are subjected to high forces during a movement of the heddle frame 1. It is therefore provided in accordance with the invention that the heddles 2 are produced from a plastic in which nanotubes, in particular carbon nanotubes, are embedded as the reinforcing material.

For example, carbon nanotubes can be used that are marketed under the name of Nanocyl®. A suitable plastic material is for example POM copolymer. Depending on the mass fraction or percentage by mass of the carbon nanotubes, a heddle can be provided of which the electrical conductivity is comparable with that of metal. For example, a 4% percentage by mass of carbon nanotubes is advantageous. With nanotubes of this type, a plastic heddle is therefore provided that in use does not become statically charged, or if so only insubstantially.

The plastic heddle 2 with embedded nanotubes can for example be manufactured by injection moulding, extrusion and/or compression moulding. It is obvious that by use in accordance with the invention of a plastic with embedded nanotubes, the heddle 2 can be designed in almost any shape required. It is possible here to individually adapt the form of the heddle 2 to specific requirements of a weaving device. In the following, various possible designs for heddles are shown.

Fig. 2 shows a heddle 2 in accordance with a first embodiment of the invention. The heddle 2 has a needle-like body 22, with an extent in the longitudinal direction L greater than that transverse to it. Seen in the longitudinal direction L, guide elements 21 are provided at the ends of the body 22 of the heddle 2. In the embodiment shown, the guide elements 21 are O-shaped eyelets by which the heddles 2 can be suspended in the profiled rails 12 shown in Fig. 1. Seen in the longitudinal direction L of the heddle 2, the body 22 has in its centre a thread eye 20 through which a warp thread 3 is passed, as shown schematically. The body 22 of the heddle 2 shown in Fig. 2 has in the area of the eye 20 a narrow portion such that the heddle 2 has an hourglass shape in the view shown. This narrow portion enables a reduction of the material used for the body 22, while in the area of the guide elements 21 sufficient material is available for forming the guide elements 21 and for attachment to the heddle frame 1 shown in Fig. 1. In other embodiments, not shown, of

the invention, the body 22 has no narrow portion or a narrow portion of differing shape.

Fig. 3 shows schematically a heddle 102 in accordance with a second embodiment of the invention. The heddle 102 corresponds substantially to the heddle 2 in Fig. 2, and consistent reference numbers are used for identical elements. A detailed description of these elements is omitted. The body 22 of the heddle 102 has at its ends two guide elements 121 designed substantially as C-shaped eyelets. The C-shaped eyelets 121 each have an opening 123. The opening 123 is in use of the heddle 102 on a heddle frame shown in Fig. 1 facing the profiled rails 12. The openings 123 simplify suspension of the heddles 102. A size of the opening 123 and/or a length of webs 124 forming the opening can be adapted here to specific requirements.

Fig. 4 shows schematically a heddle 102 in accordance with a third embodiment of the invention in a partially cutaway view. The heddle 202 substantially corresponds to the heddle 2 in accordance with Fig. 2, and consistent reference numbers are used for identical elements. Guide elements 221 are provided at the ends of the body 22, with only one guide element 221 being visible in Fig. 4. The guide element 221 is designed as a substantially J-shaped eyelet. The J-shaped eyelet 221 shown has two substantially parallel webs 224, 225, wherein the web 225 is considerably shorter than the web 224 such that an opening is formed. On the shorter web 225, a lug 226 projecting into the inside of the eyelet 221 is provided, by which lug the fastening of the heddle 202 to the profiled rails 12 shown in Fig. 1 , for example, is easily achieved.

Fig. 5 shows a heddle 302 in accordance with a fourth embodiment of the invention in a partially cutaway schematic view. In Fig. 5, only a thread eye 20 of the heddle 302 is visible, and the ends with the guide elements are not shown. The guide elements are for example O-shaped

in accordance with Fig. 2, C-shapeci in accordance with Fig. 3 or J- shaped in accordance with Fig. 4. The body 22 of the heddle 302 has in the area 320 of the eye 20 a widened portion such that a width B ₂ o in the area of the eye 20 is greater than a width B ₂₂ of the body 22 above and/or below the eye 20. This enables the thread eye 20 to be designed in a sufficient size, while at the same time material is saved in other areas of the heddle 302. Thanks to a high strength of the heddle 302 in accordance with the invention, it is possible to select a very low width B ₂₂ of the body 22 in order to save on material and hence on costs and weight. A transition between the widths B20 and B22 has in the embodiment shown a radius 327.

Fig. 6 shows a heddle 402 in accordance with a fifth embodiment of the invention in a partially cutaway perspective view. As can be seen in Fig. 6, in the embodiment according to Fig. 6 a width B ₂ o in the area of an eye 20 is also greater than the width B ₂₂ of the body 22 in the areas above and below the eye 20. The eye 20 has a slit 420 through which a warp thread, not shown, can be introduced simply into the eye 20. The slit 420 describes an angle a with a longitudinal direction L of the heddle 402. The slit 420 as a result runs transverse to a tendential warp thread direction. This prevents the warp thread in use from leaving the eye 20 in an unwelcome manner via the slit 420. The guide elements of the heddle 402 are not shown in Fig. 6. It is obvious that the guide elements can be selected as required, for example in accordance with Figs. 2, 3 or 4.

Fig. 7 shows schematically a section of a cutaway side view of a heddle 502 in accordance with a sixth embodiment of the invention. As can be seen in Fig. 7, a body 522 of the heddle 502 is substantially flat, as is usual for heddles. The body 522 of the heddle 502 is however twisted in the area 520 of an eye 20 so that a warp thread 3 passed through the eye 20 is in better contact with the body 522.

Fig. 8 shows schematically a heddle 602 in accordance with a seventh embodiment of the invention. The heddle 602 is substantially needle- like, with an eye 20 for a warp thread, not shown in Fig. 8, being provided in the centre. The heddle 602 has at each end a guide element 621 designed as a V-shaped eye with two legs 624 by which the heddle 602 can be fastened to a heddle frame not shown in Fig. 8.

Fig. 9 shows schematically a heddle 702 in accordance with an eighth embodiment of the invention. The heddle 702 shown in Fig. 9 is de- signed as a single-sided needle having at one end an eye 20 and at the opposite end a guide element 721 for attachment to a heddle frame, not shown in Fig. 9. The guide element 721 is designed as a U-shaped guide element with two engaging lugs 724. The heddle 702 designed as a single-sided needle is usable for example for moving or guiding a warp thread in a loom for making a cross or leno weave. Of course, such hed- dles can equally well be designed with other guide elements.

Fig. 10 shows schematically a half-heddle 4 in accordance with the invention of a cross or leno weaving device, not shown. The half-heddle 4 is substantially U-shaped with two legs 41, wherein an eye 20 for a warp thread, not shown in Fig. 10, is formed between the legs 41. At the ends of the legs 21 opposite the eye 20, areas 42 are provided of a magnetizable metal, so that the half-heddle is movable by means of a magnet, not shown in Fig. 10, of lifting heddles.

Fig. 11 shows a lifting heddle 5 in accordance with the invention of a cross or leno weaving device for driving the half-heddle 4 shown in Fig. 10. The lifting heddle 5 furthermore has a magnet 52 for moving the half- heddle 4 shown in Fig. 10. A half-heddle is usually moved with two lifting heddles.

Fig. 12 shows schematically a lamella 6 in accordance with the invention of a warp thread detector. The lamella 6 has an eye 620 for a warp thread not shown in Fig. 12, said eye being open to one end of the lamella 6 such that the warp thread detector can be placed on a warp thread, not shown.

Fig. 13 shows schematically a weaving reed dent 7, wherein warp threads not shown in Fig. 13 are guided between two weaving reed dents 7. The reed dent 7 shown furthermore has a U-shaped recess 720, wherein the recesses 720 of the weaving reed dents 7 of a weaving reed arranged one behind the other form a weft insertion channel for a weft thread not shown in Fig. 13. The use of plastic with embedded nanotubes, in particular with embedded carbon nanotubes, for manufacture of a weaving reed dent therefore has an advantageous effect not only in contact with the warp threads, not shown in Fig. 13, but also relative to the weft thread.

The heddle forms shown and/or forms of the other weaving elements are only examples. It is obvious that by injection moulding, compression moulding, casting and/or extrusion or the like plastic weaving elements with embedded nanotubes, in particular embedded carbon nanotubes, can be manufactured in almost any form required. The weaving elements all have the common features high strength, low wear and a good electrical conductivity.