The present invention relates to a rapier rod for weaving machines, comprising a holder profile, which delimits a mounting cavity, with a bottom and side walls that are erected relative to the bottom and a gear rack with several teeth, which is applied in the mounting cavity and which is made of a thermoplastic material.

The bottom and side walls are considered here to be in the holder profile itself, relative to the mounting cavity. In the mounted state of the rapier rod in a weaving machine this mounting cavity does not open upwards, but sideways, and said bottom is not arranged at the bottom, but sideways in the rapier rod.

Rapier weaving machines comprise one or more rapiers for inserting weft yarns in a shed between warp yarns, to form a fabric. These rapiers are fitted on rapier rods and are moved through the shed by means of this rapier rod in the rapier weaving machine.

The rapier rods to which the present invention relates are provided with a gear rack for driving this motion.

The most important function of the rapier is to position the weft.

On the one hand this weft must be positioned correctly in the weft direction. For driving, the teeth of a pinion must be able to engage accurately in the teeth of the gear rack of the rapier rod. For guiding and carrying the rapier, the rapier rod must be of sufficiently rigid, straight and flat construction.

Furthermore, this weft must be positioned correctly in the vertical direction and in the warp direction. For guiding and carrying the rapier, the rapier rod must also be of sufficiently rigid, straight and flat construction.

For making ever faster weaving machines, it is necessary to make said rapier rod lighter, yet stiff enough to ensure correct positioning of the rapier. An example of a rapier rod with a gear rack that is mounted in a holder profile is known from DE 1 535 491 A1. In this case the gear rack is glued in the holder profile, but this is a rather weak joint. In DE 1 710 293 B 1 it is therefore envisaged to provide the gear rack with side walls, so that a better glued joint can be produced. However, a disadvantage is that extra material is required for these side walls of the gear rack, so that the combination of the gear rack and the tooth profile is heavier.

In EP 0 394 639 A1 and DE 101 20 954 A1 the gear racks are not provided with side walls. By means of a die, the gear racks are formed from a plate in such a way that they acquire a wavy profile. In addition, they are provided with a suitable fibre reinforcement so as to be able to make the complete rapier rod lighter. As stated in EP 0 394 639 Al, a gear rack of this kind is also mounted in a holder profile so as to ensure the necessary stiffness.

In DE 196 08 254 Al, the bottom of the holder profile is omitted so as to be able to produce a lighter rapier rod. However, a rapier rod of this kind is quite complex and expensive to produce.

The aim of the present invention is to provide an alternative lighter rapier rod.

This aim is achieved by providing a rapier rod, comprising:

a holder profile, which delimits a mounting cavity with a bottom and side walls that are erected relative to the bottom;

and a gear rack with several teeth, which is applied in the mounting cavity and is made of thermoplastic material;

wherein the holder profile is made of a thermoplastic material that is compatible with the thermoplastic material of the gear rack and that is reinforced with reinforcing fibres that mainly extend in the longitudinal direction of the holder profile and wherein the gear rack is bonded chemically with the holder profile.

Compatible thermoplastics are thermoplastics that are mutually joinable (weldable) chemically. In chemical bonding of this kind, molecules diffuse from the holder profile and/or the gear rack so that this holder profile and the gear rack are joined together by entanglement or "hooking together" of molecules. In contrast to gluing, for example, no extra component is added for making this joint.

Chemical bonding of this kind is more effective than the joints that are typically used in known gear racks.

By means of chemical bonding of this kind, the teeth can be connected precisely on the holder profile, and are bonded well with this holder profile. Excessive mass can be avoided to the greatest possible extent thereby.

With chemical bonding, the joint is almost as strong as the matrix material of the holder profile and the gear rack. The different parts may then form a strong whole together but with less excess material. Together, the parts ensure the necessary stiffness and torsional resistance, although the individual components are less strong. With chemical bonding, the holder profile and the gear rack form almost a whole, wherein specific characteristics may nevertheless be ascribed to the different parts thereof.

By applying the reinforcing fibres of the holder profile mainly in the longitudinal direction of the holder profile, a relatively light holder profile is obtained with maximum stiffness in the longitudinal direction. As many reinforcing fibres as possible should then be oriented in the longitudinal direction of the profile, and preferably at 0°. Optionally, a limited proportion of the reinforcing fibres may also be applied in another direction in order to limit the splitting susceptibility of the holder profile to some extent, provided that on average, all reinforcing fibres present in the holder profile extend predominantly in the longitudinal direction. For this purpose, the holder profile may for example be built up from different layers, which may be a combination of unidirectional fibres with different orientations or layers of fabrics, in which different fibre directions are already present.

Owing to these reinforcing fibres that extend mainly in the longitudinal direction and the chemical bonding of the gear rack to the holder profile, a particularly light gear rack can be produced, which nevertheless has sufficient stiffness to guarantee accurate positioning.

Preferably the fibre volume fraction of the reinforcing fibres that extend in the longitudinal direction in the holder profile is between 35% and 75% and even more preferably between 40% and 70%.

The fibre volume fraction of reinforcing fibres that extend in some other direction than the longitudinal direction in the holder profile is preferably at most 15% and even more preferably at most 7%.

In a preferred embodiment, the gear rack comprises several tooth units, wherein each tooth unit comprises one or more teeth of the gear rack. In an embodiment of this kind, each tooth unit is bonded chemically to the holder profile.

Because the gear rack is applied in several tooth units, it is easier to bond the teeth chemically to the holder profile, without the complexity of joining different long parts, wherein for example distortion and end effects are more difficult to control.

The number of teeth is preferably selected as a well-considered compromise between obtaining an easy production process and controlling the complexity when joining the different parts during this production process.

For reduction of mass, preferably as many individual tooth units as possible are provided, which comprise as few teeth as possible.

Preferably the tooth units comprise at most 24 teeth. Even more preferably at most 16 teeth, at most 8 teeth or at most 4 teeth.

The gear rack is preferably bonded chemically to the bottom and to the side walls of the holder profile.

By chemically bonding the gear rack both to the bottom and to the side walls of the holder profile, the torsional stiffness of the assembly of the holder profile and the gear rack can be increased. A possible weakened torsional stiffness of a holder profile wherein the reinforcing fibres are applied maximally in the longitudinal direction of the holder profile may in this way be compensated by the gear rack.

With several tooth units, preferably each tooth unit is then bonded chemically to the bottom and to the side walls. In any case, each tooth of the gear rack is preferably bonded chemically to the bottom and to the side walls of the holder profile.

The teeth of the gear rack delimit tooth holes. At the level of these tooth holes, the gear rack is preferably constructed at least partially free from side walls, in order to limit excess material. However, when side walls are applied partially at the level of these tooth holes, these may be made with a minimum thickness. Preferably, however, the gear rack is almost completely free from side walls at the level of these tooth holes.

The teeth of the gear rack are more preferably reinforced with reinforcing fibres. With these reinforcing fibres, the gear rack can be made lighter while obtaining the same strength and wear resistance.

In order to ensure that the teeth can be produced easily, preferably fibres are selected with a length that is less than the respective dimension of the teeth. It may range from fibres to nanoparticles.

These reinforcing fibres of the teeth preferably each extend individually in a respective tooth. In this way, the rapier rod is as light as possible and hardly any mutual transmission of forces takes place between the teeth, but forces acting on the teeth are transmitted directly to the holder profile.

Thus, the holder profile is not only provided for the stiffness of the rapier rod, but more directly absorbs the forces resulting from the transmission of motion.

Preferably these reinforcing fibres of the teeth are applied with random orientation to ensure an overall strength (isotropic behaviour). For wear resistance, these reinforcing fibres are preferably directed tangentially to the surface of the teeth, but with random orientation. For example, polyamide 6, polyamide 6.6, polyamide 12 or polyphthalamide (PPA) may be selected as thermoplastic matrix material for the holder profile and/or for the gear rack. These materials have a relatively low density, a relatively low stiffness, a relatively low melting point and good friction properties.

Optionally recycled material may be selected as said thermoplastic material. For example, existing rapier rods could be ground, wherein the material thereof may optionally be supplemented with fibre material and/or additional matrix material.

For example, carbon, aramid and/or glass fibre may be selected as the material for the reinforcing fibres.

Preferably carbon fibres are used as reinforcing fibres for the teeth. The weight may thus be kept low and the necessary strength and stiffness are ensured.

Optional reinforcing fibres of the teeth are preferably applied in a carbon fibre fraction between 10% and 50%. Even more preferably this carbon fibre fraction is between 10% and 30%.

The fibre fractions selected are preferably low in order to obtain good damping and to give the teeth the necessary toughness. With a lower fibre fraction it is easier to absorb geometric deviations with respect to the engagement ratio of the teeth of the gear rack relative to the teeth of the pinion. This pinion engages in the gear rack for driving.

Lubricant additives, for example such as polytetrafluoroethylene (PTFE) or polyethylene (PE), may optionally also be added to the material of the teeth.

In order to limit possible adverse effects of these additives on the bond between the gear rack and the rapier profile, the teeth may for example be formed in two steps. In a first step the teeth may for example be made by injection moulding. They may be bonded to the holder profile either during injection moulding or retrospectively. In a second step, then for example a thin layer of material, to which the lubricant additives are added, can be sprayed on the surface of the gear rack. Moreover, it is also possible optionally to apply a wearing layer on the outer side of the holder profile, for example by gluing, co-extrusion or welding.

Carbon fibres are preferably selected as reinforcing fibres of the holder profile. The weight can be reduced thereby and the necessary strength and stiffness are assured. The reinforcing fibres of the holder profile are preferably applied in a carbon fibre fraction between 50% and 80% and even more preferably between 65% and 70%. With a relatively high percentage to fibres in the holder profile, this holder profile can be made relatively thin-walled. With thinner walls, the splitting susceptibility increases. Since a thermoplastic is used as matrix material, this splitting susceptibility is, however, better than if a thermoset were selected, as was typically the case in the prior art. This splitting susceptibility may also be compensated partially owing to the good bond between the holder profile and the gear rack.

The gear rack of a rapier rod according to the present invention is preferably made more flexible than the holder profile.

With relative flexibility of the gear rack, the contact force can be distributed better and the transmission of force can be improved.

The teeth of the gear rack are more preferably hollow or made with a lighter, more flexible core material, on the one hand to improve the acoustic properties of the rapier rod and on the other hand to reduce the material thereof even further so as to obtain a lighter rapier rod. The cavity of the teeth may then preferably be provided in the core of the teeth, so that roughly sufficient material is still present all round. On the one hand, preferably as large a contact area as possible is maintained with the bottom and the side walls of the holder profile to provide chemical bonding. On the other hand, preferably as large a contact area as possible is maintained to allow the teeth of the gear rack to engage in the teeth of the pinion, which is provided for driving the gear rack. There are several ways of making the holder profile of a rapier rod according to the present invention.

The holder profile may for example be made by pultrusion. Several rapier rods may thus be produced in line and then cut to length. Pultrusion allows a large amount of reinforcing fibres to be incorporated and allows good control of the straightness of the profile.

Alternatively, the holder profile may be made for example by continuous compression moulding (CCM).

The gear rack may be formed for example by injection moulding or by pressing, in one part or in different parts, such as said tooth units.

There are also several ways of performing chemical bonding between the holder profile and the gear rack, for example such as by pressing, welding or overmoulding.

In a specific embodiment, chemical bonding is effected by welding. In welding, thermoplastic material of the holder profile and thermoplastic material of the gear rack are heated so as to melt together and produce the joint after cooling. For this purpose, the gear rack may be welded to the holder profile for example by ultrasonic welding or by laser welding or by induction welding. In induction welding, heat can be generated for example with an inserted piece at discrete places where this is desired for the joint. This also allows a complete gear rack to be fastened to a holder profile, wherein deformation of the material is kept under control. With several tooth units, ultrasonic welding or laser welding then makes it even easier to manufacture rapier rods in a continuous process. The holder profiles may then be made to any length and be provided with teeth, after which they can be cut to length in order to form rapier rods. In a preferred embodiment, chemical bonding is effected by injection moulding of the gear rack on top of the holder profile. This production technique is also known as overmoulding.

The gear rack may in principle be applied before the cooling process for forming the holder profile is completed, which ensures a particularly good joint between the two parts. Separate assembly of the holder profile and the rapier rod is thus avoided, since the production process for the rapier rod is itself also the assembly process at the same time.

However, it is also possible, after the holder profile has been formed and has cooled, to reheat the holder profile in order to apply the gear rack by injection moulding on the holder profile, so that both production processes can be controlled individually more easily.

Preferably the gear rack is made by overmoulding in several tooth units. With several tooth units, which are applied by injection moulding on top of the holder profile, rapier rods can be produced more easily in a continuous process, and to any length. Alternatively, however, it is also possible to injection-mould the gear rack for example by exjection®, for example as described in WO 2018/172128 Al . The holder profiles may then be produced in line. With continuous production of the holder profile, the tooth units or the complete gear rack can be applied by injection moulding on top of this holder profile during the production process of the holder profile, preferably when the cooling process for forming the holder profile is not yet completed. Smaller tooth units, which are applied by injection moulding, allow more possibilities for design and choice of material of the teeth. Higher-grade materials may be used in injection moulding of shorter pieces than in injection moulding of longer pieces.

Teeth may then also be provided over the full length of the rapier rod. This increases the rigidity and resistance to splitting. Teeth at the level of the zone where the rapier head or heel is fastened may for example be partially machined in order to produce an interlocking joint with said rapier head or said heel. In an advantageous embodiment, the holder profile and the tooth units comprise the same thermoplastic material. In this way, recycling of the rapier rod is also possible, wherein for example ground rapier rods can be used as raw material for new tooth units with addition of extra thermoplastic matrix material.

Preferably the holder profile undergoes one or more surface treatments for the purpose of obtaining a rougher, textured and/or cleaner surface so that adhesion between the holder profile and the gear rack is improved. For this, selection may be made from several treatments.

The surface of the holder profile may be cleaned and optionally prepared, for example with solvents or water-based liquids, or by plasma cleaning. The chemical bond may be further improved by application of plasma coating.

Typical mechanical surface treatments are for example roughening, sand blasting or bead blasting or applying a relief in the surface by hot rolling with a rough jacket. A pattern or a relief may also be applied by means of a laser or plasma.

Alternatively or additionally, when making the holder profile by pultrusion, a peel ply may be used to obtain a rougher surface, and may or may not be removed subsequently. A peel ply of this kind is a layer of nylon or polyester fabric, which is applied to the surface during manufacture. A thin polymer layer may also be co-extruded on the holder profile.

The aim of the present invention is also achieved by providing a weaving machine that comprises a rapier rod according to the present invention.

The present invention is now explained in more detail on the basis of the following detailed description of a preferred embodiment of a rapier rod according to the present invention. The purpose of this description is exclusively to give explanatory examples and to point out further advantages and features of the invention, and is thus not to be interpreted as a limitation of the field of application of the invention or of the patent rights claimed in the claims. In this detailed description, reference is made to the appended drawings by means of reference numbers, wherein

in Fig. 1 , a gear rack for a rapier rod according to the present invention is shown in cross-section;

in Fig. 2, a holder profile for a rapier rod according to the present invention is shown in cross-section;

in Fig. 3, an embodiment of a rapier rod according to the present invention with a gear rack from Fig. 1 and a holder profile from Fig. 2 is shown in cross- section;

in Fig. 4, the rapier rod from Fig. 3 is shown in longitudinal section;

in Fig. 5, the rapier rod from Fig. 4 is shown in longitudinal section, with machined teeth in the zones where the rapier head and the heel are to be fastened;

in Fig. 6, a part of the rapier rod from Fig. 3 is shown in perspective.

The rapier rod (1) illustrated comprises a holder profile (2), in which a gear rack (6) is fitted.

The holder profile (2) is made by pultrusion from thermoplastic material as matrix material that is reinforced with reinforcing fibres, which are applied in the longitudinal direction of this holder profile (2).

Polyamide 6, polyamide 6.6, polyamide 12 or PPA material is selected as the thermoplastic material. Alternatively, for example poly ether ether ketone (PEEK) could also be used.

The reinforcing fibres are carbon fibres, which are applied in a carbon fibre fraction between 50% and 80%, at approximately 0° relative to the longitudinal direction. Preferably the carbon fibres are applied in a carbon fibre fraction between 55% and 75%. Alternatively, a fraction of carbon fibres may also be applied at 45° and/or at 90° relative to the longitudinal direction. The carbon fibre fraction of carbon fibres that extend in the longitudinal direction is then preferably between 40% and 55%.

Aramid and/or glass fibre may also be selected as the material for the reinforcing fibres, instead of carbon.

During pultrusion, the holder profile (2) may be reinforced with reinforcing fibres that extend in the longitudinal direction, by unreeling these reinforcing fibres from bobbins, passing them through a bath of molten matrix material, and then pulling them through a heated die.

Reinforcing fibres in directions other than the longitudinal direction may be applied in pultrusion in the form of woven or nonwoven cloth on the outer side of the holder profile (2) and/or introduced into the mounting cavity on the inside of the holder profile, in order to increase the bending stress of the holder profile (2). This fibre- reinforced cloth may for example be 0.15 mm thick, so that on applying such cloth, on the inside and on the outer side of a basis profile with a thickness of 0.8 mm together, a holder profile (2) with a thickness of 1.1 mm can be formed.

Alternatively, the holder profile may also be made in pultrusion by injecting the matrix material into the bundle of reinforcing fibres.

In an alternative embodiment, the holder profile (2) may for example also be made from several layers of thermoplastic material, which are pressed onto the holder profile (2) in a continuous process, for example by means of rolls. The various layers may each be made separately, for example by pultrusion. Thus, the holder profile may for example be made from 8 layers of thermoplastic material, each about 0.136 mm thick, together forming a holder profile about 1.1 mm thick.

The holder profile (2) comprises a bottom (4) and two side walls (5) erected on either side of this bottom (4), together delimiting a mounting cavity (3). The gear rack (6) is fitted in this mounting cavity (3). The gear rack (6) shown is made up of several tooth units (8), wherein each tooth unit (8) comprises four teeth (7). Within each tooth unit (8), the gear rack (6) comprises, at the level of the tooth holes (9), a side wall (11) with minimum thickness, which for example may be between 0.1 and 0.3 mm, when the wall thickness of the holder profile is selected between 1.6 and 1.7 mm. Between two successive tooth units (8) there is a free space (12), where the gear rack (6) is free from side walls (11).

The tooth units (8) are made by injection moulding from thermoplastic material as the matrix material, which is reinforced with reinforcing fibres. A material that is compatible with the material of the holder profile (2) is selected as the thermoplastic material. The reinforcing fibres are carbon fibres, which are applied in a carbon fibre fraction between 10% and 30%. These reinforcing fibres are only applied in respective teeth (7) and for this purpose have a length that is less than the respective dimension of the teeth (7). These reinforcing fibres are applied with random orientation to ensure an overall strength (isotropic behaviour). For wear resistance, these reinforcing fibres are directed tangentially on the surface, but with random orientation.

After the cooling process for forming the holder profile (2) is completed, this holder profile (2) is reheated and the tooth units (8) are applied directly on the holder profile (2) by injection moulding. In this way, the tooth units (8) are bonded chemically to this holder profile (2) over their complete contact surface with the holder profile (2), both to the bottom (4) and to both side walls (5) of the holder profile (2).

The holder profile (2) is made by pultrusion in a continuous process, wherein the tooth units (8) are applied continuously on the holder profile (2) by overmoulding. Then the assembly of the holder profile (2) and the tooth units (8) is cut to length to form rapier rods (1). In the zones (10) where the rapier and where the heel are to be fastened, the teeth are then machined, more specifically filed off, as can be seen in Fig. 5.