Jet and method

Abstract

An improved system for fabricating alternating S/Z cabled yarn, for alternating S/Z twisted yarn and for (whether or not alternately) applying a torsion to a yarn, in which critical air flow conditions are obtained at least at the outlet of the torsion chamber of the devices. A method for fabricating alternating S/Z cabled yarn, for alternating S/Z twisted yarn and for (whether or not alternately) applying a torsion to a yarn under critical air flow conditions at least at the outlet of the torsion chamber used in the method, and a product according to these methods.

Claims

1. System for fabricating alternating S/Z twist plied yarns, comprising: (a) a feeding member for separately feeding at least two individual yarns; (b) a member for tensioning every yarn; (c) at least two air jet devices, for alternately applying a, respectively, S and Z torsion in at least two of the individual yarns, for obtaining at least one S/Z twisted yarn, in which zones without net twist separate zones with S torsion of the at least one S/Z twisted yarn from zones with Z torsion of the at least one S/Z twisted yarn; (d) a fixation member for joining the at least two individual yarns, and for connecting the alternating S/Z twisted yarns at the place of the zones without net twist, for obtaining alternating S/Z twist plied yarns; (e) a control member for combining the feeding member, the member for tensioning every yarn and the fixation member in a coordinated way; wherein at least one of the at least two air jet devices is an air jet device comprising: (a) a longitudinally extending chamber comprising: (i) one or more side walls; (ii) a yarn inlet at a first longitudinal end of the chamber, in which the yarn inlet has a cross-sectional area; (iii) a yarn outlet at a second longitudinal end of the chamber, in which the yarn outlet has a cross-sectional area, in which the first and the second longitudinal end are located oppositely; (iv) and one or more air inlets; (b) one or more air inlet channels for creating an air flow, said one or more air inlet channels ending in the one or more side walls of the chamber, in which said one or more air inlet channels have a cross-sectional area and said one or more air inlet channels are oriented so that the one or more air inlet channels are suitable for generating an air flow in the chamber; wherein the ratio of the cross-sectional area of the yarn outlet of the chamber to the cross-sectional area of said one or more air inlet channels for generating the air flow is such that a critical air flow can be provided at the yarn outlet of the chamber when a predetermined overpressure is applied at the one or more air inlets, wherein the ratio of the cross-sectional area of the yarn outlet to the cross-sectional area of the one or more air inlet channels generating the air flow, is between 1.5 and 8.

2. System for fabricating alternating S/Z cabled yarns or a connected alternating S/Z twist plied yarn, comprising: (a) at least two systems for fabricating alternating S/Z twist plied yarns, in which the systems are adapted to work in parallel; (b) at least two overtwisting air jet devices, for alternately applying a, respectively, S and Z torsion in at least two of the alternating S/Z twist plied yarns, for obtaining at least two overtwisted alternating S/Z twist plied yarns, in which zones approximately without net twist separate zones with S torsion of the alternating S/Z twist plied yarns and zones with Z torsion of the alternating S/Z twist plied yarns, and in which the zones approximately without net twist of the overtwisted alternating S/Z twist plied yarns coincide with the zones approximately without net twist of the alternating S/Z twist plied yarns; (c) at least one feeding member for feeding the alternating S/Z twist plied yarns of the system for fabricating alternating S/Z twist plied yarns to the at least two overtwisting air jet devices; (d) a second fixation member for joining the overtwisted alternating S/Z twist plied yarns, and for connecting the overtwisted alternating S/Z twist plied yarns at the place of the zones approximately without net twist, for obtaining alternating S/Z cabled yarn or connected alternating S/Z twist plied yarn; wherein at least one of the systems for fabricating alternating S/Z twist plied yarns is a system of claim 1.

3. The system of claim 2 for fabricating an alternating S/Z cabled yarn, wherein at least one of the overtwisting air jet devices alternately applying the, respectively, S and Z torsion in the separate alternating S/Z twist plied yarns, is an overtwisting air jet device comprising: (a) a longitudinally extending chamber comprising: (i) one or more side walls; (ii) a yarn inlet at a first longitudinal end of the chamber, in which the yarn inlet has a cross-sectional area; (iii) a yarn outlet at a second longitudinal end of the chamber, in which the yarn outlet has a cross-sectional area, in which the first and the second longitudinal end are located oppositely; (iv) and one or more air inlets; (b) one or more air inlet channels for creating an air flow, said one or more air inlet channels ending in the one or more side walls of the chamber, in which said one or more air inlet channels have a cross-sectional area and said one or more air inlet channels are oriented so that the one or more air inlet channels are suitable for generating an air flow in the chamber; wherein the ratio of the cross-sectional area of the yarn outlet of the chamber to the cross-sectional area of said one or more air inlet channels for generating the air flow is such that a critical air flow can be provided at the yarn outlet of the chamber when a predetermined overpressure is applied at the one or more air inlets, wherein the ratio of the cross-sectional area of the yarn outlet to the cross-sectional area of the one or more air inlet channels generating the air flow, is between 1.5 and 8.

4. System for fabricating alternating S/Z twist plied yarns of claim 1, in which a critical air flow can also be provided at the yarn inlet of the chamber when the predetermined overpressure is applied to the air inlets.

5. System for fabricating alternating S/Z twist plied yarns of claim 1, wherein the ratio of the cross-section of the yarn outlet to the cross-sectional area of the one or more air inlet channels generating the air flow, is between 2 and 6.

6. System for fabricating alternating S/Z twist plied yarns of claim 1, wherein the predetermined range of overpressure at the one or more air inlets for generating the critical air flow at the yarn outlet, is between 1 and 7 bar.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1A-E shows longitudinal cross-sections of a chamber for an air jet device according to the invention.

(2) FIG. 2 shows an isometric sight of a chamber for an air jet device according to the invention.

(3) FIG. 3 show a system for fabricating n alternating S/Z cables yarns according to the invention.

(4) FIG. 4A, FIG. 4B, FIG. 4C, FIG. 4D, FIG. 4E, FIG. 4F and FIG. 4G show a longitudinal cross-section of an air jet device for applying torsion to yarns, with two successive chambers according to a possible embodiment.

(5) FIG. 5A, FIG. 5B and FIG. 5C show cross-sections of an air jet device for tacking (filaments of) yarns according to a possible embodiment, FIG. 5A show a transversal cross-section, FIG. 5B shows a longitudinal cross-section perpendicular parallel to the air inlet channel, FIG. 5C shows a longitudinal cross-section perpendicular to the air inlet channel.

DETAILED DESCRIPTION

(6) Unless otherwise specified, all terms used in the description of the invention, including technical and scientific terms, shall have the meaning as they are generally understood by the worker in the technical field of the invention. For a better understanding of the description of the invention, the following terms are explained specifically.

(7) “A”, “an” and “the” refer in this document to both the singular and the plural unless otherwise specified by the context. For example, “a segment” means one or more than one segment.

(8) When “approximately” or “about” are used in the document together with a measurable quantity, a parameter, a period or moment, etc., variations of +/−20% or less, preferably +/−10% or less, more preferably +/−5% or less, still more preferably +/−1% or less, and even still more preferably +/−0.1% or less than and of the cited value are meant, as far as such variations apply to the invention that is described. It will however be clearly understood that the value of the quantity at which the term “approximately” or “about” is used, is itself specified.

(9) The term “include”, “including”, “consist of”, “consisting of”, “provide with”, “comprise”, “comprising”, “involve”, “involving” are synonyms and are inclusive of open terms that indicate the presence of what follows, and that do not exclude or prevent the presence of other components, characteristics, elements, members, steps, known from or described in the state of the art.

(10) The term “yarn” refers to a spun thread, in this case comprising several filaments, of BCF yarns (bulked continuous filament). The individual yarns typically have a diameter between 0.2 mm and 2 mm, the already twist plied yarns have a larger diameter, between 0.5 mm and 5 mm, dependent on the circumstances. In this respect, it should be noted that BCF yarn is compressible and that therefore, the diameter or thickness of the yarn is indicated preferably by means of yarn numbers, as the ratio of the mass and length of a piece of yarn. Practically, for individual yarns, this means a range between 250 dtex and 4000 dtex, and for twist plied yarns, a range between 2000 dtex and 10000 dtex. Smaller ranges are possible, for example 600 dtex to 2000 dtex for individual yarns, and 2000 dtex to 5000 dtex for twist plied yarns, but this is however not limiting the applicability of the invention.

(11) The term “choked flow” or “critical flow”, more specifically with respect to air flows, refers to circumstances in which an, in this case, air flow flows through a narrowing to a zone with a lower pressure. In this case, the flow rate increases as the differential pressure before and after the narrowing increases, relatively and/or absolutely. Critical flow is reached at a moment at which the flow rate of the air flow does not further increase at a larger differential pressure before and after the narrowing. There reason therefore is that the flow rate of the air flow is limited to the local sound velocity. When the flow rate of the air flow through the narrowing is too high, the flow becomes supersonic and turbulence and other effects are generated involving energy losses, and moreover decreasing the effective mass flow rate. In practice, the generation of a critical flow also leads to shock waves further downflow. A way to detect the critical flow at the outlet of the air jet device is thus to observe any possible shock waves. This can be done by means of Schlieren photography. Schlieren photography is generally used for studying the flow of fluids, and in particular for studying the flow around and higher than the sound velocity. The technique itself is well-known and will not be further discussed in the present document, unless necessary for understanding the invention. Schlieren photography can also be used for mapping shock waves after the yarn outlet. Obviously, this also applies to shock waves at the yarn inlet, where a critical flow can exist.

(12) The term “overpressure” at air inlets refers to the differential pressure between the pressure at the air inlets and the pressure after the outlet of the chamber, in which a positive overpressure indicates a higher pressure at the air inlets than the pressure after the outlet of the chamber. In other words, it is the overpressure of the air that is introduced in the chamber via the air inlets.

(13) The term “overpressure” of the chamber refers to the differential pressure between the chamber and the yarn inlet and/or yarn outlet.

(14) The terms “twist plying” and “twist plied” refers to the procedure, or a characteristic of the product thereof, in which one or more yarns are intertwined with another set of one or more yarns.

(15) The term “twist” and “twisted” refers to the procedure, or a characteristic of the product thereof, in which torsion is applied to a yarn, leading to a deformation in which the energy of the torsion is stored in the yarn, and visually leads to a twisted yarn.

(16) The term “tack” or “tacking” refers to the connection of more separate yarns, or more separate, twist plied yarns, in which the yarns comprise several filaments. When tacking, the yarns are connected by intertwining some of these filaments with each other over a limited length, for example by bringing the separate yarns close to each other and subsequently applying an air flow pulse, thus leading to the intertwining of the filaments via air vortexes.

(17) The term “cabled” refers to a product that is obtained by twisting two or more already twist plied yarns.

(18) The term “connected alternating S/Z twist plied yarns” refers to a yarn that is fabricated by in counter-phase joining alternating S/Z twist plied yarns, and connecting these in the torsion-free short zones. Here, there is no self-twist as the connected yarns have an opposite torsion. The opposite torsions compensate each other and present de-torsioning of the yarns.

(19) The term “alternating S/Z twisted” and “alternating S and Z twisted” refer to the condition of a yarn onto which a spatially alternate torsion has been applied.

(20) The terms “alternating S and Z twisted” and “alternating S/Z twisted” refer to yarns that have been twisted with each other as a result of applying an alternate S/Z torsion to the yarns and subsequently self-twisting the yarns with each other.

(21) The inventions described in the present document, both methods, air jet devices and covering devices, and the products fabricated according to the methods all have different advantages with respect to the state of the art related to the present subject. As said, very high volumes of yarns are produced with these systems, at very high speeds. In order to fabricate a high-quality product, the application of sufficient torsion, that is applied in an equal and controlled way, is crucial. This process is carried out in the devices according to the state of the art at very high overpressures in the devices, of about 8 bar or higher. Maintaining this overpressure requires a lot of energy, and is thus very expensive. Moreover, this overpressure is maintained by system especially developed therefore that, in order to be able to generate higher pressure, are also more complex, more fragile and more expensive. By obtaining a critical flow at the yarn outlet, a more efficient energy consumption is moreover also achieved, without the losses due to turbulences and other undesired flow effects that occurs at a supercritical air flow, a problem that occurs at the old known systems and methods. In order to avoid supercritical flows without maintaining the overpressure therefore excessively high, the energy consumption when using the devices and/or methods of the present document is further reduced, and also the yarn feed is stabilized.

(22) When determining the dimensions of the chamber, air inlet channels, yarn outlet, yarn inlet, air inlet and other elements, one should take into account the fact that they are adjustable to the operational parameters, the yarn thickness and other factors, while the adjustments of the dimensions do not change the principle onto which the invention is based, namely the provision of a critical air flow at the yarn outlet and/or the yarn inlet. The dimensions referred to in this document are conventional dimensions, but do not limit the applicability of the present invention.

(23) In a preferred embodiment, the cross-section of the chamber is for example between 12 mm.sup.2 and 60 mm.sup.2, but it can also have higher and/or lower external limits, for example 5 mm.sup.2 and/or 100 mm.sup.2, or it can be smaller, for example between 20 mm.sup.2 and/or 40 mm, such as 25 mm.sup.2, 30 mm.sup.2 and/or 35 mm.sup.2. Moreover, the cross-section of the yarn outlet is between 1 mm.sup.2 and 10 mm.sup.2, but it can also have higher and/or lower external limits, for example 0.5 mm.sup.2 and/or 20 mm.sup.2, or it can be smaller, for example between 2 mm.sup.2 and/or 7 mm.sup.2, 3 mm.sup.2, 4 mm.sup.2, 5 mm.sup.2 and/or 6 mm.sup.2 as upper or lower limit. The cumulative cross-section of the air inlet channels for generating the air flow is for example between 0.2 mm.sup.2 and 2.5 mm.sup.2, but it can also have higher and/or lower external limits, for example 0.1 mm.sup.2 and/or 5 mm.sup.2, or it can be smaller, for example between 0.5 mm.sup.2 and/or 1.5 mm.sup.2. Moreover, the cross-section of the yarn inlet is preferably between 1 mm.sup.2 and 10 mm.sup.2, such as 2 mm.sup.2, 3 mm.sup.2, 4 mm.sup.2, 5 mm.sup.2, 6 mm.sup.2, 7 mm.sup.2, 8 mm.sup.2 and/or 9 mm.sup.2, but it can also have higher and/or lower external limits, for example 0.5 mm.sup.2 and/or 20 mm.sup.2, or it can be smaller, for example between 2 mm.sup.2 and/or 7 mm.sup.2, or 3 mm.sup.2, 4 mm.sup.2, 5 mm.sup.2 and/or 6 mm.sup.2.

(24) The length of the chamber, that is the shortest distance between the yarn inlet and the yarn outlet, is between 2 mm and 40 mm, preferably between 5 mm and 30 mm, such as 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 26 mm and/or 28 mm, although these dimensions depend on the yarn thickness and other parameters.

(25) The passage of the air inlet channels to the chamber (via the air inlets) in each plane is described by means of functions. In a preferred embodiment, the air inlets and/or the air inlet channels and/or the chamber can be adjusted so that these functions have a third derivative that is a continuous function, in order to ensure an optimal passage of the air flow out of the air inlet channels to the chamber.

(26) In a preferred embodiment, the air inlet channels have a length that is at least equal to the diameter of the air inlet channels in order to be able to generate a uniform air flow at the air inlet to the chamber, to avoid turbulence (energy loss) and/or to avoid an undesired Laval nozzle in the air flow. The length is preferably between 1 and 10 times the diameter of the air inlet channels. Preferably, it is between 1 and 5 times. Practically, a length between 1 and 1.5 times the diameter of the air inlet channels is suitable. In this way, an all too big pressure loss can be avoided over the air inlet channels.

(27) In a possible embodiment for the chambers of an air jet device, the chambers have two air flow channels generating an air flow that end in the air inlets of the side wall of the chamber, adjacent to the yarn inlet of the chamber. The two air inlet channels are oriented in such way that a first air inlet channel is suitable for supplying the airflow for applying an S torsion, and a second air inlet channel for supplying the air flow for applying a Z torsion. Preferably, the air inlet channels are positioned closer to the yarn inlet than to the yarn outlet.

(28) The air inlet channels can have a circular, oval, square, rectangular, triangular, polygonal, polygonal rounded or other cross-section, as well as combinations of two or more of the above-mentioned forms, or they can have cross-section that narrow or broaden, adjusted to an optimal passage of the air flow in the air inlet channels to the chamber. At an air jet device for applying a torsion to yarn, the air inlet preferably has the form of a rectangle so as to allow the air flow to be as tangential as possible in the chamber. This ensures that the supersonic expansion of the air flow does not touch the yarn. The rectangle must be oriented in such way that the long side of the rectangle are tangential to the chamber, because in this way, the tangential air flow could transfer sufficient torsion to the yarn. However, the shorter the short side, the higher the pressure drop and friction losses. Therefore, an equilibrium must be found between the length of the long sides and the short sides. An air inlet that is too small, can for example cause higher hydraulic losses. Alternatively, one can also choose an oblate as the cross-section of the air inlet, with similar orientation for the same reasons.

(29) In a preferred embodiment for the methods and the air jet device, a subsonic air flow is generated at the outlet, and preferably also at the inlet, of the chamber. The subsonic air flows can be generated by adjusting structural parameters of the chamber, such as the cross-sections of the yarn inlet and/or of the yarn outlet and/or of the chamber and/or of air inlet channels and/or environmental parameters, such as overpressure at the air inlets and/or mass flow rate of the air inlet channels and/or diameter of the yarn and/or other. Note that the critical air flow (or critical air flows) still occur at the yarn outlet and/or yarn inlet of the chamber, but mostly not in the rest of the air jet device. In this respect, ‘outlet’ must also be understood as the part preceding the yarn outlet of a chamber, and ‘inlet’ as the part following the inlet of the yarn inlet of a chamber. In these zones, it is thus more interesting to work under said subsonic air flows.

(30) In a preferred embodiment, the chamber is at least partially cylindrical. However, the chamber can also be elliptic-cylindrical or it can have any other form, or a combination of more parts. Preferably, the cross-section of the chamber narrows towards the yarn outlet and/or towards the yarn inlet in a continuous and/or stepped manner. Alternatively, it can thus also narrow down in a phased way, as said, thus combinations of different continuous and/or stepped parts. The form of the chamber will be further discussed in the examples.

(31) The number of steps occurring in the stepped narrowing is between 1 and 10, preferably between 1 and 5 and more preferably 2 or 3. Moreover, the steps can bevel to a next ‘step’, in order to ensure a smooth transition, which is advantageous for preventing local turbulence. These bevelled steps can occur in an angle of 15° to just below 90°. Preferably, it lies between 45° and 70°, more preferably it is about 60°.

(32) At a continuous narrowing, the narrowing can also bevel with respect to a central zone of the chamber with angles between 15° and just below 90°, and preferably between 45° and 70°, preferably about 60°. Other angles are however not excluded and can depend on the design of the complete chamber and operational parameters (overpressure, mass flow rate, . . . ). At a continuous narrowing, the side walls can be a straight line, as will be described in example 1, or a curve, for example a parabola or another function. The narrowing itself can for example be a truncate cone, or a truncate paraboloid or other geometrical figures.

(33) Finally, as said, combinations of stepped narrowing and continuous narrowing are also possible.

(34) The above-mentioned stepped and/or continuous narrowing are configured for avoiding a too strong practical passage narrowing through a too narrow vena contracta (narrowest practical passage, where a flow moves), in which the practical flow section at an abrupt narrowing is much smaller than the physical flow section. In this way, the diameter of the yarn inlet and of the yarn outlet can be minimized without further narrowing due to the effect of the vena contracta. By minimizing the diameter of the yarn inlet and the yarn outlet, the yarn can be positioned more precisely in the whether or not tangential air flow. This can cause a decrease of the used flow section up to 64%. By means of the optimal passage from the chamber with a large flow passage to the narrowing, a non-abrupt passage, as said, will at least partially solve this problem. Moreover, the avoidance of vena contracta comes along with a turbulence, in which the turbulence becomes stronger as the effect of the vena contracta increases. As said, a stronger turbulence leads to energy losses and must therefore be avoided or limited. In addition, the invention is not at all limited to the embodiments described in the present document, but it included all combinations thereof.

(35) In a last aspect, the invention relates to a system of two or more separate air jet devices (preferably two) for manipulating yarns through an air flow, in which the air jet devices are as described in the present document, and in which the air jet devices are arranged for operating in parallel, and so that the processed yarns are discharged at the same side. This does not only allow an easier installation and adjustment of such a system, but also allow a more efficient process. In practice, for alternately S/Z twisting yarns, two separate yarns must be twisted before they can be tacked. By having the separate air jet devices working in parallel, the distance over which the yarns must be led before being tacked, can be limited. This distance should be kept as short as possible, both for avoiding the so-called ‘de-twisting’ and other problems, and for having to keep the yarns as short as possible in twisted position.

(36) In the following, the invention will be described by means of non-limiting examples illustrating the invention. These examples are not meant or cannot be interpreted as limiting the scope of the invention. The figures in the examples are, unless otherwise specified, not provided with preferred dimensions or angles or ratios and cannot be interpreted as such.

EXAMPLES

Example 1

(37) In a first example of the form of an air jet device (4), and more in particular the chamber (41) thereof, it is referred to FIG. 1A. Here, the longitudinal cross-section is shown, along the longitudinal axis of the chamber (41), in which the chamber (41) narrows towards the yarn inlet (44) and also towards the yarn outlet (43), in a continuous way. The angle (θ) under which the chamber (41) narrows, can vary, and can for example be 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70° or more, but it can also almost be a curve, or a combination of more of the above-said routes. The yarns is fed centrally along the longitudinal axis of the air jet device (4) from the left to the right. An air inlet channel (42) with air inlet is visible close to the end of the yarn inlet (44) of the chamber (41), and is suitable for providing a whether or not tangential air flow around the yarn, dependent on the location and orientation of the air inlet channel (42). A second air inlet channel can also be present, preferably also at the end of the yarn inlet (44) of the chamber (41).

(38) This is also shown in isometric perspective in FIG. 2.

(39) In a further detailed form, as illustrated in FIG. 1B, there is also a stepped passage after a central, cylindrical part of the chamber (41) present before the yarn outlet (43), and also a stepped passage before the central, cylindrical part of the chamber (41) after the yarn inlet (44). Optionally, this is present only at one of the ends (43, 44).

(40) It should be further noted that at the air jet device (4), the air inlet channels (42) are oriented to cause a tangential air flow in the chamber (41), preferably with the possibility to provide this in the two rotation directions around the longitudinal axis. For so-called tack jet devices, the air inlets are oriented to provide an air flow crossing the central axis, so that one oppositely turning vortexes exist that can in this way tack the filaments of one or more yarns that are led through the tacking or intertwining device, with each other.

Example 2

(41) In a second example of the form of an air jet device (4), and more in particular the chamber (41) thereof, it is referred to FIG. 1C. Here, the longitudinal cross-section is shown, along the longitudinal axis of the chamber (41), in which the chamber (41) narrows abruptly towards the yarn inlet (44) and also towards the yarn outlet (43). For a description, reference is made to example 1. In a further detailed form according to FIG. 1D, there is a stepped passage after a central, cylindrical part of the chamber (41) present before the yarn outlet (43), and also a stepped passage before the central, cylindrical part of the chamber (41) after the yarn inlet (44). Optionally, this is present only at one of the ends (43, 44).

(42) Again, it will be noted that the chamber can be adjusted to serve as a tack jet device, by means of an adjusted orientation and/or location of the air inlet channels and air inlets.

(43) In a further embodiment, a curved passage can also be provided from the chamber to the yarn inlet and yarn outlet, as is illustrated in FIG. 1E.

Example 3

(44) In this example, the system for fabricating alternating S/Z cables yarns of FIG. 3 is discussed, as well as the method for operating such device.

(45) The illustrated method is a continuous process: i.e. the introduced yarns and the produced yarns are led continuously through the process and the device at a speed of 200-1500 m/min and even at high speeds, and this without intermittent stops. The individual yarns (2, 2a, 2b and 2c) come from a yarn supply. This are mostly bobbins (1, 1a, 1b and 1c).

(46) By means of yarn tensioners (3, 3a, 3b and 3c), the yarns (2, 2a, 2b and 2c) are brought to the desired yarn tension, and subsequently led to the air jet devices (4, 4a, 4b and 4c).

(47) Such air jet devices are generally known: by alternately introducing compressed air at the air inlets and/or air inlet channels (5 and 6, resp. 5a and 6a, 5b and 6b and 5c and 6c) alternating S/Z twisted yarns (7, 7a, 7b and 7c) are produced at the discharge side of the air jet devices.

(48) Immediately after the air jet devices (4 and 4a), the alternating twisted yarns (7 and 7a) are joined, preferably in phase. This means, with the zones of equal twist direction and the short zones next to each other.

(49) This joining can take place in the node fixator (8), that connects the short zones of the alternating twisted yarns (7 and 7a) with each other. A node fixator (8) refers to a fixator for fixing torsion-free short zones to each other. Such node fixator can be an intertwining jet (device) or tack jet (device), as is generally known in the industry. In parallel, the same happens with the yarns (7b and 7c): they are joined as soon as possible, and their short zones are connected in node fixator (8a).

(50) By means of a self-twist process, an alternating S/Z twist plied yarn (9 resp. 9a) with alternating zones of S twist and Z twist is fabricated immediately after the node fixator (8 resp. 9a), with in between the short zones.

(51) In the overtwist jet or cabling device (11 resp. 11a), the alternating twist plied yarns (9 resp. 9a) are in turn twisted alternately, preferably in phase with the already formed alternating S/Z twist ply on the alternating twist plied yarns. In this way, the unbalanced alternating S/Z twist plied yarns (12 and 12a) are created.

(52) These yarns (12 and 12a) are also joined as soon as possible, and their short zones are connected to each other in a node fixator (15).

(53) However, the overtwisting creates a very high yarn tension, as a result of which the fibres or filaments in the short zones cannot easily be tack with each other anymore. Moreover, the fibres or filaments only have limited movement freedom with respect to early made internodal connections between the alternating S/Z twisted yarns. Therefore, optionally, between the overtwist jets (11 resp. 11a) and the node fixator (15), a yarn supply (13 resp. 13a) is provided, so that the yarn tension in the unbalanced alternating S/Z twist plied yarns (14 resp. 14A) can be reduced to a suitable level for a good operation of the node fixator (15).

(54) The yarn supplies (13 and 13a) can in the generally known ways be carried out, such as nipping rolls, capstan overfeed rolls, open-roll systems, ridged rolls, belt nips or evens by means of air.

(55) If the unbalanced alternating S/Z twist plied yarns (14 and 14a) are joined in phase, they will spontaneously start to self-twist after the node fixator (15), so that an alternating S/Z cabled yarn (16) is created. The yarn tension reduction with respect to the yarn supply (13 and 13a) also improves this self-twist process.

(56) If the unbalanced alternating S/Z twist plied yarns (14 and 14a) are joined in counter-phase, they will not start to self-twist after the node fixator (15). The torsion tensions in both yarns are namely opposite.

(57) The connection of the short zones in both yarns (14 and 14a) enables both yarns to maintain their unbalanced twist, also over the short zones, and the produced yarn(16) is essentially made of both yarns (14 and 14a) next to each other, however not connected to each other in the short zones, as so-called connected alternating S/Z twist plied yarns.

(58) In a preferred embodiment of the invention, a control system (18) regulated the yarn supplies (13 and 13a) based on a yarn tension meter (17), that measures the tension on the yarn (16), so that the yarn tension variations between the node fixator (15) and the following process (19) can be minimized.

(59) In another embodiment of the invention, the tensiometer (17) is replaced by a member that can accumulate an amount of yarn between node fixator (15) and the following process (19), for example a dancer arm; in this case, the yarn supplysystems (13 and 13a) are regulated base on the amount of accumulated yarns, for example by measuring the position of the dancer arm.

(60) In another embodiment of the invention, the alternating S/Z twist plied yarns (9 and 9a) are heated before the overtwist jets (11 and 11a), by means of generally known yarn heaters (10 and 10a), such as infrared heaters, to soften the filaments and additionally improve the ‘tackiness’ of the short zones in the node fixator (15). In this way, the twisting levels can also be increased when overtwisting.

(61) In still another preferred embodiment of the invention, a hot fluid such as hot air or steam is used in the overtwist jets, to soften the filaments and additionally improve the ‘tackiness’ of the short zones in the node fixator (15). In this way, the twisting levels can also be increased when overtwisting.

(62) In a further preferred embodiment of the invention, a hot fluid such as hot air or steam is used in the node fixator (15), to soften the filaments and additionally improve the ‘tackiness’ of the short zones in the node fixator (15).

(63) In still another preferred embodiment of the invention, also some fluid additives can be applied to the fibres or filaments, to reduce mutual friction, and thus to additionally improve the ‘tackiness’ of the short zones in the node fixator (15). These additives can be applied to the yarns with generally known applicators (21 and 21a) (kiss-roll moistening jets, etc.) in the yarn path before the node fixator (15), or they can be mixed with the fluid in the node fixator (15).

(64) Finally, in each of the embodiments, a control unit (22) must be provided for the coordinated control of all of the actuators.

Example 4, 5 and 6

(65) In a first possible embodiment according to FIG. 2, the dimensions are as follows: The air inlet channels (42) have a cross-section of about 0.4 mm, in which the yarn outlet (43), and preferably also the yarn inlet (42), have a diameter of about 1.7 mm.

(66) In a second possible embodiment according to FIG. 2, the dimensions are as follows:

(67) The air inlet channels (42) have a cross-section of about 1.2 mm.sup.2, in which the yarn outlet (43), and preferably also the yarn inlet (42), have a diameter of about 2.1 mm.

(68) In a third possible embodiment according to FIG. 2, the dimensions are as follows: The air inlet channels (42) have a cross-section of about 1.6 mm.sup.2, in which the yarn outlet (43), and preferably also the yarn inlet (42), have a diameter of about 2.7 mm.

(69) For these dimensions, the applicant has noted for twist jets (devices for applying a torsion to one or more yarns) that at lower overpressures (lower than 9 bar, and even at overpressures of 3 to 6 bar), a critical air flow is obtained a the yarn outlet, in which a sufficient torsion was applied to the yarn.

Example 7

(70) In a possible embodiment, an air jet device is provided with two successive chambers (41a and 41b). In this respect, different designs are possible, in which different types of chambers are combined, of which examples are shown in FIG. 1A-1E, and described in EXAMPLE 1. Possible combinations thereof are described in FIG. 4A to FIG. 4G. Here, it should be noted that for the angles θ.sub.1, θ.sub.2, θ.sub.3 and θ.sub.4, there are several possibilities and that they should not necessarily be equal. Finally, it should also be noted that, although not in case of the configuration of the figures, the chambers should not perfectly follow each other and that this can occur under an angle or other asymmetries. Furthermore, it should be noted that in FIG. 4D-4G, the air inlet channels (42b) of the second chamber (41b) are positioned closer to the yarn outlet (43) of the second chamber (41b). Here, it should also be noted that in FIG. 4G, the chamber passage must not explicitly be present, since a yarn outlet of the first chamber (41a) can pass continuously to a yarn inlet of the second chamber (41b).

(71) Both chambers (41a and 41b) are provided with air inlet channels (41a and 42b), that are however positioned differently, so that both cause a substantially tangential air flow in the chambers, however with an opposite rotation direction. The first chamber (41a) is provided with a yarn inlet (44) and ends via a chamber passage (45) into the second chamber (41b) that has a yarn outlet (43) at the other end. Possible dimensions have already been cited in EXAMPLE 4, 5 and 6.

Example 8

(72) A possible embodiment of a so-called tacking device (or tack jet) is shown in FIG. 5A, FIG. 5B and FIG. 5C. The chamber (41) is adapted because the air inlet channel (42) is suitable for providing a radial air flow in the chamber (41), and because the air inlet channels (42) is provided more closely to the yarn outlet (43) than to the yarn inlet (44) as is illustrated in FIG. 5B. Moreover, the yarn outlet (43) has a smaller cross-section that the yarn inlet (44). In this embodiment, the chamber (41) has a cross-section in the form of a semi-circle, in which the air inlet channel (42) ends at the convex side (46) opposite to the flat wall (47), as is clearly illustrated in FIG. 5A. In this way, air flows from this air inlet channel (42) are directed towards the opposite flat wall (47), so that they cause two vortex flows (48a, 48b) that have however an opposite rotation direction, as is illustrated in FIG. 5A. The vortex flows (48a, 48b) are suitable for manipulating filaments of yarns that are led through the chamber (41) and in this way tacking them to each other, in order to connect the yarns.

(73) It will be clear that the present invention is not limited to the embodiments that have been described above and that some adjustments or modifications can be added to the described examples still falling with the scope of the attached claims. The present invention has for example been described with reference to the application of an alternating S/Z torsion to a yarn, but it will be clear that the invention, as well as methods, torsion members and devices can be applied to e.g. several yarns in a chamber, or other raw materials than yarns, or for applying one single, non-alternating torsion to a yarn, or to several, twisted or not, yarns, or for tacking the filaments of one or more yarns.