Patent Application
20090031693
The invention relates to a method for producing knotted yarn and/or twisted yarn from DTY (draw twist yarn) and/or smooth yarns with highly regular knots by means of air nozzles with a yarn treatment channel as well as blown air which is blown in transverse to the yarn treatment channel, with the blown air creating one double eddy each in the direction of yarn transport as well as against the direction of yarn transport to create the knots. The invention additionally relates to an entanglement nozzle for producing knotted yarn having highly regular knots, with a continuous yarn treatment channel as well as a blown air feed channel, with the blown air feed channel being directed toward the longitudinal reference axis of the yarn treatment channel.
In recent times, the filaments being produced have become increasingly finer. They are called microfilaments if the denier per filament (dpf) is between 0.5 and approx. 1.2. The yarns produced from said filaments are called microfilament yarns. The term “super-microfilaments” refers to yarns with a dpf of <0.5. The term “microfilament” in the following also includes super-microfilaments, unless noted otherwise. Yarns with a dpf greater than 1.2 already require gentle processing to avoid breakage of either individual filaments or the entire yarn. This applies even more so to microfilament yarns. With microfilament yarns, the composite of all filaments plays an important role. It must be ensured that no individual filaments protrude and thus create a risk of breakage. “DTY yarns” are “draw twist yarns.”
In the market, entangled yarns with so-called air entanglement are used on a relatively large scale. Two trends have become apparent on the market. Well-developed, strong and stable knots, well-formed by air entanglement, are required for many applications. The air nozzle must be designed for this with respect to all parameters. The situation is different with fine filament yarns, especially microfilament yarns. These yarns are used to produce fine fabrics, which must have a very supple and silky feel to the touch. It is found here that the development of very stable knots that are almost impossible to undo may be a disadvantage in that the knots act as a type of grid, especially on extremely fine fabric dyed in a solid color. Although knots may be desired within yarn processing, they should subsequently disappear completely during the processing of the fine yarns to woven fabrics or other fabrics. So-called knotted yarn is produced by entanglement using entanglement nozzles. The knots ensure local incorporation of all filaments and short sequences of knots over the entire yarn run. The goal of entanglement is to achieve a high knot count per meter with regular spacing between knots. The conditions in terms of equipment are given with a yarn treatment channel having a blown air feed running across the yarn channel. In this process, the blown air flows out on both sides of the yarn channel, forming a so-called double eddy due to the air being blown approximately centrally in the direction of yarn transport and also opposite the direction of yarn transport. When the yarn is passed through the corresponding eddy zone, this results in a type of alternating air movement which is ultimately partially responsible for repetitive formation of knots with short interruptions between the knots. The skill here lies in finding the optimum among the three yarn quality criteria:
DE 197 00 817 shows a special form of an entanglement nozzle for carpet yarn, i.e., for very coarse BCF yarn. A method for continuous production of spin-textured filament yarn in a continuous yarn channel and/or entanglement channel of a swirl nozzle has been assumed. The filament yarn is entangled by a stream of blown air directed transversally into the swirl nozzle and flowing out of the yarn channel in both forward and reverse directions, and the exhaust air of the rear eddy is released from the yarn feed area approximately opposite the blown air feed. The approach proposed here is to produce two unequally strong eddies in the entanglement channel, the forward eddy being designed to have a stronger effect than the rear eddy.
DE 37 11 759 is directed to finer yarns to medium yarns and attempts to improve the processability of the yarn in the subsequent processing, e.g., on weaving, knitting, weft-knitting and tufting machines. The inventor describes an entanglement device for entanglement of multifilament yarns, said machine having at least one yarn channel, with yarn guides arranged at intervals from the inlet opening to the outlet opening of the yarn channel and each of the filaments of a multifilament yarn being entangleable in the yarn channel by means of a blowing nozzle of compressed air that can be blown into it. The yarn undergoes a change of direction of less than 90° on entering and departing from the yarn channel and the blowing angle of the air nozzle is less than 90°. As a new approach, it is proposed here that the yarn guides shall be arranged in such a way that they guide the yarn into the yarn channel when the compressed air feed is shut down so that the yarn extends through the yarn channel, where it is parallel to the longitudinal direction of the latter and is in contact with the outlet opening of the at least one air nozzle. The distance of the yarn guides from the neighboring yarn channel openings is max. 30 mm. The length of the yarn channel is max. 40 mm with uncrimped multifilament yarn and max. 30 mm with crimped multifilament yarn. DE 37 11 759 at least succeeds in introducing the finding of the positive effect of a short yarn channel for production of knotted yarn to a broader technical world. In concrete terms, a yarn channel length of 10-28 mm is proposed for textured and/or crimped yarn. In particular a yarn channel length in the range of 10 mm is understood to be short.
The latest findings have shown that the use of air nozzles for the production of knotted yarn, which is widespread per se, is not satisfactory with very fine filaments, especially microfilaments. With regard to fine yarns, in particular microfilament yarns, in any case, however, a highly regular knot sequence is required in certain applications with weak knots that are temporarily constant but are reversible, i.e., knots that are undone again during yarn processing. The knots must not be discernible in the finished fabric. There have been many attempts to operate state-of-the-art nozzles, e.g., with lower air feed pressures. It is known that weaker knots are formed at lower air pressures but this is associated with the frequently unacceptable disadvantage of a lack of regularity in knot strength and/or knot stability as well as the spacing between knots.
Recently the market has shown a very strong trend toward the use of so-called microfilament yarns. The question of the regularity of the knots and at least adequate stability of knots for further processing plays a central role in many applications. In most cases, the number of knots must not be significantly less than 140 knots/m, which is achievable at the present time. Furthermore, the pressure required for the blown air must be reducible in view of the energy consumption.
The object of the present invention is to discover a method and an entanglement nozzle with which the aforementioned quality criteria can be achieved in the production of fine filament yarns, in particular microfilament yarns, even at high yarn transport speeds, with the four objectives:
The inventive method is characterized in that the blown air in the inlet area to the yarn treatment channel creates two strong stationary air eddy currents, virtually undisturbed by filament bundles, in an air twist chamber.
The entanglement nozzle in accordance with the invention is characterized in that a blown air channel enlargement is formed in the opening area of the blown air feed channel in the yarn treatment channel to form an air twist chamber for two stationary air eddy currents in opposite directions, whereby the blown air channel enlargement protrudes by less than 22% but more than 5% of the yarn channel width.
With respect to the novel invention, two entanglement nozzles are known in the state of the art:
It is interesting here that a high knot count is achieved in the former case. However, it is a disadvantage that the stability of the knots and the regularity of the knot sequence are tangibly inferior even with a slight reduction in the blown air pressure. In the second case, the knot stability is adequate but the knot count is not sufficient for many applications.
This novel invention is a departure from the so-called vortex chamber. A vortex chamber is understood to comprise a relatively great enlargement of the yarn channel before and after the area of the air injection site. The purpose was to give the yarn, i.e., the individual filaments, an opportunity to oscillate back and forth within the vortex chamber. However, the novel invention seeks an improvement on the air side. An air twist chamber or micro-vortex chamber for the air is proposed. It is true that knot stability has been increased with the vortex chamber. However, this has been achieved at the expense of the knot count. Fewer knots are created per meter of yarn. However, the individual knots are longer. In a completely surprising result, laboratory experiments with the novel inventive approach revealed that a knot stability that was previously impossible to achieve with uniform knots could be achieved with virtually no sacrifice with regard to the knot count. The micro vortex for air alone is possible because the local air flow is in the sonic and supersonic range and supersonic flow phenomena are utilized by inducing two strong stationary air eddy currents in a locally limited manner.
The inventor has also recognized that an inadequate model of knot formation was assumed in the previous methods. The contra-rotating eddies in each direction of outflow are stable as long as no yarn is present in the yarn channel. The presence of the yarn causes the eddy to oscillate back and forth. Investigations by the applicant have shown that the very short-term back and forth oscillation of the two contra-rotating eddies is at the center of the knot forming process. A combination of the two large eddies and an indefinable number of extremely small eddies causes the individual filaments to be thrown back and forth and thereby knotted. It is a fact here that the contra-rotating eddies are completely unstable when yarn is being transported through the yarn channel. On the other hand, according to the state-of-the-art model, attempts have been limited to the development of double eddies. This overlooks the resulting contradiction. The inventor has now recognized that the situation in the treatment of fine yarns can be tangibly improved if, instead of a continuous uniform yarn channel or a yarn eddy chamber, an air twist chamber is mounted in the blown air inlet area in the yarn treatment channel, so that the air stream creates two strong, undisturbed eddy currents at the respective location. The air twist chamber constitutes a miniature blown air channel enlargement and forms a transition between a completely stable eddy current in the area of air injection and the adjacent eddy zone, which is just as completely unstable, up to the outlet from the yarn channel. There is thus a sharp eddy formation in the direction of yarn transport and also opposite the direction of yarn transport. Air flow is at sonic or supersonic speed, so the corresponding phenomena may additionally be utilized.
The present invention allows a number of advantageous embodiments. In the model used here, a short area with a stable eddy current is created in the air twist chamber, followed by an alternating eddy zone in the direction of yarn transport and also opposite the direction of yarn transport. The table below summarizes the various types of yarns with the corresponding filament fineness.
Endless filament yarns: classification of conventional yarn and filament fineness
Large-scale experimental series with the inventive approach have shown that for the blown air, compressed air at more than 0.5 bar but less than 3 bar may be used, and a knotted yarn with highly stable knots can be produced. Yarns finer than 2 to 5 dpf, especially less than 1 dpf, were treated in this way. The yarn channel cross section is preferably designed to be a semicircle or U-shaped, with the yarn channel width (W) being greater than the yarn channel depth (D). The air twist chamber is a cup-shaped air channel enlargement in the yarn channel. The air twist chamber is designed to be at least approximately symmetrical, protruding less than 0.5 mm beyond the lateral yarn channel walls on both sides. One very important feature of the new approach is that the air twist chamber is designed in a miniaturized form, so the yarn bundle cannot penetrate completely into the lateral enlargement of the air twist chamber. The air twist chamber protrudes beyond the yarn channel wall by only a fraction of one millimeter. For example, for a yarn channel 1.6 mm wide, the greatest width of the air chamber as proposed here is 2.2 mm. For all those involved, it was initially completely surprising that such major effects could be achieved with such a tiny adjustment. However, the explanation lies in the targeted embodiment of supersonic air flow.
The novel invention has been investigated with large-scale experimental series using DTY yarns (false twist yarns). The results were good with fine, medium and coarse yarns. Results were most surprising in the case of fine yarns, especially microfilament yarns. Preliminary experiments with smooth yarns were positive, although the result turned out to be less clear-cut in relation to DTY yarns. The novel invention may also be used with BCF yarns, at least on the basis of theoretical considerations, in which case the air twist chamber should protrude max. 22%, min. 5% of the yarn channel width in the case of BCF yarns because of the much larger yarn channel widths of up to 8 mm.
The novel invention also allows a large number of advantageous embodiments of the yarn entanglement nozzle. For example, it is proposed that the yarn treatment cross section should be designed to be semicircular or U-shaped and should have a planar baffle cover.
All experiments have shown clearly that the actual critical dimensions of the air twist chamber include the lateral protrusion and the longitudinal dimensions. The air twist chamber is designed as a miniaturized cup with respect to the cross section of the yarn treatment channel to have a similar shape at the side, with the air twist chamber protruding less than 0.5 mm beyond the yarn treatment channel on both sides. The protruding amount of less than 0.5 mm has been confirmed with yarns up to 500 denier, i.e., with yarn channel widths up to 3 mm.
Comparative experiments: Influence of the eddy chamber length
With yarn channel widths greater than 3 mm, a protruding amount of less than 22% and more than 5% of the yarn channel width is specified. The protruding amount is preferably between 10% and 20% of the yarn channel width. The air twist chamber also preferably has an approximately circular symmetrical outside contour and forms an extension of the central axis of the blown air feed channel. To intensify the development of lateral air eddies, the width of the yarn channel cross section is most especially preferably greater than the yarn channel depth in the direction of the blown air feed. The [yarn] treatment channel may be designed as a wide channel having a width of preferably 0.6 to 3 mm, especially preferably with a ratio of the yarn channel width (W) to the yarn channel depth (D) of 1.2 to 2.5. According to experiments, the length of the air twist chamber is preferably less than 1.3 times the yarn channel width. The length of the air twist chamber in relation to the width of the yarn channel is preferably approximately 0.7 to 1.6, preferably 0.8 to 1.2, which is significantly less than the LAN ratio of approximately 1.75 times that of the state of the art.
According to another preferred embodiment idea, the blown air feed channel is designed to be round or oval or oval with a triangular character or Y-shaped, the side dimension of the blown air feed channel being at most equal to or less than the corresponding yarn channel width. The yarn channel width (W) is designed to be greater than the air feed channel width d, preferably with a W/d ratio of 1.1 to 3.
According to another very advantageous approach to achieving this effect, it is proposed that the yarn channel shall be formed by a planar displaceable baffle plate and a nozzle plate with the blown air feed. The yarn channel is preferably designed by a nozzle plate and a baffle plate that is displaceable thereto (as a so-called SlideJet) with an open position of the yarn channel for threading the yarn into it and a closed position of the yarn channel for producing a knotted yarn. The nozzle plate is designed as a plate-shaped ceramic disk, so that the ceramic disk together with a sliding part can be installed into and removed from the entanglement nozzle and/or the ceramic disk as a replaceable plate can be installed into and removed from the sliding part.
The present invention will now be explained in greater detail on the basis of a few exemplary embodiments with additional details, in which:
a-1f show the embodiment of the state-of-the-art yarn treatment channel with the new findings of the contra-rotating eddies on both outflow sides;
a-2d show the inventive approach with an air twist chamber;
a-3c show various cross-sectional shapes of the blown air feed channel;
a shows the result of a model calculation for strong, stationary eddy currents in the area of the air twist chamber;
b shows the non-stationary eddies, which are stationary in the model calculation in the absence of yarn;
c shows a schematic model of the stationary eddy currents in the area of the air twist chamber and the non-stationary eddies in the two outflow directions of the treatment air;
a-5e show different details of a nozzle plate with air twist chambers mounted thereon;
a-6d show a complete entanglement nozzle of the SlideJet type in the open and closed positions and with the nozzle plate removed (
a-7f show the most important following steps for removal of the sliding plate and/or the nozzle plate;
a-8d show the installation and/or removal of a nozzle plate in a sliding part of the entanglement nozzle;
a shows schematically an untreated smooth yarn;
b shows a knotted yarn with soft knots;
c shows a knotted yarn with hard knots (dark lines);
d shows a state-of-the-art knotted yarn with very irregular knot formation;
a-10c in contrast with
a and 12b show a special form of the blown air feed channel with a Y-shaped cross section;
c shows another example of the embodiment of an inventive air twist chamber 11′;
a through 13d show a state-of-the-art approach by the present applicant with an oversized yarn entanglement channel;
a shows an inventive approach and
b and 14c show state-of-the-art approaches for comparison with
a through 15c show a comparison of results with state-of-the-art approaches (
a and 16b show important quality differences from comparative laboratory tests with state-of-the-art approaches and with the novel invention;
a through 1f show the classical model for producing a knotted yarn 2′ by using an entanglement nozzle 1. In doing so, with the individual filaments, knots K are formed in an unentangled smooth yarn 2 by the action of blown air BL in a yarn treatment channel 3, these knots being formed in the direction of yarn transport 7 as well as opposite the direction of yarn transport within the yarn treatment channel 3 from a double eddy formed by the blown air according to the traditional understanding. Blown air BL enters through a blown air channel 4 in the direction of the arrow 5 and creates the typical double eddy 6, as indicated in
Large-scale investigations have recently revealed that the knot formation results have been very incomplete. In fact, knots are not formed simply from the two stable double eddies 6. The following fact is a basic prerequisite for formation of knots:
a through 2d illustrate an inventive approach. In contrast with
a through 3c illustrate three different cross-sectional shapes for the blown air feed channel.
The
a through 5e illustrate the inventive approach of
a and 6b show an entire entanglement nozzle 1 designed as a SlideJet.
a illustrates the closed operating position. The shift lever 26 is in a lowered position of the yarn channel 3 for the passage of the yarn for an air treatment, to which end, compressed air can be supplied through a connection and/or a compressed air bore. The sliding part 23 is shifted forward by the upward movement of the shift lever 26 (
a through 8c illustrate a very specific advantageous connection.
a shows untwisted yarn 2. However, this yarn may also be smooth or may be textured with a false twist. The individual filaments 45 are indicated with straight lines.
a through 10c show a few examples with irregular knot formation.
a and 12b illustrate the possibility of using a Y-shaped blown air channel cross section with a corresponding main air channel H and secondary air channel N.
a through 13c illustrate an approach according to the state of the art, which the present applicant has already been manufacturing for more than 20 years. A long yarn entanglement chamber with a relatively large width and length is typical here. Behind this approach there is the model wherein the yarn oscillation can decay as far as possible in the yarn twist chamber.
a shows an approach in accordance with the invention and two state-of-the-art approaches for comparison (
a, 15b and 15c show a comparison of the knot formation:
The two
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CH2006/000155 | 3/16/2006 | WO | 00 | 5/8/2008 |
