EP0361257A1 - Delivery rollers for a drawing frame - Google Patents

Abstract

Winding fibres are produced by being deflected out of the conveying plane of the drawing frame by means of airflows (LS) and/or a bonding effect on the pair of delivery rollers (LP). <IMAGE>

Description

This invention relates to the pair of delivery rollers (also called output roller pair or outlet roller pair) of a drafting device for false twist spinning, in particular nozzle spinning.

It is well known that the delivery roller pair of a drafting system must meet particularly strict requirements. The rollers of this pair must rotate with the highest number of revolutions of all rollers of the drafting arrangement. The clamping line formed by the rollers defines a limit of the last draft field in the entire drafting system which determines the main draft. On its output side, this pair of rollers delivers the fibers to be spun into the so-called spinning triangle, where they are twisted together. The conditions around this pair of rollers have a decisive influence on the yarn quality.

This pair of rollers is also attached to the fibers exposed to the rollers, which can lead to so-called winding.

The above remarks apply to the drafting system in the conventional spinning process (ring spinning) as well as in the newer spinning process (false twist, especially nozzle spinning). For the new spinning process, however, there is also the fact that the delivery speed is much higher than with the conventional spinning process (up to 300 m / min.) And that very high delays (more than 100 times) must be used. The resulting air flows in the area of the delivery roller pair can have a decisive influence on the fiber movements on the delivery roller pair.

Already in the history of false twist spinning, thought was given to the air currents in the area of the delivery roller pair - see US Pat. No. 3,487,619 from 1966. It suggests that the lower roller can be provided with air channels so that the air flow on the input side of the Delivery roller pair can be routed via these air channels to the output side of the roller pair. However, holes would have to be provided in the fiber-guiding region of the lower roller, which was almost certainly the reason that these arrangements have not become established in practical use.

The normal corrugated delivery cylinder allows a certain amount of air to pass from the inlet to the outlet side of the pair of delivery rollers. But this is not enough to bring up the desired effect.

Recently there is a new attempt to solve the same Chen problem has been made - see U.S. Patent 4,718,225. In this case, the lower or the upper roller (or even both rollers) can be provided with air flow channels, but these channels are seen laterally from the fiber-guiding region of the delivery roller pair. In the latter area itself, the rolls were provided with "smooth, uninterrupted clamping surfaces for moving a bundle of threads". Such an arrangement is known per se from US Pat. No. 2,244,461.

So far, both the air currents around the rollers of the delivery pair and the tendency of the fibers to adhere to the rollers have been regarded as problems. This invention is based on a new assessment of these effects.

The drafting system plays a particularly important role in false twist (especially nozzles) spinning because it not only has to refine the sliver, but also split it up in order to provide the so-called wrapping fibers. In conventional theory, the wrapping fibers are often also referred to as "edge fibers", it being assumed that the fibers in the central region of the clamping line get into the core of the yarn, the fibers outside this "core zone" form the wrapping fibers. A method based on this theory can be found e.g. in U.S. Patent 4,598,537, where air currents on the input side of the pair of delivery rollers are used to produce edge fibers.

This simple picture may apply to spinning coarser yarns. It is wrong when spinning finer yarns. As can be seen from our EP 131 170 is, wrapping fibers can arise both from the "core zone" of the spinning triangle and from the edge areas. It has even been shown that the wrapping fibers emerging from the core zone attach themselves better to the yarn core than the edge fibers and are therefore better able to contribute to the yarn strength. The production of wrapping fibers in the middle of the spinning triangle must therefore be promoted by all means.

It is accordingly the object of this invention to promote the formation of wrapping fibers in all areas of the spinning triangle.

A drafting system according to this invention is characterized in that the pair of delivery rollers for deflecting fibers is formed and / or operated from the conveying plane. The conveyor level is a level that includes a straight extension of the main fiber flow from the pair of delivery rollers.

In a preferred variant, the pair of delivery rollers comprises a first roller made of metal and a second roller made of a relatively elastic material. The two rollers are in contact with one another to form a clamping line of a predetermined length. The length of this clamping line is determined by the axial length of the elastic roller. The surfaces of the rollers that are in contact with one another are continuous cylindrical surfaces, ie without cuts, recesses or other interruptions of any kind. In particular, these mutually contacting outer surfaces of the rollers through no air passage channels (according to US 4,718,225 and / or US 3,487,619), corrugation (e.g. according to US 2,199,842) or incisions containing fibers (eg according to US 3,090, 081 and / or 3,296,664) interrupted. Such surfaces are referred to as "smooth" surfaces in the following description.

The elastic material of the second roller preferably has a Shore hardness in the range from 60 to 70, a hardness of approximately 65 Shore being preferred. This material can be made of rubber as well as a synthetic material (elastomer). The axial length of this roller, which determines the length of the clamping line, can be in the range 28 to 32 mm, preferably 30 mm.

The second roller could be formed as a smooth roller made of metal, but would not then have the same deflecting effect. The hardness of the material can, however, be partially compensated for by increasing the pressure pressing the rollers.

The drafting system is designed for use in a false twist spinning machine with a relatively high delivery speed (above 150 m / min). The drive of the pair of delivery rollers must be formed accordingly, such drive systems are already known.

In operation, such a drafting arrangement should work together with a suction nozzle in such a way that the suction nozzle sucks in the wrapping fibers supplied by the drafting arrangement and leads to the wrongly twisted yarn core. This nozzle can itself cause the false twist in the yarn core or can work together with another false twist element, for example another nozzle or a mechanical twister.

The suction nozzle is arranged opposite the drafting system and generates such an air stream (e.g. an air stream at such a high speed) that it leads the fibers deflected by the pair of delivery rollers back to the main fiber stream as wrapping fibers.

• Fig. 1: eine Streckwerkanordnung in Seitenansicht,
• Fig. 2: eine Draufsicht des Lieferwalzenpaares vom Streckwerk gemäss Fig. 1,
• Fig. 3: eine isometrische Darstellung des Lieferwal­zenpaares,
• Fig. 4: eine Seitenansicht des Lieferwalzenpaares in Kombination mit einer ersten Variante einer Saugdüsenanordnung, und
• Fig. 5: eine Seitenansicht des Lieferwalzenpaares in Kombination mit einer zweiten Variante einer Saugdüsenanordnung.

To illustrate, some designs of drafting systems according to this invention will now be explained in more detail with reference to the drawings, these designs should only serve as examples. It shows:

• 1: a drafting arrangement in side view,
• 2: a top view of the pair of delivery rollers from the drafting system according to FIG. 1,
• 3: an isometric representation of the pair of delivery rollers,
• 4: a side view of the pair of delivery rollers in combination with a first variant of a suction nozzle arrangement, and
• 5: a side view of the pair of delivery rollers in combination with a second variant of a suction nozzle arrangement.

The drafting system shown in FIG. 1 comprises an input roller pair EP, a middle roller pair MP, and a delivery roller pair LP. Each pair of rollers includes a first driven roller made of metal and a second roller (pressure roller) made of rubber. Each printing roller DW is printed by a carrier system, not shown, against its respective metal roller MW, so that the rollers of the delivery pair LP meet one another along a clamping line Touch KL (Fig. 2 + 3). The arrangement of the input roller pair is the same. The rollers of the middle pair MP each have an apron R1, R2 to improve the fiber guidance in the main draft zone between the middle roller pair MP and the delivery roller pair LP. This arrangement is well known and will therefore not be described in more detail here. It is also not essential to this invention.

Instead of the double apron guide shown, the invention could be used in combination with a so-called KEPA drafting system, e.g. in a drafting system according to our Swiss patent application No. 2723/88. The pre-drafting field between the input roller pair EP and the middle roller pair MP can be carried out with or without a push rod according to our Swiss patent application No. 3260/88. The invention is also not limited to the 2-zone drafting arrangement shown, but can also be used in drafting systems with three or more draft fields. The metal roller MW of the middle roller pair MP is preferably capped in order to ensure that the strap R2 is carried along. The metal roller of the input roller pair EP can be corrugated or can be smooth e.g. according to US Pat. No. 2,244,461 or US Pat. No. 2,199,842.

The invention relates to the design and operation of the delivery roller pair LP and the following description therefore focuses on this pair and the elements following it. However, an overall arrangement according to FIG. 1 is assumed, so that the fiber stream supplied by the drafting system flows from left to right in all figures and, accordingly, each metal roller MW around its own Axis clockwise and each printing roller DW rotates counterclockwise about its own longitudinal axis.

In high drafting systems for the jet spinning process, the delivery speed can reach relatively high values, e.g. up to 300 m per minute (for comparison, the drafting system of a conventional ring spinning machine works with a delivery speed of up to approx. 25 m per minute). As indicated schematically, the fiber material flows through the drafting system in the form of a fiber stream FS. This current lies in a plane which is determined by the clamping lines of the roller pairs and the current leaves the delivery roller pair in the same plane.

The high speed generates on the input side of the delivery roller pair LP air flows adhering to the surfaces of the rollers LS1 (FIG. 1), which come together in the nip of the roller pair and then flow along the nip line KL from the central region against both end regions of the nip line (FIG. 2) . On the output side of the pair, however, air flows LS2 (FIG. 2) flow from both end regions against the center of the clamping line, where they are carried along by the roller surfaces (FIG. 1). In order to reduce the disruptive effects of such air flows, the air passage channels according to US Pat. No. 4,718,225 and US Pat. No. 3,487,619 and the "shielding effects" of the straps R1 and R2 according to EP PS 107 828 have been provided in the prior art.

No such air passage channels are provided in a pair of delivery rolls according to this invention. On the contrary, the mutually contacting lateral surfaces MF (FIG. 3) of the pressure rollers DW and metal roller MW are in the Delivery roller pair LP both continuous (uninterrupted) cylindrical surfaces with an axial length L, which corresponds to the axial length of the pressure roller DW. The axial length of the metal roller of this pair of rollers can either be equal to the length L of the pressure roller DW (shown in dashed lines in FIG. 3) or longer than the axial length of the pressure roller (shown in solid lines in FIG. 3). In the latter case, the metal roller MW can either be assigned a single spinning position of the spinning machine, not shown, or it can extend over several such spinning positions (if need be, over an entire machine side).

The metal roller MW is normally made of steel and can be polished in the area MF contacting the pressure roller DW in accordance with US Pat. No. 2,199,842 or sandblasted or plasma-coated in accordance with US Pat. No. 2,244,461 or treated in some other way.

The pressure roller DW comprises a support body TK (only shown schematically in FIG. 3) and a cover UZ made of rubber or another elastomeric material which is applied to this support body. This coating has a Shore hardness in the range 60 to 70, preferably approximately 65. The length L of the pressure roller DW is in the range 28 to 32 mm, preferably 30 mm.

This design of the rollers in the delivery roller pair LP favors air flows LS1 and LS2 in the circumferential directions of the two delivery rollers by the rotation of these rollers. The air flows LS1 (Fig. 2) spread fibers from the edges of the fuse, which is conducive to the formation of the aforementioned "edge fibers". Such edge fibers are also for that False twist spiders are useful, but are not the primary objective of this invention.

The design of the rollers in the pair of delivery rollers LP acts on the fibers supplied by the drafting system in such a way that a smaller number of fibers in relation to the total fiber quantity are deflected in the circumferential directions of the delivery rollers, even within the actual spinning triangle.

This effect is achieved in part by the influence of the lust currents LS2 (Fig. 2). These flows are reinforced by the "smooth" shape of the rollers.

The above-mentioned effect is also achieved by the adhesive effect between the fibers and the rollers of the pair of delivery rollers. This adhesive effect is favored by the use of a relatively soft material for the roller coating. It can also be supported by a relatively high pressure applied to the platen. This pressure can be selected in relation to the hardness of the cover so that the cover is slightly deformed on the harder lower cylinder, which also favors the desired effect. With a very high pressure this result could even be achieved between two metal rollers.

These effects would be highly undesirable in the conventional spinning process because deflected fibers result in a hairy yarn or even get lost as a flight, while (worse) adhering fibers could form a wrap around the pressure roller DW or metal roller MW. In a false twist spinning process with a suction nozzle arranged on the pair of delivery rollers on the other hand, the suction nozzle itself works to prevent the undesired effects mentioned, as will now be explained in more detail with reference to FIGS. 4 and 5.

Fig. 4 shows the delivery roller pair LP in combination with a single spinneret SD, e.g. according to EP 121 602 or DE-PS 33 01 652. Such a nozzle has an opening M which is relatively wide in the circumferential direction of the rollers DW and MW and sucks air A from the environment into this opening. A fiber deflected by the air flows LS2 (FIG. 1) or the adhesive effect is therefore redirected again by the opposite air flows A and guided back into the channel K of the suction nozzle SD. As a result, it is brought together with the yarn core (not shown) and wound around this core. Since this method is known, it will not be described in detail here.

The invention enables the "three-dimensional" (3-D) production of the wrapping fibers in contrast to the two-dimensional production (US Pat. No. 4,598,537) by using the "edge fibers" alone. This advantageous “3-D” effect is achieved in that various properties, which are normally undesirable, of a pair of delivery rollers are combined to produce advantageous fiber movements and are used in combination with a subsequent suction system.

In Fig. 5 the delivery roller pair LP is shown again in combination with a suction nozzle D, which nozzle does not work alone as a spinneret, but prepares the fibers for a further false twist element (not shown). Such a nozzle is known from US Pat. No. 4,457,130 or from DE-PS 3,437,343. Although this nozzle D is not in the circumferential directions of the Rolls has wide opening, it also generates air flows A by suction behavior, which counteract the air flows LS2 (Fig. 1) or the adhesive effect and reinsert the deflected fibers into the suction channel SK of the nozzle D.

In both cases, the air flows LS2 and the adhesive effect (FIG. 1) work in such a way that additional fibers are released from the yarn core and are later articulated to the yarn core again as wrapping fibers. Such wrapping fibers can arise both from the edge regions at the outer ends of the clamping line and in the central region of the clamping line, the latter fibers being particularly desirable, as was already explained in the introduction to this description. The invention is particularly advantageous when spinning coarser yarns using the nozzle method, since it is particularly difficult in connection with such yarns to produce a sufficient number of wrapping fibers.

As already indicated, the invention is not restricted to the details of the embodiments shown. Where a double strap guide is used, one strap (in Fig. 1 strap R2) may extend closer to the pair of delivery rollers LP than the other strap (in Fig. 1 strap R1). Such an arrangement has been dealt with both in US Pat. No. 4,718,225 and in EP Pat. No. 107,828. However, the invention can also be used in connection with a conventional apron guide, for example according to US Pat. No. 3,296,664. The straps R1 and R2 are preferably considerably wider than the intermediate fiber stream, so that the movement of the driven straps (in Fig. 1 of the straps R2) is transferred by touching between the straps themselves on the upper straps (in Fig. 1 to the straps R2). A strap width of more than 35 mm, preferably about 40 mm, is advantageous.

In order to obtain sufficient clamping force in spite of smooth rollers, the smooth rollers preferably have a certain surface roughness, which e.g. can be generated by hard chrome plating, plasma coating or similar processes. This roughness must under no circumstances allow an air passage effect (cf. the conventional bordering), but can give the surfaces an "orange peel character".

Surprisingly, it has been shown that the pressure or the hardness of the pressure roller in the pair of delivery rollers has an influence on the spinning tension after the spinneret. By increasing the pressure or using a softer pressure roller, the spinning tension can be increased for a given spinning speed. This enables a higher spinning speed with the same strength, since the yarn strength is dependent on the spinning tension in such a way that a maximum strength is obtained at a certain spinning tension and the spinning tension decreases with increasing spinning speed. It appears that the increase in the number of wrapping fibers causes more friction of these fibers on the nozzle entrance, forcing the trigger system to generate a higher trigger force and thereby a higher spinning tension. However, the invention is not limited to this explanation of the phenomenon.

It is proposed to match the pressure and the hardness of the pressure roller. With a pressure roller hardness of approx. 68 Shore, a pressure (on this roller) of 6 to 10 kg has proven to be advantageous. In contrast, with a Shore hardness of 83, a pressure of 10 to 15 kg has proven to be advantageous.

Claims (12)

1. A drafting system for a false twist spinning machine, characterized in that the pair of delivery rollers for deflecting fibers from the conveyor plane is formed and / or operated. 2. A drafting system according to claim 1, characterized in that the contacting surfaces of the rollers of the delivery pair are formed as continuous cylindrical surfaces without interruptions. 3. A drafting system according to one of the preceding claims, characterized in that one of the delivery rollers is relatively soft. 4. A drafting system according to claim 3, characterized in that the relatively soft roller is provided with a cover made of rubber or a synthetic elastomer. 5. A drafting system according to claim 4, characterized in that the rubber cover has a Shore hardness in the range 64 to 68. 6. A drafting system according to one of the preceding claims, characterized in that the rollers are pressed together by such a pressure that at least one roller is slightly deformed at the clamping line. 7. A drafting system according to one of the preceding claims, characterized in that the axial length of the clamping line is between 28 and 32 mm. 8. A drafting system according to one of the preceding claims in combination with a suction nozzle of a false twist spinning device. 9. A stretch value according to claim 8, characterized in that the suction nozzle generates air currents in order to redirect fibers which have been deflected by the rollers in their circumferential directions, and to introduce them into a suction chamber of the nozzle. 10. A false twist spinning process characterized in that the delivery roller pair of a drafting device deflects fibers in the circumferential directions of the rollers and these fibers are redirected by a suction nozzle and applied to a yarn core as winding fibers. 11. A false twist spinning process characterized in that at least one of the rollers of the pair of delivery rollers of a drafting system is slightly deformed in operation to supply fibers to be spun. A nozzle spinning process according to claim 11, characterized in that the deformation of the roll has an influence on the spinning tension after the spinneret.

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