Cooling filament yarns

Abstract

 A filament spinning installation conventionally comprises a cooling chute to receive filaments from a spinneret and a blower for directing a stream of cooling air across the path of movement of the filaments in the chute. The filaments are mutually spaced in an array until they have solidified to a degree permitting collection to a thread and contact with devices for further processing of the thread. In a chute according to the invention, at least one element is provided to lead air from a location in the vicinity of the filament array to the exterior of the chute by diverting the air flow into a direction transverse to the length of the chute.

Description

[0001] The present invention relates to cooling of filament yarn immediately following extrusion of molten polymer through a spinneret to form filaments.

State of the Art

[0002] It is standard practice to cool filament,yarn by subjecting it to a flow of air as the yarn is transported vertically downwardly away from the spinneret. The yarn is usually enclosed within a protected space (a "chute") while it is cooling. In the configuration most frequently used in practice, the stream of cooling air is intended to flow transversely across the upper part of the path of movement of the yarn. In practice, some of the cooling air is carried along in the direction of movement of the yarn and the amount of air dragged along with the yarn in this way increases as a function of the delivery speed of the yarn. This can lead to multiple problems in the lower part of the cooling chute, which problems have been recognised in Barmag US 5433591 and Crown Zellerbach US 4472886. In both cases, means is provided to remove air from the immediate neighbourhood of the yarn moving away from the spinneret, the arrangement shown in US 5433591 being especially relevant as the predecessor to the present invention.

[0003] The arrangements according to US 5433591 will be described in some detail below with reference to Figure 1; accordingly, a detailed description is superfluous here.

[0004] In contrast to the prior art, the present invention enables air to be stripped from newly-spun filaments and removed from the cooling chute before the filaments have been collected to a yarn or thread, e.g. by means of a convergence guide. This enables an increase in the quantity of cooling air fed to the filaments upstream from the stripping device. In one arrangement according to the invention, the air stripping means itself is designed to fulfil, at least partly, the function of the convergence guide, for example by converting a filament array into a ribbon form.

[0005] The invention therefore provides both a new installation for spinning filaments, and a new method of cooling newly-spun filaments. In one embodiment, the invention provides a portion of a chute structure particularly adapted for use in an installation and/or method according to the invention.

[0006] Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1

shows a schematic front elevation of a conventional installation for production of filament yarn;

Figure 2

shows a side elevation of the same installation;

Figure 3

is a schematic representation of the thread path immediately following the spinneret;

Figure 4

shows a schematic elevation of a cooling chute of the kind illustrated in Figure 4 of US 5433591;

Figure 5

shows a diagrammatic sectioned elevation of a first embodiment of the present invention;

Figure 6

shows a detail of a first modification of the device shown in Fig. 5;

Figure 7

shows a schematic view in section a second modification of the device shown in Fig. 5;

Figure 8

shows a view similar to Figure 5 of a second embodiment of the invention;

Prior Art

[0007] The installation shown schematically in Figs. 1 and 2 comprises an extruder 10 with an infeed 12 for raw material, e.g. polymer in the form of chips. The raw material is converted by the extruder 10 to a molten polymer mass which is supplied at high pressure to a spin beam 14, for example as shown in US 5601856, where it is distributed between spin packs for example as shown in US 5662947. Each spin pack comprises a spinneret, indicated diagrammatically at 15 in Fig. 3, through which the polymer is extruded continuously and vertically downwardly in the form of a multiplicity of individual filaments 17; the number of filaments shown in Fig. 3 is symbolic only. The polymer forming the filaments 17 leaves the spinneret in a molten, fluid, state. The individual streams emerging from the spinneret are mutually spaced in an array predetermined by the arrangement of holes (not shown) in the spinneret, so that the filaments do not come into contact with each other while the polymer is still in this highly fluid state. At some point, however, as indicated diagrammatically at C (convergence point) in Fig. 3, the individual filaments 17 are brought together to form a yarn or thread.

[0008] Referring once again to Fig. 1 and 2, the downwardly moving streams of molten polymer pass from the spinneret into a protective enclosure 16. In the upper region 18 of this enclosure the streams are subjected to a flow of cooling air which is blown transversely across the vertical movement path of the polymer. Arrangements of this kind are discussed for example in Chemiefasern/Textil-Industrie, April 1978, pages 315 to 323, and examples of chute designs for this purpose are shown in DE-B-3318096 and DE-A- 3414602. The filaments continue downwardly within the enclosure 16 until they have cooled and solidified to such a degree that the individual filaments can be collected together, as previously described, and the whole filament assembly can be further processed as a yarn or thread without deterioration in filament quality, especially without filament damage. Such further processing takes place in an installation of the type shown in Fig. 1 and 2 in the machines diagrammatically indicated at 20, but these particular machines are shown by way of example only. Each processing machine should in any event include a winder to take up each yarn or thread to form a package (not shown - see for example US 6059217).

[0009] The length of the chute 16 from the spinneret to the further processing machines is also not necessarily as shown in the example of Figs. 1 and 2. The present invention relates specifically to the configuration of this chute and will be described in the following paragraphs by comparison with the closest prior art, namely a chute according to US 5433591 as shown in Fig. 4.

[0010] It is well-known that the "bundle" of filaments travelling along the chute drags air downwardly from the region 18 (Fig. 1 and 2). This effect tends to increase with the linear speed of the filaments, which are therefore "accompanied" in their travel by a layer of already heated air. The apparatus shown in Figure 4 is designed to divert hot air from a "yarn" 24 made up of spun filaments as the filaments travel downwardly, as indicated by arrow P, in a cooling chute 40. Chute 40 comprises a casing 42 having a rectangular cross-section with side walls that converge towards the lower end of the chute. Two opposite side walls 44, 46 are each formed with parallel slots 48a to 48f which are arranged in pairs, each pair comprising a slot in the wall 44 and an opposite slot in the wall 46.

[0011] Located at the lower edge of each slot 48 is a hinge 50a to 50f, each hinge carrying a respective sheet-like baffle or air-deflecting element 52a to 52f. These baffles are pivotable on their respective hinges between their operating positions, shown in full lines, and respective threading-up positions shown in dotted lines. When the baffles are in this latter position, a yarn 24 can be passed through the chute (threaded-up) without difficulty.

[0012] As described in US 5433591, each sheet-like element 52 is preferably bent at its edge remote from the hinge 50, so that when the baffle is in its operating position the bent portion of the edge is aligned with yarn 24 substantially parallel and close thereto. This portion serves to divert the hot air from the yarn 24 advancing in the direction of the arrow P - the diverted air exits the casing 42 through slots 48. Openings 56a, 56b, 56c are provided in the end walls joining side walls 44,46 to permit fresh cooling air to enter the chute downstream from each pair of baffles 52. According to the description in US 5433591 this fresh cooling air is diverted by the pair of sheet-like elements 52 following next in direction of yarn advance, and is then discharged through the corresponding slots 48. As illustrated, this procedure is repeated altogether three times and the air supplied through the last opening 56 is discharged with the cooled yarn 24 through opening 58 in the bottom of the chute. According to US 5433591, the exchange of air surrounding the yarn makes it possible to shorten the conventional length of the yarn chute without reducing its cooling capacity.

[0013] As indicated above, US 5433591 describes the body of filaments as a "yarn" 24 and it must be assumed that this yarn is illustrated below the point of convergence C (Fig. 3) of the individual filaments. This seems to be confirmed by the other figures in US 5433591, but those figures have not been shown here because they do not assist an understanding of the present invention. The embodiment illustrated here in Figure 4 appears to be shown in US 5433591 in contrast with another embodiment in which the point of convergence of the filaments is located downstream from the air diverters. However, that other embodiment does not use simple diverter plates, but rather a relatively complex set of coaxial tubes, which do not appear to remove the air from the interior of the chute.

First embodiment of the invention (Fig. 5)

[0014] Fig. 5 shows schematically an array of filaments travelling downwardly (arrow P) in a protective structure having a rectangular cross-section with long walls 60, 62 (illustrated in section) and side walls 64, only one of which is visible in Fig. 5. These walls together form an open-ended structure 65, having a downstream end 66. The schematic illustration in Fig. 5 shows only one central filament 17C and the filaments 17E occupying opposite edges of the array as viewed in the figure. It will be understood that many other, mutually spaced, filaments are present in the array (or bundle) between the edge filaments 17E. It is to be noted, therefore, that the array of filaments has not been collected to form a yarn before it leaves the structure 65. The point of convergence (C, Fig. 3) is not shown in Fig. 5 but could be anywhere downstream from the illustrated structure.

[0015] The protective structure is fitted with two air diverter elements formed in this example by plates 68, 70, each connected by means of a respective hinge 69 to a respective wall 60, 62. The width of each plate is preferably equal to the width of the corresponding wall 60, 62. The plates can be pivoted between operative positions shown in Fig. 5 and threading positions (not shown) parallel to the walls 60, 62. In this respect, they resemble closely the elements 52 shown in Fig. 4. When the plates are in their operative positions as shown, the inner edges of the plates lie close to the outer filaments of the array but without touching those filaments. As viewed in section, each plate extends downwardly at an angle from its inner edge to its respective hinge 69, as shown also for the elements 52 in Fig. 4. As illustrated, the inner edges of the plates can have upwardly projecting extensions (not specially referenced) parallel to the direction or path of movement P of the filaments, but this is not essential. Each plate is so designed that air stripped from the vicinity of the array will be directed downwardly and outwardly to the associated hinge 69 where it can exit the structure 65 by way of a respective slot-opening 72 in the wall 60 or 62 respectively.

[0016] In the preferred arrangement, the uppermost edges of the plates 68, 70 are spaced vertically along the path P, as illustrated diagramatically by the spacing S in Fig. 5. The arrangement therefore gives a first location, on one side of the array, at which air is removed from the boundary layers which lie adjacent and are dragged along with the outer filaments, and a second location, on the other side of the array where a similar air stripping and diverting action takes place. In the preferred arrangement, these two locations are spaced along the path so that boundary air is removed firstly from one side and then from the other side of the array. The spacing S preferably lies in the range 5 to 500 mm. The provision of this spacing can assist substantially in reducing turbulence within the chute structure.

[0017] In the detail shown in Fig. 6, portions of the plates 68A, 70A are viewed from above, i.e. in the direction movement P. As seen in Fig. 6, these plates 68A and 70A overlap at their inner edges 74, 76, but plate 68A is formed at its inner edge 74 with a cut-out 78 forming a passage through which the filaments (not shown) can pass. Of course, the two plates could each be provided with a cut-out secton, these sections being aligned to provide the required filament passage when the plates are in their operative positions. In the modification illustrated schematically in Fig. 7, the plate 70B is shaped approximately as an aerofoil when viewed in section. This streamlined shape improves flow of diverted air without turbulence until it has left the chute structure 65. Obviously, both plates 68 and 70 can have this form.

[0018] The device shown in Figs. 5 and 6 fulfils the function previously described for Fig. 4, i.e. it enables removal of heated air from the environment of the filaments. It differs from Fig. 4 in that this function is carried out at a point upstream from the convergence point C (Fig. 3). It would be advantageous to locate the point of convergence in such a position relative to the diverter plates that the array of filaments takes on a fan-shaped (substantially two-dimensional) form in the region of the diverter plates. However, this will not usually be achievable, so that the array will normally still occupy a three-dimensional space in the region of the diverter plates.

[0019] In any event, the air removal function is now performed by only one pair of plates and there is no feed of fresh cooling air following the air removal step. The stream of air that passes plates 68, 70 with the filaments continues to flow along the path P and leaves the structure 65 at its lower, open end 66. This end 66 can be spaced much further from the diverter plates than the symbolic spacing shown in Fig.5; the optimal position of the diverter plates relative to the end of the chute is dependent on the thread speed and can be established empirically. The device proposed here also enables a reduction in turbulence in the chute, as also suggested in US 5433591.

[0020] In addition, the invention enables a considerable increase in the quantity of cooling air that can be fed to the upper region 18 (Fig. 1 and 2) of the cooling chute. By means of a cooling chute according to the invention, it is possible, for example, to increase the quantity of cooling air, relative to conventional chutes for the same purpose, by up to 30%. In conventional arrangements, the quantity of cooling air fed to the upper region 18 is limited by the tendency of the filaments to drag this air along with them through the chute - the greater the quantity of air blown across the path P in the region 18, the greater the quantity of air that is dragged downwardly by the filaments into the chute.

[0021] The quantity of air dragged downwardly with the filaments is also a function of the threadline speed. In order to obtain specified filament yarn characteristics (e.g. tensile strength, extensibilty etc.), it is desirable to be able to select threadline speed and quantity of cooling air independently of each other. However, turbulence within the lower portions of the chute structure normally sets an upper limit to the cooling air quantity that can be fed in at the upper end of the chute. The additional air carried along by the filaments is superfluous within the chute, causes the previously mentioned turbulence problems and increases the difficulty of designing an optimum chute configuration.

Second Embodiment (Fig. 8)

[0022] In view of the detailed explanation of the first embodiment, many features of the second embodiment will be clear from the illustration in Fig. 8 without extensive description. The same reference numerals have been used as far as possible in Figs. 5 and 8, and the additional description of Fig. 8 will concentrate on the differences between the two embodiments. In Fig. 8, there is only one diverter plate 90 having an inner edge (not specially indicated) that is in contact with the filaments. Downstream from the plate 90, the filaments are drawn away under at least slight tension. The array of filaments 92 is thus converted at least to a ribbon form in the region in which the filaments are brought into engagement with the plate edge, provided the filaments are free to spread out along the edge of the plate 90. If the free edge of plate 90 is formed with a confining means (not shown) for restricting spread of the filaments, then this confining means can function effectively as a thread guiding means and the filaments are then collected into a yarn. However, normally there will be no additional confining means. The portion of the plate 90 contacted by the filaments can in any event be made of or coated with a wear-resistant material e.g. ceramic (or a diamond-like carbon - "DLC" - coating). The surface contacted by the filaments should also resist accumulation of deposits, e.g. of monomer. It should be self-cleaning under contact with the filaments. Further, in an advantageous modification, the air diverter structure can be adapted to apply spin finish to the filaments in contact with it.

[0023] As in the case of the embodiment shown in Fig. 5, air is stripped from the array and removed from the chute via an opening 72 upstream from the convergence point, but in this case the stripping function immediately adjoins the convergence point C. This can have the advantage that air is squeezed out of the interior of the filament array and is immediately diverted out of the chute.The plate 90 shown in Fig. 8 is simply triangular in section, but could clearly be formed as an aerofoil, similar to the plate 70B in Fig. 7 Clearly, also, more than one diverter plate could be provided in an arrangement in which one such plate acts as a convergence guide.

[0024] The wall or walls providing the protective enclosure are not necessarily configured to define a chute of rectangular cross-section. Normally these walls will be constructed of light sheet metal, but any other material providing adequate isolation of the chute interior from the surrounding environment can be used. The chute can be closed at its lower end in the same way as the prior art chute shown in Fig. 4, but the open-ended structure is preferred because it facilitates threading-up and does not present an end surface on which deposits can accumulate. The chute can in any event have a convergent configuration in the downstream direction, as also shown in the prior art.

[0025] The air diverter unit or module shown in Fig. 5 and/or Fig. 8 can make up a portion of an elongated chute structure like the structure 16 shown in Figs. 1 and 2. The prefabricated unit can be assembled with other sections to make up the complete chute. Alternatively, the air diverter plates can be built into an otherwise conventional chute structure. The chute structure can have a length in the range 2 to 15 metres.

Claims

1. Filament spinning installation comprising

- a device for forming an array of filaments which can be collected to form a yarn;

- an elongated structure defining a protected space to receive said filaments vertically below said device;

- means for directing a stream of cooling air across the path of movement of the filaments,

characterised in that

- at least one element is provided to lead air from a location in the vicinity of the filament array to the exterior of the structure by diverting it in a direction transverse to the length of the structure.

2. Installation as claimed in claim 1 characterised in that said element has a streamlined cross-section adapted to induce a predetermined airflow pattern, e.g. an aerofoil shape.

3. Installation as claimed in claim 1 or claim 2 characterised in that said element has a portion which forms a convergence guide enabling collection of the filaments to form a yarn.

4. Installation as claimed in claim 3 characterised in that the portion is made of or coated with a wear-resistant material, e.g. ceramic or a diamond-like carbon (DLC) material.

5. Installation as claimed in claim 1 or claim 2 characterised by a convergence guide downstream from said element.

6. Installation as claimed in any one of claims 1 to 5 characterised in that a second element is provided to lead air from a second location in the vicinity of the filament array to the exterior of the structure by diverting it in another direction transverse to the length of the structure.

7. Installation as claimed in claim 6 characterised in that the structure is open-ended and the elements are so arranged that, in use, air travelling with the filaments beyond the second element must leave the structure by way of the downstream open end of the structure.

8. Installation as claimed in claim 6 or 7, characterised in that at least one (and preferably each) element is movable between an operable condition in which it can lead air away from the filament array and an inoperable condition spaced away from the path of movement of the filaments.

9. Installation as claimed in any one of claims 6 to 8, characterised in that the first and second locations are disposed on opposite sides of said path.

10. Installation as claimed in any one of claims 6 to 9, characterised in that the first and second locations are spaced longitudinally along the path.

11. Installation as claimed in any one of claims 6 to 10, characterised in that the first and second elements overlap when viewed along the path and at least one element has a cut-away portion to enable free passage of the filaments.

12. A method of cooling newly-spun filaments comprising the step of stripping air from the immediate vicinity of the array of filaments at or upstream from the convergence point of the array.

13. A portion of a chute structure for use in an installation as defined in claim 1 characterised in that the said portion of the chute structure includes an element adapted to form a point of convergence for a filament array within the chute and also adapted to lead air diverted from the array to the exterior of the chute portion.

Drawing