GB2135629A - A spinning installation for synthetic filaments - Google Patents

Abstract

A spinning installation for synthetic filaments includes a blowing box (4) and a spinning shaft (3) which directly adjoins a spinneret (1). The spinning shaft (3) is surrounded at its upper end by the blowing chamber (4) is guided directly up to the spinneret, and in particular the part thereof which is directly adjacent to the spinneret is permeable to air, for example is perforated or pierced or is made of a porous material. Inlet 23 is perpendicular to shaft 3, the shaft is not perforated in the region of inlet 23 and the arrangement is such that the air flow in bore 28 is irrotational and parallel to the shaft. To facilitate the operations at the spinning head, the spinning shaft (3) may be divided in two. The lower part (6) is stationary, while the upper part (7) supporting the 4-blowing chamber (4) may be moved telescopically in the lower part (6). The specification also relates to a filament transporting die 31 comprises three apertures through which tows of filaments may be passed, a compression chamber 41, an inlet for compressed fluid 32 and annular orifices 40 for escape of the fluid. <IMAGE>

Description

SPECIFICATION A spinning installation for synthetic filaments This invention relates to a spinning installation for synthetic filaments comprising a blowing chamber which is connected to the spinnerets, and a spinning shaft.

It is known that the individual filaments which issue in a molten condition from the spinning bores of a spinneret during the spinning operation of synthetic filaments must be cooled not only intensively, but also highly uniformly, because the degree of uniformity of individual threads with respect of the variation coefficient of double refraction depends to a considerable extent in particular on uniform cooling, i.e., cooling which is substantially the same as far as possible for all the individual filaments of a bundle of filaments.

Of the various possible methods of cooling, which is usually carried out by blowing or by means of ambient air which is entrained by the filament bundle central blowing was considered to be particularly suitable, especially for very fast spinning speeds and/or for large numbers of filaments. However, the use of central blowing from the inside or from the outside of a filament bundle has hitherto demanded considerable compromises to be made in its realization, on account of the need for accessibility of the spinnerets for cleaning and changing purposes.

Consequently the ideal all-round blowing remained an ideal, although it has been the subject of a number of proposals. As far as the prior art is concerned with all-round blowing, the cleaning and exchange of spinnerets and the difficulties associated therewith are not mentioned. For example, in one known proposal, cooling air is forcibly guided inside the filament bundle through the centre axis of the individual spinning stations and is blown out radially, perpendicularly to the general direction of filament travel (EP-A 0,050,483).In another proposal (DE-OS 1 941,556), after the filament bundle has passed through a so-called shut-off area which begins at the spinneret and into which no air is blown or conveyed in any other way, it passes into a section of the spinning shaft which is perforated and gives ambient air access to the filament bundle. Since the freshly spun filaments are hardly cooled in the so-called shut-off area, the necessary cooling area is greatly extended until a stable condition is reached and it therefore extends into the region which, with the known adverse consequences, is open to the access of ambient air without an effective possibility of control.

Thus, an object of the present invention is to provide a spinning installation which ensures a regular all-round blowing, protecting in particular freshly-spun filaments.

According to the present invention there is provided a spinning installation for synthetic filaments, comprising a spinning shaft which is connected to a spinneret and is in the form of a pipe, part of the length of which, adjacent to the spinneret, is perforated and penetrates a blowing chamber, wherein the blowing chamber comprises an inlet part and a distributor chamber, a supply channel for a blowing medium runs into the inlet part substantially perpendicularly to the spinning shaft, the spinning shaft is not perforated in the region of the inlet part and the inlet part and the distributor chamber are separated by guide elements for the production of an irrotational flow having an orientation which is parallel to the spinning shaft in the distributor box.

The spinning shaft may advantageously be divided in two, and the upper part of the spinning shaft, emanating from the spinneret, may be moved telescopically with respect to the lower, stationary part.

Attention is to be paid to air tightness in the connection of the upper movable part with the spinning head. Only leakage of air means that the air penetrating inside the spinning shaft receives an upwardly directed flow which then leads to cooling of the spinneret and consequential adverse effects on the spinning. For this reason, first of all the spinning head should be thermally insulated in a suitable manner with respect to the blowing chamber and the spinning shaft.

Secondly, a seal which can be easily opened and closed should be provided between the spinning head and the blowing chamber. This may advantageously be a two-part labyrinth seal which comprises annular grooves on the blowing chamber and rings on the spinning head which extend into the grooves. A particularly effective sealing action is provided if the grooves are filled with a non-evaporating liquid, or preferably with sand. A temperature-resistant glass pipe is preferably also provided in this region, so that it is possible to see inside the spinning shaft.

In order to ensure that the air penetrating inside the perforated part of the spinning shaft definitely receives only a downwards flow, a suction removal device may be provided at the lower stationary end of the spinning shaft. A suction removal device of this type also has advantages if monomers evaporate during spinning, which could lead to a soiling of the spinning shaft.

To prevent the lower part of the spinning shaft from becoming solid by condensing monomers, the lower part of the spinning shaft may be rinsed with water continuously or at certain time intervals, as a result of which a film of water runs down the inside wall of the shaft and is removed by the suction removal device. The risk of monomers condensing exists in particular in the lower stationary part of the shaft where the cooling of the monomers which have evaporated immediately after spinning has progressed to a correspondingly advanced stage.

The present invention proceeds from a prior art as described in, for example US-PS 3,672,801.

In that spinning apparatus for synthetic filaments, a blowing chamber comprising several parts is provided below the spinning head immediately adjoining the spinneret. The part located immediately below the spinneret has double walls. Fine bores positioned in a circle lead out of the closed cavity to which a suction removal device is connected, into the interior and they are used for removing by suction gases which escape, and possibly smoke. The actual blowing chamber is connected to this part and it comprises an external, cylindrical casing and two successive inserts.

The actual blowing part is the part which lies closest to the spinneret. A relatively short cylindrical piece of pipe having a perforated wall has a cylindrical insert consisting of several layers of wire mesh material. An outlet pipe which extends down to the bottom of the blowing chamber is connected to the cylindrical insert and the bottom of this pipe is sealed off by a perforated screen which determines the shape of the issuing filaments bundle. A spinning shaft within the normal sense is not provided. Instead, another perforated screen which may be moved along the filament bundle is provided at some distance from the bottom of the blowing chamber and it is supposed to act as a shaper and guide for the filament bundle. The spinning installation which is described in the U.S. patent does not provide a solution to the problem to which the present invention is directed.

Where, in the preceding description of the present invention and in the following description with reference to the drawings, blowing air or a blowing medium is mentioned, it is to be understood that generally at room temperature is supplied to the blowing chamber in order to cool the individual filaments issuing from the spinneret. However, other gaseous media may also be used, as long as they are suitable for the spinning process, such as in particular an inert gas, for example steam, nitrogen or mixtures of such media with air.

Likewise, the term "cooling" which is used herein is to be understood as meaning that there is a temperature gradient between the temperature of the filaments and the blowing medium, without a qualitive statement being made about the extent of the temperature gradient. Since the blowing chamber and the spinning shaft according to the present invention constitute a substantially closed system, by means of which it is possible to intentionally act on the filaments below the spinneret, it is to be stressed that the spinning installation according to the present invention is suitable not only for cooling the resulting filaments very uniformly to a temperature below the solidification temperature of the polymer melt, but also, on account of its construction, for controlling the temperature while the filaments are being cooled, for example for controlling the course of the cooling process, in order to adhere to certain procedural parameters and, for example to influence the extension behaviour or the crystallinity or the like of the filaments.

The present invention will now be described in more detail with reference to the accompanying drawings, in which: Fig. 1 schematically shows a section along the axis of the spinning shaft; Fig. 2 shows a view of the blowing chamber and a supporting device; and Fig. 3 to 5 show a pressure chamber of a filament-transporting die in, respectively, a sectional view, a top view of the pressure chamber closed, and a top view of the pressure chamber open.

Fig. 6 and 6a are vertical sections through a connection for connecting the blowing chamber to the spinning head; and Figs. 7 and 8 show two forms of the lower portion of the spinning shaft.

The spinning shaft 3 which extends in the extrusion direction of the filaments 2, i.e, usually vertically downwards, is directly connected to the spinneret 1. At its upper part which commences in the immediate vicinity of the spinneret 1 , the shaft 3 is surrounded by a blowing chamber 4 with an air supply 5. In the embodiment shown, the spinning shaft 3 is divided into a lower, stationary part 6 and an upper part 7 which may move telescopically inside the part 6. The movable part 7 of the spinning shaft 3 is permeable to air, for example it is perforated, pierced or made of a porous material, in the region which is directly adjacent to the spinneret.

The air-permeability is restricted to the part extending inside a distributor chamber 28 of the blowing chamber 4, but it may also be provided below the inlet part 27 over the complete length of the part 7 of the spinning shaft or over a substantial length thereof. If necessary, it may also include an adjoining section of the stationary part 6 of the shaft. It is important that the spinning shaft is not perforated in the region of the inlet part. Only by this means is it possible to achieve non-turbulent laminar flow of air in the shaft.

The stationary part 6 of the spinning shaft 3 passes through the scaffold-or storey base 8 to which it is anchored by means of a suitable construction 9 and from which the spinning stations are usually serviced. The movable part 7 of the spinning shaft sits with its upper part adjoining the spinneret 1 in the blowing chamber 4 and is connected thereto by a flange 10 to produce a single unit. The blowing chamber 4 and the spinning shaft 3 are suspended on a supporting device comprising a supporting arm 11 and a guide block 12. A slide bar 13 is- used for guiding the block 12 and, in the embodiment shown, is a vertical column 13 which is embraced by the block 1 2. The bar is anchored to the base 8, and in this case is also connected by means of a tie-bar 14, a wall 1 5 of the building which is indicated. Two deflection rollers 1 6 and 1 7 are positioned on the tie-bar 1 4 and a cable 1 9 connecting a counterweight 1 8 to the guide block 12 runs over these roller 1 6 and 17.

Fig. 2 shows a view of the top of the blowing chamber 4 which is positioned adjacent the spinneret 1. Unlike Fig. 1, in this case the supporting device 11, 1 2 is positioned together with the air supply 5 on one side, which corresponds to an arrangement which is conventional for most cases of use. Although the arrangement in Fig. 1 was selected primarily for its greater clarity, it also represents a suitable embodiment for a number of cases.

During a spinning operation, the blowing chamber 4 is connected, together with the spinning shaft 3, to counter flanges 21 of the spinning head 22 by means of its flange 20.

Fig. 6 shows a suitable connection. As shown in Fig. 6 the flange 20 to which the blowing box 4 and the porous spinning shaft 3 are attached, is provided with an annular groove 47. An insulating piece 46 is positioned first of all on the counter flange 21 of the spinning head 22, thereby to inhibit the transfer of heat from the spinning shaft or blowing chamber, to the spinneret. A ring 48 sits on the insulating piece and extends into the groove 47. The groove may be filled with a suitable flowable material. This may be a nonevaporating liquid, but is preferably sand. As a result of this, the inside of the spinning shaft is sealed off, without preventing movement of the spinning shaft 3 with the blowing chamber 4. The ring 48 may consist of temperature-resistant glass, so that it is possible to check inside the shaft visually.This is shown in the detailed view of Fig. 6a.

The blowing chamber is supplied with blowing air through the air supply line 5 which discharges into the conically widened inlet part 23 which sits on the blowing chamber 4. The air supply 5 preferably also has in the vicinity of the blowing chamber a quick-release connection, for example a flange connection 24, 25. Once the two connections 20, 21 and 24 and 25 have been released, in the embodiment shown in Figures 1 and 2, the movable part 7 of the spinning shaft may be pushed manually into the stationary part 6 of the shaft 3 against the action of the counterweight 18, whereafter the individual spinning stations are easily accessible. The part 7 of the spinning shaft may also be moved in and out by other means, for example by a reversible motor drive, or by a hydraulic or pneumatic drive.

The above described design of the spinning shaft 3 and blowing chamber 4, means that the filaments 2 are shielded from the ambient atmosphere in a region in which they are most sensitive and they are cooled exclusively by the prepared air which is introduced by means of the air supply device 5, 23 into the blowing chamber 4, and from there through the air-permeable wall of the spinning shaft part 7 onto the filaments 2. During this procedure, the air flow is stabilized, in particular by a sieve-shaped insert 26 between the inlet part 27 and the outlet part 28 of the blowing chamber 4, so that an irrotational flow prevails without pressure fluctuations in the outlet part 28. The cooling air may then travel along the filament path and issue through the perforations in the spinning shaft.

Fig. 7 shows the form of the lower, stationary part 6 of the shaft. In its upper region, the part 6 has an annular nozzle 53 through which a layer of water is guided onto the inner surface of the shaft part 6 from a connection line 51 and an annular channel 52. The layer of water is removed by suction at the lower end of the part 6 through an annular channel and an annular nozzle 50, together with the cooling air and evaporated monomers.

In the embodiment according to Fig. 8, the lower end of the part 6 of the shaft is open. Below the shaft, there is located an obliquely positioned sheet 55 which has a narrow filament slot 56.

The cooling air, and also the water which may be introduced into the spinning shaft through the connection 51, the annular channel 52 and the annular nozzle 53 is deflected laterally by these sheets and removed by suction at this point by suction removal devices 57 having a suction connection 58. Reference numeral 59 indicates a filter through which condensing monomers in particular are filtered from the outgoing air.

As already mentioned, other gaseous or vaporous blowing media instead of air may be supplied through the blowing chamber, for example steam or like. These media may be at room temperature or at a substantially higher temperature, for example above 1000C.

Consequently, the cooling rate may be influenced in the blowing shaft and specific procedural parameters which are favourable with respect to the properties of the filaments may be produced.

Fig. 3 shows a longitudinal section, taken on line Ill-Ill in Fig. 4, through the pressure chamber of a filament-transporting die 31, the connection 32 of which is joined to a source (not shown) of a medium, for example compressed air. The die 31 creates an air-jet which transports the material being extended by the spinneret at the start of spinning of the exit of the spinning shaft. There it can be caught by hand and pulled to the first godet or winder, whereafter the die 31 no longer needs to operate. The pressure box of the die 31 which comprises a lower cover 33 and an upper cover 34 has holes 35 and 36 which align with one another and each form a passage for a filament bundle 2. The cross section of the holes 35 and 36 substantially corresponds to the cross section of the spinning shaft 3 (or 7 respectively).

A ring 37 having a nozzle lip 38 is inserted into the hole 35 of the lower cover 33. The ring 37 lies on a sealing ring 39. The nozzle lips 38, together with the inside surface of the upper cover 34 form an annular nozzle gap 40 which is from 0.1 to 0.5 mm wide, preferably 0.25 mm wide. The ring 37 is surrounded by an annular chamber 41. Figs. 3 and 5).

Fig. 4 shows a top view of the upper cover 34 or of the closed pressure chamber 33, 34. The inner boundary of the rings 37 may be seen in each case in the holes 36 in the upper cover 34.

Fig. 5 shows a top view of the lower cover 33 (the cover 34 having been removed). The pressure chamber has holes for transporting three filament bundles. The encircling stepped edge 42 of each hole forms annular chambers 41 with the outer surface of each of the rings 37 inserted into the hole. Annular chambers 41 are charged with the compressed medium, in particular compressed air, through channels 45, 44, 43.

Adjacent annular chambers 41 overlap to some extent over sections of their circumference.

The annular chambers 41 are connected to longitudinal channels 44 via cross channels 43, and the longitudinal channels 44 are connected to a compressed medium connection 32 by means of channels 45.

The compressed medium which enters the annular chamber 41 through the connection 32 and the channels 45, 44 and 43 in each case through the nozzle gap 40 formed by the annular nozzle lip 38 and the inside surface of the upper cover 34, along the inside wall of the ring 37 in an axial, downwards direction. The nozzle lips 38 are shaped so that the flow of the compressed medium substantially clings to the inside wall of the ring 37. As this takes place, the beginnings of filaments issuing from the spinnerets 1 are carried along downwards.

In Figs. 3 to 5, the die 31 has three transporting devices. However, the nozzle 31 may have more or less than three devices for transporting filaments, depending on the number of spinnerets in a spinning installation. The die 31 may be positioned at the inlet or at the outlet of the distributor box 28 (Fig. 1).

It is to be mentioned in connection with the previously described die 31 that this die 31 may be used as an additional means for controlling the process during the spinning operation. In addition to the compressed medium connection, the pressure box may also have other connections through which processing agents, preferably cooling agents within the meaning of the above definition, may be introduced into the blowing shaft in order to influence the cooling rate of the filaments, the crystallation of the polymer, or the like. In the case of a substantially closed blowing system, this presents an additional possibility for controlling certain procedural parameters of the spinning process at a spacing from the spinneret openings where the surface of the filaments is already at a temperature which, depending on the spacing of the die 31 from the spinnerets 1, is substantially lower than the spinning temperature, but, if appropriate, is still above the freezing temperature.

Claims (9)

1. A spinning installation for synthetic filaments comprising a spinning shaft which is connected to a spinneret and is in the form of a pipe, part of the length of which, adjacent to the spinneret, is perforated and penetrates a blowing chamber, wherein the blowing chamber comprises an inlet part and a distributor chamber, a supply channel for a blowing medium runs into the inlet part substantially perpendicularly to the spinning shaft, the spinning shaft is not perforated in the region of the inlet part, and the inlet part and the distributor chamber are separated by guide elements for the production of an irrotational flow having an orientation which is parallel to the spinning shaft in the distributor box.

2. A spinning installation according to claim 1, wherein the inlet channel into the blowing chamber is located below the distributor box.

3. A spinning installation according to claim 1 or 2, wherein the spinning shaft is divided into an upper part which is telescopically movable with respect to a lower stationary part, the upper part being connected in an air-tight manner to the spinning head by an annular labyrinth, preferably an annular labyrinth which is filled with a liquid or with sand.

4. A spinning installation according to claim 3, wherein the annular labyrinth is filled with a liquid or with sand.

5. A spinning installation according to any preceding claim, wherein the blowing chamber is provided with a filament transporting die which comprises a pressure chamber which is connected to a source of compressed medium, the pressure box having upper and lower covers which are provided with holes defining passages substantially corresponding to the cross section of the spinning shaft, the passages towards the inside of the chamber between the upper and lower covers being sealed by rings such that the rings form a circular nozzle lip with a downwardly directed flow of the compressed medium.

6. A spinning installation according to claim 5, wherein the source of compressed medium is a source of compressed air.

7. A spinning installation substantially as herein described with reference to Figures 1, 2, 6, 6a, 7 and 8 of the accompanying drawings.

8. A filament-transporting die for transportive filaments in spinning installations, which comprises a pressure chamber which is connected to a source of compressed medium, the pressure box having upper and lower covers which are provided with holes defining passages substantially corresponding to the cross section of the spinning shaft, the passages towards the inside of the chamber between the upper and lower cover being sealed by rings such that the rings form a circular nozzle lip with a downwardly directed flow of the compressed medium.

9. A die according to claim 8, wherein the source of compressed medium is a source of compressed air.

1 0. A filament-transporting die substantially as herein described with reference to Figures 3 to 5 of the accompanying drawings.