EP0515762A1 - Process for centrifugal spinning - Google Patents

Abstract

The thread leaving a drawing train (1, 2) is guided into a centrifugal spinning can (20). Once a particular length of thread has accumulated against the wall of this can, the thread is cut by a cutting member (11, 13, 14) and the end, freed in this way, of the length of thread which is in the can (20) is driven by a nozzle (35), supplied with compressed air and arranged in an extraction member (22), into a discharge conduit (33) terminating at a storage bobbin (41). As regards the other end which is no longer connected to the twist induced in the can (20), a pretwist is imparted to it at the same time as a pull by a helical airflow generated in the feed member (4) by compressed air admitted through an orifice (10) and issuing into a channel (5) for the entry of the thread through nozzles (8) inclined relative to the axis of this channel and opening into it tangentially. The cutting member (11, 13, 14) blocks the passage of air in the branch (6), and its passage (14) guides the air towards the can (21) by way of the branch (7), thereby driving the thread with it. This cycle is subsequently repeated indefinitely. <IMAGE>

Description

The present invention relates to a centrifugal spinning process in which the bundle of fibers produced from a drawing train is deposited against the lateral face of a pot driven in rotation, the bundle is cut upstream of this pot as soon as 'a certain length of wire is accumulated against this wall, one directs one of the cut ends, forming the end of this length of wire thus accumulated towards a storage reel and one directs the other cut end against the lateral face of a second pot driven in rotation, the beam is cut again as soon as a certain length of wire is accumulated against the side wall of this second pot and this cycle is repeated continuously.

Centrifugal spinning is a spinning process the idea of which was proposed by a certain de Feranti in 1904 already. The advantage of this spinning mode lies essentially in the fact that it avoids the friction problems of the continuous ring-cursor system and can therefore reach much higher speeds with excellent quality of the thread.

The disadvantage of this process comes from the fact that it is not possible to work continuously since the pot must be emptied periodically. To avoid an interruption of the process during the evacuation of the wire produced in this pot, and a considerable reduction in the yield, it has been proposed to have two pots per spinning unit, so as to fill the second pot while we empty the first pot and vice versa.

A device intended to implement this spinning process using two pots per spinning unit has been described in US Pat. No. 3,343,358. To this end, this device comprises a fiber bundle supply conduit which has two branches, each of which leads to a pot. Each branch includes a beam cutting device and pneumatic means are intended to direct a cut end into the other branch while other pneumatic means send the other cut end forming the end. of the length of wire formed in the first pot, in a discharge conduit which leads to a winding device.

With this spinning mode, the wire is twisted in two phases: when it enters the pot and when it leaves it. It follows that the wire in the pot has about 50-60% of the final twist. As a result, the torsion induced during the first phase being lower than that induced with the ring-cursor process for example, the torsion rises less along the yarn and the lack of cohesion between the fibers does not allow general not to ensure the continuity of the process, which partly explains why this process has no industrial application, despite the fact that it makes it possible to obtain a high quality yarn at a high production speed due to the fact that 'it eliminates the friction problems of the ring-cursor system.

Another still unsolved problem of this spinning mode comes from the fact that as soon as one cuts the bundle of fibers to change the pot, the end thus freed which one must bring to the second pot loses all its twist , no longer attached to the wire which is in the pot and the fibers of the stretched ribbon leaving the stretching train which are absolutely parallel are therefore not capable of withstanding the traction necessary to bring this end into the second pot. As a result, the spinning process is interrupted at each change of pot and since the length of yarn that can be accumulated in a pot is relatively small, interruptions are frequent. This is undoubtedly another reason for which this spinning process has not been industrially implemented even though its principle dates back almost a century.

Pneumatic air jet spinning is another spinning mode that has been talked about for a while as a very promising system, particularly in terms of productivity. We find a schematic diagram of this process in an article published in No 5/1989 of Meilland Textilberichte - page 324 - figure 4. According to this process, the bundle of fibers formed at the exit of the stretching train is taken in a first vortex helical directed in one direction then in a second vortex holicoïdal directed in opposite direction. When we examine the structure of the wire produced by this process, we notice that the twist affects only a surface layer of the wire, while the fibers of the core remain parallel and therefore do not participate in the resistance wire, as shown in Figure 3 - page 318 of the same number of the "Meilland" mentioned above and explained on this same page.

The object of the present invention is to remedy the drawbacks of the above-mentioned spinning methods.

To this end, the subject of this invention is a centrifugal spinning process according to claim 1, as well as a spinning loom, according to claim 2.

This process makes it possible to induce a pretortion on the bundle of fibers leaving the stretching train, sufficient to bring it into the spinning pots where it receives the real twist. This process also makes it possible to pass the bundle of fibers from one pot to another, despite the cutting of the bundle which must occur to allow this change of pot and thus eliminates the connection between the bundle of fibers leaving the drawing train and the means that communicate part of its twist to it. Thanks to this process, there is therefore no break in the spinning despite the break in the bundle and the pretortion communicated to it is sufficient to bring the released end of the bundle into the other pot, where the centrifugal spinning process takes place. continues. Given the fact that in the first phase, the wire receives only about 60% of its total twist, this pretorsion is also essential to add to the twist that goes up the wire from the pot and communicate it sufficient cohesion to allow it to pass from the outlet of the drawing train to the centrifugal spinning pots without breaking. It should also be noted that, unlike the air jet spinning system, the thread is constantly twisted in the same direction so that the twist affects all of the fibers making up the thread.

The accompanying drawing illustrates, schematically and by way of example, an embodiment and a variant of the spinning loom for the implementation of the process which is the subject of the invention.

Figure 1 is an elevational view partially in section of this spinning device.

FIG. 2 is a sectional view along line II-II of a detail in FIG. 1.

FIG. 3 is an enlarged partial view of FIG. 1.

FIG. 4 is a partial enlarged view of a detail of FIG. 3.

Figure 5 is a perspective view of a spinning device similar to that of Figure 1 with formation of a continuous wire and winding of this wire.

The portion of spinning loom illustrated in FIG. 1 represents only a centrifugal spinning unit of a spinning loom. Only the parts necessary for understanding the invention have been illustrated without regard to the drive mechanisms which are well known to those skilled in the art.

The device which is part of a spinning loom comprises a pair of rollers 1, 2 for feeding the bundle of fibers. One of these rollers 2 is integral with a drive shaft 3 driven in rotation by the motor mechanism of the spinning loom. Advantageously, the rollers 1 and 2 constitute the last pair of rollers of a drawing train (not shown).

At the exit of the stretching train, the bundle of fibers enters a feed member 4, a section of which is illustrated in FIG. 2. This feed member comprises a duct 5 whose inlet is conical for receiving the bundle of fibers leaving the stretching train and which is divided into two branches 6 and 7.

Four nozzles 8 open tangentially along the duct 5. These nozzles 8 communicate with an annular supply channel 9 which itself communicates with the outside via an opening 10 intended to connect the nozzles 8 to a source of pressurized air (not shown). As illustrated in FIG. 1, these nozzles 8 are inclined relative to the axis of the conduit 5. Taking into account this inclination and the fact that these nozzles open tangentially in the conduit 5, they induce in this conduit a helical flow directing towards branches 6 and 7.

A drawer 11 is slidably mounted in a housing 12 of the supply member. This drawer has two passages 13 and 14 which are arranged so as to connect the conduit 5 respectively with the conduits 6 and 7, in the two limit positions that the drawer can occupy in the housing 12. Two openings 15 and 16 are formed respectively at the two ends of the housing 12 for connecting it by two separate supply lines 17 respectively 18 selectively to a source of pressurized air (not shown) via a control valve 19, so that the drawer 11 can be moved between its two limit positions to connect the duct 5 either with the duct 6 or with the duct 7. It should be noted that the space separating the entries from the passages 13 and 14 of the drawer 11 is slightly less than the diameters of the duct 5 so that by moving the slide 11 between its two positions, the pressurized air can still flow in the conduits 6 and 7 and is not discharged against the current in the conduit 5, this which would interrupt the spinning process.

By moving the slide 11 from one to the other limit position, the edges of the inlet openings of the passages 13 and 14 move relative to the outlet opening of the duct 5 which allows the fiber bundle to be sheared . On the contrary, the face of the drawer 11 located between the outlets of the passages 13 and 14 provides a clearance 11a with the wall of the housing 12 to avoid pinching the end of the bundle of fibers which has been cut.

As illustrated in FIG. 1, each branch 6 and 7 leads to a centrifugal spinning pot 20 respectively 21 passing through an extraction member 22 respectively 23. These pots are driven in rotation by means (not shown). The tubular parts 24 respectively 25 leading to the extraction members 22, 23 in the respective pots 20 and 21 is surrounded by a telescopic tube 26 respectively 27. These telescopic tubes are integral with a support 28 driven in an alternating vertical movement as indicated by the double arrows F, by a drive mechanism of the machine (not shown). The lower ends of these telescopic tubes 26, 27 are therefore displaced along the longitudinal axes of the centrifugal spinning pots 20, respectively 21, in order to distribute the wire exiting at the base of this telescopic tube, along the internal lateral faces. centrifugal spinning pots 20 and 21.

Each telescopic tube 26, 27 is surrounded by a sleeve 29 respectively 30 which aims to provide at its end a flared profile 31 for example, as illustrated in FIG. 4, serving to guide the bundle of fibers before it leaves the end of this sleeve 29 to deposit on the internal face of the pot 20. This flared profile 31 is connected to the external lateral face of the sleeve 29 by a convex profile 32. This shape of the lower end of the sleeve 29 has has been studied in order to prevent the bundle of fibers emerging therefrom from wrapping around this sleeve, in particular during the descent of the telescopic tube 26, when the bundle of fibers makes an acute angle with the external face of the sleeve 29 .

Two evacuation conduits 33, 34 exit from the extraction members 22 respectively 23 and terminate in a reel for storing the wire 41 produced in the pots 20 and 21. Nozzles 35 and 36 selectively connected to the source of pressurized air (not shown) by the supply conduits 18 respectively 17 open into the conduits 6 respectively 7 by forming an oblique angle directing the air jet in the evacuation conduits 33 respectively 34. Two shutters 37 and 38 are slidably mounted in the extraction members 22 respectively 23 parallel to the conduits 6 respectively 7, just at the junction of the extraction conduits 33 respectively 34. These shutters 37 and 38 are each integral with a pneumatic actuating device 39 respectively 40 comprising a cylinder and a double-acting piston, connected in inverse relation to one another to the supply conduits 17 and 18, so that one of the obturates urs closes its exhaust duct while the other opens it and vice versa, as illustrated in Figure 1.

Figure 5 shows a variant according to which it is possible to produce a continuous yarn with the centrifugal spinning process object of the invention.

We recognize in this figure the feed member 4 disposed at the outlet of the stretching train, the outlet rollers 1 and 2 deliver the drawn bundle of fibers obtained from a fiber ribbon R. We recognize the branches 6 and 7 leaving the supply member, the extraction members 22,23, the centrifugal spinning pots 20,21 as well as the discharge conduits 33 and 34. These conduits enter a first wire reserve device 43 of known type which makes it possible to feed and extract wire at variable speeds. There follows a device for reattaching wires 42 which is preferably a reattaching device such as that described in EP-A1-0 249 578 belonging to the applicant. This reattachment device is followed by a second known wire supply device 43a. These known wire reserve devices are, for example, of the type described in US Pat. No. 3,796,384. Such a feeding device makes it possible to receive wire at variable speed and, thanks to its reserve, to supply it simultaneously at another speed. A reel 44 associated with a winding shaft 45 driven by the drive mechanism of the spinning loom, continuously receives the thread leaving the feed device with reserve of thread 43a. The winding speed corresponds to the spinning speed.

Let us now return to FIGS. 1 to 4 to examine the operation of the device for implementing the spinning method which is the subject of the invention.

The drawn bundle of fibers leaving the drawing train 1,2 enters the duct 5 of the supply member 4 and is subjected to the helical force induced by the air flows leaving the nozzles 8. When arriving at the branches 6 and 7, the pressurized air carrying with it the wire is directed into that of the branch lines which is open, that is to say that which is connected to the conduit 5 by a passage 13 or 14. In this example, it is the branch 6 which is open. The wire which has undergone a pretortion in the conduit 5 then passes through the conduit 6, passes through the extraction member 22 and terminates in the centrifugal spinning pot 20 at the outlet of the telescopic tube 26 animated by a vertical movement in an alternating direction to distribute the wire against the internal side wall of this spinning pot.

When a certain quantity of wire has thus been deposited undergoing a determined torsion induced by the rotation of the centrifugal spinning pot 20, the valve 19 switches the source of pressurized air from the supply duct 17 to the supply duct 18 The drawer 11 is pushed from left to right in the housing 12, thereby cutting the wire and simultaneously communicating the conduit 5 with the branch 7 through the passage 14. The air which can no longer flow into the branch line 6 then goes to the spinning pot 21 through branch line 7, the ejection member 23, the conduit 25 and the telescopic tube 27.

Also at the same time, pressurized air is sent into the evacuation channel 33 through the nozzle 35 to direct the released end of the wire into the evacuation duct 33 and to draw the wire out of the spinning pot. 20. Since the latter continues to rotate during the wire extraction operation, an additional axial twist is induced on the wire, so that the twist occurs both when entering and exiting the spinning pot centrifugal.

During this time, the spinning of the bundle of fibers continuously leaving the stretching train continues in the centrifugal spinning pot 21. When the bundle is cut by the movement of the slide 11, the new end linked to the thread leaving the stretching train does not receive plus the twist that goes up from the centrifugal spinning pot. However, thanks to the helical flow communicated to the pressurized air exiting the nozzles 8, the pretortion which is thus induced on the fiber bundle as it leaves the drawing train, gives it sufficient cohesion to allow the beam to be brought into the second centrifugal spinning pot 21.

FIG. 5 illustrates a solution making it possible to transform this spinning process by nature discontinuous into a continuous process starting directly from a ribbon R of fibers carded, as in an "open-end" spinning process, but with a wire quality equal to or even superior to that of a ring-cursor system.

The wire is brought from a pot 20 respectively 21 to the first wire reserve device 43. Another length of wire is stored on the second wire reserve device 43a which continuously feeds the spool 44. The front end of the length of wire being wound on the wire reserve device 43 is brought directly into the reattachment device 42. This already retains the rear end of the wire stored on the wire reserve device 43a. The two ends are connected as described in EP-A1-0 249 578 while the wire is wound on the first wire reserve device 43 and extracted from the second wire reserve device 43a to feed the coil 44 continuously. As soon as the reattachment is carried out and the thread is no longer retained by the reattachment device, it is wound on the second device with reserve of yarn 43a and its rear end is retained in the reattachment device 42 to be attached to the 'front end of the length of wire extracted from the other spinning pot and the cycle is thus repeated constantly. The winding speed of the reel 44 corresponds exactly to the speed of production of the wire. The second wire reserve device must have a higher storage speed than the production speed to take account of the downtime required for the reattachment. The first wire reserve device performs storage during the reattachment but it can only be emptied once the reattachment is finished and therefore at the same speed as the wire is stored on the second wire reserve device 43a. It is therefore also necessary that its storage speed be higher than the speed of production of the yarn, since it must be loaded and unloaded during the filling time of a centrifugal spinning pot.

Claims (8)

Centrifugal spinning method according to which the bundle of fibers produced from a drawing train is deposited against the side face of a pot driven in rotation, the bundle is cut upstream of this pot as soon as a certain length of yarn is accumulated against this wall, one of the cut ends is directed, forming the end of this length of wire thus accumulated towards a storage reel and the other cut end is directed against the side face of a second pot driven in rotation, the beam is cut again as soon as a certain length of wire is accumulated against the side wall of this second pot and this cycle is repeated continuously, characterized in that between the exit of said stretching train and the point where the the beam is cut, a helical force is induced on this beam to bring said other cut end alternately against the respective lateral faces of said pots by communicating a pretortion p to this beam or allow it to support the traction component exerted on it. Spinning machine, comprising two centrifugal spinning pots (20,21) for alternately receiving the bundle of fibers, a conduit (5) divided into two branches (6,7) to guide this bundle towards each of said pots and two passages for extraction of the wire (33,34) communicating respectively with each branch, means (28) for causing a relative displacement between the outlet end of the branches and said pots (20,21) in the axial direction of these pots, means (8) intended to be connected to a source of pressurized fluid to send this fluid into this conduit (5) in order to entrain the beam, means for cutting (11,13,14) of the beam arranged at the start of each branch (6,7), means (11,13,14) for passing the bundle from one to the other branch and means for extracting (35,36) from the cut end of the wire, characterized by the fact that the means (8) for sending a fluid under pressure into said conduit (5) are constituted by nozzles arranged to communicate a helical flow to it to induce pretorsion and traction on the fiber bundle simultaneously. Spinning machine according to claim 2, characterized in that the cutting means (11,13,14) are shaped to alternately close and clear the passage section of the respective branches (6,7) and thus serve as means for making pass the bundle of fibers from one to the other branch. Spinning machine according to claim 2, characterized in that the extraction means (35,36) comprise extraction conduits (33,34), the outputs of which lead to a wire reserve device (43) on which the wire can be fed and extracted at different speeds, the output of this device serving to feed a wire joining device (42) which is followed by a second wire reserve device (43a) on which the wire can be fed and extracts at different speeds, the output of this second device serving to supply a storage coil (44). Spinning machine according to claim 2, characterized in that movable shutter members (37,38) are mounted respectively at the intersections between the branches (6,7) and the extraction ducts (33,34), these shutter members being associated with double action actuation means selectively connected to a source of energy in phase opposition with respect to one another so that one of these members is in the closed position of its conduit d extraction when the other is in the open position and vice versa. Spinning machine according to claim 2, characterized in that said means (11,13,14) for passing the bundle of fibers from one to the other branch, comprise a drawer (11) mounted to slide in a housing (12), the two ends of which are selectively connected to a source of pressurized fluid to move the slide between two limit positions, the latter comprising two passages (13, 14) arranged to make said duct (5) communicate alternately with the two branches (6,7) in the two respective limit positions of the drawer (11). Spinning machine according to claim 6, characterized in that the spacing between the inlet openings of the passages (13.14) is less than the diameter of said duct (5). Spinning machine according to claim 5, characterized in that the respective outlet ends of two branches are formed by a telescopic element (26) integral with drive means (28) in an alternating axial movement and that these outlet ends are shaped to have a flared part (31) surrounded by an annular face (32) whose inclination relative to the axis of the telescopic element (26) is reversed relative to said flared part.

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