Device and procedure for preparing the thread end to start or resume open-end spinning

Abstract: The thread end (4) to be used for rejoining in an open-end spinning frame is prepared by cutting it to size and then introducing it into a pipe (15) with a vigorous air flow running through it and in contact with a vibrating blade (16), freeing it of short fibres, tapering its end and untwisting the fibres that comprise it.

Description: The present invention generally relates to open-end spinning and in particular concerns preparing a thread end to give it a tapered end and starting or resuming open-end spinning. in which a ring of singularised fibres is deposited in the groove of a rotor that turns at very high speed, into which is reintroduced the prepared end of the thread which links with the singularised fibres deposited in the groove. By extracting the thread end thus introduced, thread production is resumed, the thread being twisted by the rotation of the rotor. The thread is extracted by extraction rollers and wound onto reels. The number of twists imparted to the thread is proportional to the ratio between the rotor speed and the thread extraction speed. In an open-end or free-end spinning unit the thread must be rejoined on starting or, more frequently, when the thread is broken or when production of a new reel is begun, having completed the previous reel. In order to perform this operation correctly, the thread end is reintroduced into the rotor using devices which ensure that a precisely-determined length of thread is inserted into the rotor, at controlled times and speeds of the various organs involved. In order to produce a good-quality yarn, in the section of thread produced in the joining operation between the thread end introduced into and fibres picked up from the rotor, the yarn must not be irregular or of a different diameter and must be of the same strength. In other words, in good-quality yarns the sections in which rejoining has taken place must be the same as the rest of the yarn. If this is not the case, the yarn produced must undergo an additional spooling operation to eliminate imperfections due to irregularities in the diameter or twists, to weak points and so on. In order to achieve a proper connection between the singularised fibres and the thread end reintroduced into the rotor with an opposite motion to that of extraction, in the state of the art it is known that the said thread end must be properly prepared, removing from it the existing twists and making the fibres that comprise it essentially parallel, in order to improve penetration between the fibres of the reintroduced thread end and the singularised fibres deposited in the rotor. The thread end must be tapered so as to prevent there being a thickened section at the rejoining point. During such preparation it is very important also to remove shorter fibres, damaged both when breaking the thread and during the actual preparation operation. These fibres would cause the join to have a lower mechanical strength. In the state of the art very different methods of preparing the thread end have been described. A known method of preparing the thread end consists in cutting the thread to the required size and untwisting and fraying out the thread end with jets of air directed at right angles, parallel or inclined in relation to the axis of the thread, eliminating the twists and removing the short fibres. Such a method is disclosed in DE-A-2 361 787 which constitutes the most relevant state of the art. This type of preparation produces an insufficiently tapered thread end, giving rise to a strong but thickened join which gives an irregular and variable result. The present invention concerns an improved method for preparing the thread end to be used when rejoining the thread in an open-end spinning unit according to claim 1 and a relative improved device according to claim 5. In order to better understand the characteristics and advantages of the present invention, one of its typical embodiments is described, shown in Figures 1 and 2, given for the purpose of illustration but in no way limiting, including also the operations that precede and follow the preparation of the thread end according to the present invention. Figure 1A shows a side view of the spinning unit and Figure 18 is a front view thereof. A reel 1, which carries the thread end to be used for rejoining, is rotated slowly and in the opposite direction to that of extraction by the action of an auxiliary rotating roller 2 which is brought against it in order to slowly unwind the thread. A first suction nozzle 3 is brought close to the generatrix of the reel 1 and picks up the thread end 4, which is paid out to it by the counter-rotation of reel 1. If, however, the spinning unit is to be started or a new reel of thread is begun, the thread end 4 is picked up - instead of from a reel of thread 1 already produced - from a reserve of thread on board of the spinning frame. The first suction nozzle 3 withdraws to position 3A taking with it the thread 4. An arm with a V-shaped introducer 5 descends in order to position the thread 4 in front of a second suction nozzle 6 of the end-preparation device 7, the components of which will be described later in more detail. Thread 4 is now in a V configuration with one part 4 and a second part 4" upstream and downstream respectively of introducer 5. Introducer 5 has a cutter 5' which cuts the thread 4 while the second nozzle 6 produces a suction effect; on cutting the thread, its part 4" is sucked up by the first suction nozzle 3, whereas the end of its part 4' is picked up by second suction nozzle 6 while the reel 1 continues to pay out thread. The thread is now delivered to the second suction nozzle 6 of the end-preparation device. Nozzle 3 and introducer 5 can withdraw to the at-rest position. The end-preparation device 7 rotates to position 7A opposite the end-introduction pipe 9. Its rotation to position 7A takes place around an axis lying in the plane of Figure 1A, as shown in Figure 1B. The thread is now in position 4'''. During this rotation the thread follows the edge of the second suction nozzle 6 at an angle equal to the rotation and encounters the open clamp 10, entering its jaws. A thread diverter rod 11 approaches the thread in position 4''' and diverts it to assume the configuration 4 IV shown by an unbroken line, so as to make available a set length of thread between reel 1 and spinning rotor 8, in order to reintroduce the thread end along a constant and exact length. Reel 1 is stopped and clamp 10 closed. Roller 2 is moved away from reel 1 and placed in the at-rest position. Figures 2A, 2B and 2C, which are side, plan and cross-sectional views respectively, show the end-preparation device 7 according to the invention, the preceding part of the procedure of picking up and presenting the thread 4 being already known in the state of the art at least as regards its essential aspects. According to the present invention, the end-preparation device 7 is integral with the second suction nozzle 6 formed in said first body that picks up and feeds thread 4 to the spinning rotor 8 in order to resume or start spinning so that problems of precision positioning and movement between the two organs are avoided. The second suction nozzle 6 is formed in a first body which is not shaped as a straight line, and has a longitudinal slot 12 which, when the end preparation device 7 is in position 7A, constitutes the shortest route from the clamp 10 to a suction pipe 13 for thread 4, which spontaneously assumes the position shown in Figure 2A, which represents a side view. The thread 4 is gripped by clamp 10 and the free thread end enters suction pipe 13 along whatever length it is and falls between the open blades of a cutter 14. The suction pipe 13 is connected to said second suction nozzle 6. In this position thread 4 enters a corresponding slot 12' in a second body of device 7, which has a through channel 15, essentially at right angles to the direction of slots 12 and 12'. The cutter 14 is closed and the section of thread beyond the cutter 14, sucked away by pipe 13, is cut whereas the end cut to size, held by clamp 10, enters channel 15, which is blasted through with a vigorous air flow in the direction of the arrow in Fig. 2B or 2C. This air flow is supplied to channel 15 at the same time or subsequent to cutting the excess section of thread 4. Inside channel 15 is a flexible blade 16, embedded in the wall of channel 15 or fixed by equivalent means, which due to the effect of the air flow vibrates vigorously, causing in the end of thread 4 - stressed by the vibration of the blade and by the air flow - a series of flexural oscillations which release the short fibres, tapering the thread end and untwisting its fibres. In a very short time the thread end assumes a fairly long tapered configuration, with the fibres parallel and free of lengths of short fibres which would give rise to poor mechanical strength in the section containing the join. In the state of the art the use of vibrating blades to prepare thread ends for pneumatic splicing is known, for example from EP-A-053093 in the name of Fomento de Inversiones Industriales or from Italian patent N° 1 218 199 corresponding to DE-A-3 804 684 in the name of Mesdan SpA. These patents refer to the possibility of using vibrating-blade devices also to untwist threads produced in open-end spinning units, but without mentioning the method of use of these devices in the context of an open-end spinning unit and in particular in rejoining. The present invention solves the technical problem of using these devices to prepare the thread end of a single rejoining thread in open-end spinning units, and in their inclusion in the service devices of a spinning frame, according to the requirements of the said spinning technique. In the example of an embodiment shown in Figures 2, channel 15 - in the part to the right of slot 12' - has a U-section, the opening of the U facing the part from which the thread end comes after cutting with cutter 14. This arrangement facilitates insertion of the thread end into channel 15, where it comes into contact with blade 16, and makes it easier to fit the blade. The thread end will enter channel 15, however, provided that the latter has a sufficiently large tubular section, since in this case too the flexibility of the thread allows the air flow to bend it and attract its end into channel 15 and lay it against the blade. The U-shape section of channel 15 is also preferred because a smaller cross-section is required to ensure that the thread end is introduced into the channel. After preparing the thread end, clamp 10 moves to position 10A (Fig. 1A) to present the prepared thread end 17 to the end-introduction pipe 9 of spinning rotor 8. As rotor 8 rotates, it creates a vacuum and pipe 9 sucks the thread end 17 in. Thread-diverter rod 11 moves slightly back paying out the length required for thread end 17 to be caught and held by the suction of pipe 9, clamp 10 opens and releases the thread end to pipe 9. When rotor 8 reaches the required speed and its groove contains the ring of singularised fibres suitable for rejoining, thread-diverter rod 11 completely releases the thread 4. As an indication, the thread length suitable for introduction into the rotor for rejoining corresponds to just less than the circumference of rotor 8. After a short precisely-determined time, the thread extraction rollers, not shown in the Figure, are activated and thread winding is resumed to form reel 1. Preparation of the thread according to the invention enables a thread end of the desired shape and length to be created. These characteristics of the prepared thread end are dependent on the position of blade 16 in channel 15, in relation to the thread end. It has in fact been found that the length of the thread end Which goes beyond the end of the free extremity of blade 16 has a substantial influence on the result of the preparation, the other treatment parameters being equal, and it is therefore necessary to be able to vary this length to suit the yarns produced in the spinning unit. This may be done by changing the position of cutter 14 along the body of the second suction nozzle 6 - possibly by changing the position of clamp 10 immediately after cutting the thread end - and/or changing the position of blade 16 in relation to slot 12, for example by replacing only the part containing U-shaped channel 15 with another component having blade 16 in a different position. Depending on the count and twists of thread 4, preparation may be altered by changing the speed of the air flow in the channel 15, throttling its supply, and the treatment times. As an indication, the finer yarns with more twists require more drastic treatment conditions, i.e. longer times and higher flow speed, which means higher air supply pressures. As an indication, the treatment time vary from 0.2 to 2 seconds, while the pressure of the service air varies from 3 to 7 bar. The thicker yarns are more rigid and placed under greater stress by the vibration of the blade 16 and their preparation requires milder conditions. The length of the tapered section is limited by the length of the fibres, but the relative position of the blade 16 enables its shape to be determined within this limit. Vibrating blade 16 may be made of a natural or synthetic elastomer material or of metal, for example spring steel. In any case, the edges and surfaces of the blade should preferably not be rough or have abrasive profiles which would damage the fibres. Treatment using a vibrating blade 16 is more sensititve and adjustable than the state of the art treatments and does not damage the fibres, being based on a series of flexures induced at the resting point of the blade 16 which loosen the links between the fibres and stretch them out. The device according to the invention is preferably fitted on board the service carriage of the spinning frame which serves the various spinning units that make up the open-end spinning frame. This carriage also has service devices which are used for starting, lifting, cleaning and rejoining the thread of the spinning units, such as devices for catching the thread end, on which preparation of the thread according to the invention is carried out, and its subsequent feeding to the spinning rotor.

Claims: A method for preparing a thread end to give it a tapered end of constant and predetermined lenght, comprising untwisted essential parallel and Integral fibers, and for starting or resuming open-end spinning in an open-end spinning unit having a spinning rotor and an end-introduction pipe, the thread to be prepared being delivered from a thread reel or a thread reserve, the method comprising in sequence the steps of: a) unwinding the thread end from the thread reel or the thread reserve; b) picking up said unwound thread end by means of suction; c) tranferring said picked up thread end opposite the end-introduction pipe of the open-end spinning unit, always maintaining the thread controlled by means of suction; d) diverting the thread between the thread reel and the end-introduction pipe; e) stopping said thread unwinding; f) clamping the thread at a clamping point; g) cutting the thread end a predetermined distance from said clamping point for making a fixed thread lenght; h) feeding said cut thread end into a channel having disposed therein a flexible blade having a free extremity disposed inside said channel and supplying a vigorous air flow through said channel, whereby said blade is vibrated by means of said air flow; i) placing said cut thread end inside said channel in contact with said vibrating blade so that a portion of said cut thread end extends beyond the free extremity of the blade and so as to subject said cut thread end for a predetermined time to a large number of flexures of the blade, whereby the end of thread which extends beyond the free excremity of said blade is prepared by being freed of short fibers, tapered, untwisted and parallelly oriented; j) moving said thread clamping point and said prepared thread end in proximity to the end-introduction pipe; k) releasing said thread clamping point and a portion of said diverted and tightened thread; l) sucking said fixed thread length and said prepared thread end into the end-introduction pipe; and m) completely releasing said diverted and tightened thread for totally recovering said fixed thread length and for feeding said prepared thread end into the spinning rotor of the open-end spinning unit for starting or resuming open-end spinning. Method according claim 1, characterised in that the preparation of the cut thread end is regulated by the axial position of the thread end in relation to the free end of the vibrating blade in the channel. Method according to claim 2, characterised in that the axial position of the cut thread end in relation to the free end of the vibrating blade is adjusted by changing the constant and predetermined length to which the thread is cut. Method according to claim 1, characterised in that the preparation of the cut thread end is regulated by the duration of the vibration of said blade by said air flow. A device for preparing a thread and to give it a tapered end of constant and predetermined length, comprising untwisted essential parallel and integral fibres and for starting or resuming open-end spinning in an open-end spinning unit having a thread reel (1) or thread reserve, a spinning rotor (8) and an end-introduction pipe (9), wherein the thread to be prepared is delivered from said thread reel (1) or thread reserve, said device comprising: a) an integral catching, holding and preparation means (6,7) rotatable between a first position proximate to the thread reel (1) or thread reserve and a second position (7A) opposite said end-introduction pipe (9) and comprising a first body forming a suction nozzle (6) for catching in said first position the thread (4) delivered from said thread reel (1) or thread reserve, a longitudinal slot (12) in said first body, a clamping means (10) for holding the end of the caught thread (4) in position for preparation thereof, a cutting means (14) for cutting said thread end held in said clamping means (10) a predetermined distance from said clamping means (10) for thereby providing a free thread end to be prepared, a suction pipe (13) connected to said suction pipe (6) for sucking away the thread section beyond said cutting means (14), a second body (7) with a slot (12') therein and having a channel (15) for receiving said free thread end to be prepared, said second body slot (12') being in a substantially traverse direction to said channel (15) and opposite said longitudinal slot (12) in said first body, a flexible blade (16) disposed in said channel (15) and having a free extremity disposed inside the channel (15), means for supplying a vigorous air flow through said channel (15) substantially parallel to the length of said free thread end to be prepared for vibrating said blade (16) and for vibrationally impacting said free thread end in response to said air flow, whereby said free thread end is freed of short fibres and is untwisted, b) a thread diverting and tightening means (11) positioned between said first position and said second position (7A) of said catching, holding and preparation means (6,7) for making a fixed thread length when said catching, holding and preparation means (6,7) is positioned in said second position (7A) and before said clamping means (10) holds the end of the caught thread, wherein said fixed thread length is recovered when said preparation thread end is introduced into the end-introduction pipe (9) of the open-end spinning unit. A device according to claim 5, characterised in that the first body forming said suction nozzle (6) is not shaped as a straight line whereas its longitudinal slot (12) is in a straight line from said clamping means (10) to said suction pipe (13), wherein said cutting means (14) is disposed along the slot (12) and between said clamping means (10) and said suction pipe (13) for cutting the thread to said predetermined length. A device according to claim 6, characterised in that said cutting means (14) is adjustably positioned along said first body forming said suction nozzle (6) for varying said predetermined thread length cut by said cutting means (14). A device according to claim 6, characterised in that said clamping means (10) is adjustably positioned along said first body forming said suction nozzle (6) for varying said predetermined thread length cut by said cutting means (14).

Inventors: CASTELLARIN DONATO, FERRO FRANCESCO, PAGURA ERNESTO, CASTELLARIN, DONATO, FERRO, FRANCESCO, PAGURA, ERNESTO
Applicants: SAVIO MACCHINE TESSILI SPA, SAVIO MACCHINE TESSILI S.P.A.
Application year: 1990
Main classification: D01H4
IPC codes: D01H4