More specifically, the invention relates to a yarn guide unit of the type including a pair of belts or other flexible members, arranged side by side and with paths that cross each other to enable the yarn to be transferred from a carrier integral with one of said belts to a carrier integral with the other.

State of the art In the production of yarns destined for subsequent weaving operations, be they on a loom, on knitting machines or otherwise, it is necessary to wind the yarn around small tubes or supports to produce reels of various shapes, e. g. cylindrical, conical or biconical. To do so, the yarn is fed to a yarn guide unit, or traversing unit. The yarn guide unit supplies the yarn with a reciprocating motion substantially parallel to the axis of the winding tube, which is kept rotating at a controlled speed in order to wind the yarn in helical turns at a variable angle of inclination.

Speed is crucial in the winding operation as it has an effect on production cost. On the other hand, the thread or yarn has to move without excessively straining the yarn in order to avoid it breaking.

Production speed is limited on the one hand by the need to avoid over- straining the yarn, and on the other by the difficulty in controlling the yarn guiding members.

In more traditional devices, the yarn carrier is guided in a helical groove created inside a cylindrical cam. Examples of devices of this type are described in USA patent No. 4, 026, 482 and in the German patent 1560467.

US patent No. 5,082, 193 describes an electronic thread guide unit, in which the yarn is guided in its reciprocating motion by a thread guide carried by a small rod moving with a reciprocating motion powered by an electronic motor. This device appeared to be extremely effective. However, it presents a drawback in the fact that the thread guiding rod has a reciprocating motion and is therefore subject to inertia strains that limit its operating speed.

In US patents Nos. 3,374, 961; 4,505, 437; 4,505, 436; 5,566, 905 and in

British patent 1.168. 983 yarn guide units are described in which the yarn is guided along an arc-shaped trajectory by rigid members rotating in opposite directions around two parallel, non-coinciding axes that alternately receive or release the yarn. A similar principle is applied in the device described in EP-B-0114642.

Other devices or yarn guide units are based on the use of an endlessly moving belt that drives a yarn carrier. A device of this type is described in DE-A- 2102615, wherein a reciprocatingly moving carrier is alternately engaged to a higher or lower branch of an endlessly moving belt. In this way, the carrier or thread guide has a reciprocating motion. Similar devices are described in USA patents no. 3,333, 782, in DE-A-4214237 and DE-A-3919369.

DE-A-3531034 describes a yarn guide unit with two belts, each of which has two carriers for the yarn. The belts are turned around pulleys located so that the active branch of one belt crosses over the active branch of the other. The yarn is transferred from a carrier integral with one belt, to a carrier integral with the other, in order to reverse the direction of motion. To transfer the yarn, there are transfer wheels coaxial to the pulleys on which the belts turn, but larger in diameter than the latter. At the end of each stroke, the yarn comes into contact with the respective transfer wheel, which pushes the yarn out of the carrier in which it is momentarily engaged, which is integral with one of said belts, and moves it into a suitable position so that it can be engaged by the carrier moving in the opposite direction and integral with the other belt.

This configuration is particularly effective because it does not rely on reciprocatingly moving members, thus avoiding the problems connected with inertia. The mechanism by means of which the yarn is transferred from one carrier to the other gives rise to excessive strains, however, especially for some yarns.

Objects and summary of the invention The of the invention is to provide a yarn guide device or unit that overcomes or at least limits some of the drawbacks of traditional devices and that enables the strains on the yarn to be reduced even at high spooling speeds.

Substantially, the invention relates to a yarn guide device or unit for winding yarn on bobbins or reels, including: a first flexible member turning around a first guide wheel or pulley and around a second guide pulley or wheel ; a second flexible member turning around a third guide pulley or wheel and around a fourth guide pulley or wheel, the guide wheels of the first flexible member rotating in the

opposite direction to the guide wheels of the second flexible member; a plurality of carrier members, integral with said first flexible member and with said second flexible member, for carrying the yarn with a reciprocating motion along a path roughly parallel to the axis of the winding bobbin or reel ; at the ends of its reciprocating path, the yarn is transferred from a carrier memlter integral with one of said flexible members to a carrier member integral with the other of said flexible members. Characteristically, the first and fourth guide wheels are coaxial to each other and have two different diameters; and the second and third guide wheels are coaxial to each other and have two different diameters; overlapping branches of said two flexible members crossing over in an intermediate area of the reciprocating path of the yarn.

Advantageously, the first and third guide wheels have the same diameter and the second and fourth guide wheels have the same diameter, and the two flexible members are substantially of the same length.

To facilitate and regulate the transfer of the yarn from, one carrier member to the other in the changeover area at the end of the reciprocating path covered by the yarn, according to one advantageous embodiment of the invention, along the reciprocating path of the yarn there is an arched guide. This may advantageously have a concave profile for guiding the yarn and may be shaped in such a way so that, at each end of said reciprocating path, it facilitates the transfer of the yarn from the carrier member of one of said flexible members to a corresponding carrier member of the other of said flexible members.

In a projection on a plane orthogonal to the rotational axes of the guide wheels or pulleys of the two flexible members, the arched guide is advantageously located beyond the space occupied by the larger-diameter guide wheels.

In a possible embodiment of the invention, the arched guide can move with at least one component substantially orthogonal to the plane whereon the axes of said guide wheels lie. This motion generates a so-called"disruption"in the distribution of the yarn being wound, so as to facilitate its subsequent unwinding from the reel, when this has to feed a textile machine for instance, such as a knitting machine. As an alternative to, or in combination with, the movement of the arched guide, a random distribution of the yarn on the reel or bobbin formed by the yarn guiding device can be obtained by adjusting the speed of the electronically- controlled motor driving the carriers. In fact, said speed can be changed in relation

to the winding speed to alter the inclination of the turns of yarn on the reel in the most appropriate way for the purpose of facilitating the subsequent unwinding process.

In a possible embodiment of the invention, each of said carrier members has a support profile abutting against the corresponding flexible member and a support profile for the yarn. Said support profile is shaped so as to enable the unrestricted motion of the carrier member around the guide wheels of the flexible member. It can substantially be in the shape of an arc of a circle.

In an advantageous embodiment of the invention, each of said carrier members has a support profile for the yarn, including a first portion for detaining the yarn, in a position closer to the corresponding flexible member, and a second portion for surrendering the yarn, in a position further away from the corresponding flexible member. For example, and advantageously, this support profile may have a concave shape, and a V shape in particular. The yarn is situated inside the concavity, which is oriented according to the direction of the yarn's reciprocating movement. In the area where two carrier members integral with the two flexible members cross over each other, the yarn runs along the support profile in order to move from one of the carrier members to the other, facilitated in this by the arched guide.

The carrier members can be made of shaped metal wire, for instance, especially if it is chrome-plated, or coated with plastic material (possibly self- lubricating) or otherwise surface-treated to reduce the friction coefficient.

Alternatively, the carrier members may be solid elements, e. g. using shaped plastic plates, with edges suitably beveled or rounded to avoid damaging the yarn.

Further characteristics and advantageous embodiments of the yarn guide unit according to the invention are illustrated in the attached dependent claims and Will be described in greater detail below, with reference to an example of an embodiment.

Brief description of the drawings The invention will be better understood by following the description and the attached drawing, which shows practical, not restrictive embodiments of the invention. More specifically, in the drawing: Fig. 1 shows a section of the device according to the plane identified by l-l in Fig. 2;

Fig. 2 shows a section along H-H in Fig. 1; Figs. 3A-3C schematically show layouts of three subsequent relative positions of the yarn carrier members integral with the two flexible members; Fig. 4 shows a view of one of the carriers made with a shaped metal wire; Figs. 5A-5C schematically show layouts of three different positions for the carriers in a modified embodiment; Figs. 6 and 7 show one of the carrier members of Figs. 5A-5C, where Fig. 7 is a view along line VII-VII in Fig. 6 ; Fig. 8 is a schematic layout of an embodiment with means for recording the stroke of the carriers; Fig. 9 shows a side view of a modified embodiment on a plane containing the axles supporting the idler wheels for turning the flexible members ; Fig. 10 shows a layout of one of the flexible members from Fig. 9; Fig. 11 shows a layout of one of the carriers of the embodiment in Fig. 9; and Fig. 12 shows a view along line XII-Xll in Fig. 11.

Detailed description of embodiments of the invention With reference to Figs. 1 to 4, the device includes a plate 1 to which a motor 3 is fixed, with a toothed pulley 7 keyed onto its output shaft 5. The motor 3 is advantageously an electronically-controlled motor, that can work at variable speed.

A double-sided toothed belt 9 turns around the pulley 7, driving two toothed pulleys 11 and 13. The numeral 15 indicates a guide pulley, which enables the path of the belt 9 to be established so that it drives pulley 13 with the outer teeth and pulley 11 with the inner teeth.

The two pulleys 11 and 13 are fitted on parallel shafts indicated respectively as 17 and 19 9 (see Fig. 2 in particular). A larger-diameter toothed pulley 21 is cantilevered on the shaft 17, supported by bearings 18 mounted on a block 20 integral with plate 1, while bearings 23 idly support a smaller-diameter toothed pulley 25. The larger-diameter pulley 21, which is driven into rotation by the shaft 17, is situated in an axially intermediate position between the driving pulley 11 and the idle pulley 25.

A toothed pulley 27, of the same diameter as pulley 21 is cantilevered on the shaft 19, supported by bearings 24 on a block 26 integral with plate 1. A

toothed pulley 29 is idly fitted between the toothed pulley 13 and the toothed pulley 27 on the shaft 19.

A first flexible member 31, comprising a toothed belt, turns around the pulleys 21 and 29, while a second flexible member 33, comprising another toothed belt, turns around pulleys 25 and 27.

As can be seen in particular in Figs. 3A-3C, the two belts 31 and 33 are so arranged as to vertically overlap with each other, and in such a manner that the two branches of each of them lie at a given angle relative to the corresponding branches of the other, so that in a plan viewy they cross in a central position between the axes of the shafts 17 and 19.

Two respective yarn carriers are anchored on each of the two belts 31 and 33. The carriers conveyed by belt 31 are indicated by the numerals 35A, 35B, while those conveyed by belt 33 are indicated as 37A, 37B. Given that the shafts 17 and 19 rotate in opposite directions, the carriers 35A, 35B and 37A, 37B cross over as they follow the trajectory imposed on them by the motion of the belts. As will become clear from the following description, this enables the thread fed to the device to be transferred from one carrier to the other, moving with a reciprocating motion along a near rectilinear trajectory. The respective positions occupied by the carriers 35A, 35B and 37A, 37B are illustrated in the sequence of Figs. 3A, 3B, 3C. Vice versa, in Fig. 2 they are illustrated in a position that they do not really occupy, i. e. overlapping two by two in line with the outermost ends of their respective trajectories : this is done merely for the purpose of illustrating how they lie on two orthogonal planes to shafts 17,19 and very close to each other.

Underneath the pulleys 25 and 27, there is an idler roller 41 for supporting the tube T, on which the thread or yarn F fed to the device is wound. The tube T is kept rotating by a known system, not described herein. The reel of yarn F forms around said tube.

Above the plane on which the carriers 35A, 35B move and at an intermediate distance along the axial development of the pulleys 21 and 29 there is an arched guide 43, supported at its ends by the holders 45. The arched guide 43 lies on a plane orthogonal to the axes of the shafts 17,19 and has a curvature whose convex side faces towards said shafts, while the concave side faces the yarn F being fed to the device. The arched guide is positioned symmetrically relative to a median plane between the two shafts 17, 1-9. The yarn F runs on it as

it is carried by the carriers 35A, 35B, 37A, 37B. The curvature of the guide facilitates-as will be more clearly described below-the transfer of the yarn from one of two carriers to the other when they cross over each other as they move in opposite directions.

The device hitherto described functions as follows. The yarn F is fed from above as shown by arrow F0, in a manner known per se, and is wound around tube T to form a reel B. To this end, it is supplied with a transversal and reciprocating motion parallel to the axis of the tube T by means of the device described.

With reference to the sequence of Figs. 3A, 3B, 3C, in Fig. 3A the yarn F is engaged in the carrier 35B and is surrendered by said carrier, which moves as shown by arrow F1, and transferred to the carrier 37B, which moves in the opposite direction, as shown by arrow F2, thanks to the motion induced by the motor 3 in the two shafts 17,19 and the belts 31 and 33, to which the carriers are connected.

In Fig. 3B, the carrier 37B is just beyond halfway along its active stroke, i. e. on a level with the reel that is forming on the tube T. At the same time, the second carrier 35A, conveyed by belt 31, is in a position around the pulley 21. The positions of the carriers are phased so that the carrier 37B crosses the path of the carrier 35A at the end of the yarn's path in a direction parallel to the axis of the tube T. It is here that the yarn F is transferred from carrier 37B to carrier 35A.

Then it reverts its trajectory and is taken back to the point where it was in Fig. 3A, to be surrendered to the carrier 37A integral with the belt 33 (Fig. 3C).

In this way, the yarn reciprocatingly moves roughly parallel to the axis of the tube T over a distance substantially equal to the height of the reel B that is being formed on said tube.

The passage or transfer of the yarn from on of the carriers 35A, 37A and 35B, 37B to another is achieved primarily thanks to the shape of the carriers themselves, that will be described In more detail beZow with reference to Fig. 4.

One of the carriers is illustrated here, and they are all substantially the same. They are made of metal wire, chrome-plated or treated as appropriate to reduce their friction coefficient. In addition, a hardening treatment can be applied to reduce the wear determined by the yarn's passage.

The numerals 51 and 53 indicate the ends that fit into corresponding seats

on the belt to which the carrier is anchored. The shaped wire forming the carrier defines approximately straight front profiles or stretches, indicated as 55 and 57, inclined towards each other to form a V shape, with a tip 59. The V-shaped profile faces with its concave surface in the direction in which the carrier progresses. The numeral 61 indicates a portion of the carrier that rests on the belt.

As can be seen especially from the sequence of Figs. 3A-3C, as the yarn advances, engaged on the carrier 37B (Fig. 3B), it is in contact with the carrier approximately at the mid-point 59. When the two carriers 35,37 approximately overlap and the yarn has to be transferred or moved from one of the two carriers to the other, it runs along the portion 57 of the carrier to which it is engaged until it overrides the bend 57B. At the same time, the (overlying or underlying) carrier that is moving closer receives the yarn in line with the stretch 55. The yarn runs along this stretch until it returns to the point 59 on the new carrier.

The sliding movement of the yarn along stretch 57 up to the bend 57B in order to be surrendered to the carrier arriving from the opposite direction is facilitated on the one hand by the curvature of the carriers'path, imposed by the curvature of the belts 31,33 ; on the other hand, the arched guide 43 is positioned so as to come to bear on the yarn approaching the area where the direction is reversed, pushing it outwards, i. e. inducing it to run from the point 59 along the stretch 57 to the bend 57B.

Clearly the carriers, which are represented here as made of bent metal wire, can also be made in other ways; for instance, they can be made of solid plate suitably cut and with its edges shaped to avoid damaging the yarn that runs along it. The edges can be machined and/or treated to reduce the friction coefficient and increase the hardness and consequent resistance to the wear caused by the passage of the yarn.

A different embodiment of the carriers ia illustrated in Figs. 6 and 7. Here again, one of the carriers is shown which is made of bent metal wire. Numerals 71 and 73 indicate the ends that are inserted in seats on the respective be ! t. Here the active profile of the carrier is made of three portions shown at 75,76 and 77 forming three consecutive stretches of the profile on which the yarn is slidingly supported, the yarn being moved from one carrier to the other when it passes beyond the bend 77B of the carrier to which it is engaged and coming to rest on the stretch 75 of the carrier that approaches from the opposite direction. The

numeral 79 indicates a stretch resting on the belt with which the carrier is integral.

Figs. 5A-5C show the same operational sequence as Figs. 3A-3C, but using carriers shaped as shown in Figs. 6 and 7.

The configuration of the device can be perfected with a view to enabling the length of the backward and forward stroke of the yarn to be recorded. This may be useful in making reels of different axial heights. Fig. 8 schematically shows a layout of a solution of this type. Numeral 1 again indicates a plate for supporting a motor 3. Instead of being rigidly attached to the plate, this is supported by a slide 3A, which can slide along adjustment guides 4 integral with plate 1. The slide 3A can be fixed to plate 1 in any position along the adjustment guides 4. By means of ties 6, the slide 3A is attached to two slides 8 adjustable along adjusting guides 10, integral with the plate 1. The numeral 12 indicates compression springs that push the two slides 8 towards one another.

The slides 8 carry the shafts 17,19 with corresponding pulleys, around which the belts 9,31 and 33 are positioned.

By modifying the position of the slides 3A along the guides 4, the slides 8 can be induced to slide, thereby enabling the distance between the centers of the shafts 17 and 19 to be modified. Dandy rolls, not shown, are used to keep belts 9, 31,33 taut, so that the stroke of the carriers conveyed by the belts 31 and 33, and consequently also the stroke of the yarn along the axis of the tube T on which the reel B is formed, can be modified.

Figs. 9 to 12 show a modified embodiment of the device according to the invention. The same numbers are used to indicate parts that are the same as, or equivalent to, those described in the previous embodiments. The solution shown in Figs. 9 to 12 differs in the different positioning of the pulleys driving the shafts carrying the guide wheels of the flexible members and in a different shaping of the members 35A, 35B ; 37A, 37B carrying the yarn F. ! n this case, the carrier members are in the form of plates made of metal, ceramic, plastic or other appropriate material. They are bolted onto the outer face of the respective belt.

This can be done using rivets, screws or other means of connection to the belt. As in the example of Figs. 1 to 3, the carriers are V-shaped. Each shape has two approximately straight front profiles or stretches, indicated again as 55 and 57, inclined towards each other to form a V-shaped profile, with a tip 59. The V- shaped profile has its concave side facing in the direction in which the carrier

advances. The yarn F is engaged by the carrier in line with the profile or portion 55 and runs along it up to the tip 59. From here, when it has to be surrendered to the other carrier moving in the opposite direction, it starts to run along the profile 57, which ends with the rounded area 57B. As already mentioned, the edges of the plate can be machined and/or treated to reduce the friction coefficient, eliminate any sharp edges that might damage the yarn and increase the hardness and the consequent resistance to wear.

The system for connecting the carrier members to the outer side of the zu respective belt using screws or rivets, or similar means, can also be used when the carrier members are made of metal wire, e. g. by providing the metal wire with a loop in which to insert the rivet, screw or other fixing device.

In the previous description and in the attached drawings, reference is made to a device in which a motor drives only one pair of flexible members to control the traversing movement of a single thread or yarn. It should however be noted that the same motor can control several devices or units in parallel, in order to form more bobbins or reels simultaneously. The various pairs of flexible members conveying the yarn carrier members can be driven by the motor by means of one or more drive belts.

Clearly, the drawing does not show more than one practical embodiment of the invention, which may vary in shape and arrangement, without departing from the spirit and scope of the invention. Any reference numbers in the attached claims are intended merely to facilitate the reader in interpreting the above description and attached drawings, and shall in no way restrict the applicability of the patent.