DURING YARN TRANSFER IN TURRET AUTOWINDER

Field of the invention:

The present invention relates to automatic turret type winders and more particularly to yarn traverse guide used for laying a continuously arriving yarn around a rotating bobbin while traversing the yarn, further helps in improving yarn transfer efficiency of continuous advancing yarn during the bobbin changeover operation.

Background of the invention:

In the following description, the term "yarn" is intended to also include the threads, tapes, profile tapes, fibrillated tapes and slit-film bands of various linear mass density, diameter, width and thickness. The term "bobbin" is intended to include any metallic or non-metallic tubes on which the yarn is wound to form a suitable package. The term 'yarn' is also used to describe yarn with multiple threads or ends that a single winder might receive.

Automatic turret type winders are used in production or take-up process of continuously advancing yarn, for example, in yarn extrusion machines or in rewinding process for making plurality of small size yarn packages from a large yarn package. In general, the turret type automatic winders are positioned side by side in the horizontal direction and stack one above the other in vertical direction. The number of winding positions is exemplary both in horizontal row and vertical row.

The yarn transfer operation is important in the automatic yarn winding operation. If the yarn is not transferred in the first attempt, the continuously advancing yarn gets wasted until it is rethreaded. Worse still, the continuously advancing yarn, if not controlled properly in case it fails to transfer onto the empty bobbin, may interfere with the other yarn winders on the same machine and cause the entire machinery to stop which results in a huge amount of wastage, machine downtime and economic loss. In the worst situations, some parts of the machinery may get damaged.

In automatic turret type winders, a continuously advancing yarn is generally wound on an initially empty bobbin to form a suitable yarn package. When the pre-determined package size (length/diameter/time) is achieved on a bobbin installed on one of the bobbin holders, generally known as a spindle, the continuously advancing yarn is transferred by an automatic transfer device to an empty bobbin installed on another spindle to make a new yarn package without interrupting the winding operation. During the bobbin changeover operation, the empty bobbin is positioned in the path of the advancing yarn by rotating the turret. The continuously advancing yarn is then guided onto a yarn grasping device or a catching device by axially shifting or displacing the bobbin spindle or the traversing unit, such that the yarn is clamped at grasping device and then laid across the empty bobbin. Simultaneously, the yarn connecting the bobbin under winding and the full bobbin is severed.

In the most of known prior art, the yarn is transferred to traverse guide using complicated yarn transfer mechanism as described in EP 03725171. One drawback of the system disclosed in WO2009/031163A1 is that the yarn needs to be led to the traverse guide in a very precise manner. Lack of precision could lead to yarn slippage, particularly during the yarn return phase of the yarn transfer process, and consequently to yarn transfer failure. The system required to exercise precision is complicated and therefore prone to operator error. Hence, there is need to developed an improved yarn traverse guide which can assist in laying of yarn on bobbin even when the yarn is not transfer precisely to yarn traverse guide.

As shown in Figures la and lb, there are two types of traverse guides available, namely the self picking type (a) and the one to be used with an auto winder (b). The self picking guide is characterized by the profile that has wings or flanks whose slopes fall away from the central notch thereby forming an inclusive angle of greater than 180°. Whereas the guide to be used in auto winders is characterized by the wings or flanks which slope towards the central notch, thereby forming an inclusive angle of less than 180°. A common drawback of these two types is that these are prone to malfunction unless the placement of yarn during the winding process is accurate. In the case where yarn is placed outside their safe 'catchment zones' there's a high probability of yarn getting caught in the winder leading to winder shutdown and associated problems and losses.

Objects and advantages of the invention:

The main object of the invention is to provide a device with improved yarn transfer efficiency during shifting the advancing yarn from the yarn guide to a grasping device and returning the advancing yarn, after yarn has been grasped in the grasping device, to the traverse guide. Another object of the present invention is to provide a simple mechanism, designed to return yarn back into the traverse guide without any precise control over placement of yarn on traverse guide. Further object of this present invention is to provide a yarn shift and yarn return device that is independent of the yarn grasping device.

Summary of the invention:

The present invention comprises a traverse guide of a novel design which ensures that advancing yarn is transferred successfully to the bobbin even when the yarn is not precisely transferred back to the traverse guide. Brief description of figures:

Figures la and lb: Currently used traverse guides Figure 2a: A typical turret type automatic yarn winder Figure 2b: Empty bobbin positioned for winding Figure 3a: Preferred profiles of the traverse guide and the transfer link Figure 3b: Definition of the inclusive angles

Figure 3c and 3d: Alternative profiles of the traverse guide (symmetric profiles)

Figure 3e: Alternative profile for the traverse guide (asymmetric profile)

Figure 4: definition of zones in which the yarn may undesirably fall Figure 4A: Illustration of how yarn, if accidentally fallen in zone 1 , finds its way into the groove

Figure 5: Illustration of how yarn, if accidentally fallen in zone 2, finds its way into the groove

Figure 6: Illustration of how yarn, if accidentally fallen in zone 3, finds its way into the groove

Figure 7: Illustration of how yarn, if accidentally fallen in zone 4, finds its way into the groove List of parts:

1. Full bobbin

2. Empty bobbin

3. Advancing yarn 4. Traverse device

5. Traverse guide; stem (5a), groove (5b), ceramic element (5bl), flank (5c), external edge (5cl), internal edge (5c2), external profile (5c3), inner profile (5c4), first inclusive angle (5d), delivery zone (5e), second inclusive angle (5f), third inclusive angle (5g), 6. Transfer link, hook (6a), transfer part (6b), restricting edge (6c) return part

(6d), the notch (6e), mounting axis (6f),

7. Grasping device

8. Spindle

9. Turret bar

Detailed description of the invention:

Figure 2a shows a typical turret type yarn winder in which yarn is wound on bobbins to form suitable packages. Figure 2b shows a bobbin that is fully wound to its predetermined package size and an empty bobbin (2) that is ready for winding. The position of the yarn shown in figure 2b is the correct functioning position whereby the yarn is eventually placed inside the groove (5b) of a traverse guide (5).

The device of the present invention essentially comprises a novel traverse guide (5) that helps guide the advancing yarn (3) efficiently and accurately into the groove (5b) provided in the traverse guide (5), where it remains secure.

The traverse guide (4) moves laterally along a traverse device (4), typically provided in the form of a traverse device.

In one aspect, the traverse guide of the present invention is characterized by the unique profile of its edges. The traverse guide along with the two obstacles provided at the two ends of the cam box work together in a unique way to ensure that the advancing yarn finds its way into the groove (5b) during the yarn transfer process. A first obstacle is provided at the far end of the cam box (that is the end away from the turret plate) and a second obstacle is provided at the turret end of the cam box. The first obstacle is in the form of a transfer link (6) which preferably has a rotational degree of freedom. However it may also be in a simple form of a bar or a rigid strip attached to the cam box. The second obstacle is in the form of a rod or a rigid strip attached to the cam box. The operation of the automated yarn winder using the device of the invention is now explained.

In its yarn shift phase, the device shifts the advancing yarn (3) from the traverse guide (5) towards the grasping device (7) that is typically provided at the end of the bobbin, or alternatively at the end of spindle (8) on which a bobbin is mounted. Once the yarn is grasped by the grasping device (7), the device of the present invention, in what is termed as the yarn return phase, returns the yarn to the traverse guide (5) so that the winding of the advancing yarn (3) can begin on the empty bobbin (2).

The key feature of the present invention is the yarn traverse guide of an innovative profile. As shown in figure 3, it comprises a pair of flanks (5c) to catch the yarn and a stem (5a). The stem (5a) is preferably positioned in a direction perpendicular to the direction of motion of the guide (5). Alternatively, the stem (5a) may be configured in any angle that facilitates the movement of the traverse guide (5) across the cam box (4). The two flanks (5c) are either formed integrally with the stem (5a) or formed separately and fixedly attached to it. Each of the flanks (5c) has an external edge (5cl) and an internal edge (5c2) on either side of the groove (5b). The internal edge (5c2) is the edge of the guide (5) that is close to the cam box and the external edge (5cl) is the edge that is further from the cam box.

In the preferred embodiment of the invention, the external edge (5cl) has an inner profile (5c4) and an external profile (5c3). The inner profiles (5c4) of the two flanks (5c) form a first inclusive angle (5d) (see Figure 3a) between them which is less than 180°, preferably between 180° and 100°. The external profiles (5c3) of the external edge (5c 1) fall away towards the cam box such that the external profiles form a second inclusive angle (5f) between them which is (see Figure 3b) less than 180°, preferably between 180 ⁰ and 100 °. Alternatively, the external edge (5cl) on either side of the groove (5b) is provided in a single convex in profile (see Figure 3 c).

The flanks may be placed symmetrically or asymmetrically with respect to the stem. The flanks (5c) may have different profiles with respect to each other (see Figure 3e).

In another embodiment of the invention, multiple grooves are provided; the advancing yarn may be placed in any one of these for efficient and smooth operation of the winder.

The position of the groove, either the single groove, or multiple grooves, may not be symmetrical in any way with respect to the traverse guide. As shown in Figure 3d, the internal edge on either side of the groove (5b) has a concave profile. Alternatively it is a straight edge so that internal edges on either side of the groove (5b) form a third inclusive angle (5g) between them which is less than 180 °, preferably between 180 ⁰ and 100 °.

As can be seen from figure 3b, the ideal delivery zone (5e) for the traverse guide is the extent between the peaks of the external edges (5cl and 5c2). This zone is the ideal zone for receiving the advancing yarn. When the yarn falls within this zone, the yarn winding process is carried out at its best and the wound package is the most uniform. One of the key advantages of the present invention is that even if the yarn falls outwit the ideal delivery zone (5e), the yarn winding process continues with acceptable performance and the package is formed with acceptable level of uniformity of winding.

A cam box (4) or a similar traversing arrangement houses the traverse guide (5) of the present invention. As shown in figure 3 a, the traverse guide (5) has at least one groove (5b) to guide advancing yarn (3). The groove (5b) is preferably of a smooth profile without sharp edges. The groove (5b) is optionally fitted with a ceramic element (5bl) through which the advancing yarn (3) passes. Figure 3a shows the unique profile of the traverse guide of the present invention which ensures that the yarn finds its way into the groove (5b) regardless of where the yarn is placed during the yarn return phase. This is a novel feature of the traverse guide of the present invention as it ensures that the yarn is transferred by the guide into its groove (5b) either during the forward or return movement of the guide (5), the forward movement being when it is moving away from the turret plate and the return movement being when it is moving towards the turret plate.

Figure 2b shows the traverse guide together with a transfer link (see figure 3a for details). The transfer link (6) element is provided, typically attached to any appropriate part on winder, preferably near the far end of cam box (4), that is the end of the cam box that is away from the turret plate, or on the traverse box housing. The transfer link (6) assists the traverse guide (5) to direct the advancing yarn (3) towards the grasping device (7) that is provided on the bobbin or on the spindle (8). The transfer link (6) is mounted so that it can freely rotate about the axis of mounting (6f) like a hinge (see figure 2).

The transfer link (6) is provided with a hook-shaped profile (see figure 3) such that the transfer link (6):

A. picks up the yarn (3) from the traverse guide (5) effectively, and

B. after the pick up of the yarn (3) from the traverse guide (5), the yarn (3) does not slip out of the transfer link's (6) control throughout the yarn transfer operation. Phase A above refers to the yarn shift phase and phase B the yarn return phase. The novel design of the present invention has ensured that the yarn can be left off virtually anywhere along the cam box and it will still find its way into the groove (5b) when required.

Yarn shift phase: When a bobbin that is being wound on the winder attains its predetermined package size, the turret rotates such that the full bobbin (1) moves away from the cam box (4) and the empty bobbin (2) is positioned in the path of advancing yarn (3). Next, the traverse guide (5) moves to its extreme position near the bobbin-end fitted with the grasping device (7) and comes to a standstill state at a position detected by a suitable sensor, the preferable position being the end of the traverse stroke. The transfer link (6) rotates about mounting axis (6f) in suitable direction to collect the advancing yarn (3) in the hook (6a).The transfer link (6) continues its rotation away from the traverse guide (5), to carry the advancing yarn (3) away from the winding zone towards the grasping device (7). The grasping device (7) grasps the introduced advancing yarn (3).

It is important that the movement of the transfer link (6) and consequently that of the advancing yarn (3) remains jerk- free during the yarn shifting phase of the yarn transfer operation. The profile of the hook (6a) (see figure 3) is of particular relevance in this respect. The hook (6a) has two prominent parts - a transfer part (6b) that ensures secure transfer of the yarn to the grasping device (7), a return part (6d) that ensures return of the advancing yarn(3) to the traverse guide (5). The preferred profile of transfer part (6b) includes a convex shaped (see figure 3) restricting edge (6c) such that preferably a notch (6e) is formed at the yarn picking end of the hook (6a). As shown in figure 3A the novel profile of the restricting edge (6c) ensures that the yarn (3) is securely restricted to the notch (6e) during the yarn' s movement from the traverse guide (5) to the grasping device (7) so that the yarn does not jerk about during this movement. Alternatively, any other shape that would achieve the jerk-free movement of the yarn may be provided to the transfer part (6b). The speed of the angular movement of the transfer link (6) is maintained under control by any suitable mechanism, typically like electro- pneumatic mechanism such that angular movement of transfer link (6) is not too slow to form uneven winding in yarn package or too fast to break the yarn or cause jerk.

Yarn return phase: Once the yarn (3) has been grasped by the grasping device (7), the transfer link (6), with the advancing yarn (3) still within its hook (6a), rotates towards the traverse guide (5) and with the yarn (3) controlled by the return part (6d) shifts the yarn onto the delivery zone (5e) of the traverse guide (5). Under the effect of the continued tension in the yarn (3), and the novel shape of the traverse guide (5) that partly characterizes the invention, the yarn (3) finds it way back into the groove (5b) of the traverse guide (5) or the optional ceramic element (5bl) that is provided within the groove (5b). The conventional traverse guides are typically small in size so that when the transfer link (6) or a similar device returns the advancing yarn (3), after being grasped, to the traverse guides, the positional synchronization between the various parts of the machinery becomes quite critical.

The novel shape of the traverse guide (5) of the present invention is such that even if the yarn is not accurately placed in the ideal delivery zone (5e) of the traverse guide, the yarn does not slip off the traverse guide and is always directed back into the central groove, either during the forward or backward movement of the traverse guide.

It is crucial for advancing yarn (3), after been grasped in yarn transfer process, the advancing yarn (3) is returned to the groove (5b) swiftly and in the first attempt so that the yarn transfer from the full bobbin (1) to empty bobbin (2) can take place without glitches. The specially designed winged shape of the traverse guide (5) and the hooked shape of the transfer link (6) are crucial for the invention to work to achieve the above said effect. A failure to do so may cause interruption in the yarn winding process, leading to yarn wastage.

In the conventional system it was imperative to ensure that the returning yarn fell into a control zone. Given the speeds involved in the whole operation, it becomes quite cumbersome to practically design the parts of the system to achieve such tight control. The new system of the present invention with its novel profile of the traverse guide ensures that there's no need for a control zone. This results in a system that is simple to implement and reduces the operator induced errors. In the case where the running yarn doesn't fall in the delivery zone (5e), but instead falls into zones from where it will not be possible for it to get transferred in the first attempt, the present invention makes it possible to complete the transfer by eliminating the risk of the winder shutdown. This is achieved with the help of the traverse guide in combination with the first obstacle and the second obstacle. The two obstacles restrict the lateral movement of the advancing yarn (that is the movement along the cam box) so that the yarn remains within the operating area. The second obstacle is typically in the form of a bar, hitherto referred to as a turret bar, which may be straight or bent downward at its end. It is preferably attached to the cam box at its turret end, either fixedly or in any manner that allows its function.

The advantage derived by the operation of the traverse guide and the two obstacles is illustrated with the help of figures 4 to 7.

Figure 4 shows four zones, namely zone 1 , zone 2, zone 3, and zone 4, in which if the yarn falls, it could lead to accidental interruption of the winding processes when used with conventional traverse guides. Figures 4A to 7 illustrate the inventive mechanism due to which the yarn finds its way back into the central groove even if it falls into any of the undesirable ones, zones 1-4.

With respect to Figure 4, it is important to know that the shown positions become undesirable only when the yarn guide moves in the directions shown at the time of placement of the yarn.

With respect to the figure 4A, the yarn is shown to find itself behind the left wing of the traverse guide while the guide is moving towards the turret end (part a of the figure). In the conventional systems, the yarn would have no mechanism to find its way into the groove. In the present invention, as the guide continues its movement towards the turret end, it pushes the yarn along with it till its motion reverses from the turret end (part b of the figure). Upon the reversal of motion of the guide, the yarn, which is under tension, slips out from behind the left wing and finds itself somewhere along the cam box (Fig 4A - part c). The traverse guide reaches the transfer link end of its course and reverses its motion once again (Fig 4A - part d). During this movement towards the turret end, the yarn is now situated in a right position with respect to the yarn guide and easily finds itself in the groove (Fig 4A - part e). Throughout this process the turret bar keeps the yarn within the reach of the traverse guide as necessary. With respect to the figure 5, the yarn is shown to find itself behind the right wing of the traverse guide while the guide is moving towards the transfer link end (Fig 5 - part a). In this situation, in the conventional systems, the yarn would have no mechanism to find its way into its intended position. In the present invention, the intended position is in the groove. As the guide completes its course towards the transfer link, and reverses its course to move towards the turret, the yarn, which is under tension, slips out from behind the guide and finds its way somewhere along the cam box (Fig 5 - part b). The guide during its next motion towards the transfer link is able to slip under the yarn thereby allowing the yarn to slip over the external edge and get into its intended position (Fig 5 - parts c and d).

With respect to the Figure 6, the yarn finds itself inside the 'C shape of the transfer link while the traverse guide is moving towards the turret end (Fig 6 - part a). In this scenario, the traverse guide travels up to the turret end (Fig 6 - part b) and upon its return finds itself positioned under the yarn when it reaches the transfer link (Fig 6 - part c) thereby allowing the yarn to slip over its external edge and get into its intended position (Fig 6 - part d).

Finally, with respect to Figure 7, the yarn could be placed over the left wing of the guide or at any position along the cam box, while the traverse guide is moving towards the transfer link (Fig 7 - part a). In this scenario, the traverse guide simply reverses its motion at the transfer link end and moves towards the turret end. There are two ways in which the present invention works at this point. In the first scenario, the wing tip of the traverse guide will get underneath the yarn and the yarn, which is under tension, will pull itself into the central groove. In the second scenario, the traverse guide pushes the yarn right up to the turret end of the cam box where with the help of a turret bar, it gets underneath the yarn (Fig 7 - part b) thereby allowing the yarn to get into its intended position (Fig 7 - part c).

It can thus be seen that even if the yarn is not placed in its intended position in the first attempt of the yarn transfer, the positioning of the advancing yarn in its intended position is guaranteed with the use of the traverse guide of the present invention.

One other key feature of the present invention is that is smaller in size than some of the conventional guides. This improves the performance of the guide, which operates at a very high speed, and also is more economical. Further, it has been observed that the innovative inner profile (5e), particularly near the central groove (5b), facilitates easy entry of the yarn into the central groove (5b). Consequently, the advantage of the present invention is that the positional synchronization between the movements of traverse guide, transfer device and other relevant automatic winder parts becomes either irrelevant or unimportant and invented device performs with more reliability. It is evident from the foregoing description that the present invention has the following embodiments:

1. A novel device for efficiently guiding the advancing yarn during yarn winding in a turret type autowinder, said device comprising a traverse guide characterized in that the profile of its two flanks is selected from a group comprising

a. one that includes a first inclusive angle, a second inclusive angle, a third inclusive angle,

b. another one that has an external edge which is convex in profile, and an internal edge that is either concave or linear in profile, or a combination thereof; and said traverse guide further has at least one groove (5b) for securing in place the advancing yarn (3), and said two flanks (5c) being attached to a stem (5 a) with which it is fitted in a turret type autowinder, and wherein said traverse guide moves laterally along the traverse device while guiding the advancing yarn during the yarn transfer process.

2. A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in embodiment 1, said device further comprising a first obstacle and a second obstacle, said first obstacle being provided near the far end of the traverse device and said second obstacle being provided at the turret end of the traverse device.

A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in embodiments 1 and 2, wherein said first obstacle is a transfer link (6).

A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in embodiments 1 to 3, wherein said second obstacle is a turret bar, said turret bar being attached to said traverse device at the turret end of the traverse device.

A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in embodiments 1 to 4, wherein said traverse guide (5) is further characterized in that said stem being positioned in a direction perpendicular to the direction of motion of the guide and each of said first inclusive angle, said second inclusive angle, and said third inclusive angle is less than 180°, preferably between 180° and 100°.

A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in embodiments 1 to 5,

wherein said transfer link (6) has a hook (6a), and further wherein said traverse guide (5) and said transfer link (6) are positioned relatively to each other by positioning said traverse guide (5) along the traverse device

(4) at a predetermined location, preferably at the end of the traverse stroke, and by rotatably connecting said transfer link (6) to said traverse device (4) to allow the rotational movement of said transfer link (6) in its own plane, so that the process of yarn movement from said traverse guide (5) to the grasping device (7) and back to said traverse guide (5) is made through the rotational movement of the transfer link (6), such that said yarn (3) always remains secured by said outer wing (5c) and said hook (6a), and wherein said turret bar is positioned near the turret end of the traverse device,

said device being mounted on a traverse device of a typical automatic turret transfer machine.

A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in any of embodiments 1 to 6, wherein said transfer link (6) is rotatably connected to a suitable part of the winder, preferably at the end of the traverse device (4) or a traverse box such that said transfer link (6), during its rotational movement towards said grasping device (7), picks up said yarn (3) from said traverse guide (5).

A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in any of embodiments 1 to 7, wherein said traverse guide (5) is further characterized in that said wings of said traverse guide (5) are positioned such that the angle of said wings is in a range that said transfer link (6), during the yarn return phase, easily places the returning yarn (3) within the delivery zone of said wing of said traverse guide (5).

A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in any of embodiments 1 to 8 wherein said transfer link (6) is further characterized in that the profile of said hook (6a) comprises a transfer part (6b) and a return part (6d), such that said advancing yarn (3) remains secured within said hook (6 a) throughout the process of transferring said yarn (3) to said grasping device (7) and back into said traverse guide (5). A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in any of embodiments 1 to 9 wherein said transfer link (6) is further characterized in that the restricting edge (6c) that forms a part of said transfer part (6b), is of any shape that allows a jerk-free operation of transfer of said yarn (3) to said grasping device (7), preferably a shape that forms a notch (6e) and a convex restricting edge (6c), and in that the return edge that forms a part of said return part (6d), is of any shape that allows a jerk-free operation of returning the yarn (3) to said traverse guide (5), preferably a notch (6e) and a convex edge. A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in any of embodiments 1 to 10 wherein all edges of said guide and said transfer link (6) that come in contact with said yarn (3) are smooth. A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in any of embodiments 1 to 11, wherein said flanks are placed symmetrically or non-symmetrically with respect to said stem. A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in any of embodiments 1 to 12, wherein the number of grooves is two. A novel device for efficiently guiding the advancing yarn during yarn transfer in a turret type autowinder as described in any of embodiments 1 to 13, wherein the at least one of the grooves is fitted with a ceramic element.

While the above description contains much specificity, these should not be construed as limitation in the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. It must be realized that modifications and variations are possible based on the disclosure given above without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.