DE69906543T2 - METHOD AND DEVICE FOR UNWINDING A STRAND - Google Patents

Abstract

Spooling method from hanks and relative reeling-off device to transfer yarns (11) from a hank (12) to a spool (13), wherein the hank (12) is mounted on a reel (14) suitable to rotate around an axis (24), the method providing to use a magnetic drawing assembly (38) to supply a contribution of power for the rotation of the reel (14) such as will not contrast with or brake the normal unwinding of the yarn (11), the drawing assembly (38) comprising at least a drawing element and a drawn element made to rotate by the magnetic forces generated between the said two elements, the rotation of the drawn element being transferred to the reel (14) by means of a mechanical connection between the drawn element and the rotation shaft (23) of the reel (14).

Description

FIELD OF INVENTION

The invention relates to a method for unwinding strands and the unwinding device that carries out the method, as specified in the corresponding main claims.

To be more precise, the invention is used in unwinding processes of strands, in which the yarn is transferred from the strands to the bobbins to be used subsequently.

The invention is advantageously used in all cases where yarns are unwound from strands in order to increase the winding speed onto the bobbin and at the same time to reduce the yarn tensions and thereby reduce the risks of yarn damage and yarn breakage.

BACKGROUND OF THE INVENTION

The state of the art includes unwinding machines or unwinding/winding machines which are used for transferring the yarn from the strands to the bobbins.

After the mercerisation and/or dyeing processes or after the shrinking and/or dyeing processes, the skein is placed on a reel located above or outside the winding heads and the yarn is unwound from the skein exerting a tensile force generally determined by the rotation of the winding heads.

The process of unwinding yarn from the skein can be performed in two ways:

- in the first type, the unwinding method, the reel is set in rotation by the unwinding of the yarn;

- in a second method, the take-off method, the reel is kept stationary and the yarn is taken off the reel in the axial direction. Unwinding by unwinding allows the yarn to be unwound from the skein more regularly and reduces the risk of tangling and therefore of yarn breakage and machine interruptions, but the fact that the skein is set in rotation makes this method unsuitable for heavy or large skeins because it severely limits the speed for fine yarns or yarns with a low breaking load.

On the other hand, the unwinding process can also be used for large strands, but has problems in the case of fine yarns because of the frequent snags, tangles and twists of the yarn that occur, causing breakage and machine stoppages. Of the two processes, however, the unwinding process itself has proven to be the more effective process because in the majority of cases in which it is used, it allows for a more uniform unwinding without snags and formation of spirals.

However, this process has also shown its limitations in the possible low operating speeds, which result from the increasingly frequent use of large and heavy strands.

In these cases, users are required to reduce the unwinding speeds considerably, to maximum values of approximately 250-300 m/min for thinner and less resistant yarns, and approximately 400-500 m/min for thicker yarns that are easier to unwind, such as acrylic yarns.

Numerous methods have been proposed to achieve higher unwinding speeds without causing excessive increases in yarn tension.

For example, patent application UD93A000133 in the name of the present applicant proposed the use of an auxiliary unwinding element mounted idly on the reel shaft and which is rotated by the yarn itself as it is unwound from the reel.

The function of the auxiliary unwinding element is to assist in unwinding the yarn from the skein, to reduce unwinding tensions and to minimize the risk of blockages and tangling.

However, this solution did not produce satisfactory results in terms of increasing the speed and expected productivity of the unwinder.

Another proposed solution was to use a reel controlled by an autonomous motor. This solution also did not produce satisfactory results because it is impossible to instantly adapt the unwinding speed of the unwound yarn supplied by the skein rotated under command to the speed of the yarn taken up by the collecting head.

In other words, since the yarn no longer comes out freely from the skein due to the pulling force caused by the collecting head alone, but is essentially unwound by the motor that rotates the reel, two things can happen:

- either the driven reel rotates too slowly relative to the spool and the motor of the reel then forms a brake for the rotation of the collecting head and thus does not reduce the tension in the unwound yarn;

- or the driven reel rotates too fast and the yarn then winds back onto the reel.

An example of this solution is shown in DE-A-38 84 00, which provides for associating a pulley controlled by a motor with the reel axis.

The pulley causes the reel to rotate in the same direction and at the same speed as the unwinding yarn to minimize the resistance with which the yarn is removed from the strand.

This solution is theoretically valid, as indicated above, but has proved to be impracticable in practice, since it is extremely difficult to synchronise perfectly and in every situation the speed of the spool that draws off the yarn with the speed of the motor that rotates the reel.

The present Applicant has designed, tested and carried out this invention to overcome these disadvantages and has arrived at a solution which allows the unwinding speed of the yarn from the skein to be increased without causing increases in tension in the unwound yarn.

SUMMARY OF THE INVENTION

The invention is set out and characterised in the relevant main claims, while the dependent claims describe other features of the invention.

The purpose of the invention is to provide a reel-unwinder in which the reel on which the strand is arranged is drawn into rotation not only by the yarn gathered by the winding head, but also by additional devices whose action There is assistance that does not in any way hinder or slow down the normal unwinding of the yarn.

In other words, the action of the additional device provides a driving contribution to the rotation of the reel which reduces the traction exerted on the yarn by the winding head; this contribution is strictly and directly dependent on the increase in yarn tension resulting from the use of high unwinding speeds and it allows the unwinding speed to be increased considerably without increasing the yarn tension.

This invention therefore drastically reduces the risk of yarn breakage or damage, such as thinning or chafing, caused by high tensions in the yarn due to high unwinding speeds and/or high weight of the strand.

The invention makes it possible to achieve high unwinding speeds of the order of at least 500 to 800 m/min and even more depending on the type of yarn being processed, even when the strands are very heavy.

The device according to the invention contains a magnetic traction arrangement which cooperates with the rotating shaft on which the reel is mounted and which is suitable for providing an additional energy contribution for the rotation of the reel.

The magnetic train arrangement essentially consists of two elements:

- a first element or traction element comprising a pulley or disk on whose circumference several pairs of magnets are mounted, the pulley being associated with means suitable for setting it in rotation;

- a second element or drawn element consisting of a plate or a ring made of ferromagnetic material, arranged coaxially with the pulley and substantially opposite it and suitable for being set in rotation by the action of the magnetic forces exerted by the rotating pulley.

According to the invention, the magnetic pulling effect of the pulling element on the pulled element occurs in such a way that the speed of the pulling element is always greater than that of the pulled element.

The second element or drawn element is mechanically associated with the rotating shaft of the reel, and therefore the pulling torque that occurs between the two elements as a result the magnetic forces generated are transferred to the reel as an additional energy contribution to its rotation.

In this way, since the energy required to rotate a strand of predetermined weight at a predetermined speed is a defined value, the energy contribution provided by the magnetic traction arrangement reduces the remaining energy required from the yarn and therefore the yarn tension.

With this structure, which achieves the basic properties of the invention, the rotating shaft of the reel is not forced to rotate, as would be the case if a motor were mechanically connected to the shaft, but rather it is "helped" to rotate, while remaining free.

The invention provides for correlating the torque or energy provided by the magnetic pulling arrangement with the yarn tension so that at any given moment the contribution provided by the pulling arrangement partially compensates for the energy required for a given unwinding speed.

In a preferred embodiment, the contribution provided by the magnetic traction arrangement is in the order of 75-98% of the total energy required to rotate the reel, but is never more than 100%, since in this case the yarn would be rewound onto the reel.

In a first embodiment of the invention, the magnetic traction assembly is arranged substantially coaxially with the rotating shaft of the reel and comprises a magnetic disk associated with means for causing it to rotate and a ring element fixedly connected to the rotating shaft of the reel.

According to a further embodiment, the magnetic pulling arrangement is arranged offset in relation to the rotating shaft of the reel, and transmission devices are provided to transmit the movement of the pulled element to the reel shaft.

This embodiment is preferred because it is not necessary to correlate the rotation speed of the turntable with the speed of the reel; in this way it is possible to assume speeds such that optimal effectiveness of the pulling arrangement is guaranteed.

In one embodiment of the invention, the means for rotating the magnetic disk consists of a belt driven by the winding head; the drive of the belt is therefore suitably correlated with the speed of the collecting head.

In another embodiment, the magnetic disk is rotated by an autonomous motor controlled by an inverter.

In this case, the magnetic disc can be mounted axially with the motor or at any intermediate position between the motor axis and the reel axis; in this second case, there are suitable first transmission and return means which transmit the movement from the motor to the disc and second transmission means which transmit the movement from the disc or ring to the reel.

In a variant of this second embodiment, the motor driving the magnetic disk is controlled by sensor means which continuously monitor the tension of the yarn during the unwinding process, regulate the speed of the motor and therefore regulate the energy contribution in such a way that the tension is maintained at a substantially constant value.

In an equivalent variant of the embodiments described above, the functions of the magnetic disk and the ring or plate can be interchanged, the ferromagnetic ring or plate associated with the rotating device (e.g. the belt driven by the collecting head or an autonomous motor) being used as a pulling element and the associated magnetic disk being a pulled element mechanically connected to the rotating shaft of the reel.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are to be considered as a non-limiting example and show some preferred embodiments of the invention as follows:

Fig. 1 is a schematic partial side view of the unwinding device according to the invention;

Fig. 2 is a partial front view on an enlarged scale of the unwinding device shown in Fig. 1;

Fig. 3 is a front view of a possible embodiment of the magnetic disk used in the invention;

Fig. 4 shows a detail of a variant of Fig. 2;

Fig. 5 shows a variant of Fig. 3 of the magnetic disk used in the embodiment of Fig. 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The unwinding device 10 shown schematically in Fig. 1 is suitable for transferring the yarn 11 from a strand 12 to a spool 13.

The strand 12, arranged on a reel 14, is unwound according to the unwinding method due to the tensile force exerted by the coil 13 being formed, which is rotated by friction by a first cylinder 17a controlled by the shaft 15.

Furthermore, a cylinder 17b is provided on which a traveler 16 is mounted in a known manner, which travels axially back and forth along the bobbin 13 and deposits yarn spirals in successive layers on the bobbin 13.

The movement of the two cylinders 17a and 17b and also of the rotor 16 by a motor 20 and a belt 21 or by two separate motors is generally known in the art and is therefore not described further here.

The inclusion of an oscillating arm 18 is also widely known; it has one or more small rollers 19 at the end over which the yarn 11 issuing from the strand 12 passes; the function of the arm 18 is to build up a yarn reserve in combination with the return roller 36 and the yarn feed rollers 22.

The swing arm 18 can, as known in the art, move from a high position (shown by a solid line) to a low position (shown by a dot-dash line) to build up the yarn reserve to allow the spool 13 and the reel 17 to be stopped by known braking devices without yarn breakage occurring in the event of a blockage.

In the case shown in Fig. 1, between the reel 14 and the bobbin 13 there are three rollers 22 over which the yarn 11 runs and which serve to reduce and stabilize the tension before winding begins and also to be able to obtain, in combination with the tensioning and waxing devices 28 and 37 respectively, bobbins 13 of any desired shape for the various purposes.

The path followed by the yarn 11 includes the passage over the rollers 19 and the yarn feed rollers 22 and is shown with a dot-dash line; the dotted line shows an alternative path for the yarn 11 for high speeds and for yarns which are simply unwound, which provides for essentially direct winding without any devices between the strand 12 and the bobbin 12 for creating a yarn reserve.

The reel 14 is mounted on a shaft 23 with a longitudinal axis 24 which is cantilevered at one end of a support 25 as shown in Fig. 2. The shaft 23 and the reel 14 are supported by means of bearings 27 on a bushing 26 which is firmly connected to the support 25.

According to the invention, a magnetic traction arrangement 38 is provided which cooperates with the shaft 23 and consists of a magnetic disk 30 and an associated plate or ring element 35.

The magnetic pulling arrangement 38 is adapted to provide an additional energy contribution for the rotational drive of the reel 14, which helps to reduce the pulling effect on the yarn 11 caused by the rotation of the spool 13.

In the embodiment shown in Fig. 2, the disk 30 is mounted in direct cooperation with the shaft 23 and is adapted to rotate on bearings 29 on the bushing 26.

In this case, the disk 30 is rotated by a belt 31 connected on one side to the disk 30 and on the other side to a small pulley 32 fixed to the rotary shaft 15 which moves the spool 13.

In the embodiment shown here, the small pulley 32 has three grooves in which the belt 31 can be alternatively arranged in order to change the speed ratio between the spool 13 and the pulley 30.

Magnet pairs 34, which are arranged in close proximity to a ring 35 firmly connected to the rotary shaft 23 of the reel 14, are attached to the disk 30, in this case on the circumference thereof (Fig. 2 and 3).

The ring 35 is made of ferromagnetic steel; the composition and the relative level of magnetism of the steel can vary according to the type of application and the results to be obtained.

In the variant shown in Fig. 4, the magnetic arrangement 38 is driven by means of an autonomous motor 33.

In this embodiment, the motor 33 is adapted to rotate the plate element 35 facing the magnetic disk 30 which carries the magnet pairs 34 on the front side.

The magnetic disk 30, which is held on bearings 39, is rotated by the plate element 35 due to the magnetic forces generated between the plate 35 and the magnets 34.

In this case, the magnetic disk 30, which is here the drawn element, is connected to the rotating shaft 23 of the reel 14 via a return consisting of a pair of small disks 40 and 41, which are connected to the magnetic disk 30 and the shaft 23 respectively via corresponding belts 42 and 43.

According to a variant of this embodiment, not shown here, the magnetic disk is connected directly by disks or belts to the shaft 23 of the reel 14 without intermediate return elements.

According to another variant, not shown here, the magnetic traction assembly 38, consisting of the disk 30 and the plate 35, is arranged at an intermediate point between the axis 44 of the motor 33 or the axis of the small disk 32 connected to the shaft 15, and the axis 24 of the reel 14, also including transmission means such as pulleys, belts and return rollers to transmit the movement from the motor 33 to the assembly 38 and from the assembly 38 to the shaft 23 of the reel 14.

The embodiment which provides the pulling assembly 38 off-axis with respect to the reel 14, for example that shown in Fig. 4 or other equivalents, is preferred because it is not necessary to correlate the speed of the pulled part with that of the reel and therefore it is possible to operate the magnetic assembly 38 with maximum efficiency.

The unwinding device described above works as follows:

During the unwinding process, the reel 14 is rotated by the tensile force exerted by the yarn 11 as it is taken up by the rotation of the spool 13.

Together with the coil 13, the magnetic disk 30 is also set in rotation, either directly by means of the belt 31 in the case of Fig. 2 or by drive from the autonomous motor 33 in the case of Fig. 4.

Due to the magnetic forces generated between the magnet pairs 34 and the ring or plate 35 mechanically connected to the rotating shaft 23 of the reel 14, the rotation of the disc 30 produces an energy contribution to the rotation of the reel 14 which is added to the residual energy required by the yarn 11 taken up by the bobbin 13 and which is the energy which produces the actual tension in the yarn.

By appropriately acting on the additional torque provided thanks to the magnetic traction, it is possible to maintain the residual energy required by the yarn 11 at a low level, for example 10 to 20%, at any unwinding speed, and this makes it possible to use high unwinding speeds at relatively low tensions in the yarn 11.

The magnitude of the additional torque depends not only on the number of magnet pairs 34, the size of the air gap and the materials used, but also on the relative speed between the pulling and pulled element, since the magnitude of the torque increases as this relative speed increases.

Depending on the application, the speed of the pulling element can deviate from the speed of the pulled element by between 1.3 and 4 times.

In the case of Fig. 4, the motor 33 is advantageously controlled by a voltage sensor 45 which, via a suitable electronic control logic, controls the motor chopper in such a such that the variations - either increases or decreases - in the tension of the yarn 11 are compensated by variations - either increases or decreases - in the speed of the motor 33.

According to a variant of the embodiment shown in Fig. 4, the plate or ring 35 and the magnets 34 are arranged in such a way that they can be adjusted axially in order to move them away from each other or bring them closer together.

This makes it possible to vary the torque applied by the magnetic arrangement 38 to the reel 14 and thus the relative additional energy supplied as desired.

Although this embodiment has been described, all equivalent embodiments fall within the field and scope of this invention, for example the embodiment which provides in Fig. 2 that the magnets 34 are fixedly connected to the rotating shaft 23 of the reel 14 and the ring 35 is rotated by the belt 31; or the embodiment which provides in Fig. 4 that the magnetic disk 30 is mounted on the axis of the motor 33 and the plate 35 is driven in rotation due to the magnetic forces generated.

Claims (19)

1. A method of winding strands for transferring yarns (11) from a strand (12) to a spool (13), the strand (12) being arranged on a reel (14) having a shaft (23) capable of rotating about an axis (24) due to the pulling action exerted by the yarn (11) when it is taken up by the spool (13), characterized in that it provides for the use of a magnetic pulling arrangement (38) cooperating with the rotating shaft (23) of the reel (14) to provide an energy contribution to the rotation of the reel (14) in such a way that it does not conflict with the normal unwinding of the yarn (11) or brake it, the pulling arrangement (38) comprising at least one pulling element (30 or 35) and one pulled element (35 or 30), the pulling action causing the pulled element to rotate, to induce a free rotation in the drawn element due to the magnetic forces generated between the two elements and to transmit the rotation of the drawn element to the rotary shaft (23) of the reel (14) through a mechanical connection between the drawn element and the shaft (23). 2. Winding process according to claim 1, characterized in that it provides that the energy contribution to the rotation of the reel (14) depends on the magnitude of the tension of the yarn (11) during the unwinding process. 3. Winding device according to claim 1 or 2, characterized in that it provides for the drawn element of the pulling arrangement (38) to be set in rotation by the take-up movement directly from the rotating elements (15) of the spool (13). 4. Winding device according to claim 1 or 2, characterized in that it provides for the drawn element of the pulling arrangement (38) to be set in rotation by the receiving movement of autonomous drive devices (33). 5. Winding device according to one of the preceding claims, characterized in that it provides that the pulling arrangement (38) makes a contribution to the rotary drive of the reel (14) of approximately 75 to 98% of the total energy required. 6. Winding process according to one of the preceding claims, characterized in that it provides that the speed of the pulling element is 1.3 to 4 times greater than the speed of the pulled element. 7. Unwinding device for transferring yarns (11) from a strand (12) to a spool (13), comprising a reel (14) carrying the strand (12) and fixed to a shaft (23) rotating about an axis (24), a shaft (15) suitable for setting the spool (13) in rotation, guide means for the yarn (11) arranged between the strand (12) and the spool (13), the unwinding device being characterized in that it comprises a magnetic traction assembly (38) cooperating with the rotating shaft (23) of the reel (14) and comprising at least a first element or pulling element (30 or 35) associated with means (31, 33) suitable for setting it in rotation and a second element or pulled element (35 or 30) arranged coaxially with the pulling element and suitable for magnetic forces by the pulling element, the pulled element (30 or 35) being mechanically connected to the rotating shaft (23) of the reel (14) and being suitable for supplying to the shaft (23) a free and additional energy contribution which is added to the pulling action of the yarn (11) exerted by the spool (13) in order to correspondingly reduce the tension in the yarn (11) generated by the pulling action caused by the spool (13). 8. Device according to claim 7, characterized in that the first element is a rotating disk (30) which carries magnet pairs (34) on its circumference, and the second element is a plate or ring element (35) which is arranged substantially opposite and coaxial with the rotating disk. 9. Device according to claim 8, characterized in that the magnet pairs (34) are arranged on the edge on the circumference of the magnetic disk (30). 10. Device according to claim 8, characterized in that the magnet pairs (34) are arranged frontally on the circumference of the magnetic disk (30). 11. Device according to claim 8, characterized in that the rotating disk (30) and the plate or ring element (35) are arranged coaxially to the axis of rotation (24) of the reel (14). 12. Device according to claim 11, characterized in that the plate or ring element (35) is firmly connected to the rotary shaft (23) of the reel (14). 13. Device according to claim 8, characterized in that the rotating disk (30) and the plate or ring element (35) are arranged axially offset from the axis of rotation (24) of the reel (14), also including devices for transmitting the movement for transmitting the movement from the plate or ring element (35) to the rotating shaft (23) of the reel (14). 14. Device according to one of claims 7 to 13, characterized in that the means which set the pulling element (30 or 35) in rotation comprise a belt (31) which receives the movement from the means (15) which is suitable for setting the reel (13) in rotation. 15. Device according to one of claims 7 to 13, characterized in that the means which sets the pulling element (30 or 35) in rotation is an autonomous motor (33). 16. Device according to claim 15, characterized in that the pulling element (30 or 35) and the pulled element (35 or 30) are arranged coaxially with the motor (33), wherein the pulling element (30 or 35) is mechanically connected to the motor (33) and the pulled element (35 or 30) is mechanically connected to the shaft (23) of the reel (14) by motion transmission devices. 17. Device according to claim 16, characterized in that the movement transmission device contains at least one return device (40, 41) which is suitable for distinguishing the number of revolutions of the pulling element (30 or 35) from the number of revolutions of the reel (14). 18. Device according to claim 15, characterized in that the pulling element (30 or 35) and the pulled element (35 or 30) are arranged at an intermediate position between the motor (33) and the rotary shaft (23) of the reel (14), wherein transmission means are included which transmit the movement from the motor (33) to the pulling element, and transmission means are included which transmit the movement from the pulling element to the shaft (23). 19. Device according to claim 15, characterized in that it contains a device (45) for monitoring the instantaneous tension of the unwound yarn (11), which is suitable for influencing the operation of the motor (33).