Apparatus and method for controlling air-bag and winding unit comprising the same

Abstract

The present disclosure relates to a device for controlling air loops and a winding unit comprising the device, wherein the device for controlling air loops comprises: - a first limiting element having a longitudinal axis and a through opening adapted to pass the yarn to be left from the bobbin; - a support adapted to support the first limiting element and to be fixed to the structure of the winding unit; wherein the first limiting element comprises a first limiting part and a second limiting part; wherein the support comprises a first arm and a second arm, the first limiting part and the second limiting part being positioned on the first arm and on the second arm, respectively; wherein the device comprises a drive device adapted to move the first arm and the second arm, and therefore the first limiting part and the second limiting part, between a first position and a second position; and wherein the device comprises a second limiting element. The device allows an increase in productivity and a reduction in the phenomenon of several loops being simultaneously detached from the bobbin and in the number of yarn breaks.

Description

TECHNICAL FIELD

[0001] The present invention relates to a device for controlling the balloon during unwinding of an online bobbin, a winding unit provided with such a device, and a method for controlling the balloon during unwinding of an online bobbin. BACKGROUND

[0002] As is known, industrial winding machines comprise a plurality of winding units, which are independent from one another and controlled by a programmable control unit.

[0003] The winding device serves to wind the yarn on a support, usually conical, to produce a spool that will be used for weaving, knitting or other subsequent processing. The yarn is wound on the support in a predetermined winding type to optimize the subsequent unwinding of the yarn from the spool during the weaving phase.

[0004] In the present discussion, the term "thread" or "filament" or "continuous thread" refers to a single filament or continuous strand (for example in the case of silk, rayon or synthetic fibers), while the term "yarn" refers to a group of variable length elementary fibers arranged in parallel and joined by twisting. In the following, either term will be used indistinctly, it being understood that the application of the invention is not limited to one type or the other.

[0005] The yarn is wound on the spool, preferably by means of a drum that is in contact with said spool and rotates around an axis substantially parallel to the axis of the spool. The drum is provided with a seat of predetermined geometry that engages and guides the yarn during the winding thereof on the spool.

[0006] It is evident that a high winding speed of the yarn on the spool corresponds to a high unwinding speed of the bobbin from which the yarn is supplied.

[0007] One of the main consequences of increasing the unwinding speed of the bobbin is an increase in tension due to the unwinding, which in some cases can cause the yarn to break and, in any case, is harmful to the yarn, since the defect can increase the specific pressure in the contact points of the thread.

[0008] The yarn near the bobbin forms a so-called balloon: as the yarn is unwound from the bobbin, the balloon, which is related to the shape of the yarn wound on the bobbin, becomes wider and this widening extends above the bobbin up to a cylindrical connection point located above the tube. The more the unwinding speed increases, the more the diameter of the balloon increases, until it collapses and slides onto the tube, losing its characteristic shape. Basically, at the speed increase, the centrifugal force is not enough to overcome the other forces involved (mainly the Coriolis force, also the aerodynamic resistance), and the balloon approaches the tube.

[0009] In addition, when the spool is emptied, the tension further increases due to the lowering of the thread from the pick-up point of the spool, and the height of the balloon increases, which can collapse.

[0010] The correlation between the diameter of the balloon and the tension due to unwinding is known; in particular, it is known that as the unwinding speed of the spool increases, the diameter of the balloon increases and, consequently, the unwinding tension also increases. Moreover, in the case of collapse of the balloon, the tension is further raised by the friction generated between the thread and the tube. This friction can in particular deteriorate the yarn.

[0011] The prior art attempts to solve this problem by making the yarn pass inside a containment element which is part of a system known as balloon eliminator and which is substantially cylindrical, coaxial to the spool and located near the upper end of the spool, trying to limit the diameter of the balloon.

[0012] When the spool is emptied, the yarn lowers from the pick-up point of the spool, increasing the height of the balloon and, consequently, the maximum diameter of the balloon increases until it collapses. This increase in height causes the containment effect to be lost, significantly reducing the effectiveness of this system.

[0013] For this reason, the balloon eliminators of the known type provide additional functions, such as the downward movement of the containment element when the amount of yarn remaining on the spool decreases.

[0014] This solution is particularly advantageous because it allows to maintain an optimal distance between the yarn still wound on the spool and the containment element, thus allowing to optimally contain the balloon inside the containment element.

[0015] However, since each winding machine can comprise several tens of winding units, comprising several tens of such devices, the system is technically complex and expensive.

[0016] In fact, the movement is performed by means of a motor connected to a screw element, parallel to the direction of movement of the containment element, using a so-called screw-nut coupling.

[0017] The device also comprises a sensor, for example an optical sensor, adapted to detect the height of the portion of the spool covered by the yarn and to transmit this information to a programmable control unit which therefore commands the motor to lower the containment element.

[0018] Therefore, as mentioned above, the solution proposed by the prior art, although widely used and functional, is not without drawbacks.

[0019] First of all, this system is very complex, since it requires continuous monitoring of the winding condition of the yarn on the on-line spool, in order to continuously move the limiting element.

[0020] Moreover, as mentioned above, this system is an expensive system, since it envisages the use of motors, means to convert the rotational movement into a translational movement of the limiting element, and sensors to evaluate the quantity of yarn wound on the spool.

[0021] Therefore, it is evident that the cost of incorporating these means into all the winding units has a considerable impact on the final cost of the winding machine.

[0022] These systems also make the system rise in the event of yarn breakage, to allow the free pick-up of the thread from the spool with a suitable suction nozzle, or even provide additional means for holding the thread.

[0023] Moreover, the reduction of the tension achieved for some yarns can worsen the hairiness of the yarn due to the friction generated. SUMMARY

[0024] Therefore, there is a need to at least partially solve the drawbacks and limits mentioned in the prior art.

[0025] Therefore, there is a need to provide a device for controlling the tension of the loop that enables the unwinding tension to be better managed and increases the production speed without increasing the hairiness of the thread. This device should have a simpler structure than the devices of the prior art, and therefore be easy and inexpensive to implement in the winding units.

[0026] Moreover, from the point of view of simplifying the structure of the device, there is a need for a system that does not require the use of additional sensors to establish the winding condition of the yarn on the on-line spool.

[0027] Furthermore, there is a need for a device for controlling the loop that is more efficient than the devices of the prior art.

[0028] The present disclosure relates to a device for controlling a balloon during the unwinding of a yarn from a bobbin in a winding unit, said device for controlling a balloon comprising: - a substantially tubular first limiting element having a longitudinal axis and a through opening adapted to pass the yarn to be taken off the bobbin; - a support adapted to support the first limiting element and to be fixed to the structure of the winding unit; wherein the first limiting element comprises a first limiting part and a second limiting part; wherein the support comprises a first arm and a second arm, the first limiting part being positioned on the first arm and the second limiting part being positioned on the second arm; wherein the device for controlling a balloon comprises drive means adapted to move the first arm and the second arm, and therefore the first limiting part and the second limiting part, between two positions: a first position in which the first limiting part and the second limiting part are spaced apart, and a second position in which the first limiting part and the second limiting part are closer together with respect to the first position; and wherein the device for controlling a balloon comprises a stationary second limiting element arranged downstream of the first limiting element, the second limiting element being arranged with a second through opening comprising a base portion which, in use, faces the first limiting element, the base portion having a substantially rectangular cross section with respect to the longitudinal axis.

[0029] The present disclosure also relates to a winding unit comprising the aforementioned device for controlling a balloon during the unwinding of a yarn from a bobbin.

[0030] The present disclosure also relates to a method for controlling a balloon by the aforementioned device for controlling a balloon, said method comprising: a step a. of measuring an operating parameter during the unwinding of a yarn from a bobbin; a step b. of comparing the operating parameter with a predetermined value of the operating parameter; and a step c. of operating the first limiting element based on the comparison in step b. so that the first limiting part and the second limiting part move from the first position to the second position, or to an intermediate position if present.

[0031] The device and method for controlling a balloon make it possible to increase the production rate and to reduce the phenomenon of several loops coming off the bobbin at the same time and the number of yarn breaks. BRIEF DESCRIPTION OF DRAWINGS

[0032] Further characteristics and advantages of the present invention will become better apparent from the following detailed description of a preferred, non-limiting embodiment of the present invention, illustrated by way of non-limiting example in the accompanying drawings wherein:

[0033] Figure 1schematically shows a front view of the device for controlling a balloon according to the present application;

[0034] Figure 2 schematically shows a perspective view of the device for controlling a balloon according to the present application;

[0035] Figure 3 schematically shows a perspective view of the device for controlling a balloon according to the present application;

[0036] Figure 4a 、 Figure 4b and Figure 4c schematically shows three possible unwinding steps according to an embodiment of the method for unwinding a yarn from a bobbin according to the present application;

[0037] Figure 5 schematically shows a front view of a cross section of a portion of the device for controlling a balloon according to the present application;

[0038] Figure 6 schematically shows a front view of the device for controlling a balloon according to the present application;

[0039] Figure 7 schematically shows a front view of a cross section of a component of the device for controlling a balloon according to the present application;

[0040] Figure 8 schematically shows a perspective view of a component of the device for controlling a balloon according to the present application;

[0041] Figure 9 schematically shows a plan view from above of a portion of the device for controlling a balloon according to the present application;

[0042] Figure 10 schematically shows a plan view from below of a portion of the device for controlling a balloon according to the present application; and

[0043] Figure 11 schematically shows a front view of a portion of the device for controlling a balloon according to the present application.

[0044] In the following, elements or parts of elements that are identical with the described embodiments will be denoted with the same reference signs. DETAILED DESCRIPTION

[0045] In Figure 1 , the reference sign 12 is used to denote in its entirety a device for controlling a balloon during the unwinding of a yarn 14 from a bobbin 16 in a winding unit 18.

[0046] The device for controlling a balloon 12 comprises:

[0047] - a substantially tubular first containment element 20 having a longitudinal axis X and a through opening 22 adapted to pass the yarn 14 to be unwound from the bobbin 16; and

[0048] - a support 24 adapted to support the first containment element 20 and to be fixed to the structure of the winding unit 18.

[0049] As shown, the first containment element 20 comprises a first containment part 120 and a second containment part 220. Moreover, the support 24 comprises a first arm 124 and a second arm 224, on which the first containment part 120 and the second containment part 220 are respectively positioned.

[0050] The device 12 for controlling the air loop comprises a driving device 26 adapted to move the first arm 124, the second arm 224, and therefore the first containment part 120, the second containment part 220, between a first position, in which the first containment part 120, the second containment part 220 are spaced apart from each other, and a second position, in which the first containment part 120, the second containment part 220 are closer together with respect to the first position.

[0051] According to one possible embodiment, in the second position, the first containment part 120, the second containment part 220 can be in contact with each other.

[0052] In other words, in the first position, the first containment part 120, the second containment part 220 can be spaced apart so as to substantially not interact with the air loop formed during the unwinding of the yarn 14 from the bobbin 16.

[0053] While, in the second position, the first containment part 120, the second containment part 220 can be closer together, and possibly in contact with each other, so as to substantially interact with the air loop formed during the unwinding of the yarn 14 from the bobbin 16.

[0054] According to one possible embodiment, one or more intermediate positions can be provided between the first position and the second position of the first containment part 120, the second containment part 220, so as to allow to limit the air loop according to the size of the air loop.

[0055] According to one possible embodiment, in the second position, the through opening 22 can be substantially cylindrical and have an outward flared portion 28 at the input portion of the yarn 14.

[0056] In fact, as for example Figure 1 or Figure 2As shown, the first limiting member 120, the second limiting member 220 can have a widening and therefore the diameter of the through opening 22 increases at the input portion of the yarn 14.

[0057] According to a possible embodiment, the through opening 22 can have a narrowing 29 at a position opposite the input of the yarn of the through opening 22.

[0058] According to a possible embodiment, which can be seen for example in Figure 3 the first arm 124 and the second arm 224 can rotate in opposite directions around respective rotation axes Y, Z which are spaced apart from each other and substantially parallel to said axis X.

[0059] The first arm 124 and the second arm 224 can be provided with cogwheels 126, 226 integral with their respective arms, which cogwheels mesh with each other and are adapted to rotate around their respective axes Y, Z, so that the rotation of one arm causes the rotation of the other arm and therefore the rotations are synchronized.

[0060] One such embodiment is shown for example in Figure 9 where the cogwheels 126, 226 are shown, which can also be incomplete and provided only at a portion of the circumference of the cogwheels.

[0061] According to a possible alternative embodiment, the drive means can comprise an alternative system to the cogwheels 126, 226, for example articulated quadrilateral kinematic movements or crank mechanisms.

[0062] According to a possible embodiment, the drive means 26 can comprise a linear actuator 260 connected with the second arm 224 of the arms, which linear actuator is connected to the lever 128 provided on the second arm 224, whereby a linear movement of one operating end of the linear actuator 260 causes the rotation of the second arm 224 and therefore of the first arm 124.

[0063] The linear actuator can be for example a pneumatic or electric actuator, which is known per se to the person skilled in the art.

[0064] According to alternative embodiments, the first arm 124, the second arm 224 can be driven in a different technical way, for example by using a rotary actuator or the like. Also in this case, the actuator used can be for example pneumatic or electric.

[0065] More specifically, it is also possible to envisage providing two actuators, one for each arm. In this case, the arms can also not be coupled with cogwheels.

[0066] According to an alternative embodiment, the drive device 26 can be adapted to move the first limiting member 120, the second limiting member 220 in a rectilinear direction. For example, a linear actuator can be provided which is shared by both the first limiting member 120, the second limiting member 220 or a linear actuator is provided for each linear element.

[0067] Furthermore, the drive device can be adapted to cause the first limiting member 120, the second limiting member 220 to implement an asynchronous movement.

[0068] In another alternative embodiment, the linear actuator can be keyed directly to one of the limiting members, for example, and can also cause the movement of the other limiting member by means of a mechanical transmission.

[0069] The device 12 for controlling the air loop comprises a stationary second limiting element 50 arranged downstream of the first limiting element 20, the second limiting element comprising a second through opening 52 arranged with a base portion 54 facing, in use, the first limiting element 20, the base portion having a substantially rectangular cross section with respect to the longitudinal axis X.

[0070] Advantageously, the second limiting element 50 can be arranged on the same support 24 as the first limiting element 20.

[0071] According to one possible embodiment, the base portion 54 of the second through opening 52 can have a substantially square cross section. More specifically, the base portion can have a substantially square cross section with sides having a size of 20 mm to 30 mm, preferably of 24 mm to 28 mm, even more preferably of about 26 mm. Furthermore, along a longitudinal direction perpendicular to the cross section of the second through opening 52, the height of the base portion 54 of the second through opening 52 can be of 30 mm to 45 mm and preferably of 35 mm to 40 mm.

[0072] According to one possible embodiment, the substantially rectangular or square cross section can comprise inward protrusions at the midpoints of each side constituting the rectangular or square cross section.

[0073] The second through opening 52 can comprise a central portion 56 having a substantially truncated pyramid shape with a larger base at the base portion 54 in a position opposite the input section of the yarn in the second limiting element 50.

[0074] According to one possible embodiment, the truncated pyramid-shaped central portion 56 comprises a smaller base having a substantially circular shape, opposite the larger base. The second through opening 52 can also comprise a final portion 58 having a substantially cylindrical shape.

[0075] In other words, according to one possible embodiment, during the unwinding phase of the bobbin, the yarn 14 can pass within the first limiting element 20 and subsequently within the second limiting element, in particular within the base portion 54, the central portion 56 and the final portion 58.

[0076] As shown in the figures, the second limiting element 50 has a cross section which is, for example, rectangular or square. Figure 10 As shown, the edges of the cross section of the second limiting element 50 can be, for example, joined together so that there are no internal edges.

[0077] In fact, it is precisely due to the rectangular or square cross section that the continuity of the loop is interrupted during its formation. Figure 4a More specifically, the continuous friction and collision of the yarn on the sides of the limiting element delays the formation of the loop and, therefore, the increase in the longitudinal tension component of the yarn.

[0078] As the amount of yarn in the bobbin decreases, the loop tends to form in a lower position than before.

[0079] In fact, it can be seen that, in the first part of the unwinding of the bobbin Figure 4a , the limitation of the loop is less effective than the continuous breaking by the second limiting element 50. In this way, because the height of the loop is limited, the tension can be limited.

[0080] Once the bobbin starts to empty, for example approximately through half of the bobbin, the second limiting element 50 is ineffective as the height of the loop increases (and therefore the tension of the yarn increases).

[0081] This height causes the thread to slide on the top end of the tube, therefore no longer in contact with the inner surface of the second limiting element 50. Figure 4b

[0082] At this point, the first limiting element 20 is closed in the second position.

[0083] The method for controlling the loop by means of the device 12 for controlling the loop mainly comprises:

[0084] Step a. measuring an operating parameter during the unwinding of the yarn 14 from the bobbin 16;

[0085] Step b. comparing the operating parameter with a predetermined value of the operating parameter, for example in a programmable control unit (not shown in the figures); and

[0086] Step c. based on the comparison in step b., actuating the first limiting element 20 so that the first limiting member 120 and the second limiting member 220 move from the first position to the second position, or to the intermediate position if present.

[0087] According to one embodiment, the operating parameter used can be the percentage of yarn unwound from the bobbin.​

[0088] According to one possible alternative implementation, the operating parameter can be, for example, the yarn tension measured downstream of the device 12 for controlling the balloon.

[0089] Therefore, the first limiting element 20 can be actuated from the first position to the second position, or to the intermediate position if present, when the yarn tension measured downstream of the device exceeds a certain value.

[0090] Moreover, in order to prevent tension peaks from impairing the effective actuation of the first limiting element, the actuation of the limiting element from the first position to the second position or to the intermediate position if present can be performed when a certain tension value is exceeded a predetermined number of times or for a predetermined length of time.

[0091] In this way, temporary disturbances in the system can be prevented from impairing the winding.

[0092] For example, a thread tension regulation system already installed on the winding machine can be used. In fact, thread tensioning systems usually work between a minimum value and a maximum value respectively corresponding to the maximum winding tension and to the minimum winding tension, and the winding speed and the actuation of the first limiting element can be regulated with said system.

[0093] In particular, the thread tension regulation system can be used so that the first limiting element is actuated when the thread tensioner operates near the minimum value, corresponding to the high winding tension, or when a certain value is exceeded a predetermined number of times or for a predetermined length of time.

[0094] As for the regulation of the distance between the device 12 for controlling the balloon and the tube of the bobbin, this depends on the unwinding parameters, as will be apparent to those skilled in the art. More specifically, the distance between the device and the tube of the bobbin can be regulated as a function of, for example, the behaviour of the balloon at a certain unwinding speed and of the number of yarns.

[0095] For example, the distance between the second limiting element and the tube of the bobbin can be approximately 10-30 mm, while the distance between the first limiting element and the second limiting element can be approximately 4-12 mm.

[0096] According to one possible implementation, the distance between the end of the tube of the bobbin and the narrowing 29 of the first limiting element can be between 4 mm and 12 mm.

[0097] According to one possible implementation, the through opening 22 can have a diameter of approximately 26-42 mm. The narrowing 29 can have a diameter of approximately 22-40 mm.

[0098] In the attached figures, only a portion of the winding unit is shown, at least because the other components are known per se to those skilled in the art.

[0099] Therefore, the advantages of the method according to the present application are now also evident.

[0100] First of all, a device and a method for controlling the balloon have been provided which allow a more efficient control than the devices of the prior art.

[0101] In particular, unlike the devices of the prior art, the balloon is controlled indirectly by measuring the tension of the yarn during the step of unwinding from the bobbin.

[0102] In other words, the degree of filling of the bobbin or the balloon condition is not determined using a dedicated optical sensor or the like.

[0103] Advantageously, the first limiting member 120 and the second limiting member 220 close just above the point where the yarn is detached from the wound coil. Doing so creates a controlled tension which is sufficient to avoid friction with the tube, but which is not so high as to unwind several coils at a time, or even worse to break the yarn.

[0104] The main advantages that can be achieved are therefore stability and reduction of the unwinding tension, fluctuations of which can stress the yarn during said unwinding. In this way, it is possible to increase the unwinding speed in the final step, even by 30-40%.

[0105] The result is an increase in productivity, since the traditional winding systems, on the contrary, reduce the winding speed.

[0106] Furthermore, the phenomenon of several coils coming off the bobbin at the same time is also continuously reduced, as well as the number of yarn breakages.

[0107] The person skilled in the art can make modifications to the above-described embodiments, or replace the described elements with equivalent elements, in order to meet specific requirements, without departing from the scope of the attached claims.

Claims

1. Device (12) for controlling a loop during the unwinding of a yarn (14) from a bobbin (16) in a winding unit (18), said device for controlling a loop comprising: - a tubular first limiting element (20) having a longitudinal axis (X) and a through opening (22) adapted to pass the yarn (14) to be taken off from the bobbin (16); - a support (24) adapted to support the first limiting element (20) and to be fixed to the structure of the winding unit (18); wherein the first limiting element (20) comprises a first limiting part (120) and a second limiting part (220); wherein the support (24) comprises a first arm (124) on which the first limiting part (120) is positioned and a second arm (224) on which the second limiting part (220) is positioned; wherein the device for controlling a loop (12) comprises drive means (26) adapted to move the first arm (124) and the second arm (224), and therefore the first limiting part (120) and the second limiting part (220), between a first position in which the first limiting part (120) and the second limiting part (220) are spaced apart and a second position in which the first limiting part (120) and the second limiting part (220) are closer together than in the first position; and wherein the device for controlling a loop (12) comprises a stationary second limiting element (50) arranged downstream of the first limiting element (20), the second limiting element (50) being arranged with a second through opening (52) comprising a base portion (54) which, in use, faces the first limiting element (20), the base portion having a rectangular cross section with respect to the longitudinal axis (X).

2. A device (12) for controlling air pockets according to claim 1, characterized in that In the second position, the first limiting part (120) and the second limiting part (220) are in contact with each other.

3. A device (12) for controlling air pockets according to claim 1 or 2, characterized in that The first limiting part (120) and the second limiting part (220) have a widening and therefore the diameter of the through opening (22) increases at the input portion of the yarn (14).

4. A device (12) for controlling air pockets according to claim 1 or 2, characterized in that The first arm (124) and the second arm (224) rotate in opposite directions about respective rotation axes (Y, Z) which are spaced apart and parallel to the longitudinal axis (X).

5. A device (12) for controlling air pockets according to claim 4, characterized in that The first arm (124) and the second arm (224) are provided with cogwheels (126, 226) integral with the respective arms, which cogwheels mesh with each other and are adapted to rotate about the respective rotation axes (Y, Z) so that the rotation of the first arm (124) and of the second arm (224) is synchronized.

6. A device (12) for controlling air pockets according to claim 5, characterized in that The drive device (26) comprises a linear actuator (260) connected to the second arm (224), the linear actuator (260) being connected to a lever (128) provided on the second arm (224) so that a linear movement of one operating end of the linear actuator (260) causes a rotation of the first arm (124).

7. A device (12) for controlling air pockets according to claim 1 or 2, characterized in that The drive device (26) comprises an electric type actuator for moving the first limiting member (120) and the second limiting member (220).

8. A device (12) for controlling air pockets according to claim 1 or 2, characterized in that The base portion (54) of the second through opening (52) has a square cross section.

9. A device (12) for controlling a gas cushion according to claim 8, characterized in that The edge of the square cross section of the second through opening (52) has a size of 20 mm to 30 mm.

10. A device (12) for controlling air pockets according to claim 1 or 2, characterized in that The height of the base portion (54) of the second through opening (52) in a longitudinal direction perpendicular to the cross section of the second through opening is 30 mm to 45 mm.

11. A device (12) for controlling air pockets according to claim 1 or 2, characterized in that The second through opening (52) comprises a truncated pyramid shaped central portion (56) having a larger base at the base portion (54) in a position opposite to an input section of the yarn into the second limiting element (50).

12. A device (12) for controlling air pockets according to claim 11, characterized in that The truncated pyramid shaped central portion (56) comprises a smaller base having a circular shape opposite to the larger base.

13. A device (12) for controlling air pockets according to claim 1 or 2, characterized in that The second through opening (52) comprises a cylindrical final portion (58).

14. A device (12) for controlling air-bag according to claim 1 or 2, characterized in that, The device for controlling the air loop comprises a programmable control unit adapted to compare the measured operating parameter value with a reference value and, based on the comparison, to operate the first limiting element (20) accordingly so that the first limiting member (120) and the second limiting member (220) are moved from the first position to the second position or, if an intermediate position exists, to the intermediate position.

15. The device (12) for controlling air-bag according to claim 9, characterized in that, The edge of the square cross section of the second through opening (52) has a size of 24 mm to 28 mm.

16. The device (12) for controlling air-bag according to claim 9, characterized in that, The edge of the square cross section of the second through opening (52) has a size of 26 mm.

17. The device (12) for controlling air-bag according to claim 10, characterized in that, The height of the base portion (54) of the second through opening (52) in a longitudinal direction perpendicular to the cross section of the second through opening is 35 mm to 40 mm.

18. A winding unit (18) comprising a device (12) for controlling the air loop during unwinding of a yarn (14) from a bobbin (16) according to any one of the preceding claims.

19. Method for controlling a gas cushion by means of a device (12) for controlling a gas cushion according to any one of claims 1 to 17, characterized in that The method comprises: a. measuring an operating parameter during unwinding of a yarn (14) from a bobbin (16); b. comparing the operating parameter with a predetermined value of the operating parameter; and c. operating the first limiting element (20) based on the comparison in step b so that the first limiting member (120) and the second limiting member (220) are moved from the first position to the second position or, if an intermediate position exists, to the intermediate position.

20. The method for controlling air-bag according to claim 19, wherein, The operating parameter is a yarn tension measured downstream of the device for controlling the air loop (12).

21. A method for controlling a gas cushion according to claim 19 or 20, characterized in that, The actuation of the first limiting element from the first position to the second position, or to the intermediate position if present, occurs when the yarn tension measured downstream of the device for controlling the air loop exceeds a certain value.

22. The method for controlling a gas cushion according to claim 19 or 20, wherein The actuation of the first limiting element from the first position to the second position, or to the intermediate position if present, occurs when a certain yarn tension value is exceeded a predetermined number of times or for a predetermined length of time.

23. The method for controlling air-bag according to claim 19, wherein, The actuation of the first limiting element from the first position to the second position, or to the intermediate position if present, occurs when the unwound yarn exceeds a certain percentage.

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