Production line for producing tubes made of web-like material

Abstract

A production line for producing a tube (1) made of a web-like material, comprising: a core winder (9); an unwinder (3) comprising a rotating device on which a first mandrel and a second mandrel are arranged; and a robot (5) adapted to load a roll of web-like material onto the unwinder (3) and to remove a depleted roll from the unwinder (3).

Description

Technical Field

[0001] The present invention relates to improvements in machines and apparatus for producing tubes by winding one or more webs of web-like material around a forming spindle. Background Art

[0002] In many industries, there is a need to wind continuous web materials around a tubular winding core. For example, in the production of household paper rolls (such as toilet paper rolls, kitchen paper rolls, etc.), it is known to wind single-layer or multi-layer webs around a tube or tubular winding core.

[0003] Typically, these tubes or tubular winding cores are produced using a paperboard web wound around a forming mandrel. The machines that form these tubes or tubular cores are referred to in the industry as "core winders". Typically, a core winder winds one or more web-like materials (typically paperboard) around a forming mandrel to form a continuous tube. The tube is cut into pieces, each of which forms a winding core. The core winder has a system for unwinding the web-like material, called an unwinder, which feeds the web of material unwound from a reel toward the forming mandrel. The reel consists of a core on which a web-like material (e.g., a strip of paperboard) is wound. Whenever a reel is used up, it must be removed from the unwinder and replaced with a new reel. These operations are typically done manually by an operator.

[0004] A similar process is used to form cylindrical containers, which are used, for example, to package food.

[0005] Examples of prior art core winders are disclosed in US7695420, US7452318, US20100204031, US20080009399.

[0006] EP3981915 discloses a machine for making a tube by helically winding three strips of overlapping and interlaced web material strips.The web roll is supported by a mandrel carried by a stationary unwinding structure.

[0007] EP3418229 discloses a system for unwinding rolls of web-like material. The system comprises an anthropomorphic arm robot which picks up a single roll from a stack and supports the single roll in an unwinding position until it is exhausted. Thus, each robot simultaneously represents a member for picking up a roll and a support system for the roll during unwinding.

[0008] WO2016 / 173851 discloses a system for unwinding a large mother roll of plastic film to feed a production line. A robot loads the mother roll onto a stationary unwinding mandrel.

[0009] Managing the consumables used by these machines is often cumbersome and burdensome for production line personnel. Furthermore, the operations for removing exhausted rolls and loading new rolls are performed manually, requiring the operator to handle heavy loads. In fact, a new roll may weigh up to 100 kg.

[0010] After loading on the core winder, the cardboard rolls are used up very quickly, usually in less than half an hour, in some cases even after a quarter of an hour. This leads to very frequent changes, making the work of the operators working on the core winders even more tiring and dangerous. Finally, the repetitive and dangerous nature of the work also inevitably leads to a loss of productivity, since the cardboard rolls are often incorrectly loaded on the unwinder and incorrectly prepared for unwinding, causing the core winder to jam and therefore stop.

[0011] Therefore, there is a need to provide a production line for producing tubes by winding a web-like material which completely or partially overcomes the disadvantages of existing production lines. Summary of the invention

[0012] In order to completely or partially overcome the disadvantages of the prior art, a production line for producing a tube made of a web-like material is provided, the production line comprising: a core winder; at least a first unwinder, comprising a rotating device, on which a first mandrel and a second mandrel are arranged; and a robot, adapted to load a roll of web-like material onto the unwinder and to remove an exhausted roll from the unwinder. As will be explained later, the rotating device is configured so that its rotation exchanges the positions of the first mandrel and the second mandrel. This facilitates the loading operation of the roll by the robot.

[0013] Further features and embodiments of the production line for producing tubes or winding cores according to the invention are described below and are set out in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention will become more apparent from the description and the accompanying drawings, which show exemplary and non-limiting embodiments of the invention. More specifically, in the drawings:

[0015] Figure 1A , Figure 1B shows a schematic side view of a production line for producing tubes or winding cores;

[0016] Figure 2 Shown according to Figure 1A The plane diagram of line II-II;

[0017] Figure 3 Shows Figure 1A and Figure 2 A magnified image of the robot's head;

[0018] FIG. 4A to FIG. 11B The operating sequence of loading and removing a roll from an unwinder is shown;

[0019] Fig.12 and Fig.13 An alternative embodiment of the steps for applying adhesive to the roll is shown;

[0020] Fig.14 and Fig.15 Another alternative embodiment of the step for applying adhesive to the roll is shown. DETAILED DESCRIPTION

[0021] Figure 1A , Figure 1B Schematically shown is a side view of a production line for producing tubes or tubular paperboard cores by means of a core winder, in which a robot or manipulator for handling paperboard rolls is included. More specifically, Figure 1A An initial part of a production line, generally marked with 1, is shown. In the initial part of the production line 1, an unwinder 3 and a numerically controlled manipulator (e.g., a robot), generally represented by 5, are arranged in combination. The robot 5 can be a robot consisting of or including a mechanical arm 5 (e.g., an anthropomorphic mechanical arm). The anthropomorphic mechanical arm can generally be an open motion manipulator. In some cases, the mechanical arm can include multiple numerically controlled movement axes to perform complex movements that can grip and manipulate rolls from a stack, load rolls on the unwinder, and remove exhausted rolls from the unwinder. For example, the mechanical arm can be an arm with a spherical wrist and three numerically controlled axes, the spherical wrist being an end that can rotate around a spherical joint. The end can include an end effector.

[0022] Figure 1B The final part of the production line 1 is schematically shown, comprising a core winder 9. The latter can be configured in any way. In the embodiment shown, a core winder is provided which produces a tube by winding a single web-like material, i.e. a single paperboard web wound helically around a forming mandrel. In other embodiments, the tube can be manufactured by helically winding two paperboard webs staggered relative to each other. The possibility of producing a tube by winding two or more webs longitudinally around a forming mandrel cannot be excluded.

[0023] Considering that the structure of the core winder 9 is known and it can be arbitrary, it will not be described in detail. Generally speaking, in the embodiment shown, the core winder 9 includes a first section 9A with a winding head 11, which receives a web-like material (which in this case is represented by a single cardboard web N) and winds the web-like material around a forming mandrel 13 using a belt or other suitable winding member. The forming mandrel 13 extends towards a second section 9B of the core winder 9, where a cutting assembly 15 is arranged. The tube is continuously formed around the forming mandrel 13, and the tube is divided into tubular parts (e.g., individual tubular winding cores) using a cutting assembly 15. As described below, the cutting assembly can include a serrated blade mounted on a rotating arm, but any other cutting device, such as a pressure cutting device, can also be used. Examples of these types of core winders are disclosed in EP1631425, WO95 / 10399, EP2203303.

[0024] Returning to the initial part of the production line 1, the anthropomorphic arm 5 is configured to pick up individual rolls B1, B2, ... Bn of web-like material, such as cardboard webs, from a stack P positioned in a picking station 19. In the stack P, the rolls B1, B2, ... Bn are stacked with their axes oriented vertically, i.e., orthogonal to a supporting surface, such as a pallet.

[0025] In this specification, “vertical” means a direction parallel to the gravity direction, and “horizontal” means a direction orthogonal to the vertical direction.

[0026] In the embodiment shown, the robot 5 comprises a base 5.1, a head 5.5, and three arms 5.2, 5.3 and 5.4 pivoted to each other. Five numerically controlled axes of rotation are indicated by X1, X2, X3, X4 and X5, around which various parts of the anthropomorphic robot 5 can move to perform the movements and operations described below.

[0027] The head 5.5 of the robot 5 includes an ejector 5.6 and a mandrel 5.7. The mandrel 5.7 may be an extendable mandrel and is configured to be inserted into the axial hole of the roll B1, B2, ... Bn to be manipulated to engage with it from the center. The ejector 5.6 is configured to eject the roll engaged with the mandrel 5.7 from the mandrel 5.7.

[0028] from Figure 2As can be seen in the plan view of , the robot 5 can be designed to serve two separate unwinders, both indicated by 3, which can supply the cardboard web to two separate core winders. Basically, in this case, the robot 5 serves two tube production lines. In this case, advantageously, two pick-up stations 19 are preferably provided, at which two stacks of rolls B1, B2, ... Bn are placed.

[0029] In other embodiments, one or each production line may comprise two unwinders arranged side by side so that they can be loaded by the same robot 5. This is useful when the core winder 9 produces a tube by winding two or more webs instead of just one. An exemplary embodiment of this type will be described later.

[0030] Each unwinder 3 comprises a base 3.1 on which a rotating device 3.2 is rotatably mounted. The axis of rotation of the rotating device 3.2 is indicated with 3A. A first mandrel 3.3 and a second mandrel 3.4 are arranged on the rotating device 3.2.

[0031] If especially in Figure 2 As can be seen in the plan view of , a respective ejector 3.5, 3.6 is associated with each spindle 3.3, 3.4. Furthermore, each spindle 3.3, 3.4 is associated with a brake 3.12, 3.13 comprising a disc 3.7, 3.9 and a jaw 3.8, 3.10. Figure 1A In the figure, 3.15 denotes a sensor which is used to detect the leading edge of each new roll B1, B2, ... Bn loaded on the mandrel of the unwinder, the new roll being located on one side of the sensor 3.15, i.e., on the Figure 1A The position is on the mandrel 3.4.

[0032] In addition to the mandrels 3.3 and 3.4, the rotary device 3.2 also carries two guide rollers 3.16 and 3.17, which are used for correct guidance of the cardboard web during the various roll change steps, as described below.

[0033] The three mandrels 5.7, 3.3, 3.4 can be identical to each other and as Figure 3 5.5 for the head 5.5 of the robot 5. The mandrel 5.7 is configured as shown in the side view of the robot 5. The extendable element (e.g. pneumatic control element) of the mandrel 5.7 is indicated by 5.9, which is used to clamp the inner surface of the core or the axial hole of the roll B1, B2, ... Bn. The annular element is indicated by 5.8, which can be moved according to the arrow f58 parallel to the axis of the mandrel 5.7 of the ejector 5.6. The movement of the movable annular element is used to eject the roll from the mandrel.

[0034] FIG. 4A to FIG. 10BThe sequence of replacing a depleted roll with a new roll using the robot 5 of the production line 1 described previously, the roll being made of a web-like material (cardboard web) is shown.

[0035] Figure 4A and Figure 4B The following step is shown in side view and plan view respectively, where the roll B0 loaded on the spindle 3.3 is exhausted, while the spindle 3.4 is empty and ready to receive a new roll B1 at the top of the stack P, which will be picked up by the robot 5. Figure 4A , Figure 4B In the embodiment, the robot 5 is arranged with its mandrel 5.7 positioned above the stack P and coaxially with the rolls B1, B2, ... Bn.

[0036] In this step, the robot can perform an operation for centering the head 5.5 relative to the stack P using a centering system (for example a laser centering system) carried by the head 5.5. Figure 4A Starting from the position of the roll B1, when the head 5.5 is lowered in the vertical direction, the mandrel 5.7 of the robot is inserted into the axial hole of the roll B1, and the extendable element 5.9 is extended to engage with the roll B1. The movement for inserting the mandrel requires the simultaneous retreat of the ejector 5.6.

[0037] In this step, the ejector 3.6 associated with the empty mandrel 3.4 may be in the extracted position to ensure that the mandrel 3.4 is free of remnants of a previous roll.

[0038] Figure 5A , Figure 5B Similar to Figure 4A , Figure 4B The view of FIG. 1 shows the complex movement by which the robot picks up the roll B1 from the stack P and transports it in front of the mandrel 3.4 of the unwinder by rotating it from a horizontal position of placement (axis oriented in the vertical direction) to a vertical position of placement (axis oriented in the horizontal direction and coaxial with the axis of the mandrel 3.4). The movement of the robot is controlled so as to minimize the time that the roll B1 remains with its axis oriented vertically (horizontal placement of the roll). In fact, due to the small axial dimensions of the roll, when this roll is lifted from the lower roll B2 in the stack P, the turns of the wound web tend to slide on each other, causing deformation of the roll with the risk of complete unwinding.

[0039] To avoid this drawback, in an advantageous embodiment, the robot is controlled in such a way that the first movement performed is a gradual rotation of the roll B1 , starting from the lifting movement of the stack P. Subsequently, a translation movement is performed until a position coaxial with the mandrel 3 . 4 of the unwinder mandrel 3 .

[0040] Fig. 6A , Figure 6BThe steps of transferring the roll B1 from the mandrel 5.7 of the robot 5 to the mandrel 3.4 of the unwinder are shown. This transfer is achieved by activating and translating the ejector 5.6 of the head 5.5 of the robot 5 outwards after deactivating and retracting the extendable element 5.9, and by moving back the ejector 3.6 of the mandrel 3.4 if it has not already been moved back.

[0041] The subsequent Fig. 7A , Figure 7B The stretchable element (similar to element 5.9 ( Figure 3 )) Step of extending to move the head 5.5 of the robot 5 away from the mandrel 3.4 of the unwinder 3, wherein the roll B1 is engaged with the mandrel 3.4.

[0042] Figure 8 A- Figure 8 D shows in a side view a 180° rotation of the rotating device 3.2 of the unwinder 3, by which the positions of the mandrels 3.3 and 3.4 are exchanged. In this step, the guide rollers 3.17 are used to correctly guide the web N1 and form a path N of the web that extends under the new roll B1 that has just been loaded on the unwinder 3. This part of the web path N1 is located between the new roll B1 and the cutting and splicing device 21 for cutting the web N0 from the roll that is about to be exhausted.

[0043] Before performing a 180° rotation of the rotating device 3.2, the roll B1 can be angularly positioned so as to carry the leading edge of the web N1 wound thereon to a predetermined angular position. This rotation can be done manually or by providing a motor for driving the spindle 3.4 in rotation. Once the desired angular position has been reached, the brake 3.13 can be activated to lock the angular position of the roll B1 relative to the rotating device 3.2. The desired position can be detected using a sensor 3.15.

[0044] In another embodiment, the angular rotation of the roll B1 can be performed by the robot 5 before transferring it from the spindle 5.7 to the spindle 3.4. Fig. 6A , Figure 6B Before the insertion step, the robot 5 rotates the spindle 5.7 until the leading edge of the new roll is detected. Subsequently, the rotation of the roll is locked and, as described above, the roll is transferred to the spindle 3.4, with the advantage that the roll is already correctly oriented. Similarly, before performing a 180° rotation of the rotating device 3.2, once the desired angular position has been reached, the brake 3.13 can be activated to lock the angular position of the roll B1 relative to the rotating device 3.2.

[0045] In the embodiment described herein, the rolls B1, B2, ... Bn are provided with a double-sided adhesive tape BA at the leading edge of the wound web. The double-sided adhesive tape BA is used on the one hand to keep the leading edge closed and on the other hand to adhere the leading edge of the web N1 to the trailing edge or tail of the web N0 after cutting, as described below with reference to Figure 8 A- Figure 8 D. In this case, during the rotation of the roll B1 , by the robot 5 , the sensor 3 . 15 can be used to detect the double-sided adhesive tape BA.

[0046] like Figure 8 A. Figure 8 As shown in D, the cutting device 21 includes a Figure 8 D shows a pressure roller 21.2 and a blade 21.1 on a pivot arm schematically shown at 21.3. Figure 8 A. Figure 8 B. Figure 8 C shows the rotation of the rotating device 3.2. Figure 8 C and Figure 8 In D, BA is used to represent the angular position where the double-sided adhesive tape BA is placed. Figure 8 D, the pivoting of the arm 21.3 causes the blade 21.1 to cut the web N0. At the same time, the pressure roller 21.2 presses the tail of the web N0 produced by the cutting onto the double-sided adhesive tape BA applied at the leading edge of the web N1 wound on the roll B1. The pressure of the roller 21.2 causes the tail of the web N0 and the leading edge of the web N1 to adhere to each other. The subsequent pulling of the rest of the web N0 starts the unwinding of the web N1.

[0047] Next Fig. 9A , Fig. 9B and Fig. 10A , Fig. 10B The step of aligning the mandrel 5.7 with the mandrel 3.3 on which the remaining part of the roll B0 residue is found is shown. Using the ejector 3.5, the residual roll B0 is transferred to the mandrel 5.7 of the robot 5 to be transferred by the robot to the accumulation area 23, see Fig.11A , Fig. 11B , which shows the movement of transferring the residual roll B0 to the accumulation area 23 using the robot 5.

[0048] The double-sided adhesive tape BA may not be pre-applied to the rolls B1, B2, ... Bn, but may be applied after the new roll has been loaded onto the mandrel of the unwinder 3 before the rotating device 3.2 is rotated. Fig.12 and Fig.13 Shown in. Fig.12Schematically shown is a side view of the unwinder 3 and the robot 5 in a step of loading a new roll B1 on the mandrel 3.4. Means for applying adhesive in the form of means for applying a double-sided adhesive tape BA are indicated with 31. Fig.13 An enlarged view of the apparatus for applying the double-sided adhesive tape is shown.

[0049] The application is performed at the desired point, ie at the head of the web N1 wound on the roll B1 , which can be detected by the sensor 3 . 15 as described above.

[0050] The device for applying the double-sided adhesive tape 31 receives a roll R1 of double-sided adhesive tape from which the double-sided adhesive tape BA is unwound, separating the protective liner wound on the roll R2 from it. Two rollers 33, 35 and a cutting blade 37 allow a portion of the double-sided adhesive tape to be applied to the leading edge or head of the web N1 forming the roll B.

[0051] The cycle for replacing depleted rolls with new rolls is essentially the same as described in connection with FIGS. 1 to 11 .

[0052] Instead of means for applying the double-sided adhesive tape, the unwinder 3 may comprise a liquid adhesive dispenser. The application may be performed using a nozzle or in another way, for example using a roller applicator. Fig.14 A side view of the initial part of the production line 1 comprising an unwinder 3 and a robot 5 is shown, in a step for loading a roll B1 onto an empty mandrel of the unwinder 3. In this embodiment, the unwinder 3 comprises an adhesive dispenser in the form of a coating gun 39. See also, in particular, Fig.15 Magnified view of the adhesive being applied to the area of ​​the roll where the leading edge is found, detected by the sensor 3.15.

[0053] The stack P is positioned in a predetermined position relative to the base 5.1 of the robot so that the robot 5 can always execute the same trajectory to load the rolls B1, B2, ... Bn. This position may not always be accurate, either because the operator does not position the stack P with the required accuracy, or because the stack P may be slightly displaced due to vibrations, or simply because the stacking of the rolls B1, B2, ... Bn on the transport platform is not always exactly the same, that is, the position of the rolls B1, B2, ... Bn relative to the transport platform may vary from platform to platform. In the latter case, an alignment system consisting of V-shaped blades can be provided in a fixed position relative to the base 5.1 of the robot 5, and the outer surface of the stack P is close to the alignment system. This allows positioning errors to be significantly reduced. However, also in this case, a step is preferably provided for centering the head 5.5 relative to the stack P of rolls B1, B2, ... Bn.

[0054] As described above, the centering step can be performed by the robot 5, for example, by means of a laser centering system carried by the head 5.5. In this case, starting from a predetermined point, the head 5.5 of the laser moves until it detects, by means of the laser, a first edge point of the core of the first upper roll of the stack P. Subsequently, the head 5.5 of the robot is translated along the chord of the core of the roll (i.e., the chord of the circumferential edge of the tubular core) until a second point in the circumferential edge of the core is detected. Once the two points that determine the chord are detected, the head 5.5 of the robot is positioned at half of the chord. Subsequently, the head 5.5 of the robot is translated in a direction orthogonal to the chord so as to pass through the center of the core of the roll until a third point is detected. Once three points are detected, the theoretical center of the roll can be calculated, or the head 5.5 of the robot 5 can be translated backwards in a direction orthogonal to the previously detected chord to detect a fourth point on the edge of the core of the roll by means of a laser sensor. The third and fourth points define the diameter of the roll. The midpoint of the straight line segment connecting the third and fourth points determines the center of the roll.

[0055] Alternatively, a centering system other than a laser sensor may be provided, which includes a camera which uses an algorithm to detect the center of the top roll of the stack P and communicates this to the central control unit of the robot 5 .

[0056] The centering step may preferably be performed only when the platform of the roll is positioned relative to the base 5.1 of the robot. Alternatively, if necessary, the centering operation may be performed for each roll to be loaded, or whenever the operator deems it necessary.

[0057] In this context, the robot 5 is shown as an open motion robot with 5 axes. In an alternative embodiment, an anthropomorphic robot can be used. For example, a robot with 6 axes can be used, i.e. a robot with 3 axes for positioning in space plus three axes for orienting the head 5.5 as required. If the movements for loading and removing the rolls require an easier trajectory, a robot with fewer axes can also be used.

[0058] In a further modified embodiment, the cutting device 21 may only include the blade 21.1 but not the pressure roller 21.2, thereby separating the cutting step from the splicing step. This requires coordinating two different actuators to operate the cutting step and the splicing step respectively.

[0059] In order to avoid malfunctions when changing rolls, the head 5.5 of the robot may also include a load sensor, i.e. a weight sensor, such as a load cell or other suitable sensor, for measuring the weight of the new roll to be lifted. This allows detecting the situation in which two adjacently stacked rolls remain coupled (i.e. attached to each other) during the lifting step and being able to stop the changing procedure by generating an alarm or by executing a procedure that seeks to separate the two rolls.

[0060] In some embodiments, the two spindles 3.3 and 3.4 can each be provided with a sensor (e.g. a laser sensor) for measuring the diameter of the roll being unwound. This information can be used to detect when to replace the exhausted roll with a new roll, i.e. when to actuate the pivot arm 21.3. The diameter of the exhausted roll can also be used to detect when to rotate the rotary device 3.2 by 180°. Finally, the diameter of the roll being unwound can be used to detect when to start loading a new roll onto the empty spindle. In fact, in order to reduce the overall size of the rotary device 3.2, the distance between the two spindles 3.3 and 3.4 can be less than the sum of the diameters of the new roll. Therefore, in this case, before loading a new roll, it is necessary to wait until the roll being unwound reaches a predetermined diameter.

[0061] Fig.16 , Fig.17 and Fig.18 Shows something like Figure 2 9, wherein several webs N are fed to a single production line and thus to a single core winder 9. In the embodiment shown, two webs N are fed to the core winder 9 (at Fig.16 , Fig.17 , Fig.18 Not shown, see Figure 1A , Figure 1B ). In other embodiments, more than two webs N may be fed to a single core winder.

[0062] exist Fig.16 , Fig.17 and Fig.18 In each of the first and second unwinders, a first unwinder and a second unwinder are arranged side by side and served by a single robot 5. In other words, the mutual position of the two unwinders, which feed two webs N to the same core winder, is such that the same robot 5 can load the rolls onto the mandrels of both unwinders.

[0063] The first unwinder and the second unwinder can be identical to each other, ie they can have the same components to perform the same functions. Thus, both unwinders can be configured as previously described for the unwinder 3 .

[0064] More specifically, in Fig.16 In the embodiment, two unwinders 3 are placed side by side and one after the other in the advancing direction F of the web N towards the core winder 9.

[0065] exist Fig.17 In the embodiment, two unwinders 3 are placed side by side and one in front of the other. Fig.17In this case, the position is such that the rotation axes 3A of the two corresponding rotating devices 3.2 coincide, but this mutual position is not binding. The two rotation axes 3A of the two unwinders can also be staggered, for example kept parallel. In other cases, the two rotation axes of the rotating devices 3.2 can also be non-parallel. Fig.17 In the embodiment, the web N is fed in a direction F. A deflecting element 41 can be placed along the path of one of the two webs, which brings the trajectories of the two webs N closer together.

[0066] exist Fig.18 In the embodiment, the two unwinders 3 are placed side by side at different inclinations, i.e. the rotation axes 3A of the respective rotation devices 3.2 are inclined to each other instead of being parallel, so that the trajectories of the two webs N (arrows F1, F2) converge towards the core winder 9. In this way, the use of a deflecting member 41 becomes unnecessary.

[0067] In each case, a single robot 5 is able to load the reels B onto the mandrels 3 . 3 , 33 . 4 of both unwinders 3 .

Claims

1. A production line for producing a tube made of web-like material, the production line comprising: Core Winding Machine; at least a first unwinder comprising a rotating device on which a first mandrel and a second mandrel are arranged; wherein the first unwinder is arranged upstream of the core winder along a path for supplying web-like material to the core winder; wherein the rotating device of the first unwinder is adapted to rotate about a rotation axis to exchange the position of the first mandrel and the second mandrel; A robot is adapted to load rolls of web-like material onto the first unwinder and to remove exhausted rolls from the first unwinder.

2. The production line according to claim 1, wherein: The robot includes an anthropomorphic arm having multiple axes of rotation.

3. The production line according to claim 1 or 2, wherein: The first mandrel and the second mandrel each include an ejector for ejecting the spent roll from the mandrel.

4. The production line according to claim 1, 2 or 3, wherein: The robot comprises a head adapted to engage with a roll from the stack of waiting rolls and transfer it to the first spindle or the second spindle, and to pick up an exhausted roll from the first spindle or from the second spindle.

5. The production line according to claim 4, wherein: The head of the robot includes an ejector for ejecting the roll from the head of the robot.

6. The production line according to one or more of the preceding claims, wherein: The first mandrel and the second mandrel each include a brake for braking rotation of the respective mandrel.

7. The production line according to one or more of the preceding claims, wherein: The first unwinder includes a cutting and splicing member adapted to cut a web-like material from an exhausted roll arranged on one of the first and second mandrels, form a trailing edge of the web-like material, and splice the trailing edge to a leading edge of a new roll of web-like material arranged on the other of the first and second mandrels.

8. The production line according to claim 7, wherein: The cutting and splicing member comprises a cutting blade and a pressure roller.

9. The production line according to one or more of the preceding claims, wherein: The first unwinder comprises an adhesive applicator for interengaging a trailing edge of a web material from a expiring roll with a leading edge of a web material from a new roll.

10. The production line according to claim 9, wherein: The adhesive applicator is selected from the group consisting of: a liquid adhesive dispenser; Double-sided adhesive tape applicator.

11. The production line according to one or more of the preceding claims, wherein: The first unwinder comprises means for detecting the leading edge of a new roll.

12. The production line according to claim 11, wherein: To detect the leading edge, the new roll is mounted on one of the first mandrel and the second mandrel, or the new roll is supported by the head of the robot.

13. The production line according to one or more of the preceding claims, wherein: The head of the robot comprises a picking mandrel adapted to be inserted into the hole of the roll to be processed, and centering means for centering the head relative to the hole of the roll to be picked up.

14. The production line according to one or more of the preceding claims, wherein: The head of the robot comprises a sensor, preferably a weight sensor, for detecting the number of rolls engaged by the head of the robot.

15. The production line according to one or more of the preceding claims, comprising a second unwinder having a second rotating device on which the third mandrel and the fourth mandrel are arranged; wherein The second rotating device is suitable for rotating around a second rotation axis to exchange the positions of the third mandrel and the fourth mandrel; wherein the first unwinder and the second unwinder are placed close to each other, that is, side by side, so that both the first unwinder and the second unwinder can be loaded by the robot; and wherein the first unwinder and the second unwinder are preferably identical to each other.

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