DESCRIPTION

The present invention refers to a machine for bonding a number of layers of film by gluing, thus a so-called laminating machine.

In the food and packaging industry it is especially required the use of wrappers made of multilayer film, i.e. a film consisting of multiple layers coupled to each other usually by glue means. In particular in the food industry, wrappers with a first layer made of a material suitable for contact with food are usually required, while the other bonded layer or layers must be such as to provide to the wrapping the suitable waterproofing and mechanical resistance.

The known laminating machines generally comprise a plurality of winder assemblies for the grasping of a reel. Each winder assembly may also act both for unwinding and for winding the reel. These assemblies are typically provided not only in laminating machines but also in printing machines and in general in machines that process reels of flexible material.

For example, in a known arrangement, the machine comprises an unwinding unit, to unwind a strip of film material from a reel. Once unwound, the strip is coated with an adhesive and then associated with a second layer, in turn unwound from a reel by means of a respective unwinding unit. The multilayer strip material thus obtained is then wrapped in a reel by another winder assembly.

Each winder assembly further comprises a supporting and gripping system of the reel. This system in turn comprises two arms arranged parallel to each other from which shafts protrude for the rotary insertion into the reel. In known solutions, one of the two arms is motorised while the other is fixed; therefore, the gripping of the reel is obtained by approaching one arm to the other. The gripping of the reel, i.e. the application of the suitable counterforce of the motorised arm against the fixed arm in order to secure the reel in the correct position, is exerted through hydraulic or pneumatic pushing means, such as linear actuators.

However, these known systems present several drawbacks.

Firstly, the linear actuator is provided with sensors to evaluate the pushing force exerted on the reel. It goes without saying that an incorrect pushing force can cause problems such as the incorrect grasping of the reel (if the pushing force is less than that required) or on the other hand damage to the reel or to the whole system (if the force applied is higher than that required). However, in the present systems, the sensor is able to detect only the minimum and maximum force values exerted by the actuator; the setup of the whole system is made on the basis of a certain width of the reel, so that the gripping position of the reel corresponds to the position of maximum force exerted by the actuator. It is therefore not possible to adapt this system to reels of widths different from the desired width value on the basis of which the system has been calibrated.

A further problem associated with known systems is that the reel can not have a width less than the length of the chamber of the piston of the linear actuator; indeed the chamber is placed between the arms and represents a bulk that becomes critical when small reels have to be processed.

Therefore the known systems are not adaptable to reels of different widths, have constructive complications and are also difficult to drive. Indeed, the control of the hydraulic pushing system (both in terms of management of the hydraulic circuit and in terms of the measurement of the exact applied force) results difficult.

The general object of the present invention is therefore to solve the problems set out above.

A first particular object of the present invention is to provide a winder assembly for the gripping of a reel that obtains the stable and correct grip of reels of different widths.

A further object of the assembly according to the invention is to ensure a safe grip to avoid the risk of the reel being dropped.

Yet a further object is to provide an assembly that allows for a dynamic or real-time evaluation of the exerted pushing force, so as to avoid the accidental or too quick grasping of the reel, avoiding a potential risk for the operator staff.

These objects are achieved with the winder assembly according to the invention, the essential features of which are defined by the first of the appended claims.

The characteristics and advantages of the winder assembly according to the invention will become apparent from the following description of an embodiment thereof, provided by way of example and not limitative, with reference to the attached drawings wherein: - Figure 1 is a perspective view of a laminating machine with a winder assembly according to the invention, with a reel in a grasped position;

- Figure 2 shows the machine without the reel;

- Figure 3 is an enlarged view of the winder assembly according to the invention; - Figure 4 shows the machine in a schematic top view, with some elements represented in a sectional view for clarity;

- Figure 5 is a view of the winder assembly with detector means represented in a sectional view;

- Figures from 6a to 6f show the steps of grasping of the reel ;

- Figure 7 is a perspective view of the detecting means using three sensors according to Table 2;

- Figure 8 is a side (section) view of the detecting means of Figure 7;

- Figure 9 and 7 are two sections of the detecting means defined in Figure 8. With reference to the above figures, a laminating machine comprises a frame T supporting a winder assembly 1 according to the invention, for the grasping and the winding/unwinding of a reel B of a strip of a material in a film or a sheet form (such as paper or plastic material).

The winder assembly comprises a first arm 1 0 and a second arm 1 1 slidingly engaged with linear rails 1 2 that define a transversal axis X (figure 1 ). The arms slide on the rails in order to approach each other according to the approaching direction X, by means of driving means 1 3, 1 3' (figure 4). In detail, each arm 1 0, 1 1 comprises own independent driving means, therefore each arm has an autonomous sliding movement, independent from the other arm. The driving means comprise an endless screw 1 30, 130', arranged according to the transversal axis X and first motor means 131 , 131 ' such as an electric motor that, engaging with said screw, obtains the sliding movement of the respective arm.

The arms can be moved also in a mutually opposite way, that is to move them away from each other.

The first and the second arm are engaged with the linear rails in a substantially perpendicular arrangement with respect to the X axis, in order to project from the frame T. In the arrangement shown in the figures, each arm comprises a triangular-shape plate, with slanting sides of substantial equal length. The engagement with the linear guides 12 is obtained on the two inner vertices 1 0a, 10b, 1 1 a, 1 1 b of such a triangular shape, while an opposite vertex 10c, 1 1 c protrudes from the frame of the laminating machine. The screw 130' is arranged between the inner vertices and passes through the arms.

The first arm 1 0 and the second arm 1 1 are respectively associated with gear means 14, 15 aligned according to the axis X; the gear means 14 associated with the first arm 10 are of driven nature, while the gear means 1 5 associated with the second arm 1 1 are of driving nature. Each of said gear means defines a respective rotation axis X', X", parallel to the X axis, the two rotation axis being aligned with each other. The driving gear means 15 are functionally linked to the second motor means 1 6, such as an electric motor, that drive the rotation of said driving gear means around its rotation axis X". As consequence of the rotation of the driving gear means 15, the driven gear means 14 rotate around the relative rotation axis X'.

The gear means 14, 15 are adapted to engage, in a working position, with opposite ends of a tubular core B1 of the reel B, around which the film is wound. Thanks to the engagement with the gear means 14, 15 the reel is supported in a rotatable manner around the rotation axis defined by them.

The rotation of the driving gear means 1 5 promotes the rotation of the core reel and, as consequence, of the reel (while the other gear means 14 are idly driven), so that the winding or unwinding movement of the film strip is carried out, depending on the working needs.

In a preferred arrangement of the invention, the gear means comprise bevel gears 14, 1 5 supported by each arm 1 0, 1 1 in correspondence to mutually opposite vertices 10c, 1 1 c.

In order to engage each bevel gear with the respective end of the tubular core B1 , the arms 10, 1 1 approach each other along the direction X, as shown by the arrow in figure 5.

The winder assembly according to the invention further comprises detection means 17 that detect the pushing force exerted by the second arm 1 1 on the reel B.

The detection means 1 7 are functionally linked with the motor means 1 31 ' of the endless screw 130', and control them in order to maintain the pushing force F appropriate for a safe grasping, i.e. a pushing force F comprised between a minimum threshold value Fmin and a maximum threshold F _max .

Indeed, if the pushing force F is lower than the minimum value F _m in, the grasping of the reel is not safe, the engagement of the bevel gears and the reel being not stable, with the risk of the reel itself being dropped. On the contrary, if the pushing force F exerted by the second arm 1 1 against the first arm 1 0 is greater than the maximum value F _max , the reel could be squashed, and the strip of material could be damaged; moreover, as a consequence of an excessive pushing force the reel might incur in an incorrect rotation, even not rotate at all.

In detail, the detection means 1 7 comprise a slider element 1 70 that slides according to the approaching direction X and elastic means 1 72 arranged between said slider element and an abutment surface 1 71 . The latter is, in a preferred arrangement, perpendicular to the approaching direction X.

The abutment surface 171 is defined by a box-shaped frame 1 73 projecting from the second arm 1 1 and integrally connected with it. A chamber 1 70a of the box-shaped frame 173 is defined between the abutment surface 1 71 and a surface of the second arm. The elastic means 172 and the slider element 1 70 are housed inside the chamber 170a in a sliding arrangement along said direction X. The endless screw 130' passes through the chamber 170a. The elastic means 1 72 are mounted coaxially with said screw 130' so that the collapsing direction of the elastic means is coaxial with the approaching direction X. The elastic means 172 comprise a spring or a group of springs 1 72 an end of which is connected with the abutment surface 1 71 , while the opposite end is associated with the sliding element 1 70. The sliding element 170 is associated with the screw 130' by means of a nut 1 74. The nut, by pushing on the sliding element 170, drives the motion thereof along the axis X.

The detection means 1 7 further comprise two sensors adapted to detect the position, or more exactly the variation of the position of the slider 1 70. In a preferred embodiment of the invention, the position sensors are arranged on a vertical wall 171 ' of the box-shaped frame perpendicular to the abutment surface, at staggered positions with respect to the approaching direction X and in an opposite position to each other i.e. spaced at 180° (with respect to the direction X). With reference to figure 5, a first sensor 175, or lower sensor is adapted to detect the minimum force F _m in exerted by the arm on the reel; a second sensor 176 or upper sensor instead detects the maximum force F _max exerted by the arm on the reel.

The position sensors may be placed at the same position along direction X (but at different angles) if the slider is guided in a well-defined orientation and comprises a specific opening in front of each sensor. The position sensor may also be staggered along direction X using the same approach.

In a preferred embodiment, the position sensors are positioned at staggered positions with respect to the approaching direction X. They may advantageously be placed at different angles (i.e. distributed along direction X), which is the preferred solution when the distance, along axis X between the sensors, is small compared the sensor size (by small we means smaller than twice the sensor size measured along X).

The position sensors are of on/off type, i.e. they emit a signal when the slider is no more detected/viewed.

With reference to the operation of the winder assembly, when the reel B is arranged between the arms 10, 1 1 (figure 6a), the arms are driven in order to approach together until the gears 14, 1 5 arrive at the tubular core B1 (figures from 6d to 6f). With reference also to figure 5, at this first approaching step corresponds the rotation of the endless screw 130' and as a consequence the movement of the nut 174 along its axis. At the movement of the nut there responds the sliding of the slider 170 according to the direction X; the motion of the slider causes, in turn, the drive of the arm 1 1 (at which the slider is integrally connected through the elastic means 1 72 and the abutment surface 171 of the box-shaped frame 1 73). In this step the pushing action of the slider on the spring 1 72 is negligible because the arm 1 1 does not oppose the motion along the endless screw and thus the direction X.

Instead, when the arms 1 0, 1 1 abut against the reel B, as consequence of the engagement of the gears 14, 15 on it, any further approaching movement of the arms has to be prevented in order to avoid the squashing of the reel.

As the second arm 1 1 abuts on the reel, there occurs an opposing force at the movement along X. Therefore, the further rotation of the endless screw 1 30' and the consequent translation of the nut 1 74 cause a pushing action of the slider 1 70; however the movement along X of the arm 1 1 is prevented by the abutment against the reel, so the slider 170 moves along the direction X inside the box-shaped frame pushing on the spring 172.

The extent of the compression of the spring is proportional to the force exerted by the second arm 1 1 on the reel B and is measured by detecting the variation of position of the slider 170. In detail, until the slider 170 is in a position such that it can be targeted or detected by both the position sensors 175, 176, the force exerted by the arm 1 1 on the reel is lower than the minimum threshold value F _m in. When the slider 170 moves in a position such that the lower sensor 175 does not detect it, the sensor changes its logical status. This changing of status is indicative of a force equal or greater than the minimum threshold value F _m in. The further movement of the slider 170 inside the box-shaped frame causes that also the upper sensor 176 does not detect its presence anymore. At the change of logical status of the second sensor 176 there corresponds the indication of a force equal or greater than the maximum threshold value F _max . This behaviour is summarized in Table 1 . Thus, if the state on table 1 indicates "Minimal compression", force exerted by the arm 1 1 on the reel is larger or equal to the minimum threshold value Fmin, and it smaller than the maximum threshold value F _ma x.

Table 1 : basic state machine for a system using two sensors, without the detection of the optimal position.

When using a (rotationally) symmetric slider, when the arm 1 1 is in the approaching step the slider 170 is detected by both the sensors 175, 176. When the arm 1 1 abuts on the reel B and the slider 170 starts to move to a significant extent, a detection of the minimum value of pushing force is obtained. Thanks to this detection it is possible to act on the driving of the screw 130' in order to maintain the force exerted by the arm 1 1 within a certain range. If the maximum value is exceeded (both sensors no longer detect the slider), the screw 130' is moved in the opposite direction, in order to move the arm 1 1 away from the reel.

In a further embodiment of the invention, also using a symmetric slider, according to Figures 7 to 10, a third position sensor 177 can be provided. The third sensor is arranged at an intermediate position between the first 175 and the second sensor 1 76, so that the slider 170 is always detected by at least two sensors. This solution makes the assembly particular safe because it permits to detect the movement of the slider 170 from a position correspondent to the value of a target working force before the maximum threshold value is reached. The behaviour of the system with three position sensors can be found in Table 2.

Table 2: state machine for a winder with a symmetric slider and three sensors

The third sensor can be arranged in the box-shaped frame angularly displaced at 90° (around the direction X) with respect to the first and second sensor.

In another embodiment, the orientation of the slider is well defined, for example using a slot all along the interior of the box-shaped frame and parallel to axis X, and a corresponding piece on the slider who travels in the slot. This embodiments can reach the same advantages of the former embodiment, which uses a symmetric slider and three sensors, with only two sensors by using table 3. Specific slots must be machined in the slider to achieve the configuration of table 3: one slot group aligned in front of each sensor. Please note that the state machine of table 3 can also be reached using a symmetric slider, with the two sensor staggered along axis X and an opening on the slider at the location of the "0" (or at the locations of the "1 ", by inverting the sensor signals).

Table 3: state machine for a winder with a non-symmetric slider with a well- defined orientation and a specific pattern for each sensor.

In another embodiment, we use a symmetric slider, and place appropriately the sensors 175 and 176 to get the situation of table 4. As one can see on the table 4, the slider may be implemented as a ring, and the second sensor is placed such that when the winder is open, the sensor is at one side of the ring (i.e. it does not see the ring), and when the compression is maximal, it is at the other side of the ring (i.e. it does not sense the ring).

Table 4: state machine for a winder with a symmetric slider with an arbitrary orientation and a specific pattern for each sensor.

Please note that in the examples of table 1 to 4, the ordering of the lines in the tables follows the position of the slider. Also, when transitioning from one configuration to the neighbouring one, i.e. from one line to the next, only one of the sensor changes state. This has the advantage that when the system is in-between two configurations, it will "jump", due to randomness in the sensor reading, in either of the neighbouring states and will never jump into a remote state, which would cause some problems. For example, when the system is between "minimal compression" and "optimal compression", only the second sensor might return an ambiguous reading, resulting into one of these two states, and never into "Maximal compression" nor "Winder is open".

In another alternative, the system is built using three sensors and can function if only two of the three sensors are working. This makes the system robust to sensor failure. The system is preferably built with a slider whose orientation is well defined so that the code obtained as a function of the slider position can be constructed by drilling the appropriate slits in the slider in front of each sensor (although it is also possible to build it with a symmetric slider, by stacking the patterns). The code is constructed such that the value S3 of the third sensor is equal to S1 xor S2, where S1 is the value of the first sensor and S2 the value of the second sensor; "xor" being the exclusive "or" logical operation. There are two possible usage of the redundancy introduced by the three sensors. The first is used to check the consistency of the reading: S3 must be equal to S2 xor S1 , otherwise there is a problem. The second usage consists in reconstructing the S1 & S2 signals from the S1 , S2 and S3 signals provided that one sensor may not respond. If S1 does not respond, its value is replaced by S2 xor S3. If S2 does not respond, its value is replace by S1 xor S3. In this way, the state of the compression car be read even if one sensor is broken. The code and system states are summarized in Table 5.

Table 5: state machine for a winder with a non-symmetric slider with a well- defined orientation and a specific pattern for each sensor. Furthermore, in a further embodiment of the invention, both the arms 10, 1 1 can be provided with detecting sensor means, such as described above.

The winder assembly according to the invention presents many advantages. In particular, thanks to the regulation of the force by means of the position sensor

175, 176, it is possible to grasp reels B with different width because the winder assembly is not merely calibrated in order to exert a certain working force when a given distance of the arms is reached, but rather the force is adjusted continuously.

The winder assembly according to the invention is also adapted for grasping small reels, i.e. reels with reduced width because the approach run of the arms is longer with respect to the known assemblies, considering that the hydraulic pushing means of the known system are here no longer provided for.

The winder assembly is also particularly safe during operation because the force of gripping exerted on the reel is continually detected and maintained into the desiderated range.

Thanks to the fact that the arms 1 0, 1 1 are independently moved, the mutual approaching speed is reduced, so the operator responsible of the driving of the machine and of the reel positioning works in a safer condition.

Furthermore, the winder assembly, but also the sensor means, are simple from a constructive point of view, so they obtain the above mentioned advantages without significant structural changing of the machine.

Possibly, the winder assembly according to the invention can be arranged also on printing machines and in general on machines that process reels of a flexible material (paper, plastic, aluminium, etc.).

The present invention has been described with reference to a preferred embodiment thereof. It should be understood that there can be other embodiments that belong to the same inventive concept, inasmuch as they fall within the scope of protection of the following claims.