FOLDING OR INTERFOLDING MACHINE OF SHEETS MADE OF PAPER OR SIMILAR MATERIAL

Abstract

Folding or interfolding machine for forming stacks of a predetermined number of sheets comprising a first and a second folding or interfolding roll, arranged to rotate about respective rotation axes to fold or interfold the sheets according to a predetermined folding or interfolding configuration, obtaining a forming stack of folded or interfolded sheets which grows in height along a predetermined forming direction. A separation group is, furthermore, provided for separating a finished stack from a following forming stack of sheets. A transfer group is also provided for transferring the finished stack of folded or interfolded sheets towards a discharge zone. At least one between the separation group and the transfer group comprises at least a detection device for detecting the force exerted by the forming stack, or by the finished stack on the separation group, or on the transfer group.

Claims

1. A folding or interfolding machine for forming stacks of a predetermined number of folded or interfolded sheets according to a predetermined folding or interfolding configuration, said machine comprising: a first and a second folding or interfolding roll, arranged to rotate about respective rotation axes, said first and second folding or interfolding rolls being configured to fold or interfold said sheets according to said predetermined folding or interfolding configuration, thus obtaining a forming stack of folded or interfolded sheets adapted to grow in height along a predetermined forming direction; a separation group configured to separate a finished stack of folded or interfolded sheets, from a following forming stack of folded or interfolded sheets; a transfer group configured to transfer said finished stack of folded or interfolded sheets towards a discharge zone; wherein at least one between said separation group and said transfer group comprises at least a detection device configured to detect the force exerted by said forming stack, or by said finished stack on said separation group, or on said transfer group.

2. The folding or interfolding machine according to claim 1, wherein said or each detection device is selected among: a load cell; a strain gage; a thin film pressure sensor; a thin film force sensor; or a combination thereof.

3. The folding or interfolding machine according to claim 1, wherein said separation group comprises a first and a second plurality of separation members and wherein at least one between said first and said second plurality of separation members comprises at least a detection device.

4. The folding or interfolding machine according to claim 1, wherein said transfer group comprises a first and a second transfer table and wherein at least one between said first and said second transfer table comprises at least a respective detection device.

5. The folding or interfolding machine according to claim 3, wherein said first and second pluralities of separation members are, respectively, associated to a first and a second detection device.

6. The folding or interfolding machine according to claim 4, wherein said first and second transfer tables are, respectively, associated to a third and a fourth detection device.

7. The folding or interfolding machine according to claim 1, wherein a control unit is, furthermore, provided configured to acquire the data of force Fi detected by said or each detection device and to calculate a deviation value F among each of said detected data of force Fi and a predetermined threshold value F*.

8. The folding or interfolding machine according to claim 7, wherein said control unit is adapted to generate an alarm signal when said deviation value F exceeds a predetermined threshold value F*.

9. The folding or interfolding machine according to claim 7, wherein said control unit is, furthermore, configured to operate said separation group and/or said transfer group to keep said data of force Fi detected by said or each detection device within a predetermined error range with respect to said predetermined threshold value F*.

10. The folding or interfolding machine according to claim 1, further comprising at least one image acquisition device configured to acquire at least one image of said forming stack, or of said finished stack, said or each image being processed by a control unit to determine the value of a quality parameter of formation of said forming stack.

11. The folding or interfolding machine according to claim 10, wherein said control unit is configured to compute said or each image of said forming stack, or of said finished stack with a reference image and to determine said quality parameter of formation by calculating a deviation value between said or each acquired image and said reference image.

12. The folding or interfolding machine according to claim 10, wherein said control unit is arranged to define said quality parameter of formation by a processing software adapted to detect at least one parameter of said forming stack or of said finished stack selected among: stack height, stack density, wrong folding of the sheets, wrong interfolding of the sheets, preferably said processing software being an artificial intelligence algorithm such as neural network and/or machine learning software.

13. The folding or interfolding machine according to claims 3, wherein each separation element of said first and second pluralities of separation members, and said or each transfer table are provided with a respective support surface at which said forming stack or said finished stack is arranged to be positioned in contact with in such a way to be supported, and with at least one lateral portion, which, instead, is not arranged in contact with said forming stack or with said finished stack, and wherein said or each detection device is mounted on said lateral portion and/or on said support surface.

14. The folding or interfolding machine according to claim 1, wherein said separation group comprises a displacement group configured to move said separation group, and wherein said or each detection device is positioned at a portion of said displacement group.

15. The folding or interfolding machine according to claim 1, wherein said transfer group comprises a supplementary displacement group configured to move said transfer group, and wherein said or each detection device is positioned at a portion of said supplementary displacement group.

16. The folding or interfolding machine according to claim 14, wherein said displacement group comprises a first and a second displacement device configured to move, respectively, said first and second pluralities of separation members along respective movement trajectory to move the same from a position external to said forming stack to a position internal to said forming stack, and wherein a first and a second detection device are provided integral respectively to said first and to said second displacement device.

17. The folding or interfolding machine according to claim 15, wherein said supplementary displacement group comprises a first and a second supplementary displacement device configured to move, respectively, said first and second forming table and wherein a first and a second detection device are provided integral respectively to said first and to said second supplementary displacement device

18. The folding or interfolding machine according to claim 4, wherein a displacement group configured to move said first and second pluralities of separation members, and a supplementary displacement group configured to move said first and second transfer tables are, furthermore, provided, said displacement group and said supplementary displacement group comprising respective first movable supports configured to slide in a first sliding direction along a respective first linear guide by a respective first skid and wherein said first linear guide is constrained to a second movable support arranged to slide in a second sliding direction along a second linear guide by a respective second skid, said or each detection device being positioned in at least a detection position selected among: a position between said first or said second plurality of separation members and said respective first movable support; a position between said first or second transfer table and said respective first movable support; a position between said second movable support and said second skid of said first or second plurality of separation members; a position between said second movable support and said second skid of said first or second transfer table.

19. The folding or interfolding machine according to claim 3, wherein said or each separation element is provided with a respective support surface at which said forming stack or said finished stack, is arranged to be positioned in contact with, in such a way to be supported, and wherein each detection device is arranged to be housed within a respective seat provided at said or each separation element, in such a way not to protrude from said respective support surface, or however to protrude from the same without, anyway, substantially modify its geometry.

20. The folding or interfolding machine according to claim 4, in said or each transfer table is provided with a respective support surface at which said forming stack, or said finished stack, is arranged to be positioned in contact with, in such a way to be supported, and wherein said or each detection device is arranged to be housed within a respective seat provided at said or each transfer table, in such a way not to protrude from said respective support surface, or anyway to protrude from the same without substantially changing its geometry.

21. A folding or interfolding machine for forming stacks of a predetermined number of folded or interfolded sheets according to a predetermined folding or interfolding configuration, said machine comprising: a first and a second folding or interfolding roll, arranged to rotate about respective rotation axes, said first and second folding or interfolding rolls being configured to fold or interfold said sheets according to said predetermined folding or interfolding configuration, obtaining a forming stack of folded or interfolded sheets adapted to grow in height along a predetermined forming direction; a separation group configured to separate a finished stack of folded or interfolded sheets, from a following forming stack of folded or interfolded sheets; a transfer group configured to transfer said finished stack of folded or interfolded sheets towards a discharge zone; and an image acquisition device configured to acquire at least one image of said forming stack, or of said finished stack, said or each image being processed by a control unit to define a quality parameter of formation of said forming stack, or of said finished stack.

22. A method for forming a stack of folded or interfolded sheets according to a predetermined folding or interfolding configuration, said method comprising the steps of: folding or interfolding a plurality of sheets in succession to each other according said predetermined folding or interfolding configuration by a first and a second folding or interfolding roll arranged to rotate about respective rotation axes, in such a way to form a forming stack of folded or interfolded sheets adapted to grow in height along a predetermined forming direction; separating by a separation group a finished stack of folded or interfolded sheets from a following forming stack of folded or interfolded sheets, once that a predetermined number of sheets is reached; transferring said finished stack towards a discharge zone by a transfer group; during said step of separating and said step of transferring, at least one between said forming stack and said finished stack being supported by at least a support surface; and detecting the force exerted by said forming stack or by said finished stack, on said or each support surface during said step of separating and/or said step of transferring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention will now be shown with the following description of its exemplary embodiments, exemplifying but not limitative, with reference to the attached drawings in which:

[0043] FIG. 1 diagrammatically shows a side elevation perspective view of a first embodiment of a folding or interfolding machine, according to the invention in a working configuration;

[0044] FIGS. from 2 to 15 diagrammatically show in respective side elevation perspective views some possible alternative embodiments of the folding or interfolding machine of FIG. 1;

[0045] FIG. 16 shows an enlargement of a portion of FIG. 15 to highlight some technical characteristics.

DETAILED DESCRIPTION OF SOME EXEMPLARY EMBODIMENTS OF THE INVENTION

[0046] As diagrammatically shown in FIG. 1, a folding or interfolding machine 100 for forming stacks 50 of a predetermined number of folded or interfolded sheets 5, according to a predetermined folding or interfolding configuration, comprises a first and a second folding or interfolding roll, 1a and 1b. These rotate about respective rotation axes 101a and 101b and are configured to fold or interfold, in particular, at a folding zone defined between the same, the aforementioned sheets according to the aforementioned predetermined folding or interfolding configuration. The first and second interfolding rolls 1a and 1b can be provided with elements for keeping the sheets of mechanical or pneumatic type (as for example described in U.S. Pat. No. 7,771,337, EP1457444, or EP0982256, or WO2020/021490) or of mixed type (see for example WO2019207434).

[0047] In particular, in the case that the elements for keeping of the first and second rolls 1a and 1b are of pneumatic type, these can be provided with a predetermined number of longitudinal rows of suction holes adapted to be selectively and alternatively put in pneumatic communication with a device for generating a predetermined vacuum degree to suck the sheets on the surface 2a, or 2b, of the respective roll 1a, or 1b, only at predetermined angular portions of these.

[0048] Independently from the type of elements for keeping that are used, however, a forming stack 50 is obtained of folded or interfolded sheets which grows in height along a predetermined forming direction 150, in particular a vertical direction.

[0049] The machine 100 comprises, furthermore, a separation group 20 configured to separate a finished stack 50 of folded or interfolded sheets, from a following forming stack of sheets 50, and a transfer group 30 which transfers the finished stack 50 towards a discharge zone 60. According to what is foreseen by the present invention, at least one between the separation group 20 and the transfer group 30 comprises at least one detection device 40 configured to detect the force exerted by the forming stack 50, or by the finished stack 50 on the separation group 20, or on the transfer group 30.

[0050] More in detail, as diagrammatically shown in the embodiment of FIG. 1, the separation group 20 can comprise a first and a second plurality of separation members 21a and 21b configured to enter from opposite sides the finished stack 50 of folded or interfolded sheets, and to separate the same from a following forming stack 50 of folded or interfolded sheets (see FIG. 2). In particular, the first and second pluralities of separation members 21a and 21b are adapted to support the forming stack 50, at least at the beginning of the formation of the same.

[0051] The forming stack 50 can be moved, for example, among lateral containment grids 15a and 15b, the size of which in FIG. 1 is diagrammatically indicated with a broken line. In particular, the separation group 20 can be provided with a displacement group 120 configured to move the separation group 20 same. More in particular, the displacement group 120 can comprise a first and a second displacement device 121a and 121b configured to move, respectively, the first and second pluralities of separation members 21a and 21b along respective movement trajectories for moving the same from a position external to the forming stack 50 to a position internal to the same. More precisely, as soon as the last sheet of the stack 50 is detached from the respective folding roll 1a, or 1b, and put on the forming stack of folded or interfolded sheets 50, the respective plurality of separation members, for example the separation members 21a, is introduced into the stack 50 for a corresponding portion, for example up to half of the width of the stack 50, thus carrying out a separation between a sheet 5 and the following one. The other plurality of separation members, for example the separation members 21b, is introduced into the stack 50 from the other side, but staggered, for example for half of a sheet, with respect to the plurality of separation members 21a. In other words, a plurality of separation members 21a, or 21b, is introduced into the stack 50 time staggered with respect to the other plurality of separation members 21b, or 21a. The time staggering generally corresponds to half of a sheet. In this way, the separation is carried out between a finished stack 50 and the following forming stack 50 according to a technology known in the field of the paper converting machines. The machine 100 can, furthermore, provide, advantageously, a detachment group 10 comprising a first plurality of detaching elements 11a, or detaching fingers, and a second plurality of detaching elements 11b, which are shown in FIG. 1 with broken lines. More precisely, the detaching elements 11a and 11b act, respectively, at the first and at the second folding roll 1a and 1b to remove the sheets from the respective folding or interfolding roll, 1a, or 1b. More precisely, the first and second pluralities of detaching elements 11a and 11b are, advantageously, moved in phase with the folding rolls 1a and 1b, in such a way to be able to, alternately, laterally advance towards the sheet 5, for example by a rotation about respective rotation axes parallel to the aforementioned rotation axes 101a and 101b, and to remove the sheet 5 same from the respective roll 1a, or 1b, to cause the sheet to be detached from the surface 2a or 2b of the roll 1a or 1b, to which it adheres.

[0052] As diagrammatically shown in the embodiments shown as an example in the figures from 1 to 14, the transfer group 30 can, for example, comprise a first and a second support element, for example a first and a second transfer table 31a and 31b. These move at opposite sides with respect to the forming direction 150 between a position external to the forming stack 50, that is not shown in the figures for simplicity, and a respective support position (see for example FIG. 1), where they are positioned below the forming stack 50 and support, at opposite sides, the same at least for the final part of the formation of the stack 50. Advantageously, the first and second transfer tables 31a and 31b can be configured to move independently from each other. In particular, a supplementary displacement group 130 is provided comprising a first and a second supplementary displacement device 131a and 131b, which move, respectively, the first and second transfer tables 31a and 31b. The operations carried out by the transfer tables 31a and 31b will not be here described in detail because of known type in the technical field and are, for example, described in EP1415945, or EP1640305.

[0053] In particular, according to an operational sequence of known type, before that the first support element 31a is adapted to withdraw to be positioned in the respective support position, the second support element 31b can be adapted to be positioned below the first support element 31a to press any portion of a border of sheet 5 protruding from the first support element 31a. Then, the first support element 31a can withdraw to be positioned in the respective support position and the second support element 31b can move at the same, or Substantially the same, height of the first support element 31a to support together the forming stack 50 (FIG. 1). In particular, the first and second transfer tables 31a and 31b support the forming stack 50 at least for the final part of its formation. More in particular, at least one between the first and the second transfer table transfers the finished stack 50 towards the aforementioned discharge zone 60.

[0054] According to what is foreseen by the invention, at least one between the separation group 20 and the transfer group 30, more in particular at least one between the first and the second plurality of separation members 21a and 21b, or at least one between the first and the second transfer table 31a and 31b, can be provided with at least one detection device 40. This is, in particular, configured to detect the force exerted by the stack 50 on the separation group 20 and/or on the transfer group 30, in particular at least a plurality of separation members 21a, and 21b, or at least one between the first and the second transfer table 31a, and 31b. The force exerted by the stack 50 on the separation group 20 and/or on the transfer group 30, is generated both by the weight force of the sheets 5, and by the pressure generated by the positioning of the separation group 20 and/or the transfer group 30 with respect to the folding rolls 1a and 1b and/or by the detaching elements 11a and 11b. In practice, approaching or departing from the separation group 20 and/or the transfer group 30 with respect to the folding rolls 1a and 1b, it is possible to change the space where the forming stack 50 grows by pressing or loosening. This pressing or loosening creates a load or force which is added to the weight force of the forming stack 50. In order to have a good formation of a stack, it is necessary that the force detected by the detection device 40 is substantially equal to a reference value or that it swings within a determined reference range. These reference values can change according to the product and/or according to the velocity of production of the folding or interfolding machine 100, i.e. can change according to the paper basis weight, the number of sheets which form the stack, the type of folding, the number of folds or panels which form the single sheet, if the sheets are only folded but they are not interfolded, and vice versa, from the length or the size of the folding or interfolding machine 100, from the number of stacks per minute that are produced.

[0055] In particular, the or each detection device 40, for example a load cell, can be positioned at a portion of the displacement group 120. In the example of FIG. 1, a first and a second detection device 40a and 40b are provided integral, respectively, to the first displacement device 121a, and to the second displacement device 121b.

[0056] As diagrammatically shown in FIG. 2, in an embodiment alternative to the previous one, a detection device 40 can be provided integral to at least a portion of the supplementary displacement group 130. More in detail, in the example of FIG. 2, a first and a second detection device 40a and 40b, for example load cells, are provided integral, respectively, to the first supplementary displacement device 131a and to the second supplementary displacement device 131b.

[0057] In the further embodiment that is diagrammatically shown in FIG. 3, instead, detection devices 40a-40d are provided, each of which integral to a respective displacement device 121a and 121b of the displacement group 120 and to a respective supplementary displacement device 131a and 131b of the supplementary displacement group 130.

[0058] In the further alternative embodiment diagrammatically shown in FIG. 4, where the detaching elements 10 are not shown for clarity reason, at least one detection device 40 is provided integral to at least a separation element 21a of the first plurality of separation members 21a, or to at least a separation element 21b of the second plurality of separation members 21b.

[0059] More in detail, in FIG. 4, as an example, the case is shown where a first and a second detection element 40a and 40b are provided, respectively, integral to the first plurality of separation members 21a and to the second plurality of separation members 21b. More precisely, the or each detection device 40a, and 40b, can be a strain gage. In this case, a detection device 40a, 40b can be positioned for each element of the first plurality of separation members 21a and the second plurality of separation members 21b or a detection device 40a, 40b can be positioned for a subset of elements of the first plurality of separation members 21a and/or of the second plurality of separation members 21b. Preferably, each detection device 40, for example the strain gage, can be mounted at an end portion 22a, or 22b, of the respective separation element 21a, or 21b. In particular, the strain gage is able to detect, during working conditions of the machine 100, also for little dimensional deformation of one or more separation members 21a, 21b with respect to a predetermined deformation. Some embodiments foreseen by the present invention where the detection device 40 can be a strain gage are diagrammatically shown for example in the FIGS. 9 and 11.

[0060] According to still another embodiment foreseen by the invention and diagrammatically shown in FIG. 5, alternatively to the detection devices 40 positioned at the first and at the second plurality of separation members 21a and 21b, at least one detection device 40 can be provided positioned at least at one transfer table 31a, or 31b, in the example of FIG. 5 a first and a second detection device 40a and 40b, for example load cells, or strain gages, positioned, respectively, at the first and at the second transfer table 31a and 31b.

[0061] With reference to FIG. 6, where the stack 50 of folded or interfolded sheets is shown with broken line for clarity reason, each transfer table 31a and 31b is provided with a respective support surface 35a and 35b. In particular, during working condition, the stack 50 is positioned in contact with the aforementioned support surfaces 35a and 35b, which, therefore, support the forming stack 50, or the finished stack 50, until the transfer group 30 does not transfer the same at the discharge zone 60. Each transfer table 31a and 31b is provided, furthermore, with a respective lateral portion 36a and 36b external to the aforementioned support surfaces 35a and 35b. More precisely, during working condition, the lateral portions 36a and 36b are not positioned in direct contact with the forming stack 50, or with the finished stack 50. According to a possible embodiment foreseen by the invention, the or each detection device 40a, or 40b, in particular, the or each strain gage can be mounted at the or each aforementioned lateral portion 36a and 36b.

[0062] Analogously, each plurality of separation members 21a and 21b is provided with a support surface 25a and 25b, which, during the step for separating the stack 50 from the following one and for supporting the stack 50 until the transfer on the transfer tables 31a and 31b is positioned in contact with at least a sheet 5 of the forming stack 50 of folded or interfolded sheets. In particular, if alternatively or in addition to the aforementioned detection devices 40 associated to the transfer tables 31a and 31b, at least a detection device 40 is provided, at least at one element for separating the separation group 30, for example a first and a second detection device 40a and 40b positioned, respectively, at the first and the second plurality of separation members 31a and 31b, the or each detection device 40a and 40b is, preferably, positioned at a respective lateral portion 26a and/or 26b of the or each separation element 31a or 31b external to the aforementioned support surfaces 25a and 25b (FIG. 7).

[0063] In particular, a control unit 300 can be, furthermore, provided (see FIG. 8, and figures from 11 to 14) configured to acquire the data of force Fi detected by the or each detection device 40, and to calculate a deviation value AF of each of the detected data of force Fi from a predetermined threshold value F*. More in particular, the control unit 300 can be adapted to generate an alarm signal, for example an audio signal, or a light signal, when the aforementioned deviation value F=FiF* exceeds a predetermined threshold value F*, i. e. when |F|>F*.

[0064] According to an aspect of the invention, the control unit 300 can be, furthermore, configured to operate the separation group 20 and/or the transfer group 30 to keep within a predetermined error range the aforementioned deviation value F with respect to the predetermined threshold value F*, that means in such a way that FF*<e.sub.max, where e.sub.max is the maximum value of the deviation value that can be admitted by the threshold value. For example, the control unit 300 can be configured to control the first and/or the second displacement device 121a and/or 121b, and/or the first and/or the second supplementary displacement device 131a and/or 131b, in such a way to change the positions of the separating elements 21a and/or of the second separating elements 21b, and/or of the first transfer table 31a and/or of the second transfer table 31b, or, more in general, their relative positions. In addition or alternatively, the control unit 300 can be configured to change the velocity of one or more of the displacement devices 121a, 121b, 131a, or 131b. For the aforementioned purposes, for example, the control unit 300 can execute an closed-loop algorithm of control of known type such as a PID, an adaptive PID, or other known algorithm, in such a way to minimize and completely eliminate the deviation value FF*. In practice, according to the error e=FF* or e=FiF*, the control unit 300 dynamically calculates the position and/or the velocity and/or the acceleration of the first and/or the second displacement device 121a and/or 121b, and/or of the first and/or the second supplementary displacement device 131a and/or 131b for minimizing or completely eliminating the aforementioned error. The reference force values can be determined as described above. Furthermore, the reference value can be both a fixed numeric value and a variable numeric value that means that can be a function of the typology of product or the time of the cycle for forming the stack or the way in which a stack has to be formed, for example very pressed at the beginning and more lightening towards the end of the formation step, or a combination of these parameters. In the case of a variable reference value, the function can be continuous or discontinuous, for example a threshold function, and is comprised between a starting value which corresponds to the beginning of the formation of the stack, that means when the separating elements 21a and/or the second separating elements 21b are introduced and a final value which corresponds to when the first transfer table 31a and/or the second transfer table 31b starts to move the finished stack towards the discharge zone 60. It is, therefore, possible to move, in an automatic and controlled way the separation group 20 and/or on the transfer group 30 in function of the value of force detected by the or each detection device 40.

[0065] In a further alternative embodiment of the invention, which is diagrammatically shown in FIG. 8, at least an image acquisition device 70 is, furthermore, provided configured to acquire at least an image of the forming stack 50, or of the finished stack 50b, and to send the or each image to the control unit 300, which elaborates the same to define a parameter of quality of the forming stack 50. In particular, the aforementioned control unit 300 can be adapted to compute the shape of the forming stack 50 which is present on the, or each, acquired image, with a predetermined reference shape or image Q*. The control unit 300 can be, furthermore, adapted to assign a value Qi, to the quality of the forming stack 50 as much as the shape of the same can be superimposed to the reference shape Q*. In the case that the aforementioned value of quality differs, instead, more than a predetermined limit value Q from the value Q of the reference shape, the control unit 300 can be adapted to emit an alarm signal, for example an audio signal, or a video signal. At this purpose, to determine if the quality of the finished stack 50 or of the forming stack 50 is different from the quality of a reference finished or forming stack, the control unit 300, or another dedicated control unit, which is not shown in the figure for simplicity, can use IA algorithms such as neural networks or machine learning algorithms.

[0066] In particular, the image acquisition device 70 can be positioned at a fixed position. In an alternative embodiment which is not shown in figure for simplicity, the aforementioned image acquisition device 70 can be mounted on a movable support element, for example provided with a straight guide portion, in such a way to cause the image acquisition device 70 to slide along the aforementioned vertical direction 150. More in particular, the movable support element can be configured in such a way that the slide of the image acquisition device 70 is carried out synchronously with the movement of the forming stack 50, in particular to acquire a series of following images Qi of the forming stack 50 during the growth in height of the same, or of the finished stack 50.

[0067] Alternately, the image acquisition device 70 can have a fixed position and acquire one or more images depending on the formation or the position of the stack 50. For example, the image acquisition device 70 can acquire one image each predetermined number of sheets 5 stacked on each other on the forming stack. In addition or alternatively, the image acquisition device 70 can acquire an image at the inserting instant in and/or at the withdrawal instant from the stack 50 of the inserting elements 21a and/or the second separating elements 21b and/or of the first transfer table 31a and/or of the second transfer table 31b. Finally, the image acquisition device 70 can acquire only one image of the finished stack 50.

[0068] According to an embodiment of the invention, the control unit 300 can be, in particular, adapted to define the aforementioned parameter of quality Qi by a software which detects at least one parameter of the forming stack 50, or of the finished stack 50, selected among: stack height, stack density, wrong folding of the sheets, wrong interfolding of the sheets. One or more of these parameters of the forming stack 50, or of the finished stack 50, can be used together or in mutual relation with the value of quality Qi or the difference between Qi and the reference image Q*. For example, the aforementioned software can be an IA algorithm such as a neural network and/or a software of machine learning. The software can be, therefore, adapted to determine the aforementioned parameters of the forming stack 50, or of the finished stack 50 in addition to a parameter of quality computed according to the IA algorithms described above. The parameter of quality Qi and/or the parameters of the forming stack 50, or of the finished stack 50, can be used to calculate or to dynamically change, i.e. in real time, the reference value F* both in the case that F* is a numerical value both if F* is a function.

[0069] According to an aspect of the invention, it is possible to adjust and to automatically move the position and/or the velocity and/or the acceleration H the separation group 20 and/or of the transfer group 30 in function of the value del parameter Qi and/or of the parameters O f the forming stack 50, or of the finished stack 50 calculated by the control unit 300 starting from the or each image acquired by the image acquisition device 70. For example, if the density of the forming stack is too high, it is possible to operate the separation group 20 and/or the transfer group 30 in order to increase the growing space available to the stack thus decreasing as a consequence the density of the forming stack 50.

[0070] By movement of the separation group 20 and of the transfer group 30 it is intended the movements along the forming direction 150, substantially vertical or along the direction going from and towards the folding rolls 1a, 1b, the horizontal movements adapted to introduce or withdraw the separating elements 21a and/or the second separating elements 21b and/or the first transfer table 31a and/or the second transfer table 31b from the forming stack 50 or from the finished stack 50 or a combination of these movements.

[0071] According to another aspect of the invention, the machine 100, at the discharge zone 60, can, furthermore, provide a discharge device 80, for example a conveyor belt, or a chute, configured to move along a displacement direction 180, preferably coincident with the aforementioned vertical direction 150, from and towards the transfer group 30, in particular from and towards the transfer tables 31a and 31b. More in particular, a displacement device 90 can be provided operatively connected to the aforementioned discharge device 80 and configured to move the discharge device 80 same along the aforementioned displacement direction 180. For example, the displacement device 90 can be adapted to engage the discharge device 80 at least at one side 81 in such a way to cause the same to be moved in a guided way along the aforementioned displacement direction 180.

[0072] For example, the displacement device 90 can provide a motor 95 which causes a rotation of a drive pulley 91 on which a transmission belt 96 is mounted that ends at an idler pulley 92. More in particular, the belt 96 can be engaged by an engagement device 97 to the aforementioned discharge device 80. In addition, a supplementary guide device, such as for example a linear guide upon which a skid slides, can be provided that cannot be seen in figure for clarity reason, that is constrained to the transmission belt 96 and engaged to the discharge device 80 to guide the same along the aforementioned displacement direction 180.

[0073] According to an embodiment of the invention that is diagrammatically shown in particular in FIG. 10, the first and second displacement devices 121a and 121b adapted to move the first and second pluralities of separation members 21a and 21b can provide a respective first movable support 122a and 122b, each of which slidingly mounted on a respective linear guide 123a and 123b to slide along a respective first sliding direction 124a and 124b, in particular by a respective first skid 125a and 125b. More in detail, the aforementioned linear guides 123a and 123b are constrained to respective second supports 126a and 126b slidingly mounted along second sliding directions 127a and 127b, for example by second skids 128a and 128b engaged to respective second linear guides 129a, 129b, in particular vertically oriented. The motion of the second skids 128a and 128b can be, for example, obtained by respective belts 140a and 140b respectively running over a determined number of pulleys 141a and 141b, at least one of which is motorized. The motion of the second skids 128a and 128b is, furthermore, guided by engaging the same on the linear guides 129a and 129b. Analogously, the first and second supplementary displacement devices 131a and 131b which move the first and second transfer tables 31a and 31b can provide a respective first movable support 132a and 132b, each of which slidingly mounted on a respective linear guide 133a and 133b to slide along a respective first sliding direction 134a and 134b, in particular by a respective first skid 135a and 135b. More in detail, the aforementioned linear guides 133a and 133b are constrained

To Respective Second Supports 136a and 136b Slidingly

[0074] mounted along second sliding directions 137a and 137b, for example by respective second skids 138a and 138b engaged to respective second linear guides 139a and 139b. These can, for example, coincide, respectively, with the aforementioned linear guides 129a and 129b, or they can be different from these as diagrammatically shown in FIG. 10. Also the motion of the aforementioned second skids 138a and 138b along the respective linear guides 139a and 139b can be obtained by a system with belt and pulleys, for example, but not necessarily, coincident with the belts 140a and 140b and with the respective pulleys 141a and 141b described above with reference to the motion of the second skids 128a and 128b along the respective linear guides 129a and 129b.

[0075] In general, the or each detection device 40 can be positioned at a detection position arranged between the second support 126a and/or 126b and the second skid 128a and 128b of the first and second displacement devices 121a and 121b, and/or between the second support 136a and/or 136b and the second skid 138a and 138b of the first and second supplementary displacement devices 131a and 131b. In practice, it is sufficient to place the detection device 40 in any position on the first and/or on the second displacement device 121a and 121b and/or on the supplementary displacement device 131a and/or 131b adapted to detect the force, or the load, exerted by the forming stack 50 and/or by the finished stack 50.

[0076] As diagrammatically shown in the embodiment of FIGS. 15 and 16, the detection device 40 can be a thin film pressure sensor, or a thin film force sensor, consisting, in practice, of a strip of a material sensitive to pressure or force. For example, a first, a second, a third and a fourth detection device 40a-40d can be provided positioned, respectively, at the support surfaces 25a, 25b, 35a and 35c. Preferably, as diagrammatically shown in the enlargement of FIG. 16, the or each detection device 40 can be housed within a respective seat 27 made at a respective separation element 21a, 21b, and/or at a respective seat 37 made at a respective forming table 31a, 31b, in such a way not to protrude from the surface of the aforementioned support surfaces 25a-25d, or 35a-35c, or anyway, to protrude from the same without, anyway, substantially changing the geometry.

[0077] In this configuration the detection device 40 has, advantageously, a width equal to, or less than, the width of the support surface 25a, 25b, 35a, 35b. In particular, in this embodiment the detection device 40 can directly detect the force or the pressure exerted by the forming stack 50 or by the finished stack 50 without taking into account the mechanical construction of the displacement devices 121a and 121b and/or the supplementary displacement devices 131a and 131b. In this configuration the detection device 40 produces, in particular, an electrical signal which is proportional to the force or pressure exerted by the stack on the support surface 25a and/or 25b and/or support surface 35a and/or 35b. The electric signal can be processed by the control unit 300 to determine the value of the detected force Fi. Preferably, when the support surface 25a, 25b, 35a, 35b are provided with the detection device 40 having a height which cannot be neglected, for example higher than 0.2 mm, the respective first or second separating elements 21a, 21b or the respective first or second transfer tables 31a, 31b can be provided with a seat for positioning the detection device 40 in such a way that all the support surfaces 25a, 25b, 35a, 35b, provided or not with the detection device 40, are all at the same height, that means in such a way to form a support plane even though not continuous, but arranged at the same height to uniformly support the stack and in order not to have erroneous readings of the detection device 40.

[0078] What described above with reference to the figures from 1 to 10, can be applied both to folding or interfolding machines of the type that is fed with two different continuous webs from which by respective cutting groups two different flows of sheets are obtained, i.e. machines of the type for example described in EP3746386, EP0982255, EP0982256 and in EP2462044, and to machines fed with a single continuous web which is cut to form a sequence of sheets fed to the folding rolls along a single feeding line to be, for example, L or Z folded, as for example described in EP1826165 and EP2308786.

[0079] In particular, in the first case, the machine 100 will comprise a first feeding group configured to feed towards the first and second folding or interfolding rolls 1a and 1b a first plurality of sheets 5 along a first feeding path. In this case, furthermore, a first cutting group will be provided configured to cut the first continuous web of a web-shaped material into a first plurality of sheets.

[0080] In the second case, instead, the machine 100 will comprise also a second feeding group configured to feed towards the first and second folding or interfolding rolls a second plurality of sheets along a respective feeding path. In this case, furthermore, a second cutting group will be provided configured to cut a second continuous web of a web-shaped material into the second plurality of sheets.

[0081] The foregoing description exemplary embodiments of the invention will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt for various applications such embodiment without further research and without parting from the invention, and, accordingly, it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiments. The means and the materials to realize the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology that is employed herein is for the purpose of description and not of limitation.