Suction roll of a laminar product

Abstract

A suction roll (1) of laminar products (5) comprises a fixed tubular body (10) having an external lateral surface (11) and an internal lateral surface (12) which communicates with each other through at least a first plurality of circumferential apertures (15a). The internal lateral surface (12) delimits a longitudinal suction chamber (16). A rotating tubular body (20) is, furthermore, provided mounted coaxially to the fixed tubular body (10) having an external lateral surface (21) and an internal lateral surface (22). The rotating tubular body (20) rotates about a longitudinal axis (120) and is provided with at least a first plurality of suction channels (23) organized according to a predetermined number of longitudinal rows (3). The rotation of the rotating tubular body (20) puts in pneumatic connection the longitudinal suction chamber (16) with at least a row (23) of suction channels (23) at respective angular position. A device for generating an air-flow (50) selected among : a compressor, a centrifugal compressor, a fan, a centrifugal fan, is, furthermore, provided that is pneumatically connected to the longitudinal suction chamber (16) in order to cause a worked laminar product (5), at a time, to be sucked by at least one row of suction channels (23) and to adhere to the external lateral surface (21) of the rotating tubular body (20) at the aforementioned different angular positions.

Description

[0001] TITLE

[0002] SUCTION ROLL OF A LAMINAR PRODUCT

[0003] DESCRIPTION

[0004] Field of the invention

[0005] The present invention relates to the field of paper, and similar products , converting, and in particular it relates to a suction roll , such as an advancement roll , a cutting roll , a folding or interfolding roll of a machine for interfolding a web, or sheet of paper, of the type provided with suction holes which, connected to a vacuum system, allows the sheet , or web, of paper to adhere on the surface of the same .

[0006] The invention, furthermore , relates to a paper converting machine comprising at least such a suction roll .

[0007] Description of the prior art

[0008] As known, many machines used in the industry of the paper, for example rewinding, interf olding, and folding, machines equipped with systems to cause the worked web, or sheet of paper, to adhere on the surface of the rolls , in determined working steps , in order to feed the sheets or webs of paper along a desired path .

[0009] In particular, such systems are used to carry out the fundamental operations of the cut of the paper, or its very quick trans fer from a roll to another one or still of the final fold of the paper same .

[0010] In the last years in the field of paper converting machine , suction rolls provided with pneumatic systems have had a wide di f fusion which causes the worked sheet or web of paper and its adhesion on a determined portion of the external lateral surface of the suction roll . More precisely, as for example described in EP1457444 , or in EP2514698 , the aforementioned suction systems provide a device for generating a determined vacuum degree which is pneumatically connected to the inside of the suction rolls . More precisely, a suction roll of this type comprises a rotating tubular body adapted to rotate about a longitudinal rotation axis and a fixed tubular body positioned coaxially to the rotating tubular body and internally to the same . The surface of the rotating tubular body is provided with a determined number of couples of longitudinal rows of suction holes , normally 3 , or 4 , couples of rows of holes . The fixed tubular body is , instead, provided with a longitudinal row of apertures . Between the rotating tubular body and the fixed tubular body a vacuum distribution device is provided comprising a first and a second sealing element , or gaskets , which are arranged longitudinally to the suction roll at two di f ferent angular positions and at opposite sides with respect to the aforementioned row of apertures of the fixed tubular body . In this way, the internal lateral surface of the rotating tubular body, the external lateral surface of the fixed tubular body and the longitudinal sealing elements form a suction chamber .

[0011] During the rotation of the rotating tubular body with respect to the fixed tubular body, the aforementioned rows of holes are selectively put in pneumatic connection with the aforementioned vacuum generation device dal aforementioned vacuum distribution device . More precisely, only the holes of the rotating roll arranged at a determined instant between the two sealing elements will exert a suction action on the worked sheet, or web, of paper, causing it to adhere on the corresponding portion of an external lateral surface of the suction roll.

[0012] However, these typologies of suction rolls have some drawbacks .

[0013] In particular, normally, a paper converting machine is provided with more than one suction roll, each of which directed to carry out a determined operation of the production cycle. For example, a folding or interfolding machine has, generally, a cutting roll, one or more transfer rolls, and a couple of folding or interfolding rolls. The different suction rolls of the machine are, normally, all connected by a series of ducts to the same vacuum generation device, such as a vacuum pump. This, therefore, must be dimensioned in such a way to guarantee a determined vacuum degree within all the suction rolls, in spite of the pressure drops which, unavoidably, occur along the suction line. These suction lines provide, furthermore, a series of valves for insulating or dividing the vacuum in the different parts of the machine, in particular the different suction rolls, in order to carry out the maintenance or the replacement of each suction roll without disassembling the whole line or adjusting the vacuum degree more functional to the machine. This, therefore, means further concentrated pressure drops along the vacuum suction line and long time for the adjustment in the starting configuration step of the machine.

[0014] In light of the above, it is necessary to oversize the device for vacuum generation in order to compensate the aforementioned pressure drops and to guarantee the ef fectiveness of the suction of the di f ferent rolls . However, this implies high costs of plant and exercise , in particular owing to the high electrical power consumption of the vacuum generation device and to the cost of the generator same .

[0015] In addition to the above , during the functioning of the suction rolls , dusts and fragments of material , in particular of paper, which are present in the environment surrounding the suction roll and produced during the working cycle , are , unavoidably, sucked by the suction line and can, over time , cause at least a partial obstruction both of the suction holes and of the ducts which connect the vacuum generation device to the di f ferent distribution devices , therefore , causing a los s of ef fectiveness of the suction system which is reflected unavoidably in a loss of quality for the final product . Therefore , the suction rolls of known type have to be necessarily periodically subj ected to maintenance interventions for cleaning the di f ferent parts which form the same . The maintenance interventions provide the disassembly of all the connections which keep together the roll same , normally flanged connections . Then, the several ducts , which can have also a length of several dozens of metres , are disassembled in order to be able to clean them, and then connected again to each other and to each suction roll once they have been cleaned .

[0016] The same action is also carried out for the ordinary maintenance interventions which are periodically programmed to replace the sealing elements . These , in fact , because of the friction generated during the rotation of the rotating tubular body about its longitudinal axis , owing to their dragging against the internal lateral surface of the rotating tubular body, are subj ected, over time , to wear .

[0017] In light of the above , therefore , also the maintenance interventions of a prior art suction roll are complex and extremely expensive in terms of workforce , and, therefore , of costs , and of time , both in the case of interventions for cleaning the several parts of the suction roll , and in the case of interventions for replacing the sealing elements .

[0018] The suction rolls of prior art have , furthermore , the disadvantage of not be able to control very well at high production speed i f the sheet or web adheres or not . In fact , the rolls have rows of suction holes which have to hold the veil , or the veils , of paper on the external lateral surface of the rotating roll . The active surface , that means the surface of the holes exerting the holding force of the paper is very small and, therefore , inef fective to control the hold, the advancement and the release of the sheets or webs of paper .

[0019] Examples of suction rolls of known type with the aforementioned drawbacks are described in EP3724112 and US 10294058 .

[0020] Summary of the invention

[0021] It is therefore an obj ect of the present invention to provide a suction roll per paper converting machine able to overcome the drawbacks of the prior art rolls .

[0022] It is in particular an obj ect of the present invention to provide a suction roll for paper converting machine which is able to simpli fy and speed up the ordinary and extraordinary maintenance interventions , in particular to carry out the replacement of the gaskets of which is provided .

[0023] These and other obj ects are achieved by a suction roll per suck a laminar product in such a way to cause the laminar product to advance along an advancing direction, said suction roll comprising : a fixed tubular body provided with an external lateral surface and with an internal lateral surface delimiting a longitudinal suction chamber, said external lateral surface and said internal lateral surface being arranged to communicate with each other through at least a first plurality of circumferential apertures distributed along a first longitudinal row, each circumferential aperture of said plurality being placed along a respective circumferential portion of said fixed tubular body; a rotating tubular body mounted coaxially to said fixed tubular body having external lateral surface and an internal lateral surface and configured to rotate externally to said fixed tubular body about a longitudinal rotation axis , said rotating tubular body being provided with at least a first plurality of suction channels organi zed according to a respective predetermined number of longitudinal rows , said rotation of said rotating tubular body about said longitudinal rotation axis being adapted to put in pneumatic connection said longitudinal suction chamber with at least one row of said first plurality of suction channels at respective predetermined angular positions of said rotating tubular body; a device for generating an air-flow configured to cause the worked laminar product to be sucked by at least one row of said suction channels at a time and to adhere to the external lateral surface of the rotating tubular body at the predetermined angular positions ; whose main characteristic is that said device for generating an air-flow is selected among : a compressor, a centrifugal compressor, a fan, a centrifugal fan, pneumatically connected to said longitudinal suction chamber .

[0024] Other features o f the present invention and related embodiments are set out in the dependent claims .

[0025] In particular, the rotating tubular body can be, furthermore, provided with at least a second plurality of suction channels organized according to a respective predetermined number of longitudinal rows .

[0026] In particular, the fixed tubular body can be , furthermore , provided with a second plurality of circumferential apertures positioned along a second direction longitudinal to the fixed tubular body .

[0027] Advantageously, the first and second pluralities of circumferential apertures can be circumferentially staggered with respect to each other . In this way, the first and second rows of suction channels can be put in pneumatic connection with the longitudinal suction chamber at the aforementioned predetermined angular positions of the rotating tubular body .

[0028] According to an embodiment of the invention, the device for generating an air- flow can be provided with a main body integral to the fixed tubular body . More in particular, the device for generating an air- flow can comprise , furthermore , an impeller adapted to be housed in the main body and operatively connected to a motor to generate the air- flow inside the longitudinal suction chamber . In an advantageous embodiment , the aforementioned device for generating an air- flow is arranged to generate an air- flow at a predetermined pressure ( Pi ) less than the atmospheric pressure .

[0029] In particular, the rotating tubular body can be, furthermore, provided with at least a third plurality of suction channels organi zed according to a predetermined number of longitudinal rows . More in particular, the or each longitudinal row of the first and of the second plurality of suction channels can be positioned on the rotating tubular body in such a way to be put in pneumatic connection at said respective angular position with the first plurality of circumferential apertures , while the or each longitudinal row of the third plurality of suction channels is positioned on the rotating tubular body in order to be put in pneumatic connection with the second plurality of circumferential apertures at respective predetermined angular positions .

[0030] In an embodiment of the invention, the plurality of the first and second suction channels can be organi zed in a plurality of suction groups placed on a plurality of rows circumferential to said rotating tubular body .

[0031] In particular, each suction group of the aforementioned plurality can comprise at least a first suction channel of the first plurality and at least a second suction channel of the second plurality divided by a partition wall .

[0032] In particular, the suction channels can be configured in such a way that the cross-section passage of each suction channel of the aforementioned first and second pluralities of suction channels are adapted to increase , at least for a portion of its length, going from the internal lateral surface towards the external lateral surface of the rotating tubular body .

[0033] Analogously, the cross-section passage of each suction channel of the aforementioned third plurality of suction channels can increase going from the internal lateral surface to the external lateral surface of the rotating tubular body .

[0034] In particular, the first and second pluralities of circumferential apertures of the first and of the second longitudinal row of the fixed tubular body have respective circumferential portions arranged side by side or at least partly side by side going along a longitudinal direction .

[0035] According to another aspect of the invention, a suction roll of a laminar product configured to cause the laminar product to advance along an advancing direction comprises : a fixed tubular body provided with an external lateral surface and with an internal lateral surface delimiting a longitudinal suction chamber, said external lateral surface and said internal lateral surface being arranged to communicate through a first plurality of circumferential apertures distributed along a first longitudinal row, each circumferential aperture of said plurality being placed along a respective circumferential portion of said fixed tubular body; a rotating tubular body mounted coaxially to said fixed tubular body having an external lateral surface and an internal lateral surface and configured to rotate externally to said fixed tubular body about a longitudinal rotation axis , said rotating tubular body being provided with at least a first plurality of suction channels organized according to a predetermined number of longitudinal rows , said rotation of said rotating tubular body about said longitudinal rotation axis being adapted to put in pneumatic connection said longitudinal suction chamber with at least one row of said first plurality of suction channels at a time at respective predetermined angular positions of said rotating tubular body; a device for generating an air-flow arranged to generate an air-flow at a determined pressure within said longitudinal suction chamber in such a way to cause the worked laminar product to be sucked and to adhere to the external lateral surface of the rotating tubular body at the predetermined angular positions ; said fixed tubular body being, furthermore , provided with a second plurality of circumferential apertures distributed along a respective second longitudinal direction, each circumferential aperture of said first and of said second plurality of circumferential apertures being arranged along a respective circumferential portion of the fixed tubular body to put in pneumatic connection said longitudinal suction chamber with at least a row of the first plurality of suction channels , at predetermined angular positions of the rotating tubular body .

[0036] According to another aspect of the invention, a paper converting machine comprises at least a treatment unit selected among : a folding or interfolding unit adapted to fold or interfold a web or a plurality of sheets made of laminar material , in particular paper, according to a predetermined folding or interfolding configuration; a cutting unit configured to cut a continuous web made of laminar material into a plurality of sheets of predetermined length; an advancement unit arranged to cause a web or sheet of paper to advance along a predetermined advancing direction; or a combination thereof ; wherein said or each treatment unit comprises at least a suction roll as described above .

[0037] Brief description of the drawings

[0038] The invention will be now illustrated with the following description of an exemplary embodiment thereof , exempli fying but not limitative , with reference to the attached drawings wherein :

[0039] - Fig . 1 diagrammatically shows a perspective side elevation view of a first embodiment of a fixed tubular body of a suction roll according to the invention;

[0040] - Fig . 2 diagrammatically shows a perspective side elevation view of a first embodiment of a suction roll according to the invention;

[0041] - Fig . 3 diagrammatically shows a longitudinal section of the suction roll of figure 2 ;

[0042] - Fig . 4 diagrammatically shows a transversal section of the suction roll of figure 2 ;

[0043] - Fig . 5 diagrammatically shows a longitudinal section of an alternative embodiment of the suction roll of figure 2 ;

[0044] - Fig . 6 diagrammatically shows an enlargement of a portion of the figure 5 to highlight some technical characteristics ;

[0045] - Fig . 7 diagrammatically shows a perspective side elevation view of an embodiment of the fixed tubular body alternative to that of figure 1 ;

[0046] - Figures 8 and 9 diagrammatically show a perspective side elevation view of two possible alternative embodiments of the suction roll of figure 2 ;

[0047] - Fig . 10 shows an enlargement of a portion of the figure 9 to highlight some technical characteristics ;

[0048] - Fig . 11 shows another alternative embodiment of the suction roll according to the invention;

[0049] - Fig . 12 diagrammatically shows a possible embodiment of a suction group which can be used by the suction roll according to the invention in an engagement configuration;

[0050] - Fig . 13 shows a cross-section of the suction group of figure 12 according to arrows XI I I-XI I I ;

[0051] - Fig . 14 diagrammatically shows the suction group of figure 12 in a disengagement configuration;

[0052] - Fig . 15 diagrammatically shows a supplementary suction group which can be used by the suction roll according to the invention;

[0053] - Figures 16 and 17 diagrammatically show two di f ferent transversal sections of the suction roll of figure 11 ;

[0054] - Figures from 18 to 20 diagrammatically show in side elevation perspective views further embodiments of the suction roll according to the invention; - Fig . 21 diagrammatically shows a perspective side elevation view of another embodiment according to the invention of the fixed tubular body .

[0055] Detailed description of some exemplary embodiments of the invention

[0056] As diagrammatically shown in figure 1 , a suction roll 1 , according to the invention, of the type used for feeding a laminar product, for example a web, or sheet of paper, along an advancing direction, in particular in a paper converting machine , or similar products , comprises a fixed tubular body 10 provided with an external lateral surface 11 and of an internal lateral surface 12 delimiting a longitudinal suction chamber 16. More in particular, according to a first embodiment according to the invention diagrammatically shown in figure 1 , the fixed tubular body 10 is provided with a first plurality of circumferential apertures 15a positioned along a first longitudinal direction 13 and adapted to put in pneumatic connection the external lateral surface 11 with the internal lateral surface 12 .

[0057] The suction roll 1 , furthermore, provides a rotating tubular body 20 mounted coaxially to the fixed tubular body 10 and configured to rotate externally to the same about a longitudinal rotation axis 120 . The rotating tubular body 20 is provided with an external lateral surface 21 and with an internal lateral surface 22 . In particular, between the rotating tubular body 20 and the fixed tubular body 10 can be provided with elements which allows a rotation with respect to each other , for example 4 bearings 85, as diagrammatically shown in figure 3 , or brasses , or other analogous devices .

[0058] More in detail , the rotating tubular body 20 is provided with at least a first plurality of suction channels 23 organized according to a predetermined number of longitudinal rows 3 .

[0059] In an alternative embodiment of the invention, a second plurality of suction channels 24 is , furthermore provided organized according to a respective number of longitudinal rows 4 .

[0060] In the embodiment diagrammatically shown in the figures from 2 to 4 , the rotating tubular body 20 is provided with 5 rows 3a-3e of the first plurality of suction channels 23 of the quale in figure 2 the first two rows 3a and 3b are shown, and of 5 rows 4a-4e of the second plurality of suction channels 24 , of which in figure 2 the first two rows 4a and 4b are shown . The number of rows 3a, 3b of the rotating tubular body 20 can be changed depending on the production and functional needs of the machine where the suction roll 1 is used .

[0061] A device for generating an air- flow 50 is , furthermore, provided arranged to generate an air-flow at a predetermined pressure , in particular a pressure less than the atmospheric pressure, within the longitudinal suction chamber 16.

[0062] In particular, the device for generating an air- flow 50 is configured to move the air- flow through the longitudinal suction chamber 16 between an inlet 16a and an outlet 16b of which the fixed tubular body 10 is provided with . In this way, during rotation of the rotating tubular body 20 about the rotation axis 120 , it is possible to cause the worked laminar product to be sucked and to adhere to the external lateral surface 21 at predetermined angular positions .

[0063] As diagrammatically shown in figure 18 or 19 , the device for generating an air-flow 50 can be a device adapted to generate an air- flow at a predetermined vacuum degree, for example a vacuum pump . In an alternative embodiment according to the invention and diagrammatically shown in figure 5, the device 50 for generating an airflow can be arranged to generate a j ump of pressure in an air-flow 55 between a suction zone and a pump zone, for example a compressor, a centri fugal compressor, or an axial compressor, or a rotating compressor, or a fan, in particular a centri fugal fan, or an axial fan, or other known typologies . In this case , the device 50 is , advantageously, connected at the suction to the longitudinal suction chamber 16 in order to generate a pressure less than the atmospheric pressure within the longitudinal suction chamber 16 and higher downstream of the device 50 for generating an air- flow, that means in the pump zone . In other words , the device 50 for generating an air- flow creates an air- flow 55 which enters into the suction roll 1 , passes through the device 50 for generating an air- flow and exits through a pump aperture of the device 50 at a pressure greater than the atmospheric pressure . In particular, the device 50 for generating an air-flow can be connected to the aforementioned longitudinal suction chamber 16 through a duct 60 . In particular, each circumferential or curved aperture , 15a of the first plurality is placed along a respective circumferential portion of the fixed tubular body 10 to put , respectively, in pneumatic connection the longitudinal suction chamber 16 with at least a row 3a-3e , or 4a-4e, of the first and of the second plurality of suction channels 23 , 24 , when the rotating tubular body 20 reaches the aforementioned predetermined angular positions during rotation of the same about the rotation axis 120 . In the suction roll 1 is possible to cause the head, or the portion of head, of a sheet to adhere to the rows 4a- 4e of the second plurality of suction channels 24 and the tail of a sheet to the rows 3a-3e of the first plurality of suction channels 23 . In the folding and / or advancement rolls of the prior art , it is known to use holes on the external lateral surface of a rotating tubular body to suck, hold and move a web or a sheet . The suction is obtained by a vacuum pump and, therefore , in order not to lose too much suction capacity, the holes are of small diameter . Normally, the holes are aligned to each other along a row . Each row has a predetermined number of holes according to the aim to reach, that means that at each row of holes corresponds a precise portion of sheet to be treated . For example , a row of holes can be used to hold the initial edge, or head, of a sheet , another row of holes can be used to hold the end edge, or tail , still another row of holes can hold the centre portion of a sheet . In some cases , the centre portion of the sheet can be held by two distinct rows of holes , each of the two rows can have a dif ferent number of holes . Generally, each row of holes can have a dif ferent number of holes and the holes same can be of di fferent diameter from a row to another . The total number of holes for each row is function of the si ze of the converting line , that means , in other words , is function of the length of the rotating tubular body 20 . For each suction hole on the external lateral surface of the rotating tubular body 20 corresponding to a suction channel which put in pneumatic connection the external lateral surface of the rotating tubular body 20 with its internal lateral surface . These channels are generally straight because made by subj ecting to a mechanical drilling operation the rotating tubular body 20 . In other cases , as described in EP3724112 , it is possible to configurate the groups or blocks provided with groups of suction holes screwed on the rotating tubular body in order to make the external lateral surface of the block coincide with the external lateral surface of the rotating tubular body . Also in this case, rows of holes are obtained where each row is used to hold a specific portion of a sheet . For example, in EP3724112 , each block is provided with a group of holes formed by two rows of three holes aligned to each other, at most , which are substantially equivalent to the holes directly made by drilling the rotating tubular body as shown in EP3826950 . The blocks are mounted aligned to each other along the longitudinal direction of the suction roll in order to form altogether rows of holes fully equivalent to the rows of holes directly made on the rotating tubular body . Generally, the distribution of the holes of each row of holes can be non-homogeneous in longitudinal direction both in the case that the holes are obtained by directly perforating the rotating tubular body and in the case that the holes are provided at the blocks previously described .

[0064] All the holes described above have substantially a constant cross-section except for the mechanical operation of countersink which can be present or not . In EP3724112 each group of holes has , at most, two rows of suction holes , for example, respectively one row of holes for sucking the head and one for sucking the tail of a sheet . In other cases , one or two rows of holes can be used for sucking the centre portion of a sheet .

[0065] In the suction rolls of prior art, the active surface , that means the sucking one in contact with a sheet, it is formed by the area of the holes in addition to the i f present . For example, the holes can have a maximum diameter of about 3 . 5 mm with a countersink of 1 .25 mm, obtaining an active circular sucking surface with a diameter equal , at most , to 6 mm at the external lateral surface of the suction roll . The diameter of the holes can change depending on the paper, of its basis weight , of the velocity of production for which the machine has been designed and many other factors . For example, the diameter of each hole can vary from about 2 mm to 3 . 5 mm, as well as the countersink can vary from 0 . 5 mm to 1 .25 mm . Generally, on the external lateral surface of the rotating tubular body, the opening corresponding to each hole is approximately comprised between about 7 mm2to 30 mm2considering also any countersinking operation .

[0066] Furthermore, in the groups of holes , the respective rows of the holes can be formed by a variable number of holes . For example , a generic advancement roll of the sheets can have groups of holes aligned to each other formed by a row of three holes with diameter equal to 3 . 5 mm to hold the head of the sheet and by a row formed by a single hole of 3 . 5 mm of diameter to hold the tail of the sheet .

[0067] In the prior art, with respect to a suction roll whose external lateral surface is about 2750 mm and wherein each row of suction holes is formed by groups of three suction holes aligned to each other of diameter equal to 6 mm included the countersink and wherein the groups of three holes are 45 , the total sucking surface is equal to about 3815 mm2calculated multiplying the area of each hole by the number of the holes of the row . In the rolls of prior art therefore, on average , the sucking surface for each mm of length of the external lateral surface of the suction roll has a maximum value of about 1 . 4 mm2per mm, obtaining dividing the total suction roll by the length of the external lateral surface of the suction roll .

[0068] According to the present invention, each suction channel 23 , or 24 , of the first and of the second plurality, is associated to a sucking area at the external lateral surface 21 of the rotating tubular body 20 greater than or equal to 1 . 5 mm2per mm that means per mm of length of the external lateral surface 21 of the rotating tubular body 20 . The apertures 23 and 24 can be provided at a plurality of suction groups 30 . Preferably, the suction groups 30 are longitudinally arranged side by side in a direction parallel to the first longitudinal direction 13 forming a linear sucking surface which corresponds to a row of holes of the prior art . In other words , each aperture 23 , 24 can be used to hold a predetermined portion of the sheet . For example , the plurality of apertures 23 aligned can hold the tail of a sheet, whereas the row of apertures 24 aligned to each other can hold the initial edge of a sheet . The apertures 23 , 24 can be defined by a rectangular surface . In this case, the height and the length of the apertures 23 , 24 , disregarding any bevel or angular fittings , are such to obtain the ratio between the total suction roll and the length of the external lateral surface 21 greater than 1 . 5 mm2per mm . The total suction roll is equal to the sum of the apertures of each suction group aligned along the first longitudinal direction 13 . In some embodiments , it is possible to change the length of the suction groups 30 and / or to modi fy the size of the sides of the sucking surface or to change the shape of the apertures 23 , 24 keeping the si ze of the smaller aperture equal to 1 . 5 mm2per mm of length of the external lateral surface of the rotating tubular body 20 .

[0069] In this way, an effective sucking action of the laminar product by the suction channels 23 and 24 is obtained . Increasing the active surface of the external lateral surface 21 of the rotating tubular body 20 , that means increasing that portion of the external surface 21 , adapted to hold the paper, to cause the sheet or web to adhere on the external lateral surface 21 of the rotating tubular body 20 is much more distributed obtaining a stronger and more stable adhesion with respect to the suction rolls of prior art . In this case , the suction type to be used can be of any kind, that means that it is possible to use a vacuum pump, a centri fugal compressor, an axial or radial fan or any other device adapted to create an air- flow within the longitudinal suction chamber 16 , in particular at a pressure less than the atmospheric pressure outside the rotating tubular body 20 , advantageously less than 0 . 9 atm . , for example less than 0 . 8 atm .

[0070] As diagrammatically shown in figure 1 , the circumferential portion of the external lateral surface 11 of the fixed tubular body 10 at which the circumferential apertures 15a are positioned, is comprised between the 2 same generatrixes 101 and 102 of the fixed tubular body 10 .

[0071] As , instead, diagrammatically shown in figure 7 , in an alternative embodiment foreseen, the fixed tubular body 10 can be provided with a first and with a second plurality of circumferential apertures 15a and 15b positioned, respectively, along a first and a second longitudinal direction 13 and 14 . In particular, in the embodiment of figure 7 , the circumferential portions at which are positioned the circumferential apertures 15a and 15b are foreseen circumferentially staggered with respect to each other . More in particular, as shown in figures 5 and 11 , the circumferential portions at which the circumferential apertures 15a and 15b are positioned, can be partly overlapped to each other . In other words , the first and second pluralities of circumferential apertures 15a and 15b of the fixed tubular body 10 can be distributed on a first and on a second longitudinal row 13 and 14 arranged side by side , or substantially side by side, going circumferentially along a longitudinal direction . More in particular, le aforementioned circumferential apertures 15a and 15b can have respective circumferential portions 17a and 17b arranged side by side going along a longitudinal direction, that means , as diagrammatically shown in figure 7 , going along predetermined generatrixes of the cylindrical body both the circumferential portions 17a and the circumferential portions 17b are met . More in particular, each circumferential or curved aperture , 15a of the first plurality can be positioned close to a respective circumferential or curved aperture, 15b of the second plurality, for example at a distance comprised between 1 mm e 150 mm, advantageously at a distance comprised between 1 . 5 mm e 100 mm, preferably at a distance comprised between 1 . 5 mm e 50 mm, for example at a distance comprised between 2 mm e 50 mm.

[0072] As for example diagrammatically shown in figure 21 , the device for generating an air-flow 50 can comprise a main body 51 where an impeller 52 can be mounted, diagrammatically shown in figure . The impeller 52 can be operatively connected to a motor 56 to cause it to rotate about a rotation axis .

[0073] The device for generating the air- flow 50 can be put in pneumatic connection with the aforementioned longitudinal suction chamber 16 through at least a duct 60 , or can be integrally mounted to the fixed tubular body 10 ( see figure 19 ) . In both the cases , the device for generating an air- flow 50 is arranged to generate within the longitudinal suction chamber 16 a determined air- flow 55 at a predetermined pressure ( Pi ) , preferably a pressure less than the atmospheric pressure .

[0074] As diagrammatically shown for example in the embodiment of figure 8 , the rotating tubular body 20 can be , furthermore , provided with at least a third plurality of suction channels 25 organi zed according to a respective predetermined number of longitudinal rows 3 . In particular, the aforementioned suction channels 25 of the third plurality can be used for folding the sheet, or web, of laminar material , for example paper, or cardboard, but also non-woven fabric, and similar materials . For example , as diagrammatically shown in the embodiment of figure 16 , but as a skilled person in the art of the technical field of reference , will have no di fficulty to understand, also valid for the embodiments of the invention, the suction channels 23 and 24 of the first and of the second plurality can be used to suck, respectively, the head and the tail 6 and 7 of at least a sheet of laminar material 5 at a time, in particular to transfer the same downstream of a cutting section, not shown in figure for simplicity .

[0075] In an embodiment foreseen, the or each longitudinal row of suction channels 23 and 24 of the first and of the second plurality of suction channels can be positioned on the rotating tubular body 20 , in such a way to be put in pneumatic connection at the aforementioned respective predetermined angular positions with the first plurality of circumferential apertures 15a . Instead, the or each longitudinal row of suction channels 25 of the third plurality of suction apertures can be positioned on the rotating tubular body 20 in order to be put in pneumatic connection with the second plurality of circumferential apertures 15b at the respective predetermined angular positions . For example , whereas , as described above , the first and second pluralities of suction channels 23 and 24 can be adapted to suck on the surface 21 of the rotating tubular body 20 the head, or a portion of head, and the tail , or the portion of tail , of a sheet of laminar material , in particular paper, the third plurality of suction channels 25 can be adapted to suck the aforementioned sheet at the centre portion of the sheet , in particular to allow the suction roll 1 to carry out the folding or the interfolding at a folding or interfolding section, cooperating with a second suction roll 1 counterrotating with respect to it .

[0076] In an embodiment according to the invention, and diagrammatically shown in the figures from 12 to 17 , the first and second pluralities of suction channels 23 and 24 can be organi zed in a plurality of suction groups 30 . These can be arranged on a plurality of rows 36 circumferential to the rotating tubular body 20 . Each suction group 30 comprises , in particular, a first suction channel 23 of the first plurality and a second suction channel 24 of the second plurality divided by a partition wall 27 .

[0077] In a further embodiment a fourth plurality of suction channels 26 is , furthermore , provided organized according to at least a row longitudinal to the rotating tubular body 20 .

[0078] In the case that also the aforementioned fourth plurality of suction channels 26 is present, a second plurality of suction groups 30 ' can be provided . In particular, as for example diagrammatically shown in figure 19 , each suction group 30 ' of the second plurality can comprise at least a suction channel 25 of the third plurality and at least a suction channel 26 of the fourth plurality divided from each other by a partition wall 27 ' . Also the suction channels 26 can be involved in the sucking step of the centre portion 8 of the sheet 5 .

[0079] In particular, the longitudinal rows of the first and second suction groups 30 and 30 ' can be , preferably, positioned alternating to each other on the rotating tubular body 20 .

[0080] As diagrammatically shown in figure 23 , at least a pressure sensor 80 can be , furthermore , provided arranged to detect the pressure within the longitudinal suction chamber 16 . In particular, the or each pressure sensor 80 can be arranged to send a corresponding pressure signal P ( ti ) to a control unit 300 arranged to operate the aforementioned device for generating an air- flow 50 . More in particular, the control unit 300 can be arranged to adj ust the device for generating an air- flow 50 in function of the received pressure signal P ( ti ) , in particular by acting on a motor 56 of which this is provided of . In this way, the air-flow 55 can be increased or decreased, to increase or decrease the pressure P ( ti ) within the longitudinal suction chamber 16 and to bring the same to be equal to a predetermined value of pressure P* , or anyway to dif fer from it less than a predetermined deviation value AP* , that means I P ( ti ) -P* I <AP* .

[0081] As , for example , shown in the figures 3 , 4 , 6 , and from 13 to 15 , the cross-section passage of each suction channel of the first and / or of the second plurality of suction channels 23 and 24 can increase at least for a portion of the respective length, moving from the internal lateral surface 22 to the external lateral surface 21 of the rotating tubular body 20 . Advantageously, each suction channel 23 and 24 of the first and of the second plurality, and in case each channel 25 and 26 of the third and of the fourth plurality, i f present, is associated to a respective shield member 40 . This can be, in particular, provided with a plurality of holes 41 of a si ze such that the worked product of laminar material , in particular a web or sheet of paper, is prevented from entering in the suction channels 23 , 24 , and analogously in the suction channels 25 and 26 , if these are present, and allow, at the same time , that it can be sucked to adhere at the predetermined angular portions of the external lateral surface 21 of the rotating tubular body 20 at the circumferential apertures 15a and 15b, in such a way to allow the transfer of the same downstream of the suction roll 1 along the aforementioned advancing direction .

[0082] In particular, as diagrammatically shown in the figures from 16 to 19, each suction group 30 can comprise a hollow body 31 provided with the first and of the second suction channel 23 and 24 ( figures from 16 to 18 ) , or of the third and of the fourth suction channel 25 and 26 ( figure 19 ) .

[0083] In particular, each suction group 30 can be associated to a respective shield member 40 , advantageously provided with a plurality of holes 41 . The shield member 40 can be configured to move from an engagement configuration ( figures 16 and 17 ) to a disengagement configuration ( figure 18 and 19 ) , for example by a coupling that can be dismantled by screws , or bolts , or similar engagement elements , not shown in the figure for simplicity . In this way, in the case of need, or during programmed interventions of ordinary maintenance, it is possible to remove the shield member 40 in such a way that it is possible to reach the hollow body 31 and, therefore, to carry out cleaning interventions for cleaning dusts or fragments of worked product the suction channels 23 , 24 , 25 and 26 where, unavoidably, enter during the functioning of the machine provided with the , or each, suction roll 1 , according to the invention . In addition, it is possible to change the shield member 40 with another of di fferent type , for example having a di fferent number of holes 41 or, in general , having a di f ferent total sucking area, to modi fy the air-flow which passes through the shield member 40 same . In particular, each hollow body 31 is housed, in use , in a respective seat 28 of which the rotating tubular body 20 is provide with .

[0084] More precisely, the shield member 40 is provided with the aforementioned plurality of holes 41 . These are adapted to put in pneumatic connection each suction channel 23 , 24 , 25, and 26 , advantageously having an inlet opening 23a, 24a, 25a and 26a of si ze less than the outlet opening 23b, 24b, 25b and 26b con the external lateral surface 21 of the rotating tubular body 20 .

[0085] As diagrammatically shown in the embodiment of figure 18 , the shield member 40 can be provided with a longitudinal lowered portion 45. In this way, in working conditions , it is possible to avoid obstruction of the action of a cutting blade of a cutting section if present , not shown in figure for simplicity, positioned downstream of the suction roll 1 to divide a continuous web made of laminar material into a plurality of sheets of predetermined length .

[0086] As diagrammatically shown in the figures from 1 to 25 , each suction channel 23 , 24 , 25 and 26 is configured in such a way to extend longitudinally to the rotating tubular body 20 .

[0087] Analogously, each circumferential aperture 15a and 15b can be configured in such a way to extend longitudinally to the fixed tubular body 10 .

[0088] In the embodiment diagrammatically shown in figure 24 , a cover member 70 is provided adapted to be positioned at the inlet 16a of the longitudinal suction chamber 16 . In particular, the cover member 70 can be provided with a passageway opening 71 through which the air-flow 55 enters into the longitudinal chamber 16 sucked by the device for generating an air- flow 50 , and wherein an adj ustment group 77 is , furthermore, provided to increase or decrease , the cross-section passage of the passageway opening 71 . For example , as diagrammatically shown in figure 24 , the adj ustment group 77 can comprise a series of movable elements 75 adapted to engage in respective guide 76 to be moved in a guided manner and to increase or decrease depending on the need, the cross-section of the passageway opening 71 .

[0089] In the further embodiment diagrammatically shown in figure 25, between a circumferential aperture 15a, or 15b, and the following circumferential aperture 15a or 15b, the fixed tubular body 10 can be , advantageously, provided with an annular portion 18 adapted to pneumatically divide the same .

[0090] The suction roll 1 as described above can be installed in a treatment unit of a paper converting machine .

[0091] In particular, at least a first and a second counterrotating suction roll 1 can be installed at a folding or interfolding unit configured to fold or interfold a web or a plurality of sheets according to a predetermined folding or interfolding configuration .

[0092] The suction roll 1 , as described above , can be also installed at a cutting unit configured to cut a continuous web made of laminar material into a plurality of sheets to provide them to advance downstream of the aforementioned cutting unit . In an embodiment foreseen the suction roll 1 , as described above, can be installed at an advancement unit arranged to cause a web or sheet of paper to advance along a predetermined advancing direction .

[0093] According to a further aspect of the invention, for example in an interfolding machine , it is possible to change the angular position of the fixed tubular body 10 in order to record the beginning and the end of the suction of the suction channels 23 , 24 and 25 where they are present . The angular adj ustment of the fixed tubular body 10 can be carried out by an actuator connected to an end of the fixed tubular body 10 . The adj ustment can be carried out by commands given by an HMI interface (Human Machine Interface ) both during a testing phase and during the working phase of the interfolding machine .

[0094] Alternatively, it is possible to program a control unit to automatically change the angular position of the fixed tubular body 10 depending on one or more operating parameters such as for example the velocity of feeding of the sheets , the basis weight of the sheets , the number of packages per minute produced by the interfolding machine , the air permeability of the sheets . For example , the control unit can be programmed to anticipate the beginning and / or the end of the suction by the suction channels 23 , 24 and / or 25 and / or 26 of the suction roll 1 when the velocity of feeding of the sheets increases , and vice versa, postpone the same when the velocity of feeding of the sheets decreases . The angle variation, therefore, of the advance or of the delay of the beginning and / or the end of the suction by the suction channels 23 , 24 and / or 25, can occur progressively during the working phase of the machine. The progressive change can be in continuous form or at speed threshold, that means that the fixed tubular body 10 is caused to rotate in a clockwise or counterclockwise direction at a desired angle of degrees for each predetermined increasing or decreasing of velocity of feeding of the sheets. For example, it is possible to change the angular position of the fixed tubular body 10 each 50 m al min of increasing or decreasing of velocity of feeding of the sheets. The steps of velocity and the quantity of rotation of the fixed tubular body 10 can be changed in function of the product and / or the velocity of feeding same. It is possible to program the control unit to change the delay or the advance by rotating the fixed tubular body 10 at speed threshold that means changing the angular position of the fixed tubular body 10 once that a predetermined velocity of feeding of the sheets is reached.

[0095] The foregoing description of a specific embodiment 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 an embodiment without further research and without parting from the invention, and it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiment. The means and the materials to realise 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 employed herein is for the purpose of description and not of limitation.

Claims

CLAIMS1. A suction roll (1) per suck a laminar product in such a way to cause said laminar product to advance along an advancing direction, said suction roll (1) comprising: a fixed tubular body (10) provided with an external lateral surface (11) and with an internal lateral surface (12) delimiting a longitudinal suction chamber (16) , said external lateral surface (11) and said internal lateral surface (12) being arranged to communicate through at least a first plurality of circumferential apertures (15a) distributed along a first longitudinal row (13) , each circumferential aperture (15a) of said plurality being arranged along a respective circumferential portion of said fixed tubular body (10) ; a rotating tubular body (20) mounted coaxially to said fixed tubular body (10) having an external lateral surface (21) and an internal lateral surface (22) and configured to rotate externally to said fixed tubular body (10) about a longitudinal rotation axis (120) , said rotating tubular body (20) being provided with at least a first plurality of suction channels (23) organized according to a predetermined number of longitudinal rows (3) , said rotation of said rotating tubular body (20) about said longitudinal rotation axis (120) being adapted to put in pneumatic connection said longitudinal suction chamber (16) con at least a row (23) of said first plurality of suction channels (23) at respective predetermined angular positions of said rotating tubular body (20) ;a device for generating an air-flow (50) configured to cause said worked laminar product (5) to be sucked by at least one row of said suction channels (23) at a time and to adhere to said external lateral surface (21) of said rotating tubular body (20) at said predetermined angular positions; said suction roll (1) being characterized in that said device for generating an air-flow (50) is selected among: a compressor, a centrifugal compressor, a fan, a centrifugal fan, pneumatically connected to said longitudinal suction chamber (16) .

2. Suction roll (1) according to claim 1, wherein said device for generating an air-flow (50) is configured to generate said air-flow at a predetermined pressure (Pi) and is provided with: a main body (51) ; an impeller (52) adapted to be housed in said main body (51) and operatively connected to a motor (56) in order to rotate about a rotation axis for generating said determined air-flow in said longitudinal suction chamber (16) .

3. Suction roll (1) according to claim 1, wherein said main body (51) is integral to said fixed tubular body(10) .

4. Suction roll (1) according to claim 2, or 3, wherein said predetermined pressure (Pi) is less than the atmospheric pressure.

5. Suction roll (1) according to one or more of the previous claims, wherein said rotating tubular body (20) is, furthermore, provided with at least a secondplurality of suction channels (24) organized according to a respective predetermined number of longitudinal rows ( 4 ) .

6. Suction roll (1) according to one or more of the previous claims, wherein said fixed tubular body (10) is, furthermore, provided with a second plurality of circumferential apertures (15b) positioned along a second longitudinal row (14) , said prima and said second plurality of circumferential apertures (15a, 15b) being circumferentially staggered with respect to each other .

7. Suction roll (1) according to claim 6, wherein each circumferential or curved aperture (15a) of said first plurality is positioned at a distance comprised between 1 mm and 150 mm from a respective circumferential or curved aperture (15b) of said second plurality.

8. Suction roll (1) according to any claim from 5 to 7, wherein said rotating tubular body (20) is, furthermore, provided with at least a third plurality of suction channels (25) organized according to a respective predetermined number of longitudinal rows (5) , wherein said or each longitudinal row (3, 4) of said prima and of said second plurality of suction channels (23, 24) are positioned on said rotating tubular body (20) in such a way to be put in pneumatic connection at said respective angular position con said first plurality of circumferential apertures (15a) , whereas said or each longitudinal row (5) of said third plurality of suction channels (25) is positioned on the rotating tubular body (20) in order to be put inpneumatic connection con said second plurality of circumferential apertures (15b) at respective predetermined angular positions.

9. Suction roll (1) according to one or more of the previous claims, wherein said first and second pluralities of suction channels (23, 24) are organized in a plurality of suction groups (30) arranged on a plurality of longitudinal rows (36) a said rotating tubular body (20) , each suction group (30) of said plurality comprising a first suction channel (23) of said first plurality and a second suction channel (24) of said second plurality divided by a partition wall (27) .

10. Suction roll (1) according to one or more of the previous claims, wherein is at least a pressure sensor (80) is provided arranged to detect the pressure in said longitudinal suction chamber (16) and to send a corresponding pressure signal (P(ti) ) to a control unit (300) arranged to control said device for generating an air-flow (50) depending on said pressure signal (P(ti) ) .

11. Suction roll (1) according to one or more of the previous claims, wherein said suction channels (23) are configured in such a way that the section of passage (s) of each suction channel (23) of said first plurality of suction channels (23) is adapted to increase going from said internal lateral surface (22) to said external lateral surface (21) of said rotating tubular body (20) .

12. Suction roll (1) according to claim 6 or 7, whereinsaid first and second pluralities of circumferential apertures (15a, 15b) of said first and second longitudinal rows (13,14) of said fixed tubular body (10) have respective circumferential portions (17a, 17b) arranged side by side going along a longitudinal direction .

13. Suction roll (1) according to any claim from 9 to 12, wherein each suction group (30) of said plurality is associated to a respective shield member (40) provided with a plurality of holes (41) dimensioned in such a way to impede that said worked laminar product enters in said suction channels (23, 24) of said first and second pluralities, and to allow, at the same time, that said worked laminar product is sucked to adhere to said predetermined angular portions of said external lateral surface (21) of said rotating tubular body (20) .

14. Suction roll (1) according to one or more of the previous claims, wherein is, furthermore, a cover member (70) is provided adapted to be positioned at said inlet (16a) of said longitudinal suction chamber (16) , said cover member (70) being provided with a passageway opening (71) through which said air-flow is adapted to enter in said longitudinal chamber (16) sucked by said device for generating an air-flow (50) , and wherein is, furthermore, an adjustment group (77) is provided adapted to increase or decrease said crosssection passage of said passageway opening (71) .

15. Suction roll (1) according to claim 10, wherein said control unit (300) is arranged to act on said motor(56) to increase or decrease said air-flow (55) depending on said pressure signal (P(ti) ) to bring said pressure signal (P(ti) ) to be equal to a predetermined pressure value (P*) , or to differ from the same less than a predetermined deviation value (AP*) .

16. Suction roll (1) according to claim 5, wherein said first plurality of suction channels (23) is arranged to suck on said surface (21) of said rotating tubular body (20) a head portion of said sheet, and said second plurality of suction channels (24) is arranged to suck on said surface (21) of said rotating tubular body (20) a tail portion of said sheet.

17. Suction roll (1) according to claims 8 and 16, wherein said third plurality of suction channels (25) is arranged to suck said sheet on said surface (21) of said rotating tubular body (20) at a centre portion, in such a way to carry out a fold on said worked sheets.

18. Suction roll (1) according to claim 13, wherein said shield member (40) is provided with a longitudinal lowered portion (45) , in such a way not to obstruct the action of a cutting blade positioned upstream of said suction roll ( 1 ) .

19. Paper converting machine comprising at least a treatment unit selected among: a folding or interfolding unit arranged to fold or interfold a laminar product, according to a predetermined folding or interfolding configuration; a cutting unit configured to cut a continuous web made of laminar material in a plurality of sheets; an advancement unit arranged to cause a laminarproduct to advance along a predetermined advancing direction; or a combination thereof ; said machine being characterized in that said at least a treatment unit comprises at least a suction roll according to any claim from 1 to 18 .

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