Suction roll of a laminar product

Abstract

A suction roll (1) for sucking a laminar product (5) fed along an advancing direction in a paper converting machine comprises a rotating tubular body (20) which rotates about a longitudinal rotation axis (120) and is provided with an external lateral surface (21) and with an internal lateral surface (22) in pneumatic connection with each other through a plurality of suction channels (23) organized according to a predetermined number of longitudinal rows (3). A suction chamber (16) is, furthermore, provided pneumatically connected to a device for generating an air-flow (50) and to a suction distribution device (40) which selectively puts in communication the suction chamber (16) with at least one longitudinal row (3) of suction channels (23) at predetermined angular positions of the rotating tubular body (20) to cause the worked laminar product (5) to be sucked and to adhere to a corresponding portion of the external lateral surface (21) of the rotating tubular body (20). The suction channels (23), at the external lateral surface (21) of the rotating tubular body (20), has a suction surface area greater than 1 mm2 for each mm of length.

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 conversion and similar products , 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 a sheet of paper of the type which is provided with suction holes , which connected to a vacuum system causes the sheet , or web, of paper to adhere on its surface .

[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 paper industry, for example rewinding, interf olding, and folding, machines are equipped with systems for causing 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 the final fold of the paper same to obtain packages of sheets interfolded according to a desired folding configuration .

[0010] In the last years in the field of paper converting machine , suction rolls have had a wide di f fusion provided with pneumatic systems for causing the worked sheet or web of paper to be sucked an to adhere 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 producing a determined vacuum degree , in pneumatic connection with the interior 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 and inside the rotating tubular body . 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 suction distribution device is provided comprising a first and a second sealing element , or gasket , which extend longitudinally to the suction roll at two di f ferent angular positions and from opposite sides with respect to the aforementioned row of aperture of the fixed tubular body . In this way, the internal lateral surface of the rotating tubular body, the external 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 device for vacuum generation from the aforementioned suction distribution device . More precisely, only the holes of the rotating roll positioned at a determined instant between the two sealing elements will exert a suction action on the worked sheet , or web, of paper , causing the same to adhere on the corresponding portion of the external lateral surface of the suction roll .

[0012] In the folding and / or advancing rolls of the prior art , it is known to use holes on the external surface of a rotating tubular body to suck, hold, fold and drag a web or a sheet of paper . The suction is obtained by a vacuum pump and, therefore, in order not to lose too much suction, the holes are of small diameter . Generally, the suction holes are organi zed according to a predetermined number of longitudinal rows . The number of suction holes of each longitudinal row is selected according to the aim to be reached, because to each row of holes corresponds an exact portion of sheet to be held . For example , a row of suction holes can be used to hold the initial portion, or head, of a sheet , another row of holes can be used to hold the end portion, or tail , still another row of holes can hold the middle portion of a sheet . In some cases , the middle portion of the sheet can be held by two di fferent rows of holes , each of which having a dif ferent number of holes . Generally, each row of holes can have a dif ferent number of holes and the holes can be of di fferent diameter from one row to another .

[0013] The total number of suction holes of each longitudinal row depends on the si ze of the converting line , that means , in other words , depends on the length of the rotating tubular body . To each suction hole on the external surface of the rotating tubular body corresponds a suction channel which puts in pneumatic connection the external surface of the rotating tubular body with its internal lateral surface . These channels are generally straight because made by a mechanical drilling operation of the rotating tubular body . In other cases , as described in EP3725112 , it is possible to use groups or blocks provided with groups of suction holes screwed to the rotating tubular body in order that the external surface of the block coincides with the external surface of the rotating tubular body . Also in this case rows of suction holes are provided where each longitudinal row is adapted to hold a speci fic portion of a sheet . For example , in EP3725112 , each block is provided with a group of holes formed by two longitudinal rows having a number of three suction holes at most which are aligned to each other that 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 on the whole rows of holes absolutely equivalent to the rows of holes directly made on the rotating tubular body . Generally, the distribution of the holes of each longitudinal row of suction holes can be non-homogeneous along the longitudinal direction both in the case that the holes are directly made by drilling the rotating tubular body and in the case that the holes are made in the abovedisclosed blocks .

[0014] All the suction holes described above have a crosssection passageway substantially constant for all the thickness of the rotating tubular body . An exception is the case where at the end portion of the suction hole , that means at the portion placed at the external surface of the roll , the countersink of the holes is present , whereby considering the countersink as part of the holes , a small widening of the hole is provided .

[0015] Therefore, in the suction rolls of prior art, the "active surface" , that means the one that carries out the suction and, therefore, the adhesion of a sheet, is the area of the holes plus the countersink, if present .

[0016] Furthermore, in the groups of holes , the respective longitudinal rows of the suction holes can be formed by a number of holes which can vary from case to case .

[0017] In the rolls of prior art, the active surface is very small and is not suf ficient to accurately control the catching, the feed, and the release of the sheets or webs made of paper, or another material permeable to the air, in particular at high production speed .

[0018] Furthermore , in the case of holes with a so limited active surface , the maintenance is highly di f ficult , particularly in the case when it is necessary to remove obstructions from the holes .

[0019] Examples of suction rolls with the aforementioned drawbacks are described in JP2012 / 034867 and US2007 / 228607 . In particular, in JP2012 / 034867 a trans fer roll is described in the field of paper converting machines comprising longitudinal rows of holes with a diameter of 5 mm and a distribution of the same going from 3 to 10 holes each 230 mm . Therefore , the average suction surface is less than 1 mm2each mm of length and, therefore , it is not suf ficient to guarantee a suitable suction . Therefore , it is not possible to have a high productivity without compromising the product quality .

[0020] In US2007 / 228607 a suction roll is described positioned within a drying chamber for drying a film of polymeric material .

[0021] Summary of the invention

[0022] It is therefore an obj ect of the present invention to provide a suction roll for paper converting machines that is able to overcome the drawbacks of the rolls of prior art .

[0023] It is in particular obj ect of the present invention to provide a suction roll for paper converting machine able to simpli fy and speed up the ordinary or extraordinary maintenance interventions , in particular to carry out the replacement of the gaskets of which it is provided .

[0024] It is also obj ect of the present invention to provide a suction roll for paper converting machines that is able to improve the suction in order to assist the adhesion of the sheets or laminar products , on its external surface under the same vacuum degree , or suction degree , that is used .

[0025] It is a further obj ect of the invention to increase the sucking surface area on the external surface of the suction roll to distribute in a more ef ficient and ef fective way the vacuum or suction degree that is used on the suction roll .

[0026] These and other obj ects are achieved by a suction roll for sucking a laminar product , such as a web or sheet of paper or another material permeable to the air, that is fed along an advancing direction in a paper converting machine , said suction roll comprising : a rotating tubular body configured to rotate about a longitudinal rotation axis in a predetermined direction of rotation, said rotating tubular body being provided with an external lateral surface and of an internal lateral surface in pneumatic connection through a plurality of suction channels organi zed according to a predetermined number of longitudinal rows ; a suction chamber defined internally to said suction roll and pneumatically connected to a device for generating an air- flow; a suction distribution device configured to selectively put in pneumatic connection said suction chamber with at least a longitudinal row of suction channels of said plurality at predetermined angular positions of said rotating tubular body, in such a way to cause the worked laminar product to be sucked and to adhere at a corresponding portion of said external lateral surface of said rotating tubular body; whose main characteristic is that at least one of said longitudinal rows of suction channels has an average suction surface at said external lateral surface of said rotating tubular body greater than 1 mm2for each mm of length .

[0027] Other features of the present invention and related embodiments are set out in the dependent claims .

[0028] In particular, the average suction surface at the external lateral surface of the rotating tubular body of at least one of the aforementioned longitudinal rows of suction channels can be greater than 1 . 2 mm2for each mm of length, advantageously greater than 1 . 5 mm2for each mm of length . In an embodiment of the invention, all the longitudinal rows of suction channels can have the aforementioned average suction surface area at the external lateral surface of the rotating tubular body greater than 1 mm2for each mm of length, in particular greater than 1 .2 mm2for each mm of length, advantageously greater than 1 . 5 mm2for each mm of length .

[0029] In particular, at least a suction channel of said plurality has a first cross-section passage s i having a first suction surface Al at said external surface of said rotating tubular body and a second cross-section passage s2 having a second suction surface A2 at said internal lateral surface of said rotating tubular body .

[0030] In an embodiment of the invention, at least a suction channel has the first suction surface area Al greater than the second suction surface area A2 .

[0031] In particular, at least a suction channel of said plurality, at the external lateral surface of the rotating tubular body, is divided into a plurality of suction apertures . More in particular, each suction channel , at the internal lateral surface of the rotating tubular body is provided with at least an outlet aperture .

[0032] More in particular, at least a suction channel of the aforementioned plurality can have a first total suction surface area (Atot) calculated by adding the suction surfaces of all the suction apertures of the aforementioned plurality, greater than the second suction surface area A2 , that means A1>A2 .

[0033] In particular, at least a suction channel of the aforementioned plurality can be provided with a connection portion arranged to pneumatically connect the aforementioned plurality of suction apertures with the or each outlet aperture .

[0034] More in particular, the aforementioned connection portion can have a cross-section passage ( s ) which increases going from the plurality of suction apertures towards the or each outlet aperture .

[0035] In an embodiment of the invention, the aforementioned plurality of suction apertures of at least a suction channel has a total suction surface area (Atot ) , calculated by adding the suction surfaces area of each suction aperture , greater than 35 mm2, advantageously greater than 50 mm2, preferably greater than 80 mm2.

[0036] In particular, a plurality of insert members can be provided, each of which provided with at least a suction channel of the aforementioned plurality . More in particular, each insert member is arranged to removably engage the aforementioned rotating tubular body .

[0037] In an embodiment of the invention, each insert member of the aforementioned plurality can comprise a main body provided at least with the aforementioned plurality of suction apertures adapted to be connected, in use , to the same suction channel .

[0038] In an embodiment of the invention, at least an insert member of the aforementioned plurality, furthermore, comprises at least a connection duct , or chamber, of a respective suction channel .

[0039] In particular, the aforementioned device for generating an air- flow pneumatically connected to the longitudinal suction chamber can be selected among : a compressor ; a centrifugal compressor ; a fan; a centrifugal fan; a vacuum pump .

[0040] In an embodiment of the invention, the suction distribution device can comprise a fixed tubular body mounted coaxially to the interior of the rotating tubular body .

[0041] In particular, the fixed tubular body can be provided with the aforementioned longitudinal suction chamber in pneumatic connection with the device for generating the predetermined air-flow . More in particular, the fixed tubular body can be provided with at least one row of circumferential apertures arranged to put in pneumatic connection the longitudinal suction chamber with at least a row of the aforementioned suction channels at a time , at predetermined angular positions of the rotating tubular body .

[0042] In particular, each insert member of the aforementioned plurality can be provided with a respective cover member provided with said plurality of suction apertures . More in particular, each suction aperture can be sized in such a way to prevent the worked laminar product from going beyond the external surface of the rotating tubular body, and, at the same time, to allow the worked laminar product to be sucked in order to adhere to the predetermined angular portions of the external surface of the rotating tubular body .

[0043] 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 according to a predetermined folding or interfolding configuration; a cutting unit configured to cut a web of continuous web material into a plurality of sheets ; an advancement unit arranged to cause a web or sheet of paper to advance along a predetermined advancing direction; or a combination thereof ; wherein at least a suction roll as described above is provided .

[0044] In particular, the fixed tubular body can be , furthermore , provided with a second plurality of circumferential apertures positioned along a second row longitudinal to the fixed tubular body .

[0045] 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 .

[0046] According to an embodiment of the invention, the device for generating an air- flow can be provided with a main body integral to fixed tubular body . More in particular, the device for generating an air- flow can comprise , furthermore , an impeller adapted to house in the main body and operatively connected to a motor for generating the air- flow within 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 .

[0047] In particular, the rotating tubular body can be, furthermore, provided with at least a third plurality of suction apertures organized in a predetermined number of longitudinal rows . More in particular, the or each longitudinal row of the first and of the second plurality of suction apertures 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 , whereas the or each longitudinal row of the third plurality of suction apertures 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 .

[0048] Brief description of the drawings

[0049] 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 :

[0050] - Fig . 1 diagrammatically shows a perspective side elevation view a first embodiment of a suction roll according to the invention;

[0051] - Fig . 2 diagrammatically shows a longitudinal section of a possible embodiment of the suction roll of figure 1 ;

[0052] - Fig . 3 diagrammatically shows an enlargement of a part of figure 2 to highlight some technical characteristics of the rotating tubular body of the suction roll of figure 2 ;

[0053] - Figures 4 and 5 diagrammatically show a perspective side elevation view of two possible alternative embodiments of a suction roll according to the invention;

[0054] - Fig . 6 diagrammatically shows a perspective side elevation view of a possible embodiment of a fixed tubular body which can be used in the suction roll according to the invention;

[0055] - Fig . 7 diagrammatically shows a longitudinal section of an alternative embodiment of the suction roll of figure 2 ;

[0056] - Fig . 8 diagrammatically shows an enlargement of a part of figure 7 to highlight some technical characteristics of the rotating tubular body of the suction roll of figure 7 ;

[0057] - Fig . 9 diagrammatically shows a transversal section of the suction roll of figure 7 ;

[0058] - Fig . 10 diagrammatically shows a longitudinal section of another alternative embodiment of the suction roll of figure 2 ;

[0059] - Fig . 11 diagrammatically shows an enlargement of a part of figure 10 to highlight some technical characteristics of the rotating tubular body of the suction roll of figure 10 ;

[0060] - Fig . 12 diagrammatically shows a perspective view from the above of an insert member that can be used in the alternative embodiment of the suction roll of figures 10 and 11 ;

[0061] - Fig . 13 shows the insert member of figure 12 in a section view according to arrows XI I I-XI I I ; - Fig . 14 diagrammatically shows a longitudinal section of still another alternative embodiment of the suction roll of figure 2 ;

[0062] - Fig . 15 diagrammatically shows an enlargement of a part of figure 14 to highlight some technical characteristics of the rotating tubular body of the suction roll of figure 14 ;

[0063] - Fig . 16 diagrammatically shows a perspective view from the above of an insert member which can be used in the embodiment of the suction roll of figures 14 and 15 ;

[0064] - Fig . 17 shows the insert member of figure 16 in a section view according to arrows XVI I-XVI I ;

[0065] - Fig . 18 diagrammatically shows a perspective view from the above of an alternative embodiment of the insert member which can be used in the embodiment of the suction roll of figures 14 and 15 ;

[0066] - Fig . 19 shows the insert member of figure 18 in a section view according to arrows XIX-XIX ;

[0067] - Fig . 20 diagrammatically shows a perspective view from the above o f a further alternative embodiment of the insert member which can be used in the embodiment of the suction roll of figures 14 and 15 ;

[0068] - Fig . 21 shows the insert member of figure 20 in a section view according to arrows XXI-XXI ;

[0069] - Fig . 22 diagrammatically shows a perspective view from the above in a disassembled configuration, of still a further alternative embodiment of the insert member which can be used in the embodiment of the suction roll of figures 14 and 15 ;

[0070] - Fig . 23 diagrammatically shows a perspective side elevation view of another alternative embodiment according to the invention for the suction roll of figure 1 ;

[0071] - Fig . 24 diagrammatically shows a perspective side elevation view of an alternative embodiment according to the invention for the fixed tubular body of figure 6 ;

[0072] - Fig . 25 diagrammatically shows a perspective side elevation view of another alternative embodiment of an insert member which can be used in the suction roll according to the invention;

[0073] - Fig . 26 shows a perspective side elevation view of still another alternative embodiment of the suction roll according to the invention with the end portion of the suction channels that has been removed to show some technical characteristics ;

[0074] - Fig . 27 diagrammatically shows a perspective side elevation view of still another alternative embodiment of an insert member which can be used in the suction roll according to the invention;

[0075] - Figures from 28 to 30 show 3 di f ferent transversal sections of further embodiments of the suction roll according to the invention;

[0076] - Fig . 31 shows a perspective side elevation view of still a further alternative embodiment of the suction roll according to the invention;

[0077] - Fig . 32 diagrammatically shows a side elevation view of a suction roll according to the invention;

[0078] - Figures 33 and 34 show an enlargement of 2 di f ferent portions of the suction roll of figure 32 to highlight some technical characteristics ; - Fig . 35 diagrammatically shows a side elevation view of a folding unit provided with a first and a second suction roll according to the invention .

[0079] Detailed description of some exemplary embodiments of the invention

[0080] As diagrammatically shown in figure 1 , a suction roll 1 , according to the invention, of the type used for feeding a laminar product 5 , for example a web, or sheet of paper, or another material permeable to the air, for example non-woven fabric, along an advancing direction, in particular in a machine for converting paper, or similar products , comprises a rotating tubular body 20 configured to rotate about a longitudinal rotation axis 120 in a predetermined direction of rotation . As diagrammatically shown in the figures 2 and 3 , the rotating tubular body 20 is provided with an external lateral surface 21 and an internal lateral surface 22 in pneumatic connection with each other through a plurality of suction channels 23 , in particular organized according to a predetermined number of longitudinal rows 3 . The suction roll 1 , furthermore , provides a longitudinal suction chamber 16 defined internally to the same and pneumatically connected to a device for generating an air- flow 50 . This , as diagrammatically shown in figure 4 , 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 , such as a compressor, for example a centri fugal compressor, or an axial compressor, or a rotating compressor, or a fan, in particular a centrifugal fan, or an axial fan, or other known typologies . In this case , the device 50 is , advantageously, connected at the suction zone to the longitudinal suction chamber 16 in order to generate a pressure less than the atmospheric pressure within the longitudinal suction chamber 16 and greater downstream of the device 50 for generating an air- flow, that means at the pump zone . In other words , the device 50 for generating an air- flow creates an air- flow 55 which enters 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 .

[0081] In particular, in the case of figures 1 and 2 , the longitudinal suction chamber 16 is internal to a fixed tubular body 10 which is internal and coaxial to the rotating tubular body 20 . The rotating tubular body 20 is configured to coaxially rotate about the fixed tubular body 10 . At this purpose a mechanical coupling can be provided between the fixed tubular body 10 and the rotating tubular body 20 carried out by ball bearings , brasses or other devices which allows them to move one with respect to the other . For example , a ball bearing can be positioned between the fixed tubular body 10 and the rotating tubular body 20 at both the ends of the rotating tubular body 20 . In other cases , when the axial length is very long, for example greater than 2 metres or preferably greater than 2 . 80 metres , a further device for the reciprocal movement can be positioned at a middle position comprised between the ends of the rotating tubular body 20 .

[0082] A suction distribution device 40 is , then, provided configured to selectively put in pneumatic connection the suction chamber 16 with at least a longitudinal row 3 of suction channels 23 , at predetermined angular positions of the rotating tubular body 20 . In this way, the suction of the worked laminar product 5 is caused, in particular of the sheet , or the web of paper, or another material permeable to the air, such as non-woven fabric, and its adhesion to a corresponding portion of the external lateral surface 21 of the rotating tubular body 20 .

[0083] In an embodiment of the invention, diagrammatically shown in figure 6, the suction distribution device 40 comprises the fixed tubular body 10 coaxially mounted within the rotating tubular body 20 . The fixed tubular body 10 is provided with an external surface 11 and an internal lateral surface 12 . In particular, the fixed tubular body 10 is provided with the aforementioned longitudinal suction chamber 16 in pneumatic connection with the device 50 for generating a predetermined air- flow 55 . More in particular, the fixed tubular body 10 is provided with a first plurality of circumferential apertures 15 positioned along at least a first longitudinal row 13 and arranged to put in pneumatic connection the external surface 11 with the internal lateral surface 12 and, therefore, to put the longitudinal suction chamber 16 in pneumatic connection with at least a longitudinal row 3 of suction channels 23 at a time at the aforementioned predetermined angular positions of the rotating tubular body 20 . In particular, each suction channel 23 of the longitudinal rows 3 is aligned with a respective circumferential aperture 15 , in order to be put in pneumatic connection with the suction chamber 16 at the circumferential apertures 15.

[0084] In particular, the device for generating the air-flow 50 , when it is not a vacuum pump, can be configured to move the air- flow through the longitudinal suction chamber 16 between an inlet 16a and an outlet 16b directly connected to the device 50 for generating an air- flow or to the duct 60 . Preferably, the inlet 16a can have a cross section less than the cross section of the outlet 16b . In this way, during the 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 . In the case that the device 50 for generating an air- flow is a vacuum pump, the inlet 16a is not provided, or it is closed, in order not to lose vacuum degree at the internal of the longitudinal suction chamber 16 .

[0085] In an alternative embodiment of the invention, which is called with internal tube suction, as diagrammatically shown in figure 9 , the suction distribution device 40 can comprise a first and a second sealing element 18a and 18b integral to the fixed tubular body 10 from opposite sides with respect to an aperture 15 , which is , in this case , provided longitudinally on the fixed tubular body 10 . In particular, the first and second sealing elements 18a and 18b are positioned longitudinally to the fixed tubular body 10 . Circumferential sealings can be provided, in particular at the two ends of the fixed tubular body 10 , at a zone comprised between the external surface 11 of the tubular body 10 and the internal lateral surface 22 of the rotating tubular body 20 . In this way, a suction chamber is provided delimited by the first and second sealing elements 18a and 18b, the external surface 11 of the fixed tubular body 10 , and the internal lateral surface 22 of the rotating tubular body 20 , and the circumferential sealings when they are present . In the case that the device 50 for generating an air- flow is a vacuum pump, advantageously the inlet 16a is not provided, or can be provided closed, in order not to lose the vacuum degree within the longitudinal suction chamber 16 .

[0086] In this case the suction channels 23 are put in pneumatic connection with the suction chamber 16 at an angular portion delimited by the first and second sealing elements 18a and 18b .

[0087] In another alternative embodiment of the invention, the suction distribution device 40 can be carried out by a so called "bell" device that means that one or more longitudinal rows 3 of suction channels 23 are pneumatically connected, respectively, to a respective longitudinal suction chamber 16 positioned internally to the rotating tubular body 20 . In particular, the longitudinal suction chamber 16 3 is provided within the rotating tubular body 20 and is arranged longitudinally along the axial direction of the suction roll 1 . More than one longitudinal suction chamber 16 can be provided in the rotating tubular body 20 . The longitudinal suction chambers 16 are pneumatically connected to the suction distribution device 40 positioned at one or both the ends of the suction roll 1 , preferably positioned externally to the rotating tubular body 20 . In this case , that means when the suction is of "bell" type , it should be understood that the internal lateral surface 22 of the rotating tubular body 20 put in pneumatic connection with the external lateral surface 21 through a plurality of suction channels 23 , is the one related to each longitudinal suction chamber 16 . The suction distribution device 40 has suction channels of ad arco in such a way to put in suction the longitudinal suction chambers 16 only when these , during the rotation of the rotating tubular body 20 , move at the arch-shaped suction channels . The suction distribution device 40 is connected in turn to the device for generating the air- flow 50 . This type of suction distribution is known in the field and is described, for example , in US 6488194 . The suction rolls 1 can have mixed suction types that means that one or more rows of holes are associated to a suction system of "bell" type , whereas one or more rows of holes are associated to a suction system of " internal tube" type as described above , or to a suction system of the type described with reference to fig . 6 . This configuration is described for example in EP1457444B2 .

[0088] According to the invention, both in the case that the suction is of "bell" or "internal tube" type and in the configuration of figures from 2 to 6, the plurality of suction channels 23 , at the external lateral surface 21 of the rotating tubular body 20 , has an average suction surface area greater than 1 mm2for each mm of length . In particular, the average suction surface area can be greater than 1 .2 mm2for each mm of length, more in particular, greater than 1 . 5 mm2, advantageously greater than 2 . 0 mm2for each mm of length, preferably greater than 3 . 0 mm2for each mm of length . In other words , the plurality of suction channels 23 , at the external lateral surface 21 , has an average distribution of the suction surface area along a row of holes on the external lateral surface 21 or along a single suction channel 23 , in order to have a sucking area greater than 1 . 5 mm2for each mm of length, advantageously greater than 2 . 0 mm2for each mm of length, preferably greater than 3 . 0 mm2for each mm of length .

[0089] It should be noted that with the expression "mm2for each mm of length" it can be understood that the aforementioned suction surface area can be calculated with reference to the length of the suction roll 1 , or of the rotating tubular body 20 . In particular, the average suction surface area, or the average distribution of the suction surface area, of a row of suction channels 23 can be calculated by adding all the areas of the sections of each suction channel 23 at the external lateral surface 21 of a row of suction channels 23 and dividing this sum by the longitudinal length L of the rotating tubular body 20 . The section of each suction channel 23 at the external lateral surface 21 , can also comprise the mechanical operation of countersinking, if present .

[0090] In order to further clari fy the concept , in figure 32 is depicted, as an example, the case of a suction roll 1 where , for reasons of clarity, a single longitudinal row 3 of suction channels 23 is shown . More precisely, in figure 32 , the suction roll 1 has a predetermined length L, for example equal to 1600 mm, and the aforementioned longitudinal row 3 of suction channels 23 has a predetermined number of suction channels 23 . For example , the longitudinal row 3 can comprise 61 suction channels 23 with a surface of 35 mm2, only some of which are shown for simplicity in figure 32 , and another predetermined number of suction channels 23 ' , for example 10 suction channels 23 ' with a di fferent suction surface area, for example a suction surface equal to 30 mm2. Therefore , the total surface area of the longitudinal row 3 will be, in this case , equal to 2435 mm2which, divided by the aforementioned length L, determines an average suction surface for the row 3 equal to 1 . 52 mm2for each mm of length .

[0091] In other embodiments of the invention, generally, it is possible to have a determined number of groups of suction channels 23 and 23 ' can have, for example both with a suction surface at the circular or substantially circular external surface 21 . In the case of figures 33 and 34 , the first group of suction channels 23 has a diameter dl , and the second group of suction channels 23 ' a diameter d2 con d2<dl . However, as a skilled person in the field will have no di fficult to understand, the possible combinations of si ze of suction channels 23 and of suction surfaces area within the same inventive concept are unlimited . Among these the present invention provides both the case that the aforementioned suction channels 23 of the longitudinal row 3 have all the same suction surface area, and the opposite case that the suction channels 23 have all a dif ferent suction surface area with respect to each other, as well as mixed cases where the suction channels 23 are organized according to dif ferent group, each of which having a predetermined number of suction channels 23 with a predetermined suction surface .

[0092] The technical solution provided by the present invention allows , in particular, to carry out an ef fective sucking action of the worked laminar product 5 independently from the type of suction distribution device 40 . In particular, with respect to the prior art solutions , the active surface of the external lateral surface 21 of the rotating tubular body 20 is increased, that means that the portion of the same which holds the worked laminar product 5 , this allows to distribute on a larger surface the adhesion of the sheet or web on the external lateral surface 21 of the rotating tubular body 20 that is much more distributed obtaining a stronger and stable catching with respect to the suction rolls of prior art . Furthermore , the increase of the useful surface to hold the laminar product 5 is obtained without modi fying the starting and the ending point of suction with respect to the prior art, and without signi ficantly losing the vacuum degree or, generally, the suction degree generated by the device for generating the air- flow 50 , that means under the same suction power installed .

[0093] In particular, as diagrammatically shown in the figures 2 , 3 , and from 7 to 11 , each suction channel 23 of the aforementioned plurality can have a first crosssection passage si having a first suction surface area Al at the external lateral surface 21 where a suction aperture , or inlet aperture, 24 , is present , and a second cross-section passage s2 having a second suction surface area A2 at the internal lateral surface 22 . In particular, at least a suction channel 23 of the aforementioned plurality is configured in such a way that the first suction surface area Al is greater than the second suction surface area A2 where an outlet aperture 25 is present . In particular, as shown in figures from 3 to 11 , the suction channels 23 can have at least a portion where the cross section increases in the direction going from the suction roll 1 towards the outside . The cross section which increases of the suction roll 23 di f fers from the prior art where the holes had a countersink because this mechanical operation is to be considered as a superficial working, that means involving the holes at the external lateral surface 21 and not the suction channel 23 . In this way, the useful surface at the external lateral surface 23 , that is the one that is adapted to hold the laminar product 5 by suction, is greater with respect to the rolls of prior art .

[0094] In a preferred embodiment of the invention, diagrammatically shown for example in the figures 1 , 7 , 8 and 9 , at least a suction channel 23 of the aforementioned plurality, at the external lateral surface 21 , can be provided with a plurality of suction apertures 24 . Alternatively, at the external lateral surface 21 , to a plurality of suction channels can correspond a plurality of suction apertures 24 in common . In particular, at least a suction channel 23 , in this case , can be provided with a connection portion 26 arranged to pneumatically connect a plurality of suction apertures 24 with the or each outlet aperture 25 . For example, the connection portion 26 can have a cross-section passage s which decreases going from the plurality of suction apertures 24 towards an outlet aperture 25 . This latter is positioned at the end of the suction channel 23 opposite to the plurality of suction apertures 24 . In practice , the suction channel 23 has a variable cross section, that means increasing for at least a portion in a direction going from the suction roll 1 towards the external lateral surface 21 of the rotating tubular body 20 .

[0095] In particular, the plurality of suction apertures 24 of the same suction channel 23 has a total suction surface area Atot, calculated by adding the suction surfaces area of each suction aperture 24 , greater than 30 mm2, preferably greater than 50 mm2, advantageously greater than 80 mm2.

[0096] The plurality of suction apertures 24 form a sucking grid which prevents the laminar product 5 from being partly sucked within the suction roll 1 , and allows to extend the sucking surface adapted to hold the portion of a laminar product 5 , for example the head and / or the tail or the middle portion . In fact, with respect to the prior art , the sucking surfaces areas are greater and, in some cases , such to be able to suck at least partly the laminar product 5 which would cause mal functions and obstructions .

[0097] In an embodiment of the invention diagrammatically shown from figure 10 to figure 17 , the suction roll 1 comprises a plurality of insert members 30 arranged to engage the rotating tubular body 20 , advantageously removably, for example by a determined number of screws , or similar blocking elements , at a respective seat 28 made in the rotating tubular body 20 same . In this case, in the seat 28 , the end is present of one or more suction channels 23 that is closer to the external lateral surface 21 in order to pneumatically connect the insert members 30 with the suction channels 23 and, therefore, with the or one longitudinal suction chamber 16. In particular, each insert member 30 comprises a main body 31 where at least the aforementioned plurality of suction apertures 24 is provided ( figures from 10 to 13 ) . One or more suction channels 23 can be pneumatically connected to each insert member 30 . In particular, the suction channels of the same longitudinal row 3 adapted to suck the same portion of laminar product 5 , for example the middle portion or the tail or the head, can be connected to the same insert member 30 . In other cases , to the same insert 30 can be connected suction channels adapted to suck di fferent portions of laminar product 5 , for example the head and the tail of the laminar product 5, or the middle portion only . In a preferred embodiment , each insert member 30 of the aforementioned plurality comprises both the plurality of suction apertures 24 and the connection portion 26 of a respective suction channel 23 ( figures from 14 to 17 ) . In this case the insert member can comprise a suction channel 23 or the connection portion 26 of a respective suction channel 23 , with a cross section which is not constant , preferably which increases for at least a portion in the direction going from the side in contact with the seat 28 towards the plurality of suction apertures 24 , that means towards the external lateral surface 21 of the rotating tubular body 20 . Also in this case , it should be understood at least an increasing portion is considered without the countersink, that means the countersink working which is present on the prior art holes , is to be considered as a superficial working of the rotating tubular body 20 and, therefore , as not part of the suction channel 23 or of the connection portion 26 . In other embodiments the insert member 30 can simply have the hollow main body, that means that it forms a suction chamber internal to the insert member 30 same . The insert member can comprise a suction channel 23 or the connection portion 26 of a respective suction channel 23 with a cross-section which is not constant , preferably increasing for at least a portion in the direction going from the side in contact with the seat 28 towards the plurality of suction apertures 24 , that means towards the external surface 21 of the rotating tubular body 20 . It should be understood that at least an increasing portion is considered without the countersink, that means that the countersink working present at the holes of prior art, is to be considered as a superficial working of the rotating tubular body 20 and, therefore, not as a part of the suction channel 23 .

[0098] In an embodiment of the invention diagrammatically shown in the figures 18 and 19 , the main body 31 of the or each insert member 30 can comprise a portion of base 32 arranged to engage the rotating tubular body 20 and a covering portion 33 provided with the aforementioned plurality of suction apertures 24 . More in particular, the covering portion 32 and the portion of base 31 are arranged to mutually engage with each other, advantageously in a dismountable manner, for example by screws , bolts , or similar engagement elements of dismountable type .

[0099] Analogously to what has been described above , the insert members 30 according to the invention can have a first cross-section passage s i having a first suction surface area Al at the external lateral surface 21 where a suction aperture , or inlet aperture 24 is present, and a second cross-section passage s2 having a second suction surface area A2 at the side in contact with the seat 28 . In a not limiting embodiment of the invention, second cross-section passage s2 placed at a respective suction channel 23 , can have a surface area which is substantially equal to the cross section of the respective suction channel 23 which, in this case , can have , preferably but not limited to , a constant section for example because made by drilling the rotating tubular body 20 . In other cases , the second suction surface area A2 can have a surface area di fferent from that of the cross section of the respective suction channel 23 , preferably greater than this .

[0100] In an alternative embodiment of the invention the insert members 30 can be pneumatically connected to more than one suction channel 23 . In this case the passageway sections s2 are more than one , preferably each at a respective suction channel 23 .

[0101] In an embodiment diagrammatically shown from figure 16 to figure 19 , each insert member 30 can be provided with at least a first plurality of suction apertures 24a in pneumatic connection con a first outlet aperture 25a, and a second plurality of suction apertures 24b in pneumatic connection with a second outlet aperture 25b . The first outlet aperture 25a and second outlet aperture 25b can be arranged to be in pneumatic connection with the longitudinal chamber 16 at a predetermined angular position of the rotating tubular body 20 or at respective di fferent predetermined angular positions of the rotating tubular body 20 . The first outlet aperture 25a and the second outlet aperture 25b can be arranged to be put in pneumatic connection with a respective suction channel 23 , which is in turn pneumatically connected to the longitudinal suction chamber 16 . In particular, the first plurality of suction apertures 24a of an insert member 30 can be adapted to hold, in working conditions , the end portion, or tail , of a worked sheet, whereas the second plurality of suction apertures 24b can be adapted to hold the initial portion, or head, of another sheet . In another case , the first plurality of suction apertures 24a of an insert member 30 can be adapted to hold a first portion of a sheet adj acent to the middle portion of the worked sheet , whereas the second plurality of suction apertures 24b can be adapted to hold a second portion of a sheet adj acent to the middle portion of the worked sheet .

[0102] In particular, at least an insert member 30 of the aforementioned plurality can be provided with at least a first and a second plurality of connection portions 26a and 26b . These can be separated by a partition wall 27 ( figure 22 ) . The plurality of connection portions 26a and 26b can have a di fferent suction surface area Al at the external lateral surface 21 and / or can have a di fferent second suction surface area A2 at the side in contact with the seat 28 . For example, as shown in figure 22 , the first connection portion 26a can be greater than the connection portion 26b and can be placed at suction apertures 24a adapted to hold the head of the laminar sheet 5 whereas the connection portion 26b can be placed at suction apertures 24b adapted to hold the tail of the laminar sheet 5 .

[0103] In particular, as diagrammatically shown in particular in the figures 18 , 22 and 23 , between the first and the second plurality of suction apertures 24a and 24b a lowered portion 35 can be provided, in particular longitudinal to the respective insert member 30 . In this way, in working conditions , it is possible to avoid the mechanical interference with an element protruding from the external surface of a roll positioned upstream of the suction roll 1 , for example a cutting blade of a cutting section for dividing a continuous web made of laminar material into a plurality of sheets of predetermined length, or an insertion wedge, not shown in the figure for simplicity .

[0104] According to a possible embodiment of the invention, at least an insert member 30 of the aforementioned plurality can be made by a moulding process of plastic material , in particular ABS , or high-density Polyethylene , or similar plastic materials , or by a moulding or deposition process of metallic material .

[0105] As diagrammatically shown in figure 24 , in an alternative embodiment provided by the invention, the fixed tubular body 10 can be provided with a first and a second plurality of circumferential apertures 15a and 15b positioned, respectively, along a first and a second longitudinal row 13 and 14 . In particular, the circumferential portions where the circumferential apertures 15a and 15b are positioned, are provided circumferentially staggered with respect to each other . More in particular, as shown in figure 24 , the circumferential portions where the circumferential apertures 15a and 15b are provided, 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 a second longitudinal row 13 and 14 partly circumferentially arranged side by side going along a longitudinal direction . 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 and 150 mm, advantageously at a distance comprised between 1 . 5 mm and 100 mm, preferably at a distance comprised between 1 . 5 mm and 50 mm, for example at a distance comprised between 2 mm and 50 mm.

[0106] In this case, a first group of insert members 30 as above described, and a second group of insert members 30 ' are , advantageously, provided . In particular, the insert members 30 of the first group can be provided, as described above , with at least a first plurality of suction apertures 24a adapted to suck the initial portion, or head, of a worked laminar product 5 and / or to suck the end portion, or tail . The insert members 30 can be also provided with a second plurality of suction apertures 24b adapted to suck the end or tail portion of another laminar product 5 . The insert members 30 ' can be, instead, provided with at least a third plurality of suction apertures 24c, adapted to hold the middle portion of a laminar product 5 .

[0107] For example, in this case, the suction apertures 24a and 24b of the insert members 30 of the first group can be arranged in such a way to be put in suction to hold the worked product 5 by the circumferential apertures 15a of the first row 13 , whereas the suction apertures 24c of the insert members 30 ' of the second group can be arranged in such a way to be put in suction to hold the worked product 5 by the circumferential apertures 15b of the second row 14 .

[0108] More precisely, as can be seen in particular in figure 26 , where the end portion of the suction channels 23 has been removed to show some technical characteristics of the invention, a first and a second plurality of suction channels 23a and 23b are provided associated to the insert members 30 of the first group, which are made in the rotating tubular body 20 , in such a way to be put in pneumatic connection with the longitudinal suction chamber 16 at first predetermined angular positions of the rotating tubular body 20 , and a third plurality of suction channels 23c is , then, provided associated to the insert members 30 ' of the second group which are made in the rotating tubular body 20 , in such a way to be put in pneumatic connection with the longitudinal suction chamber 16 at second predetermined angular positions of the rotating tubular body 20 .

[0109] In a further alternative embodiment of the invention diagrammatically shown in figure 27 , the insert members 30 ' of the second group can be , furthermore, provided with a fourth plurality of suction apertures 24d and with a respective fourth connection portion 26d . In particular, the third and fourth connection portions 26c and 26d can be separated by a partition wall 27 ' . In particular, when the insert 30 ' is used to hold the middle portion of a laminar sheet 5, it is possible to hold a first portion of a sheet adj acent to the middle portion of the worked sheet by the third connection portion 26c and to hold the second portion of a sheet adj acent to the middle portion of the worked sheet by the third connection portion 26d .

[0110] In particular, the aperture of the connection portions 26a-26c can have a substantially rectangular shape , and, more in particular, a rectangular shape with rounded corners .

[0111] As diagrammatically shown in transversal section views in the figures 28 and 29, in the case that the first, the second, the third and the fourth pluralities of suction apertures 24a-24d and the respective connection portions 26a-26d are present, but, as can be easily understood by a skilled person in the art, also valid in the case that only some of the pluralities of suction apertures 24a-24c are present, the insert members 30 of the first group and the insert members 30 ' of the second group alternate to each other along the periphery of the rotating tubular body 20 and, therefore, of the suction roll 1 in such a way that the inserts 30 are adapted to hold the head and the tail of a laminar sheet 5 and the inserts 30 ' are adapted to hold the middle portion of a laminar sheet 5.

[0112] In particular, the insert members 30 of the first group and the insert members 30 ' of the second group are organized according to a respective predetermined number of longitudinal rows 3a and 3b . In the embodiment diagrammatically shown in the figures 28 and 29 , the rotating tubular body 20 is provided with 5 rows 3a of the first plurality of suction channels 23a and 23b and with 5 rows 3b of the second plurality of suction channels 23c and 23d . The number of rows of the rotating tubular body 20 is , however, generally, variable and is selected according to the production or functional needs , of the machine where the suction roll 1 according to the invention is used . Generally, a suction roll 1 , especially in the case of a folding or cutting roll , has a diameter which is equal to a multiple of the desired length of a laminar product 5 . The number of sheets which can lay on the suction roll 1 determines the number of longitudinal rows 3a and 3b .

[0113] There is also the possibility that the head and the tail , or alternatively, the middle portion, of the worked laminar products 5, can be sucked by a suction roll 1 according to the invention to cause it to adhere to the external lateral surface 21 of the rotating tubular body 20 , by a di fferent suction system, for example a suction system normally called "bell" , or a suction system of the type described in EP1457444B1 . For example , it is possible to cause the adhesion of the middle portion of the laminar product , or the worked sheets 5 by a suction system as described in EP1457444B1 , or according to a system as described with reference to the figures from 2 to 3 or in figure 6 , whereas the head and the tail of the worked laminar products 5 is held by a "bell" system. Depending on the production needs , it is possible to combine the suction distribution devices 40 up to here described, to hold the portions of head 6 , of tail 7 or the middle portion 8 of the laminar products 5 , for example sheets .

[0114] In a further alternative embodiment according to the invention and diagrammatically shown in figure 30 , the suction distribution device 40 can comprise a plurality of sealing elements , for example a first and a second sealing element 29a and 29b integral to the rotating tubular body 20 , in particular positioned longitudinally to the same . Each sealing element 29a and 29b of the aforementioned plurality can be associated to at least a row 3 of the aforementioned suction channels 23 and can be positioned laterally to it, in such a way to put in pneumatic connection the external lateral surface 21 of the rotating tubular body 20 with the longitudinal suction chamber 16 at predetermined angular positions . In this case the longitudinal suction chamber 16 is in the fixed tubular body and the suction angular positions are determined by the angular position of the aperture 15 which, in this case , has not an annular, but a longitudinal shape . In practice , the suction channels 23 contain the sealings 29a and 29b, which move and rotate together with the rotating tubular body 20 unlike the solution described in figure 9 where to the aperture 5 , also in this case longitudinal and not annular, are associated longitudinal sealings fixedly arranged on the fixed tubular body 10 .

[0115] The configurations described for the suction channels 23 and / or for the insert members 30 can be applied independently from the suction distribution device 40 that means that it is equally effective in the first embodiment described, which is shown in figure 6, in the case that the suction is of the so called " internal tube" type shown in figure 9 or of the "bell" type or of the solution shown in figures from 24 to 26 or of the solution of figure 30 or of a combination of these solutions and can be applied also independently from the typology of device for generating the air- flow 50 . In fact , independently from the sucking distribution system 4 , the adhesion of the laminar product 5 is improved owing to the better di f fusion on the external lateral surface 21 of the sucking force obtained by using the sucking surfaces and / or the sucking channels up to here described .

[0116] The invention is fully ef fective also in the case that only some of the longitudinal rows 3 of suction channels 23 are provided according to the invention and also in the case that only some suction channels 23 of some longitudinal rows 3 are provided according to the invention because , in some cases , it is suf ficient to improve the adhesion of the worked sheet on the external surface of the suction roll 1 only for some portions along its axial length or only for some portions of the worked sheet . For example, it is possible to improve only the adhesion of the middle portion of the sheet , or only of the head or of the tail or a combination of them in function of the typology of product to be produced and of the typology of material or paper which is worked .

[0117] According to still another embodiment of the invention diagrammatically shown in figure 31 , the device for generating an air-flow 50 can comprise a main body 51 in which an impeller 52 can be mounted that is diagrammatically shown in figure . The impeller 52 can be operatively connected to a motor 56 to cause the same to rotate about a rotation axis .

[0118] Still with reference to the embodiment of figure 31 , but also valid for the other embodiments of the suction roll 1 shown in the figures from 1 to 30 , at least one pressure sensor 80 can be provided arranged to detect the pressure within the longitudinal suction chamber 16 . In particular, the or each pressure sensor 80 is , furthermore, arranged to send a corresponding pressure signal P ( ti ) to a control unit 300 . This is , advantageously, arranged to control the device 50 for generating the air-flow 55 , in particular the motor 56 of the same , for example a vacuum pump, or a compressor, or a fan, in function of the received pressure signal P ( ti ) .

[0119] 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 .

[0120] The suction roll 1 , as described above , can be also installed at a cutting unit configured to cut a web of continuous web material into a plurality of sheets to cause them to advance downstream of the aforementioned cutting unit .

[0121] In an embodiment provided by the invention, 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 .

[0122] In the case that the product in laminar material is a sheet in laminar material , for example paper, or another material permeable to the air, having a head portion, a tail portion and a middle portion placed between the head portion and the tail portion, the plurality of suction channels 23 of the suction roll 1 can comprise at least a first longitudinal row 3 ' of suction channels 23 ' arranged to suck on the external surface a head portion 6 of the sheets 5, at least a second longitudinal row 3" of suction channels 23" arranged to suck on the external surface 21a a tail portion of the sheets 5 , and at least a third longitudinal row 3"' of suction channels 23"' arranged to suck on the external surface a middle portion 8 of the sheets 5 same . In this case , at least one between the first , the second and the third longitudinal row 3'" of the suction channels 23 has , preferably, an average suction surface area greater than 1 . 5 mm2.

[0123] The suction roll 1 , as described above , can be also , furthermore, installed at a folding unit configured to fold and / or interfold a web or sheet of paper, or another material permeable to the air, according to a predetermined folding and / or interfolding configuration .

[0124] In particular, in the case diagrammatically shown in figure 35 , wherein a first and a second suction roll la and lb are installed at the folding or interfolding unit 100 , each suction roll la and lb is , advantageously, provided with at least a first longitudinal row 3"'a arranged to suck, at a folding or interfolding zone 105 positioned between two rolls la and lb, in addition to the middle portion 8a of the first sheet 5a, also the head portion 6b of a second sheet 5b overlapped to the first sheet 5a, and at least a second longitudinal row 3"'b, arranged to suck, in addition to the middle portion 8a of the first sheet 5a, also a tail portion 7c of a third sheet 5c overlapped to the first sheet 5a . In this case, the at least a first longitudinal row 3"'a and / or the at least a second longitudinal row 3"'b of the first and / or the second suction roll la and lb has an average suction surface area greater than 1 mm2for each mm of length, advantageously greater than 1 . 5 mm2for each mm of length . Although, in figure 35 , the activation or deactivation of the suction channels 23 of the longitudinal rows 3"'a and 3"'b is operated by a suction distribution device 40 comprising a first and a second sealing element 18a and 18b integral to the fixed tubular body 10a, or 10b, from opposite sides with respect to a aperture 15a, or 15b, and the activation or deactivation of the suction channels 23 of the longitudinal rows 3 ' and 3" is operated by a "bell" system, a skilled person in the field of the invention will have no dif ficult to understand that other operating devices can be used for the longitudinal rows 3 ' and 3" and / or for the third longitudinal rows 3"'a and 3"'b .

[0125] 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 regulate, or adj ust , the beginning and the end of the suction by the suction channels 23 , 24 and 25 where they are present . The adj ustment angular of the fixed tubular body 10 can be operated by an actuator connected to an end of the fixed tubular body 10 . The adj ustment can be operated by commands given by an HMI-interf ace (Human Machine Interface ) both during a testing phase and during the working phase of the interfolding machine .

[0126] Alternatively, it is possible to program a central control unit for automatically changing the angular position of the fixed tubular body 10 in function of 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 for 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 of the suction channels 23 , 24 and / or 25 of the suction roll 1 when the velocity of feeding of the sheets increases , and vice versa to postpone it when the velocity of feeding of the sheets decreases . The change in the angle , therefore, the advance or the delay of the beginning and / or the end of the suction by the suction channels 23 , 24 and / or 25, can be carried out progressively during the working phase of the machine . The progressive change can be in continuous form or for steps of velocity, that means clockwise or counterclockwise rotating the fixed tubular body 10 of a desired number 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 mmin of increasing or decreasing of the velocity of feeding of the sheets . The steps of velocity and the angle of rotation of the fixed tubular body 10 can change in function of the product and / or the velocity of feeding same . The control unit can be programmed for changing the advance or the delay by rotating the fixed tubular body 10 at thresholds of speed that means changing the angular position of the fixed tubular body 10 when predetermined velocities of feeding of the sheets are reached .

[0127] The foregoing description of a speci fic embodiment wil l so ful ly reveal the invention according to the conceptual point o f view, so that others , by applying current knowledge , wil l be able to modi fy and / or adapt for various appl ications such an embodiment without further research and without parting from the invention, and it i s there fore 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) for sucking a laminar product (5) fed along an advancing direction in a paper converting machine, said suction roll (1) comprising: a rotating tubular body (20) configured to rotate about a longitudinal rotation axis (120) in a predetermined direction of rotation, said rotating tubular body (20) being provided with an external lateral surface (21) and with an internal lateral surface (22) in pneumatic connection with each other through a plurality of suction channels (23) organized according to a predetermined number of longitudinal rows ( 3 ) ; a suction chamber (16) defined internally to said suction roll (1) and pneumatically connected to a device for generating an air-flow (50) ; a suction distribution device (40) configured to selectively put in pneumatic connection said suction chamber (16) with at least a longitudinal row (3) of suction channels (23) at predetermined angular positions of said rotating tubular body (20) in such a way to cause the worked laminar product (5) to be sucked and to adhere to a corresponding portion of said external lateral surface (21) of said rotating tubular body (20) ; said suction roll (1) being characterized in that at least one of said longitudinal rows (3) of suction channels (23) , at said external lateral surface (21) of said rotating tubular body (20) , has an average suction surface area greater than 1 mm2for each mm of length.

2. Suction roll (1) of a laminar product, according to claim 1, wherein said average suction surface is greater than 1.2 mm2for each mm of length.

3. Suction roll (1) of a laminar product, according to claim 1, wherein said average suction surface is greater than 1.5 mm2for each mm of length.

4. Suction roll (1) of a laminar product, according to one or more of the previous claims, wherein said laminar product (5) is a sheet comprising a head portion (6) , a tail portion (7) and a middle portion (8) positioned between said head portion and said tail portion (6,7) , and wherein said plurality of suction channels (23) comprises at least a first longitudinal row (3' ) of suction channels ( 23 ’ ) arranged to suck on said external surface (21) said head portion (6) , at least a second longitudinal row (3") of suction channels (23") arranged to suck on said external surface (21) said tail portion (7) , and at least a third longitudinal row (3"') of suction channels (23"') arranged to suck on said external surface (21) said middle portion (8) of said sheets (5) , and wherein at least one among said first, said second, and said third longitudinal row (3', 3", 3'") of suction channels (23) has said average suction surface .

5. Suction roll (1) of a laminar product, according to claim 4, wherein at least said third longitudinal row (3'") of suction channels (23) has said average suction surface .

6. Suction roll (1) of a laminar product, according to one or more of the previous claims, wherein each suctionchannel (23) has a first cross-section passage (si) having a first suction surface area (Al) at said external surface (21) of said rotating tubular body (20) , and a second cross-section passage (s2) having a second suction surface area (A2) at said internal lateral surface (22) of said rotating tubular body (20) and wherein at least a suction channel (23) is configured in such a way that said first suction surface area (Al) is greater than the second suction surface area (A2) .

7. Suction roll (1) according to claim 6, wherein at least a suction channel (23) of said plurality, at the external lateral surface (21) of said rotating tubular body (20) , is divided into a plurality of suction apertures (24) and wherein at least a suction channel (23) of said plurality has a first total suction surface area (Altot) calculated by adding the suction surfaces of all the respective suction apertures (24) , greater than the second suction surface area (A2) , that means Altot>A2.

8. Suction roll (1) according to one or more of the previous claims, wherein at least a suction channel (23) of said plurality is provided with a connection portion (26) arranged to pneumatically connect said plurality of suction apertures (24) with an outlet aperture (25) positioned at the opposite end of said suction channel (23) with respect to said plurality of suction apertures (24) .

9. Suction roll (1) according to claim 8, wherein said connection portion (26) has a cross-section passage (s)configured to decrease going from said plurality of suction apertures (24) towards said outlet aperture (25) .

10. Suction roll (1) according to any claim from 7 to 9, wherein said plurality of suction apertures (24) of the same suction channel (23) has a total suction surface area (Atot) greater than 35 mm2.

11. Suction roll (1) according to any claim from 7 to 9, wherein said plurality of suction apertures (24) of the same suction channel (23) has a total suction surface area (Atot) greater than 80 mm2.

12. Suction roll (1) , according to any previous claims, wherein a plurality of insert members (30) is provided each of which arranged to removably engage said rotating tubular body (20) , each insert member (30) of said plurality comprising a main body (31) provided at least with said plurality of suction apertures (24) arranged to be connected, in use, to the same suction channel (23) .

13. Suction roll (1) according to claim 12, wherein each insert member (30) of said plurality comprises, furthermore, at least a connection portion (26) of a suction channel (23) .

14. Suction roll (1) , according to one or more of the previous claims, wherein said device (50) for generating said air-flow (55) pneumatically connected to said longitudinal suction chamber (16) is selected among : a compressor; a centrifugal compressor;a fan; a centrifugal fan; a vacuum pump.

15. Suction roll (1) according to one or more of the previous claims, wherein said suction distribution device (40) comprises a fixed tubular body (10) mounted coaxially to the internal of said rotating tubular body (20) , said fixed tubular body (10) being provided with said longitudinal suction chamber (16) in pneumatic connection with said device (50) for generating a predetermined air-flow and being provided with at least one row of circumferential apertures (15) arranged to put in pneumatic connection said longitudinal suction chamber (16) with at least one row of said suction channels (23) at a time at predetermined angular positions of said rotating tubular body (20) .

16. Suction roll (1) , according to one of the claims from 1 a 14 wherein said suction distribution device (40) comprises a first and a second sealing element (18a, 18b) integral to said fixed tubular body (10) from opposite sides rispetto a said or each row of circumferential apertures (15) , said first and second sealing elements (18a, 18b) being positioned longitudinally to said fixed tubular body (10) .

17. Suction roll (1) according to one of the claims from 1 to 14, wherein said suction distribution device (40) comprises a plurality of sealing elements (17,18) integral to said rotating tubular body (20) and positioned longitudinally to the same, each sealing element (17,18) of said plurality being associated toat least one row of said suction channels arranged to put in pneumatic connection said external lateral surface ( 21 ) with said longitudinal suction chamber ( 16 ) .

18. Suction roll ( 1 ) according to one of the claims 1 to 14 , wherein said rotating tubular body (20 ) comprises said longitudinal suction chamber ( 16 ) in pneumatic connection with said suction distribution device ( 40 ) fixedly mounted at an end of said rotating tubular body (20 ) .

19. Suction roll ( 1 ) according to one of the claims from 8 to 14 wherein each insert member of said plurality is provided with a respective cover member ( 40 ) provided with said plurality of suction apertures ( 24 ) .20 . Paper converting machine comprising a folding or interfolding unit arranged to fold or interfold a laminar product, in particular a web or a plurality of sheets , according to a predetermined folding or interfolding configuration characterized in that it comprises a first and a second suction roll ( la, lb) according to any claim from 1 to 19 .21 . Paper converting machine comprising a cutting unit configured to cut a continuous laminar product into a plurality of sheets characterized in that it comprises at least a suction roll according to any claim from 1 to 19 .

22. Paper converting machine comprising an advancement unit arranged to cause a laminar product, in particular a web or sheet of paper, to advance along a predetermined advancing direction characterized in that it comprises at least a suction roll according to any claim from 1 to 19.

23. Paper converting machine according to claims 2 and 20, wherein each of said first and second suction rolls (la, lb) comprises at least a first longitudinal row (3a'") arranged to suck, in addition to said middle portion (8a) of said first sheet (5a) also said head portion (6b) of a second sheet (5b) overlapped to said first sheet (5a) , and at least a second longitudinal row (3b'") arranged to suck, in addition to said middle portion (8a) of the first sheet (5a) , also a tail portion (7c) of a third sheet (5c) overlapped to said first sheet (5a) , said machine being characterized in that said at least said first longitudinal row (3a'") and / or said at least said second longitudinal row (3b'") has an average suction surface area greater than 1 mm2for each mm of length.

Images