Patent Publication Number: US-11034541-B2

Title: Folding roller and interfolding machine employing said roller

Description:
TECHNICAL FIELD 
     The present invention relates to the field of paper converting machines, in particular of the so called tissue paper converting machines, to produce handkerchiefs, napkins or the like. Embodiments described below relate to interfolding machines and to components for said machines. 
     BACKGROUND ART 
     In the field of tissue paper conversion, there are known machines, so called interfolding machines, to divide a continuous web material into single sheets which are bended and then folded over one another. Examples of interfolding machines are described in U.S. Pat. Nos. 6,228,014, 7,097,607, 7,517,309, WO2004/071921, EP1457444 and in prior documents cited in the aforesaid publications. 
     The interfolding machines have a couple of folding rollers placed side by side and with parallel axes, among which is defined a folding nip. Each folding roller receives cut ribbon-shaped material sheets, which are bended and folded in the folding nip. Complex suction systems are used to manage the passage of the borders of the single sheets from a roller to another in the folding nip. The activation and the interruption of the suction must be timely to allow a fast working of the interfolding machine. 
     This requires the need of complex opening and closure means of suction valves. Despite all the efforts dedicated to the development of these machines, the inertia existing in the pneumatic circuits inside the folding rollers create serious problems and set limits to the operating speed of the machines. Moreover, the control mechanisms of activation and interruption of the suction are complicated and subject to breakdowns. 
     The level of technological complexity needed to manufacture the aforesaid rollers is expensive and requires a high degree of specialization. 
     A further drawback of the known rollers is high power consumption, both to activate and deactivate the suction flows with continuous inertias. 
     There is therefore the need to realize folding rollers and interfolding machines employing such rollers which overcome in whole or in part the limits of the traditional machines. 
     DISCLOSURE OF INVENTION 
     According to a first point of view, a folding roller is shown comprising a cylindrical sleeve having a rotation axis, an outer surface and an inner surface defining an axial cavity of the cylindrical sleeve. The folding roller comprises, furthermore, an inner body which axially develops in the axial cavity which is inside the cylindrical sleeve, which is arranged to rotate around the inner body. 
     Furthermore, a suction chamber inside the cylindrical sleeve and a plurality of suction holes are provided, such holes extending from the outer surface to the inner surface of the cylindrical sleeve. 
     The suction holes are arranged with longitudinal alignments, nearly or substantially parallel to the rotation axis of the cylindrical sleeve and angularly staggered one another. 
     According to embodiments described below, inside the suction chamber is arranged a plurality of stationary shutters, for example integral with the inner body, with a closing surface which cooperates with the inner surface of the cylindrical sleeve, such closing surface being shaped and arranged to close the suction holes which, during the rotation movement of the cylindrical sleeve around the rotation axis, pass in front of the shutter. 
     For stationary shutters are meant shutters not rotating with the rotating cylindrical sleeve of the folding roller during operation in normal conditions of the folding roller. 
     By means of the plurality of shutters, spaced and aligned one another along the rotation axis of the cylindrical sleeve of the roller, it is possible to selectively close the holes of some longitudinal alignments of suction holes, leaving the holes of other longitudinal alignments opened. 
     In particular, this way it is possible, by means of use of the only shutters, to maintain the suction alive through some longitudinal alignments for a rotation angle, along which, vice versa, the suction is interrupted through other longitudinal alignments. 
     Advantageously, the suction holes can be arranged with circumferential alignments. Each shutter also has circular arc shape for an appropriate angle, determined on the basis of the activation and deactivation phases of the suction through the opening. 
     To obtain selective opening and closure of the different alignments of the suction holes, it is possible to provide that the suction holes of at least a first longitudinal alignment are arranged along circumferential lines coinciding with the position of the shutters. Vice versa, the suction holes of at least a second longitudinal alignment are arranged along circumferential lines which are interposed between adjacent shutters. 
     This way, while the cylindrical sleeve rotates around its own axis, the suction holes of the first longitudinal alignment are closed, i.e. they are closed by the shutters, while the holes of the second longitudinal alignment are not closed by the shutters. Consequently, along the angle corresponding to the arc along which the shutters develop, the suction holes of the first alignment don&#39;t suck, while the suction holes of the second alignment suck, being arranged in flow communication with the suction chamber in which are situated the shutters. 
     In other embodiments, rather than using a stagger in axial direction of the suction holes, so that they are selectively partially closed by the shutters and partially they remain opened, it is possible to provide that the suction holes have a suitable shape. For example, it is possible to make the suction holes, whose suction must not be interrupted by the shutters, shorter, realizing for example hollows or longitudinal grooves on the inner surface of the cylindrical sleeve. 
     In correspondence with the hollows or grooves there are entrances of the suction holes which must not be closed by the shutters. The distance between shutters and inner surface of the cylindrical sleeve in the grooves or longitudinal hollows area ensures the shutters not to close the suction holes. 
     After all, with the arrangement according to the invention we obtain a suction roller or folding roller in which, with simple, reliable and easy to make means, it is possible to activate and deactivate the suction through suction holes selectively during rotation of the cylindrical sleeve of the folding roller, so that along at least a rotation angle the suction is activate through the suction holes of a first set, while it is deactivate through the suction holes of a second set. 
     Depending on the radial dimension of the folding roller it is possible to provide a number of longitudinal alignments of suction holes higher than two. In such event, it is advantageously provided that the longitudinal alignments are split in two groups, interposed one another, so that each longitudinal alignment of suction holes belonging to a first set of suction holes is located between two longitudinal alignments of suction holes of the other set of suction holes. 
     According to another aspect, it is described an interfolding machine comprising a couple of folding rollers as described, disposed with respective rotation axis nearly parallel to one another and put near each other to form a folding nip. 
     Further advantageous features and possible embodiments of the folding roller and the interfolding machine are described below with reference to the enclosed drawings and are defined in the enclosed claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The enclosed drawings show an illustrative embodiment of a folding machine according to the invention. Figures are not necessarily drawn to scale. More particularly, in the enclosed drawings: 
         FIG. 1  illustrates a schematic section of an interfolding machine, according to a plane which is orthogonal to the rotation axis of the folding and cutting rollers of the interfolding machine; 
         FIG. 2  illustrates a broken axonometric view of one of the folding rollers of the interfolding machine of  FIG. 1 ; 
         FIG. 3  illustrates a partial and top view of the two folding rollers of  FIG. 2 ; 
         FIGS. 4(A), 4(B) &amp; 4(C)  illustrate a first step in an illustrative operative sequence of the interfolding machine; 
         FIGS. 5(A), 5(B) &amp; 5(C)  illustrate a second step in the operative sequence of the interfolding machine; 
         FIGS. 6(A), 6(B) &amp; 6(C)  illustrate a third step in the operative sequence of the interfolding machine; 
         FIGS. 7(A), 7(B) &amp; 7(C)  illustrate a fourth step in the operative sequence of the interfolding machine; 
         FIGS. 8(A), 8(B) &amp; 8(C)  illustrate a fifth step in the operative sequence of the interfolding machine; 
         FIGS. 9(A), 9(B) &amp; 9(C)  illustrate a sixth step in the operative sequence of the interfolding machine; and 
         FIGS. 10 and 11  show a modified embodiment of the folding roller. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With initial reference to  FIG. 1 , Numeral  1  generically indicates an interfolding machine which can comprise a couple of folding rollers  3  each rotating around a respective rotation axis  3 A, substantially parallel to one another. Between the folding rollers  3  is defined a folding nip  5 . 
     In the embodiment illustrated in  FIG. 1 , each folding roller  3  cooperates with a respective cutting roller  7  equipped with a plurality of cutting blades  9 . In the illustrated embodiment, each cutting roller  7  has three cutting blades  9 , spaced apart from one another by 120°. The cutting rollers  7  rotate around a respective rotation axis  7 A, parallel to one another and substantially parallel to the rotation axis  3 A of the folding rollers  3 . 
     The number of cutting blades is illustrative and non-limitative. In other embodiments can be provided blades in a number different from three. Generally, it is provided a plurality of blades  9  spaced apart from one another by a substantially constant angular step around the cylindrical surface of the respective cutting roller  7 . 
     The blades  9  of each cutting roller  7  cooperate with a respective stationary counter-blade  11 , supported on a bearing structure  13  of the interfolding machine  1 . Each cutting roller  7  defines, together with the respective folding roller  3 , a transfer nip  15 . 
     To each cutting roller  7  a respective continuous web material is provided, schematically indicated with N 1  and N 2  in  FIG. 1 , for the two cutting rollers  7 . The two web materials are cut in single sheets by the cutting rollers  7  cooperating with the counter-blades  11 . The single sheets carried out by the cutting are transferred to the folding rollers  3  and bended and folded by means of the folding rollers  3  as described below in more detail. 
     Each folding roller  3  cooperates with a respective removing comb  17 , that provides for removing the bended sheets from the folding rollers  3  to stack them in the area below the folding nip  5 . The folded sheets form piles of a predetermined number of sheets which are then directed to a packing machine, not shown. 
     The folding rollers  3  are externally grooved as evident in particular in  FIGS. 2 and 3 . In the annular grooves, indicated with  3 S, of the two folding rollers  3  are housed the ends of the respective removing combs  17  which oscillate around respective rotation axes  17 A. 
     The cutting rollers  7  have an external cylinder liner  7 C which rotates according to the respective arrows f 7  around the axes  7 A. Inside the cylinder liners  7 C there are fixed hollow elements  7 F, which form, by means of radial walls  7 R, a respective suction chamber  21 . 
     The suction chamber  21  of each cutting roller  7  develops from a feeding area to the respective cutting roller  7  of the web material N 1 , N 2 , up to a position almost corresponding to the transfer nip  15 . 
     The cylindrical sleeve or liner  7 C has radial suction holes  7 X which cross the thickness of the cylinder liner  7 C and are situated near the blades  9 . The radial suction holes  7 X connect the external surface of the cylinder liner  7 C of each cutting roller  7  with the respective suction chamber  21 . 
     This way, when the holes  7 X are in the range of action of the suction chamber  21 , along the angle α, through the radial suction holes  7 X, a suction action of the web material N 1 , N 2  is generated. 
     The suction keeps the web material very near the blades  9 , where the web material N 1 , N 2  is cut to form single sheets of web material to bend and fold in the described way. 
     The structure of the folding rollers  3  is now described in details with specific reference to  FIGS. 1-3 . 
     Each folding roller  3  has an external cylindrical sleeve  3 C, rotating around an axis  3 A of the respective folding roller. The cylindrical sleeve  3 C comprises an outer surface  3 X and an inner surface  3 Y. The inner surface  3 Y defines an axial cavity  23  inside the cylindrical sleeve  3 C, which extends parallel to the longitudinal axis or rotation axis  3 A of the respective folding roller  3 . 
     In the axial cavity  23  of the folding roller  3  there is an inner body  25  which, during the operation of the interfolding machine  1 , remains substantially fixed, i.e. stationary with respect to the bearing structure  13 . In some embodiments the angular position of the inner body  25  can be adjusted for a fine registration of the operation of the roller and of the machine to which the folding roller  3  belongs. 
     The registration can occur with a manual or servo-assisted system, not shown. The inner body  25  can for this purpose have end means, not shown, which protrude from the folding roller  3  and which are mounted into supports of the interfolding machine  1 , on which can eventually act angular registration members. 
     The inner body has two radial walls  27 ,  29  which radially extend up to the inner surface  3 Y of the cylindrical sleeve  3 C. The edges of the radial walls  27 ,  29  can be equipped with gaskets, not shown, which cooperate with the inner surface  3 Y of the cylindrical sleeve  3 C of the respective folding roller  3 . 
     In the illustrated embodiment the two radial walls  27 ,  29  are angularly staggered with respect to each other at an angle β slightly higher than 180°, e.g. around 190°. 
     In some embodiments the angle β can be different. The possibility that the angle β is recordable is not excluded. The radial wall  27  is slightly upstream of the transfer nip  15  with respect to the rotation direction f 3  of the cylindrical sleeve  3 C. 
     The radial wall  29  is, vice versa, substantially downstream of the folding nip  5  with respect to the rotation direction f 3  of the cylindrical sleeve  3 C. More exactly, the radial wall  29  is nearly located in the action area of the respective removing comb  17 . 
     Between the two radial walls  27 ,  29  of each folding roller  3 , on the side facing the folding nip  5 , is defined a suction chamber  23 A, which takes up the portion of the cavity  23  inside its folding roller  3  delimited by the inner body  25 , by its radial walls  27 ,  29  and by the inner surface  3 Y of the cylindrical sleeve  3 C. The suction chamber  23 A is in fluid communication, through openings  31  carried out in the inner body  25 , with a suction volume  33  axially carried out into the inner body  25 . The suction volume  33  is permanently engaged with a suction line, not shown, e.g. through one or both the ends of the respective folding roller  3 . 
     Shutters  37  are integral with the inner body  25 , such shutters being comb-shaped better represented in the axonometric broken view of  FIG. 2 . As it can be observed, in  FIG. 2  the shutters  37  are parallel and spaced from one another forming a comb structure. 
     Each shutter  37  has an arched, radially external closing surface  37 A, having a substantially cylindrical shape, with a bend radius corresponding to the bend radius of the inner surface  3 Y of the cylindrical sleeve  3 C. The closing surface  37 A of each shutter  37  substantially touches the inner surface  3 Y of the cylindrical sleeve  3 C, or it is at a distance which is limited by said inner cylindrical surface, e.g. at a distance of some tenth of a millimeter. The closing surface  37 A can be made of a material with a low friction coefficient. 
     The angular position of the shutters  37  can be adjustable, e.g. acting on the respective inner body  25  which can be angularly adjusted. In other embodiments it can be supposed a possibility of angular adjustment of the inner body  25  with respect to the bearing structure  13  of the interfolding machine, and further possibility of adjustment of the shutters  37  with respect to the inner body  25 . 
     The two folding rollers  3  are substantially symmetrical, but the comb structures carried out by the shutters  37  are staggered with respect to one another as is comprehensible from the section of  FIG. 1 . Substantially the shutters  37  of the right (in the drawing) folding roller  3  face the empty spaces between the shutters of the left folding roller  3  and vice versa. 
     Each folding roller  3  has a plurality of radial suction holes, arranged in the described way below. The suction holes are indicated with  41  and  43  and are carried out in correspondence with the annular projections between annular grooves  3 S, as it can be better seen in  FIGS. 2 and 3 . 
     The suction holes  41 ,  43  are arranged along longitudinal alignments altogether indicated with  42  and  44  ( FIG. 3 ) aligned one another. Between two longitudinal alignments  42  is placed a longitudinal alignment  44  and, vice versa, between two longitudinal alignments  44  is placed a longitudinal alignment  42 . As it will be clear from the description below, the two longitudinal alignments  42 ,  44  differ from one another in the position between suction holes relative to the shutters  37 . 
     In the illustrated embodiment, each longitudinal alignment  42 ,  44  comprises two adjacent rows of suction holes  41 ,  43 . 
     With reference to a single folding roller  3 , each longitudinal alignment  42  comprises suction holes  41 , while each longitudinal alignment  44  comprises suction holes  43 . The suction holes  41  of a longitudinal alignment  42  are axially staggered with respect to the corresponding suction holes  43  of the adjacent longitudinal alignment  44  (see in particular  FIGS. 2 and 3 ). 
     The distance in axial direction, indicated with D in  FIG. 3 , of suction holes  41  which are axially consecutive is identical to the axial distance, also indicated with D, of suction holes  43  of the adjacent alignment. The distance D corresponds to the step between the shutters  37 . 
     This way, as clearly illustrated in  FIG. 2 , all the suction holes  41  of an alignment  42  are located in correspondence with respective shutters  37 , while all the suction holes  43  of the adjacent longitudinal alignment  44  are located in correspondence of the empty space between adjacent shutters  37 . 
     This arrangement is identical for both the folding rollers  3 . 
     As observed above, the folding rollers  3  are symmetrical except that the shutters  37  of one of them ( 3 ) are staggered with a different step with respect to the shutters  37  of the other one. Analogously the suction holes  41  and  43  will be staggered with respect to one another in the longitudinal direction, i.e. substantially parallel to the rotation axis  3 A. 
     This is easy to understand from the sectional view of  FIG. 1 , where for the left folding roller  3  the suction holes  43  are on the sectional plane (and thus shown with solid lines) and the suction holes  41  are behind the sectional plane (shown with dashed lines), while for the right folding roller  3  the situation is the opposite: the suction holes  41  are visible since they are located on the sectional plane (which dissects also the respective shutter  37 ) while the suction holes  43  are shown with dashed lines, since they are located behind the sectional plane (and thus between two consecutive shutters  37 ). 
     Always with reference to  FIG. 1  it must be observed that for the right folding roller  3  on the sectional plane there is a shutter  37  which corresponds to the position in the longitudinal direction, i.e. parallel to the rotation axis  3 A, of the suction holes  41  while for the left roller the sectional plane is located staggered with respect to the position of the shutter  37 . 
     The alignments  42 ,  44  of the holes  41 ,  43  are staggered with respect to one another with an angle equal to nearly 60° around the rotation axis  3 A of the respective folding roller  3 , since on each folding roller  3  are provided six of such alignments, placed according to a constant angular step, for a total of twelve rows of holes. 
     In other embodiments can be provided a number different from six (always even numbers) of longitudinal alignments  42 ,  44  of holes alternated with respect to one another as described above. 
     Between adjacent rows of each alignment  42  of suction holes  41  notch-shaped folding members or notches  47  can be found, defined in the annular projection defined by adjacent annular grooves  3 S. Analogous notches  49  can be found between the two rows of suction holes  43  of each longitudinal alignment  44 . 
     These or those notches  47 ,  49  can be replaced by protrusions, so that in the folding nip  5  a sequence of notches and a sequence of protrusions will correspond to each other from time to time in the sense described below. 
     The two folding rollers  3  rotate at the same peripheral speed and in opposite directions according to the arrows f 3  ( FIG. 1 ). They are phased one another in such a way that in the folding nip  5  holes  43  of a roller and holes  41  of the other roller will be found from time to time corresponding to one another. 
     Moreover, each folding roller  3  and the respective cutting roller  7  are angularly synchronized to one another so that during rotation of the rollers  3 ,  7 , which rotate at a substantially identical peripheral speed, in the transfer nip  15  of the alignments  42  of suction holes  41  are located in correspondence with the cutting blades  9 . Vice versa, the suction holes  43  of the alignments  44  are located in an intermediate position between cutting blades  9  consecutively with respect to the cutting roller  7 . 
     The operation of the interfolding machine till now summarily described can be better understood by examining the operative sequence of  FIGS. 4-9 . 
     In  FIGS. 4-9  the two folding rollers are indicated with the references  3 L (the left folding roller) and  3 R (the right folding roller), for a better understanding of the description. In the sequence of  FIGS. 4(C), 5(C)  . . .  9 (C) are indicated with letters (a), (b), (c), (d), (e) and (f) the six longitudinal alignments of suction holes of the folding roller  3 L. 
     With the references F 1 , F 2 , F 3  . . . Fn are indicated sheets of web material with cutting carried out by means of the cutting rollers  7  and by the respective counter-blades  11 , the two ribbons of web material N 1 , N 2 . The sheets F 1 , F 3 , F 5  (the odd sheets, coming from the web material N 1 ) are fed in a sequential way to the folding roller  3 R and the sheets F 2 , F 4 , F 6  (the even sheets, coming from the web material N 2 ) are fed to the folding roller  3 L. 
     The six groups of figures  FIG. 4 - FIG. 9  show the angular position assumed in a sequential way by the folding rollers  3  and by the cutting rollers  7  during the operation cycle, i.e. a complete rotation of 360°, with a step of 60°.  FIGS. 4(A), 5(A)  . . .  9 (A) show the section according to the first section plane A-A of  FIG. 3 , while  FIGS. 4(B), 5(B)  . . .  9 (B) show the section according to the outline plane B-B in  FIG. 3 . 
     In more details, in  FIG. 4(A)  is shown the section of the folding rollers  3 L,  3 R on the outline sectional plane A-A in  FIG. 3 . The outline plane A-A intersects the shutters  37  of the folding roller  3 R, while it passes between two adjacent shutters  37  of the folding roller  3 L, so an adjacent shutter of the folding roller  3 L is forwardly visible. 
     Therefore, in  FIG. 4(A)  the suction holes  43  of the folding roller  3 L are on the sectional plane, while the suction holes  41  are behind the sectional plane. Vice versa, for the folding roller  3 R the suction holes  43  are behind the sectional plane and the suction holes  41  are on the sectional plane. 
       FIG. 4(B)  shows the same folding rollers  3 L and  3 R in the same angular position of  FIG. 4(A) , but sectioned according to the plane B-B in  FIG. 3 , which is staggered with respect to the plane A-A of a step corresponding to a half of the distance between the two shutters  37 . 
     So  FIG. 4(B)  shows, for the folding roller  3 L, the suction holes  41  in the sectional plane and the suction holes  43  behind the sectional plane. For the folding roller  3 R, instead, the suction holes  41  are behind the sectional plane and the suction holes  43  are shown exposed in the sectional plane. The shutters  37  of the folding roller  3 L are on the sectional plane, while in the folding roller  3 R the sectional plane passes through two adjacent shutters  37 , so in  FIG. 4(B)  an adjacent shutter of the shutters of the folding roller  3 R is forwardly visible. 
       FIG. 4(C)  shows in a schematic way and for a better representation all the six alignments of suction holes in both the folding rollers  3 R and  3 L. For this latter the six alignments are countermarked with letters from (a) to (f). In  FIG. 4(C)  the inner members of the folding rollers  3 R and  3 L (radial walls  27 ,  29 , shutters  37 ) are omitted. 
     In  FIGS. 4(A) and 4(B)  the inner zone of the respective cylindrical sleeves  3 C of the folding rollers  3 L,  3 R in which there is suction is shaded. 
       FIGS. 4(A)-4(C)  show the following condition. The suction holes  43  of the longitudinal alignment indicated with letter (a) ( FIG. 4(C) ) of the folding roller  3 L are positioned in the folding nip  5 , in front of or facing the corresponding suction holes  41  of the folding roller  3 R. A first sheet F 1  is in detachment phase from the folding roller  3 R. 
     The sheet F 1  has been carried out by the cutting of the web material N 1  fed to the folding roller  3 R. In  FIG. 4  the sheet F 1  is folded in the middle and kept off the surface of the folding roller  3 R along the central folding line by means of the alignment of the suction holes  43  directly downstream the folding nip  5  with respect to the rotation direction. 
     The border downstream (Fv) of the sheet F 1  has been previously detached from the folding rollers, while the border upstream of the sheet F 1  is sticking to the folding roller  3 R and it is kept therein by suction through the suction holes  41  of the folding roller  3 R which are located in the folding nip  5 , see  FIG. 4(A) . 
     In the folding nip  5 , in front of the upstream border of the sheet F 1 , there is the middle of a second sheet F 2 , which has been carried out by cutting the web material N 2  fed to the folding roller  3 L. The downstream border of the sheet F 2  is sticking to the folding roller  3 R, and it is kept by the suction holes  43  which keep also the folding line of the middle of the sheet F 1 . 
     Basically, the second sheet F 2  is placed half sticking to the folding roller  3 R, and half sticking to the folding roller  3 L. The middle line of the sheet F 2  is kept by suction on the folding roller  3 L by means of the suction holes  43  of the longitudinal alignment countermarked by the letter (a) in the folding nip  5 . The upstream border of the sheet F 2  is placed in correspondence with the suction holes  41  of the alignment (f) of the folding roller  3 L, see  FIG. 4(C) . 
     A sheet F 3 , carried out by cutting web material N 1 , is sticking to the surface of the folding roller  3 R, by means of the three alignments of the suction holes  41 ,  43 ,  41 , of the folding roller  3 R. 
     More in particular, the downstream border of the sheet F 3  is kept by the suction holes  41  of the folding roller  3 R which are placed in the folding nip  5 , while the upstream border is sucked by the suction holes  41  of the folding roller  3 R which are placed in the transfer nip  15  between the folding roller  3 R and the corresponding cutting roller  7 . The middle of the sheet F 3  is sucked by the alignment of suction holes  43  which is placed on the folding roller  3 R immediately upstream (with respect to the rotation direction) of the folding nip  5 . 
     In  FIGS. 4(A), 4(B)  with reference to the folding roller  3 L it is observed that the suction holes  43  of the alignment (a), placed in the folding nip  5 , remain in communication with the suction chamber  23 A for the following rotation of nearly 60° (adjustable acting on the angular position of the wall  29 ), because they  43  are placed between adjacent shutters  37  and thus they are not closed by the shutters  37 . 
     Vice versa, the suction holes  41  of the folding roller  3 R which are placed in the nip  5  stop sucking from this position forward, since they are closed by the shutters  37  of the folding roller  3 R and thus they are no more in communication with the suction chamber  23 A inside the folding roller  3 R. Also the holes  43  of the roller  3 R downstream the folding nip  5  (alignment (b) of suction holes) that reach the radial wall  29 , stop sucking (interrupted). 
       FIGS. 5(A), 5(B) and 5(C)  show the same views of  FIGS. 4(A), 4(B) and 4(C)  after a rotation of 60° of the folding rollers  3 L,  3 R and of the respective cutting roller  7 . The sheet F 1  has been detached, by means of respective removing comb  17 , from the folding roller  3 R. 
     The most advanced half of the second sheet F 2  is interfolded with the sheet F 1  and the most advanced border of the second sheet F 2  has been detached from the folding roller  3 R. The detachment of the sheets of web material from the folding roller  3 R is carried out by the combined effect of the removing combs  17  and of the stop of suction through the suction holes  43  of the roller  3 R which have been closed by the shutters  37  of the folding roller  3 R. 
     Always with reference to  FIGS. 5(A)-5(C)  the second sheet F 2  is engaged in correspondence with the middle fold from the suction holes  43  (position (a),  FIG. 5(C) ) of the folding roller  3 L which are going to reach the radial wall  29  of the folding roller  3 L, where the suction will be interrupted. 
     The rear border of sheet F 2  is engaged to the suction holes  41  (alignment (f) of the folding roller  3 L) which reached the folding nip  5 . Here, because of the effects of the shutters  37  of the roller  3 L, the suction on the upstream border of sheet F 2  by the roller  3 L stops and such border will be attracted by the alignment of suction holes  43  of the folding roller  3 R which are located in the folding nip  5  and which will remain in communication with the suction chamber  23 A of the folding roller  3 R for the next rotation of 60°. This because these suction holes  43  of the folding roller  3 R are staggered with respect to the shutters  37  and are not closed by these latter. 
     The most advanced border of sheet F 3  has been detached from the folding roller  3 R, because the suction holes  41  of the folding roller  3 R (of  FIG. 4  and not of  FIG. 5 ) which were keeping it stopped sucking ( FIG. 4 ) starting from the nip  5  being closed by the shutters  37  inside the folding roller  3 R. The most advanced border of sheet F 3 , so, has been engaged by the suction of the suction holes  43  of the alignment (a) of the folding roller  3 L and it is sticking to the roller  3 L in the point of middle fold of sheet F 2 . 
       FIGS. 6(A)-6(C)  show the following phase, after a new rotation of 60° of the folding rollers  3 L,  3 R and of the respective cutting rollers  7 . The sheet F 2  has been completely detached by the folding roller  3 R by means of the combined effect of the stop of suction through the suction holes  43 , which stop sucking reached the radial wall  29 , and of the removing comb  17 . Between the two folded halves of sheet F 2  there is the half of sheet F 1  and half of sheet F 3 . 
     The other half of sheet F 3  is still sticking to the folding roller  3 R. The central fold line of sheet F 3  is kept by the suction holes  43  of the folding roller  3 R, which  43  keep also the downstream border of the following sheet F 4 . The suction will stop once the radial wall  29  of the folding roller  3 R is passed. The upstream border, i.e. the rear one, of sheet F 3  is sticking to the folding roller  3 R because attracted by the suction holes  41  which in  FIG. 6  are in the folding nip  5 . 
     The suction stops in this point because of the closure of such suction holes  41  by the shutters  37  of the folding roller  3 R. The upstream border of sheet F 3  will thus be attracted on the surface of the folding roller  3 L because of the effect of the suction through the suction holes  43  of the alignment (e) which are in the nip  5 , suction which will be maintained for the following rotation of 60°, up to the reaching of the radial wall  29  of the folding roller  3 L. 
     The suction holes  43  of the alignment (e), which in the angular position of  FIGS. 6(A)-6(C)  are in the folding nip  5 , keep sticking to the folding roller  3 L also the central line of the following sheet F 4  which has been carried out by cutting web material N 2 . The upstream border of sheet F 4  is kept on the surface of the folding roller  3 L by effect of suction through the suction holes  41  of the alignment (d), see  FIG. 6(B) . 
     The following  FIGS. 7-9  show, with a rotation of 60° from a figure to another, the movement of the folding roller  3 L,  3 R and of the respective alignments of suction holes  41 ,  43 , as well as the effect of interruption of suction operated by the stationary shutters  37  which are inside the folding roller  3 L and  3 R with repetition of phases described above, for the following sheets F 3 -F 7 . 
     After all, as it is understood from the sequence of  FIGS. 4-9  the sheets F 1 , F 2 , F 3  . . . Fn carried out by cutting the web material N 1 , N 2  and alternatively fed to the folding roller  3 R,  3 L are bended and interfolded by means of the effect of alternated suction through suction holes  41 ,  43  of the two folding rollers. 
     The presence of the shutters  37  with comb structure and the longitudinal stagger of the alignments of the suction holes  41 ,  43  allows to activate and deactivate the suction in angular correct positions to carry out the bending of the sheets and the interfolding of the bended sheets. Movable members for opening and closing the suction and relative control softwares and hardwares are not necessary. 
     Moreover, as the shutters  37  act directly on the suction holes  41 , the minimum volume between the suction point (mouth of the suction hole  41  of the outer surface  3 X of the sleeve  3 C of the folding roller  3 ) and the interception point or closure of the suction (inner surface  3 Y of the sleeve  3 C of the folding roller  3 ) is minimized. 
     The opening and closure of the suction are carried out in a timely and precise way, without typical inertias of systems in which suction opening and closure members are spaced with respect to the suction holes on the external cylindrical surface of the folding rollers. 
     Numerous variants are possible for the exemplificative and non-limitative structure above described and represented in the enclosed drawings. For example, while in the described machine are provided two cutting rollers  7  and two folding rollers  3  cooperating with the cutting rollers, as well as fixed counter-blades  11  cooperating with blades  9  carried by the cutting rollers, so as to transfer cut sheets from each cutting roller  7  to the respective folding roller  3 , in other embodiments blades  9  may be placed on the folding rollers  3  and let such folding rollers  3  and the respective cutting blades cooperate directly with the counter-blades  11 . The cutting rollers  7  would be in that case omitted. 
     In the described embodiment with reference to  FIGS. 1-9  the suction holes  41  and the suction holes  43  are staggered with respect to each other in a longitudinal direction, i.e. substantially parallel to the rotation axis  3 A of the respective folding roller  3 , or more exactly of the cylindrical liner or sleeve  3 C of the roller. 
     This way the suction holes  43  are interposed between adjacent surfaces  37 A of the comb shutters  37 , while the suction holes  41  are in phase with the surfaces  37 A of the comb shutters and are closed by these latter. This configuration is actually preferred, because it simplifies the mechanical manufacturing of the cylindrical sleeve  3 C of the folding roller  3 . 
     Nevertheless, there are other ways to obtain opening and closure of the suction through the suction holes  41 ,  43  according to the angular position of the folding roller  3 . 
     An alternative embodiment is illustrated in  FIGS. 10 and 11 , where  FIG. 10  is a cross section of one of the sucking folding rollers  3 , while  FIG. 11  is a partial side view of the side surface of the folding roller. 
     In this embodiment shutters  37  with a comb structure are provided as in  FIGS. 1-9 , see  FIG. 11 , the holes  41  and the holes  43  are arranged according to longitudinal alignments, substantially parallel to the rotation axis  3 A of the cylindrical sleeve  3 C of the folding roller. In opposition to the embodiment of  FIGS. 1-9 , in  FIGS. 10 and 11  the holes  41  and  43  are not staggered in an axial direction, but aligned along circumferential lines (see  FIG. 11 ). The circumferential lines are aligned with the surfaces  37 A of the comb shutters  37 . 
     With this arrangement, the holes  41  are closed by the surfaces  37 A of the comb shutters  37  in such an identical way described above with reference to  FIGS. 1-9 . Since also the holes  43  are aligned with the comb shutters  37  and the respective closing surfaces  37 A, in order to avoid that the holes  43  are closed by the shutters  37 , in the embodiment illustrated in  FIGS. 10 and 11  along the longitudinal alignments  44  of the suction holes  43 , of the inner surface  3 Y of the cylindrical sleeve  3 C are made longitudinal nips  46 , which ensure the suction holes  43  are not to be closed by the closing surface  37 A of the comb shutters  37 . 
     Basically, the suction holes  43  are shorter than the suction holes  41  and end in the nip  46 . This way, when the suction holes  43  are in front of the corresponding closing surface  37 A, this latter cannot close the suction holes through which the suction is generated by effect of the nip  46  which connects the holes  43  with the empty spaces between adjacent shutters  37 . 
     With this arrangement, so, the suction through the suction holes  41  and  43  is opened and closed in such an identical way described above with reference to  FIGS. 1-9 , even if a staggered position in a longitudinal direction (parallel to the axis  3 A) of the holes  41  with respect to the holes  43  is not provided. 
     In all the illustrated embodiments it is obtained a substantial simplification of the folding roller and thus of the folding machine employing it. Also advantages concerning the reduction of the inertia of the suction system are obtained. 
     Basically, by using the shutters placed inside the cylindrical sleeve, this can be made with a thinner thickness with respect to the traditional rollers. The volume of the empty space in which it must be generated in order to carry out the suction timed with the angular position of the roller is thus very little, this substantially reducing inertia.