Patent Description:
As it is known, many machines are used in the paper industry, for example winding and interfolding machines, which are equipped with systems for causing the processed web, or sheet of paper, to adhere on the surface of the rolls, in determined working steps, in such a way to guide the sheets or webs of paper along a desired path through the machine.

In particular, these systems are used to carry out the very important operations of cutting the paper, or transferring very quickly the paper same from a roll to another one, or also to provide the final fold of the paper in order to obtain a folded or interfolded product.

The systems which cause the aforementioned adhesion can provide mechanical pliers, or pneumatic suction systems.

In the case of pneumatic systems, a device for generating a determined vacuum degree, normally a vacuum pump, is provided that is pneumatically connected to the inner part of the suction roll. More precisely, the surface of the suction roll provides a determined number of rows of suction holes distributed on the surface of the roll in such a way to cause the processed web or sheet to adhere only at determined portions. Normally, a suction roll provides <NUM>, or <NUM>, couples of rows of suction holes close to each other positioned at <NUM>°, or <NUM>°, one with respect to the other, and pneumatically connected with the vacuum generation device at determined angular positions of the suction roll, in such a way to cause the processed web or sheet of paper to adhere at a determined portions of the surface of the suction roll.

A known type of suction rolls is, for example, described in <CIT>. In particular, the suction roll of <CIT>, that can be an advancement roll, or a folding roll, comprises a tubular body provided with the aforementioned plurality of rows of holes, for example <NUM> couples of rows of holes arranged at <NUM>° with respect to each other and configured to rotate during working conditions about a longitudinal axis. The suction roll is, furthermore, provided with a second tubular body coaxially mounted within the aforementioned tubular body. In particular, the inner tubular body is pneumatically connected to a device for generating a determined vacuum degree and two sealing members are, furthermore, provided that extend longitudinally between the aforementioned tubular bodies at opposite sides with respect to the, or each aperture. In this way, the inner tubular body, the internal surface of the outer tubular body and the two longitudinal sealing members, define a suction chamber at a determined position of the suction roll. Therefore, the web or sheet of paper is sucked by the suction chamber at a first point P1 having a first predetermined angular position, at which a longitudinal row of suction holes is positioned by the rotation of the outer tubular body at the aforementioned suction chamber, or, more precisely, immediately downstream of the sealing member. The web or sheet of paper is, then, released at a second point P2, having a second predetermined angular position, at which the aforementioned longitudinal row of suction holes is positioned by the rotation of the outer tubular body at a position external to the aforementioned suction chamber, or, more precisely, immediately downstream of the second sealing member. Therefore, the web or sheet of paper is held on the portion of the suction roll surface arranged between the first and second points P1 and P2 to carry out the aforementioned cut, or fold, or advancement operation along the machine.

However, the solution described in <CIT>, as well as other analogous prior art solutions, have some drawbacks.

In particular, the advancement speed of the processed web or sheet of paper along the machine in which the suction roll described in <CIT> is installed, as well as other analogous suction rolls, cannot overcome a predetermined threshold value, normally about <NUM>-<NUM>/min, value that is imposed by constructional and functional limits of determined machine components.

The aforementioned values of the advancement speed of paper along the machine are also used, together with the path to be followed, to design the suction roll, in particular for positioning the sealing members at predetermined angular positions. If, instead, the aforementioned speed values used to design the suction roll are not observed during the functioning of the machine, it is possible to have problems of different kind. In particular, if the aforementioned threshold values are exceeded, due to the inertia of paper, the processed web or sheet, remains adhered to the surface of the suction roll even after the second angular position, i.e. at a portion of the surface positioned downstream of the second sealing member. This causes the web or sheet of paper to imprecisely move through the different sections of the machine and, in addition to unavoidably compromise the quality of the final product, in particular forming unwanted folds, can also cause the paper to be jammed and the need to stop the machine to remove the jammed paper thus losing time and productivity.

For example, in the case that the suction rolls described in <CIT> are used as folding rolls to obtain an interfolded product, exceeding the determined speeds, the stack of interfolded sheets is inaccurately formed and, in some cases, the machine can block.

Therefore, in order to avoid the aforementioned functional drawbacks and loss of quality of the final product, it is necessary to operate at predetermined speeds beyond which it is not possible to work.

Analogous drawbacks in the prior art machines, also in the case that a web or sheet of paper is to be processed having a paper weight different from the paper weight on the basis of which the aforementioned suction roll is designed. In fact, due to the higher inertia that a paper with a higher paper weight shows with respect to a paper having a smaller paper weight, if a web or sheet of paper with a paper weight higher than a predetermined paper weight is processed, the processed web or sheet of paper remains adhered to the suction roll beyond the predetermined releasing point P2*, and, in general, cover a distance higher than that caused by the suction of the roll, thus causing the aforementioned functional drawbacks and of loss of quality of the product. Therefore, the prior art machines provided with suction rolls are rigid because they have to accept arrangements of quality to work webs, or sheets of paper with different paper weights.

Some examples of the prior art machines are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, and <CIT>.

It is, therefore, an object of the present invention to provide a suction roll, in particular a cutting roll, or a folding or interfolding roll, that is able to overcome the aforementioned drawbacks of the suction rolls of prior art.

It is, in particular, object of the present invention to provide a suction roll, which is able to prevent wrinkles, or "creases", on the processed sheets and, therefore, to guarantee the obtainment of a final product of excellent quality independently from the advancement speed of the web and in particular with advancement speeds higher than the threshold limits above disclosed.

It is also an object of the present invention to provide a folding or interfolding unit equipped with a couple of this kind of suction rolls able to carry out the folding or the interfolding of the web or sheet of paper at high speed without compromising the quality of the final product.

It is another object of the present invention to provide a method for sucking a web or sheet of paper in a paper converting machine having the aforementioned advantages with respect to the prior art methods.

These and other objects are achieved by a suction roll according to the invention, namely a suction roll of a web, or sheet, of paper, fed along an advancing direction in a paper converting machine, or similar products, said suction roll comprising:.

wherein a displacement device is, furthermore, provided configured to move said vacuum distribution device, in such a way to change the angular position of said catching point (P1) and/or said releasing point (P2) of said web or sheet of paper, and therefore, to anticipate, or postpone, the catching instant (ta) and/or the releasing instant (tr) in which said web or sheet of paper adheres to or leaves said external lateral surface of said suction roll, said suction roll being characterized in that the displacement device is configured to move said vacuum distribution device during said rotation of said tubular body about said longitudinal rotation axis, in such a way to progressively follow the increase or decrease of the advancement speed of the web or sheet of paper.

Other technical characteristics of the present invention are defined in the dependent claims.

According to another aspect of the invention, provided is a method for feeding a web or sheet of paper in a paper converting machine comprising the steps of:.

wherein a displacing step is, furthermore, provided to move said vacuum distribution device, in such a way to change the angular position of said catching point (P1) and/or said releasing point (P2) of said web or sheet of paper, and therefore, to anticipate or postpone, the catching instant (ta) or the releasing instant (tr) in which said web or sheet of paper adheres to, or leaves, said external lateral surface of said suction roll, wherein said displacing step to move said vacuum distribution device is carried out by a displacement device, and wherein the displacing step is carried out by said displacement device during said rotation of said tubular body about said longitudinal rotation axis, in such a way to progressively follow the increase or decrease of the advancement speed of the web or sheet of paper.

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

As diagrammatically shown in the figures from <NUM> to <NUM>, a suction roll <NUM> of a web, or sheet, of paper <NUM> fed along an advancing direction <NUM> in a paper converting machine, or similar products, comprises a tubular body <NUM> configured to rotate in a predetermined sense of rotation <NUM>, for example clockwise, about a longitudinal rotation axis <NUM>, as in the case of <FIG>. More precisely, the tubular body <NUM> of roll <NUM> is provided with an external lateral surface <NUM> and with an internal lateral surface <NUM> communicating with each other through a plurality of suction holes <NUM>.

In particular, the suction holes <NUM> of the suction roll <NUM> can be organized according to a plurality of suction groups <NUM>, for example <NUM>, or <NUM>, or <NUM>, suction groups <NUM>, arranged at predetermined angular positions of the suction roll <NUM>, for example at <NUM>°, <NUM>°, or <NUM>° one with respect to the other. Generally, the angular position of the suction groups <NUM> depends on the number of sheets <NUM> which can be arranged adjacent on the external lateral surface <NUM> of suction roll <NUM>. The circular arc comprised between a suction group <NUM> and the following one is equal to the length of a processed sheet <NUM>. Therefore, in function of the diameter of the suction roll <NUM> it is possible to have <NUM>, <NUM>, <NUM> or even more suction groups <NUM>. For example, if on suction roll <NUM>, five suction groups <NUM> are present, the angular distance between the suction groups <NUM> will be <NUM>°. In the examples described below, the suction roll <NUM> provides <NUM> suction groups <NUM> each of which comprising <NUM> longitudinal rows of suction holes <NUM> close to each other. The suction roll <NUM> provides, furthermore, a suction chamber <NUM> arranged within the aforementioned tubular body <NUM>, and pneumatically connected to a device for generating a predetermined vacuum degree, in particular a suction device, for example a vacuum pump, not shown in the figures for simplicity, but however of known type to a skilled person in the art. It is, furthermore, provided a vacuum distribution device <NUM> configured to selectively put into pneumatic communication the suction chamber <NUM> with at least one row of suction holes <NUM> of the aforementioned plurality, at predetermined angular positions of the tubular body <NUM>. In this way, as known, the processed sheet or web of paper is caused to be sucked and to adhere only at a determined portion of the external lateral surface <NUM> of the suction roll <NUM> comprised between a catching point P1 and a releasing point P2 having determined angular positions, in particular with respect to a predetermined reference system (Xo,Yo,Zo). According to the invention, a displacement device <NUM> is provided configured to move the aforementioned vacuum distribution device <NUM>, in such a way to change the angular position at least of the releasing point P2, in particular with respect to a predetermined angular position P2* which this occupies with respect to the aforementioned predetermined reference system (Xo,Yo,Zo). The displacement device <NUM> is operated by a main control unit, for example a PLC, an industrial PC, or equivalent control units, not shown in the figures for simplicity. The main control unit can be interfaced with an operator by an interface panel, or HMI "Human Machine Interface", through which an operator can command and/or adjust the machine <NUM>.

In this way, it is possible to anticipate or postpone, the instant ta in which the web or sheet of paper adheres to the aforementioned external lateral surface <NUM> of the suction roll <NUM>, and/or the instant tr in which the web or sheet of paper <NUM> leaves the aforementioned external lateral surface <NUM> of the suction roll <NUM>.

In particular, the aforementioned displacement device <NUM> can be configured to move the aforementioned vacuum distribution device <NUM> as a function of at least one predetermined working parameter of the machine <NUM> within which the suction roll <NUM> is installed. For example, the aforementioned predetermined working parameter can be the advancement speed of the web or sheet of paper along the machine <NUM>.

In this case, in particular, if the advancement speed v of the web or sheet of paper is greater than a predetermined reference value v*, the displacement device <NUM> will be arranged to move the vacuum distribution device <NUM> in such a way to anticipate the instant tr in which the web or sheet of paper is released from the suction roll <NUM>. In particular, the displacement device <NUM> can be configured, in this case, in such a way to rotate the aforementioned vacuum distribution device <NUM> in the sense opposite to the aforementioned sense of rotation <NUM> of the suction roll <NUM> about the rotation axis <NUM> (<FIG>).

Instead, if the machine <NUM> is operated at a slower advancement speed of the paper with respect to the aforementioned reference value v*, the displacement device <NUM> is arranged to move the aforementioned vacuum distribution device <NUM> in such a way to postpone the detaching of the web or sheet of paper with respect to a reference condition. More precisely, the displacement device <NUM> will be, in this case, arranged to rotate the aforementioned vacuum distribution device <NUM> in the same sense of the aforementioned sense of rotation <NUM> of the suction roll <NUM> about the rotation axis <NUM> (<FIG>).

In a preferred configuration of the invention, it is possible to rotate the vacuum distribution device <NUM> as a function of at least one working parameter, for example the advancement speed of the paper. In this case, the main control unit operates the displacement device <NUM> to cause the appropriate rotation of the vacuum distribution device <NUM>. The main control unit can operate the displacement device <NUM> according to a predetermined function or on the basis of algorithms computed in real time, for example self-learning algorithms or, in general, artificial intelligence algorithms.

In an alternative embodiment of the invention, it is possible to control the position of the catching point P1 and/or the detaching point P2 alternating the angular position of the vacuum distribution device <NUM> between at least two predetermined positions. For example, the position P1 can correspond to the slow advancement speed of the paper, whilst the position P2 can correspond to a high speed of the paper. In this case, a threshold of the speed can be set beyond which the displacement device <NUM> is operated to move the vacuum distribution device <NUM> from position P1 to position P2 anticipating or postponing, the detachment of the web or sheet of paper, <NUM>. The operation command of the displacement device <NUM> can be given directly by the main control unit <NUM>, or by an operator, through an interface device, for example of HMI (Human Machine Interface) type. Another working parameter of the machine <NUM> in function of which the displacement device <NUM> can be arranged to move the vacuum distribution device <NUM> can be the thickness s, or in general the paper weight of the processed web or sheet. In particular, if the thickness of the paper is greater than a predetermined reference thickness s*, the displacement device <NUM> can be arranged to move the vacuum distribution device <NUM> in such a way to anticipate the instant tr in which the web or sheet of paper <NUM> is released from roll <NUM>, in particular with respect to a releasing reference instant tr*.

In particular, in this case, the displacement device <NUM> can be arranged to rotate the vacuum distribution device <NUM> in the sense opposite to the sense of rotation <NUM> of the tubular body <NUM> about the longitudinal axis <NUM>. Instead, in the case that the thickness paper is smaller than the predetermined reference thickness s*, the displacement device <NUM> is arranged to move the vacuum distribution device <NUM>, in such a way to postpone the instant in which the web or sheet of paper is released from roll <NUM>. In particular, in this case, the displacement device <NUM> can be arranged to rotate the vacuum distribution device <NUM> in a sense of rotation consistent with the sense of rotation of the tubular body <NUM> about the longitudinal axis <NUM>.

In this case, it is possible to adjust the machine <NUM> in function of the product i.e. in function of the characteristics of the paper which has to be processed. The displacement device <NUM> can be operated in a different way in function of the type of paper or product to be processed thus obtaining great advantages in terms of setting times of the machine <NUM> during a product change. Each product or type of paper can correspond to specific movements of the displacement device <NUM> or to a specific reference value of the paper speed v* optimizing the catching point P1 and the releasing point P2 for a specific product, or paper.

In a preferred embodiment of the invention, the aforementioned displacement device <NUM> can be configured to rotate the vacuum distribution device <NUM>, to postpone, or anticipate, the instant tr in which the web or sheet of paper is caused to be detached from the surface <NUM>, during working conditions of the machine <NUM>, which means during the rotation of the tubular body <NUM> about the aforementioned longitudinal rotation axis <NUM>. In this way, it is possible to move the vacuum distribution device <NUM>, in such a way to progressively follow the increase or the decrease of the advancement speed of the web or sheet of paper.

In particular, in a first embodiment, the aforementioned vacuum distribution device <NUM> can comprise a fixed tubular body <NUM> coaxially mounted within of the aforementioned tubular body <NUM>. More in particular, the aforementioned fixed tubular body <NUM> is pneumatically connected to the device for generating a predetermined vacuum degree and at least one aperture <NUM> is provided. More precisely, the vacuum distribution device <NUM> can comprise, furthermore, a first and a second sealing member 27a, and 27b integral to the fixed tubular body <NUM> at opposite sides with respect to the, or each, aperture <NUM> and positioned longitudinally to tubular body <NUM>. In particular, the displacement device <NUM> can be configured to cause a rotation of the fixed tubular body <NUM> about the aforementioned longitudinal rotation axis <NUM>.

More in particular, as diagrammatically shown in <FIG>, the aforementioned displacement device <NUM> can be arranged to engage the fixed tubular body <NUM> at least at one actuation portion <NUM>, advantageously a portion which axially protrudes from an end of the tubular body <NUM>.

In particular, if the aim is to anticipate the releasing instant tr with respect to the reference condition tr* (broken line in <FIG>), for example because the machine <NUM> is operated at an advancement speed of the paper higher than the reference speed, in particular to increase the productivity, or to work a type of paper with a paper weight s less than a reference paper weight s*, the displacement device <NUM> can be arranged to rotate the fixed tubular body <NUM> in the sense opposite to the predetermined sense of rotation <NUM> of the tubular body <NUM>. In this way, in fact, as diagrammatically shown in <FIG>, the releasing point P2 of the sheet or web of paper from surface <NUM> of the tubular body <NUM>, is moved upstream of the reference releasing point P2* going in the sense of rotation <NUM>.

Instead, if the aim is to operate the machine at a speed slower than the reference speed v*, or to work a type of paper with a paper weight higher than the reference paper weight s*, the displacement device <NUM> can be arranged to rotate the fixed tubular body <NUM> about the longitudinal rotation axis <NUM> in a sense of rotation consistent with the predetermined sense of rotation <NUM> of the tubular body <NUM> to postpone the instant tr in which the web or sheet of paper <NUM> is released with respect to the reference releasing instant tr* (see <FIG>). In this way, in fact, as diagrammatically shown in <FIG>, the point P2 at which the sheet or web of paper is released from surface <NUM> of the tubular body <NUM>, is moved downstream of the reference releasing point P2*.

In an alternative embodiment of the invention, the position of point P1 and/or of point P2 changes with the change of the speed of the machine <NUM>, opportunely anticipating or postponing at least one between the two instants ta and tr in which the sheets <NUM> are respectively held on and released from the external lateral surface <NUM> of roll <NUM>. In this case, to anticipate, or postpone, the two instants ta, or tr, a predetermined speed v* is not taken into account and is, instead, the main control unit to compute the positions of the points P1 and/or P2 in function of the speed of the machine <NUM> and to command the displacement device <NUM> directly, or indirectly, by an operator who gives the command through an interface device, for example a HMI.

As diagrammatically shown in the figures from <NUM> to <NUM>, and in particular in <FIG>, the displacement device <NUM> can comprise an actuation device <NUM>. In particular, the actuation device <NUM> can be an actuator, for example a pneumatic actuator, or a mechanical actuator, or an electromechanical actuator. Preferably, the actuation device <NUM> can be an electric motor provided with a motor shaft (not visible in figure) arranged to rotate about a rotation axis <NUM>. The motor shaft of motor <NUM> can be arranged to mesh with an worm screw <NUM> sliding along a sliding direction <NUM>. More precisely, the worm screw <NUM> is pivotally connected at an engagement portion <NUM>, to an actuation portion <NUM> integral to said fixed tubular body <NUM>.

Therefore, to cause a rotation of the fixed tubular body <NUM> in a first sense, in particular in the sense opposite to the sense of rotation <NUM> of the tubular body <NUM>, the motor <NUM> is operated in such a way to cause a rotation of the motor shaft about the rotation axis <NUM> in a first sense of rotation <NUM> (see <FIG>). In this way, as anticipated above, the releasing point P2, in the case of <FIG> also the catching point P1, is positioned in an angular position upstream of the angular position of the reference releasing point P2*. Therefore, the releasing instant tr is anticipated with respect to the reference case tr* (see also <FIG>).

Instead, in order to cause a rotation of the fixed tubular body <NUM> in a second sense of rotation, in particular in the sense consistent with the sense of rotation <NUM> of the tubular body <NUM>, the motor <NUM> is operated in such a way to cause a rotation of the motor shaft about the rotation axis <NUM> in a second sense of rotation <NUM>' (see <FIG>). In this way, as anticipated above, the releasing point P2, in the case of <FIG> also the catching point P1, is positioned in an angular position downstream of the angular position of the reference releasing point P2*. Therefore, the releasing instant tr is postponed with respect to the reference case tr* (see also <FIG>).

In an alternative embodiment of the invention, the actuation device <NUM> can be a linear electric actuator i.e. an electric motor whose axis can slide instead of rotating. In this way it is possible to directly connect the electric motor at the engagement portion <NUM> to the actuation portion <NUM> integral to said fixed tubular body <NUM>.

In particular, in the embodiments described above and shown in particular in the <FIG>, <FIG>, <FIG>, <FIG> and <FIG>, the suction chamber <NUM> is pneumatically connected to the suction holes <NUM> by a vacuum distribution device <NUM> equipped with the first and second sealing members 27a and 27b radially oriented and positioned at opposite sides with respect to the, or each, aperture <NUM>. In particular, between the first and second sealing members 27a and 27b is not present any other element that is able to close the suction holes <NUM>.

In the alternative embodiment diagrammatically shown in the <FIG> the aforementioned vacuum distribution device <NUM> comprises a fixed tubular body <NUM> coaxially mounted within the tubular body <NUM> and pneumatically connected to the device for generating a predetermined vacuum degree. More in detail, the fixed tubular body <NUM> is provided with at least one aperture <NUM> having a predetermined angular amplitude, in particular substantially corresponding to the length of the panel, i.e. substantially to half the length of the sheet <NUM> to be processed, or the portion of the path which the web or sheet <NUM> has to cover on the roll.

The vacuum distribution device <NUM> comprises in this case a plurality of sealing members <NUM> integral and positioned longitudinally to the tubular body <NUM>. More in particular, each sealing member <NUM> is associated to at least one row of suction holes <NUM> arranged to pneumatically connect the external lateral surface <NUM> with the device for generating a predetermined vacuum degree through aperture <NUM>. Furthermore, between a sealing member <NUM> and the following sealing member <NUM> associated to two different suction groups <NUM>, annular sealing members <NUM> can be provided. In this case, the displacement device <NUM> is, advantageously, configured to rotate the fixed tubular body <NUM> about the longitudinal rotation axis <NUM>. More precisely, as shown, for example in the detail of <FIG>, to anticipate the releasing instant tr of a sheet or web of paper <NUM> with respect to the reference condition tr*, the fixed tubular body <NUM> can be rotated in the sense opposite to the sense of rotation <NUM> of the tubular body <NUM>. In this way, the releasing point P2 is positioned, moving in the sense of rotation <NUM>, upstream of the angular position of the reference releasing point P2*, because the suction holes <NUM> leave the web or sheet <NUM> in advance with respect to the reference case (diagrammatically depicted in figure with a broken line).

In the further alternative embodiment diagrammatically shown in <FIG>, analogously to what is describe above with reference to the embodiments shown in the <FIG>, <FIG>, <FIG> and <FIG>, a first and a second sealing member 27a and 27b are provided that extent longitudinally to the tubular body <NUM> between the internal lateral surface <NUM> and a fixed tubular body <NUM>. In this case, however, at least one sealing member, for example the sealing member 27b, is mounted on a support <NUM> that can move with respect to the fixed tubular body <NUM>, for example within a guide <NUM> made peripherally to the fixed tubular body <NUM>. In this case, therefore, the displacement device <NUM> can be configured to move, in particular to rotate about the longitudinal axis <NUM>, the movable support <NUM>.

In this way, it is possible to change only the releasing position P2, whilst the catching position P1 can be a fixed position and coincident with a reference angular position P1*.

Alternatively, a first and a second displacement device 70a and 70b can be provided, one configured to move the movable support <NUM> and the other configured to move the tubular body <NUM>. In this way it is, therefore, possible to change the catching point and the releasing point P1 and P2 independently from each other (<FIG>).

In an alternative embodiment of the invention that is not shown, it is possible to mount the first and the second sealing member 27a and 27b on two supports, movable independently with respect to each other, to adjust the catching point P1 and/or the releasing point P2 maintaining the fixed tubular body <NUM> fixed.

The aforementioned suction roll <NUM> can be used as folding or interfolding roll in a paper converting machine <NUM>.

In particular, according to another embodiment of the invention, as diagrammatically shown in <FIG>, a folding or interfolding unit <NUM> of a machine <NUM>, can comprise a first and a second suction roll 1a, and 1b as described above with reference to the figures from <NUM> to <NUM>. In particular, the first and the second suction roll 1a and 1b are configured to fold or interfold, the web, or sheet, of paper according to a predetermined folding or interfolding configuration, at a folding or interfolding zone <NUM> defined between them.

In a possible alternative embodiment of the invention, the displacement device <NUM> comprises a linear, an electric, or electromechanical, or pneumatic, actuator arranged to force the rotation of the vacuum distribution device <NUM> against a movable abutment member. In this way, changing the position of the movable abutment member, it is possible to adjust the angular position of the vacuum distribution device <NUM>.

Advantageously, in addition to the first and second suction rolls 1a and 1b, the folding or interfolding unit <NUM> can comprise a first and a second plurality of detaching fingers 40a and 40b arranged to operate in phase, respectively, with the first and the second suction roll 1a and 1b to operate the detachment of a respective web or sheet of paper <NUM> from the surface <NUM> of a respective tubular body 10a and 10b. In particular, a first and a second actuation group 80a and 80b can be provided configured, respectively, to cause a back-and-forth oscillatory motion of the first and of the second plurality of detaching fingers 40a, and 40b from/towards the aforementioned folding or interfolding zone <NUM>. In particular, the first and the second actuation group 80a and 80b, can be, furthermore, configured to delay or anticipate, the oscillatory motion of the first and of the second plurality of detaching fingers 40a, and 40b, in particular with respect to a predetermined reference oscillatory motion, in such a way to delay or anticipate, the instant tr in which the first and the second plurality of detaching fingers 40a, and 40b are arranged to cause the detachment of the web or sheet of paper <NUM> from the respective suction roll 1a, and 1b, preferably, with respect to a predetermined releasing reference instant tr*.

In particular, in a first embodiment diagrammatically shown in <FIG>, the first and the second actuation group 80a, and 80b comprise, respectively a first and a second actuation group 91a and 91b provided, respectively, with a first and a second motor group 85a, 85b. These are, advantageously, operatively connected, respectively, to a first and a second motor shaft 86a and 86b. More precisely, the first and the second motor group 85a, 85b are arranged to cause a rotation of the first and of the second motor shaft 86a and 86b about respective axes of rotation 185a and 185b. The first and the second actuation group 80a, and 80b can comprise, respectively also a first and a second oscillator device 90a and 90b, in particular a first and a second mechanical oscillator, configured to convert the rotational motion on the inlet axis to an oscillatory motion on the outlet axis, in particular as a function of a mechanical cam 84a and 84b provided in the first and the second oscillator device 90a and 90b provided within the first and with the second oscillator device 90a and 90b. The oscillator device is known to the skilled person in the art and is not described here in detail. The first and the second motor shaft 86a and 86b can be connected to the inlet of the first and the second oscillator device 90a and 90b, whilst the exit shaft is, advantageously, connected to the first and to a second transmission group 81a, and 81b arranged to transfer the oscillatory motion to said first and second pluralities of detaching fingers 40a, 40b. In this way, the phase between the detaching fingers 40a, 40b and the other part of the machine <NUM> is obtained causing the first and the second motor group 85a, 85b to rotate at a determined speed. In general, it is possible to use any kinematic mechanism, for example a crank and connecting rod mechanism, to convert the rotational motion of the first and of the second motor group 85a and 85b to an oscillatory motion of the first and the second transmission group 81a, 81b. Advantageously, it is possible to adjust the phase of the detaching fingers 40a, 40b, i.e. to delay or anticipate, the oscillatory motion with respect to the other mechanical organs of the machine <NUM>, slackening, or accelerating, for the necessary time, the first and the second motor group 85a, 85b. In other words, if the first and the second motor group 85a, 85b rotate at a reference speed vm*, for an interval of time Δt*, the motors 85a, 85b, are slacken, or accelerated, and then their speed are brought back to the reference speed vm*. In practice, increasing or decreasing for a determined period of time the speed of rotation, of the first and of the second shaft of rotation 86a, 86b, with respect to the set speed, the oscillatory motion of the first and of the second plurality of detaching fingers 40a, and 40b are, respectively, anticipated or postponed.

Also in the alternative embodiment diagrammatically shown in <FIG>, the first and the second actuation group 80a, and 80b comprise, respectively, a first and a second motor group 85a, and 85b which are provided with a first and a second motor shaft 86a, and 86b arranged to rotate about a respective axes of rotation 185a and 185b. Also in this case a first and a second transmission group 81a, and 81b are provided arranged to transmit the oscillatory motion produced at the outlet of the first and of the second oscillator device 90a and 90b, respectively, to the first and to the second plurality of detaching fingers 40a, and 40b. In this case, however, differently from what stated above with reference to <FIG>, the first and the second oscillator device 90a and 90b are, advantageously, associated, respectively, to a first and to a second adjustment device 94a and 94b configured to adjust the phase of the first and of the second plurality of detaching fingers 40a and 40b with the respective suction rolls 1a and 1b. In particular, the first and the second adjustment device 94a and 94b are arranged to anticipate, or to postpone, the instant tr in which the first and the second plurality of detaching fingers 40a, 40b are arranged to hit the web or sheet of paper <NUM> to cause the same to be detached from the respective folding or interfolding roll 1a and 1b.

Advantageously, the first and the second adjustment device 94a and 94b comprise, respectively, a first and a second phase-shifter gearbox 95a, and 95b of type known to the skilled person in the art. More precisely, in this case, the first and the second phase-shifter gearbox 95a and 95b can be operatively connected, respectively, to the first and second motor group 85a and 85b, for example by a first transmission belt 87a, and 87b, and to an actuation group by a second transmission belt 88a and 88b. Advantageously, the actuation group comprises a first and a second actuation device 91a and 91b operatively connected, respectively, to the first and the second phase-shifter gearbox 95a and 95b by a first and a second transmission belt 87a and 87b.

More precisely, the first and the second actuation group 91a and 91b are arranged to transmit the rotational motion to the first and to the second oscillator device 90ae 90b which convert the rotational motion to the aforementioned oscillatory motion, which is transmitted to the first and to the second plurality of detaching fingers 40a and 40b. The first and the second phase-shifter gearbox 95a and 95b are, respectively, provided with a first and a second electric motor 96a and 96b. These are arranged to adjust the speed of rotation of the first and of the second actuation group 91a and 91b adjusting the speed and the sense of rotation of a first and a second epicycloidal gear that are housed, respectively, within the first and the second phase-shifter gearbox 95a and 95b. The first and the second electric motor 96a and 96b can be normally still in such a way not to change the phase of the detaching fingers 40a and 40b with respect to the other parts of the machine <NUM>, in particular to the folding rolls 1a, 1b. In the case that is necessary to change the phase of the detaching fingers 40a and 40b, the first and second electric motors 96a and 96b are operated to temporarily accelerate, or decelerate, the second transmission belt 88a and 88b introducing a delay or an advance to the instant tr in which the first and the second plurality of detaching fingers 40a, and 40b are arranged to cause the detachment of the web or sheet of paper <NUM> dal respective suction roll 1a, and 1b.

In the further embodiment diagrammatically shown in <FIG>, downstream of the first and of the second suction roll 1a and 1b a third and a fourth suction roll 1c and 1d are provided configured to cut a respective web of paper, respectively, in a predetermined first and second plurality of sheets of predetermined length. According to the present embodiment, also the third and the fourth suction roll 1c and 1d can be provided with respective displacement devices 70c and 70d configured to move, according to one of the embodiments described above with reference to the figures from <NUM> to <NUM>, a respective vacuum distribution device <NUM> in such a way to postpone, or anticipate, depending on the aim, the releasing point P2, and, in case, also the catching point P1, of the respective processed web or sheet of paper. In this case, the suction rolls 1c and 1d are equipped with blades cooperating with counter-blades to carry out a complete cut or a partial cut of the web of paper. The adjustment of the catching point P1 and of the releasing point P2 improves the transfer of the web, or sheet <NUM>, from a roll to another one, for example, as shown in <FIG>, from suction roll 1c to suction roll 1a or from suction roll 1d to suction roll 1b.

The reference values cited above can be computed in different ways. For example, the reference positions P1* and P2* can be those related to a starting position, or point of zero, as known to the skilled person in the art. Alternatively, the reference positions P1* and P2* can be positions referred to a particular condition of the machine, i.e. can be computed considering a machine operating at a determined speed. The reference positions P1* and P2* correspond, respectively, the instants ta* in which the web or sheet of paper <NUM> adheres to the aforementioned external lateral surface <NUM> of the suction roll <NUM>, and tr* in which the web or sheet of paper, <NUM> leaves the aforementioned external lateral surface <NUM> of the suction roll <NUM>. In practice, it is possible to change, as a function of at least one parameter, the position of points P1 and P2 starting from a starting position, or position of zero, changing as a consequence, the instants ta and tr. The parameters can be the speed of the machine, the paper weight, the type of product to be produced.

Claim 1:
A suction roll (<NUM>) of a web, or sheet, of paper, (<NUM>) fed along an advancing direction in a paper converting machine, or similar products, said suction roll (<NUM>) comprising:
- a tubular body (<NUM>) configured to rotate about a longitudinal rotation axis (<NUM>) in a predetermined sense of rotation (<NUM>), said tubular body (<NUM>) being provided with an external lateral surface (<NUM>) and with an internal lateral surface (<NUM>) communicating with each other through a plurality of suction holes (<NUM>) organized according to a plurality of longitudinal rows;
- a suction chamber (<NUM>) defined within said suction roll (<NUM>) and pneumatically connected to a vacuum generation device configured to generate a predetermined vacuum degree;
- a vacuum distribution device (<NUM>) configured to selectively put into pneumatic communication said suction chamber (<NUM>) with at least one row of suction holes (<NUM>) of said plurality, at determined angular positions of said tubular body (<NUM>), and to cause the processed sheet or web of paper (<NUM>) to be sucked, and to adhere at a corresponding portion of said external lateral surface (<NUM>) of said suction roll (<NUM>) arranged between a catching point (P1) and a releasing point (P2) having determined angular positions;
wherein a displacement device (<NUM>) is provided configured to move said vacuum distribution device (<NUM>), in such a way to change the angular position of said catching point (P1) and/or of said releasing point (P2) of said web or sheet of paper, and, therefore, to anticipate, or postpone, the catching instant (ta) and/or the releasing instant (tr) where said web or sheet of paper (<NUM>) adheres to, or leaves said external lateral surface (<NUM>) of said suction roll (<NUM>), said suction roll (<NUM>) being characterized in that said displacement device (<NUM>) is configured to move said vacuum distribution device (<NUM>) during said rotation of said tubular body (<NUM>) about said longitudinal rotation axis (<NUM>), in such a way to progressively follow the increase or decrease of the advancement speed of the web or sheet of paper.