SUCTION ROLL FOR PAPER CONVERTING MACHINES

Abstract

A roll (1) for folding, or interfolding, a web, or sheet, of paper, (100) fed along an advancing direction in a paper converting machine, or similar machines, comprises a tubular body (10) configured to rotate about a longitudinal rotation axis (101), and having an external lateral surface (11) and an internal lateral surface (12) pneumatically communicating through a plurality of suction holes (3a, 3b) organized in a predetermined number of suction groups (60). Each suction group (60) comprises a predetermined number of close longitudinal rows (30a, 30b) of suction holes (3a, 3b) distributed along the tubular body (10). A suction chamber (20) is, then, provided arranged internally to the roll (1) for folding, or interfolding, and pneumatically connected to a suction device generating a predetermined vacuum level. Each suction group (60) comprises at least 3 close longitudinal rows (30a, 30b, 30c) of suction holes (3a, 3b, 3c) configured to hold each sheet, or web, of paper (100) on the roll (1) at a respective portion of the external lateral surface (11).

Claims

1. A roll (1) for folding, or interfolding, a web, or sheet, of paper, (100) fed along an advancing direction in a paper converting machine, or similar machines, said roll (1) for folding, or interfolding, comprising: a tubular body (10) configured to rotate about a longitudinal rotation axis (101), said tubular body (10) providing an external lateral surface (11) and an internal lateral surface (12) pneumatically communicating with each other through a plurality of suction holes (3a,3b) organized in a plurality of suction groups (60) comprising a predetermined number of suction groups (60), each suction group (60) of said plurality comprising a predetermined number of close longitudinal rows (30a,30b) of suction holes (3a,3b) distributed along said tubular body (10); a suction chamber (20) provided internally to said roll (1) for folding, or interfolding, and pneumatically connected to a suction device configured to generate a predetermined vacuum level; a vacuum distribution device (50) configured to selectively put in pneumatic connection said suction chamber (20) with at least a row of suction holes (3a,3b) of said plurality, at predetermined angular positions of said tubular body (10) in such a way to cause the suction of the processed sheet, or web, of paper (100), and its adhesion at corresponding portions of said external lateral surface (11) of said roll (1) for folding, or interfolding; said roll (1) for folding, or interfolding, being characterized in that each suction group (60) comprises at least 3 close longitudinal rows (30a,30b,30c) of suction holes (3a,3b,3c) configured to hold each sheet, or web, of paper (100) on said roll (1) at a respective portion of said external lateral surface (11) in that said suction groups (60) of said plurality are distributed on said external lateral surface (11) in such a way that the arch of circumference arranged between a suction group (60) and the following suction group (60) is equal to the length of a processed sheet of paper (100) and in that said vacuum distribution device (50) is configured to selectively put each longitudinal row (30a,30b,30c) of suction holes (3a,3b,3c) of each suction group (60) in pneumatic connection with said suction chamber (20) at respective predetermined angular positions of said tubular body (10).

2. Roll (1) for folding, or interfolding, a web, or sheet, of paper, according to claim 1, wherein each suction group (60) comprises at least 4 close longitudinal rows (30a,30b,30c,30d) of suction holes (3a,3b,3c,3d).

3. Roll (1) for folding, or interfolding, a web, or sheet, of paper, according to any of the previous claims, wherein at least 2 of said close longitudinal rows (30a,30b,30c,30d) of suction holes (3a,3b,3c,3d) of each suction group (60a,60b,60c,60d) are arranged according to directions lying on incident planes (γa,γb,γc,γd) arranged to intersect each other in a line parallel to said longitudinal rotation axis (101) of said roll (1).

4. Roll (1) for folding, or interfolding, a web, or sheet, of paper, according to claim 3, wherein said line is positioned at a distance from said external lateral surface that is smaller than the radius r of said roll.

5. Roll (1) for folding, or interfolding, a web, or sheet, of paper, according to any of the previous claims, wherein said close longitudinal rows (30a,30b,30c,30d) of suction holes (3a,3b,3c,3d) of a same group (60a,60b,60c,60d) are aligned with respect to the direction longitudinal to said roll (1), in such way that the axes (103a,103b,103c,103d) of the respective suction holes (3a,3b,3c,3d) lie on a same plane orthogonal to said longitudinal rotation axis (101).

6. Roll (1) for folding, or interfolding, a web, or sheet, of paper, according to any claims from 1 to 4, wherein said close longitudinal rows (30a,30b,30c,30d) of suction holes (3a,3b,3c,3d) of a same group (60a,60b,60c,60d) are staggered to each other with respect to the direction longitudinal to said roll (1), in such way that the axes (103a,103b,103c,103d) of the respective suction holes (3a,3b,3c,3d) lie on different planes.

7. Roll (1) for folding, or interfolding, a web, or sheet, of paper, according to claim 3, wherein said incident planes (γa,γb,γc,γd) form an angle (θ1,θ2,θ3) having an amplitude comprised between 0.1° and 5°.

8. Roll (1) for folding, or interfolding, a web, or sheet, of paper, according to claim 7, wherein said incident planes (γa,γb,γc,γd) form an angle (θ1,θ2,θ3) having an amplitude comprised between 1° and 5°.

9. Roll (1) for folding, or interfolding, a web, or sheet, of paper, according to claim 3, wherein said incident planes (γa,γb,γc,γd) form an angle (θ1,θ2,θ3) having an amplitude comprised between 2° and 20°.

10. Roll (1) for folding, or interfolding, a web, or sheet, of paper, according to claim 9, wherein said incident planes (γa,γb,γc,γd) form an angle (θ1,θ2,θ3) having an amplitude comprised between 4° and 15°.

11. Machine for folding, or interfolding, a web, or sheet, of paper, characterized in that it comprises an interfolding unit equipped with first and second rolls for folding, or interfolding, according to any claims from 1 to 10, configured in such a way to be counter-rotating.

12. Method for making a roll for folding, or interfolding, a web, or sheet, of paper, (100) in a paper converting machine comprising the steps of: disposing a roll having a tubular body having an external lateral surface and an internal surface, said roll being provided of a longitudinal rotation axis; disposing a drilling tool; making by said drilling tool a plurality of suction holes arranged to put into pneumatic communication said external lateral surface with said internal surface, said plurality of suction holes being organized in a plurality of suction groups (60) comprising a predetermined number of suction groups (60), each suction group (60) of said plurality comprising a predetermined number of close longitudinal rows of suction holes distributed along said tubular body; arranging a suction chamber (20) internally to said roll (1), said suction chamber (20) being pneumatically connected to a suction device configured to generate a predetermined vacuum level; providing a vacuum distribution device (50) configured to selectively put in pneumatic connection said suction chamber (20) with at least a row of suction holes (3a,3b) of said plurality in such a way to cause the suction of the processed sheet, or web, of paper (100), and its adhesion at corresponding portions of said external lateral surface (11) of said roll (1) for folding, or interfolding; said method being characterized in that each suction group (60) comprises at least 3 close longitudinal rows (30a,30b,30c) of suction holes (3a,3b,3c) configured to hold each sheet, or web, of paper on said roll at a respective portion of said external lateral surface (11), in such a way to control in an accurate way the folding of each said sheet (100), or web, of paper during formation of a stack (150) of folded, or interfolded, sheets, in that said suction groups (60) of said plurality are distributed on said external lateral surface (11) in such a way that the arch of circumference arranged between a suction group (60) and the following suction group (60) is equal to the length of a processed sheet of paper (100) and in that the vacuum distribution device (50) is arranged to selectively put each longitudinal row (30a,30b,30c) of suction holes (3a,3b,3c) of each suction group (60) in pneumatic connection with said suction chamber (20) at respective predetermined angular positions of said tubular body (10).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] 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:

[0038] FIG. 1 diagrammatically shows a folding, or interfolding, unit, of prior art;

[0039] FIG. 2 shows an enlargement of the releasing zone of the sheets in machine in FIG. 1 in order to highlight some characteristics;

[0040] FIG. 3 diagrammatically shows in a perspective side elevation view a first embodiment of a roll for folding, or interfolding, according to the invention;

[0041] FIG. 4 diagrammatically shows an enlargement partially sectioned, of a portion of the external lateral surface of the roll for folding, or interfolding of FIG. 3;

[0042] FIG. 5 diagrammatically shows a first embodiment of a folding, or interfolding, unit, according to the present invention;

[0043] FIG. 6 shows an enlargement of the releasing zone of the sheets in the machine of FIG. 5 in order to highlight some technical characteristics;

[0044] FIG. 7 diagrammatically shows in a perspective side elevation view an alternative embodiment of the roll for folding, or interfolding, FIG. 5;

[0045] FIG. 8 diagrammatically shows an enlargement partially sectioned, of a portion of the external lateral surface of the roll for folding, or interfolding, of FIG. 7;

[0046] FIG. 9 diagrammatically shows a folding, or interfolding, unit, equipped with 2 rolls for folding, or interfolding, according to the invention;

[0047] FIG. 10 shows an enlargement of the realising zone of the sheets in the machine of FIG. 9 in order to highlight some technical characteristics;

[0048] FIG. 11 diagrammatically shows an enlargement of a suction group of a further alternative embodiment of a roll for folding, or interfolding, according to the present invention.

DETAILED DESCRIPTION OF SOME EXEMPLARY EMBODIMENTS OF THE INVENTION

[0049] As diagrammatically shown in FIGS. 3 and 4, a roll 1 for folding, or interfolding, a web, or sheet, of paper, 100 fed along an advancing direction in a paper converting machine, or similar machines, comprises a tubular body 10 configured to rotate about a longitudinal rotation axis 101. More precisely, the tubular body 10 of roll 1 has an external lateral surface 11 and an internal lateral surface 12 pneumatically communicating through a plurality of suction holes 3. In particular, the suction holes 3 of roll 1 are organized in a predetermined number of suction groups, for example 3 suction groups 60a, 60b, 60c positioned in predetermined angular positions of roll 1, for example each 120°. In general, the angular position of suction groups 60 depends on the number of sheets 100 that can lie adjacent to each other on the external lateral surface 11 of roll 1. The arch of circumference arranged between a suction group and the following one is equal to the length of a sheet 100 and, therefore, depending on the diameter of roll 1 is possible to have two, three, four or more suction groups 60. For example if on roll 1 five suction groups 60 are present, the angular position between the suction groups 60 is 72°. According to the invention, each suction group 60a-60c comprises at least 3 close longitudinal rows 30a, 30b and 30c of suction holes 3a-3c. The roll 1 for folding, or interfolding, furthermore, provides a suction chamber 20 arranged internally to the above mentioned tubular body 10, and pneumatically connected to a suction device, not shown in the figure for reasons of simplicity, but, however, of known type to a skilled person in the field, and configured to generate a predetermined vacuum level. A vacuum distribution device 50 is, furthermore, provided positioned between the internal lateral surface 12 of roll 1 and the suction chamber 20. More precisely, the vacuum distribution device 50 is configured to selectively put in pneumatic connection 1a suction chamber 20 with at least a row 30a-30c of suction holes 3a-3c of the above mentioned plurality, at predetermined angular positions of the tubular body 10. In this way the suction of a processed sheet, or web, of paper 100, is carried out and its adhesion only at determinate portions of the external lateral surface 11 of roll 1. Therefore, the particular technical solution of the present invention with respect to the prior art solutions, in addition to the two close longitudinal rows 30a and 30b of holes 3a and 3b that are normally present in each suction group of the suction rolls of the interfolding, or folding, machines of the prior art, provides for each suction group 60a-60c, at least a further row 30c of suction holes 3c close to the first two. In this way, with respect to the solutions of prior art, it is possible to control in a more accurate way the fold of the sheet 100, or web, of paper during formation of the stack 150 of folded, or interfolded sheets on the formation table 155. More in particular, the technical solution according to the invention allows to control the folding of the first half of the whole sheet, in the case of FIG. 6 the sheet 100b coming from right roll 1b, on which the tail of the previous sheet is overlapped, in figure, the sheet 100a coming from the left roll. Preferably, the auxiliary suction holes 3c of the longitudinal rows 30c are arranged downstream of the “standard” holes 3a and 3b of the respective group 60a, with respect to the rotation direction of the rolls 1a and 1b for folding, or interfolding. Therefore, it is possible to avoid that folds, or wrinkles, can be formed, thus considerably increasing the quality of the final product with respect to the prior art solutions.

[0050] In the alternative embodiment shown in the figures from 7 to 10, each suction group 60a-60c provides 4 close longitudinal rows 30a-30d of suction holes 3a-3d. In this way, it is possible to further increase the accuracy of the fold of the sheet 100b when the same releases the respective roll 1b.

[0051] As diagrammatically shown in FIGS. 4 and 8, respectively, where each suction group 60a-60c comprises 3, or 4, close longitudinal rows 30a-30c, or 30a-30d, of suction holes 3a-3c, or 3a-3d, at least 2 of the close longitudinal rows of each suction group 60a-60c can be positioned according to the directions lying on incident planes γa, γb, γc, γd. In this way the sheet 100 held due to the suction action of the holes 3a, 3b, 3c, 3d on the external lateral surface 11 of roll 1, is released at a same releasing angle, i.e. at a same angular position, thus overcoming the drawbacks of the prior art solutions providing parallel close longitudinal rows of suction holes. In this way a greater suction force and a better suction distribution on the sheets 100a and 100b is achieved, thus assuring a better adhesion of the sheets 100a and 100b on the external lateral surface 11 of roll 1. The improved adhesion of the sheets 100a and 100b to the external lateral surface 11 of roll 1 avoids can be released in advance, thus avoiding formation of undesirable wrinkles in the stack of sheets in particular when the rolls for folding 1a and 1b operate at high speed.

[0052] In a possible alternative embodiment, at least 2 of the above mentioned close longitudinal rows 30a-30c, or 30a-30d, of rows of suction holes, of each suction group 60a-60c are staggered to each other along the direction longitudinal to roll 1. The suction holes 3a-3c, or 3a-3d, of each suction group 60a-60c are, therefore, arranged at respective directions that can intersect each other before reaching axis 101 of the roll 1 for folding, or interfolding.

[0053] In the embodiment shown in particular in FIG. 11, the close longitudinal rows 30a-30d of the same suction group 60a-60d, are arranged aligned with respect to the direction longitudinal to the roll 1. Therefore, the axes 103a-103d of the suction holes 3a-3d of a same suction group 60a-60d lie on a same plane orthogonal to the longitudinal rotation axis 101. In other words, the axes 103a-103d of the suction holes 3a-3d of at least a same suction group 60a-60d, that are positioned on a same circumference coaxial to the longitudinal rotation axis 101 of roll 1, are positioned on a plane orthogonal to the longitudinal rotation axis 101.

[0054] In a particular embodiment of the invention, the above mentioned incident planes γa-γd define angles θ.sub.1-θ.sub.3.

[0055] These can have the same, or different, amplitude, advantageously an amplitude, anyway, comprised between 0.1° and 5°, preferably between 1° and 5°.

[0056] Alternatively, the amplitude of the above mentioned angles can be comprised between 2° and 20°, advantageously between 4° and 15°.

[0057] In an alternative embodiment, not shown in the figure for reason of simplicity, at least 2 of the above mentioned close longitudinal rows 30a30c, or 30a-30d, of rows of suction holes, are staggered to each other along the direction longitudinal to roll 1. Therefore, the suction holes 3a-3c, or 3a-3d, of 2 the close longitudinal rows 30a and 30b, are oriented with the respective axes 103a-103d positioned along respective skew directions that means belonging to different planes. According to the invention, a “mixed” solution of the above mentioned embodiments is also possible, i.e. an embodiment wherein roll 1 for folding, or interfolding, provides a plurality of suction holes comprising both suction groups with close rows 30a-30d of suction holes 3a-3d such that the axes 103a-103d of the suction holes of at least two close longitudinal rows 30a-30d of a same group 60a-60d are arranged on a same plane orthogonal to the longitudinal rotation axis 101 of roll 1, and suction groups 60 wherein the close longitudinal rows 30a-30c, or 30a-30d, are longitudinally staggered to each other.

[0058] In the FIGS. 5 and 9, two different embodiments are diagrammatically shown having, respectively, 3 close longitudinal rows 30a-30c, and 4 close longitudinal rows 30a-30d for each suction group 60a-60c, of a folding, or interfolding, unit of a paper converting machine, equipped with first and second rolls 1a and 1b for folding, or interfolding, according to the invention configured in such a way to be counter-rotating.

[0059] As shown for example in FIG. 5, in a possible embodiment of the invention, the vacuum distribution device 50 can provide a fixed tubular body 25 coaxially mounted within the above mentioned tubular body 10, communicating with a system for generating a predetermined vacuum level. More precisely, the fixed tubular body 25 provides an opening 26 and is associated to two walls 27a and 27b arranged longitudinally to tubular body 10. In this way, the volume delimited between the two walls 27a and 27b, the fixed tubular body 25 and the internal surface 12 of roll 1 define the above mentioned suction chamber 20 constantly pneumatically communicating with the vacuum generation system. Therefore, the rotation of roll about its longitudinal rotation axis 101, selectively brings the different longitudinal rows 30a-30c of suction holes 3a-3c of roll 1 to pneumatically communicate with the vacuum generation system, thus causing the adhesion of the web, or sheet, of paper on the roll surface, between the position of the first longitudinal wall 27a and the position of the second longitudinal wall 27b.

[0060] In particular, the two longitudinal walls 27a and 27b, at ends directed towards the internal surface 12 of roll 1, are advantageously provided of pneumatic sealing elements 28a and 28b, in particular made of rubber, plastic, or similar materials, in order to guarantee the necessary conditions of pneumatic sealing, thus insulating the suction chamber from the remaining portion of volume defined between the internal surface 12 of roll 1 and the fixed tubular body 25. Furthermore, the longitudinal walls 27a, 27b can provide push elements, preferably springs, not shown in the figure for reasons of simplicity, and configured to push the above mentioned sealing elements 28a and 28b against the internal surface 12 of roll 1. The foregoing description exemplary embodiments of the invention will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt for various applications such embodiment without further research and without parting from the invention, and, accordingly, it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiments. The means and the materials to realize the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology that is employed herein is for the purpose of description and not of limitation.