EP1457444B1

EP1457444B1 - Interfolding machine of a web or sheet of paper with a vacuum conveying roller

Info

Publication number: EP1457444B1
Application number: EP04003595A
Authority: EP
Inventors: Alessandro De Matteis
Original assignee: MTC Macchine Trasformazione Carta SRL
Current assignee: MTC Macchine Trasformazione Carta SRL
Priority date: 2003-02-18
Filing date: 2004-02-18
Publication date: 2011-11-09
Anticipated expiration: 2024-02-18
Also published as: EP1457444B2; EP1457444A2; EP1457444A3

Description

Field of the invention

The present invention relates to the field of machines for converting paper and similar products, and in particular it relates to an interfolding machine of a web or sheet of paper.
In particular, the invention relates to an interfolding machine having a paper conveying roller having circumferentially a plurality of holes which, connected to a vacuum system, allow the sheet or web of paper to adhere on their surface.

Description of the prior art

As known, many machines used in the paper converting field, for example rewinding and interfolding machines, are equipped on the surface of their rollers with systems for capturing the web or the sheet of processed paper, in certain operative phases, in order to cause the paper to follow a predetermined path.
In particular, such systems are used to provide the main operations of cutting the paper, of transferring it quickly from a roller to another, of final folding the paper same. To this object, the machines are normally equipped either with mechanical clamps or with pneumatic suction means.
In the latter case, the air suction systems, owing to a certain vacuum grade created within the rollers, cause the processed paper to adhere on the roller surface by means of rows of suction holes.
In more detail, as shown diagrammatically in figures 1 and 2, in a paper conveying roller 101, of known art, the vacuum is transmitted through a plurality of longitudinal channels 102 into roller 101, causing the paper 120 to adhere selectively to the roller surface same by means of a plurality of holes 103. Normally, holes 103 are arranged according to longitudinal rows with respect to the axis 104 of the cylinder (transversal with respect to the paper) since the vacuum is made selectively by distributor means. This causes a division of the roller surface into paper suction fields, i.e. where the rows of holes are enabled for suction, and into fields where the processed paper is instead freed from the roller for being for example transferred onto another roller or folded, i.e. the respective rows of holes are not enabled for suction.
In particular, the paper conveying roller is normally coupled, at an end thereof, to a bell-shaped vacuum distributor element 110 to it co-axial but whose rotation is impeded by means of suspension on ball bearings. The vacuum distributor 110 is equipped with an inlet 111 connected to the suction system of the machine and communicating with a curved opening 112 determined on the distributor same. More in detail, the curved opening 112 extends for a certain angle and, during the rotation of the roller about its own axis, selectively communicates with longitudinal channels 102 and then with the respective rows of holes 103. This way, a portion of roller surface (hatched area in figure 1) is obtained in which the sheet or the web of paper is captured by suction and adheres on the roller surface.
With this system, channels 102 are at atmospheric pressure except from when they are in communication with the vacuum distributor. This causes, however, the row of holes 103, which is enabled to suction by alignment with curved opening 112, to start the suction of the sheet on the roller surface 101 only after that the air present in the respective longitudinal channel 102 has been removed. Therefore, there is a delay between the beginning of the suction in channel 102 and the moment where the portion of roller surface located at holes row 103 can actually start the suction of the paper, owing to the vacuum inertia for the presence of air channel 102 and the propagation time of the vacuum for all the row of holes length. Furthermore, as soon as channel 102 is not more enabled for suction, even if there is a delay of the vacuum to disappear, then, in any case, the vacuum is lost and the channel returns to the atmospheric pressure.
A not efficient suction by the holes, on the other hand, can affect the successive operations of the machine causing paper jamming and stop of production.
In any case, the maximum air flow rate is limited.
In order to limit this drawback it is therefore necessary:

to limit the length of the roller and then the volume of the chambers in it; this causes a subsequent limitation in the maximum width of the paper that can be processed and then reduces productivity of the machines that have such rollers;
starting/stopping the suction of the air channel with a vacuum advance, so that the suction in all the holes starts/stops at a predetermined moment; with a vacuum advance, it is necessary to change the vacuum timing as varies the speed of operation of the machine;
working with a high vacuum grade for reducing the time necessary for a row of suction holes to be fully operative.

As described in US4207998 paper dragging rollers also exist formed by a fixed cylinder that form a longitudinal chamber, about which a concentric roller rotates formed by a inner stiff tubular shell having a plurality of holes, and an outer resilient tubular shell, having a plurality of deformable holes. When contacting the paper the deformable holes are open and bring into communication the paper with the holes of the inner shell and the suction chamber, preventing the roller from sliding with respect to the paper. The sealing ability of the holes, however is limited to the contact with a web of paper and with a certain pressure, whereby this type of roller is unsuitable for applications with sheets of paper. Furthermore, it is suitable only for narrow fields of suction.
The document US 3037557 describes a vacuum roller that can be used in printing presses and coating apparatus, in paper making machines, for stretching a web of paper in order to remove the humidity surplus, as well as in machines for laminating a film thin. It comprises a fixed inner body and an outer cylinder having a plurality of longitudinal radial holes capable of rotating with respect to the inner body. The fixed inner body has inside a suction chamber communicating with vacuum means and having a peripheral opening. In the external surface of the fixed body are sectors are provided having each friction seals that slide against the inner wall of the outer cylinder. The seals define a zone communicating with the suction chamber through said opening and that transmit then a vacuum to the corresponding holes of the cylindrical body. Such a roller, however, is not suitable for interfolding machines as the present invention. In fact, interfolding machines must move with precision a web of paper for all the length of the roller, even 2-3 metres, and such a division into sectors is not feasible.
GB691990 discloses a means for feeding sheets in a printing-machine comprising a hollow rotatable cylinder connected to a source of suction, a number of peripheral holes leading to the interior of the cylinder, and an automatically-controlled tubular member which is slotted and adapted to establish communication between the holes and the interior of the cylinder, or with the atmosphere, respectively, according to whether a sheet is to be held on or released from the cylinder.
EP0982256 discloses a method for the production of interfolded stacks formed by a plurality of sheets, The method comprises the steps of transversally cutting or tearing sheets obtained from at least one web and offset with respect to one another so that a sequence of offset sheets is created; passage of the sheets on folding rollers which comprise sucking means for the alternate holding of the sheets in order to obtain an interfolded disposition; formation of a continuous interfolded stack downstream of the folding rollers.
WO91/1961 discloses a vacuum roll for paper handling machine, such as is used in interfolding paper machinery. The vacuum roll comprises an outer rotating roll member which rotates around an internally coaxial static vacuum feed. Both the length of time for which vacuum is applied, and the part of the circle of rotation over which it is applied, can be varied from outside the machine and whilst the machine is running.

Summary of the invention

It is a feature of the present invention to provide an interfolding machine having a roller a roller equipped with suction points for conveying a web or sheet of paper which allows to provide a high production rate even with a low vacuum grade and then not much expensive with respect to the prior art.
It is another feature of the present invention to provide an interfolding machine having such a paper conveying roller for increasing productivity and flexibility of the machine on which it is mounted, in order to work webs or sheets of paper of different type and wide enough without affecting the efficiency of the process.
These and other objects are achieved by the interfolding unit according to claim 1.

Brief description of the drawings

In the drawings, figures 1 and 2 already commented in the introductory part show the following:

figure 1 is a perspective view of a paper conveying roller for paper converting machines and of the vacuum distributor to it associated, as known in the art;
figure 2 shows a longitudinal cross section of a conveying roller according to the prior art coupled to a vacuum distributor.

Further characteristics and the advantages of the roller according to the present invention, equipped with suction points for conveying a web or sheet of paper in paper converting machines, will be made clearer with the following description of an embodiment thereof exemplifying but not limitative, with reference to the attached drawings wherein:

figures 3 and 4 show a cross sectional view of a paper conveying roller for paper converting machines, according to the present invention, in two relative different positions between the first and the second cylindrical tubular body;
figure 5 shows a cross sectional view of a interfolding machine that has conveying rollers according to the invention.

Description of a preferred exemplary embodiment

In figures 3 and 4 a cross sectional view is shown of a roller 1 used for conveying a web or sheet of paper 20 for paper converting machines, for example, a rewinding machine, a winding machine, an interfolding machine. It comprises a first outer cylindrical tubular body 2, equipped with a plurality of radial holes 3 arranged according to substantially longitudinal rows, capable of rotating with respect to a second inner fixed body 4, co-axial to the former and connected to a suction system not shown. The second body 4, which as shown in the embodiments of figures 3 and 4 has tubular cylindrical geometry like first body 2, has a plurality of apertures 5 and two radial boards 7 at opposite sides with respect to apertures 5.
The inner surface of first cylindrical tubular body 2, radial boards 7 and the external surface of second tubular body 4 define a suction chamber 6 that, during the relative rotation of the two bodies, brings selectively in communication some rows of holes 3 of first cylindrical tubular body 2 with the apertures 5 of second tubular body 4 and then with the suction system of the machine. Therefore, a web or sheet of paper 20 adheres to the external surface of first body 2 only in the portion P₁P₂ of the surface set between the rows of holes 3' that communicate with the suction chamber (figure 4).
The apertures 5 made on the surface of second tubular body 4 are arranged longitudinally and are enough to allow a quick outlet of the air present in holes 3' that in turn overlap to the suction chamber 6. This is possible also because chamber 6 is fixedly kept at a determined vacuum grade.
In particular, radial boards 7, between which the apertures 5 extend, are arranged radially for all the length of second cylindrical tubular body 4 and have high sealing capability of the suction chamber from the remaining space comprised between bodies 2 and 4. This result is obtained with radial boards 7 having a fixed portion 10, integral to the second inner tubular body 4 and forming a longitudinal channel, and a movable portion 8 that engages with fixed portion 10 and is pushed elastically against the inner surface of first tubular body 2 urged by springs 9. Springs 9 can be located, as in the case of figures 3 and 4, about pins 11 which are constrained in a housing within fixed portion 10.
This way, it is possible to define with high precision the portion of the roller surface 1 enabled for the suction of the paper 20 and to make easier possible cutting operations, which can be made between two adjacent rows of holes 3.
This is for example effected in case of an interfolding unit shown diagrammatically in figure 5. In particular, conveying rollers 1 are provided as above described that work in cooperation with folding rollers 40. The unit works for example in the way described in EP0982255 or in EP0982256 in the name of the same applicant. Differently by rollers 1, rollers 40 have six couples of rows, wherein three couples of rows of holes spaced 120° capture the end of a sheet, and other three couples of rows of holes spaced 120°, shifted 60° with respect to the former, capture through the central portions of a sheet, the end of a second overlapped sheet and ready for being interfolded. Therefore, the first three couples of holes must be enabled for suction between two consecutive cuts, for a sector between the point of contact of rollers 1 with rollers 40 up to the contact between the two opposite rollers 1, whereas the other three couples of holes must be enabled for suction between two consecutive cuts, for a sector between the point of contact of rollers 1 with rollers 40 up to the contact between the two opposite rollers 1, whereas the other three couples of holes must be enabled for suction between the contact between the two rollers 40 and the point where the fold is made.
Therefore, rollers 40 are shown in figure 5 having a "mixed" structure as a combination of a roller of prior art and a roller 1 according to the invention. More in detail:

the sheet is captured from roller 1 up to the point of contact between two rollers 40 by means of a traditional suction system, with suction channel and bell-shaped vacuum distributor; in fact, for capturing and holding the sheet a light vacuum grade and a not high angular precision are enough and this system is sufficient;
the passage of a sheet from an interfolding roller 40 to the other is made with a system according to the invention, since higher angular precision and higher vacuum in suction are required.

Obviously, a roller can be made that enables to suction three couples of rows of holes all with a system according to the invention. For example, the inner second body may have three radial boards, forming three chambers, one not enabled to suction and two enabled to suction with a different vacuum grade.
In figures from 6 to 8 two possible different exemplary embodiments are shown of the roller 1 shown in figures from 1 to 5. The roller provides a cylindrical tubular body 202 capable of rotating about an axis 210 and a chamber 206 pneumatically connected to a suction system. According to this exemplary embodiment at each row of holes 203 a longitudinal rod 230 is provided free of rotating about its own axis with respect to roller 202 and have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Claims

An interfolding unit comprising conveying rollers (1) working in cooperation with folding rollers (40), said folding rollers (40) adapted to capture a web or sheet of paper from said conveying rollers (1) up to the point of contact between two folding rollers (40) by means of a suction system, the interfolding rollers (40) being arranged for causing the passage of the web or sheet from one interfolding roller (40) to another, said interfolding rollers comprising:
- a cylindrical tubular body (2) capable of rotating about an axis of rotation, said cylindrical tubular body (2) having a plurality of radial holes (3) arranged according to substantially longitudinal rows,

- a chamber (6) in said roller (40) that extends for all its length and is always connected to a suction system, whereby said chamber (6) is always under vacuum,

- an interposition means (7) between said chamber (6) and at least one row of radial holes (3) suitable for selectively connecting said chamber (6) with said at least one row of holes (3) at determined angular positions of said roller (40) to provide a suction effect on the sheet or web of processed paper (20) only at said positions;
wherein said chamber (6) is defined by a hollow body (4) fixed in said cylindrical tubular body (2), said interposition means comprising sealing elements (8) sliding against the inner surface of said cylindrical tubular body (2).
Interfolding unit, according to claim 1, wherein said interfolding rollers (40), have six couples of rows of holes, wherein three couples of rows of holes are spaced 120° and are adapted to capture the end of a sheet, and other three couples of rows of holes are spaced 120°, shifted 60° with respect to the former, and are adapted to capture through the central portions of a sheet, the end of a second overlapped sheet and ready for being interfolded.
Interfolding unit, according to claim 2, the first three couples of holes are enabled for suction between two consecutive cuts, for a sector between a point of contact of conveying rollers (1) with interfolding rollers (40) up to a contact between the interfolding rollers (40), whereas the other three couples of holes are enabled for suction between the contact between the two interfolding rollers (40) and a point where the fold is made.
Interfolding unit, according to claim 1, wherein said interposition means provides two radial boards, between which at least one opening is present, which extends between the first and the second tubular body for all the length of the roller in order to define the suction chamber.
Interfolding unit, according to claim 4, wherein each radial board comprises a fixed portion, forming a guide arranged longitudinally with respect to the conveying roller, within which a bar can slide radially forced elastically against the inner surface of the first cylindrical tubular body, forming said sliding sealing element.