EP3009385B1

EP3009385B1 - Roller to process a continuous web material and device comprising said roller

Info

Publication number: EP3009385B1
Application number: EP15188310.5A
Authority: EP
Inventors: Mauro Ricci; Alessio PAOLINELLI
Original assignee: Fabio Perini SpA
Current assignee: Fabio Perini SpA
Priority date: 2014-10-13
Filing date: 2015-10-05
Publication date: 2018-03-14
Anticipated expiration: 2035-10-05
Also published as: EP3009385A2; CN205853433U; EP3009385A3; ES2673602T3

Description

FIELD OF THE INVENTION

The present invention relates to rollers for devices to process continuous web materials. More in particular, some embodiments described herein refer to a pressure roller configured to co-act with a second roller, for instance an embossing roller, with which it forms a nip through which the web material passes. The web material is subjected to the action of the two rollers pressed against each other, when passing in the nip therebetween.
A device is also described to process or treat a web material, comprising a first roller and a second roller, defining a nip therebetween, through which a path for a web material extends.
Some embodiments described herein refer to pressure rollers and/or embossing rollers to process paper, for instance, although without limitation, tissue paper, for the production of toilet paper, paper towels, paper napkins or handkerchiefs and the like.

BACKGROUND TO THE INVENTION

In many industrial applications it is requested to process a substantially continuous web material, for instance a plastic film, a paper web, a non-woven fabric, a metal foil or the like. These web materials pass through a nip between two rollers pressed against each other under high pressure.
Among this kind of operations there are, for instance, the calendering of both sheets and webs of paper or of other materials, like metal foils or the like, leather, artificial leather or other materials.
Apart from calenders, in the paper converting field embossing or embossing-laminating devices are used, wherein a single-ply or multi-ply web material moves between a first roller, or pressure roller, provided with a yielding surface, and a second roller, or embossing roller, typically made of steel, provided with protuberances. The yielding of the pressure roller and the compressive stress exerted between the first roller and the second roller cause the embossing of the web material, i.e. the permanent deformation thereof, with partial breakage or deformation of the cellulose fibers forming it.
Embossing is used both to produce a pattern on the material and to modify the technical features thereof, like softness, volume, absorbency etc. Embossing is also used to join a plurality of separately embossed plies, to form a multi-ply material. Joining can be obtained by applying a glue on the protuberances generated by embossing on one or more plies to be bonded.
Just by way of example, embossing machines and devices of this type are disclosed in US-A-3,961,119 ; EP-A-370972 ; EP-A-426548 ; WO-A-9720687 .
The embossing devices may have different arrangements of the pressure rollers and the embossing rollers, as well as different methods for the lamination of the separately embossed plies, to join them together, for instance by gluing. The plies may be laminated between the embossing rollers, or between an embossing roller and a laminating roller, or in other manners. Independently of the structure of the embossing device, the drawbacks described below occur, due to the roller deflection resulting from the high operating pressures and the weight of the rollers.
Figure 1 schematically illustrates a longitudinal cross section of a pressure roller for an embossing unit according to the prior art.
The roller, indicated with 101, comprises a substantially cylindrical sleeve 103, that is hollow inside, whose inner hollow volume is indicated with 104. Pads 105A and 105B are inserted in the inner hollow volume 104 of the sleeve 103 and near two ends 103A and 103B of the sleeve, respectively. Each pad 105A, 105B is provided with a respective support and rotation journal 107A, 107B for the roller 101. Through the support and rotation journals 107A, 107B, the roller 101 is supported by support and rotation bearings 109A, 109B mounted in flanks 111A, 111B of a machine, for instance an embossing device or unit comprising the roller 101. Reference number 114 indicates a yielding coating, made for instance of rubber, synthetic rubber or the like.
Coupling between the pads 105A, 105B and the hollow cylindrical sleeve 103 is usually a thermal coupling, wherein the sleeve 103 is thermally expanded and the suitably refrigerated pads 105A, 105B, are introduced therein, so that the temperature difference between sleeve 103 and pads 105A, 105B eliminates the reciprocal interference between said members, and allows freely to introduce the pads 105A, 105B inside the cavity 104 of the sleeve 103. When the sleeve 103 and the pads 105A, 105B have again the same temperature, an interference arises between the cylindrical outer surface of the pads 105A, 105B and the cylindrical inner surface of the sleeve 103. The interference is sufficient to torsionally and axially couple the pads 105A, 105B to the sleeve, making them integral with the latter, so that the roller 101, constituted by sleeve 103 and pads 105A, 105B, rotates like a single member. Coupling between the pads 105A, 105B and the sleeve is thus obtained by interference fit.
In other known embodiments, the pads are fastened to the ends of the sleeve by means of bolts.
The pressure between pressure roller and embossing roller causes deflection of these components. In general, in addition to this deflection there is also the bending of the rollers due to their weight. This deflection, with the consequent formation of a camber on the axis of both the pressure roller and the embossing roller, causes an embossing defect. The defect consists in a more marked embossing along the edges and a less marked embossing in the central area of the web material. The defect could be also so significant, that the product cannot be accepted. This is due to the fact that the deflection of the pressure roller and the embossing roller can be significant.
In some cases, to avoid this inconveniency, the pressure roller and the embossing roller are mounted with slightly skewed axes, so as to increase the pressure in the central area of the nip therebetween, thus balancing the deflection. However, this solution has the drawback that it generates transverse forces on the web material and causes rapid wear of the mechanical members.
According to a different approach, a roller is provided comprising a fixed, i.e. non-rotating central shaft, around which a cylindrical mantle rotates. Actuating members are arranged between the fixed shaft and the cylindrical mantle, that are typically actuated by means of a pressurized liquid and deform the cylindrical mantle. The actuating members are aligned to one another along the roller axis and in the plane of the nip between the two rollers co-acting with each other. Solutions of this type are disclosed in US patents 5.897.476 ; 5.599.263 ; 5.103.542 ; 4.856.155 . Practically, when the actuating members are activated, the roller is deformed and takes a "banana" shape. These systems have several drawbacks due to both the mechanical complexity thereof and the high dynamical stresses to which the members forming the roller are subjected, in particular the support bearings and the cylindrical mantle.
To balance the deflection, crowned rollers are often provided, i.e. rollers with a not perfectly cylindrical surface, namely a surface having a gradual change in the diameter of the cross section thereof. More in particular, the diameter of the cross section is greater in the central area and smaller in the end areas. The main limit of this solution is that the crown, i.e. the difference between maximum diameter and minimum diameter of the roller cross section, is fixed; therefore, it can balance the deflection only under one specific operating condition, i.e. only for one value of reciprocal load between the rollers.
In many cases, however, the need arises to change the pressure between pressure roller and embossing roller. It could be necessary, for example, to vary the linear load between pressure roller and embossing roller in order to have different patterns or processing conditions for the material in the nip between the rollers, as well as a different embossing depth. In other cases, it could be necessary to modify the load to process different materials, or to balance a change in the hardness of the yielding coating of the pressure roller caused by the operating temperature. Moreover, different load conditions can be required as the embossing pattern varies. Namely, a denser embossing usually requires a greater load.
If the linear load (kg/cm) applied between pressure roller and embossing roller changes, the crown of the pressure roller surface could be excessive with respect to deflection, thus causing a defect opposite to that caused by deflection, or it could be too small, and thus insufficient to balance the deflection.
Rollers have been therefore developed having a variable crown. An example of a variable crown roller is disclosed in EP1622757 . This embodiment allows to adapt the roller crowning to the working conditions, for instance to changes in the linear load (force per axial length of the roller). However, variable crown rollers are quite complex and expensive.
Other approaches to solve the problems mentioned above are based on the use of rollers comprising an outer sleeve supported on an inner shaft by means of supports mounted deeply inside the sleeve, i.e. between the centerline of the outer sleeve and the ends of the outer sleeve.
WO-A-2009/010999 discloses, for instance, pressure rollers comprising an outer sleeve and an inner shaft. The inner shaft is supported fixed by the flanks of the machine, while the outer sleeve is supported idle on the inner shaft, by means of support bearings arranged deeply inside the sleeve. The sleeve is driven into rotation by means of a suitable motor, in order to rotate around the axis of the respective fixed shaft. As the bearings are arranged inside the sleeve, the construction is complex and difficult to manage, because mounting and lubricating the bearings is difficult.
EP-A-2497633 discloses a pressure roller comprising an outer sleeve supported on an inner shaft. The inner shaft is, in turn, supported on fixed flanks by means of bearings. Both the shaft and the sleeve rotate and are reciprocally fastened at the ends of the sleeve by means of a flexible system, allowing the inner shaft to be deflected, independently of the sleeve, which, basically, has no deflections or has only limited deflections. Spherical joints are mounted inside the sleeve, arranged in an intermediate position between the axial ends of the outer sleeve and the centerline thereof. Also this configuration is complex and expensive, because it requires mounting spherical joints deeply inside the outer sleeve of the roller and providing a deformable mechanical coupling between the inner shaft and the outer sleeve.
Further rollers are disclosed in EP-A-20650602 and DE20319527 .
There is therefore a need for more efficient and less complex solutions for the problems mentioned above due to the deflection of the rollers in the processing machines for web materials.

SUMMARY OF THE INVENTION

In embodiments described herein, a roller is provided comprising a rotation axis, an outer sleeve that is hollow inside, and a pair of side pads inserted in the sleeve. Each pad comprises a support and rotation journal for the roller, and a body integral with the support and rotation journal, which forms a torsional and axial coupling with the outer sleeve. The peripheral surface of the body of each pad, coupled to the outer sleeve, has an axial dimension at least equal to a transverse dimension of the body.
According to some embodiments described herein, a roller is provided to process a continuous web material, for instance a pressure roller, comprising a rotation axis, an outer sleeve having a substantially cylindrical outer surface, an inner surface that defines a hollow inner space, and two axial ends; and a pair of side pads, torsionally and axially coupled to the sleeve so as to rotate integrally therewith, substantially forming, all together, a single body. Each pad comprises a support and rotation journal for the roller, projecting from one of the axial ends of the outer sleeve. Each pad also comprises a body, integral with the support and rotation journal. Suitably, the body is inserted in the hollow inner volume of the outer sleeve and has a peripheral surface in contact with the inner surface of the outer sleeve. This contact is a pressure contact, with reciprocal interference between outer sleeve and body of the pad. The interference provides an axial and torsional coupling between the side pad and the outer sleeve, so that the two side pads rotate integrally with the outer sleeve. The peripheral surface of each body has a dimension in axial direction, i.e. in the direction of the roller axis, at least equal to a transverse dimension of the body. When the outer sleeve has a cylindrical inner surface and also the bodies of the side pads have a peripheral cylindrical surface, the transverse dimension corresponds to the diameter of the peripheral cylindrical surface. Otherwise, "transverse dimension" means the greater dimension of the cross section of the pad body.
It has been surprisingly discovered that, if the coupling surface between the body of the pad and the outer sleeve is sufficiently long in axial direction, and thus extends towards the inside of the outer sleeve and towards the roller centerline, the roller is subjected to a smaller deflection than that of the traditional rollers provided with short pads applied to the ends of the sleeve.
According to advantageous embodiments, the axial dimension of the peripheral surface of the body is at least 1.2, preferably at least 1.5, more preferably at least 1.8 times the transverse dimension of the body of the side pad, for instance equal to, or greater than, 2 times the transverse dimension of said body of the side pad.
Reduced deflections allow providing a very limited crowning of the outer surface of the sleeve, or even no crowning. Moreover, the decreased absolute value of the deflection, i.e. of the camber formed by the axis of the cylindrical outer sleeve of the roller, allows using the same roller, crowned if necessary, also when the load conditions are very variable, without the need for a variable crowning, or for using different rollers with different crowning according to the load conditions.
Substantially, the configuration of embodiments described herein allows to significantly reduce the drawbacks due to the deflection of the roller when loaded (camber), without the need for complex support systems between inner shaft and outer sleeve. In fact, according to the embodiments described herein, the outer sleeve and the end pads forming the support and rotation journals are joined together so as to form a single body, as in the case of simpler rollers according to the prior art (figure 1). However, the particular geometry and the dimensional ratios between outer sleeve and pads allow to limit or overcome the drawbacks due to an excessive deflection of the roller axis.
To achieve particularly efficient results in terms of deflection reduction, each support and rotation journal has a diameter smaller than the transverse dimension of the respective body of the side pad. Moreover, between the body of the side pad and the respective support and rotation journal a connecting portion is comprised, having a transverse dimension that is smaller than the transverse dimension of the body of the side pad, but greater than the diameter of the support and rotation journal. In this way, the resistant section of the side pads is increased, and they are subjected to limited deflections even when their axial dimension is particularly long to allow the respective body to be inserted deeply inside the sleeve, i.e. at a distance from the respective end of the sleeve.
The cross-section of the connecting portion may have constant dimension, for instance circular in shape. In this case, the connecting portion has a substantially cylindrical shape. In other embodiments, the connecting portion may have a tapered shape, wherein the cross section thereof gradually decreases from the inside of the sleeve, where the respective body of the side pad is located, towards the end of the sleeve. In this case, the connecting portion may be shaped substantially like a truncated cone. It is also possible to have mixed connecting portions, having cylindrical segments and segments shaped like a truncated cone.
In advantageous embodiments, the connecting portion is substantially integrally housed inside the outer sleeve. Preferably, each connecting portion extends almost up to the end of the sleeve, while the support and rotation journals extend outside the sleeve.
According to some embodiments, the connecting portion may have a transverse dimension equal to at least 2, preferably to at least 2.5 times the diameter of the support and rotation journal. When the support and rotation journal and/or the connecting portion have a cross section with a variable dimension, the above mentioned dimensional ratio refers to the minimal values of the diameter of the support and rotation journal and of the transverse dimension of the connecting portion. These dimensional ratios allow a high resistant section, and therefore a decreased deflection of the connecting portions. These latter may have a great length, to allow the bodies of the side pads to be deeply inserted in the inner volume of the sleeve, without excessive deflections.
In advantageous embodiments, each side pad is inserted and housed inside the hollow volume of the outer sleeve at such a depth that the distance between the body of the side pad and the respective axial end of the outer sleeve is equal to at least 1, preferably to at least 1.2, more preferably to at least 1.5 times, for instance 2 times the transverse dimension of the body of the side pad. This allows the outer sleeve to be supported by the respective side pads in an area nearer the roller centerline, furthermore reducing the overall deflection of the roller. When, between the body of each side pad and the respective support and rotation journal, a connecting portion is comprised having a transverse dimension (constant or axially variable) smaller than the transverse dimension of the body of the side pad, the axial length of this connecting portion may be equal to the above mentioned distance between body and end of the sleeve. In this way, roller resistance and flexural stiffness are optimized.
In some embodiments, the dimension in the axial direction of the body of each pad and the position thereof inside the outer sleeve are such that the reciprocal distance between the bodies of the side pads (i.e. between the end surfaces, facing each other, of the bodies of the side pads) is smaller than the transverse dimension of the bodies of the side pads, and preferably smaller than 1/2, more preferably smaller than 1/5, and more preferably equal to or smaller than 1/10 of the transverse dimension of the bodies of the side pads.
To make the overall structure of the roller lighter, the bodies of the side pads may be hollow inside.
If necessary, the outer surface of the outer sleeve may have a crowning, i.e. it may have a cross section whose diameter slightly varies from the center (maximum diameter) to the ends (minimum diameter).
Rollers configured as described above can be advantageously used as pressure rollers or laminating rollers in embossing or embossing-laminating devices. In this case, the outer surface of the outer sleeve may be formed by a layer of elastically yielding material, preferably an elastomeric material. In some embodiments, the hardness of the elastically yielding material may be comprised between about 40° Shore A and about 70° Shore A, preferably between about 50° Shore A and about 60° Shore A . In other embodiments, the hardness of the yielding material may be comprised between 40° and 80° Shore D.
According to a further aspect, a device is described to process a continuous web material, comprising at least a first roller configured as described above, arranged along a feeding path for the web material. Advantageously, the roller co-acts with a second roller, forming a nip therewith, through which the path for the web material extends.
In some embodiments, the first roller is a pressure roller or a laminating roller, the second roller is an embossing roller, and the device is an embossing or an embossing-laminating device.
Also the second roller may be configured as described above, to reduce the deflection thereof. In this case, eliminating the deflection of the pressure roller and the embossing roller, which are of concern for the embossing result, and increasing the pressure between the rollers, the camber at the center of the rollers is not increased.
The roller, or both the first and second rollers, may be supported by flanks through, possibly self-aligning bearings, which allow the deflection of the support and rotation journals. One of said first and second rollers may be motorized. The other roller may also be motorized, or it may be driven into rotation by the friction with the motorized roller.
For example in the case of embossing units, the pressure roller, preferably coated with elastically yielding material, may be driven into rotation by the friction between the pressure roller and the embossing roller, which is motorized. Furthermore, the device may have actuators to modify the pressure of the two rollers against each other.
The embossing unit may also comprise one or more laminating rollers. The laminating rollers can co-act with one or more embossing rollers. The laminating roller(s) may be configured as described above and may be coated, if necessary, with an elastically yielding material. The laminating rollers may be motorized or driven into rotation by friction between the laminating roller and the corresponding embossing roller.
In advantageous embodiments, one or more pressure rollers and/or laminating rollers may be associated with pressure actuators, which can be controlled to change the force applied between pressure roller, or laminating roller, and embossing roller. For example, the applied load may be such as to generate a linear load comprised between 5 and 100 kg/cm, preferably between 10 and 70 kg/cm. The indicated values are typical for tissue paper processing, but they have been indicated just by way of non-limiting example.
Features and embodiments are disclosed here below and are further set forth in the appended claims, which form an integral part of the present description. The above brief description sets forth features of the various embodiments of the present invention in order that the detailed description that follows may be better understood and in order that the present contributions to the art may be better appreciated. There are, of course, other features of the invention that will be described hereinafter and which will be set forth in the appended claims. In this respect, before explaining several embodiments of the invention in details, it is understood that the various embodiments of the invention are not limited in their application to the details of the construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception, upon which the disclosure is based, may readily be utilized as a basis for designing other structures, methods, and/or systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by following the description and accompanying drawing, which shows non-limiting practical embodiments of the invention. More particularly, in the drawing:

figure 1 illustrates a longitudinal sectional view of a pressure roller according to the prior art for an embossing unit or the like;
figure 2 illustrates a schematic side view of an embossing-laminating unit, where the rollers described herein can be used;
figure 3 is a longitudinal sectional view of a pressure roller according to a first embodiment;
figure 4 is a longitudinal sectional view of a pressure roller according to a further embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

The following detailed description of exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Additionally, the drawings are not necessarily drawn to scale. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.
Reference throughout the specification to "one embodiment" or "an embodiment" or "some embodiments" means that the particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase "in one embodiment" or "in an embodiment" or "in some embodiments" in various places throughout the specification is not necessarily referring to the same embodiment(s). Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
Figure 2 shows an embossing-laminating unit, indicated as a whole with number 1 and comprising a plurality of rollers, one or more of which can be configured as described herein.
The embossing-laminating unit may comprise a first pressure roller 3 co-acting with a first embossing roller 5. An embossing nip 6 is provided between the first pressure roller 3 and the first embossing roller 5. A first ply V1 of web material, for example tissue paper, is fed along a feeding path extending around the pressure roller 3 and through the embossing nip 6, so that the protuberances 5P provided on the cylindrical surface of the embossing roller 5, by penetrating the elastically yielding coating 3R of the pressure roller 3, permanently deform the ply V1, thus forming embossing protuberance thereon. The pressure roller 3 may be pressed against the embossing roller 5 by means of an actuator 7.
Furthermore, the embossing-laminating unit 1 may have a second pressure roller 9, provided with an elastically yielding coating 9R, for instance made of rubber, synthetic rubber or the like, co-acting with a second embossing roller 11 provided with embossing protuberances 11P. A second embossing nip 10 is defined between the second pressure roller 9 and the second embossing roller 11; through the nip 10 a feeding path extends for a second ply V2, driven around the pressure roller 9 and passing through the embossing nip 10, where it is embossed due to the protuberances 11P penetrating the elastically yielding coating 9R of the pressure roller 9. Reference number 13 indicates an actuator that can generate the pressure at which the pressure roller 9 is pressed against the embossing roller 11.
Reference numbers 15 and 17 schematically indicate motors that drive the two embossing rollers 5 and 11 into rotation, through suitable belts 16, 18.
In a known manner, on the protuberances generated on the ply V1 a glue can be applied by means of a glue dispenser 21, provided with a glue tank 23, a screen roller 25 and an application roller 27.
In the embodiment shown in figure 2, the ply V2, embossed in the embossing nip 10, is moved away from the second embossing roller 11 and put onto the ply V1 driven around the first embossing roller 5, so that the two plies can be glued together by lamination in a laminating nip defined between the first embossing roller 5 and a laminating roller 29. The bonded plies form a continuous multi-ply material N. The laminating roller 29 may be pressed against the outer surface of the first embossing roller 5 by means of an actuator 31. In other embodiments, the two plies V1 and V2 may be bonded by lamination in the nip 8 defined between the first embossing roller 5 and the second embossing roller 11, to form the multi-ply material N. In this case, the two embossing rollers 5 and 11 are pressed against each other. The laminating roller 29 can be omitted or put in idle position.
The embossing-laminating unit or device 1 described above is well known.
The force of the pressure rollers 3 and 9 against the respective embossing rollers 5 and 9 can be changed, for instance according to the embossing pattern, the type of embossed web material, the operating conditions (temperature) and other parameters.
Due to their own weight and the pressure between each pressure roller 3, 9 and th respective embossing roller 5, 11, the rollers 3, 5, 11, 9 may be subjected to deflection. This results in a camber from the axis of the respective roller. The deflection results in lack of uniformity in the processing of the web material V1 or V2. In fact, in case of no deflections, the contact area between embossing roller and respective pressure roller has a substantially rectangular elongated profile. The greater dimension corresponds to the axial dimension of the rollers. The smaller dimension depends on the deformation by crushing, in particular of the yielding material of the pressure roller coating. Due to this deformation by crushing, the contact is not linear as it would be if the roller surfaces would not be deformed by crushing.
Due to the deflection, if any, and the consequent camber, the contact surface tends to take a rectangular shape, wherein the longer sides, i.e. the sides parallel to the axis of the rollers, are curved, with a concavity facing the outside of the contact area. In other words, the contact area tends to decrease in the central area.
In some embodiments, to reduce deflection of the pressure roller 3 and/or of the pressure roller 11, particularly shaped and sized pads are used in combination with an outer cylindrical sleeve forming the outer surface of the pressure roller 3 or 9. Figure 3 shows a schematic longitudinal sectional view of a pressure roller according to a possible embodiment. In particular, figure 3 shows an embodiment of the pressure roller 3, but it should be understood that the pressure roller 9 and/or the laminating roller 29 may have the same structure as the pressure roller 3 illustrated in figure 3 or an equivalent configuration. Figure 3 shows also flanks 33A, 33B of the embossing-laminating unit 1, onto which the rollers of the unit are supported by means of bearings.
In the embodiment of figure 3, the pressure roller 3 comprises a substantially cylindrical outer sleeve 35, whose outer surface is indicated with 35A. Apart from any crowning made to the outer surface 35A during the production thereof, the outer surface is substantially cylindrical. A-A indicates the geometrical axis of the outer sleeve 35. Reference numbers 35X, 35Y indicate the axial ends of the sleeve.
The outer sleeve 35 may have a core 37, and an outer coating 3R defining the substantially cylindrical outer surface 35A of the outer sleeve 35. The core 37 can be made of steel or other metal. The outer coating 3R can be made of a yielding material, for instance an elastically yielding material, such as natural or synthetic rubber. In other embodiments, the outer sleeve 35 can comprise a single metal layer, or a double layer made of different metals. The outer sleeve 35 may also be configured differently, according to the different use of the roller 3. The outer sleeve 35 is hollow inside; the inner hollow volume thereof is indicated with 39.
Two pads 40A and 40B are inserted inside the inner hollow volume 39 of the outer sleeve 35. Each pad 40A, 40B has a main body 41A, 41B and a support and rotation journal 43A, 43B. As shown in the drawing, the main body 41A, 41B of each pad 40A, 40B is completely inserted inside the outer sleeve 35, so that between the main body 41A, 41B of each pad 40A, 40B and the corresponding end edge of the outer sleeve 35 there is a distance A2. A connecting portion 47A, 47B may be provided between each main body 41A, 41B and the respective support and rotation journal 43A, 43B. In other embodiments, the support and rotation journals 43A, 43B may be directly coupled to the main bodies 41A, 41B of the pads 40A, 40B. In the embodiment of figure 3, the connecting portions 47A, 47B have a substantially cylindrical shape, similarly to the pads 41A, 41B, and an outer diameter smaller than the outer diameter of the main bodies 41A, 41B.
The main body 41A, 41B of each pad 40A, 40B has an outer surface 42A, 42B adhering to the inner surface 35B of the outer sleeve 35. The coupling between the pads, or, more precisely, between them main bodies 41A, 41B thereof, and the outer sleeve 35 may be a thermal coupling, i.e. an interference fit, as described above with reference to the embodiment of figure 1. To this end, the outer surface of the main bodies 41A, 41B of the pads 40A, 40B may be substantially cylindrical or may have, anyway, the same shape as the inner surface 35B of the outer sleeve 35.
The main bodies 41A, 41B of the pads 40A, 40B may have a transverse dimension D1 and an axial dimension A1, i.e. a length A1 in the direction of the rotation axis A-A of the pressure roller 3. If the main bodies 41A, 41B of the pads 40A, 40B are cylindrical, the diameter dimension D1 is represented by the respective diameter.
In advantageous embodiments, the axial dimension A1 is at least equal to the transverse dimension D1, i.e. to the diameter of the main body 41A, 41B of the pad 40A, 40B. Preferably, the axial dimension A1 is substantially greater than the diameter dimension D1. In some embodiments, the axial dimension A1 is equal to at least 1.2, preferably to at least 1.5, more preferably equal to or greater than 2 times the diameter or transverse dimension D1 of the pad. In some embodiments, the axial dimension A1 may be equal to, or greater than 1.8, preferably equal to or greater than 2 times the diameter dimension D1 of the main body 41A, 41B of the pad 40A, 40B.
The connecting portions 47A, 47B may have a transverse dimension D2 smaller than the transverse dimension D1 of the bodies of the pads 41A, 41B, so that no interference occurs between the side surfaces of the connecting portions 47A, 47B and the inner surface 35B of the outer sleeve 35.
The diameter dimension D2 of the connecting portions 47A, 47B may be substantially greater than the diameter dimension D3 of the support and rotation journals 43A, 43B.
In some embodiments, the diameter dimension D2 of the connecting portions 47A, 47B is equal to at least 2, and preferably at least 2.5 times the diameter of the support and rotation journal 43A, 43B, indicated with D3 in figure 3. When (as in the illustrated case) the support and rotation journal 43A, 43B has a variable diameter dimension, i.e. a cross section that is not constant along the extension thereof, the diameter dimension D3, acting as a reference for defining the dimensional ratio between diameter dimension of the support and rotation journal and diameter dimension of the connecting portion 47A, 47B, is the minimum diameter of the support and rotation journal 43A, 43B.
Each support and rotation journal 43A, 43B of the pads 40A, 40B is engaged in a respective support, for instance a rolling bearing 45A, 45B. The bearings 45A, 45B may be mounted in the flanks 33A, 33B of the embossing-laminating unit 1.
In advantageous embodiments, the bearings 45A, 45B may be self-aligning bearings, so as to allow a deflection of the pressure roller 3 resulting in a flexion of the rotation axis A-A, as schematically indicated by the dashed line A'-A' in figure 3. The deflection of the pressure roller 3 occurs almost only on the pads 40A, 40B and in particular on the support and rotation journals 43A, 43B, while the outer sleeve 35 remains substantially rectilinear. In other words, the applied load causes a deflection of the pads, whose axis bends in A'-A', forming a camber which can be significant. Vice versa, the outer sleeve 35 is subjected to a very limited deflection, and lower by about one order of magnitude with respect to the deflection of the rollers according to the prior art illustrated in figure 1. The use of support bearings capable of pivoting in the plane of the axis A'-A' allows the journals to bend also significantly, without generate excessive constraint reactions.
In some embodiments, the connecting portions 47A, 47B may extend axially up to the end 35X, 35Y of the outer sleeve 35 or even slightly outside of the outer sleeve 35. On the opposite side, i.e. towards the inside of the outer sleeve 35, the connecting portion 47A, 47B may extend for a variable entity, depending on the overall lenght L of the roller 3 and on the axial dimension A1 of the peripheral surfaces 42A, 42B of the main bodies 41A, 41B of the pads 40A, 40B, as well as on the reciprocal distance "d" between the ends of the main bodies 41A, 41B of the pads 40A, 40B. The distance d may be substantially smaller than that occurring in rollers of the current art. In some embodiments, the reciprocal distance d between the two pads 40A, 40B is equal to, or lower than the transverse dimension D1 of the main bodies 41A, 41B of the pads 40A, 40B. The distance d may be, for example, equal to, or lower than, 1/2 of the transverse dimension D1, preferably equal to, or lower than, 1/5 of the transverse dimension D1.
Practically, the distance "d" is advantageously smaller than the distance A2 between each main body 41A, 41B and the corresponding end of the outer sleeve 35, i.e., more precisely, between the end face of the main body 41A, 41B, facing the corresponding end of the outer sleeve 35, and the end of the outer sleeve 35.
With this arrangement, inside the outer sleeve 35 a support is formed, defined by the peripheral surface 42A, 42B of the main bodies 41A, 41B of the pads 40A, 40B, and extending up to near the centerline M of the pressure roller 3. Having the support area for the outer sleeve 35 so inside the same outer sleeve, it is therefore possible to reduce the deflection, to which the outer sleeve 35 of the roller 3 is subjected due to the weight thereof and the stress applied to press the pressure roller 3 against the corresponding embossing roller 5.
Experiments proved that, given the same outer diameters of the rollers and under same operating conditions, i.e. linear load applied between pressure roller and embossing roller, the deflection of the roller according to figure 3 is smaller, by about one order of magnitude, than the deflection of a pressure roller according to figure 1.
The table below summarizes the deflections detected on the sleeves 35 for different loads (in the first column) in a roller of the current art (second column) and in a roller according to figure 3 (third column). The deflection, in mm, is given by the camber generated at the centerline of the pressure roller 3:

Load (kg/cm) Roller (Fig. 1) (mm) Roller (Fig. 3) (mm)

50 0.270 0.037

40 0.220 0.030

30 0.166 0.022

20 0.111 0.015

10 0.055 0.007
As it is clearly apparent from the table above, as the linear load changes from 10 to 50 kg/cm, the camber, i.e. the deflection of the pressure roller 3, increases by about 5 times in both cases. However, the absolute value of the deflection is smaller by one order of magnitude in the case of the roller according to the configuration of figure 3. This allows not only to reduce the defects resulting from deflection, but also allows to use a single crowning value for the pressure roller 3 to balance the defect resulting from deflection.
In fact, moving from a 10 kg/cm load to a 50 kg/cm load, the variation of the absolute value of the camber is equal to 0.03 mm in a roller according to figure 3. Vice versa, in a roller according to the prior art, moving from a 10 kg/cm load to a 50 kg/cm load, the variation of the camber is equal to 0.22 mm. This variation forces to change the crowning of the roller, as the load changes. This change in the crowning requires to use a variable crowning roller, as disclosed in the prior art documents mentioned above, and, in particular, in EP 1622757 , this roller having a complex structure and being expensive. Alternatively, it is necessary to have pressure rollers with different crowning to be used based on the different loads. This means high costs, the need for storing unused rollers, as well as long and complex operation for replacing the rollers.
Vice versa, the roller according to figure 3 allows to suitably balance the deflection by means of an average crowning, that is sufficient and not excessive for any load, thanks to the reduced deflection of the pressure roller 3 and, above all, the small change, in absolute value, of the camber resulting from this deflection.
Figure 4 illustrates a further embodiment of a pressure roller 3. Equal numbers indicate equal or equivalent parts to those described above with reference to figure 3. These elements will not be described again.
The difference between the pressure roller 3 of figure 3 and the pressure roller 3 of figure 4 is that the connecting portions 47A and 47B of each pad 40A, 40B are substantially shaped like a truncated cone, with a diameter dimension that can vary from a value D2 to a value D4.
Usually, the use of connecting portions 47A, 47B with cross section greater with respect to the support and rotation journals 43A, 43B, allows to reduce the overall deflection of the pads 40A, 40B, and therefore the slanting of the roller axis A-A in the plane containing the axis, thanks to the greater resistant section of the major part of the axial extension of the pads 40A, 40B.
In advantageous embodiments, to make the overall structure of the pressure roller 3 lighter, taking into account the great axial extension of the pads 40A, 40B, said pads may have a lightening inner cavity 50A, 50B extending from the faces of the main bodies 41A, 41B of the pads 40A, 40B, facing each other and contained inside the outer sleeve 35, up to near the support and rotation journals 43A, 43B. The cavities 50A, 50B are shown in the cross section of figure 3. While they are not visible, but can be present, in the configuration of the pressure roller 3 of figure 4. The structure described above for the pressure roller 3 can be used for the pressure roller 9 and, if necessary, for the laminating roller 29, if any. In some cases, the outer coating 3R of the outer sleeve 35 can be omitted and replaced with a metal outer surface.
In some embodiments, also the embossing rollers 5 and 11 may have a structure similar to the one described above for the pressure rollers 3 with reference to figures 3 and 4.
The structure described above for the pressure roller may be used, in general, also for other rollers subjected to an either uniform or concentrated deflection load. The described structure may be used, for example, in calender rollers. In the specific case of paper converting machines, in particular of machines for tissue paper converting, the described structure may be advantageously used also to produce counter-rollers for ply-bonding units, wherein a series of ply-bonding wheels press against the counter-roller to mechanically bond to one another paper plies passing through ply-bonding rollers and counter-roller. In this case, the counter roller is subjected to concentrated loads, applied in several positions along the axial extension thereof, which can result in deflection. This deflection is reduced, for the outer surface of the counter-roller, by arranging pads deeply inside the sleeve, as described above.
While the particular embodiments of the invention described above have been shown in the drawing and described integrally in the description above with features and characteristics relating to different example embodiments, those skilled in the art will understand the modifications, changes and omissions are possible without however departing from the innovative learning, the principles and the concepts described above and the advantages of the object described in the attached claims. Therefore, the scope of the invention described shall be determined only based upon the widest interpretation of the attached claims, so as to understand all the modifications, changes and omissions.

Claims

A roller (3) for processing a continuous web material, comprising:
a) a rotation axis (A-A);

b) an outer sleeve (35) having an outer substantially cylindrical surface (35A), an inner surface (35B) that defines a hollow inner space, and two axial ends (35X, 35Y);

c) a pair of side pads (40A, 40B), each side pad comprising:
- a support and rotation journal (43A, 43B) for the roller (3), projecting from a respective axial end of the outer sleeve;

- a body (41A; 41B) integral with the support and rotation journal (43A, 43B) and inserted in the hollow inner space of the outer sleeve (35), said body (41A, 41B) having a peripheral surface in contact with the inner surface (35B) of the outer sleeve (35), providing an axial and torsional constraint between the side pad and the outer sleeve (35), so that the two side pads (40A, 40B) rotate integral with the outer sleeve (35);

wherein: the peripheral surface (42A, 42B) of each body (41A, 41B) has an axial dimension equal to at least a transverse dimension of the body; characterized in that each support and rotation journal (43A,43B) has a diameter smaller than the transverse dimension of the respective body (41A, 41B) of the side pad (40A, 40B); and in that between the body (41A, 41B) of the side pad (40A, 40B) and the respective support and rotation journal (43A, 43B9 there is comprised a connecting portion (47A, 47B) having a transverse dimension that is smaller than the transverse dimension of the body (41A, 41B) of the side pad (40A, 40B) but greater than the diameter of the support and rotation journal (43A, 43B).
Roller (3) according to claim 1, wherein the inner surface (35B) of the outer sleeve (35) is cylindrical and the body of each side pad (40A, 40B) is cylindrical, said transverse dimension being the diameter of the body (41A, 41B).
Roller (3) according to claim 1 or 2, wherein said connecting portion (47A, 47B) is integrally housed inside the outer sleeve (35).
Roller (3) according to one or more of the preceding claims, wherein said connecting portion (47A, 47B) has a minimum transverse dimension at least twice, preferably 2.5 times, the diameter of the support and rotation journal (43A, 43B).
Roller (3) according to one or more of the previous claims, wherein the dimension in the axial direction of the peripheral surface(42A, 42B) of the body (41A, 41B) is equal at least 1.2, preferably at least 1.5, more preferably at least 1.8 times the transverse dimension of the body (43A, 43B) of the side pad (40A, 40B).
Roller (3) according to one or more of the previous claims, wherein the body of each side pad (40A, 40B) is completely inserted inside the hollow space of the outer sleeve (35), distanced from the respective axial end (35X, 35Y) of the outer sleeve (35).
Roller (3) according to claim 6, wherein the distance between the body (41A, 41B) of each side pad (40A, 40B) and the respective axial end (35X, 35Y) of the outer sleeve (35) is equal to at least 1, preferably at least 1.2, more preferably at least 1.5, and even more preferably at least 2 times the transverse dimension of the body (41A, 41B) of the side pad (40A, 40B).
Roller (3) according to one or more of the previous claims, wherein the dimension in the axial direction of the body (41A, 41B) of each side pad (40A, 40B) and the position thereof inside the outer sleeve (35) are such that the reciprocal distance between the side pads (40A, 40B) is smaller than the transverse dimension of the bodies (41A, 41B) of the side pads (40A, 40B), and preferably smaller than 1/2, more preferably smaller than 1/5, and more preferably equal to or smaller than 1/10 of the transverse dimension of the bodies of the side pads (40A, 40B).
Roller (3) according to one or more of the previous claims, wherein the body (41A, 41B) of each side pad (40A, 40B) is inserted inside the hollow space of the outer sleeve (35) at a distance from the respective axial end (35X, 35Y) of the outer sleeve (35); and wherein the reciprocal distance between the bodies (41A, 41B) of the side pads (40A, 40B) is shorter than the distance of the body (41A, 41B) of each side pad (40A, 40B) from the respective end (35X, 35Y) of the outer sleeve (35).
Roller (3) according to one or more of the previous claims, wherein the bodies (41A, 41B) of the side pads (40A, 40B) are hollow inside.
Roller (3) according to one or more of the previous claims, wherein the outer surface of the sleeve (35) has a crown.
Roller (3) according to one or more of the previous claims, wherein the outer surface (35A) of the sleeve (35) is formed by a layer of elastically yielding material, preferably an elastomeric material.
A device (1) to process a continuous web material (V1, V2, N), comprising at least a first roller (3) configured according to one or more of the previous claims, arranged along a feeding path for the web material.
Device (1) according to claim 13, wherein said first roller (3) co-acts with a second roller (5), forming a nip (6) therewith, through which the path for the web material extends.
Device (1) according to claim 14, wherein the second roller (5) is configured according to one or more of claims 1 to 12.
Device (1) according to claim 14 or 15, wherein said second roller (5) is an embossing roller, having a substantially cylindrical outer surface provided with a plurality of embossing protuberances (5P).
Device according to one or more of claims 13 to 16, wherein said first roller (3) is supported by means of self-aligning bearings.