Embosser with control of the approaching of pressure rollers and method

Abstract

The embosser comprising a first embossing roller, supported on a stationary load-bearing structure, and a first functional roller cooperating with the first embossing roller and defining with the first embossing roller a first nip through which a feed path for a first ply of web-like material extends. The first functional roller is supported on the stationary load-bearing structure at a first axial end by a first movable load-bearing member and at a second axial end by a second movable load-bearing member. An arrangement of approaching actuators, force transducers and position transducers serves to correctly position the functional roller with respect to the embossing roller at the start of a production cycle.

Description

EMBOSSER WITH CONTROL OF THE APPROACHING OF PRESSUREROLLERS AND METHODDESCRIPTIONTECHNICAL FIELD

[0001] The present disclosure relates to the field of machines for converting of web-like materials. Embodiments described herein relate in particular to machines for converting of paper, and in particular what of is called tissue paper, for the production of toilet paper, paper towels, tissues and paper napkins and similar products.

[0002] Specifically, improvements to embosser or embosser-laminator units for the converting of a multi-ply web-like material, especially into tissue paper, are disclosed herein.BACKGROUND ART

[0003] Items made of cellulosic material, for example toilet paper rolls, paper towel rolls, tissues and paper napkins, are produced using a cellulosic web-like material, typically tissue paper, fed by one or more parent reels wound in a continuous production machine.

[0004] In some cases, the parent reels are unwound and rewound into reels or rolls of smaller diametrical and / or axial dimensions into what are called slitter-rewinders or in what are called rewinders.

[0005] The reels coming from the continuous machine or from the slitter-rewinder are intended to feed converting lines for the production of items intended for consumption, for example napkins, tissues or rolls of toilet paper, paper towels and similar.

[0006] The converting line usually contains an unwinding station, adapted to unwind one or more reels of cellulosic web-like material. One or more plies of cellulosic web-like material are fed, along the same path or along separate paths, to machines placed along the converting line downstream of the unwinding station, to undergo one or more converting operations, to finally obtain the products intended for sale and consumption.

[0007] Typically, a converting line comprises, downstream of the unwinding station, at least one embosser unit, which carries out an embossing operation on one or more plies forming the continuous cellulosic web-like material. The embossing consists of a permanent deformation of the cellulosic web-like material by passing the cellulosic web-like material into an embossing nip defined between an embossing roller, provided with embossing protuberances, and a pressure roller. The embossing roller is usually a roller made entirely of steel or having at least one external jacket made of steel, or other hard material, provided with said embossing protuberances. The pressure roller is a roller which can have a hard, engraved outer surface with engravings complementary to the embossing protuberances of the embossing roller. In more widespread embodiments, the pressure roller has a smooth outer surface, where smooth is intended as a surface generally free of engravings or protuberances, formed by a yielding layer, preferably elastically yielding.

[0008] In this context, "elastically yielding" means a material which deforms elastically under normal conditions of use of the embosser. In particular, the elastically yielding coating of the pressure roller is a material into which the embossing protuberances of the embossing roller penetrate due to elastic deformation. The "hard" material with which the embossing roller is made is a material which that does not undergo deformations, or in any case undergoes negligible and non-significant deformations, under normal conditions of use.

[0009] In use, the pressure roller and the embossing roller are pressed against each other in the embossing nip. If the pressure roller is coated with a yielding material, the pressure between the embossing roller and the pressure roller is such as to cause at least a partial penetration of the embossing protuberances of the embossing roller into the yielding coating of the pressure roller, while the embossing roller and the pressure roller rotate in opposite directions at substantially the same peripheral speed. This causes the permanent deformation of the web-like material which is fed through the embossing nip at an advancement speed substantially equal to the peripheral speed of the embossing roller and the pressure roller.

[0010] In some cases, the converting line can comprise an embosser unit having a single embossing roller and a single pressure roller, which form a nip through which the web-like material passes, which can consist of one or more plies of cellulosic fi-bres.

[0011] More frequently, the converting line can comprise an embosser unit with more than one embossing roller, each cooperating with a respective pressure roller, so as to separately emboss two plies of cellulose fibres, each of which can in turn be made of one or more layers of cellulosic fibres. An embosser unit of this type is more specifically called "embosser-laminator unit", as it comprises a lamination system, where the two (or more) separately embossed plies are bonded together by means of the application of a functional fluid, by means of mechanical ply-bonding, or in other manner. The laminating system can comprise, for example, a laminating nip defined between two opposite and counter-rotating embossing rollers, or a laminating nip defined between an embossing roller and a laminating roller. The result is a multi-ply embossed cellulosic web-like material.

[0012] In some embodiments, bonding of the plies in the embosser-laminator unit occurs using a glue, which can be in aqueous suspension. More in general, a functional fluid can be used, typically a functional liquid. In some cases the functional fluid can be simply water, without the addition of glue. The functional fluid has the function of promoting the formation of hydrogen bonds between the fibres of the cellulosic layers. Therefore, in the present context "functional fluid" means a generic fluid which, applied as described below, contributes to bonding the plies. The functional fluid is, in this sense, a glue and therefore (unless otherwise indicated) the term glue in the present description and in the claims indicates a fluid, typically in the liquid state, which acts as a functional fluid adapted to obtain, facilitate or promote the joining of cellulosic plies.

[0013] The embossed cellulosic web-like material which exits from the embosser unit is further converted in converting stations downstream of the embosser unit, for example wound in logs, i.e., rolls with a diameter equal to the diameter of the finished rolls and an axial length which is a multiple of the axial dimension of the finished rolls. The logs are then cut into individual rolls, which are subsequently packaged for transport and distribution. In this case a rewinder is placed in the converting station.

[0014] In other converting lines, a converting station is arranged downstream of the embosser unit, which comprises an interfolding machine, or a cutting and foldingmachine, to produce paper napkins or tissues or logs of napkins or tissues, which can possibly be interfolded together (in the case of interfolding machines). The logs or stacks of napkins or tissues are also subsequently cut into individual packets, which are then wrapped for marketing.

[0015] One of the critical aspects in managing the embosser is controlling the cooperation between the embossing roller and the pressure roller, i.e., the roller which presses against the embossing roller to generate the protuberances in the ply of weblike material which passes in the nip between the embossing roller and the pressure roller. The embossing depth, i.e., the height of the embossed protuberances generated in the ply of cellulosic material, must be correctly set to obtain the required characteristics in the finished web-like material. In particular, the embossing depth must be sufficient to obtain a product with an adequate apparent thickness and an optimal aesthetic appearance, characterised by the embossing patterns. The softness and absorption capacity characteristics can also be influenced by the embossing depth, which must therefore be controlled and correspond to the desired value.

[0016] As mentioned, some embossers provide two or more pairs of rollers consisting of an embossing roller and a corresponding pressure roller. Each embossing roll- er / pressure roller pair embosses a respective ply of web-like material. The two embossed plies must then be bonded together. Bonding is obtained by applying a functional liquid, for example a glue, to at least some of the tops (i.e., the head surfaces) of the protuberances of one of the embossed plies. In some cases, the two embossed plies are then overlapped and laminated, to exert a pressure between the two plies at the areas where the functional fluid was applied.

[0017] In some embossers of this type, also known as embossers-laminators, as they perform an embossing operation and a laminating operation, the two embossed plies are laminated in a nip defined between one of the two embossing rollers and a laminating roller.

[0018] In some cases, one of the two plies is not embossed and is bonded by means of lamination to an embossed ply.

[0019] In any case, when a laminating roller is present, the laminating pressure must be correct in order to obtain a quality finished product.

[0020] In general, the pressure rollers are coated with an elastically yielding material, such as natural or synthetic rubber. Similarly, in some cases the laminating rollers are also coated with elastically yielding material, such as natural or synthetic rubber, usually harder than the elastically yielding material used for the pressure roller coatings.

[0021] Yielding material coatings are subject to wear due to the pressure against the embossing roller. This causes a gradual change in the diameter of the pressure rollers and the laminating rollers.

[0022] It is therefore necessary to precisely adjust the position of the pressure roller and / or of the laminating roller with respect to the corresponding embossing roller, so as to obtain correct embossing and correct lamination.

[0023] In general, when starting each production cycle it is necessary to correctly set the relative position between the embossing roller and the pressure roller or laminating roller.

[0024] According to one aspect, an embosser is proposed herein which solves the problem of an easy, precise and correct positioning of a pressure roller and / or of a laminating roller with respect to a corresponding embossing roller.SUMMARY

[0025] According to one aspect, an embossing unit is disclosed , also simply referred to hereinafter as “embosser”, comprising a first embossing roller, supported on a stationary load-bearing structure, and a first functional roller cooperating with the first embossing roller and defining with the first embossing roller a first nip, through which a feed path of a first ply of web-like material extends. The first functional roller is supported on the stationary load-bearing structure at a first axial end by a first movable load-bearing member, and at a second axial end by a second movable loadbearing member. A first actuator for approaching the first functional roller to the first embossing roller is associated with the first movable load-bearing member and a second actuator for approaching the first functional roller to the first embossing roller is associated with the second movable load-bearing member. The two actuators allow to approach the functional roller to the embossing roller or distance it therefrom.

[0026] A first position transducer associated with the first axial end of the first functional roller and a second position transducer associated with the second axial end of the first functional roller are adapted to detect a displacement of the first functional roller with respect to the first embossing roller.

[0027] A first force transducer of the first functional roller, associated with the first axial end of the first functional roller and a second force transducer associated with the second axial end of the first functional roller are adapted to detect a contact condition between the first functional roller and the first embossing roller when the first functional roller is approached to the first embossing roller by the first approaching actuator and the second approaching actuator.

[0028] The first functional roller can be a pressure roller which has the function of embossing a ply of continuous web-like material in the nip formed between the first embossing roller and the first functional roller. In other embodiments, the first functional roller can be a laminating roller, adapted to laminate together a first ply of web-like material and a second ply of web-like material in a laminating nip formed by the functional roller and the embossing roller.

[0029] In general, the arrangement allows to adjust the initial position of the functional roller relative to the embossing roller, for optimum embossing and / or lamination of the web-like material, through control of the embossing and / or lamination by means of a position control of the functional roller.

[0030] In some embodiments, the embosser can comprise a second embossing roller or even more than two embossing rollers, each combined with a pressure roller. One or more of such further embossing rollers can constitute functional rollers in the sense mentioned above, and thus be equipped with arrangements for transducing the position and contact force, as well as with approaching actuators acting on movable support members.

[0031] In some embodiments, the movable load-bearing members each comprise a pivoting arm, hinged to the fixed load-bearing structure about a pivoting hinge. Each pivoting arm can also be hinged around a further hinge to the respective actuator, for example to a rod or a cylinder of a hydraulic or pneumatic cylinder-piston actuator, which is also hinged (at the opposite end) to the fixed load-bearing structure.

[0032] As will be clear from the following description, more than one functional roller can be provided, for example a first pressure roller and a second pressure roller and / or a laminating roller, cooperating with the first embossing roller and / or with a second embossing roller. Each functional roller can be mounted on two pivoting arms, one at each end.

[0033] Force transducers can advantageously be mounted on the respective pivoting arms, for example on the supports with which the roller is mounted on the pivoting arms, or at a hinge constraining the pivoting arm to the stationary load-bearing structure, or again at a hinge connecting the pivoting arm to the respective actuator. Thereby, a resistant, compact and low-cost structure is obtained, which is also adapted to exert high pressure forces on the embossing rollers, and to measure these forces precisely.

[0034] Further advantageous features and embodiments are described below and set forth in the attached claims.

[0035] According to a further aspect, a method is described herein for adjusting, in an embosser, the relative position between an embossing roller carried by a stationary load-bearing structure and a functional roller, which is movable with respect to the stationary load-bearing structure and adapted to define, with the embossing roller, a nip through which a ply of continuous web-like material passes. The method comprises a step in which, by means of a first approaching actuator and a second approaching actuator, associated respectively with a first axial end and a second axial end of the functional roller, the functional roller is approached to the embossing roller, until the functional roller comes into contact with the embossing roller, detecting the contact by means of a first force transducer associated with the first axial end of the functional roller and a second force transducer associated with the second axial end of the functional roller. The position in which the functional roller touches the embossing roller is set as the reference position. By means of the first approaching actuator and the second approaching actuator, the functional roller is further moved towards the embossing roller by a predetermined extent with respect to the reference position, detecting the approach of the functional roller to the embossing roller by means of a first position transducer and a second position transducer, associated with the first axial end and the second axial end of the functional roller.

[0036] In some embodiments, the method can further include the following steps. Once the reference position has been found, the functional roller is distanced from the embossing roller by an equal extent for the first actuator and the second actuator, until a position of mutual non-contact is reached. Since the two ends of the functional roller are moved by the first actuator and the second actuator by the same extent, the functional roller remains parallel to itself, or at least in the final position of mutual non-contact the functional roller has the axis thereof parallel to the position in which such an axis was located in the reference position.

[0037] Subsequently, the functional roller is gradually advanced, keeping it parallel to itself, by means of equal advancement of the two actuators up to a position of first contact with the embossing roller. From this position, which can be identified in various ways as described below, the first actuator and the second actuator continue to advance the functional roller by equal strokes for a predetermined extent of advancement, which corresponds to a required degree of penetration of the embossing protuberances of the embossing roller into an elastically yielding coating of the functional roller.

[0038] The first contact position can be identified based on the detection of a peak of a parameter related to a cooperation condition between the functional roller and the embossing roller. For example, the position of first mutual contact between the functional roller and the embossing roller can be identified based on a peak in the force or thrust exerted by the first actuator and the second actuator, detected by means of a load cell or by means of a pressure switch, preferably one pressure switch for each actuator, when the actuators are cylinder-piston actuators, of which the pressure switch or switches read the pressure of the working fluid.

[0039] In other embodiments, the position of first mutual contact between the embossing roller and the functional roller can be identified by reading an electrical parameter of the motor which rotates the embossing roller. In such a case, during the step of mutual approach the embossing roller is kept rotating by an electric motor. This absorbs a current (and therefore a power) which remains substantially constant until the first contact between the functional roller and the embossing roller occurs. This contact causes a sudden increase in the resistant torque which the motor must overcome to keep the embossing roller rotating. Such a peak in resistant torque cor-responds to a peak of the current absorbed by the motor. The position taken by the functional roller at the moment in which the peak of absorbed current is read is the position of first mutual contact between the functional roller and the embossing roller during this step of gradual approach of the functional roller to the embossing roller. In still other embodiments, the sudden increase in torque can be measured by a torque sensor on the drive shaft between the motor and the embossing roller.

[0040] Further advantageous features and embodiments of the method of the present disclosure are illustrated below and set forth in the attached claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Embodiments are illustrated in the attached drawing, in which:Fig. l shows an embosser-laminator unit;Fig. lA shows a schematic enlargement of the detail indicated with A in Fig.l;Fig. IB shows a schematic enlargement of the detail indicated with B in Fig. l;Fig.2 shows a detail of a pressure roller and the respective embosser; andFig.3 shows a view according to III-III of Fig.2.DETAILED DESCRIPTION

[0042] In the following, reference is made to an embosser-laminator, comprising two units each consisting of a pressure roller and a respective embossing roller, for separately embossing two plies of cellulosic web-like material. The described embosser-laminator further comprises a laminating roller to facilitate bonding the plies, which have been separately embossed by the two units comprising the embossing roller and the pressure roller.

[0043] However, as will be clear to those skilled in the art from reading the following description, the novel aspects described herein can also be used in simple embossers, which comprise a single pair formed by an embossing roller and a pressure roller.

[0044] It is also possible to use the novel elements described herein in an embosserlaminator without a laminating roller, in which the lamination between separately embossed plies occurs, for example, between two opposite embossing rollers, which define a lamination nip therebetween. This occurs, for example, in so-called tip-to-tipembosser-laminators.

[0045] The possibility that the embosser comprises more than two embossing rollers with respective pressure rollers, or embossing rollers with which more than one pressure roller cooperates, is not excluded.

[0046] When multiple pressure rollers are provided, it is advantageous for each of them to be provided with systems for adjusting the position with respect to the respective embossing roller, but this is not strictly necessary.

[0047] Returning now to the drawings, in the embodiment illustrated in Fig. 1, an embosser-laminator unit 5 (in the present context also briefly referred to as "embosser unit" or simply "embosser") is shown comprising a first embossing roller 21 equipped with embossing protuberances 21P (Fig. 1A) and cooperating with a first pressure roller 23, which can have an outer surface 23A consisting of a coating of yielding material, in particular elastically yielding, for example rubber. The embosser-laminator unit 5 also comprises a second embossing roller 25 equipped with embossing protuberances 25P (Fig. IB) and cooperating with a second pressure roller 27, which can have an outer surface 27A consisting of a coating of yielding material, in particular elastically yielding, for example rubber.

[0048] The first pressure roller 23 can be supported on a pair of movable loadbearing members. In the illustrated embodiment, the movable load-bearing members comprise pivoting arms 24, hinged around an axis 24A to a stationary structure 45. The two pivoting arms 24 are placed at the two opposite axial ends of the first pressure roller 23. The axis 24A is preferably parallel to the rotation axis 21A of the first embossing roller 21 and the rotation axis 25 A of the second embossing roller 25. When properly positioned and in use, the rotation axis 23 A of the first pressure roller 23 is also parallel to the axis 24A and the axis 21A.

[0049] To press the first pressure roller 23 against the first embossing roller 21, two actuators are provided for approaching the first embossing roller 21 to the first pressure roller 23. The two approaching actuators are indicated with 26 and each of them is hinged to one of the two pivoting arms 24 and to the stationary load-bearing structure 45. The numbers 26 A and 26B indicate the hinge connecting each actuator 26 to the respective pivoting arm 24 and to the stationary load-bearing structure 45, respec-lively. In the following, the approaching actuators are also briefly referred to as “actuators”.

[0050] The second pressure roller 27 can be supported on a pair of movable loadbearing members. In the illustrated embodiment, the movable load-bearing members comprise pivoting arms 28, hinged around an axis 28 A to the stationary structure 45. The two pivoting arms 28 are placed at the two opposite axial ends of the second pressure roller 27. The axis 28A is preferably parallel to the rotation axis 21A of the first embossing roller 21 and the rotation axis 25 A of the second embossing roller 25. When properly positioned and in use, the rotation axis of the second pressure roller 27 is also parallel to the axis 28A and the axis 21A.

[0051] To press the second pressure roller 27 against the second embossing roller 25, two approaching actuators 30 (hereinafter simply “actuators”) are provided, each hinged to one of the two pivoting arms 28 and to the stationary load-bearing structure 45. The numbers 30A and 30B indicate the hinge connecting each actuator 30 to the respective pivoting arm 28 and to the stationary load-bearing structure 45, respectively.

[0052] A first embossing nip 31 is formed between the first embossing roller 21 and the first pressure roller 23, into which the first ply VI is fed. A second embossing nip 33 is formed between the second embossing roller 25 and the second pressure roller 27, into which the second ply V2 is fed.

[0053] The two embossed plies are bonded together in a laminating nip which can be formed between the first embossing roller 21 and the second embossing roller 25, for example in the case of what is called a tip-to-tip embosser unit. Alternatively, as illustrated in Fig.l, the embossed ply V2 can be detached from the second embossing roller 25 and guided around the first embossing roller 21, to pass together with the ply VI through a laminating nip 36, formed between the first embossing roller 21 and a laminating roller 35.

[0054] The laminating roller 35 can be supported on a pair of movable load-bearing members. In the illustrated embodiment, the movable load-bearing members comprise pivoting arms 38, hinged around an axis 38A to the stationary structure 45. The two pivoting arms 38 are placed at the two opposite axial ends of the laminating roll-er 38. The axis 38A is preferably parallel to the rotation axis 21 A of the first embossing roller 21 and the rotation axis 25 A of the second embossing roller 25. When properly positioned and in use, the rotation axis 38A of the laminating roller 35 is also parallel to the axis 24A and the axis 21 A.

[0055] To press the laminating roller 35 against the first embossing roller 21, two approaching actuators 40 (hereinafter briefly referred to as “actuators”) are provided, each hinged to one of the two pivoting arms 38 and to the stationary load-bearing structure 45. The numbers 40 A and 40B indicate the hinge connecting each actuator 40 to the respective pivoting arm 38 and to the stationary load-bearing structure 45, respectively.

[0056] The laminating roller 35 can have an outer surface of elastically yielding material, typically harder than the outer surface 23 A, 27A of the pressure rollers 23, 27. In other cases, the outer surface of the laminating roller 35 can be made of steel or other material of such a hardness as to not deform significantly under the load determined by the pressure with which the laminating roller is pressed against the embossing roller. In both cases, whether the outer surface of the laminating roller 35 is elastically yielding or not, the position adjustment procedure described below is the same.

[0057] To bond the two plies VI, V2 to one another, a functional liquid can be used, for example a glue, applied to the ply VI, when this is guided around the first embossing roller 21 and engaged therewith after having been permanently deformed in the embossing nip 31, so that embossed protuberances are formed in the ply VI and are adherent to the embossing protuberances 2 IP of the first embossing roller 21.

[0058] To apply a functional liquid, for example, a dispensing unit for adhesive or other functional liquid, for example simply water, is provided. Here after this dispensing unit of adhesive or other functional fluid will be referred to simply as "dispenser" or "dispensing unit" and is indicated overall with 37 in Fig. 1.

[0059] In embodiments described herein, the dispenser 37 comprises a slide 41 guided along guides 43, which can be integral with the stationary load-bearing structure 45 that supports the embosser-laminator unit 5. The slide 41 can be engaged with the guides 43 by means of skids 47. In other embodiments, it is possible to con-strain the dispensing unit 37 to the stationary load-bearing structure 45 by means of a rotoidal joint so as to rotate the dispensing unit 37 around a rotation axis and cause it to move towards and away from the first embossing roller 21.

[0060] The dispenser 37 can comprise a dosing roller, hereinafter referred to as anilox roller, indicated with 57, which withdraws functional liquid, for example an adhesive, from a tank or other source of functional liquid indicated with 59. The anilox roller 57 transfers the functional liquid to an applicator roller 61, which can be equipped with an interchangeable plate, not shown in detail. The applicator roller, or plate roller, 61 is configured to transfer functional liquid received from the anilox roller 57 to the embossed ply VI and more precisely onto at least some of the embossed protuberances of such a ply VI which are engaged to the embossing protuberances 21P of the first embossing roller 21. For this purpose, the applicator roller 61 is located with the outer surface thereof, on which the anilox roller 57 doses the functional liquid, at a distance from the heads of the embossing protuberances 2 IP which is equal to or preferably less than the thickness of the ply VI at the embossing protuberances 2 IP.

[0061] The pressure rollers 23, 27 and the laminating roller 35 constitute respective functional rollers cooperating with a respective embossing roller 21, 25. As mentioned in the introduction, the correct positioning of each functional roller with respect to the embossing roller is an important aspect in the operation of the embosser 5. In general, each of the pressure rollers 23, 27 and the laminating roller 35 can be positioned correctly with respect to the corresponding embossing roller in the manner described below. In other embodiments, the position adjustment can be envisaged for only one or for each of the pressure rollers and not for the laminating roller, for example if this is not envisaged or if it has a very high hardness. In other embodiments, the adjustment of the laminating roller and not of the pressure rollers may be envisaged.

[0062] The actuators 26, 30, 40 are interfaced with a control unit 42, as schematically depicted with the references Cl, C3, C5.

[0063] Continuing to refer to Fig. 1, the members and operations for adjusting the relative position of one or the other functional roller with respect to the corresponding embossing roller are described below with reference to Figs. 2 and 3. In thesefigures, a generic functional roller is shown and indicated with 100. The functional roller 100 may be one or other of the above-described first pressure roller 23, second pressure roller 27 and laminating roller 35. Therefore, the members and functions described with reference to Figs. 2 and 3 may be those of one or more of these three functional rollers 23, 27, 35. Reference 100A indicates the rotation axis of the functional roller 100. The first axial end and the second axial end of the functional roller 100 comprise respective necks which engage in end supports. The axial ends are indicated with 100B in Fig. 3 and the necks of the two axial ends are indicated with 100C.

[0064] The movable load-bearing members of the functional roller 100 are indicated with 102. In the illustrated embodiment, the movable load-bearing members comprise pivoting arms supporting the generic functional roller 100, which may represent the pivoting arms 24 and / or the pivoting arms 28 and / or the pivoting arms 38. Reference 102A indicates the pivoting axis of the pivoting arms 102. Reference 104 indicates the two approaching actuators (in short “actuators”), which press the generic functional roller 100 against the respective embossing roller, which can be the first embossing roller 21 or the second embossing roller 25. Each actuator is hinged at 104 A to the respective pivoting arm 102 and at 104B to the stationary load-bearing structure 45.

[0065] Furthermore, Fig. 2 shows a stop 106 which is fixed with respect to the stationary load-bearing structure and which serves to arrange the respective functional roller in the correct position with the rotation axis 100A thereof parallel to the rotation axis 21A or 25A of the corresponding embossing roller 21 or 25, as described in greater detail below.

[0066] Each pivoting arm 102 (and therefore each arm of one or more pairs of arms 24, 28, 38) is associated with a position transducer which has the function of detecting a position of the respective functional roller 102 (i.e., 23, 25, 35).

[0067] In the illustrated embodiment, each position transducer comprises, for example, an encoder associated with the respective actuator, or incorporated therein, as schematically indicated with 108. Reference CIO indicates a connection of the encoders 108 and actuators 104 to the control unit 42. The connection CIO of Fig. 2 therefore corresponds to each of the connections indicated with Cl, C3, C5 in Fig. 1.

[0068] Furthermore, each actuator 104 is associated with a force transducer, configured to detect a force generated by the mutual contact between the generic functional roller 100 and the corresponding embossing roller 21, 25. In the illustrated embodiment, a force transducer is incorporated in the hinge 104A which connects each pivoting arm 102 to the respective actuator 104. Each force transducer may comprise one or more load cells, for example associated with a pin of the respective hinge. The force transducers are generally labeled 110 in Figs. 2 and 3. Each force transducer 110 may represent a force transducer associated with either end of the first pressure roller 23, a force transducer associated with either end of the second pressure roller 27, and a force transducer associated with either end of the laminating roller 35.

[0069] Although in Fig. 2 the force transducers 110 are inserted in the connecting hinges between the pivoting arms 102 and the respective actuators 104, this is not the only possible arrangement. For example, the force transducers can be inserted in the end supports of the functional roller 100. The supports are indicated with 103 in Fig. 3. In other embodiments, the force transducers may be inserted in the hinges with which the pivoting arms 102 are connected to the stationary structure, i.e., in the hinges defining the axes 24 A, 28 A, and 38 A. It should be understood that the force transducers can be arranged differently for the three functional rollers 23, 25, 35. Preferably, the force transducers are mounted on the pivoting arms, i.e., at the above- mentioned hinges and / or the roller carried by the pivoting arms.

[0070] In some embodiments, it is also possible to place the force transducers in the supports of the respective embossing roller 21, 25. In the case of the second embossing roller 25, the force transducers inserted in the embossing roller supports detect the force exchanged between the second embossing roller 25 and the second pressure roller 27. In the case of the embossing roller 21, the force transducers may be used to detect the force exchanged between the first pressure roller 25 and the first embossing roller 21 and / or the force exchanged between the first embossing roller 21 and the laminating roller 35. To this end, transducers capable of detecting the force in a specific direction can be used, or the force exchanged between the embossing roller and the functional rollers (pressure roller 25 and laminating roller 35) can be detected in different and sequential steps of an adjustment process, described below.

[0071] In Fig. 2, C20 indicates a connection of the respective force transducer to the control unit 42. The connection C20 therefore corresponds to one or other of the connections indicated with C2, C4, C6 in Fig. 1.

[0072] With the members illustrated in Figs. 2 and 3, it is possible to carry out a position adjustment step on the generic functional roller 100 at the beginning of a production cycle. Such an adjustment step, described below with reference to the functional roller 100, can be carried out for one or more of the functional rollers described with reference to Fig. 1, namely: the first pressure roller 23, the second pressure roller 27, the laminating roller 35, each adjusted in position as described herein with reference to the generic functional roller 100.

[0073] If the stops 106 are provided, fixed to the stationary load-bearing structure 45 (stops omitted in Fig. 1), a first step of the positioning procedure of the functional roller 100 involves bringing the pivoting arms 102 into contact with the respective stops 106 by means of the actuators 104. In the absence of stops, the initial position can be defined in another manner, for example a fully retracted position of the actuators 104, which control the movement of the functional rollers.

[0074] From this initial position, by actuating the actuators 104, the two pivoting arms 102 are rotated around the hinge axis 102A to approach the functional roller 100 to the embossing roller 21 or 25. The advancement movement of each actuator 104 is interrupted by the control unit 42 when the respective force transducer 110 generates a signal, due to the force generated by the contact between the functional roller 100 and the embossing roller 21, 25. By using two separate approaching actuators 104 and two separate force transducers 110 for the two opposite axial ends of the functional roller 100, it is ensured that the pivoting arms 102 are stopped in a position where there is complete contact, along their entire axial length, of the functional roller 100 and the embossing roller 21, 25.

[0075] If one or the other of the rollers in mutual contact (functional roller 100 and embossing roller 21 or 25) are crowned, stopping the advancement when both force transducers detect a contact force still ensures the parallelism between the rollers.

[0076] The position at which the approach of the functional roller 100 to the embossing roller 21 or 25 is stopped is a zero position. From this position, the functionalroller 100 is moved further towards the embossing roller 21 or 25, again by means of the approaching actuators 104, with an advancement controlled by means of the respective encoders 108. In practice, the control unit 42 advances each actuator 104 by a pre-established stroke, which corresponds to a pre-established penetration of the protuberances 2 IP, 25P of the embossing roller into the elastically yielding coating of the functional roller 100. The penetration of the protuberances 2 IP, 25P varies according to the desired characteristics to be obtained on the embossed web-like material, and can be set automatically by the control unit 42 based on the recipe of the embossed web-like material.

[0077] Once the desired movement (and thus the final position) has been reached, as detected by the encoders 108, the pivoting arms 102 are stopped and held in this position by the actuators 104 which lock.

[0078] The position reached is the working position, characterized by the desired degree of penetration of the protuberances into the elastically yielding coating of the functional roller.

[0079] This procedure ensures the correct positioning of the functional roller 100 with respect to the embossing roller 21, 25, regardless of any variations in the diameter of the rollers, in particular regardless of the gradual reduction in the diameter of the functional roller 100, whose elastic coating layer is subject to wear, with consequent reduction in the diametral dimension.

[0080] The adjustment of the mutual position of the functional roller 100 occurs automatically or manually, but with the aid of a control panel or other interface 44 (see Fig. l) associated with the control unit 42. The operator can simply set the mutual distance between rollers 100, 21 or 100, 25 by means of the interface 44 and the described system will carry out the positioning cycle.

[0081] If the functional roller 100 is the laminating roller 35, it is possible to envisage positioning the functional roller at a distance not in contact with the tips 2 IP of the embossing roller 21 but less than the thickness of the plies which pass through the laminating nip 36, thereby avoiding the phenomenon known as “re-embossing” by those skilled in the art. In such a case, once the contact position between the laminating roller and the embossing roller has been reached, as detected by the forcetransducers, the pivoting arms supporting the laminating roller are made to swivel, moving the laminating roller away from the embossing roller.

[0082] Once the final position of the functional roller 100 with respect to the embossing roller 21, 25 has been reached, the production step can begin, during which the system maintains the desired mutual position between roller 100 and roller 21 or 25.

[0083] If, for some reason, it is desired to work by controlling the mutual pressure instead of the position between roller 100 and roller 21 or 25, this different operating mode can be set by means of the control unit 42, during which the functional roller 100 is no longer held in a fixed position with respect to the embossing roller 21, 25, but what remains constant is the mutual pressure between the functional roller 100 and the embossing roller 21, 25. For this purpose, the control unit detects the force signal coming from the force transducers 110 and, using a control loop, will ensure that such a signal value remains constant by acting on the actuators 104 of the respective functional roller.

[0084] It is also possible to envisage, for example, that one of the functional rollers is pressure-controlled and another functional roller is position-controlled. For example, it can be envisaged that the pressure rollers 23, 27 are controlled in position, to always ensure the correct embossing depth, while the laminating roller 35 is controlled in pressure, to always ensure the correct lamination pressure and thus an optimal joining between the plies VI, V2.

[0085] In some cases, it may occur that at the beginning of the alignment process described above the functional roller is strongly skewed (not parallel) with respect to the embossing roller. This condition can be detected for example in the following manner. In general, at the beginning of the alignment procedure between the embossing roller and the functional roller, the functional roller 100 may not be parallel to the embossing roller. Therefore, when the functional roller 100 is brought closer to the embossing roller 21 / 25 by means of the two actuators 104, the mutual contact between the functional roller 100 and the embossing roller will occur first at one end and then at the other. Therefore, the first contact condition will first be detected by the load cell of one of the actuators 104 and then by that of the other. If there is a strong non-parallel condition, this means that the second actuator (the second onewhich detects the contact) must perform a long stroke before obtaining contact between the functional roller and the embossing roller; or to have an equal force on the two ends of the functional roller it is necessary to reach very high force values, which may not be compatible with the embossing conditions to be maintained.

[0086] In such a case, a search for parallelism can be carried out in subsequent steps. In the first step, which of the two ends of the functional roller 100 comes into contact with the embossing roller first is identified. If necessary, then a partial correction of the non-parallelism is carried out, keeping the actuator of the side of the functional roller which has come into contact with the embossing roller stopped and advancing the other end of the functional roller by a predetermined stroke. Even if the parallelism condition has not been reached, at this point the functional roller is distanced from the embossing roller while keeping it parallel to itself (i.e., with identical strokes for the two actuators 104) up to a distancing position. The cycle is repeated from here.

[0087] In practice, the parallelism between the functional roller and the embossing roller is thereby reached in subsequent stages or steps.

[0088] In a modified embodiment, the arrangement illustrated in Figs. 2 and 3 can carry out the following procedure.

[0089] By means of the two actuators 104, the functional roller 100 is moved closer to the embossing roller 21, 25, until the functional roller comes into contact with the embossing roller. The contact is detected by means of a first force transducer associated with the first axial end of the functional roller 100 and a second force transducer associated with the second axial end of the functional roller 100. The position in which the functional roller touches the embossing roller is set as the reference position. Subsequently, by means of the two actuators 104, the functional roller 100 is distanced from the embossing roller 21, 25, keeping the functional roller parallel to itself, i.e., performing equal strokes with the two actuators 104. Subsequently, the functional roller 100 is gradually moved closer to the embossing roller 21, 25 again by means of the two actuators 104 and a first mutual contact position between the functional roller 100 and the embossing roller 21, 25 is detected. From the first contact position, the functional roller 100 is advanced towards the embossing roller by means of the actuators 104 by a predetermined extent starting from the first contactposition.

Claims

CLAIMS1. An embosser, comprising: a first embossing roller, supported on a stationary load-bearing structure; a first functional roller cooperating with the first embossing roller and defining with the first embossing roller a first nip through which a feed path for a first ply of web-like material extends; wherein the first functional roller is supported on the stationary load-bearing structure at a first axial end by a first movable load-bearing member and at a second axial end by a second movable load-bearing member; a first actuator for approaching the first functional roller to the first embossing roller, the first approaching actuator being associated with the first movable loadbearing member; a second actuator for approaching the first functional roller to the first embossing roller, the second approaching actuator being associated with the second movable load-bearing member; a first position transducer associated with the first axial end of the first functional roller and a second position transducer associated with the second axial end of the first functional roller; wherein the first position transducer and the second position transducer are adapted to detect a displacement of the first functional roller with respect to the first embossing roller; a first force transducer of the first functional roller, associated with the first axial end of the first functional roller, and a second force transducer associated with the second axial end of the first functional roller; wherein the first force transducer and the second force transducer are adapted to detect a contact condition between the first functional roller and the first embossing roller when the first functional roller is approached to the first embossing roller by the first approaching actuator and the second approaching actuator.

2. The embosser of claim 1, comprising: a second functional roller cooperating with the first embossing roller and defining with the first embossing roller a second nip through which the feed path of the first ply of web-like material extends; wherein the second functional roller is supported on the stationary load-bearing structure at a first axial end by a third movableload-bearing member and at a second axial end by a fourth movable load-bearing member; a third actuator for approaching the second functional roller to the first embossing roller, the third approaching actuator being associated with the third movable load-bearing member; a fourth actuator for approaching the second functional roller to the first embossing roller, the fourth approaching actuator being associated with the fourth movable load-bearing member; a third position transducer associated with the first axial end of the second functional roller and a fourth position transducer associated with the second axial end of the second functional roller; wherein the third position transducer and the fourth position transducer are adapted to detect a displacement of the second functional roller with respect to the first embossing roller; a third force transducer of the second functional roller, associated with the first axial end of the second functional roller, and a fourth force transducer associated with the second axial end of the second functional roller; wherein the third force transducer and the fourth force transducer are adapted to detect a contact condition between the second functional roller and the first embossing roller when the second functional roller is approached to the first embossing roller by the third approaching actuator and the fourth approaching actuator.

3. The embosser of claim 1, wherein the first functional roller is a pressure roller.

4. The embosser of claim 1, wherein the first functional roller is a laminating roller.

5. The embosser of claim 2, wherein the first functional roller is a pressure roller and the second functional roller is a laminating roller.

6. The embosser of claim 1, comprising a second embossing roller and a third functional roller cooperating with the second embossing roller and defining with the second embossing roller a third nip through which a feed path for a second ply of web-like material extends.

7. The embosser of claim 6, wherein the third functional roller is supported on the stationary load-bearing structure at a first axial end by a fifth movable loadbearing member and at a second axial end by a sixth movable load-bearing member; a fifth actuator for approaching the third functional roller to the second embossing roller, the fifth approaching actuator being associated with the fifth loadbearing member; a sixth actuator for approaching the third functional roller to the second embossing roller, the sixth approaching actuator being associated with the sixth movable load-bearing member; a fifth position transducer associated with the first axial end of the third functional roller and a sixth position transducer associated with the second axial end of the third functional roller; wherein the fifth position transducer and the sixth position transducer are adapted to detect a displacement of the third functional roller with respect to the second embossing roller; a fifth force transducer of the third functional roller, associated with the first axial end of the third functional roller, and a sixth force transducer associated with the second axial end of the third functional roller; wherein the fifth force transducer and the sixth force transducer are adapted to detect a contact condition between the third functional roller and the second embossing roller when the third functional roller is approached to the second embossing roller by the fifth approaching actuator and the sixth approaching actuator.

8. The embosser of any one of the preceding claims, wherein each force transducer comprises at least one load cell.

9. The embosser of any one of the preceding claims, wherein the movable load-bearing members of at least one of said functional rollers comprise respective pivoting arms.

10. The embosser of any one of the preceding claims, wherein the movable load-bearing members of at least one of said functional rollers are associated with stops that are fixed with respect to the stationary load-bearing structure and defining a zero position of the movable load-bearing members and of the respectivefunctional roller; wherein the respective actuators are adapted to arrange the movable load-bearing members in contact with the fixed stops with a movement of the movable load-bearing members which is opposite with respect to a approaching movement of the functional roller to the embossing roller.

11. The embosser of any one of the preceding claims, wherein each pair of movable load-bearing members of each functional roller comprises a pair of pivoting arms, hinged to the stationary load-bearing structure; each pivoting arm being hinged to the stationary load-bearing structure and to the respective approaching actuator.

12. The embosser of claim 11, wherein the force transducers of each functional roller are arranged in at least one of the following positions: at supports of the functional roller on the respective pivoting arms; at hinges articulating the pivoting arms to the load-bearing structure; at hinges connecting the pivoting arms to the respective approaching actuators.

13. The embosser of any one of the preceding claims, further comprising a control unit, programmed so that, for each functional roller comprising a respective pair of approaching actuators, the following operations are carried out: moving the functional roller closer to the embossing roller, until the functional roller is brought into contact with the embossing roller, detecting the contact by means of the respective force transducers associated with the axial ends of the functional roller; setting the position in which the functional roller touches the embossing roller as the reference position; by means of the approaching actuators, further moving the functional roller closer to the embossing roller by a predetermined extent with respect to the reference position, detecting the approach of the functional roller to the embossing roller by means of the respective position transducers.

14. The embosser of any one of claims 1 to 12, further comprising a control unit, programmed so that, for each functional roller comprising a respective pair of approaching actuators, the following operations are carried out: moving the functional roller closer to the embossing roller until the functional roller is brought into contact with the embossing roller, detecting the contact by means of the respective force transducers associated with the axial ends of the functional roller; settingthe position in which the functional roller touches the embossing roller as the reference position; by means of the approaching actuators, mutually distancing the functional roller from the embossing roller; moving the functional roller towards the embossing roller again; detecting a first contact position between the functional roller and the embossing roller; from such a first contact position, advancing the functional roller towards the embossing roller by a predetermined amount with respect to the first contact position.

15. A method for adjusting, in an embosser, the relative position between an embossing roller carried by a stationary load-bearing structure and a functional roller, which is movable with respect to the stationary load-bearing structure and adapted to define with the embossing roller a nip through which a ply of continuous web-like material passes, wherein the method comprises the following steps: by means of a first approaching actuator and a second approaching actuator, associated respectively with a first axial end and a second axial end of the functional roller, moving the functional roller closer to the embossing roller, until the functional roller comes into contact with the embossing roller, detecting the contact by means of a first force transducer associated with the first axial end of the functional roller and a second force transducer associated with the second axial end of the functional roller; and setting the position in which the functional roller touches the embossing roller as the reference position; by means of the first approaching actuator and the second approaching actuator, further approaching the functional roller to the embossing roller by a predetermined extent with respect to the reference position, detecting the approach of the functional roller to the embossing roller by means of a first position transducer and a second position transducer, associated with the first axial end and the second axial end of the functional roller.

16. A method for adjusting, in an embosser, the relative position between an embossing roller carried by a stationary load-bearing structure and a functional roller, which is movable with respect to the stationary load-bearing structure and adapted to define with the embossing roller a nip through which a ply of continuous web-like material passes, wherein the method comprises the following steps: by means of a first approaching actuator and a second approaching actua-tor, associated respectively with a first axial end and a second axial end of the functional roller, moving the functional roller closer to the embossing roller, until the functional roller comes into contact with the embossing roller, detecting the contact by means of a first force transducer associated with the first axial end of the functional roller and a second force transducer associated with the second axial end of the functional roller; and setting the position in which the functional roller touches the embossing roller as the reference position; by means of the first approaching actuator and the second approaching actuator, distancing the functional roller and the embossing roller from each other while keeping the functional roller parallel to itself; gradually approaching the functional roller to the embossing roller again by means of the first approaching actuator and the second approaching actuator; detecting a position of first mutual contact between the functional roller and the embossing roller; advancing the functional roller towards the embossing roller by means of the first approaching actuator and the second approaching actuator by a predetermined extent starting from the first contact position.

17. The method of claim 15 or 16, wherein the functional roller is a pressure roller, preferably coated with elastically yielding material.

18. The method of claim 15 or 16, wherein the functional roller is a laminating roller.

19. The method of any one of claims 15 to 18, wherein the functional roller is supported by a first movable load-bearing member and a second movable load-bearing member; and wherein the method comprises a preliminary step of aligning the functional roller in a position parallel to the embossing roller by bringing the first movable load-bearing member and the second movable load-bearing member into contact with fixed stops.

20. The method of claim 19, wherein the first movable load-bearing member and the second movable load-bearing member comprise a first pivoting arm hinged to the stationary load-bearing structure and a second pivoting arm hinged to the stationary load-bearing structure.

21. The method of claim 18, 20, wherein the force transducers of the functional roller are arranged in at least one of the following positions: at supports of the functional roller on the respective pivoting arms; at hinges articulating the pivoting arms to the load-bearing structure; at hinges for connecting the pivoting arms to the respective approaching actuators.

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