Method and apparatus for producing coreless logs of web material

Abstract

The method comprises the following steps: inserting a first removal pin (65.1) into the first end of the tubular mandrel and inserting a second removal pin into the second end of the tubular mandrel; axially engaging the first removal pin i(65.1) inside the first tubular half-mandrel and the second removal pin inside the second tubular half-mandrel; removing the first tubular half-mandrel from the log through an axial movement of the first removal pin, and removing the second tubular half-mandrel from the log through an axial movement of the second removal pin (65.1), the axial movement of the first removal pin and the axial movement of the second removal pin being in opposite directions.

Description

METHOD AND APPARATUS FOR PRODUCING CORELESS LOGS OF WEB MATERIALDESCRIPTIONTECHNICAL FIELD

[0001] The present invention relates to methods and apparatuses for producing coreless logs of web material. Embodiments described herein especially relate to methods and apparatuses for manufacturing tissue paper logs.

[0002] Specifically, embodiments described herein provide methods and apparatuses for winding logs of web material, such as especially tissue paper, around winding mandrels, which are later removed from the logs to obtain a wound coreless log.BACKGROUND ART

[0003] In many industrial sectors, it is customary to wind a web material around a winding mandrel or winding core. Typically, in the paper converting industry, particularly tissue paper converting, it is known to wind a paper web, consisting of one or more plies, around a winding core or winding mandrel to form a log. The logs are usually produced in rapid sequence in a rewinder, such as a continuous automatic peripheral rewinder. Examples of rewinding machines of this type are disclosed in EP2621844, EP 1725485, EP0694020.

[0004] Typically, the logs have an axial length significantly greater than the finished products, which consist of rolls of shorter axial length, obtained by transversally cutting the logs produced by the rewinder.

[0005] In some cases, the web material is wound around tubes of paper, cardboard, or plastic, which remain inside the logs and are cut together with the logs.

[0006] In the past, systems have been studied to remove the winding core or winding mandrel from the finished log, in order to reuse the mandrels multiple times in subsequent cycles for winding more logs. In this way, there is no longer the need to produce large quantities of winding cores or mandrels, which are a cost for the log manufacturer and a source of pollution. In fact, when the winding core is cut togetherwith the log and remains inside the rolls for the end consumer, the end consumer throws the winding core away once the roll, for example a roll of toilet paper or kitchen towels, is exhausted.

[0007] EP 1056667 discloses a peripheral rewinder that winds logs of web material, typically tissue paper, around removable mandrels. The mandrels are made in two halves, i.e. two half-mandrels that are coupled together along the winding axis. An extracting device is provided downstream of the rewinder, that removes the two half- mandrels from the two ends of the logs leaving the rewinder; the two half-mandrels are then sent back to the rewinder inlet and coupled together before being inserted into the rewinder to perform a new winding cycle. This known machine has some limitations. First of all, the extracting device for removing the half-mandrels is placed along the paper converting line and constitutes an additional station that increases the overall bulk of the line. In addition, the extracting device slows down the production cycle of the rewinder.

[0008] EP2678257 discloses a production line for paper logs, particularly tissue paper logs, which comprises a rewinder and a log accumulator. The logs are ejected from the rewinder and loaded onto the log accumulator, downstream of which other converting machines are provided, particularly a log saw that cuts the logs into smaller rolls intended for the end consumer. Between the rewinder and the log accumulator, an extractor is provided that removes the half-mandrels from the two ends of the logs that are unloaded from the rewinder. The extractor has a long extension along the converting line, and takes a lot of space between the rewinder and the accumulator. This space is necessary because the extractor works by gradually removing the mandrels from the logs as they move forward along the feed path. Removal is achieved by a combination of a forward motion of the logs along the line and an extraction motion along a diagonal direction of a series of grippers that simultaneously engage multiple half-mandrels of multiple logs. This extracting device is fast, but requires a lot of space and greatly increases the length and the complexity of the converting lines. Moreover, the lateral dimensions reduce the accessibility to the machines downstream of the rewinder and make the maintenance difficult.

[0009] WO2020 / 245319 discloses a device for removing mandrels from tissue paper logs through a combined motion of axial translation and rotation of the mandrel aroundits own axis, to facilitate the mandrel extraction by reducing the friction between the mandrel and the log. The device is extremely bulky and constitutes an additional element along the converting line, significantly increasing the bulk thereof. Moreover, this device has a very low productivity, as it can only remove one mandrel at a time.

[0010] US20240025686 discloses a further extractor for removing winding mandrels from tissue paper logs, which uses an expandable member to grip the mandrel. The expandable gripping member is either pneumatic or mechanical. This device is also bulky and greatly increases the size of the converting line.

[0011] DEI 9957990 discloses an expandable gripping member for removing winding mandrels from paper logs.

[0012] EP2771320 and the equivalent disclose methods and devices for producing coreless logs of web material, wherein a mandrel is used to wind the logs and is then removed from the logs to obtain coreless logs. The mandrels are tubular and made of plastic material having such characteristics to cause a reduction in the diameter of the tubular mandrel when tensioned during the step of removal from the log. This well- known device requires very complex removing means.

[0013] One of the drawbacks of the known devices is the large bulk within the converting line. Another drawback of some of these devices is the low productivity.

[0014] The object of embodiments disclosed herein is to alleviate one or more of the drawbacks of the prior art removal devices and methods.

[0015] Managing the mandrel removal step has multiple critical aspects. For example, when the mandrel to be removed consists of two portions, i.e. two halfmandrels, the removal of the two half-mandrels from opposite ends of the log may be difficult due to the depressurization formed inside the mandrel, which acts against the removal of the half-mandrels.SUMMARY

[0016] According to an aspect, a method is disclosed herein for producing a coreless log of web material by winding a web material around a tubular mandrel to form a log of web material wound around the tubular mandrel; wherein the tubular mandrelincludes: a first tubular half-mandrel having an inner cylindrical surface and an outer cylindrical surface and forming a first end of the tubular mandrel, and a second tubular half-mandrel having an inner cylindrical surface and an outer cylindrical surface and forming a second end of the tubular mandrel; and wherein the first tubular halfmandrel and the second tubular half-mandrel are coaxial with each other and consecutive to each other. The method comprises the following steps: inserting a first removal pin into the first end of the tubular mandrel and inserting a second removal pin into the second end of the tubular mandrel; axially engaging the first removal pin inside the first tubular half-mandrel and the second removal pin inside the second tubular half-mandrel; and removing the first tubular half-mandrel from the log through an axial movement of the first removal pin, and removing the second tubular halfmandrel from the log through an axial movement of the second removal pin, the axial movement of the first removal pin and the axial movement of the second removal pin being in opposite directions;

[0017] The first tubular half-mandrel and the second tubular half-mandrel are made of a flexible elastic material.

[0018] Preferably, the flexible elastic material has a flexural modulus between 100 MPa and 8000 MPa.

[0019] In the present description, the term "coreless" means a log that is without winding core at the end of the production cycle. As it will be clearly apparent from the description below, to form the log, the web material is wound around a winding mandrel, which is then removed by extraction from the log, to obtain a coreless finished product or semi-finished product.

[0020] According to another aspect, an apparatus is disclosed herein for producing coreless logs of web material, including a rewinding machine comprising at least a plurality of motorized winding rollers that are configured to wind the web material around a tubular mandrel to form a log of web material wound around the tubular mandrel. The tubular mandrel is formed by a first tubular half-mandrel having an inner cylindrical surface and an outer cylindrical surface and forming a first end of the tubular mandrel, and a second tubular half-mandrel having an inner cylindrical surface and an outer cylindrical surface and forming a second end of the tubular mandrel. Thefirst tubular half-mandrel and the second tubular half-mandrel are coaxial with each other and consecutive to each other. The first tubular half-mandrel and the second tubular half-mandrel are made of a flexible elastic material, with a flexural modulus between 100 MPa and 8000 MPa.

[0021] In embodiments described herein, the apparatus also comprises a removal device for removing tubular mandrels, including a first radially expandable removal pin, adapted to be inserted into the first end of the tubular mandrel, and a second radially expandable removal pin, adapted to be inserted into the second end of the tubular mandrel.

[0022] Advantageously, the removal device may be configured to perform the following steps: inserting the first removal pin into the first end of the tubular mandrel and inserting the second removal pin into the second end of the tubular mandrel when the tubular mandrel is contained within a log wound around the tubular mandrel; axially engaging the first removal pin inside the first tubular half-mandrel and the second removal pin inside the second tubular half-mandrel; removing the first tubular half-mandrel from the log through an axial movement of the first removal pin, and removing the second tubular half-mandrel from the log through an axial movement of the second removal pin opposite to the movement of the first removal pin;

[0023] In advantageous embodiments, the mandrel has an annular stiffness between 4xlO'6N / mm2and 4xlO'4N / mm2or between 2xlO'4N / mm2and 6xlO'3N / mm2or between 2xlO'2N / mm2and 30 N / mm2, according to ISO 9969:2016, where the annular stiffness is defined aswhereinE is the flexural modulusD is the average diameter of the mandrelI is the moment of inertia of the mandrel wall area in longitudinal direction per unit of length, equal towhere s is the thickness of the cylindrical wall of the mandrel.

[0024] Further advantageous characteristics and embodiments of the method and the apparatus disclosed herein are illustrated below with reference to the accompanying drawings, and are defined in the appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention shall be better understood by following the description and the accompanying drawings, which show non-limiting examples of embodiment of the invention. More particularly, in the drawings:Fig. 1 is a front view of a removal device for removing winding mandrels from logs of web material, comprising a log accumulator, according to an embodiment;Fig. 2 is a simplified side view of the device of Fig. 1, wherein some parts have been omitted;Fig. 3 shows an enlarged detail of Fig. 2;Fig. 4 is an axonometric view of the device, wherein the accumulator has been omitted;Figs. 5 and 6 show enlargements of the two sides of the device of Fig. 5;Fig. 7 shows an enlarged detail of Fig. 5;Fig. 8 shows an enlarged detail of Fig. 6;Fig. 9 shows a further enlargement of Fig. 7;Figs. 10(A) to 10(1) are side views of the operational sequence of a cycle for removing winding mandrels;Figs. 11(A) to 11(D) are front views of steps of the operational cycle;Fig. 12 shows a step of discarding a log, from which the winding mandrel has not been extracted;Figs. 13(A) to 13(C) show steps of transferring half-mandrels, removed from the logs, to a mandrel conveyor;Figs. 14 and 15 show the structure and the operation of the expandable pin for removing the winding mandrels in two different operating position; Fig. 16 shows an enlargement of the expandable pin;Fig. 17 shows a section of a further embodiment of an expandable pin;Fig. 18 is an axonometric view of a further embodiment of an expandable pin;Fig. 19 is a schematic front view according to the line XIX-XIX of Fig. 20 of a further embodiment of a device for removing mandrels;Fig, 20 is a side view according to XX-XX in Fig. 19.Figs. 21 to 24 show example diagrams of rewinders for an apparatus according to the present invention; andFigs. 25 to 27 show a modified embodiment of a tubular winding mandrel.DETAILED DESCRIPTION

[0026] Figs. 1 to 13 show various views of an embodiment of a device for handling logs and removing mandrels. Innovative features described herein can be incorporated into devices of even substantially different form than that illustrated in the figures, as will be clarified below with reference to a different embodiment. Specifically, in this first embodiment the device for removing the winding mandrels is combined with a log accumulator, to achieve some advantages that will be clear to those skilled in the art from the description below. However, innovative features of the extractor described in combination with the device of Figs. 1 to 13 can also be used in devices for handling logs and removing mandrels that, for example, are not combined with an accumulator.

[0027] The device for removing winding mandrels from logs of web material, for example logs of tissue paper coming from a rewinder, is indicated as a whole with the reference number 1. In this embodiment, the device comprises a log accumulator 3. The log accumulator 3 comprises a bearing structure 4, on which an endless flexible member 5 is provided. The endless flexible member 5 consists of a pair of continuous chains 5A, 5B, driven around idler sprockets 7. In the diagram of the attached figures, the log accumulator 3 consists of a relatively short closed path of the endless flexible member 5, consisting of a single ring driven around two pairs (one for each chain) of idler sprockets. However, it should be understood that the log accumulator 3 can also be much larger and more complex than that illustrated. The log accumulator 3 can be configured, for example, as disclosed in W02012104881A1.

[0028] As particularly visible in Figs. 2 and 3, the endless flexible member 5 comprises a vertical rectilinear section, along which other members of the extracting device are arranged, described below.

[0029] Supports for the logs R are connected to the chains 5 A, 5B that constitute theendless flexible member 5. In the illustrated embodiment, the supports comprise channels 9 extending longitudinally between the two chains 5A, 5B according to a direction parallel to the axis of the logs R that are collected in the channels 9. The channels 9 are preferably arranged at a constant pitch along the extension of the endless flexible member consisting of the two chains 5A, 5B. Each channel 9 is pivoted to the two chains 5A, 5B around a respective longitudinal pivot axis 9A, which is parallel to the longitudinal extension of the channels 9.

[0030] The channels 9 may be removable from the endless flexible member 5, in order to be placed in different positions, preferably at constant pitch, as described again in W02012104881A1.

[0031] The movement of the continuous chains 5A, 5B along the closed path, indicated by the arrow f5, sequentially brings each channel 9 in front of a log loader 12, adapted to load individual logs R onto the channels 9. In the illustrated embodiment, the log loader 12 comprises either a chute 11 that receives the logs R from an upstream machine, such as a rewinder, not shown, or a gluing unit that receives the logs from a rewinder and glues the free edge of the wound web material, to prevent it from interfering with the subsequent operations. In the illustrated embodiment, the loader 12 further comprises a distributor 13, which rotates around an axis 13A parallel to the axes of the logs R and the axes 9A of the channels 9 according to the arrow fl 3. The distributor 13 is configured to distribute individual logs R, coming from the chute 11, to the channels 9.

[0032] The log accumulator 3 is also provided with a log unloading device, not shown, that may be arranged on the descending branch of the chains 5 A, 5B. If the log accumulator 3 is larger than that schematically shown, the chains 5 A, 5B can define a large number of ascending and descending sections, and the one furthest downstream relative to the forward movement of the logs R along the log accumulator 3 may be provided with an unloading device, in a known manner.

[0033] The device 1 comprises, in addition to the log accumulator 3, a removal unit indicated as a whole with the reference number 15.

[0034] The removal unit 15 comprises at least one removal cradle, on which the logs R, from which the winding mandrel shall be removed, are arranged one at a time. Inthe illustrated embodiment, the removal unit 15 comprises four removal cradles indicated with the reference number 17, which are substantially equal to, and arranged over, one another. The number of removal cradles 17 is merely indicative and may change, for example also depending on the size of the log accumulator 3, and more particularly on the height thereof, or on the cycle times to be achieved.

[0035] The removal cradles 17 are aligned with one another in a direction parallel to a section of the closed path defined by the endless flexible member 5 (chains 5A, 5B). Advantageously, in the illustrated embodiment, the cradles 17 are arranged one over the other along the vertical extension of the first ascending section of the endless flexible member 5. More specifically, the removal cradles 17 are arranged along the ascending section of the endless flexible member 5 that extends above the loader 12.

[0036] For the purposes that will be explained below, the removal cradles 17 are movable to selectively take: a receiving position, for receiving a log R from a respective channel 9 of the accumulator 3; a removal position, for removing the winding mandrel from the log R arranged in the removal cradle 17; and an unloading position for unloading the log R, devoid of the winding mandrel, from the removal cradle 17 to a channel 9 of the accumulator 3. The log R is preferably unloaded from the removal cradle 17 to the channel 9 from which it had been taken.

[0037] In the illustrated embodiment, the removal cradles 17 are integral with one another and carried by two slides 19, placed at opposite ends of the removal cradles 17. The slides 19 are omitted in Fig. 1 and shown in Figs. 2 to 9.

[0038] Each slide 19 is provided with a movement in horizontal direction, indicated with the double arrow fl9x, and a movement in vertical direction, indicated with the double arrow fl9y. The movement fl9x allows the slide 19 (and therefore the removal cradles 17) to move toward, and away from, the closed path of the chains 5 A, 5B and thus toward, and away from, the path of the channels 9. The vertical movement according to the arrow fl9y is parallel to the movement direction f9 of the channels 9 along the closed path defined by the chains 5 A, 5B.

[0039] The movement fl9x, fl9y is achieved by means of a carriage 20, on which the slides 19 are mounted. The carriage 20 comprises two flanks 21, between which the removal cradles 17 and the slides 19 are positioned. More specifically, the slides19 are mounted on the flanks 21 by means of guides 23 (in this case integral with the flanks 21) and shoes 25 (in this example integral with the slides 19), see in particular Figs. 7 and 8. The movement according to fl9x is achieved by means of a motor 27 (see Fig. 8) that drives pinions 29 meshing with racks 31 that are integral with the slides 19. A torsion bar 30 transmits motion from one flank 21 to the other.

[0040] The carriage 20 is mounted on vertical guides 33 integral with the structure 4 and is provided with a lifting and lowering movement, according to fl9y, along the vertical guides 33 controlled by a motor 34 through toothed belts or other flexible members 35. A torsion bar 37 is provided for transferring the motion from the motor 34 to the opposite flank.

[0041] Each removal cradle 17 is provided with a rotational movement about its own rotation axis 17A, parallel to the axes 9A and the channels 9, as well as to the axes of the logs R arranged in the removal cradles 17.

[0042] In the illustrated embodiment, each removal cradle 17 is provided with an actuator 39 that controls the rotation of the respective cradle 17 around the cradle rotation axis 17A through a toothed belt or other endless flexible member 41, see in particular Figs. 6, 8. The actuator 39 may comprise, for example, an electric motor.

[0043] Each removal cradle 17 is provided with at least one pusher 45 co-acting with the pivoting channels 9. More specifically, in the illustrated example, each removal cradle 17 is provided, at its longitudinal ends, with two pushers 45. The pushers 45 are visible in particular in Fig. 3, while they are partially omitted in the remaining figures for the sake of clarity. The pushers 45 co-act with cams or stops 47 integral with the channels 9, also visible particularly in Fig. 3. As will be clarified below with reference to the operational sequence, when the removal cradle 17 rotates around the axis 17A in a clockwise direction (observing Fig. 3), the pushers 45 co-act with the respective cams 47, causing the respective channel 9, which is in the position adjacent to the removal cradle 17, to pivot in the opposite direction.

[0044] Each removal cradle 17 also comprises at least one stop adapted to hold axially the log R while the winding mandrel is removed therefrom. Since, in the illustrated embodiment, the winding mandrel is comprised of two halves, axially aligned with each other, each removal cradle 17 actually comprises two holding stops,adapted to axially hold the log R at both ends while the mandrel is being removed. The two stops are indicated with the reference number 49 and are provided with a movement toward, and away from, the log R controlled by an actuator, for example a cylinder-piston actuator, indicated with the reference number 51. The movement of the stops 49 is indicated with the double arrow f49 (see especially Figs. 6-9).

[0045] The removal unit 15 comprises an extractor adapted to remove the mandrels from the logs R arranged in the removal cradles 17. In the illustrated embodiment, which is configured to remove mandrels divided into two halves, the removal unit, i.e. the extractor thereof, comprises a first extraction member 63 and a second extraction member 63, wherein the first extraction member and the second extraction member are positioned on two opposite sides of the log accumulator 3, and therefore at opposite longitudinal ends of the removal cradles 17. Each extraction member 63 is movable on a respective guide 61. In the illustrated example, each guide 61 is double.

[0046] In the illustrated embodiment, each extraction member 63 comprises, for each removal cradle 17, a respective gripping element 65, adapted axially to engage a halfmandrel around which the log R, arranged in the respective removal cradle 17, is wound. Therefore, in the illustrated embodiment four gripping elements 65 are provided on each side of the set of removal cradles 17.

[0047] More specifically, in the illustrated embodiment, the removal unit 15 comprises, on each side of the device 1, a guide on which a respective extraction member 63 translates. For the sake of simplicity, both the extraction members 63 are shown in Fig. 1, while in Figs. 4 to 9 only one extraction member 63 is shown.

[0048] Actuators 67, for example electric motors, control the horizontal movement of the extraction members 63 according to the double arrow f63, see Fig. 1. The movement can be transmitted, for example, through a rack and pinion mechanism, as schematically shown in the example illustrated in the attached drawing.

[0049] The device 1 also comprises a handler for each removal cradle 17. The handler is adapted to grip a winding mandrel engaged by the extractor after it has been removed from the log R arranged in the corresponding removal cradle 17. The handler may be configured to transfer the mandrel to a mandrel conveyor.

[0050] In the illustrated embodiment, since the winding mandrels are divided into two halves, each of which is removed from one end of the respective log, the handler is double and comprises two handling members, one on each side of the device 1.

[0051] More specifically, Fig. 4 shows a handling member 71. The symmetric handling members on the other side of the device 1 are omitted for the sake of simplicity of representation. The handling members 71 are provided with a horizontal movement, orthogonal to the guides 61 and schematically indicated with the double arrow f71. The movement according to the double arrow f71 allows each half-mandrel, removed from the respective log, to be engaged and transferred to a mandrel conveyor, schematically indicated with the reference number 73 and shown only in Figs. 13(A) to 13(C).

[0052] An operational cycle of the device described above is illustrated in Figs. 10 to 12 and will be described in detail below.

[0053] The first step of the removal cycle is shown in Fig. 10(A). Seven logs R are arranged on the log accumulator 3. It should be understood that also the remaining channels 9 may be full. The removal cradles 17 are placed at a certain distance (in the horizontal direction) from the feed path defined by the chains 5 A, 5B. On the chute 11, more logs R are arranged that will be loaded in the subsequent steps. In Fig. 10(B), the slides 19 that support the removal cradles 17 have been approached to the ascending rectilinear section of the closed path of the channels 9, defined by the endless flexible member 5 (chains 5A, 5B). The mutual position in the vertical direction of the removal cradles 17 and the channels 9 is such that the approaching movement causes the channels 9 to pivot around the axes 9A due to the interaction between the cams or stops 47 and the pushers 45. Consequently, the logs R that are in the four channels 9 co-acting with the four removal cradles 17 are unloaded from the channels 9 and roll into the removal cradles 17, as shown in Fig. 10(C).

[0054] In the following step, shown in Fig. 10(D), the slides 19 move away from the ascending path of the channels 9, and thus allow the channels 9 to return to the rest position, and the chains 5 A, 5B to move forward, so that the subsequent logs can move upward, without interfering with the removal cradles 17 and the logs lying therein.

[0055] At this point, the two half-mandrels, that constitute each winding mandrel forthe logs R arranged in the removal cradles 17, are removed by the extraction members63, in the manner described below with reference to Figs. 11(A)-11(E).

[0056] After the half-mandrels have been removed from the four logs R arranged in the removal cradles 17, the cradles translate upward as shown in Fig. 10(E), see the arrows in the figure. This movement brings the removal cradles 17, where the logs R, from which the winding mandrel has been removed, are arranged, in alignment with the channels 9, from which these logs had previously been unloaded (step of Fig. 10(C)). In fact, these channels are empty, while the channels below are occupied by logs R, from which the winding mandrels have not removed yet.

[0057] In the step of Fig. 10(F), the slides 19 are approached to the path of the channels 9. In this step, the mutual position, in the vertical direction, of the channels 9 and the removal cradles 17 is such that the pushers 45 and the cams 47 do not co-act with one another, and the channels 9, constituting the supports for the logs R of the accumulator 3, remain in the rest position.

[0058] In the subsequent step of Fig. 10(G), the removal cradles 17 rotate in such a direction to unload the respective logs R, devoid of the winding mandrel, onto the channels 9 from which they had previously been taken. In Fig. 10(H), the logs R devoid of the mandrels have been transferred from the removal cradles 17 to the channels 9, and the slides 19, with the respective empty removal cradles 17, move away in the horizontal direction and then return downward along the feed path of the channels (see Figs. 10(1) and 10(J)) so as to be arranged again in the arrangement of Fig. 10(A). In Fig. 10(J), the logs Rl, R2, R3, and R4 are devoid of the winding mandrel, while the logs R5-R11 still contain the winding mandrel. In the next cycle, the mandrels of the logs R5, R6, R7, and R8 will be removed, with the same cycle as previously described.

[0059] The mandrels, or more precisely the two half-mandrels that (coupled together and axially aligned) form each winding mandrel, are removed preferably when the removal cradles 17 are in the position of Fig. 10(D), with the operations schematically illustrated in the sequence of Figs. 11(A) to 11(E).

[0060] In Fig. 11(A) the logs R, from which the mandrels shall be removed, are loaded into the removal cradles 17. The two extraction members 63 are spaced fromthe removal cradles 17. The stops 49 are spaced from each other sufficiently to allow the insertion of the logs R into the removal cradles 17.

[0061] In the following step, illustrated in Fig. 11(B), the stops 49 approach the axial ends of the logs R in each removal cradle 17, to hold the log in a central position during the subsequent removal step. In alternative embodiments, the stops 49 may be omitted if the friction force that must be overcome to remove the two half-mandrels from the log R is equal or approximately equal for the two half-mandrels. In further embodiments, the stops 49 are fixed. In this case, even if the friction forces on the two half-mandrels are not balanced, the longitudinal movement of the log due to the traction exerted on the two mandrels is limited and does not compromise the proper removal of the two half-mandrels.

[0062] In Fig. 11(C) the two extraction members 63 approach the removal cradles 17 and the eight gripping elements 65 are inserted into the two half-mandrels of each of the four logs R arranged in the four removal cradles 17.

[0063] In Fig. 11(D), the two extraction members 63 have moved away from the removal cradles 17 and have removed, from each log R, the two half-mandrels Ml, M2, which in this step remain engaged to the gripping elements 65, the structure and operation of which will be described in detail below. During the removal step, a downward-directed force can be generated between each gripping element and the respective half-mandrel, for example to facilitate the transfer of an adhesive, previously applied to the mandrel consisting of the two half-mandrels Ml, M2 before the beginning of winding, from the half-mandrels to the inner coils of the web material. The downward thrust, which can be realized for example by lifting the slides 19, is also useful to facilitate the mutual gluing of the innermost coils of the web material forming each log.

[0064] In this step, each half-mandrel Ml, M2 faces a respective set of handling members 71, which engage the half-mandrels Ml, M2. In the following step (Fig. 11(E)), the gripping elements 65 are removed from the mandrels, with an extrastroke movement of the extraction members, so that each half-mandrel Ml, M2 remains engaged only to the respective handling member 71. At this point, with a movement orthogonal to the plane of Fig. 11(E), the handling members 71 transfer thehalf-mandrels to the mandrel conveyor 73, which recycles the half-mandrels sending them toward a rewinder, not shown.

[0065] In this step, as shown in Fig. 11(E), the stops 49 are moved away from the ends of the logs R, to allow the subsequent transfer thereof to the channels 9, from which they had been taken in the initial step of the cycle.

[0066] Figs. 13(A) to 13(C) show a side view of one of the handling members 71 and the movement with which it engages the half-mandrels Ml removed from the logs R, to transfer them to the mandrel conveyor 73 with a movement according to the arrow f71. The reference number 74 indicates supports for the half-mandrels along a closed path of the mandrel conveyor 73.

[0067] Fig. 12 shows a step of discarding a log R, from which one or both halfmandrels have not been removed. In the example, the log R arranged in the uppermost removal cradle is discarded through a rotation according to fl7x, in a direction opposite the direction of rotation with which the logs R are transferred from the removal cradles 17 to the channels 9. The reference number 90 indicates a discard chute, and the reference number 92 indicates a removal conveyor, if any, for removing the discarded logs. The conveyor 92 may be a belt conveyor, provided with a movement parallel to the axis of the logs R. Since the event of a log being discarded is very rare, it is possible to accumulate the discarded logs in a static hopper rather than removing them through a conveyor.

[0068] An embodiment of the gripping elements 65 and the operation thereof are described below with reference to Figs. 14, 15, and 16.

[0069] In this embodiment, each gripping element 65 of each extraction member 63 comprises a radially expandable pin 65.1 that comprises a conical distal portion 65.2 integral with a stem or rod 65.3. At the opposite end with respect to the conical distal portion 65.2, each gripping element 65 comprises an actuator 65.4. In the illustrated embodiment, the actuator 65.4 is a cylinder-piston actuator, for example of hydraulic or electric type, or preferably a pneumatic actuator. In some embodiments, the cylinder-piston actuator 65.4 is a single-acting cylinder-piston actuator. In other embodiments, the cylinder-piston actuator 65.4 is a double-acting actuator.

[0070] The rod or stem 65.3 is guided in a guide 65.6. One or more elastically deformable annular bodies 65.7 are provided between the part of the guide 65.6 facing the distal end of the rod 65.3 and the conical distal portion 65.2. Three elastically deformable annular bodies 65.7 are provided in the illustrated example. Each elastically deformable annular body is mounted on the rod 65.3 so as to be able to slide relative to the rod. The elastically deformable annular body furthest from the distal end of the rod is only partially free to slide relative to the rod due to a stop 65.9 integral with the guide 65.6.

[0071] Moreover, each elastically deformable annular body 65.7 may have a cylindrical or toroidal shape, with an axis coincident with the axis of the rod 65.3 and a hollow interior, forming the axial passage for the rod 65.3.

[0072] A spacer 65.8 is interposed between adjacent elastically deformable annular bodies 65.7. Each spacer 65.8 may be approximately cylindrical and has a through- hole, into which the rod 65.3 is inserted. Each spacer 65.8 is free to slide relative to the rod 65.3. The spacers 65.8 may be rigid, contrary to the elastically deformable annular bodies 65.7. It should be understood that the terms "rigid" and "elastically deformable" are relative terms and refer to the conditions of use of the described device. Therefore, the spacers 65.8 are rigid in the sense that they do not undergo detectable compressive deformation under normal use conditions, while the elastically deformable annular bodies 65.7 compress axially and expand radially in use, in the manner and for the purpose described below.

[0073] The set of spacers 65.8 and elastically deformable annular bodies 65.7 is arranged between a radial stop formed by the conical distal portion 65.2 and the radial stop 65.9 formed by the guide 65.6.

[0074] In rest conditions, when the rod 65.3 is in the extracted position, as shown in Fig. 14, the elastically deformable annular bodies 65.7 are in an undeformed condition, i.e. in a condition of minimum energy and minimum radial dimension. The outer diameter of the elastically deformable annular bodies 65.7, of the conical distal portion 65.2, and of the spacers 65.8 is such that in this condition the gripping element 65 can be inserted into the half-mandrel Ml (or M2), on which a log R is wound.

[0075] Once the insertion position has been reached (Fig. 14), the rod 65.3 with theconical distal portion 65.2 can be retracted into the position of Fig. 15. Since the elastically deformable annular bodies 65.7 and the spacers 65.8 are free to slide on the rod 65.3, they remain in a substantially unchanged position relative to the half-mandrel Ml (M2) and the log. The contraction caused by the retraction of the radial stop formed by the conical distal portion 65.2 causes the axial contraction of the elastically deformable annular bodies 65.7 and the consequent radial expansion thereof. As a result of this deformation, the elastically deformable annular bodies 65.7 are pressed against the inner surface of the half-mandrel. The friction thus generated between the elastically deformable annular bodies 65.7 and the inner surface of the half-mandrel Ml (or M2) is sufficient to remove the half-mandrel from the log R by retracting the respective extraction member 63.

[0076] Essentially, each of the two extraction members 63 therefore comprises an expandable element that engages by friction from the inside the respective hollow halfmandrel. The use of the elastically deformable annular bodies 65.8 described above avoids the need to use expandable elements of the hydraulic or pneumatic type inside the mandrels. This makes the system of mutual engagement between the extraction member and the mandrel significantly simpler, avoids the need for working fluid conduits, and avoids problems arising from possible leakage or seepage.

[0077] The elastically deformable annular bodies can be produced at low cost and can be easily replaced in case of wear, by simply removing the conical distal portion 65.2, which for this purpose may be for example screwed to the rod 65.3.

[0078] Moreover, this avoids to engage the half-mandrel from the inside and the outside as occurs in clamp-type gripping members, which can damage the halfmandrel or mandrel. Moreover, by acting only by friction from inside the half-mandrel, it is possible to use mandrels that do not exceed the length of the log R, since there is no need to have an outer surface that a clamp-type gripping member can grip.

[0079] In advantageous embodiments, in order to facilitate the removal of the halfmandrels Ml, M2 by the two opposite radially expandable pins 65.1 of the gripping elements 65, avoiding a pressure drop inside the axial hole of the log R, each radially expandable pin 65.1 includes an inner duct 65.10 to supply air into the log R and, more specifically, into the axial hole of the log R. Each inner duct 65.10 of each radiallyexpandable pin 65.1 also includes at least one air outlet 65.11, arranged at or near the distal end of the radially expandable pin 65.1, formed on the distal conical tip 65.2. In the illustrated embodiment, two sets of air outlets 65.11 are provided, configured in the form of two circular sets of holes inclined relative to the axis of the radially expandable pin 65.1.

[0080] In some embodiments, the inner duct 65.10 is directly fluidly coupled to the external environment, e.g. it has a proximal end, i.e. an end opposite the distal end65.12 of the radially expandable pin, open toward the external environment. In this way, when the radially expandable pins 65.1 are inserted into the ends of the log R and engage, with the elastically deformable annular bodies 65.7, the inner surface of the two half-mandrels (see Fig. 15), when the gripping elements 65 are moved away from each other to remove the half-mandrels Ml, M2, no pressure drop is generated inside the central hole of the log R with respect to the ambient pressure, because, through the inner duct 65.10 and the air outlets 65.11, air is taken from the environment into the inside of the volume formed by the hole where the mandrel Ml, M2 is housed.

[0081] In order to further facilitate the removal of the half-mandrels Ml , M2, in some embodiments it is possible to supply pressurized air inside the log R. In this case, the inner duct 65.10 may be coupled to an outer tube 65.13, for example a flexible tube, that takes air from a fan or a compressor schematically indicated with the reference number 66, or in general from a pressurized air network that may be provided in the apparatus where the production line of the logs R is installed. A valve 68 on the tube65.13 can selectively control the supply of pressurized air into the inner duct 65.10. This allows, for example, to supply pressurized air only when the radially expandable pins 65.1 have been expanded and have tightly engaged the inner surface of the respective half-mandrels Ml, M2.

[0082] The embodiment of the radially expandable pins 65.1 illustrated in Figs. 14, 15 and 16 is particularly advantageous because the expansion mechanism is mechanical and does not require the use of expandable sealing elements. However, it is also possible for the radially expandable pins 65.1 to be differently configured, for example with pneumatically expandable bodies. An embodiment of a radially expandable pin 65.1 with a pneumatically expandable body is schematically shown in Fig. 17. The same reference numbers indicate the same or equivalent parts to thosedescribed with reference to Figs. 14 to 16, that will be not described again.

[0083] Instead of one or more mechanically expandable bodies, such as the bodies 65.7 shown in Figs. 14 to 16, the embodiment of Fig. 17 includes one or more pneumatically expandable bodies. In the schematic embodiment of Fig. 17, a single pneumatically expandable body 65.21 is provided. Preferably, the pneumatically expandable body 65.21 is an annular body. In other embodiments, to provide more frictional grip between the radially expandable pin 65.1 and the half-mandrel Ml, M2, two or more pneumatically expandable bodies 65.21 may be provided, aligned with each other along the axial extension of the radially expandable pin 65.1.

[0084] The expansion of the pneumatically expandable body(ies) 65.21 can be achieved by supplying compressed air along the inner duct 65.10. This can be achieved, for example, by providing air outlets 65.11 of very small cross section, so as to generate a high localized pressure drop at the outlets. In this way, with a single supply of compressed air, it is possible to have, inside the duct 65.10, a pressure sufficient to expand the pneumatically expandable body(s) 65.21, and a modest air flow toward the inside of the log R, sufficient to avoid depressurization that can hinder the removal of the half-mandrels Ml, M2. Such a solution is schematically shown in Fig. 17, where the pneumatically expandable bodies 65.21 are fluidly coupled to the inner duct 65.10 through one or more radial holes 65.25.

[0085] In other embodiments, two inner ducts are provided inside each radially expandable pin 65.1 : a first inner duct to supply air (possibly at ambient pressure or slight overpressure) to the outlets 65.11; and a second inner duct to supply compressed air into the pneumatically expandable bodies 65.21.

[0086] Regardless of how the radially expandable pins 65.1 are configured, the inner duct(s) 65.10 allow to reduce or to nullify the pressure drop inside the axial cavity of the log R during the half-mandrel removal movement.

[0087] In this way, it is possible to ensure effective adhesion of the radially expandable pins 65.1 to the inner surface of the respective half-mandrels along the entire annular extension of the expandable bodies 65.21 or 65.7, without interruption of the contact surface, while avoiding resistance against removal due to depressurization of the inner axial cavity of the logs.

[0088] To further increase the efficiency and proper operation of the extractors 63 and the respective gripping elements 65, each radially expandable pin 65.2 can be associated with a sensor adapted to verify that the radially expandable pin is gripping the mandrel or half-mandrel during the removal step, so that an alarm is generated if (for any reason) one or both the half-mandrels are disengaged from the radially expandable pin during removal, or if one or both the half-mandrels remain constrained to the respective radially expandable pin once the removal of the mandrel from the log R has been completed.

[0089] Fig. 18 shows an axonometric view of a gripping element 65 similar to the gripping element 65 of Figs. 14, 15, 16, with a sensor 70. In the embodiment shown in Fig. 18, the sensor 70 is integral with the guide 65.6, and thus it moves with it, participating in the removal motion with which the gripping element 65 is provided.

[0090] The sensor 70 is configured to detect the presence of a winding mandrel engaged to the radially expandable pin 65.2. In the illustrated embodiment, the winding mandrel is configured in the form of two half-mandrels Ml, M2; therefore, two opposite extractors are provided, each of which is equipped with one or more gripping elements for gripping as many half-mandrels. Thus, in this embodiment, each sensor 70 is configured to detect the presence of one half-mandrel. If, on the contrary, the winding mandrel is made in one piece, only one extractor is provided with at least one gripping element on only one side of the device, to engage the winding mandrel at only one of the two ends of the log R.

[0091] The winding mandrel presence detection sensor works equivalently in the two cases. In one case, two sensors are provided, one for each of the two opposite gripping elements; in the other case, only one sensor is provided for the single gripping element.

[0092] The sensor 70 can be, for example, a capacitive sensor, or an optical sensor. In the embodiment schematically shown in Fig. 18, the sensor 70 is an optical sensor that projects an optical beam F onto a portion of the radially expandable pin 65. The sensor 70 detects whether a mandrel or half-mandrel Ml -M2 is present on the portion hit by the optical beam F, based on the characteristics of the optical radiation reflected or backscattered by the surface hit by the optical beam F. The optical sensor 70 can be a laser sensor adapted to project at least one laser beam, or laser ray, in the directionof the mandrel, or half-mandrel, to measure the distance and, based on it, to detect the presence or absence of the mandrel, or half-mandrel.

[0093] Other embodiments of the sensor 70 are also possible. For example, the sensor 70 can be a pressure sensor that detects the pressure in a suction duct, or in a pressurized air duct, that exits at a point of the outer surface of the radially expandable pin 65.1 that, under normal operating conditions, is covered by the mandrel or halfmandrel. The pressure in the duct, detected by the sensor, is a function of the presence or absence of the mandrel closing the end of the duct. If the sensor works with pressurized air, it can detect a lack of pressure, or insufficient pressure in the duct if the mandrel (or half-mandrel) does not properly cover the end of the duct. If, on the contrary, the duct is a suction duct, the sensor can detect the absence of the mandrel if the pressure in the duct is above a limit value.

[0094] In still further embodiments, the sensor is a capacitive sensor, adapted to detect the presence or absence of the mandrel (or half-mandrel) on the radially expandable pin. In other embodiments, the sensor is a load sensor that detects a force or pressure exerted radially from the outside of the radially expandable pin, toward the axis of the radially expandable pin. If the mandrel is not properly positioned, the force or pressure sensor detects an insufficient or null load, and can signal that the mandrel or half-mandrel has not been gripped.

[0095] In other embodiments, the sensor comprises a micro-switch that is capable of closing a circuit if it co-acts with the mandrel (or half-mandrel) properly engaged to the radially expandable pin. In case of absence or loss of the mandrel during removal, the circuit in which the micro-switch is inserted opens (or closes in reverse operation) and an alarm is generated for loss or failure to grip the mandrel by the radially expandable pin.

[0096] In further embodiments, the sensor 70 is a camera or a video camera. In this case, the sensor 70 shoots the portion of the radially expandable pin where the mandrel, or half-mandrel, should be present, or absent in the case of the step of releasing the expandable pin from the mandrel, or half-mandrel, when the removal has been completed. The images or photographs shot by the sensor 70 are processed by a vision algorithm that, for example, by comparing the detected images or videos withreference images or videos, recognizes the presence or absence of the mandrel or halfmandrel from the radially expandable pin.

[0097] In other embodiments, the sensor is a photoelectric sensor, a reflective photoelectric sensor, preferably a background suppression reflective photoelectric sensor. The latter type of sensors is particularly advantageous under certain operating conditions, as these sensors, through triangulation, not only evaluate the light intensity reflected from the detected object, in this case the mandrel when present or the radially expandable pin, but also detect the distance of the object from the sensor itself. The variation in the distance detected by the sensor allows to detect the presence or absence of the mandrel on the radially expandable pin.

[0098] In general, and irrespective of the nature and type of sensor used, such a sensor can promptly signal the absence of the mandrel on the radially expandable pin and can therefore provide, for example to a control unit, a piece of information on the basis of which the device in which the extractor is inserted can be stopped, or it can provide an alarm.

[0099] The mandrel or half-mandrel presence sensor can also be used in combination with gripping elements of other types and configured differently than what illustrated herein.

[0100] In fact, the use of a gripping element with a radially expandable pin as described herein has multiple advantages. For example, the grip of a tubular mandrel (in one piece or divided into two half-mandrels) allows to use tubular mandrels of a simple shape, without the need to make projections, shanks or other external gripping features. In addition, it is possible to grip the mandrel even if the end thereof does not protrude from the wound web material that forms the log. The grip from the inside is also less likely to mechanically damage the mandrel. Gripping the tubular mandrel with a radially expandable pin may avoid the need for a double gripping member, with gripping members placed radially outside and radially inside the mandrel. This makes the configuration of the gripping element easier.

[0101] However, at least some of the advantages that can be obtained by a sensor mounted so as to move with the gripping element and adapted to detect the presence of the mandrel (in one piece or divided into two half-mandrels) can also be obtainedwith differently shaped gripping elements, for example with a blocking system that acts from outside the mandrel with an action from the outside toward the axis of the mandrel.

[0102] In the above description, the various embodiments and the different features of the gripping element of the extractor have been described with reference to a complex device, in which the mandrel removal is combined with a log accumulation system, and in which the removal occurs simultaneously on a plurality of logs coming from the accumulator (see Figs. 1 to 13). However, multiple advantageous features and embodiments of the mandrel extractor and the respective gripping element can also be used in differently shaped mandrel removal devices.

[0103] Figs. 19 and 20 schematically show a different embodiment of a device for removing winding mandrels from logs of web material. The device is indicated with the reference number 101 and can be arranged downstream of a station 103 of a converting line. The station 103 may comprise, for example, a tail sealer for sealing the tail edge of the logs coming from a rewinder, not shown. The logs R coming from the gluing unit 103 roll on a chute 105 A, 105B, along which, in an intermediate position, a mandrel removal station 107 is provided. In the illustrated embodiment, the device 101 is configured to remove two-piece mandrels, i.e. mandrels consisting of two half-mandrels axially aligned with each other and coupled at two ends facing each other and placed inside the logs R.

[0104] In the illustrated embodiment, the removal station 107 is configured to process one log R at a time. The removal station 107 includes a rotating dispenser 109, adapted to rotate stepwise around an axis 109 A.

[0105] The device 101 comprises two extractors 112 arranged on the sides of the path of the logs R, as in this embodiment the device 101 is configured to remove halfmandrels, rather than a one-piece mandrel. Each extractor 112 comprises a gripping element 113. Each gripping element 113 comprises a radially expandable pin 115. Each gripping element 113 is mounted on a slide 117. The two slides 117 are aligned on the two sides of the removal station 107 and each slide can move according to the double arrow fl 17, for example along guides 119. The movement of the two slides 117 can be synchronous and specular. The gripping elements 113 and the radiallyexpandable pins 115 can be configured as the gripping elements 65 and the radially expandable pins 65.1, described above in one or more of embodiments of Figs. 1 to 18.

[0106] The device 101 operates as follows. The logs coming from the tail sealer 103 (or other upstream station) are stopped one at a time and sequentially in the removal station 107. The gripping elements 113 engage the mandrel M at both ends of the log R through an insertion movement of the radially expandable pins 115 and a subsequent radial expansion of the radially expandable pins 115. Once the radially expandable pins 115 have firmly engaged by expansion inside the two ends of the opposite halfmandrels Ml, M2 forming the winding mandrel M, the two slides 117 are moved away from each other to remove the half-mandrels from the log R. The log can be properly held in position, avoiding translation thereof in the axial direction, by means of stops 111 on both the sides of the path of the log R (see Fig. 19, omitted in Fig. 20). Once the half-mandrels Ml, M2 have been removed from the log R located in the removal station 107, the rotating dispenser 109 rotates to discharge the log R along the chute 105B toward a downstream station while the half-mandrels Ml, M2 are conveyed toward a downstream or upstream station, where they are again coupled together to form a winding mandrel that will be used for forming a new log R. The station for coupling, or coupling again, the two half-mandrels can be integrated in a rewinder for winding the logs R, which is not shown for the sake of simplicity of the description.

[0107] While in Figs. 19 and 20 the logs are held in position in the removal station 107 by means of the rotating dispenser 109 and the stops 111, it is understood that different systems may be used for positioning the logs and keeping them in position, for example a cradle defined by parallel rollers, or other systems.

[0108] From Figs. 19 and 20 it is clearly apparent that the above-described features of the gripping elements 65.1 can be used in very different removal devices.

[0109] As illustrated particularly in Figs. 14 to 17, the winding mandrel, made in two portions or half-mandrels, has a tubular shape of reduced thickness and preferably constant inner and outer diameter, except possibly in the area where the two halfmandrels are coupled together. The mutually coupled ends of the two half-mandrels forming the winding mandrel can be, for example, shaped with variable diameters toform a front snap-coupling between the two half-mandrels.

[0110] In advantageous embodiments, each half-mandrel is made of an elastic flexible material of such characteristics that it can be easily used in automatic and continuous peripheral rewinding machines, where each winding around a new mandrel requires, at an early stage of winding, deformation by pressure of the winding mandrel. As known to those skilled in the art, in the peripheral rewinders (also called surface rewinders), the winding of logs is done by keeping the winding mandrel and the log being formed in contact with a plurality of peripheral members, which move, for example rotate, and are in contact with the cylindrical surface of the mandrel and then of the log being wound. The torque that keeps the winding mandrel, and the log forming around it, rotating is transmitted to the peripheral members by friction. In general, the peripheral members include two or more motorized winding rollers. In some embodiments, the peripheral members also include belts or other flexible members, possibly combined with motorized winding rollers.

[0111] Figs. 21 to 24 show diagrams of peripheral rewinding machines of this type, described for example in detail in WO2012042549A1. It should be understood that what is depicted in the figures are exemplary and not limiting embodiments of continuous peripheral rewinders that can be used in the methods and apparatuses of the present invention. Therefore, the structure of the rewinder that can be used to produce logs according to the method described herein is not limited to what is shown in Figs. 21 to 24. For example, other types of rewinders compatible with the method described herein are disclosed in WO2014135933, WO9421545. In general, the rewinder can be a peripheral rewinder comprising a plurality of winding rollers that define at least one nip, through which the winding mandrels pass during a step of the log winding cycle. In some embodiments, the rewinder also comprises a stationary rolling cradle or plate, which defines, together with one of the winding rollers, a channel for introducing the winding mandrels.

[0112] In general, without going into the construction and operation details of each rewinder shown just by way of example in Figs. 21 to 24, the rewinder 100 comprises a first winding roller 101, a second winding roller 102, and a third winding roller 103. In the embodiment of Figs. 21, 22, 23, the rewinder also comprises a fourth winding roller 104. The reference number 106 indicates an introducer for introducing thewinding mandrels M into the winding head of the rewinder 100, which comprises the three or four winding rollers. In these embodiments, the winding mandrels M are introduced into a channel 107 formed by the first winding roller 101 (in Fig. 21) or the fourth winding roller 104 (in Figs. 22 and 23) and a stationary cradle or plate 109. The width of the channel 107, i.e. the distance between the cylindrical surface of the winding roller 101 and the rolling surface of the mandrels M, defined by the plate or cradle 109, is slightly smaller than the outer diameter of the winding mandrels M, for example 0.5% to 10% smaller than the outer diameter of the winding mandrels. In this way, when a winding mandrel M is inserted into the channel 107, it is slightly pressed between the plate 109 and the winding roller 104. The resulting friction brings the winding mandrel M into rotation, which, in this way, begins to roll along the plate 109 until it enters a nip defined between the winding rollers 104 and 102. The width of this nip, i.e. the distance between the cylindrical surfaces of the winding rollers 104 and 102, is equal to, or slightly less than, the diameter of the winding mandrel M and any coils of web material N that begin to form around it.

[0113] In general, the cycle of winding the logs R around the mandrels M in so-called "peripheral" rewinders may therefore involve a step of elastic deformation, due to pressure, of the winding mandrels M, resulting in the (normally circular) section of the winding mandrels taking an oval shape. This elastic deformation results from the mutual distance between two members (two winding rollers, or a winding roller and a stationary plate), that are essentially rigid. In the present description, the term “essentially rigid” means that these members do not perceptibly deform under the load applied during the normal winding cycle.

[0114] In order to achieve proper flexural behavior of the winding mandrels M at this early stage of the winding cycle, and to be able to utilize the entire axial length of the winding mandrels M in order to wind the web material N around them, it is advantageous for the winding mandrels M to have a cylindrical tubular, i.e. hollow, shape and a substantially constant elastic deformability characteristic along their axial development. It is also advantageous for the winding mandrels M to have a flexural behavior that allows elastic deformation in elastic field during normal use, so that they deform, due to pressure, during the step of introduction and angular acceleration in the winding head of the rewinder.

[0115] These elastic deformability characteristics, combined with the production of the winding mandrel M in two half-mandrel Ml, M2 removable from opposite ends of the log R, allow improved winding and removal of the mandrels compared with what can be achieved in prior art removable mandrel winding systems.

[0116] In addition, it is particularly advantageous that the two half-mandrels Ml, M2 are engaged from the inside, that is, from the inner cylindrical surface of the tubular half-mandrel, by the gripping elements of the extractor. This allows effective and secure gripping without damaging the mandrel, even when the mandrel consists of a thin-walled tubular structure, to ensure the elastic deformability mentioned above.

[0117] For example, a removal device as disclosed in EP4079667, which involves gripping a portion of the mandrel protruding from the log R by means of a clasp, has the major disadvantage of compulsory using mandrels that are significantly longer than the log R, which results in having a wider and bulkier processing line for the same axial length of the log R. In addition, to generate a frictional force sufficient for removing the mandrel, the clasp-shaped extractor must strongly press the end of the mandrel protruding from the log R, thus shortening the useful life of the mandrel due to the inevitable breakage at the clasping point. This drawback is amplified in the case of mandrels formed in a single piece.

[0118] Furthermore, winding mandrels that employ a shank for removal, as shown in WO 99 / 42393 or in IT1201390, are particularly disadvantageous because the shank severely unbalances the mandrel during the winding step, inevitably compromising the production speed and thus the total productivity of the production line. These mandrels are also significantly more expensive and complex.

[0119] With the combination of a rewinder and a removal device as described above, it is possible to implement a method for forming a coreless log of web material by winding a web material around a tubular mandrel comprising two half-mandrels that are coupled together and can be extracted from the complete log by traction from opposite ends of the log, with a removal cycle comprising the following steps: inserting a first removal pin into the first end of the tubular mandrel and inserting a second removal pin into the second end of the tubular mandrel;axially engaging the first removal pin inside the first tubular half-mandrel and the second removal pin inside the second tubular half-mandrel; removing the first tubular half-mandrel from the log through an axial movement of the first removal pin, and removing the second tubular halfmandrel from the log through an axial movement of the second removal pin, the axial movement of the first removal pin and the axial movement of the second removal pin being in opposite directions.

[0120] The removal pins are advantageously radially expandable and, in the following, they will also be referred to as “radially expandable pins”, or “radially expandable removal pins”.

[0121] To facilitate the step of winding the logs R, the half-mandrels Ml, M2 are made of a flexible elastic material, with a flexural modulus between 100 MPa and 8000 MPa.

[0122] In this context, the flexural modulus is defined according to ISO 178:2019.

[0123] In particularly advantageous embodiments, the material of which the halfmandrels Ml, M2 are made can have a flexural modulus between 100 MPa and 6000 MPa.

[0124] The thickness of the winding half-mandrels can vary depending on the outer diameter. For example, the outer diameter can be between 10 mm and 150 mm. In other embodiments, the outer diameter is between 25 mm and 100 mm, or between 25 mm and 60 mm.

[0125] In some embodiments, the thickness of the tubular winding mandrel is comprised between 0.2 mm and 15 mm or between 0.2 mm and 10 mm, or between 0.2 mm and 6 mm, for example between 0.2 mm and 5 mm. In other embodiments, the thickness of the tubular winding mandrel is comprised between 0.4 mm and 10 mm, or between 0.4 mm and 6 mm, or between 0.4 mm and 0.5 mm.

[0126] In some embodiments, the ratio of thickness to outer diameter of the tubular winding mandrel is comprised between 0.01 and 0.13, or between 0.05 and 0.10.

[0127] The materials that are particularly suitable for the production of tubularwinding mandrels, i.e. of the two tubular half-mandrels that form the tubular winding mandrel, have a ratio of tensile strength to flexural modulus of 1.25% or more.

[0128] Advantageously, the materials having flexural modulus and tensile strength that are particularly suitable for producing half-mandrels are, for example, polymer- based materials, or fiber-reinforced polymer materials, for example reinforced with carbon fibers, or glass fibers, or aramid fibers.

[0129] The polymer material can be chosen from the group comprising: polytetrafluoroethylene, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidenefluoride, polyoxymethylene homopolymer, polyoxymethylene copolymer, polyamide 6, polyamide 66, high density polyethylene, high molecular weight polyethylene, ultra high molecular weight polyethylene, polypropylene, hard unplasticized polyvinyl chloride, polyetheretherketone, acrylonitrile, butadiene, styrene, polycarbonate, polymethylmethacrylate, polyethylene terephthalate, polyimide, acetal resin, acrylonitrile-butadiene-styrene copolymer, polyvinyl fluoride, polysulfone, methacrylate, polyamide 12. The polymer material can be or not be fiber reinforced, for example with carbon fibers, glass fibers, aramid fibers.

[0130] As described above, the inner surface of each tubular winding half-mandrel can be a uniform cylindrical surface, at least for the section adj acent to the end opposite the end intended for coupling with another half-mandrel. Preferably, the inner surface of each tubular winding half-mandrel is uniformly cylindrical over the entire length of the half-mandrel, from the free end, i.e. the end not intended to be coupled to another half-mandrel, to the end for coupling to another half-mandrel, with the sole possible exception of one or more elements or components for mutual coupling between halfmandrels, positioned at the coupling end.

[0131] In this case, the step of removing the two half-mandrels from the log comprises the step of axially engaging the first radially expandable removal pin to the first tubular half-mandrel and the second radially expandable removal pin to the second tubular half-mandrel by radial expansion of the two removal pins only. The axial engagement between the half-mandrel and the respective radially expandable pin is achieved by friction between one or more expandable elements of the radially expandable pin and the inner cylindrical surface of the half-mandrel.

[0132] This allows to produce each tubular winding half-mandrel with uniform thickness and thus uniform elasticity even at the respective ends that, during the winding step, are at the log ends. This results in particularly advantageous behavior in the elastic deformation step due to pressure, when the tubular winding mandrel begins to rotate inside the rewinder, pressed diametrically to allow angular acceleration and gripping of the web material to be wound.

[0133] In some embodiments, for example for producing particularly compact logs, or logs for which it is useful or necessary to apply a glue to the outer surface of the tubular winding mandrel for a more secure adhesion of the leading edge of the web material to be wound, it may be useful to ensure a more reliable axial connection between removal pins and half-mandrels, or an axial connection capable of resisting higher tensile forces than those that can be obtained by simple friction between the radially expandable pin and the respective half-mandrel.

[0134] In this case, in some embodiments the first end of the tubular winding mandrel, formed by coupling two tubular winding half-mandrels, comprises a first inner protrusion, and the second end of the tubular mandrel comprises a second inner protrusion. In this case, the step of axially engaging the first radially expandable pin to the first tubular winding half-mandrel and the second radially expandable pin to the second tubular winding half-mandrel includes the step of expanding the first radially expandable pin and the second radially expandable pin, thus causing an interference between the first radially expandable pin and the first inner protrusion and between the second radially expandable pin and the second inner protrusion.

[0135] This embodiment is shown in Figs. 25, 26 and 27, where Fig. 25 shows a section of a free end of a tubular winding half-mandrel Ml, M2 according to a plane containing the mandrel axis A-A. The letter "s" indicates the thickness of the tubular half-mandrel, DI indicates the outer diameter, and D2 indicates the inner diameter. The end of the tubular winding half-mandrel Ml, M2 comprises an inner protrusion. In the illustrated embodiment, the inner protrusion comprises a plurality of inner projections 120, angularly spaced from one another, each of which projects radially inward. The letter H denotes the height of each projection 120, i.e. the radial dimension of the projection measured from the inner cylindrical surface Si of the tubular winding half-mandrel.

[0136] Each projection 120, forming part of the radial protrusion, can be applied to the inner cylindrical surface Si of the tubular winding half-mandrel Ml, M2. In other embodiments, for ease of assembly, the projections 120 can be produced in a single piece including an annular band 122 joining the various projections 120. The band 122 has a very small thickness, for example a few tenths of a millimeter, so that the flexibility (and thus the flexural modulus of the tubular winding half-mandrel) is not significantly modified.

[0137] Fig. 26 shows an axonometric view of one end of a log R formed around a tubular winding mandrel consisting of two coupled tubular winding half-mandrels, each having its free end accessible through an axial hole in the log R or protruding from it, as shown in Fig. 26. The tubular winding half-mandrels are made as described with reference to Fig. 25.

[0138] Fig. 27 shows the step of inserting a radially expandable removal pin 65.1 into the respective tubular winding half-mandrel Ml, M2, around which the log R is formed. The radially expandable pin 65.1 comprises a radially expandable body 65A. In other embodiments, the radially expandable pin 65.1 is made as shown in Figs. 14 to 18 and previously described.

[0139] The expandable body 65A can be expanded by mechanical compression, by pneumatic or hydraulic expansion with a pressurized fluid, or in any other way. In some embodiments, the expansion of the expandable body 65A is such that the outer surface of the expandable body 65A touches the inner cylindrical surface Si of the respective half-mandrel M1 / M2. The contact pressure between the expandable body 65A and the inner surface Si of the half-mandrel M1 / M2 may be insufficient to allow the removal of the half-mandrel from the log R. In other embodiments, the expansion of the expandable body 65A may be insufficient to generate pressure between the expandable body and the inner surface of the half-mandrel.

[0140] In any case, the radial dimension of the expandable body 65 A before and after radial expansion is such that: in the absence of radial expansion, the expandable body 65A can penetrate into the tubular winding half-mandrel by passing over the projections 120; when radially expanded, the radially expandable body 65 A has a radial dimension such that it abuts against the projections 120 and is not able to goover them. The traction of the radially expandable pin 65.1 discharges onto the projections 120 and thus onto the half-mandrel Ml, M2, ensuring an axial coupling sufficient to cause the removal of the half-mandrel Ml, M2 from the log R.

[0141] With the method described above, and with a apparatus comprising an automatic peripheral rewinder and a half-mandrel removal system as described above, using radially expandable pins, and using half-mandrels with the flexural modulus characteristics described herein, it is possible to wind logs of web material, particularly logs of tissue paper, around removable half-mandrels, which are elastically deformed by compression during the start-up step of each winding cycle, allowing diametral contraction between winding rollers and / or in the channel for inserting the winding mandrels into the rewinder. Moreover, the special design of the half-mandrels and the radially expandable removal pins allows efficient handling of the half-mandrels during the removal step, with effective gripping from inside the tubular winding halfmandrels, which avoids or reduces the mechanical damage to the mandrels, that in this way can be reused a substantial number of times. The use of half-mandrels also reduces the problems of side bulk of the processing line where the half-mandrel removal system is inserted, reduces the forces involved in removal, and allows for a balanced distribution of stresses on the logs, resulting in less mechanical stresses on the logs, which suffer less damages than those generated by extraction systems that act on only one side of the log by removing whole winding mandrels from one end of the roll. The balanced stress on the log during the removal step reduces the reaction forces required to hold the log in place. If the system is properly balanced, the reaction forces on the log are null. In addition, the traction force to be generated by each radially expandable pin on the respective half-mandrel is about half the force required if the mandrel is one-piece and must be removed from a single side.

[0142] Furthermore, for removing the mandrel, the use of radially expandable pins that engage the inner surface of the winding mandrel, or of each half-mandrel, allows the use of winding mandrels that do not need to protrude excessively in axial direction from the ends of the log R, and therefore shorter and more manageable winding mandrels. In addition, the winding mandrels are also less expensive than, especially, the mandrels that have engagement shanks at the ends for removal.

[0143] Advantageously, by using mandrels and half-mandrels that are shorter thanwhat is needed in prior art methods and apparatuss, thanks to the fact that the removal is done by gripping of the radially expandable pin inside the half-mandrels, it is possible to use half-mandrels that, when coupled, form winding mandrels, the length of which is slightly longer than the width of the web material to be wound, and thus the axial length of the logs. In some embodiments, each mandrel protrudes, from each end of the log R, 100 mm or less, or 60 mm or less, preferably 30 mm or less.

[0144] The high elasticity of the half-mandrels is advantageous not only because it allows the tubular winding mandrel to deform by radial pressure in the first winding step without breakage for a large number of production cycles. It also reduces the risk of breakage due to impact of the half-mandrels at all stages of half-mandrel handling during the work cycle: mutual coupling; insertion into the rewinder; Removal from the logs; transfer back to the rewinder.

Claims

CLAIMS1. A method for producing a coreless log of web material by winding a web material around a tubular mandrel to form a log of web material wound around the tubular mandrel; wherein the tubular mandrel includes: a first tubular half-mandrel having an inner cylindrical surface and an outer cylindrical surface and forming a first end of the tubular mandrel, and a second tubular half-mandrel having an inner cylindrical surface and an outer cylindrical surface and forming a second end of the tubular mandrel; and wherein the first tubular half-mandrel and the second tubular half-mandrel are coaxial with each other and consecutive to each other; wherein the method comprises the following steps: inserting a first removal pin into the first end of the tubular mandrel and inserting a second removal pin into the second end of the tubular mandrel; axially engaging the first removal pin inside the first tubular half-mandrel and the second removal pin inside the second tubular half-mandrel by radially expanding the first removal pin and the second removal pin; and removing the first tubular half-mandrel from the log through an axial movement of the first removal pin, and removing the second tubular halfmandrel from the log through an axial movement of the second removal pin, the axial movement of the first removal pin and the axial movement of the second removal pin being in opposite directions; wherein the first tubular half-mandrel and the second tubular half-mandrel are made of a flexible elastic material, with a flexural modulus between 100 MPa and 8000 MPa.

2. The method of claim 1, wherein the flexible elastic material has a flexural modulus between 100 MPa and 6000 MPa.

3. The method of claim 1 or 2, wherein the tubular mandrel has an outer diameter between 10 mm and 150 mm, or between 25 mm and 100 mm, or between 25 mm and 60 mm.

4. The method of any one of the preceding claims, wherein the thickness of the tubular mandrel is between 0.2 mm and 15 mm, or between 0.2 mm and 10 mm, or between 0.2 mm and 6 mm, or between 0.2 mm and 5 mm, or between 0.4 mm and 10 mm, or between 0.4 mm and 6 mm, or between 0.4 mm and 0.5 mm.

5. The method of any one of the preceding claims, wherein the ratio of thickness to outer diameter of the tubular mandrel is between 0.01 and 0.13, or between 0.05 and 0.10.

6. The method of any one of the preceding claims, wherein the material of which the first tubular half-mandrel and the second tubular half-mandrel are made has a ratio of tensile strength to flexural modulus of 1.25% or more.

7. The method of any one of the preceding claims, wherein the step of removing the first tubular half-mandrel and the second tubular half-mandrel includes the step of applying to the first tubular half-mandrel and the second tubular halfmandrel forces that are substantially aligned with the axis of the tubular mandrel comprised of the first tubular half-mandrel and the second tubular half-mandrel, and oriented in opposite directions.

8. The method of any one of the preceding claims, wherein during the step of removing the first tubular half-mandrel and the second tubular half-mandrel from the log, the log is held axially.

9. The method of claim 8, wherein during the step of removing the first tubular half-mandrel and the second tubular half-mandrel, the log is held axially by a first stop acting on the first axial end of the log and a second stop acting on the second axial end of the log.

10. The method of any one of the preceding claims, wherein each of the first and second tubular half-mandrels has a constant inner diameter and a constant outer diameter at least in respective sections forming the first end and the second end of the mandrel.

11. The method of any one of the preceding claims, wherein the material of which the tubular mandrel is made is a polymer-based material.

12. The method of claim 11, wherein the material of which the tubular mandrel is made is fiber reinforced, preferably with carbon fibers, or glass fibers, or aramid fibers.

13. The method of any one of the preceding claims, including the step of axially engaging, by friction, the first removal pin and the second removal pin to the inner surface of the first tubular half-mandrel and the second tubular half-mandrel.

14. The method of any one of the preceding claims, wherein the first half-mandrel and the second half-mandrel have an approximately uniform cross- sectional area along the entire length.

15. The method of any one of claims 1 to 13, wherein the first end of the tubular mandrel includes a first inner protrusion and the second end of the tubular mandrel includes a second inner protrusion; and wherein the step of axially engaging the first removal pin to the first tubular half-mandrel and the second removal pin to the second tubular half-mandrel includes the step of expanding the first removal pin and the second removal pin, thus causing an interference between the first removal pin and the first inner protrusion and between the second removal pin and the second inner protrusion.

16. The method of claim 15, wherein each of the first and second inner protrusions comprises a plurality of radial projections that extend from the inner surface of the mandrel and are angularly spaced from each other.

17. The method of claim 16, wherein the radial projections of each end of the tubular mandrel are joined together by an annular band, whose thickness is lower than that of the tubular mandrel.

18. An apparatus for producing coreless logs of web material, including: - a rewinding machine comprising at least a plurality of motorized winding rollers that are configured to wind the web material around a tubular mandrel to form a log of web material wound around the tubular mandrel; wherein the tubular mandrel is formed by a first tubular half-mandrel having an inner cylindrical surface and an outer cylindrical surface and forming a first end of the tubular mandrel, and a second tubular half-mandrel having an inner cylindrical surface and an outer cylindrical surface and forming a second end of the tubular mandrel; wherein the first tubular half-mandrel and the second tubular half-mandrel are coaxial with each other and consecutive to each other; and wherein the first tubularhalf-mandrel and the second tubular half-mandrel are made of a flexible elastic material, with a flexural modulus between 100 MPa and 8000 MPa;- a removal device for removing tubular mandrels, including a first removal pin, adapted to be inserted into the first end of the tubular mandrel, and a second removal pin, adapted to be inserted into the second end of the tubular mandrel; wherein the first removal pin and the second removal pin include at least one expandable element adapted to engage the inside of the first half-mandrel and the second half-mandrel, respectively; wherein the removal device is configured for:■ inserting the first removal pin into the first end of the tubular mandrel and inserting the second removal pin into the second end of the tubular mandrel when the tubular mandrel is contained within a log wound around the tubular mandrel;■ axially engaging the first removal pin inside the first tubular half-mandrel and the second removal pin inside the second tubular half-mandrel; and■ removing the first tubular half-mandrel from the log through an axial movement of the first removal pin, and removing the second tubular halfmandrel from the log through an axial movement of the second removal pin opposite to the movement of the first removal pin;19. The apparatus of claim 18, wherein the flexible elastic material has a flexural modulus between 100 MPa and 6000 MPa.

20. The apparatus of claim 18 or 19, wherein the tubular mandrel has an outer diameter between 10 mm and 150 mm, or between 25 mm and 100 mm.

21. The apparatus of any one of claims 18 to 20, wherein the thickness of the tubular mandrel is between 0.2 mm and 15 mm, or between 0.4 mm and 10 mm, or between 0.4 mm and 6 mm.

22. The apparatus of any one of claims 18 to 21, wherein the material of which the first tubular half-mandrel and the second tubular half-mandrel are made has a ratio of tensile strength to elastic modulus of 1.25% or more.

23. The apparatus of any one of claims 18 to 22, wherein the material of which the tubular mandrel is made is a polymer-based material.

24. The apparatus of claim 23, wherein the material of which the tubular mandrel is made is fiber reinforced, preferably with carbon fibers, or glass fibers, or aramid fibers.

25. The apparatus of one or more of claims 18 to 24, wherein the rewinding machine includes a tubular mandrel insertion device configured to sequentially insert one tubular mandrel at a time into an insertion path when a previous log has been completely wound.

26. The apparatus of claim 28, wherein the insertion path includes a portion where the tubular mandrels pass, which has a size smaller than the diameter of the tubular mandrels.

27. The apparatus of claim 25 or 26, wherein the insertion path includes: a channel formed between one of the winding rollers and a stationary rolling plate; and a nip formed between two winding rollers, the nip being arranged downstream of the channel relative to the feed direction of the winding mandrel; the portion where the tubular mandrels pass being arranged in the channel or in the nip.

28. The apparatus of any one of the preceding claims, wherein the expandable element of each of the first removal pin and the second removal pin is adapted to engage the inner surface, preferably the inner cylindrical surface, of the first tubular half-mandrel and the second tubular half-mandrel, respectively; and / or a first inner protrusion of the first end of the tubular mandrel and a second inner protrusion of the second end of the tubular mandrel.

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