Cylinder for paper manufacturing machines

Description

1 / 24 Cylinder for paper manufacturing machines Separated from BR112023013743-8, filed on January 12, 2022. FIELD OF TECHNIQUE

[001] The present invention relates to machine components used in plants for the production of cellulose webs, in particular in paper manufacturing plants. Some embodiments disclosed in the present invention relate especially to cylinders for machines producing cellulose layers or webs, such as paper or tissue paper. In particular, hollow cylinders are described, which are adapted to be pressurized by means of steam or other heat transfer fluid and designed to dry cellulose layers or webs conducted around the cylinders. BACKGROUND OF THE TECHNIQUE

[002] Wet methods are generally used for the production of cellulose webs, sheets, and layers, such as paper layers. According to these methods, cellulose fibers are suspended in water; the resulting suspension is distributed into the forming fabrics by means of headboxes so as to form a layer of cellulose pulp. The water content in the pulp is reduced by drainage systems until a layer of cellulose fibers is formed, the solids content of which is sufficient to transfer the layer to one or more drying cylinders that further remove moisture from the cellulose layer by evaporating it thanks to heat transferred to the cellulose layer from the inside of the cylinder through the cylindrical wall of the cylinder. Heat is usually supplied by a heat transfer fluid flowing in the drying cylinder. For this purpose, the drying cylinder is hollow.

[003] The heat transfer fluid is usually high-pressure steam. High pressure values ​​are used to allow for temperature Petition 870260076793, dated 07 / 31 / 2026, page 7 / 111 2 / 24 operating speeds high enough to efficiently remove moisture from the pulp layer until the desired residual moisture level is obtained before removing the resulting pulp layer from the drying cylinder.

[004] Therefore, drying cylinders must be manufactured in such a way as to withstand high pressures under dynamic load conditions and high operating temperatures.

[005] Yankee cylinders, which are commonly used for paper production, especially toilet paper, as well as drying rolls, operate under particularly heavy conditions. These machine members are bulky and critical from a safety standpoint due to the operating pressures and temperatures and the resulting thermal and mechanical stresses. High-speed rotation of Yankee cylinders and other drying rolls used in papermaking machines generates fatigue stresses, which are particularly critical due to the risk of breakage in case of cracks or defects in the metal from which the cylinders are made.

[006] Originally, drying rolls and Yankee cylinders were mainly made of cast iron. Recently, several systems have been studied for manufacturing drying rolls and Yankee cylinders made of steel. This material is particularly suitable for drying rolls and Yankee cylinders since it allows for better heat transfer to the cellulose layer conducted around the outer surface of the cylinder. Steel cylinders are comprised of parts that are welded together, typically a cylindrical casing with two axial ends, to which respective end walls are welded; these walls carry the pins for support and rotation of the cylinder.

[007] Examples of welded Yankee cylinders are described in US 438,752, EP1838922, WO2020 / 194358, DE202020106010, Petition 870260076793, dated 07 / 31 / 2026, page 8 / 111 3 / 24 WO2019 / 209164, EP3556936, US2016 / 0228969.

[008] AT-11146U1 describes a steel Yankee cylinder including a cylindrical liner, whose axial ends form respective annular projections facing the axis of the cylindrical liner. Along each annular projection a respective end wall is connected. The perimeter edge of each end wall and the radially inner edge of the respective annular projection are machined so as to connect the end wall and the annular projection by means of an inner weld bead and an outer weld bead. The maximum diameter of each end wall is equal to or less than the minimum inner diameter of the respective annular projection of the axial end of the cylindrical liner. In this way, the end wall can be positioned with its respective peripheral edge aligned with the annular projection of the axial end of the cylindrical liner, and the two members can be welded to each other by the inner and outer weld beads.The axial mechanical stresses generated in each end wall by the steam pressure inside the Yankee cylinder are fully supported by the weld beads, which represent critical points from the perspective of the Yankee cylinder's mechanical strength.

[009] The welds joining the end walls and the cylindrical lining in Yankee cylinders and drying rolls for papermaking machines must meet very high quality and safety standards, since these cylinders are, in practice, pressure vessels. The welds must withstand the stresses generated by the pressure, the weight of the cylinder, and thermal expansion. These stresses vary as the temperature changes and, due to the rotation of the cylinders and changes in operating conditions, they can be cyclical, thus inducing fatigue stresses. Therefore, the welds must not have defects that could cause dangerous ruptures. Therefore, only Petition 870260076793, dated 07 / 31 / 2026, page 9 / 111 4 / 24 highly specialized personnel can perform these welds, and the welds must be checked using X-rays, both at the start of operation and periodically over time. This significantly affects both production costs and times, and the operational cost over the cylinder's lifespan.

[0010] In any case, welds still remain a potential cause of even catastrophic cylinder ruptures, with a risk of accidents that can be fatal due to the operating temperatures and pressures of these machine parts.

[0011] In addition to being less thermally efficient, cylinders made of cast iron also require that the end walls and cylinder liner be joined by means of threaded couplings. These couplings greatly affect the production costs of the cylinder, since they require a lot of boring and threading processing, as well as long assembly times.

[0012] It would therefore be beneficial to provide Yankee cylinders and other drying rolls for use in papermaking machines that would partially or completely overcome the disadvantages of the prior art cylinders mentioned above. SUMMARY OF THE INVENTION

[0013] According to one aspect, a cylinder of a paper-making machine is disclosed, which comprises a cylindrical lining that defines an axis of the cylinder and has opposite axial ends, to which two end walls are attached, closing the hollow internal space of the cylinder. The respective pins for supporting and rotating the cylinder may be attached to the two end walls. At least one of the axial ends of the cylindrical lining comprises an internal annular projection that extends radially towards the axis of the cylinder and has a minimum diameter that is smaller than the maximum diameter of the respective end wall. The wall Petition 870260076793, dated 07 / 31 / 2026, page 10 / 111 The 5 / 24 end is then mounted so that a portion of the end wall having the maximum diameter is positioned axially inside relative to a portion of the inner annular projection having the minimum diameter. In this way, in use, the pressure in the cylinder pushes the end wall to abut the inner annular projection of the respective axial end of the cylinder, thus discharging the stress caused by the pressure on the axial end.

[0014] Unlike Yankee cylinders of the prior art, in particular the Yankee cylinder of the ATI 1146U1, the axial thrust generated by the vapor pressure in the Yankee cylinder is not applied to the weld.

[0015] There is therefore no need for expensive welding or bolt connections to join the end wall and the liner. A cheaper and safer cylinder is then provided, which may also require less manufacturing time.

[0016] Preferably, the same mounting criterion is applied to both end walls of the cylinder, using radial projections within the two axial ends of the cylindrical casing.

[0017] Essentially, according to one aspect, the invention provides a cylinder with an outer cylindrical coating and two opposing end walls, wherein at least one axial end, and preferably both axial ends, of the coating define an annular projection forming a recess, against which the respective end wall is fixed from the inside. In practice, the end walls have a maximum diameter that is greater than the minimum inner diameter of the respective projection.

[0018] The recess can be formed by providing an end wall having two portions of different diameters, and preferably cylindrical in shape, placed one on top of the other along the axis of the cylinder. The portion with the larger diameter is disposed within one of the portions. Petition 870260076793, dated 07 / 31 / 2026, page 11 / 111 6 / 24 smaller diameter of the annular projection. In further embodiments, the recess is formed by providing an annular projection having a radially internal surface of truncated-conical shape and a corresponding end wall having a truncated-conical perimeter surface, the shape of which is substantially identical to that of the internal truncated-conical surface of the annular projection. The two truncated-conical surfaces are oriented so that the larger base faces the interior of the cylinder, while the smaller base faces the exterior of the cylinder.

[0019] To allow mounting, the projection and / or end wall have at least one notch or flattened part or recess, allowing the back wall to be inserted beyond the annular projection.

[0020] According to a further aspect, a method is provided for manufacturing a cylinder for paper-making machines, which comprises the following steps: provision of a cylindrical casing defining an axis of the cylinder and having a first axial end and a second axial end; wherein the first axial end comprises an internal annular projection that extends radially towards the axis of the cylinder; insertion, in the cylindrical lining, of at least one first end wall having a maximum diameter greater than a minimum diameter of the first annular projection; wherein the insertion of the first end wall through the first annular projection is permitted by at least one of the following: a radial notch in the first annular projection, a radial perimeter recess of the first end wall.

[0021] Further advantageous features and modalities of the cylinder and manufacturing method will be described below and are presented Petition 870260076793, dated 07 / 31 / 2026, page 12 / 111 7 / 24 in the attached claims, which form an integral part of this description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention will be better understood by following the description and accompanying drawings, which show exemplary, non-limiting embodiments of the invention. More specifically, in the drawing: Figure 1 is a schematic cross-section of a cylinder in one embodiment; Figure 2 shows an enlargement of detail I from Figure 1; Figure 3 shows an enlarged detail of Figure 2 in an additional mode; Figure 4 shows an enlarged detail of Figure 2 in an additional mode; Figures 5A, 6A, 7A, 8A and 9A are front views of a sequence for assembling an end wall in a cylindrical casing; Figures 5B, 6B, 7B, 8B, 9B and 10 are side views of the same assembly sequence; Figures 11 to 17 show a sequence for assembling the rod and the support and rotation pins on the two end walls of the cylinder; Figures 18A and 18B show, respectively, a front and a side view of equipment for assembling end walls; Figure 19 shows a detail of one embodiment of a cylinder with internal grooves for condensate collection; Figures 20A, 21A, 22A and 23A are front views of a sequence for assembling an end wall in a cylindrical casing in a further embodiment; Figures 20B, 21B, 22B, and 23B are side views of Petition 870260076793, dated 07 / 31 / 2026, page 13 / 111 8 / 24 same assembly sequence as Figures 20A-23A; Figures 25A, 26A and 27A are front views of an additional sequence for assembling an end wall in a cylindrical casing in an additional embodiment; Figures 25B, 26B, and 27B are side views of the same assembly sequence as Figures 25A-27A; Figure 28 is a schematic front view of an end wall in an additional embodiment, before being mounted on the cylinder; Figure 29 shows a side view according to XXIXXXIX of Figure 28; Figure 30 is a side view of one end of the cylindrical casing to be combined with the end wall of Figures 28, 29; Figure 31 shows a cross-section according to XXXI-XXXI of Figure 39; Figure 32 is a side view of the end wall of Figures 28, 29 aligned with the cylindrical lining to be mounted on it; Figure 33 shows a cross-section according to XXXIII-XXXIII of Figure 32; Figure 34 shows a view analogous to that of Figure 32 in a subsequent assembly step; Figure 35 shows a cross-section according to XXXV-XXXV of Figure 34; Figure 36 shows a view analogous to that in Figure 34 at a subsequent assembly stage; Figure 37 shows a cross-section according to XXXVII-XXXVII of Figure 36; Figure 38 shows a view analogous to that in Figure 36. Petition 870260076793, dated 07 / 31 / 2026, page 14 / 111 9 / 24 in a subsequent assembly step; Figure 39 shows a cross-section according to XXXTX-XXXTX from Figure 38; Figure 40 shows a cross-section along the XL-XL line of Figure 34; Figure 41 shows a cross-section along the XLI-XLI line of Figure 36; and Figure 42 shows a cross-section along the XLII-XLII line of Figure 38. DETAILED DESCRIPTION

[0023] As will become clear from the detailed description below of some embodiments, in order to have a simpler and safer cylinder structure, it is planned to manufacture a cylindrical casing with axial ends that are provided with internal annular projections forming respective ridges, against which the respective end walls rest and to which they are fixed and welded. In this way, the pressure inside the cylinder, generated, for example, by the heating of the steam, generates an impulse in the end wall, which is discharged in the annular projection instead of being discharged entirely in the welds or screw couplings that join the end wall and the cylindrical casing. Even though, in principle, this technique can be applied to only one of the two end walls of the cylinder, it is, however, advantageous to adopt it for both end walls.

[0024] To allow the insertion of an end wall into the cylindrical casing beyond the annular projection having a diameter that is smaller than the outer diameter of the end wall, the end wall and / or the annular projection may be provided with one or more notches or recesses, i.e., flattened parts, so as to have points on the end wall where the diameter is smaller than the diameter. Petition 870260076793, dated 07 / 31 / 2026, page 15 / 111 10 / 24 maximum diameter and / or points of the annular projection where the internal diameter is greater than the minimum diameter.

[0025] As will be detailed below, this arrangement is preferably provided for both end walls. In other words, both end walls, with their respective internal annular projections, are shaped so as to allow the end wall to be inserted into the cylindrical casing beyond the annular projection. However, in currently less advantageous embodiments, it is possible to use this technique to mount only one of the two end walls, having it pass beyond an annular projection of smaller internal diameter, while mounting the other in a different manner.

[0026] With reference to the drawing, Figures 1 and 2 show a cross-section according to a plane containing the axis of rotation, of a simplified embodiment of a cylinder according to the invention. The cylinder is indicated with the reference number 1 and its axis of rotation is identified as AA.

[0027] Cylinder 1 may be a Yankee cylinder for a wet papermaking machine. Cylinder 1 may also be a different drying cylinder, for example, a drying roll for a papermaking machine.

[0028] The cylinder comprises a cylindrical casing 3 having a first axial end and a second axial end, both indicated as 3A. Each axial end is closed by a respective end wall 5. Within the end walls 5 and the cylindrical casing 3, a hollow internal space 7 is defined, where a heat transfer fluid can be provided and / or flow. If the cylinder 1 is a drying cylinder or a Yankee cylinder for papermaking machines, the hollow internal space 7 can be used to circulate hot steam, thereby transferring heat. Petition 870260076793, dated 07 / 31 / 2026, page 16 / 111 11 / 24 laughing heat for the paper conducted around the cylindrical surface of the cylindrical lining 3. The end walls 5 are integral with the respective pins 9 to support and rotate the cylinder 1.

[0029] At least one of the axial ends 3A of the cylindrical casing 3 comprises an internal annular projection. In the illustrated example, each of the two axial ends comprises a respective internal annular projection 11 that extends radially towards the AA axis of the cylinder 1. Figure 2 shows an enlargement of a detail of one of the two annular projections 11 in an embodiment. The enlarged portion corresponds to the area indicated with I in Figure 1.

[0030] In figures 1 and 2, the minimum internal diameter of the internal annular projection 11 is indicated as DI, and the maximum diameter of the respective end wall 5 is indicated as D2. The minimum internal diameter DI of the internal projection 11 is smaller than the maximum diameter D2 of the end wall 5. Thus, the force generated in each end wall 5 by the pressure of the fluid filling the internal space 7 of cylinder 1 is discharged in the respective annular projection 11.

[0031] Each end wall 5 and its respective annular projection 11 can be welded together by means of a first weld bead 13 provided on the outer surface of the end wall. The weld bead 13 does not serve as a structural resistance element, since the impulse generated by the pressurized fluid inside the cylinder 1 is discharged, as mentioned above, from the end wall 5 to the lining 3 through the annular projection 11. The main function of the weld bead 13 is to provide a seal preventing leakage of pressurized fluid from the internal space 7 of the cylinder 1.

[0032] To prevent oxidation in the interface area between the wall of Petition 870260076793, dated 07 / 31 / 2026, page 17 / 111 12 / 24 end 5 and projection 11, a second weld bead 15 may be advantageously provided, applied to the inner surface of the end wall. Generally, the dimensions of cylinder 1 are such as to allow a person to enter cylinder 1 through an inspection well (not shown) provided in one of the two end walls 5, to make the inner weld bead 15.

[0033] In the embodiment of Figure 2, the end wall 5 comprises a first portion 5A and a second portion 5B. In this embodiment, portions 5A and 5B have a cylindrical shape. The first portion 5A has a smaller diameter than that of the second portion 5B. More specifically, portion 5A has a diameter approximately equal to the minimum internal diameter DI of the annular projection 11 and is surrounded by the annular projection 11. In the illustrated embodiment, portion 5A has a thickness, that is, an axial dimension (dimension parallel to the axis AA of cylinder 1) smaller than the axial dimension of the annular projection 11, so that the weld bead 13 is within the annular projection 11.

[0034] The second portion 5B is the end wall portion having the maximum diameter D2. In the embodiment illustrated in Figure 2, the diameter D2 is smaller than the inner diameter of the cylindrical casing 3, so as to leave sufficient space for the inner weld bead 15.

[0035] Figure 3 shows an enlargement of detail I of Figure 1 in a second embodiment. The same reference numbers indicate parts that are equal or equivalent to those described with reference to Figures 1 and 2 and that will not be described again. In Figure 3, near each axial end 3A, the cylindrical casing 3 comprises a groove 3B to optimize the distribution of stresses generated within the cylindrical casing 3 by the pressure in the internal space 7 of the cylinder 1. Petition 870260076793, dated 07 / 31 / 2026, page 18 / 111 13 / 24

[0036] Figure 4 shows an enlargement of detail I of Figure 1 in a third embodiment. The same reference numbers indicate parts equal or equivalent to those described with reference to Figures 1 and 2, which will not be described again. In Figure 4, the end wall 5 has a first truncated-conical portion 5A and a second cylindrical inner portion 5B. The maximum diameter D2 (diameter of the larger base of the truncated cone) of the truncated-conical portion 5A is greater than the minimum inner diameter DI represented by the diameter of the smaller base of the truncated cone, corresponding to the smaller diameter of the annular projection 11, which is smaller than the maximum diameter D2. This conical coupling between the annular projection 11 and the end wall 5 has the same result of unloading the forces applied to the end wall 5 onto the annular projection 11, in particular the stress in the axial direction.

[0037] The cylindrical lining 3 with its respective annular projections 11 can be manufactured using any known technique. For example, the axial ends 3A of the cylindrical lining 3 can be welded to a central portion of constant annular cross-section; or they can be created from a blank cylindrical piece by chipping a layer of material of thickness equal to the radial thickness of the inner surface along the entire axial length of the cylindrical piece. In further embodiments, the cylindrical lining 3 can be forged. These two techniques (chip removal and forging) avoid the need for circumferential welds in the cylindrical lining.

[0038] The sequence of Figures 5A, 5B to 9A, 9B shows how to assemble the end walls 5. In the illustrated embodiment, the end walls 5 are symmetrical and are assembled in the same way. The sequence of Figures 5A-9B shows the assembly of only one of the end walls 5. In this sequence, the figures Petition 870260076793, dated 07 / 31 / 2026, page 19 / 111 Figures 14 / 24 indicated with the letter A show the assembly in a cross-section according to a plane containing the axis of cylinder 1, while figures indicated with the letter B show the assembly from a main view, that is, observing cylinder 1 along a line of sight parallel to the axis AA of cylinder 1.

[0039] Following Figures 5A-9B, the embodiment of Figures 2 is shown. The same assembly sequence can be used to assemble the end walls of the embodiment of Figures 3 and 4.

[0040] Furthermore, while in Figures 1 and 2 a simplified cylinder is shown, in the sequence of Figures 5A-9B the assembly of a cylinder 1 adapted to be provided with a central rod joining the two end walls 5 together is shown. Figures 10 to 17 show the steps for assembling the rod and the support and rotation pins which, in this case, are applied to the rod, which in turn is connected to the end walls 5. If a rod is not provided, the support and rotation pins can be pre-assembled on the end walls or, preferably, mounted on the end walls once the latter have been fixed to the cylindrical casing.

[0041] Returning to the sequence of Figures 5A-9B, in Figures 5A, 5B The step is shown when an end wall 5 is moved towards the respective axial end 3A of the cylindrical casing 3. The end wall is held rotated 90° relative to the end position, that is, it is held with its mid-plane in a plane containing the axis AA of cylinder 1.

[0042] In this embodiment, for insertion of the end wall within the cylindrical casing 3 beyond the internal annular projection 11 with a minimum internal diameter DI smaller than the diameter D2 of the end wall 5, the annular projection 11 comprises two notches di Petition 870260076793, dated 07 / 31 / 2026, page 20 / 111 15 / 24 metrically opposed 11A of such depth that the end wall 5 can be moved beyond the inner annular projection 11, aligned with the notches 11A, as shown in Figures 5A, 5B, 6A, 6B.

[0043] In the illustrated embodiment, each end wall 5 has a central hole 5C for anchoring the axial rod, as described below.

[0044] In Figures 6A, 6B, the end wall 5 has been inserted beyond the inner annular projection 11 and can be rotated around an axis with a diameter parallel to the alignment of the notches 11A, as shown in Figures 7A, 7B, until it is orthogonal to axis AA, as shown in Figures 8A, 8B. Now, each end wall can be moved parallel to axis AA until it touches the inner annular projection 11, as shown in Figures 9A, 9B. In this position, one or both welds 13, 15 can be performed.

[0045] Figure 10 shows cylinder 1 partially assembled, with end walls 5 welded to cylindrical casing 3. Welds can be made at notches 11A for sealing the internal space 7 of cylinder 1.

[0046] In a modified embodiment, a single notch 11A of greater depth may be provided in an internal annular projection 11 which may have a greater radial extension than that shown in the figures. This modification of embodiment may be less preferred, since the opening that remains in the notch after mounting the end wall 5 is of larger dimensions and therefore requires more precise welding to seal the internal space 7 of the cylinder 1.

[0047] Figures 11 to 17 show an assembly sequence of the axial rod and the support and rotation pins 9.

[0048] As shown in Figure 11, in this mode the pins Petition 870260076793, dated 07 / 31 / 2026, p. 21 / 111 Support and rotation 9 16 / 24 are integrated with two portions 21 of an axial rod 23 (Figure 17) connecting the two end walls 5 to each other. Each portion of the rod 21 is inserted through the hole 5C of the respective end wall 5, as shown in Figure 12, until the two portions of the rod 21 touch each other (Figure 16). More specifically, in the illustrated embodiment, the two rod portions 21 are inserted into the holes 5C (Figures 11, 12) by an overhead crane, not shown, supporting the portions through overhead support members 31. Subsequently, a lower support 33 is inserted for each rod portion 21. By supporting each rod portion 21 through its respective end wall 5 and its respective lower support 33, it is possible to move the overhead support members 31 so as to engage the support and rotation pins 9 (Figure 14).The lower supports 33 are removed (Figure 15) and the two rod portions 21 are fully inserted into cylinder 1 until the two inner ends 21A of the rod portions 21 touch each other. At end 21A, each rod portion 21 comprises an inner flange 21B. The two inner flanges 21B are used to join the two rod portions 21, for example, by bolt coupling or welding, not shown. The inner dimension of the rod 23 is such as to allow a person to enter, through an inspection well (not shown), into at least one of the two rod portions 21 to join the two portions 21.

[0049] The coupling between the two rod portions 21 can be such as to put rod 23 under tensile stress. For this purpose, the mutual coupling between the two rod portions 21 is advantageously achieved by means of bolts and nuts.

[0050] Each rod portion 21 comprises, at the end opposite end 21A, a flange 21C which is inserted into a seat provided on the outer face of the respective end wall 5. Petition 870260076793, dated 07 / 31 / 2026, page 22 / 111 17 / 24 The end wall 5 and the corresponding flange 21C of the rod portion 21 can be joined by means of a bolt-nut coupling, not shown.

[0051] Figure 17 shows cylinder 1 fully assembled. In this figure, the screws connecting rod 23 to the end walls 5 are also shown schematically, as well as the screws connecting the two rod portions 21.

[0052] Figures 18A and 18B show schematically a device 34, which can be used for mounting a flange 5 on the cylindrical lining 3 of cylinder 1. Device 34 can be supported by an overhead crane (not shown).

[0053] In some embodiments, the cylindrical lining 3 of cylinder 1 may be provided with annular grooves 3S to collect the condensate that is formed during machine operation due to the heat transfer of vaporization of the steam within the internal space 7 of cylinder 1 through the cylindrical lining 3 towards a cellulose layer conducted around the outer cylindrical surface of the cylindrical lining 3.

[0054] Similar to the sequence in Figures 5A to 9B, the Figures Figures 20A, 20B, 21A, 21B, 22A, 22B, 23A, and 23B show an assembly sequence of an end wall 5 in the cylindrical casing 3 in an additional embodiment. The same numbers indicate parts equal or equivalent to those in the previous figures, which will not be described again.

[0055] The main difference between the embodiment of Figures 5A-9B and the embodiment of Figures 20A-23B is that, in this case, to insert the end wall 5 into the cylindrical casing 3 beyond the inner annular projection 11, the end wall 5 comprises two radial perimeter recesses 5D in the form of chord sectors removed from the circular edge of the end wall 5. The two chord sectors Petition 870260076793, dated 07 / 31 / 2026, page 23 / 111 18 / 24 of the recesses are arranged in two diametrically opposed peripheral areas and are identified by two respective chords ideally parallel to each other. The distance between the two flattened parts forming the recesses 5D is such that the end wall 5 can be inserted beyond the inner annular projection 11, whose minimum inner diameter DI is less than the maximum diameter D2 of the end wall.

[0056] The subsequent operations for assembling cylinder 1 are essentially the same as those described above. The two openings that remain along the inner annular projection or edge 11 corresponding to the flattened parts or recesses 5D can be closed by welding.

[0057] In a modified embodiment, only a single deeper radial perimeter recess 5D is provided instead of two diametrically opposed recesses. However, in this case, the opening to be welded between the end wall 5 and the inner annular projection 11 is larger.

[0058] Figures 24A, 24B to 27A, 27B show an assembly sequence of an end wall 5 in the cylindrical casing 3 in an improved embodiment. The same numbers indicate parts equal or equivalent to those of the previous embodiments, which will not be described again.

[0059] Following Figures 24A to 27B, an end wall 5 is provided, which comprises two diametrically opposed radial flattened parts or perimeter recesses 5D and an internal annular projection 11 with two diametrically opposed notches 11A. With this configuration, the depth of the notches 11A and the radial perimeter recesses 5D can be halved in relation to the depth of the notches 11A and the radial perimeter recesses 5D of the previous embodiments. For example, the depth of the notches 11A and the consequent depth of the recesses 5D po Petition 870260076793, dated 07 / 31 / 2026, page 24 / 111 19 / 24 must be such that the recesses 5D are provided only in the larger diameter portion 5A of the end wall 5. The smaller diameter portion 5B, essentially equal to the minimum internal diameter DI of the internal annular projection 11, has no recess and maintains a continuous circular profile.

[0060] In this way, once the end wall 5 has been inserted into the internal space 7 of the cylindrical casing 3, it has been rotated around the axis orthogonal to the AA axis of the cylindrical casing (Figures 25A, 26A) and abutted against the internal annular projection 11 (Figures 26A, 26B), it is rotated around the AA axis so as to bring the recesses 5D into an angularly displaced position relative to the notches 11A. In this way, there is no opening along the annular edge of the end wall 5, and the latter is sealed by continuous weld beads 13, 15 without the need for additional material to close the openings which, in other embodiments, remain in correspondence with the notches 11A or the recesses 5D. In fact, the radial perimeter recesses 5D are sealed by whole (unnotched) portions of the annular projection 11.

[0061] In a modified embodiment, a single radial notch 11A is provided in the annular projection 11 and a single recess 5D is provided in the end wall 5, which are then offset angularly relative to each other in order to mechanically seal the end wall 5 through the entire portion of the annular projection 11.

[0062] In all embodiments of Figures 20A and following, an axial rod 23 is mounted, as shown in Figures 5A-19.

[0063] In other embodiments, for example, for cylinders of smaller dimensions, the axial rod 23 may be omitted, as schematically indicated in Figure 1.

[0064] In the illustrated embodiments, in which notches are provided in the radial projections to allow or facilitate the passage of the pa Petition 870260076793, dated 07 / 31 / 2026, page 25 / 111 20 / 24 end mesh, each inner annular projection is provided with at least one radial notch, beyond which the respective end wall passes. This configuration is particularly advantageous since it allows insertion of each end wall directly into the axial end of the cylindrical casing at the position where the end wall is then to be fixed. In further embodiments, only one inner annular projection is provided with one notch or with two diametrically opposed radial notches. In this case, both end walls are inserted beyond the same inner annular projection. One of the two end walls is translated along the entire axial length of the cylindrical casing until it reaches the axial end opposite to the one beyond which it was inserted. The other end wall is inserted through the axial end, to which it is then fixed.

[0065] It is also possible that one annular projection has one or two radial notches while the other projection has no notches, and that the end wall associated with the inner annular projection without notches is inserted through one or two opposite perimeter recesses provided in the end wall.

[0066] Figures 28 to 42 schematically show an additional embodiment of a cylinder and the related mounting method. Only one axial end of the cylindrical casing and the assembled cylinder is shown in these figures for simplicity.

[0067] More specifically, Figures 28, 29 show a front view and a side view of an end wall 5 and Figures 30 and 31 show a front view and a side view of an axial end 3A of the cylindrical casing 3 thus configured to be coupled to the end wall of Figures 28, 29.

[0068] The axial end 3A of the cylindrical casing 3 comprises an internal annular projection 11 which, in this embodiment, with Petition 870260076793, dated 07 / 31 / 2026, page 26 / 111 21 / 24 comprises, or is formed by, a plurality of first radial teeth 1 IB preferably arranged in constant pitch around the AA axis of the cylindrical casing 3. The first radial teeth 1 IB project radially towards the interior of the cylindrical casing, i.e., towards the AA axis of the cylindrical casing, and extend in the tangential direction, i.e., they have an angular extension around the AA axis of the cylindrical casing 3. The teeth of each pair of consecutive first radial teeth 11B are spaced from each other by a radial recess or notch 11A. Therefore, unlike the embodiments described above, the inner annular projection 11 comprises several radial notches greater than two. In the illustrated embodiment, the radial notches 11A and the first radial teeth 11B have approximately the same angular extension, i.e., approximately equal length in the tangential direction, but this is not mandatory.

[0069] As shown in Figures 28 and 29, the end wall 5 has a shape complementary to that of the axial end 3A of the cylindrical casing 3. More in particular, the end wall 5 comprises a perimeter edge defining a plurality of perimeter recesses 5D, the sequence of which around the perimeter edge of the end wall 5 defines a plurality of second radial teeth 5E, extending opposite to the AA axis of the end wall. The shape of the radial teeth 5E and their respective notches 5D is complementary to the shape of the first radial teeth 11B and their respective notches 11A, such that the end wall 5 is inserted into the cylindrical liner 3 with a reciprocating motion between the cylindrical liner 3 and the end wall 5 in a direction parallel to the AA axis of the cylindrical liner, with the cylindrical liner 3 and the end wall 5 arranged coaxially to each other, as shown in Figures 32 and 33. Petition 870260076793, dated 07 / 31 / 2026, page 27 / 111 22 / 24

[0070] In figures 32 and 33, the mutual angular position of the end wall 5 and the cylindrical lining 3 is such that the second radial teeth 5E are aligned, that is, they are in angular phase, with the notches 11A of the annular projection 11. In this way it is possible to insert the end wall 5 into the cylindrical lining 3, even if the maximum diameter D2 of the end wall, that is, the diameter of the cylindrical surface of the envelope of the second teeth 5E, is greater than the minimum diameter D1 of the axial end 3A of the cylindrical lining 3. The minimum diameter D1 is the diameter of the cylindrical surface tangent to the first radial teeth 11B.

[0071] An annular stop 50 is associated with each axial end 3A of the cylindrical casing 3, the stop having an internal diameter D3 and projecting radially inward, i.e., towards the AA axis of the cylindrical casing 3.

[0072] The annular stop 50 is arranged at such a distance from the inner projection 11 as to form an annular seat for the end wall 5. The annular seat is indicated with the reference number 53. The axial dimension of the seat 53 is substantially equal to the thickness of the end wall 5 or, more precisely, of the portion of its outer perimeter.

[0073] The assembly of the end wall 5 in the cylindrical liner 3, which was described with reference to Figures 28 to 31, is performed as shown in the sequence of Figures 32 to 38. In Figures 32 and 33, the end wall 5 was positioned in axial alignment with the cylindrical liner 3 and opposite the end 3A of the shell, mutually aligning the second teeth 5E and the notches 11A. In the subsequent step, shown in Figures 34 and 35, the end wall 5 was inserted into the seat 53 causing the second teeth 5E to pass through the notches 11A.

[0074] Once end wall 5 has been inserted into Petition 870260076793, dated 07 / 31 / 2026, page 28 / 111 23 / 24 seat 53, preferably in contact with the annular stop 50, the end wall 5 and the cylindrical lining 3 are rotated relative to each other around the axis AA, so as to bring the second teeth 5E into an angular position corresponding to the first radial teeth 11B, as shown in Figures 36, 37 (intermediate angular position), and in Figures 38, 39, the latter showing the final mutual angular position between the end wall 5 and the cylindrical lining 3.

[0075] Once the position shown in Figures 38, 39 has been achieved, the end wall 5 can be welded to the cylindrical casing 3.

[0076] In some embodiments, to have a more reliable and precise positioning of the end wall 5 relative to the cylindrical lining 3, the first radial teeth 11B and the second teeth 5E have a wedge-shaped cross-section. More specifically, the first radial teeth 11B and the second teeth 5E have a wedge-shaped cross-section along a cylindrical cross-sectional surface coaxial with the cylindrical lining 3. Figures 40, 41 and 42 show a cross-section according to a cylindrical surface, indicated with a dashed line in Figures 34, 36 and 38, at three distinct mutual angular positions of the end wall 5 and the cylindrical lining 3.S5 and S11 preferably indicate flat surfaces of the first radial teeth and the second radial teeth 5E facing each other and adapted to be in mutual contact when the end wall 5 is mounted on the cylindrical coating 3, as shown in Figures 38, 39 and 42.

[0077] Because the mutual contact surfaces S5 and S11 are inclined relative to a flat surface orthogonal to axis AA, the mutual rotation between end wall 5 and cylindrical lining Petition 870260076793, dated 07 / 31 / 2026, page 29 / 111 24 / 24 drico 3 generates an axial thrust of the end wall 5 against the annular stop 50, thus defining a unique end position of the end wall 5 relative to the cylindrical casing 3. Once this position has been reached (Figure 42), the end wall 5 is welded to the cylindrical casing 3 by an internal weld bead or by an external weld bead or by an internal and an external weld bead. In the drawing, the weld bead is not shown for simplicity.

[0078] The mounting criterion described can also be used for mounting the second axial end (not shown) of the cylindrical casing 3. Petition 870260076793, dated 07 / 31 / 2026, page 30 / 111

Claims

1 / 2 CLAIMS 1. Cylinder (1) for papermaking machines comprising: a cylindrical liner (3) defining an axis (AA) of the cylinder; a first end wall (5) fixed to a first axial end (3A) of the cylindrical liner (3); and a second end wall (5) fixed to a second axial end (3A) of the cylindrical liner (3); the first end wall (5), the second end wall (5) and the cylindrical liner (3) defining a pressurizable hollow internal space (7) of the cylinder (1);wherein: at least one of said first axial end and second axial end (3A) of the cylindrical coating (3) comprises an internal annular projection (11), which extends radially towards the axis (AA) of the cylinder (1) and has a minimum internal diameter (D1) smaller than a maximum diameter (D2) of the respective end wall (5), and the respective end wall (5) is mounted in such a way that a portion (5B) of the end wall (5) having the maximum diameter (D2) is disposed in a position axially more internal relative to a portion of the internal annular projection (11) having the minimum internal diameter (D1); and characterized in that each internal annular projection (11) of the cylindrical coating (3) is constituted by a plurality of first radial teeth (11B) projecting towards the axis (AA) of the cylinder (1) alternating with radial notches (11A) interposed between the first radial teeth (11B);wherein, in a position axially more internal in relation to each internal annular projection (11), the cylindrical lining (3) comprises a respective annular stop (50) projecting radially towards the axis (AA) of the ci Petition 870260076793, of 07 / 31 / 2026, page 31 / 111 2 / 2 cylindrical lining (1); the respective end wall (5) has a perimeter edge defining a plurality of second radial teeth (5E), a respective perimeter recess (5A) being disposed between each pair of consecutive second radial teeth; and each second radial tooth (5E) of the end wall (11) is locked between the annular stop (50) and a respective first radial tooth (11B) of the cylindrical lining (3).

2. Cylinder (1), according to claim 1, characterized in that the first radial teeth (11B) and the second radial teeth (5E) have, along a surface with a cylindrical cross-section coaxial with the cylinder (1), a wedge-shaped cross-section, opposite and mutually touching surfaces (S5, S11) of the first radial teeth (11B) and the second radial teeth (5E) being inclined with respect to a plane orthogonal to the axis (AA) of the cylinder (1). Petition 870260076793, dated 07 / 31 / 2026, page 32 / 111

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