ITFI20100124A1 - "METHOD FOR THE PRODUCTION OF A MONOLUCID AND CYLINDER CYLINDER SO 'OBTAINED" - Google Patents

Description

"METHOD FOR THE PRODUCTION OF A MONOLUCIDO AND CILIN-DRO CYLINDER SO OBTAINED"

Description

Technical field

The present invention relates to the field of paper production machines and more particularly improvements to the so-called Yankee cylinders or Yankee cylinders.

State of the art

The paper webs are normally produced with wet techniques which provide for the formation of a pulp of cellulosic fibers in aqueous suspension with a low dry content. The mixture is fed from inflow boxes onto a formation canvas and with subsequent passages the water is drained until the dry content in the layer formed by the mixture on the canvas is considerably increased. Once an adequate amount of solid material has been reached, that is cellulosic fibers, the layer is fed around a so-called Yankee cylinder or Yankee cylinder, internally heated for example by water vapor. The layer of cellulosic fibers sent around the Yankee cylinder heats up and dries and is subsequently detached from the Yankee cylinder to be sent to further processing steps.

According to the most consolidated techniques, the Yankee cylinders are typically made of cast iron by means of casting processes. In more recent times, the production techniques of single-gloss steel cylinders have become established. An example of a steel Yankee cylinder is described in W02008105005.

The working front of paper making machines is very broad. In order to reduce production costs and increase production speed, the working front and therefore the width of the cellulosic mixture layer produced continuously by the infeed boxes tend to increase more and more in order to obtain paper rolls of large axial dimension. This requires the construction of very large Yankee cylinders. The internal and external surfaces of the Yankee cylinders must be properly machined. More specifically, annular grooves to collect the condensate formed by the water vapor fed into the Yankee cylinder are made on the internal cylindrical surface. This condensate must be eliminated and for this purpose the annular grooves are provided in which the ends of the condensate suction tubes penetrate.

Machining the internal surfaces of Yankee cylinders of this size requires complex equipment. These are column volumes suitable for mechanical processing of the internal surfaces of large cylindrical structures. These machine tools, as well as in the production of large-size Yankees, are typically used for the machining of important structural components for nuclear plants. These are special machine tools with a very high cost. In fact, there are a limited number of machines in the world suitable for such processes. This involves serious drawbacks:

the rarity of these machines means that the processes are sold by the proprietary companies at very high costs caused both by the cost of the machine and by the lack of alternatives for the buyer;

Γ the use of such machinery is planned in order to keep them saturated, this means that the availability of production windows for the eventual processing of a Yankee is always very late compared to the needs of the market;

the rarity of these machines means that they are located at a great distance from the place of manufacture of the Yankee. Therefore it is necessary to organize an international exceptional transport (round trip, as this is an intermediate process) for a component of considerable weight and dimensions (up to 70-80 tons, 5.5m in diameter and 6.5m in width). This transport heavily affects the costs and times of realization of the finished Yankee.

Summary of the invention

The invention proposes a method for the production of a Yankee cylinder that allows to reduce in whole or in part the drawbacks of traditional production techniques.

Basically, the invention provides for a method comprising the steps of:

- making at least a first cylinder portion and a second cylinder portion;

- machining at least the internal cylindrical surfaces of said first cylinder portion and of said second cylinder portion to form a plurality of annular condensate collection grooves;

- joining said first cylinder portion and said second cylinder portion by welding with an annular welding.

According to a preferred embodiment of the invention, the process involves the following steps:

- making a first cylinder portion, a second cylinder portion and a third cylinder portion;

- machining at least the internal cylindrical surfaces of said first, second and third cylinder portions to form a plurality of annular condensate collection grooves;

- joining said first, second and third cylinder portions by welding with an annular welding.

With this procedure it is possible to work the various portions of the cylinder, before assembling them, with much less complex equipment than those necessary for the processing of a Yankee cylinder of dimensions equal to the final size obtained by assembling the various portions. In fact, the processing of the internal surfaces, being carried out on limited portions, can be carried out on column volumes of reduced dimensions, or on much more common and widespread machinery. It therefore becomes possible to simplify the production process and carry out the production of the Yankee cylinder on site without the need to transport it to the few companies that have equipment of sufficient size for the processing of large-size Yankee cylinders.

Preferably, the annular welding is carried out in correspondence with an intermediate annular condensate collection groove which is formed in the coupling area between the first cylinder portion and the second cylinder portion.

According to an advantageous embodiment, after welding the first cylinder portion and the second cylinder portion, machining is carried out by chip removal of the intermediate annular groove formed in correspondence with the coupling area. If there are three portions forming the cylinder, a similar processing is performed on the intermediate annular groove formed in correspondence with the coupling area between the first and second portion and between the second and third portion. This chip removal process is advantageously carried out for a depth sufficient to bring the weld bead to the surface at the bottom of the annular groove.

To correct any deformations due to the welding process, it is possible to provide annular grooves adjacent to the one formed by coupling two portions of the cylinder, with a smaller size to subsequently perform a machining on them by chip removal.

According to advantageous embodiments of the method according to the invention, it is provided that on front annular surfaces for mutual coupling between the first cylinder portion and the second cylinder portion (and between the second and third cylinder portion, when the cylinder is made in three portions) frontal annular profiles are formed for mutual coupling and centering of the adjacent cylinder portions. Advantageously, an annular weld seam is formed between the front annular coupling profiles and external cylindrical surfaces of the adjacent cylinder portions.

When the cylinder is formed by three welded portions, the central one is preferably longer than the two end portions.

In some advantageous embodiments, the annular grooves adjacent to the intermediate annular groove corresponding to the weld line between two adjacent portions of the cylinder are initially machined with smaller dimensions than the remaining annular grooves and subsequently enlarged by a chip export machining after welding. reciprocal of the two respective cylinder portions.

Preferably, two bottoms are joined, preferably by welding, to a mantle formed by the welds of the cylinder portions forming the mantle, after the welding of said cylinder parts and the processing of the intermediate annular grooves corresponding to the weld seams.

Advantageously, the external cylindrical surface of the Yankee cylinder formed by the coupling of the various portions and preferably of the bottoms is turned after mutual welding.

According to a different aspect, the invention also relates to a Yankee steel cylinder comprising a mantle and two bottoms, said mantle having a smooth outer cylindrical surface and an inner cylindrical surface comprising a plurality of adjacent annular grooves for collecting condensate, in which the The mantle comprises at least two portions joined together by means of an annular welding bead aligned with one of said annular grooves. Preferably, the weld bead surfaces in the bottom of the corresponding annular groove.

According to advantageous embodiments of the invention, the mantle is formed by a central portion and two end portions, joined to the central portion by respective welding beads, each aligned to a respective annular groove. Preferably the central portion has a greater axial development than each of the end portions. For example, the central portion has an axial development approximately double the axial extension of each of the end portions, which preferably have an axial development approximately equal to each other.

Brief description of the drawings

The present invention will be better understood by following the description and the attached drawing, which shows a practical non-limiting embodiment of the invention. More specifically, in the drawing they show: the

Fig. 1 a partially sectional side view of a Yankee cylinder according to the invention; there

Fig. 2 an enlarged detail of a welding area before the internal processing after the welding; there

Fig. 3 a section similar to the section of Fig. 2 after machining the internal groove in correspondence with the weld: and la

Fig. 4 a schematic sequence of the main phases of the process according to the invention.

Detailed description of an embodiment of the invention

In Fig. 1, a mono-glossy steel cylinder that can be obtained with the process according to the invention is indicated overall. The cylinder, indicated as a whole with 1, comprises a cylindrical mantle or wall 3 defining a hollow volume 5 inside, where saturated steam or superheated steam is fed to heat the cylinder. Bottoms 9 equipped with pins or tangs 11 are applied to the shell 3 to support the Yankee cylinder 1. Advantageously, according to one embodiment, the bottoms 9 are applied to the shell 3 by welding according to what is described for example in WO2008 105005, whose content is incorporated into this description.

Inside the Yankee roller 1 there may be tie rods, not shown here for greater simplicity of the drawing. The internal cylindrical surface of the mantle 1 is equipped with annular grooves 13, in which the condensate formed by the steam is collected by transferring heat to the outside. The condensate is collected from the annular grooves 13 by means of ducts arranged inside the Yankee cylinder and not shown, per se known to those skilled in the art.

According to the invention, the cylindrical mantle 3 is actually formed by three cylinder portions indicated with 3A, 3B and 3C respectively. In the following these portions will be indicated with the technical term of "ferrules". Preferably each ferrule 3A, 3B, 3C is in turn formed by a steel plate plastically deformed until it assumes the cylindrical shape, with longitudinal edges connected to each other and welded. Preferably, the central ferrule 3B has a greater longitudinal development than the two end ferrules 3A and 3C. For example, the length L of the central shell 3B is between 3000 and 4000 mm, preferably between 3300 and 3700 mm, for example 3500 mm. The shells 3A and 3C have a longitudinal length 1 comprised for example between 1000 and 2000 mm and preferably between 1300 and 1800 mm. The diameter of the cylinder, indicated by D in Fig. 1, can vary for example between 3000 and 6000 mm, preferably between 3600 and 5500 mm. It must be understood that the dimensions indicated here are only indicative and not limiting. What is relevant is that the cylinder is preferably made in three portions, of which the central one has a longitudinal development, i.e. in the axial direction along the axis A-A of the cylinder, greater and preferably greater than double the length of each of the side shells 3A and 3C.

The ferrules 3A, 3B and 3C are joined together along annular welding lines S indicated in Fig. 1, in correspondence with which respective welding seams are made, indicated below with C.

According to the invention it is advantageously provided that the three ferrules 3A, 3B and 3C are machined internally, to obtain the annular grooves 13, before the mutual coupling of the ferrules themselves, in order to simplify the processing. In fact, in this way it is possible to use equipment of more modest dimensions to carry out the internal machining of chip removal to form the grooves 13, since the maximum longitudinal dimension on which to work is constrained by the maximum dimensions that can be machined on the tomes normally present. on the market and is equal to the length L of the central ferrule 3B.

According to advantageous embodiments of the method according to the invention, the ferrules 3 A, 3B and 3C are machined by creating the annular grooves 13 inside them and creating turned edges on the ends of the ferrules which must be joined and welded to form the cylindrical mantle 3 Once these operations have been carried out, the ferrules are welded together and subsequently a further internal processing is carried out only in the area of the grooves which are located in correspondence with the annular welding lines.

Fig. 2 shows an enlarged detail of the welding performed in the joint area between two ferrules. The example illustrates the welding line between the ferrules 3A and 3B, but it must be understood that a similar welding is provided between the ferrules 3B and 3C. As can be seen in Fig. 2, the shell 3A, of which the external surface is indicated with 4, has a plurality of annular grooves 13 separated from each other by annular edges 14 protruding radially towards the inside of the shell. The last annular edge 14X has an overall width indicated by X, greater than the annular edges 14 and its external face, corresponding to the end of the shell, has been machined to generate a coupling seat with the ferrule 3B.

More particularly, in the example illustrated on the external face of the annular edge 14X an annular tooth 17 has been formed projecting in the axial direction of the ferrule 3 A and having a radially innermost portion 17X with a greater axial protrusion and a radially outermost portion 17Y axially less protruding. Between the portion 17Y of the projection 17 and the cylindrical outer surface 4 of the shell 3A a machining 19 is made according to a substantially conical surface to define a welding channel. The surface 19 is joined in 19X, by means of a surface with a large radius of curvature, with the portion 17 Y of the annular projection 17.

Similarly, the ferrule 3B has an annular edge 14Y which is thicker than the remaining annular edges 14.

On the external face, facing towards the ferrule 3A, of the projection 14Y, having a thickness Y, there is an annular tooth 21 which is coupled to the annular tooth 17 of the ferrule 3 A. It is connected to the annular tooth 21, with a 23X wide surface radius of curvature, a conical flank 23 of the face of the ferrule 3B facing towards the ferrule 3A. The conical surfaces 19 and 23 define the volume of the weld bead.

The annular teeth 17 and 21 are sized in such a way that the opposite faces of the annular projections 14X and 14Y are at a mutual distance "d" equal to the width of the annular grooves 13. This is because, at the end of the machining, this area included between the two projections 14X and 14Y it will form a groove substantially identical to the remaining grooves 13 of the ferrules 3A and 3B.

Fig. 2 also shows the material forming the welding seam C which fills the section space preferably wedge-shaped between the sides 19 and 23 obtained by machining the opposite front surfaces of the ferrules 3A and 3B.

In the exemplary embodiment illustrated in Fig. 2, the two annular grooves or grooves 13 Y closest to the welding seam C are of lesser depth for the purposes described below. In some embodiments it can also be provided that these grooves have a smaller width than the remaining grooves or grooves 13.

Once the welding has been carried out as shown in Fig. 2, inside the cylindrical mantle formed by the ferrules 3A, 3B and 3C a sequence of annular grooves 13 substantially identical to each other is formed, with the exception of the grooves of smaller radial dimension which are generated in correspondence of the coupling and welding interfaces between the ferrules 3A, 3B and between the ferrules 3B, 3C and with the exception of the grooves immediately adjacent to them.

The welding seam C does not have an internal recovery, but is completely contained between the flanks 19 and 23 and the surfaces 19X and 23 X of the teeth 17 and 21.

Fig. 3 shows the subsequent processing phase, in which the welding interfaces between the ferrules are machined in correspondence with the groove defined by the projections 14X, 14Y and by the tooth 17. As can be seen in Fig. 3, this groove has been machined by chip removal until assuming the same radial dimension with respect to the remaining grooves 13 inside the ferrules 3A, 3B. Similar processing is performed on the coupling area by welding between the ferrules 3B and 3C.

In Fig. 3 the new groove generated at the weld bead C is indicated by 13X. The depth of the machining, the radial dimension of the weld bead C and the position of the teeth 17 and 21 are such that once the groove 13X has reached the radial dimension equal to that of the adjacent grooves 13, the material forming the bead of weld C has been brought to the surface inside the groove 13X, so that the weld bead C essentially assumes the conformation of a bead made by internal recovery, although in reality this bead has been made without internal recovery.

As can be seen in Fig. 3, at the end of the machining the welding bead C is substantially in a symmetrical and centered position with respect to the corresponding groove 13X, a position that could not be obtained by making the grooves 13, 13X after the welding of the ferrules.

In addition to the machining of the annular groove or groove 13X, a machining of the grooves 13 Y is also carried out adjacent to each of the two annular grooves 13X along which the welding seams C for joining the end ferrules 3A, 3C to the central ferrule 3B extend. In this way, grooves 13, 13X, 13Y are obtained, all of the same size, compensating for any deformations due to welding on the grooves 13Y adjacent to the bead C. The initial machining of the grooves 13 Y with smaller dimensions than the remaining grooves 13 has the purpose of allowing the their final processing after welding in order to obtain a greater dimensional regularity of all the grooves. It must be understood that the different dimension of the grooves or grooves adjacent to the zone in which the ferrules will be welded to each other can be adopted not only for the immediately adjacent groove, but also for those at a greater distance from the welding zone, if necessary.

The cylindrical mantle that has been completed in this way is subsequently processed by external turning in order to eliminate any excess material from the welding seam C. If required, subsequent treatments or coatings are also carried out to increase the surface hardness.

The machining of chip removal of the groove 13X between the annular projections 14X and 14Y at each connection interface between the ferrules 3 A, 3B and 3B, 3C is made easier by the fact that the weld seams C are located closer together at the ends of the cylindrical mantle 3 with respect to the center line, thanks to the fact that the cylindrical mantle is formed by the coupling of the three distinct ferrules and that the ferrules 3A and 3C have a smaller axial development than the central ferrule 3B. This also makes it possible to reduce the mechanical stresses on the weld seams C, since these are found closer to the ends of cylinder 1.

Once the processing of the internal grooves of the mantle formed by the union of the ferrules 3A, 3B, 3C has been completed, the bottoms 9 can be joined by welding with the pins IL. The bottoms can also be joined by different means, for example by bolts. The turning process and any hardening treatment of the external surface can be performed after the union of the bottoms 9, so that this final processing can also affect the cylindrical surfaces of the bottoms.

The manufacturing process described above is schematically summarized in the sequence of Fig. 4.

It is understood that the drawing only shows an exemplification given only as a practical demonstration of the invention, which may vary in forms and arrangements without however departing from the scope of the concept underlying the invention. The possible presence of reference numbers in the attached claims is intended to facilitate the reading of the claims with reference to the description, and does not limit the scope of protection represented by the claims.

Claims (16)

"METHOD FOR THE PRODUCTION OF A MONOLUCIDO AND CILIN-DRO CYLINDER SO OBTAINED" Claims 1. A method of producing a Yankee cylinder comprising the steps of: - making at least a first cylinder portion and a second cylinder portion; machining at least the internal cylindrical surfaces of said first cylinder portion and of said second cylinder portion to form a plurality of annular condensate collection grooves; - joining said first cylinder portion and said second cylinder portion by welding with an annular welding. 2. Method according to claim 1, wherein said annular weld is made in correspondence with an intermediate annular condensate collection groove which is formed in the coupling area between the first cylinder portion and the second cylinder portion. Method according to claim 2, in which after the welding of the first cylinder portion and the second cylinder portion, machining is carried out by chip removal of the intermediate annular groove formed in correspondence with the coupling area. 4. Method according to claim 3, in which the machining of the intermediate groove is carried out until the weld bead is brought to the surface. 5. Method according to claim 3 or 4, comprising a step of machining by removing chips from the annular grooves adjacent to the intermediate groove. Method according to one or more of the preceding claims, wherein on front annular surfaces of reciprocal coupling between said first cylinder portion and said second cylinder portion, front annular profiles are formed for mutual coupling and centering of said first cylinder portion and of said second cylinder portion, and in which an annular weld bead is formed between the front annular coupling profiles and external cylindrical surfaces of said first cylinder portion and said second cylinder portion. 7. Method according to one or more of the preceding claims, wherein said Yankee cylinder is formed by coupling a first portion of the central cylinder and two end portions of the cylinder, the central portion of the cylinder having a greater axial development than each of said end portions of the cylinder. Method according to one or more of the preceding claims, wherein the annular grooves adjacent to the intermediate annular groove are initially machined with smaller dimensions than the remaining annular grooves and subsequently enlarged by means of a chip export machining after the mutual welding of said at least a first cylinder portion and a second cylinder portion. Method according to one or more of the preceding claims, in which two bottoms are welded to a mantle formed by the welds of said at least one first cylinder portion and said at least one second cylinder portion, after the welding of said cylinder parts and machining of the intermediate annular groove. Method according to one or more of the preceding claims, wherein the outer cylindrical surface of the Yankee cylinder is turned after the mutual welding of said at least a first cylinder portion and a second cylinder portion. 11. A monolucid steel cylinder comprising a mantle and two bottoms, said mantle having a smooth outer cylindrical surface and an inner cylindrical surface comprising a plurality of adjacent annular grooves for collecting condensate, in which said mantle comprises at least two portions between them joined by means of an annular weld bead aligned with one of said annular grooves. 12. Polished cylinder according to claim 11, in which said weld bead surfaces in the bottom of the corresponding annular groove. 13. Yankee cylinder as per claim 11 or 12, in which said mantle is formed by a central portion and two end portions, joined to the central portion by respective welding beads, each aligned to a respective annular groove. 14. Yankee cylinder as per claim 13, wherein said central portion has a greater axial development than each of the end portions. 15. Yankee cylinder as per claim 14, wherein said central portion has an axial development approximately double the axial development of each of the end portions, which preferably have an axial development approximately equal to each other. 16. Yankee cylinder according to one or more of claims 11 to 15, comprising more than three portions welded together forming the cylindrical mantle.