SE541319C2

SE541319C2 - An intermediate product in the manufacturing process of a yankee drying cylinder

Info

Publication number: SE541319C2
Application number: SE1751437A
Authority: SE
Inventors: Andreas Hjärtqvist; Erik Warmland; Magnus Högman; Rune Skogsberg; Stefan Engström; Stefan Thyberg
Original assignee: Valmet Oy
Priority date: 2017-11-22
Filing date: 2017-11-22
Publication date: 2019-07-02
Also published as: SE1751437A1; DE202018106322U1; CN209873446U

Abstract

The invention relates to an intermediate product (IP) in the manufacturing process of a steel-made Yankee cylinder (1). The intermediate product (IP) comprises a shell (2) that extends in an axial direction about a central axis (A) and has axial ends (3, 4). An end wall (8, 9) is connected to each end (3, 4) by a weld bead (11). Each axial end (3, 4) has a protruding guide (12) along its circumference and each end wall (8, 9) has a protruding guide (13) that engages the guide (12) of the axial end (3, 4). The guides (12, 13) have opposing surfaces that abut each other to define a position of the end wall (8, 9) in relation to the shell (2) and in which a groove (28) is defined between the end wall (8, 9) and the shell (2). The groove (28) extends from the outer surface of the shell (2) inwards to a bottom defined by at least one of the guides (12, 13). The guides (12, 13) form a bulge (36) on the inner surface which bulge protmdes towards the central axis (A) and can be removed to form a smooth transition.

Description

AN INTERMEDIATE PRODUCT IN THE MANUFACTURING PROCESS OF A YANKEE DRYING CYLINDER FIELD OF THE INVENTION The present invention relates to an intermediate product in the manufacturing process of a Yankee drying cylinder which Yankee drying cylinder is to be used for the purpose of drying a wet fibrous web.

BACKGROUND OF THE INVENTION In the manufacturing process of a Yankee drying cylinder for drying a fibrous web which is initially wet, a number of methods have been proposed that can be described in terms of the intermediate product that is a step on the way to the final product, i.e. the Yankee drying cylinder. In WO 2015/076718, an intermediate product is disclosed which is later to become a Yankee drying cylinder. In that document, an end wall which is connected to a shell may be provided with a lip that that is ring-shaped and serves as a backing material such that welding can be performed from the outside only. After welding, the lip can be removed by grinding. The way of forming an intermediate product in this way makes it possible to perform welding only from the outside but the lip cannot serve to simultaneously define both the axial and the radial position of the end wall in relation to the shell. CN 203977226 U discloses a Yankee drying cylinder in an end wall is connected by welding to a shell and there are cooperating guide parts on both the end wall and the shell. However, the cooperating guide parts are formed at a point which, in the radial direction, is located between the outer surface of the Yankee drying cylinder and the inner surface of the Yankee drying cylinder. This means that both an inner groove and an outer groove is formed between the end wall and the shell and welding must be performed both from the inside of the shell and the outside of the shell. This makes the manufacturing process more complicated and entails the risk that the final weld connection becomes weaker. It is an object of the present invention to provide an intermediate product which can be easily manufactured, and which makes it possible to achieve a high precision and, finally, a Yankee drying cylinder of a high quality. These and other objects are achieved by means of the present invention.

DISCLOSURE OF THE INVENTION The present invention relates to an intermediate product in the manufacturing process of a steel-made Yankee drying cylinder for drying a fibrous web. The inventive intermediate product comprises a shell that has a circular cylindrical shape and extends in an axial direction about a central axis. The shell has two axial ends and an inner surface in which circumferential grooves are formed. For each axial end of the shell, the intermediate product comprises an end wall which is connected to the axial end by at least one weld bead such that the shell and the end walls define an enclosed space within the intermediate product. Each end wall has an outer surface that forms a part of the exterior surface of the intermediate product and an interior surface that faces the enclosed space such that the interior surfaces of the end walls face each other, and the inner surface of the shell and the interior surfaces of the end walls together form an interior surface of the entire intermediate product. Each axial end of the circular cylindrical shell has a protruding guide along at least a part of its circumference. Each end wall has a protruding guide along at least a part of its circumference that engages and cooperates with the at least one protruding guide of the axial end of the circular cylindrical shell to which the end wall is connected by the at least one weld bead. The protruding guides having opposing surfaces that abut each other to define a predetermined position of the end wall in relation to the shell and in which predetermined position a circumferential groove is defined between the end wall and the shell. The circumferential groove extends from the outer surface of the shell radially inwards to a bottom of the groove which bottom is defined by at least one of the protruding guides. The protruding guides form a bulge on the inner surface of the intermediate product which bulge protrudes into the enclosed space towards the central axis of the intermediate product. The bulge can be removed by grinding or machining such that, after removal of the bulge, there can be a smooth transition between the inner surface of the shell and the interior surface of the end wall.

In embodiments of the invention, at least one of the protruding guides is a circumferential guide that extends over the entire circumference of an end wall or the shell.

It is conceivable that both the protruding guides of the end walls and the protruding guide at each axial end of the shell are circumferential guides that extend over the entire circumference of the end wall and the shell.

Embodiments are also possible in which at least one end wall has a plurality of protruding guides that are separated from each other and distributed along the circumference of the end wall while the axial end of the shell that is connected to that end wall has a continuous protruding guide that extends over the entire circumference of the shell at is axial end.

In other embodiments, at least one end wall has a continuous protruding guide that extends over the entire circumference of the end wall and the axial end of the shell that is connected to that end wall has a plurality of protruding guides that are separated from each other and distributed along the circumference of the shell at its axial end.

In embodiments of the invention, the at least one protruding guide of an end wall is so placed in relation to the protruding guide of the shell with which it cooperates that at least a part of the protruding guide of the end wall is placed radially inside the protruding guide of the shell.

At least one end wall is welded to an axial end of the shell by a plurality of weld beads that are distributed along the circumference of the circumferential groove and separated from each other and arranged in pairs of opposing weld beads that are separated from each other by 175°- 185°.

BRIEF DESCRIPTION OFD THE DRAWINGS Figure 1 is a side view of a Yankee drying cylinder during paper manufacturing.

Figure 2 is a schematic cross-sectional view of a Yankee drying cylinder which has gone through the complete manufacturing process and is ready to be taken into use.

Figure 3 is a schematic representation of an intermediate product which is to become a Yankee drying cylinder.

Figure 4 is a cross-sectional representation of a part of an end wall and a part of a circular cylindrical shell before they have been connected to each other to form the inventive intermediate product.

Figure 5 is a figure similar to Figure 4 but showing the end wall and the circular cylindrical shell when they have been brought together.

Figure 6 is a figure similar to Figure 5 but showing how the end wall and the shell have been connected to each other and Figure 6 can thus be seen as representing a part of the inventive intermediate product.

Figure 7 is similar to Figure 6 but schematically indicating a following manufacturing step.

Figure 8 is a figure similar to Figure 6 and Figure 7 but showing the result of a previous grinding or machining step.

Figure 9 is a side view of the shell and indicates a possible distribution of weld beads.

Figure 10 is a schematic representation of how welding may be performed.

Figure 11 is a figure similar to Figure 4 but shows an alternative embodiment.

Figure 12 is a figure similar to Figure 5 but shows the same embodiment as Figure 11.

Figure 13 is a figure similar to Figure 6 but shows the same embodiment as Figure 11 and Figurer 12.

Figure 14 is an entirely schematic representation of a technology that differs from that of the present invention and is intended to explain a technical problem which the present invention solves.

Figure 15 is a schematic illustration similar to Figure 14 and showing a following step in the manufacturing sequence.

Figure 16 is a simplified schematic representation of one of the principles behind the present invention.

DETAILED DESCRIPTION OF THE INVENTION With reference to Figure 1, a short description of how the final product will be used. In Figure 1, a Yankee drying cylinder 1 is shown as rotating about an axis A in the direction of arrow R. In Figure 1 and 2, it can be seen how that the Yankee drying cylinder 1 has journals 24 and bearings 25 that allow rotation. The Yankee drying cylinder 1 is heated from the inside by hot steam that may be at an overpressure. A wet fibrous web W travels on a fabric 30 that may be, for example, an endless waterabsorbing felt that runs in a loop around guide rolls (not shown) or, in some cases, a fabric that does not absorb water but is textured such that it may imprint a threedimensional structure into the fibrous web W. In Figure 1 , the direction of movement of the fabric 30 is indicated by the arrows C. A roll 32 is placed inside the loop of the fabric 30 and arranged to form a nip with the outer surface of the Yankee drying cylinder 1. In the nip between the roll 31 and the Yankee drying cylinder 1, the fibrous web W is transferred to the outer surface of the Yankee drying cylinder 1. The outer surface of the Yankee drying cylinder 1 is normally much smoother than the surface of the fabric 30 and this makes it easier to achieve transfer of the web W to the Yankee drying cylinder 1 since the wet fibrous web W tends to follow/adhere to the surface that is smoothest. The fibrous web W will then travel over the outer surface of the Yankee drying cylinder 1 as the Yankee drying cylinder 1 rotates in the direction of arrow R. As the fibrous web W is in contact with the outer surface of the Yankee drying cylinder 1, the fibrous web W is dried since the Yankee drying cylinder is very hot due to the heating from inside by steam. The fibrous web W which is initially quite wet will thus be dried by evaporation. The fibrous web W that has been dried on the Yankee drying cylinder 1 can then be creped off from the Yankee drying cylinder 1 by a doctor 29.

It should be understood that the fibrous web W that has been creped off from the Yankee drying cylinder will normally be passed on and eventually wound to a roll in a reel — up, for example such a reel-up as disclosed in US patent No. 5,816, 528 or US patent No. 9,511,968.

With further reference to Figure 2, it can be seen that the Yankee drying cylinder 1 has a shell 2 which is a circular cylindrical shell. The shell 2 extends in an axial direction about a central axis A. It should be understood that the central axis A is the axis around which the Yankee drying cylinder 1 will rotate when the Yankee drying cylinder 1 is in operation in a paper making machine.

As can be seen in Figure 2, the shell 2 has two axial ends 3, 4 and an inner surface 5 in which circumferential grooves 6 are formed. When the Yankee drying cylinder 1 is used to produce paper, hot steam will condensate in the grooves 6 and heat will be transferred to the outer surface of the circular cylindrical shell 2 such that the fibrous web W which is initially wet will be dried by evaporation due to contact with the hot shell 2.

Condensated water may then be evacuated from the inside of the Yankee drying cylinder, for example by an arrangement as disclosed in US patent No. 8,959,790 or US patent No. 5,537,756.

For each axial end 3, 4 of the circular cylindrical shell 2, an end wall 8, 9 is connected to the respective axial end 3, 4 by a weld bead 11 such that the shell 2 and the end walls 8, 9 define an enclosed space V within the Yankee drying cylinder 1.

With further reference to Figure 2, it can be seen that the Yankee drying cylinder 1 may be provided with a tubular structure 22 interposed between and connecting the end walls 8, 9 to each other. The tubular structure 22 may be arranged to receive hot steam coming from a conduit that goes through one of the journals 24 (not shown in the figures). The hot steam may then exit through openings 23 in the tubular structure 22 and reach the inner surface 5 of the shell 2 and heat the shell 2.

It should be understood that Figure 2 is only a schematic representation of a Yankee drying cylinder 1 and that exact shape and relative dimensions of all details shown in Figure 2 do not necessarily correspond to the actual Yankee drying cylinder. Flowever, it should be understood that the Yankee drying cylinder 1 that is shown in Figure 2 may be understood as representing a device which is the result of further work operations that have been carried out on the inventive intermediate product to which the present invention relates.

Reference will now be made to Figure 3 which is a schematic representation of the entire intermediate product IP. In Figure 3, it can be seen that that each end wall 8, 9 may have an opening 41 to receive a journal 24 which can be fastened to the end wall 8, 9 by any suitable means, for example by bolts. Figure 3 also shows how at least one end wall 8, 9 may have a manhole 42 allowing inspection of the Yankee drying cylinder from the inside. As with Figure 2, it should be understood that Figure 3 is only a schematic representation, and this applies in particular to the weld seams 11 that are only symbolically indicated in Figure 3.

Reference will now be made to Figure 4 which illustrates a part of the manufacturing process for the intermediate product that may later be transformed into a Yankee drying cylinder as explained previously with regard to Figure 1 and Figure 2. Figure 4 represents a stage in the manufacturing process in which the shell 2 has not yet been connected to the end walls 8, 9. In Figure 4, only one end wall 8 and only one axial end 3 of the shell 2 are shown but it should be understood that everything that is described with reference to the end wall 8 and the axial end 3 is also applicable to the other end wall 9 at the other axial end 4 of the shell 2.

As can be seen in Figure 4, the shell 2 has a protruding guide 12 that is located in connection to the inner surface 5 of the shell 2, i.e. away from the outer surface 43 of the shell 2 and the end wall 8 has a protruding guide 13 that is located at a distance from the outer circumference of the end wall 8 such that it can meet and engage the protmding guide 12 of the shell 2.

In the embodiment shown in Figure 4, the protruding guide 12 of the shell 2 has an axial surface 15 facing outwards and is parallel to the central axis A of the shell 2. the protmding guide 13 of the end wall 8 has a corresponding axial surface 14 which is designed to match the surface 15 such that the surfaces 14, 15 can cooperate with each other and define the radial position of the end wall 8 in relation the shell 2. The protruding guide 12 of the shell 2 also has a surface 17 that is perpendicular to the central axis A of the shell 2 and the protruding guide 13 of the end wall 8 has a corresponding surface 16 that is parallel to the surface 17 on the protruding guide 12 on the shell 2. The surfaces 15 and 17 can cooperate with each other to define an end position of the end wall 8 and the shell 2 in the axial direction. The shell 2 and the end wall 8 have opposing slanted surfaces 26 that serve to define a groove 28 (see Figure 5) between the shell 2 and the end wall 8 when the shell 2 and the end wall 8 have been brought together. The groove 28 will have a shape that is generally V-shaped. In relation to the central axis A of the shell 2, the slanted surfaces have an angle that is relatively high and may be, for example, in the range of 60° - 85°. In embodiments of the invention, the slanted surfaces 26 may be followed, closer to the bottom of the groove 28, by slanted surfaces 27 that have an angle in relation to the central axis A that is smaller than the angle of the slanted surfaces 26, for example 5°- 25° smaller. For example, if the slanted surfaces 26 have an angle in relation to the central axis A that is 70°, the slanted surfaces 27 may have an angle in relation to the central axis A that is 45°. In this way, there is a smoother transition to the bottom of the groove 28.

Figure 5 shows the situation where the end wall 8 has been brought against the shell 2 such that the protruding guides 12, 13 engage with and cooperate with each other to define the position of the end wall 8 in relation to the shell 2, both axially and radially. In advantageous embodiments, the protmding guides 12, 13 may be ring-shaped segments that are designed such that, in a pair of cooperating protruding guides, one has an outer radius which is smaller than the inner radius of the other. In this way, the protmding guide with the smaller radius can be placed radially inside the protmding guide with the greater radius such that the protmding guides 12, 13 can determine/define the radial position of an end wall 8, 9 in relation to the shell 2. The protmding guides 12, 13 may then serve to determine the relative position of the end wall 8, 9 in relation to the shell 2 in both a radial and an axial direction.

In Figure 6, it can then be seen how the end wall 8 has been connected to the shell 2 by at least one weld bead 11. The weld bead 11 may be a circumferential weld bead 11 that goes all the way around the circumference of the shell 2 to connect the shell 2 to the end wall 8. Flowever, the weld bead 11 in Figure 6 does not necessarily have to be interpreted as a continuous circumferential weld bead but it could be understood as a number of weld beads separated from each other along the circumference of the shell 2 or it could be understood as a weld bead that is continuous but does not extend over the entire circumference of the shell 2. What has here been said about the end wall 8 and the axial end 3 of the shell 2 is also applicable to the other end wall 9 at the other axial end 4 of the shell 2.

Reference will now be made to Figure 7. In Figure 7, it can be seen how the protruding guides 12, 13 together form a bulge 36 that protmdes into the enclosed space towards the central axis A. When the intermediate product IP is further processed to arrive at the final product, i.e. the Yankee drying cylinder, this bulge 36 will normally be removed by grinding or machining. In Figure 7, a tool 37 is symbolically indicated that can act in the direction against the bulge 36 as symbolically indicated by arrow T. The tool 37 may be understood as a grinding tool or a machining tool.

With reference to Figure 8, it can be seen that, after removal of the bulge 37, there is now a smooth transition area 38 between the end wall 8 and the shell 2. The same can be seen as applicable also at the other axial end 4 of the shell 2 where the end wall 9 is welded to the shell 2.

On advantageous way of performing the welding will now be explained with reference to Figure 9 and Figure 10. Instead of making one continuous weld bead 11 that is circumferential and goes all the way 360°along the groove 28, a number of separate weld beads 11a, 11b, 11c, 11d, 11e, 11f, 11g 11h may be formed in such a pattern that each weld bead 11 belongs to a pair of weld beads that are separated from each other in the circumferential direction by an angle of 180° or close to 180°. For example, they can be separated from each other by 175°- 185°. Such separate weld beads are preferably made in a sequence where opposite weld beads in the same pair are made following each other. In this way, the effects of heat deformation can be more evenly distributed around the shell 2 which is an advantage for further machining on the shell 2 if shell thickness is to be uniform over the final product, i.e. the Yankee drying cylinder. With reference to Figure 9, a possible welding sequence may then be such that the weld bead 11a is made first. Thereafter, the second weld bead 11b is made at a point which is 180°away from the first weld bead 1 la (or close to 180°). A third weld bead 11c is made at a point which is 90°away from the first weld bead 11a in the circumferential direction of the shell 2 (or close to 90°, for example 85°- 95°). A fourth weld bead 11d is then made opposite the third weld bead 11c, i.e. 180°or about 180°away from the third weld bead lie. The following weld beads are then made in opposing pairs as indicated by Figure 9 and the alphabetical order (11a, 11b, 11c...) may be seen as an indication of a possible order in which the weld beads 11 are made. In this way, heat deformation caused by the welding can be more evenly distributed. When the shell 2 has a diameter in the range of 2 m - 8 m, the number of such separate weld beads may suitably be 16 32. Each such separate weld bead 11a, 11b, 1 lc...may suitably have a length of 100 mm - 250 mm or 150 mm - 200 mm but other numerical values may be considered. In advantageous embodiments of the invention, the angular distance a between adjacent weld beads (11a, 11b, 1 lc . ) is the same for all such separate weld beads 11. It should be understood that Figure 9 is intended as a schematic representation which has been made with reference to the shell 2 (or rather an axial end 3, 4 of the shell 2) but that the weld beads 11a, 11b, 1 lc, lid... also connect the shell 2 to an end wall 8,9. In Figure 9, the weld beads 11a, 11b, 11c, 11d, 11e, 11f, 11g, 11h are shown as distributed along the circumference of the shell 2 but they are, of course, also distributed along the corresponding part of the circumference of the end wall 8, 9.

With reference to Figure 10, the spaces between separate weld beads 11 may be filled by intermediate/interconnecting weld beads 39. Finally, a continuous weld bead 40 which is an exterior weld bead that is performed from the outside.

In the state represented by Figure 3 in combination with Figure 6 and Figure 7, the inventive intermediate product IP can thus be described as an intermediate product IP in the manufacturing process of a steel-made Yankee drying cylinder 1 for drying a fibrous web W. The intermediate product IP comprises a shell 2 that has a circular cylindrical shape and extends in an axial direction about a central axis A. The shell 2 has two axial ends 3, 4 and an inner surface 5 in which circumferential grooves 6 are formed. For each axial end 3, 4, an end wall 8, 9 is connected to the axial end 3, 4 by at least one weld bead 11 such that the shell 2 and the end walls 8, 9 define an enclosed space V within the intermediate product IP. Each end wall has 8, 9 has an outer surface 34, 35 that forms a part of the exterior surface of the intermediate product IP and an interior surface 32, 33 that faces the enclosed space V such that the interior surfaces 32, 33 of the end walls 8, 9 face each other and the inner surface 5 of the shell 2 and the interior surfaces 32, 33 of the end walls 8, 9 together form an interior surface 7 of the entire intermediate product IP. Each axial end 3, 4 of the circular cylindrical shell 2 has a protmding guide 12 along at least a part of its circumference and each end wall 8, 9 has a protruding guide 13 along at least a part of its circumference that engages and cooperates with the at least one protruding guide 12 of the axial end 3, 4 of the circular cylindrical shell 2 to which the end wall 8, 9 is connected by the at least one weld bead 11. Here, it should be understood that the protmding guides 12, 13 of the end walls 8, 9 and the shell 2 are preferably circumferential such that the extend over 360° but that embodiments are conceivable in which the protmding guides 12, 13 extend only over parts of the circumference. The protmding guides 12, 13 have opposing surfaces that abut each other to define a predetermined position of the end wall 8, 9 in relation to the shell 2. In this predetermined position, a circumferential groove 28 is defined between the end wall 8, 9 and the shell 2. The circumferential groove 28 extends from the outer surface 43 of the shell 2 radially inwards to a bottom of the groove 28 which bottom is defined by at least one of the protruding guides 12, 13. The protruding guides 12, 13 form a bulge 36 on the inner surface 7 of the intermediate product IP and the bulge 36 protrudes into the enclosed space V towards the central axis A. This bulge 36 can be removed by grinding or machining such that, after removal of the bulge 36, there can be a smooth transition or transition area 38 between the inner surface 5 of the shell and the interior surface 32, 33 of the end wall 8, 9.

In preferred embodiments, at least one of the protruding guides 12, 13 is a circumferential guide 12, 13 that extends over the entire circumference of an end wall 8, 9 or the shell 2.

Embodiments are conceivable in which both the protruding guides 12 of the end walls 8, 9 and the protruding guide 13 at each axial end 3, 4 of the shell 2 are circumferential guides that extend over the entire circumference of the end wall 8, 9 and the shell 2.

In other possible embodiments of the inventive intermediate product, at least one end wall 8, 9 may have a plurality of protruding guides 13 that are separated from each other and distributed along the circumference of the end wall 8, 9 while the axial end 3, 4 of the shell 2 that is connected to that end wall 8, 9 has a continuous protruding guide 12 that extends over the entire circumference of the shell 2 at is axial end 3, 4.

Embodiments are also conceivable in which at least one end wall 8, 9 has a continuous protruding guide 13 that extends over the entire circumference of the end wall 8, 9 while the axial end 3, 4 of the shell 2 that is connected to that end wall 8, 9 has a plurality of protruding guides 12 that are separated from each other and distributed along the circumference of the shell 2 at its axial end 3, 4.

As shown in the figures, at least one protruding guide 13 of an end wall 8, 9 may be so placed in relation to the protruding guide 12 of the shell 2 with which it cooperates that at least a part of the protruding guide 13 of the end wall 8, 9 is placed radially inside the protruding guide 12 of the shell 2. However, it should be understood that the opposite may be the case and that embodiments are conceivable in which a protruding guide 13 of an end wall 8, 9 is so placed in relation to the protruding guide 12 of the shell 2 with which it cooperates that at least a part of the protruding guide 13 of the end wall 8, 9 is placed radially outside the protruding guide 12 of the shell 2. With reference to Figure 11, Figure 12 and Figure 13, it can be seen how the protruding guides 12, 13 may be placed in a different radial position in relation to each other than is the case in the embodiment shown in Figure 4 - Figure 7. Apart from the radial position of the protmding guides 12, 13, everything that has been explained above with reference to Figure 4 - Figure 7 is also applicable to the embodiment shown in Figure 11 - Figure 13.

In all embodiments, it may be so that at least one end wall 8, 9 is welded to an axial end 3, 4 of the shell 2 by a plurality of weld beads 11 that are distributed along the circumference of the circumferential groove 8 and separated from each other and arranged in pairs of opposing weld beads that are separated from each other by 175°-185°.

The inventive intermediate product confers several advantages. One such advantage is that the cooperating guides on both the end walls 8, 9 and the shell 2 make it possible to achieve a good positioning of the end walls 8, 9 in relation to the shell 2. Another advantage is that the protruding guides 12, 13 are placed such that they define a groove that can be welded entirely from the outside while the protruding guides 12, 13 form a bulge 36 on the inside of the shell 2 which bulge 36 can easily be removed by grinding or machining. In this way, welding from the inside becomes unnecessary. Therefore, the inventive intermediate product is a way to achieve an effective manufacturing process. It can be added that, since the inventive intermediate product has a design that allows welding only from the outside, the manufacturing process is advantageous with regard to the health of workers since welding inside the shell 2 may expose workers to gases that may endanger the health of the workers.

Another advantage will now be briefly explained with reference to Figure 14, Figure 15 and Figure 16. Figure 14 is a schematic and symbolic representation of an end wall 8 and a shell 2 that are to be welded together. In this case, the end wall 8 and the shell 2 do not abut each other and it should be understood that each of them may be held in a rig or they may be separated by one or several spacers. In Figure 15, it is shown how a weld bead 11 has been applied to connect the end wall 8 to the shell 2. When the weld bead 11 cools off, the material in the weld bead 11 will tend to shrink which may cause tensions as indicated by the arrows F. As several weld beads 11 are made or as a continuous weld bead 11 is made all around the circumference, separate weld beads 11 or different parts of a continuous weld bead may cool and shrink at slightly different times which may have the undesired result that the distance between opposing surfaces of the end wall 8 and the shell 2 changes before the welding has been completed. While the use of spacers may reduce this risk, spacers add a further element with new possible sources of error. Figure 16 is a symbolic and schematic representation of the case when the end wall 8 and the shell 2 abut each other, i.e. are in direct contact with each other. In this way, the relative position in the axial direction of the end wall 8 and the shell 2 is clearly determined by opposing surfaces and shrinking in the weld bead will not change the relative position in the axial direction of the end wall 8 and the shell 2. In Figure 16, no opposing guides are shown since Figure 16 is only intended to illustrate the principle of opposing surfaces in contact with each other.

It should be understood that, while the invention has been defined here in terms of an intermediate product, the invention may also be defined in terms of a method of making a Yankee drying cylinder which method uses the steps described above (in the various embodiment of the invention).

Claims

1. An intermediate product (IP) in the manufacturing process of a steel-made Yankee drying cylinder (1) for drying a fibrous web (W), the intermediate product (IP) comprising a shell (2) that has a circular cylindrical shape and extends in an axial direction about a central axis (A), the shell (2) having two axial ends (3, 4) and an inner surface (5) in which circumferential grooves (6) are formed; for each axial end (3, 4), an end wall (8, 9) which is connected to the axial end (3, 4) by at least one weld bead (11) such that the shell (2) and the end walls (8, 9) define an enclosed space (V) within the intermediate product (IP), each end wall (8, 9) having an outer surface (34, 35) that forms a part of the exterior surface of the intermediate product (IP) and an interior surface (32, 33) that faces the enclosed space (V) such that the interior surfaces (32, 33) of the end walls (8, 9) face each other and the inner surface (5) of the shell (2) and the interior surfaces (32, 33) of the end walls (8, 9) together form an interior surface (7) of the entire intermediate product (IP), and wherein each axial end (3, 4) of the circular cylindrical shell (2) has a protruding guide (12) along at least a part of its circumference, characterized in that each end wall (8, 9) has a protruding guide (13) along at least a part of its circumference that engages and cooperates with the at least one protruding guide (12) of the axial end (3, 4) of the circular cylindrical shell (2) to which the end wall (8, 9) is connected by the at least one weld bead (11), the protmding guides (12, 13) having opposing surfaces that abut each other to define a predetermined position of the end wall (8, 9) in relation to the shell (2) and in which predetermined position a circumferential groove (28) is defined between the end wall (8, 9) and the shell (2), the circumferential groove (28) extending from the outer surface of the shell (2) radially inwards to a bottom of the groove (28) which bottom is defined by at least one of the protmding guides (12, 13) and the protmding guides (12, 13) forming a bulge (36) on the inner surface (7) of the intermediate product (IP) which bulge protrudes into the enclosed space towards the central axis (A) and which bulge (36) can be removed by grinding or machining such that, after removal of the bulge (36), there can be a smooth transition between the inner surface (5) of the shell and the interior surface (32, 33) of the end wall (8, 9).

2. An intermediate product (IP) according to claim 1, wherein at least one of the protmding guides (12, 13) is a circumferential guide (12, 13) that extends over the entire circumference of an end wall (8, 9) or the shell (2).

3. An intermediate product (IP) according to claim 2, wherein both the protmding guides (12) of the end walls (8, 9) and the protmding guide (13) at each axial end (3, 4) of the shell (2) are circumferential guides that extend over the entire circumference of the end wall (8, 9) and the shell (2).

4. An intermediate product (IP) according to claim 1, wherein at least one end wall (8, 9) has a plurality of protruding guides (13) that are separated from each other and distributed along the circumference of the end wall (8, 9) while the axial end (3, 4) of the shell (2) that is connected to that end wall (8, 9) has a continuous protmding guide (12) that extends over the entire circumference of the shell (2) at its axial end (3, 4).

5. An intermediate product (IP) according to claim 1, wherein at least one end wall (8, 9) has a continuous protmding guide (13) that extends over the entire circumference of the end wall (8, 9) and the axial end (3, 4) of the shell (2) that is connected to that end wall (8, 9) has a plurality of protmding guides (12) that are separated from each other and distributed along the circumference of the shell (2) at is axial end (3, 4).

6. An intermediate product (IP) according to any of claims 1 - 5, wherein the at least one protmding guide (13) of an end wall (8, 9) is so placed in relation to the protmding guide (12) of the shell (2) with which it cooperates that at least a part of the protmding guide (13) of the end wall (8, 9) is placed radially inside the protmding guide (12) of the shell (2).

7. An intermediate product (IP) according to any of claims 1 - 6, wherein at least one end wall (8, 9) is welded to an axial end (3, 4) of the shell (2) by a plurality of weld beads (11) that are distributed along the circumference of the circumferential groove (8) and separated from each other and arranged in pairs of opposing weld beads that are separated from each other by 175°- 185°.