Abstract:
The invention relates to a device and a method for producing and/or transforming a web of fibrous material, in particular a paper or cardboard web. Said device includes a heatable and rotatable cylinder, in particular a drying cylinder of a drying section, and a cylinder sleeve which can be impinged from the inside by a heating fluid. In order to improve the heating power below the external surface of the cylinder sleeve, at least one channel is provided in order to guide the heating fluid.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a continuation of PCT application No. PCT/EP2005/056144, entitled “DEVICE AND METHOD FOR PRODUCING AND/OR TRANSFORMING A WEB OF FIBROUS MATERIAL”, filed Nov. 22, 2005, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a device for producing and/or finishing a web of fibrous material, in particular a paper or paperboard web, having a heatable and rotatable cylinder, in particular a drying cylinder of a drying section, having a cylinder shell which can be loaded from the inside with a heating fluid.  
         [0004]     2. Description of the Related Art  
         [0005]     A heated cylinder of this type is known from DE 102 60 509.2. In the known cylinder, tensile stresses which are produced because the inner region of the cylinder expands in a more pronounced manner than the outer region are minimized by the fact that the cylinder shell includes at least two shell layers and the material of the outer shell layer has a greater coefficient of thermal expansion at an assembly temperature which lies below the mean operating temperature and a smaller coefficient of thermal expansion at an assembly temperature which lies above the mean operating temperature than the material of the inner shell layer. A further measure consists in that the layer thickness of the outer shell layer is smaller than that of the inner shell layer.  
         [0006]     In drying cylinders of this type, a temperature gradient toward the surface is produced during paper drying. The surface temperature of the cylinder is lower than the temperature of the steam, with which the cylinder is heated; the drying capacity is therefore restricted. Increasing the saturated steam temperature is usually not appropriate for economic reasons.  
         [0007]     EP 0 559 628 B1 has disclosed a dryer for drying a web of fibrous material, in which dryer a throughflow cylinder is used in conjunction with a blowing hood. The latter is provided with a nozzle arrangement, with the aid of which drying gas jets are applied to the outer surface of the web which is to be dried, while said web is guided around the heated cylinder over a sector of approximately 270° or more. The circumference of the cylinder is provided with a system of channel lines, into which a coolant can be guided from a coolant source. Water in the web is evaporated outward as a result of the drying gas jets and removed via spaces in the blowing hood. Secondly, water from the web condenses on the cooled circumferential surface of the cylinder and is extracted by suction via the perforation in the outer shell of the cylinder and a vacuum which prevails in the interior of the cylinder. The entire inner space of the cylinder is available for receiving the condensate. As a result, the inner wall of the cylinder has to have a certain minimum wall thickness, in order for it to be possible to withstand the pressure loadings in the case of the cylinder diameters which are used.  
         [0008]     What is needed in the art is to increase the drying performance of a heatable cylinder.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention provides at least one channel for passing the heating fluid through which is formed below the outer surface of the cylinder shell.  
         [0010]     As a result of the present invention, the heating fluid can be brought very close to the outer surface of the heatable cylinder. As a result, the temperature gradient is lower than in the case of the known devices of the abovementioned type, and the drying performance is increased accordingly.  
         [0011]     According to a refinement of the invention, in order to form the at least one channel, a further cylinder shell which is spaced apart from the outer cylinder shell is arranged within the cylinder shell. This can be achieved satisfactorily in structural terms and has the advantage that the entire inner side of the outer cylinder shell can be loaded with heating fluid.  
         [0012]     According to a further refinement of the invention, the outer cylinder shell is supported on the inner cylinder shell. As a result, the wall thickness of the outer cylinder shell can be kept small, as the inner cylinder shell acts as a carrying cylinder. As a result, the drying performance can be increased still further.  
         [0013]     In order to support the outer cylinder shell on the inner cylinder shell, in particular webs, rods, pins, rivets, bolts, screws and/or other connecting ways can be provided. It is important that the connecting ways are distributed over the surface of both cylinder shells, in order to ensure uniform support.  
         [0014]     The webs or other connecting elements can extend axially, in the circumferential direction and/or in a direction which lies between them. In all cases, satisfactory support can be achieved.  
         [0015]     In particular in the case of webs which extend in the circumferential direction, it is advantageous if they are provided at least partially with passage openings for the heating fluid. The heating fluid can then flow not only in the circumferential direction but also in the longitudinal direction of the drying cylinder.  
         [0016]     The inner shell and the outer shell can be composed of the same or of a different material. In any case, it is advantageous if it is a metallic material, as satisfactory thermal conduction and sufficient stability are then ensured.  
         [0017]     As material, in particular, for the outer shell, material having high thermal conductivity can be used. In particular, steel, such as boiler steel, copper, aluminum or bronze, may be suitable. Satisfactory thermal transmission onto the web of fibrous material can therefore be ensured.  
         [0018]     The configuration of the inner cylinder as a thick-walled tube is advantageous in structural terms. A satisfactory carrying property is therefore also ensured.  
         [0019]     The inner cylinder can also include two or more individual shells. As a result, the thermal expansion behavior and the loadability can be improved.  
         [0020]     However, the inner cylinder can also be configured as a framework or as a frame/rib construction. This can also be advantageous in specific applications.  
         [0021]     According to a further refinement of the invention, the inner side of the outer cylinder shell is provided with elevations. As a result, the condensate which collects on the inner side of the outer cylinder shell is subjected to turbulence, as a result of which the thermal transfer is improved. The condensate which collects namely has a thermally insulating effect and increases the temperature gradient to the cylinder surface.  
         [0022]     According to a refinement of the invention, the inner side of the outer cylinder shell face is configured with ribs and/or lugs and/or a grid or honeycomb structure. Satisfactory swirling of the condensate can therefore be achieved.  
         [0023]     The height of the elevations on the inner side of the outer cylinder shell can be selected in such a way that they protrude out of the fluid condensate which is formed during operation. In this way, the elevations have direct contact with the heating fluid, as a result of which the heat can be transferred in an improved manner to the outer surface of the drying cylinder. Moreover, the increase in the surface area as a result of the elevations has a positive effect on the heat transfer. Elevations having a smaller height than the height of the condensate are therefore also advantageous.  
         [0024]     The elevations can extend in the cylinder longitudinal direction and/or along a helical line. A special conveying action for condensate discharge can be achieved by a helical line.  
         [0025]     According to one refinement of the invention, one or more siphons is/are provided for discharging condensate which is formed during operation. They can be configured such that they are stationary or co-rotate with the drying cylinder. The condensate quantity which collects on the inner side of the outer cylinder shell can be reduced as a result.  
         [0026]     The outer surface of the drying cylinder can be provided with a coating or covering. The latter serves, in particular, for corrosion or abrasion protection or for improving the surface, for example in order to avoid adhesion of paper.  
         [0027]     According to one special refinement of the invention, web plates which are connected to the inner cylinder shell are provided as connecting elements between the inner and outer cylinder shells. The outer cylinder shell can be formed by covering plates which are likewise connected to the web plates.  
         [0028]     In another special refinement of the invention, the web plates and covering plates are combined to form profiles, preferably U-shaped or T-shaped.  
         [0029]     According to another special refinement of the invention, the outer shell and the connecting elements are manufactured in one piece, in particular by welding, milling from a tube, casting or by way of other manufacturing processes.  
         [0030]     The outer cylinder shell and the inner cylinder shell can advantageously be connected to one another by a press fit. Another possibility includes a screwed connection. Moreover, a conical seat or a form-fitting connection, in particular an L-connection, T-connection or dovetail connection, is advantageous. In order to produce play in the connection, a soldering material can additionally be attached, which melts during subsequent heating of the cylinder and then hardens again. However, the tolerances can also be selected in such a way that there is no play.  
         [0031]     Other possibilities for connection include clamping elements, a self-locking or a latching connection. Combinations of all abovementioned connections are also possible, for example a T-groove connection with a conical seat or a T-groove connection with screws.  
         [0032]     According to a further refinement of the invention, the inner cylinder shell is formed from individual metal sheets which are connected to the connecting elements and to one another in a suitable manner, for example welding. Both the inner cylinder shell and the outer cylinder shell can also be manufactured in this way.  
         [0033]     According to a further special refinement of the invention, bolts are provided as connecting elements between the inner and outer cylinder shells, which bolts are introduced into holes in the outer cylinder shell and are connected to the inner cylinder shell, for example by rotary friction welding or resistance pressure welding or by screwing in. The connection of the bolt and the outer cylinder shell in the holes can take place subsequently, for example by welding. Instead of bolts which are introduced into holes of the outer cylinder shell, bolts can also be provided which are introduced into holes of the inner cylinder shell and are then connected to the outer cylinder shell.  
         [0034]     According to a further refinement of the invention, the inner cylinder shell and the outer cylinder shell can be manufactured in each case in one piece over their entire length, for example by casting.  
         [0035]     According to another refinement of the invention, only one cylinder shell is provided which is configured as a thick-walled tube and in which channels for the heating fluid are made, for example by deep-hole drilling or milling. In this way, the heating fluid can also be brought close to the outer surface of the drying cylinder and the drying performance can therefore be increased.  
         [0036]     In another refinement of the invention, the inner cylinder shell and the connecting elements are manufactured as one piece, to which the outer shell is then fastened by way of a suitable process.  
         [0037]     One advantageous connecting type results if the webs between the inner cylinder shell and the outer cylinder shell are divided obliquely over their height. That is to say, one part web is provided in each case on the inner cylinder shell and one part web is provided on the outer cylinder shell. By rotation of the inner and outer cylinder shells with respect to one another, said web parts are brought into connection with one another and a force-transmitting connection is produced.  
         [0038]     In order to feed in and discharge the heating fluid, corresponding channels can be provided in the axle of the drying cylinder. The feed channel and the return channel can be nested inside one another here. This saves space and simplifies the construction.  
         [0039]     The heating fluid can be distributed onto the hollow space between the inner and outer cylinder shells via radial channels, in particular at least in the cover on the feed side. This is particularly advantageous when, as viewed over the circumference, a large number of individual channels are arranged next to one another, for example in the case of continuous webs in the longitudinal direction of the drying cylinder between the inner and the outer cylinder shells or in the case of a drilled single shell.  
         [0040]     Moreover, it can be advantageous to turn the outer shell face. As a result, a smooth surface can be achieved.  
         [0041]     The elevations on the inner side of the outer cylinder shell can be milled, drawn, pressed, rolled or cast. Other manufacturing types are also possible.  
         [0042]     The webs, metal sheets or other connecting elements between the inner and outer cylinder shells can be manufactured by removing material, by primary forming technology or by forming technology. A combination of these processes is also possible.  
         [0043]     An apparatus of the abovementioned type can be used for producing a web of fibrous material, in particular a paper or paperboard web. Here, a drying cylinder of the abovementioned type or a plurality of drying cylinders of this type can be used. A drying cylinder according to the present invention can also be combined with conventional drying cylinders.  
         [0044]     During production, contact with the web of fibrous material can be made by the drying cylinders in each case on the same side. However, contact on both sides is also possible. Depending on the application, one or the other variant is advantageous.  
         [0045]     All known auxiliary devices can be used for web guidance, for example a suction or blower box, an evacuated or nonevacuated roll, an airblade or a dryer fabric.  
         [0046]     In particular, cylinder drying, the boost dryer process, the Condebelt process, a yankee cylinder and a HiDryer may be suitable as conventional drying processes.  
         [0047]     Together with the web of fibrous material and optionally a felt, a metal belt can also be guided over the drying cylinder. The latter can be cooled and under stress. As a result, the temperature gradient over the web of fibrous material can be increased and rapid removal of the moisture can therefore be achieved.  
         [0048]     The drying performance can be increased by the method according to the invention and the device according to the invention. As a result, a finished dried paper can be achieved with a relatively low dwell time. This can be utilized firstly by the fact that less space is required in comparison with a drying section according to the prior art, which results in savings in the basic price, the building costs for the hall, the machine frames and the fume extraction hood, and also the operating costs for drives and hood ventilation. Secondly, this can be utilized by the fact that a speed increase is achieved with existing space conditions, for example papermaking machine conversions, with an identical length of the drying section. As a result, the papermaking machine can be operated more economically. Moreover, the steam pressure can be reduced with the same drying performance. For example, the differential steam pressure could be utilized for electricity generation, or the energy for steam generation can be minimized.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0049]     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0050]      FIG. 1  shows a longitudinal section through a drying cylinder of a device according to the invention;  
         [0051]      FIG. 2  shows a partial plan view of the end side of the drying cylinder of  FIG. 1 ;  
         [0052]      FIG. 3  shows a partial cross section through a drying cylinder of a device according to the invention;  
         [0053]      FIG. 4  shows a variant of  FIG. 3 ;  
         [0054]      FIG. 5  shows a further variant of  FIG. 3 ;  
         [0055]      FIG. 6  shows a partial longitudinal section through a drying cylinder of a device according to the invention;  
         [0056]      FIG. 7  shows a variant of  FIG. 6 ; and  
         [0057]      FIG. 8  shows a simplified longitudinal section through a further drying cylinder of a device according to the invention. 
     
    
       [0058]     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0059]     Referring now to the drawings, and more particularly to  FIG. 1 , there is shown a drying cylinder in the drying section of a papermaking machine. The drying cylinder includes an outer cylinder shell  1  and an inner cylinder shell  2  which is arranged concentrically in the former. The inner cylinder shell  2  is fastened via screws  3  to two end-side covers  4  which are of disk-shaped configuration and in each case have one bearing axle  5 ,  6 . The drive side is situated on the left-hand side in  FIG. 1 , and the operator side of the drying cylinder is situated on the right-hand side.  
         [0060]     The outer cylinder shell  1  has an outer surface  7 , over which a paper web which is to be dried is guided. The outer surface  7  of the outer cylinder shell  1  is of flush configuration with the circumferential faces  8  of the two covers  4 . As a result, a continuous contact face for the paper web is provided.  
         [0061]     The outer cylinder shell  1  has a thickness d 1  which is smaller than the thickness d 2  of the inner cylinder shell  2 . The inner circumferential face  9  of the outer cylinder shell  1  is at a spacing from the outer circumferential face  10  of the inner cylinder shell  2 , with the result that an annular hollow space  11  is formed between the outer cylinder shell  1  and the inner cylinder shell  2 . This annular space  11  is connected to radial channels  12 ,  13  in the two axles  5 ,  6  of the covers  4  on both end sides of the two cylinder shells  1 ,  2  via channels (not shown here) in the covers  4 . For their part, the radial channels  12  of the axle  5  of the operator-side cover  4  are connected to an axial channel  14  which is provided centrally in the axle  5  of the operator-side cover  4  and opens in a connection end  15 . The radial channels  13  of the axle  6  of the drive-side cover  4  are likewise connected to an axial channel  16 . Starting from the drive-side cover  4 , said channel  16  is guided concentrically with respect to the rotational axis I of the drying cylinder centrally through the two cylinder shells  1 ,  2  and the axle  5  of the operator-side cover  4 , and likewise opens in a connection end  17 . Here, the channel  16  penetrates the channel  14  concentrically, with the result that the channel  14  has an annular cross section.  
         [0062]     The above-described construction results in a channel system which makes the circulation of heating fluid possible through the hollow space  11  between the outer cylinder shell  1  and the inner cylinder shell  2 . For this purpose, for example, heating fluid is fed into the annular channel  14  via the connection end  15 . From there, the heating fluid passes via the radial channels  12  into the channels (not shown) in the operator-side cover  4  and, from the latter, into the hollow space  11  between the outer cylinder shell  1  and the inner cylinder shell  2 . The heating medium then flows from the operator side through the hollow space  11  to the drive-side and passes there via the channels (not shown) in the drive-side cover  4  into the radial channels  13  of the drive-side axle  6 . From there, the heating fluid in turn flows via the central channel  16  back to its connection end  17 .  
         [0063]     On both end sides, the outer cylinder shell  1  has in each case tapered sections  18 , with which the outer cylinder shell  11  rest in each case on a corresponding seat  19  on the circumferential sides of the covers  4 . As a result, the outer cylinder shell  1  is supported on the two covers  4 . However, the main support of the outer cylinder shell  1  takes place over its length by way of connecting elements  20 , as are shown by way of example in  FIG. 2  and which are distributed over the circumferential faces of the outer cylinder shell  1  and the inner cylinder shell  2 . Moreover,  FIG. 2  also shows a siphon  21  which is provided for removing condensate at the end-side end of the hollow space  11 . Siphons  21  of this type can be provided both on the drive side and on the operator side and are of either co-rotating or stationary configuration. A plurality of siphons of this type can also be provided in the circumferential direction.  
         [0064]     Different variants of the connecting elements  20  between the outer cylinder shell  1  and the inner cylinder shell  2  are shown in FIGS.  3  to  5  and will be described in the following text.  
         [0065]     FIGS.  3  to  5  show a circumferential section of a drying cylinder according to the invention having an outer cylinder shell  1  of small thickness d 1  and an inner cylinder shell  2  of greater thickness d 2  in comparison. There is a hollow space  11  for guiding a heating fluid through between the outer cylinder shell  1  and the inner cylinder shell  2 .  
         [0066]     At A 1  in  FIG. 3 , a screwed connection is shown between the outer cylinder shell  1  and the inner cylinder shell  2 . For this purpose, the inner cylinder shell  2  has holes  22 , through which screws  23  are guided. Lying opposite the holes  22  in the inner cylinder shell  2 , the outer cylinder shell  1  has radially inwardly pointing projections  24 , in which threaded holes  25  are provided, into which the screws  23  can be screwed. The outer cylinder shell  1  is supported on the inner cylinder shell  2  via the radial projections  24 , and the screws  23  fix the two cylinder shells  1 ,  2  with respect to one another. A radial projection can be provided in each case only in the case of the screws  23  or can extend continuously in the axial direction of the drying cylinder or in another direction.  
         [0067]     At A 2 , a similar connection is shown between the inner cylinder shell  2  and the outer cylinder shell  1 . The only difference is that here, lying opposite the radial projection  24 , in each case one tangentially milled seat  26  is provided on the outer circumferential face  10  of the inner cylinder shell  2 . As a result, improved support can be achieved.  
         [0068]     At A 3 , a connection is shown which largely corresponds to the connection of A 2 . The only difference is that the diameter of the screw holes  22  and the screws  23  is smaller here than the corresponding diameters at A 2 . For example, screws of the size M 10  can be used at A 2  and screws of the size M 8  can be used at A 3 . The smaller screws save weight in comparison with the larger screws.  
         [0069]     A further variant of the connection of A 3  is shown at A 4 . The difference is that the seat  26  here is not milled tangentially but at an angle of 2° with respect to the tangential direction. The milling serves to clamp the outer cylinder shell  1  with respect to the inner cylinder shell  2 . For this purpose, after it has been fed onto the inner cylinder shell  2 , the outer cylinder shell is rotated in the direction of the rising seat  26 , that is to say to the right in  FIG. 3  about the axis I of the drying cylinder.  
         [0070]     A stronger clamping action is realized in the connection which is shown at A 5 . Here, the angle of the milling is 5° with respect to the tangential direction. Otherwise, this connection corresponds to the connection of A 4 .  
         [0071]     In the variant which is shown at A 6 , there is in turn a seat  26  which is milled at 5° with respect to the horizontal direction. However, the radial projection  24  of the outer cylinder shell  1  is not of straight configuration as in the above-described variants, but has an L-shape. The base  27  of the L-shaped projection  24  is supported here on the milled seat  26 . As a result, the support becomes more stable.  
         [0072]     It is shown at A 7  that an L-shaped projection  24  can also be combined with a seat  26  which is milled at 0° or a seat  26  which is milled at 10°.  
         [0073]     Finally, it is shown in  FIG. 3  that the outer cylinder shell  1  can be provided with elevations  28  on its inner circumferential face  9 . These serve to impart turbulence to the collecting condensate, in order to improve the thermal conductivity to the outer surface  7  of the outer cylinder shell  1 . In addition to the shape which is shown, other shapes are also possible. The height of the elevations  28  can be selected in each case in such a way that they protrude at least to a certain extent from the condensate, in order that they can be loaded directly by the heating medium and therefore bring about satisfactory additional thermal conduction to the outer surface  7  of the outer cylinder shell  1 .  
         [0074]      FIG. 4  shows different variants of the form-fitting connection between the outer cylinder shell  1  and the inner cylinder shell  2 . As shown at B 1 , the outer cylinder shell  1  can be provided for this purpose on its shell inner side  9  with projections  29  which extend in the axial direction or another direction and in which T-shaped grooves  30  are provided which open toward the inner cylinder shell  2 . Corresponding T-shaped grooves  31  which open toward the outer cylinder shell  1  are provided in the outer surface  10  of the inner cylinder shell  2 . Via I-beams  32  which are inserted into the grooves  30 ,  31 , a form-fitting connection is then effected between the outer cylinder shell  1  and the inner cylinder shell  2 , which form-fitting connection at the same time brings about support of the outer cylinder shell  1  on the inner cylinder shell  2 . Here, the I-beams  32  can have such an external dimension that a play results between them and the T-grooves  30 ,  31 , in particular a rearward and lateral play. Assembly takes place by pushing the I-shaped beams  32  into the grooves  30 ,  31  after the outer cylinder shell  1  has been pushed onto the inner cylinder shell  2 .  
         [0075]     In the variant which is shown at B 2 , likewise T-shaped grooves  33  are provided in the outer surface  10  of the inner cylinder shell  2 . However, projections  34  of T-shaped cross section on the shell inner side  9  of the outer cylinder shell  1  engage into them. Assembly takes place here by simply pushing the outer cylinder shell  1  onto the inner cylinder shell  2 . The connection can also be configured with or without play here.  
         [0076]     Like the groove  31  in the above-described variant, the groove  33  can be milled into the outer surface  10  of the inner cylinder shell  2 . However, other production processes are also possible.  
         [0077]     The variant which is shown at B 3  differs from the variant which is shown at B 2  in that the groove  33  for receiving the projection  34  of T-shaped cross section is not milled into the outer surface  10  of the inner cylinder shell  2  but is formed by a corresponding groove profile  35  being welded on. The projection  34  is of correspondingly shorter configuration and is supported on the outer surface  10  of the inner cylinder shell  2  via the groove profile  35 . The connection can also be configured here with rearward and lateral play. In comparison with the variant of B 1 , no groove is therefore required here in the inner cylinder shell  2 .  
         [0078]     The variant of B 4  corresponds largely to the variant of B 3 . The difference is only in that the groove profiles  35  are not welded to the inner cylinder shell  2  but are screwed via screws  36 . For this purpose, the groove profiles  35  have lateral threaded holes  37 .  
         [0079]     The variant which is shown at B 5  is distinguished by the fact that profiles  38  are screwed onto the outer circumferential side  9  of the inner cylinder shell  2 , which profiles  38  have, on their radial outer side, a section  39  of T-shaped cross section which can be introduced into the groove  30  of a projection  29  which corresponds in principle to the projection  29  which is shown at B 1 . For this purpose, screws  36  are screwed into corresponding threaded holes  41  which are provided in lateral flanges  40  of the profile  38 . In this variant, there can also be rearward and lateral play between the T-section  39  and the groove  30 .  
         [0080]     The variant which is shown at B 6  is similar to the variant which is shown at B 5 . Instead of the profile  38 , a T-profile  42  is provided here, which is inserted into a groove  43  on the outer side  10  of the inner cylinder shell  2 . Moreover, for fastening of the profile  42 , only one row of screws  36  are inserted into corresponding threaded holes  44  of the profile  42 .  
         [0081]     The variant which is shown at B 7  corresponds largely to the variant of B 4 . Here, however, the groove profile  45  is configured with two in each case outwardly pointing flanges  46 , in which in each case threaded holes  47  are provided for screwing in the screws  36 . Moreover, the groove profile  45  is moved more closely to the inner surface  9  of the outer cylinder shell  1 , with the result that the projection  34  of T-shaped cross section is correspondingly shorter.  
         [0082]     The variant which is shown at B 8  in turn corresponds largely to the variant of B 3 . Here, however, the groove profile  48  is not welded to the inner cylinder shell  2  but is connected via screws  36  again. For this purpose, the groove profile  48  has corresponding threaded holes  49  on its side which faces the inner cylinder shell  2 . Here, as in the variant of B 7 , the groove profile  48  is also moved closer to the inner surface  9  of the outer cylinder shell  1  and interacts with projections  34  of correspondingly shorter configuration on the inner side  9  of the outer cylinder shell  1 .  
         [0083]     In the form-fitting variants which are shown in  FIG. 4 , elevations  28  for generating turbulence in the condensate which is formed can also be provided on the inner side  9  of the outer cylinder shell  1 . The elevations  28  can again have all possible shapes and orientations, but preferably protrude from the condensate to a small extent.  
         [0084]      FIG. 5  shows four further form-fitting variants. At C 1 , one variant is shown, in which an angled profile  50  is welded to the outer upper side  10  of the inner cylinder shell  2 . A projection  51  of L-shaped cross section which is formed integrally on the inner side  9  of the outer cylinder shell  1  interacts with this angled profile  50 . The base  52  of the profile  51  engages under the angled profile  50  and is supported on the seat  53  which is milled at 5° on the outer side  10  of the inner cylinder shell  2 . Corresponding profiling of the projection  51  results in a self-locking connection between the outer cylinder shell  1  and the inner cylinder shell  2 .  
         [0085]     For assembly, the outer cylinder shell  1  is pushed axially onto the inner cylinder shell  2  in the position of the projection  51  which is shown with dashed lines at C 1 . The outer cylinder shell  1  is then rotated with respect to the inner cylinder shell  2  in the direction of the angled profile  50 , that is to say to the right in  FIG. 5 , about the axle of the drying cylinder by the spacing r 2 , with the result that the projection  51  engages under the angled profile  50  by way of its base  52  and is fixed in a self-locking manner.  
         [0086]     The variant which is shown at C 2  corresponds largely to the variant of Cl. Instead of the self-locking profiling of the projection  51 , only a screwed connection is provided here for fixing the outer cylinder shell  1  with respect to the inner cylinder shell  2 . For this purpose, the inner cylinder shell  2  is provided with holes  54 , through which screws  55  are guided which can be screwed into threaded holes  56  which are provided in extensions  57  which are provided at suitable spacings in the axial direction on that side of the projection  51  which faces away from the base  52  of the L-shaped projection  51 . The assembly takes place in a corresponding manner to the variant of C 1 , only the screws  55  also being screwed in after rotation of the two cylinder shells  1 ,  2  with respect to one another.  
         [0087]     In the variant which is shown at C 3 , the two cylinder shells  1 ,  2  are also fixed with respect to one another via screws  55 . However, in a difference from the variant of C 2 , these are screwed into threaded holes  58  here which are provided in the angled profile  59  which is connected to the inner cylinder shell  2 . Moreover, in this variant, there is no milled seat on the outer side  10  of the inner cylinder shell  2 .  
         [0088]     There is a milled seat of this type in turn in the variant which is shown at C 4 . This seat  60  is milled tangentially in this variant. Otherwise, this variant corresponds to the variant of C 3 . In both variants of C 3  and C 4 , the assembly takes place by rotation of the outer cylinder shell  1  with respect to the inner cylinder shell  2  after the outer cylinder shell  1  has been pushed on and the screws  55  have subsequently been screwed in, in accordance with the variant of C 2 .  
         [0089]     The partial longitudinal section of  FIG. 6  once again generally shows the connection and support of the outer cylinder shell  1  to or on the inner cylinder shell  2  via connecting elements  20  which are represented here as screws. In order to seal the hollow space  11  between the inner cylinder shell  2  and the outer cylinder shell  1  to the outside, sealing rings  61  are provided between said outer cylinder shell  1  and the covers  4  in the circumferential faces of the covers  4 . Sealing to the inside is not required in principle.  
         [0090]     In the variant which is shown in  FIG. 7  and which otherwise corresponds to the variant of  FIG. 6 , seals  62  are provided instead of the sealing rings  61 , which seals  62  engage around the screws  63 , by way of which the covers  4  are fastened to the inner cylinder shell  2 . As a result, improved sealing to the outside can be ensured.  
         [0091]     Finally,  FIG. 8  once again shows in simplified form the construction of the drying roll in its entirety with an outer cylinder shell  1  and an inner cylinder shell  2  which is fastened to the two covers  4  which are in turn arranged on axles  5 ,  6 . The operator-side axle  5  has the radial channels  12  and the concentric axial channels  14  and  15 ; the drive-side axle  6  likewise has radial channels  1 . The connecting channels are also not shown here between the radial channels  12  and  13  and the hollow space  11  between the outer cylinder shell  1  and the inner cylinder shell  2 . The flow direction of the heating fluid is shown by way of arrows II.  
         [0092]     While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.  
       LIST OF DESIGNATIONS  
       [0093]      1  Outer cylinder shell  
         [0094]      2  Inner cylinder shell  
         [0095]      3  Fastening screw  
         [0096]      4  Cover  
         [0097]      5  Operator-side axle  
         [0098]      6  Drive-side axle  
         [0099]      7  Outer side of  1   
         [0100]      8  Circumferential face of  4   
         [0101]      9  Inner side of  1   
         [0102]      10  Outer side of  2   
         [0103]      11  Hollow space  
         [0104]      12  Radial channel  
         [0105]      13  Radial channel  
         [0106]      14  Axial channel  
         [0107]      15  Connection end of  14   
         [0108]      16  Axial channel  
         [0109]      17  Connection end of  16   
         [0110]      18  Tapered section of  1   
         [0111]      19  Seat  
         [0112]      20  Connecting element  
         [0113]      21  Siphon  
         [0114]      22  Hole  
         [0115]      23  Screw  
         [0116]      24  Projection  
         [0117]      25  Threaded hole  
         [0118]      26  Seat  
         [0119]      27  Base of  24   
         [0120]      28  Elevation  
         [0121]      29  Projection  
         [0122]      30  Groove  
         [0123]      31  Groove  
         [0124]      32  I-beam  
         [0125]      33  Groove  
         [0126]      34  Projection  
         [0127]      35  Groove profile  
         [0128]      36  Screw  
         [0129]      37  Threaded hole  
         [0130]      38  Profile  
         [0131]      39  T-section of  38   
         [0132]      40  Flange  
         [0133]      41  Threaded hole  
         [0134]      42  T-profile  
         [0135]      43  Groove  
         [0136]      44  Threaded hole  
         [0137]      45  Groove profile  
         [0138]      46  Flange  
         [0139]      47  Threaded hole  
         [0140]      48  Groove profile  
         [0141]      49  Threaded hole  
         [0142]      50  Angled profile  
         [0143]      51  Projection  
         [0144]      52  Base of  51   
         [0145]      53  Seat  
         [0146]      54  Hole  
         [0147]      55  Screw  
         [0148]      56  Threaded hole  
         [0149]      57  Extension  
         [0150]      58  Threaded hole  
         [0151]      59  Angled profile  
         [0152]      60  Seat  
         [0153]      61  Annular seal  
         [0154]      62  Seal  
         [0155]      63  Screw  
         [0156]     I Rotational axis  
         [0157]     II Flow direction  
         [0158]     d 1  Thickness of  1   
         [0159]     d 2  Thickness of  2   
         [0160]     r Spacing  
         [0161]     r 2  Spacing