Patent Abstract:
The invention relates to a device for producing and/or transforming a web of fibrous material, in particular a paper cardboard web. Said device includes a heatable and rotatable cylinder, in particular a dry cylinder of a dry part, including a cylinder sleeve which can be impinged upon from the inside by a heating fluid. At least one channel is provided in order to guide the heating fluid such that the heating capacity can be improved and the production below the external surface of the cylinder cover can be simplified. The dry cylinder is at least partially modular.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a continuation of PCT application No. PCT/EP2005/056166, entitled “DEVICE AND METHOD FOR PRODUCING AND/OR TRANSFORMING A WEB OF FIBROUS MATERIAL”, filed Nov. 23, 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 and to simplify manufacture.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention provides at least one channel for guiding through the heating fluid which is formed below the outer surface of the cylinder shell, as well as a drying cylinder which is of at least partially modular construction.  
         [0010]     As a result of the 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. The manufacture is simplified as a result of the modular construction.  
         [0011]     According to one refinement of the present 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 low, as the inner cylinder shell acts as carrying cylinder. As a result, the drying performance can be increased still further.  
         [0013]     Open and/or closed profiles can form a module. In particular, segments firstly of the inner cylinder shell and/or of the outer cylinder shell and secondly of one or more connecting elements can form a module. This is advantageous in terms of manufacture and makes simple assembly possible. Moreover, it is readily possible to realize different overall sizes with identical modules as a result.  
         [0014]     The drying cylinder can be of modular construction, both in the axial direction and in the circumferential direction, but also in both directions. The individual modules are then positioned next to one another in the circumferential direction and/or axially. Axial modules can have a length, for example, of up to 7 m, and circumferential modules can have a length, for example, of 1 m.  
         [0015]     According to one particular refinement of the invention, cylinder rings having the cross section of the drying cylinder form a module. They can then be arranged simply behind one another and connected to one another, for example welded.  
         [0016]     Annular segments having the partial cross section of a drying cylinder can also form modules which are then assembled to form rings and are arranged behind one another in the axial direction. This is also advantageous in terms of manufacture and assembly.  
         [0017]     It is particularly advantageous if module rings or module part rings which form or have the channels are pushed onto a carrying tube. The prefabricated annular modules or part annular modules can therefore be mounted simply and connected to one another.  
         [0018]     Particular advantages result when a module at the same time forms a functional element of the drying cylinder. For example, a module can form one or more guide channels for the heating fluid. The desired channel system is produced by said modules being positioned next to one another, without it being necessary for the individual modules to be sealed with respect to one another. A further advantage of this construction is that the pressure forces are absorbed within the modules and do not load the connections between the modules.  
         [0019]     In addition to welding, the modules can also be connected by soldering, screwing, by a form-fitting connection or by a force-transmitting connection. Combinations of these are also possible.  
         [0020]     In particular, webs, rods, pins, rivets, bolts, screws and/or other connecting ways can be provided for supporting the outer cylinder shell on the inner cylinder shell. It is important that the connecting ways are distributed over the surface of both cylinder shells, in order to ensure uniform support.  
         [0021]     The webs or other connecting elements can extend axially, in the circumferential direction and/or in a direction which lies between them. Satisfactory support can be achieved in all cases.  
         [0022]     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.  
         [0023]     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 is collected 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.  
         [0024]     According to a further 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.  
         [0025]     The elevations can extend in the cylinder longitudinal direction and/or along a helical line. A particular conveying action for condensate removal can be achieved by a helical line.  
         [0026]     The outer surface of the drying cylinder can be provided with a coating or covering. The latter serves, in particular, for protection against corrosion and/or abrasion, or for improving the surface, for example in order to avoid the adhesion of paper.  
         [0027]     According to a further refinement of the invention, web metal sheets 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 cover plates which are likewise connected to the web metal sheets.  
         [0028]     In another refinement of the invention, the web metal sheets and cover plates are combined to form profiles, such as with a U-shape or T-shape.  
         [0029]     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.  
         [0030]     Moreover, it can be advantageous to turn the outer circumferential face. As a result, a smooth surface can be achieved.  
         [0031]     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.  
         [0032]     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.  
         [0033]     A device of the abovementioned type can be used for manufacturing a web of fibrous material, in particular a paper or paperboard web. Here, a drying cylinder of the above-mentioned 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.  
         [0034]     Suitable conventional drying processes are, in particular, cylinder drying, the boost dryer process, the Condebelt process, a yankee cylinder and a HiDryer.  
         [0035]     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  
       [0036]     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:  
         [0037]      FIG. 1  shows a longitudinal section through a drying cylinder of a device according to the invention;  
         [0038]      FIG. 2  shows a partial plan view of the end side of the drying cylinder of  FIG. 1 ;  
         [0039]      FIG. 3  shows a partial cross section through a drying cylinder of a device according to the invention;  
         [0040]      FIG. 4  shows a variant of  FIG. 3 ;  
         [0041]      FIG. 5  shows a further variant of  FIG. 3 ;  
         [0042]      FIG. 6  shows a side view of a drying cylinder of a device according to the invention; and  
         [0043]      FIG. 7  shows a cross section through the drying cylinder of  FIG. 6 . 
     
    
       [0044]     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  
       [0045]     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.  
         [0046]     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.  
         [0047]     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.  
         [0048]     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 .  
         [0049]     On both end sides, the outer cylinder shell  1  has in each case tapered sections  18 , with which the outer cylinder shell  11  rests 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 corotating or stationary configuration. A plurality of siphons of this type can also be provided in the circumferential direction.  
         [0050]     Different variants of the modular construction of the drying cylinder according to the invention are shown in FIGS.  3  to  7  and will be described in the following text.  
         [0051]     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 through a heating fluid between the outer cylinder shell  1  and the inner cylinder shell  2 .  
         [0052]     Modules  22  which are attached to the inner cylinder shell  2  as carrying tube are provided in the variants which are shown in FIGS.  3  to  5 . Here, the modules  22  are arranged so as to adjoin one another in the circumferential direction and together form the outer cylinder shell  1  and the hollow space  11  between the outer cylinder shell  1  and the inner cylinder shell  2 .  
         [0053]     The outer cylinder shell  1  is supported on the inner cylinder shell  2  via the modules  22  themselves.  
         [0054]     In the variant which is shown in  FIG. 3  at D 1 , the modules  22  are configured as tubes  23  which are substantially rectangular at their outer circumference and extend in the longitudinal direction of the drying cylinder. The hollow spaces  24  of the rectangular tubes  23  form channels for the heating fluid and, in a joint manner overall, the hollow space  11  between the outer cylinder shell  1  and the inner cylinder shell  2 . As shown in the right-hand tube  23  at D 1 , elevations  27  which load a heating fluid condensate which collects there during operation with turbulence are arranged on the inner side  25  of the outer section  26  of the tube  23 .  
         [0055]     The tubes  23  are connected to the inner cylinder shell  2  by screws  28 . For this purpose, the inner cylinder shell  2  has holes  29  at a corresponding location. There are associated threaded holes  30  in the two lateral sections  31  of the tubes  23 . Moreover, the tubes  23  which are arranged next to one another can be welded to one another. In order to achieve a smooth surface, the outer side  7  of the outer cylinder shell  1  can then be turned.  
         [0056]     The variant which is shown at D 2  in  FIG. 3  coincides largely with the variant of D 1 . The single difference is that here the tubes  23  which have a substantially rectangular cross section have a shoulder  32  in each case on the left-hand side in  FIG. 3  and a projection  33  on the right-hand side, which projection  33  is formed with an accurate fit with respect to the shoulder  32 . The result of the projections  33  and the shoulders  32  engaging in one another is additionally a form-fitting connection between the adjacent modules  22 . A welded connection can optionally be dispensed with here.  
         [0057]     In the variant of  FIG. 3  which is shown at D 3 , a form-fitting connection is also provided between the adjacent tubes  23 . Here, in a difference from the variant of D 2 , the tubes  23  have an upwardly bent, rounded projection  34  on their left-hand side and a correspondingly shaped recess  35  on their right-hand side, into which recess  35  the projection  34  engages. A welded connection between the tubes  23  can also be dispensed with here. The variant which is shown at D 4  in  FIG. 4  coincides practically completely with the variant at D 3  in  FIG. 3 . The only difference is that the cross section of the projections at D 4  is smaller than in the variant of D 3  in  FIG. 3 , and correspondingly the cross section of the recesses  35  is also smaller.  
         [0058]     At D 5 ,  FIG. 4  shows a variant which coincides completely with the variant at D 4  in terms of the outer circumference. However, the tubes  23  do not have one but two chambers  24  which are arranged next to one another in the circumferential direction of the drying cylinder. Moreover, the threaded holes  30  for screwing in the fastening screws  28  are not provided here in the lateral sections  31  of the tubes  23 , but in the dividing wall  36  between the two chambers  24 . In this variant, therefore, only one row of screws  28  is provided in the longitudinal direction of the drying cylinder per tube  23 , in a deviation from the variants which have been described previously.  
         [0059]     A variant which coincides largely with the variant at D 5  is shown at D 6  in  FIG. 4 . The only difference is that the tubes  23  have a greater width here in the circumferential direction of the drying cylinder.  
         [0060]     In the variant of  FIG. 5 , there is likewise an inner cylinder shell  2  which serves as carrying tube. Profiles  37  of U-shaped cross section which extend in the longitudinal direction of the drying cylinder are welded onto this inner cylinder shell  2 . Here, the opening of the U-shape points toward the inner cylinder shell  2 , with the result that channels  38  for the heating fluid are formed between the U-profiles and the inner cylinder shell  2 .  
         [0061]     The U-profiles  37  are arranged on the inner cylinder shell  2  in a manner which is spaced apart from one another in the circumferential direction of the drying cylinder. Adjacent U-profiles  37  are connected to one another in each case via flat profiles  39  which are welded to the U-profiles  37  at the level of the base  40  of the latter. As a result, in each case further channels  42  for the heating fluid are formed between the limbs  41  of two adjacent U-profiles  37 , the flat profile  39  which is arranged there and the inner cylinder shell  2 . The bases  40  of the U-profiles  37  and the flat profiles  39  together form the outer cylinder shell  1  and are configured with a flush outer side  7 . The channels  38  and the channels  42  together form the hollow space  11  between the outer cylinder shell  1  and the inner cylinder shell  2 .  
         [0062]      FIG. 6  shows a drying cylinder, in which annular modules  43  are arranged behind one another in the longitudinal direction of the drying cylinder. Here, not only two but also more modules  43  can be arranged behind one another. The drying cylinder is closed at the end by covers  4  which in each case have an axle  5 ,  6 . The modules  43  are connected to one another and to the covers by welding.  
         [0063]     In  FIG. 7 , the cross section of the modules  43  of  FIG. 6  can be seen. These are in each case a solid ring or tube section  44 , in which channels  45  are made which extend in the longitudinal direction of the drying cylinder. Here, the channels are arranged just below the outer side  7  of the drying cylinder and serve for passing through the heating fluid. This ensures satisfactory thermal transfer onto the web of fibrous material.  
         [0064]     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  
       [0000]    
       
           1  Outer cylinder shell  
           2  Inner cylinder shell  
           3  Fastening screw  
           4  Cover  
           5  Operator-side axle  
           6  Drive-side axle  
           7  Outer side of  1   
           8  Circumferential face of  4   
           9  Inner side of  1   
           10  Outer side of  2   
           11  Hollow space  
           12  Radial channel  
           13  Radial channel  
           14  Axial channel  
           15  Connection end of  14   
           16  Axial channel  
           17  Connection end of  16   
           18  Tapered section of  1   
           19  Seat  
           20  Connecting element  
           21  Siphon  
           22  Module  
           23  Tube  
           24  Hollow space  
           25  Inner side of  26   
           26  Outer section of  23   
           27  Elevations  
           28  Screw  
           29  Hole  
           30  Threaded hole  
           31  Lateral section of  23   
           32  Shoulder  
           33  Projection  
           34  Projection  
           35  Recess  
           36  Dividing wall  
           37  U-profile  
           38  Channel  
           39  Flat profile  
           40  Base of  37   
           41  Limb of  37   
           42  Channel  
           43  Module ring  
           44  Tube  
           45  Channel  
          I Rotational axis  
          II Flow direction  
          d 1  Thickness of  1   
          d 2  Thickness of  2

Technology Classification (CPC): 3