CROSS REFERENCE TO RELATED APPLICATIONS
BACKGROUND OF THE INVENTION
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.
1. Field of the Invention
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.
2. Description of the Related Art
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.
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.
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.
- SUMMARY OF THE INVENTION
What is needed in the art is to increase the drying performance of a heatable cylinder and to simplify manufacture.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Moreover, it can be advantageous to turn the outer circumferential face. As a result, a smooth surface can be achieved.
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.
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.
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.
Suitable conventional drying processes are, in particular, cylinder drying, the boost dryer process, the Condebelt process, a yankee cylinder and a HiDryer.
BRIEF DESCRIPTION OF THE DRAWINGS
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.
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:
FIG. 1 shows a longitudinal section through a drying cylinder of a device according to the invention;
FIG. 2 shows a partial plan view of the end side of the drying cylinder of FIG. 1;
FIG. 3 shows a partial cross section through a drying cylinder of a device according to the invention;
FIG. 4 shows a variant of FIG. 3;
FIG. 5 shows a further variant of FIG. 3;
FIG. 6 shows a side view of a drying cylinder of a device according to the invention; and
FIG. 7 shows a cross section through the drying cylinder of FIG. 6.
- DETAILED DESCRIPTION OF THE INVENTION
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.
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.
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.
The outer cylinder shell 1 has a thickness d1 which is smaller than the thickness d2 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.
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.
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.
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.
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 d1 and an inner cylinder shell 2 of greater thickness d2 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.
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.
The outer cylinder shell 1 is supported on the inner cylinder shell 2 via the modules 22 themselves.
In the variant which is shown in FIG. 3 at D1, 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 D1, 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.
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.
The variant which is shown at D2 in FIG. 3 coincides largely with the variant of D1. 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.
In the variant of FIG. 3 which is shown at D3, a form-fitting connection is also provided between the adjacent tubes 23. Here, in a difference from the variant of D2, 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 D4 in FIG. 4 coincides practically completely with the variant at D3 in FIG. 3. The only difference is that the cross section of the projections at D4 is smaller than in the variant of D3 in FIG. 3, and correspondingly the cross section of the recesses 35 is also smaller.
At D5, FIG. 4 shows a variant which coincides completely with the variant at D4 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.
A variant which coincides largely with the variant at D5 is shown at D6 in FIG. 4. The only difference is that the tubes 23 have a greater width here in the circumferential direction of the drying cylinder.
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.
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.
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.
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.
- LIST OF DESIGNATIONS
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.
- 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
- d1 Thickness of 1
- d2 Thickness of 2