US20150152599A1

US20150152599A1 - Machine for producing a fibrous web, comprising an inclined wire former and a dewatering device

Info

Publication number: US20150152599A1
Application number: US14/615,490
Authority: US
Inventors: Klaus Afflerbach
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2012-08-06
Filing date: 2015-02-06
Publication date: 2015-06-04
Also published as: EP2880216A1; WO2014023728A1; EP2880216B1; CN104520504A

Abstract

The invention relates to a fibrous web formation device comprising an inclined wire former, an inclined wire headbox and a drainage device. The inclined wire headbox has at least one conveyor wire which transports the fibrous web in the direction of travel thereof and which has a portion that runs at an angle from the horizontal, in which portion the inclined wire headbox is arranged. The inclined wire headbox allows a fibrous suspension to be applied to the conveyor wire. In a drainage device that has a roll, a drainage wire lying against said roll, and a pressing wire pressing against said roll, the fibrous web being arranged between the drainage wire and the pressing wire in the region of the drainage device, drainage can be performed gently so that the fibrous web at least partially maintains voluminous structures.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of PCT application No. PCT/EP2013/066476, entitled “MACHINE FOR PRODUCING A FIBROUS WEB, COMPRISING AN INCLINED WIRE FORMER AND A DEWATERING DEVICE”, filed Aug. 6, 2013, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The current invention relates to a fibrous web forming device including an inclined wire former, an inclined wire headbox and a dewatering device. The invention moreover relates to a machine for the production of a fibrous web which includes a fibrous web forming device of this type, as well as utilization of a dewatering device of this type in a machine for the production of a fibrous web.
2. Description of the Related Art
With a fibrous web forming device which features an inclined wire former and an inclined wire headbox special fibrous web products, for example long-fiber papers, wet-laid nonwovens or filter media can be produced for a wide range of applications. An advantage of the inclined wire technology is the ability to form voluminous fibrous web products. Generally a fibrous suspension having a comparably low fiber content is applied by way of an inclined wire headbox onto a section of a transport belt which progresses at an angle relative to the horizontal. After the inclined wire headbox, viewed in direction of travel of the fibrous web, the web having been created from the fibrous suspension must now be successively dewatered. This is accomplished by dewatering elements, for example suction boxes, gravimetric strippers, suction rolls or similar devices. After reaching a predetermined dry content, final drying can be undertaken in conventional dryer sections or by means of TAD (Through-Air-Drying) drying. Press sections are generally seldom utilized in inclined wire products in order to maintain the voluminous structure of the inclined wire products as much as possible. However, when drying in conventional dryer sections sufficient drying of the fibrous web can only be achieved with great technological effort. As a result, production of the fibrous web becomes more expensive. This applies also to TAD drying since in that case drying is implemented by means of a high fluid mass stream which in turn results in an increase of production costs. Moreover, the desired composition of the fibrous web, in particular for specific applications cannot be achieved, or can be achieved only to a limited extend with either method.

SUMMARY OF THE INVENTION

The current invention provides an improved, or at least an alternative design for a fibrous web forming device for a machine for the production of a fibrous web with such a fibrous web forming device; and for utilization of such a dewatering device in a machine for the production of a fibrous web which is characterized by an efficient and cost effective drying or respectively dewatering and in particular by a possibility of an alternative composition of the fibrous web.
In one aspect of the invention it is therefore suggested to provide a fibrous web forming device with an inclined wire former, an inclined wire headbox and a dewatering device, wherein the inclined wire former includes at least one transport belt which transports the fibrous web in the direction of travel thereof and which has a section that progresses at an angle to the horizontal, or horizontally, in which the inclined wire headbox is arranged by way of which a fibrous suspension can be deposited onto the transport belt. The dewatering device includes a roll, a dewatering belt which fits closely against the roll, and a press belt pressing against the roll, whereby the fibrous web is arranged in the region of the dewatering device between the dewatering belt and the press belt. Inclined wire formers and inclined wire headboxes are also referred to as inclined belt formers or inclined belt head boxes and are therefore understood to be synonymous.
Advantageously at least one of the belts from the group of transport belt, dewatering belt and press belt is permeable, in particular for fluids such as gasses and/or liquids.
With a dewatering device of this type a gentle and efficient dewatering of the fibrous web can be implemented within the fibrous web forming device, so that a drying device following the fibrous web forming device can be dimensioned smaller. Overall, drying can thereby be more efficient and cheaper. Moreover, dewatering by maintaining at least partially the voluminous structure of the fibrous web is possible due to the gentle mechanical pressure being applied by the press belt. Thus it is possible to achieve an efficient and cost effective production of the fibrous web while maintaining a voluminous structure.
The dewatering effect of the dewatering device is based on the gentle pressing of the fibrous web between the press belt and the dewatering belt, due to which the fibrous web fluid migrates at least partially into the dewatering belt, thereby amongst other factors causing dewatering of the fibrous web.
An inclined wire headbox is understood to be a headbox which deposits a fibrous suspension on the section of the transport belt progressing at an angle to the horizontal, or the horizontally progressing section of the transport belt which transports the fibrous web in the direction of travel. In contrast to headboxes which spray a fibrous suspension stream under increased pressure from one nozzle, for example onto a Fourdrinier wire or spray into an opening between two wires, the fibrous suspension emerging from the inclined wire headbox is generally fixed by lateral limitations above the transport belt and carried by same at least partially, in direction of travel. It is hereby not absolutely necessary that the partial section is arranged ascending at an angle. The partial section may also be arranged horizontally or even descending at an angle. To assess whether an inclined wire headbox or inclined wire former exists in the broadest sense, the design of the headbox is mainly considered. In a narrower sense the partial section in which the inclined wire headbox is in addition arranged at an angle to the horizontal. The inclined wire headbox can be a 1-, 2-, 3-, 4-, 5- or 6-layer design. In the case of a multi-layer design at least two layers of different fibrous suspension are placed on top of one another on the transport belt. On the partial section of the transport belt progressing at an angle to the horizontal, or horizontally one or several dewatering elements such as suction boxes or gravimetric dewatering elements with which the fibrous suspension can be dewatered to produce the fibrous web can be arranged opposite the inclined wire headbox. The transition from fibrous suspension to fibrous web can thereby be arranged seamlessly. The fibrous web is normally formed when the individual fibers of the fibrous web material are immobilized due to dewatering. This means that the dry content of the fibrous web at the immobilization point is in a range greater than 3% (corresponds to 30 g/l), in particular greater than 4% (corresponds to 40 g/l).
The entire height of the layers of fibrous suspension deposited by the inclined wire headbox onto the transport belt is very high in the case of the inclined wire formers and amounts to more than 50 mm, in particular more than 100 mm, and in actual cases even more than 300 mm. In multi-layer operation the layer heights of the individual layers are accordingly smaller.
The fibrous suspension leaving the inclined wire headbox has a very low solids concentration in order to disperse and form the fiber material uniformly. At the beginning of the transport belt which represents the forming wire the solids concentration is less than 5 g/l, preferably less than 2 g/l and in some cases even less than 0.8 g/l. The lowest value can be around 0.1 g/l. These low solids concentrations result in the aforementioned high layer heights. The advantage is homogeneous dispersing of the solids and gentle, slow dewatering which is supported by the inclined progression of the inclined wire former. This results in a voluminous fibrous web at the end of the immobilization point.
An inclined wire former has a transport belt by way of which the fibrous web can be transported in direction of travel. At least one section which progresses at an angle from the horizontal, or horizontally and in which also the inclined wire headbox is arranged and which places the fibrous suspension onto the transport belt is provided. It is hereby not absolutely necessary that the partial section is arranged ascending at an angle. The partial section may also be arranged horizontally or even descending inclined. Additional dewatering elements, for example suction boxes, gravimetric strippers, suction rolls or similar devices can be arranged between the inclined wire headbox and the dewatering device. Pre-dewatering of the fibrous web may be performed by way of these dewatering elements, so that the drainage efficiency of the dewatering device may be optimized.
Belts are understood to be wires, woven fabrics, knitted fabrics, meshed fabrics, felts, nonwovens, and similar fabrics, possibly continuous or in the form of a loop which are guided over guide rollers and/or are driven by at least one guide roller. In the broadest sense the term “belt” also encompasses a flexible roll cover.
The fibrous suspension includes at least one predominantly water suspending fiber material. If necessary, fillers or additives as well as auxiliary materials can also be added to the fibrous suspension. Any type of fiber consisting of various materials and in a desired combination can be used as fiber material. It is therefore conceivable to use synthetic fibers, aramid fibers, glass fibers, carbon fibers, pulp fibers from wood, cotton and other plant matter, wool and other animal fibers, metal fibers or the like. Normally, long fibers are preferably used in the inclined wire technology. It is however also conceivable that a long fiber/short fiber mixture of a differing proportional combination is used. When using at least some pulp fibers or other natural fibers their length is greater than 2 mm, in particular longer than 3 mm or even advantageously greater than 4 mm. When using at least some of the above mentioned synthetic fibers their length is greater than 4 mm, in particular greater than 5 mm.
In one practical case two-ply fibrous webs having a basis weight in the range of 15 g/m2 to 250 g/²are produced. The bottom layer hereby includes between 50% and 85%, in particular 70% to 80% pulp fibers. In contrast, the top layer includes 15% to 35%, in particular 22% to 28% synthetic fibers, for example polypropylene fibers. The arrangement is hereby selected so that the bottom layer comes into direct contact with the transport belt. Dewatering of the top layer occurs to at least the immobilization point through the bottom layer. In the dewatering device the top layer comes into direct contact with the dewatering belt. There, further dewatering of the bottom layer occurs at least partially through the top layer.
Direction of travel of the fibrous web in the fibrous web forming device or respectively in the machine for the production of a fibrous web is understood to be the direction and orientation in which the fibrous web is transported through the fibrous web forming device or respectively the machine. The direction of travel is possibly determined tangentially. In contrast hereto, the machine direction is understood to be the production direction, in other words the direction between beginning and end of the fibrous web forming.
The transport belt can moreover be arranged in the region of the dewatering device between the dewatering belt and the press belt.
With this type of arrangement of the transport belt the fibrous web previously placed on the transport belt can advantageously remain on the transport belt during its travel through the dewatering device, so that lower constructive expenditure is necessary in the region of the fibrous web forming device.
The dewatering device can moreover include a blower hood surrounding the roll partially in circumferential direction for the supply with a liquid of at least one blow zone of the roll surrounded by the blower hood. The blower hood can be designated to the roll in circumferential direction on a circumferential length—in other words circular arc length of the imagined sector—of 1 m to 3 m, preferably 1.3 m to 2 m. The appropriate circle sector angle of the blower hood is between 50° and 270°, in particular between 80° and 200° and for example between 90° and 120°. The blow zone can be consistent with the circumferential length of the blower hood. It is however also conceivable that the blow zone covers only a partial section of the circumferential length designated to the blower hood. This partial section can be between 50% and 100% of the circumferential length allocated to the blower hood. The diameter of the roll is greater than 1 m. It is preferably in the range between 1.2 and 5 m, in particular between 1.5 m and 2.5 m.
The blow zone may be formed by an impinging flow device, and the blower may be supplied with a pressurized fluid.
The fibrous web which is arranged between the blower hood and the roll can be advantageously dewatered on the one hand by way of fluid flow drying and on the other hand by displacing the fibrous web liquids into the dewatering belt by way of the fluid flow. The dewatering efficiency can hereby be enhanced and supported by the press belt. Air, heated air, in particular overheated steam or such can be used as fluid.
The dewatering device may include an additional press device which would be arranged in direction of travel after the roll.
Additional dewatering of the fibrous web can be implemented advantageously by this additional press device which may include two press rolls between which the transport belt, the dewatering belt as well as the fibrous web which is arranged between them are guided. The additional press device supports the partial transition of the remaining fibrous web fluid into the dewatering belt.
The dewatering device can moreover be located in direction of travel after the inclined wire headbox, whereby at least one dewatering element is arranged between the inclined wire headbox and the dewatering device.
Such positioning of at least one additional dewatering element aids to advantageously optimize the dewatering efficiency of the fibrous web forming device. The fibrous web can furthermore be brought to a predefined dry content by way of such an additional dewatering element, before it enters into the dewatering device.
The dewatering device can moreover be positioned in direction of travel following a turn roller in such a way that at least one dewatering element is arranged between the turn roller and the dewatering device. The turn roller hereby limits the partial section progressing at an angle to the horizontal, or horizontally in direction of travel; and in direction of travel after the turn roller the fibrous web can be arranged such that the direction of travel and the gravitational direction form a pointed angle α.
Preferably by way of such positioning of an additional, preferably suction equipped dewatering element, the fibrous web can be further dewatered, and a predetermined dry content of the fibrous web prior to entering the dewatering device, of for example greater than 14%, in particular greater than 15% can be reached. Furthermore, if the direction of travel occurs under a pointed angle relative to the gravitational direction, a dewatering element arranged after the turn roller when viewed in direction of travel can advantageously prevent detachment of the fibrous web from the transport belt. In other words, it can be prevented that the fibrous web falls off the transport belt when the fibrous web is carried upside-down on the transport belt.
Moreover, the dewatering device can be positioned in machine direction, preferably in direction of travel directly before the transfer position of the fibrous web to a drying device which is positioned after the fibrous web forming device, viewed in direction of travel.
With such positioning of the dewatering device directly before the transfer position to the drying device the desired and required dry content of the fibrous web can be adjusted advantageously for the drying device by way of the dewatering device.
The dewatering device can further also be positioned so that the turn roller is the roller of the dewatering device.
Such a high dry content can thereby be achieved advantageously so that detachment of the fibrous web in direction of travel after the turn roller can be avoided in those regions of the fibrous web forming device where the fibrous web is no longer supported on the transport belt, but is arranged upside-down on the transport belt.
The dewatering device can furthermore be positioned such that the fibrous web is supported on the dewatering belt and the transport belt is supported on the press belt.
Through such favorable positioning of the fibrous web between the transport belt and the dewatering belt an especially fast and sufficient transition of the fibrous web fluid into the dewatering belt is achieved when the press belt presses the sandwich consisting of transport belt, fibrous web and dewatering belt against the roll. Dewatering of the fibrous web can be achieved especially effectively with this arrangement. Moreover, a possible structuring of the transport belt can further act upon the fibrous web.
For structuring and/or to avoid pressing of partial regions (protected regions) the transport belt can furthermore have a structured surface which is oriented toward the fibrous web.
With such a structured surface which has cavities or respectively protected regions and elevations or respectively press regions, a required composition or respectively a profiling and structuring of the fibrous web can be achieved which advantageously includes protected regions with increased accumulation of fibrous web material and a voluminous structure, as well as press regions having a pressed structure and increased structural strength. The completed fibrous web can hereby exhibit increased air permeability and at the same time a greater cleaning efficiency in the protected regions, due to the accumulated fibrous web material. This fibrous web structure is required in particular on filter media in order to increase filter efficiency. This represents a clear improvement when compared with TAD drying which is currently used among other systems in the inclined wire technology. Due to the specific method of TAD drying, thinning of the fibrous web material caused by a stretching effect can occur in the protected regions or respectively cavities. Therefore, fibrous webs produced with TAD drying may exhibit voluminous regions having a low fiber material content, so that fibrous webs thus produced are less suited for filter media.
The cavities or protected regions of the surface of the structured transport belt have a depth greater than 0.5 mm, preferably greater than 0.7 mm, in particular greater than 1 mm.
Furthermore, the transport belt can have a structured surface with a press region of <40% relative to 100% of an imaginary planar reference surface, arranged vis-à-vis the structured surface. It is also conceivable that the structured surface has a press region of 10-30%, possibly of 10-25%, in particular 15-25% and for example 15-20%.
A desired structural strength of the fibrous web can be achieved advantageously through such a dimensioned press section, so that the voluminous protected regions are protected and fixed by the surrounding press regions. Desired tear strength can also be achieved thereby, in particular relative to the application of pressure.
The transport belt can furthermore have a structured surface with a protected region of >60% relative to 100% of an imaginary planar surface, arranged vis-à-vis the structured surface. It is also conceivable that the structured surface has a protected region of 70-90%, possibly 75-90%, in particular 75-85% and in particular 80-85%.
Furthermore, a high voluminous part which offers high air permeability combined with excellent absorption capability can be achieved with such a generously dimensioned protected region, preferably in concert with the great depth of the protected regions.
The transport belt can furthermore have a partial section progressing at an angle to the horizontal in such a way that the section progresses at a pointed angle of essentially greater than 0° to 45° relative to the horizontal. Here, a pointed angle of 5° to 45° is also advantageous, in particular one of 10-40°, possibly 10-30°, 15-25° and for example 20+/−3° is conceivable.
By way of such a section progressing at an angle, the fibrous suspension can be placed on the transport belt optimally, especially with regard to a multi-layer headbox, so that the individual layers of the fibrous suspension only intermingle negligibly, thus making a multi-layer structure of fibrous web possible.
The roll of the dewatering device can moreover be in the embodiment of a suction roll.
By designing the roll as a suction roll the fibrous web fluid can be transferred advantageously at least partially into the dewatering belt through suction by way of the suction roll, in addition to pressing with the press belt and possibly blowing with the blower hood. This serves to further increase the dewatering efficiency of the dewatering device. If necessary, fibrous web fluid can also be suction removed from the dewatering belt, at least partially.
The fluid from the blower hood flows preferably in the following sequence first through the press belt, through the transport belt, through the fibrous web and through the dewatering belt into the suction roll which is equipped with a suction zone.
The roll can furthermore be designed as a suction roll having a suction zone extending partially in circumferential direction, whereby a suction zone angle determined in the direction of roll circumference has a value of 50° to 270°, in particular between 80° and 200° and for example between 90° and 120°. The blower zone angle can hereby also have a value of 50° to 270°, possibly 80° to 200°, in particular of 90° to 120°.
The suction zone angle is preferably greater than the blower zone angle.
In a practical case the suction zone angle is greater than the corresponding circle segment angle of the blower hood which surrounds the roll partially.
It is furthermore advantageous if the suction length of the suction zone extending in circumferential direction of the roll is greater than 300 mm, preferably greater than 800 mm. The suction length is preferably in the range of between 300 mm and 2500 mm. With a roll diameter of 1.4 m the suction length is for example 1300 mm.
By designing the suction roll as a suction zone roll the dewatering device can be dimensioned smaller in regard to the vacuum that is to be produced; moreover the thereby reducible vacuum can be purposefully applied in the suction zone.
The dewatering belt can furthermore be in the embodiment of felt.
When designed as felt, the high and proficient absorption capacity of fibrous web fluid from the fibrous web is advantageous. The felt can moreover be compressed, at least partially by the press belt, so that with diminishing pressure due to the relaxation of the felt additional fibrous web fluid can transition from the fibrous web into the felt.
Due to wrapping around the roll, the dewatering belt can furthermore have a defined dewatering zone having a dewatering zone angle of 10° to 270° which is determined in the direction of the roll circumference. The dewatering zone angle can also have a value of between 50° to 270°, in particular between 80° and 200° and for example between 90° and 120°.
The dewatering zone angle is preferably greater than the circle sector angle of the blower hood which surrounds the roll partially.
The suction zone angle is preferably greater than the dewatering zone angle.
The dewatering section can advantageously be dimensioned sufficiently large due to such a dewatering zone angle. The vacuum that is to be applied by the roll in the embodiment of a suction roll can for example be reduced, or the diameter of the roll can be reduced.
Moreover, the press belt can have a belt tension of 10-80 kN/m. The belt tension can also be 15-65 kN/m, if required 20-60 kN/m, in particular 20-55 kN/m and for example 30-50 kN/m.
Such a belt tension advantageously aids in achieving the desired gentle mechanical pressing of the fibrous web, thus providing at least partially the voluminous structure.
The press belt can furthermore have a calculated contact pressure onto the roll of greater than 20 kPa, in other words a contact pressure which is calculated from the tension of the press belt and the diameter of the roll. It is hereby conceivable that the contact pressure is greater than 35 kPa, if required greater than 45 kPa, in particular greater than 60 kPa and if required greater than 80 kPa
Due to the configuration of the arrangement of the dewatering device and the structure of the transport belt, the press pressure onto the fibrous web in the area of the protected regions is considerably lower, and in the area of the press regions surrounding the protected regions considerably higher than the stated calculated contact pressures.
Based on such contact pressure the voluminous structure of the fibrous web can advantageously be maintained, at least partially also during dewatering by means of the dewatering device.
Furthermore, the press belt can have an open surface of at least 25% relative to 100% of an imaginary planar reference surface, arranged vis-à-vis the press belt. The open surface can hereby also be at least 50%, if required at least 70%, in particular at least 75% and for example at least 80%.
Because of such a large open surface, in particular when using a blower hood, the fluid applied by the blower hood can act advantageously upon the fibrous web or respectively the transport belt, so that the fibrous web fluid strengthened by the blower effect transitions into the dewatering belt or is carried along at least partially by the fluid stream.
Furthermore, the press belt can have a pressing surface of at least 10% relative to 100% of an imaginary planar reference surface, arranged vis-à-vis the press belt. It is hereby also feasible that the pressing surface is at least 50%, if required at least 30%, in particular at least 25% and for example at least 20%.
Based on such a dimensioned pressing surface, sufficient and uniform transfer of the contact pressure generated by the press belt, onto for example the transport belt can advantageously be achieved, so that uniform compression of the fibrous web becomes possible.
Due to wrapping around the roll, the press belt can furthermore have a defined press zone having a press zone angle of 10° to 270° which is determined in the direction of the roll circumference. The press zone angle can also have a value of between 50° to 270°, in particular between 80° and 200° and for example between 90° and 120°.
The press zone angle is preferably smaller than the dewatering zone angle.
Due to such a press zone angle the contact pressure with which the press belt presses against the roll can also be achieved advantageously though a lower belt tension.
If an angle is thereby determined in the direction of roll circumference, then the angle is determined from the beginning of the respective zone to the end of the respective zone in circumferential direction of the roll. In the case of the suction zone the beginning and the end of the suction zone are determined by the occurring vacuum. In the case of the blower the beginning and the end of the blower zone are predetermined for example by the blower hood. In the case of belts the beginning and the end of the respective zones are determined by direct and indirect contact of the belt on the roll. The respective zones can be congruent or can deviate from each other in their position by a maximum of 10% of the respective angle and/or their progression.
The press belt may moreover also be in the embodiment of a cover of a shoe press.
By way of the design in the form of a shoe press a comparatively simple press arrangement in the dewatering device can advantageously ensure the necessary and possibly controllable contact pressure.
A machine for the production of a fibrous web having a fibrous web forming device as described above is described in an additional aspect of the invention, wherein the machine includes at least one dryer device located downstream from the fibrous web forming device, viewed in direction of travel.
Final drying of the fibrous web can be accomplished advantageously by way of a dryer device located downstream from the fibrous web forming device, viewed in direction of travel, so that after the dryer device the fibrous web can be transported and further processed without significant impairment.
The machine can further include a press roll allocated to the fibrous web forming device, with which the fibrous web is transferred at a transfer point into the dryer device, whereby the press roll which is preferably designed as a suction pressure roll or as a roll having a closed surface makes contact with a line force of 60 to 120 kN/m, in particular with 70 to 90 kN/m.
With contact pressure of this type disadvantageous influence of the voluminous components of the fibrous web can be largely avoided and the fibrous web can be transferred securely into the dryer device by way of the contact pressure.
The machine can further include a Yankee-cylinder allocated to the dryer device, whereby a blower hood can be provided which partially surrounds the Yankee-cylinder in circumferential direction.
By using a Yankee-cylinder, gentle drying which maintains the voluminous structures of the fibrous web can be advantageously implemented, whereby drying can be enhanced by way of a blower hood.
A Yankee cylinder is a dryer cylinder having a minimum diameter of 3 m. The minimum diameter may also be 3.6 m and for example at least 4.5 m.
The machine may furthermore include a TAD system.
The fibrous web can moreover be advantageously dewatered or respectively dried in an additional drying process by way of a TAD system.
The machine may furthermore include a dryer cylinder arrangement assigned to the dryer device, including at last one dryer cylinder.
By way of such alternative drying, drying of the fibrous web by way of a conventional dryer cylinder arrangement can also be arranged advantageously.
The machine may further include a pick-up roll allocated to the dryer device, which may be in the embodiment of a suction roll and with which the fibrous web is taken at the transfer point into the dryer device.
A secure transfer of the fibrous web from the fibrous web forming device into the dryer device can be implemented advantageously with such a suction roll or respectively pick-up roll.
A further aspect of the invention utilizes a dewatering device, as described above in a machine for the production of a fibrous web, including at least one inclined wire former, whereby the dry content of the fibrous web is increased by the dewatering device to a value of 14-60%. It is hereby also conceivable that the dry content is increased to 25-55%, if required to 30-50%, in particular to 30-45% and for example to 35-35%.
By way of such a dewatering device the fibrous web can be advantageously brought to a dry content within the fibrous web forming device which makes sufficient and required drying within the dryer device possible, so that the fibrous web can be further processed following the dryer device.

BRIEF DESCRIPTION OF THE DRAWINGS

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 an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is one possible design of a fibrous web forming device or respectively a machine for the production of a fibrous web,

FIG. 2 one preferred arrangement of press belt, fibrous web, transport belt and dewatering belt, as well as a roll of a dewatering device,

FIG. 3 structuring of the fibrous web in the dewatering device.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention and such exemplification is not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

Forming device 100 for a fibrous web as shown in FIG. 1 illustrates an inclined wire headbox 110 and an inclined wire former 120. In addition, a dewatering device 130 is provided, by way of which at least partial dewatering of a fibrous web 140 deposited by inclined wire headbox 110 can be implemented in fibrous web forming device 100.
Inclined wire former 120 includes a transport belt 150 which is guided over a plurality of guide rollers 160, 160′. Transport belt 150 further includes a section 170 progressing at an angle to the horizontal, in which inclined wire headbox (110) is located. Section 170 located or respectively progressing at an angle to the horizontal 172 is understood to be the section of transport belt 150 which is arranged at an angle β relative to horizontal 172, so that it inclines in direction of travel 180 of fibrous web 140. One design form is also conceivable whereby section 170 progresses horizontally.
At least one dewatering element 190 can be arranged on transport belt 150 vis-à-vis inclined wire headbox 110. The fibrous suspension emerging from inclined wire headbox 110 is thereby dewatered by such a dewatering element 190, thus promoting the formation of fibrous web 140 from the fibrous suspension.
Section 170 is limited in direction of travel 180 by a turn roller 200. After this turn roller 200, transport belt 150 can be arranged so that the direction of travel forms a pointed angle α together with gravitational direction 202. In other words, in the previously described region fibrous web 140 hangs upside-down on transport belt 150 and is no longer supported or carried by same. Consequently, detachment of fibrous web 140 from transport belt 150 can occur in this region.
In order to let dewatering of fibrous web 140 proceed further, at least one dewatering element 210 can be arranged in the previously described region. It is however conceivable that additional dewatering elements 210, 210″ are arranged between turn roller 200 and dewatering device 130. These can again serve to dewater fibrous web 140 and at the same time serve to prevent detachment of fibrous web 140 from transport belt 150.
Dewatering device 130 comprises a roll 220, a dewatering belt 230 and a press belt 240. Transport belt 150 is arranged in the region of dewatering device 130 between press belt 240 and dewatering belt 230. The sandwich consisting of transport belt 150, fibrous web 140 and dewatering belt 230 is thereby pressed by press belt 240 against roll 220. In a preferred design form, fibrous web 140 is arranged between the transport belt and dewatering belt 230. Gentle dewatering by way of dewatering belt 230 can be accomplished by such a press belt 240, whereby the compression pressure generated by press belt 240 is calculated so that the fibrous web can be dewatered while maintaining at least somewhat of a voluminous structure. Roll 220 can furthermore be designed as a suction roll which can also comprise a suction zone 250. Hereby it may be advantageous if a suction zone angle 260 is approximately consistent with a dewatering zone angle and a press zone angle 280. According to FIG. 1, suction zone angle 260 is consistent with dewatering zone angle 270 and press zone angle 280.
Furthermore a blower hood 290 may be provided with which a blower zone 300 of roll 220 can be supplied with a fluid, for example air, steam, overheated steam or similar media. A blower zone angle 310 which is determined in direction of roll circumference can thereby be approximately consistent with the other angles 270, 280, 260. According to FIG. 1, blower zone angle 310 is approximately the same size as the aforementioned angles 260, 270, 280.
Dewatering belt 230 can be carried continuously over several guide rollers 320. Inside a travel loop provided by dewatering belt 230, one dewatering element 340 or a plurality of dewatering elements 340, 340′ can be arranged so that fibrous web fluid extracted from fibrous web 140 can be extracted from the system of dewatering belt 230. Dewatering belt 230 may hereby be for example in the embodiment of a felt.
Downstream from dewatering device 130 viewed in direction of travel 180, a press device 350 including two press rolls 360, 360′ can be arranged. Transport belt 150 and dewatering belt 230 can hereby be routed through this press device 350. Fibrous web 140 can again be arranged between dewatering belt 230 and transport belt 150. Additional dewatering of fibrous web 140 is possible by way of press device 350. A transition of fibrous web fluid into dewatering belt 230 can be promoted by way of contact pressure generated by press device 350.
A drying device 370 can be arranged after the fibrous web forming device, viewed in direction of travel. Drying device 370 may for example include a Yankee cylinder 380. This Yankee cylinder 380 can be surrounded at least partially by a blower hood which is not shown in FIG. 1 and with which drying of fibrous web 140 can be additionally forced. Fibrous web 140 can be transferred at a transfer point 390 for example by way of a press roll 400 from transport belt 150 into drying device 370.
FIG. 2 shows the arrangement of roll 220 relative to transport belt 150, dewatering belt 230, press belt 240 and fibrous web 140. Transport belt 150 is hereby structured so that it features several protected regions 410 and several press regions 420. Fibrous web 140 remains largely non-compacted, so that voluminous structures can form in protected regions 410, whereas fibrous web 140 is pressed in press regions 420, so that the press regions contribute substantially to the structural stability of fibrous web 140. Normally there is increased air permeability in protected regions 410, whereas press regions 420 have low air permeability. In addition there is also more effective filtration of air penetration. In one design variation, dewatering belt 230 fits closely against roll 220. Fibrous web 140 is arranged between dewatering belt 230 and transport belt 150 and the sandwich consisting of transport belt 150, fibrous web 140 and dewatering belt 230 is pressed by press belt 240 against roll 220.
As shown in FIG. 3—as with the previously described arrangement of press belt 240, transport belt 150, fibrous web 140, dewatering belt 230 and roll 220—the production of a textured fibrous web 140 with protected regions 410 and press regions 420 is possible with a structured transport belt 150. The fibrous web material can hereby accumulate increasingly in protected regions 410, in particular during application of the fibrous suspension by way of the inclined wire headbox; the material being largely protected against compression by way of press belt 240, as well as possibly by way of press roll 400 while maintaining at least partially the voluminous structure. Since fibrous web 140 is applied directly onto transport belt 150 by inclined wire headbox 110, resulting in the protected regions filling increasingly with the fibrous web material, no pulling apart of fibrous web 140 occurs in protected regions 410, as can occur for example with the TAD process. In the TAD process the fibrous web is transferred from a largely planar transport belt onto a structured belt during TAD drying. Because of this transfer of the substantially planar fibrous web onto a structured belt, pulling apart of the fibrous web occurs mainly in the cavities of the structured belt, so that a voluminous structure can indeed be maintained in the cavities. However the fibrous web material is diluted since now a larger surface has to be covered with the planar fibrous web. In contrast, the inventive method exhibits an accumulation of the fibrous web material, especially in the protected regions, so that utilization of thus produced fibrous webs 140 is advantageous for example as filter media.
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.

Claims

What is claimed is:

1. A fibrous web forming device for forming a fibrous web, comprising:

an inclined wire headbox;

an inclined wire former including at least one transport belt which transports the fibrous web in a direction of travel thereof and which has a section that progresses at an angle to a horizontal in which the inclined wire headbox is arranged and a fibrous suspension can be applied onto the at least one transport belt; and

a dewatering device including a roll, a dewatering belt which fits closely against the roll, and a press belt, wherein the fibrous web is arranged in a region of the dewatering device between the dewatering belt and the press belt.

2. The fibrous web forming device according to claim 1, wherein the transport belt is arranged in the region of the dewatering device between the dewatering belt and the press belt.

3. The fibrous web forming device according to claim 1, wherein the dewatering device includes at least one of the following characteristics:

a blower hood surrounding the roll partially in circumferential direction for a supply of a liquid of at least one blow zone of the roll surrounded by a blower hood, wherein a blow zone angle which is determined in a circumferential direction of the roll has a value of between 10° to 270°; and

an additional press device arranged in a direction of travel after the roll.

4. The fibrous web forming device according to claim 1, wherein the dewatering device includes at least one of the following characteristics:

the dewatering device is positioned in the direction of travel after the inclined wire headbox; wherein the at least one dewatering element is arranged between the inclined wire headbox and the dewatering device;

the dewatering device is positioned in the direction of travel after a turn roller which limits a partial section progressing at an angle to the horizontal in the direction of travel, wherein the fibrous web is arranged in the direction of travel after the turn roller such that the direction of travel and a gravitational direction form a pointed angle (α), wherein between the turn roller and the dewatering device at least one dewatering element can be arranged;

the dewatering device is positioned in the direction of travel immediately before a transfer point of the fibrous web into a drying device which is positioned after the fibrous web forming device, viewed in the direction of travel;

the dewatering device is positioned so that the turn roller is the roll of the dewatering device; and

the dewatering device is positioned so that the fibrous web fits closely against the dewatering belt and the transport belt fits closely against the press belt.

5. The fibrous web forming device according to claim 1, wherein the transport belt includes at least one of the following characteristics:

a structured surface which is oriented toward the fibrous web;

a structured surface having a protected region of greater than between 60% to 100% of an imaginary planar surface, arranged vis-à-vis a planar reference surface;

a structured surface having a press region of between less than 40% to 100% of the imaginary planar reference surface, arranged vis-à-vis the structured surface;

a partial section progressing at an angle relative to horizontal in such a way that a partial section progresses at a pointed angle (β) of greater than between 0° to 45° relative to the horizontal.

6. The fibrous web forming device according to claim 1, wherein the roll is designed as a suction roll having a suction zone extending partially in a circumferential direction, wherein a suction zone angle determined in the circumferential direction has a value of between 10° to 270°.

7. The fibrous web forming device according to claim 1, wherein the dewatering belt includes at least one of the following characteristics:

designed as a felt; and

a dewatering zone which is defined by wrapping around the roll, having a dewatering zone angle of between 10° to 270° which is determined in a circumferential direction of the roll.

8. The fibrous web forming device according to claim 1, wherein the press belt includes at least one of the following characteristics:

a belt tension of between 10 to 80 kN/m;

a contact pressure onto the roll of greater than 20 kPa;

an open surface of between at least 25% to 100% of an imaginary planar reference surface, arranged vis-à-vis the press belt;

a pressing surface of between at least 10% to 100% of an imaginary planar reference surface, arranged vis-à-vis the press belt;

a press zone which is defined by wrapping around the roll, having a press zone angle of between 10° to 270° which is determined in a circumferential direction of the roll; and

designed as a cover of a shoe press.

9. The fibrous web forming device according to claim 1, wherein the dry content of the fibrous web is increased by the dewatering device to a value of between 14 to 60%.

10. The fibrous web forming device according to claim 1, further including at least one of:

a dryer device arranged downstream from the fibrous web forming device, viewed in the direction of travel, a press roll allocated to the fibrous web forming device, with which the fibrous web is transferred at a transfer point to the dryer device, wherein a press roll makes contact with a line force of between 60 to 120 kN/m, a Yankee-cylinder allocated to the dryer device, and a blower hood which partially surrounds the Yankee-cylinder in a circumferential direction of the Yankee cylinder;

a TAD system;

a dryer cylinder arrangement assigned to the dryer device, including at last one dryer cylinder; and

a pick-up roll allocated to dryer device, including a suction roll and with which the fibrous web is taken at a transfer point into the dryer device.