US20030066618A1

US20030066618A1 - Machine for the production of a fiber web

Info

Publication number: US20030066618A1
Application number: US10/262,694
Authority: US
Inventors: Joachim Henssler; Alfred Bubik; Karl Mueller; Mathias Schwaner
Original assignee: Voith Paper Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2001-10-04
Filing date: 2002-10-02
Publication date: 2003-04-10
Also published as: DE10148921A1; EP1300509A1

Abstract

The current invention relates to a machine for the production of a fiber web, specifically a paper or cardboard web, from at least one fiber stock suspension comprising at least one porous belt, specifically a wire belt, a felt belt, or similar belt, running continuously in the direction of web travel. Further including at least one suction box, including a closed box that can be connected to a vacuum source. On its upper surface that is in contact with the belt, a multitude of cover strips are mounted at certain distances from each other and vertical to the direction of travel L of the belt, forming suction slots. At least one suction box cover strip at which a pressure differential exists due to various prevailing ambient pressures, and has a width making contact with the wire, viewed vertically to the direction of travel of the belt, and having a value factor a* of the average width of the cover strips that are contacting the wire, whereby the value factor takes on a numerical value in the range of 0.05 to 0.95, preferably of 0.1 to 0.9 and whereby the average wire-contacting width of the cover strips is in the range of 10 mm to 30 mm.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The current invention relates to a machine for the production of a fiber web, specifically a paper or cardboard web, from at least one fiber stock suspension.

2. Description of the Related Art

Equipment of this type, including belt and suction box is already known from the prior German art documentation by the applicant, DE 196 46 792 A1 (PB 10395 DE). Suction boxes of this type are utilized in the wet section that generally also includes the wire section and the press section of paper or cardboard machinery, in order to improve dewatering of the fiber web. Such suction boxes normally extend across the entire machine width and are supplied with vacuum. The wire belt or felt belt on which the fiber web is supported runs over cover strips that extent vertically to the direction of web travel. Suction slots are formed between the individual cover strips through which a vacuum that is applied to the suction box acts upon the fiber web.

The dry content of a fiber web in the wet section following the dewatering process, is strongly prejudiced by the remoistening effect of the belts, particularly the wire belts, supporting the fiber web. This is especially true when separating the fiber web from the supporting belt. One reason for this is the water is not removed effectively from the belt mesh (“belt dewatering”) due to air velocity being too slow above the suction box. The velocity with which the air flows vertical to the belt surface through a belt depends on the applied vacuum (pressure differential, currently to 0.068 Mpa max.) and on the web characteristics (basis weight, raw material, freeness value, dry content, etc.) and cannot, as a rule, be further increased. The velocity with which the air flows through a belt at the belt surface plane, again, depends on the applied pressure and the panel width of the suction box covers. The panel width of the suction box covers of flat suction boxes, wet suction boxes and other suction boxes is currently larger than or equal to 10 mm. These dimensions make it increasingly difficult to suck the air in the belt surface plane through the belt mesh.

What is needed in the art is a machine for the production of a fiber web with improved belt dewatering, and remoistening of the fiber web through the supporting belts is further reduced, preferably completely eliminated. Consequently, the dry content of the fiber web resulting from this is also clearly increased.

SUMMARY OF THE INVENTION

The present invention provides at least one suction box cover strip at which a pressure differential exists, due to various prevailing ambient pressures, with a width making contact with the wire viewed vertically to the direction of wire travel, and having a value factor a* of the average width of the cover strips contacting the wire, whereby the valve factor takes on a numerical value in the range of 0.05 to 0.95, preferably of 0.1 to 0.9 and whereby the average wire-contacting width of the cover strips is in the range of 10 mm to 30 mm.

The invention comprises, in one form thereof, at least one porous belt, specifically a wire belt or similar belt, running continuously in the direction of web travel. It further includes at least one suction box having a closed box that can be connected to a vacuum source. On its upper surface that is in contact with the belt, a multitude of cover strips are mounted at certain distances from each other, and vertical to the direction of travel of the belt, forming suction slots.

An advantage of the present invention is positively increased air velocity in the belt surface plane above the cover strip based on a reduction of the contact area that is relevant for the throttle effect.

Another advantage of the present invention is increased air velocity in the belt surface plane causing removal of the water from the belt mesh (“belt dewatering”), thereby further reducing the remoistening of the fiber web and clearly increasing the dry content of the fiber web.

Yet another advantage of the present invention is generally, the desired effect increases with decreasing contact area, whereby a venturi-effect can be created with a suitable design.

A further advantage is, the cover strip according to the present invention can be utilized as any desired strip in the suction box.

Since it is advantageous to drain off the belt mesh at the end of a suction box, the current invention suggests that the suction box cover strip, viewed vertical to the direction of belt travel, with that type of outer contour facing the belt, be the last cover strip on the suction box. However, the first cover strip on the suction box may also be provided with such a contour.

Because repeated increases in the air velocity in the belt surface plane provide a positive effect upon the removal of water from the belt mesh and therefore a further reduction in remoistening of the fiber web and a clear increase of the dry content in the fiber web, it is hereby suggested that the majority of the suction box cover strips have contours of preferably identical form, facing the belt.

Naturally, all of the cover strips may have such a wire-contacting width, whereby under those circumstances the reference length has to be changed accordingly. This also applies to a two-strip suction tube, whose cover strips on the inlet and outlet side can be configured accordingly.

The outer contour of the cover strip has, in accordance with an embodiment of the present invention, preferably a stable curved, arched, parabolic and/or a polygon form. In another embodiment the outer contour of the cover strip in accordance with the present invention has a horizontal form, progressing preferably parallel to the belt. Here, the outer contour has preferably at least one ascending and/or descending radius having a value of 1 mm to 10 mm, preferably of 2.5 mm to 7.5 mm. The outer contour may however, also be deburred or beveled on the end. Under consideration of constructive, stability and fluidic aspects, the outer contour of the cover strip is located centrally or outside the center, preferably offset in the direction of belt travel.

In order to counter damaging the belt, for example to prevent splitting or similar damage, the invention provides that, the cover strip is equipped with a multitude of reinforcing ribs in the area of the outer contour, that progress preferably in the direction of travel of the belt and that are in contact with the belt. According to the present invention, the reinforcing ribs, viewed in the direction of belt travel, are 1 mm to 15 mm wide, preferably 2 mm to 12 mm wide and have preferably at least one ascending and/or descending radius having a value of 0.5 mm to 10 mm, preferably of 1 mm to 7.5 mm. The outer contour can however be also designed as a debur or a bevel.

There are several options with regard to positioning the reinforcing ribs as viewed in direction of belt travel: they may be positioned at approximately uniform distances across preferably the entire width of the cover strip, or they may be positioned at an approximately uniform distance in the center area and at smaller, preferably approximately uniform distances at the two edge areas of the cover strip, or they may be positioned exclusively at approximately uniform distances in the two edge areas of the cover strip. All aforementioned layout options definitely support prevention of damage to the belt.

In order to support the increase of air velocity in the belt surface plane with the aforementioned effects, the basic body of the cover strip is located at a distance of 2 mm to 20 mm, preferably 5 mm to 15 mm from the belt.

In addition the at least one suction box cover strip, viewed vertical to the direction of belt travel, can possess a meander outer contour form facing the belt, so that it contacts the belt with a contact area of less than 75%, preferably less than 50%, of a cross sectional surface in its basic body, progressing preferably parallel to the belt. This meander form also positively increases the air velocity in the belt surface plane above the cover strip, based on a reduction of the contact area that is relevant for the throttle effect. The increase of the air velocity in the belt surface plane, again, effects removal of the water from the belt mesh (“belt dewatering”), thereby further reducing the remoistening of the fiber web and clearly increasing the dry content of the fiber web.

According to the present invention, the belt may be the wire in a twin wire former, in an endless wire former or in a hybrid former, or a felt belt in a press section. In contrast the suction box may be part of a forming suction box, a wet suction box or a HiVac box of twin wire former, part of a wet suction box, a flat suction box or a HiVac box of an endless wire former or a hybrid former, or a component for intermediate conditioning of press felts that are running in a true tandem configuration. In a true tandem configuration, the press felt runs through two press nips, in between which part of the water that is carried along in the felt is extracted in a suction box.

In another embodiment of the present invention, the cover strip may also be located in a suction couch roll, preferably as the last strip, viewed in the direction of travel. As a conclusion to the suction zone by way of a special cover strip (wire flushing strip) the belt (wire) can be dewatered at the end of the suction zone by way of flushing air.

It is understood that the aforementioned characteristics of the present invention that are also discussed below in further detail can be utilized not only in the cited combination, but also in other combinations, or free-standing, without leaving the scope of the present invention.

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 embodiments of the invention taken in conjunction with the accompanying drawings, wherein: [0024]
FIG. 1 is a schematic side view showing a partial view of a machine for the production of a fiber web, with a suction box in accordance with the known state of the art (prior art); [0025]
FIG. 2 is a schematic side view of an embodiment of a machine for the production of a fiber web, showing an embodiment of a suction box equipped with cover strips, in accordance with the present invention; [0026]
FIG. 3 is a schematic side view of another embodiment of a machine for the production of a fiber web, showing an embodiment of a suction box equipped with cover strips, in accordance with the present invention; [0027]
FIG. 4 is a schematic side view of another embodiment of a machine for the production of a fiber web, showing an embodiment of a suction box equipped with cover strips, in accordance with the present invention; [0028]
FIG. 5 is a schematic top view of a machine for the production of a fiber web, showing a suction box equipped with cover strips in accordance with an embodiment of the present invention; [0029]
FIG. 6 is a schematic top view of a machine for the production of a fiber web, showing a suction box equipped with cover strips in accordance with another embodiment of the present invention; [0030]
FIG. 7 is a sectional view taken along section line [0031] 7-7 in FIG. 5;
FIG. 8 is a sectional view taken along section line [0032] 8-8 in FIG. 5; and
FIG. 9 is a partial sectional view of a suction box equipped with a cover strip, in accordance with an embodiment of the present invention. [0033]
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. [0034]

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a schematic side view (prior art) of a [0035] machine 1 that is not illustrated in further detail, for the production of a fiber web 2, equipped with a suction box 3, in accordance with the state of the art. Machine 1 serves to produce fiber web 2, specifically a paper or cardboard web, from at least one fiber stock suspension 4. The equipment includes at least one porous belt 5, specifically a wire belt or similar belt, running continuously in the direction of web travel L (arrow). It further includes at least one partially illustrated suction box 3, including closed box 6 that can be connected to vacuum source 7. On its upper surface 8 that is in contact with belt 5, a multitude of cover strips 9, 9.1 are mounted at certain distances A_Bfrom each other and vertical to the direction of travel L of belt 5, forming suction slots 10.
It can be clearly seen in FIG. 1 that cover strips [0036] 9, 9.1 have an approximately constant cross section F_Qprogressing parallel to belt 5, according to the known state of the art. Consequently, as previously mentioned, the water is not removed sufficiently (“belt dewatering”) from the belt mesh due to insufficient speed V_L(arrow) above suction box 3. This allows the already described disadvantages of the known state of the art, for example remoistening of fiber web 2 or a low dry content in fiber web 2, to occur.
FIGS. 2 through 4 each depict a schematic side view (partial view) of an embodiment of [0037] machine 1 for the production of fiber web 2 with suction box 3, equipped with cover strips 9.2 in accordance with the present invention. For the general description of machine 1 we refer you to the description of machine 1 in FIG. 1. Basic body 13 has width or cross section F_Q
In FIG. 2 the present invention provides that at least one [0038] suction box 3 cover strip 9.2 at which a pressure differential Δp exists due to various prevailing ambient pressures p_a(atmospheric pressure), p_u(vacuum, produced by vacuum source 7) has a wire-contacting width B_B, viewed vertically to the direction of wire travel, that has a value factor a* of the average wire-contacting width B_Bof the cover strips 9.1, 9.2, whereby the factor a* takes on a numerical value in the range of 0.05 to 0.95, preferably of 0.1 to 0.9, and whereby the average wire-contacting width B_Bof the cover strips 9.1, 9.2 is in the range of 10 mm to 30 mm.
This positively increases air velocity V[0039] _L(arrow) in the belt surface plane above cover strip 9.2, in accordance with the present invention, based on a reduction of contact area 12 that is relevant for the throttle effect. The increase of air velocity V_L(arrow) in the belt surface plane effects removal of the water from belt mesh 5 (“belt dewatering”), thereby further reducing the remoistening of fiber web 2 and clearly increasing the dry content of fiber web 2.
Cover strip [0040] 9.2 of suction box 3, viewed vertical to direction of travel L (arrow) of belt 5, with this type of outer contour 11 facing belt 5, may be the last cover strip mounted on the suction box 3 in FIG. 1 it is the first cover strip located on suction box 3. Also, the majority of the cover strips 9.2 on suction box 3 may have such outer contours 11 of preferably identical form facing belt 5, whereby FIG. 1 does not depict this option, that is however easily utilized.
In accordance with an embodiment of the present invention, [0041] outer contour 11 of cover strip 9.2 has preferably a stable curved, an arched, a parabolic and/or a polygon form. Naturally, a combination of the aforementioned forms is also possible. However, other known forms are also possible, alone or in combination with itself and/or other cited forms. In addition, belt 5 may be the wire in a twin wire former, in an endless wire former or in a hybrid former, or the felt belt in a press section. Due to a general knowledge of these cited formers or the press section, no detailed illustrations are provided of these units. Obviously, suction box 3 may be part of a forming suction box, a wet suction box or a HiVac box of a twin wire former, part of a wet suction box, a flat suction box or a HiVac box of an endless wire former or a hybrid former, or a component for intermediate conditioning of press felts that are running in true tandem configuration. We have also refrained from providing these illustrations.
As illustrated in FIG. 3, an embodiment of the present invention provides that cover strip [0042] 9.2 is equipped with a multitude of reinforcing ribs 14 in the area of outer contour 1 1, that progress preferably in the direction of travel L (arrow) of belt 5, and that are in contact with belt 5.
Reinforcing [0043] ribs 14, viewed in the direction of travel L of belt 5, have a preferred width B_Sof 1 mm to 15 mm, preferably of 2 mm to 12 mm and have preferably at least one ascending and/or descending radius R_Shaving a value of 0.5 mm to 10 mm, preferably of 1 mm to 7.5 mm. Reinforcing ribs 14, viewed in direction of travel L of belt 5, may be positioned at approximately uniform distances T_Sacross preferably the entire length L_Bof cover strip 9.2, or they may be positioned at an approximately uniform distance T_Sin the center area M_Band at smaller, preferably approximately uniform distances T_Sat the two edge areas RB_Bof the cover strip 9.2; or they may be positioned exclusively at approximately uniform distances T_Sin the two edge areas RB_Bof the cover strip 9.2. Since these reinforcing rib arrangements according to an embodiment the present invention can easily be accomplished, we have refrained from detailed illustration. In FIG. 3 outer contour 11 of cover strip 9.2 has a preferably stable parabolic form, and it is mounted in a central position.
In FIG. 4, an embodiment of the present invention provides that [0044] outer contour 11 of cover strip 9.2 has a horizontal plane form, progressing preferably parallel to belt 5. Here, outer contour 11 has at least one ascending and/or descending radius R_Bhaving a value of 1 mm to 10 mm, preferably 2.5 mm to 7.5 mm, and the body of cover strip 9.2 is located at a distance A_Gof 2 mm to 20 mm, preferably 5 mm to 15 mm, from belt 5. In addition, the outer contour of cover strip 9.2 is located off-center, preferably offset in the direction of travel L (arrow) of belt 5.
FIGS. 5 and 6 illustrate two additional schematic top views of a machine for the production of [0045] fiber web 2, with suction box 3, equipped with cover strips 9.2 in accordance with an embodiment of the present invention. The present invention provides that the two cover strips 9.2 of suction boxes 3, viewed vertical to direction of travel L of belts 5, have meander 15 type outer contours facing the belts 5, so that they contact belts 5 with a respective contact surface 12 of less than 75% or less than 50% of a non-visible cross sectional surface in their respective basic body 13, progressing preferably parallel to the respective belt 5,
FIG. 7 is a schematic cross section view of FIG. 5 along section line [0046] 7-7, whereas FIG. 8 is a schematic section view of FIG. 5 along section line 8-8. In FIG. 7 the meander-shaped cover strip 9.2 is easily recognizable, where the resulting panels 16.1-16.4, preferably progressing in the direction of travel L of belt 5, are clearly visible. Based on the construction, zones 17.1-17.3 are created between the panels 16.1-16.4—zone 17.2 with vacuum supply and zones 17.1, 17.3 with atmospheric pressure. Between zones 17.1-17.3 the already discussed air velocities V_Soccur in the belt surface plane above cover strips 9.2. In another embodiment panels 16.1-16-4 may also be mounted progressing at an angle to the direction of travel L of belt 5. This would avoid streaky dewatering of belt 5. FIG. 8 illustrates on a diagonal longitudinal section the meander type cover strip 9.2. FIG. 8 shows that cover strip 9.2 may include several components, possibly of different types of material.
FIG. 9 illustrates a sectional partial side view of a suction couch roll [0047] 18 (not illustrated in further detail) with cover strip 9.2 according to an embodiment the present current invention, whereby cover strip 9.2 is located preferably last, viewed in the direction of travel L of belt 5. By concluding the suction zone with a special cover strip (flushing strip) 9.2, belt (wire) 5 can be dewatered at the end of the suction zone by means of flushing air. Utilization of cover strip 9.2, according to an embodiment the present invention, is not restricted to only suction couch roll 18, but moreover, it can be used with any desired roll type.
In conclusion it is to be noted, that the present invention creates a machine providing that belt dewatering is considerably improved and remoistening of the fiber web through the supporting belts is further reduced, and preferably totally eliminated. Consequently the resulting dry content of the fiber web is considerably improved. [0048]
While this invention has been described as having a preferred design, 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. [0049]

Claims

What is claimed is:

1. A machine for the production of a fiber web from at least one fiber stock suspension, comprising:

at least one porous belt movable in a direction of travel;

at least one suction box including a closed box connected to a vacuum source and an upper surface proximate to said belt, said suction box including a plurality of adjacent cover strips on said upper surface defining a plurality of suction slots therebetween, each said cover strip having a height orthogonal to a direction of travel of said belt, each said cover strip having an atmospheric side at prevailing ambient pressure and a vacuum side at prevailing vacuum pressure of said vacuum source thereby creating a pressure differential between said atmospheric side and said vacuum side, said belt side having a wire-contacting width being said direction of travel, at least one said wire-contacting width being between approximately 10 mm to 30 mm, and a value factor associated with at least one said wire-contacting width between approximately 0.05 to 0.95.

2. The machine of claim 1, wherein said value factor is between approximately 0.1 to 0.9.

3. The machine of claim 1, wherein a single said cover strip has said wire-contacting width between approximately 10 mm to 30 mm, and a value factor associated with said wire-contacting width between approximately 0.05 to 0.95, said single cover strip being a last cover strip as viewed in said direction of travel.

4. The machine of claim 1, wherein one of said cover strip has said wire-contacting width between approximately 10 mm to 30 mm, and a value factor associated with said wire-contacting width between approximately 0.05 to 0.95, said one cover strip being a first cover strip as viewed in said direction of travel.

5. The machine of claim 1, wherein each said cover strip has a form, a majority of said plurality of cover strips having a same form.

6. The machine of claim 1, wherein at least one said cover strip has a contour of horizontal plane form, facing said belt.

7. The machine of claim 6, wherein said contour has at least one of an ascending radius and a descending radius, both said ascending radius and said descending radius having a value between approximately 1 mm to 10 mm.

8. The machine of claim 7, wherein both said ascending radius and said descending radius are between approximately 2.5 mm to 7.5 mm.

9. The machine of claim 1, wherein at least one said cover strip has a contour facing said belt of one of stable curved, arched, parabolic and polygon.

10. The machine of claim 9, wherein said contour is located in one of said central position and off-center position.

11. The machine of claim 9, wherein said off-center position is offset in said direction of travel.

12. The machine of claim 9, wherein at least one said cover strip also has a meander shape as viewed vertical to said direction of travel.

13. The machine of claim 9, wherein at least one said cover strip having a contour includes at least one reinforcing rib in contact with said belt.

14. The machine of claim 13, wherein at least one said reinforcing rib has a width in said direction of travel of between approximately 1 mm to 15 mm, at least one said reinforcing rib includes at least one of an ascending radius and a descending radius, both said ascending radius and said descending radius being between approximately 0.5 mm to 10 mm.

15. The machine of claim 14, wherein said width is between approximately 2 mm to 12 mm.

16. The machine of claim 14, wherein both said ascending radius and said descending radius are between approximately 1 mm to 7.5 mm.

17. The machine of claim 13, wherein said reinforcing strips are positioned at approximately uniform distances as viewed in said direction of travel across preferably an entire length of at least one said cover strip.

18. The machine of claim 13, wherein at least one said cover strip has a center area and two edge areas bounding said center area, at least one said reinforcing rib being positioned at an approximately uniform first distance in said direction of travel in said center area and an approximately uniform second distance in said direction of travel in said edge areas, said uniform second distance smaller than said uniform first distance.

19. The machine of claim 13, wherein at least one said cover strip has two edge areas, said at least one reinforcing ribs are positioned an approximately uniform distance in said direction of travel in said edge areas.

20. The machine of claim 13, wherein at least one said cover strip includes a basic body located a distance orthogonal to said direction of travel from said belt of between approximately 2 mm to 20 mm.

21. The machine of claim 20, wherein said orthogonal distance is between approximately 5 mm to 15 mm.

22. The machine of claim 1, wherein said belt is a wire in one of a twin wire former, an endless wire former and a hybrid former.

23. The machine of claim 1, wherein said belt is a felt in a press section.

24. The machine of claim 1, wherein at least one said suction box is part of one of a forming suction box, a wet suction box and a HiVac box of a twin wire former.

25. The machine of claim 1, wherein at least one said suction box is part of one of a wet suction box, a flat suction box and a HiVac box in one of an endless wire former and a hybrid former.

26. The machine of claim 1, wherein at least one said suction box is a component for intermediate conditioning of press felts that are running in a tandem configuration.

27. A machine for the production of a fiber web from at least one fiber stock suspension, comprising:

at least one porous belt movable in a direction of travel;

at least one suction couch roll connected to a vacuum source and including a surface proximate to said belt; and

at least one cover strip on said surface, each said cover strip having a height vertical to a direction of travel of said belt, each said cover strip having an atmospheric side at prevailing ambient pressure and a vacuum side at prevailing vacuum pressure of said vacuum source thereby creating a pressure differential between said atmospheric side and said vacuum side, said belt side having a wire-contacting width in said direction of travel, at least one said wire-contacting width being between approximately 10 mm to 30 mm, and a value factor associated with at least one said wire-contacting width is between approximately 0.05 to 0.95.