Patent Grant
8236137
1. Field of the Invention
The invention relates to a headbox for a machine for producing a fibrous web, in particular a paper or cardboard web from at least one fibrous stock suspension which comprises a feed device feeding the at least one fibrous stock suspension, a perforated distribution pipe plate arranged immediately downstream thereof and having a plurality of channels arranged in rows and columns, an intermediate channel arranged downstream thereof, extending over the width of the headbox and having a plurality of means for dosing of a fluid in partial fluid streams to the at least one fibrous stock suspension in a preferably adjustable/controllable manner, the means being spaced apart from each other in width direction of the headbox and the individual means comprising a plurality of dosing channels having respective dosing channel openings and an opening center line, discharging at different heights and being connected to a common supply channel. The headbox further comprises a downstream turbulence generator having a plurality of flow channels arranged in rows and columns and a headbox nozzle comprising a nozzle gap, located immediately adjacent to the turbulence generator.
2. Description of the Related Art
A headbox of this type is known for example from German disclosure documents DE 44 16 898 A1, DE 44 16 899 A1 and DE 44 16 909 A1.
German disclosure document DE 44 16 898 A1 describes a headbox for a paper machine; including a feed device for the stock suspension comprising a guiding element with a plurality of channels; upstream from a guiding element a mixing chamber with several infeed devices which are distributed over the headbox for a fluid which is to be added into the stock suspension and which differs in its characteristics from the stock suspension; and with a nozzle chamber forming an outlet opening for the stock suspension, located immediately downstream from the guiding element. The feed devices for the fluid which is to be added extend essentially vertically in the mixing chamber and comprise several dosing openings located on top of each other.
German disclosure document DE 44 16 899 A1 describes a headbox for a paper machine including a feed device for the stock suspension, with a first guiding element comprising a plurality of channels, a second guiding element comprising a plurality of channels, a mixing chamber located between them, a contiguous nozzle chamber forming an outlet opening for the stock suspension, and several feed lines distributed over the headbox for the fluid which is to be added. The majority of the channels of the guiding elements are positioned and dimensioned so that the outlet opening of the upstream guiding element is not aligned with a confluence into the downstream guiding element. The feed lines for the fluid which is to be added are equipped with dosing openings, the majority of which align respectively with a confluence into the downstream guiding element.
In addition, German disclosure document DE 44 16 909 A1 describes a headbox for a paper machine with a feed device for the stock suspension, a downstream contiguous guiding element equipped with a plurality of channels, located downstream thereto a mixing chamber extending across the width of the headbox with several separation walls distributed across the headbox and extending essentially in flow direction, as well as feed devices for a fluid which is to be added, distributed in cross direction of the headbox and which are equipped with dosing openings, downstream an additional guiding element equipped with a plurality of channels and adjacent to it, one nozzle chamber forming an outlet opening for the stock suspension.
The feed devices for the fluid which is to be added extend into the mixing chamber and the sectional area which is formed in the mixing chamber by the separation walls begins in the region of the dosing openings from where it extends essentially in flow direction to the second guiding element.
Based on their operational conditions the head boxes described in these three documentations possibly display unstable operating characteristics which are reflected especially in the properties of the fibrous web which is to be produced. The negatively influenced properties can be especially the base weight and the fiber orientation in the fibrous web which is to be produced. In addition, usage of chemicals, especially retention agents can be high. Also, the pressure requirement of a headbox is used in a manner known to the expert, for the fluidization of the at least one fibrous stock suspension, for homogenization and orientation of the flow and for acceleration of the at least one fibrous stock suspension in the headbox nozzle. The pressures required for homogenization or respectively orientation and fluidization are losses.
It is therefore the objective of the current invention, and what is needed in the art is, to improve a headbox of the type described at the beginning in such a manner, that the aforementioned disadvantages of the current state of the art are significantly, preferably completely eliminated. To provide a distribution of the fibrous stock suspension which is preferably as uniform as possible the pressure loss should be as low as possible and optimally distributed. Also, the energy consumption of the headbox should be significantly reduced, the stability of the fiber orientation (cross) profile improved and the usage of chemicals, especially retention agents reduced.
According to the present invention this objective is met with, and the present invention provides, a headbox of the type described at the beginning in that, based on its design it shows a system pressure loss which is substantially composed of a first pressure loss between the feed device and the intermediate channel and a second pressure loss in the turbulence generator, whereby the second pressure loss and the first pressure loss are in a ratio in a range of 8:1 to 1:1, preferably of 4:1 to 1:1, especially of 2:1 to 1:1.
The inventive objective is completely met in this manner.
The inventive design of the headbox of the type described at the beginning provides a far reaching, preferably complete elimination of the aforementioned disadvantages of the current state of the art and a substantially improved realization especially of the technological requirements. The pressure loss in particular is kept as low as possible and optimally distributed, for distribution of the fibrous stock suspension, so that the continuous production of a high quality fibrous web becomes possible. In addition, the energy consumption of the headbox is significantly reduced and a good to very good functional fulfillment of the headbox with the described dosing system is still sufficiently ensured, even with possibly greater changes in the operating conditions. And, the stability of the fiber orientation (cross) profile is improved; the usage of chemicals, especially retention agents is reduced.
In addition, at least one separation element which is well known to the expert, in particular a lamella may be provided in the headbox nozzle of the inventive headbox. In the event that several separating elements, in particular lamellas are arranged in the headbox nozzle of the inventive headbox, different lengths and possibly also different properties such as surface profiles and similar may occur.
The second pressure loss in the intermediate channel is preferably in a range of 0.1 to 1.5 bar, preferably 0.2 bar to 1.0 bar, especially 0.3 to 0.5 bar.
In an additional design form the feed device includes a cross distribution pipe mounted to the perforated distribution pipe plate, and the perforated distribution pipe plate is equipped with hydraulic elements for pressure recovery, for examples with diffusers, step diffusers or similar equipment. This flow control allows a trouble free and obstruction free flow into the perforated distribution pipe plate in the distribution pipe at a speed in the range of 4 to 16 m/s. The diffusers in the perforated distribution pipe plate convert this flow energy again into pressure.
In an alternative design form the feed device includes a central distributor, equipped with a plurality of tubes which are connected with the channels in the perforated distribution pipe plate. And, the plurality of tubes is equipped with hydraulic elements for pressure recovery, for example with diffusers, step diffusers or similar equipment. In this feed design the system can be designed for low flow speeds of less than 10 m/s in the tubes.
Also, the at least one fibrous stock suspension which is supplied to the feed device can be fed exclusively to the channels of the perforated distribution pipe plate arranged adjacent downstream. Herewith a headbox without recirculation of the fibrous stock suspension can be realized and the volume of fibrous stock suspension on the edge varies substantially less.
The impingement point of the center line of the individual dosing opening onto the turbulence generator can be located approximately central, preferably central between the two column planes of two adjacent flow channels. With this design form the throughput constancy of fluid in width direction of the headbox in the turbulence generator can be rendered independent from the different volumes of fibrous stock suspension which can be added in width direction of the headbox.
The dosing channel opening of the means for preferably adjustable/controllable dosing of the fluid in partial fluid streams into the at least one fibrous stock suspension is moreover positioned preferably at a vertical distance from the turbulence generator in the range of 1 to 100 mm, preferably 3 to 50 mm, especially 5 to 30 mm. These ranges in distance allow for the necessary blending quality of the fluid with the fibrous stock suspension, even with different operating parameters, so that optimum parameters are given for the production of a fibrous web having good to very good quality properties.
The respective means for preferably adjustable/controllable dosing of fluid in partial fluid streams into the at least one fibrous stock suspension preferably comprises a dosing sword as described and illustrated in the German patent application DE 10 2008 054 898.7 (Applicant File: HPA14265 DE and Applicant-Title:“MJ II-DoS-TE-Geometry”) with same German application date as the German patent application corresponding to the present application. The relating disclosure content of German patent application DE 10 2008 054 898.7 is herewith made subject matter of the current description.
The fluid consists preferably of water, especially clarified water or of a fibrous stock suspension, especially white water whose concentration is different than the average concentration of the at least one fibrous stock suspension in the headbox. These types of fluids have already proven themselves well in similar applications.
The inventive headbox is extremely well suited for utilization in a machine for the production of a fibrous web, especially a paper or cardboard web. The fibrous web produced in the machine with at least one inventive headbox without exception possesses outstanding properties, since among other advantages, control of its fiber orientation cross profile as well as its base weight cross profile is possible.
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:
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.
Headbox 1 comprises one feed device 4 in the embodiment of a cross distribution pipe 5.1 which is known to the expert, supplying the one fibrous stock suspension 2 (arrow).
Perforated distribution pipe plate 6 which is equipped with a plurality of channels 7 which are arranged in rows Z and columns S is located downstream adjacent to feed device 4.
Again located adjacent downstream from perforated distribution pipe plate 6 is an intermediate channel 8, extending across width B (arrow) of headbox 1 and being equipped with several means 9 for a preferably adjustable/controllable dosing of a fluid 10 in partial fluid streams 10.T (arrows) into the fibrous stock suspension 2 (arrow), the means being spaced apart from each other in width direction of headbox 1. The individual means 9 for the preferably adjustable/controllable dosing respectively comprises several dosing channels 11 (compare
A turbulence generator 13 having a plurality of flow channels 14 arranged in rows Z and column S is located downstream from intermediate channel 8. During operation of headbox 1 the fibrous stock suspension 2 (arrow) is divided into partial fibrous stock suspension streams in turbulence generator 13 and, after emerging from the turbulence generator is brought together again in a machine-wide chamber 15 in the embodiment of a headbox nozzle 16 comprising a nozzle gap 17 in order to enable formation of a machine-wide fibrous web 3. As already known, flow channels 14 are in the embodiment of preferably thin-walled turbulence pipes and/or turbulence pipe inserts with at least partially constant, at least partially divergent, at least partially convergent and/or stepped cross sectional surfaces. A separating element which is well known to the expert and which is not explicitly illustrated, especially a lamella, may also be provided in headbox nozzle 16. If a multitude of separating elements, especially lamellas are provided in headbox nozzle 16, they can have different lengths and possibly also different properties, such as surface profiles, etc.
As indicated by broken lines, on its outlet side headbox nozzle 16 may be equipped with an aperture 18, at least on one side which is indicated by broken lines.
Due to its design, headbox 1 has a system pressure loss which is substantially composed of a first pressure loss Δp1 between feed device 4 and intermediate channel 8, and a second pressure loss Δp2 in turbulence generator 13, the second pressure loss Δp2 and the first pressure loss Δp1 being in a ratio in a range of 8:1 to 1:1, preferably 4:1 to 1:1, especially 2:1 to 1:1. The second pressure loss Δp2 in turbulence generator 13 is in a range of 0.1 to 1.5 bar, preferably 0.2 to 1.0 bar, especially 0.3 to 0.5 bar.
Perforated distribution pipe plate 6 is equipped with hydraulic elements 19 for pressure recovery, for examples with diffusers, step diffusers or similar equipment (compare
Furthermore, fibrous stock suspension 2 which is supplied to feed device 4 is fed exclusively to channels 7 of perforated distribution pipe plate 6 arranged adjacent downstream. Headbox 1 therefore shows no recirculation for the fibrous stock suspension 2 fed to it by means of feed device 4.
Impingement point P of opening center line 11.M of individual dosing opening 11.O of dosing channel 11 onto turbulence generator 13 is located approximately central, preferably central between the two column planes of two adjacent flow channels 14 of turbulence generator 13. Dosing channels 11 of means 9 in the form of dosing sword 9.1 for preferably adjustable/controllable dosing discharging at different height levels are located at equal distances, and dosing channel 11—connected with respective common supply channel 12—of means 9 for preferably adjustable/controllable dosing has a circular cross sectional surface 11.Q with a diameter of 11.D of 2 to 10 mm, preferably 4 to 6 mm. In contrast, common supply channel 12 of means 9 for preferably adjustable/controllable dosing has a circular cross sectional surface 12.Q with a diameter 12.D of 6 to 20 mm, preferably 10 to 15 mm (compare
Means 9 in the form of dosing sword 9.1 for preferably adjustable/controllable dosing has a length 9.L in the range of 60 to 350 mm, preferably 100 to 250 mm and, depending upon the height of the intermediate chamber of headbox 1 has a height 9.H in the range of 50 to 300 mm, preferably 75 to 250 mm. Means 9 for preferably adjustable/controllable dosing are at a preferably uniform spacing T in width direction of headbox 1 in the range of 10 to 100 mm, preferably 25, 33, 50 or 66 mm.
Dosing sword 9.1 is described and illustrated in the German patent application DE 10 2008 054 898.7 (Applicant File: HPA14265 DE and Applicant-Title: “MJ II-DoS-TE-Geometry”) with same German application date as the German patent application corresponding to the present application. The relating disclosure content of German patent application DE 10 2008 054 898.7 is herewith made to the subject matter of the current description.
Moreover, dosing opening 11.O of means 9 for preferably adjustable/controllable dosing of fluid 10 in partial fluid streams 10.T (arrows) into fibrous stock suspension 2 is positioned preferably at vertical distance A in the range of 2 to 100 mm, preferably 3 to 50mm, especially 5 to 30 mm from turbulence generator 13 (compare
Feed device 4 of this headbox 1 includes a central distributor 5.2, equipped with a plurality of tubes 5.21. Said tubes 5.21 are connected with channels 7—which are arranged in rows Z and in columns S—of perforated distribution pipe plate 6. Central distributor 5.2 which is known to the expert is generally also referred to as round distributor.
Perforated distribution pipe plate 6 is again equipped with hydraulic elements 19 for pressure recovery, for examples with diffusers, step diffusers or similar equipment (compare FIG. 3).
Due to its design, headbox 1 also has a system pressure loss which is essentially composed of a first pressure loss Δp1 between feed device 4 and intermediate channel 8, and a second pressure loss Δp2 in the turbulence generator, the second pressure loss Δp2 and the first pressure loss Δp1 being in a ratio in a range of 8:1 to 1:1, preferably 4:1 to 1:1, especially 2:1 to 1:1. The second pressure loss Δp2 in turbulence generator 13 is in a range of 0.1 to 1.5 bar, preferably 0.2 to 1.0 bar, especially 0.3 to 0.5 bar.
A separating element which is well known to the expert and which is not explicitly illustrated, especially a lamella, may also be provided in headbox nozzle 16. If a multitude of separating elements, especially lamellas are provided in headbox nozzle 16, they can have different lengths and possibly also different properties, such as surface profiles, etc.
Perforated distributor pipe plate 6 comprises five rows Z1 through Z5 of channels 7 and a plurality of columns S of channels 7. All channels 7 have without exception a round channel cross section 7.Q, however in different forms and designs. All channels 7 are also equipped on their inlet side with an inlet chamfer 20 which is known to the expert.
Channels 7 of the two upper rows Z4, Z5 initially have a constant channel cross section 7.Q which lastly experiences a continuous expansion 21, especially a cone 21.1 with a cone angle a of ≦30°.
Channels 7 of middle row Z3 have again initially a constant channel cross section 7.Q which lastly experience two rapid expansions 22, especially step expansions 22.1, 22.2.
Channels 7 of the two lower rows Z1, Z2 have again initially a constant channel cross section 7.Q which lastly experience only one rapid expansion 22, especially one step expansion 22.1.
Each individual channel 7 of perforated distribution pipe plate 6 therefore initially has a round channel cross section 7.Q with a channel diameter 7.D and then also forms a hydraulic element 19 for pressure recovery based on at least one expansion 21, 22. The middle channel diameter 7.DM of channel 7 of perforated distribution pipe plate 6 and length 6.L of perforated distribution pipe plate 6 have a ratio of 1:2 to 1:10, preferably 1:3 to 1:8, especially 1:4 to 1:5.
Dosing channels 11 of means 9 for preferably adjustable/controllable dosing which discharge at different height levels are located at equal distances, and dosing channel 11—connected with respective common supply channel 12—of means 9 for preferably adjustable/controllable dosing has a circular cross sectional surface 11.Q with a diameter of 11.D of 2 to 10 mm, preferably 4 to 6 mm. In contrast, common supply channel 12 of means 9 for the preferably adjustable/controllable dosing has a circular cross sectional surface 12.Q with a diameter 12.D of 6 to 20 mm, preferably 10 to 15 mm. The impingement point P of opening center line 11.M of individual dosing opening 11.O of dosing channel 11 onto turbulence generator 13 is located approximately central, preferably central between the two column planes of two adjacent flow channels 14 of turbulence generator 13.
Fluid 10 flowing through respective headboxes 1 illustrated in
Headbox 1 illustrated in the respective figures is especially suited for utilization in a machine to produce a fibrous web 3, in particular a paper or cardboard web from at least one fibrous stock suspension 2.
In summary it must be stated that a headbox of the type described at the beginning is improved by the invention in that the aforementioned disadvantages of the current state of the art are eliminated to the greatest possible extent, preferably completely. The pressure loss for distribution of the fibrous stock suspension that is as uniform as possible is hereby kept as low as possible and is optimally distributed. The energy consumption of the headbox is also significantly reduced, the stability of the fiber orientation (cross) profile is improved and the use of chemicals, especially retention agents is reduced.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 054 896 | Dec 2008 | DE | national |
This is a continuation of PCT application No. PCT/EP2009/063846, entitled “HEADBOX FOR A MACHINE FOR PRODUCING A FIBROUS WEB”, filed Oct. 22, 2009, which is incorporated herein by reference.
| Number | Date | Country |
|---|---|---|
| 44 16 898 | Nov 1995 | DE |
| 44 16 899 | Nov 1995 | DE |
| 44 16 909 | Nov 1995 | DE |
| 19926805 | Dec 2000 | DE |
| 102 45 154 | Apr 2004 | DE |
| 10 2008 043 145 | Apr 2010 | DE |
| 10 2008 054 898 | Jun 2010 | DE |
| 0629739 | Jun 1994 | EP |
| 0 629 739 | Dec 1994 | EP |
| 0 683 266 | Nov 1995 | EP |
| 0 824 157 | Feb 1998 | EP |
| 2 199 459 | Jun 2010 | EP |
| Number | Date | Country | |
|---|---|---|---|
| 20110265968 A1 | Nov 2011 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2009/063846 | Oct 2009 | US |
| Child | 13102688 | US |
