Paper making and fiber liberation – Processes and products – With measuring – inspecting and/or testing
Reexamination Certificate
1999-08-04
2001-03-20
Silverman, Stanley S. (Department: 1731)
Paper making and fiber liberation
Processes and products
With measuring, inspecting and/or testing
C162S216000, C162S208000, C162SDIG004, C162SDIG004, C162S252000, C162S253000, C162S258000, C162S336000, C162S344000, C162S183000, C162S164600, C702S127000
Reexamination Certificate
active
06203665
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for setting a uniform characteristic cross-direction profile for a paper web with regard to at least formation, basis weight, and fiber orientation in a paper machine via a headbox, in which consistency is sectionally adjusted and which has an adjustable die exit opening.
2. Discussion of Background Information
The Voith Sulzer publications “Module Jets®: the New Headbox for Independent Control of Cd Basis Weight and Fiber Orientation Profiles,” p2919e, (March 1994); “Module Jet—erste Betriebserfahrungen mit dem neuen Stoffauflaufkonzept,” Wochenblatt für Papierfabrikation 122, No. 12, pages 485-491 (1994), and “Stoffdichteabhängige Querprofilregelung—Betriebserfahrungen,” Das Papier, volume 49, issue 10A, pages V99-V105 (1995) disclose the state of the art with regard to the process generally discussed above, and the disclosures of these documents are expressly incorporated by reference herein in their entireties.
From the above-noted publications, it is known to locally adjust the amount of solid matter deposited by an appropriate mixing of pulp slurry and a dilution liquid, eg., backwater, to reduce basis weight irregularities in a consistency-regulated headbox. It is further disclosed that the cross flow can be adjusted, and, therefore, the fiber cross-direction profile can be improved, by adjusting the sectional flow rate of pulp slurry at the die exit opening. These documents seek to achieve as even a flow across or over the screen at the die exit opening as possible. Moreover, it is assumed that there is a connection or relationship between the specific pulp slurry flow rate (measured in liters per meter of machine width) deposited at the headbox and the formation cross-direction profile, especially in twin wire formers.
Therefore, in the state of the art, problems arise in providing a process for operating a headbox, which maintains the known good quality of the basis weight cross-direction profile and the fiber orientation cross-direction profile that can be achieved by a consistency-regulated headbox and simultaneously has a positive influence on the fiber orientation cross-direction profile.
SUMMARY OF THE INVENTION
The present invention does not suffer from the above-noted drawbacks of the prior art.
Accordingly, the present invention relates to a process for setting a uniform characteristic cross-direction profile for a paper web with regard to at least formation, basis weight, and fiber orientation in a paper machine. The paper machine can include a headbox with an adjustable die exit opening and within which the consistency is sectionally adjustable. The process includes measuring and setting a desired basis weight cross-direction profile by adjusting the sectional consistency in the headbox, adjusting the formation cross-direction profile by adjusting a sectional, specific pulp slurry flow rate at the die exit opening, and one of enlarging the die exit opening at positions along a width of the paper machine in which a pulp slurry flow rate is higher than in other positions along the width of the paper machine and increasing the pulp slurry flow rate for positions along the width at which the die exit opening is larger than at other positions along the width. In this manner, a desired fiber orientation cross-direction profile is attained.
In accordance with a feature of the present invention, the adjustment of the formation cross-direction profile may be performed subsequently to the measuring and setting of the desired basis weight cross-direction profile.
According to another feature of the present invention, the one of enlarging the die exit and increasing the pulp slurry flow rate can be performed one of subsequently to and simultaneously with, adjustment of the formation cross-direction profile.
According to still another feature of the instant invention, the process can further include changing the die exit opening proportionally to a change in the pulp slurry flow rate associated with the position of the die exit opening.
In accordance with a further feature of the present invention, the change in the die exit opening may provide a desired speed cross-direction profile at the die exit opening after adjustment.
According to a still further feature of the instant invention, the paper machine can also including a control device that executes a control loop to perform at least one of the measuring and setting a desired basis weight cross-direction profile, adjusting the formation cross-direction profile, and one of enlarging the die exit opening and increasing the pulp slurry flow rate.
According to another feature of the present invention, the process may further include introducing chemicals to at least one of slow down and speed up the dewatering process. Further, the chemicals may be introduced in an edge area.
According to still another feature of the present invention, the process may further include one of sectionally adding and removing liquid. In this manner, the adjustment of the pulp slurry flow rates in a respective section can be attained. Further, the one of the adding and removing of liquid can occur in a z-direction in the edge areas.
In accordance with a further feature of the instant invention, the process may further include adding filler in areas with a higher flow rate. Further, the adding of filler includes sectional addition of liquid.
According to yet another feature of the present invention, the process may be performed in combination with a twin wire former.
The present invention also relates to a process for controlling cross-direction profiles in an apparatus having a sectioned headbox and a die exit opening. The process includes adjusting a sectional pulp slurry flow rate at the die exit opening, whereby a formation cross-direction profile is adjusted, and one of (a) adjusting the a gap size of the die exit opening at positions across a width of the apparatus in accordance with the adjusted pulp slurry flow rate associated with the positions, and (b) adjusting the pulp slurry flow rate at positions across a width of the apparatus in accordance with a gap size of at least a portion of the die exit opening associated with the positions.
In accordance with a feature of the instant invention, after the adjustment of the sectional pulp slurry flow rate, the process includes measuring and setting a desired basis weight cross-direction profile by adjusting a sectional consistency in the sectioned headbox.
According to another feature of the present invention, the one of enlarging the die exit and increasing the pulp slurry flow rate can be performed one of subsequently to and simultaneously with, adjustment of the sectional pulp slurry rate.
According to still another feature of the invention, the process may further include changing the die exit opening proportionally to a change in the pulp slurry flow rate associated with the position of the die exit opening.
In accordance with a further feature of the present invention, the change in the die exit opening provides a desired speed cross-direction profile at the die exit opening after adjustment.
In accordance with a still further feature of the present invention, the apparatus may include at least one spindle coupled to the die exit opening, and the process can further include driving the at least one spindle to adjust the gap size of the die exit opening.
According to yet another feature of the instant invention, the apparatus may include spindles coupled across the width of the die exit opening, and the process can to further include individually driving the spindles to individually adjust respective gap sizes of the die exit opening.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.
REFERENCES:
patent: 4898643 (1990-02-01), Weisshuhn
patent: 5560807 (1996-10-01), Hauser
patent: 5944957 (1999-08-01), Fagerlund
patent: 4239845 (1993-05-01), None
Begemann, “Module Jet®: The New Headbox
Greenblum & Bernstein P.L.C.
Halpern Mark
Silverman Stanley S.
Voith Sulzer Papiertechnik Patent GmbH
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