Paper making and fiber liberation – Processes and products – Running or indefinite length work forming and/or treating...
Reexamination Certificate
1999-04-13
2001-09-25
Hastings, Karen M. (Department: 1731)
Paper making and fiber liberation
Processes and products
Running or indefinite length work forming and/or treating...
C162S216000, C162S123000, C162S343000
Reexamination Certificate
active
06294051
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an apparatus and method for improving the edge strength of a fibrous mat. More specifically, this invention relates to an apparatus and method for improving the edge strength and basis weight uniformity at the very edges of a fibrous mat during its formation.
BACKGROUND OF THE INVENTION
In producing a fibrous mat, such as a tissue sheet, on a fibrous mat making machine having a roll former, such as a Crescent former, it is common for one or both edges of the fibrous mat to be lower in basis weight than the center of the mat. This lower basis weight at one or both edges can lead to productivity delays due to tears. Since the edges are trimmed off later in the manufacturing process, the effect on the finished fibrous mat is minimal unless the low basis weight area is very wide. When the non-uniformity of the basis weight extends beyond the width of the material that is intended to be trimmed off of one or both edges, the quality of the manufactured product will be affected.
Therefore, there is a desire and need by manufacturers to improve the strength of the edges of a newly formed fibrous mat, as well as obtaining basis weight uniformity at the edges of the newly formed fibrous mat.
SUMMARY OF THE INVENTION
Briefly, this invention relates to an apparatus and method for forming a thin fibrous mat, such as a tissue sheet, with improved edge strength. The apparatus includes a headbox having a top, a bottom, a pair of lateral sides, a back with an inlet formed therein and a front with an outlet formed therein. The headbox is designed to receive a first aqueous slurry having a predetermined fiber consistency at the inlet. This first aqueous slurry is directed through the headbox to the outlet. A first conduit is connected to the inlet of the headbox and flow therethrough is regulated to convey the first aqueous slurry at a desired rate into the headbox. A second conduit is connected to one of the lateral sides of the headbox for directing a second aqueous slurry into the headbox. The flow rate of the second aqueous slurry is regulated to be at a much lower flow rate than the first aqueous slurry. The first and second aqueous slurries are blended to form a commingled aqueous slurry. The apparatus also includes a mechanism for draining water from the aqueous slurry exiting the outlet to form a thin fibrous mat. The thin fibrous mat has increased edge strength adjacent to an edge located downstream from the second conduit relative to a mat without a second conduit.
The method includes the steps of introducing the first and second aqueous slurries into the headbox, blending the slurries, passing the commingled slurry out of the headbox and then draining water from the aqueous slurry to form a fibrous mat.
The general object of this invention is to provide an apparatus and method for improving the edge strength of a fibrous mat. A more specific object of this invention is to provide an apparatus and method for improving the edge strength and basis weight uniformity at the very edges of a fibrous mat during its formation.
Another object of this invention is to provide an apparatus and method for improving the edge strength of a tissue sheet.
A further object of this invention is to provide an apparatus and method for producing a fibrous mat that is less likely to tear along an edge during manufacture.
Still another object of this invention is to provide an apparatus and method for improving the edge strength of a fibrous mat such that the fibrous mat has a uniform basis weight in the cross-direction at the edges of the mat.
Still further, an object of this invention is to provide an economical and efficient apparatus and method for improving the edge strength of a fibrous mat
Other objects and advantages of the present invention will become more apparent to those skilled in the art in view of the following description and the accompanying drawings.
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Beuther Paul Douglas
Urquhart Richard Martin
Charlier Patricia A.
Connelly Thomas J.
Hastings Karen M.
Kimberly--Clark Worldwide, Inc.
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