Patent Application
20080190510
1. Field of the Invention
The present invention relates to a papermaking machine, and, more particularly, to a press fabric utilized by a papermaking machine.
2. Description of the Related Art
In the art of papermaking multiple steps occur from the introduction of a pulp slurry to the production of a finished paper product. The initial introduction of the slurry is that portion of a papermaking machine known as the wet end. Here, the slurry, or fiber suspension, is initially dewatered when the slurry is introduced onto a moving forming fabric, in the forming section of the papermaking machine. Varying amounts of water is removed from the slurry through the forming fabric, resulting in the formation of a fibrous web on the surface of the forming fabric.
The forming fabric addresses the dewatering of the slurry and also sheet formation, which contributes to the sheet quality as the web forms on the forming fabric. The roll of the forming fabric also includes the conveyance of the fibrous web to the press section of the papermaking machine.
The web is conveyed to a press section where the web encounters at least one press fabric either directly or adjacent to a fabric carrying the web. The press fabric is utilized with a shoe press or a roll press and the press fabric may exert a pressing force upon the web to further reduce the moisture content of the web.
The current state of the art press fabrics start with a high volume, which is gradually reduced down to an acceptable value after 8 to 48 hours by a procedure known as running in the fabric. The running in of the fabric results in lost production time and/or at the very least non-optimal dewatering efficiency of the papermaking machine. This running in sequence and non-optimal nip dewatering resulting therefrom leads to a condition of increased contamination of the press fabric mainly in the surface batt structure, which leads to an increased flow resistance.
What is needed in the art is a press fabric structure that allows immediate startup for more efficient use of the papermaking machine.
The present invention provides a press fabric for use in a papermaking machine that does not require a run-in before use.
The invention in one form is directed to a press fabric for use in a papermaking machine, the press fabric including a base fabric and a layer of fine fibers combined with a polymer reinforcement. The layer being associated with the base fabric. The layer being no more than 125 grams/m2. The press fabric being pre-compacted to a density greater than 750 kg/m3.
An advantage of the present invention is that it significantly reduces the time needed for the running in time of the fabric.
Another advantage of the present invention is that it reduces initial contamination of the press fabric.
Yet another advantage of the present invention is that it allows the use of a fine surface batt structure that yields improved paper surface quality and higher dryness.
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, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Referring now to the drawings, and more particularly to
Now, additionally referring to
Base fabric 22 is preferably woven from single monofilaments only, with machine direction yarns not courser than 0.30 mm. Further, base fabric 22 is preferably woven in only one layer. Adjacent to base fabric 22 is non-woven component 20, which may be a Vector non-woven component. Non-woven component 20 helps provide a mark-free impression on the paper web and provides a void volume in press fabric 14.
No fibers courser than 11 dtex are included in press fabric 14, except for in non-woven component layer 20. Fine layer 16, batt layer 18, non-woven component 20, base fabric 22 and batt layer 24 are needled and pre-compacted to a high density of at least 750 kg/m3. Advantageously the pre-compacting of press fabric 14 allows for the use of a thin layer of fine fibers, which are not contaminated during a running in sequence of prior art press fabrics. Press section 12 may utilized more than one press fabric 14. The pre-compaction of press fabric 14 allows for constant and retained properties of press fabric 14 throughout the life of press fabric 14. The constant properties allow a lower initial void volume, which offers immediate nip dewatering and conditioning and also allows the finer fiber layer 16 structure to be used.
Now, additionally referring to
Now, additionally referring to
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.
