Patent Application
20090084460
1. Field of the Invention
The present invention relates to papermaking machines, and, more particularly, to press fabrics used in papermaking machines.
2. Description of the Related Art
In the papermaking process a fibrous slurry is formed and deposited onto a moving forming fabric in a forming section of a papermaking machine. A significant amount of water is drained from the slurry through the forming fabric, leaving the fibrous web on a surface of the forming fabric. The formed fibrous web passes from the forming section to a press section, which may include press nips or press belts. The fibrous web passes through the pressing section as compressive forces squeeze water from the web. The fibrous web proceeds to a drying section that may include one or more rotatable dryer drums or cylinders, such as Yankee dryers. The formed web may travel through a serpentine path sequentially around a series of drums, which serve to further drive the web into paper or fiberboard product.
The fabrics used in the forming, press and dryer sections all take the form of endless loops that are utilized by the papermaking machine and function in a manner that facilitates the conveyance of the web through its change from a slurry to a fibrous sheet.
Press fabrics are utilized in an endless belt form because a forming fibrous web is susceptible to marking in the press section and any non-uniformity in the press fabric may result in a marking on the paper. That is why it is important in the seaming region of a press fabric that the seam perform as the rest of the fabric or as closely thereto as possible. One method of seaming the belts together is the use of seaming loops that are formed in the machine direction yarns of the fabric. The seam is closed by bringing the two ends of the press fabric together by interdigitating the seaming loops at the ends of the fabric, and by directing a pin or pintel through the passage defined by the interdigitated seaming loops to thereby lock the ends of the fabric together.
What is needed in the art is a method of facilitating an accurate aligning of the ends of the fabric as well as facilitate the seaming thereof.
The present invention provides a fabric that is treated and seamed together and a method for treating the fabric thereof.
The invention in one form is directed to a fabric for use in a papermaking machine, the fabric includes a first end portion of the fabric having a first flexibility, and a second end portion of the fabric having a second flexibility. The first end portion and for the second end portion are treated with an agent to reduce the flexibility associated therewith. The first end portion and the second end portion are coupled together. The agent is substantially removed from the first end portion and the second end portion. The reduced flexibility of the first end portion and/or the said second end portion define a stiffness that is substantially unaffected by a humid environment.
An advantage of the present invention is that it is easier to seam ends of fabric that are not highly flexible.
Another advantage of the present invention is that the treatment is easily removed after the ends of the fabric are seamed together.
Another advantage of the present invention is that the treatment is removed from the fabric by the normal operation of the papermaking machine.
Yet another advantage of the present invention is that the stiffness of the end portions is substantially unaffected by prolonged storage in a high humidity environment.
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 an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention, in one form, and such exemplification is 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
Once end portions 22 and 24 are seamed together the treatment agent is removed so that the water absorption characteristics and airflow characteristics in end portions 22 and 24 are not substantially different from the rest of belt 14, 16 or 20. The removal of the treatment agent can be an incidental treatment of simply operating the papermaking machine causing the treatment agent to fracture and depart from belt 14, 16 or 20.
The treatment agent may be a resin, such as polyvinyl acetate, phenoxy and/or may be a water-based treatment that imparts a stiff yet brittle characteristic to end portions 22 and 24. The brittle property of the coating leads to a short-term life of the treating agent once the belt is cycled through the papermaking machine 10. Since end portions 22 and 24 would be subjected to pressing pressures as well as bending moments the fracturing of the coating comes as a material with the operation of papermaking machine 10. The stiffer end portions 22 and 24 are easier to install, and in general the seaming area is easier and faster to join together.
Fabric 14, 16 or 22 may be pre-stiffened in the manufacturing operation by application of the thermoplastic resin, and more particularly a phenoxy resin. The phenoxy is a high molecular weight thermoplastic polyether resin based on bisphenol-A and epichlorohydrin with bisphenol-A terminal groups. The agent may be a water base type treatment, thereby being cost effective to apply. The agent may be considered a sacrificial resin application that has a brittle nature once applied, which leads to a short-term life once installed on papermaking machine 10. Once the treatment agent has been removed there is a permeability change of no more than 25% and preferably no more than 15% in end portions 22 and 24 as compared to untreated fabric in the rest of the fabric 14, 16 or 20. The treatment agent utilized on end portions 22 and 24 retains a stiffness even in hot and high humidity storage conditions yet it is brittle and a temporary bonding with the textile substrate. When installed on the papermaking machine the treatment quickly shatters and dissipates when exposed to the press nip and cleaning showers so there is little risk of it changing any performance of the fabric nor does the treatment change how the fabric is constructed. The treatment agent creates a stiffness when dry, but is also largely hydrophobic. The phenoxy resin, such as PKHW-34, from InChem of Rockhill, S.C., may be sprayed at approximately 5-25% solids in the seam area, also known as end portions 22 and 24. The quantity applied amounts to approximately 50 gsm of solids that are added on to the fabric. The treatment may be dried or cured at approximately 140° C. surface temperature with a 1.5 minute dwell time. End portions 22 and 24 may be approximately six inches in length across the full width of belts 14, 16 and 20.
Alternatively, the agent can be applied as a powder or a scrim. The agent applied is then melted to the fabric to provide the stiffness and other characteristics noted herein.
The agent applied in the treatment of end portions 22 and 24 substantially maintains the stiffness of end portions 22 and 24 while the belt is in storage even though the storage may be for a prolonged period of time and the storage condition include a humid and/or moist environment. It is the nature of the agent used in the present invention that interacts with end portions 22 and 24 to maintain the stiffness, yet have the flexibility and permeability of end portions 22 and 24 restored once belt 14, 16 or 20 is utilized in the papermaking machine. The fracturing of the agent when cycled a few times in the papermaking machine causes the agent to separate from the fabric of end portions 22 and 24 and to no longer influence the operation of the belt. Subsequent washing of the belt also serves to remove portions not separated from the belt once it is fractured. The removal of the agent can be considered a dissipation of the agent, which means that the agent is not interacting with the fabric and is so incidental that the agent may simply leave the papermaking machine as a part of the product, part of the belt washings or when routine cleaning is done in the work area in which the belt is being used.
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.
