Presses – Methods
Reexamination Certificate
1999-11-04
2001-07-03
Gerrity, Stephen F. (Department: 3721)
Presses
Methods
C100S15500G, C100S176000, C162S205000, C428S036300, C428S036400, C492S020000, C492S048000, C492S059000
Reexamination Certificate
active
06253671
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 of German Patent Application No. 198 51 936.2, filed on Nov. 11, 1998, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a process for glazing a material web, in particular a paper web, in which the material web is guided through at least one nip, which is formed by a roller having an elastic covering made of a plastic reinforced with fibers or appropriate fillers and an opposing roller. The invention further concerns a roller for a glazing calender with a uniform structure on its surface.
The invention is explained in the following with reference to a paper web as an example of a material web. It is, however, also applicable with other material webs for which the conditions are similar.
2. Discussion of Background Information
In one of the final production steps, a paper web is glazed, i.e., guided through at least one, but usually a plurality of nips or roll gaps of a calender, where it is subjected to pressure and high temperature. The paper web is more than merely compacted by this. It is also desirable to influence other properties of the paper web, for example, glaze and smoothness. Another property which can be influenced during glazing is transparency. In printing papers, high opacity, i.e., low transparency, is often desired. In contrast, in so-called technical papers, such as silicon paper, glassine, and drawing paper, high transparency is often desired.
High transparency is obtained with prior art super-calenders when glazing is performed under high temperature, high pressure, and high humidity. Here, a black glazing undesirable in other papers, is deliberately produced. It is assumed that in this glazing the paper fibers are crushed to a point at which light permeability is, in contrast, possible.
Tests have demonstrated that transparency may be deliberately influenced only with relatively great difficulty using plastic rollers, i.e., rollers with an elastic covering made of a fiber-reinforced plastic. In particular, it has been relatively difficult to date to produce high transparency using plastic rollers.
SUMMARY OF THE INVENTION
The invention resides in influencing or controlling the transparency of a material web using plastic rollers.
This is accomplished by a process of the type mentioned in the Background, in that the primary orientation of the fibers in the roller covering is selected as a function of the desired glazing result.
The orientation of the fibers in the covering is used as an additional influencing variable. To obtain high opacity, i.e., low transparency, fibers which lie substantially parallel to the roller surface are used. The paper web is then acted on by the “broad side” of the fibers such that the compressive stress is distributed over a relatively large zone of the reinforcing fibers. Accordingly, the local stress on the paper web, i.e., the stress on individual paper web fibers, remains low. In contrast, if high transparency is desired, then the fibers are oriented perpendicular to the roller surface, i.e., virtually radially. In this case, the paper web comes into contact with the cross-sections of the reinforcing fibers such that a compressive stress acting on a reinforcing fiber is substantially concentrated on the cross-section of this fiber. Accordingly, the paper web is relatively highly stressed locally, which results in the aforementioned crushing or destruction of the paper fibers, which is so extensive that light can pass through. This yields the desired high transparency. It is possible, within certain limits, to control the transparency of the paper web with the orientation of the fibers. If the fibers are oriented at an angle substantially between 90° and 0° relative to the surface of the roller, this yields different sized fiber cross-sections depending on the angle. These, in turn, are responsible for the appropriate stress on the surface of the paper web. The steeper the fibers stand, i.e., closer to 90°, the greater the transparency that is achievable. This basically involves only the orientation of the fibers on the roller surface. In lower-lying layers below this surface, differently oriented fibers may also be present or the individual fibers in lower layers may be folded. Consequently, a “primary orientation” refers only to the zone of the covering and below the surface which is provided for the processing of the paper web. Of course, the orientation of the fibers (in the following, the term “fibers” also always refers to comparable fillers) can be such that they can pass beyond the thickness of the covering, i.e., protruding. The selection of the fiber orientation takes place through the preparation and subsequent use of a roller with the desired fiber orientation.
Preferably, a fiber cross-sectional size and shape (e.g. diameter for a circular fiber) is selected as a function of the desired glazing result and the primary orientation of the fibers. The fiber cross-section size also naturally has an influence on the stress applied to the paper web or the paper web fibers. The greater the fiber diameter, for example, the greater the surface on which the pressure can be distributed. The distances between the fibers also increase according to the size of the fibers, i.e., the zones of the surface filled only with plastic become larger. Given that the “transparency” of a paper web results basically from an accumulation of very small spots, it is clear that it is possible to influence the degree of transparency by selecting the size of the spots.
The fiber cross-section is selected such that it corresponds to, for example, the diameter of the paper fiber. Alternatively, the fibers may have cross-sectional sizes and shapes which are polygonal, circular, oval, or other similar shapes. While the fibers are described herein in terms of a diameter cross-section, other cross-sectional shapes are contemplated by the invention. Referring again to the paper web, it is further noted that paper fibers have a certain scatter range of their diameter. However, it suffices for the diameter of the reinforcing fibers to be within the range of the diameters of the paper fibers. In selecting the diameter of the reinforcing fibers, it is simultaneously possible to consider the type of paper web as well. Here also, there are certain differences in the diameter of the paper fibers. If the diameter of the reinforcement fibers is adapted to the diameter of the paper fibers, the practical result is that an adequate number of paper fibers are acted upon by a reinforcing fiber and thus crushed. Thus, the desired high transparency is achieved.
The invention is also attained by having a roller, of the type mentioned in the Background, include a uniform nonhomogeneous hardness distribution over the entire surface.
With a roller of this type, it is possible to process the paper web very deliberately such that high transparency is obtained. The entire surface is macroscopically homogeneous, i.e., has a uniform surface structure. However, microscopically, the hardness of the surface differs from zone to zone. Thus, the hard zones are capable of crushing the paper fibers since an appropriately high compressive stress prevails there. In contrast, there is only a very low transfer of force to the paper web in the soft zones. Since the “harder” and “softer” zones can be extremely close to each other and have only a very small area, it is possible to produce a group of light-permeable points in the glazed paper web which are so close together that the paper web as a whole obtains high transparency.
The surface has adjoining surface zones of different hardness, such that the size of an individual hard surface zone is on the order of the size of the diameter of a paper fiber. This applies at least to the size of the hard surface zones. The soft surface zones located between them may be even smaller. With such a design, it is guaranteed that an adeq
Gerrity Stephen F.
Greenblum & Bernstein P.L.C.
Voith Sulzer Papiertechnik Patent GmbH
LandOfFree
Process for glazing a material web and roller for a glazing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for glazing a material web and roller for a glazing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for glazing a material web and roller for a glazing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2466704