Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Woven fabric – Including strand which is of specific structural definition
Reexamination Certificate
1999-04-16
2001-07-24
Cole, Elizabeth M. (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Woven fabric
Including strand which is of specific structural definition
C442S196000, C428S397000, C162S900000, C162S902000
Reexamination Certificate
active
06265331
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 of German Patent Application No. 198 17 050.5, filed on Apr. 17, 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 wire-screening fabric for a machine for the production and/or finishing of a cellulosic or pulp web, in particular a paper, cardboard, or tissue web comprising at least one layer of lengthwise fibers oriented in the direction of travel of the wire-screening fabric, and crosswise fibers running at a right angle thereto, woven together.
2. Discussion of Background Information
Such wire-screening fabrics are known, for example, from DE-OS 41 41 139, which is hereby incorporated by reference herein in its entirety. In addition to good stability, there is also a high water vapor permeability, so that the water vapor can be discharged through the wire. Moreover, the wire-screening fabric is designed largely closed to mark the pulp web as little as possible. In the aforementioned published application, this is accomplished in that the fibers have a trapezoidal cross-section, whereby the parallel sides run parallel to the direction of travel. However, the adhesion of the pulp web on the wire-screening fabric of the above-cited document is in need of improvement.
SUMMARY OF THE INVENTION
In wire screening fabrics in accordance with the invention, at least some of the crosswise fibers have a generally drop-shaped or substantially three-sided, acute-angled cross-section, whereby a pointed (or narrower) end is oriented roughly in the direction of travel of the wire-screening fabric. A mixture of crosswise fibers having either of such cross-sections may be employed.
The flow of air along the crosswise fibers as a result of the travel of the screen generates a vacuum downstream (with respect to the relative travel of air and the screen) from the crosswise fibers, because of the special shape of the cross-section, which improves the adhesion of the pulp web on the wire-screening fabric. This can be further improved in that the angle between the bisector of the pointed end of the respective cross-section and the surface of the wire-screening fabric contacted by the pulp web is between about 2° and about 70°, preferably between 5° and 40°. An increased portion of the air flow divided by the pointed end of the crosswise fiber is diverted away from the surface contacted by the pulp web, which increases the vacuum downstream from the crosswise fiber. This effect of the formation of a vacuum is also very pronounced when the side of the crosswise fiber facing the pulp web runs roughly parallel to the pulp web or is angled relative thereto such that the distance between the two increases opposite the direction of travel of the wire-screening fabric. Moreover, advantageous aspects of the screen, such as good water vapor the stability, and closed design are affected little thereby.
To ensure an adequate adhesion, it is sufficient in some embodiments that substantially only the crosswise fibers in the region of the surface of the wire-screening fabric contacted by the pulp web have a drop-shaped or substantially three-sided, acute-angled cross-section. In this case, the crosswise fibers in the region of the surface of the wire-screening fabric not contacted by the pulp web have a flat cross-section and are preferably oriented roughly in the direction of travel. In instances where a strong adhesion is desired, for example, with heavy papers, all crosswise fibers in accordance with the invention should have either a roughly drop-shaped or substantially three-sided, acute-angle cross-section.
The lengthwise fibers should always be flat or round, which reinforces the stability and has little influence on the flow relationships on the crosswise fibers. A mixture of lengthwise fibers having a flat or round cross-section can be employed. The wire-screening fabric is particularly well suited for use in a former, in a pressing section, or in a drying section of a paper machine.
A relatively simple way in which the fibers used in the invention, having the cross-sections according to the invention, may be produced comprises guiding fibers through the molding gap of two rolls, whereby at least one roll has a groove running in the circumferential direction to form the cross-sectional profile of the crosswise fibers. Moreover, it is possible to obtain this shape already during initial fiber formation, such as casting (extrusion) of the crosswise fibers by means of an appropriate nozzle (die).
In certain aspects the invention provides a wire-screening fabric for a machine for the production or finishing of a cellulosic web, the machine comprising a side for contacting the cellulosic web comprising at least one layer of lengthwise fibers oriented in a direction of travel of the wire screening fabric, and crosswise fibers generally transverse thereto, the fibers being woven together. At least some of the crosswise fibers comprise fibers having a cross sectional shape comprising a wide end and a narrow end, the shape selected from a shape which is substantially drop-shaped; and a shape which is substantially three-sided, and acute-angled. The narrow end of the cross sectional shape is oriented generally in the direction of travel of the wire-screening fabric.
In certain embodiments, the crosswise fibers are oriented at a right angle to the lengthwise fibers.
In certain embodiments, the narrow end of the cross-sectional shape of the crosswise fibers comprises a bisector, and the angle between the bisector of the narrow end and of the side of the wire-screening fabric for contacting the cellulosic web is between about 2° and about 70°. In certain embodiments, the angle is between about 5° and about 40°.
The crosswise fibers may comprise a side facing the side of the wire-screening fabric for contacting the cellulosic web, wherein the side is generally parallel to the side of the wire-screening fabric for contacting the cellulosic web or is angled relative thereto such that the distance between the side of the crosswise fiber and the side of the wire screening fabric increases opposite the direction of travel of the wire-screening fabric.
The wire-screening fabric may comprise a region contacted by a cellulosic web, and having crosswise fibers therein, and a region not contacted by a cellulosic web having crosswise fibers disposed therein, wherein substantially only the crosswise fibers in the region of the wire-screening fabric contacted by the cellulosic web have the above cross-sectional shape.
The crosswise fibers in the region of the wire-screening fabric not contacted by a cellulosic web may have a flat cross-sectional shape having a major axis, the major axis being oriented generally in the direction of travel of the wire screening fabric.
Substantially all of the crosswise fibers may have Such cross-sectional shapes. Of such shapes, substantially all may be either substantially drop-shaped substantially three-sided and acute-angled, or the fibers may be made up of a mixture of such fibers.
The lengthwise fibers may comprise fibers having cross sectional shape selected from flat or round, and substantially all lengthwise fibers may have a flat cross sectional shape, or have a round cross sectional shape, or the lengthwise fibers may be made up of a mixture of such fibers.
Such wire-screening fabrics may be employed in paper machines, such as in the former, press section or drying section.
In other aspects, the invention relates to a combination, comprising a cellulosic web and a wire-screening fabric for a machine for the production and/or finishing of a cellulosic web. The wire-screening fabric comprises a side contacting the cellulosic web and at least one layer of lengthwise fibers oriented in a direction of travel of the wire screening fabric, and crosswise fibers generally transverse thereto, the fibers being woven together. At least some of the crosswise fibers comprise fibers
Cole Elizabeth M.
Greenblum & Bernstein P.L.C.
Ruddock Ula C.
Voith Sulzer Papiertechnik Patent GmbH
LandOfFree
Wire-screening fabric, methods of using the same, and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wire-screening fabric, methods of using the same, and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wire-screening fabric, methods of using the same, and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2538862