Measurement of paper curl tendency using specular and diffuse light reflection
AssigneeInternational Paper Company
InventorsDavid W. Vahey, James F. Suska
Life of this patent
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Abstract
A method for determining the tendency of a non-woven web to curl, where the web has a machine direction (MD), a cross-machine direction (CD) and the web includes a wire side and a felt side. The method comprises determining a wire ratio which is the ratio of the number of fibers oriented in the MD to the number of fibers oriented in the CD, where the fibers are associated with the wire side of the web, a felt ratio which is the ratio of the number of fibers oriented in the MD to the number of fibers oriented in the CD, where the fibers are associated with the felt side of the web, and determining the wire to felt ratio which is a measure of the tendency of the web to curl.
Claims5
A method for determining the tendency of a nonwoven web to curl, wherein said web has a machine direction, MD, a cross-machine direction, CD, and said web includes a wire side and a felt side, said method comprising:
- determining a wire ratio, (M/C).sub.w, which is the ratio of the number of fibers oriented in the MD to the number of fibers oriented in the CD, wherein said fibers are associated with the wire side of said web;
- determining a felt ratio, (M/C).sub.f, which is the ratio of the number of fibers oriented in the MD to the number of fibers oriented in the CD, wherein said fibers are associated with the felt side of said web;
- and
- determining a wire to felt ratio, (M/C).sub.w /(M/C).sub.f, which is the ratio of the wire ratio to the felt ratio, whereby the wire to felt ratio is a measure of the tendency of said web to curl.
An apparatus for determining the tendency of a non-woven web to curl, wherein said web has a machine direction, MD, a cross-machine direction, CD, and said web includes a wire side and a felt side, said apparatus comprising:
- means for mounting said web in a plane;
- a source of light, wherein said light is collimated into a beam of light angled to project onto the plane of said web at an incident angle;
- a specular detector for detecting the amount of light, S, reflected from the surface of said web at the specular angle from the plane of said web;
- a diffuse detector for detecting the amount of light, D, reflected from the surface of said web normal to the plane of said web;
- and
- a signal processor for processing S and D and thereby determine the tendency of said nonwoven web to curl, whereby said signal processor determines a wire ratio, (M/C).sub.w, which is a measure of the ratio of the number of fibers associated with the wire side of said web oriented in the MD to the number of fibers associated with the wire side of said web oriented in the CD, according to the equation:
- ##EQU11## wherein .alpha. is the angle of the beam of light with respect to the MD of said web, said signal processor determines a felt ratio, (M/C).sub.f, which is a measure of the ratio of the number of fibers associated with the felt side of said web Oriented in the MD to the number of fibers associated with the felt side of said web oriented in the CD, according to the equation:
- ##EQU12## and said signal processor determines a wire to felt ratio, (M/C).sub.w /(M/C).sub.f, which is the ratio of the wire ratio to the felt ratio, wherein the wire to felt ratio is a measure of the tendency of said web to curl.
Dependencies are inferred from the claim text.