Geometrical instruments – Distance measuring – Of flexible material
Reexamination Certificate
1998-12-31
2001-01-30
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Distance measuring
Of flexible material
C033S0010BB, C033S501020, C033S712000, C033SDIG002
Reexamination Certificate
active
06178657
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a method of measuring a length of a sheet of material. More particularly, the present invention is directed to a method of measuring the internal web length differences of a width of sheet material, for example, a photographic film, paper, or base Support.
BACKGROUND OF THE INVENTION
During the manufacturing of web or sheet material, differential tensions can form across the width of the web or sheet material, for example, from thermal or length variations. These differential tensions cause differential strains or distortions to exist in the web or sheet material, resulting in the web or sheet material exhibiting distortions or non-planarity when positioned on a flat surface. The web or sheet material can exhibit non-flatness characteristics such as bumps, wariness at the edges, or ripples across the width.
FIG. 1
shows an exaggerated view of an unflat sheet
10
exhibiting wariness at the edges and
FIG. 2
shows an exaggerated view of unflat sheet
10
exhibiting bumps in a central portion of the sheet.
As mentioned above, these differential tensions can result from length variations, i.e., internal material length difference in the web or sheet material. For example, referring to
FIG. 3
, if sheet
10
were cut into a plurality of strips
12
, any strip
12
a
which exhibits a non-flatness characteristic (e.g., bump, wariness, or ripple) would have a length greater than (i.e., would be longer than) a strip
12
b
which does not exhibit a non-flatness characteristic.
Such internal length differences may be of particular concern when the sheet is used in a particular application. For example, in the printing industry or graphics art field, a final image may be generated using several different overlays. That is, several sheets each having a portion of the final image may be separately disposed in overlapping/overlaying registration onto each other to form the final image. If one of the sheets has sufficient internal length differences, the portions (of the final image) from the separate sheets will not properly register to each other. Consequently, the a final image that is produced may be unacceptable or unusable for its intended purpose.
Several methods have been employed to determine if a sheet includes non-flatness characteristics. For example, a user may conduct a simple visual inspection of the sheet. Such a visual inspection can be conducted by laying the sheet (or the section of the web material) on a flat surface or table, and then manually counting the number of bumps or waves in a given length. Such a visual inspection is time-consuming and prone to errors. In addition, this visual inspection does not provide a method for measuring the internal length differences in a web or sheet material.
An on-line web planarity measurement apparatus may provide an indication of whether the sheet includes non-flat characteristics. Such an apparatus is disclosed in U.S. Pat. No. 5,678,447 (Graff), commonly assigned and incorporated herein by reference. As noted above, the planarity of the web or sheet material is related to internal length differences. However, this reference does not provide a method for measuring the internal length differences in a web or sheet material.
In another method, the sheet is cut into individual strips, and then each strip length is measured. Such a method is accomplished by laying a section of the web material on a flat surface or table and then cutting a sheet from the web material. The resulting sheet has a uniform length across its width such that, as shown in
FIG. 3
, if the sheet is measured in it's full width form, the length X of the sheet is the same at every position Y across the sheet. The resulting sheet is then cut/slit into plurality of strips
12
. Each strip is then disposed within a mechanical apparatus to measure it's length. Such a method is time-consuming and prone to errors. In addition, many mechanical apparatus do not have the resolution required to measure the minute differential lengths necessary for Applicant's application, which are in the range of microinches. For example, if a raised area of the sheet has a dimension 0.005 inches from the flat surface with the length of the raised area being 3 inches in length in the direction of the measurement (i.e., in the X direction; the direction of the cut/slit), the additional length of material in the sheet is about 0.000023 inches (23 microinches).
Accordingly, while each of these methods may have achieved certain degrees of success in their particular applications, a need continues to exist for an apparatus and method for measuring the relative differential length of a web or sheet material. The apparatus should be suitable for measuring minute differential lengths, and the method should not be time-consuming or prone to errors. In addition, the method should not adversely affect the web or sheet material whose differential length is being measured.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus and method for measuring the relative differential length of a web or sheet material.
Another object of the present invention is to provide such an apparatus and method which is not time-consuming or prone to errors.
Still another object of the present invention is to provide such an apparatus and method which provides a high degree of resolution and accuracy.
Still a further object of the present invention is to provide such an apparatus and method which provides objective measurements with minimal operator handling and with minimal operator training.
Yet another object of the present invention is to provide such an apparatus and method which is suitable for use with photosensitive web material, including un-coated photographic base support material.
These objects are given only by way of illustrative example. Thus, other desirable objectives and advantages inherently achieved by the disclosed invention may occur or become apparent to those skilled in the art. The invention is defined by the appended claims.
According to one aspect of the invention, there is provided an apparatus for measuring the relative differential length of a sample of a web or sheet material, the sample having a top surface and a bottom surface. The apparatus comprises a substantially flat surface adapted to support the sample and an air exhausting means for removing air disposed between the sample and the substantially flat surface to dispose the sample in an unrestrained state. A plurality of non-contact sensors are adapted to sense the distance from a reference plane to the sample and generate a signal representative of the distance sensed. A translation member translates the plurality of non-contact sensors in a first direction along the length of the sample. A data collection system collects the generated signals and determines a relative differential length of the sample from the generated signals.
According to another aspect of the present invention, there is provided a method for measuring the relative differential length of a sample of a web or sheet material, the sample having a top surface and a bottom surface. The method comprising the steps of stationarily positioning the sample on a substantially flat surface such that the bottom surface of the sample is adjacent the substantially flat surface; removing air disposed between the bottom surface of the sample and the substantially flat surface such that the sample is in an unrestrained state; translating a plurality of non-contact sensors in a first direction along the length of the sample; sensing the distance from a reference plane to the top surface of the sample; generating a plurality of signals which are representative of the distance sensed; and determining a length from the generated signals, the length corresponding to the relative differential length of the sample.
The present invention provides an apparatus and method for measuring the relative differential length of a web or sheet material. The apparatus provides a h
Eastman Kodak Company
Fulton Christopher W.
Parulski Susan L.
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