Title: Strip shape measuring device

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Abstract: For use in a rolling mill, a deformable, deflection roll with a continuous, unitary surface and a system for detection of roll deflection when a strip of sheet material is passed over the roll. The roll construction may include a dimpled or perforated surface or a multilayered roll may be provided of appropriate materials. The deflection detection system typically employs an optical scanning technique. This invention relates to the processing of metal strip particularly that which has been reduced to its final thickness by cold rolling. Ideally, metal strip should be of constant thickness throughout and should also be completely flat. This flatness should also be retained even after the strip is sheared or slit into smaller portions, for this operation frequently releases residual stresses in the metal. In practice strip flatness is extremely difficult to accomplish, and there is a tendency to overroll portions of the strip giving rise to the formation of centre or edge waves. Metal strip is usually cold rolled whilst being held under longitudinal tension so these edge or centre waves are not always obvious to a mill operator, additionally, such mills operate at high speed and with minimum operator supervisor so that even obvious waves, buckles and strip shape variations may not be detected. Several methods of controlling the shape of metal strip are available, but these require a suitable means of shape measurement. Previous shape measuring systems have attempted to measure shape by detecting stress distribution across the strip width, either by a non-contact electromagnetic sensor, or by deflecting the strip over a segmented roll, and measuring the force exerted by the strip on each segment. A limitation of these methods is their inability to measure the shape variation, or stress distribution with any accuracy in the vicinity of buckled or wavy areas, and their limited resolution near the strip edges due to the finite size of the sensing devices, even when these are reduced to a practical minimum width. To overcome this problem, the invention provides a method of measuring the shape of a moving strip, which method comprises passing the strip, held under tension, over a resilient deflection roll having a resilient outer surface, and measuring the depth of compression of the outer surface of said resilient deflection roll by the strip. The depth of compression is directly related to the stress distribution, which in turn is a measure of the variation in flatness. The depth of compression may be measured by measuring the distance of one or both surfaces of the strip from a fixed datum at the required number of positions across the width of the strip. This may be accomplished by any known distance measuring device, for instance, a triangulation method using either a scanning light source, or a line beam - the light source generally being a laser. This distance measurement can then be translated into a shape signal, which represents the combined effect of internal stress variations and surface buckling caused by the elongation variations .


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