Apparatus for detecting surface elevations on a moving sheet

Claim 1

In an apparatus for inspecting a moving sheet of normally smooth surfaced material, such as paper, including light-gate means including a light gate member arranged for yieldably contacting a surface of said sheet material, the line of contact of said member with said surface normally being continuous throughout the length thereof in the absence of unwanted surface elevations on said sheet material, said line extending in a direction transverse to the direction of motion of said material past said member, illumination means illuminating one side of said line of contact, and detection means, including photoelectric means for generating an electric signal in response to light emanating from thE other side of said line of contact, the appearance of surface elevations at said line of contact causing said member to yield and move away from said surface, thereby interrupting said continuous contact and permitting light from said illuminating means to reach said photoelectric means, the improvement which comprises: a. a plurality of groups of elongated, light-transmitting fibers of transparent material, 1. each fiber having a longitudinal axis and longitudinally spaced first and second end faces transverse of said axis, 2. said first end faces being juxtaposed in the direction of said line of contact on said other side of said line, 3. the first end faces of the fibers in each group being directed toward an associated longitudinal section of said line for receiving light from said illumination means when the corresponding portion of said member moves away from said surface; b. said photoelectric means including a plurality of photoelectric cells, said second faces of said groups being directed toward said cells respectively.