Crack detector for edge of moving strip which discriminates between cracks and pin-holes

Claim 2

Apparatus for detecting cracks in an edge of a moving strip, comprising: a. a source of light disposed on one side of said strip; b. first light-sensitive means, disposed on the other side of said strip, adapted to receive only light from said source which passes through a first area of said strip; c. second light-sensitive means, disposed on the other side of said strip, adapted to receive only light from said source which passes through a second area of said strip, said second area being spaced apart from said first area both longitudinally and laterally of said strip; d. means for producing a first signal indicating that light from said source has impinged on said first light-sensitive means; e. means for producing a second signal indicating that light from said source has impinged on said second light-sensitive means; and f. means for producing an output signal indicative of a crack only when said first signal precedes said second signal by the time required for the strip to travel from said first area to said second area.

Claim 3

Apparatus for detecting cracks in an edge of a moving strip, comprising: a. a source of light disposed on one side of said strip; b. first and second light-sensitive means disposed on the other side of said strip in substantial alignment with said source of light, said light-sensitive means being spaced apart longitudinally of said strip; c. means, interposed between said strip and said light-sensitive means, for permitting only light from said source which passes through a first and a second area of said strip to impinge on said first and second light-sensitive means, respectively, said first and second areas being spaced apart from each other both longitudinally and laterally of said strip; d. means for producing a first signal indicating that light from said source has impinged on said first light-sensitive means; e. means for producing a second signal indicating that light from said source has impinged on said second light-sensitive means; and f. means for producing an output signal indicative of a crack only when said first signal precedes said second signal by the time required for the strip to travel from said first area to said second area.

Claim 4

Apparatus for detecting cracks in an edge of a moving strip, comprising: a. a source of light disposed on one side of said strip; b. first and second light-sensitive means disposed on the other side of said strip in substantial alignment with said source of light, said light-sensitive means being spaced apart longitudinally of said strip; c. means, interposed between said strip and said light-sensitive means, for permitting only light from said source which passes through a first and a second area of said strip to impinge on said first and second light-sensitive means, respectively, said first and second areas being spaced apart from each other both longitudinally and laterally of said strip; d. means for producing a first signal indicating that light from said source has impinged on said first light-sensitive means; e. means for producing a second signal indicating that light from said source has impinged on said second light-sensitive means; and f. means for producing an output signal indicative of a crack only when said first signal precedes said second signal by the time required for the strip to travel from said first area to said second area.

Claim 5

Apparatus as recited in claim 2, in which means (c) comprises: a. light-shielding means, positioned adjacent said edge of said strip, comprising a shielding element having an inner edge extending beyond said edge of said strip between said strip and said light-sensitive means; and b. first and second apertures in said shielding element, said apertures being adapted to permit only light from said source which passes through said first and second areas, respectively, to impinge on said first and second light-sensitive means, respectively.

Claim 6

Apparatus as recited in claim 3, in which said light-shielding means further comprises a second shielding element, disposed between said source of light and said strip, having first and second apertures therein in registry with the apertures in the shielding element extending between said strip and said light-sensitive means.

Claim 7

Apparatus as recited in claim 1, in which means (f) comprises: a. gating means, connected to the output of means (e) adapted to be opened by a control signal supplied thereto; b. means, connected to said gating means, for producing a signal indicative of a crack only when a signal from means (e) passes through said gating means; c. means for producing pulses at a rate proportional to the speed of said strip; and d. means for counting said pulses only when the signal of means (d) is produced, and for supplying a control signal to said gating means whereby said gating means is opened for a short time interval after a predetermined number of said pulses have been counted.

Claim 8

Apparatus as recited in claim 4, in which means is provided for maintaining the position of said light-shielding means constant relative to said edge of Said strip.

Claim 9

Apparatus for detecting cracks in an edge of a moving strip, comprising: a. a housing positioned adjacent said edge and adapted to move transversely with respect to the direction of strip movement, said housing comprising a first section which extends inwardly of said edge on one side of said strip and a second section in registry with said first section on the other side of said strip; b. a source of light disposed in said first section; c. first and second light-sensitive means disposed in said second section in substantial alignment with said source of light, said light-sensitive means being spaced apart from each other longitudinally of said strip; d. light-shielding means, positioned between said first and second sections of said housing and adapted to move in said housing transversely with respect to the direction of strip movement, comprising first and second shielding elements, in substantial registry, having an inner edge extending between said source of light and said strip and said light-sensitive means and said strip, respectively; e. first and second apertures in each of said shielding elements, said apertures being disposed in substantial alignment with said source of light and said first and said second light-sensitive means, respectively, and being spaced apart from each other both longitudinally and laterally of said strip; f. means connected to said light-shielding means for maintaining the position thereof constant relative to said edge of said strip; g. means for producing a first signal indicating that light has impinged on said first light-sensitive means; h. means for producing a second signal indicating that light has impinged on said second light-sensitive means; and i. means for producing an output signal indicative of a crack only when said first signal precedes said second signal by the time required for the strip to travel from said first aperture to said second aperture.

Claim 10

Apparatus for detecting cracks in an edge of a moving strip, comprising: a. a housing positioned adjacent said edge and adapted to move transversely with respect to the direction of strip movement, said housing comprising a first section which extends inwardly of said edge on one side of said strip and a second section in registry with said first section on the other side of said strip; b. a source of light disposed in said first section; c. first and second light-sensitive means disposed in said second section in substantial alignment with said source of light, said light-sensitive means being spaced apart from each other longitudinally of said strip; d. light-shielding means, positioned between said first and second sections of said housing and adapted to move in said housing transversely with respect to the direction of strip movement, comprising first and second shielding elements, in substantial registry, having an inner edge extending between said source of light and said strip and said light-sensitive means and said strip, respectively; e. first and second apertures in each of said shielding elements, said apertures being disposed in substantial alignment with said source of light and said first and said second light-sensitive means, respectively, and being spaced apart from each other both longitudinally and laterally of said strip; f. means connected to said light-shielding means for maintaining the position thereof constant relative to said edge of said strip; g. means for producing a first signal indicating that light has impinged on said first light-sensitive means; h. means for producing a second signal indicating that light has impinged on said second light-sensitive means; and i. means for producing an output signal indicative of a crack only when said first signal precedes said second signal by the time required for the strip to travel from said first aperture to said second aperture.