Yarn inspector

Claim 1

Yarn inspecting means for inspecting a sheet of yarn comprising a multiplicity of yarns running side-by-side in a common plane for minor yarn defects, major yarn defects and yarn defects per unit length of said yarn sheet, comprising illuminating means at one side edge of said sheet for directing a light beam across said sheet in a direction perpendicular to the direction of travel of the yarn and in the plane of said sheet, receiving means at the opposite side of said sheet including photoelectric transducing means and optical means for receiving the light of said light beam and projecting an umbral edgewise image of said yarn sheet on said transducing means to produce an electrical input signal responsive to changes in the size of said image, and thereby responsive to yarn defects comprising portions projecting upwardly or downwardly from the plane of said yarn sheet, said signal comprising oscillations in a central band representing background noise resulting from normal characteristics of the yarn, positive peaks extending up from said central band and representing yarn defects and negative peaks extending down from said central band and representing yarn defects, means for preamplifying said signal; minor defect detecting means receiving signals from said preamplifying means and comprising means for selectively setting the sensitivity of said minor defect detecting means to determine the magnitude of minor defects detected, noise barrier means for blocking out the portion of said signal in said central band while leaving said positive peaks and negative peaks representing yarn defects, means for amplifying the remaining unblocked peak signals, representing defects means for counting minor defects exceeding a predetermined magnitude; major defect detecting means receiving signals from said preamplifying means and comprising means for selectively setting the sensitivity of said major defect detecting means to determine the magnitude of major defects detected, noise barrier means for blocking out the portion of said signal in said central band while leaving said positive peaks and negative peaks representing yarn defects, means for amplifying the remaining unblocked peak signals, representing defects, means for counting major defects exceeding a predetermined magnitude, means for detecting the number of defects per unit length of said sheet receiving signals from said preamplifying means and comprising means for selectively setting the sensitivity of said defects per unit length detecting means to determine the magnitude of defects detected, noise barrier means for blocking out the portion of said signal in said central band while leavIng said positive peaks and negative peaks representing yarn defects, means for amplifying the remaining unblocked peak signals, representing defects means for selecting a unit of length in which defects are to be detected, means for selecting the number of defects of said selected magnitude permitted in said selected unit of length, means for producing a signal herein designated a DPL signal when the number of defects of said selected magnitude occurring in said selected unit of length exceeds said selected number, and means for counting said DPL signals; output means selectively receiving signals from said minor defect detecting means, said major defect detecting means and said defects per unit length detecting means and supplying an output signal for effecting indicating and machine control functions.