Apparatus for recognizing residual yarn remaining on textile bobbins after unwinding utilizing a sensing device comprising a photooptic detector with a receiver lens

Apparatus for recognizing the presence of residual yarn on a textile bobbin comprising a device for optically sensing yarn and means for moving one of the sensing device and the textile bobbin relative to the other longitudinally with respect to the axis of the textile bobbin, said sensing device comprising a light transmitter for generating a limited beam of light rays, a transmitter lens for focusing the light rays onto the surface of the textile bobbin, and a photooptic detector having a receiver lens for receiving the light rays reflected off the surface of the textile bobbin, said transmitter lens and said receiver lens having respective optical axes which, during relative movement between said sensing device and said textile bobbin:

• (a) intersect one another in the area of the surface of the textile bobbin, (b) are oriented relative to the textile bobbin such that a line bisecting said optical axes deviates from a line which is perpendicular to the surface of the bobbin and which intersects the point of intersection of the optical axes by an angle of deviation of at least about ten degrees (10.degree.), and (c) lie in a common plane oriented at an angle of at least about ninety degrees (90.degree.) relative to a line representing the path of relative movement of the focused light rays from said transmitter lens longitudinally along the surface of the textile bobbin.