Device for the continuous monitoring of the condition of the needle heads on a circular knitting machine

Apparatus for the continuous monitoring of the condition of the needle heads of a circular knitting machine which move past a predetermined point one after the other at a definite frequency, comprising a housing having a tube, an illuminating component and a receiving component disposed side by side in said housing, said illuminating component comprising:

• a light source, a condensing lens, a slit and focusing lenses for producing a light spot in the form of a line situated in the plane of an illuminated needle head, without light projecting laterally beyond it, said focusing lenses being disposed in the tube and consisting of a semicircular lens occupying substantially half the cross-section of the tube and a round aspherical lens occupying the entire cross-section of the tube disposed behind the semi-circular lens, the focal point of the semi-circular lens lying in said slit, said light spot being projected into an aperture substantially the size of the image of the light spot, a photo-receiver disposed behind said aperture and adapted to emit an electrical pulse signal in proportion to the luminous flux passing through the aperture, and a threshold value electronic device for receiving said signal, which when said signal undergoes a predetermined change is adapted to deliver a warning signal.