GB1406392A - Container flaw inspection apparatus - Google Patents

Abstract

1406392 Photo-electric flaw detectors BARRY-WEHMILLER CO 14 March 1973 12186/73 Heading G1A In a transparent container flaw inspection apparatus each container is conveyed in a vertically upright position to an inspection station where it is illuminated by a plurality of laterally spaced light sources and the inside of the container is scanned by means of an image condensing lens system and a further optical system including a rotating prism by means of which bright spots produced by the illumination of flaws are focussed on to a photo-detector. The containers are transported by a conveyer to the inspection point where they are illuminated by three light beams each produced by a lamp having an integral parabolic reflector in front of which is positioned an adjustable rectangular aperture which is imaged by means of a lens at a plane positioned on the remote side of the container. The three beam systems are angularly spaced about the axis of the container to ensure that any flaw is illuminated irrespective of the orientation of the container. The flaws are detected by means of the scanning head shown in Fig.4 which is positioned vertically above the container C. A condensing lens system 25, 26 produces an image of the inside of the container in the plane Y and this image is scanned by means of a collimating lens 27 a dove prism 28 and a projection lens 29 across an array of three photocells 21 to 22. The prism 28 is mounted in a cylinder 30 which is rotated by means of a motor. A pair of carriers 36, 37 contain a plurality of collimating lenses 27 and projection lenses 29, a suitable pair being selectable by rotation of knob 35. In use flaws, such as spikes and birdswings, in the container are illuminated to produce bright spots of light on a dark background which are scanned across the detectors as the prism 28 rotates. The presence of the container at the measuring station is determined by the interruption of a light beam to produce a signal which primes a reject circuit. Detection of a flaw then triggers a solenoid to operate a reject mechanism. The use of a condensing lens system results in the formation of closely spaced images from containers of considerably different heights thus allowing the apparatus to be used with different size containers merely by adjusting the position of the head relative to the neck of the container to achieve the desired field of view. In a modification, Fig.6 (not shown), the image is produced by the condensing lens close to the lower end of the dove prism and the "collimating" lens is moved to a position above the prism close to the projection lens. In a further modification, Fig.7 (not shown), the prism used is a double dove prism, i.e. two dove prisms with their reflecting faces cemented together.