Patent GB-997105-A (GB)
Title: Empty bottle inspection system
IPC: G01N33/00
Filed: 1962-11-29
Abstract: 997,105. Examining bottles photo-electrically. BARRY-WEHMILLER MACHINERY CO. Nov. 29, 1962 [March 19, 1962], No. 45135/62. Heading G1A. [Also in Division H3] An image of an empty bottle 14, Fig. 4, which is to be examined for cleanliness, is formed on a stationary scanning disc 56, Fig. 5, by means of a rotating optical assembly 48, 50, 52 whereby the bottle is scanned in a pattern of radial paths, Fig. 6, the arrangement being characterized by the provision of an apertured mask 54 of a size sufficient to encompass wholly two of the apertures 58 in disc 56 and the space therebetween. Furthermore apertures 58 are made larger than lines produced by lettering on the-bottom of the bottle but smaller than the minimum size of any undesired object in the bottle it is desired to detect. A photo-multiplier 24 responds to light traversing aperture 56, the light only falling to zero when an undesired object is encountered. In another embodiment, Figs. 1-3 (not shown), the scanning is effected by a rotating disc which operates in conjunction with a stationary apertured mask. The disc is formed with a spiral pattern of apertures, the angular spacing of which varies, becoming progressively smaller at the beginning and end of the spiral, so that the mask aperture, which is circular always encompasses wholly two of the disc apertures and the space therebetween. The photo-multiplier is included in a circuit, Fig. 7, which causes a solenoid 174 to be operated when the photo-multipler output falls to a low level, whereby the bottle is removed by reject mechanism (not illustrated). The output of the photo-multiplier is applied through amplifier 62, 64, 66, 68 and stages 74, 76 to stage 146 which is normally non-conducting but is rendered conducting when the photo-multiplier output falls to a low level in response to interruption of the light by an undesired object. Stage 74 is normally conducting but is cut off when its base potential is driven below the emitter bias level set by adjustable potentiometer 140 which determines the operation level of the circuit. The output from 146 is amplified in stage 152 and applied to trigger a silicon controlled rectifier 166 which actuates a relay 168. The relay isolates itself from rectifier 166 at contact 168A but remains operated for a time sufficient to charge capacitor 169. Contact 168A completes the circuit of reject solenoid 174 and an indicating lamp 176. In order that the circuit should operate only when a bottle is correctly located in an inspiration station, the signal path between stages 146 and 152 is rendered ineffective by a normally-conducting clamp stage 154 which is rendered non-conducting by brief impulse which is applied to its base from stage 162 via C.R. network 155, 15 6 when a switch 20 operates in response to a bottle becoming correctly located. Automatic compensation for variation in average light level caused by variation in the darkness and colour of the bottles is effected by applying the output of amplifier stage 68 through low-pass filter 84, 86 and stage 78 to an amplifier 96, 98, 100 which controls regulator 108, 110 in series with the power supply 120 for the photo-multiplier. Negative feed-back to the input stage 96 of the amplifier is applied from the final dynode via resistor 94. The feature of automatic compensation for variation in light level forms the subject of Specification 997,106. The output of stage 78 is also applied to a stage 80 which is biased at the emitter by adjustable potentiometer 142. When the photo-multiplier output falls below a level set by potentiometer 142, thereby indicating insufficient illumination, stage 80 is rendered conducting and operates stage 146 to actuate the reject mechanism.