GB1333220A - System for detecting dark blemishes on coins or like objects - Google Patents

Abstract

1333220 Inspecting coins and the like NORTH ATLANTIC RESEARCH PRODUCTS Ltd 26 Oct 1970 [11 Nov 1969] 55205/69 Heading G1A A system for detecting blemishes in coins and like objects travelling past an inspection station comprises an array of photo-cells coupled to an electronic logic circuit the circuit being designed so that a coin without any blemishes will produce a continuous signal for the duration of its passage past the photo-electric array and so that the presence of any blemish will interrupt the signal to produce two or more signals in sequence and therefore the blemishes can be detected by a count of two in a "counter" in the logic circuit. In the embodiment an illuminated coin travels past a vertical array of 12 photo-cells 2, the output of each photo-cell being connected to a separate differential amplifier 3 whose output is connected to a one shot multi-vibrator 18, a delay amplifier 10, a further one shot multivibrator 9 and to one input of a "12 OR gate" 6. The one shot amplifier 18 and delay amplifier 10 are connected to a "2 OR gate" whose output is connected as shown to a "3 AND gate". The aforementioned circuit elements cause the "3 AND gate" to provide a continuous signal for a coin without blemish and provide a succession of two or more signals if the coin has a blemish above a predetermined size. The "3 AND gate" is connected to a counter 13 which provides a signal to one input of a further "12 OR gate" 14 each time it receives two successive signals, the "12 OR gate" then sets a reject memory 15. When all the photo-cells stop receiving light at the trailing edge of the coin, the last one to receive light closes the "12 OR gate" which sends a signal transferring the decision in memory 15 to a hold memory 16 and also resets memory 15 as well as setting each counter back to zero via line 17. The hold memory can operate alarm counters or reject diversion gates.