Patent GB-968595-A (GB)
Title: Monitoring system
IPC: G06K13/067
Filed: 1960-12-16
Abstract: 968,595. Photo-electric control. BURROUGHS CORPORATION. Dec. 16, 1960 [Dec. 24, 1959], No. 43440/60. Heading G1M. [Also in Divisions B3 and B8] A monitoring system for items being conveyed along a path comprises first and second monitoring signal sources at stations along the path, the first source producing both a signal in response to the leading edge of an item entering the first station and another whenthe trailing edge leaves it and the second source producing a further signal when a predetermined edge of an item passes through the second station, signal detecting means being connected to receive all three signals and being responsive if the signal from said second'source is received in a predetermined time relative to one of the signals from the first source. In a cheque sorting machine in which cheques are conveyed at a nominally constant speed past three stations the passage of each cheque past a station is sensed photo-electrically and cheques greater than a predetermined length, or an interval between cheques of less than a standard amount, or gross departures from the nominal speed, are detected to cause operation of an alarm and interruption of the feeding of cheques to the conveyer system. At each station interruption by a passing cheque of light incident upon a phototransistor 137, Fig. 3A, causes reduction of the collector current for the duration of the interruption. The resultant negative going voltage excursion of the collector is differentiated by the transformer 143 to produce a negative going pulse when the leading edge of a cheque passes the station followed by a positive going pulse when the trailing edge passes. These pulses are shaped by transistor circuits 151 and 161 which respectively form sources of leading and trailing edge monitoring signals (as square shaped negative pulses) utilized in the circuit of Fig. 2. As a cheque passes the first station 37, Fig. 1, it gives rise to a leading edge monitoring signal Lb from a source 35 and then a trailing edge signal Tb from a source 39. Similarly the passing of the second station 43 occasions a leading edge signal Lc from a source 41 and a trailing edge signal Tc from a source 45, whilst a trailing edge passing the third station 49 gives rise to a signal Td from a source 47. An Lb signal is recorded by its action of setting a bistable stage 67 whose output conditions an AND gate 71 to an "allow" condition. If the next Tb pulse arrives at the bistable stage 67 before an Lc pulse arrives at the AND gate 71 from a delay line 77, the bistable stage is reset to provide an "inhibit" action at the gate and cheques continue to circulate. If, however, the item is over length the Lc signal will arrive'at the AND gate whilst this is in the' "allow" condition and in consequence a further bistable stage 87 will be set and an "overlength item" alarm 89 operated. The maximum length of cheque acceptable is dictated by the sum of the physical separation of the first two stations and the product of the conveyance speed and the delay introduced by the delay line 77, and this may be varied. For detecting a space between cheques less than the distance between the second and third station the sequence of the leading edge of the second cheque at the second station 43 giving rise to an Lc signal before the generation of a Tc signal consequent upon the trailing edge of the first cheque passing the third station 49 serves as a criterion. The trailing edge of the first cheque at the second station 43 gives rise to a Tc signal which sets a bistable stage 119 to apply an "allow" condition to an AND gate 117. Hence if the Lc signal corresponding to the second, following, cheque's leading edge at the second station arrives at the AND gate 117 before the Td signal due to the first cheque at the third station resets the bi-stable stage 119, yet another bi-stable stage 125 is set and an "underspaced items" alarm 127 is operated. Delay may be introduced into the passage of the Lc signal from its source 41 to the AND gate 117 and its effect is to reduce the minimum acceptable distance and it may be made variable. Either alarm condition will cause another AND gate 101 to be conditioned to the "allow" state so that the next cheque to be fed from the input hopper 13 past a further station 103 gives rise to a monitoring signal Ta which passes through gate 101 to set a bistable stage 107 whose output signal disconnects supply to the feed motor 25. If, for either test, delay is introduced into the circuit of the Lc signals the delay would serve as the time scale against which departures of the conveying speed from the nominal value would be measured. It is stated that the apparatus may be applied to any sequence of physical and analytical operations such as the machining and inspection of castings. Specifications 888,718, 926,247 and 968,596 are referred to.