GB973150A - Improvements in or relating to the sorting of letters and other thin flat articles - Google Patents

Abstract

973,150. Statistical apparatus: sorting machines. POSTMASTER GENERAL. Aug. 23,1962 [Aug. 24, 1961], No. 30612/61. Heading G4M. In a letter sorting machine the letters are printed with a series of uniformly spaced dark bars, Fig. 1, the spacing of the bars corresponding to their destinations. The letters are illuminated as they pass through the machine, light reflected from the code patterns being sensed by a first photo-cell, and the leading edge of the letters being sensed by a second photo-cell. Detection of the leading edge of the letter causes monostable circuits 102, 103, 104, Fig. 4 to be triggered. Monostable circuit 102 removes an inhibiting bias from detectors 44-46 for,a period corresponding to the length of the pattern of bars on each letter. Filters 41-43 are tuned to respective different frequencies corresponding to the destinations and supply detectors 44-46 which in turn supply an output only if a signal is present at their input for more than a predetermined period in order to reduce the effect of transient signals. An output from detector 44 or 45 energizes one or other winding of polarized relay 49 whose contact 50 prepares a circuit for operating magnet 51 or 52 of deflector 16 or 17, Fig. 2, and through OR gate 53 sets bi-stable circuit 54. When monostable circuit 103 restores to normal, circuit 54 is reset and monostable circuit 55 is triggered to operate relay 56 and energize the selected magnet 51 or 52 in time to deflect the letter to pocket 20 or 21. If, on the other hand, detector 46 produces an output, bi-stable circuit 57 is set,the latter being reset on the restoration to normal of circuit 104, and the resulting pulse from circuit 54 after being delayed by successive monostable circuits 105-109 operates relay 110 to energize magnet 112 of deflector 23 at the appropriate instant so as to direct the letter into pocket 26. Unmarked letters are directed into pocket 27. The sorter can be used for sorting envelopes of a different football pool promoters from each other and from ordinary mail, or for sorting paid cheques into groups corresponding to the originating banks.