Patent GB-675556-A (GB)
Title: Letter facing machine
Inventor: COPPING GEOFFREY PERCY
IPC: B07C1/20
Filed: 1949-02-02
Abstract: 675,556. Photo-electric sorting machines. POSTMASTER GENERAL. Feb. 2, 1949, No. 2910/49. Class 40 (iii). [Also in Group XL (c)] Letters are " faced before franking and sorting by feeding them to photo-electric scanning devices which locate the stamp corner. System, Fig. I.-Letters 9 are fed by a conveyer, with the long edge horizontal and a constant spacing between them to a device 10, which diverts those which are extra long or are spaced too close to the preceding letter, into piles 10a, 10b. The letters then proceed to the first scanning device 11 which may be that described in Specification 468,448. If a stamp is detected in area P in the leading corner the letter is diverted along route 12, if not it proceeds to a second scanning device 13. If a stamp is detected in the trailing corner Q the letter is diverted along route 14, if not, it proceeds to a device 15 which turns it over and then to scanners 16, 18 to examine corners R, S. If a stamp is detected there the letter is diverted to route 17 or 19 to join those from 12 and 14 respectively. If a stamp is not detected at P, Q, R, S, the letters proceed to a pile 20. Letters diverted into the two streams proceed to cancelling machines 22, 22a, and sizing machines 23, 23a, which sort them into piles 24, 25, 24a, 25a. The construction of the letter diverting and reversing devices is given in Figs. 7 and 8 respectively (not shown). Scanning unit, Fig. 2.-Leading edge letters passing from right to left along chain-dotted line 26, interrupt light beams to photo-cells BP, AP, C1P, to send impulses to the control unit Fig. 5, and then pass in front of the lens 27 of the scanning head. A dummy letter face 32 is viewed by the scanning head, in the " space " between the letters on the conveyer to provide a standard signal level for the amplifier A.V.C. (see Group XL (c)). The signals from the scanning head are fed after suitable amplification and demodulation to a control unit, together with the leading or trail edge pulses, Fig. 3 (not shown). Trailing edge.-The letters are assumed to pass from left to right along line 26 in front of the scanning head to actuate photo-cell AP, BP, C2P by increased illumination as the photocell passes. Control circuit, Fig. 5.-The symbol key is shown on the drawing, boxed symbols refer to trailing edge units. Operation-General.-The divertor control circuit comprises (a) gate valves requiring two positive input potentials to operate, and (b) trigger circuits which either transmit steady positive or negative potentials when reversed in one direction or the other. Pulses from the cells BP, AP, at the start and finish of the stamp area, together with the stamp signals cause either trigger 55 (with a stamped letter) or 59 (with an unstamped letter) to become reversed so that when the final pulse is sent from cell CP either 55 or 59 (which ever was reversed) are restored to normal to send a negative pulse 64 or 70 to trigger 58 controlling the letter divertor. The divertor remains set in one or other position re-operated. The " stamp " signal is fed after amplification to one input 50 of a gate valve 4B having a steady positive potential applied to the other input so that the gate is operated only by the high level " stamp signal " and not by background signals. Synopsis of operation (given in detail Fig. 5a). By stamped letter-leading edge unit.-Signals are received from cell BP, stamp scanner, cell AP, cell CP, in that order: (i) B(L-D) reverses triggers 51, 53 sending positive pulse 61 to get 4A stamp. (ii) 4B conducts restoring 51 to normal to send pulse 60 to trigger 52 which reverses and sends a positive pulse 62 to gate 4A which conducts. (iii) A(L-D) restores trigger 53 to normal, removing the second positive pulse to 4A which becomes non-conducting and reverses trigger 55. A(L-D) also reverses trigger 57 supplying positive potential 68 gate 6A. (iv) C1(L-D) restores trigger 55 to normal sending negative pulse to divertor trigger 58. Trigger 57 is also restored to normal removing potential 68 from gate 6A which is not operated. As the letter leaves the unit A(D-L) restores trigger 52 to normal ready for next operation. Unstamped letter-leading edge unit: (i) B(L-D) reverses trigger 51, 53 as before. In the absence of a stamp signal 4A does not conduct and trigger 55 remains normal. (ii) A(L-D) restores trigger 53 as before reverses trigger 57 causing gate 6A to conduct and reverse trigger 59. (iii) C1(L-D) does not affect trigger 55 which is normal, but restores 59 to send a negative pulse 70 to the diverter trigger 58. All triggers are now normal except 51 which is reset by the stamp signal from the dummy which causes 4A to conduct in the space between letters. Trailing edge units.-Operate similarly considering the boxed symbols instead of those in brackets on Fig. 5.