| 摘要 |
1,155,181. Sorting apparatus; character recognition. LUNDY ELECTRONICS & SYSTEMS Inc. 1 June, 1966 [1 June, 1965], No. 24525/66. Headings G4M and G4R. Character sensing apparatus develops an analogue signal of variable polarity in response to each character, a plurality of fixed threshold levels are made effective at predetermined times relative to the beginning of the analogue signal, and the polarity of the portions of the analogue signal which exceed the effective threshold levels is used to produce digital signals representative of the sensed character. Document transport.-Documents fed from a stack are aligned against a fence by skewed rollers before reaching a magnetic sensing station through which they are fed at constant speed by aluminium, knurled rollers driven by a synchronous motor. The documents are then slidingly engaged by belts 80, Fig. 3B to reduce their speed, and then rollers 81, 93 feed the documents to the pockets 90. The deflectors are leaf springs which are normally flush with plates 250, but which may be raised by an associated solenoid to direct documents round roller 93 and between rollers 93 and 232 into the pockets, the document being stiffened by flexing transversely against a wire as it enters. Another wire deflects the trailing edge to the left to ensure that a following document is stacked on top. A further wire 241 actuates a microswitch when a pocket is full to light an associated lamp 245 and stop the machine. Document detectors.-Photo-cells 95 are placed between pockets 3-9 for synchronizing the operation of the deflectors to the progress of the documents. A photo-cell 94 is used to gate out the pocket selection signal from the character recognition circuitry, and further photocells disposed on either side of the sensing station are used for the field selection and jam detection functions. Jam detection.-While a photo-cell is covered by a document, a respective capacitor is allowed to charge up, and if the voltage across the capacitor reaches a predetermined level, signifying that the document speed is too low, a jam detector relay is energized to stop the trans port and feeding mechanisms. The photo-cells arranged on either side of the sensing station are also used to trigger the jam detector relay if the spacing between documents is too small. Field selection.-Document detectors such as 82, Fig. 17A are spaced from the sensing station so that as the leading edge of a document covers a detector, the corresponding field enters the sensing station. A signal from a selected one of these detectors is derived from jam detector circuit 365 and is applied to field verification circuit 360, the latter enabling a drive trigger 385 to supply one pulse per character to counter 406, provided the signal from 365 arrives not more than 6 milliseconds before the detection of the first character on the check or one of the field symbols as selected by switch 86. If there is a larger gap between the signals, circuit 360 resets character output gate circuits 415 througl OR gate 400, Fig. 17B. Column selection.-Switch 407 selects the position of a character in a field on which sorting is to be based, and enables gates 415 to set the appropriate one of these circuits in accordance with the output of character recognition gates 340. Deflector control.-The pocket selection signal stored in gates 415 is read out through gates 420 on detection of the document leading edge by photo-cell 94. Pocket "0" is actuated directly pockets 1 and 2 after respective delays 262, and the remaining pockets are actuated when the respective pocket selection signals have been passed through a chain of delay flip-flops 262 by gates 263 which are enabled by the successive document detectors 95. Character recognition.-The signal from the sensing head 187 is applied to an amplifier having an A.G.C. circuit which is set in dependence on the amplitude of the initial positive pulse which is produced by the leading edge of each character. This amplifier is followed by a differentiating and noise clipping circuit, Fig. 19A (not shown), and feeds negative and positive threshold devices 295, 296 through respective gates. The initial positive pulse is able to pass directly to device 296 which starts clock 300 to supply gating pulses to 295, 296 and to step counter 302. In response to successive outputs from counter 302, generator 297 supplies respective different threshold levels to 295, 296 for seven successive sampling instants during the reception of a character waveform. Whenever one of the threshold levels is exceeded at a sampling instant, the corresponding + or - gate 330, 331 is enabled and a bi-stable circuit associated therewith is set. The complementary outputs 332, 333 are connected in appropriate combinations to recognition gates 340 to set a bi-stable circuit in the appropriate one of gate circuits 415. Under certain circumstances, a character e.g. "1" may be read as itself and also as another character e.g. "2", and whenever such a pair of outputs appears from gates 415, one of the outputs is reset by a gate 418. This resetting takes place within a short time interval, and if, at the end of this interval, a multiple output still exists, check circuit 440 resets gates 415. A further check circuit 445 resets gates 415 if any of the latter produce an output for an excessive period.
|
