Document Monitor By Light Transmittance For Enabling Printer

Abstract

The invention is concerned with the feeding of sheet material into a printing machine which can be set to print in a plurality of print positions corresponding to a plurality of types of document. The invention provides a feeding mechanism which monitors the type of document present by means of its light transmittance and enables or disables printing according as the detected type corresponds or not with the print position set. The apparatus is particularly useful in conjunction with machines for printing codes on documents such as cheques and bank credit transfers.

Description

This invention relates to machinery for printing sheet material, and provides a mechanism for receiving sheet material in such a machine.

The use of magnetic ink character recognition (MICR) and optical character recognition (OCR) for sorting documents such as cheques and credit transfers is well-known. It is necessary with these techniques to print each document with codes, for example account numbers, and these printed codes must be very accurately positioned (commonly to within twenty thousandths of an inch) with regard to some datum point. The datum point is generally the lower right-hand corner of the document, and it is known to position documents for printing by dropping a document into a slot and then forcing it downwards and to the right against a stop.

However, there are situations in which a more sophisticated procedure is required. For example, in some banking systems two type of documents are in common use, namely cheques which are supplied as single sheets of paper and credit transfers which are supplied as two-part-plus-carbon sets held together by detachable perforated portions to right and left. Therefore, to print an account number on the latter so that its position after separating the set corresponds to that on a cheque, it is necessary to print at a greater distance from the datum defined by the detachable portion. For this purpose machines are known which can be set manually to print in either of two positions.

It is obviously desirable to prevent printing when the printing position chosen does not correspond with the document fed in, and an object of this invention is to provide a mechanism for doing so.

Accordingly, the present invention provides a mechanism for receiving a sheet material for printing, including means for receiving the sheet material for printing, means for selecting one of a plurality of printing positions, a light source, a photo-responsive element positioned adjacent to the light source such that the sheet material when in said receiving means is positioned between the light source and the photo-responsive element, whereby the output of the photo-responsive element provides a measure of the light transmittance of the sheet material, and enabling means responsive to said output to enable printing when said output corresponds in a predetermined manner with the printing position selected and to inhibit printing when said output does not so correspond.

Preferably the means for receiving the sheet material comprises a substantially vertical slot, a stop at one end of the slot, and means for driving the sheet material against the stop.

Preferably, also, the means for selecting the printing position is a switch having one input contact selectively connectible to one of two output contacts to define a corresponding one of two positions, and in which said enabling means comprises two transistors each having its base connected to receive the output of the photo-responsive element and its collector-emitter path biased via a respective output contact of the switch whereby the conduction of the transistors is dependent on the occurence of an output signal from the photo-responsive element which corresponds to the selected switch position.

The mechanism may further include switching means operable to actuate a printing mechanism, and in which said transistors control a shunt means across the switching means to enable or inhibit printing.

The switching means may suitably be a thyristor arranged to discharge a capacitor through a solenoid coil.

The mechanism preferably also includes further photo-responsive means for operating the switching means when a sheet material is received in the receiving means.

The further photo-responsive means may comprise second and third photo-responsive elements spaced along the foot of the slot and a reset photo-responsive element spaced from the foot of the slot, the second, third, and reset photo-responsive elements being connected to said switching means through an AND-gate.

Preferably, the second, third and reset photoresponsive elements are connected to a further AND-gate arranged to inhibit further printing until the sheet material has cleared all three elements.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic front elevation of part of a document printing machine;

FIG. 2 is an end view corresponding to FIG. 1; and

FIG. 3 is a circuit diagram of control circuits associated with the device of FIGS. 1 and 2.

Referring now to FIGS. 1 and 2, a document printing machine includes a slot member 10. A sheet material to be printed such as a cheque 12 is dropped into the slot member 10 and is driven to the right by a rubber-covered wheel 14 until it abuts a stop 16. The mechanism also includes three lamps 18, 20, 22 which shine through apertures in the slot member 10 towards photo-responsive devices, in this embodiment phototransistors, 24, 26, 28 and 30, the two phototransistors 28 and 30 being adjacent and both illuminated by the upper lamp 18.

The lower phototransistors 24 and 26 and their respective lamps 20 and 22 are located at the bottom of the slot member 10 and co-operate with the circuit of FIG. 3 to ensure that the cheque 12 is fully down in the slot member before printing takes place, as will be explained.

The upper phototransistors 28 and 30 also work in conjunction with the circuit of FIG. 3, the former to prevent printing occuring a second time if the cheque 12 bounces, and the latter in accordance with the invention to distinguish between two types of documents, in this embodiment cheques and credit transfers of the type described above.

Turning now to FIG. 3, the circuit comprises positive and earthed supply lines 32 and 34, whose voltage is regulated by a Zener diode 36, supplied by a conventional rectifying circuit (not shown). A smoothing capacitor 38 is provided. The lamps 18, 20, 22 are connected in series across the lines 32, 34. The phototransistors 24-30 are each connected across the lines 32, 34 in series with a biasing resistor 40 and a variable resistor 42 which can be used to set the sensitivity of the phototransistor. Each phototransistor 24-30 is shunted by a capacitor 45 to minimise the effect of noise in the supply. The collector of each of the three phototransistors 24-28 is connected to the base of a respective switching transistor 44, 46 or 48, each connected to the supply lines 32, 34 by appropriate collector and emitter resistors 50.

The emitters of the three switching transistors 44-48 are connected to a "fire" AND-gate 52 formed by diodes 54, 56, 58 and their collectors are connected to a "reset" AND-gate 60 formed by diodes 62, 64, 66.

When a document is dropped into the slot member 10 and assumes the correct position, the illumination of the phototransistors 24, 26, 28 is obscured. This caused the switching transistors 44, 46, 48 to turn on, and the AND-gate 52 thus passes an output signal to the base of a transistor 68, through a resistor 69, causing it to turn on and fire a thyristor 70. This in turn causes a capacitor 72 to discharge through a solenoid coil 74 to operate the printing mechanism (not shown).

Correspondingly, when the document is completely removed, all three phototransistors 24, 26, 28 are illuminated and the reset AND-gate passes a signal to turn off a transistor 76 which turns off a transistor 77 which fires a second thyristor 78 via a resistor 79 to recharge the capacitor 72. It will be appreciated that as soon as one of the phototransistors 24-28 is illuminated, the signal to the gate of the first thyristor 70 is removed, and commutation is assured by a capacitor 80 interconnected between the anodes of the thyristors 70 and 78.

The method by which different types of document are distinguished will now be described. The particular embodiment is designed to print on cheques and credit transfers of the type described above. These can be distinguished by the fact that the credit transfer set has a different transparency than the cheque document. Therefore, in accordance with the invention, the fourth phototransistor 30 is used to detect the type of document by measuring the light transmitted and this is compared with the setting of a print position selector switch 82 (FIG. 3) to enable or inhibit printing, by means of the remainder of the circuit of FIG. 3 as will now be described.

Assume that the selector switch 82 is set to select the "short" printing position corresponding to a cheque. This is the position shown in FIG. 3, and it causes a "short" indicator lamp 84 to be connected via the switch 82 across the lines 32, 24 and therefore illuminated.

If now a cheque is fed into the machine, the phototransistor 30 receives sufficient illumination to conduct. This brings the collector side of the phototransistor down to almost zero volts and turns off two transistors 86, 88 whose bases are connected thereto. This in turn turns off a transistor 90 fed from the collector of the transistor 86, and thus holds off a further transistor 92 shunted across the gate of the thyristor 70 and earth. However, if a credit transfer document is fed, the phototransistor 30 does not conduct, and the transistors 86, 90, 92 and 100 are caused in sequence to conduct, thus short-circuiting the gate of the thyristor 70 and inhibiting printing. It should be noted that the other transistor 88 connected to the phototransistor 30 still does not conduct since its emitter is held at the positive supply voltage by the switch 82, via a lamp 94.

Similarly, setting the selector switch 82 to its other position causes illumination of a "long" indicator lamp 94. If then a credit transfer form is fed in, the phototransistor 30 does not conduct (owing to the relative thickness of the document) and the transistor 88 turns on. This turns on a further transistor 95 whose base is fed from the collector of transistor 88, and in turn this action switches on a transistor 96 which shunts the inhibiting transistor 92, allowing the machine to print.

The transistor 96 performs a further function. A fault light 98 is provided which is switched across the supply 32, 34 by switching transistor 100 whenever the inhibiting transistor 92 is on. To prevent the fault light 98 from illuminating when there is simply no document in the machine, when 82 is in "long" position, the base of the transistor 96 is connected via a resistor 102 to the collector of a transistor 104 whose base is fed by the emitter of 48 controlled by the reset phototransistor 28 and whose emitter is biased by resistors 106 and 108, arranged so that the emitter is two-thirds down from the potential of the positive line 32. Thus if no document is present, the transistor 104 conducts, holding the transistor 96 off and hence keeping the fault light off.

The present invention thus provides a mechanism for a printing machine which receives sheets to be fed and checks that the correct type of a number of types of sheets is present, in a simple manner. Furthermore, it will inhibit printing if two or more single sheets are inadvertently fed at the same time. I claim:

Claims

1. A mechanism for receiving a sheet material for printing, including means for receiving the sheet material for printing, means for selecting one of a plurality of printing positions, a light source, a photo-responsive element positioned adjacent to the light source such that the sheet material when in said receiving means is positioned between the light source and the photo-responsive element, whereby the output of the photo-responsive element provides a measure of the light transmittance of the sheet material, and enabling means responsive to said output to enable printing when said output corresponds in a predetermined manner with the printing position selected and to inhibit printing when said output does not so correspond.

2. A mechanism as claimed in claim 1, in which the means for receiving the sheet material comprises a substantially vertical slot, a stop at one end of the slot, and means for driving the sheet material against the stop.

3. A mechanism as claimed in claim 1, in which the means for selecting the printing position is a switch having one input contact selectively connectible to one of two output contacts to define a corresponding one of two positions, and in which said enabling means comprises two transistors each having its base connected to receive the output of the photo-responsive element and its collector-emitter path biased via a respective output contact of the switch whereby the conduction of the transistors is dependent on the occurence of an output signal from the photo-responsive element which corresponds to the selected switch position.

4. A mechansim as claimed in claim 3, including switching means operable to actuate a printing mechanism, and in which said transistors control a shunt means across the switching means to enable or inhibit printing.

5. A mechanism as claimed in claim 4, in which the switching means is a thyristor arranged to discharge a capacitor through a solenoid coil.

6. A mechanism as claimed in claim 3 including further photo-responsive means for operating the switching means when a sheet material is received in the receiving means.

7. A mechanism according to claim 6, in which the receiving means comprises a slot, a stop at one end of the slot, and means for driving the sheet material against the stop; and in which the further photo-responsive means comprises second and third photo-responsive elements spaced along the foot of the slot and a reset photoresponsive element spaced from the foot of the slot, the second, third and reset photo-responsive elements being connected to said switching means through an AND-gate.

8. A mechanism according to claim 7, in which the second, third and reset photo-responsive elements are connected to a further AND-gate arranged to inhibit further printing until the sheet material has cleared all three elements.