IL42699A - Device for counting sheets of paper - Google Patents

Description

CONTROL MECHANISMS FOB DOCUMENT HANDLING APPARATUS D»DBOO-J 7130? 1Ϊ^Γ>Π7 m?2 ΐ1Π30 " V The present invention relates to electronic control means and more particularly to novel electronic control means for use with document handling equipment for feeding, separating and stacking documents which electronic equipment monitors all phases of the physical operations to provide reliable and accurate feeding, counting and stacking and to prevent jamming.

BACKGROUND OF THE INVENTION Document handling devices are presently employed in a large number of different applications. Some examples of such document handlers are devices for counting checks, punch cards, food stamps, paper currency and bank coupons, to name just a few. The basic requirements of such devices are to provide reliable operation at relatively high operating speed in the feeding, separating^ endorsing and stacking of the documents being handled. For example,during such high speed operations, a separation between documents may be quite small, requiring a sensing device capability of detecting such small separation distances.

It is also well known that the documents feeders providing such high speed operation generate an appreciable amount of dust which, together with other ambient conditions, serves to deteriorate the sensitivity and hence the capability of the sensing means to function properly.

BRIEF DESCRIPTION OF THE INVENTION AND OBJECTS The present invention is characterised by providing means for overcoming all of the aforementioned disadvantages through the use of novel sensing means having a capability of automatically adjusting its sensitivity in accordance with changes in ambient conditions and responding to deviations from a predetermined level.

The sensing means further incorporates means for counting the documents and sensing the gap between separated documents and further incorporates means for distinguishing gaps greater than a predetermined size between adjacent documents from smaller perforations provided within documents (such as punch cards ) or slits or tears and the like which may be formed as a result of partial or even severe mutilation of a document by means of signals that persist for greater than a predetermined time period.

All of the above capabilities are obtained in a control means which has the further novel capability of increasing the flexibility and effectiveness of the documents handling apparatus to perform a variety of document handling operations such as, for example, endorsing/batching and statistical sampling not heretofore capable of being obtained through document-handlers and control devices which have heretofore been available. w It is therefore one object of the present invention to provide a novel control means for document handlers and the like capable, of automatically adjusting its reading sensitivity in accordance with changes in any one of a variety of ambient conditions affecting the operation.

Another object of the present invention is to provide novel electronic control means for document-handlers and the like having a capability of distinguishing between adjacent separated documents for counting purposes while ignoring perforations, punches, slits or mutilations within a document as an erroneous indication of a separation between documents.

These as well as other objects of the present invention will become apparent when reading the accompanying description and drawing in which : Fig. 1 is a simplified elevational view of a document handling device for feeding, separating, counting and stacking paper documents and the like.

Fig. 2 shows a plan view of the various feed elements of Fig. 1.

Fig. 3 ia e .schematic diagram of the compensating quantizin threshold device employed for counting documents separated by the document-handler of Figs. 1 and 2.

Figs. 4a- 4f are schematic diagrams which form the control circuitry for the document-handling device of iFigs. 1 and 2.

Figs. 5a - 5c show waveforms useful in explaining the circuitry of Figs. 3 and 4a - 4f. f '.

DETAILED DESCRIPTION OF THE FIGURES ^ Figures 1 and 2 show, in simplified fashion a document- handling device which is described in greater detail in «©» - Ts rael i Patent jss ue.d 29 2 7fi --pending.-application Serial No.41445, £½le y-Z½s- -l½-7-Zt and assigned to the assignee of the present invention. The detailed structure of the document-handling device of the Is rael i Patent aforementioned H?S-.—ap{l-i€at The document-handling device has the major functions of providing means for feeding sheets of varying thicknesses, sizes, finishes and the like and of accepting such dissimilar sheet sizes without first collating sheets into groups having similar dimensional and/or surface characteristics and include means for separating and counting the sheets and stacking the sheets once separated.

Device 10 of figures 1 aiwi 2 is comprised of a housing 1 having a base portion 12 for supporting device 10 upon any suitable surface such as, for example, a table or counter. The relatively small size and light weight of the device greatly enhances its portability and facilitates handling of the devic to enable its use in practically any desired location.

The housing 11 is provided with a front face 13 which forms a portion of the front of housing 11 which is further provided with an infeed hopper 14 consisting of a plate/member 15 for stacking sheets or other documents S. The stack S has a portion of its weight resting upon rearward end 15a of plate 15 and the sheets have their forward edges resting against a plate 16a. The inclination of the infeed stacker 14 is such that the weight of the sheets within the stack serve to retain application and will be omitted herein for purposes »f simplicity.

A picker wheel 19 mounted to rotate about shaft 20 Is provided with an nsert or raised portion 19a which protrudes through a suitable opening provided 1n plate 15a to engage the lowermost sheet within the stack and advance this sheet toward a drive wheel 23 mounted to rotate in a direction shown by arrow 26 about shaft 24. Positioned above the drive wheel Is a stripper wheel 52 mounted to rotate upon a shaft 47 and being resHlently mounted 1n a manner described 1n detail In the aforementioned U.S. application to perform a stripping operation. Wheel 52 rotates 1n the direction shown by arrow 54 and serves to move documents other than the bottom-most sheet 1n a re award direction so as to permit only one document to pass between wheels 23 and 52 toward an acceleration wheel assembly to be more fully described.

The coefficient of friction of the periphery of wheel 23 1s greater than the coefficient of friction of the periphery of wheel 52 so that when only a single sheet passes between these wheels (as the result of either a stripping operation or the feed of only a single sheet) , drive wheel 23 exerts the major Influence upon the sheet causing 1t to be fed 1n the forward feed direction toward acceleration wheel 60 mounted to rotate 1n the direction shown by arrow 62 about shaft 61. The acceleration wheel 60 cooperates with free-wheeling rollers 64 mounted to rotate about shaft 66. The acceleration wheel 60 rotates at a speed greater than the rotating speed of wheel 23 causing the sheet to be fed between wheel 60 and free-wheeling roller 64 to be advanced toward a stacking location at a speed greater than the speed achieved by a sheet passing between wheels 23 and 52. This operation causes a small gap to be formed between the trailing edge of the sheet fed between wheels 60 and 64 and the leading edge of the next document being fed toward wheel 60 by wheels 23 and 52. This gap 1s sensed by means of a light source 65 cooperating with a light sensitive transistor 72 or other suitable Ught-sensltlve devi ce which generates a count pulse when the "gap" 1s 1n the region between light source 65 and transistor 72. Obviously plates 15 a and 16a are provided with suitable openings (not shown) to permit the passage of " " Sheets advanced by acceleration wheel 60 are "kicked" into a stacker mechanism comprised of a stacker plate 81 and a kicker wheel 84 mounted to rotate about a shaft 85 in the direction shown by arrow 91 so as to neatly stack counted sheets within the stacker mechanism. The stacking plate 81 is urged in the direction of arrow 97 by suitable bias means dexcribed in greater detail in the aforementioned U.S. application. As the number of sheets in the stacker is increased, the sheets urge plate 81 in the direction shown by arrow 98 against the force of the biasing means to firmly retain the sheets within the stacker.

Figure 2 shows the driving meahanisms employed for operating the various wheels described hereinabove in connection with Figure 1. The apparatus is provided with a motor M having an output shaft 129 extending through machine frame F to which motor M is securely fastened. A pulley 130 is rigidly secured to shaft 129 and drives the acceleration wheel shaft 61 by means of a belt 63 entrained about pulley 130 and a pulley 62 mounted to acceleration wheel shaft 61. The opposite end of shaft 61 is provided with pulleys 133 and 134. Pulley 133 is locked to shaft 61 and drives the kicker wheel shaft 85 by a belt 132, which is entrained about pulley 133 and a pulley 89 locked to shaft 85. Belt 132 is a resilient 0-ring type belt and is looped in a "figure-eight" fashion to rotate ahaft 85 in a direction reverse from that of shaft 61. Thus, whenever motor M is energized, shafts 61 and 85, which are directly coupled thereto, are rotated.

Shaft 61 is further provided with a clutch mechanism 131 which, when energized, causes the pulley 134 mounted upon clutch 131 to rotate. When deenergized, clutch 131 causes pulley 134 to be free-wheeling relative to shaft 61. Belt 135 is entrained about pulley 134 and a pulley 136, locked to one end of drive wheel shaft 24.

The opposite end of drive wheel shaft has two pulleys 25 and 138 locked to the shaft . A belt 142 is entrained about pulley 25 and pulley 21, which is locked to the picker wheel shaft 20. Belt 140 is entrained about pulley 138 and idler shaft pulley 42 which is locked to the idler shaft 39. Shaft 39 serves to impart rotation to the stripper wheels 52, 52 by means of a belt 45 entrained about pulleys 44 and 38, respectively, locked to shafts 39 and 31. A second pulley portion of pulley 38 imparts rotation to a pulley 51 mounted to stripper wheel shaft 47 by means of a belt 50. This "floating mechanism" for the stripper wheels 52, 52 serves to impart rotation to stripper wheels 52, 52 while freely permitting the stripper wheel Assembly 30 to "float" above the drive wheels 23-23c in a manner which is set forth in detail in the aforementioned U.S.patent application.

Pulleys 133 and 89 are provided with semi-circular grooves around their periphery for receiving 0-ring type belt 132. All of the remaining pulleys are provided with gear-like outer peripheries for engaging teeth provided on the belts which they engage, which belts are commonly referred to as timing belts. All of the belts have been shown in Figure 2 in phantom line fashion to facilitate and simplify an understanding of Figure 2.

An electromagnetic brake 137 is fastened to machine frame F and selectively engages one end 20a of picker wheel shaft 20. When energized, brake 137 abruptly stops shaft 20 from rotating. When deenergized, brake 137 permits shaft 20 to freely ro£a¾©X).

In operation, shafts 61 and 85 continuously rotate so long as motor M is energized. Clutch 137 permits drive wheel shaft 24, idler shaft 39, and picker wheel shaft 20 to be selectively disengaged from motor M when it is energized. Clutch 131 and brake 137 are operated substantially simultaneously to both disengage and abruptly halt the rotation of shafts 24, 39 and 20, even though motor M is energized.

Turning now to a description of the electronic control means for reliably and accurately operating the , document-handling device, Figure 3 shows the document detector 300 which is comprised of a light-sensitive transistor 72.

The emitter is activated when a gap between separated documents is detected. The collector of transistor 72 is coupled to a D.C. source †V while the emitter electrode is coupled through resistor Rl to ground bus 301. The emitter is also connected through lead 302 to the base of transistor 303 whose collector is coupled through resistor R2 to the D.C. source +V. The emitter electrode of 303 is coupled through capacitor CI to ground bus 301 and through resistor R3 to one input 304b of an operational amplifier 304 which is utilized in circuit 300 as a comparator. Resistor R3 is further coupled through resistor R4 to ground bus 301. The emitter electrode of light-sensitive transistor 72 is further coupled to the remaining input 304a of operational amplifier 304.

In the quiescent state, i.e., when no "gap" is sensed, transistor 72 is in the non-conductive state so thereby applying a ground potential to the base of transistor 303. The emitter of 303 thus applies ground potential to input304a of comparator 304. The ground potential applied to the base electrode of transistor 303 maintains 303 in the non-conductive state.

Resistors R3 and R4 form a voltage divider, hose output point is the common terminal 305 therebetween.

Resistor R4 has a substantially high resistance value of the order of 100 k Ohms which preferably is greater than the resistance value of resistor R3.

Before describing the operation of the detector 300, a brief description of the characteristics of the circuit and the problems which the circuit solves will first be given.

In the handling of documents ot high speed, it can be appreciated that a significant amount of dust is created in such high speed paper or document handling.

The dust particles eventually come to rest upon various components of the document handler, including, but not limited to, the light source 65 and the light-sensitive surface of transistor 72. Dust will be accumulated gradually and after long periods of time, for example, of the order of days or weeks, such accumulations will significafuLly reduce the amount of light emitted by light source 65 and the amount of light whihh can pass through dust accumulated upon the light-sensitive surface of transistor 72. Therefore, the threshold level above which a pulse developed by transistor 72 will be detected as a "gap" and below which threshold level an output pulse will not be detected as a "gap" will, if the threshold level is maintained constant for lon eriods level of the light-sensitive transistor and an output level of the light-sensitive transistor which will occur as a result of passage of light through documents which, while not being transparent, are nevertheless translucent and will permit some portion of the light from source 65 to be transmitted through the document. The threshold level will thus be adjusted accordingly dependent upon the light transmitting characteristics of the documents or sheets to be handled by the device 10 of Figure 1.

Other physical conditions which tend to affect the sensitivity of the detector device are heat and general deterioration of the circuit components. The effects of these physical occurrences are to gradually reduce the sensitivity of the detector until after a time period of sufficient length, a reduction in the sensitivity of the light-sensitive transistor in conjunction with maintenance of an absolutely co¾tant threshold level will cause a detector to provide an erroneous output. It is therefore extremely important to provide a detector device with self-compensating means for adjusting the threshold level to accommodate for such gradual changes in detector sensitivity.

Let is be assumed that the device 300 of Figure 3 is operating under ideal conditions in that light source 65 and light-sensitive transistor 72 are free of any dust or dirt particles and that light soured 63 is operating to emit light of its maximum intensity capacity. Impingement of light upon the photo-seasitive emitter of transistor 72 causes the transistor to conduct, establishing a conductive path between the positive source V and ground bus 301. A voltage drop is thus developed across resistoft Rjhaving a \ a voltage level Ew (see Figure 5a). Let it be assumed that the voltage of source V is 5 volts D.C. and that the voltage drop across transistor 72 when conducting is so small as to be negligible, Thus, resistor will develop a voltage drop of 5 I !volts across its terminals representative of the maximum "white" condition Ew.

A 5 volt level at the emitter of transistor 72 is thus applied to the base electrode of transistor 303 causing the transistor to conduct so as to charge capacitor at a very rapid rate. The +5 volt D.C. level (E W) is also applied to input terminal 304a of comparator 304 for comparison against the "threshold level" in a manner to be more fully described.

Capacitor CI charges at a rapid rate to develop a voltage E due to its coupling to the emitter' of transistor 303 so as to charge to the level of +5 volts D.C. The voltage divider network comprised of resistors Rj and R4 develops a voltage Ε¾ at terminal 305 which represents the threshold level against which the output voltage level E will be compared. In the example given hereinabove, this level will be of the order of 3 1/3 volts. Operational amplifier 304 functions to generate a positive output level whenever the voltage level at, its input 304a exceeds the voltage level at its input 304b. In the particular example, E is greater than E causing a positive level to be developed at output 304c.

It should be understood that the resistances Rj and may be made adjustable so as to adjustably .select the threshold level E^. For example, let is be assumed that a sheet having some light transmissive properties passes "f sheet S1 causing transistor 72 to partially conduct whereby the output level at its emitter electrode will be a level equal to or less than the E¾ level established during the previous gap. This level will be sufficient to drive transistor 303 into conduction to charge capacitor and develop a threshold level which preferably should be greater than the level at the emitter of 72 to cause comparator 304 to be prevented from developing a positive level. It is obvious therefore that the threshold level E^ must be sufficiently greater than the level Egj so as to prohibit light passing through a light transmissive, or partially light-transmissive (i.e. , translucent) document from being erroneously detected as a "gap" between the two documents.

The self-compensating feature of the circuit is obtained as follows: As we have previously mentioned, resistors Rj and is have restive values which collectively are relatively high so that the sums of these resistances are of the order of greater than 100,000 Ohms to provide a relatively long time constant for the discharge of capacitor as will be more fully described hereinbelow.

The sheets being handled by the document handler 10 of Figures 1 and 2 are preferably moved at a rate of the order of 60 inches per second. Assuming the length of a document measured in the feed direction to be of the order of 3'·, the movement of the document in passing between light source 65 and light sensitive transistor 72 will be of the order of SO milliseconds. Considering Figure 5φ let it be assumed that at time tQ the leading edge of a document S1 moves between light source 65 and light sensi (assuming that the document is partially light trans issive as opposed to opaque) and will allow some light to pass therethrough. The output at the emitter electrode of transistor 72 will be at the level Egl which level is applied to input 304a of comparator 304. Due to the low discharge rate of capacitor (to be more fully described) the level at terminal 305 of the voltage divider network will be at E¾ which level is applied to input 304b of comparator 304, thus causing the output of comparator 304 to assume ground (0) level.

At time t^ the trailing edge of document S' will pass out of the region between light source 65 and light sensitive diode 72 causing trans istoi72 to go fully conductive and develop a voltage level Ew at its emitter electrode.

Simultaneously therewith voltage E is applied to the emitter electf^ide of transistor 303 causing capacitor to rapidly charge approximately the level of Ew. The voltage divider .

» A. applies a threshold voltage level..E^to comparator 304. Since the level Ew is greater than the level Et comparator 304 assumes a positive level thereby detecting the presence of a "gap" between document S' and the next document S''. The level E„ is retained at the emitter electrode of transistor 72 until the leading edge of sheet S** moves into the region between light source 65 and transistor 72 at time 2 causing the conductive state of transistor 72 to be significantly reduced thereby dropping to ;the level ) Es^ and causing to discharge very slightly. This level will be sustained until time tj when the trailing edge of document S'* leaves the region between light source 65 and transistor 72 and before the leading edge of the next document (not shown for purposes of simplicity) enters into the aforesaid region.

At time t7 when the output level at the emitter electrode of transistor 72 abruptly drops to level gj, the voltage resistance values of resistors Rj and and the capacitance of capacitor causes to discharge at a very slow rate.

For example, in one preferred embodiment, the value of capacitator and of resistors Rj and is such as to cause capacitator to be fully discharged over a time interval of the order of 500 milliseconds. Since the time between the passage of each document is of the order of 50 milliseconds, capacitor discharges at a rate such as the voltage across its terminals is close tp 90% of the voltage Ε¾.

Let it be assumed that over the passage of time, a gradual change occurs in the maximum output level at the emitter electrode of transistor 72 due to such conditions as the collectionofo dust or the effect of heating of the components through long ocontinued use. It can be seen from Figure 5b that the level Ew will gradually decrease to a level Ewl at time t^, to level E^ at time t5 and to level Ew3 at time tg and so forth. Each of these reductions in the output level of emitter electrode of transistor 72 consequently reduce the voliage applied to the base electrode of transistor 303 causing capacitor to charge to a correspondingly lower value, thereby dropping the threshold level Et accordingly, as shown by curve 306 in Figure. 5b. It can thus be seen that the detector 300 of Figure 3 automatically adjusts the threshold level E^ in accordance with gradual changes:) in the output voltage level of transistor 72. It shouid be understood that wave form 307 of Figure 5b shows a series of pulses which occur over a substantial elapsed time which may be of the order of days or weeks. j Figure 5c shows a portion of waveforms 306 and 307 in greatly enlarged fashion to more clearly explain the operation of capacitor and the voltage divider network comprised of resistors R3 and R^. Let is be assumed that the document feeder is turned on. At this time, since no documents have been fed into the unit, light source 65 causes the capacitor to charge rapidly as shown by portion 306a of waveform 306. At time tQ the first document passes through the region between lamp 65 and transistor 72 causing the output level of the emitter electrode of transistor 72 to drop to the voltage level Bfil. At this time, capacitor will discharge at a slow rate as shown by the waveform portion 306b where capacitor will drop to a voltage level of the order of 90% of its maximum voltage Et« At time t^, the trailing edge of the document will move- out of the region between lamp 65 and transistor 72 causing the output level of transistor 72 to go to Ew.

At this time capacitor will charge to its full value in a very brief time period as shown by the portion 306c of waveform 306. Capacitor will become lly charged and remain at the level Et until time t2 at which time the leading edge of the next document moves into the region between elements 65 and 72 causing the output level at the emitter electrode of transistor 72 to drop to the level Esl* ~At this time the capacitor will again discharge at a very slow rate as is represented by the portion 306d of waveform 306. This operation is continuously repeated in the same manner as was described hereinabove for each additional "gap" sensed between the documents being handled by the device 10. As the gradual build-up in dust or heating effects reduces the sensitivity of transistor 72, the output level Ew will gradually be reduced as was des- cribed hereinabove causing capacitor to charge to a lower voltage level due to the reduced to the base electrode of transistor 303. Thus, the threshold level Et will continue to be gradually reduced, but will remain at a level which remains proportional to the maximum output level Ew, Ewj» Ew2 and so forth, as the sensitivity of transistor 72 is gradually reduced. It can thus be seen that the detector of Figure 3 fully compensates for any gradual changes in the sensitivity of the detector.

Comparator 304 is designed so as to develop an output level of zero volts during the time when the document is passing in the region between elements 65 and 72 and is adapted to develop a sensttive output level of the order of f5 volts during the time that a gap is detected.

To enhance the flexibility of the document-handling device 10 so as to accommodate ^ all sorts of documents and/or sheets it is important to provide means for preventing an erroneous indication of the presence of a "gap".

For example, let it be assumed that the document-handling device 10 is being employed to count punch-cards. Some of ' the holes punched in the punch cards may be positioned so as to coincide with the positions of light source 65 and transistor 72 causing the output pulse or spike such as the spike 308 shown in Figure 5c to be developed. , Since this pulse will reach the level Ew which is clearly above the threshold level E^ of waveform 30C (see waveform portion 306d) , comparator 304 at this time will develop an output level of |5 volts to indicate the presence of a "gap".

Another possible way in which such a narrow pulse may be developed may result from perforations, cuts, slits or tears which may appear in a document either for deliberate reasons or because the document has become torn or mutilated through handling. Such narrow pulses must therefore be prevented from being interpreted as a "gap" between adjacent documents separated by the document-handling device 10.

As was discussed hereinabove, the elapsed time tl"t0 rePrese, ts tne "time between which the leading edge of a document enters into the region between elements 65 and 72 and the time at which the trailing edge of the documents leaves the aforesaid region. The circuit 310 which prevents such narrow inpulses from being erroneously interpreted as a "gap" between documents is shown in Figure 4a and is comprised of an input terminal 311 coupled to the output of the output 304c of comparator 304 receiving count pulses. Series connected capacitor C2 and resistor Rg are coupled in series between †5 volts D.C. and gtound with their common terminal 312 coupled to input line 311 which is coupled to the output of comparator 304. C2 and R,. provide filtering against high frequency noise such as that generated by motors, etc. which may be magnetically or electrically coupled into line 311. Input line 311 is coupled to (one input of NAND gate 313. The operation of NAND gate 313 is such as. to develop a high voltage level when any one or more of its inputs are low and to develop a low level when all of its inputs are at a high level. The output of NAND gate 313 is coupled to one input of inverter 314 ivhose output is simultaneously coupled to one input of NAND gate 315 and one input of NOR gate 316. NOR gates 316°and 317 are cross-coupled to form a "single shot filter" circuit (SS-Filter) which operates in a manner to be more fully described. The output of NOR gate 316 is coupled to one input of NOR gate 317 while the output or NOR gate 317 is coupled to the remaining input of NOR gate 316. The output of NOR gate 316 is further coupled to one input of NAND gates 315 and 318 and to the inout 319a of a one-shot multivibrator 319. The remaining input of NOR gate 317 is coupled to one terminal of capacitor Cj whose opposite terminal is coupled to ground.- Parallel connected diode CR^ and resistor R^ are coupled in parallel between the output of NAND gate.315 and capacitor C3.

The output of NAND gate 318 is coupled to the D.C. supply-terminal +V through resistor R^.

However, the capacitance of capacitor C-, and the resistance value of resistor R^ are chosen to cause capacitor ¾ to discharge at a slow rate whereby the high level at the terminal of capacitor C3 coupled to one input of NOR gate 317 is retained thus preventing the bistable circuit comprised of NOR gates 316 and 317 from changing state and ..thereby preventing an erroneous pulse from being applied to one-shot Multivibrator 319 until capacitor C3 has had sufficient time to discharge. The discharge rate of capacitor Cj is appropriately adjusted so as to permit the capacitor to fully discharge during a 20 millisecond time duration which lies well within the normal time interval of a " gap " but is adjusted to prevent the capacitor from bein discharged within shorter time intervals which would occur as a result of holes, tears, or mother mutilations in the document passing between lamp 65 and detector (transistor 72). -17- Summarizing the operation of the circuits 300 and 310 of Figures 3 and 4a, the objective of these circuits is to distinguish between a "gap" between the trailing edge of a document and the leading edge of the next document, as they pass the sensor 72, and the presence of holes or tears within the body of a document, so as . such "holes" will not be erroneously interpreted as a "gap" so that to prevent an erroneous count pulse from being generated. This problem is extremely important in the countin of documents which have punched codes provided therein.

Let is be assumed that the trailing edge of a document has just passed sensor 72 (Fig.3) (just prior thereto, capacitor C3 (Fig.4a) has been fully charged). The output of comparator 304 (Fig.3) goes high. The output of gate 313 and inverter 314 go low and high respectively.

The count pulse Igg is latched with 316a high, applying a high to one input of 315. Since the output of inverter 314 is high, the output of gate 315 goes low causing Cj to discharge. When Cj discharges to a level below the reset threshold level of reset input 317b of the single shot (SS) gate 317, this causes the output 317a to go high. This causes the output 316a of 316 to go high. The interval of elapsed time typically required for C3 to discharge from a full charge (approximately 5 V.D.C.) to the reset threshold level (approximately 0.8 V.D.C.) is of the order of 10 milliseconds. In this time interval assuming a rate of movement of documents as 60 inches per second, the trailing edge of the last document will have travelled a distance of the order of 0.60 inches.

Since the ;»ariLnal gap distance between documents is of the order of 0.70 inches, the leading edge of the Since the reset level has been reached by the discharge of Cj and the output 317a has gone high, the output of gate 315 goes high causing Cj to begin charging before the leading edge of the next document is detected by sensor 72. Once the leading edge is detected the output of 304 goes low causing the output of 313 to go high and the output of 314 and the input 316b of 316 to go low whereby the output 316a of 316 goes high, which is applied to one input of 317 and 315. However, the low output of 314 is applied to the remaining input of 315, thereby maintaining^' ¾¾ output high of 315, thus Cj continues to charge and becomes fully charged well before the next trailing edge passes sensor 72 (see the waveform of Figure 5c, for exam le). The above operations are then repeated for each succeeding document.

The presence of a punched hole in a passing document which punched hole may be located in the region of sensor 72, causes the output level of comparator 304 to go high. However, the typical length of a punched hole is of the order of 0,125 inches. With the document travelling at a rate of 60 inches per second the "hole" will pass the sensor in about 1 millisecond during which time C3 has discharged only slightly and will be at a voltage level well above the threshold level of the reset input 317b, Thus, Isg will not reset. The circuit will also prevent resetting an entire column of punches (typically there are a maximum of 12 positions in a column) will not permit Cj to drop below the reset threshold level. Mutilations or holes of types other than punched holes and are of the order of 0.50 inches or less in the direction of movement can thus be prevented from being interpreted as a "gap".

There is no maximum length of a gap between trailing and leading edges of successive documents. However, the minimum length of a gap is dictated by the minimum response of the circuitry and should preferably be of the order of 0.40 inches.

It can be seen from the foregoing description that the present invention provides novel control meane for document handling devices and the like which are adapted for accepting sheets or other documents, preventing more than one document from passing through the drive and stripper means and for providing a gap betvreen the separated document for counting purposes wherein the control means provides the functions of counting small or large numbers of documents, and fur¾ er provides means for protecting the equipment against damage due to delays by anticipating any potential delay.

The electronics of the control system is further adapted to provide count pulses by sensing the separation between documents before they pass through the stacker to automatically adjust for changes in ambient conditions which may effect the sensitivity of the detector and to prevent perforations or mutilations within the documents themselves from being eroneously interpreted as a "gap" between separated documents. The circuit 310 of Figure 4a is adapted so as to prevent such erroneous detections for mutilations or other perforations within the document passing between the lamp and light-sensitive transistor of openings as large as three-quarter inches measured in the direction of feed of the documents.

Although there has been described a preferred embodiment of this novel invention, many variations and the specific disclosure herein, but only by the appending -21-

Claims (13)

WHAT IS CLAIMED IS

1. Means for counting documents by the detection of a gap of at least minimum duration between adjacent documents fed in a first direction and at spaced intervals with said gaps serving to facilitate counting of the documents and being defined by the trailing edge of a document and the leading edge of the next document, said means comprising: a light source positioned to one side of the path of movement of the documents being fed at spaced intervals; light sensitive means positioned on the opposite side of said path to receive light of maximum intensity from said light source when the trailing edge of a document passes said light source and light sensitive means and to receive light of lower intensity when a document is positioned between the light source and light sensitive means; threshold setting means for establishing a predetermined threshold level; comparator means for comparing the output level of said light sensitive means with said threshold level means fur generating a signal having a first level when said light sensitive means output is at least equal to said threshold level and having a second level when said threshold level is greater than the output level, one of said levels representing the presence of a gap; said counting means being characterised by comprising delay means responsive to the initiation of said gap level for beginning a delay period of a predetermined interval; first logical gating means responsive to said delay means and the charge of said comparator signal from the gap level to the remaining level to generate a count pulse, said logical gating means including second gating means to prevent generation of said count pulse unless said delay interval terminates prior to removal of said gap level to assure that gap intervals shorter than said predetermined interval are prevented from being erroneously interpreted as a valid count pulse.

2. The counting mef.ns of claim 1 in which the delay means is further characterised by comprising: charge storing means and diode means coupled between said first logical gating means and said charge storing means for rapidly chatging said storing means when no gap level is present at the output of said comparator means, and circuit means for limiting the discharge rate i£ said storing means xdien said gap level is present.

3. The counting means of claim 1 being further characterised by comprising noise suppression means coupled to said comparator means for preventing spurious pulses from being passed as count pulses,

4. The counting means of claim 1 being further characterised by comprising second delay means for initiating a second interval when said gap level terminates and third gate means for preventing said first logical gating means from generating a count pulse responsive to termination of said second delay interval.

5. The counting me^ns of claim 4 further characterised in that said second delay means is reset upon the reoccurrence of each gap level.

6. The counting means of claim 4 being further characterised in that the delay interval of said second delay means is greater than the time required for the longest document being counted to pass the light sensitive means so that the second delay means is normally reset by the reoccurrence of each successive gap level before timing out.

7. The counting means of claim 1, wherein said threshold setting means is further characterised by comprising means for adjusting the threshold level as a function of the output signal strength of said light sensitive means to compensate for component aging and other ambient operating conditions.

8. Sensing means for counting documents fed in a predetermined direction at spaced intervals ¾rith a gap between the trailing edge of each document and the leading edge of the next folloiiing document comprising: detecting means for detecting said gaps to generate a first output level during the occurrence of each gap as the trailing edge of each document passes said detecting means and a second output level as the leading edges of each succeeding document passes said detecting means; said sensor being characterised by comprising bistable means having first and second inputs and an output, said first input coupled to said detecting means for generating a first output level at the output of said bistable circuit when each leading edge passes said detecting means; gate means having inputs coupled to said detector means and the output & ^^^^:^>$i% ^'. ircuit for coupling a setting signal at its output to said bistable circuit second input to permit said bistable circuit to be set when the leading edge of a document is sensed by said detecting means; energy storage means being charged by the output of said gate means, means coupled to said energy storage means to prevent said second input from being reset for a predetermined time interval after the passage of each trailing edge during which time interval said energy storage means is prevented from dis- charging below a predetermined level to prevent setting of bistable means due to the detection of apertures in said documents by said detection means.

9. The sensing means of claim 8 characterised in that the energy storage means is a capacitor adapted to charge rapidly during setting of said bistable circuit and to discharge slowly is when said first level ^generated by said detecting means to prevent reset of said bistable circuit.

10. The sensing means of claim 9 being further characterised wherein the capacitance of said capacitor is selected to prevent resetting of said bistable circuit when said first level persists for a time less than the interval of a gap between documents.

11. The sensor of claim 1 being further characterised by comprising a bistable circuit having first and second inputs and a first output; said first input being coupled to the output of said comparator means; gate means having first and second inputs coupled respectively to said comparator means and said second output, and having an output coupled to said second input; energy storage means coupled to the output of said gate means and being adapted to charge rapidly and discharge slowly; said bistable circuit being reset when sail comparator detects a gap to discharge said energy storage means; said energy storage means being adapted to prevent resetting of aaid bistable circuit until it has discharged within a predetermined time interval thereby preventing said bistable circuit from being reset during a time interval less than the time of passage of a gap to prevent spurious pulses, developed as a document is passing said light sensitive means, from setting said bistable circuit; until it has been reset whereby apertures in said docuoaftts passing said detecting means are prevented from being detected as a gap.

12. Sensing means for counting documents fed in a predetermined direction at spaced intervals with a gap between the trailing edge of each document and the leading edge of the next succeeding document and for preventing the generation of spurious counts due to apertures, slits, tears or other openings in said documents comprising; means for detecting said documents to generate a first level signal as the trailing edge of a document passes said detection means and to generate a second level signal as the leading edge of the next succeeding document passes said detection means; the sensing means being characterised by charge storing means coupled to said detection means for storing electrical energy developed by said detection means during the time that each leading and trailing edge passes said detection means and for discharging electrical energy during the time that the gaps between documents pass said detection means; bistable means having inputs coupled to said storing means and to said detection means for being set when the output of said detection means is at said second level and reset when said energy storing means discharges to a predetermined threshold level and the output of said detection means is at first said level

13. The sensing means of claim 12 wherein the gap distance between documents is a minimunv f 0.6 inches and wherein said second means is characterised by enabling said energy storage means discharge below taid threshold in slightly less time thaJi the time interval during which a gap passes said detection means to prevent openings in said documents less than 0.4 inches long (measured in the direction of travel) are thereby prevented from being interpreted as a gap between documents.