Control mechanisms for document-handling apparatus

Abstract

In a document-handler adapted for feeding, separating and stacking sheets and the like, control means for sensing and counting separated sheets and having a capability of counting, statistically sampling and batching and including means for anticipating jam conditions to protect the counting mechanism, as well as the sheets, from being damaged. The sensing mechanism has the capability of self-adjustment to automatically compensate for any and all conditions which affect the sensitivity of the sensing device, and further has a capability of distinguishing between separated documents and apertured or mutilated documents. In accordance with the desired operation, the electronic circuitry controls the mechanical functions to achieve the desired counting, separating, batching and statistical sampling operations.

What is claimed is: 
     
       1. A sensor for detecting the presence of gaps between documents fed in a first direction at spaced intervals with said gaps occurring between the trailing edge of a document and the leading edge of the next document, said sensor comprising: a light source positioned to one side of the path of movement of the documents;   light sensitive means positioned to receive light of maximum intensity from said light source when the trailing edge of each document passes said light sensitive means to activate said light sensitive means and to receive light of a minimum intensity when a document is positioned between said light sensitive means and said source, said light sensitive means developing a signal at its output which varies with the intensity of light;   energy storage means;   first means coupled to said light sensitive means output for rapidly charging said energy storage means when said light sensitive means is activated by light of maximum intensity;   comparator means .Iadd.normally maintained at a first output signal level and .Iaddend.having first and second inputs for generating .[.an.]. .Iadd.a second .Iaddend.output signal .Iadd.level different from said first output signal level .Iaddend.when the signal level at its first input exceeds the signal level at its second input;   said first input being coupled to the output of said light sensitive means;   second means coupled between said .[.first.]. .Iadd.energy storage .Iaddend.means and said comparator means second input for coupling a portion of the signal level developed by said storage means to said second input;   said second means providing a discharge path for said energy storage means and being adapted to cause said energy storage means to discharge at a rate much slower than the charging rate to cause a substantial portion of the signal level developed by said storage means to be retained when said light sensitive means is deactivated due to the movement of the document past said light source.Iadd.; .Iaddend.   storage means coupled to said comparator means and being charged to a first level when said comparator means develops said first output signal level and being discharged towards a second lower level when said comparator means develops an output which is at said second output signal level;   logical gating means responsive only to the simultaneous presence of said comparator means second output signal level and the discharge of said storage means to said second lower level to generate a count pulse representative of the passage of a document.   
     
     
       2. The sensor of claim 1 wherein said second means is a voltage divider comprised of resistance elements and said storage means is a capacitor coupled in parallel across said voltage divider; said voltage divider forming a discharge path for said capacitor.   
     
     
       3. .[.The sensor of claim 1 further comprising.]. .Iadd. 
     
     
       A sensor for detecting the presence of gaps between documents fed in a first direction at spaced intervals with said gaps occurring between the trailing edge of a document and the leading edge of the next document, said sensor comprising: a light source positioned to one side of the path of movement of the documents;   light sensitive means positioned to receive light of maximum intensity from said light source when the trailing edge of each document passes said light sensitive means to activate said light sensitive means and to receive light of a minimum intensity when a document is positioned between said light sensitive means and said source, said light sensitive means developing a signal at its output which varies with the intensity of light;   first energy storage means;   first means coupled to said light sensitive means output for rapidly charging said first energy storage means when said light sensitive means is activated by light of maximum intensity;   comparator means having first and second inputs for generating an output signal when the signal level at its first input exceeds the signal level at its second input;   said first input being coupled to the output of said light sensitive means;   second means coupled between said first energy storage means and said comparator means second input for coupling a portion of the signal level developed by said first energy storage means to said second input;   said second means providing a discharge path for said first energy storage means and being adapted to cause said first energy storage means to discharge at a rate much slower than the charging rate to cause a substantial portion of the signal level developed by said first energy storage means to be retained when said light sensitive means is deactivated due to the movement of the document past said light source; .Iaddend.   a bistable circuit having first and second inputs and a first output;   said .Iadd.bistable circuit .Iaddend.first input being coupled to the output of said comparator means .Iadd.for setting said bistable circuit.Iaddend.;   gate means having first and second inputs coupled respectively to said comparator means and .[.said second output.]. .Iadd.the first output of said bistable circuit.Iaddend., and having an output coupled to said .Iadd.bistable circuit .Iaddend.second input;   .Iadd.second .Iaddend.energy storage means coupled to the .[.output.]. .Iadd.second input .Iaddend.of said .Iadd.bistable circuit for resetting the bistable circuit and including means coupled to said .Iaddend.gate means .[.and being adapted.]. .Iadd.enabling the second energy storage means .Iaddend.to charge rapidly and discharge slowly .Iadd.under control of the gate means.Iaddend.;   said bistable circuit being reset when said comparator detects a gap to discharge said .Iadd.second .Iaddend.energy storage means;   said .Iadd.second .Iaddend.energy storage means being adapted to prevent resetting of said bistable circuit until it has discharged .Iadd.to a suitable level .Iaddend.within a predetermined time interval thereby preventing said bistable circuit from being reset during a time interval less than the .Iadd.predetermined time interval which represents the .Iaddend.time of passage of a gap .Iadd.of at least a predetermined length .Iaddend.to prevent spurious pulses, developed as a document is passing said light sensitive means, from setting said bistable circuit.[.;.]. .Iadd., .Iaddend.until it has been reset whereby apertures in said documents .Iadd.shorter than said predetermined length .Iaddend.passing said detecting means are prevented from being detected as a gap.   
     
     
       4. 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 following 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;   bistable means having first and second inputs and .[.and.]. .Iadd.an .Iaddend.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 of bistable circuit 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 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 psssage of each trailing edge during which time interval said energy storage means is prevented from discharging below a predetermined level to prevent setting of bistable means due to the detection of apertures in said documents by said detection means.   
     
     
       5. The sensing means of claim 4 wherein the energy storage means is a capacitor adapted to charge rapidly during setting of said bistable circuit and to discharge slowly when said first level generated by said detecting means is to prevent reset of said bistable circuit. 
     
     
       6. The sensing means of claim 5 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. 
     
     
       7. Control means for operating apparatus for counting and stacking documents comprising: first means for receiving a stack of documents;   stacking means;   second means for separating said stack of documents and advancing said separated documents, one at a time to said stacking means whereby a gap is provided between the trailing edge of each document and the leading edge of the next document;   sensing means arranged at a predetermined location for detecting the presence of each gap to generate counting pulses;   means coupled to said sensing means for counting said documents;   jam detector means for generating a first output level when the time interval between succeeding count pulses is greater than the time required for one document to pass said sensing means, said jam detector being reset by said sensing means each time a count pulse is generated by said sensing means to normally prevent generation of said first output level;   gate means coupled to said jam detector means for preventing said sensing means for transferring count pulses to said counting means when said jam detection means generates said first output level.   
     
     
       8. The control means of claim 7 further comprising second gate means coupled to said jam detection means for halting said second means upon the occurrence of said first output level. 
     
     
       9. Control means for operating apparatus for counting and stacking documents comprising: first means for receiving a stack of documents;   second means for separating said stack of documents and advancing said separated documents one at a time in a feed direction;   stacking means;   third means for accelerating documents advanced by second means toward said stacking means to create gaps between adjacent documents;   motor means;   clutch means for selectively coupling said second means to said motor means;   braking means for selectively halting said second means;   means coupled between said motor means and said third means for operating said third means so long as said motor means is energized;   sensing means for detecting the presence of each gap to .[.geneate.]. .Iadd.generate .Iaddend.counting pulses;   means coupled to said sensing means for counting said documents;   settable means for setting said counter means to any predetermined count N, said settable means including first gate means responsive to said counting means for generating an output when said counting means reaches a count of N-1;   diverter gate means for normally extending into the path of movement of said documents diverting documents accelerated by said third means away from stacking means;   second gating means coupled between said gate means and diverter means for moving said diverter means out of the path movement of said documents when said first gate means detects a count of N-1;   said second gating means including means for operating said braking means and said clutch means to decouple said second means from said motor means to to abruptly halt said second means to provide sufficient time for said diverter means to move out of the path of movement of said documents;   means coupled between said sensing means and said second gating means for causing said second gating means output to terminate after a predetermined time interval to cause said braking means to be released and said clutch means to couple said motor means to said second means;   third gating means coupled to said counting means for generating an output when said counting means reaches a count of N;   means coupled between said third gating means and said diverter means for moving said diverter means into the path of movement of the documents;   said third gating means including first bistable means coupled to said brake and clutch means for decoupling said second means from said motor means and abruptly halting said second means when a count of N is achieved;   delay means coupled to said third gating means for resetting said bistable means after a predetermined interval to release said brake means and cause said clutch means to couple said motor means to said second means after said diverter means is moved into the path of movement of said documents.   
     
     
       10. 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 or other openings in said documents comprising: means for detecting said documents to generate a first level 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;   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 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 said first level;   second means coupled between said energy storage means and said detection means for enabling said energy storage means to charge rapidly after said detection means reaches said second level and for causing said energy storage means to discharge at a slow rate after said detection means reaches said first level;   said second means being adapted to permit said energy storage means to discharge to a level below said threshold level before the leading edge of the next document is detected by said detection means to permit resetting of said bistable means and being further adapted to prevent said energy storage means from discharging below said threshold level when said detection means detects openings, slits or other mutilations in said documents which cause said detection means to generate said first level output for a time duration shorter in length than the time interval for a gap to pass said detection means whereby the detection of openings, slits or other mutilations in said documents are prevented from being interpreted as the gap between documents;   means coupled to said bistable means for generating a count pulse when said bistable circuit is set.   
     
     
       11. The sensing means of claim 10 further comprising means coupled to said pulse generating means for accumulating a count of said pulses. 
     
     
       12. The sensing means of claim 10 wherein the gap distance between documents in a minimum of 0.6 inches and wherein said second means enables said energy storage means discharge below said threshold in slightly less time than 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. 
     
     
       13. The sensing means of claim 10 further comprising timing means coupled between said detection means and said bistable means for preventing setting of said bistable means when said bistable means has not been reset within a predetermined time interval which is greater in duration than the time required for a document to pass said detection means. 
     
     
       14. The sensing means of claim 13 further comprising second timing means coupled to said bistable means for generating a signal a second predetermined time after said bistable means is reset to generate a jam signal, said second predetermined time being greater in duration than the time required for the leading edges of two successive documents to pass said sensing means; means coupled to said second timing means for halting the feeding of said documents.   
     
     
       15. Apparatus for detecting documents moving along a path at spaced intervals comprising: a light source positioned on one side of said path;   a light detector positioned on the remaining side of said path and adapted to generate a signal at its output whose signal amplitude is at a first level when a document is passing between the source and the detector and is at a second level when no document is between the source and the detector;   a comparator having first and second inputs, said first input being coupled to the output of said detector;   a capacitor;   means coupled to said detector output for developing a charging current to instantaneously charge said capacitor upon the occurrence of one of said signal levels and for terminating said charging current upon the occurrence of the remaining one of said signal levels;   a discharge circuit coupled to said capacitor for discharging said capacitor at a slower rate than the charging rate of said capacitor;   said discharge circuit comprising a voltage divider circuit for applying a portion of the voltage across said capacitor to the second input of said comparator;   said comparator being adapted to generate an output .Iadd.of a predetermine level .Iaddend.only when the signal level at its first input is greater than the signal level at its second input.Iadd.; .Iaddend.   storage means coupled to said comparator means and being charged to a first level when said comparator means output is not at said predetermined level and being discharged to a second lower level when said comparator means ouput is at said predetermined level;   logical gating means responsive only to the simultaneous presence of said predetermined level at the output of said comparator and the discharge of said storage means to said second level to generate a count pulse representative of the passage of a document. .Iadd.   
     
     
       16.  The apparatus of claim 1 further comprising diode means coupling said storage means to said comparator means to permit rapid charging of said storage means and resistance means coupling said storage means to said comparator means for causing the discharge of said storage means to occur at a reduced rate. .Iaddend. .Iadd. 17. Apparatus for detecting documents moving along a path at spaced intervals comprising: a light source positioned on one side of said path;   light detector means positioned on the remaining side of said path and adapted to generate a signal at its output whose signal amplitude is determined by the magnitude of the light impinging upon said detector means;   means for establishing a threshold level;   comparator means coupled to the threshold means and the output of said light detector means for generating a first output level when the amplitude of said detector means output is above said threshold level and for generating a second output level when the amplitude of said detector means output is below said threshold level;   means responsive to said detector means output for adjusting the threshold level to thereby automatically compensate for deviations in the detector means due to ambient conditions, components aging, and the like;   storage means coupled to said comparator means and being charged to a first level when said comparator means output is at one of its first and second levels and being discharged to a second lower level when said comparator means output is at the remaining one of said first and second levels;   logical gating means responsive only to the simultaneous presence of said one of said first and second levels at the output of said comparator means and the discharge of said storage means to said second level to generate a count pulse representative of the passage of a document. .Iaddend.