Abstract:
An envelope feeder for a printer having two aligned conveyors moving at different speeds is disclosed. An upstream conveyor moves a backwards slanted procession of envelopes having aligned upper edges onto an inline downstream conveyor that accelerates the envelopes along a curved upper edge so that by the time any single envelope arrives at the printer ingestion or feed slot, the envelope is almost completely flat yet supported upwards slightly so that the pickup roller of the printer can easily and reliably ingest the envelope for processing. Due to the speed of the downstream conveyor, envelopes are continually and reliably presented to the printer to avoid printer stalls. The configuration reduces the amount of skill and operating labor required to establish a high-speed envelope feed source for high-speed printing.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to sheet feeder mechanisms for electrographic printing machines. In greater particularity, the present invention relates to the use of conveyors to feed paper media into a printing machine. In even greater particularity, the present invention relates to conveyor based envelope feeders for laser or inkjet printers. 
     BACKGROUND OF THE INVENTION 
     Envelope feeders are typically used by organizations such as banks or insurance companies, print shops, and mailing houses that service such organizations, to produce a large volume of mail pieces. For example, banks send out monthly balance ledgers, insurance companies send out claim summaries, and for corporations shareholders might receive quarterly income/dividend statements. Each envelope must be labeled in order to properly utilize the U.S. Postal System, and each must meet certain USPS printing positional requirements. While in the past “windowed” envelopes were utilized in order that preprinted envelopes might be combined with individually printed sheets of paper oriented to show through the envelope window, most modern mail printing systems include the ability to individually print envelopes using on-site, relatively inexpensive laser or inkjet printers. This allows for the combining of customized envelopes with customized printed sheets at the point of disembarkation. 
     However, the feeding of envelopes into relatively inexpensive commercial laser or inkjet printers can be problematic. The typical configuration is to have an “envelope stacker” or “envelope shoe” holding dozens or even hundreds of envelopes in a stacked column from which individual envelopes are pulled from the bottom of the stack and conveyed along a conveyor deck that is positioned to feed envelopes into the manual feed tray of a printer. A pair of friction rollers commonly referred to as “footballs” presses down upon a leading edge of an envelope held in the stacker and in conjunction with a pair of conveyor rolling belts engages the envelope to sheer it away from the bottom of the envelope stack. The footballs include removable donut weights on a spindle that extends upward from the feed deck so that the pressure of the footballs may be adjusted in response to envelope size and thickness, and other conditions. Alternatively, the footballs are biased downwards with a spring which may be adjusted with a tensioning knob or screw. The sheered envelope then moves forward under the weight of additional passive rollers on the conveying rollers to keep consistent friction between each envelope and the conveyor so that the envelopes maintain edge alignment relative to a receiving input or ingestion area on a printer, such as a manual input tray. 
     However, these “stacker” based envelope feeders are operator intensive because a myriad of elements require continuing adjustment and attention by an operator. First, the footballs must be made with a consistent friction coefficient and, hence, the material diopter must be closely monitored during manufacturing. Second, the weight of envelopes changes with the envelope stack height and consistent sheering of envelopes can typically be maintained only for a certain range of envelope stack height which may vary with each new batch of envelopes. In addition, adjustments to the side walls and backstop retaining wall in the envelope stacker must be adjusted for a particular weight and size of envelope. Finally, as conveyor belt friction varies with time, and due to variations in humidity, dust, and other environmental factors, football weight, position of the footballs relative to the leading edge of an envelope, and the backstop wall angle must be adjusted frequently in order to provide a consistent feeding of envelopes into the input tray or slot of a printer. Hence, an operator must become accustomed to each feeder and skilled at making minute adjustments to the feeder elements to keep a consistent flow of envelopes into a printer. 
     The issue affects more than just print job speed completion. Modern laser printers are designed for high printing speeds and the processing of large batches of stock media. Often such systems apply toner images to a transfer belt and roller in anticipation of receiving a fast moving group of media sheets. Printers have sensors at their source input channels and if a few envelopes are processed and then the next expected envelope does not appear in an expected time interval a “stall” condition occurs within the printer and the transfer belt and roller may need to be cleaned and reprocessed in order to prepare for the arrival of a new batch of envelopes. Hence, great amounts of toner may be wasted and the life expectance of a printer&#39;s transfer roller may also be decreased. The problem is exacerbated in color laser printers. 
     Hence, what is needed is an envelope feeder that will work with relatively inexpensive inkjet or laser printers and keep those printers continuously fed or “primed” with envelopes without stalls, and without the constant and continuous operator attention required by conventional envelope feeders. 
     SUMMARY OF THE INVENTION 
     The invention is an envelope feeder for a printer having two aligned conveyors moving at different speeds. An upstream conveyor moves a backwards slanted procession of envelopes having equal height upper edges onto a downstream conveyor that accelerates the envelopes along a curved upper edge so that by the time any single envelope arrives at the printer ingestion or feed slot, the envelope is almost completely flat yet supported upwards slightly so that the pickup roller of the printer can easily and reliably ingest the envelope for processing. The conveyors create a stack of envelopes at a pickup assembly in the input slot of the printer and a sensor is positioned at the pickup assembly so that when the stack of envelopes is sufficiently depleted, a signal is sent to a control assembly in the feeder to advance the conveyors for a set duration, thereby replenishing the envelope stack at the printer. The entire feeder is a movable, self-contained unit that may be mated to varying types of high-speed printers. 
     Other features and objects and advantages of the present invention will become apparent from a reading of the following description as well as a study of the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A envelope feeder incorporating the features of the invention is depicted in the attached drawings which form a portion of the disclosure and wherein: 
         FIG. 1  a top perspective view of the envelope feeder; 
         FIG. 2  is a bottom perspective view of the envelope feeder; 
         FIG. 3A  is a left side elevational view of the envelope feeder; 
         FIG. 3B  is a right side elevational view of the envelope feeder; 
         FIG. 4A  is a top plan view of the envelope feeder; 
         FIG. 4B  is a magnified top plan view of the envelope feeder with the acceleration conveyor assembly removed from the horizontal feed assembly and positioned to the left; 
         FIG. 5  is a bottom plan view of the envelope feeder; 
         FIG. 6  is a diagrammatic view of the envelope feeder connected to a printer; 
         FIG. 7  is a diagrammatic view of the envelope feeder showing the relative positions of envelopes with respect to the conveyors during operation; 
         FIG. 8  is a movement flow diagram of the envelope feeder; 
         FIG. 9  is an electrical control schematic for the envelope feeder; and, 
         FIG. 10  is magnified view of the envelope feeder connected to a printer and showing one embodiment of an envelope pickup sensor assembly. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings for a better understanding of the function and structure of the invention,  FIGS. 1-5  show the envelope feeder  10  from different views showing all of the major components of the invention. A printer  11  is shown in phantom having the invention positioned so that the output of the feeder  10  inserts envelopes into the input tray or input slot  12  of printer  11 . The feeder  10  includes a horizontal feeder assembly  14  that supports an acceleration conveyor assembly  16  and a feed conveyor assembly  17 . Both the acceleration conveyor assembly  16  and feed assembly  17  are laterally supported by guide plates  19   a,b  and side plates  20   a,b , and the entire assembly  14  is slidably supported below by a base  21 . 
     As shown, the acceleration conveyor  16  is positioned toward the downstream end  23  of the feeder  10 , and the feed conveyor  17  is positioned toward the upstream end  24  of the feeder  10 . The acceleration conveyor assembly  16  is positioned over a cover  26  that is also laterally supported by the guide plates  19   a,b . The feed conveyor assembly  17  includes a deck  27  over which four (4) belts  28  traverse for movement of envelopes as will be discussed. A triangular backstop  29  is positioned along the length of the conveyor feed assembly  17  to provide a support to a stack of envelopes loaded onto the deck  27 . The position of the backstop is determined by the amount of envelopes loaded onto the conveyor feed assembly deck  27 . As seen, the left guide plate  19   b  is somewhat shorter than the right guide plate  19   a  to facilitate operative access to the upstream portion of the deck  27  and for the loading and unloading of envelopes against the backstop  29 . 
       FIG. 2  shows the underside of the feeder  10  and provides a better view of how the horizontal feed assembly  14  slides relative to the printer. The base  21  includes two slide panels  31   a,b , each having a vertical portion  37   a,b  and an angled horizontal portion  38   a,b . Each horizontal portion  38  includes mounting holes  32  for mounting the base  21  on a work table or other suitable platform (see  FIG. 6 ) for the feeder  10 . The work table typically might be mounted on lockable wheels so that the entire feeder  10  might be moved into a general relative position next to printer  11  to which the feeder  10  would be mated. The slide panels  31   a,b  are connected together by three struts  32  that stabilize the base  21  so that as the horizontal assembly  14  is moved toward or away from the printer  12  the slide panels  31  will not buckle. A pair of slide rails  36  is affixed to the top edge of each slide panel  31  and the horizontal feed assembly  14  includes two pairs of rollers  41  bolted onto its lower side edges sized so that they lock into rails  36 . The arrangement allows for the horizontal feed assembly  14  to be finely positioned toward the printer after the work table on which the feeder  10  rests has been positioned within the general vicinity of the printer  11 , thus facilitating mating. 
     A series of guide mount assemblies  43  laterally support the right guide plate  19   a  so that it may be moved inward and outward relative to the acceleration conveyor assembly  16  and the conveyor feed assembly  17  to accommodate different lengths of envelopes. A linear guide mount plate  44  is bolted to the right support plate  20   a  and a hollow sleeve  46  is mounted on the inside surface of the guide mount plate  44 . A guide mounting plate  51  is bolted to the outside surface of the guide plate  19   a  and a shaft  47  affixed to the plate  19   a  such that the shaft extends laterally away from the guide plate  19   a . The shaft  47  extends through the hollow sleeve  46  so that the guide plate  19   a  is supported by the shaft as it translates through the sleeve  46 . A guide locking plate  48  is affixed to the top of the guide mounting plate  51  which has a channel formed in the center of the plate. A locking handle  49  is screwed into the top of mount plate  44  and extends through the locking plate channel such that when the handle  49  is tightened movement of the locking plate  51  is arrested, thereby locking the guide plate  19   a  in place at a selected position along the locking channel. The three guide mount assemblies  43  are identical and provide lateral, adjustable support for moving the right guide plate  19   a  in and out from the envelope flow area. 
     On the left side of the feeder  10 , generally the side from where an operator controls the feeder  10 , the left guide  19   b  is laterally adjusted with a “C” shaped guide handle  57  that is part of a left guide mount assembly. The handle  57  is mounted to the guide plate  19   b  with a plate  58  bolted to the guide plate. The arms of the handle  57  extend through two guide blocks  59  that are affixed to the top of another mounting plate  61  that is bolted to the left support plate  20   b  at its lower end. The arms of the handle  57  include slots or channels  62  on each arm and a pair of locking bolts  63  extend through each channel screw into the blocks  59 . The blocks  59  are formed such that the handle  57  may be moved inward and outward to effect lateral movement of the left guide  19   b  and then locked into place by tightening the bolts  63 . 
     Referring now to  FIG. 4A  and  FIG. 4B , the feeder includes an acceleration conveying assembly  16 . For illustration purposes in  FIG. 4B , the acceleration conveyor assembly  16  has been exploded from its normal position within in the horizontal feeder assembly  14  shown in  FIG. 4A . The acceleration conveyor assembly  16  includes a pair of bearing mount members  66   a,b  that rotatably support five (5) shafts spanning the distance between the mounts  66   a,b . Two rubber conveying belts  68  surround the shafts  67  from the right-most shaft to the left-most shaft. A belt separator bracket  69  spans the two bearing mount members  66   a,b  and provides additional support between the pair of bearing mount members  66   a,b . The belt separator bracket  69  also includes a plurality of guide screws  71  that extend upwards from the bracket  69  to guide the lower belt portion during travel around the shafts  67 . 
     The right-most shaft  67   a  includes a drive motor  73  and gearing assembly  74  that turns shaft  67   a  via a short drive belt (not shown) at the left most extent of the shafted  67   a  to power belts  68 . Due to the elastic tension that the belts  68  exert on the shafts  67 , when shaft  67   a  rotates, the other shafts passively rotate in response thereof. 
     Referring also to  FIG. 5 , it may be seen that envelope feed conveyor assembly  17  includes a motor drive assembly  34  connected to a drive shaft  81  positioned between a upstream preparation deck  55  and loading deck  27 . The drive assembly  34  includes a gearing assembly next to a standard electric drive motor that drives a gear positioned on the metal shaft of the shaft  81 . A similar passive idler shaft  82  is positioned on the other end of deck  27  toward the downstream end  23 . Each shaft  81 , 82  includes four recessed belt engagement portions  83  having raised surface features to increase friction. Each recessed portion  83  on roller  81  has an aligned companion recessed portion, and four belts  28  span the two rollers at each recessed portion  83  as shown. The belts are made of plastic fabric, and while resilient their surface features are such that the underside surface glides easily over the top of loading deck  27  while being supported by same. 
     Underneath loading deck  27 , a series of roller belt guides  84  that are rotatably supported at their ends by brackets (not shown) affixed to the underside of deck  27  and interior surfaces of the support plates  20   a,b . The brackets are formed such that they are adjustably spaced from the underside of the deck  27  to impart a selected amount of tension to each belt  28  toward the underside surface of deck  27 . Also, each belt guide  84  includes a plurality of spacers affixed to the primary shaft of the belt guide to separate each belt  28  from one another and maintain a preselected spatial relationship between them. Typically, three guides  84  are utilized underneath deck  27  spaced at equal distances from each other and from the end rollers  81  and  82 . 
     At the downstream end, deck  27  includes at least one guide finger  86  extending toward the downstream direction and over roller  82  so that envelopes moving in the downstream direction do not fall in between rollers  82  and  67   a  during movement toward printer  11 . Envelope feed conveyor  17  also includes an underside cover  86  covering most of the underside of deck  27  and the belts  28 , and a second cover  87  covering the feeder drive shaft  81  and, generally, the belts  28  in upstream end of the envelope feeder  17 . 
     For holding envelope boxes and related envelope container paraphernalia, the feeder  10  includes a preparation deck assembly  53  that is supported by two rail plates  54   a,b  having their ends bolted to the upstream extent of the right support plate  20   a . The plates  54   a,b  are of sufficient thickness so that relatively heavy envelope boxes may be placed on the deck  55  such that the operator may have an ample supply of envelopes for each job. In order to avoid tipping of the feeder due to boxes of envelopes laid on the preparation deck  55 , the base  21  includes mounting apertures  32  in the lower portions of the slide panels  31   a,b  which preferably are used to firmly mount the base on a work table (see  FIG. 6 ). 
     As may be seen in  FIG. 6 , the feeder  10  is preferably bolted securely onto a table  40  and moved into a position adjacent to the printer  11  with collator  110  abutting the manual input ingestion  12  area on the printer so that the downstream end  23  of the feeder  10  abuts the pickup roller assembly  13  on the printer  11 . The horizontal feeder assembly  14  may also be finely adjusted using the horizontal feed assembly rollers  41  so that roller  67   e  discharges envelopes directly into the pickup roller assembly  13  across a gap between roller  67   e  and pickup roller  18  (see  FIG. 7 ). As may be understood, the gap between the feeder  10  and the printer  11  may be adjusted to suit the type of printer to which the feeder  10  is being mated and the type of envelope media being printed. 
     Referring now to  FIG. 7 , it may be seen that the envelope feeder  10  is designed to provide a two stage feed flow  100  that suits the ingestion of envelopes for printing at a rate adapted to suit most high-speed printers. Conveyors  16  and  17  are oriented longitudinally and in the same horizontal plane to create a continuous smooth liner movement of envelopes  101  along the feeder  10  from an upstream end  24  toward a downstream end  23 . Preferably, envelopes  101  are stacked against backstop  29  at approximately a sixty (60) degree backward slanting angle  105  and laid in a grouped parallel fashion  103  on the feed conveyor belts  28  such that the backward angle is maintained, thereby creating a horizontal plane  113  along the upper edges of the envelopes  101  parallel to the loading deck  27 . Other backward facing angles will work also, however, the inventors have found about sixty (60) degrees to be optimal. When actuated, the conveyors  16  and  17  operate at different speeds with the accelerator feed conveyor  17  moving at approximately eight (8) times that of feed conveyor  17 . Movement is coordinated with a microprocessor (see  FIG. 9 ) so that conveyors  16  and  17  move simultaneously. However, since the acceleration conveyor  16  is moving faster than the feed conveyor the lower edge of each envelope  101  advances more rapidly as soon as an envelope reaches the separation point  104  (a slight gap) between each conveyor. As the lower edges of the envelopes advance toward the downstream end  23 , the lower edges of each envelope spread out relative to any adjacent envelope moving along the acceleration feed conveyor  16 , thereby creating a shingled feed grouping of envelopes  102  that form a curve  114  along their upper edges as shown. In three dimensions, the curve  114  is actually a curved plane formed along the upper edges of the envelopes. The severity of the curve angle  114  will vary depending upon the height of the particular envelope being fed along the conveyors, the speed of the acceleration feed conveyor, and the length of the acceleration feed conveyor  16 . But, generally the curve  114  will have a downward slope that is most severe from the gap  104  to about the mid-way point of the acceleration feed conveyor toward the downstream end, with a more moderate curve slope within the second half of the acceleration feed conveyor. 
     The shingled envelope group  102  terminates at the downstream end of the acceleration feed conveyor with an envelope pickup stack  117  in an engagement/pickup zone  116  of pickup assembly  13 . As the envelopes move toward the printer pickup roller assembly  13  a stack of envelopes forms below a pickup roller  18 , being partially supported and moved into place by roller  67   e , at which point the overlap of each envelope over one another increases considerably. The stack height is typically at least 6 envelopes deep which raises the upper most envelope to easy engagement with the pickup roller  18  and facilitates the ingestion of envelopes into the printer  11  at a speed suitable for high-speed printer processing. Since the acceleration feed conveyor is continuously moving envelopes into place at the bottom of the envelope stack  117 , the stack  117  is continuously replenished at a rate that will sustain the availability of an envelope to the pickup roller  18  at all times until all envelopes on the acceleration feed conveyor are consumed. A sensor  118  is positioned below the envelope stack  117  in the pickup zone  116  and is configured to deflect backward and downward at the presence of any envelopes within the pickup zone  116 . When the pickup zone  116  is absent of envelopes, the sensor  118  moves upward and provides a signal to indicate a “paper-out” condition to the printer  11 , or to the feeder  10  if desired and as will be further discussed. 
     Referring to  FIG. 8  in view of  FIG. 7 , it may be seen that the process  120  of feeding envelopes utilizing feeder  10  involves a combination of operator and automatic controls  128 . An operator loads a stacked collection of envelopes against the backstop  122  and initiates a continuous advancement of the acceleration and feed conveyors ( 16  and  17 )  123  utilizing a switch  124  until a satisfactory envelope pickup stack  117  has been established  126 . Although a stack of about six (6) envelopes is preferred, as long as one envelope is present in the pickup zone the automatic feeding process will proceed successfully under automatic control. Once envelopes are available for the printer  11  to process in the pickup zone  116 , the conveyors are switched off  127  and the printer  11  initiated  129 . As part of the pickup assembly  13 , an optical proximity sensor ( 153  in  FIGS. 9 and 10 ) detects the travel distance of the pickup roller  18  as it moves down to pick up an envelope by detecting a reflective surface ( 163  in  FIG. 10 ) on the roller  18 . As the envelope pickup stack  117  depth diminishes due to printer ingestion, the travel distance of the pickup roller must increase to pickup remaining envelopes. The sensor  153  is calibrated to detect a certain length of movement of the pickup roller  18  downward corresponding with a depletion of the envelope stack to a known quantity of envelopes, typically less than or equal to 6 envelopes. When the sensor  153  is triggered, it sends a signal  131  to a control system  140  (see  FIG. 9 ). The control system  140  responds by advancing both conveyors for about one half (½) a second  132  causing several envelopes (typically 4-6) within the shingled envelope group  102  to advance into the envelope stack  117  at the bottom-most position of the stack. As can be understood by steps  131 ,  132 , and  134 , the acceleration feed conveyor  16  will continue to feed envelopes into the envelope stack for consumption by the pickup roller  18  as long as envelopes are present within the stack  117  responsive to continuing pickup roller sensor signals. While the inventors have found that one half (½) a second of conveyor advancement is satisfactory for standard, low-cost electric drive motors, the period of time for advancing the conveyors in coordinated unison will depend upon the envelope ingestion speed (i.e. the print speed of the printer) and the movement speed of the conveyors  16 , 17 . However, once the conveyor activation time duration has been satisfactorily established, the conveyors will be continually advance envelopes at coordinated intervals to replenish the envelope stack  117  irrespective of the speed at which the envelopes arrive at the pickup zone  116 , and irrespective of how long or the type of envelope media that has been loaded onto the conveyors. Moreover, such replenishment is done without operator intervention. 
     When no further envelopes are present in the stack  117 , the paper out sensor  118  will rotate upwards and send a signal  136  to indicate on a display  137  that a paper-out condition has occurred. The signal can be processed internally by the printer pursuant to known processing within the printer electronics when paper is unavailable, and/or the signal can simultaneously be processed by the control system  140  to stop the conveyors  16  and  17  from further movement. Alternatively, an operator can simply actuate a switch on the feeder  10  to disengage further movement of the conveyors. 
     As shown in  FIG. 9 , the control system  140  includes a micro-controller  141  connected to a group A of sensors  147 , including the optical proximity sensor  153  for sensing the movement downward of the pickup roller  18 , indicating a depletion event in the height of the envelope stack  117 , and at least one sensor  151  to indicate a paper out condition in the envelope stack. The micro-controller  141  may be any known 4 or 8 bit micro-controller that can be programmed as is understood in the industry. Additional sensors  152 , such as an envelope alignment condition within the pickup zone  116 , may also be included to form a second sensor sub-group B  149 . Micro-controller  141  also controls motor drivers  145  that turn-on and initiate rotation of two motors  142 . Motor  143  drives acceleration feed conveyor  16  and motor  144  drives feed conveyor  17 . Two variable resistor elements  156  and  157  control the voltage supplied to the motors  142 , and thereby vary the speed of each motor by providing a varying voltage value to the micro-controller  141 . Manual switch  154  actuates immediate and continuous movement of the motors  142  pursuant to the loading step  122 / 123  in  FIG. 8 , and power supply  159  provides power to the control system  140 , including all sensors and motors from an AC source  161 . 
     It will be noted that for the herein described embodiment, feeder  10  does not need the presence of sub-group B  149  sensors to operate. For example, mechanical sensor  151  arranged within the pickup assembly  13  (e.g. element  118  in  FIG. 7 ) may be left unconnected to control system  140  and provide an internal signal to the printer  11  only. Further, sensor group A  147  may be varied as may be understood to enhance the timing and speed of ingestion of envelopes into printer  11 . For example, optical proximity sensor  153  might be replaced with a pressure switch adjacent to the stack to determine its height, or by a lever switch in contact with the pickup roller to determine its movement downward. Nevertheless, the inventors prefer the use of an optical proximity sensor to determine a depletion event in the pickup stack  117  at the pickup zone  116  because of its ease of calibration for different types of printers. 
     Preferably, the micro-controller  141  is programmed to actuate the motors  142  upon the receipt from sensor  153 , indicating a stack depletion event, for a time period of approximately one half (½) of one second, although a movement actuation range of 0.3 to 0.7 seconds will typically satisfy the pickup speed for most printers using a pickup roller to ingest an envelope for processing. The duration of the movement actuation should be evaluated prior to feeder  10  operation so that movement duration may be pre-programmed into the micro-controller  141 , or a simple variable resistor knob for each roller (e.g. elements  156  and  157 ) may be adjusted to set the speed of each conveyor drive motor and, thereby, the speed of each conveyor. 
     The inventors have found that an optimal configuration for the feeder  10  is a speed of 46 inches/minute for the acceleration feed conveyor  16  combined with a speed of 5.7 inches/minute for the feed conveyor  17 , thereby yielding an 8:1 speed ratio, with a dual conveyor activation period of 0.5 seconds. However, higher and lower ratios are possible. A low ratio of 5:1 is possible with the acceleration feed conveyor  16  moving at 46 inches/minute and the feed conveyor  17  moving at 9.2 inches/minute, and the conveyors would need to be activated for 0.3 seconds. A high ratio is also possible with the acceleration feed conveyor  16  moving at 46 inches/minute and the feed conveyor  17  moving at 3.8 inches/minute, but the conveyors would need to be activated for at least 0.7 seconds to keep the pickup stack satisfactorily filled. As the ratio decreases, an increase in overlap between envelopes results on acceleration feed conveyor  16  so that a smaller activation period is necessary to replenish the pickup stack for a given conveyor speed. As the ratio increases, the degree of overlap in envelopes on the acceleration feed conveyor  16  decreases such that a longer conveyor activation period is necessary to replenish the pickup stack. However, irrespective of the ratio selected, it is critical that the acceleration feed conveyor  16  must move with sufficient speed to deliver replenishment envelopes to the envelope stack  117  faster than the printer can ingest the envelope pickup stack  117 . Further, it is critical that the acceleration feed conveyor  16  be substantially faster than the envelope feed conveyor  17  so that a shingled column is created having a curve similar to the curve  114  shown in  FIG. 7 . Such a speed differential results in the lying flat or “lying down” of envelopes such that a satisfactory envelope stack  117  is formed within the manual input tray area of printer  11  to allow rapid pickup and ingestion by the pickup roller assembly  13  without stalls. 
       FIG. 10  provides a detailed view of the pickup roller assembly  13  with an envelope stack  117  already formed beneath the assembly  13  trailed by a shingled set of waiting envelopes  102 . As shown, at the point of pickup of an envelope, roller  18  moves down to capture the top-most envelope and moves it forward into the printer for processing. Other envelopes are stacked in shingled fashion below the lead envelope supporting one another within the pickup zone  116 . Paper out sensor  118  is depressed while any envelope is present within the pickup zone  116 , thereby stopping the sending of any signal by the sensor  118 . Pickup roller  18  includes just below sensor  153  an optically reflective surface  163  capable of reflecting light frequencies detected by sensor  153 . When pickup roller  18  moves downward a preselected distance, sensor  153  detects a calibrated loss of reflected light by the sensor due to the distance the reflective surface has moved downward and away from sensor  153 . When the pickup roller travels the calibrated distance, sensor  153  sends a signal to the micro-controller  141  as previously discussed and conveyors  16  and  17  activate to replace the envelopes ingested by the printer  11  for a specified time period. Since, optimally, the acceleration conveyor  16  moves at eight (8) times the rate of conveyor  17 , a flat shingled procession of envelopes is continually presented to the pickup roller  18  in an orientation that facilitates envelope pickup and at a feed rate that maintains envelopes in the correct orientation in the pickup zone  116  until all envelopes on the acceleration feed conveyor  16  have been exhausted. Guides  19   a  and  19   b  assist to keep the envelope procession structured such that each envelope arrives at the pickup zone  116  with an orthogonally oriented leading edge. 
     While I have shown my invention in one form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit thereof.