Patent Publication Number: US-7223223-B2

Title: Method of folding and stacking multiple sheet sets

Description:
RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 10/921,278, filed 19 Aug. 2004, now U.S. Pat. No. 7,094,195 which is a continuation-in-part of U.S. patent application Ser. No. 10/456,419, filed 5 Jun. 2003, now U.S. Pat. No. 7,066,871. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention pertains to processing thin sheets of material, and more particularly to apparatus that feeds, processes, and stores large numbers of individual or sets of thin sheets. 
   2. Description of the Prior Art 
   Numerous types of equipment have been developed to process sheets of paper. For example, machines for feeding, folding, and sealing paper sheets are well known and in widespread use. 
   Some prior machines combine the functions of folding and sealing paper sheets. Representative combination folding and sealing machines may be seen in U.S. Pat. Nos. 6,080,251; 6,080,259; 6,086,698; and 6,264,592. Typical mechanisms for feeding paper sheets are shown in U.S. Pat. Nos. 4,394,009; 5,246,221; and 6,145,831. U.S. Pat. No. 6,554,271 discloses a gate tip paper feeder that may be used with a paper folding machine. 
   Most prior sheet processing equipment was limited to handling only one sheet at a time. Although there have been exceptions, in general considerable effort was expended in the past to prevent more than one sheet from feeding at a time, because feeding multiple sheets was likely to cause jams downstream. In some equipment, a supply stack of multiple sheets was loaded at an in-feed station, but only one sheet at a time was removed from the stack for being propelled downstream for processing. In other equipment, the sheets were supplied individually from a source such as a printer to a downstream station for further processing. 
   In many situations it is desirable to fold two or more sheets together as a single set. Most prior folding equipment was not capable of performing that function, because, as mentioned, the feeding devices of the prior machines could not feed more than one sheet at a time, so there was no way to propel multiple sheets together to the folding mechanism. One prior machine was capable of folding more than one sheet at a time as a set. That machine was limited to folding sheets that were fed by hand to the folding mechanism, however. It was not capable of feeding sheets one at a time from a supply stack or other equipment to the folding mechanism. 
   Another problem with prior sheet feeding and folding machines was that they could not hold all the folded sheets that came from a supply stack. The machines normally included an output tray that held the folded sheets. However, the tray was too small to hold the number of folded sheets equal to the capacity of the machine at the supply stack. Consequently, an operator had to be present and remove the folded sheets from the output tray. Otherwise the folded sheets would spill off the output tray onto the floor. 
   Thus, a need exists for a way to process multiple sheets simultaneously, as well as for other improvements to sheet processing equipment. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, a method of folding and stacking multiple-sheet sets is provided that is also capable of processing individual sheets. This is accomplished by apparatus that includes a folder having both a sheet in-feed station and a set feeder that guides the sets directly to a processing station. 
   The folder in-feed station propels sheets one at a time in a downstream direction from a source of the sheets to the processing station. The source of sheets may be other equipment, such as a printer, that discharges sheets directly to the folder of the invention. In one embodiment of the invention, the source of sheets is a feed mechanism having a tiltable hopper on which a supply stack of sheets is loaded. The feed mechanism includes a pickoff wheel and is operable to remove one sheet at a time from the supply stack and propel the sheets in the downstream direction to the processing station, such as a folding mechanism. After the processing has been completed, the sheets are discharged from the processing station. 
   The set feeder is located between the in-feed station and the processing station. In its simplest form, the set feeder comprises a cover in the frame of the folder. The cover defines an elongated opening near the inlet of the processing station. A person inserts a set of sheets, which may be stapled together, through the cover opening. The cover opening directs the set to the processing station, which folds or otherwise processes the set. 
   According to another aspect of the invention, the set feeder includes a guide mechanism that is removably mounted to the cover. The cover opening is along the base of the guide mechanism. Preferably, there is a lower guide inside the cover and aligned with the opening and the guide mechanism. The lower guide has an end that is close to the inlet of the processing station. The lower guide may be used in combination with the guide mechanism, or the lower guide may be used without using the guide mechanism. 
   In the lower guide and close to the cover opening is a sensing device. The sensing device is connected electrically to a motor that operates the processing station. For example, the processing station may be a folding mechanism. In that case, the motor operates a series of rollers that propel sheets through the folding mechanism. 
   In a first mode of operation of the folder, the in-feed station propels one sheet at a time in the downstream direction from the supply stack or other source. The sheets enter the processing station, where they are processed according to the manner of the particular machine. 
   In a second mode of operation of the folder, the in-feed station is not operated. Instead, a person places a set of multiple sheets, which may be stapled together, against the set feeder guide mechanism. The set of sheets is slid down the guide mechanism such that its leading edge enters the cover opening. The paper slide guides the set leading edge to the input of the processing station, such as the input nip of a folding mechanism. 
   As the leading edge of the set of sheets enters the cover opening, the sensing device signals the motor to activate the processing station, such as the rollers of a folding mechanism. However, the in-feed station does not operate, so no sheets are propelled downstream from there. The input nip rollers contact the set top and bottom sheets and draw them together in the downstream direction through the rest of the folding mechanism or other processing station in the same manner as a single sheet. When the set is fully processed, it is discharged from the processing station. In one preferred embodiment of the invention, the motor stops running after a selected time and remains idle until another set is slid into the set feeder. In that manner, sets of sheets by-pass the in-feed station and are processed without danger of the sheets becoming separated from each other or jamming in the processing station. Further, the processing of the sets is completely independent of the supply sheets stacked at the in-feed station or other source of sheets. When no more sets of sheets are to be processed, the folder can be operated in the usual way to again process individual sheets from a supply stack at the in-feed station or from another source. 
   It is an important feature of the invention that the set feeder need not include a sensing device. In an alternate embodiment, the mechanical portions of the set feeder are identical to the embodiment described with the sensing device. The folder is controlled to operate the processing station, but not to propel any sheets to it from a stack or other supply source. Alternatively, the folder in-feed station may be operated in the normal way but without any sheets there. In either case, the operator slides the set of sheets along the guide mechanism and into the cover opening in the same way as with the sensing device embodiment. When the set has been processed, the folder can be operated in the normal way. 
   Further in accordance with the present invention, the folder is capable of holding a number of processed sheets equal to or greater than the number of sheets in the supply stack loaded at the in-feed station. For that purpose, the processed sheets are discharged from the processing station onto a telescoping stacker. The telescoping stacker comprises a deck and at least one extension tray. One end of the deck is fixed to the folder frame. The extension tray is slideable on the deck between a retracted location and an extended location. In the retracted location, the extension tray is nested inside the deck. In the extended location, the extension tray extends from the deck. 
   The folder may have an output conveyor at the downstream end of the processing station. In that case, the deck supports a downstream shaft of the conveyor. The extension tray is almost entirely under the conveyor and is nested in the deck when the extension tray is in the retracted location. A stop on the extension tray contacts the conveyor downstream shaft to set the extended location for the extension tray. 
   During operation of the folder, the extension tray is normally pulled to its extended location. The processed sheets are discharged onto the extension tray, which holds a large number of them. For even greater holding capacity, a second tray is incorporated into the telescoping stacker. The second tray is slideable along the extension tray between a retracted location where it nests within the extension tray and an extended location. When the second and extension trays are extended for their full lengths from the deck, the telescoping stacker can hold a number of processed sheets equal to or greater than the capacity of the paper in-feed station supply stack. Consequently, the folder of the invention can be operated for its full capacity without the presence of an operating person. 
   The method and apparatus of the invention, using a set feeder, thus enables the folder to process both individual sheets as well as multiple-sheet sets. The folder is capable of holding a number of processed sheets equal to the number of sheets at the in-feed station, even though an operator need not be present during processing operations. 
   Other advantages, benefits, and features of the present invention will become apparent to those skilled in the art upon reading the detailed description of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a broken partial front view of the folder of the invention. 
       FIG. 2  is a partial back view of the present invention. 
       FIG. 2A  is an enlarged view of selected portions of  FIG. 2 . 
       FIG. 3  is a partial view taken along line  3 — 3  of  FIG. 1 . 
       FIG. 4  is a broken front view of the set feeder of the present invention. 
       FIG. 5  is a top view of  FIG. 4 . 
       FIG. 6  is a cross-sectional view taken along line  6 — 6  of  FIG. 4 . 
       FIG. 7  is a simplified schematic diagram of the control circuit of the present invention. 
       FIG. 8  is view taken along line  8 — 8  of  FIG. 2   
       FIG. 9  is a view generally similar to  FIG. 2 , but showing the extension tray of the telescoping stacker in the extended location. 
       FIG. 10  is view showing the second tray of the telescoping stacker in the extended location. 
       FIG. 11  is a cross-sectional view taken along line  11 — 11  of  FIG. 6 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   General 
   Referring first to  FIGS. 1 ,  2 ,  2 A, and  5 , a sheet processing machine  1  is illustrated that carries out the method of the present invention. The particular sheet processing machine  1  is in the general form of a paper folding machine, and the machine will be referred to as a folder  1 . However, it will be understood that the invention is not limited to any particular type of sheet processing equipment. 
   The folder  1  has a frame  3  that includes parallel side walls  5  and  6 . The side walls  5  and  6  define a longitudinal center plane  100  of the folder. At an upstream end  7  of the folder is an in-feed station that supplies individual sheets in a downstream direction  11  from a source of sheets to a processing station. For example, the source may be a printer or other equipment, not shown, located in the upstream direction  8  of the folder. In the particular in-feed station  9  shown, the source of sheets is a supply stack represented at phantom line  12 . In the downstream direction  11  from the in-feed station  9  is a folder station  13 . 
   Looking also at  FIG. 4 , a cover  85  extends between the frame side walls  5  and  6  and overlies the folder station  13 . The cover  85  has side walls  87  and a top wall  89 . There is a pin  91  in each cover side wall  87  that protrudes into the adjacent frame side wall. The pins  91  are close to the downstream end of the cover. In each frame side wall near the upstream end of the cover as a second pin  93 . As shown in  FIGS. 1 and 2 , the cover is in a working position whereat the cover side walls rest on the associated pins  93 , and the cover top wall  89  is generally horizontal. When the cover is in the working position, it generally overlies the folder station  13 . From the working position, the cover is pivotable in the direction of arrow  95  about the pins  91  to an open position. When the cover is in the open position, it is generally vertically oriented, and the folder station is open from the top of the folder  1 . 
   The sheets are propelled one at a time from the supply stack  12  or other source in the downstream direction  11  to the folder station  13 . After being folded, the finished sheets  10  are discharged from the folder  1 . The specific folder illustrated is shown equipped with an output conveyor  14 , but an output conveyor is not necessary for the proper functioning of the present invention. After folding is completed at the folder station, the sheets are deposited onto the output conveyor  14 . 
   In-Feed Station 
   The in-feed station  9  is comprised of a hopper  15  that is rotatable in the frame walls  5  and  6  by means of a shaft  17 . The supply stack  12  of paper sheets is loaded on the hopper  15  between side guide plates  19 . The weight of the supply stack causes the hopper  15  to pivot in the direction of arrow  21  about the shaft  17 . The leading edges of the sheets are held in place along a curved front guide  23 . A counterbalance system collectively represented at reference numeral  24  causes the topmost sheet in the supply stack to press against a pickoff wheel  25  of a feed mechanism  27 . The pickoff wheel  25  is connected to a shaft  26  that is rotatable in the frame  3 . 
   Paper feed mechanisms are well known in the art, and any of a wide variety of feed mechanisms may be used with the folder  1 . An exemplary paper feed mechanism is disclosed U.S. Pat. No. 6,554,271. The feed mechanism  27  propels one sheet at a time from the supply stack  12  in the downstream direction  11  to the folder station  13 . 
   As mentioned above, the particular in-feed station  9  is not mandatory to the operation of the folder  1 . Any source of individual sheets, such as a printer, may be used to propel the sheets in the downstream direction  11  to the folding station  13 . 
   Folder Station 
   The particular construction of the folder station  13  is not critical to the functioning of the folder  1 . As illustrated, the folder station is comprised of four rollers  29 ,  31 ,  33 , and  35 . The rollers  29  and  31  cooperate to form an input nip  37 . The rollers  31  and  33  form an intermediate nip  39 . The rollers  33  and  35  form an output nip  41 . The folder station further has a first fold chute  43  and a second fold chute  45 . The fold chutes  43  and  45  have respective stops  47  and  49 . The stops  47  and  49  are adjustable to produce selected folded configurations to the sheets, as is well known in the folder art. 
   The folder station input nip  37  receives the leading edge of a sheet propelled from the feed mechanism  27  of the in-feed station  9 . The sheet is propelled by the rollers  29  and  31  into the first fold chute  43  and up against the stop  47 . The sheet is caught and folded along a first fold line in the intermediate nip  39 . The rollers  31  and  33  of the intermediate nip propel the partially folded sheet to the second fold chute  45 . The sheet is caught a second time and folded along a second fold line in the output nip  41 . The rollers  33  and  35  of the output nip discharge the completely folded sheet  10  onto the output conveyor  14 . 
   Drive Train 
   To operate the in-feed station and the folder station, the folder further comprises a drive train. The construction and operation of the drive train is dependent on the particular type of in-feed and processing stations may vary without affecting the scope of the invention. For example, the drive train may operate the in-feed station and the processing station independently of each other. The particular folder  1  illustrated has a drive train  51  that rotates the feed mechanism pickoff wheel  25  and the folder station rollers  29 ,  31 ,  33 , and  35 . The drive train  51  has an electric motor  53  with a pulley  55  on the motor shaft. An idler pulley  57  is mounted on a shaft  65  for rotation on the frame wall  5 . There is another pulley  59  connected to the roller  33 , and another pulley  61  connected to an upstream shaft  63  of the output conveyor  14 . A timing belt  69  is trained around the pulleys  55 ,  57 ,  59 , and  61 . Energizing the motor  53  causes rotation of the pulleys  57 ,  59 , and  61  and thus of the shafts and rollers  65 ,  33 , and  63 . The folder station rollers  29 ,  31 , and  35  rotate because of friction between them and the roller  33 . 
   On the shaft  65  with the idler pulley  57  is a second pulley  67 ,  FIG. 3 . A second timing belt  70  is trained over the pulley  67  and also over a pulley  71  that is on the shaft  26  of the in-feed station pickoff wheel  25 . The pulley  71  is part of an electric clutch  73 . When the clutch  73  is energized, the shaft  26  rotates together with the pulley  71 . When the clutch  73  is de-energized, the shaft  26  does not rotate with the pulley  71 . 
   Output Conveyor 
   In addition to the shaft  63 , the output conveyor  14  also has a downstream shaft  75 . The downstream shaft  75  is supported on a deck  79  of a telescoping stacker  81  that will be described in detail below. The deck  79  is fixed to the frame walls  5  and  6 . One or more belts  77  are trained over the shafts  63  and  75 . Operation of the electric motor  53  causes the upper flight of the belt  77  to travel in the downstream direction  11 . 
   Set Feeder 
   In accordance with the present invention, a set feeder  83  is incorporated into the folder  1 . The set feeder  83  enables multiple sheets of paper to be folded together as a set at the folder station  13  without jamming. Operation of the set feeder is independent of the operation of the feed station  9 , as will be explained. 
   The set feeder  83  makes use of the cover  85  that overlies the folder station  13 . Also see  FIGS. 4 and 5 . To accommodate the set feeder, an elongated transverse opening  97  is formed in the cover top wall  89 . One end of the opening  97  has a short length  98  that is wider than the rest of the opening. The opening is offset from the longitudinal center plane  100  of the folder  1 . As illustrated, the opening is closer to the frame side wall  5  than to the wall  6 , but the reverse offset is also acceptable. 
   In its simplest form, the set feeder  83  utilizes only the opening  97  in the cover top wall  89 . The opening  97  is located close to the input nip  37  of the folder station  13 . The folder  1  is operated by inserting a set of sheets through the cover opening. The set of sheets may, but need not, be stapled together. The cover opening directs the set leading edge to the folder station input nip. The drive train  51  is controlled such that the in-feed station  9  does not propel any sheets in the downstream direction  11 , but the folder station rollers  29 ,  31 ,  33 , and  35  do rotate. The set is thus drawn into the folder station for complete folding and ultimate discharge from the folder. 
   In the illustrated embodiment, the set feeder  83  comprises a guide mechanism  101  that upstands from the cover  85 . In the illustrated construction, the guide mechanism  101  includes a yoke  103 . The yoke  103  has end plates  105  that span the length of the cover opening  97 . The yoke end plates  105  have tabs  106  that fit into corresponding slots  108  in the cover top wall  89 . Between the yoke end plates  105  is a back plate  107 . The bottom  109  of the back plate  107  is close to the cover top wall opening. 
   Also part of the guide mechanism  101  is a back plane  111 . The back plane  111  comprises a flat area  113  that overlies a portion of the yoke back plate  107 . An end strip  115  is at a right angle to the flat area  113 . The back plane is joined to the yoke by a fastener  117 , such as a stud welded to the flat area and passing through a hole in the yoke back plate  107  and fastened with a nut. 
   To accommodate the tolerances inherent in the manufacture of the various components of the set feeder  83 , the back plane  111  is adjustable relative to the yoke  103 . For that purpose, the yoke and back plane have respective aligned tabs  119  and  121 . A spring  122  is interposed between the tabs  119  and  121 . A screw  123  is inserted through a hole in the back plane tab and through the spring  122  and is threaded into the yoke tab. By turning the screw  123 , the back plane swivels in the directions of arrows  124  about the fastener  117 , thereby changing the orientation of the end strip  115  relative to the cover opening  97 . 
   The guide mechanism  101  further comprises an adjuster  125 . According to one aspect of the invention, the adjuster  125  has a central plate  127  that partially underlies the flat area  113  of the back plane  111 . The adjuster also has an end leg  129  that overlies part of the back plate  107  of the yoke  103 . There is an edge strip  130  along the end leg  129 . The adjuster is adjustable linearly in the directions of arrows  132  relative to the back plane and yoke by means of a slot  131  in the central plate  127 . A pair of studs  133  or similar elements fixed to the back plane flat area pass through the adjuster slot  131  to slidingly guide the adjuster. A fastener  135 , such as another stud with a nut, also fixed to the back plane flat area and passing thorough the adjuster slot, is used to lock the adjuster in place. 
   To mount the guide mechanism  101  to the cover  85 , a pair of latches  160  are employed. Each latch  160  is pivotally connected by a respective pin  162  to an end plate  105  of the yoke  103 . There is a finger end  165  on one side of the pin  162 , and a hook  167  on the other side of the pin. The latch hooks  167  fit into slots  136  in the cover top wall  89 . A torsion spring, not shown, fits over each pin  162 . The torsion springs bias the latch hooks into engagement with the cover slots  136 . 
   To remove the guide mechanism  101  from the cover  85 , the latches  160  are manually pivoted against the torsion springs in the direction of arrow  138  to disengage the latch hooks  167  from the slots  136 . The entire guide mechanism is tilted in the direction of arrow  138  such that the tabs  106  on the yoke  103  also disengage from the cover slots  108 . The entire guide mechanism is thus easily removable from and remountable to the cover. 
   The set feeder  83  may also include a lower guide  134 . See  FIGS. 6 and 11 . The lower guide  134  is illustrated as being in addition to the guide mechanism  101 . However, the versatility of the present invention is such that the set feeder is operable with either the guide mechanism alone or with the lower guide  134  alone, as well as with the combination of the guide mechanism and the lower guide. The lower guide  134  is comprised of a paper slide  137 . The paper slide  137  has an upper flange  139  that is welded or otherwise secured to the underside of the cover top wall  89 . A junction  141  of the paper slide flange  137  with an angled section  143  is at the upstream edge of the cover opening  97 . The paper slide angled section  143  curves with a large radius and terminates at an end  145  that is close to the input nip  37  of the folder station  13 . In the paper slide angled section is an opening that receives a sensing device  146 , such as a photoelectric eye. The sensing device  146  may be held in place to the paper slide angled section by a bracket  148  and fasteners  149 . 
   There is a paper guide  147  associated with the paper slide  137 . The paper guide  147  has a pair of end plates  151  that span the paper slide. The paper guide end plates  151  have respective flanges  153  that are welded to the cover top wall  89 . A bottom plate  155  extends between the end plates and supports the paper slide end  145 . A spanner bar  159  connects the paper guide end plates to each other. The spanner bar  159  is spaced a short distance from the paper slide end  145  such that there is a gap  157  between the spanner bar and the paper slide end. The gap  157  is close to the folder station input nip  37 . There is also a guide rod  164  above the paper slide angled section  143  near the gap  157 . The guide rod  164  is secured to the paper guide end plates. 
   Operation 
     FIG. 7  shows in schematic form the salient components used to control the operation of the folder  1 . To operate the folder in the normal manner for folding sheets ( FIG. 2A ), a supply stack  12  is loaded on the feed station hopper  15 . A main on-off switch  161  is closed. A control  163  energizes the clutch  73  and the motor  53 . The motor pulley  55  ( FIG. 1 ) drives the belt  69  to rotate the shafts  65  and  33  and also the pickoff wheel shaft  26  ( FIG. 3 ). The folder thus operates as a normal sheet folding machine. 
   The set feeder  83  enables a set of multiple sheets to be folded together. For example, the sheets may be taken from a copy machine and stapled together. However, the folder  1  is also capable for folding multiple sheets that are not stapled together. To fold the set, the main switch  161  is opened. The fastener  135  of the adjuster  125  is loosened, and the adjuster is slid relative to the back plane  111  in the direction of arrow  132  such that the adjuster edge strip  130  is at the correct distance from the back plane end strip  115  for the width of the paper in the set. The studs  133  in the back plane guide the adjuster slot  131  when sliding the adjuster. 
   After the fastener  135  is retightened, the set of sheets is laid against the back plane  111  and adjuster  125 . The side edges of the sheets are justified against the end strip  115  of the back plane  11  and the edge strip  130  of the adjuster  125 . A leading edge of the set is placed close to the cover opening  97 . If the set is stapled, the staple is aligned with the opening wider length  98 . The set is slid down into the opening in the direction of arrow  195 ,  FIG. 11 , and into contact with the paper slide  137 . As soon as the sensing device  146  senses the leading edge of the set, the control  163  operates to energize the motor  53  and thus turn the rollers  29 ,  31 ,  33 , and  35  at the folder station  13 . However, the control does not energize the clutch  73 , so the pickoff wheel  25  does not operate to feed any sheets from the supply stack  12  at the in-feed station  9 . The leading edge of the set of sheets is guided along the paper slide angled section  143  toward the gap  157 . The guide rod  164  assures that the set of sheets slides properly to the gap. From the gap, the set of sheets enters the input nip  37  of the folder station. The set is folded in the same manner as a single sheet, but the set by-passes the in-feed station. After processing, the set  10  is discharged onto the output conveyor  14 . After the motor as been energized a selected time, such as five seconds, the motor is de-energized. At that point, the folder  1  is ready either to be turned on by means of the switch  161  for folding individual sheets in the normal manner, or to receive another set of sheets through the set feeder  83  and cover opening. 
   According to another aspect of the invention, the electric clutch  73  and the sensing device  146  are not required. Rather, the belt  69  is trained over a pulley, not illustrated in the drawings, directly on the pickoff wheel shaft  26 . Consequently, the shaft  26  always rotates whenever the motor  53  is energized. When a person wants to fold a set of sheets, he places the set against the guide mechanism  101  as described previously. If no supply stack  12  of sheets is at the in-feed station hopper  15 , the person turns on the folder main on-off  161  switch and slides the set in the direction of arrow  195  through the cover opening  97 . The folder  1  functions to fold the set as previously described. 
   If, however, a supply stack  12  of sheets is loaded at the in-feed station hopper  15 , the person manually tilts the hopper about the shaft  17  in the direction of arrow  21  such that the sheets are out of contact with the pickoff wheel  25 . Then the person turns on the main on-off switch  161  and slides the set through the cover opening  97 . In that way, a conventional control may be used to fold sets with the set feeder  83 . As mentioned, other drive trains and modes of operation of the in-feed station are also usable with the set feeder 
   Telescoping Stacker 
   Further in accordance with the present invention, the folder  1  is capable of holding at least as many folded sheets  10  as the capacity of the in-feed station hopper  15 . After processing, the completed sheets are discharged from the folder. If the folder is not equipped with the output conveyor  14 , the finished sheets are discharged directly to the telescoping stacker  81 . If the folder is equipped with the output conveyor  14 , the finished sheets are deposited on the belts  77 , and the conveyor propels the completed sheets to the telescoping stacker. 
   Looking also at  FIGS. 8–10 , the telescoping stacker  81  is comprised of the deck  79  and one or more slideable trays. In the illustrated construction, the telescoping stacker has a first extension tray  169  and a second tray  171 . To support the extension tray  169 , the deck has a pair of allochiral flanges  173  for the full length of the deck. The extension tray has a flat base  175  with side legs  177  depending from opposite sides of the base. The extension tray legs  177  are slideable on the deck flanges  173 . A pair of pull tabs  179  are on the downstream end of the base  175 . 
   To limit the travel of the extension tray  169  on the deck  79 , the extension tray further comprises a pair of stops  181 . Each stop  181  may be a continuation of a side leg  177 . Each stop is depicted as having an arcuate surface  183  of the same radius as the radius of the conveyor shaft  75 . By pulling the pull tabs  179  in the downstream direction  11 , the extension tray slides until the stops contact the conveyor shaft  75 ,  FIG. 9 . At that point, the conveyor belts  77  propel the folded sheets  10  onto the flat base  175  of the extension tray. When the extension tray is not needed, it is pushed to nest inside the deck. 
   For even greater capacity of the telescoping stacker  81 , the second tray  171  is used. The second tray has a top base  185  that is bent at the downstream end into an angle  187 . The second tray has opposed legs  189  that are slideable on allochiral flanges  191  depending from the flat base  175  of the extension tray  169 . The second tray preferably has a back leg  193 . The second tray is slideable within the extension tray between a retracted location whereat it is nested within the extension tray, and an extended location whereat it extends in the downstream direction  11  from the extension tray. The back leg  193  contacts stops on the extension tray flanges  191  to limit the travel of the second tray relative to the extension tray. The lengths of the extension and second trays are designed to hold at least as many folded sheets  10  as the capacity of the in-feed hopper  15 . In one embodiment of the invention, for instance, the in-feed station hopper  15  is capable of storing 500 sheets, and the telescoping stacker  81  is capable for holding 750 processed sheets. In that manner, all the sheets in a supply stack  12  loaded at the in-feed station  9  can be folded and collected at the telescoping stacker without constant attention from a person. 
   SUMMARY  
   In summary, the results and advantages of folded sheets can now be more fully realized. The folder  1  is capable of processing both individual sheets and multiple-sheet sets in an equally efficient manner. This desirable result comes from using the combined functions of the set feeder guide mechanism  101  and lower guide  134 . The set feeder  83  guides a set directly to the input nip  37  of the folder station  13 . Because the set by-passes the in-feed station  9 , there is no danger of jamming due to multiple sheets being propelled by the feed mechanism  27 . The guide mechanism  101  removably mounts to the cover  85 , which, except for the opening  97  and slots  108  and  136 , may be a standard component of conventional folding machines. The versatility of the invention is further demonstrated by the fact that sets can be processed by means of the electric clutch  73 , the sensing device  146 , and control  163  in which case the feed mechanism does not operate. Alternately, the folder main on-off switch  161  may be used to operate the folder station to process sets, in which case the clutch and sensing device are not required. The telescoping stacker  81  has one or more trays that are extendable to hold at least as many processed sheets  10  as the capacity of the in-feed station hopper  15 , so a person need not give complete attention to the folder during operation. 
   It will also be recognized that in addition to the superior performance of the folder  1 , its construction is such as to cost little, if any, more than traditional processing machines. In fact, the versatility and increase productivity of the set feeder  83  and telescoping stacker  81  enable the folder to quickly recoup any increased initial costs. 
   Thus, it is apparent that there has been provided, in accordance with the invention, a method of folding and stacking multiple-sheet sets that fully satisfies the aims and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art: in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.