FIELD OF THE INVENTION 
     The present disclosure relates to a booklet stacking apparatus and method. More particularly, the disclosure relates to a booklet stacking mechanism and method of its use with which printed booklets can be stacked in a vertically stacked arrangement. 
     BACKGROUND OF THE INVENTION 
     Many electrophotographic imaging devices such as printers can be equipped with booklet making apparatus that are configured for printing booklets, i.e., collections of various sheets of paper that are folded by the apparatus and then, typically, stapled along the fold line by the apparatus. Due to the particular media handling requirements for booklets, such booklets are often output by the booklet making apparatus to a stack-slide tray that is designed to receive booklets. With such a tray, the booklets are stacked in a linear, horizontal arrangement. An example of a stack-slide tray  100  is illustrated in FIG.  1 . 
     As indicated in FIG. 1, the stack-slide tray  100  generally comprises an elongated tray  102  that extends horizontally outward from the booklet making apparatus  104 , typically to a side of the apparatus. The stack-slide tray  100  typically further comprises a stop  106  that is used to prevent booklets  108  from falling off of the tray  102  as they are deposited thereon. As shown in FIG. 1, the stack-slide tray  100  is configured to receive booklets  108  with the stapled end  110  of the booklets facing away from the apparatus  104 . More particularly, the stack-slide tray  100  is configured to begin in an initial retracted position (not shown) in which the stop  106  is positioned in relative close proximity to the booklet making apparatus  104 , and gradually (typically incrementally) extend outwardly from the apparatus as booklets  108  are deposited in the tray  102 . This gradual extension normally occurs in response to information sensed by a sensing arm  112 , which senses the presence of booklets  108  in close proximity to the booklet making apparatus  104 . 
     Operating in the manner described above, the stack-slide tray  100  functions to arrange the booklets  108  in a sequential, layered orientation such as that indicated in FIG.  1 . As is evident from FIG. 1, booklets  108  are deposited in the stack-slide tray  100  until the height of the booklets activates the sensing arm  112  so as to cause the tray to extend away from the booklet making apparatus  104 . As can be appreciated from FIG. 1, the partially overlapping manner in which the booklets  108  are deposited on the tray  102  is necessary in that the portion of the booklets  108  adjacent the stapled sides  110  is thicker, due to a pillowing effect, than the opposite sides of the booklets. Accordingly, if the partially overlapping orientation were not used, the booklets  108  would be unbalanced and would eventually topple off of the tray  102 . As can further be appreciated from FIG. 1, however, the stack quality of the booklets  108  can be poor when a conventional stack-slide tray  100  is used. In particular, the booklets  108  can be deposited in disarray. If the fill level of a stack-slide tray  100  is not closely monitored, booklets  108  can fall to the floor, particularly where the stack-slide tray  102  is used to receive other (i.e., non-booklet) media. Accordingly, stack-slide trays such as that shown in FIG. 1 typically do not work well in multi-use environments. 
     Even where the booklets  108  do not fall from the slide-stack tray  100 , the booklets can be deposited such a random order that it is difficult to determine the printing order. Although not a problem where each booklet is identical, disorder of the booklets can be disadvantageous where different booklets are printed (e.g., in separate printing jobs) in that the booklets then must be manually re-ordered by a human being. Finally, another disadvantage of stack-slide trays is the relatively large amount of space that is required for full extension of the tray. 
     From the foregoing, it can be appreciated that it would be desirable to have an apparatus and method for stacking booklets that avoids one or more of the aforementioned problems associated with conventional booklet stacking arrangements. 
     SUMMARY OF THE INVENTION 
     The present disclosure relates to a booklet stacking apparatus and method. More particularly, the present disclosure relates to a booklet stacking mechanism. In one arrangement, the booklet stacking mechanism comprises a gate that is adapted to be placed adjacent an output area of a booklet making apparatus, the gate being positionable in a closed position and an open position, a delivery path along which booklets can be delivered when the gate is in the open position, and a flipping mechanism that is adapted to receive booklets, invert them, and deposit them in an output bin. 
     The present disclosure also relates to a method for stacking booklets. In one arrangement, the method comprises the steps of permitting a booklet to be deposited in a vertical stacker bin, preventing another booklet from being deposited in the vertical stacker bin and instead delivering the other booklet to a flipping mechanism with which the booklet is inverted, and delivering the other booklet to the vertical stacker bin in the inverted orientation such that the booklets are arranged in a staggered configuration within the vertical stacker bin. 
     Additionally, the present disclosure relates to a printing device. In one arrangement, the printing device comprises means for attracting toner to a surface of a print medium, a booklet making apparatus, a vertical stacker bin, and a booklet stacking mechanism that comprises a gate positioned adjacent an output area of the booklet making apparatus, the gate being positionable in a closed position and an open position, and a flipping mechanism that is adapted to receive booklets, invert them, and deposit them in the vertical stacker bin. 
     The features and advantages of the invention will become apparent upon reading the following specification, when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. 
     FIG. 1 is a schematic view of a stack-slide tray of the prior art. 
     FIG. 2 is a schematic view of an electrophotographic imaging device having a booklet stacking mechanism. 
     FIG. 3 is a schematic of the booklet stacking mechanism shown in FIG.  2 . 
     FIG. 4 is perspective view of a flipping mechanism of the booklet stacking mechanism shown in FIG.  3 . 
     FIG. 5 is schematic view of the booklet stacking mechanism of FIG. 3 operating in a first mode. 
     FIGS. 6A-6D are schematic views of the booklet stacking mechanism of FIG. 3 showing sequential stages of operation in a second mode. 
     FIG. 7 is schematic view of an alternative booklet stacking mechanism. 
    
    
     DETAILED DESCRIPTION 
     Referring now in more detail to the drawings, in which like numerals indicate corresponding parts throughout the several views, FIG. 2 illustrates a schematic side view of a printing device  200  that incorporates a booklet making apparatus  201  and a booklet stacking mechanism  202 , which is described in detail below. By way of example, the printing device  200  comprises a laser printer. It is to be understood, however, that the device  200  can, alternatively, comprise any other imaging device that produces or otherwise handles booklets including, for instance, a photocopier. 
     In the example of FIG. 2, the printing device  200  is arranged as an electrophotographic imaging device that includes a charge roller  204  that is used to charge the surface of a photoconductor drum  206  to a predetermined voltage. A laser diode (not shown) is provided within a laser scanner  208  that emits a laser beam which is pulsed on and off as it is swept across the surface of the photoconductor drum  206  to selectively discharge the surface of the photoconductor drum. In the orientation shown in FIG. 2, the photoconductor drum  206  rotates in the clockwise direction. A developing roller  210  is used to develop a latent electrostatic image residing on the surface of photoconductor drum  206  after the surface voltage of the photoconductor drum has been selectively discharged. Toner  212  is stored in a toner reservoir  214  of an electrophotographic print cartridge. The developing roller  210  includes an internal magnet (not shown) that magnetically attracts the toner  212  from the toner reservoir  214  to the surface of the developing roller. As the developing roller  210  rotates (counterclockwise in FIG.  2 ), the toner  212  is attracted to the surface of the developing roller  210  and is then transferred across the gap between the surface of the photoconductor drum  206  and the surface of the developing roller to develop the latent electrostatic image. 
     Print media  216 , for instance sheets of paper, are loaded from an input tray  218  by a pickup roller  220  into a conveyance path of the device  200 . Alternatively, the print media  216  can be placed into the conveyance path from an internal bin  222  of the device  200 . Each recording medium  216  is individually drawn through the device  200  along the conveyance path by drive rollers  224  such that the leading edge of each print medium is synchronized with the rotation of the region on the surface of the photoconductor drum  206  that comprises the latent electrostatic image. As the photoconductor drum  206  rotates, the toner adhered to the discharged areas of the drum contacts the print medium  216 , which has been charged by a transfer roller  226 , such that the medium attracts the toner particles away from the surface of the photoconductor drum and onto the surface of the medium. Typically, the transfer of toner particles from the surface of the photoconductor drum  206  to the surface of the print medium  216  is not completely efficient. Therefore, some toner particles may remain on the surface of the photoconductor drum. As the photoconductor drum  206  continues to rotate, the toner particles that remain adhered to the drum&#39;s surface are removed by a cleaning blade  228  and deposited in a toner waste hopper  230 . 
     As the print medium  216  moves along the conveyance path past the photoconductor drum  206 , a conveyer  232  delivers the medium to a fusing system  234 . The print medium  216  passes between a fuser roller  236  and a pressure roller  238  of the fusing system  202 . As the pressure roller  238  rotates, the fuser roller  236  is rotated and the print medium  216  is pulled between the rollers. The heat applied to the print medium  216  by the fusing system  234  fuses the toner to the surface of the print medium. 
     Where the print media  216  are to be combined to form a booklet, the collected print media (typically two or more pieces of paper) are delivered to the booklet making apparatus  201  by output rollers  242 . The booklet making apparatus  201  folds and, if desired, staples the media together to form booklets, which ultimately are deposited in a vertical stacker bin  248  that, by way of example, comprises a conventional output tray  250  which can be vertically displaced (as indicated by the double-sided arrow  252 ) depending upon the fill level of the bin. 
     As is further identified in FIG. 2, the printing device  200  can also include a formatter  254  and a controller  256 . The formatter  254  receives print data, such as a display list, vector graphics, or raster print data, from a print driver operating in conjunction with an application program of a separate host computing device. The formatter  254  converts the print data into a stream of binary print data and sends it to the controller  256 . In addition, the formatter  254  and the controller  256  exchange data necessary for controlling the electrophotographic imaging process. In particular, the controller  256  supplies the stream of binary print data to the laser scanner  208 . The binary print data stream sent to the laser diode within the laser scanner  208  pulses the laser diode to create the latent electrostatic image on the photoconductor drum  206 . 
     In addition to providing the binary print data stream to the laser scanner  208 , the controller  256  controls a high voltage power supply (not shown) that supplies voltages and currents to the components used in the device  200  including the charge roller  204 , the developing roller  210 , and the transfer roller  226 . The controller  256  further controls a drive motor (not shown) that drives the printer gear train (not shown) as well as the various clutches and feed rollers (not shown) necessary to move print media  216  through the conveyance path of the device  200  and, as is discussed below, operate the booklet stacking mechanism  202 . A power control circuit  258  controls the application of power to the fusing system  234 . Normally, the power control circuit  258  is configured such that the power to the fusing system  234  is linearly controlled and the power levels can be smoothly ramped up and down as needed. 
     As identified above, conventional booklet stacking methods, such as those implementing a stack-slide tray, can be disadvantageous. Accordingly, improved booklet stacking apparatuses and methods will be described. As identified above, the printing device  200  includes a booklet stacking mechanism  202  that is shown in greater detail in FIG.  3 . As indicated in this figure, the booklet stacking mechanism  202  is normally positioned in close proximity to output rollers  244  located downstream from the booklet making apparatus  201 . The booklet stacking mechanism  202  generally comprises a gate  300 , a delivery path  302 , and a flipping mechanism  304 . The gate  300  is generally elongated (extending in a direction into the page) and is positioned at an opening  306  of the delivery path  302 . Typically, the gate  300  is mounted to a shaft  308  that is driven by a drive mechanism (not shown) such that the gate can be pivoted about the shaft from a closed position (identified in FIG. 3) in which print media exiting the electrophotographic imaging device  200  may pass to the stacker bin, to an open position (identified in dashed lines) in which booklets can be directed into the delivery path  302 . To ensure that the various print media are directed into the stacker bin when the gate  300  is in the closed position, the gate typically is constructed of a rigid material and may further have an curved outer surface. 
     The delivery path  302  is configured for efficient delivery of the booklets from the opening  306  of the path to the flipping mechanism  304 . Accordingly, the delivery path  302  is sized and configured such that each booklet has enough momentum (provided by the output rollers  244 ) to reach the flipping mechanism  304 . Alternatively, the delivery path  302  can be sized and configured such that each booklet reaches the flipping mechanism  304  while still being driven by the output rollers  244 . In yet another alternative, the delivery path  302  can comprise its own conveyance means, such as a conveyor and/or one or more rollers, which ensure that the booklets reach the flipping mechanism  304 . In any case, the delivery path  302  can be defined by upper and lower members  310  and  312 . Additionally, the delivery path  302  can be laterally defined with side walls (not shown), if desired. Preferably, the inner surfaces of at least the lower member  312  are smooth to reduce friction created between the delivery path  302  and the booklets that pass along it. 
     The flipping mechanism  304  is configured to invert booklets (e.g., every other booklet output from the booklet making apparatus  201 ) when multiple booklets are printed such that the booklets can be stacked in an alternating manner in the stacker bin, such as that depicted in FIG.  2 . As is indicated in FIG. 3, the flipping mechanism  304  generally comprises a main roller  314  and one or more pressure rollers  316 . An example configuration for the flipping mechanism  304  is provided in greater detail in FIG.  4 . As shown in that figure, the main roller  314  is typically formed as an elongated cylinder  400  that is composed of a rigid material such as a metal (solid or hollow). Normally, the main roller  314  includes a resilient coating  402  made of an elastomeric material, e.g. rubber, which is disposed about the outer surfaces of the cylinder  400  to better grip booklets. The main roller  314  is fixedly mounted to a drive shaft  404  that is used to drive the flipper roller  304 . Disposed about the drive shaft  404  are collars  406  (only one visible in FIG. 4) that form part of a clutch mechanism  408  used to intermittently rotate the pressure rollers  316  in unison with the main roller  314  such that the pressure rollers revolve about a central longitudinal axis of the main roller (see FIG.  3 ). The clutch mechanism  408  can comprise an internal electromagnetic clutch (not shown) that engages or disengages when power is delivered to the mechanism such that the collars  406  will rotate with the shaft  404  or remain fixed in position, as desired. 
     Attached to the collars  406  are link members  410  that extend in a direction radially outward from the drive shaft  404 . These link members  410  are connected to a support beam  412  on which the one or more pressure rollers  316  are mounted. The pressure rollers  316  are normally rotatably mounted to the support beam  412  such that the pressure rollers can rotate freely (i.e., idle) about the support beam. Typically, the pressure rollers  316  are composed of an elastomeric material, such as rubber, to better grip booklets that arrive in a nip  414  that is formed between the pressure rollers and the outer surface of the main roller  314 . 
     With reference back to FIG. 3, the main roller  314  is adapted to rotate in the counterclockwise direction (in the orientation shown in FIG.  3 ). In addition, the pressure rollers  316  are adapted to, when the clutch mechanism  408  is engaged, rotate in unison with (i.e., orbit) the main roller  312  when a booklet arrives in the nip  414  of the flipping mechanism  304  so that the booklet can be inverted, as is discussed below in greater detail. By way of example, the clutch mechanism  408  can be engaged to begin to rotate the pressure rollers  316  from an approximate twelve o&#39;clock position down (FIG. 3) to an approximate six o&#39;clock position (indicated in phantom). At this point, the clutch mechanism  408  can be disengaged to allow a booklet to be deposited in the stacker bin, and then be re-engaged to return the pressure rollers  316  back to the initial approximate twelve o&#39;clock position. 
     The general construction of an example booklet stacking mechanism  202  having been described above, the operation of the mechanism will now be discussed with reference to FIGS.  5  and  6 A- 6 D. FIG. 5 illustrates a first mode of operation of the booklet stacking mechanism  202 . In this mode, the gate  300  is in the closed position such that a booklet  500  (or other print media) that is output from the booklet making apparatus  201  with the output rollers  244 , is directed down to the vertical stacker bin  248  (FIG.  2 ). In such an arrangement, the booklets  500  will be oriented with their stapled sides  502  facing away from the electrophotographic imaging device  200 . 
     After one or more booklets  500  have been deposited in the stacker bin  248  in the manner described above in reference to FIG. 5, one or more booklets can be deposited in the stacker bin in an opposite orientation, i.e., with the stapled side  502  facing the electrophotographic imaging device  200 . Accordingly, the booklet orientation can be staggered such that an even, high capacity stack of booklets is formed and toppling due to booklet pillowing is avoided. To arrange booklets in the staggered orientation, the booklets  500  are turned through 180 degrees such that they are inverted before being deposited in the stacker bin  248 . This inversion is accomplished through use of the booklet stacking mechanism  202  while operating in the second mode. 
     Referring now to FIGS. 6A-6D, the second mode of operation of the booklet stacking mechanism  202  will be described in sequential order. Beginning with FIG. 6A, the sequence starts with the gate  300  being pivoted about the shaft  308  such that the gate is placed in the open position. While the gate  300  is in this position, the booklet  500  cannot pass directly to the stacker bin  248  but instead, as indicated in FIG. 6A, is diverted into the delivery path  302  of the stacking mechanism  202 . At this point, the main roller  314 , if not already rotating, begins to rotate in the counterclockwise direction (in the orientation shown in FIGS.  6 A- 6 D). The booklet  500  then travels along the delivery path  302  and into the nip  414  formed between the main roller  314  and the pressure rollers  316 , as indicated in FIG.  6 B. 
     Once a predetermined portion of the booklet  500  has passed through the nip  414 , e.g., an inch or two measuring from the stapled side  502 , the clutch mechanism  408  (FIG. 4) engages. The degree of penetration of the booklet  500  through the nip  414  can be detected through use of a sensor (not shown), for example, a photodetector. Alternatively, the engagement of the clutch mechanism  408  can be timed based upon the completion of some event, e.g., the booklet  500  leaving the output rollers  244 . In a further alternative, engagement can be activated in response to a predetermined amount of pressure being detected between the pressure rollers  316  and the main roller  314 . In any case, once the clutch mechanism  408  engages, the collars  406 , link members  410 , support beam  412 , and pressure rollers  316  rotate in unison with the main roller  314 , as indicated in FIG. 6C, such that the booklet  500  is likewise rotated with the main roller and eventually turned upside down. The booklet  500  can be securely held between the main roller  314  and the pressure rollers  316  during this inversion due to the relative stiffness of the booklet adjacent its stapled side  502 . 
     With reference now to FIG. 6D, once the pressure rollers  316  have traveled nearly through 180 degrees, the clutch mechanism  408  can be released such that revolution of the pressure rollers about the main roller  314  is interrupted. However, in that the main roller  314  is fixedly mounted to the drive shaft  404 , it continues to rotate and the booklet  500  is driven to the stacker bin  248 . As shown in FIG. 6D, the booklets  500  can, for instance, be deposited in the stacker bin  248  in a staggered vertical stack  600  such that the booklets vary in orientation between the stapled side  502  facing the printing device  200  and facing away from the device. By way of example, every other booklet  500  can be arranged such that the stapled side  502  is oriented away (or toward) the printing device  200 . With this arrangement, the relatively thick portions of the booklets  500  adjacent the stapled sides  502  are alternated so as to achieve a balanced, high packing density stack  600  of booklets far superior to that obtainable with stack-slide trays. As will be appreciated by persons having ordinary skill in the art, such a stacking arrangement permits a larger number of booklets  500  to be deposited. 
     FIG. 7 illustrates an alternative booklet stacking mechanism  700 . As indicated in this figure, the booklet stacking mechanism  700  shares many of the same components discussed above with reference to the first embodiment shown in FIGS. 3-6. Accordingly, the booklet stacking mechanism  700  can include a gate  300 , a delivery path  302 , a flipping mechanism  304  including a main roller  314  and one or more pressure rollers  316 , an opening  306  to the delivery path, a shaft  308  about which the gate can pivot, and upper and lower members  310  and  312  that define the delivery path. In addition, however, the booklet stacking mechanism shown in FIG. 7 further includes a guide  702  that is positioned proximate to the flipping mechanism  304 . 
     As indicated in FIG. 7, the guide  702  is generally C-shaped when viewed from the side. More particularly, the guide  702  can, by way of example, comprise a substantially arcuate portion  704  and a substantially linear portion  706 . The guide  702  is elongated (into the page) and typically has the same length of the flipping mechanism  304 . With this configuration, the guide  702  can aid in the booklet flipping process conducted by the flipping mechanism  304  and further guide the booklet into the stacker bin  248 . Specifically, the arcuate portion  704  can maintain a generally arcuate configuration of a booklet held by the flipping mechanism  304  as the booklet is inverted by the roller (see FIG. 6C) and the linear portion  706  can serve to guide the inverted booklet into the stacker bin  248 . 
     Although the booklet stacking mechanism  700  shown in FIG. 7 is illustrated and described as including pressure rollers  316 , it is to be appreciated that, depending upon the configuration of the guide  702  in relation to the flipping mechanism  304 , the pressure rollers may not be necessary in that the main roller  314  in combination with the guide may be enough to properly invert the booklet and deliver it in the correct orientation to the stacker bin  248 . 
     While particular embodiments of the invention have been disclosed in detail in the foregoing description and drawings for purposes of example, it will be understood by those skilled in the art that variations and modifications thereof can be made without departing from the scope of the invention as set forth in the following claims.
The present disclosure relates to a booklet stacking apparatus and method. More particularly, the present disclosure relates to a booklet stacking mechanism. In one arrangement, the booklet stacking mechanism comprises a gate that is adapted to be placed adjacent an output area, the gate being position able in a closed position and an open position, a delivery path along which booklets can be delivered when the gate is in the open position, and a flipping mechanism that is adapted to receive booklets, invert them, and deposit them in a output bin.