Abstract:
A set feeding apparatus ( 10 ) separates an uppermost set of paper sheets from a staggered stack of sets ( 36 ) with a platform ( 34 ) that biases the stack toward a carriage ( 42 ) that is moveable with respect to the stack. The carriage includes a cam-activated pic and a knife head that combine to raise the uppermost set from the stack. A plow then engages the raised portion of the uppermost set to move the set off of the stack.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention generally pertains to devices for handling sets of paper sheets. More specifically, the invention relates to a device that will separate and remove individual sets of sheets from a stack of sets arranged in a staggered, or offset, manner.  
         BACKGROUND OF THE INVENTION  
         [0002]    Publishing, photocopying, and otherwise processing large quantities of printed materials such as books, loose-leaf collections, and other assemblages of individual sheets is often a multi-step process. Typically, printing or photocopying of individual copies, also known as sets, of the subject materials is followed by various other operations such as punching, binding, counting, sorting, and the like. Often, after each individual set comprising a copy of particular work passes through a process, it is stacked with other copies of the same work in preparation for feeding into subsequent process devices. Additional processing may occur “on-line” or “off-line.” In on-line processing, a single set of sheets is typically forwarded directly to the next process. In off-line processing arrangements, a stacked arrangement of identical, or differentiated, individual sets facilitates efficient bulk transfer of the sets between sequential processing stations that may or may not be located in physical proximity to each other. Thus, stacking individual sets of documents in a staggered or offset fashion eliminates the need for costly set separators and is the most efficient way to feed sets into processing equipment that only accepts sets fed one-by-one, rather than as an entire stack of sets.  
           [0003]    Although a staggered arrangement of individual sets in a stack creates efficiencies in the selection and feeding of individual sets, feeding individual sets from a staggered stack can still be a time-consuming and labor-intensive undertaking. This is true of any paper-handling situation where individual sets are separately selected and removed from a stack. Each set must be carefully gathered, engaged, and handled without losing or separating individual sheets from a set, and without mixing sets. Further, many processing operations, even ordinary photocopying, require the individual page edges of a set to be in precise alignment. Sheets or edges, such as tabs, which extend beyond the general edge of the set may hamper reliably feeding large numbers of sets into processing equipment. Automated devices have been proposed to handle the task of separating and removing complete sets of sheets from a stack of identical or differentiated sets for feeding the individual sets into processing equipment.  
           [0004]    A device for mechanically feeding a set of sheets for further processing is disclosed, for example, in U.S. Pat. Nos. 6,126,384, 5,820,334, and 5,556,254 to Darcy et al. In the set feeder disclosed in the Darcy patents, the sets are disposed in a hopper and fed from the lowermost end by a driven shutter mechanism. The force exerted by the stack of sets in such bottom-feeding apparatus, however, can effect the accuracy of the set feeding, particularly when the stack is relatively have or large.  
         OBJECTS AND BRIEF SUMMARY OF TEE INVENTION  
         [0005]    It is a primary object of the invention to provide an automated device that reliably selects, gathers, and removes a set of sheets from a staggered stack of identical or differentiated sets. It is a related object of the invention to provide a set feeding apparatus which eliminates the effect of stack weight.  
           [0006]    It is a further object of this invention to provide an automated means of feeding individual sets of sheets from a stack of substantially identical sets into processing equipment used in on-line applications or in off-line applications, including multi-stage printing or photocopying operations.  
           [0007]    Another object of the invention is to provide a set feeding apparatus that can accommodate different sizes of sheets and protrusion from the edge of the set, such as tabs.  
           [0008]    The present invention is directed to a set feeder apparatus for separating an uppermost set of paper sheets from a previously staggered stack of similar sets and individually feeding the uppermost set into a subsequent processing station. The invention provides a vertically movable platform which has a pliable, resilient upper surface or a foam pad or the like disposed along its upper surface. Thus, the stack of sheet sets resting on the platform can deflect downward when a pressure or force is applied to the upper sets.  
           [0009]    A frame supports a movable carriage, a stabilizing unit for stabilizing the stack of sets during an initial separation operation, and a plow assembly which pushes the uppermost set from the apparatus. The movable carriage supports the elements which provide an initial separation of one edge of the uppermost set from the remainder of the stack so that the plow can engage the uppermost set for removal. Thus, the movable carriage supports a pair of sensors for detecting the exact positions of the sets of the stack, a pic for providing an initial separation between the top two sets, and profiled knife for enhancing the separation between the top two sets for removal by the plow.  
           [0010]    Once the platform is loaded, and the operator has input the paper dimensions, the platform raises the stack towards the moveable carriage. As the stack moves upward, the exposed edge portion of the set immediately below the uppermost set contacts one of the sensors disposed on the carriage, thus initializing the invention to begin the process of selecting and removing the uppermost set from the stack. The carriage sensors are disposed at opposite ends of the carriage to facilitate sensing at either end of the stack. Thus, each time the uppermost set is removed, the carriage can shift to detect the newly exposed edge portion at the opposite end of the stack.  
           [0011]    The cam-activated pic on the movable carriage is configured to rotate to lift and separate an edge portion of the uppermost set from the stack. In operation, after the exposed edge portion of the set immediately below the uppermost set contacts the sensor, the pic moves into position at the exposed edge. The stabilizer unit is always preferably exerting a downward force on the stack during the operation of the pic and the knife. The eccentric, cam-driven rotation of the pic initially moves the pic downwardly, into contact with the exposed edge portion. After passing the lowest point of its travel, the pic rotates upwardly into contact with the bottom of the uppermost stack, lifting an edge portion thereof, and creating a gap between the two uppermost sets. A profiled knife, likewise disposed on the carriage, is advanced into the gap created by the pic between the two uppermost sets, so as to further lift and separate a portion of the uppermost set from the stack, while simultaneously exerting a downward force on the stack. When the pic is disposed at the end of the stack proximal to the plow, the knife is advanced into the gap immediately after the “pick” is performed. If the pic is operating at the end of the stack distal to the plow, the carriage moves the pic engaged between the top two sets to the end proximal the plow before the knife is advanced into the gap. Thus, the more significant separation due to the profiled knife is always ultimately disposed at the end proximal the plow.  
           [0012]    Once an edge portion of the uppermost set of sheets is lifted above the remaining stack by the knife, the stabilizer unit releases the downward pressure on the stack, and a plow is deployed to engage the edge of the uppermost set raised by the knife. The plow travels in a horizontal path above the level of the unlifted stack, so that it only engages the uppermost set when the uppermost set is raised by the knife. Once the plow has engaged the uppermost set, the plow pushes this set off of the stack. The plow thus removes the uppermost set from the top of the stack without interfering with the rest of the stack. Significantly, neither the pic, the blade, nor the plow interfere with the use of tabs or the like which protrude from the front edge of the sets.  
           [0013]    The knife and plow then return to their predetermined operating positions, the carriage positions itself to detect the next exposed edge portion, and the entire process will continue repeating itself, until all of the sets have been moved off of the platform.  
           [0014]    The operation of the set feeding apparatus is thus an improvement over the prior art. These and other advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein. 
       
    
    
     BRIEF DESCRIPTION OF THEE DRAWINGS  
       [0015]    [0015]FIG. 1 is a perspective view of a preferred embodiment of paper set feeding apparatus constructed according to teaching of the present invention.  
         [0016]    [0016]FIG. 2 is a front elevational view of the apparatus shown in FIG. 1.  
         [0017]    [0017]FIG. 3 is a top plan view of the embodiment of the invention shown in FIG. 1.  
         [0018]    [0018]FIG. 4 is a side elevational view of the embodiment of the invention shown in FIG. 1.  
         [0019]    [0019]FIG. 5 is a perspective view of the stabilizer component of the present invention.  
         [0020]    [0020]FIG. 6 is a perspective view of the carriage portion of the present invention.  
         [0021]    [0021]FIG. 7 is an exploded perspective view of the carriage portion of the present invention shown in FIG. 6.  
         [0022]    [0022]FIG. 8 is a perspective view of the plow portion of the present invention.  
         [0023]    [0023]FIG. 9 is a side elevational view of the plow portion of the present invention.  
         [0024]    [0024]FIG. 10 is a perspective view of the pic and associated cam of FIGS. 6 and 7.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]    Turning now to the drawings, FIGS.  1 - 4  show a set feeder apparatus  10  constructed according to the present invention. The apparatus  10  has a rear  110  and a front  112 . The apparatus  10  consists of a base  12  that carries a support surface or platform  34 , which supports a stack of offset or staggered sheet sets  36 , and a frame  11  which supports other powered elements of the set feeding apparatus  10 . The frame  11  preferably includes upfront supports and horizontal elements connecting the upfront supports. In the preferred embodiment illustrated, front support  14  and a rear support  16 , secured to the base  12 , and extending generally upward therefrom. As best seen in FIGS. 1 and 2, the front support  14  is disposed and constructed such that it does not interfere with the movement of the individual sets of the stack of sheets  36  through the front end of the apparatus  10 . In order to support mechanized components of the apparatus  10 , the top  18  of the front support  14  is coupled to the top  20  of the rear support  16  by carriage rods  22 ,  24  and bracket  26  is coupled to support  14 . It will be appreciated that the carriage rods  22 ,  24  also serve to further enhance the rigidity of the skeleton.  
         [0026]    In accordance with the invention, the apparatus  10  includes powered elements which act on the stack of sets  36  supported on an upwardly biased platform  34  to separate the uppermost stack and advance it out of the front of the apparatus  10 . The structure and each of these powered elements, as well as the platform  34 , will be described in turn. In short, the apparatus  10  includes a movable support platform  34  which advances the stack of sets  36  upward until the uppermost set  37  is positioned adjacent a set picker assembly  69 , which separates and slightly lifts the top set  37  from the second set  38 , a stabilizer unit  49 , which stabilizes the stack of sets  36  during the picking operation, and a plow assembly  88 , which functions to push the uppermost set  37  from the stack of sets  36 .  
         [0027]    The platform  34  preferably includes not only a horizontal plate portion which supports the stack of sets  36 , but at least one vertical element  34   a  against which an edge of the stack  36  may be disposed to ensure proper positioning. In the preferred embodiment illustrated, two such vertical elements  34   a  along the side and back of the apparatus  10  may be seen in FIGS.  2 - 4 . Significantly, the vertical elements  34   a  are disposed such that they will not interfere with the operation of the powered elements of the apparatus  10 .  
         [0028]    To ensure that the sets always feed to the same position as they are fed out of the front  112  of the apparatus  10 , the platform  34  is biased or powered to advance the stack of sets  36  upward to position the uppermost set  37  at the desired feed level, adjacent the set picker assembly  69  and plow assembly  88 . In order to support the platform  34 , platform rods  28 ,  30 , 32  are provided which extend upwardly from the base  12 . Coupling brackets  35  slidably mounted on the platform rods  28 ,  30 ,  32  and secured to the platform  34  facilitate the vertical motion of the platform  34  along the platform rods  28 ,  30 ,  32  to vertically move a previously staggered stack  36  of sheet sets. The interface of the coupling bracket  35  with the platform rods  28 ,  30 ,  32  may consist of a reversible drive apparatus such as a motor which engages with one or more of the platform rods  28 ,  30 ,  32 , via gears, frictionally, or via some other reversible means of facilitating vertical motion along the platform rods  28 ,  30 ,  32 . Alternately, the platform  34  may be biased into the desired uppermost position by adjustable springs of the like. Thus, it will be appreciated by those of skill in the art that any appropriate mechanism may be utilized, so long as the uppermost set  37  is ultimately disposed at the desired location.  
         [0029]    According to an important feature of the invention, the platform  34  preferably incorporates a pliant, resilient pad (not pictured) or has a resilient upper surface. In this way, the stack  36  of sheets may locally deflect in response to downward pressure, the significance of which will be apparent upon an explanation of the set picking device below. This pad may be made of foam or other suitable material, which is sufficiently pliable to allow deflection, yet resilient enough to return to its original state when the downward force is removed. In the currently preferred embodiment, a urethane foam having a minimum thickness of apparently one inch (1″) or 25 mm is utilized. It has been determined that such a foam pad permits a deflection on the order of ⅜ inch. It will be appreciated that the required deflection will be dependent upon the dimensions of the set picker, as will be described below.  
         [0030]    In order to properly position the stack of sets  36  so that the set picker assembly  69  and plow assembly  88  may separate and advance the uppermost set  37  from the stack  36 , the apparatus  10  is preferably provided with one or more sensors  44 ,  46 . The sensor(s)  44 ,  46  arranged so that they sense when the stack  36  is disposed with the uppermost and second sets  37 ,  38  in the desired position. In a stack of sets  36 , the uppermost set  37  and the second set  38  are offset from one another such that a portion  39  of the second set  38  is exposed at one end of the uppermost set  37 . In the preferred embodiment of the invention, two sensors  44 ,  46  are provided and are disposed to sense this exposed portion  39  at the front and the back, respectively, of the stack of sets  36 . During operation, when the sensor  44 , 46  is just in from the edge of the stack of sets  36  (typically on the order of ¼″ to ¾″, depending upon the degree of offset in the staggering), the platform  34  will move upward until the sensor  44 ,  46  is activated or closed, at which time the platform  34  stops. In this way, the uppermost set  37  is appropriately positioned to be “picked,” and the set feeding sequence is initialized.  
         [0031]    Due to the alternating staggered arrangement of the stack  36 , each time the uppermost set is removed, the successive exposed portion  39  of the new second set  38  is located at an opposite end of the stack than was the previous exposed portion. Accordingly, the set picker assembly  69  as well as the sensors  44 ,  46  are preferably disposed on a movable carriage unit  42 . The carriage unit  42  is attached to carriage rods  22 ,  24  by a carriage bracket  43 . It will be appreciated that the interface of the carriage bracket  43  with the carriage rods  22 ,  24  may consist of any appropriate reversible drive apparatus such as a motor which engages with one or more of the carriage rods  22 ,  24  via gears, frictionally, or via some other reversible means of facilitating motion along the carriage rods  22 ,  24 .  
         [0032]    In use, as the platform  34  raises, the sensor  46  senses the exposed portion  39  of the second set  38  at the rear  110  of the stacked sets  36  (as may be seen in FIG. 4) to arrest the movement of the platform  34 . The set picker assembly  69  is then moved into position to begin the picking operation, as will be explained in greater detail below. It will be appreciated that when the uppermost set  37 , as shown in FIG. 4 is removed, the exposed portion  39   a  of the new second set will be disposed at the opposite or front end  112  of the stack of sets  36 . When the exposed portion  39   a  is so disposed at the front end, the opposite sensor  44  is moved to a position at the front of the stack of sets  36  such that the platform  34  moves upward to raise the stack  36  to a position where the exposed surface  39   a  actuates or closes the sensor  44 , at which point the platform  34  stops. The set picker assembly  69  is then moved into position to begin the picking operation at the front end of the stack  36 . Thus, the positioning of the sensors  44 ,  46  to the front or rear of the set picking assembly  69  allows the sensors  44 ,  46  to perform the sensing function on opposite ends of the stack  36  as the uppermost set is removed, and the stack  36  continues to move upwardly toward the carriage  42 . By utilizing two sensors  44 ,  46 , to detect an exposed portion  39 ,  39   a  on either end of the stack  36 , the range of motion of the carriage unit  42  can be minimized, thus reducing the overall size of the set feeding apparatus  10 .  
         [0033]    In order to stabilize the stack of sets  36  and prevent shifting of individual sheets or sets while the set picker assembly  69  lifts the uppermost set  37 , a stabilizer unit  49  is provided. The stabilizer unit  49  is disposed such that it may be actuated to apply a downward force on the stack of sets  36  to sandwich the stack  36  between the stabilizer unit  49  and the platform  34 . While the stabilizer unit  49  may be actuated before or after the set picker assembly  69  is moved into position, the stabilizer unit  49  is preferably actuated to apply a downward force immediately after the sensor  44 ,  46  is closed by exposed portion  39 ,  39   a  of the stack of sets  36 .  
         [0034]    As shown in FIGS.  1 - 3 , channel  54  of the stabilizer unit  49  is secured to bracket  26  by bolts or the like. The detail of the stabilizer unit  49  itself is best depicted in FIG. 5, a perspective view. The stabilizer unit  49  includes a stabilizer pad  50  to which rods  58 ,  60 , 62  are mounted. The rods  58 ,  60 , 62  are slidably mounted to the channel  54  with bearings or the like such that sliding the rods  58 ,  60 ,  62  relative to the channel  54  moves the pad  50  downward or upward to move the pad  50  into or out of contact with the stack of sets  36 . The stabilizer unit  49  further includes stabilizer motor or actuator  52  which provides such vertical movement to the pad  50  and rods  58 ,  60 ,  62 . The actuator  52  is preferably coupled to the pad  50  by a rack and pinion gear arrangement  56 ,  57 . The shaft of the pinion gear  57  extends through the bracket  54  and meshes with the rack  56  disposed along one of the rods  60 . In this way, as the actuator  52  imparts a rotating motion to the pinion gear  57 , the pad  50  is moved upward or downward with the rod  60 . In operation, the stabilizer pad  50  contacts the uppermost set  37  and applies a downward force thereto in order to hold the uppermost set  37  of sheets in place and together as a group while an edge is lifted from the remaining stack  36 .  
         [0035]    Once the stabilizer unit  49  has applied a downward force to the uppermost set  37 , the uppermost set  37  is ready for lifting for eventual separation from the remaining stack  36 . As previously mentioned, the carriage  42  may be shifted so that the set picker assembly  69  is appropriately positioned to lift the uppermost set  37  either before or after the stabilizer unit  49  has established the stabilizing downward force on the stack  36 , so long as the set picker assembly  69  is not actuated until after the force has been applied.  
         [0036]    Turning to FIGS. 6 and 7, the set picker assembly preferably includes a protrusion or pic  70 , which provides an initial lifting of the uppermost set  37  from the stack  36 , and a separation enhancer or knife  76 , which is subsequently advanced to a position between the uppermost and second sets  37 ,  38  to enhance the separation for the final removal of the uppermost set  37  from the stack  36 . The pic  70  itself has an elongated structure and is preferably formed of a relatively low friction material so that it does not shift the papers of the second set during the “pick” operation. In order to actually lift the corner edge of the uppermost set  37  from the second set  38 , the pic  70  is mounted on an eccentric, rotatable cam arrangement  71  to the pic actuator  72  (shown in more detail in FIG. 10). Significantly, the pic  70  may be rotated in either a clockwise or counterclockwise direction, the significance of which will become apparent upon further explanation.  
         [0037]    When the carriage  42  shifts to position the set picker assembly  69 , the pic  70  is positioned above the exposed portion  39 ,  39   a  of the second set  38 . Specifically, the carriage  42  will shift such that the pic  70  is located at substantially the same position relative to the stack  30  that the sensor  44 ,  46  was previously located. Once the carriage  42  has shifted (and the stack  36  is stabilized by the downward pressure of the stabilizer pad  50 ), pic actuator  72  eccentrically rotates the pic  70  downward and toward the centerline of the stack  36  from a predetermined position above the lowest point of the rotational path of pic  70 . As the eccentric motion of the actuator  72  rotates the pic  70 , initially in a downward arc, the pic  70  depresses the exposed portion  39  of the second set  38 . Inasmuch as the platform  34  includes a pliant, resilient pad along its upper surface, the stack  36  below the pic  70  deflects downward as the pic  70  continues to rotate downward. As the pic  70  passes the lowest point of its rotation, the continuing eccentric motion of the pic actuator  72  will cause the pic  70  to move in an upward circular motion. The upward circular motion of the pic  70  will thus bring the pic  70  into contact with the bottom of the uppermost set  37 . The continued upward motion of the pic  70  raises the uppermost set  37  to a predetermined level, creating a space between the uppermost set  37  and the second set  38 . Upon reaching a predetermined, uppermost position, the rotation of the pic  70  ceases, thus maintaining the space between the sets.  
         [0038]    It will be appreciated by those of skill in the art that the pic  70  always moves down and inward toward the stack  36  during the “pick” operation. Thus, when exposed portion  39  is disposed at the rear  110  of the apparatus  10  (i.e., to the left as shown in FIG. 4), the pic  70  is moved in a counterclockwise direction. Conversely, when the exposed portion  39  is disposed at the front  112  of the apparatus  10  (i.e., to the right as shown in FIG. 4), the pic  70  moves in a clockwise direction.  
         [0039]    In order to provide a more significant separation between the uppermost and second sets  37 ,  38 , the set picker assembly  42  further includes a separation enhancer, in this case a profiled knife  76 . The knife  76  is rotatably coupled to a knife rod  80  which is further coupled to a powered knife actuator  74 . The extending and retracting motion of the knife  76  is facilitated by a knife cam  78  driven by the knife actuator  74 . The eccentric motion of the knife cam  78  imparts a longitudinal reciprocating motion to the knife rod, between the horizontal extreme portions of the knife cam  78  rotational path. To provide the knife  76  some vertical and lateral flexibility so that the knife  76  can engage the stack  36  over a wide positional tolerance range, a knife spring  82  disposed adjacent the knife  76 . Although the knife  76  is biased to the illustrated position, the knife spring  82  permits some rotational movement of the knife  76  about the axis of the knife rod  80 .  
         [0040]    In operation at the rear end  110  of the apparatus  10 , after the pic  70  has stopped, the knife actuator  74  fires, pushing the profiled knife  76  into the space created between the uppermost set  37  and the next set  38  by the pic  70 . Significantly, the knife  76  is advanced into the stack  36  at a point further from the edge of the uppermost set  37  than where the pic  70  is engaged. In this way, the knife  76  increases the spacing between the uppermost set  37  and the second set  38  not only as a result of its higher profile, but also as a result of its more distal disposal. The knife  76  then remains in this position, maintaining the space between the uppermost set  37  and the second set  38 , in preparation for the uppermost set  37  removal operation. Thus, when the carriage sensor  44  detects the exposed edge surface  39  at the rear end  110  of the stack  36 , the entire lifting and separating operation will occur at the rear end  110  of the stack.  
         [0041]    When the carriage sensor  44  detects the stack  36  and initializes the lifting operation from the front end  112  of the stack, however, the pic  70  will engage and lift the uppermost set from the front end  112 . In order to position the knife  76  for firing, the carriage unit  42  then moves toward the rear end  110  of the stack  36  with the pic  70  still engaged in the stack  36 , stopping before the pic  70  clears the end of the uppermost set  38 . It will be appreciated that the pic  70  and knife  76  are now disposed in the same position at the rear  110  of the apparatus  10  as if the pic  70  had originally performed the separation operation entirely at the rear  110 , as explained above. With the pic  70  still engaged with the uppermost set  38 , now at the rear end  110  of the stack  36 , the profiled knife  76  is advanced into the pic-created opening in the stack  36 , increasing the separation between the uppermost sets.  
         [0042]    Thus, the set picker assembly  69  presents a gap between the uppermost and second set  37 ,  38  at the rear  110  of the stack  36 , whether initial separation by the pic  70  occurred at the front  112  or rear  110  of the stack  36 . Once the knife  70  is advanced to so separate the sets  37 ,  38 , the stabilizer unit  49  is actuated to retract the stabilizer pad  50  and discontinue the downward stabilizing force on the stack  36 .  
         [0043]    In order to remove the spaced, uppermost set  37  from the remaining stack  36 , a set removal device, here, a plow assembly  88  is provided, as shown in detail in FIGS. 8 and 9. It will be appreciated by those of skill in the art, however, that an alternate removal device, such as a grasping device, may be provided. The plow assembly  88  includes a plow blade  90 , which is mounted for linear movement to engage the separated, uppermost set  37 , and push it from the stack  36 , and an actuator or motor  108  for driving the blade  90 . The motor  108  is coupled to the rear bracket  16  by a cradle  100 . As best seen in FIG. 8, plow guide rods  92 ,  94 ,  104 , in this case, three such guide rods, are secured to the plow blade  90  at one end and slidably mounted in bores  96 ,  98  in the cradle  100 . Axial motion is imparted to the plow guide rods  92 ,  94 ,  104  from the motor  108  by a rack and pinion system. More specifically, a rotatably driven gear  106  is mounted to engage a rack  105  disposed along one of the guide rods  104 . Thus, as the motor  108  rotates the gear  106 , the rack  105  moves the guide rod  104  in an axial direction to drive the plow blade  90  either forward to push the set  37  from the apparatus  10 , or rearward to retract the plow blade  90 .  
         [0044]    Thus, during operation while the edge of the uppermost set  37  is lifted off of the stack  36  by the knife  76 , a plow blade  90  moves forward and engages the uppermost set  37 . The plow blade  90  continues forward to a predetermined point, at which the uppermost stack  37  has been completely removed from the stack  36 . As shown in FIGS. 8 and 9, the plow blade  90  includes a protruding lower edge  91  which prevents the uppermost set  37  from falling back onto the stack  36  during this step.  
         [0045]    After this final operation, the plow blade  90  and the knife  76  retract to their predetermined starting positions. The carriage unit  42  is then shifted to the opposite staggered side of the stack  36 , and the entire lift, separate, and push sequence is repeated to remove a newly uncovered set from the stack  36 .  
         [0046]    It will be appreciated by those of skill in the art that the motors or actuators  52 ,  72 ,  74 ,  108  may be of any appropriate type or design. Further, the motors or actuators  5 ,  72 ,  74 ,  108  may be coupled together by any appropriate means so that signals may be conveyed between them as necessary to initiate operation.  
         [0047]    While this invention has been described with an emphasis upon preferred embodiments, variations of the preferred embodiments can be used, and it is intended that the invention can be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications encompassed within the spirit and scope of the invention as defined by the following claims.  
         [0048]    All of the references cited herein, including patents, patent applications, and publications, are hereby incorporated in their entireties by reference.