FIELD OF THE INVENTION 
       [0001]    The present invention is generally directed to stackers. More specifically, the present invention is directed to a stacker that can generally stack product in a vertical fashion at a high rate of speed and an interleaver, stacker and loading system for high speed food packaging. 
       BACKGROUND 
       [0002]    Many manufacturing processes, particularly food handling processes, require the high speed stacking of products in a vertical fashion. Typically, to prevent the products from sticking together when packaged, refrigerated, and/or frozen, a high-speed paper, film, or foil interleaving system is used in conjunction with the stacker to insert a substrate beneath each individual product, which then serves as a separator between stacked products. The vertically stacked products are then typically loaded into a tray, box, or other container, or conveyed to a packaging machine. 
         [0003]    Prior known stackers, for example for hamburger patties, typically run at 150 to 200 patties per minute for a single lane. Newer production techniques, however, allow production of patties at higher speeds for single lanes, for example, speeds of up to about 310 patties per minute. The known prior art stackers cannot keep up with the production speed, and thus the production speed is slowed or the product is split into two lanes for separate stacking. Higher cost or slower production results. It would therefore be desirable to address this with a stacker that allows faster production from the overall system by providing an improved high speed stacker. 
       SUMMARY 
       [0004]    Briefly stated, the present invention is directed to a stacker adapted to generally stack product in a vertical fashion. The stacker includes a first generally vertical conveyor having a first conveyor belt and a first plurality of flights mounted generally perpendicularly to the first conveyor belt. The first plurality of flights at least partially defines a plurality of stacking platforms. At least one positioning sensor for sensing a relative position of the flights is provided. An advancement sensor is provided for sensing product entering the stacker. A first drive incrementally drives the first conveyor responsive to the advancement sensor so that the stacking platforms descend. Each of the stacking platforms can receive a stack of the items to be stacked, and then be indexed downwardly to allow the next stack to be formed on the subsequent stacking platform. 
         [0005]    In another preferred aspect of the invention, the stacker further includes a second generally vertical conveyor having a second conveyor belt and a second plurality of flights mounted generally perpendicularly to the second conveyor belt. The first and second conveyors are mounted opposite each other with the flights on facing sides of the first and second conveyors being generally aligned to define the stacking platforms, which are synchronously moved. 
         [0006]    In another aspect, the invention provides a stacking-loading system for stacking and loading a lane of products. The system includes a feed conveyor for providing products in a lane and an interleaver that places a substrate under each of the products as they are carried by the feed conveyor. A stacker for stacking the interleaved product in a generally vertical fashion is provided, which is preferably of the type described above, with either the one or two conveyor belts with the flights defining stacking platforms. A removal conveyor that receives the stacked product from the stacker is also provided. 
         [0007]    The invention also provides a method of stacking products which includes:
       a. Providing stacker including a first generally vertical conveyor having a first conveyor belt and a first plurality of flights mounted generally perpendicularly to the first conveyor belt, the first plurality of flights at least partially defines a plurality of stacking platforms, at least one positioning sensor for sensing a relative position of the flights, an advancement sensor for sensing product entering the stacker, and a first drive for incrementally driving the first conveyor responsive to the advancement sensor.   b. Sensing a first advancing product with the advancement sensor.   c. Introducing the first advancing product onto a first one of the stacking platforms located in a loading position.   d. Sensing a next advancing product with the advancement sensor.   e. Indexing the stacking platform downwardly.   f. Introducing the next advancing product onto the prior product located on the stacking platform.   g. Repeating steps d., e., and f. until a desired number of the products is located the first one of the stacking platforms.   h. Indexing the first conveyor to bring a next one of the stacking platforms into the loading position.   i. Repeating steps c. through g. for the next one of the stacking platforms; and   j. Unloading stacks of product from the stacking platforms.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The following detailed description of the preferred embodiment of the present invention will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It is understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
           [0019]      FIG. 1  is a rear elevation view of a currently preferred embodiment of a stacker-loader according to the present invention showing product being dispensed into a tray, box or removal conveyor (not shown), and a stack of product received from a feed conveyor (not shown) supported by opposing, aligned flights; 
           [0020]      FIG. 2  is a side elevation view of the stacker of  FIG. 1 ; 
           [0021]      FIG. 3  is a top plan view of the stacker of  FIG. 1 ; 
           [0022]      FIG. 4A  is a top view of an alternative embodiment of a stacker-loader according to the present invention wherein the two vertical conveyors are adjustably mounted for adjustment of the gap between the vertical conveyors to allow the stacking of different sized products; 
           [0023]      FIG. 4B  is a front end elevation view of the stacker-loader of  FIG. 4A ; 
           [0024]      FIG. 4C  is a right side elevation view of the stacker-loader of  FIG. 4B ; and 
           [0025]      FIG. 5  is a top view of an alternative embodiment of a stacker-loader according to the present invention wherein multiple stacker-loaders, each comprised of a single set of descending flight, are offset to stack products from multiple closely spaced lanes of product. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Certain terminology is used in the following description for convenience only and is not limiting. The words “right,” “left,” “top,” and “bottom” designate directions in the drawings to which reference is made. The term “containment space” means “the area bounded on the bottom by flights  220   a   i ,  220   b   i , on top by flights  220   a   i+1 ,  220   b   i+1 , in the rear by product stop  240 , in the front by the feed conveyor, and on the sides by belts  210   a ,  210   b , where i is 0, 1, 2, . . . n−1.” The words “a,” “and,” “one,” as used in the claims and in the corresponding portions of the specification, are defined as including one or more of the referenced item unless specifically stated otherwise. This terminology includes the words above specifically mentioned, derivatives thereof, and words of similar import. 
         [0027]    Referring to  FIGS. 1-3 , wherein like numerals indicate like elements throughout, the presently preferred interleaver, stacker and loading system  10  of the present invention is shown. The system  10  includes an interleaver  50  that interleaves a substrate  60  under product  110 , as shown in  FIG. 2 , as it is transported along a generally horizontal feed conveyor system generally designated  102 . The interleaver  50  preferably has a roll of substrate material  62  that is fed between feed rollers  64  to a perforation roller  66  in order to delineate a break line in the continuous sheet of substrate material. Acceleration rollers  68  then accelerate the end of the continuous sheet of substrate so that the piece of substrate to be interleaved is separated from the continuous sheet at the perforation and inserted under the product as it passes over a gap in the conveyor system  102 . The interleaving of the substrate  60  can take place based on a photoeye or other product sensor located along the conveyor  102 . 
         [0028]    The system  10  further includes a stacker, generally designated  100 , that receives the preferably interleaved product  110  for generally vertical stacking. Those skilled in the art will understand from the present disclosure that depending on the type of product, it may not be necessary to interleave the product with the substrate  60 . A removal conveyor generally designated  104  is also preferably provided, or the stacked product can be placed in boxes or trays directly, which can be conveyed on the removal conveyor  104 . 
         [0029]    Briefly stated, the horizontal feed conveyor  102  conveys product  110 , which can be provided with or without interleaving substrates by the interleaver  50 , in a single lane to the stacker  100 . The stacker  100  stacks the product  110  and places the stacked product in a tray or box, which is preferably, but not necessarily carried on the removal conveyor, or on the removal conveyor  104 . The removal conveyor  104  conveys the stacked product to a packaging machine or an area for further processing. 
         [0030]    The stacker  100  is preferably formed by two vertical conveyors  200   a ,  200   b . The conveyors  200   a ,  200   b  are preferably positioned parallel to and facing each other. Specifically, the descending side of the belt  210   a  of conveyor  200   a  faces the descending side of the belt  210   b  of conveyor  200   b . The conveyors  200   a ,  200   b  may alternatively be placed at a slight angle to create a funneling or tapering effect. 
         [0031]    The belt  210   a ,  210   b  of each respective conveyor  200   a ,  200   b  has a plurality of flights, generally  220   a ,  220   b , and more specifically  220   a   1 ,  220   a   2  . . .  220   a   n ;  220   b   1 ,  220   b   2  . . .  220   b   n  extending generally perpendicularly outward from the surface of the belt  210   a ,  210   b . Preferably, the total number of flights n is the same on each respective belt  210   a ,  210   b . Furthermore, the relative positioning of the flights  220   a   1 ,  220   a   2  . . .  220   a   n  of belt  210   a  are identical to the relative positioning of flights  220   b   1 ,  220   b   2  . . .  220   b   n  of belt  210   b . The flights  220   a ,  220   b  on the facing sides of the belts  210   a ,  210   b  are aligned, as described hereinafter, directly across from each other to create a series of platforms for the product  110 . 
         [0032]    The conveyors  200   a ,  200   b  are spaced at a distance such that the aligned flights  220   a ,  220   b  have a space between them as they are moved in unison to preferably lower the series of platforms, with the space being less than the size of the product being stacked. A drop opening is created as the flights  220   a ,  220   b  round the lower roller  230   a ,  230   b  of each respective conveyor  200   a ,  200   b . When the drop opening becomes larger than the size of the product  110  or stack of products  111 , the product  110  or stack of products  111  passes between the flights  220   a ,  220   b  and drops to the removal conveyor  104 . The spacing of the conveyors  200   a ,  200   b  and the dimension of the flights  220   a ,  220   b  can be adjusted to allow the stacker  100  to accommodate varying size products  110 . 
         [0033]    A product stop  240  is positioned between conveyors  200   a ,  200   b  on the rear of the stacker  100 . The product stop  240  is positioned in the area of the stacker  100  where product  110  is received from the feed conveyor (not shown). The product stop  240  assists the orderly stacking of product  110  by confining all product  110  to the containment space. The product stop  240  further prevents the product  110  from overshooting the containment space. 
         [0034]    The stacker  100  further comprises positioning photoelectric sensors  250   a ,  250   b  for sensing the location of each respective conveyor&#39;s  210   a ,  210   b  flights  220   a ,  220   b . The positioning photoelectric sensors  250   a ,  250   b  are preferably mounted on the return (ascending) side of each respective conveyor  200   a ,  200   b , and are vertically adjustable. An advancing product photoelectric sensor  255  is mounted adjacent to the feed conveyor  102  to sense product approaching the stacker  100 . While photoelectric sensors are preferred, other types of positioning sensors could be used. 
         [0035]    Preferably, the belts  210   a ,  210   b  of respective conveyors  200   a ,  200   b  are moved by servo drives  260   a ,  260   b . Referring particularly now to  FIG. 2 , the servo drive  260   a  drives roller  230   a  via coupling  261   a . A drive mount  262   a  secures the servo drive  260   a  to the conveyor  200   a . While the preferred embodiment has been described using a servo drive  260   a  to drive the conveyor  200   a , a stepper drive or other incremental drive or incremental drive methods are also usable in the present invention. As referred to hereinafter, the motion of the flights  220   a ,  220   b  is such that the containment space is moved downward, unless specifically noted. 
         [0036]    The exposed mechanics of the stacker  100  are preferably constructed from stainless steel. Where stainless steel cannot be used, sanitary materials are substituted. Sanitary design is also implemented where possible, such as, for example, reducing crevices, providing smooth, wipeable surfaces, and eliminating horizontal platforms where liquids may pool. 
         [0037]    The stacker  100  is preferably controlled by a programmable logic controller (PLC). Other types of control systems are possible such as, for example, a distributed control system (DCS) or other similar control system. The PLC is preferably housed in a water-tight enclosure, such as a NEMA-4X enclosure, for example. 
         [0038]    The stacker  100  of the present invention, upon initial startup, identifies the position of flights  220   a ,  220   b  in a procedure termed “homing”. The PLC instructs the servo drives  260   a ,  260   b  to perform the homing procedure, the characteristics of which are stored at the servo drives  260   a ,  260   b . The servo drives  260   a ,  260   b  increment their respective belts  210   a ,  210   b  and flights  220   a ,  220   b  until the photoelectric sensors  250   a ,  250   b  sense the position of a flight. A variable offset distance from the positioning photoelectric sensors  250   a ,  250   b  to the sensed flight can be programmed so that products  110  of different thicknesses can be handled by the stacker  100 . Upon completion of homing, the stacker  100  is ready to receive product  110  from the feed conveyor. 
         [0039]    There are two motion profiles utilized by the stacker  100  for receiving product  110 . The first motion profile is termed the stacking sequence. In the stacking sequence, the advancement photoelectric sensor  255  identifies an incoming product, for example a hamburger patty, approaching the stacker  100  on the horizontal feed conveyer at a high rate of speed. Upon sensing the incoming patty, the advancement sensor notifies the PLC of the incoming patty. After a programmed delay to allow the patty to enter and settle into the containment space (if this is the first patty in the group) or on to a previously stacked patty (if this is not the first patty in the group), the PLC instructs the servo drive to increment the flights  220   a ,  220   b  a programmed distance. The programmed distance is such that the next patty will come to rest on top of the first patty upon entering the containment space. A stack count, which is simply a count of the number of products  110  which have entered the stacker  100 , is then incremented. This stacking sequence is repeated until the adjustable stack count is reached. It should be noted that while the stack count is adjustable, there is an upper limit to the height of the stack inherent in the spacing between flights  220   a ,  220   b.    
         [0040]    When the stack count reaches a programmed value, the PLC instructs the servo drive to execute the loading sequence. The loading sequence advances the flights  220   a ,  220   b  and stops the motion when the next set of flights is in the loading position, preferably when the positioning photoelectric sensor is triggered. The stack count is then reset to zero. An adjustable, programmable offset is provided for controlling the stopping position of the loading sequence. Additionally, the vertical position of the positioning photoelectric sensors  250   a ,  250   b  on each respective conveyor  200   a ,  200   b  is adjustable. When the stacker  100  executes the loading sequence, the product  110  or stack of products  111  that has moved to the lowest containment space is dropped onto the removal conveyor  104 , as described above. A tray, box or other receptacle may be placed on, or be part of, the removal conveyor  104 . 
         [0041]    A thickness detecting photoelectric sensor, or other device capable of detecting thickness, can also be employed along the feed conveyor  102  to detect a thickness of product  110  fed into the stacker  100 . Using the thickness detector, the travel distance of the flights  220   a ,  220   b  during stacking could be adjusted for each individual product  110  to be stacked, if desired. This is especially useful when stacking product that has considerable product thickness variability. 
         [0042]    Additionally, depending on the type of product  110  being stacked, the position of the flights  220   a ,  220   b  can be adjusted so that the product does not slide from the conveyor system  102  onto the flights  220   a ,  220   b  or previously stacked product  110 , but rather the flights or previously stacked product  110  are spaced downwardly from the level of the conveyor  102  so that the product  110  being stacked is lofted (i.e. airborne) as it travels onto the flights  220   a ,  220   b  or previously stacked product  110 . This is especially important for soft or sticky products, such as fresh meat patties. The incremental movement down of the flights  220   a ,  220   b  can be pre-set for a particular product thickness for generally uniform thickness products, or can be adjusted based on the use of a product thickness sensor. 
         [0043]    In another embodiment of the present invention, the stacker  100  can be used as an up or down elevator to raise or lower single products or stacked products to a higher or lower level in tight spaces. Especially, when space is limited and an inclined conveyor system is not practical. 
         [0044]    Referring to  FIGS. 4A ,  4 B, and  4 C, another embodiment of the present invention in the form of an adjustable width stacker-loader  400  is shown. Two flighted vertical conveyors  410   a ,  410   b , which are similar to conveyors  210   a ,  210   b  described above, are adjustably supported for movement towards and away from each other in a controlled manner, preferably by mounting the vertical conveyors  410   a ,  410   b  on slide shafts  420   a ,  420   b  or other suitable linear guides. A frame  430  supports the slide shafts  420   a ,  420   b . A crank  440  is connected to a first acme screw  450  mounted on the frame  430 . A belt or chain  460  is connected from the first acme screw to a second acme screw  470 . Attached to each vertical conveyor  410   a ,  410   b  are preferably screw couplings  480   a ,  480   b , respectively, that engage the acme screws  450 ,  470 . Turning the crank  440  causes the lateral movement of the vertical conveyors  410   a ,  410   b  when the acme screws  450 ,  470  are turned. In this manner, an operator of the stacker-loader  400  can easily adjust the gap between the vertical conveyors by turning the crank  440 , and the stacker-loader  400  can be quickly and easily adjusted to handle stacking and loading of various size products, as desired. 
         [0045]    It should be understood by those skilled in the art that although the stacker-loader is depicted as having a manual crank  440  and ball screws  450 ,  470  for adjusting the spacing between the vertical conveyors  410   a ,  410   b , a servo motor or other manual or automated device for achieving the adjustment can be easily implemented in connection with ball screws or other suitable linear guides and drives. A stacker-loader with automated adjustment of the spacing between the flights may also be equipped with a photoeye for sensing the size of an approaching product, and automatically adjusting the spacing of the vertical conveyors to accommodate the sensed product. 
         [0046]    Referring to  FIG. 5 , another embodiment of the present invention comprising of a multilane stacker-loader  500  is shown. In this embodiment, three single vertical flighted stacking conveyors  510   a ,  510   b ,  510   c , which are similar to the conveyors  210  and  410   a , receive product  520  from a multiple lane feed conveyor  530 . Product guides  540   a ,  540   b , and  540   c  guide the multiple lanes of product  520  approaching the vertical conveyors  510   a ,  510   b , and  510   c , respectively, so that the products  520  enter a single flight of a respective vertical conveyor. The vertical conveyors  510   a ,  510   b , and  510   c  are offset so that the product lanes can be closely spaced together yet still allow for the vertical stacker. One or more exit conveyors or loading stations would be positioned below the stacking conveyors  510   a ,  510   b ,  510   c  to receive the stacked products  520  in the same manner as discussed above in connection with the first embodiment of the invention. 
         [0047]    One skilled in the art will recognize that the various automation techniques described above in reference to the single lane stacker can be implemented in this embodiment of the present invention. For example, optical sensors may be positioned along the feed conveyor  530  to detect incoming product  520 , as described above. Optical sensors may also be positioned to determine the position of the flights of each vertical conveyor  510 A,  510 B,  510 C, and for stepping the flights by way of a servo motor or other means controlled by a PLC, as described above. An interleaver may be positioned prior to the stacker-loader  500  for placing a substrate under the product  520  to be stacked, as described above. It should be understood that while three vertical conveyors are shown in  FIG. 5 , this is merely exemplary, and the number of vertical conveyors can be selected as desired. 
         [0048]    It will be recognized by those skilled in the art that changes may be made to the above described embodiments of the invention without departing from the broad inventive concept thereof. For example, the conveyers  200   a ,  200   b  need not be mounted vertically, but instead slightly offset from vertical. Similarly, the spacing of the flights  220   a ,  220   b  need not be uniform, thereby allowing stacking of various sized products. Additionally, for single flight stacking, such as using the stacking conveyors  510   a ,  510   b ,  510   c , the product can hang over the edge of the flight to some extent. While a preferred embodiment of a stacker is shown, any conveyor having rollers can be used in conjunction with the system provided by the present invention. 
         [0049]    It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but is intended to cover all modifications which are within the spirit and scope of the invention as defined by the appended claims; the above description; and/or shown in the attached drawings.
A stacker adapted to generally stack product in a vertical fashion is provided. The stacker includes a first generally vertical conveyor having a first conveyor belt and a first plurality of flights mounted generally perpendicularly to the first conveyor belt. The first plurality of flights at least partially defines a plurality of stacking platforms. At least one positioning sensor for sensing a relative position of the flights is provided. An advancement sensor is provided for sensing product entering the stacker. A first drive incrementally drives the first conveyor responsive to the advancement sensor so that the stacking platforms descend. Each of the stacking platforms can receive individual or single items to be stacked into a tray or can sequentially receive multiple items, either pre-stacked or stacked on a given flight, and then be indexed downwardly to allow the next stack to be formed on the subsequent stacking platform. A method and system for handling and stacking products is also provided.