Abstract:
A synchronized palletizer includes a row conveyor and a layer head, each vertically reciprocating within a frame. An infeed conveyor delivers in series items row-by-row onto the row conveyor. The row conveyor moves to vertically coincide with the layer head and laterally transfer a row items onto the layer head. Once a complete item layer has been constructed on the layer head, the layer head collapses the layer together and drops the layer through its floor onto a pallet or stack of item layers therebelow. Generally, the layer head vertical position follows the top of stack of item layers and the row conveyor travels reciprocally between the infeed conveyor and the layer head to deliver items row-by-row to the layer head. A variety of alternative relative positioning schemes, however, may be implemented.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to article manipulation devices and particularly to a palletizing device and method of operation.  
           [0002]    Palletizers receive a sequence of items and produce a palletized stack of items. Generally, items are formed into rows, rows formed into layers, and layers stacked upon a pallet to form a palletized stack of items. Thus, a typical palletizer receives a series of items and organizes the items by row, by layer, and ultimately as a palletized stack of items on a pallet.  
           [0003]    Palletizing calls for efficiency. In many applications, time is most critical. A palletizer more efficiently, i.e., more quickly, organizing an incoming series of items into a palletized stack of items represents advantage in greater production levels, i.e., greater item throughput.  
           [0004]    Another important palletizing consideration is size. A more compact machine takes less floor space and, if necessary, accommodates more palletizing machines in the same area as would be occupied by relatively larger palletizing machines. Compact size is, therefore, a desirable feature in a palletizer.  
           [0005]    Accordingly, it would be desirable to provide a palletizer having both improved time efficiency and reduced overall size relative to conventional palletizing devices. The subject matter of the present invention provides such a palletizer.  
         SUMMARY OF THE INVENTION  
         [0006]    A synchronized palletizer under the present invention receives serially items for palletizing on a vertically reciprocating row conveyor. A vertically reciprocating layer head receives items laterally row-by-row from the row conveyor and serves as a layer construction site. The layer head drops completed item layers therethrough onto a pallet therebelow or onto a stack of item layers resting on a pallet therebelow.  
           [0007]    The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation of the invention, together with further advantages and objects thereof, may best be understood by reference to the following description taken with the accompanying drawings wherein like reference characters refer to like elements. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which:  
         [0009]    [0009]FIG. 1 illustrates in perspective a synchronized palletizer according to a preferred embodiment of the present invention.  
         [0010]    [0010]FIG. 2 illustrates in plan view the synchronized palletizer of FIG. 1 as taken along lines  2 - 2  of FIG. 1.  
         [0011]    [0011]FIG. 3 illustrates in side view a layer head of the palletizer of FIG. 1.  
         [0012]    [0012]FIG. 4 illustrates in perspective the layer head of FIG. 3.  
         [0013]    [0013]FIG. 5 illustrates in perspective a dead plate of the layer head of FIGS. 3 and 4. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]    [0014]FIG. 1 illustrates in perspective and FIG. 2 in side view a palletizer  10  according to a preferred embodiment of the present invention. In FIGS. 1 and 2, palletizer  10  includes a frame  12  of generally box-form configuration. Frame  12  includes four vertical posts, individually posts  12   a - 12   d , supporting an upper structure comprising horizontal beams  12   e - 12   h . Thus, the lower end of each of posts  12   a - 12   d  rests on a floor and the upper ends of posts  12   a - 12   d  support beams  12   e - 12   h . Beams  12   e - 12   h  provide a generally horizontal rectangular structure maintained at a given level above floor level. Generally, frame  12  provides a relatively compact overall structure supporting therein elements of palletizer  10  as described more fully hereafter.  
         [0015]    Adjacent frame  12 , palletizer  10  includes an infeed conveyor  14 . Infeed conveyor  14  is a “production level” conveyor receiving, for example, output from a production or manufacturing operation or from a repackaging operation. Infeed conveyor  14  includes along its length a series of live, i.e., powered, rollers  14   a . Infeed conveyor  14  also includes a case turner  16 . Case turner  16  manipulates incoming items  18 , e.g., cases of products, appropriately according to programmed layer building patterns. Use of case turner  16  and layer building methods and patterns are well known in the art.  
         [0016]    Generally, infeed conveyor  14  moves a series of items  18  therealong for presentation to the remaining portions of palletizer  10  as operating within frame  12 . As may be appreciated, infeed conveyor  14  and turner  16  operate cooperatively to appropriately orient a sequence of items  18  according to a programmed layer building pattern including contemplation of necessary sequential row patterns interfitting to form layer patterns and layer patterns interrelating to produce a stable stack of items on a pallet  40 . Thus, it will be understood that items  18  are not necessarily symmetrical and may be oriented according to a specific predefined layer building pattern taking into account row-by-row variations within a layer and layer-to-layer variations for adjacent layers on a stack of item  18  layers resting on pallet  40 .  
         [0017]    Within frame  12 , palletizer  10  includes a vertically reciprocating row conveyor  20  and a vertically reciprocating layer head  22 . A row conveyor lift motor  24  when actuated vertically reciprocates conveyor  20  as indicated at reference numeral  21 . A layer head motor  26  when actuated vertically reciprocates layer head  22  as indicated at reference numeral  23 . Generally, each of row conveyor  20  and layer head  22  are independently suspended within frame  12 . More particularly, row conveyor  20  hangs from four suspension points  25 . Layer head  22  hangs from four suspension points  27 . Each of conveyor  20  and layer head  22  carry a pair of guides  29 . Each of vertical posts  12   a - 12   d  carry on their inner surface a corresponding guide track  31 . Thus, guide tracks  31  on posts  12   a  and  12   d  interfit guides  25  of row conveyor  20  and maintain conveyor  20  along a vertical path within frame  12 . Similarly, guide tracks  31  on vertical posts  12   b  and  12   c  interfit with guides  27  on layer head  22  to maintain layer head  22  along a vertical path within frame  12 .  
         [0018]    Suspension chains and associated sprockets couple each of row conveyor  20  and layer head  20  to the respective motors  24  and  26 . More particularly, row conveyor  20  hangs within frame  20  from a first set of four suspension chains  32  routed through appropriate sprockets  34  and coupled to motor  24 . Actuation of motor  24  in a first direction lowers row conveyor  20  and actuation in the opposite direction raises row conveyor  20 . Specifically, the output shaft  24   a  of drive motor  24  extends the length of horizontal beam  12   e  (shown only partially in FIG. 1) and carries at each end a pair of sprockets  34   a . Suspension chains  36  engage sprockets  34   a  and move in response to rotation of sprockets  34   a . One end of each of chains  32  couples to a suspension point  25  and the other end of each of suspension chains  32  carries a counter weight (not shown) depending directly below each pair of sprockets  34   a . In this manner, chains  32  remain engaged relative to sprockets  34   a  and, therefore, relative to drive motor  24 .  
         [0019]    Similarly, a second set of four suspension chains  36  and sprockets  38  suspend layer head  22  within frame  12  and couple to motor  26 . Actuation of motor  26  in a first direction moves layer head  22  upward and actuation in the opposite direction lowers layer head  22 . Specifically, the output shaft  26   a  of drive motor  26  extends the length of horizontal beam  12   g  (shown only partially in FIG. 1) and carries at each end a pair of sprockets  38   a . Suspension chains  36  engage sprockets  38   a  and move in response to rotation of sprockets  38   a . One end of each of chains  36  couples to a suspension point  27  and the other end of each of suspension chains  36  carries a counter weight (not shown) depending directly below each pair of sprockets  38   a . In this manner, chains  36  remain engaged relative to sprockets  38   a  and, therefore, relative to drive motor  26 .  
         [0020]    Thus, row conveyor  20  and layer head  22  operate independently and may be vertically positioned by appropriately actuating and controlling motors  24  and  26 , respectively.  
         [0021]    Row conveyor  20  moves to a lower position vertically coincident with the height of infeed conveyor  14  to receive from infeed conveyor  14  one row of items  18 . As discussed above, the row of items  18  presented to row conveyor  20  at the output of conveyor  14  correspond to an ongoing layer building pattern, i.e., particular ones of the items  18  within a given row are suitably oriented according to and overall sequence of item  18  orientation pattern. As live rollers  14   a  propel a sequence of items  18  onto row conveyor  20 , live rollers  20   a  activate and collect the sequence of items  18  as a row onto conveyor  20 . As may be appreciated, live rollers  20   a  are suitably operated in coordination with live rollers  14   a  of conveyor  14  to pass serially a given set of items  18  from conveyor  14  onto conveyor  20 . In this manner, conveyor  20  receives one row of items  18  from conveyor  14 . Conveyor  20  is then vertically positioned as necessary to vertically coincide with a current height of layer head  22  to pass the row of items  18  from conveyor  20  to layer head  22 .  
         [0022]    As may be appreciated, because both row conveyor  20  and layer head  22  independently vertically reciprocate a broad combination of relative movements may be accomplished by programmed control to transfer a row of items  18  from conveyor  20  to layer head  22 , i.e., one of the two devices may be moved to match the height of the other or both moved to match some intermediate or predetermined height according to programmed control. Generally, however, it is contemplated that the relatively higher speed conveyer  20  “chase’ layer head  22 , i.e., seek out a current height for layer head  22 , when transferring a row of items  18  from conveyor  20  onto layer head  22 . In this particular embodiment, conveyor  20  includes a row pusher  30  of generally conventional design including a pneumatic cylinder  30   a  for pushing a row of items  18  from conveyor  20  onto layer head  22 . Thus, row conveyor  20  vertically aligns itself with a current vertical position of layer head  22  and passes laterally a row of items  18  from conveyor  20  to layer head  22 .  
         [0023]    Generally, layer head  22  tracks the height of a stack of items  18  layer as positioned on a pallet  40 . Pallet  40  rests at floor level and receives layer-by-layer items  18  from layer head  22 . Once a complete layer of items  18  has been built row-by-row on layer head  22 , layer head  22  deposits the entire layer as a next layer on pallet  40  or on a stack of layers resting on pallet  40 . As will be described more fully hereafter, layer head  22  withdraws its support from below a layer of items  18  and drops the layer onto a pallet  40  below or onto a stack of item  18  layers resting on pallet  40  below. Layer head  22  then repositions itself, i.e., raises, to prepare to receive a next item  18  layer row-by-row from row conveyor  20 .  
         [0024]    [0024]FIGS. 3 and 4 detail layer head  22  as detached from frame  12 . FIG. 5 illustrates a dead plate  108  of layer head  22 , but detached therefrom for purposes of illustration. In FIGS.  3 - 5 , layer head  22  includes a set of free rollers  100  carried on a pair of chains  102   a  and  102   b . Sprockets  103   a  constrain chain  102   a  to an L-shaped path. Similarly, sprockets  103   b  restrict chain  102   b  to a corresponding L-shaped path. Rollers  100  attach to a length segment of chain  102   a  and thereby create a removable floor relative to layer head  22 . A drive shaft  105  couples to one of sprockets  103   a  and one of sprockets  103   b  and thereby ties together chains  102   a  and  102   b . Drive motor  104  turns shaft  105  to move chains  102   a  and  102   b  along their respective and coordinated L-shaped paths. A pair of vertical plates  110 , individually  10   a  and  110   b , support shaft  105  and also carry thereacross a stop  111 , i.e., a raised edge formation. Stop  111  engages a leading lower edge of an item  18  layer while being dropped from layer head  22 .  
         [0025]    Floor drive motor  104  operates to move chains  102  and thereby withdraw rollers  100  from a supporting or floor position relative to an item  18  layer to an open position allowing an item  18  layer to drop through layer head  22  onto a pallet  40  therebelow or onto a stack of item  18  layers therebelow. Advancing rollers  100  rightward, in the view of FIGS. 3 and 4, moves rollers  100  out of a floor position as illustrated in FIG. 4 and into an open position occupying the vertical portion of the L-shaped path provided by sprockets  103  and chains  102 . Once the leading edge of the item  18  layer engages stop  111 , the item  18  layer holds its position and rollers  100  continue to move out from thereunder to drop the item  18  layer therebelow. The first row of items  18  to fall from layer head  22  is the row most distant from stop  111 . Thus, the first-to-arrive row of items  18 , i.e., the row first placed on layer head  22  when constructing a layer, is the last row to fall from layer head  22  when releasing an item  18  layer. The last-to-arrive row is, therefore, the first row dropped from layer head  22 . In this manner, a complete item  18  layer drops through the opened floor of layer head  22 .  
         [0026]    Layer head  22  includes conditioning mechanisms to better organize a given item  18  layer thereon prior to dropping the layer on a pallet  40  or a stack of layers therebelow. As discussed above, palletizer  10  accommodates an ongoing layer building pattern. Items  18  of varying orientation must be organized into a layer. A relatively loose, i.e., with space therebetween, initial organization of items  18  better facilitates layer building patterns. Thus, as initially organized on layer head  22 , items  18  are loosely packed but possess the required relative orientations to form, when brought together, a desired and compact overall item  18  configuration within a given layer. Generally, layer head  22  includes conditioning mechanisms to collapse together along orthogonal dimensions a loosely packed item  18  layer into a tightly packed item  18  layer.  
         [0027]    A pair of side clamps  106 , individually  106   a  and  106   b , move laterally inward in a first dimension and compress together an item  18  layer in preparation for deposit on a stack of item  18  layers therebelow. A pneumatic cylinder  106   c  couples by way of scissor mechanism  107  (shown partially at reference numeral  107   a  in FIG. 4) to operate clamps  106   a  and  106   b  in parallel, i.e., move laterally inward in parallel and coordinated orientation. A dead plate  108  (shown separately in FIG. 5) rotates about an axis  108   a , i.e. flips up into and past a vertical position, to compress a layer of items in a second dimension. Thus, operating side clamps  106  and pivoting dead plate  108  compresses together, in first and second mutually orthogonal dimensions, a layer of items  18  prior to deposit on a surface therebelow. Thus, the process of building a layer row-by-row on lift head  22  results in some disorganization or loose fitting layers requiring, for optimal stacking, that the layers be compressed together in two dimensions, i.e. squeezed inward by bars  106  and plate  108 , to make a compact organized layer ready for stacking on a surface therebelow.  
         [0028]    In fact, a palletizer which permits significant disorganization in an item  18  layer while constructing such layer row-by-row promotes rapid construction of the layer. For example, certain layer building patterns require an interfitting relationship between rows within a layer. When such interfitting is required, it is easier and faster to initially form the layer as a loose organization of items  18  to better facilitate rows having items  18  interfitting with other rows.  
         [0029]    Palletizer  10  facilitates such loose organization of a layer of items  18  during construction thereof at upward-facing side plates  109   a  and  109   b . Generally, side plates  109  are upward facing, smooth surfaces adjacent the ends of rollers  100  on each side of layer head  22 . Rollers  100  are of sufficient length to support a tightly-packed item  18  layer thereon. In accordance with the present invention, rollers  100  need not be any wider than necessary to support an item  18  layer thereon by virtue of support at side plates  109   a  and  109   b . More particularly, a loosely fitting item  18  layer occupies more area, i.e., requires a greater support surface, than a tight-fitting item  18  layer. Side plates  109   a  and  109   b  support the outer edges of a loosely-fitting item  18  layer and thereby provide a greater area for supporting an item  18  layer during construction. In other words, layer head  22  tolerates significant disorganization among layers during layer formation and thereby facilitates rapid layer construction on layer head  22 .  
         [0030]    Once the layer has been loosely organized on the upward facing surfaces of layer head  22 , i.e., on rollers  100  and side plates  109   a  and  109   b , dead plate  108  and side clamps  106  operate to drive together and compress the loosely organized item  18  layer into a tightly fitting item  18  layer resting entirely on rollers  100 .  
         [0031]    As best seen in FIG. 4, the length of dead plate  108  corresponds to the length of rollers  100 . Dead plate  108  includes, at each end, notches  108   b  and  108   c , respectively. When plate  108  pivots upward, as indicated at reference numeral  108   d  in FIG. 5, notches  108   b  and  108   c  leave an open space therebelow to accommodate inward movement of clamps  106 , i.e., inward and past the ends of dead plate  108 . With dead plate  108  moved to its “clamping” position, i.e., pivoted inward to engage and compress and item  18  layer resting on layer head  22 , side clamps  106  move inward and if necessary reach beyond the ends of rollers  100  to thereby compress together in coordination with dead plate  108  an entire item  18  layer from a loosely organized item  18  layer into a tightly-fitting item  18  layer. As may be appreciated stop  111  operates in coordination with clamps  106  and dead plate  108  to compress together an item  18  layer resting upon layer head  22 . More particularly, stop  111  resists movement of an item  18  layer in response to dead plate  108  pivoting into its clamping position.  
         [0032]    In FIG. 5, a pivot shaft  108   g  mounts rotatably to layer head  22  and carries thereon dead plate  108 . A pair of pneumatic cylinders  108   e  couple by way of corresponding levers  108   f  to pivot shaft  108   g . Thus, actuation of cylinders  108   e  causes movement of dead plate  108  between a transition position as shown in FIGS. 4 and 5 and a clamping position, i.e., pivoted inward as indicated at reference numeral  108   g.    
         [0033]    Thus, dead plate  108 , rollers  100 , side plates  109 , stop  111  and side clamps  106  cooperatively tolerate significantly loose organization among items  18  when forming an item  18  layer and compress together items  18  in a tight fitting layer supported entirely on rollers  100 .  
         [0034]    Dead plate  108  provides a transition surface filling a gap between row conveyor  20  and layer head  22 . Conventional dead plates, i.e., transition devices, are generally fixed in position. Dead plate  100  goes beyond a transition function and provides a compression function. The horizontal position of dead plate  108  provides, therefore, a transition surface function when item  18  rows are pushed onto layer head  22 . After the last-to-arrive row of items  18  is located on layer head  22 , dead plate  108  pivots up to compress and provide a secondary backstop for proper layer construction. Plate  108  thereby provides an ability to lower into a generally horizontal conventional dead plate position for a net fit between a reciprocating layer head  22  and whatever it mates with for receiving rows, e.g., a row conveyor  20 . Pivoting dead plate  108  provides also a layer compression device which operates in opposition to stop  111  as provided across plates  110 . In other words, dead plate  108  can push a layer against the stop  111  and thereby squeeze or compress the layer between plate  108  and stop  111 .  
         [0035]    Dead plate  108  provides a particularly important advantage during layer release, i.e., when rollers  100  are pulled from under an item  18  layer to drop the item  18  layer through layer head  22 . As discussed above, dead plate  108  pivots into clamping or compressing engagement relative to an item  18  layer to better organize and make compact the item  18  layer in preparation for stacking. Leaving dead plate  108  in such engagement improves release of the first row of items dropped through layer head  22 . More particularly, and especially with respect to smaller dimensioned items  18 , dead plate  108  maintains a given and desired position for a row of items  18  when it remains in contact with the row of items  18  as they fall from of rollers  100  and onto a supporting surface therebelow. By guiding this first-to-drop row of items  18 , dead plate  108  serves an additional guiding function relative to items  18  when releasing a row of items  18  from layer head  22 . This first-to-drop row of items  18  then serves a similar guiding function relative to a next-to-drop row of items  18 . Eventually, the last-to-drop row of items  18 , i.e., those adjacent stop  111 , fall through layer head  22  and find their final resting position on pallet  40  or on a stack of item  18  layers resting on pallet  40 .  
         [0036]    Prior art roller floors pulling support from under a layer of items suffer from a “loose” row which becomes more troublesome for narrower item  18  dimensions. In other words, the narrower item  18  is the greater its tendency to rock out of position when falling from rollers  100 . In accordance with the present invention, however, dead plate  108  guides the first-to-drop item  18  row into position and begins a cascading series of supporting elements, i.e., each row is guided into position by the previous row and the first row is guided into position by dead plate  108 . In this manner, an item  18  layer compressed together on layer head  22  achieves a more stable and better compressed final position after dropping through layer head  22  as it finds its final resting place on pallet  40  or on a stack of item  18  layers resting on pallet  40 .  
         [0037]    Compressive forces applied to an item  18  layer by virtue of the item  18  layer being captured and compressed between dead plate  108  and stop  111  also eliminate a dependence on conventional and undesirably variable compressive forces supplied by roller floors. In systems using only free rollers pulled from under an item  18  layer, the compressive force, i.e., against a fixed stop, varies as the roller bearings become more free turning by the unweighting thereof as items  18  fall therefrom. For particularly heavy items  18  and particularly free turning rollers  100 , moving rollers  100  out of a supporting position does not generate significant compressive forces relative to a load, i.e., the load does not bear heavily against a fixed stop under such conditions. Under the present invention, however, dead plate  108  maintains static compression relative to an item  18  layer regardless of item  18  layer weight and degree of free-turning characteristic of rollers  100 . As a result, an item  18  layer dropped through layer head  22  enjoys a more compact and better organized final resting place on pallet  40  or on a stack of item  18  layers resting on pallet  40 .  
         [0038]    Side plates  109  enhance use of rollers as a floor for a layer conveyor. The span occupied by rollers  100 , i.e., as supported at each end thereof at chains  102 , is limited by the strength and deflection characteristics of rollers  100 . As may be appreciated, minimizing the length of rollers  100  to occupy just sufficient distance to support an entire item  18  layer minimizes the cost and structural requirements of rollers  100 . Side plates  109  tolerate loose organization within an item  18  layer during construction thereof. In conventional practice, a forty inch wide finished width for a given item  18  layer requires a roller floor of over fifty inches wide to accommodate the layer during construction. Under the present invention, however, rollers  100  need only be forty inches wide because side plates  109  support the outer edges of a layer during construction thereof. As the roller floor, i.e., the support provided by rollers  100 , width increases, the strength of the rollers must increase to avoid unacceptable deflection caused by the longer roller length. Increased strength requires increased weight and requires larger diameter rollers  100  as flooring for layer head  22 . Both aspects negatively an inefficiently affect machine performance when roller length exceeds item  18  layer dimensions. In accordance with the present invention, however, rollers  100  are of minimal length just sufficient to support a tightly-organized item  18  layer thereon.  
         [0039]    Thus, a synchronized palletizer has been shown and described. The synchronized palletizer of the present invention provides a compact overall size with high item throughput. Most low infeed, i.e., production level infeed, palletizers require a pallet position, a layer build position, and a row build conveyor. In accordance with the present invention, however, the layer build position is essentially eliminated by building layers row-by-row on the layer head  22  which also serves also as a layer placement mechanism, i.e., placing item  18  layers on a pallet  40  or stack of item  18  layers. This feature of the present invention is believed to save approximately 25% to 35% of otherwise required floor space. The synchronized palletizer of the present invention utilizes a relatively high speed row conveyor to chase down a current position of the layer head  22 . Generally, conventional layer building brings each row to a fixed and maximum height, i.e., above any potential height for a stack of item  18  layers, for each and every row. In accordance with the present invention, however, each row need only be raised to the height of the current stack level, i.e., to where layer head  22  is positioned just above pallet  40  or a stack of item  18  layers resting on pallet  40 . In this manner, the present invention reduces travel distance and travel time for rows conveyed to a layer building site.  
         [0040]    While illustrated as having two side plates  109 , one at each end of rollers  100 , the present invention may be practiced with only one side plate  109 . The important function being the presence of a support area beyond rollers  100  and adjacent thereto to facilitate loose packing of item  18  rows during construction of an item  18  layer on layer head  22 .  
         [0041]    It will be appreciated that the present invention is not restricted to the particular embodiment that has been described and illustrated, and that variations may be made therein without departing from the scope of the invention as found in the appended claims and equivalents thereof.