Abstract:
A palletizer ( 10 ) for stacking a series of items on a pallet (P), the palletizer ( 10 ) including a pallet hoist ( 34 ) for supporting a stuck of pallets therein; a pallet lift mechanism ( 82 ) mounted for vertical movement within the pallet hoist ( 34 ) adjacent to and relative to the stack of pallets (P), the pallet lift assembly ( 82 ) including a pair of spaced, opposed pallet support members ( 110 ) mounted on the pallet lift assembly ( 82 ) for movement between a retracted position wherein there is clearance between the pallet support member ( 110 ) and the stack of pallets, and an extended position wherein the pallet support member ( 110 ) is in an interference position relative to the stack of pallets; a top frame dispenser ( 38 ) for supporting a supply of top frames (T); and a carriage for moving pallets and top frames from the pallet hoist ( 34 ) and the top frame dispenser ( 38 ), respectively.

Description:
RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119 of co-pending U.S. Provisional Patent Application Ser. Nos. 60/016,853; 60/017,014; and 60/016,845, all filed May 3, 1996. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The invention relates generally to material handling systems, and particularly to palletizers for arranging articles on a pallet. 
     2. Related Prior Art 
     A palletizer is operable to arrange objects, such as beverage containers, into an organized pattern and place the objects onto a pallet. It is known to provide such palletizers with a container conveyor assembly, apparatus to organize the objects into a pattern, a pallet dispenser, a separator sheet dispenser and a main hoist for holding the pallet in a position to receive a layer of objects and to move the pallet and layers of objects so as to receive an additional layer of objects. 
     SUMMARY OF THE INVENTION 
     The invention provides a palletizer assembly having improved apparatus for handling pallets upon which objects are placed and for handling top frames which are placed on top of the uppermost tier of a stack of layers of objects. The pallet and top frame handling apparatus include improvements to the pallet hoist and the main hoist. The palletizer, including the pallet and top frame handler, incorporates a modular design permitting various features of the invention to be independently incorporated into the palletizer. 
     The invention simplifies operation of the palletizer assembly, thereby improving the service life of the palletizer and simplifying maintenance and manufacturability of the palletizer assembly. 
     More particularly, in one embodiment of the invention, the palletizer assembly includes a pallet dispenser and a pallet hoist. The pallet hoist lifts individual pallets into an elevated, staging position wherein the pallet is received by a top frame handler. The staging position is in close proximity to the top of the main hoist so that the pallet need travel only a minimal distance to an initialized position wherein the pallet is located in the main hoist and positioned to receive a first layer of objects. 
     The top frame handler moves a top frame from a stack of top frames to the staging position underneath a pallet in the staging position and subsequently transports the pallet and top frame into the main hoist. The movements of the pallets and top frames are coordinated by the pallet hoist and top frame handler so that movements of the pallet and top frame into the staging position occur during stacking of containers. 
     Upon completion of a stack of objects, the top frame handler moves into the main hoist, thereby positioning the pallet and top frame into position for stacking. Because the top frame, when in the staging position, is in close proximity to the top of the stack, the top frame is moved into position on top of a newly created stack of containers quickly. 
     The top frame handler then releases the top frame to drop onto the top tier of stack of layers of objects while the stack of containers is located within the main hoist. 
     The palletizer also includes a pallet lift located in the main frame shaft. At the time the top frame handler releases a top frame onto a newly created stack of layers of containers, the pallet lift in the main hoist removes the pallet from the top frame carrier and into the initialized position for receiving a first layer of objects. The pallet lift, which is mounted on the main hoist frame, also positions the pallet so as to be supported by the main hoist. 
     The palletizer thus provides apparatus for handling a pallet and a top frame in a manner which minimizes the distances the pallet and top frame must travel from respective storage positions into a stacked position with containers. When the pallet is in the staging position, the pallet is maintained in a position above a top frame immediately prior to introduction of the pallet and top frame into the main hoist. This placement of the pallet above the top frame prior to placement of the top frame on a stack of containers reduces the cycle time of the palletizer assembly. 
     Another advantage provided by the invention is the provision of a palletizer assembly that places a top frame on a stack of containers before the stack leaves the main hoist. Because the stack of containers is eventually moved laterally outside the confines of the main hoist, which can tend to cause tipping of the stack or disrupt the arrangement of the containers on the pallet, the placement of a top frame on the stack before such lateral movement occurs enhances the stability of the stack. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a palletizer embodying the invention. 
     FIG. 2 is a side elevation view of the palletizer shown in FIG.  1 . 
     FIG. 3 is an elevation view of the pallet hoist taken generally along line  3 — 3  in FIG.  2 . 
     FIG. 4 is a sectional view taken along line  4 — 4  in FIG.  3 . 
     FIG. 5 is a an enlarged top view of a portion of the pallet hoist shown in FIG.  4  and showing a pallet in phantom. 
     FIG. 6 is a top view of the pallet hoist shown in FIG. 5 showing a pallet in phantom. 
     FIG. 7 is a side elevation view of the palletizer shown in FIG. 1 with various components removed to illustrate the top frame handler and pallet hoist. 
     FIG. 8 is view taken generally from line  8 — 8  in FIG.  7 . 
     FIG. 9 is a view of the main hoist taken generally along line  9 — 9  in FIG.  2 . 
     FIG. 10 is a sectional view taken generally along line  10 — 10  in FIG.  9 . 
     FIG. 11 is an enlarged view of a portion of the main hoist shown in FIG.  9 . 
     FIG. 12 is a front view of the portion of the main hoist shown in FIG.  11 . 
    
    
     Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A palletizer assembly  10  embodying the invention is illustrated in the drawings. The palletizer  10  comprises (see FIG. 1) a container conveyor assembly  14 , apparatus  18  for arranging containers (denoted generally by reference letter “C”) received from the conveyor  14  into a pattern, apparatus  22  for sweeping a discrete number of containers from the pattern forming apparatus  18  into a layer of containers, a main hoist  26  for supporting a pallet (denoted generally by reference letter “P”) in position to receive a layer of containers from the sweep apparatus  22 . 
     The pallets are delivered to the main hoist  26  of the palletizer  10  by means of a pallet dispenser  30  which supports a supply of pallets. The palletizer assembly  10  also includes a pallet hoist  34  for receiving a stack of pallets from the pallet dispenser  30  and for lifting individual pallets upwardly. 
     The palletizer assembly  10  also includes a top frame dispenser  38  which supports a supply of top frames (denoted generally by reference letter “T”) on a pallet. The palletizer assembly  10  also includes a top frame handler assembly  42  (FIG. 2) for moving individual top frames from the top frame dispenser  38  into the main hoist  26  into a position on top of a completed stack of objects. 
     The sweep apparatus  22  and the top frame handler assembly  42  are further described in the following co-pending International (PCT) patent applications, which are assigned to the assignee hereof and which are incorporated herein by reference: Ser. No. 97925432.3, filed concurrently herewith and titled “Container Sweep Apparatus for a Palletizer”; and Ser. No. 97922645.3, filed concurrently herewith and titled “Separator Sheet Handler for a Palletizer”. 
     The palletizer assembly  10  also includes a separator sheet dispenser  46  and a separator sheet handler assembly  50  for delivering individual sheets to the main hoist  26  for separating tiers of containers stacked on a pallet. A complete stack conveyor  54  is located at the bottom of the main hoist  26  for receiving a completed stack of containers comprising a pallet supporting multiple tiers of containers with separator sheets between the tiers of containers, and a top frame supported by the upper surface of the uppermost tier of containers. 
     More particularly, and with reference to FIG. 2, the pallet dispenser assembly  30  includes a pallet dispenser conveyor  70  for supporting a stack of pallets for use by the palletizer assembly  10 . The pallet dispenser conveyor  70  delivers a stack of pallets to the pallet hoist  34  on an as needed basis. 
     As shown in FIGS. 2-4, the pallet hoist  34  includes a frame  74  and a backstop  78  fixed to one side of the frame  74 . The backstop  78  prevents over-travel of stacks of pallets introduced into the frame  74  by the pallet dispenser conveyor  70 . For reasons discussed below, the frame  74  includes two pairs of parallel, vertical rails  86  which extend upwardly through interior of the pallet hoist frame  74  and which are fixed to opposite sides of the frame  74 . 
     Once a stack of pallets is delivered to the pallet hoist  34 , the pallet hoist  34  is operable to move individual pallets from the stack of pallets upward into position to be carried by the top frame handler  42 . More particularly, and with reference to FIGS. 3-6, the pallet hoist  34  includes a pair of pallet lift assemblies  82  which can be indexed from a position in the lower portion of the pallet hoist  34  adjacent the uppermost pallet in the stack of pallets in the pallet hoist  34  to a staging position (shown in FIGS. 3 and 4) wherein a pallet is held above the pallet hoist frame  74 . 
     The pallet lift assemblies  82  are located in opposed facing relation on opposite sides of the pallet hoist frame  74 . Each pallet lift assembly  82  is supported by a pair of the rails  86 . A drive mechanism  90  associated with the pallet hoist  34  is operable to raise and lower the pallet lift assemblies  82  in tandem along the rails  86  between the lower region of the pallet hoist frame  74  and the staging position. 
     Each pallet lift assembly includes a subframe  94  which extends between and is supported by a pair of the vertical rails  86 . Each pallet lift assembly  82  also includes a pair of pallet support members or arms  98  which are pivotably mounted on, and extend upwardly from, the subframe  94 . Each arm  98  is located adjacent a respective rail  86  and extends upwardly from a respective end of the subframe  94 . The arms  98  are supported by the subframe for pivotable movement about their longitudinal axis through a range of at least  90  degrees. As shown in FIGS. 3 and 4, when the pallet lift assemblies  82  are in the staging position, the subframe  94  is adjacent the uppermost extent of the pallet hoist frame  74  and the arms  98  extend above the uppermost extent of the pallet hoist frame  74 . 
     Each pallet lift assembly  82  also includes a pair of actuators  102  mounted on the upper surface of the subframe  94 . The actuators  102  have respective ends fixed to the subframe  94  and piston rods which are connected to a respective crank arm  106  fixed to a respective arm  98 . The crank arms  106  are operably connected to respective actuators  102  such that extension and retraction of the actuators  102  rotates the arms  98  through a range of movement of approximately 90 degrees. Each extended arm  98  includes at the distal end thereof, an elongated finger  110  which extends radially relative to the axis of the extended arms  98 . The fingers  110  are oriented relative to the extended arms  98 , the frame  74 , and to each other, such that when the actuators  102  are retracted, the fingers are in a retracted position (shown in FIGS. 3 and 4) such that the fingers  110  are generally parallel to the subframe  94 . When the actuators  102  are extended as shown in FIG. 5, the arms  98  are rotated 90 degrees from the retracted position so that the fingers  110  are parallel and perpendicular to the subframe  94 . When fingers  110  are so rotated into an extended position, the fingers  110  extend into the space above the pallet hoist frame  74  so that they are in an interference position relative to the stack of pallets. 
     The pallet hoist  34  also includes a pallet position sensor assembly  114  supported by one of the pallet lift assemblies  82  to provide a control signal to the drive  90  indicating the arrival of the pallet lift assemblies  82  to the position adjacent a pallet to be lifted. The position sensor assembly  114  is supported by the subframe  94  and holds a sensor (not shown) in position to detect the location of a lifting surface on a pallet relative to the fingers  110 . 
     As mentioned above, the pallet hoist  34  is operable to move individual pallets from a stack of pallets located in the lower region of the pallet hoist frame  74  to the staging position located above the pallet hoist frame  74 . Such raising of the individual pallets is accomplished as follows: 
     The pallet lift assemblies  82  are moved downwardly along the vertical rails  86  to a position adjacent the uppermost pallet in the stack of pallets. When the pallet lift assemblies  82  are so positioned, the actuators  102  and fingers  110  are retracted and move into a clearance on either side of the individual pallet to be lifted. Upon registration of the fingers  110  relative to the undersurface of the pallet, the pallet position sensor  114 , at the level of the fingers  110 , sends a signal to the drive mechanism  90  to stop downward movement of the subframe  94 . 
     The actuators  102  are then extended thereby moving the fingers  110  into the extended position and into engagement with the undersurface of the uppermost pallet, i.e., the interference position relative to the stack of pallets. The drive  90  then raises the assemblies  82  and the pallet supported thereby along the vertical rails  86  to the staging position. Once in the staging position (see FIG.  7 ), the lower surface of the pallet is spaced above the upper extent of the pallet hoist frame  74  and is held in position to be received by the top frame handler  42  in a manner discussed below. 
     In general, the pallet is released by the lift assemblies  82  through the rotation of the fingers  110  into their retracted positions, thereby dropping the pallet supported thereby onto the upper surface of the top frame handler  42 . The pallet lift assemblies  82  are then indexed downwardly into registration with the next uppermost pallet and the stack of pallets for subsequent cycling of the pallet hoist  34  to lift the next uppermost pallet to the staging position. 
     Referring to FIGS. 1 and 2, the top frame handler assembly  42  includes a top frame dispenser conveyor  130  (FIG. 1 only) for receiving a pallet supporting a stack of top frames. The top frame dispenser conveyor  130  is operable to move the pallet and the stack of top frames supported thereby into position on a top frame dispenser lift assembly  134 . The top frame dispenser  38  also includes a top frame pallet discharge conveyor (not shown) and stage  138  for moving an empty pallet from the top frame dispenser lift assembly  134  into a position for retrieval by, for example, a forklift. 
     The top frame handler  42  also includes (see FIG. 8) a pair of spaced apart parallel rails  146  which extend along the upper extent of the top frame dispenser lift assembly  134  and the pallet hoist frame  74 . As shown in FIG. 8, the rails  146  are spaced slightly outside the arms  98  of the pallet lift assemblies  82 . 
     The top frame handler assembly  42  also includes a carriage  150  which is supported for reciprocating movement along the rails  146  by four pairs of rollers  154  (two pairs shown in FIG.  7  and two pairs shown in FIG.  8 ). Each pair of rollers  154  includes a respective roller located on opposite sides of a rail  146 . The carriage  150  is selectively and reciprocally driven by a belt drive (not shown) along the rails  146 . 
     The carriage  150  is movable through a range of positions along the rails. The carriage  150  is in an initial position when it is in an extreme position directly above the top frame dispenser conveyor  130  (to the far right in FIG.  7 ). The carriage  150  can be driven to an intermediate position (to the left in FIG. 7) wherein the carriage is approximately above the top frame lift assembly  134  and, as discussed below, the carriage is positioned to receive a pallet held in the staging position by the pallet hoist  34 . The carriage  150  can then be driven to a second extreme position, or discharge position, wherein the carriage  150  is located over the pallet hoist  34  and extends into the main hoist  26  so that a top frame can be released into the main hoist  26 . 
     The top frame handler  42  includes a carrier  158  extending from the carriage  150  in a cantilevered manner from the carrier in a position between the rails  146 . When the carriage  150  is located in the initial position (see FIG.  7 ), the carrier  158  extends into a position immediately over the top frame dispenser lift assembly  134 . The carrier  158  is somewhat narrower than the carriage such that the lateral edges of the carrier  158  can be (FIG. 8) located between the arms  98  of the pallet hoist  34 . More particularly, when the carriage  150  is advanced into the intermediate position, the carrier  158  is directly above the pallet hoist frame  74 , can be moved into position located immediately below the lower surface of a pallet suspended by the pallet lift assembly  82  in the staging position disclosed above. When so positioned, the carrier is located between the arms  98  and thereafter receives a pallet suspended by the fingers  110  in a manner discussed below. 
     The carriage  150  also includes four top frame clamps  162  mounted on the carrier  158 . Each clamp  162  includes opposing clamp members  160 . The clamps  162  are arranged on the carrier  158  such that respective pairs of clamps  162  are located adjacent each rail  146  on opposite sides of the carrier  158  and are spaced apart so as to receive there between a top frame. The clamp members  160  extend downwardly from the carrier  158  and, when the carriage is in the initial position, the clamp members  160  are engageable with the lateral edges of a top frame supported by the top frame lift assembly  134 . 
     The carriage  150  also includes a clamp actuating assembly  166  on the carrier  158  for selectively moving the clamps in unison closer together and farther apart so as to engage and release a top frame. The top frame dispenser lift assembly  134  can be indexed upwardly so that the uppermost top frame is located between the clamps  162  and the clamp actuating assembly  166  closes the clamps  162  to clasp therebetween the uppermost top frame. 
     In order to support a pallet thereon, the upper surface of the carriage includes a pair of pallet supports  170  and a pallet stop  174 . 
     The top frame handler operates as follows: when in the initial position (shown in FIG. 7) the carrier  158  picks a top frame from the top frame lift assembly  134 . The carriage  150  then moves along the rails  146  from the initial position toward the pallet hoist  34  (to the left in FIG.  7 ). When the carriage moves along the rails  146 , the carrier  158  carries a top frame from the top frame dispenser lift assembly  134 . The carrier moves into position immediately below a pallet suspended in the staging position by the pallet lift assemblies  82 . 
     When the top frame handler is located in the staging position, the pallet lift assembly  82  is operated so that the fingers  110  rotate into the retracted position, thereby dropping the pallet from the pallet lift assembly  82  onto the pallet supports  170 . The pallet and top frame are thereafter carried by the carrier  158  into the main hoist  26  and, once the pallet lift assembly  82  is in a retracted position, the pallet lift assembly indexes downwardly in the manner discussed above, to provide clearance to the carriage to advance along the rails  146  toward the main hoist and the discharge position. 
     FIGS. 9-12 illustrate the main hoist  26 . The main hoist  26  is located adjacent the pallet hoist  34  and is configured and operable to receive a top frame and pallet carried by the top frame handler  42 . More particularly, the main hoist  26  includes a main hoist frame  190  defining an interior space or main hoist shaft  194 . 
     The main hoist  26  also includes a plurality of flight bars  198  (two pairs of flight bars  198  shown in FIG. 10) extending across the main hoist shaft  194 . The flight bars  198  are supported at their respective opposite ends by chain belt drives  202  which are operable to move the flight bars  198  from a position adjacent the upper extent of the main hoist frame  190  to a lower position adjacent the complete stack conveyor  54 . The flight bars  198  are selectively indexable by the chain belt drives  202  so as to support a pallet and to move incrementally downwardly so that the pallet is positioned to receive subsequent layers of objects from the container conveyor assembly  14  and the forming and sweeping apparatus  18  and  22 . In this regard, the main hoist  26  also includes an upper square assembly  206  and a lower square assembly  208  mounted on the upper extent of the main hoist frame  190  for assuring the proper arrangement of containers once a layer of containers is moved onto a pallet. 
     The main hoist  26  also includes (FIGS. 10-12) a pair of pallet lift subassemblies  210  which operate in unison for removing a pallet from the pallet supports  170  on the top frame carrier  158 . Each pallet lift subassembly  210  includes a frame  214  having a lower end  218  pivotally supported by one side of the main hoist frame  190 . Each pallet lift assembly  210  also includes a tip cylinder  222  mounted to the main hoist frame  190  and operably connected to the frame  214 . When the tip cylinder  222  is retracted (as shown in phantom in FIGS.  9  and  11 ), the frame  214  is substantially coplanar with the main hoist frame  190 . When the tip cylinder  222  is extended, however, the frame  214  pivots about the hinge  218  inwardly of the main hoist shaft  194  such that the upper extent of the frame  214  is located inwardly of the main hoist shaft  194  relative to the lower end  218 . 
     Each pallet lift subassembly  210  also includes (FIGS. 10 and 12) a pair of extension arms  226  telescopically received by the upper end of the frame  214 . Extending between the respective distal ends of the extension arms  226  is an “L” bracket  230 . A lift cylinder  234  is mounted on the frame  214  and is operable to move the arms  226  and “L” bracket  230  from a retracted position to an extended position wherein the arms  226  and “L” bracket  230  are moved upwardly away from the upper end of the frame  214 . When the arms  226  and “L” bracket  230  are extended, the tip cylinder also extends and the “L” bracket  230  is lifted into a position adjacent the lower square assembly  208  at the upper extent of the main hoist  26 . 
     A notable aspect of the operation of the pallet lift subassemblies  210  is that the “L” brackets  230  converge slightly upon extension of the arms  226  because of the inwardly angled position of the frame  214  when the tip cylinders  222  are extended. As discussed below, this convergence of the “L” brackets during extension squares a pallet supported on the “L” bracket as the pallet is lifted to the upper region of the main hoist adjacent the lower square assembly  208 . This squaring of the pallet upon delivery of the pallet to the top of the main hoist helps properly orient the pallet for receiving a layer of containers from the sweep apparatus  22 . 
     The palletizer assembly  10  is operable as follows: 
     Assuming an initial condition wherein a pallet is supported by the main hoist  26  in position to receive an initial layer of containers from the sweep apparatus  22 , a first layer of containers is swept onto the upper surface of the pallet by the sweep apparatus  22 . The flight bars  198  supporting the pallet then index downwardly through operation of the chain drive belts  202  to a lowered position such that a subsequent layer of containers can be moved onto the upper surface of the layer of containers supported by the pallet. Prior to the next cycle of the sweep assembly  22  and the main hoist  26  to move the next tier of containers on top of the first tier of containers, the separator sheet handler assembly  50  places a sheet on top of the first tier of containers. The main hoist  26 , sweep apparatus  22  and sheet handler assembly  50  cooperate in this manner until the pallet is positioned in the lower region of the main hoist shaft  194 . 
     During this operation, the top frame handler  42  supports a top frame and a pallet in the staging position, i.e., the top frame and pallet are supported by the carrier  158  immediately above the pallet hoist frame  74 . Once the pallet in the main hoist  26  is fully loaded, the carriage  150  is driven on the rails  146  into the discharge position such that the carriage  150  is then located over the pallet hoist frame  74  and the carrier is introduced into the upper region of the main hoist shaft  194 . When the top frame handler  42  is in the discharge position, the clamp actuator assembly  166  of the top frame handler  42  releases the clamps  162  and the top frame carried by the carrier  158  drops onto the upper surface of the uppermost layer of containers in the main hoist  26 . 
     At the same time, the pallet lift subassemblies  210  in the main hoist  26  remove the pallet from the pallet supports  170  on the carrier  158 . This is accomplished by extension of the pallet lift subassemblies from the retracted position to an extended position. More particularly, the respective tip cylinders  122  move the pallet lift subassembly frames  214  inwardly so that the “L” brackets  230  engage opposite sides and the undersurface of the pallet on the carrier  158 . The lift cylinder  234  is then extended to lift the pallet upward toward the lower square assembly  208 . As mentioned above, this raising of the pallet on the “L” brackets tends to square the pallet as it is lifted. 
     Once lifted to the uppermost extent of the pallet lift subassembly, a pallet is held in position while the chain drive belts  102  index a pair of flight bars  198  into position below the pallet. The pallet lift subassemblies  210  then retract so that the arms  226  move back into telescoped relation with the frame  214  and the tip cylinders  222  retract to pull the frame  214  into planar relation with the main hoist frame  190 . 
     Once the pallet lift subassemblies  210  are retracted, the main hoist shaft  194  is substantially cleared so that the flight bars can index downwardly. 
     Upon removal of the pallet from the carrier  158 , the carriage  150  retracts along the rails  146  into its initialized position. While the main hoist  26  and sweep assembly  22  cycle to load a pallet with layers of containers, the top frame handler assembly  42  and pallet hoist  34  operate in the above described manner. The pallet hoist operates so that the pallet lift assemblies  82  raise a pallet from a lower region of the pallet hoist frame  74  upward into a position over the pallet hoist frame  74 . The top frame lift assembly  134  indexes upwardly so that a top frame is situated between the clamps  162  on the carrier  158 . The top frame is then engaged by the clamps  162  and the carrier  150  advances such that the carrier is located below the pallet supported on the fingers  110  of the pallet lift assemblies  82 . Once the carrier  158  is located in this staging position, the fingers  110  on the pallet lift assemblies  82  retract and the pallet drops onto the pallet supports  170 . The palletizer assembly  10  is thus returned to the assumed initial position. 
     Various features of the invention are set forth in the following claims.