Abstract:
A material handling apparatus includes a robotic arm having a clamshell gripping mechanism depending therefrom adapted to selectively engage opposite sides of a packaging container. A fork-type loader also depends from the robotic arm. The fork-type loader is adapted to selectively support a bottom portion of the packaging container. The clamshell gripping mechanism and the fork-type loader can be used independently or in a cooperating manner to support and move the packaging container from a container to a pallet.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates in general to a pick and place robotic material handling unit for picking packages from a conveyor and dropping or placing the packages on a pallet, and more specifically, to a fork/clamshell material handling unit for palletizing bundles and containers from a conveyor.  
         [0002]     Robotic systems for unloading of various types of packages from a conveyor line typically utilize either a clamshell gripper or a fork-type support member. A clamshell gripper is a compression type gripper where force is applied to two opposite sides of a container type package to secure the container during an unloading or loading process. Clamshell grippers do not support containers from the bottom and, therefore, typically require a high amount of pressure on the sides of the container to overcome a lack of support on the bottom side of the container. Damage can occur to products packaged within the container due to the forces exerted on the sides of the container especially in cases where soft containers (e.g. cardboard) or heat-shrunk bundles are being moved.  
         [0003]     A fork-type support member typically picks up packages from the bottom similar to a spatula, supporting the package only from the bottom thereof with either one or an opposed pair of forks. The fork-type support member is commonly used with roller conveyor systems. The forks of the fork-type support member protrude into spaces between the rollers on a typical accumulation roller conveyor to engage and pickup the package from the bottom. The fork-type support member may include a top bar or pad to apply top pressure to secure the package to avoid tipping of the package during motion of the robotic system which is especially important when moving open top containers.  
         [0004]     Fork-type support members have issues with meeting high production rates of bulk material due to slow actuation times of the mechanical linkages. Linear motion is commonly used as a maneuver in driving the forks under the package. Typical fork-type support members require that fork lengths cover nearly 80% of the package footprint to properly support the package during the unloading and loading process. Due to the nature, length, and necessary approach positions of using linear forks for loading packages, actual loading times can take up to two seconds. Furthermore, unloading placement times can be in excess of one second due to the time needed for the linear forks to clear the bottom of the package. Additionally, because one set of grippers of a set length is not flexible to handle a wide range of package sizes, it is difficult to offer flexibility that a customer may desire in a material handling apparatus.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention has the advantage of using a fork-type support member and a clam-shell gripping mechanism in an independent or a cooperating manner to efficiently and reliably unload packages from a conveyor system and place the packages on a pallet or the like.  
         [0006]     In one aspect of the apparatus according to the present invention, a material handling apparatus includes a robotic arm adapted for vertical and horizontal movement. A clamshell gripping mechanism depending from the robotic arm is adapted to selectively engage the sides of a package. A fork-type loader also depends from the robotic arm. The fork-type loader is adapted to selectively support the package from one side of the bottom thereof. The clamshell gripping mechanism and the fork-type loader can be used in either an independent or a cooperating manner to support and move the package.  
         [0007]     A material handling apparatus according to the present invention for moving packages between a conveyor and a destination location includes a robotic arm having a free end, a clamshell gripper means pivotally attached to the free end of the robotic arm and extending on opposite sides of a longitudinal axis thereof, and a first moving means attached to the free end of the robotic arm and to the clamshell gripper means for moving the clamshell gripper means between a clamped position and an unclamped position. A fork-type loader is attached to the free end of the robotic arm and is positioned adjacent one side of the clamshell gripper means. A second moving means is attached to the free end of the robotic arm and to the fork-type loader for moving the fork-type loader between a pick position and an open position.  
         [0008]     A control means is connected to the first and second moving means for selectively operating the clamshell gripper means and the fork-type loader in independent and cooperative modes whereby the clamshell gripper means engages opposite sides of a package in the clamped position and the fork-type loader supports a bottom of the package in the pick position. An adjustable “hard stop” and/or a “soft stop” can be provided to selectively limit the swing of the clamshell gripper means and the fork-type loader when desirable. The adjustable stop also can be applied to a case/bag gripper unit having opposed fork-type support members. An upper support pad and associated third moving means are attached to the free end of the robotic arm and the control means is connected to the third moving means for engaging the upper support pad with a top of the package. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a side elevation view of a robotic material handling unit in accordance with the present invention for the handling of packages from a conveyor system;  
         [0010]      FIG. 2  is a front elevation view of the fork/clamshell unit shown in  FIG. 1  in a pickup ready position;  
         [0011]      FIG. 3  is a view similar to  FIG. 2  with the fork/clamshell unit in an unload ready position;  
         [0012]      FIG. 4  is a block diagram of the control for the robotic material handling unit shown in  FIGS. 1-3 ;  
         [0013]      FIG. 5  is a flowchart of a method in accordance with the present invention for operating the robotic material handling unit shown in  FIGS. 1-4  to unload packages from a conveyor system;  
         [0014]      FIG. 6  is a block diagram of an adjustable stop used with the fork/clamshell unit according to the present invention; and  
         [0015]      FIG. 7  is a front elevation view of a fork-type gripper unit showing the use of the adjustable stop. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0016]     Referring now to the drawings, and particularly to  FIG. 1 , there is shown in side elevation a system according to the present invention for material handling a package  18 , such as a container, from a conveyor system. Although a “hard” sided container is shown in the drawings, the package  18  can be “soft” sided such as a plurality of bags wrapped in plastic shrink-wrap. A conveyor  16  comprises a plurality of plurality of spaced-apart (spaces  21 ) transverse rollers  22  and extends longitudinally for transporting a plurality of packages  18  (only one is shown) from another location to a robotic material handling unit  10 . The conveyor  16  may be motorized  23 , or alternatively, the conveyor system may be a free-spinning sloped roller conveyor where the packages  18  are gravitationally transported to an unloading station.  
         [0017]     The robotic material handling unit  10  includes a robotic arm  11 , an overhead base unit  12 , and a fork/clamshell unit  14 . The robotic arm  11  can be a commercially available material handling robot such as the “M series” manufactured by Fanuc Robotics America, Inc. of Rochester Hills, Mich. The overhead base unit  12  depends from a free end of the robotic arm  11  and mounts the downwardly extending fork/clamshell unit  14 . The robotic arm  11  connects to a controller  13  for controlling the movements of the arm  11  and the material handling operations of the fork/clamshell unit  14 . The unit  14  extends about a generally horizontal longitudinal axis L parallel to a path of travel of the packages  18  (from right to left in  FIG. 1 ) on the conveyor  16 .  
         [0018]      FIG. 2  shows the fork/clamshell unit  14  in more detail. A fork-type loader  15  depends from an underside of the base unit  12  at one side of a path of travel of the package  18 . A fork-type support member  20  of the fork-type loader  15  is coupled to a spaced pair of arms  19  that move in an arc-like direction (arrow A) between an open position (counterclockwise) and a pick position (clockwise). In the preferred embodiment, the arms  19  are generally S-shaped. Alternatively, the arms  19  may be of any suitable shape. A first or upper end of each arm  19  is coupled to a first end of a first pneumatic cylinder  30  by a first coupling member  48 . The first coupling member  48  includes a pin that allows pivotal movement between the first pneumatic cylinder  30  and the arms  19 . An opposite end of the first pneumatic cylinder  30  is securely fastened to a pneumatic cylinder support member  46  to stabilize the first pneumatic cylinder  30  during operation.  
         [0019]     The arms  19  are pivotably secured at an intermediate point to a first vertical support member  40  by a first pivoting member  38 . The support member  40  is attached to and extends downwardly from the base unit  12 . The first pivoting member  38  allows the arms  19  to be pivotably driven by the first pneumatic cylinder  30  between the open and pick positions. The fork-type support member  20  is coupled to the lower ends of the arms  19  which all are connected together for simultaneous movement.  
         [0020]     In the preferred embodiment, the fork-type support member  20  comprises a plurality of L-shaped forks (see  FIG. 2 ). The L-shaped forks are preferably metal and have a metallic chrome finish. Alternatively, metal composites or alloys as well as other as other various finishes may be utilized. The L-shaped forks are spaced a predetermined distance apart from one another corresponding to the spacing  21  of the rollers  22 . When in the pick position ( FIG. 3 ) the fork-type support member  20  engages a bottom surface of the package  18 . Each individual fork extends into a corresponding one of the plurality of spaces  21  (shown in  FIG. 1 ). This allows the L-shaped forks  20  to engage and lift the package  18  from the bottom without interference from the plurality of rollers  22 .  
         [0021]     A clamshell gripper mechanism  17  of the fork/clamshell unit  14  comprises a first side support mechanical linkage  24  and a second side support mechanical linkage  25  disposed on opposite sides of the longitudinal axis L and the travel path for the package  18 . Each of the linkages  24  and  25  has a pair of downwardly extending arms. As shown in  FIG. 1 , the arms of the first linkage  24  are positioned between the arms  19 . A first or upper end of the first side support mechanical linkage  24  is coupled to a first end of a second pneumatic cylinder  31  ( FIG. 4 ) similar to the first cylinder  30  by a second coupling member similar to the first coupling member  48 . The second cylinder  31  and second coupling member are hidden behind the first cylinder  19  and the first coupling member  48  in  FIG. 2 . An opposite end of the second pneumatic cylinder  31  is securely fastened to the pneumatic cylinder support member  46 . The first side support mechanical linkage  24  is pivotably secured to the first vertical support member  40  by the first pivoting member  38 . The first pivoting member  38 , disposed between the ends of each of the arms of the first side support linkage  24 , allows the second pneumatic cylinder  31  to pivotably drive the arms of the linkage  24  between the open or unclamped position and the pick or clamped position along an arc B.  
         [0022]     Likewise, a first or upper end of the second side support mechanical linkage  25  is coupled to a first end of a third pneumatic cylinder  32  by a third coupling member  49 . The second linkage  25  is pivotably secured to a second vertical support member  41  by a second pivoting member  39  between the opposite ends of a pair of arms of the second linkage  25 . The second pivoting member  39  allows the third pneumatic cylinder  32  to pivotably drive the second linkage  25  between the unclamped and clamped positions along an arc C.  
         [0023]     A lower end of each of the arms of the first linkage  24  is securely fastened to a first side support plate  26 . Likewise, a lower end of each of the arms of the second linkage  25  is securely fastened to a second side support plate  27 . The side support plates  26  and  27  are elongated structural members extending a predetermined length and width to engage opposite sides of the package  18 . In the preferred embodiment the side support plates  26  and  27  are rectangular. The bottom portions of the side support plates  26  and  27  each include a plurality of forks  36  and  37  respectively. The forks  36  and  37  extend generally vertically and are spaced apart. As the side support plates  26  and  27  engage the respective sides of the package  18 , each individual fork of the side support plates  26  and  27  displaces within a corresponding one of the spaces  21  (shown in  FIG. 1 ) of the conveyor  16  without interference from the plurality of rollers  22 . This allows for increased speed when clamping the package  18  since the plurality of forks  36  and  37 , and the spaces therebetween, eliminate a potential interference condition with the plurality of rollers  22 . Otherwise tight tolerances and slow maneuvering would be required for transitioning the side support plates against the sides of the package  18  to fully engage the package  18  directly above the plurality of rollers  22 . As the side support plates  26  and  27  transition between the unclamped and clamped position, the side support plates  26  and  27  contact opposite sides of the package  18  and apply a low predetermined compression force to the package  18 . The low predetermined compression force stabilizes the package  18  while the package  18  is being unloaded from the conveyor  16  and transferred to a desired location such as a shipping pallet (not shown).  
         [0024]     The stabilization attained by utilizing the first and second side support mechanical linkages  24  and  25  permits less than 50% of a footprint (i.e., bottom surface) of the package  18  to be supported by the fork-type support member  20 . This allows for flexibility in handling a wide range of package sizes. With the combined use of the fork-type loader  15  and the clamshell gripper mechanism  17 , sufficient material handling support is provided so that typical heat shrink bundles can be handled reliably and efficiently even when the heat shrink is loosely wrapped.  
         [0025]     Furthermore, the present invention transitions the fork-type loader  15  between the open and pick positions using a swing out arc-like motion as opposed to a drop down and linear slide motion. The actuation time to transition between the unloaded and loaded positions is less than 0.25 seconds. This fast actuation time allows for containers or bundles to be loaded and unloaded at a much higher rate than conventional pick and place robotic units, and as a result, higher production rates are achieved.  
         [0026]     Additionally, an upper support pad  35  may be utilized to provide a downward force to further secure the package  18  during motion of the robotic material handling unit  10 . A fourth pneumatic cylinder  34  is attached to the base unit  12  and is used to drive the upper support pad  35  against a top surface of the package  18 . The upper support pad  35  is positioned vertically inline with a portion of the fork-type support member  20  in the pick position ( FIG. 3 ) so that a compression force may be applied to a top and bottom portion of the package  18  that is disposed between the upper support pad  35  and the fork-type support member  20 . The cylinder  34  is controlled by the controller  13  to raise the pad  35  to a disengaged position ( FIG. 2 ) and lower the pad to an engaged position ( FIG. 3 ). The support member  20  and the pad  35  cooperate to reduce the amount of pressure required to be applied by the plates  26  and  27  in order to stabilize the package  18 .  
         [0027]      FIG. 3  illustrates the robotic material handling unit  10  in the clamped pick position. The second pneumatic cylinder  31  (not shown) and the third pneumatic cylinder  32  are actuated to drive the first and second side support linkages  24  and  25  to the clamped position. The first and second side support plates  26  and  27  are clamped against opposing sides of the package  18 . At approximately the same time, the arms  19  are driven to the loaded position by the first pneumatic cylinder  30 . The fork-type support member  20  engages a bottom surface of the package  18 . The upper support pad  35  is driven into contact with the upper surface of the package  18  by the fourth cylinder  34  to further stabilize the package  18 . The package is then picked up from the conveyor  16  and positioned over a drop location by movement of the robotic arm  11 .  
         [0028]     At a designated placement location the picking process is reversed to drop the package  18  onto, for example, a pallet. The articulating arms  19  are driven to the open position by the first pneumatic cylinder  30 . The fork-type support member  20  is retracted in the arc-like motion A from the bottom surface of the package  18 . The first side support mechanical linkage  24  is opened slightly to relieve pressure from the sides of the package  18 . The upper support pad  35  is then retracted. The material handling unit is upwardly displaced by the robotic arm  11  to clear the package  18 . Both side support linkages  24  and  25  are then fully retracted to the unclamped positions as the robotic material handling unit  10  is returned to the position over the conveyor  16  shown in  FIGS. 1 and 2  to pick the next package.  
         [0029]      FIG. 4  is a block diagram showing the control system for the robotic material-handing unit  10 . The controller  13  is connected to the robotic arm  11  to selectively control the movement of the base unit  12  and attached material handling unit  14  between the conveyor  16  and a destination such as a pallet (not shown). The controller  13  is connected to each of the first  30 , second  31 , third  32  and fourth  34  pneumatic cylinders to actuate the fork-type loader  15 , the first linkage  24 , the second linkage  25  and the pad  35  respectively.  
         [0030]     In a second preferred embodiment of the apparatus and method of operation, a servo drive unit  42  ( FIG. 4 ) connected to the controller  13  can be utilized if packages of different known sizes are to be unloaded from the conveyor  16 . Typically, clamshell gripper  17  is configured to clamp to a predetermined position to pick up uniform packages of the same dimensions. If known different width packages are transported along the conveyor  16 , the robotic material handling unit would need to adjust the spacing between the side support plates  26  and  27  to accommodate the width of each package. If the width of each package is known as it transitions to the pick position along the conveyor  16 , the servo drive unit  42  could adjust the first side support linkage  24  and first side support plate  26  accordingly to accommodate each known different width package.  
         [0031]     To adjust the first side support mechanical linkage  24  laterally, the servo drive unit  42  is coupled to a linear guide mount (not shown). The first side support mechanical linkage  24  is also coupled to the linear guide mount. As the servo drive unit  42  drives the linear guide mount laterally (transverse to the longitudinal axis L), the first linkage  24  is also driven laterally either toward or away from the package  18  depending upon the package width relative to the width of the previous package. To pick a package, both of the side support mechanical linkages  24  and  25  and the fork-style support member  20  transition to the clamping and pick positions. As the first side support mechanical linkage  24  moves in an arc-like manner to the clamp position, the servo drive unit  42  simultaneously moves the first side support linkage  24  laterally to adjust to the known package width. A soft float may further be utilized with the servo drive  42 . A soft float is incorporated into the software of the controller  13  of the robotic material handling unit  10 . As the first side support mechanical linkage  24  transitions to the clamped position, the controller  13  senses the pressure exerted on the side of the package  18 . To maintain a small amount of force on the sides of the package  18  so as only to stabilize the package  18 , the controller  13  adjusts the servo drive unit  42  accordingly to apply a predetermined amount of compression force to the package  18  as required to maintain stabilization.  
         [0032]     The servo drive unit  42  may further be used in unclamping the package  18  by laterally relieving pressure from the side of the package  18  engaged against the first side support mechanical linkage  24 . After the fork-style loader  20  is retracted from the pick position toward the open position, the servo drive unit  42  laterally drives the first side support mechanical linkage  24  via the linear guide mount partially away from the package  18  to relieve the compression force. This allows the package  18  to drop vertically to the destination location without any tilting of the package. Both side support mechanical linkages  24  and  25  thereafter are fully retracted to the open positions.  
         [0033]      FIG. 5  illustrates a method for unloading a package from a conveyor system. In a step  50 , the robotic material handling unit  10  is vertically positioned over the conveyor system. The conveyor system transports a plurality of packages  18  in sequence to an unloading station where the robotic material handling unit  10  is disposed vertically above the conveyor  16 . In a step  52 , the second  31  and third  32  pneumatic cylinders are actuated to drive the first  24  and second  25  support member linkages in an arc-like motion to the clamped position. As the support member linkages  24  and  25  are driven to the clamped position, the first  26  and second  27  side support plates will apply the low predetermined compression force to the opposing sides of the package  18 . Simultaneously, the first pneumatic cylinder  30  drives the arms  19  into the pick position. The fork-type support member  15  will move in the arc-like motion A from the open position to the pick position and engage against a bottom surface of the package  18 . Each of the L-shaped forks of the support member  20  will transition into the corresponding space  21  between the rollers  22  to engage the bottom surface of the package  18 . In a step  54 , the top support pad  35  is lowered to engage against a top surface of the package  18  to further stabilize the package. In a step  56 , the robotic material handling unit  10  is vertically raised to pick the package  18  from the conveyor  16 . In a step  58 , the robotic material handling unit  10  transitions to a dedicated location for placement of the package  18 . In a step  60 , the first pneumatic cylinder  30  is actuated to drive the fork-type support member  15  to the open position. The fork-type support member  15  will be disengaged from the bottom surface of the package  18  with the arc-like motion A to the open position. In a step  62 , the second pneumatic cylinder  31  is actuated to retract the first side support member  24  a predetermined distance from the side of the package  18  so that the first side support plate  26  slightly relieves pressure on the side of the package allowing the package to drop. In a step  64 , the robotic material handling unit  10  is displaced upwardly to clear the package  18 . In a step  66 , the robotic material handling unit  10  is returned to the package pickup location over the conveyor  16  package picking station. During the transition from the drop or unloading location to the package pickup location, the side support members  26  and  27  are returned to the unclamped positions.  
         [0034]     In some applications, it is desirable to limit the arcuate travel of the arm  19  and/or the linkages  24  and  25  to less than full travel. For example, two of the robotic material handing units  10  can be positioned side-by-side to unload two adjacent conveyors. By limiting the outward swing of the arm  19  and/or the linkages  24  and  25  to, for example, approximately 15°, the distance between the conveyors and the units  10  can be minimized for space savings. However, this swing limitation may cause interference with previously stacked packages when attempting to stack another package.  
         [0035]     In  FIG. 6 , there is shown an adjustable stop system for use with the robotic material handing units  10 . The controller  13  is connected to control a linkage actuator  70  which can be any of the pneumatic cylinders  30 ,  31  and  32 . The linkage actuator  70  is connected a linkage  72  which can be the one of the arm  19  and the linkages  24  and  25  corresponding to each of the pneumatic cylinders  30 ,  31  and  32 . A linkage position sensor  74  is connected to the controller  13  for sensing a position of the linkage  72  and providing that position data to the controller. In this manner, the controller  13  can control the linkage actuator  70  to stop the swing of the linkage  72  at any predetermined “stop” position including different positions for picking up and dropping the package. As an alternative to or combined with the sensor  74 , the linkage actuator  70  can provide position feedback to the controller  13 . This method of control provides an adjustable “soft stop” since no mechanical stop engages the linkage  72 .  
         [0036]     The controller  13  can be connected to control a stop actuator  76  which is connected a mechanical stop  78  for engaging one of the one of the arm  19  and the linkages  24  and  25 . A stop position sensor  80  is connected to the controller  13  for sensing a position of the stop  78  and providing that position data to the controller. In this manner, the controller  13  can control the stop actuator  76  to position the stop  78  at any predetermined “stop” position including different positions for picking up and dropping the package. As an alternative to or combined with the sensor  80 , the stop actuator  76  can provide position feedback to the controller  13 . This method of control provides a “hard stop” since there is a mechanical stop engaging the linkage  72 . The linkage position sensor  74  can be used to confirm the position of the linkage  72  to the controller  13 .  
         [0037]     The adjustable stop also can be utilized with a robotic material handling unit  90  of the conventional case/bag gripper type. The unit  90  includes a robotic arm  91 , an overhead base unit  92 , and a case/bag gripper unit  94 . The robotic arm  91  can be like the arm  11  shown in  FIGS. 1-4 . The overhead base unit  92  depends from a free end of the robotic arm  91  and mounts the downwardly extending case/bag gripper unit  94 . The robotic arm  91  connects to a controller  93 , similar to the controller  13  of  FIGS. 1 and 4 , for controlling the movements of the arm  91  and the material handling operations of the case/bag gripper unit  94 .  
         [0038]     The unit  94  includes a pair of pivot points  97   a  and  97   b  at opposite sides of a path of travel of a package  98  such as a case or a bag. Each arm of a pair of associated arms  99   a ,  99   b  has an upper end rotatably attached to the respective one of the pivot points  97   a ,  97   b  for movement in an arc-like direction (arrows D and E respectively) between an open position (counterclockwise) and a pick position (clockwise). An associated fork-type support member  100   a ,  100   b  is coupled to lower ends of the arms  99   a ,  99   b  respectively. In the preferred embodiment, the fork-type support member  100   a ,  100   b  comprises a plurality of L-shaped forks (see member  20  in  FIG. 2 ).  
         [0039]     The arms  99   a ,  99   b  are coupled to the actuator  96  which preferably can be a pneumatic cylinder. Under the control of the controller  93 , the arms can pivot to a maximum open position of approximately 100° as illustrated by the arm  99   b  in  FIG. 7  to minimize interference with packages  98  already present when palletizing. However, one or both of the arms can be limited by the stop  78  ( FIG. 6 ) to any selected limited open position. For example, the arm  99   a  is shown in a stop-limited open position at approximately 15° from vertical.  
         [0040]     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.