Abstract:
A device for mechanically picking and palletizing rectangular objects of various sizes for attachment to a robotic arm. The device includes a pair of rails having a plurality of longitudinally spaced, elongated L-shaped grips extending there through. The distance between the respective rails can be adjusted to accommodate various width containers. The L-shaped grips are capable of pivotal rotation such that their grip ends rotate under the object for picking and palletizing. A pair of pallet hooks having suction cups attached thereto is also provided on the device.

Description:
This is a divisional of application(s) Ser. No. 09/173,010 filed on Oct. 15, 1998 now U.S. Pat. No. 6,082,080. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of grasping, transporting and palletizing objects such containers for packaged goods and specifically to a device that is capable of loading and palletizing empty, partially filled or completely filled open-topped or unsealed containers. Open-topped or unsealed containers, and especially those that are empty or partially filled, are difficult to pick up, hold and transport, due to their relatively thin flexible walls and lack of structural integrity. 
     At the end of a conveyor line, manufactured products often arrive packaged in containers. While the container serves the primary purpose of protecting the product during shipping, the container may also serve the function of identifying the product. On more elaborately printed containers, there may appear indicia advertising the product, its benefits or its application. This latter type of packaging design is commonly found on products sold at the retail store level. Therefore the container must be aesthetically attractive and visually appealing. Accordingly, it is of utmost importance that each container, and especially its product indicia, not be damaged during removal from the assembly line and palletizing for shipment. 
     In most instances the task of removing the container from the conveyor line and palletizing the containers for shipping has been carried out manually. While having some advantages, such as insuring that the container is not damaged, manually handling containers is relatively a strenuous and tedious task. The continued lifting and moving of multiple containers can cause workers to strain and injure their backs. Further, depending upon the output speed and configuration of the conveyor line, many workers may be required to remove and properly palletize the containers. In an effort to reduce workforce size and injury costs, there has been a significant move toward automating this process by utilizing robots. As is known in the art, industrial robots may be fitted with various grasping devices, known as “end-effectors”, for picking up and moving objects, including containers. 
     Most product containers are rectangular in shape and include four side walls, a bottom wall, and a top wall. Provided that the container has been properly sealed, the container is likely to have sufficient structural integrity allowing it to be grasped in a number of manners from the assembly line by a robotic end-effector and transported to a pallet. For example, the container may be removed from the assembly line by one or more suction cups that temporarily adhere to the top wall of the container. Alternatively, a pair of arms may apply a small amount of pressure to opposing side walls of the container such that the container may be lifted and transported. 
     However, if the container to be transported from the assembly line to the pallet lacks a top wall or if the container is not sealed, its structural integrity is greatly diminished. Suction cups cannot be attached to a container lacking a top wall. If a pair of arms were employed to apply a sufficient amount of pressure against opposing side walls of an open-topped or unsealed container, the container would most likely collapse or crush before the exerted force was great enough to lift and transport the container. 
     Another factor that controls the choice of device employed for palletizing containers is the consistency of container size. If each container coming off the conveyor line has the same physical size, the robotic end-effector can be designed specifically for that specific container size. However, if the container size varies, the end-effector must be capable of adjusting its grasping mechanism to accommodate the various container sizes. 
     A third factor that often dictates the means of removing containers from conveyor lines and transporting them to pallets is the amount of space available at the end of the conveyor line for this operation. Often times there is very little space allocated at the end of the conveyor line for palletizing containers. If a robotic end-effector is to be utilized, it must be sufficiently compact to allow for installation and operation within the allotted space available for such a device. 
     Accordingly, there is a need for a device that may be used for the removal and transportation of open-topped or unsealed containers. There is also a need for a device capable of easily grasping and palletizing containers of various sizes on the same pallet. More specifically, there is a need for a device that is compact enough to be positionable and operationable at the end of an conveyor line and that can pick up open-topped or unsealed containers of various sizes and transport those containers to pallets. Furthermore, the device must be able to properly palletize the containers to insure stability of the pallet during shipment. 
     SUMMARY OF THE INVENTION 
     According to the present invention, the foregoing and other objects and advantages are attained by providing an apparatus which may be used in a confined environment to pickup and transport open-topped or unsealed containers of various sizes from a pick up position such as the packaging end of a conveyor line. The containers can then be palletized on a pallet or placed into a case. The apparatus may also be used to pick open-topped or unsealed containers from a pallet and transport each container onto another pallet, into a case or onto a conveyor line. 
     A further object of the present invention is to provide an end-effector for an industrial robot, the end-effector being capable of picking up a container from a pick up position and transporting the container to a pallet for shipping or a case for packaging and shipping. The end-effector is also capable of picking up a container from a pallet and transporting the container to an other location, such as a case or conveyor-line. 
     In accordance with another aspect of the invention, the device can be utilized in a relatively confined area as it requires a minimum amount of space around the periphery of the container for grasping and palletizing the container. 
     A further advantage of the invention is to provide an end-effector for use with a robot that is easily adjustable to grasp containers of various sizes. 
     A further advantage of the invention is to provide a robotic end-effector that is capable of grasping more than one container from a pick up position and palletizing each respective container in a separate location. 
     These and other objects and advantages are achieved in an end-effector including a support frame suspended from a centrally located stanchion, which in turn, may depend from the distal end of a 4- or 6-position robot arm. The support frame includes a pair of linear bearings supporting a pair of parallel rails arranged for relative lateral movement on said bearings to accommodate various width containers. A plurality of longitudinally spaced, elongated L-shaped fingers extend through longitudinally spaced apertures in the respective rails, and are arranged for pivotal rotation to a desired position by means of a gear secured to the top end portion of each finger extending through the respective apertures. Each gear preferably abuts an adjacent gear and is in gear meshing contact therewith for simultaneous rotative movement of the respective fingers. 
     The carton-supporting arms of the series of adjacent L-shaped fingers normally face one another and lie in the same plane. The fingers are moved inwardly for lateral pickup and support of a container resting thereon. The arms face one another to permit simultaneous rotation inwardly and outwardly, since the abutting gears will be rotated in opposite directions. The gears may be of conventional toothed configuration. Pre-selected gears may have portions cutaway to provide a means of zoning of selected groups of fingers. 
     Pallet hooks are provided on the rails for pickup of supporting pallets from a pallet supply and delivery of pallets to the palletizing area near the pick up position. Vacuum cups are provided at one end of the rails for pickup and delivery of flat sheets to be placed on a supporting pallet or between container layers. Robotic controls also permit the entire frame to be rotated for placement of alternate rows of stacked containers for greater stacking stability of the containers. 
     In a preferred embodiment, the invention may be described as an apparatus for grasping, transporting and palletizing a container having opposed side walls and opposed bottom edges, the apparatus having a pair of parallel rails spaced at a predetermined distance from one another and laterally movable with respect to one another; a rotatable link positioned between said parallel rails; first and second tie rods, each said tie rod pivotally secured to one rail and to the rotatable link; a plurality of longitudinally spaced apertures being formed along each rail; a plurality of L-shaped fingers, each finger being received in an aperture; and each finger being rotatably movable and coupled to at least one adjacent rotating finger along each rail. 
     In another preferred embodiment, the present invention is a robotic end-effector for an industrial robot, said robotic end-effector having a frame capable of being coupled to the robot, the frame including at least one linear bearing attached thereto; a pair of rails arranged for respective lateral movement on said linear bearing; a plurality of longitudinally spaced apertures formed in each rail; a plurality of longitudinally spaced, elongated L-shaped rotating fingers extending through said apertures, each rotating finger having a top portion; and a gear being attached to each rotating finger top portion, said gears abutting one another for simultaneous rotative movement of the rotating fingers along each rail. In a highly preferred embodiment the end-effector includes a zoning mechanism for interrupting the transportation of a group of containers supported by the rotating fingers wherein at least one of said gears has an interrupted periphery, is in non-meshing contact with an adjacent gear or is removed. 
     In addition, the invention may be described as a system for gripping, transferring and palletizing containers lacking structural integrity from a pick up position, the system comprising a supply of pallets; an industrial robot with an end-effector, said end-effector having a pair of parallel rails arranged for lateral movement with respect to one another, means for providing lateral movement of said rails, a plurality of L-shaped rotating finger extending longitudinally from said rails, means for providing rotational motion of said rotating fingers, a pair of pallet hooks pivotally extendable from said rails, and means for providing pivotal motion of said pallet hooks; and a palletizing station adjacent said pick up position. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective, environmental view depicting an industrial robot arm, the end-effector of the present invention transporting an open-topped container and a plurality of palletized open-topped containers. 
     FIG. 2 is a perspective view of the present invention. 
     FIG. 3 is a cross-sectional plan view of the present invention taken on line  3 — 3  of FIG.  2 . 
     FIG. 4 is a front plan view of the present invention showing both pallet hooks extended and gripping a pallet. 
     FIG. 5 is a partial front plan view, of the present invention, rotated 90° with respect to the view of FIG. 5 showing the pallet hook extended and the suction cups gripping a cardboard sheet. 
     FIG. 6 is a cross-sectional end view of the present invention taken on line  6 — 6  of FIG.  3 . 
     FIG. 7 is a cross-sectional bottom plan view of the present invention taken on line  7 — 7  of FIG.  6 . 
     FIG. 8 is a partial top plan view of the rail, a plurality of gears and the gear rotating mechanism in its retracted position. 
     FIG. 9 is a partial perspective view of the L-shaped grips, the rail and the gears depicting the orientation of the gripping fingers in the engaged, supporting position. 
     FIG. 10 is a partial top plan view of the rail, plurality of gears and the gear rotating mechanism in its engaged position. 
     FIG. 11 is a partial perspective view of the L-shaped grips, the rail and the gears depicting the orientation of the gripping fingers in the retracted, non-engaging position. 
     FIG. 12 is a partial perspective view of the rail, plurality of gears and rotating fingers where a portion has been removed from one gear. 
     FIG. 13 is a top plan view taken on line  13 — 13  of FIG.  12 . 
     FIG. 14 is a partial perspective view of the rail, plurality of gears and rotating fingers. 
     FIG. 15 is a top plan view taken on line  15 — 15  of FIG.  14 . 
     FIG. 16 is top plan view of an alternate embodiment for engaging and disengaging the L-shaped rotating fingers. 
     FIG. 17 is a cross-sectional plan view of an alternate embodiment of the present invention taken on line  3 — 3  of FIG.  2 . 
     FIG. 18 is a top plan view of an alternate method of zoning. 
     FIG. 19 is a top plan view of another alternate method of zoning. 
    
    
     DETAILED DESCRIPTION 
     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
     The present invention comprises an improved end-effector apparatus  10  for grasping, transporting and palletizing open-topped or unsealed containers. In brief, the apparatus includes a stanchion  30 , a supporting base plate  40 , a pair of bearing rails  50 , a pair of linear bearing assemblies  60 , a linkage assembly  70  for maintaining a synchronized relationship of the bearing rails  50 , a rail width adjusting mechanism  90 , a plurality of L-shaped rotating fingers  100 , a finger rotating mechanism  140  and a pair of pallet hooks  170 . 
     With particular reference to FIG. 1, the environment of the present invention is shown with the end-effector apparatus  10  for grasping, transporting and palletizing containers  20  and the industrial robot  12  to which it is attached being shown in phantom. A container  20 , having an open top  22 , is shown grasped between the L-shaped rotating fingers  100  of the apparatus  10 . Adjacent the robot  12  and the apparatus  10  is a pallet  24  containing a plurality of containers  20 . The containers  20  are palletized in a predetermined order on the pallet  24 . As can be seen in FIG. 1, the palletized containers  20  may be of different sizes. As will be discussed in detail below, the ability to grasp and stack containers of various sizes is a benefit of the present invention. To better stabilize the palletized load  26 , and to prevent any damage to the containers  20 , a sheet of cardboard  28  is routinely inserted between each layer of containers  20 . 
     The present invention is shown in greater detail in the view of FIG. 2. A conventional 4- or 6-position robot arm  13  of the industrial robot  12  (shown in phantom) is connected to the stanchion  30  at its proximate end  32 . The distal end  34  of the stanchion  30  is connected to the supporting base plate  40 . While both the proximate and distal end connections are shown to be achieved by utilizing a flange  36  and tube  38 , it is to be understood that any conventional way of connecting the industrial robot arm to the base plate  40  could be utilized. 
     Supporting plate  40  has an upper surface  42  (see FIG. 6) and a lower surface  44  (see FIG.  7 ). Referring now to FIG. 7, mounted to the lower surface  44  of base plate  40  is a plurality of linear bearing assemblies  60 . Linear bearings are known in the art. They typically include a bearing housing  62  and a bearing rail or shaft  66 . The bearing housings  62  are mounted to the lower surface  44  of base plate  40 . Ends  64  of bearing shafts  66  are each attached to one of the bearing rails  50 . The bearing shafts  66  passes through bearing rod openings  52  formed in the pair of bearing rails  50 . Four linear bearing assemblies  60  are utilized in the preferred embodiment. One pair has its fixed end  64  attached to the first bearing rail  50  and its bearing shaft  66  passes through apertures  52  formed in the opposite bearing rail  50 . The second pair is arranged in the reverse order such that its fixed ends  64  are attached to the bearing rail  50  having openings or apertures  50  for receiving the first pair of linear bearings shafts  66 . Accordingly, each bearing rail  50  slides in a linear fashion with respect to the base plate  40 . The aforementioned arrangement of linear bearings  60  also provides a constant parallel relationship between the bearing rails  50 . 
     As best shown in FIGS. 3,  6 , and  7 , a linkage assembly  70  is provided to maintain an equal distance between the center of the supporting plate  40  and each bearing rail  50 . The adjustment mechanism  70  comprises a shaft  72 , a center link  74  and a pair of tie rods  78 . The first end of shaft  72  is connected to base plate  40  and the opposite end is connected to the central portion of center link  74 . Center link  74  has two link ends,  76 . The pair of tie rods  78  couples each center link end  76  to one of the bearing rails  50 . Referring to FIGS. 6 and 7, it is can be seen that one end of each tie rod  78  is pivotally connected to each bearing rail  50  and the other tie rod end is pivotally connected to each center link end  76 . The length of each tie rod  78  can be adjusted in a know manner. 
     Now referring specifically to FIG. 7, as the linkage assembly  70  rotates about shaft  72 , the parallel rails  50  are each translated an equal distance on linear bearing assemblies  60 . The result is, provided the length of each link end  76  is equivalent and the length of each tie rod  78  is equivalent, bearing rails  50  equally, linearly, and parallely translate along linear bearing assemblies  60  as shown by arrows  84 . 
     Referring specifically to FIG. 6, a bearing rail width adjustment mechanism  90  is also provided. The rail adjustment mechanism provides the gripping force of the end-effector apparatus  10 . The mechanism  90  includes a pair of linear actuators  92  such as pneumatic cylinders or ball screws. Each actuator  92  has a fixed end  94  and a moving end  96 . The fixed end  94  of each actuator  92  is attached to base plate  40  by means of a bracket  46 . The fixed end of one actuator  92  is attached proximate to one corner of the base plate  40 . The fixed end of the other actuator is attached to the diagonally opposed corner. Each actuator  92  extends across the upper surface  42  of base plate  40  where its moving end  96  is coupled to bracket  54 . Each bracket  54  is attached to a respective bearing rail  50 . When the moving end  96  of each actuator  92  is extended, the distance between each bearing rail  50  is increased. When the moving end  96  of each actuator  92  is retracted, the distance between each bearing rail  50  is decreased. The actuators  92  are connected to the same fluid supply means or rotary motion means (not shown). While the preferred embodiment utilizes two actuator assemblies, it should be noted that only one actuator assembly is required. The arrangement of linear bearing assemblies  60  and linkage assembly  70  provide for a constant parallel relationship between bearing rails  50  as they perform their gripping function. 
     With reference to FIGS. 6 and 7, a plurality of openings  56  are formed perpendicular to the apertures  52  formed in the bearing rails  50  for the linear bearing rods  66 . Each opening  56  is capable of receiving a L-shaped rotating finger  100 . As shown in FIG. 6, L-shaped rotating fingers  100  have top ends  102  and lower distal ends  104  angularly formed to provide container supports  106 . A gear  120  (see FIGS. 9,  14  and  15 ) is affixed to the top end  102  of each rotating finger  100 . The portion of the finger  100  just beneath the top end  102  passes through an opening  56  formed in bearing rails  50 . Just beneath each bearing rail  50 , a collar  122  is affixed to each finger  100 . The top end of the finger  100  is thus rotationally supported within bearing rail  50 . The length of each finger  100  is greater than the height of the tallest container the present invention  10  has been designated to grasp, transport and palletize. The distal end  104  of each rotating finger  100  is bent approximately ninety degrees to form a container support  106 . 
     Referring again to FIG. 2, it can be seen that a plurality of L-shaped rotating fingers  100  and gears  120  are uniformly arranged along the length of each bearing rail  50 . A gear  120  is fixedly attached to the upper end  102  of each L-shaped rotating finger  100 . As best shown in FIG. 15, the teeth  122  of each gear  120  mesh with the adjacent gear&#39;s teeth. The uniformly spaced gears  120  are in rotational contact along the length of each bearing rail  50 . Accordingly, when one gear  120  is rotated about its aperture  56  in bearing rail  50 , all of the other contacting gears rotate an equivalent amount. 
     The mechanism  140  for rotating the meshing gears  120  is shown in FIGS. 8 and 10. Another linear actuator  142 , such as a pneumatic cylinder or ball screw, is attached at its fixed end  144  to each bearing rail  50 . The moving end  146  of the actuator  142  is attached to a connecting link  150 . End  152  of connecting link  150  is pivotally attached to the moving end  146  of actuator  142 . The opposite connecting link end  154  is fixedly attached to a L-shaped rotating finger  100  at the finger top end  102 . 
     When each actuator  142  is in its fully retracted position, as shown in FIG. 8, the container supports  106  of L-shaped rotating fingers  100  are oriented as shown in FIG.  11 . It is important to note that supports  106  do not all face the same direction but instead are arranged in an alternating fashion  108 . The reason for this is that when the rotating fingers  100  are actuated, they do not all rotate in the same direction. Instead, each finger rotates in an opposite direction as compared to its immediately adjacent fingers. Accordingly, the rotational forces of the containers supports  106  substantially cancel each other out and the rotating fingers  100  do not move the container forward or backward during their rotation. When each actuator moving end  146  extends, as shown in FIG. 10, the linear motion of the moving end  146  is translated into rotational motion of connecting link  150 . The result is the rotation of the L-shaped fingers  100  to which connecting link  150  is fixedly attached. As stated above, each L-shaped finger  100 , including the L-shaped finger to which connecting link  150  is attached, is coupled to a gear  120 . As shown by-arrows  124  in FIG. 10, the rotational motion is further imparted to each additional gear  120  that is in gear meshing contact. When the rotational motion is complete, the container supports  106  are oriented in their container supporting position  110  as shown in FIG.  9 . 
     The present invention is also provided with two pairs of pallet hooks  170  and two pairs of suction cups  190 . The pallet hooks are best shown in FIGS. 2 and 4. Each pair of hooks  170  is pivotally attached to one bearing rail  50 . The hooks are movable from a retracted position (shown in FIG. 2) to an extended position (shown in FIG.  4 ). Each hook  170  is pivoted by the mechanical combination of another linear actuator  172  and a connecting link  178 . The fixed end  174  of each actuator  172  is attached to the inside of the bearing rail  50 . The moving end  176  of each actuator  172  is pivotally attached to the first end of each connecting link  178 . The second end of each connecting link  178  is fixedly attached to each pallet hook shaft  180 . Each shaft  180  is rotatably supported by a bracket  182  attached to the underside of each bearing rail  50 . When each actuator  172  is in its fully extended position, as shown in FIG. 2, each pallet hook  170  is retracted and positioned adjacent to each bearing rail  50 . When the actuator moving end  174  is retracted, each pallet hook  170  pivots into its pallet gripping position as shown in FIG.  4 . While the preferred embodiment of the present invention  10  includes four pallet hooks  170 , it is to be understood that a fewer number could be utilized to pick up and properly position a pallet  24 . 
     A pair of suction cups  190  is attached to one pair of pallet hooks  170  as shown in FIG.  2 . The function of the suction cups  190  is to pick up and place a sheet of cardboard  28  between each layer of containers  20  in a palletized load  26 . This is accomplished when the pair of pallet hooks  170  is in its extended position as shown in FIG.  5 . 
     The present invention is utilized in the following manner. The pallet hooks  170  are extended over a stack of pallets  24  located in the vicinity of the industrial robot  12 . A single pallet is engaged by the pallet hooks (as shown in FIG. 4) and transported to the palletizing location. The pair of pallet hooks  170  including suction cups  190  are extended over a stack of cardboard  28  also located within the working area of the industrial robot  10 . A vacuum is applied to the suction cups  190  and a single sheet of cardboard  28  is removed from the stack. The sheet of cardboard  28  is placed on the pallet  24 . The industrial robot arm  12  next moves to the pick up position to pick up a container  20 . The present invention is positioned by the robot  12  directly over the container  20  at the pick up position and is next lowered so that its L-shaped rotating fingers  100  pass downward along opposite sides of the container  20 . When the container supports  106  have just cleared the lower edge of the container  20 , actuators  142  are actuated to rotate the L-shaped fingers  100  into their gripping position (as shown in FIG.  9 ). At substantially the same time, actuators  92  are retracted until the L-shaped fingers contact and place a minimal amount of pressure on opposite sides of the container  20 . 
     The container  20  is next lifted from the pick up position and transported to the pallet  24  where the industrial robot  12  places containers  20  in their proper position upon the pallet  24 . One of the many advantages of the present invention  10  is that it requires a minimal amount of clearance on the opposite gripping sides of the container  20 . Accordingly, the container  20  can be placed into a tight opening as shown in FIG.  1 . The present invention  10  may also be use to place and remove containers from cases or other enclosures where there exists a minimal amount of clearance for the end-effector apparatus. 
     When one or more layers of containers  20  have been stacked, a new sheet of cardboard  28  is retrieved and placed over the containers  20 . When the pallet  24  has been filled with the proper number of containers  20 , the palletized load  26  is removed with a forklift truck (or other suitable means) and the pallet hooks  170  are utilized to retrieve the next empty pallet  24 . 
     The end-effector  10  may be provided with a zoning mechanism for interrupting the transportation of a group of containers  20  supported by the rotating fingers  100 . Now referring to FIGS. 12 and 13, it can be seen that the rotational motion of the gears  120  can be interrupted by replacing a gear  120  with a gear  126  having a portion of its periphery removed or interrupted. In FIGS. 12 and 13, the removed section is an arcuate sectional portion. Zoning may also be achieved by positioning one gear  120  in non-meshing contact with another gear  120  (FIG.  18 ). Alternatively, zoning may be achieved by removing a gear  120  or only attaching gears  120  to selected rotating finger top portions  102 . (FIG.  19 ). In both instances, a space is created between adjacent gears  120 . The space is of sufficient size to prevent the gears  120  from meshing and thus imparting rotational motion to one another. 
     Furthermore, additional gear rotating mechanisms  140  can be added to each bearing rail  50  to create rotating finger zones. Two or more zones may be created allowing the present invention  10  to grasp two or more containers  20  simultaneously, transport those containers  20  to the pallet  24 , release the first container on the pallet, reposition itself, and release the second container on the pallet. Depending upon container size, any number of gripping and palletizing zones could be created. 
     In addition to gears  120 , other mechanical elements may be utilized in the present invention for rotating fingers  100 . For example, gears  120  may be replaced with rollers having a high fiction surface on their outer cylindrical periphery. The high friction surface insures that the rollers rotate in unison and that the fingers  100  maintain a consistent alignment. A number of links could also be utilized in place of the gears  120  for rotating each finger between its open and gripping position. 
     FIG. 16 depicts another way of achieving the alternating finger rotation of fingers  100  discussed above. The gears or rollers attached to the top end of each finger are replaced with cogs  160  and a belt  162 . The belt is threaded in a serpentine fashion around each cog thus producing the required rotational motion discussed above. A pair of return cogs  164  is provided to complete the belt loop. As discussed above, a similar rotating mechanism is utilized to actuate or rotate the fingers  100 . 
     Now referring to FIG. 17, an alternative embodiment of the present invention is shown. Another bearing rail adjustment mechanism  130  is provided to adjust and maintain the distance between the two bearing rails  50 . This adjustment mechanism  130  comprises a motor  132 , an output shaft  134 , a center link  74  and a pair of tie rods  78 . The motor  132  is mounted to the upper surface  42  of the base plate  40  and housed within stanchion  30 . Preferably, the motor  132  is a stepper motor or servo motor capable of exerting a predetermined rotational motion to its output shaft  134 . A known control for the motor also provided (but not shown). The motor  132  must also be capable of being locked in the selected rotational position so that the bearing rails  50  do not move during the gripping operation. Output shaft  134  is connected to the central portion of center link  74 . Center link  74  has two link ends,  76 . The pair of tie rods  78  couples each center link end  76  to one of the bearing rails  50 . Referring to FIGS. 6 and 7, it is can be seen that one end of each tie rod  78  is pivotally connected to each bearing rail  50  and the other tie rod end is pivotally connected to each center link end  76 . 
     Now referring again to FIG. 7, when the motor  132  rotates output shaft  134  in either a clockwise or counter clockwise direction as shown by arrow  80 , ends  76  of center link  74  moves in the same direction (as shown by arrows  82 ). The rotational motion is translated into linear motion by virtue of linear bearings  60  and the above described orientation. The final result is that bearing rails  50  are linearly translated along linear bearing assemblies  60  as shown by arrows  84 . If the length of each link end  76  is equivalent and the length of each tie rod  78  is equivalent, bearing rails  50  will move the same distance relative to base plate  40 . 
     This alternate embodiment may be utilized in the following manner. After the pallet and cardboard sheet have been properly positioned, the industrial robot arm  12  moves to the pick up position to pick up a container  20 . While in motion toward the pick up position or prior to this time, motor  132  exerts a predetermined amount of rotational motion to center link  74  thereby adjusting the spacing between bearing rails  50  to a distance slightly greater than the width of the container  20  to be palletized. The L-shaped rotating finger supports  106  are oriented as shown in FIG.  11 . The present invention is positioned by the robot  12  directly over the container  20  at the pick up position and is next lowered so that its L-shaped rotating fingers  100  pass downward along opposite sides of the container  20 . When the rotating finger supports have just cleared the lower edge of the container  20 , actuators  142  are actuated to rotate the L-shaped rotating fingers  100  into their gripping position (as shown in FIG.  9 ). At substantially the same time, actuators  92  are retracted until the L-shaped rotating fingers contact and place a minimal amount of pressure on opposite sides of the container  20 . Alternatively, the motor  132  may be again energized thereby supplying an additional amount of rotational motion to center link  74  that in turn would apply the gripping force to the container  20 . 
     The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.