Abstract:
A method of handling an object using a robot end effector. The method includes providing a robot having an end effector supporting a pair of carriages, providing a pair of fingers for each carriage, moving the end effector over an object, grasping an object with the fingers, moving the object with the end effector to a container, and depositing the object by counter-rotating the pairs of fingers. One or both of the carriages is movable toward the other carriage to engage objects on a conveyor system with the fingers. The robot moves the end effector between the conveyor system and shipping containers for shipping the objects. Because the pairs of fingers counter-rotate, the friction forces between each finger and the tray is offset by the friction forces between the other finger in the pair and the tray. The improved handling method thereby maintains objects substantially in the desired stacking orientation within the shipping container. Preferably, an actuator is provided for each finger. A change-out mechanism may also be provided to facilitate replacing the fingers.

Description:
RELATED APPLICATIONS  
       [0001]    This application is a divisional of U.S. patent application Ser. No. 09/521,226, filed Mar. 8, 2000, which claims the benefit of U.S. Provisional Application No. 60/124,427, filed on Mar. 15, 1999. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to systems and devices used to load containers. More particularly, the present invention relates to a robotic end effector used to load mail trays of different shapes and sizes into containers.  
         BACKGROUND OF THE INVENTION  
         [0003]    Millions of pieces of mail are deposited with the postal service every day. The deposited mail is sorted, generally by ZIP or other code, and shipped to the proper destination. Generally, the sorting process involves placing mail with the same or related codes into trays. The trays are then placed in containers for shipment. Some parts of this process have been automated, including the sorting of mail by ZIP code. However, the trays are often placed in the containers manually. With ever-increasing mail demands, faster, more efficient methods of and devices for loading containers with mail trays are needed.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides an improved end effector for handling mail trays and tubs. The end effector includes first and second carriages, each having a pair of fingers depending therefrom. At least one of the carriages is movable toward the other carriage to grasp a tray between the respective pairs of fingers. The pairs of fingers counter-rotate to cause the support portions to engage and disengage the tray.  
           [0005]    Each carriage has a body and first and second fingers. Each finger has a support portion and a journal portion having a longitudinal axis. The journal portion of each finger is supported by the body for rotation about the longitudinal axis. The support portion is angled with respect to the longitudinal axis. At least one actuator selectively causes the journal portions to counter-rotate with respect to each other. Because the fingers counter-rotate with respect to each other, the friction forces between each finger and the tray offset the friction forces between the other finger and the tray, such that the tray remains substantially in the desired stacking orientation.  
           [0006]    In a preferred construction, the carriage includes first and second actuators, and the first and second actuators cause the first and second fingers, respectively, to selectively rotate. A pair of spaced-apart journal bearings supports the journal portion of each finger for rotation with respect to the body. A split clamp and actuator arm may be disposed between each pair of journal bearings to interconnect each finger with an associated actuator. The clamp includes a change-out mechanism to facilitate replacement of the fingers. Spacers may be provided to facilitate rotation of the fingers, clamps, and actuator arms with respect to the body.  
           [0007]    Preferably, the end effector also includes a harness assembly for supply lines between the end effector and the rest of the robot. The harness reduces the likelihood of tangling and pinching the supply lines as the end effector moves with respect to the rest of the robot. The end effector also preferably includes a shelf lowering mechanism to manipulate shelves in the containers.  
           [0008]    The present invention also provides a method for handling a tray. The method includes using an end effector having fingers to pick up and move the tray to a container, and counter-rotating the fingers to release the tray in the container.  
           [0009]    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.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a partially exploded, perspective view of a system embodying the present invention.  
         [0011]    [0011]FIG. 2 is an enlarged perspective view of an end effector from the system in FIG. 1 taken from above the end effector.  
         [0012]    [0012]FIG. 3 is a perspective view of the end effector of FIG. 2 taken from below the end effector.  
         [0013]    [0013]FIG. 4 is a side elevational view of the end effector of FIG. 2.  
         [0014]    [0014]FIG. 5 is an end view of the end effector of FIG. 2.  
         [0015]    [0015]FIG. 6A is an enlarged exploded view of a carriage of the end effector of FIG. 2.  
         [0016]    [0016]FIG. 6B is an enlarged exploded view of the coupling assembly shown in FIG. 6A.  
         [0017]    [0017]FIG. 7A is a cross-sectional view taken along line  7 - 7  in FIG. 4 illustrating the actuators in an extended condition.  
         [0018]    [0018]FIG. 7B is a cross-sectional view taken along line  7 - 7  in FIG. 4 illustrating the actuators in a retracted condition.  
         [0019]    [0019]FIG. 8 is an enlarged side elevational view of a portion of the end effector illustrated in FIG. 2. 
     
    
       [0020]    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 the 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 understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of “consisting of” and variations thereof herein is meant to encompass only the items listed thereafter. The use of letters to identify elements of a method or process is simply for identification and is not meant to indicate that the elements should be performed in a particular order.  
       DETAILED DESCRIPTION  
       [0021]    [0021]FIG. 1 illustrates a containerization and palletizing system  30 . The illustrated system  30  includes two cells  32 ,  34 , each equipped with a gantry or overhead-type robot  36 . As one of ordinary skill in the art will appreciate, the invention may alternatively be embodied in a system having one cell and one robot, more than two cells and robots, or having other types of robots.  
         [0022]    Each cell  32 ,  34  has a frame  38  which may be secured to a hard surface such as a concrete floor  40 . The space between the frame members may be enclosed with a perimeter fence  42 , a mesh, a similar material, or even other types of walls. One or more gates or doors  44  may be provided to permit access to the interior of the cell. Each cell  32 ,  34  has a plurality of places or bays  46  for pallets  49 , carts  50 , and any other suitable transport device (generically referred to herein as “containers”). Sensors (not shown) sense the presence or absence of containers in the bays  46  and that information is communicated to a system controller  55 .  
         [0023]    Mail trays, tubs, flats, and similar cartons (generically referred to herein as “trays”)  60  are brought into the cells  32 ,  34  by a conveyor system  66 . The illustrated conveyor system  66  includes two generally parallel conveyors. Sensors (not shown) positioned along the conveyors detect the location and presence of trays  60  on the conveyors. Information from the sensors is communicated to the system controller  55 .  
         [0024]    The robot  36  in each cell  32 ,  34  is mounted on beams  76 ,  78  spanning the cell. The beams  76 ,  78  are mounted on powered and guiding tracks  80 ,  82 , respectively. The robot  36  is movable along the beams  76 ,  78  and the beams  76 ,  78  are movable on the tracks  80 ,  82 . The tracks  80 ,  82  are positioned generally parallel to the floor  40 . Each robot  36  includes a vertically telescoping arm  90 , a turning disc or wrist  92 , and an end effector or gripper  95  (FIGS.  2 - 6 ).  
         [0025]    FIGS.  2 - 5  illustrate the end effector  95 , which is substantially identical for both robots  36 . The end effector  95  includes a pair of carriages  97  supported by a chassis  105 . Each carriage  97  has a pair of fingers  107  associated therewith. The fingers  107  include a journal portion  110  having a longitudinal axis  112  (FIG. 6A), and a bent or support portion  114  angled with respect to the longitudinal axis  112 . Preferably, the bent portion  114  is angled about 80° with respect to the longitudinal axis  112 . The fingers  107  are shaped to accommodate a wide variety of trays  60 . As will be described in more detail below, the fingers  107  are rotatable to an engaged position shown in solid lines in FIGS.  2 - 5 , and to a disengaged position shown in phantom in FIGS. 2 and 5. The bent portions  114  are disposed beneath a tray  60  when the fingers  107  are in the engaged position, and are rotated clear of the tray  60  when the fingers  107  are in the disengaged position.  
         [0026]    With reference to FIGS. 2 and 5, in order to load containers having shelves, the end effector  95  may also include a shelf-lowering assembly including an actuator  115  slidable on a pair of rods  115   a,  a finger  116   a,  and a shelf latch release mechanism  116   b.  The actuator  115  is oriented with one rod  115   a  above the other to create a high, narrow profile. This orientation provides a more compact end effector  95 , as the actuator  115  does not consume a large amount of horizontal space. The actuator  115  selectively causes the finger  116   a  and latch release mechanism  116   b  to extend into the container. The latch release mechanism  116   b  engages a latch that holds the shelf in an upright condition, and releases the latch so that the finger  116   a  catches the shelf. The end effector is then lowered by the robot to lower the shelf to a horizontal position. The robot then continues to load trays into the container.  
         [0027]    Referring to FIGS. 3 and 4, one of the carriages  97  is a movable carriage coupled to a track  117  by a plurality of slides or wheels  119  and moved by a carriage actuator  121  (such as a rodless cylinder, but preferably a multiple-pressure clamp cylinder) coupled to the chassis  105 . The clamp force of the carriage actuator  121  may be controlled using a valve, such as an open/closed air control valve, and a proximity switch, such as an intermediate-open proximity switch.  
         [0028]    The end effector  95  also includes a mail measurement and containment plate  160 , which is used by the controller  55  to detect and measure the height of trays  60  in containers. The measurement and containment plate  160  includes two long arms  164  (FIG. 2) and a pair of cross members  166 , although the plate  160  can have other shapes and provide similar functionality. The measurement and containment plate  160  is gravity driven, supported by a pair of linear rods  170  which are mounted in bearings  176  (FIG. 3).  
         [0029]    [0029]FIG. 6A illustrates one of the carriages  97 ; it being understood that both carriages  97  of each end effector  95  are substantially identical unless specifically described otherwise. The carriage  97  includes a body  208  and two actuators  210  which may be pneumatic, hydraulic, electric, or any other appropriate actuators. Each actuator  210  includes a cylinder  214  with a first end  218  that is fixed to the carriage body  208  with a suitable fastener or pin  222 . Each actuator  210  also includes a piston  226  slidable with respect to the cylinder  214 . A pin or other suitable fastener  230  extends through the distal end of each piston  226 . Alternatively, a clevis may be attached to or integrally formed with the piston  226  and the pin  230  may extend through the clevis.  
         [0030]    Each end of the carriage body  208  includes a cavity or space  234  in which a coupling assembly  238  is positioned. A pair of spaced-apart holes in each end of the carriage body  208  serves as journal bearings  240  for the fingers  107 . The journal portion  110  of one of the fingers  107  extends through the coupling assembly  238  and the journal bearings  240 . The finger  107  is held in the journal bearings  240  above and below the coupling assembly  238 . Because both ends of the carriage  97  are substantially identical to the other end, only one end is described below.  
         [0031]    With reference to FIGS. 6A and 6B, the coupling assembly  238  includes a clamp  242 , an actuator arm  246 , and a pair of spacers  250 . As best seen in FIG. 6B, the clamp  242  is a split clamp including first and second portions  258 ,  262 , respectively. The first portion  258  includes a pair of holes through which the journal portion  110  of the finger  107  extends. The second portion  262  includes a pair of clearance apertures for fasteners  266 , and an aperture for a coupling pin  270 . The fasteners  266  extend through the clearance holes and thread into the first portion  258  to hold the first and second portions  258 ,  262  together. The coupling pin  270  extends through the aperture in the second portion  262  and into a hole in the journal portion  1   10  to couple the clamp  242  and finger  107  together. The clamp  242  also includes cleats  274  for coupling the clamp  242  and actuator arm  246  as described below.  
         [0032]    The clamp  242  is preferably configured such that the finger  107  is tightly sandwiched between the first and second portions  258 ,  262  so that the coupling pin  270  is not exposed to all the shear stress caused by the weight of trays  60  being transported by the finger  107  and caused by rotation of the finger  107 . The finger  107  may be removed and replaced by removing the fasteners  266  and coupling pin  270 , letting the finger  107  drop through the assembly  238  under the influence of gravity, inserting a replacement finger  107  through the assembly  238 , and reattaching the second portion  262  of the clamp  242 , the fasteners  266 , and the coupling pin  270 .  
         [0033]    The coupling pin  270  may be used to support the finger  107  and free up one hand of the installer when the replacement finger  107  is installed, making it easier to insert the fasteners  266 . As an alternative to the coupling assembly illustrated, and to further facilitate replacing fingers, the coupling pin  270  may be integrally formed with either the first or second portions  258 ,  262  of the clamp  242 , and the fasteners  266  may be replaced with an over-center clasp or another quick-release fastener. The illustrated clamp  242  and coupling pin  270 , and variations thereof and alternatives thereto, provide a change-out or quick-release mechanism that facilitates a relatively easy and quick changing of damaged or worn fingers  107 .  
         [0034]    Still referring to FIG. 6B, the actuator arm  246  includes a finger hole  278  at one end, an actuator pin hole  282  at the opposite end, and a plurality of cleat holes  286 . The journal portion  110  of the finger  107  extends through the finger hole  278 . The cleat holes  286  receive the cleats  274  of the clamp  242  to couple the actuator arm  246  and clamp  242 . The actuator pin hole  282  receives the pin  230  extending through the piston  226  of the actuator  210 . If the end of the piston  226  includes a clevis, the actuator arm  246  may extend into the clevis and be pinned there. Thus, linear actuation of the piston  226  causes the actuator arm  246  to rotate about the longitudinal axis  112  of the journal portion  110  of the finger  107 , which causes the clamp  242  to rotate due to the cleat  274  coupling, which in turn causes the finger  107  to rotate due to the coupling pin  270  and sandwiching clamp portions  258 ,  262 .  
         [0035]    [0035]FIG. 7A illustrates the actuators  210  in an extended condition, whereby the fingers  107  are in the disengaged position (shown in phantom in FIGS. 2 and 5). FIG. 7B illustrates the actuators  210  in a retracted condition, whereby the fingers  107  are in the engaged position. The fingers  107  associated with each carriage  97  are counter-rotated by the actuators  210 . As used herein with respect to the relative rotation of the pair of fingers  107  associated with each carriage  97 , “counter-rotate” means that one finger  107  rotates clockwise and the other finger  107  rotates counterclockwise with respect to the fingers&#39; respective longitudinal axes  112 , as shown in FIGS. 7A and 7B.  
         [0036]    Referring again to FIGS. 6A and 6B, the spacers  250  extend at least partially into the journal bearings  240  and abut the clamp  242  or actuator arm  246 . The spacers  250  thereby space the clamp  242  and actuator arm  246  from the carriage body  208  to reduce friction. The spacers  250  are preferably made of a low-friction, wear-resistant material, such as high molecular density plastic. The spacers  250  may also include roller bearings to further facilitate the rotation of the fingers  107 .  
         [0037]    With reference to FIG. 8, fluid and electrical supply lines or hoses  290  extend through the telescopic arm  90  to the end effector  95 . The fluid supply hose supplies the fluid used to actuate the various actuators  115 ,  121 ,  210  on the end effector  95 , and may, for example, provide pressurized air or hydraulic fluid. The electrical supply line provides electricity for the various sensors and electrically-powered components of the end effector  95 . Other lines may also extend through the telescoping arm  90 , such as cables for relaying information from sensors to the controller  55 . The lines  290  are coiled on a support plate  294  to prevent or reduce tangling of the lines and pinching of the fluid hose during operation of the robot  36 . Plugs  298  are provided in the telescopic arm  90  and the end effector chassis  105  to easily disconnect and replace the lines  290 . The plugs  298  facilitate servicing the robot  36 .  
         [0038]    The operation of the system  30  will now be described in light of the above disclosure. A tray  60 , to be loaded into a container, is moved by the conveyor system  66  beneath one of the robots  36 . The controller  55  moves the robot  36  over the tray  60  and the end effector  95  is lowered to position a pair of fingers  107  on either side of the tray  60  with the fingers  107  in the disengaged position. The fingers  107  are rotated to the engaged position by actuation of the actuators  210  to the retracted condition (FIG. 7B) and the movable carriage  97  is moved toward the fixed carriage  97  until the bent portions  114  of the fingers  107  are beneath the tray  60 . Then the end effector  95  is raised, lifting the tray  60  with the fingers  107 . The downward force exerted on the top of the tray  60  by the containment plate  160  helps maintain the grip of the fingers  107 . The robot  36  is moved over the container and the end effector  95  lowered until the tray  60  rests on the container or on another tray  60  in the container. The height of the stacked trays  60  is measured with sensors monitoring the movement of the linear rods  170  and is used by the controller  55  to determine when the container is fully loaded. The actuators  210  are extended (FIG. 7A) to counter-rotate the fingers  107  to the disengaged position and the end effector  95  is raised or otherwise moved clear of the tray  60  and container.  
         [0039]    The present invention can be embodied in alternative systems. For example, each carriage  97  may support more than two fingers  107 . The fingers  107  may include substantially straight portions having bent portions disposed at 90° with respect to the straight portions. Both carriages  97  may be movable toward each other such that the carriages  97  center the tray  60  with respect to the end effector  95 . A single actuator  210  may be used to counter-rotate two or more fingers  107  through a linkage. Other possible combinations and alternative constructions of the features described herein would be readily apparent to those of ordinary skill in the art and are not discussed.