Abstract:
An end effector ( 10 ) for an industrial robot has the ability to pick up plural objects, selectively rotate same and adjusts the spacing between the plural objects as the products are being carried by the robot to a desired deposit location. This functionality is achieved by locating a rotary actuator ( 16 ) at the end ( 8 ) of a robot arm and providing a lazy tong linkage assembly ( 60 ) to which plural product graspers ( 62 ) are affixed where the lazy tong assembly is carried by a rotatable platform ( 18 ) of the rotary actuator. The rotary actuator, the lazy tong assembly and the product graspers are preferably pneumatically actuated.

Description:
BACKGROUND OF THE INVENTION 
   I. Field of the Invention 
   This invention relates generally to pick-&amp;-place robotics, and more particularly to end effectors used on such equipment. 
   II. Discussion of the Prior Art 
   In the packaging industry, many of the tasks that had been carried out manually are now performed by industrial robots. As an example, such robots have been designed to pick up individual products from a first conveyor exiting a high-speed wrapping machine and transporting the wrapped products to a box or carton traveling along a second conveyor. A problem results, however, if the product size and/or shape are such that it can fit into a carton only if oriented precisely in a certain disposition. Then, too, if the robot is to simultaneously pick up a plurality of products from a conveyor, rather than one at a time, and the products are traveling down a flighted conveyor, it presents a problem of how to deposit the products as a group into a carton in a contiguous relationship. 
   For purposes of example only, assume for the moment that the products leaving the wrapping machine are candy bars of a defined length, width and thickness dimension and that they are traveling between lugs or fins of a flighted conveyor that maintains a predetermined gap between products. Assume further that it is desired to deposit a predetermined count of the candy bars, say, one dozen, in an open top rectangular carton as the carton moves down a second conveyor running parallel to the first. The robot employed must be able to simultaneously pick up plural bars from the flighted conveyor, squeeze the several bars together to eliminate the spacing therebetween and then deposit the plural bars as a group in the carton and then repeat the process until the desired count has been boxed. Depending on the dimensions of the candy bars and the dimension of the carton, it may also be necessary to rotate the group of bars while in transit, via the robot, so that they will be properly aligned for deposit into the box. 
   It is the principal object of the present invention to provide an improved end effector for an industrial robot for use in pick &amp; place applications. 
   Another object of the invention is to provide an end effector capable of compressing and expanding the spacing between plural product grasping devices comprising the end effector. 
   Still another object of the invention is to provide an end effector for a robot having a rotatable head capable of both rotating plural products and expanding and contracting the spacing between the plural products picked up by the end effector as the products are being carried by a robot. 
   SUMMARY OF THE INVENTION 
   The foregoing objects are realized by providing an end effector for an arm of an industrial robot that comprises a plurality of suction tubes coupled in fluid communication to a vacuum manifold where each of the suction tubes is capable of grasping a product. The end effector also includes a means for varying the spacing between the plurality of suction tubes as well as a means for rotating the vacuum manifold and the means for varying the spacing between the plurality of suction tubes relative to the arm of the industrial robot carrying the end effector. 
   Without limitation, the means for varying the spacing between the plurality of suction tubes may comprise a lazy tong linkage assembly that is coupled to a linear actuator such that extension of the linear actuator results in a spreading of the distance between the suction tubes and retraction of the linear actuator results in a squeezing of the plurality of suction tubes together. 
   The means for rotating the vacuum manifold preferably comprises a pneumatically operated rotary actuator having a rotary platform journaled to a body member where the rotary actuator is disposed between the arm of the industrial robot and the vacuum manifold. 

   
     DESCRIPTION OF THE DRAWINGS 
     The foregoing features, objects and advantages of the invention will become apparent to those skilled in the art from the following detailed description of a preferred embodiment, especially when considered in conjunction with the accompanying drawings in which: 
       FIG. 1  is a perspective view of a preferred embodiment of an end effector constructed in accordance with the present invention; 
       FIG. 2  is a side elevational view of the end effector of  FIG. 1 ; 
       FIG. 3  is an end view of the embodiment of  FIG. 1 ; and 
       FIG. 4  is an exploded view of a rotary actuator employed in the embodiment of  FIG. 1 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Certain terminology will be used in the following description for convenience in reference only and will not be limiting. The words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the device and associated parts thereof. Said terminology will include the words above specifically mentioned, derivatives thereof and words of similar import. 
   Referring first to  FIG. 1 , there is indicated generally by numeral  10  an end effector for use on an industrial robot such as a Delta Robot of the type described in U.S. Pat. No. 4,976,582 to Raymond Clavel (the Clavel &#39;482 patent). The patent describes a robot for handling products in a three-dimensional space and those skilled in the art may refer to that patent for a description of a robot with which the present invention may be utilized. Such a robot is designed for high-speed and high-accuracy pick-&amp;-place applications, such as may be effectively used in the packaging machine industry, for picking products from a conveyor belt and placing them in cartons or to the infeed of a high-speed wrapping machine with a predetermined orientation and spacing between products. 
   Referring to  FIG. 2  of the Clavel &#39;482 patent, the Delta Robot includes a generally triangular-shaped main casting  1  having three rotatable shafts  2  journaled for rotation about horizontal axes extending generally parallel to the three sides of the triangular casting  1 . Each of the three shafts is arranged to be driven by a servo motor  3  for rotating the arms  4  in a vertical plane. Rotary encoders  7  on the servo motor  3  feed positional information to a main controller module  12 . At the free ends of the arms  4  are crossbars of a predetermined length dimension and carrying a detachable connector, such as ball &amp; socket joints  26 , at a opposed ends thereof. The detachable ball &amp; socket joints  26  couple the cross bars to a pair of rods comprising a total of six forearms  5 , all of equal length. 
   Suspended from the lower ends of the six forearms  5  is a triangular-shaped base plate member  8 . More particularly, cross rods project laterally from the base plate  8  proximate the three vertices thereof and detachable connectors, e.g., ball &amp; socket joints  27 , are used to join the lower ends of the forearm members  5  to the cross rods. Supported from the underside of the base plate  8  is an end effector  9  which may comprise a vacuum cup or other type of gripping member. In that the forearms  5  are of equal length, as the respective servo motors impart rotation to the arms  4 , the base plate  8  carrying the end effector  9  undergoes pure translation without rotation in first swinging to pick up a product located in a first area and transporting it to a second area for release. 
   In  FIG. 1  hereof, the base plate  8  of the Delta Robot is shown with the end effector  10  of the present invention attached to the undersurface thereof by a series of bolts, as at  12 , which extend into threaded bores formed in the top surface  14  of a rotary actuator  16 . Without limitation, the rotary actuator  16  may be of a type manufactured and sold by Numatics Incorporated of Highland, Mich. As will be explained in greater detail herein below with the aid of  FIG. 4 , the rotary actuator  16  includes a rotary platform  18  ( FIG. 2 ) journaled to a body member  20  where the body member  20  is affixed to the underside of the base plate  8  of the Delta Robot. Under pneumatic forces, the rotary platform  18  can be made to swivel through a predetermined arc. 
   The rotary actuator  16  is mounted on a frame structure that is indicated generally by numeral  22  in  FIG. 1 . More particularly, a series of standoffs as at  24 , secure the rotary actuator  16  to the frame  22  so as to maintain a predetermined distance between the underside of the rotary platform  18  and the upper surface of the frame  22 . 
   The frame  22  comprises first and second tubular vacuum manifolds  26  and  28  that are held in parallel, spaced-apart relationship by opposed end plates  30  and  32 . As can be seen in  FIG. 1 , the tubular manifold  28  has a vacuum inlet port  34  adapted to be connected by flexible tubing, not shown, to a vacuum source. The tubular manifold member  26  also has a vacuum inlet port  36  that is hidden from view in  FIG. 1 , but visible in the end view of  FIG. 3 . A vacuum can be selectively applied to one or both manifolds. Each of the manifold members  26  and  28  has a plurality of vacuum outlet ports, as at  38 . 
   As perhaps best seen in  FIG. 2 , bolted to the underside of the rotary platform  18  are first and second linear actuators  40  and  42 . Each comprises a pneumatic 2-way cylinder whose reciprocally movable outlet shafts  44  and  46  terminate in fittings  48  and  50 . These fittings are pivotally connected by a pin  52  that passes through a standoff  54  to end linkages  56  and  58  of a lazy tong linkage assembly that is indicated generally by numeral  60 . The lazy tong linkage assembly  60  comprises a plurality of pairs of diagonal linkages, where the members of each pair are pivotally joined at their centers and are also pivotally joined to an adjacent pair of diagonal linkages at their respective ends, as perhaps best seen in the perspective view of  FIG. 1 . 
   Turning momentarily to  FIG. 2 , attached to the lazy tong assembly  60  proximate the center of the diagonal linkages thereof are product graspers, here shown as downwardly extending rigid tubes, as at  62 , each supporting a pair of suction cups, as at  64 , that are in fluid communication with the central lumen of the rigid tubes  62  by way of tubular stubs, as at  66 . While the illustrated embodiment uses pneumatic graspers, it is to be understood that other mechanical or electrically operated graspers may also be used. 
   Short lengths of flexible plastic tubing as at  67  in  FIG. 3  are used to connect the manifold outlet ports  38  to corresponding input ports  68  near the upper ends of the rigid tubes  62 . Thus, when a vacuum source is connected to the manifolds  26  and  28  by way of the vacuum inlet ports  34  thereof, suction forces are developed proximate the lower ends of all of the suction cups  64 . If a vacuum is applied to only one of the manifolds, only those suction cups associated with that manifold will be active to grasp a product. 
   Turning now to  FIG. 4 , the constructional features of the rotary actuator  16  will be described. The body member  20  thereof includes a pair of bores  70  and  72  that receive generally cylindrical pneumatic pistons  74  and  76  therein. The piston members include a gear rack  78  machined into a flattened portion of the periphery of the otherwise cylindrical pistons. O-rings, as at  80 , fit into circumferential grooves  82  formed proximate the opposed ends of the pistons and serve as seals between the pistons and the walls of the bores in which they reside. 
   The body member  20  includes a centrally located vertical cylindrical bore  84  for receiving a pinion gear  86  and bearings  88  and  90  therein. The gear teeth on the pinion  86  are arranged to mate with the gear rack  78  on the pistons  74  and  76  such that when the pistons are made to move reciprocally in the bores  70  and  72 , the pinion gear  86  will rotate about its central axis. 
   Once the pistons  74  and  76  have been inserted into the respective bores  70  and  72 , tubular caps as at  92  are screwed into threads formed the bores  70  and  72  of the body member  20 . Thus, when air, under pressure, is introduced through the central bore  94  of the end caps  92 , the pistons can be made to move toward the center of the body member  20 , rotating the spur gear  86  in a first direction. With a pressure applied through the bore  95 , the alternate pistons will be forced toward the periphery of the body member  20  causing the pinion gear  86  to rotate in the opposite direction. 
   A retainer ring  96  is fastened by screws  98  to the surface face of the body member  20  holding the bearings  88 ,  90  and  100  that journal the pinion gear  86  in place. 
   The rotary platform  18  is secured to an upwardly projecting shaft  102  of the pinion gear  86  so as to rotate with the pinion gear. Formed in the undersurface of the rotary platform  18  is an annular groove (not shown) into which a projection  104  on the body member  20  is arranged to fit. Threaded bores  106  and  108  extend radially into the peripheral surface of the rotary platform  18  and intersect with the annular groove. Setscrews  110  and  112  are inserted into the threaded bores  106  and  108  to cooperate with the stop  104  to define the end points of the arc through which the rotary platform  18  may rotate. 
   Having described the construction features of the preferred embodiment, attention will now be directed to the mode of operation. 
   With the rotary actuator  16  affixed to the robot&#39;s base plate  8  at the lower ends of the robot&#39;s arms and with pressure hoses (not shown) connected to the end caps  94  of the rotary actuator and with a source of negative pressure connected through tubing (not shown) to the manifold inlet ports  34  and  36 , a suction can be drawn through the suction cups  64  to grip and hold a plurality of products at the lower ends of the rigid tubes  62 . With valving (not shown), the linear actuators  40  and  42  can have their piston rods  44  and  46  extended or retracted, thereby varying the spacing between the plurality of rigid tubes and the products carried thereby by virtue of the lazy tong linkage mechanism that is operatively coupled to the reciprocally movable piston rods  44  and  46 . 
   At the same time, by controlling the air pressure acting on the pistons  74  and  76 , the rotary platform  18  can be made to spin through a predetermined arc as set by the adjustment screws  110  and  112  to thereby rotate the frame  22 , the lazy tong assembly  60  and the rigid tubes  62  relative to the base plate  8  of the robot arm with which the end effector  10  of the present invention is used. 
   As has been explained in the Background of the Invention section hereof, a plurality of objects may simultaneously be picked up from a conveyor belt for placement in a carton traveling along an adjacent conveyor belt. The spacing between the objects can be varied in transit. Likewise, all of the objects can be rotated through a present arc while the objects are in transit under control of the robot arm from a “pick” position to a “place” position. 
   This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself.