Abstract:
A direct clamp robotic finishing system is provided including a robot, a gripper secured to the robot, and a pair of fingers secured to the gripper. A tray assembly is also provided for supporting a plurality of implants for picking up by the fingers. An implant reorientation station is provided for supporting the implant being maneuvered by the robot as the robot re-grips the implant from a new direction. The fingers directly clamp the implant thereby eliminating the need for dedicated implant support bars.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a divisional of U.S. patent application Ser. No. 10/967,914 filed on Oct. 18, 2004. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to robotic finishing systems and, more particularly, to direct clamp tooling for robotic prosthetic knee finishing systems.  
       BACKGROUND OF THE INVENTION  
       [0003]     Metalworking of cast metal articles such as prosthetic knee implants typically requires surface finishing such as buffing, polishing, deburring, grinding and satin finishing. Traditionally, these finishing steps were performed by hand. More recently, however, automated processing replaced most manual operations. As compared to manual finishing, automated finishing provides greater efficiency, precision, and safety.  
         [0004]     An important aspect of robotic finishing knee implants is the need to manipulate the implant to expose all surfaces to a finishing device such as a wheel or belt. To accomplish this, the implant must be held by the robot and maneuvered to various orientations relative to the finishing device. Importantly, the robot must hold the implant against the finishing device with pressure yet not mar the surface of the implant when picking it up or putting it down.  
         [0005]     One technique for enabling a knee implant to be picked up and manipulated by a robot in a finishing operation is to mount the knee implant to a metal support bar. In this technique, the knee implant is fixed to a central region of a metal bar through the use of fasteners such as screws. The bar laterally extends beyond the both outboard edges of the knee implant to provide two graspable handles for the robot. The robot may then use jaws to clamp onto one handle of the bar and manipulate the knee implant relative to the finishing device. The knee implant and bar assembly may then be set down while the robot repositions its jaws to the other graspable handle of the bar. The knee implant may then be further manipulated relative to the finishing device.  
         [0006]     While the use of support bars for finishing knee implants has been widely accepted, there is room for improvement in the art. For example, each knee implant must be fixed to a dedicated support bar by way of fasteners such as screws. This is a labor intensive process. Also, one support bar must be provided for every knee implant in a particular batch to be finished. Assuming that twelve knee implants are provided in each batch and finishing operations continue throughout the various working shifts, a large number of bars must be kept in stock. Also, since the finishing process wears the support bars, each support bar must be periodically replaced. Given the large number of bars in a typical inventory, this can be expensive.  
         [0007]     In view of the forgoing, it would be desirable to provide a tooling system for enabling the direct clamping of knee implants to thereby eliminate the need for support bars.  
       SUMMARY OF THE INVENTION  
       [0008]     The above and other objects are provided by a direct clamp robotic finishing system comprising a robot, a gripper secured to the robot, and fingers secured to gripper. The gripper and fingers are operable in an open mode and a closed mode for gripping an implant. A tray assembly is also provided for supporting a plurality of implants for picking up by the fingers. An implant reorientation station supports the implant being maneuvered by the robot as the robot re-grips the implant from a new direction.  
         [0009]     In accordance with the teachings of the present invention, at least one implant is moved from a loading area to the interior of a robotic cell by way of the tray assembly. The tray assembly is configured to support the knee implants in a pre-selected orientation and with minimum contact so as not to mar the surface of any pre-finished surfaces. The robot moves the fingers to the implant in an open mode and when properly oriented relative to the implant, switches the fingers to a closed mode so that the fingers abutingly engage clampable surfaces of the implant. The robot may then lift and manipulate the implant relative to a finishing device. Upon completion of a first finishing process, the robot places the implant on the implant reorientation station and moves the fingers to an open mode. The implant reorientation station minimally contacts the implant so not to mar any pre-finished surfaces. The robot then re-orients the fingers and re-grips the implant from a direction 180 degrees relative to the initial gripping direction. A subsequent finishing process may then be performed. Advantageously, no implant support bar need be secured to the implant for the finishing process. Further, improved trays and implant reorientation stations are employed since an implant support bar no longer needs to be accommodated.  
         [0010]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0012]      FIG. 1  is an illustration of a robotic cell including the tooling of the present invention.  
         [0013]      FIG. 2  is a front view of a tray assembly of the present invention.  
         [0014]      FIG. 3  is a side view of the tray assembly of the present invention.  
         [0015]      FIG. 4  is a plan view of part of the tray assembly of the present invention.  
         [0016]      FIG. 5  is a front view of a gripper and finger assembly of the present invention.  
         [0017]      FIG. 6  is a plan view of the gripper and finger assembly of the present invention.  
         [0018]      FIG. 7  is a front view of a finger assembly of the present invention.  
         [0019]      FIG. 8  is a side view of one finger of the finger assembly of the present invention.  
         [0020]      FIG. 9  is a top view of the finger assembly of the present invention with the fingers shown in an open and closed mode.  
         [0021]      FIG. 10  is a side view of the other finger of the finger assembly of the present invention.  
         [0022]      FIG. 11  is a front view of an implant reorientation station of the present invention.  
         [0023]      FIG. 12  is a side view of the implant reorientation station of the present invention.  
         [0024]      FIG. 13  is a plan view of the implant reorientation station of the present invention.  
         [0025]      FIG. 14  is a side view of a gripper and finger assembly according to a second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0027]     Referring to the drawings,  FIG. 1  illustrates a robotic cell  10  used for robotically finishing metal articles such as knee implants. The cell  10  includes a robot  100 , a revolving implant supply device  200 , an implant reorientation station  300 , and two finishing devices  400  in the form of stacked wheel heads. In operation, the robot  100  picks up a knee implant from the revolving part supply device  200  and manipulates the implant relative to the finishing devices  400  to perform buffing, polishing, and the like. To expose all surfaces of the implant to the finishing devices  400 , the robot  100  sets the implant down on the implant reorientation station  300  and picks it back up from an opposite side. Finishing operations are thereafter continued.  
         [0028]     Although other robots may be employed, it is presently preferred to employ a Fanuc M16iB Robot with a 20 kg payload. Further, although stacked wheel heads are described above as the finishing devices  400 , other finishing apparatuses may substitute therefore. Finally, although a knee implant is used throughout this description as an example of the part to be finished, the present invention is not limited to tooling for finishing knee implants.  
         [0029]     Turning now to  FIGS. 2-4 , a tray assembly  302  of the revolving implant supply device  300  is illustrated. The tray assembly  302  includes a vertically oriented base plate  304  formed of, for example, aluminum. A plurality of vertically spaced apart mounting plates  306  are independently fixed to the base plate  304  by fasteners  308  such as screws. In the illustrated example, six base plates  304  are cantilevered to the base plate  304 .  
         [0030]     Each mounting plate  306  includes a slide block  310  mounted to a first channel  312   a  formed along a first outboard edge of the top surface of the mounting plate  306  by fasteners such as recessed screws. The slide block  310  may be formed of, for example, hot rolled steel. Each mounting plate  306  also includes a part support  314  mounted to a second channel  312   b  formed along a second outboard edge of the top surface of the mounting plate  306  by fasteners such as recessed screws. The part support  314  may be formed of, for example, Teflon (Registered Trademark) and is preferably disposed parallel to and laterally spaced apart from the slide block  310 .  
         [0031]     A pair of adjustable part locators  316  are mounted to each slide block  310  by way of fasteners  318  in the form of, for example, knurled head screws. Each part locator  316  includes a slot  320  to accommodate the associated fastener  318  and enabling fore and aft movement relative to the slide block  310 . Each part locator  316  also includes a tang  322  projecting therefrom and adapted to abuttingly engage a relieved surface of the implant  500 . The tang  322  preferably projects orthogonally relative to the slide block  310  to position the implant  500  in a pre-selected location and orientation on the part support  314  for consistent gripping by the gripper  102 . The tang  322  also prevents the implant  500  from tilting in one direction when rotating with the base plate  304  or when grabbing by the gripper  102 . The tang  322  provides a stop that can be exploited when applying pressure to the implant  500  during the grabbing sequence.  
         [0032]     The part support  314  includes a pair of chamfered edges  324  for abuttingly engaging the implant  500  along pre-selected areas which will later be subject to polishing. This ensures that the part support  314  does not mar the surface of the implant  500  which could require further processing. The width of the part support  314  and, in particular, the pair of chamfered edges  324  is carefully selected relative to the patella groove of the implant  500 . In particular, the chamfered edges  324  support the implant  500  without contacting the inboard flat surfaces along the patella groove which are typically pre-finished.  
         [0033]     The height of the part support  314  is also carefully selected to provide sufficient clearance between the implant  500  and the mounting plate  306  to allow the implant  500  o be tipped toward the mounting plate  306  during the grabbing sequence. This enables the implant  500  to clear the tang  322  and be removed from the support part  314 . This clearance is also carefully selected to limit the maximum tipping of the implant  500  toward the mounting plate  306  within a given tolerance. The tolerance is controlled so that the implant  500  tends to return to horizontal during the grabbing sequence. In this event, the tang  322  acts as a stop.  
         [0034]     The part support  314  is laterally spaced apart from the slide block  310  by a distance more than adequate to support the widest implant  500  expected to be finished. More narrow implants  500  can be supported equally as well by adjusting the position of the part locators  316 . Advantageously, implants  500  of all widths are supported along a common center line by the part support  314 .  
         [0035]     Turning now to  FIGS. 5 and 6 , a detailed view of the gripper  102  of the robot  100  is illustrated. The gripper  102  is preferably a Schunk Parallel Gripper, PGN series, stroke  1 , with a spring to close (#PGN Plus 125 1/AS #371-403). The gripper  102  is fixed to the end of the robot  100  by an adapter plate  104 . Preferably, screws  106  pass through the adapter plate  104  and into the robot  100  while screws  108  pass through the adapter plate  104  and into a first end of the gripper  102 .  
         [0036]     A pair of L-shaped fingers  110  is fixed to a second end of the gripper  102  opposite the robot  100 . The first finger  110   a  is fixed to one outboard end  112   a  of the gripper  102  while the second finger  110   b  is fixed to a second outboard end  112   b  of the gripper  102 . The gripper  102  is pneumatically operated to move the fingers  110  between an open mode (shown in phantom in  FIG. 6 ) and a closed mode (shown in solid in  FIG. 6 ). In an open mode, the fingers  110  are pneumatically biased outwardly to allow the fingers  110  to fit on opposite sides of a clampable surface  502  of the implant  500 . In a closed mode, the fingers  110  are pneumatically biased inwardly to allow the fingers  110  to abutingly engage the clampable surface  502  of the implant  500 .  
         [0037]     The clampable surface  502  is not particularly limited to any specific configuration and most projections will suffice. In some versions, the implant  500  is provided with posts  504  used during an operation to secure the implant  500  to a patient. Posts  504  provide an ideal clampable surface  502 . In other versions, threaded openings are provided within the implant  500 . These threaded openings can be fit with threaded members (see  FIG. 14 ) to provide the clampable surface  502 . In yet another version, a box-shaped projection may be present within the implant  500 . This box may also serve as the clampable surface  502 .  
         [0038]     The gripper  102  preferably includes a spring (not shown) biasing the fingers  110  toward one another. In the unlikely event pneumatic force is lost, the spring urges and/or maintains the fingers  110  in the closed mode. This prevents the implant  500  from being dropped and potentially damaged. The gripper  102  also preferably includes a proximity switch (not shown) that senses the relative position or state of the fingers  110 . In this way, the proximity switch can be used to determine whether or not the implant  500  is being clamped by the fingers  110 .  
         [0039]     It should be noted that the gripper  102  has a fully open position, a fully closed position, and a working position between the fully open and fully closed positions. In the working position, the gripper  102  is in a state suitable for clamping the clamping surface of the implant  500  but still has a distance to go to reach the fully closed position. The fingers  110  do not abut one another in the working position. Advantageously, this “gapped” working position prevents the fingers  110  from wearing on one another to increase their usable working life.  
         [0040]     Turning now to  FIGS. 7-10 , an exemplary embodiment of the fingers  110  is illustrated. Although other materials are available, it is presently preferred that the fingers  110  be made of a pre-hardened alloy steel. Each of the fingers  110  is generally L-shaped and includes a mounting leg  114  extending essentially orthogonally relative to a clamping leg  116 . The inboard transition between the mounting leg  114  and the clamping leg  116  is preferably radiused to increase strength and wearability.  
         [0041]     As best viewed in  FIG. 9 , the outboard edge  118  of each mounting leg  114  extends substantially perpendicular to a mounting surface  120 . The front face  122  of each mounting leg  114  extends substantially perpendicular to the outboard edge  118  and parallel to the mounting surface  120 . The transition between the outboard edge  118  and the front face  122  is chamfered to form a corner surface  124 . Preferably, the corner surface  124  angles at about 45 degrees relative to the outboard edge  118  and the front face  122 .  
         [0042]     An outboard face  126  of each clamping leg  116  extends substantially perpendicular to the mounting surface  120 . A working surface  128  of each clamping leg  116  extends substantially parallel to the outboard face  126 . Each working surface  128  includes a pair of spaced apart clamping channels  130 . The channels  130  compliment one another to form a clam shell gripping surface when the fingers  110  are brought close together. Although the channels  130  are illustrated with a constant depth relative to the working surface  128 , the channels  130  may be tapered to provide a tapered clam shell gripping surface. The channels  130  preferably compliment the shape of the clampable surface of the implant as much as possible.  
         [0043]     As best seen in  FIG. 7 , chamfered sidewalls  132  extend at an angle between the working surface  128  and the outboard face  126 . Similarly, chamfered sidewalls  134  extend at an angle between the front face  122  and the mounting surface  120 . This yields a substantially trapezoidal cross section to the mounting leg  114  and clamping leg  116 . Of course, a relatively small top surface  136  and a relatively small bottom surface  138  are provided between the sidewalls  132  and the working surface  128 . Similarly, a top surface  140  and a bottom surface  142  are provided between the sidewalls  134  and the mounting surface  120 .  
         [0044]     As best seen in  FIGS. 8 and 10 , each clamping leg  116  includes a front end face  144  extending substantially perpendicular to the working surface  128  and parallel to the mounting surface  120 . An angled surface  146  extends between the front end face  144  and the top surface  136 . A substantially square shaped opening  148  is formed within each clamping leg  116  from the working surface  128 . The opening  148  accommodates a box that is often provided within knee implants (between the clampable surfaces) so that the box and the fingers  110  do not interfere.  
         [0045]     A pair of pins  150  extends from the clamping leg  116  orthogonal to the working surface  120  of the first finger  110   a . Complimentary slots  152  are provided in the second finger  110   b  for receiving the pins  150  (both modes are illustrated in  FIG. 9 ). The pins  150  provide a greater contact surface area compared to the bottom surfaces  138  of the fingers  110  which are separated by a gap. As such, a line contact can be established with the implant just prior to clamping.  
         [0046]     The many chamfered surfaces of the fingers  110  increase the clearance between the fingers  110  and the finishing devices used to finish the implant gripped by the fingers  110 . Maximum attention is paid to robustness and wearability juxtaposed with interference concerns.  
         [0047]     Turning now to  FIGS. 11-13 , the implant reorientation station  300  is shown in greater detail. The station  300  includes a base  302  securable to a floor and a generally U-shaped riser  304  extending substantially vertically from the base  302 . A top plate  306  is secured to the riser  304  opposite and substantially parallel to the base  302 .  
         [0048]     A turnaround support  308  is fixed to the top plate  306  by fasteners such as screws. The turnaround support  308  includes a, e.g., Teflon, stand  310  projecting away from a major surface  312 . The stand  310  includes a pair of parallel sidewalls  314  extending substantially perpendicular to the major surface  312  so as to be substantially vertical. A top surface  316  extends substantially perpendicular to the sidewalls  314 . The transitions between the top surface  316  and the sidewalls  314  are chamfered to yield angled contact surfaces  318 . The width of the stand  310  is carefully controlled relative to the finished surfaces implant  500  so that the implant  500  is only supported by the contact surfaces  318  at pre-selected locations. These locations are selected to avoid pre-finished surfaces and are designated to be finished in later processing steps.  
         [0049]     A bracket  320  is fixed to the turnaround support  308  at a first end and supports a proximity switch  322  at a second end. The proximity switch  322  senses whether or not an implant  500  is located on the turnaround support  308 .  
         [0050]     Referring now to  FIG. 14 , an alternate embodiment gripper assembly  1000  is shown. The gripper assembly  1000  includes a 90 degree angle bracket  1002  fixed to an end of a robot  100 ′, a gripper  102 ′ fixed to the bracket  1002 , and fingers  110 ′ fixed to the gripper  102 ′. The bracket  1002  includes a first bar  1004  extending perpendicular to an end face  1006  of the robot  100 ′. A second bar  1008  extends perpendicular to the first bar  1004  and is coupled thereto. A corner flange  1010  is provided at the interface of the first and second bars  1004  and  1008  to increase the strength of the connection therebetween.  
         [0051]     The gripper  102 ′ is preferably identical to the gripper  102  of the first embodiment and therefore its description will not be repeated here. The fingers  110 ′ include first and second fingers  110   a ′ and  110   b ′. The fingers  110 ′ slide open and closed under the operation of the gripper  102 ′. Inasmuch as the fingers  110 ′ extend perpendicular to the gripper  102 ′, it is preferably that the first finger  110   a ′ is mounted flush to the gripper  102 ′ while the second finger  110   b ′ is offset from the gripper  102 ′ by at least the width of the first finger  110   a′.    
         [0052]     A guide pin  1012  is fixed to the second finger  110   b ′ and is accommodated by a slot  1014  formed in the first finger  110   a ′. The guide pin  1012  prevents the first and second fingers  110 ′ from becoming offset relative to one another. In other words, the guide pin  1012  keeps the fingers  110 ′ in a preselected orientation relative to one another.  
         [0053]     The first and second fingers  110 ′ include reliefs  1016  which are shaped to complement the clampable surfaces  502 ′ of the knee implant  500 ′. In the illustrated embodiment the knee implant  500 ′ includes pins that are screwed into the implant  500 ′. As such, the reliefs  1016  mirror the shape of the screw heads and shafts. A notch  1018  is provided in the second finger  110   b ′ to allow the second finger  110   b ′ to fit over the clampable surface  502 ′ of the implant  500 ′. Thereafter, the fingers  110 ′ slide outboard to abutingly grip the implant  500 ′ by nesting the clampable pins  502 ′ in the reliefs  1016 .  
         [0054]     From the foregoing description it can be appreciated that tooling for a direct clamp robotic system is provided. The tooling centers around the provision of fingers for a gripping robot that eliminate the need for an implant support bar to be mounted to each implant. By eliminating the bar, more sophisticated trays and implant reorientation stations can also be employed. This provides an important cost savings measure for implant manufacturers.  
         [0055]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.