Patent Publication Number: US-7715947-B2

Title: System for lapping ring and pinion gears

Description:
This application is a continuation of co-pending U.S. patent application Ser. No. 11/440,376 filed May 24, 2006 and entitled “Process For Lapping Ring And Pinion Gears”, now U.S. Pat. No. 7,299,533, the disclosure of which is hereby incorporated by reference as if fully set forth in detail herein. 

   INTRODUCTION 
   The present invention generally relates to manufacturing methods and tooling for the high-volume finishing of gearsets for automotive differentials and more particularly to manufacturing methods and tooling for processing a ring gear and pinion gear through a lapping operation. 
   Modern automotive vehicles typically include a differential for controlling the transmission of drive torque to the driven wheels of the vehicle. The differential can include an input pinion and a ring gear. The input pinion can receive torque from the vehicle transmission or transfer case and can transmit the torque to the ring gear via the meshing teeth of the input pinion and ring gear. The ring gear can be coupled to a differential case, which can house a plurality of pinion gears and a pair of side gears that cooperate to differentiate drive torque between the two side gears. 
   As the input pinion can be driven at relatively high rotational speeds, relatively small variances in the shape of the teeth of the input pinion and/or the ring gear can generate noise and vibration that can be transmitted into the interior of the vehicle. Typically, the input pinion and ring gear are processed through a lapping operation wherein the teeth are micro-finished such that the teeth of one component more exactingly match the teeth of the other component. This matched set of gears is thereafter assembled to a differential. 
   The machine tool for lapping the input pinion and the ring gear includes first and second spindles that are arranged about perpendicular axes. As automotive differentials are commonly produced in high volume, a feed system is typically employed to automate the loading and unloading of the spindles 
   Heretofore, all of the known feed systems for loading input pinions and ring gears into a lapping machine tool employed two gantry-type loaders, wherein a first one of the gantry-type loaders loaded and unloaded ring gears and the other gantry-type loader loaded and unloaded input pinions. As the cycle time for the lapping operation can be relatively long, it is not uncommon for a gantry-type loader to service several lapping machine tools. 
   Gantry-type loaders have been employed to automate the loading and unloading of lapping machine tools due to the relatively small zone that is provided by those machine tools for the loading and unloading operation. This zone appears to permit access to the spindles from only two orthogonal directions: a vertical direction downwardly to the spindles and a horizontal direction into the front of the machine tool. Given considerations for minimizing floor space by the equipment for performing the lapping operation, and as gantry-type loaders can shuttle the input pinions and ring gears in an vertical direction, the horizontal loading direction has largely been ignored and the industry appears to have focused exclusively on gantry-type loaders for performing this operation. 
   While gantry-type loaders can work well for this function, we have noted several drawbacks. For example, a gantry-type loader mandates that the lapping machine tools be arranged in rows. Such arrangements, however, may be difficult to obtain where the arrangement is being fitted into an existing production facility that is relatively full of other equipment. In such cases, it may be necessary to relocate/re-arrange other areas (often times at significant cost) simply to obtain an area that is shaped to accommodate an arrangement that employs gantry-type loaders. 
   Yet another drawback concerns the cost of gantry-type loaders. As will be appreciated, gantry-type loaders are relatively complex and sophisticated pieces of equipment. Consequently, they can be relatively expensive to procure, operate and maintain. Furthermore, as the bulk of the cost of a gantry-type loader is associated with its loading portion rather than its gantry portion, it is typically not cost-effective to employ gantry-type loaders in situations where production volumes are relatively low initially but expected to ramp up over the course of several years (to volumes that readily justify gantry-type loaders). Consequently, while a gantry-type loader can be scaled to a variety of production volumes, it is frequently not possible to justify such automation at relatively low manufacturing volumes. 
   SUMMARY 
   In one form, the present teachings provide a system for lapping gear sets that include a ring gear and a pinion gear. The system includes a lapping machine tool and a robot. The lapping machine tool has a first spindle and a second spindle. The second spindle is rotatable about an axis that is generally perpendicular to a rotational axis of the first spindle. The lapping machine tool has a loading zone for loading the first and second spindles. The robot has an end effector with a first end that is configured to hold one of the gear sets. The robot is configured to position the first end of the end effector into the loading zone and to load the first gear set to the lapping machine tool without removing the end effector from the loading zone such that the ring gear is loaded onto the first spindle and the pinion gear is loaded onto the second spindle. 
   In another form, the present teachings provide a system for lapping gear sets that include a ring gear and a pinion gear. The system includes a robot and an end effector. The robot has an articulating arm with a first arm member and a second arm member that is pivotally coupled to the first arm member. The end effector has a beam portion, a first tooling set and a second tooling set. The beam portion includes a first end and a second end opposite the first end. The beam portion includes a rotational axis that is disposed between the first and second ends. The first tooling set being coupled to the first end of the beam portion and includes a first tooling subset and a second tooling subset. The first tooling subset has a first set of jaws that are arranged about a first gear axis and which are configured to releasably engaging the ring gear of a first one of the gear sets. The second tooling subset has a second set of jaws that are arranged about a second gear axis, which is perpendicular to the first gear axis. The second set of jaws are configured to releasably engage a second gear. The second tooling set is coupled to the second end of the beam portion and is identical to the first tooling set. 
   Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
       FIG. 1  is a schematic illustration of an exemplary facility that is configured for performing a lapping operation in accordance with the teachings of the present disclosure; 
       FIG. 2  is a perspective view of a portion of the facility of  FIG. 1  illustrating a conveyance system and a robot with an end effector in more detail; 
       FIG. 3  is a perspective view of a portion of the conveyance system illustrating a pallet with a pinion and a ring gear in more detail; 
       FIG. 4  is a top plan view of a portion of the facility of  FIG. 1  illustrating a lapping machine tool in more detail; 
       FIG. 5  is a front elevation view of the lapping machine tool; 
       FIG. 6  is an enlarged portion of  FIG. 4  illustrating the ring gear and the pinion gear loaded to the spindles of the lapping machine tool; 
       FIG. 7  is another perspective view of the robot, the end effector and a portion of the conveyance system; 
       FIG. 8  is a top plan view of the robot, the end effector and a portion of the conveyance system; 
       FIG. 9  is a partial side elevation view in partial section of a portion of the facility showing a portion of the robot, the end effector and a portion of the lapping machine tool when a pinion is loaded into/unloaded from an associated spindle of the lapping machine tool; 
       FIG. 10  is a side view of a portion of the end effector, illustrating a portion of the first tooling subset with a ring gear loaded thereto; 
       FIG. 11  is a top plan view of a portion of the end effector illustrating a portion of the second tooling subset with a pinion loaded thereto; 
       FIG. 12  is a top plan view of a portion of the facility of  FIG. 1  illustrating the loading/loading of a pinion to/from an associated spindle; and 
       FIG. 13  is a front view of a portion of the facility of  FIG. 1  illustrating the loading/unloading of a pinion to/from an associated spindle. 
   

   DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS 
   With reference to  FIGS. 1 and 2  of the drawings, an exemplary facility for performing a lapping operation in accordance with the teachings of the present disclosure is generally indicated by reference numeral  10 . The facility  10  can include a conveyance system  20 , a plurality of lapping machine tools  22 , a robot  24  and an end effector  26 . The conveyance system  20  can include a conventionally constructed power-and-free type conveyor system  30  and a plurality of pallets  32 . In so far as the present disclosure is concerned, the conveyance system  20  can be constructed in a conventional and well known manner and as such, need not be discussed in particular detail herein. Briefly, the conveyor system  30  can include a plurality of stations, including a loading station  36 , and can be configured to transport the pallets  32  between the various stations in a desired manner. The power-and-free aspect of the conveyor system  30  can be employed to accumulate pallets  32  at one or more of the station, as well as to hold a pallet  32  in a stationary condition at one or more of the stations (e.g., at the loading station  36 ). 
   With reference to  FIGS. 2 and 3 , the pallet  32  can be configured to transport a gear set  40  that can include a ring gear  42  and a pinion gear  44  of the type that are employed in a differential assembly (not shown) for an automotive vehicle (not shown). The ring gear  42  can have a plurality of gear teeth  46  that are disposed about a rotational axis  48 . The pinion gear  44  can have a plurality of gear teeth  50 , which are disposed about a rotational axis  52 , and a shaft member  54 . The pallet  32  can include a first holder  56  and a second holder  58  that can engage the ring gear  42  and the pinion gear  44 , respectively, to thereby locate the ring gear  42  and the pinion gear  44  in predetermined locations and orientations. In the particular example provided, the first and second holders  56  and  58  are configured to present the ring gear  42  and the pinion gear  44  such that their rotational axes  48  and  52  are parallel one another. 
   With reference to  FIGS. 4 through 6 , the lapping machine tools  22  can be any type of lapping machine, such as a L50 lapping machine tool that is commercially available from Oerlikon Geartec AG. As the lapping machine tools  22  can be conventionally constructed, a detailed discussion of the lapping machine tools  22  need not be provided herein. Briefly, each lapping machine tool  22  can include a frame  60 , a first spindle  62 , a second spindle  64  and a shroud  66 . The frame  60  can be a structure that supports the first and second spindles  62  and  64 . The first spindle  62  can have a first rotational axis  68 , while the second spindle  64  can have a second rotational axis  70  that can be perpendicular to the first rotational axis  68 . The shroud  66  can be movably coupled to the frame  60  and can translate between a first position, which clears the first and second spindles  62  and  64  to permit gears to be loaded to or unloaded from the lapping machine tool  22 , and a second position, which shrouds the first and second spindles  62  and  64  when the lapping operation is to be performed. 
   Each lapping machine tool  22  can have a loading zone  72  which may be employed to load gears into and unload gears from the lapping machine tool  22 . In the example provided, the loading zone  72  is defined by the shape and construction of the frame  60  as well as by the amount by which the shroud  66  may translate relative to the first and second spindles  62  and  64 . The dimensions of the loading zone  72  can be about 1000 mm wide×about 1000 mm tall×about 1000 mm deep. In the particular example provided, the dimensions of the loading zone are about 600 mm wide×700 mm tall×about 800 mm deep. 
   Returning to  FIG. 2  and with additional reference to  FIGS. 7 and 8 , the robot  24  can be any type commercially-available industrial robot having an articulating arm configuration, such as a Nachi 166L Robot manufactured by Nachi Robotic Systems, Inc., of Novi, Mich. In the example provided, the robot  24  includes a base  80 , a first arm  82 , a second arm  84 , a knuckle  84  and a rotary coupling  88 . The base  80  can be rotatable about a generally vertical axis  90 . The first arm  82  can be pivotally coupled to the base  80  and can be movable in a vertical plane that includes the vertical axis  90 . The second arm  84  can be pivotally coupled to an end of the first arm  82  opposite the base  80  and can be movable in the aforementioned vertical plane. The knuckle  84  can include a first knuckle portion  92  and a second knuckle portion  94 . The first knuckle portion  92  can be coupled to an end of the second arm  84  opposite the first arm  82  and can be rotatable about the longitudinal axis of the second arm  84 . The second knuckle portion  94  is pivotally coupled to the first knuckle portion  92  and can be pivoted in a plane that includes the longitudinal axis of the second arm  84 . The rotary coupling  88  can have a first coupling portion  96  and a second coupling portion  98 . The first coupling portion  96  can be fixedly coupled to an end of the second knuckle portion  94  opposite the first knuckle portion  92 , while the second coupling portion  98  can be rotatably coupled to the first coupling portion  96  so as to be rotatable about a longitudinal axis  100  of the rotary coupling  88 . 
   With reference to  FIG. 9 , the end effector  26  can include a beam portion  120  and first and second tooling sets  122  and  124  that are coupled to opposite ends  126  and  128  of the beam portion  120 . The beam portion  120  can fixedly but removably coupled to the second coupling portion  98 . As the first and second tooling sets  122  and  124  can be identically configured, only the first tooling set  122  will be described in detail herein. The first tooling set  122  can include a first tooling subset  130  and a second tooling subset  132 . 
   With reference to  FIGS. 9 and 10 , the first tooling subset  130  can include a first concentric gripper  140  and a first thrust assembly  142 . The first concentric gripper  140  can include a commercially available first gripper module  144 , such as a Robohand 3 jaw gripper manufactured by Robohand Inc., of Monroe, Conn., and a plurality of first jaws  146 . The first gripper module  144  can be coupled to the first end  126  of the beam portion  120 . The first jaws  146  can be coupled to the first gripper module  144  and arranged about a first tooling axis  150  (those of ordinary skill in the art will appreciate that the first jaws  146  are only partially shown in  FIGS. 10 and 13  for purposes of clarity). The first gripper module  144  can be employed to translate the first jaws  146  so that they may grasp and release the ring gear  42 . In the particular example provided, the first gripper module  144  translates the first jaws  146  radially inwardly and outwardly relative to the first tooling axis  150  to grasp and release the ring gear  42 . 
   The first thrust assembly  142  can include a cylinder assembly  154  and a thrust plate  156 . The cylinder assembly  154  can include a fluid-powered cylinder  158  (e.g., a hydraulic or pneumatic cylinder) with a rod  160  that can be translated along the first tooling axis  150 . In the particular example provided, the cylinder assembly  154  is mounted to the first end  126  of the beam portion  120  and the rod  160  is received through the first gripper module  144 . The thrust plate  156  can be coupled to the rod  160  and can be located between the beam portion  120  and the portion of the first jaws  146  that contacts the ring gear  42 . 
   With reference to  FIGS. 9 and 11 , the second tooling subset  132  can include can include a second concentric gripper  180  and a second thrust assembly  182 . The second concentric gripper  180  can include a commercially available second gripper module  184 , such as a Robohand Parallel Gripper manufactured by Robohand Inc., of Monroe, Conn., and a plurality of second jaws  186 . The second gripper module  184  can be coupled to the first end  126  of the beam portion  120  and the second jaws  186  can be coupled to the second gripper module  184  and arranged about a second tooling axis  188  that is generally perpendicular to the first tooling axis  150  ( FIG. 10 ). The second gripper module  184  can be employed to translate the second jaws  186  so that they may grasp and release the pinion gear  44 . In the particular example provided, each second jaw  186  has a generally U-shaped end  190  that may translate inwardly around the shaft member  54  of the pinion gear  44  and abut a rear-facing surface  192  of a portion of the pinion gear  44  on which the gear teeth  50  are formed. 
   The second thrust assembly  182  can be mounted to the second concentric gripper  180  and can include a thrust member  198  that is configured to urge the pinion gear  44  against the U-shaped ends  190  of the second jaws  186  and optionally to aid in positioning the pinion gear  44  relative to the second tooling axis  188 . In the particular example provided, the thrust member  198  is a pin having a conical surface  200  that is configured to matingly engage a conical recess  202  that is formed in the pinion gear  44  (e.g., via a center drill). A fluid-powered (e.g., hydraulic or pneumatic) cylinder (not shown) may be employed to move the thrust member  198  along the second tooling axis  188 , but in the particular example provided, a compression spring  206  is employed to bias the thrust member  198  toward the second jaws  186 . 
   With reference to  FIG. 12 , the second tooling set  124  can be identical to the first tooling set  122  as noted above and as such, need not be described in detail herein. Briefly, the first jaws  146  of the first tooling subset  130  of the second tooling set  124  can be disposed about a tooling axis  150   a , while the second jaws  186  of the second tooling subset  132  of the second tooling set  124  can be disposed about a tooling axis  188   a . It will be appreciated, however, that the second tooling set  124  will be coupled to the second end  128  of the beam portion  120  in a manner that is mirrored the rotational (longitudinal) axis  100  of the rotary coupling  88  about a first mirror plane, which is parallel to the first tooling axis  150  and a second mirror plane, which is parallel to the second tooling axis  188 . Stated another way, the first tooling subset  130  of the second tooling set  124  is located on a side of the beam portion  120  opposite the side on which the first tooling subset  130  of the first tooling set  122  is located, and the second tooling subset  132  of the second tooling set  124  is located on a side of the beam portion  120  opposite the side on which the second tooling subset  132  of the first tooling set  122  is located. In this way, the first and second tooling subsets  130  and  132  of the first and second tooling sets  122  and  124  can be presented to the lapping machine tool  22  in a consistent manner when the end effector  26  is rotated about the rotational (longitudinal) axis  100  of the rotary coupling  88 . 
   With reference to  FIGS. 2 ,  12  and  13 , the facility  10  can be operated such that a first gear set  40  can be transported on a pallet  32  to the loading station  36  and the robot  24  can be employed to load the first gear set  40  into the first tooling set  122  on the first end  126  of the end effector  26 . In the particular example provided, the ring gear  42  is unloaded from the pallet  32  prior to the pinion gear  44 , but it will be appreciated that this order may be reversed. 
   Loading of the ring gear  42  to the first end  126  of the end effector  26  can include aligning the robot  24  and the end effector  26  to the ring gear  42  such that the first tooling axis  150  is generally parallel to, and preferably conincident with, the axis  48  of the ring gear  42 ; lowering the end effector  26  onto the ring gear  42 ; actuating the first concentric gripper  140  to clamp the first jaws  146  to the ring gear  42  to thereby hold the ring gear  42  such that its rotational axis  48  is coincident with the first tooling axis  150 ; and lifting the ring gear  42  from the pallet  32  in a direction that is parallel to the rotational axis  48  of the ring gear  42 . 
   Loading of the pinion gear  44  to the first end  126  of the end effector  26  can include aligning the robot  24  and the end effector  26  to the pinion gear  44  such that the second tooling axis  188  is generally parallel to, and preferably conincident with, the axis  52  of the pinion gear; lowering the end effector  26  onto the pinion gear  44  such that the conical surface  200  ( FIG. 11 ) of the thrust member  198  engages the conical recess  202  ( FIG. 11 ) in the pinion gear  44  and moves the thrust member  198  ( FIG. 11 ) rearwardly toward the beam portion  120  of the end effector  26 ; actuating the second concentric gripper  180  to clamp the second jaws about the pinion gear  44 ; and lifting the pinion gear  44  from the pallet  32  in a direction that is parallel to the rotational axis  52  of the pinion gear  44 . 
   From the foregoing discussion of the first and second tooling subsets  130  and  132 , it will be appreciated that the ring gear  42  and the pinion gear  44  are releasably coupled to the first end  126  of the beam portion  120  such that the axis  48  of the ring gear  42  is generally perpendicular to the axis  52  of the pinion gear  44 . 
   The robot  24  and the end effector  26  can be operated to place the second end  128  of the end effector  26  into the loading zone  72  of the lapping machine tool  22 . The second end  128  of the end effector  26  can be employed to remove a second gear set  40   a  (which has undergone the lapping operation) from the lapping machine tool  22  without removing the second end  128  of the end effector  26  from the loading zone  72 . More specifically, the second end  128  of the end effector  26  can be employed to remove a ring gear  42   a  from the first spindle  62  and a pinion gear  44   a  from the second spindle  64 . In the particular example provided, the ring gear  42   a  is removed from the first spindle  62  prior to the removal of the pinion gear  44   a  from the second spindle  64 , but it will be appreciated that this order may be reversed. 
   Unloading of the ring gear  42   a  from the first spindle  62  to the second end  128  of the end effector  26  can include aligning the robot  24  and the end effector  26  to the ring gear  42   a  such that the first tooling axis  150  is generally parallel to and preferably coincident with the axis  48   a  of the ring gear  42   a  and the first rotational axis  68  of the first spindle  62 ; translating the end effector  26  onto the ring gear  42   a ; actuating the first concentric gripper  140  to clamp the first jaws  146  to the ring gear  42   a  to thereby hold the ring gear  42   a  such that its rotational axis  48   a  is parallel to and preferably coincident with the first tooling axis  150   a ; and translating the ring gear  42   a  away from the first spindle  62  in a direction that is parallel to the first rotational axis  68  of the first spindle  62 . Unloading of the pinion gear  44   a  from the second spindle  64  to the second end  128  of the end effector  26  can include aligning the robot  24  and the end effector  26  to the pinion gear  44   a  and the second spindle  64  such that the second tooling axis  188   a  is generally parallel to and preferably coincident with the axis  52   a  of the pinion gear  44   a  and the second rotational axis  70 ; moving the end effector  26  onto the pinion gear  44   a  such that the conical surface  200  ( FIG. 11 ) of the thrust member  198  engages the conical recess  202  ( FIG. 11 ) in the pinion gear  44   a  and moves the thrust member  198  rearwardly toward the beam portion  120  of the end effector  26 ; actuating the second concentric gripper  180  to clamp the second jaws about the pinion gear  44   a ; and moving the pinion gear  44   a  from the second spindle  64  in a direction that is parallel to the second rotational axis  70 . 
   The robot  24  can move the end effector  26  out of the loading zone  72 , reposition the end effector  26  and move the first end  126  of the end effector  26  into the loading zone  72 . In the example provided, the end effector  26  is lifted vertically out of the loading zone  72 , the robot  24  and the end effector  26  are oriented such that the rotational axis  100  of the rotary coupling  88  is disposed in a vertical orientation, the end effector  26  is rotated 180°, the robot  24  and the end effector  26  are oriented such that the beam portion  120  of the end effector  26  is arranged vertically with the second end  128  below the first end  126  and the end effector  26  is lowered vertically into the loading zone  72  where the gear set  40  can be loaded to the first and second spindles  62  and  64  (so that the lapping operation may be performed) without removing the first end  126  of the end effector  26  from the loading zone  72 . In the example provided, the pinion gear  44  can be loaded to the second spindle  64  prior to the loading of the ring gear  42  to the first spindle  62 , but it will be appreciated that this order could be reversed. 
   Loading of the pinion gear  44  from the first end  126  of the end effector  26  to the second spindle  64  can include aligning the robot  24  and the end effector  26  to the second spindle  64  such that the second tooling axis  188  and the axis  52  of the pinion gear  44  are generally parallel to and preferably coincident with the second rotational axis  70 ; moving the end effector  26  such that the shaft member  54  of the pinion gear  44  is received into the second spindle  64 ; actuating the second concentric gripper  180  to unclamp the second jaws  186  from the pinion gear  44  to thereby cause the thrust member  198  to urge the pinion gear  44  into the second spindle  64 ; and moving the first end  126  of the end effector  26  in a direction that is parallel to the second rotational axis  70 . 
   Loading of the ring gear  42  from the first end  126  of the end effector  26  to the first spindle  62  can include aligning the robot  24  and the end effector  26  to the first spindle  62  such that the first tooling axis  150  and the rotational axis  48  of the ring gear  42  are generally parallel to and preferably coincident with the first rotational axis  68  of the first spindle  62 ; moving the end effector  26  such that the ring gear  42  is received onto the first spindle  62 ; actuating the first concentric gripper  140  to unclamp the first jaws  146  from the ring gear  42 ; actuating the cylinder assembly  154  to extend the rod  160  to cause the thrust plate  156  to push against the ring gear  42  to seat the ring gear  42  on the first spindle  62  so that the ring gear  42  is abutted against a shoulder  250  that is formed on the first spindle  62 ; actuating the cylinder assembly  154  to retract the rod  160 ; and moving the first end  126  of the end effector  26  in a direction that is generally parallel to the first rotational axis  68  of the first spindle  62 . 
   With the gear set  40  loaded to the first and second spindles  62  and  64 , the robot  24  can withdraw the end effector  26  from the loading zone  72  and can manipulate the end effector  26  relative to another pallet  32   b  at the loading station  36  to load a third gear set  40   b  from the pallet  32   b  to the first end  126  of the end effector  26 . As the loading of gear sets from a pallet to the end effector has been discussed in detail above, a discussion of this portion of the methodology need not be provided herein. It will suffice to say that an untapped gear set can be loaded from the pallet  32   b  to the first end  126  of the end effector  26  to thereby provide spaces on the pallet  32   b  for the receipt of the lapped gear set that is held by the second end  128  of the end effector  26 . In the example provided, the ring gear  42   a  is unloaded from the second end  128  of the end effector  26  to the pallet  32   b  prior to the unloading of the pinion gear  44   a.    
   Loading of the ring gear  42   a  from the first end  126  of the end effector  26  to the pallet  32  can include aligning the robot  24  and the end effector  26  to a predetermined second location on the pallet  32 ; lowering the ring gear  42   a  to the second predetermined location on the pallet  32  in a direction that is parallel to the rotational axis  48  of the ring gear  42   a ; actuating the first concentric gripper  140  to unclamp the first jaws  146  from the ring gear  42   a ; and withdrawing the end effector  26  from the ring gear  42   a.    
   Loading of the pinion gear  44   a  from the second end  128  of the end effector  26  to the pallet  32  can include aligning the robot  24  and the end effector  26  to a predetermined location on the pallet  32 ; lowering the pinion gear  44   a  to the predetermined location on the pallet  32  in a direction that is parallel to the rotational axis  52  of the pinion gear  44   a ; actuating the second concentric gripper  180  to unclamp the second jaws from the pinion gear  44   a ; and withdrawing the end effector  26  from the pinion gear  44   a.    
   While specific examples have been described in the specification and illustrated in the drawings, it will be understood by those of ordinary skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure as defined in the claims. Furthermore, the mixing and matching of features, elements and/or functions between various examples is expressly contemplated herein so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one example may be incorporated into another example as appropriate, unless described otherwise, above. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular examples illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the scope of the present disclosure will include any embodiments falling within the foregoing description and the appended claims.