Abstract:
A dispensing apparatus is disclosed which includes a support assembly for defining at least one dispensing location. A storage container is secured to the support assembly for holding a plurality of stackable objects. These stackable objects may include shims, washers, gaskets and seals. An escapement is operably associated with the support assembly. The escapement is operable for moving between a first position and a second position for transporting at least one of the stackable objects from the storage container to an external access location. The escapement may also be designed to be easily operated by a robot or robot actuated apparatus.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a divisional application of U.S. patent application Ser. No. 08/961,591, filed Oct. 31, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates generally to a dispensing apparatus and more particularly to a robot-actuated dispensing station for dispensing a variety of similarly dimensioned objects. 
     2. Discussion 
     The implementation of robots to automate various manufacturing processes has dramatically increased in an effort to reduce the labor and production costs associated with these processes. Robots now perform many of the more hazardous and highly repetitive operations in the manufacturing process. These operations include dispensing, deburring, grinding, polishing, painting, finish coating, cutting and welding. Robots are capable of achieving even greater efficiency when several of these operations are combined at a single workstation. For example, providing a robot with welding and grinding tools allows a single robot to first weld the workpiece, and then grind the workpiece as necessary at a single workstation. For even greater efficiency, the same robot may be equipped with an optical system for finally inspecting the quality of the finished weldment. Robots may also be used to assemble various components, measure or inspect the tolerances of these components, and finally perform any necessary adjustments to the subassembly for completing the requisite operations. 
     An exemplary implementation of robots for automating an assembly operation is the assembly of the components associated with an automobile rear end axle. Conventional assembly techniques require that a shim or adjusting washer be placed on the pinion stem between the pinion gear and the pinion&#39;s conical bearing. A shim of the correct thickness must support the pinion gear on the inner race of the conical bearing for properly positioning the pinion gear within the rear axle housing. 
     In an exemplary assembly process, a partially assembled rear axle housing travels along a palletized conveyor and enters an assembly and gaging station. The parts to be assembled are contained on the pallet. A robot located within the workstation places the conical bearing upon the gage head. At this point, no shim is present between the gage head and conical bearing. As the robot moves away from the subassembly, a gaging mechanism is lowered onto the conical bearing for measuring the various tolerances associated with the subassembly. At this point, the gaging station is capable of calculating the proper thickness shim which must be placed between the pinion gear and conical bearing. As this occurs, the gaging mechanism is lifted away from the subassembly and a call for a particular shim is sent to the robot&#39;s controller. The robot then moves to a static dispensing station located in the cell and selects the correct size shim. 
     The robot presents the shim to the automated verifier. If this thickness is correct, or within accepted tolerance levels, the robot selects the verified shim and places the shim on the pinion stem. The robot removes the conical bearing from the gage head and sets the conical bearing on the pinion stem and moves away from the subassembly. If the tolerances are within the acceptable range, the gaging mechanism is lifted away and the pallet moves toward the next workstation. If the tolerances are unacceptable, the pallet can be rejected, or the components disassembled so that the assembly process can again be cycled. 
     The conventional technique for supplying the robot with the correct thickness shim was to locate a motorized and automated dispensing apparatus within the workstation. The conventional dispensing apparatus utilized a round, rotary table having a plurality of storage tubes mounted at the perimeter. Each storage tube was then filled with a stack of shims having the same thickness. Rotation of the table was controlled by a programmable servo-driven gear box for rotating the table to align the proper storage tube over a fixed position powered escapement. Once the proper tube was correctly aligned, the powered escapement was actuated for dispensing the shim into a shim thickness verifier. After measuring and verifying the correct shim thickness, the robot could select the shim from the verifier and place it onto the subassembly. This conventional design was based upon many tubes which were actuated by a single powered escapement. 
     While this conventional technique for dispensing similarly dimensioned parts automates the dispensing process, this automated technique also duplicates several of the functions which can be performed by the robot for achieving greater efficiency. In addition to the expense associated with the electronically controlled robot, the rotary indexing table also requires expensive electronic equipment and control systems for powering and automating the rotary table. Further, the conventional rotary table shim dispensers utilize a single universal escapement which must be capable of accommodating all sizes of shims. Such a design can lead to jamming of the shims within the escapement, which requires intervention by an operator, and may lead to assembly line shutdown. Further, cycle time associated with a rotary table varies from cycle to cycle, and is dependent upon the distance the table must rotate. Accordingly, an assembly process dependent upon a rotary dispensing table must be designed to operate at the longest cycle time, rather than upon a constant cycle time. An additional disadvantage is that when a wide range of different sized shims must be dispensed, the rotary table circumference increases and requires a large area of the manufacturing floor. Adding a second table increases floor space demands and doubles the cost for equipment. Finally, the robotic manufacturing cell and rotary table must be shut down in order to restock the storage containers with a new supply of shims. All of these factors significantly increase the cost associated with the manufacturing cell and automated dispensing apparatus. These considerations also contribute to the reliability of the apparatus, and the skill level of the operator required for maintaining the automated dispensing apparatus. 
     Accordingly, it is desirable to provide a dispensing station which can overcome the complexity and cost problems associated with conventional shim dispensing stations and maximizes the use of the robot&#39;s features. It is also desirable to provide a low cost shim dispensing station which eliminates the need for powered components, and does not require wires, switches, or other manufacturing facility utilities. Such a device would eliminate the need to have air hoses, steam lines, and multiple electrical lines brought into the manufacturing cell to power the dispensing station. Further, it is desirable to provide a dispensing station which can be refilled with components without shutting off the power, or interrupting the production line. As the cycle times within the manufacturing cell are an increasing concern, it is desirable to provide a dispensing station for reducing the cycle time required to dispense the individual components. Further, it is desirable to provide a dispensing station which can dispense more components using less floor space. Finally, it is desirable to provide a dispensing station having individual escapements which can be custom sized to accommodate the part or shim that is stored in that escapement&#39;s storage container. 
     SUMMARY OF THE INVENTION 
     Pursuant to the present invention, a dispensing apparatus is disclosed which overcomes many of the disadvantages associated with conventional dispensing stations. The dispensing apparatus of the present invention includes a support assembly for defining at least one dispensing location. A storage container is secured to the support assembly for holding a plurality of stackable objects. These stackable objects may include, but are not limited to shims, washers, gaskets, seals and bearings. An escapement is supported by the support assembly. The escapement is operable for moving between a first position and a second position for transporting at least one of the stackable objects from the storage container to an external access location. In the preferred embodiment, the escapement is actuated between the first and second positions by a multi-axis robot. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional objects, advantages, and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a side elevation view of the dispensing station according to the preferred embodiment of the present invention shown in association with a robot based manufacturing and gaging station; 
     FIG. 2 is a top plan view of the dispensing station having two rows of storage containers and dispensing ports according to one preferred embodiment of the present invention; 
     FIG. 3 is a side elevation view of the dispensing station according to a second preferred embodiment of the present invention; 
     FIG. 4 is an enlarged side elevation view showing a section of the dispensing station and its guiding assembly according to a preferred embodiment of the present invention; 
     FIG. 5 is an exploded front elevation view of one dispensing location of the dispensing apparatus according to a preferred embodiment of the present invention; 
     FIG. 6 is a top plan view of the escapement associated with the dispensing station of the present invention; 
     FIG. 7 is a front elevation view of the escapement associated with the dispensing station of the present invention; and 
     FIG. 8 is a top plan view of the robotic gripping apparatus for use in conjunction with the dispensing station according to a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its applications or uses. 
     The present invention is directed to a simplified and low cost dispensing station which serves to reduce cycle times, and which may be actuated by a robot. Referring now to FIG. 1, the manufacturing environment which is supported by the dispensing apparatus of the present invention is illustrated. More particularly, the preferred manufacturing environment is robot based manufacturing cell  10  for assembling and gaging the pinion gear subassembly associated with the rear axle housing of an automobile. Robot based manufacturing cell  10  operates in conjunction with a palletized conveyor system  12  along which the various components of the rear axle housing travel. Positioned above palletized conveyor system  12  is a gaging station  14  which is capable of measuring the tolerances associated with the pinion gear subassembly under a variety of simulated load conditions. The rear end components  16  contained on a pallet are transported into gaging station  14  where the various assembly and measuring operations are performed. As disclosed, gaging station  14  is an automated machine that works in conjunction with a multi-axis robot  18  for completing the requisite operations. 
     In keeping with the conventional techniques for assembling an automotive rear axle housing, a shim of the correct thickness must be placed between the pinion gear and the conical bearing for aligning the pinion gear within the rear axle housing. The goal of robot based manufacturing cell  10  is to quickly and efficiently measure for the correct thickness shim, and place this shim onto the pinion gear stem using a low cost automated process. In the preferred embodiment, a pair of nearly identical dispensing stations  20 ,  21  in accordance with the teachings of the present invention are provided for storing and dispensing the full range of shims required in the assembly process. As will be appreciated, dispensing stations  20 ,  21  are mechanical devices with no automated or powered controls. Thus, each dispensing station  20 ,  21  must be manually actuated, preferably by a multi-axis robot  18 , which is provided with a multi-function robotic gripping apparatus  22 . 
     In this exemplary assembly process, robot  18  removes a shim from one of the dispensing locations  30  associated with dispensing station  20  using the gripping arm  22  and places the shim on the stem of the pinion gear. The robot  18  then grabs the conical bearing from the pallet and places the conical bearing onto the pinion stem and moves away. Gaging station  14  then measures the tolerances associated with this subassembly. During this measurement operation, robot  18  moves back toward dispensing station  20  and actuates the escapement  50  (FIG. 3) of the dispensing location  30  from which the shim was just removed for dispensing or indexing a new shim for refilling that dispensing location  30 . 
     If the measurements produced by gaging station  14  fall within an acceptable tolerance range, the pallet and components  16  are transported by conveyor system  12  to the next workstation. In this preferred manufacturing process, 29 different shims can be accessed by robot  18  for completing the pinion gear subassembly. As such, 29 different dispensing locations are required for dispensing these shims. As seen in FIG. 1, these 29 separate dispensing locations are provided by two dispensing stations  20 ,  21  which are preferably offset from each other by 45°. Each dispensing station  20 ,  21  is essentially identical to the other. However, in one preferred embodiment, one of the dispensing locations  30  of dispensing station  20  is replaced with a shim thickness verification device  110  (FIG.  2 ). According to this preferred embodiment, dispensing station  20  includes fourteen (14) separate dispensing locations  30  (FIG.  2 ), and dispensing station  21  includes fifteen (15) separate dispensing locations  30  (not shown). Each dispensing station  20 ,  21  is positioned within robot based manufacturing cell  10  so that robot  18  can efficiently access each of the dispensing locations  30 . 
     With reference now to FIGS. 1 and 2, the components associated with dispensing station  20  are described in more detail. However, as will be appreciated, the following description also applies to dispensing station  21 . As disclosed, dispensing station  20  includes an upper dispensing block  24  which is positioned above and forward of a lower dispensing block  26 . FIG. 1 illustrates robot  18  accessing one of the dispensing locations  30  located in the lower dispensing block  26 . The upper dispensing block  24  is supported by a connecting bracket  28  which is interconnected to the supporting structure of the dispensing station  20 . Connecting bracket  28  provides the requisite clearance so that gripping apparatus  22  is capable of reaching underneath upper dispensing block  24  for accessing lower dispensing block  26 . The lower dispensing block  26  is secured to a mounting plate  32  supported by mounting post  34  (FIG.  1 ). A base plate  36  is bolted to the manufacturing floor and rigidly supports mounting post  34 . A reinforcing bracket  38  (FIG. 1) welded between mounting post  34  and base plate  36  provides additional support for the dispensing station  20 . 
     FIG. 2 illustrates a top view of one preferred embodiment of dispensing station  20  which includes fourteen (14) separate dispensing locations  30 , each dispensing a different sized shim  96 . However, one skilled in the art will appreciate that dispensing station  20  is not limited to dispensing shims, and may be modified to dispense a variety of stackable objects without departing from the scope of the present invention. Each dispensing location  30  includes a manually actuated escapement  50  which dispenses and supports a shim  96 . A shim thickness verifier  110  is provided at the right side of upper dispensing block  24 . In comparison, dispensing station  21  is provided with a fifteenth dispensing location  30  (not shown) in place of shim verifier  110 . Although this alternate embodiment of dispensing station  21  is not specifically shown, one skilled in the art will readily appreciate that the number of dispensing locations  30  can be increased or decreased without deviating from the scope of the present invention. 
     The individual sized shims  96  are stacked within separate storage containers  90  mounted to the top surface of upper and lower dispensing blocks  24 ,  26 . A significant benefit provided by dispensing station  20  is that the operator may restock each storage container  90  with additional components from the back side of dispensing station  20 . As such, the manufacturing cell  10  does not have to be shut down to restock each dispensing station  20 . Further, the operator may safely restock each storage container  90  from the back side without entering the area of operation of the robot  18 . 
     Turning now to FIGS. 3 through 7, the components associated with each dispensing location  30  are illustrated in more detail. Each dispensing block  24 ,  26  is defined by a lower plate  40  having an upper plate  42  bolted thereto. Lower plate  40  includes a series of threaded apertures into which threaded studs  44  are secured. Each threaded stud  44  is provided with a spacer  48  having a uniform height. Upper plate  42  is provided with a series of smooth bores for receiving the top portion of each threaded stud  44 . Each threaded stud  44  is then provided with a washer  45  and retaining nut  46  which secures the upper plate  42  in parallel alignment with the lower plate  40 . 
     Each dispensing location  30  is defined by an escapement  50  which is disposed between the lower and upper plates  40 ,  42 . Each escapement  50  is moveable between a forward position, best shown in FIG. 3, and a rearward position, best shown in FIG.  4 . Escapement  50  normally remains in the forward position so that shim  96  is accessible to the robotic gripping apparatus  22 . After the shim  96  is removed from dispensing location  30 , the escapement  50  may be moved or actuated into the rearward position (FIG. 4) for acquiring a new shim  96  from the storage container  90 , and then moved back into the forward position for transporting the shim  96  to the dispensing location  30 . 
     To accomplish the dispensing of individual shims, each escapement  50  is provided with a recess  52  within its top surface. The depth of each recess  52  is selected to best accommodate the thickness of the particular shim  96  dispensed by that particular escapement  50 . While it is preferred that recess  52  take on an arcuate shape for dispensing arcuate shims, recess  52  can be formed to accommodate a variety of objects for dispensing. Each escapement  50  is also provided with a cut-out portion  54  for exposing the forward portion of each shim  96 , and facilitate the selection of the shim from recess  52  by the gripping arm  22 . Each escapement  50  is also provided with a forward tab  56  having an aperture  58  bored therethrough. Forward tab  56  provides a location for the gripping apparatus  22  to grasp and actuate the escapement  50 . Aperture  58  allows light from a fiber optic sensor associated with gripping apparatus  22  to pass therethrough. As such, the gripping apparatus  22  can determine if escapement  50  is correctly positioned within dispensing station  20 . 
     The underside of each escapement  50  is provided with an elongated slot  60  having a forward stopping end  62  and a rearward stopping end  64 . Preferably, stopping ends  62 ,  64  are rounded. Elongated slot  60  works in conjunction with a guiding assembly  70  for defining the stroke or range of travel of the escapement  50 . Guiding assembly  70  includes a forward roller and threaded stud assembly  72 , and a rearward roller and threaded stud assembly  76 . Forward roller  72  is secured to lower plate  40  with fastener  74 , and rearward roller  76  is secured to lower plate  40  with fastener  78 . The forward and rearward rollers  72 ,  76  are disposed within the elongated slot  60  of each escapement  50 . As can be appreciated, guiding assembly  70  works in conjunction with elongated slot  60  for guiding escapement  50  between its forward and rearward positions. The engagement of rearward stopping end  64  with rearward roller  76  defines the forward position of escapement  50 . Likewise, the engagement of forward stopping end  62  with forward roller  72  defines the rearward position for escapement  50 . As disclosed, forward and rearward rollers  72 ,  76  are preferably a roller bearing assembly in which the inner race (not shown) is rigidly secured to the threaded stud portion, and the outer roller functions as a cam mechanism for rollingly guiding the escapement  50  via elongated slot  60 . Accordingly, elongated slot  60  acts as a follower. 
     With specific reference to FIGS. 4 and 5, the circular apertures  80  which are machined into upper plate  42  for further defining each dispensing location  30  are described in more detail. Each circular aperture  80  includes a first retaining aperture  82  which is straight bored through approximately one half the thickness of upper plate  42 . A second tapered aperture  84  is milled within the intermediate thickness of upper plate  42 , and a third aperture  88  having the smallest diameter is bored through the lower portion of upper plate  42 . The milled portion between the first retaining aperture  82  and second tapered aperture  84  defines a shoulder portion  86  for supporting the lower end of the storage container  90 . As best viewed in FIG. 4, the tapered circumference of second tapered aperture  84  serves to guide each shim  96  through the transition from the storage container  90  into the third aperture  88 , and into recess  52  of each escapement  50 . This unique feature serves to prevent any binding of the shims as they move downwardly for dispensing by the escapement  50 . 
     Each storage container  90  is secured within its retaining aperture  82  by a pair of retaining plates  100 . The design of storage containers  90  and retaining plates  100  also facilitates the easy removal of each storage container  90 . The storage containers  90  are provided with a pair of retaining grooves  92  milled into opposing sides. A pair of locating pins  98  (FIGS. 2,  5 ) are located on each side of the circular apertures  80 . A threaded aperture  99  is located directly behind each locating pin  98 . Each retaining plate  100  includes a U-shaped channel  102  (FIGS. 2,  5 ) in its forward end for alignment with locating pin  98 , and an aperture  104  (FIG. 2) located in its rearward end for alignment with threaded aperture  99  formed in upper plate  42 . Each storage container  90  is mounted to upper plate  42  by inserting the lower end into first retaining aperture  82 . The pair of retaining plates  100  are inserted into retaining grooves  92  and moved forwardly so that locating pin  98  fully engages U-shaped channel  102 . A threaded fastener  106  is inserted through aperture  104  of each retaining plate  100  and into threaded aperture  99  for rigidly securing the retaining plate  100  and thus the storage container  90  to upper plate  42 . 
     The storage containers  90  also include a pair of opposing cut-away portions  94  which allow the quantity of shims  96  held within the storage container  90  to be viewed by the operator, and also allow a fiber optic detection system associated with gripping arm  22  to automatically verify the presence of shims. Optionally, a part ID plate  112  (FIG. 2) can be affixed to the top surface of upper plate  42  in the area directly behind each storage container  90  for identifying the thickness of the shims to be held in that particular storage container  90 . 
     Turning now to FIG. 8, the robotic gripping apparatus  22  which is suitable for use with the dispensing station  20  of the present invention is illustrated. The sixth axis of robot  18  is secured to an actuating motor housing  122 . A pair of opposing gripping arms  124  are mounted through opposite sides of the actuating motor housing  122 . Each gripping arm  124  is provided with a gripping tip  126  having a fiber optic cable  128  disposed through a central portion thereof. Gripping tips  126  provide several functions to gripping apparatus  22 . As disclosed, gripping tips  126  are formed from a softer plastic or rubber composition for providing a shim carrier  130  when the gripping tips  126  are moved together. The central core of each gripping tip  126  acts as an optical sensor. More specifically, a shim which is properly disposed between gripping tips  126  will break the fiber optic light beam traveling through fiber optic cable  128 . As such, the robot&#39;s controller can determine the presence of a properly located shim  96 . Likewise, when gripping tips  126  grasp aperture  58  of forward tab  56 , thus allowing light traveling within fiber optic table  128  to pass therethrough, the robot&#39;s controller can determine whether the escapement  50  is located in its proper position prior to grasping forward tab  56  and actuating the escapement  50 . Finally, gripping apparatus  22  is provided with a conical bearing carrier  132  for grasping the bearing and placing the bearing upon the pinion stem as described above. 
     With reference now to all of the Figures, the preferred operation of dispensing station  20  is described. While an exemplary manufacturing environment which utilizes the preferred embodiment of dispensing station or stations  20  has been described, one skilled in the art will appreciate that dispensing station  20  is not limited to dispensing annular shims  96 . It can further be appreciated that the dimensions of escapement  50  and storage container  90  can be varied to accommodate a wide variety of stackable objects without deviating from the scope of the present invention. Such objects may include, but are not limited to, metallic or non-metallic disks, washers, seals, gaskets, bearings, as well as any other type of similarly dimensioned components. 
     The preferred mode of operation for dispensing station  20  is to fully stock each storage container  90  with a quantity of shims  96 . Prior to the commencement of assembly operations within robot based manufacturing cell  10 , either the cell operator or the robot  18  can verify that a shim  96  is located within recess  52  at each dispensing location  30 , and that each escapement  50  is properly located in the forward position. The fiber optic inspection system associated with fiber optic cable  128  provides an exemplary sensor for making such a preliminary inspection. During the assembly operations within robot based manufacturing cell  10 , gaging station  14  will provide the robot controller with the required shim thickness information. 
     Upon receiving this information, robot  18  moves to the proper dispensing location  30  and withdraws the shim  96  from recess  52 . Once the fiber optic system within gripping tips  126  senses the presence of a shim, the shim is moved into shim verifier  110  to verify that the correct thickness shim has been dispensed. If the shim  96  passes this tolerance check, the robot  18  installs the shim onto the pinion stem. If this tolerance check fails, the shim is discarded and a new shim is dispensed. If this verification procedure fails more than three times, the operator will be notified for implementing corrective procedures. 
     Assuming the correct shim has been properly installed upon the pinion stem, the robot  18  grasps the conical bearing using bearing carrier  132  and places the conical bearing upon the pinion stem and then moves. The shim and conical bearing are then pressed down upon the pinion stem by the press portion of the gaging station  14  and the tolerances are verified. During this idle time, the robot  18  returns to the last dispensing location  30  to dispense a new shim within recess  52  in order to prepare for the next assembly cycle. This is accomplished by gripping apparatus  22  checking the proper location of escapement  50  by placing the opposing gripping tips  126  over aperture  58  and closing. If the beam of light provided by fiber optic cable  128  remains unbroken, the controller can determine that the escapement  50  is properly positioned. The robot  18  then actuates escapement  50  by moving the escapement  50  to the rearward position, guided by guiding assembly  70 . As recess  52  becomes aligned directly beneath the stack of shims  96  contained within storage container  90 , the shim  96  located at the bottom of the stack will fall into recess  52 . Tapered aperture  84  helps to guide the shim  96  and prevent the shim  96  from jamming. The robot  18  holds the escapement  50  in the rearward position momentarily, and then moves the escapement  50  back into the forward position which then exposes a new shim  96  at that dispensing location  30 . The robot  18  can then be moved into its home position and the controller notified that the robot  18  is ready to begin the next assembly cycle. 
     Upon reviewing the above specification in light of the appended drawings, one skilled in the art will readily appreciate the advantages presented by the dispensing station of the present invention. A significant cost savings can be achieved by providing a dispensing station having very few moving parts, and without motorized or automated features and controls. Additionally, the reduction in cycle time achieved by the dispensing station associated with the present invention can be realized because each escapement dispenses a shim in the same amount of time. Finally, the provision for reloading the storage containers allows an operator to restock the dispensing station in a safer environment. 
     The foregoing discussion discloses and describes exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications, and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.