Abstract:
The present invention is directed to a conveyor system for transporting a workpiece. The conveyor system includes a drive assembly and a carrier plate. The drive assembly includes a frame, a drive belt, and a drive mechanism supported by the frame and engaging the drive belt. The carrier plate is adapted to support a workpiece and is disposed on the drive belt to move with the drive belt.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/310,487, filed Aug. 8, 2001, the entire disclosure of the application is considered part of the disclosure of this application and is hereby incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a conveyor system and, more particularly, to a system that includes a workpiece carrier plate and a belt conveyor that transports the plate and workpiece.  
           [0003]    Manufacturing facilities, particularly automobile assembly plants in Europe, have for some time used moving pallets or skillets to conveyor large parts such as vehicle bodies. The skillets are larger than the workpiece so as to permit a worker to ride the skillet along with the workpiece and to perform a production task as the skillet passes through a production area.  
           [0004]    A representative prior art configuration of a plurality of skillets within a production area is shown in FIG. 1. The skillets  10 ,  12 , and  14  are moved through the production area in a train such that adjacent skillets abut one another. The train is driven by friction drive assemblies which may include opposed drive mechanisms  18  and  20  located at the entrance to the production area. Each drive assembly has friction wheels that are positionable to engage the sides of the skillets and push the skillets forward in an end-to-end train through the production area. Retarding friction drives  24  maintain the abutting relationship of the skillets within the production area while acceleration drives  26  may be used to accelerate the skillets exiting the production area. Each skillet also includes wheels  28  that extend from the underside of its platform and ride on guide rails.  
           [0005]    The skillet itself has robust construction that provides a sturdy platform for the workers, sufficient structural strength to accommodate the loadings, and a side surface depth that permits engagement by the friction drive wheels. To achieve the desired strength, skillets commonly include a robust steel frame and wood decking. While a robust design is generally necessary to accommodate the operational requirements of existing skillet systems, the strength comes at a cost, greater weight and expense. Moreover, the guide rails, friction drive assemblies, and other components of existing skillet systems are correspondingly robust, heavy, complex, and costly.  
           [0006]    A further deficiency in the art with respect to friction driven skillet systems relates to maintaining the skillets in end-to-end abutting relationship throughout the production area. Specifically, despite the use of retarding drives, non-uniform movement of skillets within the train can create gaps between adjacent skillets. These gaps interrupt the continuity of the worker platform. The depth of existing skillets and the necessity for installation pits can create undesirably large elevation drops in the gaps.  
         SUMMARY OF THE INVENTION  
         [0007]    With the above in mind, a need exists for a conveyor system that provides the benefits of existing skillet systems, particularly the continuous working platform that moves with the workpiece, while addressing the deficiencies in the prior art. The present invention is directed to a conveyor system that includes a drive assembly and a carrier plate. The drive assembly includes a frame, a drive belt, and a drive mechanism supported by the frame and engaging the drive belt. The carrier plate is adapted to support a workpiece and is disposed on the drive belt to move with the drive belt.  
           [0008]    Further scope of applicability of the present invention will become apparent from the following detailed description, claims, and drawings. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The present invention will become more fully understood from the detailed description given here below, the appended claims, and the accompanying drawings in which:  
         [0010]    [0010]FIG. 1 is a top plan view of a prior art skillet system;  
         [0011]    [0011]FIG. 2 is a top plan view of the conveyor system of the present invention;  
         [0012]    [0012]FIG. 3 is a section view taken along the line  3 - 3  shown in FIG. 2;  
         [0013]    [0013]FIG. 4 is a side elevation view of the system illustrated in FIG. 2; and  
         [0014]    [0014]FIG. 5 is a top plan view of a representative exit configuration for the conveyor system. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    A detailed description of an embodiment of the present invention will now be provided with reference to FIGS.  2 - 5 . The illustrated embodiment shows an application of the invention wherein car bodies are transported through a production area through the use of a driven belt and carrier plates. Notwithstanding this specific illustration, it should be appreciated that the drive belt and carrier plate, as well as other features described and claimed herein, have wide spread application in the material handling industry. Further, from this description, drawings, and appended claims, various modifications within the general knowledge and ability of those skilled in the art will become apparent.  
         [0016]    FIGS.  2 - 4  illustrate a conveyor system  30  including a drive assembly  32  and a plurality of carriers plates or platens  34 . The conveyor system  30  is configured to transport workpieces through a production area while maintaining a substantially continuous working platform around and between the workpieces. The conveyor system is shown within an area where workers would commonly perform assembly tasks on the workpiece as it is moved by the drive assembly  32 . Each workpiece  36  is fixed to one of the carrier plates  34  and the assemblies are delivered to and taken from the production area via any of a variety of transfer methods known in the art. A representative transfer method and structure is described below with reference to FIG. 5.  
         [0017]    As is best illustrated in FIGS. 2 and 3, the drive assembly  32  includes a support frame  40 , a drive belt  42 , and a drive mechanism  44  coupled to the frame  40  and configured to drive the belt  42 . It is desirable that the belt be formed of a solid composite and have a modular and hinged configuration such as the series  400  acetyl belt distributed by Intralox, Inc. of Harahan, La., a division of The Laitram Corporation. The drive assembly  32  also preferably includes a mechanical interlocking engagement between the drive mechanism  44  and the belt  42  such as through a sprocket and slot configuration. Examples of representative belt and drive configurations may be found in available literature, including U.S. Pat. No. 4,729,469 issued May 8, 1988 to Lapeyre; U.S. Pat. No. 4,821,872 issued Apr. 18, 1992 to Lapeyre; U.S. Pat. No. 4,925,016 issued May 15, 1990 to Lapeyre; U.S. Pat. No. 4,974,724 issued Dec. 4, 1990 to Lapeyre; U.S. Pat. No. 5,105,937 issued Apr. 21, 1992 to Gundlach; and U.S. Pat. No. 5,921,379 issued Jul. 13, 1999 to Horton, the disclosures of which are hereby incorporated by reference. Other belt, frame, and drive assembly configurations generally available in the art may also be used with the present invention without departing from the scope of the appended claims. Further, while a single drive assembly  32  is illustrated and described herein, it should be appreciated that the drive assembly may include a plurality of drive modules each with a separate moving belt loop. The carriers and corresponding workpieces may be transferred from drive module to drive module to provide production areas of extended length.  
         [0018]    The drive mechanism  44  is illustrated in the appended drawings to include a drive motor  46  and a rotating drive shaft  48  having toothed sprockets that mechanically engage a slot in the belt or belts. The mechanical engagement, as opposed to frictional engagement commonly used by fabric conveyor belt drives, positively tracks the belt to the drive mechanism. The drive belt  42  illustrated in FIG. 3 has separate first, second, and third segments  50 ,  52 , and  54 , respectively (FIG. 3), each driven by the single sprocketed shaft  48  such that the belt segments are positively tracked and indexed to one another. The upper support surface defined by the three belt segments has a width that is preferably slightly narrower than a width of the support frame  40 . Notwithstanding this representative illustration, those skilled in the art will appreciate that a variety of belt configurations may be used. For example, a single wide belt may be preferable in certain applications, particularly where a continuous transverse support surface from the belt is desirable.  
         [0019]    The support frame  40  may have a variety of configurations designed to support the anticipated loads as well as provide a low friction support surface for all or each of the belt segments. As is generally known in the art, the support frame  40  may include an extruded aluminum structure covered on the upper bearing surface by an ultra-high molecular weight plastic sheet  62 . The sheet may be fixed to the frame by conventional means, such as double-sided tape, mechanical fasteners, adhesives, and the like. The use of some manner of adhesive or double-sided tape provides the additional benefit of eliminating the use of mechanical fasteners that may adversely effect the smoothness of the slide surface. The frame and sheet support the modular plastic drive belt  42  in a manner that adequately distributes the loads to the frame while providing a low friction surface engaging the moving belt. This and similar frame arrangements provide an effective drive for the plates  34  while permitting the plates to have a less robust design than conventional skillets thereby decreasing the weight, cost, and complexity of the carrier plate design.  
         [0020]    As is illustrated in the drawings and noted above, each workpiece is coupled to and moves with a carrier plate  34 . Three adjacent carrier plates  34   a,    34   b,  and  34   c  are illustrated in FIGS. 2 and 4 in abutting engagement to one another and supporting separate automobile bodies  80   a,    80   b,  and  80   c.  Each automobile body or other workpiece may be coupled to its associated carrier plate prior to the production area entrance and transferred with the carrier through the production area. The carriers  34  are configured to provide the desired continuous work area around and between workpieces within the production area as well as being effectively and efficiently transported to and from different production areas. For example, it may be desirable to transport the carrier and workpiece assembly a greater distance than may be accommodated by a single drive belt and support frame. In these instances, multiple drive assemblies (such as the aforementioned drive modules) may be placed in series and the workpiece and carrier units being passed to subsequent drive modules. The carrier plates facilitate such transport by smoothly traversing the interface between adjacent drive units without the need for additional hardware.  
         [0021]    As noted above, the carrier plates  34  preferably have a low profile and are light in weight relative to prior art skillets. The carrier plates  34  are preferably substantially rigid so as to permit the transfer of the carriers to and from the belts of each drive assembly as well as between transfer mechanisms and the drive belts while having a design and material characteristics that accommodate the loading of a particular application. Notwithstanding the variety of acceptable configurations and materials, it is contemplated that the carrier plate may include a frame, such as from aluminum as well as a continuous top member, such as wood, to provide the support surface for the workers about the workpiece. While the height or thickness of a carrier may vary depending on a specific application, it is commonly desirable to minimize the thickness of the carrier plate which may, in many instances, be approximately 1 inch or less. These low profile carrier plates are capable of supporting large and heavy workpieces such as the illustrated automobile bodies due, in part, to the distributed support provided by the underlying belt  42  and frame  40 . As noted above, it should be appreciated that the carriers may be manufactured of a variety of materials depending on the desired performance characteristics.  
         [0022]    The low profile of the carrier plate not only reduces the overall weight and cost of the carrier and the overall conveyor system, but it also provides other operational benefits. For example, adjacent carriers are preferably arranged in abutting engagement as shown in FIGS. 2 and 4. The frictional engagement between each carrier plate and the drive belt minimizes the opportunity for relative movement between the carriers and belt and therefore between adjacent carriers. Accordingly, the occurrence of gaps between the carriers is minimized. Should gaps occur, the low profile of the carrier and the substantially continuous transverse surface of the belt minimizes the vertical drop in the gaps. Thus, the present invention effectively maintains a substantially continuous worker platform throughout the production area. Additionally, unlike prior art skillet systems which provide structural support at discrete points, the continuous transverse support provided by the belt  42  enhances the stability of the system without requiring an unduly robust carrier plate design. The lighter weight and low profile of the carrier plate also facilitates the transfer of the plate and workpiece assembly to and from different belt segments and permits the use of a variety of transfer assemblies to feed the plates and workpieces to and from the drive assemblies.  
         [0023]    Just as with conventional power systems, it may be desirable in certain applications to continuously or intermittently communicate power to the carrier plates. The power may be used in a variety of ways such as, for example, to power a scissor-lift  92  (FIG. 4) fixed to the carrier plate to support the workpiece and to raise and lower the workpiece to place it in the position that facilitates performance of the production task by the worker. To this end, as noted above, the drive belt  42  is illustrated in FIG. 3 to include three separate belt segments  50 ,  52 , and  54 . Adjacent segments are spaced from one another to define a gap  84  therebetween. A conductor bar  86  may be coupled to the frame  40  to function as a direct current bus. The bar  86  is positioned within the gap  84  and vertically proximate the upper surface of each drive belt segment. Contacts or brushes  88  may be positioned along the bottom surface of the carrier plate  34  to contact the conductor bar  86  at predetermined locations along the length of the frame to provide power from an external source through the conductor bar  86  and to the carrier plate  34 . A plurality of conductor bars  86  may be strategically placed longitudinally along the gap to selectively power the lift or other carrier plate accessory.  
         [0024]    As noted above, the assembly formed by the workpiece and carrier are preferably passed to and from the drive belt as a unit. A representative transfer arrangement is illustrated in FIG. 5 to include a transfer drive belt  94  similar to the drive belt  32  described above and oriented perpendicular thereto. The movement of the transfer drive belt  94  is preferably indexed by a controller and sensor assembly to the movement of the exiting workpiece and carrier plate so that the plate and workpiece assembly is not moved in the exit direction indicated by arrow  96  until the assembly has been moved completely out of engagement with the production area drive belt  32 . The transfer drive belt  94  includes a plurality of rollers  98  on its support surface to rollingly support the carrier and workpiece assembly and permit movement thereof onto the drive belt. A representative rollered drive belt is described in U.S. Pat. No. 6,148,990 issued Nov. 21, 2000 to Lapeyre et al., the disclosure of which is hereby incorporated by reference. Those skilled in the art will appreciate that a similar transfer mechanism may be used to feed carriers and workpieces onto a drive assembly such as through the use of a mechanical pusher or other arrangement. While a representative transfer arrangement has been described herein, those skilled in the art will appreciate that a variety of alternative embodiments may be used without departing from the scope of the present invention.  
         [0025]    The foregoing discussion discloses and describes an exemplary embodiment 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 true spirit and fair scope of the invention as defined by the following claims.