Abstract:
A wheel assembly kit for a Mecanum wheel is provided. The kit includes a convex hub having a central axis and a perimeter. The perimeter comprises a plurality of flat spoke faces extending therearound. A spoke is releasably couplable to each spoke face. The spoke is alignable on the spoke face in a first orientation for one of left-handed and right-handed drive. When the spoke is rotated ninety degrees about its respective spoke face, the spoke is alignable in a second orientation for the other of the left-handed and the right-handed drive. A method of assembling the wheel assembly is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority from U.S. Provisional Patent Application Ser. No. 61/035,773, filed on Mar. 12, 2008, which is incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    A Mecanum wheel assembly is well known for providing a drive mechanism to a vehicle that allows the vehicle to move in all directions, including laterally, by rotating the wheel assemblies of the vehicle in different directions. Each wheel assembly includes a plurality of rollers disposed around the perimeter of a central hub. An exemplary prior art design of a Mecanum wheel is disclosed in U.S. Pat. No. 3,876,255, and incorporated herein by reference. 
         [0003]    The hub geometry of a standard Mecanum wheel assembly is relatively complex, with roller axes being formed obliquely to a central hub axis. Further, both left-handed and right-handed hubs are required, at least one for each side of the vehicle. Left-handed hubs are mirror images of right-handed hubs, requiring spares of each of left-handed and right-handed hubs in the event of the failure of one of the hubs. There exists a need to improve the hub geometry of the Mecanum wheel. 
       SUMMARY OF THE INVENTION 
       [0004]    Briefly, the present invention provides a wheel assembly kit comprising a convex hub having a central axis and a perimeter. The perimeter comprises a plurality of flat spoke faces extending therearound. A spoke is releasably couplable to each spoke face. The spoke is alignable on the spoke face in a first orientation for one of left-handed and right-handed drive. When the spoke is rotated ninety degrees about its respective spoke face, the spoke is alignable in a second orientation for the other of the left-handed and the right-handed drive. 
         [0005]    Further, a method of assembling a wheel assembly is also provided. The method comprises the steps of providing a hub; determining whether the wheel assembly is a right-handed or a left-handed wheel assembly; and coupling a plurality of spokes to the hub to provide the determined right-handed or left-handed assembly. 
         [0006]    Additionally, the present invention also provides a method of changing a directional alignment of a wheel assembly. The method comprises the steps of determining the directional alignment of the wheel assembly, the wheel assembly comprising a hub and a plurality of spokes extending therefrom in an original position; removing the plurality of spokes from the hub; rotating each of the plurality of spokes relative to hub relative to the original position; and reattaching the plurality of spokes to the hub. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The forgoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings, which are incorporated herein and constitute part of the specification. For the purposes of illustrating the invention, there are shown in the drawings exemplary embodiments of the present invention. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings, the same reference numbers are employed for designating the same elements throughout the several figures. In the drawings: 
           [0008]      FIG. 1  is a perspective view of a wheel assembly according to an exemplary embodiment of the present invention; 
           [0009]      FIG. 2  is a partially exploded perspective view of the wheel assembly of  FIG. 1 ; 
           [0010]      FIG. 3  is an exploded perspective view of a roller assembly used with the wheel assembly of  FIG. 1 ; 
           [0011]      FIG. 4  is a side view of a wheel hub of the wheel assembly of  FIG. 1 ; 
           [0012]      FIG. 5  is a sectional view of the wheel hub taken along line  5 - 5  of  FIG. 4 ; 
           [0013]      FIG. 6  is a bottom plan view of the wheel hub taken along lines  6 - 6  of  FIG. 4 ; 
           [0014]      FIG. 7  is a front elevational view of a spoke of the wheel assembly of  FIG. 1 ; 
           [0015]      FIG. 8  is a side elevational view of the spoke of the wheel assembly of  FIG. 1 ; 
           [0016]      FIG. 9  is a top plan view of the spoke of the wheel assembly of  FIG. 1 ; 
           [0017]      FIG. 10  is a top plan view of a blank used to form the spoke of  FIGS. 7-9 ; 
           [0018]      FIG. 11  is a side elevational view of the blank of  FIG. 10 ; 
           [0019]      FIG. 12  is a top plan view of a spoke coupled to the wheel hub in a right-handed configuration; and 
           [0020]      FIG. 13  is a top plan view of the spoke of  FIG. 12  coupled to the wheel hub in a left-handed configuration. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Although the invention is illustrated and described herein with reference to a specific embodiment, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of the equivalence of the claims and without departing from the invention. The invention is best understood from the following detail description when read in conjunction with the accompanying drawing figures, which show exemplary embodiments of the invention selected for illustrative purposes. The invention will be illustrated with reference to the figures. Such figures are intended to be illustrative rather than limiting and are included herewith to facilitate the explanation of the present invention. 
         [0022]    Referring to the figures in general, a wheel assembly  100  according to an exemplary embodiment of the present invention is shown. Wheel assembly  100  may be constructed from a kit that includes a hub  102  and a plurality of spokes  104  that may be arranged and releasably coupled to hub  102  in a configuration that results in an assembled wheel to meet the operational requirements of the user. For example, wheel assembly  100  may be assembled to provide either a left-handed or a right-handed wheel for use in an omni-directional vehicle that allows for sideways vehicle movement as well as rotation of the vehicle about a vehicle axis.  FIGS. 1 and 2  show a wheel assembly  100  in a right-handed configuration. A roller assembly  106  may be rotatably coupled to each spoke  104 . 
         [0023]    If, however, the user desires to change the orientation of spokes  104  with respect to hub  102  in order to change wheel assembly  100  from, for example, a right-handed wheel to a left-handed wheel, spokes  104  may be removed from hub  102 , rotated to a left-handed orientation, and then reassembled to hub  102 . In an exemplary embodiment, this action may be performed without removing roller assembly  106  from its respective spoke  104 . 
         [0024]    Referring to  FIGS. 3-6 , hub  102  includes a generally convex body  110  having a longitudinal axis  111 . A body is “convex” if every line segment drawn between any two points inside the figure lies entirely inside or on the figure. Body  110  includes a plurality of spoke faces  112  that extend around an outer perimeter  113  of body  110 . As shown in  FIG. 4 , six spoke faces  112  are used in the exemplary embodiment. Those skilled in the art, however, will recognize that more or less than six spoke faces  112  may be used. A spacing face  114  separates each spoke face  112  from an adjacent spoke face  112  and provides room for roller assemblies  106  (shown in  FIGS. 1 and 2 ) around hub  102 . Each spoke face  112  includes a plurality of threaded openings  116  to accept threaded fasteners  118  (shown in  FIGS. 2 and 3 ) for releasably coupling spoke  104  to spoke face  112 . 
         [0025]    Hub  102  may be machined from hexagonal bar stock. In an exemplary embodiment, hub  102 , as well as spokes  104 , may be constructed from aluminum or other light weight material. Cut-outs  120  maybe formed in body  110  of hub  102  to reduce weight without adversely compromising the structural integrity of hub  102 . 
         [0026]    Referring to  FIGS. 7-9 , each spoke  104  has a generally “T-shaped” cross section, as shown in  FIG. 8 . Spoke  104  include a base  124  with a flange  126  that extends perpendicularly from base  124 . Base  124  is generally square, with flange  126  extending between two opposing corners of the square. A base opening  128  is formed on either side of flange  126  proximate to a remaining corner of base  124 . Base openings  128  are sized to allow threaded fasteners  118  to extend therethrough. 
         [0027]    While  FIG. 3  illustrates threaded fasteners  118  being inserted through threaded openings  128  in spoke  104  and then into threaded openings  116  in spoke face  112  on hub  102 , optionally, as illustrated in  FIG. 2 , threaded fasteners  118   a  may be first threaded through threaded openings  116  in spoke face  112 , and then into threaded openings  128  on spoke  104 . This connection arrangement provides the advantage of being able to connect spoke  104  to or disconnect spoke  104  from hub  102  without having to disassemble roller assembly  106 , which may be required if threaded fasteners  118  are first inserted through threaded openings  128  in spoke  104  and then into threaded openings  116  in spoke face  112 . While, in the exemplary embodiment present described, both openings  116  and  128  are threaded openings, those skilled in the art will recognize that only one of openings  116  and  128  need be threaded, with fastener  118  first extending into the unthreaded hole  116  or  128 , and then into the threaded hole  128  or  116 . 
         [0028]    Spokes  104  are alignable with hub  102  to provide either a left-handed or a right-handed drive. Referring to  FIG. 1 , wheel assembly  100  is configured for a right-handed drive. In order to obtain the right-handed configuration, spokes  104  are aligned relative to spoke face  112  such that threaded fasteners  118  extend through base openings  128  into threaded openings  116   a,    116   b  as shown in  FIG. 3 . If wheel assembly  100  is to be configured for a left-handed drive, spoke  104  may be rotated 90 degrees relative to spoke face  112 , and threaded fasteners  118  are inserted through base openings  128  in spoke  104  and threaded into threaded openings  116   c,    116   d.    
         [0029]    In an exemplary embodiment spokes  104  may be constructed from an elongated piece of T-stock  140 , as shown in  FIGS. 10 and 11 . Base openings  128  and roller axle openings  130  may be formed in T-stock  140 . Spoke  104  may then be cut from T-stock  140  along dashed lines as shown in  FIG. 10 . 
         [0030]    Referring to  FIG. 3 , an exemplary embodiment of roller assembly  106  may be constructed from a pair of curved rollers  150  mounted, on either side of flange  126  at roller axle opening  130 . Roller bushings  152  are directly mounted to flange  126  at roller axle opening  130  (shown in  FIG. 7 ). A set screw  154  extends through roller axle opening  130  and roller bushings  152 , and is threaded into one end of a roller shaft  160 . Rollers  150  are mounted for rotation on each roller shaft  160 . A flange bearing  162  and a sleeve bearing  164  support roller  150  on roller shaft  160  (only one each of flange bearing  162  and sleeve bearing  164  are shown in  FIG. 3  for clarity). A roller washer  166  and a thrust washer  168  are mounted on a second end of each roller shaft  160 . A cap screw  170  retains roller washer  166  and thrust washer  168  on roller shaft  160 . 
         [0031]    While roller assembly  106  is shown and described herein, those skilled in the art will recognize that other types of roller assemblies may be used with the wheel assembly of the present invention. For example, roller  150  may be constructed with a core (not shown) that includes a polymer base impregnated with a lubricious material, such as, for example, molybdenum disulfide. An advantage to such a construction is that, with such a core, at least flange bearings  162  and sleeve bearings  164  may be eliminated. 
         [0032]    An advantage that wheel assembly  100  provides is that wheel assembly  100  may be assembled according to whether the user needs a left-handed or a right-handed drive wheel. Spoke  104  is alignable in a first orientation for one of left-handed and right-handed drive, and when spoke  104  is rotated ninety degrees about its respective spoke face, spoke  104  is alignable in a second orientation for the other of the left-handed and the right-handed drive. For example,  FIG. 12  shows spoke  104  coupled to hub  102  in a right-handed configuration, while  FIG. 13  shows the same spoke  104  coupled to hub  102  in a left-handed configuration. 
         [0033]    Wheel assembly  100  reduces the need to carry spare left-handed and right-handed hubs, which can reduce maintenance costs for wheel assembly  100 . Additionally, in the event that a spoke  104  bends or breaks from hub  102 , the entire wheel assembly  100  does not need to be replaced; only the bent or broken spoke  104  needs to be removed from hub  102  and replaced with a replacement spoke  104 . 
         [0034]    Further, the modularity of wheel assembly  100  eliminates the need for complex machining to machine a hub with integrated spokes. Wheel assembly  100  may be machined relatively easily from hexagonal bar stock and T-stock. This manufacturing process greatly reduces the cost of manufacturing each wheel assembly  100 . 
         [0035]    Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.