Abstract:
In the trucking industry, a wheel stud having a recess at either end to accommodate a sacrificial insert of metal higher in the electromotive series of metals than the metals of the wheel stud assembly, the lug and the components joined thereby and being of sufficient difference in color from the surrounding materials so as to be readily visible without disassembling the combination, and a method for its use.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of priority to U.S. application Ser. No. 10/654,755, filed Sep. 4, 2003 and entitled “Zinc Stud Insert,” incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates generally to fasteners and more particularly to a means for reducing corrosion and binding of wheel assemblies on heavy trucks.  
         [0003]     The traditional means for removably attaching single or dual wheels to heavy truck axles involves a hub with hardened steel lugs pressed though its circumference which extend through aligned holes in the metal wheel and are secured thereto by single or double lug nuts. These removable components oft times weld together or bind due to corrosion and/or metal transfer, and efforts to separate them result in damage thereto.  
         [0004]     Typically, water and road salts in the operating environment aid in the formation of corrosion/rust on the holding thread and/or splines of the wheel studs, so that the lugs become stuck on the wheel studs or the wheel studs become stuck in the hub. As a result, the studs have to be removed and replaced in order to prevent the wheel from becoming detached from the hub.  
         [0005]     The use of fasteners with corrosion-inhibiting, fitted washers, such as J. E. Jones U.S. Pat. No. 3,574,080 and K. J. Shomber U.S. Pat. No. 3,060,112, or merely using washers made of non-conductive material between the components of the fastener assembly and the components to be fastened together, are known and utilized in the aviation industry and other high-tech assemblies. The unique arrangement of the components for removably attaching wheels to hubs on an axle of a heavy-duty truck place steel, steel alloys, and other dissimilar metals in close proximity, so a galvanic coupling is set up in the operating environment. The transfer of metal results in such corrosion that the lug can weld to the threaded end of the wheel stud or to the longitudinal splines on the end of the wheel stud pressed into the hub and the hubs corresponding mating splines. The problem of welding or corrosion of these components is that the components may be damaged in order to separate them for regular maintenance. This condition is what gave rise to W. H. Oliver U.S. Pat. No. 3,330,177, an impact cap for the threaded end of the wheel lug, to protect it when it is driven out of the wheel hub.  
       SUMMARY OF THE INVENTION  
       [0006]     Particular aspects of the present invention provide a replaceable stud insert in the stud, at either or both ends, so that the strength of the wheel stud is undiminished, yet the stud insert acts as a sacrificial anode, made from metal higher on the electromotive series of metals, to protect the components of the wheel assembly from corrosion or transfer of metals from galvanic action.  
         [0007]     Additional aspects provide the stud insert in a location, and of a color dissimilar to the surrounding metals, to enable easy visual inspection without disassembling the wheel assembly. As the stud insert is eaten away, it can be re-set, staked, or replaced by pressing in a replacement insert.  
         [0008]     Further aspects provide a method of using the stud insert, to include a spherical cavity in the wheel stud, a swaging tool to install the stud insert, and staking the insert at its convex end extending from the end of the stud. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The invention, both as to its composition and method of operation, together with further objectives and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings. In the drawings:  
         [0010]      FIG. 1  is a sectional elevational view of one side of a dual wheel assembly.  
         [0011]      FIG. 2  is a sectional elevational view of one side of a single wheel assembly.  
         [0012]      FIG. 3  is a quarter side elevation of the concave side of a wheel.  
         [0013]      FIG. 4  is a quarter side elevation of the convex side of a wheel.  
         [0014]      FIG. 5  is a side elevation of the hub.  
         [0015]      FIG. 6  is a front elevation of a single wheel assembly.  
         [0016]      FIG. 7  is a side elevation partly in section of a preferred wheel stud for a single wheel assembly.  
         [0017]      FIG. 8  is a side elevation partly in section of a preferred wheel stud for a dual wheel assembly.  
         [0018]      FIG. 9  is a side elevation partly in section of a preferred wheel stud for a dual wheel assembly with the dual threaded lug and dual over-lug.  
         [0019]      FIG. 10  is a side elevation partly in section of a preferred dual threaded lug.  
         [0020]      FIG. 11  is an expanded side cross sectional view of the stud pin section of the preferred stud assembly for a single wheel assembly. 
     
    
     DETAILED DESCRIPTION  
       [0021]      FIG. 1  shows one side of an axle ( 2 ) to which a dual wheel assembly ( 1 ) is removably attached, comprised of an inside wheel ( 3 ) and tire ( 4 ), a hub ( 5 ), and outside wheel ( 7 ) and tire ( 8 ). As shown in  FIG. 3 , the wheel ( 3 ), ( 7 ) has a concave face ( 14 ) and, in  FIG. 4 , the wheel ( 3 ), ( 7 ) has a convex face ( 13 ).  
         [0022]      FIG. 2  shows one side of an axle ( 2 ) to which a single wheel assembly ( 12 ) is removably attached, comprised of a wheel ( 3 ) and tire ( 4 ) and a hub ( 5 ). With reference to  FIG. 5 , a hub ( 5 ) is shown, being comprised of a disk of sufficiently strong material of sufficient thickness, having an axle passage ( 32 ) from the inside face ( 33 ) through to the outside face ( 34 ) and having a means to removably secure it to the axle ( 2 ). Regularly spaced in the hub ( 5 ) around the axle passage ( 32 ) are stud passages ( 9 ) from the inside face ( 33 ) through to the outside face ( 34 ) and being so arranged around the axle passage ( 32 ) so as to align with stud holes ( 35 ) in the wheels ( 3 ), ( 7 ). The stud passage ( 9 ) has splines ( 18 ) machined into its face and so arranged as to mate with splines ( 19 ) on the stud so that the stud assembly ( 6 ), ( 15 ) is prevented from turning in the stud passage ( 9 ).  
         [0023]      FIG. 7  shows a single wheel stud assembly ( 15 ) comprised of an elongated substantially cylindrical member, shank ( 40 ), having an enlarged stud head ( 17 ) at one end thereof, similar in shape to a bolt, of greater diameter than the diameter of the stud passage ( 9 ) in the hub ( 5 ). The diameter of the larger diameter section ( 36 ) of the cylindrical member of the stud ( 39 ) extending from the enlarged stud head ( 17 ) is of slightly smaller dimension than the inside diameter of the stud passage ( 9 ) and of length coincident with the distance from the inside face ( 33 ) to the outside face ( 34 ) of the hub ( 5 ) and has splines ( 19 ) on its outside circumference arranged laterally thereon and regularly spaced around its circumference so as to engage the splines ( 18 ) in the stub passage ( 9 ). Extending from the end of the larger diameter section ( 36 ) of the cylindrical member opposite the enlarged stud head ( 17 ) is a stud pin ( 20 ) of a slightly smaller diameter and having threads ( 21 ) throughout its length.  
         [0024]     The preferred embodiment of the invention and method for use is shown in  FIGS. 7 and 11 , wherein there is, at the end ( 22 ) of the stud pin ( 20 ), a plug cavity ( 30 ) continuing through the end ( 22 ) of the stud pin ( 20 ) and extending into the stud pin ( 20 ) along its center line, no more than the diameter of the threads ( 21 ) on the stud pin ( 20 ) (D 1 ), terminating in a spherical end ( 31 ) and having a diameter (D 2 ) of no more than 37.5% of the diameter of the threads ( 21 ) on the stud pin ( 20 ) (D 2 =37.5% D 1 ), provided at least 5 threads ( 21 ) on the stud pin ( 20 ) extend beyond the lug ( 16 ) when properly torqued. Thus the maximum cross-sectional area ( 37 ) of the convex end of the stud insert ( 25 ) is determined by the formula ( 37 )=√P.D 1  where P is the area of the threaded ( 21 ) end of the stud pin ( 22 ). The same formula applies for determining the maximum cross sectional area ( 37 ) of the convex end of the stud insert ( 23 ) in the plug cavity ( 24 ) in the enlarged stud head ( 17 ) for dual wheel assembly ( 1 ) application. The convex end of the stud insert ( 23 ) extends beyond the end ( 22 ) of the stud pin or the end of the enlarged stud head ( 17 ) so that the stud insert ( 25 ) can be staked during service, should the stud insert ( 25 ) become loose during normal service. The stud insert ( 25 ) is swaged into the plug cavity ( 30 ), ( 24 ) to keep it in place and provide electrical continuity between the stud insert ( 25 ) and the metal of the stud assembly ( 15 ), ( 6 ) and the metal of the wheel assembly ( 1 ), ( 12 ). Frequent inspection will be required to determine the security of the stud insert ( 25 ) and the rate it is sacrificed. This is the reason for the color of the stud insert ( 25 ) being clearly different than the color of the components of the wheel assembly ( 1 ), ( 12 ). In the preferred embodiment the stud insert ( 25 ) is made of zinc with the properties of Military Specification MIL-A-18001 J.  
         [0025]      FIG. 2  shows the single wheel assembly ( 12 ) with the preferred embodiment of the single wheel stud assembly ( 15 ) as installed at one end of an axle ( 2 ).  
         [0026]      FIGS. 3 and 4  show a wheel ( 3 ), ( 7 ) with the center being spanned by a single plate ( 10 ) having a concave face ( 14 ) and the reverse side of the same having a corresponding convex face ( 13 ) and stud holes ( 35 ) there through regularly spaced around the circumference of the single plate ( 10 ) spanning the center of the wheel ( 3 ), ( 7 ) and so arranged as to accommodate the stud pins ( 20 ) installed in a hub ( 5 ). The center of the single plate has an opening ( 38 ) at its center of sufficient diameter to accommodate the axle ( 2 ). As shown in  FIG. 6 , in the single wheel assembly ( 12 ) configuration, the convex end ( 23 ) of the stud insert ( 25 ) is visible in the end ( 22 ) of the stud pin ( 20 ) with the wheel ( 3 ) installed on the hub ( 5 ) and the lug ( 16 ), or nut, properly torqued against the convex face ( 13 ) of the wheel ( 3 ).  
         [0027]     In the circumstance, as shown in  FIG. 1 , where a dual wheel assembly ( 1 ) is used, the hub ( 5 ) has stud passages ( 9 ) of slightly smaller diameter to accommodate the smaller diameter of the spines ( 19 ) on the larger diameter section ( 36 ) of the cylindrical member of the stud ( 39 ) extending from the enlarged stud head ( 17 ). Similarly, the stud pin ( 20 ) has a slightly smaller diameter.  
         [0028]     With reference to  FIGS. 8, 9 , and  10 , the components of the dual wheel stud assembly ( 6 ) are shown. The dual wheel stud assembly ( 6 ) is composed of a stud ( 39 ), a dual threaded lug ( 26 ) shown in  FIG. 10 , and a dual over-lug ( 11 ). The stud ( 39 ) is installed in the hub ( 5 ), as described above, and the inside wheel ( 3 ), with its concave face ( 14 ) toward the hub ( 5 ), is engaged on the hub ( 5 ) with the stud pins ( 20 ) extending through the stud holes ( 35 ). The dual threaded lug ( 26 ), having inside threads ( 27 ) and outside threads ( 28 ), is threaded on the stud pin ( 20 ) and tightened to the proper torque by means of its nut end ( 29 ) to secure the inside wheel ( 3 ) to the hub ( 5 ). Then the outside wheel ( 7 ), with its convex face ( 13 ) toward the hub ( 5 ), is engaged on the hub ( 5 ) with the dual threaded lug ( 26 ) extending through the stud holes ( 35 ). The dual over-lug ( 11 ) is threaded on the dual threaded lug ( 26 ) and tightened to the proper torque to secure the outside wheel ( 7 ) to the hub ( 5 ).  
         [0029]     With reference to  FIGS. 8, 9  and  10 , the preferred embodiment of this invention for use with a dual wheel assembly is shown. Because the end of the stud pin ( 22 ) is covered by the dual threaded lug ( 26 ), the condition of the stud insert ( 25 ) in the end of the stud pin ( 22 ) is not available for easy visual inspection when the dual wheel assembly ( 1 ) is in operation. In addition, there are more communicating metal components in the dual wheel assembly ( 1 ), so that additional sacrificial material is needed to protect these metal components from corrosion and binding. Therefore, in the preferred embodiment, a plug cavity ( 24 ) is provided in the enlarged stud head ( 17 ), having the same relative dimensional limitation as the plug cavity ( 30 ) in the end of the stud pin ( 22 ), and the stud insert ( 25 ) also is provided with a convex end ( 23 ) to allow staking should the stud insert ( 25 ) become loose in operation. The condition of the stud insert ( 25 ) can be visually inspected without disassembling the dual wheel assembly ( 1 ). In addition, another plug cavity ( 30 ) may be provided in the nut end ( 29 ) of the dual threaded lug ( 26 ), maintaining the same relative dimensional limitation as the plug cavity ( 30 ) in the end of the stud pin ( 22 ).  
         [0030]     As can be seen from the foregoing preferred and alternative embodiments of this invention, there is a central principle applied which involves a new and improved means and method of protecting metal components removably joined by means of a fastener from galvanic corrosion, wherein the fastener is provided with an integral, replaceable, sacrificial amount of metal, higher in the electromotive series than the metal of the assembly, and so located as to be readily seen upon inspection and replaceable without separating the assembly.  
         [0031]     The foregoing disclosure and description of the invention are illustrative and explanatory thereof and, it will be understood by those skilled in the art, that various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made within the scope of the appended claims without departing from the scope or spirit of the invention.