Abstract:
A rubber tired wheel assembly is provided with two wheel rim blanks welded together after the installation of ball bearing assemblies in each of the rim blanks. The bearing assemblies are retained by casing caps confining the bearing outer races in wells in the rim blanks, the casing caps being projection welded to the rim blanks to locate and secure the bearing assemblies concentric with tire receiving surfaces of the rim blanks.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to wheels, and more particularly to ball bearing wheels for small, light-weight devices such as lawn mowers, for example. 
     2. Description of the Prior Art 
     Typical prior art construction has employed a couple of wheel rim blanks welded together with one or more bearing assemblies pressed into the assembled rim blanks. This has required use of bearing assemblies which have the strength to withstand the forces involved in installing them in the wheel blanks. It also requires some degree of precision in the rim blanks in order to be sure that the bearing receiving surfaces are concentric with the tire receiving surfaces of the assembled rim blanks so that the bearing assemblies, when installed, will be concentric with the tire. 
     SUMMARY OF THE INVENTION 
     Described briefly, according to a typical embodiment of the present invention, a wheel assembly is made by employing a pair of rim blanks. Each blank has a bearing assembly installed in the rim blank by capturing the bearing assembly between the rim blank and an inner casing cap which is projection welded to the rim blank. The rim blanks are then welded together and a tire is installed to complete the wheel assembly. 
     It is an object of the present invention to provide a ball bearing wheel assembly of lighter weight and lower cost than obtainable with conventional construction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of a wheel assembly employing wheel-cased bearing assemblies according to a typical embodiment of the present invention, with the center portion being broken out to show the inner casing cap installation. 
     FIG. 2 is a cross section taken at line 2--2 in FIG. 1 and viewed in the direction of the arrows. 
     FIG. 3 is an exploded sectional view of half of the rim and bearing sub-assembly of FIG. 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings in detail, the wheel assembly of FIG. 1 includes the rubber tire 11 mounted on the rim assembly 12 having a bearing assembly in it at 13 with an axle-receiver inner race tube 14. The central portion of one of the rim blanks of the rim assembly is broken away at 16 in FIG. 1 to expose the bearing assembly 13, axle-receiving inner race tube 14, and inner casing cap 17, which parts are identified also in FIG. 2 by the same reference numerals. 
     The rim assembly 12 comprises a rim blank 12A and rim blank 12B. These blanks are identical or similar and are spot welded together at a suitable number of circularly spaced points on their web portions 18A and 18B, respectively. Accordingly, the concavo-convex outer perimetrical surfaces thereof cooperate to form a tire receiving groove or channel 19. 
     According to a typical embodiment of the present invention, the rim blank is dished and includes a well 21, and the bearing sub-assembly 13 is received in the well 21 in the rim blank 12B. This bearing sub-assembly includes an axle receiving inner tube 14 having a circumferential bearing receiver groove 22 therein receiving the ball bearings 23. The outer race 24 is typically a discontinuous ring of roll-formed wire having an end gap of approximately 0.030 inch which, upon assembly, may be reduced to approximately 0.005 inch. Accordingly, this outer race wire confines the bearing balls in the inner race groove 22 even with the 0.030 inch end gap in the wire. When it is installed in the well 21, the conical or chamfer lead-in guide and locating wall 26 in the well receives and pilots the outer race ring 24. The inner casing cap 17 provided according to the present invention, has a like well 27 with conical lead-in surface 28 thereon. It also has four dimples 29 formed therein to facilitate projection welding to the rim blank 12B. Accordingly, the two pieces, namely the inner casing cap 17 and rim blank 12B, are welded together by projection welding at the dimples, with the casing cap carefully located so that its cone surface 28 and the cone surface 26 of the rim blank are concentric with each other and with the tire bead margin 31 of the rim blank. In this way, as the casing cap is installed on the rim blank, the conical surfaces 26 and 28 close on the roll-formed wire outer race ring 24, closing the end gap to more nearly 0.005, with a result that the bearing assembly is centered on the axis 32 so that the axle receiving inner race tube 14 is concentric with the tire receiving portion 31 of the rim. 
     The bearing assembly in the rim blank 12A is installed in exactly the same way. Following that, the two assemblies are mounted with their web portions 18A and 18B together, and a dowel rod or axle is received through the respective axle receiving inner race tubes of the two bearing assemblies, whereupon the rims are spot welded together in at least four circularly spaced locations around the webs. They are preferably spot welded in at least seven locations. Then the assemblies are painted. Following that, the tire is installed. Installation of the tire can be done with the assistance of heat and/or simply mechanical installation tools or machines utilizing the resilience of the rubber to accommodate the stretch needed to get the tire over the rim edge of maximum diameter, and return it to snug self-retention on the rim assembly. 
     As an example of the bearing sub-assemblies which can be used, the sub-assembly PA 641-4 provided by the Freeway Corporation of 9301 Allen Drive, Cleveland, Ohio 44125, is suitable. Another is the No. BF 1127-502A sub-assembly manufactured by Kendale Industries of 7600 Hub Parkway, Valley View, Ohio 44125. That sub-assembly is normally part of their bearing assembly No. XB 1330, but the entire bearing assembly is not needed due to the present invention. 
     Although such bearing assemblies can be installed without closing the end gap, the feature of the present invention using the combined action of the conical surfaces on the rim blank and casing cap significantly improves run-out of the tire tread 35 in the complete assembly, the run-out being the difference between the maximum and minimum distance of the tire thread from the bearing axis 32 as the wheel turns about the axis 32 of its bearing assembly inner races. 
     The axle receiving tubes 14 of the bearing assemblies project through the apertures 33A and 33B of the rim blanks 12A and 12B, respectively, and beyond planes normal to axis 32 and tangent the sidewalls 34 and 36 of the tire. Although this is a feature of the illustrated structure, it is not essential to the practice of the invention. It is beneficial because it facilitates stand-off of the tire from the frame of the lawn mower or other device to which the wheel assembly is to be mounted. 
     As shown in FIG. 3, a dirt shield 37 is provided between the bottom of the well 21 and the bearing balls. This may be made of a heat resistant plastic material such as &#34;Mylar&#34; brand film, 0.008 to 0.010 inches thick, for example. The inner edge 38 of the central aperture of the dirt shield would be of slightly greater diameter than that of surface 14A of the bearing inner race. The outside diameter would be slightly less than the inside diameter of the outer race. Therefore, it fits between the races and covers the gap between the inner race and the rim blank aperture. It thus excludes dirt from the bearings. This dirt shield is provided in each of the rims outboard of the bearings as shown in FIG. 2. The dirt shields can be omitted, if desired. Whereas the enclosed drawings show a typical bearing sub-assembly, there are many similar sub-assemblies, including ones which provide for touching inner races. This is accomplished by having longer inner races on said sub-assemblies. This invention is equally applicable to these. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.