Numerous wheel assemblies have been devised employing various types of anti-friction rolling elements, including planetary systems, for permitting the wheel to be rotatably supported on or relative to an axle. While such wheel assemblies have normally performed in a manner which has been considered satisfactory, nevertheless there has been a long term and continuous effort to improve on such wheel assemblies so as to make them more free-wheeling, as by minimizing the internal friction of the wheel assembly, while at the same time maintaining or improving the durability of the wheel assembly. This problem of providing a wheel assembly which is substantially free-wheeling, that is possesses minimum friction, and at the same time possesses desirable wear and durability characteristics, has been further compounded by the additional difficulties created due to the use of many wheels under contaminating environmental conditions (such as snow, water, liquids, dust and the like) which tend to contaminate the bearings, thereby greatly increasing both wear and rolling friction.
My copending application Ser. No. 185,108 filed Sept. 8, 1980, the disclosure of which is incorporated herein by reference, discloses a wheel assembly which provides significant improvement in the rotational characteristics by minimizing the rolling friction within the wheel assembly, while at the same time resulting in a wheel assembly having desirable durability, which improvements are achieved by providing the wheel assembly with an increased number of rotational freedoms so that the wheel more closely approaches a freely rotating system. While my aforesaid wheel assembly does provide for significantly improved rotational freedom, nevertheless I have continued to study, develop and improve upon this wheel assembly so as to still further improve the free rotational characteristics thereof, while at the same time increasing the durability of the wheel assembly while minimizing the complexities relative to manufacture and assembly.
Thus, this invention relates to still further improvements in a wheel assembly, which further improvements are believed to result in a wheel assembly which even further minimizes rolling friction so that the wheel more closely approaches a free-wheeling system, and at the same time possesses substantially increased durability and resistance to wear. This improved wheel assembly also possesses characteristics which are believed to enable it to operate in a highly satisfactory and desirable manner over long periods of time under conditions where the wheel assembly is exposed to numerous contaminants, such as water, snow, dirt, ice and other corrosives, such as when the wheel assembly is utilized on supermarket shopping carts. At the same time, this improved wheel assembly possesses structural and functional characteristics which not only simplify manufacture of the individual components, but also simplify the assembly of these components into the completed wheel arrangement.
In the improved wheel assembly of this invention, the wheel includes an annular rim having an outer bearing race formed directly on the inner periphery thereof. A minimal number of substantially cylindrical rollers are positioned within the rim so as to be in rolling engagement with the outer bearing race, which rollers in turn are rollingly engaged with an inner bearing race formed on a central sleevelike support shaft, which latter shaft is adapted to be telescoped onto an appropriate support axle. The cylindrical rollers are themselves individually rotatably supported on suitable axles, which axles in turn are rotatably supported on and extend between a pair of retainer rings. The retainer rings are freely rotatable relative to both the rim and the support shaft. The rim has one end cap integrally fixed thereto for closing one end of the annular region wherein the rollers are confined, and a removable end cap is fixedly seated on the rim adjacent the other axial side thereof for closing the other end of this annular region. The retainers have narrow annular ribs on the outer axial faces thereof which rotatably slidably bear against the inner faces of the end caps. The retainers, on their inner axial faces, have peripherally extending ramp cams disposed between the axle-receiving grooves to facilitate installing and proper positioning of the axles on and between the retainers. Each roller includes two cylindrical portions integrally joined together and spaced axially apart by an intermediate annular groove which is defined between opposed sidewalls which are preferably tapered or sloped, and the central support shaft has a similarly shaped annular ridge projecting outwardly therefrom and snugly but slidably accommodated within the grooves defined by the rollers for providing effective internal transfer of axial thrust forces therebetween.
In a preferred embodiment of the wheel assembly according to this invention, the rim is formed with a shallow outwardly opening channel therein, whereupon a semi-pneumatic tire can be positioned and retained therein.
Other objects and purposes of the invention will be apparent to persons familiar with wheel assemblies upon reading the following specification and inspecting the accompanying drawings.