BACKGROUD OF THE INVENTION 
     The present invention relates to a ball balancing mechanism for dynamically balancing rotating objects. 
     Dynamic balancing of rotating objects utilizing balance rings having spherical weights is known in the prior art. However, certain disadvantages are encountered with prior art devices, particularly when the balancing ring is made from plastic. The spherical weights are usually made from metal and during the rotation of the object the spherical weights can deform or damage the plastic as a result of centripetal force. 
     Therefore, a primary object of the present invention is the provision of an improved ball balancing mechanism for rotating objects. 
     A further object of the present invention is the provision of an improved ball balancing mechanism having structure that is stiff enough to allow the balls to roll freely even at high centripetal acceleration. 
     A further object of the present invention is the provision of a rolling surface for the balls which is strong enough to withstand the contact stresses of the rolling balls. 
     A further object of the present invention is the provision of an improved ball balancing mechanism which is economical to manufacture, efficient in operation, and durable in use. 
     SUMMARY OF THE INVENTION 
     The foregoing objects may be achieved by a ball balancing mechanism formed from an annular ring having a hollow cross section creating an enclosed hollow annular cavity therein. An annular race is placed within the hollow cavity and extends around the entire circumference of the ring. A plurality of spherical weights are retentively contained with the annular race and are free to roll in a circumferential direction within the annular race around the circumference of the annular ring. 
     According to one feature of the invention the annular race is comprised of metal and the annular ring is comprised of plastic. 
     According to another feature of the invention a damping fluid is contained within the hollow cavity and bathes the spherical weights to cause damping of the movement of the spherical weights in the race. 
     According to another feature of the present invention the race has a C-shaped cross section and the opening of the C-shaped cross section faces generally in an inner radial direction with respect to the annular center of the ring. 
     The preferred use for the balancing ring is in connection with either a vertical or horizontal axis washing machine tub wherein the annular ring is mounted to the washing machine tub with its central axis aligned with the rotating axis of the washing machine tub. 
     While the use of the annular ring with a washing machine tub is preferred, the annular ring maybe used for other rotating objects without detracting from the invention. 
     According to the method of the present invention a balancing ring having a central ring axis is attached to a rotatable object in a position wherein the central ring axis of the balancing ring is aligned with the rotating axis of the object. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS 
     FIG. 1 is a sectional view taken along line  1 — 1  of FIG.  2 . 
     FIG. 2 is a sectional view taken along line  2 — 2  of FIG.  1 . 
     FIG. 3 is an enlarged view taken along line  3 — 3  of FIG.  1 . 
     FIG. 4 is an enlarged view taken along line  4 — 4  of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings the numeral  10  generally designates a tub having a bottom wall  12  and a side wall  14  with an upper edge  16 . It is anticipated that the tub can also be spherical in shape. Protruding downwardly from the bottom wall  12  of the tub  10  is a shaft  18  which is adapted to be rotatably mounted within a washing machine so that the tub will rotate about a tub axis formed by the shaft  18 . 
     Mounted to the upper edge  16  of the tub  10  is an annular donut shaped balancing ring  20 . Balancing ring  20  is attached to the upper edge  16  by a plurality of studs  22  spaced circumferentially around the circumference of the edge  16 . 
     Balancing ring  20  includes an upwardly protruding flange  26  which forms an access opening  24  at the top of tub  10 . A perforated surface  28  is tapered radially inwardly and downwardly so as to cause fluids to drain towards the center of the tub. 
     The annular balancing ring  20  includes an outer wall  30 , a bottom wall  32  (FIGS.  3  and  4 ), a curved inner wall  34  and a top wall  36 . Top wall  36  is initally detached during assembly and after assembly is welded over the top of the balancing ring  20 . 
     Enclosed within the balancing ring  20  is an annular cavity  38  which extends around the circumference of the ring  12 . Within cavity  38  are an inner confining flange  40 , and a pair of lower support flanges  42 ,  44 , all of which extend around the circumference of the ring  20 . A plurality of circumferentially spaced ribs  46  are shown in FIG. 2 to be spaced around the circumference of the ring  20 . Each rib  46  includes a semicircular upwardly presented cut out  48  (FIG.  4 ). 
     Also fitted within the annular cavity  38  is a circular ball race  50  which is C-shaped in cross section as can be seen in FIGS. 3 and 4. The open ends of the C-shaped cross section are presented radially inwardly, and the race  50  provides an outer radial surface for absorbing any centripetal force exerted by a plurality of spherical weights or balls  52 . 
     While the materials used for the balance ring may vary without detracting from the invention, it is preferred that the ring housing itself be formed from plastic, and that the ball race  50  be formed from metal. This enables the ball race  50  to provide a smooth hard surface against which the balls  52  can roll during the rotation of the tub  10 . The race  50  fits within the arcuate cut outs  48  of the ribs  46  and is supported by this arcuate cut out  48 . The balls  52  are confined by the race  50 , the lower support flanges  42 ,  44 , and the inner flange  40 . These objects confine the balls  52  so that they remain embraced by the race  50  and are free to roll in a circumferential direction to any position around the circumference of the balancing ring  20 . 
     A damping fluid such as mineral oil or silicone oil partially fills the cavity  38  and bathes the spherical weights  52 . This oil has the effect of damping the movement of the balls  52  as they rotate, and also facilitates the lubrication and smooth rolling of the balls  52 . 
     The use of steel for the race  50  provides a smooth hard surface which permits the spherical weights or balls  52  to roll more freely. If the spherical weights or balls  52  are permitted to roll against the plastic housing of the annular ring, they can possibly deform the plastic housing and be inhibited from free rolling motion after extended rotation of the tub  10 . Therefore the use of a metal race or a race formed from a hard material other than metal provides an improved result by permitting the free rolling of the spherical weights or balls  52  without being deformed. 
     In the drawings and specification there has been set forth a preferred embodiment of the invention, and although specific terms are employed, these are used in a generic and descriptive sense only and not for purposes of limitation. Changes in the form and the proportion of parts as well as in the substitution of equivalents are contempated as circumstances may suggest or render expedient without departing form the spirit or scope of the invention as further defined in the following claims.
A ball balancing mechanism includes an annular ring having a hollow cross section forming an enclosed hollow cavity therein. A circular race is placed within the hollow cavity and extends around the circumference of the annular ring. A plurality of balls are retentively contained within the annular race and are free to roll within the race around the circumference of the ring.