Cart wheel with molded bearing components

Abstract

A wheel assembly for a material handling cart includes a spanner bushing having a cylindrical outer surface, a central axis, and an opening through the spanner bushing along the central axis. A bearing has an inner race and an outer race, wherein the inner race surrounds and contacts the cylindrical outer surface of the spanner bushing. A bushing is located adjacent to the bearing, wherein the bushing surrounds and contacts the cylindrical outer surface of the spanner bushing, and the bushing has a non-cylindrical outer surface contour. A hub is centered about the central axis and contacts the outer race of the bearing and the outer surface of the bushing, wherein the bushing rotates with the hub on the cylindrical outer surface of the spanner bushing. Lubricant cavities in the bushing lubricate the bearing and the spanner bushing. Bushing ridges and lips fix the bushing in relation to the hub.

What is claimed is:  
     
         1 . A wheel assembly comprising: 
 a spanner bushing having a cylindrical outer surface, a central axis, and an opening through the spanner bushing along the central axis;    a bearing having an inner race and an outer race, wherein the inner race surrounds and contacts the cylindrical outer surface of the spanner bushing;    a bushing adjacent to the bearing, the bushing surrounding and contacting the cylindrical outer surface of the spanner bushing, and having a non-cylindrical outer surface contour; and    a hub centered about the central axis and contacting the outer race of the bearing and the outer surface of the bushing, wherein the bushing rotates with the hub.    
     
     
         2 . The wheel assembly according to  claim 1  further including a second bushing adjacent to the bearing, and surrounding and contacting the cylindrical outer surface of the spanner bushing, wherein the second bushing is on a side of the bearing opposite the bushing.  
     
     
         3 . The wheel assembly according to  claim 1  wherein the bushing further includes a lubricant cavity having an opening in an inner surface that surrounds and contacts the cylindrical outer surface of the spanner bushing.  
     
     
         4 . The wheel assembly according to  claim 1  wherein the bushing has an inner face adjacent to the bearing, and the inner face further includes a lubricant recess formed in the inner face adjacent to the inner race of the bearing, and wherein the inner face contacts the outer race.  
     
     
         5 . The wheel assembly according to  claim 1  wherein the non-cylindrical surface contour of the bushing further includes ridges that extend radially into the hub and extend parallel to the central axis for engaging the hub surrounding the bushing to prevent movement of the bushing with respect to the hub.  
     
     
         6 . The wheel assembly according to  claim 6  wherein the ridges on the bushing are adapted to form a press fit joint with the hub.  
     
     
         7 . The wheel assembly according to  claim 6  wherein the bushing has an inner face adjacent to the bearing and an outer face opposite the inner face, and wherein the ridges do not extend to the outer face.  
     
     
         8 . The wheel assembly according to  claim 1  wherein the bushing further comprises a circumferential lip located adjacent to the bearing, and extending into the hub, the lip preventing the bushing from moving along the central axis with respect to the hub.  
     
     
         9 . The wheel assembly according to  claim 1  wherein the bushing comprises a circumferential lip located outside the hub and structured and arranged to be adjacent to a yoke.  
     
     
         10 . A material handling cart comprising: 
 a frame;    a material support structure coupled to the frame;    a plurality of wheels coupled to the frame, wherein one of the wheels includes: 
 a spanner bushing having a cylindrical outer surface, a central axis, and an opening through the spanner bushing along the central axis;  
 a bearing having an inner race and an outer race, wherein the inner race surrounds and contacts the cylindrical outer surface of the spanner bushing;  
 a bushing adjacent to the bearing, the bushing surrounding and contacting the cylindrical outer surface of the spanner bushing, and having a non-cylindrical outer surface contour; and  
 a hub centered about the central axis and contacting the outer race of the bearing and the outer surface of the bushing, wherein the bushing rotates with the hub.  
   
     
     
         11 . A method of making a wheel comprising the steps of: 
 locating a bearing along a central axis in the center of a wheel-shaped mold;    locating a bushing on each side of the bearing, wherein the bushings are located along the central axis and include axial and circumferential radial extensions; and    injecting plastic material into the wheel-shaped mold to produce a wheel, wherein plastic material surrounds the bearing and bushings, and wherein the radial extensions extend into the plastic material.    
     
     
         12 . The method of making a wheel according to  claim 11  wherein the bushings have a cylindrical opening through the bushing along the central axis defined by an inner surface, and wherein the bushings include one or more lubrication cavities in the inner surface of the cylindrical opening for containing lubricant.  
     
     
         13 . The method of making a wheel according to  claim 11  further including the steps of: 
 placing lubricant in the lubricant cavities; and  
 inserting a spanner bushing in the cylindrical opening.  
 
     
     
         14 . A method of making a wheel comprising the steps of: 
 locating a bearing along a central axis in the center of a wheel-shaped mold, wherein the bearing includes an outer race;    injecting plastic material into the wheel-shaped mold to produce a wheel, wherein plastic material surrounds the bearing and contacts only the outer race; and    press fitting a bushing on each side of the bearing, wherein the bushings are located along the central axis and include radial extensions that engage the plastic material.    
     
     
         15 . The method of making a wheel according to  claim 14  wherein the bushings have a cylindrical opening through the bushing along the central axis, and wherein the bushings include lubrication cavities in a surface of the cylindrical opening for containing lubricant.