Spherical ball bearings are composed of a convex spheroidal inner ring and an outer ring with a corresponding spheroidal concave surface in its inner surface. The bearing is an assembly that serves as a link between a shaft and its housing, allowing tilting or oscillating movements.
The rings undergo a phosphating treatment and a molybdenum disulfide (MoS2) coating to reduce the coefficient of friction of the surfaces in contact. Some spherical bearings have an outer ring coated with PTFE (Teflon), which allows maintenance-free use for applications where lubrication is impossible or not recommended.
Spherical bearings are used for chassis hinges, hydraulic tipper cylinders, front and rear suspension arms, dump trucks steering cylinders, chassis hinges, upper and lower steering cylinders, loader buckets and fork jacks.
Rod Ends
The spherical end is a ball joint mounted at the end of a male or female threaded rod. Better known as Rod End, rod ends are mainly used on automobile suspension arms and hydraulic cylinders.
The following is the description of spherical plain bearing
Once the assembly is done, there must be an impeccable slip between the inner ring and the outer ring of the spherical bearing. In order to achieve this, the inner ring must be firmly attached to the shaft and the outer ring to its housing. When mounting the outer ring in its housing, the tool must allow a perfect alignment of the outer ring with the axis of the housing. In addition, the bearing could move due to excessive axial load. It is therefore important to provide staves or stop segments to prevent slippage of the outer ring.
As regards to the mounting of the shaft in the inner ring of a ball joint, it is essential that the shaft be mounted dry. Improper mounting can adversely affect the life of the ball joint, resulting in failure. A too tight fit between the outer ring and housing, improper tooling and excessive force applied are other mistakes made when mounting a ball joint.
Protection and lubrication of materials
Some models of rod ends require regular maintenance to maintain proper operation. To protect the swivel from external pollution such as dust, abrasives, corrosion and chemical agents, a dust seal must be used. It is placed on the outer ring and is impregnated with silicone grease. In addition to its protective action, it provides permanent lubrication. However, it is not recommended for applications where the inner ring performs full rotations or high speed rotations, since it may become detached from the rod end.
Generally the outer ring of the spherical bearing is manufactured with a groove which allows the lubricant to reach the sliding surface. It is important not to neglect the lubrication of a spherical bearing. Maintenance prevents any corrosion being formed by steel to steel friction. Proper maintenance increases the service life of these items.
