Optional Bearing Components

The following ball bearing components enhance the performance and life of the bearing. These components are not added to the bearing unless specifically ordered. Each component is assigned an alphabetical or alpha/numeric code for clarity when ordering.

Shields and Seals

Shields and seals are most commonly used on grease lubricated bearings in applications where the bearing can be exposed to external elements. The main function of the shields and seals is to keep possible contamination away from the most critical internal working components while keeping the lubricant clean and contained within the bearing.

Shields

Shield (ZZ)

The shield is a stamped, profiled sheet metal disc. It is pressed into a very small groove on the inside edge diameter of the outer ring. A small space or gap remains open between the outside diameter of the inner ring and shield. Because the shield does not contact the inner ring of the bearing, there is no added friction between the shield and bearing. This results in a bearing that has a very low torque (the amount of twisting force required to rotate the inner ring of the bearing relative to the outer ring). Shields keep larger particles of contamination from entering the bearing and are effective for many general bearing applications. NTN’s designation for a shield applied to only one side of the bearing is the suffix Z; if shields are needed on both sides the suffix designation is ZZ.

Seals

Seals are available in a variety of types and composition, the most common being synthetic rubber molded to a steel plate. The seal is also inserted into the very small groove on the inside, edge diameter of the outer ring. The inner edge of the seal is molded into a specifically designed lip configuration. NTN’s generic suffix designation for any type of seal applied to one side of the bearing is L; for seals required on both sides it is LL. NTN’s standard seals are provided in two different configurations, contact and non-contact.

The Non-Contact Seal

Non-Contact Seal (LLB)

The non-contact seal is NTN’s unique single lip seal design. When assembled into the bearing, the seal’s moulded, single lip fits into a specially designed seal groove machined on the outside edge diameter of the inner ring. The lip of the seal does not come into contact with the inner ring of the bearing, hence the name non-contact seal. The circular concave lip of the seal combines with the V-shaped trough of the inner ring to create an open area where grease is allowed to collect. These factors combine to form a very effective labyrinth seal--so called because the combination of the seal’s design, the groove in which it fits and the grease combine to create a difficult maze through which the contaminants must pass to penetrate the seal.

There are many unique benefits associated with the non-contact seal: it requires very little torque to rotate, it is highly resistant to dust buildup, and operating temperatures are comparable to that of a shielded bearing. The non-contact seal offers the benefits that are usually provided by a shield with the additional advantages offered by seals. This type of seal was specially designed to meet the demanding requirements of modern day electric motors.

NTN’s suffix designation for a non-contact seal placed on one side only is LB; when applied to both sides it is LLB. NTN generally molds the synthetic rubber non-contact seal in the color black, visually simplifying the identification process in comparison with other types of seals.

The Contact Seal

Contact Seal (LLU)

The contact seal is another option. Other manufacturers offer contact seals but the NTN design is unique in that it utilizes a molded, double lip seal to insure optimum protection from dust penetration. When assembled in the bearing, the inner lip of the seal contacts the inside edge of the seal groove on the inner ring. This is why the seal is called a contact seal.

A slight gap remains between the outer lip of the seal and the inner ring of the bearing, forming an area for grease to accumulate (hence a secondary labyrinth seal). Should friction cause the inner lip of the seal to wear, the outer lip will compensate for the wear by constricting around the outer landing of the bearing’s inner ring. This preserves the perfect protection afforded by the NTN contact seal.

NTN’s contact seal, as well as those manufactured by other companies, encounters sliding friction as the seal rubs the inner ring of the bearing:

• requiring a higher torque to rotate the bearing; and,
• generating heat (thus causing the bearing to operate at a slightly higher temperature), the effect of this is to reduce the speed limits of the bearing.

NTN’s suffix designation for a contact seal on only one side is LU ; for contact seals applied to both sides it is LLU. Also, NTN generally molds the synthetic rubber contact seals in the color red to aid in recognition.