Page 50 - needle bearings

Sealing Devices
NTN

Table 9.2 Seals (Contact seals)
Seal type Seal using mainly direct contact Contact seals Seal using mainly fluid lubrication and boundary lubrication

Seal name Seal ring (felt seal, etc.) V-shaped ring seal,
Oil seal,
O-ring,
mechanical seal
piston ring

This seal type seals a fluid perfectly by pressing its elastic body < Oil seal >
onto the sliding surface with a constant contact pressure. This seal type intended to seal lubricant at the sliding portion
Generally the contact seals are more excellent in sealing between its lip and a shaft has good sealing effect and is an
effective seal in the most frequent use.
performance than the non-contact seals, but the friction torque
Features and temperature rise thereof are greater than those of the The lip must be oriented outward to prevent invasion of water
non-contact seals.
content and foreign matter from outside and oriented inward to
<Felt seal>
This is the simplest of the contact seals, which is mainly used for prevent lubricant from leaking out of the housing. Furthermore,
another seal type with two or more lips is also available for
grease lubrication and suited to prevention of fine dust, but oil preventing lubricant leak and dust-proofing individually.
penetration and outflow are occasionally unavoidable to some
extent.

Fig. 9. 7 Felt seal
Application examples

Fig. 9. 8 Z type grease seal Fig. 9.10 Oil seal

Fig. 9. 9 GS type grease seal

A-46