In the type of gearbox we contact, the most commonly used are labyrinth and hoop spring.

The labyrinth:

Labyrinth seal is to make the internal oil chamber and external channels of the machine like a maze, in order to increase the path of medium leakage and medium leakage friction, so as to reduce the loss of medium. It is a non-contact sealing ring.

Hoop reed:

To understand this sealing principle, we need to talk about the lip seal. The lip seal is made of a specially designed material (nitrile rubber) and is in contact with the moving parts to prevent the outflow of lubricant and the entry of stolen goods. The hoop spring type uses annular spring or hoop spring to exert a basically constant inward pressure on the sealing lip to overcome the wear and tear of the sealing lip and strengthen the sealing effect. This is a contact seal.

It is important to note that since the sealing lip on the axis of rotation, inevitable meeting produces friction on the contact surface, therefore, also can have energy loss, the friction depends on many factors, such as, and seal lip contact shaft rotational speed, diameter, surface finish/roughness, research has shown that an installation on the 100 mm diameter shaft oil seal, When the shaft speed reaches 500rpm, the energy loss caused by friction is about 20W, and usually more than one oil seal is installed in a gear box, so the loss may reach 100W. In addition, during the start-up period of time, this resistance will be greater, that is to say, more wear.

Again, the amount of loss depends on the size of the seal and the rotational speed of the shaft.

Also note: if a gear box axis deflection error, so the resistance of the sealing ring is not dependent on the external load, also does not change along with the change of external load, that is to say, we can use the motor no-load current and the no-load current of with the gear box to estimate the total wear (including the seal, bearing, gear friction and lubricant churning loss)