A bearing is a machine element that constrains relative motion between moving parts to only give the desired motion. The design of bearing may be provide for free linear movement of the moving parts or free rotation around a fixed axis or it may prevent motion by controlling the vectors of normal forces that bear on the moving parts .They are mainly used to minimize the friction between moving parts.
The invention of the rolling bearing, within the sort of wood rollers supporting, or bearing, associate object being affected is of nice antiquity, and may predate the invention of the wheel. The ball bearing was originally described by GALILEO in the 17th century.
Bearings played a significant role in technological revolution allowing the new industrial machinery to work with efficiency. There are various types of bearings. The most common bearing is plain bearing which uses lubricant between the rubbing surfaces.
Types of bearings:
- Plain Bearing
- Journal bearing
- Sleeve bearing
Common motions permitted by bearing are as follows
- Axial Rotation
- Linear Motion
- Spherical Rotation
- Hinge Motion
Bearings are designed on the basis of the following subjects
Maintenance and Lubrication of a Bearing is very important. The external factors that effect a bearing are electrical signals, temperature,exposure to environment. To prevent bearing from these external factors they should be frequently lubricated and maintained properly.
They have rubbing surfaces with lubricants between them .Friction factor depends on the material and construction. Stiffness is good. Life depends on application and also depends on lubrication
Ball or rollers are used between rotating surfaces. This prevent and minimize the friction. Life is moderate and speed changes according to requirements. These kind of bearings are widely used now a days.
Jewel bearing has an off centre bearing rolls in seating. Friction of this bearings is very low. Speed and life are low.
In these bearings fluid is forced between two faces and held in by edge seal. Friction is zero at zero speed. Stiffness is very high. Can be used for high speed applications. Life is infinite in some applications.
The two faces of bearing are kept separate by magnets. Zero friction at zero speed but eddy currents are often induced. Stiffness is low and there is no practical limit for speed and life.
These bearings are provided with material flexes to give any constrain movement. Friction is very low. Stiffness is low, and speed can be very high with high life.
Reducing friction in bearings is commonly important for efficiency. It helps to cutback the wear and tear and to facilitate extended use at high speeds and to avoid heating and premature failure of the bearing. Friction of a control depends on its form, material, and fluid used between two surfaces applied on bearings. Completely different bearing operative have different operational speed limits. Plain bearings generally handle only lower speeds. However the gap between the components that are separated by the bearing varies with load. Forces working on the bearing may be radial, axial or bending moments perpendicular to the most axis.