The classification of the gears is done on the following basis:
1. On the Basis of Arrangement of Shafts of Gears
(i) Parallel Gears
When two parallel and coplanar shafts are connected by gears as shown in the figure above, the types of gears are called as spur gears. The arrangement of gears is called spur gearing.
Spur gears have teeth parallel to the axis of the wheel.
Examples: Spur gear, helical gear, double helical gear (herringbone gear)
(ii) Intersecting Gears
When two non-parallel or intersecting but coplanar shafts are connected by the gears as shown in the figure given above is called bevel gears. And such arrangement is called as bevel gearing.
Examples: Bevel gear, helical bevel gear, miter gear.
(iii) Non-Intersecting and Non-Parallel
When non-intersecting and non-parallel i.e. non-coplanar shafts are connected by gears as shown in the figure given above is called as skew bevel gears or spiral gears. And the arrangement is called as skew bevel gearing or spiral gearing.
Examples: Spiral gears.
2. On the Basis of the Peripheral Velocity of the Gears
(ii) Medium Velocity: The gears which have velocity in between 3 m/s and 15 m/s are called as medium velocity gears.
(iii) High Velocity: The gears which possess velocity more than 15 m/s are called as high velocity gears.
3. On the Basis of the Types of Gearing.
(i) External Gearing
When gears of two shafts mesh externally as shown in the figure given above, than the gears are called as external gears. In external gearing the larger of the two meshed gears is called spur or gear and the smaller is called as pinion. The motion of the two wheels in external gearing is always unlike (i.e. if one moves clockwise than other will move in anticlockwise direction).
(ii) Internal Gearing
When the gears of the two shafts mesh internally with each other as shown in figure given above, than it is called as internal gearing. In internal gearing the larger of the two wheels is called as annular wheel and the smaller wheel is called as pinion. The motion of the two wheels in the internal gearing is always like (i.e. if one moves clockwise than the other will also moves in clockwise direction).
(iii) Rack and Pinion
Sometimes what happen, the gears of a shaft meshes externally and internally with the gears in strait line (i.e. strait line is also defined as the wheel of infinite radius). Such type of gear is known as rack and pinion. In rack and pinion types of gears the straight line gear is called rack and the circular gear is called pinion. Rack and pinion gears are used to convert linear motion into rotary motion and vice-versa.
4. On the Basis of the Position of Teeth on the Gear.
Straight gears have straight teeth on the surface of the wheel rim. For example: Spur gear.
The inclined gears have inclined teeth on the surface of the wheel rim. For example: Helical gears.
Curved gears have curved teeth on the surface of the wheel. For example: Spiral gears.
Types of Gears
Now we will discuss each classification of gears one by one in detail.
1. Spur gear
spur gear is the simplest types of gear among all types of gears and easy to manufacture. It has straight teeth parallel to the axis of the wheel or shaft. It is used to transmit power between parallel shafts. Only one tooth of the spur gear meshes at a time. It is regularly used for speed reduction or increase, resolution and accuracy enhancement for positioning systems, torque multiplication. It creates noise during its operation.
2. Helical Gears
The helical gears have inclined teeth (teeth cut at an angle to the face of the gear) on the surface of the wheel. Its operation is smoother and quitter as compared with the spur gear. It is mostly commonly used in transmission gear boxes.
Helical gear can be further sub divided into two types
(i) Single Helical Gears
It is gear that has inclined tooth on its wheel surface. Single helical gear possesses axial thrust.
(ii) Double Helical Hears or Herringbone Hears
Herringbone gear is a type of double helical gear in which there is side to side combination of two helical gears of opposite hands. If we look from the top than each helical groove on this gear looks like V letter. The herringbone or double helical gears have zero axial thrust which is not so with the single helical gear. Unlike helical gears it has advantage of transmitting power smoothly because it meshes two teeth at time.
3. Bevel Gears
These are the gears which transfers powers between two non parallel or intersecting shafts. These types of gears are mostly commonly used in the differentials drive of automobile.
The bevel gear are further classified as
(i) Straight Bevel Gear
This gear has straight teeth, conical pitch surface and tapering towards apex.
(ii) Skew Bevel Gears or Spiral Bevel Gear
this has curved teeth at an angle that allows gradual and smooth contact of the tooth.
(iii) Zerol Bevel Gear
these gears are similar to the bevel gear but it has curved teeth with a spiral angle of zero, so the ends of the tooth align with the axis.
(iv) Hypoid Bevel Gear
these types of gears are similar to the spiral bevel gear but the pitch surface is hyperbolic and not conical.
(v) Miter Gear
It is a type of bevel gear in which the two shafts are intersects at right angles with each other. It is used to transmit powers at right angles.
4. Internal Gearing
In internal gearing the two gears are meshed internally with each other.
5. External Gearing
In external gearing the two shafts are connected with the gears that mesh with each other externally.
6. Rack and Pinion Gears
In rack and pinion gears, a shaft meshes externally and internally with a straight line gear. The circular gear is called as pinion and the straight line gear is called as rack. The rack and pinion gear is shown in the figure given below.
7. Worm Gear
This is all about the types of gears used in power transmission from one shaft to another. If you have any query about this than comment us. And if you found this article informative and useful than share and like us on Facebook and Google+.