1. Power Transmission Devices
Belt drive,
chain drive,
gear drive

2. In belt drives, slipping of belt may occur.
Chain Drive
In belt drives, slipping of belt may occur.
In order avoid slipping, steel chains are used,
The chains are made up of rigid links which are hinged together in order to avoid the necessary flexibility for warping around the driving and driven wheels.

3. The wheels have projecting teeth and fit into the corresponding recesses, in the links of The chain.
The wheels and the chain are constrained to move together without slipping and ensures perfect velocity ratio.
The toothed wheel are known as sprocket wheels or simply sprockets.
These wheels resemble to spur gears

4. Link Chain These chains are used for hoisting and hauling purposes.
The links of this type of chain are of oval or square shape.
The joint of each link is welded. The sprockets which are used for this type of chain have receptacles to receive the links.
Such type of chains are used only at low speeds such as in chain hoists and in anchors for marine works, cranes and dredges.

5. Block Chain
These chains are used for transmission of power, when the distance between the centers of shafts is short. These chains have provision for efficient lubrication.
A block or bush chain is shown in figure. This type of chain was used in the early stages of development in the power transmission.
It produces noise when approaching or leaving the teeth of the sprocket because of rubbing between the teeth and the links. Such type of chains are used to some extent as conveyor chain at small speed.

6. Roller Chain
A roller chain consists of outer plates or pin link plates, inner plates or roller link plates, pins, bushes and rollers. A pin passes through the bush which is secured in the holes of the roller between the two sides of the chain. The rollers are free to rotate on the bush which protect the sprocket wheel teeth against wear. The pins, bushes and rollers are made of alloy steel.

8. Advantages of Chain Drive over Belt Drive
As no slip takes place during chain drive, perfect velocity ratio is obtained.
Since the chains are made of metal, therefore they occupy less space in width than a belt or rope drive.
The chain drives can be used when the distance between the shafts is less.
It has high power transmitting capacity than belt drive.
It gives high transmission efficiency (Upto 98%).

9. The chain drive gives less load on the shafts.
A number of shafts can be driven in the same or opposite direction by means of chain from a single driving sprocket.
It permits high speed reduction ratio upto 10 : 1 in one step.
It can be operated under adverse temperature and atmospheric conditions.
Chain drives are more compact than belt drive

10. Dis-advantages of Chain Drive over Belt Drive
Compared with belt drives, chain drive require precise alignment of shafts.
Compared with belt drives, chain drives require proper maintenance, particularly lubrication and slack adjustment.
The production cost of chain is relatively high.
They generate noise.

11. Application Chain Drive
Bicycles, motor cycles
Agriculture machinery
Conveyors
Rolling mills
Road rollers
Metal and wood working machinery
Textile industry
Building construction
Material handling equipment