CHAIN DRIVES PPT Flashcards
In order to avoid slipping, unlike in belt and rope drives where slipping may occur, __________ are used.
steel chains
are made up of number of rigid links which are hinged together by pin joints in order to provide the necessary flexibility for wraping round the driving and driven wheels.
Chains
These wheels have projecting teeth of special profile and
fit into the corresponding recesses in the links of the
chain.
These toothed wheels are known as _________ wheels or
simply _________.
sprockets
The chains may also be used for long center distance of up to
8 metres
The chains are used for velocities up to ________ and for power up to ________.
25 m/s, 110 kW
the distance between the hinge centre of a link and the corresponding hinge centre of the adjacent link
Pitch of chain, p
the diameter of the circle on which the hinge centers of the chain lie, when the chain is wrapped around a sprocket.
Pitch circle diameter of chain sprocket, D
The value of C obtained should be decreased by _________ in order to accommodate initial sag in the chain.
2 to 5 mm
For best results, the minimum center distance should be ___________ the pitch.
30 to 50 times
Used for ________ and __________ purposes and operate at a
maximum velocity of 0.25 m / s.
Hoisting and Hauling Chains
The links of this type of chain are of oval shape; joint of each link is welded. The sprockets which are used for this type of chain have receptacles to receive the links.
Chain with oval links
The links of this type of chain are of square shape. Such type of chains are used in hoists, cranes, dredges. The manufacturing cost is less than that of chain with oval links, but in these chains, the kinking occurs easily on overloading.
Chain with square links
These chains are used for elevating and conveying the
materials continuously at a speed up to 2 m / s.
* The ___________ run at slow speeds of about 0.8 to
3 m / s.
* The ____________ are of the following two types:
1. Detachable or hook joint type chain and
2. Closed joint type chain
Conveyor Chains
These chains are used for transmission of power, when the distance between the centres of shafts is short.
These chains have provision for efficient lubrication
Power Transmitting Chains
This 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. These chains are used mainly for conveyor application at small speed
Block or bush chain
(also known as inverted tooth chain) is designed to eliminate the adverse effects caused by stretching, and when properly lubricated, this chain gives durable service and runs very smoothly and quietly.
- There is no relative sliding between the teeth of the inverted tooth chain and the sprocket wheel teeth.
- The economical speed is of the order 4000 fpm (20 m/s).
Silent 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.
* The economical speed is of the order 2500 fpm (13 m/s).
Bush roller chain
In order to have smooth operation, the minimum number of teeth on the smaller sprocket or driver sprocket may
be taken as _____ for moderate speeds and _____ for high
speeds; or preferably ____ teeth.
17, 21, 24
The angle through which a chain link turns on its pin as it engages with the sprocket is equal to
180 / T
From an operating standpoint, ___________ is desirable
large sprocket
It is usually preferable to use __________ of teeth on a sprocket.
odd number
For the number of teeth of the small sprocket, it is recommended to use not fewer than ____ and preferably not fewer than _____.
11, 24
In the chain number: the right-hand digit ___ indicates a rollerless bushing chain
5
In the chain number: the right-hand digit
___ indicates a lightweight chain
1
In the chain number: the right-hand digit
___ indicates a chain of usual proportion with roller.
0
Oil applied periodically with brush or spout can (100 fpm maximum chain speed)
Type I. Manual Lubrication
Oil applied between link plate edges from a drip lubricator (300 fpm maximum)
Type II. Drip Lubrication
Oil level maintained at predetermined height in casing (1000 fpm maximum)
Type III. Oil Bath or Oil Slinger
The range of chain widths should be between p and 10p, but preferably between ___ and ____.
2p and 6p
In small sprockets, it is necessary to determine whether the number of teeth and the pitch selected will result in a sprocket large enough to be mounted on the shaft with due allowance for a keyway.
On this basis, the following relations may be used to determine the minimum number of teeth that may be used with a given pitch for a sprocket with bore d.
Maximum Sprocket Bore
The length in links should be used as an even number unless it is desired to use an ________
An advantage of the _________ is that the adjustment of center
distance may be in units of one link instead of a pair of links.
offset or hunting link
- Means of adjusting center distance should be provided to secure proper chain tension when the drive is installed and to make adjustments for wear of the chain in service.
- There should be a small amount of slack in the chain.
- Idler sprockets may be used to minimize the slack of the chain to be installed on the slack side.
Adjustment for Chain Tension
Chain drives should be enclosed to provide proper chain lubrication, to keep dirt and grit from the chain and sprocket and to ensure the safety of the operator.
* The case should be easy to install and to open for inspection, maintenance and lubrication.
Chain Cases and Lubrication
