Coupling
It is the mechanical element used to connect two shaft of a
transmission system and transmit the torque from one shaft to
another
Coupling
COUPLING
It is the mechanical element used to connect two shafts of a transmission system and
transmit the torque from one shaft to another.
Functions of coupling:

It connects the shafts of two different units such as an electric motor and
machine.

It introduces mechanical flexibility between two connected units and
tolerates small misalignment between the connecting shafts.
It reduces the transmission of vibrations and shocks between two
connected units.

Requirements of good coupling
• It should transmit the full power from one shaft to another.
• It should keep the shafts in perfect alignment.
• It should absorb the slight misalignment that may be present
between the driver and drive shaft.
• It should be easy to connect and disconnect.
• It should have no projecting parts.
Types of Coupling
• Rigid couplings
– Muff and sleeve coupling
– Split muff or compression coupling
– Flanged coupling
• Flexible Couplings
– Bushed-pin type flexible coupling
– Oldham coupling
– Universal coupling
Rigid Couplings
• Rigid couplings are used to connect two shafts which are perfectly aligned.
• These couplings are not capable of tolerating any misalignment between
two shafts.
• These couplings are not capable of absorbing shocks and vibrations.
• These are simple and inexpensive.
.
Rigid Flanged coupling
Rigid couplings
• Rigid couplings do not allow any misalignment
of connecting members.
• Not of absorbing shocks and vibration.
•Muff and sleeve coupling
•Split muff or compression coupling
•Flanged coupling
Use to connect two line shafts
Muff and sleeve coupling
A protected type rigid
flange coupling
It consists of two flanges :
one keyed to the driving shaft and
other to the driven shaft. One of the
flange has projected portion and
other has a corresponding recess.
This helps to bring two shafts in
line and maintain the alignment.
The two flanges are coupled
together by means of bolts and nuts.
The number of bolts used are
generally three, four or six. The two
keys are staggered at right angles
along the circumference of the
shafts.
• The flanges are made of cast iron,
cast steel, or steel.
The torque is transmitted from the driving shaft to
the left side flange through the key. It is then
transmitted from the left side flange to the right side
flange through the bolts. Finally, it is transmitted
from the right side flange to the driven shaft
through the key.
Advantages
1. The flange coupling is easy to assemble and
disassemble.
2. It has high torque transmitting capacity.
Disadvantages
1. The flange coupling cannot tolerate misalignment
between driving and driven shafts.
2. It requires more radial space.
Applications
The flange coupling is used for connecting electric
motor to pump or compressor.
Split muff or compression coupling
Flexible couplings
• It is used to connect shafts having small
amount of lateral or/and angular
misalignment.
• These coupling are capable of absorbing
shocks and vibration.
•Bushed-pin type flexible coupling
•Oldham coupling
•Universal coupling
Bushed-pin type flexible coupling
Used to connect diesel engine to generator
Oldham coupling
Use to connect Two eccentric shafts
Universal coupling
Sr.
No.
Comparison Parameters
Rigid Coupling
Flexible Coupling
1
Purpose
To connect two shafts which
are perfectly aligned
To connect two
shafts having small
misalignment
2
Alignment
Cannot tolerate any
misalignment
Can tolerate any
misalignment
3
Shock and vibration
Cannot absorb Shock and
vibration
Can absorb Shock
and vibration
4
Deflection
Deflection is less
Deflection is more
5
Cost
Less expensive
More expensive
Bearings
Introduction
• Bearing is a mechanical element, which supports the
rotating element. Thus it permits the relative rotating
motion between two parts.
• Due to relative motion, a moving part comes in contact
causing friction with the stationary part, resulting wear
of mating surface. To reduce the frictional resistance
and wear, a lubricant is provided between the mating
surface.
• A lubricant is a substance placed between the two
surfaces which reduces friction, wear and takes away
heat is known as lubricant.
• Generally mineral oil, vegetable oil or grease are used as
lubricant in bearings.
Types of Bearings
a) Sliding Contact Bearings
b) Rolling Contact Bearings
Sliding Contact Bearings
• In sliding contact bearings, the motion between the
shaft and the bearing is purely sliding. Because of the
surface contact, the friction between the rotating
shaft and bearing surface is high and hence
lubrication is necessary.
• They are used for crankshaft in I.C. engine, ball mills,
centrifugal machines in sugar industry, turbogenerators centrifugal pumps. etc.
Rolling Contact Bearing
• Rolling motion takes place along the surfaces
of contact between the parts. Steel balls or
rollers are interposed between the moving
and fixed elements, which offer rolling
friction. They are also known as antifriction
bearings. They have point or line contact with
moving element.
Ball bearing
Single Row
Double Row
The Ball Bearing
• It is as shown in Fig.
• It also consists of four major
parts.
(i) Outer race
(ii) Inner race
(iii) Balls and
(iv) Cage
• It consist of number of balls placed between the races. The balls are
placed properly by the cage, which acts like a separator. All balls are
free to rotate within the cage and are able to roll inside the outer
race and inner race.
• A position clearance is kept between the races to accomplish slight
misalignment of balls due to load.
• Ball bearings are able to take only radial loads. It is used in high speed
applications like grinders, cutters etc.
• Deep groove ball bearings are able to sustain radial load as well as
axial (thrust) load.
Deep Groove Ball Bearing
Cylindrical Roller Bearing
Angular Contact Bearing
Taper Roller Bearing
Self-Aligning Bearing
Thrust Ball Bearing
Sr. No.
Comparison parameter
Ball bearing
Roller Bearing
1
Rolling bearing
Spherical ball
Cylindrical roller
2
Nature of contact
Point contact
Surface contact
3
Load carrying capacity
low
High
4
Radial dimensions
More
Less, use for
compactness
5
Axial dimensions
less
more
Sr. No.
Comparison parameter
Sliding contact bearing
Rolling contact bearing
1
Nature of relative motion
sliding
rolling
2
Starting friction
high
low
3
Running friction
low
High
4
Load carrying capacity
More
Less, use for compactness
5
Nature of load
Can take shock load
Poor in taking shock load
6
Type of load
Either radial or axial
Can take combine radial & axial
7
speed
Suitable for high speed application
Not suitable for high speed
8
Life
More
Less
9
Positional accuracy
Poor
Good
10
Lubrication
Required continuous supply
Not Required continuous supply
11
Noise
Noise less
More noise
12
Initial cost
High
Low
13
Maintenance
More
less
14
Application
Steam and gas engine, crankshaft
bearing, marine, conveyors, centrifugal
pumps
Automotive gear box, m/c spindle,
automobile