Couplings and Clutches are power and motion
They are used to transmit power from one shaft
to another shaft.
The brake is a frictional device which is used to
control the motion.
Classification of Couplings
Sleeve or Muff
Bushed pin type
Rigid Couplings are used to connect two shafts which are
perfectly in axial alignment.
Sleeve or Muff Coupling
It is the simplest type of rigid coupling which is made from
The hollow cylinder (muff) is fitted over the ends of the two
shafts with the help of taper sunk key.
Disadvantage: It is difficult to assemble when there is no
perfect alignment between shafts.
Split Muff Coupling
The muff or sleeve is made into two halves of cast iron.
They both are joined by nut and bolts.
Assembling and disassembling of the coupling is possible
without the changing the position of shaft.
This coupling is used for heavy power transmission at
This coupling is having two
separate cast iron flanges.
The flanges can be of
protected type or
The flange couplings are
rigid and accurate.
It is used for heavy power
transmission at low speed.
Flexible couplings are used to protect the driving and
driven machines from effect of shocks, excessive stresses
due to deflection and vibration which may arise from
misalignment of shafts.
Bushed pin type flange coupling
This type of coupling allows for imperfect alignment of two
This type of coupling has pins which works as a coupling
bolt. The rubber or leather bushes are used over pins.
Rubber bush absorbs shocks and vibrations during
It is generally used to couple electric motor and machine.
It is used in connecting two
parallel shafts whose axes are
at small distance apart.
The flanges have projections
and disc is provided with two
slots on both sides which are
right angle to each other.
The rotation of drive shaft
causes the rotation and sliding
of disc which transmits the
motion and power to the
This coupling is used to
connect two shafts whose axes
The angle between the shaft
axes may vary slightly during
It is widely used in automobile
and machine tools.
Jaw & Toothed Clutch
This type of clutch provides
engagement without slippage.
The jaw clutch consists of segmental
projections or dogs on one side of
flange and corresponding recess on
other side of flange.
Driving flange is rigidly attached to the
end of driving shaft while the other
flange is keyed to the other shaft by
feather key so it can slide on the shaft.
The shifting device is accommodated
on the hub of the sliding flange.
Automobiles and Tractors
There are two flanges in such type of clutches.
One rigidly keyed to driving shaft and other fitted to driven
shaft by feather key or splines.
The amount of torque transmitted depends upon axial
pressure, radius of the friction surfaces and coefficient of
When large torque transmission is required the multidisc
clutches are used. It is having more number of contact
surfaces discs on driving and driven shaft.
The clutch consists of an internal cone fixed to the driving
member and a movable cone free to slide axially is keyed
to the driven member.
The slope of cone is from 8º to 15º.
The clutch parts are held together by springs producing
required axial force.
Advantage of cone clutch over the disc clutch is very
simple and required less axial pressure to disengaged the
In this clutch the engagement and
dis-engagement takes place at
certain running speed.
The shoes are held against the hub
or spider on the driving shaft by
means of suitable springs.
The driven member consists of a
cylindrical drum in which shoes
slide to make the contact through
friction surfaces with inner linings
of drum due to centrifugal force on
It is a device by means of which frictional
resistance is applied to a moving machine member
in order to retard or stop the motion of a machine.
Brakes are used in automobiles, trains, vehicles,
hoists, elevators, presses, etc.
Brakes absorbs kinetic energy of moving member
in automobiles and brakes absorbs potential
energy of lowering member in hoists or elevator
Block Brake Band Brake
This brake consists of blocks which are pressed against
the rim of revolving brake wheel or drum.
The friction between the wheel and the blocks tend to
prevent the rotation of the wheel.
Single Block :Railway train, Tram. Prony brake is an
example of block brake.
Double block :Electric cranes.
Bicycle brake is an example of double block brake.
A band brake consists of a flexible band of leather or steel
lined with friction material.
The friction between the band and the wheel surface
provides the braking force to decrease or stop the motion
of the wheel.
This type of brakes are used in civil construction
equipments and also in automobiles as hand brake.
Simple band brakes and differential band brakes.
Internal Expanding shoe Brake
The shoes are housed in the rotating
Under released condition, sufficient
gap between shoes and inner surface
of drum is maintained.
The rotation of cam tends to expand
the shoes outwards eliminating gap
and making contact between the
shoes and inner surface of the
Applications are in motor cars and