CLUTCHES

Couplings, Clutches & Brakes Couplings and Clutches are power and motion transmission elements.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

Rigid couplingsRigid Couplings are used to connect two shafts which are perfectly in axial alignment.Sleeve or Muff CouplingConstruction:It is the simplest type of rigid coupling which is made from cast iron.The hollow cylinder (muff) is fitted over the ends of the two shafts with the help of taper sunk key.Working:Disadvantage: It is difficult to assemble when there is no perfect alignment between shafts.

Sleeve or Muff Coupling

Rigid couplingsSplit Muff CouplingConstruction:The muff or sleeve is made into two halves of cast iron.They both are joined by nut and bolts.Advantage: Assembling and disassembling of the coupling is possible without the changing the position of shaft.Application:This coupling is used for heavy power transmission at moderate speed.

Split Muff Coupling

Rigid couplingsFlange CouplingThis coupling is having two separate cast iron flanges.The flanges can be of protected type or unprotected type.The flange couplings are rigid and accurate.It is used for heavy power transmission at low speed.

Flange couplings

Protected type flange couplings

Flexible couplingsFlexible 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 couplingThis type of coupling allows for imperfect alignment of two joining shaft.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 operation.It is generally used to couple electric motor and machine.

Flexible couplings

Bushed pin type flange coupling

Flexible couplingsOldhams CouplingIt 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 driven shaft.

Oldhams Coupling

Flexible couplingsUniversal CouplingConstruction:Working:Application:This coupling is used to connect two shafts whose axes will intersect.The angle between the shaft axes may vary slightly during operation.It is widely used in automobile and machine tools.

Universal Coupling

CLUTCHES Clutch is a form of coupling which is used to transmit the power from driver shaft or an input shaft to driven shaft of machine which may be required to start or stop frequently.

CLUTCHES

CLUTCHESJaw & Toothed ClutchThis 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

CLUTCHES

Jaw & Toothed Clutch

CLUTCHESDisc ClutchThere 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 friction.AutomobilesWhen large torque transmission is required the multidisc clutches are used. It is having more number of contact surfaces discs on driving and driven shaft.

Disc Clutch

Disc Clutch

CLUTCHESCone ClutchThe 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 8 to 15.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 clutch.

CLUTCHES

Cone Clutch

CLUTCHESCentrifugal ClutchIn 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 the shoes.

Centrifugal Clutch

BRAKESIt 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 brake.

BRAKES

BRAKESBlock BrakeThis 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.

BRAKESBand BrakeA 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.

Simple band brakes

Differential band brakes

BRAKESInternal Expanding shoe BrakeThe shoes are housed in the rotating drum.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 rotating drum.Applications are in motor cars and light trucks.

Difference between a brake and a clutch