3. Clutches
๏ Clutch is a one of the form of coupling.
๏ Clutches is used to transmit the power from
driving shaft to driven shaft of machine which
may be required to start or stop frequently.
๏ It is so designed that the two members may be
engaged or disengaged whenever required either
by a hand operated device or automatically by the
action of some power driven devices.
5. Disc clutches
๏ This type of clutch consists of two flanges, one
flange is rigidly to the driving shaft and other flange
fitted to the driven shaft.
๏ Single disc clutches are used in automobiles.
๏ When large torque transmission is required the
multi disc clutch are used.
๏ Multi disc clutch has more number of contact
surfaces discs on driving and driven shaft.
7. Cone clutch
๏ The cone clutch consists two cones , one internal cone
fixed to the driven shaft and another cone fitted on the
driven shaft.
๏ The operating lever used only for disengagement of the
clutch.
๏ The main advantage of cone clutch over the disc clutch
is very simple and required less axial pressure to
disengaged the clutch.
9. Centrifugal clutch
๏ It consists of a number of shoes on the inside of a
drum or rim of the pulley.
๏ The upper surface of the shoes are covered with a
friction material.
๏ The spider is fitted on the driving shaft.
๏ When centrifugal force is equal to spring force, the
shoe is just floating. But, when centrifugal force higher
than the spring force, the shoes moves outward and
comes into contact with the driven member and pressure
against it.
๏ The increase of speed causes the shoes to press
harder and clutch transmit more power.
11. Jaw clutch
๏ It is consists of segmental projections on one of the
flange and corresponding recesses on other flange on
the driven shaft.
๏ Driving flange rigidly keyed to the driving shaft
while the other flange is keyed to driven shaft by
splines so that it can slide on that shaft.
๏ The sliding flange engage with the fixed flange to
transmit the motion and power from driving shaft.
๏ This clutch is used for the transmission of power in
agricultural equipment like tractor, thresher, etc.
14. Brakes
๏ A brake is a mechanical device which produces
frictional resistance against moving machine member, in
order to slow down the motion of machine.
๏ In the process of performing this function, the brake
absorbs kinetic energy of moving member and the brake
absorbs potential energy of lowering member.
๏ The energy absorbed by brakes is released to
surrounding in form of heat.
15. Brake Application
๏ A brake is mechanical device which produce frictional
resistance against moving machine member ,in order to
slow down of machine.
๏ In the process of performing this function, the brake
absorbs kinetic energy of moving member and brake
absorbs potential energy of lowering number.
๏ The energy absorbed by brake is released to
surrounding in form of heat.
17. Block brake
(1)Single block or shoe brake:
A single block is consists of a block which is
pressed against the rim of revolving brake
wheel drum.
This brake is used in railway trains and tram cars.
The prony brake is example of block brake.
19. Double block or shoe brake:
๏ It consist of two brake blocks at the opposite ends of
the wheel.
๏ These shoes apply force to both the sides of wheel and
reduces the Unbalanced force on the shaft.
๏ This spring pull the upper end of the brake arms
together and Brake is applied.
๏ When a force is applied to the bell crank level , the
spring is Compressed and the brake is released.
๏ This brake is used in electric cranes.
The bicycle brake is example of double block brake.
21. Band brake
๏ A band brake consists of a flexible steel band lined
with friction material, which wrap to the brake drum.
When an upward force is applied to the lever end, the
lever turns about the fulcrum pin and tightens the band
on the drum and hence the brakes are applied.
๏ The friction between the band and the drum provides
the braking force.
๏ This type of brake is used in civil construction
equipment and also in automobiles as hand brake.
The rope brake is example of band brake.
23. Internal expanding shoe brake
๏ An internal expanding shoe brake consists of two
shoes.
๏ The outer surface of the shoes are covered with
friction material.
๏ Each shoe is pivoted at one end about a fixed
fulcrum and other end rests against cam.
๏ When the cam is operated, the shoe are pushed
outwards against brake drum.
๏ The friction between the shoes and the drum
produces the braking torque.
๏ This type of brake is commonly used in motor cars
and light trucks.
25. Disc brake
๏ Disc brakes are different from drum brakes
in that the drum is replaced by a circular
metal disc and the brake shoe are replaced by a
caliper which supports a pair of friction
pads , one on each side of the disc.
๏ These pads are forced inward by the operating
force and also retard the disc.
