Clutches

Question 0

positive contact

Answer 0

• depend on interlocking parts for engagement and do not allow slippage
• starts with a bang right away

Question 1

Purpose of clutches

Answer 1

-to engage or disengage a driven machine without starting or stopping the prime mover.

Question 2

Types of positive contact clutches

Answer 2

-square jaw, spiral jaw, multiple-tooth design

Question 3

Square Jaw

Answer 3

• bidirectional, one jaw is splined or keyed and can move axially to engage the other
• engaged only at very low speed 10 RPM

Question 4

Spiral Jaw

Answer 4

• engaged at higher speeds 150 RPM

- one direction only as a rotation in the opposite direction causes the clutch to disengage aka over running

Question 5

Multiple Tooth

Answer 5

• use a large number of small gear teeth or serrations to provide engagement
• engaged at 300 RPM

Question 6

Friction Clutches

Answer 6

• smooth transfer of power
• depend on coefficient of friction between the clutch surfaces and a pressure plate
• engage at any speed

Question 7

Clutch Plates

Answer 7

• dampening devices (springs) to reduce shock and torsional vibration
• solid or discs of steel or bronze
• sintered bronze bonded to a steel backing

Question 8

Radial Clutches

Answer 8

• expanding shoe

- contracting shoe

Question 9

Expanding Shoe

Answer 9

• a set of shoes connected to one shaft. Expand outward to engage the inner section of a drum connected to another shaft
• engaged by external linkage that can be over centred
• receives extra force on the shoes from centrifugal force
• activated mechanically

Question 10

Contracting Shoe

Answer 10

-Disengagement is assisted by centrifugal force pushing the pads away from the drum (opposite of expanding shoe)

Question 11

Axial Clutches

Answer 11

• single disc
• multidisc
• cone

Question 12

over centering

Answer 12

-locking it in. (will show a handle being pushed forward)

Question 13

Axial Friction Clutches

Answer 13

-use a soft friction disc sandwiched between harder pressure plates

Question 14

Types of Axial Friction Clutches

Answer 14

-single, multi friction and cone

Question 15

Single Friction

Answer 15

• clutch plate is sandwiched between the pressure plate and the flywheel when engaged
• actuation is spring applied and mechanical release
• a release bearing or sleeve is used to push on fingers of the pressure plate to disengage the clutch

Question 16

Multi-Disc

Answer 16

• the more discs the more power

- increase power without adding to disc diameter

Question 17

Electromagnetically Activated

Answer 17

-uses magnetic field to pull a moveable arm with a friction disc mounted to its face

Question 18

Cone Clutches

Answer 18

• the cone wedges provide a mechanical advantage due to the wedge in the drum
• they have a tendency to grab

Question 19

Hydraulic clutch

Answer 19

• similar to a fluid coupling except its fluid can be controlled
• speed depends on speed of impeller and the amount of oil in the coupling

Question 20

Scoop Tube

Answer 20

-

Question 21

Electric and Magnetic

Answer 21

• Torque transmitted is proportional to the coil current or strength of the magnetic field
• Hysteresis
• magnetic particle
• eddy current

Question 22

Hysteresis

Answer 22

• electronically activated
• electromagnetic coil on the input rotor and a hardened steel drag cup on the output shaft
• can slip

Question 23

Eddy Current

Answer 23

• two drums running very close to each other on soft iron rotors
• transmit high torque with moderate speeds
• can slip

Question 24

Magnetic Particle

Answer 24

- output housing contains magnetic metal particles - when coil is energized the metal particles form a link between the input and output - can slip

Question 25

Torque Limiting Clutches

Answer 25

- driven member is held between friction plates under a predetermined amount of pressure - main adjustment is a torque bolt with fine adjustments with cap screws

Question 26

One way (overrunning) clutches

Answer 26

- roller ramp - cam type - wrap spring

Question 27

Roller Ramp

Answer 27

-compression springs and rollers transmit the power

Question 28

Cam Type (Sprag)

Answer 28

-if the inner race attempts to rotate clockwise at a higher rpm than the outer race, the cam will lock and power from the inner race will be transferred to the outer.

Question 29

Wrap Spring (very basic clutch)

Answer 29

-used on extremely low power applications and moderately large torque

Question 30

One way or over running

Answer 30

- simple overrunning - indexing - holdbacks/backstops

Question 31

Over running

Answer 31

-driven is allowed to keep running after the driver has stopped -

Question 32

Indexing

Answer 32

- position contact in one direction | - move, fill, move

Question 33

Dynamic Brakes

Answer 33

-the brakes need to slow or stop the inertia and mass of the load, as well as all of the moving and rotating parts

Question 34

Disc Brakes compared to drum brakes

Answer 34

-disc brakes are stronger because they have a larger sweep area.

Question 35

Hydraulic Brakes

Answer 35

- similar to fluid couplings but the turbine or runner is anchored - to activate fluid is pumped into the retarder

Question 36

One way clutch

Answer 36

-to move freely in one direction but to lock up in the opposite direction