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Second Year > Clutches > Flashcards

Clutches Flashcards

0
Q

positive contact

A
  • depend on interlocking parts for engagement and do not allow slippage
  • starts with a bang right away
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1
Q

Purpose of clutches

A

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

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2
Q

Types of positive contact clutches

A

-square jaw, spiral jaw, multiple-tooth design

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3
Q

Square Jaw

A
  • bidirectional, one jaw is splined or keyed and can move axially to engage the other
  • engaged only at very low speed 10 RPM
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4
Q

Spiral Jaw

A
  • engaged at higher speeds 150 RPM

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

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5
Q

Multiple Tooth

A
  • use a large number of small gear teeth or serrations to provide engagement
  • engaged at 300 RPM
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6
Q

Friction Clutches

A
  • smooth transfer of power
  • depend on coefficient of friction between the clutch surfaces and a pressure plate
  • engage at any speed
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7
Q

Clutch Plates

A
  • dampening devices (springs) to reduce shock and torsional vibration
  • solid or discs of steel or bronze
  • sintered bronze bonded to a steel backing
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8
Q

Radial Clutches

A
  • expanding shoe

- contracting shoe

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9
Q

Expanding Shoe

A
  • 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
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10
Q

Contracting Shoe

A

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

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11
Q

Axial Clutches

A
  • single disc
  • multidisc
  • cone
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12
Q

over centering

A

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

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13
Q

Axial Friction Clutches

A

-use a soft friction disc sandwiched between harder pressure plates

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14
Q

Types of Axial Friction Clutches

A

-single, multi friction and cone

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15
Q

Single Friction

A
  • 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
16
Q

Multi-Disc

A
  • the more discs the more power

- increase power without adding to disc diameter

17
Q

Electromagnetically Activated

A

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

18
Q

Cone Clutches

A
  • the cone wedges provide a mechanical advantage due to the wedge in the drum
  • they have a tendency to grab
19
Q

Hydraulic clutch

A
  • 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
20
Q

Scoop Tube

A

-

21
Q

Electric and Magnetic

A
  • Torque transmitted is proportional to the coil current or strength of the magnetic field
  • Hysteresis
  • magnetic particle
  • eddy current
22
Q

Hysteresis

A
  • electronically activated
  • electromagnetic coil on the input rotor and a hardened steel drag cup on the output shaft
  • can slip
23
Q

Eddy Current

A
  • two drums running very close to each other on soft iron rotors
  • transmit high torque with moderate speeds
  • can slip
24
Q

Magnetic Particle

A
  • output housing contains magnetic metal particles
  • when coil is energized the metal particles form a link between the input and output
  • can slip
25
Q

Torque Limiting Clutches

A
  • 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
26
Q

One way (overrunning) clutches

A
  • roller ramp
  • cam type
  • wrap spring
27
Q

Roller Ramp

A

-compression springs and rollers transmit the power

28
Q

Cam Type (Sprag)

A

-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.

29
Q

Wrap Spring (very basic clutch)

A

-used on extremely low power applications and moderately large torque

30
Q

One way or over running

A
  • simple overrunning
  • indexing
  • holdbacks/backstops
31
Q

Over running

A
32
Q

Indexing

A
  • position contact in one direction

- move, fill, move

33
Q

Dynamic Brakes

A

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

34
Q

Disc Brakes compared to drum brakes

A

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

35
Q

Hydraulic Brakes

A
  • similar to fluid couplings but the turbine or runner is anchored
  • to activate fluid is pumped into the retarder
36
Q

One way clutch

A

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

Second Year (19 decks)

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