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Industrial Mechanic 2nd Block, Harmonized > Alb Mod Clutches and Brakes > Flashcards

Alb Mod Clutches and Brakes Flashcards

1
Q

The purpose of a clutch in a power transmission system is to:

A

engage or disengage a driven machine without starting and stopping the prime mover

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2
Q

Clutches can connect two shafts together, or connect power to:

A

A sheave, sprocket or gear

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3
Q

Clutches can be used to provide _____, constant torque, limited torque, automatic disconnection, quick starts or stops

A

variable speeds

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4
Q

Positive contact clutches depend on ____ for engagement and do not allow slippage

A

interlocking parts

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5
Q

Positive clutches can be used for timing applications. What are two disadvantages to positive clutches?

A
  • Cannot be engaged at high speeds (shock loads)

- May not line up when at rest

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6
Q

This clutch is a positive contact clutch. Uses square jaws that lock into mating recesses. These are bidirectional. One jaw is splined or keyed and can move axially for engagement. Generates no heat, must be engaged at low speeds (under 10 RPM)

A

Square jaw clutch

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7
Q

This clutch is a positive contact clutch. It can be engaged at higher speeds than the square jaw, but still causes shock on engagement. Engaging surfaces are square on one side and sloped on the other. Slides axially for engagement. Can drive in one direction only.

A

Spiral jaw clutch

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8
Q

This clutch is a positive contact clutch. Uses a large number of teeth to provide engagement. Can be engaged at a higher speed than square and spiral jaw, and still causes shock loading on engagement. Activated mechanically or electrically.

A

Multiple tooth clutch

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9
Q

Friction clutches provide a ____ transfer of power on engagement. Can engage or disengage at any speed.

A

smooth

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10
Q

Friction clutches can be designed with _____ in the friction plate to reduce shock and torsional vibration

A

dampening devices (springs)

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11
Q

Friction material may be non-metallic, metallic, or:

A

A mixture of both

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12
Q

A wet clutch is a:

A

Clutch flooded with oil

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13
Q

Radial clutches have the pressure applied against the:

A

rim or drum

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14
Q

axial clutches have contact pressure applied against the:

A

face

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15
Q

This is a radial friction clutch. Has a set of shoes connected to one shaft. They expand outward and engage the inside of the drum, which is connected to the other shaft. Once engaged, extra force is applied via centrifugal forces.

A

Expanding shoe clutches

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16
Q

This is a radial friction clutch. Has a drum on one shaft and a rim with the shoes on the other. The shoes are attached to a bladder, which inflates to apply pressure. Can engage and disengage quickly. Disengagement aided by centrifugal force

A

Contracting shoe clutch

Note: Alignment of the two machines must be accurate

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17
Q

Axial friction clutches use a soft friction disc sandwiched between two:

A

harder pressure plates

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18
Q

What is the main wearing surface of an axial friction clutch?

A

friction disc (clutch disc or clutch plate)

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19
Q

Rapid wear of a friction clutch indicates:

A

clutch is undersize

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20
Q

This is an axial friction clutch. It has a single clutch disc splined to the driven shaft. Has a larger surface area than a drum clutch and occupies less space. Has a single, spring loaded pressure plate connected to a fly wheel. Sandwiches the clutch disc when engaged.

A

Single disc friction clutch

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21
Q

This is an axial friction clutch. Same as the single disc clutch, but has multiple clutch discs so it can transmit more power. Uses an intermediate pressure plate between the clutch discs.

A

Multiple disc friction clutch

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22
Q

This style of friction clutch uses clutch plates with external teeth that mate with a ring with internal teeth, and can slide axially within it. The clutch plates are pressed against a pressure plate, which has internal teeth and mates with a splined shaft.

A

Pneumatically engaged friction clutch

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23
Q

Clutch plates that are in segments have the advantage of:

A

Being easily replaced

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24
Q

This type of friction clutch uses an activated magnetic field that pulls a friction disc into contact to transfer power

A

Electromagnetically activated clutch

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25
Q

This clutch is a cross between a radial and axial clutch. It’s contact surfaces are engaged at an angle usually between 10-15°. Smaller the angle, the greater the wedge and grip. Have a tendency to grab and to hold on when disengaging. Can be used submerged in oil.

A

Cone clutch

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26
Q

The main difference between a fluid clutch and a fluid coupling is the fluid clutch is designed so the amount of fluid is:

A

Controlled, via scoop tube. Regulates slip

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27
Q

The impeller of a fluid clutch is located on the ___ shaft

A

input

28
Q

The turbine of a fluid clutch is located on the ____ shaft

A

output

29
Q

Fluid couplings will always slip unless a ___ is used in the design

A

lock up clutch

30
Q

Magnetic clutches are ____ clutches

A

non friction

Engage without any direct mechanical connection

31
Q

True _____ clutches have no contact at all between driving and driven parts

A

electromagnetic

32
Q

The disadvantage of electromagnetic clutches is:

A

Cannot transmit as much torque

33
Q

This clutch uses an electromagnetic coil (or permanent magnet) on the input rotor to generate a magnetic field. Actuated by turning on the power supply to the magnet, torque is transferred to the hardened steel drag cup proportional to the current or strength of the magnetic field. Used for light high speed applications. Quick response time

A

Hysteresis clutch

34
Q

This clutch contains magnetic metal particles between the input rotor and output housing. When a coil is energized, the particles form a link and transmit torque proportional to the current. Used for high power transmissions and has a quick response time.

A

Magnetic particle clutch

35
Q

This clutch has two drums that run close together. Have soft iron rotors. Coupled through a magnetic field, requires slip to develop torque. Torque depends on strength of magnetic field and on slip. Should be liquid cooled for larger HP units. Can have infinite speed regulation. Transfers high HP at moderate speed.

A

Eddy current clutch

36
Q

On this clutch, a driven member is held between friction plates under a pre determined pressure. When the clutch is overloaded, the driven member slips. Power transferred adjusted by tightening/loosening nut/bolts

A

Torque limiting clutch

37
Q

A one way clutch comes in three types: (3)

A
  • Roller ramp clutch
  • Sprag (cam) clutch
  • wrap-spring clutch
38
Q

The wrap spring clutch is used on very low power applications and moderately large torque. It works because it ____ and transfers power in only one direction

A

tightens

39
Q

What are the 3 applications for one way clutches? (3)

A
  • Simple overrunning
  • Indexing
  • Holdbacks/backstops
40
Q

With a one way clutch, _____ allows multiple drive sources, and allows the shaft to turn even if one is stationary.

A

-Simple Overrunning

41
Q

With a one way clutch, _____ allows reciprocating motion to be changed to one way intermittent rotary motion

A

-Indexing

42
Q

With a one way clutch, ____ stops a drive, say on a conveyor, from running backwards when the load has stopped.

A

-Holdback or backstop

43
Q

____ are a power control device used to stop a machine or control speed or direction

A

brakes

44
Q

Most brakes transform mechanical energy to _____

A

heat

Note: may have fins to aid air cooling, can be cooled by liquids

45
Q

The friction materials for brake pads are usually made from _____ materials

A

heat resistant

46
Q

Brake capacity is expressed in ____

A

braking torque

47
Q

Brake effectiveness depends on:

A

Coefficient of friction of the material

48
Q

What are the 3 classes of brakes? (3)

A
  • Mechanical
  • Hydraulic
  • Electrical
49
Q

A dynamic brake is one that:

A

Not only holds, but slows and stops a load

50
Q

A brake used in personal safety is:

A

overdesigned

51
Q

If a retarder is used on a braking system, it does:

A

most of the braking but won’t fully stop a load

52
Q

The duty cycle of a brake refers to:

A

how often it is used

53
Q

The two basic types of brakes are: (2)

A
  • Drum

- Disc

54
Q

External drum brakes use a brake band, internal drum brakes use:

A

brake shoes

55
Q

Does a disc brake or a drum brake have more surface area for braking?

A

disc

56
Q

Disc brakes can have ____ force applied vs drum

A

more,

equal loading on both sides, no warping

57
Q

Caliper style disc brakes have the advantage of: (2)

A
  • pressure

- heat dissipation

58
Q

What are the two types of disc brakes? (2)

A
  • Rotating disc (caliper)

- Stationary disc

59
Q

This type of drum brake has a block that presses onto the side of the drum to stop the machine

A

block brake

60
Q

This type of drum brake has a band of material that applies pressure to the drum. braking power can be enhanced by using a differential pivot.

A

band brake

61
Q

This type of drum brake has two shoes on the outside, works like two block brakes.

A

external shoe brake

62
Q

This type of drum brake has two anchored shoes inside a drum.

A

Internal shoe brake

63
Q

Retarders are very similar to fluid couplings, except the ____ is anchored

A

turbine

64
Q

Retarders are activated by:

A

pumping fluid into it.

More fluid, more braking power

65
Q

Magnetic particle brakes have a stator, a rotor, a coil, and magnetic particles. It works the same as a magnetic particle clutch, except:

A

One member is held or anchored.

Braking power is determined by the intensity of the magnetic field

66
Q

Eddy current brakes work like an eddy current clutch, except one member is held or anchored. Works purely on the electrical principle of the:

A

repulsion of same poles

67
Q

When installing a clutch, bearings should be _____ to the clutch

A

as close as possible

Industrial Mechanic 2nd Block, Harmonized (28 decks)

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