Couplings, Clutches and Brakes Flashcards by Mark Mathot

What are the 4 basic types of couplings

Rigid, Flexible, U-joints, Cetrifugal

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What are the 3 types of misalignment

Angular, Parallel (offset), Axial

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This coupling is a long, heavy-walled tube with a precision bore and a keyway cut along the the length

Sleeve coupling (low speed, low torque)

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Types of rigid flange couplings

Spigot and recess (keyed), Compression (no keys)

Can be same size or different diameter shafts

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Clamp (muff) couplings are for high or low speed drives?

Low speed (unbalanced weight), heavy load and torque

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What are the 3 types of Flexible couplings

Mechanically, elastomeric, universal

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Couplings of this type get their flexibility from the sliding or rolling of mating parts and usually require lubrication

Mechanically flexible

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This flexible coupling is composed of two jawed hubs and a slider block between them. Designed for low speed and high torque

Jaw and slider (allow for angular and offset misalignment)

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This coupling have two hubs with curved external teeth joined by an outer member with internal teeth

Gear-type double engagement (can operate at high speeds)

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Gear-type couplings allow for angular misalignment of this many degrees

1.5 degrees

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What types of chain are available for chain couplings

Roller (moderate speed), silent (heavy duty drives up to 5000rpm), and synthetic (light power)

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In these couplings multi-grooved flanges hold a flat steel grid what weaves in and out through grooves

Metallic grid

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These metallic couplings need no lubrication, are double-engagement and allow high-speed operation and are well balanced

Metallic disk (no backlash permitted)

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This coupling uses elastomeric elements called spiders

Jaw elastomeric (lovejoy)

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These couplings transmit torque through shear loading of the elastomer

Unclamped doughnut coupling

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These couplings have an elastomeric, split doughnut with metal inserts permanently moulded into them

Clamped doughnut couplings

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These couplings have a flexing element with reinforcement at the outermost radii

Clamped tire coupling

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These couplings are used to connect high-inertia drives to low-inertia driven members

Bushed pin coupling (diesel engine to hydrostatic pump)

High rotational speeds

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These couplings accommodate large amounts of offset alignment without creating side load on the shafts

Offset coupling

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These are used to accommodate shafts which have misalignment greater than flexible couplings allow

U-joints

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A single U-joint is used to connect shafts with this type of misalignment

Angular

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Two U-joints are used to connect shafts with this type of misalignment

Angular and/or offset (U-joints cannot accommodate axial misalignment (end play)

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The recommended maximum shaft angles for a U-joint

15 degrees below 100 rpm, up to 45 degrees (5 degrees minimum)

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The two simplest types of U-joints

Block and pin, cross-and-bearing

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The 3 types of centrifugal couplings

Mechanical (clutch-style), hydraulic (fluid coupling), dry fluid

Allowing the prime mover to reach a set rotational speed before applying the load of driven equipment is known as this

A soft start

This safety device trips a switch when the coupling reaches a critical temperature

Thermal cutout

In this type of coupling centrifugal force causes weights to press friction material against a drum to transmit power

Clutch-style

These couplings have a impeller and turbine (runner)

Fluid coupling

This occurs at start-up when the impeller is turning and the turbine is not moving

High vortex

This occurs when the impeller and turbine run at almost equal speeds

Low vortex

Torque development in this coupling depends on the amount of fluid available in the working section

Constant fill

This type of fluid coupling uses a reservoir and offers excellent overload protection

Delayed fill

This fluid coupling uses an external lever

Variable fill

At this many rpm centrifugal lockup couplings are mechanically linked 1:1

850 rpm (called lockup)

These couplings have in their housings a single rotor and a predetermined amount of heat-treated metal shot

Dry fluid (shot) couplings

The shot in a dry coupling is called this

flow charge

The two categories of clutches

Mechanical and electromagnetic

This type of mechanical clutch has square teeth that lock into mating recesses in facing members

Square jaw (engage at up to 10 rpm)

This type of mechanical clutch has sloped on one side of the jaw for easy engagement

Spiral jaw (engage at up to 150 rpm)

This mechanical clutch have two mating rings with a large number of small teeth or serrations

Multi-tooth (engage up to 300 rpm)

The two mating surfaces of a friction clutch or brake

Cast iron as a disk, band or drum. Other surface is a friction facing of moulded organic material bound by heat-cured resin (plate, pad, or shoe)

This is a protective device that limits the torque transmitted to the equipment

Torque limiter

The two types of drum units

Constricting and expanding

These clutches are units which allow unidirectional power transmission

Over-running

These clutches have pieces composed of two non-concentric curves of different radius

Sprag

In these clutches the input and output shafts are connected by a coiled spring

Wrap spring (ID of spring slightly smaller than OD of shaft hubs)

These clutches transmit torque through rollers that ride on the ramped or cammed surface

Roller-ramp

The three basic types of electromagnetic clutches and brakes

Magnetic particle, eddy current, hysteresis

This electromagnetic clutch/brake has dry iron particles fill the space between input and output members

Magnetic particle (good for continuous changes of speed)

These clutches have an input drum, a stationary field coil, and an output rotor

Eddy current (not used to hold a load)

In this clutch a coil generates a magnetic field in the input rotor and in the output element called a drag cup

Hysteresis (used in fractional horsepower applications)

Methods of actuation for clutches and brakes

Mechanical, electrical, pneumatic, hydraulic, self-activating

The simplest cheapest way to engage clutches and brakes

Mechanical

An electromagnetic clutch or brake has two basic parts

annular electromagnet (coil), and an armature

The most frequent method of actuation for clutches and brakes in industrial equipment

Pneumatic (up to 200 psi)

This type of actuation actuates and releases because of differences in speed or direction of rotation

Self-activating

This is a special type of coupling commonly used on applications such as vertical pumps

Threaded couplings

The axial travel for a chain coupling can be up to this

1/4"

A smaller more compact version of the rubber tire coupling

Bonded rubber type

These joints are used when the joint angles are uneven

Constant velocity joints (CV joints)

The amount of slip on a fluid coupling can be between this percentage

2-6%

Fluid couplings use these in the couplings housing if an overload continues

Fusible plugs (sometimes uses a switch that can be triggered)

Fluid couplings should be filled to a maximum of this percentage of their total capacity

80%

This coupling is used where the drive component cannot be located close to the driving motor

Floating shaft coupling (spool)

Couplings over this many rpm's need to be dynamically balanced

3600 rpm

The gap between halves on a split rigid coupling should be this much

1/16" to 1/8"

Cone clutch engagement angles

10-15 degrees

Silent chain couplings are for speeds up to

5000 rpm

The amount of axial movement on a metallic grid coupling

3/16" on a 2 to 4 inch diameter coupling

How hot should you heat the coupling for a shrink fit

180F above ambient temp for every 0.001" of interference per inch of hub diameter

Coupling used for high torque and power applications

``` Gear coupling Universal joints Silent chain Flange-face Flexible metal disk ```

Couplings used for low HP

``` Sleeve Roller chain Rubber tire Steel grid Jaw and spider Splined rubber (unclamped doughnut) ```