Couplings Flashcards
Types of couplings
- rigid
- flexible
- special purpose
Shaft couplings
-power transmission components used to connect the driving and driven shaft end to end
Rigid coupling
- provides a fixed union between two shafts
- doesn’t allow for any deviation in alignment between the two shafts.
- has no provision for end float
Types of rigid couplings
- sleeve
- compression/flange
- ribbed/muff
- flange face
- threaded
Sleeve Coupling
- very simple rigid coupling used at low speeds and low torque
- has set screws
Compression or Flange coupling
- Wedging action connects the coupling to the taper on the shaft
- Grip the shaft by using tapered sleeves in tapered hubs so when they are drawn together they clamp to the shaft
- handle light or moderate loads
- shafts can be the same or different diameters
Ribbed or “Muff” coupling
- Used in heavy load or torque services
- have machined key ways in both shafts
- clamping forces keeps all the parts together but the torque is transmitted from the keys
- easy to remove and reconnect
Flanged face or “spiggett & recessed” coupling
- can connect both the same diameter & different diameter shafts
- the flange halves are made with male female hubs
Threaded couplings
-A special type of rigid coupling commonly used on vertical pumps where the drive unit is connected to the pump by a series of drive shafts joined by threaded coupling
The direction the shaft rotates on a threaded coupling?
-in the direction of thread of the coupling
How big of gap should be between the coupling halves on rigged and other split couplings?
-1/16 to 1/8
Rigid multibore
-Made for shafts with different diameters
Flexible couplings
- most common coupling
- compensate for some misalignment
Classifications of flexible couplings
- mechanical flexibility
- material flexibility
- combination flex
Mechanical Flexibility
- permit limited flexibility by allowing the coupling components to move relative to each other.
- they have sufficient internal clearances to allow for movement
Types of mechanical flex couplings
- roller chain
- silent chain
- synthetic chain
- gear
Chain coupling
- very easy to disconnect
- chain can be replaced without moving either the drive or driven shaft
- the clearance between the chain, sprocket teeth and internal clearance allows for some misalignment
- 1/4 axial travel in some cases
Roller chain coupling
- have two sprockets keyed to the shafts connected with a length of standard pitch
- flanges which are cut to receive roller bushing
- suitable for moderate speed & power applications
Most common roller chain
-double strand roller chain
Single Strand roller chain
-allows for more end float in your drive because of the absence of the pin link and roller link plates in the centre of the chain
Silent Chain Coupling
- heavy-duty drives at speeds of up to 5000RPM
- allow for very minor misalignment and some endplay
- remain in balance at high rotational speeds
Synthetic Chain Coupling
- for light power transmission drives
- are used because they do not require lubrication
- non-corrosive
- some torsional flexibility due to the resilience for the synthetic material
Gear Coupling
- two identical hubs with external gear teeth and a cover or sleeve having machine internal gear teeth
- teeth in the hub are straight sided and the teeth on the hub have curved sides
- allow for considerable axial float and some offset alignment with curved teeth
gear coupling covers
- can be one piece or two
- sealed to hold in the lubricant
- during installation remember to install covers before the hubs
Material flexibility
- The material of a specific part of the coupling is designed to bend or compress
- allows load change, reversing, and shock load
- no lubrication
Types of material flexible
- rubber tire
- elastomeric
- pin and biscuit
- flexible metal disc
Rubber tire
- Uses flexible rubber element
- driving element can be changed without removing the hubs
- allows for any type of misalignment and end float
- best for torsional flexibility
Elastomeric
- Transfer torque through an elastomeric element
- can be changed out quickly
Pin & biscuit
- uses rubber or neoprene biscuit moulded to steel sleeves
- allows for considerable deflection, torsional flexibility and axial float
Flexible metal disc
- Uses a series of thin steel plates to form a flexible steel disc to provide the coupling with material flexibility
- no backlash
- high temperature and high torque operations
Single set metal disc coupling
-Allows for angular misalignment only
Double flexible disc coupling
- Allows for both angular and offset misalignment
- high torsional rigid to make it good for high speed and high load
Combination mechanical and material flexibility
- Have some sliding movement between the coupling parts and require some material flexibility within coupling
- May require some lubrication
Types of combo couplings
- steel grid
- jaw & spider
- splined rubber
- pin & disc connected
- pin & rubber bushing
Non-conductive
-couplings that use non metallic flexing elements
Steel grid
- Two hubs with slotted flanges connected by a resilient spring steel grid.
- allows torsional flexibility and minor misalignment
- must be lubricated
- change grid when coupling shows wear
Jaw & Spider (love joy)
- 2 metal hubs which have 3 machined or cast jaw sections that interlock with the spider
- spider acts as a dampener, reducing shock & vibration
Splined rubber
- Two metal hub flanges that are manufactured with internal gear teeth that engage a flexible rubber sleeve with external gear teeth
- can tolerate shock loads, reversing and dampen vibration
- excellent resistance to electrical conductivity
Pin & disc connector
- Uses pins that are bolted or pressed into both coupling hubs
- between the hubs a flexible disc is positioned to engage with the pins in the hubs
- allows for minor misalignment
- if positioned with some clearance between the coupling halves it can also handle axial movement
Pin & rubber bushing
- Cast iron or steel flanged hubs with one hub fitted with a number of steel studs or pins with rubber or synthetic bushings mounted on the pins
- the other hub is drilled to accommodate the pins and bushings when it slides together
- will allow axial misalignment
Types of special purpose
- universal joints
- centrifugal
- shear pin
- floating shaft
- spacer
- brake wheel
Phase
-When the yokes are in the same position on each end of the shaft
Centrifugal design
- Soft start
- smooth acceleration
- overload protection
- dampening shock load
Fluid coupling
- consists of impeller (pump,input) and turbine (runner,output)
- never 100% engaged
- cannot tolerate any misalignment or end float
- 80% full
- fusible plugs
- 2-6% slip
- high vortex flow at start up
Turbine
-output member
Dry shot
-only no-slip
-usually has a flexible coupling added to compensate for any misalignment
-uses heat treated steel shot contained in the housing
-high temperature will degrade the shot
-
Centrifugal shoe
- retention spring
- use mechanical contact between the friction shoes and the drum, but application is through centrifugal force which causes the weighted shoes to move outwards from their neutral position and contact the outer rim of the coupling
Shear pin
- can be an add on to most couplings
- can be solid or turned down to form a step in the pin
- be sure to pull the pin at the large end first
Floating shaft
-similar to spacer
High torque & power couplings
-gear, universal joints, silent, flange face & flexible metal disc
Low horsepower
-sleeve, roller chain, rubber tire, steel grid, jaw and spider & splined rubber
Universal joints
- single only angular misalignment
- double has angular and parallel offset
- constant velocity handles anything
- splined connection allows for axial movement
Single universal joint
-can allow axial movement if it is fitted with a splined connection
