CouplingsBy Taylor Amarel and Justin Skrzyniarz

A coupling is a device used to connect two shafts together for the purpose of transmitting power.

Two types of couplings◦ Rigid◦ Flexible also known as compensating

What are Couplings

Couplings interact with other devices by joining two shafts together in order to transmit power from one shaft to another shaft.

How Does a Coupling Interact With Other Things

Rigid couplings are used when precise shaft alignment is required; shaft misalignment will affect the coupling's performance as well as its life.

Rigid Couplings

Friction coupling◦ Clutch

Fluid coupling◦ Torque converter

Hirth joint◦ High power gas turbines

Flanged◦ Pipe

Types of Rigid Couplings

Clutch•Clutches are a friction based rigid coupling that transmits power by joining two shafts using a friction plate.•Clutches are located on manual cars, automatic cars, ships, and other industrial applications.

Pros Cons

•Inexpensive•No fluid/ lubricant required•Can be disengaged while in motion

•Require maintenance and friction plate is consumed over time

Torque Converter•A torque converter in a fluid based rigid coupling used to transmit power from one shaft to another shaft via a fluid median. As the input shaft spins it rotates a turbine causing fluid to move and turn the turbine on the output shaft.•Torque converts are commonly found in automatic cars, hydraulic motors, and turbines.

Pros Cons

•Last a long time•Can dynamically changed the relative motion between the input and output shaft

•Require fluid•Expensive

Hirth Joint•Hirth joints are a type of rigid coupling that transmits power by using two shafts that have interlocking teeth.•Hirth joints are commonly found on high speed high torque industrial machinery that benefits from the hirth joints self centering capabilities. Common applications include gas turbines, turboprops, steam generators.

Pros Cons

•Self centering•Transmit large amounts of power•Can be disengaged while in motion

•Require lubricant•Expensive

Flanged

•Flanged couplings are a type of rigid coupling that utilizes flanges and bolts to couple to shafts together.•Common applications of flanged couplings is joining two pipes together in order to transmit water pressure, it can also be used to extend a rotating shaft.

Pros Cons

•Cheap•Simple•Effective•No maintenance or replacing lubricant required.

•Can not be disengaged while in motion

Clutch

Flexible couplings are designed to transmit torque while permitting some radial, axial, and angular misalignment. Flexible couplings can accommodate angular misalignment up to a few degrees and some parallel misalignment.

Flexible/Compensating Couplings

Universal joint◦ Drive shaft on cars

Cardan joint◦ Train cars

Ball joints◦ Car steering assembly

Thompson couplings◦ High torque industrial drive shafts

Types of Flexible/Compensating Couplings

Universal Joints

•Universal joints are a type of flexible coupling that utilized a yoke and cross to connect two shafts and allow shafts to be at an angle relative to each other. •Common application of Universal joints include car drive shafts, steering columns.

Pros Cons

•Inexpensive •Wears out over time

Cardan Joint•Cardan joints are a type of flexible coupling that connects two shafts using two pivots and a connecting rod.•Couplings are often used for steering column and ratchet extensions.

Pros Cons

•Inexpensive •Can not transfer high torque or high speed loads

Thompson Coupling•Thompson coupling is a flexible coupling that utilizes a configuration of two cardan joint assemblies, and a modified universal joint•Common application include high power generators, trailer hitches, and gas turbines.Pros Cons

•Very strong, can transmit large amounts of torque•Reduce almost all friction, and stress on the coupling•Very efficient

•Require lubrication•Very expensive

Ball jointBall joint is a flexible coupling that uses a spherical ball and socket like configuration in order to allow a shaft to pivot while pivoting.Common applications include car axle assemblies, the human hip joints, throttle bodies, and gas springs.

Pros Cons

•Inexpensive•Provides 3 axes of rotation

•Require and consume lubricants

Thompson Coupling

Cardan Joint

Ball Joint

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Nice, Karim.  "How Torque Converters Work"  25 October 2000.  HowStuffWorks.com. <http://auto.howstuffworks.com/auto-parts/towing/towing-capacity/information/torque-converter.htm>  10 February 2011.

Work Sited