An elastic coupling (also commonly called a flexible coupling) is a mechanical device used to connect two rotating shafts, primarily for the purpose of transmitting torque from a driving shaft (e.g., from a motor) to a driven shaft (e.g., to a pump or gearbox).
Its primary defining feature is the incorporation of an elastic or flexible element made of materials like rubber, polyurethane, or various elastomers. This elastic component allows the coupling to accommodate certain types of misalignment and system irregularities, while also providing additional benefits.
Key Functions and Characteristics:
Compensates for Misalignment: It can accommodate small amounts of parallel misalignment, angular misalignment, and axial displacement (end float) between the two connected shafts. This protects connected equipment from excessive loads caused by imperfect alignment.
Vibration Damping and Torsional Flexibility: The elastic element acts as a shock absorber. It damps torsional vibrations and cushions the system against shock loads from sudden starts, stops, or torque fluctuations. This smooths out power transmission and protects both the driving and driven equipment.
Electrical Insulation: Non-metallic elastic materials can provide electrical insulation between shafts, preventing the flow of stray electrical currents (e.g., from variable frequency drives) that could cause bearing damage.
Wear Compensation: It can tolerate minor wear in connected components without immediate failure.
No Lubrication Required: Most types are maintenance-free, as the elastic element does not require lubrication.
Common Types:
Jaw Coupling / Spider Coupling: Features two metal hubs with interlocking "jaws." A spider-shaped elastomeric insert (the "spider") fits between the jaws, transmitting torque while providing flexibility.
Tyre Coupling / Radial Flex Coupling: Uses a rubber or polyurethane tire-like element bolted between two flanges. Excellent for damping and accommodating angular misalignment.
Pin & Bush Coupling: Uses rubber or polyurethane bushes inserted into holes, with pins transmitting torque through them.
Beam Coupling (Helical Coupling): A single piece of metal (often aluminum or steel) machined in a helical cut. While not elastomeric, it provides flexibility through mechanical bending and is used for precise motion control (a different category, but sometimes grouped under "flexible couplings").
