A flexible coupling provides mechanical power in the form of torque to pieces of rotary equipment. They must perform three major functions: efficiently transmit mechanical power directly from one shaft to another while maintaining constant velocity, compensate for misalignment with minimum power loss and without inducing high stress and allow for axial movement of either shaft without creating excessive thrust on the other.
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Design of Flexible Couplings
Flexible shaft couplings are cylindrical in shape, and specific details vary depending on the different types and their functions.
- Flexible couplings are most commonly made out of stainless steel and aluminum. Stainless steel protects against corrosion and increases torque capacity and strength, and aluminum is a lighter and less expensive option. The material used for the coupling depends on the type of coupling and its purpose.
Applications of Flexible Couplings
Flexible couplings have many applications. For example, they are used to connect drive shafts in automobiles and they isolate driveline vibration, propeller pulse, and gear chatter in motorized boats. Other industrial applications include use in printing machines, paper making machines, roll forming machines, hydraulic pumps, blowers, compressors, and wind turbines. Industrial sectors such as mining, quarrying, mineral processing, metal manufacture, cement and power generation also utilize flexible couplings for various purposes.
Types of Flexible Couplings
Most flexible couplings are characterized as belonging to one of three main categories: mechanical, elastomeric and metallic. Flexible couplings are identified by the degree and method of flexibility they offer.
- Mechanical Flexible Couplings
- Made of loosely fitted parts that are able to move past each other, often by a sliding and rolling action. They maintain high torsional rigidity and allow a considerable degree of angular misalignment; however, they require occasional maintenance and lubrication. Examples of mechanical couplings include jaw/spider couplings, Oldham couplings, and servo couplings.
- Elastomeric Flexible Couplings
- Use a resilient material such as plastic or rubber to transmit torque between two metallic hubs. A few advantages of this coupling are the high vibration dampening, shock absorption abilities, and toleration of a high degree of misalignment. They are also inexpensive and of lighter weight than mechanical couplings and require no lubrication. One popular elastomeric coupling is the bellows coupling.
- Metallic Flexible Couplings
- Obtain flexibility through the bending of a membrane within the coupling and generally do not allow offset misalignment. Metallic membrane couplings require low maintenance and no lubrication; however, these couplings may be more expensive than mechanical flexible couplings. Other general types of flexible couplings include bushed pin, universal, resilient and disc couplings.