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Elastomeric Coupling

Elastomeric Coupling

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Elastomeric couplings are a form of flexible coupling that uses an insert made of an elastomeric polymer to help transmit torque. The design of elastomeric couplings means that the elastic material is meant to wear out before any metal components. This not only saves time and money on maintenance but also means that the couplings do not require any form of lubrication.

Jaw type couplings are general purpose and consist of an elastomeric element, commonly referred to as a spider, sandwiched between two metal hubs with interlocking teeth. The spider acts as a shock absorber for the coupling and helps to reduce vibrations and, in some applications, electrical isolation.  Jaw couplings are considered to be fail-safe because if the spider were to fail, the teeth of the two hubs would interlock and continue to transmit torque. This would decrease coupling performance but would prevent damage to the machine and give engineers time to shut the system down.

Gear type couplings consist of two hubs with external teeth that engage internal teeth on a two- or one-piece sleeve. The teeth may be straight or curved (crowned). Often these couplings use a metal sleeve, but elastomer sleeves are available. These elastomer-based couplings, however, have lower torque and speed capabilities because of the limitations of the elastomers natural lubrication abilities.

Tire type couplings, not surprisingly, resemble the tires on a car. This design consists of two flanged hubs equipped with clamping plates, which grip the coupling’s hollow, ring-shaped element, by its inner rims. Tire coupling elements are usually rubber derivative elastomers with layers of cord, such as nylon, vulcanized into the tire shape. The coupling transmits torque through the friction of the clamp applied to the inner rims of the tire and a shearing of the element. Axial forces on the shaft caused by centrifugal forces working on the elastomer, restrict the speed of these couplings. Additionally, their bulky size limits what applications they could be applied to, although there is a variant with the tire inverted to reduce the coupling’s size.

Like other flexible couplings, elastomeric couplings are meant to not only transmit torque, but accommodate for misalignment between shafts as well. The amount of misalignment that these couplings can accommodate varies by type and by manufacturer.