Flexible Couplings
A flexible coupling 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. Flexible couplings have
many applications; 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. The most common materials
used for flexible couplings are 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. Flexible shaft
couplings are cylindrical in shape, and specific details vary depending on the
different types and their functions.
There are three main categories determined by the method
of flexibility that most flexible couplings fall into. Mechanical flexible
couplings are 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 membrane 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.