A flexible coupling must provide three basic functions:

1. Physically couple together two rotating shafts for efficient transmission of mechanical power, transferring the torque of one shaft to the other, directly and with constant velocity.

2. Compensate for all types of misalignment between rotating, connected shafts without inducing abnormal stresses and loads on connected equipment, and without tangible loss of power.

3. Compensate for end or axial movement of the coupled shafts, preventing either shaft from exerting excessive thrust on the other and allowing each to rotate in its normal position.

Three types of misalignment must be effectively accommodated by a flexible coupling.

1. Parallel Offset – axes of connected shafts are parallel, but not in the same straight line.

2. Angular – axes of shafts intersect at center point of coupling, but not in the same straight line.

3. Combined Angular-Offset – axes of shafts do not intersect at point of coupling and are not parallel.

Nylon gear flexible coupling.