is a mechanical device for transmitting torque between two shafts that
are not coaxial. It consists of a flexible joint fixed to each shaft. The
two joints are connected by a third shaft, called the spindle.
Each joint consists of a 1:1 gear ratio internal/external gear pair. The
tooth flanks and outer diameter of the external gear are crowned to allow
for angular displacement between the two gears. Mechanically, the gears are
equivalent to splines with modified profiles. They are called gears because
of the relatively large size of the teeth.
Gear couplings and universal joints are used in similar applications.
Gear couplings have higher torque densities than universal joints designed
to fit a given space while universal joints induce lower vibrations. The
limit on torque density in universal joints is due to the limited cross
sections of the cross and yoke. The gear teeth in a gear coupling have high
backlash to allow for angular misalignment. The excess backlash can
contribute to vibration.
Application
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