is the connector designed to accommodate misalignment
between two rotating power transmission shafts. Flexible couplings minimize
noise and vibration and prevent excessive bearing loads. Some types of
flexible couplings use metallic or rubber diaphragms that require no
lubrication. Of the kind that require
lubrication, there are two principal types: grid type and gear
type. The grid-type flexible coupling consists of grooved hubs attached
to the shaft ends and connected to each other by a spring-steel grid that
fits into grooves around the circumference of each hub. The grid flexes and
absorbs shock that might otherwise be transmitted from one shaft to another.
A fairly stiff grease can be used because the
movement of the grid against the grooves serves to keep the lubricant
well-distributed. A gear-type flexible coupling consists of geared
hubs fitted to the shaft ends and connected to each other by means of a
sleeve with internal gear teeth that engage the teeth of the hubs. The hubs
rock back and forth within the sleeve to accommodate angular misalignment.
Gear-type couplings depend on centrifugal force to distribute the lubricant
and thus require a relatively soft grease with good migrating properties.
Certain gear-type couplings can be oil-lubricated.