Gear couplings are designed to transmit torque between two shafts that are not collinear. They typically consist of two flexible joints—one fixed to each shaft—which are connected by a spindle, or third shaft. The gear coupling connects the drive motor to the gearbox in hoist mechanisms, but it can also connect the gearbox directly to smaller wire rope drums using a flanged half.
In terms of their design, gear couplings transmit torque via hubs with crowned gear teeth that are in permanent mesh with the straight gear teeth of the sleeves—a design that provides the highest torque transmission for the smallest size. They also run at high speeds, conform to the AGMA bolting pattern and compensate for angular, radial and axial shaft misalignment.