Gear Couplings
Gear couplings transport torque between two shafts that are not coaxial. Each shaft consists of a flexible joint, which is fixed to the shaft. The joints of the shafts are connected by a spindle, a third shaft. Gear couplings offer efficient torque transmission in a compact mechanism and permit a high degree of axial movement. However, gear couplings require piloting and may malfunction at very high or very low torques. Crowned tooth flanks allow angular displacement to occur between each gear.
Two coaxial shafts can also be connected by a single joint gear coupling, known as a gear-type flexible or flexible coupling. Slight misalignments are tolerated by this type of gear coupling.
Gear couplings and universal joints are used in similar applications, most predominantly in the automobile industry. While gear couplings have higher torque density, universal joints induce lower vibration than gear couplings. The gear teeth in a gear coupling have high backlash, which can contribute to vibration, to allow for angular misalignment. Gear couplings are found in all rear-wheel and four-wheel driven passenger cars.