Though one may not think about gears as being flexible, gear couplings are very much regarded as a flexible coupling. A equipment coupling can be a mechanical device made to transmit torque between two shafts that aren’t collinear. The coupling typically includes two versatile joints, one fixed to each shaft. These joints are often linked by a third shaft called the spindle.
Each joint generally consists of a 1:1 equipment ratio internal/external gear set. The tooth flanks and outer size of the exterior equipment are crowned to permit for angular displacement between the two gears. Mechanically, the gears are equal to rotating splines with altered profiles. They are called gears due to the relatively large size 
of the teeth. Gear couplings are generally limited by angular misalignments of 4 to 5°.
Equipment couplings ordinarily come in two variations, flanged sleeve and continuous sleeve. Flanged gear couplings consist of short Speed Gear box sleeves encircled by a perpendicular flange. One sleeve is definitely positioned on each shaft so the two flanges fall into line face to face. A series of screws or bolts in the flanges keep them collectively. Continuous sleeve equipment couplings feature shaft ends coupled jointly and abutted against one another, which are after that enveloped by a sleeve. Generally, these sleeves are constructed with metal, however they may also be manufactured from Nylon.
Single joint gear couplings are accustomed to connect two nominally coaxial shafts. In this application the device is named a gear-type versatile, or versatile coupling. The one joint allows for minimal misalignments such as installation errors and adjustments in shaft alignment because of operating conditions. These kinds of equipment couplings are generally limited to angular misalignments of 1/4 to 1/2°.