Though one might not think about gears to be versatile, gear couplings are very much considered to be a flexible coupling. A gear coupling is definitely a mechanical gadget designed to transmit torque between two shafts that aren't collinear. The coupling typically consists of two versatile joints, one set to each shaft. These joints tend to be linked by a third shaft known as the spindle.
Each joint generally includes a 1:1 gear ratio internal/external gear pair. The tooth flanks and outer size of the exterior equipment are crowned to allow for angular displacement between the two gears. Mechanically, the gears are equivalent to rotating splines with altered profiles. They are known as gears because of the relatively large size of the teeth. Gear couplings are usually 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 sleeves surrounded by a perpendicular flange. One sleeve is positioned on each shaft therefore the two flanges fall into line face to face. A number of screws or bolts in the flanges keep them jointly. Continuous sleeve gear couplings feature shaft ends coupled together and abutted against one another, which are then enveloped by a sleeve. Generally, these sleeves are constructed with metal, however they can also be made of Nylon.
Single joint equipment couplings are used to connect two nominally coaxial shafts. In this application the device is named a gear-type flexible, or flexible coupling. The single joint allows for minimal misalignments such as for example installation errors and adjustments in shaft alignment because of operating conditions. These kinds of gear couplings are usually limited by angular misalignments of 1/4 to 1/2°.