Though one might not think of gears as being versatile, gear couplings are very much regarded as a flexible coupling. A gear coupling is certainly a mechanical gadget made 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 connected by a third shaft known as the spindle.
Each joint generally includes a 1:1 equipment ratio internal/exterior gear pair. The tooth flanks and external diameter of the exterior equipment are crowned to allow for angular displacement between your two gears. Mechanically, the gears are equal to rotating splines with modified profiles. They are known as gears due to the relatively large size of the teeth. Equipment 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 sleeves surrounded by a perpendicular flange. One sleeve can be positioned on each shaft therefore the two flanges fall into line face to face. A number of screws or bolts in the flanges hold 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 made from metal, but they can also be manufactured from Nylon.
Single joint equipment couplings are used to connect two nominally coaxial shafts. In this application these devices is called a gear-type flexible, or versatile coupling. The one joint allows for small misalignments such as installation errors and adjustments in shaft alignment because of operating circumstances. These types of gear couplings are generally limited to angular misalignments of 1/4 to 1/2°.