Simply put, a coupling is a mechanical device that serves as a connector between two elements. In the case of shaft couplings, the elements are shafts. Such unions serve one of two major purposes. In many of these applications the principle goal is the transfer of motion. The shaft couplings used to transfer movement from a vehicle transmission to its wheels are a prime example of this application which enables the proliferation of the rotational movements. Power generation, however, is an example of the second purpose of shaft couplings which is to effectively transmit energy from one shaft to another, as with a wind turbine transmitting energy from the spinning blades into the power grid.
Many applications employ multiple types of shaft couplings within a single unit. Automotives are one of the best examples of this as a single car or truck may employ motor couplings, flywheel couplings, fluid couplings and still more examples of shaft couplings. The plethora of application specific shaft couplings can largely be divided into two specific categories. The first, rigid shaft couplings keep the conjoined shafts in perfect alignment. As the name would suggest these are of solid construction and once in place cannot be bent or twisted no matter the torque to which they are subjected. In applications where precision is less essential or where a small degree of misalignment is even preferred, flexible shaft couplings are used. Flexible couplings are made to bend, just slightly, allowing for two shafts to maintain connection without being perfectly in line with one another.
As is made evident by their wide use in industrial, commercial and residential equipment and appliances, shaft couplings are incredibly diverse. From the home to the commute to the work place, shaft couplings are omnipresent in machines and appliances whether they are brand new or even a century old. More than just enabling the transmission of motion and energy within a machine, properly maintained couplings ensure the safe and continuous operations of those devices. So while the mechanisms of modern living have a seemingly extreme inclination towards change, shaft couplings are the tried and true method for putting it all together.