A jaw coupling is a type of motion control

Motion control

Motion control is a sub-field of automation, in which the position or velocity of machines are controlled using some type of device such as a hydraulic pump, linear actuator, or an electric motor, generally a servo...

 (servo) coupling designed to transmit torque (by connecting two shafts) while damping system vibrations, which protects other components from damage. Jaw couplings are composed of three parts: two metallic hubs and an elastomer

Elastomer

An elastomer is a polymer with the property of viscoelasticity , generally having notably low Young's modulus and high yield strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber, although the latter is preferred...

 insert called an element, but commonly referred to as a "spider". The three parts press fit together with a jaw from each hub fitted alternately with the lobes of the spider. The curved jaws of the hubs reduce deformation of the spider to maintain the zero-backlash

Backlash (engineering)

In mechanical engineering, backlash, sometimes called lash or play, is clearance between mating components, sometimes described as the amount of lost motion due to clearance or slackness when movement is reversed and contact is re-established...

 fit.

The elastomer of the spider can be made in different hardnesses, which allows the user to customize the coupling so that it absorbs more or less vibration. The more damping ability the coupling has, the less torsional strength it possesses. Jaw couplings are best suited for applications that rely on a stop-and-go type of movement, where accuracy needs to take place upon stopping in order to perform any number of precision tasks, such as taking a high resolution

Image resolution

Image resolution is an umbrella term that describes the detail an image holds. The term applies to raster digital images, film images, and other types of images. Higher resolution means more image detail....

 picture (machine vision

Machine vision

Machine vision is the process of applying a range of technologies and methods to provide imaging-based automatic inspection, process control and robot guidance in industrial applications. While the scope of MV is broad and a comprehensive definition is difficult to distil, a "generally accepted...

 system). Absorbing vibrations decreases the settling time the system needs, which increases through-put. The jaw coupling is less suited for applications that rely on a constant scanning type of motion, where accuracy is required during movement, which requires a torsionally stronger coupling.

The drawback of the jaw coupling is the lack of misalignment capability. Too much axial motion will cause the coupling to come apart, while too much angular or parallel misalignment will result in bearing loads that are higher than most other servo/motion control couplings. Jaw couplings are also considered fail-safe

Fail-safe

A fail-safe or fail-secure device is one that, in the event of failure, responds in a way that will cause no harm, or at least a minimum of harm, to other devices or danger to personnel....

. If the spider fails, the jaws of the two hubs will mate, much like teeth on two gears, and continue to transmit torque. This may or may not be desirable to the user depending on the application.

Jaw couplings are well balanced and able to tolerate high RPM. With its damping capability and interchangeable spiders, jaw couplings make a great solution for shock absorption.