Jaw Couplings

Jaw couplings are a type of compression coupling that control motion by transmitting torque and dampening vibrations that could cause damage to other system components. They are composed of a polyurethane-based elastomeric part called a spider that joins two hubs made of sintered metal, aluminum, standard steel, stainless steel, bronze or iron. These three parts are press fitted together with a jaw from each hub fitting into the elastomeric element’s grooves.

Jaw couplings are resistant to oil, dirt, grease, sand and moisture and do not require any lubrication. One drawback of jaw couplings is that they lack misalignment capability. Unlike a bellows coupling which is flexible, jaw couplings will come apart if the axial motion is too great. Angular or parallel misalignment can cause it to bear loads that are higher than other similar couplings. Jaw couplings have the basic shape of a gear but are in fact quite different from gear couplings.

Jaw couplings do not use the large blunt teeth to move or rotate as would be the case in a set of gears. Instead they provide interlocking action for the spider and hub, keeping the assembly together while providing effective vibration dampening. Jaw couplings are used as motor couplings for pumps, gear boxes, compressors, blowers, mixers and conveyers for industrial manufacturing applications.

The elastomeric element is often referred to as a spider because of its shape-circular with an even number of legs jutting out. It serves to dampen impulse loads and minimize shock to a motor. The polyurethane used can be either soft, which provides better vibration dampening, or hard, which gives the spider more strength. The elastomeric material that the spider is made out of is available in different degrees of hardness which gives the operator more control over how much vibration the coupling absorbs.

Jaw In-Shear Coupling
Jaw Couplings – Lovejoy, Inc.

It can be customized to the specific application. The hubs have curved jaws that interlock and reduce deformation of the spider which prevents backlash. These couplings are considered fail safe because if the spider malfunctions, the jaws of the two hubs interlock and create direct power transmission so the vehicle can shut down safely. Jaw couplings perform the best for applications that use a stop-and-go type of movement that also require accuracy.

Varying amounts of vibration absorption have a direct effect on the length of settling time where the system pauses briefly to perform an action or movement quickly and precisely. If vibrations are mostly absorbed then the system does not have to hesitate before performing an action which increases the speed of the line. Jaw couplings are accurate while still; they are not optimal for applications in which precise movements are required during movement.