Oldham Couplings
Oldham couplings are constant velocity couplings used for connecting two parallel shafts that are close together and run at the same speed. They are composed of three parts-a center piece sandwiched in between two hubs. Torque transmission is accomplished by interlocking the slots of the center piece with the drive tenons of the hubs. They fit together by snapping into place, which creates zero backlash. Oldham couplings are flexible and designed for general purpose use up to 4000 rpm because they have few disadvantages. Their widespread uses include CNC machines, homokinetic transmission, servo or robotic machines, copy and printing machines and instrumentation. Their advantages include no velocity variation, high lateral misalignments, high torque capacity and easy disassembly. Their only disadvantages are their limited angular displacement of shafts and their need for lubrication.
The two hubs of Oldham couplings are generally made out of steel, stainless steel or aluminum, while the center component is usually a plastic material (rarely metal). One hub, or disc, is coupled to the input, while the other is coupled to the output, and the center piece is joined to the other two by a series of tongue and grooves. During operation, the center element slides on a hub tenon to accommodate misalignment. This wares down the discs, which may create backlash. Springs are often employed to prevent this, and worn discs are easily and inexpensively replaced. The bearing loads won't increase when misalignment increases, and Oldham couplings allow a small amount of angular misalignment and axial motion.