the interengaging parts including a continuous or interrupted circumferential groove in the surface of one of the coupling parts (circlips for retaining hubs on shafts F16B21/18)

Full Title

Couplings for rigidly connecting two coaxial shafts or other movable machine elements (attachment of wheels to axles for railway carriages B60B; for attachment of cranks to their shafts F16C3/10) > Quick-acting couplings in which the parts are connected by simply bringing them together axially > having retaining means rotating with the coupling and acting by interengaging parts, i.e. positive coupling > the interengaging parts including a continuous or interrupted circumferential groove in the surface of one of the coupling parts (circlips for retaining hubs on shafts F16B21/18)