Heico Fasteners offers machine builders an insight into how the company's threaded fastener locking products work
Conventional fasteners often rely on the physics of friction instead of tension to maintain clamp load, for example metal lock nuts, safety-wire, or threadlocking adhesives, but these methods offer limited performance says the company. It describes HEICO-LOCK® as a unique tension based design of washer system whihc it claims provides superior resistance to constant vibration,high dynamic loads and thermal cycling.
The system consists of a pre-assembled pair of washers featuring inclined cams on the inside and radial teeth on the outside.Tightening of the nut or bolt creates a ‘gripping’ action of the teeth thus seating the mating surfaces.
The angle of the cams between the HEICO-LOCK® washers is greater than the thread pitch of the bolt. This angle means that the expansion in thickness of the HEICO-LOCK® washers is greater than the possible longitudinal movement of the bolt along the thread. With HEICO-LOCK®, the company states that any bolt loosening results in the internal cams separating and their movement across each other results in an increase in tension and clamp load. During removal, only the cam surfaces move, resulting in low off-torque force.
The cams on the separation plane (joint face) of the individual washers of the pair show a much lower friction coefficient than that whihc exists on the radial ridges on the outside of the pair of washers, so any loosening through a dynamic load will always lead to movement only across the face of the cams of the washers.