US Patent 6976288 Rod gripper

A bar or rod gripper for arresting the linear axial movement of a rod, e.g. the piston rod of a door closure between a door open or closed position, that includes a compressible bushing slidably disposed about the rod or bar, and a canter washer disposed about the compression bushing whereby the canter washer, when tilted, will cause the compression bushing to compress to impose a surface to surface frictional force onto the bar or rod to resist or restrain the axial movement thereof without scoring, pitting or indenting the outer surface of the rod.