US Patent 7025713 Weight lifting system with internal cam mechanism

A weight lifting system includes: (i) a handle; (ii) a plurality of weights; and (iii) first and second locking mechanisms that couple a respective weight to the handle. The locking mechanisms each include a cam assembly that selectively engages threads on an interior surface of the handle. The cam assembly includes (i) a threaded cam rotatably coupled to a sleeve that extends into the handle; and (ii) a push rod configured to selectively move the cam between a locked position and an unlocked position within the handle. Twisting the cam in one direction tightens the threads of the cam against the threads of the handle. Twisting the cam in an opposing direction threads the locking mechanism out of the handle.