Two-piece crank hanger set for bicycles
View Patent ↗A two-piece crank hanger set including a left crank arm having a tubular crank spindle attached thereto and a right crank arm having at least one chain sprocket wheel attached thereto. The crank spindle extends through a bicycle crank tube. Bearing cups are removably attached to both ends of the crank tube. Bearing retainers having tapered roller bearings engage the bearing cups. A tubular stop member is held in place on the outer end of the crank spindle by a spline mechanism. A preload and attachment bolt passes through the right crank arm and chain sprocket wheel and into threadable engagement with a threaded inner surface of the outer end of the tubular crank spindle. The preload and attachment bolt is tightened to preload the bearings.
1. A preload and attachment bolt assembly comprising an external sleeve, a coil spring, and an internal sleeve;
said external sleeve having an external sleeve body that is a hollow cylinder having an inner end and an outer end, said external sleeve body having internal and external cylindrical surfaces having internal and external helical threads located thereon, respectively, said external threads adapted to threadably engage an attachment member, at least two expansion slots located in the inner end of said external sleeve body, said inner end of said external sleeve body having a thickened internal taper projection that projects into the hollow cylinder and tapers such that the hollow cylinder sleeve body is thickest at the innermost inner end, an external sleeve flange located on the outer end of said external sleeve body, and a spring stop member located within said external sleeve flange;
said internal sleeve having an internal sleeve body that is a hollow cylinder having an inner end and an outer end, said internal sleeve body having an external cylindrical surface having external helical threads located thereon adapted to mate with said internal helical threads of said external sleeve body, and an internal sleeve flange located on the outer end of said internal sleeve body;
said coil spring having an inner and outer end, said coil spring adapted to being positioned around said internal sleeve body with said inner end of said coil spring being in abutment with said spring stop member of said external sleeve and said outer end of said coil spring being in abutment with said internal sleeve flange;
said internal sleeve body adapted to be completely screwed into said external sleeve body to thereby cause the inner end of said internal sleeve body to engage said thickened internal taper of said external sleeve body and to cause said inner end of said external sleeve body to expand.
2. The apparatus of claim 1 wherein said coil spring has a compression resistance that prevents said internal sleeve from being completely screwed into said external sleeve until a prescribed torque load has been placed upon said attachment member.
3. The apparatus of claim 2 wherein said external sleeve body and said internal sleeve body each have a longitudinal axis, and said internal threads of said external sleeve body and said external threads of said internal sleeve body are oriented at a mating angle of between about 40 degrees and about 50 degrees to the longitudinal axis of their respective sleeve bodies.
4. The apparatus of claim 3 wherein said mating angle is about 45 degrees.
5. The apparatus of claim 3 wherein said internal threads of said external sleeve body and said external threads of said internal sleeve body are coarse.