Patent ID: 6612033
Filing Date: 2003-09-02
Classification: B21C,B21D,B21J,B21K,B62K,B62M,Y10T

Abstract:
A method for making a hollow bicycle crank, comprising:step of forging a prototype: forging a piece by putting a piece between a first mold and a second mold, an opening defined between the first mold and the second mold, a third mold having a prong which is inserted in the opening to make a recess in a first end of the piece which becomes a prototype; step of forming a hollow first end of the crank: putting the first end of the forged prototype in the step of forging into a cone-shaped passage in a fourth mold, a pushing member forcing the first end of the prototype to go through the cone-shaped passage from a wide opening to a narrow opening of the cone-shaped passage, the recess being sealed when the first end of the prototype passes through the narrow opening of the cone-shaped passage; step of thermo-forming: putting the first end of the crank in the step of forming in mold under heat and deforming the first end to have an angle relative to a second end of the crank; step of setting: putting the first end of the crank in the step of thermo-forming in a cold-forging mold to set the shape of the crank.