Method of manufacturing hollow bicycle crank arm
AssigneeShimano Inc.
InventorMasahiro Yamanaka
Life of this patent
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Abstract
In a method of manufacturing a hollow bicycle crank arm, a sand mold core is positioned into a casting mold so that a melt space is formed around the sand mold core, molten metal is poured into the casting mold, and the molten metal is solidified to form a crank billet. Sand is preferably removed through an opening in the crank billet. This may be accomplished by drilling the crank billet to form the pedal attachment hole in a location that communicates with the sand mold and then removing sand through the pedal attachment hole.
Claims12
A method of manufacturing a hollow bicycle crank arm comprising the steps of:
- positioning a sand mold core into a casting mold so that a melt space is formed around the sand mold core;
- pouring molten metal into the casting mold;
- solidifying the molten metal to form a crank billet;
- drilling the crank billet to form a first opening, wherein the first opening communicates with the sand mold core;
- and
- removing sand through the first opening.
A method of manufacturing a hollow bicycle crank arm comprising the steps of:
- positioning a sand mold core into a casting mold so that a melt space is formed around the sand mold core;
- pouring molten metal into the casting mold;
- solidifying the molten metal to form a crank billet;
- removing sand through a first opening in the crank billet;
- forging the crank billet;
- and
- wherein the step of removing the sand further comprises the step of removing sand from only a portion of the crank billet prior to forging the crank billet.
Dependencies are inferred from the claim text.