Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-01-28
2001-01-30
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C074S594100
Reexamination Certificate
active
06178631
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to methods of manufacturing metal structures and, more particularly, to a method of heating and quenching a hollow metal member such as a bicycle crank arm during a manufacturing process.
Bicycle crank arms and other metal structures are often manufactured using a forging process wherein the crank arm is heated and quenched to strengthen the crank arm after a forging step. Problems arise when the heating and quenching steps are performed on hollow crank arms. More specifically, when a crank arm having a fully enclosed hollow space is heated, the air or other gas in the hollow space expands to a high pressure, thus causing deformation of the crank arm. One solution to this problem is to drill a hole on the side of the crank arm body to allow the gas to escape during the heating process. However, this requires an extra machining step, and the hole often allows the quenching liquid to enter the hollow space. The liquid in the space is difficult to remove easily and effectively, and it may cause future corrosion or oxidation. A cap or cover could be placed over the hole before the quenching step, but that would add additional steps, complexity and parts to the manufacturing process.
SUMMARY OF THE INVENTION
The present invention is directed to a method of heating and quenching a hollow metal member such as a bicycle crank arm, wherein an opening may be easily formed to allow gas to escape during heating of the hollow metal member. The hole also may be small enough to inhibit liquid entry during a later quenching step.
In one embodiment of the present invention, a method of manufacturing a metal member includes the steps of forming a metal body having a hollow core, wherein a side of the metal body defines a core opening exposing the hollow core; placing a filament through the core opening into the hollow core; closing the core opening around the filament; and heating the metal body so that the filament disintegrates to form a filament hole sufficient to allow gas within the hollow core to escape through the filament hole. As noted above, this method has particular usefulness when manufacturing a bicycle crank arm. If a filament such as a thin cotton thread is used, then the resulting hole will be large enough to allow gas to escape during the heating process while minimizing or preventing liquid entry during a subsequent quenching step.
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Sugimura Daisuke
Tanabe Shin
Arbes Carl J.
Deland James A.
Shimano Inc.
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