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US 4,484,756 AGranted
Blank tube and main frame for two-wheeled vehicle
AssigneeBridgestone Cycle Co., Ltd.
InventorsKikuzo Takamiya, Hiroshi Todoroki, Shuichi Taniguchi
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AssigneeBridgestone Cycle Co., Ltd.
InventorsKikuzo Takamiya, Hiroshi Todoroki, Shuichi Taniguchi
Estimating the term…
A blank tube constituting a main frame for a two-wheeled vehicle, comprises a main tubular portion having thicker walls in the proximity of its ends subjected to the largest forces and tubular expanded portions extending from the ends of the tube for receiving a head tube and a seat tube without using separate parts such as lugs. The blank tube further comprises a gradually enlarged diameter portion adjacent to the tubular expanded portions to more improve the strength of the tube. The thicker walls, tubular expanded portions and gradually enlarged diameter portion are formed simultaneously in dies by bulging. Moreover, the dies are formed with recesses, so that the blank tube is formed with protrusions. The protrusions are formed with apertures for passing brake wires or electric wires through the tube. The main tubular portion of the blank tube is formed in a particular cross-section effectively increasing its strength by pressing by means of the dies including corresponding sectional cavities.
A blank tube for a two-wheeled vehicle, comprising a main tubular portion having thicker walls towards the ends and tubular expanded portions extending in a direction substantially transverse to a major axis of said tube from at least one end of the thicker wall of said main tubular portion, said thicker walls and said tubular expanded portions being formed in dies by applying high hydraulic pressure to an inside of said tube and simultaneously applying compressive force to said tube in its axial direction.
A main frame for a two-wheeled vehicle, comprising a blank tube including a main tubular portion having thicker walls towards the ends and tubular expanded portions extending in a direction substantially transverse to a major axis of said tube from at least one end of the thicker wall of said main tubular portion, said thicker walls and said tubular expanded portions being formed in dies by applying high hydraulic pressure to an inside of said tube and simultaneously applying compressive force to said tube in its axial direction, distal ends of said tubular expanded portions being cut off to form through-holes and at least one compressed end of said main tubular portion being cut off to form an opening;
Dependencies are inferred from the claim text.