Motor vehicles – Frame
Reexamination Certificate
2001-03-30
2004-02-24
Morris, Lesley D. (Department: 3611)
Motor vehicles
Frame
C180S219000, C280S281100
Reexamination Certificate
active
06695089
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a motorcycle frame, and more particularly to an advantageous structure of a down frame running from a head pipe and sloping downwards to the front of an engine.
2. Description of the Relevant Art
Japanese Patent No. 2951338 discloses a structure of a mainframe extending from a head pipe. The mainframe uses an angular cross section pipe towards the rear, and a down frame extending diagonally downwards. The down frame is formed by a swaging process.
Because the pipe cross-section of the pipe frame is decided in line with sections where stress is a maximum, the pipe section is formed having the same cross section for sections where stress is less. Because the same cross section is used throughout, a weight of the frame is increased.
The above described swaging process of the related art forms a circular pipe into a tapered shape by rotational swaging. Next, the pipe is formed into an angular cross section by press molding, or the like. This means that the thickness of particular places is varied inside one original cross section, and it is not possible to perform swaging for a pipe having a cross section, such as a bisected rectangle.
Therefore, there exists a need in the art for a vehicle frame having a cross sectional shape conforming to a required stress distribution. There is a need in the art for such a vehicle frame, having a reduced weight. And, there is a need in the art for such a vehicle frame, which can be made easily.
SUMMARY OF THE INVENTION
It is an object of the present invention to alleviate one or more of the drawbacks of the background art by addressing one or more of the existing needs in the art.
In order to solve the above described problems, a motorcycle frame of the present invention comprises a main frame running from a head pipe, above an engine and towards the rear of the vehicle, and a down pipe running from the headpipe and sloping diagonally downwards to the front of the engine. The down frame is formed of an angular cross section pipe member, with a strengthening rib being integrally provided on an inner surface of the down frame.
The down frame of the present invention has the rib formed on the inner surface of a front side section, which means that the front side of the down frame, which has maximum stress sections, can be made especially rigid, while other sections can be made comparatively thin. This arrangement allows the down frame to have a cross sectional shape conforming to an actual stress distribution. Further, the arrangement contributes to reduction in the overall weight of the vehicle frame.
A pipe, having this type of angular cross section has the rib integrally formed on the inner surface and a previously extruded angular cross section pipe can be easily obtained using a swaging process. At the time of production, it is also possible to form an asymmetrical shape, having only a rear side surface section tapered.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 4662645 (1987-05-01), McMurtrey
patent: 4742884 (1988-05-01), Ishikawa
patent: 4805716 (1989-02-01), Tsunoda et al.
patent: 5261504 (1993-11-01), Katsura
patent: 5701853 (1997-12-01), Takahashi
patent: 5845728 (1998-12-01), Itoh et al.
patent: 6182994 (2001-02-01), Gogo et al.
patent: 6186550 (2001-02-01), Horii et al.
patent: 6332505 (2001-12-01), Tateshima et al.
patent: 6360839 (2002-03-01), Urano et al.
patent: 2002/0043415 (2002-04-01), Okuma et al.
patent: 60094817 (1985-05-01), None
patent: 02074488 (1990-03-01), None
patent: B2-2951338 (1999-07-01), None
Adachi Eiji
Okuma Takanori
Morris Lesley D.
Yeagley Daniel
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