Endless belt power transmission systems or components – Positive drive pulley or guide roll – And additional coaxial surface for engaging same belt in...
Reexamination Certificate
2000-02-11
2001-08-14
Wright, Dirk (Department: 3681)
Endless belt power transmission systems or components
Positive drive pulley or guide roll
And additional coaxial surface for engaging same belt in...
Reexamination Certificate
active
06273836
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to chain driven bicycles. More particularly, the present invention relates to a sprocket used on such bicycles which has stiffening fins to axially reinforce and strengthen the sprocket.
The majority of bicycles are chain driven in that the rider pushes downwardly with his or her feet on pedals placed at the ends of crank arms which are attached to a chain sprocket. The pedaling force rotates the typically circular or semi-circular sprocket. A chain interconnected between the teeth of the sprocket and a gear associated with the rear wheel of the bicycle is moved by the rotation of the sprocket, causing the rear wheel to rotate and propelling the bicycle forward.
In order to conserve the amount of materials used and to minimize the weight of the sprocket, it is typically constructed so as to be relatively thin. So long as only a moderate force is applied to the pedals, the sprockets in use today function adequately. However, when large forces are applied to the pedals, the sprocket tends to flex axially. This is oftentimes the case with bicycle moto-cross (BMX) or mountain bikes which are generally ridden off-road or under other strenuous conditions, such as dirt jumping and ramp riding. When applying great force to the pedals axial flexing or even permanent bending of the sprocket may occur. For example, if the rider is jumping or performing tricks or if the rider lands or crashes in such a way, sprocket bending may occur. This flexing or bending can cause chain disengagement from the sprocket and/or difficulty in shifting gears. Chain disengagement can result in valuable time lost in racing situations, and is also quite dangerous to the rider as control of the bicycle may be lost and the loose chain can become tangled with objects on and around the bicycle. In extreme cases, the rider is not able to continue to ride at all.
Therefore, what is needed is a chain sprocket which is reinforced and strengthened axially in order to prevent axial flexing. Further, there is a need for a reinforced chain sprocket which can be used in a variety of existing bicycles without modifying other components of the bicycle. The present invention fulfills these needs and provides other related advantages.
SUMMARY OF THE INVENTION
The present invention resides in a chain sprocket comprising a disc-like base including an outer rim having teeth on its outer periphery, a hub, and a plurality of spokes extending radially from the hub to the outer rim, and stiffening fins formed integrally with at least some of the spokes and extending axially from the spokes. The chain sprocket is typically used in a chain drive system interconnected between a rear wheel and a frame of a bicycle.
In a preferred embodiment, a crank arm-accepting slot is formed within the hub, and the base includes a crank arm supporting platform having an aperture therethrough. The supporting platform extends from the hub for the securement of a crank arm thereto.
The stiffening fins generally extend axially from one side of the base a distance in excess of the thickness of the outer periphery and preferably a distance approximately equivalent to the thickness of the crank arm. The fins have a greatest axial dimension adjacent to the hub and taper towards the outer rim. The hub also extends axially to match the adjacent portion of the stiffening fins.
Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
REFERENCES:
patent: 4009621 (1977-03-01), Segawa
patent: 5133695 (1992-07-01), Kobayashi
patent: 5242028 (1993-09-01), Murphy et al.
patent: 5791203 (1998-08-01), Chen et al.
Kelly Bauersfeld Lowry & Kelley LLP
Wright Dirk
LandOfFree
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