Endless belt power transmission systems or components – Pulley with expansible rim means or pulleys with alternately... – Structure for variably adjusting radius of rim section
Reexamination Certificate
2000-05-30
2001-12-25
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Pulley with expansible rim means or pulleys with alternately...
Structure for variably adjusting radius of rim section
C474S049000, C474S080000
Reexamination Certificate
active
06332852
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to drive systems for vehicles. More specifically, the present invention is concerned with a drive system having a variable ratio obtained through a variation of the diameter of a sprocket.
BACKGROUND OF THE INVENTION
Variable diameter sprockets are well known in the art. For example, U.S. Pat. Nos. 4,030,373; 4,832,660; 5,041,061; 5,013,284; 5,094,653; and 5,104,357 all naming Hamlin Leonard as an inventor, each describes variable speed drive systems for bicycles provided with variable diameter pulleys. As is well known, by modifying the diameter of the variable diameter pulley, the ratio of the front to rear pulleys is modified without requiring a cluster of sprockets.
The systems described by Leonard do not use a conventional bicycle chain but instead use a flexible driving means under the form of a V-belt. The different mechanisms described by Leonard have the same common drawback that the diameter changing mechanisms provided to modify the diameter of the pulley are generally complex.
The use of a V-belt is also a drawback since it must usually be heavily tensioned to prevent it from slipping from the pulleys. It is also to be noted that adverse temperature conditions, such as rain, may nevertheless cause the V-belt to slip in the pulleys.
To overcome the drawbacks described hereinabove with respect to the systems proposed by Leonard, the applicant describes in an international application published under publication number WO99/43539, a variable ratio drive system using a conventional chain and a simple sprocket diameter changing mechanism. It has been found however, that the friction between the sprocket diameter changing mechanism and the sprocket portions is somewhat detrimental to the performance of the drive system.
OBJECTS OF THE INVENTION
An object of the present invention is therefore to provide an improved variable ratio drive system.
It is a further object of the present invention to provide a variable ratio drive system using a conventional chain.
It is also an object of the present invention to provide a variable ratio drive system provided with an improved sprocket diameter changing mechanism.
SUMMARY OF THE INVENTION
More specifically, in accordance with the present invention, there is provided a variable ratio drive system comprising:
a variable diameter sprocket including:
a support having a rotation axis and at least three radial apertures; each aperture being provided with at least two stopping element;
at least three sprocket portions, each being so mounted to a respective one of the three radial aperture of the support as to be radially movable therein; each of the three sprocket portions includes a movable element configured and sized to interconnect with the two stopping element to selectively maintain the sprocket portion in a desired radial position; each sprocket portion also includes a biasing element mounted thereto to bias the movable element towards the two stopping element;
a sprocket diameter changing mechanism including:
a fixed portion; and
a movable portion mounted to the fixed portion; the movable portion including a pushing surface so positioned and configured as to overcome a biasing action of the biasing element through a pushing action on the movable element of the sprocket portion; the pushing action causing the disengagement of the movable element from one of the stopping element; the movable portion also including at least one guiding surface configured and sized to reposition the sprocket portion in a second desired position and to engage the movable element with a corresponding stopping element.
According to another aspect of the present invention, there is provided a variable ratio drive system comprising:
a variable diameter sprocket including:
a support having a rotation axis;
at least three sprocket portions having a longitudinal body provided with opposite ends; each the three sprocket portions being so mounted to the support as to be radially movable with respect to the rotation axis; each of the three sprocket portions is so configured that it may be selectively maintained in a desired radial position; each the three sprocket portion comprising a dented portion provided near one of the opposite ends of the longitudinal body;
a sprocket diameter changing mechanism configured to interact with the three sprocket portions to selectively maintain the sprocket portions in the desired radial position.
According to a third aspect of the present invention, there is provided a variable ratio drive system comprising:
a variable diameter sprocket including:
a support having a rotation axis and at least three sprocket portion retaining means each being provided with at least two sprocket portion position maintaining means;
at least three sprocket portions, each being so mounted to a respective one of the three sprocket portion retaining means of the support as to be radially movable; each of the three sprocket portions includes means to interconnect with the two sprocket portion position maintaining means to selectively maintain the sprocket portion in a desired radial position; each sprocket portion also includes biasing means so mounted thereto to bias the interconnecting means towards the two sprocket portion position maintaining means;
means for changing the diameter of the variable diameter sprocket, the sprocket diameter changing means including:
a fixed portion; and
a movable portion so mounted to the fixed portion as to be movable; the movable portion including means for overcoming a biasing action of the biasing means through a pushing action on the interconnecting means of the sprocket portion; the pushing action causing the disengagement of the interconnecting means from one of the sprocket portion retaining means; the movable portion also including at least one guiding means configured and sized to reposition the sprocket portion in a second desired position and to engage the interconnecting means with a corresponding sprocket portion retaining means.
According to a final aspect of the present invention, there is provided a variable ratio drive system comprising:
first and second variable diameter sprockets, each including:
a support having a rotation axis and at least three radial apertures; each aperture being provided with at least two stopping element;
at least three sprocket portions, each being so mounted to a respective one of the three radial aperture of the support as to be radially movable therein; each of the three sprocket portions includes a movable element configured and sized to interconnect with the two stopping element to selectively maintain the sprocket portion in a desired radial position; each sprocket portion also includes a biasing element mounted thereto to bias the movable element towards the two stopping element;
first and second sprocket diameter changing mechanisms each including:
a fixed portion; and
a movable portion so mounted to the fixed portion as to be movable; the movable portion including a pushing surface so positioned and configured as to overcome a biasing action of the biasing element of a corresponding variable diameter sprocket through a pushing action on the movable element of the sprocket portion; the pushing action causing the disengagement of the movable element from one of the stopping element; the movable portion also including at least one guiding surface configured and sized to reposition the sprocket portion in a second desired position and to engage the movable element with a corresponding stopping element.
Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings.
REFERENCES:
patent: 3956944 (1976-05-01), Tompkins
patent: 3969948 (1976-07-01), Pipenhagen, Jr.
patent: 3994180 (1976-11-01), Ackerman
patent: 4030373 (1977-06-01), Leonard
patent: 4129044 (1978-12-01), Erickson et al.
patent: 4260386 (1981-04-01), Frohardt
pat
3561020 Canada Inc.
Bucci David A.
Johnson Vicky A.
Nixon & Vanderhye PC
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