Land vehicles – Wheeled – Occupant propelled type
Patent
1992-11-06
1994-06-28
Focarino, Margaret A.
Land vehicles
Wheeled
Occupant propelled type
280230, B62M 102
Patent
active
053240570
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention:
The present invention relates to a two-wheel drive cycle, i.e. a bicycle or motorcycle, comprising a power train capable of driving the front wheel substantially as efficiently as the rear wheel.
2. Brief Description of the Prior Art:
A prior art two-wheel drive bicycle is disclosed in International patent application published under number WO 91/12167 (Biannic et al.) on Aug. 22, 1991.
This bicycle comprises a rear wheel driven through the conventional pedals, cranks, chain wheel, chain and sprocket cluster. An additional sprocket is mounted on the rear wheel to drive the front wheel through first and second chains. The first chain is meshed with the additional sprocket of the rear wheel while the second chain is meshed with a sprocket mounted on the front wheel.
To enable easy steering of the front fork assembly, on which the front wheel rotates, the first and second chains are interconnected through a cardan joint mounted on the pivotal connection between the fork assembly and the frame of the bicycle, that is on the head tube of that frame.
The two-wheel drive bicycle of International patent application WO 91/12167 presents the following drawbacks:
the head tube of the frame as well as the fork assembly must be cast and/or machined to receive the cardan joint;
a cardan joint is complex and additional pieces such as bushings, needle bearings, etc. are required upon installation; it is therefore very expensive;
in the cardan joint used in International patent application WO 91/12167, the rotational speeds of the input and output shafts are different during two angular portions of each revolution;
the major disadvantage is that the different pieces of the cardan joint and those necessary to its installation withstand important stresses and therefore produce a lot of frictional losses; these losses obviously require an additional effort from the cyclist, which effort is not used to drive the bicycle; and
all the pieces of the cardan joint requires specialized maintenance as well as frequent lubrication.
The present inventor has constructed a two-wheel drive bicycle using a cardan joint as disclosed in the aforementioned International patent application, and obtained poor results due to the above mentioned drawbacks related to the use of a cardan joint.
OBJECT OF THE INVENTION
An object of the present invention is therefore to overcome the above discussed drawbacks of the prior art by interconnecting the sprockets of the front and rear wheels directly through a single chain appropriately guided between the two sprockets.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a two-wheel drive cycle comprising a frame, a front fork assembly mounted on this frame through a pivotal connection to steer the cycle, a front wheel mounted on the fork assembly to rotate about a first axis, a rear wheel mounted on the frame to rotate about a second axis, a mechanism for driving the rear wheel, a front sprocket mounted on the front wheel and centered on the first axis to drive the front wheel, a rear sprocket mounted on the rear wheel, centered on the second axis, and driven through the driving mechanism, a chain forming a closed loop and meshed with both the front and rear sprockets, and means for guiding the chain between the front and rear sprockets, these chain guiding means comprising a set of grooved or toothed wheels engaging the chain and rotatively mounted on the cycle close to the pivotal connection.
In operation, the front wheel is driven through the driving mechanism, the rear sprocket driven by this mechanism, the chain meshed with both the front and rear sprockets, and the front sprocket driven through the chain.
In accordance with preferred embodiments of the present invention:
the chain guiding means comprises a spring mechanism for lengthening and shortening the chain loop as the front fork assembly is pivoted about the pivotal connection;
the front and rear sprockets are lying in respective planes, and the cha
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Auron, Lary; "Snake: Le velo a deux roues motrices"; Velo Vert, Jan.-Feb. 1992, pp. 28-30.
WO,A,9 112 167 (Biannic) Aug. 1991.
Focarino Margaret A.
Mattix C.
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