Improvements in Driving Mechanism especially Applicable for the Propulsion of Cycles.
Year: 1898

page_text: Date of Application, 10th Aug., 1898-Accepted, 20th May, 1899
COMPLETE SPECIFICATION.
Improvements in Driving Mechanism especially Applicable for the
Propulsion of Cycles.
We, HENRI BLANQUET and CHARLES CAILLE, both of No. 62, Rne de Provence,
Paris, in the French Republic, Engineers, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:
In cycles at present in use, the impulse exercised on the pedal by the foot
of the cyclist is transmitted to the driving wheel by means of sprocket wheels
and chains, or by a series of circular gear-wheels.
If it be assumed that the cyclist exercises a constant force on the pedal, the
impulse received by the driving wheel, which impulse causes the propulsion of
the machine; is nil at the dead point; that is to say, when the crank is vertical
to the ground; while on the other hand it is a maximum when the crank is
parallel to the ground. As a matter of fact the impulse received is a function of
the lever arms formed by the radii of the toothed wheels of the transmission gear
and the lever arm formed by the crank. But the lever arms formed by circular
cogged wheels are constant for a given machine and depend on the radii of those
wheels, while the lever arm by which the force which acts upon the said wheels
is multiplied, is nil when the crank is vertical to the ground and increases more
and more as the crank approaches to parallelism with the ground, when it becomes
a maximum. It follows that in the neighbourhood of the dead point the impulse
received is almost ni, and that during a longer or shorter period the forward
movement of the machine is effected only by the momentum already acquired.
The irregularity in the amount of the impulse received which can only be com-
pensated for by variations in the amount of force exercised by the cyclist, is
very perceptible.
The invention which forms the subject of the present application refers to an
arrangement for transmitting the motion which enables the value of the impulse
received to be very appreciably rendered regular by increasing it in the neigh-
bourhood of the dead point and so diminishing the time during which the machine
moves forward only by its acquired momentum.
We have designed an arrangement for varying the length of the lever arms
formed by the cog-wheels of the driving gear in such a manner that they reach
their maximum at the moment when the lever arm formed by the crank is near
its minimum, and we obtain this result by employing oblong or oval cog-wheels
for the driving gear. This method of transmission as applied to a cycle is repre-
sented in the accompanying drawing.
Figure is a side elevation.
Figure 2 is a horizontal section through crank and driving wheel axles.
On the pedal axle we key an oval or oblong wheel A in such a manner that
its major axis A' A' is parallel to the line of the cranks m m' and that its minor
axis a, a is normal to the latter. Between the pedal axle and the axle d of
the driving road wheel and parallel to them, we arrange an intermediate axle b.

page_text: On the hub of this axle 6 and in the plane of the oval or oblong wheel A is keyed
a second oval or oblong wheel B of the same curves and diameters as the wheel A
and engaging with it; this latter wheel (B) is mounted on its shaft in such a posi-
tion that its major axis B₁ B¹ is normal to the line of the cranks m' m², and that
its minor axis bib is in the same plane and parallel to the said line m, m'. The
shape that should be given to the wheels A and B to enable them when turning
on their centres to engage throughout their length, may be easily ascertained by
projection. On the hub of the axle b at the side of the wheel B and in the
same plane with the pinion D, keyed to the hub of the driving road wheel, is
fixed a circular toothed wheel C engaging with the said pinion 1). The whole of
these wheels and pinion revolve in a frame F which carries the axle b and is
rigidly secured by bolts and nuts to the pedal bracket and the axle of the driving
road wheel.
It is the form or shape of the wheels A and B that constitutes the characteristic
peculiarity of this driving gear. It results therefrom that, as may be seen, in
the neighbourhood of the dead-point the impulse received by the driving wheel
will be much greater than if the wheels A and B were of the same size and of
circular periphery. The secondary lever arms vary in inverse proportion to the
primary lever arms, the lever arms formed by the cog-wheels being at the mini-
mum when the crank is parallel to the ground, that is to say, at the moment
when its lever arm is a maximum.
The employment of oval or oblong toothed or cog-wheels is more rational in
the neighbourhood of the dead-point, as the position of the leg is less advanta-
geous at this point, and the cyclist has the tendency to diminish the impulse
imparted to the pedal in a sense contrary to that required by the work to be
performed.
Having now particularly described and ascertained the nature of our said in-
vention and in what manner the same is to be performed, we declare that what
we claim is:-
1 The improved driving mechanism for cycles consisting of the combination
with the driving cranks of an oval or oblong gear wheel mounted fast on the
driving-crank axle, with its major axis parallel to the line of the cranks and its
minor axis normal to the said line, an axle supported intermediately between
the driving-crank axle and that of the driving road-wheel and parallel to them,
a similar oval or oblong gear wheel mounted fast on the hub of the said inter-
mediate axle and in such position that its major axis is normal to the line of
the cranks, said wheel gearing with first-mentioned oval or oblong gear wheel,
a pinion fast on the hub of the driving road-wheel, a circular gear wheel mounted
fast on the same hub as and by the side of the second mentioned oval or oblong
gear wheel and engaging with the said pinion, substantially as described and
illustrated.
2. The combination with the improved driving mechanism for cycles, consist-
ing of the combination of oval or oblong gear wheels and circular gear wheel
and pinion arranged, constructed and operating as described, of a casing enclos-
ing all the said mechanism, said casing being secured to the bottom or pedal
bracket and to the axle of the driving road-wheel, substantially as described
and illustrated.
PHILLIPS & LEIGH,
No. 22, Southampton Buildings, Chancery Lane, London, W.C..
Agents for the Applicants.