Improvements in Driving Mechanism for Cycles.
Year: 1896

page_text: Date of Application, 2nd Apr., 1896-Accepted, 2nd Apr., 1897
Improvements in Driving Mechanism for Cycles.
I, WILLIAM W. GREEN, of 48 South Clinton Street, Chicago, in the County of Cook
and State of Illinois, United States of America, Gentleman, 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 :----
My invention relates to certain improved means employed to propel a bicycle or
other analogous vehicle.
My invention has for its object the provision of means whereby in the use of pedals.
for propulsion, the foot of the rider shall be caused to travel the shortest possible
distance, that is through a circle of travel of the smallest possible circumference, and
yet at the same time be capable of exerting a maximum degree of energy and leverage
when the pedals arrive at and pass through that part of the circumference of the circle,
or path of their travel, in which the foot of the rider is about to move or is moving
downward and his weight or pressure brought upon the pedals. In addition to the
foregoing feature it is my object to provide such a construction and arrangement as.
to utilize completely the desirable advantages of a compound leverage whereby to
effect a transformation in the intensity of the applied energy.
As another feature of my invention it is my object to accomplish the foregoing
results in such a manner as to avoid that retardation incident to a dependence upon
the momentum of the pedals, whereby to bring the pedals to that position in which
the power is applied and to provide means whereby the pedal levers and pedals may
be disposed at such relative angles as to invariably cause each lever and pedal in turn
to occupy that position aforesaid in which to apply the power, when the other lever
and pedal has passed or nearly passed that point of the arc of the circle of travel in
which the power is applied.
Another object of my invention is to provide means whereby the foregoing
enumerated features of advantage may be retained and the power transmitted by a
single connection from the driving mechanism to the rear wheel.
My invention has certain other objects in view and consists in certain features.
to be particularly described, reference being now had to the accompanyiny drawings
in which:
Figure 1 is a side view of my improved propelling mechanism.
Figure 2. is a central vertical section through the sprocket wheel and a horizontal
section through the hanger..
Figure 3 is a section on the line x-x of Figure 2.
In carrying out my invention I provide a crank shaft 25 which has fixed to one of
its ends a crank arm or lever 26 carrying a pedal, this crank shaft 25 passing loosely.
through the crank hanger 27 and rotatively mounted upon the ball bearings 28 and 29.
Secured rigidly to the other end of the crank shaft 25 by means of the key 30 is a
sprocket driver arm 31 which is formed as a loop passing about and engaging the pin
or stud 32 on the sprocket drive wheel 33. Mounted loosely upon the crank shaft 25
is the other sprocket drive arm 34 engaging the stud or pin 35 on the sprocket
drive wheel 33, the crank arm or lever 36 of the other pedal being directly and
rigidly connected with the drive arm 34.
It will be apparent that the crank arm or lever and its pedal on that side of the
bicycle opposite to the side thereof on which the sprocket wheel is located, is.
connected by the crank shaft and the drive arm, which is rigidly secured to the

page_text: crank shaft. to its stud on the sprocket wheel, and that the crank arm or lever on
the same side as that of the sprocket wheel is connected with the said sprocket
wheel in like manner, except that the drive arm and crank are loosely mounted about
the crank shaft, the crank arm or lever being directly and rigidly connected to the
said drive arm.
I mount the sprocket wheel 53 upon a shaft 38 through which the crank shaft 25
passes and relatively to which it is disposed eccentrically said shaft being connected
rigidly to the hanger 27. The hub 39 of the sprocket wheel 33, travels about
the shaft 38, this-hub having the form of a T shaped ring in cross section the
flange of which ring is secured to the sprocket wheel.
With this form of construction I obtain an increase in the intensity of the applied
energy by means of a compound leverage employing the various lever arms as
follows:
From the center of rotation of the crank arms to the point of application of the
power at the pedal and from said center or axis to the point of application of the
power to the sprocket wheel and from said latter point to the axis of rotation of
the sprocket wheel and from the said axis to the point of resistance on the periphery
of the sprocket wheel.
It is desirable that the power should be applied to each pedal lever when or before
the power is withdrawn from the other pedal lever in order that it shall be unnecessary
to depend upon momentum to bring each pedal lever into the position at which the
power is applied. It will be readily evident that such a dependence upon momentum;
presents a considerable drawback especially when mounting a hill and in any event
the foot of the rider retards such momentum more or less. "In order that each pedal
and its lever may be brought into position whereby to apply the power before the
other pedal and its lever has passed beyond the point of application of the power.
I provide the construction as described, employing a bell crank form and in-
conjunction with this form elevate or position the axis of the pedal lever above the
horizontal plane of the axis of the sprocket wheel. By reference to Figure 1 and
comparison of the positions assumed by the pedal lever in said figure, it will be
observed that while the one pedal lever is still traveling through that part of the are
of the circle in which the power is applied and is approaching the end of the same,
the other pedal lever has entered upon that part of its travel in which the power is
applied. This construction and disposition of parts thereby provides means which
overcome the necessity of a dependence upon momentum of the pedal lever to bring
them into operative position.
It will be apparent that when the pedal is in the position in which the pressure,
weight and power of the rider is about to be applied, or is being applied, the power
arm of the pedal from the point of application of the power at the pedal to the point
of application at the center of the driving sprocket wheel is of a maximum or greatly
extended length and therefore a maximum leverage is obtained, and when the power
is withdrawn in the further travel of the pedal in an upward direction it is evident
that this distance or length aforesaid is greatly reduced, the pedals being. caused to
travel through the same circle in each revolution.
The foregoing result, it is evident, is attained by reason of that construction whereby
the pivot of the pedal lever arm on the axis of the crank shaft is located forward of the
center or axis of the sprocket wheel.
. It is further evident that as one of the pedal lever. arms is fast to the crank shaft i
and the other loose thereon, these pelal lever arms are permitted a slight change of.
position relative to each other, which is necessary in. the present construction, as
1-have shown it, owing to the eccentric position of the crank shaft to the center of the
sprocket wheel.
It is evident that to obtain the maximum intensity of applied power during the
travel of the pedal through the are of the circle in which the foot of the rider moves'
downward, it is necessary that the length of the drive arm from the axis of the crank
or pedal lever to the point of attachment to the sprocket wheel should be as short as
possible and the length of the pedal lever from the center of the sprocket wheel to the

page_text: pedal, at its maximum length, and this decreased and increased length of the drive.
arm and pedal lever respectively should extend and be maintained for as great a
portion of this arc of the circle as possible. By the use of the curved pedal
levers and the consequent acute angled bell, crank lever this latter result is
accomplished.
The position of the sprocket wheel shaft, and the ball bearings between it and
the hub of the sprocket wheel; and the ball bearings about the crank shaft, is such.
that the strain of the sprocket chain is distributed directly over said ball bearings
thus avoiding the usual overhanging strain.
Having now particularly described and ascertained the nature of my said inven-.
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. In a cycle, a driving mechanism therefor, consisting of two cranks having
pedals thereon, a driving sprocket wheel adapted to rotate about a given axis and
two drive arms for the sprocket wheel adapted to rotate about another axis which is
positioned forward of the axis of the sprocket wheel aforesaid.
2. In a cycle, a driving mechanism therefor consisting of a driving sprocket
wheel rotating about a given axis, pedal levers and drive arms for the sprocket
wheel together forming bell crank levers and means whereby the axis of rotation.
of the pedal levers and drive arms constituting said bell crank levers are located
forward of the axis of the sprocket wheel aforesaid to obtain a compound leverage.
3. In a cycle, a driving mechanism therefor consisting of a driving sprocket
wheel rotating about a given horizontal axis, a crank shaft disposed in a different
horizontal plane from that of the axis of the sprocket wheel, cranks or pedal levers
secured on either end of the crank shaft and sprocket wheel drive arms each of
which is connected to the sprocket wheel and operated respectively by each crank or
pedal lever, the axis of rotation of the cranks or pedal levers being in advance.
of the axis of rotation of the sprocket wheel whereby a compound leverage is
obtained.
4. In a cycle, a driving mechanism therefor consisting of a crank shaft, cranks
or pedal levers, drive arms rigidly secured to each of the cranks or pedals at the
same angle, one of said cranks or pedal levers and its drive arm being rigidly
secured to the crank shaft and the other crank or pedal lever and drive arm loosely
mounted thereon, a sprocket wheel and a sprocket shaft held stationary and mounted
loosely and eccentrically upon the crank shaft, said sprocket wheel traveling about.
the sprocket wheel shaft, whereby the pivotal center of the cranks or pedal levers
is in advance of the center of rotation of the sprocket wheel and a compound
leverage obtained.