Improvements in Crank Mechanism for Transmitting Motion.
Year: 1899

page_text: Date of Application, 1st Mar., 1899-Accepted, 22nd Apr., 1899
COMPLETE SPECIFICATION.
Improvements in Crank Mechanism for Transmitting Motion.
I, CHARLES COFFIN PROTHEROE, of Richmond Hill, Borough of Queens, City
and State of. New York, United States of America, Attorney and Counsellor at
Law, 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 ;-
The invention is a device for transmitting motion whereby power may be trans-
mitted for example between two rotary shafts. It is especially adapted (among
ether uses) to application to a bicycle for the purpose of transmitting power from
the pedal crank to suitable gearing actuating the shaft of the driving wheel.
In the accompanying drawings Figs. 2 and are side elevations of my device,
showing the connecting lever in three positions. Fig. 4 is a top view Fig. 5 is
an illustrative detail view showing the lever in the position represented in Fig. 1
and the ball in section. Fig. 6 is a vertical cross-section on the line of Fig. 2.
Fig. 7 is a similar cross-section showing a roller fulerum substituted for the ball.
Fig. 8 shows my mechanical motion applied to power transmission in a bicycle.
Fig. 9 shows the same on a larger scale than in Fig. 8, certain parts being broken
away and the mechanism being viewed from the side opposite to that shown in
Fig. 8.
Similar letters, and numbers of reference indicate like parts.
Referring first to Figs. 1 to 6 inclusive. A is a supporting bar. B is a shaft
journaled near one, end of said bar, and having a crank arm' C. D is a gear or
pulley, the shaft E of which is journaled near the opposite end of said bar. In
the pulley or gear 1) is a radial slot or guideway F.
G is a lever connected at one end to the pin H of crank C, and carrying at
the other end a pin I which projects at right angles from said lever and is received
in the slot or-guideway Fin gear 1).
on bar Aby the arms is
In the bar A is a longitudinal slot J. Supported
a plate M which is parallel to the side face of bar A and has in it a slot similar
to slot J. K is a ball preferably of hardened steel. The distance between the
face of bar A and the opposite face of plate M is less than the diameter of said
ball. Hence said ball while entering said slots J. Jis supported by and freely
rolls along the edges of said slots as shown particularly in Fig. 6 So also the
diameter of said ball is greater than the transverse width of either slot, J, J.
Hence said ball is prevented from coming through said slots-or, in other words,
is retained between the plate M and bar A while free to move to and fro in the
guideway formed said slots.
...
.
The connecting lever G passes between the bar A and the plate M. and' has
formed in it a longitudinal slot Owhich is of suitable transverse width to receive
in it the ball K. It will be understood therefore that said ball lies in slot and
also in slots or guideways J.J
It will be obvious that when either end of the lever G is moved over a curvilinear
path.--as by the rotation of crank C or gear Dsaid lever will have a movement

page_text: of translation and also a vibratory movement around the ball K as a fulcrum.
As the said ball however is free to move in the guide slots J, J' it will be moved
to and fro in said slots by the action upon it of an advancing edge of the slot O
in the lever G. This will be better understood from Fig. 5. Thus assuming
the lever G is in the position shown in, and is moving to the left of, that figure,
as indicated by the arrows, while also turning on said ball as a fulcrum, it is
obvious that the edge a of the slot O is the advancing edge positively acting
upon a point on the spherical surface of said ball, and thus causing said ball to
roll to the left in its guide slots J, J. If, on the other hand, we consider in the
same figure that the lever G is moving to the right, while turning on the ball
as a fulcrum, then the edge of the slot O would be the advancing edge positively
acting as before.
Now referring to Figs. 1, 2 and 3 and considering the lever G as shown_attached
to the crank arm C, and said arm to rotate in the direction of the arrow: In Fig. 1
the advancing edge of the slot in lever G will roll the ball to the right in
the guideways J, J. But the edges of slot are now constantly approaching
parallelism to those of slots J, J, and when the lever reaches the position shown
in Fig. 2 they become parallel-or, in other words, the longitudinal component
of force acting on the ball disappears and the onward motion of the ball ceases.
As the crank continues its rotation the lever G moves in the opposite direction—.
that is to the left, and as it turns on the ball as a fulcrum the slot 0 presents
again an advancing edge which carries the ball to the left. Hence the ball is
caused to make an excursion in the guideways J, J' forward and back for each
rotation of the crank C. It will be obvious that the transverse edges of the slot (
do not necessarily strike the ball-nor is the ball in its excursion necessarily
carried against the transverse edges of the slots J, J. The means whereby its
travel in the guideways J, J is limited and controlled is solely the lever G-of
which it is a rolling fulcrum, while it will always adjust itself to the movement
of that lever.
Recurring again to Figs. 1, 2 and 3. It will be observed that the length of
lever G between the centers of pin I and crank pin H is there shown as greater than
the distance between the centers of crank shaft B and gear shaft E. The pin I at the
end of lever G being also free to move in the slot Fin gear D the rotary motion
of the crank C may therefore be transmitted to the gear D so that the movement
of a point on the circumference of gear 1) may synchronize with the movement
of the crank pin H with sufficient approximation to permit this arrangement of
the invention to be utilized under conditions where it is desirable that uniform.
rotary motion of the driving shaft should cause approximately corresponding
uniform rotary motion of the driven shaft. Such an application of my invention
lies in its embodiment in a bicycle, one way of accomplishing which is disclosed
in Figs. S and 9.
1, 2 and 3 are members of the bicycle frame, 4 is the rear or driving wheel,
having on its axle a pinion 5. 6 and 7 are pedal cranks. Projecting rearward
from the pedal crank shaft bearing is a bar 8 which has in it the elongated slot J.
Projecting forward from the rear member of the frame is a bar 9 in which is the
elongated slot J. The bars 8 and 9 are connected by a cross arm L which is
here shown as forged integral with said bars, but which may be a separate piece
and detachably secured to said bars, or made integral with one bar and detachably
secured to the other in any suitable way. The gear D is a toothed pinion having
its shaft journaled in bar 9 and engaging with the pinion 5 on the driving axle.
The lever G is secured at one end to the crank pin H on the pedal crank 6 and
the pin I enters the slot F in pinion D as already described. The ball K is
received in the slots J, J and in the slot in lever G.
When the pedal cranks 6 and 7 are operated by the rider in the ordinary way,
rotary motion is communicated through the lever G to the pinion D and so to
pinion 5 whereby the driving wheel is turned in direction to propel the machine.
At the ends of the slots J, J I may provide buffers P of rubber, leather or

page_text: other elastic material, to receive any chance impact of the ball K in case of its
abnormal displacement. So also I may apply similar buffers Q at the ends of the
slot F in gear D) to receive the impact of pin I in case of necessity.
Although I deem the ball fulcrum as preferable, I may employ a roller fulcrum R
received in the slots J, J¹ and O as represented in Fig. 7. In order to keep the
axis of this roller truly at right angles to its line of movement I provide washers S,
which washers bear on the bar A and plate M.
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. A device for transmitting motion comprising a driving part, a driven part,
and a connecting lever between said parts, the fulcrum of which lever is movable
and controlled by the movement of said lever.
2. A device for transmitting motion comprising a driving part, a driven part,
a connecting lever between said parts and a movable ball fulcrum for said lever,
constructed and arranged substantially as set forth.
3. A device for transmitting motion comprising a driving crank, a driven crank
and a connecting lever having a movable fulcrum controlled by the movement of said
lever, one of the ends of said lever being connected to the driven crank so as to
move radially to the crank shaft.
4. A device for transmitting motion comprising a driving crank, a driven
crank having a radial slot and a connecting lever having a movable fulcrum
controlled by the movement of said lever, one of the ends of said lever being
secured and freely movable in said slot.
5. A bicycle or other vehicle having a driving part, and a driven part, and
for transmitting power between said parts the connecting lever provided with
the movable controlled fulcrum and constructed and arranged substantially as
described.
Dated this 16th love of Fahmar 1900
CHARLES COFFIN PROTHEROE,
Haseltine, Lake & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.
CHARLES COFFIN PROTHEROE,
Haseltine, Lake & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.