Improvements in and relating to Pedal Mechanism for Bicycles.
Year: 1897

page_text: Date of Application, 2nd Mar., 1897-Accepted, 15th May, 1897
Improvements in and relating to Pedal Mechanism for Bicycles.
I, JAMES CALDWELL ANDERSON, a citizen of the United States of America,
of 939 Rookery, in the City of Chicago, County of Cook and State of Illinois,
United States of America, 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 new and useful improvements in bicycles, and
particularly to the driving pedals thereof.
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In bicycles as at present constructed and used it is common to connect the pedal
cranks rigidly to the opposite ends of a driving shaft carrying a sprocket wheel
over which, and another sprocket wheel on the axle of the rear driving wheel
traverses an ordinary sprocket chain. The speed and power in such a construction
are regulated by the relative sizes of the sprocket wheels and the length of the
pedal cranks, and it is a well recognized principle that when what is known as
high gear
is provided to secure greater speed, a concomitant disadvantage
ensues in the fact that the leverage of the cranks is decreased and consequently
when the bicycle is driven up grade the ordinary power is applied at a disadvantage,
or in other words, greater power is required than would be necessary in low gear;
and it is also a well recognized fact that in driving the crank of a bicycle that
under the law of human anatomy a greater range of movement can be given in a
forward direction than in a downward, rear and upward movement of the foot; and
in view of these considerations my invention has for its objects to increase the
speed of bicycles by the employment of high gearing and at the same time utilize
the applied power with greater advantage; and with these ends in view my
invention consists in the construction and arrangement of the cranks and pedals
hereinafter more fully described, whereby the cranks are extended and contracted
during their revolutions, so that the power exerted by the rider is applied with the
greatest advantage.
In order that those skilled in the art to which any invention appertains may
know how to make and use the same, I will proceed to describe the construction
and action of my improvements, referring by letters to the accompanying drawings,
in which-
Figure 1 is a side view of my improved crank and pedal at the highest point of
its travel and just before it begins its forward movement.
Figure 2 is a similar view showing the change that takes place immediately after
the forward movement of the crank has begun.
Figure 3 is a similar view showing the relation of the parts as the crank
approaches a horizontal position on the downward stroke.
Figure 4 a similar view showing the relation of the parts as they approach a
horizontal line on the rear and upward stroke.
Figure 5 is a top or plan view with the crank broken away.
Figure 6 is an exterior or end view of the disc hub of the pedal, and
Figure 7 is an interior plan view of a revoluble disc or small pulley mounted
upon an eccentric extension of the crank, as will be hereinafter more fully
explained.
Similar letters of reference indicate like parts in the several figures of the
drawings.

page_text: A represents a crank of ordinary construction so far as relates to the way in
which it may be secured to the crank shaft, but longer than the usual six and a
half inch crank. The free end of the crank is formed with a spur or shoulder B
to limit the movement of the extension piece C, which, as clearly shown, is pivoted
at D to the crank.
The extension piece is bifurcated at its pivoted end so as to embrace the end of
the crank A and is grooved obliquely on the under edge so that it may fold upon
the crank, as clearly shown at Figure 4. The outer end of the extension piece C
is formed with an eccentric wrist a, which constitutes a journal for a loose pulley
or disc, presently described.
E is an ordinary pedal frame of rat-trap or other construction and with the usual
hollow or tubular axle F rotating on ball bearings around the pedal shaft G, which
is secured by screw thread centrally in the end of the extension C so that the
circular wrist a becomes eccentric to the axis of the pedal shaft, as clearly shown
in Figures 1, 2, 3 and 4.
Ou the inner end of the pedal frame E is secured a metal dise H through which
the pedal shaft passes and this disc is provided with diametric cylindrical studs 6 b,
but if deemed desirable one of said studs may be dispensed with, as will be
hereinafter explained.
I is a loose pulley or disc which is grooved circumferentially to constitute a track
for a light chain J which is pivotally connected at one end to a lug c on the
periphery of the said disc, and at the other end to a lateral wrist d extending from
the crank A. The disc I is cut away on its exposed face leaving a hube and rim f,
and the intervening groove may be used as a scat for a spring if so desired to hold
the disc against unnecessary rotation, and the interior face of the disc is preferably
countersunk as shown at y, Figure 7, to take a bearing upon a circular extension
or hub on the nut K, which secures the ball bearings in place. This disc is
provided on the face adjacent to the disc end H of the pedal with a cylindrical
stud which is adapted to contact with the studs on the face of disc H, or with
the single stud thereon when the other is dispensed with, as will be better understood
from the description given of the operation of the several parts.
The pedal frame is provided with toe pieces M, and if thought desirable each
pedal may be provided with two toe pieces arranged on opposite sides. The
drawings represent a crank of the usual length extended a distance equal to the
length of the extension C, so that it will be understood that when the said extension
is folded up, as shown at Figures 1 and 4 the leverage length of the crank is
substantially such as the ordinary crank (six and one-half inches) and when the
extension C is thrown out into the position shown at Figures 2 and 3 the power is
applied at the point D (the pivot of the extension piece) which is designed to be
two inches further from the crank shaft than the point where the power is applied
when the extension is folded, as shown at Figures 1 and 4.
Assuming that the crank is in the position shown at Figure 1 the forward
movement of the leg and foot of the rider will cause the extension C to travel
outward two inches and into the position seen Figure 2, so that the power is
then applied two inches further away from the axis of the crauk shaft and con-
sequently greater leverage is secured. As the crank is moved downwardly and
reaches a horizontal position the stud L on the loose chain pulley I comes in
contact with the stud b on the disc H, as seen in dotted lines at Figure 3 (which is
shown slightly above the horizontal, simply for convenience of arrangement of the
figures on the sheet) thus interlocking the chain pulley I and pedal disc H, and the
chain J is stretched into taut condition, the discs H and being held against
independent rotation by the contact between the studs L and b. The continued
rotation of the crank causes the chain J to wind upon the periphery of the disc I
as the pedal rotates upon its shaft, (the chain pulley and pedal disc being interlocked
as described) and thus pull the free end of the extension C and the pedal toward
the crank and into the position shown in Figures 1 and 4, which will occur when
the crank has passed a vertical line below the axis of motion, and after passing that

page_text: line toward the position shown in Figure 4 the eccentric rotation between the
studs Land 6 permits the stud L to roll past the stud b and consequently the disc I
is free to rotate upon the wrist a and slacken the chain J so that the outward
movement of the extension C may again take place.
I have described the operation where only one stud b on disc H is used, but it
will be apparent that two such studs can be used if placed diametric to each other
in order that either tread surface of the pedals may be used.
I do not wish to be limited to the exact details of construction shown and
described as they may be varied to some extent without departing from the spirit
of my invention which rests in the idea of a crank of greater length than those
usually employed, and provided at its free end with a pivoted extension carrying
the pedal, and mechanism intermediate between the pedal frame and the main
crank which through the revolution of the pedal frame on its axis causes the
pedal extension to fold upon the crank proper as the latter moves rearwardly and
upwardly.
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 crank mechanism for bicycles, the combination with a crank A, pedal E F,
and pivoted crank extension C, intermediate mechanism between the crank A and
the pedal shaft whereby the travel of the pedal shaft and rotation of the pedal
causes the extension C to approach the crank during the rear and upward travel of
the pedal, as herein before described.
2. In combination with the crank A, pivoted extension C having eccentric wrist a,
and the pedal shaft G secured in the end of extension C, the pedal E-F, disc H,
having stud b, chain pulley disc 1 with stud L, and connecting chain J, substantially
as and for the purpose set forth.
1 1
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.