Improvements in Bicycle Cranks.
Year: 1899

page_text: Date of Application, 22nd Aug., 1899-Accepted, 23rd Sept.,
1899
COMPLETE SPECIFICATION.
Improvements in Bicycle Cranks.
I, JOSEPH BULOVA, of No. 57, Maiden Lane, New York City, County and State
of New York, United States of America, Manufacturer, 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:-
This invention relates to a crank for bicycles which is so constructed that tho
leverage from the pedal may be increased to a greater or less extent during the
downstroke so that it is in the power of the rider to adjust such leverage
according to the steepness of the grade to be overcome, while on the level roads.
the normal leverage may be retained.
In the accompanying drawing:
Fig. 1 is a side elevation of my improved bicycle crank.
Fig. 2 an elevation of the right crank, showing it in a different position.
Fig. 3 a rear view partly in section of the right pedal and crank.
Fig. 4 an inner view of a modification of the crank, and
Fig. 5 a rear view partly in section of the same.
The letter, represents the crank arm of a bicycle keyed as usual to the
driving shaft b, and made of normal length. To the outer side of the free end
of the arm a, is connected a freely revoluble link a', by a pivot a³, which passes
freely through the link a, and is tapped into arm a. To the outer side of the
free end of link a¹, is in turn pivoted the pedal c, which may have a toe-clip c¹,
if desired. Thus it may be seen that the link a', is revoluble around arm a,
while the pedal c, is revoluble around the link a', as well as around the arm a.
The parts a, a, are adapted to be interlocked at different angles, during the
downstroke, by a suitable clutch mechanism, such as a pawl and ratchet wheel.
The ratchet wheel d, is made integral with or secured to the outer side of arm a,
around the pivot a³, (Fig. 3) and has a series of teeth on its forward edge, while
the teeth on the rear edge may be omitted. It is engaged by a pawl e, influenced
by a spring el, and pivoted to the inner side of link a¹.
In use the link a¹, with the pedal c, normally depends at a³, from the arm a.
When the upper pedal has been carried somewhat beyond its uppermost position
(upper pedal Fig. 1) and it is desired to increase the leverage, the foot is thrown
out, more or less, (Fig. 2) in accordance with the increase of leverage desired.
This throwing out of the foot will cause the link a, to be likewise swung outward
and the pawl e', to be carried over a greater or less number of teeth of the
ratchet d, and to engage that one of the teeth, with which it is ultimately in
alignment.
Thus it will be seen that a rigid connection between the parts a, a', is estab-
lished, and that the length of the leverage represented by the distance of the
pedal c, from the axle b, may be readily altered by the rider to conform to the
road grade, such leverage being readily changeable at every single downstroke.
When the pedal has arrived somewhat back of its lowermost position (lower
pedal Fig. 1) the arm a, will be revolved by the descent of the other foot, and
the pawl will liberate the teeth of the ratchet wheel, so that the link a', will swing

page_text: freely downwards from pivot a². In this way the radius of revolution is again
decreased and this diminished, radius is maintained until the pedal has again
passed its uppermost position, when the foot may be again thrown outwards to
increase the stroke-radius as heretofore described.
On level roads or on downgrades where it is not desired to increase the stroke-
radius, the foot is not thrust forward at the beginning of the downstroke, but
the link a', is permitted to depend vertically from pivot ², so that in this
way no increase in leverage is produced.
Thus it will be seen that it is placed within the power of the rider to increase the
leverage to any suitable extent, if he so desires, or to maintain the normal leverage
is that should be preferable.
In Figures 4 and 5, the pawl and ratchet mechanism is not located between
the parts a, and a', but on the inner side of the part a. Here the pivot a³, is
rigidly connected to the link a', but passes freely through arm . On its inner
end the pivot a³, carries the ratchet wheel f, that is thus revolved together with
link a, and is engaged by the pawl g, pivoted to the inner side of arm a, and
influenced by spring g¹.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. In a bicycle driving mechanisin, a crank shaft, a crank of normal length
secured thereto, a swinging link pivotally attached at the outer end of the crank,
a pedal pivoted to the outer end of the link, and a clutch mechanism between
the crank and the link, to lock the link to the crank in the act of forward propul-
sion, substantially as specified.
2. A bicycle crank, substantially as herein shown and described.