Year: 1897

page_text: I, JAMES STEPHEN YABSLEY, of 76, Gainsborough Terrace, Mutley, Plymouth, in
the County of Devon, Engineer, do hereby declare the nature of this invention to be
as follows:
This invention relates to a cycle pedal crank by which the radius of the crank arm
can be extended at will by the rider exerting extra pressure upon the pedal.
According to this invention a front portion of the crank arm is jointed, to the end
of this jointed part the pedal is attached. The jointed part is held at an angle to
the crank arm proper by a spring sufficiently strong for average riding to hold it in
the angle position, but when increased power is required as for ascending a hill, upon
extra pressure being put upon the pedal, the jointed part is brought in a line with
the crank arm, thereby increasing the leverage. Instead of a jointed portion held
by a spring, a front portion of the crank arm may be made as a spring and set to be
normally at the position the jointed part is held by the spring.
FREDERIC PRINCE,
Agent for Applicant,
I, JAMES STEPHEN YABSLEY, of 76, Gainsborough Terrace, Mutley, Plymouth, in the
County of Devon, Engineer, 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 cycle pedal cranks so constructed as hereafter described,
that the radius of the crank arm can be extended at will by the rider exerting
extra pressure upon the pedal.
I will describe my invention with reference to the accompanying drawings, whereon
I have shewn several constructions.
Figure 1, is an elevation, and Figure 2 a plan of a construction where the pedal
crank is jointed and maintained at its shortest length by a spring. Figure 3, is a
sectional elevation of a crank having a jointed part controlled by a spring encased
in a tube this view being drawn to a smaller scale than the previous figures.
Figure 4, is an elevation of an extensible crank where a portion of same is made to
act as a spring.
:
According to my invention with particular reference to Figures 1, and 2, I form the
crank proper A, bored as usual at A¹, to take onto the crank axle; to the outer

page_text: end of the crank A, I pivot an arm B, upon the outer end of which the pedal C, of any
desired construction is fixed. The angular motion of the arm B, upon its pivot
pin B¹, is controlled within desired limits: thus at Figure 1, the arm may be moved
from the position shewn until its axis coincides with the axis of the crank A, and is
in the same straight line therewith.
The jointed arm B, is held at an angle to the crank A, by a spring D, one end being
attached at D', to the arm B, and the other end at D2, to the crank proper A.
The spring is of sufficient strength to hold the arm B, in the angular position shewn
for average riding, but when increased power is required as for example when ascending
a hill and extra pressure is put upon the pedal by the rider, the jointed arm B, is
brought into a line with the crank A, and the effective leverage is thereby increased.
At Figures 1, and 2, the arm B, is shewn bifurcated at its pivotted end, embraces a
reduced end A2, of the crank A, and is formed with a square part B2, which forms a
stop, by contact with the shoulders A³, of the crank when the arm is in its extended
position. Obviously the end of the crank itself might be forked to receive the
pivotted end of the arm B.
In some cases and as shewn in Figure 3, I may encase the spring D, in a tube, and
I may cause it to act by expansion when drawing up the arm B, to its angular
position. In the construction shewn, E, is the tube, having one end fitted with a screwed
rod D2, while the opposite end is closed by a plug E¹. D8, is a rod passing through
the plug E¹, and fitted with a piston E2, on its end. The spring D, being located
around the rod D¹, between the piston E and the plug E¹. The rod is secured to the
arm B, while the rod D², is secured to the crank A. A convenient construction is to
pass the rod D² through a hole in the crank cotter pin A, and to provide a nut on the
rod D², to act against the cotter pin, so that the tension of the spring D, may be
adjusted thereby as required. The end of the rod D¹, may be pivotted to or into the
-arm B.
Instead of fitting the crank with a jointed portion held by a spring, I may make
the pedal end B, of the crank A, as a spring in itself as shewn at Figure 4, such spring
being set to be normally at or about the position at which the jointed part previously
described is normally held.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I declare that what I
claim is :-
1-The construction and arrangement of pedal crank whereby the radius or acting
length of the crank is automatically extended by the application of increased pressure
by the foot of the rider and the leverage thereby increased, as described.
2-In extensible cycle cranks, each composed of a main part fixed to the crank
axle at one end, an arm pivotted thereto at the other end, and a pedal carried at the
end of the pivotted arm in combination with the spring devices for maintaining the
pivotted arm normally in an angular position as and for the purposes described with
reference to Figures 1, 2, and 3, of the accompanying drawings.
3-The construction of an extensible crank as described with reference to
Figure 4.
Dated this 29th day of December 1897.
FREDERIC PRINCE,
37, Cursitor Street, London, E.C., Agent for Applicant.