Year: 1896

page_text: I, PERCY MORGAN, of 14 Allison Road, Harringay, in the County of Middlesex,
Gentleman, do hereby declare the nature of this invention to be as follows:-
My invention relates to variable-throw cranks and is more especially applicable to
velocipedes and other machines driven by foot-power.
The object of my said invention is to provide an improved form of variable-throw
crank, that is to say, a crank which will lengthen and thus afford a more powerful
leverage during the operative portion of its throw, and which will decrease in length
and thus diminish the arc of the circle passed through during the inoperative portion
of the said throw.
According to my said invention I provide at the outer extremity of each crank-arm
a circular portion or ring wherein is arranged to turn or rotate freely, upon a ball or
roller race or other bearing surface, a disc, at a suitable distance from the edge or
periphery of which, is fixed the pedal pin. Each of these discs may be cut away for
lightness, or the said pedal pin may be fixed in a boss placed eccentrically relatively
to a suitable rim and connected to the latter by arms, the said rim being rotatably
mounted within the above mentioned ring upon the crank-arm as above described.
In order to cause the above discs, wheels, or eccentrics carrying the pedal pins to
rotate within the rings upon the crank-arms during the revolution of the latter, and
thus to vary the throw or length of the said cranks at the proper time, I provide
upon the centre of each of the said discs, wheels, or eccentrics a suitable chain or
sprocket wheel, and I connect each of the latter with another chain or sprocket
wheel of corresponding diameter mounted upon the crank-axle by means of a chain
or the like.
It will be seen that by a proper proportioning of these chain wheels the discs,
wheels, or eccentrics can be so rotated during the revolution of the crank-arms as to
bring the eccentricity of the pedal pin of each of them relatively to the crank axle,
inwardly or towards the latter during the inoperative portion of the throw of the
crank, and outwardly or away from the said crank axle during the operative portion
of the said throw, thus practically alternately shortening and lengthening the
crank-arms.
It is evident that the amount of variation in the length of my improved variable-
throw cranks will be regulated by the diameter of the rings at the extremities thereof,
and the amount of eccentricity that can in consequence be given to the pedal pins
relatively to the centres of the discs, wheels, or eccentrics upon which they are
supported.
Instead of employing chain or sprocket wheels and chains or the like for effecting
the revolution of the discs, wheels, or eccentrics carrying the pedal pins, during the
rotation of the cranks, it is obvious that I may provide any convenient form of
toothed or spur gearing, or friction gearing, for that purpose.

page_text: My invention is obviously applicable to the driving gear of velocipedes or the like,
or to that of lathes, sewing machines, and other tools driven by foot-power.
Dated this 7th day of October 1896.
A. F. SPOONER,
124 Chancery Lane, W.C., Agent for the Applicant.
Improvements in variable-throw Cranks."
I, PERCY MORGAN, of 14 Allison Road, Harringay, in the County of Middlesex,
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 variable-throw cranks and is more especially applicable to
velocipedes and other machines driven by foot-power.
The object of my said invention is to provide an improved form of variable-throw
crank, that is to say, a crank which will lengthen and thus afford a more powerful
leverage during the operative portion of its throw, and which will decrease in length
and thus diminish the arc of the circle passed through during the inoperative portion
of the said throw.
In the accompanying drawings I have shown how my said invention may be con-
veniently and advantageously carried into practice.
Figure 1 is a side elevation showing an application or my said improvements to a
rear driven bicycle, and
Figure 2 is a similar view showing a modification hereinafter described.
Like letters indicate corresponding parts throughout the drawings.
a is a portion of the frame; b is the chain or sprocket wheel; c is a portion of the
driving or pitch chain; d is the bottom bracket; e is the crank axle, and
the cranks.
one of
According to my said invention, and referring first more particularly to Figure 1,
I provide at the outer extremity of each crank-arm e¹ a circular portion or ring e
wherein is arranged to turn or rotate freely, upon a ball or roller race or other bearing
surface, a disc f, at a suitable distance from the edge or periphery of which is fixed
the pedal pin g carrying a pedal g¹. Each of the discs and cranks e is preferably
f
cut away for lightness as shown. In order to cause the disc, wheel, or eccentric f
carrying the pedals g¹ to rotate within the ring upon the crank-arm during the
revolution of the latter, and thus to vary the throw or length of the said crank at the
proper time, I provide upon the centre of the said disc, wheel, or eccentric fa
suitable chain or sprocket wheel h and I connect each of the latter through a pitch
chain with another chain or sprocket wheelj of corresponding diameter fixed to
the bottom bracket or other support.
It will be seen that by a proper proportioning of the chain wheels h and j to the
diameter of the disc, wheel, or eccentric f the latter can be so rotated during the
revolution of the crank-arm e' as to bring the eccentricity of the pedal pin g relatively
to the crank axle e, inwardly or towards the latter during the inoperative portion of
the throw of the said crank-arm e¹ and outwardly or away from the said crank axle e
during the operative portion of the said throw, thus practically alternately shortening
and lengthening each of the crank-arms e¹.
It is evident that the amount of variation in the length of my improved variable
throw cranks will be regulated by the diameter of the rings at the extremities
thereof, and the amount of eccentricity that can in consequence be given to the pedal
pins g relatively to the centres of the disc, wheels, or eccentrics upon which they
are supported.

page_text: I may, as shown in Figure 2, materially reduce the size of the rings e² and mount
the chain or sprocket wheels h upon spindles h¹ supported in ball or other bearings
provided in the free ends of the crank-arms el and to the other extremities of which
spindles h¹ are attached supplementary cranks k carrying at their free ends the pedal
pins g and pedals g¹.
Instead of employing chain or sprocket wheels and chains or the like for effecting
the revolutions of the discs, wheels, or eccentrics f, or supplementary cranks k, carrying
the pedal pins g during the rotation of the cranks e¹ it is obvious that I may provide
any convenient form of toothed or spur gearing, or friction gearing for that purpose.
I have herein before shown and described my invention as applied to the driving
gear of a safety bicycle, it is however obviously applicable to the driving gear of any
other description of velocipedes or the like, or to that of lathes, sewing machines, and
other tools or apparatus driven by foot-power.
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 variable-throw crank gear wherein the pedal pin and pedal are mounted upon
a disc or crank adapted to be so moved or rotated through chain gearing or its
equivalent during the throw or rotation of the main crank as to bring the eccentricity
of the pedal-pin relatively to the crank axle inwardly or towards the latter during the
inoperative portion of the said throw or rotation and outwardly or away from the said
crank axle during the operative portion of the said throw or rotation substantially as
and for the purpose set forth.
2. The improved variable-throw crank gear constructed substantially as described
with reference to Figure 1 or to Figure 2 of the accompanying drawings.
Dated this 7th day of August 1897.
A. F. SPOONER,
323 High Holborn, London, Agent for the Applicant.