Improvements relating to Driving Mechanism for Velocipedes.
Year: 1898

page_text: Date of Application, 19th Oct., 1898
Complete Specification Left, 19th July, 1899--Accepted, 19th Aug., 1899
PROVISIONAL SPECIFICATION.
Improvements relating to Driving Mechanism for Velocipedes.
We, EDWARD KOHLER, of 106, King's Cross Road, in the County of London,
Engineer, and FREDERIC GEORGE BATE, of 55 and 56, Chancery Lane, in the
County of London, Commission Agent, do hereby declare the nature of this
invention to be as follows:
The object of this invention is to provide for the effect produced by what is
now known as an expanding crank.
To this end we provide a bell-crank or elbow lever, which is pivotted to the
outer end of the crank arm. One arm of this lever is connected by a link to
the back axle or other part of the frame, and the other arm, which is turned
towards the front of the machine, carries a pedal.
By these means, the pedal arm will be made to extend beyond the crank arm,
on the down-stroke, and thus increase the length of the crank, and it will come
inside the pivot on the up-stroke, thus shortening the crank to the same extent.
The path of the pedal will, during the down-stroke, be more or less circular,
but on the up-stroke the curve will be much flattened, and thus, as an incidental
advantage, the strain on the rider, due to an entirely circular motion, will be
relieved.
The longer diameter of this figure will lean forwards at a slight angle to a
vertical line.
Dated this 19th day of October 1898
NEWTON & SON,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements relating to Driving Mechanism for Velocipedes.
We, EDWARD KOHLER, of 106, King's Cross Road, in the County of London,
Engineer, and FREDERIC GEORGE BATE, of 55 and 56, Chancery Lane, in the
County of London, Commission Agent, 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 what is generically termed an "expanding crank,"
that is to say, to a device by means of which an increase in the length of crank

page_text: is produced on the down-stroke, so as to obtain greater leverage, and the crank
is shortened on the up-stroke, in order to relieve the rider by reducing the
throw of the crank.
Many attempts have been made to produce this result, but hitherto without
any very great amount of success, and it is the object of the present invention
to obtain the effect desired in a simple manner, without causing undue strain
on the parts of the mechanism employed, and without adding much to the
weight of the machine.
To this end, the invention consists in adapting to each crank an elbow lever,
one arm of which carries a pedal, while the other arm is pivotally connected
by a link to the back part of the frame of the machine.
In the accompanying drawings, Fig. 1 is a side elevation of the mechanism,
Fig. 2 being a front or edge view thereof.
A is a pedal crank axle, which is mounted in the usual way; B is a crank,
and C is the forked back-stay.
To the end of the pedal crank B is pivotted an elbow lever, the arms D D¹ of
which will be set at something less than a right angle. To the arm D of this
lever (the length of which will be regulated according to the distance it is
desired to expand" the crank) the pedal E is attached. The arm D is pivotted
to the rod F, which in turn is pivotted to the back part of the frame, at or near
the axle of the driving wheel.
The length of the arm D¹ must be greater than that of the crank B, and the
rod F must extend from its pivot, at or about the axle of the driving wheel,
at least to a vertical line drawn through the crank axle, as clearly shewn in
Fig. 1.
This rod F may be of the lightest possible character, as the only strain upon
it is a pulling strain.
The dotted line in the figure indicates the throw of the crank, while the dot
and dash line shows the path of the pedal.
This path, it will be seen, is during the down-stroke nearly circular, and
outside of, or excentric to, the throw of the crank. At the bottom of the
stroke, however, it coincides, or practically coincides, with the throw of the
crank, in order that the rider shall not have to reach" beyond the throw
of the crank, at the lowest point of the stroke, while during the upstroke the
path is much flattened, and comes inside the throw of the crank.
66
The figure thus presented is an irregular oval, the longest diameter of which
is on a line leaning forward at an angle from the vertical, its lowest point practi-
cally coinciding with the lowest point of the throw of the crank, the foot of
the rider passing behind the crank axle on the up-stroke.
By means of this arrangement of driving mechanism, the dead centre is
practically overcome, because the stroke does not commence to descend before
the crank has passed the vertical, and the effective portion of the stroke is not
completed until after the crank has passed the vertical; the necessity, there-
fore, for "toeing" round the crank, that is to say, pressing the crank past the
dead centre by the action of the toes, is obviated.
It may be here remarked that devices have been suggested in which a figure
analogous to that above described has been produced, but the longer axis of the
figure has been leaning towards the rear. In this case, the thrust of the rider's
foot has been necessarily forward at the most effective portion of the stroke,
instead of downwards, thus increasing the work, and reducing to a consider-
able extent the effective portion of the stroke. A link-rod has generally been
employed, but the strain has been a thrusting strain, and it has therefore been
necessary to have the link of considerable strength, and consequently weight.
Although the invention is shown as applied to a bicycle, the same mechanism
may be applied to a tricycle with equally good results.
It is unnecessary to shew the application to a tricycle, as the slight modifi-,
cation necessary for the purpose will be obvious to any competent person.

page_text: 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. The driving mechanism for velocipedes, consisting of an elbow lever,-
the angle of the elbow being about or slightly less than a right angle,―
pivotted to the end of the crank, and carrying at one end a pedal pin, the other
end being connected by a link rod to the back part of the frame, as shewn and
described.
2. In a driving mechanism for velocipedes, the use of an elbow lever, the angle
of which is about, or slightly less than, a right angle, and consisting of a short
arm of about half the length of the crank (more or less), carrying the pedal,
and a long arm of greater length than the crank, connected to the frame at or
near the axle of the driving wheel by a link-rod, as herein shewn and described.
3. In a driving mechanism for velocipedes, the use of an elbow lever of the
character described, and carrying a pedal in combination with a link rod pivotted
to the frame at or near the axle of the driving wheel, and of a length to extend
up to a vertical centre line drawn through the crank axle, as herein shewn and
described.
4. A driving mechanism for velocipedes, in which the path of the pedal forms
an irregular oval, that is to say, on the down-stroke it is nearly circular, and
excentric to the throw of the crank; at the bottom of the stroke it coincides
or practically coincides with the throw of the crank; on the upstroke the path is
fattened, and comes between the throw of the crank and the crank axle; while
at the top it rises to a line slightly above the throw of the crank, the longer
axis of the figure being set at an angle leaning forward from a vertical line
drawn through the crank axle, as shewn and described.
5. An "expanding crank" mechanism for velocipedes consisting of an elbow
lever carrying the pedal, and mounted on the crank, so arranged that the strain
on a link rod connecting the pedal lever with the back of the frame, is a pulling
strain, as shewn and described.