Improvements in or relating to Cranks applicable to Velocipedes and. the like.
Year: 1897

page_text: Date of Application, 4th Dec., 1897--Accepted, 19th Mar., 1898
COMPLETE SPECIFICATION.
Improvements in or relating to Cranks applicable to Velocipedes and.
the like.
(A communication from JoHN DICKINSON, GEORGE EDWARD BEAUMONT, &
WILLIAM DICKINSON, of Roslyn Mills, Kaikorai Valley, near Dunedin, New
Zealand, Engineers.)
1, JOHN Ross, Merchant and Manufacturer, of 63, Finsbury Pavement, in the
County of Middlesex, 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 pedal-cranks used upon velocipedes and the like and
its object is to provide a crank having mechanism whereby its length is varied
at different parts of the stroke, so that a rider may have greater leverage during
the thrust of the foot than upon the return stroke with the effect that he has
advantages to be gained by a long crank whilst the pedal is always well within
reach of his foot.
The present description will be confined to the application of the invention to
a safety bicycle as a skilled person will be able readily to adapt the principle
to other machinery.
The object of the invention is carried into effect by fixing an eccentric rigidly
to the pedal and pivoting an eccentric rod upon the one portion of the crank, which
crank is made in two parts so that the one part may slide upon the other, which is
keyed to the crank shaft in the ordinary manner. Means are provided for readily
setting the eccentric in relation to the pedal as required and the parts may be
covered in to exclude dust.
In back pedaling, that is when restraining the progress of the machine as upon
a declination in the road by using the feet to impede the revolution of the pedals,
the pedal may be reversed so that the bottom becomes the top side and the crank
will then be extended in a manner the converse of that when pedaling forwards.
The pedal is revolved by the rider in the ordinary manner the effect of the
eccentric in forward pedaling being to extend the sliding portion of the crank on
the down stroke and withdraw the same on the upward stroke, or at such parts of
the stroke where an extension or shortening of the crank will be most effectual.
In order that my invention may be most easily understood reference will be
made to the accompanying drawing, on which,
Figure 1 is a side view of a bicycle fitted with the gear.
Figure
2 is an elevation of the cranks on a larger scale.
Figure 3 is a plan of the right hand crank and pedal.
Figure 4 is a similar view of the left, hand crank and pedal.
Similar letters refer to corresponding parts.
Describing the invention with the aid of the drawing, the pedal (a) is rigidly
fixed to the eccentric (6) which runs on ball bearings (6¹) in the eccentric
strap (2). The eccentric rod (63) is rigidly attached to the strap (62) and pivoted
at (6) to the crank (c), the outer end of which crank is formed into a socket or

page_text: bridge (c) wherein the other portion (d) of the crank may slide whilst it is guided
by its slot (d) Figure 2 engaging the stud (d). The outer end of this portion (d)
receives the end of the pedal axle (f) and forms a bearing whereon the eccentric (b)
may revolve.
It will be seen by reference to Figure 2 that, since the pedal (a) is maintained
in a horizontal position or nearly so during its revolution, it will describe an orbit
shewn by the dotted circle (a¹), and for a similar reason the eccentric will follow
the orbit shewn by the dotted circle (65), with the result that when revolving in
the direction shewn by the arrows, the pedals will be nearer the crank-shaft (g)
whilst ascending and more remote whilst descending. It thus results that the
pedals describe an orbit practically similar to the orbit of the centre of the eccentric
but that such orbits are not concentric, and as the eccentric revolves in a circle
with the crank-shaft (g) as its centre, the pedal with the centre of its axle fixed
near to the periphery of the eccentric alternately extends and withdraws the
portion (d) of the crank.
By reference to this same Figure 2 it will be obvious that if the pedals are
turned upside down, the extension of the cranks will occur during the ascent of
the pedals and the shortening of the same during the descent. Such a movement
is of advantage when "back pedaling" to retard or stop the progress of the
machine.
-
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. A crank having a sliding portion capable of advancing and receding under
the action of an eccentric which is fixed to a pedal or handle and the strap of which
is pivoted to the said crank, substantially as and for the purposes set forth
herein.
2. In combination with a crank (c) a sliding portion (d) an eccentric (b) a pedal
or handle (a) an eccentric strap (63) and ball bearings (61) all arranged substan-
tially as and for the purposes set forth herein.
3. In combination with a velocipede a pedal attached to an eccentric moveable
upon the pedal axle and upon ball bearings within its strap which is pivoted to a
crank made in two parts so that one part may be advanced or withdrawn under
the action of the eccentric, substantially as and for the purposes set forth herein.
4. The improvements in or relating to pedal-cranks for velocipedes and the like
consisting of parts constructed arranged and operating substantially as and for
the purposes set forth herein and illustrated on the accompanying drawing.
Dated this 4th day of December 1897.
BOULT & WADE.
Agents for the Applicant.