An Improvement in Eccentric Cranks for Driving Cycles, Motors and the like.
Year: 1899

page_text: Date of Application, 24th Jan., 1899-Accepted, 10th June, 1899
COMPLETE SPECIFICATION.
An Improvement in Eccentric Cranks for Driving Cycles, Motors
and the like.
THOWALD FREDERIK THEODOR FISCHER, of 97, Godiva Street, in the City of
Coventry, Mechanic, 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:―
Its object is to obtain the maximum of leverage on the down stroke with a
quick return on the up stroke whilst retaining the circular pedal path, thus im-
proving the propelling power of the machine. This is effected by affixing on
each side of the bottom bracket an eccentric plate (Nos. 1 & 2 see drawings--
Figs. 1, 2 & 3) with the centres forward, in these plates a hole is cut of the same
size as the bracket cups, the cups which are made with a shoulder pass through
the hole in the plates, and by means of the shoulder hold the plates rigidly against
the face of the casing. Around the circumference of these plates steel rings
or straps (Nos. 3 & 4 see drawings Figs. 1, 2 & 3) revolve, running upon balls or
any other suitable bearing. These rings are grooved on the inside to receive the
balls, and slotted in one place with a screw for connection to obtain adjustment,
and the rims of the plates are grooved to correspond. To these rings or straps
elongated arms or cranks (Nos. 5 & 6 see drawings Figs. 1, 2 & 3) are attached,
being constructed in one solid piece with the rings or joined thereto by screws
or otherwise. To the end of these arms the pedal pins (Nos 7 & 8 see drawings
Figs. 1, 2 & 3) are fixed. The arm on the chain wheel side (No. 3 see drawings
Figs. 1, 2 & 3) is cranked at the root in order to pas through the wheel and work
on the outside, and the chain wheel is designed accordingly to allow for the
eccentric movement of this arm without touching. The driving cranks (Nos. 9 &
10 see drawings Figs. 1, 2 & 3) one of which is fixed to the driving wheel, are
attached to the driving spindle in the ordinary manner with cotter pins or flat
keys. These cranks are slotted at the end, which slots must be twice the length
of the distance from the centre of the driving crank to the centre of the eccentric
plate. The cranks work outside the eccentric arms, and the back ends of the pedal
pins pass through the slots, and are screwed into the arms, soldered or otherwise
securely fastened. The parts of pedal pins working in the slots are made plain
or may be fitted with small rollers to reduce friction. When pressure is applied
to the pedals, the pedal pins act upon the slotted cranks, but as the arms, to which
the pedal pins are attached are fixed eccentrically to the crank spindle the pedal
pins will necessarily slide forward to the end of the slot on the downward stroke,
and towards the centre of the crank shaft on the upward stroke. Thus an ex-
tended thrust is obtained on the downward stroke giving additional leverage
power and thereby improving the propelling power of the machine, whilst still
retaining the circular path of the pedals.

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
That the above arrangement whereby I pass the pedal pins through
elongated slots in the driving cranks and fasten them to the ends of arms ex-
tending from rings or straps revolving around the rims of eccentric plates placed
one on each side of the bottom bracket casing is entirely new and my own
invention. I also claim that this arrangement secures the objects aimed at, i.e.
additional leverage power, improving the propelling power of the machine and
retention of the circular pedal path.
Dated this Twenty-first day of January 1899