Improvements in Crank Mechanism for Cycles.
Year: 1897

page_text: Date of Application, 28th May, 1897-Accepted, 10th July 1897
CUMILEIE DIECIFICATION.
Improvements in Crank Mechanism for Cycles.
I, GUILLAUME LOUIS VAN DOORNUM of 282 Brinklaan Apeldoorn in the Kingdom
of Holland, Oud-Major, 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:-
The present invention relates to an improved crank mechanism devised especially
for cycles, by means of which a much more favourable utilisation of the power in
the different positions of the crank is obtained as compared with the ordinary
crank mechanism.
The arrangement is illustrated in the accompanying drawings, in which :-
Figure 1 shows a bicycle provided with the mechanism in question.
Figures 2 to 4 show on a larger scale the various parts in plan, front view and side
view or section respectively, whilst
Figure 5 indicates diagrammatically the relative power for the different positions of
the crank.
The pins A of the pedals are screwed by their threaded ends into a corresponding
hole in the ring C which is placed revolubly upon the periphery of a disc D. In
order to diminish the friction, balls d are placed in a race between the surfaces in
contact. The true driving axle E supported in ball bearings is placed excentrically
in a projection of the disc D, which is firmly screwed to the frame of the cycle in the
manner hereinafter set forth.
The ball bearing of the axle E is closed by means of the ring F screwed upon it. To
the front of the bearing the axle E is prolonged in a pin f upon which the piece G is
keyed, and there is placed upon the front side of the same the guide piece B which
is controlled by the pieces K K secured by means of screws l upon the piece G. The
said piece B surrounds the pin A by means of an eyelet and is loosely placed upon
the said pin.
In order to diminish the friction the side of B and the corresponding surface of K
are provided with races for the reception of balls k1. The aforesaid crank mechanisms
are attached to both ends of the driving axle; the pedal pins are placed at an angle
of 180 degrees with regard to one another.
The discs D are secured by means of the screws d¹ in a suitable manner to the
frame, the chain wheel is fixed between the two discs D. When the pedal pin A
(Figure 3) is depressed, the ring C will revolve around the fixed disc D, consequently
there will result a turning of the axle E in the eccentric projection of D. In conse-
quence of this the piece G K will take part in this movement and the bar B will on the
continued motion of the pedal be drawn out of its guide G K, until the same having
arrived at the perpendicular lowest position, then makes the opposite motion and
returns in the guide piece. In the mechanism on the other side of the machine the
motion of its parts takes place simultaneously in the opposite sense. The amounts of
power developed for the various positions of the pedals may be calculated directly
from Figure 5. The angles therein shown correspond to the pedal positions 1, 2,
3, 4, 5, 6, and it is accordingly clear that the power is utilized more effectively

page_text: than by means of the ordinary pedal crank and much more regular and uniformly
altering application of power takes place.
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. The improved crank mechanism for cycles characterised by the combination of
parts consisting essentially of a crank pin fixed at one side of a ring such as C, which
ring is placed revolubly upon the periphery of a disc such as D fixed to the cycle
frame whilst the driving axle E is supported in bearings excentrically in the said disc,
which axle ends in front in a guiding piece G K having a sliding bar B pivoted upon
the pedal pin A and sliding in the aforesaid guide piece G K, so that the motion of
the pedal around the ring C and the disc D causes the turning of the driving axle A
through the action of the sliding bar B in the guide piece G K substantially as
described and shown in the accompanying drawings.
1607
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester, and Birmingham,
Patent Agents for the Applicant.