Improvements in Driving Mechanism for Bicycles, Tricycles and the like.
Year: 1898

page_text: Date of Application, 19th Feb., 1898.-Accepted, 9th Apr., 1898
COMPLETE SPECIFICATION.
Improvements in Driving Mechanism for Bicycles, Tricycles and
the like.
We; HENRY ARTHUR PURDON, Civil Engineer, and HARRY ERNEST WALTERS,
Civil Engineer, both of 2, Great George Street, Westminster, 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:-
Our invention consists in improvements in the driving mechanism of bicycles,
tricycles and the like, propelled by foot power.
Hitherto in most instances cycles have been driven by foot pedals attached to
crank arms, which directly rotate the driving sprocket wheel or wheels or other
means by which motion is transmitted to the cycle.
The object of our invention is to increase the efficiency of the power transmitted
through the pedals in driving cycles and the like, and at the same time provide
that the pedal shall travel in a path that approximately forms an elipse instead of a
circular path; the mechanism being so arranged that the major axis is vertical or
nearly so.
We will now describe our invention with reference to the accompanying
drawings:-
Figure 1 is a side elevation of part of a bicycle fitted with our improved driving
mechanism, Figure 2 being a plan of same. Figures 3 and 4 are corresponding
views of a modified form of our invention.
Referring to Figures 1 and 2 we actuate the driving sprocket wheel or wheels,
crank arms, or other means of communicating motion to the machine, by means of.
a lever a to one end of which any ordinary form of pedal is attached, the other
end 6 sliding in an oscillating block e provided with trunnions c¹ c³ (Figure 2) said
oscillating block being pivoted at one apex of a swinging triangle d pivoted at e
to the framework of the cycle or other vehicle. At a convenient distance between
the ends of the lever a it is pivotally connected direct to the driving wheel g, or
other means by which motion is given to the machine, at a suitable distance from
the centre thereof, by means of a pivot or short crank f. The position of the
pivote on the framework of the machine on which the triangle d swings is behind
the centre of the driving wheel g, at the same time such pivot may be either above
or below the centre of rotary motion herein mentioned. To the pivot or connec-
tion which rotates in lever a and attaches it direct to the driving
wheel
a connecting rod or link his also pivoted at j and by
a further pivot k forms connection to the third apex 1 of swinging
triangle d. The connecting rod h may be pivoted at a greater radial distance
from the centre of rotation mentioned than the pivot of lever a and from thence
be connected to the third apex of the swinging triangle.
The whole of the mechanism just described moves in parallel planes of action.
Referring to Figures 3 and 4 which illustrate a modification of our invention, in
this case the oscillating block c through which the lever a slides is pivoted on the
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page_text: end of a sliding bar m which travels in horizontal or approximately horizontal
guide bars n n¹ attached to the frame of the cycle or vehicle. To the other end of
the sliding bar m the connecting rod h (see Figures 1 and 2) is pivoted, the other
end of rod being connected to the same pivot by which the lever a is connected
to the sprocket wheel g.
Ball bearings may be provided to any or all the pivoted joints of the mechanism
and likewise friction wheels may be provided for the bars to slide upon. The
oscillating block c, through which the end of lever a slides, constitutes a travelling
fulcrum and the mechanism described provides that the fulcrum may on the down
stroke travel to a point, opposite, or in front of, the centre of rotation on the frame
of the driving wheel or wheels, direct crank arm, or other means by which motion
is communicated to the cycle. By this means an advantageous leverage is obtained
for the foot power when the pedal stroke is only of the same length and diameter
as the circular path performed by a pedal on a crank arm as in the ordinary driv-
ing mechanism now generally in use, and in this invention the foot power expended
in concentrated to less than 180 degrees of circular pedal movement.
The end of the sprocket wheel or crank axle. opposite to that on which the said
sprocket or driving wheel is attached is provided with a short crank to which the
end of the sliding rod h on that side of the machine is pivotally connected, the
distance from the centre of the driving wheel axle to the centre of the pivot being
the same as from the centre of the sprocket wheel g to the centre of the pivot j.
We are of course aware that levers have been previously employed to actuate
driving wheels, crank arms or the like, and also that an eliptical or approximately
eliptical pedal path has been obtained, but in this invention the moving fulcrum
provides a more efficient leverage than has hitherto been obtained combined with
an approximately eliptical pedal path. We do not, therefore, claim an eliptical
path per se.
Having now particularly described and ascertained the nature of our said in-
vention and in what manner the same is to be performed, we declare that what we
claim is:
1. In a bicycle or the like a lever such as a pivoted to the sprocket wheel (crank
arm or other wheel for communicating rotary motion) with its sliding fulcrum
pivoted to a swinging link such as d, substantially as described and as illustrated
in Sheet 1 of the drawings annexed.
2. In a bicycle or the like, a lever such as a pivoted to the sprocket wheel (crank
arm, or other wheel communicating rotary motion) with its sliding fulcrum pivoted
to a sliding arm such as m moving in the fixed frame or casing n, substantially as
herein described and as illustrated in Sheet 2 of the drawings annexed.
3. In driving gear for cycles and the like, the combination with the ordinary
sprocket wheel (or other direct means of communicating rotary motion), of a swing-
ing triangular frame such as d carrying an oscillating block c, a pedal lever a
pivoted on said sprocket wheel (or on a crank on the axle thereof) one end of lever a
sliding in block c, and a pivoted connection h from the sprocket wheel or its axle
to swinging frame d, all arranged and operating substantially as herein described,
for the purpose specified and as illustrated in the accompanying drawings.
1111 1
Th
1000
4
ebruary 1898.
JOHN P. O'DONNELL, Fel. Chart. Inst. P.A.
Agent for the said Applicants,
70 and 71, Palace Chambers, Westminster, S.W.