Improvements in the Driving Gear of Bicycles and other Pedal Operated Vehicles or Machines.
Year: 1896

page_text: Reprinted as amended in accordance with the decision of the Comptroller-
General, 27th day of July 1900.
Date of Application, 24th Dec., 1896
Complete Specification Left, 9th Feb., 1897-Accepted, 13th Mar., 1897
Improvements in the Driving Gear of Bicycles and other Pedal
Operated Vehicles or Machines.
I, WILLIAM FREDERICK WILLIAMS, of 32, Shaftesbury Avenue, London, W., Gentle-
man, do hereby declare the nature of this invention to be as follows:-
My invention relates to driving chain gear of bicycles or other pedal-operated
vehicles or machines in which the ratio of the gear during the revolution is so varied
by means of an elliptic chain wheel or wheels as to decrease the effective leverage of
the pedals at the dead points and increase it at the points where power may be most
advantageously applied.
The object of my improvement is to maintain constant the tension of the chain
notwithstanding the varying effective ratio of the driving and driven wheels and it
consists in causing the one wheel to move in its own plane towards and from the other
wheel so as to compensate for the varying angular relation of the two members of the
chain.
This transverse motion of the wheel relatively to its axis may be produced either
positively by means of an eccentric or crank pin working directly in a slot or through
a radius link or equivalent connection whereby the wheel is constrained to move along
a given diameter relatively to its axis in order to take up the slack of the chain or to
yield to the tension of the chain at certain points in the revolution, or the motion may
be imparted by means of springs, the wheel being in either case so connected to its
shaft by a clutch or equivalent coupling as to permit the said sliding motion whilst
ensuring a driving connection of the wheel with its shaft.
The elliptic chain wheel or wheels need not be toothed around the entire periphery
it being sufficient for driving purposes to provide a certain number of teeth at each
end of the ellipse leaving the greater portion of the sides of the ellipse devoid of teeth
but grooved for the chain to lie in.
Instead of making the entire wheel movable in its own plane as above
mentioned, the toothed end portions of the ellipse only may be made movable
for accommodating the tension of the chain as above described, these end portions
being acted on by springs and revolving as one with the body portion, which in that
case would be fast on its shaft.
Dated this 23rd day of December 1896.
A. M & WM. CLARK,
Chartered Patent Agents, 53 Chancery Lane, London.

page_text: Improvements in the Driving Gear of Bicycles and other Pedal
Operated Vehicles or Machines.
I, WILLIAM FREDERICK WILLIAMS, of 32, Shaftesbury Avenue, London, W.,
Gentleman, 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 :-
My invention relates to driving chain gear of bicycles and other pedal-operated
vehicles and machines in which the ratio of the gear during the revolution of
the pedal axle is so varied by means of an elliptic sprocket wheel (geared by a chain
with a circular wheel or it may be with another elliptical wheel) that the effective
leverage of the pedals is decreased at the dead points and increased at the points
where power may be most advantageously applied.
The object of my invention is to maintain constant the tension of the chain
notwithstanding the varying effective ratio of the driving and driven sprocket wheels,
by causing the ene elliptic driving wheel to move in its own plane back and forth
transversely in relation to the pedal arle so as to compensate for the varying length of
chain required at certain points in the revolution consequent on the varying angular
relation of the two straight portions of the chain.
The invention will be described with reference to the accompanying drawings
forming part of this specification wherein Figure 1 is a diagram illustrating the
combination of an elliptic driving sprocket wheel with a circular sprocket pinion and
the motion of the former in its own plane whereby the slack of the chain is taken up
at required moments. Figure 2 is a face view and Figure 3 a section on the major
axis of the elliptic sprocket wheel shewing the means by which this motion of the
wheel in its own plane is produced.
The elliptic sprocket wheel A is loose on the pedal axle B but is connected thereto
so as to ensure a driving connection therewith by any suitable meaus, such for instance
as studs C playing in slots D) in the direction of the major axis of the ellipse the studs
being fixed to arms D¹ on a hub keyed on the pedal axle and the slots being inade in
the web of the wheel or vice versa so as to permit of a sliding motion of the wheel A
in its own plane relatively to the pedal axle B. This motion is communicated to the
wheel A by a stationary disc E eccentric to the axis of the pedal axle, working in a
transverse oblong slot in the boss of the wheel A, the width of the slot in the
direction of the major axis of the elliptic wheel corresponding to the diameter of the
eccentric disc so that the wheel in revolving about the eccentric is constrained by
the eccentric to move along the direction of its major diameter, the position of the
eccentric and its effective radius being such that the direction of this notion of the
sprocket wheel is towards and from the driven pinion, as shewn in Figure 1, so as to
accommodate the varying length of chain required in the different positions assumed
by the elliptic wheel during its revolution.
The necessity for this compensation will be apparent from the diagram. Assuming
the elliptic wheel to be in the position indicated by A, the distance of the extremity a
of the major diameter of the ellipse from the corresponding tangent point f of the
chain F with the driven pinion is greater than would be the distance of the
extremity a of the minor diameter of the ellipse from the same point were
the elliptic wheel turned a quarter round about the axle of the pedal axle as a centre,
as shewn by A¹, the difference being approximately equal to the versed sine of the
are a. This difference is compensated by the action of the eccentric by which the
ellipse in turning is gradually moved to the position A2 so as to maintain the tension
of the chain.

page_text: The eccentric E may be carried by the screw gland G of the pedal axle ball bearing
and if made in one therewith the adjustment of the pedal axle bearings for wear would
be taken up by the gland at the opposite side of the machine. In order however to
provide for the independent adjustinent of the gland G and eccentric the eccentric
inay be mounted on an outwardly projecting boss g formed on the gland and be
secured by a set screw gl passing through a slot in the eccentric and screwing into
any one of a ring of holes tapped in the disc of the gland so that the eccentric may be
adjusted in proper position notwithstanding the circular adjustment of the gland
which in any case would be locked in position to which it is set by usual means. By
merely substituting the eccentric carrying gland for the ordinary one the improved
gear may be readily applied to an existing machine. Or the eccentric may be mounted
in position in any other suitable way.
In order to diminish friction between the eccentric and the sides of the slot in
which it works, the eccentric is provided with a peripheral set of balls e running in a
grooved path formed around the eccentric and retained therein by the converging
Hanges ele between which the balls project sufficiently to come in contact with the
sides of the slot F. To provide for easy renewal in case of wear beyond what can be
taken up by adjustinent of the ball bearing paths, the slot F may have a steel liner
ring fitted in it as will be easily understood, which may be replaced by a new one
when worn. Circular cover plates H are fixed at each side of the eccentric and enclose
the slot so as to exclude dust.
The pedal cranks P are fixed to their axle B at right angles to the major diameter
of the elliptic wheel or in such other angular relation thereto as will give the most
effective result.
I have described the tensional compensating motion as applied to an elliptic wheel
driving a circular pinion but it will be obvious that both might be elliptic. end-that
the-same-effect would be produced were-the-compensating-motion-to-be applied-to-e
circular-wheel-used-in-connection with-an-elliptie-wheel so that the-compensating
motion might theoretically be applied to the driven-wheel-or-pinion, or-the-driving
wheel-maybe circular-and-compensating and the-driven-wheel-or-pinion-may be
elliptic provided that the ratio between the driving and driven-wheels-is-us-2-(or
a-multiple-thereof) to 1. For constructional reasons--however--the--compensation
would-be-generally applied to the driving wheel.
The elliptic chain wheel or wheels need not be toothed around the entire periphery,
it being sufficient for driving purposes to provide a certain number of teeth at each
end of the ellipse leaving the greater portion of the sides of the ellipse devoid of
teeth but grooved for the chain to lie in.
It will be obvious that instead of producing the compensating motion directly by
an eccentric engaging in a slot, it might be imparted through an eccentric strap and
link from an eccentric fixed on the bottom bracket the link being connected to a stud
on the wheel.
Having now particularly described and ascertained' the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1. A-elmin--driving gear in which the slack of the chain at certain angular posi-
tions of the elliptic wheel is taken up by motion of the one-wheel in its own plane
towards and away from the other wheel substantially as described.
In an elliptic chain gear the combination, with the elliptic chain driving
wheels one of the chain wheels, of means substantially as described (acting indepen-
dently of the chain) whereby the wheel is caused to move in its own plane twice in
each revolution towards and from the other chain wheel so as to compensate for
the varying length of chain required to connect the driving and driven wheels in the
different angular positions of the elliptic wheel as specified.
In an elliptic chain gear the combination, with the elliptic chain wheel in
driving connection with its axle but free to move relatively thereto, of a stationary
eccentric by which the wheel is constrained to move in its own plane in such

page_text: manner as to accommodate the varying length of chain required at different points in
the revolution of the gear substantially as specified.
In an elliptic chain gear the combination, with the elliptic chain wheel in
driving connection with its axle by studs and slots permitting of motion of the wheel
in its own plane relatively to the axle, of a stationary eccentric by which the wheel
is constrained to move in its own plane in such manner as to accommodate the
varying length of chain required at different points in the revolution of the gear
substantially as specified.
4 In an elliptic chain gear the combination, with the elliptic chain wheel in
driving connection with its axle but free to move relatively thereto, of a stationary
eccentric mounted upon the adjacent gland of the pedai-axle ball-bearing the eccentric
engaging in a transverse slot in the wheel so that the latter in revolving about the
eccentric is constrained to move in its own plane in such manner as to accommodate
the varying length of chain required at different points in the revolution of the gear
substantially as specified..
6.5 In an elliptic chain gear the combination, with the elliptic chain wheel in
driving connection with its axle but free to move relatively thereto, of a stationary
eccentric mounted upon the adjacent gland of the pedal-axle ball-bearing with
capability of independent adjustment of the eccentric and gland, the eccentric
engaging in a transverse slot in the wheel so that the latter in revolving about the
eccentric is constrained to move in its own plane in such manner as to accommodate
the varying length of chain required at different points in the revolution of the gear
substantially as specified.
6 In an elliptic chain gear the combination, with the elliptic chain wheel in
driving connection with its axle by studs and slots permitting of motion of the wheel
in its own plane relatively to the axle, of a stationary eccentric on the bottom bracket
coupled by a strap and link to the wheel so as to constrain the wheel to move in its
own plane in such manner as to accommodate the varying length of chain required at
different points in the revolution of the gear substantially as specified.
Dated this 8th day of February 1897
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.