An Improved Variable Speed Driving Gear for Cycles and other Machines.
Year: 1898

page_text: Date of Application, 6th Jan., 1898
Complete Specification Left, 6th Oct., 1898-Accepted, 12th Nov., 1893
PROVISIONAL SPECIFICATION.
An Improved Variable Speed Driving Gear for Cycles and other
Machines.
I, ALFRED WILLIAM BEVIS, Engineer, residing at Brunswick Villa, Malvern
Road, Acock's Green, in the County of Warwick, do hereby declare the nature
of this invention to be as follows:-
This invention pertains to the driving mechanism of cycles and other machines,
where the motion between the driving & driven wheels, is transmitted by a
chain or belt, and consists in an improved construction of driving gear which
will allow of altering the power & the speed of the gear while the machine
is in motion as:-
1st. Changing it from a quick & less powerful gear to that of a slow or
more powerful gear, or the reverse of this.
2nd. Varying the speed of the crank in each revolution so as to give a quicker,
or slower motion to it, during that portion of the revolution when the driving
power is applied to the greatest advantage.
3rd. To connect or disconnect the gear with both cranks so that they remain
stationary while the machine is running.
The invention has been chiefly considered in connection with existing chain
driven cycles and its application is such that it may readily be fitted to any
existing machine of the ordinary safety type, without materially increasing the
weight, or making any alteration to the wheels or frame. The improved gear
as aforesaid is put into, and out of action, in a very simple manner while riding,
either from the handle bar, or any other convenient part of the frame. The
work required being either to lock to the cycle frame, an elliptical toothed
pinion, or to allow it free to rotate concentric with the cranks axis. The gearing
is characterised by the following component parts:-a toothed elliptical pinion,
preferably having an enlarged concentric collar, is loosely mounted on the cranks
axis to work against the face of the bottom bracket, the disposition of the ellip-
tical pinion being outwards of the collar. The collar is provided with holes to
engage a sliding bolt, working transversely underneath the bottom bracket, or
to be clamped by a band brake, or its equivalent; for the purpose of arresting &
holding stationary the elliptical toothed pinion in any desired position, as if in
one piece with the bottom bracket:
Gearing with the teeth of this elliptical pinion is one or two elliptical pinions
of the same size carried free to rotate on a pin which is fixed to the crank.
Fastened to the side & concentric with this elliptical pinion, is a toothed circular
pinion, thus the pair rotate together having the same axis, & turn bodily round
with the crank. This toothed circular pinion gears with an inside toothed
annulus, which is concentric with the cranks axis. The outer circumference of
this annulus is provided with teeth as an ordinary chain wheel, and is mounted
A complete
in any suitable manner to rotate freely round the cranks axis.
gearing is now effected between the central elliptical pinion and the chain
wheel-It is necessary however the gear shall be provided with a ratchet

page_text: the
arrangement so that the chain wheel can only rotate in advance of the cranks.
This may be effected by a pawl being placed on, or connected to the crank, and
engaging with ratchet teeth placed on the annulus, or on one or more of the
pinions. The ratchet teeth however should be placed in such positions that
when any of them are engaged with the pawl, the major axis of the central
elliptical pinion shall be in exactly the same relative position to the cranks
in each case.
The object of this is so that the rider. shall at any moment know
while riding what position the major axis of the central elliptical pinion is in,
whether vertical or horizontal. As before described the central elliptical pinion
is loose on the cranks axis, as also is the chain wheel, but the cranks
pin or pins carrying the intermediate pinions are fast to the axis & revolve
round with it. The chain wheel is of such a diameter as to constitute, the low
speed or power gear, when the central elliptical pinion is left free to rotate. The
whole of the gear now rotates as one rigid piece, the pawl on the crank engaging
in one of the ratchet teeth drives the chain wheel forward at the same rate as
the crank. To increase the speed of the gear the central elliptical pinion is
locked rigidly to the bottom bracket, either by the bolt, or band brake, in which
case the intermediate pair of pinions will roll round the central elliptical pinion
& drive the annulus or chain wheel in advance of the crank. If this locking of
the central elliptical pinion is effected when either of the cranks are vertical,
the major axis of the central elliptical pinion will be vertical, & thus impart to
the intermediate pair of pinions a quicker forward rotary motion around their
own axis, when the cranks are vertical, than they will have when the cranks are
horizontal, thus the chain wheel or annulus will be driven forward, in its relation
to the cranks, more quickly when the cranks are vertical than when the cranks
are in an horizontal position. If the central elliptical pinion is locked to the
cycle frame when the cranks are horizontal the reverse of this will be the case.
This varying motion of the chain wheel or annulus is due to the gearing of the
elliptical pinions with each other, and is transmitted to the annulus or chain
wheel through the intermediate circular pinion, which as before described is
fastened to the side of the intermediate elliptical pinion. It will be seen with
this gear is action that you cannot drive the machine backwards, but it does
allow of back pedalling, also that the central elliptical pinion may be locked in
that position, to give the greatest mechanical advantage of the gearing during
that portion of the revolution, that is found best to suit the varying turning
conditions as, the
moments of the power applied to the crank, under the many
gradient of the road, the strength of the wind, and the position, and disposition,
of the rider. So far it has been found practical to lock the central elliptical
pinion to the bottom bracket by a holt, holes being arranged in the collar to
receive the bolt's end, but the same may be performed in any convenient way,
and also to place two ratchet teeth on the intermediate pinion & the pawl on
the crank, but the ratchet connection as before stated may be placed in any con-
venient part of the gearing.
Dated this 5th day of January 1898.
COMPLETE SPECIFICATION.
An Improved Variable Speed Driving Gear for Cycles and other
Machines.
I, ALFRED WILLIAM BEVIS, of Brunswick Villa, Malvern Road, Acock's Green,
in the County of Warwick, Engineer, do hereby declare the nature of this

page_text: 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 pertains to the driving mechanism of cycles and other machines,
where the motion between the driving and driven wheels, is transmitted by a
chain or belt, and consists in an improved construction of driving gear which
will allow of altering the power and the speed of the gear while the machine
is in motion as follows:-
1st. Changing it from a quick and less powerful gear to that of a slow or
more powerful gear, or the reverse of this.
.
2nd. Varying the speed of the crank in each revolution so as to give a quicker
or slower motion to it during that portion of the revolution when the driving
power is applied to the greatest advantage.
3rd. To connect or disconnect the gear with both cranks so that they remain
stationary while the machine is running.
The accompanying sheet of drawings illustrate the application of the gear to
a bicycle.
Figure 1 is a front elevation of the gear with the cover plate removed.
Figure 2 is a sectional front elevation from the same side as Figure 1 with
the crank removed.
Figure 3 is a vertical section on the line ab (Figure 1)..
Figures 4 and 5 are respectively side and end elevation of a ratchet wheel
forming a detail of the gear.
The invention has been chiefly considered in connection with existing chain
driven cycles and its application is such that it may readily be fitted to any
existing machine of the ordinary safety type, without materially increasing the
weight or making any alteration to the wheels or frame. The improved gear
as aforesaid is put into and out of action in a very simple manner while riding,
either from the handle bar or any other convenient part of the frame, the
work required being either to lock to the cycle frame an elliptical toothed
pinion, or to allow it free to rotate concentric with the cranks axis.
The gearing as illustrated in Figures 1 to 5 of the drawings is characterised
by the following component parts. A toothed elliptical pinion A preferably
having an enlarged concentric collar B is loosely mounted on the crank axle Č
to work against the face of the bottom bracket D, the disposition of the ellip-
tical pinion A being outwards of the collar B. The collar is provided with holes
such as EE to engage the sliding bolt F working transversely underneath the
As a substitute for
bottom bracket D and operated by the rider when desired.
this pin F and holes E within the collar B, the collar may be extended to form
a pulley and a band brake employed to grip and hold stationary this pulley and
therefore the elliptical toothed pinion A when required. Gearing with the
teeth of this first elliptical pinion A is a second elliptical pinion G of the same
size and carried free so as to rotate upon a pin H fixed to the crank I.
Fastened to the side of and concentric with this second elliptical pinion G is a
toothed circular pinion J and these two are integral one with the other and turn
bodily about the same axle pin H carried on the crank I.
The toothed circular pinion J gears with an inside toothed annulus K which
is concentric with the crank axle C. The outer circumference of this annulus K
is provided with teeth and forms an ordinary chain wheel L and is mounted
in any suitable manner to rotate freely round the crank axle C. Thus it is
evident that a complete gearing is effected between the central elliptical pinion 1)
and the chain wheel L. It is necessary, however, that the gear should be provided
with a ratchet arrangement so that the chain wheel L can only rotate in advance
of the cranks. This is effected by a pin pawl M mounted on a spring N on the
crank and gearing with three ratchet depressions O. These ratchet depressions
are formed upon one side of the boss of the pinion J and their shape and position
are clearly shown in Figures 4 and 5 of the drawings. The ratchet depressions

page_text: or teeth O are always arranged in such relative positions to the elliptical pinion G
that when engaged with the pawl the major axis of the central elliptical pinion A
shall be in exactly the same relative position to the cranks in each case.
The
object of this is so that the rider shall at any moment know while riding what
position the major axis of the central elliptical pinion D is in, whether vertical 5
or horizontal. In the construction shown in the drawings a three armed exten-
sion Q is attached to the crank and this extension carries pulleys RR which
run in an internal groove formed in the chain wheel L, this serves the purpose
of steadying the action of the gear. It is of course to be understood that more
than one set of pinions carried by the crank may be employed without departing 1
from the subject of the present invention.
The gear is operated in the following manner-As before described the central
elliptical pinion A is loose on the central axle C as is also the chain wheel L,
but the cranks I and the pin H carrying the two pinions G and J are carried
round with the cranks and attached fast thereto by the pawl pin M. The chain 1
wheel L is of such a diameter as to constitute the low speed or power gear when
the central elliptical pinion A is left loose as just described and the two pinions J
and G are keyed by the pawl attachment. The whole of the therefore
gear
rotates as one rigid piece the pawl M on the crank I engaging in one of the
ratchet depressions to drive the chain wheel L forward at the same rate as
the crank.
To increase the speed of the gear the central elliptical pinion A is locked
rigidly to the bottom bracket D either by the pin F as shown or by the equivalent
band brake not illustrated but hereinbefore described. In this case the ellip-
tical pinion G will roll round the central elliptical pinion A and therefore the 2
other pinion J will drive the annulus or chain wheel in advance of the crank I
as the chain wheel L is not only carried round at the speed of the crank but is
plus the additional speed given to it by the rotation of the pinions G, J, upon
their axle H. If the locking of the central elliptical pinion A is effected when
either of the cranks are vertical the major axis of the central elliptical pinion 3
will be vertical and thus impart to the intermediate pair of pinions G, J, a
axis when the cranks are
quicker forward rotary motion around their own
vertical than they will have when the cranks are horizontal. The chain wheel
or annulus will thus be driven forward in its relation to the cranks more
quickly when the cranks are vertical than when the cranks are in a horizontal:
position. If the central elliptical pinion A were locked to the cycle frame when
the cranks were horizontal the reverse of this would be the case. This varying
motion of the chain wheel or annulus L is due to the gearing of the elliptical
pinions A, G, with each other and is transmitted to the annulus or chain wheel L
through the intermediate circular pinion J which as before described is fastened
to the side of the intermediate elliptical pinion G.
It will be seen with this gear in action that a rider cannot drive the machine
backwards and that it also does not allow of back pedalling and further that the
central elliptical pinion can be locked in the position that gives the greatest
mechanical advantage of the gearing during that portion of the cranks revolution
that is found best to suit the varying turning moments of the power applied to
the crank by the foot of the rider under many varying conditions, such as road
gradient and wind pressure.
It is to be clearly understood that the locking of the central elliptical pinion
to the bottom bracket may be performed in any known mechanical manner
other than the two methods hereinbefore described and further that the applicant
does not limit his ratchet gear to the particular construction illustrated and
described but that the ratchet teeth and pawl may be of any known construction
and placed in other convenient portions of the gearing as long as the effect is
produced of permitting the chain wheel to revolve ahead of the crank when upon
the high gear.

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―
1. In variable speed driving gear for cycles and other machines in combina-
tion, an elliptical toothed pinion carried upon the crank axle, an internally
toothed annular chain wheel also carried upon the crank axle, a second elliptical
pinion or pinions carried by or from the crank and gearing with the central
elliptical pinion, a toothed wheel or wheels integral with the second elliptical
pinion or pinions carried by the crank and gearing with the inner teeth of the
chain wheel, and a locking device for the central elliptical pinion when on the
high speed and means for connecting the crank to the chain wheel when on the
slow speed substantially as hereinbefore described.
2. In variable speed driving gear for cycles and other machines as claimed
in the preceding claim the provision of means for locking the elliptical gear
when the major axis of the central elliptical pinion is in a fixed relative position
to the crank so that the effort of the rider may be varied throughout one revolu-
tion of the pedal substantially as hereinbefore described.
3. The improved variable speed driving gear for cycles and other machines
substantially as herein before described with reference to Figures 1, 2, 3, 4, and 5
of the accompanying drawings.
Dated this oth day of October 1898.
MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.