Improvements in Variable Speed Driving Gears.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in Variable Speed Driving Gears.
HENRY JAMES YELDHAM Fernlea Cavendish Road Sutton Surrey do hereby
declare the nature of this invention to be as follows:-
My Invention relates more particularly to Driving Gears where a variation of
speed is essential, or advantageous, and by its adoption the speed, at which any
machine or shafting may be made to rotate, can be increased or diminished at will
without the necessity of varying the speed of the driving power. Or the speed of
the driving power may be increased, or diminished whilst the speed of the driven
mechanism may remain constant. For instance when the improved gearing is
applied to a Bicycle, or other similar machine or carriage the speed at which
such may be travelling can be instantly increased or diminished without extra
exertion, or otherwise on the part of the rider, or other motive power propelling
such machine, and without increasing or diminishing the revolutions of the
cranks or pedals.
My invention consists in the employment of a suitable spur wheel or pulley
in which is contained a silent ratchet mechanism securely attached to the
shafting.
For example in the case of a bicycle I attach this ratchet mechanism to the
hub or axle or other suitable part.
Alongside and also securely fastened to the shafting or hub or axle is an exter-
nally toothed wheel or pinion.
Geared to this pinion is an internally toothed wheel capable of revolving upon
an axis of its own and which axis is bored eccentrically to enable it to revolva
upon the shaft or axle and the pitch line of which internally toothed wheel has a
greater diameter than has the pinion, and its centre is necessarily eccentric to the
centre of the pinion.
Firmly fastened to the side of this internally toothed wheel is a disc containing
a slot or slots, and to the spur wheel or pulley before mentioned I firmly secure
a pin or stud (of a suitable size to fit into the said slot) in such a manner as to receive
the power or motion transmitted to it through the spur wheel, or pulley, by the
chain or toothed gearing, or strap or other means.
When the speed is normal the spur wheel or pulley, and the toothed wheels
being locked together (by the pin or stud resting in the slot of the disc) revolve as
one piece on one axis, but when the axis of the larger toothed wheel is held fast,
which I provide suitable means of doing the larger wheel is driven forward by
the pin of the spur wheel or pulley, and the pinion and shafting (or in
the case of a bicycle the hub, or axle) being (by reason of the in-
ternal ratchet) free to revolve faster than the spur wheed or pulley does so at
an increase of speed due to the difference in the diameters of the two toothed
wheels.
When the axis of the larger and internally toothed wheel is released the spur
wheel or pulley and the two toothed wheels revolve together on a common axle,
and the speed is normal but when the axis of the larger toothed wheel is
"

page_text: prevented from revolving the pin or stud of the spur wheel or pulley by its move-
ments in the slot of the disc causes the larger wheel to revolve, and transmits the
power derived from the chain, or other means through the larger toothed wheel,
to the pinion so increasing the speed of the driven axle, or shaft, or wheel with-
out increasing that of the driving power.
The action is similar when applied to any mechanism driven by independent
power.
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1
Improvements in Variable Speed Driving Gears."
I, HENRY JAMES YELDHAM of "Fernlea" Cavendish Road, Sutton in the County
of Surrey, 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:-
This invention relates to variable speed driving gears and it consists of certain
improvements hereinafter more particularly specified.
In the accompanying drawing which-by way of example illustrates this
invention as applied to the driving wheel of a velocipede:-
Figure 1 is a view in longitudinal section.
Figure 2 is an end view.
Figure 3 is an end view of the clutch gear, and
:-
Figures 4 and 5 are views in longitudinal section and end view respectively of a
modification.
Throughout the views similar parts are marked with like letters of reference.
Referring to Figures 1, 2 and 3. On to one end of the hub A is loosely mounted
the chain wheel B, which is connected with the hub by means of any suitable
clutch gear such for instance as that illustrated by Figure 3, which consists of a
dise B₁ having inclined recesses b in its periphery in which lie balls or rollers b¹
adapted to engage with the exterior wall of a recess in the chain wheel B.
To the outer side of the chain wheel B is attached a disc C having one or more
radial slots c. On to the end of the hub A. outside the disc C is fixed a spur
pinion D with which engages an internally toothed spur wheel E of larger diameter
which is mounted on a collar F mounted eccentrically on the axle X. This
collar preferably carries a disc F1 which fits inside the internal spur wheel E
and acts as a guide for it. On the spur wheel E is mounted a pin G which engages
with one or other of the radial slots c in the disc C.
If the eccentric boss F is allowed to run free on the axle X the whole of
the mechanism revolves together and the hub of the driving wheel is driven at the
same speed as the chain wheel B by reason of the clutch mechanism, but if the
eccentric boss F is prevented from rotating an increased speed of rotation is im-
parted to the hub of the driving wheel by reason of the increased speed imparted
to the spur pinion D by the internal spur wheel E which is caused to rotate on its
eccentric bearing F by means of the pin G engaging with one of the slots c in the
disc C fixed to the chain wheel B.
A convenient method of preventing the eccentric collar F from rotating on the
axle X is to 'cut away a portion of its periphery so as to form a stop f with an
adjustable arm or pin carried by the frame of the machine can be engaged.
In the modification shown in Figures 4 and 5 the pin G is carried by the cam
disc B' which is fixed to a disc B on to the boss of which the chain wheel B is
fixed, and it engages with a slot e in the internal spur wheel E which is mounted.

page_text: on an eccentric disc F carried by a sleeve F2 encircling the axle X and of such
a length that it extends beyond one end of the hub A which is mounted on the
said sleeve. On the end of the sleeve is fixed the operating stop f. The spur
pinion D is mounted or formed on the hub A as shown.
By the employment of the clutch gear all strain is taken off the spur gearing
when the machine is at its normal speed i.e, when the speed of the driving chain
wheel and of the driving wheel is identical.
I am aware that the employment of an external spur pinion and an internal
spur wheel in a two speed gear is not broadly new, and I do not therefore claim
such as my invention, but
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:-
The combination of parts herein described and illustrated by the accompany-
ing drawing forming an improved variable speed gear.
Dated this 28th day of October 1807
ROBERT E. PHILLIPS Assoc. M. Inst. C.E., M.I.Mech. E.,
Consulting Engineer & Patent Agent
70, Chancery Lane, London, W.C., Agent for the Applicant.