An Improved Differential Driving Gear for Cycles.
Year: 1893

page_text: Date of Application, 22nd Apr., 1893
Complete-Specification Left, 22nd Jan., 1894-Accepted, 21st Apr., 1894
PROVISIONAL SPECIFICATION.
An Improved Differential Driving Gear for Cycles.
I, GEORGE GATTON MELHUISH HARDINGHAM, of 191 Fleet Street, in the
County of Middlesex, Civil Engineer, do hereby declare the nature of this
invention to be as follows:-
."
This invention relates to means whereby the driving wheel of a bicycle or similar
machine, mounted concentrically with the pedal-shaft, may be driven at either of
two speeds, both being greater than that at which the pedal-shaft rotates.
The general character of the gear resembles that in which a central spur pinion
is surrounded by an internally toothed wheel; there being interposed between the
central pinion and the surrounding wheel one or more epicyclic wheels mounted on
an arm or arms, or upon a disc, extending from or secured to the pedal-shaft. For
the purpose of equally distributing the strain, it is usual to employ two, three or
four intermediate wheels arranged equiangularly.
In a differential gear adapted to accomplish the objects of the present invention,
the internally geared wheel has two series of teeth, or the teeth are extended in
width, so as to admit of engagement with two intermediate wheels, or two sets of
intermediate wheels, in different planes, and mounted at different radii on arms, or
on a disc, extending from the -pedal-shaft. These intermediate wheels, or sets of
wheels, gear with central but separate spur-pinions of different diameters mounted
to rotate freely on the pedal-shaft; each of the said pinions being provided with a
sleeve, which extends towards one of the bearings in the fork or frame of the
machine and there engages with a catch, whereby it may be locked to the fork and
held stationary. The outer or internally toothed wheel forms part of, or is in
permanent connection with, the driving wheel of the machine; the power being
transmitted thereto from the pedal-shaft through one or the other of the inter-
mediate wheels, or sets of intermediate wheels, according to whichever of these
wheels, or sets of wheels, gears with the central pinion for the time being locked to
the frame and temporarily serving as a pivot.
When the high speed is required, the larger pinion is locked to the fork, and the
power is transmitted to the internally toothed wheel and to the driving wheel of the
machine through the intermediate wheel, or set of wheels, mounted at the longer
radius from the axis of the pedal-shaft; the other central pinion and the inter-
mediate wheel, or set of wheels, appertaining thereto running free. When,
however, a reduction of speed and increase of power are desired, the larger pinion
is released and the smaller one locked to the fork, the power being in this case
transmitted to the internally toothed wheel and to the driving wheel of the machine
through the intermediate wheel or set of wheels mounted at the shorter radius from
the axis of the pedal-shaft.
According to an alternative method of construction, the intermediate wheels,
instead of being mounted at different radii, may be arranged at the same radius
from the axis of the pedal-shaft; the two series of teeth, with which the internally
geared wheel is provided, having pitch lines of different diameters. Under such
circumstances, two intermediate wheels may be mounted on the stud or on each of
the studs with which the arm or arms or disc, extending from the pedal-shaft, is
furnished. The intermediate wheels gear with central spur-pinions of different
diameters, as before described.
Duplex differential spur gear of the kind hereinbefore referred to may moreover
be designed in such a manner that the diameters of the two central pinions are
equal; whilst the radii at which the intermediate wheels are mounted are unequal,

page_text: the diameters of the pitch lines of the two series of teeth of the circumscribing
wheel being also unequal. Such a system of construction is, however, less com-
mendable, having regard to the maximum and minimum sizes of the wheels desirable
in practice.
The driving wheel runs on bearings on one of the pinion-sleeves; that side of the
hub wherein the gearing is placed being covered by a plate which serves to exclude
dust. Or the wheel may run on bearings one of which is on one of the pinion-
sleeves; the other being on the other pinion-sleeve. Under such circumstances,
the ball-race on one side is partly in the pinion-sleeve and partly, in the cover-
plate, the latter being made stronger than usual. and contributing to the support of
the wheel. In this construction, the bearings for the wheel are brought as far
apart as possible. One or both sets of teeth appertaining to the circumscribing
gear-wheel may be formed as circular racks adapted for separate introduction; and
one of these may be conveniently formed integral with the cover-plate. If
preferred, each bearing may be in a plate or disc secured to the hub.
The engaging devices for locking the one or the other of the central pinions may
be actuated by means of suitable connections, extending up the fork to the head
or handle-bar of the machine, and may be operated whilst the machine is in
motion.
Although the hereinbefore described duplex differential driving gear is specially
adapted for use with cycles of the type in which the driving wheel is concentric
with the pedal-shaft, it will be obvious that similarly constructed change gear is
applicable to cyles of other types; as, for example, that in which the motion is
transmitted from the pedal-shaft through a pitch-chain to the driving wheel. Under
such circumstances, the pitch-chain may be placed about the circumference of the
internally toothed wheel.
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COMPLETE SPECIFICATION.
An Improved Differential Driving Gear for Cycles.
I, GEORGE GATTON MELHUISH HARDINGHAM, of 191, Fleet Street, in the
County of Middlesex, Civil Engineer, do hereby declare the nature of this inven
tion 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 means whereby the driving wheel of a bicycle or
similar machine, mounted concentrically with the pedal-shaft, may be driven at
either of two speeds, both being greater than that at which the pedal-shaft
rotates.
The general character of the gear resembles that in which a central spur-pinion
is surrounded by an internally-toothed wheel; there being interposed between the
central pinion and the surrounding wheel one or more epicyclic wheels mounted on
an arm or arms, or upon a disc, extending from or secured to the pedal-shaft. For
the purpose of equally distributing the strain, it is usual to employ two, three or
four intermediate wheels arranged equiangularly about the central pinion.
In the accompanying drawings,
Fig. 1 is a vertical transverse section through the hub and fork of a front-driving
bicycle embodying my invention; Fig. 2 being a section on the line x, x
(Fig. 1).
Fig. 3 is a side elevation of one of the fork-ends showing one of the clutches ;
Fig. 4 being a separate view of the clutch.
Fig. 5 is a side elevation of one of the collars with which the clutches engage.
Figs. 6 and 7 correspond with Figs. 1 and 2, but illustrate an alternative mode
of construction.

page_text: In a differential gear adapted to accomplish the objects of the present invention,
the internally-geared wheel has two series of teeth A, A', or the teeth are extended
in width, so as to admit of engagement with two intermediate wheels, or two sets of
intermediate wheels, B, B', B-C, C¹, C' in different planes and mounted at
different radii on arms B3, B4 B-C, C, C³, or on opposite sides of a disc,
extending from the pedal-shaft D. These intermediate wheels or sets of wheels
gear with central but separate spur-pinions E, E'. of different diameters
mounted to rotate freely on the pedal-shaft D; each of the said pinions being
provided with a sleeve E' or E³, which extends towards one of the bearings in the
fork F or frame of the machine. Each sleeve is furnished with a detachable
collar E or E, which by a feather ex is prevented from rotating on the sleeve.
Each collar has a recess or recesses e in which the catch G or G' engages, and
whereby the collar, and consequently the sleeve and pinion, may be locked to the
fork and held stationary therein. The outer, or internally-toothed, wheel A A¹ is
in connection with, or forms part of, the driving wheel of the machine; the power
being transmitted thereto from the pedal-shaft D, through one or the other of the
gear-trains (BEA, CE' A'), according to whichever of these embraces the central
pinion E or E' for the time being locked to the fork F or frame and temporarily
serving as a pivot.
When the high speed is required, the pinion E, which is the larger, is locked to
the fork F, and the power is transmitted to the teeth A of the internally-toothed
wheel A A', and consequently to the driving wheel of the machine, through the
intermediate wheel, or set of wheels B, B1, B2; the latter being mounted at the
longer radius from the axis of the pedal-shaft D. Meanwhile the other pinion E¹
and the intermediate wheel, or set of wheels C, C1, C2, pertaining thereto, is free
to turn with or upon the pedal-shaft. When, however, a reduction of speed and
increase of power are desired, the pinion E is released by raising the catch G and
the pinion E¹ locked to the fork by a catch G', the power being in this case
transmitted to the internally-toothed wheel and consequently to the driving wheel..
of the machine through the intermediate wheel, or set of wheels C, C, C³, which .
is mounted at the shorter radius from the axis of the pedal-shaft.
According to an alternative method of construction, the intermediate wheels,
instead of being mounted at different radii, may be arranged at the same radius
from the axis of the pedal-shaft, as shown in Figs. 6 and 7; the two series of
teeth A3, A3, with which the internally-geared wheel is provided, having pitch-lines
of different diameters. Under such circumstances, two intermediate wheels BX, C* .
may be mounted on the stud H or on each of the studs with which the arms K, K¹, K²
or disc, extending from the pedal-shaft D, is furnished. The intermediate
wheels B, C gear with central spur-pinions E6, E7, of different diameters and each
capable of heing locked to the fork as before described.
Duplex differential spur-gear of the kind hereinbefore referred to may moreover
be designed in such a manner that the diameters of the two central pinions are
equal; whilst the radii at which the intermediate wheels are mounted are unequal,
the diameters of the pitch-lines of the two series of teeth of the circumscribing
wheel being also unequal. Such a system of construction is, however, less com-
mendable, having regard to the maximum and minimum sizes of the wheels
desirable in practice.
It will be understood that the principal moving parts may be fitted with ball-
bearings; but these, although advantageous, do not form essential features of the
present invention, and plain bearings are shown for the sake of simplicity.
The driving wheel may run on bearings one of which is on the pinion-sleeve E³
and the other on the pinion-sleeve E³. Under such circumstances, the ball-race on
one side is partly in the pinion-sleeve E' (or E³) and partly in the cover-plate L
(or L'); the latter contributing to the support of the wheel, and being made
stronger than would be necessary if serving simply as a dust-excluder. Either
cover-plate can be detached to expose the interior mechanism without removing
the spokes of the wheel. The advantage of having the bearings in the cover-plates

page_text: is that, without interfering with the accessibility of the gear, the bearings are spread
as far apart as possible, thus ensuring accuracy and freedom in running.
The sets of teeth A, A¹ or A2, A pertaining to the circumscribing gear-wheel
may be formed as circular racks adapted for separate introduction, and may be.
conveniently made integral with the cover-plates L and L' respectively.
The engaging devices G and G¹ for locking the one or the other of the central
pinions may be actuated by means of suitable connections extending up the fork F.
to the head or handle-bar of the machine, and may be operated whilst the machine
is in motion. Clutches or locking devices of other descriptions may if preferred be
substituted.
Although the hereinbefore-described duplex differential driving gear is specially
adapted for use with cycles of the type in which the driving wheel is concentric
with the pedal-shaft, it will be obvious that similarly constructed change-gear is
applicable to cycles of other types; as, for example, that in which the motion is
transmitted from the pedal-shaft through a pitch-chain to the driving wheel.
Under such circumstances, the pitch-chain may be placed about the circumference
of the internally-toothed wheel.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I claim :-
1. The improved duplex differential driving gear for cycles arranged substantially
as herein described, whereby the driving wheel of the machine can be operated at
either of two speeds both greater than that of the pedal-shaft.
2. The improved duplex differential driving gear for cycles, constructed substan-
tially as herein described, and comprising an internally-toothed wheel, two central
pinions either of which can rotate freely on the pedal-shaft when the other is
locked to the fork or frame of the machine, two intermediate wheels or sets of
wheels respectively gearing with the pinions and with the internally-toothed wheel,
these intermediate wheels being mounted on arms (or on an arm) or on a disc
extending from the pedal-shaft, and means for locking either pinion to the fork or
frame so as to constitute a fixed point about which the intermediate wheel or set
of wheels gearing therewith works, imparting through the internally-toothed wheel
a differential rotative motion to the driving wheel of the machine.
3. In duplex differential driving gear for cycles, the employment of two central
pinions either of which can be locked to the fork or frame of the machine and
utilised as a fixed pivot for the epicyclic gear-train temporarily in operation, the
other pinion being meanwhile free to rotate with or upon the pedal-shaft,
substantially as and for the purpose herein set forth.
Dated the 22nd day of January 1894.