Improvements in Differential Driving Gear for Cycles.
Year: 1893

page_text: Date of Application, 5th Dec., 1893.
Complete Specification Left, 5th Sept., 1894-Accepted, 1st Dec., 1894
PROVISIONAL SPECIFICATION.
Improvements in 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 primarily 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
ceutral pinion and the surrounding wheel one or more epicyclic wheels mounted
on a radial 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.
A differential gear of this nature, and adapted for operating the driving wheel
of the machine at either of two speeds both greater than that of the pedal-shaft,
forms the subject of my application for Letters Patent filed the 22nd day of
April, 1893, No. 8189. Gear constructed in the manner therein described, when
arranged concentrically with the driving wheel, only affords facilities for increasing
the speed within moderate limits; that is to say, if a high peripheral speed of
wheel be desired, the diameter of the driving wheel must also be considerable.
The object of my present invention is to provide means whereby a greater range
of differential speed may be obtained, so as to admit of a high peripheral speed being
imparted to a driving wheel of comparatively small diameter.
In a differential gear constructed according to my present invention, instead of
the intermediate wheel meshing both with the central pinion and with the surrounding
toothed wheel, a pair of toothed wheels of different diameters is substituted, the
smaller one meshing with the pinion and the larger one meshing with the internally
toothed wheel, the increase of speed being thus effected in two stages.
In combining two such trains of gear for affording two different speeds, the
internally toothed wheel and the larger of the pair of intermediate wheels before
referred to are or may be common to both trains of gear. Under such circumstances,
a complete set of intermediate wheels comprises three wheels, all fixed upon a
spindle which is mounted in bearings formed in an arm or in a pair of arms
extending radially from the pedal-shaft. The larger of the three wheels meshes
with the internally toothed wheel, whilst the remaining two, which are of different
diameters, respectively mesh with pinions of different diameters mounted to rotate
freely on the pedal-shaft. Each of these pinions is provided with a sleeve which
extends towards one of the bearings in the fork or frame of the machine and is
furnished with a clutch 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 trains of intermediate gearing,
according to whichever of these trains meshes 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 central pinion is locked to the fork,
the other central pinion runs free, and the intermediate wheel meshing with the
latter becomes an idle wheel. When, however, a reduction of speed and increase
of power are desired, the larger central pinion is released, and the smaller one

page_text: locked to the fork; the power being. then transmitted through the intermediate
wheel previously idle.
The clutches or other 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 herein before 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.
When so applied, the pitch-chain may be placed about: the circumference of the
internally toothed wheel.
By a modification of the duplex differential.gear herein before described, a single
differential gear may be produced; the same being adapted for more equally
distributing the strain incidental to communicating the power from the pedal-shaft
to the hub of the driving wheel. According to this construction, the two central
pinions are of equal diameter and both are locked to the frame of the machine. The
intermediate toothed wheels, which are also of equal diameter, are fast on a spindle
carried in bearings formed in the arms which extend radially from the pedal-shaft ;
and fast on the same spindle is a toothed wheel of larger diameter, which meshes
with the internally toothed wheel. Under such circumstances, the driving power
is derived equally from the opposite extremities of the pedal-shaft, and may be
applied centrally to the hub of the driving wheel.
Dated the 5th day of December 1893.
COMPLETE SPECIFICATION.
Improvements in 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 primarily 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
a radial 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.
A differential gear of this nature, and adapted for operating the driving wheel
of the machine at either of two speeds both greater than that of the pedal-shaft,
is described in the Specification to my Letters Patent dated 22nd April, 1893,
No. 8189. Such gear, when arranged concentrically with the driving wheel, only
affords facilities for increasing the speed within moderate limits; that is to say, if
a high peripheral speed of wheel be desired, the diameter of the driving wheel
must also be considerable.
The object of my present invention is to provide means whereby a greater
range of differential speed may be obtained, so as to admit of a high peripheral
speed being imparted to a driving wheel of comparatively small diameter.

page_text: Fig. 1 is a vertical transverse section through the hub and fork-ends of a front-
driving bicycle embodying my invention; Fig. 2 being a section on the zigzag
line, (Fig. 1).
.
Fig. 3 is a side elevation of one of the fork-ends showing the clutch mechanism
for locking one of the central spur-pinions;
Fig. 4 being a corresponding plan of the clutch mechanism removed from the
fork.
Figs. 5 and 6 are views corresponding with Figs. 1 and 2, but illustrating a
modified form of construction particularly adapted for racing machines and in
which, alterable speed-gear not being required, means for locking either the one or
the other of the central spur-pinions to the fork or frame of the machine is not
necessary.
Fig. 7 is a face view of the fork-end showing the manner in which the parts of
the bearing may, after adjustment, be locked.
In a differential gear constructed according to my present invention, for an
intermediate wheel meshing both with the central pinion A or A' and with the
surrounding toothed wheel B, there is substituted a pair of toothed wheels of
different diameters, the smaller one meshing with the pinion A or A and the
larger one meshing with the internally toothed wheel B, the increase of speed
being thus accomplished in two stages.
In combining two such trains of gear for affording two different speeds, the
internally toothed wheel B and the larger of the pair of intermediate wheels before
referred to are or may be common to both trains of gear. Under such circumstances,
a complete set of intermediate wheels comprises three wheels C. C' and Cx (the last
being common to both trains) all fixed upon a spindle D which is mounted in bearings d
and d¹ formed in an arm or in a pair of arms E and E¹ extending radially from the
pedal-shaft F. The wheel C* meshes with the internally toothed wheel B, whilst the
wheels C and C, which are of different diameters, respectively mesh with pinions A
and A', also of different diameters, mounted to rotate freely on the pedal-shaft. Each
of these pinions is provided with a sleeve A² or A3, which extends towards one of the
bearings in the fork J J or frame of the machine and is furnished with a clutch
whereby it may be locked to the fork and held stationary. The outer or internally
toothed wheel B forms part of, or is in permanent connection with, the hub G of
the driving wheel of the machine; the power being transmitted thereto from the
pedal-shaft F through one or the other of the trains (C C A B or C¹ C* A! B)
of gearing, according to whichever of these trains includes the central piniou A
or A' for the time being locked to the fork or frame and temporarily serving as a
pivot.
When the high speed is required, the larger pinion (A) is locked to the fork or
frame, the other central pinion (A) runs free, and the intermediate wheel C
meshing with the latter becomes an idle wheel; the power being then transmitted
through C and Cx to B. When, however, a reduction of speed and increase of
power is desired, the larger central pinion (A') released, and the smaller one (A)
locked to the fork or frame; the power being then transmitted through the
intermediate wheel C (which was previously idle) and Cx to B.
If it be desired to increase the peripheral speed of the driving wheel without
increasing its diameter, the difference between the diameters of the wheels A'
and C, or between the diameters of the wheels C and C* may be increased, or
both these differences may be increased; the wheels A and C being similarly
trented.
The clutches or other engaging devices, for locking the one or the other of the
central pinions A, A', 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. The clutch mechanism illustrated in the present design
comprises a baud H which embraces a grooved drum A* secured to the sleeve ou
one of the central pinions. The ends of the band H are connected by pins k with

page_text: plates pivoted on a pin j screwed into the fork-end J. The free ends of the
plates are jointed by a pin to a rod L, which extends upwards and is connected to
a hand-lever or other suitable device, whereby the rod L appertaining to the one
or the other fork-end of the machine may be raised, and in that position secured,
thereby bringing one or the other of the straps H into operation to grip one or the
other of the collars A* and to lock one or the other of the central pinions A, A¹
to the frame, as may be desired.
Although the hereinbefore described 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. When so applied,
the pitch-chain may be placed about the circumference of the internally toothed
wheel.
By a modification of the change gear herein before described, the single specil
differential gear represented in Figs. 5 and 6 is produced; the same being adapted
for more equally distributing the strain incidental to communicating the power
from the pedal-shaft F to the hub G' B* G2 of the driving wheel. According to
this construction, the two central pinions A and A' are of equal diameter and both
are secured to the fork or frame of the machine. The intermediate toothed
wheels C and C³, which are also of equal diameter, are fast on a spindle D carried
in bearings d and d formed in the arms E and E¹; and fast on the same spindle is
the toothed wheel C× of larger diameter, which meshes with the internally toothed
wheel B*. Under such circumstances, the driving power is derived equally from
the opposite extremities of the pedal-shaft F, and is applied centrally to the hub
of the driving 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 two-speed differential driving gear for cycles, constructed
substantially as described with reference to Figs. 1 and 2 of the accompanying
drawings.
2. The improved single-speed differential driving gear for cycles, constructed
substantially as described with reference to Figs. 5 and 6 of the accompanying
drawings.
3. In a two-speed differential driving gear for cycles, the combination, with an
internally toothed wheel and a spur-wheel meshing therewith and mounted on an
intermediate spindle, of two unequal spur-wheels mounted upon the aforesaid
spindle and meshing with two unequal and centrally arranged pinions respectively
capable of being locked to one of the fork-ends of the machine, substantially as
herein described and for the purposes set forth.
4. In a single-speed differential driving gear for cycles, the combination, with an
internally toothed wheel and a spur-wheel meshing therewith and mounted on an
intermediate spindle, of two equal spur-wheels mounted upon the aforesaid spindle
and meshing with two equal and centrally arranged pinions respectively disposed
towards the opposite fork-ends of the machine and secured thereto, substantially as
herein described and for the purposes set forth.
5. In concentric differential driving gear for cycles, the employment of two
intermediate wheels of different diameters both fixed on the same spindle, the smaller
intermediate wheel meshing with a pinion (of larger diameter) locked to the fork
and the larger intermediate wheel meshing with the internally toothed wheel,
substantially as herein described, and whereby the increase of speed is accomplished
in two stages.
Deted the 5th der of Sentember 1991