Improvements in Chain Wheels for Cycles.
Year: 1895

page_text: Date of Application, 22nd July, 1895-Accepted, 24th Aug., 1895
Improvements in Chain Wheels for Cycles.
We, JACOB BERNHEIMER and THEODOR MANGER, of 4, Grüner Markt,
Bamberg, in the Kingdom of Bavaria and German Empire, Manufacturers, do
ereby 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 chain wheels used for driving cycles, and it consists in
so constructing the wheel that the diameter of the toothed rim can be increased or
diminished, the object being to provide for varying the ratio of the gearing at all
times with rapidity.
In the accompanying drawing which illustrates our improved chain wheel :-
Figure 1 is a view in side elevation.
Figure 2 is a view in section on the line r, v, of Figure 1.
Figure 3 is a view in section showing a detail of construction.
Figure 4 is a view in partial side elevation of a modification, and
Figure 5 is a view in section thereof on the line w, w, of Figure 4.
Throughout the views similar parts are marked with like letters of reference.
The body of the wheel consists of a series of parts such for instance as
segments a. The toothed rim is formed by a spring band 6 which is placed'
around the assembled segments, and on which the teeth are formed or fixed. One
end of this spring band is fastened to a segment at a and its other end y is guided
in a groove formed in the periphery of the said segment by means of a sliding
block of dove-tail shape in cross section fixed to said end of the spring band.
In the arrangement shown by Figures 1 to 3, all the segments are provided on
one side with two studs c each of which extends through a radial slot c¹ in a disc d
that fits up against the sides of the segments. Each of these studs is screw-*
The disc d is fixed
threaded externally of the said disc and carries a thumbnut c².
on the pedal-crank axle. Fitting against the other side of the segments is a
similar disc d' which is also fixed on the axle. The studs e fixed on this side on
Their ends are
the segments also extend through radial slots e¹ in the disc d'.
adapted to slide in grooves e²-which are formed more tangentially than radially,
that is to say, obliquely-in the surface of the disc f which lies up against the
outer surface of the disc d¹.
On the outer surface of the disc f which is loose on the crank axle, is fixed a
knob by means of which the disc can be rotated. A nut f' secures the disc f
from axial movement. The disc is also provided with a mark or pointer g which,
when the disc is rotated, moves over a scale provided on the larger outer surface of
the disc d'.
When it is desired to increase the diameter of the wheel (which is shown in the
drawing, contracted to its smallest diameter) the thumbnuts c² are first slacked,
then the disc f is rotated in the proper direction until the mark g is brought
over that division of the scale provided on the disc d', which corresponds to
the desired ratio of gearing. Then the thumbnuts are tightened up again. By
the rotation of the disc f, all the segments a are caused by the guidance of
their studs e in the oblique grooves 2 of the disc f to move radially outwards,
so that their studs cand e move respectively in the slots c and e¹ of the discs d
and d. It is obvious that this movement of the segments will render the periphery
of the wheel non-circular, but this result is obviated by the spring band b, whose

page_text: end y is caused by the aforesaid movement of the segments to slide along in the
corresponding groove in the respective segment away from its end x, and thereby
form always an almost complete circle which will have a diameter corresponding to
the particular position for the time. being of the segments, that is to say, will have
the desired diameter.
Now as regards the effect upon the pitch of the increase or decrease in the
diameter of the wheel, it is merely necessary to increase or diminish the number of
the teeth by one, two or any number of teeth according to the alteration in the
diameter of the wheel, that is to say, according to the step from a determined ratio.
of gearing to the desired ratio, whilst the pitch of the teeth can remain unchanged.
The increase in the number of the teeth is effected in the following manner :--
--The.
segment of the wheel to which the end of the spring band & carrying the fixed teeth
is fastened, and in which there is arranged the groove for guiding the other end
of the spring band, is provided with a number of teeth h which are adapted to move
radially, under the action of a spring, h¹ in and out of suitable recesses in the
periphery of the segment.
At, the smallest, diameter of the driving wheel, that is to say, when, as shown.
in the drawing, the segments and the two ends of the spring band b are close up
against one another, the teeth are forced-in opposition to the spring -
completely into the segment, but as soon as, on increasing the diameter of the
wheel, the end y of the spring band b moves in the groove in this segment, then
according to the amount of said increase, only the tooth h situated nearest to the
end, or starting from the end, the teeth will be forced outwards one after the
other in succession by the action of their springs h'. Thus the spring-impelled
teeth fill the place of the teeth which are fixed on the spring band 6 and which
occupied the same spot previously. The pitch of the spring-impelled teeth is of
course equal to that of the permanent pitch. In order that the spring band 6 shall
not slip sideways off the segment, the material of the segment projects on both sides
slightly beyond the band and thus affords a secure bed for the latter. The discs d
and d also serve at the same time to guide the segments and to protect the entire
mechanism from dust and external injury.
The form of construction shown in Figures 4 and 5 differs advantageously from
that just described by the fact that the discs d and d' which might perhaps in some
cases increase the weight of the cycle beyond allowable limits, are dispensed with,
and in their place, pins d' are employed which are screwed into a boss or hub keyed
fast on the crank axle, and engage in suitable recesses in the segments, and thus
serve to guide the latter in their radial movement.
From the preceding description it will be readily understood, although in both
arrangements the change of the ratio of the gearing is quickly and easily effected
by simply slacking the thumbnuts c², suitably rotating the disc f, and tightening
up the thumbnuts again, that the segments of the wheel are always securely held in
all positions, and the toothed rim always remains approximately of circular shape,
and has a constant pitch, but with a number of teeth varying according to the ratio
of the gearing in each case.
With reference to the tension of the driving chain, it may be stated that any
differences caused by the change of the ratio of the gearing may be compensated by
suitable adjustment of a guide pulley over which the chain runs.
Having now particularly described and ascertained the nature of our said inven
tion; and in what manner the same is to be performed, we declare that what we
claim is::-
(1.). The improved chain wheel for cycles as hereinbefore described and illustrated
by the accompanying.
(2) A chain wheel adapted to change the ratio of the gearing in cycles, consisting
essentially of a. body formed of a series of segments such as a, the said segments
rotating with the crank axle and being adapted to be moved radially inwards or
outwards according to the desired ratio of gearing to be obtained, of suitable guides

page_text: such as c, c', e, e', for the segments a, of a disc such as f mounted loose on the axle
and adapted to operate the segments a, the arrangement being such that to each
segment there is fixed a stud e which is capable of sliding in an oblique groove e³ in
the said discs, as set forth.
(3.) A chain wheel adapted to change the ratio of the gearing according to
Claim 2, in which the teeth are arranged partly upon a spring band b, which
surrounds the wheel segments and is fixed at one end to a segment and can slide
with the other end y in a dove-tail groove in the said segment, and partly
with spring-action h, h, in suitable recesses in the periphery of the said segment,
so that on outward movement of the segments, that is to say, on an increase in the
diameter of the wheel, the spring band will yield, and equalize the differences
produced in the periphery of the wheel, whilst the teeth that have become uncovered
by the movement of the free end of the spring band are forced outwards by their
springs, as set forth.
(4.) A chain wheel of the type claimed by Claims 2 and 3 arranged as
illustrated by Figures 1 to 3, in which the wheel segments are arranged between
two discs d and d' keyed fast on the driving axle, and are guided by means of
studs c, e, which are fixed to said segments and work in radial slots c, el, in said
discs, and can be fixed by means of nuts c³ in their positions for the time being, as
set forth.
(5.) A chain wheel of the type claimed by Claims 1 and 2 arranged as shown by
Figures 4 and 5, in which the wheel segments are guided by means of pins d³, which
are screwed radially into a hub keyed fast on the driving axle, and which engage in
suitable recesses in the segments, as set forth.
Dated this 22nd day of Julv 1805
ROBERT E. PHILLIPS, Assoc. M. Inst. C.E., M.I. Mech. E.,
Consulting Engineer and Patent Agent,
70, Chancery Lane, London, W.C., Associate Agent.