An Improved Sprocket Wheel, specially applicable to Velocipedes..
Year: 1896

page_text: Date of Application, 29th Dec., 1896-Accepted, 30th Jan., 1897
COMPLETE SPECIFICATION.
An Improved Sprocket Wheel, specially applicable to Velocipedes..
I, JAMES ALEXANDER WALKER, of Folkestone, Lavender Bay, North
Sydney, in the Colony of New South Wales, Engineer, 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 an improved sprocket wheel specially applicable to.
velocipedes so constructed that the friction and wear of the wheel and chain are
considerably reduced and the wear and extension of the chain can be compensated
allowing the chain to do effective work for a longer period than with sprocket
wheels of ordinary construction.
The sprocket wheel according to this invention has two peculiar features. One of
these peculiarities is an absence of teeth except at arbitrary, preférerably opposite,
When
points on the circumference where there are groups, each of a few teeth.
the sprocket wheel is operated by cranks as in velocipedes these groups are prefer-
ably so arranged relatively to the cranks that the teeth gear with the chain when
the cranks are at their least operative points or their "dead centres." The other
of these peculiarities is the insertion of adjustable peripheral pieces or "com-
pensators" in the circumference of the wheel midway between the groups of teeth.
so that the peripheral distance between these groups can be extended as the chain
wears or becomes extended.
But in order that this invention may be clearly understood reference will now.
be made to the accompanying drawings.
Figure 1 is a side elevation of a wheel constructed according to this invention.
and having two opposite groups each of three teeth, arranged so as to engage the
chain when the cranks are at their dead centres, compensators (shewn in their initial
positions) being provided midway between the groups of teeth. Two construotious
of the compensators are illustrated but in practice both compensators in one wheel
would be of the same construction.
Figure 2 is a side elevation of the left haud part of the wheel shewing the
compensator in its most extended position.
Figures 3 and 4 are face or edge views of right hand part of the wheel looking
upon it respectively with the compensator in place and with the compensator
removed and
Figure 5 is partial face or edgo view of the internal periphery of the wheel.
The wheel A on the spindle a having eranks a', instead of having teeth all
round its circumference has two groups each of three teeth A¹ situated
diametrically opposite to one another, the rest of the circumference having no
teeth. The peripheral pieces or compensators B and B are inserted in the face of
the rim A midway between the groups of teeth and fastened and adjusted as
bereinafter explained. In order to allow of increased adjustment, the rim A² is.
ovalled or made of less diameter at this part, (as shown in Figures 1 and 2 where
the continuation of the rim, if .it were circular, is indicated by the dotted lines b)...
The compensators occupy a recess in the rim of the wheel; their outer faces.
forming parts of the periphery upon which the chain travels between the teeth A¹.
Each peripheral part is by adjustment extended outwards to increase the length of
the are between the groups of teeth A'. The coinpensators B may be made of:

page_text: elastic or flexible material such as steel, or sets of rigid pieces B' may be used
each having a different peripheral length increasing by steps.
The elastic or flexible compensator B is fastened or rivetted at one end as at C*
to the rim and has a boss or face C on which bears a set screw C having a lock
nut C, and at the other end, it has a countersunk bolt C passing through a slotted
hole in the rim and secured by the nut C. To adjust or compensate for increased
length of the chain E owing to wear and stretching, the nuts C and C² are
loosened and the set screw is screwed out to force out the compensator B (see
Figure 2) to the desired extent, and then the nuts C2 and C are again tightened.
The rigid compensator B' fits also in a recess in the rim and is fastened to the rim
by three countersunk bolts and nuts D. To adjust in this case, the nuts of the
bolts D are removed and a larger compensator Bi is put in the recess in the rim
and secured by its bolts D.
Though I have shown only two groups each of three teeth A¹ there may be more
teeth in each group and there may be more groups than two, in which case there
would be a compensator between each pair of groups. It is also to be understood
that though the compensators B and B are shown with plain faces they may have
flanges or other devices for retaining the chain upon their peripheries.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what I
olaim is :-
1. A sprocket wheel specially applicable to velocipedes having groups each of
a few teeth on its circumference and between these groups compensators for
extending the periphery, substantially as and for the purpose herein set forth.
2. In combination with an axle or spindle driven by cranks a sprocket wheel,
such as is above referred to, having the groups of teeth so arranged as to engage
with the chain when the cranks are on their dead centres, substantially as
described.
3. In a sprocket wheel such as is above referred to, an adjustable compensator,
consisting of an elastic or flexible peripheral piece adapted to be bowed outwardly,
substantially as described.
4. For a sprocket wheel such as is above referred to, adjusting devices or
compensators, consisting of removable peripheral pieces adapted to be exchanged,
the one for the other, to increase the length of the periphery between the groups
of teeth, substantially as described.
Dated this 29th day of December 1896:
ABEL & IMRAY,
Agents for the Applicant.