Improvements in Sprocket-wheels.
Year: 1895

page_text: Date of Application, 3rd Dec., 1395-Accepted, 4th Jan., 1896
Improvements in Sprocket-wheels.
I, PETER FORG, of 50 Park Street, Somerville, Massachusetts, United States of
America, Manufacturer, 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 a chain or sprocket wheel especially designed and
adapted for use on bicycles and like vehicles.
The sprocket-wheel herein shown as embodying this invention is composed of a
rim portion detachable from the center or body of the wheel, and one feature of
this invention consists in an improved interlocking of these parts whereby they may
be more securely and effectually secured together.
Another feature of this invention consists in providing the teeth of a sprocket-
wheel with superior wearing surfaces, which are preferably integral with each
other and formed from a single piece of metal as will be described.
These and other features of this invention will be pointed out in the claims at
the end of this Specification.
Fig. 1 is an elevation of one side of a sprocket-wheel embodying this invention.
Fig. 2, an elevation of the opposite side of the wheel shown in Fig. 1.
Fig. 3, a sectional detail on an enlarged scale of the wheel shown in Figs. 1
and 2, the section being taken on the line 3-3, Fig. 2, and
Fig. 4, a detail on an enlarged scale to be referred to.
The sprocket-wheel herein represented as embodying my invention, may and
preferably will have its center or body portion A detachably secured to the rim A. 1,
but the improvement in the construction of the rim, which will be hereinafter
specifically pointed out, may be embodied in sprocket wheels in which the center
or body is not detachable from the rim portion.
In bicycles, as now commonly constructed, it is especially desirous to reduce the
weight of the various parts to a minimum without sacrificing strength, and in
order that this result may be accomplished with relation to the sprocket wheel, I
prefer to make the said sprocket wheel after the manner herein shown.
In accordance with this invention, therefore, the center or body portion A and
the main portion of the rim A 1 are struck or stamped out of sheet metal, preferably
soft or mild steel, while the wearing portion of the said rim and teeth are also
struck or stamped out of a harder or superior grade of steel, preferably tool
steel.
The body or center A is preferably composed of a hub a and spokes a 1, which,
for the best results, are offset for the greater portion of their length with relation
to a vertical plane extended through the center of the rim and the bub. The main
portion of the rim consists of a substantially narrow ring a 2, preferably of soft
steel, having a series of inwardly projecting arms a 3 corresponding in number to
the spokes or arms a 1, and either the spokes a 1 are made wider than the arms a 3
or vice versa, so that the wider part may be provided with a slot or recess into
which a flange, finger or interlocking projection on the other part may fit somewhat
snugly to join or connect together the said parts.
In the present instance, the arms a 3 of the ring a 2 are made wider than the
spokes a 1, and the arms a 3 are each provided with a slot a 5 into which projects
a bent finger or flange a 6 on the spoke a 1, which, in the construction herein
shown, constitutes the interlocking projection, the said finger or flange fitting

page_text: the slot a 5 somewhat snugly so as to lock the rim and center of the wheel
together.
The spokes a 1 and arm a 3 may be firmly but detachably secured together by
screws or threaded rods or bolts a 7, inserted through a suitable opening in the
arms a 3 and into and preferably through a threaded hole or opening in the spoke a 1,
and if desired, the threaded end of the screw or bolt a 7 projecting beyond the
spoke al may be provided with a nut a 8 as represented in Figs. 2 and 3, but
this is not absolutely essential and may be dispensed with. In this case, the end
of the screw-rod or bolt a 7 may be flush with the outside of the spoke a 1.
The screw rods or bolts firmly fasten together the two parts of the sprocket
wheel, but this construction, broadly speaking, I do not claim, as sprocket wheels
of this construction have heretofore been made, but this construction of sprocket
wheel is objectionable, as in practice, a very considerable strain comes upon the
screw rods or bolts, which soon work loose, thereby destroying the effectiveness of
the wheel.
By my improved construction, it will be seen that the strain comes upon the
interlocking parts, which are fitted snugly together and the two parts of the
wheel are locked against movement with relation to each other, and consequently
the screw rods or bolts are relieved from strain and do not work loose, so that,
the sprocket wheel made in two parts, as herein shown, is as strong as if the
spokes and rim were integral.
This feature of my invention may be embodied in a sprocket wheel in which
the rim may be of any desired or suitable construction, but I prefer to make the
rim after the manner herein shown.
In accordance with this second feature of this invention, the ring a 2 is
provided at suitable intervals about its periphery with teeth b, Figure 3, which
are preferably integral with the said ring, the said teeth, ring and arms a 3 being
preferably made of soft or mild steel, to obtain the desired strength, and the
said parts are preferably cut out of sheet stock in one piece.
When the teeth 6 are made of soft or mild steel, they are preferably
re-enforced with jackets 62, preferably of harder metal, such as tool steel, which
jackets constitute the wearing surface for the teeth and take the wear of the
link chain commonly employed on bicycles.
The jackets 2 for the teeth 6 of the rim, may be made integral or separate,
but I prefer to make them integral with each other, which result may and
preferably will be accomplished as will now be described.
A flat strip of sheet metal, preferably tool or hardened steel of the desired
width, is cut out by a suitable die, not shown, so as to leave openings 64
separated by cross pieces or end walls b5, and bounded by side walls b6, 67,
after the manner shown in Fig. 4. The opening 64 is preferably made hexagonal
in shape and the end walls 65 are each composed of frustum-shaped parts 10, 12,
the bases of which parts are joined with the side walls or bars 66 67, and the
narrower portions of which parts are united substantially on a central line, so
that, the strip thus formed may be bent longitudinally on a central line, which
bending may be effected by acting upon the flat strip with suitably shaped dies
or rolls, which give to the bent strip an annular form approximating the form of
the sprocket wheel rim.
By the operations just described, the parts 10-12 are shaped to fit over and
embrace the teeth 6 of the rim, while the side walls 66 67 embrace the opposite
sides of the ring a 2, and the inner edges 14-15 of the side walls 66 67 of each
opening, are substantially flush with the outer circumference of the ring a 2 and
constitute wearing surfaces for that portion of the ring a 2 between the teeth b.
When the re-enforcing strip shown in Fig. 4 is shaped as described, and applied
to the ring a 2 after the manner represented in Figs. 1, 2 and 3, the ends of the
re-enforcing strip may be brazed together or the strip may be fastened on opposite
sides of the point of contact of the two ends of the re-enforcing strip, by means of
rivets or pins c c 1 inserted through the re-enforcing strip and the ring a 2 or in any

page_text: other suitable manner. This construction of the rim portion of the sprocket wheel
permits the ring a 2 to be made of substantially thin metal and of a soft steel to
obtain increased strength, while at the same time, the wearing surface of the
sprocket wheel is of the desired hardness.
This re-enforcing feature of my invention, when coupled with the interlocking
feature of the invention, produces a sprocket wheel, which is light yet strong, and
cheap to manufacture.
1, however, do not desire to limit the re-enforcing feature of this invention to a
sprocket wheel made in two parts and interlocked as described, as the re-enforcing
feature may be applied to a sprocket wheel in which the rim and center or body
are in one piece, and in this case, the center or body and rim may be made of a
soft steel to obtain increased strength, and the desired hardness may be obtained
by the re-enforcing band or wearing surface.
I prefer that the re-enforcing wearing surface should be made after the manner
above described, that is, with the jackets for the teeth b connected by the side
walls 66 67, but I do not desire to limit my invention to a re-enforcing wearing
surface in which the jackets for the teeth are connected together, as each jacket
may be separated from its adjacent jacket and riveted or otherwise suitably secured
to the rim of the sprocket wheel.
By reference to Figs. 1, 2 and 3, it will be seen that the spokes are made by
offsetting or dishing out a piece from which the spokes are formed, which offset
construction gives increased strength to the sprocket wheel and permits the center
of the wheel to be made very light and of a minimum amount of metal.
In order to obtain a substantially long bearing for the shaft, the hub a is pressed
or drawn out to elongate the same.
Believing myself to be the first to construct a sprocket-wheel with interlocking
rim and spokes whereby the fastening screws or devices are relieved from strain,
do not desire to limit my invention to the particular construction shown.
Having now particularly described and ascertained the nature of my said
invention and in what mauner the same is to be performed I declare that what I
claim is :-
1. A sprocket-wheel comprising the following instrumentalities, viz. :-A metal
rim provided with teeth, a center or body portion detachably secured to the rim
and interlocked therewith by the engagement of one part with a slot or recess in
the other part, and devices extended through the said interlocked parts to firmly
but detachably secure said parts and which devices are relieved from strain by the
interlocking of the said parts, substantially as described.
2. A sprocket-wheel comprising the following instrumentalities, viz. :-A metal
rim provided with teeth integral therewith and composed of a substantially soft
metal, a metal body or center interlocked with said rim, devices extended through
the said interlocking parts to firmly but detachably secure the said parts together
and which devices are relieved from strain by the interlocking of said parts, and
metal jackets for the said teeth composed of a harder or superior metal and
embracing only the sides of the teeth and forming superior wearing surfaces
therefor, substantially as described.
3. A sprocket-wheel, comprising the following instrumentalities, viz. :-A metal
rim provided with teeth integral therewith and composed of a substantially soft
metal, and a re-enforcing metal strip provided with openings separated by cross
pieces and connected side walls, the said strip being composed of a harder metal
than the rim and being longitudinally bent on a substantially central line to form
the cross pieces into jackets to embrace the sides of the teeth and form wearing
surfaces thereof, and leave the side walls embracing the sides of the rim and
forming the wearing surfaces thereof between the teeth, substantially as described.
4. A sprocket-wheel comprising the following instrumentalities, viz. :-A metal
rim provided with teeth, a center or body portion attached to said rim, and a
re-enforcing connected jacket embracing both sides of the said teeth and the said

page_text: rim, and consisting of a metal strip provided with openings separated by cross
pieces and connected side walls, and bent longitudinally on a substantially central
line, the said cross pieces embracing the sides of the teeth and the said side walls
embracing the sides of the rim, the openings in the jacket leaving uncovered the
front and rear ends of the teeth and the outer circumference of the rim between
the teeth, substantially as described.
Doted the 2nd day of December 1805
D. YOUNG & Co.,
11 & 12 Southampton Buildings, London, W.C.,
Agents for the Applicant.