Improvements in Sprocket Wheels.
Year: 1896

page_text: Date of Application, 13th June, 1896-Accepted, 18th July, 1896
Improvements in Sprocket Wheels.
I, ALFRED THOMAS MASON, No. 50 Buel Street, in the City of Pittsfield, in
the County of Berkshire and State of Massachusetts, United States of America,
Professor of Music, 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 transmission of power by sprocket wheel and chain
connections as employed, for example, in power-driven vehicles, or in places where
positive transmission of power is desired, and has for its object the improved
construction of the sprocket-wheels of such power transmitting devices, whereby
the friction between said wheel and its chain is reduced to a minimum; and the
invention consists in the construction of the said sprocket-wheel, as hereinafter
fully set forth in the specification and pointed out in the claims.
In the drawings forming part of this specification,-
Figure 1 is a side elevation of two sprocket-wheels embodying this invention,
and a chain connecting said two wheels.
Figure 2 is a top edge view of one of said sprocket-wheels.
Figure 3 is a section through a portion of the sprocket-wheel and chain on
line 3-3, Figure 1.
Figure 4 is a similar section on line 4-4, Figure 1.
Referring to the drawings, A. A', are two sprocket-wheels provided with the
teeth a, of the usual construction. The face of the said wheel, where the base of
the teeth unites with said face, is made wider than the bases of said teeth providing
thereby the flanged portion F, of about the width of the thickness of the side
links d, of the chain H, and whereon portions of said links have a bearing. The
said chain is made up of the blocks m, and the side links d, pivotally connected to
each other by the pins o, in the usual manuer.
On the face of the sprocket-wheel, where the under side of the chain members
bear thereon, portions of said face are cut away, as at D, on the flanged portion F,
and at E, substantially midway between the edges of said flanged portion. The
purpose of the said cuts D and E, in the edges and face of the sprocket-wheel is
to the end that where the members of the chain H, pass over the face of the wheel
in engagement with the teeth a, thereof, that the ends of said chain members d,
may bear on the flanged portion F, only when one end of the chain members m,
with which said members d, are pivotally connected, finds itself located over the
depression E, cut in the face of the wheel; that is to say, (referring to Figure 2,)
that when one end of a block m, has a bearing on the portion D2, of the face of the
wheel, its other end is over the depression E, therein, and is supported only by the
pin o, passing through it and its side links d, d, which have a bearing on the flanged
portion F, outside of the line of the sprocket-teeth a. And the end of said block m,
bearing on the portion D2, of the face of the wheel, supports the ends of the next
following pair of said members d, d, which are connected pivotally to it by the
più o, passing through said members d, d, and m, the ends of said members d, as
shown, being in a position directly over the cut-away portions D, D, on the edges
of the face of the wheel; and said ends d, d, have no other support than said pin o,
while so located over said cuts D, D.
Therefore, when one end of said chain member m, bears on the face of the
sprocket-wheel, the ends of the members d, d, which are pivotally connected

page_text: thereto, are free from all contact with said sprocket-wheel and are, therefore, free
to revolve on the pivot-pins o, without friction, while said ends of the members d, d,
are so supported over the cut-away portions D, of the sprocket-wheel, by the
bearing of the member m, of the chain H, on the face of the wheel, that the
opposite ends of the members d, d, are in contact with the face of the wheel on
the flanged portion F, thereof, and are supporting, free from contact with the face
of the sprocket-wheel, the end of the next member w, of said chain.
Therefore, it will be observed that as the chain passes onto the top of the driving
sprocket A, during the rotation of the latter in the direction of the arrow (see
Figure 1,) the ends of the side members d, d, which have last come in contact with
the upper side of the said sprocket-wheel, (which ends for clearer identification
are numbered 2,) are supporting between them, by means of the pin o, the forward
end of the block-member m, which, until its opposite end, (following the rotary
movement of the wheel A), finds a bearing on the face of the said wheel at the
base of the next following tooth a, is free from contact at any point with the face
of the sprocket, or the tooth thereon.
When said opposite end of block m, falls into its place in front of said tooth, as
above described, it bears on the solid portion of the face of the wheel between the
two oppositely located cuts D, D, thereby supporting the ends of the next
advancing pair of side members d, d, free from contact with the flanged portion F,
of the face of the wheel, and in which position said side members are free to rotate
about their pin o, free from contact at any point with the face of the said sprocket-
wheel or tooth.
As each successive division of the chain H, arrives at a position for engagement
with the teeth a, of the driving or driven sprocket-wheels, the above movements
are repeated, and it is, therefore, apparent that the deflection of the chain from a
substantially straight line to the curvature of the sprocket-wheel, whether said
wheel be of large or small diameter, takes place with practically no friction
between the chain members and the teeth or face of the sprocket-wheel, for the
reason that one end of each member of the chain is always free from contact with
the surface of the wheel over which it is passing, and can, therefore, take its proper
position on a sprocket-wheel of any diameter without friction between it and the
surface of said wheel. .
The above statement applies equally when the chain H, leaves the sprocket-
wheel at its lower side.
This construction of sprocket-wheel can be adapted to any form of driving-chain
with slight variations in the positions of the cut-away portions thereof.
It is obvious also, that slight variations in the construction above described may
be practised without departing from the spirit of this invention, which consists
essentially in preventing the contact with the periphery or face of the sprocket-
wheel, or a tooth thereon, of the forwardly advancing ends of either the central
block portions m, or side portions d, d, if a sprocket-chain, and which ends
maintain said positions of non-contact during the period of engagement of the
chain with the sprocket-wheel.
One of the above referred to variations in construction by which the above
described action could be obtained would be to make a wheel having in front of
each tooth thereon a raised portion of about the width of the said tooth whereby
the rear end of the members m, would be supported at a greater distance from the
center said wheel than the forward end of said member m, thereby doing away
with the cut-away portion E, E, in the edges of the face of the wheel; and the
rear ends of the side links d, d, could be made of larger diameter than the forward
end of the members m, to which they are connected, whereby said forward ends of
the members m, of the chain would be supported free from contact with the face
of the sprocket thereby doing away with cut-away central portion D, of the
face of the wheel; but such construction has not been found in practice to give as
good results as that shown in the drawings, wherein it is seen that the pivot-pins o
in their course around the sprocket-wheel are at equal distances from the axis of

page_text: the wheel; whereas in the above described variations, the centers of the pivot-
pins o, are at varying distances from said axis and the chain does not run as
smoothly as when the sprocket-wheel is constructed according to the drawings
forming part of this specification.
It is obvious, also, that by omitting either one of the cut-away portions D, D,
or E, and using the other alone, that the friction of the chain on the wheel would
be materially reduced, as compared with a sprocket not provided with said cut-away
portion; such a construction, though not desirable, would still be within the scope
of this invention.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The herein described sprocket-wheel having clearance spaces in the peripheral
surface of said sprocket-wheel, which spaces are alternately in line with the side
members, and with the central members of the chain elements running on said
wheel, whereby the contact of one end of each of said side and central members of the
sprocket-chain with the peripheral surface of said wheel is prevented, substantially
as described.
2. The herein described sprocket-wheel having on its periphery alternating
bearing surfaces for one end only of the side members and central members of the
links of a sprocket-chain, substantially as described.
3. A sprocket-wheel provided with teeth of less width than its face, flanges along
its opposite edges and which are provided with depressions adjacent to the teeth,
and the depressions E, at the forward ends of the spaces between the teeth,.
substantially as described.
4. A sprocket-wheel provided with teeth of less width than its face, and provided
with a flange along each of its outer edges, so as to form depressions between the
teeth and flanges in the peripheral face of the wheel, substantially as set forth.
5. A sprocket-wheel having teeth of less width than its face and flanges along
each edge, the flanges being provided with depressions just in advance of the
teeth, and the clearance spaces between the teeth and flanges with depressions in.
the rear of the teeth, substantially as set forth.
De 5th day of June 1906
ALFRED THOMAS MASON.
Haseltine, Lake & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.