Improvements in Sprocket Gears
Year: 1897

page_text: Improvements in Sprocket Gears,
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, do hereby
declare the nature of this invention to be as follows:-
--
This invention is an improvement in sprocket and chain gear, more especially
adapted for use in bicycles and other velocipedes, but applicable generally to other
purposes for which such devices are employed. "
In all ordinary sprocket wheels such as are commonly used on bicycles and other
velocipedes, whether driving or driven by a chain composed of open and solid links,
there is a serious loss of power due to friction between the solid links and the
periphery of the sprocket wheel. This friction occurs at points immediately
adjacent to each tooth and on the side opposite to that upon which the pull or
stress between sprocket and chain is exerted, and which, for convenience, may be
considered as being in front of the teeth.
This is due to the fact that since the peripheral surface or edge of the sprocket
wheels conforms practically to a circle from which the teeth project radially, the
ends of the solid links of the chain not only rest, but fulcrum, upon the periphery
of the sprocket, the ends which lie over the points in front of the teeth actually
turning about their pivotal connections with the open links while in such contact
with the sprocket.
This action wears out depressions in the sprocket at the points indicated, which
are easily observable in every sprocket of this kind after even a comparatively
short period of use.
If the direction of the application of the power be reversed, as in back-pedalling,
the tendency to wear is shifted to the other side of the teeth, or to what then
becomes, with relation to the direction of applied and transmitted power, the front
of the teeth. Such wear is not, however, so objectionable, and in fact the friction.
may even be an advantage in adding to the force exerted in back-pedalling to
restrain the movement of the wheel.
In order to obviate the wear occurring in the first instance, and the consequent
loss of power due to friction, sprockets have been devised of a special character in
which the position of engagement of the open links of the chain with the teeth is
such that the solid links turn on their pivotal connections with the engaging links
out of contact with the edge of the sprocket.
This plan, although effective, involves a form of sprocket which is not as readily
and cheaply made as the ordinary sprocket, and it was with the object of overcoming
this objection that the present invention was devised.
The improved sprocket resembles those ordinarily made, except in the form of
the teeth. The distinction between the new and previous forms lies in this, that it
is cut in such form that there will be practically no tendency of the solid links to

page_text: turn with reference to the open links at any point where they are held by the
tension of the chain in contact with the sprocket, the relative movement
between the members of the chain being confined to the turning of the open
links with reference to the solid links except, of course, at the points where the
chain leaves the driving or reaches the driven sprocket, and where it is not under
tension.
This is accomplished, in general, by cutting the sprocket in such manner that
supporting surfaces for those ends of the solid links which receive or apply the
pressure are provided immediately back of the several teeth, while the remaining
portions of the periphery of the wheel between any two teeth is cut away so as not
to afford a fulcrum support for the solid links.
If this plan be followed, it is evident that each pivotal point between the open
and solid links immediately in front of a tooth will lie in the same right line
with two pivotal points on opposite sides of it, which lie immediately back of the
'teeth.
In a driven sprocket constructed on this plan, when any one of the open links is
raised from the wheel and disengaged from a tooth, the pivotal movement which
takes place between such link and the solid link immediately back of the tooth
from which it is lifted is transferred to the pivotal connection back of the next tooth
in the rear, and no sensible movement of the links relatively to each other takes
place between two teeth.
In the case of the driving sprocket, a similar action takes place, but when the
direction of the applied force is reversed, as in back-pedalling, the solid links will
turn with reference to the open links, and while in contact under strain with the
edge of the sprocket. This form of sprocket, therefore does not avoid the wear
incident to friction independently of the direction of applied and transmitted force,
but this may not be an objection, as the loss due to friction may be utilized in back-
pedalling, or in general when power is applied, for the purpose of retarding the
rotation of the sprockets.
This effect may be increased in a useful manner in some applications of the
invention, as in bicycles, by cutting or forming the sprockets so that the points of
support for the ends of the solid links immediately back of the teeth, are upon
ledges or shoulders, either flat or hollowed out, but so that the bearing surface
remote from the tooth against which the ledge abuts is inclined away from the
centre of the wheel. In such a sprocket, when the direction of applied or trans-
mitted power is reversed, any tendency of the solid links to ride up the sides of
the teeth forces those ends which rest upon the ledges or shoulders over the inclined
portions of the ledges, and this has a similar effect to increasing the diameter of the
sprockets, and thereby tightening the chain.
In one sprocket, for example, the driven sprocket, there will be little or no wear
on the pivotal connections immediately in front of the teeth, but in the other or
driving sprocket the wear falls on these connections and not on the others, so that
the wear on the chain is evenly distributed.
The improvement is not limited to the precise form of sprocket wheels described,
as it is evident that the form may be considerably modified while still retaining the
essential features and advantages of the invention.
Dated this 11th down of Tenu 1907
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant,

page_text: 43335
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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 is an improvement in sprocket and chain gear, more especially
adapted for use in bicycles and other velocipedes, but applicable generally to other ·
purposes for which such devices are employed.
In all ordinary sprocket wheels such as are commonly used on bicycles and other
velocipedes, whether driving or driven by a chain composed of open and solid links,
there is a serious loss of power due to friction between the solid links and the
periphery of the sprocket wheel. This friction occurs at points immediately
adjacent to each tooth and on the side opposite to that upon which the pull or
stress between sprocket and chain is exerted, and which, for convenience, may be.
considered as being in front of the teeth.
This is due to the fact that since the peripheral súrface or edge of the
sprocket wheel conforms practically to a circle from which the teeth project
radially, the ends of the solid links of the chain not only rest, but fulcrum, upon
the periphery of the sprocket, the ends which lie over the points in front of the
teeth actually turning about their pivotal connections with the open links while in
such contact with the sprocket.
This action wears out depressions in the sprocket at the points indicated, which
are easily observable in every sprocket of this kind after even a comparatively
short period of use.
If the direction of the application of the power be reversed, as would be the case
when a rider of a bicycle applies power to the pedals to check the forward
movement of the machine, the tendency to wear is shifted to the other side of the
teeth, or to what then becomes, with relation to the direction of applied and
transmitted power, the front of the teeth. Such wear is not, however, so
objectionable, and in fact the friction may even be an advantage in adding to
the force exerted in holding back the pedals to restrain the movement of the
wheel.
In order to obviate the wear occurring in the first instance, and the consequent
loss of power due to friction, sprockets have been devised of a special character in
which the position of engagement of the open links of the chain with the teeth is
such that the solid links turn on their pivotal connections with the engaging links
out of contact with the edge of the sprocket.
This plan, although effective, involves a form of sprocket which is not as readily
and cheaply made as the ordinary sprocket, and it was with the object of
overcoming this objection that the present invention was devised.
The improved sprocket resembles those ordinarily made, except in the form of
the teeth. The distinction between the present and the previous forms lies in this,
that the former is cut in such form that there will be practically no tendency of
the solid links to turn with reference to the open links at any point where they are
held by the tension of the chain in contact with the sprocket, the relative
movement between the members of the chain being confined to the turning of the
open links, with reference to the solid links except, of course, at the points where
the chain leaves the driving or reaches the driven sprocket, and where it is not
under tension.
This is accomplished, in general, by cutting the sprocket in such manner that
supporting surfaces for those ends of the solid links which receive or apply the

page_text: pressure are provided immediately back of the several teeth, while the remaining
portion of the periphery of the wheel between any two teeth is cut away so as not
to afford a fulcrum support for the solid links.
If this plan be followed, it is evident that each pivotal point between the open
and solid links immediately in front of a tooth will lie in the same right line
with two pivotal points on opposite sides of it, which lie immediately back of the
teeth.
In a driven sprocket constructed on this plan, when any one of the open links is
raised from the wheel and disengaged from a tooth, the pivotal movement which
takes place between such link and the solid link immediately back of the tooth
from which it is lifted is transferred to the pivotal connection back of the next
tooth in the rear, and no sensible movement of the links relatively to each other
takes place between two teeth.
In the case of the driving sprocket, a similar action takes place, but when the
direction of the applied force is reversed, as in applying pressure to the pedals to
check the forward movement of the wheel, the solid links will turn with reference
to the open links, and while in contact under strain with the edge of the sprocket.
This form of sprocket, therefore, does not avoid the wear incident to friction
independently of the direction of applied and transmitted force, but this may not
be an objection, as the loss due to friction may be utilized when power is applied,
for the purpose of retarding the rotation of the sprockets.
This effect may be increased in a useful manner in some applications of the
invention, as in bicycles, by cutting or forming the sprockets so that the points of
support for the ends of the solid links immediately back of the teeth, are upon
ledges or shoulders, either flat or hollowed out, but so that the bearing surface
remote from the tooth against which the ledge abuts is inclined away from the
center of the wheel. In such a sprocket, when the direction of applied or trans-
mitted power is reversed, any tendency of the solid links to ride up the sides of the
teeth forces those ends which rest upon the ledges or shoulders over the inclined
portions of the ledges, and this has a similar effect to increasing the diameter of
the sprockets, and thereby tightening the chain.
In one sprocket, for example, the driven sprocket, there will be little or no wear
on the pivotal connections immediately in front of the teeth, but in the other
or driving sprocket the wear falls on these connections and not on the others, so
that the wear on the chain is evenly distributed.
The improvement
not limited to the precise form of sprocket wheels described,
as it is evident that the form may be considerably modified while still retaining the
essential features and advantages of the invention.
Referring now to the drawing which illustrates the improved sprocket and chain
gearing:
Fig. 1 is a view of the driving and driven sprocket and chain ;
Fig. 2 is a side view of a sprocket wheel and chain embodying the invention, but
of modified form.
Assume that in Fig. 1 the pull on the chain is in the direction of the arrow.
Then ordinarily there will be a tendency of the solid links A to fulcrum on the
periphery of the sprockets at the points a which may be considered as lying in
front of the teeth B. But if the portions of the sprocket between the teeth be so
formed that the links do not touch the periphery in front of the teeth, but are
supported by the other links which rest upon the periphery immediately back of
the teeth, or in other words, if the sprocket be cut so that any three pivotal
points b, c, d, lic in a right line, no such effect is produced. In such case when any
link as C, during the rotation of the wheel, is lifted off from a tooth B, the pivotal
movement at b is transferred to d and no sensible movement of the links relatively
to each other takes place at c.
To better utilize the frictional effect for retarding the movement of the sprockets
the latter may be cut as shown in Fig. 2. In this case the points of support for
the ends of the solid links immediately back of the teeth, are upon ledges or

page_text: shoulders D, either flat or hollowed out, but so that the bearing surface remote
from the teeth against which the ledges abut will be inclined away from the center
of the wheel. In such sprocket, as above stated, when the direction of applied or
transmitted power is reversed, any tendency of the solid links to ride up the sides
of the teeth forces those ends which rest upon the ledges or shoulders D over the
inclined portions of the ledges, and this has a similar effect to increasing the
diameter of the sprockets, and thereby tightening the chain.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is :-
1. The combination of a sprocket wheel and a sprocket chain composed of open
and solid links, the solid links entering between the teeth, and the wheel being
cut or formed between each two teeth with a peripheral supporting surface for
one end of the solid link and a peripheral cut-away or relatively lower portion for
reception of the other end of the solid link without affording fulerum support
for the same.
2. The combination of a sprocket wheel and a sprocket chain composed of open
and solid links, the solid links entering between the teeth and the wheel being
cut or formed between each two teeth with a peripheral supporting surface
adjacent to one tooth for one end of a solid link, the said surface inclining
outwardly from the teeth, and with the remaining portion of the space between
the two teeth cut away for the reception of the other end of the solid link without
affording fulcrum support for the same.
Dated this 10th da
1007
HASELTINE, LAKE & Co.,
45 Southampton Buildings, W.C., Agents for the Applicant.