Year: 1896

page_text: I, THOMAS CURLEY, of 98 Lyman Street, in the City of Waltham, in the County
of Middlesex, and State of Massachusetts, United States of America, Attorney
at Law, do hereby declare the nature of this invention to be as follows:-
The invention has reference to improvements in devices wherein power is trans-
mitted from one sprocket gear rotatably mounted to another sprocket gear, also
rotatable.
The objects which are sought to be attained by the improvements herein dis-
closed, are, the reduction in the wear on the sprockets and chain, by reducing the
friction between these parts, and the increased efficiency of action between the
sprocket and the chain."
To more clearly define my invention, it may be stated that the gears, to which
the improvements are particularly applicable, usually consist of a pair of disks,
each mounted to rotate, and having teeth extending radially from their peripheries.
These disks are connected by a chain formed of a series of blocks, which are
adapted to be received between the teeth of the disks, and side plates pivoted to
the blocks, which, as the chain passes over the disks, receive the teeth between
them.
The blocks pass on to the peripheries of the disks, or sprockets, tangentially to
the peripheries, and leave the same in similar directions, so that, in passing on to
the sprockets, the forward portions of the blocks first seat themselves against the
peripheries, then, as the chain seeks the circular peripheral path of the
sprockets, the front portions of the blocks are ground against the peripheries of
the sprockets, until the rear ends of the blocks seat themselves on the peripheries;
on leaving the sprockets, the grinding action is reversed, as the forward ends of
the blocks first leave the circular path. Thus in passing on and off the sprockets,
grinding action is set up between the ends of the blocks and the peripheries of
the sprockets, which ultimately wears the sprockets, in concavities, to reduced
diameters; the ends of the blocks being also worn, so that while the diametrical
pitch of the sprockets is reduced, the link pitch of the chain is increased.
My invention will be more clearly understood if the pitch line, in its relation
to the chain and sprocket, be defined. The pitch line of the chain, is understood
to be a line drawn through the axes of the pivots, longitudinaly of the chain.
The pitch line of the sprockets is understood to be a circular line on which the
pitch of the sprocket teeth is determined, this line being that in which the teeth
of the sprockets act on the chain. The pitch line of the chain may also be termed
the draft line of the same; as the tendency of the sprocket teeth is to act on the

page_text: chain in this line, while the chain naturally seeks a position on the sprockets
which permits of this action.
In more precisely ascertaining the nature of my invention, I would state that I
construct a pair of sprocket disks each having radially extending sprocket teeth
which are furnished with lateral extensions, the outer surfaces of which lie in the
peripheral pitch line of the sprocket; between the teeth are posts which extend
to this pitch line, and between these posts and the teeth are concavities, or
depressions, which extend into the edge of the disk.
The chain comprises a series of blocks, alternating with pairs of side plates
connected to the ends of the blocks by pivots. The ends of the blocks, and side
plates, extend below the pivots, for a distance equal to the extension of these parts
above the pivots, but intermediate these end portions, the lower edges of the
side plates and blocks are cut away to a straight surface, which lies in the axial
line of the pivots.
It will now be seen, that as the chain passes onto one of the sprockets, the posts,
between the teeth, will enter the cut away portions of the blocks, until the ends
of the posts, lying in the peripheral pitch line of the sprocket, meet the straight
under surfaces of the blocks, which lie in the pitch line of the chain, or in the
axial line of the pivots; the side plates being in like manner, supported by the
lateral extensions of the sprocket teeth.
In the operation of my improved gear, there will be no grinding action by the
ends of the blocks, as these are supported out of contact with the portions of
the sprockets against which, in the ordinary construction, they would grind. The
chain, moreover, does not seek to assume a different position from that designed
for it, as it is supported in a position where the sprocket teeth will act on the chain
directly on its draft line.
My invention may be described, as a chain comprising pivoted portions, con-
suucted to be supported at the axial line of its pivots, and a sprocket constructed
to support the chain at the pitch line of the sprocket. The chain is more
specifically described, as comprising blocks having bodies which lie above the
axial line of the pivots, and engageable ends depending below such line, together
with side plates of similar shape, pivotally secured to the blocks.
Dated the Twenty-first day of October 1896
Improvements in Driving Chains and Sprocket Wheels.
I, THOMAS CURLEY, of 98 Lyman Street, in the City of Waltham, in the County
of Middlesex, and State of Massachusetts, United States of America, Attorney
at Law, 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 improvements in drive-gears, and particularly to that
class of drive-gears in which power is transmitted from one sprocket wheel to
another by means of a chain.
The object of the invention is to increase the effectiveness of action between
the sprocket teeth and chain.

page_text: Another object of the invention is to reduce the wear on the sprocket teeth, and
on the chain.
Another object is to reduce the friction between the chain and the sprocket.
The invention consists in a sprocket wheel having means for supporting the
5 chain on the pitch line of the sprocket, and a chain formed of members constructed
to receive supports on the pitch line of the members.
The invention also consists of a chain comprising link plates and connecting
blocks pivotally connected and cut away at their lower portions to straight surfaces
on lines with the axes of the pivots.
The invention also consists in such other novel features of construction and
combination of parts as shall hereinafter be more fully described and pointed out
in the claims.
Figure 1, represents a side elevation of portions of the chain and the sprockets
which are particularly adapted for use with this chain.
Figure 2, represents a cross-section of a part of the sprockets, showing a section
of one of the chain blocks, on lines b, b, Figure 1.
Figure 3, represents a similar view, taken on a line a, a, Figure 1.
Figure 4, represents a perspective view of a portion of the chain.
Similar numbers of reference designate corresponding parts throughout.
Gears of the nature herein described, generally comprise two sprockets, usually
of different diameters, and a chain which is composed of alternate blocks and pairs
of side links, or plates, pivoted to the ends of the blocks, the ends of the blocks
being somewhat rounded to reduce the friction between them and the sprocket
teeth. The blocks being proportioned to the pitch of the sprocket, so that when
in position on the sprockets, they would rest on the periphery of the wheel,
between the teeth; the side plates of the chain lying at the sides of the teeth.
When such a sprocket is rotated to take up, or drive the chain, the action of the
teeth is against the rear ends of the blocks. Now as one of the teeth carries its
block along, the side plates draw the next block into position to be engaged, at its
rear end, by the succeeding tooth; before this engagement however, the periphery
of the wheel, passing beneath the forward end of the block, receives this portion,
which, as the rear end of the block is brought frim the straight line in which it
approaches the sprocket, to the curved path in which it passes around the sprocket,
grinds on the periphery of the sprocket, this being repeated by the rear end of
the block as its forward end assumes the straight path on leaving the sprocket.
The result of the grinding action of the ends of the blocks against the periphery
of the sprocket, is to wear both. The sprocket being worn into concavities on its
periphery, its diameter is continually and irregularly decreased, while the wear
on the blocks increases the looseness of the chain on the sprockets. Adding to
these the ordinary wear on the pivots of the chain, by which the pitch of the same
is increased, and after slight use, the operation of the gear is irregular, unpleasant
to the operator, and highly destructive to the chain and sprocket.
In carrying my invention into practice, it has been my desire to so construct
a gear of this nature, that this friction on the periphery of the sprockets, and on
the ends of the chain blocks, shall be prevented, and at the same time, to increase
the effectiveness of the chain.
For this purpose, I construct a sprocket having alternate teeth and supporting
members, the teeth having lateral supports for the chain plates, and the supporting
members having their peripheral supporting surfaces lying in the pitch line of the
sprocket. With this sprocket I use a chair the links and blocks of which are
cut away between their ends, to a lower surface lying in the pitch line of the
chain.
In the drawings 5 and 6, indicate sprocket wheels particularly adapted for use
in this gear, the sprocket teeth and the general construction of both being similar;
these sprockets have the engaging teeth 7-7 and the supporting members 8-8
The teeth 7-7 are generally slightly tapering from their bases to their ends, and
have lateral projections 9-9, the upper surfaces of which lie in the peripheral

page_text: pitch line of the sprocket. The supporting members 8-8 extend from the wheel,
only to the peripheral pitch line of the sprocket, and may, or may not, have the
lateral projections 10-10.
The chain comprises a series of blocks 12-12, having the back 13, the circular
ends 14-14, and the straight surface portion 15, which lies in line with the axes
of the circular ends 14-14; this line being the pitch line, and the draft line of
the chain. The blocks 12-12 are connected by the side plates 16-16, pivoted to
the blocks, and corresponding to them in shape, except in thickness, these plates
have the circular ends 17-17 and the lower edge 18, lying in line with the axes
of the ends 17-17.
When the chain passes on to the sprocket, the bodies of the blocks are brought
to bear on the supporting members, and the rear ends 141 of the blocks bear on
the front edges of the teeth 7-7, while the lower edges 18, of the side plates 16
rest on the supporting portions 9-9 of the teeth 7-7. The blocks 12 being thus
supported on the members 8-8, slightly prior to the engagement of the ends 14
by the teeth, and in the pitch and draft line of both the sprocket and the chain,
no wearing action is set up between the ends of the blocks and the periphery of
the sprocket or the edges of the teeth 7-7.
It is thought that the action of undue wear, between the sprocket and the chain,
arises in great measure from the tendency of each to assume, with relation to the
other, the position best adapted to secure the most effective results from both.
The theory here presented being, that the most effective position of the chain and
the sprocket, is such that no obstruction is interposed to prevent the positioning of
the pitch, or draft, line of the chain in the peripheral pitch line of the sprocket.
The province of the members 8-8, is wholly to support the chain blocks, so that
the axial line of their pivots will lie in the peripheral pitch line of the sprocket,
and to accomplish this with the least possible frictional wear between the blocks
and these supports. For this purpose the supports are proportioned to meet the
blocks centrally between the ends 14-14, and must not act as propelling means
for any portion of the chain, therefore the drawing shows a clearance between
the front edge of each support and the depending end of the block. The teeth 7-7,
and the supports 8--8, are independent erections, or extensions, from the periphery
of the sprocket, and the clearance of the ends of the chain members is one of the
results of supporting these members above the periphery.
Having now particularly described and ascertained the nature of my said in-
vention, and in what manner the same is to be performed, I declare that what I
claim is
Claim 1. In a drive-gear, a sprocket chain comprising blocks, having bodies
lying above the draft line of the chain, and engageable ends depending below
such line, and side plates pivoted to said blocks, and having bodies lying wholly
above the draft line of the chain.
Claim 2. In a drive-gear, the combination with a wheel having sprocket teeth and
supports, the supporting surfaces of the supports fying in the peripheral pitch line
of the sprocket, of a pivoted link chain, having engageable portions connected by
bodies lying outside the axial line of the pivots.
Claim 3. A drive-gear sprocket having a series of drive teeth arranged around its
periphery and furnished with lateral extensions, the supporting surfaces of which
are in the peripheral pitch line of the sprocket, and a series of independent sup-
ports arranged alternately with the teeth, extending from the periphery of the
sprocket, and adapted to act wholly in said peripheral pitch line.
Claim 4. The combination with the sprocket 5 having the teeth 7-7 and mem-
hers 8-8, the teeth 7-7 having lateral projections, of a chain comprising a series
of blocks 12 having the ends 14--14' and the surfaces 15 extending in the axial
plane of said ends, and the plates 16-16 pivoted to the blocks and having the
end portions 17-17 and the lower edges 18, as described.

page_text: Claim 5. In a drive-gear, a chain comprising pivoted portions constructed to
be supported at the pitch line of the chain, in combination with a sprocket having
means for supporting such chain in the pitch line of the sprocket.
Dated
this First day or
THOMAS CURLEY.
Haseltine, Lake & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.