Year: 1899

page_text: Date of Application, 2nd Mar., 1899
Complete Specification Left, 2nd Dec., 1899-Accepted, 20th Jan., 1900
I, HAROLD DENNIS TAYLOR; of Trenfield, Holgate, York, Optician, and a Director
of T. Cooke & Sons, Ltd., Buckingham Works, York, do hereby declare the nature of
this invention to be as follows:-
In the accompanying drawings the upper diagram is a side view of my chain and a
sprocket wheel. To the left it is shown more or less in section and partially
wrapped upon the wheel B; & in elevation to the right. The lower figure is partly
horizontal section and partly plan. It consists essentially of open or built up links
alternating with solid links L, L &c., which latter are preferably kept as short. as
possible. Thus a complete link consists of one open liuk and one solid link jointed
together, and any number of complete links inay form a chain. The open links are
formed of two side plates s, s &c. placed parallel to and opposite one another and
coupled together by three shouldered rivets p etc. Each end rivet passes through the
bore of the next solid link L, while the rivet which is fixed between the centres of the
side plates acts as a pivot on which rotates one of the driving rollers 7. In the form
of the chain shown in the drawings, each driving roller does not rotate directly'
upon its rivet, but I place between the rivet & the inner periphery of the roller a set
of small hard steel wires placed parallel to the rivet and of same length as the roller ».
These act as comparatively frictionless roller bearings for the driving roller's r&c.
Also, between the inner periphery of the holes bored through the solid links L &c, and
the rivets connecting the side plates 8-8, which pass through them I place a similar
set of anti friction rollers a,―a. Thus each chain joint & driving roller works very
freely upon roller bearings.
My device of mounting the driving rollers r, &c. half way & in a straight line
between the two end rivets of each open link enables me to arrive at a very favourable
form of tooth for the sprocket wheels, as may be seen from the drawings. B is sup-
posed to be the back sprocket wheel & the chain is pulling it round from left to right
& transmits its pull to the wheel teeth by means of the driving rollers r; r &c. only,
no other parts of the chain being allowed to come into working contact with the
wheel. It is also obvious that, when the chain is wrapped around the sprocket wheel,
the driving roller's r, &c. fall, nearer to the centre of the sprocket wheel than the
chain joints. This leads to the teeth being actually undercut on their rear flanks &
obviates all tendency for the teeth to exert a wedging off action on the chain or for
the driving rollers to mount up the flanks of the teeth. Thus the teeth receive the
pull of the chain in a direction which also tends to keep the driving rollers home
against the wheel until the moment arrives when the rollers should begin to leave it.
In the case of the front or large sprocket wheel the teeth are reversed in general shape;
their front or preceding flanks being undercut & imparting the thrust to the driving
rollers of the chain. Thus the chain is so placed upon the sprocket wheels that the
driving rollers fall in front of the teeth of the front or driving sprocket wheel and fall
behind the teeth of the rear or driven sprocket wheel. Thus, when driving forward,
the driving rollers r, r &c. receive & impart the propelling force from & to the sprocket

page_text: wheels and the solid links or chain joints only come into working contact with the
sprocket wheel teeth when back pedalling: This form of chain is designed to be specially
free from friction, owing to the joints and driving rollers all being mounted on roller
bearings; but I can also make my chain in another & cheaper -form in which the
roller bearings are dispensed with & both the driving rollers 7 and the solid links L
are made to fit over & directly work upon their respective rivets.
I reserve the working details of both forms of my chain to be more exactly set forth
in my Complete Specification.
1
1000
I, HAROLD DENNIS TAYLOR, of Trenfield, Holgate, York, Optician, and a Director
of the Firm of T. Cooke & Sons, Limited, Buckingham Works, York, 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:-
Since filing my Provisional Specification 1 have not found it requisite to make any
alteration in the essential construction of the form of chain described therein except
in the way of modifying the relative lengths of the blocks and open links of which
each complete section is composed.
Sheet gives full details of my invention. The uppermost figure is partly a plan,
on the right hand and partly a horizontal section, on the left hand, of a short length
of my chain, which is composed of any number of what I may call "sections" each
section being composed of a short and practically solid joining link L jointed to a
longer open link S composed of two side plates $ rivetted together by two end
rivets and a centre rivet on which last is mounted an anti friction driving roller R.
The lower figure is a detailed side view of the chain shown partly in vertical section
near A where it is shaded, partly in side elevation above the letter D, and the rest,
where it coils around the two sprocket wheels A and B, in outline section showing
how the chain engages with the teeth of the sprocket wheels.
The objects I have had in view in inventing this chain and the appropriate forms
of sprocket wheel teeth for cycles are as follows:-
First to substantially get rid of the friction which attends the working of the
majority of cycle chains and at the same time to retain the-well known superior
strength of the block chain as far as possible.
The friction attendant upon the working of an ordinary block chain arises first
from the bending of the chain joints as the chain-coils upon or uncoils from the
sprocket wheels and secondly from the rubbing of the ends of the blocks against the
sides or flanks of the sprocket wheel teeth as the blocks settle down between or rise
from between the said teeth.
In order to get rid of the first form of friction I make use of a set of roller bear-
ings between each joint rivet and the block L, the two ends of the said blocks
being bored out about a tenth of an inch larger than the rivets in order to leave
room for the set of rollers w, which are pieces of hardened steel wire about inch
long and about 05 thick. But I claim no novelty for the use of roller bearings as
applied to the chain joints, the device having been publicly described before; but I
employ the device as supplementary to the novel features of my chain. I thus get
rid of the joint friction. In order to get rid of the friction attendant upon the chain
blocks rubbing against the flanks of the sprocket wheel teeth I resort to the plan of

page_text: keeping the blocks out of real contact with the teeth and employing a separate
driving roller R to engage with the teeth of the sprocket wheels. One of these
driving rollers is mounted upon frictionless roller bearings in the centre of each open
link upon a pivot firmly fixed in and connecting the centres of the two side plates S.
The two ends of each pair of side plates are also firmly connected together by the
rivets which I have above alluded to as forming the joint pivots.
The driving rollers R come in front of the teeth of the large sprocket wheel B
which is mounted upon the crank axle and receive the thrust from it, whereas they
come behind the teeth of the back sprocket wheel A and impart the pull thereto.
At the same time the chain joints or blocks L do not actually touch the sprocket
teeth nor need they actually touch the edge of the wheel. Mounting the driving
roller R in the centre of each open link permits a form of sprocket tooth to be em-
ployed which is far better adapted to give or receive the thrust without loss of power
or slipping, than the usual form of tooth.
In the case of the tooth shown near the letter A in the back sprocket wheel it is
easy to see that the limiting forms of the tooth which will just permit of the chain
wrapping on or unwrapping from the wheel with freedom are defined thus. In the
first place the curve of the lower left hand part or base of the tooth A will best be a
circular curve,. about a quadrant, to fit the roller R, while the upper left hand part or
flank of the tooth is a circular curve whose centre is the centre of the next joint on
the right which lies on the opposite side of the tooth. The mutual tangent ₺ to both
these curves obviously does not point to the centre of the sprocket wheel but forward
of it by an amount equal to the radius of the driving roller R. Thus the surface of
the tooth just where it receives the full thrust from the driving roller R is undercut
and instead of there being any tendency for the thrust partly resolving itself into a
force causing the roller to mount up on the tooth or wedge off, there is a tendency,
if anything, for the roller to keep itself bedded at the bottom of the tooth. As to
the opposite side of the tooth, its contour is composed of a hollow circular base
almost fitting or concentric with the circular end of the block L, while the upper
flank is a circular curve having its centre at the centre of the next chain joint on the
left. Hence the mutual tangent to the two curves is parallel to the tangent t-t and
the front side of the tooth is overcut. But this overcut flank of the tooth is not
brought into action or contact with the adjacent chain block unless back pedalling
is resorted to, when the wedging off action between wheel and chain is of no conse-
quence.
In the case of the front or driving sprocket wheel B it will be easily seen that the
mutual tangent t-t to the two curves forming the front contour of the tooth B falls
behind the centre of the sprocket wheel by a distance equal to the radius of the
driving roller R. Thus the front of the tooth which drives the chain is undercut
and the back of the tooth. is overcut. Here again there is no wedging off tendency
but the opposite tendency for the rollers R to keep home in the bottom of the
tooth.
It will be noticed that a straight line drawn down the centre of any one of the
teeth intermediate to the tangents t―t does not pass through the centre of the sprocket
wheel as does the centre line of the ordinary sprocket tooth and the teeth may be
described as eccentric, being far to one side of the centre of each open link. . In the
case of ordinary sprocket wheels and chains each sprocket tooth occupies the centre
of each open link and it will easily be seen that in such case the two flanks of the
tooth must be overcut shaped in order that the chain may coil and uncoil freely.
The tangents to the flanks where cut by the pitch circle must embrace the centre of
the sprocket wheel between them.
While that part of each tooth which is close to the pitch circle or middle line of
the chain is thus shaped, I yet recommend that the flanks of the teeth nearer their
points be cut-away slightly more in order to ensure more certainty of clearance when
the chain coils upon or uncoils from the sprocket wheels.
For this purpose I place the centres of the curves forming the contours of the
points of the teeth not exactly at the centres of the adjacent chain joints but points

page_text: 03 in. nearer to the centre of the sprocket wheels. Sheet 1 gives the correct form
of teeth for sprocket wheels of 6 and 14 teeth respectively, supposing that the pitch
of the chain or distance between the centre of one driving roller R and the next one
is 1.5 inches. That is 1.5 inches is the length of one complete section of the chain, each
.section being composed of a solid link or block L of a length of 4 inches between
centre and centre of its two bores and rivets, and an open link composed of two side
plates S conrected by three rivets of which the centre one carries the driving roller,
while the length between centre and centre of the two end rivets is 1.1 inches.
On Sheet 2 are given correct drawings of two teeth each for sprocket wheels having
the various numbers of teeth indicated by the figures below them. At G and G are
shown examples of two templets or guages, for testing the forms of the teeth when
actually cutting them, the heel furnishing a check upon the cutters being set to
the proper tilt. The tip of h should only just touch the bottom of the place where
the next driving roller rests, when the templet fits correctly between and against the
two teeth. In order to make these diagrams correct for taking off the forms of such
templets of guages it will be first be necessary to enlarge them by careful photo-
graphing until the scale of inches actually reads to inches exactly. At D is shown a
cross section, viewed in the plane of the wheel of one of the teeth. The pitch circle
should be considered to pass through the centres of the driving rollers R when home
on the wheel; but the bottoms of such driving rollers will of course rest upon the
very bottoms of the spaces between the teeth and I call the circle which just touches
the driving rollers when home the inner pitch circle. Its diameter is obviously less
than the diameter of the pitch circle by the diameter of the driving rollers and it
forms the lower or inner limit to which the spaces between the teeth must be cut out.
On each side of every sprocket wheel there is a flange or ledge shown in section at D,
mainly for giving strength to the wheel. In cutting these sprocket wheels the out-
side periphery of this flange is first turned in the lathe until of a diameter exactly
equal to the inner pitch circle which is necessary for the particular number of teeth
required, and given in the following tables. Then when cutting the teeth the cutter
which cuts out the part where the driving rollers fall must cut only just deep enough
to graze the flange or inner pitch circle. Then the wheel is of the correct diameter
and the templet or gauge appropriate to that number of teeth settles the rest.
Since this chain when wrapped around a wheel forms a mixed polygon, special
formula have to be used for calculating the sizes of the inner pitch circles and of the
outer circles which pass through the centres of the chain joints.
If N is the number of teeth required then
360°
2 N
gives a certain angle Q; then the
=
•55
cosec. qo
or
angle Q must be divided into two parts p and q such that cosec. p
cosec. p=2.75 cosec. q. Then 2 (half the length of chain block) multiplied by
cosec. "p") will give the radius "t" of outer circle passing through centres of the
chain joints. And then "t" multiplied by cosine "q" will give the radius " v" of
the circle which passes through the centres of the driving rollers.
_
Then 2 w (w being the diameter of the driving rollers, here supposed to be
35 inch) will give the diameter of the inner pitch circle, to which the flange is
turned.
In this way the following table of inner pitch circles has been calculated. -

page_text: The width of the chain blocks and teeth measured parallel to the axes of the
sprocket wheels is 25 in. The width between the side plates of the open links is
26 in. the diameter of the rivets is 15 in. and they are supposed to be shoul lered
down to 125 in. where they enter the side plates.
The side plates are about 05 thick, and the holes bored through the solid links are
about 25 diameter and the wire rollers about 05 diameter.
At the chain junction a solid link may have one of its holes bored smaller in order
to fit the connecting pin.
my said
Having now particularly described and ascertained the nature of
invention and in what manner the same is to be performed I declare that what I
claim is :-
1. A gear chain for cycles, composed of any number of complete sections, each
section being composed of a short and practically solid joining link jointed to a longer
open link formed of two side plates joined together by three rivets and carrying a
hollow cylindrical anti friction driving roller mounted upon roller bearings disposed
round the middle rivet, which is placed half way and in a straight line between the
centres of the two adjacent chain joints; which anti friction driving rollers bed
themselves behind the teeth of the rear or hub sprocket wheel and transmit the pull
thereto and bed themselves in front of the teeth of the crank sprocket wheel and
receive the thrust therefrom and are the only parts of the chain allowed to come into
working contact with the flanks and bases of the sprocket, wheel teeth, while the
form of the latter is such that their flanks which receive or give the thrust in forward
driving are slightly undercut, thereby obviating any slipping or wedging off reaction
between the chain and sprocket wheels.
2. The combination of parts forming the sections of a gear chain for cycles sub-
stantially as illustrated by the accompanying drawings and herein described.
3. Sprocket wheels for cycles having teeth substantially as herein described and
illustrated for use in conjunction with the form of chain substantially as herein
described and illustrated.
Dated this 30th day of November 1899