Improvements in Chain Gearing for Cycles.
Year: 1897

page_text: COMPLETE
SPECIFICATION.
Improvements in Chain Gearing for Cycles.
I, WILLIAM SCOTT, of 76, Agnes Street, Belfast, Ireland, Engineer, 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
These improvements refer to the driving chains of the "block" type and are
intended to minimise the number of stretching and wearing points and also to enable
a block chain to be used with fine pitches of wheels.
In the ordinary block chain the block link fits in between two teeth of the driving
wheels giving one link to each pitch of wheel each link having two driving faces and
two rivets and stretching points for each pitch or tooth of wheel. In my improved
chain the block link has a tooth at each end which are connected by a curved bridge
rising in the middle high enough to pass above the wheel or tooth without touching
it. This double tooth link has four driving faces on it and is capable of engaging
with two teeth or pitches of the wheel at the same time and has only one rivet or
stretching point for each pitch of wheel.
In each alternate link of this form of chain no stretch can possibly take place and
therefore the pitch of the whole chain is more accurately maintained than in any
other form.
The block links are connected by side links of equal pitch which pass over the side
of wheel guiding the chain in the usual way.
The construction is shown in drawing Figs. 1—1—1.
This form of chain can be made in any pitch, it works on the wheels after the
manner of roller chains the same wheels being suitable for both.
In another form of double tooth block link Fig. 2, the teeth are connected by a
straight bridge running right through the middle. The teeth project from each side
as shown in drawing Figs. 3. This bridge is made thin so as not to make the chain
too broad strength being secured by additional depth.
This chain can also be made in any pitch.
The side links are of the usual torm.
The teeth in wheels on which this chain works have a groove in the middle wide
enough to admit the straight bridge of block link. Care is taken that the divided
teeth have strength and bearing surface at least equal to any ordinary tooth of
driving wheels.
A section of tooth and portion of rim of wheel is shown in drawing Fig. 4.
The advantage of using fine pitches on the chain ring of back hub in order to secure
sweet running is obvious same increasing as its diameter is reduced but it is also
clear that no such advantage is to be gained by its use on the sprocket wheel it being
plain that a one inch pitch chain will run as sweetly on a six inch diameter wheel as
a half inch pitch chain will on a three inch diameter wheel. Therefore to secure
practically all the advantage of fine pitch in cycles fitted for the ordinary block chain
of one inch pitch it only necessary to alter the chain ring on back hub to half inch
pitch and work a half inch pitch chain in the manner shown in drawings
Fio. A and B.

page_text: I further reduce the stretching points in chains working on half inch pitch wheels
by the use of treble tooth block links of one inch pitch with half inch pitch teeth in
which no stretch can occur. This is shown in drawing Fig. 5.
These treble tooth links engage with three teeth of chain ring at the same time.
The centres of teeth being set on a circle of the same diameter as the chain ring on
which they are intended to work.
The side connecting and guiding links are of half inch pitch. The links are
alternately one inch and half inch pitch with half inch pitch teeth.
When working on sprocket wheel this chain acts as of one inch pitch. Owing to
the comparative flatness of the six inch diameter wheel the middle tooth does not
engage with wheel.
In this form of chain two pitches which cannot stretch are followed by one pitch
which can so that the stretch is minimised to a very large extent.
In describing chain I call the ends of block link teeth and the connecting part a
bridge.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
First. The use in cycle chains of block links having a tooth at each end and
capable of engaging with two pitches or two teeth of wheels at the same time.
Second. The use on cycles of fine and coarse pitch wheels working with fine pitch
chains in the manner and for the purpose described.
Third. The use in chains of cycles of treble tooth block links of the form and for
the purpose described.
That L 1
1.
1007