Improvements in Adjusting the Driving Chains of Tandem Bicycles and other Velocipedes.
Year: 1895

page_text: Date of Application, 21st Nov., 1895
Complete Specification Left, 27th July, 1896--Accepted, 3rd Oct., 1896
PROVISIONAL SPECIFICATION.
Improvements in Adjusting the Driving Chains of Tandem Bicycles
and other Velocipedes.
We, HENRY CROMWELL FIELD of the Firm of Alfred Field and Company,
of Edmund Street, Birmingham, in the County of Warwick, Merchants, and
ANDREW WILLIAM STOREY, of "Sandown," College Road, Moseley, in the
County of Worcester, Mechanical Engineer, do hereby declare the nature of this
invention to be as follows:-
The said invention has reference to such driving chain adjusting mechanism as
consists essentially of an adjustable rotating cylindrical bearing working in the
case of the bottom bracket, the said bearing carrying the spindle of the driving
chain wheel, and being provided at its ends with eccentric discs which work in the
ends of the case of the bottom bracket. By turning the said eccentric bearing
more or less in the case of the bottom bracket, the spindle of the chain wheel can
be moved further from or nearer to the other chain wheel of the velocipede and
the chain passing over the said chain wheels thereby adjusted as is well
understood.
The said invention consists of the arrangement or combination of parts herein-
after described for giving the necessary rotary motion to the eccentric bearing
referred to in its bracket so as to adjust the driving chain.
By this invention the adjustment of the position of the eccentric bearing in the
bottom bracket for the purpose described is effected with great nicety land
facility.
The said invention is especially applicable to the front bottom bracket of the
front driving chain of a tandem bicycle and we will describe it as applied to such a
bracket.
In place of making the discs of the eccentric bearing plain on their peripheries
as usual, we form on the periphery of one of the said discs inclined teeth so as to
convert it into a worm wheel and we drive or give rotary motion to the said
toothed disc or worm wheel and to the hearing forming part of it, by a rotating worm
or screw, situated beneath the said worm wheel aud at right angles to the axis of
the bearing. The said worm or screw is situated and works in a cross lug at one
side of the bottom of the bracket the acting part of the worm or screw protruding
through a hole in the said lug and gearing with the toothed disc or worm wheel of
the bearing. The said worm or screw is fixed by a screw nut. By relaxing the
screw nut and giving the necessary rotary motion to the worm or screw the eccentric
bearing in the case of the bottom bracket is moved through the required angle to
bring the spindle of the front chain wheel nearer to or further from the rear chain
wheel so as to adjust the driving chain.
The worm or screw having been locked by its nut the adjusted eccentric bearing
may be more firmly fixed in position in the bottom bracket by any of the well
known appliances.
We do not limit ourselves to any particular kind of worm and worm wheel.
For example, the worm wheel may be made by forming a concave trough or
groove in the periphery of the disc of the eccentric bearing and forming inclined V
or square screwlike threads in the trough or groove, the worm or screw having
correspondingly shaped threads for engaging with those of the worm wheel. Or
D

page_text: instead of sunken inclined teeth or threads the periphery of the disc of the eccentric
bearing may be provided with projecting teeth or threads.
Dated this Twenty-first day of November 1895.
3
W. T. WHITEMAN,
Agent for the Applicants.
Improvements in Adjusting the Driving Chains of Tandem Bicycles
and other Velocipedes.
We HENRY CROMWELL FIELD, of the Firm of Alfred Field and Company,
of Edmund Street, Birmingham in the County of Warwick, Merchants, and
ANDREW WILLIAM STOREY, of "Sandown," Cellege Road, Moseley, in the
County of Worcester, Mechanical Engineer, do hereby declare the nature of the said
invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement :-
The said invention has reference to such driving chain adjusting mechanism as
consists essentially of an adjustable rotating cylindrical bearing working in the
case of the bottom bracket, the said bearing carrying the spindle of the driving
chain wheel and being provided at its ends with eccentric discs which work in the
ends of the case of the bottom bracket. By turning the said eccentric bearing
more or less in the case of the bottom bracket, the spindle of the chain wheel can
be moved further from or nearer to the other chain wheel of the velocipede, and
the chain passing over the said chain wheels, thereby adjusted as is well
understood.
The said invention consists of the arrangement or combination of parts herein-
after described for giving the necessary rotary motion to the eccentric bearing
referred to in its bracket so as to adjust the driving chain.
By this invention the adjustment of the position of the eccentric bearing in
the bottom bracket for the purpose described is effected with great nicety and
facility.
The said invention is especially applicable to the front bottom bracket of the
front driving chain of a tandem bicycle and we will describe it as applied to such a
bracket.
In place of making the discs of the eccentric bearing plain on their peripheries
as usual, we form on the periphery of one of the said discs inclined teeth so as to
convert it into a worm wheel and we drive or give rotary motion to the said
toothed disc or worn wheel and to the bearing forming part of it, by a rotating
worm or screw situated beneath the said worm wheel and at right angles to the
axis of the bearing. The said worm or screw is situated and works in a cross lug
at one side of the bottom of the bracket the acting part of the worm or screw
protruding through a hole in the said lug and gearing with the toothed disc or
worm wheel of the bearing. The said worn or screw is secured in the lug by a
screw nut. By giving the necessary rotary motion to the worm or screw the
eccentric bearing in the case of the bottom bracket is moved through the required
angle to bring the spindle of the front chain wheel nearer to or further from the
rear chain wheel so as to adjust the driving chain.
The adjusted eccentric bearing is firmly fixed in position in the bottom bracket
by any of the well known appliances.
For
We do not limit ourselves to any particular kind of worm and worm wheel.
in
example, the worm wheel may be made by forming a concave trough or groove
the periphery of the disc of the eccentric bearing and forming inclined V or square
screw like threads in the trough or groove, the worm or screw having correspondingly
shaped threads for engaging with those of the worm wheel. Or instead of sunken

page_text: inclined teeth or threads, the periphery of the disc of the eccentric bearing may be
provided with projecting teeth or threads.
Figure 1 of the accompanying drawing represents in side elevation the bottom
bracket of a safety or tandem bicycle and parts connected therewith to which the
improvements in chain adjusting mechanism constituting the said invention are
applied; Figure 2 is a plan of underside of a portion of the same the cranks being
omitted;
Figure 3 is a vertical section taken through the axis of the crank axle ;
Figure 4 is a cross section taken on the dotted line x, x Figure 3;
Figure 5 is an elevation of the side of the bottom bracket opposite to that
represented in Figure 1, the chain wheel, crank and crank axle being omitted;
Figure 6 is an elevation of the bearing case separately and
Figures 7, 8, 9, 10 and 11 represent parts of the mechanism detached as herein-
after described.
The same letters of reference indicate the same parts in the several figures of the
drawing.
a is the bearing case in which the crank axle c rotates as usual, the said bearing
case a being situated eccentrically in the bottom bracket b. The bearing case a
has on its ends eccentric discs marked respectively a', as which eccentric discs fit
the opposite ends of the tubular part of the bottom bracket b and are fixed therein
on the adjustment of the tension of the driving chain in the manner hereinafter
described.
The periphery of the eccentric disc a' is plain but the periphery of the eccentric
disc as is grooved and the groove is provided with inclined teeth so as to form the
eccentric disc a³ into a worm wheel. In a lug on the underside of the bottom
bracket 6 a worm or screw d (shown separately in Figure 7) is secured by a
washer e (see Figure 8) and screw nut f. The opposite end of the bottom bracket b
is preferably provided with a split lug one part of which is internally screw
threaded. By means of a screw pin g the two parts of the split lug 6 are drawn
together and the end of the bottom bracket is thereby made to clip the eccentric
disc a and securely lock the bearing case a in the position to which it has been.
adjusted.
The extent of the throw or range of adjustment of the driving chain wheel i will
be seen by reference to Figure in which the chain wheel i is indicated in dotted
lines in its normal or non-adjusted position and is represented in full lines in its
fully withdrawn position for tightening the driving chain.
The adjustment of the tension of the driving chain is effected as follows;—The
screw ping having been turned in the direction proper to relax the split lug b' the
worm dis rotated in one or other direction by means of the thumb and finger and
a partial rotation of the eccentrics a³, a³ in the bottom bracket b thereby effected.
By the partial rotation of the eccentrics a³, a' the bearing case a and crank axle c
therein are made to recede from or advance towards the driven chain wheel until
the desired tension of the driving chain is obtained. The bearing a is secured by
the screwing home of the screw pin g and the contracting of the split end 62 of the
bottom bracket bon the eccentric disc a². The accidental movement of the bearing
in the bottom bracket is thereby prevented.
By the construction and arrangement of parts herein before described and
represented a very fine and simple adjustment of the tension of the driving chain
is obtained.
Although we have described and represented the eccentric disc a³ with concave
teeth on its periphery yet we wish it to be understood that we do not limit ourselves
to this construction as convex or projecting teeth may be formed on the periphery
of the said eccentric disc a³ with the same or nearly the same effect.
We prefer to fix the driving chain wheel i on the crank axle cand also the cone h
at the driving chain wheel end of the crank axle by the following construction and
arrangement of parts. We form on the crank axle c a series (preferably four) of
radial studs (see Figure 9) and we make in the outer side of the cone h crossing

page_text: grooves which engage when the said cone is passed onto the crank axle c with
the inner sides of the radial studs c hereinbefore referred to. The inner side of
the driving chain wheel i has similar crossing grooves which engage, when the
chain wheel is in place with the outer sides of the studs c³, the chain wheel i being
fixed in position by the screw nut k (see Figure 3). The cranks are fixed to the
opposite ends of the crank axle c in the ordinary way.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare 'that we claim
as the said invention :-
The improvements in adjusting the driving chains of tandem bicycles and other
velocipedes hereinbefore described and represented in the accompanying drawing,
the said improvements consisting in forming on the periphery of one of the eccentric
discs of the bearing, inclined or worm wheel teeth and in arranging in a lug on one
end of the tubular case of the bottom bracket a worm to engage with and operate
the said toothed eccentric disc the parts being locked after adjustment substantially
as herein before described and illustrated.
Dated the Twentieth day of July 1896.
HENRY CROMWELL FIELD.
ANDREW WILLIAM STOREY.