improved means тог Tightening or Taking up the Driving Chains Employed in Safety Bicycles.
Year: 1887

page_text: improved means
тог Tightening or Taking up the
Driving Chains Employed in Safety Bicycles.
Slack
ΟΙ
We, JOHN MARSTON, of Paul Street Works, Wolverhampton in the County of
Stafford, cycle manufacturer, and JOHN MUIR, foreman in the employment of
the said John Marston, do hereby declare the nature of this invention to be as
follows:-
The object of this invention is to provide simple and efficient means whereby the
driving chains of safety bicycles may be readily tightened up after elongation by
wear, or under other circumstances, without liability of the treadle axle being thrown
out of parallelism with the driving axle.
The ineans employed, according to this invention, for the above purpose, consist, in
the case of a safety bicycle in which the treadle axle is carried in a single bracket
fixed to the framing of the machine, of a turned cylindrical part (hereinafter termed,
for convenience of reference, "the drum") fitted to be capable of being turned
axially within a hole bored through such bracket transversely to the longitudinal axis
of the machine, and of means by which the drum may be readily fixed within the
bracket so as not to turn axially therein but be readily unfixed so that it may be
turned as required, and of a sleeve formed as a projection on each side of the drum
but excentric therewith, through which and through the drum the treadle axle
passes, such sleeve being formed or provided with bearings in which the treadle axle
turns.
The drum is originally fixed within the bracket, with the axis of the sleeve,
preferably at its extreme point on the side of the coinmon axis of the bracket and
drum which is towards the driving axle, and the chain is tightened up. if originally
slack, or after it has elongated by wear, by turning the drum axially within the
bracket so as to move the common axis of the sleeve and treadle axle further from
the driving axle. It will readily be seen that by moving the treadle axle in this
manner its parallelism with the driving axle is completely maintained.

page_text: A convenient means of fixing the drum within the bracket, consists in forming
the bracket split along one side and tightening the sides of the slit towards one
another by means of a bolt passing through lugs on the bracket arranged on
opposite sides of the slit. When the bolt is slackened the bracket will spring open
sufficiently to allow the drum to be turned as required. The drum may be readily
turned, when not tightened within the bracket, by means of a spanner employed in
combination with flats formed therefor on the sleeve.
The parts of the sleeves forming the bearings may be made separately from the
sleeves and be screwed thereon, if desired, whereby the drums and sleeves may be
made of malleable iron and the bearings of hardened steel.
Dated this 21st day of November 1887.
STEPHEN WATKINS,
Wolverhampton and Walsall,
Agent for the Applicants.

page_text: 66
Improved Means for Tightening or Taking up the Slack" of
Driving Chains Employed in Safety Bicycles.
We, JOHN MARSTON, of Paul Street Works, Wolverhampton in the County of
Stafford, cycle manufacturer, and JOHN MUIR, foreman in the employment of the said
John Marston, 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 :-
دو
This invention will be readily understood on reference to the accompanying
drawings, of which figure 1 is a side elevation of the hind wheel and the hinder part
of the framing and of the driving gear, of a safety bicycle in which the hind wheel
is driven by a single chain, and shews a chain-tightening device, forming the subject
of this invention, as applied in combination with the crank spindle. Figure 2 is a
section, to an enlarged scale, taken on line x x of figure 1. In this view the cranks
are broken off short, for convenience of illustration, and the hind wheel is omitted.
Figure 3 is a section taken on line y y of figure 2. The same letters of reference
indicate corresponding parts throughout the views. The crank axle A is carried in
bearings B B which are formed with or fixed to a sleeve CC¹ upon which is formed
or fixed an excentric D (termed a
"drum
in the provisional specification). This
excentric is turned to fit within a bored bracket E which is itself brazed or otherwise
fixed to a downwardly projecting part F of the framing of the machine, just as
ordinary crank axle brackets are usually fixed to the frame. The bracket E, however,
is split on its forward side, and ears a a are formed out one on each side of the
slit, and a pin 6 is passed through holes formed one through each ear so that the ears
may be tightened towards one another and thus tighten the bracket firmly around
the excentric D to fix it. When the pin b is slackened the excentric may be readily
turned axially, owing to a slight springing open of the bracket. The excentric is
originally placed in such position within the bracket that the centre of the axle A is
nearer to the centre of the hind wheel than is the common centre of the excentric
and bracket, and it will readily be seen that by turning the excentric the axle A may
be carried forward to a greater distance from the centre of the hind wheel and
thereby cause the tightening up of the chain c, and such tightening may be effected
in a greater or less degree if the axle A is in any position other than at an extreme
point on the opposite side of the common centre of the excentric and bracket to that
on which the hind wheel axle occurs. In order to facilitate the turning of the
excentric a pair of flats may be formed upon the part C¹ of the sleeve (see specially
figure 3) for the reception of a spanner. In order to prevent the excentric D from
being moved sideways whilst it is being turned in the bracket a groove d may be
turned in the periphery of the excentric, and a pin e be screwed through the bracket
with its point entering somewhat within the groove d. The parts of the bearings for
receiving the balls (when ball bearings are employed, as shewn) may be screwed upon
the sleeve CC, as shewn, so that such parts may be of hardened steel while the sleevo
and excentric are of soft metal.

page_text: By the employment of this invention the crank axle may be readily moved towards
or from the driving wheel axle without any liability of throwing the two axles out of
parallelism with one another.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is :-
1. A device for tightening the chain employed in driving the hind wheel of a safety
bicycle, consisting of an excentric carrying the bearings for the crank axle and itself
carried in a bracket fixed to the framing and split so as to be capable of being
tightened up around the excentric to fix it, substantially as described.
2. A device for tightening the chain employed in driving the hind wheel of a safety
bicycle, consisting of an excentric carrying the bearings for the crank axle and itself
carried in a bracket fixed to the framing, said excentric having a groove turned therein
into which the point or end of a pin fixed within the bracket enters to prevent the
excentric moving sideways when slack within the bracket, substantially as described.
3. A device for tightening the chain employed in driving the hind wheel of a safety
bicycle, as described with reference to the drawings herewith.
STEPHEN WATKINS,
Wolverhampton and Walsall,
Agent for the Applicants.