Year: 1897

page_text: Date of Application, 25th Nov., 1837-Accepted, 8th Jan., 1898
COMPLETE SPECIFICATION.
I, DAVID PURVES, of Greenfields, Green Hill Road, Allerton, Liverpool,
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:-
My invention relates to certain improvements in the driving and brake
mechanism of cycles and the like. My invention is applicable to a driving
sprocket wheel of a cycle of the class in which the sprocket wheel is formed of a
number of parts which are so arranged that when the driving or pedal axle passing
through same is turned in a forward or driving direction some of the parts bind
against others so that the wheel forms a solid whole which is capable of trans-
mitting power by means of a chain or the like, while when the rotation of the
axle is stopped as by the rider ceasing pedalling a portion (such as the rim) of
the wheel is able to run alone so that the rider may keep his feet at rest on the
pedals when desired such as for instance when going down hill or when the
machine has otherwise sufficient momentum or again when the axle is rotated in
the opposite direction as would be produced by back pedalling, the parts may be
jammed so that the wheel may retard the movement of the chain thus acting as a
brake.
In the accompanying drawings is illustrated one form of my invention as
applied to machines of the above class. In these
Fig. 1 is an elevation of my improved construction of sprocket wheel looking at
it from the side furthest from the crank a part being removed.
Fig. 2 is a similar view from the opposite side the crank and an enclosing disc
being removed.
Fig. 3 is a vertical cross section through Figs. 1 or 2 with all the parts present.
Fig. is a section on line a Fig. 2.
Fig. 5 is a view shewing a part omitted in Fig. 1.
Fig. 6 is a section through the braking ring and
b
Fig. 7 is a view of one of the toggles or struts employed in the wheel.
The wheel is composed of an outer ring a to which is secured a skeleton ring
carrying the sprocket teeth. The ring a in the construction shown is provided
with two interior surfaces or diameters ed. Inside the diameter or part c is
situated a split or expansible ring e carrying a leather face f. The ring e is pro-
vided at its free end with a few notches 9 (shown on the left hand side of Fig. 1)
though it may be notched all round if required.
The other end of this ring is held and prevented from moving by a lug h of a
disc or plate h (which is removed in Fig. 1) forming part of or secured to the
usual bottom bracket i of a bicycle in which the axle is supported by the usual
bearings.
To steady the ring I prefer also to employ a further lug on the opposite side
of the disc h both of these lugs entering slots h³ in the ring e one of such slots
being well shown in Fig. 6 which also shows the manner in which it is preferred
to cut the ends of the ring e so that while the free end is allowed to expand it
1 L

page_text: The diameter or part
the angle of such notches
notches g.
of the ring is preferably notched all the way round,
being oppositely arranged to that of the angle of the
The axle carries the usual crank, the boss j of which is screwed into an inner
driving ring or boss k and locked by a pin 7. The ring in the arrangement
shown has a number of recesses m in which are loosely held toggles or struts n
(eight being employed in the arrangement shown) retained in place by a disc or
plate o bolted or attached to the ring as shown in Fig. 4 said disc also serving to
keep the outer ring a in place.
k
This disc or plate is omitted in Fig. 2. The ring khas further a projection kl
Figs. 2 and 4 broken away at intervals where the toggles are held in the ring so
that a number of lugs are formed which lugs or interrupted ring passes into a
groove on the ring e and abuts against the side of the part of the outer ring a
and serves to keep said outer ring in place and prevent it from rubbing against
the ring e.
In place however of being loose these toggles may be pivotted if desired.
Each toggle has two oppositely curved or angled faces n¹ n³ as shown best in
Fig. 7, one of these faces is adapted to work against one of the notches and the
other against one of the notches g of the expansible ring or it is evident that
instead of one toggle having the two faces n¹ n³ two separate toggles or struts on
the same plane or approximately the same plane could be employed.
For propelling the cycle in a forward direction the crank is revolved in the
direction of the arrows Figs. 1 and 2 so that the faces n' of one or more of the
toggles n engage in one or more of the notches of the outer ring. One of these
faces is shown as engaging in the lower side of Fig. 2 by reason of the fact that
it has been in the lowest position at the moment the power was applied and hence
having fallen downward in its recess m its nose or point has been ready when
tilted by the forward movement of the ring k to engage the notch which it was
first brought into contact with. If the crank is now checked it will be seen that
the momentum of the machine will through the chain and sprocket teeth carry the
outer ring a round freely while if the crank is driven in the reverse direction the
face n of the toggle n which is in the lowest position will come into contact with
the first notch of the split or expansible ring e (or if it should miss it into con-
tact with the next), so that the free end of said ring is expanded and according to
the force exerted a braking effect is produced on the diameter or part c of the
freely moving outer ring a.
In place of the inner ring, toggles, and braking ring, driving and controlling
an outer ring carrying sprocket teeth, said outer ring may carry bevel gear teeth
and the arrangement will thus be adapted for what are known as chainless" or
spur gear cycles which are driven from the rear wheel.
Various modifications of the parts may be arranged without departing from
the essential features of my invention.
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:-
1. The combination in a sprocket or gear wheel having a driving ring, and a
driven ring carrying the sprocket or gear teeth, of toggles or struts having
oppositely curved or shaped faces one of which acts to drive the driven ring while
the other acts in the opposite direction as a brake through an intermediate brake
ring substantially as described.
2. The combination in a sprocket or gear wheel having a driving ring, and a
driven ring carrying the sprocket or gear teeth of toggles or struts having
oppositely curved or shaped faces or oppositely arranged to each other and in the
same plane and carried in recesses in the driving ring such toggles or struts being
arranged to engage with notches or the like on the inside of the driven ring and
upon an intermediate braking ring substantially as described.

page_text: 3. The combination of parts forming the sprocket wheel substantially as and for
the purpose described and illustrated in the accompanying drawing.
Dated the 24th day of November 1897.
PHILIP M. JUSTICE,
55 & 56 Chancery Lane, London, Chartered Patent Agent,
For the Applicant.