Improvements in Sprocket Wheels.
Year: 1897

page_text: Date of Application, 27th Nov., 1897--Accepted, 8th Jan., 1898
Improvements in Sprocket Wheels.
I, GEORGE CARVER, of Mitre Hotel, Hadlow Road, Tonbridge, Kent, Cycle
Mechanic, 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:-
-
This invention relates to an improved construction of sprocket wheel, intended
for use with chain driven machinery, motor cars, cycles and the like, and has for
its object to provide a means whereby the friction between the said sprocket wheel
and the chain is reduced to a minimum, and also to provide a means whereby the
stretching of the chain and the consequent alteration of the pitch of the said chain
may be counteracted, it being found that an ordinary chain which fits a sprocket
wheel when new, after a certain amount of wear stretches and then rides on the
teeth at the upper part of the wheel and slips down the face of the teeth as it travels
round with the sprocket wheel.
In carrying out my invention I provide a central disc or wheel which is formed
on the periphery with teeth. These teeth are adapted to engage with the chain
in the usual manner, and the base or root of each tooth is provided with two
projections or noses one at each side. This central wheel or disc is fitted or formed
with a projecting flange or rim on each side which are both cut on the inside with
screw thread.
To this central disc is secured two rings one at each side, the two forming a
bearing or seating for a number of balls which are placed between the teeth and
on which the chain rides.
These balls, two of which are placed between each pair of teeth, are secured in
position by means of the thin metal ring or Hange on the periphery of the central
wheel, and a portion of the latter is removed between each two teeth to allow the
balls to be placed in position, and also adjusted when necessary.
These side rings are screwed to the flange of the central disc and locked in
position by means of small screws or bolts and nuts, any number of which are
employed as found most suitable.
To preveut the adjacent balls getting too near the root of the tooth or otherwise
out of position, the projection before mentioned is employed which keeps the ball
in the best position for its purpose.
The smaller sprocket wheel fixed to the hub of the rear or driving wheel is con-
structed similarly.
To adjust the wheel to fit the chain when the latter has become stretched the
locking screws are removed and the side rings or discs screwed closer together
thereby pressing the balls further outwards and increasing the effective diameter
of the wheel and the consequent pitch of the teeth.
In order that the invention may be more clearly understood, reference is had to
the accompanying sheet of drawings, in which Fig. 1 is a front elevation of my
improved sprocket wheel, Fig. 2 is a sectional elevation at right angles to Fig. 1,
Fig. 3 is a view of the side ring, and Fig. 4 is a sectional side elevation of the
wheel applied to the hub of the rear or driving wheel, and Figs. 5 and 6 are views
showing the application of the chain.

page_text: A is the central disc or wheel and as shown is formed with the radial arms 1.
The central portion of this disc is fixed to the crank arm B which carries the pedal
in the usual manner.
Around the periphery of this disc is formed the projecting teeth C which engage
with the chain. At the base of the teeth the projections or noses c are formed,
against which the balls 1) abut a portion of the disc at the base of the teeth being
removed to allow the balls to drop into position.
The side discs E are secured to the central disc A by means of the flanges a
and are locked in position by the small screws e and to allow of being adjusted the
holes el are provided. These screws pass through one side ring and also the central
dise or wheel, and screw into the other side ring, the holes in the latter being
tapped with a screw thread for this purpose.
Near the periphery of the side ring the metal is thickened, so as to provide a
seating for the balls, and the outer edge of the periphery is cut with a screw
thread and screws into the flange a¹.
The arrangement shown in Fig. 4 for the hub of the rear or driving wheel is
exactly similar to the larger wheel.
The arrangement described and shown illustrates the arrangement applicable
for a cycle but the invention can be applied to any form of driving gear such as for
a motor car or transmitting motion (increased or otherwise) for any class of
machinery where chain driving is employed and I may use rollers or prismatic
blocks or any other suitably shaped pieces of metal which can be adapted to slide
outwards on screwing home the side rings. The block F of the chain is provided
with the shaped groove f as shown in Figs. 5 and 6 and bears upon the balls c.
Although I have described my invention as employing two balls in the interval
between each two teeth, I may use one, or even three according to the size and pitch
of the chain.
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 :
(1) An improved construction of sprocket wheel provided with means by which
the effective diameter can be increased or diminished at will, substantially as
described and for the purposes specified.
(2) In sprocket wheels, a central disc having teeth formed on its periphery,
projecting rings or flanges screwed internally side rings or discs screwing into the
said flanges and forming adjustable bearings constructed and operating substan-
tially and described and shown.
(3) In an improved sprocket wheel the combination with a central disc having
teeth on its periphery and side flanges or rings screw threaded internally of rings
or discs at each side screwed into flanges bevelled bearing surfaces at the edges of
the rings or discs, and balls within the said bearings adjusted by the discs, sub-
stantially as described and for the purposes specified.
(4) An improved sprocket wheel having balls arranged around its periphery and
teeth having projections or noses at the root of each tooth against which the said
balls abut, of a bevelled bearing surface for the balls and a V shaped groove in
each of the blocks of the chain, adapted to bear on said balls, substantially as
described and for the purposes specified.
(5) An adjustable sprocket wheel having small prisms, rollers, or one or more
balls for the purpose of reducing friction and adjusting the effective diameter of the
wheel, substantially as described and for the purposes specified.
Dated this 4th day of November 1897
GEO. H. RAYNER,
37, Chancery Lane, London, Agent for the Applicant.