Sprocket Wheel.
Year: 1894

page_text: Date of Application, 26th June, 1894-Accepted, 28th July, 1894
COMPLETE SPECIFICATION.
Sprocket Wheel.
1, WILLIAM AUGUSTUS LEGGO, Jr., resident of Hartsdale, in the County of
Westchester, State of New York, United States of America, Photo-lithographer,
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 sprocket wheels, and has for its object to provide a
device of this character, the diameter of which may be instantaneously increased or
reduced at will to enable a change of leverage or of speed to be had, a sprocket-
wheel embodying my invention thus possessing two available effective diameters of
different dimensions.
My invention is applicable to any class of sprocket wheels used in conjunction
with a chain but is hereinafter more particularly described as applied to the
driving-gear of a safety bicycle, such being one of its most obvious applications,
and that for which the invention is primarily designed.
In the accompanying drawings forming part of this Specification, in which like
letters of reference designate corresponding parts throughout,
Figure 1 is a side elevation of a sprocket wheel embodying my invention, a half
section of its outer plate or surface being broken away to more clearly illustrate the
interior construction and mechanism.
Figure 2 is a transverse section taken through the exact centre of the same.
Figure 3 is a perspective view of the swinging arms forming part of the
invention.
Figure 4 is a modified form of the device.
In the practice of my invention, I secure to the axle A of the wheel by any
approved means, the hub B, having secured thereto, or formed integrally therewith,
a disk C, to which is secured by means of bolts a a disk C', an intervening space
being left between this and the disk C.
These bolts serve as pivots for a plurality of swinging arms D, illustrated in
detail in Figure 3, each having formed thereon a slotted elbow b, projecting
inwardly rearward of the pivots, the outer portion of the arm having formed
thereon the teeth c and d which respectively engage with the chain when the
sprocket-wheel is reduced to its lowest diameter, and when the same is expanded.
Each of the disks C and C¹ have formed therein tangential grooves e serving to
limit the movement of the arms D outwardly or inwardly and to sustain and
strengthen the same, the said arms having near the top thereof below the teeth d
pins, which enter the grooves e and work therein.
Upon the axle A is mounted a collar E of such form as to fit within the centre
of the disk C, which is open throughout inwardly of the bolts a. Upon the under
side of the collar E are secured pins y equal in number to the swinging arms D,
and resting in the slots in the elbows 6 thereof. Secured upon the top of the
collar, which is revoluble upon the axle A, is a beveled gear-wheel F, the collar
being rotated by means of this gear-wheel through the agency of suitable
connections leading to any convenient point upon the vehicle.
In place of employing this gear-wheel F, the collar E may be actuated by an
extended lug or crank G secured upon the same, and operative either by the hand
or by the foot as desired. This lug is preferably located upon the side of the
sprocket-wheel adjacent to the pedal, by reason of its being more accessible in such
position, while with the beveled gear it will in practice be found more convenient
to mount the same upon that side of the wheel which faces the frame, this

page_text: and other like details being always arranged with reference to the particular
use to which the wheel is to be put, or to the class of devices on which it is
employed.
Upon the upper surface of the disk C', I secure a spring H, which bears upon
the periphery of the collar E and is adapted to rest in recesses h formed therein at
intervals, thereby tending at either diameter of the wheel, to prevent disarrangement
of the parts through the jarring of the machine, this spring however being readily
dislodged by the rotation of the collar E.
The operation of the device will be clearly understood from the foregoing
description taken in connection with the accompanying drawings. To increase the
diameter of the sprocket wheel it is necessary only to impart a rotary movement to
the collar E by means of the beveled gear or of the lug G, the partial rotation of
the said collar causing the pins g thereon to swing the arms D outwardly, the free
ends of the said arms, as this is started, raising the chain which surrounds the
sprocket wheel from engagement with the teeth c which enter the links of the said
chain when the wheel is at its lowest diameter. When the arms have been fully
extended, the links of the chain fall upon the teeth d, which project radially from
the wheel when the same is expanded to the utmost. The diameter of the wheel is
reduced by the converse operation of the collar E, which causes the arins D to
swing inwardly, the chain thereby changing from the teeth d back to the teeth c.
The disks C and C' serve to prevent lateral movement of the chain.
C
It will be observed that in order to securely lock the arms D in either of the two
effective positions, I have so constructed the slotted elbows that, in either position,
the pressure of the same upon the pins will be radial to the axle, either toward or
away from the same according to the direction of rotation of the wheel. The
latter pressure, however, will not ordinarily be brought into use, as the pins f
upon the arms D, which slide in the grooves e, will abut against the upper and
lower edges of the said grooves and be incapable of further movement in such
direction.
By a construction such as shown in Figure 4, I may do away with the slotted
elbows and the pins upon the collar E, the said collar being secured to the disk (
by means of the bolts a. The disk C is revolubly mounted upon the said collar,
the grooves e therein ranging in a direction opposite to those in the disk C. The
disk C' is rotated to increase or reduce the diameter of the sprocket-wheel, the
grooves therein acting upon the pins fon the arms D, in such manner as to thereby
swing the said arms either inwardly or outwardly according to the direction of
rotation of the disk C¹.
The grooves in the said disk C' I prefer to form as shown in Figure 4, such
starting concentrically to the axle, ranging obliquely thereto with slightly curved
edges, and then branching off at right angles concentrically as before. By this
means the pins of serve in either position of the wheel to lock the arms in the
position to which they are swung. I prefer, with this construction, to mount the
pins, which work in the grooves of the disk C', somewhat forward of the teeth d,
in order that the said pins shall not pass a point radial to the axle in entering the
outer concentric portions of the grooves e in the said disk C¹. By this means I
ensure a more certain locking of the arms in position.
In this modified form of wheel, two of the collars E may be employed and be
secured rigidly together, or the said collars may be entirely dispensed with, which
is the exact construction shown in Figure 4 and the disk C¹ be continued toward
the centre, being mounted upon an annular flange i projecting upwardly from
the disk C, the pivot bolts a in this case being rigidly secured to the disk C
and extending upwardly to the under surface of the disk C₁ but not passing
therethrough.
It will be obvious that while the one set of teeth or projections d must be present
upon the outer end of the swinging arms D or adjacent thereto, and the opposite
series of the teeth c near the pivots of the same, their exact position relatively to
the pivots and to each other may be varied, by distributing among the various arms

page_text: of one sprocket-wheel the necessary number of teeth, at the required distances
apart, to correspond to the length of the links comprising the chain to be used.
In carrying out this method of adjustment of the teeth, it may be necessary to
omit the same from some of the arms and even change or vary the position of the
teeth upon the said arms, and in some wheels, more than one of either form of tooth
may be secured upon each arm.
Where but one sprocket wheel upon the vehicle is constructed according to my
invention it will be necessary, or desirable, to provide a tension roller, idler, or
other equivalent means for tightening the chain when the sprocket wheel is reduced
to the lower diameter, and for permitting the loosening thereof when the said wheel
is expanded. This adjustment of the chain may be effected by either the hand or
the foot, or it may be so arranged as to be operated coincidently with the expansion
or contraction of the sprocket-wheel's diameter.
I do not desire to confine myself in this direction or in respect to any other
unimportant or variable details. In particular, I wish to make it optional whether
or not the disks are used, or rather extended beyond the ends of the arms as shown,
since, the function of these disks or the extended portion thereof being to prevent
lateral movement of the chain, I may in place thereof employ other means, such as
extensions or projections upon the arms.
Having now particularly described and ascertained the nature of my inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is;
1. The combination in a sprocket-wheel, with a disk, of a circular range of arms,
each having two projections in line with each other, one near the pivot and the
other at or near the outer end, and adapted to engage the chain, and means for
swinging the arms to enlarge the effective diameter of the sprocket wheel or the
reverse, substantially as set forth.
2. The combination in a sprocket wheel, of two disks between which the chain
runs, swinging arms, and pivots for connecting the arms and the disk, slotted elbows
upon the arms, a collar movable around the axis of the sprocket wheel, and
pins upon the collar engaging the slotted elbows and acting to swing the arms,
substantially as set forth.
3. The combination in a sprocket wheel, of disks between which the chain is
received, arms, and pivots connecting the arms and the disks, said arms having two
sets of projections for engaging the chain, slotted elbows thereon, a collar, and pins
upon the collar for giving motion to the slotted elbows and to the arms, substantially
as set forth.
4. The combination in a sprocket wheel, of disks between which the chain is
received, arms, and pivots connecting the arms and the disks, said arms having two
sets of projections for engaging the chain, slotted elbows thereon, a collar, pins
upon the collar for giving motion to the slotted elbows and to the arms, and means
upon the collar for turning the same, substantially as set forth.
5. The combination in a sprocket wheel, of pivoted arms and two sets of
projections upon the arms to engage the chain, a collar, and connections therefrom
for moving the arms, and mechanism for acting upon the collar to give to the same
a partial rotation to swing the arms, and increase or decrease the effective diameter
of the sprocket wheel without necessarily stopping the rotation of such wheel,
substantially as set forth.
Dated this 26th day of June 1894
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C., Agents.