Improvements in Power Transmitting Gear.
Year: 1899

page_text: Date of Application, 15th Sept., 1899-Accepted, 15th Sept., 1900
COMPLETE SPECIFICATION.
Improvements in Power Transmitting Gear.
We, CILARLES FREDERICK STOKES, 332, Oakwood Boulevard, Chicago, Illinois,
Manufacturer, and CHARLES EDWARD MCGLINCHEY, Highlandville, Massachusetts,
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:-
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This invention relates to improvements in gears adapted to transmit power at
an angle, the object of the invention being to cause the driving gear to impart
motion to the driven gear with minimized friction, noise and shock and with
an advantageous leverage. The invention is adapted for use in chainless bicycles
as well as in other connections where motion is transmitted at an angle through
rotary gear.
The gist of the invention lies in providing a gear wheel having round-faced
anti-friction teeth extending outward from the axis of rotation and preferably
arranged to project radially from the gear centre and in providing a second gear-
wheel having teeth so shaped that they will glidingly engage with elongated
surface contact and move spirally against the teeth of the first wheel in a direc-
tion toward and from its axis of rotation. Thus when the gears are constructed
with reasonable accuracy, they work with a degree of smoothness and silence
approximating that of a worm-gear, and with an advantageous leverage and
minimized friction.
The drawing shows in Figure 1, a desirable form and embodiment of the in-
vention for transmitting motion from one shaft to another, the shafts being at
an angle to each other. Figures 2 and 3 are face views of the gear-wheels;
Figure 4 a side view of the wheel shown in Figure 3; Figures 5 and 6, sectional
views showing two ways of mounting the rotary teeth; and Figure 7 a view illus-
trating the spiral engagement of the teeth. The gear wheel a is upon a shaft b,
which is preferably, though not necessarily, the drive shaft; and the gear-wheel c
is upon a shaft d. The wheel a is frusto-conical in form with peripheral teeth c
and concave interdental recesses f as shown in Figures 3 and 4, a substantial
part of the sides of which conform to the surface of the driven teeth through
their contact.
In the construction of this wheel a it is preferred to observe the following
characteristics: The thickness of the cone-frustum is approximately the length
of the roller k which constitutes the tooth of the driven gear. This thickness
affords a root or base line of the drive gear tooth. The vertical line of the tooth
from the root line to the extremity should be approximately the same as the
diameter of the roller k at its base. The outer surface of the cone-frustum has a
general conical angle, but in practice it is found desirable slightly to curve this
line, as indicated in Figure 1. The sides of the interdental space have such
a face contour as to present a transverse line of contact covering a substantial
part of the width of the tooth during the whole of the time that the driven
gear tooth is being engaged and driven by the drive gear. tooth.
The wheel c has an annular recess g in its face and presents an inner ring h

page_text: and an outer flange i. In the recess g are radially disposed teeth k, axially rotat-
able to render them in a great measure, at least, anti-frictional. Preferably
the teeth are in the form of cone-frustums and disposed with their bases
adjacent to the inner ring h. To maintain uniform contact with the, teeth k
the recesses should taper, in the direction longitudinal of the shaft b, in the
direction opposite to that of the conical teeth which they engage. In other
words, the concavity at the shallower ends of each recess f describes the arc
of a larger circle than the concavity at the deeper end t. The teeth may be
mounted to rotate upon pins 1, and for convenience of construction the pins may
rest at their inner ends in recesses m in the ring hand pass through openings n
in the flange . The outer ends of the pins may extend beyond the flange and be
reduced, and flattened at opposite sides, to enter recesses in a slip-ring 2, which,
being slipped over the flange and fastened, as by screws q, locks the pins securely
in place. Figure 6 shows a modified construction wherein the teeth are
mounted to rotate on pins or screws engaging recesses in opposite ends of the
teeth.
In the rotation of the gear wheels, the teeth of the wheel a engage the teeth k
primarily toward the outer ends of the latter and describe a spiral course in the
direction centripetal to the wheel c (as indicated by the dotted line in Figure 7)
rendered in a great measure anti-frictional by the freedom of the teeth k, to
rotate on their axes.
The line of engagement of the drive gear teeth and driven gear teeth changes
from a point at or near the extremity of the driven gear tooth to a point
nearer the base of the tooth, the movement being on a spiral line by reason of
rising and advancing on the curved surface. Throughout the period of engage-
ment, however, the line contact is so near the dead centre line of the driven
gear roller that the whole pressure of driving contact is exorted against the
pin which supports the roller, with the consequence that the driving pressure is
exerted in advancing the gear to the same extent as if the pin and roller were
integral, thus forming a solid tooth. At the same time, the change of line
contact along the spiral line (as indicated by the dotted line in Figure 7)
produces a rotation of the roller upon its own axis, whereby friction is largely
overcome, the friction of the roller on its own axis being immaterial. This
rotation of the roller is produced fully as much by the spiral inward as by the
spiral upward movement of the teeth one upon the other. It is entirely within
our invention, however, entirely to ignore any tendency to friction which may
result from the engagement of the teeth, and we therefore desire it understood
that the prevention of friction in this manner, though desirable, is not an essen-
tial part of our invention.
According to this invention there is produced a gliding spiral engagement
with line, or elongated surface, contact between the gear-teeth, as distinguished
from what is termed "point contact," all with resultant constancy of pressure,
minimized wear, advantageous leverage and uniformity of power transmission.
In the drawings the driven gear teeth are shown as radial and at right angles
to the axis but it will be understood that a variation from a right angle posi-
tion is intended to be included in this invention, provided that the variation be
not so great as to approximate parallellism with the shaft.
The exact shapes of the teeth of the wheels shown, though preferred, are not
of the essence of the invention broadly considered, and the construction may be
variously modified as to details without departing from the spirit of the in-
vention.
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;
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1. Power transmitting gear-mechanism, characterised by a wheel having round
faced teeth extending outward from the axis of rotation, and a second wheel

page_text: having teeth which glidingly engage and move spirally against the teeth of the
first said wheel in the direction toward and from its axis of rotation.
2. The power transmitting gear-mechanism characterised in Claim 1, having
the teeth of the first named wheel rotatable on their own axes to minimize
friction.
3. The power transmitting gear-mechanism characterised in Claim 1, having
the teeth of the first named wheel of frusto-conical form and rotatable on their
own axes.
4. The power transmitting gear-mechanism characterised in Claims 1 and 3,
having the second named wheel formed with peripheral concave interdental sur-
faces tapering in the direction longitudinally of the axis of said wheel inversely
to the cone surfaces of the rotary teeth which they engage.
5. In angle gearing the combination with a driving gear having round-faced
radially projecting teeth, of a drive gear having bevel shaped teeth and inter-
dental spaces, the sides of which are formed to conform to the opposing face of
the driven gear teeth during driving engagement in their movement through
their arc of rotation to preserve line-contact during said engagement, substan-
tially as described.
6. In angle gearing, the combination with the driven gear having round-faced
radial teeth supported at opposite ends as described, of a drive gear frusto-conical
in shape with curved interdental spaces the bases of which are parallel with
the driven gear teeth at the moment of most intimate meshing of the gears,
and
the sides of which are formed to maintain line-contact with the driven gear-
teeth throughout the period of the application of driving power substantially
as described.
7. The power transmitting gears a and c constructed as shown and described.
Dotod thie 15th dov of Sontomber 1899
BOULT, WADE & KILBURN,
Agents for the Applicants.