Improvements in Driving Gear for Bicycles and Tricycles, and for other Purposes.
Year: 1898

page_text: Date of Application, 10th May, 1898-Accepted, 20th Aug., 1898
COMPLETE SPECIFICATION.
Improvements in Driving Gear for Bicycles and Tricycles, and for
other Purposes.
I, THOMPSON GRAVES SALSBURY, of 5, Rue Davy, Paris, France, Mechanical
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 has for its object to provide a novel chainless power-transmitting
device or gear for cycles, which, as compared with other like devices hitherto
devised or built with the object of doing away with chains and their numerous
drawbacks, presents certain advantages which will clearly be made apparent here-
inafter.
Chainless driving gears by means of levers and ratchets and pawls or the like
have not offered great advantages over gears employing chains, and, besides
being usually somewhat complicated, they do not afford means for producing a
high geared cycle.
Power-transmitting mechanisms by means of bevel pinions and an intermediate
shaft, besides requiring skill in the adjustment of the same, and being likely to
become bent, require very careful and minute adjustment and only give satis-
factory results under special conditions of construction and keeping in repair.
My invention has for its object to do away with the said inconveniences and
to provide a power-device which shall be simple, strong, low in cost, incapable
of getting out of adjustment, run very smoothly and be capable of any desired
multiplication. It consists in the novel multiplying mechanism and in the details
of construction and arrangements of parts to be hereinafter described with refer-
ence to the accompanying drawings, in which:
Fig. 1 is an elevation of the pedal mechanism and of a portion of the rear wheel,
showing as much of a cycle as is required for a proper comprehension of my
invention.
Fig. 2, on a much larger scale, is a detail of my improved multiplying mechan-
ism.
Fig. 3 is a vertical longitudinal section of the pedal mechanism and multiply-
ing mechanism on the line 3, 3 of Fig. 2, looking in the direction of the arrows.
Fig. 4 is a diagram to be hereinafter referred to.
The cycle frame may be of any approved usual form. In the drawings I have
shown portion of a diamond frame, of which a is the front tube and a¹ the saddle-
post, whilst a are the tubes of the rear fork and a³ the horizontal connecting
tubes. b is the pedal or centre bracket located, as usual, at the connecting point
between the front tube a and saddle-post a¹,
In the pedal bracket b is fitted a tube c upon which are formed cone-bear-
ings c, running on balls d, held in casings 61 72 screwed into the respective
ends of the pedal bracket b. The tube c projects at both ends of the pedal bracket
and carries near each end an eccentric e, el respectively. These eccentrics, which,
as shown in the drawings, may be integral with the tube c or be connected thereto

page_text: by brazing or in any suitable manner, are at 90 degrees to each other. Each of the
eccentrics e, e¹ carries a strap f, f¹ respectively, which runs on balls 9, g¹ inter-
posed between the strap and the eccentric, and held in place by a casing f, f³
screwed into the eccentric strap.
At its ends and exterior to the eccentrics e, e¹, the tube c is provided with
casings c³, c, containing balls h, h¹ upon which bears the pedal shaft or axis i,
carrying two casings ¹, of which is preferably formed on the shaft itself, whilst
the other is screwed into the said shaft, for the purpose of suitably adjusting
the ball bearings. At its ends, the shaft i has cranks j, j made fast in any suit-
able manner.
On one of the eccentric straps, preferably the right one f, are rotatably fitted
a number of bowls k, k¹, k², placed at an equal distance from each other on the
same circumference, concentrically to the circle of motion of the strap. In the
drawings I have shown three bowls, but I do not limit myself to this particular
number, for it will be readily understood, as will appear hereinafter, that any
other number may be employed, according to the desired multiplication and by
selecting accordingly the number of teeth of the internally-toothed crown with
which the said bowls co-operate, as will be described.
i
On to the crank on the same side, viz., the crank j, is secured in any suitable
manner (for instance by means of screws 1, 11, 12 engaging both the said crank
and arms, integral therewith, as shown,) a disk m having a number of inner
hypocycloidal teeth, the faces of which are so determined and drawn as to act upon
the bowls k, k¹, 12 in succession and consecutively, as will be described.
Finally, each of the eccentric straps f, f¹ is connected by one or preferably
two rods n, n, n', n¹ to the corresponding straps o, ol of similar eccentrics P, P
mounted upon the two ends of the axle q of the rear wheel and placed at 90 degrees
to each other, so as to co-operate respectively with the eccentrics e, e¹. It is
obvious that the eccentrics o, p, o¹ p¹ might be replaced by suitably long cranks
fastened at 90 degrees to each other upon the axle y, the said cranks, in this
instance, being connected respectively by a single rod to each of the eccentric
straps for f respectively.
In order that the operation of the device may be clearly understood, I will
describe the same first with reference to the diagram shown in Fig. 4.
It is well known that, when an eccentric is revolving, every point of its strap
describes a circle the radius of which is precisely equal to the radius of eccentricity
of the eccentric. This being so, let it be assumed, with reference to Fig. 4, that s
be the imaginary circle drawn upon the eccentric strap f and passing through
the centres of the bowls k, k¹². Every point of the said circumference and
especially the centre of each of the bowls k, k, will describe, while revolving
around the eccentric, a circle t, t1, t2, the radius of which will be equal to the
radius of eccentricity, y of the eccentric. Vice versa, it is obvious that if the
centre of each of these. bowls be caused to describe the said circle, the strap will
receive the requisite motion for causing the eccentric to revolve. On the other
hand, let us consider the centre of any one of the bowls, say k, when the said centre
assumes a position most distant from the axis of rotation of the eccentric and
let us draw, from the point r taken as a centre, a circle u passing through the
point and therefore internally tangential, at that point, to the circles s and t.
It will be clear that, if the two imaginary circles and t be assumed to revolve
within each other in the direction of the arrows 1 and 2 respectively, the trajectory.
of the relative movement of the point of the circle with reference to
the circle will be the hypocycloid, and that, if the respective diameters of the
circles and are suitably selected so that the one shall be contained in the
other an exact number of times, the point.k of the circle t will return exactly to
the starting point of the circle u after describing, in accomplishing its motion
with reference to the said circle, a series of hypocycloidal trajectories' which may
be represented by, vl, and the number of which will be precisely equal to the
numeral which will express the ratio between the diameters of and t.

page_text: Vice versa, it will be readily understood that if the circle u be assumed to
revolve in the direction of the arrow 2 by causing the point k of the circle to
follow the hypocycloidal directrix r, the circle t will revolve in the direction of
the arrow 1.
It therefore follows that, if within the disk m, are cut teeth having a hypocy-
cloidal profile drawn through the directrix of Fig. 4, the number of the teeth
being so calculated, for a given number of bowls k, k₁, and for a given ratio
of pitch lines and u, that the hypocycloid described by each bowl with refer-
ence to the pitch line u shall comprise an arc of the said circle u equal to the
fraction of the said circle corresponding to the number of bowls k, l, and to the
ratio of the diameters of the pitch lines and u and if the disk m be caused to
revolve in the direction of the arrow 2, Fig. 4, or of the arrow 3, Fig. 2, starting
from the position shown in these figures, then the hypocycloidal face of the
tooth m', Fig. 4, will first act upon the bowl and cause its centre to become
displaced according to the circle t, which movement will be imparted, as will be
understood, to every point of the strap f and consequently to the bowls and k²
until the face w reaches the position and ceases to act upon the bowl k; which
will then assume the position k°; at that time, the face z of the tooth m² will have
reached the position z¹ and will begin to act upon the bowl which will then have
assumed the position 10, and motion is continued to be imparted as hereinbefore
explained, by means of the bowl, then again by means of the bowl k and so on,
the required teeth of the disk m thus successively engaging the bowls k, k¹, k², so as
to impart to the eccentric f a continuous circular movement, the angular speed
of which, with reference to that of the disk m, will be precisely in the same ratio
as the diameters of the pitch lines u and t.
Motion is transmitted through the tube c, eccentrics f, f' and rods n, n, n', n
to the eccentrics p, p¹ which impart motion to the rear or driving wheel r, Fig. 1,
as will be readily understood.
It is to be understood that I do not limit myself strictly to the details of con-
struction herein shown, for many modifications might be introduced in the parts
illustrated, without departing from the scope or spirit of my invention, the
application of which is not limited, either, to cycles, since it is capable of being
applied with equal advantage to horseless carriages and generally in all cases where
it is desired to transmit, while multiplying it, continuous circular motion from
a rotary part to another rotary part.
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. A chainless power-transmitting device comprising, in combination with the
pedal bracket, the pedal shaft and the pedals: a tube concentric with the said
pedal shaft, upon which it runs in ball bearings and which is also mounted in ball-
bearings on the pedal-bracket: eccentrics placed at 90 degrees to each other on
the said tube with which they revolve; straps for these eccentries upon which
they are fitted in ball bearings, of which one carries a number of bowls concentric
with the periphery of the eccentric and a disk having internal hypocycloidal teeth
fastened to the crank on the same side as the eccentric.having bowls, and the
teeth of which engage the said bowls, substantially as described and shown.
2. In a chainless power-transmitting device of the herein before described kind,
the combination, with a shaft, a support therefor and means for rotating the same,
of a disk mounted concentrically on one end of the said shaft so as to rotate there-
with a tube concentric with the shaft and revolving thereon in ball-bearings and
In the support; an eccentric mounted at each end of the said tube; means between
he said disk and one of the eccentrics for transmitting rotary motion to the said
otary tube at a greater angular speed than that of the said disk; and means
between the said eccentrics and the axis of the driven wheel for imparting motion
o the latter, substantially as described and shown.

page_text: 3. In a chainless power-transmitting device of the hereinbefore described kind,
a multiplying device comprising a disk having inner hypocycloidal teeth mounted
concentrically upon the driving shaft and revolving therewith; an eccentric loose
with reference to the said shaft; a strap on the said eccentric, united by a rod to
the strap of a similar eccentric fast upon the shaft of the driving wheel, and
bowls mounted to rotate on axes arranged upon the strap, concentrically to the
inner periphery of the said strap, the said bowls engaging the teeth of the disk
and being actuated by the hypocycloidal faces of the said teeth as the disk
revolves with the driving shaft, substantially as described and shown.
4. The hereinbefore described driving gear, constructed, arranged and operating
substantially as herein before set forth and illustrated in the accompanying draw-
ings.