Improvements in Driving Mechanism for Bicycles and other Velocipedes.
Year: 1896

page_text: Date of Application, 4th Feb., 1896-Accepted, 11th Apr., 1896
COMPLETE SPECIFICATION.
Improvements in Driving Mechanism for Bicycles and other
Velocipedes.
I, GERARD BEEKMAN, of No. East 34th Street, New York, County and State
of New York, United States of America, Gentleman, 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 means for changing the relative number of revolutions
of the driving and driven parts of a bicycle by varying the pressure of the feet on
the pedals, and the object of my invention is to utilize the drive chain in a rear
driven bicycle as the means of effecting the said change when the feet are
depressed, and the object is also to concentrate certain parts within the sprocket
wheel of the crank shaft.
My invention consists in certain novel features hereinafter fully described and
claimed.
Referring to the accompanying drawings;
Figure 1, is a side elevation of a bicycle embodying my invention.
Figure 2, is an enlarged detail sectional view taken transversely to the machine
on the line a-b, Figure 1.
Figure 3, is a side elevation of Figure 2, partly in section, and taken at the
side opposite that seen in Figure 1.
Figure 4, is a horizontal section at y-y, Figures 2 and 3.
Figure 5, is a cross-section of a sprocket wheel showing a modification of the two
part friction device.
Figure 6, is a side view partly in section of Figure 5.
Figure 7, is a cross-section of a sprocket wheel, showing another modification of
the two part friction device.
The crank shaft hanger A is made movable in the frame B, and is movable in a
direction angular to the perpendicular of a line intersecting the shaft centers C, D.
Hence the elevation or depression of the crank shaft hanger A, will vary the
tension of the drive chain E. The sprocket wheel F is in two parts 1, 2. The
part 1 is fast to the crank shaft C, and the part 2 is movable on the part 1,
but when the shaft hanger A is depressed by the pressure of the feet on the
pedals 4, 4, the part 2 is brought into tractional frictional contact with the part 1
by reason of the tension of the drive chain E, and is carried in revolution by
the part 1 at a speed which is variable at will according to the foot pressure
exerted.
The spring 5 serves to raise the shaft hanger A, wheu the foot pressure is
relieved or reduced, allowing the parts 1 and 2 to slip the one with relation to the
other. The spring 5, is compressed under the washer 7 connected by the tension
adjusting screw 8 to the shank 9 of the movable shaft hanger A, and said
spring 5 abuts on the washer 6 resting on the bushing 10 fixed to the frame B.
The lower end of the bushing 10, is secured to the frame union 11 by a removable
screw 12, and may be readily removed together with the shaft hanger A and
connections.
In order to promote easy working, I provide ball channels 14, 14, on each side
of the shank 9, and channels 15, 15, in each side of the bushing 10, to receive steel
balls 16, which serve both to facilitate longitudinal motion and to prevent rotary
displacement of the shank 9 in the frame bushing 10. The axis of the crank

page_text: shaft C, is thereby maintained in parallel relation to the shaft D of the rear
wheel.
The tension of the drive chain E, may be regulated by the usual adjustment
of the shaft D in the slots 17, at each side of the rear frame fork 18.
Referring now to the more particular details of construction of the two part
friction device in the sprocket wheel F; I have shown in Figures 2 and 3, my
preferred form. The part 1 is fixed to the shaft C, and has flanges 20, under
which the removable flanges 22, of the part 2 project and form ways 23 for bearing
balls 24 which are also supported on ways 25 on the elastic india rubber spring
rings 26, inside of the flange 20. The rubber rings 26, give clearance to the
part 2 to allow lateral expansion when vertically compressed and these spring rings
tend to center the two parts 1 and 2, and when the said parts are centered they
will be permitted to revolve freely with reference to one another on the ball
bearings 24.
The frictional engaging surfaces are composed of the smooth inner surface of the
rim 28 of the part 2, and the outer surface of the india rubber ring 30, which is
corrugated at its inner surface to fit upon the corrugated periphery of the part 1,
to hold it firmly thereto as seen in Figure 3.
The ring 30 is slightly smaller in external diameter than the internal diameter
of the rim 28, giving clearance when the drive chain E, is free from tension; that
is to say, when the pressure of the feet is insufficient to overcome the spring 5. In
addition to the feature of ball bearings shown in Figure 2, the construction therein,
affords the advantage of lateral support of the sprocket rim 28 of the part 2 by the
contact of its plates 31 with the flange 20 of the part 1, in case of lateral displace-
ment of the part 2.
In Figures 5 and 6, the ball bearings and spring rings are dispensed with, and
the india rubber friction ring 30 is employed exclusively; being fixed to the
part 1 by a corrugated fit, as before, and having its slipping contact within the
part 2.
In Figure 7, the part 41 is provided with a convex friction rim of V-shaped
cross-section, and the part 42 is provided with a separable concave groove of
corresponding shape; the use of rubber being dispensed with.
It is of course to be understood that the frictional surfaces of the parts 1 and 2
may be of any suitable material such as india rubber, leather, raw bide, or metal
upon metal.
The operation is as follows; The crank shaft hanger A is movable in a line a-b
which is at an angle a-c to a line c-d perpendicular to line e-fintersecting the
shaft centers C, D. During the act of mounting, the cranks are idle, making it
easy to at once place the feet on the pedals. As soon as a down thrust is made on
either of the pedals, the crank shaft hanger A is forced downward on the line a-b
compressing the spring 5, and the distance between centers C, D, being therefore
increased, the drive chain E is made taut to its limit and thenceforth the
outer part 2 of the sprocket wheel F is diametrically moved with relation to the
part 1, and drawn to a position slightly eccentric to the crank shaft center or
axis C. The two part friction device is thus brought into engagement during each
downward thrust of the feet of the rider, and during the passage of each pedal in
that portion of its orbit most effective between the dead centers. Intervening said
down thrusts, and during the passage of the pedals in the portion of their orbits
least effective and including the dead centers, the cranks and crank shaft and
part 1 of the sprocket wheel F may revolve independently of the part 2 either
faster or slower, thereby changing the relative number of revolutions. According
as the run is on a level or on a grade, up or down, the periods of the engagements
between parts 1 and 2, are varied by the natural change in action of the feet of the
rider. On a level, the periods are repeated in a slow or fast series at will, according
to speed desired. On an ascending grade, the periods are repeated in rapid series,
and loss of headway is avoided by reducing or practically eliminating the dwell
and interruption of work between the ascendant and descendant motions of the

page_text: pedals at the dead centers of the cranks and the attendant loss of stored momentum
as in the case when a fixed rotative relation of the driving and driven parts is
maintained throughout the entire revolution. On a descending grade, the periods
of engagement of the parts 1 and 2, are repeated in a slow series, saving fatigue,
and at any part of the revolution the pedals may be allowed to rest and support
the feet in coasting. In all cases, the pedals when depressed while at rest, will
cause the two friction parts 1 and 2, to act as a brake and stop or regulate the
speed of the machine at pleasure.
It is to be understood that I do not confine my invention of utilizing the drive
chain in the manner set forth, to the control of a two part engaging device of the
character shown, but that I intend to cover broadly the use of such chain in a
bicycle to operate any diametrically movable speed changing part.
The rear sprocket wheel 32 may be constructed of two frictionally engaging
parts in lieu of the front sprocket wheel being so constructed.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, 1 declare that what I
claim is;
1. In a velocipede, the combination with a frame and traction wheel, of a two
part rotary device consisting in a driving part connected to the pedal shaft and
a driven part connected by suitable means to impart motion to said traction
wheel, both said parts being yieldingly mounted and diametrically movable with
reference to said frame, and means for limiting the diametric movement of said
driven part whereby the same is engaged by the diametric movement of the
driving part produced by the foot pressure of the rider.
2. In a velocipede, the combination with a frame and traction wheel, of a
propelling device comprising sprocket wheels, a drive chain, and a pedal shaft
carrying one of said sprocket wheels and diametrically movable with reference to
said frame in a direction whereby said chain is drawn taut by each impulse in the
driving action of the rider; one of said sprocket wheels being constructed of two
engaging parts of which one part is revolubly and diametrically movable with
reference to the other part, to effect their engagement when the said chain is
drawn taut.
3. In a rear driven bicycle, the combination with a frame and traction wheel,
and a rear sprocket wheel attached to the traction wheel, and a drive chain, of a
pedal shaft and front sprocket wheel thereon yieldingly mounted on said frame so
as to move in a direction oblique to the length of said chain and produce tension
of the same when the foot pressure of the rider is applied to the pedals; said
front sprocket wheel being constructed of two parts revolubly and diametrically
movable with reference to each other, the one part connected to said pedal shaft,
and the other part carrying said drive chain and having its diametric movement
limited thereby, said parts having suitable frictional engaging surfaces adapted to
engage and bind the one with the other, when the said chain is drawn taut.
4. In a rear driven bicycle, the combination with a frame and traction wheel,
and a rear sprocket wheel attached to the traction wheel, and a drive chain, of a
pedal shaft, and a front sprocket wheel constructed of two frictionally engaging
parts revolubly and diametrically movable with reference to each other, the one
part connected to said pedal shaft and the other part carrying said drive chain and
having its diametric movement limited thereby, and a shaft hanger yieldingly
attached to said frame and carrying said pedal shaft and front sprocket wheel,
and rendering the same diametrically movable in a direction oblique to the length
of said chain so as to draw the same taut when the pedal shaft is depressed,
substantially as and for the purpose described.
5. In a rear driven bicycle, the combination with a frame and traction wheel,
and a rear sprocket wheel attached to the traction wheel, and a drive chain, of a
pedal shaft and a front sprocket wheel constructed of two frictionally engaging
parts revolubly and diametrically movable with reference to each other, the one

page_text: part connected to said pedal shaft and the other part carrying said drive chain and
having its diametric movement limited thereby, and a shaft hanger yieldingly
attached to said frame and carrying said pedal shaft and front sprocket wheel, and
rendering the same diametrically movable in a direction oblique to the length of
said chain so as to draw the same taut when the pedal shaft is depressed, and a
spring for raising the said hanger, substantially as and for the purpose described.
6. In a velocipede, the combination of a frame and wheels, a yieldingly
mounted hanger on the frame, a drive shaft mounted in the hanger, a drive chain,
a clutch part fast upon the shaft, a second clutch part yieldingly mounted upon
said first clutch part and carrying said chain which limits the movement of said
second clutch part so as to engage the same by the driving action of the rider.
7. In a bicycle, a two part sprocket wheel, the one member diametrically
movable with reference to the other to effect transmission, and elastically
supported annular guides upon the one said part tending to center and serving
to guide the other said part, substantially as set forth.
Dated this 3rd day of February 1896.
H. D. FITZPATRICK,
70 Wellington Street, Glasgow, Agent.