Improvements in Cranks.
Year: 1896

page_text: Date of Application, 14th Oct., 1896-Accepted, 14th Nov., 1896
COMPLETE SPECIFICATION.
Improvements in Cranks.
I, ALFRED ANTHONY of "Inglewood," 19 Beaconsfield Avenue, Colchester, in
the County of Essex, 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:-
This invention relates to an improved variable throw crank which is particularly
adapted for use in velocipedes, motor cars and the like, and it consists essentially
of a crank arm to the outer end of which is connected-by means of a ball bearing
-a short swinging link the free end of which is adapted to carry the pedal or its
equivalent, the movement of the said link being controlled by a spring so arranged
and adapted to operate that when the swinging link is forced to the extreme limit
of its movement it becomes automatically locked in that position by the said spring,
the object being to automatically produce an elongation of the crank during that
portion of the stroke at which power is applied for propulsion in a manner more
perfect than at present obtains.
I am aware that many attempts have been made already to construct a variable
throw crank but those of which I am aware have failed from theoretical as well as
practical reasons.
To obtain the best results it is essential first that the crank shall commence to
extend at the earliest possible point after passing the upper vertical position.
Secondly, that the extension shall take place gradually and smoothly and not
suddenly with a jerk. Thirdly, that the swinging link be so guided with respect
to the crank arm that the strain caused by the overhanging pedal shall not twist
or distort the swinging link. Fourthly, that the length of the swinging link be as
short as possible and the bearing by which it is attached to the crank arm be of
maximum size, so that the whole of the strain on the pedal shall be carried by the
said bearing without any other guide. Fifthly, that the construction shall be such
as will cause the greatest possible amount of the power applied to the crank to be
transmitted to the latter through the pivot of the swinging link, and the least
possible amount thereof through the spring controlling it, thus avoiding over-
straining of the spring and enabling a lighter spring to be used.
In the accompanying drawing which illustrates this invention:-
Figure 1 is a view in side elevation of one form the invention may assume.
Figure 2 is a similar view of a modification thereof, and
Figure 3 is a view in cross section on line Figure 1.
Throughout the views similar parts are marked with like letters of reference.
The crank arm A. is provided with the usual eye a at one end adapted to receive
the axle to which it is attached by a transverse cottar pin in the manner well-
known. On the other end of the crank arm is formed a disc a¹ having curved
recesses adapted to form parts of two races of a double ball bearing by which a
swinging arm B is pivotted to the crank arm A, the other parts of the said races
being formed by a disc & formed on the swinging arm B and on the head c of the
pivot pin C, respectively as shown, the said pin being adapted to screw into the
lise 6 for the purpose of adjustment and being provided with a lock nut c¹ for
ocking it. The free end of the swinging arm B is provided with an eye b to
eceive the pedal pin. This eye may be of the construction shown or of any other
uitable construction.
To the periphery of the disc b' is pivotted a rod D adapted to slide in a
ylinder D pivotted to a snug or projection a' on the crank arm A. Part of the

page_text: rod D is threaded to adapt it to carry a collar d adapted to slide in the cylinder D¹.
On to the open end of the cylinder D₁ is screwed a cap D2 provided with a suitable
hole for the passage of the rod D. On the rod Dare mounted two springs E and E
the one-the stronger-being located within the cylinder D¹ between its closed end
and the collar d and the other between the collar d and the cap D2. The spring E
is adapted to act between the crank arm A and the swinging arm B to return the
latter to its normal position after it has swung out to increase the effective leverage
of the crank, and the spring El acts as a cushion to prevent the too sudden return
of the arm B. By arranging the point at which the cylinder D' is pivotted to the
crank arm A as shown by Figure 1 the spring E will act as shown in dotted lines.
as a lock to retain the swinging arm B in its extreme position for elongating the
crank arm until it is released by jerking the pedal with the foot.
The swinging arm B may be arranged either below the crank arm A as shown
by Figure 1 or above it as shown by Figure 2, but I find from experiment that the
former gives the best results in practice.
Although I prefer to pivot the swinging arm B to the arm A by means of a
disc double ball bearing as shown, I do not limit myself to the use of such a pivot
bearing as a double cone bearing will fulfil the conditions.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
(1) The combination of parts hereinbefore described and illustrated by the
accompanying drawing forming an improved variable throw crank.
(2) In a crank, the combination with an arm adapted to be fixed to the axle to
which motion is to be imparted, of a swinging arm adapted to carry the pedal and
pivotted to the free end of the arm fixed to the axle, and of a compound spring
connection between the fixed arm and the swinging arm, as and for the purpose
set forth.
(3) In a crank, the combination with an arm adapted to be fixed to the axle to
which motion is to be imparted, of a swinging arm adapted to carry the pedal and
pivotted to the free end of the arm fixed to the axle by means of a disc double ball
bearing, and of a compound spring connection between the fixed arm and the
swinging arm, as and for the purpose set forth.
(4) In a crank, the combination with an arm adapted to be fixed to the axle to
which motion is to be imparted, of a swinging arm adapted to carry the pedal and
pivotted to the free end of the arm fixed to the axle, of a spring connection
between the said arms so arranged that it acts as a lock to retain the swinging arm
in its extreme position for elongating the crank, as and for the purpose set forth.
Dated his 4th day of Och 1006.
ROBERT E. PHILLIPS, Assoc. M. Inst. C.E., M.I. Mech. E.,
Consulting Engineer and Patent Agent,
70, Chancery Lane, London, W.C., Agent for the Applicant.