Improvements in Crank Mechanisms.
Year: 1889

page_text: Date of Application, 24th Aug., 1889-Accepted, 12th Oct., 1889
COMPLETE SPECIFICATION.
Improvements in Crank Mechanisms.
I, OTTO FREDRIK ALFRED JORGENSEN of Helsingfors in the Duchy of Finland,
Russian Empire, Mechanician do hereby declare the nature of this invention to be
as follows:-
This invention relates to a crank, so disposed, that it during a revolution moves
with a greater speed with relation to the crank shaft, when the turning force acting
upon the crank has its least moment and with a less speed with relation to the
shaft, when the force has its greatest moment. As however the turning force
behaves differently at such a crank, moved by means of a common treadle, as for
instance at a spinning wheel or a bicycle than at for instance a steam engine
crank, inasmuch as the force in the first case acts only once during the stroke, but in
the last case twice, namely the first time when the piston moves in the one direction,
and the second time when the piston moves in the opposite direction, this con-
struction is also somewhat different for the one and the other kind of cranks,
owing to the division just mentioned.
In the figs.
and 2 on the annexed drawing, it is thus shown how a crank of
the first kind is disposed and in the figs. 3, 4, 5 and 6 its motion is schematically
represented. The other figures show the disposition of the crank belonging to the
second type.
The
Reverting now to figs. 1 and 2, A is the crank shaft and B a bearing supporting
the shaft. C is a crank lever loosely fixed on the end of the shaft A, and D is
the crank pin.
A little further up on the shaft there is an eccentric E fixed at
the bearing B so as not to partake in the rotatory motion of the shaft.
eccentric is surrounded by a ring F, from which two arms G project radially in
two diametrically opposite directions. The arms G pass displaceably through two
pivots H, the one fixed to the crank lever and the other to another lever I firmly
united with the shaft A at its extreme end. The levers C and I are pivotted on
the same centre. The crank is in figs. 3, 4, 5 and 6 represented in four different
positions. For the sake of comparison, an elongation I" of I towards the crank pin
may be considered as a common crank lever. The lines in the said figures have,
besides, the same designations as the parts in figs. 1 and 2 which they are intended
to represent. Fig. 3 shows schematically the relative position of the parts in fig. 2.
Owing to the eccentrics I and G forming an anglo to each other, the crank lever C
united with G is therefore in front of I" with respect to the direction shown by
the arrow.
Imagining now the whole system to turn as shown by the arrow, it will be seen,
that after a quarter of a revolution of the shaft, fig. 4, 1" and C are just opposite
After still a quarter of
one another, has thus moved with less speed than I¹¹.
a revolution, fig. 5, C has got behind 1" and has thus continued to move with
less speed than I". After the next quarter of a revolution (fig. 6) I and C are
again just opposite each other and Chas thus commenced to move with a greater
speed than I so as to have reached the same. During the next following quarter of
a revolution, C moves likewise with a greater speed than I¹¹, so as to surpass it, fig. 3,
and will be in advance as much as it, half a revolution previously, was behind I". The
crank pin D moves thus during the half revolution, the right side figs. 3-6, more
slowly, and during the next half revolution, the left side, same figures, more rapidly
than I or the shaft A. If the crank constitutes the crank of a bicycle, the eccentric
is located as shown on the drawing, so that the treading takes place during last part
of the revolution, when the crank moves with less speed than the shaft. In order to
produce the same effect at a common crank and in employing the same force, such a
crank must be actuated during more than half a revolution. The both cranks of the

page_text: bicycle get in the usual diametrical position to one another twice during a revolution,
figs. 4 and 6, but will never be in the same plane when passing the dead point but
will then form an angle, so that the cranks help one another over the centre.
If the crank is moved by means of a simple treadle that is to say a treadle pivotted
at its one end and not at its middle, it is only to be looked to that the eccentric has a
right position so that the motion of the crank with relation to the greatest and the
least moment of the force, will be in analogy with what has already been said.
At, for instance, a steam engine crank or such a crank as is moved by means of a
treadle pivotted at its middle, as at a sewing machine, the disposition of the crank
must be different, as that which is gained during the one half revolution, would other-
wise be lost during the next half revolution. For that purpose the crank is so disposed
that it moves more rapidly at the both occasions, when it passes the centre, and in the
meantime with a lesser speed, thus, during a revolution, twice with a greater and twice
with a lesser speed. This is effected by putting also the eccentric in motion, in the
opposite direction with relation to the crank.
Fig. 8 shows the construction of the crank, figs. 7, 9, 10 and 11 are details and
figs. 12-20 show schematically the motions of the crank.
The arrangement is in substance the same as shown in figs. 2 and 1. The crank
lever is at its outer end united with the one arm G¹ of the eccentric ring F.
The other arm of the eccentric ring is united in the same way with another arin I'
fixed on the shaft. In order to show the pivotted connection at the ends between
the arms the arm 1' is represented separately in fig. 7. It has in the end a hole,
into which a pin a is screwed in against which rests another movable pin b, fig. 10,
being forked in part of its length, so as to clasp the arm G while itself it is
clasped by a ring c, projecting from the arm I and intercepted in two places.
The eccentric E. surrounds a nave of the crank lever C, constituting itself a nave
to a conic toothed wheel d gearing with one of two other toothed wheels e and f
gearing with one another. The pin a is provided with a flange, or also a ring a¹
may be screwed upon it, for the purpose of putting against G so that the arm
in its order closes tightly to a rebate on d. The wheel is fixed firmly on the
shaft A', wherefore the wheel d will move in the opposite direction of that of the
shaft, when the latter is turned. The toothed wheels are likewise of the same size,
so that while the shaft makes one revolution in the one direction, the wheel d or
the eccentric makes a revolution in the opposite direction. Fig. 12 corresponds
with fig. 9, and in all the figures 12-19 a common crank is represented by an
elongation I of the line corresponding to the part I. The crank is considered
to rotate in the direction of the arrow and to be acted upon by a horizontal con-
necting rod as at a steam engine with a horizontal cylinder. The eccentric moves
in the opposite direction of the crank. Figs. 12-14 constitute of a revolution,
at the beginning of which, fig. 12, C₁ is in advance of I" but at the end of which,
fig. 14, C is behind 1", thus C has moved with a less speed than I". The next
of a revolution figs. 14-16, C₁ moves anew with a greater speed than I so that
it is in advance of 1" at the end of the same period although it at the beginning
was behind.
The next quarter of a revolution, figs. 16-18, C¹ moves with a less
speed than I and at the following quarter of a revolution, fig. 18, 19 and 12 again
with a greater speed. Fig. 20 shows the whole run during a revolution.
vto the crank moves more slowly, from a to y more rapidly, from y to z again more
slowly and from z to v again more rapidly than the crank shaft. During the course
from to y and from z to the crank passes by the dead points and moves thus
midway between these points, when the force has its greatest moment, with a less
speed. If a double-acting treadle is employed (treadle pivotted at its middle) the
arrangement will be quite the same, but the whole system must be imagined as
having made of a revolution, so that the connecting rod, in lieu of being horizontal
will be vertical.
From
For the sake of still greater clearness fig. 21 represents in plan two cranks in the
supposition that two single acting treadles are to be employed. The arrangement is
somewhat simplified inasmuch as the crank pin D is fixed directly at the eccentric

page_text: fork G. The pin moves with this construction in a circular trajectory concentric with
the eccentric and eccentric with the centre of the shaft, and in this way the distance
from the axis to the pin will be greater during the down stroke and shorter during
the up stroke. In order to diminish the friction balls are placed between the
eccentric E, fig. 21, and the eccentric rod just as at a ball bearing. B' are bearings
for the shaft A. The pin D2 is concentric with the eccentric and runs in a separate
bearing.
Finally, figs. 22 and 23 show a modification of the said crank construction. On the
crank shaft A, there is a toothed wheel A2 firmly united with the bearing B of the
shaft, so as not to partake in the rotatory motion of the shaft. On the shaft there is
further fixed by means of a key, a pulley A³, containing in its turn a little crank
pulley B2 on the shaft of which, traversing the great pulley is fixed a toothed wheel A*
gearing in and being of the same size as the toothed wheel A². A bearing A fixed
on the pulley A serves as support for the shaft of the pulley B². On the end of the
shaft A is loosely passed a crank lever C2 provided with an elongation into which a
little slider is inserted into which the eccentric pin B³ of the crank pulley B² enters,
or also only provided with a radial slot for the said pivot. In turning the crank the
pulley B² makes a revolution at every stroke of the crank, by which the crank-lever C
is put in an oscillating motion past the centre of the pulley B². The position of the
crank-pin after each of a revolution is indicated by the construction lines in
fig. 23. If the rotatory motion takes place in the direction of the arrow, it will be
seen, that departing from the position indicated in fig. 23 and approaching the
horizontal one and during still as long a way, the motion is decreasing and during the
rest of the stroke to the starting point increasing. The treading continues thus more
than during half a revolution. For a double acting treadle two toothed wheels of
different size may be used, that, fixed on the shaft of the pulley B³, half as great as the
other. The pulley B² will then move twice as fast, its pin making two revolutions
during one revolution of the shaft A, and the crank-lever C oscillates twice during
the same time. It will then be the same case, as shown by the figures 12-20).
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed I declare that what I claim
is :
1. The arrangement of a crank in order to render its motion intermittent with
respect to the shaft when being turned, consisting therein that the crank pin is fixed
either on a ring of an eccentric fixed on the shaft and immovable with respect to the
latter, or also on an arm, movable on the shaft and loosely connected with the ring,
while the ring in both cases is loosely connected with another arm firmly fixed on the
shaft.
2. At the arrangement of the crank described in claim 1, the modification that the
eccentric constitutes a nave of, or is connected with a toothed wheel loosely fixed on
the shaft, this wheel being, by means of an intermediate wheel gearing with another
toothed wheel fixed on the shaft, with the view that the eccentric may, at the rotatory
motion of the shaft, rotate in the opposite direction of the shaft.
3. At the arrangement of cranks designed in claim 1, the modification that in lieu
of the eccentric there is inserted into a pulley fixed on the shaft a smaller pulley
provided with a crank pin entering into a slot in an elongation of the crank-lever
passing on the other side of the centre, or into a slider in this slot, while the smaller
pulley on its shaft is provided with a cylindric toothed wheel gearing in a corresponding
wheel fixed loosely the crank shaft this wheel being stationary with respect to this
shaft.
London August 92nd 1880.
OTTO FREDRIK ALFRED JÓRGENSEN.
Per C. R. Bonne & Co.,
41, Eastcheap E.C., Registered Patent Agents.