Improvements in Differential Pullies for Rope Tackle.
Year: 1892

page_text: Date of Application, 12th Mar., 1892
Complete Specification Left, 12th Dec., 1892-Accepted, 21st Jan., 1893
PROVISIONAL SPECIFICATION.
Improvements in Differential Pullies for Rope Tackle.
I, LJUBOMIR KLERITJ, Professor of the Polytechnical High School at Belgrad,
Servia do hereby declare the nature of this invention to be as follows:--
The differential pullies usually employed for raising and lowering loads and for
holding them when raised are usually worked with chains which engage with
projections and recesses in the peripheries of the pullies in such a manner that they
do not slip.
My invention relates to the construction and arrangement of differential-pullies
in such a manner that they can be worked with ropes instead of chains. For this
purpose, instead of making the system consist of a single large and a single small
pulley on one axis, I fix several large and several small pullies say for example
three of each, side by side, ou the one axis with guide pullies by which the rope
is led over the three larger pullies successively then under the suspending pulley
and from it over the three smaller pullies successively.
Thus by multiplying the friction of the rope on a number of pullies I prevent it
from slipping. In order to obtain as much friction as possible I arrange the guide
pullies so that the part of the rope passing to each acting pulley crosses the
part passing from it, thus causing the rope to embrace nearly the whole
circumference.
Instead of placing all the large and all the small pullies on one axis, I may
divide them into a number of pairs, each pair consisting of a large and a small
pulley on one axis, and I mount these pairs in a suitable framing and lead the rope
from the large pulley of one-pair to the large pulley of another pair, and so on,
then under the suspending pulley and thence over the smaller pullies successively.
I arrange the pairs of pullies relatively to each other in such a manner that the part
of the rope passing to each crosses the part passing from it, thus causing the rope
to embrace nearly the whole circumference.
Dated this 19th day of March 1892
ABEL & IMRAY,
Agents for the Applicant?
COMPLETE SPECIFICATION.
Improvements in Differential Púllies for Rope Tackle.
I, LJUBOMIR KLERITI, Professor of the Polytechnical High School at Belgrad,
Servia,-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 :-
The differential pullies usually employed for raising and lowering loads and for
holding them when raised are usually worked with chains which engage with
projections and recesses in the peripheries of the pullies in such a manner that they
do not slip.
My invention relates to the construction and arrangement of differential pullies
in such a manner that they can be worked with ropes instead of chains. For this
purpose, instead of making the system consist of a single large and a single small-
pulley on one axis, I fix several large and several small pullies say for example
three of each, side by side, on the one axis with guide pullies by which the rope is
led over the three larger pullies successively then under the suspending pulley and
from it over the three smaller pullies successively.

page_text: Thus by multiplying the friction of the rope on a number of pullies I prevent it
from slipping. In order to obtain as much friction as possible I arrange the guide
pullies so that the part of the rope passing to each acting pulley crosses the
part passing from it, thus causing the rope to embrace nearly the whole
circumference.
Instead of placing all the large and all the small pullies on one axis, I may
divide them into a number of pairs, each pair consisting of a large and a small
pulley on one axis, and I mount these pairs in a suitable framing and lead the rope
from the large pulley of one pair to the large pulley of another pair, and so on,
then under the suspending pulley and thence over the smaller pullies successively.
arrange the pairs of pullies relatively to each other in such a manner that the
part of the rope passing to each crosses the part passing from it, thus causing
the rope to embrace nearly the whole circumference."
'I
On the accompanying drawings are shewn various forms of differential pullies
constructed according to my above described invention.
Figs. 1 and 3 shew constructions with three differential pullies, and Figs. 2 and 4
shew constructions with four such pullies, these being mounted on axes parallel
to each other arranged either at the corners of a polygon, such as a triangle as at
Fig. 1 or a square or parallelogram as at Fig. 2, or in line with each other as at
Fig. 3, or both in line and at the corners of a polygon as at Fig. 4.
Figs. 5 and 6 shew a side and front view of an arrangement in which all the
differential pullies are arranged upon a common axle, in a similar manner to a
differential drum.
Figs. 7 to 10 shew a modification of the construction at Figs. 5 and 6.
In the construction illustrated by the Figs. 1 to 4 the small pullies are shown in
front of the larger ones, and the pullies of the same size are in the same plane.
The differential puilies I, II, III, IV turn upon parallel axes A, B, C, D, which
are journaled in a framing G that is suspended by a hook F from a fixed support.
In addition I employ a loose pulley V, the axle of which supports the load Q by
means of a hook L. The parts of the endless rope stretched by the half load (Q)
are s and s¹.
The part s represented in full lines, is led around the larger circumferences, and
the parts s shewn in dotted lines, runs around the smaller pullies; they end in the
parts and which are united so as to form an endless rope.
The manner in which the rope travels around the pullies is shewn in the drawing
by arrows and is so effected that the rope embraces the whole or nearly the whole
circumference of the differential pullies in order to augment the friction. In Fig. 3
the loose parts are conducted laterally by small guiding pullies t t.
Assuming the radius of the larger pullies to be R, and that of the smaller ones r,
then the winding of the rope around the larger pullies by the strain Q, working
at s, will effect the turning of all the differential pullies with the moment Qx R;
the winding of the rope around the smaller pullies effects a movement, but in
the opposite direction. Leaving the axle-friction out of consideration the tendency
of turning of the whole system has a moment QR Q Q (R).
-
↑ー
In order to have a statical equilibrium or to raise the load Q, there must be
applied to the part 2 of the rope a force P, which works upon the larger pulley
with the moment PR. For the static equilibrium PR=Q (R − r), provided
that the moving force P
Q (R―r).
2 K
=
-
-
A and 2 R=D: P
1
=
D
Ris the width of the ring of the differential pullies and 2 R is the diameter
of the larger pulley therefore, if R-
Q which is
the equation for the known differential tackles. In order that the ropes may not
slip by the downward pull of the load Q, it is necessary to employ a force p upon
the not strained part s and of the endless rope which force is produced by the
band brakes and of which the first one works upon the large circumference,

page_text: the other upon the smaller circumference of the differential pullies and brake the
rope.
The small force required to be exerted upon the band brakes the one end of
which is fixed at E, is provided by a small weight g, suspended at the other end,
but it is obvious that a spring may be used for this purpose. The brake is however
seldom necessary, as the number of differential pullies is taken in correspondence
with the load to be raised, so that only a few pounds are necessary to prevent the
slipping of the rope, which force is abundantly produced by the loose rope hanging
down.
In Figs. 5 and 6 is represented a modified construction of tackle, with differential
pullies arranged parallel to each other, which have a common axle or shaft æ.
The pullics are here formed as a differential drum with two diameters, D. and d,
D being larger than d.
The part of the drum with the larger diameter is divided into a certain number
of grooves such as three, as shewn in the drawing marked 'I'III', and which
are parallel and receive the windings of the endless rope.
Also the part with the smaller diameter d is divided into an equal number of
grooves II" III" in which also runs the endless rope. In order to prevent a
helical or screw like motion of the rope in an axial direction due to the like
winding of the endless rope I employ a corresponding number of guiding pullies or
rollers Z, arranged upon a common stationary axle y, which guiding pullies are
also provided with grooves and are usually of equal diameter.
In addition I employ a loose pulley V, from the axle of which is suspended the
load Q by means of a fork K and hook L.
The travel of the rope is indicated by arrows in the Figs. 5 and 6 it runs alter-
nately around the drum and the loose guiding-rollers.
The slipping of the loose parts, 5, of the rope, when no lifting force works, is
prevented by the brake-blocks 2 pressed on by the springs ff, but as that
force is smaller than the weight of the loosely hanging rope so, the brake-blocks
may be dispensed with.
The tackle illustrated in the Figs. 5 and 6 may also be used as differential rope
windlass, if the drum is rotated by means of a crank applied to the axle X.
In the Figs. 1-4 and 6 the edges of the pullies, which prevent a lateral
displacing of the rope, are omitted for the sake of clearness.
Experience has shewn that the construction of differential tackle, illustrated in
Figs. 5 and 6 is subject to some inconveniences, as the parts of the rope, wound in
the grooves III III and I" "II" may be subject to increasing tensional
strains, whereby the axle y'y of the guiding rollers Z Z will be subjected to so
great a transverse strain that the working of the apparatus may be stopped, or
even a slipping of the rope in the opposite direction to that of the motion may take
place whereby the rope would become rapidly worn out and break at III or III".
The cause of this defect lies in the fact that it is nearly impossible to make the
diameters of the grooves of the small drum, among themselves, and those of the
great drum, among themselves, mathematically equal, as every groove must be
separately turned. For example if the differences in the diameters of the
grooves III III" of the small drum were but 0.2 "/m, this would be sufficient
to create in the ropes running in these grooves, a tension or strain, progressively
increasing by the turning motion, so that finally a slipping, stopping and breaking
of the rope would result.
ง
These evil effects would be still further increased if the grooves I' 11' III' of
the larger drum were also of varying diameters.
In these cases the grooves III III operate relatively to each other as
differential pullies; the pullies Z Z would then act in respect to the several
grooves as the loose pulley V in respect to the whole gearing so that the pullies Z
would be powerfully drawn up towards the axis XX.
In order to avoid the above inconvenience, I prefer to employ the construction
shewn in the Figs. 7 to 10.

page_text: Here the drumuis made of two cylinders of the same length, but of different
diameter, which cylinders are limited by projecting flanges a and b c and form a
solid block, as may be seen in section at Fig. 9.
Each cylindrical part, (between ab and c) is divided by 2 grooves k¹ k² respec-
tively into 3.rings and R R R³, which are turned upon a lathe of an
exact uniform diameter d and D so that the inconvenience mentioned above is
prevented..
In order to prevent a lateral displacing of the rope wound around these rings in
the direction of the axis X X, I fit into the grooves annular flanges sc
which may either be stationary or rotate with the drum and which may be made
of two parts (as shown in Fig. 10) connected together by plates nn and rivets or
screws.
Having now particularly described .and. ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that, what I
claim is :-
1. A rope-differential tackle, consisting of several pullies or rings I II III.
Figs. 1to 4, each of which turns upon a stationary system of parallel axes A, B, C
in a common plane, and over which is wound an endless rope in such a manner that
it passes from the pulley V carrying the load on the one side over the part of sinall
diameter and on the other side over the part of large diameter of the differential
pullies, the rope being made to embrace the whole or nearly the whole of the
circumference of the pullies in order to prevent slipping substantially as set forth.
2. The modified construction of the apparatus set forth in the first claim wherein
the differential pullies are formed as an integral drum mounted upon an axle X X
Figs. 5 and 6 and in which the rope-is led alternately over grooves of the
differential drum and over special guiding rollers Z Zlin order to prevent a helical
motion of the rope, such guiding rollers being mounted upon an axle Y. Y parallel to
the drum axis XX and capable of. turning independently of each other and of
sliding in the direction of the axis, in order to be enabled to follow automatically
the movements of the rope wound around the drum; substantially as set forth.
3. In the modified construction referred to in the second claim the arrangement,
illustrated in Figs. 7 and 8, whereby the differential drum is formed of two
cylinders of different diameter, which are limited by flanges or rims a b c and is
divided between these flanges by annular grooves k₁k into an equal number of
rings R₁¨R₂ Rį r¹³µ³, Fig. 9, into which grooves may be fitted moveable rings.c
Fig. 10 for preventing the lateral shifting of the rope, substantially as set forth.
Dated this 12th day of December 1892.
ABEL & IMRAY,
Agents for the Applicant.