IMPROVEMENTS IN PULLEY BLOCKS
Year: 1876

page_text: LETTERS PATENT to William Andrew Comber, of Birmingham, in the County
of Warwick, Engineer, for the Invention of "IMPROVEMENTS IN PULLEY
BLOCKS."
aled the 30th September 1876, and dated the 14th August 1876
PROVISIONAL SPECIFICATION left by the said William Andrew Comber
at the Office of the Commissioners of Patents on the 14th August 1876.
WILLIAM ANDREW COMBER, of Birmingham, in the County of Warwick,
Engineer. "IMPROVEMENTS IN PULLEY BLOCKS."
This Invention has for its objects the simplification of the arrangements
hitherto used in differential pulley blocks, the power of substituting ropes or other
smooth flexible substances for chains, the arrangement of power and weight in one
line or plane, and the use of the friction of the ropes themselves to cause the weight
lifted to be self sustaining.
The Invention consists in making pulley wheels or blocks with a deep circum-
ferential groove wide enough to allow a hauling rope to make easy entrance or
exit, and in arranging such pulleys in one line or plane, the top pulley being
suitably connected or slung to any fixed support, and the lower pulley being used
as the rising and falling block to which the weight to be lifted is attached;
in using in combination with such an arrangement of pulleys a hauling rope made
endless and passed round each pulley three or more times, commencing and
finishing with the top one, each layer of rope resting on the preceding one.
and
A differential arrangement is thereby obtained, for as the outer layer of rope
is hauled off the top pulley the inner layer is fed on to it, and the lift of load is in
proportion to the difference of the circumferences or radii of the inner and outer
ropes divided by the circumference or radius of the outer one, and by twice the
number of turns of rope round the bottom pulley. The difference between the
power and weight is increased by the increase of the pulleys, the size of rope
remaining the same.
In raising or lowering as all the layers of rope move with each pulley in the
same direction, and at a rate proportional to their respective distances from the
centres thereof, there is no friction between them, but as they would have to move

page_text: in opposite directions, supposing the weight sustained ran down through the
influence of gravitation, the friction between them would in that case be con-
siderable, as the weight has a tendency to pull them closely together, and the
friction thereby caused is found to be more than sufficient to counteract the power
of the weight to overcome the inertia of the rope, thus an increase of weight gives
an increased power of self sustainment.
This self-acting friction arrangement thus allows of the use of such smooth flexible
substances as ropes in the place of chains for pulley blocks in which the load is
self sustaining, but chains can be used for the purposes of the Invention equally as
well as ropes. It also dispenses with extra friction clutches, which have been
introduced where ropes are used as ordinarily.
The top pulley may be keyed or otherwise fixed on a shaft which may be driven
by ordinary means, either with hand or steam power.
Two of the pulleys, as above described, may be keyed on the same shaft in juxta
position, and the same rope may be used on both, but wound round them in
opposite directions, so that as the falling block of the one pulley rises that of the
other one falls. In this arrangement if the pulleys are of equal diameter the slack
hauling loops of the rope will always remain the same length, and if of unequal
diameter one falling block will travel faster than the other with proportionally
reduced power of lift. It may therefore be used with advantage to gain time with
light weights.
For quick speed with a ratio of power to weight of about 1 to 6, and as a cheap
& effectual substitute for ordinary three or four sheave pulley blocks, the endless
rope is wound once only round the rising & falling pulley. In the fixed frame
above this pulley the rope is carried over two pulleys side by side, and the rope
friction necessary to sustain the load is obtained by passing the rope under an
intermediate pulley placed as low down in the frame as is found necessary; or a
self-acting clutch is employed to act on the rope between the two pulleys above
mentioned, the clutch being released from the ropes by an independent cord
arranged for such purpose.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Andrew Comber in the Great Seal Patent Office on the
14th February 1877.
WILLIAM ANDREW COMBER, of Birmingham, in the County of Warwick,
Engineer. "IMPROVEMENTS IN PULLEY BLOCKS."
This Invention has for its objects the simplification of the arrangements hitherto
used in differential pulley blocks, the power of substituting ropes for chains where
desirable, the arrangement of power and weight in one line or plane, and the use
of the friction of the layers of rope in causing the weight lifted to be self
sustaining.
The Invention consists in making pulley wheels or blocks with a deep circum-
ferential groove wide enough to allow a hauling rope to make easy entrance or
exit, and in arranging such pullies in one line or plane, the top pulley being
suitably connected or slung to any fixed support, and the lower pulley being used
as the rising and falling block to which the weight to be lifted is attached; and
in using in combination with such an arrangement of pullies an endless hauling
rope passed partly around each pulley three or more times, commencing and ending
with the top one, cach layer of rope resting on the preceding one.
A differential arrangement is thereby obtained, for as the outer layer of rope is
hauled off the top pulley the inner layer is fed on to it, and the lift of load is in pro-
portion to the difference of the circumferences or radii of the inner and outer ropes
divided by the circumference or radius of the outer one, and by twice the number

page_text: of turns of rope round the bottom pulley. The difference between the power and.
weight is increased by the increase in diameter of the pullies, the size of rope
remaining the same.
In raising or lowering as all the layers of rope move with each pulley in the
same direction, and at a rate proportional to their respective distances from the
centres thereof, there is no friction between them, but as they would have to move
in opposite directions supposing the weight sustained ran down through the
influence of gravitation the friction between them would in that case be con-
siderable, as the weight has a tendency to pull them closely together, and the
friction thereby caused is more than sufficient to counteract the power of the
weight to.overcome the inertia of the rope, thus an increase of weight gives an
increased power of self sustainment.
This self-acting friction arrangement thus allows of the use of such smooth
flexible substances as ropes in the place of chains for pulley blocks in which the
load is self sustaining, but chains can be used for the purposes of the Invention
equally as well as ropes. It also dispenses where desirable with extra friction
clutches, which have been introduced where ropes are used ordinarily.
The top pulley may be keyed or otherwise fixed on a shaft which may be
driven by ordinary means, either with hand or steam power.
Two of the pullies, as above described, may be keyed on the same shaft in juxta-
position, and the same rope may be used on both but wound round them in
opposite directions, so that as the falling block of the one pulley rises that of the
other one falls. In this arrangement if the pullies are of equal diameter the slack
hauling loops of the rope will always remain the same length, and if of unequal
diameter one falling block will travel faster than the other with proportionally
reduced power of lift. It may therefore be used with advantage to gain time with
light weights.
For quick speed with a ratio of power to weight of about 1 to 6, and as a cheap
and effectual substitute for ordinary three or four sheave pulley blocks, the endless
rope is wound once only round the rising and falling pulley. In the fixed frame
above this pulley the rope is carried over two pulleys side by side, and the rope
friction necessary to sustain the load is obtained by passing the rope under an
intermediate pulley placed as low down in the frame as is found necessary; or a
self-acting clutch is employed to act on the rope between the two pullies above
mentioned, the clutch being released from the ropes by an independent cord
arranged for such purpose.
On the accompanying Drawings 1, 2, Figures 1 and 2 represent a pair of pullies
of equal diameter formed with the said deep circumferential grooves 3, which in
this instance are deep enough to allow of four or five thicknesses of endless hauling
rope 4 being wound round the pullies in the manner shown. The top pulley Ĭ
being slung to any fixed support, and a weight being attached to the bottom
pulley 2, the weight is slowly raised by pulling on the right hand side 5 of the
slack loop of the rope 4, and is slowly lowered by pulling on its left hand side 6.
(The number of coils of rope may be increased, and the pullies need not be
necessarily of the same diameter. The frame and hook are of the ordinary con-
struction.) This arrangement is self sustaining when left to itself, the power of
self sustainment being mostly due to the side wedging pressure of the layers of
ropes, as shown at their section at 7; as a further security the part of the top frame
of the pulley which surrounds it for the purpose of keeping the rope in place may
be inade of two side bars 8 turning loosely on the centre pin 9; and a heavy roller,
as at 10, may be placed to bear on to the outer layer of rope, tending to keep it
pressed to the others and prevent it slipping, or a roller may be placed on both sides
in such a manner as to press the ropes inwards and close to one another.
The pullies are shown solid, as though made of hard wood, but they may be
made with arms and hollow bays for obtaining lightness when made of iron.
Having now described the nature and objects of my said Invention, together
with the manner in which the same is to be or may be performed, or carried into

page_text: practical effect, I would remark in conclusion that I do not limit myself to the
precise details of the improvements herein-before described or shown on the
accompanying Drawings, as the principle of my Invention may be carried into
practice in various ways; but what I more particularly claim as my Invention is,
the general construction and arrangement of differential pulloy wheels or blocks (for a
the purpose of lifting and lowering weights, or for drawing objects together with great
force) having deep circumferential grooves in one line or plane, so that the whole
strain, both of the lifting power and the weight, will act centrally therein, and
otherwise arranged as specified, and in combination with which chains or endless
round flexible substances, such as ropes, are used, being coiled around in layers on 1
or above one another, so that as one side or end is drawn off the other is drawn
on, and so that the friction thereof is utilized in causing the load to be self
sustaining.
In witness whereof, I, the said William Andrew Comber, have hereunto set
my hand and scal, this Thirteenth day of February, in the year of our Lord 1
One thousand eight hundred and seventy-seven.