Improvements in Self Locking Differential Pulley Blocks.
Year: 1889

page_text: Date of Application, 17th Sept., 1889-Accepted, 19th Oct., 1889
COMPLETE SPECIFICATION.
Improvements in Self Locking Differential Pulley Blocks.
1, CHARLES FRANKLIN BATT, of No. 327, Jefferson Avenue, Brooklyn, in the State
of New York, United States of America, Mechanical Engineer, do hereby declare
the nature of my said Invention and in what manner the same is to be performed
to be particularly described and ascertained in and by the following statement :-
The object of this Invention is to make a self-locking differential hoisting pulley
block of the simplest possible construction.
In the accompanying drawings, Fig. 1. is a side view of the improved self-locking
differential hoisting pulley, provided with a runner.
Fig. 2. is a corresponding edge view of the same.
Figs. 3, and, 4, are vertical sections of the differential pulley block, at right angles
to each other, drawn to an enlarged-scale, and
Fig. 5, is a view of a modification, drawn to a smaller scale.
In Figs. 1, and, 2, A, is the block containing the differential pulley wheel and
having a suitable hook, B, for the suspension of the tackle by the yoke, G, through
which the centre pin, P, passes. The rope, D, carries in one of its bottom loops the
runner, R, from which the weight is to be suspended and which may be of any suitable
construction.
In differential pulleys of ordinary construction, the pulley wheel is usually provided
with two separate grooves of different diameters for the two turns of chain or rope,
the hoisting power of the differential tackle depending on the difference between
these diameters.
In this improved differential pulley, however, the two turns of rope are so guided that.
they lie one on the top of the other where they pass over the pulley wheel and an
important feature of the invention is the combination with the pulley wheel and the
two turns of rope lying over each other on the wheel, of dovices to automatically
grip the rope under the weight of the load. For this purpose there is provided the
pulley wheel, E, having a single deep guiding groove for the two turns of rope with
a series of gripping levers, F, pivoted to the wheel and of such a construction that
the strain upon the rope of the weight being hoisted will so act upon these levers
that they will grip the outer turn of the rope and prevent the wheel from turning
except when the hoisting power is applied. By this means the pulley is self-locking
with the load at any height and the holding power of the levers is in exact proportion
to the load.
The differential pulley may be either mounted to turn on the centre pin, P, or may
be fixed to the pin which will then turn in bearings in the block. In the latter
case, the hoisting power may be applied to the differential pulley, instead of directly
to the rope.
It is preferred to construct the gripping levers, F, of the elbow-lever form
illustrated in Fig. 3. and to pivot them within lateral notches in the side flanges of
the groove of the wheel. Ears, e, are formed at the edges of the notches for
convenience in pivoting these levers and for purposes of strength. It is preferred to
mount these gripping levers in both flanges of the grooved pulley, on opposite
sides of the rope, although this may not be necessary in hoisting pulleys for light
loads. It is preferable when using gripping levers on both sides of the rope, to
arrange them in pairs, as illustrated in Fig. 4. but a little out of line with each
other, so that the lower arms of the two elbow lovers may overlap each other, as
shown in Fig. 3. and so that the upright arms of these two elbow levers may
grip the rope with a better holding effect, as will be understood on reference to
Fig. 2.
In order to guide the two turns of rope properly onto and off the differential
pulley, two openings, p, are formed in the lower part of the block, each opening

page_text: of a flattened oval shape and with antifriction rollers, b, at the edges for the outer
turn of rope to run against.
It will be understood that at any one moment in the operation of the pulley, only
those gripping levers which are above the horizontal plane passing through the axis
of the pulley, are so acted upon by the strain on the turns of rope as to grip the
outer turn of rope, and as the two ropes pass off the pulley, the pressure on the
inner arms of the gripping levers is removed at that point and the grip upon
the outer rope is accordingly relieved. The long arms of the elbow levers then
drop back by gravity and leave the groove open as shown at the lower part of Fig. 3.
until the oncoming turn of rope at the otlier side of the wheel presses against the
short arms of the elbow levers. As the turns of the rope travel together and the
difference of speed between the two is in exact proportion to and in fact due to
the difference of the radial distances of the centre lines of the rope from the axis
of the pulley, there is no rubbing friction between the two ropes.
Although the differential pulley has been shown as provided with eight pairs of
gripping levers, the invention is not to be restricted at all in this respect, as their
number may vary according to circumstances. For ordinary purposes six pairs of
such levers will suffice.
The block of the pulley may be constructed in any suitable way.
In the present
instance it is shown as made in two parts and held together by the pins, b, of
the anti-friction rollers, b, and by the centre pin, P, on or with which the differential
wheel turns.
If it is desired to construct the block for very heavy work, there may be com-
bined with the differential wheel in the block an additional loose wheel, W, over
which the endless rope would be carried, and in such case, of course, an additional
wheel or sheave would be needed on the runner, as shown in Fig. 5.
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. A differential pulley block having a wheel with two turns of the rope passing
over the wheel one on top of the other and gripping levers to grip the outer
turn and lock the pulley under the weight of the load, all substantially as
described.
2. A differential pulley block having a wheel with two turns of the rope passing
over the wheel one on top of the other and gripping levers carried by the wheel
to be acted on by the inner turn of rope to grip the outer turn, all substantially as
described.
3. A differential pulley block having a wheel, with a single deep groove, two
turns of rope passing over the wheel, one on top of the other in this groove, and
gripping levers pivoted in notches in the flanges of the grooved wheel to be
acted on by the inner turn of rope to grip the outer turn, all substantially as
described.
4. A differential pulley block, having a wheel, two turns of rope passing over
the wheel one on top of the other and gripping levers on opposite sides of the
rope, to be acted on by the inner turn to grip the outer turn, all substantially as
described.
5. A differential pulley block having a wheel, two turns of rope passing over
the wheel, one on top of the other, and pairs of gripping levers to be acted on by
the inner turn to grip the outer turn, the two levers of each pair being on
opposite sides of the rope and out of line with each other, all substantially as
described.
Dated this 17th day of September 1889.
'
DAY, DAVIES & HUNT,
321, High Holborn, London, W.C., Agents for the Applicant.