IMPROVEMENTS IN DIFFERENTIAL PULLEYS OR PULLEY BLOCKS."
Year: 1878

page_text: LETTERS PATENT to George Tangye, of the Firm of Tangye Brothers, of
Birmingham, in the County of Warwick, Manufacturers, for the Invention of
IMPROVEMENTS IN DIFFERENTIAL PULLEYS OR PULLEY BLOCKS."
"
PROVISIONAL SPECIFICATION left by the said George Tangye at the
Wood Office of the Commissioners of Patents on the 8th August 1878.
GEORGE TANGYE, of the Firm of Tangye Brothers, of Birmingham, in the County
of Warwick, Manufacturers. IMPROVEMENTS IN DIFFERENTIAL PULLEYS OR
PULLEY BLOCKS."
My Invention has reference to differential pulleys or pulley blocks of the kind
commonly known in commerce as Weston's differential pulley blocks, but my said
Invention is also applicable to differential pulley blocks in general.
The object of my Invention is to prevent the loose loop of the chain from being
displaced from the teeth and grooves of the pulley by accident or carelessness, as
well as to determine the certain engagement of the chain with the teeth and grooves
of the pulleys. When the chain is jerked or twisted it does not readily engage with
the teeth of the pulleys, and this inconvenience is remedied by my Invention.
My Invention consists in the employment of guide tubes through which the loose
or pulling loop of the chain passes. One of these guide tubes is carried by a radial
arm or plate swivelling on one end of the axis of the differential pulley, and another
of the guide tubes is carried by another radial arm or plate swivelling on the
opposite end of the axis of the differential pulley. One side of the loose loop passes
through one of the said guide tubes, and the other side of the loose loop through the
other of the guide tubes. The said guide tubes are not fixed rigidly to the outer
ends of the radial arms or plates carrying them, but are capable of swivelling thereon.
When the parts are in their normal positions the two arms carrying the guide tubes
CD 31

page_text: make an angle of nearly 90 degrees with one another, and the guide tubes are both
vertical, and consequently parallel. When the loose loop of the chain is paid out or
drawn in vertically the radial arms and guide tubes retain the positions described.
When however either side of the loose loop is deflected from a perpendicular posi-
tion the guide tube through which it passes takes a similar inclination, and the
radial arm carrying it rises or falls so as to preserve the same or nearly the same
angle with the chain.
I prefer to give the guide tubes the same internal sectional figure as that of the
chain, so that in passing through the guide tube either to or from the pulley the
twisting of the chain is prevented.
I do not however confine myself to that sectional figure, as a square internal
sectional figure may be employed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said George Tangye in the Great Seal Patent Office on the 25th January
1879.
GEORGE TANGYE, of the Firm of Tangye Brothers, of Birmingham, in the County
of Warwick, Manufacturers. "IMPROVEMENTS IN DIFFERENTIAL PULLEYS OR
PULLEY BLOCKS."
My Invention has reference to differential pulleys or pulley blocks of the kind
commonly known in commerce as Weston's differential pulley blocks, but my said
Invention is also applicable to differential pulley blocks in general.
The object of my Invention is to prevent the loose loop of the chain from being
displaced from the teeth and grooves of the pulleys by accident or carelessness, as
well as to determine the certain engagement of the chain with the teeth and grooves
of the pulleys. When the chain is jerked or twisted it does not readily engage with
the teeth of the pulleys, and this inconvenience is remedied by my Invention.
My Invention consists in the employment of guide tubes through which the loose
or pulling loop of the chain passes. One of these guide tubes is carried by a radial
arm or plate swivelling on one end of the axis of the differential pulley, and another.
of the guide tubes is carried by another radial arm or plate swivelling on the
opposite end of the axis of the differential pulley. One side of the loose loop passes
through one of the said guide tubes, and the other side of the loose loop through the
other of the guide tubes. The said guide tubes are not fixed rigidly to the outer
ends of the radial arms or plates carrying them, but are capable of swivelling thereon.
When the parts are in their normal positions the two arms carrying the guide tubes
make an angle of nearly 90 degrees with one another, and the guide tubes are both
vertical and consequently parallel. When the loose loop of the chain is paid out or
drawn in vertically the radial arms and guide tubes retain the positions described.
When however either side of the loose loop is deflected from a perpendicular posi-
tion the guide tube through which it passes takes a similar inclination, and the
radial arm carrying it rises or falls so as to preserve the same or nearly the same
angle with the chain.
I prefer to give the guide tubes the same internal sectional figure as that of the
chain, so that in passing through the guide tube either to or from the pulley the
twisting of the chain is prevented.
I do not however confine myself to that sectional figure, as a square or circular
internal sectional figure may be employed.
I will now proceed to describe, with reference to the accompanying Drawing, the
manner in which my Invention may be performed.
Figure 1 represents, in side elevation, and Figure 2, in front elevation, a diffe-
rential pulley block of the kind known as Weston's differential pulley block, the
said pulley block being provided with my Invention.
Figure 3 represents in plan one of the guide tubes constructed according to my
Invention, in conjunction with its swivelling arm or plate.
The same letters of reference indicate the same parts in Figures 1, 2, and 3.
a, a, represent the differential pulleys of the pulley block constructed in the
ordinary way, and turning on the axis b, carried by the suspended frame c, as usual;
d and e represent the two sides of the loose or pulling loop of the chain. As this
loop is the only loop of the two loops of the chain of the differential pulley with
which my Invention is concerned, I do not think it necessary to refer to the other
loop in which the snatch-block is placed. ƒ and g are the guide tubes through
which the loose or pulling loop d, e, of the chain passes. These guide tubes have
the same internal sectional figure as the chain as seen in Figure 3; that is, the
guide tube has a cruciform opening in it, so that the chain in passing through it in
one or other direction is prevented from being twisted.
Although I prefer to give to the guide tube the sectional form represented in
Figure 3, yet I do not limit myself thereto, as the opening through which the

page_text: chain passes may be square or circular in section, instead of having a cruciform
figure as represented.
Each of the guide tubes f, g, is carried on the lower end of a radial arm or plate.
These radial arms or plates are marked respectively h and i, and are capable of
swivelling or moving through a small angle on the axis b of the differential pulleys
The arm or plate h swivels or turns on one end of the axis b, and the other
arm or plate i swivels or turns on the opposite end of the said axis b, as best seen
in Figure 2.
a, a.
It will be seen by reference to the Drawing that the said guide tubes f, g, are not
rigidly fixed to the lower ends of the radial arms h, i, carrying them, but are capable
of swivelling thereon. This is effected by passing screw pins 1, l, through holes in
the arms h, i, the ends of the said screw pins taking into snugs on the faces of the
guide tubes (see Figure 3), but the swivelling joints of the said guide tubes may be
made in other ways. The guide tubes f, g, are thus capable of swivelling upon the
said arms h, i, when the latter move from their normal positions.
The side d of the loose or pulling loop of the chain passes through the guide
tube f, and the other side e of the said loose loop passes through the other guide
tube g. The normal position of the two radial arms h, i, carrying the guide tubes
fg, with respect to one another, is that represented in Figure 1; that is, the said
radial arms make an angle of nearly 90 degrees with one another. When the radial
arms h, i, are in this position the guide tubes f, g, are both vertical, and conse-
quently parallel, as represented in Figure 1.
So long as the loose loop d, e, of the chain of the differential pulley is vertical the
radial arms h, i, retain the normal position represented in the Drawing. Should
however one or other side d or e of the loose loop be deflected from its normal per-
pendicular position the guide tube for g through which it passes takes a similar
inclination, the said guide tube swivelling on its radial arm, and the said radial arm
rises or falls so as to preserve the same or nearly the same angle with the chain, as
will be understood by an examination of the Drawing. By means of the said guide
tubes and parts connected therewith the accidental displacement of the loose or
pulling loop of the chain from the teeth and grooves of the pulleys is prevented, and
the position of the chain to effect its certain engagement with the said teeth and
grooves is determined with the greatest nicety.
Although I have only represented my Invention in connection with Weston's
differential pulley or pulley block, yet my said Invention is equally applicable to
differential pulley blocks of other constructions.
Having now described the nature of my Invention, and the manner in which
the same is to be performed, I wish it to be understood that I claim as my Inven-
tion the improvements in differential pulleys or pulley blocks, herein-before
described, and illustrated in the accompanying Drawing; that is to say, the
addition to or combination with differential pulleys or pulley blocks of guide
tubes through which the loose or pulling loop of the chain passes, the said guide
tubes being carried by and swivelling on the outer ends of radial arms or plates
swivelling on opposite ends of the axis of the differential pulley, the said guide
tubes being constructed, arranged, and working substantially as and for the pur-
poses described and illustrated.
In witness whereof, I, the said George Tangye, have hereunto set my hand
and seal, this Twenty-second day of January, in the year of our Lord
One thousand eight hundred and seventy-nine.
Witness,
HAROLD WRIGHT,
Birmingham.
GEORGE TANGYE. (L.S.)