IMPROVEMENTS IN DIFFERENTIAL PULLEYS, PORTIONS OF WHICH ARE APPLICABLE TO OTHER CHAIN WHEELS
Year: 1872

page_text: LETTERS PATENT to Thomas Aldridge Weston, of Ridgewood, Bergen
County, New Jersey, in the United States of America, for the
Invention of "IMPROVEMENTS IN DIFFERENTIAL PULLEYS, PORTIONS OF WHICH
ARE APPLICABLE TO OTHER CHAIN WHEELS."
Scaled the 6th August 1872, and dated the 12th June 1872.
PROVISIONAL SPECIFICATION left by the said Thomas Aldridge
Weston at the Office of the Commissioners of Patents, with his
Petition, on the 12th June 1872.
I, THOMAS ALDRIDGE WESTON, of Ridgewood, Bergen County, New
Jersey, in the United States of America, do hereby declare the nature
of the said Invention for "IMPROVEMENTS IN DIFFERENTIAL PULLEYS, PORTIONS
OF WHICH ARE APPLICABLE TO OTHER CHAIN WHEELS," to be as follows:-
My Invention is an improvement upon the differential pulley for
which Letters Patent were granted me bearing date April 25th, 1859,
No. 1033, and has for its paramount object to retain the chain in its
appropriate position within the grooved faces of the upper and lower
sheaves more effectively than by the means known or used prior to my

page_text: Invention, and to diminish friction and save power when the operator is
placed at a distance horizontally from the pulley, and it consists,-
First. In providing the upper block with radial vibrating or oscillating
arms pivoted upon the ends of the central shaft which sustains the
differential sheave, the said arms carrying at their outward or vibrating
ends a small grooved pulley or pulleys (or equivalent fixed segments
or keepers), which confine the chain to the grooves of the differential
sheave, at the same time by the vibratory motion of the arms per-
mitting the hoisting chain to be led off from the sheave at various
angles without deflecting it, as is the case when the guide pulleys and
arms are affixed to the pulley block, frame, or yoke.
Second. In providing the lower block with a keeper or guide affixed
to the frame side or yoke vertically under the sheave in the same
relative position to the hook and yoke as that of the keepers of the
upper pulley in my aforesaid Patent, and in extending the grooved face
of the said keepers around the lower side of the pulley, forming a
concave sheath or pocket for retaining the chain in contact with the
grooved face of the pulley and for other purposes, as hercin-after set
forth.
Third. In making the casing of the lower block capable of partial
rotation on the axle of the pulley, independent of the hook and yoke,
so that the latter may swing freely upon the axle in attaching to a load,
without disturbing the normal position of the said casing or frame, and
the sheave within it:
Upon the opposite ends of the axle of a differential pulley, I attach
two pairs of swinging arms, each pair embracing the pulleys, and carrying
at their outer ends grooved guides or keepers which preferably consist
of a pulley or pulleys of different diameters conforming to the faces of
the differential sheaves, the said keepers being situated on opposite
sides of the differential pulley. These arms have a free vibratory or
oscillating motion upon the said axle, enabling the keepers to assume
any position upon the face of the pulley that may be required by leading
the chain off at a tangential line.
The lower block is provided with a keeper or guide affixed to the
frame or yoke vertically underneath the pulley, which guide may consist
of metal formed with its under side or face grooved or concave to
approximate to the general shape of the chain in cross section, the said

page_text: metal being extended from the lower side of the pulley in both directions
a sufficient distance to form an efficient guide or pocket to retain the
chain in contact with the pulley, and prevent its leaving the surface
thereof when slack.
The casing of the lower block is so connected with the axle of the
pulley, being loosely hung thereon, that it is capable of partial rotation,
independent of the hook and yoke, so that the latter may swing freely
upon the axle in attaching to a load without varying the position of the
casing and of the sheave within it.
The action is as follows:- Upon leading off the hoisting chain
obliquely from the pulley block to where the operator stands at a distance
horizontally from the pulley, the small guide pulleys are raised by the
tension upon the chain, and the chain can freely and without deflexion
assume a tangential line from the differential sheave, avoiding the wear
and friction arising from fixed guide pulleys or keepers, or from contact
with the fixed arms of the yoke as shewn and described in the Specifica-
tion of my aforesaid Patent; at the same time the radial arms, in every
position, effectually retain the guide pulleys, chain, and differential sheave
in their true relative position with cach other.
The effect and purpose of the keeper of the lower block is to prevent
the formation of a slack loop of chain below the sheave, and to retain
the chain from dropping out of the lower portion of the groove in the
same.
The purpose of connecting the lower block to an independent yoke
swinging from the central shaft of the pulley is to give greater freedom
in attaching it to a load. If desired, still further freedom of motion
may be obtained by interposing, as a connector between the hook and its
voke, a ring or loose shackle.
30
SPECIFICATION in pursuance of the conditions of the Letters Patent
filed by the said Thomas Aldridge Weston in the Great Seal Patent
Office on the 12th December 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
ALDRIDGE WESTON, of Ridgewood, Bergen County, New Jersey, in the
United States of America, send greeting,

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twelfth day of June, in the year of our
Lord One thousand eight hundred and seventy-two, in the thirty-fifth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Thomas Aldridge Weston, Her special licence
that I, the said Thomas Aldridge Weston, my executors, administrators,
and assigns, or such others as I, the said Thomas Aldridge Weston, my
executors, administrators, and assigns, should at any time agree with,
and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, nsc,
exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "Im-.
PROVEMENTS IN DIFFERENTIAL PULLEYS, PORTIONS OF WHICH ARE APPLICABLE TO
OTHER CHAIN WHEELS," upon the condition (amongst others) that I, the
said Thomas Aldridge Weston, my executors or administrators, by an
instrument in writing under my, or their, or one of their hands and
scals, should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters