IMPROVEMENTS IN SCREW Jacks
Year: 1875

page_text: LETTERS PATENT to Walter MacLellan, of the Firm of P. and W.
MacLellan, of Glasgow, in the County of Lanark, Iron Merchants,
for the Invention of “IMPROVEMENTS IN SCREW Jacks."—A communi-
cation from abroad by Edward Goodman Sheward, of Negapatam,
India.
Sealed the 1st June 1875, and dated the 1st April 1875.
PROVISIONAL SPECIFICATION left by the said Walter MacLellan at
the Office of the Commissioners of Patents, with his Petition, on
the 1st April 1875.
I, WALTER MACLELLAN, of the Firm of P. and W. MacLellan, of
Glasgow, in the County of Lanark, Iron Merchants, do hereby declare
the nature of the said Invention for "IMPROVEMENTS IN SCREW Jacks,”
to be as follows :—
a
This Invention consists in constructing screw jacks with a double
casing and central screw in combination, so as to obtain with a
screw jack of a given height nearly double the lift which is obtained by
using screw jacks of ordinary construction, that is to say, the central

page_text: screw instead of working into a simple nut terminating at the outer
casing, has its body prolonged the whole length of the screw jack so as
to form a complete casing round the central screw; this prolongation of
nut or casing has a screw thread on its outer surface which works into a
female screw at the upper end of the fixed outer casing. In operating
this screw jack, when the lift exceeds that which can be obtained by the
lift of the central screw alone, the central screw is worked up to its limit,
when a cotter or pin is introduced through the inside moveable casing
and central screw so as to cause them to act together, the lift is then
continued by the action of the outside screw of the inner casing working 1
into the insido screw of the fixed outer casing.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Walter MacLellan in the Great Scal Patent Office
on the 3rd September 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WALTER
MACLELLAN, of the Firm of P. and W. MacLellan, of Glasgow, in the
County of Lanark, Iron Merchants, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the First day of April, in the year of
our Lord One thousand cight hundred and seventy-five, in the thirty-
eighth year of Her reign, did for Herself, Her heirs and successors, give
and grant unto me, the said Walter MacLellan, Her special licence
that I, the said Walter MacLellan, my executors, administrators, and
assigns, or such others as I, the said Walter MacLellan, 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 terin
therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
SCREW JACKS," (a communication to me from abroad by Edward Goodman
Sheward, of Negapatam, India,) upon the condition (amongst others)
that I, tho said Walter MacLellan, my executors or administrators, by
an instrument in writing under my, or their, or one of their hands and
seals, should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and cause

page_text: 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 Patent.
NOW KNOW YE, that I, the said Walter MacLellan, do hereby
declare the nature of the said Invention, and in what manner the
5 same is to be performed, to be particularly described and ascertained in
and by the following statement thereof, reference being had to the
accompanying Drawings, that is to say :-
This Invention consists in constructing screw jacks with a double
casing and central screw in combination, so as to obtain with a screw
jack of a given height nearly double the lift which is obtained by using
screw jacks of ordinary construction, that is to say, instead of the central
screw working into a simple nut terminating at the outer casing the nut
has its body prolonged the whole length of the screw jack so as to form a
complete casing round the central screw; this prolongation of nut or
casing has a screw thread on its outer surface which works into a female
screw at the upper end of the fixed outer casing. In operating this
screw jack when the lift exceeds that which can be obtained by the
lift of the central screw alone, the central screw is worked up to its limit,
when a cotter or pin is introduced through the inside movable casing
and central screw so as to cause them to act together, the lift is then
continued by the action of the outside screw of the inner casing working
into the inside screw of the fixed outer casing.
Figure 1 of the accompanying Drawings is a sectional elevation,
Figure 2 an end elevation, and Figure 3 a plan of a screw jack con-
structed according to this Invention. A is the central screw working
into a nut B. This nut instead of terminating at the outer fixed casing
O, has its body prolonged, so as to form a casing D round the central
screw A. The prolongation D is formed with a screw thread on its
outer surface, as shown, which thread works into a female screw E at the
upper end of the fixed casing O. It will be readily seen that when the
central screw A has been worked up to its limit, a cotter or pin F,
Figure 4, introduced (at G) through the movable casing D and central
screw will cause them to act together, so that the lift can be continued
by the action of the screw on D working into the female screw E. The
improvement is shown in connection with a traversing screw jack, but it
is evident it is applicable to all kinds of screw jacks.
And having now described the nature of the said Invention, and in
what manner the same is to be performed, I declare that I claim¸—

page_text: •
Constructing screw jacks substantially as herein-before described and
represented in the accompanying Drawings.
In witness whereof, I, the said Walter MacLellan have hereunto
set my hand and seal, this First day of September, One thousand
eight hundred and seventy-five.