IMPROVE- MENTS IN THE CONSTRUCTION OF THE SCREW OR SCREW PROPELLER FOR SHIPS
Year: 1871

page_text: LETTERS PATENT to George Downing, of 8, Quality Court, Chancery
Lane, in the County of Middlesex, for the Invention of "IMPROVE-
MENTS IN THE CONSTRUCTION OF THE SCREW OR SCREW PROPELLER FOR SHIPS."
-A communication from abroad by John de Normann, a Civil
Engineer, of Corfu, in the Kingdom of Greece.
PROVISIONAL SPECIFICATION left by the said George Downing at the
Office of the Commissioners of Patents, with his Petition, on the
17th November 1871.
I, GEORGE DOWNING, of 8, Quality Court, Chancery Lane, in the
County of Middlesex, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN THE CONSTRUCTION OF THE SCREW OR SCREW
PROPELLER FOR SHIPS," a communication to him from abroad by John de
Normann, a Civil Engineer, of Corfu, in the Kingdom of Greece, to be
o follo

page_text: usually affixed, and which I effect by means of a circular ring A (see
accompanying Drawings, Fig. 1), one-third the whole diameter of the
propeller fixed to the shaft 6 through its greatest diameter. The two
blades c, c, at their lowest extremity are portions of a cylinder bolted to
the ring a at right angles, the pitch of the screw being altered with the
greatest facility. Fig. 2 shows the ordinary "Griffith" screw sphere d,
blades e, e.
The following are the advantages of this change of form in propellers:-
Its extraordinary lightness, combined with great strength, the avoidance
of churning the water caused by the boss; its great holdfast of the
water, and little or no vibration; this last advantage, obtained by the
vacuity through the ring, which also effects complete displacement of
the water backwards in a straight line with the ship's keel, thus allowing
a steady helm. It will be observed that most propellers churn the water
and send it obliquely backwards, churning it as it passes.
In ordinary propellers the propelling effect of each blade only begins
from the circumference of the sphere, while by this Invention the whole
surface of the blade is useful, and a powerful leverage is gained.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said George Downing in the Great Seal Patent Office on
the 17th May 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
DOWNING, of 8, Quality Court, Chancery Lane, in the County of
Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventeenth day of November, in the year of our
Lord One thousand eight hundred and seventy-one, in the thirty-fifth
year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said George Downing, Her special licence that
I, the said George Downing, my executors, administrators, and assigns,
or such others as I, the said George Downing, my executors, adminis-
trators, and assigns, should at any time agree with, and no others, from
time to time and at all times thereafter during the term therein

page_text: 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 THE
CONSTRUCTION OF THE SCREW OR SCREW PROPELLER FOR SHIPS," a communica-
tion to me from abroad by John de Normann, a Civil Engineer, of Corfu,
in the Kingdom of Greece, upon the condition (amongst others) that I, the
said George Downing, 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 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 George Downing, do hereby declare
the nature of the said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and
by the following statement and accompanying Drawing, that is to
say:―
This Invention consists chiefly in the suppression of the trailing sphere
as used in some propellers, and of the boss to which the blades are
usually affixed, and which I effect by means of a circular ring A (see
accompanying Drawings, Fig. 1), one-third the whole diameter of the
propeller fixed to the shaft 6 through its greatest diameter. The two
blades c, c, at their lowest extremity are portions of a cylinder bolted to
the ring A. at right angles, the pitch of the screw being altered with the
greatest facility. Fig. 2 shows the ordinary “Griffith” screw sphere d,
blades e, e.
The following are the advantages of this change of form in propellers:-
Its extraordinary lightness, combined with great strength, the avoidance
of churning the water caused by the boss; its great holdfast of the
water and little or no vibration; this last advantage obtained by the
vacuity through the ring, which also effects complete displacement of
the water backwards in a straight line with the ship's keel, thus allowing
a steady helm. It will be observed that most propellers churn the water
and send it obliquely backwards, churning it as it passes.
In ordinary propellers the propelling effect of each blade only begins
from the circumference of the sphere, while by this Invention the whole
surface of the blade is useful, and a powerful leverage is gained.

page_text: Having. thus described the nature of the said Invention, I declare that
what I claim and desire to be secured by the herein-before in part recited
Letters Patent is, the improvements in the form of the screw or screw
propeller for ships, as herein-before described and shewn on Drawing, or
any mere modification thereof.
In witness whereof, I, the said George Downing, have hereunto set
my hand and seal, this Seventeenth day of May, in the year of
our Lord One thousand eight hundred and seventy-two.