IMPROVEMENTS IN SCREW OR SUBMERGED PROPELLERS
Year: 1857

page_text: LETTERS PATENT to Richard Atkinson Coward, of Laurence Pountney
Lane, in the City of London, for the Invention of "IMPROVEMENTS IN
SCREW OR SUBMERGED PROPELLERS."-A communication.
Sealed the 3rd September 1857, and dated the 5th March. 1857.
PROVISIONAL SPECIFICATION left by. the said Richard Atkinson Coward
at the Office of the Commissioners of Patents, with his Petition, on the
5th March 1857.
I, RICHARD ATKINSON COWARD, of Laurence Pountney Lane, in the City
of London, do hereby declare the nature of the Invention for "IMPROVEMENTS
IN SCREW OR SUBMERGED PROPELLERS," to be as follows:-
The peculiar characteristics of this new screw or submerged propeller, and
the principles on which it is constructed, are widely different in all their lead-
ing features from those hitherto in general use, which for the most part have
been portions of a true screw, and the common object has been to obtain the
greatest amount of effective propelling surface with the least amount of
friction; and it has been hitherto thought that the effective part of the screw.
is that near its circumference, the inner portions being considered of little
use in propelling. In the screw which it is now sought to describe, on the
contrary, the greatest amount of effective propelling surface is brought as near
as it can be got to the axis, the object being to take advantage of the well-known.
tendency which many screws are known to possess, of drawing the water from.

page_text: the circumference towards the centre and forcing it back in the form of a cone,
expanding as it recedes.
The Inventor of the present propeller. does not purpose confining himself to
any particular pitch or diameter, or proportion of pitch to diameter. The
pitch of this propeller, as of other screws, or the angle at which the blades are
set, differs necessarily with the power of the engine and the form of the vessel,
that is, with the anticipated speed of the vessel.
The end view of an ordinary screw propeller represents two isosceles
triangles whose vertices are conterminous at the axis. The end view of the
present propeller represents two trapeziums in the reversed positions; in fact,
the shape of the arms of this propeller in some slight degree resemble those
known as Griffiths' propellers, differing, however, essentially both in their size
and their general principles. In the present Invention the sphere, which is
the distinguishing characteristic of Griffiths' propeller, is dispensed with, and
the space, which in Griffiths' arrangement is filled in with a sphere of metal
with a view to diminish friction about the axis, is according to the present
improvements taken full advantage of by the blades coming to the axis where
they are made widest, and they diminish from thence to the circumference.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Richard Atkinson Coward in the Great Seal Patent Office.
on the 3rd September 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, RICHARD
ATKINSON COWARD, of Laurence Pountney Lane, in the City of London, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fifth day of March, in the year of our Lord
One thousand eight hundred and fifty-seven, in the twentieth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto
ine, the said Richard Atkinson Coward, Her special licence that I, the
said Richard Atkinson Cöward, my executors, administrators, and assigns,
or such other's as I, the said Richard Atkinson Coward, 'my executors,
ádministrators, 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, 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 OR SUBMERGED

page_text: PROPELLERS," a communication, upon the condition (amongst others) that I,
the said Richard Atkinson Coward, my executors or administrators, by an
instrument in writing under my, or their, or one of their bands 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 imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Richard Atkinson Coward, 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 thereof, that is to say:-
The peculiar characteristics of this new screw or submerged propeller, and
the principles on which it is constructed, are widely different in all their lead-
ing features from those hitherto in general use, which for the most part have
been portions of a true screw, and the common object has been to obtain the
greatest amount of effective propelling surface with the least amount of
friction; and it has been hitherto thought that the effective part of the screw
is that near its circumference, the inner portions being considered of little use
in propelling. In the screw which it is now sought to describe, on the
contrary, the greatest amount of effective propelling surface is brought as near
as it can be got to the axis, the object being to take advantage of the well-
known tendency which many screws are known to possess, of drawing the water
from the circumference towards the centre and forcing it back in the form of
a cone, expanding as it recedes.
The Inventor of the present propeller does not purpose confining himself to
any particular pitch or diameter, or proportion of pitch or diameter, the pitch
of this propeller, as of other screws, or the angle at which the blades are set,
differs necessarily with the power of the engine and the form of the vessel,
that is, with the anticipated speed of the vessel.
The end view of an ordinary screw propeller represents two isosceles
triangles whose vertices are conterminous at the axis. The end view of the
present propeller represents two trapeziums in the reversed positions; in fact,
the shape of the arms of this propeller in some slight degree resemble those
known as Griffiths' propellers, differing, however, essentially both in their size
and their general principles.
In the present Invention, as indicated by the Drawing, where Figure 1 is an
end view, and Figure 2 an edge view, the sphere, which is the distinguishing
characteristic of Griffiths' propeller, is dispensed with, and the space, which in
Griffiths arrangement is filled in with a sphere of metal with a view to

page_text: liminish friction about the axis, is according to the present improvements
taken full advantage of by the blades coming to the axis, where they are made
widest, and they diminish from thence to the circumference.
In witness whereof, I, the said Richard Atkinson Coward, have hereunto
set my hand and seal, this First day of September, in the year of our
Lord One thousand eight hundred and fifty-seven.
Witness,
W COWARD.
R. A. COWARD. (L.S.)