AN APPENDAGE TO SCREW PROPELLERS
Year: 1854

page_text: Sealed the 31st October 1854, and dated the 31st May 1854.
PROVISIONAL SPECIFICATION left by the said George Alfred de
Penning at the Office of the Commissioners of Patents, with his
Petition, on the 31st May 1854.
I, GEORGE ALFRED DE PENNING, of Calcutta, Civil Engineer, do hereby
5 declare the nature of the said Invention for "AN APPENDAGE TO SCREW
PROPELLERS" to be as follows:-
My Invention consists in fitting a semi-cylinder or cylindrical guard on each
side of screw propellers, whereby the screws will be protected from injury by
any bodies coming in contact with them; and I anticipate an increased speed
from screw propelled vessels fitted with this guard, as the water will have a
direction given to it backwards from the vessel.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirty-first day of May, in the year of our Lord One
thousand eight hundred and fifty-four, in the seventeenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
George Alfred de Penning, Her special licence that I, the said George Alfred
de Penning, my executors, administrators, and assigns, or such others as I,
the said George Alfred de Penning, 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, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention for
"AN APPENDAGE TO SCREW PROPELLERS," upon the condition (amongst others)
that I, the said George Alfred de Penning, by an instrument in writing
under hand and seal, 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.
my
NOW KNOW YE, that I, the said George Alfred de Penning, do hereby
declare the nature of my 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, reference being had to the Drawings hereunto
annexed, that is to say:
My Invention consists in fitting a semi-cylinder or cylindrical guard on each
side of screw propellers, whereby the screw blades will be protected from injury
by any
bodies coming in contact with them; and I anticipate an increased
speed from screw propelled vessels fitted with this guard, as the water will
have a direction given to it to leave the blades immediately backwards from
the vessel, and so also remedy the unpleasant vibrating motion at present
experienced.
Figure 1 of the Drawings annexed is a side elevation of part of a screw
propelled vessel, having my Invention applied thereto; and Figure 2 is an
end view of the same. A is the hull of the vessel, and B, B, are the two
semi-cylinders or cylindrical guards, which are fixed one on each side of the
aperture in which the screw works, by means of bolts and nuts; C, C, the bolts
passing through the dead wood of the vessel and the flanges D, D, formed on
the semi-cylinders. E, E, are stays, by which the semi-cylinders B, B, are
maintained rigidly in their position. The diameter of the cylindrical chamber

page_text: formed by the semi-cylinders B, B, should be equal to the height of the aper-
ture in which the screw works, and its width should be as great as it con-
veniently may be without contracting the entrance for the water forward, and
without interfering with the movements of the rudder at the after part.
5 The principal use of this appendage is to protect the blades of the screw
propeller from breakage and injury by contact with floating bodies, such as
logs of wood, &c., generally found in all seas; the stays E, E, would mainly
contribute to this object, as from their position and form (for any desired
amount of curvature and projection may be given them), they will serve effec-
tually to fend off such bodies as might otherwise come in contact with the
screw blades. This will obviate a great source of inconvenience to screw pro-
pelled vessels, for there can be no doubt that collision with such inert floating
bodies has been in most cases the cause of the breakage of screw blades.
Another advantage which I anticipate from the use of this appendage is a
great increase of speed, as all the water sent off laterally from the screw blades,
by reason of their inclination, will be deflected by the cylindrical chamber in a
backward direction parallel with the keel, thus saving the power that would
otherwise be lost without it, and which loss at present results from the counter-
action of the inclined reacting resistance of the water sent off laterally from
the blades. Besides this, from the circumstance of the interposition of the
cylinder between the surrounding water and the vacuum formed on the nega-
tive side of the blades, consequent on their ever changing their position when
in motion, the surrounding water will always be kept off from supplying this
vacuum or taking its place, and the blades will then, from the increased
pressure on their positive side, from the vacuum being held perfect for a
longer period, be moved onward through a greater space towards the water"
immediately before them, though in appearance the water would seem to be
driven out with increased velocity from being caused to move towards the
blades with greater force. Moreover, from the perfection of the vacuum on
the negative side of the blades, owing to its not being affected by the sur-
rounding water, a greater resistance will be obtained, so that with a given
velocity the screw will be able to perform a greater amount of work, thus
diminishing the excessive amount of slip now experienced with the screw, as
compared with the paddle wheel, and thereby remedying the main objection to
which the screw in its present simple form is liable.
And having now described the nature of my said Invention, and in what
manner the same is to be performed, I declare that what I claim as of my
Invention is, the adaptation to screw propellers of an open-ended cylindrical

page_text: chamber surrounding the screw, and within which the screw revolves, in
manner and for the purpose herein-before explained.
In witness whereof, I, the said George Alfred de Penning, have hereunto
set my hand and seal, this Twenty-eighth day of November, One
thousand eight hundred and fifty-four.
GEORGE ALFRED DE PENNING. L.S.