Method and Apparatus for Protecting Ships' Bottoms.
Year: 1890

page_text: Date of Application, 5th Sept., 1890
Complete Specification Left, 2nd June, 1891-Accepted, 4th July, 1891
PROVISIONAL SPECIFICATION.
Method and Apparatus for Protecting Ships' Bottoms.
I, BENJAMIN JOSEPH BARNARD MILLS, of 23 Southampton Buildings, in the
County of Middlesex, Patent Agent, do hereby declare the nature of this invention,
a communication to me from abroad by, Thomas Alva Edison, of Llewellyn Park,
in the County of Essex, and State of New Jersey, United States of America, to
be as follows:-
For the construction of the hulls of ships, steel is a material which has lately
come into use ou account of its strength and lightness. It has been used particularly
for the hulls and armour of war ships for these reasons and because of its resistance
to penetration. Experience has shown that the action of the sea water upon the
submerged portions of the hull of a steel ship produces a rapid erosion of the
exposed surface, causing the weakening and eventual destruction of the steel shell.
Unless this difficulty is overcome, the use of steel in the construction of ships' hulls
seems likely to be abandoned.
The principal object of the present invention is to overcome this difficulty. The
inventor has found that the erosion of steel in sea water is wholly prevented by
causing the circulation of an electric current of considerable quantity through the
sea water between the steel and another submerged electrode, the current flowing in
the direction to produce the evolution of hydrogen upon the steel. To do this the
steel is connected with the negative pole of the source of electric energy.
The
inventor has found by experiment that a current of from one-half to one ampere
per square foot of surface is a sufficient current to accomplish the purpose, but it
will be understood the invention is not limited to the employment of any definite
current so long as it is sufficient in quantity to prevent the erosion under the
particular conditions. It may also be desirable to use different strengths of current
with different qualities of steel, since the rapidity of the action, and hence the
quantity of current necessary to arrest it, is probably greatest with steel containing
the most carbon.
In carrying out the invention the steel ship is provided with one or more dynamo
electric machines of sufficient capacity to supply the considerable current strength
required, which machines are preferably operated by an independent steain engine.
One pole of the source of current (the negative) is connected electrically with the
steel shell, while the other pole is connected with one or more cables passing out
through suitable ports and running to submerged electrodes at a greater or less
distance from the hull. These cables are well marlined so that the cables themselves
will not be attacked vigourously by the current but only the electrodes, which will
be arranged for replacement when eaten away enough to impair their utility.
While the ship is at anchor, these electrodes (one or more) may be sunk to the
bottom directly beneath or at a greater or less distance from the ship, the cables
running from the ship to the electrodes under water, or the cables may be carried
on out-riggers above the water and the electrodes only be submerged, or even with
out-riggers the cables may run to the botton at the ends of the out-riggers to
sunken electrodes. Many arrangements of the electrodes will suggest themselves
to suit the particular conditions, and the invention is not limited to any particular
arrangement, it being understood that the purpose subserved by the use of a
number of electrodes, or by locating one electrode at a distance from the hull, or
by a judicious employment of both of these features, is to obtain as nearly as practicable
a uniform distribution of the current over the entire submerged surface of the hull,
thus insuring the protection of the entire surface with the maximum economy in the
use of the electric current.

page_text: If it is desired to protect the ship while under way, one or more trailing electrodes
may be employed, although the protection of the ship while at anchor is of more
importance.
Not only will the erosion of the ship's bottom be prevented by the employment
of this invention, but organic matter will not attach itself in the presence of a
current of the strength necessary to prevent rusting, and hence the fouling of the
shell is in addition prevented.
Further, by keeping the surface clean, the skin friction will be reduced and
painting will be rendered unnecessary.
So far as preventing the fouling of ships' bottoms is concerned, the invention may
also be usefully employed with iron ships, and with wooden ships sheathed with
copper or other metal, where the erosive action is not present to a destructive extent.
Dated this 5th day of September 1890,
B. J. B. MILLS.
By Harris & Mills,
23, Sonthampton Buildings, Loudon, Agents,
COMPLETE SPECIFICATION.
Method and Apparatus for Protecting Ships' Bottoms.
I, BENJAMIN JOSEPH BARNARD MILLS of 23 Southampton Buildings in the
County of Middlesex Patent Agent do hereby declare the nature of the said inven-
tion a communication to me from abroad by Thomas Alva Edison of Llewellyn
Park in the County of Essex and State of New Jersey in the United States of
America, and in what manner the same is to be performed to be particularly
described and ascertained in am by the following statement. :-
For the construction of the hulls of ships, steel is a material which has lately
come into use on account of its strength and lightness. It has been used particularly
for the hulls and armour of war ships for these reasons and because of its resistance
to penetration.
Experience has shown that the action of the sea water upon the submerged
portions of the hull of a steel ship produces a rapid erosion of the exposed
surface, causing the weakening and eventual destruction of the steel shell.
Unless this difficulty is overcome, the use of steel in the construction of ships'
hulls seems likely to be abandoned.
The object of the present invention is to overcome this difficulty. The inventor
has found that the erosion of steel in sea water is wholly prevented by causing the
circulation of an electric current of considerable quantity through the sea water
between the steel and another submerged electrode, the currcut flowing in the
direction to produce the evolution of hydrogen upon the steel.
To do this the steel is connected with the negative pole of the source of electric
energy. The inventor has found by experiment that a current of from one-half to
one ampere per square foot of surface is a sufficient current to accomplish the
purpose, but it will be understood the invention is not limited to the employment
of any definite current so long as it is sufficient in quantity to prevent the erosion
under the particular conditions. It may also be desirable to use different strengths
of current with different qualities of steel, since the rapidity of the action, and
hence the quantity of current necessary to arrest it, is probably greatest with steel
containing the most carbon.
In carrying out the invention, the steel ship is provided with one or more dynamo
electric machines of sufficient capacity to supply the considerable current strength
required, which machines are preferably operated by an independent steam engine.
One pole of the source of current (the negative) is connected electrically with the
steel shell, while the other pole is connected with one or more cables passing out
through suitable ports and running to submerged electrodes at a greater or less

page_text: distance from the hull. These cables are well marlined so that the cables them-
selves will not be attacked vigorously by the current but only the electrodes
which will be arranged for replacement when eaten away enough to impair their
utility.
While the ship is at anchor these electrodes (one or more) may be sunk to the
bottom directly beneath or at a greater or less distance from the ship, the cables
running from the ship to the electrodes under water or the cables may be carried
on outriggers above the water and the electrodes only be submerged, or even with
outriggers the cables may run to the bottom at the ends of the out-riggers to sunken
electrodes. Many arrangements of the electrodes will suggest themselves to suit
the particular conditions, and the invention is not limited to any particular
arrangement, it being understood that the purpose subserved by the use of a
number of electrodes, or by locating one electrode at a distance from the hull, or
by a judicious employment of both of these features, is to obtain as nearly as
practicable a uniform distribution of the current over the entire submerged surface
of the hull, thus insuring the protection of the entire surface with the maximum
economy in the use of the electric current.
If it is desired to protect the ship while under way, one or more trailing electrodes
may be employed, although the protection of the ship while at anchor is of more
importance.
Not only will the erosion of the ship's bottom be prevented by the employment
of this invention, but organic matter will not attach itself in the presence of a
current of the strength necessary to prevent rusting and hence the fouling of the
shell is in addition prevented.
Further, by keeping the surface clean, the skin friction will be reduced and
painting will be rendered unnecessary.
In the accompanying drawing forming a part hereof,
Figure 1 is a cross section of a ship's hull showing the invention applied thereto
while at anchor, and
Figure 2 is a side elevation of a ship's hull showing the invention applied thereto
while under way.
A is the steel shell of a ship. B is a dynamo electric machine or other suitable
source of electric energy, having its negative pole connected electrically with the
shell, and its positive pole connected with one or more insulated cables C'extending
to submerged electrodes D.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
The method of and apparatus for protecting the bottom of a steel ship from
erosion, consisting in providing the ship with an adequate source of electrical energy
connected by a cable or cables with one or more submerged electrodes, and causing
the circulation of a sufficiently strong and well distributed electric current through
the water from the submerged electrode or electrodes to the shell of the ship,
substantially as hereinbefore described.
Dated this 2nd day of July 1891.
Dated this 2nd day of July 1891.
D. J. B. MILLS.
By Harris & Mills,
23, Southampton Buildings, London, W.C., Agents.