Improvements in the Preservation of Screw Propeller Blades.
Year: 1892

page_text: Date of Application, 17th Feb., 1892
Complete Specification Left, 16th Nov., 1892-Accepted, 17th Dec., 1892
PROVISIONAL SPECIFICATION.
Improvements in the Preservation of Screw Propeller Blades.
CHARLES FREDERICK AMOS of 28 Albion Street in the Borough of Kingston-
upon-Hull Engineer do hereby declare the nature of this invention to be as
follows:-
I fix by means of heat or cement or both combined a sheet of gutta percha,
india-rubber or other similar elastic medium on such part of the blade as it is
desirable to protect.
Dated this 16th day of February 1892.
CHARLES FREDERICK AMOS.
COMPLETE SPECIFICATION.
Improvements in the Preservation of Screw Propeller Blades.
I CHARLES FREDERICK AMOs of 28 Albion Street, in the Borough of
Kingston-upon-Hull, Engineer, do hereby declare the nature of this invention
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
It has been found that propeller blades, when in use, become rapidly worn or
cut away from slightly below the trailing angle forwards and downwards, in a
more or less diagonal line, towards the entering edge, so that the effective part of
the blade breaks off, or otherwise becomes reduced, thereby necessitating constant
renewal of the propeller blades.
Scientists are not agreed as to the cause of this rapid wearing away of the
effective portion of the propeller blade, but the fact remains, and it is the object
of my present invention to endeavour to overcome this difficulty, and thereby
increase the life of the propeller blades.
The appearance of that part of the blade which becomes worn away, is as if the
blade had been peppered with small shot, and presents a series of pit holes, due, as
I believe, to a kind of pelting action of the water drops on the blade.
My present invention consists in applying to such part of the blade as it is
desirable to protect, a tough elastic medium, which will yield more or less to the
impact of the atoms of water, which will thus expend their force on a yielding
surface.
In carrying out my invention, I make a compound of the following materials ;-
gutta percha, pitch and oil, in the following proportions: 6 parts of gutta percha,
1 part of pitch, and a quarter of a part of boiled linseed oil. I then heat the
propeller blade slightly, make the compound hot, and apply it, in a molten
condition (taking care not to keep it in a molten condition long enough to affect
its elasticity), to the portion of the blade above described, to a thickness of about
quarter of an inch.
The above compound has been found to answer the desired purpose, but I do
not wish to confine myself to the exact ingredients given, as, for instance, I may,
in the place of pitch, use resins or asphalts, and, in the place of boiled oil, I may
use other vegetable or mineral oils, slightly varying the proportions from those
before given, the object being to produce an elastic medium to protect the surface
of the blade.
Instead of applying my composition as before described, I may make it into
sheets, and secure it to the blades either by heating, or by a suitable cement.

page_text: 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 :--
Preventing the wearing away of the blades of screw propellers by the applica-
tion to the blades' surface, of a tough elastic medium as set forth.
Dated this 16th day of November 1892.
5
NEWTON & SON,
Agents for the Applicant.