Improvements in Screw Propellers.
Year: 1894

page_text: Date of Application, 17th Mar., 1894
Complete Specification Left, 12th Dec., 1894--Accepted, 9th Mar., 1895
PROVISIONAL SPECIFICATION.
Improvements in Screw Propellers.
I, ALFRED THEODOR ZEISE, of the Firm of Theodor Zeise, of 7 Friedens-
allée, Altona-Ottensen, in the Empire of Germany, Engineer, do hereby declare
the nature of this invention to be as follows:-
My invention relates to screw propellers.
Experience has shown that, commencing at the upper part of the rear side of a
propeller blade, a gradual destruction of the cast iron or steel takes place which
proceeds to the front surface of the blade, thereby weakening the latter and
rendering it unserviceable. The cause of this destruction has not yet been fully
ascertained, but attempts have been made to obviate the inconvenience by tinning
the rear surface of the blade or by providing it with metal plates attached thereto
by means of rivets or screws. It has however been found that metallic covers
thus fixed to the blade soon become severed again during the use of the propeller,
or allow water to penetrate to the metal of which the propeller is made, and do
not therefore afford a durable protection.
These unfavourable conditions have led to the idea of providing the part of the
surface of the blade which is to be protected, directly in the manufacture of the
propeller, with depressions so that their lateral surfaces will undercut the surface
of the blade in various directions. Upon the surface thus prepared I cast a some-
what thick cover of a metal which will resist the action deleterious to the material
of the blade, and this protecting cover is securely held upon the latter by tenons
which after the cooling of the cast metal fill up the depressions in the surface of
the blade. At the points of contact between the protecting cover and the surface
of the blade I obtain such an intimate union of the two metals that there will be
no liability of water to pass between the surfaces.
Dated this 17th day of March 1894.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.
I, ALFRED THEODOR ZEISE, of the Firm of Theodor Zeise, of 7 Friedens-
allée, Altona-Ottensen, in the Empire of Germany, 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:—
My invention relates to screw-propellers, and is illustrated in the accompanying
drawing in which

page_text: proceeds to the front surface of the blade, thereby weakening the latter and
rendering it unserviceable. The cause of this destruction has not yet been fully
ascertained, but 'attempts have been made to obviate the inconvenience by tinning
the rear surface of the blade or by providing it with metal-plates attached thereto
by means of rivets or screws. It has however been found that metallic covers thus
fixed to the blade soon become severed again during the use of the propeller, or
allow water to penetrate to the metal of which the propeller is made, and do not
therefore afford a durable protection.
By reason of these unfavourable conditions I was led to the idea, illustrated by
the accompanying drawing, of providing the part of the surface of the blade which
is to be protected, directly in the manufacture of the propeller, with depressions so
that their lateral surfaces will undercut the surface of the blade in various
directions. Upon the surface thus prepared I cast a somewhat thick cover a of a
metal which will resist the action deleterions to the material of the blade, and this
protecting cover is securely held upon the latter by tenons which after the
cooling of the cast metal fill up the depressions in the surface of the blade. At
the points of contact between the protecting cover and the surface of the blade
I obtain such an intimate union of the two metals that there will be no liability of
water to pass between the surfaces.
As regards the material to be used for the cover a any metal may be taken
which (1) does not crack on cooling, (2) is anti-corrosive and (3) does not cause
any galvanic action with the blade of the propeller and the adjacent parts of the
vessel. A material consisting of an alloy of about 85 parts lead and 15 parts
antimony will, for example, auit the purpose.
In carrying the invention into practice, I preferably proceed as follows: Upon
the cast iron or steel blade provided directly in the manufacture with the
depressions above referred to a layer of loam or sand corresponding with the
thickness and form of the metallic protecting cover is formed so as to serve as a
sort of pattern over which a mould is produced in any customary manner. After
the properly dried mould is removed from the blade and the said loam or sand
pattern still adhering to the latter the depressions in the blade are thoroughly
freed and cleaned from the sand or loam, the mould is again fastened to the blade
and then the molten metal designed for the protecting cover poured into the mould.
In this manner the protecting cover is in a most reliable way firmly secured to the
blade of the cast iron or steel propeller so that an intimate union of the two metals
is obtained and there will be no liability of water passing between their contact
surfaces.
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 :-
In screw propellers, with a cover at the rear side of the blades, providing the
part of the blades to be protected with depressions, whose lateral faces undercut
the surface of the blade in various directions, and casting thereon a layer of non-
deleterious metal which is designed to cover said surface of the blade and to fill up
the depressions therein after cooling, substantially as and for the purpose set
forth.
Dated this 10th do ot Dah
1004
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.