Year: 1888

page_text: I, ANGILBERT VALERY COMTE DE VISMES of La Colline Nyon Canton de Vaud in
the Republic of Switzerland 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 :-
This Invention relates to the construction of screw propellers for ships or vessels
and it has for its object causing the action of the propeller rotating in water to
resemble as nearly as possible that of a screw rotating and advancing in a solid nut.
A ship or vessel provided with an ordinary screw propeller advances only when
the angular speed of the propeller blades exceeds the speed with which the water
acting as a nut is displaced and in consideration of this fact it may be concluded
that the blades of the screw produce no useful effect except at the parts near the
outer ends or beyond the point where their speed commences to exceed that of the
displacement of the water. Moreover the spaces between the blades near the centre
of rotation act as injurious spaces giving rise by friction to conflicting currents and
All these
disturbances which are prejudicial to the proper action of the screw.
considerations have led me to modify the construction of the propeller and to make
it in a form enabling it to produce a maximum of useful effect as hereinafter
described.
And in order that my said Invention may be fully understood I shall now proceed
inore particularly to describe the same and for that purpose shall refer to the several
figures on the annexed sheet of drawings the same letters of reference indicating
corresponding parts in all the figures.
•
Figure 1 of the accompanying drawings represents in side elevation a propeller
according to this Invention and Figure 2 is a front view of the same.
The screw propeller represented in this drawing is constructed with a solid central
disc A carrying blades B projecting from its periphery the said arms being arranged
to cominence at that distance from the centre where the angular speed is sufficient to
produce a useful effect.
The proportion indicated in the drawing between the length of the radius of the
disc A and that of the arms B is not fixed but must evidently vary in practice
according to the build of the vessel and the speed of the current of water produced
astern of the screw when the vessel is running at its normal or ordinary rate of

page_text: speed. The number of blades and the shape of the blades may also vary according
to circumstances.
The disc may be so constructed as to be capable of expanding and contracting so
as to enable the effective length of the blades to be adjusted according to the intensity
of the current.
The blades B may be cast in one with the disc A or be attached to its periphery
by any suitable means.
These blades may be compared to the threads of a screw the disc forming the
shaft.
In order to obviate the injurious resistance which would result from the solid
dise A acting on the body of water between it and the vessel the space behind the
disc is filled up by a cylinder C which may consist of the tube or casing of the
propeller shaft enlarged to the diameter of the disc or may be formed of plates
suitably curved and rivetted to the skin of the vessel.
This cylinder is closed at the stern where a slight play only is allowed between it
and the disc A of which it constitutes a species of extension merging into the lines
of the hull.
The principal advantages obtained by means of these improvements are as
follows:-
(1.) Economy of motive power.
(2.) Strengthening of the propeller blades.
(3.) Facility for increasing the diameter of the propeller without weakening the
blades. (4.) Reduction of the vibration.
(5.) A considerable diminution in the number of revolutions performed in a unit
of time to attain a given speed.
Having now particularly described and ascertained the nature of the said Inven-
tion and in what manner the same is to be performed I declare that what I
claim is: :-
1st. The improved construction and arrangement of screw propellers for ships or
vessels substantially as hereinbefore described.
2nd. A screw propeller constructed with a solid central disc A provided with any
suitable number of blades B commencing at a point to be determined by calculation
at which the angular speed of the propeller when the vessel is travelling at its average
or normal rate is approximately equal to the speed of displacement of the water astern
of the propeller all in the manner and for the purpose substantially as herein before
set forth with reference to the accompanying drawings.
3rd. In combination with the central solid disc or boss A a cylindrical tube or
casing C of the same diameter as the dise and formed by an enlargement of the
propeller tube or by means of suitably curved plates attached to the hull of the vessel
in the manner and for the purpose substantially as hereinbofore described and illustrated
in the accompanying drawings.
Datod 9 not 1908