Improvements in Propellers for Ships.
Year: 1898

page_text: Date of Application, 6th Dec., 1898 -Accepted, 22nd July, 1899.
CUMILIE DIECIFICATION.
Improvements in Propellers for Ships.
I, GIOVANNI CARDOSA, of Genoa, Via S. Chiara No. 11, Kingdom of Italy, 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:-
The blades of screw propellers as at present in use are formed with a helicoidal
surface fixed perpendicularly to the head or boss or nave.
The part of the helicoidal surface utilized for the blades is that included
between the ends of the head or boss; the length of the blades is proportionate to
the size of the ship, the power of the engine and the speed desired.
The
This form of propeller causes vigorous reaction between the water and the
blades which produces a great resistance to the revolution of the screw.
improvement which I have introduced and which is the object of the present
application does away with these disadvantages a fact which has been established
by numerous satisfactory experiments.
The improved screw which I have introduced and which is illustrated in the
annexed drawing 'differs from that at present in use not only in its form but also
in its construction. On the circumference of the head or boss is fixed a certain
number of blades C, C-preferably three--at equal distances from one another.
The position of each is determined by a plane passing through the centre of the
head or boss which forms with the axis of the latter an angle A of 45 degrees.
This plane cuts the lateral cylindrical surface of the head or boss in the form of a
segment of an ellipse. If a straight line is drawn from any point on this segment
of ellipse making with the axis of the head or boss an angle B of 45 degrees
towards the bow then this line determines the angle of the general slope of the
blades from the boss or axis. This blade is attached to the head or boss at its
extremity towards the stern and is rounded off towards the bow, the whole some-
what representing the shape of a birds wing. The tips which have to cut the
water are tapered off. The size, length and number of blades for this improved
screw are dependent on the practical application of the propeller of the special
ship to which it has to be affixed. The inclination of the blades to the head
or boss can also be altered as I do not intend to adhere definitely to an angle
of 45 degrees seeing that in practice it might be more expedient to take a greater
or less angle. I intend simply to affirm the principle of the novel shape given to
the screw. It is easy to understand that this screw turns to the advantage of
propelling power the vigorous reaction between the water and the blades, men-
tioned above which opposes so much resistance to the revolution of the screw.
The work of propelling is always equally distributed at any point of the surface
at any speed. Consequently there is less waste of power than with the ordinary
form of proneller.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
CLAIM.
The improvements in screw propellers, the blades of which are planes extending
rearward more or less, the said blades being formed like the wing of a bird and have
essentially a direction of 45 degrees with the axis of the head or boss towards the
bow. The whole as set forth above and illustrated in the drawing.
Dated this 5th day of December 1898
GIOVANNI CARDOSA.
By George Barker,
ellow of the Chartered Institute of Patent Agents,
Agent for Applicant,
77, Colmore Row, Birmingham.
GIOVANNI CARDOSA.
By George Barker,
ellow of the Chartered Institute of Patent Agents,
Agent for Applicant,
77, Colmore Row, Birmingham.