IMPROVEMENTS IN STEAM SHIP SCREWS
Year: 1882

page_text: LETTERS PATENT to Gerard Wenzeslaus von Nawrocki, Proprietor of the
firm of J. Brandt & G. W v Nawrocki, Patent Solicitor and Civil Engineer
of 124 Leipzigerstrasse Berlin Germany for an invention of "IMPROVEMENTS
IN STEAM SHIP SCREWS" A communication from Fritz Maringer of the City
of Düsseldorf, Prussia Germany
PROVISIONAL SPECIFICATION left by the said Gerard Wenzeslaus von
Nawrocki at the Office of the Commissioners of Patents on the 10th May
1882.
GERARD WENZESLAUS VON NAWROCKI, Proprietor of the firm of J. Brandt
& G. W. v Nawrocki, Patent Solicitor and Civil Engineer of 124 Leipzigerstrasse
Berlin Germany "IMPROVEMENTS IN STEAM SHIP SCREWS (A Communication
from Fritz Maringer of the City of Düsseldorf, Prussia, Germany)
"
A fault of all known systems of the blades of ship's screw propellers is, that it is
not possible profitably to apply an engine power increased at will so as to increase
the speed of the vessel proportionately and further that those parts of the water
grasped by the screw are partly more or less pushed to the side, for which a part
of the power exerted must be expended, instead of the mass of water which is
grasped being in a wholly solid form sent along backwards in the keel line of
the ship.
The inventor obviates these defects in such a manner that he makes the screw
blades with parabolas, and on the convex side he furnishes them with ribs or
paddles which are arranged helically parallel to each other. The front surface
provided with ribs is convex, the back surface concave whilst the edges of the
blades are parabolical as they form sections of the parabolically curved screw
surfaces and with two parallel surfaces which are vertical to the screw's axis. The
front surface of the blade is therefore convex both in length and breadth section.
The ribs situate on this front surface are so arranged that when the screw
revolves, they dip successively in the water and exercise a certain pressure on the
water by their more or less slanting position to the axis of rotation, and hence like
the blades themselves increase the axial force and besides hold the water together,
so that they create a body of rotation in the water itself.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Gerard Wenzeslaus von Nawrocki in the Great Seal Patent Office on
the 10th November 1882.
GERARD WENZESLAUS VON NAWROCKI, Proprietor of the firm of J. Brandt
& G. W. v. Nawrocki, Patent Solicitor and Civil Engineer, of 124, Leipzigerstrasse,
Berlin, Germany "IMPROVEMENTS IN STEAM SHIP SCREWS (A Communication
from Fritz Maringer of the City of Dusseldorf, Prussia, Germany)
وو
A fault of all known systems of the blades of ships' screw propellers is, that
it is not possible profitably to apply an engine power increased at will so as
to increase the speed of the vessel proportionately and further that those parts of
the water grasped by the screw are partly more or less pushed to the side, for
which a part of the power exerted must be expended instead of the mass of water
which is grasped being in a wholly solid form sent along backwards in the keel
line of the ship. The inventor obviates these defects in such a manner that he
makes the screw blades with parabolas, and on the convex side he furnishes them
with ribs or paddles which are arranged helically parallel to each other. A three
bladed screw of that sort is shown in the accompanying drawings. Figure 1 shows
a perspective view of same, Figure 2 section of blade at the nave, in the middle of
the blade, and at the periphery of same, while Figure 3 represents a longitudinal
section through the blades. As the Figures show, the front surface provided with
ribs, is convex, the back surface concave, whilst the edges of the blades are
parabolical, as they form sections of the parabolically curved screw surfaces and
with two parallel surfaces which are vertical to the screw's axis. The front
surface of the blade is therefore convex both in length and breadth section. The
ribs situate on this front surface are so arranged, that when the screw revolves they
dip successively in the water and exercise a certain pressure on the water by their
more or less slanting position to the axis of rotation, and hence, like the blades
themselves increase the axial force and besides hold the water together, so that
they create a body of rotation in the water itself.
The action of this new construction of screw blades is shown in Figures 4 to 6.
Let us suppose the fan in the position shown in Figure 4, then every point will
have a movement vertical to the direction of the radius going through this point.
This motion can be divided into a vertical and a horizontal direction, consequently
on the working power in every point. The first will help towards the augmentation
of the driving power the other to the holding fast of the water. In the position
shown in Figure 5, the amount of the two forces will be different, as also the action
of a whole blade. When the blade is in the position shown in Figure 6 it will in
its further motion push the water to the side while the ribs will also press
vertically on the water. In the continued motion the vertical pressure of the
blades themselves on the water increases and that of the ribs decreases, until finally
in the horizontal position the action of the blades has become a maximum and that
of the ribs a minimum, in order then respectively to decrease and increase.
Hereby is chiefly obtained a greater uniformity in the action of the screw and
hence a quieter motion of the ship as has been fully proved by experiments.
This was the action of the ribs for the increase of the axial force; their action in
the way of holding the water results from a peculiarity of the ribs consisting
therein that they widen downwards so that the part of the surface first entering
the water has a much larger line of entry than the one entering last.
By this means the volume of water, which collects between the blades is forced
to go through the intervening space of the blades, and is therefore more and

page_text: more compressed and held fast. Further it is deserving of notice that the action
of the ribs on the blades is easily explained when considering that by the rotation
and simultaneous progress of the saine, every rib describes part of a curved screw
surface and must consequently work in the same manner as the motion of the
blades is a similar one. The position of the blades to the boss is so arranged, that
the ribs on it only have the described effect in that position.
The screw described is a right handed one and moves in the direction of the
arrow, so that the convex edge of the blade lying next to the boss as well as the
points a, b, c, d and e of the ribs dip into the water first.
By this new screw a considerably greater speed can be obtained by the
employment of sufficient power which speed increases in proportion to the height
of the ribs, and as besides the continually disturbing movements of the water are
done away with, a regular motion of the vessel is attained.
I Claim as the invention communicated to me :-
First The application to screw propellers of blades the generatrix of which is a
parabola, and the edges parabolical, these parabolas being so arranged that the
front surface of the blade is convex, and the back surface concave.
Second: The application of ribs on the front convex surface of screw propeller
blades as and for the purpose set forth
In Witness whereof I the said Gerard Wenzeslaus von Nawrocki have
hereunto set my hand and seal this Fourth day of November in the year of
our Lord one thousand eight hundred and eightytwo :-
CTATIC״Nגע
BOX NAWROCKT
CTATIC שחוננת
VON NAWROCKT
(1.S.)