Improvements in and relating to Screw Propellers.
Year: 1898

page_text: Date of Application, 30th Mar., 1898
Improvements in and relating to Screw Propellers.
I, JOHANN BAPTIST HIRSCHMANN, of Eltville, Rheingau, Rhenish Prussia, in
the Empire of Germany, Merchant, do hereby declare the nature of this inven-
tion to be as follows:-
The screw propeller which forms the subject of the present invention is charac-
terized by so constructing the same that it approaches as closely as possible the
true screw surface and further by the fact that the parts of the screw surface
nearest the axis are omitted thus forming a space at such axis.
The radius of this space; or the distance from the axis to the inner circum-
ference of the screw, compared with the outer radius of such screw, is in the
proportion of about 1:5, which proportion may however, be varied as desired.
The screw has further only one thread, but screws with two or more threads if
possessed of the other features herein set forth are of greater power. After
numerous experiments however it has been proved that the screw produces the
best result when it has only a single thread and only about one convolution or
a little more.
The number of convolutions or turns however varies, according to the work to
be done, for ships designed to travel at a high speed about one turn is used, for
ships conveying heavy loads the convolutions may vary between one and two.
In this form the body of the screw is fastened at one end only to a boss or hub
or is made in one piece with the said boss, while the other end remains free.
The boss or hub of the usual ball shape, is secured to the shaft by means of a
wedge or key; or, in the case of small screws it is connected with the shaft by
a set screw, so that, if required, the screw may be adjusted upon the shaft to the
most suitable position.
Experiments have further shown that the improved screw works best when
arranged at an angle of 40 to 50° to either the horizontal or the vertical
plane; two screws so arranged and having oppositely arranged threads are
placed for this purpose at the rear part of the ship, or on both sides of the
same. At this inclination the middle portion of the screw which would be almost
horizontal cuts into the water in moving forward, whilst the other nearly ver-
tical portions press with their surfaces on the water and throw it backwards so
that with the minimum amount of friction the maximum amount of work
is obtained. Furthermore the particularly simple manner of fixing the screw
by means of the shaft has the advantage that the driving arrangement can also
be very simple; for example the driving may be effected by means of a steam
turbine fastened directly to the shaft. Instead of a steam turbine however 1
may use a water turbine, an electro motor, a rotary steam engine or other rotary
motor, or a benzine or petroleum motor. Each screw may be arranged to be
worked separately, for steering purposes and so that the turning of the ship
may be effected with the greatest ease, especially in narrow water
ways. In
such case the one screw is worked forward and the other backward,

page_text: This object is accomplished by arranging the screws on both sides of the
centre of the ship as above mentioned. When so arranged the ship can be
turned almost as on a pivot. This arrangement is such that the main shaft
driven in any suitable manner is provided with a belt pulley which drives a
smaller belt pulley on the cross shaft, on the ends of which are bevel wheels,
which, by means of similar bevel wheels, operate the screw shafts, and the
screws on both sides of the centre of the ship. This arrangement has the further
advantage that the angle at which the screw works may be altered with com-
paratively little trouble.
Dated this 30th day of March 1898
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.
I, JOHANN BAPTIST HIRSCHMANN, of Eltville, Rheingau Rhenish Prussia, in
the Empire of Germany, Merchant, do hereby declare the nature of this inven
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement;-
The screw propeller which forms the subject of the present invention is charac-
terised by constructing the same in such a manner that it approaches as closely
as possible the true screw surface, and further by the fact that the parts of the
screw surface nearest the axis of the screw are omitted thus forming a space at
the axis of the screw.
This invention is illustrated in the accompanying drawing the figures of
which are hereinafter referred to.
a represents the screw propeller, the hub, c the set screw by which it is
attached to the said hub, and is the shaft for carrying the said propeller.
As shown in Figure 1 there is formed around the axis a space having a radius y
which compared to the radius h of the outside of the blade is in the proportion
of about 1:5, which proportion may however be varied as desired. The pro-
peller has further only one blade or thread, but propellers with two and more
threads, if possessed of the other features herein set forth are of greater power:
After numerous experiments however it has been proved that the screw produces
the best result when it has only a single thread and only about one convolution
or a little more, as shown in Figure 1, The number of convolutions or turns
however varies according to the work to be done, for ships designed to travel
at a high speed about one turn is used, for ships conveying heavy loads the con-
volutions may vary between one and two.
In this form the body a of the propeller is fastened at one end only to a boss
or tube, b, or is made in one piece with the said boss, while the other end remains
free. The boss or hub b, of the usual ball shape, is secured to the shaft d by
means of a wedge or key; or in the case of small screws, it is connected with
the shaft by a set screw c, so that, if required the propeller a may be adjusted
upon the shaft d to the most suitable position,
Experiments have further shown that the improved propeller works best when
arranged at an angle of about 40 to 50° to either the horizontal or the vertical
plane two propellers so arranged and having oppositely arranged threads are
placed for this purpose at the rear part of the ship, as shown in Figures 2 and 3,
or on both sides of the same as shown in Figures 4 and 5. At this inclination,

page_text: the middle portion of the screw which would be almost horizontal cuts into the
water in moving forward, whilst the other nearly vertical portions press with
their surfaces on the water and throw it backwards, so that with the minimum
amount of friction the maximum amount of work is obtained. Furthermore
the particularly simple manner of fixing the screw by means of the shaft d has
the advantage that the driving arrangement can also be very simple; for
example, as shown in Figures 2 and 3 the driving may be effected by means
of a steam turbine f fastened directly to the shaft. Instead of a steam turbine
however, I may use a water turbine, an electro motor, a rotary steam engine or
Each screw may be arranged
other rotary motor or a benzine or petroleum motor.
to be worked separately, for steering purposes and so that the turning of the ship
In
may be effected with the greatest ease, especially in narrow water ways.
such case the one screw is worked forward and the other backward.
This object is accomplished by arranging the screws on both sides of the
centre of the ship as shown in Figures 4 and 5. When so arranged the ship
can be turned almost as on a pivot. This arrangement is such that the main
shaft m, driven in any suitable manner is provided with a belt pulley k, which
by means of a small belt i drives a smaller belt pulley h and the shaft gl on
the ends of which are bevel wheels g, which, by means of a similar bevel wheel,
operate the propeller shaft and the propellers a a¹ on both sides of the centre of
the ship. This arrangement has the further advantage that the angle at which
the screw works may be altered, with comparatively little trouble.
"
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed, I declare that what I
claim is:-
-
1. A ship's propeller the blade of which forms but one or at most two helical
convolutions and in which the screw blade does not extend to the central axis,
the propeller shaft and hub being omitted for the greater part of its length.
2. A ship's propeller of the kind described in Claim 1, which is inclined at
an angle of 40° to 50° to the horizontal.
3. The driving of a ship's propeller of the kind described in Claims 1 and 2,
either directly in the manner shewn in Figures 2 and 3 by means of a rotary
motor, or indirectly by means of bevel gearing in accordance with Figures 4
and 5.
Dated this 20th day of December 1898.
HASELTINE, LAKE & Cb.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.