Improvements in Screw Propellers.
Year: 1894

page_text: Date of Application, 17th Oct., 1894
Complete Specification Left, 16th Feb., 1895-Accepted, 23rd Mar., 1895
Improvements in Screw Propellers.
I, BENJAMIN WADDY MAUGHAN, of 1 Helmet Court, 338 Strand, in the Parish
of Saint Mary-le-Strand, London, in the County of Middlesex, Engineer, do hereby
declare the nature of this invention to be as follows:-
My invention relates to screw propellers, and is intended to provide improved
propellers especially adapted for ocean-going vessels.
In the Specification of prior Letters Patent No. 13,014 of 1893, I have described
and shown a propeller of three blades or fans occupying the entire disc area as seen
from a position behind the stern of the vessel.
Further consideration has shown that having regard to the violence of the ocean
waves, the occupation by the blades of the entire disc area is undesirable inasmuch
as too great a surface is thereby presented to the waves for the motive power usually
employed.
My present improvements relate to the reduction of the disc area occupied by the
blade or blades of the propeller to about 40 % or less of the entire disc area, for
ocean-going vessels as usually constructed.
The configuration of the perimeter of a blade or of each of the blades of my
improved propeller is or may be decided upon in accordance with the data furnished,
or obtained of any specified vessel and its motive power.
In other respects my improved propeller is constructed with dihedral angles, and
a tip helical flange in the manner fully described in the abovementioned prior
Specification.
The root of the blade is designed to have in practice sufficient strength of
metal, or other material, to withstand the stress to which the blade may be
subjected, and may be formed with double convex lines representing surfaces or
otherwise.
I do not confine myself to any specified number of angles on the blade, the
number employed in any particular case depending upon the depth of immersion
beneath the surface of the water, and the number of revolutions per minute of the
propeller. Neither do I confine myself to the use of any particular number of
blades in the construction of the improved propeller herein described.
The blades referred to in the foregoing description of my improvements are
designed upon the basis of a true helix or screw.
There are however certain classes of vessels such as torpedo boats, torpedo boat
catchers, passenger vessels and the like, (which are intended to be propelled at high
rates of speed) for which the surfaces forming dihedral angles are or may advan-
tageously be constructed as follows.
(1) They may be based upon a helix or screw of increasing pitch from the root
to the tip of each blade of my improved propeller.
(2) They may be designed so that the slip pitch surfaces on the driving or
front side of one or of each blade of the propeller, shall successively have an
increased pitch from the leading slip pitch surface to the trailing slip pitch
surface, or
(3) So that the increasing pitch described in (1) and the increasing pitches of
the slip pitch surfaces described in (2) are both and each of them utilized in the
design and construction of each blade of the propeller.

page_text: There are also certain classes of vessels used for towing other vessels, and for
similar purposes, which move at a slow rate of speed for which the surfaces
forming dihedral angles are or may be advantageously constructed as follows:-
that is to say, such surfaces may be based upon a helix or screw of decreasing
pitch from the root to the tip of each blade of my improved propeller, but no
advantage would be gained by successively diminishing instead of increasing the
pitches of the slip pitch lines.
In consequence of the mechanical assistance to the motive power caused by the
impact of the water on the back of the blade or blades I am enabled to use
propellers of larger diameter in proportion to the stroke of the engine than can be
used with other forms or designs of propeller blade heretofore in use.
The definitions of the technical terms used in this Specification will be found in
the beforementioned prior Specification.
Dated this 16th day of October 1894.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.
I, BENJAMIN WADDY MAUGHAN, of 1 Helmet Court, 338 Strand, in the Parish
of Saint Mary-le-Strand, London, in the County of Middlesex, 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 intended to provide improved
propellers especially adapted for ocean-going vessels.
In the Specification of prior Letters Patent No. 13,014 of 1893, I have described
and shown a propeller having three blades or fans occupying the entire disc area as
seen from a position behind the stern of the vessel. Further consideration has
shown that having regard to the occasional violence of the ocean waves, the
occupation by the blades of the entire disc area is undesirable inasmuch as too
great a surface is thereby presented to the waves for the motive power usually
employed.
My present improvements relate to the reduction of the disc area occupied by the
blade or blades of the propeller to about forty per cent. (40%) or less of the entire
disc arca, for ocean-going vessels as usually constructed.
In other respects my improved propeller is constructed with dihedral angles,
and a tip helical flange in the manner fully described in the abovementioned
prior Specification wherein will be found the definitions of the technical terms
herein used.
The configuration of the perimeter of a blade or of each of the blades of my
improved propeller is or may be decided upon in accordance with the data, furnished
or obtained, of any specified vessel and its motive power.
The rout of the blade is designed to have in practice sufficient strength of
metal, or other material, to withstand the stress to which the blade may be
subjected, and may be formed with double convex surfaces.
I do not confine myself to any specified number of angles on the blade, the
number employed in any particular case depending upon the depth of immersion
beneath the surface of the water, the number of revolutions per minute, and the
required weight, of the propeller. Neither do I confine myself to the use of any
particular number of blades in the construction of my improved propeller.
The blades referred to in the foregoing description of my improvements are
designed upon the basis of a true helix or screw. There are however certain

page_text: classes of vessels such as torpedo boats, torpedo boat catchers, passenger vessels
and the like, (which are intended to be propelled at high rates of speed) for which
the surfaces forming dihedral angles are or may advantageously be constructed as
follows.
(1) They may be based upon a helix or screw of increasing pitch from the root
to the tip of each blade of my improved propeller.
(2) They may be designed so that the slip pitch surfaces on the driving or
front side of one or of each blade of the propeller, shall successively have an
increased pitch from the leading slip pitch surface to the trailing slip pitch
surface, or
(3) So that the increasing pitch described in (1) and the increasing pitches of
the slip pitch surfaces described in (2) are both and each of them utilized in the
design and construction of each blade of the propeller.
There are also certain classes of vessels used for towing other vessels, and for
similar purposes, which move at a slow rate of speed for which the surfaces
forming dihedral angles are or may be advantageously constructed as follows:
that is to say, such surfaces may be based upon a helix or screw of decreasing
pitch from the root to the tip of each blade of my improved propeller, but no
advantage would be gained by successively diminishing instead of increasing the
pitches of the slip pitch liues.
In consequence of the mechanical assistance to the motive power caused by the
impact of the water on the back of the blade or blades I am enabled to use
propellers of larger diameter in proportion to the stroke of the engine than can be
used with other forms or designs of propeller blade heretofore in use.
In the accompanying drawings which illustrate my invention,
Figure 1 shows an "extended" or developed blade with flange A B, at
the tip.
Figures 2, 3 4 and 5 are "extended" helical sections of the "extended" blade
Figure 1 at those parts of the blade opposite which the sections are placed.
Figure 6 indicates the helical pitches and other lines used in arriving at the
Figures 1, 7 and 8. The pitch lines vary with every variety of vessel and depend
on the data relating to the hull, the motive power, and other factors. Their use is
explained in my beforementioned prior Specification.
Figure 7 is an end elevation, and
Figure 8 is a side elevation of the "extended" blade Figure 1 drawn as aforesaid
by aid of the lines shown in Figure 6.
Figure 9 is an "extended" blade of another form, with a helical flange A B, at
the tip.
"
Figures 10, 11, 12 and 13 are "extended" helical sections of the "extended
blade, Figure 9, at those parts of the blade indicated by the curved cross lines
opposite which they are placed.
Figure 14 indicates the helical pitches and other lines used in arriving at the
Figures 9, 15 and 16. These lines may vary as aforesaid with every vessel.
Figure 15 is an end elevation, and
Figure 16 is a side elevation of the "extended" blade Figure 9 drawn as
aforesaid by aid of the lines indicated in Figure 14.
Figure 17 shows an "extended" blade, the leading and trailing corners of which
are cut off, leaving a small length of helical flange A B at the tip.
Figure 18 shows a similar extended blade constructed to have an increased
length of helical flange A B, at the tip.
Figure 19 shows several "extended" blades having different perimeters, or
configurations superimposed one upon the other to show that the angles described
in my said prior Specification may be applied to any configuration preferred for
any specified vessel.
Figure 20 is a radial section of my improved blade, having a flat flange A B,
(that is to say, a flange that is straight in cross section) overhanging the front and
the back of the blade.

page_text: Figure 21 is a radial central section of a blade having a curved flange, A, B
overhanging the front and the back of the blade.
Figure 22 shows an example of the increasing pitch lines from the root C D, to
the tip C P, of a blade the diameter of which is specified to be four times the
stroke of the engine. The dotted lines V D, V E, V F, V P, show the pitch lines
of a true helix or screw.
Figure 23 shows an "extended "helical section of one example of the tip of a
blade the diameter of which is specified to be four times the stroke of the engine;
the leading slip pitch line of the said section is or may be at a pitch S P, suitable
for a specified vessel, having regard to the successively increasing pitches of the
slip pitch lines M_N, QR, TU, respectively parallel to the dotted pitch
lines M', P, Q, P, T' P. The other dotted lines are the same as those referred to
in my said prior Specification.
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 :-
1. A propeller constructed substantially as herein described, and in which the
blades occupy less than the whole of the disc area, for the purpose specified.
2. Such a propeller having at the tip either on the front, or back, or on both
front and back, a helical flange which may be straight or curved in transverse
section, substantially as described.
Dated this 16th day of February 1895.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.