Improvements in Screw Propellors.
Year: 1889

page_text: Date of Application, 27th Dec., 1889
Complete Specification Left, 29th Sept., 1890-Accepted, 1st Nov., 189U
PROVISIONAL SPECIFICATION.
Improvements in Screw Propellors.
I, EDMUND EDWARDS, of 35, Southampton Buildings, Chancery Lane, in the
County of Middlesex, Civil Engineer, do hereby declare the nature of this invention
to be as follows:-
This invention relates to the screw propellors ordinarily used for propelling vessels.
It may be applied to propellors having two, three, or any other number of blades,
and supposing that it is to be applied to one having two blades I make each blade in
the following manner.
I take a central boss which is fixed in the usual way upon the
propellor shaft, and I make cach blade consist of two separate parts where it joins the
boss. These parts are fixed in such a position upon the boss that a space is left
between them, through which as the screw revolves the water can pass in a direction
parallel or nearly so to the surface of the blades, and I make that one of the two parts
which forms the front of the screw, when the vessel is moving forward, with a pitch or
angle which the screw is required to have, and the other part with a more or less
increased pitch or angle so that the parts form together a blade of increasing pitch. I
make the back or propelling side of the blades (when the vessel is moving forward)
preferably curved somewhat so as to form parts of a true screw of gradually increasing
pitch, having between them a space through which the water passes as already
described.
I join together the outer ends of the two parts of the blade by a curved plate
extending a sufficient distance iuward from the extreme ends of the blades, which
distance may be about one third of the length of the blade or more or less as may be
found advisable.
The outer part of the blade so formed is also preferably curved so as to form
part of a blade of increasing pitch corresponding with that of the two parts first
described.
I make the edges of the blades as thin as possible and in order to obtain the
necessary strength I make their backs (or non-propelling sides when the vessel is
moving forward) curved so that they are thicker at or near the centre of their
width.
Where the outer plate described joins the two inner blades (of which it forms a
part) I make the junction in suitable gradual curves, so as to prevent as far as possible
any sudden change in the direction of movement of the water.
The other blade of the propellor is formed in a precisely similar way upon the
opposite side of the boss.
Where three or more blades are used they are formed in a similar way upon the
boss at equal angles apart.
In some cases the outer uniting plate may be omitted, the inner separate blades
being continued in the shape described to the full diameter of the propellor.
Instead of two inner parts of different pitch as described, three or more may be
used, each blade being of somewhat less pitch than the one behind it.
I am aware that the blades of screw propellors have been formed with angular
openings through them, but by my invention the efficiency of the propellor is increased
by the improved method of shaping the different parts of the blades as described.
Dated this 27th day of December 1889.
EDWARDS & Co.,
35, Southampton Buildings, London, Agents for the Inventor.

page_text: COMPLETE SPECIFICATION.
Improvements in Screw Propellors.
I, EDMUND EDWARDS, of 35, Southampton Buildings, Chancery Lane, in the
County of Middlesex, Civil 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 and accompanying drawing, that is
to say:
This invention relates to the screw propellors ordinarily used for propelling vessels.
It may be applied to propellors having two, three, or any other number of blades,
and supposing that it is to be applied to one having two blades I make each blade in
the following manner. I take a central boss which is fixed in the usual way upon the
propellor shaft, and I make each blade consist of two separate parts where it joins the
boss. These parts are fixed in such a position upon the boss that a space is left
between them, through which as the screw revolves the water can pass in a direction
parallel or nearly so to the surface of the blades, and 1 make that one of the two parts
which forms the front of the screw, when the vessel is moving forward, with a pitch
or angle which the screw is desired to have, and the other part with a more or less
increased pitch or angle so that the parts form together a blade of increasing pitch. I
make the back or propelling side of the blades (when the vessel is moving forward)
preferably curved somewhat so as to form parts of a screw of gradually increasing
pitch, having between them a space through which the water passes as already
described.
I join together the outer ends of the two parts of the blade by a curved plate
extending a sufficient distance inward from the extreme ends of the blades, which
distance may be about one third of the length of the blade or more or less as may be
found advisable.
The outer part of the blade so formed is also preferably curved so as to form part of
a blade of increasing pitch corresponding with that of the two parts first described.
I make the edges of the blades as thin as possible and in order to obtain the
necessary strength I make their backs (or non-propelling sides when the vessel is
moving forward) preferably curved so that they are thicker at or near the centre of
their width.
Where the outer plate described joins the two inner blades (of which it forms a
part) I make the junction in suitable gradual curves so as to prevent as far as possible
any sudden change in the direction of movement of the water.
The other blade of the propellor is formed in a precisely similar way upon the
opposite side of the boss.
Where three or more blades are used they are formed in a similar way upon the boss
at equal angles apart.
The accompanying drawing is in illustration of my invention,
Figure 1 being a view perpendicular to the blade a and Figure 2 a view in the
direction of the centre line of the shaft.
Figures 3, 4, and 5, illustrate approximately the curves of the blades at the
lines A B, C D, and E F, respectively.
bis the central boss, and c, c, d, d', are the separate parts of the blade, e being
the space between them, and the curved plate connecting their ends and having an
increasing pitch.
In some cases the outer uniting plate may be omitted, the inner separate blades
being continued in the shape described to the full diameter of the propellor.
Instead of two inner parts c, cl, and d, d, of different pitch as described and shewn,
three or more may be used, each blade being of somewhat less pitch than the one
behind it.
j am aware that screw propellors have been made having angular openings
through their blades, and I do not claim such openings but by my invention the

page_text: efficiency of the propellor is greatly increased by the improved method of shaping and
arranging the different parts of the blades as described.
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. In a screw propellor, the blade consisting of two parts of different pitch attached
to the boss, and having a space between them, their ends being connected by the
curved plate of increasing pitch, substantially as described and shewn.
2. In a screw propellor, the blade consisting of three or more parts of different pitch
attached to the boss, and having a space between them, their ends being connected
by a curved plate of increasing pitch, substantially as described.
3. In a screw propellor, the blade consisting of two or more parts of different pitch
attached to the boss, and having a space between them, their outer ends not being
connected together, substantially as described.
Dated th¦ 07:11. of Santambon 1800
EDWARDS & Co.,
35, Southampton Buildings, Chancery Lane, London,
Agents for the Patentee.