IMPROVEMENTS IN SCREW PROPELLERS, AFPLICABLE ALSO FOR RAISING AND FORCING WATER AND OTHER LIQUIDS, AND OBTAINING MOTIVE POWER FROM THE SAME
Year: 1860

page_text: LETTERS PATENT to Arthur Irwin Mahon, of Dublin, for the Invention of
"IMPROVEMENTS IN SCREW PROPELLERS, AFPLICABLE ALSO FOR RAISING AND
FORCING WATER AND OTHER LIQUIDS, AND OBTAINING MOTIVE POWER FROM THE
SAME."
Sealed the 27th March 1861, and dated the 3rd October 1860.
PROVISIONAL SPECIFICATION left by the said Arthur Irwin Mahon at
the Office of the Commissioners of Patents, with his Petition, on the
3rd October 1860.
I, ARTHUR IRWIN MAHON, of Dublin, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN SCREW PROPELLERS, APPLICABLE ALSO FOR
RAISING AND FORCING WATER AND OTHER LIQUIDS, AND OBTAINING MOTIVE POWER
FROM THE SAME," to be as follows:-
The Invention consists of a screw propeller constructed in the following
manner: I fix a thin spiral or helical flange or blade of sheet iron or any
suitable material to an axis or shaft, so as to form a screw of one, two, or
several turns, and I incase this screw in a cylindrical case which may either
revolve with it or be fixed. This cylinder may project beyond the screw to
confine and direct the water. This screw may be placed outside the vessel in
a channel beneath it, or in a case within the vessel communicating at each
When a great length of screw is required, I divide the
end with the water.

page_text: screw into two or more lengths and support each end of each length, and I
place a belt round the junction to confine the water. The Invention is also
applicable for obtaining motive power from liquids. Thus, a fall of water may
be directed through the screw, and will cause it to revolve. Or, in some cases
I apply the propeller to produce and drive a current of water against or on to
a water wheel. The screw is also applicable for raising water and other
liquids by immersing one end or a pipe from one end in the liquid, and causing
the screw to revolve by the application of any suitable power. The screw
must be filled or partially filled with liquid before starting.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Arthur Irwin Mahon in the Great Seal Patent Office on the
3rd April 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ARTHUR
IRWIN MAHON, of Dublin, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Third day of October, in the year of our Lord One
thousand eight hundred and sixty, in the twenty-fourth year of Her reign, did,
for Herself, Her heirs and successors, give and grant unto me, the said Arthur
Irwin Mahon, Her special license that I, the said Arthur Irwin Mahon, my
executors, administrators, and assigns, or such others as I, the said Arthur
Irwin Mahon, my executors, administrators, or assigns, should at any
time agree with, and no others, from time to time and at all times there-
after during the term therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "IM-
PROVEMENTS IN SCREW PROPELLERS, APPLICABLE ALSO FOR RAISING AND FORCING
WATER AND OTHER LIQUIDS, AND OBTAINING MOTIVE POWER FROM THE SAME," upon
the condition (amongst others) that I, the said Arthur Irwin Mahon, my
executors or administrators, by an instrument in writing under my hand and
seal, or under the hand and seal of one of them, should particularly describe
and ascertain the nature of the said Invention, and in what manner the same
was to be performed, and cause the same to be filed in the Great Seal
Patent Office within six calendar months next and immediately after the
date of the said Letters Patent.
NOW KNOW YE, that I, the said Arthur Irwin Mahon, do hereby declare
the nature of my said Invention, and in what manner the same is to be per-

page_text: formed, to be particularly described and ascertained in and by the following
statement, reference being had to the accompanying Drawings, and to the
letters and figures marked thereon, that is to say :-
My said Invention relates to a peculiar construction and arrangement of
screw. propeller which is applicable also to the raising and forcing of water,
and to the obtainment of motive power. According to my Invention I fix a
thin spiral of helical flanges or blades of sheet iron or any suitable material on
to an axis or shaft so as to form a screw of one or more turns, and threads or
helices, and I enclose this screw in a cylindrical case which may either revolve
with it or remain stationary. This cylindrical case may project beyond the
screw so as to confine and direct the water. I propose to place this screw
and casing when used as a propeller outside the vessel in a channel beneath it,
or in a case within the vessel communicating at each end with the water.
When a great length of screw is required I divide the screw into two or more
lengths or sections, and support each end of each length or section in suit-
able bearings, and I place a belt round the junction to confine the water.
This apparatus is also applicable to the obtaining of motive power from liquids
by directing a fall of water through the screw, and thereby causing it to
revolve. Or, if desired, it may be employed for the purpose of producing and
driving a current of water against or on to a water wheel. This peculiar
screw is also applicable for raising water and other liquids by immersing one
end, or a pipe leading from one end of the cylinder or casing in the liquid
and causing the screw to revolve by the aid of any suitable power. The
cylinder or casing enclosing the screw must be filled or partially filled with
liquid before starting when used as a pump.
And in order that my said Invention may be fully understood, I shall now
proceed more particularly to describe the same, and for that purpose I shall
refer to the several Figures on the Sheets of Drawings hereunto annexed,
the same letters of reference indicating corresponding parts throughout all the
corresponding Figures.
Figure 1 represents in longitudinal sectional elevation a short length or
section of one form of my improved screw propeller, the outer case or cylinder
being shown in section; and Figure 2 is a corresponding end view of the
same.
A is the shaft of the propeller, forming at the same time the axis of the
screw, which may be of any length desired, (in my Drawing I have shewn the
ends broken away for that purpose), and B, B, are the flanges or blades which
are secured at one end to the circumference of the shaft A, and at the other
to the interior of the cylinder or outer casing C, where such casing is intended

page_text: to rotate with the screw as shewn in my Drawings, but when the screw is
required to rotate, whilst the cylinder remains stationary, the outer ends of the
blades are detached from the cylinder, and are connected by spiral bands
which extend from blade to blade in each series or helix so as to act as a stay
in keeping each blade in its proper position as regards its neighbour. In
fixing the proper positions of the several blades, I first describe a spiral line
round the axis or shaft A as shewn by the red line a, a, in Figure 1. I now
arrange any desired number of blades B, B, at any suitable distances apart
on either or both sides of this spiral a, the blades being disposed at an angle
therewith, those on one side of the spiral being placed at the exact reverse
angle, whatever that may be, to those on the opposite side, as will be clearly
seen on referring to Figure 1. To obtain motion in the direction E, D,
Figure 1, the screw is to revolve to the right in the contrary direction to
which the spiral line a, a, on shaft works forwards. By this arrangement each
individual blade acts separately and independantly, and upon a separate and
distinct portion of the water, whereas were they placed or disposed parallel to
or in the direction of the spiral line a, they would each follow the other in the
same line through the water as portions of one and the same helix. In
Figures 3 and 4 the same principle is carried out in a slightly modified
manner. Here the effect of a four-thread screw, or rather of four separate
screws, is obtained, but the blades B, in place of following each other, (as would
be the case with an ordinary four-threaded helix) break joint with each other,
being fitted opposite to the intervening spaces between the preceding and.
succeeding blades, so that no two consecutive blades will follow in the same
course or track, but will act independently and individually upon the water
each with its full power.
Figure 5 (Sheet 2) represents a longitudinal section of my propeller as
applied to a ship, and Figure 6 is a transverse section of the same. In this
arrangement the cylinder is stationary. Figure 5 shews one turn of the
screw, which is constructed on one revolution of the spiral. A spiral line a of
the intended pitch is drawn on the shaft in either direction; I then divide the
spiral, marking the places where the flanges B are required; and I support
the shaft on centres or bearings, so that it may revolve freely while placing
the flanges round it. I now place the flanges or blades on each side of the
spiral, at equal opposite and downward angles, all those on one side being
forward, whilst those on the other side are backward, as shewn in the Drawing,
Figure 5. The object is to place the flanges so that each shall have full and
independant power, whilst the force of the whole in one direction is obtained.
By placing these flanges to the right side of the spiral at the forward and

page_text: downward angle, and those on the left side at the backward and downward
angle, on reversing the screw each of the blades as they come round from the
way they are placed move the whole forward, and the whole force is in the
line of the screw formed by the regular or helical direction of the flanges along
the spiral. The flanges in the Drawing are shewn as blades, because their
manner of acting is more easily understood. The flange is formed and shaped
to fit the cylindrical surfaces of the cylinder and shaft on the principle of an
ellipse, being the section of a cylinder at any angle, and as the flanges are
planes of resistance at an angle on the shaft, and bounded by a cylinder or
belts, both the outside curves adjoining the cylinder or belt, and the inside
curve adjoining and coinciding with the shaft, are ellipses or portions of
ellipses. To obtain the ellipse or outside curve of the flanges I determine the
angle at which they are to work, and the diameter of the cylinder or screw
when the same is complete. The major axis of the ellipse will be practically
the hypotheneuse of a right-angled triangle, one of whose sides is equal to the
proposed diameter of the screw, and having one angle equal to the proposed
angle at which they must all work. The minor axis is taken as the diameter
of the screw.
Having described the large ellipse in the centre of it, I describe the
smaller ellipse, which merely depends for area, &c., on the diameter of the
shaft, with which it is intended to be adapted and coincides. On removing
the smaller ellipse there remains a perfect flange, which may be bisected or
divided into any number of blades, and when applied to the shaft will coincide
with it, as also with the internal surface of the cylinder, or belt, or band, to
which on the outside it is to be attached. The flanges or blades may be fixed
to the shaft and cylinder in any manner either by angle irons or twisted angle
bands.
A, A, in Figure 5, represent the cylinder or chamber in the vessel with a
flange turned inwards sufficiently to present a resistance or end bearing to the
screw, and effect a junction with the tubes fore and aft. This cylinder or
chamber may have a plate fitted and covered in on the top similar to the
manhole of a steam boiler, so that the inside may be readily got at for repairs
and cleaning. B¹, B¹, represents that portion of the chamber between the
tubes and the cylinder, and uniting both, as shewn in the Drawing. The
screw may be worked by means of the chain wheel and chain, the latter
working through upright tubes to communicate with any prime mover over-
head for driving the screw. These tubes are intended to reach above the
water line. The overflow tube c and valve at d prevent the water rising when

page_text: the vessel is backed with velocity. The tubes fore and aft should be of
sufficient diameter to admit a constant and adequate supply of water to the
chamber in which the screw works. It is intended to have stop-cocks g, g,
which will shut off all communication with the supply from outside, and so
allow the chamber to be emptied, if necessary, and the vessel used as a sailing
vessel only. Tubes should be protected by a grating at the ends. E, E, are
hoops or bands at the extremities of the screw, containing rollers which
project sufficiently to work freely against the internal flange attached to the
chamber, as shewn; these hoops or bands form also the junction of the tie
rods x and y connecting the shaft and hoops. D, D, are the spiral bands or
belts forming the boundary of the screw, and helping to tie or unite the flanges,
strengthen the whole, and retain the water during the thrust, whilst they are
themselves kept in rigid position by the tie rods which connect the end bands.
When applying the screw as a pump, I would merely turn up the tube at the
end where the power is not applied into the water, and as the screw is
immersed in water and worked in cylinder (or attached in some cases) the
water rises in the tube. I wish it to be understood that I do not consider
myself bound to adopt the method or manner of working this screw by the
chain and rollers, as shewn, or the minor details of the plan, for it can be
worked as readily by a connecting rod and crank, or other suitable mechanical
contrivance. I do not confine myself to any particular angle at which the
flanges ought to work, as that may vary according to the speed and power
required; but I have found that the nearer the angle approaches a per-
pendicular to the axis of the shaft, the more power is gained, whilst for speed
the nearer it approaches forty-five, or is increased proportionally to the power
employed, the better. The tubes may be of less diameter than the screw.
Two or more such screws might be worked by the same power if placed
transversely in the vessel, by connecting the cranks in the same way that any
number of driving wheels are worked in a locomotive engine. When a
number of spirals are to be applied, they are traced parallel to each other on
opposite sides of the shaft, and the flanges applied thereto as described above,
thus making several series of flanges (see Figures 1 and 2) in lieu of a single
series only, as in Figure 5.
Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the same is or may be used or carried
into effect, I would observe, in conclusion, that what I consider to be novel and
original, and therefore claim as the Invention secured to me by the herein-
before in part recited Letters Patent, is,-

page_text: First, the general construction, arrangement, and combination of apparatus
for propelling vessels, raising and forcing water, and obtaining motive power,
as herein-before described, and illustrated by my Drawings.
Second, the application of the flanges acting independently and together,
whether forming a spiral themselves on the shaft, or arranged on each side of
a spiral, or forming a number of spirals on a shaft, as illustrated in Figure 5
of my Drawings.
In witness whereof, I, the said Arthur Irwin Mahon, have hereunto set
my hand and seal, this Thirtieth day of March, One thousand eight
hundred and sixty-one.
ARTHUR IRWIN MAHON. (L.S.)
ARTHUR IRWIN MAHON. (L.S.)