IM- PROVEMENTS IN SCREW AND PADDLE PROPELLERS, AND A SUBMARINE PROPELLER, ALSO APPLICABLE TO THE RAISING AND FORCING OF WATER OR OTHER FLUIDS
Year: 1863

page_text: PROVISIONAL SPECIFICATION left by Arthur Irwin Mahon at the Office
of the Commissioners of Patents, with his Petition, on the 12th.January
1863.
I, ARTHUR IRWIN MAHON, of 25, Leinster Square, Rathmines, in the County,
of Dublin, C.E., do hereby declare the nature of the said Invention for "IM-
PROVEMENTS IN SCREW AND PADDLE PROPELLERS, AND A SUBMARINE PROPELLER,
ALSO APPLICABLE TO THE RAISING AND FORCING OF WATER OR OTHER FLUIDS,"
to be as follows:-
This Invention relates to various forms of screws and screw blades, and their
combination and arrangement, so that the vacuum caused by the ordinary
working and their different currents may be taken advantage of, and so that the
centres of screws may be made to work more effectively, and for the employ-
ment of the principle that the natural tendency of water is to overcome vacuum
whether produced artificially or not in the form of a propeller that may com-
bine the advantages of the paddle and screw, and which may be called a
paddle.
According to oue arrangement any number of small planes are used of a
circular or other form, and placed along radial arms at angles on the screw
principle, but bent at the edges, so as to direct the water, but not to retain it,
as in Griffiths' screw.
A second arrangement consists of a cylindrical screw constructed as follows:-
On the band forming the hollow cylinder, the pitch lines of the screw are
traced, and a portion or portions of the band along the screw lines is cut; so

page_text: that it can be turned in when the band is brought round in a cylindric, conical,
or other form; there are a series of spiral or screw openings on the outside,
and of screw threads or spirals turned in the openings thus made run along the
top or back of the threads, and the cylinder represents a series of parallel screw
or spiral openings on its circumference; any number of these cylinders may be
encased one within another about the same axis, and the whole may be
brought round in front to any form desired, and it may also be either wholly
or partially closed in front, and may take in water only at the side. This form
may be used as a pump, turbine, or water wheel. It may be made to bear
while working directly against the stern, by means of a system of friction rollers
placed on radial arms which move freely on the shaft, and independent of it,
and also on either side of a vessel on the same plan.
In a third arrangement the whole or part of the face of the common or other
form of screw is perforated with holes or open spaces in such a manner that
water will most easily pass through the blade while same is working. This
is also applicable to paddle floats.
A fourth arrangement consists in getting the whole form of the screw or
blade in a line with the shaft, so that the useful effect may be increased, and
the necessity for removing the screw avoided. Thus, take any plane of metal
(it may have an even thickness throughout) about the area of an ordinary
screw blade, and having divided it into sections, so as more readily to give to
each its proper pitch, trace out on each a number of lines, so that the whole
of each section for each pitch, when the parts are turned into position form a
number of minute parts or blades as it were, and so also that the water
acted on by any one part will not affect any other, and sufficient space also
left between each part, so that there is room for a certain portion of water to
pass through, which will occupy the position of the ordinary vacuum, and
prevent the fulcrum, or what ought to remain still water, from being disturbed,
and which water would otherwise move; in the course of the screw one or
more arms are placed across the shaft, according to the strength required, and
each series attached thereto forming rows of small planes or blades, each series
having its proper pitch; this propeller need not be of greater width than the
shaft upon which it is placed; also there may be a system (and in the same
plane) of blades, but at angles, so as to prevent any tendency from the return
water, which sometimes occurs when a screw is continued for any length.
Another arrangement consists in a plane of any form, almost surrounded by.
parts which, taken together, act on the screw principle, be they each ever so
minute, and this placed transversely to the axis or shaft, or ran through the centre
of said plane, and so fixed to the shaft. The best form, and that which I have
.

page_text: found to give a greater effect than any other screw, is an ellipse surrounded by
parts such that, were all in one plane, a parallelogram covering all would touch
the axis major and minor of the ellipse, all the parts forming the parallelogram
except the ellipse to be cut in towards the ellipse, and each of the minute parts
thus created turned, at the same time keeping up a relative pitch towards the
vertices of the ellipse; there then appears the general form of four blades sur-
rounding the ellipse, and each alternate pair are made so as to act together.
The general form of this propeller may vary very much, as for instance, a
square inscribed in a circle, a larger square or other figure, and the exterior
parts made the screw.
it
may
The proposed submarine propeller is intended to work either partially or
wholly under water, and be capable of steering, stopping, or backing a vessel,
without interfering with the work of the engines, which may be kept at full
power, and the propeller all the while have the same motion of revolution, or
be simply used as a propeller. It may be placed at the stern, bow
sides, quarters, or in any position that the power of an engine can be applied,
and worked either vertically or transversely, and any number of them may
work together with advantage. It is formed by the combination of certain blades
or floats in such a manner and form that they, when revolving, and in connec-
tion and arrangement with shields or other protectors, in such form (with
reference to other parts) as to have perfect command of and regulate the
direction of the supply of water, which, when partly cut off from part of the
revolution by them is admitted to another part, and a discharge effected there
in any desired direction by a movement of the parts commanding the supply,
and also that it be so arranged that opposite forces can by similar means be
produced at the same instant, and that water may be taken from the 'front
surrounding parts or sides as the construction is modified, but on the same
general plan.
For example, the floats or blades may be of almost any form, but that is the
best which naturally tends to produce the strongest tendency to vacuum, con-
sistent with a propelling effect. Thus each may be arranged varying from a
tangent or right angle to a radial line at the circumference of the circle to a
considerably greater angle in proportion as the radius decreases, and thus the
area of the circle may be worked upon, and the blades or floats will each act
without going in the course of each other, and a strong tendency to vacuum
will be produced at the same time that they are working. These floats, when
considered together, may be taken, any series of them, as a blade. The floats
are intended to be attached to shields which protect or prevent any supply
being worked or taken from the side; thus, suppose a pair of these shields with

page_text: the blades attached, and inclining towards each other, arranged on a shaft
sufficiently apart to allow water to pass between them for the floats to work
upon, it is clear that if they are made to revolve a continual displacement of
water all round will be the result; but in order to proat this there are other
shields placed on the shaft and as close as possible to the floats without touching,
and covering one part of the revolution only, and thus the supply is admitted to
the remaining portion of the revolution (or area of the circle) which is driven
out in any direction according as the inside shields are moved round the shaft,
and if then the open part of these shields be closed, there will be no propelling
effect, all the floats or blades working freely. It is clear that, suppose a shield
on either side of any system of floats or blades, with a part cut off from each,
so as to allow a partial supply, that then the water will be driven out just as
well, and those shields may command the supply in any direction by being
moved round, but the first form is more perfect, because it neither takes the
water from the side, nor allows any return water to be worked upon, and
clearly takes the water from the front. The floats may also be at an angle, and
work in a manner towards each other, the shields being arranged and adapted
accordingly.
.
The principle upon which this propeller works is that the natural supply
being partly cut off, a constant tendency to vacuum takes place, and a supply
can be then taken, given, and discharged, all the blades and floats working
freely, and all tending to the one object. It is obvious that the con-
struction and form of the parts of such a propeller can readily be made to
vary considerably, and the blades and floats may or may not be attached to
shields, which may be of different forms; but so that there is the general com-
bination of parts, or of those parts named on the principle or nature already
explained, the results and objects specified are attained.
It is intended also to apply this principle to the present paddle, so that
feathering may be avoided, and that it may go any depth. Also to use it as a
pump where it can be wholly or partially immersed.