IMPROVEMENTS IN SCREW PROPELLERS. AND IN MACHINERY OR APPARATUS FOR ACTUATING THE SAME."
Year: 1861

page_text: LETTERS PATENT to Robert Wilson, of Patricroft, in the County of
Lancaster, Engineer, for the Invention of "IMPROVEMENTS IN SCREW
PROPELLERS. AND IN MACHINERY OR APPARATUS FOR ACTUATING THE SAME."
PROVISIONAL SPECIFICATION left by the said Robert Wilson at the
Office of the Commissioners of Patents, with his Petition, on the 15th
January 1861.
I, ROBERT WILSON, of Patricroft, in the County of Lancaster, Engineer,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN SCREW
PROPELLERS, AND IN MACHINERY OR APPARATUS FOR ACTUATING THE SAME," to be as
follows, that is to say:-
This Invention relates to the arrangement and construction of what are
known as screw propellers for moving ships or vessels through the water. The
essential feature of this part of the present Invention is, that the improved
propeller in its passage through the water presents the form of a solid of least
resistance, and consequently that the particles of water as they impinge upon
the face or foremost surface of the propeller glide smoothly and without resist-
ance over a surface which in its cross section represents a long and narrow
ellipse, with pointed extremities. Both the fore and aft surfaces of the pro-
peller presenting this figure to the water, it follows that on rotatory motion

page_text: being communicated to it that the propeller will pass through the water as
though the fluid were a solid, and in manner similar to that of an augur
making its way through wood. With this arrangement the propeller passes
through the water in a perfectly smooth and uniform manner, and as it does
so without the usual disturbance and breaking up of the water, there is no loss
of power, and slip is avoided. The blades or vanes of the propeller are, by
preference, formed of malleable iron or of steel, the extremities being thinned
off, so as to give a certain degree of flexibility to the blade, and at the same
time combine lightness with the requisite degree of strength. The boss of the
propeller is also formed so as to present no obstructive surface to the water
or prevent its passing away unimpeded, and the propeller shaft is, by pre-
ference, formed of steel, to admit of its being made as small in diameter as
possible.
The arrangement of the engine to which preference is given for driving the
screw propeller is one in which the cylinders are arranged overhead, and are
connected directly to the crank shaft beneath. The sole plate has four
wrought-iron tubular columns arranged at the angles; these columns support
an entablature on which the cylinders are placed. The piston rods are
attached in the usual way by means of connecting rods to the crank shaft
beneath the cylinders, and the crank shaft is connected by means of a coupling
to the propeller shaft. On the free extremity of the crank shaft is a disc,
having a laterally projecting crank pin, which is connected to a lever arranged
on a level with the lower end of the cylinders. This lever works the air and
bilge pumps. The disc keyed on the end of the crank shaft is fitted with
radially projecting handles for handling or adjusting the propeller when the
engines are not in motion. The extreme compactness of these engines admit
purposes than
of greater space being devoted to the stowage of coal or other
can be obtained with engines of the diagonal or horizontal classes. In order to
prevent priming, the boilers are arranged in the following manner :-On each
side of the fire tubes, which extend longitudinally through the water space,
there is arranged a metal plate, which extends from above the fire tubes down-
wards towards the furnace tubes, and by preference curving slightly inwards.
Between the two ranges of fire tubes two other plates are disposed vertically,
and at the bottom of these plates is a V-shaped plate, the edges of which do
not quite touch the lower margins of the central parallel plates. With this
arrangement the colder portions of the water in contact with the boiler shell
pass down beneath the outer plates, and also down between the central plates,
and out by the longitudinal openings. In this way the less heated portions of
the water are caused to circulate in such manner as to be brought into contact

page_text: with the highly heated surfaces of the furnace and fire tubes, and thus effec-
tually prevent priming. The steam is, if required, superheated by passing it
into a steam jacket which encircles the smoke box immediately beneath the
funnel. From the jacket the steam passes through a helical coil of copper
pipe arranged within the smoke box, and through which the whole of the
highly heated products of combustion pass on their way to the funnel.
This arrangement provides very effectively and economically for the super-
heating of the steam and depriving it of aqueous particles, and thus increasing
its efficiency as a motive agent.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Robert Wilson in the Great Seal Patent Office on the
15th July 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ROBERT
WILSON, of Patricroft, in the County of Lancaster, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fifteenth day of January, in the year of our Lord
One thousand eight hundred and sixty-one, in the twenty-fourth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Robert Wilson, Her special license that I, the said Robert Wilson, my
executors, administrators, and assigns, or such others as I, the said Robert
Wilson, my executors, administrators, or assigns, should at any time agree
with, and no others, from time to time and at all times thereafter 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 "IMPROVEMENTS IN SCREW PRO-
PELLERS, AND IN MACHINERY OR APPARATUS FOR ACTUATING THE SAME," upon the
condition (amongst others) that I, the said Robert Wilson, 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 Robert Wilson, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following

page_text: 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 the arrangement and construction of what are
known as screw propellers for moving ships or vessels through the water.
The essential feature of this part of the present Invention is that the improved
propeller in its passage through the water presents the form of a solid of least
resistance, and consequently that the particles of water as they impinge upon
the face or foremost surface of the propeller, glide smoothly and without
resistance over a surface which in its cross section represents a long and
narrow ellipse with pointed extremities. Both the fore and aft surfaces of the
propeller presenting this figure to the water, it follows that on rotatory motion
being communicated to it, that the propeller will pass through the water as
though the fluid were a solid, and in manner similar to that of an augur
making its way through wood. With this arrangement the propeller passes
through the water in a perfectly smooth and uniform manner, and as it does
so without the usual disturbance and breaking up of the water, there is no
loss of power, and slip is avoided. The blades or vanes of the propeller are,
by preference, formed of malleable iron or of steel, the extremities being
thinned off so as to give a certain degree of flexibility to the blade, and at the
same time combine lightness with the requisite degree of strength. The boss
of the propeller is also formed so as to present no obstructive surface to the
water or prevent its passing away unimpeded, and the propeller shaft is, by
preference, formed of steel, to admit of its being made as small in diameter as
possible. The arrangement of the engine to which preference is given for
driving the screw propeller is one in which the cylinders are arranged over-
head, and are connected directly to the crank shaft beneath. The sole plate
has four wrought-iron tubular columns arranged at the angles; these columns
support an entablature on which the cylinders are placed. The piston rods
are attached in the usual way by means of connecting rods to the crank shaft
beneath the cylinders, and the crank shaft is connected by means of a coupling
to the propeller shaft. On the free extremity of the crank shaft is a disc,
having a laterally projecting crank pin, which is connected to a lever arranged
on a level with the lower end of the cylinders; this lever works the air and
bilge pumps. The disc keyed on the end of the crank shaft is fitted with
radially projecting handles for handling or adjusting the propeller when the
engines are not in motion. The extreme compactness of these engines
admits of greater space being devoted to the stowage of coal or other purposes
than can be obtained with engines of the diagonal or horizonal classes.
order to prevent priming the boilers are arranged in the following manner :-
In

page_text: On each side of the fire tubes, which extend longitudinally through the water
space, there is arranged a metal plate, which extends from above the fire tubes
downwards towards the furnace tubes, and by preference curving slightly
inwards. Between the two ranges of fire tubes two other plates are disposed
vertically, and at the bottom of these plates is a V-shaped plate, the edges of
which do not quite touch the lower margins of the central parallel plates.
With this arrangement the colder portions of the water in contact with the
boiler shell pass down beneath the outer plates, and also down between the
central plates and out by the longitudinal openings. In this way the less
heated portions of the water are caused to circulate in such manner as to be
brought into contact with the highly heated surfaces of the furnace and fire
tubes, and thus effectually prevent priming. The steam is, if required, super-
heated by passing it into a steam jacket, which encircles the smoke box
immediately beneath the funnel. From the jacket the steam passes through
a helical coil of copper pipe arranged within the smoke box, and through
which the whole of the highly heated products of combustion pass on their
way to the funnel. This arrangement provides very effectively and economi-
cally for the superheating of the steam and depriving it of aqueous particles,
and thus increasing its efficiency as a motive agent.
And in order that my said Invention of improvements in screw propellers,
and in machinery or apparatus for actuating the same, may be properly
understood, I shall now proceed to describe the several Figures on the two
explanatory Sheets of Drawings which I have hereunto appended for the
purpose of showing certain modifications under which my improvements may
he judiciously carried out in practice, that is to say :-
Figure 1, on Sheet
of the accompanying Drawings, is a plan of one
modification of a screw propeller constructed according to my improvements;
Figure 2 is a partially longitudinal section of the same; and Figure 3 is a
series of transverse sections taken through the lines marked 1 to 8 in Figures
and 2; Figure 4 is a side view, and Figure 5 an edge view of a screw pro-
peller with its blades somewhat modified from the arrangement shown in
Figures 1 and 2; Figure 6 is a partially sectional elevation of a boiler specially
suited for the engines of screw propellers; and Figure 7 is a corresponding
transverse section.
Figure 1 on Sheet 2 of the accompanying Drawings is an elevation showing
the arrangement of the engine which I prefer to use for actuating screw
propellers. Referring to Figures 1 to 5 on Sheet 1, the blades of the screw
propeller are formed so as to approximate as nearly as possible to the form of
the geometrical figure which is known as the solid of least resistance; the

page_text: object of this arrangement being that the propeller shall move through the
water without disturbing it, and with the least possible resistance. To accom-
plish this end the blades A of the propeller are made with both surfaces
corresponding in their curvature, as shown in the transverse sectional views,
Figure 3. Thus, near the boss B of the propeller, the metal of the blade
in its transverse section on the line 1 forms a long and comparatively
narrow ellipse, having pointed extremities. From this part outwards to the
margin the blade becomes gradually thinner and the ellipse is lengthened
in proportion, so that on the line 8 the two surfaces become very nearly
parallel, and thus from the margin of the blade to the boss no resistance
whatever is offered to prevent the particles of water from gliding smoothly
away; so also if the longitudinal section of the propeller blade be taken as an
example of this system of construction, it forms, as shown in the sectional view,
Figure 2, a narrow wedge-shaped figure, the best adapted for passing casily
through the water. The boss B of the propeller is formed as small as possible
consistent with the necessary degree of strength, and to obtain this, combined
with the smallest amount of weight, the propeller is preferred to be made
either of steel or of wrought iron. Where it is practicable it is preferred to
use steel for the propeller shaft C, in order that the increased tenacity of this
metal may admit of a corresponding reduction in the diameter of the shaft.
In the side view of the propeller as delineated in Figures 4 and 5, the
propeller blades A appear wider at the shank part near the junction of the
blade with the boss or central part than in the view shown in Figure 1,
but this difference is only apparent, and is caused by the twist of the blade and
different angle under which it is viewed. The blades A are narrowed at the
part D, by cutting away a portion of the metal, this admits of the angle of
the blades being more easily changed to the required angle and adjusted to the
slip so as to save power and not disturb the water during its rotatory motion.
If made of steel these improved propellers will not require more than one-
half the weight of metal as compared with cast iron or brass, and if wrought
iron is the material made use of the weight need not exceed five-eighths of the
weight of a similiar propeller formed of cast iron or brass. In this way then
speed is gained by the improved form of the propeller, the little resistance that
it offers in its rotatory movement enabling it to pass through the water as
smoothly as though it were penetrating a comparatively solid body. This
facility of motion is also attended with another advantage, for it effects a con-
siderable saving in the amount of steam power required to impart to the
propeller a given number of revolutions. In this way not only is the speed of
the vessel greatly improved by the use of this form of propeller, but from the

page_text: steam.
smoothness of its motion the highly unpleasant vibration ordinarily imparted to
the vessel when the screw propeller is driven at a high velocity is altogether
avoided. The arrangement of boilers which I prefer to use in conjunction
with the engines of screw propellers is represented in the vertical and
transverse sectional views, Figures 5 and 6. These views embody my improve-
ments in preventing "priming" and also the arrangement for superheating the
To prevent priming, two curved plates E are arranged longitudinally
within the boiler; they are fitted outside the tubes F, and parallel, or nearly so,
to the shell G of the boiler. Between the two ranges of fire tubes F are
fitted the two vertical plates H, which diverge slightly from each other
towards the upper part. Beneath the plates H are arranged the two narrow
diverging plates I, which run nearly parallel with the curved surfaces of the
furnace tubes K, a narrow longitudinal opening being left at the lower part of
the duplex plates. As the water is beated by its contact with the tubes F and
flues K, the heated portions ascend and displace the water of lower tempe-
rature, which is thus caused to descend in a current between the plates E
and the shell of the boiler, and also between the central plates H. The
descending current of water circulating between the plates E and the shell of
the boiler is thus brought into contact with the highly heated surface of the
tubular flues K; whilst the current which is descending between the
plates H comes into contact with the diverging plates I, and is by them
diffused over the more highly heated surfaces of the flues K. This arrange-
ment of the plates thus provides for a continuous and uniform circulation of
water, and the mode of bringing the less heated portions in contact with the
flues K, so raises the temperature as to effectually prevent priming. The
steam as it is evolved passes off by the pipe L into the steam chest or annular
space surrounding the lower part of the chimney, here it gains an accession of
heat from the body of highly heated gaseous matters passing off from the
furnaces. The heat thus imparted is further augmented by causing the steam
to pass through the tubular coil of copper pipe M, which is arranged within
the lower part of the chimney. The steam passes in at the upper end of the
tubular coil M, and out through the lower part of the steam chest to an
external valve box, by means of which its supply to the engine is regulated.
If preferred a second steam pipe is fitted in direct communication with the
upper part of the boiler, which conveys the saturated steam into a valve box
arranged in connection with the pipe proceeding from the valve box of the
superheating apparatus. In this way the superheated and the saturated
steam may be mixed or blended on their way to the engine, and supplied
thereto in the proportions found most economical in working.

page_text: The arrangement of the engines which I prefer to use for the purposes of
screw propulsion is delineated in Sheet 2 of the accompanying Drawings,
Figure 1 being a side elevation, and Figure 2 a plan of the same.
On the sole plate N are arranged four tubular columns supporting an
entablature on which the cylinders O are arranged. The steam passes from
the steam pipe into the valve boxes P, in which are fitted the rotatory ex-
pansion valves for which British Letters Patent were granted to me and J. W.
Child, and dated 12th September 1853. By means of these valves the steam
may be cut off at any portion of the stroke, and the mechanical arrangement
for effecting this will be presently referred to. The piston rods Q work out
through the usual stuffing boxes in the end covers, and are connected by
means of the rods R to the crank shaft S. On one extremity of this shaft is
a dise T, in which is fitted a crank pin U, which serves to connect it by means
of the rod V and lever. W with the horizontal shaft X, which is carried in
pedestal bearings arranged on the entablature. From the shaft X the air
pump Y, as also the feed and bilge pumps Z, are worked. The disc T bas a
series of holes formed in its periphery to admit of the crank shaft being turned
by means of a hand lever when the engines are not in motion. This arrange-
ment is very useful either for adjusting the valves or to ship or unship the
propeller, and for other purposes. To the opposite extremity of the crank
shaft S is keyed a bevel wheel a, which gears with the pinion 6 on the lower
extremity of the oblique shaft c; the footstep and collar bearings of this shaft
are carried in brackets projecting laterally from the sole plate and entablature.
The bevel pinion d on the upper extremity of the shaft c gears with the
wheel e on the horizontal shaft f, which extends across the front of the engines.
On the shaft fare two screw wheels g, which give motion to the corresponding
wheels h on the valve spindles i, and in this way a uniform rotatory movement
is communicated to the valves in the boxes P. The vertical adjustment of
the valves for the regulation of the "cut off" is obtained from the worm or
endless screw j, which is carried in a bracket arranged on the sole plate N,
and is actuated by means of a winch handle. The worm j gears with a worm
wheel on the horizontal shaft l extending across the engine and parallel with
the shaft f above it. The shaft 7 has fitted to it two small pinions, which gear
respectively with the vertical racks m, the upper parts of which form the
footstep bearings of the spindles i. Thus by simply turning the worm j the
valve spindles and their connected valves are simultaneously raised or lowered
at pleasure whilst the engines are in motion. The steam after performing its
work in the cylinder passes away by the exhaust n, which opens into a valve
box o, in which is fitted a stop valve; the lower part of the valve box opens

page_text: into the discharge pipe p, which communicates with the bot well in the usual
way. Engines arranged according to this plan are particularly well adapted
for screw propulsion, as they occupy but comparatively little space, and are
free from vibration; they are also easily accessible in all the parts.
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 novel and
original, and therefore claim as the Invention secured to me by the herein-
before in part recited Letters Patent, is,―
First, the system or mode of constructing screw propellers in such manner
as to offer the least possible resistance in passing through the water, which is
obtained by forming the blades in the manner herein-before described and
delineated in the accompanying Drawings.
Second, the system or mode of preventing "priming" in steam boilers by
means of internal plates arranged for facilitating the circulation of the water,
and also the apparatus for superheating the steam, as herein-before described
and shown in the accompanying Drawings.
Third, the general arrangement and construction of steam engines for
actuating screw propellers, as herein-before described and delineated in the
accompanying Drawings.
In witness whereof, I, the said Robert Wilson, have hereunto set my
hand and seal, this Twelfth day of July, One thousand eight hundred
and sixty-one.
ROBERT WILSON.
(L.S.)