IMPROVEMENTS IN THE CONSTRUC- OF SCREW PROPELLERS FOR SHIPS OR VESSELS, AND IN FITTINGS CONNECTED THEREWITH
Year: 1878

page_text: LETTERS PATENT to Robert Smyth, of Dunning, in the County of Perth,
North Britain, Agent, for the Invention of "IMPROVEMENTS IN THE CONSTRUC-
OF SCREW PROPELLERS FOR SHIPS OR VESSELS, AND IN FITTINGS
CONNECTED THEREWITH."
TION
Sealed the 16th July 1878, and dated the 22nd January 1878.
PROVISIONAL SPECIFICATION left by the said Robert Smyth at the Office
of the Commissioners of Patents on the 22nd January 1878.
ROBERT SMYTH, of Dunning, in the County of Perth, North Britain, Agent.
"IMPROVEMENTS IN THE CONSTRUCTION OF SCREW PROPELLERS FOR SHIPS OR
VESSELS, AND IN FITTINGS CONNECTED THEREWITH."
This Invention has reference specially to certain improvements in the mode of
shaping, constructing, and fitting the acting blades of screw propellers and their
bosses, and the parts of the ship leading to and from the same, and in fenders or
protectors therefor, which will make such screw propellors so constructed and fitted
much more effective and safe for the propulsion of steamships or vessels than screw
propellers have been as heretofore constructed.
And the nature and novelty of the Invention or improvements consist, first, in
forming the propelling part of the screw blades all at the outer part or extremity
of their carrying radial arms in contradistinction to the usual practice of making
the largest surface part of the blades near the boss; the arms being only made
broad enough to give sufficient strength to secure them to their boss, and the blades
are made not more than one-half the depth or radius of the whole propellers; the
radius of the eye or boss, and the length of the arm making up the rest of the entire
radius.
These improved short radial screw blades are preferably made either pro-
portionately more numerous, as from four to eight round the boss, or longer
spirally or circumferentially, or both; and they are preferably made of malleable
iron or steel plates, with their advance and back ends rounded or curved so as to
D...AX1

page_text: have no corners to catch any solid floating matters, but rather tend to glide past or
fend or push such off from them; the propelling face of the blades being made to
the true or ordinary advance curve of screw desired, as well as that of the arm,
which would be made thick behind, and broad where welded or rivetted to their
blades, and strong towards the boss, in which it might be inserted and secured by a
stem as some other screw blades are; and the blades might have a strengthening
curved plate behind rivetted to them with the arm between the plates.
A further improvement consists in securing all the outer central extremities of
these improved blades by a hoop or ring, preferably broad or thin and flat in sec-
tion, and heated and shrunk on as the hoops of carriage or cart wheels are, but with
checks or snugs on the inside or on the blades, where both are attached.
In some cases this improved screw propeller, with outer blades and strengthening
circumferential ring, may, according to a further improvement, be made with a very
large boss or eye, so as to get shorter, and consequently stronger arms, or nearly
dispense with these, and form a part of the ship in a line therewith round the shaft
or axis of the screw to the same circular shape, gliding off gradually or conically
into the lines or curvature of the ship, or behind the screw, also when convenient,
without disturbing the free action of the rudder.
A further 'improvement consists in forming or fitting a vertical edge plate down
from the ship and parallel to the keel and centre line of the screw shaft, some
distance out from and on each side of the screw propeller, and in advance of it to
act as a guard or fender, and prevent any floating materials or loose ropes fouling
the screw while sailing or in harbour. And these new or improved screw-propellers
may be all otherwise placed and fitted in the centre of the stern or bow, below the
water level, as other screws are; or for twin screws they would be placed under
the quarters of the ship when desired, in which case only one protecting fender
would be required, projecting down from under the quarter outside of each screw,
to guard it.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Robert Smyth in the Great Seal Patent Office on the 19th July
1878.
ROBERT SMYTH, of Dunning, in the County of Perth, North Britain, Agent.
"IMPROVEMENTS IN THE CONSTRUCTION OF SCREW PROPELLERS FOR SHIPS OR
VESSELS, AND IN FITTINGS CONNECTED THEREWITH."
My said Invention has reference specially to certain improvements in the mode of
shaping, constructing, and fitting the acting blades of screw propellers and their
bosses, and the parts of the ship leading to and from the same, and in fenders or
protectors therefor, which will make such screw propellers so constructed and
fitted much more effective, steadier, and safe for the propulsion of steamships or
vessels than screw propellers have been as heretofore constructed.
And in order that the full nature, novelty, and mode of performing my said
Invention may be properly understood, I shall now proceed to describe the several
Figures on the Sheet of Drawings, which I have hereunto appended for that purpose,
the same reference letters indicating the same or equivalent parts in the several
Figures where shown.
Figures 1, 2, and 3 are respectively a back or stern end view, plan, and edge or
side view of one modification or arrangement of the parts of a screw propeller as
detached or separated from the ship, all constructed in accordance with and
illustrative of my Invention, or improvements connected therewith.
Figure 4 is a face view of one blade corresponding to Figures 1 to 3 on the angle
to show its full width and acting area; while Figure 5 is a side view of the stern
part of a steamship z, with the screw propeller shown to a smaller scale than in
Figures 1 to 4, and fitted in position on its shaft B.
Figures 6, 7, and 8 show an end view, plan, and edge view, all respectively of a
screw propeller, substantially the same as that shown in Figures 1 to 3, but with a
large boss or eye A², and consequently shorter and stronger arms A¹ than shown in
the former arrangement; and Figure 9 is a side view of the stern quarter of a steam-
ship z with the screw propeller shown in Figures 6 to 8 as overhung on the extreme
end of its screw propeller shaft B.
Referring to Figures 1 to 4 inclusive, the full nature, novelty, and mode of per-
forming my said Invention or improvements consist, first, in forming the propelling
part A of the screw blades, all at the outer part or extremity of their carrying
radial arms A¹, in contradistinction to the usual practice of making the largest
surface part of the blades near the boss. The arms A¹ in this case are made only
broad enough to give sufficient strength to secure them to their boss A¹¹, and the
acting parts or blades A are made preferably about one-fourth, and not more than
one-third the depth or radius of the whole propeller; the radius of the eye or
boss A and the length of the arm A¹ making up the remainder of the entire
radius.
These improved short radial screw blades are preferably made either propor-
tionately greater in number or more numerous, as from four to eight (six
being the number preferred, as shown in the Drawings) round the boss A¹¹, or
otherwise, they are made longer, spirally or circumferentially, or both, as seen in
Figure 4, so as to give as much superficial acting area as given in the ordinary
screw propellers. The inner advance and back ends or edges of these improved
blades A are preferred to be rounded or curved at a so as to have no sharp corners
to catch any solid floating matters, but rather tend to glide past, or fend, or push such
off from them. The propelling faces of the blades A are made to the true or ordinary
advance curve of the screw desired as well as the acting face of the arm A¹, which,
however, wou'd be made thicker behind and broad where they joined their blades,
all as seen in the end or cross sections of the blade in Figure 4 A, and strengthened
still more behind towards the boss, into which each arm may be inserted and

page_text: secured by a stem as some other screws are when not all formed or cast in one steel
casting. But in some cases the blade parts A might be made of strong steel plate in
front, and have the arm A¹ broadened out and rivetted or welded to it behind, with
a strengthening curved plate behind, rivetted to them, with the strong arm between
the plates.
A further improvement consists in securing all the outer central extremities of
these improved blades A of the screw propeller by a hoop or ring b, preferably of
round bar iron or steel, which would give strength to the blades without pro-
ducing much friction in the water, and fixed by snugs as at 61 to the back of the
blades A, or otherwise secured as desired. Broad, thin, or flat sectional hoops
might be heated and shrunk on to effect the same purpose of strengthening or
staying the outer extremities of the blades A either with or without checks or
snugs on the inside of the hoop or on the blades where they are attached thereto.
Referring to Figures 6 to 8, in some cases this improved screw propeller,
with the acting blades A, formed at the outer extremity of the arms A¹,
may, according to a further improvement, be made with a very large boss
or eye A² so as to get shorter, and consequently stronger arms A¹, or greatly
dispense with these; and, as seen in Figure 9, have a part B2 of the ship in the
dead wood or keel, in line with the boss, formed round the shaft or axis B of
the screw to the same circular shape, or slightly larger than the boss A² of the screw,
as seen at B2, and tapered or gliding off gradually or conically into the line or
curvature of the ship z, behind the screw, as seen at 21, so as to allow of the free
flow of the water upwards along the dead wood or keel to the upper part of the
screw propeller, as indicated by the arrows at z', in Figure 9. And when con-
venient, without disturbing the free action of the rudder, the boss A² is also tapered
off sharply towards the stern, as seen at A³..
Referring to Figures 5 and 54, which latter is an end view corresponding to
Figure 5, a further improvement consists in forming or fitting a vertical edge plate
C, C, down from the ship's quarter, over and forward off the sides of the propeller
or towards the front, and parallel to the keel and centre line of the screw shaft B;
that is, some distance out from and on each side of the screw propeller blades A,
and in advance of them, projecting down into the water to act as a guard or fender,
and prevent any floating materials or loose ropes from fouling the screw while
sailing or in harbour, and yet allow of the free flow of the water inside the guard
below the quarter to the upper part of the screw propeller.
These new or improved screw propellers may be all otherwise placed, and fitted
in the centre of the stern or bow, below the water level, as other screws are; or for
twin screws they may be placed under the quarters of the ship when desired, in
which case only one protecting fender C would be required, projecting down from
under the quarter, outside of each screw to guard it, and cause any floating materials
to glide past it.
It will be further understood that these improved screw propellers may be
formed or constructed solid, of cast steel, or have the blades A cast or secured
on to their small or large boss A11 or A2 by stems or flanges on their arms A¹,
or having the new or improved blade parts A made of sheet malleable iron or
steel, and rivetted or otherwise secured to their arms, all much as other screws
have been, the novelty of my Invention not consisting in this, but in forming
the acting screw blades A, all quite out at the extreme outer end or radii of their
arms, not extending inwards to more than one-third of the whole radius of the
propeller, preferably only one-fourth thereof, as I have found by experimental trials
that this gives from 10 to 25 per cent. of a gain of power over the best ordinary
constructions of propellers I could make and try against my said new or improved
screw propeller, besides giving a much steadier action.
Having now described the nature of my said Invention, and the mode and means
by which it is or may be put into effect or practice, I wish it to be understood that
I do not confine myself to the precise details of construction or mode of fitting the
parts together, or the number or pitch of the screw blades which I have had

page_text: occasion to show or delineate in the Drawings, as these may be varied without
departing from the essential features of my Invention; but 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 construction of screw propellers for steamnships or vessels, with their
acting blades A, all at the outer extremity of their arins, and not extending to more
than one-third the radius of the propellers inwards from that, all substantially as
herein described in reference to and shown in the accompanying Drawings, or any
mere modification thereof.
Second. The construction and use of a guard or fender C, consisting of a simple
plate, vane, or feather projecting down from the outside of the ship, below the
surface level of the water, on the outside of and forwards from or in advance of the
screw propeller to direct or fend off all floating objects passing the sides of the ship
quite clear of and past the screw propeller, all substantially as herein described in
reference to and shown in the accompanying Drawings, or any mere modification
thereof.
In witness whereof, I, the said Robert Smyth, have hereunto set my hand and
seal, this Eighteenth day of July, in the year of our Lord One thousand
eight hundred and seventy-eight,
ROBERT SMYTH. (L.S.)