IMPROVEMENTS IN SCREW PROPELLERS
Year: 1879

page_text: LETTERS PATENT to Nicholas Demetrius Spartali, of Liverpool, in the County
of Lancaster, Steam Ship Agent, for the Invention of "IMPROVEMENTS IN
SCREW PROPELLERS."
Sealed the 28th October 1879, and dated the 29th April 187
PROVISIONAL SPECIFICATION left by the said Nicholas Demetrius Spartali
at the Office of the Commissioners of Patents on the 29th April 1879.
NICHOLAS DEMETRIUS SPARTALI, of Liverpool, in the County of Lancaster, Steam
Ship Agent. "IMPROVEMENTS IN SCREW PROPELLERS."
This Invention relates to an improvement upon the screw propellers for which I
obtained Letters Patent, dated July 15th, 1876, No. 2906.
The blades in the most approved propellers now in use have their foundation in
a massive spherical or cylindrical boss, and by the great breadth of their lower
connections to the boss and their too close proximity to each other, leave the
available water spaces between them too limited and confined, so that much water
is lost to any useful propelling action, a great part of it being simply rubbed
against by the metal, and partly carried round the confined circle, and a great part
of the water at the back of the lower portion of the wide and deep foundations is
practically lost, owing to the comparatively large flat surface of metal remaining
neutral.
My new propeller differs from all other propellers inasmuch as I am enabled to
dispense with the central boss, and convert that portion of the propeller into a
useful propelling surface.
In constructing my new propeller I form an elongated central piece, which will
support six blades, viz., two main blades, and four cross blades arranged in two sets
of three each, on opposite sides of the centre, there being one main blade and two
cross blades arranged at right angles to the main blade in each set. The four cross
blades are placed in such positions relative to each other as regards distances apart,
curves, angles, and inclines, as to act most effectively and powerfully on the centre
water. Each half of their centre piece supporting two cross and one main blade is
placed slightly diagonally or excentrically to the other half, and each side of this
centre piece is made somewhat elliptical, so that the sides thereof, as well as the
Price 8d71

page_text: blades, will act on the water. The inclined sides of this centre piece are carefully
scooped out, and gradually arched and sloped on each side so as to form so many
recesses, into which the lower portions of the blades enter. The top and bottom ends
of the said elongated centre piece leave a considerable triangular space for the two
long and powerful main blades, and offer a very wide scope for propelling action in
a large expanse of water, partly to the rear, and partly over the range and orbit of
the central blades. Thus it will be seen that the centre piece itself, as well as all
the blades, have a continuous but independent propelling action in equal succession
to the front and rear of each other, and plenty of free water to act upon; the
spaces between being very wide and equally spread and subdivided, and in such a
way as to act in a duplicate manner, the four cross blades acting upon the water in
a comparatively horizontal, and the two main blades in a comparatively vertical
and diagonal manner.
The pitch of the blades is gradually developed in extent on their travel around
the shaft, the lower part of the same presenting a much more gently inclined surface
to the water than the upper part. The two main blades are made longer than the
cross blades, but can be made all one length if desired. The travel of the main
blades is, say, about one half more than that of the cross blades, the connection of
the outer edges of the slopes or recesses of each blade being continued far into the
back of the preceding blade, thus forming a triangular ridge or back to it, which is
a source of great strength. If desired the whole of the back of the blades of these
propellers may be made triangular or prismatic, so as to obtain additional strength
to compensate for their length, and the blades may also at times be shaped so as to
present a double edge to the water, but the outward edge should be made smaller
and narrower than the front and main part of the blade, so as to prevent any
lifting of water or friction.
The propeller may be constructed of one casting, or made in sections, which may
be rivetted, bolted, or otherwise connected together, or the centre piece of the
propeller with its sloping recesses may be made in halves or in sections, and the
blades may be connected to it separately.
In order to ensure sufficient strength for the propeller at the point of connection
with its shaft, and to give greater stability to the whole structure I make the
central part of the propeller thicker in transverse section for about one sixth more
or less of its total length.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Nicholas Demetrius Spartali in the Great Seal Patent Office on the
29th October 1879.
NICHOLAS DEMETRIUS SPARTALI, of Liverpool, in the County of Lancaster, Steam
Ship Agent. IMPROVEMENTS IN SCREW PROPELLERS."
"
This Invention relates to an improvement upon the screw propellers for which I
obtained Letters Patent, dated July Fifteenth, One thousand eight hundred and
seventy six, No. 2906.

page_text: The blades in the most approved propellers now in use have their foundation in
a massive spherical or cylindrical boss, and by the great breadth of their lower
connections to the boss, and their too close proximity to each other, the available
water space between them is too limited and confined, so that much water is lost
to any useful propelling action, a great part of it being simply rubbed against by
the metal, and partly carried round the confined circle, and a great part of the
water at the back of the lower portion of the wide and deep foundations is
practically lost, owing to the comparatively large flat surface of metal remaining
neutral.
My new propeller differs from all other propellers, inasmuch as I am enabled to
dispense with the large central boss, and convert the central portion of the propeller
into a useful propelling surface.
By my present improvement I so connect the base of the one blade to the other
as to add materially to their mutual strength, and obtain by this connection
additional propelling surface between each blade; I also construct the foundation or
centre piece, which supports the blades of these propellers, at convenient spaces
apart in such a manner as to form of itself a most useful and effective portion of
the propeller, thus utilising almost every part of the surrounding water without
slip or loss, and obtaining a complete and most powerful propelling effect on the
centre water, to which is imparted as much speed as is obtained only from the
upper part of the blades of the present propellers.
I prefer to make my propellers in several parts, and I fit these parts together as
may be desired to form two, four, or six-bladed propellers, but each part may be
employed separately, the new and useful effects being obtained in the latter caso
equally as well as in the former.
At Figures 1, 2, 3, 4, and 5, Sheet I. of the accompanying Drawings, I have
shewn what I may term the rudiments of my propellers, a combination of two or
more of them forming my four or six bladed propellers, thus combining two of
either; Figures 1 and 2 will give forms corresponding to the four bladed propellers
shewn at Figures 6 and 7, Sheet I., or Figures 8 and 9, Sheet II., and a combination
of two of either of Figures 3, 4, and 5, will give results equivalent to Figures 10
and 11, Sheet II., while the form of six-bladed propellers shewn at Figures 12 and 13,
Sheet I., and Figs. 14 and 15, Sheet II., would result from a combination of two of
either of Figures 3, 4, and 5, with Figures 1 or 2. In all these Figures the blades are
set at a very slight angle at the centre, whereby the resistance of the water to the
blades is reduced to a minimum, while the greatest amount of pitch is obtained by
the inclination of one half of the centre over the other.
In constructing my new propeller I use instead of a central boss an elongated
centre piece (clearly shewn at Figures 3, 4, and 5) to support the blades.
My six-bladed propeller, as shewn at Figures 12 to 15 inclusive, consists of two
main blades and four cross blades arranged in two sets of three each on opposite
sides of the centre, there being in each set one main blade, and two cross blades
arranged at right angles thereto. The four cross blades in these Figures, as well as
in the other Figures shewn, are placed in such positions relative to each other as
regards distances apart, curves, angles, and inclines, as to act most effectively and
powerfully on the centre water. Each half of the centre piece is placed slightly
diagonally or excentrically to the other half, and each side of this centre piece is
made somewhat elliptical, so that the sides thereof, as well as the sides, will act
on the water.
The inclined sides of this centre piece are carefully scooped out, and gradually
arched and sloped on each side so as to form so many recesses, into which the
lower portions of the blades enter. The top and bottom ends of the said elongated
centre piece leave a considerable triangular space for the two long and powerful
main blades, and offer a very wide scope for propelling action in a large expanse of
water, partly to the rear and partly over the range and orbit of the central blades.
Thus it will be seen that the centre piece itself, as well as all the blades, have a
continuous but independent propelling action in equal succession to the front and

page_text: rear of each other, with plenty of free water to act upon. The four cross
blades will act upon the water in a comparatively horizontal, and the two
main blades in a comparatively vertical and diagonal manner. The pitch of
the blades is gradually developed in extent on their travel around the shaft,
their lower parts presenting à inore gently inclined surface to the water than
their upper parts. The two main blades are, by preference, made longer than
the cross blades, but can be made all one length if desired. The travel of the main
blades is about one half more than that of the cross blades. The connection of the
outer edges of the slopes or recesses of each blade is continued far into the back of
the succeeding blade, thus forming a triangular ridge or back to it, which is a
source of great strength. If desired the whole of the back of the blades of these
propellers may be made triangular or prismatic, so as to obtain additional strength
to compensate for their length, and the blades may also at times be shaped so as to
present a double edge to the water, but the outward edge should be made smaller
and narrower than the front and main part of the blade, so as to prevent any
lifting of water or friction.
As already stated, the propeller is by preference made in sections which may be
rivetted, bolted, or otherwise connected together, or the centre piece of the propeller
with its sloping recesses may be made in halves or in sections, and the blades may
be connected to it separately, or the whole propeller may be cast in one.
In order to ensure sufficient strength for the propeller at the point of connection
with its shaft, and to give greater stability to the whole structure, I make the
central part of the propeller thicker in transverse section for about one-sixth more
or less of its total length.
The blades may be made wider or narrower, longer or shorter, and more or less
massive, but in either case the reduction in the weight and bulk of the metal
employed will be considerable as compared with ordinary propellers, and will effect
an immense saving both in cost of manufacture and in cost of driving.
Figures 16, 17, and 18, Sheet III., are further modifications of my two bladed
propeller; and Figures 19, 20, and 21, further modifications of my four bladed
propeller; Figures 19 and 20 being front and back views of a propeller having
straight blades arranged in the form of a cross, and Fig. 21, a four bladed propeller
with curved blades.
Fig. 22, Sheet I., represents a further modification of my six bladed propeller.
Having now described the nature of my Invention of "Improvements in Screw
Propellers," and explained the manner of carrying the same into effect, I wish it to
be. understood that under the above in part recited Letters Patent I claim,
constructing screw propellers as herein shewn and described.
In witness whereof, I, the said Nicholas Demetrius Spartali, have hereunto
set my hand and seal, the Twenty seventh day of October, in the year of
our Lord One thousand eight hundred and seventy nine.
N D CDADTATT