IMPROVEMENTS IN SCREW PROPELLERS
Year: 1868

page_text: LETTERS PATENT to Charles Denton Abel, of No. 20, Southampton
Buildings, Chancery Lane, in the County of Middlesex, Patent
Agent, for the Invention of "IMPROVEMENTS IN SCREW PROPELLERS."
-A communication from abroad by Adolphe Aubert, of Nogent le
Rotrou. Eure et Loire, France.
Sealed the 1st April 1869, and dated the 12th October 1868.
PROVISIONAL SPECIFICATION left by the said Charles Denton Abel
at the Office of the Commissioners of Patents, with his Petition, on
the 12th October 1868.
I, CHARLES DENTON ABEL, of No. 20, Southampton Buildings,
Chancery Lane, in the County of Middlesex, Patent Agent, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN SCREW
PROPELLERS," to be as follows:-
This Invention consists in constructing a propeller composed of a
helical or screw blade fixed upon a driving shaft, and enclosed by a
cylinder open at the ends, which cylinder is fixed to the outer cir-
cumference of the screw blade, and is consequently made to revolve
therewith.

page_text: The screw blade is, by preference, made to extend round half the
circumference of the cylinder only, and in some cases, according to the
propelling power required, two or more screw blades may be fixed in
the cylinder. By this arrangement the violent lateral displacement of
the water by the centrifugal force produced by screw propellers of
ordinary construction is entirely obviated, and the whole body of water
acted upon by the screw being forced to pass out of the cylinder in the
direction of the axis of the screw a much greater propelling power is
thus obtained.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Charles Denton Abel in the Great Seal Patent Office
on the 10th April 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
DENTON ABEL, of No. 20, Southampton Buildings, Chancery Lane, in
the County of Middlesex, Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twelfth day of October, in the
year of our Lord One thousand eight hundred and sixty-eight, in the
thirty-second year of Her reign, did, for Herself, Her heirs and sub-
cessors, give and grant unto me, the said Charles Denton Abel, Her
special licence that I, the said Charles Denton Abel, my executors,
administrators, and assigns, or such others as I, the said Charles
Denton Abel, my executors, administrators, and 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 Inven-
tion for "IMPROVEMENTS IN SCREW PROPELLERS," (a communication to me
from abroad by Adolphe Aubert, of Nogent le Rotrou, Eure et Loire,
France,) upon the condition (amongst others) that I, the said Charles
Denton Abel, my executors or administrators, by an instrument in
writing under my, or their, or one of their hands and seals, 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

page_text: months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said Charles Denton Abel, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and by
the following statement thereof, reference being had to the accompanying
Sheet of Drawings, and to the figures and letters marked thereon, that is
to say:-
This Invention consists in constructing a propeller composed of a
helical or screw blade fixed upon a driving shaft, and enclosed by a
cylinder open at the ends, which cylinder is fixed to the outer cir-
cumference of the screw blade, and is consequently made to revolve
therewith.
The fixing of the cylinder to the screw blade forms the essential
feature of the Invention, as by this means the eddies, contrary currents,
and other causes of loss of effect in ordinary screw propellers are
obviated.
The construction and mode of action of the improved propeller will
be readily understood by reference to the accompanying Sheet of
Drawings.
Figure 1 shews a transverse section of the improved or
"spiro-
cylindrical" propeller with two straight screw blades; Figure 2 shews
a longitudinal section of the same; Figures 3, 4, and 5 shew transverse
sections of arrangements with screw blades produced with curved
generating lines; Figures 6 and 7 shew a transverse section and
longitudinal section of an arrangement in which the screw blade is.
formed with a curved directrix. For obtaining the maximum useful
effect it is preferred to make the cylindrical casing a of a length equal
to its diameter, and to make the screw blade or blades 6 with one
complete turn round the axis c. The screw blades may, however, have
more or less than one complete turn, depending upon the power required
and the tonnage of the vessels which they are required to propel. It is
requisite to effect a perfectly solid union of the cylinder a with the
screw blades, for which purpose they are fixed together with angle
irons d, or otherwise. This propeller is placed, as usual, at the stern.
of the vessel, completely immersed, the shaft e being connected to the
engine. On imparting to the propeller a rapid rotary motion the action
of the screw blades effects the propulsion of the vessel, while the

page_text: casing a prevents the displacement of the water in a lateral direction
by the action of the screw, causing the whole of the water that enters
the front end of the cylinder to pass out at the back end, and thus
subjecting the whole of the same to the action of the screw blades
without producing eddies or contrary currents. It has been found
from repeated observations that the results are most favorable when the
screw blade is produced by certain generating curves, either as applied
to the transverse section or in the longitudinal direction of the blade.
Various of these generating curves are indicated at Figures 3, 4,
and 5 of the Drawings. In Figure 3 the curve f of each blade, formed
as part of a circle, is tangential to the boss g, and the centre from
which the curve is struck will be found in a line perpendicular to and
central on the line drawn from the point to the point i. In Figure 4
the curve is also an aro of a circle struck from a centre situated in a
line drawn perpendicularly from the centre of a line connecting the
centre o with the extreme point k. In Figure 5 the centre of curvature
of the line is in a perpendicular line drawn from the centre of a line
connecting the point m of the circumference with the point n of the
circumference of the boss. In Figures 6 and 7 the transverse sections
of the screw blades are straight, but it will be seen that they are so
curved longitudinally that the projection of the line of intersection of
the screw blades with the cylinder shews as a curved line p, q, of which
the curvature is entirely in one and the same direction.
There are various modes of constructing such surfaces; for instance,
the projection of the contour of the screw upon the cylinder may be
taken as the directrix, and as generating line may be employed any
straight or curved line arranged to move in the direction of the directrix
in conformity with any predetermined conditions; or, again, the line of
intersection with the boss may also be taken as a directrix, and the
helical surface be generated by means of a straight or curved line, which
while remaining in a plane parallel to itself shall always follow the two
directrices.
Having thus described the nature of this Invention, and in what
manner the same is to be performed, as communicated to me by my
foreign correspondent, I wish it to be understood that I do not limit
myself to any particular form, number, or material of the screw blades,
or of the enclosing cylinder, nor do I claim the before-described peculiar
form of screw blades when taken separate and apart from the com-

page_text: bination as described as forming any part of my present Invention;
but what I claim is, the construction and employment of the before-
described "spiro-cylindrical" screw propeller wherein one or more screw
blades are enclosed in a cylinder fixed thereto or formed in one there.
with, and caused to revolve therewith, for preventing eddies and other
losses of useful effect.
In witness whereof, I, the said Charles Denton Abel, have here.
unto set my hand and seal, this Tenth day of April, in the year of
our Lord One thousand eight hundred and sixty-nine.
CHAS, D. ABEL. (L.S.)