IMPROVEMENTS IN SCREW PROPELLERS
Year: 1867

page_text: LETTERS PATENT to Christopher Jobson, of Newcastle-on-Tyne, and John
Jobson, of Poplar, in the County of Middlesex, Marine Engineers, for
the Invention of "IMPROVEMENTS IN SCREW PROPELLERS."
Sealed the 24th April 1868, and dated the 31st October 1867.
PROVISIONAL SPECIFICATION left by the said Christopher Jobson and
John Jobson at the Office of the Commissioners of Patents, with their
Petition, on the 31st October 1867.
We, CHRISTOPHER JOBSON, of Newcastle-on-Tyne, and JOHN JOBSON, of
Poplar, in the County of Middlesex, Marine Engineers, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN SCREW PROPELLERS," to be
as follows:-
Our Invention consists in increasing the length of the boss or axis on which
the propelling blades are fixed, and arranging the blades on different parts of
its length and circumference in such a manner that in cross section each part
of the boss forms a separate propeller with a single blade; and the object of.
this arrangement of the blades is to prevent the breaking up of the water and
the tendency to choke the propeller when in action, such object being effected
by arranging the blades on the boss or axis in such a manner that the pro-
pelling face of each blade in succession is caused to act on a fresh or unbroken
body of water. The blades and boss may be constructed either in one piece
or in separate pieces, each consisting of one blade and a portion of the boss,
thereby affording the facility of renewing a blade or blades if necessary.

page_text: Each blade with a portion of the boss forms a separate single propeller, and
the several blades are arranged so as in revolving to act successively on the
water without resistance due to the previous breaking up of the body of water
on which the blade is caused to act. For a propeller with three blades, the
leading blade is fixed on the fore end of the boss, and the leading edge of this
blade forms a straight line at the end of the boss-at right angles to the centre
line of the boss to within a short distance of the outer edge where it is rounded
off.
The next following blade is fixed on the after end of the boss, and the
following edge of such blade forms a straight line at the after end of the boss
eorresponding with that of the leading edge of the before-named blade at the
front end of the boss. The central blade is fixed on the middle part of the
boss in such a position as to cause its propelling face to follow the second
blade in the same manner as this blade followed the first. By this arrange-
ment of blades on the boss, whether two, three, or more blades be employed,
the following blade or blades is or are caused to act in succession on the water.
without impediment from the action of the leading blade. The blades are flat on
the propelling face and convex on the back to the extent required for adequate
strength. The blades are not in the form of a true helix, but the pitch at the
boss is made less than at the extreme edge of the blade, in the proportion of
from about eleven to twenty per cent., according to the particular lines of the
ship or vessel to which the propeller is adapted and applied.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Christopher Jobson and John Jobson in the Great Seal
Patent Office on the 29th April 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, CHRISTOPHER
JOBSON, of Newcastle-on-Tyne, and JOHN JOBSON, of Poplar, in the County of
Middlesex, Marine Engineers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirty-first day of October, in the year of our Lord
One thousand eight hundred and sixty-seven, in the thirty-first year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto us,
the said Christopher Jobson and John Jobson, Her special licence that we,
the said Christopher Jobson and John Jobson, our executors, administrators,
and assigns, or such others as we, the said Christopher Jobson and John
Jobson, our executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during the

page_text: 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," upon the condition (amongst others) that we, the said Christopher
Jobson and John Jobson, our executors or administrators, by an instrument
in writing under our, or their, or one of their hands and seals, should par-
ticularly 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 John Jobson, on behalf of myself and
of the said Christopher Jobson, do hereby declare the nature of our said
Invention, and in what manner the same is to be performed, to be par-
ticularly described and ascertained in and by the following statement,
reference being had to the Drawings hereunto annexed, and to the letters and
figures marked thereon (that is to say) :-
Our Invention of "Improvements in Screw Propellers," consists in increasing
the length of the boss or axis on which the propelling blades are fixed, and
arranging the blades on different parts of its length and circumference in such
a manner that in cross section each part of the boss forms a separate propeller
with a single blade; and the object of this arrangement of the blades is to
prevent the breaking up of the water, and the tendency to choke the propeller
when in action, such object being effected by arranging the blades on the boss
or axis in such a manner that the propelling face of each blade in succession
is caused to act on a fresh or unbroken body of water. The blades and boss
may be constructed either in one piece or in, separate pieces, each consisting
of one blade and a portion of the boss, thereby affording the facility of
renewing a blade or blades if necessary. Each blade with a portion of the
boss forms a separate single propeller, and the several blades are arranged so
as in revolving to act successively on the water without resistance due to the
breaking up of the body of water on which the blade is caused to act. For
a propeller with three blades, the leading blade is fixed on the fore end of the
boss, and the leading edge of this blade forms a straight line at the end of the
boss at right angles to the centre line of the boss to within a short distance of
the outer edge, where it is rounded off. The next following blade is fixed on
the after end of the boss, and the following edge of such blade forms a straight
line at the after end of the boss, corresponding with that of the leading edge
of the before-named blade at the front end of the boss. The central blade is
fixed on the middle part of the boss in such a position as to cause its propelling

page_text: face to follow the second blade in the same manner as this blade followed the
first. By this arrangement of blades on the boss, whether two, three, or more
blades be employed, the following blade or blades is or are caused to act in
succession on the water without impediment from the action of the leading
blade. The blades are flat on the propelling face and convex on the back.to
the extent required for adequate strength. The blades are not in the form of
a true belix, but the pitch at the boss is made less than at the extreme edge
of the blade, in the proportion of from about eleven to twenty per cent.,
according to the particular lines of the ship or vessel to which the propeller
is adapted and applied.
Having thus stated the nature of the said Invention, we will proceed to
describe more particularly in what manner the same is to be performed by
reference to the accompanying Drawings, in which are represented different
views of the propeller in illustration of the characteristics of the same above
referred to.
DESCRIPTION OF THE DRAWINGS.
In the side view, Fig. 1, A is the elongated boss of the propeller; B is the
leading blade fixed on the fore end of the boss, the leading edge of which
blade forms a straight line at the end of the boss at right angles to the centre
line thereof to within a short distance of the outer edge where it is rounded
off; C is the next following blade, which is fixed on the after end of the boss,
the following edge of which blade forms a straight line at the after end of the
boss at right angles to the centre line thereof; D is the third blade fixed in
the middle part of the boss in such a position as to cause its propelling face to
follow that of the blade C in the same manner as the propelling face of the
blade C followed that of the leading blade B.
Fig. 2 is an end view of the propeller, shewing the propelling faces of the
three blades B, C, and D, at similar inclinations.
Fig. 3 is a side view representing the relative positions of the three blades
after the propeller has proceeded through a third of a revolution from the
positions represented in Fig. 1.
Figures 4, 5, and 6, shew the division of the boss with a separate blade on
each portion thereof. Fig. 4 represents the propelling face of the leading
blade B; Fig. 5 represents the back of the third blade D, and Fig. 6 represents
the propelling face of the second blade C. Fig. 7 is a section through the
third blade D.
By the arrangement of the three blades on the boss, in the manner
described, the two blades C and D are caused to act in succession on the

page_text: water without impediment from the action of the leading blade B, thereby
producing the effect of a continuous action of a single blade on unbroken
water, giving a large amount of clearance at the boss, and diminishing the
ordinary liability to choke, and also diminishing the vibration in the stern of
the vessel.
Although an arrangement consisting of three blades is preferred, yet the
Invention is not confined to this number, provided the blades be arranged so
as to act successively on a continuous line of unbroken water in the manner
described.
Having thus described the nature of the said Invention, and in what manner
the same is to be performed, we hereby declare that what we claim as of our
Invention is, the construction of screw propellers composed of two or more
blades (by preference three) with a pitch at the boss less than at the extreme
edge of the blade, in about the proportions stated, and arranged on the boss in
such a manner as to cause the propelling face of the following blade or blades
to act on water unbroken by the previous action of the leading blade, as
herein-before described.
In witness whereof, I, the said John Jobson, on behalf of myself and
of the said Christopher Jobson, have hereunto set my hand and seal,
the Fifteenth day of April, One thousand eight hundred and sixty-
eight.
JOSEPH WATSON,
27, Green Street,
So. Shields.
JOHN JOBSON. (L.S.)