PROPELLER FOR STEAM SHIPS AND THE LIKE VESSELS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by the said Robert Gibb at the Office
of the Commissioners of Patents on the 26th September 1882f
*
ROBERT GIBB of Liverpool in the County of Lancaster,
PROPELLERS FOR STEAM SHIPS AND THE LIKE VESSELS,"
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IMPROVEMENTS IN
In screw propellers as constructed at present a great loss of power is caused from
the 'dead water near the boss. Now I have found that if the bases of the blades
those parts of the blades adjacent to the boss are formed of a continuous spirál a
great benefit' results. ...
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I accordingly make my blades by preference with their junction to the boss at an
angle of 45 degrees with the shaft and "all" of them in one uniform spiral. Each
blade however as it leaves "this spiral' presents a 'surface" more and more nearly
approaching a plane at right angles to the shaft.
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30.2 98 17
Consequently though the more central portion of all the blades forms a single
spiral the outer portions do not 'form'a continuous spiral but each forms a segment
of a spiral or a slightly curved surface quite independent of the others."
From my experiments I am of the opinion 'that fifty per cent gain will result
from the adoption of my plan as all the surface will be of service instead of part
being employed in merely churning up the water.
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1. a

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Robert Gibb in the Great Seal Patent Office on the 24th March
1883.
ROBERT GIBB of Liverpool in the County. of Lancaster.
PROPELLERS FOR STEAM SHIPS AND THE LIKE VESSELS"
"IMPROVEMENTS IN
In screw propellers as constructed at present a great loss of power is caused from
the dead water near the boss. Now I have found that if the bases of the blades-
those parts of the blades adjacent to the boss-are formed of a continuous spiral,
a great benefit results.
I accordingly make my blades by preference with their junction to the boss at
an angle of say about 45 degrees with the shaft and all of them in one uniform
spiral. Each blade however as it leaves this spiral can present a surface more and
more nearly approaching a plane at right angles to the shaft.
Consequently though the more central portion of all the blades forms a single
spiral, the outer portions do not form a continuous spiral but each forms a segment
of a spiral or a slightly curved surface quite independent of the others.
The drawings annexed show a plan (Fig. 1) and edge view (Fig. 2) of a four
bladed screw on my plan adapted to suit a steamer already built for ordinary
screws. Fig. 3 diagram showing centres for blades.
If however the ship can be built with the view to the application of my
invention, I prefer a boss at least one fourth the diameter of the screw in depth
and one blade of the screw springing from a point as near as possible to one end
and another blade from a point as near as possible to the other end of the boss, the
remaining blade or blades being in the spiral connecting these points. I find from
experiment that the greater the pitch of the spiral the more power is obtained
from the screw, but on the other hand a spiral of great pitch requires a larger
screw opening and consequent structural difficulties. Hence why I on the whole
prefer to limit the length of the boss to about one fourth the diameter of the screw.
With these proportions my experiments indicate an increase of utilized power to the
extent of thirty per cent over screws with the blades all springing from the boss in
one transverse plane.
;
Having now described my invention and the best method of carrying it into
effect, I wish it to be understood that what I believe to be new and desire to
protect under the Letters Patent is :-
1st A propeller constructed substantially as and for the purposes described.
2nd A propeller with blades proceeding from the boss not in one plane at right
angles to the axis of the boss, but from different points in that boss forming a spiral
extending from one end of the boss to the other.
In witness whereof I the said Robert Gibb have hereunto set my hand and
seal this Twenty second day of March in the Year of our Lord one
thousand eight hundred and eighty three.