IMPROVEMENTS IN STEAM SHIPS SCREW PROPELLERS
Year: 1884

page_text: I, GEORGE EDWARD SERJENT of 150 Commercial Road, Newport in the county
of Monmouth Ironmonger, Brass, and Iron, Founder, do hereby declare the nature
of my invention for IMPROVEMENTS IN STEAM SHIPS SCREW PROPELLERS to be as
follows:-
I make the Propeller of cast Iron, cast Steel, cast Brass, or other suitable metal.
The said Propeller-when required to have four blades-I cast in two pieces, with
two blades to each piece; and when the two parts of two blades each are fitted
together upon the Propeller shaft-the said blades, will be set at right angles, and
the inner part of each joining together will be provided with suitable clutches for
maintaining their position at right angles. The said parts of two blades each can
be used separate as each piece is complete in itself. The said Propeller will be
made to any diameter and to any given pitch.
In constructing the Propeller, the two parts of two blades each will be exactly
the same in design; and, in laying out the Propeller the lines will be drawn
directly from the front of one blade to the back of the other blade on the opposite
side of centre, passing gradually over the centre, and forming a concave line-and,
when the two parts of the Propeller are coupled together upon the shaft-the
concave of each part will form a semicircle in the centre between the two edges of
the blades.
By these improvements a propeller of four blades being made in two pieces will
greatly facilitate the moulding, and casting; and be lighter to handle. Also, when
one blade breaks as is often the case the two blades can be easily and inexpensively
fitted on without destroying the whole propeller of four blades as is the case with
those cast in one.
It will also be found to be very compact for stowing aboard ship...
The graduating lines from the front of one blade over the centre to the back of
the other blade at the opposite side of centre will allow the spent water to easily.
pass away, by which a great saving in steam power will be effected..

page_text: COMPLETE SPECIFICATION.
I, GEORGE EDWARD SERJENT of No 150 Commercial Road, Newport in the
county of Monmouth, Ironmonger, Brass and Iron Founder do hereby declare the
nature of my invention for IMPROVEMENTS IN STEAM SHIPS SCREW PROPELLERS
and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement :—
This Screw Propeller is so designed that it can be made with two or four blades
as required, the design being such that each part with two blades is a completo two
blade propeller, while a four blade propeller consists of two of these parts-each
part being equal and exactly the same in design-fixed at right angles to each
other on the propeller shaft and maintained in that position by two steel studs, or
other suitable means. See sectional drawings. The design is such that the lines
passing directly from the front of the one blade to the back of the other on the
opposite side of the centre, and passing gradually over the centres of both form a
concave line; and when the two parts are fixed on the shaft the concave of each
part will form a semicircle in the centre between the two blades of the two parts,
thus forming a Complete Screw.
Being constructed in this manner there is no obstruction in the centre, it will
therefore revolve through the water so easily as to produce the least possible waste
of engine power. There is not a great weight of water being continually lifted at
the root of the blades and being uselessly agitated by a large centre boss-thus
wasting a large amount of engine power without producing any forward motion to
the Ship.
From the construction of this propeller it will-when necessary to avert a
collision-move the ship as fast astern as abead, as shewn by drawings,
These improvements will greatly facilitate the moulding and casting: and, being
in two parts they will be very convenient to manage and stow away on board the
ship, thus making it more convenient for the carrying of a spare one. These
propellers can be made of any pitch, and cast of any suitable metal. Should one
blade break it is only necessary to change the broken part, the delay and cost of
which will be very small, compared with the time and cost of changing those cast
in one.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is
1. Ease of Working.-This Screw Propeller from its design, having no centre
boss works in undisturbed water, thus affording all the Engine power to the ship
for propulsion and so producing the same speed with less Engine power.
2. Requiring less Engine Power, there is therefore a great saving in the
consumption of coal,
3. The form of this propeller enables it to work without oscillation, thus greatly
reducing the strain on the ship.
4. It will when necessary to avert a collision propel as fast astern as ahead,

page_text: 5. They will be much cheaper to make, more convenient to carry on board ship
as they take much less room, and are much lighter to manage, being cast in two
equal parts.
6. They will be less expensive to change, as the work can be done in much less
time, thus lessening the delay to the ship; and when one blade breaks it is only
necessary to change and do away with the broken part, thus saving the great
expense attending the changing of a propeller cast in one.