Improvements in Screw Propellers.
Year: 1899

page_text: Date of Application, 20th Jan., 1899
PROVISIONAL SPECIFICATION.
Improvements in Screw Propellers.
We, REUBEN THOMAS PRESTON, of the Firm of J. Stone & Co., of Deptford,
in the County of Kent, Engineers, and William HAMILTON MARTIN, of Flushing,
Holland, Engineer, do hereby declare the nature of this invention to be as
follows:-
In casting propeller blades of large sizes it is well known that the metal in
the centre of the thick part of the blades from the root to about one half or
one third of its length, is much weaker than the remainder of the casting, owing
to the fact that the grain of the metal is necessarily more open than in the
thinner parts.
In addition to this it is also well known that the metal at the centre or neutral
axis is of comparatively little value in resisting the strains to which the blades
are exposed.
This invention consists in hollowing out the centre, or weak part of the metal
of the blade, and distributing the weight over the outside dimensions of the part
of the blade so hollowed out. By this means a much stronger blade is obtained,
without at all increasing the weight of same; or a blade of equal strength can
be produced of lighter weight than when made as hitherto.
Dated this 20th day of January 1899.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.
Improvements in Screw Propellers.
We, REUBEN THOMAS PRESTON, of the Firm of J. Stone & Co., of Deptford,
in the County of Kent, Engineers, and WILLIAM HAMILTON MARTIN, of Flushing,
Holland, Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:---
In casting screw propeller blades of large sizes it is well known that the metal
in the centre of the thick part of the blades from the root to about one half or
one third of its length is much weaker than the remainder of the casting, owing
to the fact that the grain of the metal is necessarily more open than in the
thinner parts.
In addition to this it is also well-known that the metal at the centre or neutral
axis is of comparatively little value in resisting the strains to which the blades
ara arnosed

page_text: This invention consists in hollowing out the centre or weak part of the metal
of the blade and distributing the weight over the outside dimensions of the part
of the blade so hollowed out. By this means a much stronger blade is obtained
without at all increasing the weight of same; or a blade of equal strength can
be produced of lighter weight than when made as hitherto.
The drawing is a sectional side elevation of a two bladed screw propeller to
which the invention is applied as an example. The part marked No. 1 shews
an expanded blade having a series of cross sections drawn thereon at equal
distances; the part marked No. 2 shews the blade in longitudinal section. Each
blade is hollowed out or chambered in the centre for some distance from the
root or flange end. Starting from a round hole at the root part A the chamber
quickly assumes the form of a segment of a circle as shewn at B, and this kind
of shape but with gradual reduction in height is maintained for some distance
as indicated by the sections C and D. The chamber then terminates at E.
In the case of large propeller blades the chamber may be divided up by one
or more longitudinal ribs (or be provided with stays or studs) for further increase
of strength.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
Constructing screw propeller blades with an interior space or chamber in the
region of the neutral axis substantially as and for the purpose set forth.
1000
uay
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.