Improvements in Screw Propellers.
Year: 1895

page_text: Date of Application, 19th July, 1895
Complete Specification Left, 18th Apr., 1896-Accepted, 23rd May, 1896
PROVISIONAL SPECIFICATION.
Improvements in Screw Propellers.
1, JOHN ROCHFORD, of 4 Clarinda Park West, Kingstown, County Dublin,
Ireland, Engineer, do hereby declare the nature of this invention to be as
follows
This invention has reference to screw propellers for propelling navigable vessels,
and consists in so constructing the blades of propellers that the water is kept in
more intimate contact with the blades, and is not thrown so quickly off when the
propeller is revolving, thereby giving greater resistance and increase of efficient
propelling effect.
According to this invention, the blades of screw propellers are provided with
corrugated or equivalently formed surfaces, the corrugations being of circular,
angular, rectangular, or other form; or, the surfaces of the blades are provided
with projections in the form of ribs or gills placed at any desired angle on the
blades.
The corrugations or projections are preferably concentric on the blades, and the
curves may be uniform, or increase or decrease in curvature, as may be desired.
Dated this 18th day of July 1895.
CHEESBROUGH & ROYSTON,
15 Water Street, Liverpool, Applicant's Patent Agents.
Improve
I, JOHN ROCHFORD, of 4 Clarinda Park West, Kingstown, County Dublin,
Ireland, 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 :-
This invention has reference to screw propellers for propelling navigable vessels,
and consists in so constructing the blades of propellers that the water is kept in
more intimate contact with the blades, and is not thrown so quickly off when the
propeller is revolving, thereby giving greater resistance and increase of efficient
propelling effect.
According to this invention, the blades of screw propellers are provided with
corrugated or equivalently formed surfaces, the corrugations being of circular,
angular, rectangular, or other form; or, the surfaces of the blades are provided
with projections in the form of ribs or gills placed at any desired angle on the
blades.
The corrugations or projections are preferably concentric on the blades, and the
curves may be uniform or increase or decrease in curvature as may be desired.
Various modifications illustrating my invention are shewn in the accompanying
drawings, in which
Figures 1, 2, 3, 4, 5 are sections of a propeller blade having my improvements
in five different modified forms.
Figure 6 shews an end elevation of a four bladed propeller, the four different
blades being of the formation illustrated in Figures 1, 2, 3, and 4, respectively.

page_text: Referring to the drawings, a represents generally the blades of the propeller,
and the boss.
In the modification shewn in Figure 1, the formation of the surface of the blade
above described is provided by casting ribs c on the surface of the blade, com-
paratively closely together, the webs shewn in this case being rounded on their
outer surface, and curved in the direction of their length, the radii of the different
ribs from the boss to the tip, having as their common centre, the centre of the
boss. The uppermost blade of the propeller in Figure 6, shews the surface of the
blade constructed as in Figure 1.
The modification shewn in Figure 2 is substantially of the same construction as
that shewn in Figure 1, with this difference, that the ribs c are rectangular in
cross section, and project rather further from the surface than those of the former
case. The elevation of this construction is shewn on the right hand blade in
Figure 6.
;
In the construction shewn in Figure 3, a similar form of projection or rib to
that shewn in Figure 2 is used, but the ribs in this case consist of angle bars c, as
shewn such bars being fastened to the blades by rivetting or other suitable
means; whilst in the former case, under Figure 2, such ribs are cast on and form
one with the blade. The blade of the propeller in Figure 6 at the left hand side
shews the elevation of this construction.
In the modification shewn in Figure 4, the improvement according to this
invention is effected by forming the blade of the propeller in corrugations, such
corrugations being of substantially rectangular shape, and have a curvature in the
direction of their length, the radii of which have as their common centre, the
centre of the boss of the propeller. This formation is shewu in elevation in
the lowermost blade of the propeller shewn in Figure 6.
The blades in this case
may be made of wrought or forged metal, suitably fixed or secured to the boss; or
they may be of cast metal, and cast in one with the boss, or separately fixed to it.
The modification shewn in Figure 5 is of similar nature to that shewn in
Figure 4, with the exception that the corrugations of the blades are made up of
curves instead of rectangular portions, as in the former case.
From these examples, it will be seen that the ribs, corrugations, or gills, may be
differently constructed as to their form or shape, without departing from the
essential characteristic of the invention; and that, therefore, it is not restricted to
the forms more particularly represented in the drawings.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
The improved screw propeller herein described, namely, a propeller having
blades with corrugated, ribbed, or gilled surfaces or formations, whereby a greater
thrust and an increased or more efficient propelling effect is obtained; substantially
as herein set forth, and as shewn in the drawings hereto annexed.
Dated this 17th day of April 1896.
CHEESBROUGH & ROYSTON,
15 Water Street, Liverpool, Applicant's Patent Agents.