Improvements in Screw Propellers.
Year: 1894

page_text: Date of Application, 2nd July, 1894
Complete Specification Left, 30th Mar., 1895-Accepted, 4th May, 1895
PROVISIONAL SPECIFICATION.
Improvements in Screw Propellers.
I, JOHN WHITE BOYD, M.I.M.E. of 6, Oswald Street, in the County of the
City of Glasgow, North Britain, Engineer, and Surveyor, do hereby declare the
nature of this invention to be as follows, that is to say :—
My said invention has for its object to improve the forms and arrangement of the
blades of screw propellers in a manner to obtain increased speed and to avoid the
production of or action on broken water.
In carrying out my invention in the case of a four-bladed screw propeller
I arrange the blades in two diametrical pairs which may be termed the forward and
after pair.
I make the forward blades with their outer parts extending in advance
or forwards from their roots or junctions with the boss, and I make the after blades
to extend similarly backwards. The outer parts of the forward blades act on solid
water or water not broken by the action of parts near the boss; whilst there being
a greater space between the outer parts of the forward blades and the outer parts
of the after blades than in four-bladed screws of ordinary construction, the action
of the after blades will be more effective because the water they act on is less
disturbed by the action of the forward blades.
The propelling surfaces of all the blades may be portions of like helical surfaces,
with uniform, increasing, or expanding pitch, or the after blades may be more or
less different from the forward blades.
The propeller may be made with six or other even number of blades. The
improvements are applicable to a single screw, but will probably be more con-
veniently applicable to twin screws.
Dated this Thirtieth day of June 1894.
EDMUND HUNT,
Applicant's Agent.
Improvements in Screw Propellers.
I, JOHN WHITE BOYD, M.I.M.E., of 6, Oswald Street, in the County of the
City of Glasgow, North Britain, Engineer and Surveyor, 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, that is
to say :-
My said invention has for its object to improve the forms and arrangement of the
blades of screw propellers in a manner to obtain increased speed and to avoid the
production of or action on broken water.
On an accompanying sheet of explanatory drawings a four-bladed screw
propeller is represented as made according to my invention, Figure, 1, being a side
elevation and Figure, 2, a sectional front elevation.
In the propeller shown in the drawings the blades are arranged in two
diametrical pairs, A, B, and C, D, which may be termed the forward and after
pair. I make the forward blades, A, B, with their outer parts extending in

page_text: advance or forwards from their roots or junctions with the boss, E; and I make
the after blades, C, D, to extend similarly backwards. The outer parts of the
forward blades, A, B, act on solid water or water not broken by the action of
parts near the boss, E; whilst there being a greater space between the outer parts
of the forward blades, A, B, and the outer parts of the after blades, C, D, than in
four-bladed screws of ordinary construction, the action of the after blades will be
more effective because the water they act ou is less disturbed by the action of the
forward blades.
The propelling surfaces of all the blades may be portions of like helical surfaces,
with uniform, or increasing, or expanding pitch; or the after blades may be more
or less different from the forward blades."
The propeller may be made with six or other even number of blades. The
improvements are applicable to a single screw, but will probably be more con-
veniently applicable to twin screws.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
The improved construction of screw propellers in which the blades are arranged
in forward and after pairs extending forwards and aft respectively substantially as
herein before described and as shown in the accompanying drawings.
Dated this Twenty-ninth day of March 1895.
EDMUND HUNT,
Applicant's Agent.