Improvements in Screw Propellers.
Year: 1894

page_text: Date of Application, 30th Oct., 1894-Accepted, 1st Dec., 1894
COMPLETE SPECIFICATION
Improvements in Screw Propellers.
I WILLIAM HENRY JAY, Mechanic of 188 Sherburne Street Providence, State
of Rhode Island United States of America 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:-
My invention has relation to screw-propellers, but more particularly to a novel
construction of the propeller-blades or wings.
Usually heretofore, so far as I am aware, screws of this character have been
provided with blades having the length of the forward or entering side or edge
substantially the same as the rear or discharging side. Moreover, such former
screws have been practically alike with respect to the form of the two radial edges
of the blades. By reason of such construction the blade in working enters the
water at its full leverage and pressure, thereby subjecting the shaft and motive
power to a continuous series of shocks or jars which act not only to shorten the
life of the machinery but at the same time produces a disagreeable sensation and
noise.
The object I have in view is to overcome the defects or disadvantages just
referred to; to that end my invention consists, essentially, of a screw-propeller
having the entering edge and a small area of each blade formed with a slightly
greater inclination or pitch than the major portion of the blade while the rear or
discharging edge is reversely bent or curved; the outer peripheral edge of the
blade is non-concentric with the shaft, its greatest radius being at the rear edge,
and its greatest width near the hub of the screw; whereby the leading portion of
the blade has a coarser pitch than the main portion. By means of this construction
and arrangement the blades are adapted to enter the water easier; the gradually
increasing area of the blade causing it to cut through the water with less slip, and
consequently greater efficiency; the curved portion of the rear edge of the blade
at the same time operating to prevent a too free release of the impinging water
from the working face of the blade, all as will be more fully hereinafter set forth
and claimed.
.
is a
In the accompanying sheet of drawings, Figure 1 is a side elevation of a screw-
propeller embodying my improvement; Fig. 2 is an end view; Fig
perspective view, viewed at right angles with the plane of the blade, and Fig. 4 is
a transverse sectional view, taken on line x x of Fig. 1.
In
In carrying out my improvement I would state that neither the hub of the wheel
nor the manner of securing the blades thereto form any part of my present inven-
tion, as the latter resides solely in the novel construction of the blade itself.
the drawings A indicates a two-bladed screw-propeller provided with my
improvement. The hub portion is designated by h, and a indicates the blades.
The blades as drawn are formed integral with the hub, but they may be made
independently of it and secured thereto in any well known manner.
The position or location of the blades with reference to the hub is such that they
stand at an oblique angle of about 45° (see Fig. 4), although the angle may be
changed to suit varying conditions. The forward or entering portion 6 of the
blade a is bent inboard, or toward the vessel, as clearly shown in Fig. 4, thereby
forming with the major portion of the working area a', if continued, an acute
angle m, as indicated by the broken line in said figure. When thus bent or formed
it will be seen that the blade will present a working surface having an included
angle exceeding 180°, as indicated by the dotted curved line e, in the horizontal
sectional view. Fig. 4. The part a' of the working area forms a substantially plane

page_text: -
or flat surface arranged obliquely with the hub. The rear or discharge edge c of
the blade is bent in a reverse direction or toward the shaft, as clearly represented
in Fig. 4. The path described by the outer peripheral edge p is not a true circle n
(see dotted lines Fig. 2) because I prefer to so make said edge that it is bounded
or limited by radii having varying lengths; by this arrangement the power exerted
in propelling the vessel against the resistance or pressure of the water is more
gradually utilized. At the same time the bent portion of the rear edge c operates
to prevent the water, impinging against the working surface a' of the blade, from
escaping too readily, thereby decreasing the percentage of slip. I also prefer to
make the widest portion of the blade at or near the hub, as indicated at o o, Fig. 3,
thus greatly strengthening the blade as well as increasing the leverage at that
point. In screw-propellers of comparatively small diameter I prefer to employ two
blades, but larger screws may have three or more.
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 :
1. A screw-propeller blade consisting essentially of a forward or leading
portion bent inboard and a main portion a¹ arranged at an angle therewith
exceeding 180°, whereby the said leading portion of the blade has a coarser pitch
than the main portion, substantially as described.
2. A screw-propeller blade having its forward portion bent inboard to form an
obtuse angle with the plane of the major portion of the blade, and having its rear
or releasing portion reversely bent toward the shaft, substantially as herein before
described and for the purpose set forth.
3. A screw-propeller blade having its outer peripheral edge bounded by radial
lines gradually increasing in length from the front to the rear, the front portion
being bent inboard to form an obtuse angle with the plane of the major portion of
the blade, its rear or releasing. portion being reversely bent toward the shaft, and
having the greatest width of the blade at or near the hub, substantially as herein-
before described.
4. The screw-propeller, substantially as hereinbefore described, consisting of a
hub portion adapted to be fixed to a driving-shaft, and having a plurality of bent
blades a secured to or integral with said hub; each of said blades having a forward
or leading portion & bent inboard and a main portion a' arranged at an angle
therewith exceeding 180°, and having the rear or releasing portion c of said main
part bent reversely toward the shaft, whereby the said leading portion of the blade
has a coarser pitch than the main portion.
Dated the 3rd day of October 1894.
WILLIAM HENRY JAY