Improvement in Screw Propellers.
Year: 1891

page_text: Date of Application, 3rd June, 1891.
Complete Specification Left. 3rd Mar., 1892-Accepted, 28th May. 1892
PROVISIONAL SPECIFICATION.
Improvement in Screw Propellers.
1. WILLIAM Evans of Bute Chambers, Docks, Cardiff, in the County of
Glamorgan, Naval Architect, Surveyor and Consulting Engineer, do hereby declare
the nature of this invention to be as follows :-
My invention relates to screw propellers for steam boats and similar propellers
for other purposes and consists in an improved arrangement of the blades of said
propellers. Hitherto the blades of such propellers have all been placed at the same
angle relatively to the axis of the propeller shaft either square to the axis or set
back at the same angle. My improvement consists in placing or setting one or
more of the blades at a different angle or at different angles to the axis from the
remainder of the blades. The blades when of even number may be set at a different
angle alternately, for instance in a four bladed propeller the first and third blade
may be square to the axis and the second and fourth blade set back at a certain
angle, or the first and third blade may be set back at a certain angle and the
second and fourth blade at a different angle. Or the blades may cach be set at a
different angle to the axis. The blades set at different angles may have the same
pitch and surface or may have different pitches and surfaces, as may be required
for obtaining the greatest efficiency of the propeller. The invention is applicable
to propellers with two or any greater number of blades.
Dated this 2nd day of June 1891.
W. T. EMMOTT,
Agent for the Applicant.
COMPLETE SPECIFICATION.
Improvement in Screw Propellers.
1, WILLIAM EVANS, of Bute Chambers, Docks, Cardiff, in the County of
Glamorgan, Naval Architect, Surveyor and Consulting Engineer, do hereby
declare the nature of this invention and in what manner the saine is to be
performed, to be particularly described and ascertained in and by the following
statement :-
The invention relates to screw propellers for steam boats and similar propellers
for other purposes and consists in an improved arrangement of the blades of said
propellers.
Hitherto the blades of such propellers have all been placed at the same angle
relatively to the axis of the propeller shaft either square to the axis or set back at
the same angle.
My invention consists essentially in placing or setting each blade or one or more
of the blades at a different angle or at different angles to the axis from the
remainder of the blades.
The invention will be fully described with reference to the accompanying
drawings in which is shewn a four bladed propeller constructed in accordance with
my invention.
Figure 1. is a sectional elevation showing two blades thrown back at a
considerable angle from the vertical plane of rotation of the centre of the boss.
Figure 2. sectional elevation of alternate blades projecting from the boss in
about the same plane with each other and
Figure 3. front or end elevation of propeller.
In carrying out my invention I construct the boss or hub A in the usual manner

page_text: with an eye a by means of which it is supported upon the propeller shaft. The
blades B. C. D and E may also be constructed in the usual manner and attached
to the boss by bolts, studs or the like, or they may be formed integral therewith or
even so connected that the angles of the various blades to the horizontal may be
increased or decreased as may be desired. The centres of all the blades may
project from the boss in straight lines radiating from the axis of the propeller
shaft, that is to say, looking at the propeller from behind, the blades may be kept
straight, or may be curved back as shown by the broken lines in Fig. 3, or curved
forward of the vertical line if desired as shown by Fig. 1. In looking at the
propeller sideways the blades B and D (Fig. 2) are set vertically square to the
centre line of the shaft or thereabouts, while the alternate blades C and E are
thrown back from the plane in which B and D work, as shewn in Fig. 1; the
extent of the angle of throw being regulated by the aperture of the ship.
Whilst I have shown a four bladed propeller with two blades set out at different
angles to those alternating, I would have it understood that the invention is
applicable to propellers having two or more blades each of which may project from
the boss at a different angle to that preceding or succeeding, the essential feature
of my invention being as before stated, the setting or placing of each biade or one
or more of the blades at a different angle or at different angles to the axis of the
propeller shaft from the remainder of the blades.
The blades set at different angles may have the same pitch and surface or may
have different pitches and surfaces, as may be required for obtaining the greatest
efficiency of the propeller.
The advantages to be derived from propellers constructed as before described,
are that greater efficiency is obtained, as the two front blades cut solid water
similar to a two bladed propeller whilst the churning of the water which takes place
with ordinary propellers revolving at a high speed is to a great extent obviated.
There is also less slip and vibration and greater speed in comparison to the number
of revolutions.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1st. A propeller for steamships or the like constructed with each blade or one or
more blades placed or set at a different angle or different angles to the axis or
shaft upon
which they are mounted, from the remainder of the blades substantially
as described.
2nd. A screw propeller constructed substantially as described and shown with
reference to the accompanying drawings.
Dated this Second day of March 1892.
Per pro EMMOTT & CO., LIMITED,
Robert Wood, Secretary,
2, New Bridge Street, Manchester, Agents for the Applicant.