Improved Steamship Propeller.
Year: 1893

page_text: Date of Application, 6th June, 1893
Complete Specification Left, 18th July, 1893-Accepted, 16th Sept., 1893
PROVISIONAL SPECIFICATION.
Improved Steamship Propeller.
I THOMAS WILLIAMS of No. 11 Catherine Row in the Parish of Saint Mary's
Cardigan in the Town and County of Cardigan Master Mariner do hereby declare
the nature of this invention to be as follows:-
Although in one sense the propeller of a steamship acts as a screw in a block of
wood, the effect upon the water is different; the propeller revolves in a circle and
the outer half (measuring from the tip of the blade to the centre of the shaft)
travels at twice the speed of the inner half to the centre, or in other words the
propelling power is greater at the tip of the blade than any other portion thereof
and gradually diminishes to nothing at the centre. It is therefore very important
in order to secure the same uniform pressure upon the water from the boss to the
tip of the blade so that no part of the blade acts as a drag to the other parts and
consequently cause the vibration felt in steamships.
Also inasmuch as the outer half of the blade travels twice as fast as the inner
half I twist the blade from the fore and aft line of the centre of the shaft to the
required angle at the tip of the blade so as to obtain a good hold upon the water.
The angle of the outer half (from the fore and aft line) will be double that of the
inner half thereby causing the pressure to be uniformly from the boss to the tip
of the blade. The thread of the screw as it acts upon the water will gradually
decrease from the boss to the tip of the blade therefore the decrease in the thread
of the blade from the boss to the tip will counteract the effect of the increasing
speed of the propeller from the boss to the tip, and the four blades (in a four blade
propeller) will cross each other at right angles in the centre of the shaft at both
sides of the propeller, the two blades that are in a line with one another will form
a regular symmetrical curve, the thickest part of the blades at the boss to corre-
spond with the thickest part on the opposite side and to be in a line with each
other. By adopting this principle more blades can be added to the four if required
in large steamships and whatever the necessary thickness of the boss that part of
the stern facing the fore part of the boss (where the shaft comes out) should be the
same diameter and tapered forehead in the usual manner, the boss will then not
require to be tapered on the fore part thereof and will complete the working of the
propeller.
By the adoption of this improvement the speed will be greatly increased, the
consumption of coal lessened and the vibration done away with &c.
Dated this Fifth day of June 1893.
THOMAS WILLIAMS.
COMPLETE SPECIFICATION.
Improved Steamship Propeller.
THOMAS WILLIAMS, of No. 11 Catherine Row, in the Parish of Saint Mary's
Cardigan in the Town and County of Cardigan, Master Mariner 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 for its object improvements in screw propellers for steam
and other vessels. In order that this invention and the means by which it is to be
carried into practical effect, may be thoroughly understood I will now describe the

page_text: same in detail, referring for this purpose to the accompanying drawings, which are
to be taken as part of this Specification and read therewith.
Fig. 1 shows in end elevation a screw propeller constructed according to this
invention.
Fig. 2 and 3 are side elevations of such a propeller hereinafter referred to,
Fig. 3 being partly in section.
Fig. 4 is a diagram.
As the circumferential speed of any point of the blades of a screw propeller
varies directly as the distance of such point from the axis of the propeller, and as
the circumference of the circle in which the tip of the blade revolves, measures
double the circumference of a circle drawn half way to the centre, or in other
words, as the circumference of each circle drawn at a regular distance from each
other from the tip, would gradually decrease and diminish to nothing if drawn to
the centre. It will be obvious that the propelling power of each blade will
gradually vary from the boss, where it is least, to the tip where it is greatest,
consequently the propelling power of the outer half of each blade, measuring from
the centre of the propelling shaft, will be double that of the inner half, or in other
words the propelling power will be greater at the tip of the blade than any other
part thereof, and gradually diminishes to nothing at the centre of the shaft.
Now the object of my invention is to so construct the blades of screw propellers
that the propelling power thereof shall be effective on the whole surface of the
blades from the boss to the tip, and so that no part of the blades shall act as a
drag to the other parts, and thereby cause the vibration usually felt in steamships
driven by screw propellers as heretofore constructed.
For this purpose I so curve or form each blade of the propeller as shown in
Fig. 1 that the pitch will be regular and consistent on all the different parts of
the blades, according to the different propelling power on every part thereof, the
pitch or curvature being such that the root of each blade at the boss would, if
continued to the axis of the propeller or the centre of the screw shaft upon which
it is fastened, there occupy a direct fore and aft position.
This will be better understood from the diagram Fig. 4 in which a b represents
the axis of the screw propeller (or the fore and aft line at the centre of the shaft)
ac the tip of one of its blades, bac the angle of such tip, and abc the screw
surface as seen in plan of such blade. This surface starts at the line a b and
terminates at the line ac the angle in the intermediate portion of the blade,
gradually increasing from a b to a c.
In the example shown Fig. 1 and 2 the angle of inclination of the tip of each
blade to the axis of the propeller is about 60 degrees.
In order to decrease the pitch and to obtain better hold upon the water, this
angle can be increased as shown in Fig. 4, or the blades can be uniformly curved
from the line ab to any required pitch, or to the required angle at the tip of the
blade.
Therefore the angle cab of the outer half of the blade, will be double the
angle dab of the inner half, which will counteract the effect of the double speed
or double propelling power of the outer half, thereby causing the propelling power
to be rendered effective throughout on the whole surface of the blades.
The thread of the screw as it acts upon the water will gradually decrease from
the boss to the tip, therefore the decrease in the thread of the blades from the
boss to the tip will counteract the effect of the increasing speed or increasing
propelling power of the blades from the boss to the tip.
In carrying out my invention the blades 1 are of course carried by a boss 2, so
that the actual roots of the blades will be inclined to the axis of the screw
propeller to a degree corresponding to the distance of such roots from the said
axis.
By constructing the blades of screw propellers in the manner described, the
formation of the blades thereof is made perfect, and the efficiency of the screw
propeller greatly increased.

page_text: As will be obvious my invention can be applied to screw propellers having
different number of blades, and the more the diameter of the propeller the more
will be the propelling power.
In a four blade propeller the blades will cross each other at right angles on the
fore and after part, the imaginary line of intersection being at the axis of the
propeller. In this case the curvature of each pair of blades that are opposite each
other will be continuous from the tip of one to the tip of the other, the transverse
centre line of the two blades coinciding with the axis and the longitudinal centre
line of such blades being at right angles to such axis, and radial to the boss
carrying the blades.
The forward edges of the blades may be made convex, and the rearward edges
concave as shown in Fig. 2. or both sets of edges may be made convex as shown
in Fig. 3. as may be desired.
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. For navigable vessels a screw propeller having blades, the angular point of
which commence at the axis of the propeller (or in a fore and aft line at the centre
of the shaft) the angle of each blade from such point to gradually increase to the
required angle at the tip, according to the pitch required, or in other words the
blades to be uniformly curved from the boss to the tip, the curving of each blade
being such that if it was continued from the boss to the axis of the propeller, or
the centre of the propelling shaft, the blades would all meet at that point in a
direct fore and aft position, substantially as herein before described for the purpose
specified.
2. My improved screw propeller for navigable vessels constructed as described
and shown.
Dis 15th day of Jul 1893
THOMAS WILLIAMS.