Improvements in Screw Propellers, Fans, and other Apparatus in which Screw Blades or Vanes are Used.
Year: 1893

page_text: Date of Application, 7th July, 1893
Complete Specification Left, 2nd Jan., 1894-Accepted, 10th Mar., 1894
PROVISIONAL SPECIFICATION.
Improvements in Screw Propellers, Fans, and other Apparatus in
which Screw Blades or Vanes are Used.
I THOMAS WILLIAMS of No. 11 Catherine Row Cardigan in the Parish of
St. Mary's and County of Cardigan Master Mariner do hereby declare the nature
of this invention to be as follows:-
This invention has for its object improvements in screw propellers, or fans,
for steam & other vessels, ventilators, fluid injecting or ejecting apparatus to
propel balloons, and other air machines, also for use as water turbines, and
windmills.
The forming and mode of fixing the true and perfect curve in the blades.
All the above mentioned work on the same principle whether propelling or being
propelled by the action of air or water, they revolve in a circle like a wheel.
The propelling power is greater at the tip of the blade than any other part
thereof, and it gradually diminishes to nothing at the centre, or in other words
the propelling power is double on the outer half (measuring from the tip of the
blade to the centre) to what it is on the inner half. It is therefore very important
that the whole formation of the blades shall be effective, so that no part of the
blades act as a drag to the other parts. I therefore curve each blade from the
fore and aft line in the centre to the required angle or pitch (and in a four blade
propeller) the blades will cross each other at right angles in the centre, and
the curve in the two blades that are in a line with each other will continue the
same from tip to tip. The angle of the outer half of each blade at the tip (from
the fore and aft line) will be double that of the inner half, which will therefore
counteract the effect of the double propelling power of the outer half, thereby
causing the pressure to be effective throughout on the whole surface of the blades.
The thread of the screw as it acts upon the air or 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 of the blades
through the air or water from the boss to the tip.
Any number of blades can be utilized as required, and by the adoption of this
improvement they can be made to work perfect.
Dated this Sixth day of July 1893.
THOMAS WILLIAMS.
COMPLETE SPECIFICATION.
Improvements in Screw Propellers, Fans, and other Apparatus in
which Screw Blades or Vanes are Used.
1, THOMAS WILLIAMS, of 11 Catherine Row, Cardigan, in the Parish of
St. Mary's and County of Cardigan, South Wales, 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 reference to improvements in screw propellers, fans and in
other similar apparatus such as ventilators, fluid injecting and ejecting apparatus,
water turbines, ship's patent logs, sounding machines, windmills, anemometers, and
certain kinds of fish hooks, in which screw blades or vanes are used either for

page_text: propelling the bodies, such for examples as steam and other navigable vessels,
and balloons and other aerial machines to which they are applied, or for propelling
fluids such as water or air through tubes for propelling or ventilating purposes;
or which are themselves rotated by the action thereon of fluids such as water or
air, as in the case of turbines, logs and windmills.
The object of my invention is to so construct and arrange the screw blades or
vanes, (hereinafter referred to as blades) of such apparatus that the propelling
power thereof, or the action thereon of a fluid by which they are driven, as the
case may be, shall be uniform, or approximately uniform, from root to tip, and
so that no part of the blades shall act as a drag to the other parts, thereby
increasing the efficiency of such propellers fans or like apparatus, and preventing,
in the case of screw propellers for navigable vessels, the disagreeable vibration
usually felt in such vessels when driven by screw propellers as heretofore
constructed.
For this purpose I form and arrange the screw blades in the improved manner
I will now proceed to explain by aid of the accompanying drawings in which,
Figs. 1 and 2 show in front end elevation and plan respectively, a screw
propeller or fan with its blades constructed and arranged according to this
invention.
Figs. 3, 4 and 5 are diagrammatic views hereinafter referred to.
Each of the screw blades 1 shown in Figs. 1 and 2 is so shaped or formed that,
considered by itself, it is of practically uniform pitch or twist from root to
tip. Each of these screw blades however is so arranged relatively to the axis of
the propeller, that its root, would, if continued to the axis of the propeller, as
shown in the diagrammatic view Fig. 3, there occupy a direct fore and aft position,
consequently the pitch of the screw surface, relatively to this fore and aft position,
will decrease from the root, where it is infinite, to the tip, where it is made of any
desired amount, according to circumstances. This decrease of pitch from root to
tip will be better understood from the diagram Fig. 4 where a b represents the
axis of the screw propeller; a c the tip of one of its screw blades; bac the angle
or pitch of such tip relatively to the axis or line a b; and a bc the screw surface,
as seen in plan, of such blade. This surface starts at the line a b, which is in a
fore and aft position and corresponds to an infinite pitch, and terminates at the
line a c, which is so inclined to the line ab that it represents the desired pitch of
the blade at the tip, the pitch of the intermediate portions of the screw surface,
relatively to the line a b, gradually and uniformly decreasing from a b to a c so
that the angle of the outer half of each blade at the tip relatively to the fore
and aft line a c will be double that of the inner half measured at a distance half
way between the tip of the blade and the said fore and aft line.
In carrying out my invention, the screw blades I 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 an extent depending upon the distance of such roots from the
said axis.
In the application of a screw propeller constructed as described to a ship,
that part of the stern of the vessel through which the propeller shaft projects
should not be less in width than the diameter of the boss, in order that the boss
shall not offer resistance to motion through the water.
The angle of inclination of the tip of each screw blade can be varied to suit
requirement. In the case of screw propellers for ships the angle at the tip may
be made equal to about five points of the compass, (56° 15') as in the example
illustrated in the drawings, though in some cases it may be found desirable to
increase this angle, in which case the angle at the tip can be regulated by the
angle or pitch, of the other parts of the screw blade in such a manner as not to
cause the tip to exert a drag upon such other parts of the blade. The angle and
circumferential speed of or distance passed through by each part of the blade
will give the pitch for such part in one revolution, as indicated in the diagrammatic
view Fig. 5, where de represents the line of advance, d f the circumferential

page_text: rate of speed or the distance travelled in one revolution by the blade tip, and also
the direction in which the tip of the blade travels, and e f the pitch.
As will be obvious the propelling power of each blade starts from the centre
of the propeller or fan and gradually increases to the tip in accordance with the
gradually increasing circumferential speed of each part of the blade from root to
tip as indicated by the dotted circles shown in Fig. 3.
By constructing and arranging the screw blades in the manner described, the
decrease in pitch from the boss to the tip of each blade will counteract the effect
of the increasing angular speed and propelling power of the blades from the boss
to the tip, so that the said blades will be rendered capable of acting in the most
effective manner, with the result that the efficiency of the propeller will be
considerably increased as compared with the screw propellers usually employed.
As will be obvious my invention can be applied to screw propellers, fans and
like apparatus having different numbers of blades. In a four bladed propeller or
fan, such as shown, the pairs of blades will cross each other at right angles, the
imaginary line or intersection being at the axis of the propeller. In this case the
curvature of the 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 of the propeller, and the longitudinal centre line de
(Fig. 1) of such blades being at right angles to such axis and radial to the boss
carrying the blades.
The screw blades for other apparatus of the kind hereinbefore referred to are
similarly formed and arranged and their application will be readily understood
without further description. The width and length of the blades can in each case
be varied to suit requirement.
In the example shown, each blade is made of practically uniform width from
root to tip, but obviously the width can be varied. Thus each screw blade may
if desired, be made of gradually increasing width from root to tip, as is commonly
done with some types of screw propellers now in use. Again, the forward edges of
the blades may be made convex and the rearward edges concave, as shown, or both
sets of edges may be made convex.
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 :-
A screw propeller, fan, or other similar apparatus of the kinds herein referred
to, having screw blades each of which, considered by itself, is of practically
uniform pitch or twist from root to tip and is so arranged relatively to the axis
about which it turns that its root would, if continued to such axis, occupy a direct
fore and aft position, whilst the pitch of the surface of the said screw blade,
relatively to said axis, gradually and uniformly decreases from the root to the
tip, the arrangement moreover being such that the tips or outer parts of the blades
exert no drag upon the other parts of the blades substantially as hereinbefore
described and shown for the purpose specified.
Dated this 30th day of December 1893.
THOMAS WILLIAMS.
W. Lloyd Wise,
46, Lincoln's Inn Fields, London, W.C., Applicant's Agent.