Improvements in Screw Propellers or Helices for the Propulsion of Boats or Balloons, or for use as Ventilators and Pumps to Propel Aëriform and Liquid Fluids.
Year: 1893

page_text: Date of Application, 9th Jan., 1893—Accepted, 6th May, 1893 -
COMPLETE SPECIFICATION.
Improvements in Screw Propellers or Helices for the Propulsion of
Boats or Balloons, or for use as Ventilators and Pumps to Propel
Aëriform and Liquid Fluids.
I, AUGUSTE RATEAU, of 27, Rue de la République, St. Etienne (Loire) France,
Professor at The École des Mines, do hereby declare the nature of this invention
and in what manner the same is to be performed to be particularly described and
acertained in and by the following statement :-
This invention has reference to the construction of screw-propellers or helices for
the propulsion of boats, or balloons, or for use as ventilators and pumps to propel
aëriform and liquid fluids. In the first case the helices have their opposition or
resistance in the fluid (water or air), and push the vessel. In the second case they
bear upon a stationary support, and propel the fluid. The helices now in use for
these purposes, are generally formed of blades, few in number (four, six or sometimes
eight) fixed upon a hub of greater or less diameter. Each blade or wing is usually
a part of a right helicoid, i.e., its section when cut by a cylinder concentric with
the axis is in every portion a helix. The extremities of the blades or wings are
generally free. Sometimes they may have secured to them a cylindrical flange or
a flange flaring into a diverging cone.
It is easy to conceive that helices thus made cannot have a great working
capacity, because they work by a succession of shocks or concussions.
If it is desired to approach theoretical perfection it is necessary to realize the
following conditions.
(1) The blades must take the fluid without any shock at the outer edge.
(2) The blade must then progressively push the fluid, and to this end it is
necessary that its section when cut by a cylinder concentric with the axis should be
an arc of a circle.
(3) The blades should be sufficiently close together to effect a regular flow of
fluid between them, and thus avoid swirls and eddies, which produce retardation.
(4) As the compound centrifugal force is directed toward the axis, and is
generally greater than the impelling centrifugal force (force centrifugal
d'entrainement) it is necessary. that the channels formed by the blades or wings
should converge instead of diverge.
(The terms "compound centrifugal force," and "impelling centrifugal force"
are used in accordance with the well known theory of Coriolis and are expressions
of accelerations rather than of forces. By calculation it is found that the former
is nearly twice as great as the latter.)
In order to conform to these theoretical conditions, which I have only outlined,
I form my helices in the following manner: The blades or wings are made of
steel sheets, and are cut from right conoids or out of right or oblique cylinders.
They are fixed upon a large hub, whose radius comprises between one half and
four fifths of the exterior radius of the helix. They are, for example, from 24
to 30 in number, and their extremities may be free, or may be rivetted to a flange.
The peripheral surface of the helix, is a cone converging towards the issue, that is
in the direction which the fluid takes.
In order to enable my invention to be carried into practice I will describe the
same by reference to the accompanying drawings, in which :-
Figure 1 represents in elevation, partly in section, a propeller for vessels:
embodying the invention;
Figure 2 is a partial end view of the same,
Figure 3 represents partly in elevation and partly in section a helicoidal, venti-
lator with annular diffuser ·

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T
Figure 5 is an elevation partly in section of a duplex helicoidal ventilator and a
volute diffuser, and
Figure 6 is a section thereof transverse to the axis.
HELIX FOR PROPELLING BOATS,
The helix is formed of a hub A B upon the flange C of which are fixed the
sheet-steel blades or wings a, b, c, d (Figure 1). The extremities of these blades
are rivetted to a strong sheet iron cone of which a section is seen at D E. In
front of the hub is an ogive F G H which is fastened to the boat and designed to
displace without too great resistance, the liquid streams, and to carry them to the
working portion of the helix. This ogive carries by means of the web I the bearing
through which passes the shaft J K of the helix. In the rear of the hub and
attached to the flange thereof, is another ogive L M also of sheet iron, the object
being to avoid the seething or violent agitation of the water passing through the
screw.
The blade or wing seen endwise at a, b, c, d in profile at a¹, b', c', d' (Figure 1,)
and in face view, in Figure 2, at a², 63, c², d2, is part of a right conoid engendered by
a straight line resting at one end upon the axis A B and perpendicular thereto, and
at the other upon a curve a b traced upon a cylinder NE which passes through
the extremity of the blade. This curve is an are of a circle traced upon the
cylinder. At its origin, it makes with the plane of entrance of the helix E E, an
angle, of which the tangent is equal to the ratio between the speed g.h of the boat,
and the peripheral speed e f of the helix. From the entrance a to exit b the
curvature is from 5° to 10° as the case may be.
HELICOIDAL VENTILATING FAN WITH ANNULAR DIFFUSER (Figures 3 and 4).
The ventilator is composed of three parts, the distributor O, the turbine.P Q
and the diffuser R S.
The distributor is analogous to those of parallel turbines of the Fountaine type,
and is formed of twenty-four blades of sheet iron curved in arcs of circles i, j
sustained between two walls of cast iron. These blades are fixed, and their object
is to give the streams or currents of air a direction inclined about 45° to the axis,
as indicated by the trajectory k, l. The current of air is then seized by the turbine.
This is composed of twenty four blades or wings formed from cylindrical iron
sheets a, b, c, d, supported on the flange of a hub P Q. These blades will be
seen endwise at a, b, their curvature being about 10°. They seize the air emerging
from the distributor, and return it parallel with the axis, propelling it forward
along the trajectory m, n.
The passage without shock from one end to the other of the edge a', 6' of the
blade is effected by means of the edge i, j of the blade of the distributor, the said
edge being cut obliquely with respect to the generatrix so that the trajectory of the
air is the more deflected as it approaches the axis.
The edge a, b of the blades or wings moves with as little play as possible
between it and the outer casing T, which is turned conically to avoid losses by
friction of the air.
At the exit of the turbine the current enters the annular diffuser R S, where the
velocity is diminished by giving rise to increase of pressure. This diffuser is
composed of two casings or shells one conical and the other cylindrical, united by
means of radial wings o, p, q, r.
The air trajectory k, l, m, n, is shewn in dotted lines. The turbine could be used
without the diffuser, but the working capacity would not be as great.
A greater pressure may be obtained by arranging several apparatus. one behind
the other on the same shaft with or without the interposition of the winged
distributor.

page_text: When the ventilator is used as a blower the casing O is open to the atmosphere..
When it is used as an aspirator the air is brought to the distributor by a cylindrical
tubing whose axis may coincide with that of the ventilator; but it would be better
to arrange this delivery tube perpendicular to the axis of the ventilator, so that it
may be tangential to the periphery of the casing O. The current is then thrown
obliquely to the axis, and the partitions of the distributor may be planes. They
may also be entirely omitted by forming the channel of admission into a volute:
around the annular orifice of the shell or casing.
THE HELICOIDAL VENTILATOR WITH VOLUTE DIFFUSER.
Figures 5 and 6 represent in elevation and section a duplex ventilator
symmetrically arranged with two helicoidal turbines, and a diffuser in the volute
form. There is no distributor in this case, or rather it is reduced to a shell U
contracting towards the turbine. The latter is formed by twenty four blades a', ',.
c', d', made of sheet metal, in the manner already explained and secured upon the
flange VW of a hub of cast iron. At a, b will be seen the section of a blade in an
arc of a circle. To allow of the entrance of air without shocks the edge of the
wing is cut obliquely with reference to the generatrix, as seen at a¹, b'.
The two
turbines are coupled by means of a sheet iron cylinder V X. At the exit of the
turbines the air enters a volute of rectangular section, enclosed by the casing Y Y,
Z Z. And on the surface which is seen in section in Figure 6, it has the spiral
form s, t, u, V. The trajectory of the air is shewn by dotted lines w, x, y, z. The
shaft A' has a pulley B¹.
The two systems of ventilation herein described may also be used as pumps to
elevate liquids, in which case the shaft is usually placed in a vertical position.
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 for the purposes specified, consisting of numerous blades.
(for example 24 to 30) set upon a hub of a diameter greater than one half the
diameter of the screw, substantially as described.
2. A screw propeller comprising numerous blades secured to a hub of relatively
large radius, each blade being cut from a right conoid, or from a right or oblique
cylinder, so that a section of the blade when cut by a cylinder concentric with the
axis is a circular arc, substantially as described.
3. A screw propeller comprising blades set close together upon a hub of
relatively large diameter, the said blades presenting in section an arc of a circle
when cut by a cylinder concentric with the axis, and being confined by a conical
peripheral flange converging toward the exit of the fluid, substantially as
described.
4. The combination with the propelling helix or screw formed of numerous.
blades upon a hub of relatively large diameter, as specified, of a distributor having
fixed guiding or deflecting partitions, whereby the fluid is delivered to the helix
obliquely to the axis thereof, substantially as set forth.
5. The combination with the helix or screw formed of numerous blades upon a.
hub of relatively large diameter, of a distributor having fixed deflecting partitions,
and a diffuser, substantially as described.
6. The combination with the propelling helix or screw, formed of numerous.
blades set upon a hub of relatively large diameter, of a distributor having guiding
partitions, and a volute diffuser, substantially as set forth.
7. The combination of a plurality of propelling screws or helices upon the same
shaft each screw or helix being composed of numerous blades set upon a hub of
relatively large diameter and curved in profile or section in the arc of a circle,.
substantially as described.

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8: The manufacture and use of the improved screw propeller hereinbefore
described and illustrated in the accompanying drawings.
Dated this 9th day of January 1893.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.