Improvements in Helical Propellers for Ships and other like Vessels, being also applicable to Aerostats or Vessels employed in Aerial Navigation.
Year: 1892

page_text: Date of Application, 13th Sept., 1892-Accepted, 22nd Oct., 1892
COMPLETE SPECIFICATION.
Improvements in Helical Propellers for Ships and other like Vessels,
being also applicable to Aerostats or Vessels employed in Aerial
Navigation.
We, LOUIS ADRIEN BOISSET and OCTAVE LOUIS MERCIER both of
45 Rue St. Sebastian Paris in the Republic of France Engineers 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:-
Our invention relates to helical propellers or screws employed on ships, boats and
other like vessels and is also applicable to the propellers of aerostats or machines
employed in aerial navigation.
According to our said invention the blades or arms of the improved screws or
helical propellers are made of peculiar configuration and curvature and of certain
proportions as hereinafter described so that the effect of centrifugal force is.
neutralised, the fluid. liquid or gaseous, in which the propeller works being forced
to the rear and in the direction of the axis of rotation. This effect due to the
shape of the propellers presents important advantages connected with the propelling
power and enables two propellers inversely arranged and rotating in opposite
directions to be coupled together this having a good effect with regard to the
stability of the vessel when in motion and especially when making evolutions the
latter being enabled to be performed with great promptitude by utilizing the pro-
pellers for steering or guiding the vessel.
And in order that our said invention may be fully understood we shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the annexed sheet of drawings, the same letters of referénce
indicating corresponding parts in all the figures.
Figure 1 of the accompanying drawings represents the development of the
surface of two arms or blades of a propeller constructed according to this
invention.
Figure 2 represents the propeller in side elevation shewing the inclination or
pitch of the blades.
Figure 3 is a view of a propeller blade in end elevation.
Figure 4 represents a series of transverse sections taken through equidistant
planes at right angles to the blades as indicated at 1-2, 3-4, 5-6, 7-8, 9-10
(Figures 1 and 2).
Figure 5 represents two propellers arranged inversely and rotating in opposite
directions on the same axis.
Figure 6 represents two similar propellers arranged tandemwise or on the same
axis with the blades of one propeller at right angles to the blades of the other
propeller.
The arms or blades of the propellers constructed according to our invention are
arranged in the same diametrical line that is to say in a line with one another and
are included in a circle the diameter of which is preferably equal to six sevenths of
the draught of water of the vessel the said diameter being in all cases made as long
as possible consistently with the proper action of the propellers. The maximum
width of the blades is equal to one fifth of this diameter the widest part being
situated at about three-fifths of the length of the blade reckoning from the boss.
The pitch is about six times the diameter of the enclosing circle and the inclination
or angle of the outer extremities of the blades is about 64 degrees.

page_text: In accordance with the data hereinbefore given the propellers are formed as next
hereinafter described. The blades marked A and A' in the drawing are made of
the form indicated by the development of their surfaces in one plane represented in
Figure 1. Their widest part situated at about three fifths of the length from the
boss B and at this place the width of the blade is equal to about one fifth of the
diameter of the circumscribed circle. The outer edge is not rounded but is straight
with connecting segments of circles at the corners. There is a slight ridge or
protuberance on each side of the boss the blades at this part being slightly wider
than the boss.
The sectional area of the blades diminishes progressively from the boss to the
extremities. Near the boss (section 1-2 Figure 4) the acting surface Z is slightly
convex gradually becoming flat or straight and farther on (sections 3--4, and 5-6
Figure 4) it is slightly concave again becoming flat or straight at the extremity as
indicated at 7-8 and 9-10.
The surfaces of the blades are not true planes but are of curved or helical form
being cast in this form in one piece with the boss B in any suitable metal according
to the purpose for which they are to be employed.
The curvature of the surfaces is so regulated that the angles, st indicated
by the dotted lines in Figure 4 obtained by successive sections taken on the
lines 1-2, 3-4, 5-6, 7-8, and 9-10 are of a regular progression that is to say
that starting from 0 degrees at the axis the angles gradually become wider being
equal to 64 degrees at the extremity of the blade. This progression is indicated in
Figure 3 and in the several sections in Figure 4.
The backs of the blades are
curved or rounded so as to constitute a species of rib which strengthens the blades
especially at the part nearest to the boss.
It results from this progression of the angles and from the widths of the different
parts of the blades that the edge formed at a b c on the left hand blade as
represented in Figure 2 for example is straight at the part ab and curved at the
part bc. These two parts which are equal to three fifths and two fifths respectively.
of the radius are tangential to one another and the straight part ab of one arm is
in a straight line with the corresponding part a b' of the other arm.
The arms being made of this peculiar form the particles of water or air being
taken up by the propellers near the boss, are spread over the acting surfaces of the
blades which tend to drive them towards the axial line at the rear at a point
situated at a distance equal to about twice the diameter of the enclosing circle.
The central projection of these particles or molecules produces in fact a fluid cone
forming a point of support for the propulsion contrarily to what takes place with
ordinary propellers which tend to drive the fluid molecules towards the circumference
and thus produce a centrifugal agitation prejudicial to the progress of the vessel.
This fact has been ascertained by trials made for the purpose of comparison with
the improved propellers and with propellers of ordinary construction.
The liquid or gaseous fluid being thrown backwards and towards the axis of the
propellers enables two propellers to be coupled or combined together as represented
in Figures 5 and 6 with advantage the said propellers being inversely arranged and
caused to rotate in opposite directions by two independent concentric shafts driven
by suitable gearing this arrangement or combination imparting great stability to
the vessel when in motion and especially when the propellers are employed for
guiding or steering.
It is evident that the improved propellers may be made of any suitable dimensions
and materials.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is:
The improvements in the structure of screws or helical propellers for ships or
vessels and aerostats or aerial machines consisting in the proportions, the form and

page_text: the curvature of the blades, designed with a view to forcing back the liquid or
gaseous fluid to the rear and towards the axial line of the propeller shafts
substantially as hereinbefore described with reference to the accompanying
drawings.
Dated this 13th dox of Sentember 1892.
J. H. JOHNSON & Co.,
Agents.