IMPROVED APPARATUS FOR INCREASING THE EFFICIENCY OF A SCREW PROPELLER, AND FOR ASSISTING IN THE STEERING OF THE VESSEL
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Alexander Melville Clark at the Office
of the Commissioners of Patents on the 11th May 1878. A communication
from abroad by Le Comte Albert Conti de Barbaran, of Paris, France.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Mid-
dlesex, Patent Agent. "IMPROVED APPARATUS FOR INCREASING THE EFFICIENCY
OF A SCREW PROPELLER, AND FOR ASSISTING IN THE STEERING OF THE VESSEL"
[A communication from abroad by Le Comte Albert Conti de Barbaran, of Paris,
France.]
This Invention relates to improved means for utilising the centrifugal force of
the current generated by the rotation of a screw propeller for the propulsion of the
vessel, and it consists in the employment of a fixed conical ring or rings encircling
the propeller, thereby avoiding the necessity of making the propeller blades of
a special form for the purpose of utilising the centrifugal current and relieving
the blades of the extra strain.
In order that the Invention may be more readily understood, I have illustrated
in the accompanying Drawings several arrangements of apparatus by way of
example.
Figure 1 is a vertical section on line A, B; and Figure 2 a plan, partly in section,
on line C, D, Figure 3.
Figure 3 is a face view of the apparatus, and stern view of the vessel.
Figure 4 is a face view of one of the rings of which the propeller is composed;
and Figure 2, an edge view of same.
Figure G is a side view of the propelling apparatus.
Figure 7, a similar view of a propeller composed of a single ring, and Figure 8,
plan of same; while Figure 9 shows a plan of the casing for utilising the centrifugal
currents, and auxiliary steering gear.
a, a, aro two brackets or frames fixed to the stern of the vessel n in a line with
the screw shaft in which are mounted the three rings b, b, b, (Figures 2, 3, 4, 6)
forming the propeller casing.
The rings are provided with flanges d', d, and d, d, by which they are bolted to
the vessel and brackets a, a, and their interior surfaces i, i, are inclined at an angle
to the plane of rotation of the screw, being placed at such distances as will allow of
the rotation of the latter, but sufficiently near to the point o, Figure 2, to receive
the action of the centrifugal current produced by the motion of the screw.
ection on line A, B; and Figure 2 a plan, partly in section,

page_text: The surfaces i, i, may be either plane or curved, and their angles of inclination
be varied (in the example shown they are placed at an angle of 43°). They sustain
the force of the centrifugal current, the re-action of the water impinging against the
said surfaces resulting in a movement of propulsion to the vessel, and the water
afterwards passing out through the spaces between the rings in the opposite direction
to such movement.
The arrows at O and P, Figure 2, indicate the way in which the centrifugal
currents are deflected by the inclined surfaces of the rings, so as to produce a re-
action which assists in the propulsion of the vessel. Several of these rings are combined
in order to avoid impeding the progress of the vessel.
In Figures 7 and 8, the apparatus is represented as composed of a single ring
surrounding the screw.
a, a, are the bracket arms carrying the ring; d, d, flanges for fixing the same;
m, n, are curved surfaces on the rear edges of the casing for diverting the current
in a backward direction, and also for producing a greater impulsive effect on the
surface, which sustains the impulsive effort due to the re-action of the water thereon.
The surfaces of the apparatus receiving the pressure are placed at an angle to the
direction of the centrifugal current, and being fixed, a saving of power is thus
realised, compared with a propeller having curved extremities for the purpose of
utilising the centrifugal current; moreover as the centrifugal currents between the
blades, as well as those along the surfaces of the blades, impinge upon the ring or
rings, a greater portion of the centrifugal force is utilised for the purpose of propul-
sion than is the case where the screw is specially constructed for the purpose of
utilising the centrifugal force, and which force would be wasted were the pressure
of the current not received upon the inclined surfaces of the propeller casing.
If the blades or propelling surfaces based on the theory of inclined planes and
helicoidal surfaces require in the case of the screw to be set in motion in order
to obtain a propulsivo effect, the centrifugal current which is thereby developed
needs only in order to be transformed into a propelling current, to strike against
and re-act upon suitable fixed inclined surfaces placed at the circumference of
the circle of rotation described by the screw, to receive the action of the current.
It is not, however, necessary that these surfaces should move, and there is in
fact an advantage in fixing them, as it relieves the screw and machinery, affords
additional strength, and also prevents loss of power, as the object of these
inclined surfaces is not to act upon the water, but simply to support the cen-
trifugal force of the current and the resulting re-action.
The agitation of the surrounding water, produced by the rotation of the screw,
which is apparent upon the surface, is an evidence that with the ordinary system
there is a certain loss of power. This effect is transformed by the apparatus of this
Invention into a current nearly perpendicular to the plane of rotation of the screw,
and in a contrary direction to the propulsive effort exerted upon the casing.
Where a single annular casing is used, I may make two apertures b, b', therein,
one on the port, and one on the starboard side, as shown in Figure 9, which may be
opened or closed at will by means of the hand gear & placed on deck through tho
shaft c and slide e.
A portion of the centrifugal current thus escapes at one side of the ring when
one of said apertures is unclosed, thereby rendering the pressure unequal on the
two opposite sides of the ring, which greatly facilitates the steering of the vessel,
so that the latter can be turned in a circle of much smaller diameter than with the
rudder only.