US-12623761-B2 - Propeller with folding blades and propulsion system

US12623761B2US 12623761 B2US12623761 B2US 12623761B2US-12623761-B2

Abstract

A propeller with folding blades for the propulsion of a mobile vehicle inside a fluid is provided having a movement mechanism rotatable around a central rotation axis of the propeller; and a plurality of blades. Each blade has a root end connected to the movement mechanism by a gear to allow the movement of the blade from an opening position to a closed position and vice versa, wherein in the closed position the plurality of blades are configured to form a continuous solid in the form of a spindle wherein a leading edge of a first blade (S′) is configured to osculate a trailing edge of a second blade following the first blade (S′) in such a way as to form a continuous surface between the first blade (S′) and the second blade (S″).

Inventors

Roberto BAFFIGO
Paolo Bellomi

Assignees

VELETTRICA S.R.L.

Dates

Publication Date: 20260512
Application Date: 20230317
Priority Date: 20220323

Claims (11)

1 . A propeller with folding blades for the propulsion of a mobile vehicle inside a fluid, the propeller comprising: a movement mechanism rotatable around a central rotation axis of the propeller; and a plurality of blades, wherein each blade comprises a root end connected to the movement mechanism by means of a gear to allow the movement of said blade from an opening position to a closed position and vice versa, wherein in the closed position the plurality of blades is configured to form a continuous solid in the form of a spindle wherein a leading edge of a first blade is configured to osculate a trailing edge of a second blade following the first blade in such a way as to form a continuous surface between the first blade and the second blade, and wherein, in the transition from the opening to the closed position and vice versa, the blade is configured to rotate around a rotation axis of the blade forming an angle α with the central axis of rotation of the propeller, wherein said angle α is different from 90 degrees.
2 . The propeller according to claim 1 , wherein the gear comprises a central rod provided with a longitudinal portion with spiral teeth and a plurality of sections of toothed wheels, each one fixable to the root end of the blade and rotatable around the rotation axis of the blade, wherein the central rod extends along the central axis of rotation of the propeller and is coupable to the movement mechanism and to each of the sections of toothed wheels.
3 . The propeller according to claim 2 , wherein, in the passage from the opening to the closed position and vice versa, the central rod is configured to translate along the central axis of rotation of the propeller and to rotate together with a hub.
4 . A method for defining the rotation axis of the blade of a propeller according to claim 2 , the method comprising: a. positioning the blade in the opening position keeping fixed a first end, terminal point of the root chord, the root chord being the chord at the root end; b. placing a second end of this root chord equidistant with respect to the central axis of rotation of the propeller and with the correct pitch setting, and c. positioning the vertex at the apex end of the blade on the point of greatest distance from the central axis of rotation of the propeller, wherein the axis of rotation of the blade is determined by the intersection of a first plane with a second plane, wherein the first plane is a plane passing through a first bisector relative to the angle whose vertex is the common terminal point of the root chords and the sides are the lines on which the chords of the root sections lie in the opening and closed position, and perpendicular to a first straight line passing through the first vertices of the two chords, and the second plane is a plane passing through a second bisector of the angle whose vertex is the end point of the root chords and the sides are the lines passing through the second vertices of the blade in the opening and closing position, and perpendicular to a second straight line passing through the second vertices of the blade in the opening and closed positions.
5 . The propeller according to claim 1 , wherein the gear is a bevel gear formed by a central wheel fixable to the movement mechanism and rotatable around the central axis of rotation of the propeller and a plurality of secondary wheels, each of which fixable to the root end of a blade and rotatable about the axis of rotation of the blade.
6 . The propeller according to claim 5 , wherein the secondary wheel comprises a crown consisting of a smooth portion and a toothed portion, wherein the smooth portion comprises a pin for connecting the blade, in particular for the co-molding of said blade, and the toothed portion is in contact with the central wheel.
7 . The propeller according to claim 5 , wherein the movement mechanism comprises a nut screw and a rapid-pitch screw, in which the nut screw is integral with the central wheel, and is coupled to said rapid-pitch screw, the nut screw and the rapid-pitch screw being coaxial to the central rotation axis of the propeller, and wherein the rapid-pitch screw is constrained to rotate together with a hub and is axially translatable with respect to said hub such as to cause a rotation of the central wheel with respect to the hub.
8 . The propeller according to claim 1 , wherein the angle α is between 20 degrees and 60 degrees.
9 . A propulsion system connectable to a mobile vehicle, the system comprising: an electric motor; an electrical energy accumulator connected to the electric motor; at least one propeller according to claim 1 , and a control unit connected to the electric motor and the propeller.
10 . A mobile vehicle comprising a propeller according to claim 1 .
11 . A method for forming a blade of a propeller according to claim 1 , wherein the propeller comprises a radius and a diameter when the blades are in the opening position and the blade comprises an apex end opposite the root end, the method comprising: a. determining the diameter of the propeller and the pitch setting angles of the cords of the profiles for a predefined number of sections of the blade from the root end to the apex end; b. determining the length of the portion of a solid in the form of a spindle from which the blades are to be obtained by subtracting the radius of the section, on which the root end of the blades weigh on, to the radius of the propeller, wherein the desired expanded area for the propeller is approximately equal to the surface of the portion of the solid in the form of a spindle used to obtain the blades, wherein the diameter and in part the shape of the solid in the form of a spindle are determined by the measure of said surface; c. positioning the blade sections on the solid in the form of a spindle starting from the root end, wherein each section has the vertexes of the chord lying on the normal circular section of the solid in the form of a spindle corresponding to the blade section, wherein the length of the chord corresponds to that of the side of the regular polygon inscribed in this section having a number of sides equal to the desired number of blades and wherein each chord is rotated to have the correct relative pitch setting angle with respect to the base chord; and d. obtaining the shape of the blade by connecting the sections.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a 371 national phase entry of PCT/IB2023/052632, filed Mar. 17, 2023, which claims the benefit of Italian Patent Application No. 102022000005693, filed Mar. 23, 2022. FIELD OF THE INVENTION The present invention relates to a propeller with folding blades for the propulsion of a mobile vehicle within a fluid. Furthermore, the present invention relates to a propulsion system and a mobile vehicle comprising said propeller. In addition, the present invention relates to a method for making the blade and a method for defining the rotation axis of the blade. BACKGROUND OF THE INVENTION The use of the electric motor for marine propulsion has recently opened up new possibilities for propeller design. In fact, this is no longer dependent on the torque curves typical of diesel engines; there are also, at the same power output, almost infinite combinations of torque and rotational speeds. The problem of battery life related to the low energy density of batteries compared to fuels reinforces the need to seek maximum efficiency in the propulsion system. In an electrical system, efficiency of the propeller is the key element for maximizing efficiency. The propellers currently available, most of which are designed to be coupled to internal combustion engines, do not have excellent efficiency, since they are the result of a compromise between engine performance and a reduced drag. In fact, simulations and tests show that for the typical speeds of a sailing propeller the most efficient propeller should be significantly larger (i.e. about twice the standard diameter), slower and with a higher pitch than those currently used. In particular, the most efficient propeller should have a significant elongation, a low ratio between expanded area and disc area and a pitch equal to the diameter, conditions poorly satisfied by the propellers normally used. In addition, the high torque required by a propeller with a high pitch and diameter is incompatible with the curves of a diesel engine, unless using a speed reducer with a high reduction ratio that, however, introduces other performance, weight, cost and maintenance problems. Even using an electric motor on the sailing vehicle, there are still problems to be solved in order to install a propeller with the above characteristics that are essentially linked to the sailing conditions. In fact, for a sailing vehicle there are four different sailing conditions: forward, reverse, recharging of the accumulators during sailing and so-called “pure sailing”. In the forward driving condition (first condition), the ideal propeller should have high efficiency and good thrust when maneuvering or in a headwind. In the reverse driving condition (second condition), the ideal propeller should have good thrust under all conditions. The condition of recharging the accumulators during sailing (third condition) is possible using the electric motor as a generator. In this phase of sailing, the ideal propeller is the one that allows as much energy as possible to be produced without excessively slowing down the vehicle, i.e. one that has a high efficiency. However, since during recharging the angle of incidence of the blades with respect to the flow is reversed, it is necessary to adopt some solution to optimize the efficiency of the propeller in this phase without compromising this for the propulsion phase. In the pure sailing condition (fourth condition), the propeller represents a parasitic resistance to the progression of the sailing vehicle. The solutions adopted so far include using a small propeller to reduce friction. However, this would result in poor propulsion performance and insufficient regeneration against a non-negligible residual friction. Another solution is to use propellers with blades that are completely without twist, that are flat and symmetrical with respect to the flow, and have automatic feathering. However, this would result in poor performance in propulsion and regeneration. A further solution is to use propellers with blades folding around a secant or twisting axis typically located at about 90 degrees relative to the axis of the propeller that open by centrifugal force or inertia. However, in this case, the shape of the blades is determined by a trade-off between efficiency in the open position and friction in the closed position. The centrifugal opening makes these propellers very inefficient in reverse and regeneration. Another solution is to use retractable systems. However, these systems are complex and expensive, require maintenance and take up a lot of space inside the boat. Meeting all four of these conditions at the same time is complicated; the solutions adopted so far are compromises that do not allow optimisation of the performance of the propeller according to the criteria of the requirements. In fact, according to the requirements, a propeller that maximizes the performance and thrust in the first and second