EP3976463A1

EP3976463A1 - Automatic variable pitch propeller

Info

Publication number: EP3976463A1
Application number: EP20737261.6A
Authority: EP
Inventors: Christophe DEPRES; Pascale BALLAND; Laurent Bernard
Original assignee: Universite Savoie Mont Blanc
Current assignee: Universite Savoie Mont Blanc
Priority date: 2019-05-29
Filing date: 2020-05-20
Publication date: 2022-04-06
Anticipated expiration: 2040-05-20
Also published as: FR3096654B1; WO2020240119A1; EP3976463B1; FR3096654A1

Abstract

The present invention relates to a device comprising a variable pitch propeller (11) and means adapted to modify the pitch of the propeller by Venturi effect.

Description

DESCRIPTION

Automatic variable pitch propeller

The present patent application claims the priority of the French patent application FR19 / 05753 which will be considered as forming an integral part of the present description.

Technical area

The present description relates generally to variable-pitch propellers and, more particularly, a device for controlling the pitch of a variable-pitch propeller. The present description applies in particular to propellers with a variable pitch propeller.

Prior art

[0002] Propeller thrusters are already widely used to set machines in motion, typically for navigating boats, for flying aircraft, etc. For example, motorized propeller thrusters usually equip small boats capable of sailing over a wide range of speeds. Where applicable, these thrusters are often fitted with variable-pitch propellers, so that the propeller's pitch increases as the speed of the boat increases. This makes it possible to maintain a substantially constant engine speed whatever the speed of the boat. This improves the efficiency of the propellant.

[0003] The modification of the pitch of the propeller of a variable-pitch propeller thruster is generally carried out automatically. The thruster then comprises a system for slaving the pitch of the propeller with respect, typically, to the speed of the boat and / or with respect to an engine torque applied to a propeller shaft. [0004] Among the most widespread propeller pitch control systems, we find in particular hydraulic, electrical, mechanical or hydrodynamic systems. These systems, which are often expensive and very sensitive to operate, are also complex to design and build. Their development raises, in particular, many sealing problems. In addition, they do not generally make it possible to obtain satisfactory control of the pitch of the propeller over the entire speed range of the boat.

[0005] In addition, there are manually controlled propeller pitch control systems. These manual systems, although often less complex in constitution than the automatic systems mentioned above, nevertheless require very delicate adjustment on the part of the pilot of the boat. Manual propeller pitch modification systems are therefore, in practice, difficult to use, which makes them inconvenient to use by a large public.

[0006] Document US Pat. No. 6,358,007 describes a universal boat propulsion system with variable pitch at constant speed.

[0007] Document WO 2007/016804 describes a boat engine.

[0008] Document US Pat. No. 5,219,272 describes a variable-pitch marine thruster with hydrodynamic variation.

Summary of 1 ¹ invention

[0009] There is a need to improve the pitch control devices of an existing variable-pitch propeller.

[0010] One embodiment overcomes all or part of the drawbacks of the pitch control devices of a known variable-pitch propeller. [0011] One embodiment provides for a device comprising a variable-pitch propeller and means adapted to modify the pitch of the propeller by the Venturi effect.

[0012] According to one embodiment, an external flow of a fluid generates, by Venturi effect, a depression in a first compartment of a chamber comprising one or more first orifices not parallel to an axis of rotation of the propeller, a variation of this depression causing a displacement of a movable partition actuating a mechanism for modifying the pitch of the propeller.

[0013] One embodiment provides a device comprising:

a variable pitch propeller;

a chamber comprising one or more first orifices not parallel to an axis of rotation of the propeller;

a movable partition delimiting, inside the chamber, a first compartment communicating with the outside through this or these first orifices; and

a mechanism for modifying the pitch of the propeller, associated with the movable partition.

[0014] According to one embodiment, a variation of a vacuum, in the first compartment, causes a modification of the pitch of the propeller.

[0015] According to one embodiment, an increase in the depression causes an increase in the pitch of the propeller.

[0016] According to one embodiment, a decrease in the vacuum causes a decrease in the pitch of the propeller.

[0017] According to one embodiment, at least one additional part forms, relative to an external surface of the chamber, a constriction in the vicinity of this or these first orifices. According to one embodiment, the movable partition further defines, inside the chamber, a second compartment communicating with the outside through one or more second orifices parallel to the axis of rotation of the propeller.

[0019] According to one embodiment, the movable partition is linked to a return spring to a position corresponding to an extreme value of the pitch of the propeller.

According to one embodiment, the movable partition is a piston having an inclined surface, relative to the axis of rotation of the propeller, on which rests a cam adapted to actuate the pitch modification mechanism of the propeller.

According to one embodiment, the movable partition is associated with a gear, consisting of a rack and a pinion, adapted to actuate the mechanism for modifying the pitch of the propeller.

[0022] According to one embodiment, the mechanism for modifying the pitch of the propeller modifies a blade pitch angle over an angular range of less than 90 °, preferably of the order of 15 °.

[0023] According to one embodiment, the propeller comprises at least two blades disposed radially and separated from the axis of rotation by a distance of approximately 35 mm, preferably equal to 35 mm, these blades having a length of about 240 mm, preferably equal to 240 mm.

One embodiment provides a propellant device comprising a device as described.

[0025] One embodiment provides for a human-powered craft comprising at least one propellant device as described. [0026] One embodiment provides an energy recovery device, comprising a device as described.

Brief description of the drawings

These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the accompanying figures, including:

[0028] Figure 1 illustrates schematically and partially, in a side view and in section, an embodiment of an automatic variable-pitch propeller thruster;

[0029] Figure 2 illustrates schematically and partially, in a side view and in section, another embodiment of an automatic variable-pitch propeller thruster;

[0030] Figure 3 illustrates schematically and partially, by side views (A) and (B) and in section, yet another embodiment of an automatic variable-pitch propeller thruster;

[0031] Figure 4 shows, by views (A) and (B) in perspective and cut away, yet another embodiment of an automatic variable-pitch propeller thruster;

FIG. 5 shows an example of a boat equipped with an automatic variable-pitch propeller thruster; and

[0033] FIG. 6 partially shows an embodiment of a thruster propeller.

Description of embodiments

The same elements have been designated by the same references in the various figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been shown and are detailed.

Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected or coupled together, it means that these two elements can be connected or be linked or coupled through one or more other elements.

In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "rear", "top", "bottom", "left", "right", etc., or relative, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc. ., Reference is made unless otherwise specified in the orientation of the figures or to a boat or a thruster in a normal position of use.

Unless otherwise specified, the expressions "approximately", "approximately", "substantially", and "of the order of" mean within 10%, preferably within 5%.

The embodiments described take for example a propeller fitted to a thruster. However, these embodiments apply more generally to any variable-pitch propeller system in which similar problems arise, for example wind turbines or tidal turbines.

[0040] FIG. 1 schematically and partially illustrates, in a side view and in section, an embodiment of a propeller 1 with an automatic variable-pitch propeller. According to this embodiment, the thruster 1 comprises a propeller 11 consisting of two blades 111 and 112. The blades 111 and 112 are arranged in opposition, perpendicularly to an axis 113 of rotation of the propeller 11. The axis 113 of rotation of the propeller 11 is, in Figure 1, parallel to the section plane. The blades 111 and 112 are mounted to pivot relative to a common axis 115, perpendicular to the axis 113 of rotation of the propeller 11. To facilitate understanding, the axis 115, around which the blades 111 and 112 pivot. 'helix 11, is, in Figure 1, oriented perpendicular to the cutting plane

A pivoting (or rotation) of the blades 111 and 112, around the axis 115, makes it possible to vary the pitch of the propeller 11 of the thruster 1. In particular, the pivoting, relative to the axis 115 , of the blade 111 of the propeller 11 modifies a pitch angle Q, or angle of attack, of the blade 111. Likewise, the pivoting, with respect to the axis 115, of the blade 112 of the propeller 11 modifies a pitch angle, or angle of attack, of the blade 112. The thruster 1 is therefore provided with a propeller 11 with variable pitch. In other words, the thruster 1 is a variable pitch thruster.

The angle Q corresponds, in this example, to an angle formed by a chord (straight line joining a leading edge to a trailing edge of a profile) of the blade 111 with respect to a normal to the axes 113 and 115. Likewise, the angle corresponds, still in this example, to an angle formed by a chord of the blade 112 with respect to a normal to the axes 113 and 115. According to a preferred embodiment, the pitch angle of the blade 112 has a value equal to that of the pitch angle Q of the blade 111. This makes it possible to balance the rotation of the propeller 11 around the axis 113, thus limiting the appearance of vibrations.

Assuming that we look at the thruster 1 from its rear part to its front part (from the right to the left, in Figure 1), a rotation of the propeller 11 in a clockwise direction (arrow 114) causes a flow (arrow 116, FLOW) of a fluid towards the rear of the thruster 1 at a speed v. The speed v of this flow depends in particular on:

a possible movement of the medium in which the propellant is located (current of the fluid);

the profile (or geometry) of the blades 111 and 112;

a speed w of rotation (or angular speed) of the propeller 11 around the axis 113; and

of the pitch of the propeller 11, that is to say of the angles Q and of pitch respectively modified by pivoting (arrow 116) of the blades 111 and 112 around the axis 115.

The speed w of rotation of the propeller 11 is, for example, imposed by a motor driving a shaft connected to the propeller 11. In the example of Figure 1, the more the angles of attack and Q increase , for a rotational speed w that is assumed to be constant, and the more the flow speed v increases.

In the example of Figure 1, the thruster 1 comprises a body 13 in which is arranged a cavity (or recess) forming a chamber 15. The body 13 of the thruster 1 has one or more orifices 131 not parallel to the 'axis 113 of rotation of the propeller 11. In Figure 1, for example, two orifices 131 are made in a direction perpendicular to the axis 113 of rotation of the propeller 11. The orifices 131 thus form through holes which open out inside the chamber 15.

[0047] According to one embodiment, the chamber 15 comprises a first compartment 151 separated from a second compartment 153 by a movable partition 17 or piston. In the example of FIG. 1, the first compartment 151 communicates, via the two orifices 131, with the outside of the chamber 15. The second compartment 153 of the chamber 15 is, as for him, completely closed and therefore does not communicate with the outside of the room 15.

In the example of Figure 1, the propellant 1 is immersed in a fluid, for example water, constituting an external environment where the chamber 15 and the propeller are placed in particular 11. The first compartment 151 of the chamber 15 is therefore, in Figure 1, filled with water. Water exchanges can thus occur freely, via the orifices 131 (or water intakes), between the interior and the exterior of the chamber 15. The second compartment 153 is, still in this example, preferably filled with a gas, for example air. The movable partition 17 provides, where appropriate, a dynamic seal between the first compartment 151 and the second compartment 153, so that the air contained in the second compartment 153 thus remains trapped therein whatever the position of the movable partition 17. .

We consider a flow of the fluid along the body 13, for example caused by a displacement of the propellant 1 in the middle, typically under the effect of a rotation, around the axis 113, of the two blades 111 and 112 of the propeller 11. Such a flow causes, by Venturi effect, a depression inside the first compartment 151 of the chamber 15. Assuming that a pressure PI prevails in the first compartment 151 and that a pressure P3 reigns in the second compartment 153, the value of the pressure PI decreases (the depression increases) then as the water flow speed v increases. Conversely, the value of the pressure PI increases (the depression decreases) as the speed v of water flow decreases.

The pressure P3 is chosen or adjusted so that at rest, that is to say for a zero flow speed v, the pressure P3 is lower than the pressure PI. The movable partition 17 thus occupies, for a zero speed v, a stowed position located near the front of thruster 1 (left, in figure 1).

It is assumed that the pressure PI decreases, by increasing the speed v, until it becomes lower than the pressure P3. The movable partition 17 is then pushed (or sucked) towards the rear of the thruster 1 (towards the right, in FIG. 1). This simultaneously causes, by increasing the volume of the second compartment 153, a decrease in the pressure P3. This decrease in pressure P3, opposing the decrease in pressure PI, tends to bring the movable partition 17 towards the front of the thruster 1 (towards the left, in FIG. 1). The movable partition 17 therefore becomes immobilized in an intermediate position allowing the pressures PI and P3 to balance or to compensate.

It is now assumed that the pressure PI increases, by reducing the speed v, until it becomes greater than the pressure P3. The movable partition 17 is then brought back towards the front of the thruster 1 (towards the left, in FIG. 1). This simultaneously causes, by reducing the volume of the second compartment 153, an increase in the pressure P3. This increase in pressure P3, opposing the increase in pressure PI, tends to push the movable partition 17 towards the rear of the thruster 1 (to the right, in FIG. 1). The movable partition 17 therefore becomes immobilized in another intermediate position allowing the new pressures PI and P3 to balance or compensate for each other.

In summary, the pressures P1 and P3 both tend to move the piston 17 in opposite directions. The piston 17 therefore comes to a standstill, at non-zero speed v, in a position resulting from a dynamic equilibrium being established between the pressures PI and P3.

According to the embodiment exposed in relation with Figure 1, the movable partition 17 comprises a rack 171 arranged parallel to the axis 113 of rotation of the propeller 11. On this rack 171 a pinion 173 engages. The pinion 173 is, in FIG. 1, kept integral with the blade 111 of the propeller 11. The rack 171 is mounted such that a displacement of the movable partition 17 towards the rear of the thruster 1 (towards the right, in FIG. 1) causes an increase in the pitch angle Q of the blade 111. A similar mechanism (not shown), making it possible to modify the angle of the blade 112 of the propeller 11, is also implemented.

As mentioned above, an increase in the speed v leads, by the Venturi effect, to a decrease in the pressure PI in the first compartment 151. This thus causes a displacement of the movable partition 17 towards the rear of the thruster 1 ( to the right, in figure 1). This movement of the movable partition 17 tends, by means of the gear consisting of the rack 171 and the pinion 173, to increase the angle Q of attack of the blade 111. Likewise, a decrease in the speed v leads, by Venturi effect, to an increase in the pressure PI in the first compartment 151. This thus causes a displacement of the movable partition 17 towards the front of the thruster 1 (towards the left, in FIG. 1). This movement of the movable partition 17 tends, via the rack 171 and the pinion 173, to reduce the angle Q of attack of the blade 111. Similar modifications take place, thanks to the movement of the movable partition 17, on the angle of attack of the blade 112. The displacement of the piston 17 in the chamber 15 between extreme positions thus leads to modifying the angles of attack Q and over an angular range of less than 90 °, preferably by around 15 °.

We can therefore, by the Venturi effect, automatically modify the angle of attack of the blades 111 and 112 by function of the speed v of water flow around the thruster 1. In other words, the movable partition 17 allows, by moving, to control the pitch of the propeller 11 as a function of the speed v. The thruster 1 is therefore well equipped with an automatic variable-pitch propeller 11. In other words, the thruster 1 is an automatic variable pitch thruster.

Alternatively, the medium in which the propellant 1 is placed is air. The first compartment 151 of the chamber 15 is, where appropriate, filled with air. A flow of air along the body 13 of the thruster 1 causes, by the Venturi effect, a depression in the first compartment 151. This depression tends, as explained above, to shift the piston 17 towards the rear of the thruster 1 (towards the right, in figure 1), therefore to increase the pitch of the propeller 11.

FIG. 2 schematically and partially illustrates, in a side view and in section, another embodiment of a propeller 2 with an automatic variable-pitch propeller.

The propellant 2 of FIG. 2 comprises elements common to the propellant 1 of FIG. 1. These common elements will not be detailed again below.

The thruster 2 of Figure 2 differs from the thruster 1 of Figure 1 mainly in that the thruster 2 comprises at least one additional or additional part 135. This part 135 forms, relative to an external surface of the chamber 15, a constriction 137 narrowing in the vicinity of the orifices 131. The constriction 137 is, in FIG. 2, accentuated by a particular geometry (or curve, or shape) of the body 13 of the thruster 2 near the orifices 131. The part 135 is, for example, a ring surrounding the body 13 and fixed to the thruster 2 in several places (not shown in the sectional view). The constriction 137 is adapted to locally accelerate the flow of the fluid in the vicinity of the orifices 131. In other words, the fluid flows locally, near the orifices 131, at a speed greater than the speed v overall flow. This local acceleration of the flow makes it possible to accentuate the Venturi effect and thus increase the depression produced inside the first compartment 151 of the chamber 15. In the example of FIG. 2, the pressure PI prevailing in the first compartment 151 of the thruster 2 will therefore, at an equal flow speed v, be less than the pressure PI prevailing in the first compartment 151 of the thruster 1 (FIG. 1).

According to a preferred embodiment, the thruster 2 also comprises, in addition to the two first orifices 131, one or more second orifices 133 parallel to the axis 113 of rotation of the propeller 11. In FIG. 2, for example, two second orifices 133 are made in the thruster 2. The orifices 133 thus form through holes (or water intakes) which open into the interior of the chamber 15. When the thruster 2 is immersed, water exchanges can thus occur freely, through the orifices 131 and 133, between the interior and the exterior of the chamber 15. In the example of FIG. 2:

the first compartment 151 communicates, via the two first orifices 131, with the outside of the chamber 15; and the second compartment 153 communicates, via the two second orifices 133, with the outside of the chamber 15. The second compartment 153 is then, in FIG. 2, no longer filled with air as in FIG. 1, but with water.

The second orifices 133 allow, when the flow speed v increases, to increase the pressure P3 prevailing inside the second compartment 153 of the chamber 15. The result is that an increase in the speed v not only causes a decrease, by Venturi effect, of the pressure PI, but also an increase of the pressure P3. In the example of FIG. 2, the pressures PI and P3 therefore both tend to move the piston 17 in the same direction, here towards the rear of the propellant 2 (towards the right, in FIG. 2), unlike the example of Figure 1 where the pressures P1 and P3 tend to move the piston 17 in opposite directions.

In order to constrain or limit this movement of the piston 17, the propellant 2 of FIG. 2 is, moreover, provided with a return spring 19, for example, with non-contiguous turns. The return spring 19 is arranged along the axis 113 of rotation of the propeller 11. This spring 19 bears:

on the one hand on a surface of the piston 17 delimiting the first compartment 151 of the chamber 15; and

on the other hand on an internal face of the compartment 151 located at the rear of the thruster 2.

The spring 19 thus tends, by a return force directed parallel to the axis 113, to push the movable partition 17 towards the front of the thruster 2 (towards the left, in FIG. 2), in other words towards a position corresponding to an extreme value of the pitch of the helix 11. The extreme value of the pitch of the propeller 11 is equivalent, in FIG. 2, to a minimum value of the pitch also called “small pitch”.

We thus come back to an operation equivalent to that of Figure 1, except that the piston 17 is immobilized, for each speed v, in a position resulting from a dynamic equilibrium being established either between the PI and P3 pressures only, but between:

on the one hand, the pressures PI and P3, which tend to push the piston 17 towards the rear of the thruster (towards the right, in FIG. 2); and

on the other hand the force exerted by the spring 19 of return, which tends to bring the piston 17 towards the front of the thruster (towards the left, in FIG. 2).

At zero speed v, the pressures PI and P3 are substantially equal. The position of the piston 17 is then located in front of the thruster 1 (on the left, in FIG. 2), that is to say in the position which corresponds to the small pitch of the propeller 11. When the speed v increases , the piston 17 compresses the spring 19 by moving to a position corresponding, in FIG. 2, to a maximum value of the pitch, also called “large pitch”, of the propeller 11.

An advantage of the embodiment explained in relation to FIG. 2 lies in the fact that the pitch of the propeller 11 of the thruster 2 is regulated by a force of hydrodynamic origin, linked in a one-to-one manner to the speed of 1 'flow.

Another advantage of the embodiment of Figure 2 over that of Figure 1 is that it is freed from a constraint of maintaining a dynamic seal between the compartments 151 and 153 of the chamber 15 The compartments 151 and 153 can, in fact, exchange small amounts of water, compared to the volumes of the compartments 151 and 153, without this however disturbing the operation of the mechanism for modifying the pitch of the. propeller 11. This makes it possible in particular to relax any precision constraints in the manufacture of the chamber 15 and of the piston 17.

The thruster described in Figure 1 or 2 further comprises a mechanism for automatically modifying the pitch of the propeller 11 consisting of a small number of components. This thruster 2 is therefore overall simpler to design, to produce and to develop than the existing automatic variable-pitch thrusters. Figure 3 illustrates schematically and partially, by side views (A) and (B) and in section, yet another embodiment of a propeller 3 with automatic variable pitch propeller.

The thruster 3 of Figure 3 comprises elements common with the thruster 2 of Figure 2. These common elements will not be detailed again below.

The thruster 3 of Figure 3 differs from the thruster 2 of Figure 2 mainly in that it is devoid of the gear consisting of the rack 171 (Figure 2) and the pinion 173 (Figure 2).

According to this embodiment, the piston 17 has an inclined surface 175, or inclined face, with respect to the axis 113 of rotation of the propeller. A cam 177 is adapted to bear (or roll, or slide) against the surface 175 to actuate the propeller pitch modification mechanism 11. In the example of Figure 3, the cam 177 is mounted at one end of the propeller. 'a lever 179. The other end of the lever 179 is held integral with the blade 111 of the propeller 11, or of the pivot pin 115. In other words, the gear consisting of the rack 171 (Figure 2) and the pinion 173 (Figure 2) is replaced, in Figure 3, by the inclined surface 175 of the piston 17, the cam 177 and the lever 179.

Views A and B illustrate different pitch positions.

It is considered, initially (view A), that the propeller 11 of the thruster 3 rotates at a speed w around the axis 113. The fluid flows towards the rear of the thruster 3 (arrow 116 ) at a speed vl, for example under the effect of a displacement of the thruster 3 caused by the rotation of the propeller 11. The blade 111 then forms, with respect to a normal to the axes 113 and 115, a certain angle of timing Q1. Likewise, the blade 112 then forms, with respect to a normal to the axes 113 and 115, a certain pitch angle a1.

For simplicity, we consider hereafter that the pitch angle of the blade 111 is always equal to the pitch angle of the blade 112. We are not interested in the variations of the angle of timing of the blade 111, the variations in the pitch angle of the blade 112 being effected by a similar mechanism.

It is then assumed that the speed of the flow increases (view B) to reach a value v2 greater than vl. The piston 17 then moves, as explained in relation to FIG. 2, in the direction of the rear of the thruster 3 (arrow 118), thus compressing the spring 19. Thanks to the inclined plane 175, the end of the lever 179 on which is mounted the cam 177 therefore approaches the axis 113. This causes a rotation (arrow 120) of the blade 111 about the axis 115. In view B, the blade 111 then forms, with respect to a normal to the axes 113 and 115, a new setting angle Q2 greater than the setting angle Q1 (view A). Likewise, the blade 112 then forms, with respect to a normal to the axes 113 and 115, a new pitch angle a2 greater than the pitch angle a1 (view A).

A thruster such as the thruster 3 is particularly suitable for equipping low-power craft, for example human-powered craft, where maximum efficiency of the propeller 11 is desired. The regulation of the pitch of the propeller 11 can then be easily adapted as a function of the physical capacities of a user of the boat, for example by installing a spring 19 having a different stiffness constant, or by modifying the shape of the cam. 177.

FIG. 4 shows, through views A and B in perspective and in cutaway, yet another embodiment of a propeller 4 with an automatic variable-pitch propeller. Views A and B illustrate different pitch positions.

The propellant 4 of FIG. 4 comprises elements in common with the propellant 3 of FIG. 3. These common elements will not be detailed again below.

The propellant 4 of FIG. 4 differs from the propellant

3 of FIG. 3 mainly in that piston 17 drives a slide 47 in translation. This slide 47 actuates a lever 45 connected to the blade 111. Another lever 45 (not shown) is also connected to the blade 112.

The body 13 of the propellant 4 is, in Figure 4, consisting of a hub 130 fitting into a cone 132. On the cone 132 is fixed the part 135 for accentuating the depression, caused by the Venturi effect, in the vicinity of the first orifices 131. The propeller 11 is fixed to a propeller shaft 43 passing through a part 41 for mounting to the system with which it is associated, for example a boat (not shown).

The propellant 4 is, in view A, shown in a position where the spring 19 is relaxed. This position corresponds to the small pitch of propeller 11.

The propellant 4 is, in view B, shown in a position where the spring 19 is completely compressed. This position corresponds to the large pitch of propeller 11.

FIG. 5 represents an example of a boat equipped with an automatic variable-pitch propeller thruster.

In the example of Figure 5, a boat 7 (for example, a human-powered boat or pedal boat) comprises at least one thruster 4 with automatic variable-pitch propeller, for example a single thruster 4. The thruster

4 is fixed to a hull 71 of the boat 7. The boat 7 is provided with a transmission 73 adapted to modify the speed of rotation of the propeller 11 of the thruster 4. The boat 7 also has foils 77 or adjustable profiled wings by means of a control device 75 or feeler 75 making it possible to gauge a sinking of the boat 7 with respect to the surface of the water.

The thruster 4 allows the boat 7 to sail on the water. When the boat 7 is sailing, the thruster 4 is placed in a flow of water, the overall speed v of which is equal to a speed of movement of the boat 7 on the water. The pitch of the propeller 11 of the thruster 4 is thus adapted or controlled as a function of the displacement speed of the boat 7. This allows, for example, a user of the boat 7, causing the propeller to rotate. 11 with the strength of his legs, to maintain a substantially constant pedaling rate whatever the speed of movement of the boat 7.

FIG. 6 partially shows an embodiment of a propeller 11 of the thruster.

According to this embodiment, the blade 111 of the propeller 11 has dimensions adapted according to the application. The blade 112, shown partially in FIG. 6, preferably has dimensions identical to those of the blade 111. For a human-powered craft, such as the craft 7 (FIG. 5), the blade 111 has a length, denoted LP, of approximately 240 mm, preferably equal to 240 mm.

It is assumed that the propeller 11 rotates, at an angular speed w, around an axis 113 of rotation, as explained previously in relation to Figures 1 to 5. A lower end 1111 of the blade 111 is arranged, relative to this axis of rotation 113, at a distance, denoted DA, of approximately 35 mm, preferably equal to 35 mm. Likewise, a lower end 1121 of the blade 112 is arranged, relative to the axis of rotation 113, at a distance DA of approximately 35 mm, of preferably equal to 35 mm. In other words, the lower ends 1111 and 1121 of the blades 111 and 112, respectively, are approximately equidistant from the axis of rotation 113, preferably equidistant from the axis of rotation 113. The lower ends 1111 and 1121 are also called "blade feet".

A quantity, called "geometric pitch", is defined as being equal to a distance theoretically traveled by the propeller 11 when its blades 111 and 112 make a complete turn around the axis of rotation 113. The geometric pitches of propeller 11 are as follows:

a large geometric pitch of approximately 1 m, corresponding to the setting angles Q2 and a2 (FIG. 3, view (B)) which is approximately negative; and

a small geometric pitch of approximately 0.67 m, corresponding to setting angles Q1 et al (FIG. 3, view (A)) approximately equal to -10 °.

The propeller 11, installed on the thruster 4 of the boat 7, thus makes it possible to achieve:

at high pitch, a thrust of about 110 N for a rotation speed w of about 400 rev / min, which corresponds, for the boat 7, to a displacement speed approximately equal to 20 km / h; and

in small steps, a thrust of about 120 N for a rotation speed w of about 400 rev / min, which corresponds, for the boat 7, to a displacement speed approximately equal to 10 km / h.

Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these various embodiments and variants could be combined, and other variants will be apparent to those skilled in the art. In particular, the implementation of any type of mechanism likely to transform the translational movement of the piston 17 in a pivoting movement of the blades 111 and 112 about their axis 115 is within the abilities of those skilled in the art based on the indications provided above.

Finally, the practical implementation of the embodiments and variants described is within the abilities of those skilled in the art based on the functional indications given above. In particular, it is possible to extend the embodiments described above to a configuration where the propeller 11 has a number of blades greater than two.

Claims

1. Device comprising a propeller (11) with variable pitch and means adapted to modify the pitch of the propeller (11) by the Venturi effect.

2. Device according to claim 1, wherein an external flow (116) of a fluid generates, by Venturi effect, a depression in a first compartment (151) of a chamber (15) comprising one or more first orifices (131). ) not parallel to an axis (113) of rotation of the propeller (11), a variation of this depression causing a displacement of a movable partition (17) actuating a mechanism for modifying the pitch of the propeller (11)

3. Device comprising:

a variable-pitch propeller (11);

a chamber (15) comprising one or more first orifices (131) not parallel to an axis (113) of rotation of the propeller (11);

a movable partition (17) delimiting, inside the chamber (15), a first compartment (151) communicating with the outside through this or these first orifices (131); and

a mechanism for modifying the pitch of the propeller (11), associated with the movable partition (17).

4. Device according to claim 3, wherein a variation of a vacuum, in the first compartment (151), causes a change in the pitch of the propeller (11).

5. Device according to claim 2 or 4, wherein an increase in the vacuum causes an increase in the pitch of the propeller (11).

6. Device according to any one of claims 2, 4, or 5, wherein a decrease in the vacuum causes a decrease in the pitch of the propeller (11).

7. Device according to any one of claims 2 to 6, wherein at least one additional part (135) forms, relative to an external surface of the chamber (15), a constriction (137) in the vicinity of this or these. first orifices (131).

8. Device according to any one of claims 2 to 7, wherein the movable partition (17) further defines, inside the chamber (15), a second compartment (153) communicating with the outside by a or several second orifices (133) parallel to the axis (113) of rotation of the propeller (11).

9. Device according to any one of claims 2 to 8, wherein the movable partition (17) is linked to a spring (19) for returning to a position corresponding to an extreme value of the pitch of the propeller (11).

10. Device according to any one of claims 2 to 9, wherein the movable partition (17) is a piston having a surface (175) inclined relative to the axis (113) of rotation of the propeller (11). ), on which rests a cam (177) adapted to actuate the mechanism for changing the pitch of the propeller (11).

11. Device according to any one of claims 2 to

10, in which the movable partition (17) is associated with a gear, consisting of a rack (171) and a pinion (173), adapted to actuate the mechanism for modifying the pitch of the propeller (11).

12. Device according to any one of claims 2 to

11, in which the mechanism for changing the pitch the propeller (11) modifies an angle (q,; Q1, al; Q2, a2) of the pitch of the blades (111, 112) over an angular range of less than 90 °, preferably of the order of 15 °.

13. Device according to any one of claims 1 to

12, in which the propeller (11) comprises at least two blades (111, 112) arranged radially and separated from the axis (113) of rotation by a distance (DA) of approximately 35 mm, preferably equal to 35 mm, these blades having a length (LP) of about 240 mm, preferably equal to 240 mm.

14. A propellant device (1; 2; 3; 4) comprising a device according to any one of claims 1 to

13.

15. Human-powered craft (7) comprising at least one propellant device according to claim 14.

16. Energy recovery device, comprising a device according to any one of claims 1 to 13.