WO2015087256A1

WO2015087256A1 - Steering system for a propeller-driven vehicle

Info

Publication number: WO2015087256A1
Application number: PCT/IB2014/066761
Authority: WO
Inventors: Marco MASTRANGELI; Angelo ODETTI
Original assignee: Hovertech Ltd
Priority date: 2013-12-12
Filing date: 2014-12-10
Publication date: 2015-06-18

Abstract

A steering system for a vehicle, comprising at least one propulsion unit (2) comprising drive means for driving at least one propeller (21). The steering system comprises flow diverting means (3) located downstream from said propulsion unit (2). The orientation of said diverting means (3) is adjusted relative to the airflow generated by the propeller (21) by means of a control member (5), said flow diverting means (3) consisting of at least two flow diverting systems, said at least two systems being symmetric with respect to the direction of the airflow generated by the propeller. Each of the at least two flow diverting systems (3) is adapted to be independently driven by said control member (5). Said diverting system is characterized by a surface that allows backward travel when in the maximum open state, and by an axis of rotation that lies beyond the surface of the aileron.

Description

STEERING SYSTEM FOR A PROPELLER-DRIVEN VEHICLE The present invention relates to a steering system for a vehicle, said vehicle comprising at least one propulsion unit comprising drive means for driving at least one propeller.

Therefore, the present invention is particularly suitable for use in all the means that use propellers as propulsion means, as these vehicles comprise steering members that do not afford precise and abrupt direction changes.

Namely, direction adjustments in these vehicles are particularly difficult, even to experienced pilots .

This affects maneuverability of such vehicles. A number of known vehicles use propeller-driven propulsion systems, such as hovercrafts, airboats, airships, submarines, etc.

Particularly, a hovercraft is a vehicle that uses a system for generating an air film which acts as a lubricant in the part that would otherwise contact the support surface, thereby reducing friction with the surface to very low levels. Thus, it has amphibious capabilities, allowing it to operate in seas, rivers and flat soils. In order to achieve relatively high speeds, while operating in confined environments and with obstacles such as banks, rocks, manufactured parts or other boats, it must be as agile and have as small a radius of curvature as possible. Due to isolation from the "overflown" surface no steerable friction drive means are provided, such as wheels or rudders, which are designed for steering or braking in other vehicles; conversely, steering is performed by airflows and is forcibly restricted by the thrust of the propeller. Low absolute velocities, of less than 100 km/h, do not allow effective operation of passive rudders, similar to those of aircrafts, and the propulsion flow should be conveniently addressed to movable conveyors, by acting on stern propellers, if any, by rotations, different rotation speeds or blade inclinations.

Hovercrafts generally operate by directly changing the flow of the main propeller, with the help of control surfaces, and large hovercrafts combine the actions of the various propellers, with different combinations of thrust directions and intensities, and possibly with reversed flow directions in response to very short radii of curvature or rotations about their axes.

Although this may result in a considerable action, the hovercraft system has poor steerability and driving precision as compared with wheeled or friction-driven systems. When steering wheeled vehicles, the rudder is operated to change the trajectory along which the vehicle was previously running: the trajectory is dependent on the direction of the steering wheels. Here, the force component associated with the lateral friction generated between the tire and the ground imparts a considerable centripetal force to the vehicle, which acts on the center of gravity and easily allows it to follow a curved trajectory. Likewise, the same result is obtained in boats by acting upon a submerged rudder .

Single-propeller hovercrafts may simulate a behavior similar to the action of multiple propellers, and a partially improved radius of curvature may be obtained by partial motion reversal in part of the flow in the inner side of the desired direction.

With an active force, this system simulates the different thrusts of multiple propellers but, in case of a sharp turn, it has a thrust component that opposes the forward motion and when wide spaces are available, rudders are preferably used without flow reversal .

The use of differently channeled airflows, which are efficient but have a limited maximum power, involves low response, which has to be compensated for by efficient and quick controls, which may be set with a given advance only by experienced pilots.

Therefore, the systems that provide propeller flow diversion should be simply controlled and allow intuitive airflow directing operation, for optimized hovercraft control .

Furthermore, these systems must be particularly durable and resistant to wear, as they are often used in harsh environmental and operating environments.

Also, while the above mentioned problems have been discussed with reference to hovercrafts, these drawbacks may be easily found to apply to all steering systems for vehicles that use airflow for propulsion, including the vehicles in which the propulsion unit is submerged, such as submarines. Therefore, there exists a yet unfulfilled need for a steering system for propeller-driven vehicles that is efficient, easy to use, and allows intuitive control of the vehicle itself, without involving the drawbacks of prior art hovercrafts.

The present invention fulfills the above purposes by providing a steering system as described hereinbefore, which comprises flow diverting means located downstream from the propulsion unit, the orientation of the diverting means being adjusted relative to the airflow generated by the propeller through a control member.

Furthermore, the flow diverting means consist of at least two flow diverting systems, which are symmetrical with respect to the direction of the airflow generated by the propeller, each of the at least two flow diverting systems being adapted to be independently actuated through the control member.

Therefore, the deflection of the propeller flow is controlled by one control signal only, which can simultaneously or independently and intuitively set both flow diverting systems to steer the vehicle.

Further advantages will be clearly understood from the following characteristics of the steering system of the present invention, namely those concerning the provision of the flow diverting systems and the control member.

Thus, according to a preferred embodiment, each of the two flow diverting systems consists of at least one aileron, which is rotatably mounted about a horizontal axis of rotation perpendicular to the fore-and-aft axis, such that the aileron rotates from the maximum open position, in which it has its aileron surface parallel to the flow direction, when the vehicle is in the forward travel state, in which the airflow generated by the propeller is allowed to pass parallel to the fore-and-aft axis, to a maximum closed position, in which it has its aileron surface perpendicular to the flow direction, when the vehicle is in the backward travel state, in which the airflow is intercepted and reversed.

As described below, the ailerons-rudders of the two flow diverting systems may be actuated simultaneously or independently of each other.

In either case, as they rotate, their aileron surface tends to oppose the generated airflow whereby in addition to an airflow diverting action they have a braking action or even a reversing action in the maximum closed position, which can be advantageously obtained in a very short time even at the maximum propeller power.

This advantage will be more readily understood from the description of the control member.

Furthermore, according to a further embodiment, the aileron comprises at least two surfaces, lying on two incident planes, having a common straight line.

The two planes join smoothly at their point of incidence, such that when the aileron is in its maximum closed position, it has a concave profile oriented toward the propulsion unit.

It will be appreciated that the arrangement and rotation of the aileron allows precise control of the vehicle.

Indeed, the aileron surface may either have no impact on the airflow, for undisturbed forward motion of the vehicle, or interfere with the airflow until it reverses the motion of the vehicle.

As more clearly shown by the disclosure of a few illustrated exemplary embodiments, as the ailerons rotate between the maximum open state and the maximum closed state, the vehicle may be steered in different manners, in response to the diversified rotary motion of each aileron.

Furthermore, especially with particular reference to vehicles such as hovercrafts or airboats, the horizontal arrangement of the ailerons also provides vehicle trim control, in terms of lowering/lifting of the vehicle relative to the ground, due to a component of the vertical thrust created by the impact of the propeller flow with the aileron surface of the aileron.

Preferably, each of the two flow diverting systems consists of at least two of said ailerons, which have the aileron surfaces perpendicular to the flow direction in the maximum closed position, to form a continuous surface opposing the airflow.

It shall be noted that the ailerons of the flow diverting systems are designed to convey the airflow in a direction that changes as they rotate, whereby the ailerons oppose the airflow in the direction in which they intercept such flow and deflect it relative to its normal direction parallel to the direction of the airflow as it is generated by the propeller.

Furthermore, the axis of rotation of the aileron is incident upon both of said planes on which the aileron surfaces lie. As a result the profile of the ailerons is neither perpendicular nor parallel to the fore-and- aft axis or the direction of flow, which will afford thrust optimization through the various aileron positions.

Preferably, the diverting means are connected via transmission means to a control member consisting of a single control element having a finite number of degrees of freedom.

The displacement of the control member causes the displacement of the flow diverting means to provide a corresponding directional behavior or travel state of the vehicle.

Particularly referring to hovercrafts or airboats, the use of a single control member for adjusting the direction of the vehicle, facilitates steering thereof.

Indeed, the steering system of the present invention combines the control of various types of motion affecting members, particularly those that affect the motion direction of the hovercraft, into a single control member, which will only engage the two hands of the pilot, with the movements of the individual motion affecting members being converted into simple intuitive movements of the control member .

Unlike prior art systems, the steering system of the present invention only requires the use of the arms and, as shown below, the structure may be sturdy enough to be used as a support; the pilot may be in a sitting or standing position, sit upon cushioned "saddle" seats or stand with his/her legs slightly bent and ready to absorb wave impacts: this is the best position to detect the trim of the hovercraft and allows minor weight displacements on the legs which, at high speed and on the cushion, can effectively correct the ratio of the weight of the pilot to that of the launched vehicle.

This configuration can also make the movement of the control member similar to the typical movement of the control members of the other vehicles, in which a straight trajectory is diverted to the right or left by a corresponding right or left rotation of the control member.

Therefore, the steering system of the present invention is intuitive, with each position of the control member corresponding to an action of the flow diverting means, which will both reduce the pilot training time and also allow the pilot to instinctively perform the actions that would be expected for a similar control, especially under emergency conditions.

In accordance with a possible embodiment, the control member may comprise at least one lever control or the like, which is adapted to control the operation of the drive means to drive the at least one propeller of the propulsion unit.

As discussed above, particularly referring to hovercrafts or vehicles that need other controls, such as acceleration, in addition to steering controls, such control may be integrated on the control member through devices such as levers or the like.

This will allow the vehicle to be controlled by only using the control member, as the accelerator may be divided into two separate controls placed in different positions on the control member.

Furthermore, with this arrangement the vehicle on which the control member is mounted may be controlled using a single hand, which is sometimes required, at low speeds, in mooring operations, with the pilot coming alongside while maintaining some steering control.

Preferably, the control member consists of a handlebar, a joystick or the like having two degrees of freedom, i.e. a first rotation about an axis perpendicular to the horizontal plane and a second rotation about an axis parallel to the horizontal plane and perpendicular to the fore-and-aft axis.

The combination of these two movements affords control through all end and intermediate positions, required for low- and high-speed steering, using a single handlebar on the drive side.

Preferably, the first rotation controls the orientation of the two flow diverting systems independently of each other, whereas the second rotation controls the orientation of the two flow diverting systems at the same time.

As clearly shown by the following exemplary embodiments, with this arrangement the control member may integrate other features in addition to left- right steering, such as reversing and trim control, which are obtained by forward and back movements of the control members .

■ The advantages of the steering system of the present invention and the way of making its components are mainly simple construction, intuitive control and easy maneuverability. These advantages are achieved by a steering system which is composed of a few easily assembled and replaceable elements, affording quick maintenance and construction.

These have been the design criteria particularly for the flow diverting means and the control member.

According to a further improvement, the control member has limit stop elements for limiting the amplitude of the first and/or said second rotations, an elastic element being provided for maintaining the control member in a neutral position when no external force acts thereupon.

This improvement is particularly beneficial when the transmission means consist of a first push-pull cable for connecting the control member with one of the at least two flow diverting systems and a second push-pull cable for connecting the control member with the other of the flow diverting systems.

Alternatively, the transmission means may consist of an electronic controller connected to the control member and the flow diverting systems, which electronic controller converts the movement of the control member into corresponding control signals for the flow diverting systems, which control signals control the movement of said flow diverting systems.

For example sensors, such as accelerometers may be provided for detecting the movement of the control member and sending an input signal to the electronic controller.

The controller processes these signals according to predetermined settings to generate control signals for position adjustment of the flow diverting systems . Particularly, these control signals may contain information about the rotary motion of the ailerons, according to the direction that has been set by the control member.

Also, an electric, hydraulic or electro- hydraulic system may be provided, i.e. hydraulic actuators may be provided downstream from the control member to move the ailerons of the flow diverting systems.

The actuators may be connected to the control member either via hydraulic conduits or via the electronic controller.

Finally, the combination of the first and second rotations of the control member may be designed to independently regulate the amplitude of rotation of the ailerons of the two flow diverting systems.

These and other features and advantages of the present invention will appear more clearly from the following description of a few embodiments, illustrated in the annexed drawings, in which:

Figs, la to lc show three views of a hovercraft having the steering system of the present invention;

Figs. 2a to 2h show various views of the flow diverting systems in the steering system of the present invention;

Figs. 3a to 3c show three views of the control unit of the system of the present invention;

Figs. 4a and 4b show a possible embodiment of the control member of the system of the present invention;

Figs. 5a to 5d show various positions of the control member and the ailerons of the system of the present invention; Figs. 6a to 6e show the steering system of the present invention installed on various types of vehicles.

It shall be understood that the variant embodiments as shown in the accompanying figures are only given by way of illustration and for clearer explanation of concepts and advantages of the steering system of the present invention, and shall not be intended to limit the inventive concept of the present patent application, which consists in the provision of a steering system for a propeller-driven vehicle that allows both vehicle trajectory changes and propulsion, by intuitive movements of the pilot, while ensuring simple construction, strength and durability of the system.

It shall be further noted that while Figures la to 5d show the variant embodiment of the system of the present invention when mounted on a hovercraft vehicle, the features as described above concerning both the flow diverting systems and the control member will clarify that the steering system of the present invention may be mounted on any propeller- driven vehicle, without difficulty and without requiring changes to the steering system.

Figure la shows a possible embodiment of the steering system of the present invention, which is preferably designed for a hovercraft, comprising at least one hull 1 with a propulsion unit 2 mounted thereon, which comprises drive means for driving at least one propeller 21.

Furthermore, the steering system comprises flow diverting means 3, located downstream from the propulsion unit 2, whose orientation is regulated relative to the airflow generated by the propeller 21 through a control member 5.

The flow diverting means 3 consist of at least two flow diverting systems, which are symmetric with respect to the fore-and-aft axis X of the hovercraft and can be actuated in different manners using the control member 5.

Particularly, Figure lc shows the possibility of using the steering system of the present invention on a hovercraft that has multiple propulsion units 2.

Here, each propulsion unit 2, namely each propeller 21, may have a flow diverting system 3 associated therewith, as shown in Figure lc, without requiring any change to the steering system, concerning the features as described above and below.

Each of the two flow diverting systems consists of at least one aileron 31, as shown in Figure 2a, which is rotatably mounted about a horizontal axis of rotation C perpendicular to the fore-and-aft axis X, such that the aileron 31 rotates from the maximum open position, in which it has its aileron surface parallel to the flow direction, when the hovercraft is in the forward travel state, in which the airflow generated by the propeller 21 is allowed to pass parallel to the fore-and-aft axis X, to a maximum closed position, in which it has its aileron surface perpendicular to the flow direction, when the hovercraft is in the backward travel state, in which the airflow is intercepted and reversed,

Furthermore, the aileron 31 comprises at least two surfaces, lying on two incident planes, having a common straight line. The two planes join smoothly at their point of incidence, such that when the aileron 31 is in its maximum closed position, it has a concave profile oriented toward the propulsion unit 2.

Particularly referring to the figures, the aileron 31 has a profile that follows two mutually incident segments A and B, see Figures 2b and 2c, such profile having a concavity that faces the propulsion unit 2.

The two segments A and B are oriented to form an obtuse angle toward the propulsion unit 2.

Particularly referring to Figure lb, the steering system of the present invention is composed of two flow diverting systems 3, each consisting of a plurality of ailerons 31 arranged with their longitudinal axes parallel to one another.

Particularly, the right flow diverting system is in its maximum open position, i.e. it allows the passage of the flow of the propeller 21, whereas the left flow diverting system is in its maximum closed position, i.e. each aileron 31 has its aileron surface opposed to the flow of the propeller 21.

Preferably, the left ailerons 31 in their maximum closed position have their aileron surfaces perpendicular to the flow direction, to thereby create a continuous surface that opposes the direction of the airflow parallel to the fore-and-aft axis, and such surface allows the flow to be directed outwards and conveyed in the reversed thrust direction.

Figures 2a and 2c show the particular shape of the aileron 31, and particularly Figure 2c shows a top view of the aileron 31. The profile of the aileron follows the two lines A and B, and is particularly composed of three parts 311, 312 and 313, which are smoothly joined together.

The first part 311 has a convexity that faces the propulsion unit 2 and is tangent to the line A in two or more points, the second part 312 is a curve that is tangent to both lines A and B and has a concavity that faces the propulsion unit 2, whereas the third part 313 has a concavity that faces the propulsion unit 2 and is incident to the line B in two or more points.

As clearly shown in Figure 2a, each aileron 31 is a cylinder generated by an open curve. Each plane orthogonal to the generators of the surface intersects such surface in a curve that is the directrix of the cylinder.

As shown in Figures 2d to 2f, preferably the axis of rotation C of the ailerons 31 is incident to at least one of the two segments A and B.

Particularly, the axis of rotation C is incident both to the first part 311 and to the second part 313 of the aileron 31.

Particularly, with the position of the axis of rotation C and the shape of the aileron 31 a single element, i.e. the aileron 31 will provide different behaviors of the hovercraft according to different positions of the aileron 31, as shown in Figure 2f.

As clearly shown by the description hereinbelow, the particular shape of the aileron 31 and the position of the axis of rotation C provide a control surface that generates, in combination with the airflow and in a variable manner as it rotates, a thrust acting transverse to the fore-and-aft axis of the hovercraft.

In addition to the above described aspects, the particular inclination of the two planes that form the aileron 31 afford synergistic operation of the left flow diverting system and the right flow diverting system, at predetermined angles of rotation of the ailerons 31, to create a transverse thrust acting in a common direction.

This may occur, for instance, when the angles of rotation of the ailerons of the right flow diverting system range from 0° to 90° and those of the ailerons of the left flow diverting system range from -30° to 0°, a common hovercraft steering component being generated at such values.

For a better understanding of the hovercraft behavior in response to the rotation of the aileron 31, reference is made in the figures to three main axes, an axis X (fore-and-aft axis) , a vertical axis Z, and an axis Y perpendicular to X and Z.

Particularly, when the aileron 31 is in its maximum open state, it only exposes its profile to the airflow generated by the propeller 21, whereby negligible airflow deflection is provided and the hovercraft may continue its forward travel, with no diversion or bend.

When the aileron 31 is in its maximum closed state, it exposes its entire aileron surface to the airflow, and acts as a flow reverser, such that the hovercraft is pushed back, i.e. in the backward direction.

From the maximum open state, as soon as the aileron 31 starts to rotate, its aileron surface opposes the airflow of the propeller 21, thereby causing the hovercraft to change its trajectory, by acting as a rudder/flap combination.

For a better understanding of this action, the figures show the aileron surface as approximated to two joined surfaces, particularly a surface containing the line A and a surface containing the line B.

Particularly referring to Figures 2g and 2h, a designates the angle formed by the line A with the airflow, such angle ranging from 0° to 90° and causing the airflow to be diverted sideways.

On the other hand β designates the angle formed by the line B with the airflow, such angle being always greater than 90° and having the purpose of reversing the direction of flow and, as a result, the thrust of the propulsion unit 2.

From the maximum open state of the ailerons 31, if the rotation of the aileron 31 about the axis of rotation C ranges from 0° to 90°, then the airflow impacts on the aileron surface and generates a force that may be divided into three different components, along the X, Y and Z axes.

At first it creates a downwardly directed component along the axis Z. The Z axis component, which acts on the center of pressure of the aileron

31, affects trim and transverse stability of the hovercraft.

Indeed when this force is multiplied by the transverse arm relative to the center of gravity, it creates a hovercraft inclining moment, whereas when it is multiplied by the longitudinal arm relative to the center of gravity, it creates a downward pushing moment on the stern.

A X component is also generated, which opposes resistance to the forward thrust of the hovercraft.

When this force is multiplied by the arm obtained from the distance between force application and the center of gravity of the vehicle, a steering moment is obtained.

Finally, there is a transverse component which acts on the center of pressure of the aileron and allows orientation of the hovercraft and adjustment of its transverse stability.

When this component is multiplied by its longitudinal arm relative to the center of gravity, it creates at steering moment that allows the aileron 31 to operate as a common vertical rudder.

As clearly shown by the above described features, the shape of the aileron 31 provides a transversely acting component, i.e. a Y-axis component, which may be of considerable magnitude and would not be obtained using prior art ailerons, which are horizontally arranged with the axis of rotation lying on the aileron surface, and have a single X- axis component.

Conversely, if such component is multiplied by its transverse arm with respect to the center of gravity, it creates a moment that inclines the hovercraft in a direction opposite to that of the moment generated along the Z-axis.

From the maximum open state of the ailerons 31, if the rotation of the aileron 31 about the axis of rotation C ranges from -30° to 0°, then the airflow impacts on the aileron surface and generates a force that may be divided into three different components, along the X, Y and Z axes.

At first it creates an upwardly directed component along the axis Z. The Z axis component, which acts on the center of pressure of the aileron 31, affects trim and transverse stability of the hovercraft.

Indeed when this force is multiplied by the transverse arm relative to the center of gravity, it creates a hovercraft inclining moment, whereas when it is multiplied by the longitudinal arm relative to the center of gravity, it creates a downward pushing moment on the bow.

When this component is multiplied by the longitudinal arm relative to the center of gravity, it creates at steering moment that allows the aileron 31 to operate as a common vertical rudder.

As discussed above, the steering moment is obtained due to the shape of the aileron 31 as shown in the previous figures.

Conversely, if such component is multiplied by its transverse arm with respect to the center of gravity, it creates a moment that inclines the hovercraft in a direction opposite to that generated by the Z-axis component.

As discussed above, the two systems composed by the right ailerons 31 and the left ailerons 31 may be controlled by the control member 5.

Figures 3a to 3c show a possible embodiment of the control member 5 of the steering system of the present invention.

As shown in Figures 3a to 3c, the control member 5 consists of a handlebar, a joystick or the like having two degrees of freedom, i.e. a first rotation B about an axis perpendicular to the horizontal plane and a second rotation φ about an axis parallel to the horizontal plane and perpendicular to the fore-and- aft axis.

Advantageo sly, the first rotation B controls the orientation of the two flow diverting systems 3 independently of each other, whereas the second rotation φ controls the orientation of the two flow diverting systems at the same time.

The handlebar 5 is connected to transmission means for controlling the flow diverting means 3, and in the illustrated variant embodiment the transmission means consist of push-pull cables, particularly a first push-pull cable 41 and a second push-pull cable 42.

The handlebar 5 may rotate about its own axis and about an axis orthogonal thereto, allowing elongation of the push-pull cables either for rotation about the main axis, i.e. the rotation β, or for rotation about the secondary axis, i.e. the rotation φ. Particularly referring to the figures, the control member comprises at least one lever control 51 or the like, which is adapted to control the operation of the drive means to drive the at least one propeller 21 of the propulsion unit 2.

The handlebar 5 may comprise multiple levers 31 to integrate various controls in addition to the actuation of the propulsion unit, such as trim control, etc.

Figures 4a and 4b show a variant embodiment of the system of the present invention, particularly of the control member 5, which has limit stop elements 52, 53 for limiting the amplitude of the first and/or second rotations, an elastic element being further provided for maintaining the control member 5 in a neutral position when no external force acts thereupon.

Particularly, the figures show two possible embodiments of the limit stop elements 52 and 53, dictated by the particular construction of the control member 5.

The limit stop element 51 restricts the amplitude of the rotation β by engaging a tooth in a corresponding seat, whereas the amplitude of the rotation φ is restricted by elements 53 that stop the travel of the handlebar 5 at its front and rear ends.

In accordance with a possible embodiment, the transmission means may consist of an electronic controller connected to the control member 5 and the flow diverting systems 3, which electronic controller converts the movement of the control member 5 into corresponding control signals for the flow diverting systems, which control signals control the movement of the flow diverting systems.

Particularly, the control signals are adjustments of the rotation of the ailerons 31, i.e. parameters obtained by predetermined and preset algorithms consisting of functions that regulate the inclination of the ailerons 31 according to the position of the control member 5.

Irrespective of the type of transmission, the description of the features of the steering system of the present invention clearly shows that the combination of the first and second rotations, β e φ, of the control member 5 regulates the rotation of the ailerons 31 of the flow diverting systems in an independent manner, thereby regulating the behavior of the hovercraft.

Such combination of rotations provides all the movements required for the desired maneuvers, based on the above described effects of the rotation of ailerons 31 on the airflow and the thrust of the hovercraft .

As clearly shown in the figures, the handlebar 5 can provide full hovercraft control, by regulating direction, acceleration and air cushion formation.

Particularly referring to the figures, the handlebar 5 is connected by the first push-pull cable 41 to the right flow diverting system and by the second push-pull cable 42 to the left flow diverting system.

This configuration provides such a behavior of the handlebar 5 that the first rotation β controls the orientation of the two flow diverting systems independently of each other, whereas the second rotation φ controls the orientation of the two flow diverting systems at the same time.

This is because the first rotation β causes diversified displacements of the first cable 41 and the second cable 42, whereas the second rotation φ causes equal back and forth displacements of the first cable 41 and the second cable 42.

This aspect is clearly shown in Figures 5a to

5d.

Figure 5a shows that the rotation φ simultaneously displaces the ailerons 31 of both flow diverting systems, and particularly the maximum closed state is shown here, with all the ailerons 31 rotating to create a continuous surface opposing the airflow.

On the other hand, Figures 5b e 5c show that the rotation β of the handlebar 5, provides diversified displacement of the cables 41 e 42 and hence the ailerons 31 of the left and right flow diverting systems for diversified steering of the hovercraft, particularly for leftward or rightward rotation of the hovercraft.

Finally, Figure 5d shows that the combination of rotations of the handlebar 5 may be used to obtain any position of the ailerons 31.

Particularly referring to this figure, the ailerons 31 of the right flow diverting system are in the maximum closed state, which is obtained for both right and left systems by the rotation <p, followed by a rotation β for opening the ailerons 31 of the left flow diverting system. The above description clearly shows that the steering system of the present invention may be easily installed on any known propeller-driven vehicle, i.e. on any vehicle that is driven by a propeller-generated airflow.

Indeed, the above described flow diverting systems are not associated with particular vehicles, and the only condition is that they can divert the airflow direction to correct the trajectory of the vehicle.

Likewise, the above described control member 5 may be used on any vehicle, without requiring changes thereto.

As mentioned above, the transmission means between the control member 5 and the flow diverting systems 3 may be adapted to better meet the requirements of the vehicle on which the steering system of the present invention is mounted.

Thus, the transmission means may be cable- operated, consist of an electronic controller, or be hydraulic or electro-hydraulic transmission means.

Furthermore, these transmission means may be power-assisted.

Figures 6a to 6e show that the steering system of the present invention may be provided on any propeller-driven vehicle and provide examples thereof.

Particularly, Figure 6a shows the steering system of the invention mounted on an airboat.

Here, the above described features of the control member 5 and the transmission means 4 are adapted to airboat vehicles. Figures 6b and 6c are rear and front views respectively of the inventive steering system, particularly the flow diverting means that are mounted on the propulsion units of an airship.

Finally, Figures 6d and 6e show that the steering system of the present invention may be also installed on propeller-driven underwater vehicles, and particularly an autonomous underwater vehicle (known as AUV) , Figure 6d, and a submarine. Figure 6e, are shown.

Obviously, in the cases as shown in Figures 6b to 6e, the control member will preferably send control signals for aileron positioning through an electronic controller.

Finally, it shall be noted that the control member may be any control member known in the art, such as a steering wheel, a handlebar, a joystick, a rudder, an automatic or manual electronic control unit, etc.

Claims

1. A steering system for a vehicle/ said vehicle having at least one propulsion unit (2) comprising drive means for driving at least one propeller (21) , characterized in that

said steering system comprises flow diverting means (3) located downstream from said propulsion unit (2) ,

the orientation of said diverting means (3) being adjusted relative to the airflow generated by the propeller (21) by means of a control member (5) , said flow diverting means (3) consisting of at least two flow diverting systems, said at least two systems being symmetric with respect to the direction of the airflow generated by said propeller,

each of said at least two flow diverting systems (3) being adapted to be independently driven by said control member (5) .

2. A system as claimed in claim 1, wherein each of the two flow diverting systems consists of at least one aileron (31) , said aileron (31) being rotatably mounted about a horizontal axis of rotation (C) perpendicular to the fore-and-aft axis (X) , such that said aileron (31) rotates from a maximum open position, in which said aileron (31) has the aileron surface parallel to the flow direction, when the hovercraft is in the forward travel state, in which the airflow generated by the propeller (21) is allowed to pass parallel to the fore-and-aft axis, to a maximum closed position, in which said aileron (31) has the aileron surface perpendicular to the flow direction, when the hovercraft is in the backward travel state, in which the airflow is intercepted and reversed.

3. A system as claimed in claim 2, wherein said aileron (31) comprises at least two surfaces, lying on two incident planes, having a common straight line,

said planes joining smoothly at their point of incidence, such that when said aileron (31) is in its maximum closed position, it has a concave profile oriented toward said propulsion unit (2) .

4. A system as claimed in one or more of the preceding claims, wherein each of the two flow diverting systems (3) consists of at least two of said ailerons (31) , said two ailerons (31) having the aileron surfaces perpendicular to the flow direction in the maximum closed position, to form a continuous surface opposing the airflow.

5. A system as claimed in one or more of the preceding claims, wherein said axis of rotation (C) is incident upon both of said planes.

6. A system as claimed in claim 1, wherein said diverting means (3) are connected via transmission means (4) to a control member (5) consisting of a single control element having a finite number of degrees of freedom,

the displacement of said control member (5) causing the displacement of said flow diverting means (3) to provide a corresponding directional behavior or travel state of the vehicle.

7. A steering system as claimed in claim 6, wherein said control member comprises at least one lever control (51) or the like, which is adapted to control the operation of said drive means to drive the at least one propeller (21) of said propulsion unit (2) .

8. A system as claimed in one or more of the preceding claims, wherein said control member (5) consists of a handlebar, a joystick or the like, said handlebar having two degrees of freedom, i.e. a first rotation about an axis perpendicular to the horizontal plane and a second rotation about an axis parallel to the horizontal plane and perpendicular to the fore-and-aft axis.

9. A system as claimed in claim 8, wherein said first rotation controls the orientation of said two flow diverting systems independently of each other, whereas said second rotation controls the orientation of said two flow diverting systems at the same time.

10. A system as claimed in claim 8, wherein said control member (5) has limit stop elements (52, 53) for restricting the amplitude of said first and/or said second rotations, an elastic element being provided for maintaining said control member (5) in a neutral position when no external force acts thereupon.

11. A system as claimed in one or more of the preceding claims 1 to 10, wherein said transmission means (4) consist of an electronic controller connected to said control member (5) and the flow diverting systems, said electronic controller converting the movement of said control member into corresponding control signals for said flow diverting systems, which control signals control the movement of said flow diverting systems.

12. A system as claimed in one or more of the preceding claims, wherein the combination of said first and said second rotations of the control member (5) independently regulates the amplitude of rotation of said ailerons (31) of said flow diverting systems (3) .