DESCRIPTION

A FLYING AIRCRAFT SUPPORTED BY A BIROTOR HAVING DIHEDRAL BLADES

The subject of this invention is a flying aircraft, suitable for different uses, that is supported by a birotor having dihedral blades.

As birotor is to be understood a rotating aerodynamic support device resulting from the combination of two superimposed and coaxial blade rotors that are provided with means which render them counter-rotating. The birotor has find some uses, however of low diffusion, as the supporting device for helicopters, and in this application it has the major drawback of a difficult compatibility with the complex mechanisms intended to generate a cyclic modification of the blade incidence, that are needed for ensuring the stability and maneuverability of an helicopter.

One object of this invention is to confer an intrinsic stability to a sup- porting device using a birotor, whereby such a device may find suitable applications to the support of flying aircrafts different from the helicopters, wherein the rotation of the blade rotors, which causes the support of the aircraft, is produced entirely or partially by an air flow (natural wind, running wind or descent wind). As a consequence of the attainment of an intrinsic stability, as well as of the fact that flying aircrafts different from helicopters do not need any cyclic modification of the blade incidence, these applications of a birotor do not involve the difficulties that have hindered the use of a birotor in helicopters.

Therefore, the flying aircrafts to which the invention can be applied with advantage are those that are raised in height for being supported by a natural wind, those that are supported by the running wind produced by a propulsion device (namely gyroplanes), and those that are used for slowing down the descent of a charge, wherein the rotating device for support is operated by a descent wind. The principle on which the invention is based is to confer intrinsic stability to a birotor by dihedrally shaping, entirely or partially, the rotor blades forming the birotor.

Therefore, the object of the invention is a flying aircraft of the type in which the support is operated by a rotating device whose rotation is produced

entirely or partially by an air flow, characterized in that the rotating device for support is formed by the combination of two superimposed and coaxial blade rotors provided with means that render them counter-rotating, thus forming a birotor, and in that the blades of both the blade rotors forming the birotor are entirely or partially shaped as a dihedron.

The dihedral shape is well known in the design of unmovable wings of airplanes, and it is also well known the increase in stability that this shape produces in the airplanes. We have now ascertained that the same advantage of a high increase in stability is attained also by imparting a dihedral shape to the blades (rotating wings) of a supporting blade rotor, and that this stabilization effect is completed by the combination of two symmetrically counter-rotating blade rotors, that ensures a complete compensation of the actions of the blades advancing with respect of the air flow, which are different from the actions of the blades backing with respect of the air flow. The number of blades used in forming each blade rotor of the birotor may vary according to the, needs of each application. In most cases may be of advantage to foresee four blades for each blade rotor being part of the birotor.

In the case of flying aircrafts that do not require to be maneuvered, the blades of each blade rotor can be fixed with an invariable incidence on the respective hubs. On the contrary, in the case of flying aircrafts that should undergo controlled maneuvers, it may be needed that the blades are mounted on the hubs by means of pivots, in the presence of devices intended to modify the incidence of all the blades. Such devices, however, do not involve the difficulties encountered in helicopters, because the incidence modi- fication that they produce is stable and it is not cyclic, and therefore these devices are substantially simple. In some cases, this incidence modification is to be effected under voluntary control, whereas in other cases the incidence modification can automatically result from specific operation conditions, for example from the rotational speed of the birotor and/or the aerody- namic load applied to the blades.

In the case of flying aircrafts of the type of gyroplanes, it is needed that there is a propulsion blade screw operated by a propulsion engine, but preferably there is also provided a supporting engine intended to operate the rotation of the birotor, in specific conditions and especially at the takeoff and at the vertical landing.

The flying aircraft according to the invention can have the character of a gyroplane for sports or commercial uses but, when it is capable of receiving from the wind an energy in excess to the energy needed for its support, the birotor can with advantage be connected to an electric generator, thus embodying a flying eolian energy conversion device. Such an aircraft may be caused to operate at a height very larger that the height at which operates the energy converter of an eolian tower, and thus it can exploit more intense and regular winds. It may be provided with an anchorage cable also serving for transmitting at the ground level the produced electric energy. These and other features, objects and advantages of the subject of this invention will appear more clearly from the description which follows of some non-limiting examples of embodiment, with reference to the accompanying drawings, wherein:

Figure 1 shows in a perspective view a flying aircraft embodied ac- cording to the invention, of the type of a gyroplane.

Figures 2, 3 and 4 show the outline of three different possible shapes of the dihedral blades.

Figures 5 to 11 show a device for automatically modifying the inclination at which the blades are connected. Figures 12 to 18 show another device for modifying, automatically or under control, the inclination at which the blades are connected.

With reference to Figure 1 , there is shown a flying aircraft of the type of a gyroplane, which has a guidance place 1 for a pilot, a rear extension 2 supporting a rudder 3 and a diving rudder 4, and a propulsion blade screw 5 operated by a propulsion engine E1. The support of the aircraft is operated by a birotor including two hubs 7 mounted on a shaft 6 and carrying the blades connected to them. A mechanism (not represented) connects the two hubs 7 to one another by imposing to them rotation movements symmetrically opposite. In the embodiment shown, to each hub 7 are connected four blades, but it is to be understood that the number of blades forming each blade rotor of the birotor can be chosen in a different manner. The fact that the supporting device is formed by a birotor is the first essential feature of the flying aircraft according to the invention.

It is suitable that the rudder 3 and possibly the diving rudder 4 be situated beyond the space interested by at least the major part of the vertical

air flow produced by the birotor. This is of particular importance for the motionless flight. The shaft of the propulsion blade screw 5 is suitably ori- entable in view of favoring the tacks of the aircraft. Preferably, moreover, there is provided a supporting engine E2 intended to operate the birotor in particular circumstances, particularly at the takeoff and the vertical landing. Both support and propulsion engines E1 and E2 may be replaced by a sole engine provided with suitable couplings for operating, under control, the propulsion blade screw 5, the birotor 5-7 or both these devices.

A second essential feature of the flying aircraft according to the in- vention is that all blades connected to the hubs 7 are, at least in part, shaped as dihedrons. In the shown embodiment, each blade is composed by a proximal portion 8 fixed on the hub 7, and a distal portion 9 which extends the proximal portion 8 along the same horizontal direction thereof but forming in the height a dihedron with the proximal portion 8 of the blade. This at least partial shaping as dihedron of the blades, along with the fact that the support is done by a birotor, confers to the flying aircraft the unique stability characteristics aimed by the invention.

Of course, the aircraft should be provided with all the needed controls, according to the known technique. The at least partial dihedral shape of the blades may be embodied in various manners, as shown by Figures 2 to 4.

According to Figure 2, a blade 10 is oriented as a dihedron (with respect to the opposite blade) along its entire length. From the hub situated at 7, to which the proximal end portion of the blade is connected, the blade 10 has a length L1 and it is inclined by an angle A with respect to a plane 0 perpendicular to the rotation axis of the birotor. Therefore the projection of blade 10 onto the plane 0 has a length L2 = L1 cos A , whereas its distal end has a height H1 = L1 sin A with respect to the plane 0 . The various thus defined parameters may be chosen in each application, either by theo- retical way or by experimental way, in such a manner as to attain the performances considered preferable.

According to Figure 3, a blade 11-12 forms a dihedron only in a part of its extension. From the hub situated at 7, to which is connected the proximal end of a proximal blade, portion 11 , the proximal blade portion 11 has a length L3 and it is parallel to the plane 0 perpendicular to the rotational

axis of the birotor, whereas the distal blade portion 12 has a length L4 and is inclined by an angle B with respect to the plane 0 . Therefore, the projection of blade 11-12 onto plane 0 has a length L5 = L3 + L4 cos B , whereas the blade distal end has a height H2 = La sin B with respect to the plane 0 . Also in this case, the various thus defined parameters may be chosen in each application, either by theoretical way or by experimental way, in such a manner as to attain the performances considered preferable.

According to Figure 4, a blade 13 forms a dihedron along all its length, but with an inclination that varies from point to point, because the blade is bent. From the hub situated at 7, to which is connected the proximal end of the blade, the blade 13 has a length L6 and it is inclined in a variable manner with respect to the plane 0 perpendicular to the rotational axis of the birotor. Its projection onto plane 0 has a length L7 , whereas its distal end has a height H3 with respect to the plane 0. The various thus defined pa- rameters m, and particularly the course of the variable bend of the blade, may be chosen in each application, either by theoretical way or by experimental way, in such a manner as to attain the performances considered preferable.

All the different types of blades according to Figures 2 to 4 may carry out the stability conditions aimed by the invention, but in different manner and measure. Therefore the designer will select the one or the other type of blade by taking into account the needs of each particular application and also the preferences for the manufacture. As it will be understood, the embodiment of the aircraft represented in Figure 1 makes use of the blade type cor- responding to Figure 3.

As already said, in those cases in which the flying aircraft is not required to undergo special maneuvers, blades 8 may be fixed to the hubs 7 in an invariable manner. On the contrary, when the flying aircraft should undergo controlled maneuvers, the blades should be able to be moved with re- spect to the hubs for taking different incidences. In this case, each blade is connected to the respective hub by means of a pivot whose axis is oriented along the longitudinal direction of the blade, and suitable devices are foreseen for modifying in the desired manner the incidence of all blades.

An example of such a device is represented in Figures 5 to 11. Fig- ure 5 is the plan view of a hub 17 to which are connected four blades 18, of

which only the proximal portions are shown. Figures 6, 8 and 10 show in plane view the connection of a single blade 18 to the hub 17, in different operation conditions, whereas the corresponding Figures 7, 9 and 11 illustrate the incidence correspondingly taken by the blade. Each blade 18 is connected to the hub 17 by a pivot 16 that, in addition to the possibility of rotation in the hub 17, may axially slide, and it is charged by a spring 15 to displace towards hub 17. A cross pin 19 carried by pivot 15 is engaged in an inclined guide split 14 of hub 17, whereby an axial displacement of pivot 16 causes a rotational displacement of the same and therefore a modification of the inclination of incidence in the connection of blade 18. The centrifugal force due to the rotation of the birotor acts on the blades 18 and, against the action of the springs 15, determines the axial position of the pivots 16 and therefore the corresponding incidence of the blades 18. The incidence of blades 18 is therefore automatically determined by the rotational speed of the birotor. The inclination of the blades varies thus between a negative value (-) and a positive value (+), as it is shown by the Figures 7 to 11.

Another device intended to modify the inclination in the connection of the blades is represented in Figures 12 to 18. Figure 12 shows a plan view of a hub 27 to which are connected four blades 28, of which only the proximal portions are represented. Figures 13, 15 and 17 show in plan view the connection of a single blade.28 to the hub 27, in different operative conditions. The corresponding Figures 14, 16 and 18 show the inclination of incidence correspondingly taken by blade 28. Each blade 28 is connected to the hub 27 by a pivot 26 that is ro- tatably mounted in the hub 27. A cross key 29 of pivot 26 is engaged in a corresponding guide slit of a plate 24. Plate 24 can rotate with respect to hub 27 and it is controlled by actuation members 25 suitable for causing plate 24 to rotate with respect to the hub 27. Therefore, the rotation of plate 24 causes a modification of the inclination of blade 28 in its connection to hub 27. Both the aerodynamic forces acting onto the blade 28 and the actuation members 25 aim to determine the angular position of the pivots 26 and therefore the incidence of the blades 28. The actual incidence of blades 28 is therefore determined as the result of both these ac- tions.

The actuation members 25 may be springs, and in this case the incidence of the blades 28 is automatically determined by the aerodynamic actions applied to the blades. As an alternative, the actuation members 25 may be subjected to a voluntary control, for example they may be hydraulically operated piston-cylinder devices, and in this case the incidence of the blades is determined by the control action applied to the actuation members.

In this case too, the inclination of the blades 28 varies between a negative value (-) and a positive value (+), as it is shown by the Figures 14 to 18. A flying aircraft similar to that represented in Figure 1 , having a suitable size, may be provided with an electric generator operated by the birotor and connected to descent cables being parts of an anchorage cable. Such a flying aircraft may operate in a manner similar to that of the eolian towers, converting the eolian energy in electric energy suitable for being used. Such device has the advantage that it may operate at a greater height than the blade screws of the eolian towers, taking advantage of more intense and stable air flows. Moreover, the cost of such an energy converter could be reduced with respect of the cost of an eolian tower, which needs a costly supporting structure, and it occupies a more reduced space to be subtracted to the agriculture.

For such application a propulsion blade screw and the corresponding engine are not required. In order to raise in the height the aircraft, the same may be towed, or the electric generator, suitably designed, may be used as a motor for raising the aircraft up to a height at which it may be supported by action of the wind.

It is to be understood that the invention is not limited to the embodiments shown and described. Several possible modifications have been stated in the description, and others are within the capacity of the skilled persons. These modifications and others can be applied to what has been de- scribed and shown, without departing from the spirit of the invention and the scope of this Patent, as specified by the Claims.