DESCRIPTION

A FLYING TOY SUPPORTED BY A BIROTOR WHOSE BLADES ARE PARTIALLY FLEXIBLE

The subject of this invention is a flying toy equipped with a birotor whose blades have flexible end portions.

It is well known that the blade rotors appertain to two categories, the rotors of one category being operated by an engine in order to produce an air flow or to serve as supporting device for a flying aircraft, and the rotors of the other category being intended to be operated by an air flow in order to con- vert the air flow energy or to exploit the air flow as supporting means for a flying aircraft. In the usual technique, the rotors of both above categories are equipped with substantially identical blades. From the searches of Applicant, on the contrary, has emerged that the rotors intended to be operated by an air flow can provide better performances when they are equipped with blades that are designed in special manner for this category of rotors. Therefore, this invention proposes improvements in the rotor blades appointed to form rotors intended to be operated by an air flow, these blades being characterized by the provision of end portions that are flexible. Moreover the invention proposes improvements in the supporting devices using a rotor, characterized by the combination of two superimposed and coaxial rotors provided with synchronization means that cause the rotors to rotate symmetrically in opposite directions, both rotors and the synchronization means forming a birotor.

The subject of this invention is an aircraft intended to be used as a flying toy, which is supported by such a birotor provided with blades whose end portions are flexible.

A rotor blade improved according to the invention is characterized in that it comprises a substantially rigid proximal portion whose cross section has the shape and the inclination incidence suggested by the laws of the aerodynamics, and comprises a distal portion having a noticeable capability of undergoing flexional deformations.

In view of this unique structure, an air flow that strikes such rotor blades acts as usually onto the rigid proximal portions of the blades and thus

applies to the rotor a torque acting around the rotation axis of the rotor, that causes the rotor to rotate and therefore to perform its supporting action, but the air flow also acts onto the flexible distal portions of the blades and inflects the same in a measure depending on the angle subtended between the direction of the rotor axis and the direction of the air flow, as well as on the intensity of the air flow. This effect results to be extremely useful when the rotor is applied to a flying aircraft intended to be supported by the air flow, because it causes the blades to behave as dihedrons, with a highly stabilizing effect capable of opposing to any possible tendency of the flying aircraft to incline or to slip.

Said flexible distal portion of the blades may have a cross section identical or similar to the cross section of the rigid proximal portion of the blades, or it may have a simplified cross section. The rigid proximal portion extends from the rotor hub up to beyond the pressure center determined by the whole of the proximal and distal portions of the blade, and preferably beyond the 70% of the whole extension of the blade.

Said flexible distal portion of the blade may be an extension of the rigid proximal portion along the same direction thereof, or else the flexible distal portion of the blade may be pivoted near to the end of the rigid proximal portion around an axis at least approximately parallel to the rotor axis, whereby the distal portion of the blade can orientate itself with respect to the proximal portion.

In this case the distal section may be retracted in a position adjacent to the proximal portion when the rotor is not in operation, thus reducing the encumbrance, and it extends spontaneously under the action of the centrifugal force when the rotor is put in rotation, thus aligning itself at least approximately with the direction of the proximal portion. Moreover, during the operation of the rotor, the distal section is able to train with respect to the proximal portion, by advancing or receding with respect to the same, thus adapting its position to the conditions of the air flow.

From the point of view of the manufacture, the proximal portion of the rotor blade, when it is of reduced size, may be solid, whereas when it has a relatively large size it may have a cellular structure. In this case one may use with advantage the structure that has been described, for the wings of flying aircrafts, in the Italian Patent Application No. TO 2005 A 000 862.

The supporting means improved by the invention is a birotor for a flying aircraft that comprises a pair of superimposed and coaxial blade rotors, each including a number of rotor blades having the features prescribed by the invention, and mutually connected by a synchronization mechanism that obliges the two blade rotors to rotate symmetrically in opposite directions.

The number of rotor blades used for each blade rotor may vary according to the needs of each application. In most cases it is preferable to use four rotor blades for each blade rotor.

A birotor shaped in this way is capable of exploiting, in a manner more complete and rational than a simple blade rotor, the action of an air flow that causes the same to rotate. In the application to the support of a flying aircraft, the attained advantages are especially interesting, because a complete symmetry with respect to the air flow is attained, and more particularly there is attained a complete compensation of the different behaviors between the rotor blade that in its rotation proceeds against the air flow, and the rotor blade that in its rotation moves back with respect to the air flow. The consequence is a special stability of the flying aircraft.

The flying aircraft specifically foreseen by the invention makes use of the combination of the rotor blades and the birotor that have been described, and it embodies a flying toy that may be dragged in height and then maintained in flight by wind action, being controlled and maneuvered by means of an anchorage cable in a manner similar to a kite. Such a flying toy, though being easily controlled like a kite, has much more attraction than a usual kite because, in addition to effect the maneuvers of a kite, presents itself as a dy- namic object whose appearance is similar to a helicopter.

These and other features, objects and advantages of the subject of this invention will appear more clearly from the description which follows of a non-limiting example of embodiment, with reference to the accompanying drawings, wherein: Figure 1 shows in a plan view an example of a rotor blade embodied according to the invention, of the type in which the two blade portions are mutually articulated.

Figure 2 shows the outline of the rotor blade according to Figure 1 , in the configuration extended but not stressed by an air flow.

Figure 3 shows the outline of the rotor blade according to Figure 1 , in the configuration extended and inflected by the stress of an air flow.

Figures 4 to 7 show on a very larger scale the cross sections of the rotor blade in correspondence of the regions IV-IV, V-V, VI-VI and VII-VII of Figure 1.

Figure 8 shows in a perspective view a flying aircraft equipped with a birotor formed by blades according to Figure 1.

Figure 9 shows in an axial section a mechanism for the synchronization or inversion of the rotational movement, used in the birotor of the flying aircraft according to Figure 8.

With reference to Figures 1 to 7, there is represented a rotor blade improved according to this invention. Number 1 designates a proximal portion of the rotor blade, that has characters substantially corresponding to a usual rotor blade, namely, it is formed by a substantially rigid material and has a cross section, represented in Figure 5, that is the conventional one imposed by the laws of aerodynamics. This proximal portion 1 of the rotor blade is provided at its proximal end with means 2 for its connection to corresponding connection means 5 of the hub 6 of a rotor, and as it is customary this connection is done in such a manner as to confer to the rotor blade a certain angular incidence, suitable for its operation.

According to the main feature of this invention, the proximal portion 1 of the rotor blade is extended, at its distal end, by a distal portion 3 that has a noticeable flexibility. This flexibility may be attained by the use of a suitably flexible material, or else by simply reducing the thickness of the material forming the proximal portion 1 of the rotor blade. The cross section of the distal portion 3 of the rotor blade may correspond to the cross section of the proximal portion 1 , or else it may be somewhat simplified, as shown by example in Figure 7.

The distal portion 3 of the rotor blade may be an extension of the proximal portion 1 along the same direction thereof, and in this case the distal portion 3 may be rigidly fixed to the proximal portion 1 or may be formed in one piece therewith. In this latter case the transition from the characteristics of the proximal portion 1 to the characteristics of the distal portion 3 may also be gradual.

However, in the more elaborated embodiment shown in Figures 1 to 3, the distal portion 3 of the rotor blade is connected to the proximal portion 1 by means of an articulation formed by a pivot whose axis is substantially perpendicular to the plane of the proximal portion 1 and the distal portion 3 of the rotor blade and approximately parallel to the axis of hub 6, which is the axis of the rotor equipped with the rotor blade 1-4.

Thanks to the described structure, the rotor blade 1-4, in the not stressed condition represented in Figures 1 and 2, has its portions 1 and 3 aligned, but when the rotor blade is struck by an air flow its distal portion 3 having noticeable flexibility is inflected as represented in Figure 3, in a measure depending on the intensity of the received air flow. It ensues the behavior described above.

For a correct operation it is suitable that the proximal portion 1 of the rotor blade extends from its basis, represented by the connection means 2, past the aerodynamic pressure center determined by the whole of the proximal and distal portions of the rotor blade. Because this pressure center is situated approximately at 2/3 of the extension of the rotor blade, it is preferable that the rigid proximal portion extends more that 70% of the whole extension of the rotor blade 1-4. When the described blades are connected to hubs 6 provided with connection means 5 complementary to the connection means 2 of the rotor blades 1-4, the blades form rotors of the kind of those represented as examples in Figure 8. It is to be remarked that, when an articulation 4 is foreseen between the portions 1 and 3 of each rotor blade, as in the represented ex- ample, it is possible to rotate the distal portions 3 of the rotor blades by arranging the same adjacent to the proximal portions 1 , whereby the encumbrance of the device may be reduced when the rotor is not in operation. Then, when the rotor rotates, with a not negligible speed, the centrifugal force automatically rotates the distal portions 3 outwards and towards the position in which they are aligned with the corresponding proximal portions 1. Moreover, during the operation, ^' the distal portions 3 are allowed to somewhat displace angularly, by advancing or remaining behind with respect to the corresponding proximal portions 1 , according to the stresses received.

In the rotors having a reduced size, the proximal portions 1 of the rotor blades may be made of solid material. For the rotors of larger size, in

order to reduce the ratio weight/rigidity of the proximal portions 1 , it is of advantage that these proximal portions have a cellular structure, for example and preferably such as that described, for the wings of flying aircraft, in the Italian Patent Application No. TO 2005 A 000 862. Figure 8 represents an example of a flying toy that uses a birotor equipped with rotor blades according to the invention. This flying toy may be controlled in a manner similar to that of a kite, by exploiting the supporting action produced by the rotors when put in rotation by the wind. This toy has an appearance similar to that of a helicopter and has a body 7 with a front portion 8 simulating a nacelle, a longitudinal bar 9 carrying a rudder 10 and a diving rudder 11 , and a pair of landing sliders 12.

The toy is intended to be connected to an anchorage cable (not represented) fixed to a suitable point of the toy, by means of which the flying toy may be controlled in a manner similar to that of a kite, by regulating its incli- nation and its orientation with respect to the wind direction, in order to attain the supporting action and possibly causing particular maneuvers.

In operation, the inflection of the distal portions 3 of the rotor blades carries out the action of a dihedron that confers stability to the flying aircraft and prevents unwanted slips and inclinations. More stability and a better ex- ploitation of the air flows are attained by the flying aircraft, as represented, being provided with a birotor formed by two superimposed, coaxial and counter-rotating blade rotors, mutually connected by a synchronization device that obliges the two rotors to effect symmetrical rotations in opposite directions.

In the represented example, each blade rotor is composed of four rotor blades, and this blade number is considered preferable, however it is to be understood that the number of blades forming each rotor may be chosen in view of the needs of each application and of the desired characteristics. For example, the blade number of each rotor may be two or three, or an even number of blades above four may be chosen. An embodiment of a synchronization mechanism suitable for the considered application is represented in Figure 9. Each rotor hub 6 forms a bowl 14 wherein is fixed a conical toothed wheel 15, and both these conical toothed wheels 15 are mutually coupled by conical pinions 16 carried by a plate 17 connected to a fixed shaft 18 solid with the body 7 of the flying toy. The fixed shaft 8 carries bearings on which rotate the hubs 6 of the rotors.

However the synchronization mechanism may be shaped in other manners, by using either toothed wheels or friction couplings.

As it will be understood, the flying toy according to the invention is suitable for being used without difficulties in a manner similar to that of a kite, and when it is in flight it may be maneuvered and controlled in the manner known for the maneuver and control of kites, but its attractive, representing the flight of a helicopter, is very greater than that of a usual kite. Both the control easiness and the regularity of the maneuvers are favored by the flight stability resulting from the use of a birotor having partially flexible blades, as foreseen by the invention.

Of course, the invention is not limited to the embodiments described and shown as examples. Several possible modifications have been stated in the course of the description, and others are within the capacity of those skilled in the art. These modifications and others and any replacement by technically equivalent means may be applied to that has been described and shown, without departing from the spirit of the invention and the scope of this Patent, as resulting from the appended Claims.