Patent Description:
Various propulsion systems are known for rotary wing aircraft, such as helicopters.

In particular, propulsion systems applied to the ends of the rotor wing blades have already been tested, but these systems showed problems of interference with the collective cyclic apparatus of the means to which they were applied.

Known propulsion systems of this type include primarily the so-called cold jet or tip jet system.

Developed by French technicians, the apparatus included a turbine installed solely for the purpose of producing high-pressure air to be conveyed through the mast, namely the shaft of the rotating wing, and then with a complex system, through the helicopter blade to the end of the same where there was a nozzle from which air came out, thus setting the blades in motion and allowing flight.

The cold jet system was abandoned because the jet of air coming out at the ends of the blades produced considerable problems when the pitch of the blade was acted upon, namely when the blade varied angle to create lift. At that time, the propulsion jet pushed the blades upwards.

Imagine then when the cyclic control was activated with which the blade continuously changes its pitch and then the jet produced an oscillating thrust as a function of the inclination of the cyclic pitch.

Also, this jet prevented almost totally the tilt of the blade (movement along the vertical axis of the mast) being always "pushing" and never free to tilt.

This is true of the flapping movement, which was influenced by the thrust jets.

This project dates back to the early '<NUM> and has been abandoned. There was no benefit in terms of vehicle weight, flight duration, payload.

The only advantage was the absence of the main rotor, of the tail rotor and of the freewheel, this in view of the fact that the mast was free and there were no torque problems when transmitting the motion.

Another system that has been tried and tested in the past is the so-called hot jet system.

This system included ramjets installed at the end of the helicopter blades.

The hot jet system, although simpler than the cold jet, produces the same problems because since the ramjets are placed at the ends of the blades it produces significant drawbacks mentioned above: alteration of the blade pitch, cyclic, tilting and flapping.

To these problems it must be added the problem of consumption, which makes it absolutely impossible to fly for more than <NUM>-<NUM> minutes with very high consumption.

All the other existing propulsion systems are connected directly to the mast via the rotor - crown/sprocket, thus having to provide a required power significantly higher than the invention An additional propulsion system for rotary wing aircraft that overcomes the above mentioned problems is described in the Italian patent application <CIT> and in the corresponding <CIT>.

This propulsion system is based on the concept of using a rotating pole, also called a "power mast" which is connected to the rotating shaft of the aircraft, where the rotating shaft puts the rotating wing into rotation.

The mast shall be mechanically attachable to the rotating shaft of the aircraft, and at least one end of the mast shall be fitted with a motor configured to rotate the mast so that the rotation of the mast can be used to rotate the rotating wing.

Document <CIT> illustrates an aircraft provide with two pairs of propellers, wherein each pair of propellers is placed at one end of a rotary wing of a powered aircraft.

Document <CIT> illustrates a drone, which is referred to as "unmanned" in the text of said document.

Document <CIT> illustrates a drone. The acronym UAV - Unmanned Aerial Vehicle indicates as known vehicle not capable of carrying people. The abstract of said document states, inter alia, that the UAV is provided with means to cancel background noise from audio data collected by the UAV.

The purpose of this invention is to improve the performance of power mast systems both in terms of efficiency and safety.

A further aim of the invention is to create a rotary wing aircraft with reduced costs compared to existing aircraft.

These and other purposes, which will be evident from reading this description, are achieved by a rotary wing aircraft according to appended claim <NUM>.

An advantage of this embodiment is that the configuration of the counter-rotating propellers claimed allows first of all to reduce the length of the rotating pole, thus bringing the counter-rotating propellers closer to the axis of the rotating mast and thus reducing the centrifugal acceleration to which the motors are subjected.

In particular, according to one embodiment of the invention, the pole is less than half the length of the rotating wing.

A second, important, advantage of the invention is given by the fact that being the counter-rotating propellers belonging to each of the pairs of motors reduces to zero the total gyroscopic moment that acts on the "power mast".

According to one embodiment of the invention, the counter-rotating propellers are not enclosed in motor gondolas.

An advantage of this embodiment is that, by avoiding motor gondolas, possible problems of structural integrity of the gondolas themselves when operating under high centrifugal forces are avoided.

The counter-rotating propellers are electrically powered.

In addition, the presence of the engine gondolas would contribute to the rotor's resistance and the aircraft's forward resistance. According to another embodiment of the invention, profiles are applied along the pole that allow, during the rotation of the pole, to generate a counternoise that reduces the total noise produced by the aircraft in flight.

Further features of the invention can be inferred from the dependent claims.

Further characteristics and advantages of the invention will be evident from the reading of the following description provided as an example and not limited to, with the help of the attached figures, in which:.

<FIG> schematically illustrates an embodiment of the rotary wing aircraft <NUM> which is equipped with the propulsion apparatus, according to a realization of the invention, the apparatus being globally indicated with the numerical reference <NUM>.

In general, the propulsion apparatus <NUM> for rotary wing aircraft of the invention is associated with a rotary shaft <NUM> mechanically connected to said rotary wing <NUM>.

In general, in this description, a rotary wing aircraft is an aircraft heavier than air that uses the lift generated by particular wing surfaces, called blades, rotating around a shaft.

Propulsion apparatus <NUM> includes a pole <NUM>, mechanically connectable to the rotating mast <NUM> of the aircraft, wherein at each end of pole <NUM> attached to the rotating mast <NUM> of the aircraft a motor <NUM> is applied, wherein each of the motors <NUM> contributes a rotating torque to rotate the pole <NUM> around its own axis of rotation coinciding with the axis of rotation of the rotating mast <NUM> for the rotation of the rotating mast <NUM> of the aircraft.

The motors can be, for example, electrically powered counter-rotating propellers <NUM>,<NUM>', also known as e-fans.

The power supply of the counterrotating propellers <NUM>,<NUM>' can be derived from a battery pack placed on board the aircraft <NUM>.

In particular, each of the motors <NUM> includes a pair of counter-rotating propellers <NUM>,<NUM>' arranged in such a way as to generate a rotation torque to rotate the pole <NUM>.

In the proposed system, i.e. coaxial counter-rotating propellers, the power generated by an electric motor is used to rotate two propellers arranged along the same axis, but which are made to rotate in opposite directions.

In <FIG> it is visible a detail of the propulsion system of <FIG> in which figure, indicatively, the direction of rotation of the propeller <NUM> has been indicated with the arrow W1 and the (opposite) direction of rotation of the propeller <NUM>' has been indicated with the arrow W2 all of which in order to generate a rotation movement of the pole <NUM> in the direction of the arrow F1. An advantage of this embodiment is that the configuration of the counter-rotating propellers (e-fan) claimed allows first of all to reduce the length of the rotating pole <NUM>, thus bringing the counter-rotating propellers closer to the axis of the rotating mast <NUM> and thus reducing the centrifugal acceleration to which the motors are subjected.

In particular, according to one realization of the invention, the pole is less than half the length of the rotating wing <NUM>.

Note that the centrifugal acceleration to which the electric propeller (e-fan) <NUM> motor units are subjected during the rotation of the pole <NUM> is equal to: <MAT> wherein reFan is the distance of the motors <NUM> (or of their centre of gravity) from the rotation axis of pole <NUM> and S2 is the rotation speed of pole <NUM>.

By bringing the electric counter-rotating propellers (e-fan) closer to the rotation axis of pole <NUM> and thus reducing the length of pole <NUM>, the centrifugal forces acting on the motors and their components are proportionally reduced.

A second, important, advantage of the invention is given by the fact that since the counterrotating electric propellers (e-fan) <NUM>,<NUM>' belong to each of the pairs of counterrotating electric propellers (e-fan) the total gyroscopic moment acting on the "power mast" is reduced to zero.

In particular, the total gyroscopic moment is given by <MAT> where Iprop is the moment of inertia of the propeller, and ΩeFan is the angular speed of the motor units <NUM>.

Using counter-rotating propellers reduces the total gyroscopic momentum to zero.

Preferably the number of blades per propeller is <NUM>, but a different number of blades can also be used.

According to one embodiment of the invention, the counter-rotating propellers <NUM>,<NUM>' are not enclosed in motor gondolas.

In addition, the presence of the engine gondolas would contribute to the rotor's resistance and to the aircraft's forward resistance. According to an embodiment of the invention, electrical connection cables and power supply through the inside of pole <NUM> can also be provided.

In another variation of the invention, the pole <NUM> is mechanically connected directly to the rotating mast <NUM> of the aircraft via a rigid coupling <NUM>.

Alternatively, the pole <NUM> is mechanically connected to the rotating mast <NUM> of the aircraft by a rigid or semi-rigid or articulated coupling.

In general, the rotation of pole <NUM> takes place in a different plane from the rotation of the rotating wing <NUM>.

In particular, the point of attachment of the pole to the aircraft's rotating mast <NUM> may be placed above or below the aircraft steering system, e.g. above (as in the example in <FIG>) or below the aircraft's collective plate and swashplate <NUM> system.

It is to be noted that the collective plate and swashplate <NUM> system of the aircraft is of a known type and is controlled by the pilot in a manner known in the art.

The shape of the pole <NUM> can be any shape with the caveat that the pole <NUM> should not create significant lift during its rotation. Alternatively, according to examples not covered by the presently claimed invention, pole <NUM> can also be made with a shape that can create lift when rotated.

Preferably, pole <NUM> is made of carbon fiber.

The propulsion system as illustrated in <FIG> differs substantially from those illustrated in the introduction and known in the art.

In fact, the propulsion system <NUM> is not applied to the ends of the blades of the vehicle and that constitute the flight system as in the cases in the introduction.

In fact, the propulsive system object of the present invention consists of a pole <NUM> (also called power mast) of adequate size applied rigidly to the shaft or mast of the helicopter or other flying means having vertical take-off and is completely independent from the blades of the same.

The pole no longer has the rotor (pinion gear system) but turns freely on a suitable support (thrust bearing or other) moved by the propeller(s) at the ends.

According to an embodiment of the invention, profiles are applied along the pole <NUM> that allow, during the rotation of the pole <NUM>, to generate a counternoise that reduces the total noise produced by the aircraft <NUM> in flight.

As an alternative or in addition to this counter-noise solution it is possible to provide a loudspeaker that generates a counter-noise as a function of the revolutions of the counter-rotating propellers, or pole <NUM> or other factors.

In the operation of the propulsion system <NUM>, motors <NUM> generate a rotation torque for the rotating pole <NUM> and, by means of the connection to the rotating mast <NUM>, generate a corresponding rotation of the rotating wing <NUM>.

The propulsive apparatus can also be used as a torque multiplier system as it can be powered with a lower energy to be used, even in non aeronautical applications, i.e. for all those applications that can benefit from the leverage effect generated by the pole <NUM> (example: battery recharging, energy production from electric or endothermic rotary motion to the electric one, etc..

Claim 1:
A rotary wing aircraft (<NUM>) equipped with a propulsion apparatus (<NUM>), wherein said aircraft (<NUM>) includes a rotating wing (<NUM>) and a rotating mast (<NUM>) that rotates said rotating wing (<NUM>), and where said propulsion apparatus (<NUM>) includes a pole (<NUM>) mechanically connected to the rotating mast (<NUM>) of the aircraft (<NUM>), wherein a shape of the pole (<NUM>) is such that it does not create lift when rotated, wherein at each end of the pole (<NUM>) is placed a motor group (<NUM>) configured to rotate the pole (<NUM>) around an axis of the rotating mast (<NUM>) in such a way that a rotation of the pole (<NUM>) can be used to rotate the rotating wing (<NUM>), wherein the rotation of the pole (<NUM>) takes place in a different plane with respect to a rotation plane of the rotating wing (<NUM>), characterized by the fact that each motor group (<NUM>) includes a pair of counter-rotating propellers (<NUM>,<NUM>'), said pair of counter-rotating propellers (<NUM>,<NUM>') being arranged in such a way as to generate a rotational torque to rotate the pole (<NUM>), the counter-rotating propellers being configured to reduce to zero a total gyroscopic moment given by Mgyro = IpropΩeFanΩ, where Iprop is a moment of inertia of the propeller, ΩeFan is an angular speed of the motor groups (<NUM>) and Ω is a rotation speed of the pole (<NUM>).