The present invention concerns a device for steering a helicopter.

Such helicopters are driven, as is known, by at least one main rotor comprising several adjustable rotor blades and which provides for the buoyant force of the helicopter.

In particular, the rotor blades are hinge-mounted around their longitudinal axis, whereby the pivot angle is adjustable, such that the buoyant force that is created during the rotation of the rotor can be adjusted.

It is known that, to steer a helicopter, in particular forward or backwards, but also sidewards, use is made of the aforesaid adjustability of the rotor blades of the main rotor.

To this end, the rotor blades, depending on the position in which the pilot moves his steering elements, are adjusted differently, individually and in a cyclic manner, so that they each develop a different buoyant force, as a result of which the helicopter is asymmetrically loaded, and, as a consequence, a moment of force is created which makes the helicopter heel over in the required direction and makes the helicopter move in this direction.

Until now, in order to adjust the rotor blades to steer the helicopter, use is made of a device with mechanical transmission means between the above-mentioned control elements of the pilot and the adjusting mechanism of the rotor blades.

Such known devices are disadvantageous in that the above- mentioned mechanical transmission means are very complex and moreover comprise many moving parts which are subject to wear, require a lot of maintenance and adjustment and which moreover, due to their complexity, require specialised staff for their repairs and maintenance. It is clear that helicopters with such devices are very expensive and moreover imply major operating costs.

The present invention aims to remedy the above-mentioned and other disadvantages.

To this end, the invention concerns a device for steering a helicopter, comprising at least one rotor formed of several rotor blades provided crosswise on the rotor shaft and which are hinge-mounted around their longitudinal axis; at least one steering element for flying forward and backwards and a steering element for flying sidewards; and finally transmission means between these steering elements and the rotor blades for hinge-mounting the rotor blades around their longitudinal axis, characterised in that these

transmission means comprise electric drive means provided on the rotor.

This offers the advantage that far less mechanical parts are required since the drive means are situated on the rotor, i. e. very close to the adjusting mechanism of the rotor blades on the one hand, and that the connection between the drive means and the steering elements can be realised with electric or electronic components.

The drive means preferably consist of one or several electric motors and the transmission means comprise an electric universal joint connected between the motors and the steering elements, so that the device can be realised in a simple and thus cost-efficient manner.

The invention is also particularly suitable to be applied on a remote-controlled model helicopter with two adjustable rotor blades.

According to a preferred embodiment, the device in this case comprises one or several converters generating a stress signal which is proportional to the movement of the control elements of the remote control, and the above- mentioned universal joint mainly consists of a part which is fixed in relation to the body of the helicopter on the one hand, provided co-axially around the rotor shaft and having an insulating core provided with four contact shoes on the outside, and of a rotating part having two sliding

contacts provided diametrically opposed to each other on the rotor shaft on the other hand.

Such a remote-controlled model helicopter is very easy and cheap to realise, as opposed to the known model helicopters which are also very complex and which make use of expensive servomotors, gyroscopes, accelerometers and microprocessors for their steering, together with the necessary expensive software.

Apart from the conventional known remote control, a model helicopter according to the invention makes use of standard and cheap components, namely an electric motor, one or several voltage converters and a universal joint that is easy to realise.

Thanks to the simplicity of such a model helicopter with a device according to the invention and the lacking of any complicated controls as found in the known model helicopters, no special technical knowledge is required to compose such a model helicopter from a building kit or the like, nor to further maintain such a helicopter.

As a result, such a model helicopter comes within anyone's reach without any technical luggage being required, and moreover it is no longer necessary to distribute such a model helicopter via specialist shops.

In order to better explain the characteristics of the invention, the following preferred embodiments of a device according to the invention are described as an example only without being limitative in any way, with reference to the accompanying drawings, in which: figure 1 schematically represents a helicopter in perspective, equipped with a device according to the invention; figure 2 represents the part indicated by F2 in figure 1 to a larger scale; figure 3 represents a disassembled view of the part represented in figure 2; figure 4 represents a section according to line IV-IV in figure 2; figure 5 represents a section according to line V-V in figure 4; figure 6 represents the part indicated by F6 in figure 1 to a larger scale; figure 7 represents a section according to line VII- VII in figure 6; figure 8 represents a side view of the helicopter from figure 1 ; figure 9 represents a section according to line IX-IX in figure 1 ; figure 10 represents a section as in figure 9, but for another position; figure 11 represents a diagram of the successive positions of the rotor blades of the helicopter ;

figure 12 represents a view as in figure 8, but for another position; figure 13 represents a variant of the embodiment of a device according to the invention; figure 14 represents a top view of yet another embodiment of a device according to the invention.

Figure 1 represents a helicopter 1 which is equipped with a device according to the invention.

The helicopter 1 is in this case a model helicopter steered by means of a conventional remote control with a transmitter part 2, connected wireless to a receiver part 3 in. the helicopter 1, and whereby the transmitter part 2 is among others provided with a steering element 4 in the shape of a toggle or the like which can be moved in two directions in relation to a neutral position in order to steer the forward or backward flying, and a similar steering element 5 for flying sideways.

The helicopter 1 mainly consists of a body 6 and a rotor 7 provided upon it, which in this case is provided with rotor blades 8, namely two rotor blades 8A and 8B.

The rotor 7 has a rotor shaft 9 which is bearing-mounted in a bearing bush 10 fixed to the body 6 and which is driven at its lower end by means of a drive formed for example of a motor 11 and a reduction gearbox 12.

As is represented in figures 2 to 5, a fork-shaped support 13 is provided centrally on the top end of the rotor shaft 9, having two legs 14 which are parallel to the rotor shaft 9 and a cross piece 15 connecting the two legs 14 and which is fixed crosswise on the rotor shaft 9.

Around the support 13 is provided a rocker arm 16 with a central, hollow part, whereby said rocker arm 16 is mounted on said support 13, such that it can freely pivot around a geometric oscillatory axis Y-Y, by means of two coaxial shafts 17 and 18 respectively, provided in the above- mentioned legs 14 of the support 13, such that they can freely rotate through the passages 19 therein, and which are fixed on two parallel walls 20 of the rocker arm 16 situated opposite to one another, for example because they are provided in a bore in these walls 20 by means of a press fit.

On either side of the support 13, on the outside of the above-mentioned walls 20, are fixed plate-shaped flanges 22, situated in each other's prolongation and upon which the rotor blades 8A and 8B are provided.

The rotor blades 8 are in this case fixed on the above- mentioned flanges 22 in a fixed manner, for example by means of a press pen 23, provided through the passage 24 of the flange 22, such that the rotor blades 8A-8B, as represented in figure 9, enclose a specific adjustment angle H in relation to a plane of symmetry 22A of the

plate-shaped flanges 22, such that the rotor blades 8A and 8B are erected such that their front edge 25, which is the front tip of the rotor blades 8, is always directed in the sense of rotation of the rotor 7.

On the cross piece 15 of the support 13 are provided drive means 26 according to the invention which, in this case, consist of an electric motor 27 fixed on the cross piece 15 and which is coupled to the rocker arm 16 by means of a gear wheel transmission 28, whereby this gear wheel transmission 28 consists of a first gear wheel 28A fixed on the shaft of the motor 27 and a second gear wheel 28B working in conjunction with it which is fixed to the above- mentioned shaft 17 of the rocker arm 16.

Although, in this case, an electric motor 27 is used for the drive means 26, other electric drive means which can provide for a torque or a force, such as actuators, servomotors or the like are not excluded.

Also according to the invention, the above-mentioned motor 26 is electrically connected to the receiver part 3 of the above-mentioned remote control, by means of an electric universal joint 29 provided on the rotor shaft 9 and which is itself connected to two converters 30 and 31 respectively, converting the signals from the receiver part 3 of the remote control in two separate stress signals which are proportional to the movements of the two above- mentioned control elements 4-5 respectively.

The above-mentioned universal joint 29 is provided with a part 29A that is fixed in relation to the body 6, consisting of an insulating ring-shaped core 32 which is provided co-axially around the rotor shaft 9 and which is provided with four contact shoes on the outside, two opposite contact shoes 33 and two other opposite contact shoes 34 respectively, rotated 90° in relation to one another.

The opposite contact shoes 33-34 form contact pairs which are connected to the above-mentioned converters 30-31 by means of conductors 35-36 respectively.

The universal joint 29 is further provided with a rotating part 29B consisting of a lath 37 provided diagonally on the rotor shaft 9 in a centred manner, whereby a sliding contact 38 is hinge-mounted on each far end of this lath 37 on a shaft 39 which is parallel to the rotor shaft, and whereby these sliding contacts 38 are held against the outside of the above-mentioned fixed part 29A by means of a spring which is not represented in the figures.

The above-mentioned sliding contacts 38 are each connected to a connection contact 41 of the above-mentioned motor 27 by means of a conductor 40.

The working of the device is as follows:

While the rotor 7 is being driven by the motor 11, the rotor blades 8 move through the air, as a result of which, as is known, since they enclose a specific angle of incidence, B and C respectively, in relation to the plane of rotation 42 in which they move, they are subjected to a buoyant force or what, is called a lift which is perpendicular to the above-mentioned plane of rotation 42.

When the steering elements 4-5 are in a neutral position, the signals emitted by the converters 30-31 are equal to zero, as a result of which the motor 27 will be dead and the rocker arm 16 will be situated in a corresponding neutral position at that time, as represented in figure 9, whereby the plane of symmetry 22A of the flanges 22 is perpendicular to the rotor shaft.

For this neutral position of the rocker arm 16, the aforesaid angles of incidence B and C of the rotor blades 8A and 8B are equal to one another and moreover equal to the above-mentioned adjustment angle H, so that the lifts, indicated with LA and LB respectively, of the two rotor blades 8A and 8B will be equal, as a result of which no moment is exerted on the rotor 7 and a situation is created, for example, as represented in figure 10, whereby the common buoyant force L is in balance with the weight G of the helicopter 1, as a result of which it will for example stay hanging on the spot.

When for example, as represented in figure 12, the steering element 4 of the remote control is pushed forward in order to make the helicopter 1 fly forward, the converter 30 will generate a positive voltage applied on the contact shoes 33 via the conductors 35.

Each time the rotor blades 8 extend mainly according to the longitudinal axis of the helicopter 1, the sliding contacts 38 make contact with said contact shoes 33, as a result of which the above-mentioned voltage is transmitted to the connection contacts 41 of the motor 27 via the conductors 40.

When the rotor blades 8 rotate further into a lateral position in relation to the helicopter 1, the sliding contacts 38 will make contact with the dead contact shoes 34, as a result of which the voltage at the connection contacts 41 of the motor 27 will then drop out until the rotor blades 8 mainly extend in the longitudinal direction of the helicopter again, and the sliding contacts 38 again make contact with the live contact shoes 33, and so on.

The thus obtained voltage gradient between the contact poles 41 of the motor 27 is schematically represented in the upper diagram of figure 11 as a function of the position of for example the rotor blade 8A over an entire revolution of the rotor 7, whereby 0° corresponds to the most forward directed position of this rotor blade 8A, as represented in figure 1.

Each time the rotor blades 8A-8B are mainly directed in the longitudinal direction of the helicopter 1, i. e. for the positions corresponding to 0° and 180°, the motor 27 is excited, so that the rocker arm 16, as represented in figure 10, is rotated over a certain angle in proportion to the voltage applied, and thus in proportion to the movement of the steering element 4, for example in the direction indicated by the sense of rotation E.

As is clear from figure 10, this angular displacement of the rocker arm 16 has for a result that the angle of incidence A of the rotor blade 8A becomes smaller, and thus smaller than the neutral adjustment angle H, whereas the angle of incidence B of the rotor blade 8B simultaneously and to an equal extent becomes larger, and thus larger than the neutral adjustment angle H, so that for the above- mentioned positions corresponding to 0° and 180°, the lift LA of the rotor blade 8A in this case gets larger, whereas the lift LB of the rotor blade 8B gets smaller to the same extent, so that the common lift L remains as large as before, but as a result of which a moment of force is created which makes the rotor 7 and thus also the entire helicopter 1 heel over forward, as represented in figure 12. The lift L which is always perpendicular to the plane of rotation 42 thus obtains a forward directed component LV which makes the helicopter 1 fly forward.

Each time the rotor blades 8 are directed laterally, i. e. for the positions corresponding to 90° and 270°, the tension at the contact poles 41 of the motor 27 drops out, so that the rocker arm 16 and the rotor blades 8 return to their neutral position for these positions, whereby the angles of incidence A and B are equal to the adjustment angle H, so that the rotor blades 8A-8B are symmetrically loaded, as a result of which the rotor 7 and thus also the helicopter 1 are laterally stabilised and kept in balance, so that it will not heel over sideways.

The progress of the angles of incidence A and B and of the lifts LA and LB are represented in the diagrams of figure 11 for one revolution of the rotor blade 8A.

Thus, from what precedes, it appears that by pushing the steering element 4 forward, the helicopter 1 moves forward.

When this steering element 4 is pulled backward, the converter 30 will generate a negative signal, as a result of which the rocker arm 16, each time the rotor blades 8 mainly extend in the longitudinal direction of the helicopter 1, will tilt in the opposite sense compared to the preceding case, so that this time the lift of the rotor blade 8 situated at the front becomes larger, whereas the lift of the rear rotor blade, 8 becomes smaller, so that in this case the helicopter 1 will heel over backward and will also fly backward.

It is clear that, in the same manner, for example by pushing the steering element 5 to the left, the converter 31 will this time generate a voltage applied to the contact poles 41 of the motor 27 each time the rotor blades 8 are directed sideways, so that in this case, according to an analogous argumentation, the rotor will heel over to the left, so that the helicopter 1 is steered to the left.

It is also clear that the control elements 4-5 can be used in combination to make the helicopter 1 move in a slanting manner.

Since the tensions generated by the converters 30-31 are proportional to the movement of the control elements 4-5 concerned, the above-mentioned effect will be all the greater the more the control elements 4-5 are moved, so that the resulting speed will also increase in proportion to the movement of the control element 4-5 concerned.

In order to rise or lower the helicopter 1, the rotational speed of the motor 11 can be altered in a conventional manner, by operating an additional control element 43 on the remote control, so that the receiver part 3 can control said motor 11 via the conductor 44.

Figure 13 represents a variant of a device according to the invention, whereby the rocker arm 16 is not driven directly by the motor 27 in this case, but indirectly by making use of the aerodynamic operation of two additional vanes 45

fixed on either side of the rocker arm 16 on a common shaft 46 which is provided on the rocker arm 16 in a rotating manner and which extends crosswise to the above-mentioned rotor blades 8A-8B. On the above-mentioned shaft is provided a gear wheel segment 47 working in conjunction with a gear wheel 48 of the motor 27.

When the motor 27 does not receive a stress signal in this case, the additional vanes 45 will rotate in the plane of rotation 42 of the rotor 7, and the rocker arm 16 will be in its neutral position.

However, when the motor 27 receives a stress signal from a converter 30-31, the vanes 45 are rotated in a particular direction, so that one vane 45 develops a buoyant force and the other vane 45 develops a downward force, such that a moment of force is obtained which makes the rocker arm 16 tilt in a certain direction, as a result of which, in the same manner as in the preceding embodiment, the rotor blades 8A and 8B are loaded asymmetrically and the helicopter l. is heeled over in a certain direction.

The use of such additional vanes 45 is advantageous in that they can develop a great moment of force, such that a motor 27 with a smaller torque can be used to drive the rocker arm 16.

Another advantage of these vanes 45 is that they have a stabilising effect on the helicopter 1, such that no extra

stabilising equipment with gyroscopes, accelerometers and the like is required.

Figure 14 represents yet another variant of a device according to the invention, whereby the rotor 7 is equipped with rotor blades 8 in this case which are provided on a rotor head 49 in a rotating manner, joint with the rotor shaft 9, and whereby separate drive means. 26 are provided for each rotor blade 8, each for example in the shape of a motor 27 and a gear wheel transmission 28.

In this case, all rotor blades 8 can be steered separately, either in common so as to increase or reduce the lift, or according to a cyclic movement, as in the preceding embodiments, to steer the helicopter 1 in a particular direction. It is clear that another type of electric universal joint is required for this, which can be easily realised by a craftsman of the related technical domain.

Although we only speak of remote-controlled model helicopters in what precedes, it is clear that the invention can also be applied to real helicopters with the same advantages, whereby the necessary electric stress signals to control the motors 27 can be obtained in this case with sensors provided on the pilot's steering elements.

The invention is by no means limited to the above-described embodiments represented in the accompanying drawings; on the contrary, such a device can be made in all sorts of shapes and dimensions while still remaining within the scope of the invention.