HELICOPTER SINGLE-BLADE ROTOR

Abstract: The present invention relates to a single-blade main rotor for helicopters designed so that the component of the blade lift normal to the rotational axis of the rotor is compensated by the inertial force obtained through the self-adjustment of the position of the rotor centre of mass relative to its rotation axis, it being provided that the position of the rotor centre of mass is determined by the coning angle of the blade.

Description: Description HELICOPTER SINGLE-BLADE ROTOR The present patent application for industrial invention relates to a single- blade rotor designed to be used as main rotor in helicopters and other types of rotorcraft. The rotor supports the helicopter during hovering and translated flight and, by means of its controls, allows execution of the manoeuvres typical of this type of vehicle. To this end, helicopters are usually equipped with vertical axis rotors provided with two or more identical blades joined by hinges or similar means to a central propeller hub, which is in turn fixed to the upper end of a vertical mast driven by a system for the transmission of the rotary motion connected to one or more engines. When maintained in rotation at the appropriate speed, the blades support the helicopter because of the upward lift produced as a consequence of the relative air speed with respect to the aerodynamically profiled blades. Moreover, the blades are subject to the weight force and, due to rotation, to the centrifugal force. The balance of all these forces and their moments with respect to the joints of the blades to the rotor hub and the mast, to which the weight of the rotorcraft is applied, determines the geometrical position of the blades, which, with respect to the plane orthogonal to the rotational axis, are directed upwards with a normally small coning angle. The entity of the total lift is adjusted by the pilot through the collective control lever that acts on the blade pitch by means of rods, levers, and rotating mechanisms connected with suitable pitch horns located on the hub of each blade, coupled in a rotary way to the rotor hub, with rotational axis sensibly parallel to its own longitudinal axis. The control mechanisms allow the pilot to change the pitch of each blade with the cyclic control lever, with respect to the average value determined by the collective control, in order to create pitch differences symmetrical to this average value, in positions diametrically opposed to the rotational axis, inducing the rotor disk to tilt, thus causing the helicopter to move in the corresponding direction of tilting. Rotors are usually manufactured according to multiple solutions, all of which, in order to guarantee correct operation, require the blades to be identical in terms of entity and mass distribution and as similar as possible in terms of shape and aerodynamic behaviour, while the joints at the rotor head and the kinematic chain that controls their pitch must have the same characteristics for all the blades of the rotor. Therefore, in order to maintain acceptable performance, such rotors require frequent maintenance works of blades tracking and balance, involving complicated procedures and methods and using special equipment. In such multi-blade rotors, the lifting surface is divided between the blades of the rotor. With the same diameter and solidity, in a multiblade rotor each blade has a shorter mean chord which, for a given rotor tip, results in a lower value of the ratio between the product of the speed multiplied by the chord and the kinematic viscosity of the air (Reynolds Number). Since this lower value results in an increased blade drag coefficient for a given lift, it is therefore convenient to reduce the number of blades. Moreover, it must be stressed that the rotation of each lifting blade produces a wake that can disturb the following blade, especially during hovering or low speed flight, with negative effects on its performance. The time interval between the passage of one blade in a disk area and the following increases as the number of rotor blades decreases, under given conditions, thus reducing the perturbation of the air in which the rotor operates. In view of the above considerations, whenever possible, the adoption of a reduced number of blades can give aerodynamic advantages over similar rotors with a higher number of blades. Moreover, the reduction in the number of blades decreases the number of components and moving parts, leading to the simple bi-blade rotor with suspended hub connected to the mast with a horizontal hinge normal to the rotational axis. Experiments have also been carried out with single-blade rotors in which the blade is balanced by a counterweight, but the difficulties in obtaining an acceptable balance between the forces and moments acting on such rotors under various operating conditions have not allowed the application and diffusion of such solutions. The main purpose of the present invention is to overcome the inconveniences found in multi-blade and single-blade helicopters of known type, by means of a main rotor system for helicopters consisting of a single blade with central hub, a counterweight and balancing devices, having high flexibility and adaptability and characterised by easy construction, safe use and efficient operation. The second purpose of the present invention is to create a single-blade rotor system, with working mechanisms, in which the balance of the forces and moments acting on its parts is obtained by means of the reciprocal positions assumed by these parts as the coning angle of the single blade varies. The mechanisms controlling rotor balancing may be kinematic systems of known type, or other electromechanical or hydraulic devices. In any case, the horizontal component of the lift of the single blade is balanced by an identical opposed misbalance of centrifugal inertial forces, obtained by moving the rotor centre of mass relative to its rotation axis. The third purpose of the present invention is to devise a rotor system, with control mechanisms, which does not require blades-tracking to ensure correct operation. Last, but not least, another aim of the present invention is to design a mechanism capable of creating and maintaining a stable balance between the elements of the single-blade rotor during operation. These and other aims, which will be highlighted in the description below, can all be achieved by the present invention, a single-blade rotor system for helicopters and other types of aircraft using lifting rotors, comprising: - A helicopter blade, whose hub features a lag hinge, of virtual type also, provided with damper or equivalent means, axis almost parallel but eccentric to the rotation axis of the rotor, this blade being connected to a central hub by the pitch hinge only, thus being rigidly fixed to the hub both in the plane identified by its longitudinal axis and the rotational axis of the rotor, and in the rotational plane. - A counterweight, made up of various elements and connected to the central hub with a hinge, appropriately fitted with friction devices with axis perpendicular to its longitudinal axis, lying on a plane normal to the rotational axis; - Mechanical systems connecting the mast to the hub, allowing the latter to incline upwards together with the blade, assuming the appropriate coning angle, and allowing the blade-hub-counterweight assembly to oscillate around an hinge located at the top of the mast, enabling the rotor to tilt stably in all directions, under the action of the cyclic control of the blade pitch; Operational devices, consisting of kinematic mechanisms or electromechanical or hydraulic actuators, of known type, in charge of positioning the rotor centre of mass with respect to the rotational axis of the mast according to the coning angle assumed by the blade, due to the lift, through the motion of the hub relative to the counterweight, acting on the parts connecting the hub with the mast, and thus keeping the aerodynamic and inertial forces acting on the rotor in equilibrium. Further characteristics and advantages of the invention will become more evident from the following description of three different embodiments, with reference to the enclosed drawings, which are intended for purposes of illustration and not in a limiting sense, whereby: - Fig. 1 is a schematic side view of the single-blade rotor and the devices used to maintain the balance, normal to the rotational axis of the rotor and the longitudinal axis of the blade according to a first embodiment; - Fig. 2 shows the same embodiment in an exploded axonometric view; - Fig. 3 and 4 are the same as Fig. 1 , with the rotor blade inclined at a given coning angle; - Fig. 5 is a schematic side view of the single-blade rotor and the devices used to maintain the balance, normal to the rotational axis of the rotor and the longitudinal axis of the blade according to a second embodiment; - Fig. 6 is a schematic side view of the single-blade rotor and the devices used to maintain the balance, normal to the rotational axis of the rotor and the longitudinal axis of the blade according to a third embodiment. The above figures show that the hub (1) of the rotor is joined to the support (14) of the blade (8) and made up of a vertical pair of plates (1a and 1 b) symmetrical to the mast (7). The blade (8) is joined to the support (14) by a pitch hinge of known type, so that the blade can rotate around its longitudinal axis (A-A), changing its geometrical pitch through joints and devices of known type, very similar to those generally used in helicopter rotors, applied to the pitch horn (9) of the blade, controlled by the rod (10). The blade (8) is also fitted with an hinge, of virtual type also, with axis (B-B) in vertical and eccentric position with respect to the axis (Y-Y) of the mast which allows it to assume an angular position in the plane orthogonal to the rotational axis (Y-Y), the said hinge being equipped with a damper or similar known devices. The two plates (1a and 1 b) making up the hub (1 ) contain two holes (1c) on the same axis (R-R) in which the cylindrical body (2) is coupled in a rotary way, the said body being centrally hollow and coupled in a rotary way also to the top of the mast (7) by means of a pair of opposing hinges (7a), appropriately provided with friction devices, with axis (X-X) normal to the same mast. The two opposite sides of the cylindrical body (2) also house two rotating coaxial cylinders (3) with axis (T-T) eccentric to the other axis (R-R) and (X-X) in a rotary way. The cylinders (3) are housed in an opposing coaxial pair of eccentric holes (2b) located in the afore mentioned hollow body (2), which features another opposing coaxial pair of holes (2a), housing the hinge (7a) mentioned above. These cylinders (3) are in turn connected through revolving eccentric pins (4) to two pairs of identical levers (5) of the hub (11) of the counterweight, comprising the hub (11) placed at the end of an arm (12), featuring a profiled mass (13) at the other end. The hub (11) is hinged in a rotary way to the rotor hub (1) by conaxic hinges (6) with appropriate friction devices, normal to the longitudinal axis of the counterweight. More exactly, the hinges (6) are housed in two opposite coaxial holes located on the plates (1a and 1 b) of the hub (1) along an axis (W-W) parallel to, but underlying, the axis (R-R). When the blade rotates without lift (Fig. 1), it rotates in almost the same horizontal plane as the counterweight , whose axis is formed by extending the axis (A-A). When the pilot increases the geometrical pitch of the rotating blade with the collective control, the -lift inclines the blade upwards at a coning angle (β) such that the lift balances with the other forces and moments acting on the blade (Fig. 3). When executing this movement the blade (8) drags the hub (1 ) to which it is joined, which rotates around the axis (R-R) of the cylindrical body (2) at a corresponding angle (β). The rotation also takes place with respect to the counterweight, which maintains its longitudinal axis orthogonal to the rotation axis. Thanks to this relative motion, the cylinders (3) linked by the revolving eccentric pins (4) to the levers (5) of the counterweight and the cylindrical body (2), coupled in a rotary way to the hub (1) rotate around each other, determining a new position of the hub (1) relative to the rotational axis (Y-Y) passing through (X- X), that is, a different position of the rotor centre of mass with respect to the rotational axis. Since the lift is perpendicular to the blade, the coning of the blade involves a horizontal component of the lift, directed towards the centre of rotation. The horizontal force composes with the inertial forces affecting the blade and the counterweight. By appropriately dimensioning the relative positions of the pins (4), the hinges (6) and the axes (R-R), (X-X), (T-T) using known calculation methods of known type and considering the masses and positions of the relative barycentres of the blade, counterweight and the other components of the rotor and the mutual joints, it is possible, within the normal range of coning values to set up a sufficiently approximate and stable balance which remains constant on variating the coning angle and is practically independent of the rotational speed of the rotor, since the forces that act on the rotor - whether due to lift or inertia - all proportional to the square of the rotational speed. The pitch variations, caused by the pilot acting on of the cyclic control from the pilot or determined by the asymmetry of the air flow investing the blade during horizontal flight, cause the rotational plane of the counterweight to tilt, with consequent tilting of the entire rotor around the axis (X-X), as illustrated in Fig. 4, thus allowing the helicopter to be moved and controlled. Fig. 5 illustrates a second embodiment - but not last - of the present invention in which the displacement of the rotor centre of mass relative to the rotational axis, in order to balance the horizontal component of the lift, is carried out by an electromechanical actuator (15) acting between pins (16) and (17), respectively joined to the hub (1) of the rotor and the cylindrical body (2), which is in turn coupled in a rotary way with the hub, electrically controlled by a control box (18) according to the value detected and transmitted with electrical signals by the telescopic detection device (19) of known type of the relative distance assumed by the points (20) and (21), in relation to which the detector (19) is respectively hinged to the hub (11) of the counterweight and the hub (1) of the rotor, as the coning of the blade (8) changes. In fact, the control box is designed and programmed using known calculation methods and construction systems, so that for each coning value of the blade as measured by the detector device (19), the actuator (15) causes the cylindrical body (2) to rotate around the hub (1) so that the rotor centre of mass relative to the rotation axis, passing through (X-X), assumes the correct position to ensure balance between the aerodynamic and inertial forces acting on the rotor. Fig. 6 illustrates a third embodiment of the present invention, in which the actuator (15) controlled by the control box (18) radially displaces the mobile mass (22) that slides on the rod (12) of the counterweight, according to the coning angle measured by detector (19), thus changing the position of the rotor centre of mass relative to the rotational axis of the rotor. The actuator (15) is joined by hinging pins (16 and 16a) to one of the plates of the hub (1) and to the mobile mass (22). In this construction version the two plates of the hub (1) only show two opposing holes located along the same axis (X-X) perpendicular to the rotational axis (Y-Y) of the rotor. The holes house the pins (7a) located at the top of the mast (7). The present invention can be presented in different embodiments, modifications and versions, which are all included in the scope of the present invention. Furthermore, all the elements can be replaced with other technically equivalent items; the materials used, as well as dimensions and number of components, may vary according to the specific requirements.

Claims: Claims 1 ) Single-blade main rotor for helicopters comprising: • a blade, made according to known systems, provided with a lag hinge with friction or equivalent device near the hub eccentric to the rotational axis of the rotor, with vertical axis and pitch hinge, or equivalent device, coaxial to the blade and joined to the hub; • a counterweight; • a central hub; • mechanisms connecting the hub to the mast; • adjusting devices; characterised by the fact that the component of the blade lift, normal to the rotational axis of the rotor, is compensated by the inertial forces obtained through the self-adjustment of the position of the rotor centre of mass relative to its rotation axis, and that the position of the centre of mass being determined by the coning angle of the blade. 2) Single-blade rotor for helicopters, according to the above claim, characterised by the fact that, when the coning of the blade changes, the relative motion between the blade and the counterweight causes simultaneous displacement of the rotor centre of mass relative to the rotational axis by means of kinematic mechanisms, or other types of known actuators, connecting the hub of the rotor, the counterweight and the parts connecting the hub to the mast. 3) Single-blade rotor for helicopters, according to claim 1 , characterised by the fact that, when the coning of the blade changes, the relative motion between the blade and the counterweight causes simultaneous displacement of the rotor centre of mass relative to the rotational axis by means of known devices that displace mobile masses on the counterweight with respect to the rotational axis of the rotor. 4) Single-blade rotor for helicopters, according to claims 1 and 2, of the type comprising: • a mast (7) with vertical rotational axis (Y-Y); • a hub (1) joined to the mast (7) and provided with a support (14) for the blade (8); • a single blade (8) joined to the support (14) by a pitch hinge of known type that allows it to rotate around its longitudinal axis (A-A); • a counterweight made up of a profiled mass (13) located at the end of an arm (12) with a hub (11), at the other end, used to hinge it to the hub (1 ) of the rotor; characterised by the fact that: • the hub (1 ) can oscillate with respect to an axis (R-R) orthogonal to the rotation axis (Y-Y) of the mast (7); • the hub (11 ) of the counterweight (13) is hinged to the hub (1 ) of the rotor with the possibility of oscillating, with friction, with respect to an axis (W- W) parallel to the axis (R-R), underlying it; • the oscillation of the hub (1 ) with respect to the axis (R-R) caused by a variation of the coning angle of the blade (8) does not determine the corresponding inclination of the rotational plane of the counterweight (13), whose rotational plane remains orthogonal to the rotational axis (Y-Y) of the mast (7); • the oscillation of the hub (1) around the axis (R-R) causes the displacement of the rotor centre of mass relative to the rotation axis (Y-Y), with subsequent balance of the lift component of the blade (8), normal to the rotational axis of the rotor (Y-Y). 5) Single-blade rotor for helicopters, according to claim 4, characterised by the fact that the rotor comprises: • an opposing pair of identical plates (1a and 1b) featuring one opposing pair of holes (1 c) and a second opposing pair of holes (1d); • a cylindrical body (2) featuring a deep hollow, into which the top of the mast (7) is inserted, featuring an opposing coaxial pair of pins (7a), appropriately fitted with friction, that are housed in two corresponding eccentric holes (2a) in the body (2), that features another opposite coaxial pair of eccentric holes (2b), which house the cylinders (3), to which the levers (5) located on the hub (11) of the counterweight (13) are fixed by means of revolving eccentric pins (4), with the levers joined to the plates (1a and 1b) by means of pins (6), fitted with friction devices and inserted in the holes (1d); it being provided that: • the plates (1a and 1 b) are free to oscillate on the body (2) around an axis (R-R) passing through the centre of the opposite pair of holes (1 c) and in orthogonal position with respect to the rotation axis (Y-Y) of the mast (7); • the body (2) is free to revolve on the opposing pair of pins (7a) around an axis (X-X) orthogonal to the rotational axis (Y-Y) of the mast (7), • the rollers (3) are free to revolve in their housings (2b) around an axis (T- T) parallel to the axis (X-X); • the hub (11) is free to revolve, with friction, on its supporting pins (6) around an axis (W-W), perpendicular to the mast (7) intersecting the latter below than the pins (7a). 6) Single-blade rotor for helicopters, according to claim 4, characterised by the fact that the rotor comprises: • an opposing pair of identical plates (1a and 1b) featuring an opposing pair of holes (1c); • a cylindrical body (2) featuring a hollow opening into which the top of the mast (7) is inserted, featuring an opposing coaxial pair of pins (7a), appropriately fitted with friction devices, that are housed in two corresponding eccentric holes (2a) of the body (2); • an actuator (15) of electromechanical type, whose hinging pins (16 and 17) are respectively joined to one of the plates of the hub (1) and to the cylindrical body (2); • a telescopic detection device (19) whose ends are respectively hinged to the hub (11) of the counterweight and to one of the plates of the hub (1); • a control box (18) that controls the actuator (15) according to the distance between the points (20) and (21) detected and transmitted by the device (19); it being provided that: • the plates (1 a and 1 b) are free to oscillate on the body (2) around an axis (R-R) passing through the centre of the opposing pair of holes (1c) ■5 orthogonal to the rotational axis (Y-Y) of the mast (7); • the body (2) is free to revolve on the opposing pair of pins (7a) around an axis (X-X) orthogonal to the rotational axis (Y-Y) of the mast (7), • the hub (11) is free to revolve on the pins used to hinge it to the plates (1 a and 1 b) around an axis perpendicular to the mast (7) and coinciding with the hinging pin (16) of the actuator (15). 7) Single-blade rotor for helicopters, according to claims 1 , 3 and 4, characterised by the fact that the rotor comprises: • a hub (1) made up of: • an opposing pair of identical plates (1a and 1b) featuring an opposing pair of holes (1c) along the same axis (X-X) perpendicular to the rotational axis of the mast (7); • a mast (7) featuring an opposing coaxial pair of pins (7a), appropriately fitted with friction devices housed in the eccentric holes (2a) of the body (2); • an actuator (15) of electromechanical type, whose hinging pins (16 and 16a) are respectively joined to one of the plates of the hub (1) and to a mobile mass (22) that slides on the arm (12) of the counterweight (13); • a telescopic detection device (19) whose ends (20 and 21 ) are respectively hinged to the hub (11) of the counterweight and to one of the plates of the hub (1); • a control box (18) that controls the actuator (15) according to the distance between the points (20) and (21) detected and transmitted by the device (19); it being provided that: • the hub (11) is free to revolve around the axis (X-X); • the displacement of the mobile mass (22) causes a displacement of the rotor centre of mass with respect to the rotation axis (Y-Y) with subsequent balance of the lift component of the blade (8), normal to the rotational axis of the rotor (Y-Y).

Inventors: LIDAK VLADIMIRO, LIDAK, VLADIMIRO
Applicants: LIDAK VLADIMIRO, LIDAK, VLADIMIRO
Application year: 1999
Main classification: B64C27
IPC codes: B64C27