MX2008009001A - Stiff-in-plane gimbaled tiltrotor hub - Google Patents

Abstract

A rotor-hub for a rotary-wing aircraft is disclosed. The rotor-hub comprises a yoke comprising a plurality of yoke arms and a plurality of yoke straps, wherein the yoke arms are joined together by the yoke straps, and wherein a plurality of inner walls of the yoke define a central void space. A pitch horn is movably connected to the yoke and a portion of the pitch horn is located within the central void space. A connecting shell is fixedly attached to the yoke.

Description

CONVERTIPLAN BASE SUSPENDED TO THE RIGID PLANE CARDAN TECHNICAL FIELD This invention relates to the field of rotor bases of rotary wing aircraft. In particular, this invention relates to a base of convertiplan suspended to the gimbal of rigid plane.

BACKGROUND OF THE INVENTION Rotor bases have been used for several years. There are numerous successful designs of rotor bases for various types of rotary wing aircraft. The rotor bases are generally designed for, and therefore particularly suitable as, means for connecting rotor blades to a rotating shaft or mast. It is common for those skilled in the art of rotary wing aircraft designs to classify rotor bases into two important categories: "rigid plane" and "smooth plane". A rigid plane rotor base is used in the rotary wing aircraft where the natural frequency of plane vibration / advance-retardation of rotor blades is higher than the rotary frequency of the rotor and the natural frequency of vibration outside the rotor. plane / flapping of the rotor blades. A soft plane rotor base is used when the natural frequency of plane vibration / advance-retardation of the rotor blades is less than the rotating frequency of the rotor and the natural frequency of vibration out of plane / flapping of the blades of rotor. It is well known that the associated rotor blades and rotor base of a rotary wing aircraft become less dynamically stable while the natural frequencies of plane / flutter vibration of the rotor blades and vibration in plane / advance- delay of the rotor blades converge towards equal values. Therefore, it is not unusual for a rotary wing aircraft to be designed in such a way that the natural frequencies of the plane / flutter vibration of the rotor blades and the plane vibration / advance-delay of the rotor blades maintain a minimum separation of approximately 25% of the rotating frequency of the rotor. When choosing between rigid plane and soft plane systems, several high level generalizations are generally considered while designing a rotating wing craft. The combined weight of the rotor base and the rotor blades of a rigid plane rotating wing aircraft is generally heavier than the combined weight of the rotor base and rotor blades of a smooth plane rotary wing aircraft. However, it is currently thought that the set of rigid plane components are a better solution for traveling at high speeds and / or producing greater thrust, while more easily maintaining dynamic vibratory stability.

One of the numerous variables in achieving the desired dynamic vibrational stability of the rotor base and the rotor blades of a rigid plane rotating wing aircraft is the angle d3. Figure 1 of the prior art shows a diagram of a rotor base illustrating the angle 83 in relation to a rotor system. Because one end of the steering shaft is contained by the pitch connection and the other end of the steering shaft is attached to the blade, a pitch change will occur while the blade flaps. Therefore, the angle d3 represents a correlation between the rotor flutter and the rotor blade pitch. While the rotor blade flaps upwards, a rotor system with a positive angle d3 will experience a downward pitch, while a rotor system with a negative angle d3 will experience an upward pitch. Angle 83 is manipulated to provide dynamic stability as well as to reduce the rotor's flapping amplitudes during burst alterations and / or pilot maneuvers. As an example, the angle d3 in a three-bladed convertiplane aircraft is generally set to values close to -15 degrees, which provides an adequate level of stability and flutter attenuation. The demand is increasing for rotary wing aircraft to achieve more thrust, high speeds and carry heavier loads. For example, there is a demand for more powerful convertiplano aircraft. One way to produce more thrust is to increase the number of rotor blades. The current convertiplano aircraft generally uses three-blade rotor systems. In three-blade rotor systems, the steering shaft and the pitch connection (see Figure 1 of the prior art) are generally located in plane with the rotor base and outside the rotor base. However, achieve small angles 63 (for example d3 angles near -15 degrees) for a multi-bladed rotor having four or more blades, while locating the steering axis and pitch connection generally in plane with the base and Outside the base presents an important design challenge. The configuration of the rotor base, as described above for multi-blade rotor systems, does not allow the steering axes to be located in the proper positions due to structural interference. Further, it is widely accepted as desirable by those skilled in the art of rotary wing aircraft design to configure the rotating component assembly of the rotor system to remain as close as possible to the axis of rotation to decrease the resulting undesired forces that lead to premature failure of the component. While the rotor base advances described above represent important developments in the design of rotor bases, some considerable defects remain.

BRIEF DESCRIPTION OF THE INVENTION There is a need for an improved rotor base. Therefore, it is an object of this invention to provide an improved rotor base that allows the connection of four or more rotor blades while maintaining optimum angles d3. This objective is achieved by providing a rotor base in which the pitch connections and steering axes are located within an internal vacuum of the rotor base. For example, the rotor base may be configured: (1) with a connecting frame located on the rudder; (2) with a connecting frame located below the rudder; and (3) with two connecting frames, a connecting frame located on the rudder and a connecting frame located under the rudder. This invention provides important advantages that include: (1) allowing the use of more than three blades in a rotor system of a convertiplano aircraft; (2) reduce the chance of damage to the steering shaft due to debris or ballistic attack; (3) reduce the chance of damage to the impulse connection due to the debris or ballistic attack; (4) offer a regulation of the base spring; and (5) improve the transfer of force between the base springs and the rudder. Objectives, characteristics and additional advantages will be evident in the following description.

BRIEF DESCRIPTION OF THE DRAWINGS The novel features of the invention are set forth in the appended claims. However, the invention itself, as well as the preferred mode of use, and other objects and advantages thereof will be better understood by means of the references of the following detailed description when read in conjunction with the accompanying drawings in which: Figure 1 of the prior art is a simplified schematic representation of the effect of the angle d3 in a rotor system; Figure 2 is an elevation view of a convertiplane aircraft having a rotor base according to the preferred embodiment of this invention; Figure 3A is a perspective view of a rotor base used in the convertiplano aircraft of Figure 2; Figure 3B is a perspective view of the rudder of the rotor base of Figure 3A; Figure 4 is a perspective view of the rotor base of Figure 3A with the connection frame removed; Figure 5 is a top view of the rotor base of Figure 3A with the connecting frame removed; Figure 6 is a top view of the rotor base of Figure 3A; Figure 7 is a cross-sectional view of the rotor base of Figure 3A taken along line 7-7 in Figure 3A; Figure 8 is a partial perspective view of the rotor base having a connecting frame located below the rudder according to an alternative embodiment of the invention; Figure 9 is a cross-sectional view of the rotor base of Figure 8 taken along the line 9-9 in Figure 8; Figure 10 is a perspective view of the rotor base having two connection frames according to an alternative embodiment of this invention; and Figure 11 is a cross-sectional view of the rotor base of Figure 10 taken along line 11-11 in Figure 10.

DETAILED DESCRIPTION OF THE INVENTION This invention is an improved rotor base that allows the connection of four or more rotor blades while maintaining optimum d3 angles. There are three main embodiments of the invention: (1) with a connection frame located on the rudder; (2) with a connecting frame located below the rudder; and (3) with two connecting frames, a connecting frame located on the rudder and a connecting frame located under the rudder. However, the scope of this invention is not limited to the particular embodiments described herein in the drawings. The rotor base of this invention allows the incorporation of four-bladed rotor systems in rotary wing aircraft of convertiplan. NeverthelessWhile specific reference is made to using this invention with convertiplan rotary wing aircraft, this invention may alternatively be used with any other rotary wing vehicle / craft. In addition, the rotor base of this invention can alternatively be used with a rotating system having more or less than four rotor blades. Figure 2 shows a rotary wing aircraft of convertiplano incorporating a rotor base of this invention. Figure 2 illustrates a convertipplane aircraft 11 in a flight operation airplane mode. The wings 15, 17 are used to raise the body of the ship 13 in response to the action of the rotor systems 19, 21. Each rotor system 19, 21 is illustrated with four rotor blades 23. The nacelles 25, 27 substantially enclose rotor bases 29 which prevent the rotor bases 29 from being seen in Figure 2. Of course, each rotor system 19, 21 is driven by a motor (not shown) substantially housed within each gondola 25, 27 respectively . Figure 3A illustrates a perspective view of the preferred embodiment of the rotor base 29 of this invention. The rotor base 29 is illustrated with a rudder 31 having rudder arms 33 and rudder strips 35. The rudder arms are integrally connected to the rudder strips 35. In one embodiment, the rudder 31 is constructed of composite materials. More specifically, the rudder 31 is constructed of a multiplicity of differently bonded layers of directional fiber material. However, the rudder 31 may alternatively be constructed from any suitable material in any suitable manner. Further, while the rudder 31 is illustrated with four rudder arms 33, other rotor base configurations according to this invention may comprise more or less than four rudder arms 33 for connection with more or less than four rotor blades 23 respectively. The rotor base 29 is further illustrated with representative pitch change axes 37A, 37B, on which the pitch of the rotor blades 23 (see FIG. 2) is altered. Additionally, the rotor base 29 is illustrated with a rotational axis of the representative mast 39, on which a mast (not shown) is rotated when driven by an operably associated transmission (not shown). The outer pawl bearings 41 allow at least some degree of rotation of the rotor blades 23 on the pitch change axes 37A, 37B. The centrifugal force bearings (CF) 43 are attached to the outer flange bearings 41. The bearings CF 43 are main intermediate connection devices between the rotor blades 23 and the rotor base 29. The bearings CF 43 support the centrifugal force generally large generated by the rotating rotor blades 23 on the axis of rotation of the mast 39.

Figure 3B illustrates a simplified view of the rudder 31 of the rotor base 29. A central void space 30 is defined by the inner walls 32 of the rudder 31. As illustrated in Figure 7, the base spring 45 includes an inner core 47 comprising a first series of several alternatively stacked rubber elements and metal spacer elements (none shown in detail) between an upper and outer connecting frame 49 and an internal frame 51 and a second series of several rubber elements stacked alternately and of metal spacer elements between an outer bottom layer 50 and another inner layer 51. The frames 49-51 are illustrated as being constructed of metal. The base spring 45 allows the suspension to the gimbal of the rudder 31 with respect to the mast and the axis of rotation of the mast 39. The base spring 45 also accommodates the flapping of the rotor blades 23 and transfers the thrust. As can be seen more clearly in Figure 4, where the rotor base 29 is illustrated without the connecting frame 49, the rotor base 29 further comprises four steering axes 53. The steering axes 53 comprise axle arms. direction 55 and internal beams of the steering shaft 57. The steering axes 53 are rotatably connected to intersections 59 through the internal flange bearings 61. The internal flange bearings 61 are centered substantially along the axes of corresponding pitch change 37A, 37B. The internal pads 61 are operably associated with openings of similar size on the steering axes 53 located substantially at the intersection of the steering shaft arms 51 and the internal beams of the steering axles 57. The grips (not samples) are connected to the internal beams of the steering shaft 57 such that when the steering axes 53 are rotated about their corresponding pitch change axes 37A, 37B, the handles cause the rotor blades 23 (shown in FIG. 2), which are attached to the grips, to rotate correspondingly on the pitch change axes 37A, 37B. The ends 63 of the steering axes 53 are illustrated in a neutral / nominal position when the ends 63 are substantially centered on the plane created by the pitch change axes 37A, 37B. The ends 63 of the steering axes 53 are connected to the upper ends of the pitch connections 65. The pitch connections 65 are rod-like elements oriented substantially parallel to the mass rotation axis 39. The movement of the pitch connections 65 in either direction along a path parallel to the axis of rotation of the mast 39 will raise or lower the ends 63, thereby rotating the steering shaft arms 55 and the internal beams of the steering shafts 57 on their axes of rotation. pitch change 37A, 37B, changing the pitch of the rotor blades 23. The direction axes 53 are located substantially within the central void space 30. A central void column is defined by extending the vertical boundaries of the central void space 30 upwards and downwards and represents the vertical footprint of the central empty space 30. For example, the central empty column occupies at least the space between the upper print 34A and the lower print 34B as illustrated in FIG. 3B. In this embodiment, the arms 55 extend out of the central empty column. However, in other embodiments of this invention, arms 55 may alternatively remain within the central empty column. As can be clearly seen in Figure 5, where a top view of the rotor base 29 is illustrated without the connecting frame 49 and the upper lower frame 50, the rotor base 29 further comprises a constant speed / constant velocity joint ( not shown completely) which comprises impulse connections 67. The impulse connections 67 are oriented substantially parallel to the plane created by the pitch change axes 37A, 37B. One end of each impulse connection 67 is adapted for connection to a trunnion (not shown) by slotting into the shaft of the mast / pulse (not shown). The trunnion transfers the rotational force from the mast to the impulse connections 37. The other end of each impulse connection 67 is adapted for the attachment to the legs 68 of the connection frame 49 (see figures 10 and 11) which it transfers the rotational force, from the impulse connections 67 in the connecting frame 49. The connecting frame 49 is connected to the rudder 31 along rudder strips 35 in such a way that the rotating force is transferred from the connecting frame 49 at the rudder 31. Figure 6 illustrates a top view of the rotor base 29, while figure 7 illustrates a cross-sectional view of the rotor base 29 taken along line 7-7 of figure 3A which corresponds to the axis of pitch change 37A, 37B. Referring now to Figures 8-9 in the drawings, a rotor base embodiment according to this invention also incorporates a base spring 71 similar to the base spring 45. However, the connecting frame 72 of the base spring 45 it is located under a rudder 73. As illustrated in Figure 8, a rotor base 69 is substantially similar to the rotor base 29 and comprises substantially similar components with three important differences: (1) the connecting frame 72 is located in the lower part of the rudder 73 more than in the upper part of the rudder 73; (2) the steer axes 75 are curved, rod-like structures, portions that are located slightly above the plane created by the pitch change axes 77A, 77B, but which are within a central void space defined by the internal walls 32 of rudder 73; and (3) the impulse connections 81 are illustrated located slightly below the plane created by the pitch change axes 77A, 77B but even substantially within the central void column. It will be noted that the rotor base 69 may alternatively comprise steering axes 53, which may be substantially within the plane created by the pitch change axes 77A, 77B. Similar to the embodiment of Figures 3-7, the base spring 71 permits suspension to the gimbal of the rudder 73 with respect to the mast and the axis of rotation of the mast 39 (shown in Figure 3A).

The base spring 71 also accommodates the flapping of the rotor blades 23 (shown in Figure 2) and transfers the thrust. With respect to Figures 10-11 in the drawings, a rotor base embodiment according to this invention having a base spring 85 comprises two connecting frames 86. As shown in Figure 10, the rotor base 83 is substantially similar to the rotor base 29 and comprises substantially similar components except that two connecting frames 86 are inside the rotor base 83. A connecting frame 86 is mounted on the bottom of the rudder 87 while the other frame of connection 86 is mounted on top of the rudder 87. An important advantage of the rotor base 83 is the adjustment of the connecting frame 86. For example, if one of the connecting frames 86 is damaged by bullets or fails for any reason , the remaining connection frame 86 can continue to operate normally. Another important advantage of a modality having two connecting frames 86 is the improved distribution resulting from the forces that are transferred from the base springs 85 to the rudder 87. Similar to the embodiments of Figs. 3-7, the base springs 85 they allow the suspension to the gimbal of the rudder 87 with respect to the mast and the axis of rotation of the mast 39 (shown in Figure 3A). The base springs 85 also accommodate the flapping of the rotor blades 23 (shown in Figure 2) and transfer the thrust. An important advantage of the invention is that, while providing for the use of four or more rotor blades per rotor base, most of the components are packed substantially substantially within an interior void space between the rudder strips. This arrangement makes the rotor bases of this invention a more difficult target for enemy combatants and a likely minor target for unintentional debris. In addition, this invention allows numerous variations in the path of the steering shaft. For example, when a connecting frame is only located at the top of a rudder, more space is available for the path of the downward direction axis. Similarly, when a connecting frame is only located at the bottom of a rudder, more space is available for the path of the ascending direction shaft. Also, when the connecting frames are located both on the top and bottom of a rudder, the path of the steering axle can be divided more evenly between the up travel and the down travel. Finally, for each of the embodiments described above, a CF bearing failure could generally not result in the loss of a rotor blade. However, the steering shaft associated with the damaged CF bearing could be dragged towards the cross associated with the rudder, such that at least temporarily, the safe operation of the aircraft could occur. It is clear that an invention with important advantages has been described and illustrated. Although this invention is shown in a limited number of ways, it is not limited to only these forms, but is willing to several changes and modifications without departing from the spirit of the invention. same

Claims (20)

NOVELTY OF THE INVENTION CLAIMS

1. - A rotor base for a rotary wing aircraft comprising: a rudder having a plurality of rudder arms, adjacent rudder arms that are joined by a rudder strip, rudder arms and rudder strips define a space central vacuum, the empty space is adapted to receive a central axis through it; at least one steering shaft having an internal beam of the steering shaft and a steering shaft arm wherein the steering shaft is hingedly connected to the rudder and the inner beam of the steering shaft is substantially positioned within the empty space central; and a constant velocity joint adapted to transfer forces from the central shaft to the rudder and wherein the constant velocity joint is substantially positioned within a central empty column.

2. The rotor base according to claim 1, further characterized in that the rudder is constructed in differentiated layers of directional fiber material.

3. The rotor base according to claim 1, further characterized in that it additionally comprises: a base spring having a first external connection frame attached elastically to the rudder.

4. - The rotor base according to claim 3, further characterized in that it additionally comprises: a second base spring having a second external connection frame attached elastically to the rudder.

5. The rotor base according to claim 1, further characterized in that the constant velocity joint comprises a pulse connection substantially positioned within the central void space.

6. The rotor base according to claim 1, further characterized in that the steering axes are configured to produce an angle d3 of about -15 degrees.

7. The rotor base according to claim 1, further characterized in that the rudder is configured to accommodate at least four rotor blades.

8. The rotor base according to claim 1, further characterized in that the rotor base is configured for use with a converlane aircraft.

9. A rotor base for a rotary wing aircraft comprising: a rudder having at least four rudder arms, each pair of adjacent rudder arms being joined by a rudder strip, the rudder arms and the rudder arms. rudder define a central empty space, the central empty space is adapted to receive a central axis through it; a steering shaft having an internal beam of the steering shaft, and a steering shaft arm wherein the steering shaft is hingedly connected to the rudder and the inner beam of the steering shaft is substantially positioned within the empty column central; and a CV joint adapted to transfer force from the central axis to the rudder, the CV joint is substantially positioned within the central empty column and wherein the steering axes are configured to produce an angle d3 of approximately -15 degrees.

10. The rotor base according to claim 9, further characterized in that the rudder is formed of a composite material constructed of differentiated layers of directional fibers.

11. The rotor base according to claim 9, further characterized in that it additionally comprises: a first base spring coupled elastically to the rudder.

12. The rotor base according to claim 11, further characterized in that it additionally comprises: a second base spring that is elastically coupled to the rudder.

13. A rotary wing aircraft comprising: a fuselage; at least one engine carried by the fuselage to provide the torque; at least one rotating wing element; a central axis for transmitting the torque to the rotating wing element; and a rotor base coupled between the central shaft and the rotating wing element, the rotor base comprises: a rudder having a plurality of rudder arms, adjacent rudder arms that are joined by a rudder strip, the arms of rudder and rudder strips define a central empty space, the empty space is adapted to receive the central axis through it; a steering shaft having an internal beam of the steering shaft and a steering shaft arm, wherein the steering shaft is hingedly connected to the rudder and the inner beam of the steering shaft is substantially placed within an empty space central; a first base spring comprising a first external connection frame that is fixedly attached to the rudder; and a homokinetic joint coupled between the central axis and the rudder, wherein the CV joint is placed substantially inside a central empty column.

14. The rotary wing aircraft according to claim 13, further characterized in that the rudder is constructed in differentiated layers of directional fiber material.

15. The rotary wing aircraft according to claim 13, further characterized in that it additionally comprises: a second base spring comprising a second external connection frame wherein the second external connection frame is fixedly attached to the rudder.

16. The rotary wing aircraft according to claim 13, further characterized in that the steering shaft is adapted to produce an angle 63 of about -15 degrees.

17. The rotary wing aircraft according to claim 13, further characterized in that the rudder is operably associated with at least four rotor blades.

18. - The rotary wing aircraft according to claim 13, further characterized in that the rotary wing aircraft is a convertiplan ship.

19. A method for adjusting the pitch of a rotor blade comprising the steps of: providing a rudder having a plurality of rudder arms, or adjacent arms that are joined by a rudder strip; and rotating a steering shaft located in a central empty column by moving a pitch connection within the central empty column, wherein the rotation of the steering shaft adjusts the pitch of a rotor blade.

20. The method according to claim 19, further characterized in that it further comprises the steps of: providing a constant velocity joint comprising pulse connections located within the central empty column.