Passive pitch angle adjustment apparatus

Abstract

A rotor or propeller may have rotor blades and a passive pitch angle adjustment apparatus. The passive pitch angle adjustment apparatus may include levers, rods, and central rod. Levers may be connected to rotor blades and rotate them around a respective pitch axis. Rods may be connected to levers and mechanically link levers with each other via central point that is located outside rotor plane. Central rod may connect central point with base point that is located in a longitudinal direction of rotor axis. The passive pitch angle adjustment apparatus may enable a cyclic pitch adjustment of the rotor blades and block a collective pitch adjustment of the rotor blades.

Claims

1. A passive pitch angle adjustment apparatus for a rotor with rotor blades that rotate around a rotor axis in a rotor plane, comprising: a first lever that is connected to a first rotor blade of the rotor blades and rotates the first rotor blade around a first pitch axis; a second lever that is connected to a second rotor blade of the rotor blades and rotates the second rotor blade around a second pitch axis; characterized by first and second rods that mechanically link the first and second levers via a central point that is located outside the rotor plane; and a central rod that connects the central point with a base point that is located in a longitudinal direction of the rotor axis, wherein a change of a first pitch angle of the first rotor blade in reaction to aerodynamic forces causes a first rotation of the first rotor blade around the first pitch axis, and wherein the first lever through the first rod, the second rod, and the second lever in connection with the central rod adjusts a second pitch angle of the second rotor blade through a second rotation of the second rotor blade with the second lever around the second pitch axis.

2. The passive pitch angle adjustment apparatus of claim 1, wherein the first rotor blade has a center of lift that is offset from the first pitch axis and creates a torsion moment that rotates the first lever around the first pitch axis in reaction to the aerodynamic forces thereby causing the change of the first pitch angle.

3. The passive pitch angle adjustment apparatus of claim 2, wherein the first lever through the first rod, the second rod, and the second lever in connection with the central rod causes an increase of the second pitch angle in response to a reduction of the first pitch angle and a reduction of the second pitch angle in response to an increase of the first pitch angle.

4. The passive pitch angle adjustment apparatus of claim 1, further comprising: a third lever that is connected to a third rotor blade of the rotor blades and rotates the third rotor blade around a third pitch axis; and a third rod that, together with the first and second rods, mechanically links the third lever to the first and second levers via the central point.

5. The passive pitch angle adjustment apparatus of claim 1, wherein the first lever, the first rod, the second rod, and the second lever in connection with the central rod enable a cyclic pitch adjustment of the rotor blades and block a collective pitch adjustment of the rotor blades.

6. The passive pitch angle adjustment apparatus of claim 5, wherein a first attachment of the first lever with the first rod and a second attachment of the second lever with the second rod perform a nearly linear movement, and wherein the central point performs a spherical movement around the base point.

7. The passive pitch angle adjustment apparatus of claim 1, wherein the first and second rods are flat straps made from a composite material.

8. The passive pitch angle adjustment apparatus of claim 7, wherein fibers of the composite material from the first rod extend into the second rod such that the first and second rods form a single coupling connection.

9. The passive pitch angle adjustment apparatus of claim 8, wherein the single coupling connection is twisted by 90 degrees between a first attachment of the first lever with the first rod and the central point and between a second attachment of the second lever with the second rod and the central point.

10. The passive pitch angle adjustment apparatus of claim 1, further comprising: a dampening device coupled between the central rod and the base point, wherein the dampening device introduces a phase shift when, in response to the change of the first pitch angle, the first lever through the first rod, the second rod, and the second lever in connection with the central rod adjusts the second pitch angle.

11. The passive pitch angle adjustment apparatus of claim 10, wherein the central rod has an enlarged foot and wherein the dampening device further comprises: an elastic plate that is connected to the enlarged foot and enables an inclination of the central rod at the base point in any direction.

12. The passive pitch angle adjustment apparatus of claim 10, further comprising: weights that are connected with the central rod at a predetermined distance from the central rod and achieve a stabilizing momentum on the central rod.

13. The passive pitch angle adjustment apparatus of claim 1, wherein the rotor further comprises first and second rigid arms that connect the first and second rotor blades to a rotor hub and bearings that are connected to the first and second rigid arms to enable flap and pitch movements of the first and second rotor blades.

14. The passive pitch angle adjustment apparatus of claim 1, wherein the rotor further comprises first and second flexible arms that connect the first and second rotor blades to a rotor hub and enable flap and pitch movements of the first and second rotor blades through elastic deformation.

15. A rotorcraft with at least one passive pitch angle adjustment apparatus according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments are outlined by way of example in the following description with reference to the attached drawings. In these attached drawings, identical or identically functioning components or elements are labeled with identical reference numbers and characters and are, consequently, only described once in the following description.

(2) FIG. 1 is a diagram of an illustrative rotary wing aircraft in accordance with some embodiments,

(3) FIG. 2 is a diagram of an illustrative passive pitch angle adjustment apparatus with bearings between rotor blades and a rotor hub in accordance with some embodiments,

(4) FIG. 3 is a diagram of illustrative spherical movements of a central point and illustrative nearly linear movements of lever-rod attachments in accordance with some embodiments,

(5) FIG. 4 is a diagram of an illustrative passive pitch angle adjustment apparatus with flexible arms between rotor blades and a rotor hub in accordance with some embodiments,

(6) FIG. 5 is a diagram of illustrative plate with flexible arms that connect respective rotor blade attachments for receiving rotor blades with a middle part that is mountable to a rotor hub in accordance with some embodiments, and

(7) FIG. 6 is a diagram of an illustrative passive pitch angle adjustment apparatus with a dampening device between a central rod and a base point and illustrative rods made from two flat straps that form a single coupling connection in accordance with some embodiments.

DETAILED DESCRIPTION OF THE INVENTION

(8) Exemplary embodiments may be included with any rotor or propeller having at least two rotor blades. For example, embodiments may be included in a rotor or a propeller of a transportation vehicle, if desired. FIG. 1 shows an example of a transportation vehicle. A transportation vehicle may be an airplane, a quadcopter, a helicopter, or any other rotary wing transportation vehicle. As shown in FIG. 1, the transportation vehicle may be a rotorcraft 1 that is exemplarily illustrated as a helicopter. Thus, for purposes of simplicity and clarity, the rotorcraft 1 is hereinafter referred to as the helicopter 1.

(9) Illustratively, helicopter 1 may have a fuselage 2 that forms an airframe of the helicopter 1. The fuselage 2 is connected to a suitable landing gear and exemplarily forms a cabin 2a and a rear fuselage 2b. The rear fuselage 2b is connected to a tail boom 3.

(10) Illustratively, helicopter 1 may have at least one multi-blade rotor 1a for providing lift and forward or backward thrust during operation. The at least one multi-blade rotor 1a comprises a plurality of rotor blades 1b, 1c that are mounted at an associated rotor head 1d to a rotor shaft 1e, which rotates in operation of the helicopter 1 around an associated rotor axis if in a rotor plane 1g.

(11) By way of example, helicopter 1 may include at least one counter-torque device 4 configured to provide counter-torque during operation, i.e. to counter the torque created by rotation of the at least one multi-blade rotor 1a for purposes of balancing the helicopter 1 in terms of yaw. If desired, counter-torque device 4 may be shrouded. The at least one counter-torque device 4 is illustratively provided at an aft section of the tail boom 3 and may have a tail rotor 4a. The aft section of the tail boom 3 may include a fin 5. Illustratively, the tail boom 3 may be provided with a suitable horizontal stabilizer 3a.

(12) If desired, the at least one multi-blade rotor 1a and/or the tail rotor 4a may include a passive pitch angle adjustment apparatus for adjusting the pitch angle of the respective rotor blades. FIG. 2 shows an illustrative passive pitch angle adjustment apparatus for a rotor.

(13) As shown in FIG. 2, the rotor may include rotor shaft 18, rotor hub 11, rotor blades 17a, 17b, 17c, rigid arms 16a, 16b, 16c to which rotor blades 17a, 17b, 17c are connected, respectively, and bearings 22a, 22b, 22c between rigid arms 16a, 16b, 16c and rotor hub 11 to enable flap movements around respective flap axes and pitch movements of rotor blades 17a, 17b, 17c around respective pitch axes 13a, 13b, 13c.

(14) The passive pitch angle adjustment apparatus may include levers 15a, 15b, 15c, rods 19a, 19b, 19c, and central rod 20. Levers 15a, 15b, 15c may be connected to rotor blades 17a, 17b, 17c and rotate rotor blades 17a, 17b, 17c around the respective pitch axis 13a, 13b, 13c. Rods 19a, 19b, 19c may be connected to levers 15a, 15b, 15c at respective lever-rod attachments 25a, 25b, 25c and mechanically link levers 15a, 15b, 15c with each other via central point 23 that is located outside rotor plane 1g. Central rod 20 may connect central point 23 with base point 24 that is located in a longitudinal direction of the rotor axis 1f. The passive pitch angle adjustment apparatus may enable a cyclic pitch adjustment of the rotor blades and block a collective pitch adjustment of the rotor blades.

(15) During operation of the rotor, rotor blades 17a, 17b, 17c rotate around rotation axis 1f, and aerodynamic forces may act on the center of lift 14a, 14b, 14c of the respective rotor blades 17a, 17b, 17c. Rotor blades 17a,17b, 17c may have a center of lift 14a, 14b, 14c that is offset from pitch axis 13a,13b, 13c, and the aerodynamic forces may create a torsion moment that rotates levers 15a, 15b, 15c around the respective pitch axis 13a, 13b, 13c. As an example, consider the scenario in which aerodynamic forces cause a change in lift of rotor blade 17a leading to a rotation of rotor blade 17a around pitch axis 13a, thereby causing a change of the pitch angle of rotor blade 17a. In this scenario, lever 15a through rod 19a, rods 19b, 19c, and levers 15b,15c in connection with central rod 20 may adjust the pitch angles of rotor blades 17b, 17c, respectively, through a rotation of rotor blades 17b, 17c with levers 15b, 15c around pitch axis 13b, 13c.

(16) In some embodiments, adjusting the pitch angles of rotor blades 17b, 17c in response to a pitch angle change of rotor blade 17a may involve predetermined movements of lever-rod attachments 25a, 25b, 25c and/or predetermined movements of central point 23. FIG. 3 is a diagram of illustrative spherical movements of a central point and illustrative nearly linear movements of two lever-rod attachments in accordance with some embodiments.

(17) As shown in FIG. 3, central rod 20 may be in position 21a and connect base point 24 with the central point that is in position 23a. Rods 19a, 19b may be linked at the central point and connected to levers at respective lever-rod attachments that are in lever-rod attachment positions 26a and 27a, respectively.

(18) Consider the scenario in which aerodynamic forces cause a change in lift of a rotor blade. For example, aerodynamic forces may increase the lift of the rotor blade, leading to a rotation of the rotor blade around a pitch axis, thereby causing a change of the pitch angle of the rotor blade. As an example, an increase in lift of rotor blade 17a of FIG. 2 may rotate rotor blade 17a clockwise around pitch axis 13a. In this scenario, lever 15a that links rotor blade 17a to rod 19a may cause lever-rod attachment 25a to move downward. As shown in FIG. 3, the lever-rod attachment may move from lever-rod attachment position 26a to lever-rod attachment position 26b. The movement between lever-rod attachment positions 26a and 26b may be a nearly linear movement that, through rod 19a, may move, central rod 20 from central rod position 21a to central rod position 21b. Since central rod 20 is connected to base point 24, the central point may perform a spherical movement around base point 24 from central point position 23a to central point position 23b. The movement of the central point from central point position 23a to central point position 23b may, through rod 19b, cause the lever-rod attachment of rod 19b with a lever to perform a nearly linear movement from lever-rod attachment position 27a to lever-rod attachment position 27b. As an example, lever-rod attachment 25b of FIG. 2 may cause lever 15b to move upwards, which may cause a rotation of rotor blade 17b counter clockwise around pitch axis 13b, leading to an increase in lift of rotor blade 17b.

(19) In some scenarios, aerodynamic forces may decrease the lift of a rotor blade, leading to a rotation of the rotor blade around a pitch axis, thereby causing a change of the pitch angle of the rotor blade. As an example, a decrease in lift of rotor blade 17b of FIG. 2 may rotate rotor blade 17b counter clockwise around pitch axis 13b. In this scenario, lever 15b that links rotor blade 17b to rod 19b may cause lever-rod attachment 25b to move upward. As shown in FIG. 3, the lever-rod attachment may move from lever-rod attachment position 27a to lever-rod attachment position 27b. The movement between lever-rod attachment positions 27a and 27b may be a nearly linear movement that, through rod 19b, may move, central rod 20 from central rod position 21a to central rod position 21b. Since central rod 20 is connected to base point 24, the central point may perform a spherical movement around base point 24 from central point position 23a to central point position 23b. The movement of the central point from central point position 23a to central point position 23b may, through rod 19a, cause the lever-rod attachment of rod 19a with a lever to perform a nearly linear movement from lever-rod attachment position 26a to lever-rod attachment position 26b. As an example, lever-rod attachment 25a of FIG. 2 may cause lever 15a to move upwards, which may cause a rotation of rotor blade 17a clockwise around pitch axis 13a, leading to a decrease in lift of rotor blade 17a.

(20) In other words, aerodynamic forces may cause a change in lift at one or more rotor blades of a rotor or propeller, which may cause a pitch angle change of the corresponding rotor blade. The passive pitch angle adjustment apparatus described above may transfer this pitch angle change to the other rotor blades. For example, a rotor blade with high lift (e.g., a rotor blade that rotates against the flight direction of helicopter 1 of FIG. 1) may reduce its pitch angle. The passive pitch angle adjustment apparatus may transform the pitch angle reduction of the rotor blade through a mechanical coupling mechanism into a pitch angle increase of the other rotor blades (i.e., of the rotor blades that have a lower lift). Therefore, the passive pitch angle adjustment apparatus provides a pitch-pitch coupling between the rotor blades, which leads to an automatic balancing of lift over all rotor blades of the rotor or propeller and therefore to a more efficient rotor or propeller in non-axial inflow fields (e.g., in case of lateral air flow during forward flight of a helicopter such as helicopter 1 of FIG. 1).

(21) In some embodiments, the rotor or propeller may have flexible arms between rotor blades and a rotor hub. FIG. 4 is a diagram of an illustrative passive pitch angle adjustment apparatus with flexible arms between rotor blades and a rotor hub in accordance with some embodiments.

(22) As shown in FIG. 4, the rotor may include rotor shaft 18, rotor hub 11, rotor blades 17a, 17b, 17c, flexible arms 62a, 62b, 62c between rotor hub 11 and rotor blades 17a, 17b, 17c, respectively, to enable flap movements around respective flap axes and pitch movements of rotor blades 17a, 17b, 17c around the respective pitch axes 13a, 13b, 13c.

(23) The passive pitch angle adjustment apparatus may include levers 15a, 15b, 15c, rods 19a, 19b, 19c, and central rod 20. Levers 15a, 15b, 15c may be connected with rotor blades 17a, 17b, 17c and/or flexible arms 62a, 62b, 62c and rotate rotor blades 17a, 17b, 17c around the respective pitch axis 13a, 13b, 13c. Rods 19a, 19b, 19c may be connected to levers 15a, 15b, 15c at respective lever-rod attachments 25a, 25b, 25c and mechanically link levers 15a, 15b, 15c with each other via central point 23 that is located outside the rotor plane (i.e., in front, behind, above, below, left, or right of the rotor plane, or any combination thereof, based on the perspective and the mounting of the rotor). Central rod 20 may connect central point 23 with base point 24 that is located in a longitudinal direction of the rotor axis 1f. In some embodiments, base point 24 may be located in the rotor plane. If desired, base point 24 may be located outside the rotor plane.

(24) FIG. 5 is a diagram of illustrative plate 60 with flexible arms 62a, 62b, 62c that connect respective rotor blade attachments 61a, 61b, 61c for receiving rotor blades with a middle part 63 that is mountable to a rotor hub such as rotor hub 11 of FIG. 4 in accordance with some embodiments. As shown in FIG. 5, flexible arms 62a, 62b, 62c may enable flap movements and pitch movements of rotor blades that are attached to rotor blade attachments 61a, 61b, 61c. If desired, rotor blade attachments 61a, 61b, 61c may receive levers such as levers 15a, 15b, 15c of FIG. 4, respectively.

(25) Flexible arms 62a, 62b, 62c may have a rectangular cross section with a width (i.e., the dimension in direction of the flap axis) that is significantly bigger than the height (i.e., the dimension perpendicular to the flap and the pitch axis) to enable a flap motion and minimize a lead-lag motion of the rotor blades.

(26) In some embodiments, flexible arms 62a, 62b, 62c may be made from a composite material. Constituent materials of the composite material may include core materials, matrix materials, which are sometimes also referred to as matrix phase or background materials, and transforming materials, which are sometimes also referred to as reinforcements or reinforcing phase. Examples for core materials include polyurethane (PU) foam, polyvinyl chloride (PVC) foam, or other foams, honeycomb cores, woods, just to name a few. Examples for reinforcements may include fibers and fabrics such as glass fibers, carbon fibers, flax, textiles, ceramic fibers, as well as carbon nanotubes, etc. Examples for matrix materials include resins, polymers, ceramics, etc. In some embodiments, plate 60 is made in one piece using a composite material.

(27) If desired, flexible arms 62a, 62b, 62c may include fibers or other reinforcements that are oriented in direction from middle part 63 to rotor blade attachments 61a, 61b, 61c (i.e., in direction of the pitch axis) and perpendicular to this direction (i.e., in direction of the flap axis). Flexible arms 62a, 62b, 62c may have a relatively high bending stiffness for flap movements of the rotor blades and a relatively low bending stiffness for pitch movements of the rotor blades, if desired. In some embodiments, a dedicated lay-up may provide a tailored stiffness for each deflection direction. For example, middle part 63 and/or rotor blade attachments 61a, 61b, 61c may be laminated with a close to quasi-isotropic lay-up. If desired, middle part 63 and/or rotor blade attachments 61a, 61b, 61c may be thicker than flexible arms 62a, 62b, 62c.

(28) Fasteners may attach middle part 63 between clamps 12 of rotor hub 11 of FIG. 4. If desired, fasteners may attach rotor blades 17a, 17b, 17c and/or levers 15a, 15b, 15c of FIG. 4 to rotor blade attachments 61a, 61b, 61c of FIG. 5. Fasteners may include bolts and nuts, rivets, screws, clips, or any other types of fasteners that may be suitable to attach middle part 63 between clamps 12 and/or rotor blades 17a, 17b, 17c and/or levers 15a, 15b, 15c to rotor blade attachments 61a, 61b, 61c.

(29) In some embodiments, a passive pitch angle adjustment apparatus, such as the passive pitch angle adjustment apparatus of FIG. 4, may include a component that performs a phase shift in control input. Such a component may include a dampening device and/or weights attached to the central rod. FIG. 6 is a diagram of an illustrative passive pitch angle adjustment apparatus with a dampening device between a central rod and a base point.

(30) As shown in FIG. 6, the passive pitch angle adjustment device may include central rod 20, dampening device 54 coupled between central rod 20 and base point 56, and rods 59a, 59b that connect lever-rod attachments 25a, 25b with each other via central point 53.

(31) Dampening device 54 may include enlarged foot 58 of central rod 20 and elastic plate 52. Elastic plate 52 may be made from any material that enables an inclination of central rod 20 at base point 56 in any direction without significant friction effects. For example, elastic plate 52 may include elastomers, such as natural rubber, synthetic rubber, or any other elastic material that is suitable to introduce a phase shift when, in response to the change of a pitch angle, a lever through rods 59a, 59, and the second lever in connection with the central rod adjusts the second pitch angle.

(32) In some embodiments, elastic plate 53 may encapsulate enlarged foot 58 of central rod 20. For example, elastic plate 53 may completely surround enlarged foot 58, thereby providing a positioning in all directions. If desired, elastic plate 53 may include two or more components that clamp enlarged foot 58 from top and bottom.

(33) In some embodiments, the passive pitch angle adjustment device may include weights 55a, 55b. Weights 55a, 55b may be connected with central rod 20 at a predetermined distance 57 from the central rod. As an example, the predetermined distance 57 of weights 55a, 55b from central rod 20 may be selected to effectively use the Coriolis effect and achieve a stabilizing momentum on the central rod 20.

(34) Rods 59a, 59b may be made from two flat straps. The two flat straps may form a single coupling connection between lever-rod attachments 25a and 25b. For example, the two flat straps that form rods 59a, 59b may be made from a composite material, and the fibers or other reinforcements of the composite material from rod 59a may extend into rod 59b such that rods 59a, 59b form a single coupling connection. If desired, the straps may be oriented horizontally at central point 53, and each strap of the single coupling connection may be twisted by 90 degrees between central point 53 and a respective lever-rod attachment 25a, 25b.

(35) It should be noted that the above described embodiments are merely described to illustrate possible embodiments of the present invention, but not in order to restrict the present invention thereto. Instead, multiple modifications and variations of the above described embodiments are possible and should, therefore, also be considered as being part of the invention.

(36) For instance, the bearings 22a, 22b, and 22c may be hinges. The passive pitch angle adjustment apparatus of FIG. 3 or 6 may have as many rods and lever-rod attachments as the corresponding rotor has rotor blades. For example, the passive pitch angle adjustment apparatus of FIG. 3 or 6 may have two, three, four, or five rods and lever-rod attachments, or any other number that is greater than or equal to two. Similarly, the rotor and passive pitch angle adjustment apparatus of FIG. 2 or 4 and/or plate 60 may accommodate a number of rotor blades, levers, and rods that is different than three. For example, the rotor and passive pitch angle adjustment apparatus of FIG. 2 or 4 and/or plate 60 may have two, four, five, or six of each of rotor blades, levers, and rods, or any number of each of rotor blades, levers, and rods that is greater than or equal to two. Moreover, in FIG. 2 or 4, levers 15a, 15b, 15c are shown in direction of the leading edges of rotor blades 17a, 17b, 17c, respectively. If desired, levers 15a, 15b, 15c may be connected in direction of the trailing edges of rotor blades 17a, 17b, 17c, respectively.

REFERENCE LIST

(37) 1 rotary wing aircraft

(38) 1a multi-blade rotor

(39) 1b, 1c rotor blades

(40) 1d rotor head

(41) 1e rotor shaft

(42) 1f rotor axis

(43) 1g rotor plane

(44) 2 fuselage

(45) 2a cabin

(46) 2b rear fuselage

(47) 3 tail boom

(48) 3a horizontal stabilizer

(49) 4 counter-torque device

(50) 4a tail rotor

(51) 5 fin

(52) 11 rotor hub

(53) 12 clamp

(54) 13a, 13b, 13c pitch axis

(55) 14a, 14b, 14c center of lift

(56) 15a, 15b, 15c lever

(57) 16a, 16b, 16c rigid arm

(58) 17a, 17b, 17c rotor blade

(59) 18 rotor shaft

(60) 19a, 19b, 19c rod

(61) 20 central rod

(62) 21a, 21b central rod position

(63) 22a, 22b, 22c bearing

(64) 23, 23a, 23b central point

(65) 24 base point

(66) 25a, 25b, 25c lever-rod attachment

(67) 26a, 26b, 27a, 27b lever-rod attachment position

(68) 52 elastic plate

(69) 53 central point

(70) 54 dampening device

(71) 55a, 55b weights

(72) 56 base point

(73) 57 distance

(74) 58 enlarged foot

(75) 59a, 59b rod

(76) 60 plate with flexible arms

(77) 61a, 61b, 61c rotor blade attachment

(78) 62a, 62b, 62c flexible arm

(79) 63 middle part