Tension-torsion belt of a rotor head of a rotorcraft

Abstract

The disclosed invention describes a pull-tow strap (7) as part of a rotor head (3) of a rotorcraft, comprising in the direction of the longitudinal axis a first peripheral region (700) with a connection eye (70), a central portion (71) and a second peripheral region (720) with a connection eye (72), wherein the integral pull-tow strap (7) is made of a plurality of joined layers, wherein a perfect production and mounting is achieved, resulting in a more simplified maintenance. This is because the pull-tow strap (7) shows an overall asymmetric shape with respect to the transversal axis due to the two non-equiform peripheral regions, which cannot be aligned when folded around the transversal axis.

Description

Technical Field

[0001] The present invention describes a tension band as part of the rotor head of a rotorcraft, comprising a first peripheral region having a connecting eye, a central portion, and a second peripheral region having a connecting eye in the direction of the longitudinal axis, wherein the integral tension band consists of multiple bonding layers and the rotor head of the rotorcraft, including at least a rotor hub, a rotor drive hub, and multiple blade retainers, wherein the multiple blade retainers can be fixed by multiple associated tension bands. Background Technology

[0002] Torque belts, as part of the rotor head of a rotorcraft, are known. The rotor head includes at least a rotor hub, a rotor drive hub, and multiple blade retainers, wherein the multiple blade retainers are secured to the rotor drive hub by multiple associated torque belts. Torque belts or components, as anti-torque devices or part of the rotor head of a rotorcraft, absorb centrifugal force during flight operation.

[0003] A single tension-torsion belt is known from EP3315403, in which each of these torsion-resistant beams is fixed to the blade and hub, specifically designed to absorb centrifugal forces borne by the blade. Each tension-torsion belt has sufficiently low torsional stiffness to allow the blade to rotate about its pitch axis. As explicitly mentioned and depicted in EP3315403, the tension-torsion belt is constructed of multiple layers that exhibit an overall symmetrical shape, with connecting eye portions formed in the same manner in the peripheral region.

[0004] The tension-torsion tape of US8834128 exhibits a layered structure and is typically thicker than other prior art tension-torsion tapes. If the peripheral regions are folded around the transverse axis, the connecting eyes or perforations in the peripheral regions are formed in the same manner, and the two peripheral regions are perfectly aligned. The inclined planes in the peripheral regions are also aligned on both sides, thus the tension-torsion tape is mirror-symmetrical with respect to both the longitudinal and transverse axes. This results in an overall symmetrical shape with respect to the transverse axis, or in other words, the rotational symmetry characteristic of prior art tension-torsion tapes. Summary of the Invention

[0005] The purpose of this invention is to create an optimized type of tension-torsion band for the rotor head of a rotorcraft and rotor heads of rotorcraft with multiple such tension-torsion bands, thereby ensuring perfect production and installation. Simplified maintenance is possible, and potential weaknesses can be identified before failure. Therefore, maintenance of the rotor head's tension-torsion band is simplified, resulting in more efficient maintenance of the rotorcraft.

[0006] Because the manufacturing of the tension-torsion belt is optimized and errors are avoided during assembly, maintenance intervals can even be extended.

[0007] Because cracks or subsequent fractures are easier to detect, this means that time-consuming disassembly of many parts can be temporarily avoided. Attached Figure Description

[0008] Preferred exemplary embodiments of the subject matter of the present invention, with some additional optional features, are described below with reference to the accompanying drawings.

[0009] It should be noted that the accompanying drawings do not always represent different embodiments of the invention, and the same parts have the same reference numerals or the same part names. The disclosure contained throughout the description can be similarly applied to the same parts having the same reference numerals or the same part symbols.

[0010] Figure 1 An exploded view of the rotor of a rotorcraft is shown, in which the rotor head is partially disassembled, for example, the rotor blade connection assembly before attachment to the tension belt.

[0011] Figure 2a The diagram shows a perspective view of the rotor head, actually a perspective view of the rotor hub after the hub cover has been removed.

[0012] Figure 2b It shows Figure 2a The AA section diagram shows the longitudinal section of the tension-torsion belt in the installed state.

[0013] Figure 3a A perspective view of the tension-torsion belt is shown, in which the asymmetry is clearly visible, while

[0014] Figure 3b The diagram shows a partial cross-section through a typical forming tensile-torsional band edge, where several layers of metallic material are formed, exhibiting three distinct layer regions.

[0015] Figure 3c It shows that according to Figure 3a A top view of a torsion belt, in which different curvatures are observed in the outer or boundary regions.

[0016] Figure 4 A perspective view of a tethered band is shown, wherein the tethered band has an index in a peripheral area and a wrapping covering the central portion.

[0017] Figure 5a A perspective view of a tension-torsion strip with an indexed cross-section is shown, which is hexagonal in this text. Figure 5b The indexed cross section along CC is shown in more detail, thus revealing the layered structure. Detailed Implementation

[0018] As an example describing the present invention Figure 1The image shows a portion of the tail rotor of a rotorcraft. For simplicity, possible shrouds and multiple rotor blades are omitted. A rotor head 3 can be connected to the rotor drive system, which is connected to the gearbox. The rotor head 3 includes a rotor hub 4, a rotor drive hub 5 in the form of a connecting element separate from or integrated into the rotor hub 4, and multiple blade retainers 6 with associated tension bands 7, which are detachably secured by mounting bolts 8. A pitch control unit 9 is rotatably connected to at least the multiple blade retainers 6 and the entire rotor drive hub 5, and all of them can be covered by a hubcap 10. The rotor head 3 is capable of rotating about the central axis shown in the dashed line.

[0019] In this document, the blade retainer 6 comprises two parts: a band retainer 60 and a blade retainer 61. Since this document does not focus on the rotor blades, the blade retainer 61 will not be described further. In this document, the two parts are integrally formed. The band retainer 60 shows a connection hole 600 through which a band retaining bolt 601 can be inserted to retain one side of the tension band 7. An integrally formed pitch rocker arm 602 or a fixed pitch rocker arm 602 provides connection to the pitch control unit 9 of each blade retainer 6 and indirectly to each rotor blade. During assembly, the blade retainer 6 is partially located within a cavity in the rotor hub 4. At least the blade retainer 61 of each blade retainer 6 protrudes from the cavity.

[0020] The tension band 7 basically shows three parts: a first connecting eye 70, a central portion 71, and a second connecting eye 72. The first connecting eye 70 is incorporated into the central portion 71, and the central portion 71 is incorporated into the second connecting eye 72, and all parts are made of a flat or planar layer.

[0021] The connection to the blade retainer 6 is possible via the first connecting eye 70. After the retaining bolt 601 passes through the connecting hole 600, the two parts are connected by screws or pins. This achieves a linearly consistent fastening. When fastened, the tension band 7 protrudes through the opening in the rotor hub 4 to the rotor drive hub 5. On the other side, the tension band 7 is connected to the blade retainer 6, more specifically to the band retainer 60 mounted within the circumference of the rotor hub 4. The blade retainer 6 can also be designed in different ways, as will be clear to those skilled in the art.

[0022] The rotor drive hub 5 can be detachably attached via the second connecting eye 72 and the tension band 7. For this purpose, a corresponding opening is provided in the rotor drive hub 5 through which the mounting bolt 8 can be pushed to retain the second connecting eye 72. Different types of connections (including screw connections or plug connections as described herein) are possible. The entire tension band 7 must have a certain degree of flexibility to allow the pitch control unit 9 to deflect the rotor blades with the blade retainer 6 accordingly.

[0023] According to Figure 2a In the perspective view of the rotor head 3, multiple tension bands 7 connected to one side of each rotor drive hub 5 are depicted, reaching through openings in the rotor hub 4 and protruding radially to the corresponding blade retainer 6. The tension bands 7 are secured inside by mounting bolts 8, which are in turn secured by nuts. At the band retainer 60, band retaining bolts 601 hold the tension bands 7 inside the blade retainer 6. A detachable connection via pins is also used in this paper. After each pitch control arm 602 is connected at the pitch control unit 9, each tension band 7 can pivot longitudinally by a minimum angle. Some rotor blades are represented by dashed lines, in which the longitudinal axis of the tension bands 7 is also indicated.

[0024] Figure 2b The diagram shows a corresponding cross-sectional view of the installed tension belt 7. The tension belt 7 is clamped in the direction of its longitudinal axis L and is detachably connected between the rotor hub 4 and the rotor drive hub 5. The outer region 700 of the tension belt 7 is connected to the rotor hub 4, and the inner region 720 is connected to the rotor drive hub 5.

[0025] The shape of the tension-torsion belt 7 ensures the advantageous results of the invention described herein.

[0026] The tension-torsion belt 7, along its longitudinal axis L, shows a first connecting eye 70 in the outer region 700, a central portion 71 in the inner region 720, and a second connecting eye 72. The tension-torsion belt 7 has a layered structure comprising at least two layered regions, each comprising a different layer of material. Using a layered structure to achieve the desired torsional properties is advantageous.

[0027] The overall shape along the longitudinal axis L of the tension-torsion belt 7 must be asymmetrical, such as... Figure 3a As described. Asymmetry refers to the different shapes of the outer regions 700 and 720 or the non-uniform design of the outer regions 700 and 720. The degree of asymmetry must be large enough that the differences between the outer regions 700 and 720 are correspondingly visible to the naked eye.

[0028] By using this asymmetrical tension band 7, the correct installation orientation can be indicated, which can be easily determined visually. In addition to this visual aid, the asymmetrical shape also adapts to its counterpart, making it impossible for parts to be installed incorrectly. This achieves a true fault-proofing system.

[0029] In particular, this asymmetry in the outer regions may result in outer regions with different characteristics. In terms of strength, the outer region 700 is the stronger portion 700 compared to the inner region 720, which is the weaker portion 720. If the section of the tension-torsion band 7 reaches the weaker portion 720, then that end will first show signs of fatigue failure. This makes inspection easier, as only the weaker portion 720 can be inspected. Therefore, the associated cut should be placed in the cover of the blade pitch control star wheel or the rotor drive hub 5 or the rotor head 3.

[0030] Figure 3b The typical layered arrangement of the tension-torsion band 7 is depicted. As tested, preferred metal sheets of a first material or different metals are used, which can be alternately arranged or fixed with plastic layers. The use of several materials in the different layers 73, 74, 74' results in the structure exhibiting the lowest possible torsional stiffness while maintaining axial tension strength. The result of using multiple materials is lower torsional stiffness compared to using a single material. Optimal results are achieved by using different metal / plastic compounds in the first layer region 73, the second layer region 74, and the third layer region 74'. In particular, when these different layers 73, 74, 74' are as follows... Figure 3b The alternating arrangement shown yields the lowest possible torsional stiffness. We found that alternating arrangements of at least two different layer regions 73 and 74 exhibit good results. Some layers can be made of plastic instead of fiber reinforcement. However, they are single-layered, not a complete strip. Therefore, we can say that they can be cut from 2D sheets, which makes them easier to manufacture.

[0031] like Figure 3c As clearly depicted, the asymmetry of the tension-torsion belt 7, especially the asymmetry of the outer regions 700 and 720, can be achieved through different curvature forms.

[0032] The outer region 700 exhibits a stronger curvature cs, while the inner region 720 exhibits a weaker curvature cw. In the longitudinal direction away from the longitudinal axis L, the curvature cs in the outer region 700 is significantly smaller than that in the inner region 720. Therefore, the shape of the first eyelet 70 is larger in the length direction than the shape of the second eyelet 72. The two eyelets 70 and 72 are easily distinguishable from each other, and the alignment of this tension-torsion band 7 is easily and correctly performed. The individual layers of the tension-torsion band 7 must be adapted to the overall asymmetry of the tension-torsion band 7 to be achieved.

[0033] Another feature that ensures the correct arrangement of the tension belt 7 during manufacturing and placement between the rotor hub 4 and the rotor drive hub 5 is the arrangement of the index 75.

[0034] Similarly, by using a primer 75 through at least one peripheral region 700, 720, an asymmetric tension-torsion band 7 with asymmetric peripheral regions 700, 720 can be obtained.

[0035] The primer 75 can be located on either the end face or the side face of the outer region 700 or the inner region 720. In this case, the primer 75 is preferably located in the region of the inner region 720, protruding from the outside of the inner region 720 and protruding away from the side face of the inner region 720 in the longitudinal direction L.

[0036] Therefore, even using only the primer 75, the overall asymmetry of the entire tension-torsion band 7 can be achieved.

[0037] To ensure visibility of the correct pre-assembly of the tension band 7, an index 75 is added to one side of the tension band 7, for example, formed as an arrow as depicted herein. The arrow 75 protrudes from the outer surface of the peripheral regions 700, 720, and is located on the side of the second connecting eye 72 herein, indicating direction by its arrowhead.

[0038] Due to the asymmetry of the tension-torsion belt 7 achieved by the method described herein (with or without the guide 75 at the tension-torsion belt 7), incorrect installation of the entire tension-torsion belt 7 in the rotor head 3 (in the rotor hub 4 and / or rotor drive hub 5, respectively) can be prevented.

[0039] In this document, the stronger portion 700 and the weaker portion 720 must be in the correct positions. Therefore, the tension band 7 surrounding the portion in the rotor head 3 is designed such that the protruding index 75 or another type of index 75' described below will collide with it. This eliminates the possibility of incorrectly installing the tension band 7 in the rotor head 3.

[0040] To improve torsional properties, different layers 73, 74, and 74' can have different shapes and materials.

[0041] The asymmetric tension-torsion band 7 is asymmetrical relative to the transverse axis Q, having two peripheral regions 700 and 720 with unequal shapes. When folded around the transverse axis Q, these peripheral regions 700 and 720 cannot be aligned.

[0042] The main purpose of the asymmetrical tension band 7, with or without the index 75, is to prevent incorrect installation of parts.

[0043] To enhance the stability of the asymmetric tension band 7 with or without the index 75, a wrapping material 76 is used to wrap around the central portion 71. This wrapping material 76 is a composite material, preferably made of a transparent or translucent elastomer. Preferably, the wrapping material 76 is designed to be annular or tubular. The wrapping material should be in direct contact at least partially with the outer surface of the central portion 71.

[0044] Possible elastomers or polymers for the wrapper 76 are sufficiently flexible polymers, particularly in the form of heat shrink tubing. Preferably, the wrapper 76 is made of a very soft material so as not to provide additional unintended stiffness or attract stress injection, such as a molded elastomer of silicone.

[0045] The wrapping 76 is tightly wrapped and arranged linearly and immovably, and can be attached by heat shrink to all layers 73, 74, 74' around the central portion 71 of the tension-torsion band 7.

[0046] According to Figure 5a In the perspective view of the torsion band 7, the layered structure can be easily identified. In addition to improving the absorption of centrifugal force while still providing sufficient torsional properties, the layered structure can be used as a primer 75'.

[0047] In this paper, the indexing cross-section Si of the tension-torsion band 7 is used as the indexer 75', where adjacent layers have different shapes or different layer profiles, designed in a manner that produces a prescribed shape, thereby visualizing the correct assembly of the tension-torsion band 7. The indexing cross-section Si of the rotor head 3 in this paper shows a hexagonal shape with multiple layers 73, 74, each with different layer profiles. Directly adjacent layers display different layer profiles, resulting in an overall hexagonal indexing cross-section Si. The correct assembly of the tension-torsion band 7 is easily identified because incorrect ordering of individual layers 73, 74 can be directly read.

[0048] Similarly, the indexing cross section Si of the indexing element, i.e., the tension-torsion belt 7, can correspond to the shape of surrounding components, such as the rotor hub 4, the rotor drive hub 5, and / or the blade retainer 6. The cross section Si is formed to optimize torsional stiffness and drive the stress in the tension-torsion belt 7.

[0049] Of course, the indexing cross section Si can have shapes other than hexagons, such as polygons, star polygons, and especially regular polygons, each constructed from directly adjacent layers of different shapes. Figure 5b As indicated, layers 73 and 74 may also comprise groups of layers with different materials and / or shapes. In this document, at least two groups of different shapes and materials are used in layers 73 and 74 for strength and stiffness adjustment. So far, this has been accomplished through the shapes of different layers, but in this document, we have added an additional adjustment method by selecting different materials.

[0050] In the cross-section Si, the material of the inner layer 73 is particularly hard or rigid than the material of the outer layer 74. Furthermore, using different materials can improve the interlayer wear behavior.

[0051] Typically, the traction band 7 does not require additional or external components to be attached to its main body (i.e., the bonding layers 73, 74, and 74', respectively) to achieve an overall asymmetrical body. Therefore, no component will be connected incorrectly or accidentally detached.

[0052] All the tension-torsion strips 7 according to the present invention can be described as a single layered structure. The shape of the tension-torsion strip 7, i.e., the shape of each layer 73, 74, 74' respectively, provides a technical advantage and solves the problem. Due to the forming process, the tension-torsion strip 7 does not exhibit rotational symmetry with respect to the transverse axis.

[0053] List of reference numerals

[0054] 3. Rotor head

[0055] 4. Rotor hub

[0056] 5. Rotor drive hub

[0057] 6-blade retainer

[0058] 60 with retaining part / tubular part

[0059] 600 connection hole

[0060] 601 with retaining bolt

[0061] 602 Variable Pitch Rocker Arm

[0062] 61 Blade holding section

[0063] 7. Tension-torsion tape (layered structure / asymmetrical integral shape, different molding layers, index on one side, special cross-section)

[0064] 70 First Connecting Eye

[0065] 700 Outer Area / Stronger Section

[0066] The curvature of the stronger part of cs

[0067] 71 Central Part

[0068] 72 Second Connecting Eye

[0069] 720 Outer Area / Weaker Part

[0070] The curvature of the weaker portion of cw

[0071] 73 First layer area / sheet (preferably metal)

[0072] 74, 74' Second / Third Layer Area / Sheet (Preferably Metal)

[0073] 75 primers

[0074] 75' cross-sectional layer primers

[0075] 76 Packages

[0076] Indexed cross-section of Si TT tape

[0077] 8 Mounting bolts

[0078] 9. Pitch Control Unit

[0079] 10 Hub Cover

[0080] L is the longitudinal axis of the tension-torsion belt.

[0081] Q Horizontal axis

Claims

1. A pull-twist tape (7) as part of a rotor head (3) of a rotorcraft, comprising a first peripheral area (700) with a connection eye (70) in the direction of a longitudinal axis (L), a central portion (71) and a second peripheral area (720) with a connection eye (72), wherein the pull-twist tape (7) is unitary and made of a plurality of joined layers (73, 74), wherein the pull-twist tape (7) shows an overall asymmetry with respect to a transverse axis (Q) due to two non-equiform first and second peripheral areas (700, 720) which cannot be aligned when folded around the transverse axis (Q) without attaching additional components at the main body of the pull-twist tape (7), i.e. at the joined layers (73, 74), respectively, characterized in that the non-equiform first and second peripheral areas (700, 720) show different forming curvatures (cs, cw) between the central portion (71) and the first and second peripheral areas (700, 720), wherein in longitudinal direction away from the longitudinal axis (L) the curvature (cs) in the first peripheral area (700) is significantly smaller than the curvature (cw) in the second peripheral area (720), wherein the first peripheral area (700) is on the outside and the second peripheral area (720) is on the inside.

2. The pull-twist tape (7) according to claim 1, wherein a reference (75) is attached at the first or second peripheral area (700, 720) forming the overall asymmetrical shape of the pull-twist tape (7) and thus cannot be aligned when folded around the transverse axis (Q).

3. The pull-twist tape (7) according to claim 2, wherein the joined layers (73, 74) are formed to realize the non-equiform first and second peripheral areas (700, 720).

4. The pull-twist tape (7) according to claim 2 or 3, wherein the reference (75) is formed as an arrow protruding from an outer or side surface of the first or second peripheral area (700, 720) by which the arrow indicates a direction.

5. The pull-twist tape (7) according to any of the preceding claims, wherein at least the central portion (71) of the pull-twist tape (7) shows a non-square polygonal reference cross-section built from directly adjacent joined layers (73, 74, 74') with different shapes.

6. The pull-twist tape (7) according to claim 5, wherein the reference cross-section (Si) at least partially has a hexagonal or a regular polygonal or a star polygonal shape.

7. The pull-twist tape (7) according to claim 5, wherein the joined layers (73, 74, 74') are formed from different groups of joined layers comprising different shapes and / or materials and with different properties.

8. The tensile-torsional band (7) according to claim 7, wherein at least two different sets of engagement layers (73, 74, 74') of different shape and / or material form the indexing cross section (Si) in the central portion (71).

9. The tensile-torsional band (7) according to any one of the preceding claims, wherein a wrapping (76) is attached, which covers the central portion (71), which is made of a synthetic material, has a hose-like shape in contact with the outer surface of the central portion (71).

10. The tensile-torsional band (7) according to claim 9, wherein the wrapping (76) is made of an elastomer.

11. The tensile-torsional band (7) according to claim 9, wherein the wrapping (76) is made of a transparent or translucent polymer.

12. A rotor head (3) of a rotary-wing aircraft, comprising at least a rotor hub (4), a rotor transmission hub (5) and a plurality of blade holders (6), wherein the plurality of blade holders (6) are fixable at the rotor transmission hub (5) with a plurality of associated tensile-torsional bands (7) according to any one of claims 1 to 11, which protrude through through-holes in the rotor hub (4).

Images