Connection between the pitch control unit arm and the pitch angle piece

Abstract

The present invention describes a detachable connection between a pitch control unit arm (5) and a pitch angle piece (8) of a blade holder (7) in a tail rotor head (3) of a tail rotor (1) of a rotary wing aircraft, said detachable connection comprising a pin connecting said pitch angle piece (8) attached to the blade holder (7) with said pitch control unit arm (5) of a pitch control unit (4), thereby reducing material wear and shortening the maintenance cycle. This is achieved because said pin is designed as a sliding pin (9) protruding between the pitch angle piece (8) and the pitch control unit arm (5), which in its length direction passes through a spherical bearing in the form of a ball (6) with a central ball through hole (61), wherein the ball (6) and the part of the sliding pin (9) are surrounded by an outer ring (60) of the spherical bearing, thus allowing a sliding and pivoting movement of the sliding pin (9) inside the spherical bearing.

Description

Technical Field

[0001] This invention describes a detachable connection between a pitch control unit arm and a pitch angle member of a blade retainer in the tail rotor head of a rotorcraft, the detachable connection including a pin that connects the pitch angle member attached to the blade retainer to the pitch control unit arm of the pitch control unit by protruding through an arm through-hole and passing through a pitch angle member through-hole at another edge; a tail rotor head for a rotorcraft, including a pitch control unit having multiple pitch control unit arms, multiple blade retainers having connected tail rotor blades, wherein each blade retainer is connected to each pitch control unit arm by a connection; and the use of a sliding pin including a pin retaining washer, a slotted nut, and a threaded end with a spherical bearing; and a tail rotor for a rotorcraft. Background Technology

[0002] US7604460 discloses a tail rotor or helicopter anti-torque rotor comprising a tail rotor head and a plurality of rotor blades attached by associated rotor blade holders and tensioning straps. Each rotor blade holder includes a pitch member, which is connected to a pitch control unit arm or control lever. As disclosed in US7604460, screws are used for securing the rotor by extending the screw between the pitch member and the pitch control unit arm, protruding through through-holes in both the pitch member and the pitch control unit arm. Thus, the screw and the pitch member form a rigid connection to absorb centrifugal forces during operation, i.e., rotation of the tail rotor shaft. The through-hole in the pitch control arm actually moves within the special tip of the screw. It is a cylindrical bushing in the pitch control unit arm, leading to a threaded spherical tip. The screw is subjected to high stress as the pitch control unit rotates around the pitch control unit arm and thereby rotates the pitch member of each blade holder, increasing the need for maintenance of this component. This screw can be considered a weak point in the fastening and requires special attention. In practice, this screw has been damaged, making it impossible to guarantee uniform pivoting of all blades. This connection has not been given sufficient attention until now. The spherical surface of the bushing secured by the screw rubs against the cylindrical tubular surface in the star wheel. This creates point or line contacts that result in significant wear.

[0003] Furthermore, other existing technical documents do not take any special precautions to provide a sufficiently stable attachment between the pitch component and the pitch control unit arm (and correspondingly, the pitch control unit). Therefore, the connection is susceptible to mechanical failure and requires frequent maintenance for safety reasons. Worse still, the maintenance (and replacement) of the screws between the pitch component and the pitch control unit arm involves the removal of other components, which, to date, is far from easy and requires extensive disassembly, including the tail rotor. Summary of the Invention

[0004] The purpose of this invention is to create a tail rotor head for a rotorcraft, and an optimized connection between the pitch control unit arm for the tail rotor head and the pitch angle member of the blade holder, thereby reducing material wear, shortening maintenance cycles, and achieving simplified maintenance of mechanically more robust components.

[0005] By introducing sliding pins and spherical bearings, simplified maintenance of the tail rotor head and thus the rotorcraft can be achieved. A special type of sliding pin is desired to simplify and expedite the maintenance of the rotorcraft's anti-torque mechanism.

[0006] The sliding pin can be inspected or replaced without removing or disassembling other components, such as rotor blades, rotor hubs, or control star wheels, and can be accessed at any time from the tail rotor head, and correspondingly from the outside of the tail rotor hub. Attached Figure Description

[0007] The subject matter of the invention is described in detail below with reference to the accompanying drawings. The essential features, details, and advantages of the invention will become apparent from the following description, which sets out in detail preferred embodiments and some additional or optional features.

[0008] Variations or minor modifications to the combination of features of the present invention will be found in the detailed description, illustrated in the accompanying drawings, and included in the dependent claims. Those skilled in the art will understand that all combinations of the features of the patent claims presented herein may be applied.

[0009] Figure 1 This shows a perspective view of the tail rotor with attached tail rotor blades, with the optional shroud removed.

[0010] Figure 2a An exploded view of the tail rotor, showing a partially disassembled tail rotor head, tail rotor blades, blade retainers, pitch control unit, and tensioning band, is shown.

[0011] Figure 2b A perspective view of the tail rotor head is shown, along with a partial cross-section and details of the connection between the pitch component and the pitch control unit arm.

[0012] Figure 3a A portion of the top view of the tail rotor nose is shown, while

[0013] Figure 3b A detailed partial cross-sectional top view showing a portion of the connection area between the blade retainer and the pitch control unit.

[0014] Figure 4a The side view of the pitch control unit in different states is shown, but the connected pitch control unit arm is not depicted in the background.

[0015] Figure 4b Another partial sectional view shows a detailed top view of the connection between the pitch angle member and the pitch control unit arm at different cross-sectional planes, while

[0016] Figure 4c The top view of the inner side of the tail rotor head on the pitch control unit is shown, indicating the axis, angle, and displacement of the sliding pin, and the possible pitch control unit arm in operation. Detailed Implementation

[0017] Figure 1 The rotor 1 of a rotorcraft, such as the tail rotor 1, is shown, but a common circumferential shroud spaced around the axis of rotation L is not shown. At the center of the tail rotor 1, the tail rotor head 3, comprising multiple components, is shown. Only the hub 10 without the hub cover is visible in this figure. Multiple tail rotor blade holders are attached to the tail rotor head 3. The tail rotor blades 2 are directly attached to the blade holders and thus indirectly attached to the tail rotor head 3.

[0018] Exploded view Figure 2a The components of the rotor head 3 are shown in more detail, thus this figure shows only one rotor blade 2 attached to the rotor hub 10 and pitch control unit 4 via a blade retainer 7 and tensioning straps TT as an example. Based on the blade retainer 7 and tail rotor blade 2 attached later, the tail rotor head 3 is formed by at least the hub 10, the pitch control unit 4, and multiple tensioning straps TT. In operation, signals from the rotorcraft's control system are transmitted to the tail rotor blade 2 via the rotor blade retainer 7 through the pitch control unit 4 and multiple pitch control unit arms 5. The tensioning straps TT are secured to the hub 10 using one of their connecting eyes, each connecting eye protruding through a designated hole in the hub 10. The hub 10 provides support for the multiple blade retainers 7.

[0019] The pitch control unit 4 is positioned partially inside the hub 10, and the portion of the pitch control unit arm 5 for connecting the tail rotor blade holder 7 is shown. The pitch control unit 4 also shows an opening or recess that allows the blade holder 7 to protrude radially.

[0020] Each blade retainer 7 can be connected to a designated tensioning band TT and a designated pitch control unit arm 5 of the pitch control unit 4. After the blade retainer 7 is indirectly attached to the hub 10, a hub cover can be used to cover the hub 10. A portion of the blade retainer 7 protrudes from the hub 10. Each tail rotor blade 2 is secured to its designated blade retainer 7 using two bolts, with at least one bolt required. The connection between the blade retainer 7 and the hub 10 is achieved via the tensioning band TT.

[0021] In this document, the blade retainer 7 includes a strap retainer and a blade retainer molded together at a straight distance from each other. However, the retainer design can also be accomplished in other ways. A tensioning strap TT is detachably connected to the blade retainer 7. The connection between the blade retainer 7 and the pitch control unit 4 is achieved by connecting the pitch angle member 8 at each pitch control unit arm 5 using at least one sliding pin 9 and a pin-fixing washer 90, wherein the sliding pin 9 protrudes into the control unit arm 5. As indicated by the double arrows, this connection allows the blade 2 to subsequently pivot about the blade span axis, thereby allowing rotational movement from the pitch control unit 4 to the blade retainer 7. The washer 90 is optionally a removable component and can be equivalently replaced by an integrated shape of the pitch angle member 8.

[0022] exist Figure 2b The partial cross-sectional view shows the assembled tail rotor head 3, where the tail rotor blades 2 are not shown. To reduce material wear, create more robust components, and extend maintenance intervals, the detachable connection between the pitch control unit arm 5 and the pitch angle member 8 of the blade retainer 7 is optimized, as described in more detail below.

[0023] To achieve a detachable connection, the sliding pin 9 is held by a spherical bearing comprising a ball 6 inside each pitch control unit arm 5. Each pitch control unit arm 5 shows an arm through-hole 50 into which a spherical bearing in the form of a ball 6 with a ball through-hole 61 and an annular outer ring 60 of the spherical bearing are inserted.

[0024] In another embodiment, the spherical bearing may also be placed in the pitch angle member through hole 80, and thus this solution will be understood in accordance with the solution described herein.

[0025] Figure 3a This shows an overall diagram of the tail rotor 1, in which multiple tail rotor blades 2 are connected to the tail rotor head 3. Figure 3b A partial cross-sectional top view shows the connection between the pitch member 8 and the pitch control unit arm 5. It can be seen that the pitch member 8 is detachably connected to the pitch control unit arm 5 via a sliding pin 9.

[0026] The sliding pin 9 is held between the pitch member 8 and the pitch control unit arm 5 by a pin retaining washer 90. The sliding pin 9 protrudes between these components through a pitch member through-hole 80 in the pitch member 8, passes through a ball through-hole 61 in the spherical bearing 6, and extends from the ball 6 facing the pitch control unit 4. The ball 6 is arranged at the center of the arm through-hole 50 and is surrounded therein by the outer ring 62 of the spherical bearing. The outer ring 62 is fixed in the arm through-hole 50. Therefore, the sliding pin 9 can be detachably mounted to completely traverse both the pitch member through-hole 80 and the arm through-hole 50.

[0027] One side of the sliding pin 9 includes a threaded end 92, which can be effectively connected with a nut 91 (e.g., a slotted nut 91) for fastening via a removable pin connection. A removable pin connection can be formed by a pin through a removable pin hole 93 on the sliding pin 9. Figure 3b Not shown in the diagram. A self-locking nut may also be used instead of the slotted nut 91, as the opening pin required for installing and removing the slotted nut 91 is often challenging and time-consuming to maintain.

[0028] After the sliding pin 9 is fixed, it can rotate slightly relative to the pitch control unit arm 5, as indicated by the double arrows. The sliding pin 9 and the ball 6 can slide by the movement of the ball 6 along a first sliding surface 62 on the outer surface of the ball 6, which contacts the inner surface of the outer ring 60 of the spherical bearing, thereby causing the sliding pin 9 and the ball 6 to rotate or pivot relative to the pitch control unit arm 5. The inner surface of the outer ring 60 is the surface pointing towards the center of the arm through hole 50.

[0029] If the spherical bearing is placed inside the through hole 80 of the pitch angle fitting, a similar pivoting motion will occur.

[0030] Due to the second sliding surface 63 on the inner surface of the ball-through hole 61 and the outer surface of the sliding pin 9, the sliding pin 9 can slide linearly within the ball-through hole 61 along its length axis. The sliding pin 9 can move axially inside the ball-through hole 61 due to the centrifugal force pulling out the pitch control unit arm 5. Sliding is required whenever a yaw input from the pilot arrives because of the relative displacement between the pin and the ball.

[0031] The sliding pin 9 is always fully secured. After being secured via the detachable pin connection described herein, the sliding pin 9 will not slide out of the through hole 80 of the pitch member 8 and the through hole 50 of the pitch control unit arm 5.

[0032] The first sliding surface 62 between the ball 6 and the outer ring 60 allows rotation, corresponding to the rotational movement of the ball 6 within the outer ring 60. Both the ball 6 and the outer ring 60 are integral parts of the spherical bearing.

[0033] Instead of placing the second sliding surface 63 on the outer surface of the sliding pin 9, it can also be attached to the bore 61 in the ball 6 of the spherical bearing. The second sliding surface 63 allows axial displacement between the sliding pin 9 and the ball 6 of the spherical bearing. The second sliding surface 63 can be an integral part of the sliding pin 9, or it can be bonded or coated onto the sliding pin 9. It can be a single material, a fiber-reinforced matrix, a sintered material, or a substance coated onto the outer surface of the sliding pin 9. A dedicated friction device should be used.

[0034] To precisely assemble the sliding pin 9 to the pitch member 8, a tapered pin retainer 90 is used in this paper, but other assemblies for the sliding pin 9 exist. It is possible to secure the sliding pin 9 using a threaded end 92 with associated external threads and a nut 91 (in this paper, a slotted nut 91), which allows for linear movement of the sliding pin 9 relative to the ball 6 within the arm through-hole 50. A removable pin prevents the slotted nut 91 from loosening.

[0035] The sliding pin 9 shown may include two tapered outer regions and a centrally thickened inner region, wherein a second sliding surface 63 is arranged, attached to, or formed in the centrally thickened inner region. The cross-section of the sliding pin 9 in the two tapered outer regions is smaller than its cross-section in the centrally thickened inner region. Another possible design for the sliding pin 9 is a tapered outer region and a thickened outer region including a central region.

[0036] Figure 4 below shows a schematic diagram and a rough explanation of the movement of the pitch member 8, the blade retainer 7, and the sliding pin 9 inside the spherical bearing.

[0037] During operation, when the pilot applies a yaw input, it is transmitted through the control system to the pitch control unit 4, which moves a distance Z. The direction of Z depends on the direction of the yaw signal. Since the pitch control unit 4 is connected to the pitch member 8, which can rotate freely about its axis C1, via a sliding pin 9, the blade holder 7 rotates or pivots at an angle α1 or α2 according to the direction and magnitude of the distance Z.

[0038] The axial displacement Y of the sliding pin 9 is caused by rotation or pivoting at angles α1 or α2. It also forces the pitch control unit 4 to rotate around its axis C2 (as shown). Figure 4c The rotation of the axis L is equal to the length axis L, thereby generating a rotation angle β and a pitch control unit arm 5 after the sliding pin 9 is fixed to the pitch member 8, and thus a displacement X between the ball 6 and the pitch member 8.

[0039] Due to the sliding of the spherical bearing and sliding pin 9, the relative movement between sliding pin 9 and pitch control unit arm 5 is achieved as follows:

[0040] Rotation with α1 or α2 is achieved on either the first sliding surface 62 or the second sliding surface 63. Rotation or pivoting with β is achieved in the spherical bearing or ball 6 on the first sliding surface 62, while displacement X is achieved on the second sliding surface 63. When the pitch control unit 4 rotates in operating mode, Figure 4c The sliding pin 9 is shown to pivot at a small angle β of less than 30°.

[0041] exist Figure 4cIn this case, only rotation is indicated, and there is no axial displacement along the length axis of the pin. When such movement occurs, this axial displacement must be free. Existing technical documents attempt to solve this problem by making the component flexible in this direction, so that the component is not overloaded due to forced displacement and rotation of the blade holder 7, where the forced displacement comes from the centrifugal force that pulls the blade 2 out a bit, and the rotation of the blade holder 7 changes the actual distance from the rotor axis to the contact point to the star wheel. When some blade pitch is applied, the star wheel rotates slightly relative to the rotor hub.

[0042] Sliding surfaces 62 and 63 are surfaces that allow the sliding pin 9 to slide fully relative to the ball 6, the outer ring 60, or the ball through-hole 61. Sliding surfaces 62 and 63 should be adequately prepared to achieve sliding characteristics. A coating may be used as the sliding surfaces 62 and 63, or the material used may have sufficient properties.

[0043] Sliding surfaces 62 and 63 should be dedicated low-friction, high-wear-resistant surfaces, which may consist of, but are not limited to, a dedicated low-friction coating applied to at least one of the interfacing moving parts; a liner (fiber-reinforced matrix) bonded / coated to at least one of the moving parts; and a layer of plastic or sintered material that can be mounted between or bonded / coated to at least one of the moving parts.

[0044] Sliding surfaces 62 and 63 must withstand load pressure and require a low coefficient of friction; the coating or material pair typically has a coefficient of friction below 0.15 or better, below 0.1. An advantage of this invention is that the load is supported by a surface rather than by a point / line, which allows for the use of a wider range of coatings. Expensive, complex, and extremely hard coatings such as tungsten carbide are known and used in industry to cope with extremely high localized contact pressures; however, due to wear, this solution provides a sufficient but not optimal service life.

[0045] List of icon numbers

[0046] 1. Tail rotor

[0047] 2. Tail rotor blades

[0048] 3. Tail rotor head

[0049] 4. Pitch control unit (transmits yaw signals from the control system to 3)

[0050] 5. Pitch control unit arm

[0051] 50-arm through hole

[0052] spherical bearings

[0053] 6 balls (in holes 5 or 8)

[0054] 60 spherical bearing outer ring

[0055] 61 Ball Through Hole

[0056] 62 First sliding surface

[0057] 63 Second sliding surface

[0058] 7. Blade retainer

[0059] 8. Pitch Angle Fittings

[0060] 80° pitch angle fitting through hole

[0061] 9 Sliding pins

[0062] 90 pin retaining washer / preferred conical washer

[0063] 91. Slotted Nut

[0064] 92 Threaded end

[0065] 93 Detachable pin hole

[0066] 10. The wheel hub is part of (4) and provides support for (7).

[0067] C1, C2 axes

[0068] Angles α1 and α2

[0069] X, Y, Z displacement

Claims

1. Detachable connection between a pitch control unit arm (5) and a pitch angle piece (8) of a blade holder (7) in a tail rotor head (3) of a tail rotor (1) of a rotary wing aircraft, said detachable connection comprising a pin connecting the pitch angle piece (8) attached to the blade holder (7) with the pitch control unit arm (5) of a pitch control unit (4) by protruding through an arm through hole (50) and on the other side through a pitch angle piece through hole (80), characterized in that the pin is designed as a sliding pin (9) protruding between the pitch angle piece (8) and the pitch control unit arm (5), the sliding pin extends in its length direction through a spherical bearing in the form of a ball (6) having a central ball through hole (61), wherein the ball (6) and a part of the sliding pin (9) are enclosed by an outer ring (60) of the spherical bearing, thus allowing a sliding and pivoting movement of the sliding pin (9) inside the spherical bearing, wherein the sliding pin (9) shows a threaded end (92) and is fixed at the pitch angle piece (8) by a pin fixing washer (90) and a nut (91) with the threaded end (92), wherein the sliding pin (9) is held between the pitch angle piece (8) and the pitch control unit arm (5) by the pin fixing washer (90) and protrudes between the pitch angle piece (8) and the pitch control unit arm (5) through the pitch angle piece through hole (80), through the ball through hole (61) in the spherical bearing and out of the ball (6) facing the pitch control unit (4).

2. Detachable connection between a pitch control unit arm (5) and a pitch angle piece (8) according to claim 1, wherein a first sliding surface (62) is formed at the ball outer surface and / or at an inner surface of the outer ring (60) and / or a second sliding surface (63) is formed at the outer surface of the sliding pin (9) and / or at the inner surface of the ball through hole (61), thus allowing a sliding movement along the first sliding surface (62) of the ball (6) relative to the outer ring (60) and / or along the second sliding surface (63) of the sliding pin (9) relative to the ball through hole (61).

3. Detachable connection between a pitch control unit arm (5) and a pitch angle piece (8) according to claim 2, wherein a slotted nut (91) and a split pin holder are used.

4. Detachable connection between a pitch control unit arm (5) and a pitch angle piece (8) according to one of claims 1 to 3, wherein the ball (6) and the outer ring (60) are fixed in the arm through hole (50) of the pitch control unit arm (5).

5. Detachable connection between a pitch control unit arm (5) and a pitch angle piece (8) according to one of claims 1 to 3, wherein the ball (6) and the outer ring (60) are fixed in the pitch angle piece through hole (80) of the pitch angle piece (8), thus achieving the pivoting and sliding movement of the sliding pin (9).

6. The detachable connection between a pitch control unit arm (5) and a pitch horn (8) of claim 2, wherein the first sliding surface (62) is attached or integrated at the outer surface of the ball and the second sliding surface (63) is attached or integrated at the outer surface of the sliding pin (9).

7. The detachable connection between a pitch control unit arm (5) and a pitch horn (8) of claim 2 or 6, wherein the second sliding surface (63) is bonded or coated to the outer surface of the sliding pin (9) comprising a single material, a fiber reinforced matrix or a sintered material.

8. The detachable connection between a pitch control unit arm (5) and a pitch horn (8) of claim 3, wherein the pin fixation washer (90) is formed as a conical washer (90).

9. A tail rotor head (3) for a tail rotor of a rotary wing aircraft comprising a pitch control unit (4) with a plurality of pitch control unit arms (5), a plurality of blade holders (7) with connected tail rotor blades (2), wherein each blade holder (7) is connected to each pitch control unit arm (5) by a detachable connection of one of claims 1 to 3.

10. A tail rotor (1) for a rotary wing aircraft comprising a tail rotor head (3) according to claim 9, wherein the sliding pin (9) is configured to be detached and replaced without removing any other component than the nut (91) on the tail rotor (1) fully installed on the rotary wing aircraft.

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