Pitch changing mechanism for aircraft engine

Abstract

A pitch mechanism for an aircraft engine includes a coordination ring, a plurality of crankshafts coupled to the coordination ring and configured to receive a plurality of blades, an inner shaft coupled to the plurality of crankshafts and the coordination ring, and actuator cylinders and actuator pistons. An actuator cylinder is coupled to the inner shaft and configured to move relative to the actuator piston along a longitudinal axis of the pitch mechanism. Movement of the actuator cylinder relative to the actuator piston is translated into rotation of each of the plurality of crankshafts about a longitudinal axis of each of the plurality of crankshafts to vary a pitch of the plurality of vanes.

Description

Technical Field

[0001] The present disclosure generally relates to a pitch change mechanism for an aircraft engine. Background Art

[0002] Current propeller blade pitch change mechanisms rely on a system of counterweights to rotate the propeller blades toward the feathered position due to centrifugal force. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The foregoing and other features and advantages will become apparent from the following more particular description of various exemplary embodiments as illustrated in the accompanying drawings, wherein like reference numerals generally indicate identical, functionally similar, and / or structurally similar elements.

[0004] Figure 1 is a longitudinal cross-sectional view of a pitch changing mechanism of an aircraft engine for changing the pitch of a plurality of blades of the aircraft engine according to an embodiment of the present disclosure.

[0005] Figure 2 A longitudinal cross-sectional view of a pitch change mechanism according to an embodiment of the present disclosure is shown with the blades oriented in a feathered position.

[0006] Figure 3 A longitudinal cross-sectional view of a pitch change mechanism according to an embodiment of the present disclosure is shown with the blades oriented in a fine position. DETAILED DESCRIPTION

[0007] Additional features, advantages, and embodiments of the present disclosure are set forth or apparent by consideration of the following detailed description, drawings, and claims. Furthermore, the foregoing summary and the following detailed description of the present disclosure are exemplary and are intended to provide further explanation without limiting the scope of the present disclosure as claimed.

[0008] Various embodiments of the present disclosure are discussed in detail below. Although specific embodiments are discussed, this is for illustrative purposes only. Those skilled in the relevant art will recognize that other components and configurations may be used without departing from the spirit and scope of the present disclosure.

[0009] As used herein throughout the specification and claims, approximating language may be used to modify any quantitative representation that may be permissibly varied without resulting in a change in the basic function to which it is related. Thus, values ​​modified by terms such as "about," "approximately," and "substantially" are not limited to the precise values ​​specified. In at least some cases, approximating language may correspond to the precision of an instrument used to measure the value.

[0010] As used herein, the terms "axial" and "axially" refer to directions and orientations that extend substantially parallel to the centerline of an aircraft engine or combustor. Additionally, the terms "radial" and "radially" refer to directions and orientations that extend substantially perpendicular to the centerline of an aircraft engine or fuel-air mixer assembly.

[0011] A pitch-changing mechanism can be used to change the pitch of the blades of an aircraft. The pitch change orients the blades relative to the incoming airflow. When the aircraft is stationary and the propeller is spinning (in relatively calm air), the airflow vector for each blade is primarily from one side of the blade (feathered position). However, as the aircraft begins to move forward, the relative airflow vector gradually faces the leading edge of the blade. In order to maintain the blade's angle of attack relative to the airflow, the pitch of the blade is adjusted to a fine position.

[0012] The first propeller engines are provided with propeller blades having a fixed pitch. However, these propeller engines are not efficient over a certain range of flight conditions. For example, if the angle of the propeller blades is set for takeoff and climb performance, the propeller engine will be inefficient in cruise flight because the propeller blades will have a low angle of attack. On the other hand, if the angle of the propeller blades is set for cruise performance, the propeller engine may stall at lower speeds because the propeller blades will have an angle of attack that is too high. Therefore, a propeller engine with an adjustable propeller blade angle is more efficient over a certain range of conditions for operating an aircraft engine. A propeller engine provided with propeller blades having a variable pitch can have an almost constant efficiency over a certain range of airspeeds.

[0013] As will be described in further detail in the following paragraphs, the mechanism for changing the pitch of the blades uses a combination of pitch change mechanism functional features controlled by an integrated system and may be implemented by a hydraulic dual-channel axial actuator, an electric auxiliary feathering pump, an oil transfer bearing, and one or more oil passages. This arrangement eliminates counterweights and reduces weight, thereby improving fuel efficiency.

[0014] The axial actuator is configured to rotate with the propeller shaft and comprises an axially movable cylinder connected to the blades via a connecting rod yoke. The axial movement of the actuator cylinder is converted into a change in the pitch angle of the blades. In normal operating mode, oil is supplied to the actuator at a certain pressure through an oil delivery bearing with engine oil, or in case of a drop in engine oil pressure, the actuator is supplied with oil by an electrically driven auxiliary hydraulic pump with a separate auxiliary oil reservoir. The auxiliary oil reservoir can be located, for example, in a space inside the main engine oil tank, as a tank within a tank configuration. The pitch locking function is realized by a hydraulic system or a mechanical lock controlled by this system. Figure 1is a cross-sectional view of a pitch change mechanism 101 of an aircraft engine 100 for changing the pitch of a plurality of blades of the aircraft engine 100 according to an embodiment of the present disclosure. The term "aircraft engine" as used herein includes, but is not limited to, an open fan engine, an unducted fan engine, or any engine having blades outside the nacelle of the aircraft engine, a propeller engine, or a turboprop engine, etc. Figure 1 A pitch change mechanism 101 of an aircraft engine 100 is shown. The aircraft engine 100 includes a plurality of blades 102. The plurality of blades 102 are coupled to the pitch change mechanism 101. The plurality of blades 102 extend radially from the pitch change mechanism 101. The pitch change mechanism 101 has a plurality of crankshafts 104. The plurality of crankshafts 104 are configured to receive the plurality of blades 102. Each of the plurality of blades 102 is connected to a corresponding one of the plurality of crankshafts 104. Each crankshaft 104 is configured to rotate about its longitudinal axis 104A, which generally corresponds to the longitudinal axis of the propeller blade 102. The pitch change mechanism 101 further includes a unison ring 106. Each of the plurality of crankshafts 104 is coupled to the unison ring 106 by a corresponding connecting rod yoke of a plurality of connecting rod yokes 108.

[0015] The pitch change mechanism 101 also includes an inner shaft 110. The unison ring 106 is coupled to the inner shaft 110. For example, in one embodiment, the unison ring 106 is coupled to the inner shaft 110 by a plurality of fasteners 110A. The inner shaft 110 is thus coupled to the plurality of crankshafts 104.

[0016] The pitch changing mechanism 101 includes an actuator cylinder 112 and an actuator piston 114. The diameter of the actuator cylinder 112 is larger than the diameter of the actuator piston 114. The actuator cylinder 112 is coupled to the inner shaft 110. The actuator cylinder 112 is configured to move relative to the actuator piston 114 along the longitudinal axis 101A of the pitch changing mechanism 101. In an embodiment, the actuator piston 114 is fixed in the longitudinal direction. The pitch changing mechanism 101 also includes an actuator cylinder support 116 configured to support the actuator cylinder 112. The actuator cylinder support 116 is coupled to the actuator piston 114. The actuator cylinder support 116 contacts the actuator cylinder 112 at different points along the longitudinal axis 101A of the pitch changing mechanism 101 via a plurality of sealing joints 112A. In addition, the actuator cylinder support 116 further contacts the actuator piston 114. The sealing joint 112A is connected to the actuator cylinder support 116 and is immovable when the actuator cylinder 112 moves relative to the actuator piston 114. In an embodiment, the sealing joint 112B can move relative to the actuator piston 114 on the surface of the actuator piston 114 together with the actuator cylinder 112. The rear end of the actuator cylinder support 116 contacts the front end of the actuator piston 114. The diameter of the actuator cylinder support 116 is larger than the diameter of the actuator piston 114. The actuator piston 114 has a cylinder portion 114A disposed at the front end and a conical portion 114B disposed at the rear end. The cylinder portion 114A defines a chamber 114C of the actuator piston 114. In one embodiment, the sealing joint 112B moves on the surface of the cylinder portion 114A of the actuator piston 114 together with the actuator cylinder 112.

[0017] The inner shaft 110 has a conical shape or a funnel-like shape extending within a chamber 116A ("rough chamber") defined by an actuator cylinder support 116. The inner shaft 110 has a conical portion 110B and a cylindrical portion 110C connected to the conical portion 110B. The actuator cylinder 112 is connected to the conical portion 110B of the inner shaft 110. The conical portion 110B extends radially to connect with the unison ring 106. The cylindrical portion 110C is configured to be enclosed within the chamber 116A defined by the actuator cylinder support 116 of the actuator cylinder 112.

[0018] The pitch change mechanism 101 further includes a mechanical pitch lock 118. The mechanical pitch lock 118 is disposed within the chamber 116A of the actuator cylinder support 116. The mechanical pitch lock 118 includes an annular pitch lock member 118A surrounding the cylindrical portion 110C of the inner shaft 110.

[0019] The pitch change mechanism 101 also includes an oil bearing 120. The oil bearing 120 is disposed within a chamber 114C of the actuator piston 114. The oil bearing 120 is coupled to the actuator piston 114 by a plurality of fasteners 120A. In one embodiment, the oil bearing 120 includes an oil passage 122. In another embodiment, the oil bearing 120 is attached to a static portion of the aircraft engine 100. Oil is supplied to the oil bearing 120 through an oil conduit 124. For example, oil is supplied from the oil conduit 124 to the oil bearing 120, which in turn supplies oil to the oil passage 122 of the oil bearing 120. The oil from the oil passage 122 is supplied to a chamber 112C (“fine chamber”) defined by the space between the actuator cylinder 112 and the actuator piston 114. The oil supplied into the chamber 112C through the oil passage 122 causes the actuator cylinder 112 to move rearwardly toward the conical portion 114B of the actuator piston 114. On the other hand, the oil is supplied to the chamber 116A defined by the actuator cylinder support 116 through the central opening passage 123 in the central portion of the oil delivery bearing 120, causing the actuator cylinder 112 to move forwardly relative to the actuator piston 114, as will be described in further detail in the following paragraphs.

[0020] In one embodiment, the pitch change mechanism 101 further includes a static interface 126 (e.g., a bellows) coupled to the oil transfer bearing 120. The static interface 126 provides flexible support for the oil transfer bearing 120. The static interface 126 allows the oil transfer bearing 120 to move with the pitch change mechanism 101 while being connected to the static portion of the aircraft engine 100.

[0021] In one embodiment, the pitch change mechanism 101 further includes an exhaust shroud 128. The exhaust shroud 128 is coupled to the actuator cylinder 112 at one end 128A and is coupled to the conical portion 114B of the actuator piston 114 at an opposite end 128B. The end 128A is a movable sealing interface at the outer diameter of the cylinder, while the opposite end 128B is fixed to the conical portion 114B of the actuator piston 114. In the event of oil leakage due to wear of the movable sealing joint 112B, the exhaust shroud 128 is provided to shield or isolate various components outside the pitch change mechanism 101. In one embodiment, the pitch change mechanism 101 further includes a guide rod 150. The guide rod 150 is configured to tangentially position the actuator cylinder 112.

[0022] Figure 2 1 shows a longitudinal cross-sectional view of a pitch change mechanism 101 according to an embodiment of the present invention, wherein the blades 102 are oriented in a feathered position. Figure 2 As shown, the feathered position is an orientation of the blade 102 such that the edge 102A of the blade 102 faces the airflow 200, or the face 102B of the blade 102 is parallel to the airflow 200. In the feathered position, the actuator cylinder 112 is in the Figure 2 Move forward or left.

[0023] like Figure 2 As shown, in the feathered position, the actuator cylinder 112 moves forward relative to the actuator piston 114. In order to move the actuator cylinder 112 forward relative to the actuator piston 114, oil at a certain pressure is provided to exert pressure on the entire oil chamber 114C, and thus, a force is applied to the rear surface 110D of the cylindrical portion 110C of the inner shaft 110 to move the actuator cylinder 112 forward.

[0024] Figure 3 FIG. 1 shows a longitudinal cross-sectional view of a pitch change mechanism 101 according to an embodiment of the present invention, wherein the blades 102 are oriented in a fine position. Figure 3 As shown, the fine position is an orientation of the blade 102 such that the face 102B of the blade 102 is substantially perpendicular to the airflow 200. In the fine position, the edge 102A faces substantially perpendicular to the airflow 200. Figure 3 As shown, in the fine position, the actuator cylinder 112 moves rearward relative to the actuator piston 114. In order to move the actuator cylinder 112 rearward relative to the actuator piston 114, oil under a certain pressure is supplied to the oil delivery bearing 120 through the oil conduit 124, and is supplied to the chamber 112C between the actuator cylinder 112 and the actuator piston 114 through the oil passage 122. The oil supplied into the chamber 112C through the oil passage 122 applies pressure to the entire chamber 112C, and thus applies a force on the actuator cylinder 112 (as shown by arrow 300), which moves the actuator cylinder 112 rearward. Since the actuator cylinder 114 and the actuator cylinder support 116 are immovable, the oil in the chamber 112C exerts a force on the rear wall 112D of the actuator cylinder 112 to move the actuator cylinder 112 relative to the actuator piston 114 and the actuator cylinder support 116 .

[0025] In the fine position, the actuator cylinder 112 moves to the rearward direction or Figure 3 The blade 102 is in the feathering position (eg Figure 2 ) than in fine position (as shown Figure 3 shown) experience less resistance.

[0026] Rear wall 112D has a surface area that is less than the surface area of ​​chamber 116A ("coarse chamber"). Thus, for the same oil pressure, a greater magnitude of force is generated by actuator cylinder 112 to move blade 102 to the feathered position, while a smaller magnitude of force is generated by actuator cylinder 112 to move blade 102 to the fine position to facilitate actuation toward the feathered (coarse) position.

[0027] The mechanical pitch lock 118 is provided as a fail-safe emergency measure when there is insufficient oil pressure or an unexpected drop in oil pressure occurs. In the event of a drop in oil pressure, the mechanical pitch lock 118 locks the pitch change mechanism 101 so that the orientation of the blades 102 is maintained.

[0028] The angle of the blades 102 relative to the airflow 200 depends on the flight conditions. The feathered position is used to minimize drag. In normal operation, the feathered position is achieved by means of the main engine oil pump 201. With the engine off, the feathered position is achieved by using an electrically driven auxiliary hydraulic oil pump 202.

[0029] The above-described pitch-changing mechanism 101 provides various benefits:

[0030] (a) No external movable seals are used in chamber 116A (coarse chamber) because the use of any movable seals may wear over time, which may cause external oil leakage. Therefore, static external seals are used in the coarse chamber instead. The term static external seal as used herein refers to a seal that does not change position between two components or a seal that is not movable, that is, the relative position of the seal between the two components does not change.

[0031] (b) Guide rods are provided to tangentially position the actuator cylinder.

[0032] (c) The blade position is controlled by a blade position control system.

[0033] (d) The blade position control system may use a closed control loop.

[0034] (e) The oil transfer bearing (OTB) 120 provides three oil lines: (1) a coarse line that supplies the coarse chamber to cause movement toward the feathered position, (2) a fine line that supplies the fine chamber to cause movement toward the fine position, and (3) a pitch lock (PL) line that unlocks the mechanical pitch lock when the PL line is pressurized. Insufficient pressure in the PL line causes the mechanical pitch lock to engage and lock the pitch of the blade.

[0035] (f) An oil transfer bearing (OTB) is supported by a bearing and exposed to the rough chamber 116A to reduce or eliminate the need for an additional connection system to reduce weight and complexity and supply oil pressure to move the actuator cylinder 112.

[0036] Further aspects of the disclosure are provided by the subject matter of the following clauses.

[0037] A variable pitch mechanism for an aircraft engine includes a unison ring; a plurality of crankshafts configured to receive a plurality of blades and each of the plurality of crankshafts having a longitudinal axis; an inner shaft coupled to the plurality of crankshafts and the unison ring; an actuator piston and an actuator cylinder coupled to the inner shaft. The actuator cylinder is configured to move relative to the actuator piston along the longitudinal axis of the variable pitch mechanism. Movement of the actuator cylinder relative to the actuator piston is transmitted as rotation of each of the plurality of crankshafts about the longitudinal axis of each of the plurality of crankshafts to change the pitch of the plurality of blades.

[0038] The pitch changing mechanism according to the preceding clause, further comprising an oil transfer bearing, the actuator piston being coupled to the oil transfer bearing to supply oil through the oil transfer bearing to move the actuator cylinder.

[0039] The pitch change mechanism according to any one of the preceding clauses, further comprising a unison ring and a plurality of connecting rod yokes, each of the plurality of crankshafts being coupled to the unison ring through a corresponding connecting rod yoke of the plurality of connecting rod yokes. The inner shaft is coupled to the unison ring.

[0040] The pitch change mechanism according to any of the preceding clauses, the unison ring being coupled to the inner shaft by a plurality of fasteners.

[0041] The pitch change mechanism according to any one of the preceding clauses, wherein the diameter of the actuator cylinder is greater than the diameter of the actuator piston.

[0042] The pitch changing mechanism according to any of the preceding clauses, further comprising an actuator cylinder support coupled to the actuator piston, the actuator cylinder support being configured to support the actuator cylinder.

[0043] A pitch change mechanism according to any of the preceding clauses, the actuator cylinder support contacting the actuator cylinder via a first plurality of sealing joints at different points along the longitudinal axis of the pitch change mechanism.

[0044] The variable pitch mechanism of any of the preceding clauses, the first plurality of sealing joints being coupled to the actuator cylinder support and being immovable when the actuator cylinder moves relative to the actuator piston.

[0045] According to any one of the preceding clauses, the actuator cylinder further contacts the actuator piston via a second sealing joint, the second sealing joint being movable together with the actuator cylinder relative to the actuator piston on the surface of the actuator piston.

[0046] The pitch change mechanism according to any of the preceding clauses, further comprising a mechanical pitch lock disposed within a chamber defined by the actuator cylinder support, the mechanical pitch lock being configured to lock the pitch change mechanism.

[0047] A pitch changing mechanism according to any one of the preceding clauses, wherein the oil transfer bearing is arranged in a chamber defined by the actuator piston, and the oil transfer bearing has an oil conduit for supplying oil to a chamber defined by the space between the actuator cylinder and the actuator piston to move the actuator cylinder relative to the actuator piston.

[0048] In the pitch change mechanism according to any one of the preceding clauses, the oil transfer bearing is arranged in a chamber defined by the actuator piston.

[0049] The pitch changing mechanism according to any one of the preceding clauses, the inner shaft having a conical portion and a cylindrical portion connected to the conical portion, the conical portion radially extending to connect to the unison ring, the cylindrical portion being configured to be enclosed in a chamber defined by the actuator cylinder.

[0050] The pitch change mechanism according to any of the preceding clauses, further comprising a drain shield coupled to the actuator cylinder and the actuator piston, the drain shield being configured to shield various components outside the pitch change mechanism in the event of an oil leak.

[0051] An aircraft engine includes a plurality of blades and a pitch changing mechanism. The pitch changing mechanism includes a unison ring; a plurality of crankshafts configured to receive a plurality of blades and each of the plurality of crankshafts having a longitudinal axis; an inner shaft coupled to the plurality of crankshafts and the unison ring; an actuator piston; and an actuator cylinder coupled to the inner shaft. The actuator cylinder is configured to move relative to the actuator piston along the longitudinal axis of the pitch changing mechanism. Movement of the actuator cylinder relative to the actuator piston is transmitted as rotation of each of the plurality of crankshafts about the longitudinal axis of each of the plurality of crankshafts to change the pitch of the plurality of blades.

[0052] According to the aircraft engine as described in the preceding clause, the pitch change mechanism further comprises an oil transfer bearing, the actuator piston is coupled to the oil transfer bearing.

[0053] The aircraft engine according to any one of the preceding clauses, the pitch change mechanism further comprising an actuator cylinder support, the actuator cylinder support being coupled to the actuator piston, the actuator cylinder support being configured to support the actuator cylinder.

[0054] An aircraft engine according to any of the preceding clauses, the actuator cylinder support contacting the actuator cylinder via a first plurality of sealing joints at different points along the longitudinal axis of the pitch change mechanism.

[0055] An aircraft engine as described in any of the preceding clauses, the first plurality of sealing joints being coupled to the actuator cylinder support and being immovable when the actuator cylinder moves relative to the actuator piston.

[0056] Aircraft engine according to any of the preceding clauses, the actuator cylinder further contacting the actuator piston via a second sealing joint, the second sealing joint being movable together with the actuator cylinder relative to the actuator piston on a surface of the actuator piston.

[0057] An aircraft engine according to any of the preceding clauses, wherein the pitch change mechanism further comprises a mechanical pitch lock disposed in a chamber defined by the actuator cylinder support, the mechanical pitch lock being configured to lock the pitch change mechanism.

[0058] An aircraft engine according to any of the preceding clauses, wherein the aircraft engine is an open fan engine, an unducted fan engine, or a propeller engine having blades disposed externally of a nacelle of the aircraft engine.

[0059] An aircraft engine according to any preceding clause, wherein each of the plurality of blades is connected to a corresponding one of the plurality of crankshafts of the variable pitch mechanism.

[0060] A method of changing the pitch of a plurality of blades in an aircraft engine using a pitch changing mechanism, the pitch changing mechanism having a unison ring; a plurality of crankshafts coupled to the unison ring and configured to receive a plurality of blades, each of the plurality of blades being connected to a corresponding one of the plurality of crankshafts, each of the plurality of crankshafts having a longitudinal axis; an inner shaft coupled to the plurality of crankshafts and the unison ring; an actuator piston; and an actuator cylinder coupled to the inner shaft. The method includes moving the actuator cylinder relative to the actuator piston along the longitudinal axis of the pitch changing mechanism. The method further includes transferring the movement of the actuator cylinder relative to the actuator piston into rotation of each of the plurality of crankshafts about the longitudinal axis of each of the plurality of crankshafts to change the pitch of the plurality of blades.

[0061] According to the method of the preceding clause, the pitch changing mechanism further comprises an oil transfer bearing, the actuator piston being coupled to the oil transfer bearing.

[0062] The method according to any of the preceding clauses, the pitch changing mechanism further comprising an actuator cylinder support coupled to the actuator piston, the actuator cylinder support being configured to support the actuator cylinder.

[0063] A method according to any of the preceding clauses, the actuator cylinder support contacts the actuator cylinder via a first plurality of sealing joints at different points along the longitudinal axis of the pitch change mechanism.

[0064] A method as in any of the preceding clauses, the first plurality of sealing joints being coupled to the actuator cylinder support and being immovable when the actuator cylinder moves relative to the actuator piston.

[0065] According to the method of any of the preceding clauses, the actuator cylinder further contacts the actuator piston via a second sealing joint, the second sealing joint being movable together with the actuator cylinder relative to the actuator piston on a surface of the actuator piston.

[0066] A method according to any of the preceding clauses, wherein the pitch change mechanism further comprises a mechanical pitch lock disposed within a chamber defined by the actuator cylinder support, the mechanical pitch lock being configured to lock the pitch change mechanism.

[0067] A method according to any of the preceding clauses, wherein the aircraft engine is an open fan engine, an unducted fan engine, or a propeller engine having blades disposed externally of a nacelle of the aircraft engine.

[0068] A method as in any of the preceding clauses, wherein each of the plurality of blades is connected to a corresponding one of a plurality of crankshafts of the variable pitch mechanism.

[0069] Although the foregoing description is directed to the preferred embodiments of the present disclosure, other changes and modifications will be apparent to those skilled in the art and may be made without departing from the spirit or scope of the present disclosure. In addition, the features described in conjunction with one embodiment of the present disclosure may be used in conjunction with other embodiments, even if not explicitly stated above.

Claims

1. A pitch-changing mechanism for an aircraft engine, characterized in that: The pitch-changing mechanism comprises: Coordination ring; a plurality of crankshafts coupled to the unison ring, the plurality of crankshafts configured to receive a plurality of blades and each of the plurality of crankshafts having a longitudinal axis; an inner shaft coupled to the plurality of crankshafts and the unison ring; an actuator piston; and an actuator cylinder coupled to the inner shaft, the actuator cylinder being configured to move relative to the actuator piston along a longitudinal axis of the pitch changing mechanism, wherein movement of the actuator cylinder relative to the actuator piston is transmitted as rotation of each of the plurality of crankshafts about the longitudinal axis of each of the plurality of crankshafts to change the pitch of the plurality of blades.

2. The pitch-changing mechanism according to claim 1, characterized in that: in, The inner shaft has a conical portion and a cylindrical portion connected to the conical portion, the conical portion radially extends to connect to the unison ring, and the cylindrical portion is configured to be enclosed in a chamber defined by the actuator cylinder.

3. The pitch changing mechanism according to claim 1, characterized in that: Further included is an exhaust shield coupled to the actuator cylinder and the actuator piston, the exhaust shield being configured to shield various components outside the pitch change mechanism in the event of an oil leak.

4. The pitch changing mechanism according to claim 1, characterized in that: Further included is an oil transfer bearing to which the actuator piston is coupled to supply oil through the oil transfer bearing to move the actuator cylinder.

5. The pitch changing mechanism according to claim 4, characterized in that: in, The oil transfer bearing is disposed in a chamber defined by the actuator piston, and has an oil conduit for supplying oil to a chamber defined by a space between the actuator cylinder and the actuator piston to move the actuator cylinder relative to the actuator piston.

6. The pitch changing mechanism according to claim 1, characterized in that: Further included is a plurality of connecting rod yokes, each of the plurality of crankshafts being coupled to the unison ring via a corresponding connecting rod yoke of the plurality of connecting rod yokes.

7. The pitch changing mechanism according to claim 6, characterized in that: The unison ring is coupled to the inner shaft via a plurality of fasteners.

8. The pitch changing mechanism according to claim 1, characterized in that: Further included is an actuator cylinder support coupled to the actuator piston, the actuator cylinder support configured to support the actuator cylinder.

9. The pitch-changing mechanism according to claim 8, characterized in that: Further included is a mechanical pitch lock disposed in a chamber defined by the actuator cylinder support, the mechanical pitch lock being configured to lock the pitch changing mechanism.

10. The pitch changing mechanism according to claim 8, characterized in that: Wherein the actuator cylinder support contacts the actuator cylinder at different points along the longitudinal axis of the pitch change mechanism via a first sealing joint.

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