Description:1 Title of the Invention
Rotor In-Plane Forces and Torque Suppressing Pylon Support for Rotorcraft
2 Field of the Invention
The present invention relates to a suspension system of a helicopter rotor and particularly to a system positioned between the bottom of the main transmission box and the top of the fuselage of a helicopter and exposed to vibrations which have to be damped and to in-plane forces and rotor torque which has to be suppressed, capable of filtering out movements and vibration between the main rotor, and the fuselage of the helicopter, occurring when the helicopter is used.
3 Background of the Invention
In rotary-wing aircraft, such as helicopters, the operation of the rotor blades generates vibratory forces which are transmitted to the fuselage through the pylon and pylon mounts. These vibratory forces are caused by the asymmetric airflow over the rotating rotor blades and unbalance in the rotor system. Therefore, it is necessary to isolate the fuselage from these blade-induced forces or vibrations to improve crew and passenger comfort and increase the aircraft's performance capability. This can be achieved through the use of pylon mounts and a suspension system positioned between the bottom of the main transmission gearbox and the top of the fuselage of the helicopter, which is designed to absorb and dampen the rotor vibratory forces. The suspension system reduces the effects of in-plane forces and rotor torque, which can cause unwanted movements and vibrations in the helicopter. The suspension system incorporates various damping and suppression mechanisms, such as shock absorbers, springs, and other components, which work together to absorb and dissipate energy from the vibrations and forces encountered during flight. These mechanisms help to isolate the rotor from the rest of the helicopter, providing a stable and reliable platform for flight. the suspension system described in this invention is an important component of modern helicopter design, enabling safe and efficient flight even in challenging conditions.
3.1 Prior Art
Among the known suspension systems for rotorcraft rotors positioned between the bottom of the main transmission box and the top of the fuselage of a helicopter, capable of suppressing rotor in-plane forces and torque thereby attenuating fuselage vibrations, one particular suspension system is described in US Patent US3502290, titled “Vibration Damping Helicopter Rotor Support”, 1970; as best shown in Figure 1, a flexible connection between the rotor and fuselage of a helicopter. The elastic link is composed of a base plate made of titanium or a titanium alloy that is cut away to form a resilient assembly with parallel blades. If the flexibility required is uni-directional, the plate is in the form of a grille. If bi-directional flexibility is required, the plate is in the form of two intersecting grilles connected to each other. The plate is fixed to the bottom of the main gearbox casing, which is supported by an assembly of inclined bars. These bars are connected to the top part of the gearbox on one side and to the fuselage on the other side. The known baseplate is easy to manufacture and inexpensive when flexibility is required in only one axis. However, if flexibility is required in several axes, two or more grids interconnected by rigid members must be used, which makes the mechanism more expensive to manufacture. This is because the material used to fabricate the baseplate is a titanium alloy, which is more expensive and challenging to machine than aluminum or steel.
Other arrangements of suspension plate between the lower part of the main gearbox and the top of the fuselage are described in US Patent US4274510, titled “Multi-Directional Suspension Means for Rotor Aircraft” 1981: as best shown in Figure 2, it comprises a plate rigid with the suspended member and located in a plane substantially at right-angles to the axis, an assembly of rotationally rigid connecting elements between the plate and the structure ensuring absorption of the torque on the structure, and an assembly of elements for flexible translatory connection between the plate and the structure allowing the plate to perform movements of limited extent in any direction in its plane.
The high cost of such a connecting means motivated the applicants to propose US Patent US3920202, titled “Suspension System for Rotorcraft Rotors”, 1975: as best shown in Figure 3, a means of suspension between the gearbox and fuselage of a helicopter comprises a baseplate having a pair of shoulders radially extending in opposed directions is fastened to the housing of the transmission box. Structural members on top of the helicopter fuselage have fixed relatively thereto radial projections independent of the baseplate and extending in opposition to shoulders to cooperate therewith for limiting rotary movement of the baseplate. For absorbing the compressive force of said movement, resilient means are interposed between shoulders and projections.
According to the invention, the two functions-absorption of the torque and elastic suspension are separated and are fulfilled by two different assemblies of connecting elements, one ensuring rotationally rigid connection while an ability to undergo deformation allows a freedom of translatory movement, the other ensuring a flexible translatory connection of a multi-directional nature and having clearly defined degrees of stiffness in each of the two aforesaid directions which are at right-angles to each other.
On a helicopter, such a suspension makes it possible to absorb into the fuselage the reaction of the main rotor torque, preventing rotation of the gearbox, and making it possible to damp the vibrations via a flexible suspension offering considerable longitudinal and lateral flexibility, and therefore flexibility in any direction at right-angles to the axis of the rotor. The present invention has as its object the provision of a rotor suspension system that overcomes the disadvantages of the known stems, and provides a simple economical means for suspending rotors in all types of rotorcrafts.
another object of the present invention is to provide a rotor suspension system for placement between the main rotor and fuselage of a helicopter, consisting of an inexpensive and easy-to-fabricate torque strip capable of absorbing in-plane forces and torque produced by the helicopter rotor system.
4 Brief Summary of the Invention
Briefly, the pylon support system according to the invention includes three torque strips and two tie rods assembled at an interval around the base of the pylon. These torque strips and tie rods serve to mount the pylon on the fuselage and provide a means of suppressing vibratory in-plane forces and torque arising from the rotor system.
Torque strips are arranged in a triangular fashion on the transmission deck area for connecting to the pylon base. Each torque strip on both ends is connected to the transmission deck through attachment brackets. The pylon base is connected to these torque strips at an appropriate location by Z-plates. The torque strips, Z-plates geometry, and materials were optimized to get the required high in-plane stiffness and low out-of-plane stiffness. These tailored stiffnesses will make the torque strip and Z-plate assembly into a high-rigidity member in the transverse direction which will react to the rotor in-plane forces, and torque and act as a flexible member in the vertical direction, thus allowing the pylon to oscillate freely in the vertical direction to adjust the misalignments of the engine, transmission lines to pylon.
In addition to the torque strips, two tie rods are also connected between the pylon base and the transmission deck to react with the rotor torque and in-plane force resulting from the rotor pitching moment, and the same is verified in the transmission deck assembly test performed at the ground test center. These tie rods are positioned at the LH and RH side of the pylon base rear along the helicopter longitudinal direction.
The following description, accompanied by non-limiting exemplary drawings, will provide a clear understanding of how the invention can be implemented.
5 Detail Description of the Drawings
The distinctive characteristics are believed to be representative of the embodiments described in the claims of the current application. However, understanding the embodiments themselves, along with a preferred mode of use, and additional objectives and advantages thereof, is best achieved by referring to the following detailed description when viewed alongside the accompanying drawings, where:
Figure 1 (prior art): A flexible connection between the rotor and the fuselage of a helicopter described in US Patent US3502290 - “Vibration Damping Helicopter Rotor Support”.
Figure 2 (prior art): Multi-Directional Suspension Means for Rotor Aircraft a US Patent US4274510 shows the arrangement of suspension plate between the lower part of the main gearbox and the top of the fuselage.
Figure 3 (prior art): A US Patent US3920202, titled “Suspension System for Rotorcraft Rotors” shows a means of suspension between the gearbox and fuselage of a helicopter comprising a baseplate having a pair of shoulders in opposed directions is fastened to the transmission box.
Figure 4: Isometric view of a rotorcraft having a pylon-mounted system to suppress rotor in-plane forces and torque.
Figure 5: A perspective view depicting the attachment of a rotor pylon onto a helicopter transmission deck, as described in the illustrative embodiment of the current application.
Figure 6: An exploded perspective of the rotorcraft pylon system assembly, including the gearbox assembly with tie rods, three torque strip assemblies designed to counteract rotor in-plane forces, and the torque and transmission deck assembly where the torque strip is affixed.
Figure 7: Bottom view of the gearbox illustrating the interface connections between the gearbox and three torque strip assemblies.
Figure 8: A schematic layout depicting the arrangement of three torque strip assemblies and their connections to the gearbox and transmission deck.
Figure 9: Isometric view of the Transmission deck, illustrating the interface connections with torque strip and tie rod assemblies.
Figure 10: Sectional view of the forward Z-plate connection to the rotorcraft pylon system bottom interface and forward torque strip assembly.
Figure 11: Sectional view of the forward torque strip assembly connection to the transmission deck assembly.
6 Detail Description of the Invention
The invention disclosed in this article is about the rotorcraft pylon support system to suppress rotor in-plane forces and torque. The following specification particularly describes the invention and the manner in which it is to be performed. The invention can be better understood with the support of the drawings illustrated in Figures 4 through 11.
Figure 4 portrays the general systems of a Rotorcraft (H) in isometric view, a main rotor system (1), a fuselage (3), a landing gear (5) connected to the helicopter fuselage (3), a tail boom installed with empennage (4) at the rear of the fuselage (3) and a tail rotor system (2) mounted at the end of the tail boom (4).
The main rotor system (1) together with the gear box (G) is connected to the transmission deck (300) that is the upper portion of the helicopter fuselage (3) through a rotor pylon system (100). The gearbox (G) with the transmission deck is interfaced through a device, that is formed of multiple parts, which is named herein this document as a torque strip assembly (200), to suppress the in-plane vibrations associated with the in-plane forces and torque of rotor pylon system as illustrated in Figure 5.
The rotor system (1) along with the rotor pylon system (100) bottom is supported through plurality of tie rod (9) and a torque strip assembly (200) mount onto the transmission deck (300) via structural mounting brackets and fasteners. The entire torque strip assembly (200) is comprising of a torque strip assembly forward (10), a torque strip assembly right hand side (20) and a torque strip assembly left hand side (30). Figure 6 shows enlarged perspective view of the rotor pylon system (100) with tie rods (9) and torque strip assemblies (200) illustrating one embodiment of the subject system of the present invention consisting of three torque strips (10,20,30) connecting the transmission deck (300) of the helicopter.
Referring to Figures 7 through 9, rotor pylon system (100) bottom interface is connected with tie rods (9) to transmission deck (300) tie rod attachment brackets (47,48). Also, rotor pylon system (100) bottom interface (6,7,8) is connected to 3-torque strip assemblies (10,20,30) through 3 Z-plates (16,26,36).
As schematically shown in Figure 6 through 9, the rotor pylon support system at bottom (200) comprises of 3 torque strips (11,21,31), 3 Z-plates (16,26,36) which is connected by means of a circle of fasteners (18,28,38) to the bottom of rotor pylon system (100). The Z-plates (16,26,36) are connected to torque strips (11,21,31) through plural of fasteners (17,27,37). The torque strips (11,21,31) are arranged in a triangular fashion at the bottom of the rotor pylon support system (200). Ends of forward torque strip (11) are connected to Transmission deck (300) through attachment brackets (12,13,14,15) at locations (42,46) respectively. Similarly, ends of LH torque strip (31) are connected to Transmission deck (300) through attachment brackets (32,33,34,35) at locations (44,45) and ends of RH torque strip (21) are connected to Transmission deck (300) through attachment brackets (22,23,24,25) at locations (41,43). All the torque strip attachment brackets are connected to the fuselage through Hi-loks (76) and collars (77) to ensure rigid connection. Alternatively, the torque strips can be arranged in quadrilateral or in any other multilateral fashion by more than 3 or less than 3 torque strips at the bottom of the rotor pylon support system (300).
The torque strips (11,21,31) are made up of tailored composite layers and are assembled maintaining a gap between the torque strip and the bottom deck panel interface (48) as shown in Figure 10, provides the flexibility of the rotor pylon system (100) in the vertical direction. The torque strip (11,21,31) and Z-plate (16,26,36) due to the inherent geometry and arrangement, results into substantial rigidity in transverse direction and maintains better flexibility in vertical direction.
As schematically shown in Figure 8, the three torque strips (11,21,31) arranged in-plane are made up of carbon composite layers. The layers are selected and arranged symmetrically, then tailored in a manner to meet the required stiffness in-plane and vertical directions. The cross-section of the torque strip (11,21,31) is selected to have plane surface at the bottom to have a proper mating surface with Z-plates (16,26,36). The edges of the torque strip (11,21,31) comprise of crimp to avoid delamination of the layers and to provide required stiffness while transferring loads. The geometrical shape of Z-plate (16,26,36) made up of metallic material is so chosen to transfer the loads while maintaining the appropriate bearing surface with the torque strip (11,21,31).
As illustrated in Figure 10, the forward bottom flange interface of gearbox (G) is connected to forward Z-plate (16) through bushes (51) and Z-plate connecting fasteners bolt (52), washer (53) and self-locking nut (54). The Z-plate (16) is connected to the torque strip (11) through torque strip in -built bushes (55), torque strip-z plate through bushes (56) and torque strip -z-plate connecting fasteners bolt (57), washer (58) and self-locking nut (59). The concept of bush in bush mentioned in the above connection involving Z-plate (16) and torque strip (11) facilitates the load transfer through shear connection. The close tolerance is maintained for torque strip-z plate through bushes (56) to achieve uniform load transfer. Similar installation is achieved in LH and RH Z-plate - torque strip assemblies (20, 30) at interfaces (27,28,37,38). The z-plates (16, 26, 36) are positioned at the bottom of torque strip (11,21,31) to have proper bearing surface while load transfer from rotor pylon system (100) to the transmission deck (300).
Figure 11 shows the schematic connection of forward torque strip (11) to the transmission deck (300) at RH end (42) through top and bottom attachment brackets (14,15). The connection is achieved through bush in bush concept which involves arrangement of bushes (61,62). The bush (62) passes through close tolerance hole of torque strip inbuilt bush (61), top and bottom bracket (14,15) and facilitates uniform load transfer through shear connection. The arrangement also involves torque strip-bracket connecting fasteners bolt (63), washers (64) and self-locking nut (65).
The top and bottom bracket (14,15) are connected to the fuselage at (42) through bracket fuselage connecting fasteners Hi-loks (76) and collars (77). At LH end (46), forward torque strip (11) is connected to the transmission deck (300) through top and bottom attachment brackets (12,13). These interface connection at ends (42,46) facilitates a fixed-fixed connection of torque strip (11) maintaining a gap with bottom panel (49) to facilitate flexibility of pylon system in vertical direction. Similar installation is achieved in LH and RH torque strip assemblies (30, 20) with transmission deck (300) at ends (41,43,44,45).
, Claims:We Claim,
1. Rotor In-Plane Forces and Torque Suppressing Pylon Support for Rotorcraft that is having a main rotor (1), a fuselage (3), a landing gear (5), a tail boom (4) extended rear of fuselage (3) and an empennage together with a tail rotor (2) mounted on the tail boom (4) comprising:
a rotor system (1), a rotor pylon system (100) together with a gear box (G) and a transmission deck (300) as the upper most structure of said fuselage (3);
a pylon interfacing system (200) having plurality of a torque strip assembly (10,20,30) for mounting said rotor pylon system (100) on to said transmission deck (300) of said fuselage (3);
plurality of holes on the bottom face of gearbox (G) for fastening provision (6,7,8);
wherein, said torque strip assembly (10,20,30) further comprising,
plurality of torque strip (11,21,31) as a main body to form torque strip assembly (10,20,30),
wherein torque strip (11,21,31) is with fastening provisions (17) anywhere between the first and second end,
plurality of Z-plate (16,26,36) with fastening provisions (18) on first and second end, and
plurality of brackets (12,13,14,15,22,23,24,25,32,33,34,35) with fastening provisions on first and second end of said torque strip (11,21,31);
wherein said torque strip (11,21,31) connect to gear box (G) through said Z-plate by means of fastening provisions (17,18,27,28,37,38) and fastening provisions (6,7,8) on said gearbox (G);
wherein said torque strip (11,21,31) ends connect to said transmission deck (300) through said brackets (12,13,14,15,22,23,24,25,32,33,34, 35) at (41,42,43,44,45,46) as a whole said torque strips (10,20,30) form a triangular arrangement; and
plurality of tie rod (9) connects said pylon system (100) and said transmission deck (300) of said fuselage (3) through brackets (47,48).
2. Rotor In-Plane Forces and Torque Suppressing Pylon Support for Rotorcraft as claimed in claim 1, wherein torque strip (11,21,31) geometry shape include a crimp (11A) and a predetermined thickness.
3. Rotor In-Plane Forces and Torque Suppressing Pylon Support for Rotorcraft as claimed in claim 1, said plural of torque strip (10,20,30) arranged in a any other convenient arrangement by more than 3 or less than 3 said plural of torque strip.
4. Rotor In-Plane Forces and Torque Suppressing Pylon Support for Rotorcraft as claimed in claim 1, wherein Z-plate top flange and bottom flange are parallel and the connecting web is inclined by ±60° with vertical reference.
5. Rotor In-Plane Forces and Torque Suppressing Pylon Support for Rotorcraft as claimed in claim 1, wherein said fastening include bush (56) in bush (55) arrangement for said Z-plate (16,26,36) attachment with said torque strip (11,21,31) and said torque strip (11,21,31) attachment with said transmission deck (300).
6. Rotor In-Plane Forces and Torque Suppressing Pylon Support for Rotorcraft as claimed in claim 1, vertical gap maintained between said transmission deck (300) top surface and said gearbox (G) extreme bottom surface is between 10mm to 50mm.
7. Rotor In-Plane Forces and Torque Suppressing Pylon Support for Rotorcraft as claimed in claim 1, wherein said Z-plate (16,26,36) as an integral part of said torque strip (11,21,31).
8. Rotor In-Plane Forces and Torque Suppressing Pylon Support for Rotorcraft as claimed in claim 1, wherein said torque strips (11,21,31) are further connected each other with a plate.