WO2017002054A1

WO2017002054A1 - A rotor arrangement with offset hubs for the air crafts

Info

Publication number: WO2017002054A1
Application number: PCT/IB2016/053917
Authority: WO
Inventors: Ismail Khan AFGHAN
Original assignee: Afghan Ismail Khan
Priority date: 2015-06-30
Filing date: 2016-06-30
Publication date: 2017-01-05

Abstract

The present invention provides a stiff in-plane and/or soft in-plane rotor head for a rotorcraft. The invention includes a vertically extending rotor shaft, a center hub disposed on the rotor shaft for conjoint rotation therewith, and a plurality of outer hubs at the opposite ends of the center hub coupled thereto through a mechanical attachment for conjoint rotation therewith, such that the outer hub is also capable of an angular range of teetering and/or lead-lag movement relative to the center hub. A plurality of rotor blades is coupled to the rotor shaft through the center hub and outer hubs by a constant velocity joint that enables the blades to be rotated in a common plane about the axis of the rotor shaft while controlling the respective pitches of the blades such that any other relative in-plane and out-of-plane movements of the blades during rotation is allowed.

Description

TITLE OF THE INVENTION

A rotor arrangement with offset hubs for the air crafts

[0001] Technical field of the invention

[0002] The present invention relates to the field of aviation and more particularly to the helicopter rotors.

[0003] Background of the invention [0004] The objective of the aeronautic industry is to develop a lifting device using wings with airfoil, called as blades, wherein the blades are made to rotate at a certain speed.

[0005] It is essential that the rotor blades in helicopter are balanced accurately for the stable movement. The unbalanced blades lead to excessive vibrations caused due to various factors such as upward and downward movement of the center of mass of the four blades, changes in the angular momentum, lift change on each blade and resultant lift from each hub etc.

[0006] In existing vertical take-off and landing (VTOL) rotorcrafts, the payload lifting abilities are restricted. This limits the efficiency and performance of such rotorcrafts.

[0007] Various types of conventional rotor arrangements for helicopter are known in the prior art, for example, co-axial, tandem, crossed type rotors etc. The US patent number US 5791592 A discloses a helicopter with coaxial counter-rotating dual rotors and no tail rotor. This prior art discusses about a helicopter having two engines driving a single rotating drive shaft on which are mounted two spaced counter-rotating coaxial rotors at the same speed. The helicopter has a tail boom free of a tail rotor and supports two horizontally spaced pairs of air foils for controlling the direction of yaw in flight. [0008] The Chinese patent number 102874406 discloses a crossed type dual-rotor unmanned helicopter which comprises a helicopter body, a rotor system, a flight control system, a power system, an electric system and a ground control system. The rotor system is of a crossed type dual-rotor structure and comprises a left main rotor shaft system and a right main rotor shaft system. The system is provided with two identical rotors, the left main rotor shaft system and the right main rotor shaft system are parallel to each other to form an inverted splayed shape. The rotors are crossed above the helicopter body and rotational directions of the rotors are opposite to each other. Each rotor comprises two pitch-variable draw bars which are completely independent from a main rotor shaft and are used for adjusting the flight speed and the flight direction of the helicopter.

[0009] The studies have shown that rotors with greater solidity are required for next-generation high speed heavy lift rotor helicopter designs. This greater rotor solidity is most efficiently delivered with a large number of blades per head. One of the conventional air craft having a teeter or semi- rigid rotor heads inherently can employ only two blades per hub and are therefore, unsuitable for high speed heavy lift helicopter configurations.

[0010] With increase in payload in a teetering or semi-rigid rotor helicopters, there is a requirement of increase in length and width of rotor blade (i.e., a change in the aspect ratio of the rotor blade). The decrease in aspect ratio increases drag and increase in blade length increases both drag and blade tip velocity exceeding the speed of the sound.

[0011] Hence, looking at the problems associated with the existing technologies in the state of the art, there is a need of blades with good aspect ratio which eliminate the drag. The blades should also provide high wing loading and wide range of center of gravity with high efficiency and good performance of rotorcrafts. [0012] Summary of the invention

[0013] The present invention overcomes the drawbacks of the technology models available in the state of the art by providing a rotor arrangement with offset hubs for the air crafts, wherein the rotor arrangement comprises a rotor head. The rotor head comprises a vertically extending rotor shaft from a mast of the aircraft. A center hub is disposed on the rotor shaft for conjoint rotation therewith. A plurality of outer hubs are coupled at both ends of the center hub. A plurality of rotor blades are coupled to the rotor shaft through the center hub and outer hubs by a constant velocity joint, wherein the joint enables the blades to rotate in a common plane about the axis of the rotor shaft while controlling the respective pitches of the blades. The outer hubs are coupled at the opposite ends of the center hub through a mechanical attachment for conjoint rotation therewith, such that the outer hub is capable of an angular range of teetering and/or lead-lag movement relative to the center hub. [0014] The outer hub comprises a plurality of yokes and a plurality of grips, wherein the grip securely holds the blade. A plurality of pitch horns are attached to the grip at one end, wherein the other end of the pitch horn is hinged to a plurality of pitch change rods, wherein the pitch change rod is connected to a rotating swash plate, which has variable horn lengths. The rotating swash plate is attached to the mast with the scissor link, wherein the rotating swash plate is fitted on a stationary swash plate, wherein the stationary swash plate transfers the received load to the rotating swash plate.

[0015] In a preferred embodiment of the invention, the outer hubs create a stiff- in-plane, wherein the teetering outer hubs are coupled to the center through a mechanical joint such that the outer hub is capable of an angular range of teetering movement relative to the center hub.

[0016] In a preferred embodiment of the invention, the outer hubs create a soft-in- plane, wherein the teetering outer hubs are coupled to the center hub through a mechanical joint such that the outer hub is capable of an angular range of teetering and lead-lag movement relative to the center hub. The plurality of non-teetering outer hubs are coupled to the center hub through a mechanical joint that prevents teetering of the hub such that the outer hub is not capable of an angular range of movement relative to the center hub. [0017] In a preferred embodiment of the invention, the outer hubs are attached to center hub that from a space there between, wherein the center hub is positioned within the space.

[0018] In a preferred embodiment of the invention, the outer hubs are further fixed but the grips are allowed to transverse movement about the chord, pitch and vertical axes.

[0019] In a preferred embodiment of the invention, said off-set hubs are further attached to the tail rotor of the air craft.

[0020] The response of the helicopter to cyclic controls is very quick. This is because the rotors are away from mast, increasing the arm from the centre. Further, when the rotor disk is unloaded, there is a reduced tendency for a blade to make an incursion into the tail boom. The angular velocity and tangential acceleration provides better torque and rotational inertia saving horse power and fuel compared to other four-bladed rotor.

[0021] The present invention provides high speed, low drag, low maintenance, stiff in-plane and/or soft in-plane rotor head for a helicopter that enables four or more rotor blades to be used per rotor. The present invention also provides high wing loading and wide range of center of gravity efficiently. Hence, ensuring the best performance of rotorcrafts.

[0022] It is to be understood that both the foregoing general description and the following details description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. [0023] Brief description of the drawings

[0024] The foregoing and other features of embodiments will become more apparent from the following detailed description of the embodiments when read in conjunction with the accompanying drawings. In the drawings, like reference numerals refer to like elements.

[0025] FIGURE 1 illustrates the perspective view of a rotor arrangement with offset hubs mounted on the aircraft, in accordance to one or more embodiments of the invention.

[0026] FIGURE 2 illustrates the perspective view of a rotor arrangement with offset hubs, in accordance to one or more embodiments of the invention.

[0027] FIGURE 3 illustrates the top view of a rotor arrangement with offset hubs, in accordance to one or more embodiments of the invention.

[0028] FIGURE 4 illustrates the side view of a rotor arrangement with offset hubs mounted on the aircraft and, on the tail rotor of the aircraft, in accordance to one or more embodiments of the invention.

[0029] FIGURE 5 illustrates the top view of a rotor arrangement with offset hubs mounted on the aircraft, in accordance to one or more embodiments of the invention.

[0030] Detailed description of the invention [0031] Reference will now be made in detail to the description of the present subject matter, one or more examples of which are shown in figures. Each embodiment is provided to explain the subject matter and not a limitation. These embodiments are described in sufficient detail to enable a person skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, physical, and other changes may be made within the scope of the embodiments. The following detailed description is, therefore, not be taken as limiting the scope of the invention, but instead the invention is to be defined by the appended claims.

[0032] The present invention overcomes the drawbacks of the technology models available in the state of the art by providing a rotor arrangement with offset hubs, wherein the rotor head for a rotorcraft, such as a helicopter, includes a vertically extending rotor shaft, a center hub disposed on the rotor shaft for conjoint rotation therewith and a plurality of outer hubs at the opposite ends of the center hub. The outer hubs are coupled at the opposite ends of the center hub through a mechanical attachment for conjoint rotation therewith, such that the outer hub is also capable of an angular range of teetering and/or lead-lag movement relative to the center hub. A plurality of rotor blades are coupled to the rotor shaft through the center and outer hubs by a constant velocity joint, wherein the joint enables the blades to be rotated in a common plane about the axis of the rotor shaft while controlling the respective pitches of the blades, such that any other relative in- plane and out-of-plane movements of the blades during rotation is allowed.

[0033] The present invention provides high speed, low drag, low maintenance, stiff in-plane and/or soft in-plane rotor head for a helicopter that enables four or more rotor blades to be used per rotor. The invention also provides high wing loading and wide range of center of gravity efficiently, hence ensuring better performance of rotorcraft s.

[0034] FIGURE 1 illustrates the perspective view of a rotor arrangement having offset hubs mounted on the aircraft, in accordance to one or more embodiments of the invention. The present invention provides an offset rotor on a helicopter mast which revolves about the main mast, wherein a set of semi-rigid/flexible rotors are mounted off the main shaft at a certain distance.

[0035] In the preferred embodiment of the present invention, a stiff in-plane, teetering rotor head for a rotorcraft comprises an elongated, vertically extending rotor shaft (108) having an axis of rotation. A center hub (101) is disposed at an upper end and is rotationally driven by the rotor shaft (108). A plurality of teetering outer hubs (102a and 102b) are coupled to the center hub (101) through a mechanical joint such that the outer hub (102) is capable of an angular range of teetering movement relative to the center hub (101). An elongated, tangentially extending set of blades (104a, 104b, 104c, 104d) relative to the rotor shaft (108) has an airfoil cross-section and an inboard end coupled to the outer hubs (102a and 102b), wherein the tangentially extending set of blades receives driving torque from the rotor shaft (108) to the set of blades (104) through the center hub (101) and outer hubs (102a and 102b). The rotational velocity of the blade about the tilted axis of rotation remains substantially constant during teetering movements of the outer hub relative to the center hub.

[0036] In another embodiment of the present invention, a soft in-plane, teetering rotor head for a rotorcraft comprises an elongated, vertically extending rotor shaft (108) having an axis of rotation. A center hub (101) is disposed at an upper end and is rotationally driven by the rotor shaft (108). A plurality of teetering outer hubs (102a and 102b) are coupled to the center hub (101) through a mechanical joint such that the outer hub (102) is capable of an angular range of teetering and lead-lag movement relative to the center hub (101). An elongated, tangentially extending set of blades (104a, 104b, 104c and 104d) relative to the rotor shaft (108) has an airfoil cross-section and an inboard end flexibly coupled to the outer hubs (102a and 102b), wherein the tangentially extending set of blades receives driving torque from the rotor shaft (108) to the set of blades (104) through the center hub (101) and outer hubs (102a and 102b). The rotational velocity of the blade about the tilted axis of rotation remains substantially constant during teetering movements of the outer hub relative to the center hub. [0037] In another embodiment of the present invention, a soft in-plane, non- teetering rotor head for a rotorcraft comprises an elongated, vertically extending rotor shaft (108) having an axis of rotation. A center hub (101) is disposed at an upper end of and is rotationally driven by the rotor shaft (108). A plurality of non- teetering outer hubs (102a and 102b) are coupled to the center hub (101) through a mechanical joint that prevents teetering of the hub such that the outer hub (102) is not capable of an angular range of movement relative to the center hub (101). The plurality of grips (103a, 103b, 103c and 103d) capable of an angular range of movement relative to the outer hub (102) is coupled to the outer hubs (102). An elongated, tangentially extending set of blades (104a, 104b, 104c and 104d) relative to the rotor shaft (108) has an airfoil cross-section and an inboard end coupled to the outer hubs (102a and 102b) through the grips (103a, 103b, 103c and 103d), wherein the tangentially extending set of blades receives driving torque from the rotor shaft (108) to the set of blades (104) through the center hub (101) and outer hubs (102a and 102b). [0038] FIGURE 2 illustrates the perspective view of a rotor arrangement having offset hubs, in accordance to one or more embodiments of the invention. In the present invention the center hub (101) is attached to the mast (109) as shown in Figure 2. The plurality of outer hubs (102) are attached at either end of the center hub (101), either rigidly or pivoted such that the outer hubs (102a and 102b) have teetering movement (like see-saw). Each outer hub (102a and 102 b) has a yoke and two grips (103). The grips (103) hold the blades (104a, 104b, 104c and 104 d). A pitch horn (105) is attached to each grip (103). Each pitch horn (105) is hinged to the pitch change rods (106a and 106b). Each pitch change rod (106) is connected to the rotating swash plate (107), which has variable horn lengths. The rotating swash plate (107) is attached to the mast (109) with scissor link. The rotating swash plate (107) bears on the stationary swash plate. The movements received by stationary swash plate from pilot controls are transferred to the rotating swash plate (107).

[0039] FIGURE 3 illustrates a top view of a rotor arrangement having offset hubs, in accordance to one or more embodiments of the invention.

[0040] FIGURE 4 illustrates the side view of a rotor arrangement with offset hubs mounted on the aircraft, in accordance to one or more embodiments of the invention. The rotor arrangement in said off-set hubs is further attached to the tail rotor (111) of the air craft. The tail rotor's position and distance from the center of gravity allows to develop thrust in the same direction as the main rotor's rotation, to counter the torque effect created by the main rotor. The pitch of the tail rotor blades is adjustable by the pilot via the anti-torque pedals, which also provide directional control by allowing the pilot to rotate the helicopter around its vertical axis. The tail rotor (111) is mounted sideways and is controllable in collective pitch, but is not capable of cyclic feathering. In the preferred embodiment, the angle of the tail rotor is controlled by the pilot's anti-torque pedals. The pedals are typically connected to the pitch change mechanism by either push pull tubes, or by cables.

[0041] FIGURE 5 illustrates the top view of a rotor arrangement with offset hubs mounted on the aircraft, in accordance to one or more embodiments of the invention.

[0042] The present invention provides high speed, low drag, low maintenance, stiff in-plane and/or soft in-plane rotor head for a helicopter that enables four or more rotor blades to be used per rotor. The present invention also provides high wing loading and wide range of center of gravity efficiently. Hence, ensuring the best performance of rotorcrafts.

[0043] It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

[0044] CLAIMS:

[0045] I claim:

1) A rotor arrangement with offset hubs for the air crafts, the rotor arrangement comprising:

a) a rotor head comprising,

i. a vertically extending rotor shaft (108) from a mast (109) of the aircraft;

ii. a center hub (101) disposed on the rotor shaft (108) for conjoint rotation therewith;

iii. a plurality of outer hubs (102a and 102b) coupled at both ends of the center hub (101);

iv. a plurality of rotor blades (104a, 104b, 104c, 104d) coupled to the rotor shaft (108) through the center and outer hubs (102a and 102b) by a constant velocity joint, wherein the joint enables the blades to rotate in a common plane about the axis of the rotor shaft while controlling the respective pitches of the blades;

v. the outer hubs (102a and 102b) are coupled at the opposite ends of the center hub (101) through a mechanical attachment for conjoint rotation therewith, such that the plurality of outer hubs (102a and 102b) are capable of an angular range of teetering and/or lead-lag movement relative to the center hub (101);

vi. the outer hubs (102a and 102b) comprises a plurality of yokes and a plurality of grips (103a, 103b, 103c and 103 d), wherein the grip (103) securely holds the blades, and yoke holds the grips (103a, 103b, 103c and 103d);

vii. a plurality of pitch horns (105a, 105b, 105c and 105d) attached to the each grip (103) at one end, wherein the other end of the pitch horns (105) are hinged to a plurality of pitch change rods (106a and 106b), wherein the pitch change rod (106) is connected to a rotating swash plate (107), which has variable horn lengths;

the rotating swash plate (107) attached to the mast (109) with the scissor link, wherein the rotating swash plate (107) is fitted on a stationary swash plate, wherein the stationary swash plate transfers the received load to the rotating swash plate (107).

2) The rotor arrangement as claimed in claim 1, wherein said outer hubs create a stiff-in-plane, wherein the teetering outer hubs are coupled to the center through a mechanical joint such that the outer hub is capable of an angular range of teetering movement relative to the center hub. 3) The rotor arrangement as claimed in claim 1, wherein the outer hubs create a soft-in-plane, wherein the teetering outer hubs are coupled to the center hub through a mechanical joint such that the outer hub is capable of an angular range of teetering and lead-lag movement relative to the center hub,

wherein the plurality of non-teetering outer hubs are coupled to the center hub through a mechanical joint that prevents teetering of the hub such that the outer hub is not capable of an angular range of movement relative to the center hub.

The rotor arrangement as claimed in claim 1, wherein the outer hubs are attached to center hub that from a space there between, wherein the center hub is positioned within the space.

The rotor arrangement as claimed in claim 1, wherein the outer hubs are further fixed but the grips are allowed to transverse movement about the chord, pitch and vertical axes. 6) The rotor arrangement as claimed in claim 1, wherein said off-set hubs are further attached to the tail rotor of the air craft.