VARIABLE CAMBER LEADING EDGE ASSEMBLY FOR AN AIRFOIL

Abstract: A variable camber leading edge device having a movable nose section (22) and an upper flexible panel (28) extending rearwardly from the nose section. To move the nose section between its upper cruise position and a high lift downwardly deflected position, there is attached to the nose section a generally arcuate cam track (46), having its forward and rear portions curving upwardly. The cam track is constrained to move in a generally arcuate path, but with a movable center of rotation, and is driven by a gear (64) engaging a radially outward rear portion (50) of the track (46).

Description: The present invention relates to a leading edge assembly for an airfoil as defined in the introductory part of claim 1. Such an assembly is known from US-A-4 351 502. The link of the flexible panel supporting means is connected to a link of an actuating linkage. The flexible panel supporting means effectively preclude skin flutter in all operative positions of the airfoil's leading edge and also maintain the curvature of the flexible skin portion constant over its chord-wise length for any given leading edge deflection angle. The position of the locating link being derived from the movement of the linkage connected therewith, the obtained curvature of the flexible skin panel is not fully correct in all deflected positions of the nose section. Therefore, it is an object of the present invention to provide a leading edge assembly of the kind set forth above, which is capable of locating the flexible skin panel continuously to the desired aerodynamic contour for all positions of the nose section. This object is achieved with the leading edge assembly according to the invention having the characteristics as mentioned in the characterizing part of claim 1. By properly configuring the cam means, the point of the locating member connected to the locating link can be accurately programmed, so that also the curvature of the flexible panel can be accurately programmed. Further preferred embodiments of the invention appear from the subclaims. The invention will be further illustrated in the following detailed description of an exemplary embodiment thereof. Description of the Drawing Figure 1 is a cord-wise sectional view of an actuating assembly of the leading edge assembly of the present invention in its upper position for cruise mode; Figure 2 is a cord-wise sectional view of a positioning device of the leading assembly of the present invention; Figures 3 and 5 are views similar to Figure 1, but showing the leading edge assembly deflected downwardly at 20° and 38.5° angles, respectively; Figures 4 and 6 are views similar to Figure 2, showing the leading edge assembly deflected downwardly at angles of 20° and 38.5°, respectively; Figure 7 is a schematic view of the outer contours of the leading edge assembly, illustrating various angles of curvature for different positions of the leading edge assembly; Figure 8 is a schematic view of the actuating assembly of the present invention, and illustrating the positioning of the drive gear and the cam rollers; Figure 9 is a schematic view illustrating the paths followed by the cam rollers and the drive gear of the actuating assembly, where the cam track of the actuating assembly is presumed to be stationary, and the cam rollers and drive gear move relative to the cam track; and Figure 10 is a table giving coordinates for various point locations along the paths of movement illustrated in Figure 9. Description of the Preferred Embodiment The leading edge assembly 10 of the present invention forms the forward portion of a wing 12, only the forward portion of which is shown. The wing 12 has an upper surface 14, a lower surface 16, a leading edge 18 and a trailing edge (not shown for ease of illustration). The wing 12 has a main support structure comprising a front spar 20 to which the leading edge assembly 10 is mounted. At the leading edge 18, there is a nose section 22 in the form of a substantially rigid beam extending in a spanwise direction along the leading edge 18. The nose section 22 has an upper surface 24 and a lower surface 26. There is a flexible upper skin panel 28 which has: a) a forward part 30 which is attached to the upper rear surface of the nose section 22 and blends into the upper surface 24 of the nose section 22; b) a rear part 32 which butts against, and is aligned with, the main upper skin 34 at the location of the front spar 20, and c) a flexible intermediate portion 36 which reaches between the front part 30 and the rear part 32. The lower surface of the leading edge assembly 10 comprises a forward portion 38 connected to and extending rearwardly from the lower surface of the nose section 22, and a rear portion 40 which is a forward extension of the main lower skin section 41 at the lower part of the front spar 20. At the front edge of the rear portion 40, there is a seal 42 to close the small gap at the juncture of the lower skin portions 38 and 40. The support and actuating assembly of the present invention, generally designated 44, functions to move the nose section 22 from an upper cruise position shown in Figure 1, through an intermediate position of Figure 3, to a fully deflected high lift position, shown in figure 5. This is accomplished in a manner that as the assembly 10 moves from the position of Figure 1 to that of Figure 5, the curvature of the upper skin panel 28 progressively increases so as to assume a proper aerodynamic contour throughout the movement of the assembly 10 from its cruise configuration to its fully downwardly deflected position. During such downward movement, the forward lower skin portion 38 moves downwardly with the nose section 22 to separate from the rear portion 40, with the rear edge of the lower skin portion 38 moving rearwardly beneath the rear lower skin portion 40. To properly locate and support the flexible intermediate portion 36 of the upper skin panel 28, there is illustrated in Figures 2, 4 and 6 a beam assembly, which functions as a locating device, generally designated 45. In the following description, there will first be a detailed description of the support and actuating assembly 44, after which the locating device 45 will be described. The support and actuating assembly 44 comprises a generally arcuately shaped cam track 46, having a forward cam track portion 48 and a rear cam track portion 50. There is a forward cam track locating means comprising upper and lower cam rollers 52 and 54, engaging upper and lower cam track surfaces 56 and 58, respectively, of the forward track portion 48. There is a rear locating and drive means comprising an upper cam roller 60, and a lower combined cam roller and drive gear 62. The upper rear cam roller 60 engages an upper surface of the rear cam track position 50. The combined roller/drive member 62 comprises a gear portion 64 made up of gear teeth 66, and a roller portion having two circular surfaces 68. The cam track 46 is made in right and left sections, spaced a short distance from one another. Thus, the teeth 66 of the roller/drive member 62 are positioned between the two sides of the roller surface 68 of the member 62. There is provided a gear segment 70 positioned between and bolted to the two sections of the cam track 46. This gear segment 70 has teeth 72 which engage the teeth 66 of the roller/drive member 62. The forward end of the cam track 46 is formed to fit between a clevis 74, which is a part of the nose section 22, and these are rigidly interconnected at two connecting locations 76. The cam rollers 52, 54 and 60, and also the roller/drive member 62 are rotatably mounted to a stationary support rib 78 which is fixedly connected to and extends forwardly from the front spar 20. The cam track 46 has a generally arcuate configuration, and has a circumferential or lengthwise axis which, for purpose of illustration, has been drawn as a circular arc, indicated at 80 in Figure 8, and having a center of curvature at 82. However, for reasons which will be explained more fully hereinafter, the actual configuration of the track 46 deviates slightly from a true circular arc so as to program the movement of the nose section 22 more precisely so as to obtain the proper degree of curvature of the upper skin panel 28 throughout its movement from the cruise position 28 throughout its movement from the cruise position of Figure 1, through the intermediate position of Figure 3, to the full down position of Figure 5, while maintaining proper engagement of the gear teeth 66 with the teeth 72 of the gear segment 70. The cam rollers 52 and 54 are positioned substantially opposite one another relative to the circumferential axis 80, and the center axes of the rollers 52 and 54 are positioned along a lien 84 that slants upwardly and rearwardly toward the center of curvature 82. The center axis of the upper cam roller 60 and the center axis of the roller/drive member 62 are positioned on a line 86 that extends upwardly and forwardly toward the center of curvature 82. In the cruise position of Figure 1, the track 46 is at its forwardmost position, so that the forward rollers 52 and 54 engage the lower rear portion of the forward cam track section 48, and the rear upper roller 60 and the roller/drive member 62 engage the upper rear portion of the rear cam track section 50. Although not illustrated herein, it is to be understood that the rollers 52, 54 60 and 68 are arranged in a suitable support structure which has side load pads that engage lateral surfaces of the cam track 46 to keep the track 46 properly located relative to the roller 52, 54 and 60, as well as properly located relative to the roller/drive member 62. Also, the track 46 is provided with suitable stop means which limits forward and rearward travel of the track 46. For example, the clevis 74 acts as a stop member relative to the lower front roller 54 to limit rearward movement of the track 46. Further, it is to be understood that the support and actuating assembly 44 is shown at only one spanwise location of the wing 10. It is to be understood that there are similar assemblies 44 at other spanwise locations along the length of the wing 12. The roller/drive members 62 at these various spanwise locations can be interconnected by a drive shaft so as to be driven from a common power source. In operation, to move the assembly 10 from the upper cruise position of Figure 1, the roller/drive member 62 is rotated clockwise, as seen in Figure 1. This causes the cam track 46 to travel in a path generally following (but deviating somewhat from) the arc approximated by the arcuate axis 80 of the track 46, so that the instantaneous center of rotation of the track 46 and the nose section 22 remains reasonably close to the center of curvature 82 of the axis or arc 80, but moves relative to the center 82. When the support and drive assembly 44 reaches the intermediate position of Figure 3, the nose section 22 has moved downwardly and moderately rearwardly, and also rotated so that is is at more of a downward and forward slant. In the particular configuration of Figure 3, the amount of rotation from Figure 1 is 20°. Further, at this location the movement of the nose section 22 has been such that the forward part 30 and the rear part 32 of the skin panel 28 have moved moderately closer to one another so as to place the flexible intermediate portion 36 of the panel 28 in a rather moderate curve, as shown in Figure 3. This curvature is such that it forms a proper aerodynamic contour of the upper skin section extending from the nose section 22 to the location of the forward spar 20. Further clockwise rotation of the roller/drive member 62 causes the cam track 46 to move further rearwardly so as to deflect the nose section 22 yet further downwardly to the 38.5° deflected position of Figure 5. Reference is now made to Figure 7, which illustrates somewhat schematically the results of an analysis of the changing geometry of the flexible upper skin panel 28 during the downward deflection of the nose section 22. The points A and C are at, respectively, the rear and forward portions of the bendable panel section 28, while the point B is a variable intermediate point. Certain radii and angles of curvature are illustrated in Figure 7, and these were determined by an iterative solution to simultaneous equations involving the panel length and tangency at all three points, A, B, and C, these equations being the following: a) Constant arc length of ACo. b) Common radial (BGD) at intersection of R₁ and R₂. c) The vertical component of arc AB plus that for arc BC equals the vertical coordinate of point C. where: ACo. is equal to the arc distance from point A to point Co. (which arc distance remains constant throughout movement of the assembly). α ₁ is equal to the angle formed by the radii extending from points A and B (this angle being shown for three different positions of the leading edge assembly) AC is the arc distance from point A to point C. k is a constant which equals to α is equal to the angle formed by the radii drawn from point A and point C. R₂ equals the distance from G to B (which is the same as the distance from G to C). R₁ equals the distance from point A to point D (with point D being shown at three different locations, namely D-1, D-2 and D-3). CF is equal to the distance from point C to point F. AF is equal to the distance from point A to point F. Z c is equal to the vertical distance of the point C below the point A. Figure 7 is not intended to give the precise results of the analysis, but rather to indicate the nature of the angular relationships that were studied. This analysis indicates that throughout not only the three positions shown on Figure 7, but also throughout the other intermediate positions, the curvature of the upper panel 28 produces the desired aerodynamic contour. To explain more fully how this is accomplished, reference is now made to Figure 9, which is a schematic illustration of the geometry of the track 46, relative to the cam rollers 52, 54 and 60, and also relative to the cam roller 68 of the roller/drive member 62. The respective centers of rotation of these members 52, 54, 60 and 68 are designated by the letters "L", "M", "N" and "H". In the illustration of Figure 9, the assumption has been made that the track 46 and the nose section 22 remain stationary, while the rollers 52, 54 and 60 and also the roller/drive member 62 are the movable members. The paths of the various center points, L, M, N, and H are shown at the 0° deflected position (with a "0" suffix designating that location), and also at the fully deflected position (where a "38.5" sufix designates that fully deflected location). Also, the circular arc 80 has been illustrated in Figure 9 to provide a visual comparison with the deviations of the track 46 from a true circular curve. It can be seen that the forward cam track portion 48 has its upper and lower surfaces 56 and 58 deflected radially outwardly from the center of curvature 82 of the arc 80. The path of the four center points, H and L-N, are illustrated by a series of "x" points which show instantaneous locations of these four centers H and L-N for various angular deflections of the assembly 10. The instantaneous center of rotation of the centers of the rollers 52, 54, 60 and the cam surface 68 relative to the track 46 is designated "E", and at the 0° position, the location of E is designated E 0 . During the travel from approximately the 0° position to about the mid-deflection point (i.e. at about 18-20° deflection), the instantaneous center of rotation E 0 of these components 52, 54, 60 and 68 moves slightly downwardly and forwardly to the location indicated at E1. During the latter half portion of travel (i.e. from the 18-20° position to the full 38.5° deflected position), the instantaneous center of rotation of these components moves back to the initial position indicated at E 0 . These various locations are presented in the Table of Figure 10, which gives these various locations of the points E, H, L and M in terms of vertical and horizontal coordinates. A numerical increase along the Z axis indicates downward movement, while a numerical increase along the X axis indicates a forward movement. From the above discussion, it can be recognized that as the cam track 46 moves along its circumferential or arcuate axis 80, the track 46 will have what might be described as a moderate rocking movement (about point H o ). This rocking movement is such that the point of tangency 96 of the roller/drive member 62 rotates moderately clockwise about H o . It has been found that with the arrangement illustrated in Figure 9, the movement of the nose section 22 is such that the upper skin panel 28 is continuously flexed to the desired aerodynamic contour for all positions. Further, the geometry of this mechanism introduces no tensile or compression forces into the plane of the upper skin panel 28, but only the bending moments due to flexing. Further, this contouring of the panel 28 is accomplished with the nose section 22 following a path that allows the cam track 46 to always remains in proper driving engagement with the roller/drive member 62. The leading edge assembly of the present invention will now be described with reference to Figures 2, 4 and 6, which show the locating device 45 in three different positions, namely, the 0° position of Figure 2, the 20° deflected position of Figure 4, and the 38.5° deflected position of Figure 6. This device 45 comprises a support beam or locating are 100 pivotally connected at its forward end 102 to an upper rear portion of the nose section 22. The rear end of the arm 100 has a cam roller 104 that rides in a cam 106 of a cam support member 108. There is a panel support or locating link 110 which has a lower end pivotally connected at 112 to the arm 100 at a location slightly behind the midlength thereof. The upper end 114 of the link 110 is pivotally connected to a spanwise stiffener 116 which, in cross-sectional configuration, comprises two right angle members joined to each other. This stiffener connects to the inside surface of the panel 28. It can readily be appreciated that the precise location of the arm 100 is at all times controlled by the position of the nose section 22 and the programming of the cam 106. Thus, the locating link 110 will always be properly located to position its connecting point 114 to the stiffener 116 at the proper location to obtain the desired aerodynamic contour of the upper skin panel 28. While the present invention is particularly adapted to be used in, and to uniquely resolve the problems of, a variable camber leading edge assembly of an airfoil, within the broader aspects of the present invention, it could be utilized in other arrangements relative to an airfoil or similar device. Specifically, in the following claims, it is to be understood that while this assembly is recited as a leading edge assembly, the term "leading edge assembly" is to be interpreted broadly enough to refer to an assembly positioned at the trailing edge of an airfoil, in which case the terms "forward" and "rear" would be reversed within the meaning of the claims.

Claims: A leading edge assembly (10) for an airfoil (12) having an upper surface (14), a lower surface (16), a leading edge (18) and a trailing edge, said assembly comprising: a. a main support structure (20) for the airfoil (12); b. a nose section (22) at said leading edge (18); c. an upper skin panel having a rear part (32) connected to said structure, a forward part (30) connected to said nose section (22), and an intermediate flexible panel portion (36) extending between the rear part (32) and the forward part (30); d. support and actuating means (44) operatively connected between the nose section (22) and the support structure (20) to move the nose section (22) about a general center of rotation between a first upper position where the flexible panel portion (36) has a lesser degree of curvature and said nose section (22) is more horizontally aligned, to a second lower position where the flexible panel portion (36) has a greater degree of curvature and the nose section (22) is aligned in a more downward slant, in a manner that curvature of the flexible panel portion (36) increases with movement of the nose section toward its second position; e. flexible panel supporting means (45) comprising a locating link (110) operatively connected to said upper skin panel (28) at a location intermediate the forward and rear parts of the skin panel (28) and a locating member (100) connected to said locating link (110), said locating member (100) having first and second end portions, said first end portion being pivotally connected to one of the nose section (22) and the main support structure (20), characterized by said second end portion being operatively connected to cam means (106) connected to the other of the nose section (22) and the main support structure (20) and arranged to move the second end portion along a predetermined path as the nose section (22) moves between its first and second positions. Assembly according to claim 1, characterized in that the first end (102) of the locating member (100) is pivotally connected to the nose section (22), and the second end of the locating member is connected to a cam member (106) defining a cam path operatively engaging a matching cam member (104) connected to the second end of the locating member (100), said cam member being connected to the main support structure (20). Assembly according to claim 1 or 2, characterized in that the locating member (100) and locating link (110) are fully separate from the support and actuating means (44).

Inventors: COLE, JAMES BYRON
Applicants: THE BOEING COMPANY
Application year: 1985
Main classification: B64C3
IPC codes: B64C3