Patent Publication Number: US-2007102587-A1

Title: Wing leading edge slat system

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates generally to an airplane wing, and more particularly, to an airplane wing leading edge slat system wherein the pinion gear assembly is located concentrically with the lower aft roller to reduce the number of components in the wing and increase space in the wing for other systems.  
      2. Background Information  
      Slats are small aerodynamic surfaces on the leading edge of an airplane wing. Leading edge slats are used for altering the aerodynamic shape of a wing airfoil section. In a normal cruise configuration, the leading edge slats are placed in a retracted position to provide the fixed wing an optimized aerodynamic configuration. During take-off and climbing, the leading edge slats are moved forward to an intermediate location to extend the effective cord length of the wing. This will improved lift performance of the wing while keeping drag within reasonable limits. In a high lift configuration, the leading edge slats are generally moved further forward from the takeoff and climb position so that the slat has a greater downward slant to increase the camber of the slat/wing combination. In this configuration, the leading edge slats form with the fixed wing an aerodynamic slot which results in airflow from beneath the slats upwardly through the slot and over the upper forward surface portion of the fixed wing. This configuration is commonly used when the aircraft is landing.  
      Due to the limited stowage volume in the wing cross-section, designing actuation systems for moving and positioning the leading edge slats in the wing has been difficult. These systems tend to take up a large amount of area in the wing cross-section. Newer airplanes are developing more aerodynamically aggressive wing plans in order to achieve greater performance. Thus, newer wing designs are getting smaller while loading of the flight control surfaces remain the same. The combination of a shorter chord for the fixed leading edge structure as well as a reduced front spar height, and relatively high flight control surface loads make the integration of actuation systems for moving and positioning the leading edge slats in the wing extremely difficult.  
      Therefore, it would be desirable to provide an actuation system for moving and positioning the leading edge slats in the wing that overcomes the above problems. The actuation system would have a reduced number of components thereby increasing the space in the wing for other systems.  
     SUMMARY OF THE INVENTION  
      A mechanism for extending and supporting a high-lift device relative to an airfoil has a pair of support ribs coupled to the airfoil. A carrier track is pivotally coupled to the high-lift device and positioned between the pair of support ribs. The carrier track has a slot opening along a lower length thereof. A gear rack is coupled within the slot opening. A pinion gear is positioned between the support ribs and below the carrier track. The pinion gear engages with the gear rack for extending the high-lift device relative to the airfoil. A plurality of rollers is rotateably coupled to the support ribs and in bearing contact with the carrier track. At least one roller is positioned above the carrier track and a second roller is positioned below the carrier track. The second roller is positioned concentrically with the pinion gear.  
      The features, functions, and advantages can be achieved independently in various embodiments of the present inventions or may be combined in yet other embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
       FIG. 1  is a plan view of an airplane wing having a series of slat panels at an extended position normal to the leading edge thereof;  
       FIG. 2  is a cross-sectional view taken in the direction indicated by the line  2 - 2  of  FIG. 1  which is normal to the leading edge of the wing and shows a slat panel in the extended position;  
       FIG. 3  is a view similar to  FIG. 2  wherein the slat panel is in a retracted or stowed position completing the leading edge profile of the wing airfoil section envelope;  
       FIG. 4  is a cross-sectional view taken along line  4 - 4  of  FIG. 2  in the direction indicated; and  
       FIG. 5  is a cross-sectional view taken along line  5 - 5  of  FIG. 3  in the direction indicated. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring to  FIG. 1 , a plan view of an outboard, leading edge section of an airplane wing  10  is shown. The wing  10  has a front wing spar  12  and a spanwise series of slat panels  14  along the leading edge of the wing  10 . A power drive system is mounted spanwise along the front wing spar  12  for extending or retracting the slat panels  14  relative to a fixed wing leading edge. In accordance with one embodiment, the power drive system, which will be described in more detail below, comprises: a power drive unit (not shown) such as a hydraulic or electric drive motor for rotating a spanwise series of axially aligned shafts or torque tubes  16  (hereinafter shafts  16 ), at a relatively high speed. The shafts  16  operate the extension or retraction mechanism of the slat panels  14  through a speed reducer and torque converter unit hereinafter referred to a rotary actuator  18 . Each of the rotary actuators  18  is mounted to a slat support track having a gear rack segment and pinion drive gear (not shown) coupled to the output drive shaft  16  of the rotary actuator  18 . The output drive shafts  16  operate through the rotary actuators  18  and function to controllably tie and synchronize one slat panel to its adjacent slat panel, without any additional slat drive synchronization mechanism being required.  
      Referring now to  FIG. 2 , a chordwise cross-sectional view taken in the direction indicated by the line  2 - 2  of  FIG. 1  shows a wing leading edge slat  14  at a fully extended position. This slat position is generally used for the landing mode of airplane operation. An aerodynamic slot  22  is formed between the leading edge of the fixed wing structure and the trailing edge of the extended slat panel  14 .  
      The fixed leading edge section of the wing has an upper surface skin panel  10 A and a lower surface skin panel  10 B. The upper and lower skin panels  10 A and  10 B are attached to a rigid leading edge nose structure  10 C having a spanwise nose beam  24 . The entire structure is supported by chordwise wing ribs  26  which are fixedly attached to a spanwise structural member such as the front wing spar  12 .  
      Each individual slat panel  14  is supported in the extended operating position by a curved slat support track  28  (hereinafter curved track  28 ). The curved tracks  28  are the main carrier tracks for the slat panels  14 . The curved track  28  is mounted on rollers  30  and positioned between a pair of the wing ribs  26 . The rotational axis  32  of each roller  30  is fixed to the pair of wing ribs  26 . Bearings  44  are placed on each side of the rollers  30  on the rotation axis  32  to support and reduce the friction of motion.  
      The forward end of the curved track  28  is pivotally coupled at  34  to the slat panel  14 . In general, there are two spanwise spaced main curved tracks  28  used to support each individual slat panel  14 . The curved tracks  28  can be located at the ends of the slat panel  14  or spaced spanwise apart at an optimum structural distance of approximately one-fourth of the length of a slat panel  14 .  
      Each curved track  28  has an internally mounted gear rack segment  36 . The gear rack segment  36  is positioned within an inverted U-shaped channel or slot of the curved track  28 . The gear rack segment  36  is located on the cross-sectional, vertical centerline of the curved track  28  in order to produce a symmetrical drive force for extension and retraction of the slat panel  14 . An asymmetrical drive force, such as that produced by a gear rack mounted to only one side of a track member, would produce unacceptable side loads, friction and driving forces. Further, if a pair of gear racks were straddle mounted, one on each side of a track member, such that a drive force was produced on both sides of the central track member, then synchronized or balanced gear tooth loading would present a problem in addition to an increase in weight and cost.  
      Fasteners  38 , such as bolts and nuts, are used to secure the gear rack segment  36  within a channel of the curved track  28 . In general, the fasteners  38  should be located at or near the low stressed neutral bending axis of the curved track  28  as shown in  FIG. 2 . If the fasteners  38  are located at different locations, such as passing through the highly stressed flanges of the curved track  28 , the bending strength characteristics of the curved track may be seriously compromised.  
      The gear rack segment  36  engages a pinion drive gear  40 . The rotation of the pinion drive gear  40  meshes with gear rack segment  36 , thereby extending or retracting the slat panel  14 . The rollers  30  support the curved track  28  as the slat panel  14  is extended or retracted. The rollers  30  are supported by bolts which form the rotational axis  32  for each roller  30 . The bolts pass through the pair of the wing ribs  26 , one on each side thereof, to provide for maximum load carrying ability. This straddle-mounted dual support contrasts with a cantilevered roller configuration which provides much less load carrying capability.  
      Referring to  FIG. 3 , the slat panel  14  is in the fully retracted position. The leading edge slat panels  14  are placed in a retracted position to provide the fixed wing an optimized aerodynamic configuration. Due to limited cross-sectional thickness of the airfoil at the location of the spanwise outboard slat panel  14 , there is a limited stowage volume for the slat actuating mechanism. However, the present invention, relates to the pinion gear assembly being located concentrically with the lower aft roller to reduce the number of components in the wing and increase space in the wing for other systems.  
      Referring now to  FIGS. 2-5 , the shafts  16  operate the extension or retraction mechanism of the slat panels  14  through the rotary actuator  18 . Each of the rotary actuators  18  is generally mounted to one of the pair of the wing ribs  26 . The drive gear  40  is coupled to the shaft  16 . An output sleeve may be placed on the shaft  16  to couple the drive gear  40  to the shaft  16 . The drive gear  40  meshes with gear rack segment  36  to extend or retract the slat panel  14 .  
      As seen more clearly in  FIG. 5 , in order to reduce the number of components in the wing and increase space in the wing for other systems the drive gear  40  is positioned concentrically between one or more rollers  30  and bearings  44 . The rollers  30  that are positioned concentrically with the drive gear  40  are generally the rollers  30  in the lower aft position. The rollers  30  positioned concentrically with the drive gear  40  may be mounted on bearings, pressed, or otherwise fixed on the shaft  16 . If the rollers  30  positioned concentrically with the drive gear  40  are pressed on the shaft  16 , the outside diameter of the rollers  30  on the shaft  16  should match as closely as possible the pitch diameter of the drive gear  40  in order to minimize scrubbing due to relative slip between the roller  30  and the curved track  28 . By positioning the drive gear  40  concentrically between the rollers  30 , the number of components in the wing  10  is reduced thereby freeing up significantly more space in the wing for other systems.  
      This disclosure provides exemplary embodiments of the present invention. The scope of the present invention is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification, such as variations in structure, dimension, type of material and manufacturing process may be implemented by one of skill in the art in view of this disclosure.