Abstract:
A seal ( 500 ) comprises a seal body ( 502 ) having a mounting portion ( 504 ), a first leg ( 506 ) and a second leg ( 508 ), a first stiffening member ( 514 ) and a second stiffening member ( 516 ) separated by an arcuate shear seal portion ( 529 ) in which the motions of the first leg ( 506 ) and second leg ( 508 ) are relatively constrained by the second stiffening member ( 516 ).

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is concerned with a flight surface seal. More particularly, the present invention is concerned with a seal positioned between two control surface components of an aircraft to seal a variable gap therebetween. 
       BACKGROUND OF THE INVENTION 
       [0002]    In aerospace design it is desirable to seal any gaps between components of flight surfaces to present a smooth surface to the passing airflow. This reduces losses and prevents undesirable fluid flow effects such as separation of the boundary layer and subsequent loss of lift, and prevents leakage over the pressure differential between the upper and lower surfaces of aerofoils. 
         [0003]    Components of aircraft flight surfaces such as wings, tail planes, fins, landing gear doors and control surfaces (e.g. flaps, slats, rudders, ailerons and spoliers) tend to move in use both intentionally in response to a control input (in the case of control surfaces) and unintentionally due to thermal expansion and contraction and stresses experienced in use. 
         [0004]    As such, the width of the gaps to be sealed between components varies depending on the relative position of the components. Known seal technology utilises resilient seals which are mounted to a first component to seal against a second adjacent component and resiliently deform to the seal gap as it varies. 
         [0005]    Such gap width variation is observed between variable camber flaps at the trailing edge of aircraft wings. The gap width between the wing and the flap not only changes due to control input, but also changes as the wing and flap thermally expand and contract with variations in operating temperature and during the flight cycle during which a range of stresses are experienced. 
         [0006]    A λ or V shaped seal has been proposed in which the flap is received within the legs of the λ or V. A problem with this type of seal is that the individual legs flex independently and as such can spread and deform with little inherent structural stiffness. Consequently phenomena such as seal flutter can be observed in which one of the legs of the seal is detached (i.e. separated or divorced) from the flap underside. 
         [0007]    It is an aim of the present invention to provide an improved flight surface seal. 
       SUMMARY OF THE INVENTION 
       [0008]    According to a first aspect of the present invention there is provided a flight surface seal for sealing a gap between a first and a second component of an aircraft flight surface, the seal having a seal body comprising a mounting portion for mounting to the first component, a first leg and a second leg projecting from the mounting portion and spaced apart to receive the second component therebetween, wherein the seal further comprises a first stiffening member configured to at least partially constrain the relative motion of the first and second legs. 
         [0009]    According to a second aspect of the invention there is provided a method of manufacture of an aircraft flight surface seal comprising the steps of:
       providing a mould,   providing at least one stiffening member within the mould,   inserting a sealing material into the mould to at least partially surround the stiffening member,   curing the sealing material,   removing the seal from the mould.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    An example seal will now be described with reference to the accompanying figures in which: 
           [0016]      FIG. 1  is a plan view of an aircraft, 
           [0017]      FIG. 2  is a side section view along II-II in  FIG. 1  of a range of motion of a flap, 
           [0018]      FIG. 3  is a side section view of a first known flap seal, 
           [0019]      FIG. 4   a  is a side section view of a second known flap seal, 
           [0020]      FIG. 4   b  is side section view of the flap seal of  FIG. 4   a  in a deformed and an undeformed state, 
           [0021]      FIG. 4   c  is a side section view of the flap seal of  FIG. 4   a,    
           [0022]      FIG. 5   a  is a side section view of a flap seal in accordance with the present invention, 
           [0023]      FIG. 5   b  is a side section view of a part of the flap seal of  FIG. 5   a,    
           [0024]      FIG. 5   c  is a side section view of the flap seal of  FIG. 5   a  in an undeformed state, 
           [0025]      FIG. 5   d  is a side section view of the flap seal of  FIG. 5   a  in a deformed state, 
           [0026]      FIG. 5   e  is a perspective view of the flap seal of  FIG. 5   a,    
           [0027]      FIG. 5   f  is a side section view of the flap seal of  FIG. 5   a  along F-F in  FIG. 5   e , and, 
           [0028]      FIG. 5   g  is a side section view of a part of the flap seal of  FIG. 5   a  in the region G of  FIG. 5   f.    
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0029]    Referring to  FIG. 1 , an aircraft  100  comprises a fuselage  102  and wings  104 ,  106 . The wing  104  comprises a flap  108  positioned at a wing trailing edge lower panel trailing edge  110 . The flap  108  can be moved to alter the aerodynamic characteristics of the wing  104 . 
         [0030]    Referring to  FIG. 2 , a leading edge  112  of the flap  108  is shown in a variety of operational positions relative to the wing trailing edge  110 . The flap  108  describes an arcuate motion in use, and as can be seen the distance between the leading edge  112  of the flap  108  and the trailing edge  110  varies considerably (L 1 , L 2 , L 3 ). It should also be noted that the vertical position of the flap  108  also varies with respect to the trailing edge  110  however this is small compared to the horizontal motion depicted by L 1 , L 2 , L 3 . A variable gap  114  therefore exists between the leading edge  112  of the flap  108  and the trailing edge  110  of the wing  104 . 
         [0031]    It is desirable to seal the gap  114  for aerodynamic reasons. Referring to  FIG. 3 , a substantially flat seal  200  as known in the art is attached to the trailing edge  110  via a fastener  202 . The flat seal is constructed from an elastomeric sealing material and contacts the flap  108  at a lower surface  109  of the flap  108 . The seal  200  is deformed slightly by virtue of its contact with the flap  108  and as such resiliently presses against the surface  109 . 
         [0032]    Although this contact seals the gap  114  when static, forces on the flap experienced by an airstream  10  can peel the seal  200  from the surface  109  and make it “flutter”. This is undesirable as air can then pass through the gap  114 . It should also be noted that the seal  200  is less effective as the flap  108  moves away from the edge  110  as the amount of force with which it abuts the surface  109  decreases (its inherent structural stiffness is less). 
         [0033]    Referring to  FIG. 4   a  a known seal  300  is shown comprising attachment means  302 , a first leg  304  projecting parallel to the edge  110  and a second leg  306  projecting in the same direction but at an angle A of approximately 45 degrees to the first leg. The first leg  304  abuts the surface  109  of the flap  108  and the second leg  306  abuts the leading edge  112  of the flap  108 . 
         [0034]    Referring to  FIG. 4   b , three flap positions X, Y, Z are shown. As can be observed, in positions X and Y the second leg  306  is abutting the leading edge  112  of the flap  108  to provide an auxiliary seal against ingress of the airstream  10 . As will be noted in position Z, no auxiliary seal is provided. 
         [0035]    Referring to  FIG. 4   c , the legs  304 ,  306  act completely independently, and even when the second leg  306  is contacting the leading edge  112  of the flap  108 , detachment and flutter of the first leg  304  is observed. Although the auxiliary sealing effect of the second leg  306  helps to reduce air ingress, the flutter action and disruption of the airstream  10  causes drag and other undesirable aerodynamic effects. 
         [0036]      FIG. 5   a  shows a seal  500  according to the present invention. The seal  500  comprises an elastomeric body  502  constructed from elastomeric material (e.g. polyurethane or silicone). The body is similar in shape to the seal  300  comprising an attachment portion  504 , a first leg  506  and a second leg  508 , and a central portion  510  therebetween. The attachment portion  504  and the first leg  506  are substantially planar, parallel and joined by the central portion  510 . The second leg  508  projects at an angle A from the central portion  510  generally in the same direction as the first leg  506 . The seal  500  therefore forms a lambda “λ” shape. 
         [0037]    At the end of the second leg  508  furthest from the central portion  510  there are positioned three anti-stiction ribs  512  facing the first leg  506 . The ribs  512  are designed to present a small contact area to the leading edge of the flap to avoid the second leg  508  catching on the flap by virtue of static friction (stiction). 
         [0038]    The seal  500  further comprises a first insert  514  and a second insert  516 . The inserts  514 ,  516  taper along the trailing edge of the wing as the seal tapers to match the wing geometry and kinematics. The inserts  514 ,  516  are constructed from a resilient material such as a carbon fibre reinforced polymer (CFRP). 
         [0039]    The first insert  514  comprises an attachment portion  518 , curved section  520  and a first shear portion  522 . Referring to  FIG. 5   b  the curved portion is wavelike and comprises a first arcuate section with radius R 1  and a second arcuate section with radius R 2  leading into the first shear portion  522  with radius R 3 . 
         [0040]    The second insert  516  comprises a first planar portion  524  and a second planar portion  526  within the first and second legs  506 ,  508  respectively. The planar portions  524 ,  526  are joined by an arcuate second shear portion  528  with radius R 4 . R 3  and R 4  share the same origin O. As such the shortest distance between the shear portions  522 ,  528  is constant to define a generally arcuate shear seal portion  529 . 
         [0041]    Referring to  FIG. 5   c , the seal  500  is mounted to the trailing edge  110  with a fixing means  530  as will be described below. In the position of the seal  500  as shown in  FIG. 5   c , the first leg  506  abuts the surface  109  of the flap  108  and the second leg abuts the leading edge  112  of the flap  108 . 
         [0042]    The second insert  516  links the first and second legs  506 ,  508  such that their motion is relatively constrained. As such, as the flap  108  pushes the second leg  508 , the legs  506 ,  508  are urged anti-clockwise when viewing  FIG. 5   c  and the first leg is pushed into firm engagement with the surface  109 . This is shown in  FIG. 5   d  when the flap  108  moves to the hidden line position, the first leg  506  is driven in direction R. 
         [0043]    The stiffness of the seal  500  can be varied by altering the distance between the shear portions  522 ,  528 . A shorter distance and/or a stiffer material will provide a stiffer hinge movement between the legs  506 ,  508  and the trailing edge  110  as the flap  108  bears against the seal  500 . 
         [0044]      FIG. 5   e  shows the seal  500  with the fixing means  530 .  FIGS. 5   f  and  5   g  show the fixing means  530  in detail. The fixing means  530  comprises a washer  532  and a ferrule  534  which are embedded in the seal attachment region  504 . The ferrule  534  passes through the attachment portion  518  of the first insert  514 . 
         [0045]    The ferrule  534  and washer  532  comprise an open bore  536  through which a bolt may be inserted to attach the seal  500  to the trailing edge  110  of the wing  104 . It should be noted that the combined thickness of the ferrule  534  and washer  532  is approximately 87 percent of the thickness of the seal  504 . Therefore when the ferrule  534  and washer  532  are fastened to the edge  110  with a bolt, the ferrule and washer are urged together to compress and clamp the seal attachment region  504  in place. 
         [0046]    The seal  500  is manufactured by providing a seal mould in the shape of the seal outer, positioning the first insert  514  and the second insert  516  within the mould, injecting a liquid sealing material into the mould to surround the insert and curing the sealing material. Finally the seal  500  is removed from the mould once the sealing material us cured. 
         [0047]    The following variations of the above embodiment fall within the scope of the present invention. 
         [0048]    The seal may be made from any appropriate flexible sealing material. The inserts may be made from any appropriate stiffening material, as long as it is stiffer than the sealing material. 
         [0049]    The inserts may contain bores to encourage bonding to the seal material during manufacture of the seal. 
         [0050]    Externally applied (e.g. bonded) stiffening members may be used instead of inserts. 
         [0051]    As such the shortest distance between the shear portions  522 ,  528  can be variable to create the desired seal behaviour.