Abstract:
One side of an access panel is trimmed while an opposite side of the panel is secured in an opening between skin sheets on the underside of an aircraft wing. The trimming apparatus includes a frame secured to one of the skin sheets with a rail extending along an edge of the opening and a trim saw assembly slideable along the rail. The frame can be secured in position by several vacuum cups, and can include index flanges engageable against an edge of the opening for precise positioning of the rail and the trim saw assembly carried thereby.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a system for trimming a panel to fit closely in an opening. 
     BACKGROUND OF THE INVENTION 
     Some modern commercial aircraft have access panels in the underside of a wing. Such panels may be cut to fit and then installed in an opening after the wing skin sheets have been installed. One application of the present invention is in trimming such access panels for a close fit in the opening. A previously known method for trimming such a panel is to measure the opening and trim the panel accordingly. Another known method is to place one edge of the panel against the adjacent skin sheet, affix the panel in the opening along that edge, mark the other edge in the area to be trimmed, scribe the desired line of the cut, detach the panel, trim the panel along the scribe marking, and remount the panel in the opening. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system for trimming a panel to fit closely in an opening. In the preferred embodiment, one side of the panel is trimmed while an opposite side is secured. The system includes a frame with a rail along which a carriage for a trim saw is moveable. The frame and rail can be secured adjacent to the opening by vacuum cups carried by the frame. Index flanges engage in the opening to position the rail adjacent to the panel edge to be trimmed. The position of the trim saw is adjustable relative to the rail to assure that the panel is trimmed precisely to fit within the opening when the frame is detached. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a somewhat diagrammatic bottom perspective of an airplane wing and a panel trimming system in accordance with the present invention. 
     FIG. 2 is a slightly enlarged bottom perspective of panel trimming components of the system of FIG.  1 . 
     FIG. 3 is a somewhat diagrammatic end elevation of components of the panel trimming system of FIG. 1 with parts broken away and parts shown in section. 
     FIG. 4 is a fragmentary top plan of components of a panel trimming system in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates the environment for one application of a panel trimming system  10  in accordance with the present invention which trims a panel to fit in an opening of a structure. An aircraft wing  12  has a leading edge  14  including one or more skin sheets  16  that terminate at a straight, spanwise extending trailing edge  22  underneath the wing. Moving aftward, the central and aft portions of the wing have one or more skin sheets  18  with leading edges  20  spaced aft of the trailing edge  22  of the skin sheet  16 . Access panels  24  are mounted in the opening  26  formed between edges  20  and  22 . With a panel removed, the opening  26  provides access to the interior of the wing during aircraft manufacture. Preferably the panels are detachable thereafter, such as for maintenance of components inside the wing. 
     For aerodynamic efficiency, it is desirable that the access panels  24  fit closely in the opening  26 . Typically one edge of the access panel, usually the leading edge, can be butted against the edge of the adjacent skin sheet. Manufacturing tolerances are sufficiently great that the panel cannot be pretrimmed for a desired close fit. Rather, after the skin sheets  16  and  18  have been installed, panels  24  are trimmed to fit within the opening  26 . Still, if too large a gap exists between adjacent edges of the trim panel and skin sheets, filler must be installed. 
     In general, the trimming system  10  in accordance with the present invention uses a frame  30  secured underneath the wing adjacent to an edge of the opening  26 . Frame  30  carries a rail  32  for a carriage  34  on which a trim saw assembly  36  is mounted. The rail is positioned such that the trim saw cuts a margin of a panel  24  which has had the opposite margin secured within the opening. Such trimming occurs as the carriage is moved along the rail. After the trimming operation is completed, the frame can be detached and repositioned for trimming the next panel. Ultimately, the trimmed edge is secured by fasteners and the exposed underside of the panel forms a smooth continuation of the wing skin. 
     More specifically, with reference to FIG. 2, FIG.  3  and FIG. 4, the frame  30  includes a rear longitudinal structural bar  40  and cross-pieces  42  secured to and extending transversely from the bar. The last structural component of the frame is the front rail  32  secured to the end portions of the cross-members  42  opposite their connection to the rear bar  40 . 
     For attaching the frame to the underside of the wing, preferably resilient vacuum cups  44  are mounted on the cross-pieces  42 . The cups extend from the cross-pieces oppositely from the rail  32 , i.e., the cups are at the top of the frame and the rail hangs from the bottom in the operational configuration. Vacuum generators  46  are mounted on the center cross-piece  42  and are operably connected to the vacuum cups  44  by hoses  47 . The vacuum generators are driven by air under pressure (shop air) supplied through hoses  48 . 
     With reference to FIG. 2, a spacer block  50  is secured to each cross-piece  42 , at the opposite side of the rail  32 . The spacer blocks carry index plates  52  which project generally transversely of the length of rail  32 , generally away from the vacuum cups. The index plates have upward projecting index tabs or flanges  54  and downward extending panel skid flanges  56 . Preferably the panel skids  56  are connected by a long, rail-like skid bar  58 , shown in broken lines in FIG.  2 . 
     The mounting of the trim saw assembly  36  to the carriage  34  is best seen in FIG. 3. A pneumatic motor  60  has a cylindrical head portion  62  clamped between front and rear mounting blocks  64  and  66  by bolts  68 . Mounting block  66  has a transverse tongue  70  offset from the bolts and received in a central channel of an adjustment block  72 . Block  72  is, in turn, secured to the carriage  34 . The output shaft  74  of the motor carries the trim saw blade  76 . A dust collector assembly  78  substantially encloses the sawblade  76  but is open at the top  80  through which the blade  76  projects. A vacuum hose  82  communicates with the interior of the dust collector assembly  78  for removal of particles resulting from the trimming operation. A blade guard  83  is mounted on the top of the front mounting block  64  and includes a tongue  85  spaced above the blade  76 . 
     Vertical adjustment of the trim- saw can be achieved by loosening the bolts  68 , shifting the motor and saw assembly up or down, and retightening the bolts. Transverse adjustment of the position of the trim saw, i.e., in a direction axially of the output shaft  74 , is by sliding the tongue  70  in the corresponding passage of the adjustment block  72 . This can be achieved by loosening a clamp bolt  84 , the shank of which passes through an elongated slot  86  best seen in FIG.  2 . For reliable fine adjustment in the horizontal direction, an adjustment bolt  88  is threaded into a bore in the end of the tongue  70  remote from the motor  60 . The adjustment bolt  88  can be rotated by an enlarged head or knob  90 . Thus, with the clamp bolt  84  released, knob  90  can be turned to slide the tongue  70  in the corresponding passage of the mounting block  72  and shift the entire motor and blade assembly. 
     With reference to FIG. 1, operation of the panel trimming system in accordance with the present invention is as follows: a panel  24  to be trimmed is mounted in the opening  26  with one edge tightly abutted against the adjacent edge of the skin sheet. Typically this will be the leading edge of the access panel against the trailing edge  22  of the skin sheet  16 , such edge of the access panel being secured in the desired abutting relationship by multiple removeable fasteners. With reference to FIG. 3, the frame  30  is positioned adjacent to the opposite edge with the index flanges  54  engaged tightly against the edge of the other skin sheet. Typically this will be the leading edge  20  of skin sheet  18 . While the frame is held in position, the vacuum generators are activated so that the vacuum cups  44  hold the frame reliably in position. The edge of the access panel  24  to be trimmed, typically the trailing edge, rides along the skids  56 ,  58  which are closely adjacent to the trim saw blade  76  (the resiliency of panel  24  biases the trailing edge upward). The position of the blade  76  is fixed relative to the frame  30  including the index flanges  54  which are engaged against the edge  20  to which it is desired to mate the trimmed edge of the panel. A very close fit of the trimmed panel edge against the adjacent edge  20  of the skin sheet  18  can be achieved, without marking the panel or detaching it from the wing. When an entire panel has been trimmed, the frame can be moved to the next panel or removed entirely from the underside of the wing, and the trailing edge of the access panel  24  secured in position by removeable fasteners. 
     While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.