SELF-ALIGNING FASTENER SYSTEM

Abstract: A fastener assembly for use in securing an access panel (16) (metallic or non-metallic) to a mating structure (12, 14) and wherein the assembly can pull a panel (16) into position in/on a mating structure (12, 14) in order to effect the alignment of the remaining fastener apertures (19) in the panel (16) during panel installation and to lift the panel (16) from engagement with the mating structure (12, 14) during panel (16) removal by accommodating the misalignment of the apertures (19) in the panel (16) and mating structure (12, 14) up to a predetermined minimum. The fastener assembly comprises a two-piece grommet assembly that when assembled provides an adjustable spherical seat for a spherical head bolt (30). When the head (31) of the bolt (30) is positioned into the grommet (20) and the spherical seat is adjusted, the adjustment is fixed by a stacking operation.

Description: SELF-ALIGNING FASTENER SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a fastener assembly having the head portion of a bolt installed within a grommet assembly that is then installed in a panel, the threaded portion of the bolt having the capability of swiveling enabling the shaft to be inserted into a misaligned aperture in a mating structure or enabling the panel to swivel around the bolt head portion as the panel is installed and pulled into shape or lifted out of engagement with the mating structure. 2. Description of the Prior Art Aircraft access panels are typically positioned into or lifted out of engagement with the aircraft mating structure, fastener assemblies commonly being utilized to pull the panel into position and to secure the panel to the mating structure and, by hand, lifting the panel out of engagement with the mating structure. If the panel contour is curved and/or required to produce a hinge-line motion/geometry, problems arise since misalignment of the panel to the mating structure may occur. This causes damage to the panel, mating structure and fastener assemblies, the damage worsening over time through repeated installation and removal cycles of the panel. This damage is particularly acute with panels and structures made from composites (non-metallic) materials. In addition, some applications, for aero-dynamic or other reasons, require the fastener assembly securing the panel to the mating structure to remain flush to the outer surface of the panel when in the installed position. The fastener assembly also must, when required, be capable of accommodating misalignment of the holes (panel and mating structure) up to a predetermined minimum angle while remaining capable of carrying full static and dynamic design loads of the panel/mating structure interface. Conventional prior art fastener assemblies were used to secure a panel having a substantially planar contacting surface to a mating surface having a matching contour and thus would not be useful with panels have a simple curved (along one axis of the panel) or compound curved (along two or more axis' of the panel) contour. Conventional prior art fastener assemblies also do not provide a means for lifting a panel out of engagement with a mating structure while accommodating the hinge-line motion/geometry of the panel during removal. What is thus desired is to provide a fastener assembly for securing composite panels having curved contours to a mating structure, the fastener assembly being capable of accommodating hinge-line motion geometry and misalignment of the panel and mating structure up to a predetermined minimum angle as the panel is pulled into the installed contour or position in/on the mating structure. The fastener assembly must also be capable of lifting the panel from engagement with the mating structure while accommodating the hinge-line motion/geometry and misalignment of the panel and mating structure up to a predetermined minimum angle as the panel is being removed. The fastener assembly must also, when required, be capable of carrying the full static and dynamic loads of the panel/mating structure interface and be flush to the outer surface of the panel when in the installed position. SUMMARY OF THE PRESENT INVENTION The present invention provides a fastener assembly for use in securing composite panels having curved contours to a mating structure, the fastener assembly of the present invention also lifts the panel from engagement with the mating structure while accommodating the hinge-line motion/geometry and misalignment of the panel and mating structure up to a predetermined minimum angle as the panel is being removed. The fastener assembly can, when required, be capable of carrying the full static and dynamic loads of the panel/mating structure interface and be flush to the outer surface of the panel when in the installed position. The fastener assembly comprises a two piece grommet assembly that when assembled provides an adjustable spherical seat for a spherical head bolt. When the head of the bolt is positioned into the grommet and the spherical seat adjusted, the adjustment is fixed by mechanical means. The remainder of the mating components, the threaded collar and retaining ring, are then loosely installed on the grommet and the complete assembly is packaged for shipment to the end user. Upon delivery to the end user, the retaining ring and threaded collar are removed from the grommet assembly and the grommet assembly is inserted into prepared aperture in a mating panel. The threaded collar is then reinstalled onto the grommet assembly using a commercially available thread locking compound, thereby captivating the grommet assembly to the mating panel. The threaded collar is provided with a lug portion having an aperture for a rivet. A rivet is then inserted through a prepared aperture in the mating panel and rivet aperture of the threaded collar and fixed by mechanical means to prevent rotation/loosening of the threaded collar. The retaining ring, which provides back-up retention for the grommet assembly should it loosen, is then reinstalled on the grommet assembly to complete the installation process. The spherical head bolt can swivel in all directions and the grom et/ball seat assembly protects the lower surface of the panel from damage while the bolt head is maintained flush with the upper surface of the panel. The flat surface of the threaded collar provides the bearing surface for the panel against the mating structure thereby protecting the bearing surface of the panel from damage. The present invention thus provides a fastener assembly especially adapted for use in securing composite panels having curved contours to a mating structure, the fastener assembly being capable of accommodating hinge-line motion/geometry and misalignment of the panel and mating structure up to a predetermined minimum angle as the panel is pulled into the installed contour or position in/on the mating structure. The fastener assembly also lifts the panel from engagement with the mating structure while accommodating the hinge-line motion/geometry and misalignment of the panel and mating structure up to a predetermined minimum angle as the panel is being removed. The fastener assembly can, when required, be capable of carrying the full static and dynamic loads of the panel/mating structure interface and be flush to the outer surface of the panel when in the installed position. DESCRIPTION OF THE DRAWINGS For a better understanding of the invention as well as other objects and further features thereof, reference is made to the following description which is to be read in conjunction with the accompanying drawing wherein: Figure 1 is a simplified partial perspective view illustrating an aircraft structure in which the fastener assembly of the present invention is preferably utilized; Figure 2 is a plan view of the structure shown in Figure 1; Figure 3 is an exploded view of the fastener assembly of the present invention; Figure 4 is a perspective view of the fastener assembly of the present invention; Figure 5 is a cross-sectional view along line 4-4 of Figure 4; and Figure 6(a) is a top view and Figure 6(b) is a bottom view of the assembly shown in Figure 4. DESCRIPTION OF THE INVENTION' Referring to Figure 1, a perspective view of a portion of an aircraft frame 10 is illustrated. Frame 10 includes representations of a main structure 12 and a wing structure 14. In certain situations, it is required that access panels be secured to the curved surface portions of the aircraft frame 10. Specifically, and as shown in Figure 1, it is necessary to secure access panels 16 (it should be noted that hinged panels can be utilized) between aircraft main structure 12 and wings 14 whereby the panels, when so secured, form a continuous curved surface. In order to accomplish this, it is necessary that the fastener assembly (schematically represented by reference numerals 18) have the capability of swiveling during the installation process as the panel 16 is pulled into the installation contour or position in/on the mating structures 12 and 14, corresponding apertures 19 for any remaining panel fasteners on the panel being brought into alignment with corresponding apertures in the mating structure for installation of the remaining fasteners. Figure 2 is a plane view of the aircraft frame 10 shown in Figure 1. Figure 3 is an exploded view of the fastener assembly 18 of the present invention. Assembly 18 comprises the following five components: internally threaded grommet 20, collar member 25, retaining ring 28, spherical head stud bolt 30 and an externally threaded plug member 34. When assembled, the fastener assembly is positioned within a prepared aperture in panel member 16, panel member 16 in turn being secured to the lug portion 26 of collar member 25 by rivet member 27. The component assembly procedure is as follows: A small amount of anti-seize compound is placed on the spherical head portion 31 of stud bolt 30. The stud bolt 30 also comprises a threaded shaft portion 32 and probe tip portion 33. Grommet 20 has a threaded external portion 21, internal threaded portion 22, and spherical hollow portion 23. The stud bolt 30 is then inserted into grommet 20 and positioned in spherical hollow portion 23 of grommet 20. Plug member 34 is then threaded into the internal threaded portion of the grommet 20 until the plug seats lightly against the spherical head portion 31 of the stud bolt 30. With the plug 34 lightly positioned against the head of the stud bolt 30, the stud bolt 30 is swiveled to both distribute the anti- seize compound and fully seat the stud bolt 30 within the spherical cavity formed by the grommet 30 and plug 34. The position of the plug is adjusted to allow the stud bolt to swivel freely with minimum drag and minimum axial clearance. A staking tool is then aligned with the four cut-outs 40 formed on the bottom surface of grommet 20 and four corresponding plug flanges 42 (Figure 4) are then staked (formed) into the cutouts 46 until it makes contact therewith, thus fixing the adjustment. Collar member 25 is then threaded loosely onto the external thread 21 of grommet 20 and retaining ring 28 is then installed into the retaining ring groove 39 formed in grommet 20, thus completing the assembly as shown in Figure 5. The assembly is then packaged and prepared for shipment to the end user. The recipient of the packaged fastener assembly then proceeds as follows: The retaining ring 28 is removed and the collar 25 is unscrewed and removed. The grommet/stud portion of the fastener assembly is then inserted into a prepared aperture in the panel member 16, collar member 25 then being screwed onto the grommet 20 and tightened to the desired torque with the rivet lug portion 26 against the bottom surface of panel member 16 thereby attaching panel member 16 to the grommet/bolt assembly. The aperture in the rivet lug portion 26 is aligned with a prepared aperture in panel member 16, rivet 27 (supplied by the user) then installed through the panel 16 and rivet lug 26 of the collar 25 to prevent rotation and loosening of collar member 25. The retaining ring 28 is then reinstalled into groove 39 on grommet 20 to provide back-up retention for the grommet assembly, should it loosen, thus completing the assembly for the end user. The spherical head portion 31 can swivel in all directions, the grommet/ball seat assembly protecting the lower surface 35 of panel member 16 from damage while head portion 31 is maintained flush with upper surface 37 of the panel member. The flat surface 41 of collar member 25 provides the bearing surface for panel member 16 against the mating structure thereby protecting the bearing surface of thereof from damage. To remove the installed fastener assembly, the stud bolt 30 is rotated to unscrew it from the mating structure receptacle (not shown) on the frame of the aircraft. As stud bolt 30 unscrews, stud bolt head 31 rotates within the spherical socket created by grommet 20 and plug 34. Since head 31 is captive within the grommet/plug assembly, as the stud bolt 30 is unscrewed, the panel structure to which the assembly is attached will be lifted through the mechanical advantage provided by threads 32. As noted hereinabove, the fastener assembly of the present invention is utilized to help position a panel for installation of other fasteners on the panel, a particularly useful feature on panels with curved or compound curved surfaces which generally exhibit fit and/or fastener hole misalignment. While the invention has been described with reference to its preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teaching of the invention without departing from its essential teachings .

Claims: WHAT IS CLAIMED IS: 1. A fastener assembly including a bolt having the capability of swiveling to locate and be inserted into an aperture formed in a mating structure comprising: a grommet having internally and externally threaded portions and a spherical hollow portion; a stud bolt having a head that is spherically shaped and a threaded shaft portion; an externally threaded plug member, the plug member being threadably engaged with the internal threaded portion of said grommet to form a spherical cavity for receiving the spherical head portion of said stud bolt; and a collar member threadably engaged with the external threads of said grommet; 2. The fastener assembly of claim 1 further including a retaining ring positioned in a groove formed on the external diameter of said grommet. 3. The fastener assembly of claim 1 wherein said grommet is positioned in an aperture formed in a panel member. 4. The fastener assembly of claim 3 wherein a f stener member extends between coaligned apertures formed in said panel member and said collar member. 5. The fastener assembly of claim 1 wherein said threaded shaft portion has a non-threaded tip portion for locating an aperture formed in a mating structure. 6. The fastener assembly of claim 3 wherein said panel member has a curved surface. 7. The fastener assembly of claim 1 wherein said grommet has a plurality of cut-outs formed on the bottom surface thereof and wherein said plug member has a plurality of flange members formed thereon. 8. The fastener assembly of claim 7 wherein said flange members are forced into said grommet cut-outs whereby the position of said plug member in said assembly is fixed.

Inventors: JENSEN CARL B, JENSEN, CARL, B.
Applicants: FAIRCHILD HOLDING CORP, FAIRCHILD HOLDING CORP.
Application year: 1997
Main classification: E05C5
IPC codes: F16B5, F16B35, F16B43, F16C11