Background of the Invention

This invention relates to aircraft floor panel installation components and system and in particular to fastener inserts for Honeycomb panels.

Aircraft floor panels are generally a compositio of two metal sheets separated By a honeycomb core structur Recently, instead of metal sheets, composite materials, i. epoxy, graphite, etc., have been utilized which provide fo an even lighter and stronger floor panel structure.

These honeycomb panel structures are fragile in the core area where fasteners are utilized to mount the panel. Accordingly, floor panel attachment methods used a separate insert and screw combination. The inserts were always bonded and potted to the floor panels during floor panel fabrication. The inserts used on honeycomb core floo panels were of two basic types, single piece and two piece.

The single piece has a body and a lower flange. The lower flange is bonded to the lower facesheet of the panel, the body goes thru the panel and is swaged over onto the upper facesheet.

The two piece inserts are two inter-locking piece each with a flange. The pieces are inserted one from each side of the panel and the flanges are bonded onto the face- sheets.

During panel installation, screws are installed through the inserts in order to secure the panels. The herein disclosed dimpled washer system is an improvement which will save time and money in the fabrication and insta lation phase. In addition, the new installation concept is specifically designed to provide for a more effective moisture sealing arrangement, and a method which would not

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dimple the facesheets and crush the core, as well as avoi conventional manufacturing steps.

Summary of the Invention The present invention is an improved installa¬ tion system for floor panels and in particular to inserts for floor panels having a honeycomb type core matrix uti¬ lized in aircraft. The system involves using two alike dimpled washers and an optional rubber grommet under the screw head effectively sealing the installation from moisture. Further, electrolytic corrosion is inhibited b the application of an aluminum-pigmented coating to the washers and the screw before installation. The dimpled washers and screws are designed to secure aircraft floor panels to floor support members. These washers are easier cheaper and lighter to install than conventional floor panel inserts.

The dimpled washer consists of a thin upper flange and a cylindrical body. Two washers are used per hole, one washer inserted in the upper panel surface and the other in the lower panel surface. The washers are either fitted or may be bonded in place using a simple col bonding process. A rubber grommet is used under the fas¬ tener head to insulate the fastener from the dimpled metal washer. Washers and fasteners may be made from titanium, steel, or aluminum. Upon installation of the washers on each side of the panel, no potting is used to the core structure and no squeezing action is needed for installing the washer inserts. These two manufacturing steps are completely deleted saving time and weight since potting compound is not used, which of course is more economical.

Furthermore, this new installation system of two opposed dimpled washers presents a novel, unique feature because the dimpled washers abut one another as soon as th screw or fastener is tightened and thus automatically pro- vides for a "stop" to the installer. In addition, each washer is slightly deformed upon fastening of the screw which offers a double biased spring force against the annu lar under surface of the screw head. Thus a non-core- ^χ \ . ι\ -. G.--PI

crushing feature, a non-face-dimpling feature and an improved sealing feature is accomplished by the present installation system. In general, an aircraft floor instal lation apparatus and system is disclosed for floor panels having an upper and a lower face sheet separated by a core and provided with fastening holes, for mounting to an air¬ plane floor beam structure provided with mounting holes. The system uses two washers, the first dimpled washer has its first washer surface positioned on the upper face shee and a first sleeve portion, a second washer surface and a second sleeve portion with a bottom edge surface, disposed inside the fastening hole.

Then the second dimpled washer has its first washer surface positioned on the lower facesheet, and a first sleeve portion and a second sleeve portion with an upper edge surface, disposed inside the fastening hole in opposed relationship to the first dimpled washer. In addition, there is a fastener with a head portion, which provides for an annular bottom head surface, and a shank portion adapted to fasten the panel onto the floor beam structure through the fastening hole and the mounting hole. Upon installation of the fastener, the annular bottom head surface applies pressure on the second washer surface of the first dimpled washer causing therein a first spring biased force which result in a sealing arrangement. Also the bottom edge surface of the first dimpled washer engages against the upper edge surface of the second dimpled washer causing a second spring biased force and a controlled installation stop to the fastener so that a spring biased, sealed and controlled positioned sunken fastener installa¬ tion is accomplished.

Brief Description of the Drawings

FIGURE 1 illustrates two different inserts utili¬ zed conventionally for aircraft floor panel installations. FIGURE 2 illustrates the preferred embodiment of two dimpled washer inserts prior to installation.

FIGURE 3 illustrates the washer/fastener arrange¬ ment when a panel is installed.

FIGURE 4 is a typical aircraft floor panel to floor beam installation,

FIGURE 5 is an isometric illustration of a seat- track floor panel installation system, FIGURE 6 is a second insert embodiment.

FIGURE 7 is a third insert embodiment.

Detailed Description of the Invention

As discussed, the conventional system Qf mounting floor panels in a,ircraft is performed with the assistance o hole insert devices 10, 12 and 14 which are squeezed, crampe or swaged into a potted hole in a floor panel 16, As illus trated in FIGURE 1, the double inserts 10 and 12 are also glued or bonded 18 to the panel 16. The swaged device 14 is bonded 20 at one side and swaged onto the panel 16 at th other side. It should be realized that the potting procedu utilizing potting compound 24 in the hole—core-area require installation time and is essential when conventional floor panel installation systems are used. The potting material hardens and reinforces the core 26 so that the inserts 10-1 14 can be squeezed and swaged onto the panel 16 without damage to the core 26 structure.

The basic operation of the installing system of the present invention is disclosed in FIGURES 2 and 3.

As illustrated, two dimpled washers 30 and 50 are utilized.

The first washer 30 has a first washer surface 32 which is positioned at the fastener hole 60 and on contact with the upper facesheet 62 of the panel 64. The washer 30 has a first sleeve portion 34, which circumference fits inside the hole 60 circumference in the panel 64, and furthermore, extends into a second washer surface 36 which is parallel to the first washer surface 32 and terminates i a second sleeve portion 38 with an annular bottom edge surface 40, The second dimpled washer 50. is positioned at the opposite side or lower facesheet 66 of the panel 64 and is positioned with its first washer surface 52 against the

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lower facesheet 66 and optionally bonded thereto by glue 68 or the like. The second washer 50 is dimpled so that a first sleeve portion 54, a second washer surface 56, a second sleeve portion 58 with a,n upper annular surface 70 is formed. In order to assure a leakproof condition a rubber grommet 72 may be inserted on the first washer 30 second washer surface 36 and also a moisture sealing glue 68 may be provided between surfaces 62 and 32,

An associated fastener or screw with a head 74 forming an annular bottom head surface 76 and a shank 78 is inserted ±n the opening 60 provided by the second sleeve portions 38 and 58 of the washers 30 and 50,

In the typical installation illustrated in FIGURES 4 and 5 a nut 80 and nut plate 82 are utilized at the air- craft floor beam structure 84 after the shank 78 is passed through the mounting hole 86 provided in the structure 84. When the installation of the floor panel 64 onto the floor beam 84 takes place, the fastener 74 will contact the second washer surface 36 of the first dimpled washer 30 and its resilient material will provide a spring biased seal By the optional addition of a rubber grommet 72 an absolute moisture sealing is obtained. Upon further tightening of the fastener the bottom edge surface 40 will come in contact with the upper edge surface 70, the gap 44 disappears, and cause a second spring biased seal but also provides for a stop. The mechanic or installer will thus know that the correct fastening or installing is obtained. The offset of the second sleeve portions 38 and 58 and the second washer surfaces 36 and 56, are illustrated in an exaggerated fashion in FIGURE 3, however the offset is in reality very slight.

The illustration in FIGURE 5 relates to the floor panel installation system where a seattrack 90 is located, It will be noted that the illustration in FIGURE 5 and the illustration in FIGURE 4 show the existence of a rubber type sealing strip 9.2 and 9.4 respectively. These strips 92 and 94 are optional and are new proposed concepts which may

be incorporated with the present conventional systems. In general, conventional systems utilize a narrow taped resili¬ ent seal at the panel edge locations.

The basic and preferred embodiment of the present

05 invention and its operational interactions are thus dis¬ closed in FIGURES 2 and 3 and their typical equivalent overall installation shown in FIGURES 4 and 5. It should be understood that it would be preferable, for economic reasons etc., thcit the two dimpled washers 30 and 50 are identical

10" and when stacked together equals almost the thickness of the floor panel but in such a way that a slight gap 44 is obtained between the facing bottom and upper edge surfaces 40 and 70 of the washers 30 and 50 respectively.

As mentioned before, a significant saving in time

15 and money is obtained because the panel 64 does not need potting material around the hole 60 or washers 30 and 50 in its core structure 46.

Bonding of the second washer ^' 50 between the first washer surface ^' 52 and the lower face sheet 66 depends on the

20 surface material that is utilized underneath the lower facesheet 66. In the present illustrations, bonding 68 is recommended because of the presence of the sealing strips 92 and 94. If no sealing strips are utilized or if the second washer rests on a flat, hard surface of the structural beam

25 84, then no bonding is needed since the fastener installa¬ tion will not be able to dislodge or push out the second washer from the fastener hole 60.

Because various modifications can be made, which basically present the same solutions as explained for the

30 preferred embodiment illustrated in FIGURES 2 through 5, it is deemed necessary to disclose a second and third pre¬ ferred embodiment, as illustrated in FIGURES 6 and 7,

In FIGURE 6 the emphasis is directed to simpler washer constructions 100 and 102, which have sleeves 104

35. . and 106 respectively. In the present illustration the sleeves have a tight fit with the hole 110, however a smaller diameter is also possible and would provide an adjustment feature in respect to the location of the

mounting hole. During installation the second washer surface 120 of the washer 100 will be tightened in contac with the second washer surface 122 of washer 102 and create a biased seal and "stop" with the fastener head area (not shown) . in FIGURE -7 the configuration of the washers 130 and 132 is somewhat similar except for the provisions of a resilient seal material 124 and 136 on th inner surface portions of 138 and 140. A slight gap 150 is shown in both embodiments which as explained before will close when the fastener is tightened upon installa¬ tion of the panel. The first embodiment provides for a definite secured "stop" situation upon tightening of the fastener while this situation is less apparent in the other embodiments. Having thus described the various details and preferred embodiment of the present invention the follow¬ ing claims are made:

No, therefore, we claim:

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