Patent Publication Number: US-2018038399-A1

Title: Lightweight floating blind panel insert

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. provisional application Ser. No. 62/371,380 filed on Aug. 5, 2016. The disclosure of the above applications is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to fasteners and more specifically to blind inserts for use in sandwich-type structures such as honeycomb panels. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Sandwich-type structures, such as honeycomb panels, are used in a variety of applications that require lightweight combined with high strength. Sandwich-type structures generally include a lightweight core with face sheets or skins secured on opposite sides of the core. One such application for sandwich-type structures is in an aircraft, and more specifically interior panels of an aircraft such as flooring or doors. 
     These interior panels often include hardware in order to secure an object thereto or to provide other functionality. In some cases, one side of the hardware is often “blind,” where access to the side is inhibited or not possible due to the assembly of surrounding components. Such hardware may include a fastener commonly referred to as a “panel insert” or an “inset panel fastener,” which generally includes a casing having a threaded nut floating therein and enclosed by a cap. An example of such a fastener is shown in U.S. Pat. No. 7,195,436. 
     As shown in  FIG. 1 , these panel inserts may be installed in the “blind” application where the back-side of the insert is not exposed to an outside environment for installation and/or removal. As shown, the panel inserts  10  generally include a body portion  12 , a cap  14 , and a nut  16  disposed within the body portion  12  and enclosed therein by the cap  14 . The panel insert  10  is installed within a sandwich panel  18 , which generally includes face sheets  20  and a core  22 . Generally, the panel inserts  10  are installed within openings formed through one face sheet  20  and the core  22 , and then are secured within the opening by a potting compound. 
     Because weight is an important design criteria in aerospace applications, designers are constantly pursuing options to reduce weight in all components, including these panel insert fasteners, while also maintaining the required structural integrity. 
     SUMMARY 
     In one form, an insert for use in a sandwich-type structure is provided that comprises a housing defining an internal bore, a proximal flange, opposed distal flanges, and an exterior wall portion extending between the proximal flange and the opposed distal flanges. The opposed distal flanges define lateral walls arranged tangentially with a wall of the internal bore. A nut is disposed within the internal bore of the housing and is configured to float therein, the nut defining a truncated flange and a hollow shaft extending from the truncated flange. The hollow shaft defines internal threads and an exterior wall, the exterior wall having a diameter equal to a thread lock diameter. In one variation, the exterior wall extends along the entire length of the hollow shaft. A cap is configured for engagement with the opposed distal flanges such that the nut is floatingly captured within the internal bore of the housing. 
     In alternate forms, the truncated flange of the nut defines opposed cutouts, which may define an arcuate geometry. In another form, the exterior wall portion of the housing defines a textured surface. In still another form, the proximal flange of the housing defines at least one radial recess to accommodate a potting compound upon final assembly of the insert and the sandwich structure. Further still, the proximal flange of the housing defines a textured sidewall in another form of the present disclosure. 
     The components of the insert may be any of a variety of materials. In one form, the housing and cap is an aluminum alloy material and the nut is stainless steel material. In another form, the components may be selected from the group consisting of a plastic material, composite material, a titanium alloy, and carbon steel. 
     In another form, the opposed distal flanges of the housing define a slotted region such that the nut is disposed within the slotted region of the housing. In other form, the outer diameter of the hollow shaft of the nut is smaller than an inner diameter of the bore of the housing. 
     In another form, a sandwich panel is provided that comprises an insert as described herein. Also, an aircraft having a sandwich panel with an insert is also provided by the teachings of the present disclosure. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which: 
         FIG. 1  is a side cross-sectional view of a prior art blind panel insert according to the prior art; 
         FIG. 2A  is a perspective view of an insert constructed in accordance with the principles of the present disclosure; 
         FIG. 2B  is a top exploded perspective view of the insert of  FIG. 2A ; 
         FIG. 2C  is a bottom exploded perspective view of the insert of  FIG. 2A ; 
         FIG. 3  is a side cross-sectional view of the insert installed within a sandwich-type structure in accordance with the teachings of the present disclosure; 
         FIG. 4  is a perspective view of a housing of the insert constructed in accordance with one form of the present disclosure; 
         FIG. 5A  is a perspective view of a nut of the insert constructed in accordance with one form of the present disclosure; 
         FIG. 5B  is a perspective view of another form of a nut of the insert constructed in accordance with one form of the present disclosure; and 
         FIG. 6  is a perspective view of the housing of  FIG. 4  and the nut of  FIG. 5  in accordance with the teachings of the present disclosure. 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     Referring to  FIGS. 2A-2C and 3  a lightweight blind insert for use in a sandwich-type structure is illustrated and generally indicated by reference numeral  30 . The insert  30  in one form of the present disclosure is provided in three (3) pieces, namely, a housing  32 , a floating internal nut  34 , and a cap  36 . As shown in  FIG. 3 , the insert  30  is blind such that the cap  36  is not accessible from the side of the face sheet  40  of the sandwich-type structure  42 . 
     As best shown in  FIG. 4 , the housing  32  defines an internal bore  50 , a proximal flange  52 , opposed distal flanges  54  defining a slotted region  56 , and an exterior wall portion  58  extending between the proximal flange  52  and the opposed distal flanges  54 . The opposed distal flanges  54  define lateral walls  60  (only one lateral wall  60  shown in  FIG. 4 ) arranged tangentially with a wall  62  of the internal bore  50  in one form of the present disclosure. The proximal flange  52  of the housing  32  also defines at least one radial recess  62  to accommodate a potting compound upon final assembly of the insert within the sandwich structure  42 . 
     Referring now to  FIG. 5A , the nut  34  defines a truncated flange  70  and a hollow shaft  72  extending from the truncated flange  70 . The hollow shaft  72  defines internal threads (not shown) to receive a threaded component (also not shown) and an exterior wall  74 . Advantageously, the exterior wall  74  has a diameter approximately equal to, or slightly greater than, a thread lock diameter, which is generally the minimum diameter at which the threads of a mating fastener will plastically deform the exterior wall  74 . This smaller diameter of the exterior wall  74  thus results in a more lightweight insert  30 . Additionally, the truncated flange  70  provides weight savings through the opposed cutouts  76 , which in one form define an arcuate configuration as shown. Such a truncated flange  70  has not heretofore been contemplated due to a decrease in strength, less efficient load path, and possible stress concentrations created by the discontinuities of the truncations. It should be understood that other shapes may be provided as truncations in order to save weight, and the arcuate configurations should not be construed as limiting the scope of the present disclosure. 
     In another form as shown in  FIG. 5B , the hollow shaft  72  may have the exterior wall  74  with a thread lock diameter extending along its entire length, rather than just a portion thereof shown in  FIG. 5A . 
     As further shown in  FIG. 6 , the nut  34  is configured to be disposed within the internal bore  50  of the housing  32  and to float therein, and more specifically, within the slotted region  56  along the axes X and Y as shown because the outer diameter of the hollow shaft  72  of the nut  34  is smaller than the inner diameter of the bore  50  of the housing  32 . This “floating” capability compensates for assembly tolerances and allows for a more efficient assembly operation when adjacent components such as a threaded component (not shown) are secured to the nut  34 . 
     Referring back to  FIGS. 2B, 2C, and 3 , a cap  36  is configured for engagement with the opposed distal flanges  54  of the housing  32  such that the nut  34  is floatingly captured within the internal bore  50  of the housing  32 . In one form, a distal edge  82  of the cap  36  is plastically deformed to capture the distal flanges  54  of the housing, which is best shown in  FIG. 3 . It should be understood that this plastic deformation is merely one form of capturing the nut  34  within the housing  32  and should not be construed as limiting the scope of the present disclosure. 
     Each of the housing  32 , nut  34 , and cap  36  may be any material depending on specific application requirements. In one form, the housing  32  and cap  36  are an aluminum alloy material, and the nut  34  is a stainless steel material. In another form, one or more of these components may be a plastic or composite material. In still another form, the cap  36  may be a titanium alloy. The nut  34  may also be a titanium alloy or a carbon steel. 
     In another form, the exterior wall portion  58  may define a textured surface (not shown) in order to provide a more secure installation of the insert  30  within the sandwich-type structure  42 . Similarly, the proximal flange  52  of the housing  32  may define a textured sidewall (not shown) for a more secure installation. 
     The lightweight insert  30  according to the present disclosure is generally used in a sandwich-type structure as illustrated herein but may also be used in other applications. Further the lightweight insert  30  is contemplated for use in an aircraft in order to provide weight savings. 
     The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.