Abstract:
A panel insert for use with a structural panel and a fastener having a hold out mechanism. The panel insert comprises a body portion disposed within the structural panel. The body portion includes a first surface, an opposing second surface, and an aperture passing therethrough for receiving the fastener. A recessed portion opening to the second surface is provided to receive the hold out mechanism and secure the fastener to the structural panel.

Description:
BACKGROUND ART 
     1. Field of the Invention 
     The present invention relates generally to panel inserts for use with structural panels and fasteners having hold out mechanisms. In particular, the present invention relates to panel inserts for use with fasteners having hold out features. 
     2. Description of Related Art 
     Grommet inserts, also referred to as panel inserts, for fastening structural panels and composite sandwich panels together are well known in the art. These panel inserts are used in a wide variety of applications, most often as a strengthening means through which a fastener, bolt, or stud nut may be passed to couple other structures to a composite panel. In most cases, these panel inserts are formed by coupling two or more pieces together, usually a male piece and a female piece, through an aperture in the composite panel. There are many different ways to couple the pieces together and prevent them from exerting too much force on the panel, including: press fitting one portion into another, ratcheting one portion into another, receiving the lip of one piece with a groove on the other piece, deformation of one piece by the other piece, and so on. Some of these panel inserts include a counter bore to receive a flush head bolt or stud nut. 
     Panel inserts generally come in two types: “protruding,” which have flanges that protrude beyond the opposing surfaces of the panels, and “flush,” which have flanges that are flush with one or both of the opposing exterior surfaces of the panel. Flush panel inserts usually involve some inward deformation of the panel surfaces near the aperture that passes through the panel. Although protruding panel inserts do not require any deformation of the panel, the flanges of the protruding panel insert often get in the way when panels or parts are being assembled or disassembled, particularly when bolts or stud nuts passing through the grommet also protrude beyond the surfaces of the panel. On the other hand, because the flanges of flush panel inserts are flush with one or more of the opposing surfaces of the panel, the panels assemble and disassemble easier and faster, with less opportunity for incidental damage from handling. 
     The primary purpose of these grommet panel inserts is to strengthen the panel at aperture through which the fastener, bolt, or stud nut passes. 
     Although these flush panel inserts may be installed flush with the exterior surfaces of the structural or composite panel, they do not adequately provide for flushly mounting fasteners having hold out mechanisms. 
     BRIEF SUMMARY OF THE INVENTION 
     There is a need for a composite panel insert having a recess to receive a hold out mechanism of a fastener or stud nut, whereby the hold out mechanism and the stud nut are flush with a surface of the composite panel when the stud nut is in a hold out position. 
     It is an object of the present invention to provide a composite panel insert having a recess to receive a hold out mechanism of a fastener or stud nut, whereby the hold out mechanism and the stud nut are flush with a surface of the composite panel when the stud nut is in a hold out position. 
     A principle advantage of the present invention is that when the hold out mechanism and the stud nut are flush, or sub-flush, with the interior surface of the composite panel, i.e., the surface of the panel that mates with another structural component, ease and speed of assembling and disassembling other parts and panels to the composite panel is greatly improved. Another advantage of the present invention is that incidental damage from handling to the composite panel and other parts and panels is reduced because fewer studs and nuts protrude out from the exterior surface of the composite panel. 
     The above, as well as, additional objects, features, and advantages of the present invention will become apparent in the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a portion of a prior-art panel having a passage through which a protruding flat head stud nut may pass, the passage including a recess to receive a hold out mechanism of the stud nut. 
     FIG. 2 is a cross-sectional view of a portion of a prior-art panel having a passage through which a flush head stud nut may pass, the passage including a recess to receive a hold out mechanism of a stud nut. A flush head stud nut having a hold out mechanism, is shown in the passage in a hold out position. 
     FIG. 3 is an exploded cross-sectional view of the panel insert with hold out recess feature according to the present invention. 
     FIG. 4 is an assembled cross-sectional view of the panel insert of FIG. 3 shown installed in a composite panel. 
     FIG. 5 is an assembled cross-sectional view of the panel inset of FIG. 3 shown installed in a composite panel with a hold-out fastener. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1 of the drawings, numeral  11  illustrates a prior-art panel having an aperture  13  passing therethrough. Panel  11  is typically made of a rigid material such as aluminum or other metallic material, but panel  11  may be made of a plastic or composite material. Panel  11  is generally not representative of panels having honeycomb construction. For purposes of the present invention, panel  11  may represent either a single panel or a plurality of panels connected in layers together. Aperture  13  is usually annular in shape and passes through panel  11  from a first surface  15  to an opposing second surface  17 . Aperture  13  allows a fastener, such as a bolt or stud nut (see FIG. 2) to pass through panel  11  and secure panel  11  to another panel or structure (not shown). A recessed area  19  is machined into panel  11  from second surface  17 . Recessed area  19  has a larger diameter than aperture  13 . Recessed area  19  is usually annular in shape and concentric with aperture  13 . Recessed area  19  receives a hold out cage (see FIG. 2) of the bolt or stud nut. Because panel  11  has no counter bore on first surface  15 , panel  11  would only be suited for protruding head fasteners. 
     Referring now to FIG. 2 in the drawings, a prior-art panel  21 , similar to panel  11 , is illustrated. An aperture  23  passes through panel  21 . As with panel  11 , panel  21  is typically made of a rigid material such as aluminum or other metallic material, but panel  21  may be made of a plastic or composite material. Panel  21  may be either a single panel or a plurality of panels layered together. As with panel  11 , panel  21  generally does not represent panels of honeycomb construction. Aperture  23  is usually annular in shape and passes through panel  21  from a first surface  25  to an opposing second surface  27 . Aperture  23  includes a counter bore  29  bored into panel  21  from first surface  25 . Aperture  23  and counter bore  29  allow a conventional flush head fastener, such as stud nut  31  to pass through panel  21  and secure panel  21  to another panel or structure (not shown). Stud nut  31  has a flush mount head  32  that is received into counter bore  29 , thereby allowing stud nut  31  to be flush with first surface  25  when in a fastened position. In FIG. 2, stud nut  31  is shown in an unfastened hold out position. A recessed area  33  is machined into panel  21  from second surface  27 . Recessed area  33  has a larger diameter than aperture  23 . Recessed area  33  is usually annular in shape and concentric with aperture  23 . 
     In a typical installation, stud nut  31  is installed through aperture  23 . A retaining ring  35  having an outside diameter larger than the diameter of aperture  23  is then installed through recessed area  33  and around a base portion  37  of stud nut  31  to prevent stud nut  31  from falling out of aperture  23 . An ring-shaped hold out cage  39  (shown in partial cross section) having an inside diameter smaller than the outside diameter of retaining ring  35  is then inserted into recessed area  33  and held in place by a press fit between the inside surface of recessed area  33  and a knurled exterior surface  41  of hold out cage  39 . The thickness of hold out cage  39  is dimensioned such that after insertion into recessed area  33 , hold out cage  39  remains flush with second surface  27  of panel  21 . Thus, when stud nut  31  is in the unfastened position, as shown in FIG. 2, stud nut  31  is held in place by retaining ring  35 , which, in turn, is held in place by hold out cage  39 . In this manner, stud nut  31  is retained in a flush, or sub-flush position relative to second surface  27 . This arrangement makes it faster and easier to assemble and disassemble panel  21  with other panels and structures. During assembly, stud nut  31  is firmly held in place and is ready to be fastened without additional alignment. In addition, incidental damage due to handling is reduced because stud nut  31  does not extend beyond surface  27  when in the unfastened position. 
     Referring now to FIGS. 3 and 4 in the drawings, the preferred embodiment of a composite panel insert with hold out recess feature according to the present invention is illustrated. As shown in FIG. 3, a rigid insert  51  includes body portion comprised of a plug portion  51   a  and a sleeve portion  51   b  that is received by plug portion  51   a . Plug portion  51   a  and sleeve portion  51   b  are preferably made of a rigid material, such as aluminum or other metallic material; however, plug portion  51   a  and sleeve portion  51   b  may also be made of a composite material. Plug portion  51   a  includes a first surface  53 , and sleeve portion  51   b  includes an opposing second surface  55 . Plug portion  51   a  and sleeve portion  51   b  are press fit together at a joint  52 , but my be coupled together by other means, such as threads, a snap fit, a ratchet fit, or other conventional means. Because insert  51  is rigid, it may be used with both rigid panels, including metallic and composite panels, and non-rigid panels, including panels made of honeycomb construction. As shown in FIG. 4, insert  51  is installed through an aperture  56  in a composite honeycomb panel  58 . Panel  58  may also be one or more composite sandwich plates. Panel  58  has a first exterior surface  58   a  and an opposing second exterior surface  58   b . Edges  58   c  surrounding aperture  56  are deformed inwardly to allow a flush mount between first surface  53  and first exterior surface  58   a , and between second surface  55  and second exterior surface  58   b . An aperture  57   a  passes longitudinally through plug portion  51   a . Likewise, an aperture  57   b  passes longitudinally through sleeve portion  51   b.    
     As shown in FIGS. 4 and 5, upon coupling of plug portion  51  a and sleeve portion  51   b , apertures  57   a  and  57   b  combine and align to form a single aperture  57 . Plug portion  51   a  includes a counter bore  59  to receive a flush head bolt or stud nut, Marked-Up and Clean Versions of Amended Paragraphs in the Specification such as stud nut  31 . It should be understood that counter bore  59  is not necessary. In the case where plug portion  51   a  does not have counter bore  59 , insert  51  would be better suited for a flat head fastener. Sleeve portion  51   b  includes a recessed portion  61 . Recessed portion  61  is very similar in form and function to recessed areas  19  and  33  which are machined into panels  11  and  21 , respectively. As such, after insert  51  is assembled by coupling plug portion  51   a  to sleeve portion  51   b , through aperture  56  of panel  58 , a fastener, such as stud nut  31  may be installed and secured in place within recessed portion  61  as described above with respect to FIG.  2 . Such plug  51   a  and sleeve  51   b  combination provides added strength to panel  58  at aperture  56 . Without some type of insert or grommet, panel  58  would not be able to adequately support a fastener through aperture  56 , and without insert  51 , panel  58  would not be able to flushly receive stud nut  31  having hold out cage  39 . Plug portion  51   a  and sleeve portion  51   b  are preferably installed in aperture  56  of panel  58  with a conventional adhesive, such as epoxy. 
     It should be understood that plug portion  51   a  and sleeve portion  51   b  may be interchanged, such that sleeve portion  51   b  inserts into plug portion  51   a . In other words, it is not necessary that counter bore  59 , if present, be in plug portion  51   a , and that recessed portion  61  be in sleeve portion  51   b . In addition, insert  51  may be of unitary construction, or may be comprised of more than two portions, depending on the particular application. It is only necessary that recessed portion  61  is available to receive the hold out cage of a bolt or stud nut, such as hold out cage  39  of stud nut  31 . 
     As with the rigid panels of FIGS. 1 and 2, when stud nut  31  is installed into insert  51 , stud nut  31  is held in place by retaining ring  35 , which, in turn, is held in place by hold out cage  39 . In this manner, stud nut  31  is retained in a flush, or sub-flush, position relative to second exterior surface  58   b . This arrangement makes it faster and easier to assemble and disassemble panel  58  with other panels and structures. During assembly, stud nut  31  is firmly held in place and is ready to be fastened without additional alignment. In addition, incidental damage due to handling is reduced because stud nut  31  does not extend beyond surface second exterior surface  58   b  when in the unfastened position. Insert  51  allows for close fit of mating components without potential interference from fasteners protruding beyond second exterior surface  58   b . By using insert  51  it is not necessary to provide additional strengthening features to composite panel  58 , such as embedding metal plates for future machining in panel  58 . Insert  51  adds strength to panel  58  without adding additional weight or cost. 
     It should be apparent from the foregoing that an invention having significant advantages has been provided. While the invention is shown in only one of its forms, it is not just limited but is susceptible to various changes and modifications without departing from the spirit thereof.