Abstract:
A captive structural fastener includes an integral hold-out feature. The fastener includes a stud assembly including a stud, a retaining ring including two oppositely disposed tabs protruding toward the center of the retaining ring, a first sleeve that is mainly engageable with a second sleeve, the second sleeve including an inwardly disposed channel for receiving the retaining ring; and a receptacle assembly, the receptacle assembly including a bracket constructed and arranged to be secured to a panel, an internally threaded nut, a retaining clamp for securing the nut in the bracket, and a grommet assembly having a bore for receiving the stud therethrough.

Description:
BACKGROUND 
     1. Technical Field 
     This disclosure relates to a structural fastener and components thereof and, in particular, to a captive structural fastener with an integral hold-out feature and components thereof. 
     2. Related Cases 
     Benefit is hereby claimed under 35 U.S.C. § 120 of the filing date of commonly owned and co-pending U.S. patent application Ser. No. 10/137,011 filed on May 2, 2002, which is incorporated herein by reference in its entirety. 
     3. Background 
     A variety of fasteners or fastener assemblies (hereinafter “fasteners”) are known for attaching a panel to a sub-structure. Such fasteners are typically designed for use in high stress environments, such as to protect aircraft access panels, and when used in such environments, are referred to as “structural” fasteners. Structural fasteners are used to maintain secure attachment of the panel to the sub-structure panel during conditions of excessive vibration and high loads applied to the panel during flight. 
     “Captive” fasteners include studs or screws that remain captive in the stud assembly when the panel is removed from the sub-structure. When panels in which captive fasteners have been installed are removed from the sub-structure, the studs remain with the cover, maintaining the position of the studs relative to the panel and eliminating the problem of stud loss or displacement. 
     Some captive fasteners have “hold-out” features that involve the use of a hollow stud in which a separate retaining mechanism is positioned. These types of studs are difficult to manufacture and assemble, and can be problematic in use because “foreign object debris” (FOD) accumulates in the hollow portion of the stud, over time leading to eventual failure of the fastener. 
     Captive fasteners are prone to failure for other reasons as well. One reason is due to the fact that other fasteners have reduced life due to breakage of retaining rings, as well as other components of the assemblies. When the retaining ring breaks, depending on the design of the fastener, it often may result in the screw or stud falling out of the assembly, defeating the purpose of using a “captive” fastener assembly. 
     Of course, breakage of any part of the fasteners may lead to failure and, in addition, may lead to failure of other fasteners if the debris travels and is accumulated in other, un-broken fasteners. Also, this debris could short-out electronic components associated with the aircraft. 
     Thus, a need in the art exists for a captive structural fastener that reduces or eliminates the problem of foreign object debris. 
     SUMMARY 
     The present disclosure provides a fastener that includes an integral “hold-out” feature that provides a closed and an extended position. 
     Another feature of the present disclosure is the provision of a solid, rather than hollow stud, which reduces the amount of foreign object debris. Even though a solid stud is preferred it is noted that in accordance with the present invention principles thereof can also be applied to hollow studs. 
     Another feature of the present disclosure is the provision of a retaining ring that “floats” within a sleeve, which sleeve protects the retaining ring and minimizes the chance of foreign object debris if the retaining ring should break. 
     Another feature of the present disclosure is the provision of a fastener with evenly distributed forces along the grommet assembly, rather than localized distribution of force at the tip of a stud. This results in a secure fit of the stud within the grommet assembly and decreases the chance that the stud may be inadvertently released from its captive position. 
     The fasteners of the present disclosure may also be configured and dimensioned to have a reduced “footprint” for use in relatively small and/or inaccessible areas. 
     In accordance with one aspect of the present invention there is provided a fastening assembly, comprising: a stud assembly including a stud, a retaining ring including two oppositely disposed tabs protruding toward the center of the retaining ring, a first sleeve that is matingly engageable with a second sleeve, the second sleeve including an inwardly disposed channel for receiving the retaining ring; and a receptacle assembly, the receptacle assembly including a bracket constructed and arranged to be secured to a panel, an internally threaded nut, a retaining clamp for securing the nut in the bracket, and a grommet assembly including means defining a bore for receiving the stud therethrough; The stud includes a base, a head, and a shank disposed therebetween, the shank including an exterior surface having a threaded section, the exterior surface including at least two longitudinal channels, each channel including at least two engagement regions for engaging the tabs of the retaining ring. 
     In accordance with another aspect of the present invention there is provided a fastening assembly, comprising: a stud assembly including a stud, a retaining ring including two oppositely disposed tabs protruding toward the center of the retaining ring, and an upper grommet assembly including an inwardly disposed channel for receiving the retaining ring; and a receptacle assembly, the receptacle assembly including a bracket constructed and arranged to be secured to a panel, an internally threaded nut, a retaining clamp for securing the nut in the bracket, and a lower grommet assembly having a bore for receiving the stud therethrough. The stud includes a base, a head, and a shank disposed therebetween, the shank including an exterior surface having a threaded section, the exterior surface including at least two longitudinal channels, each channel including at least two engagement regions for engaging the tabs of the retaining ring. The lower grommet assembly comprises first and second sleeves that are engaged between a substrate panel to form said bore. 
     In accordance with still another aspect of the present invention there is provided a fastening assembly, comprising: a stud assembly including a stud, a retaining ring including two oppositely disposed tabs protruding toward the center of the retaining ring, and at least one sleeve including an inwardly disposed channel for receiving the retaining ring; and a receptacle assembly, the receptacle assembly including a bracket constructed and arranged to be secured to a panel, an internally threaded nut, a retaining clamp for securing the nut in the bracket, and a grommet assembly including means defining a bore for receiving the stud therethrough. The stud includes a base, a head, and a shank disposed therebetween, the shank including an exterior surface having a threaded section, the exterior surface including at least two longitudinal channels, each channel including at least two engagement regions for engaging the tabs of the retaining ring. The retaining clamp engages both the bracket and the nut and provides a single point attachment of the receptacle assembly to the substrate panel. 
     The foregoing and other objects, features and advantages of the disclosure will be apparent from the following more particular description of preferred embodiments of the disclosure, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the disclosure. The principles and features of this disclosure may be employed in varied and numerous embodiments without departing from the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       It should be understood that the drawings are provided for the purpose of illustration only and are not intended to define the limits of the disclosure. The foregoing and other objects and advantages of the embodiments described herein will become apparent with reference to the following detailed description when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of an exemplary embodiment of a fastener according to one embodiment of the present invention, showing a panel attached to a sub-structure by the fastener, and with the fastener in a closed position; 
         FIG. 2  is a perspective view of the fastener shown in  FIG. 1 , showing the fastener in an extended position; 
         FIG. 3  is an exploded perspective view of the fastener shown in  FIG. 1 ; 
         FIG. 4  is an exploded view of the stud assembly of the fastener shown in  FIG. 2 ; 
         FIG. 5  is a perspective view of the stud shown in the stud assembly shown in  FIG. 3 ; 
         FIG. 6  is a sectional view of the stud shown in  FIG. 4 ; 
         FIG. 7  is a side view of the stud shown in  FIG. 4 ; 
         FIG. 8  is an exploded view of the receptacle assembly of the fastener shown in  FIG. 3 ; 
         FIG. 9  is a sectional view of the fastener shown in  FIG. 1 , showing the retaining ring positioned in the first engagement region and the fastener is the closed position as shown in  FIG. 1 ; and 
         FIG. 10  is a sectional view of the fastener shown in  FIG. 1 , showing the retaining ring positioned in the second engagement region and the fastener in the extended position as shown in  FIG. 2 . 
         FIG. 11  is a perspective view of another embodiment of a fastener according to the present invention, showing a panel attached to a sub-structure by the fastener, and with the fastener in a closed position; 
         FIG. 12  is a perspective view of the fastener shown in  FIG. 11 , showing the fastener in an extended position; 
         FIG. 13  is an exploded perspective view of the fastener shown in  FIG. 11 ; 
         FIG. 14  is an exploded perspective view of the stud assembly of the fastener shown in  FIG. 11 ; 
         FIG. 15  is a perspective view of the stud shown in the stud assembly shown in  FIG. 14 ; 
         FIG. 16  is a sectional view of the stud shown in  FIG. 15 ; 
         FIG. 17  is an exploded perspective view of the receptacle assembly of the fastener shown in  FIG. 11 ; 
         FIG. 18  is a sectional view of the fastener shown in  FIG. 11 , showing the fastener is the open or released position; 
         FIG. 19  is a sectional view of the fastener shown in  FIG. 11 , showing the fastener in the closed or locked position; 
         FIG. 20  is a perspective view of still another embodiment of a fastener according to the present invention, showing a panel attached to a sub-structure by the fastener, and with the fastener in a closed position; 
         FIG. 21  is a perspective view of the fastener shown in  FIG. 20 , showing the fastener in an extended position; 
       FIG:  22  is an exploded perspective view of the fastener shown in  FIG. 20 ; 
         FIG. 23  is an exploded perspective view of the stud assembly of the fastener shown in  FIG. 20 ; 
         FIG. 24  is a perspective view of the stud shown in the stud assembly shown in  FIG. 23 ; 
         FIG. 25  is a sectional view of the stud shown in  FIG. 24 ; 
         FIG. 26  is an exploded perspective view of the receptacle assembly of the fastener shown in  FIG. 20 ; 
         FIG. 27  is a sectional view of the fastener shown in  FIG. 20 , showing the fastener is the open or released position; 
         FIG. 28  is a sectional view of the fastener shown in  FIG. 20 , showing the fastener in the closed or locked position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present disclosure is directed to a captive structural fastener that may be used in high stress environments for attaching a panel to a sub-structure, such as covers used to close access openings in panels of an aircraft. 
     The present fastener includes a solid externally threaded stud that includes an integral “hold-out” feature, which allows the stud to be positioned in a first, closed position and in a second, extended position. The present fastener also provides containment for the retaining ring, which may be relatively delicate and prone to breakage in comparison to other components of the fastener. By providing containment for the retaining ring, should the retaining ring break, the debris will be confined to the sleeve rather than becoming FOD that might jeopardize other parts. In a preferred embodiment, the fastener also may include a nut that distributes stress uniformly in the longitudinal direction of the barrel of the nut. The fastener is sized and dimensioned to be attached to a panel using a single bolt or rivet, which is advantageous for constricted or otherwise inaccessible regions. 
     Many features of the present fastener already are disclosed in co-pending U.S. patent application Ser. No. 10/137,011; for ease of explanation, some aspects will be described again herein with reference to an exemplary embodiment of the present disclosure. 
     One exemplary embodiment of a fastener  10  according to the present disclosure is indicated generally at  10  in  FIGS. 1 and 2 , where it is shown in an assembled configuration attaching a panel “P” to a sub-structure “S” with the stud in a first, closed position ( FIG. 1 ), and in a second, extended position ( FIG. 2 ). 
     As shown in  FIG. 3 , fastener  10  includes a stud assembly indicated generally at  12  and a receptacle assembly indicated generally at  15 . Stud assembly  12  is shown in greater detail in  FIGS. 4 and 4A  when taken together. As shown, stud assembly  12  includes a stud  14 , an upper sleeve  16 , a lower sleeve  18 , and a retaining ring  20 . 
     Upper sleeve  16  has a substantially cylindrical wall defining an opening  16   a  having a diameter sized and configured to receive stud  14  therein. A flange  26  extends outwardly from one end of opening  16   a . Upper sleeve  16  has a substantially smooth interior surface  22 , including the surface of flange  26 , and a threaded exterior surface  24 . Lower sleeve  18  has an upper edge  19   a  and a lower edge  19   b , with an annular lip  30  extending outwardly from lower edge  19   b . A substantially cylindrical wall defines an opening  18   a  sized and dimensioned to receive upper sleeve  16  therein. Lower sleeve  18  has a substantially smooth exterior surface  33  and a threaded interior surface  32  with a plurality of slots  34  extending from a region adjacent to annular lip  30  to upper edge  19   a.    
     Annular lip  30  defines an interior channel  31  (see  FIG. 4A ) sized and dimensioned to receive retaining ring  20  therein, as described below. Retaining ring  20  preferably has a substantially planar circular shape and includes two opposed inwardly protruding tabs  40 , and a slot  42  (see  FIG. 4 ) that allow it to be compressed while being inserted into the interior channel  31  of lower sleeve  18 . Lower sleeve  18  and, in particular, interior channel  31 , provide containment to retaining ring  20  in case of breakage, thus minimizing FOD. 
     Thus when assembled as shown, retaining ring  20  is inserted into interior channel  31  of lower sleeve  18 , and lower sleeve  18  is inserted into an aperture Ap. Thereafter, upper sleeve  16  is threaded into lower sleeve  18 .  FIG. 4  shows the parts in an exploded position while  FIG. 4A  shows the stud assembly  12  in its finally secured position. 
     Stud  14  of stud assembly  12  is shown in greater detail in  FIGS. 5-7 . As shown, stud  14  is substantially symmetrical in construction, and includes a head  48  at one end thereof, a tip  49  at an opposite end thereof, and a shank  44  therebetween. Head  48  includes a recess  50  for receiving a tool. 
     Shank  44  has an outer surface  45  that includes a substantially smooth section  45   a  adjacent to head  48  and a threaded exterior surface section  45   b  extending from smooth section  45   a  substantially to tip  49 . Two longitudinal retaining sections  52 , which in the present embodiment are channels, are positioned diametrically opposite one another longitudinally on shank  44 . For ease of description, retaining sections  52  will be referred to hereinafter as channels. Channels  52  extend from smooth section  45   a  of shank  44  through threaded section  45   b , substantially to tip  49 . Channels  52  preferably are recessed from exterior surface  45  of shank  44 . 
     Each channel  52  includes at least two engagement regions; first engagement region  58   a  and second engagement region  58   b . Engagement regions  58   a  and  58   b  are spaced apart by a spacing member  59 , and are adapted to engage tabs  40  of retaining ring  20  when the stud and fasteners are assembled together, either in a closed position or in an extended position. In the present embodiment, spacing members  59  are defined by an arcuate region extending upwardly from a base  54  of channels  52 . For ease of description, spacing members  59  will be referred to hereinafter as lobes. Lobes  59  preferably have a substantially smooth surface extending from the engagement region  58   a  to engagement region  58   b.    
     Receptacle assembly  14  is illustrated in greater detail in  FIG. 8 . As shown, receptacle assembly  14  includes a bracket or cage  70 , a retaining clamp  72 , a nut  74 , and a spring, heli-coil or coil  76 . Bracket  70  has a collar  71  that is adapted to fit into the aperture As. The retaining clamp  72  holds the nut  74  to the bracket or cage  70 . A rivet (not shown) is placed in hole  75  to retain the cage  70  in place. Other details of the receptacle assembly are disclosed in the afore-mentioned commonly-owned and co-pending U.S. patent application Ser. No. 10,137,011, particularly the embodiment described in FIGS. 25-29. 
     As shown in  FIGS. 9-10 , when fastener  10  is assembled, tabs  40  of retaining ring  20  may be repositioned to engage each engagement region  58   a,b  in order to position stud  14  in a first, closed position at first engagement region  58   a  (see  FIG. 9 ), and a second extended position at second engagement region  58   b  (see  FIG. 10 ). Thus, stud  14  may be retracted or inserted longitudinally in the fastener, allowing tabs  40  to slide over lobe  59  until tabs  40  move between the closed and the engaged positions shown. 
     When the panels P and S are to be separated or disengaged the stud would be in the position depicted in  FIG. 10  in which the stud is disengaged from the nut  74 . The retaining ring is then in engagement with one end of the stud at  58   b . To engage or secure the panels, the stud  14  is then slid downwardly with the ring tabs  40  riding over the lobe  59  toward the position of  FIG. 9 . The stud  14  is then screwed into the nut  74 .  FIG. 9  illustrates the stud in an almost fully secured position. In that position the ring tabs  40  are at the position  58   a , as illustrated. 
     Another exemplary embodiment of a fastener  10  according to the present invention is indicated generally at  110  in  FIGS. 11 and 12 , where it is shown in an assembled configuration attaching a panel “P 1 ” to a sub-structure “S 1 ” with the stud in a first, closed position ( FIG. 11 ), and in a second, extended position ( FIG. 12 ). 
     As shown in  FIG. 13 , fastener  110  includes a stud assembly indicated generally at  112  and a receptacle assembly indicated generally at  115 . Stud assembly  12  is shown in greater detail in  FIG. 14 . As shown, stud assembly  112  includes a stud  114 , an upper sleeve  116 , a lower sleeve  118 , and a retaining ring  120 . Sleeves  116  and  118  taken together may be considered as a grommet or grommet assembly. 
     Upper sleeve  116  has a substantially cylindrical wall defining an opening  116   a  having a diameter sized and configured to receive stud  114  therein. A flange  126  extends outwardly from one end of opening  116   a . Upper sleeve  116  may have a substantially smooth interior surface and a threaded exterior surface as in the previous embodiment. Lower sleeve  118  has an upper edge  119   a  and a lower edge  119   b , with an annular lip  130  extending outwardly from lower edge  119   b . A substantially cylindrical wall defines an opening  118   a  sized and dimensioned to receive upper sleeve  116  therein. Lower sleeve  118  may have a substantially smooth exterior surface and a threaded interior surface and may be provided with a plurality of slots (not shown in  FIG. 14 ) extending from a region adjacent to annular lip  130  to upper edge  119   a.    
     In an alternate embodiment the sleeves  116  and  118  may be interengaged in another manner such as by means of a force fit between the components, by tack welding, by the use of adhesives or other appropriate means to hold the sleeves together once they are placed in engagement with the panel P 1 . It is preferred that the sleeves by engaged by a compression, swage or flair-over fit. 
     Annular lip  130  defines an interior channel  131  (see  FIGS. 18 and 19 ) sized and dimensioned to receive retaining ring  120  therein, as described below. Retaining ring  120  preferably has a substantially planar circular shape and includes two opposed inwardly protruding tabs  140 , and a slot  42  (see  FIG. 14 ) that allow it to be compressed while being inserted into the interior channel  131  of lower sleeve  118 . Lower sleeve  118  and, in particular, interior channel  131 , provide containment to retaining ring  120  in case of breakage, thus minimizing FOD. 
     Thus when assembled as shown, retaining ring  120  is inserted into interior channel  131  of lower sleeve  118 , and lower sleeve  118  is inserted into an aperture Ap. Thereafter, upper sleeve  116  is threaded into lower sleeve  118  or engaged in another appropriate manner.  FIG. 14  shows the parts in an exploded position while  FIGS. 18 and 19  shows the stud assembly  112  in its finally secured position. 
     Stud  114  of stud assembly  112  is shown in greater detail in  FIGS. 15 and 16 . As shown, stud  114  is substantially symmetrical in construction, and includes a head  148  at one end thereof, a tip  149  at an opposite end thereof, and a shank  144  therebetween. Head  148  includes a recess  150  for receiving a tool that is used in tightening the stud. The tool that may be used is a torque wrench that has the capability of controlling the level of poundage provided so as to tighten the stud to the proper amount of torque. 
     Shank  144  has an outer surface  145  that includes a substantially smooth section  145   a  adjacent to head  148  and a threaded exterior surface section  145   b  extending from smooth section  145   a  substantially to tip  149 . Two longitudinal retaining sections  152 , which in the present embodiment are channels, are positioned diametrically opposite one another longitudinally on shank  144 . For ease of description, retaining sections  152  will be referred to hereinafter as channels. Channels  152  extend from smooth section  145   a  of shank  144  through threaded section  145   b , substantially to tip  149 . Channels  152  preferably are recessed from exterior surface  145  of shank  144 . 
     Each channel  152  includes at least two engagement regions; first engagement region  158   a  and second engagement region  158   b . Engagement regions  158   a  and  158   b  are spaced apart by a spacing member  159 , and are adapted to engage tabs  140  of retaining ring  120  when the stud and fasteners are assembled together, either in a closed position or in an extended position. In the present embodiment, spacing members  159  are defined by an arcuate region extending upwardly from a base  154  of channels  152 . For ease of description, spacing members  159  will be referred to hereinafter as lobes. Lobes  159  preferably have a substantially smooth surface extending from the engagement region  158   a  to engagement region  158   b.    
     Receptacle assembly  115  is illustrated in greater detail in  FIG. 17 . As shown; receptacle assembly  115  includes a bracket or cage  170 , a retaining clamp  172 , a nut  174 , and a lower sleeve or grommet assembly that includes sleeves  176  and  177 . Bracket or cage  170  has a hole  171  that is adapted to receive the sleeve  177 . The retaining clamp  172  holds the nut  174  to the bracket  170 . A rivet  175  through the retaining clamp  172  holds the nut  174  in place, as depicted in  FIGS. 18 and 19 .  FIGS. 18 and 19  depict the rivet  175  firmly holding the nut to the substrate S. The rivet  175  extends through the retaining clamp  172 , through a hole in the cage  170  and through the hole provided in the substrate S. The retaining clamp is preferably provided with a ledge  160  that retains the nut  174  in place. This clamping effect is shown in  FIGS. 18 and 19 . The retaining clamp  172  also has an upwardly extending collar  167  that fits within the hole in the cage  170 . 
     The receptacle assembly  115  is provided with a bracket that may be similar to brackets described in earlier application Ser. No. 10/137,011. For example the bracket  170  may include a sidewall or track at  165  that receives the top plate  163  of the nut  174 . That inter-engagement along with the securing by the rivet  175  assures that the entire receptacle assembly is firmly in place and not able to loosen. 
     The sleeves  176  and  177  may be interlocked by providing threads therebetween or the sleeves may be interlocked together in another manner including, for example, by a force fit between the sleeves or by other appropriate means. The base  161  of the sleeve  177  also engages with the top plate of the nut  174 , such as is illustrated in  FIG. 18 . 
     As shown in  FIGS. 18 and 19 , when fastener  110  is assembled, tabs  140  of retaining ring  120  may be repositioned to engage each engagement region  158   a,b  in order to position stud  114  in a first, closed position at first engagement region  158   a  (see  FIG. 19 ), and a second extended position at second engagement region  158   b  (see  FIG. 18 ). Thus, stud  114  may be retracted or inserted longitudinally in the fastener, allowing tabs  140  to slide over lobe  159  until tabs  140  move between the closed and the engaged positions shown. 
     When the panels P and S are to be separated or disengaged the stud would be in the position depicted in  FIG. 18  in which the stud is disengaged from the nut  174 . The retaining ring is then in engagement with one end of the stud at  158   b . To engage or secure the panels, the stud  114  is then slid downwardly with the ring tabs  140  riding over the lobe  159  toward the position of  FIG. 19 . The stud  114  is then screwed into the nut  174 .  FIG. 9  illustrates the stud in a fully secured position. In that position the ring tabs  140  are at the position  158   a , as illustrated. 
     Thus, the fastener of the present invention has a simple hold-out feature in which the fastener can assume either the position of  FIG. 18  in which it is held out or disengaged and yet still held in place, or can assume the position of  FIG. 19  in which the fastener has been fully seated in its corresponding nut to fully secure the panels together. It is noted that even in the position of  FIG. 18  the stud is prevented from disengaging from the panel by virtue of the retaining ring holding the stud at the engagement region  158   b.    
     Still another exemplary embodiment of a fastener  210  according to the present invention is indicated generally at  210  in  FIGS. 20 and 21 , where it is shown in an assembled configuration attaching a panel “P 2 ” to a sub-structure “S 2 ” with the stud in a first, closed position ( FIG. 20 ), and in a second, extended position ( FIG. 21 ). 
     As shown in  FIG. 22 , fastener  210  includes a stud assembly indicated generally at  212  and a receptacle assembly indicated generally at  215 . Stud assembly  212  is shown in greater detail in  FIG. 23 . As shown, stud assembly  212  includes a stud  214 , an upper sleeve  216 , a lower sleeve  218 , and a retaining ring  220 . Sleeves  216  and  218  may be considered as a grommet. 
     Upper sleeve  216  has a substantially cylindrical wall defining an opening  216   a  having a diameter sized and configured to receive stud  214  therein. A flange  126  extends outwardly from one end of opening  216   a . Upper sleeve  216  may have a substantially smooth interior surface and a threaded exterior surface as in the previous embodiment. Lower sleeve  218  has an upper edge  219   a  and a lower edge  219   b , with an annular lip  230  extending outwardly from lower edge  219   b . A substantially cylindrical wall defines an opening  218   a  sized and dimensioned to receive upper sleeve  216  therein. Lower sleeve  218  may have a substantially smooth exterior surface and a threaded interior surface with a plurality of slots extending from a region adjacent to annular lip  230  to upper edge  219   a.    
     In an alternate embodiment the sleeves  216  and  218  may be interengaged in another manner such as by means of a force fit between the components, by interference fit or swage fit, by the use of adhesives or other appropriate means to hold the sleeves together. 
     Annular lip  230  defines an interior channel  231  (see  FIGS. 27 and 28 ) sized and dimensioned to receive retaining ring  220  therein, as described below. Retaining ring  220  preferably has a substantially planar circular shape and includes two opposed inwardly protruding tabs  240 , and a slot  242  (see  FIG. 23 ) that allow it to be compressed while being inserted into the interior channel  231  of lower sleeve  218 . Lower sleeve  218  and, in particular, interior channel  231 , provide containment to retaining ring  220  in case of breakage, thus minimizing FOD. 
     Thus when assembled as shown, retaining ring  220  is inserted into interior channel  231  of lower sleeve  218 , and lower sleeve  218  is inserted into an aperture Ap. Thereafter, upper sleeve  216  is threaded into lower sleeve  218  or engaged in another appropriate manner.  FIG. 23  shows the parts in an exploded position while  FIGS. 27 and 28  shows the stud assembly  212  in its finally secured position. 
     Stud  214  of stud assembly  212  is shown in greater detail in  FIGS. 24 and 25 . As shown, stud  214  is substantially symmetrical in construction, and includes a head  248  at one end thereof, a tip  249  at an opposite end thereof, and a shank  244  therebetween. Head  248  includes a recess  250  for receiving a tool that is used in tightening the stud. 
     Shank  244  has an outer surface  245  that includes a substantially smooth section  245   a  adjacent to head  248  and a threaded exterior surface section  245   b  extending from smooth section  245   a  substantially to tip  249 . Two longitudinal retaining sections  252 , which in the present embodiment are channels, are positioned diametrically opposite one another longitudinally on shank  244 . For ease of description, retaining sections  252  will be referred to hereinafter as channels. Channels  252  extend from smooth section  245   a  of shank  244  through threaded section  245   b , substantially to tip  249 . Channels  252  preferably are recessed from exterior surface  245  of shank  244 . 
     Each channel  252  includes at least two engagement regions; first engagement region  258   a  and second engagement region  258   b . Engagement regions  258   a  and  258   b  are spaced apart by a spacing member  259 , and are adapted to engage tabs  240  of retaining ring  220  when the stud and fasteners are assembled together, either in a closed position or in an extended position. In the present embodiment, spacing members  259  are defined by an arcuate region extending upwardly from a base  254  of channels  252 . For ease of description, spacing members  259  will be referred to hereinafter as lobes. Lobes  259  preferably have a substantially smooth surface extending from the engagement region  258   a  to engagement region  258   b.    
     Receptacle assembly  215  is illustrated in greater detail in  FIG. 26 . As shown, receptacle assembly  215  includes a bracket or cage  270 , a retaining clamp  272 , a nut  274 , and a lower sleeve or grommet assembly that includes sleeves  276  and  277 . Bracket or cage  270  has a hole  271  that is adapted to receive the sleeve  277 . The retaining clamp  272  holds the nut  274  to the bracket  270 . A rivet  275  through the retaining clamp  272  holds the nut  274  in place, as depicted in  FIGS. 27 and 28 .  FIGS. 27 and 28  depict the rivet  275  firmly holding the nut to the substrate S 2 . The rivet  275  extends through the retaining clamp  272 , through a hole in the cage  270  and through the hole provided in the substrate S 2 . The retaining clamp is preferably provided with a ledge  269  that retains the nut  274  in place. This clamping effect is shown in  FIGS. 27 and 28 . The retaining clamp  272  also has an upwardly extending collar  267  that fits within the hole in the cage  270 . 
     The receptacle assembly  215  is provided with a bracket that may be similar to brackets described in earlier application Ser. No. 10/137,011. For example the bracket  270  may include a sidewall or track at  265  that receives the top plate  263  of the nut  274 . That inter-engagement along with the securing by the rivet  275  assures that the entire receptacle assembly is firmly in place and not able to loosen. 
     The sleeves  276  and  277  may be interlocked by providing threads therebetween or the sleeves may be interlocked together in another manner including, for example, by a force fit between the sleeves or by other appropriate means. The base  261  of the sleeve  277  also engages with the top plate of the nut  274 , such as is illustrated in  FIG. 27 . 
     As shown in  FIGS. 27 and 28 , when fastener  210  is assembled, tabs  240  of retaining ring  220  may be repositioned to engage each engagement region  258   a,b  in order to position stud  214  in a first, closed position at first engagement region  258   a  (see  FIG. 28 ), and a second extended position at second engagement region  258   b  (see  FIG. 27 ). Thus, stud  214  may be retracted or inserted longitudinally in the fastener, allowing tabs  240  to slide over lobe  259  until tabs  240  move between the closed and the engaged positions shown. 
     When the panels P and S are to be separated or disengaged the stud would be in the position depicted in  FIG. 27  in which the stud is disengaged from the nut  274 . The retaining ring is then in engagement with one end of the stud at  258   b . To engage or secure the panels, the stud  214  is then slid downwardly with the ring tabs  240  riding over the lobe  259  toward the position of  FIG. 28 . The stud  214  is then screwed into the nut  274 .  FIG. 28  illustrates the stud in a fully secured position. In that position the ring tabs  240  are at the position  258   a , as illustrated. 
     Thus, the fastener of the present invention has a simple hold-out feature in which the fastener can assume either the position of  FIG. 27  in which it is held out or disengaged and yet still held in place, or can assume the position of  FIG. 28  in which the fastener has been fully seated in its corresponding nut to fully secure the panels together. It is noted that even in the position of  FIG. 27  the stud is prevented from disengaging from the panel by virtue of the retaining ring holding the stud at the engagement region  258   b.    
     Another feature of the fastener of the present invention relates to the ease with which the stud can be engaged with the receptacle. For this purpose the distal end  149  of the stud is provided with an annular ramp  151  as depicted in  FIG. 16 . This configuration would also be used in the last embodiment that is described in  FIGS. 24 and 25 . The ramp  151  is helpful for alignment and engagement of the stud with the receptacle assembly. 
     When used as structural components, the foregoing fastener may be formed from materials capable of withstanding high stress, such as steel. Individual components may be formed from other materials such as structural plastics, composites, shape memory alloys, and the like. In a preferred embodiment, the nut may be formed from a polyamide available under the product name VESPEL®. In other preferred embodiments, structural plastics such as fiber reinforced polymers also may be used for certain components to reduce the weight of the assembly. One type of material is a fiberglass reinforced polymer that includes about 30 percent to about 60 percent, by weight, of fiberglass. This concentration may vary, of course, depending upon the matrix polymer, the source of the material, the type of fiber, etc. 
     As mentioned previously, the bracket of each of the foregoing receptacle assemblies may be unitary or may be assembled from separate components. In addition, the length of the collars may vary in order to accommodate different panel thicknesses. When the foregoing brackets are unitary, they are typically formed by die casting, which necessitates the formation of a different cast for each desired bracket, and each collar length. One way around this problem is to form a single cast for each type of bracket, using the longest collar length, and achieving shorter collar lengths by grinding off part of the collar. Each of the foregoing is time consuming and expensive. In a preferred embodiment of the present disclosure, the bracket or cage is formed as two components: a bracket portion and a removable collar or sleeve that mates or is friction fitted with bracket portion. 
     In the embodiments described in  FIGS. 11-28  the various components can be secured together in various ways. By way of example in  FIG. 18  the sleeves  116  and  118  may be engaged by means of a compression fit between the sleeves. This preferred over a threading because in this particular structure there is only a small amount of space for threading. Also, in  FIG. 18  the sleeve  177  may be compression fit with the bracket opening  171  and, thereafter the sleeve  176  may be compression fit with the sleeve  177 . The retaining clamp may be swage-fit at collar  167  with the bracket  170 . The ledge  169  engages the plate  163  about the end with the legs. 
     Another feature of the present invention is the capability of securing the receptacle assembly in a very easy manner, preferably with the use of only a single securing member such as the illustrated rivet. Of course, other securing devices can also be used such as a bolt, screw or the like. 
     While this disclosure has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims.