Abstract:
An attachment device for attaching a substrate to a support structure includes a housing having a space defined by facing wall portions. The space captures a rotatable push nut with flexible teeth. The housing is attached to the substrate using a flange positioned opposite one of the wall portions, the substrate being crimped between the flange and the wall portion. The device may be pushed onto a threaded stud to rapidly affix the substrate to the support structure. The push nut may be rotated within the housing to disengage it from the stud and thereby remove the substrate from the support structure.

Description:
This application claims the benefit of U.S. Provisional Patent Application No. 60/531,946 filed on Dec. 23, 2003. 
    
    
     FIELD OF THE INVENTION 
     The invention concerns fasteners for rapid attachment of panels, flexible covers and other such substrates to support structures. 
     BACKGROUND OF THE INVENTION 
     As shown in  FIG. 1 , access panels and protective covers  10  are often attached to supporting structure  12  using push nuts  14  that engage threaded studs  16  extending from the supporting structure. The panel or cover  10  has holes  18  which are aligned with and receive the studs  16 , and the push nuts  14  are placed over the studs and engage the cover  10  to retain it to the structure  12 . The push nuts have flexible teeth  20  that extend radially inwardly and engage the threads of the studs and prevent the push nut from backing off of the stud. Preferably, the teeth are flexible and angularly oriented with respect to the plane of the push nut so that they may be pushed axially onto the studs  16  in the direction that increases the orientation angle of the teeth, but cannot easily be pulled from the studs in the opposite direction. The angled teeth are thus “self jamming” and resist any axially applied force trying to remove them. Because the studs are threaded, however, the push nuts may be removed by turning them around the stud in the manner of a conventional nut. 
     While it is easy to install a panel or cover using push nuts, the system as it is currently practiced suffers several disadvantages. There is a high part count as there is a separate push nut for each stud. The push nuts are loose and must be handled individually, and are prone to being lost. Assembly is relatively slow, especially if there are a significant number of studs and push nuts. There is clearly a need for a device that has the advantages of the push nut for attachment but does not suffer its disadvantages. 
     SUMMARY OF THE INVENTION 
     The invention concerns an attachment device mountable on a substrate and engageable with a threaded stud for attaching the substrate to the stud. The attachment device comprises a rim surrounding and defining an opening. A plurality of flexible teeth are positioned in spaced relation around the rim and projecting inwardly. The teeth are engageable with the stud to retain the rim thereto when the stud is inserted through the opening. The rim is captured within a housing. The housing has first and second facing wall portions positioned in spaced relation to one another that define a space between them. The rim is received within the space and retained within the housing by engagement with the wall portions. The wall portions each have respective apertures that are substantially aligned with the opening defined by the rim. The apertures are sized to expose the teeth. The rim is rotatable relatively to the housing about an axis oriented substantially coaxially with the opening for removing the rim from the stud by rotating the teeth engaged with the threads. 
     Preferably the first and second facing wall portions are integrally formed with the housing. In a preferred embodiment the housing comprises a cylindrical shell having a longitudinal axis. The first and second facing wall portions are positioned at one end of the shell and oriented substantially perpendicularly to the axis. The apertures are substantially aligned with the axis. A flange extends outwardly from the shell and is positioned in spaced relation to the first and second wall portions. The flange engages the substrate and retains the housing to it. The substrate is captured between the flange and one of the first and second wall portions. 
     In another embodiment, the attachment device comprises a housing having an aperture for receiving the stud. A plurality of flexible teeth are mounted on the housing. Preferably the teeth are formed integrally with the housing. The teeth and project inwardly into the aperture, the teeth being engageable with the stud to retain the housing thereto when the stud is inserted through the aperture. A retaining flange is attached to the housing and surrounds the aperture. The retaining flange extends outwardly to define a space between the housing and the flange. The substrate is captured between the flange and the housing, but the housing is rotatable relatively to the substrate for removal thereof from the stud. 
     The invention also includes, in combination, a substrate having an attachment device engageable with a threaded stud for attaching the substrate to the stud. The attachment device may comprise any of the embodiments described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a cover or panel attached to a supporting structure using push nuts according to the prior art; 
         FIG. 2  is a plan view of the attachment device according to the invention; 
         FIG. 3  is a sectional view taken at line  3 — 3  of  FIG. 2 ; 
         FIG. 3A  is a sectional view of an alternate embodiment of an attachment device according to the invention; 
         FIG. 4  is a plan view of an alternate embodiment of an attachment device according to the invention; 
         FIG. 5  is a cross-sectional view taken at line  5 — 5  of  FIG. 4 ; 
         FIG. 6  is a plan view of another alternate embodiment of an attachment device according to the invention; 
         FIG. 7  is a cross-sectional view taken at line  7 — 7  of  FIG. 6 ; and 
         FIGS. 8 and 9  are alternate embodiments of the attachment device according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 2  shows an attachment device  30  according to the invention mounted on a substrate  32 , partially shown. Substrate  32  could be, for example, a protective cover for a sensor used in an engine compartment or an access panel, and could be a textile or polymer sheet or a plastic or metal plate. Attachment device  30  is use to releasably attach substrate  32  to a support structure by engaging threaded studs similar to the example of  FIG. 1 . While the attachment device works most advantageously with a threaded stud, it is by no means limited in its use to threaded studs and may be used with any manner of stud or shank. 
     As best shown in cross-section in  FIG. 3 , device  30  comprises a housing  34  formed of facing wall portions  36  and  38  positioned in spaced apart relation to one another to form a space  40 . Each wall portion  36 ,  38  has a respective aperture  42 ,  44  through it, providing access to the space  40 . Housing  34  is attached to the substrate  32 , and the attachment may be effected in any number of ways. In the example shown in  FIGS. 2 and 3 , attachment between housing  34  and substrate  32  is effected via a flange  46  extending circumferentially around the housing in spaced relation to the wall portion  38 . Flange  46  preferably comprises a rolled-over portion of the housing  34 . Together, the flange  46  and wall portion  38  forcibly engage the substrate  32  to secure housing  34  to it. Alternatively, wall portion  38  may be adhesively bonded, welded or fused to the substrate  32  or fasteners such as rivets and screws may also be employed. 
     A push nut  48  is positioned within space  40 . Push nut  48  comprises a rim  50  surrounding and defining an opening  52 . Preferably, the rim is oriented within the space  40  so that its opening  52  may be substantially aligned coaxially with the apertures  42  and  44  for receiving a threaded stud  54 , shown in phantom line. 
     As shown in  FIG. 2 , a plurality of teeth  56  are positioned in spaced relation around the rim  50 . Teeth  56  are flexible and extend inwardly to engage the threaded stud  54  as shown in  FIG. 3 . Preferably, teeth  56  are angularly oriented to one side of rim  50 . Teeth  56  may be angled to either side. Angularly orienting the teeth  56  allows them to be “self jamming” when engaged with the stud  54 . Because the teeth  54  are flexible and angled, the push nut  48  can be pushed axially over the stud  54  in the direction indicated by arrow  58 . Teeth  56  engage the stud  54  and, being flexible, deflect in the direction that increases their orientation angle as they are being pushed over the stud. Once engaged with stud  54 , the angular orientation of teeth  56  resists axial force applied to the push nut  48  that would tend to remove it from the stud. Teeth  56 , being too long to deflect through the rim  50  when engaged with the threaded stud  54 , are placed under compression, are restrained by the rim, and jam the push nut  48  into engagement with the stud  54 , preventing its removal under axial force. 
     Wall portions  36  and  38  and their respective apertures  42  and  44  are sized and spaced apart so that push nut  48  is captured within space  40 . The space  40  is sized so that the push nut  48  can be rotated 360° relative to the housing  34  about an axis  60  that is substantially coaxial with opening  52  and apertures  42  and  44 . The apertures  42  and  44  are also sized to expose at least the teeth  56  of the push nut  48 . This permits access to the push nut  48  so that a tool may be used to rotate it for removal from the threaded stud  54  as one would remove a conventional nut. Preferably, the space  40  also allows lateral motion of the push nut  48  as indicated by arrow  62 . By allowing lateral motion of push nut  48  within housing  34  the tolerances of the substrate  32  need not be held very closely. This will allow multiple attachment devices  30  on a substrate  32  to easily engage multiple studs  54  on a support structure without significant distortion to the cover. 
     A preferred embodiment  31  of the attachment device according to the invention is illustrated in  FIG. 3A . In this embodiment, housing  34  comprises a cylindrical shell  33  having a longitudinal axis  35 . Facing wall portions  36  and  38  are integrally formed from the shell  33  and positioned at one end. The wall portions define respective apertures  42  and  44  that are coaxially aligned with axis  35 . Push nut  48  is captured within the space  40  defined by the wall portions  36  and  38 , the wall portions being sized so as to expose teeth  56 . A flange  37 , shown in phantom line, is provided in axially spaced relation to the wall portion  38  for attaching the device  31  to the substrate  32 . The flange  37  and the wall portion  38  form a channel for capturing the substrate  32 . In the embodiment of the invention shown in  FIG. 3A , the channel and the space  40  extend parallel to one another because the substrate  32  is flat. The substrate is captured between the flange and the wall portion. Preferably, flange  37  is formed integrally with housing  34  by deforming the end of the shell  33  to extend outwardly from the shell. Alternatively, as shown in  FIG. 9 , device  31  may be part of an assembly  70  comprising a tubular substrate  74 . Shell  33  coaxially engages with substrate  74  and may be held thereto via a friction fit for example, or by adhesive bonding. Assembly  70  may serve, for example, as a protective cover for an elongated sensor or other delicate instrument, the protected component being received through the opening  52  along axis  35 . 
     Another embodiment  41  of the attachment device according to the invention is shown in  FIG. 4 . Attachment device  41  has a perimeter  43  having a shape or surface texture that will provide purchase that will allow the device  41  to be turned relative to the substrate  32 . For example, the perimeter may have a hexagonal shape to provide wrench engageable flat surfaces  45  as shown, or the perimeter  43  may be knurled so that device  41  could be manually turned. Other shapes and surface textures are also feasible. 
     As shown in  FIG. 5 , embodiment  41  has the push nut  48  captured between facing wall portions  36  and  38  of housing  34 , the wall portions engaging the rim  50  to prevent rotation of the push nut  48  relative to the housing  34 . Instead, rotation of the attachment device  41  relative to the substrate  32  is permitted by positioning a gap  47  between the flange  46  and the wall portion  38 , the gap  47  being wider than the thickness of substrate  32  and not permitting forcible engagement between the flange  46 , wall portion  38  and substrate  32 . 
     Substrate  32  is preferably manufactured with attachment devices  41  positioned within openings that align with studs  54  on a support structure on which the substrate  32  is to be mounted. Assembly of the substrate  32  onto the studs  54  is effected by pushing each attachment device  41  onto a respective stud  54  as described above. The attachment device  41  thus permits rapid assembly. Removal of the cover is effected by using a wrench to engage the wrench engageable surfaces  45  (see  FIG. 4 ) and unscrew the device  41  from the stud. Torque applied to the housing  34  is transmitted to the attachment device  48  because it is secured between the facing wall portions  36  and  38 . This allows teeth  56  to traverse the threads of the stud  54 . However, the torque does not transfer to the substrate  32  because it does not forcibly engage flange  46  or wall portion  38  due to gap  47 . 
       FIGS. 6 and 7  illustrate yet another embodiment  49  of the attachment device according to the invention. Embodiment  49  has a housing  51  formed as a single piece, the housing  51  surrounding and defining an aperture  53  that receives the stud  54 . The flexible teeth  56  are attached directly to the single piece housing  51  and extend inwardly of the aperture  53  to engage the stud  54  to retain the substrate  32  to the support structure. Similar to embodiment  41  described above, attachment device  49  has a perimeter  43  shaped to provide purchase for turning the device, either by a tool such as a wrench or manually. Device  49  also has a flange  46  separated from housing  51  by a gap  47 , as best shown in  FIG. 7 . This allows the device  49  to turn relatively to the substrate  32  to which it is attached. The attachment device  49  may be pushed directly onto the stud  54  to mount the substrate  32  on a support structure and removed by turning it relative to the substrate  32 , either manually or using a tool such as a wrench. 
     Another embodiment  64  of the attachment device according to the invention is shown in  FIG. 8 . Embodiment  64  comprises a push nut  48  mounted within a housing  66 , the housing being attached to a mounting plate  67 . Plate  67  provides an area for attaching the housing to a substrate  32 , shown in phantom line. The substrate  32  may then be attached to a support structure using attachment device  64 . Various fastening means may be used to attach plate  67  to substrate  32 . By way of example a rivet  68  is shown, it being understood that other fastening means, such as bolts, nails, hook-and-loop fasteners and the like could also used. 
     Attachment devices according to the invention offer several advantages over the prior art method of attachment, including reduced part count as there are no loose fasteners that must be handled and become lost, more rapid assembly and reduced manufacturing costs since parts can be fabricated with greater tolerances due to the relative motion afforded between the fastening components and the cover being attached to a structure.