Abstract:
A fastener having an enlarged head and a threaded portion with an interior cavity. A plug mounted in the cavity configured similarly thereto having an enlarged head generally the same outer diameter as the enlarged end of the fastener and abutting against the same closing off the opening leading into the cavity. The plug is releasably locked in the cavity and released by magnetic action when the releasable lock is released.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to aircraft fasteners; and, more particularly, to a fastener having a magnetically actuated positive lock plug insert in its head eliminating any cavities or holes in the head while providing a positive lock therein. 
     2. Related Art 
     Various types of aircraft fasteners are known in the art. In my U.S. Pat. No. 4,822,227, commonly assigned, I disclosed fastener assembly for joining a panel to a sub-panel of an aircraft or the like comprising a receptacle assembly having a threaded stud secured to the undersurface of the sub-panel. The assembly includes a bolt having an enlarged head at one end and a nose at the other end. The panel has a countersunk opening aligned with an opening in the sub-panel. The bolt is threaded for threaded engagement to the stud. The head of the bolt has a countersunk opening configured to a tool for rotating the same. This opening includes a releasable plug which is moved downwardly upon insertion of the tool to permit rotation thereof, then returns to a position flush with the exterior of the head of the bolt surrounding the opening. 
     A spring is used to bias the plug to a position wherein the upper surface of the plug is flush with the bolt head surrounding the countersunk opening in which the plug is disposed. This spring can wear or become clogged during use and may not return the plug to its fully flush position leaving a slight recess or cavity on the bolt head. In addition, overtorquing of the bolt by the user may distort the recess or cavity on the bolt head and create burrs on top of the bolt head. Such slight cavities or recesses or burrs may be detected by sophisticated radar if the bolt is installed on an aircraft panel. 
     There is a need for a fastener having a removable head plug in its bolt head that is positively locked therein and can be easily removed when it is desired to remove the bolt. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide an improved fastener having a plug closing off a hex socket or the like in the bolt head which is positively locked therein and removable using magnetic means. 
     It is a further object of this invention to provide a fastener having a removable head plug positively locked into a socket in the bolt head using ball locking means. 
     It is still further an object of this invention to carry out the foregoing object wherein the plug has a locking element of metallic material so it can be quickly and easily removed using a magnet. 
     These and other objects are preferably accomplished by providing a fastener having a removable head plug so that no cavities are visible or detectable in the fastener head. 
     These and other objects are preferably accomplished by providing a fastener including a bolt having a plug positively locked into the bolt head and any cavities in the bolt head are eliminated. The plug cannot come out during high vibrations. The plug may have an internal locking element of a metallic material or include a magnetic material in said element so that magnetic means can be used to remove the plug to replace the fasteners. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a exploded sectional view of a fastener assembly in accordance with the teachings of the invention; 
     FIG. 2 is a detailed view of a portion of the assembly of FIG. 1; 
     FIG. 3 is an elevational sectional view of the bolt alone of FIG. 1 illustrating the locking feature thereof; 
     FIG. 4 is a view similar to FIG. 3 showing the plug in unlocked position; 
     FIG. 5 is a view of a fastener alone similar to the fastener of FIG. 1 showing a modification thereof; and 
     FIG. 6 is a view similar to FIG. 1 showing an internally threaded fastener and mating receptacle. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1 of the drawing, a fastener assembly  10  is shown comprising a fastener  11 , the fastener  11  having a main body portion  12 , a threaded lower portion  25  and a head plug  14 . A receptacle assembly  15  is shown associated with fastener  11  mounted to a pair of abutting panels  16 ,  17  as is well known in the art and will be discussed further hereinbelow. 
     Main body portion  12  includes an enlarged head  18  at one end having an undercut area  19  adapted to conform to the undercut area  20  on panel  16  leading into the aligned throughbores  21 ,  22  through panels  16 ,  17 , respectively. Head  18  has a flush outer surface  23  and an integral generally cylindrical shaft  24  terminating in threaded portion  25 . 
     Main body portion  12  also has an inner cavity  26  extending from surface  23  preferably downwardly to a point  27  above threaded portion  25 . Of course, depending on the application, point  27  could extend further downwardly adjacent threaded portion  25 . An annular groove  200  is provided in the side wall of cavity  26  for reasons to be discussed. Cavity  26  is hex shaped for receiving therein a suitable like configured tool for rotating the bolt  11  as is well known in the art. Of course, any suitable irregular configuration and like configured tool may be provided. 
     Plug  14  includes an enlarged head portion  30  having an outer flush surface  31  generally of the same outer diameter as surface  23  of head portion  18 . Enlarged head portion  30  is undercut, as at undercut portion  32 , so that it aligns with the undercut  19  of main body portion  12  of bolt  11  as will be discussed further hereinbelow and as seen in FIG.  4 . 
     Plug  14  also includes a generally cylindrical portion  33  having an outer hex shaped configuration  49  of a diameter generally related to the inner diameter of the cavity  26 . Cylindrical portion  33  includes an inner hollow chamber  34  below head  30  with a ball detent actuator  35  reciprocally mounted therein. 
     Ball detent actuator  35  has a main body portion  36  of the same diameter as the cavity  34  with upper and lower extension portions  37 ,  201  of lesser diameter than body portion  36 . Extension portion  201  tapers to main body portion  36 , at tapered portion  202 . 
     A pair of spaced openings  203 ,  204  are provided in body portion  33  with a pair of ball detents  205 ,  206  mounted in each opening  203 ,  204 , respectively, and peened therein as is well known in the art. A spacer  207  is provided in cavity  34  below extension portion  201  having a central opening  208  therein into which extension portion  201  extends. Spacer  207  is disposed within an undercut area  209  of the lower end of body portion  33 . 
     A coiled spring  210  surrounds extension portion  37  between the underside of head  30  and main body portion  36 . Spring  210  normally biases actuator  35  to the FIG. 3 position, as will be discussed further hereinbelow. 
     Actuator  35  may be made of a magnetically attractive metallic material, or, alternatively, a magnet  211  (FIG. 5) may be embedded therein for reasons to be discussed. 
     The fastener  11  is adapted to engage the threaded portion  38  of barrel  39  of receptacle assembly  15 . Barrel  39  is secured to a cage  40  as is well known in the art. 
     Thus, as also seen in FIG. 2, cage  40  has a main flange portion  41  secured to the underside of panel  17  by suitable rivets  42 ,  43  and has a pair of downwardly extending spaced flanges  44  (only one visible in FIG. 2) each having a slot  46  therethrough (FIG.  2 ). Barrel  39  has a pair of spaced outwardly extending tabs or ears  47  which enter spaced slots  46 . 
     In this manner, barrel  39  is secured to the panel  17  and the threaded portion  25  of main body portion  12  can threadably engage and be threaded to threaded portion  38  of barrel  39 . 
     The assembly of the parts of fastener  11  are shown in FIG.  3 . Plug  14  is inserted into cavity  26 , and actuator  35  is moved to a retracted position using a magnet, as previously discussed, with ball detents  205 ,  206  snapping outwardly into the groove  200  under the bias of spring  210  and release of the magnet. Detents  205 ,  206  snap into groove  200 . Extension portion  201  enters the hole  208  in spacer  207 . 
     It is noted that groove  200  assures that the plug  14  is properly positioned in the cavity  26 . The groove  200 , as seen in FIG. 1, has tapered side walls into which the ball detents  205 ,  206  align themselves (see particularly FIG.  3 ). This groove  200  assists in centering the ball detents  205 ,  206  and thus plug  14  in the correct position in cavity  26  thereby minimizing or eliminating any axial movement of plug  14  in bolt  11 . 
     The tapered undersurface  32  of head  30  aligns with the tapered undersurface  19  of head  18  of bolt  11 . This enables the plug and bolt to snugly fit to the undercut area  20  in panel  16 . 
     If it desired to remove plug  14  from bolt  11 , it is necessary to move actuator  35  upwardly against the bias of spring  210 , as shown in FIG. 4. A suitable magnet (not shown) can be used by positioning the same into contact with head  31  of plug  14  and magnetically attracting the metallic actuator  35  and pulling it upwardly unlocking ball detents  205 ,  206 . Thus, ball detents  205 ,  206  are moved out of groove  200  to the position shown in FIG.  4 . Plug  14  can now be removed from bolt  11 . It can be appreciated that, when actuator  35  is released to return to its FIG. 3 position, the downward movement of actuator  35  allows tapered portion  202  to move against detents  205 ,  206  and force them outwardly as seen in FIG. 3 to the locked position. 
     Although all or part of the body of the actuator  35  of FIGS. 1 to  4  may be of a magnetically attractive metallic material, as shown in FIG. 5, a magnet  211  may be embedded in the body of actuator  35  as seen in FIG. 5 wherein like numerals refer to like parts of FIG.  1 . Any suitable metallic tool (not shown) can thus be used to attract magnet  211  and pull the actuator  35  upwardly to release the detents. 
     Although the plug and cavity are preferably hex-shaped, any suitable irregularly configured outer shape for the plug and inner configuration for the cavity may be used as long as the plug mates with the cavity. 
     Although an externally threaded fastener is shown and described in FIGS. 1 to  5 , the fastener may be internally threaded as shown in FIG. 6 wherein like numerals refer to like parts of the fastener and receptacle shown and described in FIGS. 1 to  5 . Thus, as seen in FIG. 6, fastener assembly  100  is shown having a fastener  110  for threadable assembly to receptacle assembly  150 . Instead of an external threaded lower portion  25 , fastener  110  has an internally threaded cavity  111  adapted to matingly receive therein a threaded shaft  151  of a stud  154  of receptacle assembly  150 . Receptacle assembly  150  may be crimped at crimp  152  about the head  153  of stud  154 . In this manner, the plug and locking means of the invention can be used with either an external or internal threaded fastener. 
     While the specification describes particular embodiments of the present invention, those of ordinary skill can devise variations of the present invention without departing from the inventive concept.