Abstract:
An anti-tamper fastener with a fastener head with a first side and a second side and a shank attached to and extending out from the second side. The fastener head has a substantially square hole formed in the first side that extends into the fastener head to a base. A post is located in the hole and extends out from the base toward the first side. A driver is also disclosed which is shaped to mate with the fastener. The driver includes a substantially square shank portion with a hole formed in it. The shank portion is sized to fit within the square hole in the fastener and the hole sized to receive the post in the fastener.

Description:
RELATED APPLICATION  
       [0001]     This application is related to and claims priority from U.S. Provisional Patent Application Ser. No. 60/554,878 filed Mar. 19, 2004, the entire disclosure of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to fasteners and, more particularly, to an anti-tamper fastener, with a unique engagement slot which requires a unique mating tool for removal.  
       BACKGROUND  
       [0003]     There are many fasteners in the marketplace for use in attaching components together. Most of those fasteners are installed using widely available conventional drivers, such as a slotted driver or a Phillips head driver. As such these fasteners can be installed and removed by anyone using readily available tools.  
         [0004]     In recent years, unique anti-tamper fasteners have been developed that require the use of specific shaped drivers. These have been designed to inhibit removal of the fastener without the special driver. One such fastener is sold under the trademark TORX, Plus® by Textron Fastening Systems. The fastener includes a multi-lobed opening with a center post. The center post is designed to inhibit insertion of a conventional driver into the opening.  
         [0005]     While the TORX Plus fastener provides some degree of anti-tamper protection by inhibiting conventional drivers from being used to remove the fastener, the multi-lobe design provides limited torque capability. As such, there is a tendency of the driver to cam-out upon the application of very low torque. This limits the use of the fastener to low torque applications.  
         [0006]     A need, therefore, exists for an improved anti-tamper fastener which provides increased cam-out torque.  
       SUMMARY OF THE INVENTION  
       [0007]     An anti-tamper fastener with a fastener head with a first side and a second side and a shank attached to and extending out from the second side. The fastener head has a substantially square hole formed in the first side that extends into the fastener head to a base. A post is located in the hole and extends out from the base toward the first side.  
         [0008]     A driver is also disclosed which is shaped to mate with the fastener. The driver includes a substantially square shank portion with a hole formed in it. The shank portion is sized to fit within the square hole in the fastener and the hole sized to receive the post in the fastener.  
         [0009]     The foregoing and other features of the invention and advantages of the present invention will become more apparent in light of the following detailed description of the preferred embodiments, as illustrated in the accompanying figures. As will be realized, the invention is capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and the description are to be regarded as illustrative in nature, and not as restrictive.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     For the purpose of illustrating the invention, the drawings show a form of the invention which is presently preferred. However, it should be understood that this invention is not limited to the precise arrangements and instrumentalities shown in the drawings.  
         [0011]      FIG. 1  is an isometric view of an anti-tamper fastener according to one embodiment of the present invention.  
         [0012]      FIG. 2  is a side view of the fastener of  FIG. 1 .  
         [0013]      FIG. 3  is a top view of the fastener of  FIG. 1 .  
         [0014]      FIG. 4  is a bottom view of the fastener of  FIG. 1 .  
         [0015]      FIG. 5  is a particle sectional view of the fastener of  FIG. 1 .  
         [0016]      FIG. 6  is an isometric view of a second embodiment of an anti-tamper fastener according to the present invention.  
         [0017]      FIG. 7  is an isometric view of a driver for use with an anti-tamper fastener according to the present invention.  
         [0018]      FIG. 8  is a side view of the driver of  FIG. 7 .  
         [0019]      FIG. 9  is a front view of the driver of  FIG. 7 .  
         [0020]      FIG. 10  is a top view of the driver of  FIG. 7 .  
         [0021]      FIG. 11  is a bottom view of the driver of  FIG. 7 .  
         [0022]      FIG. 12  is an isometric view of a second embodiment of a driver for use with an anti-tamper fastener according to the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]     Referring now to the drawings, wherein like reference numerals refer to similar components throughout the views, several embodiments of the invention are shown which are currently preferred.  FIGS. 1-5  illustrate an isometric view of a fastener  10  according to one embodiment of the present invention. The fastener  10  includes a head  12  which in the illustrated embodiment is a fillister head. However, any fastener head  12  can be used without departing from the scope of the invention. The fastener also includes a shank  14  which is formed on one side of the fastener head  12 . The shank  14  is preferably cylindrical in shape, although other shapes are possibly, such as a tapered conical shape. A set of conventional threads  15 , such as 10-32 UNF, 10-24 UNF, 5 mm or 6 mm threads, are formed about at least a portion of the shank. The shank  14  includes a tip end  17 , which may be threaded or include a dog point as shown.  
         [0024]     The fastener  10  includes a fastener recess  16  formed in the fastener head  12 . The fastener recess  16  includes a substantially square aperture or slot  18 . Preferably the aperture has an opening that is either a #2 or #3 square recess. Alternatively, the aperture preferably has sides with a width at the top that is between about 0.100 inches to about 0.140 inches. The present invention is not limited to these sizes, however and, thus, encompasses various other size openings. The recess  16  also has a depth that is sized to provide a sufficient bearing surface for applying torque to the fastener. In one preferred embodiment, the depth is between about 0.052 inches to about 0.062 inches. It should be readily apparent that the depth of the recess can be varied depending on the size of the head  12  and the size of the opening  18 . The walls  18  of the recess  16  preferably taper inward approximately at an angel less than five degrees and more preferably at an angle of about 2 degrees to 3 degrees. Thus, for a #2 size square recess, the taper would be from approximately 0.123 inches at the outer edge to about 0.112 inches at the base.  
         [0025]     The fastener recess  16  also includes a center post  20  which is formed in the base  20  and protrudes upward toward the outer end  21 . The center post  20  is formed integral with the head  12  and is designed to operate in combination with the square opening to inhibit tampering of the fastener. More particularly, the inclusion of the post  20  prevents a convention square driver, as well as most conventional flat drivers, from being inserted into the recess  16 . In one embodiment of the invention, for a fastener with a #2 square opening, the center post  20  has a diameter that is between about 0.030 inches and about 0.050 inches. For a fastener with a #3 square opening, the center post  20  has a diameter that is between about 0.030 inches and about 0.080 inches. These post sizes are designed to limit the space between the post and the corners of the square opening, thus inhibiting insertion of most conventional drivers. It should be readily apparent that the diameter of the center post can vary depending on the size of the opening  18 .  
         [0026]      FIG. 6  illustrates an alternate embodiment  100  of a fastener according to the present invention. In this embodiment, the fastener  100  includes a button or pan head  112 . The fastener  110  also includes a shank  114  and recess  116  as discussed above. The recess has a substantially square opening  118  and a center port  120 .  
         [0027]     The fastener of the present invention can be made from any convention material used to make fasteners, such as metal (e.g., steel or zinc), plastic or composite.  
         [0028]     In order to attach and remove the fastener  10  to/from a structure, the present invention contemplates use of a unique driver  50 . Referring now to  FIGS. 7-11 , one embodiment of a driver  50  according to the present invention is illustrated. In this embodiment, the driver  50  is a driver bit that is used in combination with a conventional screw or ratchet drive. The driver  50  includes a square shank portion  52 . The dimensions of the shank  52  are preferably slightly smaller than the shape of the aperture of the fastener recess  16  so that the shank  52  will fit into the recess while at the same time producing a snug fit such that the fastener is held on the driver  50  during installation. For example, for a #2 size hole, the shank  52  preferably has a width W 1  of approximately 0.109 inches near its top and preferably has a length L of at least about 0.144 inches. The wall of the shank preferably tapers outwardly to a width W 2  of approximately 0.122 at the base of the square section. This is approximately a 2 degree to 3 degree outward taper, thus corresponding to the taper of the wall of the recess  16 . In one embodiment, wall tapers at an angle of approximately 92.6 degrees.  
         [0029]     A hole  54  is formed down the center of the shank  52 . The hole  54  is sized to receive the post  20  in the recess  16  of the fastener. The hole  54  preferably has a diameter of approximately 0.055 inches and a depth into the shank of at least about 0.115 inches.  
         [0030]     It should be readily apparent that the dimensions of the shank  52  and hole  54  can be varied to accommodate different recesses.  
         [0031]     A slight chamfer  53  may be formed near the tip of the shank portion  52  to facilitate insertion into the recess.  
         [0032]      FIG. 12  illustrates a slightly different embodiment of the driver bit according to the present invention.  
         [0033]     As shown in the figures and discussed above, the driver  50  is this embodiment is a drive bit. In order to engage with a convention screw or ratchet drive, the driver  50  includes a conventional shank base  56 , such as a hexagonal shank base as shown. The shank base  56  would be sized to engage with convention screw drives and ratchet drives, such as ¼ or ½ inch drives. Other sizes are also possible.  
         [0034]     It is also contemplated that the driver  50  may be formed as a key that includes a handle portion for grasping by a user. It is also contemplated that the driver may be part of a screwdriver and, thus, would include an enlarged handle that is attached to an elongated portion of the shank.  
         [0035]     The combination of the center post and the square recess provide a tamper resistant mechanism for installing and removing the fastener. Conventional drivers are inhibited from engaging with the fastener due to the existence of the center post. Hence, the fastener can only be removed and installed through the use of the special driver described above.  
         [0036]     Another benefit of the fastener configuration is its increased torque capability. A square aperture provides high cam out properties. The addition of the center post further enhances this by maintaining the driver centered within the recess, thus maximizing the transmission of torque to the fastener while inhibiting cocking of the driver as the fastener is installed or removed. In one embodiment of the invention, the configuration of the fastener is such that it can withstand torquing of at least about 8 ft-lbs.  
         [0037]     While the figures illustrate a driver bit, it is also contemplated that the driver can be formed with a screw driver handle, or as part of a key. Also, while the drawings illustrate a pan head fastener, the present invention can be incorporated into any conventional fastener.