Patent Abstract:
A mail slot door immobilizer for immobilizing a mail slot door within a main door, including an interior portion located on an interior side of the mail slot door and overlapping the mail slot door and the main door, and an exterior portion located on an exterior side of the mail slot door and overlapping the mail slot door and the main door. A fastener removably fastens the interior portion to the exterior portion to clamp the mail slot door and the main door between the interior and exterior portions and to prevent movement of the mail slot door with respect to the main door.

Full Description:
FIELD OF THE INVENTION 
     The invention relates to building security devices and, more particularly, to devices for immobilizing a mail slot door of a building to prevent access to the building through the mail slot door. 
     BACKGROUND OF THE INVENTION 
     It is common for commercial buildings to have a mail slot for allowing mail to be delivered into the building. Typically, such mail slots are located in the front door of the building and are covered by a mail slot door. The mail slot door rotates on a hinge and can be opened to allow mail to be inserted through the mail slot. 
     While such mail slot arrangements are often necessary to allow mail to be received by the building occupant, they may also allow unwanted or unsolicited items to be delivered into the building, such as trash or unwanted advertising materials. In addition to requiring cleanup, these materials may accumulate on the inside of the building and be seen by passersby through store windows or glass doors. The accumulation can be unsightly and can reflect poorly on the building occupant. 
     In some cases, it may be possible to reach through the mail slot to the interior of the building to reach a panic bar or to unlock the door. In order to prevent unwanted access to the building in such cases, it is necessary to prevent the mail slot door from being opened. 
     Thus, a need exists for a device that can be installed to prevent the unwanted opening of a mail slot door and yet be easily removed when desired to allow mail to be delivered into the building. 
     SUMMARY OF THE INVENTION 
     The mail slot door immobilizer of the present invention is a removable device that prevents the unwanted opening of a mail slot door located within a main door. The mail slot door immobilizer includes an interior portion located on an interior side of the mail slot door and overlapping the mail slot door and the main door, and an exterior portion located on an exterior side of the mail slot door and overlapping the mail slot door and the main door. A fastener removably fastens the interior portion to the exterior portion to clamp the mail slot door and the main door between the interior and exterior portions and to prevent movement of the mail slot door with respect to the main door. 
     An important aspect of the invention is that the mail slot door immobilizer is tamper resistant. In a preferred embodiment of the mail slot door immobilizer, the fastener extends through the mail slot door from the interior portion to the exterior portion. The exterior portion is provided with an opening which extends only partially through the exterior portion. The opening has a retaining surface which cooperates with a retaining surface of the fastener to retain the fastener within the opening. Because the opening extends only partially through the exterior portion, the fastener is not visible from the exterior side of the mail slot door, thereby discouraging tampering with the fastener. 
     Another aspect of the invention is the ease of installation and removal of the mail slot door immobilizer. The mail slot door immobilizer can be installed on existing mail slot doors. Once installed, the mail slot door immobilizer can easily be removed and replaced. 
     Another aspect of the invention is the relatively small surface area of the exterior portion of the mail slot door immobilizer. The mail slot door immobilizer is intended to be used primarily in commercial buildings. It is important to owners and occupants of such buildings that the overall appearance of the building or storefront not be degraded. The relatively small surface area of the exterior portion minimizes the impact of the mail slot door immobilizer on the appearance of the main door. It also facilitates the manufacture of the mail slot door immobilizer at low cost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a mail slot door immobilizer in accordance with the present invention mounted on a mail slot door of a main door. 
     FIG. 2 is a perspective view of the mail slot door immobilizer of FIG.  1 . 
     FIG. 3 is a horizontal cross-sectional view of the mail slot door immobilizer taken along the line  3 — 3  in FIG.  1 . 
     FIG. 4 is a front elevational view of the mail slot door immobilizer of FIG.  1 . 
     FIG. 5 is a rear elevational view of the mail slot door immobilizer of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A mail slot door immobilizer in accordance with the present invention is illustrated in FIG.  1 . The mail slot door immobilizer  10  is shown mounted on a mail slot door  12 . The mail slot door  12  is located within a main door  14  having a glass interior  16  and an aluminum frame  18 . 
     The arrangement of the mail slot door  12  and main door  14  shown in FIG. 1 is typical in commercial buildings. The mail slot door  12  rotates on a hinge  20  located adjacent the frame  18  of the main door  14 . A mail slot door frame  22  surrounds the perimeter of the mail slot door  12  and is secured to the glass interior  16  of the main door  14 . The mail slot door  12  is opened by rotating it about the hinge  20  with respect to the mail slot door frame  22  and main door  14 . 
     Referring to FIG. 2, the mail slot door immobilizer  10  includes an interior portion  24  and an exterior portion  26 . The interior and exterior portions  24 ,  26  are preferably fabricated from aluminum to blend with the appearance of a standard aluminum and glass door, but may be fabricated from any material of sufficient strength to resist bending or breaking by screwdrivers or similar items. 
     Each of the interior and exterior portions  24 ,  26  has a recessed area  28  defined by a base surface  30  and opposing wall surfaces  32 ,  33 . The interior portion  24  is positioned on the interior side of the mail slot door  12  so that it overlaps both the mail slot door  12  and the glass interior  16  of the main door  14 , as shown in FIGS. 1 and 3. The mail slot door frame  22  fits within the recessed area  28  of the interior portion  24 . 
     Referring to FIG. 3, the interior portion  24  is provided with openings  34  extending therethrough for receiving threaded fasteners  36 . The threaded fasteners  36  may be of any suitable type, such as standard, Phillips head, or Allen-type machine screws. 
     To install the mail slot door immobilizer  10 , holes  40  are drilled in the mail slot door  12  in register with the openings  34  in the interior portion  24 . Preferably, the holes  40  have a diameter only slightly greater than the diameter of the fasteners  36 . The interior portion  24  may be used as a template to mark the proper locations for the holes  40 . The interior portion  24  is then removed and the holes  40  are drilled through the mail slot door  12  at the marked locations. 
     Referring still to FIG. 3, the exterior portion  26  is provided with threaded openings  38  which extend only partially through the exterior portion  26 . The exterior portion  26  is positioned on the exterior side of the mail slot door  12  so that the threaded openings  38  are in register with the holes  40  in the mail slot door  12  and the openings  34  in the interior portion  24 . The fasteners  36  are inserted from the interior side through the openings  34  in the interior portion  24  and the holes  40  in the mail slot door  12 . The fasteners  36  extend into the threaded openings  38  in the exterior portion  26  and engage the threads of the threaded openings  28  to removably fasten the interior portion  24  to the exterior portion  26 . 
     The mail slot door immobilizer  10  prevents the mail slot door  12  from rotating with respect to the main door  14  by clamping the mail slot door  12  and main door  14  between the interior and exterior portions  24 ,  26 . The mail slot door  12  is not allowed to rotate about the hinge  20  toward the interior because the base surface  30  of the exterior portion  26  abuts the mail slot door frame  22 . Likewise, the mail slot door  12  is prevented from rotating toward the exterior because the base surface  30  of the interior portion  24  abuts the mail slot door frame  22 . 
     An important aspect of the invention is that the mail slot door immobilizer  10  is tamper resistant. Because the threaded openings  38  extend only partially through the exterior portion  26 , the fasteners  36  are not visible from the exterior side. As a result, tampering with the fasteners  36  is discouraged. Because the locations of the fasteners  36  are not evident from the exterior side, disabling of the mail slot door immobilizer  10  by drilling out the fasteners  36  is made more difficult. 
     The mail slot door immobilizer  10  is also resistant to tampering by prying of the exterior portion  26 . Preferably, the recessed area  28  is sized so that the base surface  30  of the exterior portion  26  abuts the mail slot door frame  22  when the fasteners  36  are fully tightened. As a result, it would be difficult to insert a screwdriver or other tool between the base surface  30  and mail slot door frame  22  in order to pry the exterior portion  26  from the mail slot door  12 . However, even if it is possible to insert a screwdriver between the base surface  30  and the mail slot door frame  22 , it would be difficult to pry the exterior portion  26  from the top or bottom because the fasteners  36  are engaged near the top and bottom of the exterior portion  26 . Thus, the lever arm created between the top or bottom of the exterior portion  26  and associated fastener  36  would be fairly insignificant. 
     The exterior portion  26  is relatively narrow horizontally. Desirably, the width of the exterior portion  26  is between 0.50 and 5.00 inches. More desirably, the width of the exterior portion  26  is between 0.75 and 3.00 inches. The width of the exterior portion is preferably 1.25 inches. Because the exterior portion  26  is relatively narrow, the lever arm created between either side of the exterior portion  26  and the fasteners  36  would likewise be fairly insignificant, thus making it difficult to pry the exterior portion  26  from either side. 
     The interior and exterior portions  24 ,  26  are relatively thick in a direction perpendicular to the plane of the mail slot door  12 . Desirably, the thickness of each of the interior and exterior portions  24 ,  26  is between 0.25 and 1.00 inches. More desirably, the thickness of each of the interior and exterior portions  24 ,  26  is between 0.40 and 0.75 inches. The thickness of each of the interior and exterior portions  24 ,  26  is preferably 0.48 inches. Because of the thickness of each of the interior and exterior portions  24 ,  26 , and the resulting strength of the mail slot door immobilizer  10 , any attempt to pry the exterior portion  26  from the mail slot door  12  would likely cause the glass interior  16  of the main door  14  to break. 
     The mail slot door immobilizer  10  also prevents opening of the mail slot door  12  by bending or bowing it. The holes  40  in the mail slot door  12  and fasteners  36  extending therethrough provide a secure attachment of the mail slot door  12  to the mail slot door immobilizer  10 . When the mail slot door  12  is bowed inwardly, the base surface  30  and wall surface  33  of the exterior portion  26  abut the mail slot door frame  22 , thereby preventing further bowing of the mail slot door  12 . Likewise, when the mail slot door  12  is bowed outwardly, the base surface  30  and wall surface  33  of the interior portion  24  abut the mail slot door frame  22 . 
     In addition, the interior and exterior portions  24 ,  26  are of sufficient height relative to the mail slot door  12  to prevent bowing of the mail slot door  12  at the top and bottom thereof. Desirably, the height of each of the interior and exterior portions  24 ,  26  is between 1.00 and 6.00 inches. More desirably, the height of each of the interior and exterior portions  24 ,  26  is between 2.00 and 4.00 inches. The height of each of the interior and exterior portions  24 ,  26  is preferably 3.00 inches. 
     Another aspect of the invention is the ease of installation and removal of the mail slot door immobilizer  10 . The mail slot door immobilizer  10  fits most existing mail slot door arrangements of the type shown in FIG.  1 . Installation of the mail slot door immobilizer  10  requires only the drilling of two small holes  40  in the mail slot door  12 . Once installed, the mail slot door immobilizer  10  can be removed and replaced simply by inserting or removing the fasteners  36  with a standard screwdriver or Allen wrench. 
     A further aspect of the invention is the relatively small surface area of the exterior portion  26  of the mail slot door immobilizer  10 . The mail slot door immobilizer  10  is intended to be used primarily in commercial buildings. It is important to owners and occupants of such buildings that the overall appearance of the building or storefront not be degraded. Desirably, the area of the surface of the exterior portion  26  which is parallel to the mail slot door  12  and main door  14  and which faces away from the mail slot door  12  and main door  14  is between 0.50 and 30.00 square inches. More desirably, the area of the surface of the exterior portion  26  which is parallel to the mail slot door  12  and main door  14  and which faces away from the mail slot door  12  and main door  14  is between 1.50 and 12.00 square inches. Preferably, this surface area is 3.75 square inches. Because of the relatively small surface area of the mail slot door immobilizer  10 , its impact on the appearance of the main door  14  is minimized, and the low-cost manufacture of the mail slot door immobilizer  10  is facilitated. 
     It will be apparent to those skilled in the art that some modification of the disclosed embodiment may be possible without departing from the spirit of the invention. For example, other means may be used to fasten the interior portion  24  to the exterior portion  26 . Instead of the threaded fasteners  36 , for example, a key lock in the interior portion  24  may be used to selectively engage a surface of the exterior portion  26  and thereby removably fasten the interior portion  24  to the exterior portion  26 . Therefore, the foregoing description is considered to be exemplary, and the true scope of the invention is that defined in the following claims.

Technology Classification (CPC): 8