Abstract:
This invention is a guard for preventing the vandalism of the keypad of a telephone. If the telephone is a pay telephone, the invention further prevents, thus preventing entry into the telephone money box from the upper housing area. The telephone guard, composed of an upper housing guard and a keypad guard, is secured by high strength visible fasteners to the upper housing of a pay telephone. The upper housing guard and keypad guard are mated tightly to prevent vandals from prying off the keypad guard. The thickness of the keypad guard is greater than the throw length of the push buttons of the keypad. Thus, the force of a blow to the keypad will be absorbed by the front of the guard rather than the push buttons.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates generally to a guard that prevents the destruction and vandalism of the keypad of a telephone. Specifically, this invention is a keypad guard mated into an upper housing guard to form a telephone guard for a telephone upper housing. The keypad guard is of sufficient strength to prevent damage to the telephone keypad, and prevents access to the money in a coin vault of a pay telephone via an opening created by destruction of the keypad. 
     Over a prolonged period of time, a large amount of coin money is retained within the vault of a pay telephone. Due to their normally isolated and unprotected location, pay telephones are the subject of frequent vandalism attempts. Vandals use a variety of means to gain access to the pay telephone vaults, including smashing through the keypad, which is typically positioned within the pay telephone directly above the open-top coin vault drawer. The present invention is directed to preventing vandalism to the telephone keypad, and to preventing access to money in the pay telephone coin vault by protecting the keypad assembly. 
     2. Related Art 
     Several inventions aimed to prevent the vandalism of pay telephone keypads are known to the prior art. Illustrative of such inventions are U.S. Pat. No. 5,509,057 issued to Anello and U.S. Pat. No. 4,160,136 issued to McGough. Both patents teach the use of embossed mini-housings around each push button of the keypad. McGough requires retrofitting the keypad with L-shaped buttons that afford a smaller side surface area to minimize lateral force from a detrimental source. Anello teaches the use of full length and width double face plates, which adds additional weight and cost of material to the pay telephone without affording significant additional keypad protection over a standard face plate. 
     Other prior art known in the field of guarding pay telephones includes single piece face plates. Prior art face plates are typically made of light metal or heavy plastic, which affords minimal security protection to the telephone. 
     It would thus be beneficial to the prior art to provide a telephone keypad guard constructed of high strength material that prevents a vandal from damaging the telephone keypad, and from smashing out the keypad to gain access to the money in the pay telephone coin vault. 
     The prior art would also benefit from a keypad guard that is relatively inexpensive, simple to manufacture, has a secure exterior appearance and requires minimal retrofitting of the existing pay telephone. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, the objectives of this invention are to provide, inter alia, a new and improved telephone keypad guard that: 
     protects the telephone keypad from striking blows or other vandalism; 
     prevents a vandal from smashing through the keypad to gain access to money in the coin vault; 
     is relatively inexpensive and simple to manufacture; 
     requires no retro-fitting of the pay telephone keypad; and 
     can be installed quickly and easily. 
     These objectives are accomplished by the structure and use of the inventive telephone guard, composed of an upper housing guard and a keypad guard, both of which are mated and secured by high strength visible fasteners to the upper housing of a telephone. A first critical feature of the invention is the close inset mating of the upper housing guard and the keypad guard, which prevents prying off the keypad guard. A second critical feature of the telephone guard is the thickness of the keypad guard. Each push button of the keypad has a throw distance, defined as the distance required to depress the keypad push button until an associated electrical switch is engaged, thus completing the electrical circuit signaling the entry of the number or function associated with the keypad push button. In the prior art, keypad push buttons are oriented such that their throw distance is reached before the keypad push button front face recedes beyond the face of the faceplate cover. In the present invention, the thickness of the keypad guard is such that the keypad push button is fully depressed only when it is flush with the keypad guard. The keypad guard alignment prevents damage to the keypad push buttons and their associated electrical switches when struck by excessive force. This damage protection further prohibits access to the interior of the telephone and money in the coin vault. 
     Other objects of the invention will become apparent from time to time throughout the specification hereinafter disclosed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of the telephone guard secured to the upper housing of a pay telephone. 
     FIG. 2 is a front view of the upper housing guard and keypad with the keypad guard removed. 
     FIG. 3 is a front view of the keypad guard. 
     FIG. 4 is a partial cross sectional view along cross section A shown in FIG. 1 of the keypad guard of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is shown in FIGS. 1-4 generally as telephone guard  10 . FIG. 1 illustrates telephone guard  10  attached to prior art pay telephone upper housing  35 . Telephone guard  10  includes upper housing guard  40 , made from a first flat plate, typically high strength stainless steel or similar strength metal, having the same general planar dimensions as the front face of upper housing  35 , and keypad guard  45 , made from a second smaller flat plate, also typically high strength stainless steel or similar strength metal. Alternatively, telephone guard  10  can be constructed of a non-metallic high strength material capable of being attached to upper housing  35  as described herein. In either embodiment, the material from which telephone guard  10  is constructed should be of sufficient strength and thickness to protect against heavy striking blows from vandals. 
     Upper housing guard  40  and keypad guard  45  are shown separately in FIGS. 2 and 3 respectively. 
     Telephone guard  10  includes cavities affording access to functional components of telephone  30 . These functional components include coin payment slot  80 , volume control cavities  71 , coin return lever  85 , handset cradle  90  and dialing information panels  95 . Telephone guard  10  also includes cavities affording access to keypad  20 , comprising a plurality of keypad push buttons  65 . 
     Telephone guard  10  provides protection for keypad  20  through the mating of upper housing guard  40  and keypad guard  45 . Upper housing guard  40  is secured to upper housing  35  by a secure form of attachment known in the art of mechanical assembly. For example, upper housing guard  40  may be welded to the front face (not shown) of upper housing  35 . Alternatively, upper housing guard  40  may be bolted to the front face of upper housing  35  with nuts positioned in the interior (not shown) of upper housing  35 , said nuts securing threaded or self-threading studs, bolts, machine screws or similar mechanical fasteners. Typically, upper housing guard  40  is secured to the front face of upper housing  35  with twelve threaded or self-threading studs of ⅛″ diameter and ½″ length projecting from upper housing guard  40  through upper housing  35 . 
     FIG. 2 shows upper housing guard  40 , including recessed section  50 . Recessed section  50  includes a plurality of passage holes  57 , which align with attachment holes (not shown) in the front face of upper housing  35 . FIG. 3 depicts keypad guard  45  having a plurality of fastener insets  47 , preferably at least four. 
     Fastener insets  47  may be countersunk circles, or in the preferred embodiment, square holes concentric with countersunk circles to secure carriage bolts used as visible fastener  60 . Visible fasteners  60  are externally visible to convey an appearance of structural substance, in order to deter vandalism. Visible fasteners  60  may be carriage bolts, flat face security screws or other similar high strength fasteners. In the preferred embodiment, visible fasteners  60  are oversized at {fraction (3/16)}″ nominal diameter. 
     In the preferred embodiment, visible fasteners  60 , as shown in cross section in FIG. 4, are carriage bolts  61  or flat top bolts  63 , each having square bolt shaft sections  49  and round shaft sections  58 . Carriage bolts  61  are used to provide the visual evidence of the security strength of visible fasteners  60 . Flat top bolts  63  provide the same appearance in a slightly modified form for typically indoor use. Both carriage bolts  61  and flat top bolts  63  shown in FIG. 4 resist shaft rotation during tightening through the mating of concentric square holes  48  and square bolt shaft sections  49 , as shown in FIG.  3  and FIG.  4 . In the preferred embodiment, each visible fastener  60  includes a visible fastener head  62 , round shaft section  58 , square bolt shaft section  49 , standard nut  52  and self locking nut  54 . Visible fastener heads  62  seat in fastener insets  47 . The seating may be such that the top of visible fastener head  62  is flush, inset or superior to keypad guard front face  75 . In the preferred embodiment, the seating is inset, as shown in FIG.  4 . The shaft of visible fasteners  60  axially traverse through passage holes  57  and the aligned attachment holes in the front face of upper housing  35 . In an alternative embodiment, the shaft of visible fasteners  60  may extend through central cavity  55  of upper housing guard  40  to connect through the attachment holes in the front face of upper housing  35 . 
     The shaft is secured within the interior of upper housing  35  with standard mechanical hardware, typically nuts. In the preferred embodiment depicted in FIG. 4, round shaft sections  58  are secured first by standard nut  52  and then self-locking nut  54 , to prevent removal of visible fasteners  60 . Thus, keypad guard  45  further secures upper housing guard  40  to the face of upper housing  35 . This provides an additional plurality of oversized fasteners securing upper housing guard  40  to upper housing  35 . 
     Within recessed section  50  is central cavity  55 , which affords axial passage of keypad  20  and plurality of keypad push buttons  65  through upper housing  35  and through keypad guard  45 . Keypad guard  45  includes a plurality of push button cavities  46 , typically twelve in number aligned in four rows of three each. Central cavity  55  is aligned behind plurality of push button cavities  46 , affording passage to the plurality of keypad push buttons  65  from upper housing  35 . 
     A critical feature of telephone guard  10  is the mating of recessed section  50  of upper housing guard  40  and keypad guard  45 . To prevent a vandal from prying off keypad guard  45 , keypad guard  45  and recessed section  50  must be closely matched in shape. Typically, both keypad guard  45  and recessed section define a similar shape. Recessed section  50  further defines recessed section inner perimeter  53 . Keypad guard  45  further defines keypad guard outer perimeter  43 . Keypad guard outer perimeter  43  is uniformly slightly smaller than recessed section inner perimeter  53 , such that gap  44  is defined between keypad guard outer perimeter  43  and recessed section inner perimeter  53 . Gap  44  is preferably no greater than {fraction (1/64)} inch. The small size of gap  44  prevents the insertion of a prybar or similar tool from being inserted into gap  44 , which would afford a vandal adequate leverage to pry off keypad guard  45 . To further prevent in the alternative embodiment, keypad guard  45  has beveled edges  41 , to prevent lateral blows from damaging or knocking off keypad guard  45 . 
     Another critical feature of telephone guard  10  is the thickness of keypad guard  45 . Keypad guard  45  is of sufficient thickness and strength to prevent smashing of keypad push buttons  65  and keypad  20 . Further, each keypad push button  65  has a throw distance, defined as the distance required to depress keypad push button  65  until an associated electrical switch is actuated, thus completing the information electric circuit signaling the entry of the number or function of keypad push button  65 . In the prior art, keypad push buttons  65  are oriented such that their throw distance is reached before keypad push button front face  70  recedes beyond the face of the keypad grid cover. In the present invention, the thickness of keypad guard  45  is of a sufficient dimension such that, when keypad guard  45  is mated with recessed section  50  to define a mated thickness, keypad push button front face  70  is flush with keypad guard front face  75  when the throw distance has been reached to engage the mechanism of each keypad push button  65  as described above. This alignment prohibits damage to keypad push buttons  65  and their associated electrical switch when struck frontally by a heavy blow to keypad guard  45 . This damage protection further prohibits access to the interior of upper housing  35  of telephone  30  and the coin vault (not shown). Vandals are unable to smash keypad  20  with a hammer or like heavy instrument normally used when trying to gain illicit access to a coin vault. This prevents deforming of the internal workings of keypad  20 , and so passage to the interior of telephone  30  remains blocked. Further, plurality of keypad push buttons  65  remain within push button cavities  46 , and keypad guard  45  remains resistant to instrument picking and striking attacks. 
     In the preferred embodiment, the thickness of keypad guard  45  is greater than the depth of recessed section  50 . As depicted in the cross section  4  in FIG. 4, keypad guard  45  has beveled edges  41 , creating a sloped face above upper housing guard  40 , preventing leveragable prying points which would damage the keypad guard  45  from a chisel or similar destructive device. 
     In an alternative embodiment, keypad guard  45  can be secured to upper housing  35  by drilling holes directly through an existing prior art single piece face plate into upper housing  35 , and securing keypad guard  45  to upper housing  35  with mechanical fasteners or similar fastening means. Typically, the prior art single piece face plate is secured to upper body housing  35  by a plurality of self-threading studs, typically twelve in number. In this embodiment, the keypad guard  45  must be sufficiently thin to allow full travel of plurality of keypad push buttons  65  as described above, when keypad guard  45  is laid over the existing prior art single piece face plate, yet still sufficiently thick to afford the protection to plurality of keypad push buttons  65  described above. 
     The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated construction may be made within the scope of the appended claims without departing from the spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents.