Abstract:
A tamper-resistant light fixture having exceptional illuminance qualities, low energy consumption, and high resistance to unauthorized enclosure penetration.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of U.S. Provisional Application No. 61/377,764, filed Aug. 27, 2010, the disclosure of which is hereby incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates to the field of specialty lighting fixtures. 
     BACKGROUND 
     Numerous and varied environments require the use of reinforced, tamper or vandal resistant light fixtures. Tamper-resistant light fixtures are often used in prisons/jails, schools, hospitals, and industrial locations. Each of these environments presents unique challenges to providing safe, efficient, and high quality lighting. 
     For example, in prisons, jails or other types of custodial facilities, inmates often attempt to breach the housings of light fixtures in their rooms to hide contraband, start fires, or remove components to be used as weapons. Another example is, in schools, where juvenile delinquents and hooligans often attempt to damage or steal lighting fixtures. Yet another example is in healthcare facilities where light fixtures are often exposed to fluids or impacts. In addition, in some public areas, such as parks, walkways or parking lots, criminals attempt to destroy lighting fixtures to reduce visibility and illumination, thereby facilitating illicit activities under the cover of darkness. 
     Over the years, various surface-mounted lighting fixtures have been developed to provide for improved tamper-resistance. These have included “shoebox,” “clamshell,” and “unibody” style lighting fixtures. Shoebox designs generally involve a box housing with a hinged top. Clamshell designs normally have a door and sidewalls that are hinged to a pan. Unibody designs involve a housing formed from a unitary structure, as described in U.S. Pat. No. 7,431,473. 
     Unfortunately, available lighting fixtures have numerous drawbacks and shortcomings that make them less than ideal for custodial, school, healthcare and outdoor uses. One problem with many currently available lighting fixtures is their high energy consumption. Another problem is that they require frequent maintenance to change burned-out incandescent bulbs, fluorescent bulbs, ballast, or in some cases compact fluorescent bulbs. Still another problem is in their abysmally poor light quality and illuminance characteristics. This latter problem is particularly important in environments where poor light quality can have a deleterious effect on morale or mood. 
     SUMMARY 
     The foregoing problems and drawbacks associated with previously available tamper-resistant lighting fixtures are resolved or at least substantially improved and a technical advance is achieved in a vandal resistant lighting fixture according to the present invention. 
     In one embodiment of the present invention, a light fixture is disclosed having a housing with a base and a side wall(s) connected to the base. A support beam extends laterally from the housing wall(s) and away from a central axis of the housing. The support beam is provided with a securing recess(es) to connect the light fixture to a ceiling or other surface. In addition, the light fixture has one or more swing doors rotatably mounted to the housing wall such that the swing doors lock against the wall and limit access to the support beam. The swing doors can be locked with cantilevered snap fit prongs, for example. In addition, a polycarbonate resin thermoplastic lens is slidably mounted between the housing walls and end caps to form an enclosure that is resistant to attack or vandalism. 
     In addition, the light fixture is provided with pedestals connected to the base. The pedestals support a light source, such as a light emitting diode, which can be selectively controlled by a user. The resulting light fixture has exceptional illuminance characteristics. 
     In another embodiment of the present invention, a light fixture is disclosed having a housing with a base and a side wall(s) connected to the base. A cantilevered snap fit mounting bracket is configured to be snap fit mounted to the housing. The cantilevered snap fit mounting bracket is provided with securing recess(es) to connect the bracket and, in turn, the light fixture to a ceiling or other surface. In addition, a polycarbonate resin thermoplastic lens is slidably mounted between the side walls and end caps to form an enclosure that is resistant to attack or vandalism. 
     Numerous additional embodiments of the present invention will become apparent to one of ordinary skill in view of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a front perspective view of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 2  illustrates a bottom perspective view of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 3  illustrates a perspective bottom view of a vandal resistant light fixture without the lower cap  20  according to one aspect of the present invention; 
         FIG. 4  illustrates a bottom side view of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 5  illustrates a bottom side view of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 6  illustrates a partial bottom view of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 7  illustrates a top view of an upper and a lower end cap of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 8  illustrates a side view of an end cap of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 9  illustrates a perspective side view of a seal of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 10  illustrates a top view of an LED panel board of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 11  illustrates a block diagram of a power supply and LED controller circuit in accordance with one embodiment of the present invention; 
         FIG. 12  illustrates a bottom perspective view of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 13  illustrates a side view of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 14  illustrates a bottom perspective view of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 15  illustrates a back perspective view of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 16  illustrates a bottom perspective view of a vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 17  illustrates a top view of an enclosed vandal resistant light fixture according to one aspect of the present invention; 
         FIG. 18  illustrates a partial cutout of a top view of a vandal resistant light fixture according to one aspect of the present invention; and 
         FIGS. 19 and 20  illustrate a partially exploded, perspective top view of a vandal resistant light fixture according to one aspect of the present invention. 
         FIG. 21  illustrates a perspective bottom view of a vandal resistant light fixture with the lower cap  20  removed showing different light sources  61 . 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description and the appended drawings describe and illustrate exemplary embodiments of the invention solely for the purpose of enabling one of ordinary skill in the relevant art to make and use the invention. As such, the detailed description and illustration of these embodiments are purely exemplary in nature and are in no way intended to limit the scope of the invention, or its protection, in any manner. It should also be understood that the drawings are not to scale and in certain instances details have been omitted, which are not necessary for an understanding of the present invention, such as conventional details of fabrication and assembly. 
     Turning to the drawings,  FIGS. 1-2  generally illustrate one preferred embodiment of a vandal resistant light fixture  10 . Referring to  FIG. 1 , fixture  10  includes a vandal resistant housing  14 , upper and lower end caps  18  and  20 , respectively, and a lens  24 . In addition, as best illustrated in  FIGS. 4-5 , a light emitting diode (LED) panel board  56  having an array of LEDs  60  is mounted within housing  14  on inclined pedestal  106 . Light sources can be selected from the group consisting of a light emitting diode, an incandescent bulb, a fluorescent bulb, and a compact fluorescent bulb. The LEDs  60  are powered by a power supply  68 , which can be provided within power supply housing  64  ( FIGS. 3-5, 12-15 ). In one embodiment, a LED controller circuit  124  is positioned adjacent lens  24  and allows a user to tap lens  24  proximate the LED controller circuit to turning on, off, or adjusting the intensity of illumination. As illustrated in  FIGS. 3-5 , housing  14  can be anchored to a surface such as a ceiling or wall with anchors connected through mounting bores  144 . In an alternative embodiment, as illustrated in  FIGS. 12-14 , housing  14  can be securely fastened or anchored to a surface such as a wall or ceiling with cantilevered snap-fit mounting bracket  102  with cantilevered snap fit prongs  120 . 
       FIGS. 1-3  illustrate housing  14 . Housing  14  is preferably formed from a hard material that can withstand severe, repeated impacts. For example, in one preferred embodiment, housing  14  is formed from an extruded metal alloy such as aluminum  6063  cut to a desired length. As shown in  FIGS. 3-5, and 12-14 , housing  14  includes a base  30  and side walls or pillars  86 . Base  30  and pillars  86  form an interior, open-ended, U-shaped channel that houses LED panel board  56 . 
     An impact-resistant, polycarbonate lens  24  ( FIG. 1 ) and end caps  18  and  20  ( FIGS. 1, 2, and 7 ) fully enclose housing  14 . Lens  24  is preferably made of a highly impact resistant, translucent material such as a polycarbonate resin thermoplastic. One preferred brand of polycarbonate resin thermoplastic is Lexan (R), which can be acquired from SABIC Innovative Plastics, Pittsfield, Mass. Lens  24  is selected based on the maximum level of impact likely to be encountered in a particular application. For example, for prisons and jails, relatively thick polycarbonate is necessary to provide a significant impact and penetration barrier. Schools, on the other hand, are likely to need a somewhat thinner lens. In addition, lens  24  is preferably provided with translucent characteristics, i.e., frosting, that diffuses light emitted from the LEDs. 
     Lens  24  is slidably mounted to housing  14 , as shown in  FIGS. 3-6 . In one preferred embodiment illustrated at  FIG. 3 , lens  24  is positioned between opposing pillars  86  ( FIG. 8 ). More particularly, lens  24  is retained in a groove formed by a skirt  84 . Once lens  24  is properly positioned, end caps  18  and  20  secure lens  24  to housing  14 . Additionally, a lens support  164  is provided to prevent flexing of lens  24  to a point where it could crack or be displaced from skirt  84 . 
       FIGS. 1 and 2  illustrate the use of top and bottom end caps  18  and  20  to enclose the top and bottom ends of housing  14 . Preferably, top and bottom end caps  18  and  20  are secured to housing  14  by one-way or security screws  128  ( FIGS. 1-2 ) inserted through bores  36  ( FIG. 7 ) in end caps  18  and  20  and into bores  37  ( FIG. 4 ) in housing  14 . Alternative means of securing end caps  18  and  20  to housing  14  will be apparent in view of the present disclosure to one of ordinary skill. End caps  18  and  20  are preferably formed from a metal alloy or other rigid material that is impact resistant. In addition, to improve moisture resistance of housing  14 , a gasket  90  can be used between each end cap and the housing. Gasket  90 , as illustrated in  FIG. 9 , is preferably provided with bores  39  that correspond with bores  36  and  37  to facilitate installation of the end caps. A seal or sealant can also be used in connection with skirts  84  to improve moisture resistance. 
     In one preferred embodiment illustrated in  FIGS. 1-6 , a locking mounting mechanism prevents unauthorized removal of housing  14  from the mounting surface on which fixture  10  is mounted. In this preferred embodiment, fixture  10  is mounted to a mounting surface with fasteners inserted through bores  144  ( FIG. 3 ) provided through lateral beam  48 . Once fixture  10  is securely mounted to the mounting surface, exterior swing doors can be moved to a locked position. In particular, as best shown in  FIGS. 4-6 , exterior swing doors  32  are hinged on one end with a hinge barrel  46  that pivots about hinge pivot  44  on lateral beam  48 . The opposite end of the exterior swing doors  32  includes a cantilevered a snap fit  40 , and tongue  42 . When swing doors  32  are moved to a closed position  80  ( FIG. 3 ), cantilevered snap fit  52  engages snap fit recess shoulder  72 , thus securing the doors  32  shut. Tongue  42  seats within groove  50  and prevents access to the cantilevered snap fit  52 , and thus opening the swing doors. 
       FIGS. 16-20  illustrate an alternative mechanism for locking swing doors  32 . In particular, a one-way or security screw  172  can be used to restrict movement of swing doors  32 . In this embodiment, instead of a cantilevered snap fit, swing doors  32  are provided with tongue  176 . As shown in  FIG. 19 , tongue  176  is configured to seat in groove  72 . In this embodiment, groove  72  is provided with a bore  180  for receiving screw  172 . When the swing doors are in a closed position ( FIGS. 19-20 ), upper cap  18  and lower cap  20  can be positioned over housing  14  such that bore holes  128  align with fastening bores  37 . When caps  18 ,  20  are in position, screws  172  can be screwed into bore  180 , thereby restricting movement of tongue  176  and, in turn, securing swing doors  32  ( FIG. 18 ). It should be noted that, although  FIG. 18  illustrates screw  172  in its final position, an end cap is not shown in order to more clearly illustrate the function of screw  172  in preventing movement of tongue  176 . In one preferred embodiment, screw  172  can be inserted over caps  18  and  20  ( FIG. 17 ). 
       FIG. 11  discloses a block diagram of the electronic components of the fixture  10 , and in particular, an LED controller circuit  124 . As illustrated, a power supply  68  is connected to the facility current point  136 , which can be an electrical outlet or other alternating current source (for example, 90vAC-277vAC). Power supply  68  is configured to provide approximately 15-30 volts of Direct Current to an LED controller circuit  124 . As shown in  FIG. 11 , LED controller circuit  124  includes a pulse width modulator  152  (PWM), a capacitance sensor reader  156  (in a preferred embodiment, CapSense Successive Approximation (CSA) reader), a capacitance sensor  160  for controlling light intensity, a FET (field-effect transistor) drive circuit  140  and the LED panel board  56 . In this embodiment, the signal from the capacitance sensor  160  controls PWM  152  so that pulses of different width are outputted to control the light intensity. PWM  152  signals are amplified by FET  140  to drive the LEDs  60 . Accordingly, in a preferred embodiment, a user can turn on, turn off and adjust the brightness of one or more LEDs  60  (or groups of LEDs in other embodiments) in fixture  10 . 
     The use of a capacitance sensor situated inside housing  14  allows a user to control the light without an external switch that is susceptible to impact, damage or removal. That is, in some embodiments, the light intensity may be selectively increased or decreased by tapping a capacitance sensor that, for example, may be attached to the inner side of the lens. In a preferred embodiment there is a multiple tap, more preferably three tap dimming cycle. In certain preferred embodiments, including those with multiple tap dimming cycles, the light may be set so that there is never an option for the light to be in a full off position, thereby increasing the lifespan of the electronics. 
     Complete enclosure of fixture  10  traps heat generated during operation. In certain embodiments, this may lead to accumulation of excess heat that could damage parts of the light fixture  10 . In certain preferred embodiments, a board for mounting the LEDs, preferably an FR4 board, includes a number of orifices  94  and metal plates  98  on a side of the board opposite to the LEDs to assist in diffusing heat generated by the LEDs. Similarly, in other preferred embodiments, a board for mounting the LED controller includes a number of orifices and/or includes one or more metal plates on a side of the board opposite to the LED controller to assist in heat diffusion from the LED components. 
     Referring now to  FIG. 4 , the LED panel board  56  ( FIG. 10 ) is mounted to a pedestal  106  with heat diffusers  146  and  148 . As illustrated in  FIGS. 4-6 and 12-14 , each of the two pedestals  106  are inclined toward a central portion of housing  14 . This pedestal arrangement creates a cone of light  114  and  118  ( FIG. 4 ) that provides high quality illuminance, as illustrated in Table 1 below. In one preferred embodiment, 32 LEDs are used to provide a vertical spread of illuminance of approximately 93.3 degrees, and a horizontal spread of illuminance of approximately 99.8 degrees. As a result, fixture  10  provides a cone of light and foot candles as disclosed in the following Table 1. 
     The foregoing detailed description provides exemplary embodiments of the invention and includes the best mode for practicing the invention. The description and illustration of embodiments is intended only to provide examples of the invention and not to limit the scope of the invention or its protection in any way.