Abstract:
An improved streetlamp featuring separate compartments for the lamp, ballast, photocell and wiring is provided. All electrical components of the streetlight are sealed from the elements and infestation from insects such as bees and wasps. All of the compartments may be readily opened without the use of tools and each electrical component and the light-glass can be readily removed and replaced with simple hand tools. Features for improved heat transfer to the atmosphere which results in a cooler running and longer lasting lamp are also provided.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to energy efficient streetlights and more particularly to an improved housing and assembly for an energy efficient streetlight wherein all major components of the lighting system may be readily removed from the housing for “in the field replacement” and wherein the housing features improved heat dissipation and isolation, among other improvements. 
       BACKGROUND OF THE INFORMATION 
       [0002]    In recent years, there have been substantial improvements in streetlight technology. Previously, high intensity discharge (“HID”) streetlights typically used mercury-vapor, high pressure sodium or metal-halide lamp technologies. Recently, newer technology electrodeless induction, LED or plasma lamps have become to be used in streetlight applications. These lamps have several advantages over older HID systems which use magnetic ballasts. In particular, the newer energy efficient technologies last 5-10 times longer, experience significantly less degradation in light output over their service lives, offer a higher quality of light and are more energy efficient. 
         [0003]    Induction lamps do, however, have certain drawbacks, mainly higher initial cost and heat sensitive components which compromise system life and performance. However, the greatly increased service life of induction lamps over that of other HID lamps offsets the increased initial costs and the heat sensitive components used in an induction lighting system can be protected via improvements to the streetlamp housing. High temperatures affect both the electrical and lamp components typically located inside the streetlight, which in turn will reduce overall service life of the system. Reducing the operating temperature of induction lamps by dissipating heat from the lamp by way of an improved housing as well as isolating heat sensitive electrical components from the lamp can significantly extend the life of the system. Improved lamp life is an important aspect of streetlight design because streetlights are typically mounted at the top of tall light-poles, which makes servicing in the field difficult and costly. 
         [0004]    Another important aspect of streetlight housing design is serviceability and installation. Serviceability is particularly important in streetlights because streetlights are typically located along busy roads and highways and, as mentioned, are also typically located at the top of tall light-poles. The service of streetlights poses unusual dangers to workers because the lamps are typically located at substantial heights and therefore require special equipment to reach, and are typically situated in locations exposed to the hazards of vehicular traffic. In addition, streetlights must often be serviced “live,” i.e. with the power on, because it is frequently not practical to shut off power along an entire road or freeway for the purpose of servicing one particular streetlight. Replacement of lamps and their associated electrical components, i.e. the ballast, with the power on exposes maintenance workers to yet another inherently dangerous condition. Also, not infrequently, workers servicing streetlamps face a hazard of the natural type, namely bees, wasps or other insects that have built a nest inside the streetlight housing. In view of the worker hazards involved, it is desirable that streetlights be easy and quick to service. 
         [0005]    It is also desirable that streetlights be quickly and easily serviced due to the high costs of maintenance. The costs associated with servicing a streetlight include replacements parts costs for the lamps, electronics and glass, but more importantly include the costs of a service crew. The costs of a service crew are significant and include worker salaries, training and insurance, as well as the cost of trucks equipped with lifts capable of reaching the streetlights. 
         [0006]    There is a need in the art for a streetlight that provides improved cooling for the newer technology induction lamps and provides improvements in the lamp housing that reduce the time required to service and install the light. Even a relatively small reduction in the time required to service an individual streetlight leads to improved worker safety and substantially decreased costs given that municipalities must service relatively large numbers of lights. Even small municipalities typically must maintain and service several hundred streetlights while large cities are faced with the task of servicing tens of thousands. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention streetlight improves upon the prior art by providing improved cooling for the newer technology induction lamps and by providing improvements in the lamp housing that reduce the time required to service the light. In its most basic form, the new streetlight comprises a main housing which includes separate, sealed, compartments for the induction lamp and the ballast or lamp electronics. Another separate compartment is provided for the photocell, the terminal block and the mast clamps. The lamp compartment of the housing features a multiplicity of heat sinks for conducting heat out of the compartment and into the housing where the heat is dissipated in the atmosphere through a combination of convection cooling and radiation. By providing separate lamp and ballast compartments, the ballast is better protected from the heat loading by the lamp. The ballast is further protected from heat by being attached to a finned heat sink (which also serves as a compartment cover). The mast clamps of the new streetlight are able accommodate a wide range of mast diameters from about 1¼″ to about 2½,″ or essentially all diameters in common use in the United States. Each of the compartments is sealed from elements and infestation from insects. In addition, the present invention streetlight includes features that allow each compartment of the light to be opened without the use of tools and the principle electrical components of the light, i.e. the lamp, ballast, and photocell can all be easily removed and replaced with simple hand tools, i.e. nothing more than a screwdriver. The light-glass which may occasionally require replacement due to breakage may also be easily removed with simple hand tools, i.e. a screwdriver. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a side view of the present invention streetlight. 
           [0009]      FIG. 2  is a top plan view of the streetlight  FIG. 1 . 
           [0010]      FIG. 3  is a bottom plan view the streetlight of  FIG. 1 . 
           [0011]      FIG. 4  is an end view of the streetlight of  FIG. 1  looking towards the end of the streetlight that is affixed to a mast or light-pole. 
           [0012]      FIG. 5  is an end view of the streetlight of  FIG. 1  looking towards the free end of the streetlight. 
           [0013]      FIG. 6  is an end perspective view of the streetlight of  FIG. 1  looking towards the end of the streetlight that is affixed to a mast or light-pole and showing the streetlight with the ballast and mast compartment covers open. 
           [0014]      FIG. 7  is a top plan view of the streetlight of  FIG. 1  showing the streetlight with the ballast and mast compartment covers open. 
           [0015]      FIG. 8  is a side perspective view, partially exploded, of the streetlight of  FIG. 1  showing the streetlight with the lamp compartment cover or lid open. 
           [0016]      FIG. 9  is a top view of the streetlight of  FIG. 1  showing the streetlight with the lamp compartment cover or lid open and with the lamp and reflector removed to reveal internal details. 
           [0017]      FIG. 10  is a side view of an induction lamp suitable for use with the present invention streetlight of  FIG. 1 , showing he base supports for the induction lamp and their ribbed or finned cooling surfaces. 
           [0018]      FIG. 11  is a top view of an induction lamp suitable for use with the present invention streetlight of  FIG. 1  showing the clamp and ribbed cooling surfaces of the supports for the induction lamp. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    The present invention will now be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The invention may, however, may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
         [0020]    With reference to  FIGS. 1 through 11 , the present invention streetlight  10  includes a main housing  12  having an outer surface  13 . The main housing  12  includes a lamp compartment  40  (see  FIGS. 8-9 ), a ballast compartment  42  (see  FIG. 6 ), and mast compartment  44  (see  FIG. 7 ). Located within the lamp compartment  40  of the main housing  12  are a lamp  26  and a reflector  24  (see  FIG. 8 ). Located within the ballast compartment is a ballast (lamp electronics)  32 . Located within the mast compartment  44  is a photocell  18  and a terminal block  34  which interconnects the electrical wiring between the lamp  26 , ballast  32  and photocell  18 . (Best shown in  FIG. 7 .) The lamp  26 , ballast  32 , and photocell  18  are connected in electrical circuit and the ballast  32  is connected to an external source of electrical power which is typically introduced to the streetlight  10  through a mast  38  and light-pole (not shown) to which the streetlight  10  is connected. 
         [0021]    Referring now to  FIGS. 2-5 , and  8 - 9  in particular, the lamp compartment  40  is closed out by a lid  16  which is hinged to the main housing at one end by hinges  28 . At the end of the lid  16  opposite the hinge, the lid  16  latches to the main housing  12  via a latch  30 . Formed in the lamp compartment  40 , about its periphery, is a channel  48  for the receipt of a seal  46 . The channel  48  and seal  46  run the full length of the periphery of the lamp compartment  40 . The lid  16  includes a sealing edge  50 . When the lid  16  is closed and latched via latch  30  to the main housing  12 , the sealing edge  50  contacts the seal  46  located in the lamp compartment  40  and thereby seals the lamp compartment  40  and the lamp  26  and reflector  24  contained therein from the elements, i.e. from the weather. The latch  30  allows the lid to be opened and closed without the use of tools in most instances and thereby reduces the time needed to service, i.e. change-out, the lamp. 
         [0022]    With reference to  FIG. 9 , in addition to the seal  46  for the lid  16 , the lamp compartment  40  of the main housing  12  also includes a plurality of reflector supports  52 . The reflector supports  52  support the reflector  24  and serve as heat sinks to conduct heat out of the lamp compartment  40 . In one embodiment, the reflector supports  52  are integrally cast with the main housing  12 . All of the reflector supports are in physical contact with the reflector  24  for the purpose of conducting heat from the reflector. Though all of the supports are in contact with the reflector, typically, only certain of the supports will include holes  60  which accept fasteners (such as screws) which attach the reflector to the supports and thus securely hold the reflector and lamp  26  within the lamp compartment  40 . 
         [0023]    Referring now to  FIG. 8 , the lid  16  which closes out the lamp compartment  40  of the main housing  12  includes a light-glass  22 . The light-glass  22  is secured to the lid  16  by a plurality of clamps  94 , which attach to the lid by means of screws. Sandwiched between the light-glass and a supporting lip  19  formed into the lid  16  is a seal  96  which prevents water or insect intrusion into the lamp compartment through the light-glass/lid interface. The light-glass  22  may be easily removed from the lid for cleaning or replacement as the clamps  94  holding the glass to the lid require nothing more than a screwdriver or removal. The hinges  28  (best shown in  FIG. 4 ) are sufficiently durable so as to prevent the light-glass from “flopping around” when the lid is opened. 
         [0024]    With reference to  FIGS. 8-11 , each lamp includes one or more lamp standoffs  54  which function to stand the lamp  26  off from the reflector  24  and to secure the lamp  26  within the lamp compartment  40 . The standoffs  54  comprise a clamp assembly  56 , which in one embodiment comprises a split-ring clamp, and a base portion  58  for interfacing with the reflector  24  and reflector supports  52 . The lamp standoffs also include a plurality of cooling fins or ribs  57  spaced radially about the perimeter of the standoffs. (See  FIG. 10 .) The lamp standoffs  54  will typically be made of aluminum though other heat resistant materials such as zinc alloys and various grades of thermoplastics are suitable and known in the art. The base portion  58  of the lamp supports  54  include holes  60  which align with like holes  60  in the reflector  24  and reflector supports  52  so that the reflector and lamp, via the lamp supports, may be secured to the main housing, via the reflector supports, by one set of fasteners. 
         [0025]    In operation, much of the heat generated by the lamp  26  is absorbed by the reflector  24  and conducted out of lamp compartment by the reflector supports/heat sinks  52 . Heat is conducted from the reflector supports to the outer surface  13  of the main housing  12 . Heat is transferred from the outer surface  13  of the main housing  12  to the atmosphere via convection cooling. The ambient air temperature surrounding the streetlight  10  will in virtually all cases be at a cooler temperature than the main housing after a few minutes of lamp operation. Thus, convection cooling occurs from the main housing to the atmosphere. 
         [0026]    Referring now to  FIGS. 6-7 , the main housing  12  also features a ballast compartment  42 . The ballast compartment  42  is separate from the lamp compartment  40  because the ballast electronics  32  are heat sensitive and it is desirable to isolate the ballast  32  from heat loading caused by the lamp  26 . The inventor has found that enclosing the ballast in a compartment separate from that of the lamp substantially reduces heat loading from the lamp. The ballast compartment is closed out by a closeout  62 . The closeout  62  includes cooling fins  66 . The ballast  32  is mounted directly to an interior surface of the closeout  62 . Heat generated by the ballast  32  is conducted through the closeout  62  and transmitted via convection, i.e. air flow past the cooling fins  66  to the atmosphere. Electrical connection between the ballast and the lamp is made via wiring which passes through a pass-through plug  70 . The pass-through plug  70  may be made from a heat resistant plastic or other material that is has good thermal and electrical insulation characteristics. 
         [0027]    The ballast  32  includes a ground wire  102 . The ground wire  102  is secured to the inside of the ballast compartment to prevent removal, either accidentally or due to an act of vandalism, when the streetlight is in use. 
         [0028]    Because the ballast  32  may occasionally fail during service and need to be replaced, the ballast closeout  62  is removably attachable to the main housing  12  via screws  64  equipped with large knobs. The knobs of the screws  64  are sufficiently large so as to allow the screws to be screwed and unscrewed without the use of tools in most instances. The ballast closeout  62  includes a weather seal  68  which encircles the periphery of the closeout  62 . When the closeout is fastened to the ballast compartment  42  by the screws  64 , the weather seal  68  contacts an outer edge or lip  74  of the ballast compartment  42  and thereby seals the compartment from the elements. The weather seal  68  may be made from numerous elastomeric materials as is known in the art. 
         [0029]    With continued reference to  FIGS. 6 and 7 , the main housing  12  also includes a mast compartment  44 . The mast compartment  44  is closed out by an upper cover  14  that is attached to the main housing  12  at one end by a hinge  20 . The mast compartment  44  and associated upper cover  14  have a hinged end  98  and a mast opening or mast receipt end  100 . (See  FIG. 1 .) The upper cover  14  features a receptacle  17  for receipt of the photocell  18 . The mast compartment  44  features one or more mast-clamps  36  which accommodate the end of the mast  38 . Masts used to mount streetlights are generally round tubes of varying diameters. Masts with diameters of about 1¼″ to about 2½″ are in common use in various locales in the United States. The mast-clamps  36  of the present invention streetlight  10  feature adjustability sufficient to accommodate the aforementioned range of diameters. This range of adjustability eliminates the need for streetlight installation and service crews to carry several sizes of clamps to accommodate the various diameters of masts in common use. 
         [0030]    Located within the mast compartment  44  is the terminal block  34  which interconnects the wiring for the ballast  32 , lamp  26  and photocell  18 . The present invention streetlight  10  by locating the majority of the wiring inside the mast compartment eliminates the need to use multiple rubber grommets to seal the wiring. 
         [0031]    At the hinged end  98  (see  FIG. 1 ) of the mast compartment  44  is a protruding surface  80  which protrudes from the main housing  12  and about which is affixed a strip seal  76 . At the mast receipt end  100  of the mast compartment is a mast seal  78 . The mast seal  78  is attached to a raised flange  82  protruding from the outer surface  13  of the main housing  12 . The mast seal includes a circular opening  84  through which the mast  38  slides when the streetlight  10  is assembled to the mast. When the upper cover  14  is closed, an inner surface  84  of the cover abuts the strip seal  76  at the hinged end  98  of the cover and seals the compartment  44  from water or insect intrusion at that end. 
         [0032]    At the opposite or mast receipt end  100  of the cover  14  (see  FIG. 1 ), the cover includes a flange  86  that has U-shaped opening  88 . When the cover is in a closed position, the U-shaped opening  88  fits about the mast and the mast seal  78  slides inside the cover and abuts an interior surface  90  of the flange  86  of the upper cover  14 . Like the ballast compartment closeout, the upper cover  14  is secured to the main housing  12  by screws  92  which are equipped with knobs that are sufficiently large to be easily removed without the use of tools in most instances. In this manner, the mast compartment is sealed from the elements and intrusion by insects and in particular by bees and wasps. 
         [0033]    Materials and methods of manufacture to make the components of the present invention streetlight  10  are known in the art. Suitable materials for the main housing  12  include various aluminum and zinc alloys. The main housing will typically be made using a casting process. The main housing  12  may also be made from various thermoplastic materials in which instance the housing would be manufactured using a molding process. The light-glass  22  is typically made from heat resistant tempered glass. The seals used in the housing may be made from numerous elastomeric materials as is known the art. Suitable induction lamps  26  are also commercially available. 
         [0034]    As may be seen from the above, an improved streetlight has been presented. The new streetlight features improved sealing from the elements, lower running temperatures and quicker servicing than has heretofore been available in streetlights. 
         [0035]    The foregoing detailed description and appended drawings are intended as a description of the presently preferred embodiment of the invention and are not intended to represent the only forms in which the present invention may be constructed and/or utilized. Those skilled in the art will understand that modifications and alternative embodiments of the present invention which do not depart from the spirit and scope of the foregoing specification and drawings, and of the claims appended below are possible and practical. It is intended that the claims cover all such modifications and alternative embodiments.