Patent Publication Number: US-7712916-B2

Title: Portable reduced-emissions work light

Description:
TECHNICAL FIELD AND BACKGROUND OF THE INVENTION 
   This invention relates to a portable, reduced-emissions work light. The invention has particular application for military use in special purpose tents, referred to as modular command post shelters (MCPS), and other mobile military systems. The invention meets military requirements for electromagnetic interference (EMI) emissions, and includes shock-absorbing components which protect the light from damage caused by dropping or other sudden impact. The invention is lightweight and may include a convenient handle at one or both ends. In addition, the invention includes snap-together components which enable quick and convenient assembly and disassembly. The light includes an integrated power supply and EMI filter. 
   SUMMARY OF THE INVENTION 
   Therefore, it is an object of the invention to provide a portable, hand-held work light which generates reduced emissions. 
   It is another object of the invention to provide a work light which is especially applicable for military use, and which meets military specifications for EMI emissions. 
   It is another object of the invention to provide a work light which does not interfere with the performance of equipment which may be potentially sensitive to magnetic fields. 
   It is another object of the invention to provide a work light which is relatively lightweight. 
   It is another object of the invention to provide a work light which includes snap-together components for ready assembly and disassembly. 
   It is another object of the invention to provide a work light which enables convenient and safe removal and replacement of a defective or inoperative ballast. 
   It is another object of the invention to provide a work light which generates a minimum of five-foot candles of light at 30 inches off the ground. 
   It is another object of the invention to provide a work light which is impact resistant. 
   It is another object of the invention to provide a work light having a ballast that can operate at multiple voltages. 
   It is another object of the invention to provide lighting for a mobile shelter, such as a military MCPS, which would include one or more reduced emissions work lights. 
   It is another object of the invention to provide a mobile shelter which includes an energy efficient lighting system. 
   These and other objects and advantages of the present invention are achieved in the preferred embodiment set forth below by providing a reduced emissions work light. The work light includes a bulb having an elongated bulb tube, a handle adjacent the bulb and adapted for being gripped by a user to manipulate the work light, an emissions containment housing positioned adjacent the bulb tube, and an integrated ballast and filter assembly. The integrated ballast and filter assembly is located within the housing and operatively connected to the bulb for providing voltage to the bulb and reducing emissions generated by the work light. 
   According to one preferred embodiment of the invention, a light-transmitting bulb shield surrounds the bulb tube to protect the bulb from damage. 
   According to another preferred embodiment of the invention, a cylindrical shock-absorbing plug is positioned within the bulb shield and engages a free end of the bulb tube to further protect the bulb from damage. 
   According to yet another preferred embodiment of the invention, the plug includes an interior web for being gripped to remove the plug from the bulb shield. 
   According to yet another preferred embodiment of the invention, a shock-absorbing end cap is positioned over an end of the bulb shield opposite the handle. 
   According to yet another preferred embodiment of the invention, a switch opening is formed in the emissions containment housing to accommodate a ballast activation switch in the handle. 
   According to yet another preferred embodiment of the invention, a removable color filter is positioned over the bulb shield to filter light emitted by the bulb. 
   According to yet another preferred embodiment of the invention, a phototriac switch allows the work light to operate at multiple voltage inputs. 
   According to yet another preferred embodiment of the invention, the reduced emissions work light includes a bulb having an elongated bulb tube, a handle adjacent the bulb and adapted for being gripped by a user to manipulate the work light, an emissions containment housing positioned adjacent the bulb tube having a predetermined interior void, and an integrated ballast and filter assembly. The integrated ballast and filter assembly is intended to correspond with the interior void in the housing, and occupy substantially all of the interior volume of the housing. 
   According to yet another preferred embodiment of the invention, the ballast includes electrical wires having respective terminal ends operatively connected to respective pins of the bulb. 
   According to yet another preferred embodiment of the invention, a bulb socket is located between the fluorescent bulb and the ballast. The bulb socket defines a plurality of longitudinal through-bores receiving respective wire ends of the ballast from a first end thereof and respective electrode pins of the bulb from an opposite second end thereof. 
   According to yet another preferred embodiment of the invention, the bulb socket includes enlarged conical openings at the first end thereof. The enlarged openings are adapted for receiving respective electrode pins into the longitudinal through-bores. 
   According to yet another preferred embodiment of the invention, the bulb socket is formed of a molded plastic material. 
   According to yet another preferred embodiment of the invention, a cylindrical resilient shock is formed around the bulb socket at an open proximal end of the cup. 
   According to yet another preferred embodiment of the invention, a transistor is connected to a zener diode to control a phototriac switch, allowing the work light to operate on multiple voltage inputs. 
   According to yet another preferred embodiment of the invention, the reduced emissions work light includes a bulb having an elongated bulb tube, a handle adjacent the bulb and adapted for being gripped by a user to manipulate the work light, an emissions containment housing is positioned adjacent the bulb tube having a predetermined interior void, and an integrated ballast and filter assembly. The integrated ballast and filter assembly is intended to correspond with the interior void in the housing, and occupy substantially all of the interior volume of the housing. In addition, a transistor is connected to a zener diode to control a phototriac switch allowing the work light to operate on multiple voltage inputs. 
   According to yet another preferred embodiment of the invention, a light reflector is located adjacent the bulb tube for enhancing illumination of the bulb. 
   According to yet another preferred embodiment of the invention, an elongated pull strip is releasably attached to the bulb for removing the bulb from the work light for replacement. 
   According to yet another preferred embodiment of the invention, a power supply cord is adapted for being connected to a power source to supply electrical power to the work light. 
   According to yet another preferred embodiment of the invention, a varistor is operatively connected to the assembly for protecting the assembly from a large transient voltage or power surge. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Some of the objects of the invention have been set forth above. Other objects and advantages of the invention will appear as the description proceeds when taken in conjunction with the following drawings, in which: 
       FIG. 1  is a perspective view of a reduced emissions work light according to one preferred embodiment of the invention; 
       FIG. 2  is a graph illustrating certain military requirements for conducted emissions applicable to the work light; 
       FIG. 3  is a graph illustrating certain military requirements for radiated emissions applicable to the work light; 
       FIG. 4  is an exploded, fragmentary perspective view of the work light; 
       FIG. 5  is an exploded perspective view of the work light; 
       FIG. 6  is a partially exploded perspective view of the handle; 
       FIG. 7  is a perspective view of the flourescent bulb and pull strip; 
       FIG. 8  is a perspective view of the ballast; 
       FIG. 9  is an exploded perspective view of the shock with the molded bulb socket; 
       FIG. 10  is an end elevation of the bulb shock and socket; 
       FIG. 11  is a side elevation of the bulb shock and socket; 
       FIG. 12  is a cross-sectional view of the bulb shock and socket taken substantially along line  12 - 12  of  FIG. 10 ; 
       FIG. 13  is a cross-sectional view of the bulb shock and socket taken substantially along line  13 - 13  of  FIG. 10 ; 
       FIG. 14  is a perspective view of the shock-absorbing end plug; 
       FIG. 15  is a second perspective view of the end plug; 
       FIG. 16  is an end elevation of the end plug; 
       FIG. 17  is a is a cross-sectional view of the end plug taken substantially along line  17 - 17  of  FIG. 16 ; 
       FIG. 18  is a cross-sectional view of the end plug taken substantially along line  18 - 18  of  FIG. 16 ; 
       FIG. 19  is an exploded perspective view showing the end cap, plug, and various strain relief components; and 
       FIG. 20  illustrates a mobile shelter system including one or more of the work lights. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE 
   Referring now specifically to the drawings, a reduced emissions work light according to the present invention is illustrated in  FIG. 1  and shown generally at reference numeral  10 . The work light  10  has particular application for military use in special purpose tents, referred to as modular command post shelters (MCPS), and other mobile military shelters.  FIGS. 2 and 3  are graphs illustrating military specifications for conducted and radiated emissions, respectively. The present work light  10  meets these specifications. The complete text outlining the military requirements for the control of EMI emissions is incorporated herein by reference. See MIL-STD-461D, Jan. 11, 1993, revised Jun. 19, 1997. Preferably, the work light  10  weighs between 3 and 5 pounds, and is manufactured in various lengths ranging from between 30 and 40 inches. 
   Referring to  FIGS. 1 ,  4 ,  5  and  6 , the work light  10  includes components, such as a shock-absorbing rubber handle  12  and end cap  14  and a light-transmitting bulb shield  15 , designed to protect the light  10  from damage during transport and use. Although the handle  12  is specially designed for being gripped by a user, an alternative handle may comprise any extension formed adjacent one or both ends of the bulb shield  15 , including an end cap  14 . A power supply cord  16  extends through the work light  10 , and includes respective male and female connectors  18  and  19  at opposite ends to allow connection of multiple lights together in series. As best shown in  FIG. 6 , a molded cap nut  21 , sleeve insert  22 , and jam nut  23  cooperate to provide cord strain relief at a distal end of the handle  12 . Cord strain relief is provided at the opposite, proximal end of the handle  12  by rings  25  and  26  and molded disk  27 . 
   The bulb shield  15  of the work light  10  is formed of a transparent, high-impact plastic. As shown in  FIGS. 4 and 7 , a replaceable bulb  30  is located inside the bulb shield  15  and includes a pair of elongated bulb tubes  31  and  32 , a pin base  33 , and electrode pins  34 . According to one embodiment, the bulb  30  is a 50-Watt, phosphor-coated fluorescent bulb. For increased illumination, a white reflector  36  is preferably attached to the bulb tubes  31 ,  32 . A perforated, tubular metal screen  38  surrounds the bulb tubes  31 ,  32  inside the bulb shield  15  and operates to reduce emissions generated during use of the work light  10 . The exterior of the shield  15  is protected against scratching and scuffing by a removable color filter  39  suitably tinted to filter certain light emitted by the florescent bulb  30 . This component of the work light  10  is fully described in the Applicant&#39;s U.S. Pat. No. 4,945,461 incorporated herein by reference. 
   A flexible pull strip  41  is located inside the bulb shield  15  for use in re-lamping the work light  10 . The pull strip  41  is formed of a non-conductive, chrome-finished polymer material. One end of the pull strip  41  includes a reinforced portion with pin holes  42  adapted for receiving the electrode pins  34  of the bulb  30 . The opposite end of the pull strip  41  extends slightly beyond the free end of the bulb  30  for convenient access. With a free end of the bulb shield  15  uncovered, the bulb  30  is removed from the work light  10  by gripping the end of the pull strip  41  and pulling in a direction away from the handle  12 . The pull strip  41  is further described in Applicant&#39;s issued patent, U.S. Pat. No. 5,738,438, incorporated herein by reference. 
   As shown in  FIGS. 5 and 8 , an electronic ballast  45  with an integrated emissions filter is stored in a containment housing  48  located within the handle  12  of the work light  10 . Ballast wires  50  connect the ballast  45  to the bulb  30 . According to one embodiment, the emissions containment housing  48  is an open-ended cylindrical metal cup designed to fit entirely within the handle  12 , and extend into an open end of the tubular metal screen  38 . The proximal ends of the metal screen  38  and metal housing  48  engage each other in a close, wedged fit to provide continuous grounding, and to prevent the escape of emissions between the screen  38  and housing  48 . 
   The ballast  45  has multiple voltage capability that allows operation from 50-60 Hz and an input source of 120 V to 240 V. The ballast  45  includes a zener diode which conducts when the input voltage is high enough, thus activating a transistor coupled to the zener diode. A phototriac switch is in the “on” position when the ballast is receiving a low voltage input, but the switch turns to the “off” position in a high voltage configuration. The zener diode, transistor and phototriac switch are contained on the printed circuit board encapsulated inside an asphalt molding located within the ballast  45 . In the initial start-up phase, the ballast  45  automatically senses the input voltage but will increase the voltage when the voltage reaches a set point, which eliminates the need for a fuse. During operation, when the voltage reaches a break point, the ballast  45  switches to a higher voltage range, i.e. 120 Volts to 240 Volts, when the transistor is activated by the zener diode conduction turning the phototriac switch to the “off” position. 
   A varistor is also included on the printed circuit board located within the ballast  45 . Preferably, a metal oxide varistor (MOV) is used that contains a mass of zinc oxide grains in a matrix of other metal oxides, sandwiched between the electrodes. When the voltage increases beyond an acceptable level, such as during a power surge, the varistor&#39;s resistance rapidly decreases, thus creating an alternative path for the voltage to travel which is grounded. The varistor protects the electrical components of the work light  10  from the potential harmful effects of a large transient voltage or power surge for which the ballast  45  cannot compensate. 
   For convenient activation of the work light  10  at the handle  12 , the ballast  45  includes an activation switch  51  extending through aligned openings  52  and  54  in the housing  48  and handle  12 , respectively. The switch  51  enables independent operation of the work light  10  regardless of the number of other work lights connected together in series. When activated, the ballast  45  provides start-up voltage for the fluorescent bulb  30  and serves to limit the electric current through the work light  10 . 
   Operation of the ballast  45  generates emissions which are substantially contained within the housing  48 . The ballast  45  has an integrated emissions filter, containment housing  48 , and perforated screen  38  which cooperates to reduce both radiated and conducted emissions generated by the work light  10 . The housing  48  and screen  38  is preferably formed of aluminum. According to one embodiment, the housing  48  is formed of 6061-T6 aluminum. The screen  38  is formed of 0.3003H14 aluminum, and is approximately 0.03 inches thick. 
   As illustrated in  FIG. 8 , the ballast  45  has a partially cylindrical shape which corresponds with the shape of the housing  48 . This shape allows the ballast  45  to correspond with the housing  48  and occupy substantially all of the intended volume for an efficient use of space. These corresponding shapes also function to keep the ballast  45  secure to prevent unintended movement resulting in damage. 
   Referring to  FIGS. 4 and 5 , a molded bulb socket  61  and rubber shock  62  are located at a proximal end of the containment housing  48  between the electrode pins  34  of the bulb  30  and wires  50  of the ballast  45 . As best shown in  FIGS. 9-13 , the bulb socket  61  is formed of a hard plastic material molded directly within the body of the shock  62 . A number of longitudinal bores  64  extend through the bulb socket  61 , and are adapted to interconnect respective pins  34  of the bulb  30  and wires  50  of the ballast  45 . Barbed connectors  65  (See  FIG. 8 ) are provided at terminal ends of the ballast wires  50  and are adapted for being inserted into a first end of the socket  61  through respective bores  64 . The electrode pins  34  of the bulb  30  are inserted into the opposite end of the socket  61  through bores  64  to engage connectors  65 . The rubber shock  62  provides impact resistance to further protect the bulb  30  from breaking if the work light  10  is dropped or damaged, and protection against vibration and loose cargo situations in its field application. According to one embodiment, the shock  62  is formed of an injection molded or extruded, medium hardness thermoplastic elastomer, such as PVC nitrile. 
   To facilitate proper placement of the bulb  30 , the shock  62  has opposing, inwardly-tapered side walls  67  and  68  defining a guide recess for directing the bulb pins  34  into the through-bores  64  of the socket  61 . The lower perimeter  69  of the guide recess is preferably contoured to secure the pin base  33  of the bulb  30 . The mouth  71  at each through-bore  64  of the socket  61  defines an enlarged, generally conical opening adapted to readily accept the bulb pins  34 . In addition, because the socket  61  is formed of a hard molded plastic, the bulb pins  34  engage the socket  61  at the enlarged conical openings and slide into respective through-bores  64  without friction interference. While the bulb socket  61  is preferably molded separately inside the rubber shock  62 , as described and shown, the bulb socket  61  and shock  62  may be integrally-formed together as a single unit. A longitudinal channel  72  is formed along one side of the shock  62  to accommodate passage of the power supply cord  16  through the interior of the work light  10 . 
   Referring again to  FIGS. 4 and 5 , a removable shock-absorbing plug  75  is located at the opposite end of the bulb shield  15  adjacent the end cap  14 . The plug  75  engages and surrounds the free end of the bulb  30  inside the shield  15 , and further protects the bulb  30  from damage caused by sudden impact to the work light  10 . As best shown in  FIGS. 14-18 , the plug  75  has a first end which defines a contoured opening  76  adapted to receive the free end of the bulb  30 . The opposite end of the plug  75  is recessed, and includes an annular flange  77  for engaging the annular peripheral edge of the bulb shield  15 . An interior web  78  is formed in the recessed area of the plug  75 , and is designed for being gripped by a user to conveniently remove the plug  75  from the shield  15  to access the bulb  30 . To accommodate passage of the power supply cord  16 , an opening  81  and channel  82  are formed in the side wall of the plug  75 . As shown in  FIG. 19 , a molded disk  84 , O-ring  85 , and sleeve insert  86  are located between the end cap  14  and plug  75  to provide cord strain relief. A molded cap nut  88  and jam nut  89  cooperate on the other side of the end cap  14  for added strain relief. According to one embodiment, the plug  75  is formed of an injection molded or extruded, medium hardness thermoplastic elastomer, such as PVC nitrile. 
     FIG. 20  illustrates a mobile shelter system  100 . One or more of the work lights  10  are located within the shelter system  100  and suspended from overhead rods or straps to provide a convenient, energy efficient lighting system. The shelter system may be a military MCPS, or any other such tent or enclosure. 
   For convenient assembly and disassembly, the components of the work light  10  include complementary snap-together attachment elements enabling ready access to and replacement of worn or damaged parts. In addition, all surface elements of the work light  10  are preferably non-conductive. The term non-conductive is defined as having sufficient dielectric to be considered non-conductive at voltages below 600 V AC. The work light  10  may also include one or more hanger hooks (not shown) for suspending the light from the overhanging support structure inside the tent or enclosure. 
   A reduced emissions work light is described above. Various details of the invention may be changed without departing from its scope. Furthermore, the foregoing description of the preferred embodiment of the invention and the best mode of practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation—the invention being defined by the claims.