Abstract:
An apparatus and method for connecting and disconnecting electrical power to an arc tube includes a high intensity discharge arc tube having a body and electrodes extending from the exterior of the body into the interior of the arc tube body. Electrical leads are connected to the exterior ends of the electrodes and have an length that allows distal ends of the leads to be extended a distance away from the arc tube. Connectors at the distal ends of the leads are adapted to connect to electrical power leads. The connectors, the leads, and the connection of the leads to the electrodes of the arc tube all are electrically insulated from human touch. Therefore, electrical power through the arc tube can be connected and disconnected at a location away from the arc tube, without direct exposure of humans to electrically conducting surfaces for safety purposes.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to light sources utilizing arc tubes, and in particular, to an apparatus and method for connecting and disconnecting electrical power to a high intensity arc tube. 
     2. Problems in the Art 
     Many high powered lights utilize arc tubes as the light source. Arc tubes can create intense light from a relatively small package. Also, arc tubes can generate such light in a relatively efficient and a economical manner. 
     Substantial amounts of electricity are required, however, to generate light from arc tubes on the scale necessary for wide area lighting, for example. A side-effect of generation of light in this manner is also the generation of substantial amounts of heat. Therefore, two matters that must be addressed, with high intensity arc tubes are the danger presented to humans because of the amount of electrical power presented to arc tubes, as well as the high levels of heat that present not only as a danger to humans, but is potentially detrimental to the longevity of the electrical connections of the arc tube to the source of electricity for the arc tube. 
     Most arc tubes have a finite life span. Therefore, there are times when the arc tubes must be replaced in a fixture. Other times repair or maintenance on the fixtures requires opening of the fixture for interior access. On the other hand, because arc tubes must be replaced, fixtures generally have quick attach/detach mounts for each end of the arc tube to make replacement of the arc tubes quicker and easier. 
     Conventionally, short electrical leads are connected to the electrodes at each of an arc tube and an electrical connector is placed at the distal ends of the short leads. The electrical connector is many times an exposed electrically conducting component that can be screwed or otherwise mounted to another electrically conducting terminal that is connected to wiring that would then go to the electrical power source. Such exposed electrical connections represent a real and significant safety risk to persons working with such fixtures. If care is not taken, human contact to such surfaces could result in electrical shock. Still further, most of those connections are, because of the short electrical leads and space constraints inside the fixture, close to the ends of the arc tube or arc lamp inside the fixture. Therefore, the electrical connections and the leads must be able to withstand such heat over many hours of operation of the arc tube. They must therefore be made of special heat-handling materials. Also, during, and for a time after operation of the arc tube, the heat is such that any human working near the arc tube would also have the real and substantial danger of burn if they touched the arc tube. 
     Because some fixtures utilizing arc tubes, for example for sports lighting, are elevated on poles well above the ground, and at a location remote from any main power disconnect for electrical power to the fixtures, there is a risk that the worker will incorrectly assume the electrical power to the fixture has been turned off. There is no easy way to check the same and therefore the worker may risk going forward with opening the fixture when the electrical power is on and thus expose himself/herself to danger. 
     Still further, if the arc lamp has malfunctioned or no longer works for some reason, the worker may be misled to think that the power is off to the fixture because the light is not on or does not turn on. Again, such a mistake could risk serious consequences. 
     Some fixture manufacturers address this problem by including in the fixture hardware which automatically is intended to disconnect electrical power to the arc tube if the access opening to the fixture is opened. Essentially, if the access door is open, this system automatically breaks the electrical circuit to the arc tube. It therefore intends, in all cases, to remove electrical shock risk when a worker is working inside the fixture. 
     However, this does not address the problem of burns from the hot arc tube or the problem with failure of electrical connections that are placed near the ends of the arc tube, because of the heat generated from the arc tube. Still further, this adds complexity and cost to lighting fixtures. For example, conventional systems for automatic disconnect of electrical power to the arc tube utilize a switch or contactor. These components can individually cost on the order of $30 to $40 each. Also, there is the possibility that such components may fail or malfunction. Furthermore, such systems do not eliminate the requirement there still must be a manual connect and disconnect of the wiring to the arc tube at a position at or near the ends of the arc tube to replace the arc tube. 
     It has therefore been identified that there is a need in the art for a better solution to a way in which electrical power is connected and disconnected to an arc tube for a lighting fixture. It is therefore a principal object of the present invention to provide an apparatus and method which improves over or solves the problems and deficiencies in the art. Other objects of the invention include an apparatus and method which: 
     1. Provide a positive, fail-safe method of connecting and disconnecting electrical power to an arc tube. 
     2. Eliminates costs and weight by eliminating a need for automatic disconnect components. 
     3. Eliminates connection and disconnection of electrical power to the electrodes of an arc tube at a position at or near the electrodes of the arc tube. 
     4. Allows placement of the connection of electrical power to the arc tube at a position away from the arc tube and the heat generated from the arc tube. 
     5. Fosters a more durable electrical connection to electrical power. 
     6. Allows more economical and less complex materials to be used for the connections. 
     These and other objects, features, and advantages of the present invention will become more apparent with reference to the accompanying specification and claims. 
     SUMMARY OF THE INVENTION 
     The present invention is an apparatus and method for connecting and disconnecting electrical power to an arc tube inside a lighting fixture. The method includes mounting into a fixture an arc tube and connecting electrical power to leads to the electrodes of the arc tube at a position substantially spaced from the arc tube in the fixture. The apparatus of the invention includes an arc tube having first and second electrodes. Electrically insulated leads are connected to the electrodes and extend to distal ends. Connectors on the distal ends are connectable to complimentary connections of electrical power leads. The connectors and the electrical leads from the arc tube, including connections of the leads at the arc tube electrodes, are all insulated or shielded from direct human exposure to the electricity. The connections to electrical power therefore are not only at a location farther away from the arc tube and more remote in the fixture from the heat generated by the arc tube during operation, but also have no exposed parts to reduce the risk of electrical shock to a person connecting or disconnecting the leads, even if electrical power is on. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a lighting fixture having a replaceable arc tube and its mounts inside the fixture, along with automatic power disconnect components. 
     FIG. 2 is an isolated enlarged view of the arc tube, mount, and power connections of the fixture of FIG. 1, and schematically showing the automatic power disconnect components. 
     FIG. 3 is similar to FIG. 1 but shows a preferred embodiment of the present invention substituted for the electrical power connections. and automatic disconnect components of the fixture FIG.  1 . 
     FIG. 4 is similar to FIG.  2  and shows the preferred embodiment of the present invention in enlarged fashion. 
     FIG. 5 is an enlarged cross-sectional view of mating electrical power connectors in disconnected position used with the embodiment of FIG.  4 . 
     FIG. 5A is similar to FIG. 5, but shows the mating power connectors in connected position. 
     FIG. 6 is a front prospective view of another fixture type with which the invention can be used. 
     FIG. 7 is a rear perspective view of the fixture of FIG. 6 showing a preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     For a better understanding of the invention, preferred embodiments will be described in detail herein. Frequent reference will be taken to the figures which have reference numerals which indicate certain parts and locations in the figures. The same reference numerals will be used to indicate the same parts and locations throughout the figures unless otherwise indicated. 
     The environment of the preferred embodiments now discussed relates to high intensity arc tubes utilized in lighting fixtures for wide area lighting such as sports field, race track, and arena lighting. To illustrate the preferred embodiment, a metal halide arc tube, such as are well know in the art, will be described in relationship to its use with two types of fixtures. It is to be understood, however, that similar principals can apply to other types of fixtures utilizing other types of arc tubes. 
     FIG. 1 illustrates a fixture  10 . Fixture  10  includes a main housing  11  which encloses a reflecting surface (not shown), a front opening and lens (not shown), mounts  12  (shown in simplified fashion) to releasably hold opposite ends of an arc tube  14 , and power connections  16  to attach arc tube leads  18  to electrical power leads  20 , which are ultimately connected to a source of electrical power  22  (See FIG.  2 ). FIG. 1 also shows power circuit interrupter blocks  24  and power circuit completer blocks  26 , which function in association with removable rear cover  28  and housing  11  to automatically disconnect power from power source  22  when cover  28  is removed from fixture  10  to expose arc tube  14  and the electrical leads  18 , connectors  16 , and power leads  20 . 
     Blocks  24  can simply have two female receivers in electrical conducting communication with sections of power leads  20 . The receivers define a gap or interruption in each power lead  20 . Blocks  26  can simply comprise two male electrical conducting members that are in electrical conducting communication with each other. When the male ends of a block  26  are inserted into the female receivers in a block  24 , there is no interruption in the corresponding electrical power lead  20 . When the male ends are removed, no electrical power can travel through the gap and it effectively, automatically disconnects electrical power to arc tube  14 , in this instance, if rear cover  28  is removed. 
     As described above, the automatic disconnect is intended to, in a fail-safe manner, cut off electrical power to arc tube  14  if cover  28  is removed to access the interior of fixture  10 . 
     FIG. 2 shows in more detail the pertinent components of FIG.  1 . It can be seen that arc tube  14  includes a quartz tubular body  32 . Electrodes  34  have adjacent ends positioned inside envelope  32 . Inner ends of electrodes  34  extend into arc tube  14 . Outer ends of electrodes  34  are encased in ceramic insulators  36  which are fused or attached to arc tube body  32 . Arc tube leads  18  extend from insulators  36  and are covered with high temperature insulation (such as Teflon). Connection posts  38  can consist, for example, of a metal screw in a metal base plate. The distal ends of leads  18  can comprise C-shaped exposed metal connectors  40  that can be inserted around screws  38 . Similarly, power leads  20  can include connections that can be secured around screws  38  or alternatively can be electrically connected to screws  38  inside connector  16 . Screws  38  are then turned down into their base plates to secure electrical connection between leads  18  and  20 . Screws  38  are turned up to release the C-shaped connectors of at least leads  18 , if arc tube  14  is to be removed from mounts  12  for replacement, repair or maintenance. 
     As can be appreciated, however, by FIGS. 1 and 2, the disconnection of arc tube  14  from mounts  12  requires a worker to physically engage screws  38 . Moreover, screws  38  are at a position that are relatively close to arc tube  14 . Therefore, if arc tube  14  had been recently operating and the worker has to replace it, the worker would be in very near proximity to the arc tube, which can be very hot during operation and for a time thereafter. 
     Still further, the heat generated by operation of arc tube  14  for a long period of time can affect the durability of the connections between leads  18  and connectors  38 , or that of power leads  20  and connectors  38 . 
     FIG. 3 shows fixture  10 A with a power connect/disconnect system according to the present invention. Arc tube  14  and its mounts  12  remain the same. However, the differences are as follows. As can be seen in FIG. 4, arc tube leads  42 , being of substantial length compared to leads  18  of FIGS. 1 and 2, are substituted for the short levels  18 . A substantial length can be on the order of around five inches or more. Leads  42  are connected to insulators  36  at ends of arc tube  14  and covered with an insulator. At the distal ends of leads  42  are connectors  44 , which in the preferred embodiment, are quick-connect electrical connectors that can connect to complimentary connectors  46  at the ends of power leads  20 . 
     Leads  42  in FIG. 4, can be of a length that allows their distal ends to be positioned sufficiently away from arc tube  14  to reduce risk of touching arc tube  14  when disconnecting electrical power and which allows use of plastic mateable connectors (as opposed to high temperature materials like ceramics) and also reduces risk of damage to the connections because of heat from the arc tube. An example is several feet long. Connectors  44  are pin and socket connectors available at electrical equipment supply retailers and wholesalers. One example is a Universal MATE-N-LOCK (1 circuit, free hanging) connector made by AMP company of, Harrisburg, Pa. telephone number 1-800-522-6752). 
     A primary characteristic of connectors  44 , and their complimentary connectors  46 , is that no electrically conducting component of such connectors is readily exposed to contact by humans. As shown in FIG. 5, both connectors  44  and  46  have outer shells  48  and  49  respectively that are made of electrically insulating material such as plastic. Inside of complimentary shells  48  and  49  are female  50  and male  52  members, respectively (See FIG.  5 ), components which mate together when shells  48  and  49  are brought together in a nesting relationship (See FIG.  5 A). Female and male members  50  and  52  are caused to be in alignment when shells  48  and  49  are brought together and create an electrical connection inside of shells  48  and  49 . There is no surface that is directly exposable to human touch. Connectors  44  and  46  also have releasable inter-locking structure which holds them together when mated, but which allows quick release. 
     It therefore can be seen in FIGS. 3-5 when door or cover  28  is removed from the back of fixture  10 A, connectors  44  and  46  are positioned away from arc tube  14 . Therefore, even if arc tube  14  had just been operating, the worker can safely grasp connectors  44  and  46 , and because of the length of leads  42 , pull that connection outside of the interior of lamp  10 A and safely pull them apart to disconnect the electrical power. Electrical power can be alternating current, and is usually of high voltage. Moreover, when reaching in to grab connectors  44  and  46 , there is not any exposed electrical surface, such as exists with posts  38  in FIGS. 1 and 2, to prevent a source of electrical shock. The worker does not have to reach in anywhere near arc tube  14 , thus reducing the risk of a burn. 
     Once connectors  44  and  46  are separated, the worker has positive and visually verifiable proof that electrical power is disconnected to arc tube  14 . Also, during operation of fixture  10 A, connectors  44  and  46  are at a position remote from arc tube  14  inside fixture  10 A. Therefore, the electrical connection is less likely to be affected by the heat generated by arc tube  14  over time. It has been found that the closer one makes the electrical connection to arc tube  14 , the more the risk of the connection going bad over time. 
     Therefore, for safety reasons, both electrical and heat, and for durability issues, the embodiment of FIGS. 3-5 addresses each. It also can allow the complete elimination of the power disconnect circuitry (e.g. blocks  24  and  26  and associated mounts and wiring) shown in FIGS. 1 and 2 which can represent a substantial cost savings in light of the fact such components can cost several tens of dollars. Those components also increase the complexity of the fixture and cause maintenance personnel to rely on the circuitry rather on any objectively verifiable power disconnect, such as is available with connectors  44  and  46  and leads  42 . Other fixtures utilize electrical components such as contractors and/or switches as an automatic disconnect. These can be eliminated by the invention. Some fixtures cut off power to ballasts instead of directly to the arc tube. Likewise, the invention eliminates the components needed to do this. 
     FIGS. 6 and 7 show another preferred embodiment of the invention, illustrating its wide application to fixtures with arc tubes. The fixture  100  of FIG. 6 comprises a housing  111  with a hinged front door  128  to access the interior of fixture  100 . For additional details about fixture  100 , one can refer to commonly owned U.S. Pat. No. 5,647,661 issued Jul. 15, 1997, incorporated by reference herein. An arc tube  14  is held suspended by appropriate structure. Arc tube leads  42  extend from opposite ends of arc tube  14 . 
     FIG. 7 shows housing  128  has a rear hinged door  129  to gain access to the rear of fixture  100 . Leads  42  extend rearwardly from arc tube  14  (See FIG. 6) back behind the reflector  115  to the rear bottom of fixture  100 . Leads  42  are each approximately  36 ″ long. Fixture  100  is roughly  2 ′ wide, by  2 ′ deep, by  2 ′ tall. Therefore, connections  44 / 46  are a substantial distance away from arc tube  14  in a much cooler position inside fixture, yet are easy to grasp and operate (connect or disconnect). 
     Different connectors could be used. Preferably, all electrically conducting surfaces would be shielded or blocked from direct human contact. 
     If connectors  44 / 46  are nearer to arc tube  14 , connectors  44 / 46  could be made of more heat-resistant materials like ceramic or Teflon or could be Teflon coated. Connections of the type needed can be made by those of one skilled in the art. Different approaches can be made to prevent direct exposure of electrically conducting surfaces while both connections  44 / 46  are so protected. 
     The cooler the position of connectors  44 / 46 , the better. Although longer leads are contra-indicated, use of longer leads provides the advantages according to the invention to diminish the thermal problems discussed herein. 
     The included preferred embodiment is by way of example only and not by way of limitation, which is solely defined by the claims herein. Variations obvious to those skilled in art will be included within the invention.