Abstract:
A sealed light fixture having a valve mounted in the housing to vent pressure that builds-up inside the housing during operation of the light and to prevent moisture and contaminants from entering the housing. The light fixture automatically creates a vacuum inside the housing to prevent condensation from causing corrosion and other problems for the light fixture. The pressure releasing mechanism permits easy installation of the housing cap and avoids damage to the fixture as a result of temperature caused pressure increases. The valve has a pressure equalizing mechanism that can be manually actuated to eliminate the vacuum and equalize the pressure inside the housing with the atmosphere so the housing can be disassembled and the lamp replaced when necessary.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/086,928 filed May 27, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     The field of the present invention relates generally to sealed light fixtures, such as those utilized for outdoor lighting. More specifically, this invention relates to sealed light fixtures that utilize a valve to prevent condensation in the fixture and to vent pressure build-up therein. Even more specifically, the present invention relates to sealed light fixtures having valves that automatically vent pressure build-up in the sealed light fixture to create a vacuum therein that prevents condensation, yet facilitates assembly and disassembly of the light fixture by equalizing the pressure in the fixture with the atmosphere. 
     B. Background 
     It is well known that many people use lights, such as spotlights and other types of lights, in outdoor applications. These applications generally require a sealed or near-sealed light fixture to prevent moisture from entering the light housing, lamp or electrical circuit components of the lighting system to prevent damage or injury that can result from moisture contact with an electrical system. The typical outdoor light fixture has a mounting assembly that includes a knuckle joint that attaches to a junction box or other source of electricity, a housing connected to the knuckle joint and a cap connected to the housing to enclose the lamp. Gaskets are typically utilized between the various members of the light fixture to prevent the intrusion of moisture. 
     Despite the significant operational and safety advantages of using a completely sealed housing, the sealing of the housing makes assembly and disassembly of the light fixture very difficult. In order to assemble the light fixture, the cap must be placed on the housing and locked into place. If the housing is sealed such that the completed assembly will be airtight, the action of placing the cap on the housing compresses the air inside the housing and makes placement of the cap on the housing difficult. Once the cap is in place on the housing, the high internal pressures that exist make locking the cap to the housing very difficult. Brute force or some type of mechanical advantage must be used in order to seal the cap onto the housing. Once the cap is installed, the sealed light fixture must be able to withstand the increased internal pressure that results from the heating of the air inside the fixture when the lamp is on. The problems with utilizing a sealed housing are compounded with larger size light fixtures which generate more heat. 
     To avoid the problems described above, most light fixtures are manufactured so they are not completely air-tight. These systems have significant disadvantages. Fixtures that are not air-tight have a mechanism to vent the pressures that result from assembling the light fixture and the pressure that results from the heating up of air inside the housing during operation. Generally, the venting is accomplished by making the knuckle joint connector such that it is not air-tight where it connects to the housing. Because it is open to the atmosphere, the knuckle joint or other non-sealing mechanism allows air to vent out of the light fixture during installation and during the heat-up and expansion caused by the lamp being on. 
     Unfortunately, while the air inside the housing is cooling after the lamp is turned off, outside air is drawn inside the housing as the pressure inside the housing lowers. This drawing in of outside air brings moisture and contaminates that are also in the air (such as salt for installations near salt water) inside the housing. The resulting moisture inside the housing can cause condensation that can result in corrosion and/or problems with the electrical components. To avoid these problems, the internal components must be manufactured out of materials that can withstand corrosion and moisture must be prevented from entering into moisture-sensitive areas. Some manufacturers utilize chemical materials inside the light fixture to absorb the moisture that enters as a result of the above process. 
     As an alternative to the non-sealed light fixtures described above, some manufacturers of light fixtures create a vacuum inside the lamp housing during the manufacturing process. The vacuum inside the housing solves the problems with moisture and contaminates getting inside the housing and reduces or eliminates the problem with condensation. However, due to the vacuum, the owner of such a light fixture can only replace the lamp by removing the entire lamp housing and shipping it to the manufacturer for replacement. This creates significant difficulty and expense for the system owner. 
     What is needed is a sealed light fixture having a mechanism for releasing the pressure build-up that occurs during the installation of the cap onto the housing and which results from the temperature increase when the lamp is on, while preventing moisture and contaminates from entering the light fixture after the lamp turns off. The mechanism should also permit the light fixture owner to equalize the pressure inside the housing to allow relatively easy removal of the cap for relamping. 
     SUMMARY OF THE INVENTION 
     The sealed light fixture of the present invention solves the problems identified above. Specifically, the present invention discloses a sealed light fixture that utilizes a valve mounted in the housing to vent pressure that builds-up inside the housing and prevent moisture and contaminates from entering the housing. The sealed light fixture having the valve of the present invention automatically creates a vacuum inside the lamp housing to ensure no condensation occurs. Additionally, the light fixture of the present invention has a valve that eliminates the vacuum so that the cap can be removed from the housing to replace the lamp or perform other repair work. 
     The light fixture of the present invention has a housing that forms a housing chamber that houses the lamp that is used to provide the desired lighting effect. A valve is disposed in an opening that connects the housing chamber with the atmosphere. The valve is configured to release pressure from inside the housing chamber that results from installing the cap on the housing and from the heating effect of the lamp when it is on. In the primary embodiment of the present invention, the valve comprises a one-way check valve with the valve body threaded into the housing opening. Disposed in the valve body is a first spool and a second spool and a valve chamber between the two spools. The first spool has a passageway that interconnects the valve chamber with the atmosphere. The second spool has a passageway that interconnects the valve chamber with the housing chamber. Disposed in the valve chamber is a diaphragm that seats against the second spool. When pressure builds up in the housing chamber, the diaphragm is pushed off its seat and the pressure vents to the atmosphere. After the pressure is released, the diaphragm reseats itself and a vacuum is created inside the housing chamber to prevent condensation. 
     To facilitate removal of the cap to replace the lamp, the valve assembly includes a pressure equalizing mechanism. In the preferred embodiment, this mechanism utilizes a spring that pushes against the second spool and, as a result, the first spool, a annular chamber between the first spool and the valve body and a relief port located in the valve body. The annular chamber is in fluid communication with the atmosphere and the relief port is in fluid communication with the housing chamber. When the first spool is pushed inward toward the housing chamber against the spring, the annular chamber becomes substantially aligned with the relief port and air flows from the atmosphere to inside the housing chamber. This equalizes the pressure and allows easy removal of the housing cap. When the lamp is turned on, the resulting increase in pressure opens the valve and removes the air and moisture from inside the housing chamber and recreates the desired vacuum condition. 
     Accordingly, the primary objective of the present invention is to provide a light fixture that provides an easy to use and self-regulating valve for discharging pressure from inside the light fixture and preventing condensation therein. 
     It is also an important objective of the present invention to provide a light fixture that has a vacuum inside the light fixture housing during operation that can be eliminated when it is necessary to open the light fixture and then automatically recreated when the fixture becomes operational again. 
     Another important objective of the present invention is to provide a light fixture that automatically discharges pressure that builds up while installing the cap on the housing and as a result of the heat generated by the lamp. 
     Yet another important objective of the present invention is to provide a light fixture that utilizes a removable pressure releasing and anti-condensation valve. 
     The above and other objectives of the present invention will be explained in greater detail by reference to the attached figures and the description of the preferred embodiment which follows. As set forth herein, the present invention resides in the novel features of form, construction, mode of operation and combination of parts presently described and understood by the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings which illustrate the best modes presently contemplated for carrying out the present invention: 
     FIG. 1 is a side view of a light fixture of the present invention; 
     FIG. 2 is a cross-sectional view showing the valve of the primary embodiment located in the interior of a light fixture housing; and 
     FIG. 3 is an alternative embodiment of the valve in use with the light fixture of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the figures where like elements have been given like numerical designations to facilitate the reader&#39;s understanding of the present invention, and particularly with reference to the embodiment of the present invention illustrated in FIGS. 1 through 2, the preferred embodiment of the present invention is set forth below. The sealed light fixture of the present invention, designated generally as  10 , includes housing  12  having a main housing body  14  and a cap  16  that removably attaches to housing body  14  to allow replacement of lamp  18  located inside the housing chamber  20  formed by housing body  14  and cap  16 . A valve  22  is shown attached to the bottom side of housing  12 , although it could be placed on the side of body  14  or on cap  16 . Housing  12  connects to a knuckle joint  24  that allows the angular adjustment of light fixture  10  a and through which the electrical wiring  26  passes. Knuckle joint  24  attaches to a junction box or some other device (not shown) that is suitable for supporting light fixture  10 . The lamp  18  is aimed at the location where light is desired. 
     The preferred embodiment of valve  22  of the present invention is illustrated with a cross-sectional view in FIG.  2 . As shown in FIG. 2, the valve  22  primarily comprises a first spool  28  and a second spool  30  in a valve body  32 . First spool  28  has a first end  28   a  and second end  28   b . Second spool  30  has first end  30   a  and second end  30   b . Valve body  32  has first end  32   a  and second end  32   b . In the preferred embodiment, second end  28   b  of first spool  28  threadably connects to first end  30   a  of second spool  30  and the externally threaded first end  32   a  of valve body  32  is threaded into an internally threaded opening  34  in housing  12 . The first spool  28  and second spool  30  assembly (collectively, the “spool assembly”) are slidably disposed inside valve body  32 . A retaining ring  36  located on the second end  30   b  of second spool  30  prevents upward movement of the bottom of second spool  30  beyond the second end  32   b  of valve body  32 . 
     A compression spring  38  on the outside of second spool  30  inside valve body  32  (as shown in FIG. 2) is biased against second spool  30  to place a force on the entire spool assembly that is sufficient to keep first spool  28  towards the atmospheric side of housing  12  to prevent unwanted downward movement of the spool assembly. O-ring  40  seals the space between first spool  28  and second spool  30  to prevent passage of fluid between spools  28  and  30  and valve body  16 . O-ring  42  seals the valve  22  to housing  12  connection to prevent passage of fluid into housing  12 . An additional O-ring  44  seals the annular space between first spool  28  and the inside of valve body  32 . Instead of O-rings, various other sealing mechanisms may be used to seal the connections described above to prevent unwanted entry of fluid into housing  12 . 
     In the preferred embodiment, annular chamber  46  is formed by utilizing a first spool  28  having a slightly smaller outside diameter than the opening provided by valve body  32  at the atmosphere side of valve  22 . Annular chamber  46  is in fluid communication with the atmosphere. Disposed in first spool  28  is upper passageway  48 . First passageway  48  extends through first spool  28 , substantially from first end  28   a  to second end  28   b  of first spool  28 . Upper passageway  48  connects valve chamber  50  to the atmosphere outside housing  12 . Disposed in second spool  30  is second passageway  52 , which connects housing chamber  20  with valve chamber  50 . In the preferred embodiment, first end  30   a  of second spool  30  comprises or forms valve seat  54  for diaphragm  56 , which is suitable for forming a one-way check valve. Diaphragm  56  can be shaped and configured to sealably abut seat  54 . Valve body  32  has relief port  58  which is open to housing chamber  20 . Upon movement of first spool  28  inward towards housing chamber  20 , relief port  58  becomes substantially aligned with annular chamber  46  to interconnect housing chamber  20  with the atmosphere. 
     In use, valve  22  is threaded into opening  34  that is placed in an otherwise air-tight housing  12  prior to or after shipment of the housing to the user. After valve  22  is threaded into housing  12 , housing  12  becomes air-tight or sealed and fluid should not be able to enter housing chamber  20  except through valve  22  as described below. When the user places cap  16  on housing body  14  the pressure build-up inside housing chamber  20  is vented to the atmosphere by entering second passageway  52 , displacing and going around diaphragm  56  and exiting through first passageway  48  to the atmosphere. O-ring  40  prevents the air pressure from being relieved through the inside of valve body  32 . The venting of the pressure build-up from inside housing chamber  20  allows the user to easily place cap  16  on housing body  14  and lock it into place to form sealed housing  12  for sealed light fixture  10 . 
     The pressure increase of the air inside housing chamber  20  that results from the increase in temperature due to lamp  18  being on is vented, along with any water vapor that may be in housing chamber  20 , through the second passageway  52 , valve chamber  50  and first  48  passageway to the atmosphere, as discussed above. When lamp  18  is turned off and the pressure drops inside housing chamber  20  due to the decrease in temperature, outside air is prevented from entering housing chamber  20  by the passive diaphragm-type check valve action of diaphragm  56  seating against seat  54 . Unlike other systems that utilize a non-sealed housing, moisture and contaminants do not flow into housing chamber during cool down. Because air cannot flow into housing chamber  20 , a vacuum is created inside housing chamber  20 , which prevents condensation and avoids corrosion and other problems associated with condensation. 
     The vacuum inside housing chamber  20  prevents anyone from being able to remove cap  16  to replace lamp  18 . To allow lamp  18  to be easily replaced valve  22  should include a pressure equalizing mechanism for allowing the user to equalize the pressure inside housing chamber  20  with the atmosphere. In the preferred embodiment, this task is accomplished by utilizing the spring-biased first spool  28 . To equalize the pressure, the user need only push on first spool  28  to cause second spool  30  to compress spring  38  towards housing chamber  20 . When the entire spool assembly moves inward, O-ring  44  moves beyond relief port  58  until annular chamber  46  is placed substantially adjacent to relief port  58  so housing chamber  20  is placed in fluid communication with annular chamber  46  and the atmosphere. Due to this operation, atmospheric air flows from outside housing  12  to housing chamber  20  to allow the user to easily remove cap  16  from housing body  14 . After lamp  18  is replaced, the entire heat-up and pressure relief process is repeated, thereby once again creating a vacuum inside housing chamber  20  to prevent condensation. 
     The above description is of the preferred embodiment of the present invention. There are numerous components described herein that can be replaced with equivalent functioning components to accomplish the objectives of the present invention. One such modification is shown in FIG. 3, which utilizes a pair of O-rings  60  around a larger annular chamber  46  and a first passageway  28  that has horizontal as well as vertical fluid exit paths. In addition, other types of sealing members, other than O-rings are available. Care should be used in selecting materials for the O-rings or other sealing members to ensure that they will be capable of withstanding the temperatures created inside the housing. The first end  28   a  of first spool  28  that is pushed to equalize the pressure inside the housing can extend beyond the wall of housing body  14  as shown in FIG. 2 or be flush with or inside the wall of housing body  14 . 
     While there are shown and described herein certain specific alternative forms of the invention, it will be readily apparent to those skilled in the art that the invention is not so limited, but is susceptible to various modifications and rearrangements in design and materials without departing from the spirit and scope of the invention. In particular, it should be noted that the present invention is subject to modification with regard to the dimensional relationships set forth herein and modifications in assembly, materials, size, shape, and use.