Abstract:
A housing, particularly for a Light Emitting Diode (LED) or otherwise lamped in-grade or under-water light fixture, is made of ceramic material, such that the housing is not affected by corrosive substances commonly found in soil, masonry, and water that surrounds the installed fixture. The ceramic housing establishes a good conductor of heat and does not conduct electricity. A lens and lens frame are secured to the housing and provisions are made to assure the integrity of the overall assembly even when the light fixture is employed in damp and wet environments and/or where heavy loads can bear down on the lens, such as when the light fixture is embedded in a paved roadway and subjected to vehicular traffic rolling there over.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/754,010 entitled “In-Grade and Under-Water Light Fixture Housing Made of Ceramic Material” filed Jan. 18, 2013. The entire content of this application is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention is related generally to housings for in-grade and under-water light fixtures. In-grade light fixtures are light fixtures typically used in architectural and landscape lighting. The housing of an in-grade light fixture is installed entirely or partially below the level of the ground surface, whether earth or covered ground surfaces, such as concrete, asphalt, tile, granite, marble, stone paver, wood, and the like. In-grade light fixtures are also known as in-ground light fixtures, direct burial light fixtures and well-lights, along with other names. Under-water light fixtures are architectural light fixtures which are entirely or partially immersed in water or other water containing liquid. Examples of under-water light fixtures are swimming pool lights, fountain lights, and the like. 
         [0003]    A common concern associated with light fixtures and other lighting apparatus wherein a significant portion of the housing of the fixture is below the ground surface, or is immersed in water, is that materials which might be present around the installed light fixture can excessively corrode, or otherwise adversely affect, the below grade or under-water portion of the fixture. These corrosive materials might be salt, acidic and alkaline materials like those that can be found in artificial fertilizers, lime, chlorine, urine, cleaning materials, solvents, and the like. 
         [0004]    Due to these concerns, certain metals, for example aluminum alloys, typically must be protected with one or more protective coatings in order to provide adequate protection against potentially corrosive materials. Protective coatings used for this purpose include thermal-setting resinous coatings (“powder coating”), resin coatings applied through electro-deposition (“E-coating”), bituminous coatings, and the like. These coatings may or may not provide true long-term protection of the metal housing under potentially corrosive conditions. Another known approach for ascertaining long-term resistance to corrosion is the use of metals other than aluminum alloys for the construction of the fixture body, such as bronze or stainless steel, or the use of plastics, or various composite materials, which contain certain plastic resins, reinforcing fibers, and other additives. 
         [0005]    One of the main concerns in light fixtures which utilize high-power Light Emitting Diodes (LEDs) as a light source involves the dissipation of the heat generated by the associated semiconductor processes. Dissipating this heat is essential for keeping the LED light fixture&#39;s luminous performance at desirable levels, and for the long-term maintenance of the originally intended luminous output. In order to effectively dissipate the heat, materials of reasonably high thermal conductivity, which can facilitate the successful transfer of the generated heat away from the LED light source, must be employed. The applied materials, in combination with the light fixture configuration, need to provide for a comprehensive thermal management system of the light fixture. 
         [0006]    While most aluminum alloys have good thermal conductivity, the conductivity might be considerably downgraded by the application of the protective coating(s). Stainless steel is costly, and is not considered to have good thermal conductivity. Bronze has reasonably good thermal conductivity, but is costly, and has a tendency to react to certain materials may be contacted under certain operating conditions in various in-ground or underwater environments. Most composite materials have poor thermal conductivity. Metals such as aluminum, stainless steel and bronze conduct electricity, which might not be advantageous in certain applications of an electrical apparatus, especially under wet or moist operating conditions as unintended contact with electrical conductors may raise various safety concerns, including the potential for a person touching the fixture getting shocked or electrocuted. 
         [0007]    Based on the above, there is seen to exist a need for in-grade and/or under-water light fixtures with improved functionality, longevity and safety. In particular, it would be advantageous for such a light fixture not to be adversely affected by salt, acid and alkaline conditions that can be expected in the water, soil, masonry or the like that surround the installed light fixture. It is also imperative that the light fixture exhibit good thermal management. 
       SUMMARY OF THE INVENTION 
       [0008]    With the above in mind, it is a primary object of this invention to provide an in-grade or under-water light or luminaire fixture that overcomes the problems and shortcomings of the prior art. More specifically, it is an object of this invention to provide a housing for in-grade and under-water light fixtures wherein the fixtures are constructed in a manner which provides for improved functionality and longevity, particularly by not being adversely affected by salt, acid and alkaline conditions that can be expected in the water, soil, masonry or the like that surround the light fixture upon installation. In accordance with the invention, the in-grade or under-water light fixture housing also facilitates good thermal conductivity and thermal dissipation and defines an exceptionally safe housing which does not conduct electricity. 
         [0009]    These and other objects of the invention are achieved by providing a light fixture wherein the below grade or immersed portion of the light fixture comprises a housing constructed entirely or predominantly from ceramic materials which are not substantially negatively affected by salt, and/or most acidic and alkaline conditions that are typically present in the soil, masonry or water that surround the installed light fixture. Such adverse conditions can originate from marine or atmospheric salt, salt used for the de-icing of roadways and walkways, artificial fertilizers, lime, chlorine, urine, cleaning materials, solvents, and the like. The housings made of these ceramic materials in accordance with the invention will neither suffer from significant corrosion, nor otherwise disintegrate under expected operating conditions. In addition, the invention takes advantage of the thermal conducting and dissipating properties associated with ceramic materials by using these materials in the housing of in-grade or under-water light fixtures. As the ceramic materials exhibit superb thermal conducting properties, a housing constructed in accordance with the invention is ideal for LED lamping applications. 
         [0010]    In accordance with certain embodiments of the invention, the overall light fixture includes the ceramic housing, which may include a separate electrical connection or gear compartment, a light source such as an LED or array of LEDs, an outer sleeve, a lens, a gasket seated between the lens and the housing, a lens frame secured to the housing, and a ring. The lens frame is attached to the housing, such as through the use of various mechanical fasteners, with the ring interposed between the lens frame and the housing. With this attachment, the gasket is clamped or sandwiched between the lens and the housing for at least partially sealing the interior of the housing in which the LED(s) and other components are located. The housing is preferably provided with external fins for heat dissipation purposes, as well as a cable entry port for accommodating suitable electrical wiring. 
         [0011]    Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a cross-sectional view of a light fixture constructed in accordance with the invention. 
           [0013]      FIG. 2  is a cross-sectional view of a light fixture, similar to that a  FIG. 1 , but wherein a ceramic housing of the fixture establishes a separate electrical connection and gear compartment. 
           [0014]      FIG. 3  is an enlarged cross-sectional view of a portion of a lens frame to housing attachment according to a first embodiment of the invention. 
           [0015]      FIG. 4  is an enlarged cross-sectional view of a portion of a lens frame to housing attachment according to a second embodiment of the invention. 
           [0016]      FIG. 5  is an enlarged cross-sectional view of a portion of a lens frame to housing attachment according to a third embodiment of the invention. 
           [0017]      FIG. 6  is an enlarged cross-sectional view of a portion of a lens frame to housing attachment according to a fourth embodiment of the invention. 
           [0018]      FIG. 7  is an enlarged cross-sectional view of a portion of the light fixture of  FIG. 2 , with the inclusion of a vessel insert for the compartment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    With initial reference to  FIG. 1 , a luminaire or light fixture in accordance with the present invention is generally indicated at  10 . As will be detailed more fully below, luminaire fixture  10  employs ceramic material to provide an enclosure for a light source and other electronics, with the ceramic material assuring that the enclosure will not be affected by corrosive conditions, while exhibiting the thermal characteristics that are desirable for LED lamping. In particular, luminaire fixture  10  includes a housing  12  made of ceramic material, with housing  12  having a plurality of circumferentially spaced, upstanding heat dissipating fins  26  located on the exterior of housing  12  for heat dissipating purposes. 
         [0020]    In the illustrated embodiment, housing  12  includes a bottom wall portion, at least one upstanding side wall and an open top portion which collectively establishes an interior optical compartment  13 . The open top portion is defined by a flange  15  of housing  12 . Inside interior optical compartment  13  is a light source  22 , which is adapted to be electrically connected to a power source through a power cable (not shown) which can be routed into housing  12  through at least one cable entry  28 . Most preferably, cable entry  28  is sized relative to the cable or, more preferably additional gasket structure is provided through the use of a waterproof cable bushing or waterproof cable gland and the like (not shown) to create a barrier around the power cable and therefore prevent the ingress of any water or other contaminants into housing  12 . At this point, it should be recognized that the number and location of cable entries  28  can be varied. For instance, cable entry  28  could alternatively be located along the side wall of housing  12 . Housing  12  can take various shapes, such as an overall round shape, oval-shape, square-shape, or rectangular-shape. 
         [0021]    As indicated above, housing  12  includes heat dissipating fins  26 . Fins  26  establish certain surface expanding features, which further enhance thermal dissipation. Heat dissipating fins  26  are located on the exterior surface of the side walls of housing  12  and serve as part of an overall heat sink, thereby facilitating better thermal management by increasing the rate of heat transfer to the environment away from light source  22 . Fins  26  are preferably, evenly spaced apart to maximize heat dissipation and can be, but are not limited to, straight fins, straight pin fins, splayed pin fins, curved pin fins, flared fins, fluted fins, curved fins or wavy fins. In the most preferred embodiment, heat dissipating fins  26  are integrally formed as part of housing  12  so as to be made of the same ceramic material. 
         [0022]    As illustrated, luminaire fixture  10  also includes a lens frame  16 . Like housing  12 , lens frame  16  can also be made of ceramic material. However, lens frame  16  can also be made from metal, plastic or composite materials. In any case, as clearly illustrated in  FIG. 1 , lens frame  16  extends across and is configured to be attached to flange  15  of housing  12 . More specifically, lens frame  16  extends about a lens  14 , which can be transparent, prismatic or translucent and made from glass or plastic materials, and is provided to secure lens  14  to housing  12 . Lens  14  itself fits into a space defined by a recess (not separately labeled) established by flange  15 , with a lens gasket  18  being interposed between flange  15  and lens  14 . Therefore, gasket  18  is seated between flange  15  and lens frame  16 , while lens frame  16  both sandwiches lens  14  with gasket  18  and also extends across an outer radial portion of flange  15 . With this arrangement, lens gasket  18  establishes a waterproof seal into interior optical compartment  13  from the open top portion of housing  12  upon attachment of lens frame  16  to housing flange  15 . 
         [0023]    It is preferable that light source  22  be a solid state light source, such as, but not limited to, light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED). These LEDs can be miniature LEDs, mid-range LEDs, high-power LEDs (HPLEDs) or high-output LEDs (HO-LEDs). Light source  22  can be monocolor or multicolor and capable of changing color. In preferred embodiments, the solid state LEDs can be directly mounted on a circuit board in a chip-on-board (COB) assembly. 
         [0024]    It is also preferable that interior optical compartment  13  contain optics  20  to enhance the performance of the light fixture. Optics are often a desirable feature in outdoor, in-ground and underwater lighting applications. Optics  20  can include, but are not limited to, a reflector, a multifaceted reflector, projector lens type optics or the like, and can be made of metal, clear or vacuum metalized plastic, and the like. 
         [0025]    When fixture  10  is installed below grade (e.g., in-ground, soil or masonry installations), an insertion sleeve assembly  24  is used. Basically, insertion sleeve assembly  24  is used to establish a receptacle into which housing  12  can be inserted. For instance, in connection with an in-ground masonry installation, insertion sleeve assembly  24  establishes a concrete mask which is initially placed in a hole in the ground and then cement or concrete is poured around insertion sleeve assembly  24 . For this purpose, sleeve assembly  24  can be constituted by a single layer of material or multiple layers. In one preferred from, sleeve assembly  24  is constituted by PVC tubing. In any case, once insertion sleeve assembly  24  is fixed in place, housing  12  can be inserted into and removed therefrom as needed. In the embodiment depicted, for purposes of mounting housing  12  within sleeve assembly  24 , insertion sleeve assembly  24  includes an interior lip or platform  25  upon which a bottom surface of housing flange  15  is adapted to rest. In an alternative arrangement (not shown), sleeve assembly  24  is provided with an external lip for supporting housing  12 . In certain preferred embodiments, lip  25  of insertion sleeve assembly  24  is provided on a separate engaging part, such as a plastic part or metal part (not shown). In situations wherein it is desired to prevent relative rotation between housing  12  and insertion sleeve assembly  24 , anti-rotation structure is interposed between these components. For example, one or more projections extending from lip  25  can actually be configured to fit in the spaces formed between one or more adjacent pairs of heat dissipating fins  26 . Certainly, other anti-rotational arrangements could be employed, including between flange  15  and insertion sleeve assembly  24 . 
         [0026]      FIG. 2  illustrates a modified configuration for housing  12  wherein housing  12  further includes an auxiliary, electrical compartment or a connection and gear compartment  32 , which is separated or divided from optical compartment  13  by a platform  27 . In some highly preferred embodiments, platform  27  is a contiguous part of ceramic housing  12  and establishes the platform on which light source  22  is mounted inside interior optical compartment  13 . This configuration can be considered particularly advantageous as auxiliary compartment  32  can be employed to house an LED driver, a DC-to-DC converter, a ballast, a capacitor, a transformer, various sensors and the like or a combination thereof. As shown, a bottom cover  34  is used in conjunction with at least one compartment gasket  30 , to close and seal compartment  32 . In the most preferred embodiments, bottom cover  34  is in partial surface contact with housing  12 , and therefore provides for further expansion of the thermal dissipating surface. In some embodiments, bottom cover  34  can be made of ceramic material, but can also be made of other suitable materials, such as metals, plastics or composite materials. However, it is preferred that bottom cover  34  is made of a material that has reasonably good thermal conductivity and thermal dissipating qualities. Bottom cover  34  also includes a cable hole or entry  29  adapted to receive a power cable (not shown) in a sealed manner, preferably through the use of a waterproof cable bushing or waterproof cable gland and the like (not shown) which prevents the ingress of foreign material and water into electrical compartment  32  of housing  12 . 
         [0027]    In some advantageous embodiments, bottom cover  34  is fastened to ceramic housing  12  with corrosion resistant fasteners (not shown), such as stainless steel screws or the like, with the fasteners being screwed or otherwise anchored to housing  12  through a plurality of internally threaded sleeves, bosses, or the like which are rigidly attached to housing  12  by mechanical and/or adhesive means or integrally formed with the ceramic housing. Most preferably, the internally threaded sleeves or bosses are separately formed of metal, plastic, composite material or a combination thereof and attached to housing  12  by mechanical or adhesive means such as resinous bonding or resinous encapsulating. In a most advantageous embodiment, bottom cover  34  is fastened to ceramic housing  12  by corrosion resistant fasteners, such as stainless steel screws or the like, and the fasteners are screwed or otherwise anchored to housing  12  through a flat ring that resembles a large washer in a manner analogous to that set forth below with reference to  FIGS. 3-6 . 
         [0028]    As indicated above, it is important in connection with the present invention that housing  12  is made substantially entirely of ceramic material and has a high ingress protection rating for below grade or immersion applications. At the very least, more than 80% of housing  12  is composed of ceramic material and the material is substantially homogeneous in composition and physical properties throughout its volume. Examples of ceramic materials that can be used in accordance with the present invention include aluminum oxide, aluminum nitride, silicon nitride, beryllium oxide, and other advanced ceramic materials with reasonably good thermal conductivity. Making housing  12  of these ceramic materials enables housing  12  not to be negatively affected by salt, as well as most acidic and alkaline conditions which can be expected in the soil, masonry, water or the like that surrounds light fixture  10  when employed in these particular environments. For instance, in the environments in which the invention pertains, adverse conditions can originate from various sources, including marine or atmospheric salt, salt used for the de-icing of roadways and walkways, artificial fertilizers, lime, chlorine, urine, cleaning materials, solvents, and the like. Because the ceramic material is unaffected by corrosive conditions for operational purposes, the surface of housing  12  does not need to be coated. Therefore, no coating materials need to be applied, which might potentially hamper thermal dissipation. In addition, the ceramic material advantageously will not conduct electricity, but instead provides an electrical isolating and insulating function so as to exhibit safety related benefits. 
         [0029]    It is also important to note that these types of ceramic materials possess good thermal conductivity. Heat can be detrimental to the performance and longevity of a solid state light fixture and the various components thereof. Excessive heat is especially detrimental to the luminous performance and longevity of LEDs and some of the electronic components which are used in conjunction with them. Therefore, the ceramic housing serves as a beneficial component of the light fixture&#39;s thermal management system. Under optimal circumstances, a significant portion of the ceramic housing is utilized as a heat-sink. Good surface contact between the heat generating components and the ceramic light fixture housing will aid in the transferring of the heat away from the heat generating components. 
         [0030]    Certainly, there exist potential disadvantages to using ceramics in light fixture housings, such as related disadvantages like hard-to-maintain tolerances and poor resistance to impact. However, the invention addresses potential drawbacks with additional structure allowing for secure attachments and even extreme forces to be exerted on lens  14 , lens frame  16  and housing  12  of light fixture  10 . In fact, one main use of the light fixture constructed in accordance with the invention concerns installing the light fixture in a paved walkway or roadway where it can be exposed to pedestrian foot traffic or where vehicular traffic can roll over the installed light fixture. At least in such situations, certain additional features of the overall invention are employed to address this concern as will now be discussed in detail with reference to  FIGS. 3-6 . 
         [0031]      FIG. 3  shows in more detail a lens frame attachment embodiment where a flat ring  42  is utilized for the attachment of lens frame  16 . In a preferred embodiment, lens frame  16  is fastened to housing flange  15  of ceramic housing  12  by a plurality of corrosion resistant fasteners  41 , such as stainless steel screws or the like, and fasteners  41  are screwed or otherwise indirectly anchored to housing  12  through ring  42  that resembles a large washer. Ring  42  is flat and has a plurality of internally threaded holes  38  that are perpendicular to the ring&#39;s flat surface and establish a means for mechanically attaching lens frame  16 , thereby avoiding any necessity to directly attach lens frame  16  to housing  12 . To this end, flat ring  42  can be made of metal, plastic or composite materials. 
         [0032]    As illustrated, the structure of each of lens  14 , gasket  18  and lens frame  16  need not change to accommodate ring  42 . Instead,  FIG. 3  simply illustrates a reduction in the height of flange  15  to account for a height of ring  42 . As shown, flat ring  42  has radial dimensions corresponding to that of flange  15  such that ring  42  has a major diameter corresponding to an outside diameter of housing flange  15 , as well as a minor diameter exposed to interior optical compartment  13 . Although flat ring  42  can be simply positioned and then sandwiched between lens frame  16  and flange  15 , ring  42  is preferably mechanically attached, fused or adhesively attached with room temperature vulcanizing (RTV) material, such as silicone rubber or the like, to housing flange  15  in a structurally sound manner. Lens frame  16  is fastened to ring  42  by corrosion resistant mechanical fasteners such as stainless steel screws and the like. In embodiments where both lens frame  16  and ring  42  are made of plastic material, the fastening may be achieved by means of ultrasonic welding. 
         [0033]    For embodiments where threaded fasteners are used, internally threaded holes  38  on flat ring  42  align with a formed or machined recess or recesses  40  in housing flange  15  that are perpendicular to the flat ring engaging edge of housing flange  15 . During assembly, after properly positioning gasket  18  and lens  14 , a plurality of through holes  36  on lens frame  16  are then aligned with the internally threaded holes  38  on flat ring  42  and recesses  40  of housing flange  15 . Fasteners  41  are inserted into the aligned holes  36 ,  38  and  40 . Again, when fasteners  41  constitute threaded fasteners, internally threaded holes  38  engage threads on fasteners  41 . The portion of the threaded shaft of fasteners  41  that projects past the thickness of flat ring  42  protrudes into recess  40  of housing flange  15 . Therefore, with this preferred construction, there is no threaded connection directly with the ceramic housing  12  while, when fully tightened to ring  42 , fasteners  41  secure lens frame  16  to housing flange  15 . In embodiments where housing  12  is not round in plan view, but rather oval or some polygonal shape, the shape and dimensions of flat ring  42  preferably matches the shape and approximate major and minor dimensions of the edge of housing flange  15  which engages flat ring  42 . 
         [0034]      FIG. 4  depicts another embodiment of the present invention wherein a ring  44  includes a returned lip to provide for additional surface contact with housing flange  15 . The returned lip is substantially perpendicular to the flat surface of flat ring  44 , and is radially located along a minor, a major, or both the minor and the major circumference of flat ring  44 . With this arrangement, the returned lip(s) engages housing flange  15  at its exterior, interior, or both exterior and the interior side portions, each of which is substantially perpendicular to the flat ring engaging edge of housing flange  15 . The returned lip or edge of flat ring  44  is configured with load bearing and/or load transferring qualities to allow for heavy weights to bear down on lens  14 , lens frame  16  and housing  12  of light fixture  10 . Again, lens frame  16  is fastened to ring  42  by corrosion resistant mechanical fasteners such as stainless steel screws and the like. In embodiments where both lens frame  16  and ring  44  are made of plastic material, the fastening may be achieved by means of ultrasonic welding. 
         [0035]      FIG. 5  shows an alternative embodiment where a flat ring  46  comprises bosses at various circumferentially spaced fastener engaging locations. The shafts of the bosses are perpendicular to the flat part of flat ring  46 . In assembly, these bosses protrude into one or more recesses  40  provided on the flat ring engaging edge of housing flange  15 . In this embodiment, the shafts of fasteners  41  are partially, or preferably entirely, retained in an internally threaded hole  47  of each boss of a respective ring  46 , which is parallel or concentric to the axis of each boss. The bosses substantially increase the surface and the number of threads that engage fasteners  41 . As should be readily apparent based on this description, flat ring  46  having the bosses will also exhibit load bearing and/or load transferring qualities which will allow for heavy weights to bear down on lens  14 , lens frame  16  and housing  12  of light fixture  10 . 
         [0036]    Referring now to  FIG. 6 , there is shown another advantageous embodiment that includes a clamping ring  48 . Clamping ring  48  engages both a bottom surface and an exterior sidewall of flange  15  of ceramic housing  12 , e.g., the surface opposite the flat ring engaging edge of housing  12  and an exterior sidewall of flange  15 . Clamping ring  48  can be made of metal, plastic or other suitable material and may or may not be adhesively or otherwise fixedly attached to ceramic housing  12 . In accordance with this embodiment, lens frame  16  is fastened to clamping ring  48  with housing flange  15  retained between lens frame  16  and clamping ring  48 . As with the other embodiments discussed above, the fastening of lens frame  16  and clamping ring  48  can be achieved by corrosion resistant mechanical fasteners  41 , such as stainless steel screws, rivets or the like, or can be achieved through the use of adhesives. In embodiments where both lens frame  16  and clamping ring  48  are made of plastic material, the fastening can be achieved by ultrasonic welding. In embodiments where both lens frame  16  and clamping ring  48  are made of metal, such as stainless steel, the fastening can be achieved by metal welding. 
         [0037]    As indicated above, bottom cover  34  can be fastened to ceramic housing  12  in various different ways, including with corrosion resistant fasteners. However, as with the case of attaching lens frame  16  to housing  12 , it can be desirable to provide an indirect attachment.  FIG. 7  shows a portion of housing  12  and illustrates an embodiment wherein a plastic, preferably injection molded vessel or cup  50  is employed in attaching bottom cover  34 . As shown, vessel  50  is inserted into compartment  32 , with vessel including a base  53  having a wire routing opening  55 . Base  53  is spaced from platform  27  by various spaced standoffs or feet elements  60  which extend from base  53  at spaced locations and abut platform  27 . Base  53  also includes a sidewall  63  which can be uniformly thick or have a main thickness generally corresponding to base  53  in combination with various circumferentially spaced, thicker regions which define bosses (as shown). Extending outwardly from sidewall  63  is a radial flange  66  which leads to a return edge or rim portion  68  of vessel  50 . 
         [0038]    When vessel  50  is concentrically positioned within compartment  32 , radial flange  66  abuts a terminal wall  75  of housing  12 , with base  53  being spaced from platform  27  by standoffs  60 , while sidewall  63  is also spaced from housing  12 . With this arrangement a cavity, including a first cavity portion  78  along sidewall  63  and a second cavity portion  79  along base  53 , is established between vessel  50  and housing  12 . Radial flange  66  is formed with an injection port  70  which leads into each of the first and second, fluidly connected cavity portions  78  and  79 . Another port (not shown) is also provided at a spaced location from injection port  70 , such as on an opposing portion of radial flange  66 . Once vessel  50  is situated in this manner and the necessary cable wires are routed from light source  22  through cable entry  28  and routing opening  55 , specifically with the use of silicone or other types of sealing plugs (not shown), housing  12  can be inverted and vessel  50  clamped or otherwise fixedly retained within compartment  32 . Thereafter, a potting or other encapsulating resin can be injected into injection port  70  to fill first and second cavity portions  78  and  79 . The port on the opposing portion of radial flange  66  can either be used to also inject resin or, advantageously, employed as both a vent hole and also as a riser to provide a visual indication of when the injection operation is complete. In any case, the injected resin will evenly fill the entire cavity and permanently bond vessel  50  to housing  12 . The resin also prevents water and other contaminants from entering optical compartment  13  through compartment  32 . In particular, an enhanced condensation barrier is established. Preferably the resin is a catalyzed, setting-type resin such as polyurethane, polyester, and the like, which hardens at a relatively fast rate. Alternative potting materials might be un-catalyzed resins, low viscosity silicone sealant, and the like. 
         [0039]    After the resin sets, a gasket  83  is positioned along radial flange  66  so as to extend over ports  70 . Thereafter, bottom cover  34  is placed upon gasket  83  within the confines of rim portion  68 . Then, corrosion resistant fasteners  85 , such as stainless steel screws and the like, are employed to removably secure bottom cover  34  onto sleeve  50  and, indirectly, to housing  12 . Although not shown in this figure, bottom cover  34  includes cable hole  29  for the directing a mains cable into compartment  32  in the same manner discussed above. At this point, it should also be noted that other encapsulation arrangements can be employed in connection with compartment  32  such as, instead of employing vessel  50 , compartment  32  could be fully filled with a resin so as to permanently retain all components and the cable within compartment  32  and avoid the need for bottom cover  34 . 
         [0040]    It should be readily apparent that the invention provides a luminaire or light fixture which employs a ceramic housing and is specifically configured for use in in-ground and under-water applications. The ceramic housing provides useful solutions to problematic aspects of in-ground and under-water applications of LED luminaires. The ceramic housing provides for good thermal management, thereby producing improved functionality, improved luminous performance, and longevity of the electronic components employed within. The ceramic housing also provides useful solution to corrosion related problems that can be expected due to corrosive substances which are often present in the water, soil, masonry or the like that surround the installed light fixture and which can adversely affecting functionality and longevity of the light fixture. The ceramic housing is electrically isolating, and therefore it provides for an exceptionally safe luminaire housing. Provisions are specifically taken to assure secure attachment of a lens frame to the housing, either directly or indirectly, and thereby preventing the ingress of potential contaminants into the housing and enabling the light fixture to be used under conditions where the above grade portion of the fixture is exposed to pedestrian or vehicular traffic. In any event, although described with reference to preferred embodiments of the invention, it should be readily understood that various changes and/or modifications can be made to the invention without departing from the spirit thereof. For instance, although the light source is shown to include its own printed circuit board (PCB), the LEDs could be mounted right on the ceramic housing so the ceramic is the PCB. In addition, other fastening arrangements for the lens frame can be employed. For example, the fastening screws for the lens frame can actually extend through bores provided in the housing frame and then screwed into the insertion sleeve assembly.