Abstract:
A thermally stabilized lamp assembly that can be de-energized without continuing to provide moving air for cooling purposes. The assembly includes an arc lamp bulb having a base and a reflector. A heat pipe containing a thermally conductive fluid is configured for thermal communication with the arc lamp base. A heat dissipation assembly is coupled in fluid communication with the heat pipe to dissipate heat produced by the lamp into the ambient environment, thereby cooling the lamp both before and after the lamp is de-energized. Accordingly, it is not necessary to provide moving air to cool the arc lamp after it is de-energized.

Description:
BACKGROUND 
   Presently, there are a wide variety of projection technologies available in the marketplace. For example, overhead projectors, front projection televisions and rear projection televisions each employ projector technologies. Current projection systems frequently employ a high-output arc lamp to provide as an illumination source. Arc lamps are known to generate significant levels of waste heat while operating, producing surface temperature differentials of several hundred degrees Fahrenheit on various portions of the lamp. Additionally, a lamp housing that typically encloses such a lamp can also reach temperatures of many hundred degrees during operation of the lamp. Consequently, most projection systems incorporate a fan to provide forced convective cooling of the arc lamp and the lamp housing. However, the significant temperatures involved frequently require that the fan continue to run for a period of time after the lamp has been de-energized in order to dissipate heat retained in the lamp and lamp housing, both to preserve the lamp and to protect other parts of the projection system from thermal stress. 
   Clearly, the need to provide forced-air convective cooling of the lamp and its assembly after the lamp has been de-energized will mandate that the projection system then continue to provide electrical power to the fan motor. However, if power to a projection system is interrupted by a power outage or a tripped circuit breaker, or by someone inadvertently pulling the power cord from a line power socket, damage to the projection system due to excessive heat build up is possible. Furthermore, operation of the fan often significantly increases the ambient noise level, which is very apparent and undesirable when the projection system is used in a quiet environment. Therefore, a projection system that allows instant interruption of electrical power without risking thermal damage to the lamp or other components of the projector system would be of particular interest. 
   SUMMARY 
   Several implementations of an interactive display are described below in detail. One such implementation includes a housing having within it a lamp and a thermal management assembly. In one exemplary embodiment described below, the lamp has a main body portion coupled to a stem portion. The stem portion can include an electrical interface at one end. A second end of the stem portion can be coupled to the main body portion. As described below, the thermal management assembly can include a heat pipe coupled to a remote heat sink. The heat pipe described in one implementation is a hollow member containing a thermally conductive fluid. The heat pipe can be disposed near the stem portion of the lamp to conduct heat away from the stem portion and to the remote heat sink assembly. 
   Another exemplary embodiment described below includes a thermally stabilized lamp assembly that can be de-energized without continuing to provide moving air for cooling purposes. This version includes an arc lamp bulb having a base and a reflector. A heat pipe that contains a thermally conductive fluid is configured for thermal communication with the arc lamp base. Also described in this embodiment is a heat dissipation assembly that is in fluid communication with the heat pipe and which is configured to dissipate heat produced by the lamp when the lamp is energized, so that the arc lamp bulb can de-energized, without the need to provide moving air to cool the arc lamp. 
   Yet another exemplary implementation described below includes a method for enabling an illumination source to be de-energized without providing moving air to cool the illumination source after it has been de-energized. This implementation provides a heat tube in thermal communication with the illumination source and circulates a thermally conductive medium through the heat tube to transfer waste heat from the illumination source to an ambient environment. 
   This Summary has been provided to introduce a few concepts in a simplified form that are further described in detail below in the Description. However, this Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 

   
     DRAWINGS 
     Various aspects and attendant advantages of one or more exemplary embodiments and modifications thereto will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a schematic diagram illustrating an exemplary thermally managed lamp assembly; 
       FIG. 2  is a second schematic diagram illustrating another exemplary thermally managed lamp assembly; and 
       FIG. 3  is a schematic diagram illustrating an exemplary interactive display table incorporating a thermally managed lamp assembly. 
   

   DESCRIPTION 
   Figures and Disclosed Embodiments are not Limiting 
   Exemplary embodiments are illustrated in referenced Figures of the drawings. It is intended that the embodiments and Figures disclosed herein are to be considered illustrative rather than restrictive. Furthermore, it should be understood in the following description and claims that when lists of alternatives are offered using the conjunctive form “and” that what is meant is “and/or.” 
     FIG. 1  is a schematic diagram illustrating an exemplary thermally managed lamp assembly  100 . As depicted in  FIG. 1 , lamp assembly  100  includes a lamp  101  having a main body portion  102  and a stem portion  103 . One end of stem portion  103  is shown coupled to main body portion  102 , while the other end of stem portion  103  is shown having an electrical connection  110 . Electrical connection  110  can be any electrical interface suitable for coupling electrical power to lamp  101 . A heat tube  130  is shown in  FIG. 1  as being helically coiled around a portion of the stem portion  103 . However heat tube  130  can be positioned proximate to stem portion  103  in any suitable manner that provides thermal communication between stem portion  103  and heat tube  130 . The heat tube can contain a thermally conductive fluid to provide heat flow away from a heat source. A remote heat sink assembly  140  is shown as including a heat dissipation device  141 . The heat tube  130  can be optionally be coupled to the remote heat sink assembly  140  via additional segments of pipe material, as illustrated in  FIG. 1 , for example, by segments  111   a ,  111   b ,  111   c , and  111   d . Segments  111   a - 111   d  can be any material suitable for coupling heat pipe  132  to remote heat sink assembly  140  so as to provide a fluid path for the fluid contained within the heat pipe. 
   Lamp  101  can be any high intensity type, such as an arc lamp. Generally, stem portion  103  of lamp  101  is made of a heatproof material, such as heat-proof glass or a ceramic. Heat tube  130  is generally a hollow elongate member and can have any cross-sectional geometry such as for example round or square, depending on the application. Heat tube  130  can be made of any suitable material such as copper, aluminum, steel, carbon composite, ceramic, or various heat-tolerant polymers. In one implementation, heat tube  130  is a closed-circuit fluid-filled pipe that serves as a heat exchanger. The thermally conductive fluid contained in the heat tube  130  can be any suitable thermal carrier such as water, various alcohols, toluene, acetone, phenol, ammonia, and halide salts. In general, the thermally conductive fluid is selected based upon the range of temperatures at which the lamp will operate in order to maximize heat flow through heat tube  130 . Remote heat sink assembly  140  can include one or more heat dissipation devices, such as a condenser, a finned heat sink, a heat exchanger, and/or a fan. 
   In one implementation, the thermally conductive fluid contained in heat tube  130  is caused by convective movement to circulate within the portion of the heat tube that is in proximity to the stem portion  103  of the lamp  101 , thereby causing heat flow from stem portion  103  to remote heat sink assembly  140  as the circulating fluid vaporizes in the part of the heat tube adjacent to stem portion  103  and condenses within remote heat sink assembly  140 . 
     FIG. 2  is a second schematic diagram illustrating another exemplary thermally managed lamp assembly. As depicted in  FIG. 2 , a lamp assembly  200  again includes a lamp  201  having a main body portion  202  and a stem portion  203 . One end of stem portion  203  is shown coupled to main body portion  202 , while the other end of stem portion  203  is again shown having an appropriate electrical connection  210  suitable for coupling electrical power to lamp  201 . A heat tube  230  shown in  FIG. 2  is helically coiled around a portion of stem portion  203 . As described above with reference to  FIG. 1 , heat tube  230  can be positioned proximate to stem portion  203  in any manner that provides thermal communication between stem portion  203  and heat tube  230 . However,  FIG. 2  shows the addition of a thermally conductive gap-filling material  250  positioned to enhance heat transfer between heat tube  230  and stem portion  203 . Thermally conductive gap-filling material  250  can be any material suitable for enhancing heat transfer such as silicone elastomers and/or polymers, which may include various fill materials, such as ceramic particles, graphite particles, and structural backing materials, such as aluminum, fiberglass, and copper. Thermally conductive gap fillers are known in the art, and a skilled practitioner will recognize that other equivalents can be added to the above list, which is clearly not intended to be limiting. Thermally conductive gap-filling material  250  can be disposed in any manner that enhances heat transfer between stem portion  203  and heat tube  230 . In one implementation, gap filling material  250  is wrapped around stem portion  203 , and heat tube  230  is helically wrapped around stem portion  203  so that the heat tube is in contact with gap-filling material  250 . 
   As described above, the heat tube can contain a thermally conductive fluid to facilitate heat flow away from a heat source. A remote heat sink assembly  240  is shown as including a heat dissipation device  241 . Heat tube  230  can be coupled to remote heat sink assembly  240  via additional segments of pipe material, as illustrated in  FIG. 2  by exemplary segments  211   a - 211   d . Segments  211   a - 211   d  can be any material suitable for coupling heat pipe  230  to remote heat sink assembly  240 . 
   As also described above, lamp  201  can be any high intensity illuminant type, such as an arc lamp. Generally, stem portion  203  of lamp  201  is made of a heatproof material such as a ceramic. Heat tube  230  can be made of any suitable material, such as copper, aluminum, steel, carbon composite, ceramic, or various heat-tolerant polymers. In one implementation, heat tube  230  is a closed-circuit fluid filled pipe that functions as a heat exchanger. The thermally conductive fluid contained in heat tube  230  can be any suitable thermal carrier, such as water, various alcohols, toluene, acetone, phenol, ammonia, and halide salts. In general, the thermally conductive fluid is selected based upon the range of temperatures at which the lamp will operate in order to maximize heat dissipation through heat tube  230 . Remote heat sink assembly  240  can include one or more heat dissipation devices, such as, a condenser, a finned heat sink, a heat exchanger, and/or a fan. 
   In one implementation, the thermally conductive fluid contained in heat tube  230  is caused to circulate within the heat tube in proximity to stem portion  203  of lamp  201 , and aided by thermally conductive gap-filler material  250 , causes heat flow from stem portion  103  to remote heat sink assembly  240 , as the circulating fluid vaporizes at the stem portion of the lamp and condenses within the remote heat sink assembly with which heat tube  230  is coupled in fluid communication. 
     FIG. 3  is a schematic diagram illustrating an exemplary interactive display table  300  incorporating a thermally managed lamp assembly. Interactive display table  300  is shown having a housing  301  that includes a thermally managed lamp  310  within a lamp housing  311 , a fan  320 , a remote heat sink assembly  330 , and display electronics  340 . Thermally managed lamp  310  is shown in thermal communication with remote heat sink assembly  330  (through a heat pipe, as explained above). A fan  320  and a thermally managed lamp  310  are shown in electrical communication with display electronics  340 .  FIG. 3  illustrates that fan  320  is configured to provide forced conductive cooling to lamp housing  311  and thermally managed lamp  310 . In one implementation, fan  320  is operative to provide forced conductive cooling only when thermally managed lamp  310  is energized. In another implementation, a lamp housing  311  is made of heat resistant ceramic material. In yet another implementation lamp housing  311  is made of a composite material such as a plastic or polymer material embedded with glass fiber or carbon fiber matrix material. 
   Thermally managed lamp  310  and remote heat sink assembly  330  are operative together to form a thermally managed lamp assembly, as described above in reference to  FIGS. 1 and 2 . Accordingly, one implementation of interactive display table  300  includes thermally managed lamp assembly  100 , and other components discussed above with reference to  FIG. 1 . Another implementation of interactive display table  300  includes thermally managed lamp assembly  200 , and other components discussed above with reference to  FIG. 2 . In general, remote heat sink assembly  330  can be physically spaced apart from display electronics  340  to further thermally stabilize and thermally isolate the heat sensitive components of interactive display table  300 . Also, additional thermal insulation (not shown) can be included in interactive display table  300  to further isolate sensitive components such as display electronics  340  from waste heat. In one implementation, remote heat sink assembly  330  includes a finned heat sink (i.e., a radiator) that is thermally coupled to an ambient environment outside of the interactive display table housing  301 . 
   In operation, the thermally managed lamp assembly (as described above) of interactive display table  300  removes heat from thermally managed lamp  310  while the lamp is in operation and after lamp  310  has been de-energized, thereby allowing power to be removed from fan  320  immediately upon de-energizing the lamp, without damage to the lamp or other components occurring because of heat build-up. Such damage is avoided due to the thermal isolation provided by insulation and through heat transfer away from the lamp assembly via a heat pipe as discussed above. 
   Another aspect of this technology is directed to an exemplary method for enabling an illumination source to be de-energized without providing moving air to cool the illumination source after it has been de-energized. A first step of the method includes the step of providing a heat tube in thermal communication with the illumination source. A thermally conductive medium is then circulated by natural convection through the heat tube to transfer waste heat from the illumination source to an ambient environment. One implementation includes the additional step of increasing thermal conductivity between the heat tube and the illumination source using a thermally conductive gap filler that is disposed between the illumination source and the heat tube. Another implementation includes the additional step of conveying the thermally conductive fluid to a remote heat dissipation device that is in thermal communication with the ambient environment. Still another implementation includes the additional step of positioning the remote heat dissipation device in order to maximize thermal communication away from the illumination source and into the ambient environment. 
   Although the present invention has been described in connection with the preferred form of practicing it and modifications thereto, those of ordinary skill in the art will understand that many other modifications can be made to the present invention within the scope of the claims that follow. Accordingly, it is not intended that the scope of the invention in any way be limited by the above description, but instead be determined entirely by reference to the claims that follow.