Abstract:
A method and apparatus for increasing the output of an infrared emitter. High temperature concerns affecting the radiant energy transfer efficiency of the infrared emitter are addressed by varying the emitter tube design and varying the locations of both the reflective and high emissivity materials located on the emitter constituent parts. A cooling fluid may be passed through the emitter from both ends to allow higher power density or to cool the emitter during its operation. Selectable wavelength infrared emissions are achieved through the design of the infrared emitter.

Description:
This application claims the benefit of U.S. Provisional Application Serial No. 60/120,955 filed Feb. 19, 1999. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an infrared emitter and, and more particularly, a method and apparatus for increasing the output of an infrared emitter. 
     BACKGROUND OF THE INVENTION 
     Infrared emitters provide radiant heat in numerous applications. For instance, they are the preferred heat source for drying paints supplied to metal surfaces, including solvent based paints, water based paints, and powder paints. They also provide heat for environmental test chambers and many industrial processes. 
     A typical infrared emitter includes a slender tubular quartz enclosure containing an elongated coiled filament that extends through the enclosure and connects to lead-in conductors at opposite ends of the enclosure. Infrared radiation emanates from the filament in all directions in a spherical pattern, and thus the power of the radiant energy decreases in proportion to the square cube of the distance from the emitter. Only the energy which is absorbed by the object is transferred to the object as heat energy, and of the energy which strikes the object, a portion will be reflected, a portion will be absorbed, and depending upon the object, a portion may be transmitted through the object. Only the radiant energy which actually strikes the object and is absorbed provides heat within the object. The remaining radiant energy is redirected or continues travelling through space, thereby reducing the overall energy transfer efficiency from the infrared emitter to the object to be heated. 
     To improve the radiant energy transfer efficiency, the radiant energy leaving the emitter is generally focused in some manner towards the object to be heated. In one approach the infrared emitters are employed within an enclosed tubular sheath having reflective walls. The energy not directly passing from the infrared emitter to the object and absorbed by the object, continues to be reflective off the surfaces of the chamber until it strikes the object, escaping from an opening in the chamber or dissipating through inefficiencies and the reflectors. 
     In another application, where the heating chamber must be kept free of articulate matter and cleanliness is essential, the heating chamber of the infrared emitter is constructed using flat walls. This reduces the amount of dust that can form on the external reflectors of the infrared emitter. 
     In yet another application, a gold reflective coating has been placed on the outer surface of the infrared emitter forming an integral reflector. This feature included with the aforementioned flat wall construction, provides an advantage of improving the radiant energy transfer efficiency and at the same time improving the cleanliness and the heating chamber environment. However, the gold reflective coating places restrictions upon the infrared emitter design. A gold metal reflector coating may simply vaporize off of the surface of the enclosure due to excessive emitter temperature caused by trapped energy within the emitter system. 
     In still yet another application, an external sheath of quartz or other high transmissive material has been placed about the infrared emitter enclosure, with a reflective metal coating applied to the outer sheath. U.S. Pat. No. 5,382,805 addressed an infrared energy emitter which included a longitudinally extending tubular enclosure infrared energy transmitting material enclosing a longitudinally extending filament. A longitudinally extending outer tubular sheath of infrared energy transmitting material covered the tubular enclosure and was provided with a reflector. This allowed the infrared emitter to run at high power densities while maintaining a relatively cool outer surface temperature. However, higher power densities adversely affect the end seals and reflective coatings. The aforementioned patent tried to overcome this high temperature concern by providing fluid conductive filters at each end of the sheath to filter cooling fluid paths through the emitter. However, the ability to cool the infrared emitter by passing a cooling fluid into the enclosure at one end does not efficiently reduce the high temperature concerns with the integrity of the emitter while attempting to improve the radiant energy transfer efficiency. 
     It is therefore a principle object of the present invention to provide a method for increasing the output power of an infrared emitter without sacrificing the structural integrity of the emitter. The high temperature concerns associated with the higher power density of the emitted infrared energy are addressed by more efficient heat venting techniques. 
     It is still another object of the present invention to provide a longitudinally extending hermetically sealed tubular enclosure of infrared energy transmitting material enclosing the filament having at least one inner tubular support device in a predetermined position including a plurality of apertures for fluid flow therethrough. 
     It is yet another object of the present invention to provide a heat sink which is intimately associated with an electrical conductor extending from the filament out through the tubular enclosure which encapsulates the emitting filament. The heat sink is used to assist in heat dissipation from the infrared emitter and the filament electrical supply conductor, typically a pin. 
     It is still yet another object of the present invention to provide a longitudinally extending outer tubular sheath of infrared energy transmitting material having an inner and an outer surface with a plurality of ports strategically located at predetermined locations along the outer surface of the sheath. The sheath will have two ends, each end will have at least one passage for fluid flow therethrough. A reflector, comprising a reflective coating on a surface of the sheath, will extend partially circumferentially with the sheath forming a central longitudinal section for the transmission and/or absorption of secondary electromagnetic wave emission. 
     A heat dissipator comprising a high or low emissivity coating and is disposed over the reflector forming an intimate contact thereto. This also aids in adjusting the temperature of the infrared emitter by strategically and controlled radiant means. 
     It is still another object of the present invention to provide that the ports be placed in the window of the outer tubular enclosure to direct the exhausted fluid toward the work in process. Alternatively, the ports can be placed so that the fluid will be channeled away from the work in process. The ports also provide pressure relief to accommodate fluid flow into one or both ends of the emitter system. 
     It is still another object of the present invention to provide high watt densities from small outer tubular diameters while simultaneously cooling the integral reflector material, the outer tubular enclosure, the reflector, and the window. The higher power output capabilities will reduce the overall quantity of emitters required for many systems without reducing the overall system output power while providing increased efficiency. 
     It is yet another object of the present invention to create different radiation emission patterns by varying the cross-sectional tubular enclosure shape. These shapes may also be combined with other shapes to include a mixture of polygons. 
     It is yet another object of the present invention to provide an inner tubular support positioned in a predetermined location with respect to the sheath. In addition to its support function, the inner tube support may include passages to permit the flow of the cooling fluid through the inner support. This may allow fluid flow passages configured to achieve a predetermined fluid flow pattern. 
     It is yet another object of the present invention to provide dual peak wavelengths of infrared emission efficiently from one infrared emitter. This may be accomplished with or without the use of a transducer housing. 
     It is still yet another object of the present invention to provide selectable electromagnetic peak wavelength emissions. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an apparatus and method for increasing the output power of an infrared emitter and addressing the concerns associated with the damaging and undesirable higher temperatures produced within the electromagnetic emitter components. The apparatus and method of the present invention use unique reflection and heat dissipation techniques to accomplish the aforementioned. 
     In a preferred embodiment of the invention, the apparatus of the present invention includes a method for heating an object with infrared energy by passing a current through an elongated filament, and may be disposed within an hermetically sealed cylindrical enclosure. Surrounding the enclosure is an outer elongated tubular sheath of infrared energy transmitting material having an inner and an outer surface with a plurality of ports strategically located at predetermined locations along the outer surface of the sheath. The sheath has two ends, and each end has at least one passage for fluid flow therethrough. There is a reflective coating on an inner surface of the sheath extending partially, circumferentially with the sheath to form a central longitudinal section referred to as a window. A coating of predetermined emissivity is disposed on the outside of the sheath and is generally congruent to the reflective coating that resides on the inner surface. The central longitudinal section of the sheath is spaced apart from the enclosure about the entire circumference of the enclosure sufficiently to protect the reflective coating from the infrared energy that is emitted by the filament. Infrared radiation from the filament is reflected off of the reflective coating on the sheath, back toward the filament, thus passing infrared radiation towards an object from the filament through the window. A cooling fluid passes through the space between the sheath and the enclosure to cool the enclosure, sheath, the reflective coating and controlled emissivity coating. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various advantage of the present invention will become apparent to one skilled in the art by reading the following specification and subjoined claims and by referencing the following drawings in which: 
     FIG. 1 is a side view of the infrared emitter arranged in accordance with the principles of the present invention and having fluid purging and exhaust ports. 
     FIG. 2 is a cross-sectional view taken along the line A—A of FIG.  1 . 
     FIG. 3 is an end view of the infrared emitter of FIG.  1 . 
     FIG. 4 is an end view of the opposite end of the infrared emitter of FIG.  1 . 
     FIG. 5 is a cross-sectional view of the infrared emitter taking along the line  5 — 5  of FIG.  4 . 
     FIG. 6 is an end view of an inner tube support device for supporting the inner tube of the infrared emitter. 
     FIG. 7 is an end view of a second inner tube support device for supporting the inner tube of the infrared emitter. 
     FIG. 8 is an end view of the inner tube support device for supporting the inner tube and for creating a helical fluid flow within the outer tube. 
     FIG. 9 is a side view of the infrared emitter having an inner tube support device and heat sink fins for cooling the electrical conductor of the infrared emitter and a wave converter housing. 
     FIG. 10 is an end view of the heat dissipator shown in FIG.  9 . 
     FIG. 11 is a cross-sectional view of an infrared emitter radiant heat dissipator having gold on the outside of the outer tube and a controlled emissivity material on the outer surface of the gold deposition. 
     FIG. 12 is a radiant heat dissipator for an infrared emitter having gold formed on the inside of the outer tube and a controlled emissivity material on the outside of the outer tube. 
     FIG. 13 is an optional configuration showing patterns of controlled emissivity material formed over the gold to regulate a percentage of radiant energy dissipated by the material. 
     FIG. 14 is an optional configuration showing a series of lines of controlled emissivity material formed over the window to provide absorption and re-radiation of a different peak infrared emission, possibly combined with the original peak emission, thereby providing a multiple peak emissions or a single longer converted peak IR emission. 
     FIG. 15 is an optional configuration showing a series of dots of controlled emissivity material formed over the window to provide absorption and re-radiation of a different peak infrared emission, possibly combined with the original peak emission, thereby providing a multiple peak emissions or a single longer converted peak IR emission. 
     FIG. 16 is a perspective view of an infrared emitter having a selective electromagnetic peak wavelength conversion device. 
     FIG. 17 is a cross-sectional view of the infrared emitter of FIG. 16 showing the wavelength conversion device arranged so that no wavelength conversion occurs. 
     FIG. 18 is a cross-sectional view of the infrared emitter of FIG. 16 showing the wavelength conversion device arranged so that a first wavelength conversion occurs. 
     FIG. 19 is a cross-sectional view of the infrared emitter of FIG. 16 showing the wavelength conversion device arranged so that a second wavelength conversion occurs. 
     FIG. 20 depicts a single tube infrared emitter having an integral reflector. 
     FIG. 21A depicts an end view of a filament support. 
     FIG. 21B depicts a side view of a filament and filament support device. 
     FIG. 22 is a three tube infrared emitter including an exhaust tube for controlled venting of purge fluid. 
     FIG. 23 is a cross-sectional view of the three tube infrared emitter of FIG.  22 . 
     FIG. 24 is a cross-sectional end view of the three tube design showing the outer exhaust tube. 
     FIG. 25 depicts the split thread fastener detail for attaching the exhaust tube to the outer tube of the infrared emitter. 
     FIG. 26 depicts an exploded side view of the split thread fastener device for attaching the exhaust tube to the outlet tube of the IR emitter. 
     FIG. 27 depicts a front view of the assembled exhaust tube fastener device. 
     FIG. 28 depicts an exploded cross-sectional view of the exhaust tube fastener device. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates an infrared emitter  10  according to the invention which emits electromagnetic radiation in the infrared portion of the spectrum. The infrared emitter  10  includes a coiled tungsten wire filament  20  enclosed within a hermetically sealed inner tube enclosure  40  containing a halogen gas  50 . A longitudinally extending outer tubular sheath of infrared energy transmitting material  30  has a plurality of ports  230  strategically located at predetermined locations along the outer surface of the sheath. The sheath  30  has two end caps  60  with each end cap  60  having at least one passage  100  for fluid flow therethrough. A reflector  110  comprising a reflective coating on a surface of the sheath  30  extends partially, circumferentially with the sheath forming a central longitudinal section henceforth referred to as the window  120 . A heat sink  190  is intimately associated with an electrical conductor  70  which extends from the filament  20  out through the enclosure  40 . The heat sink  190  assists in reducing the temperature of the electrical conductor  70  during operation of the infrared emitter  10 . 
     Referring to FIG. 2, an interior space  130  is located between the outer tube  30  and the inner tube  40 . This interior space  130  helps to protect the reflective coating  110  from the infrared energy being emitted by the filament  20 . The interior space  130  is also a passage for the cooling fluid to flow which assists in cooling the reflector material  110 , the outer tube  30 , and the window  120 . 
     The end caps  60  of the outer sheath  30  are depicted in FIG.  3 . Also depicted in FIG. 3 is a passage for fluid flow  100  through the end cap  60 . The other end cap  60  with it associated passage for fluid flow  100  is depicted in FIG.  4 . 
     The fluid flow passage in the interior space  130  is better depicted in FIG.  5 . 
     FIGS. 6 through 8 illustrate the various inner tube support devices that maintain the inner tube  40  in a predetermined position. These predetermined positions may include a position concentric with the outer tube  30 , in or at a focal point or focal area, or in any other desired position. Materials for the support devices include high temperature material such as ceramic, glass or quartz, or any other material that withstands the temperature and radiation generated by the infrared emitter  10  without breakdown. The support device may also be plated with materials that are intended to strategically reflect the radiation. 
     The inner tube support devices  150 ,  160 , and  190  include passages  140 ,  170  and  200  to permit passage of a cooling fluid through the inner support. The inner support permits the passage of fluid with a minimum of resistance or will impose a strategic resistance to direct the fluid flow. In some applications, a support desirably creates a back pressure of fluid flow to prevent a reverse flow from the opposite end with fluid flows into both ends simultaneously. In addition, because fluid can be introduced into both ends of the outer tube  30  due to certain pressure differentials which can exist within the separate fluid flow supplies that may reside on each end of the infrared emitter  10 , a strategic back pressure induced on each end assures the proper fluid flow direction on both ends within reasonable differential pressure tolerances. 
     The various passages  140 ,  170  and  200  in the inner tube support devices  150 ,  160  and  190  through their designs, can achieve a predetermined fluid flow pattern. For example, FIG. 6 depicts an inner tube support  150  with a passage  140  that provides uniform fluid flow into one or both ends of the infrared emitter  10 . In FIG. 7 the inner tube support device  160  with its associated passage  170  is designed to provide nonuniform fluid flow to create a loop-like current flow internal to the outer tube  30 . 
     FIG. 8 depicts an inner tube support device  190  with a passage  200  for fluid flow in a rotational pattern or in this case, clockwise motion. 
     It is desirable to minimize the thermal expansion of the electrical conductor that passes through the inner tube enclosure  40  on one or both ends. Thermal expansion of the electrical conductor  70  limits the current that passes through the electrical conductor  30  limiting the power output of the inner electromagnetic emitter  20 . The amount of current flow at least partially determines the generation of heat within the conductor  70  that causes the expansion. If the current exceeds a predetermined threshold, such as 15 amps, then the conductor  70  expands at a rate that differs from the expansion rate of a material like quartz, that contains it. The coefficient of expansion of the conductor material is relatively high compared to the coefficient of expansion of the quartz. If the conductor  70  becomes too hot, excessive conductor expansion resultantly cracks the hermetic seal at the end of the inner tube  40 , damaging the inner emitter tube assembly allowing the introduction of oxygen into the inner tube  40 . Oxygen damages the structural integrity of the inner filament  20 , commonly constructed from tungsten, doped tungsten, or tungsten alloy. FIG. 9 depicts a heat sink  190 , for the electrical conductor  70  of the inner tube  40  which intimately contacts the conductor  70 . Heat is transferred out of the conductor  70  and into the heat sink material by way of conduction. The heat energy is then transferred into the cooling fluid that passes over the heat sink fins which are evidenced in FIG.  10 . The heat sink  190  may be constructed from a material that possesses thermal conductivity, such as copper, aluminum, cermets or metal alloy. The heat sink  190  may also be plated with a highly reflective material that will not absorb the vast majority of wavelengths of electromagnetic energy generated by the emitter device  10 . The heat sink device  190  may act as either a conductor or insulator of electrical current depending on particular design considerations. 
     Referring to FIGS. 11-13, the invention includes a thin film integral gold, gold alloy, or high efficient reflector  110 , which is placed on the outside surface of the outer tubular enclosure  30 . Component temperatures that achieve the latent heat of vaporization of the integral reflector material  110  limit the power density, normally measured in watts per lineal inch. As the watt density increases, the outer tube enclosure  30  and integral reflective film material  110  increase in temperature and eventually attain temperatures that will vaporize the gold reflective film  110 . Trapped heat within the outer sheath limits watt density for any particular quartz sheath diameter, which is typically 0.625 inches in the outer diameter. The emitter  10  by having fluid purging that exits through exhaust ports  230  enables the infusion of a cooling fluid into the interior space  130  assist in cooling the entire assembly, including the conductor cooling fin and reflective film material  110 . 
     It is desirable to additionally dissipate the heat from the thin film reflector  110  without supplying increased internal or external air flow. This is accomplished by the use of a radiant heat dissipator  220  which can be seen in FIGS. 11 through 13. In FIG. 11, the controlled emissivity material  220  is disposed over the reflector  110 , where the reflector  110  resides on the external surface of the outer tube  30 . As the entire emitter  10  rises in temperature, heat rapidly dissipates from the system and, therefore, the gold reflective film  110  through the high emissivity material  220 . 
     If one examines the difference in magnitude between convective and radiant energy losses from any particular surface, it will become apparent that great differences exist where the surface has high emissivity. In the case of the integral gold reflector  110 , the outer surface of the integral reflector material  110  has a low emissivity of about 0.08 at room temperature and about 0.18 at approximately 900° F. It is well known in the art that emissivity increases with temperature. The emissivity factor expresses a percentage of possible emissions based on the theoretical black body emitter that is used as the reference standard for emissivity ratings. The low emissivity reflective film  110  cannot sufficiently dissipate heat by means of radiant losses. Therefore, changing the outer surface characteristics of the material  30  or  110  can modify the thermal losses from the thin film material  110 . This is accomplished by placing another film of material of controlled emissivity  220  in this embodiment, high in intimate contact with the lower emissivity reflective film  110  or sheath  30 . The heat energy then flows by conduction from the gold film reflector  110  or sheath  30  into the high emissivity material  220 , and is more efficiently dissipated into space by the new highly emissive surface by radiant means that does not require additional air movement. Examples of high emissivity materials  220  include cermets, ceramics, oxides, and organic materials. These materials may vary in thickness from a thin film to a thick coating. FIG. 12 demonstrates that the radiant heat dissipator  220  may be placed on the outer surface of the outer tube  30  with the reflector of gold  110  on the inside of the outer tube  40 . The high emissivity heat dissipation material  220  is preferably disposed adjacent and congruent to the inside reflector  1   10  and is preferably concentric to the reflector  110  when the outer tube  130  is cylindrical as is in this embodiment. The dissipation of radiant energy form the radiant heat dissipator  220  may be limited by the rate of thermal conductivity of the material of the outer tubular enclosure  30  that serves to transfer energy to the dissipation device  220 . 
     To attenuate the quantity of energy dissipated the high emissivity material  220  may be printed as a pattern on the reflector  110 , as in FIG.  13 . This permits a reduced and controlled radiant loss when using a dissipation material of very high emissivity. FIGS. 14 and 15 provide the conversion of a single peak electromagnetic emission to a modified single peak emission of a longer wavelength or to dual infrared peak emissions simultaneously from a single infrared emitter  10 . The dual emission includes the original wavelength emission from the inner emitter filament  20  and a longer wavelength from the secondary surface on the window  120  of the outer tube  30 . This is accomplished by placing on the window exterior or interior surface a high emissivity material  220  that absorbs the shorter wave energy, increases in temperature, and radiates the longer peak electromagnetic wavelength into space. This provides a fast thermal response medium or long wave emitter of high efficiency. The longer wavelength from the converting surface will be radiated from both the outside and the inside surfaces of the window. To attenuate the emission, the high emissivity material  220  may be placed on the window  120  in a pattern (see FIGS. 14,  15 ). The exhaust ports/cooling fluid ports  230  are also evident at predetermined locations, this embodiment, in the window  120 . 
     Varying the amount of high emissivity material  220  printed on the window  120  varies the percentage of power of the longer wavelength emission. The secondary wavelength can be altered by changing the distance between the primary source of the energy, in our case, the tungsten filament, and the high emissivity material  220 . This is best accomplished by changing the outer diameter of the outer enclosure  30 . A larger diameter outer tube  30  would decrease the temperature of the high emissivity material  220  that resides in the window  120 , thereby altering its wavelength toward the longer peak emission period. This occurs because the energy would now be spread over a larger area of material, but output power would remain relatively stable, except for increased convective thermal losses inherent to long wave emitters. 
     The exhaust/cooling fluid ports  230  in the outer tube of  30  of the emitter  10  enable fluid to pass into one end or both ends of the emitter  10  simultaneously. The fluid exits the exhaust ports  230 , which are arranged intermittently to the ends of the emitter  10 . As previously indicated, it is preferable to maintain the ends of the inner tube  40  and/or the filament  20  at reasonably low temperatures during the operation of the emitter system. The exhaust ports  230  of this invention permit fluid to pass over one or both ends of the inner tube  40 . This maintains the hermetic seal below the maximum recommended operating temperature of about 550 degrees F. The passage of cooling fluid into both ends of the outer tube  30  will permit the flow of cooling fluid to protect both emitter end seals. The placement of the ports  230  in the window  120  of the outer tube  30  direct the heated exhaust fluid toward the work in process. Alternatively, the ports  230  can be placed so that the fluid will be channeled away from the work in process. In addition, the exhaust ports  230  provide pressure relief to accommodate fluid flow into one or both ends of the emitter system  10  because the fluid can escape out of these strategically placed exhaust/cooling fluid ports  230 . 
     In FIG. 16, the infrared emitter  10  is encapsulated by a transducer housing  210 . The entire housing  10  can be rotated so that the short-wave infrared emission can  15  be utilized directly as in FIG.  17 . The housing  10  can be further rotated so that the short-wave emission is directed into a chamber  240  that directs all emission toward a surface that has a particular radius. In such a position, the short-wave emission is absorbed and spread over a larger area and converted to a longer wavelength, such as a two-micron peak wavelength emission, and is emitted into the environment by the new high emissivity surface that resides on the inner and/or outer surface of the utilized chamber. The focal point, or focal area, of the inside surface of the wave transducer is where the filament  20  resides itself which will promote efficiency by returning normally wasted energy back to the source of the radiant energy. The housing  210  can be further rotated to a new surface such as another chamber that has a second particular radius, for example a larger radius, as in FIG. 19. A short-wave emission is then absorbed by this larger absorbing and emitting surface and is converted to a longer wavelength, such as a three-micron peak wavelength emission. The converted wavelength may then be emitted by the new high emissivity surface that resides on the inner and/or outer surface of the utilized chamber. FIGS. 17-19 succinctly depict the transducer housing  210  with the associate chambers of varying radii  240 , in various modes of rotation around the infrared emitter  10 . 
     The transducer housing  210  is constructed from a single high temperature material such as ceramic, quartz, metal, or cermet material. The housing  210  may also be constructed from a framework of ceramic, quartz, metal, cermet, or other high temperature material, where the conversion surfaces that absorb and radiate the modified wavelength or of wavelengths of electromagnetic energy are inserted into the holding frame. The inner and/or outer conversion surfaces are coated with a material or materials that will absorb the primary radiation with great efficiency. The exterior of the conversion surface will possess a high emissivity factor to enable the converted peak wavelength to be efficiently emitted into space. The materials on the inside may differ from the materials on the outside surface of any particular conversion/emitter surface. The materials may differ on the inside and/or outside of said surfaces from one lobe  240  to the next, depended on the absorption characteristics of the particular primary wavelength, the emissivity of the outside emitting surface for any particular conversion surface temperature, and resulting peak emission from said surfaces. 
     The absorber/emitter surface of any particular lobe  240  may also be a clear thermopane construction. A fluid that contains charged isotope particles may reside within the cavity of the thermopane construction, and be aligned with an electric current. This will permit either the passage of the primary wave of radiation with high levels of transmission or a varying percentage of absorption by the electronically rotated particles. The rotated particles, if positioned to absorb the primary energy, increase in temperature, thereby increasing the emitting surface temperature of the conversion device, providing a peak wavelength conversion, or multiple peak emissions. 
     The cooling fluid from the emitter  10  passes through the cooling parts  230  in the outer sheath  30  into the particular chamber  240  that has been selected for peak wavelength emission conversion to a longer wavelength. Strategically placed exhaust ports (not shown) in the housing  210  can permit the fluid flow out of the housing  210 . These ports or holes may be placed along the perimeter of each of the conversion surfaces. This minimizes the conductive heat losses form the conversion emitter surface to the surrounding structural material, thereby increasing the radiant efficiency. In addition, the exhaust air will contain significant heat energy that will serve to increase the radiant efficiency of the secondary radiant conversion surface. The inner surface of the walls of the transducer housing  210  may also be plated, covered, or coated with a material that is highly reflective to the majority of the electromagnetic radiation emission. 
     The transducer housing  210  includes end fittings  310  that fit over each end of the transducer housing  210 . The end fittings  310  accommodate the inner tube  40 , and outer tube  30 , and generally the infrared emitter  10 . The fittings  310  act as an interface between the housing  210  and the outer tube  30 , and permit an efficient seal to minimize and control cooling fluid losses. The fittings  310  also permit the rotation of the outer housing  210  around the outer tube  30  in order to select the proper position for the desired wavelength conversion. The fittings  310  may optionally include external clutches or gear teeth so that an external drive can automatically change the housing position relative to the stationary inner tube assembly. The inner surfaces of the fittings  310  may be plated, covered, or coated with a material that will efficiently reflect the primary and/or secondary radiant emissions. The fittings  310  and housing  210  may contain cooling ports  230 , and may or may not be thermally insulated. 
     It is possible to have a single tube integral reflector emitter. FIG. 20 depicts a single tube emitter which includes solely a tube  40  for the filament  20  of an infrared emitter  10 . The single tube emitter is coated with a highly reflective material  110 , such as gold, on the inside of the tube  40  and a high emissivity material optionally on the outside of the tube  220 . The gold reflective film  110  and the high emissivity material  220  cover all but a predetermined portion of the infrared emitter  10 . The radiant energy source  20  is held in position by the filament support  80 . 
     The filament support  80  includes a high temperature material, such as tungsten, tantalum, or other high temperature alloy, which forms a wire. In FIG. 21, the filament support  80  wraps in a direction opposite the direction in which the filament coil  20  wraps in order to prevent the filament coil  20  from slipping between the windings of the filament support  80 . The filament support  80  includes a dielectric coating to electrically insulate the material from the filament  20  and the integral reflector material  110 . The dielectric coating prevents current from flowing through the reflector material  110 , resulting in an electrical short. 
     In FIGS. 22-28 an exhaust tube  250  encapsulates the inner  40  and outer  30  tube enclosures of the infrared emitter  10 . The exhaust tube  250  directs cooling fluid flow between the inner  40  and the outer  30  tubes away from the work area. The exhaust tube  250  attaches to an exhaust fitting  260  which includes exhaust holes  280  for venting the cooling fluid escaping from the outer tube  30  completely away from the work area. 
     A split thread fastener  290  connects the exhaust tube  250  to the outer tube  30  of the infrared emitter  10 . The split thread fastener  290  is split because the fastener cannot otherwise slide past the end caps  60  of the infrared emitter  10 . The split thread fastener  290  includes at lest tow pieces each having teeth which mesh to form a unitary body when the split thread fastener  290  is installed. The split thread fastener  290  also includes a refractory material  270  which is placed between the outer tube  30  and the inner surface of the fastener  290 . Then the respective halves of the split thread fastener  290  engage the outer tube  30  and the fastener  290  is threaded onto the end of the exhaust fitting  260 . The exhaust tube  250  exhausts the cooling fluid away from the work area. As depicted in FIG. 28, an O-ring  300  is interposed between the split thread fastener  290  and the exhaust fitting  260  in order to provide a seal. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification and following claims.