Abstract:
A fluid input manifold distributes injected fluid around the body of a bulb to cool the bulb below a threshold. The injected fluid also distributes heat more evenly along the surface of the bulb to reduce thermal stress. The fluid input manifold may comprise one or more airfoils to direct a substantially laminar fluid flow along the surface of the bulb or it may comprise a plurality of fluid injection nozzles oriented to produce a substantially laminar fluid flow. An output portion may be configured to facilitate fluid flow along the surface of the bulb by allowing injected fluid to easily escape after absorbing heat from the bulb or by applying negative pressure to actively draw injected fluid along the surface of the bulb and away.

Description:
PRIORITY 
     The present application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application Ser. No. 61/693,886, filed Aug. 28, 2012, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed generally toward arc lamps, and more particularly toward cooling arc lamp bulbs. 
     BACKGROUND OF THE INVENTION 
     In arc lamp and other high output bulbs, residual stress due to thermal creep is a key contributor to bulb breakage. Thermal creep is exacerbated at higher ultraviolet (UV) output power from arc lamps, either in the conventional DC discharge mode of operation or with laser sustained plasmas in lamps, due to the higher absorption of UV light in the glass which leads to increased operating temperatures. 
     Traditionally, bulbs rely on natural convection for cooling. Natural convection cooling results in a highly asymmetric temperature profile on the lamp. Also, the generally accepted operating lamp temperature limit of less than 750° C. is excessive and results in quick buildup of residual stress. A peak temperature of less than 600° C. would be more sustainable. 
     Consequently, it would be advantageous if an apparatus existed that is suitable for actively cooling high output bulbs to an operating temperature below 600° C. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a novel method and apparatus for actively cooling high output bulbs to an operating temperature below 600° C. 
     In one embodiment of the present invention, a fluid input manifold distributes injected fluid around the body of a bulb to cool the bulb below a threshold. The injected fluid also distributes heat more evenly along the surface of the bulb to reduce thermal stress. 
     In one embodiment, a fluid input manifold may comprise one or more airfoils to direct a substantially laminar fluid flow along the surface of the bulb. In another embodiment, the fluid input manifold may comprise a plurality of fluid injection nozzles oriented to produce a substantially laminar fluid flow. 
     In one embodiment of the present invention, an output portion may be configured to facilitate fluid flow along the surface of the bulb by allowing injected fluid to easily escape after absorbing heat from the bulb or by applying negative pressure to actively draw injected fluid along the surface of the bulb and away. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The numerous advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures in which: 
         FIG. 1  shows a cross-sectional view of one embodiment of the present invention having an airfoil; 
         FIG. 2  shows an environmental view of an input portion of one embodiment of the present invention; 
         FIG. 3  shows a cross-sectional, detail view of an input portion of one embodiment of the present invention; 
         FIG. 4  shows another cross-sectional, detail view of an input portion of one embodiment of the present invention; 
         FIG. 5  shows a cross-sectional, detail, overhead view of an input portion of one embodiment of the present invention; 
         FIG. 6  shows a perspective, detail view of a pilot jet assembly according to one embodiment of the present invention; 
         FIG. 7  shows a cross-sectional, detail view of an input portion of another embodiment of the present invention; 
         FIG. 8  shows a cross-sectional, detail view of an input portion of another embodiment of the present invention; 
         FIG. 9  shows a perspective, detail view of an annular nozzle according to another embodiment of the present invention; 
         FIG. 10  shows a cross-sectional, detail view of an output portion of one embodiment of the present invention; 
         FIG. 11  shows a perspective view of an output portion of one embodiment of the present invention; 
         FIG. 12  shows a perspective, detail view of an output slipclamp according to one embodiment of the present invention; 
         FIG. 13  shows a perspective, detail view of a vented bulb securing element according to one embodiment of the present invention; 
         FIG. 14  shows a perspective, detail view of an output cap according to one embodiment of the present invention; 
         FIG. 15  shows a cross-sectional view of another embodiment of the present invention; 
         FIG. 16  shows a cross-sectional view of another embodiment of the present invention; and 
         FIG. 17  shows a cross-sectional, perspective view of another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the subject matter disclosed, which is illustrated in the accompanying drawings. The scope of the invention is limited only by the claims; numerous alternatives, modifications and equivalents are encompassed. For the purpose of clarity, technical material that is known in the technical fields related to the embodiments has not been described in detail to avoid unnecessarily obscuring the description. 
     Residual stress due to thermal creep is a key contributor to bulb breakage. This effect is exacerbated at higher UV output power from arc lamps in conventional DC discharge mode and with laser sustained plasmas inside lamps due to the higher absorption of UV light in the glass which leads to increased operating temperatures. The present invention provides a way to better control and optimize lamp operating temperatures, thus reducing creep induced stress levels to safe limits and preventing bulb breakage. Using a modeling approach, safe operation temperature limits of less than 600° C. keep stress levels from increasing excessively for lamps constructed with various glass materials based on their viscosity properties. 
     Referring to  FIG. 1 , a cross-sectional view of one embodiment of the present invention having an airfoil is shown. In at least one embodiment of the present invention, an arc lamp holding node  104  may include a fluid input  100 . The fluid input  100  allows fluid to flow into a space defined by a fluid manifold  128 . In at least one embodiment, the fluid manifold  128  includes, or directs fluid flow toward, an airfoil element  106 . The airfoil element  106  may foster a substantially laminar fluid flow over the surface of a bulb  108 . Fluid flow over the surface of the bulb  108  may reduce the temperature of the bulb  108  and more evenly distribute heat across the surface of the bulb  108 , resulting in reduced thermal stress. 
     Airfoil design is effective in controlling lamp temperature for lower laser power operation, but it consumes more than the desired amount of fluid to reach circular uniformity of lamp temperature control during high laser power operation. 
     Referring to  FIG. 2 , an environmental view of an input portion of one embodiment of the present invention is shown. In at least one embodiment, a lamp includes a bulb securing locknut  204  that connects one node of a bulb  208  to a power source  206  through a delivery wire  202 . The bulb securing locknut  204  may hold a pilot jet assembly  228  in relation to the bulb  208 . The pilot jet assembly  228  receives a fluid flow through an input  200  and directs fluid flow over the bulb  208 . 
     Referring to  FIG. 3 , another cross-sectional, detail view of an input portion of one embodiment of the present invention is shown. The input portion includes a bulb securing locknut  304  to hold a straight pilot jet assembly  328  in relation to a bulb  308  and to allow a delivery wire  302  to contact a node of the bulb  308 . The straight pilot jet assembly  328  receives a fluid flow through an input  300  and directs fluid flow over the bulb  308  through a plurality of straight fluid directing jets  310 . 
     The straight pilot jet assembly  328  may be a manifold for distributing a cooling fluid such as air, nitrogen, or other suitable gasses to the plurality of straight fluid directing jets  310 . A person skilled in the art may appreciate that fluids useful in some embodiments of the present invention may also include liquids. The plurality of straight fluid directing jets  310  may be distributed substantially uniformly around the straight pilot jet assembly  328 . Straight fluid directing jets  310  may produce a high velocity plume that tends to adhere to the surface of the bulb  308 . Straight fluid directing jets  310  provide good control over directionality of fluid flow, and a reduced output nozzle (for example, 0.45 mm) may provide additional cooling effect through Joule-Thomson cooling as the fluid exits the nozzle into a lower ambient pressure. In the context of the present invention, “straight” fluid directing jets  310  may be straight in that, for each straight fluid directing jet  310 , an axis defined by the straight fluid directing jet  310  and an axis defined by the bulb  308  define a plane. Each straight fluid directing jet  310  may be oriented to direct a fluid flow toward the surface of the bulb  308 . In at least one embodiment, the straight fluid directing jets  310  may be oriented to direct the fluid flow toward the “hip” of the bulb  308  (a portion of the bulb  308  where a bulbous intersects a substantially straight portion). Straight fluid directing jets  310  may produce steady state gradients. 
     Referring to  FIG. 4 , a cross-sectional, detail view of an input portion of one embodiment of the present invention is shown. The input portion includes a bulb securing locknut  404  to hold an inclined pilot jet assembly  428  in relation to a bulb  408  and to allow a delivery wire  402  to contact a node of the bulb  408 . The inclined pilot jet assembly  428  receives a fluid flow through an input  400  and directs fluid flow over the bulb  408  through one or more inclined fluid directing jets  410 . 
     The inclined pilot jet assembly  428  may be a manifold for distributing a cooling fluid to the plurality of inclined fluid directing jets  410 . The plurality of inclined fluid directing jets  410  may be distributed substantially uniformly around the inclined pilot jet assembly  428 . Inclined fluid directing jets  410  may produce a high velocity plume that tends to adhere to the surface of the bulb  408 . Inclined fluid directing jets  410  provide good control over directionality of fluid flow, and a reduced output nozzle (for example, 0.45 mm) may provide additional cooling effect through Joule-Thomson cooling as the fluid exits the nozzle into a lower ambient pressure. In the context of the present invention, “inclined” fluid directing jets  410  may be inclined in that, for each inclined fluid directing jet assembly  410 , an axis defined by the inclined fluid directing jet assembly  410  and an axis defined by the bulb  408  do not define a plane, and the inclined fluid directing jets  410  induce a fluid flow vortex around the bulb  408 . Each inclined fluid directing jet assembly  410  may be oriented to direct an fluid flow toward the surface of the bulb  408 . In at least one embodiment, the inclined fluid directing jets  410  may be oriented to direct the fluid flow generally toward the hip of the bulb  408 . Inclined fluid directing jets  410  may reduce localized gradients and lower the impingement angle on non-cylindrical envelopes. 
     Referring to  FIG. 5 , a cross-sectional, detail, overhead view of an input portion of one embodiment of the present invention is shown. An input portion according to at least one embodiment of the present invention may include a pilot jet assembly  528  configured as a manifold to receive a cooling fluid and distribute the cooling fluid to a plurality of fluid directing jets  510 , each fluid directing jet  510  defining a nozzle  550  configured to direct a fluid toward or around a bulb  508  a bulb such that the fluid may adhere to the surface of the bulb  508  and cool the bulb  508 , or redistribute heat around the surface of the bulb  508  or both. In at least one embodiment, the fluid directing jets  510  direct the cooling fluid toward a hip portion  548  of the bulb  508 . 
     Heat load on the bulb  508  during operation is applied to the bulb  508  equator (due to radiation absorption of the glass) and at the top part of the bulb  508  (due to convection). The bottom part of the bulb  508  tends to be colder and tends to have stagnant areas for the internal gas circulation. Directing an external cooling fluid flow from the hot parts of the bulb  508  to the base of the bulb  508  allows increasing the temperature of the base, creating a more uniform temperature profile for the bulb  508 , reduces thermal stress, decreases solarization, and helps to maintain all parts of the bulb  508  in a desired temperature range. Control of the temperature for the base part of the bulb  508  is also important in applications requiring volatilization of species inside of the bulb  508 , e.g., for Hg or H 2 O containing bulbs  508 . 
     Referring to  FIG. 6 , a perspective, detail view of a pilot jet assembly  628  according to one embodiment of the present invention is shown. The pilot jet assembly  628  defines an input portion  614  for receiving a cooling fluid. The pilot jet assembly  628  distributes the cooling fluid to a plurality of fluid directing jets  610  arranged regularly around a surface of the pilot jet assembly  628 . During operation, significant pressure levels are established inside the pilot jet assembly due to the mechanical design and fluid will uniformly flow out from each fluid directing jet  610 . The fluid directing jets  610  direct the cooling fluid toward a bulb. The bulb may be connected to a power source by passing a node of the bulb through a bulb access portion  612  defined by the pilot jet assembly  628 . The plurality of fluid directing jets  610  may be straight or inclined to produce a vortex around the bulb. 
     In at least one embodiment, the pilot jet assembly  628  may be installed at the base of a bulb in another design variation. There may be an external transparent shield around the bulb that allows directing of cooling fluid flow and/or containing additional species of the cooling jet such as overheated water vapor near the bulb. 
     Referring to  FIG. 7 , a cross-sectional, detail view of an input portion of another embodiment of the present invention is shown. In at least one embodiment, a lamp includes a bulb securing locknut  704  that connects one node of a bulb  708  to a power source  706  through a delivery wire  702 . The bulb securing locknut  704  may hold an annular nozzle  728  in relation to the bulb  708 . The annular nozzle  728  receives a fluid flow through an input  700  and directs fluid over the bulb  708 . 
     Referring to  FIG. 8 , a cross-sectional, detail view of an input portion of another embodiment of the present invention is shown. The input portion includes a bulb securing locknut  804  to hold an annular nozzle  828  in relation to a bulb  808 . The annular nozzle  828  receives a fluid flow through an input  800  and directs fluid over the bulb  808  and a fluid directing collar  830  that defines one or more fluid chambers configured to create a mantle of cooling fluid circumferentially around the bulb  808 . 
     Referring to  FIG. 9 , a perspective, detail view of an annular nozzle according to another embodiment of the present invention is shown. The annular nozzle may include a fluid directing collar  930  that defines one or more fluid chambers  932 ,  934  configured to create a mantle of cooling fluid circumferentially around the bulb. An upper fluid chamber  932  and lower fluid chamber  934  may be separated by a gap configured to regulate fluid pressure and flow. In one embodiment, the gap may be 0.100 mm. In another embodiment, the gap may be 0.075 mm. The size of the gap may define the fluid flow between the upper fluid chamber  932  and the lower fluid chamber  934 , and therefore around the bulb. 
     Additionally, the present invention may include an exhaust for the cooling gas located at the base of the bulb. Exhaust helps to direct fluid flow around the bulb and to the base. Exhaust can be augmented and/or controlled by creating negative pressure in the exhaust line. 
     Referring to  FIG. 10 , a cross-sectional, detail view of an output portion of one embodiment of the present invention is shown. The output portion may include a vented bulb securing element  1020  configured to hold a node of a bulb  1008 . The vented bulb securing element  1020  may be held in place by a slipclamp  1018 . The slipclamp  1018  may comprise a conductive path to a water channel. The slipclamp  1018  may also include baffles configured to direct UV. The vented bulb securing element  1020  and slipclamp  1018  may be substantially contained within an output cap  1016 . The output cap  1016  may include one or more deflectors  1042  to deflect fluid flow to an output. The deflectors  1042  may allow electrical connection to a bulb  1008  while protecting such electrical connection from heat generated by the bulb  1008  and fluid flow after absorbing such heat. 
     Referring to  FIG. 11 , a perspective view of an output portion of one embodiment of the present invention is shown. Fluid flowing over the surface of a bulb  1108  may pass through one or more vents  1124  defined by a vented bulb securing element  1120 . The vented bulb securing element  1120  may be held in place by an output slipclamp  1118 . 
     Referring to  FIG. 12 , a perspective, detail view of an output slipclamp  1218  according to one embodiment of the present invention is shown. The slipclamp  1218  may include one or more fluid channels  1222  for directing a cooling fluid around the slipclamp  1218 . The slipclamp  1218  may be configured to securely hold a vented bulb securing element 
     Referring to  FIG. 13 , a perspective, detail view of a vented bulb securing element  1320  according to one embodiment of the present invention is shown. The vented bulb securing element  1320  may define one or more vents  1324  to allow fluid flowing over a bulb secured by the vented bulb securing element  1320  to pass through. Furthermore, the vented bulb securing element  1320  may include one or more heat sensitive elements  1340  such as a thermocouple. Heat sensitive elements  1340  allow a bulb cooling system to alter the rate of flow of a cooling fluid based on the temperature of a bulb. Temperature based feedback from heat sensitive elements  1340  provides a means of reducing the temperature to safe limits of less than 600° C. for most glass material used in lamp manufacturing. 
     Referring to  FIG. 14 , a perspective, detail view of an output cap  1416  according to one embodiment of the present invention is shown. The output cap  1416  may contain a slipclamp and a venter bulb securing element. Fluid flowing through vents in the vented bulb securing element may pass through to exit through an outlet  1426 . 
     Referring to  FIG. 15 , a cross-sectional view of another embodiment of the present invention is shown. In at least one embodiment, a lamp holding node  1504  allows electrical contact with one node of a bulb  1508 . The lamp holding node  1504  secures the bulb  1508  to a cooling fluid manifold  1528  having a cooling fluid input  1500 . Cooling fluid flows through the cooling fluid input  1500  under some pressure into the cooling fluid manifold  1528 . From there, the cooling fluid may flow into a fluid space  1552  defined by a cooling fluid jacket  1536  surrounding a portion of the bulb  1508 . The cooling fluid jacket  1536  may create a directed, substantially laminar flow over the surface of the bulb  1508  to cool portions of the bulb  1508  not surrounded by the cooling fluid jacket  1536 . The lamp holding node  1504  or cooling fluid manifold  1528  or both may include heat sink portions to further enhance cooling. 
     Referring to  FIG. 16 , a cross-sectional view of another embodiment of the present invention is shown. A lamp holding apparatus may include a lamp holding node  1604  configured to hold a node of a lamp  1608  and allow electrical contact with the node. Furthermore, the lamp holding node  1604  may secure a heatsink  1628  to the lamp  1608  and hold a cooling fluid jacket  1636  in place. The cooling fluid jacket  1636  may define a cooling fluid space  1652 . Furthermore, the cooling fluid jacket  1636  may comprise a material for absorbing certain radiation such as unused UV radiation. One embodiment of the cooling fluid jacket  1636  may be a thin flexible glass sheet rolled around the bulb  1608  in a tube fashion. The cooling fluid jacket  1636  may have antireflection coating deposited on internal or external surfaces or both. 
     A cooling fluid flows through an input  1600  and forms a substantially laminar fluid flow around the bulb  1608 . Furthermore, the cooling fluid may flow into the cooling fluid space  1652 . 
     Referring to  FIG. 17 , a cross-sectional, perspective view of another embodiment of the present invention is shown. A lamp may include a bulb securing locknut  1704  holds a node of a bulb  1708  and allows a supply current to be applied to the bulb  1708 . A cooling fluid supply tube  1700  supplies a cooling fluid. In at least one embodiment, the cooling fluid may flow into a space defined by a thermally fit nozzle  1746 . 
     The thermally fit nozzle  1746  may restrict delivery of the cooling fluid. The thermally fit nozzle  1746  may define jets that may comprise approximately 70% of fluid supply tube  1700  cross-section. Jetted injection may pull fluid over heat sinks. An insulating spacer  1744  such as a fused quartz insulating spacer may define a fluid space to direct fluid flow. In at least one embodiment, a bulb cooling apparatus may include a heatsink  1728  configured to facilitate fluid flow  1738  through a space defined by an insulating spacer  1744 . 
     The present invention thereby reduces residual stress during and after operation in arc lamps operated in conventional continuous DC discharge mode or laser pumped and sustained plasma modes resulting in an extension of the useful operation lifetime for these lamps. 
     It is believed that the present invention and many of its attendant advantages will be understood by the foregoing description of embodiments of the present invention, and it will be apparent that various changes may be made in the form, construction, and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof, it is the intention of the following claims to encompass and include such changes.