Patent Publication Number: US-7906911-B2

Title: Luminaire assembly having a bonded reflector cavity for supporting an ultra-violet lamp

Description:
RELATED APPLICATION 
     This application is related to U.S. patent application Ser. No. 12/149,446, entitled “Radio Frequency Screen Assembly for Microwave Cavities,” filed May 1, 2008, which is fully incorporated herein by reference. 
     DESCRIPTION OF THE INVENTION 
     1. Field of the Invention 
     An invention consistent with this disclosure relates to a bonded, single-piece lamp luminaire for microwave cavities, such as that used in connection with an electrode-less ultraviolet lamp. 
     2. Background of the Invention 
     Ultraviolet (UV) curing systems are in wide use. Among other uses, UV curing systems utilize UV radiation to cure adhesives and inks. UV curing presents a number of benefits over alternative curing methods. For example, UV curing may reduce costs, increase throughput, and provide a higher quality finished product. 
     Microwave-powered UV lamps, including luminaries, may be used to generate the required high energy UV radiation. Generally a curved or elliptical shaped reflector assembly is used in the luminaire to collect and focus the UV energy from the UV bulb into a highly concentrated area under the lamp system. 
     A prior art luminaire assembly  10  is shown in  FIG. 1 . The luminaire comprises one or more magnetrons and one or more waveguides encased in luminaire assembly housing  20 . Luminaire assembly  10  further comprises luminaire reflector assembly  30 . Luminaire reflector assembly  30  comprises main reflector  36  containing at least one microwave coupling slot  35  and two end reflectors  34  each with a bulb support hole  32 . Luminaire reflector assembly  30  is configured to be mated to one or more waveguides encased in luminaire assembly  20  along with curved support ridges  29 , and end reflector and gasket groove  27 . RF screen assembly  40  is configured to be mated to reflector assembly  30 . In luminaire assembly  10 , RF screen assembly  40  and luminaire reflector assembly  30  are configured to form a microwave cavity that can accommodate microwave-powered bulb  50 . Microwave-powered bulb  50  produces radiation which is collected by reflector assembly surfaces and exits the luminaire assembly through RF screen mesh material in the RF screen assembly  40 . A luminaire assembly may include bulb centering spring plate  22 . (Centering springs plate  22  allows a bulb to be inserted, or removed, into an installed reflector assembly. The centering spring plate  22  allows a microwave powered bulb  50  to be pushed through bulb support hole  32  far enough that the other end of the microwave powered bulb  50  can be inserted into the other bulb support hole  32 . The centering spring plate  22  will center and stabilize the bulb in the two support holes.) 
       FIG. 2  shows a cross-section view of an alternative prior art luminaire assembly comprising luminaire housing assembly  20 , and RF screen assembly  40 . The luminaire assembly  10  of  FIG. 2  also comprises magnetron  61  and waveguide  25 . As shown in  FIG. 2 , a prior art luminaire assembly  10  may also contain a linear gasket rail  24  and a linear RF gasket  26 .  FIG. 2  also shows radiation  60  from microwave-powered bulb  50  emitting from a microwave cavity. 
     In the UV lamp depicted in  FIG. 1 , luminaire main reflector  36 , end reflectors  34 , and radio-frequency (RF) screen assembly  40  form the walls of a microwave cavity. The curved section of the main reflector  36  is fabricated from thin aluminum reflector sheet material. The curved section of the main reflector is flexible. To maintain the desired curved shape the main reflector  36  is supported by curved ridges  29 . (In addition to supporting the main reflector, curved ridges  29  form the end of the waveguides. Curved ridges  29  further comprise a curved RF gasket.) In the prior art, the final curve shape of reflector is dependent upon installation technique. The end reflectors  34  are held in position in the luminaire by the fitting of RF gaskets in the waveguide end reflector and gasket groove  27  and by the installation of the curved main reflector  36 . (End reflector and gasket groove  27  is configured to support the end reflector, and is further configured to support a gasket.) The precision of alignment of microwave-powered bulb  50  is determined by the end reflector position. In the prior art, the microwave-powered bulb position is not controlled to high precision relative to the curved reflector. In addition, in the prior art, one skilled in the art would understand that the end reflectors generally extend beyond the outer edge of the curved reflector. Thus, one skilled in the art would understand that the end reflectors have no influence on the precision of the curved reflector shape. 
     It is important that the microwave cavity exhibits a sufficiently tight seal. Luminaire reflector  36 , end reflectors  34 , and RF screen assembly  40  require direct electrical connection. A large enough potential microwave field difference between any of these components will result in dielectric breakdown arcing. Dielectric breakdown arcing can damage components. In addition, any gap between luminaire reflector assembly  30 , RF screen assembly  40 , or the gaskets of end reflector and gasket groove  27 , or the gaskets of curved ridges  29 , will allow microwave energy to escape the cavity. Escaping microwave energy can cause interference with other electronic equipment. 
     Among other maintenance, microwave-powered UV lamps will—from time to time—require new bulbs in the microwave cavity, new RF gaskets between the components of the cavity, or new luminaire reflector portions. As with any routine maintenance that requires disassembly of the luminaire, the time required to change bulbs, gaskets, or reflectors may be considerable due to the number of luminaire parts involved, and the requirement that the assembled system exhibit a tight microwave seal. Such maintenance may require significant and expensive downtime of production lines. Further, when such maintenance involves replacing or removing the end reflectors of the lamp luminaire, the requirement that a microwave-tight seal is maintained requires that replacement RF gaskets be fitted with each replaced end reflector. Of particular concern, and because replacing RF gaskets takes substantial time, users will sometimes skip the step of replacing the RF gaskets and leave old RF gaskets in place. Old RF gaskets may become hard and stiff with age. A new reflector may have a somewhat different shape than the old reflector. Old RF gaskets may no longer have the necessary flexibility to conform to the new reflector shape. Further, old RF gaskets may not be clean or properly fitted. Re-using old gaskets can cause arcing—or dielectric breakdown—to occur and components to be damaged. 
     Consequently, it is desirable to reduce maintenance requirements in the field. It is accordingly an object of the invention to make it easier and/or faster to maintain UV lamps in the field. It is one object of the invention to make the RF gasket seal less prone to arcing and therefore more reliable. It is one object of the invention to make the shape of the ellipse more precise. It is yet another object of the invention to better control the location of the bulb at the preferred position within the ellipse. The present invention solves the aforementioned problems. 
     SUMMARY OF THE INVENTION 
     An invention consistent with the present disclosure relates to a bonded, single-piece lamp luminaire for a microwave cavity in UV lamps. The present invention provides for a luminaire reflector assembly comprising a main reflector segment bonded to two or more end reflector segments. In accordance with the present invention, the luminaire reflector assembly is improved in mechanical stability, shape precision, optical focusing performance and RF electrical contact over the prior art. The main reflector segment and the end reflector segments are mated in a manner improved over the prior art. The main reflector segment and the end reflector segments are bonded through a means that eliminates the need for an RF gasket to maintain electrical connection between the main reflector segment and the end reflector segments. 
     The present invention also provides for the luminaire reflector assembly as discussed above where the main reflector segment is bonded to the end reflector segments with metal foil tape. 
     The present invention also provides for the luminaire reflector assembly as discussed above where the main reflector segment is bonded to the end reflector segments by crimping. 
     The present invention also provides for the luminaire reflector assembly as discussed above where the main reflector segment is bonded to the end reflector segments through welding. The invention provides for the welding done by electric arc welding, laser welding, or other types of welding. 
     The present invention also provides for a luminaire assembly comprising a luminaire reflector assembly of any of the previous embodiments. The luminaire assembly further comprises at least one magnetron, a radio-frequency screen assembly, and a microwave-powered bulb. The microwave-powered bulb is supported by a first end reflector segment of the luminaire reflector assembly and a second end reflector segment of the luminaire reflector assembly. The luminaire assembly further comprises at least one waveguide which is configured to couple energy from the at least one magnetron to the microwave-powered bulb. 
     Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. 
     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, as claimed. 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view of a deconstructed prior art luminaire assembly. 
         FIG. 2  is a cross-section view of an alternative prior art luminaire assembly. 
         FIG. 3  is a view of a luminaire reflector assembly consistent with an embodiment of the present invention. 
         FIG. 4  is view of a luminaire reflector assembly and an RF screen assembly consistent with an embodiment of the present invention. 
         FIG. 5  is a view of a luminaire assembly according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the present embodiments (exemplary embodiments) of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts and may not be described in detail throughout the drawings. 
     A luminaire reflector assembly consistent with an embodiment of the present invention is shown in  FIG. 3 . Luminaire reflector assembly  70  comprises main reflector segment  78 , first end reflector segment  74 , first end reflector bulb support hole  72 , and reflector bond  76 . Luminaire reflector assembly  70  further comprises a second end reflector segment, substantially similar to first end reflector segment  74 , and a second end reflector bulb support hole, substantially similar to first end reflector bulb support hole  72 . 
     First end reflector segment  74  has a first edge that follows a substantially linear path (such as that which is proximal to RF screen assembly  40 , when assembled (see FIG.  4 )), and a second edge that follows a substantially curved path (such as that proximal to reflector bond  76 ). The substantially linear path of the first edge of first end reflector segment  74  and the substantially curved path of the second edge of first end reflector segment  74  intersect and form an enclosed region bounded by the first edge and the second edge of first end reflector segment  74 . In one embodiment, the second edge of the first end reflector segment comprises a segment of a second order curve. In another embodiment, the second edge of the first end reflector segment comprises a plurality of segments of second order curves. In another embodiment, the second edge of the first end reflector segment is a parabola. In another embodiment, the second edge of the first end reflector segment comprises a portion of an ellipse. 
     An embodiment consistent with the present invention utilizes end reflectors specially formed with a specific shape. The end reflectors are preferably constructed with an edge matching the desired curved shape for the inside of the reflector assembly. Consistent with the present invention the end reflectors are preferably positioned inside the main reflector, forcing the main reflector into the same shape. The main reflector segment and end reflector segments are then preferably bonded to retain the main reflector in the desired shape. 
     A main reflector segment and a first end reflector segment are preferably configured to be bonded.  FIGS. 3 and 4  depict exemplary reflector bond  76 . In one embodiment, main reflector segment  78  and first end reflector segment  74  are bonded together such that reflector bond  76  comprises metal foil tape. In another embodiment, main reflector segment  78  and first end reflector segment  74  are bonded by crimping such that reflector bond  76  comprises crimped edges. In another embodiment, main reflector segment  78  and first end reflector segment  74  are bonded together such that reflector bond  76  comprises welded components. In yet another embodiment, the welded components are bond by electric arc welding. In still another embodiment, the welded components are bonded by laser welding. The bonded reflector assembly has advantages over the prior art. The bonded assembly shape may be more rigid and may be maintained with better mechanical precision. Further, the bonded assembly ensures that the bulb is fixed with reference to the reflector. In this regard, for example, the bonded assembly may provide for better optical performance over the prior art. 
     A luminaire reflector assembly and an RF screen assembly consistent with an embodiment of the present invention is shown in  FIG. 4 . The luminaire reflector assembly and an RF screen assembly of  FIG. 4  are configured to be mated with a luminaire assembly. The luminaire assembly comprises a luminaire assembly housing substantially similar to  20  of  FIG. 1 . The luminaire assembly housing contains one or more waveguides, end reflector grooves, and curved support ridges. The luminaire assembly further comprises luminaire reflector assembly  70 , microwave-powered bulb  50 , and radio-frequency (RF) screen assembly  40 . Luminaire reflector assembly  70  comprises main reflector segment  78  with microwave coupling slot  75  (also shown in  FIG. 3 ), first and second end reflector segment  74 , first and second end reflector bulb support hole  72 , and reflector bond  76 . The luminaire assembly may further comprise housing bulb centering spring plates. The luminaire assembly may further comprise a linear gasket rail and an RF gasket. 
     As described above, in one embodiment, main reflector segment  78  and first and second end reflector segment  74  are bonded together such that reflector bond  76  comprises metal foil tape. In another embodiment, main reflector segment  78  and first and second end reflector segment  74  are bonded by crimping such that reflector bond  76  comprises crimped edges. In another embodiment, main reflector segment  78  and first and second end reflector segment  74  are bonded together such that reflector bond  76  comprises welded components. In yet another embodiment, the welded components are bonded by electric arc welding. In still another embodiment, the welded components are bonded by laser welding. In an embodiment the laser welding is computer automated laser welding. 
     In one embodiment of the present disclosure, a luminaire assembly  90  comprises a luminaire reflector assembly  70 , at least one magnetron  61 , a radio-frequency screen assembly  40 , and a microwave-powered bulb  50 , as shown in  FIG. 5 . The microwave-powered bulb  50  is supported by the first end reflector segment  74  and the second end reflector segment  74 . The at least one waveguide  25  is configured to couple energy from the at least one magnetron  61  of the luminaire assembly  90  to the microwave-powered bulb  50  in a manner as similarly depicted in prior art  FIG. 1 . 
     Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. For example, additional components can be incorporated into a single assembly. By way of example only, in one embodiment, and in addition to a main reflector bonded to a first end reflector segment, a microwave-powered bulb can be affixed into the assembly. In another embodiment, in addition to a main reflector bonded to a first end reflector segment, an RF screen can be affixed to the main reflector. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.