Abstract:
A lighthead for a dual-mode searchlight including a generally concave housing with an attached infrared (IR) light source assembly, an insulating barrier and air gap between the visible and IR portions of the assembly, and a reflector integral to the housing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Dual mode searchlights are used in rotorcraft to provide both visible lighting and infrared (IR) lighting modes, depending on the task and conditions the rotorcraft is operating under. U.S. Pat. No. 5,695,272 to Snyder et al. titled “Searchlight For Aircraft And Other Vehicles,” herein incorporated by reference, describes an exemplary visible and infrared lighting element in a lamp head that may be extended, retracted, and rotated. Both light sources, however, are within the same lamp head (and the same lamp face), so that heat generated from the visible light source is not dissipated sufficiently to prevent degradation of the IR light source due to high temperatures generated by the heat from the visible light source. U.S. Pat. No. 6,962,423 to Hamilton et al. titled “Multi-mode Searchlight,” herein incorporated by reference, describes a multi-mode visible and infrared lighthead for use as a landing light or searchlight. The design includes a separate reflector which must be attached to the housing, and which increases maintenance costs and time. 
         [0002]    Therefore, there exists a need for an improved dual-mode searchlight. 
       SUMMARY OF THE INVENTION 
       [0003]    Preferred embodiments of the present invention meet all of the above needs in providing a dual-mode visible and infrared (IR) searchlight assembly with an insulating barrier between the visible and IR portions of the assembly, and integral reflector. 
         [0004]    The two illumination sources are separated with insulation material and an air gap to improve illumination performance and meet severe operating conditions. The separation provides cooling from convective heat transfer and greatly reduces conductive heat transfer from the high power visible lighting portion of the canopy to the IR illumination portion of the canopy. The IR portion of the canopy is isolated to protect the IR sources from high temperatures. 
         [0005]    The reflective device for visible illumination is integrated into the housing to increase reflector area and reduce maintenance costs and time. The increase in reflector area has a direct positive effect on visible light intensity. Embodiments may include U.S. Pat. No. 6,960,776 to Machi titled “IR Diode Based High Intensity Light,” herein incorporated by reference, which describes a high intensity, low power infrared light assembly for use on aircraft or other vehicles for landing, taxi mode, or search operations. These features contribute to reducing the size of the envelope required to harness the IR illumination sources, reducing the amount of heat generated by the searchlight, and allows the visible portion of the canopy to be larger, increasing reflector area and thus visible light intensity. 
         [0006]    As will be readily appreciated from the foregoing summary, the invention provides an improved lighthead assembly for aircraft. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings: 
           [0008]      FIG. 1A  is a top rear perspective view of a housing formed in accordance with an embodiment of the present invention; 
           [0009]      FIG. 1B  is a bottom plan view of the housing of  FIG. 1A ; 
           [0010]      FIG. 1C  is a rear plan view of the housing of  FIG. 1A ; 
           [0011]      FIG. 1D  is a cross-sectional view through the line  1 D of  FIG. 1C ; 
           [0012]      FIG. 1E  is a cross-sectional view through the line  1 E of  FIG. 1C ; 
           [0013]      FIG. 1F  is a perspective view of a housing cover formed in accordance with an embodiment of the present invention; 
           [0014]      FIG. 1G  is an exploded view of a housing assembly formed in accordance with an embodiment of the present invention; 
           [0015]      FIG. 2A  is an exploded view of an infrared (IR) light source assembly formed in accordance with an embodiment of the present invention; 
           [0016]      FIGS. 2B and 2C  are perspective views of the heat sink of the IR light source assembly of  FIG. 2A ; 
           [0017]      FIG. 3A  is an exploded view of a housing and an IR diode assembly; 
           [0018]      FIG. 3B  is a front plan view of a lighthead assembly formed in accordance with an embodiment of the present invention; 
           [0019]      FIG. 3C  is a partial exploded view of the lighthead assembly of  FIG. 3B ; 
           [0020]      FIG. 4A  is a top perspective view of a lampholder assembly formed in accordance with an embodiment of the present invention; 
           [0021]      FIG. 4B  is an exploded view of the lampholder assembly of  FIG. 4A ; 
           [0022]      FIG. 5A  is an insulator formed in accordance with an embodiment of the present invention; and 
           [0023]      FIG. 5B  is an insulating bushing formed in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0024]      FIG. 1A  shows a housing  10  including a housing rear  12  defining a plurality of lens retainer attachment points  14  located around a housing perimeter  16  ( FIG. 1G ). The housing rear  12  also defines a searchlight slip ring shaft receptacle  18  and at least one searchlight slip ring shaft attachment point  20 . The housing rear  12  also defines a pair of lamp receptacles  22 , along with a plurality of lampholder attachment points  24  and housing cover attachment points  26 . In  FIG. 1B , the housing  10  also defines a plurality of infrared (IR) diode assembly attachment points  28 . In  FIGS. 1D and 1E , the housing  10  defines a reflector  30 . The reflector  30  is cleaned, base coated, and then vacuum metallized. The reflector  30  should have a smooth reflective appearance and show no signs of distortion. The reflector  30  is then coated with aluminum or other suitable material known to those having skill in the art.  FIG. 1F  shows a housing cover  31  defining a plurality of threaded receptacles  29  through which screws  108  ( FIG. 3C ) may be inserted and attached to the housing cover attachment points  26 . 
         [0025]    Referring to  FIG. 1G , a lens retainer  32  is attached to the housing  10  with a plurality of screws  34  at the lens retainer attachment points  14  ( FIG. 1A ). The lens retainer  32  holds a gasket  36  and a lens  38  in place against the housing perimeter  16 . 
         [0026]      FIG. 2A  shows an IR diode assembly  40 . The assembly  40  includes an aluminum (or other suitable material) heat sink  42  defining a plurality of retainer attachment points  44 . A retainer  46  is attached to the heat sink  42  at the retainer attachment points  44  with a plurality of screws  48 , and houses various components of the assembly  40 . A circuit card assembly  50  is attached to the heat sink  42  at a plurality of circuit card attachment points  52  with a plurality of screws  54 . Wiring  56  from the circuit card assembly  50  may be encased in tubing  58 . The wiring  56  exits the heat sink  42  through a wiring receptacle  57  ( FIG. 2C ). A plurality of thermally conductive and electrically non-conductive silicon pads  60 , IR diodes  62 , diode heat sinks  64 , aspheric lenses  66 , and diffuser retainers  68  are attached to the heat sink  42  with a plurality of screws  70  at a plurality of retainer attachment points  72 . The assembly  40  includes a diode gasket  74 , a light shaping diffuser  76 , and a lens  78  for each diode  62 ; an O-ring  80  seals the components within the retainer  46 , and the lenses  78  extend into lens receptacles  82  of the retainer  46 . Aspheric lenses  66  and light shaping diffusers  76  act to collimate the IR energy into a desired pattern. 
         [0027]    In  FIGS. 2B and 2C , the heat sink  42  defines a plurality of housing attachment points  84  through which screws  88  ( FIG. 3A ) are inserted and attached to the IR light source assembly attachment points  28  of the housing  10  ( FIG. 1B ). The wiring receptacle  57  allows the wiring  56  from the circuit card assembly  50  to exit the heat sink  42 . 
         [0028]      FIG. 3A  shows the IR light source assembly  40  and housing  10 . The IR light source assembly  40  is attached to, and only contacts the housing  10  at, the IR light source attachment points  28  of the housing  10  with a plurality of screws  88 , insulating bushings  90 , and washers  92 . Between the housing  10  and the IR light source assembly  40 , a plurality of insulating bushings  90  and an insulator  96  separate and reduce the amount of heat conduction between the canopy  10  and IR light source assembly  40 . A pair of O-rings  97  seal the wiring  56 . The insulating bushings  90  and insulators  96  are preferably made of polyethertherketone (PEEK) 1000, but other insulating materials known to those having ordinary skill in the art may be used. 
         [0029]      FIG. 3B  shows a lighthead assembly  98 . A space  99  allows air flow between the IR light source assembly  40  and the housing perimeter  16 , thus reducing the amount of heat convection between the housing  10  and the IR light source assembly  40 ; the space  99  also helps to prolong IR diode  62  life by reducing direct heat conduction between the housing  10  and the IR light source assembly  40 . The generally circular shape of the lighthead assembly  98  allows easier adaptation of the lighthead assembly  96  to conventional dual-mode lighthead envelopes (not shown). 
         [0030]      FIG. 3C  shows the lighthead assembly  98 . A pair of lampholder assemblies  100  is attached to the housing  10  with a plurality of screws  104 , with lamps  102  attached to the lampholder assemblies  100  protruding through the lamp receptacles  22 . The housing cover  31  and a housing cover O-ring  106  are attached to the housing  10  with a plurality of screws  108 , and enclose the lampholder assemblies  100 . 
         [0031]      FIGS. 4A and 4B  show one lampholder assembly  100 . The assembly  100  includes screws  110  attaching a socket  112  to a lampholder  114  via self-locking nuts  116 . Screws  118  secure the lampholder  114  to the housing  10  ( FIG. 1A ). 
         [0032]      FIGS. 5A and 5B  show an insulator  96  and an insulating bushing  90 , respectively. In an embodiment, the insulator  96  and insulating bushing  90  are made of polyethertherketone (PEEK) 1000, but could be made of any of a variety of different insulating materials. 
         [0033]    While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.