Abstract:
A lighthead mounting structure provides both precise alignment of a lighthead and an effective heat transfer path away from heat generating components of the lighthead. Cooperating aluminum brackets are configured to lock together and overlap to provide an effective heat transfer path.

Description:
BACKGROUND 
   The disclosure relates generally to warning light systems for use with motorized vehicles and, more particularly, to a lighthead mounting structure for use in such warning light systems. 
   Warning light assemblies mounted on emergency vehicles are well known in the art. The modern trend is toward compact, low profile, self-contained warning light assemblies. Compact and low profile warning light assemblies have improved arrow dynamic efficiency and significantly reduce the wind noise associated with higher profile designs. Warning lights are typically required to produce very bright light and as a consequence include light sources which generate significant amounts of heat. Warning lights also operate on emergency vehicles where they are exposed to the elements year round. As a consequence, warning light assemblies are typically sealed to protect internal components from exposure to the elements. Further, warning light assemblies are expected to withstand relatively high levels of shock and vibration present in their operating environments. Warning light assemblies are preferably field serviceable, allowing replacement of lightheads and other components to maintain safe lighting and warning on the vehicles equipped with the warning light assemblies. Thermal management and ease of maintenance have long been concerns of engineers designing warning light assemblies for emergency vehicles. 
   It would be desirable to provide a lighthead mounting structure which allows efficient field service and prevents excess accumulation of heat inside the warning light assemblies in which it is used. 
   SUMMARY 
   The disclosed lighthead mounting structure provides both precise alignment of a lighthead and an effective heat transfer path away from heat generating components of the lighthead. Each lighthead includes a substantially planar thermally conductive PC board with LEDs and current source components mounted to the board that generate heat when power is applied. The back side of the PC board is compressed against the upright portion of an L-shaped lighthead bracket. The disclosed lighthead bracket is constructed of thermally conductive sheet aluminum material and includes laterally spaced alignment tabs extending from a lower flange. The lower flange is substantially perpendicular to the upright portion of the lighthead bracket and defines a fastener opening. 
   The lighthead mounting structure includes a mounting bracket of thermally conductive material having a substantially planar mounting surface. The disclosed mounting bracket is longitudinally extended, defining sets of tab receptacles and fastener openings complementary to the alignment tabs and fastener opening of the lighthead bracket lower flange. 
   Lightheads are secured in a predetermined fixed orientation with respect to the mounting bracket by inserting the alignment tabs into a selected set of tab receptacles and inserting a fastener through the fastener openings defined by the lighthead bracket lower flange and mounting bracket. The lighthead bracket and mounting bracket overlap in face to face relationship to form a robust thermal path for heat generated electronic components in the lightheads. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a rear perspective view of a warning light sub-assembly including an embodiment of a lighthead mounting structure according to the disclosure; 
       FIG. 2  is a bottom plan view of the warning light sub-assembly of  FIG. 1 ; 
       FIG. 3  is a front elevation view of the warning light sub-assembly of  FIGS. 1 and 2 ; 
       FIG. 4  is a rear exploded view of the warning light sub-assembly of  FIGS. 1-3 ; 
       FIG. 5  is a rear perspective view of a lighthead bracket as shown in  FIGS. 1-4 ; 
       FIG. 6  is a front perspective view of a mounting bracket as shown in  FIGS. 1-4 ; 
       FIG. 7  is an enlarged side plan view of the warning light sub-assembly of  FIGS. 1-3 ; 
       FIG. 8  is a left side exploded perspective view of a lighthead according to the disclosure; and 
       FIG. 9  is a left side exploded perspective view of an alternative lighthead according to the disclosure. 
   

   DETAILED DESCRIPTION 
   Embodiments of a lighthead mounting structure will now be described with reference to the Figures, wherein like numerals refer to similar parts.  FIGS. 1-4  illustrates an embodiment of a lighthead mounting structure  10  according to aspects of the disclosure. A lighthead mounting structure  10  according to the disclosure includes a first bracket  12  fixed to each lighthead  14 , and a second bracket  16  for retaining the lightheads  14  in a predetermined fixed relationship with respect to a warning light assembly (not shown). The first and second brackets  12 ,  16  are constructed of thermally conductive material and are configured to provide a thermal path away from heat generating components in the lightheads  14 . 
     FIGS. 8 and 9  are exploded perspective views of representative lightheads  14  configured for use with the disclosed lighthead mounting structure. Each lighthead  14  includes a reflector  18 ,  20 , a PC board  22  carrying LED light sources  24  and current source components  28 , a thermally conductive gasket  30  and an L-shaped bracket  12 . The disclosed L-shaped lighthead brackets  12  are constructed of sheet aluminum that is cut and bent to the illustrated shape. Other materials and methods of manufacture may be compatible with the disclosed lighthead mounting structure. 
   Each reflector  18 ,  20  defines generally concave reflecting surfaces arranged to organize (collimate) light from the LEDs into a beam. The circular reflecting surfaces  32  of the reflector  20  shown in  FIG. 9  produce a vertically and horizontally collimated (circular) beam and may be provided with optics  34  to enhance the horizontal and/or vertical spread of the radiation pattern. The trough shaped reflecting surfaces  36  of the reflector  18  of  FIG. 8  are configured to produce a vertically collimated beam that has a wide horizontal spread (a wide angle beam). It will be understood by those familiar with this field that the terms “vertical” and “horizontal” depend upon the orientation of the lighthead. 
   Each of the illustrated PC boards  22  may be a metal core PC board or a standard fiber board. If the PC board is a fiber board, it will include thermally conductive features, such as thermal vias (copper plated through holes), arranged in proximity to the heat producing electronic components mounted to the PC board to facilitate heat transfer through the board. The illustrated PC boards show LEDs  24  and current source components  28 , such as transistors, which generate heat during operation. In the illustrated lightheads  14 , the PC board  22  and thermally conductive gasket  30  are compressed between the reflector  18 ,  20  and lighthead bracket  12  by two screws  38 . The depth and sidewalls of the reflectors  18 ,  20  make them quite rigid, while the lighthead bracket  12  is stiffened by the right-angle bend and lower flange  40 . The rigid reflector  18 ,  20  and rigid bracket  12  cooperate to compress the PC board  22  and thermally conductive gasket  30  against the bracket to provide a good thermal interface from the PC board  22  to the bracket  12 . 
   The lower flange  40  of each bracket includes a pair of spaced apart alignment tabs  42 . Each alignment tab  42  has an S-shaped configuration stepping downwardly and away from the lower flange  40 . Each alignment tab  42  also includes beveled corners as best seen in  FIG. 5 . The alignment tabs  42  are configured to be received in alignment slots  44  defined by the mounting bracket  16 . The mounting bracket  16 , illustrated in  FIGS. 1-4 ,  6  and  7 , defines three longitudinally spaced locations  46  for lightheads. Each location  46  for a lighthead includes two alignment slots  44  and a fastener opening  48 . A lighthead  14  is secured to the mounting bracket  16  by inserting the alignment tabs  42  in a selected pair of alignment slots  44  and threading a fastener  50  through the fastener opening  52  in the lighthead bracket  12  and the corresponding opening  48  in the mounting bracket. 
   As shown in  FIGS. 1-4 , the lightheads  14  are configured such that they are compatible with any lighthead location  46  on the mounting bracket  16 . The disclosed arrangement of interlocking tabs and slots  42 ,  44  provides a simple means of attaching various lightheads to a warning light structure in a fixed predetermined configuration. The disclosed arrangement of tabs and slots reduces the number of fasteners necessary to assemble a warning light. The disclosed configuration promotes ease of assembly and service. 
   One objective of the disclosed lighthead mounting structure  10  is to provide a conductive thermal path away from the heat generating components of the lighthead  14 . In this case, the brackets  12 ,  16  are manufactured from aluminum, which is an excellent conductor of heat. The lower flange  40  of each lighthead bracket  12  extends along substantially the entire length of the lighthead and extends rearwardly to provide a large surface area overlap with the mounting bracket as shown in  FIG. 7 . The fastener  50  used to secure each lighthead  14  to the mounting bracket  16  is located substantially in the middle of the lower flange  40  and when tightened compresses the lower flange against the mounting bracket  16  to promote heat transfer. The overlapping surfaces of the brackets  12 ,  16  provide a large and efficient thermal path to conduct heat away from the heat generating components of the lightheads. 
   The mounting bracket may be arranged to interface with other thermally conductive structures to continue the movement of heat away from the lightheads by conduction. It should be noted that as the temperature of the lightheads and/or brackets increase, some heat will be radiated into the ambient environment from these hot surfaces and a small amount of heat will be removed by convection via the movement of air past the brackets. 
   The disclosed lighthead mounting structure provides a simple and efficient structure for securing lightheads in a predetermined fixed relationship to a warning light assembly where the mounting structure also plays a significant role in removing heat from heat generating components of the lighthead. 
   While embodiments of the disclosed lighthead mounting structure have been shown and described, various modifications and substitutions may be made thereto. Accordingly, it is understood that the present embodiments have been described by way of illustration and not limitation.