|1.||A lamp box comprising a light source, a fiber optic cable have a light receiving end thereof optically coupled to a light path emanating from the light source and disposed within a cavity, and a blower supplying cooling air to the light receiving end of the fiber optic cable within said cavity, wherein cooling air passing through the cavity is induced to form a vortex that contacts and cools the light receiving end of the fiber optic cable.|
|2.||The lamp box according to claim 1, further comprising a filter disposed within said cavity, wherein said cooling air vortex contacts and cools said filter.|
|3.||The lamp box according to claim 2, wherein said filter is an IR or UV filter.|
|4.||The lamp box according to claim 1, wherein said fiber optic cable is comprised of a plurality of poly (methyl methacrylate) fiber optic strands.|
|5.||The lamp box according to claim 3, wherein said fiber optic cable is comprised of a plurality of poly (methyl methacrylate) fiber optic strands.|
|6.||The lamp box according to claim 1, further comprising a variable color filter disposed in the light path.|
|7.||The lamp box according to claim 6, wherein said variable color filter is a color wheel that is driven by an electric motor.|
|8.||The lamp box according to claim 1, wherein said fiber optic cable is an endemitting fiber optic cable.|
|9.||The lamp box according to claim 4, wherein said fiber optic cable is an endemitting fiber optic cable.|
|10.||The lamp box according to claim 1, wherein said fiber optic cable is a laterally lightemitting fiber optic cable.|
|11.||The lamp box according to claim 4, wherein said fiber optic cable is a laterally lightemitting fiber optic cable.|
BACKGROUND OF THE INVENTION Field Of The Invention The present invention relates to a light source for fiber optic illumination systems. More specifically, the invention relates to a lamp box type light source utilizing a vortex generation internal cooling system.
Description Of The Background Art Various kinds of lamp boxes for advertisement illumination are known. Most of the lamp boxes are provided with high voltage power sources for supplying the necessary high voltage to the illuminants. In particular, neon lamps are often used in connection with advertisements because they generate aesthetically pleasing light. Typical neon light tubes, however, have the drawback that for each tube, the color of the light it provides is unchangeable. This is due to the fact that the color of light emitted from a neon lamp is controlled by the kind of gas trapped within the lamp's tube. Thus, for a particular section of the typical neon tube, the color emitted is constant. To produce a multicolored display with neon lights requires multiple tubes, one or more tubes for each color in the display.
Various attempts have been made to produce variable color light sources which will overcome the disadvantages of the common neon lamp. Accordingly, Chinese Patent No.
ZL97241773.7 discloses a lamp box with a color variable light source that is adapted for supplying light to a fiber optic system. The lamp source utilizes a high intensity metal halide lamp together with a multi-colored filter so that the light source lamp box can output light of varying color to the fiber optic cable. While providing a multiple color light source, such a lamp box still has its drawbacks.
The temperature of the lamp box generally runs high due to the high wattage lamps employed, and the light receiving areas at the end face of the fiber optic cable are often sensitive to such high temperatures. The use of a lens to focus the light onto the end face of the fiber optic cable exacerbates this problem. Additionally, significant amounts of infrared energy are generated by the high intensity halide lamp. Due to the high temperatures and relative proximity of the fiber optic cable end face (s) and the lamp, the fiber optics may be damaged or even melted after extended operation times.
The high temperatures reached within such lamp boxes are mainly due to the heat generated by the metal halide lamp. These lamp boxes generally include an axial-flow fan that produces some airflow and thus some cooling effect within the lamp box. These cooling systems typically are designed to move a relatively high volume of air at a relatively low velocity within the boxes. When the cooling systems are made more powerful, however, their noise output increases, rendering them unsatisfactory for many uses where quit operation is desired.
Therefore, the present invention is directed to improvements to the cooling capacity of a lamp box for fiber optic illumination systems.
SUMMARY OF THE INVENTION The present invention overcomes the above-mentioned drawbacks with respect to the high temperature of light source lamp boxes, and provides in preferred embodiments a color variable light source lamp box with better heat dissipation. In accordance with the present invention there is provided a light box comprising a light source, a fiber optic cable have a light receiving end thereof optically coupled to the light source and disposed within a cavity, and a blower supplying cooling air to the cavity, wherein the cooling air passing through the cavity is induced to form a vortex that contacts and thereby efficiently cools the light receiving end of the fiber optic cable.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration of one embodiment of a lamp box of the present invention ; FIG. 2 is a perspective view of a bowl-shaped reflector, attached radiator, and radiator bracket which are suitable for embodiments of the present invention; FIG. 3 is a perspective view of a blower which is useful in embodiments of the present invention; FIG. 4 is a cut-away perspective view of an embodiment of the present invention; FIG. 5 is a cut-away top elevational view of the embodiment of FIG. 4 ; and FIG. 6 is a cut-away side view of the embodiment of FIGS. 4 and 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the figures, exemplary embodiments of the invention will now be described. The embodiments illustrate principles of the invention and should not be construed as limiting the scope of the invention.
An estimate of the required airflow through a hypothetical enclosure to provide a desired heat transfer is provided by the equation: Q = 3.16 W/TF (1) where Q = Volumetric airflow in ft3/min, or"CFM," W = Heat dissipated in Watts, and TF = Temperature difference between ambient and internal conditions in degrees F.
By way of example, for an enclosure containing a 200 Watt heat source which is desired to kept at a temperature approximately 20°F above ambient, 31.6 CFM (cubic feet per minute) of airflow would be required, assuming negligible flow losses due to friction. Airflow represents the amount of air that passes a point per unit of time and is thus a positive function of velocity and a negative function of air pressure. In commonly available lamp boxes, cooling airflow is generally achieved by moving large volumes (high mass) of low-pressure air at a relatively low velocity. Moving such large volumes of air generates substantial amounts of noise, however. The present invention provides highly efficient cooling airflow in the form of relatively high velocity and high pressure turbulent (vortex) circulation that is created in the vicinity of the light receiving end face of the fiber
optic cable. Accordingly, lamp boxes of the present invention provide greater cooling capacity than prior art devices, and at the same time are substantially quieter.
The above formula for estimating the required airflow assumes rather linear air motion. However, heat dissipation in a turbulent flow can be up to double that of a laminar flow for the same volumetric flow rate. In view thereof, the present invention advantageously uses turbulent airflow to improve the cooling capacity of fiber optic lamp boxes.
In particular, the present invention provides cooling air of high velocity over a small area to create highly efficient heat-removing, turbulent air structures such as vortexes.
Referring to a preferred embodiment of the invention as depicted in the figures, a light source lamp box 1 generally comprises a metal halide lamp 2 (in phantom), a bowl-shaped reflector 3, a power source 4, a color filter (color wheel) 5 and a drive motor 6 in its body. The lamp box may also include additional filter elements disposed in the light path, such as IR and/or UV filters or a combination IR/UV filter, designated by reference numeral 21 (FIG 6). The metal halide lamp 2 is positioned inside the reflector 3 so that the reflector 3 can focus radiant energy upon the light receiving end 20 of the fiber optic cable 12. The inner surface of reflector 3 may be coated with an infrared reflecting layer (not shown). The power source 4 provides electrical power for the metal halide lamp 2, the drive motor 6, and the exhaust fan 10. The body 13 of the lamp box is connected to a fiber optic cable 12 by means of a fiber optic cable plug assembly 7.
A wide variety of fiber optic cable technologies are suitable for use with the present invention. The invention is particularly well suited for use in combination with fiber optic cables containing a plurality of poly (methyl methacrylate) (PMMA) fiber optic strands. PMMA fiber optic strands have a lower melting point than the well-known quartz (glass) fiber optic strands, but their low cost to manufacture makes them particularly attractive for commercial lighting fiber optic systems. Thus, the present invention provides special advantages when used in combination with PMMA-based fiber optic cables. The inventive light box may be used in connection with end- emitting or laterally light-emitting fiber optic cable systems.
Although not necessary to the operation of the invention, a multi-color filter 5 is shown and is used to vary the color of the light that enters the fiber optic cable 12. The filter 5 is positioned between the metal halide lamp 2 and the fiber optic cable plug 7. Drive motor 6 drives the filter 5 to rotate and thus vary the color of the light reaching the fiber optic cable. An axial exhaust fan 10 is provided to draw hot air out of the lamp box 1.
Referring to FIG. 2, light source lamp boxes according to preferred embodiments of the present invention may utilize heat-sink structures around the lamp 2 and bowl- shaped reflector 3. As depicted in FIG. 2, such structures include a radiator 8 which is mounted around the base of the reflector 3. The radiator 8 is of a generally hollow, cylindrical shape and includes a plurality of fins to improve heat transfer away from the lamp 2. The radiator is
fixed to the body 13 of the lamp box through a radiating bracket 9. The radiating bracket 9 comprises a top and bottom holder, 91 and 92, respectively. The top holder 91 comprises a C-shaped bracket, as does the bottom holder 92.
Both holders, 91 and 92, encase the radiator and secure it in the body 13 of the box 1. Both the radiator 8 and the radiating bracket 9 are preferably made of a high heat conducting material, such as aluminum. This arrangement provides the advantage of drawing heat away from metal halide lamp 2 through the radiator 8 and radiating bracket 9, and in a direction away from the heat sensitive optical fiber 12. This heat can then more easily be removed by the exhaust fan 10.
As shown in FIGS. 1 and 3, in addition to the above radiation means, the present invention further provides a blower 11 housed inside a separate casing 16 within the body 13 of the lamp box 1. The exit vent 14 of the blower 11 is positioned to face the gap between the fiber optic plug 7 and the reflector 3. The blower 11 can be of any type commercially available in the market which is small enough to fit comfortably within the body 13, yet capable of efficiently producing in the neighborhood of 50 CFM of air at temperatures in the 20° F to 200° F range. The blower 11 is preferably a centrifugal blower. Centrifugal blowers are small but can produce output having both high pressure and high velocity airflow. The velocity of airflow output by blower 11 should be at least about 30 CFM. An acceptable centrifugal blower is commercially available from the Torin Corporation and is known as the Torin DSG380.
During operation, the blower 11 draws cooler air from outside the lamp box and produces a flow of air exiting from its vent 14 at a flow rate on the order of 50 CFM. As shown particularly by FIGS. 5 and 6, the airflow produced by the blower 11 exits the vent 14 and passes through an air flow chamber 15 in which are disposed the light receiving end 20 of the fiber optic cable 12 and the IR/UV filter 21.
Chamber 15 is designed such that it has a cross-sectional area substantially less than that of the vent 14. As will be recognized by persons skilled in the field of fluid flow, air entering chamber 15 undergoes a throttling effect whereby velocity and pressure increase and turbulent flow currents 18 are created. For the purposes of this disclosure, the turbulent airflow thus created within chamber 15 is termed a"vortex."The creation of a vortex that impinges upon the end 20 of the fiber optic cable, as well as upon filer 21, has been found to significantly increase heat transfer from those components. The cooling air subsequently is vented out and away from the chamber via exit aperture 17.
The high velocity, high pressure airflow output from the blower 11 may impinge upon and thereby cool other components of the light box in addition to the light collecting end of the fiber optic cable. In a preferred embodiment, filter 21 as well as any other components disposed within the chamber 15 can be cooled by the vortex airflow. Those skilled in this field, using this disclosure as a guide, will be able to alter the geometry of chamber 15 in order to alter the characteristics of the turbulent airflow (vortex) that is created, as desired.
FIG. 6 illustrates how the positioning of the airflow from the blower 11 in the chamber 15 encourages the turbulent flow currents 18 to form a heat removing vortex.
Turbulence in the airflow is caused in part by the imbalance of air velocity and pressure in the small volume defined by chamber 15. For example, the airflow from blower 11 may be positioned away from the center of the cavity 15 so that a spiraling air flow pattern forms. Furthermore, as described above, the cavity is designed to create a vortex in the turbulent flow currents 18 at the area to be cooled.
Since many modifications, variation, and changes in detail may be made to the described embodiments, it is intended that all the matter in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.
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