The present invention relates generally to the field of lighting fixtures. In particular, the present invention relates to a modular cell structure for heat management of lighting fixtures.
BACKGROUND OF THE INVENTION
In lighting fixtures and in lighting technology, heat is generated as a by¬product. The heat is required to be dissipated quickly and efficiently so that the lighting fixture can optimally operate and not overheat. Generally, higher the light intensity, higher the amount of heat generated. There are various ways by which heat generation and heat dissipation by/from lighting fixtures can be addressed. One way is to reduce heat generation. For example, LED technology represents a leap over incandescent lighting technology in that LEDs generate less heat as compared to incandescent lights of comparable luminosity.
Another way to improve heat dissipation is to build bigger heat sinks or with different conductive material to increase capacity to transfer heat away from the light generating source. However, such heat sinks are bulky and expensive to machine. Heat sinks are not scalable and small increase in power capacity of lighting element requires a much bigger increase in heat sink size to compensate for the heat generated. In other words, heat sinks cannot be scaled readily and can only operate in a narrow operation band.
Therefore, there is a continuing need in the art for newer solutions to heat dissipation especially in high power light fixtures.
SUMMARY OF THE PRESENT INVENTION
In an aspect of the present invention, there is provided a modular cell structure (1) comprising a plurality of polygonal cells (2), which is a heat sink for cooling a light generating element (3), wherein the cell structure is modular and

is arranged to conduct heat generated by the light generating element (3) away from the light generating element (3) by passive convection.
In another aspect of the present invention, there is provided a lighting device (5) comprising at least a light generating element (3) and a modular cell structure (1) comprising a plurality of polygonal cells (2), which is a heat sink for cooling a light generating element (3), wherein the cell structure is modular and is arranged to conduct heat generated by the light generating element (3) away from the light generating element (3) by passive convection.
In yet another aspect of the present invention, there is provided a method of manufacturing a lighting device (5), comprising: (i) providing at least a light generating element (3); providing at least a heat sink (6); providing at least a modular cell structure (1); (ii) attaching the light generating element (3) to the heat sink (6) such that at least a part of the light generating element (3) is in direct thermal contact with at least a part of the heat sink (6); and (iii) attaching the modular cell structure (1) to the heat sink (6) such that at least a part of the heat sink (6) is in direct contact with at least part of the modular cell structure (1).
In still another aspect of the present invention, there is provided a method of enhanced heat dissipation from a lighting device (5) comprising at least a light generating element (3) and a modular cell structure (1) comprising a plurality of polygonal cells (2), which is a heat sink for cooling a light generating element (3), wherein the cell structure is modular and is arranged to conduct heat generated by the light generating element (3) away from the light generating element (3) by passive convection, said method comprising: (i) transfer of heat from at least a light generating element (3) to a heat sink (6) by thermal conduction, wherein at least a part of the light generating element (3) is in thermal contact with at least part of the heat sink (6); and (ii) transfer of heat from the heat sink 6) to the modular cell structure (1) by thermal convection air flow within each polygonal

cells (2) of the cell structure (1), wherein heat flow is directed from the bottom (7) of the cell structure (1) towards the top (8) of the cell structure (2).
This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.
Figure la depicts the general schematic arrangement of the modular cell structure (1) of the present invention in a lighting fixture (5), in accordance with an embodiment of the present invention
Figure lb depicts the exploded view of a lighting fixture (5) prototype, in accordance with an embodiment of the present invention.
Figure 2 depicts a close-up view of the modular cell structure (1) of the present invention and features thereof, in accordance with an embodiment of the present invention.
Figure 3 depicts the effect of the honeycomb modular cell structure of the present invention on the temperature of LED lighting fixtures with varying number of LEDs, in accordance with an embodiment of the present invention.
Figure 4 depicts the effect of varying the height of the wall elements of polygonal cells of the claimed modular cell structure of the present invention on heat radiating capacity/efficiency of LED lighting fixtures, in accordance with an embodiment of the present invention.
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Those skilled in the art will be aware that the invention described herein is subject to variations and modifications other than those specifically described. I tis to be understood that the invention described herein includes all such variations and modifications. The invention also includes all such steps, features referred to or indicated in this specification, individually or collectively.
The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purpose of exemplification only.
Unless defined otherwise, all technical terms used herein have the same meaning as commonly understood by a person skilled in the art.
The present invention provides a modular cell structure (1) comprising a plurality of polygonal cells (2), which is a heat sink for cooling a light generating element (3), wherein the cell structure is modular and is arranged to conduct heat generated by the light generating element (3) away from the light generating element (3) by passive convection.
In an embodiment, the polygonal cells (2) have 3 sides. In yet another embodiment, the polygonal cells (2) have 4 sides. In still another embodiment, the polygonal cells (2) have more than 4 sides. In a preferred embodiment, the cell structure (1) is a honeycomb structure wherein the polygonal cells (2) are hexagonal. In an embodiment, the cell structure (1) comprises a plurality of polygonal cells (2), wherein at least 2 polygonal cells (2) have different number of sides. In a preferred embodiment, each of the plurality of polygonal cells (2) of the cell structure (1) have same number of sides. It is understood by a person skilled in the art that at least a polygonal cell (2) at the periphery of the modular cell structure (1) may have lesser number of sides than polygonal cells not at the periphery.
The polygonal cells (2) of the modular cell structure (1) comprise wall elements (4) with a defined height and width that are strip shaped and bent to

form the polygonal cells (2). It is understood by a person skilled in the art that the wall elements (4) referred to are essentially the sides of the polygonal cells (2). In an embodiment, each side/wall element of a polygonal cell is discontinuous and is physically attached to adjoining side wall element. The attachment can be by welding or any other technique known in the art. In a preferred embodiment, the wall elements (4) of a polygonal cell (2) is continuous. In a preferred embodiment, at least a wall/side element (4) of a first polygonal cell (2) is also at least a wall/side element (4) of a second polygonal cell (2). In a preferred embodiment, the wall elements (4) are perpendicular to the plane of the base of the cell structure (1). In an embodiment, the length of each wall element of a cell may be substantially the same. In an alternate embodiment, the wall elements of each cell may be of different lengths. In case of hexagonal cells, as convention, it is understood that a hexagonal cell has 6 identifiable wall elements, each wall element of the hexagonal cell delimited by the edges along the Y-axis (height) of the wall elements.
The polygonal cells (2) of the modular cell structure (1) are made of at least a heat conducting material. In an embodiment, the heat conducting material is an alloy. In another embodiment, the heat conducting material is an element. In yet another embodiment, the heat conducting material is a compound. Examples of thermally conductive materials are silver, gold, aluminum nitride, silicon carbide, aluminum, tungsten, graphite zinc, and alloys thereof. In a preferred embodiment, the material is aluminum.
In a preferred embodiment, the light generating element (3) is LED. It is understood that the light generating element (3) can be any other type of light generating element, such as, but not limited to halogen, incandescent, metal halide, neon, high intensity discharge, compact fluorescent, fluorescent, and low-pressure sodium.
The present invention also provides a lighting device (5) comprising at least a light generating element (3) and a modular cell structure (1) comprising a

plurality of polygonal cells (2), which is a heat sink for cooling a light generating element (3), wherein the cell structure is modular and is arranged to conduct heat generated by the light generating element (3) away from the light generating element (3) by passive convection.
In an embodiment, the lighting device comprises a single light generating element. In another embodiment, the lighting device comprises at least 2 light generating elements, the at least 2 or more light generating elements may be spatially arranged in any non-limiting manner. In a preferred embodiment, the at least 2 or more light generating elements are spatially arranged in the same plane.
The features of the modular cell structure (1) of the lighting device (5) are as described substantially elsewhere in the present description.
The lighting device (5) further comprises at least a heat conducting heat sink (6), which is arranged to conduct heat generated by heat generating element (3) away from the light generating element (3) by thermal conduction. The heat sink (6) has a proximal and a distal side, wherein the proximal side is closer to the light generating element (3) and the distal side is away from the light generating element (3).
At least a part of the at least a heat sink (6) is in direct physical contact with at least a part of at least a light generating element (3). In a preferred embodiment, a substantial part of the proximal side of the heat sink (6) is in direct physical contact with the light generating element (3).
The heat sink (6) is sandwiched between the light generating element (3) and the cell structure (1). The distal side of the heat sink (6) is in direct physical contact with the base of polygonal cells (2) of the cell structure (1).
The present invention further provides a method of manufacturing a lighting device (5), comprising: (i) providing at least a light generating element

(3); providing at least a heat sink (6); providing at least a modular cell structure (1); (ii) attaching the light generating element (3) to the heat sink (6) such that at least a part of the light generating element (3) is in direct thermal contact with at least a part of the heat sink (6); and (iii) attaching the modular cell structure (1) to the heat sink (6) such that at least a part of the heat sink (6) is in direct contact with at least part of the modular cell structure (1).
The light generating element can be a single element or multiple elements arranged in any manner known generally to a person skilled in the art. The manner of arrangement of multiple light generating elements is well within the expertise of a person skilled in the art and does not constrain practice of the invention. The light generating elements can be attached to the heat sink using glue or clips, or any other manner known in the art. The modular cell structure is attached to the distal surface of the heat sink by glue or clips or any other manner known in the art. Preferably, the modular cell structure is attached to the distal face of the heat sink in a detachable manner.
The present invention still further provides a method of enhanced heat dissipation from a lighting device (5) comprising at least a light generating element (3) and a modular cell structure (1) comprising a plurality of polygonal cells (2), which is a heat sink for cooling a light generating element (3), wherein the cell structure is modular and is arranged to conduct heat generated by the light generating element (3) away from the light generating element (3) by passive convection, said method comprising: (i) transfer of heat from at least a light generating element (3) to a heat sink (6) by thermal conduction, wherein at least a part of the light generating element (3) is in thermal contact with at least part of the heat sink (6); and (ii) transfer of heat from the heat sink 6) to the modular cell structure (1) by thermal convection air flow within each polygonal cells (2) of the cell structure (1), wherein heat flow is directed from the bottom (7) of the cell structure (1) towards the top (8) of the cell structure (2).
ADVANTAGES OF THE PRESENT INVENTION

It can be appreciated from the present invention that the modular cell structure (1) of the present invention can be readily adapted to lighting fixtures in a cost efficient and modular manner so as to enhance the heat dissipation in light fixtures. The heat load capacity of the lighting fixture can be modulated by simply changing the area of the cell structure (1). Adoption of the modular cell structure (1) of the present invention to enhance cooling/reduce heat load results in significant weight reduction (~40%) as compared to conventional techniques of increasing the size of (bulky) die casted heat sinks. The shape features of the modular cell structure (1) are made independent of the type of lighting fixture and can be readily adapted for use in different types of fixtures and light generating sources.
In conventional heat sink design, any change in input heat load necessitates a change in heat sink size, which requires altogether new tooling. In contrast, the modular nature of the cell structure (1) of the present invention allows for a plug-and-play functionality/feature, which avoids expensive and time-consuming retooling.
The hexagonal shape of the polygonal cells (2) is preferred to maximize efficient division of the surface into regions of equal areas with least total perimeter and reduce amount of material used. The hexagonal honeycomb structure also provides superior compression strength due to its configuration. Additionally, the particular cell structure (1) comprising a plurality of hexagonal cells (2) allows for establishing turbulent flow of heat for enhanced efficiency of heat transfer away from the heat generating source. The particular cell structure (1) and its incorporation in the lighting fixture/device (5) allows for efficient cooling even at high ambient temperatures of 45°.
EXAMPLES
The disclosure will now be illustrated with working examples, which is intended to illustrate the working of the invention. It is not intended to restrictively imply any limitations on the scope of the invention.

Figure la depicts the general arrangement of the modular cell structure (1) of the present invention in a lighting fixture (5). It can be seen that a thermally conductive plate [(heat sink (6)] is in direct contact with light generating element(s) (3), which is responsible for conducting the heat (generated by LEDs) away from the LEDs. The modular cell structure (1) is positioned/attached over the heat sink/thermally conductive plate and the heat from the heat sink is transferred away effectively by the turbulent convention by the honeycomb modular cell structure.
Figure lb depicts the exploded view of a lighting fixture (5) prototype. The lighting element (3), heat sink (6) and modular honeycomb modular cell structure (1) are highlighted.
Figure 2 depicts a close-up view of the modular cell structure (1) of the present invention. It can be seen in Fig. 2 that the cell structure (1) essentially comprises a plurality of polygonal cells (2), preferably hexagonal in shape. Each cell comprises wall elements (4) with defined height, length and width. For example, in a hexagonal cell, there will be 6 wall elements. In a rectangular or square cell, there will be 4 wall elements, and so forth. Preferably, in the case of hexagonal cells, opposite wall elements have the same height and length. It is understood that the height and length of all the wall elements of a cell can be the same or can be different as per requirement. In an exemplary non-limiting example, the total height of the honeycomb cell structure is 30mm, thickness of the wall elements is 0.2mm, diameter of the structure is 350mm and size of each hexagonal cell is 6.5x3.2mm.
In an exemplary example to demonstrate the thermal test of the honeycomb modular cell structure of the present invention, the temperature of LED lighting fixtures with varying number of LEDs with or without the modular honeycomb cell structure was evaluated.
As seen in Fig. 3, it can be seen that for various LED lighting fixtures without comprising the honeycomb modular cell structure and having LEDs

ranging from 1-27, the temperature of the fixture ranges from 92.77-95.97°. In contrast, inclusion of the honeycomb modular cell structure results in a significant decrease in temperature to 67.87-72.04°C. On average, the decease is about 27°C. This is demonstrative of efficient heat dissipation achieved by the light weight and modular cell structure of the present invention, which replaces the bulky and expensive conduction based thermal plates required for enhanced heat dissipation.
In another exemplary example, the effect of varying the height of the wall elements of polygonal cells of the claimed modular cell structure was examined on heat radiating capacity/efficiency. Lower LED temperature is indicative of efficient functioning of the modular cell structure of the present invention.
As seen in Fig. 4, for wall element having height of 18mm, the maximum LED temperature was recorded as 95.5°C. When the wall element height was increased to 30mm, it was observed that the LED temperature was recorded as 88.5°C. Surprisingly, a further increase in wall element height to 38mm resulted in increased LED temperature to 91°C. Further, unexpectedly, increase of wall element height to 50mm resulted in decrease in LED temperature to 89°C. These data suggest that progressive increase in wall element height does not lead to corresponding increase in cooling effect/heat radiating effect. In other words, after a certain wall element height, a saturation is reached beyond which no further gains in heat radiation can be realized.
These data clearly show that the modular cell structure of the present invention can effectively dissipate heat away from lighting fixtures and can readily replace usage of bulkier non modular heat conducting plates, which are also expensive.

We claim:

1. A modular cell structure (1) comprising a plurality of polygonal cells (2), which is a heat sink for cooling a light generating element (3), wherein the cell structure is modular and is arranged to conduct heat generated by the light generating element (3) away from the light generating element (3) by passive convection.
2. The cell structure (1) as claimed in claim 1, wherein the polygonal cells (2) comprise wall elements (4) with a defined height and width that are strip shaped and bent to form the polygonal cells (2).
3. The cell structure (1) as claimed in claim 1, wherein the polygonal cells (2) are made of heat conducting material, preferably aluminum.
4. The cell structure (1) as claimed in claim 1, wherein said structure is a honeycomb structure.
5. The cell structure (1) as claimed in claim 2, wherein the wall elements (4) are perpendicular to the plane of the base of the cell structure (1).
6. A lighting device (5) comprising at least a light generating element (3), and a cell structure (1) as claimed in claim 1.
7. The lighting device (5) as claimed in claim 6, further comprising at least a heat conducting heat sink (6) which is arranged to conduct heat generated by the light generating element (3) away from the light generating element (3) by conduction.
8. The lighting device (5) as claimed in claim 6, wherein the conductive heat sink (6) is sandwiched between the lighting generating element (3) and the cell structure (1).
9. The cell structure (1) as claimed in claim 1 or the lighting device (5) as claimed in claim 6, wherein said light generating element (3) is at least a LED.

10. A method of manufacturing a lighting device (5), comprising:
a. providing at least a light generating element (3); providing at least
a heat sink (6); providing at least a modular cell structure (1);
b. attaching the light generating element (3) to the heat sink (6) such
that at least a part of the light generating element (3) is in direct
thermal contact with at least a part of the heat sink (6); and
c. attaching the modular cell structure (1) to the heat sink (6) such
that at least a part of the heat sink (6) is in direct contact with at
least part of the modular cell structure (1).
11. A method of enhanced heat dissipation from a lighting device as claimed in
claim 6, comprising:
a. transfer of heat from at least a light generating element (3) to a
heat sink (6) by thermal conduction, wherein at least a part of the
light generating element (3) is in thermal contact with at least part
of the heat sink (6); and
b. transfer of heat from the heat sink (6) to the modular cell
structure (1) by thermal convection air flow within each polygonal
cells (2) of the cell structure (1), wherein heat flow is directed
from the bottom (7) of the cell structure (1) towards the top (8) of
the cell structure (2).