CA2971717A1

CA2971717A1 - Improved efficiency lighting apparatus with led directly mounted to a heatsink

Info

Publication number: CA2971717A1
Application number: CA2971717A
Authority: CA
Inventors: Anthony Maglica
Original assignee: Mag Instrument Inc
Current assignee: Mag Instrument Inc
Priority date: 2014-12-22
Filing date: 2015-12-16
Publication date: 2016-06-30
Anticipated expiration: 2035-12-16
Also published as: EP3238278A4; US20170023227A1; CN107112401B; WO2016106053A1; JP2021036527A; EP3238278B1; CN107112401A; US20170248299A1; JP2018505537A; HRP20200833T1; JP7036883B2; CA2971717C; US20160356480A1; EP3238278A1; US9671102B2; DK3238278T3; US20160252221A1; US20160178182A1; US9494308B1; US9453625B2

Abstract

LED efficiency in a lighting device, such as an aluminum flashlight, Is increased by directly mounting the LED without use of a PCB to a heatsink that is In thermal and electrical contact with an outer casing to dissipate heat, resulting in an LED that operates much cool and therefore much more efficiently.

Description

Improved Efficiency Lighting Apparatus with LED Directly Mounted to a Heatsink Background LED efficiency and light output drops as the device heats up during operation.
Typically, LEDs are mounted on laminated printed circuit boards. Some are mounted on special metal back or ceramic printed circuit boards in an attempt to conduct heat away from the LED.
SUMMARY OF THE NVENTION
The invention is generally directed to a lighting apparatus in which at least one LED is mounted to the top surface of a heat sink held within an outer casing that is thermally and electrically conductive, the LED having a first conductive member which is thermally and electrically directly connected to the heatsink without the use of a printed circuit board and a second electrically conductive member which is electrically isolated from the heatsink by an electrical insulating material held within the heatsink.
The second electrically conductive member of the LED can be soldered to a terminal held within the electrical insulating material while the first electrically conductive member of the LED can also be soldered to the heat sink and the resulting heat sink assembly can be press fit into a tube or barrel (such as an aluminum flashlight barrel) or inserted into the tube or barrel and then removably retained by a mechanical means such as a nut threaded to the tube or barrel. Alternatively, the heatsink can be integrally formed with the tube or barrel.
Accordingly, it is a primary object of the present invention to provide a lighting apparatus having improved efficiency by directly mounting an LED to a heatsink.
This and further objects and advantages will be apparent to those skilled in the art in connection with the drawings and the detailed description of the invention set forth below.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings will hereinafter be described by a brief reference to the drawings and then a description of the numerical elements identified in the drawing, Figs, IA-D show a heatsink and insulating core installed in a metal tube or .flashlight barrel having the following identified elements:
1. Tube or barrel

2. Heatsink

3. Insulator

4. Terminal to connect power to LED

5. LED

6. Thermal junction and first electrical connection between LED and heatsink

7. Second electrical connection id Fig. 1B is a cross sectional view which is shown exploded in Fig. ID
while Figs. IA and 1C are, respectively, top and bottom views looking into the apparatus shown in cross section in Fig. 16.
Figs. 2A-D show a variation on Ras. 1A-D in which the heatsink and insulating core are installed in a metal tube or flashlight barrel having the following identified elements:
r 1. Tube or barrel 2. Heatsink 3. Insulator 4. Terminal to connect power to LED
5. LED
2'0 6. Thermal junction and first electrical connection between LED and heatsink 7. Second electrical connection Fig. 28 is a cross sectional view which is shown exploded in Fig. 2D while Figs. 2A and 2C are, respectively, top and bottom views looking into the apparatus shown in cross section in Fig. 26.
25 Figs 3A-D show a one-piece heatsink similar to that shown in Figs. 2A-D
having the following identified elements:
1. Integral tube or barrel and heatsink 3. Insulator 4. Terminal to connect power to LED

5. LED
6. Thermal junction and first electrical connection between LED and heatsink 7. Second electrical connection Fig. 38 is a cross sectional view which is shown exploded in Fig. 3D while Figs. 3A and s 3C are, respectively, top and bottom views looking into the apparatus shown in cross section in Fig. 38.
Figs. 4A-D show a variation on the heatsink and insulating core in Figs. 1A-D.
In this example, there is a printed circuit board between the LED and the other end of the assembly having the following identified elements:
1. Tube or barrel 2. Heatsink 3. Insulator 4. Terminal to connect power to LED
5. LED
15 8. Thermal junction and first electrical connection between LED and heatsink 7. Second electrical connection

8. Printed circuit board

9. Insulator

10.Contact 20 Fig. 46 is a cross sectional view which is shown exploded in Fig. 4D
while Figs. 4A and 4C are, respectively, top and bottom views looking into the apparatus shown in cross section in Fig. 48.
Figs. 5A-D show a variation of the assembly shown in Figs. 4A-D having the following identified elements:
25 1. Tube or barrel 2. Heatsink 3. Insulator 4. Terminal to connect power to LED
5. LED

6. Thermal junction and first electrical connection between LED and heatsink 7. Second electrical connection 8. Printed circuit board 9. Insulator 10.Contact Fig. 5B is a cross sectional view which is shown exploded in Fig. 5D while Figs. 5A and 5C are, respectively, top and bottom views looking into the apparatus shown in cross section in Fig. 5B.
6A-D show a heatsink similar to that in Figs, 3A-D but containing a printed circuit board having the following identified elements:
1. Integral tube or barrel and heatsink 3. Insulator 4. Terminal to connect power to LED
5. LED
6. Thermal junction and first electrical connection between LED and heatsink 7. Second electrical connection 8. Printed circuit board 9. Insulator 10. Contact Fig. 6B is a cross sectional view which is shown exploded in Fig. 6D while Figs. 6A and SC are, respectively, top and bottom views looking into the apparatus shown in cross section in Fig. 6B.
Figs. 7A-D show a circular array of LEDs mounted on a common heatsink. Four LEDs are shown here but there could be any number of LEDs. Figs. 7A-D have the following identified elements:
1. Tube or barrel 2. Heatsink 3. Insulator 4. Terminal to connect power to LED
5. LED

6. Thermal junction and first electrical connection between LED and heatsink 7. Second electrical connection Fig. 7B is a cross sectional view which is shown exploded in Fig. 7D while Figs. 7A and 7C are, respectively, top and bottom views looking into the apparatus shown in cross section in Fig. 7B.
Figs. 8A-D show a circular array of LEDs mounted to a common heatsink with printed circuit boards in the insulating member. Four LEDs are shown here but there could be any number of LEDs. Figs. 8A-D have the following identified elements:
1. Tube or barrel 2. Heatsink.
.3. Insulator 4. Terminal to connect power to LED
5. LED
6. Thermal junction and first electrical connection between LED and heatsink 7. Second electrical connection 8. Printed circuit board 9. Insulator 10. Contact Fig. 8B is a cross sectional view which is shown exploded in Fig. 8D while Figs. 8A and 8C are, respectively, top and bottom views looking into the apparatus shown in cross section in Fig. 8B.
Figs. 9A-C show a linear array of LEDs on a common heatsink. Four LEDs are shown here but there could be any number of LEDs. Figs. 9A-C have the following identified elements:
2. Heatsink 3. Insulator 4. Terminal to connect power to LED
5. LED
6. Thermal junction and first electrical connection between LED and heatsink 7. Second electrical connection Fig. 98 is a cross sectional view of a single LED and Figs. 9A and 9C are, respectively, top and bottom views of a linear array of four LEDs.
Figs. 10A-C show a linear array of LEDs similar to those on Figs. 9A and 9C
but containing printed circuit boards. Four LEDs are shown here but there could be any s number of LEDs. Figs. 10A-C have the following identified elements:
2. Heatsink 3. Insulator 4. Terminal to connect power to LED
5. LED
6. Thermal junction and first electrical connection between LED and heatsink 7. Second electrical connection 8. Printed circuit board 9. insulator 10. Contact Fig. 108 is a cross sectional view of a single LED and Figs. 10A and 10C are, respectively, top and bottom views of a linear array of four LEDs.
Flo. II is a cross sectional magnified view from Fig. 1E3 which shows the top of heatsink 5 without the LED in place having the following identified elements:
6. Thermal junction and first electrical connection between LED and heatsink 7. Second electrical connection Figs, 12A-E show a typical prior art LED assembly showing the LED soldered to a PC board and the multiple thermal junctions required to conduct heat to ambient air having the following identified elements:
101. Tube or barrel 102. Heatsink 103. insulator 104. Contact for applying power to printed circuit board 105. LED
106. Housing 107. Insulator 108. Contact for connecting printed circuit board 111 to PCB 109 109. Multilayered printed circuit board 110. Ring Contact 111. Printed circuit board Fig. 128 is a cross section& view which is shown exploded in Fig. 12E while Figs. 12A
and 12C are, respectively, top and bottom views looking into the apparatus shown in cross section in Fig. 128 and Fig. 12D is an enlarged cutaway view of Fig.
128.
Figs. 13A-D show a widely used prior art star type, metal and ceramic backed PC board to which the LED is mounted and the multiple thermal functions required to conduct heat to ambient air having the following identified elements:
101. Tube or barrel 102. Heatsink 105. LED
106. First power connection 107. Second power connection 108. Star PC board Fig. 138 is a cross sectional view which is shown exploded in Fig. 130 while Figs. 13A
and 13C are, respectively, top and bottom views looking into the apparatus shown in cross section in Fig. 138.
Fig. 14 is a block diagram of a typical heatsink mounted LED with positive polarity heatsink.
Fig. 15 is a block diagram of a typical heatsink mounted LED with negative polarity heatsink.
Fig. 16 is a block diagram of a typical heatsink mounted LED with a positive polarity heatsink that incorporates a PC board with LED drive electronics..
Fig. 17 is a block diagram of a typical heatsink mounted LED with a negative polarity heatsink that incorporates a PC board with LED drive electronics.
Fig. 18 is a comparison of the performance of four different heatsinking methods or systems. Figure 2 curve is for the present invention and demonstrates superior performance with minimal drop off in lumens output over time.

I. Curve labeled Figure 1 is a graphical representation of the lumens output over time showing the drop off in performance as the LED heats and efficiency drops for the system OF Figs. 1A-D.
2. Curve labeled Figure 2 is a graphical representation of the lumens output over time showing very minimal drop off in performance as the LED heats and efficiency drops for the system of Figs. 2A-D.
3. Curve labeled Figure 13 is a graphical representation of the lumens output over time showing the drop off in performance as the LED heats and efficiency drops for the system of Figs. 13A-D.
4. Curve labeled Figure 12 is a graphical representation of the lumens output over time showing the drop off in performance as the LED heats and efficiency drops for the system of Figs. 12A-E.
Figs. 19A-Et illustrate a process for manufacturing a heat sink assembly in accordance with the present invention in which solder Si and S2 is used to solder pads of an LED 5 to a top surface of a heat sink 2 to form a heat sink assembly 200. Figs.
19C-D illustrate a press fit step of inserting heat sink assembly 200 into a tube or barrel 1.
Figs. 20A and 20B show variations on Figs. 19C-D in which the heatsink and insulating core are installed in a metal tube or flashlight barrel having the following identified elements:
I. Tube or barrel 1A. Shoulder of tube or barrel 1 1AT. Top surface of shoulder 1A
16. Nut 2. Heatsink 3. insulator 4. Terminal to connect power to LED
5. LED

DETAILED DESCRIPTION OF INVENTION
The present invention utilizes a thermally and electrically conductive metal outer member, a heatsink. The interior of the heatsink, or core, is an electrical insulating material that positions and electrically isolates a second electrically conductive member that extends out the end opposite from the LED to provide an electrical connection point. The top surface of this assembly provides a mounting surface for the LED. The anode or cathode side of the LED, and in some cases a dedicated thermal pad, is bonded to the top surface of the heatsink by soldering or some other thermally and electrically conductive method or material. The electrically opposite side of the LED
:to package is bonded to the isolated second member. Power from an appropriate electrical circuit is applied to the heatsink and the isolated terminal to turn on the LED. Heat generated by the LED is conducted through the interface with the heatsink to ambient air. The LED runs much cooler and efficiently in this system than is possible with those mounted on printed circuit boards. Figures IA through II depict variations on the is design described above. As shown, the heatsink can be different shapes depending on the application. A heatsink can also support multiple LEDs in a variety of configurations:
a circular array and a linear array are only two of many possibilities.
Electronics with a suitable interconnect method can also be suspended in the insulating core. It is also possible in all cases to provide electrically insulating material that positions and 20 electrically isolates two electrically conductive members that extend out the end opposite from the LED to provide electrical connection points. In these cases the cathode and anode LED pads are bonded to corresponding isolated pads and the LED
thermal pad is bonded to the invention's heatsink surface.
The improved heatsink method depicted in Figures IA through II does not utilize 25 a PC board for mounting the LED; instead, the LED is mounted directly to the metal surface of the heatsink. This method produces much improved heat transfer and a cooler operating, higher lumens LED, compared to PC board mounted LED designs.

The present invention provides a direct efficient path to conduct heat away from an LED to ambient air outside of a flashlight or any other lighting device such as a 30 headlamp, lantern or spotlight, as well as all types of area lighting that utilize high powered LEDs as a light source. Other heatsinking methods produce thermal paths that are interrupted by a large number of thermal junctions, some of which have poor thermal conductivity or high thermal resistance. Examples of prior art heatsinking methods are illustrated in Figures 12A through 13D. Unique to the present invention is the ability to solder the terminal and heatsink directly to the electrical and thermal pads of the LED. No thermal grease or adhesives are required. In other designs the equivalent heatsinking and electrical contact pads are on a PC board which results in more, less efficient, thermal junctions and longer, smaller cross section, thermal paths to ambient air. The use of thermal grease and adhesives in these less efficient designs helps heat transfer to some degree but not to the level of attaching the LED
directly to the heatsink. The result of the much improved heat transfer possible with the invention is that the LED operates much cooler and therefore much more efficiently.
Higher lumens are possible with no increase in power over conventional systems. It is also possible to maintain lumens at the same level as other less efficient systems but consume far less power. This is especially important in battery powered lighting systems as on-time is ex/ended without reducing lumens. The superior performance of the present invention is demonstrated by the lumens output SO seconds after applying a constant 4 amps of current to the LED. The invention was better than other systems as follows:
The present invention (Figs. 2A-D) produced 19 percent more lumens than the system in Figs. 13A-D (typical star, metal backed PC board mounted LED); and The present invention (Figs. 2A-D) produced 93 percent more lumens than the system in Figs. 12A-D (multi-layer conventional PC board with extra copper traces and vies to attempt to conduct heat away from the LED).
It is worth noting that the efficiency of the present invention can be increased or optimized, with the aid of the present disclosure, by increasing or maximizing the surface area exposure between the heatsink and the thermally and electrically conductive outer casing while also designing the heatsink to have a sufficient mass to effectively and efficiently conduct heat between the heatsink and the outer casing. Thus, for example, heatsink 2 in Figs. 2A-D will have better results than heatsink 2 of Figs.
1A-D, while Figs. 3A-D illustrate an embodiment in which the heatsink is integrally formed with the outer casing, which should result in better results than the heatsink of Figs. 2A-D.
It is also worth noting that the outer casing, which is illustrated in the exemplary embodiments depicted in Figs. 1-11 as a tube or barrel, need not be thermally and electrically conductive over its entire outer surface, a/though an outer casing which is thermally and electrically conductive over its entire outer surface may achieve better results.
It is further worth noting that the advantages obtained by the more efficient cooling of one or more LEDs obtained by the present invention can be used to create a flashlight mode use of increased lumens, or a flashlight mode with increased on-time, or one or more modes that alternate between such modes or combine elements of both such modes.
The present invention lends itself to a more efficient, less costly, lighting device that can be manufactured economically through automation. in illustrative embodiments is shown in Figs. 10C-D and 20A-B, a heat sink assembly 200 is created by soldering two electrically conductive members of an LED 5 to a top surface of heatsink 2.
Commercially available LEDs typically have three pads (see, e.g., Fig. 11D
where second electrical connection 7 has one rectangular pad while thermal junction and first electrical connection between LED 5 and heatsink 2 have two rectangular pads) which can all be used for soldering (solder S1 in Fig. 19A is for one pad whereas solder S2 in Fig. 19A is for two pads). After heat sink assembly 200 is created, it can be press fit into a tube or barrel 1 as illustrated in Figs. 19C and 19D or it can be removably inserted into tube or barrel I and then held in place by a removable holding mechanism, an example of which is nut 16 illustrated in Fig. 20A and 206. In the embodiments illustrated in Figs. 20A and 206, in an especially preferred embodiment, tube or barrel 1 and heat sink 2 are made of aluminum, heat sink 2 is coated with a metallic plating (e.g., nickel) that helps promote the soldering process, and a skin cut is made of the aluminum where heat sink 2 comes into contact with a top surface 1AT of shoulder IA
formed in tube or barrel 1 (so as to promote more efficient thermal heat transfer).
While the invention has been described herein with reference to certain preferred embodiments, those embodiments have been presented by way of example only, and not

11 to limit the scope of the invention. Additional embodiments thereof will be obvious to those skied in the art having the benefit of this detailed description.
Accordingly, it will be apparent to those skilled in the ail that still further changes and modifications in the actual concepts described herein can readily be made without departing from the spirit and scope of the disclosed inventions.

12

Claims

What is claimed is:
Claim 1: A lighting apparatus, comprising:
a thermally and electrically conductive outer casing;
a thermally and electrically conductive heatsink having a top surface, said heatsink being held within and in thermal and electrical contact with the outer casing;
an electrical insulating material held within the heatsink; and a light emitting diode ("LED") having a first and a second electrically conductive member;
wherein the LED is mounted to the top surface with the first electrically conductive member thermally and electrically directly connected to the heatsink without the use of a printed circuit board and the second electrically conductive member is electrically isolated from the heatsink by the electrical insulating material;
and wherein the LED is turned on when power from an electrical circuit is applied to the heatsink and the second electrically conductive member.
Claim 2 : The lighting apparatus of claim 1 wherein the outer casing is integrally formed with the heatsink.
Claim 3 : The lighting apparatus of claim 1 wherein the heatsink is held within the outer casing by an interference fit.
Claim 4 : The lighting apparatus of claim 1 further comprising a terminal held within the electrical insulating material which is electrically connected to the second electrically conductive member.
Claim 5 : The lighting apparatus of claim 4 wherein the outer casing is a flashlight barrel.
Claim 6 : The lighting apparatus of claim 5 wherein flashlight barrel is made of aluminum.

Claim 7 : The lighting apparatus of claim 6 wherein the lighting apparatus of manufactured by the process of:
forming a heat sink assembly by soldering both the first electrically conductive member to the top surface of the heatsink and the second electrically conductive member to the terminal; and inserting the heat sink assembly into the flashlight barrel.
Claim 8 : The lighting apparatus of claim 7 wherein the heat sink assembly is press fit into the flashlight barrel..
Claim 9 : The lighting apparatus of claim 7 wherein the heat sink assembly is removably secured within the flashlight barrel by a mechanical means.
Claim 10 : The lighting apparatus of claim 9 wherein the mechanical means is a nut threaded into the flashlight barrel.
14.