Efficiency Lighting Apparatus with LED Directly Mounted to a Heatsink

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

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application which claims priority from U.S. Ser. No. 62/095,733, filed Dec. 22, 2014, with the same title, the disclosure of which is specifically incorporated by reference herein in its entirety.

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 INVENTION

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. 1A-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

FIG. 1B is a cross sectional view which is shown exploded in FIG. 1D while FIGS. 1A and 1C are, respectively, top and bottom views looking into the apparatus shown in cross section in FIG. 1B.

FIGS. 2A-D show a variation on FIGS. 1A-D in which the heatsink and insulating core are 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

FIG. 2B 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. 2B.

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. 3B is a cross sectional view which is shown exploded in FIG. 3D while FIGS. 3A and 3C are, respectively, top and bottom views looking into the apparatus shown in cross section in FIG. 3B.

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
  • 6. Thermal junction and first electrical connection between LED and heatsink
  • 7. Second electrical connection
  • 8. Printed circuit board
  • 9. Insulator
  • 10. Contact

FIG. 4B 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. 4B.

FIGS. 5A-D show a variation of the assembly shown in FIGS. 4A-D 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
  • 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.

FIGS. 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 6C 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. 9B 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 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. 10B 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.

FIG. 11 is a cross sectional magnified view from FIG. 1B 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. 12B is a cross sectional 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. 12B and FIG. 12D is an enlarged cutaway view of FIG. 12B.

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 junctions 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. 13B is a cross sectional view which is shown exploded in FIG. 13D while FIGS. 13A and 13C are, respectively, top and bottom views looking into the apparatus shown in cross section in FIG. 13B.

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. FIG. 2 curve is for the present invention and demonstrates superior performance with minimal drop off in lumens output over time.

• • 1. Curve labeled FIG. 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 FIG. 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 FIG. 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 FIG. 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-B illustrate a process for manufacturing a heat sink assembly in accordance with the present invention in which solder S1 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:

• • 1. Tube or barrel
  • 1A. Shoulder of tube or barrel 1
  • 1AT. Top surface of shoulder 1A
  • 18. 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 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. FIGS. 1A through 11 depict variations on the 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 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 FIGS. 1A through 11 does not utilize 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 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 FIGS. 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 extended without reducing lumens. The superior performance of the present invention is demonstrated by the lumens output 60 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 vias 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, although 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 shown in FIGS. 19C-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 1 and then held in place by a removable holding mechanism, an example of which is nut 1B illustrated in FIGS. 20A and 20B. In the embodiments illustrated in FIGS. 20A and 20B, 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 1A 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 to limit the scope of the invention. Additional embodiments thereof will be obvious to those skilled in the art having the benefit of this detailed description.

Accordingly, it will be apparent to those skilled in the art 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.

Claims

1-10. (canceled)

11: A lighting apparatus, comprising:

a light emitting diode (“LED”) package having a first and a second electrically conductive member to provide power to cause a die within the LED package to emit light;

an outer casing that is thermally and electrically conductive; and

a heatsink assembly, said heatsink assembly comprising: an outer electrically conductive member that is thermally conductive and which is mechanically connected to the outer casing; a core of an electrically insulating material which is held within the outer electrically conductive member; and an inner electrically conductive member which is positioned and electrically isolated from the outer electrically conductive member by the core;

wherein the first electrically conductive member of the LED package is thermally and electrically bonded to a top surface of the outer electrically conductive member and the second electrically conductive member of the LED package is thermally and electrically bonded to the inner electrically conductive member; and

wherein the LED package is turned on when power from an electrical circuit is applied to the outer electrically conductive member and the inner electrically conductive member.

12: The lighting apparatus of claim 11 wherein the outer casing is integrally formed with the outer electrically conductive member.

13: The lighting apparatus of claim 11 wherein the heatsink assembly is held within the outer casing by an interference fit.

14: The lighting apparatus of claim 13 wherein the lighting apparatus is a flashlight and the outer casing is a flashlight barrel.

15: The lighting apparatus of claim 14 wherein flashlight barrel is made of aluminum.

16: The lighting apparatus of claim 15 wherein the lighting apparatus is manufactured by the process of:

soldering both the first electrically conductive member to the top surface of the outer electrically conductive member and the second electrically conductive member to the inner electrically conductive member; and

inserting the heat sink assembly into the flashlight barrel so that the heat sink is held by mechanical contact with the barrel.

17: The lighting apparatus of claim 16 wherein the heat sink assembly is press fit into the flashlight barrel.

18: The lighting apparatus of claim 16 wherein the heat sink assembly is removably secured within the flashlight barrel by a mechanical means.

19: The lighting apparatus of claim 18 wherein the mechanical means is a nut threaded into the flashlight barrel.

20: The lighting apparatus of claim 15 wherein the outer electrically conductive member has a circular cross section.

21: The lighting apparatus of claim 11 wherein a thermal path is created between the outer casing and the first electrically conductive member of the LED package which is only interrupted by a first thermal junction between the outer casing and the outer electrically conductive member and a second thermal junction between the outer electrically conductive member and the first electrically conductive member of the LED package.

22: The lighting apparatus of claim 12 wherein a thermal path is created between the outer casing and the first electrically conductive member of the LED package which is only interrupted by a thermal junction between the outer electrically conductive member and the first electrically conductive member of the LED package.

23: The lighting apparatus of claim 11 further comprising:

a second LED package having a third and a fourth electrically conductive member to provide power to cause a second die within the second LED package to emit light;

a third electrically conductive member which is positioned and electrically isolated from the outer electrically conductive member by the core;

wherein the third electrically conductive member of the second LED package is thermally and electrically bonded to the top surface of the outer electrically conductive member and the fourth electrically conductive member of the second LED package is thermally and electrically bonded to the fourth electrically conductive member; and

wherein the second LED package is turned on when power from the electrical circuit is applied to the heatsink and the fourth electrically conductive member.

24: A flashlight, comprising:

a flashlight barrel that is thermally and electrically conductive;

at least one light emitting diode (“LED”) package, each LED package having a first and a second electrically conductive member to provide power to cause a die within said each LED package to emit light; and

a heatsink, said heatsink comprising: an outer electrically conductive member that is thermally conductive and which is mechanically connected to the outer casing; a core of an electrically insulating material which is held within the outer electrically conductive member; and at least one inner electrically conductive member which is positioned and electrically isolated from the outer electrically conductive member by the core;

wherein the first electrically conductive member of said each LED package is thermally and electrically bonded to a top surface of the outer electrically conductive member and the second electrically conductive member of said each LED package is thermally and electrically bonded to one of the at least one inner electrically conductive member;

wherein said each LED package is turned on when power from an electrical circuit is applied to the heatsink and the at least one inner electrically conductive member; and

wherein a thermal path is created between the flashlight barrel and the first electrically conductive member of said each LED package which is only interrupted by two or less thermal junctions between the flashlight barrel and the first electrically conductive member of said each LED package.

25: The flashlight of claim 24 wherein the thermal path is only interrupted by a first thermal junction between the flashlight barrel and the outer electrically conductive member and a second thermal junction between the outer electrically conductive member and the first electrically conductive member of said each LED package.

26: The lighting apparatus of claim 24 wherein the thermal path is only interrupted by one thermal junction between the outer electrically conductive member and the first electrically conductive member of said each LED package.

27: The lighting apparatus of claim 24 wherein the first electrically conductive member of said each LED package is soldered to the top surface of the outer electrically conductive member and the second electrically conductive member of said each LED package is soldered to one of the at least one inner electrically conductive member.

28: A method for creating a flashlight mode with increased lumens or with increased on-time, comprising:

soldering both a first electrically conductive member of a light emitting diode (“LED”) package to a top surface of an outer electrically conductive member of a heat sink assembly and a second electrically conductive member of the LED package to an inner electrically conductive member of the heatsink assembly; and

inserting the heat sink assembly into a flashlight barrel so that the heat sink assembly is held by mechanical contact with the barrel and a thermal path is created between the flashlight barrel and the first electrically conductive member of the LED package which is only interrupted by a first thermal junction between the flashlight barrel and the outer electrically conductive member and a second thermal junction between the outer electrically conductive member and the first electrically conductive member of said each LED package;

wherein providing power to the first and the second electrically conductive members of the LED cause a die within the LED package to emit light;

wherein the heatsink assembly has a core of an electrically insulating material which is held within the outer electrically conductive member and the inner electrically conductive member is positioned and electrically isolated from the outer electrically conductive member by the core; and

wherein the LED package is turned on when power from an electrical circuit is applied to the outer electrically conductive member and the inner electrically conductive member.