LED lamp with heat sink assembly

An LED lamp includes a support, an envelope, a heat sink assembly and a plurality of LED modules. The envelope is coupled to the support. The heat sink assembly includes a first heat sink mounted on the envelope, a cylindrical second heat sink attached to a bottom surface of the first heat sink and positioned in the envelope, and a plurality of heat pipes. The LED modules are mounted on an outside wall of the second heat sink. The heat pipes have condensing portions embedded in the bottom surface of the first heat sink and evaporating portions sandwiched between the outside wall of the second heat sink and the LED modules.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an LED lamp, and particularly to an LED lamp with a heat sink assembly having heat pipes for improving heat dissipation of the LED lamp.

2. Description of Related Art

An LED lamp is a type of solid-state lighting device that utilizes light-emitting diodes (LEDs) as a source of illumination. An LED is a device for converting electricity into light by using a theory that, if a current is made to flow in a forward direction through a junction region comprising two different types of semiconductor, electrons and holes are coupled at the junction region to generate a light beam. The LED has an advantage that it is resistant to shock, and has an almost eternal lifetime under a specific condition; thus, the LED lamp is intended to be a cost-effective yet high quality replacement for incandescent and fluorescent lamps.

An LED lamp generally has a limited space therein and requires a plurality of LEDs. Most of the LEDs are driven at the same time, which results in a quick rise in temperature of the LED lamp. Since the limited space in the LED lamp, the heat sink has a restricted heat dissipating area and is unable to remove heat from the LEDs effectively. Operation of the conventional LED lamps thus has a problem of instability because of the rapid buildup of heat.

Besides, since an illuminant angle of the light emitted by the LEDs is generally restricted in a narrow range and the LEDs are mounted on a flattened surface of the heat sink, light of the LED lamp is of unsatisfactory spatial distribution.

What is needed, therefore, is an LED lamp which can overcome the above-mentioned disadvantages.

SUMMARY OF THE INVENTION

An LED lamp includes a support, an envelope, a heat sink assembly and a plurality of LED modules. The envelope is coupled to the support. The heat sink assembly includes a first heat sink mounted on a top of the envelope, a cylindrical second heat sink attached to a bottom surface of the first heat sink and positioned in the envelope, and a plurality of heat pipes. The LED modules are mounted on an outside wall of the second heat sink. The heat pipes have condensing portions connected with the bottom surface of the first heat sink and evaporating portions sandwiched between the outside wall of the second heat sink and the LED modules.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIGS. 1-2, an LED lamp for a lighting purpose comprises a support10, an envelope20coupled to a top of the support10, a heat sink assembly (not labeled) and four LED modules60thermally attached to the heat sink assembly. The heat sink assembly comprises a first heat sink30located on a top of the envelope20, a second heat sink40received in the envelope20and attached to a bottom surface of the first heat sink30, and four heat pipes50thermally interconnecting the first and second heat sinks30,40. The four LED modules60are mounted around the second heat sink40. A drive circuitry70is accommodated in the support10and electrically connected to the LED modules60to provide the LED modules60with electrical power, control signals, etc. A plurality of reflectors90are mounted surrounding the envelope20.

The support10is substantially a square column. A bottom of the support10can be secured on an object such as the ground to install the LED lamp on the ground. A first receiving groove14is defined in a top of the support10. The first groove14has a profile of a square ring. A first fixing hole16is defined in a middle portion of each of side edges of the top of the support10. The first fixing holes16are positioned outside of the first receiving groove14. A receiving space12is defined in an upper portion of the support10. The drive circuitry70is accommodated in the space12of the support10. A square plate80covers on the top of the support10for sheltering the drive circuitry70. A center hole81is defined in the plate80for allowing lead wires (not shown) of the drive circuitry70to extend therethrough to connect with the LED modules60.

The envelope20is substantially an elongated, square tube. A through opening is defined by four lateral walls of the envelope20. A bottom edge of the lateral walls of the envelope20is received in the first receiving groove14of the support10.

Please also referring toFIG. 3, the first heat sink30comprises a square base31and a plurality of fins32extending upwardly from the base31. A second receiving groove34is defined in a bottom surface of the base31for receiving a top edge of the lateral walls of the envelope20therein. Four through holes35are defined in the base31, positioned within the second receiving groove34and centrosymmetric to a center of the base31. A second fixing hole36is defined in a middle portion of each of side edges of the base31. The second fixing holes36are positioned out of the second receiving groove34. Four linear first receiving slots37, in which portions of the heat pipes50are received, are defined in the bottom surface of the base31. Each first receiving slot37is positioned inside of the second receiving groove34. The first receiving slots37are arrayed radially outwardly from the center of the base31and each of the first receiving slots37is located between a corresponding through hole35and a corresponding second fixing hole36.

Also referring toFIG. 4, the second heat sink40is substantially a cylindrical tube with a through hole (not labeled) defined in a center thereof. Corresponding to the through holes35in the base31of the first heat sink30, four screw holes45are defined in a top end of the second heat sink40. Screws355can extend through the through holes35and screw in the corresponding screw holes45for fixing the first heat sink30and second heat sink40together. Four ridges41, on which the LED modules60are respectively mounted, evenly and outwardly extend from an outside wall of the second heat sink40. Each ridge41is elongated along an axial direction of the second heat sink40. A second receiving slot42is defined in each of the ridges41and extends from top to bottom of the second heat sink40for receiving a portion of a corresponding heat pipe50therein.

The heat pipes50each have an identical configuration. Each of the heat pipes50is L-shaped and comprises an evaporating portion52received in a corresponding second receiving slot42of the second heat sink40and a condensing portion54received in a corresponding first receiving slot37of the first heat sink30.

Each of the LED modules60comprises an elongated printed circuit board (not labeled) and a plurality of LEDs62mounted on the printed circuit board. The LEDs62are arrayed in a line along a length of each LED module60.

Each of the reflectors90is substantially a squarely ring-shaped frame consisting of four flaps (not labeled) which are slantwise downwardly and outwardly toward the support10. A bottom surface of each of the flaps can reflect light emitted by the LED modules60downwardly to the support10. Four posts91respectively extend through the flaps of the reflectors90for fixing the reflectors90together to the LED lamp at a position around the envelope20and between the support10and the first heat sink30. Bottom ends of the posts91extend through the first fixing holes16of the support10. Top ends of the posts91extend through the second fixing holes36of the first heat sink30. A plurality of nuts912can screw in the bottom and top ends of the posts91for securing the first heat sink30, the envelope20, the support10and the reflectors90together.

In assembly of the LED lamp, the drive circuitry70is accommodated in the space12of the support10, and the plate80covers on the top of the support10. The envelope20, surrounded with the reflectors90, is coupled to the support10. The second heat sink40is attached to the bottom surface of the first heat sink30, and the heat pipes50are adhered to the first and second heat sinks30,40. The LED modules60are mounted on the ridges41of the second heat sink40. Then the first heat sink30of the heat sink assembly is coupled on the top of the envelope20, with the top of the envelope20fittingly received in the second receiving groove34, and the second heat sink40and the heat pipes50of the heat sink assembly and the LED modules60accommodated in the envelope20. In this embodiment, the numbers of the ridges41of the second heat sink40, the heat pipes50and the LED modules60are all four. Understandably, the numbers of these elements can be different in different embodiments.