LED lamp with an improved heat sink

A recessed LED lamp for being mounted in a wall or a ceiling, includes a housing (10), a printed circuit board (20) received in the housing, a plurality of LEDs (22) mounted on the printed circuit board, a casing (40) surrounding the housing, a pair of arms (50) resiliently and pivotably attached on the casing, and a heat sink (30) secured below the housing. The heat sink includes a base (32) contacting the printed circuit board and thermally connecting therewith, a plate (34) extending outwardly from the base and a plurality of fins (36) extending downwardly from the plate (34).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emitting diode (LED) lamp, and more particularly to a recessed LED lamp incorporating an improved heat sink for dissipating heat more efficiently and reducing a cost thereof.

2. Description of Related Art

As an energy-efficient light, an LED lamp has a trend of substituting the fluorescent lamp for indoor lighting purpose; in order to increase the overall lighting brightness, a plurality of LEDs are often incorporated into a signal lamp, in which how to efficiently dissipate heat generated by the LEDs becomes a challenge.

Conventionally, the LED lamp utilize a heat dissipating structure having a shape like a sunflower: a heat sink has a cylindrical post and a plurality of fins extending outwardly and radially from a circumference of the post. A bottom face of the post is used for thermally connecting with LEDs of the LED lamp. Thus, heat generated by the LEDs is conducted to the fins via the post, and dispersed to the surrounding environment from the fins.

Unfortunately, when such a conventional heat sink is used in the LED lamp, it cannot effectively dissipate heat generated by the LEDs since the LEDs act as multiple heat-generating centers, which require a heat sink with a large base to contact with the multiple heat-generating centers. However, the post of the sunflower-type heat sink cannot have a large base to contact with the LEDs due to the limitation of geometry of the cylindrical post. In addition, since in the sunflower-type heat sink, heat generated by the LEDs is firstly transferred vertically to the post and then horizontally to the fins via the post, the heat dissipating efficiency is not good enough to timely dissipate the heat generated by the LEDs.

Furthermore, the sunflower-type heat sink requires a high cost of manufacture.

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

SUMMARY OF THE INVENTION

An LED lamp includes a housing, a printed circuit board received in the housing, a plurality of LEDs mounted on the printed circuit board, a casing surrounding the housing, a pair of arms resiliently and pivotably attached on the casing, and a heat sink secured below the housing. The heat sink includes a base contacting the printed circuit board, a rectangular plate which is larger than the base being integrally formed with and extending outwardly from a bottom face of the base and a plurality of fins extending downwardly from the plate. Heat generated by the LEDs can be conducted to the base and then to the plate. From the plate, the heat is vertically transferred to the downwardly extending fins to be dissipated to surrounding atmosphere. The base has opposite arced sides which are provided with threads for threadedly engaging with threads of the housing.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIGS. 1 and 2, an LED lamp in accordance with a preferred embodiment of the present invention is used for being recessed in a wall panel of a ceiling (not shown) and projecting a light beam therefrom. Such a recessed lamp is usually used for decoration purpose in a shop or a house. The LED lamp comprises a housing10, a printed circuit board20received and concealed in the housing10, a plurality of LEDs22mounted on the printed circuit board20, a heat sink30secured below the housing10, a casing40fixed around the housing10, and a pair of arms50resiliently and pivotably attached on the casing40.

The housing10has a cylindrical configuration with a top face recessed downwardly to form a tapered space (not labeled). A bottom face of the tapered space defines a plurality of evenly distributed holes12thereon, for receiving the plurality of LEDs22therein. A pair of rectangular ears14are designed in an opposing relationship at a circumference of the housing10, wherein each of the pair of rectangular ears14extends in a direction along a height of the housing10, and has a top portion lower than the top face of the housing10, and a bottom portion coplanar with a bottom face of the housing10. The housing10is hollow and defines a large opening (viewed fromFIG. 3and it is not labeled) in the bottom face thereof. The printed circuit board20and a top portion of the heat sink30are accommodated in the opening. The opening communicates with the plurality of holes12.

The casing40consists of an annular sidewall42surrounding the circumference of the housing10, and a flange44extending outwardly and horizontally from a top of the annular sidewall42. The annular sidewall42is disposed around an upper portion of the housing10with the flange44coplanar with the top face of the housing10(illustrated inFIG. 3). The annular sidewall42defines a pair of grooves420in a bottom portion thereof, corresponding to the pair of rectangular ears14of the housing10. Each of the pair of grooves420is T-shaped, whereby the annular sidewall422forms a pair of ribs421located corresponding to a groove420and facing each other. The flange44is oriented perpendicular to the annular sidewall42, with an outer periphery thereof being wave-shaped. A pair of screws60are brought to extend through the annular sidewall42and into the pair of rectangular ears14, respectively, to thereby conveniently and firmly fix the casing40to the housing10.

Each of the pair of arms50includes a spiral portion52and a rectangular portion54formed inclinedly from the spiral portion52and abutting against the outer periphery of the flange44of the casing40. The spiral portion52is retained in a corresponding one of the pair of grooves420of the casing40by inserting the ribs421into the spiral portion52, whereby the arms50are resiliently and pivotably attached to the annular sidewall42of the casing40. The spiral portion52is able to provide a resilient force to the rectangular portion54to thereby force it returning its original position, when the rectangular portion54is rotated from the original position. The rectangular portion54is for resiliently abutting against a rear side of the wall panel or the ceiling, to thereby sandwich the wall panel or the ceiling with the flange44of the casing40, which is for closely abutting against a front side of the wall panel or the ceiling, whereby the LED lamp is secured in the wall panel or the ceiling.

The plurality of LEDs22are distributed on the printed circuit board20in a triangle relationship. The printed circuit board20has a diameter less than that of the opening in the housing10. The printed circuit board20is accommodated horizontally in the opening of the housing10with the plurality of LEDs22received within the plurality of holes12. The LEDs22are visible from an outside of the LED lamp, and light generated by the LEDs22can emit to the outside of the LED lamp.

Also referring toFIG. 3, the heat sink30, the housing10, the printed circuit board20, and the casing40are coaxial with each other. The heat sink30comprises a base32positioned parallel to the printed circuit board20and perpendicular to the pair of rectangular ears14, a plate34parallel to and integral with a bottom face of the base32, and a plurality of fins36extending downwardly and perpendicularly from the plate34. The plate34has an area larger than that of the base32, extends outwardly from a periphery of the base32and is located outside of the housing10. The base32has a pair of opposite flat sides (not labeled), and another pair of opposite arc-shaped sides (not labeled) each being provided with threads320for threadedly engaging with the housing10, thus firmly mounting the heat sink30to the housing10. An area of the base32is larger than that of the printed circuit board20, whereby when the top face of the base32contacts the bottom face of the printed circuit board20, heat generated by each of the plurality of LEDs22can be sufficiently and rapidly conducted to the base32via the printed circuit board20. The plate34is used for more evenly transferring the heat absorbed by the base32to the plurality of fins36. The plurality of fins36are spaced from each other with suitable distances therebetween, and occupy an entire bottom face of the plate34, for dissipating the heat from the plate34to ambient air quickly.

Since all of the plurality of LEDs22are located within a periphery of the base32of the heat sink30, the heat generated by the plurality of LEDs22is able to be conducted to the base32via the printed circuit board20directly. Therefore, the heat can be dissipated rapidly and sufficiently, and an overheat or a malfunction of the plurality of LEDs22is thus prevented. Moreover, since the heat sink20is provided with the plate34which is larger than the base32and integral with the base32, the heat absorbed by the base32can be quickly spread to the plate34, from which the heat is directly and downwardly transferred to the fins36to be dissipated to ambient air. Thus, the heat generated by the LEDs22can be timely dissipated to enable the LEDs22to work within their predetermined temperature range.