Embodiments of the invention relate to non-flammable enclosures for LED circuit boards.
The use of light emitting diodes (“LED”) in lighting fixtures to supply the desired illumination is becoming more prevalent. However, the voltage necessary to power an LED circuit board for use in lighting fixtures oftentimes renders the board a non-Class 2 component as defined by the National Electric Code (“NEC”). See NEC (specifically Section 725 and Table 11(B)) (2005), the entirety of which is herein incorporated by reference. Existing LED circuit boards which operate beyond the limits of Class 2 power are designated by UL as a “risk of fire” and must be contained. See UL 8750 (specifically section 3.17)(2008), the entirety of which is herein incorporated by reference. Containment requires that the LED board be enclosed so that a person cannot easily come into contact with the board. More specifically, the enclosure must be manufactured from a 5VA compliant material (one that passes stringent flammability testing pursuant to UL 94, the entirety of which is herein incorporated by reference) and the board must not be easily accessible. See UL 8750, Table 9.1. For example, the enclosure cannot be removed easily so as to gain access to the board. Rather, it should be sufficiently secured so that tools are required for its removal.
Enclosures have traditionally taken the form of a glass refractor that is secured in a lighting fixture a distance from the LED board. The refractor thereby prevents easy access to the LED board within the fixture. However, refractors are traditionally made of glass, which, while 5VA compliant, can be prone to break and thereby present additional risks to handlers. Moreover, because the light emitted from the LEDs in such fixtures must pass through the glass refractor, some of the light is lost, thereby impacting the efficiency and effectiveness of the fixture. While metal is also a 5VA compliant material, use of it in the fixture elevates the risk of electric shock and, given that it is nontransparent, impedes the transmission of the light emitted from the LEDs. Given the difficulty in designing a enclosure that satisfies the 5VA flammability rating without introducing other potential safety hazards, lighting fixture manufacturers have typically resorted to use of less hazardous Class 2 or Class 3 power sources. In this way, overall lighting system efficiency is sacrificed to avoid the need to comply with the strict requirements promulgated by the UL and NEC.
Embodiments of this invention provide an enclosure for an LED circuit board. The enclosure is manufactured from a flame resistant material and includes LED apertures through which the LEDs mounted on an LED circuit board may pass. The enclosure is designed to be positioned on the LED circuit board so that, when so positioned, the LEDs extend at least partially through the LED apertures in the enclosure. When the enclosure is positioned on the board, portions of its lower surface contact the upper surface of the board. Various fixation/retention methods may be used to retain the enclosure in position relative to the circuit board. It is preferable that such methods allow for the relatively easy separation of the enclosure from the board.
Embodiments of this invention provide an enclosure for an LED circuit board. While the enclosure is discussed for use with circuit boards incorporated into lighting fixtures, it by no means is so limited. Rather, the enclosure may be used with LED circuit boards used in any application.
The enclosure 10 is manufactured from 5VA compliant material, such as, but not limited to, flame resistant polymeric materials, metal, and glass. While use of a metal or glass to manufacture the enclosures is certainly within the scope of embodiments of the invention, given their drawbacks discussed above, they are not the most preferred materials from which to make the enclosures. Rather, flame resistant polymeric materials are more preferable, with polycarbonate being the most preferable. Suitable polycarbonates include GE 503R (f1) (available from General Electric), Dow CALIBRE 893w (available from The Dow Chemical Company), and Bayer MAKROLON 6555 (available from Bayer MaterialScience). The flame resistant polymeric materials are preferably, but not necessarily, opaque. Use of polymeric materials allows the enclosure to be injection-molded, but other manufacturing methods, such as, but not limited to, machining, stamping, compression-molding, etc., may also be employed.
As shown in
While the LED apertures 12 may be in the shape of a straight cylinder, in the embodiment illustrated in
The enclosure 10 is designed to be positioned on the LED circuit board 16 so that, when so positioned, the LEDs 14 extend at least partially through the LED apertures 12 in the enclosure 10 (see
When the enclosure 10 is positioned on the board 16, the lower surface 20 of the enclosure 10 can, but need not, contact the entirety of the upper surface 24 of the board 16. It is preferable, however, that the enclosure 10 be designed to ensure contact with the upper surface 24 of the board 16 along the perimeter of the board 16. In this way, dirt and other debris is prevented from penetrating between the enclosure 10 and the board 16. One of skill in the art will readily understand that, depending on the spatial relationship between the board 16 and the enclosure 10, it may be necessary to accommodate on the lower surface 20 of the enclosure 10 other anatomical features of the board 16, such as, for example, resisters, wire leads (see, e.g., 26), and other circuits.
The enclosure 10 may be tailored to accommodate any circuit board 16 configuration. While the embodiment illustrated in
The enclosure 10 may be retained in position relative to the board 16 in a variety of ways. The enclosure 10 may be fixed directly to the board 16 or can be fixed to other components in a lighting fixture, such as the recessed lighting fixture 30 illustrated in
The enclosure 10 need not be fixed directly to the board 16, however. Rather, the enclosure 10 may be positioned on the board 16 and screwed either directly or indirectly to other components in the fixture 30. For example, the screw 34 illustrated in
While a screw 34 is depicted in the figures, any mechanical retention device may be used to secure the enclosure 10 in a lighting fixture 30, including but not limited to, spring clips, bolts and wing nuts, rivets, resilient arms, etc. It is conceivable that grooves may be provided in a fixture component (such as a heat sink) and the board 16 and enclosure 10 mated and retained within the groove, pressed firmly within the grooves and against each other.
While various fixation/retention methods are contemplated, it is preferable, but not required, that such methods allow for the separation of the enclosure from the board (without damaging either component) for the purpose of inspection or upgrading of the components.
The enclosures pursuant to embodiments of this invention comply with the stringent “containment” requirements for high voltage non-Class 2 LED circuit boards. Thus, in conjunction with the enclosures, such higher voltage LED circuit boards may be used in lighting fixtures (such as the recessed lighting fixture 30 illustrated in
The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of the present invention. Further modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of the invention.
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