Cross Reference to Related Application

[0001] The present application is an international application, and claims the benefit of and priority to, United States Provisional Application No. 62/054,062 filed September 23, 2014, the entire contents of which are hereby incorporated by reference.

Background of the Invention

[0002] Standard linear fluorescent lamps are one of the most common lamp forms used to generate light. Given the large number of fluorescent fixtures installed in commercial, institutional, and industrial establishments, it is desirable to replace fluorescent lamps with other high efficiency, mercury-free lighting solutions having the same form factor so that replacement of the existing fixtures is not necessary. This has led to the development of solid-state replacement lamps which include linear arrays of light-emitting diodes (LEDs) on circuit boards disposed within hollow tubes. These new solid-state lamps require different construction methods than conventional fluorescent lamps and in particular novel techniques are required for mounting circuit boards with arrays of LEDs within the tubular lamp bodies.

Brief Description of the Drawings

[0003] Features and advantages of various embodiments of the claimed subject matter will become apparent as the following Detailed Description proceeds, and upon reference to the Drawings, wherein like numerals designate like parts, and in which:

[0004] Figure 1 A is a perspective view of an elongated circuit board tray for use in a tubular LED lamp according to this invention.

[0005] Figure 1 B is a cross-sectional view of a tubular lamp body for use in a tubular LED lamp according to this invention.

[0006] Figure 1 C is a slightly exploded view of a tubular LED lamp according to this invention using the circuit board tray and tubular lamp body shown in Figures 1 A and 1 B, respectively. [0007] Figure 1 D is a cross-sectional view of a tubular LED lamp according to this invention using the circuit board tray and tubular lamp body shown in Figures 1 A and 1 B, respectively.

[0008] Figure 2A is a perspective view of another circuit board tray for use in a tubular LED lamp according to this invention.

[0009] Figure 2B is a cross-sectional view of a second embodiment of a tubular LED lamp according to this invention using the circuit board tray of Figure 2A.

[0010] Figure 3A is a perspective view of yet another circuit board tray for use in a tubular LED lamp according to this invention.

[0011] Figure 3B is a cross-sectional view of a third embodiment of a tubular LED lamp according to this invention using the circuit board tray of Figure 3A.

[0012] Figure 3C is a partial perspective view of the tubular LED lamp shown in Figure 3B.

Detailed Description of the Invention

[0013] A common method of incorporating a rigid printed circuit board in a tubular LED lamp uses an aluminum extrusion for both mechanical and thermal reasons. However, mounting the circuit board to the aluminum extrusion tends to place the LEDs closer to the center of the tube which is less desirable for light diffusion and distribution. Ideally, the LEDs in a tubular lamp should be located at or near the surface of the tube opposite the front of the lamp. The further the LEDs are away from the diffusing surface, the better the light diffusion which helps eliminate "hot spots" caused by the directional nature of the light emitted by the LEDs.

[0014] In a preferred embodiment, the present invention employs a polymer tray which is mounted to, and forms a part of the tubular body of the lamp. The rigid circuit board is held in the tray which places the LEDs approximately at the circumference of tubular body of the lamp. Such an arrangement does away with the need for a complex aluminum extrusion and as described below allows for greater flexibility in mounting the rigid circuit board.

[0015] Referring to Figures 1 A-1 D, there is shown a first embodiment of the present invention. A tubular LED lamp 100 is shown having a generally tubular body comprised of a linear diffuser 1 10 and an elongated circuit board tray 102. The diffuser 1 10 is formed as a partial tube having longitudinal opening extending along its length. Preferably, the diffuser is formed of a translucent plastic material and has partial circular cross section that subtends an angle greater than 180°. The tray 102 extends along the length of diffuser 1 10 and supports a rigid elongated printed circuit board 130 on which a plurality of LEDs 136 are mounted. The tray 102 has longitudinal winglike projections 120 having a curvature that is substantially the same as the curvature of diffuser 1 10. The tray 102 is attached to diffuser 1 10 at locations 1 14. As shown, longitudinal edges 106 of tray 102 mate with longitudinal slots 122 formed in the longitudinal edges of diffuser 1 10. (Other means of attachment may also be used such as adhesives, thermal welding, or other mechanical configurations.) Tray 102 has a flat bottom base 1 16 between the projections 120 for mounting the rigid circuit board 130. Preferably, the rigid circuit board is made of a resin-impregnated fiberglass material such as FR4 and has electric circuitry for powering the LEDs. The tray 102 is comprised of a polymer material, preferably a thermoplastic polymer such as polyethylene terephtha!ate (PET). Preferably, the tray 102 holds rigid circuit board 130 such that the LEDs 136 on the circuit board are located at a distance from the top of the diffuser that is approximately equal to the diameter of the tubular lamp. This is generally equivalent to locating the LEDs on the approximate circumference of the tubular lamp. The tubular lamp body may be fitted with conventional fluorescent bi- pin ends caps (not shown) that are slightly modified to encompass the tray (including the edge of the circuit board) in order to provide an electrical interface that is compatible with existing fluorescent lamp fixtures. Additional electronics may also be provided within the tube or attached to one or both ends of the tube to provide AC-to- DC power conversion, current regulation, etc.

[0016] In a second embodiment shown in Figures 2A and 2B, the lamp 200 is constructed similarly to first embodiment except that the tray 202 has holes 225 in flat- bottomed base 216 that correspond to the LEDs 136 mounted on rigid circuit board 130. The holes 225 allow for the circuit board 130 to be mounted to the underside of the tray 202 with the LEDs 136 located in holes 225. As in the first embodiment, longitudinal wing-like projections 220 attach to the longitudinal edges of diffuser 1 10. The advantage to this embodiment is that the tray can be made more reflective than the circuit board which generally must rely on the reflectivity of the solder mask. In particular, the tray can be made of a white PET which is generally more reflective than a solder mask.

[0017] In a third embodiment shown in Figures 3A-3C, the lamp 300 is constructed similarly to the second embodiment except that the tray 302 has molded optical features 340 that are located between the holes 325 in flat-bottomed base 316 through which LEDs 136 protrude. As in the other embodiments, longitudinal wing-like projections 320 attach to diffuser 1 10 along its longitudinal edges to complete the tubular body of lamp 300. The molded optical features 340 may be designed to improve diffusion of the light and/or direct more light from the LEDs towards the diffuser. In this embodiment, the optical features 340 comprise raised reflective berms designed to reflect laterally emitted light from the edges of the LEDs towards the diffuser 1 10. Other optical features may include small pyramids or cones.

[0018] Providing the LEDs on the opposite side of the tube from the diffuser surface provides an excellent optical advantage over locating the LEDs in the center of the circular cross section as is typical for lamps with rigid circuit boards supported by extruded aluminum heatsinks. An advantage of the present invention is that the LEDs may be located further from the diffusing surface and therefore provide a more uniform appearance to the lamp. In order to obtain the greater distance, the bottom shape of the tube is altered in order to accommodate a flat, rigid circuit board. The length, width and thickness of the board shown are typical and do not limit the scope of the invention. Clearly, FR4 boards of different dimensions could be used in such a construction. When one looks at typical fluorescent T8 fixtures it is apparent that there is plenty of space for the "non-round" cross section.

[0019] Although PET is preferred for the circuit board trays, there are other polymers which are formable and have the high reflectivity and which may be used in this invention. Other shaping processes might also be used to provide the desired reflecting surface such as thermoforming or direct extrusion. The second and third embodiments provide a better optical solution in that there is a larger area of highly reflective material to back reflect light redirected by the diffuser. Since these two configurations would leave the rigid circuit board outside of the confines of the tube, they may require an additional piece to enclose the back side of the circuit board.

[0020] The polymer material might also be partially translucent instead of highly reflective. For examples, some fluorescent lamp fixtures may need light to be emitted from the back of the tube such as in overhead pendant type fixtures. Such pendant fixtures utilize both direct and indirect light. In order to provide light to the back side of the fixture one could provide a circuit board that has LED's on both sides. It would be mounted in the same fashion as in the second and third embodiments.

[0021 ] While there have been shown and described what are at present considered to be preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims.