LED filament for omnidirectional lamp

Abstract

A LED filament for an omnidirectional lamp comprises two longitudinal filament sections, and each filament section includes a plurality of LEDs. The two filament sections are electrically conductively connected by a flexible connecting section. A lamp using such LED filaments provides a light distribution having an increased homogeneity.

Claims

1. A lamp comprising: a bulb; a lamp base; a holding structure disposed within the bulb and extending from the lamp base along a longitudinal axis of the lamp; and one or more light-emitting diode (LED) filaments disposed within the bulb, fixed to the holding structure such that the one or more LED filaments angle away from the longitudinal axis of the lamp, and electrically coupled with the lamp base via the holding structure, wherein the one or more LED filaments comprise: a first longitudinal filament section comprising a first plurality of LEDs mounted on a first side of a first substrate; a second longitudinal filament section comprising a second plurality of LEDs mounted on a first side of a second substrate; and a flexible connecting section electrically conductively connecting the first longitudinal filament section and the second longitudinal filament section on an opposing second side of the respective first and second substrates and bent at an angle such that the first and second longitudinal filament sections angle away from one another in different directions, wherein the flexible connecting section is not extensible; wherein the first longitudinal filament section and the second longitudinal filament section each comprise an electrical connector at its end opposite an end with the flexible connecting section.

2. The lamp according to claim 1, wherein at least one of the first filament section and the second filament section comprises a conversion layer applied over the plurality of LEDs for converting a color of light emitted by the LEDs during operation.

3. The lamp according to claim 1, wherein the flexible connecting section is made from the same material as the electrical connectors.

4. The lamp according to claim 1, wherein the flexible connecting section comprises a metal wire.

5. The lamp according to claim 1, wherein the flexible connecting section comprises a piece of sheet metal.

6. The lamp according to claim 1, wherein the flexible connecting section is bent through an angle of about 45 or less.

7. The lamp according to claim 1, wherein the first and second filament sections are not co-planar.

8. The lamp according to claim 1, wherein the first and second filament sections are physically connected to one another only by the flexible connecting section.

9. The lamp according to claim 1, wherein the respective substrates are made from at least one of a glass, a sapphire, a printed circuit board (PCB) material, a plastic, and a metal.

10. The lamp according to claim 1, wherein at least one of: the first side on which the first plurality of LEDs is mounted is a surface of the first substrate; and the second side on which the second plurality of LEDs is mounted is a surface of the second substrate.

11. The lamp according to claim 1, wherein the first longitudinal filament section and the second longitudinal filament section are situated immediately adjacent one another such that, in an unbent state of the flexible connecting section, there is no appreciable gap between the first substrate and the second substrate.

12. The lamp according to claim 1, wherein the first substrate and the second substrate physically contact one another at the ends where the flexible connecting section is disposed.

13. The lamp according to claim 1, wherein the lamp further comprises a socket mounted to the lamp base, wherein the holding structure is mounted to the socket.

14. A lamp comprising: a bulb; a lamp base; a holding structure extending from the lamp base along a longitudinal axis of the lamp; and one or more light-emitting diode (LED) filaments disposed within the bulb, fixed to the holding structure such that the one or more LED filaments angle away from the longitudinal axis of the lamp, and electrically coupled with the lamp base via the holding structure, wherein the one or more LED filaments comprise: a first longitudinal filament section comprising a first plurality of LEDs mounted on a first side of a first substrate; a second longitudinal filament section comprising a second plurality of LEDs mounted on a first side of a second substrate; and a flexible connecting section electrically conductively connecting the first longitudinal filament section and the second longitudinal filament section on an opposing second side of the respective first and second substrates and bent at an angle such that the first and second longitudinal filament sections angle away from one another in different directions, wherein the flexible connecting section is not extensible; wherein: each of the first and second longitudinal filament sections has opposing first and second ends; the second end of the first longitudinal filament section and the first end of the second longitudinal filament section are disposed proximal one another; and the first end of the first longitudinal filament section and the second end of the second longitudinal filament section are disposed distal one another and fixed to the holding structure via respective electrical connectors such that a longitudinal length of the one or more LED filaments is generally parallel to the longitudinal axis of the lamp.

15. The lamp according to claim 14, wherein the first and second substrates are made from at least one of a glass, a sapphire, a printed circuit board (PCB) material, a plastic, and a metal.

16. The lamp according to claim 14, wherein at least one of the first filament section and the second filament section comprises a conversion layer applied over the plurality of LEDs for converting a color of light emitted by the LEDs during operation.

17. The lamp according to claim 14, wherein the flexible connecting section is made from the same material as the electrical connectors.

18. The lamp according to claim 14, wherein the flexible connecting section comprises a metal wire.

19. The lamp according to claim 14, wherein the flexible connecting section comprises a piece of sheet metal.

20. The lamp according to claim 14, wherein the flexible connecting section is bent through an angle of about 45 or less.

21. The lamp according to claim 14, wherein the first and second filament sections are not co-planar.

22. The lamp according to claim 14, wherein the first and second filament sections are physically connected to one another only by the flexible connecting section.

23. The lamp according to claim 14, wherein at least one of: the first side on which the first plurality of LEDs is mounted is a surface of the first substrate; and the second side on which the second plurality of LEDs is mounted is a surface of the second substrate.

24. The lamp according to claim 14, wherein the first longitudinal filament section and the second longitudinal filament section are situated immediately adjacent one another such that, in an unbent state of the flexible connecting section, there is no appreciable gap between the first substrate and the second substrate.

25. The lamp according to claim 14, wherein the first substrate and the second substrate physically contact one another at the ends where the flexible connecting section is disposed.

26. The lamp according to claim 14, wherein the lamp further comprises a socket mounted to the lamp base, wherein the holding structure is mounted to the socket.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred embodiments of the invention will be explained in the following, having regard to the drawings. It is shown in:

(2) FIG. 1a/b schematic drawings of a first embodiment of a LED filament according to the present invention in two configurations;

(3) FIG. 2a/b schematic drawings of a second embodiment of a LED filament according to the present invention in two configurations;

(4) FIG. 3 a schematic drawing of an embodiment of a lamp according to the present invention; and

(5) FIG. 4 a diagram of the simulated light distribution of a lamp according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(6) In the following, preferred embodiments of the invention will be described with reference to the drawings. The same or similar elements or elements having the same effect may be indicated by the same reference number in multiple drawings. Repeating the description of such elements may be omitted in order to prevent redundant descriptions.

(7) In FIG. 1a a schematic drawing of a first embodiment of a LED filament according to the present invention is shown. The LED filament comprises two filament sections 10,20, each filament section comprising a substrate 1 on which a plurality of LEDs 2 is provided. The LEDs 2 are mounted on the substrate 1 and are provided with electrical connections in the same manner as used for known LED filaments. A phosphor conversion layer 3 is applied over the LEDs 2 and converts light emitted by the LEDs 2 into a desired wavelength.

(8) The filament sections 10,20 are mechanically and electrically connected to each other by a connecting section 4 which comprises a metal wire. On the end opposite the end connected to the connecting section, each filament section 10,20 is provided with an electrical connector 5 which comprises a metal wire.

(9) FIG. 1a shows the LED filament in a straight configuration where both filament sections 10,20 essentially extend in the same direction. In FIG. 1b the same embodiment of a LED filament is shown in an angled configuration where the connecting section 4 has been bent such that the filament sections 10,20 extend in different directions which form an angle therebetween.

(10) In FIG. 2a a schematic drawing of a second embodiment of a LED filament according to the present invention is shown. The LED filament comprises two filament sections 10,20, each filament section 10,20 being configured similarly to the filament sections 10,20 of the first embodiment. As a difference between the first and the second embodiment, the LEDs 2 are positioned on the substrate 1 up to close to the end of the substrate 1 being provided with the connecting section 4. Thus, in the straight configuration shown in FIG. 2a, the gap between the innermost LEDs 2 on each filament section 10,20 is much smaller than the corresponding gap in the first embodiment. The light distribution of the LED filament according to the second embodiment, therefore, resembles the light distribution of a known, one-piece LED filament. Even in the bent configuration shown in FIG. 2b, the distance between the innermost LEDs 2 is very small, ensuring a more homogeneous light distribution.

(11) FIG. 3 shows an embodiment of a lamp according to the present invention. The lamp comprises a transparent glass bulb 30 fixed to an Edison type lamp base 31. Inside the bulb 31, several LED filaments 40 according to the present invention are fixed to a holding structure 32. The lamp may comprise 2, 3, 4, 5, 6, 7, 8 or any other number of LED filaments 40. In order to allow better understanding of the drawing, only two LED filaments 40 are shown in FIG. 3. Each LED filament 40 comprises two filament sections 10,20 which are electrically connected by a connecting section 4. The connecting section 4 is bent such that the two filament sections 10,20 are arranged under an angle of about 45. Accordingly, the LED filaments 40 emit light not only towards the side of the lamp but also in the longitudinal direction (indicated by the longitudinal axis A), creating a light distribution that is more homogenous than the light distribution of lamps using known LED filaments.

(12) The holding structure 32 is mounted to a socket 33 which in turn is mounted to the lamp base 31. A driver for the LED filaments 40 may be arranged inside the lamp base 31 and is not visible in FIG. 3. Depending on the number and operating parameters of the LED filaments 40, a driver might not necessarily be required. Socket 33 and holder 32 also comprise electrical connections for supplying electrical power to the LED filaments 40.

(13) FIG. 4 shows a diagram of the simulated light distribution of a lamp as shown in FIG. 3 using four LED filaments according to the present invention. The diagram shows in polar coordinates the relative intensities of the emitted light in different directions. The simulated intensity values are shown in FIG. 4 for a single plane including the longitudinal axis of the lamp. For <20 the intensity is very small, since the light emitted by the LED filaments is blocked by the lamp base. Starting from =20 up to =180 the intensity is high and varies only slightly and thus fulfills the Energy Star requirement that 90% of the measured intensity values in a vertical plane vary by no more than 25% from the average of all measured values.

(14) Although the invention has been illustrated and described in detail by the embodiments explained above, it is not limited to these embodiments. Other variations may be derived by the skilled person without leaving the scope of the attached claims.

(15) Generally, a or an may be understood as singular or plural, in particular with the meaning at least one, one or more, etc., unless this is explicitly excluded, for example by the term exactly one, etc.

(16) In addition, numerical values may include the exact value as well as a usual tolerance interval, unless this is explicitly excluded.

(17) Features shown in the embodiments, in particular in different embodiments, may be combined or substituted without leaving the scope of the invention.

LIST OF REFERENCE NUMBERS

(18) 1 substrate 2, 2 LED 3 conversion layer 4 connecting section 5 electrical connector 10 first filament section 20 second filament section 30 bulb 31 lamp base 32 holder 33 socket 40 LED filament