LED filament lamp

Abstract

An LED filament lamp (100), comprising: a plurality of LED filaments (110); an optically-transmissive envelope (140) covering the plurality of LED filaments (110); and a mounting arrangement for supporting the plurality of LED filaments, the mounting arrangement comprising: a central pillar (120) for mounting the plurality of LED filaments; a first polymer disc (130a) configured to support a first end of each of the plurality of LED filaments; and a second polymer disc (130b) configured to support a second end of each of the plurality of LED filaments; wherein an outer edge of the first polymer disc (130a) and an outer edge of the second polymer disc (130b) each comprise a plurality of recessed portions (131), wherein each recessed portion is configured to engage with a respective LED filament (110); wherein at least one of the first polymer disc (130a) and the second polymer disc (130b) is configured to engage with an inner wall of the optically-transmissive envelope (140); and an outer portion (135) of the at least one of the first polymer disc (130a) and the second polymer disc (130b) provides a buffer between the plurality of LED filaments (110) and the optically-transmissive envelope (140).

Description

[0001] LED filament lamp

[0002] FIELD OF THE INVENTION

[0003] The invention relates to the field of LED filament lamps.

[0004] BACKGROUND OF THE INVENTION

[0005] Many existing designs for LED filament lamps involve LED filaments welded onto a core pillar in a cylindrical arrangement and sealed in a glass bubble shell. A bracket ring may be provided at the top of the core pillar to engage with the top of the glass bubble shell.

[0006] The welding process often results in an uneven distribution of the filaments and / or to filaments that are skewed with respect to the glass bubble shell (i.e. not centered within the glass bubble shell). The skewing of filaments in an LED filament lamp can also occur due to the tolerance of the curvature at the top of the glass bubble shell and the tolerance fit of the bracket ring, if included.

[0007] The skewing and / or uneven distribution of filaments in an LED filament lamp can result in uneven heat distribution within the glass bubble shell during use, which may cause damage to the lamp.

[0008] Further, this design of LED filament lamps presents a risk of breakage of the lower (glass) part of the core pillar due to vibrations of the filaments or during transportation.

[0009] There is therefore a need for an improved LED filament lamp design.

[0010] US 2019331302A1 discloses a high output lamp being made with LED filaments. An outer surface of the LED filaments defines a mount structure perimeter that is held adjacent to an inner surface of the bulb, separated by a total diameter difference gap of substantially zero to three millimeters maximum.

[0011] SUMMARY OF THE INVENTION

[0012] The invention is defined by the claims.

[0013] According to examples in accordance with an aspect of the invention, there is provided an LED filament lamp, comprising: a plurality of LED filaments; an optically- transmissive envelope covering the plurality of LED filaments; and a mounting arrangement for supporting the plurality of LED filaments, the mounting arrangement comprising: a central pillar for mounting the plurality of LED filaments; a first polymer disc configured to support a first end of each of the plurality of LED filaments; and a second polymer disc configured to support a second end of each of the plurality of LED filaments.

[0014] The use of a polymer disc at either end of each LED filament to support the plurality of LED filaments enables the LED filaments to be mounted on the central pillar in an arrangement in which the LED filaments are evenly distributed (thus enabling a more even heat distribution during use of the lamp).

[0015] For instance, the first and second polymer discs may support the LED filaments in a desired arrangement while the LED filaments are secured to the central pillar, reducing a likelihood of disruption to the positions of the LED filaments during this process.

[0016] The use of a polymer for the first and second discs provides electrical isolation between the LED filaments.

[0017] In some examples, an outer edge of the first polymer disc and an outer edge of the second polymer disc each comprise a plurality of recessed portions, wherein each recessed portion is configured to engage with a respective LED filament. The recessed portions provide improved support for the LED filaments. In some examples, at least one of the first polymer disc and the second polymer disc is configured to engage with an inner wall of the optically- transmissive envelope. An outer portion of the polymer discs provides a buffer between the plurality of LED filaments and the optically -transmissive envelope.

[0018] In some examples, the plurality of recessed portions are evenly distributed around the outer edge of the first polymer disc and second polymer disc respectively.

[0019] In this way, the LED filaments may be supported in an arrangement in which the LED filaments are evenly spaced with respect to one another, thus improving a uniformity of light output by the LED filament lamp, and improving an evenness of heat distribution within the LED filament lamp.

[0020] In some examples, the first polymer disc and the second polymer disc are each made of a polymer having a melting point higher than 260 °C.

[0021] This allows the LED filaments to be soldered to the central pillar without melting the polymer discs.

[0022] In some examples, the polymer is one of: a polyimide, polytetrafluoroethylene or a rubber.

[0023] The heat resistance of these polymers reduces a likelihood that the polymer discs would be melted or damaged during the soldering of the LED filaments to the central pillar. In some examples, each polymer disc has athickness-to-diameter ratio between 1 :20 and 1 :40. A polymer disc having a thickness-to-diameter ratio in this range is sufficiently thick to support the LED filaments, yet thin enough to have some flexibility.

[0024] In some examples, each polymer disc has a thickness-to-diameter ratio of 1:30.

[0025] In some examples, the plurality of LED filaments are provided in a cylindrical arrangement. This provides a stable structure with an even heat distribution.

[0026] The polymer discs may thus ensure that the filament arrangement is centered with respect to the optically-transmissive envelope, thus improving an evenness of heat distribution within the optically-transmissive envelope during use of the lamp.

[0027] Further, by engaging with the inner wall of the optically-transmissive envelope, the polymer discs improve vibration resistance of the plurality of filaments, reducing a likelihood of breakage of the central pillar.

[0028] In some examples, the first polymer disc and the second polymer disc each have a Young’s modulus lower than a Young’s modulus of the optically-transmissive envelope.

[0029] The lower Young’s modulus (or higher elasticity) of the polymer discs allows the polymer discs to be compressed inside the optically-transmissive envelope, thus engaging with the inner wall(s) of the optically-transmissive envelope.

[0030] In some examples, the optically-transmissive envelope is formed from glass. The use of glass enables the optically-transmissive envelope to withstand high temperatures within the LED filament lamp.

[0031] In some examples, the LED filament lamp has a wattage of at least 19 W.

[0032] In some examples, the LED filament lamp has a luminous flux of at least 4000 Im.

[0033] In some examples, the plurality of LED filaments comprises at least six LED filaments.

[0034] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] For a better understanding of the invention, and to show more clearly how it may be earned into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0037] Figure 1 illustrates a perspective view of an LED filament lamp, according to an embodiment of the invention; Figure 2 illustrates a side view of the LED filament lamp;

[0038] Figure 3 illustrates a top view of the LED filament lamp; and Figure 4 illustrates a polymer disc.

[0039] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The invention will be described with reference to the Figures.

[0041] It should be understood that the detailed description and specific examples, while indicating exemplaiy embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0042] The invention provides an LED filament lamp comprising a plurality of LED filaments and a mounting arrangement for the LED filaments. The plurality of LED filaments are mounted on a central pillar of the mounting arrangement, and are supported by a polymer disc at each end.

[0043] Embodiments are at least partly based on the realization that providing a polymer disc at each end of the LED filaments supports the LED filaments in a desired arrangement, particularly before and during securing (e g. soldering) of the LED filaments to the central pillar.

[0044] Illustrative embodiments may, for example, be employed in lighting systems, such as street lighting systems.

[0045] Figure 1 illustrates a perspective view of an LED filament lamp 100, according to an embodiment of the invention. The LED filament lamp comprises a plurality of LED filaments 110, and a mounting arrangement for supporting the plurality of LED filaments. In Figure 1, the plurality of LED filaments consists of 10 LED filaments; however, the skilled person will appreciate that any number of LED filaments may be used.

[0046] In some examples, the LED filament lamp may be a high power / high lumen lamp. For instance, the LED filament lamp may have a wattage of at least 19 W and / or a luminous flux of at least 4000 Im. The plurality of LED filaments may comprise at least six LED filaments. In some examples, the LED filament lamp may be designed to replace a high intensity discharge (HID) lamp, such as an SON-T lamp. Each LED filament 110 may comprise at least one linear string of LED (light emitting diode) chips, which may be mounted on an elongate substrate (e g. a metal substrate). At least a light-emitting surface of each LED filament may be covered by an encapsulant. In some examples, the encapsulant may comprise a phosphor, to convert a color of light emitted by the LED chips. In Figure 1, the plurality of LED filaments are provided in a cylindrical arrangement; however, other arrangements, such as a frustrum-shaped arrangement or a differently-shaped prism, may alternatively be used for the plurality of LED filaments. The arrangement of the plurality of LED filaments may depend on the number of LED filaments in the LED filament lamp: for instance, a cylindrical arrangement may be used for an LED filament lamp comprising 6 or more LED filaments. For LED filament lamps having fewer than 6 LED filaments, other arrangements may be used.

[0047] In Figure 1, an electrode is provided at each end of each LED filament. The electrodes of each LED filament are configured to connect the at least one string of LED chips to the remainder of the LED filament lamp.

[0048] The mounting arrangement comprises a central pillar 120 for mounting the plurality of LED filaments 110, a first polymer disc 130a, and a second polymer disc 130b. The first polymer disc is configured to support a first end of each of the plurality of LED filaments, while the second polymer disc is configured to support a second end of each of the plurality of LED filaments. In Figure 1, the first and second polymer discs are each mounted on the central pillar 120.

[0049] The LED filament lamp 100 may further comprise a lamp base 160 for mounting the LED filament lamp in a socket. The lamp base is provided at one end of the central pillar 120. In Figure 1, the lamp base comprises a screw cap; however, as the skilled person will readily appreciate, the lamp base may comprise any suitable connector for fitting the LED filament lamp to a lamp-receiving socket (e.g. a bayonet cap, a pin and push cap, etc.).

[0050] The central pillar 120 and the lamp base 160 may together be configured to provide an electrical between the plurality of LED filaments 110 and a socket. For instance, the central pillar may comprise one or more conductors for forming an electrical circuit of the plurality of filaments, and the lamp base may comprise one or more conductors for provided a path for electrical power from outside the LED filament lamp 100 to the one or more conductors of the central pillar. The LED filament lamp may comprise additional circuitry (e.g. control circuitry), which may, for example, be provided in the central pillar and / or the lamp base. In Figure 1, each of the plurality of LED filaments 110 is mounted on and electrically connected to the central pillar 120 by soldering the electrode at the first end of each LED filament to a first ring 121 (not visible in Figure 1), and soldering the electrode at the second end of each LED filament to a second ring 122. The first ring and second ring are each secured to the central pillar. Until the plurality of LED filaments have been soldered to the first and second rings, each LED filament is supported in a desired position (i.e. to achieve a desired arrangement of the LED filaments) by the first and second polymer discs.

[0051] In some examples, a bracket ring 150 may be provided at an opposite end of the central pillar to the lamp base 160. The bracket ring is described in more detail below.

[0052] In some examples, the outer edge of the first polymer disc 130a and the outer edge of the second polymer disc each comprise a plurality of recessed portions 131 In Figure 1, the recessed portions are evenly distributed around the outer edge of the first polymer disc and evenly distributed around the outer edge of the second polymer disc, in order to provide even spacing between the LED filaments 110. As the skilled person will readily appreciate, alternative distributions of the recessed portions may be provided according to a desired arrangement of the LED filaments.

[0053] Each recessed portion 131 of the first polymer disc 130ais configured to engage with a respective LED filament 110. Each recessed portion of the second polymer disc 130b is likewise configured to engage with a respective LED filament. In other words, each LED filament engages with a recessed portion of the first polymer disc at the first end of the LED filament and with a recessed portion of the second polymer disc at the second end of the LED filament. For instance, in Figure 1, each electrode of each LED filament engages with a recessed portion of either the first polymer disc or the second polymer disc.

[0054] In some examples, the LED filament lamp 100 further comprises an optically - transmissive envelope 140 covering the plurality of LED filaments 110. Preferably, the optically-transmissive envelope is formed from glass; however, the optically-transmissive envelope may be formed from any other suitable transparent or translucent material, such as plastic. The optically-transmissive envelope may be secured to the lamp base 160 such that the LED filament arrangement is fully enclosed.

[0055] At least one of the first polymer disc 130a and the second polymer disc 130b may be configured may be configured to engage with an inner wall of the optically- transmissive envelope 140. In this way, the position of the plurality of the LED filaments 110 within the optically-transmissive envelope may be controlled (e.g. to center the LED filament arrangement within the optically-transmissive envelope). For instance, in Figure 1, the diameter of each polymer disc is approximately equal to the inner diameter of the optically-transmissive envelope 140 at the positions of the optically-transmissive envelope with which the first and second polymer discs are configured to engage. In some examples, taking into account tolerances in production, the polymer discs may have a slightly larger diameter than the inner diameter of the optically-transmissive envelope; an elasticity of the first and second polymer discs allows the first and second polymer discs to compress or flex slightly, if necessary, in order to fit against the inner wall of the optically-transmissive envelope.

[0056] This is shown more clearly in Figure 2, which illustrates a side view of the LED filament lamp 100, and in Figure 3, which illustrates a top view of the LED filament lamp 100. These Figures illustrate how the first and second polymer discs fit against the inner wall of the optically-transmissive envelope 140.

[0057] As Figure 2 shows, the engagement of the first and second polymer discs with the inner wall of the optically-transmissive envelope 140 centers the cylinder formed by the plurality of LED filaments 110 with respect to the optically-transmissive envelope.

[0058] In addition to controlling a position of the plurality of LED filaments 110 within the optically-transmissive envelope 140, the engagement of the first and second polymer discs with the inner wall of the optically-transmissive envelope may also improve a stability of the LED filament lamp 100, in particular by acting as a buffer between the LED filament arrangement and the optically-transmissive envelope, thus improving a vibration resistance of the plurality of LED filaments and reducing a likelihood of breakage of the central pillar. The existing of a buffer means that there is at least a gap between the LED filaments 110 and the inner wall of the optically-transmissive envelope 140, so that the LED filaments 110 won’t touch or hit the inner wall of the optically-transmissive envelope 140. This is particular advantage in a vibrating environment for the LED filament lamps, e.g., during transportation. In particular, where the first and second polymer discs fit against the inner wall of the optically- transmissive envelope, this buffer prevents lateral movement of the arrangement of LED filaments (i.e. in a direction perpendicular to the direction in which the LED filaments extend).

[0059] The first and second polymer discs may provide some improvement in stability even in examples in which the diameter of the polymer discs is smaller than the inner diameter of the optically-transmissive envelope, as an outer portion 135 of the polymer discs (see Figure 4) would still provide a buffer between the LED filament arrangement and the optically- transmissive envelope, even if the polymer discs do not entirely prevent lateral movement. Such buffer keeps the gap between the LED filaments 110 and the inner wall of the optically- transmissive envelope 140, so that they won’t touch or hit each other. This is particular advantage in a vibrating environment for the LED filament lamps, e.g., during transportation.

[0060] Figures 2 and 3 also show the bracket ring 150 more clearly. In particular, Figure 2 illustrates that the bracket ring 150 is configured to engage with an inner wall of the optically -transmissive envelope 140 at atop end of the optically -transmissive envelope (i.e. an end of the optically -transmissive envelope furthest from the lamp base 160). The engagement of the bracket ring with the top end of the optically-transmissive envelope may prevent, or at least reduce, movement of the arrangement of LED filaments in the direction in which the LED filaments extend.

[0061] In Figures 1 to 3, the plurality of LED filaments 110 are provided in a cylindrical arrangement, and the optically-transmissive envelope 140 has a cylindrical tube shape. The first polymer disc 130a and the second polymer disc 130b are therefore identical discs, each having a circular shape, with recessed portions 131 each having a same depth provided at regular intervals around the outer edge. This enables each polymer disc to support the plurality of LED filaments in the cylindrical arrangement and engage with the inner wall of the optically- transmissive envelope. As the skilled person will appreciate, alternative configurations of the first and second polymer discs may be used for different arrangements of the plurality of LED filaments and / or differently-shaped optically-transmissive envelopes. For instance, if the plurality of LED filaments are provided in a frustum-shaped arrangement, the first polymer disc may have a smaller diameter and / or deeper recessed portions than the second polymer disc.

[0062] Figure 4 illustrates a polymer disc 130. The polymer disc 130 may be used as the first polymer disc 130aand / orthe second polymer disc 130b in the LED filament lamp 100.

[0063] Figure 4 shows more clearly the provision of the recessed portions 131 at regular intervals around an outer edge of the polymer disc 130. The recessed portions shown in Figure 4 are cut-outs extending inwards from the outer edge (i.e. such that the recessed portions form part of the outer perimeter of the polymer disc). Alternatively, the recessed portions may be provided as grooves extending inwards from the outer edge of the polymer disc (i.e. the recessed portions may not extend through the entire thickness of the polymer disc). In other examples, the recessed portions may be holes provided in the polymer disc that do not extend to the very edge of the polymer disc (i.e. the recessed portions may be closed-off from the outer edge of the polymer disc).

[0064] A through-hole 132 is provided at the center of the polymer disc 130, for mounting the polymer disc onto a central pillar of an LED filament lamp (e.g. central pillar 120 of LED filament lamp 100). The diameter of the through-hole may be configured to provide a friction fit between the central pillar and the polymer disc.

[0065] The polymer discs disclosed herein may be formed from any suitable polymer. For instance, where the polymer discs are used in an LED filament lamp in which the plurality of LED filaments are secured to the central pillar by soldering, the first and second polymer discs may each be made of a polymer having a melting point above the temperature used for soldering the LED filaments (typically 260 °C). For instance, each polymer disc may each be made of a polyimide, polytetrafluoroethylene or a rubber (e.g. silicon rubber).

[0066] As previously mentioned, the first and second polymer disc may each have an elasticity that allows the polymer discs to fit against the inner wall of the optically -transmissive envelope. In particular, the first polymer disc and the second polymer disc may each have a Young’s modulus lower than a Young’s modulus of the optically-transmissive envelope. For instance, the optically-transmissive envelope may be made of glass, having a Young’s modulus of 70 GPa. The polymer discs may, for example, each have a Young’s modulus lower than 20 GPa, preferably lower than 5 GPa.

[0067] A thickness of each of the first and second polymer discs may depend on the polymer used for the polymer disc and on the diameter of the polymer disc. In some examples, the polymer disc may have a ratio of thickness to diameter in the range of 1 :20-l : 40, preferably 1:30. For instance, a polymer disc made of a polyimide or polytetrafluoroethylene may have a thickness of 0.2-1.5 mm, depending on diameter, while a polymer disc made of a rubber may have a thickness of 1.0-2.2 mm.

[0068] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0069] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0070] If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

[0071] Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. An LED filament lamp (100), comprising: a plurality of LED filaments (110); an optically-transmissive envelope (140) covering the plurality of LED filaments (110); and a mounting arrangement for supporting the plurality of LED filaments, the mounting arrangement comprising: a central pillar (120) for mounting the plurality of LED filaments; a first polymer disc (130a) configured to support a first end of each of the plurality of LED filaments; and a second polymer disc (130b) configured to support a second end of each of the plurality of LED filaments; wherein an outer edge of the first polymer disc (130a) and an outer edge of the second polymer disc (130b) each comprise a plurality of recessed portions (131), wherein each recessed portion is configured to engage with a respective LED filament (110); wherein at least one of the first polymer disc (130a) and the second polymer disc (130b) is configured to engage with an inner wall of the optically-transmissive envelope (140); and an outer portion (135) of the at least one of the first polymer disc (130a) and the second polymer disc (130b) provides a buffer between the plurality of LED filaments (110) and the optically-transmissive envelope (140).

2. The LED filament lamp (100) of claim 1, wherein the plurality of recessed portions (131) are evenly distributed around the outer edge of the first polymer disc (130a) and second polymer disc (130b) respectively.

3. The LED filament lamp (100) of any of claims 1 to 2, wherein the first polymer disc (130a) and the second polymer disc (130b) are each made of a polymer having a melting point higher than 260 °C.

4. The LED filament lamp (100) of claim 3, wherein the polymer is one of: a polyimide, polytetrafluoroethylene or a rubber.

5. The LED filament lamp (100) of any of claims 1 to 4, wherein each polymer disc (130, 130a, 130b) has a thickness-to-diameter ratio between 1:20 and 1 :40.

6. The LED filament lamp (100) of claim 5, wherein each polymer disc (130, 130a, 130b) has a thickness-to-diameter ratio of 1:30.

7. The LED filament lamp (100) of any of claims 1 to 6, wherein the plurality of LED filaments (110) are provided in a cylindrical arrangement.

8. The LED filament lamp (100) of claim 1, wherein the first polymer disc (130a) and the second polymer disc (130b) each have a Young’s modulus lower than a Young’s modulus of the optically-transmissive envelope.

9. The LED filament lamp (100) of any of claims 1 to 8, wherein the optically- transmissive envelope (140) is formed from glass.

10. The LED filament lamp (100) of any of claims 1 to 9, wherein the LED filament lamp has a wattage of at least 19 W.

11. The LED filament lamp (100) of any of claims 1 to 10, wherein the LED filament lamp has a luminous flux of at least 4000 Im.

12. The LED filament lamp (100) of any of claims 1 to 11, wherein the plurality of LED filaments comprises at least six LED filaments.

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