EP4669901A1

EP4669901A1 - LED lightbulb

Info

Publication number: EP4669901A1
Application number: EP24704447.2A
Authority: EP
Inventors: Ties Van Bommel; Rifat Ata Mustafa Hikmet
Original assignee: Signify Holding BV
Current assignee: Signify Holding BV
Priority date: 2023-02-23
Filing date: 2024-02-12
Publication date: 2025-12-31
Also published as: WO2024175394A1; CN120752472A

Abstract

A LED filament lamp comprising an envelope having a central axis, a connector attached to the envelope, and a LED filament assembly arranged inside the envelope and comprising a plurality of elongated LED filaments, wherein the LED filament assembly is rotatably arranged with respect to the connector around the central axis. A first set of LED filaments are arranged on a first side of a virtual plane which intersects the central axis and have a main direction of illumination directed generally away from the virtual plane. A second set of LED filaments are arranged on the other side of the virtual plane and have a main direction of illumination directed generally towards the virtual plane. With this design, light from both sets of LED filaments will mainly exit the same side of the envelope, more specifically the side where the LED filaments in the first set are located.

Description

LED FILAMENT LAMP

FIELD OF THE INVENTION

The present invention relates to LED filament lamps, i.e. lamps comprising an envelope containing a plurality of LED filaments, and a connector for mechanical and electrical connection of the lamp.

BACKGROUND OF THE INVENTION

In recent years, LEDs (light emitting diodes) have become the dominating type of light sources in many applications, thanks to their impressive energy efficiency. One example is LED lamps, which to a large extent have replaced incandescent lamps having a heated wire filament in an air-tight envelope.

One drawback of LED lamps is that the emitted light may be perceived as different than that emitted by incandescent lamps. Various efforts have therefore been made to make LED lamps resemble incandescent lamps. One specific result of these efforts is the LED filament, i.e. a plurality of LEDs arranged on an elongated carrier, and optionally covered by a luminescent encapsulant. The light emitted from a LED filament resembles, to a large extent, that emitted by the wire filament in an incandescent lamp.

A light bulb with LED filaments (referred to as a LED filament lamp) is designed to resemble a traditional incandescent light bulb with one or several visible LED filaments for aesthetic and light distribution purposes. LED filament lamps have become increasingly popular, and are commercially available as lamps for domestic as well as commercial use. Nevertheless, there is a constant desire to improve the appearance and functionality of these LED filament lamps.

In some applications, it is desirable to have lamps with a high degree of directivity, i.e. lamps which emit light in a specific direction rather than equally in all directions. Examples of such applications are streetlamps and lamps in horticulture (e.g. greenhouses). Directivity is typically achieved with reflectors, but with LED filament lamps, other opportunities are available.

US 2013/242580 discloses methods and systems for a solid state lighting device. In an embodiment, a device includes a solid state directional light assembly that directionally emits less than omni-directional light, a first rotation mechanism, an Edison base to receive the first rotation mechanism and a secondary movement mechanism, positioned in contact with the light assembly and first rotation mechanism to provide directional positioning of the light assembly. The first rotation mechanism allows for rotation of the solid state directional light assembly while maintaining an electrical connection through the Edison base.

GENERAL DISCLOSURE OF THE INVENTION

It is an object of the invention to provide a LED filament lamp with improved (spatial) light distribution.

This and other objects are achieved by a LED filament lamp comprising an envelope having a central axis, a connector attached to the envelope, for electrically and mechanically connecting the LED filament lamp to a socket, a LED filament assembly arranged inside the envelope and comprising a plurality of elongated LED filaments, each LED filament having a plurality of LEDs mounted on a mounting surface of an elongated carrier, so that each LED filament has a main direction of illumination substantially normal to the mounting surface and pointing away from the plurality of LEDs, wherein the LED filaments surround the central axis with each LED filament oriented substantially parallel to the central axis, wherein the LED filament assembly is rotatably arranged with respect to the connector around the central axis, wherein a first set of LED filaments are arranged on a first side of a virtual plane which intersects the central axis, wherein each LED filament in the first set having a main direction of illumination directed generally away from the virtual plane, and wherein a second set of LED filaments are arranged on a second side of the virtual plane, opposite to the first side, wherein each LED filament in the second set having a main direction of illumination directed generally towards the virtual plane.

With this design, (the majority of) light from both sets of LED filaments will (directly) exit the same side of the envelope, more specifically the side where the LED filaments in the first set are located. Consequently, substantially all light emitted by the lamp will be emitted on one side of the envelope. Such LED filament lamp has an increased directivity thus an improved light distribution. It may for example (also) result in less reflection losses e.g. due to less reflection on a reflector in which the LED filament lamp may be arranged.

The rotational arrangement of the LED filament assembly ensures that after mounting the lamp in a socket, the LED filament assembly can be rotated to achieve a desired illumination. For example, it the lamp is installed in a streetlight, the LED filament assembly can be rotated such that the LED filaments in the LED filament lamp emits (mainly) light towards the street (and e.g. not to a reflector).

The lamp may include any number of LED filaments, but there are preferably at least two LED filaments in each set, i.e. at least four LED filaments in total. Even more preferably at least five filaments, or even at least six filaments. In another embodiment the number of LED filaments is less than ten LED filaments in order to create sufficient openings/ opening spaces between LED filaments.

In one embodiment, the entire envelope (including the LED filament assembly) can be rotated with respect to the connector. Preferably, a locking member of some sort is provided to enable a user to secure the envelope in the desired position.

In another embodiment, the envelope is fixed with respect to the connector, and the LED filament assembly is rotatable inside the envelope. A suitable rotating mechanism can be provided to enable a user to rotate the LED filament assembly. The rotating mechanism is preferably configured to secure the LED filament assembly to avoid unintentional rotation of the LED filament assembly. Again, a locking member may be provided to allow fixation of the LED filament assembly inside the envelope.

Fixating the LED filament assembly in a desired rotational position may be especially advantageous in situations where the lamp, after installation, is subject to vibration causing the LED filaments (or entire envelope) to move out if their original position. One specific example is a lamp installed in a streetlight.

As an alternative, or in addition, the LED filament assembly may be freely rotatable, and the lamp may include a counter-weight configured such that, when the lamp is mounted in a socket, the LED filament assembly will rotate until the main directions of illumination (Bl, B2) point downwards.

In an embodiment, there are at least two LED filaments in the first set. The elongated carriers of the at least two LED filaments in the first set may be arranged in parallel.

In an embodiment, there is at least two LED filaments in the second set. The elongated carriers of the at least two LED filaments in the second set may be arranged in parallel.

In an embodiment, there is at least two LED filaments in the first set and in the second set. The elongated carriers of the LED filaments in the first set may be non-parallelly arranged with the LED filaments in the second set. In one embodiment, there are at least two LED filaments in the first set and at least two LED filaments in the second set. The elongated carriers of the at least two LED filaments in one or both sets may be arranged in non-parallel planes. This introduces an angular spread between the main directions of illumination of the LED filaments of a set. The angular spread in the first and/or second set is preferably less than 45 degrees, and most preferably less than 20 degrees.

However, in another embodiment, the main directions of illumination of the LED filaments in the second set are parallel, and preferably parallel to the main directions of illumination of the LED filaments in the first set. With such a design, all LED filaments (in both sets) will have the same main direction of illumination.

In one embodiment, the LED filaments in the second set are oriented such that the main directions of illumination of the LED filaments in the set crosses the central axis of the envelope. This results in an emission pattern corresponding to a point (or line) light source arranged in the central axis.

In other embodiments, at least some of the LED filaments in the second set may have main directions of illumination extending between adjacent LED filaments in the first set. With this design, less light emitted by the LED filaments in the second set will be obstructed by LED filaments in the first set, thereby increasing efficiency.

Possibly, one LED filament in the second set has a main direction of illumination crossing the central axis, and at least two LED filaments in the second set have a main direction of illumination which does not cross the central axis.

In some embodiments, the LED filaments are symmetrically arranged around the central longitudinal axis, i.e. like the bullet chambers of a revolver. This results in an even heat distribution and thus good thermal management.

In other embodiments, the LED filaments are non-symmetrically arranged, in order to provide a desired illumination effect. In one example, the LED filaments are arranged on two groups on opposite sides of the envelope. In other words, the LED filaments in the first set are arranged in a first angular sector of the envelope, and the LED filaments in the second group are arranged in a second angular sector of the envelope opposite the first angular sector. The first and second angular sectors may be less than 120 degrees, or even less than 90 degrees.

In embodiments, each LED filament may further comprise an encapsulant at least partly covering the plurality of LEDs and at least part of the mounting surface. The encapsulant may comprise a light scattering material configured to scatter at least part of light emitted by the plurality of LEDs, and/or a luminescent material configured to convert at least part of light emitted by the plurality of LEDs to converted light.

In embodiments, the plurality of LEDs may emit blue light (having a peak wavelength in the 420-480nm wavelength range). The luminescent material may be a greenyellow phosphor (e.g. YAG) and a red phosphor (e.g. KSF).

In embodiments, the elongated carrier may be light transmissive such as translucent especially transparent. An encapsulant may also be arranged on the backside (opposite to the mounting side) of the elongated carrier. The encapsulant on the backside of the elongated carrier may also comprise a luminescent and or light scattering material.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in more detail with reference to the appended drawings, showing currently preferred embodiments of the invention.

Fig. la is a perspective view of a LED filament lamp according to a first embodiment of the present invention.

Fig. lb is a perspective view of a LED filament lamp according to a second embodiment of the present invention.

Fig. 2 is a schematic perspective view of a LED filament useful for the present invention.

Fig 3a-e are cross sections of the lamp in figure 1, illustrating different arrangements of the LED filaments.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The LED filament lamp 1 in figure 1 generally includes a light transmissive envelope 3 and a connector 2 (sometimes referred to as a “cap”) configured to electrically and mechanically connect the lamp to a socket 9, e.g. the socket of a luminaire. The connector 2 may be directly connected to the envelope, or it may be indirectly connected, i.e. there may be an intermediate base between the envelope and the connector. The connector 2 is here a threaded connector complying with existing light bulb socket standards, e.g. E27. The envelope 3 may be made of glass or plastic, and may be translucent, transparent (clear) or (slightly) diffusive, depending on the desired illumination. The envelope 3 has a central longitudinal axis A, in the illustrated case an axis of symmetry. An LED filament assembly 10 including a plurality of N LED filaments 5 is arranged inside the envelope 3. The plurality of LED filaments may comprise at least 4 LED filaments, more preferably at least 5 filaments, most preferably at least 6 LED filaments.

With reference to figure 2, for the purpose of this disclosure, a LED filament comprises an elongated, and generally flat, carrier 6, on which a plurality of LEDs 7 are mounted and electrically connected by conducting paths 8 provided on the carrier. Electrical terminals for connecting the paths 8 can be provided only on one end or on both ends of the filament 5.

The carrier may be made of a rigid material, such as ceramic or metal. It may alternatively be made of a flexible material such as plastic. In the present example, the carrier 6 is non-translucent, but a translucent carrier 6 is also possible. The LEDs (and carrier) may be covered by a light-converting encapsulant 8, configured to convert at least part of light emitted from the LEDs into converted light. For example, the LEDs may be blue light LEDs, and the encapsulant may include luminescent particles for converting the blue light into white light.

In this disclosure, the LED filaments only have LEDs on one side of the carrier 6, on a mounting surface 6a. The LEDs 7, and the entire LED filament 5, has a main direction of light emission B normal to the mounting surface 6a. The side of the carrier opposite to the mounting surface may have a highly reflective surface, in order to reduce losses.

Returning to figures la and lb, the LED filaments 5 are arranged around the central axis A, like chambers in a revolver. In the illustrated case the LED filaments 5 are each parallel to the axis A, but they may alternatively be angled inwards (to form a pointed lamp) or outwards. The LED filaments 5 may also be tilted so as to form a spiral impression. If the LED filaments have flexible carriers, they may also be curved.

In the illustrated examples, all LED filaments 5 in the lamp 1 are arranged at a common distance to the inner wall of the envelope 3. For reasons of thermal management, the LED filaments 5 are preferably arranged closer to the inner wall than the central axis.

Although not shown in the figures, the lamp la, lb includes appropriate driver circuitry for driving the LED filaments 5. Depending on the type and configuration of the LED filaments 5, various types of drivers may be required/suitable, e.g. depending on if the LEDs are dimmable. In some cases, the light emitted by the LED filaments is controllable, for example, the color or color temperature of the LED filaments 5 may be controllable. In such cases, the lamp la, lb also comprises appropriate control circuitry and an antenna for wireless reception of a control signal to adjust e.g. color or color temperature of the lamp. The LED filament assembly 10 is rotationally arranged with respect to the connector 2, so that the envelope may be rotated around the axis A to a desired position after the lamp 1 has been securely mounted in the socket 11.

In figure la, the envelope 3 is rotationally fixed with respect to the connector 2, while the LED filament assembly 10 is rotationally arranged inside the envelope 3. The arrangement 10 can be rotated to a desired position by means of an annular member 4a. Preferably, the member 4a is subject to sufficient friction such that the LED filament assembly 10 will not rotate freely.

In figure lb, the LED filament assembly 10 is fixedly arranged inside the envelope 3, and the envelope 3 is instead rotationally attached to the connector 2. 1 this case the lamp lb further includes a locking member, arranged to secure the envelope 3 in a desired position. The locking member is here illustrated as an annular element 4b.

As will be discussed in more detail with reference to figures 3a-d, the LED filaments 5 are grouped into two sets 51, 52 arranged on opposite sides of a virtual plane, VP, intersecting the central axis A. The first set of LED filaments 51 may comprises more LED filaments than the second set of LED filaments 52. LED filaments 51 in the first set are oriented so that their main direction of illumination faces away from the central axis A (and thus out of the envelope 3). LED filaments 52 in the second set are oriented so that their main direction of illumination B2 faces towards the central axis A (and thus into the envelope 3). As the sets are located opposite to each other, this means that light from both sets is all emitted on the same side of the envelope, and generally in the same direction.

Various possible layouts of the LED filaments 51, 52 will be discussed with reference to figures 3a-d, showing lamps with six LED filaments.

In figure 3a, the LED filaments 51, 52 are symmetrically distributed around the central axis A. In other words, with N LED filaments 51, 52 in total, the angular separation will be 360/N degrees. The mounting surfaces 6a of the LED filaments 51 in the first set are facing radially outwards from the axis A, while the mounting surfaces 6a of the LED filaments 52 in the second set are facing radially inwards. All main directions of illumination Bl, B2 are thus aligned with radii from the axis A, and the main direction of illumination B2 of the LED filaments 52 will thus cross the axis A.

In figure 3b, the LED filaments are again evenly distributed around the axis A. In this case, however, all LED filaments 51, 52 do not have a radially aligned main direction of illumination B 1 , B2. Instead, the outer LED filaments 51 a in the first set are turned slightly inwards, so that the angular spread of the LED filaments 51 is reduced (the main directions of illumination are more collimated). In a similar manner, the outer LED filaments 52a in the second set are turned slightly outwards, so that the angular spread of the LED filaments 52 is also reduced. In the illustrated example, the angular spread of both sets is approximately 45 degrees.

If figure 3 c, the outer LED filaments 52a in the second set are directed so that the main direction of illumination extends between adjacent LED filaments 51 in the first set. Less light will therefore be reflected by the back sides of the LED filaments 51, thereby improving efficiency.

In figure 3d, the LED filaments 51, 52 are not evenly distributed around axis A. Instead, the LED filaments 51 in the first set are arranged closer together in a first angular sector 53, while the LED filaments 52 in the second set are arranged in a second angular sector 54. In the illustrated case the sectors 53, 54 are restricted to just over 90 degrees. The arrangement of the LED filaments in limited angular sectors 53, 54 leads to a separation of the two sets, allowing a more distinct light directivity.

In figures 3a-d, (the carriers of) the LED filaments 51, 52 in each set are arranged in non-parallel planes, i.e. such that the main directions of illumination B 1, B2 in each set are non-parallel within the set. In the illustrated examples, the angular spread within each set is less than 45 degrees, and it may be less than 20 degrees.

In a different embodiment, illustrated in figure 3e, the LED filaments 51, 52 are arranged in parallel planes, such that the main directions of illumination Bl, B2 are parallel in each set. In figure 3e, the LED filaments 51, 52 in both sets are also arranged in parallel planes with respect to each other, so that Bl and B2 are parallel, but this is not necessary. The LED filaments 51, 52 in the two set may shifted with respect to each other, such that the main direction of illumination B2 of the filaments in the second set extends between adjacent LED filaments 51 in the first set.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the shape and form of the envelope and connector may be different. Also, further alternative arrangements of the LED filaments, in addition to those illustrated in figures 3a-e, are possible.

Claims

CLAIMS:

1. A LED filament lamp (1), comprising: an envelope (3) having a central axis (A), a connector (2) attached to the envelope, for electrically and mechanically connecting the LED filament lamp to a socket (11), a LED filament assembly (10) arranged inside the envelope and comprising a plurality of elongated LED filaments (5; 51, 52), each LED filament having a plurality of LEDs (7) mounted on a mounting surface (6a) of an elongated carrier (6), so that each LED filament has a main direction of illumination (B) substantially normal to the mounting surface and pointing away from the plurality of LEDs, wherein the LED filaments surround the central axis (A) with each LED filament oriented substantially parallel to the central axis, wherein the LED filament assembly (10) is rotatably arranged with respect to the connector (2) around the central axis (A), wherein a first set of LED filaments (51) are arranged on a first side of a virtual plane (VP) which intersects the central axis, wherein each LED filament (51) in the first set having a main direction of illumination (Bl) directed generally away from the virtual plane (VP), and wherein a second set of LED filaments (52) are arranged on a second side of the virtual plane (VP) which intersects the central axis, opposite to the first side, wherein each LED filament (52) in the second set having a main direction of illumination (B2) directed generally towards the virtual plane.

2. The LED filament lamp according to claim 1, wherein the LED filament assembly (10) is rotationally fixated inside the envelope (3), and the envelope (3) is rotatably arranged with respect to the connector (2).

3. The LED filament lamp according to claims 1, wherein the envelope is fixated to the connector (2) and the LED filament assembly (10) is rotationally arranged inside the envelope (3), further comprising a rotation element (4a) configured to allow a user to rotate the LED filament assembly (10) with respect to the connector (2) and envelope (3).

4. The LED filament lamp (1) according to claim 2 or 3, further comprising a locking member (4a, 4b) configured to fixate of the orientation of the LED filament assembly (10) with respect to the connector (2).

5. The LED filament lamp according to any one of the preceding claims, wherein the LED filament assembly (10) is freely rotatable, and wherein the lamp further comprises a counter-weight configured such that, when the lamp is mounted in a socket, the LED filament assembly (10) will rotate until the main directions of illumination (Bl, B2) point downwards.

6. The LED filament lamp according to any one of the preceding claims, comprising at least two LED filaments (51) in the first set and at least two LED filaments (52) in the second set, wherein the elongated carriers (6) of the at least two LED filaments in the first set are arranged in non-parallel planes, and wherein the elongated carriers of the at least two LED filaments in the second set are arranged in non-parallel planes.

7. The LED filament lamp according to claim 6, wherein an angular spread of the main directions of illumination of the LED filaments (51, 52) in the first and/or second set is less than 45 degrees, preferably less than 20 degrees.

8. The LED filament lamp according to any one of the preceding claims, wherein each LED filament in the second set has a main direction of illumination crossing the central axis.

9. The LED filament lamp according to any one of the preceding claims, wherein all LED filaments are arranged in parallel planes normal to the virtual plane.

10. The LED filament lamp according to any one of the preceding claims, wherein at least some of the LED filaments in the second set have main directions of illumination extending between adjacent LED filaments in the first set.

11. The LED filament lamp according to any one of the preceding claims, wherein one LED filament in the second set has a main direction of illumination crossing the central axis, and wherein at least two LED filaments (52) in the second set have a main direction of illumination which does not cross the central axis.

12. The LED filament lamp according to any one of the preceding claims, wherein the LED filaments are symmetrically arranged around the central axis.

13. The LED filament lamp according to any one of the claims 1-11, wherein the LED filaments are asymmetrically arranged around the central longitudinal axis

14. The LED filament lamp according to claim 13, wherein the LED filaments (51) in the first set are arranged in a first angular sector of the envelope, and the LED filaments (52) in the second set are arranged in a second angular sector of the envelope opposite the first angular sector, wherein the first and second angular sectors are less than 120 degrees.

15. The LED filament lamp according to any one of the preceding claims, wherein each LED filament (5; 51, 52) further has an encapsulant (9) at least partly covering the plurality of LEDs (7) and at least part of the mounting surface (6a), the encapsulant comprising: a light scattering material configured to scatter at least part of light emitted by the plurality of LEDs (7), and/or a luminescent material configured to convert at least part of light emitted by the plurality of LEDs (7) to converted light.