FIELD OF THE INVENTION

The invention relates to lighting devices comprising a puck assembly comprising a plurality of LEDs and a cover element, the cover element comprising an inner shell element, and an outer shell element which is transparent or translucent.

BACKGROUND OF THE INVENTION

US 8,596,827 describes a lamp comprising an outer bulb, an inner optical processing member, a heat sink in which the outer bulb and the inner optical processing member are mounted and a plurality of LEDs mounted on a heat pipe and arranged in the inner optical processing member.

Such LED based solutions are however quite inefficient. The heat that is generated during operation generally leads to temperatures in the application that deteriorate the system efficacy and limit the lifetime of the LEDs and other components. In order to transfer heat to the ambient such LED devices generally use a heat sink. In most LED applications the heat sink and the light emitting surface are two separate elements. The size of the heat sink is smaller than the total lamp enclosure, limiting the heat transfer to the ambient and thus limiting the thermal performance.

Some LED based solutions enable the total enclosure to be heated, leading to an effective heat transfer to the ambient, e.g. by distributing the LEDs over the outer enclosure. Distributing the LEDs over a 3D curved outer enclosure leads to complex and expensive solutions, while the use of flat surfaces lead to deviating shapes of the lamp or luminaire.

Other LED based solutions, e.g. so-called Inca bulbs, have LEDs placed inside a transparent or translucent container and a special gas is used to enhance the internal heat transfer from the LED source(s) to the enclosure. This however leads to an LED degradation that can only be solved by adding a certain amount of oxygen, which in turn leads to an impaired thermal performance. Also, making such a bulb is critical in assembly due to the high temperatures at which the glass is processed, e.g. bulb sealing and annealing. These high temperatures during sealing also limit the amount of the special gas that can be pumped into the bulb.

Thus, there is a desire for providing a LED lighting device which is more efficient in regards of heat transfer from the LEDs to the surroundings, which provides for a longer lifetime of the LEDs and which has a simpler structure and thus is less costly to manufacture and assemble.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome this problem, and to provide a lighting device which is more efficient in regards of heat transfer from the LEDs to the surroundings, which provides for a longer lifetime and an improved power/light output of the LEDs and which is structurally simpler and thus less costly to manufacture and assemble.

According to a first aspect of the invention, this and other objects are achieved by means of a lighting device comprising a puck assembly comprising a plurality of LEDs and a cover element comprising an outer shell element adapted for forming a light exit surface of the lighting device and an inner shell element, the outer shell element and the inner shell element forming together a hermetically sealed gas chamber, the hermetically sealed gas chamber being filled with substantially one single gas adapted for functioning as a heat transferring medium for transferring heat from the puck assembly towards the outer shell element, and the inner shell element forming a cavity adapted for accommodating the puck assembly at least partially in such a way that the puck assembly is arranged outside the hermetically sealed gas chamber in a heat transferring relationship with the inner shell element and thereby with the substantially one single gas provided in the hermetically sealed gas chamber.

By providing the outer shell element and the inner shell element forming together one hermetically sealed gas chamber, a lighting device with a cover element having a particularly simple construction being particularly simple to manufacture is provided.

By providing the hermetically sealed gas chamber as being filled with substantially one single gas adapted for functioning as a heat transferring medium for transferring heat from the puck assembly towards the outer shell element, a lighting device which is very effective in regards of heat transfer from the LEDs to the surroundings is provided.

By providing the inner shell element forming a cavity adapted for accommodating the puck assembly at least partially in such a way that the puck assembly is arranged outside the hermetically sealed gas chamber in a heat transferring relationship with the inner shell element and thereby with the substantially one single gas provided in the hermetically sealed gas chamber, a lighting device which is very effective in regards of heat transfer from the LEDs to the surroundings is provided.

Furthermore, a lighting device with a generally simpler structure is provided for as the heat sink and the light exit surface is thus formed by one single element, namely the cover element.

In prior art light bulbs, such as an INCA bulb, the bulb acts a closed chemical reaction chamber, and thus reaction products stay inside the bulb and there is no refreshment of oxygen. This lack of oxygen has deteriorating effects on the LEDs. FurthermoreHence, as the plurality of LEDs are arranged outside of the hermetically sealed gas chamber, a lighting device is provided in which the plurality of LEDs are not in direct contact with the ambientsubstantially one single gas provided in the hermetically sealed gas chamber and in which the oxygen in the air in the vicinity of the LEDs may be refreshed. The LEDs are thus not subjected to deteriorating effects of the one single gasrelated to lack of oxygen. This in turn provides for a lighting device in which the LEDs have a longer lifetime and an improved power/light output.

Furthermore, with such a lighting device the arrangement of the plurality of LEDs may be placed at the outside of the cover element and thus the hermetically sealed gas chamber, thereby makesing both manufacture and particularly assembly easy. The same outer and inner shell elements form both an optical element of the LED lamp or luminaire to distribute the light all around or directionally and a mechanical enclosure or cover element of the plurality of LEDs. Thus such a lighting device is also particularly simple both in structure and to assemble and thus less costly to manufacture and assemble.

In an embodiment the outer shell element and the inner shell element forming together the hermetically sealed gas chamber are made of a glass or a ceramic and are manufactured as a separate part in one piece using a high temperature glass or ceramics processing method.

Thereby a lighting device is provided in which the outer and inner shell element may be manufactured on existing production lines and may be assembled with a puck assembly to form a lighting device under normal ambient temperature conditions.

Particularly, the outer and inner shell element may be manufactured as a separate part, allowing the full use of glass or ceramics processing like heating in an oven (e.g. to 400 °C) to remove (organic) contamination, vacuum pumping, and filling with the one single gas and subsequent hermetic sealing, i.e. "tipping", by glass processing. Similarly the wick materials can be chosen to be compatible with the working fluid. Thus, such a lighting device is also particularly simple both in structure and to assemble and thus less costly to manufacture and assemble.

In an embodiment a transition between the outer shell element and the inner shell element is formed as a continuous transition.

Thereby a lighting device is provided which is particularly simple in structure and thus less costly to manufacture, and which furthermore is particularly suitable for holding the one single gas within the hermetically sealed gas chamber.

In an embodiment the outer shell element and the inner shell element form together a hermetically sealed gas chamber, the hermetically sealed gas chamber being filled with substantially one single gas adapted for functioning as a heat transferring medium for transferring heat from the puck assembly towards substantially all of the surface of the outer shell element.

In an embodiment the inner shell element comprises a surface element extending through at least a part of the puck assembly, the surface element forming a cavity forming part of the hermetically sealed gas chamber.

Thereby a lighting device is provided which has an enlarged contact surface area between the puck assembly and the inner shell element and therefore is particularly efficient in regards of heat transfer from the puck assembly to the hermetically sealed gas chamber and thus eventually to the surroundings.

In an embodiment the lighting device, the surface element of the inner shell element extends centrally through at least a part of the puck assembly in a substantially longitudinal direction of the puck assembly.

Thereby a lighting device is provided which has a particularly large contact surface area between the puck assembly and the inner shell element and therefore is particularly efficient in regards of heat transfer from the puck assembly to the hermetically sealed gas chamber and thus eventually to the surroundings.

Thereby a lighting device is provided in which the surface area used for heat transfer to the surroundings is optimized and which is thus particularly efficient in regards of heat transfer from the LEDs to the surroundings.

In an embodiment the puck assembly comprises a heat spreading element arranged in heat transferring relationship with the plurality of LEDs and with the inner shell element in an assembled condition of the lighting device. Thereby a lighting device is provided in which is particularly efficient in regards of heat transfer from the LEDs to the hermetically sealed gas chamber and thus eventually to the surroundings.

In an embodiment the puck assembly comprises a driver element adapted for driving the plurality of LEDs and a driver element insulator, the driver element insulator being arranged such as to heat insulate the driver element from the heat spreading element in an assembled condition of the puck assembly.

Thereby a lighting device is provided in which the driver element is shielded from the heat generated by the plurality of LEDs and thus is provided with a prolonged lifetime and enlarged operational reliability.

In an embodiment the lighting device further comprising a shrink sleeve made of a Thermal Interface Material, TIM, and being adapted for extending between at least a part of the puck assembly and the inner shell element in an assembled condition of the lighting device.

Thereby a lighting device is provided in which is particularly efficient in regards of heat transfer from the puck assembly to the inner shell element, and therefore on to the hermetically sealed gas chamber and thus eventually to the surroundings.

In an embodiment the puck assembly comprises a cover element arranged such as to extend over the plurality of LEDs in an assembled condition of the puck assembly.

Thereby a lighting device is provided in which the plurality of LEDs are shielded towards the surroundings such as to avoid deterioration of the plurality of LEDs and/or the intensity of the light emitted due to outside influences such as impurities or the like, to which the plurality of LEDs may be exposed during or after assembly of the lighting device.

The puck assembly may furthermore comprise an electrical connection element.

In an embodiment the puck assembly comprises a spring bush adapted for applying a constant pressure to the plurality of LEDs, the spring bush comprising a rim adapted for alignment of the plurality of LEDs and the heat transferring element in the assembled condition of the puck assembly.

Thereby a lighting device is provided with which it is particularly simple to obtain correct alignment of the plurality of LEDs and the heat transferring element when assembling the puck assembly and subsequently the lighting device. Such a lighting device is thus particularly simple to assemble and thus also less costly to assemble. In an embodiment the puck assembly is in an assembled condition of the lighting device attached to the inner shell element by means of thermally conductive glue.

Thereby a lighting device is provided in which is particularly efficient in regards of heat transfer from the puck assembly, and in particular from the heat spreading element of the puck assembly, to the hermetically sealed gas chamber and thus eventually to the surroundings. Furthermore, a particularly durable lighting device is provided for.

In an embodiment the plurality of LEDs are arranged on a base, the base being arranged such that the plurality of LEDs are arranged in a horizontal or vertical alignment.

Thereby a lighting device is provided which has a high versatility in terms of arrangement of the plurality of LEDs and thus in light pattern.

In an embodiment the substantially one single gas is helium, helium having particularly good heat transferring capabilities and thus being a particularly well functioning medium for transferring heat from the puck assembly towards the outer shell element.

The invention furthermore concerns a lamp, luminaire or system comprising a light emitting device according to any one of the previous claims and being used in one or more of the following applications: consumer lamps or luminaires, professional lamps or luminaires, street lighting, underwater lighting and lighting in extreme environments.

It is noted that the invention relates to all possible combinations of features recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.

Fig. 1 shows a cross sectional side view of a lighting device according to a first embodiment of the invention in an assembled condition.

Fig. 2 shows a perspective sectional view of a lighting device according to Fig.

1.

Fig. 3 shows a cross sectional side view of a lighting device according to a second embodiment of the invention in an assembled condition.

Fig. 4 shows a perspective exploded view of a puck assembly of a lighting device according to Fig. 1 or Fig. 2.

Fig. 5 shows a perspective exploded view of a lighting device according to any of Fig. 1 or Fig. 2 with the puck assembly in an assembled condition. Fig. 6 shows a perspective side view of a lighting device according to a third embodiment of the invention in an assembled condition.

Fig. 7 shows a perspective exploded view of a lighting device according to

Fig. 6.

As illustrated in the figures, the sizes of layers and regions are exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of

embodiments of the present invention. Like reference numerals refer to like elements throughout.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

Fig. 1 shows a cross sectional side view of a lighting device 1 according to a first embodiment of the invention. The lighting device 1 generally comprises a puck assembly 2 and a cover element. The cover element comprises an inner shell element 3 and an outer shell element 4.

The outer shell element 4 comprises an inner surface 41 and an outer surface 42 and is adapted for forming a light exit surface of the lighting device 1 such that light is emitted from the lighting device at the outer surface 42. The outer shell element 4 may be shaped in any feasible manner, such as to form lighting devices having any desired outer shape, including but not limited to for example incandescent lighting devices and candle lighting devices. The outer shell element 4 is transparent or translucent. The outer shell element 4 may be made of glass or a suitable ceramic.

The inner shell element 3 forms a cavity 31 adapted for accommodating the puck assembly 2 at least partially. The inner shell element 3 comprises an inner surface 32 and an outer surface 33. In the assembled condition of the lighting device 1, the puck assembly 2 is in thermal contact with the inner surface 32 of the inner shell element 3 and thus with the inner shell element 3 in general.

As may be seen on Fig. 1 at least an electrical connection member 6 of the puck assembly 2 extends outside of the cavity 31. Apart from that, the inner shell element 3 may be shaped in any feasible manner. The inner shell element 3 is transparent or translucent. The inner shell element 3 may be made of glass or a suitable ceramic and is made of the same material as the outer shell element 4.

As may also be seen on Fig. 1, in the assembled condition of the lighting device 1 a space or distance is provided between the plurality of LEDs 1 1 and the inner surface 32 of the inner shell element 3 and/or between the cover element 13 and the inner surface 32 of the inner shell element 3.

The outer shell element 4 and the inner shell element 3 form together a hermetically sealed gas chamber 5 filled with substantially one single gas. The one single gas is adapted for functioning as a heat transferring medium for transferring heat from the puck assembly 2 towards the outer shell element 4 in a manner to be described further below. The one single gas is in one embodiment Helium. In other embodiments the one single gas may be Hydrogen or Neon. The outer surface 33 of the inner shell element 3 and the inner surface 41 of the outer shell element 4 are in thermal contact with the one single gas in the hermetically sealed gas chamber 5.

The outer shell element 4 and the inner shell element 3 are manufactured as a separate part in one piece using a high temperature glass or ceramics processing method. Thus, the transition 43 between the outer shell element 4 and the inner shell element 3 is a continuous transition.

Alternatively, it may be feasible to manufacture the outer shell element 4 and the inner shell element 3 as a separate part in two pieces using a high temperature glass or ceramics processing method. In this case, the outer shell element 4 and the inner shell element 3 are assembled to form one separate part before assembling the lighting device 1 in such a way that the transition 43 between the outer shell element 4 and the inner shell element 3 is a continuous transition.

Furthermore, the substantially one single gas with which the hermetically sealed gas chamber is filled is adapted for functioning as a heat transferring medium for transferring heat from the puck assembly towards substantially all of the surface of the outer shell element.

In the embodiment shown in Figs. 1 and 2, the inner shell element 3 comprises a surface element 34 extending through at least a part of the puck assembly 2 in the assembled condition of the lighting device 1. The surface element 34 forms or comprises a cavity 51. The cavity 51 forms a part of the hermetically sealed gas chamber 5 and is in direct fluid contact with the hermetically sealed gas chamber 5. Thus the cavity 51 is also filled with the substantially one ingle gas. In the embodiment shown, in the assembled condition of the lighting device 1, the surface element 34 of the inner shell element 3 extends centrally through the puck assembly 2 in a substantially longitudinal direction of the puck assembly 2. The surface element 34 forms a further contact surface with the puck assembly 2 in an assembled condition of the lighting device 1.

The surface element 34 is, however, an optional element. Fig. 3 thus illustrates a second embodiment of a lighting device 100 according to the invention in which the surface element 34 is omitted.

Referring again to Fig. 1, as the puck assembly 2 is arranged in the cavity 31 formed by the inner shell element 3, the puck assembly 2 is arranged outside the hermetically sealed gas chamber 5. Furthermore, the puck assembly 2 is arranged in a heat transferring relationship with the inner shell element 3 and thereby with the substantially one single gas provided in the hermetically sealed gas chamber 5. The materials used for the various components of the puck assembly 2 may be chosen to be compatible with the working fluid.

Referring also to Fig. 4, showing an exploded view of a puck assembly 2, the puck assembly 2 generally comprises a plurality of LEDs 1 1, an optional base 12 on which the plurality of LEDs 1 1 are arranged, a shrink sleeve 14, a heat transferring element 9, an insulator 8, a driver element 7 and an electrical connection member 6.

The puck assembly 2 may furthermore optionally comprise a cover element 13 adapted for covering the plurality of LEDs 1 1. The cover element 13 is transparent and shields the plurality of LEDs 1 1 from the outside against for example dirt and other potentially detrimental influences, such as to increase the life time of the plurality of LEDs 1 1.

The plurality LEDs 1 1 are adapted for, in operation, emitting light, which may be of any desired color. In one embodiment the plurality LEDs 1 1 are adapted for, in operation, emitting white light. In the embodiments shown in Figs. 1 to 5, the plurality of LEDs 1 1 and where present the base 12 are mounted in the puck assembly 2 such a way that the plurality of LEDs 1 1 are oriented in a substantially horizontal position, i.e. in a position perpendicular to the longitudinal extension (illustrated by means of the dash-dotted line shown in Fig. 1 and 2) of the puck assembly 2.

The base 12 carries the plurality of LEDs 1 1, and may be any suitable type of base, such as for example a printed circuit board.

The heat transferring element 9 is adapted for transferring heat generated by the plurality of LEDs 1 1 towards the inner shell element 3 in the assembled condition of the lighting device. The heat transferring element 9 is made of a material with good heat conductive characteristics, such as for example a metal.

The insulator 8 is adapted for, in the assembled condition of the puck assembly 2, insulating the driver element 7 from the heat transferring element 9, and thus from the heat generated by the plurality of LEDs 1 1. The insulator 8 is thus made of a heat insulating material.

The driver element 7 may be any driver element suitable for driving the plurality of LEDs to emit light in a suitable and desired manner.

The electrical connection member 6 may be any electrical connection member suitable for connecting the lighting device 1 to a source of electrical energy. Typically, the electrical connection member 6 is a socket. In an alternative, the electrical connection member 6 is a terminal.

The puck assembly 2 further comprises a shrink sleeve 14. The shrink sleeve 14 is adapted to function as an expandable thermal interface material and acts to hold the puck assembly 2 together in its assembled condition.

When assembling the puck assembly 2, one first inserts the driver element 7 into the insulator 8. Then the insulator 8 with the driver element 7 is inserted into the heat transferring element 9.

Next, the plurality of LEDs 1 1, optionally arranged on the base 12, is mounted on the heat transferring element 9. This may be done by means of a suitable thermal interface material, for example a thermal paste or glue. Thereby, the heat transferring element 9 is brought to be arranged in heat transferring relationship with the plurality of LEDs 11.

Then, leads of the driver element 7 are soldered to the plurality of LEDs 1 1 and the cover element 13 is mounted such as to cover the plurality of LEDs 1 1.

Next, the electrical connection element 6 is mounted onto the insulator 8, for example by snapping, pinching or gluing it onto the insulator 8.

Then, an anode is soldered onto the electrical connection element 6 or, alternatively, a clip is pressed into the electrical connection element 6, such as to enable electrical connection between the electrical connection element 6 and a source of electrical energy.

Finally, the shrink sleeve 14 is arranged over the puck assembly 2. More particularly, the shrink sleeve 14 is arranged such as to extend over the heat transferring element 9 and overlap with the insulator 8 on the one side and, where present, the cover element 13 on the other side. To complete the assembly of the lighting device 1 the puck assembly 2 is inserted into the cavity 31 formed by the inner shell element 3 (cf. Fig. 5) where it is glued to the surface of the inner shell element 3 facing the cavity 31 by means of suitable thermal interface material or glue 15 (cf. Fig. 2). The now assembled lighting device 1 is heated to shrink the shrink sleeve 14. Thereby, the heat spreading element 9 is brought to be arranged in heat transferring relationship with the inner shell element 3 via the thermal interface material or glue 15.

The thus assembled puck assembly 2 and lighting device 1 is illustrated on

Figs. 1 and 2.

Turning now again to Fig. 3, the flow or transfer of the heat generated by the plurality of LEDs 1 1 through a lighting device according to the invention will now be explained.

The heat is generated by the plurality of LEDs 1 1. From the plurality of LEDs 1 1 , the heat flows as illustrated by the arrow 16 through the thermal interface material by means of which the plurality of LEDs 1 1 , optionally arranged on the base 12, is mounted on the heat transferring element 9, to the heat transferring element 9. From the heat transferring element 9 the heat flows as illustrated by the arrow 17 along the heat transferring element 9 through the thermal interface material or glue 15 affixing the puck assembly 2 to the inner surface 32 of the inner shell element 3 through to the outer surface 33 of the inner shell element 3 and into the hermetically sealed gas chamber 5 where the heat heats up the substantially one single gas. By means of the thus heated substantially one single gas, the heat then flows as illustrated by the arrows 18 through the hermetically sealed gas chamber 5 to the inner surface 41 of the outer shell element 4, which is colder than the inner shell element 3. Finally, the heat flows through the outer shell element 4 and is as illustrated by the arrows 19 transferred from the outer surface 42 to the surroundings, thus cooling down the substantially one single gas.

The thus cooled down substantially one single gas will subsequently flow back towards the warmer inner shell element 3, thus completing the heat transfer cycle.

Turning now to Figs. 6 and 7, a perspective side view and a perspective exploded view, respectively, of a lighting device 101 according to a third embodiment of the invention is shown.

The lighting device 101 is very similar to that described above in relation to the two first embodiments shown in Figs. 1 to 5, and thus only those features that differ from from the above will be described in the following. The lighting device 101 comprises a plurality of LEDs 1 1. The plurality of LEDs 1 1 and where present the base 12 are mounted in the puck assembly 2 such a way that the plurality of LEDs 1 1 are oriented in a substantially vertical position, i.e. in a position parallel with the longitudinal extension of the puck assembly 2.

The heat transferring element 9 is therefore arranged over the plurality of

LEDs 1 1. To enable this arrangement the heat transferring element 9 is provided with a plurality of openings 91 dimensioned and sized such as to each provide for a clearance or gap between the respective LED of the plurality of LEDs 1 1 and the heat transferring element 9. The clearance or gap provided by the respective openings 91 is arranged adjacent to the solder points providing the electrical connection to the respective LED of the plurality of LEDs 1 1 and thereby provide an electrical clearance.

In this embodiment the heat transferring element 9 may be a flexible element, for example made of a graphite sheet or a suitable metal sheet. In case of a graphite sheet, an example would be those produced by GrafTech, one such being their model SS400 a graphite sheet having a thickness of 0.94 mm and a thermal conductivity of 400 W/mK.

Where a base 12 is provided for, the base 12 may likewise be a flexible base, such as a flexible printed circuit board, for example of a PA, PI or FR4 type material.

Furthermore, with reference especially to Fig. 7, the puck assembly 2 comprises in this embodiment a spring bush 20. The spring bush 20 is in the assembled condition of the puck assembly 2 arranged extending inside of and abutting the heat transferring element 9 or, where present, the base 12. The spring bush 20 further comprises a rim 201 adapted for alignment of the plurality of LEDs 1 1 and the heat transferring element 9. Thereby easy assembly of the puck assembly 2 as well as of the puck assembly 2 with the inner shell element 3 is provided for.

The spring bush 20 may be a simple plastic element, or alternatively a metal element, adapted for applying a constant pressure to the plurality of LEDs 1 1 and, where present, the base 12, such as to allow a good thermal contact with the inner shell element 3.

A lighting device 1, 100, 101 according to the invention may find application in many diverse fields. Non-limiting examples are consumer lamps, such as candles, bulbs, spot lights, TLED, professional lamps, especially street light lamps such as SON, SOX, HPL, ML lamps, consumer luminaires, such as indoor luminaires, professional luminaires, such as indoor spots, and outdoor luminaires, street lights, integrated lamp-luminaire designs. Further applications being enabled as the lighting devices according to the invention are watertight and can be easily coated with to prevent organic growth include special lighting such as lighting in extreme environments, e.g. in pigsties with high ammonia levels, and underwater lighting.

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.

Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person 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. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.