EP2459925B1 - Light bulb - Google Patents

Description

The invention relates to a lamp which has a heat sink which carries at least one light source, in particular at least one semiconductor light element, and also a cover attached to the heat sink.

In general, light-emitting diodes (LEDs) have lower brightness and lower lifetimes at higher temperatures. In LED retrofit lamps, a heat sink is used to dissipate heat or cool the LED (s). However, the available space for the heat sink is limited by a mostly standardized outer contour of the lamp to be replaced and a space required for a piston and a driver electronics. Due to the spatial limitation, the size of the effectively usable for cooling volume of the heat sink is limited and thus the cooling capacity. With the LED lamps with standard-limited size, the power of the light source and thus the brightness are limited according to the limited cooling capacity.

US 2007/0080362 A1 discloses an LED array having a high power LED chip having a first surface and a second surface, wherein the second surface is mounted on a substrate. The second surface is in intimate thermal contact with a translucent heat sink having a thermal conductivity greater than 30 W / (m · K). Providing the translucent heat sink can double the heat conduction from the LED dies, increasing lifetime, efficiency or luminosity, or balancing these three.

From the GB 2 428 467 A For example, a lamp is known in which a cover with a bead is fastened by means of a retaining ring on a heat sink. From the DE 20 2007 008 258 U1 is a lamp with a piston which is bent at its socket-side end known.

It is the object of the present invention to provide by simple means an improvement in heat dissipation of a lamp, in particular of the type mentioned.

This object is achieved according to the features of the independent claims. Preferred embodiments are in particular the dependent claims.

The object is achieved by a lamp, which has at least: a heat sink, which carries at least one light source, and an attached to the heat sink, at least partially translucent (transparent or translucent or opaque) cover or cover for the at least one light source, in particular Semiconductor lighting element, wherein the cover has a wall thickness, which tapers at least in sections continuously with increasing distance from the heat sink. In other words, the cover has a wall thickness which increases at least in sections as the proximity to (nearer to) the heat sink increases.

Due to the comparatively large wall thickness in the region of the heat sink, a correspondingly large contact area is created between the cover and the heat sink. As a result, a greater heat transfer from the heat sink in the cover is made possible as it is possible without the widened wall thickness. Consequently, the cover is heated more and gives off more heat to the environment. In other words, the widened (thermal) contact surface allows for higher heat loss across the cover. A thick wall thickness at a greater distance from the heat sink or the contact surface does not result in a significantly increased cooling effect due to the laterally distributing (laterally directed) heat flow in the cover, because by the heat dissipation to the environment (heat dissipation) at a greater distance From the contact surface less and less heat arrives through the direct lateral heat conduction.

Due to the heat dissipation through the cover or its surface better cooling of the light sources can be achieved without changing the size of the lamp. This can be dissipated without a significant increase in the dimensions of the lamp larger loss lines.
Generally, the type of light source is not limited. However, it is preferred if the at least one light source comprises at least one semiconductor light source, for example a light-emitting diode or a diode laser. Particularly preferred is the use of at least one light emitting diode as the at least one light source. In this case, the nature of the at least one light-emitting diode is not limited, but may comprise, for example, a plurality of individual LEDs or one or more LED clusters of LED chips applied to a common substrate. The color (s) of the at least one light emitting diode is also not limited and may include, for example, 'white'. The at least one light-emitting diode may be an inorganic or an organic light-emitting diode. The light sources can generally be equipped with downstream optics.
It is an embodiment that the cover has a greatest wall thickness at a contact surface to the heat sink. This allows a particularly high heat dissipation from the heat sink into the cover.
According to the invention, the wall thickness of the cover tapers continuously with increasing distance from the heat sink. Continuously reducing the wall thickness of the cover as the distance from the heat sink or contact pad to the heat sink increases, provides a good compromise between lateral and transverse heat conduction into and through the cover in the various regions of the cover.

It is an alternative embodiment, which is not part of the invention, that the wall thickness of the cover tapers in sections with increasing distance from the contact surface to the heat sink and then the wall thickness of the cover remains substantially constant.

A small wall thickness of the cover in a region remote from the heat sink, in particular in the greatest distance from the heat sink, is advantageous because there is a cooling to the ambient air largely by a transverse heat flow from a heated interior or receiving space is generated and not by the lateral Heat flow from the heat sink. The lower the wall thickness of the cover, the more effective the transverse heat flow. A small wall thickness of the cover is also advantageous from an optical point of view, since a transmission increases with decreasing wall thickness of the cover and thus at least the radiated brightness is attenuated to a lesser extent.

Also according to the invention, the cover is attached to the heat sink by means of at least one good heat conducting adhesive. The use of the adhesive has the advantage that the connection or the contact surfaces between the heat sink and the cover is geometrically simple ausgestaltbar, in particular, the connection to planar contact surfaces is possible.

The adhesive may be a thermally highly conductive adhesive, e.g. a thermal grease, a thermal adhesive or at least one Wärmeleitpad. Generally, the effect of the adhesive on heat transmission should be minimized. However, the invention is not limited to the selection of a thermally well conductive adhesive. Thus, with a small thickness of the adhesive, e.g. a thin adhesive layer, an influence of the thermal conductivity coefficient of the adhesive on a heat flow through the adhesive with a sufficiently large contact area for most adhesives low.

Alternatively, the cover can also be attached to the heat sink by means of mechanical connection means, for example by means of a plug connection or a clamp or clamp connection, etc. In this case, a small air gap between be present to the heat sink and the cover. If this air gap is narrow enough, with a sufficiently large contact surface, a significant heat transfer through the air gap can also take place. The contact surface of the cover is then a purely thermal contact surface or heat transfer surface.

Alternatively, the cover may also be screwed into the heat sink, the cover being e.g. on its contact surface with the heat sink, a helical shape and the heat sink may have a matching thread shape. This further increases the contact area between the cover and the heat sink.

The material of the cover basically does not need to be selected according to its thermal conductivity. Thus, a standard plastic or glass may be used for the cover, e.g. a conventional lamp envelope material. However, a good heat conductive material is preferred. Good heat conduction enhances lateral heat distribution in the cover, increasing the effective cooling area within the cover and allowing more heat to be dissipated to the environment. At the same time, the good heat conduction enhances transverse heat conduction from an inner space surrounded by the cover through the cover.

It is also an embodiment that the cover is made of glass. The use of glass has the advantage that glass is relatively inexpensive, colorable, easy to shape and resistant to aging. Furthermore, glass can simply be roughened or otherwise diffusely scattered in order not to make the light source directly visible from the outside.

It is a special embodiment that the cover, for example, has a thermal conductivity between 1 W / (m · K) and 2 W / (m · K). In particular, a thermally conductive Glass with a thermal conductivity coefficient λ of about 1.2 W / (m K) or more preferred. While conventional glasses, such as window glass, have a coefficient of thermal conductivity λ between 0.8 and 1.0 W / (m K), eg borofloat glass has a λ of about 1.2 W / (m K), N-BK10 a λ of about 1.32 W / (m K) and Zerodur a λ of about 1.46 W / (m K). Due to the comparatively high thermal conductivity, a large-area heat distribution in the cover and thus an efficient heat dissipation over the outer surface of the cover is achieved.

Alternatively, for example, the use of a translucent plastic (eg polycarbonate) or a translucent ceramic (eg an alumina ceramic) is possible. Thus, a translucent ceramic can achieve a thermal conductivity coefficient λ of 30 W / (m K) or more. Translucent ceramics can be used in all modifications, that is, for example, monocrystalline (ie, in the case of aluminum oxide as sapphire), quasi-monocrystalline or polycrystalline. In particular, alumina and here especially sapphire are characterized by a high thermal conductivity, resistance to environmental influences and good availability.
As a plastic, for example, a filled with a highly thermally conductive material plastic can be used.

It is also an embodiment that the cover has a dome-like shape. Such a cover is particularly suitable, for example, for a retrofit bulb.

The cover may alternatively have an open or a closed tubular shape. Such a cover is suitable, for example, for a retrofit fluorescent tube or a retrofit line lamp (eg of the Linestra type from Osram).

It is a special embodiment that a (in particular thermal) contact surface of the cover to the heat sink at least partially corresponds to a (lower) bearing surface of the cover. In the dome-like shape and the open tubular shape, the contact surface of the cover at the same time represents the bearing surface of the cover on the heat sink and thus usually the lowest point. In particular, the wall thickness can decrease with increasing distance from the contact surface or with increasing height, in particular reduce it continuously. The highest point, the apse, thus has the lowest wall thickness.

It is an alternative embodiment that the cover has a disk-like shape. As a result, the cover is suitable in particular for a PAR (Parabolic Aluminized Reflector) - headlight retrofit lamp or luminaire or for its illuminant. The cover is also particularly suitable for lamps or retrofit lamps of the type MR16, alternatively also for other MR lamp shapes, e.g. MR11 or MR8.

It is then a further special embodiment that a contact surface of the cover is arranged laterally to the heat sink. In the disc-like shape, the contact surface of the cover at the same time represents the lateral contact surface of the cover (which usually corresponds to the side edge of the cover) on the heat sink and thus usually the outermost point. In particular, the wall thickness may decrease with increasing distance from the contact surface. The innermost point of the cover, in particular its center, thus has the lowest wall thickness.

It is a further embodiment that the cover has an optical function. This has the advantage that at the same time a beam guidance or beam correction is made possible.

It is an alternative embodiment that the cover is a substantially optically inactive cover, so essentially serves to protect the lamp.

It is a further embodiment that the at least one light source, in particular semiconductor light-emitting element, is fastened on the heat sink via at least one substrate. For example, the substrate may be a substrate of an LED cluster, i. a common substrate for multiple LED chips, his. The substrate may additionally or alternatively comprise at least one printed circuit board, e.g. for contacting the LED cluster or at least one individual LED (LED module) and, if appropriate, for equipping with electronic components.

It may be a further embodiment that the cover has an at least shell-side closed tubular shape and the heat sink is at least partially received by the cover and at least partially attached to a lower portion of the cover, wherein the lower portion of the cover and an upper portion of the cover a comparatively smaller wall thickness than the two lateral areas of the cover.

It is a further advantageous embodiment that the cover on its inner side is substantially free of undercuts, that is, has substantially no undercut. This gives the possibility of production by injection molding (plastic) or pressing (glass or ceramic). The inside of the cover limits the interior of the lamp.

It may be a special embodiment that the cover has on its inside at least laterally substantially straight contours. This simplifies manufacturing by injection molding or pressing particularly.

• Eine Lampe, insbesondere eine LED-Lampe, weist einen Sockel, einen Kühlkörper, ein LED-Modul und eine semitransparente oder transparente Abdeckung, z.B. einen Lampenkolben bzw. eine semitransparente oder transparente Optik oder Abdeckscheibe auf.

Die Abdeckung (z.B. der Kolben/ die Optik / die Abdeckscheibe) ist vorzugsweise zum Kühlkörper hin dicker ausgeführt und weist eine breitflächige Anbindungsfläche bzw. Kontaktfläche zur thermischen Anbindung an den Kühlkörper auf.It is still an embodiment that the lamp is a retrofit lamp whose outer contour does not or not significantly beyond an outer contour of a lamp to be replaced.
In particular, for use with an incandescent retrofit lamp, it is advantageous that the cover in its outer dimensions of the contour, in particular rounding, follows the bulb to be replaced. This preferably applies analogously retrofit lamps to replace a lamp of conventional type, such as a line lamp, reflector lamp, etc.
In particular, the invention may comprise one or more of the following features:

• A lamp, in particular an LED lamp, has a base, a heat sink, an LED module and a semitransparent or transparent cover, for example a lamp bulb or a semitransparent or transparent optic or cover disk.

The cover (for example, the piston / the lens / cover) is preferably made thicker towards the heat sink and has a wide-area connection surface or contact surface for thermal connection to the heat sink.

The cover is over the contact surface by means of a good thermally conductive adhesive, e.g. a paste, an adhesive and / or a pad, etc. connected to the heat sink. The adhesive may in particular be a TIM (Thermal Interface Material).

Fig.1

zeigt in Seitenansicht teilweise im Querschnitt eine Kolben-Retrofitlampe;

Fig.2

zeigt einen Ausschnitt aus der Glühlampen-Retrofitlampe aus Fig.1 im Bereich einer Abdeckung;

Fig.3

zeigt in Seitenansicht teilweise im Querschnitt eine Reflektor-Retrofitlampe;

Fig.4

zeigt in Schrägansicht eine Querschnittsdarstellung einer Leuchtstoffröhren- oder Linienlampen-Retrofitlampe;

Fig.5

zeigt in Vorderansicht eine Querschnittsdarstellung der Retrofitlampe aus Fig.4; und

Fig.6

zeigt in Vorderansicht eine Querschnittsdarstellung einer weiteren Leuchtstoffröhren- oder Linienlampen-Retrofitlampe;

Fig.7

zeigt in Vorderansicht eine Querschnittsdarstellung eine Leuchtstoffröhren- oder Linienlampen-Retrofitlampe gemäß einer nicht beanspruchten Ausführungsform;

Fig.8

zeigt in Seitenansicht teilweise im Querschnitt eine Kolben-Retrofitlampe gemäß einer weiteren, nicht beanspruchten Ausführungsform;

Fig.9

zeigt in Seitenansicht teilweise im Querschnitt eine Kolben-Retrofitlampe gemäß noch einer weiteren, nicht beanspruchten Ausführungsform.

The cover becomes thinner as the distance from the heat sink contact surface increases.
In the following figures, the invention will be described schematically with reference to exemplary embodiments. there For the sake of clarity, the same or equivalent elements may be given the same reference numbers.

Fig.1

shows in side view partially in cross section a piston retrofit lamp;

Fig.2

shows a section of the incandescent retrofit lamp Fig.1 in the area of a cover;

Figure 3

shows in side view partially in cross section a reflector retrofit lamp;

Figure 4

shows in oblique view a cross-sectional view of a fluorescent tube or line lamp retrofit lamp;

Figure 5

shows in front view a cross-sectional view of the retrofit lamp Figure 4 ; and

Figure 6

shows in front view a cross-sectional view of another fluorescent tube or line lamp retrofit lamp;

Figure 7

shows in front view a cross-sectional view of a fluorescent tube or line lamp retrofit lamp according to a not claimed embodiment;

Figure 8

shows in side view partially in cross section a piston retrofit lamp according to another, not claimed embodiment;

Figure 9

shows in side view partially in cross section a piston retrofit lamp according to yet another, not claimed embodiment.

Fig.1 shows in partial side view of an incandescent retrofit lamp 1. The incandescent retrofit lamp 1 has a heat sink 2 shown in side view, which has an angle substantially symmetrical about a longitudinal axis L of the incandescent retrofit lamp 1 shape. In this case, 3 radially outwardly directed cooling fins 4 are provided on the outside of the lateral surface. On a bottom 5 of the heat sink 2, a base 6 for a light bulb socket shown in side view is present, for example, an Edison socket.

On an upper side 7 of the heat sink 2, an LED module 8 is fixed, which is powered by the base 6 with power. The LED module 8 has at least one substrate in the form of a printed circuit board 9. On the circuit board 9 there are one or more light-emitting diodes 10, here in the form of an LED cluster, in which a plurality, possibly also differently colored, LED chips are mounted on a common substrate ("Submount"). The circuit board 9 may also be additionally populated with other electronic components, e.g. a driver block.

On the upper side 7 of the heat sink 2, a dome-shaped cover 11 shown in cross-section is further glued. The cover 11 is rotationally symmetrical about the longitudinal axis L and the LED module 8 vaulted over completely. Through the cover 11 and the heat sink 2, a receiving space for the LED module 8 and an interior 12 of the incandescent retrofit lamp 1 is thus created. The cover 11 is flat with a lower contact surface 13 by means of an adhesive 14 and just on the heat sink 2.

The adhesive 14, by means of which the cover 11 adheres to the heat sink 2, can be realized, for example, as a thin adhesive layer of silver conductive adhesive or an adhesive filled with a conductive ceramic.

The cover 11 is opaque to support a substantially homogeneous radiation characteristic, which is at least approximate to that of a conventional light bulb.

The cover 11 has a wall thickness d, which tapers continuously with increasing distance (increasing height) from the heat sink 2. Consequently, the contact surface 13, which simultaneously represents the lower attachment surface of the cover 11, forms the region of the cover 11 with the highest wall thickness d.

The cover 11 is made of a glass having a thermal conductivity λ in a range between 1 W / (m · K) and 2 W / (m · K), e.g. a borofloat glass.

The cover 11 is substantially optically inactive, thus has no function a lens or the like. on.

The function of the cover 11 will be explained in more detail below.

Fig.2 shows a section of the incandescent retrofit lamp 1 in the region of the cover 11. When operating the LED module 8, this is heated due to heat loss of the LEDs 10 and possibly other electronic components. The heat loss W is partially transmitted to the heat sink 2 and partially discharged into the receiving space 12. The heat sink 2, in turn, transmits the heat W to the environment essentially by heat convection or radiant heat, in particular via the cooling fins 4.

However, part of the heat W of the heat sink 2 is transmitted to the cover 11 through the adhesive layer 14 and further through the contact surface 13. There, the heat W spreads by means of a lateral heat conduction (a laterally directed heat flow WL) within the cover 11. This emanating from the contact surface 13 warming the cover 11th causes the heat of the laterally directed heat flow WL is discharged through an outer side 15 of the cover 11 by heat convection or radiant heat to the environment, as indicated by the outgoing from the cover 11 outward arrows WL. Due to the heat emission to the outside (heat dissipation), the laterally directed heat flow WL becomes increasingly smaller as the distance from the contact surface 13 increases.

Due to the heated receiving space 12, however, also a transversely directed heat flow WT from the receiving space 12 occurs substantially vertically through the cover 11 to the outside. The two heat flows or heat distributions WL and WT overlap in the cover 11.

At and shortly behind the contact surface 13, the laterally directed heat flow WL will predominate, and away from the contact surface 13, the transversely directed heat flow WT. Especially at the highest point of the cover 11, the apse A, the influence of the laterally directed heat flow WL is lowest.

Due to the relative broadening of the wall thickness d to the contact surface 13 towards the laterally directed heat flux WL is amplified and thus the cover 11 is heated more. Thus, a heat dissipation from the cover 11 is amplified to the outside, which in turn causes increased heat dissipation from and improved cooling of the LED module (s) 8.

On the other hand, it is achieved by the relative reduction of the wall thickness d with increasing distance from the contact surface 13, that a passage of the transversely directed heat flow WT is only slightly hindered by the cover 11, so the heat insulating effect of the cover 11 is low. The smallest wall thickness d thus occurs at the apse A. The wall thickness d at each point of the cover can thus be optimized for maximum heat output to the outside become. Due to the heat fluctuations WT and WL, which typically do not change locally, in most cases a continuous change in the wall thickness d will allow particularly effective heat removal.

For an incandescent retrofit lamp 1, a change in the wall thickness d from the contact surface 13 to the apse A may advantageously be in a range between one-half and one-fifth. In other words, the wall thickness d at the contact surface may preferably be a factor of two to five times wider than at the apse A, in particular approximately four times.

Figure 3 shows in side view partly in cross-section another retrofit lamp 16, for example for use in a lamp of the type MR16 or as a PAR illuminant, eg PAR 30. In contrast to the incandescent retrofit lamp 1 off Fig.1 and Fig.2 the heat sink 17 is now cup-shaped with an upper opening 18. The opening 18 is covered by a cover 19 with a disc-like basic shape. The cover 19 and the heat sink 17 again form a receiving space 12 for the LED module. 8

In this exemplary embodiment, the contact surface 13 does not correspond to a lower support surface but to a lateral edge surface of the cover 19 which is slightly beveled for a secure fit on the heat sink 17.

In an embodiment of Fig.1 and Fig.2 In principle, a laterally directed heat flux WL is also generated by the heat sink 17 through the contact surface 13 into the cover 19, which becomes weaker the farther it moves away from the contact surface 13 or closer to a center M of the cover 19 is coming. The laterally directed heat flow WL is also superimposed by a transversely directed heat flow WT, which transports heat out of the receiving space 12 through the cover 19 to the outside.

At the midpoint M, the relative influence of the laterally directed heat flow WL is lowest, and consequently that of the transversely directed heat flow WT is greatest, so that for effective heat dissipation from the cover 19 to the environment there, a smaller wall thickness d is preferred than at the edge. On the other hand, in order to generate a strong lateral heat flow WL, a greatest wall thickness d at the contact surface 13 or at the edge region of the cover 19 is preferred.

Figure 4 shows an oblique view of a cross-sectional view of a fluorescent tube or line lamp retrofit lamp 20th Figure 5 shows the fluorescent tube or line lamp retrofit lamp 20 as a sectional front view.

The retrofit lamp 20 has a substantially tubular basic shape and is used e.g. as a substitute for a conventional fluorescent tube or a line lamp. A lower region of the retrofit lamp 20 has a heat sink 21 which extends in an elongate manner along a longitudinal axis L of the retrofit lamp 20 and has a plate-shaped base 22. On an upper surface of the plate-shaped base 22, a plurality of light emitting diodes 10 are arranged equidistantly along the longitudinal direction L, e.g. on a flexible band-shaped carrier 9. This can be realized, for example, by an LED module 8 in the form of an LED strip of the type LinearLight Flex from Osram. At an underside of the plate-shaped base 22, a plurality of cooling fins 4 are perpendicular downward.

On the upper side 7 of the heat sink 21, a correspondingly fitting elongated cover 23 is attached, which forms the receiving space 12 for the LED module 8 with the heat sink 21. In cross section, the shape of the cover 23 of the shape of the cover 11 from Fig.1 and Fig.2 substantially, so that the operation of the cover 23 at this point does not need to be carried out further, but analogous to Fig.1 and Fig.2 is referenced.

Figure 6 shows in front view a cross-sectional view of another fluorescent tube or line lamp retrofit lamp 24. In contrast to the embodiment of Figure 4 and Figure 5 the heat sink 25 with the LED module 8 is now completely surrounded by a tubular cover 26 at least on the shell side. Further, the heat sink 25 is formed of a solid material, so that it forms with the cover 26 a large-area contact surface 27, which occupies a large part of the lower half of the cover 26.

In this case, lateral vertices S have the greatest wall thickness d, while an upper vertex A1 and a lower vertex A2 have the lowest wall thickness d. It is assumed that the LED module 8 radiates into an upper half-space and the heat sink 25 is placed on a lower portion of the cover 26.

In other words, the cover 26 has an at least shell-side closed tubular shape, and the heat sink 25 is at least partially received in the cover 26. The heat sink 25 is mostly fixed to a lower portion I (lower quarter sector) of the cover 26, wherein the lower portion I and an upper portion II (upper quarter sector) of the cover 26 opposite thereto may have a comparatively smaller wall thickness d than the two lateral portions III (lateral quarter sectors) of the cover 26. In this case, the sectoring starts from a cutting line which at least essentially corresponds to the longitudinal axis L.

In particular, the wall thickness d of the cover 26 changes continuously and has the lowest wall thickness d in the upper region I at an upper vertex A1 and in the lower region II at a lower vertex A2.

By contrast, the two lateral vertices S, which are located in the respective lateral region III, the locations of the largest wall thickness d.

Such a shape of the cover 26 may for example be produced so that a cross-sectional contour of an inner side 28 of the cover 26 is substantially circular, while a cross-sectional contour of an outer side 29 of the cover 26 has a substantially oval shape.

The cover 26 thus has a wall thickness d for its upper half or its upper portion above the lateral vertices S, which tapers with increasing distance from the heat sink 25 or its contact surface 27 with the heat sink 25.

While the transversely directed heat flow WT dominates in the upper region I, it has been shown that a low wall thickness d is also advantageous at the lower region II, since there a direct heat dissipation from the heat sink 25 in the transverse direction through the cover 26 passes It has also been found that an increased wall thickness d in the lateral regions III of the cover 26 allows a more effective heat release than an optimization with respect to a transversely directed heat radiation Heat dissipation through the cover 26 therethrough.

Figure 7 shows in front view a cross-sectional view of a retrofit lamp 30 in the form of a fluorescent tube or line lamp retrofit lamp according to another embodiment. The cover 31 is in contrast to the retrofit lamp 20 off Figure 4 carried out on its outer side 15 only semi-cylindrical, so that they can be dissolved out in their preparation from a mold. On its inside 32 (which together with the base 22 of the heat sink 21, the receiving space 12 limited) it is also free of undercuts. In particular, the inner side 32 is designed in order to simplify a production by injection molding or pressing process such that a lateral surface 33 or side wall of the inner side 32 extends perpendicularly from the lower side of the cover 31. On the other hand, a ceiling surface 34 which adjoins the lateral surface 33 upwards and which covers the receiving space 12 is curved again, in particular in the form of a cylindrical sector.

The wall thickness d is greatest at the contact surface 13 and decreases continuously in a portion 35 or region which includes the lateral surface 33 as the distance from the contact surface 13 increases. The adjoining portion 36 or region containing the ceiling surface 34, however, has a constant wall thickness d. The cover 31 thus continues to have as the retrofit lamp 20 at the contact surface 13 to the heat sink 21, a greater wall thickness d than at the farthest from the heat sink 21 point, namely the (linear) Apse A. Specifically, the wall thickness d at the Contact area 13 largest.

Alternatively, the section 36 can also taper further from its approach on the section 35 to the apse A back.

Figure 8 shows in side view partially in cross section a retrofit lamp 37 in the form of a piston retrofit lamp according to another embodiment.

The cover 38 is in contrast to the retrofit lamp 1 off Fig.1 and Fig.2 executed on its outer side 15 only hemispherical, so that they can be dissolved out in their preparation from a mold. On its inner side 32 (which limits the receiving space 12 together with the heat sink 2), it is also free of undercuts. Especially is the inner side 32 designed to simplify manufacture by injection molding or pressing process so that a lateral surface 33 or side wall of the inner side 32 from the bottom of the cover 31 is perpendicular starting, ie, for example, have a cylindrical shape or cylindrical group of merging vertical surfaces can. On the other hand, a ceiling surface 34 which adjoins the lateral surface 33 and which overhangs the receiving space 12, is again arched upwards or domed, in particular spherical, in shape.

The wall thickness d is greatest at the contact surface 13 and decreases in a portion 35 or region continuously with increasing distance from the contact surface 13, which includes the lateral surface 33. The subsequent section 36 or area, which includes the ceiling surface 34, however, has a constant wall thickness d. Consequently, the cover 38 continues to have, like the retrofit lamp 1, a greater wall thickness d at the contact surface 13 to the heat sink 2 than at the point furthest from the heat sink 2, namely the (point-shaped) apse A.

Alternatively, the section 36 can also taper further from its attachment to the section 35 towards the apse A.

Figure 9 shows in side view partially in cross section a retrofit lamp 39 in the form of a piston retrofit lamp according to yet another embodiment. In contrast to the retrofit lamp 37, it now has no cover 40 with a hemispherical outer side, but a more than hemispherical outer side 15 as the cover 11 Fig.1 and Fig.2 , At the same time, the cover 40 has on its inner side 32 a vertical lateral surface 33.

Consequently, the wall thickness d is no longer greatest at the contact surface 13, but at a greatest lateral extent the cover 40 at a small distance from the contact surface 13 and decreases from there continuously with increasing distance from the contact surface 13. But also this cover 40 has at the contact surface 13 to the heat sink 2 has a greater wall thickness d than that of the heat sink This cover 40 has the advantage of greater heat dissipation from the heat sink 2 over a cover with a constant wall thickness, in particular a small wall thickness such as in the region of the apse A, for example.

Of course, the present invention is not limited to the embodiments shown.

Thus, furthermore, the cover of the shell-side closed tubular cover need not be symmetrical with respect to a longitudinal axis.

The difference in wall thickness d between the thickest point of the cover and the thinnest part of the cover may generally preferably take a factor between two and five.

LIST OF REFERENCE NUMBERS

1

Incandescent retrofit lamp

2

heatsink

3

Lateral surface of the heat sink

4

cooling fin

5

Bottom of the heat sink

6

base

7

Top of the heat sink

8th

LED module

9

circuit board

10

led

11

cover

12

accommodation space

13

contact area

14

adhesive layer

15

Outside of the cover

16

retrofit

17

heatsink

18

Opening of the heat sink

19

cover

20

retrofit

21

heatsink

22

Base of the heat sink

23

cover

24

retrofit

25

heatsink

26

cover

27

contact area

28

Inside of the cover

29

Outside of the cover

30

retrofit

31

cover

32

inside

33

lateral surface of the inside

34

Ceiling surface of the inside

35

Section of the cover

36

Section of the cover

37

retrofit

38

cover

39

retrofit

40

cover

A

apse

A1

upper vertex

A2

lower vertex

I

lower area

II

upper area

III

lateral area

L

longitudinal axis

M

Focus

S

lateral vertex

WL

laterally directed heat flow

WT

transversely directed heat flow

Claims (12)

1. Lamp (1; 16; 20; 24), comprising at least:

   - a heatsink (2; 17; 21; 25) which supports at least one light source (10), in particular a semiconductor light-emitting element, especially a light-emitting diode, and

   - a cover (11; 19; 23; 26) for the at least one light source (10), which is attached to the heatsink (2; 17; 21; 25) and is at least partly translucent,

   - wherein the cover (11; 19; 23; 26) has a wall thickness (d) which tapers at least in some sections with increasing distance from the heatsink (2; 17; 21; 25),

   - wherein the cover (11; 19; 23; 26) is attached to the cooling body (2; 17; 21; 25) by means of at least one highly thermally conductive adhesive (14),

   - characterised in that the wall thickness (d) of the cover (11; 19; 23; 26) tapers continuously with increasing distance from the cooling body (2; 17; 21; 25).
2. Lamp (1; 16; 20; 24), in particular according to claim 1, comprising at least:

   - a heatsink (2; 17; 21; 25) which supports at least one light source (10), in particular a semiconductor light-emitting element, especially a light-emitting diode, and

   - a cover (11; 19; 23; 26) for the at least one light source (10), which is attached to the cooling body (2; 17; 21; 25) and is at least partly translucent,

   - wherein the cover (11; 19; 23; 26) at a contact face (13) to the heatsink (2; 17; 21; 25) has a greater wall thickness (d) than at the point (A) spaced furthest apart from the heatsink (2; 17; 21; 25),

   - wherein the cover (11; 19; 23; 26) is attached to the heatsink (2; 17; 21; 25) by means of at least one highly thermally conductive adhesive (14),

   - characterised in that the wall thickness (d) of the cover (11; 19; 23; 26) tapers continuously with increasing distance from the cooling body (2; 17; 21; 25).
3. Lamp (1; 16; 20) according to any of the preceding claims, wherein the cover has the greatest wall thickness (d) at a contact face (13) to the heatsink (2; 17; 21).
4. Lamp (1; 16; 20; 24) according to any of the preceding claims, in which the cover (11; 19; 23; 26) has a thermal conductivity of between 1 W/(m·K) and 2 W/(m·K), in particular is made of glass with a thermal conductivity of between 1 W/(m·K) and 2 W/(m·K).
5. Lamp (1; 37; 39) according to any of the preceding claims, in which the cover (11) has at least in some sections a dome-like form.
6. Lamp (20) according to any of claims 1 to 4, in which the cover (23) has an open tubular form.
7. Lamp (1; 20; 30) according to any of the preceding claims, in which a contact face (13) of the cover (11; 23) to the heatsink (2; 23) corresponds at least partly to a lower bearing surface of the cover (11; 23).
8. Lamp (16) according to any of claims 1 to 4, in which the cover (19) has a disc-like form.
9. Lamp (16) according to claim 8, in which one contact face (13) of the cover (19) to the cooling body (17) is arranged laterally.
10. Lamp according to any of the preceding claims, in which the cover has an optical function.
11. Lamp (30) according to any of the preceding claims, in which the cover is substantially free of undercuts on its inner side.
12. Lamp (24) according to any of the preceding claims, in which the cover (26) has an at least laterally closed tubular form and the heatsink (25) is mounted at least partly in the cover (26) and is attached at least partly to a lower section (I) of the cover (26), wherein the lower section (I) of the cover (26) and an upper section (II) of the cover (26) have a comparatively smaller wall thickness (d) than the two lateral sections (III) of the cover (26).

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