WO2012114225A2

WO2012114225A2 - Lamp assembly

Info

Publication number: WO2012114225A2
Application number: PCT/IB2012/050636
Authority: WO
Inventors: Marco Joannes VAN DEN BOSCH; Vincent Stefan David Gielen
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2011-02-24
Filing date: 2012-02-13
Publication date: 2012-08-30
Also published as: WO2012114225A3

Abstract

A lamp assembly (101; 102; 103; 104) comprises: a housing (10); at least one light-generating element (21) and possible driving electronics for the light-generating element arranged within the housing; electrical terminals (12) for electrically coupling the assembly to a lamp socket. According to the invention, the housing (10) is externally provided with a tight-fitting sleeve (150). This sleeve improves the radiation emission properties of the housing, so that the housing can function as heat sink without the need to provide the housing witha coating.

Description

LAMP ASSEMBLY

FIELD OF THE INVENTION

The present invention relates in general to a lamp assembly, comprising a housing, one or more LEDs mounted in the housing, and coupling terminals for electrically coupling the lamp assembly with a lamp socket.

BACKGROUND OF THE INVENTION

The word "lamp" is a word that can have several meanings. In the context of the present invention, the word "lamp" will be used to indicate the replaceable element that is to be mounted in a lamp socket. A conventional example of a lamp in this sense, suitable for general lighting purposes and powered from mains, is an incandescent lamp, typically including a pear-shaped glass bulb with a glowing wire within a confined atmosphere of suitable composition. In later elaborations, the lamp atmosphere contains a halogen, and the size of the bulb has decreased. In a further elaboration, the small bulb is mounted in a cone- shaped reflector housing with a transparant plate, typically glass or quartz, covering the bulb. The bulb with this housing and glass window, together with electrical terminals attached to the housing, form an integral unit which is to be replaced as a whole, and which is also indicated by the word "lamp". Depending on the length scale used by the observer, the unit may be indicated as "light-generating unit", containing a bulb as "light-generating element", but within the bulb the actual light-generating element is the glowing wire. In discharge lamps, no such element can be indicated: the light is generated by a plasma inside the bulb.

In a special type of lamp, the light-generating element is constituted by one or more LEDs, which is/are mounted, together with driving electronics, within a lamp housing that is equipped with electrical coupling terminals. This combination will in the context of the present invention be indicated as "lamp assembly". Typically, but not essentially, the assembly is shaped in conformity with the shape of for instance a halogen lamp, so that it is possible to exchange a halogen lamp with such lamp assembly, or in any case the electrical coupling terminals are designed to fit in existing lamp sockets. In any case, the lamp assembly as a whole is a replaceable product, to be discarded when broken; for consumers, such product is also indicated as "LED lamp".

SUMMARY OF THE INVENTION

The lamp assembly comprises a plurality of components, as is illustrated by figures 1A-C, which show a schematic cross-section along a first longitudinal plane (Fig.lA), a schematic cross-section along a second longitudinal plane (Fig. IB), and an exploded view (Fig.lC) of a lamp assembly 1. It is noted that the shape of this lamp assembly corresponds to the well-known MR- 16 design for halogen lamps, for which LED replacements are commercially available, but it should be clear that the invention is not limited to this shape.

In general, the assembly 1 comprises a semi-spherical body 3, with an insulating base 2 carrying electrical terminals 12 which project out of the base. The body 3 has a hollow interior, at the open end of which a transparent window 5 is fitted, for instance made of glass, plastic or quartz, and typically having lens-shaped portions at its inner surface. Typically, as shown, the transverse dimension at the base 2 is smaller than the transverse dimension at the window 5, which typically is circular. In the following, the combination of body 3 and base 2 will also be indicated as housing 10.

In figures 1 A-B, the assembly 1 is shown with the base 2 down and the window 5 up. Behind the window 5 (i.e. below the window in the orientation of figure 1), the assembly 1 comprises a carrier plate 6 carrying the at least one LED 6a plus other electronic components 6b; this plate will be indicated as LED carrier plate 6, and is typically

implemented as a PCB.

Below the LED carrier plate 6, the assembly 1 comprises a second carrier plate 8 carrying electronic components of an electronic lamp driver; this plate will be indicated as driver carrier plate 8. The terminals 12 are electrically connected to respective inputs of the electronic lamp driver. Electrical connections between an output of the electronic lamp driver and the LED carrier plate 6 are not visible in these views.

The body 3 is designed to perform many functions. An important aspect of the body 3 is that it serves as a heat sink to remove the heat generated by the driver and the LEDs. In cross section, the body 3 has a general H-shape with a central plane 3 a, upper side wall 3b and lower side wall 3c. The figures show that the LED carrier plate 6 is mounted on the central plane 3 a of the body 3. Heat generated in the LED unit is transferred to the body's central plane 3 a (axial heat transfer) while the body's central plane 3 a transfers the heat to the body's outer side wall 3b, 3c (radial heat transfer). For a good axial heat transfer, it is required that the LED carrier plate 6 is pressed firmly against the body's central plane 3 a, which is done by a screw 6d extending through the LED carrier plate 6 and screwed into a screw hole of the body's central plane 3a. For reducing the interface resistance, a layer of thermal interfacing material 6e is interposed between the LED carrier plate 6 and the body's central plane 3a.

The inner surface of the body's upper side wall 3b is threaded. A ring 4 has matching threading on its outer surface, and is screwed into the body 3 for locking the window 5 and pressing the window 5 onto the LED carrier plate 6.

The driver carrier plate 8 with the electronic driver is located in the lower half of the body 3. The driver carrier plate 8 plus electronic components form an integral unit with the terminals 12 soldered thereto, and this unit is placed in the base 2, with the lower ends of the terminals projecting out of the base 2. The base plus said unit is screwed against the lower side of the body's central plane 3a, by means of screws 8d that extend through holes in the body's central plane 3 a and are screwed into screw holes of the base 2. A substantially cylindrical insulator 7 extends around the driver carrier plate 8 and the electronic driver components to assure sufficient electrical insulation between the electrical parts of the driver and the body's lower wall 3c.

An effective heat sink needs to be able to conduct the heat away from the heat- generating components quickly; for this reason, the body 3 is made of metal, usually aluminium or steel. Alternatively, possible materials are (thermal) plastics and ceramics. An effective heat sink also needs to be able to efficiently lose its heat by radiation. So it is desirable that the outer surface of the metal body 3 has a high emission coefficient. In this respect, it is a problem that bare metal, especially bare aluminium, has a relatively low emission coefficient.

Further, the outer surface of the metal body 3 determines to a large extent what the user "sees" of the lamp assembly, in other words it largely determines the visual experience of the user. In this respect, it is a problem that bare metal is not attractive aesthetically. Further, it is desirable to provide visible indicia on the outer surface of the lamp body, such as logos, power ratings, color temperature and other information. In this respect, it is a problem that it is not easy to apply indicia on bare metal in a reliable and nonerasable manner.

In order to overcome these problems, it is known to apply a coating to the outside surface of the body. Such coating can increase the thermal emission coefficient, and is typically implemented in a white color to make the product look better. Further, it is easier to apply visible indicia on such coating.

A further problem relates to safety regulations. In case of a malfunctioning, there may be a hazard of the body carrying high voltages of mains level (for instance

230 VAC in Europe). Therefore, in order to increase touch-safety and to ensure compliance with safety regulations, the metal body is sometimes over-moulded with a thick layer of thermal plastic.

This means that additional processing steps are needed to have the body fulfill its intended functionality as heat sink, and the above-mentioned processing steps are relatively expensive to perform.

Further, when the lamp assembly reaches the end of its life and is discarded, it forms a waste product. Rather than just dumping it, it would be desirable to be able to recycle as many of the components as possible, including the metal of the body. However, for being able to recycle a base material, it is necessary to obtain that material in a form as pure as possible, and in the case of a coated body this means that the coating has to be removed. If a reasonably feasible removable process is available at all, such process in any case involves costs; if no realistic process is available, so that the coating cannot be removed, the coating will remain in the recycled aluminium as pollution.

A general objective of the present invention is to overcome the above problems.

More particularly, the present invention aims to provide a simple and relatively inexpensive method for improving the emission coefficient of the metal body while at the same time improving the aesthetic appearance.

Still more particularly, the present invention aims to achieve the above objectives while allowing the metal body to remain blank metal. In an important aspect, the present invention provides the lamp assembly with a sleeve fitted tightly around the metal body. The sleeve is made of an elastic material having an emission coefficient higher than the metal of the body. The sleeve can be printed with indicia, as desired. At the end of life of the lamp assembly, the sleeve can be simply pulled of the body to reveal the bare metal, or will automatically be detached from the body in standard recycle processes such as shredding.

Further advantageous elaborations are mentioned in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of the present invention will be further explained by the following description of one or more preferred embodiments with reference to the drawings, in which same reference numerals indicate same or similar parts, and in which:

figures 1 A-C schematically show cross-sections and an exploded view of a prior art lamp assembly;

figure 2A is a perspective view of an embodiment of a sleeve;

figure 2B schematically shows a cross-section of a first embodiment of a lamp assembly according to the present invention;

figure 3 schematically shows a cross-section of a second embodiment of a lamp assembly according to the present invention;

figure 4 schematically shows a cross-section of a third embodiment of a lamp assembly according to the present invention;

figure 5 schematically shows a cross-section of a fourth embodiment of a lamp assembly according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 2B is a schematical cross-section of a lamp assembly according to the present invention, indicated by reference numeral 101. All internal components may be identical to the components of the prior art assembly, therefore these internal components are not shown again. The figure only shows, in dotted lines, the outer contour of the lamp housing 10 and the window/lens 5, which also may be identical to the housing and window of the prior art assembly. The lamp assembly 101 of the present invention is distinguished by the presence of a sleeve 150 tightly fitting around the housing 10. Figure 2A is a perspective view of the separate sleeve 150, shown as a semi-transparent entity, while an actual embodiment does not necessarily have to be transparent.

At the front side (upper side in the figure) of the lamp assembly, the sleeve 150 has an opening 153 leaving the window 13 free, such as not to hinder the light output. At the rear side (lower side in the figure) of the lamp assembly, the sleeve 150 leaves the electrical terminals 12 free. Apart from these free regions, the sleeve 150 may extend over the entire outer surface of the housing 10, i.e. extend over the entire axial length of the housing 10 (vertical direction in the drawing) plus an annular portion of the front face of the lamp housing plus an annular portion of the rear face of the housing.

However, it is also possible that the sleeve 150 leaves free a rearmost portion of the housing 10, as illustrated in figure 3, which is a schematical cross-section, comparable to figure 2B, of a second embodiment of the lamp assembly according to the present invention, indicated by the reference numeral 102. It is noted that the sleeve 150 shown in figure 2A corresponds to this embodiment.

Particularly in embodiments where the housing consists of a relatively wide front portion 14 and a relatively narrow rear portion 15 of substantially constant width, also indicated as "foot", it may be sufficient if the sleeve 150 extends at least over the entire surface of the front portion 14. Further, the outer surface of this rear portion 15 forms a mechanical interface with a lamp holder, and the presence of a sleeve may interfere or the sleeve may get damaged.

The sleeve may be implemented as a one-part whole, as illustrated in the two embodiments above. However, it is also possible that the sleeve 150 consists of two (or more) portions 151, 152 adjoining and perhaps (but not necessarily) partly overlapping each other, as illustrated in the third embodiment of figure 4, generally indicated by reference numeral 103. Such embodiment may be easier to apply.

The embodiments described in the above use the prior art design as a starting point: the sleeve can be arranged even around an existing lamp housing. However, in a further elaboration of the present invention, it is possible to more fully integrate the sleeve into the design of the lamp housing. When the material of the sleeve is chosen to have good optical properties, the sleeve can extend over the light output window, or the sleeve can even carry the lens plate or have the lens plate 105 integrated, as shown in the embodiment of figure 5, which is generally indicated by reference numeral 104. In that case, the housing 10 has a light output opening 16 and the sleeve, i.e. the sleeve's lens plate 105, is covering this opening.

The material of the sleeve preferably is a polymer or a silicone. The following is a list of examples of suitable materials, which list does not claim to be exhaustive:

Unsaturated rubbers that can be cured by sulfur vulcanization:

• Natural polyisoprene: cis- 1 ,4-polyisoprene natural rubber (NR) and trans- 1 ,4- polyisoprene gutta-percha

Synthetic polyisoprene (IR for Isoprene Rubber)

• Polybutadiene (BR for Butadiene Rubber)

Chloroprene rubber (CR), polychloroprene, Neoprene, Baypren etc.

Butyl rubber (copolymer of isobutylene and isoprene, IIR)

Halogenated butyl rubbers (chloro butyl rubber: CIIR; bromo butyl rubber:

BUR)

Styrene-butadiene Rubber (copolymer of styrene and butadiene, SBR)

• Nitrile rubber (copolymer of butadiene and acrylonitrile, NBR), also called Buna N rubbers

• Hydrogenated Nitrile Rubbers (HNBR) Therban and Zetpol

(Unsaturated rubbers can also be cured by non-sulfur vulcanization if desired).

Saturated rubbers that cannot be cured by sulfur vulcanization:

• EPM (ethylene propylene rubber, a copolymer of ethylene and propylene) and EPDM rubber (ethylene propylene diene rubber, a terpolymer of ethylene, propylene and a diene-component)

• Epichlorohydrin rubber (ECO)

Polyacrylic rubber (ACM, ABR)

Silicone rubber (SI, Q, VMQ)

• Fluorosilicone Rubber (FVMQ)

• Fluoroelastomers (FKM, and FEPM) Viton, Tecnoflon, Fluorel, Aflas and Dai- El

• Perfluoroelastomers (FFKM) Tecnoflon PFR, Kalrez, Chemraz, Perlast

• Polyether block amides (PEBA) Chlorosulfonated polyethylene (CSM), (Hypalon)

• Ethylene-vinyl acetate (EVA)

Various other types of elastomers:

• Thermoplastic elastomers (TPE), for example Elastron, etc.

• Thermoplastic vulcanizates (TPV), for example Santoprene TPV

• Thermoplastic polyurethane (TPU)

• Thermoplastic olefins (TPO)

• The proteins resilin and elastin

Polysulfide rubber

The sleeve can be made as a formpiece by injection moulding of polymer(s) or silicone(s). Alternatively, the sleeve can be made by dip-moulding. The sleeve may have a proper size smaller than the outer size of the lamp housing, and may be elastically stretched to fit around the housing. It is also possible that the sleeve is made as a shrink foil that is shrunk around the housing by a heat treatment, for instance made of PE or PET material, which foil is made by extrusion. It is also possible that the sleeve is made as a relatively small, shapeless sock that is elastically stretched to fit around the housing.

The sleeve can be provided with labeling or indicia either during the moulding process (this can for example be done by in-mould labeling or embossed features in the mould) or later.

Summarizing, the present invention provides lamp assembly that comprises a housing; at least one light-generating element and possible driving electronics for the light- generating element arranged within the housing; electrical terminals for electrically coupling the assembly to a lamp socket. According to the invention, the housing is externally provided with a tight-fitting sleeve.

The use of a sleeve around the housing of the lamp assembly, fitting like a skin in intimate contact with the outer surface of the lamp assembly, offers many advantages, wherein a key issue is that the housing of the lamp can be made of blank metal (i.e. bare metal). The sleeve can provide for a high thermal radiation emission coefficient so that the housing can properly function as a heat sink, thus avoiding the need to paint the metal.

Further, the sleeve can be printed with a labeling and/or indicia, thus avoiding the need to print the metal. During manufacture, the processing steps of coating and printing can thus be omitted, which leads to cost-reduction and reduced the environmental impact. After end of life, the uncoated metal is easier to recycle, so that the uncoated metal has a higher rest-value than coated metal.

A further advantage is that the sleeve can provide electrical insulation and thus make the lamp fulfill electrical safety requirements.

A further advantage is that the sleeve can increase the IP rating (ingress protection) of the LED lamp.

A further advantage is that the sleeve allows a designer much freedom and new possibilities with regard to Look And Feel of LED lamps. Material choice offers the possibility of high gloss, matted, soft, or even (embossed/recessed) relief surfaces.

The thickness of the sleeve may be chosen in dependency of the required functionality and on the choice of material. In general, a larger thickness will reduce the thermal radiation performance but will increase the mechanical strength, electrical insulation and fire resistance. In practice, a suitable thickness seems to be in the order of about 1 mm or less. In this respect, it is to be noted that the thickness of the sleeve 150 is not intended to be shown on scale in the figures.

If the electrical insulation is decisive, the safety standards have to be taken into account, in conjunction with the insulative properties of the sleeve material. For instance, in Europe, regulations may provide that an insulator should be able to withstand a voltage difference of 3750 VDC. If the sleeve is made from silicone, for instance grade 6050 commercially available from Momentive, having a dielectric strength of about 20 kV/mm, the minimum thickness is 0.1875 mm. If the sleeve is made from PUR, for instance grade 930 commercially available from Wevo Chemie, having a dielectric strength of about 30 kV/mm, the minimum thickness is 0.125 mm. In the USA, similar regulations may provide that an insulator should be able to withstand a voltage difference of 2500 VDC, and the

corresponding minimal thicknesses would be 0.125 mm and 0.0833 mm, respectively. For certain lamp types, the safety rating may be 500 V, in which case the minimum thickness may be as low as 0.025 mm or 0.0166 mm, respectively.

For increased safety margin, the thickness may be chosen as high as 0.3 mm. Larger thickness will improve strength and will further improve insulating properties, but the thermal properties may become an issue. For thermal emission, the heat needs to be conveyed to the outside surface, and this is improved by having a high thermal conductivity. In the case of a low thickness, such as 0.3 mm or lower, an adequate and quick heat transport to the outside surface is guaranteed even if the thermal conductivity of the material is relatively low. When the thickness of the sleeve is increased, this may result in increased wall temperature of the assembly housing if the thermal conductivity of the material is relatively low. This in turn would reduce the heat transport from the LEDs to the heat sink, thus increasing the temperature of the LEDs. Depending on the temperature rise allowed and the thermal conductivity of the sleeve material, among other things, the sleeve thickness could be selected as high as 0.5 mm or even 1.0 mm. In this respect, the lamp power of the lamp assembly, and the electrical efficiency of the lamp, also play a role.

It is noted that, while the sleeve is fitting tightly around the housing such as to have good thermal contact with the housing, it is nevertheless a separate component that is not adhering to the housing so that it can easily be removed for recycling.

While the invention has been illustrated and described in detail in the drawings and foregoing description, it should be clear to a person skilled in the art that such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments; rather, several variations and modifications are possible within the protective scope of the invention as defined in the appending claims.

Further, at the rear portion of the lamp housing, the sleeve may be provided with mechanical coupling elements, such as snap connection, screw thread, for mating with complementary elements of a lamp holder.

Further, although the invention has been described in the context of an LED lamp, the invention can also be applied in the case of lamp assemblies comprising one or more light-generating elements of a different type. Even if a light-generating element is used of a type that does not generate much heat so that the assembly housing does not need to function as a heat sink, and/or if the assembly housing is not made of metal, the use of a sleeve as described is still advantageous in view of the multiple advantages described.

In the above, the invention has been described for a lamp assembly having a shape corresponding to the MR- 16 design, and having axial connector pins of constant diameter. However, it is also possible that the lamp assembly has a different shape, for instance the shape of a classical bulb, and/or it is possible that the electrical terminals have a different shape, for instance connector pins with a T-shaped cross section for a twist-lock, or even Edison threading or a bajonet-type mount is possible.

In the above, the invention has been described for a lamp assembly comprising a housing and an LED, which assembly as a whole is fitted into a lamp socket. However, especially in the case that the light-generating element is not an LED but is for instance a halogen lamp, in which case the halogen lamp is the replaceable element and the luminaire comprises a heat sink element, it is also that the heat sink element of the luminaire is provided with a sleeve as described.

Further, while it is a great advantage of the sleeve provided by the present invention that the metal housing can be left blank, the use of the sleeve is not limited to covering blank metal housings. It is within the scope of the present invention to apply the sleeve over an existing lamp housing, which happens to be already coated, in order to improve the thermal radiation efficiency.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. Lamp assembly (101; 102; 103; 104), comprising:

a housing (10);

at least one light-generating element (21) and possible driving electronics for the light-generating element arranged within the housing;

electrical terminals (12) for electrically coupling the assembly to a lamp socket;

characterized in that the housing (10) is externally provided with a removable, flexible sleeve (150) being in tight contact with at least a substantial part of the housing's outer surface.

2. Lamp assembly according to claim 1, wherein the sleeve is made from a polymer material or a silicone material.

3. Lamp assembly according to claim 1, wherein the sleeve is implemented as a stable formpiece.

4. Lamp assembly according to claim 1, wherein the sleeve is elastically stretched to fit around the housing.

5. Lamp assembly according to claim 1, wherein the sleeve is made as one integral whole.

6. Lamp assembly according to claim 1, wherein the sleeve is divided in two or more separate parts (151, 152).

7. Lamp assembly according to claim 1, wherein the housing (10) is made of bare metal.

8. Lamp assembly according to claim 1, wherein the sleeve is in good thermal contact with the housing, and has an emission coefficient higher than the housing material.

9. Lamp assembly according to claim 1, wherein the light-generating element comprises an LED.

10. Lamp assembly according to claim 1, wherein the housing (10) comprises a relatively wide, cone-shaped or dome-shaped body portion (14) and a relatively narrow foot portion (15), wherein the terminals (12) project from the foot portion (15), wherein the housing (10) comprises a transparent window (13), wherein the sleeve at least covers the outer surface of the body portion (14), and wherein the sleeve leaves the transparent window free or wherein the sleeve includes a window portion of good optical properties covering the window (13).

11. Lamp assembly according to claim 10, wherein the housing (10) has a light output opening and wherein the sleeve covers this light output opening.

12. Lamp assembly according to claim 1, wherein the sleeve is electrically insulating, and has a thickness in the range from 0.01 mm to 1 mm, preferably in the range from 0.1 mm to 0.3 mm.

13. Luminaire comprising a lamp socket for receiving a lamp and further comprising a bare metal heat sink, and further comprising a sleeve made from a polymer or silicone material fitting tightly around the heat sink.

14. Sleeve (150) having shape and size suitable for tightly fitting around the housing of an LED lamp.

15. Method for improving the thermal emission of a lamp assembly, the method comprising the step of applying a thin, flexible skin in tight contact with the outside surface of the lamp assembly, wherein the skin material is selected to have higher thermal emission coefficient than the material of the outer surface of the lamp assembly.