WO2011061690A1

WO2011061690A1 - Lamp-holder and method for realising the same

Info

Publication number: WO2011061690A1
Application number: PCT/IB2010/055214
Authority: WO
Inventors: Livio Colosio
Original assignee: E.M.C. Colosio S.P.A.
Priority date: 2009-11-18
Filing date: 2010-11-17
Publication date: 2011-05-26
Also published as: ITMI20092026A1; IT1396609B1

Abstract

A lamp-holder comprises a body (2) made of a plastic material provided with a housing seating (3) for an end (8) of a lamp (4), further comprising at least a layer of a protective coating (5) applied to at least a portion (2a) of the body (2), the protective coating (5) being suitable for protecting the portion (2a) of the body (2) against at least an ultraviolet radiation emitted by the lamp (4). A lamp couplable with a lamp-holder has an end (8) which is destined to be housed in a housing seating (3) of a body (2) of the lamp-holder (1) and comprises at least a layer of a protective coating (5) applied to at least a portion (4a) of the lamp (4), the protective coating (5) being destined to protect at least a portion (2a) of the body (2) at least from an ultraviolet radiation emitted by the lamp (4).

Description

Lamp-holder and Method for Realising the Same.

Field of the Invention.

The present invention concerns a lamp-holder for lamps and a method for realising the lamp-holder.

The device is in particular advantageously applied in the sector of lamp-holders for lamps of the halogen type, and lamp-holder for discharge lamps (for example metal iodide lamps, metal halide lamps, mercury vapour lamps, sodium vapour lamps), but can also be advantageously used in lamp-holders for other types of lamps.

Prior Art.

In the prior art various types of lamp-holders are known, made in general specifically for corresponding types of lamps. Known-type lamp-holders are generally made of ceramic material (for example porcelain or steatite), plastic or metal (in general metal materials are used only for external casings of lamp- holders and not for the main body, for reasons of electrical insulation).

Lamp-holders thus generally comprise a body provided with a housing seating for the end of a lamp, which body is made of a ceramic or plastic material. Ceramic lamp-holders offer some advantages, among which a low cost of the raw material and a high resistance to high temperatures (ceramic material can resist temperatures of higher than 1000°C), but exhibit some drawbacks, the main of which is a greater difficulty in realising complete shapes provided for example with undercuts, due to the poor fluidity of the material in the production process.

Other drawbacks include a greater dimensional tolerance in the end product (with standard values defined by standard DIN40680), a smaller number of combinations possible in the dies for realising the ceramic body, a long duration of the production cycle, the necessity of a sintering treatment at high temperature (about 1300°C) with a consequently high energy expenditure, a weight and transport cost of significant entity.

Plastic lamp-holders are generally made using special plastics able to resist high temperatures (even up to 260°C/280°C). These lamp-holders exhibit some important advantages with respect to the lamp-holder made of ceramic material, in particular as they offer the possibility of realising more complex shapes, provided with undercuts too, thanks to the greater fluidity of the material during the production step.

Other advantages are constituted by the lower dimensional tolerance of the end product, the possibility of using a large number of combinations in the dies for realising the plastic body, a shorter duration and a lower energy consumption in the production cycle, a weight and a transport cost of lower entity.

Plastic lamp-holders exhibit some drawbacks, such as high costs for raw materials (in the case of special plastics able to resist very high temperatures) and a lower overall resistance to high temperatures with respect to ceramic lamp-holders.

As is known, lamps exhibit a characteristic emission of ultraviolet rays (UV). It is also known that some lamps, in particular halogen lamps and in particular discharge lamps (metal iodide lamps, metal halide lamps, mercury vapour lamps, sodium vapour lamps), exhibit considerable UV emission, which can lead to problems in terms of personal safety in use, and can also cause problems, for example, of deterioration of colouring of some products irradiated by the lamps.

To obviate this drawback, in the prior art a filter has been applied to the lamps, which filter is more or less transparent and able to reduce the emission of UV rays and thus reduce the above-cited drawbacks.

Also known is that some types of lamps are provided with a parabola, i.e. an element placed in the posterior part of the lamp and destined to reflect the greater quantity of light radiation towards a preferred emission direction.

The prior art also contains lamp-holders made of phenolic resins (for example Bakelite^®), typically being black in colour, which are painted with conventional paints suitable for the purpose for giving a different colour from the original colour.

The prior art also comprises lamp-holders made of thermoplastic materials which can be realised from the outset with various colorations, by adding a pigment to the material they are made of; or alternatively the lamp-holders can be painted to change their colour with conventional paints suitable for the purpose.

The applicant has found that the known lamps and the lamp-holders made of plastic material exhibit a further and not known drawback. In particular, lamp- holders of plastic material of known type, when used with lamps having a UV ray emission that is very high, exhibit a significant deterioration in the portion irradiated by the lamp, which leads not only to a reduction in the surface qualities of the lamp-holder (for example deterioration of the colour) but also to an erosion and therefore to a progressive wearing-out of the material of the lamp-holder.

The applicant has found that surprisingly the problem of deterioration due to UV rays becomes extremely significant beyond a certain limit of UV radiation emission, and that at the same time the emissions become very relevant beyond a predetermined power of the lamp. Further, the effect of the UV rays is very much stronger on the lamp-holder than on the other illuminated objects due to the very close proximity of the lamp to the lamp-holder.

Further, the lamp-holder is contemporaneously subjected to high use temperatures and the emission of UV rays.

All the cited factors add up to make the lamp-holders made of plastic material substantially inadequate for use with high-power lamps having high UV radiation levels (for example halogen type lamps, and in particular discharge lamps, but also other types), as their use in these cases can lead to potentially dangerous situations, with loss of grip of the lamp in the lamp mounting of the lamp-holder, or loss of the requisites of electric insulation of the lamp-holder. It is worthy of note that conventional UV filters applied to high-UV emitting laps do not resolve the cited problems, both because of an unsuitable positioning for protecting the lamp-holder, and especially because they are in themselves not sufficient for protecting the lamp-holder given the proximity thereof to the lamp, the high emission of the most recent-generation lamps and the poor resistance of the plastic to the UV rays in use conditions.

Other lamps are also known, provided with a reflector element or parabola incorporated in the lamp such as to direct the light radiations in a preferential direction. The known-type parabolas integrated in the lamps can be of three main types: aluminium parabolas assembled adjacent to the glass of the lamp; reflector parabolas realised by metal-coating (mirror-coating) of the glass of the lamp (dichroic lamps); or a combination between the first and the second solution, in which instead of the metallisation of the glass an actual aluminium parabola of low thickness is inserted.

In the second and third cases, typically the metallisation is performed starting from a certain distance with respect to the cathodes of the lamp such as not to create short-circuits. Known parabolas integrated in lamps are however not always capable of protecting the relative lamp-holder on which the lamp is mounted from the UV rays as the parabola part or the mirroring normal starts from a little beyond the glass zone of the lamp, close to the coupling zone with the lamp-holder.

It is also known that in some cases the parabolas are not integrated in the lamps but are mounted on the lighting devices. In these cases the problem of deterioration of the lamp-holders by the UV rays remains, as these parabolas are mounted posteriorly to the lamp-holder, or they exhibit, for reasons connected with mounting, a hole or a conformation which does not enable the lamp-holder to be protected.

The main aim of the present invention is to resolve one or more of the problems encountered in the prior art.

An aim of the present invention is to provide a lamp-holder having a body made of a plastic material which is free of the deterioration problems due to the emission of UV rays by the relative lamp.

A further aim of the present invention is to provide a lamp-holder which offers all the advantages of a plastic lamp-holder (among which for example high dimensional precision, with low tolerances, and the possibility of obtaining complex forms) and which further exhibits high resistance to ultraviolet rays, apart from high mechanical resistance and good resistance to heat.

A further aim of the invention is to realise a lamp-holder having a body made of a plastic material which is able to resist higher temperatures, for example in the order of 10-20°C with respect to a conventional lamp-holder realised in the same plastic material.

A further aim of the present invention is to provide a lamp-holder having high UV ray emission which does not lead to a deterioration in the lamp-holder on which it is mounted, even though the lamp-holder is provided with a body made of a plastic material.

A further aim of the present invention is to make available a method for realising lamp-holders having a body made of plastic material or a lamp-holder mountable on the lamp-holder, able to obviate the cited drawbacks.

These aims and others besides, which will emerge more fully from the following description, are substantially attained by a lamp-holder or a lamp and by a method for realising them according to what is set out in one or more of the appended claims, taken singly or in combination with one another. The invention also relates to a lamp-holder of one or more of the appended claims, wherein a portion of a body of the lamp-holder to which a protective coating is applied comprises at least a zone of the body which is subject to ultraviolet radiation during the functioning of a lamp mounted on the body. The invention also relates to a lamp-holder according to one or more of the appended claims, further comprising an intermediate layer of gripping material, or a preparation treatment, between the body and the layer of protective coating, destined to increase adhesion of the layer of protective coating to the body. The invention further relates to a lamp-holder comprising a body made of a plastic material provided with a housing seating for an end of a lamp, further comprising at least a layer of protective coating applied to at least a portion of the body, the protective coating being destined to protect the portion of the body at least from the heat emitted by the lamp, in order to increase the resistance of the body to the high temperatures.

The invention further relates to a lamp-holder in which the protective coating comprises at least a layer of nano-ceramic material or at least a layer of silicone paint or at least a layer of fluoro-polymeric material such as PTFE or Teflon^®. The invention further relates to a lamp-holder of one or more of the appended claims, wherein the protective coating exhibits a thickness of less than 100 micrometres (or microns), preferably less than 50 micrometers and still more preferably less than 25 micrometres.

The invention also relates to a lamp-holder of one or more of the appended claims, wherein the body is entirely coated with the protective coating.

The invention further relates to a lamp-holder as in one or more of the appended claims, wherein the coating is made of a material which is not electrically conductive.

The invention further relates to a lamp-holder as in one or more of the appended claims, wherein the coating is destined to guarantee a protection of a mechanical type and/or of a thermal type to the body.

The invention further relates to a lamp as in one or more of the appended claims, wherein the protective coating is destined to limit an ultraviolet radiation emitted by the lamp during functioning of the lamp when mounted on the body, in order to protect a portion of a body of the lamp-holder realised in plastic material.

The invention further relates to a lamp of one or more of the appended claims, wherein the protective coating is applied to a portion of the lamp which is destined to emit an ultraviolet radiation towards a portion of a body of the lamp- holder realised in plastic material.

The invention further relates to a lamp as in one or more of the appended claims, further comprising an intermediate layer of gripping material between the lamp and the layer of protective coating, or a preparation treatment, destined to increase adhesion of the layer of protective coating to the lamp.

The invention further relates to a lamp as in one or more of the appended claims, wherein the protective coating comprises at least a layer of nano-ceramic material.

The invention further relates to a lamp as in one or more of the appended claims, wherein the protective coating comprises at least a layer of silicone paint or at least a layer of fluoro-polymeric material, such as for example PTFE or Teflon^®. The invention further relates to a lamp as in one or more of the appended claims, wherein the at least a layer of protective coating is applied by spraying or by dipping or painting.

The invention further relates to a lamp-holder or a lamp as in one or more of the appended claims, wherein the fluoro-polymeric material, the PTFE or the silicone pain further comprising a predetermined percentage of graphite.

Brief Description of the Drawings.

There now follows a detailed description, by way of non-limiting example, of some preferred embodiments of a lamp-holder, a lamp and a method for realising them, wherein:

figure 1 is a perspective view of a body of a lamp-holder of the prior art;

figure 2 is a perspective view of a body of a lamp-holder of the present invention;

figure 3 is a perspective view of the body of a lamp-holder of figure 2 mounted in a respective casing and connected to respective electric wires;

figure 4 is a perspective view of a lamp of known type mounted on the lamp- holder of figure 3;

figure 5 is a perspective view of a lamp of the present invention mounted on a lamp-holder of known type as in figure 1;

figure 6 is a perspective view of the lamp of figure 5.

Disclosure of Invention.

The figures illustrate, by way of non-limiting example, an example of a lamp- holder, produced by the present applicant, and an example of a lamp, marketed under the Philips^® mark, but the invention is applicable also to lamp-holders and lamps that are different from the ones illustrated.

With reference to the appended figures, 1 denotes in its entirety a lamp-holder of the present invention. The lamp-holder 1 comprises at least a body 2 made of a plastic material provided with a seating 3 for housing an end 8 of a lamp 4. In the present description, the term "plastic material" is taken to mean plastic materials used for realising lamp-holders, such as, for example, thermoplastic materials of the type of PBT, PET, PA, PPS and LCP, or heat-hardening materials such as phenolic resins, (Bakelite^® ) or polyester.

The lamp-holder 1 comprises at least a layer of a protective coating 5 applied to at least a portion 2a of the body. In the present text, the term "protective coating" is taken to mean one or more coatings of a protective material applied on a support (for example a body of the lamp-holder or a lamp), for example by spraying, painting, dipping or the like, such as to stably cover the support. In other words, the protective coating is constituted by a material which is in the liquid, fluid or powder phase, before application thereof to the body.

The protective coating takes on its definitive conformation, complementarily shaped and solidly constrained to the portion of body, only following application thereof to the portion of body. The term "protective coating" does not comprise mechanical elements that are structurally distinct from the support and rested on the support or mechanically interposed between the support and a further element (such as for example a lamp or a body of a lamp-holder). In particular, by "protective coating", no reference is made to an element interposed removably between the elements.

The protective coating 5 is destined to protect the portion of the body at least from an ultraviolet radiation emitted by the lamp 4. The coating 5 can be further destined to guarantee a mechanical protection and/or a heat protection to the body 2. The coating can provide, for example, a protection which enables the plastic body to resist temperatures of greater by about 10-20°C with respect to the body without the coating.

The portion 2a of the body 2 comprises at least a zone of the body 2 which is subject to ultraviolet radiation during functioning of the lamp 4 mounted on the body 2. Alternatively the body 2 can be entirely coated with the protective coating 5. As can be seen in figure 3 and figure 4, the lamp-holder 1 can further comprise a casing 6 in which the body 2 is housed.

The lamp-holder 1 further comprises electrical contacts arranged internally thereof and destined to enable electrical connection of the end 8 of the lamp 4 with respective electric wires 7.

In a first embodiment of the invention, the protective coating 5 comprises at least a layer of nano-ceramic material, or alternatively several layers of the material.

In a second embodiment of the invention, the protective coating comprises at least a layer of silicone paint.

In a third embodiment the protective coating comprises at least a layer of fluoro- polymeric material for example PTFE or Teflon^®.

In the second and third embodiments, the fluoro-polymeric material, the PTFE or the silicone paint can further comprise a predetermined percentage of graphite. The coating can also be realised using other materials suitable for the purpose. The protective coating can have any thickness suitable for the purpose, but preferably the coating has as thin a thickness as possible in order to achieve the set aims.

The protective coating can have for example a thickness of the order of micrometres (micron), for example less than 100 micrometres, preferably less than 50 micrometres and still more preferably less than 25 micrometres, such as not to influence the tolerances and the dimensional precision of the body 2. The thickness of the protective coating can be for example 20 micrometres. The coating materials can further comprise additives destined to improve adhesion to the body 2. In an embodiment, the lamp-holder 1 can further comprise an intermediate layer of gripping material between the body 2 and the layer of protective coating 5, destined to increase adhesion of the layer of protective material to the body 2.

Two layers of protective material can also be provided, or even two layers of gripping material.

In a further embodiment, the lamp-holder 1 can further comprise a preparation treatment between the body 2 and the layer of protective coating 5, destined to increase adhesion of the layer of protective coating to the body 2. The layer of protective coating 5 can be applied by spraying, painting or by immersion of the body 2 in the protective material. The layer of coating 5 can be applied with any other method suitable for the purpose. The invention further relates to a method for production of lamp-holders 1 comprising at least a step of applying, to at least a portion 2a of the body 2 made of plastic material of the lamp-holder 1 , at least a layer of protective coating 5 destined to protect the portion 2a of the body 2 at least from an ultraviolet radiation emitted by a lamp 4 mounted on the body. The step of applying at least a protective coating 5 comprises the step of spraying a protect material onto the portion of body 2 and/or a step of dipping the body 2 in a protective material and/or a step of painting the body 2 with a protective material.

The method can further comprise a step of applying an intermediate layer of gripping material on the body 2, or a step of performing a preparation treatment of the body 2, destined to increase adhesion of the layer of protective coating to the body 2, before the step of applying at least a layer of protective coating 5. The protective coating can comprise a nano-ceramic material and/or a fluoro- polymeric material and/or PTFE and/or a silicone paint.

The invention further relates ton a further embodiment, illustrated in figure 5, comprising a lamp 4 that is couplable with a lamp-holder 1 and has an end 8 destined to be housed in a housing seating 3 of a body 2 of the lamp-holder 1, which can be of a conventional type.

In the invention, the lamp 4 comprises at least a layer of a protective coating 5 applied to at least a portion 4a of the lamp 4. The protective coating 5 is destined to protect at least a portion 2a of the body of the lamp-holder 2, even if of conventional type and therefore without protective coating, at least from an ultraviolet radiation emitted by the lamp 4. The protective coating 5 is destined to limit an ultraviolet radiation emitted by the lamp 4 during functioning of the lamp 4 mounted on the body 2, in order to protect a portion 2a of the body 2 of the lamp-holder 1 made of plastic material.

In the invention, the protective coating 5 is applied to a portion 4a of the lamp 4 destined to emit an ultraviolet radiation towards a portion 2a of the body 2 of the lamp-holder 1 realised in plastic material. The lamp 4 can further comprise an intermediate layer of gripping material between the lamp 4 and the layer of protective material 5, or a preparation treatment, destined to increase the adhesion of the layer of protective coating to the lamp 4. The protective coating 5 can comprise at least a layer of nano-ceramic material, or alternatively at least a layer of silicone paint or at least a layer of fluoro-polymeric material, for example PTFE or Teflon^®. The fluoro-polymeric material, the PTFE or the silicone paint can further comprise a predetermined percentage of graphite. The coating can be realised using other materials suitable for the purpose.

In a variant, the lamp 4 can be entirely coated with the protective coating in all the radiating portions thereof in the direction of the lamp-holder 1 when the lamp 4 is mounted on the lamp-holder 1. The layer of protective coating 5 can be applied by spraying, by painting or by dipping the portion 4a of the lamp 4 in the protective material, or with any other method suitable for the purpose.

The invention further relates to a method for production of laps 4 comprising at least a layer of protective coating 5 for reducing an emission of the lamp 4 from the portion 4a of the lamp 4. The protective coating 5 is destined to protect a portion 2a of the body 2 of a lamp-holder 1 made of plastic material at least from an ultraviolet radiation emitted by the lamp 4. The step of applying at least a protective coating comprises the step of spraying a protective material onto the portion 4a of the lamp 4 and/or the step of dipping the portion 4a of the lamp 4 in a protective material and/or the step of painting the portion 4a of the lamp 4 with a protective material.

The method can further comprise the step of applying an intermediate layer of gripping material to the portion 4a of the lamp 4, or the step of performing a preparation treatment of the portion 4a of the lamp 4, destined to increase the adhesion of the layer of protective coating 5 to the lamp 4, before the step of applying at least a layer of protective coating. The protective coating 5 can comprise a nano-ceramic material and/or a fluoro-polymeric material and/or PTFE and/or a silicone paint.

In the case of a coating made of a nano-ceramic material, the method further comprises a step of heating at least the portion 2a of the body 2 of the lamp- holder, or at least the portion 4a of the lamp 4, after the step of applying the layer of protective coating 5 in order to sinter the protective coating made of a nano-ceramic material. The step of heating can be performed by firing the lamp- holder (or the portion of lamp-holder) in a kiln. This step can be performed, for example, at a temperature of the order of 200°C/220°C, and for a duration of a few minutes (for example, about 5 minutes).

In the case of coating with a fluoro-polymeric material and/or PTFE, the method further comprises a step of heating at least the portion 2a of the body 2 of the lamp-holder, or at least the portion 4a of the lamp 4, after the step of applying the layer of protective coating 5, in order to polymerise the protective coating made of fluoro-polymeric material and/or PTFE.

The step of heating can be performed by firing the lamp-holder (or the portion of lamp-holder) in a kiln and can be performed for example at a temperature in the order of about 400°C/420°C, for a duration of the order of a few minutes (for example about 5 minutes).

In the case of coating with a silicone paint the method further comprises a step of heating at least the portion 2a of the body 2 of the lamp-holder, or at least the portion 4a of the lamp 4, after the step of applying the layer of protective coating 5 in order to polymerise the protective coating of silicone paint.

The step of heating can be performed by firing the lamp-holder (or the portion of lamp-holder) in a kiln and can be performed for example at a temperature of the order of about 200°C/220°C, for a duration of the order of a few minutes (for example about 5 minutes).

Obviously in all cases the temperature and the heating time can vary according to the materials used, thicknesses, etc. The step of heating is therefore performed at temperatures that are much lower than the temperature required for sintering lamp-holders internally realised in ceramic material (about 1300°C) and for much shorter durations than those required in that case (in the order of 12-24 hours according to the type of kiln used); for this reason the present method has a significantly lower energy consumption.

The present invention enables obtaining one or more of the following advantages.

First and foremost, the invention enables lamp-holders and/or a lamp able to be obtained which obviate the problems encountered in the prior art. A lamp-holder of the invention can be realised in plastic material, with all the consequent advantages (among which is included dimensional precision), but is free of the problems connected with deterioration due to the emission of UV rays by a lamp.

Further, the invention provides a lamp which though having a significant emission of UV rays does not lead to any deterioration of the lamp-holder on which it is mounted, even in a case of conventional lamp-holders having a body made of a plastic material that is sensitive to UV rays.

A further significant point is that a lamp-holder or a lamp of the invention are simple and economical to produce.

The invention further makes available a method for realising a lamp-holder having a body made of a plastic material, or a lamp which is mountable on the lamp-holder, which are simple and economical to produce and which require short working times and have a low level of energy consumption.

Claims

Claims.

1. Lamp-holder comprising a body (2) made of a plastic material provided with a housing seating (3) for an end (8) of a lamp (4), characterized in that it comprises at least a layer of a protective coating (5) applied to at least a portion (2a) of said body (2), said protective coating (5) being suitable for protecting said portion (2a) of said body (2) against at least an ultraviolet radiation emitted by said lamp (4).

2. Lamp-holder according to claim 1, wherein said protective coating (5) comprises at least a layer made of a nano-ceramic material or at least a layer made of a silicone paint or at least a layer made of a fluoro-polymeric material, such as PTFE or Teflon^®.

3. Lamp-holder according to claim 1 or 2, wherein said at least a protective coating layer (5) is applied by spraying or dipping or painting, and by subsequently heating said portion (2a) of said body (2).

4. Lamp connectable to a lamp-holder according to any one of the preceding claims and having an end (8) suitable for receiving in a housing seating (3) of a body (2) of said lamp-holder (1), characterized in that it comprises at least a layer of a protective coating (5) applied to at least a portion (4a) of said lamp (4), said protective coating (5) being suitable for protecting at least a portion (2a) of said body (2) of said lamp-holder at least against a ultraviolet radiation emitted by said lamp (4).

5. Lamp according to claim 4, wherein said lamp (4) is coated with said protective coating (5) on all portions thereof irradiating towards the lamp-holder

(1) when the lamp (4) is coupled to the lamp-holder (1).

6. Method for producing a lamp-holder (1) comprising at least a step of applying, to at least a portion (2a) of a body (2) made of plastic material of a lamp holder (1), at least a layer of a protective coating (5) suitable for protecting said portion (2a) of said body (2) at least against an ultraviolet radiation emitted by a lamp (4) coupled to said body (2).

7. Method for producing lamps comprising at least a step of applying, to at least a portion (4a) of a lamp (4), at least a layer of a protective coating (5) for reducing an emission of said lamp (4) from said portion (4a) of said lamp (4), said protective coating (5) being suitable for protecting a portion (2a) of a body

(2) of a lamp-holder made of plastic material at least against an ultraviolet radiation emitted by said lamp (4).

8. Method according to claim 6 or 7, wherein said step of applying at least a protective coating (5) comprises a step of spraying a protective material on said portion (2a) of said body (2) or on said portion (4a) of said lamp (4) and/or a step of dipping said body (2) or said portion (4a) of said lamp (4) in a protective material and/or a step of painting said body (2) or said portion (4a) of said lamp (4) with a protective material.

9. Method according to any of claims from 6 to 8, wherein said protective coating (5) comprises a nano-ceramic or fluoro-polymeric material and/or PTFE, or a silicone paint, said method further comprising a step of heating at least said portion (2a) of said body (2) or at least said portion (4a) of said lamp (4) with said layer of a protective coating (5) in order to sinter said protective coating made of nano-ceramic material or to polymerize said protective coating made of fluoro-polymeric and/or PTFE or silicone paint.

10. Method according to any one of claims from 6 to 9, further comprising a step of applying an intermediate layer of gripping material on said body (2) or on said portion (4a) of said lamp (4), or a step of performing a preparation treatment of said body (2) or said portion (4a) of said lamp (4), destined to increase adhesion of the layer of protective coating layer (5) to said body (2) or said portion (4a) of said lamp (4), before said step of applying at least one protective coating layer (5).