FR2972520A1 - Electric light bulb, has light diffusing unit transmitting light emitted from light emitting plate, into hollow body after passing through wall of hollow body, where spectrum of light is similar to that of candle flame - Google Patents

Abstract

The bulb (1) has an elongate hollow body (1a) comprising interior volume (1f) and a proximal opening (1g), where an opaque coaxial base plate (3) is provided at a base of the hollow body to seal the opening. A light diffusing unit (7) comprises a hemispherical cap (7a) arranged adjacent to the opening in the hollow body. The diffusing unit transmits light emitted from a light emitting plate, into the hollow body after passing through a wall (1e) of the hollow body, where spectrum of the light is similar to that of a candle flame.

Description

TECHNICAL FIELD The present invention relates to electric lighting fixtures intended to resemble a wax candle. To electrify the style fixtures, which were traditionally wax candle holders, we have already imagined oblong hollow body light bulbs, secured to a metal base engaged in a metal candle holder itself inserted into a tube cream-colored plastic material substantially reproducing the color of the wax. These known lighting devices are not entirely satisfactory because they reproduce only very imperfectly the appearance of a candle. Firstly, the hollow body containing the light source diffuses light from its base which itself is adjacent to the bulb base itself completely inserted into the bulb holder. As a result, light is diffused from the entire height of the hollow bulb body, i.e. from the base of the hollow body which is adjacent to the top of the plastic tube reproducing the color candle body. wax. This is unrealistic because, in a candle, the glowing gases move upwards, so that the incandescent portion of flame is usually away from the top of the wax candle body, and a relatively dark area separates the top of the wax candle body from the incandescent area. Then, the heat released by the incandescent light source bulb gradually alters the upper section of the plastic tube reproducing the candle body, and this upper section gradually darkens, unlike a wax candle body that burns gradually. without getting black. In addition, the incandescent element, in the form of an electrically conductive filament, inserted into the hollow body, does not itself have the shape of a candle flame. To mitigate this disadvantage, the hollow body itself is generally given a flame shape, with a diameter that increases from the base to a median portion and then decreases to a distal end of the hollow body. But the aspect remains distant from that of a candle flame, insofar as the hollow body necessarily has a diameter much greater than that of a candle flame, to avoid excessive heating due to the heat released by the filament incandescent producing light.

The recent development of light-emitting diodes has given rise to different attempts to make a light bulb that may look like a candle. For example, document WO 2010/044985 5822FDEP.docx 2972520 2 discloses a lamp having a shape reminiscent of a candle of flame wax, with a proximal tube surmounted by a cylindrical intermediate radiator itself surmounted by a hollow body lying along an axis of elongation of material capable of transmitting light and having an inner volume and a proximal opening. At the base of the hollow body, an opaque coaxial base closes the proximal opening and is integral with the cylindrical radiator. A light emitting diode-type light emitting plate, integral with and powered by the base, is disposed adjacent the proximal opening to emit light to the interior volume of the hollow body.

A light diffusing means is engaged in the hollow body to diffuse into the hollow body the light emitted by the light emitting plate. The light diffusing means comprises a light-transmitting cylinder, which is connected to a light-scattering sphere itself disposed in the middle part of the hollow body. The light-transmitting cylinder prevents the emission of light radially outwardly of the lamp, while the light-emitting sphere is adapted to emit light in all directions. Such a device still has an appearance of traditional lighting bulb, the hollow body having a relatively large diameter, of the order of 32 mm for housing the light diffusing means, and the light 20 being diffused from a sphere, thus giving the appearance of a ball of light, and not an aspect of elongated flame. In addition, the base of the ball of light does not have the relatively dark appearance of a candle wick. Finally, the opaque elements contained in the proximal section of the hollow body confer an appearance that deviates further from that of a candle flame.

The problem proposed by the present invention is to design a new light-emitting diode electric lighting structure to reproduce more accurately the appearance of a lighted candle. In another aspect, the invention aims to design such a structure that is particularly robust, easy to assemble, low cost.

The idea underlying the invention is to reduce the diameter of the hollow body, avoiding for this the use of a bulky light diffuser means. But an additional problem to be solved is the need for heat removal, the light-emitting diode and its supply means generating heat energy which, although reduced, requires its evacuation to avoid excessive heating of the diode. To achieve these and other objects, the invention provides an electric candle flame illumination light bulb, comprising: a hollow body, elongate along an axis of elongation, of suitable material to transmit the light, and having an interior volume and a proximal opening, - at the base of the hollow body, an opaque coaxial base, closing the proximal opening and shaped for fixing the light bulb to a bulb holder 5 and for its electrical connection, a light-emitting diode-type light emitting plate, integral with and powered by the opaque coaxial base, and disposed in the vicinity of the proximal opening to emit light towards the interior volume of the light-emitting diode. hollow body; a light scattering means for diffusing into the hollow body the light emitted by the light-emitting plate; according to the invention: - the hollow body is in a translucent material and itself has a shape and a diameter close to those of a candle flame, 15 - the light diffuser means comprises a plastic capsule disposed in the vicinity the proximal opening in the hollow body, and capable of transmitting into the hollow body a light which, after passing through the wall of the hollow body, has a spectrum close to that of a candle flame. The light emitted by the light emitting plate passes through the light diffusing means to acquire an acceptable color temperature and is then diffused by the wall of the hollow body which itself has a shape close to that of a candle flame. The opaque coaxial base prevents light transmission to the bulb holder. A light emitting plate will be chosen such that the bulb emits a luminous flux of value between 20 and 30 lumens. The tinted plastic capsule, forming the light diffuser, shall be designed so that light emitted outside the hollow body has a color temperature of between 1 800 ° K and 2 200 ° K, preferably equal to at about 2000 ° K. The hollow body may advantageously have a pointed distal end-shaped warhead shape, which has a maximum diameter in a proximal section adjacent to its base and decreases slowly in the vicinity of the base and more rapidly in the vicinity of the end. distal. In the proximal section adjacent to the base, the hollow body may have a diameter of about 16 mm. The hollow body made of glass or plastic can be made. The hollow body may advantageously be of translucent white polycarbonate. According to an advantageous embodiment, the light-emitting plate is fixed on and in thermal contact with a disk-shaped heat conductive base and itself surrounded by an insulating ring, the plate emitting light itself being encapsulated under a dome of transparent, clear silicone resin. Such a structure is easily adaptable in the hollow body.

In this case, it can be provided that: the light-emitting plate emits a white light, the diffuser means comprises a substantially hemispherical orange-colored polycarbonate capsule fixed at its base on the insulating ring, the The wall is away from the dome, and the color of which is chosen so as to obtain the color temperature of between 1800 ° K and 2200 ° K. The mounting of such a device is particularly simple. To further simplify the assembly, it can be provided that: the hollow body comprises, in its proximal section, a thinner-walled section defining an increased inner diameter and extending from the proximal opening to an inner shoulder; the hemispherical capsule of the diffuser means is connected to a peripheral sidewalk adapted to engage in the proximal section and against the inner shoulder of the hollow body, against which it is pressed by the insulating ring, the insulating ring is held by the opaque coaxial base itself fixed by gluing or clipping to the inner face of the hollow body. Note that the closure of the proximal opening does not need to be sealed, since light emitting diode-type light emitting plates do not need to be in a vacuum atmosphere, unlike filament lamps .

Preferably, the opaque coaxial base comprises: a hollow distal cylindrical section engaged and fixed in the proximal hollow body section to close the proximal opening and support the light emitting plate which is integral with it and in thermal contact; a hollow intermediate cylindrical section, of smaller cross-section than the hollow distal cylindrical section, and black in color, - a proximal fixing and connecting section, having engaging shapes for fitting into a bulb holder, and having conductive bulb connection pads for connection to corresponding conductive pads of the bulb holder.

An ampoule having an intermediate section giving the appearance of the black wick of a candle is thus produced, to approach even better the general appearance of a candle flame.

According to a particularly advantageous embodiment, the distal cylindrical section and the hollow cylindrical intermediate section of the base are made of a material that is a good heat conductor, preferably a copper and tellurium alloy, of black color. and of suitable dimensions to ensure dissipation of the heat generated by the light-emitting plate and to keep it a temperature below its maximum permissible temperature. Thus, the cylindrical intermediate section of the base ensures the double function of spark plug wick and radiator to dissipate the heat emitted by the light generating means.

Preferably, it can be provided that: the light-emitting plate comprises two supply conductors; the supply conductors axially pass through the hollow distal cylindrical section and the hollow cylindrical intermediate section. In this case, an electrical resistance can be connected in series in one of the supply conductors, and housed in the hollow intermediate cylindrical section. This electrical resistance is dimensioned so as to connect directly to the 220 Volt power supply sector the bulb thus produced, without risk of breakdown of the light emitting diodes.

Preferably, the electrical resistance has a value greater than a minimum resistance value producing in the light-emitting plate, when it is supplied by the electricity supply network, an electric current intensity equal to the nominal value. recommended. In this way, the light emission is sufficient to give the appearance of a candle flame, and this reduces the heat energy to be dissipated, and thus the heating of the light emitting plate. Preferably, the conductors are insulated son, the set of conductors being further surrounded by an insulating sleeve providing double electrical isolation vis-à-vis the hollow distal cylindrical section and the hollow cylindrical intermediate section. The proximal fixation section may advantageously comprise: an insulating diametral plate connected to the proximal end of the hollow intermediate cylindrical section by a transverse flange; the electrical conductors pass through the transverse flange and are respectively applied against the opposite faces of the transverse flange; the diametrical plate to constitute the conductive light bulb connection pads.

Other objects, features and advantages of the present invention will become apparent from the following description of particular embodiments, with reference to the accompanying figures, in which: FIG. 1 is a side view showing the general aspect of an electric lighting device according to one embodiment of the present invention, reproducing the general appearance of a wax candle; Figure 2 is a side view showing the general appearance of an ampoule according to one embodiment of the present invention; FIG. 3 is a half-sectional side view of the bulb of FIG. 2; Figure 4 is a schematic side sectional view of a light emitting diode-type light emitting plate emitter assembly incorporated in the light bulb according to Figures 2 and 3; - Figure 5 is a side view in longitudinal section of the opaque coaxial base; FIG. 6 is a plan view of the opaque coaxial base of FIG. 5; FIG. 7 is a view from below of the opaque coaxial base of FIG. 5; and Fig. 8 is a perspective view illustrating a bulb holder according to an embodiment of the present invention. FIG. 1 is first considered, illustrating in front view an electric lighting device according to an embodiment of the present invention, giving the appearance of a wax candle. The device comprises an electric light bulb 1, mounted at the upper end of a device body 2. The device body 2 is made of wax-tinted plastic, giving the appearance of the wax body of a candle.

The bulb 1 is, for its part, intended to give the appearance of a candle flame when it is supplied with electrical energy. The bulb 1 comprises an illuminating part constituted by a hollow body 1a in the shape of a warhead, surmounting an opaque coaxial base 3. The illuminating part of the bulb 1 is a hollow body 1a, in the shape of a warhead, elongated according to an elongation axis I, of material traversed by the light, such as glass or a plastic material, and containing a light source electrically connected to two electrical supply conductors axially passing through the opaque coaxial base 3. FIG. 2 illustrates an ampoule 1 according to one embodiment of the invention, adapted to be engaged on the device body 2 of Figure 1. We find in Figure 2 the hollow body 1a and the opaque coaxial base 3.

The opaque coaxial base 3 comprises a distal cylindrical section 3c (FIG. 3), then an intermediate cylindrical section 3a of smaller cross-sectional area than the hollow body 1a, and a proximal attachment and connection section 3b. The intermediate cylindrical section 3a has a length of about 10 mm, and a diameter of about 6 mm. The hollow body 1 has, ogival-shaped, has a distal apex with a small radius forming a pointed distal end 1b. The diameter D of the hollow body 1 a is maximum and of the order of 16 mm in a proximal section 1c adjacent to its base 1d, and this diameter decreases slowly in the vicinity of the base 1d, and more rapidly in the vicinity of the distal end lb. The length H (Figure 1) of the hollow body la is about 50 mm. We now consider Figure 3, illustrating the internal structure of the bulb 1 of Figure 2, on the half-section forming the right part of the figure. It can be seen that the hollow body 1a, elongate along the axis of elongation I, is formed of a wall 1 e of substantially constant thickness, delimiting an inner volume 1f open according to a proximal opening 1g. In the opaque coaxial base 3, the distal cylindrical section 3c is hollow and engages in the proximal opening 1g of the hollow body 1a. A light emitting assembly 6 is also engaged in the hollow body 1a integral with the distal cylindrical section 3c. The light emitting assembly 6 is surmounted by a light-diffusing means 7, in the form of a tinted plastic capsule, thus disposed in the vicinity of the proximal opening 1g in the hollow body 1a, and capable of transmitting into the hollow body 1a the light emitted by the light emitting assembly 6.

The hollow body 1a is of a translucent material, for example translucent glass or translucent plastic such as white translucent polycarbonate, and itself has a shape and diameter close to those of a candle flame. The light emitting assembly 6, placed in the vicinity of the proximal opening 1g, and emitting light axially along the axis 1 through the light diffusing means 7, produces a light which is diffused by the whole body. hollow, similar to the light emission of a candle flame. The luminous flux is preferably between 20 and 30 lumens, and its color temperature is between 1800 ° K and 2200 ° K, preferably about 2000 ° K. Measurements were carried out in an integrating sphere with a SPEBOS spectrophotometer and reference 1211.

FIG. 4 illustrates a possible embodiment of a light emitting assembly 6 that can be implemented in the hollow body 1a of FIG. 3. In this figure, an emitting plate of FIG. 6a light, fixed and 5 in thermal contact with a heat-conductive base 6b disc-shaped itself surrounded by an insulating ring 6c. The light emitting plate 6a is a substantially square plate 5 mm in size, which may consist of an array of elementary light-emitting diodes. The light emitting plate 6a is encapsulated under a dome 6d, for example substantially hemispherical, colorless transparent silicone resin. The electrical supply conductors of the light emitting plate 6a pass through and exit at the periphery of the insulating ring 6c. Referring again to Figure 3, there is also the dome 6d colorless transparent silicone resin, housed under the polycarbonate capsule 15 constituting the light diffusing means 7. A light emitting plate 6a will be chosen which emits a white light . Generally, in the light-emitting diode technology, such a white or warm-white color is obtained by an array of elementary light-emitting diodes which themselves produce a blue light, and which are associated with phosphors which absorb light at lengths. short waves and emit longer wavelength light in the desired spectrum. Such a light emitting assembly 6 may in particular consist of a light-emitting diode distributed by the Korea company Seoul Semiconductor under the reference AN 3220. Referring to FIG. 3, it can be seen that the light-diffusing means 7 is a substantially hemispherical capsule 7a. with a wall of constant thickness, connected to a peripheral sidewalk 7b. The light diffuser 7 may be made of orange-colored polycarbonate, obtained by introducing a filler of 4 to 5% by weight of dye to ensure the correct color temperature. The hollow body 1a comprises, in its proximal section 1c, a thinner wall section defining an increased inner diameter and extending from the proximal opening 1g to an inner shoulder 1h.

The peripheral sidewalk 7b engages in the proximal portion 1c against the inner shoulder 1h of the hollow body 1a, against which it is pressed by the insulating ring 6c, itself retained by the opaque coaxial base 3, including the 5822FDEP. The distal cylindrical portion 3c hollow is attached to the inner face of the hollow body 1a, for example by gluing, snapping or by any other means. The wall of the hemispherical capsule 7a of the light diffuser 7 remains clear of the dome 6d transparent colorless silicone resin. For this, the gap 7c is distinguished between the capsule 7a and the dome 6d. The base 6b is in thermal contact with the distal cylindrical portion 3c of the opaque coaxial base 3. This distal section 3c is itself made of a good heat-conducting metal, for example aluminum, or preferably copper or alloy of copper and tellurium. The intermediate section 3a is tinted externally in black, and forms a radiator able to dissipate to the outside the heat energy released by the light generating means. Simultaneously, the black appearance and the reduced diameter of the intermediate section 3a give the whole an appearance closer to that of a candle flame, the base resembling the black wick of the candle.

Thus, as seen in FIG. 3, the hollow distal cylindrical section 3c is engaged and fixed in the proximal portion 1c of the hollow body 1c to close the proximal opening 1g and to support the light emitting plate 6a which is solidary and in thermal contact. The opaque coaxial base 3 then comprises a hollow cylindrical intermediate section 3a, of smaller cross section than the hollow distal cylindrical section 3c, and of black color. Finally, the opaque coaxial base 3 comprises a proximal section 313 for fixing and connecting, having engaging shapes for adaptation in a bulb holder 20 (FIG. 8) and having conductive bulb connection pads for the connection to corresponding conductive pads of the bulb holder 20. The distal cylindrical section 3c and the hollow cylindrical intermediate section 3a of the opaque coaxial base 3 are made of the good heat conducting metal. The proximal section 3b is made of electrically insulating plastic material. The supply conductors 6e and 6f of the light emitting plate 6a pass axially through the hollow distal cylindrical section 3c and the hollow cylindrical intermediate section 3a. An electrical resistor 6g is connected in series in one of the supply conductors, for example the conductor 6e as illustrated in Figure 3, and is housed in the hollow intermediate cylindrical section 3a.

The electrical resistance 6g is selected with a value greater than a minimum resistance value producing in the light emitting plate 6a, when powered by the electricity supply network, an electric current intensity. equal to the nominal value recommended by the manufacturer of light-emitting diodes. For example, for the Seoul Semiconductor light-emitting diode AN 3220, given for a rated electrical current of 20 mA, it will be possible to choose an electrical resistance 6g of 8000 Ohm or 9000 Ohm, so that the electric current will be equal to about 12 to 13 mA. The reduction of the electric current also makes it possible to reduce the heating resulting from the heat energy released by the light-emitting diode and the electrical resistance 6g. It is then possible to evacuate this heat energy with a hollow cylindrical intermediate portion 3a of small diameter, close to the appearance of a black candle wick. Measurements have shown that with a hollow cylindrical intermediate section 3a whose length is 10 mm and the diameter 6 mm, the temperature of the light-emitting diode remains below 80 ° C. in an ambient temperature of 45 ° C., which is acceptable.

The proximal fixation portion 3b can for example be made as illustrated in FIGS. 5, 6 and 7. In this embodiment, the proximal attachment section 3b essentially comprises a diametrical plate 4, oriented in a plane containing the axis. I, and electrically insulating, connected to the proximal end of the hollow intermediate cylindrical section 3a by a transverse flange 3d. The electrical conductors 6e and 6f pass through the transverse flange 3d through passages 4c and 4d and are respectively applied against the opposite faces of the diametrical plate 4 to form the conductive bulb connection pads.

In practice, the power supply conductors 6e and 6f pass through corresponding passages 4c and 4d of the flange 3d and are applied against at least one main face of the diametrical plate 4, their ends engaging in the opposite face. after crossing a corresponding notch 5a or 5b. Ribs 5c and 5d provide isolation means to avoid contact of the power supply leads 6e and 6f with each other. In the distal cylindrical section 3c and in the intermediate cylindrical section 3a, the supply conductors 6e and 6f are insulated wires. The set of wires and the resistor 6g is further surrounded by an insulating sleeve 6h (FIG. 5), providing double electrical insulation with respect to the hollow distal electrical section 3c and the hollow intermediate cylindrical section 3a. The insulating sleeve 6h may be an attached tube. Alternatively, it may be a liner of electrically insulating material such as a varnish or gelatin. In the embodiment of FIG. 8, the bulb holder 20 is a screw lamp base structure, comprising a conductive peripheral wall 20a, formed as a screw lamp base thread, and comprising one end with central conductor pin 20b isolated from the conductive peripheral wall 20a. The conductive peripheral wall 20a is connected to a first conductive pad, while the central conducting pin 20b is connected to the other conductive pad inside an axial cavity 10 shaped to receive the proximal attachment section 10b The present invention is not limited to the embodiments that have been explicitly described, but includes the various variants and generalizations thereof within the scope of the following claims.

5822FDEP.docx

Claims (14)

CLAIMS1 - Bulb (1) electric lighting candle flame appearance, comprising: - a hollow body (1a), elongated along an axis of elongation (I), of material capable of transmitting light, and having a volume interior (1f) and a proximal opening (1g), - at the base of the hollow body (1a), an opaque coaxial base (3), closing the proximal opening (1g) and shaped for fixing the electric light bulb to a bulb holder and for its electrical connection, - a light-emitting diode-type light-emitting plate (6a), integral with and powered by the opaque coaxial base (3), and arranged in the vicinity of the opening proximal (1g) for emitting light towards the inner volume (1f) of the hollow body (1a), - a light diffusing means (7) for diffusing into the hollow body (1a) the light emitted by the emitter plate light (6a), characterized in that: - the hollow body (1a) is made of a translucent material and t itself has a shape and a diameter (D) close to those of a candle flame, - the light diffusing means (7) comprises a capsule (7a) of plastic material disposed in the vicinity of the proximal opening (1g) in the hollow body (1a), and able to transmit in the hollow body (1a) a light which, after passing through the wall (1e) of the hollow body (1a), has a spectrum close to that of a candle flame. 2 - Bulb according to claim 1, characterized in that it emits a luminous flux of value between 20 and 30 lumens, and whose color temperature is between 1800 ° K and 2200 ° K, preferably equal at about 2000 ° K. 3 - ampoule according to one of claims 1 or 2, characterized in that the hollow body (1a) has a pointed distal end (Id) pointed form, whose diameter (D) is maximum in a proximal section (1c) adjacent to its base (1d) and first decreases slowly near the base (Id) and more rapidly near the distal end (Ib). 4 - bulb according to any one of claims 1 to 3, characterized in that the hollow body (1a) is translucent white polycarbonate. 35 5 - Bulb according to any one of claims 1 to 4, characterized in that the light-emitting plate (6a) is fixed on and in thermal contact with a base (6b) of the heat-conducting element. 13 disc and itself surrounded by an insulating ring (6c), the light emitting plate (6a) itself being encapsulated under a dome (6d) colorless transparent silicone resin. 6 - Bulb according to claim 5, characterized in that: - the light-emitting plate (6a) emits a white light, - the diffuser means (7) comprises a capsule (7a) of orange-colored polycarbonate, substantially hemispherical, fixed at its base on the insulating ring (6c), whose wall is away from the dome (6d), and whose color is chosen so as to obtain the color temperature between 1800 ° K and 2 200 ° K. 10 7 - Bulb according to claim 6, characterized in that: - the hollow body (1 a) comprises, in its proximal section (1c) a thinner wall section defining an increased inside diameter and extending from the proximal opening ( 1g) to an inner shoulder (1h), - the hemispherical capsule (7a) of the diffuser means (7) is connected to a peripheral sidewalk (7b) adapted to engage in the proximal section (1c) and against the inner shoulder (1h) of the hollow body (1a), against which it is pressed by the insulating ring (6c), - the insulating ring (6c) is held by the opaque coaxial base (3) itself fixed by gluing or snap on the inner face of the hollow body (1a). 8 - Bulb according to any one of claims 1 to 7, characterized in that the opaque coaxial base (3) comprises: - a hollow distal cylindrical section (3c) engaged and fixed in the proximal section (1c) of hollow body (1 a) for sealing the proximal opening (1g) and supporting the light-emitting plate (6a) which is integral with it and in thermal contact, - a hollow intermediate cylindrical section (3a) of smaller cross-section than the cylindrical section distal hollow (3c), and black, - a proximal section (3b) for fixing and connecting, having engaging shapes for adaptation in a bulb holder (20), and having conductive connection pads bulb for connection to corresponding conductive pads of the bulb holder (20). 9 - Bulb according to claim 8, characterized in that the hollow distal cylindrical section (3c) and the hollow cylindrical intermediate section (3a) of the base (3) are made of a good heat conducting material, preferably an alloy copper and tellurium, of black color and of suitable dimensions to ensure the dissipation of the heat released by the light emitting plate (6a) and keep a temperature below its maximum permissible temperature. 5822FDEP.docx 2972520 14 10 - Bulb according to one of claims 8 or 9, characterized in that: - the light emitting plate (6a) comprises two supply conductors (6e, 6f), 5 - the supply conductors (6e, 6f ) pass axially through the hollow distal cylindrical section (3c) and the hollow cylindrical intermediate section (3a). 11 - Bulb according to claim 10, characterized in that an electrical resistor (6g) is connected in series in one of the supply conductors (6e, 6f), and is housed in the intermediate cylindrical section (3a). 10 12 - Bulb according to claim 11, characterized in that the electrical resistance (6g) has a value greater than a minimum value of resistance producing in the light emitting plate (6a), when it is fed by the network of power supply, an electric current intensity equal to the recommended nominal value. 15 13 - Bulb according to any one of claims 10 to 12, characterized in that the conductors (6e, 6f) are insulated son, the set of conductors being further surrounded by an insulating sleeve (6h) providing a double electrical isolation vis-à-vis the hollow distal cylindrical section (3c) and the hollow cylindrical intermediate section (3a). 20 14 - Bulb according to any one of claims 10 to 13, characterized in that the proximal section (3b) of attachment comprises: - an insulating diametral plate connected to the proximal end of the hollow intermediate cylindrical section (3a) by a flange transverse (3d), the electrical conductors (6e, 6f) pass through the transverse flange (3d) and are respectively applied against the opposite faces of the diametral plate (4) to form the conductive bulb connection pads.