EP0470002A1 - Miniature light bulb and its method of manufacture - Google Patents

Abstract

Method of manufacture of an electric light bulb (1) operating by incandescence characterised by the fact that: - one starts with a blank (10) bulb of generally "mushroom" shape having a diameter which can be as low as or close to about 25 mm; - the inner face of the rear half (13) of the flared part of the blank (10) is substantially metallised; - one starts with a foot (6) provided with a plurality of supports (7) for a filament (8) and a support is folded in two into a V and the supports are bent at their base in two opposite directions, the filament being inserted in an envelope having the general form of a truncated cone; - the foot is sealed on (6); - the air in the bulb is pumped out (1); - a base cap is sealed on (3). <IMAGE>

Description

The invention relates to a miniature light bulb and its manufacturing technique.

Electric mushroom bulbs with internal reflector are already known. Such a bulb has been available in different diameters such as 50, 63, 80, 95, 120 mm and is found under the name "SPOT" because of the brightness of its neck (truncated cone part) which returns all the light emitted towards the top of the lamp. Subsequently, an electric bulb with a diameter of 39 mm and an operating voltage most often limited to 130 V has also been proposed, the industrial mounting of a 230 V filament having too many obstacles, while manual mounting , while limiting production volumes and affecting productivity and cost price, never offers guarantees of batch homogeneity both from the point of view of flows and that of lifespans. More recently, we have succeeded in bringing the voltage to 180 V without this constituting real progress (if not of increased lifetime - in return for a sharp drop in flux - under 130 V).

There has also been proposed recently a bulb having a diameter of 30 mm for a nominal voltage of 220, 230 V and a power of 15 W. However, this bulb does not have a mushroom shape but its front part opposite to the base is laterally inscribed in a cylinder, the front wall being very flat (therefore with a large radius of curvature) and the rear truncated cone being reduced all to undoubtedly meet the constraints of internal lighting. It follows that the bulb has a singular general shape compared to the rest of the range which has a classic "mushroom" shape. This singular shape does not allow a reflection of light comparable to that obtained with a "mushroom" shape. This range also includes a "mushroom" bulb 220, 230 V and 15 W but whose diameter is 39 mm.

Such diameters, 39 or even 30 mm, are still too large for certain applications such as video and signaling. In addition, even in the field of lighting, one may want to use small diameter electric bulbs.

Reference may also be made to the following documents: US-A-3932780 in which a 28 V, 20 W bulb is coated on the outside with a reflective coating; FR-A-2244258 which relates to a miniature electric lamp for decorating or displaying indications; FR-A-2435666 which relates to a low-voltage incandescent bulb (50 to 65 V) intended for a cinematographic camera. The other documents which follow relate to bulbs not having a "mushroom" shape in combination, an overall diameter (including reflector) which can go down to 25 mm, an operating voltage of 220, 230 V: CA-A -952172; US-A-4893050; FR-A-2385980; FR-A-2364401; FR-A-2425028; FR-A-2344122; US-A-4292564; FR -A-2363052; FR-A-2441794; US-A-4342142; FR-A-2316535; DE-A-2840537.

There is also known (see document US-A-3837371) a method of shaping a filament of a floor lamp in which all the filament supports are in their middle part folded in a V, alternately in one direction and in the other. This technique makes it possible to reduce the size of the filament, all other things being equal, in particular the length of the filament. It applies more especially with a relatively short filament, intended for a bulb operating at low voltage (up to 60 V maximum). With this process, the filament fits into an envelope of generally cylindrical shape, or even is located in a plane or in the immediate vicinity of a plane.

• 1/ partir d'une ébauche d'ampoule de forme générale "champignon" ;
• 2/ métalliser intérieurement la moitié arrière de la partie renflée de l'ébauche ou l'équiper d'un réflecteur extérieur ;
• 3/ équiper un pied pourvu d'une pluralité de supports avec un filament ;
• 4/ sceller le pied ;
• 5/ Pomper l'air (ou le gaz ambiant) dans l'ampoule et, le cas échéant, le remplacer par un gaz convenable ;
  et,
• 6/ sceller le culot.

Finally, the process comprising the general steps consisting of:

• 1 / from a blank of a generally mushroom shaped bulb;
• 2 / internally metallize the rear half of the bulged part of the blank or equip it with an external reflector;
• 3 / equipping a stand provided with a plurality of supports with a filament;
• 4 / seal the foot;
• 5 / Pump the air (or ambient gas) into the bulb and, if necessary, replace it with a suitable gas;
  and,
• 6 / seal the base.

But as it is known today, this technique does not make it possible to obtain a bulb having an outside diameter which can go down to about 25 mm.

The subject of the invention is therefore an electric bulb operating by incandescence, having in combination an operating voltage of 220, 230 V, therefore directly usable on European electrical networks, a general "mushroom" shape, and an outside diameter which can go down or be around 25 mm.

Such an electric bulb can be used not only for lighting but also for video and signaling.

• on part d'une ébauche d'ampoule de forme générale "champignon" ayant un diamètre pouvant descendre ou être voisin de 25 mm environ ;
• on métallise substantiellement la face interne de la moitié arrière de la partie renflée de l'ébauche ;
• on part d'un pied pourvu d'une pluralité de supports pour un filament et on cambre en V un support sur deux, le filament s'inscrivant dans une enveloppe en forme générale de tronc de cône ;
• on scelle le pied ;
• on pompe l'air se trouvant dans l'ampoule ;
• on scelle un culot ;

To this end and according to a first possible variant embodiment, a method of manufacturing an electric bulb operating by incandescence and characterized in that:

• one starts from a bulb blank of general "mushroom" shape having a diameter which can go down or be around 25 mm;
• the inner face of the rear half of the bulged part of the blank is substantially metallized;
• one starts from a foot provided with a plurality of supports for a filament and one V arches one support out of two, the filament being inscribed in an envelope in the general shape of a truncated cone;
• we seal the foot;
• the air in the bulb is pumped;
• a pellet is sealed;

• on part d'une ébauche d'ampoule de forme générale "champignon" ayant un diamètre pouvant descendre ou être voisin de 25 mm environ ;
• on applique sur et on associe un réflecteur à la face externe de substantiellement la moitié arrière de la partie renflée de l'ébauche ;
• on part d'un pied pourvu d'une pluralité de supports pour un filament et on cambre en V un support sur deux, le filament s'inscrivant dans une enveloppe en forme générale de tronc de cône ;
• on scelle le pied ;
• on pompe l'air se trouvant dans l'ampoule ;
• on scelle un culot.

According to a second alternative embodiment, the method is characterized in that:

• one starts from a bulb blank of general "mushroom" shape having a diameter which can go down or be around 25 mm;
• a reflector is applied to and associated with the external face of substantially the rear half of the bulged part of the blank;
• one starts from a foot provided with a plurality of supports for a filament and one V arches one support out of two, the filament being inscribed in an envelope in the general shape of a truncated cone;
• we seal the foot;
• the air in the bulb is pumped;
• we seal a pellet.

• l'ébauche de forme générale "champignon" a un diamètre pouvant descendre jusqu'à 25 mm environ ;
  et,
• le filament est sélectionné pour que l'ampoule fonctionne sous une tension d'utilisation de 220, 230 V, avec une puissance de quelques watts ;

According to another aspect, the invention relates to an electric bulb operating by incandescence obtained by the method according to one of these two variants, characterized in that:

• the blank of general shape "mushroom" has a diameter which can go down to about 25 mm;
  and,
• the filament is selected so that the bulb operates at an operating voltage of 220, 230 V, with a power of a few watts;

According to a preferred embodiment, the bulb has a diameter equal to or close to 25 mm and an axial length of the order of 45 mm.

• la figure 1 est une vue en élévation d'une ampoule conforme à l'invention selon la première variante du procédé, la moitié gauche montrant la zone réfléchissante et la moitié droite montrant l'intérieur de l'ampoule, sans la zone réfléchissante ;
• la figure 2 est une vue en élévation d'une ébauche d'ampoule mise en oeuvre dans le procédé selon l'invention ;
• la figure 3 est une vue en coupe axiale d'un réflecteur mis en oeuvre dans la seconde variante du procédé selon l'invention ;

The other characteristics of the invention result from the description which follows and the following appended figures:

• Figure 1 is an elevational view of a bulb according to the invention according to the first variant of the method, the left half showing the reflective area and the right half showing the interior of the bulb, without the reflective area;
• Figure 2 is an elevational view of a bulb blank implemented in the method according to the invention;
• Figure 3 is an axial sectional view of a reflector used in the second variant of the method according to the invention;

The invention relates to an electric bulb 1 operating by incandescence. Such a bulb comprises a bulb or bulb itself 2, made of glass or equivalent, a base 3 sealed to the bulb 2 and allowing on the one hand the fixing of the electric bulb 1 (by a thread 4 in the embodiment shown or of bayonets -not shown- or other) and on the other hand the electrical connection thanks to electrical contacts 5.

The electric bulb 1 also comprises a foot 6 provided, towards its innermost end, with a plurality of radial supports 7 - in this case seven supports 7 - for a spiral filament 8 - and in this case monospiral - suitably electrically connected to contacts 5.

• une partie renflée 11, frontale et opposée au culot 3, creuse, s'inscrivant dans une enveloppe ayant une forme générale d'ellipsoïde ou de pseudo-ellipsoïde de révolution autour de l'axe 9 ayant un plan de grand axe P perpendiculaire à l'axe 9. Cette partie renflée 11 comprend elle-même une moitié avant 12 constituant l'extrémité frontale de l'ampoule électrique 1 opposée au culot 3 et une moitié arrière 13 attenante à la moitié avant 12 dans le plan P, le long d'une circonférence 14 définissant le plus grand encombrement radial de l'ampoule électrique 1 ;
  et,
• un prolongement arrière 15, cylindrique au moins vers l'avant, d'axe 9, creux également, venu de fabrication de façon monobloc avec la partie renflée 11 et associée à celle-ci le long d'une circonférence 16 constituant le bord le plus arrière de la moitié arrière 13, et duquel est associé, à l'opposé, le pied 5 et le culot 3.

The electric bulb 1 has a general axis of symmetry 9. At one end is the base 3 and from the other end extends the bulb or bulb itself 2. This bulb, therefore the blank 10 from of which it is made (Figure 2), and therefore ultimately the light bulb 1 as a whole, is generally called "mushroom". Such a form is characterized by:

• a swollen part 11, frontal and opposite to the base 3, hollow, inscribed in an envelope having a general shape of ellipsoid or pseudo-ellipsoid of revolution around the axis 9 having a plane of major axis P perpendicular to l 'axis 9. This bulged portion 11 itself comprises a front half 12 constituting the front end of the electric bulb 1 opposite the base 3 and a rear half 13 adjoining the front half 12 in the plane P, along d 'A circumference 14 defining the largest radial size of the light bulb 1;
  and,
• a rear extension 15, cylindrical at least towards the front, of axis 9, also hollow, coming from manufacturing in a single piece with the swollen part 11 and associated with it along a circumference 16 constituting the rearmost edge of the rear half 13, and of which is associated, on the opposite, the foot 5 and the base 3 .

It goes without saying that the above description is theoretical given that the bulb or bulb 2 does not include sharp angles, but, instead, leaves and rounded.

The blank 10 has the same general shape as the bulb or bulb itself 2, the rear extension 15 being completely cylindrical and of sufficient axial length.

Throughout the text, the qualifiers "front" or "front" apply to the parts situated relatively towards the bulging part 11 and the qualifier "rear" to the parts situated relatively towards the base 3, the light rays of the electric bulb 1 in operation leaving the front half 12 and being directed forward.

Such a general structure of a light bulb and such a general "mushroom" shape are in themselves known from the state of the art and for this reason need not be described further.

According to the invention, the maximum outside diameter of the electric bulb 1, that is to say the diameter of the circumference 14, is at least equal to approximately 25 mm, that is to say that this diameter can be as small as about 25mm. This diameter can go up to any desired higher value, for example 39 mm or more. In the preferential embodiment of a miniature electric bulb 1, this diameter is equal to or close to 25 mm.

In this case, the overall axial length of the electric bulb 1 between the median axial apex 17 of the front half 12 and the base 3 is equal to or close to approximately 45 mm. In addition, the filament 8 is selected so that the bulb operates on 220, 230 V, with a power of the order of a few watts (for example 7 watts).

• 1/ On part d'une ébauche 10 ayant elle aussi une forme générale "champignon", avec un diamètre extérieur au moins égal à 25 mm environ pouvant descendre jusqu'à 25 mm environ et, plus spécialement égal à ou voisin de 25 mm environ.
• 2/ On s'assure que substantiellement la moitié arrière 13 soit réfléchissante, les rayons lumineux provenant du filament 8 étant réfléchis vers la moitié avant 12.
• 3/ On réalise le pied 6 avec ses supports 7 et son filament 8.
• 4/ On scelle le pied introduit dans l'ébauche 10.
• 5/ on pompe l'air ou le gaz ambiant se trouvant dans l'ampoule et, le cas échéant, on le remplace par tout gaz souhaité.
• 6/ On scelle le culot.

To make such a bulb, a process is implemented in which:

• 1 / We start from a blank 10 also having a general "mushroom" shape, with an outside diameter at least equal to approximately 25 mm which can go down to approximately 25 mm and, more especially equal to or close to approximately 25 mm .
• 2 / It is ensured that substantially the rear half 13 is reflective, the light rays coming from the filament 8 being reflected towards the front half 12.
• 3 / The foot 6 is produced with its supports 7 and its filament 8.
• 4 / The foot introduced into the blank 10 is sealed.
• 5 / the ambient air or gas in the bulb is pumped and, if necessary, replaced by any desired gas.
• 6 / We seal the pellet.

A first problem with a light bulb 1 as it has been described, is to make the rear half 13 reflective.

This first problem is solved, in a first variant by an internal metallization by means of an appropriate metallization head and, in a second variant by a reflector 18 (FIG. 3).

As regards the first variant, it is derived from the generally known method of vacuum metallization as applied to light bulbs.

• au chargement d'un cavalier du métal (aluminium par exemple) à déposer sur un conducteur électrique spiralé reliant deux électrodes d'une tête de métallisation ;
• au chargement d'une capsule-masque métallique sur la tête de métallisation ;
• au chargement de l'ébauche d'ampoule sur la tête de métallisation ainsi chargée ;
• à la mise en place à proximité de l'ébauche de moyens générant des forces magnétiques d'attraction de la capsule-masque afin de la tenir en position convenable ;
• à la mise sous vide ;
• à réaliser une décharge électrique apte à évaporer le cavalier de métal.

In this first variant, metallization is carried out by the steps consisting:

• loading a metal jumper (aluminum for example) to be deposited on a spiraled electrical conductor connecting two electrodes of a metallization head;
• loading a metal mask capsule on the metallization head;
• loading the bulb blank on the metallization head thus loaded;
• the establishment near the blank of means generating magnetic forces of attraction of the capsule-mask in order to hold it in suitable position;
• vacuuming;
• to carry out an electrical discharge capable of evaporating the metal jumper.

• deux électrodes ;
• un conducteur électrique spiralé reliant les deux électrodes, apte à recevoir un cavalier d'un métal à déposer ;
• une capsule-masque métallique destinée à être associée fonctionnellement au cavalier pour limiter la zone de dépôt de métal surtout vers l'avant ;
• des moyens générant des forces magnétiques d'attraction de la capsule-masque afin de la tenir en position convenable une fois que la tête de métallisation est placée à l'intérieur d'une ébauche d'ampoule, les moyens générant des forces magnétiques étant placés à l'extérieur.

To this end, a metallization head (not shown) is used which comprises:

• two electrodes;
• a spiraled electrical conductor connecting the two electrodes, capable of receiving a jumper of a metal to be deposited;
• a metal mask cap intended to be functionally associated with the rider to limit the metal deposition area, especially towards the front;
• means generating magnetic forces of attraction of the capsule-mask in order to hold it in suitable position once the metallization head is placed inside a blank of bulb, the means generating magnetic forces being placed outside.

As it follows from the above, the metallization head used does not have the usually used capsule-mask support bracket, which reduces the radial size of the metallization head and allows it to be introduced into the 'restricted opening 19 of the rear extension 15. The process used is therefore devoid of the step of placing the capsule-mask on such a stirrup.

FIG. 1 represents an electric bulb 1 obtained by the method according to this first variant, the metallized part being referenced 20. The metallization being internal, no external excess thickness, however small, appears at the border of the metallized part 20.

It should be understood that if the position of the frontal limit 20a of the reflective metallized part is critical, the latter being placed substantially in the plane P or close to it, therefore conforming or close to the circumference 14, there is no the same is not true of that of the rear limit 20b which can extend more or less behind the circumference 16 and be more or less regular, as is the result of metallization.

• on part du réflecteur 18 ayant une forme comprenant une coupelle 21 et une partie cylindrique 22 ;
• on enfile la partie tubulaire 15 de l'ébauche 10 d'ampoule dans la partie cylindrique 22 de manière que la moitié arrière 13 de la partie renflée 11 soit plaquée sur l'intrados de la coupelle 21 ;
• on associe rigidement l'ampoule et le réflecteur 18.

As regards the second variant, it comprises the stages in which:

• one starts from the reflector 18 having a shape comprising a cup 21 and a cylindrical part 22;
• the tubular part 15 of the bulb blank 10 is threaded into the cylindrical part 22 so that the rear half 13 of the bulged part 11 is pressed against the lower surface of the cup 21;
• the bulb and the reflector 18 are rigidly associated.

As follows from the above, the reflector 18 has a shape complementary to that of the bulb or bulb 2 in the vicinity of the circumference 16. Such a reflector 18 fits perfectly and is applied to the bulb or bulb itself, thus creating a slight excess thickness corresponding to the thickness of the reflector. This thickness can be very small, of the order of a fraction or a few millimeters.

A second problem with a light bulb 1 as it has been described relates to the filament 8 and the fact that, simultaneously, the filament has a length sufficient to accommodate a potential difference of 220, 230 V, and its radial size must be limited to allow passage through part 15 and passage 19.

This second problem is solved by implementing the general V-curvature technique of the supports 7 of filaments as described and results from document US-A-3837371 with the particular characteristic that, alternatively, one support 7 in two is arched in V and a support 7 on two is not. All the camberings are made in the same direction, in this case, in the embodiment shown, the opening V turned towards the front half 12. Furthermore, and in combination, the supports 7, originally substantially perpendicular to the axis 9 , are brought closer to this axis therefore inclined finally thereon by being slightly bent at their base of connection with the foot 6 proper. This folding, in the embodiment considered, relates to all the supports 7, those arched in a V and those which are not. However, the folds are in two opposite directions, the non-arched supports 7 being folded forward and the arched supports 7 rearward.

It follows that the end loops 23 and holding supports 7 in which the filament 8 passes are located on two circumferences of axis 9, one front of large diameter and the other rear of small diameter, the filament 8 which itself forms part of an envelope in the general shape of a truncated cone in the same general direction as the rear half 13. This arrangement promotes the reflection of light on the reflective part of the electric bulb 1. This is all the more more than filament 8 is practically substantially arranged opposite the reflecting part 20.

To this end, use is made of a device for arching filament supports of an electric bulb which comprises a matrix and a punch shaped so that, alternately, one support in two is bent in V, and one support in two is not not arched and that both arched and non-arched supports are bent at their bases in opposite directions.

Reference is now made, more specifically to the blank 10. Such a blank 10 has, for electric bulbs 1, a diameter equal to or close to about 25 mm, a thickness of the order of 0.4 to 0.8 mm, depending on the zones and tolerances. The radii of curvature of the front 12 and rear 13 halves are adjacent. For example, in the embodiment under consideration, they are approximately 24 mm and 27.5 mm respectively. In the connection zone of the two halves 12, 13, around the circumference 14, the radius of curvature is substantially smaller, for example by about 4.8 mm. Such a blank 10 has an opening 19 of the order of 11 mm and its overall axial length is of the order of approximately 77 mm.

Claims (10)

Method for manufacturing an electric bulb operating by incandescence, characterized in that: - We start from a bulb blank (10) of general "mushroom" shape having a diameter which can go down or be around 25 mm; - The internal face of the rear half (13) of the bulged part (11) of the blank (10) is substantially metallized; - we start from a foot (6) provided with a plurality of supports (7) for a filament (8) and we camber a V support (7) on two and we fold the supports at their base in two opposite directions , the filament (8) forming part of an envelope in the general shape of a truncated cone; - the foot is sealed (6); - the air in the bulb (10) is pumped; - we seal a base (3). Method for manufacturing an electric bulb operating by incandescence, characterized in that: - We start from a blank (10) of bulb of general shape "mushroom" having a diameter which can go down or be around 25 mm; - A reflector (18) is applied to and associated with the external face of substantially the rear half (13) of the bulged part (11) of the blank (10); - we start from a foot (6) provided with a plurality of supports (7) for a filament (8) and we camber a V support (7) on two and we fold the supports at their base in two opposite directions , the filament (8) forming part of an envelope in the general shape of a truncated cone; - the foot is sealed (6); - the air in the bulb (10) is pumped; - we seal a base (3). Process according to Claim 1, characterized in that the metallization is carried out by the steps consisting: - loading a metal jumper to be deposited on a spiral conductor connecting two electrodes of a metallization head; - loading a metal mask capsule on the metallization head; - loading the bulb blank (10) onto the metallization head thus loaded; - the establishment near the blank (10) of means generating magnetic forces of attraction of the capsule-mask in order to hold it in suitable position; - vacuuming; - to carry out an electric discharge able to evaporate the metal jumper. Method according to claim 2, characterized in that: - We start from a reflector (18) having a shape comprising a cup (21) and a cylindrical part (22); - the tubular part (15) of the bulb blank (10) is threaded into the cylindrical part (22) so that the rear half (13) of the bulged part (11) of the blank (10) is pressed against the underside of the cup (21); - The bulb (10) and the reflector (18) are rigidly associated. Metallization head specially intended for implementing the process according to claims 1 and 3 characterized in that it comprises: - two electrodes; - a spiral conductor connecting the two electrodes, capable of receiving a jumper of a metal to be deposited; - a metal mask cap intended to be functionally associated with the rider to limit the metal deposition area; - Means generating magnetic forces of attraction of the capsule-mask in order to hold it in suitable position once the metallization head is placed inside a blank (10) of bulb, the means generating magnetic forces being placed outside of it. Device for arching supports of a filament of an electric bulb, specially intended for implementing a method according to one of claims 1 and 2 characterized in that it comprises a matrix and a punch shaped to that, alternatively, one support (7) in two is arched in V and one support (7) in two is not arched, the supports (7) being folded at their base in two opposite directions. Electric bulb operating by incandescence obtained by the process according to any one of Claims 1 to 4, characterized in that: - The blank (10) of general "mushroom" shape has a diameter which can go down to about 25 mm;
and, - the filament (8) is selected so that the bulb (1) operates under an operating voltage of 220, 230 V, with a power of a few watts. Electric bulb operating by incandescence obtained by the process according to any one of Claims 1 to 4, characterized in that: - The blank (10) of general "mushroom" shape has a diameter equal to or around 25 mm approximately;
and, - the filament (8) is selected so that the bulb (1) operates under an operating voltage of 220, 230 V, with a power of a few watts; - the axial length of the bulb (1) is around 45 mm. Electric bulb according to one of claims 7 and 8 characterized in that it comprises seven supports (7) for a filament (8) monospiral, the supports (7) being alternately, one in two V-shaped and one in two not arched, the supports (7) being folded at their base in two opposite directions and the filament (8) forming part of an envelope in the general shape of a truncated cone. Electric bulb according to claim 9 characterized in that the fragment (8) is substantially arranged opposite the reflecting part (20).

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