Lighting mechanism having a supplementary space formed within a crimped part

The invention relates to a lighting mechanism with an elongated shield made of transparent material, a burner disposed in the center of the shield, sealed-off burner connectors including both a proximal burner connector and a distal burner connector, each of which projects diametrically away from the burner in the longitudinal direction of the shield so as to extend into a proximal and a distal end region of the shield. Supply leads pass into the shield by way of a crimped part thereof and are joined there to the burner connectors. In the region of the crimped part a supplementary space is provided that is open to the interior of the shield and into which at least a certain region of the proximal burner connector extends.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from European Patent Application No. 04 027 383.1, filed Nov. 18, 2004, the contents of which are herein incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a lighting means comprising a tubular shield made of transparent material, in the interior of which are a burner, sealed-off burner connectors including both a proximal and a distal burner connector each of which projects diametrically away from the burner in the long direction of the shield, extending into a proximal and a distal end region of the shield, and supply leads that pass through a crimped part of the shield and there are joined to the burner connectors, as well as to a reflector lamp, in particular a metal-halogen-vapor reflector lamp which includes the lighting means in accordance with the invention.

2. Description of the Related Art

A discharge tube designated here as a “burner” is conventionally housed in an elongated shield made of transparent material, such that the elongated shield (conventional “pinch-seal” shield as shown inFIG. 4) is sealed by crimping. The leads that supply current to the burner are also conventionally passed through this pinch seal. However, an adequate minimal sealing length of the supply leads must be disposed within the crimped part in order to ensure a reliably tight seal between the material of which the shield is made and the supply leads. To accommodate this minimal sealing length, the overall outer dimensions of the shield must be made relatively long, although for a great variety of applications a shorter shield would be desirable, in particular one in which there is a smaller distance between an outer shield end directed toward a base and the center of the burner (light center length).

To obtain a light center length that is as short as possible, and/or to avoid lengthening the shield on account of the problem of sealing off the supply leads in a crimped section, other solutions are also known for sealing the elongated shield and/or making contact with the burner, such as sealing a shield that is open at its end by means of a ceramic disk in combination with special sealing materials (such a conventional disk-sealed shield is shown inFIG. 5). However, this sealing means is laborious and expensive to construct, and the kinds of glass used as material for the shield must have a high coefficient of expansion. Glass types with high coefficients of expansion, however, as a rule have a low softening temperature and are not well suited especially for compact discharge lamps; instead, the glass shield must be considerably expanded around the burner so that its distance from the burner is sufficient to avoid overheating.

The objective of the present invention, in contrast, is to disclose a lighting means of the kind cited at the outset that is as compact as possible and can be manufactured with acceptable effort and expense.

SUMMARY OF THE INVENTION

This objective is achieved by a lighting means having the characteristics where the lighting means can be designed for use with a reflector lamp, in which case because of the compact construction of the lighting means, it is possible, for the first time, to incorporate it into commercially available compact reflector lamps. Advantageous further developments are disclosed herein.

According to a central consideration, in the vicinity of the crimped part of the shield a supplementary space is provided that is open toward the interior of the shield, in particular a supplementary burner space, in which parts of the burner and/or the proximal burner connector can be accommodated, at least in particular regions. This allows the overall length to be reduced. According to another central consideration, as seen in projection onto the longitudinal plane defined by the crimped section of the shield an additional space in the proximal end region of the shield, in particular the supplementary space that communicates with the interior of the shield, is spaced further apart from the burner than the point of entry of the supply leads into the interior of the shield. Viewed in projection onto the longitudinal plane of the shield, the supply leads enter not at the end but rather at the side with reference to the interior of the shield. Viewed in the longitudinal direction of the shield, the supplementary space overlaps at least in certain regions with the crimped part that is needed to seal in the supply leads.

In one embodiment of the present invention the crimped part can have a substantially U-shaped basic form.

In one embodiment of the present invention, the crimped part includes two outer sections as well as a connecting section, in which case the supply leads pass through the outer sections.

The connecting section preferably extends in the long direction of the shield for a shorter distance than do the outer sections. The outer sections should extend in the long direction of the shield at least twice as far as does the connecting section; preferably they are 4 to 10 times, and in particular 7 to 8 times as long as the connecting section.

In another embodiment of the present invention, the supplementary space tapers in the direction away from the burner, so that it is substantially funnel-shaped.

At least in its region toward the burner the supplementary space can have a substantially circular or oval cross-sectional shape in the plane perpendicular to the long direction of the shield.

The supplementary space can have a length, in the long direction of the shield, that is preferably of the order of magnitude of the inside diameter of the shield outside the supplementary space, preferably within the range 80 to 120% of this diameter. The inside diameter of the supplementary space, i.e. its extent in the direction transverse to the long direction of the shield, can be in the range 30 to 70%, preferably about 50 to 55% of the inside diameter of the shield outside the supplementary space.

According to another aspect of the present invention the shield can be dimensioned such that the distance between the center of the burner and an outer edge of the crimped part that faces away from the burner (light center length) is smaller than in conventional lamps with a light center length L′ or L″ (L<L′ or L<L″, for a given wattage).

For example, in the case of a 20 W lamp the conventionally required light center length of 22 mm can be distinctly reduced, so that in this exemplary power range a light center length<22 mm can be obtained.

The transparent materials to be considered for the elongated shield are preferably quartz glass, hardened or soft glass, in particular vitreous aluminum silicate.

According to another aspect, the supply leads comprise a proximal as well as a distal lead, such that the proximal supply lead is bent twice, in opposite directions.

The burner connectors can either each be made integral with the supply leads or they can be joined thereto by way of electrically conductive contact sites.

According to another aspect of the present invention the burner can be constructed as a ceramic burner, in particular made of polycrystalline aluminum oxide (PCA).

According to an alternative aspect of the present invention, however, the burner can be manufactured by quartz technology.

The lighting means in accordance with the invention can be used in a reflector lamp, in particular, a metal-halogen-vapor reflector lamp including as the reflector an external enclosure with a neck region, over which a transparent cover is positioned; the lighting means can be positioned on an optical axis within this enclosure.

DESCRIPTION OF THE INVENTION

InFIG. 4a lighting means with a crimped part25′ according to the state of the art (conventional pinch-seal shield) is shown in section. An elongated, substantially cylindrically constructed shield17′ is hermetically sealed off by the crimped part25′. In the interior of the shield17′ is situated a burner18′ with burner connectors19′,20′. Because of the severe heating in the region of the burner18′, the burner connectors19′,20′ must reach to a sufficient distance away from the burner18′. The diametrically opposed burner connectors19′,20′, which project into a proximal end region21′ and distal end region22′, respectively, are joined in an electrically conductive manner to supply leads23′,24′ at contact sites36,37′, in order to supply current to the burner18′. The supply leads23′,24′ simultaneously provide mechanical fixation of the burner18′ within the interior of the shield17′. It is relatively problematic to arrange passage of the supply leads23′,24′ into the interior of the shield17′. For this purpose the supply leads23′,24′ are guided through the above-mentioned crimped part25′, certain regions of the supply leads23′,24′ being constructed in the form of a thin sheet of molybdenum40′ in order to ensure reliable sealing, even over long periods of operation, between the leads and the crimped part25′ of the shield17′, which as a rule is made of quartz glass. However, a disadvantage lies in the resulting overall length of the shield17′, in particular the large distance separating the center of the burner18′ from an outer edge33′ of the crimped part25′ (light center length L′).

A means of shortening this length is already known from the state of the art, as shown inFIG. 5: this is a lighting means16″ with a shield17″ of the conventional kind sealed off with a ceramic disk, in which case the light center length L″ is shortened by elimination of the crimped part. The shield17″ in this case is hermetically closed not by crimping but rather by the ceramic disk38″ with the aid of sealing means39″ or sealing paste between shield and ceramic disk38″. The supply leads23″,24″ accordingly need not be passed through a crimped part, but rather can be passed through the ceramic disk38″ in a gas-tight manner. However, it is difficult to complete the electrical and mechanical connection between the supply leads23″,24″ and the burner connectors19″20″ of a burner18″. In order to bring about sufficiently reliable sealing between shield, sealing means39″ and ceramic disk38″, soft glass must be used for the shield, and such glass is considerably less resistant to the heat produced by the burner18″. Hence an expanded section41″ must be provided around the burner18″, in order to avoid overheating of the shield17″. On the whole, then, especially because of the expansion41″ and the ceramic disk38″, the manufacturing expense is considerably increased.

FIGS. 1 and 2show an embodiment of a reflector lamp in accordance with the invention as it appears in two orthogonal sections. The reflector lamp comprises, firstly, an outer enclosure13constructed as a reflector11with a neck region12, with a transparent cover14positioned on top of the enclosure13. The transparent cover14can serve exclusively as a cover or can also constitute a lens by means of which the light is focused as desired. On a central optical axis A a lighting means16is disposed. The lighting means16comprises a shield17, here made of glass with a high softening point, which at its end facing the neck region12of the reflector lamp is closed in a gas-tight manner by a crimped part25. In the interior of the shield17is a burner18, which in the present embodiment is constructed as a ceramic burner. The burner18forms a metal-halogen-vapor discharge tube, whereas it has conventionally not been possible for ceramic burners suitable for a metal-halogen-vapor lamp to be used in a reflector lamp with a reflector of about 50 mm (2 inches) diameter (MR 16 or ES 50), such as are described in particular in DE 102 33 073 B3. The shield in accordance with the invention is distinguished by a very compact structure, i.e. its length along the optical axis A is small, which is achieved as follows: in the region of the crimped part25, in a proximal end region21of the shield17, a supplementary space26is formed, which is open to the interior of the shield17and into which the burner18or parts thereof, namely the burner connectors19,20, project to at least a certain extent. As a result, the distance between an outer edge33(facing away from the burner18) of the crimped part25and the center of the burner18(light center length) can be shortened.

In concrete terms, the burner18comprises burner connectors19,20oriented parallel to the optical axis A and hence diametrically opposed to one another, namely a proximal burner connector19which at its end extends into the supplementary space26, and a distal burner connector20at the opposite end of the shield. The crimped part25differs from the state of the art as shown inFIG. 5in that it is constructed not as a flat, rectangular section of the shield17but rather as a flat, substantially U-shaped element. The crimped part25in the embodiment illustrated here comprises a first outer section30as well as a second outer section31, which are joined to one another by a connecting section32. The route of the supply leads23,24through the outer sections30,31is gas-tight, and at entry points28,29the leads emerge from the crimped part25and enter the interior of the shield17. The entry points28,29as seen in projection onto the optical axis A, i.e. onto the longitudinal extent of the shield17, are closer to the burner18than is the floor of the supplementary space26. Hence the supply leads23,24enter the interior of the shield17not at its floor, but rather laterally. The supply leads23,24comprise a proximal supply lead23as well as a distal supply lead24. Within the shield17the proximal supply lead23exhibits a first bend34as well as a second bend35, such that the first bend34and second bend35are oppositely directed. The first bend34is configured as a U-shaped, 180° curve. The oppositely directed second bend35forms a 90° curve, after which the lead makes an electrically conductive junction with the proximal burner connector19within the supplementary space26, by way of a contact site36. The distal supply lead24passes through the opposite side of the crimped part25, i.e. through the second outer section31, and then runs parallel to the shield wall into the shield's distal end region22, where it makes an electrically conductive junction with the distal burner connector20by way of a contact site37. The distance separating the contact sites36,37from the center of the burner18is determined by the fact that the burner connectors must be made sufficiently long on account of the enormous amount of heat produced. If the burner connectors19,20are made too short, it cannot be guaranteed that the sealing at the burner connectors19,20will be adequate for the lifetime of the burner18.

The supply leads23,24can be passed through the crimped part25as conductors with a circular cross section if the shield17is made of hardened glass. In contrast, if the shield17is made of quartz glass the circular leads23,24are interrupted in the region of the crimped part25, and in this region are replaced by a thin sheet of material, preferably molybdenum (cf.FIG. 7).

The lighting means16is normally attached to the reflector11in combination with a base42, by means of a ceramic cement. The supply leads23and24make electrically conductive connection with contact pins in the base42.

InFIG. 3an embodiment of a lighting means16according to the invention that corresponds substantially to the embodiment illustrated inFIGS. 1 and 2is shown schematically in perspective.

The supplementary space26tapers in the direction away from the burner18, in substantially a funnel shape. Its length in the direction of the optical axis A is of the order of magnitude of the diameter of the shield17, or even greater than the diameter of the shield17.

Owing to the provision of the supplementary space26in accordance with the invention it is possible to insert a lighting means having a ceramic burner of the metal-halogen-vapor discharge lamp type into a commercially available reflector lamp with ca. 50 mm (2 inches) diameter, according to the standard MR 16 or ES 50.

InFIG. 6the lighting means in accordance with the invention that has already been described with reference toFIGS. 1 and 2is shown again, for comparison with the lighting means according to the state of the art shown inFIGS. 4 and 5, in particular to make clear the distinctly shorter light center length L. In the embodiment according toFIG. 6the shield17is made of hardened glass.

InFIG. 7another embodiment of the lighting means16in accordance with the invention is illustrated for comparison with the lighting means shown inFIGS. 4 to 6; this embodiment has again been modified, namely in that the shield17is made of quartz glass. The structure of the lighting means16according toFIG. 7corresponds substantially to that of the lighting means according toFIG. 6. To achieve sufficient sealing of the places where the supply leads23,24pass through the crimped part25in accordance with the invention, a sufficiently long section of each of the supply leads23,24is advantageously made of thin molybdenum foil40. With such a molybdenum foil section it is possible to ensure adequately thorough sealing of the crimped part25even over extremely long operating periods.