Halogen incandescent lamp

Disclosed is a halogen incandescent lamp having a lamp vessel, which is sealed at one end and in which at least one luminous element is accommodated, a vessel section 42 being in the form of a side reflector which extends only over a subregion of the lamp vessel circumference. A light-exit window 40 adjoins this vessel section 42 in the circumferential direction. According to the invention, the light-exit window 40 is comparatively slightly curved in cross section, the vessel section 42 forming the side reflector bulging out away from the light-exit window 40. This bulged-out region is preferably provided with a kidney-shaped constriction 46.

TECHNICAL FIELD

The invention relates to a halogen incandescent lamp in accordance with the preamble of patent claim1.

BACKGROUND ART

Such a side reflector lamp is described under the product designation “MINISTAR®” at the Internet domain www.osram.de. With this halogen incandescent lamp, a circumferential section of a lamp vessel is provided with a reflective coating such that a laterally arranged light-exit window remains on the lamp vessel, and this light-exit window makes it possible to use this lamp, for example, as a downlight, the lamp being mounted in the horizontal direction. Such reflector lamps have an extremely compact design and therefore require a minimum amount of installation space when they are installed.

This known design is significantly simpler than conventional reflector lamps, as are described, for example, in the European patent specification EP 0 495 194 B1. Such reflector lamps comprise a reflector, which is formed by a parabolic or ellipsoidal glass cap, and a halogen incandescent lamp which is fixed in the optical axis of the reflector.

It has been shown that the compact halogen incandescent lamps having a reflector integrated in the lamp vessel can be improved as regards the radiated luminous flux in particular when a luminous element which is accommodated in the lamp vessel is formed with at least two filament sections. Luminous elements having two filament sections are used, for example, in the case of halogen incandescent lamps envisaged for operation using the system voltage, as are described in the European patent specification EP 0 446 460 B1.

DISCLOSURE OF THE INVENTION

The invention is based on the object of providing a halogen incandescent lamp having a side reflector with which the illumination of a predetermined area is improved.

This object is achieved according to the invention by a halogen incandescent lamp having a lamp vessel, which is sealed at one end and in which at least one luminous element is accommodated, a vessel section being in the form of a side reflector which extends over a subregion of the lamp vessel circumference, and a light-exit window of the lamp vessel adjoining the vessel section in the circumferential direction, whereby, in the cross section of the lamp vessel, the vessel section forming the side reflector bulges out away from the flat or comparatively slightly curved light-exit window.

The halogen incandescent lamp according to the invention has a lamp vessel, which is sealed at one end and in which at least one luminous element is accommodated, a section of the lamp vessel being in the form of a side reflector which extends only over a subregion of the lamp vessel circumference such that a light-exit window remains. According to the invention, when viewed in cross section, the vessel section acting as the reflector bulges out away from the light-exit window which has a comparatively flat curve or is of planar design. The average radius of curvature of the light-exit window is in this case greater than the average radius of curvature of the vessel section acting as the reflector which bulges out towards the rear. That is to say the lamp vessel which is generally cylindrical is given, in the region of the reflector, a curvature which is, for example, approximately parabolic or ellipsoidal and is thus optimized as regards the reflection properties such that the luminous flux emerging from the light-exit window is greater than in the case of conventional solutions, and targeted illumination of a predetermined area is made possible.

The width, when viewed in cross section, of the light-exit window is preferably greater than the depth of the vessel section in the form of a reflector.

The invention may particularly advantageously be used in a halogen incandescent lamp, in the case of which the luminous element is designed to have two filament branches. In this case, a constriction which extends in the direction towards the light-exit window is formed at a vertex of the bulge of the reflective vessel section such that a rear wall of the vessel section is pulled in to form the shape of a kidney. In other words, the lamp bulb which is in the form of a reflector is provided with two depressions, whose geometry is designed such that the light radiation emitted by each filament branch is reflected in optimum fashion.

With this solution, it is particularly preferable if this constriction is arranged on a plane of symmetry with respect to the filament branches.

The luminous elements, in particular in the case of halogen incandescent lamps envisaged for the system voltage, are fixed using holding knobs, as are described in the European patent specification mentioned initially EP 0 446 460 B1. Such holding knobs are in principle inward curves in the lamp housing between which a subregion of the luminous element is clamped. With the solution according to the invention, a holding knob is preferably formed in the region of the emission window, and a holding knob, which is arranged diametrically with respect thereto, is formed in the region of the rearward constriction.

The luminous element is advantageously designed to have two filament branches which are preferably arranged at an angle with respect to one another and which are connected to one another via a connecting part which is gripped by the holding knobs.

In one preferred exemplary embodiment, the reflective vessel section is provided with a coating which is preferably applied to the outer circumference of the lamp vessel.

The sealed end of the lamp vessel is advantageously in the form of a base, as is described, for example, in the Unites States patent specification U.S. Pat. No. 6,075,318 B1.

In an exemplary embodiment according to the invention, the lamp vessel merges with this base via a circumferential bevel.

The base is preferably arranged closer to the vertex of the reflective vessel section than to the vertex of the light-exit window.

An exhaust tube attachment for the purpose of filling the halogen incandescent lamp can be arranged on a dome which overlaps the reflective vessel section.

According to the invention, it is preferred if the halogen incandescent lamp is designed for operation using the system voltage.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 to 3show a halogen incandescent lamp1which is designed for operation using the system voltage. In principle, however, the invention can also be used for low-voltage or medium-voltage halogen incandescent lamps.

The halogen incandescent lamp1has, as shown inFIGS. 1 and 2, a lamp vessel2, which is preferably made of quartz glass and on whose lower end section inFIG. 1is formed a base4by means of a pinch seal, it being possible for said base4to be inserted in a lampholder (not shown). This base4merges with a bulb8of the lamp vessel2via a circumferential bevel6. The end section, which is remote from the base4, of the lamp vessel2is formed by a dome10on which is formed an exhaust tube attachment12.

Arranged in the lamp vessel2is a luminous element14which is designed, in the exemplary embodiment described, to have two filament branches16,18which are connected to one another via a connecting part20. As can be seen inFIG. 1, the filament branches16,18are positioned at an angle with respect to one another such that the spacing between them is greater at the bottom, towards the base4. The two filament branches16,18merge with power supply lines22,24, whose end sections enter the base4formed by the pinch seal and are each connected to a molybdenum film26,28which are likewise embedded in the base4. In turn, these molybdenum films are connected to approximately U-shaped, outer power supply lines, referred to below as contacts30,32, whose bent-back end sections enter channels in the base4or are embedded in said channels. The filament branches16,18, the connecting part20and the two power supply lines22,24are preferably produced from tungsten.

The two power supply lines22,24, which are embedded in the base4, are not stable enough to position the two filament branches16,18in their predetermined relative position within the bulb8. Holding knobs34,36, which, in the illustration shown inFIG. 1, extend perpendicular to the plane of the drawing and, in the illustration shown inFIG. 2, extend parallel to the plane of the drawing, are therefore formed on the lamp vessel2approximately at the height of the intermediate part20. These holding knobs34,36, which lie diametrically in relation to one another, are formed by wall regions, which are deformed inwards, towards the intermediate part20, of the bulb8, i.e. the wall of the bulb8is deformed inwards in the region of these holding knobs34,36such that the connecting part20is clamped between the two end faces of the holding knobs34,36and thus the filament branches16,18are fixed in position. This technology for the knobs is explained in detail in EP 0 446 460 B1 mentioned initially. In the exemplary embodiment illustrated, the holding knobs34,36are each formed with an approximately elliptical cross section, whose longitudinal axis overlaps that region38of the connecting part20which is arranged horizontally inFIG. 1, in order to achieve a maximum connecting area between the elliptical end sides of the holding knobs34,36and the connecting part20.

During manufacture, an exhaust tube is attached to the exhaust tube attachment12, the interior of the bulb8being evacuated and being filled with a filling gas containing halogens via said exhaust tube. After filling, the exhaust tube is removed and the exhaust tube attachment12is fused in.

As can be seen in particular in the section along the line A-A inFIG. 1which is illustrated inFIG. 3, the bulb8is not designed to have a cylindrical cross section, as is the case with the prior art described initially, but has a light-exit window40, which points towards the viewer in the illustration shown inFIG. 1, a vessel section42which bulges out towards the rear, i.e. away from the light-exit window40, adjoining said light-exit window40. The light-exit window40in the process merges with the rearwardly bulged-out vessel section42via two rounded-off surface sections43,45. A light-reflecting layer44is applied to the outer circumference surface of the vessel section42(as indicated by dashed lines inFIG. 3), and this light-reflecting layer44may be, for example, a dichroitic layer or a silver or aluminum layer. The coating is indicated inFIG. 2by means of hatching. The light-exit window40is not covered by this reflective layer44.

As shown inFIG. 3, the wall regions of the vessel section42which adjoin the light-exit window40have an approximately parabolic or ellipsoidal curvature, a constriction46being formed at the vertex, owing to which constriction46the wall curves in backward again towards the light-exit window40so as to form approximately the shape of a kidney.

This constriction46forms two curved reflective regions48,50which are each associated with one of the filament branches16,18and surround sections of these at a spacing. The reflective regions48,50each form a reflector element, by means of which the light which is radiated by the associated filament branch16,18is reflected in the direction of the exit window40such that the transmission angle of the halogen lamp1is limited considerably more severely than is the case for conventional lamps, and thus uniform illumination of a predetermined area is made possible.

The constriction46extends at the rear practically over the entire height of the vessel section42up to the bevel6, the two reflective regions48,50correspondingly also extending over a region which is higher than the length of the two filament branches16,18.

The lowest point, when viewed in cross section, of the constriction46is on a plane of symmetry between the two filament branches16,18, which extends perpendicular to the plane of the drawing inFIG. 3. As illustrated inFIG. 3, the width B of the exit window is greater than the depth U, i.e. greater than the maximum spacing between the light-exit window40and the inwardly curved rear wall or the two vertices47of the vessel section42. The cross-sectional shape of the bulb8of the exemplary embodiment illustrated is also characterized by the fact that the average radius of curvature of the light-exit window40, in the view shown inFIG. 3, is greater than that for the vessel section42which bulges out to the rear.

As shown inFIG. 2, the base4is moved slightly to the left, towards the constriction46, such that the spacing T from the vertex of the exit window40is greater than the spacing t from the two vertices47of the vessel section42which are arranged perpendicular to the plane of the drawing in the illustration shown inFIG. 2and are formed by the constriction46(only visible inFIG. 3). As can be seen in particular inFIG. 2, the exhaust tube attachment12is arranged as an extension of the vertical axis of the base4and is thus likewise offset towards the vertex47of the two kidney-shaped reflective regions48,50. With the base type illustrated, the region52which is central inFIG. 1has a section removed on both sides (perpendicular to the plane of the drawing inFIG. 1) such that two webs54remain at the edge of the base4.

The coating preferably extends up to the two surface sections43,45and also overlaps the dome10and at least part of the bevel6, also that region of the bevel6which is arranged below the light-exit window40(FIG. 1) preferably being coated.