Electric lamp and discharge devices – With gas or vapor – Having electrode lead-in or electrode support sealed to...
Reexamination Certificate
1999-03-12
2001-09-18
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Having electrode lead-in or electrode support sealed to...
C313S318070, C313S274000, C313S318020
Reexamination Certificate
active
06291934
ABSTRACT:
TECHNICAL FIELD
The invention proceeds from a halogen incandescent lamp, in particular, an incandescent lamp which is pinched at two ends and has an axially arranged luminous element.
DESCRIPTION OF THE RELATED ART
Document EP-A 475 508 has already disclosed a generic halogen incandescent lamp. An end region of the cylindrical luminous element is held mechanically by a supply lead inserted therein, by virtue of the fact that the supply lead is bent asymmetrically in a plane. In detail, it is shaped such that a second limb with a free end is integrally formed on a first limb, aligned in an axially parallel fashion, of the supply lead. The free end hooks in at one side behind a turn of the luminous element which is at a distance from the end of the luminous element, while the first limb bears opposite the free end against the turns of the luminous element. The end, on the foil side, of the supply lead is welded to the foil in the usual way. The disadvantage of this design is that because of the asymmetrical shape of the supply lead, the centering of the luminous element and of the power supply system is not reliably ensured. Moreover, the welding operation is very time-consuming and costly.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a halogen incandescent lamp in accordance with the preamble of claim
1
which ensures good centering of the luminous element and whose production costs are nevertheless very low. A further object is also to provide a halogen incandescent lamp which is easy and quick to produce.
The present invention is based on a simply configured supply lead which is as symmetrically designed as possible and advantageously exerts a spring action on the luminous element and thus automatically ensures the centering of the luminous element. The concept of this supply lead has the particular advantage that the connection to the foil is not performed by welding, but by mechanical contact. As a result, not only are costs and the production period substantially lowered, but potential weak points are also eliminated. To date, it has been necessary to use an expensive platinum paste during welding. Moreover, the region of the spot weld has so far been subject to oxidation, which has shortened the service life.
In detail, the halogen incandescent lamp according to the invention has a hermetically sealed bulb which is made from transparent material and defines a lamp axis. Moreover, it has a coiled (and thus cylindrically shaped), preferably axially arranged, luminous element having two ends and a power supply system which is connected to the two end regions of the luminous element. The power supply system comprises a foil and an inner and outer supply lead, the inner end, on the side of the luminous element, of the supply lead holding the end region of the luminous element from inside. The outer end, on the foil side, of the supply lead is connected to the foil. The supply lead itself is bent in a U-shaped fashion by virtue of the fact that two free limbs, to which spring force is advantageously applied, lie in a plane and are interconnected via a straight base. The section, on the side of the luminous element, at the end of the associated foil is folded back and forms a fold in which the base is held mechanically. The ends of the free limbs project into an end region of the luminous element. At least one hook part on one of the free limbs projects outward. Said hook part engages between two turns of the luminous element.
The surface of the folded-over end section of the foil is normally rectangular. A rectangular end section, folded over in such a way, of the foil is already previously known from EP-A 780 883. However, this surface is now preferably reduced at at least one or even at both free corners. This facilitates the automatic suspension of the supply lead in the fold of the foil. Moreover, foil material is saved thereby. The folded-over section is preferably in the shape of a triangle (symmetrical or asymmetrical). However, it can also be shaped in a rounded off fashion, for example. This favorable configuration of the end section of the foil is independent in principle of the special way of providing a supply lead suspended in the foil. It is suitable in principle for both the outer and the inner supply leads. For this reason, protection is sought for this special shape of the folded-over end section with a reduced surface, independently of the special configuration of the supply lead suspended therein. This folded-over end section can also be used in principle in other types of lamp (in particular discharge lamps with a metal halide filling).
Each of the two limbs preferably has a hook part. This improves the holding, and the centering is even more effectively ensured.
The limbs are normally of equal length. However, for specific applications it is advantageous to use limbs of different lengths.
The concept of the invention is particularly well suited for a halogen incandescent lamp which is pinched at two ends, or else at one end. In this case, both end regions can be held by a novel supply lead.
The diameter of the wire which is used for the supply lead is advantageously at least as large as the spacing between two turns of the luminous element. In this way, holding is effected not only by the tensile stress between the two ends of the luminous element, but also, or chiefly, by a clamping engagement of the hook part between two turns of the luminous element. The wire diameter of the supply lead is preferably larger than the spacing between two turns of the luminous element, so that the filament is spread somewhat upon introduction of the supply lead; it is preferably 10 to 30% larger, so that the clamping engagement is easy to accomplish, on the one hand, and the holding force is nevertheless sufficiently reliable, on the other hand.
It is simplest for the hook part to be bent in the plane of the supply lead. However, it can also be bent outside this plane, it being possible for the two hook parts of the two limbs to point in opposite directions.
In order reliably to prevent the hook part from slipping out of the luminous element, the hook part preferably projects slightly outward beyond the luminous element.
The free limbs can run in a rectilinear and axially parallel fashion, and this is simplest to achieve. In another embodiment, the limbs are shaped such that the width of the foil can be selected independently of the dimensions of the luminous element. For this purpose, the limbs are either inclined inward toward the axis or, in a particularly preferred embodiment, a short distance before the end region of the luminous element, the two limbs have an inward curvature which reduces the spacing between the limb ends. This shape is ideally adapted to the end region of the luminous element, with the result that the holding and centering of the luminous element functions in a particularly reliable fashion.
The hook part preferably forms an outwardly projecting angle relative to the limb, the hook part being bent away at an angle &agr; of between 30° and 120°, in particular approximately 50° to 60°, relative to the free limb.
In order to ensure reliable holding, the limbs are to be inserted at least as far as two turns, preferably more than three turns, into the end region of the luminous element.
The supply lead is mostly fabricated from tungsten or molybdenum.
It is to be noted that the hook part must be designed such that the width, on the side of the luminous element, is always smaller in the compressed state than the inside diameter of the luminous element. The length of the two hook parts (in the case of their being bent away at right angles) or their length in projection transverse to the lamp axis (in the case when the hook parts are arranged at an acute angle to the limbs) may therefore correspond at most to half the inside diameter of the cylinder formed by the luminous element. In the case of a single hook part, a length of up to the full inside diameter is therefore permissible.
A method for producing the above-describ
Berger Helmut
Liermann Hans
Meier Reinhold
Bessone Carlo S.
Guharay Karabi
Patel Nimeshkumar D.
Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen MBH
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