ELECTRIC LAMP

Abstract: The electric lamp has a lamp vessel (1) having a pinched seal 2 in which a metal foil (3) is accommodated as current lead-through conductor, which is connected to several external current conductors (7). The current conductors (7) are secured via a metal strip (8) to a current supply wire (14). Thus, deformations of the external current conductors (7) are avoided, which lead to mechanical stresses in the pinched seal (2) and to rupture thereof.

Description: The invention relates to an electric lamp comprising a lamp vessel sealed in a vacuum-tight manner and consisting of glass having an SiO₂ content of at least 95% by weight, said lamp vessel having a pinched seal at one end, a light source within the lamp vessel, at least one metal foil with a first and a second end accommodated as current lead-through conductor in the said pinched seal, said metal foil being connected near its first end to an internal current conductor extending to the light source and connected near its second end to several external current conductors emanating from the said pinched seal, a lamp cap provided with an electrical contact, the said pinched seal being fixed in the said lamp cap, a current supply wire connected to the said electrical contact of the lamp cap and to the said several external current conductors. Such an electric lamp is known from US-A-4 499 404. The known lamp is an incandescent lamp having only one pinched seal, in which two metal foils are accommodated, which are each connected to a respective internal current conductor and to a respective pair of external current conductors. At right angles to the external current conductors a respective current supply wire is welded to each pair of external current conductors. By using more than one external current conductor per metal foil, the current density in the external current conductors and in the welds of said conductors to the metal foils is decreased and hence the heat development in the pinched seal is reduced. According as the number of external current conductor is larger, however, the risk is greater that they are not all located in a flat plane. When welding connections are made, external current conductors can then be elastically deformed, as a result of which they produce mechanical stresses in the pinched seal. These stresses can lead to rupture of the pinched seal and to the lamp becoming leaky. The invention has for its object to provide an electric lamp of the kind mentioned in the opening paragraph having a construction which reduces the risk of the mechanical stresses in the pinched seal. According to the invention, this object is achieved in that the external current conductors are connected to the current supply wire via a metal strip. By interposition of a metal strip between the external current conductors and the current supply wire, a flexible coupling is obtained between said conductors and said wire, which results in reducing stresses in the pinched seal. In a favourable embodiment, fingers are formed by incisions in the metal strip and each external current conductor is connected to a respective finger of the strip. The strip can then more readily be adapted to the positions of the external current conductors, while nevertheless only one additional component need be used for the current supply wire. Also with the use of a respective strip per external current conductor, a very flexible coupling is obtained. It is also favourable when in a particular embodiment the (respective) metal strip extends from the free end of the external current conductors to the pinched seal and is connected near the pinched seal to the current supply wire. This embodiment has the advantage that the space in the lamp cap is substantially not larger than in a lamp in which the step according to the invention has not been taken. In a variation of this embodiment, the (respective) metal strip is bent into the form of a U, which increases the flexibility of the coupling. The construction of the lamp according to the invention is particularly suitable for lamps consuming a very high power, for example a power of a few thousand Watts, such as incandescent lamps having a planar filament. These lamps generally have only one pinched seal. Embodiments of the lamp according to the invention are shown in the drawing. In the drawing: Figure 1 is a front elevation of a lamp, in which the lamp cap is partly broken away, Figure 2 shows a fragment of a variation of the lamp shown in Figure 1, Figure 3 shows a fragment of a variation of the lamp shown in Figure 1 in sectional view taken on the line A-A, Figure 4 shows another embodiment of the lamp of Figure 3. In Figure 1, the lamp has a lamp vessel 1 sealed in a vacuum-tight manner and consisting of glass having an SiO₂ content of at least 95% by weight, for example quartz glass. The lamp vessel 1 has at one end a pinched seal 2. A planar filament 15 is arranged as a light source within the lamp vessel 1. A metal foil 3 (3′) having a first end 4 and a second end 5 is accommodated as a current lead-through conductor in the pinched seal 2. The metal foil 3 (3′) is connected near its first end 4 to an internal current conductor 6 (6′) extending to the light source 15 and near its second end 5 to several external current conductors 7 emanating from the pinched seal 2. The lamp has a lamp cap 10 mainly consisting of ceramic material provided with pins 11,11′ as electrical contacts. The lamp vessel 1 is fixed with its pinched seal 2 in the lamp cap 10 by means of cement 12. the lamp cap 10 has a filling of sand 13. A current supply wire 14 is connected to the electrical contact 11 and to the external current supply conductors 7. The external current conductors 7 are each connected via a metal strip 8 to the current supply wire 14. The strip 8 can be more readily adapted to the relative position of the external current conductors 7 than the rigid current supply wire 14. In the embodiment shown, the metal strip of, for example, nickel has obtained fingers by incisions, as a result of which the strip 8 can be even more readily adapted to the external current conductors 7. Each external current conductor is connected to an individual finger 9. The lamp shown is a film studio lamp consuming during operation at 120 V a power of 5 kW. The lamp reached the calculated lifetime without damage of the pinched seal. In Figure 2, parts provided with the same reference numerals are identical to those of Figure 1. The current supply wire 24 is a straight wire connected to a strip 18 of metal, for example nickel, which is provided with fingers 19. Each finqer is connected to a respective external current conductor 7. In Figure 3, reference numerals corresponding to those in figure 1 denote like parts. A metal strip 28 is welded to the free end of the external current conductor 7 and extends through a U-shaped bend to the pinched seal 2. The strip 28 is welded near the pinched seal 2 to the rectangularly bent (cf. Figure1) current supply wire 14. Figure 4 differs from Figure 3 only in that the metal strip 38 is not bent into the form of a U. In Figures 3 and 4, the metal strip 28 and 38, respectively, may be a strip which is connected to each of the several external current conductors 7, as the case may be provided with incisions, or may be an individual strip for the one visible external current conductor. For the remaining external current conductors 7 not visible in the drawing, a similar respective metal strip 28 and 38, respectively, is then present.

Claims: An electric lamp comprising a lamp vessel (1) sealed in a vacuum-tight manner and consisting of glass having an SiO₂ content of at least 95% by weight, said lamp vessel having at one end a pinched seal (2), a light source (15) within the lamp vessel, at least one metal (3, 3') foil with a first and a second ends (4, 5) accommodated as current lead-through conductor in the said pinched seal, said metal foil being connected near its first end to an internal current conductor (6, 6') extending to the light source (15) and near its second end (5) to several external current conductors (7) emanating from said pinched seal, a lamp cap (10) provided with an electrical contact (11, 11'), the said pinched seal (2) being fixed in said lamp cap (10), a current supply wire (14) connected to said electrical contact of the lamp cap and to said several external current conductors (7), characterized in that the external current conductors (7) are connected via a metal strip (8) to the current supply wire (14). An electric lamp as claimed in Claim 1, characterized in that fingers (9) are formed at the metal strip (8) by incisions, these fingers (9) being secured to a respective external current conductor (7). An electric lamp as claimed in Claim 1, characterized in that the external current conductors (7) are connected via a respective metal strip (8) to the current supply wire (14). An electric lamp as claimed in Claim 2, characterized in that the metal strip extends from the free end of the external current conductors (7) to the pinched seal (2) and is secured near the pinched seal to the current supply wire (14). An electric lamp as claimed in Claim 3, characterized in that the metal strips (8) extend from the free end of a respective current conductor (7) to the pinched seal (2) and are secured near the pinched seal to the current supply wire (14). An electric lamp as claimed in Claim 4, characterized in that the metal strip (8) is bent into the form of a U. An electric lamp as claimed in Claim 5, characterized in that the metal strips (8) are bent into the form of a U.

Inventors: OOMS, LEO FRANS MARIA
Applicants: N.V. PHILIPS' GLOEILAMPENFABRIEKEN
Application year: 1988
Main classification: H01K1
IPC codes: H01J5, H01J61, H01K1