BODY, ESPECIALLY LAMP BODY, AND METHOD FOR PRODUCING A HERMETIC SEAL

Abstract

A body, such as a lamp body, includes a tubular element. At least one conductor is introduced into the tubular element and a glass material surrounds the conductor. The glass material forms a seal between the tubular element and the conductor. The glass material comprises a sintered glass, such as a sintered glass ring, and may completely surround the conductor.

Claims

1. A body, comprising: a tubular element made of a glass or a glass-ceramic material; at least one conductor introduced into the tubular element; and at least one further glass material surrounding the at least one conductor and connected to the tubular element, the at least one further glass material forming a hermetic seal between the tubular element and the at least one conductor and the at least one further glass material comprising a sintered glass which completely surrounds the at least one conductor after being fused on and hermetically seals it with respect to the tubular element.

2. The body of claim 1, wherein the sintered glass is a sintered glass ring.

3. The body of claim 1, wherein the at least one further glass material has a first coefficient of expansion .sub.1 and the tubular element comprises a glass or a glass-ceramic material having a second coefficient of expansion .sub.2 and the at least one conductor has a third coefficient of expansion .sub.3 and the value of the first coefficient of expansion .sub.1 lies between the value of the second coefficient of expansion .sub.2 and the third coefficient of expansion .sub.3.

4. The body of claim 1, wherein the at least one further glass material comprises a plurality of further glass materials having stepped coefficients of expansion .sub.1 to .sub.n and the tubular element comprises a glass or a glass-ceramic material having a second coefficient of expansion .sub.n+1 and the conductor has a third coefficient of expansion .sub.n+2 and the values of the stepped coefficients of expansion .sub.1 to .sub.n lie between the value of the second coefficient of expansion .sub.n+1 and the third coefficient of expansion .sub.n+2.

5. The body of claim 1, wherein a transformation temperature Tg according to ISO 7884-8 of the at least one further glass material is greater than 500 C.

6. The body of claim 1, wherein a softening temperature according to ISO 7884-3 of the at least one further glass material at a viscosity of 107.6 dPa*s of the glass material is greater than 850 C.

7. The body of claim 1, wherein the coefficient of thermal expansion .sub.1 of the at least one further glass material is in the range of 1.1*10.sup.6 K-1 to 4.0*10.sup.6 K.sup.1.

8. The body of claim 1, wherein the glass or glass-ceramic material of the tubular element is quartz glass.

9. The body of claim 8, wherein the quartz glass is transparent to UV light.

10. The body of claim 1, wherein the at least one further glass material has the following composition in wt-%: TABLE-US-00004 SiO.sub.2 78.5-85; B.sub.2O.sub.3 10-11; Al.sub.2O.sub.3 4.5-5; BaO 0.5-2; Fe.sub.2O.sub.3 <0.1; CaO 0-1; K.sub.2O 0-3; and Na.sub.2O 0-3.

11. The body of claim 1, wherein the at least one further glass material is visibly different from the tubular element.

12. The body of claim 11, wherein the at least one further glass material comprises a color component.

13. The body of claim 11, wherein the at least one further glass material is cloudy.

14. The body of claim 1, wherein the at least one further glass material incorporates air bubbles and is opaque on account of the incorporated air bubbles.

15. The body of claim 14, wherein the incorporated air bubbles are a proportion in the range of 5% to 20% of a volume of the at least one further glass material.

16. The body of claim 1, wherein a material of the at least one conductor is one of the following materials: tungsten; molybdenum; or Kovar.

17. The body of claim 1, wherein the hermetic seal exhibits a He leakage rate at least less than 1*10.sup.8 mbar s.sup.1 at a pressure difference of 1 bar.

18. The body of claim 1, wherein the at least one further glass material is a single glass material directly forming the hermetic seal between the tubular element and the at least one conductor.

19. A method for producing a hermetic seal between a tubular element made of a glass or a glass-ceramic material for a lamp body and a conductor having a further glass material in the form of a sintered glass, the method comprising the following steps: grinding the further glass material to give a glass powder; forming granules from the glass powder; dry pressing the granules to form a glass ring; sintering the glass ring; providing the conductor with the glass ring; fusing the glass ring to the conductor; and hermetically sealing the conductor and the tubular element with the glass ring by fusing.

20. A lamp body for a lamp, comprising: a tubular element made of a glass or a glass-ceramic material; at least one conductor introduced into the tubular element; and at least one further glass material surrounding the at least one conductor and connected to the tubular element, the at least one further glass material forming a hermetic seal between the tubular element and the at least one conductor and being visibly different from the tubular element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

[0038] FIG. 1 illustrates a lamp body provided according to the prior art; and

[0039] FIG. 2 illustrates steps of an exemplary embodiment of a method provided according to the present invention for producing a sealing glass ring provided according to the present invention.

[0040] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention and such exemplification is not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0041] FIG. 1 shows a lamp body consisting of a tubular element 1 into which a conductor 3, which may be made of tungsten, is inserted. At the location at which the conductor is inserted into the tubular lamp body, a glass bead 5 as sealing glass according to the prior art is provided, the glass material of the glass bead having a coefficient of thermal expansion that lies between the coefficients of thermal expansion of the conductor material and of the tubular lamp body. By fusion using the glass bead as sealing glass or as intermediate glass, on account of the choice of the coefficient of expansion of the sealing glass, a conductor is inserted, between the sealing glass and the envelope glass material, substantially without stress into the tubular element in a hermetically sealed, i.e. gastight, manner.

[0042] While applying the glass bead in the prior art was preferably performed in a laborious process, the present invention envisages using (as illustrated in FIG. 2) as sealing glass a sintered glass ring obtained according to the present invention from a glass powder with subsequent sintering, instead of a glass bead that is applied to the conductor in a laborious process.

[0043] FIG. 2 shows the individual process steps of an exemplary embodiment of a method provided according to the present invention in detail.

[0044] Firstly, a glass material having a high Tg and a high processing temperature, such as, for example, Glass 6, Glass 7, or Glass 8, is ground to give a glass powder, as illustrated in step 100. Subsequently to this, the glass powder is converted into granules as per step 102. Color components may be added to the glass powder prior to conversion to granules for the purpose of unambiguous identification. The granules are then dry pressed to form glass rings as shown in step 104. After dry pressing the glass rings, the glass rings are sintered as per step 106. The sintered glass rings are then guided over the conductors or electrodes and in this way applied or mounted on the conductors or electrodes. This is shown in step 108. Then, in step 110, the sealing glass in the form of a sintered glass ring is fused onto the conductor or the electrode and subsequently the lamp body is hermetically sealed by again fusing the conductor having the sintered sealing glass with the glass or glass-ceramic material of the lamp body. The first fusing of the compact onto the pin already hermetically seals the transition between conductor and glass bead. The glass bead itself also becomes impermeable to gas as a result. Subsequently to this, fusing with the glass or glass-ceramic material of the tubular lamp body is performed as described previously.

[0045] The method will be described in more detail herein on the basis of an exemplary embodiment, without being limited thereto.

[0046] According to the method, the glass material is firstly ground to give a glass powder. Grinding can be performed, for example, in ceramic drums with addition of ceramic grinding stones. An average particle size of the powder of 10 m is typically sought. Next, pulverulent color pigments such as, for example, CoO, Fe.sub.2O.sub.3 or CrO.sub.2 are added as needed in a proportion of 0.5-5% by volume, such as 0.5-2% by volume. The powder is mixed with an organic binder such as, for example, Plextol from Synthomer (www.synthomer.com) and atomized by a nozzle in what is known as a spray tower. The surface tension of the liquid organic binder causes round droplets to form, which, as a result of drying during spraying in the tower, then form round, free-flowing particlesthe granules. After grinding and forming granules, the granules are dry pressed to form a glass ring. To this end, in a mechanical press, a cavity that corresponds to the negative of the part to be formed is filled and mechanically pressed. This compact is subsequently freed of the organic binder and sintered in an oven process. The organic binder is expelled from the compact in a first phase at temperatures between 200-300 C. and burnt in the process. The compact subsequently passes through a zone for sintering. The sintering temperature here is the softening temperature of the respective glass. The softening temperature is defined by a glass viscosity of 10.sup.7.6 dPas. For the glass materials that are used for the sealing glass, for example Glass 6, Glass 7, or Glass 8, the softening temperature is in the range of 900 C. to 1200 C. The duration of sintering at or close to the softening temperature is 5 to 30 min.

[0047] The sintering affords a mechanically stable shaped body. The conductor is then provided with the sintered glass ring as sealing glass. In a further thermal process, this sintered body or the sintered glass ring is then fused onto the conductor. The temperature for this fusion is in the range of a glass viscosity of 10.sup.6-10.sup.4 dPas. For the glass materials used, for example Glass 6, Glass 7, or Glass 8, the processing temperatures at a viscosity in the range of 10.sup.6 to 10.sup.4 dPas are between 1200 C. and 1800 C. During the fusion, as a result of the surface tension of the viscous glass, a round glass bead that is firmly fused with the conductor is formed on the sintered glass ring. The duration for this is once again 5 to 30 min. The components are kept within the process by temperature-stable molds that cannot be wetted by liquid glass, such as for example graphite or boron nitride.

[0048] This composite of conductor and intermediate glass, obtained as described above, may subsequently be inserted for example into a tubular quartz glass body and after fusing with the lamp body permits sealing between conductor material and tubular body with the aid of the glass ring or the glass bead, with connection of the quartz glass body to the conductor via the glass ring or the glass bead in a hermetically sealed manner.

[0049] The body provided according to the present invention and the method provided according to the present invention for producing a sealing glass in the form of a sintered glass ring, compared to conventional methods, features easier producibility, high quality of the glass bead, reproducible dimensions and tolerances, and also the possibility of adding coloring components. The glass bead is further distinguished by the fact that cracks are avoided.

[0050] A further advantage of exemplary embodiments provided according to the present invention is that a color or a hidden marker can be incorporated into the sintered glass and the product can be unambiguously identified using the color or using a hidden marker, and thus protection against product counterfeits is made possible by the novel method.

[0051] Exemplary glasses that can be used as the at least one further glass material of the sintered glass are described in Table 2 and Table 3, with the compositions of each glass being provided in wt-% of the respective components.

TABLE-US-00002 TABLE 2 Exemplary compositions of the at least one further glass material Glass 1 Glass 2 Glass 3 Glass 4 Glass 5 Glass 6 SiO.sub.2 85 81 79 78.5 83 82 B.sub.2O.sub.3 10 11 11 10.5 10 13 Al.sub.2O.sub.3 4.5 5 5 5 5 5 BaO 0.5 2 2 2 1.5 0 Fe.sub.2O.sub.3 <0.1 <0.1 <0.1 <0.1 0 0 CaO 0 0 1 1 0.5 0 K.sub.2O 0 0 2 3 0 0 Na.sub.2O 0 0 0 0 0 0

TABLE-US-00003 TABLE 3 Exemplary compositions of the at least one further glass material Glass 7 Glass 8 SiO.sub.2 87 84.5 B.sub.2O.sub.3 12 10 Al.sub.2O.sub.3 0 2.5 BaO 0 0 Fe.sub.2O.sub.3 0 0 CaO 0 0 K.sub.2O 0 0 Na.sub.2O 1 3

[0052] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.