A LIGHT BULB

Abstract

A light bulb (10) comprising a feedthrough body (26) for accommodating electrical conductors (24) through a glass stem (23) of the light bulb (10) is disclosed. The light bulb (10) comprises a light engine (21) arranged within a sealed light transmissive surface structure (22), a feedthrough body (26) sealed in and extending through the glass stem (23) supporting the light engine (21), a plurality of conductive wires (24) mutually electrically isolated from each other and extending through and gastightly sealed in the feedthrough body (26), the conductive wires (24) connecting the light engine (21) to at least one power and signal source.

Claims

1. A light bulb comprising: a light engine arranged within a space enclosed by a light transmissive surface structure and a glass stem; the glass stem comprising a mutually connected flare and tubular portion, the stem supporting the light engine and is fused by its flare to the light transmissive surface structure; a feedthrough body extending through the glass stem and being fixed by fusion in said tubular portion, wherein the feedthrough body is provided with a plurality of electrical conductors electrically isolated from each other which extend through the glass stem and connect said light engine to at least one power and signal source, wherein said feedthrough carrier body is made of a ceramic, or a glass, and wherein the glass stem has a first melting point Tm1 and the feedthrough carrier has a second melting point Tm2, wherein Tm2−Tm1>=75° C.

2. The light bulb according to claim 1, wherein the space is gastightly sealed by the light transmissive surface structure and the glass stem; wherein the feedthrough body is sealingly fixed over a sealing length in a gastight manner in said tubular portion, and wherein said electrical conductors extend in a gastight manner through the glass stem.

3. The light bulb according to claim 1, wherein said glass stem has a first coefficient of thermal expansion and the feedthrough body has a second coefficient of thermal expansion, wherein the first and second coefficient of thermal expansion differ by no more than |1*10-6/K|.

4. The light bulb according to claim 1, wherein feedthrough body is a feedthrough tube, the electrical conductors are conductive wires which extend in a gastight manner through said feedthrough tube.

5. The light bulb according to claim 4, wherein said feedthrough tube is made of metal, ceramic or glass.

6. The light bulb according to claim 4, wherein said plurality of conductive wires are gastightly sealed in said feedthrough tube using an elastic and adhesive seal compound.

7. The light bulb according to claim 6, wherein said seal compound comprises one of glue and epoxy, preferably said seal compound comprises at least one of the group comprising epoxy resin, amorphous silica, titanium dioxide, non-fibrous aluminum oxide, oxybis(ethyleneoxy)bis(propylamine), butyl 2,3-epoxypropyl ether, bisphenol-A epichlorhydrin resin.

8. The light bulb according claim 3, wherein said plurality of conductive wires are individually insulated with an insulation layer having a coefficient of thermal expansion matching the coefficient of thermal expansion of said conductive wires.

9. The light bulb according to claim 8, wherein said insulation layer is made of one of mylar and silicone.

10. The light bulb according to claim 1, wherein the feedthrough body is a feedthrough carrier made of an electrically insulating material and electrical conductors are conductive tracks provided on a surface of the feedthrough carrier.

11. The light bulb according to claim 10, wherein said feedthrough carrier is made of a ceramic, or a glass and wherein the electrical conductors are conductive tracks provided on an outer surface of the feedthrough carrier.

12. The light bulb according to claim 10, wherein the tracks are made of copper or cermet material comprising alumina and/or aluminum nitride as a refractory oxide and aluminum, molybdenum and/or tungsten as a metal.

13. The light bulb according to claim 1, wherein the plurality of electrical conductors extending through the glass stem and connect said light engine to at least one power and signal source numbers at least four.

14. A method of manufacturing the light bulb in accordance with claim 1, comprising the steps of: I) fixing a feedthrough body in a tubular portion of a glass stem; II) providing the feedthrough body with a plurality of mutually electrically isolated electrical conductors; III) connecting said plurality of electrical conductors with light engine contacts supported by said glass stem; IV) arranging said light engine in a space enclosed by a light transmissive surface; and V) closing said space by assembling said glass stem and said light transmissive surface structure by fusion melting said light transmissive surface with a flare portion of the glass stem.

15. The method according to claim 14, wherein the space is gastightly sealed by the light transmissive surface structure and the glass stem, the feedthrough body is sealingly fixed over a sealing length in a gastight manner in said tubular portion, and said electrical conductors extend in a gastight manner through the glass stem, the method further comprising a step of filling a gas to said space via the tubular portion before gastightly sealing said tubular portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 schematically illustrates an incandescent bulb according to the prior art.

[0039] FIG. 2 schematically illustrates a light bulb in accordance with the present disclosure.

[0040] FIG. 3A-C schematically illustrates an enlarged view of a feedthrough body disposed in a glass stem and cross-sections of some examples of feedthrough bodies with electrical conductors sealed therein, in accordance with the present disclosure.

[0041] FIG. 4A-B schematically illustrates in accordance with the present disclosure an enlarged and detailed view of a feedthrough body with conductive tracks on an outer surface thereof, in accordance with the present disclosure.

[0042] FIG. 5 schematically illustrates in a flow chart type diagram, an embodiment of a method for manufacturing the light bulb according to the present disclosure.

DETAILED DESCRIPTION

[0043] Embodiments contemplated by the present disclosure will now be described in more detail with reference to the accompanying drawings. The disclosed subject matter should not be construed as limited to only the embodiments set forth herein. Rather, the illustrated embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0044] FIG. 1 schematically illustrates an incandescent light bulb 10 according to the prior art. The light bulb 10 comprises a filament 11 arranged within a space 9 gastightly sealed by a light transmissive surface structure 12 and a glass stem 13. The filament 11 is usually made of tungsten or outer suitable metal materials, and functions to conduct electricity and to emit light. The gas sealed light transmissive surface structure 12 typically has a shape of a globe and functions to protect inner components of the light bulb 10. The globe 12 is generally made of a hard glass such as soda-lime glass, so as to withstand higher temperatures.

[0045] The light bulb 10 further comprises the stem 13, which is made of glass and functions to protect wires 14 arranged therein and to support and lift the filament 11 into a spatial orientation within the globe 12 so as to dissipate the light with a spatial light distribution.

[0046] The wires 14, often referred to as lead-in wires, connect the filament 11 to a power source (not shown) arranged in a base 15 of the light bulb 10, to carry current from the base 15 to the filament 11. The wires 14 are usually made of nickel plated copper.

[0047] While there are often two wires 14 for the conventional incandescent light bulb 10, newly developed tunable light bulbs may require more wires, for example, three to six or ten interconnecting lines for connecting to a power source and signal lines.

[0048] A light bulb in accordance with the present disclosure will be described in the following with reference to FIGS. 2, 3A-C and 4A-B.

[0049] FIG. 2 schematically illustrates a light bulb 20 in accordance with the present disclosure. FIG. 3A schematically illustrates an enlarged view 30 of a feedthrough body, in the FIG. 3A-B a feedthrough tube, disposed in a glass stem, with conductive wires sealed therein. FIG. 3B schematically illustrates a section view 40 of another embodiment of a feedthrough tube with conductive connecting wires sealed therein. FIG. 3C schematically illustrates a section view 40 of yet another feedthrough construction.

[0050] With reference to FIGS. 2 and 3A, the light bulb 20 may comprises one or more filaments, such as Light Emitting Diode, LED, filaments 21 as a light engine 21a, arranged within a space 19 gastightly sealed by a light transmissive surface structure 22 and a stem 23. The filament or filaments 21 is supported by a glass stem 23, the glass stem comprising a flare 231 and a tubular portion 232. A plurality of conductive wires 24, 24b are arranged for connecting the filaments 21 to at least one signal and power control (not shown) disposed at or in a base 25 of the light bulb 20.

[0051] A feedthrough body 26, tube or sleeve 26b, which may be made of a glass, a metal or a ceramic, is disposed and fixed in the glass stem 23, and arranged for accommodating the plurality of electrical conductors 24, in the figure wires 24b. FIG. 2 illustrates an example of the feedthrough body, tube or sleeve 26b arranged for accommodating five conductive wires 24b, one common neutral wire and four lead wires for each conductive lead wire 24b electrically connected to a respective LED filament 21. However, it can be contemplated by those skilled in the art that there can be more or less wires 24b disposed in the feedthrough tube 26b, as illustrated for example in FIG. 3B with seven wires 24b.

[0052] The feedthrough carrier 26, in the figure a metal tube 26b, may be melted over a sealing length SL in a sealing area 233 of a tubular 232 portion of the glass stem 23, for example together during manufacturing of the glass stem 23. Optionally, the pre-manufactured glass stem 23 can be provided with a feedthrough passage in which the feedthrough tube 26b is to be fit and sealed so as to provide gas tightness and/or ingress protection conforming to the Ingress Protection Code, standard.

[0053] The gas tightness between the feedthrough tube 26b and the glass stem 23 may be maintained by selecting appropriate material combinations for the glass and the tube. As an example, commonly known combinations of those materials defined for incandescent bulbs may be used.

[0054] As an example, the feedthrough tube 26b may be made of one of a group of metals comprising kovar, vacovit, tungsten, molybdenum, (Cr)NiFe, Al.sub.2O.sub.3. In the meantime, the stem 23 may be made of a glass such as soda-lime glass. Examples of suitable glasses for the stem are given in table 1.

TABLE-US-00001 TABLE 1 Examples of soda lime glasses. Philips glass ref. nr. 342 220 Working point ° C. 1030 970 Melting point ° C. 1475 1390 Coeff of thermal exp. K.sup.−1 10.50 10.30 SiO2 66.4 63.6 B2O3 — 0.8 Al2O3 2.4 4.8 P2O5 — 0.2 Na2O 6.3 17.0 K2O 12.7 0.8 MgO 0.2 3.0 CaO 6.0 4.6 SrO — <0.15 BaO 5.6 4.9 SO3 — <0.2

[0055] The plurality of conductive wires 24, which may comprise lead-in power wires and signal lines, are planted or potted in the feedthrough tube 26b. For the purpose of guaranteeing gas tightness between the feedthrough tube 26b and the wires 24b, a sealing compound 41, for example as illustrated in FIG. 3B, may be filled in the feedthrough tube 26b and around the wires 24b.

[0056] A suitable sealing compound 41 shows sufficient elasticity and adhesion to the feedthrough tube 26b and an insulation layer 42 around the wires 24b, as described in the following with reference to FIG. 3B, so as to compensate coefficient of thermal expansion mismatch between materials of the feedthrough tube 26b and the insulation layer 42 of the wires 24b. As an example, one of the group comprising epoxy resin, amorphous silica, oxybis(ethyleneoxy)bis(propylamine), titanium dioxide, butyl 2,3-epoxypropyl ether, non-fibrous aluminum oxide, bisphenol-A epichlorhydrin resin may be used as the sealing compound 41.

[0057] To ensure the electric isolation between the conductive wires 24b, each wire 24b is individually insulated with a very thin insulation layer 42, in a way similar to Litz wires. The insulation layer 42 may be made of for example mylar or silicone. As a result there is no need to maintain isolation between the wires 24b in the feedthrough tube 26b before and after sealing of the wires 24b.

[0058] The insulation layer 42 has a thermal expansion coefficient matching the thermal expansion coefficient of the wire 24b. For example, mylar has a thermal expansion coefficient, which matches the thermal expansion coefficient 1.7×10.sup.−5 [in/in/° C.] (ASTM-D696) of copper.

[0059] An advantage of using copper wires is that they can be soldered to the power supply in the base 25 of the light bulb and the filaments directly, which is advantageous in comparison to the conventional bulb where the wires 14 in the glass stem 13 can only be welded.

[0060] Melting temperature of Mylar is ˜250° C., which will provide sufficient resistance for an assembly process as described later.

[0061] Individually insulated wires helps to guarantee the gas tightness. As a result, thermal expansion coefficient mismatch of the insulation layer and the wire material is limited. The length of the wire insulation layer and the wire interface is also advantage when it comes to sealing.

[0062] The idea is that the feedthrough tube 26b is first sealed in the glass stem 23, before the wires 24b are potted in the feedthrough tube 26b. After that the conductive wires 24b are potted or planted in the sealed feedthrough tube 26b. In this way, the wires 24b are not exposed to temperatures corresponding to glass melting of around 1400° C. As a result, a diameter of the wires 24b may be decreased with respect to traditional through glass feedthrough.

[0063] The wires 24b may have a diameter in a range of 0.2 mm to 0.5 mm. A number of wires 24b to accommodate in the tube 26b may depend on an inner tube diameter. For a five channel color filament bulb, there requires feedthrough of at least five wires 24b, which may be achieved with an inner tube diameter of 1.0 mm to 3.5 mm.

[0064] The above described gas tightness between each pair of the glass stem and the feedthrough tube, the feedthrough tube and the sealing compound, the sealing compound and the wire insulation layer around the conductive wires, and the wire insulation layer and the wire itself helps to ensure the gastight potting or planting of the plurality of conductive wires 24b in the feedthrough tube 26b while ensuring the mutual electrical isolation between the wires 24b.

[0065] FIG. 3C schematically illustrates a sectional view 40 of an alternative feedthrough construction via which the electrical conductors 24 may extend through the stem. Said alternative feedthrough construction comprises a first feedthrough body 26a, i.e. a solid bar or rod 26a, provided with the electrically conductive tracks 24a as electrical conductors 24, which functions as a substitute for the plurality of loose electric wires, and which is fixed or sealed into a second feedthrough body, i.e. the feedthrough tube 26b. The first feedthrough body 26a is fixed with potting material 41 in the second feedthrough body 26b. This feedthrough construction of combined first 26a and second feedthrough body 26b can subsequently be sealed as a single unit into the tubular portion of the glass stem to obtain the desired passing of the electrical conductors 24 through the glass stem.

[0066] FIG. 4A-B schematically illustrates an enlarged view 30 of a glass stem 23 with a mounted/supported LED light engine 21a, i.e. a plurality of, i.e. five, LED filaments 21, and with a feedthrough carrier 26, in the FIG. 4A-B a glass bar 26a, disposed in the glass stem 23, with a plurality of, i.e. seven, conductive tracks 24a deposited as electrical conductors 24 thereon, in this case via screen printing but this could alternatively be obtained via for example, pasting, PVD, CVD, CSD, or via a lithographic method. FIG. 4B schematically illustrates a more detailed view of a part of the feedthrough carrier sealed in the stem as shown in the embodiment of FIG. 4A. The glass of the glass stem 23 is composed of a first glass, i.e. glass with reference number 220 having the properties as given in Table 1. The glass bar feedthrough body 26a is composed of a second glass, i.e. glass with reference number 342 having the properties as given in table 1. The matching properties of the first and second glass enable the glass bar feedthrough body 26a as well as the conductive tracks 24a of being suitably, gastightly sealed over sealing length SL, as shown in FIG. 4A, into the tubular portion 232 of the glass stem. On the glass stem a spiral-shaped LED light engine 21a is mounted comprising a plurality of independently controllable LED filaments 21, each of the filament 21 is connected (connection not shown, but which can conveniently be obtained by a male-female, plug-like construction) to a respective conductive track 24a on the feedthrough body 26a. The electrically conductive tracks 24a are made of copper metal. The stem 23 with supported light engine 21a as shown in FIG. 4A can suitably be applied as an alternative for the stem and supported light engine as shown in the lamp of FIG. 2.

[0067] FIG. 5 schematically illustrates in a flow chart type diagram, an embodiment of a method 50 for manufacturing the light bulb according to the present disclosure.

[0068] In consideration of the high temperatures required to melt the feedthrough tube in the glass stem, as a first step 51 of the method 50 of the present disclosure, the feedthrough carrier is fixed, for example, melted in the glass stem.

[0069] Following that, at step 52, the plurality of conductive wires are fed in the feedthrough tube and then connected with light engine contacts, such as contacts of each of the plurality of filament. Alternatively, step 51 and 52 may be carried out in reverse order.

[0070] Following the steps 51 and 52, in step 53 the light engine is arranged in the space enclosed by the light transmissive surface and the glass stem.

[0071] Thereafter, at step 54, the glass stem, which now has the tube fixed/sealed therein and the conductive wires in place in the tube, is assembled with the light transmissive surface structure. This is done as in a conventional way, for example via fusion via melting the flare of the stem to the light transmissive surface structure.

[0072] After that, the bulb may optionally be filled with gas and sealed at step 55, and then the gas feeding tube may be blinded at step 56.

[0073] The present disclosure is not limited to the examples as disclosed above, and can be modified and enhanced by those skilled in the art beyond the scope of the present disclosure as disclosed in the appended claims without having to apply inventive skills and for use in any data communication, data exchange and data processing environment, system or network.