Incandescent lamp with reflection coating

Abstract

The invention relates to an electric incandescent lamp, in particular a halogen incandescent lamp (9) with a rotationally symmetrical lamp cover (10) and a layer (14) reflecting infrared radiation. This incandescent lamp has an ellipsoidal partial contour. The ellipsoidal partial contour of the lamp cover (2; 10) is generated by an ellipse section (3) whose semi-major axis and consequently its focal axis (F1F2) are perpendicular to the longitudinal axis, i.e. perpendicular to the axis of rotation (RA) of the lamp cover (10). The length of the semi-major axis is preferably R <a<R+5·wr tartományban van, aholR a lámpabura (10) legnagyobb sugara, wr a forgásszimmetrikusvilágítótest (15) legnagyobb sugara. A lámpa (9) fokozza ahatékonyságot, és emellett egyenletesen veri vissza az infravörössugárzást a lámpaburán (10) belül központosan tengelyiránybanelhelyezett, henger alakú világítótestre (15), és ezzel egyenleteshőmérséklet-eloszlást hoz létre. ŕ

Description

The invention relates to an electric incandescent lamp, in particular a halogen incandescent lamp, with a light-reflecting layer, in particular a layer reflecting infrared radiation. This incandescent lamp has a rotationally symmetrical lamp cover with a longitudinal axis and an ellipsoidal partial contour. One wall surface of the lamp cover is provided with a layer reflecting infrared radiation. The incandescent lamp also has a rotationally symmetrical light source, which is arranged axially inside the lamp cover and is held by two current leads. The two current leads are led out gas-tightly on one or both sides of the lamp cover by means of one or, if appropriate, two seals. Lamps of this type are used for both general lighting and special lighting purposes, and in combination with a reflector, for example, in projection technology. The rotationally symmetrical shape of the lamp cover and the infrared radiation reflecting layer applied to its inner and / or outer surface reflect a large part of the infrared radiation emitted by the light source. The increase in lamp efficiency thus achieved can be used, on the one hand, to increase the temperature of the light source at a constant electrical power consumption and consequently to increase the luminous flux, and on the other hand, a given luminous flux can be achieved with a lower electrical power consumption. This represents a beneficial “energy saving effect”. Another desirable effect is that, due to the infrared radiation reflecting layer, much less infrared radiation is emitted through the lamp cover - which heats the environment - than with conventional incandescent lamps. Due to the inevitable absorption losses in the infrared reflecting layer, the power density of the infrared radiation fraction within the lamp cover decreases with the number of reflections and consequently the efficiency of the incandescent lamp also decreases. In order to actually achieve an increase in efficiency, it is therefore crucial to minimize the number of reflections required to return individual infrared rays to the luminaire. For this purpose, the lamp cover with the infrared reflecting layer is specially shaped. Lamps of this type are known, for example, from US Pat. No. 4,160,929, EP-A 0 470 496 and DE-OS 44 20 607. According to US Pat. No. 4,160,929, in order to optimize the efficiency of the lamp, the geometric shape of the light source must be adapted to that of the lamp cover. In addition, the light source must be positioned as precisely as possible in the optical center of the lamp cover. As a result, the wave front originating from the surface of the light source is reflected unhindered by the surface of the cover. This minimizes aberration losses. In a spherical lamp cover, for example, the ideally centrally located, spherical light source must be present. However, due to the limited ductility of the tungsten wire usually used for this purpose, suitable spiral shapes can only be realized to a very limited extent. A cubic spiral is proposed as a rough but practical approximation of a sphere.In a further embodiment, the diameter of the spiral is largest in the middle and gradually decreases towards the two ends of the spiral. An ellipsoidal bulb shape is proposed, and a light source is provided at each of the two foci of the ellipsoid. The lamp disclosed in EP-A 0 470 496 has a spherical lamp cover, in the centre of which a cylindrical light source is arranged. According to the patent document, the deterioration of the efficiency caused by the deviation from the ideal spherical shape of the light source can be limited to an acceptable level under the following conditions. Either the diameter of the cover and the diameter or length of the light source must be carefully coordinated within a tolerance range, or the diameter of the light source must be significantly smaller (0.05 times smaller) than the diameter of the lamp cover. Furthermore, a lamp with an ellipsoidal cover is described, in which an elongated light source is arranged axially in the focal line of the cover. DE-OS 30 35 068 describes the minimization of the unavoidable aberration losses in the latter embodiment. According to this, the two focal points of the ellipsoidal lamp cover are located in the geometric axis of the cylindrical luminaire and at a given distance forward from its given ends. Finally, DE-OS 44 20 607 discloses a halogen incandescent lamp with a lamp shell which is designed as an ellipsoid or ellipsoid-like barrel body and is provided with a layer reflecting infrared radiation. The ellipsoid or, if applicable, ellipsoid-like part of the contour of the barrel body is generated by an ellipse section whose semi-minor axis ab is perpendicular to the longitudinal axis of the lamp, i.e. the axis of rotation of the lamp shell. In addition, the semi-minor axis of the generating line is smaller than the half-diameter of the shell D / 2 and is offset by approximately the radius d / 2 of the lamp body parallel to the axis of rotation. Ultimately, this results in the barrel body. The length of the lamp body is approximately equal to the distance between the two foci of the generating ellipse section. Furthermore, the light source is positioned within the lampshade in such a way that - when viewed in longitudinal section - the two focal points approximately coincide with the two corresponding corner points of the light source. The spiral is therefore heated unevenly in any case.A further disadvantage of this solution is that the achievable improvement in lamp efficiency depends relatively strongly on the dimensions of the luminaire and its placement within the lamp housing. The object of our invention is to overcome the aforementioned disadvantages and to provide an incandescent lamp which effectively redirects the emitted infrared radiation back to the luminaire and consequently has a good efficiency. In addition, it is necessary to enable the compact dimensions of the lamp and, with this, the high luminous intensity, which is primarily sought in low-voltage halogen incandescent lamps. This problem is solved according to the invention in such a way that the ellipsoidal partial contour of the lampshade is generated by an ellipse section, the major axis of which is the semi-major axis and HU 222 331 Β1 therefore the focal axis is perpendicular to the longitudinal axis, i.e. perpendicular to the axis of rotation of the lampshade. To explain the basic idea of ​​the invention, reference is made to Figure 1. This schematically illustrates the theoretical relationships and introduces some quantities important for understanding the invention. Among other things, an ellipse 1 with semi-major axis a and semi-minor axis b, as well as the two foci Fj and F2, can be seen. According to the invention, the contour of the rotationally symmetrical lamp cover 2 [shown very schematically; the current leads and the flattening(s) are not shown for the sake of simplicity] is essentially generated by an elliptical section 3 of the ellipse 1 (highlighted in FIG. 1 with a thicker line thickness). The elliptical section 3 is deliberately selected such that its semi-major axis is perpendicular to the axis of rotation RA of the lamp cover 2. A rotationally symmetrical, for example circular cylindrical, light source 4 (shown as a rectangle in the schematic longitudinal section according to FIG. 1) is centrally arranged axially within the lamp cover 2. As a result, the focal axis FjF2 - i.e. the straight line connecting the two foci FbF2 of the generating elliptical section 3 - is also perpendicular to the axis of rotation RA of the lamp cover 2. The semi-major axis of the generating ellipse segment 3 is longer than the radius R of the lamp shell 2. As a result, the shape of the lamp shell 2 is now a “real” ellipsoid of revolution.Surprisingly, it turned out that this departure from the previous concept significantly increases the efficiency of the lamp and the heating of the 4 light sources becomes more uniform. In terms of high efficiency, it has also proven to be advantageous if the length of the semi-major axis is R <a<R+5 wrtartományban, előnyös módon az R+Wr<a<R+3 · wrtartományban van, ahol R a 2 lámpabura legnagyobb sugara, wra henger alakú vagy hengerhez hasonló alakú 4 világítótest legnagyobb sugara. A generáló 3 ellipszisszakasz b fél kistengelye a 4 világítótest hosszának kb. a kétszerese. The difference with respect to the prior art becomes clear by comparing the schematic principle representation according to FIGS. 2A and 2B. FIG. 2A essentially corresponds to the conditions according to the publication document DE-OS 30 35 068. Here an ellipsoidal lamp cover 5 is shown, in the interior of which a light source 6 is arranged centrally in the axial direction in such a way that the two foci of the ellipsoid of rotation, Fj and F2, coincide with the ends of the light source 6. The focal axis FjF2 is therefore, in contrast to the present invention, parallel to the axis of rotation RA of the lamp cover 5. Finally, in FIG. 2B, the conditions according to DE-OS 44 20 607 are shown. Here, the lamp cover 7 is designed as an ellipsoid or a barrel-shaped body similar to an ellipsoid. In the schematic section, two ellipsoidal halves can be recognized, which are connected by two straight pieces. The focal points FjF2 and Fi'F2' of the two ellipsoidal halves coincide with the corner points of the light body 8. The focal axes FjFa and Fj'F2' are therefore - also different from the present invention - parallel to the axis of rotation RA of the lamp cover. The advantage of the invention - in addition to the increased efficiency - is also the increased precision with which the infrared radiation is reflected onto the spiral. This avoids local overheating which could prematurely destroy the spiral. It is also advantageous that the improvement in lamp efficiency achieved compared to DE-OS 44 20 607 is less dependent on manufacturing-induced fluctuations in the positioning of the lamp within the bulb. Axially arranged, single or double tungsten spirals are used as lighting fixtures. The geometric dimensions, i.e. diameter, pitch and length, depend, among other things, on the desired electrical resistance R of the spiral, which in turn depends on the desired electrical power consumption P for a given supply voltage U. Since P=U2 / R, the spirals are usually longer for high-voltage lamps than for low-voltage lamps. The luminaire is electrically connected to two current leads. Either both current leads are led out gas-tight together at one end of the lamp cover or separately at two opposite ends of the lamp cover. The sealing is usually achieved by flattening. However, other sealing techniques are also possible, such as fusing a plate. A design sealed on one side is primarily suitable for low-voltage applications. In this case, the relatively short luminaire allows very compact lamp dimensions to be achieved. In order to optimize the efficiency of the lamp, it is advantageous to use as much of the lamp wall as possible as an effective reflecting surface. This can be achieved primarily by having a lamp neck at one or, if appropriate, both ends of the lamp shell in the vicinity of the current supply. The lamp neck surrounds the current supply as closely as possible and extends into a seal. Details of this can be found in German Patent Application DE-OS 44 20 607. The lamp envelope is usually filled with an inert gas such as N2, Xe, Ar and / or Kr. It contains halogen additives that maintain a tungsten-halogen cycle, which counteracts blackening of the envelope. The lamp envelope is made of a light-transmitting material such as quartz glass. The lamp can be operated with an external cover. If a particularly large reduction in the infrared power emitted into the environment is desired, this can also have an infrared reflecting layer. The infrared reflecting layer can be implemented as an interference filter known per se, usually as a series of alternating dielectric layers with different refractive indices. The principle structure of suitable infrared reflecting layers is described, for example, in EP-A 0 470 496. Our invention is described in more detail with reference to its exemplary embodiments with the help of our drawings, of which the Figure 1 is a schematic representation of the principle of the invention, Figure 2 is a schematic representation of the state of the art, HU 222 331 Bl Figure 3 shows an embodiment of a low-voltage halogen incandescent lamp with an infrared-reflecting layer and an internal return spiral, as well as an optimized bulb shape according to the invention. Figure 3 schematically shows a first embodiment of a lamp 9 according to the invention. The lamp 9 is a halogen incandescent lamp with a nominal voltage of 12 V and a nominal power of 35 W, which consists of a lamp shell 10 formed as an ellipsoid-like body, flattened on one side. The ellipsoidal partial contour of the lamp shell 10 is generated by an ellipse section, the semi-major axis of which is 7.4 mm long and perpendicular to the longitudinal axis of the lamp 9. The semi-minor axis of the generating ellipse section is 6.3 mm long. The lamp shell 10 consists of quartz glass, has a wall thickness of approx. 1 mm, and a largest outer diameter of 12 mm. The first end of the lamp shell 10 passes into a lamp neck 11, which ends in a flattened seal 12. At the opposite end of the lamp shell 10 there is a pumping tip 13. The outer surface of the lamp cover 10 has a layer 14 that reflects infrared radiation, which consists of an interference filter containing more than twenty TiO2 and SiO2 layers.The infrared-reflecting layer additionally covers approximately half of the flattened gasket 12. In this way, on the one hand, the infrared-reflecting layer 14 is formed to a particularly true-to-size shape, since the outer surface of the ellipsoid body is embossed onto the outer surface of the lamp cover 10 during its production. On the other hand, since the infrared-reflecting layer 14 covers a portion of the flattened gasket 12, the individual layers are particularly uniform in the vicinity of the cover surface. This reduces color errors. The length of the lamp neck is approximately 2.5 mm, the outer diameter is approximately 6 mm. Inside the lamp cover 10 is an approx. A charge of 6670 hPa, consisting of a mixture of xenon (Xe) and nitrogen (N) in a ratio of 88:12, doped with 200 ppm dibromomethane, and an axially positioned illuminant 15, 3.07 mm long and 1.87 mm outer diameter. The illuminant 15 is made of tungsten wire with a diameter of 152 pm. The tungsten wire is wound into a single helix with a pitch of 243 pm. The current leads 16a, 16b are formed directly by the spiral wire and are connected to the molybdenum foil 17a, 17b in the flattened gasket 12. The molybdenum foil 17, 17b is connected to the outer lamp head pin 18a, 18b. The first current lead 16a is guided nearly parallel to the longitudinal axis of the lamp and is essentially flush with the outer surface of the lamp body 15. The second current lead 16b of the lamp body 15 is bent towards the longitudinal axis of the lamp and runs centrally along the geometric axis of the threads of the lamp body 15, i.e. within the spiral towards the end opposite the lamp head. In this way, any shielding of the radiation by a current lead is avoided. The color temperature of the lamp is approx. 3050 K. The luminous flux is 1000 lm, which corresponds to a luminous efficiency of approx. 20 lm / W. A comparable lamp without an infrared-reflecting layer would require an electrical power consumption of approx. 50 W for the same luminous flux. In comparison, the lamp according to the invention can save 42% of the electrical power. Two further embodiments, a 50 W and a 65 W halogen incandescent lamp, also with a supply voltage of 12 V, differ only in the parameters of the generating ellipse of the lamp shell and the parameters of the spiral. Their construction is the same as that shown in Figure 1. The following table compares the mentioned parameters of the three embodiments. Table Comparison of some bulb and filament parameters for three halogen incandescent lamps with different electrical power consumption 35 W 50 W 65 W a semi-major axis, mm 7.4 7.7 8.0 b semi-minor axis, mm 6.3 6.5 6.6 w( helix length, mm 3.07 3.75 4.02 2wr helix diameter, mm 1.87 1.97 2.3 helix pitch, pm 243 297 346 wire diameter, pm 152 185 216 PATENT CLAIMS

Claims

PATENT CLAIMS 1. An electric incandescent lamp, primarily a halogen incandescent lamp (9), having a longitudinal axis, a rotationally symmetrical lamp cover (2; 10) with an ellipsoidal partial contour, and one wall surface of the lamp cover is provided with a layer (14) reflecting infrared radiation; the incandescent lamp further has a rotationally symmetrical light source (4; 15), which is arranged axially inside the lamp cover (2; 10) and is held by two current leads (16a, 16b), and the two current leads (16a, 16b) are led out gas-tight on one or both sides of the lamp cover (10) through one or, if applicable, two seals (12), characterized in that the ellipsoidal partial contour of the lamp cover (2; 10) is generated by an ellipse section (3), the major axis of which is half a and consequently its focal axis (FjF2) is perpendicular to the longitudinal axis, i.e. perpendicular to the axis of rotation (RA) of the lamp cover (2; 10).

2. An electric incandescent lamp according to claim 1, characterized in that the semi-major axis of the ellipse section (3) generating the partial contour is longer than the largest radius R of the lamp shell (2; 10), i.e. a>R.

3. An electric filament lamp according to claim 2, characterized in that the length of the semi-major axis is R <a<R+5 wr tartományban van, ahol R a lámpabura (2; 10) legnagyobb sugara, wr a forgásszimmetrikus világítótest (4; 15) legnagyobb sugara.

4. An electric filament lamp according to claim 3, characterized in that the length of the semi-major axis is R+Wj <a<R+3 wr tartományban van.

5. An electric filament lamp according to claim 1, 2 or 3, characterised in that the layer (14) is applied to the outer surface of the lamp (9) and extends over the lamp cover (10) and at least part of the flattened gasket(s) (12).

6. An electric filament lamp according to any one of claims 1-5, characterized in that the length of the semi-minor axis b of the ellipse section (3) generating the partial contour is W| / 2 <b<3'W| tartományban van, ahol wt a világítótest (4; 15) hossza.

7. An electric incandescent lamp according to any one of claims 1-6, characterized in that in the case of a one-sided seal (12) of the lamp cover (10), the lighting body (15) is formed by a spiral, the current supply (16b) of which is further away from the seal is led back inside the spiral serving as the lighting body (15).

8. An electric filament lamp according to any one of claims 1-7, characterized in that the lamp shell (10) has a lamp neck (11) at at least one end, which surrounds at least one current supply (16a, 16b) as closely as possible, and whose end remote from the shell is sealed in a gas-tight manner.