Abstract: A high-pressure sodium discharge lamp provided with a ceramic discharge vessel, in which sodium, mercury and xenon are present, of which the xenon is at a pressure at 300K of at least 26.7 kPa. The sodium and the mercury are present in a weight ratio Na/Hg which is at least 0.075 and at most 0.125. The lamp generates in the operating condition a spectrum, in which at a wavelength of 589.3 nm a self-absorption band is present, which is limited by spectral flanks each flank having a respective maximum. There is a wavelength difference .DELTA..lambda. of at least 3.5 nm and at most 6 nm between the maxima.

Abstract: The high pressure discharge lamp has an elongate discharge vessel of ceramic material. The outside surface area of the wall of the discharge vessel is strongly increased by a relief. Since a higher heat flow from the discharge vessel to the environment is possible, the lamp can withstand a higher load. In this way, lamp properties such as luminous flux, color rendering index and/or color temperature can be improved.

Abstract: The invention relates to a high-pressure sodium vapor discharge lamp having a ceramic discharge vessel. In addition to sodium and possibly mercury the discharge vessel also comprises a rare gas. In the discharge vessel an electrode of a refractory metal is accommodated. In the operating condition of the lamp the discharge emanates from the tip of the electrode. According to the invention the electrode is free from alkaline earth metals and the electrode tip in the operating condition of the lamp has a temperature between 2400 K and 2700 K. Disappearance of sodium caused by the electrode material is prevented in this manner.

Abstract: A high-pressure sodium discharge lamp comprising a discharge vessel (3) provided with an external auxiliary electrode (11) and a built-in electric starting circuit including an electric circuit comprising a transformer winding (35a), a capacitor (33) and a semiconductor switching element (34). The circuit is connected in series with a resistor (32) electrically parallel to the discharge vessel (3) and with the transformer (35) electrically connected to the external auxiliary electrode (11). The semiconductor switching element (34) is an uncontrolled voltage-dependent breakdown element of the thyristor type having a breakdown current smaller than 1 mA at a breakdown time shorter than 10 .mu.s. The resultant lamp starts very reliably and its build-in starter dissipates only a very low power.

Abstract: The invention relates to a high-pressure metal vapor discharge lamp having an ignition auxiliary means (13) externally of the discharge vessel. The external ignition auxiliary means is connected electrically to a first main electrode (5) and in the inoperative condition of the lamp extends along the wall of the discharge vessel up to at most 3 mm beyond one end of a second main electrode (6). According to the invention the external ignition element extends at the level of the first main electrode over at most 3 mm along the first main electrode from the end of the first main electrode. In this manner a regular ignition of the lamp is obtained, variation in the ignition voltage pulse required for ignition being considerably restricted.

Abstract: A high-pressure discharge lamp having a ceramic discharge vessel comprising an ionizable filling which in the operating condition of the lamp comprises a component present in excess, and in which two electrodes are present. The electrode is connected to a pin-shaped current supply member which is surrounded with a small annular gap by an end portion of the discharge vessel. The pin-shaped current supply member and the end portion are connected in a gas-tight manner by means of a glass seal, in which the sealing glass seal extends into the small annular gap in the direction towards the electrode over such a distance that, in the operating condition of the lamp, the temperature at the surface of the glass seal facing the discharge is at least 50 degrees K. lower than the temperature of that part of the filling which determines the vapor pressure of the component present in excess.

Abstract: A high-pressure sodium vapor discharge lamp contains an electron-emitting material consisting of alkaline earth metals bound to oxygen and tungsten bound to oxygen. It has been found that such lamps of less than 400 W which have either a high Hg/Na ratio or use neon/argon as a starter gas fail prematurely when the alkaline earth metals and tungsten in the electron-emitting material are present in stoichiometric quantities.The free ends of electrodes of lamps according to the invention are wound with tungsten wire. Electron-emitting material comprising carium, strontium and calcium bound to oxygen and tungsten bound to oxygen is disposed in the cavities formed between the tungsten wire turns. The molar ration of the total barium, strontium and calcium bound to oxygen to the tungsten bound to oxygen is between 8 and 50.

Abstract: High-pressure sodium vapor discharge lamps having a color temperature of 2250 to 2750 K. and a color rendition index Ra of 60-85 emit light of a strongly reduced Ra already after approximately 2000 hours in operation. As compared with the life of normal, yellow high-pressure sodium vapor discharge lamps, this period is very short.The discharge vessel contains sodium, mercury and a rare gas, the weight ratio Na/Hg being from 1/1 to 1/9 and the sodium pressure during operation of the lamp being from 4.times.10.sup.4 to 10.7.times.10.sup.4 Pa. The rare gas pressure in the discharge vessel at 300 K. is between 1333 and 1333.times.10.sup.2 Pa.By using an emitter which contains oxygen-bound strontium and oxygen-bound tungsten in a molar ratio from 3/1 to 50/1, the initial properties of such white-light-producing lamps are maintained for a long period of time.

Abstract: High-pressure sodium vapor discharge lamps are used which contain an electron-emitting material consisting of alkaline earth metal bound to oxygen and tungsten bound to oxygen. It has been found that such lamps which have a high Hg/Na ratio, use neon/argon as a starter gas or have powers of less than 400 W fail prematurely when the alkaline earth metal and tungsten in the electron-emitting material are present in stoichiometric quantities (total alkaline earth metal oxide: WO.sub.3 =3).The free ends of electrodes of lamps according to the invention are wound with tungsten wire. Electron-emitting material consisting of strontium bound to oxygen and tungsten bound to oxygen is disposed in the cavities formed between the tungsten wire turns. The molar ratio of the strontium bound to oxygen to the tungsten bound to oxygen is between 3 and 50.

Abstract: The invention relates to a high-pressure sodium vapor discharge lamp which has a discharge vessel in which xenon and a xenon-absorbing substance are present. The xenon is absorbed partly in the absorbing substance. When the temperature is raised xenon is released.According to the invention, the xenon pressure P at room temperature has a value which satisfies 1 kPa.ltoreq.P.ltoreq.25 kPa. Herewith it is achieved that a lamp is obtained having good ignition properties and a high xenon pressure in the operating condition of the lamp, resulting in a large luminous flux.

Abstract: The invention relates to a high-pressure sodium vapor discharge lamp provided with a discharge tube containing mercury and xenon as well as sodium. The sodium vapor pressure--in the operating condition of the lamp--is within a given range.In accordance with the invention a xenon filling pressure is used which is between 50 and 1000 torr. As a result a lamp can be obtained which has a high luminous efficacy in the operating condition.

Abstract: The invention relates to an electric device provided with a switch which is constructed as a discharge tube which comprises at least two main electrodes and a reversible hydrogen getter.According to the invention the discharge tube contains a rare gas so that the current flow in the conducting state of the switch is mainly ensured by that rare gas. The non-conducting stage of the switch can be obtained by heating the getter. Namely, the hydrogen pressure in the discharge tube then becomes so high that the discharge in the tube is extinguished. Heating of the getter is preferably effected by the heat developed by the current between the main electrodes. This results in a self extinguishing breakdown element.

Abstract: The invention relates to a high-pressure sodium-vapor discharge lamp having substantially the same color temperature as an incandescent lamp. The invention provides a high-pressure sodium-vapor discharge lamp having a low re-ignition voltage.This is achieved by including xenon and mercury in the discharge tube such that (i) the weight of mercury is between 50% and 90% of the combined weight of the mercury and sodium, (ii) the pressure of the xenon at room temperature is between 100 and 1000 torr, and (iii) the sodium vapor pressure is between 300 and 800 torr in the operating condition of the lamp. The power consumed by such a lamp is typically one-fifth of that consumed by an incandescent lamp having the same light output.

Abstract: The invention relates to a high-pressure sodium vapor discharge lamp which comprises a discharge tube provided with an external starting electrode. In accordance with the invention the lamp comprises a transformer wherein the secondary winding of the transformer is connected between the starting electrode and a main electrode of the discharge tube, the primary winding of that transformer being included in an oscillatory circuit including a glow starter. These further components of the starting circuit form part of the lamp. In this construction proper starting of the lamp is achieved with minimal insulation near the input terminals of the lamp.