EP0335202A2 - High-pressure lamp, especially a high-pressure sodium vapour lamp - Google Patents

Abstract

A high-pressure discharge lamp, especially a high-pressure sodium vapour lamp, having a tubular ceramic discharge vessel (1) in whose interior there are located electrodes (19) and a filling consisting of a noble gas which can be ionised and a metallic additive (16), and which has a ceramic closing element (15) which closes the ends of the ceramic discharge vessel, if required in an integrated manner, which is provided with at least one hole and whose end surface plane, seen from the discharge chamber, has sections at different height levels, a cold chamber for the metal additive (16), especially a sodium amalgam, being formed in the closing element (15) or between the ceramic closing element (15) and the wall of the discharge vessel (1). The ceramic closing element (15), closing the tubular discharge vessel (1), is formed such that the distance between the metal additive (16) and the electrode (19) or the power supply (2) forming a unit therewith, is greater than 4 mm, measured as the length of a conducting path (17) along the surface of the ceramic closing element (15). <IMAGE>

Description

The invention relates to a high-pressure discharge lamp, in particular sodium lamp, which has a tubular ceramic discharge vessel, in the interior of which there are electrodes and a filling which maintains the discharge and contains an ionizable noble gas and a metal additive, and with a tubular ceramic discharge vessel on both sides, if appropriate integrated way, final ceramic closure element, which contains at least one bore, is formed. The surface of the ceramic closure element facing the discharge space is provided with an uneven surface.

Light sources of symmetrical and asymmetrical construction with a ceramic discharge vessel, that is to say gas discharge lamps, are known. Experience shows that no matter which assembly the light sources belong to, after their ignition the transition component of the current, ie the length of the transition from the glow arc state to the normal operating discharge state, becomes asymmetrical. The main cause of this effect is the effect of the metallic additional components of the filling, which deposit in addition to the electrodes from the discharge space and come into electrical contact with the electrodes or with the feed lines forming a unit, in the case of high-pressure sodium vapor lamps the sodium amalgam search. The additional metallic components increase the surface area of one electrode, thereby increasing the duration of the glow arc phase, ie that of the ignition phase. This process takes place in such a way that there is no metal additive next to one of the electrodes or only a negligible small amount of the additional metallic components, for example sodium amalgam; the discharge passes into the arc phase in a shorter time than in the case of the other electrode, which with a larger amount or with a larger area of additional metallic components, in particular sodium amalgam Touch comes. As a result, the electrodes are loaded asymmetrically.

Discharge lamps are also known in which an ignition electrode is installed in the vicinity of the main electrode. In this case, the metallic additional components which are deposited between the two electrodes hinder the ignition-promoting function of the ignition electrode. (To promote the ignition process on the part of the ignition electrode, it is necessary that the main electrode is electrically insulated from the adjacent ignition electrode)

After operating the light source for a shorter or longer period, i.e. the discharge lamp, the glass enamel used for soldering and the surface of the ceramic end element can become electrically conductive. In this case, it can happen that the focal spot of the resulting discharge arc does not form on the tip of the electrode, but on the sealing lacquer that has become conductive or on the surface of the ceramic closure element. This effect leads to the ceramic substance of the discharge vessel becoming damaged after a short time.

Discharge lamps are also known in which the contact between the electrically conductive metallic additional components, e.g. the sodium amalgam, and the electrodes are prevented by a special sealing element.

These solutions are either cumbersome and therefore difficult to reproduce, or additional means for heat reflection, for example a niobium or tantalum ring, are required because the distance between the electrode and the additional metallic components, for example the sodium amalgam, is too large to allow for the Set temperature of the metal additive, or it can not be guaranteed that the electrically conductive additional components are only in the storage space intended for him, in the so-called cold chamber, knock down, that is, the cold chamber is always in a constant coldest point of the discharge vessel.

Another example of such a high-pressure discharge lamp is known from GB-A 1 465 212, according to which an annular gap is formed in the closing element of the discharge tube as a storage space for the amalgam. The dimensions of the gap are not determined in the description, and since the power supply, which is designed as a niobium tube, is surrounded by a gap and the temperature of which is low enough due to the thermal conductivity of the niobium tube, the metallic additional components can also be deposited there. With this construction, it cannot be avoided with desired reliability that the amalgam comes into contact with the electrode or with the feed line forming a unit.

Furthermore, a ceramic closure element is known from HU-B 181 872, which has a bag-shaped storage space for accommodating the metallic additional component. The aim was that the coldest point of the discharge lamp is in the closure element (and not between the closure element and the wall of the discharge vessel) and that the metal additive is largely shielded from the discharge space.

DE-A1 -24 05 335 discloses such a high-pressure discharge lamp, more precisely a high-pressure sodium vapor lamp, in which the conductive metal additive, the sodium amalgam, is shielded from the electrode by an additional ceramic separating element in order to operate to prevent any flickering. This makes the structure of the end element very complicated. It has been shown that the complete shielding of the electrode against the metallic additional components is superfluous, as can be found in EP-B-74 188. In the above-mentioned patent, the formation of a ceramic shoulder around the niobium tube recommended. The height of the shoulder is determined by the fact that it should not shield the amalgam from the electrode, but the smallest possible width ensures that the electrode body has sufficient heat capacity so that the amalgam does not deposit on it. As an example for the width values from 0.2 to 0.5 mm are given, for the height 1.5 mm. The disadvantage of this solution is that a heat-reflecting agent is required at a higher shoulder height to ensure the appropriate temperature of the amalgam, but a smaller shoulder height does not prevent the conductivity between the amalgam and the electrode or the conductive electrode holder after long operation of the lamp.

The solution according to the description of EP-A-188 229 also poses similar problems. Here, the closing element of the discharge tube is formed such that an annular channel for receiving the amalgam is formed between the element and the wall of the discharge tube. The greatest depth of the channel can be equal to the inside diameter of the discharge tube. With this construction, no care was taken that the ceramic, which becomes conductive on its surface during operation, can cause a short-circuit current path at the proposed channel depth between the electrode and the amalgam.

When examining the known solutions, it was found that when manufacturing an optimally constructed high-pressure discharge lamp, in particular a high-pressure sodium lamp, on the one hand ensuring the final temperature of the discharge vessel, on the other hand avoiding the conduction on the surface between the electrode and the im Storage space accumulated metal additive, preferably sodium amalgam, represent the main tasks even during a long period of operation. After prolonged operation, this effect occurs as a result of a process that takes place during the burning of the discharge lamp known structure and is proportional to the lowering of the The amount of conductive metallic additional components, especially sodium, is an ever greater danger.

The aim of the present invention is to avoid the above-mentioned problems also with high-pressure discharge lamps of low power or high end temperature, e.g. in high-pressure discharge lamps improved color rendering, in particular in the case of sodium vapor lamps, and to achieve that not only when the lamps are operated for a short time, but also after a long period of operation, there is no electrical connection between the electrode and the conductive additional element.

During the development of the present invention, it was recognized that in order to achieve the objective described above, a ceramic closure element is required in which the discharge space delimiting, i.e. the surface closing the interior of the discharge vessel is divided into surface elements of different height levels. This structure is determined by the fact that the distance between the surface of the conductive metal additive and the electrode or the power supply unit which forms a unit therewith, which is determined as the length of a path measured on the surface of the terminating element, ensures insulation even during prolonged operation . In other words, the conduction path must be long enough to prevent electrical contact between the conductive metal additive and the electrode throughout the life of the lamp.

In the previously published solutions, the role of the length of the route was not recognized. The solutions that dealt with dimensions indicated the depth, perhaps also the width of hollows or the width of a shoulder. In general, the surface of the ceramic terminating element was designed in such a way that the length of the path traveled from the metal additive, in particular sodium amalgam, to the power supply or electrode did not reach the size of 4 mm. It was feared that the electrode tip and the metal additive would differ too much remove. As an important parameter, the latter distance was already determined in GB-A 502 321 in such a way that it advantageously makes up about 2 mm.

However, tests have shown that when the end face of the ceramic end element is formed, the length of the line path, which must be longer than 4 mm, must also be taken into account.

If the previously specified length of the conduction path is taken into account when designing the end face of the terminating element, the additional metal from the discharge space is not deposited near the power supply and even after prolonged operation there is no electrical connection between the conductive metal additive and the electrode or the power supply forming a unit with the electrode. Apart from extreme cases, the corresponding concentration of the metal additive is maintained without additional means for heat reflection in the discharge space.

Based on the above results, a high-pressure discharge lamp, in particular an improved high-pressure sodium lamp, has been developed. The high-pressure discharge lamp according to the invention, in particular high-pressure sodium vapor lamp, has a tubular ceramic discharge vessel, in the interior of which electrodes, a filling consisting of ionizable noble gas and a metal additive, in particular sodium amalgam, and one the ends of the discharge vessel, optionally in an integrated manner, final, at least one bore-containing ceramic closure element, which has parts of different height levels in the direction of the discharge space, but also a space formed in this closure element or between the connection element and the tubular wall of the discharge vessel, the so-called cold chamber, which is used to hold the metal additive, in particular Sodium amalgams is provided. The essence of the proposed solution is in particular that the Distance between the surface of the conductive metal additive and the electrode, or the power supply unit forming a unit with the latter, measured along the surface of the ceramic terminating element, is greater than 4 mm. In other words, the conduction path is more than 4 mm.

An advantageous embodiment of the ceramic closure element consists in the use of two troughs and an outstanding rib arranged between the troughs, the rib determining the so-called cold chamber with the wall of the discharge vessel. The length of the route, i.e. the distance of the conductive metal additive from the power supply, measured on the surface of the rib and the base of the inner trough, exceeds 4 mm, the trough in the vicinity of the central axis of the discharge vessel being referred to as the inner trough.

Another favorable further development is when the base areas of the troughs have different levels on both sides of the rib and in such a way that the base area of the trough lying closer to the wall of the discharge vessel is lower, as seen from the discharge space.

It is also advantageous if the storage space in the ceramic end element that forms the cold chamber is narrower than 2 mm, and if, in the case of discharge lamps of low power, the distance between the end of the electrode directed towards discharge and the storage space of the metal additive, in particular the sodium amalgam, is less than its triple distance from the wall of the discharge vessel is, in particular less than 5 mm. The outer trough advantageously forms the cold chamber.

• Fig. 1 einen schematischen Querschnitt einer Hochdruck-­Natriumdampflampe,
• Fig. 2 den Querschnitt eines keramischen Abschlußelementes des Entladungsgefäßes der Natriumdampflampe nach Figur 1,
• Fig. 3 die Ausbildung des Endes eines teilweise integriert abgeschlossenen Entladungsgefäßes im Querschnitt,
• Fig. 4 den Querschnitt der Ausbildung eines integriert abgeschlossenen Entladungsgefäßes,
• Fig. 5 ein Mittel zur Abschirmung des Endes eines Entladungsgefäßes im Querschnitt, welche bei einem in Fig. 2 gezeigten oder dazu ähnlichen keramischen Abschlußelement verwendet wird, und
• Fig. 6 den Abschluß eines in Richtung seines Endes sich verjüngenden keramischen Entladungsgefäßes.

The invention is described in more detail below with reference to the drawing, the drawing serving to illustrate the invention and the actual ones Proportions are not always true. The drawing shows:

• 1 is a schematic cross section of a high pressure sodium lamp,
• 2 shows the cross section of a ceramic end element of the discharge vessel of the sodium vapor lamp according to FIG. 1,
• 3 shows the design of the end of a partially integrated, closed discharge vessel in cross section,
• 4 shows the cross section of the formation of an integrated, closed discharge vessel,
• Fig. 5 shows a means for shielding the end of a discharge vessel in cross section, which is used in a ceramic closure element shown in Fig. 2 or similar, and
• Fig. 6 shows the conclusion of a tapering ceramic discharge vessel in the direction of its end.

The invention is used to improve high-pressure discharge lamps, in particular high-pressure sodium vapor lamps, a tubular ceramic discharge vessel 1 being arranged in a translucent outer bulb 8 (FIG. 1) and being connected to current leads 2 made of niobium. The power supply lines 2 of the ceramic discharge vessel 1 of the sodium vapor lamp shown in FIG. 1, which can be switched to a power source by a threaded base 11 or in another known manner, are coupled by support wires 3 to support elements 4, 5, which fix the ceramic discharge vessel in the outer bulb 8, whereby the discharge vessel 1 is fastened to an inner recess 7 of the outer bulb 8 with the aid of an elastic clip 6.

The electric current flows to the discharge vessel 1 through the current leads 2 made of niobium, which, with the threaded part of the threaded base 11 and one located in the lower part of the threaded base 11, by means of the latter an insulation 12 electrically separated electrical contact 13 via a frame 10, power supply lines 9, the support elements 4, 5 and the support wires 3 are connected. The base structure is known per se and the lamp construction also requires no further detailed explanation.

The innovation in the lamp construction according to the invention consists in a novel design of the end part of the tubular ceramic discharge vessel 1, various advantageous embodiments of this end part being applicable, some of which can be seen as an example from FIGS. 2 to 6.

An essential feature of the invention can be seen in FIG. 2. The tubular discharge vessel 1 is provided with a ceramic end element 15 on at least one side, e.g. closed with a ceramic stopper, the broken surface delimiting the interior of the discharge vessel 1. This division is carried out, for example, according to FIG. 2, a projecting rib 14 dividing the inner surface of the closure element 15 into an inner and an outer space. Therefore, the separation of a metal additive 16, in the given case the sodium amalgam from the power supply 2 is ensured. An inner trough 21 is advantageously formed in the central region of the closure element 15 and an outer trough 22 in the wall of the discharge vessel 1, i.e. 14 depressions are formed on both sides of the rib, one of which is provided for receiving the metal additive, for determining the cold chamber.

On the inner surface of the ceramic closure element 15, an at least 4 mm long conduction path 17, marked with a dash-dotted line, is determined as a path covered on the surface. The conduction path 17 leads from the surface of the metal additive 16, which is located next to the wall of the ceramic discharge vessel 1 in the outer trough 22, via the metal additive-free one (Amalgam-free) surface of the rib 14 and the lower surface of the inner trough 21 up to the power supply 2. The power supply 2 is connected to an electrode 19 projecting into the interior of the discharge vessel.

The wall of the discharge vessel 1 and the ceramic closure element 15 can be formed as an integrated component or the sealing of the discharge vessel is to be ensured by means of a glass enamel 18.

The level of the outer trough 22 is advantageously from the interior of the discharge vessel 1, i.e. seen in the direction of the longitudinal axis of the electrode 19, lower than the lower level of the inner trough 21.

The protruding middle rib 14, which plays an important role in determining the conduction path, can be designed with a cross section according to the given conditions. Some options can be seen in Figures 2 to 6.

Particularly in the case of high-pressure sodium vapor lamps, that embodiment of the solution according to the invention can be of greater importance, in which the distance of the tip of the electrode 19 from the surface of the metal additive 16 present in the ceramic end element 15 connected to the electrode 19 in the cold chamber is at most three times the Distance of the electrode 19 from the ceramic wall of the discharge vessel 1 is. The first distance is advantageously not greater than 5 mm.

According to the invention, the cold chamber, which advantageously has a width of less than 2 mm, can be determined by the ceramic wall of the discharge vessel 1 and the protruding rib 14.

According to the solution shown in FIG. 3, the rib 14 and the wall of the ceramic discharge vessel 1 can be made from one sintered ceramic body are formed, wherein the outer recess 22 receiving the metal additive is present in the body. The length of route 17 was also drawn here. In this case, the electrically conductive metal additive does not come into contact with the glass enamel (18).

4 shows a ceramic tube with a fully integrated termination, the electrode being inserted from the interior of the discharge vessel 1.

In Fig. 5 a closure element 15 can be seen, which is designed to accommodate larger amounts of amalgam.

The required amalgam temperature is determined by an external means 20 for heat shielding, e.g. secured by a niobium plate.

6 shows a final solution for a ceramic discharge vessel 1 which is tapered to the ends. Here, too, the length of the route 17 was entered using a dashed line.

The embodiment variants shown above show some possibilities for realizing the inventive concept, but without claiming to be complete. However, the claim for protection relates to any solution that is covered by the claims.

For the purpose of describing the invention in detail, but without restricting the nature of the invention, examples of the implementation of the proposed high-pressure sodium lamps are presented:

1. High pressure sodium lamp of 70 W power.

The inner diameter of the ceramic discharge tube is 3.3 mm, its length 58 mm.

The ceramic closure element 15 of the discharge vessel 1 was designed according to FIG. 2. The length of the line path 17 is 4.4 mm.

The high-pressure sodium lamp designed in this way was manufactured, ignited and operated in the usual way. Even after several thousand hours of operation, no harmful line developed between the electrode 19 and the amalgam 16.

This can be assessed well on the basis of the asymmetry of the transition component of the inrush current. In the transition component of the sodium vapor lamp manufactured according to the invention, the glow phase has been shortened to a third compared to the designs without the rib 14. This property was retained even during continuous operation. Shortening the glow phase and reducing the current asymmetry also reduced the asymmetrical loading of the electrodes.

2. High pressure sodium vapor lamp of 250 W.

The inside diameter of the ceramic discharge tube is 8 mm, its length 75 mm.

The ceramic closure element 15 of the discharge vessel 15 was also manufactured according to FIG. 2. The length of the line path 17 is 6.1 mm.

Here the duration of the glow phase was reduced to a quarter. This situation did not change even after continuous operation, which proves that no harmful line has developed.

The main advantage of the high-pressure discharge lamp, in which the termination element designed according to the invention is used, is that, even after continuous operation, the insulation between that part of the filling, which consists of the electrically conductive metal or such a metal alloy, for example sodium amalgam, and the electrically conductive electrode is ensured. As a result, the life of the lamp is increased without having to use a very complicated terminating element for closing the discharge vessel.

Claims (6)

1. High-pressure discharge lamp, in particular high-pressure sodium vapor lamp, which has a tubular ceramic discharge vessel (1), inside which there are electrodes (19) and a filling containing an ionizable noble gas and a metal additive (16), as well as the ends of the ceramic discharge vessel ( 1), optionally in an integrated manner, has ceramic sealing elements (15) which seal on both sides and contain at least one bore, a cold chamber for receiving the metal additive (16) in the ceramic sealing element (15) or between the ceramic sealing element and the wall of the ceramic discharge vessel , in particular sodium amalgam, is characterized in that the end face of the ceramic closure element (15) delimiting the interior of the discharge vessel (1) is broken down with surface elements of different height levels so that the distance between the surface of the metal additive (16) and the Electrode (19) or the power supply (2) forming a unit with it, measured as the length of a line path (17) on the surface of the ceramic terminating element, is greater than 4 mm. 2. High-pressure discharge lamp according to claim 1, characterized in that the end face of the ceramic end element (15) is provided with a protruding rib (14) which subdivides the surface into an inner trough (21) and an outer trough (22) which accommodates the metal additive , wherein the conduction path (17) is determined by the surface of the rib (14) and the inner base of the inner trough (21). 3. High-pressure discharge lamp according to claim 2, characterized in that - the base of the outer trough (22), which extends from the interior of the discharge vessel (1) viewed from closer to the wall of the discharge vessel (1) is located below the base of the inner trough (21). 4. High-pressure discharge lamp according to one of claims 1 to 3, characterized in that the cold chamber receiving the metal additive is designed as a storage space with a width of up to 2 mm. 5. High-pressure discharge lamp according to one of claims 1 to 4, characterized in that the distance between the end of the electrode (19) projecting from the closure element (15) into the discharge space and that in the cold chamber, in particular in the outer depression (22 ), existing metal additive (16) is at most three times the distance between the electrode (19) and the wall of the discharge vessel (1). 6. High-pressure discharge lamp according to claim 5, characterized in that the distance between the end of the electrode (19) projecting from the end element (15) into the discharge space and that in the cold chamber, in particular in the outer trough (22) Metal addition is shorter than 5 mm.

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