DE102004029364B4 - Halogen lamp for the near infrared and method for producing such - Google Patents

Abstract

Halogen lamp for generating radiation with a substantial active component in the near infrared range and high power, with - a glass body (34), - a filament (36) and - at least one connection area (30), the at least one filament contact (31) and one end, in particular a pinch area, of the glass body (34), characterized in that the glass body (34) only in a cooled area (32), namely the part of the filament (30) adjoining the connection area (30), up to the coiled part ( 36) extending section of the glass body (34) has a significantly reduced transparency for the emitted radiation, for which the cooled area (32) is provided with a coating (33) which absorbs IR radiation components and which is applied on the outside of the glass body (34) and which is designed such that the temperature is at least 250 ° C during operation.

Description

The invention relates to a halogen lamp, in particular for the production of radiation having a substantial active portion in the range of the near infrared and high power, and a method for producing such a lamp.

Halogen lamps, like normal incandescent lamps, have coiled tungsten filaments arranged in a glass bulb or glass body. Two connection areas at the ends rod-shaped or elongated U-shaped glass body each comprise a filament contact for the Stromzu- or -abführung. Ω-shaped lamps have only one connection area with two contacts. The terminal areas are usually designed as a pinch area, wherein each one end of the glass body is heated and squeezed together over a filament contact.

In contrast to normal incandescent lamps are the filling gas of the glass bulb of halogen lamps small amounts of a halogen, eg. As iodine or bromine added. These halogens combine with the tungsten vaporized by the helix to form a halide, for example gaseous tungsten iodide. If this iodide gets close to the incandescent filament, it is decomposed by the high temperature (typically well over 500 ° C) back into tungsten and iodine, and the tungsten settles again on the filament. So that the halides do not precipitate on the glass body, this must have at least a critical temperature of 250 ° C; Usually, the glass body temperatures are in the range of 300 ° C to 450 ° C, in high-performance lamps also much higher.

The described halogen cycle significantly delays the aging of the halogen lamp, which has a longer life compared to normal incandescent lamps. Also, the filament can be operated at a higher temperature, resulting in a suitable Strahlscharakterisik the halogen lamp follows. Because of these properties, preference is given to using powerful halogen lamps in numerous industrial processes, for example for drying coatings. For this purpose, in particular those halogen lamps are used whose radiation has a significant active component in the near infrared range.

The operation of modern NIR irradiation equipment for material processing where numerous emitters (halogen lamps) are densely packed in a reflector assembly to achieve the desired high power densities on the material requires active cooling to dissipate heat from the emitters and reflectors. Depending on the field of application, air and / or water cooling systems are used. In general, the emitter have an integrated water cooling, and in addition the connection areas of the lamps are cooled by compressed air, since they are particularly sensitive to thermal stress and their thermal "peaks" in the associated reflectors affect their dimensional stability. Typically, the terminal areas of the lamp are cooled to vitreous temperatures below 250 ° C.

If the temperature of the glass body falls below the critical temperature, the tungsten halides formed during operation of the lamp are no longer returned in the direction of the glowing tungsten filament, but are deposited on the glass bulb. As a result, the filament becomes thinner and thinner over time. It comes to the so-called "Halogenfraß". If the cross section falls below a certain value, the filament finally melts at a high current flow, as occurs when the halogen lamp is switched on, for example. The emitter is thus no longer operational and must be replaced.

The problem of halogen damage thus leads to a reduction in the (average) life of powerful NIR emitters. For NIR irradiation facilities for technical use, this leads to highly undesirable shortening of the maintenance intervals or to the necessity of unscheduled maintenance interventions and associated downtimes and thus to considerable cost increases and u. U. also to impaired product quality.

It is therefore an object of the present invention to provide a halogen lamp, in particular for generating radiation having a substantial active portion in the range of near infrared and high power, in which the Halogenfraß is reduced in a temperature critical range of the lamp, and a method for producing such Halogen lamp provide.

This object is achieved by a halogen lamp having the features of claim 1 and a manufacturing method having the features of claim 4.

An essential idea of the invention is to increase the temperature of the glass in the cooled area by making use of the radiation generated by the lamp itself sections again. This can be achieved in that the glass body in this area, in which the temperature of the glass is below a critical temperature during operation of the halogen lamp, has a substantially reduced transparency for the radiation emitted by the filament. This increases the absorption of the radiation by the Quartz glass, which leads to a local increase in its temperature.

The critical temperature here is to assume the one below which a halogen attack on the filament occurs, in particular 250 ° C. It is sufficient to reduce the transparency of the glass only in the region of the glass bulb in which the halogenation in the prior art actually occurs.

In a preferred embodiment of the halogen lamp according to the invention, this region comprises a section of the glass body which is cooled directly or indirectly by a fluid cooling system. This is in particular the cooled region, the portion of the glass body which adjoins the connection region and extends to the coiled part of the filament.

The reduced transparency and the resulting increased absorption leads in a surprisingly simple manner to an increase in the temperature of the glass flask to a non-critical range.

The proposed increase in the radiation absorption can - not claim - be achieved for example by a suitable corrugation of the glass bulb in the cooled area, as this extends the path of the radiation through the glass and thus also the low, but always present absorption. Furthermore, it is conceivable to increase absorption by including radiation-absorbing foreign bodies in the glass in the end region of the glass body.

According to the invention, however, the cooled area is provided with a coating absorbing the infrared (IR) radiation. In a particularly preferred embodiment of this embodiment, the coating is on the outside of the glass body. As a result, the production of the halogen lamp is particularly simple.

In further preferred embodiments, the coating is formed by a lacquer. Paints are used in numerous areas and are therefore available in a wide variety of designs. For example, it is possible to use known synthetic resin coatings in which silicone resin is used as the binder for resistance to temperatures above the critical temperature. Likewise, it is also possible to use powder coatings which are heat-resistant and can be applied in an advantageous manner.

In a particularly preferred embodiment of this embodiment, an exhaust paint is used as the coating agent. Such paints are generally deep black, so have (also in the IR range) to a very high degree of absorption, and are usually temperature resistant up to about 600 ° C or more because of their use in exhausts of motor vehicles and wheels. In addition, exhaust coatings are inexpensive to produce and easy to apply by spraying or spraying.

Alternatively (or additionally), carbon black may also be used as the coating material. Carbon black also has excellent absorption properties and is a low-cost material.

In a method for producing a halogen lamp according to the invention, the transparency of the glass of the glass body of the halogen lamp is reduced after the terminal region of the halogen lamp has been formed, in particular by pinching a glass body end. As a result, there is no need to intervene in existing production methods for halogen lamps, only a downstream processing step is supplemented.

In the method according to the invention, an IR radiation-absorbing coating is applied outside only on the glass body in the cooled area. As a result, the production of halogen emitters according to the invention is particularly simple, since no additional processing steps are required inside the glass bodies.

In preferred embodiments of the method according to the invention, a coating material is applied in solution or in liquid form. As a result, the metered application of the coating is particularly simple. In particular, a thin order can be guaranteed.

Preferably, the coating material is applied by mechanical spraying or spraying or flame spraying. As a result, the glass body can be coated without contact, which simplifies handling and avoids damage. When flame spraying can be dispensed with solvents and it can be produced temperature-resistant coatings. The melting point of the spray material can be at combustion temperatures of the fuel gas of about 3000 ° C at up to 2500 ° C. Thus, coatings that are suitable for the temperatures encountered during operation of a halogen lamp on the glass bulb, can be easily generated.

Alternatively, the or each coating material may be applied by sputtering. Thus, it may be possible to dispense with a solvent. This also makes it possible to have a coating which can be controlled very precisely in terms of thickness and therefore transparency, and excellent adhesion to the glass body.

Further aspects, advantages and expediencies of the invention will become apparent from the following description of an embodiment of the invention with reference to the figures. From these shows:

1 a schematic sectional view of a halogen emitter according to the prior art and

2 a plan view of an inventively designed halogen lamp.

First, with reference to the schematic sectional view of 1 the essential components of a conventional halogen lamp 10 shown. From the lamp 10 is a connection area 12 shown by heating and then squeezing one end of a glass body or flask 14 is formed. Embedded in this pinch area is a filament contact 16 to connect the lamp 10 to an external power source (not shown). The contact 16 is in the connection or pinch area 12 via a molybdenum connection plate 18 with a filament 20 made of tungsten. The filament 20 is in the connection area 12 and an adjacent area 22 uncoiled. An incandescent filament 24 (ie the coiled continuation of the filament 20 ) starts at some distance from the connection area 12 ,

When operating the in 1 shown halide emitter 10 this heats up strongly. It must therefore be at least the connection area 12 be cooled by an air cooling system (not shown). The cooling also affects the area 22 , both directly through the glass bulb in this area 22 passing cooling air, as well as indirectly via the heat conduction from the glass in the area 22 to the chilled glass in the pinch area 12 , In addition, in the refrigerated area 22 also the energy emission through the uncoiled filament 20 opposite the areas of the piston 14 with filament 24 reduced.

Overall, so will the operation of the lamp 10 in the refrigerated area 22 the temperature of the glass bulb 14 lowered to values below the critical temperature of 250 ° C, at which the halogen cycle process comes to a standstill. Therefore, tungsten halides on the glass bulb in the range 22 low. At the same time the filament becomes 20 in this area 22 always thinner and melts after a comparatively short service life of the lamp 10 by.

To remedy this problem, according to the invention, the transparency of the glass body 14 in his refrigerated area 22 to keep the temperature of the glass flask at temperatures above the critical temperature of 250 ° C despite cooling.

Such, inventively designed halogen emitter 28 is schematic in 2 shown in plan view. Here is the to the connection area 30 with filament contact 31 adjacent, also cooled area 32 of the glass bulb 34 by sprayed exhaust paint 33 blackened.

The exhaust paint 33 absorbs from the filament (the in 2 because of the blackening in the cooled area 32 is not visible) radiation emitted during operation, in particular the IR radiation, to a high proportion. This heats the exhaust paint 33 and releases this heat to the glass of the piston in the coated area. As a result, the temperature of the glass in this range is increased to values above 250 ° C, so that precipitate no halides on the glass bulb. The halogen cycle process is thus maintained, halogenation does not occur and the average life of the lamp 28 lengthens significantly compared to in 1 illustrated lamp 10 ,

It is sufficient such a thickness of the paint layer, in which a sufficient proportion of the radiation is absorbed to the operation of the heating of the glass bulb in the cooled area 32 to effect temperatures above 250 ° C. The required thickness of the coating 33 has been determined by appropriate operating tests with lamp and cooling system. The used, commercially available exhaust paint 33 Withstands temperatures in the range of 600 ° C easily.

The material cost of the paint 33 are small compared to the other components of the halogen lamp 28 , Also, only a downstream manufacturing step for spraying the Aufpuffeack 33 on the area 32 the lamp 28 required, can be used for the known spray cans. The exhaust paint 33 is applied in a single application and cures immediately. Thus, the production costs of the halogen lamp according to the invention increase 28 only slightly compared to a lamp without such post-processing of the cooled area, while at the same time the life of the lamp 28 is significantly increased.

In the scope of the invention, which is indicated solely by the following claims, many other embodiments are conceivable by expert action.

LIST OF REFERENCE NUMBERS

10, 28

halogen lamp

12, 30

terminal area

14, 34

vitreous

16, 31

Filament Contact

18

Molybdenum bonding pads

20

uncoiled filament

22, 32

refrigerated area

24, 36

coiled filament

33

exhaust paint

Claims (7)

Halogen lamp for generating radiation having a substantial active component in the range of near infrared and high power, comprising - a glass body ( 34 ), - a filament ( 36 ) and - at least one connection area ( 30 ), which has at least one filament contact ( 31 ) and one end, in particular a pinch region, of the vitreous body ( 34 ), characterized in that the glass body ( 34 ) only in a cooled area ( 32 ), namely to the connection area ( 30 ) adjacent, to the coiled portion of the filament ( 36 ) extending portion of the vitreous ( 34 ), has a substantially reduced transparency for the emitted radiation, to which the cooled area ( 32 ) with an IR radiation absorbing coating ( 33 ), which on the outside of the glass body ( 34 ) and which is designed such that the temperature during operation is at least 250 ° C. Halogen lamp according to claim 1, characterized in that the cooled area ( 32 ) a directly or indirectly cooled by a fluid cooling system portion of the glass body ( 34 ). Halogen lamp according to one of the preceding claims, characterized in that the coating ( 33 ) is formed by a paint or carbon black. Method for producing a halogen lamp according to one of the preceding claims, characterized in that the transparency of the glass of the glass body ( 34 ) of the halogen lamp ( 28 ) is reduced after the connection area ( 30 ) of the halogen lamp ( 28 ), in particular by crushing a glass body end, wherein an IR radiation absorbing coating ( 33 ) only in the cooled area ( 32 ) on the outside of the glass body ( 34 ) is applied. Method according to claim 4, characterized in that a coating material ( 33 ) is applied in solution or in liquid form. Method according to claim 4 or 5, characterized in that the coating material ( 33 ) is applied by mechanical spraying or spraying or flame spraying, in particular by spraying from a spray can. Method according to claim 4, characterized in that the or each coating material ( 33 ) is applied by sputtering.

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