WO2011020728A1 - Infrared emitter - Google Patents

Abstract

The invention relates to an infrared emitter comprising at least: a. a shell tube (2) and b. a heat source (4) mounted in the shell tube (2), wherein the heat source (4) comprises at least two outer segments (4a) and one inner segment (4b), and the heating capacity of the inner segment is at least 3% lower than the heating capacity of the outer segments (4a).

Description

 Saint-Gobain Glass France

infrared Heaters

The invention relates to an infrared radiator and its use.

Infrared heaters allow fast and non-contact heating of large areas. Infrared radiators typically include a heating coil or heating coating applied to a substrate. The intensity of the heating and the resulting emission of electromagnetic heat radiation can be regulated by the electrical resistance of the heating coil and by the applied voltage. The electrical resistance is mainly dependent on the material composition and the line cross-section. As the cross-section of the conductor increases, the electrical resistance and thus the intensity of the thermal radiation decreases with otherwise the same material.

In many cases, a temperature gradient occurs when heating objects and surfaces. If the object to be heated is dimensioned to be comparable to the infrared radiator, then the incoming thermal radiation is lower, especially in the peripheral areas, than in the central heating area. If the heating is used for chemical or thermal conversion, the reaction does not take place in the same way in all areas. In the thermal reaction of crystalline compounds, compounds with very different stoichiometry and composition can form depending on the temperature. The reproducibility of such processes is thus difficult to realize on larger substrates or on an industrial scale.

EP 1 168 418 A1 discloses an infrared radiator in which the heating element consists of carbon fibers in a quartz glass tube. The infrared radiator can be operated at temperatures of over 1000 ⁰ C.

DE 202 20 808 Ul discloses a tubular infrared radiator with a radiation source of cryptocrystalline carbon. The radiation source is surrounded by a housing having a window or cladding permeable to infrared radiation. DE 102 53 582 B3 discloses an infrared radiator in a gas-tight quartz glass lamp vessel. The lamp vessel is partially provided with a reflective layer, which is provided with a fume protection made of silica glass.

EP 0 410 151 A1 discloses an infrared radiator with an electrical heating coil arranged inside a cladding tube and a temperature sensor. The heating coil is wound on a silicon dioxide-containing support tube.

The object of the invention is to provide an infrared radiator, which enables a homogeneous and reproducible heating of large-area substrates.

The object of the present invention is achieved by an infrared radiator and its use according to the independent claims 1, 14 and 15. Preferred embodiments will become apparent from the dependent claims.

The infrared radiator according to the invention comprises at least one cladding tube and a heating source. The cladding tube consists of a high-temperature-stable material that is permeable to infrared radiation. The heating source comprises at least two outer segments and an inner segment. The outer segments can have a different heating capacity in the context of the invention. The heating power (as radiated heat) of the inner segment is at least 3%, preferably more than 10% lower than the heating power of the outer segments. If the two outer segments have a different heating power, then the lower heating power of the inner segment relates to the average heating power of the two outer segments.

A lower heating power can be achieved with the same material by increasing the cable cross-section. For this purpose, a thicker heat source can be selected for the inner segment. A lower heating power can also be achieved by using a better electrically conductive compared to the outer segment material. A better conductivity causes a lower electrical resistance and thus a lower heat development. The heat source is preferably either applied to a carrier tube and thus fixed in the cladding tube or is fixed by a placeholder in the cladding tube. Combinations of these two versions are possible. The support tube and / or the placeholder contain a material which is dimensionally stable even at high temperatures of 700 ^° C. to 2300 ^° C., preferably 800 ^° C. to 1500 ^° C., preferably metallic or ceramic material.

The free space between the heating source and the cladding tube is preferably filled with an inert gas, for example noble gases or vacuum. The inert gas prevents the oxidation and thus the aging of the support tube, the placeholder and the heat source.

The placeholder preferably comprises a wire mesh with guide eyelet. The wire preferably contains tungsten, palladium, platinum, nickel, chromium, manganese, iron, silver, copper, gold, potassium, silicon and / or mixtures and / or alloys thereof.

The placeholder preferably has an oval, circular and / or angular disc shape with a guide eye. The guide eyelet is preferably arranged in the center of the placeholder.

The placeholder preferably contains SiO ₂ , quartz glass, Al ₂ O ₃ , ZrO ₂ , Y ₂ O ₃ , ceramics and / or mixtures thereof.

The heating source preferably contains a heating layer and / or a wound wire and / or heating coil. The heating source can preferably also be formed exclusively by a wire and / or heating coil. The distance between the heating coil and the heating power of a segment can also be controlled and regulated. Higher heating power can be applied to the same material by e.g. achieve a closer winding of the heating coils.

The length of the inner segment is preferably at least 10% of the total length of the heat source.

The heating source preferably contains further inner segments with lower heating power than the outer segments and / or lower heating power than the inner segment. With the help of others inner segments, the temperature distribution on the object to be irradiated can be further adjusted and homogenized.

The heating source preferably contains tungsten, palladium, platinum, nickel, chromium, manganese, iron, silver, copper, gold, potassium, silicon and / or mixtures and / or alloys thereof.

The heating source preferably has an outer diameter of 100 .mu.m to 50 mm, more preferably of 1 mm to 10 mm.

The heating source is preferably heated to a temperature of 700 ⁰ C to 2300 ⁰ C. This temperature results in the context of the invention as averaged over the outer and inner segments temperature. The average heating power is preferably 500 watts to 6500 watts.

The heating source preferably has connection segments between the segments. These connection segments connect different heating segments with each other and can be designed so that they do not generate heating power themselves. Connecting segments may preferably be present as clamping contacts between the segments.

At the two ends of the heating source electrical contacts are mounted, which supply the infrared radiator with electricity and the electrical contact preferably contains gold, silver, copper, chromium, nickel, iron, tungsten, platinum, alloys and / or mixtures thereof.

The cladding tube preferably has a length of 100 mm to 2500 mm, more preferably from 700 mm to 1000 mm. The carrier tube preferably has a corresponding dimensioning.

The cladding tube preferably has an outer diameter of 5 mm to 50 mm.

The cladding tube preferably contains quartz, quartz glass, highly silicate glass, alumina, zirconium oxide and / or ceramics. The support tube preferably contains SiO ₂ , quartz glass, Al ₂ O ₃ , ZrO ₂ , Y ₂ O ₃ , and / or mixtures thereof.

The support tube preferably has an outer diameter of 1 mm to 50 mm.

The invention further includes an infrared radiator having a cladding tube and a heating source of wire coils D mounted in the cladding tube. The heat source has at least two outer segments and an inner segment. The heating power of the inner segment is at least 5% lower than the heating power of the outer segments and the diameter D of the wire helix perpendicular to the longitudinal axis L of the cladding tube in the inner segment is smaller by at least 5%, preferably 10%, particularly preferably 20% the diameter D of the wire coils in the outer segments (4a). The radiant power P can be estimated by the Stefan-Boltzmann law, where P = σ * ε * A * T ⁴ with σ = 5.67 * 10 ^"8 W m ^{" 2} K ^"4 , ε = emissivity of the radiator, A = Radiation surface, T =

Temperature. The radiation area A results from A = π * d * τj [a ² + π ² * D ² ] where d = wire diameter, D = winding diameter and a = distance of the windings.

The invention further includes the use of the infrared radiator for heating surfaces, preferably glass substrates.

The infrared radiator according to the invention is preferably used for heating coated glass substrates.

In the following the invention will be explained in more detail with reference to drawings. The drawings are purely schematic representations and not to scale. They do not limit the invention in any way.

Embodiments of the invention are illustrated in the drawings and will be described in more detail below. Show it:

1 shows a longitudinal section of an infrared radiator I according to the prior art,

FIG. 2 shows a longitudinal section of an infrared radiator II according to the invention,

FIG. 3 shows a longitudinal section of a further infrared radiator II according to the invention,

4 shows a cross section of a fiction, contemporary infrared radiator II,

5 shows a sketch of the use of an infrared radiator I according to the prior art,

FIG. 6 shows a longitudinal section of a further infrared radiator II according to the invention,

Figure 7 is a sketch of the placeholder and

FIG. 8 shows a longitudinal section of a further infrared radiator according to the invention.

FIG. 1 shows a longitudinal section of an infrared radiator according to the prior art. On a continuous support tube (1), a heating source (4) is applied. This is supplied with power via an electrical contact (3). The support tube (1), the heating source (4) and the electrical contact (3) are housed in a cladding tube (2). The gap of the cladding tube is filled with inert gas. The uniform heating power of the infrared radiator (I) causes uneven heating of substrates, if they have a comparable length as the infrared radiator (I). To the outer edge of the infrared radiator (I), the heat radiation decreases, which reaches the substrate to be heated. Accordingly, substrates that have comparable or larger dimensions than the infrared radiator, in these edge areas heat lower than in central areas.

FIG. 2 shows an infrared radiator (II) according to the invention. The segments with different heat output Sg _l (4a) and Sg ₂ (4b) cause greater heat dissipation in the edge regions (4a) of the infrared radiator (II) and a lower heat dissipation in Center (4b) of the infrared radiator (II). This compensates for the temperature differences described in FIG. 1 in the heating of glass substrates with comparable or greater dimensions than the infrared radiator.

FIG. 3 shows a further longitudinal section of an infrared radiator (II) according to the invention. The infrared radiator (II) has, in addition to the two outer segments Sg ₁ (4a) with maximum heating power and the inner segment Sg ₂ (4b), further segments Sg _{1, with i> 2} (4b.1, 4b.2 and 4b.3 ) on. The number "i" corresponds to an integer number of the series 3, 4, 5, 6, ..., etc.) With the aid of these additional segments Sg ₃ (4b.1), Sg ₄ (4b.2) and Sgs (4b .3), the temperature distribution in the infrared radiator II can be further adjusted and thus achieve a more homogeneous temperature distribution in the substrate between the individual segments Sg ₁ (4a), Sg ₂ (4b), Sg ₃ (4b.1), Sg ₄ (4b .2) and Sgs (4b.3) are arranged connecting segments (5) .These connection segments ensure the electrical contact between the segments of the infrared radiator according to the invention Preferably, the connecting segments (5) can also act as local "cold spots" even no or only small proportions generate heat radiation. The connecting segments (5) preferably produce less than 10% of the heating power of the outer segments Sg ₁ (4a).

FIG. 4 shows a cross section of the infrared radiator (II) according to the invention. On an inert support tube (1) is the heating source (4). This can be designed both as a coating and as a wound wire or heating coil. At the heat source (4), the electrical contact (3) is mounted, which supplies the heating source (4) with electricity. The infrared radiator II is surrounded by a cladding tube (2). The space between the heating source (4), parts of the carrier tube (1) and the cladding tube (2) is preferably filled with an inert gas such as N ₂ , He, Ne, Ar, Kr, Xe and / or vacuum.

Figure 5 shows a sketch of the use of an infrared radiator (I) according to the prior art. In this case, a planar substrate is irradiated with an infrared radiator with homogeneous heating power. The positioning of the substrate under the infrared radiator results in uneven heating of the substrate with hot zones in the middle and cold zones on the edge. By contrast, the use of the infrared radiator (II) according to the invention leads (not shown) to a uniform heating of the planar substrate. FIG. 6 shows a longitudinal section of a further embodiment of the infrared radiator IL according to the invention. The heating source (4) is fixed in the outer segments (4a) and in the inner segment (4b) via spacer (6) in the filling tube (2). The placeholder (6) can also be designed as wire mesh. The connecting segments (5) separate the outer segments (4a) from the inner segment (4b).

FIG. 7 shows a cross section of the placeholder (6) according to the invention. In the central area of the placeholder is a guide eye (6a), which receives the heat source (4), not shown, and fixed in the cladding tube (2).

FIG. 8 shows a longitudinal section of a further embodiment of the infrared radiator IL according to the invention. Within the enveloping tube are the heating segments (4a), (4b) and (4a). The distance (a) of the heating coils is the same in all segments. The winding diameter (D) of the heating spirals perpendicular to the longitudinal axis (L) of the cladding tube (2) is greater in the outer segments (4a) than in the inner segment (4b).

LIST OF REFERENCE NUMBERS

(1) carrier tube,

 (2) cladding tube,

 (3) electrical contacting,

 (4) heat source,

(4a) outer segments Sg ₁ ,

(4b) inner segment Sg ₂ ,

(4b.1) inner segment Sg ₃

(4b.2) inner segment Sg ₄ ,

 (4b3) inner segment Sgs,

 (5) connecting segments,

 (6) placeholders,

 (6a) guide eyelet,

 (a) distance of the turns,

 (D) winding diameter,

 (L) longitudinal axis of the cladding tube,

 (I) infrared radiators according to the prior art and

(II) Infrared radiator according to the invention.

Claims

Saint-Gobain Glass France claims 1. infrared radiator at least comprising:  a. a cladding tube (2) and  b. a heat source (4) mounted in the cladding tube (2), the heat source (4) having at least two outer segments (4a) and an inner segment (4b) and at least 3% heating power of the inner segment (4b) is lower than the heating power of the outer segments (4a). 2. Infrared radiator according to claim 1, wherein the heating source (4) on a support tube (1) in the cladding tube (2) is mounted. 3. Infrared radiator according to claim 1 or 2, wherein the heating source (4) in one  Placeholder (6) in the cladding tube (2) is mounted. 4. Infrared radiator according to claim 3, wherein the placeholder (6) comprises a wire mesh with guide eyelet (6a). 5. Infrared radiator according to one of claims 3 or 4, wherein the placeholder (6) has an oval, circular and / or angular disc shape with a guide eye (6a). 6. Infrared radiator one of claims 1 to 5, wherein the heat source (4) a  Heating layer and / or a wound wire and / or heating coil comprises. 7. Infrared radiator according to one of claims 1 to 6, wherein the length of the inner segment (4b) is at least 10% of the total length of the heating source (4). 8. Infrared radiator according to one of claims 1 to 7, wherein the heat source (4) contains further inner segments with lower heating power than the outer segments (4a) and / or lower heating power than the inner segment (4b). 9. Infrared radiator according to one of claims 1 to 8, wherein the heating source (4) has an outer diameter of 100 microns to 50 mm, preferably from 1 mm to 10 mm. 10. Infrared radiator according to one of claims 1 to 9, wherein the heat source (4)  between the segments connecting segments (5). 11. Infrared radiator according to one of claims 1 to 10, wherein the cladding tube (2) has a length of 100 mm to 2500 mm, preferably from 700 mm to 1000 mm. 12. Infrared radiator according to one of claims 1 to 11, wherein the cladding tube (2) has an outer diameter of 5 mm to 50 mm. 13. Infrared radiator according to one of claims 1 to 12, wherein the support tube (1) has an outer diameter of 1 mm to 50 mm. 14. Infrared radiator at least comprising:  a. a cladding tube (2) and  b. a heating source (4) of wire coils which are mounted in the cladding tube (2), wherein  the heating source (4) has at least two outer segments (4a) and an inner segment (4b) and the heating power of the inner segment (4b) is at least 5% lower than the heating power of the outer segments (4a) and the diameter (D) the wire helix perpendicular to the longitudinal axis (L) of the cladding tube (2) in the inner segment (4b) is at least 5% smaller than the coil diameter (D) of the wire helix perpendicular to the longitudinal axis (L) of the cladding tube (2) in the outer segments (4a ). 15. Use of the infrared radiator according to one of claims 1 to 14 for  Heating and / or the thermal reaction of planar substrates, preferably of glass substrates, particularly preferably of coated  Glass substrates.