GB2133259A

GB2133259A - Electric radiant heater

Info

Publication number: GB2133259A
Application number: GB08334544A
Authority: GB
Inventors: Hans Fritz
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-12-31
Filing date: 1983-12-29
Publication date: 1984-07-18
Also published as: GB8334544D0; NL8304380A; ATA448583A; AT401989B; DE3248740A1; FR2538986A1; DE3248740C2; NL192768B; FR2538986B1; GB2133259B; JPS59173988A; JPH0416915B2; CH664058A5; NL192768C

Abstract

A radiant heater in which a tube (2) which is made of a radiation- transparent material and which encloses a heating coil (1) is installed, together with a reflector (6) which is assigned to it, and/or together with a protective screen (7), inside a second tube (4) which is made of a radiation- transparent material, and which is evacuated or filled with an inert gas. <IMAGE>

Description

SPECIFICATION Radiant heater The invention relates to an electric radiant heater possessing a metal heating coil which is installed in a closed elongated tube which is made of a radiation-transparent material. Radiant heaters are used, in a multiplicity of designs, for heating and drying, and for melting and similar applications. Metal reflectors are employed in order to concentrate the heat output which is emitted by the radiating body, onto the material which is to be irradiated. If the reflectors operate in the air in a room, they are subject to soiling and corrosion. For this reason, it has been proposed that a metal coating should be applied to the outside of the radiating tubes.This proposal entails the disadvantages that the shape of the reflector cannot be selected independently of the shape of the tube, and the metal of the reflector tends to enter into chemical reactions with the tube material. If the reflector is installed inside the tube, together with the heating coil, difficulties result, especially in the case of halogen-filled tubes, since chemical reactions occur. The problems which affect the reflector apply in the same way to metal screens which are arranged to spatially surround the radiant heater in order to exclude the possibility of touching electrically live metal parts in the event of breakage of the lamp tube.

The object underlying the invention is to provide a radiant heater with a metal reflector, and/or with a protective metal screen, these metal parts being located near the heating coil, without being subjected to chemical deterioration as the result of corrosion or similar effects.

The invention consists in a radiant heater comprising a heating coil which is enclosed within a first tube, which is made of a radiationtransparent material, and comprising a reflector and/or a protective screen, the first tube being enclosed, together with the metal reflector and/or the protective screen, in a second tube, which is made of a radiation-transparent material and is evacuated or filled with an inert gas. Corrosion of the metal portions of the reflector, and/or of the protective screen, is reliably prevented. A further advantage resides in the fact that the lamp tube outputs very little heat through convection.

Further aims and advantages of the invention are evident from the description, and from the illustrations, in which: Figure 1 shows an embodiment of a radiant heater according to the invention, with a reflector, illustrated in a somewhat diagrammatic manner; and Figure 2 shows a section perpendicular to the longitudinal axis of a radiant heater with a reflector and a protective screen.

The heating coil 1, made of tungsten, or of another refractory metal, is fused into a first tube 2 by a method which produces a vacuum-tight seal, or, if the material is quartz glass, is crimpedin with the aid of the molybdenum foils 3. After evacuation, this first tube can be filled with substances conventionally used for radiating devices of this nature, such as lamp gas, halogens etc. This first tube 2 is fused, together with the reflector 6, and/or the protective screen 7, into a second tube 4, or is crimped-in with the aid of the fusion-seal foils 5, 8. This second tube is evacuated, or is filled with inert gas, and is sealed.

The reflector 6 does not have to be held by means of the fusion-seals 8, but can also bear, under prestress, against the inside wall of the tube 4, while the protective screen must, in all cases, be connected to protective ground. The reflector 6 can have a circular, parabolic, or elliptical profile, there being no need to install the first tube 2 centrally within the second tube 4.

In a further development of the invention, the radiant heater can be designed in a manner such that the electrical connections are made only at one end of the tube, the electrical return being routed by way of the reflector.

1. A radiant heater comprising a heating coil which is enclosed within a first tube, which is made of a radiation-transparent material, and comprising a reflector and/or a protective screen, the first tube being enclosed, together with the metal reflector and/or the protective screen, in a second tube, which is made of a radiationtransparent material and is evacuated or filled with an inert gas.

2. A radiant heater as claimed in claim 1, wherein the reflector, under prestress, bears against the inside wall of the outer tube.

3. A radiant heater as claimed in claim 1, wherein the reflector has an elliptical or parabolic profile and the axis of the first tube coincides with the focal line of the reflector.

4. A radiant heater as claimed in claim 1, wherein the electrical connections are made at one end, the electrical return conductor being routed from the distant end of the inner tube, by way of the reflector.

5. A radiant heater as claimed in claim 1, wherein the protective screen surrounds the inner tube concentrically and can be electrically connected to protective ground.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Radiant heater The invention relates to an electric radiant heater possessing a metal heating coil which is installed in a closed elongated tube which is made of a radiation-transparent material. Radiant heaters are used, in a multiplicity of designs, for heating and drying, and for melting and similar applications. Metal reflectors are employed in order to concentrate the heat output which is emitted by the radiating body, onto the material which is to be irradiated. If the reflectors operate in the air in a room, they are subject to soiling and corrosion. For this reason, it has been proposed that a metal coating should be applied to the outside of the radiating tubes.This proposal entails the disadvantages that the shape of the reflector cannot be selected independently of the shape of the tube, and the metal of the reflector tends to enter into chemical reactions with the tube material. If the reflector is installed inside the tube, together with the heating coil, difficulties result, especially in the case of halogen-filled tubes, since chemical reactions occur. The problems which affect the reflector apply in the same way to metal screens which are arranged to spatially surround the radiant heater in order to exclude the possibility of touching electrically live metal parts in the event of breakage of the lamp tube. The object underlying the invention is to provide a radiant heater with a metal reflector, and/or with a protective metal screen, these metal parts being located near the heating coil, without being subjected to chemical deterioration as the result of corrosion or similar effects. The invention consists in a radiant heater comprising a heating coil which is enclosed within a first tube, which is made of a radiationtransparent material, and comprising a reflector and/or a protective screen, the first tube being enclosed, together with the metal reflector and/or the protective screen, in a second tube, which is made of a radiation-transparent material and is evacuated or filled with an inert gas. Corrosion of the metal portions of the reflector, and/or of the protective screen, is reliably prevented. A further advantage resides in the fact that the lamp tube outputs very little heat through convection. Further aims and advantages of the invention are evident from the description, and from the illustrations, in which: Figure 1 shows an embodiment of a radiant heater according to the invention, with a reflector, illustrated in a somewhat diagrammatic manner; and Figure 2 shows a section perpendicular to the longitudinal axis of a radiant heater with a reflector and a protective screen. The heating coil 1, made of tungsten, or of another refractory metal, is fused into a first tube 2 by a method which produces a vacuum-tight seal, or, if the material is quartz glass, is crimpedin with the aid of the molybdenum foils 3. After evacuation, this first tube can be filled with substances conventionally used for radiating devices of this nature, such as lamp gas, halogens etc. This first tube 2 is fused, together with the reflector 6, and/or the protective screen 7, into a second tube 4, or is crimped-in with the aid of the fusion-seal foils 5, 8. This second tube is evacuated, or is filled with inert gas, and is sealed. The reflector 6 does not have to be held by means of the fusion-seals 8, but can also bear, under prestress, against the inside wall of the tube 4, while the protective screen must, in all cases, be connected to protective ground. The reflector 6 can have a circular, parabolic, or elliptical profile, there being no need to install the first tube 2 centrally within the second tube 4. In a further development of the invention, the radiant heater can be designed in a manner such that the electrical connections are made only at one end of the tube, the electrical return being routed by way of the reflector. CLAIMS