GB2339131A

GB2339131A - Mounting an IR lamp in a radiant electric heater

Info

Publication number: GB2339131A
Application number: GB9813975A
Authority: GB
Inventors: George Anthony Higgins
Original assignee: Ceramaspeed Ltd
Current assignee: Ceramaspeed Ltd
Priority date: 1998-06-30
Filing date: 1998-06-30
Publication date: 2000-01-12
Also published as: GB9813975D0; EP0969698A1

Description

2339131 Method of Manufacturinp, a Radiant Electric Heater This invention

concerns a method of manufacturing a radiant electric heater of tile kind incorporating an infra-red lamp, having a tubular envelope of generalk" circular configuration.

For avoidance of doubt. it is to be understood that the expression "generally circular", whenever used herein in respect of the infra-red lamp, includes polygonal arrangements which approximate to circular forms.

Radiant electric heaters of this kind are well known, particularly for use in cooking appliances having flat glass-ceramic cooking surfaces. The infra-red lamp generally has a tungsten filament supported inside a tubular envelope of generally circular configuration and comprising fused silica or quartz. A halogenated atmosphere can be provided inside the envelope. Electrical connections are brought out through hermetic pinch seals at terminal regions of the 15 envelope. It is known from EP-A0343868 to provide a radiant heater in which a laver of electrical and thermal insulating material is disposed in a container. An infra-red lamp has a protrusion extending from an envelope thereof intermediate the ends of the envelope, the lamp being 20 supported in the container at least in part by the protrusion. The protrusion can comprise a sealed tube communicating with the interior of the envelope and used to evacuate and back-fill the envelope during manufacture of the infra-red lamp. Clip and/or clamping means are provided applied to the protrusion and optionally to the envelope of the lamp. Such clip and/or clamping means are applied as an additional step after positioning the larrip-in the 25 container.

2 It is an object of the invention to provide a method of manufacturing a radiant electric heater in which such additional step of apphing the clip and/or clamping means after positioning the infi-a-red lamp is not required.

The present invention provides a method of manufacturing a radiant electric heater in which an infra-red lamp having a tubular envelope of generally circular configuration is provided with a protrusion intermediate terminal regions thereof by means of which the lamp is supported at least in part on a layer of compacted particulate insulation material in a container by Nvay of a component which has a first portion embedded in the insulation material and a second portion at least overlying the protrusion, the method comprising the steps of a) compacting particulate insulation material into the container and simultaneously embedding the first portion of the component therein and b) positioning the infi-a-red lamp and engaging the protrusion with the second portion of the component.

The insulation material ma-%r comprise nucroporous thermal insulation material.

The second portion may surround the protrusion.

The component may comprise a strip or plate, such as of metal or ceramic, having opposite end regions constituting the first and second portions.

The end region constituting the second portion may be provided with an aperture therethrough for accommodating the protrusion on the tubular envelope.

3 The end region constituting the first portion may be profiled and/or apertured whereby securing of the component in the insulation material is enhanced.

Alternativelv the component may be of looped wire or looped strip form. and may have legs providing the first portion, the legs being bent whereby securing of the component in the insulation material is enhanced, The protrusion on the envelope may comprise a sealed tube communicating with the interior of 10 the envelope. for example a tube used to evacuate and back-fill the envelope during manufacture of the infra-red lamp. The envelope may comprise fused silica or quartz and may enclose a filament such as of tungsten, 15 The invention is now described bv way of example ,vith reference to the accompanying drawings. in which: Figure I is a plan view, of a radiant electric heater manufactured by the method of the 20 invention: Figure 2 is an enlarged part-section along A-A in Figure 1, illustrating one embodiment of support component used in the method of the invention; 4 Figure 3 Is an enlarged part second along A-A in Figure 1. illustrating another embodiment of support component used in the method of the invention'.

Figure 4 is an enlarged part section along A-A in Figure 1, illustrating a further embodiment of support component used in the method of the invention.:

Figure 5 is an enlarged part section along A-A in Figure 1, illustrating a still further embodiment of support component used in the method of the invention; and Figure 6 is an enlarged part section along A-A in Figure 1, illustrating yet another embodiment of support component used in the method of the invention.

Referring to Figure 1. a radiant electric heater has a container in the form of a metal dish I containing a laver of compacted particulate thermal and electrical insulation material 2.

particularly microporous insulation material. A ring-sbaped wall 3 of insulation material extends around the periphery of the dish 1. When the heater is installed in a cooking appliance.

the wall 3 is arranged to press against the underside of a glass-ceramic cooking surface (not shown).

An infra-red heat source is provided in the form of a lamp 4. This lamp is of generally circular configuration and contains a tungsten filament 5 supported within a fused silica envelope 6.

The filament 5 is secured at each end to connections brought out through flattened hermetic pinch seals 7 at the ends of the epN,-,Iope 6. These ends are adjacent one another and the pinch seals extend generally radially of the heater through recesses provided in the underside of the peripheral wall 3 and in the layer 2 and through holes in the edge of the dish 1.

To restrain the lamp from movement relative to the laver 2. it is secured at two spaced positions. A first support point is where the ends are engaged by the peripheral wall 3. A second support point is provided diametrically opposite the first. in the form of a protrusion 8 provided on the lamp envelope 6. The lamp 4 contains an atmosphere with a halogen gas and the protrusion 8 comprises a tube formed with the envelope 6 and used to evacuate the envelope and back-fill it with gas containing halogen during manufacture of the larnp. Thereafter the tube protrusion 8 is heat sealed.

The protrusion 8 supports the lamp 4 by way of a component 9, described in detail hereafter. which has a first portion embedded in the layer 2 of insulation material during fon-nation of the laver 2, and a second portion at least overlying the protrusion 8.

1 Although the lamp 4 is shown to be of smoothly circular form, it need not be so and may be of polygonal form. approximating to a generally circular configuration.

In order to damp inrush current through the tungsten filament 5 of the lamp 4. upon initial energising of the lamp, a ballast electrical resistance heating element 10 of well known ribbon or coiled wire form is provided in the heater, electrically connected in series with the lamp 4 at 20 least during initial energisation of the lamp.

A well known forin of then-nal limiter I I is provided, extending across the heater and a terminal block 12 is arranged at the edge of the dish I for connection of the heater to a voltage supply for operation.

6 The invention resides in the method of provision of the support component 9 and engaging it with the protrusion 8 on the lamp envelope.

In the manufacture of the heater, the base layer 2 of insulation material is provided by compacting particulate insulation material into the dish 1. This is well known to be carried out by compacting. for example. powdered microporous insulation material into the metal dish I using an appropriate press tool. In the method of the present invention, a support component 9 such as is illustrated in Figures 2 to 6 has a first portion 13 thereof embedded in the insulation simultaneously with the compacting of the insulation material into the dish I to form the layer 2. This results in secure location of the component 9 in the layer 2.

In a subsequent process step the infra-red lamp 4 is positioned in the heater and the protrusion 8 engaged with a second portion 14 of the component 9, such second portion 14 at least overlying the protrusion 8.

For embedding the first portion 13 of the component 9 in the laver 2 of insulation material simultaneously with the compacting of the insulation material into the dish 1. the component 9 is suitabl-v located in the press tool which is used to compact the insulation material and such that the second portion 14 of the component 9 is received in a slot in the face of the press tool with the first portion 13 protruding from the face of the press tool.

As shown in Figure 2. the support component 9 can comprise an elongate strip or plate. such as of metal or ceramic, having a first end portion 13 embedded in the layer 2 by the method described hereinbefore. The second end portion 14 has an aperture through it which receives 7 the protrusion 8 on the lamp envelope during the subsequent process step and such that the second end portion 14 effectively surrounds the protrusion.

To enhance securing of the component 8 in the insulation laver 2, an aperture 15 maN- optionally be provided in the first end portion 13. During compacting of the insulation layer 2 and simultaneous embedding of the first end portion 13 of the component. material of the insulation laver 2 is also compacted into the aperture 15.

As shown in Figure 3. an alternative component 9 can comprise a plate. such as of metal or ceramic having a relatively wide first end portion 13 embedded in the layer 2 by the method described hereiribefore. An aperture 15 may optionally be provided in the first end portion 13 to enhance securement in the laver 2. The plate-shaped component 9 is profiled such that it has a second end portion 14 which is narrower than the first end portion 13 and has an aperture through it which receives the protr-usion 8 on the lamp envelope when the lamp is subsequentl)- located in the heater. The second end portion 14 completely surrounds the protrusion 8.

Figure 4 shows an arrangement which is similar to that of Figure 3. the essential difference being that an enlarged aperture 16 is provided in the second portion 14 of the component 9 and is shaped such that although the second portion 14 overlies the protrusion 8 at the top and sides. a portion 2A of the insulation laver 2 is arranged beneath the protrusion 8 and provides a softer contact point for the protnision 8.

Referring now to Figure 5. the component 9 can also comprise a loop. such as of metal or ceramic, having a first portion 13 embedded in the laver 2 and a second portion 14 arranged to overlie the protrusion 8 on the lamp envelope.

8 As shown in Figure 6. the component 9 could be fortned of metal Avire or strip having a first portion 13 comprising legs embedded in the laver 2 and bent as denoted by reference numerals 13A 13B to provide secure anchorage in the layer 2. The second portion 14 is arranged to overlie the protrusion 8 on the lamp envelope. As with the other embodiments illustrated in Fi ures 2 to 5. the method of the invention, in which the first portion 13 of the component 9 is 9 embedded in the layer 2 simultaneous with the compacting of powder material of layer 2 into the dish 1. makes it possible to optimise the shape of the first portion 13 for achieving firm securing of the component 9 in the layer 2.

9

Claims

1. A method of manufacturing a radiant electric heater in which an infrared lamp having a tubular envelope of generally circular configuration is provided with a protrusion intermediate terminal regions thereof by means of which the lamp is supported at least in part on a laver of compacted particulate insulation material in a container by way of a component which has a first portion embedded in the insulation material and a second portion at least overlying the protrusion, the method comprising the steps of a) compacting particulate insulation material into the container and simultaneousl,, embedding the first portion of the component therein and b) positioning the infra-red lamp and engaging the protrusion N A the second portion of the component.

2. A method according to clam 1, in which the insulation material comprises microporous then-nal insulation material.

3. A method according to claim I or 2, in which the second portion surrounds the protrusion.

4. A method according to clam 1, 2 or 3, in which the component comprises a strip or plate.

having opposite end regions constituting the first and second portions.

5. A method according to claim 4. in which the strip or plate comprises a metal or ceramic.

6. A method according to claim 4 or 5. in which the end region constituting the second portion is provided with an aperture therethrough for accommodating the protrusion on the tubular envelope.

7.A method according to claim,4,. 5 or 6, in which the end region constituting the first portion is profiled and/or apertured whereby securing of the component in the insulation material is enhanced.

S. A method according to claim 1. 2 or 3. in -,vhich the component is of looped Nvire or looped strip form.

9. A method according to claim 9. in which the looped forrn component has legs providing the first portion, the legs being bent whereby securing of the component in the insulation material is enhanced.

10. A method according to any preceding claim, in which the protrusion on the envelope comprises a sealed tube coniniunicating with the interior of the envelope.

11. A method according to claim 10, in which the sealed tube is a tube used to evacuate and back-fill the envelope during manufacture of the infra-red lamp.

12. A method according to any preceding claim, In which the envelope comprises fused silica or quartz.

13. A method according to any prz=ding claim, in which the envelope encloses a filament.

11

14. A method according to claim 13, in which the filament comprises tungsten.

15. A method of manufacturing a radiant electric heater substantially as hereinbefore described with reference to the accompanying drawings.

16. A radiant electric heater whenever produced by the method according to any preceding claim.