WO2004028209A1 - Electric heater and method of manufacture - Google Patents

Electric heater and method of manufacture Download PDF

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Publication number
WO2004028209A1
WO2004028209A1 PCT/GB2003/003931 GB0303931W WO2004028209A1 WO 2004028209 A1 WO2004028209 A1 WO 2004028209A1 GB 0303931 W GB0303931 W GB 0303931W WO 2004028209 A1 WO2004028209 A1 WO 2004028209A1
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WO
WIPO (PCT)
Prior art keywords
heating element
heater
weld points
electrical resistance
resistance heating
Prior art date
Application number
PCT/GB2003/003931
Other languages
French (fr)
Inventor
Stuart Lamb
Original Assignee
Ceramaspeed Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ceramaspeed Limited filed Critical Ceramaspeed Limited
Priority to AU2003263351A priority Critical patent/AU2003263351A1/en
Priority to GB0504799A priority patent/GB2409139B/en
Publication of WO2004028209A1 publication Critical patent/WO2004028209A1/en

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/68—Heating arrangements specially adapted for cooking plates or analogous hot-plates
    • H05B3/74—Non-metallic plates, e.g. vitroceramic, ceramic or glassceramic hobs, also including power or control circuits
    • H05B3/748—Resistive heating elements, i.e. heating elements exposed to the air, e.g. coil wire heater

Definitions

  • This invention relates to an electric heater and a method of manufacture thereof.
  • the invention relates to an electric heater having at least one elongate ribbon-form radiant electrical resistance heating element supported relative to thermal and electrical insulation means, such as in a dish-like support.
  • an electric heater is particularly applicable for use in cooking appliances, such as grills, ovens or hobs and may be arranged for use behind a cooking plate such as of glass-ceramic material.
  • the ribbon-form heating element or elements of corrugated form having a plurality of legs extending therefrom and optionally integral therewith, the element or elements being supported on edge with the legs at least partially embedded in the thermal and electrical insulation means.
  • an electric heater comprising at least one elongate ribbon-form electrical resistance heating element supported relative to thermal and electrical insulation means, the at least one elongate ribbon-form electrical resistance heating element having at least one portion thereof overlapping and welded to at least one electrically conductive element at a predetermined zone of overlap and wherein a plurality of weld points are provided directly between the at least one portion of the at least one heating element and the at least one electrically conductive element within the zone of overlap.
  • a method of manufacturing an electric heater comprising: providing at least one elongate ribbon-form electrical resistance heating element supported relative to thermal and electrical insulation means; providing the at least one elongate ribbon-form electrical resistance heating element having at least one portion thereof overlapping at least one electrically conductive element at a predetermined zone of overlap; and welding the at least one portion of the at least one heating element directly to the at least one electrically conductive element such as to provide a plurality of weld points within the zone of overlap.
  • the method of the invention may additionally include sensing location of the predetermined zone of overlap, such as by visual means or by use of one or more sensing pulses, prior to providing the plurality of weld points.
  • the plurality of weld points may be provided in a random pattern or in the form of a predetermined pattern, within the zone of overlap.
  • One or more rows of weld points may be provided within the zone of overlap and may be provided substantially parallel to, substantially normal to, or at any required angle relative to, a longitudinal axis of the at least one elongate ribbon-form electrical resistance heating element . Two or more rows of weld points may be provided intersecting one another at a predetermined angle within the zone of overlap.
  • the plurality of weld points may be provided by electrical resistance welding means.
  • Quality of each of the weld points in the plurality thereof may be established on a basis of one or more measured values of one or more electrical parameters across each of the weld points meeting one or more predetermined limit values.
  • Such one or more electrical parameters may comprise electrical resistance and/or electric voltage potential difference and/or electric current.
  • Satisfactory quality of the plurality of weld points may be established on a basis of a predetermined proportion of the weld points within the zone of overlap meeting the predetermined limit value or values.
  • the at least one elongate ribbon-form electrical resistance heating element may be of corrugated form and may be provided with a plurality of legs extending edgewise substantially along the length thereof.
  • the at least one electrically conductive element may be of strip or tab form, such as of steel, which may be stainless or provided with a weldable metal coating, and may comprise at least one terminal for the at least one elongate ribbon-form electrical resistance heating element, which may be provided in association with a terminal block which may form part of a temperature- limiting device.
  • the at least one portion of the at least one elongate ribbon-form electrical resistance heating element may comprise one or more end portions of the heating element or elements or one or more intermediate tapping points on the heating element or elements.
  • additional weld points may be provided at a free end region, or at free end regions, of the one or more end portions to secure such free end region or regions to the associated electrically conductive element or elements.
  • the at least one elongate ribbon-form electrical resistance heating element may be supported edgewise on the thermal and electrical insulation means.
  • the thermal and electrical insulation means may comprise microporous thermal and electrical insulation material and may be provided in a dish-like support, such as of metal.
  • the electric heater may be adapted for use in a cooking appliance, such as behind a cooking surface, which may comprise glass-ceramic material.
  • Figure 1 is a plan view of an embodiment of an electric heater according to the present invention
  • Figure 2 is a perspective view of part of an elongate ribbon-form electrical resistance heating element as provided in the heater of Figure 1;
  • Figure 3 is a side view of a terminal region of the heater of Figure 1, showing an end portion of the elongate ribbon-form electrical resistance heating element overlapping an electrically conductive terminal element at a zone of overlap and welded thereto by one arrangement of a plurality of weld points;
  • Figure 4 is a modification of the terminal region of Figure 3, showing an alternative arrangement of the plurality of weld points;
  • Figure 5 is a modification of the terminal region of Figure 3, showing a further arrangement of the plurality of weld points;
  • Figure 6 shows the terminal arrangement of Figure 5, with additional weld points at a free end region of the heating element
  • Figure 7 is a perspective view of a portion of an elongate ribbon-form electrical resistance heating element, for use in an electric heater according to the present invention, having an intermediate tapping point welded by a plurality of weld points to an electrically conductive terminal element.
  • a radiant electric heater 2 is provided, which is suitable for use in a cooking appliance and such as behind a cooking surface 4, which may be of glass-ceramic material.
  • the heater 2 comprises a dish-like support 6, such as of metal, containing a layer 8 of thermal and electrical insulation material, which may comprise microporous thermal and electrical insulation material.
  • a peripheral wall 10 of thermal insulation material is provided in the dish-like support 6 and contacts a rear side of the surface 4 to be heated.
  • a radiant electrical resistance heating element 12 is arranged inside the dish-like support 6. Although a single such heating element 12 is shown in Figure 1, a plurality of heating elements could be provided. As particularly shown in Figure 2, the heating element 12 is of elongate corrugated metal ribbon form and has a plurality of spaced-apart legs 14 extending edgewise therefrom substantially along the length thereof. The legs 14 may be integral with, or secured to, the heating element 12. The ribbon-form heating element 12 is supported edgewise on the layer 8 of thermal and electrical insulation material with the legs 14 at least partially embedded in the layer 8.
  • a temperature-limiting device 16 is provided for the heater 2 and comprises an elongate temperature-sensitive probe assembly 18 arranged to operate switch means 20, 22 located at one end of the probe assembly 18 in a housing 24, such as of ceramic material.
  • the probe assembly 18 comprises a differentially-expanding rod and tube assembly of known form.
  • the switch means 20 may be arranged for controlling supply of electric power from a voltage source to the heating element 12.
  • the switch means 22 may be arranged to operate an indicating device, such as a warning light, for providing a warning signal when the surface 4 to be heated is too hot to touch.
  • the temperature-limiting device 16 is mounted on the heater 2 with the probe assembly 18 extending from a front face of the housing 24, at least partly across the dish-like support 6 and overlying the heating element 12.
  • the housing 24 is located externally of the dish-like support 6 and secured thereto by means of a bracket 26.
  • the housing 24 also serves as a terminal block and has electrically conductive terminal elements 28, 30, 32, 34, 36 extending therefrom at opposite side faces thereof.
  • terminal elements suitably comprise stainless steel, but may comprise steel plated with a weldable metal, such as nickel.
  • Terminal elements 28, 30, 32 and 34 are suitably adapted for engaging a multiple connector unit 38 leading to external wiring means.
  • the ribbon-form heating element 12 has end portions 12A and 12B extending through apertures provided in the peripheral wall 10 and the dish-like support 6 of the heater 2. As will be described in detail hereinafter, the end portion 12A of the heating element 12 is arranged to overlap and be welded (directly) to a strip-like or tab-like portion 36A of the electrically conductive terminal element 36, by application of electrodes 40, 42 of an electrical resistance welding machine. The other end portion 12B of the heating element 12 is likewise arranged to overlap and be welded (directly) to a striplike or tab-like portion 28A of the electrically conductive terminal element 28.
  • a zone of overlap 44 is formed between the end portion 12A of the heating element 12 and the strip-like or tab-like portion 36A of the electrically conductive terminal element 36.
  • a plurality of weld points 46 are sequentially formed, by means of the welding electrodes 40, 42 ( Figure 1), extending in a row across the zone of overlap 44. Prior to the welding operation, the zone of overlap 44 is detected either visually or by application of suitable sensing pulses. As can be seen in Figure 3, eight weld points 46 have been provided, six of which are within the zone of overlap 44. The two extreme weld points of the row 46 have been unsuccessful, in particular the lowest weld point having fallen unsuccessfully between two adjacent legs 14 of the heating element 12.
  • the quality of each of the weld points in its row 46 is established by measuring a value of one or more electrical parameters across each of the weld points and determining whether the measured value meets one or more predetermined limit values.
  • Such one or more electrical parameters may comprise, for example, electrical resistance and/or electric voltage potential difference and/or electric current.
  • electric voltage potential drop across each weld point is measured. Satisfactory quality of welding is established if a predetermined proportion of the weld points 46 within the zone of overlap 44 meet the requirements of the predetermined limit value or values. By way of example, if three out of the seven weld points 46 meet the test criteria, successful welding is considered to have taken place.
  • the provision of the plurality of weld points 46 is advantageous over the prior art in which only a single weld point was provided and whose quality and effectiveness could not be guaranteed, particularly if the weld point fell between two adjacent legs 14 of the end portion 12A of the heating element 12.
  • the plurality of weld points 46 can be provided in a random pattern or in a predetermined pattern within the zone of overlap 44.
  • the row of weld points 46 is provided at an angle X to a longitudinal axis 48 of the ribbon-form heating element 12.
  • FIG 4 differs from the arrangement of Figure 3 in that two rows of weld points 46A and 46B are provided across the zone of overlap 44 and intersecting one another at an angle to the longitudinal axis 48 of the ribbon-form heating element 12. It is seen that, apart from two of the weld points which have fallen between adjacent legs 14 of the heating element 12 and two which have fallen above the end portion 12A, all of the weld points have been provided within the zone of overlap 44.
  • the row of weld points 46 is provided substantially normal to the longitudinal axis 48 of the ribbon-form heating element 12. Apart from the extreme lower weld point which has fallen between adjacent legs 14, all of the weld points 46 in the row are fully located within the zone of overlap 44.
  • Figure 6 shows a modification to the arrangement of Figure 5.
  • a free end region 50 of the end portion 12A of - li the heating element 12 may not remain flat against the strip-like or tab-like portion 36A of the electrically conductive terminal element 36 and may make undesirable contact with a component adjacent thereto.
  • a plurality of weld points 52 can be provided, such as by stitch welding, at the free end region 50 of the heating element 12 and suitably arranged substantially parallel to the longitudinal axis 48 of the heating element 12.
  • the other end portion 12B of the heating element 12 is likewise provided with a plurality of weld points 46, 52 where it overlaps the strip-like or tab-like portion 28A of the electrically conductive terminal element 28.
  • the present invention is also applicable where an intermediate tapping point 12C on the ribbon heating element 12 is welded to a strip-like or tab-like electrically conductive terminal element 54.
  • a plurality of weld points 46 are provided within a zone of overlap 44 of the tapping point 12C of the heating element 12 and the terminal element 54.
  • Such plurality of weld points 46 can be formed in any desired pattern, in much the same way as described with reference to the arrangements of Figures 3 to 6.

Abstract

An electric heater (2) is manufactured comprising at least one elongate ribbon-form electrical resistance heating element (12) supported relative to thermal and electrical insulation means (8). The at least one elongate ribbon-form electrical resistance heating element (12) has at least one portion (12A; 12B; 12C) thereof overlapping and welded to at least one electrically conductive element (28A; 36A; 54) at a predetermined zone of overlap (44). A plurality of weld points (46; 46A; 46B) are provided directly between the at least one portion (12A; 12B; 12C) of the at least one heating element (12) and the at least one electrically conductive element (28A; 36A; 54) within the zone of overlap (44).

Description

ELECTRIC HEATER AND METHOD OF MANUFACTURE
This invention relates to an electric heater and a method of manufacture thereof.
More particularly, the invention relates to an electric heater having at least one elongate ribbon-form radiant electrical resistance heating element supported relative to thermal and electrical insulation means, such as in a dish-like support. Such an electric heater is particularly applicable for use in cooking appliances, such as grills, ovens or hobs and may be arranged for use behind a cooking plate such as of glass-ceramic material.
In such a heater, it is known to provide the ribbon-form heating element or elements of corrugated form, having a plurality of legs extending therefrom and optionally integral therewith, the element or elements being supported on edge with the legs at least partially embedded in the thermal and electrical insulation means.
It is known to provide one or more electrical terminations for the ribbon-form heating element or elements in which one or more end portions of the heating element or elements, or one or more intermediate tapping points on the heating element or elements, is or are arranged to overlap and be welded to one or more corresponding electrically conductive terminal elements, such as of metal strip or tab form. Welding of the portion of the heating element to its associated electrically conductive terminal element is generally effected by means of welding electrodes provided on an electrical resistance welding machine, with a single weld point being provided in a zone of overlap between the heating element and its associated electrically conductive terminal element.
Problems arise with this arrangement. Firstly, because of the presence of the spaced-apart legs at the lower region of the heating element, a weld provided by the welding electrodes in this region will not be successful if the welding electrodes are applied in a region between two adjacent legs. Secondly, if the ribbon-form heating element is of small height, a small zone of overlap is provided in which to provide the single weld point, necessitating very accurate positioning of the welding electrodes. Thirdly, the position of the heating element with respect to the associated electrically conductive terminal element is difficult to maintain on account of the compliant nature of the ribbon-form heating element and a build up of tolerances affecting the relative position of the components being welded. Fourthly, the position of the ribbon-form heating element with respect to the welding electrodes is difficult to maintain as a result of positional variability associated with the welding process.
It is an object of the present invention to overcome or minimise these problems.
According to one aspect of the present invention there is provided an electric heater comprising at least one elongate ribbon-form electrical resistance heating element supported relative to thermal and electrical insulation means, the at least one elongate ribbon-form electrical resistance heating element having at least one portion thereof overlapping and welded to at least one electrically conductive element at a predetermined zone of overlap and wherein a plurality of weld points are provided directly between the at least one portion of the at least one heating element and the at least one electrically conductive element within the zone of overlap.
According to another aspect of the present invention there is provided a method of manufacturing an electric heater comprising: providing at least one elongate ribbon-form electrical resistance heating element supported relative to thermal and electrical insulation means; providing the at least one elongate ribbon-form electrical resistance heating element having at least one portion thereof overlapping at least one electrically conductive element at a predetermined zone of overlap; and welding the at least one portion of the at least one heating element directly to the at least one electrically conductive element such as to provide a plurality of weld points within the zone of overlap.
The method of the invention may additionally include sensing location of the predetermined zone of overlap, such as by visual means or by use of one or more sensing pulses, prior to providing the plurality of weld points.
The plurality of weld points may be provided in a random pattern or in the form of a predetermined pattern, within the zone of overlap.
One or more rows of weld points may be provided within the zone of overlap and may be provided substantially parallel to, substantially normal to, or at any required angle relative to, a longitudinal axis of the at least one elongate ribbon-form electrical resistance heating element . Two or more rows of weld points may be provided intersecting one another at a predetermined angle within the zone of overlap.
The plurality of weld points may be provided by electrical resistance welding means.
Quality of each of the weld points in the plurality thereof may be established on a basis of one or more measured values of one or more electrical parameters across each of the weld points meeting one or more predetermined limit values. Such one or more electrical parameters may comprise electrical resistance and/or electric voltage potential difference and/or electric current.
Satisfactory quality of the plurality of weld points may be established on a basis of a predetermined proportion of the weld points within the zone of overlap meeting the predetermined limit value or values.
The at least one elongate ribbon-form electrical resistance heating element may be of corrugated form and may be provided with a plurality of legs extending edgewise substantially along the length thereof.
The at least one electrically conductive element may be of strip or tab form, such as of steel, which may be stainless or provided with a weldable metal coating, and may comprise at least one terminal for the at least one elongate ribbon-form electrical resistance heating element, which may be provided in association with a terminal block which may form part of a temperature- limiting device. The at least one portion of the at least one elongate ribbon-form electrical resistance heating element may comprise one or more end portions of the heating element or elements or one or more intermediate tapping points on the heating element or elements. When the at least one portion of the at least one elongate ribbon-form electrical resistance heating element comprises one or more end portions thereof, additional weld points may be provided at a free end region, or at free end regions, of the one or more end portions to secure such free end region or regions to the associated electrically conductive element or elements.
The at least one elongate ribbon-form electrical resistance heating element may be supported edgewise on the thermal and electrical insulation means.
The thermal and electrical insulation means may comprise microporous thermal and electrical insulation material and may be provided in a dish-like support, such as of metal.
The electric heater may be adapted for use in a cooking appliance, such as behind a cooking surface, which may comprise glass-ceramic material.
For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which:
Figure 1 is a plan view of an embodiment of an electric heater according to the present invention; Figure 2 is a perspective view of part of an elongate ribbon-form electrical resistance heating element as provided in the heater of Figure 1;
Figure 3 is a side view of a terminal region of the heater of Figure 1, showing an end portion of the elongate ribbon-form electrical resistance heating element overlapping an electrically conductive terminal element at a zone of overlap and welded thereto by one arrangement of a plurality of weld points;
Figure 4 is a modification of the terminal region of Figure 3, showing an alternative arrangement of the plurality of weld points;
Figure 5 is a modification of the terminal region of Figure 3, showing a further arrangement of the plurality of weld points;
Figure 6 shows the terminal arrangement of Figure 5, with additional weld points at a free end region of the heating element; and
Figure 7 is a perspective view of a portion of an elongate ribbon-form electrical resistance heating element, for use in an electric heater according to the present invention, having an intermediate tapping point welded by a plurality of weld points to an electrically conductive terminal element.
Referring to the drawings, a radiant electric heater 2 is provided, which is suitable for use in a cooking appliance and such as behind a cooking surface 4, which may be of glass-ceramic material. The heater 2 comprises a dish-like support 6, such as of metal, containing a layer 8 of thermal and electrical insulation material, which may comprise microporous thermal and electrical insulation material. A peripheral wall 10 of thermal insulation material is provided in the dish-like support 6 and contacts a rear side of the surface 4 to be heated.
A radiant electrical resistance heating element 12 is arranged inside the dish-like support 6. Although a single such heating element 12 is shown in Figure 1, a plurality of heating elements could be provided. As particularly shown in Figure 2, the heating element 12 is of elongate corrugated metal ribbon form and has a plurality of spaced-apart legs 14 extending edgewise therefrom substantially along the length thereof. The legs 14 may be integral with, or secured to, the heating element 12. The ribbon-form heating element 12 is supported edgewise on the layer 8 of thermal and electrical insulation material with the legs 14 at least partially embedded in the layer 8.
A temperature-limiting device 16 is provided for the heater 2 and comprises an elongate temperature-sensitive probe assembly 18 arranged to operate switch means 20, 22 located at one end of the probe assembly 18 in a housing 24, such as of ceramic material. The probe assembly 18 comprises a differentially-expanding rod and tube assembly of known form.
The switch means 20 may be arranged for controlling supply of electric power from a voltage source to the heating element 12. The switch means 22 may be arranged to operate an indicating device, such as a warning light, for providing a warning signal when the surface 4 to be heated is too hot to touch.
The temperature-limiting device 16 is mounted on the heater 2 with the probe assembly 18 extending from a front face of the housing 24, at least partly across the dish-like support 6 and overlying the heating element 12. The housing 24 is located externally of the dish-like support 6 and secured thereto by means of a bracket 26.
The housing 24 also serves as a terminal block and has electrically conductive terminal elements 28, 30, 32, 34, 36 extending therefrom at opposite side faces thereof. Such terminal elements suitably comprise stainless steel, but may comprise steel plated with a weldable metal, such as nickel. Terminal elements 28, 30, 32 and 34 are suitably adapted for engaging a multiple connector unit 38 leading to external wiring means.
The ribbon-form heating element 12 has end portions 12A and 12B extending through apertures provided in the peripheral wall 10 and the dish-like support 6 of the heater 2. As will be described in detail hereinafter, the end portion 12A of the heating element 12 is arranged to overlap and be welded (directly) to a strip-like or tab-like portion 36A of the electrically conductive terminal element 36, by application of electrodes 40, 42 of an electrical resistance welding machine. The other end portion 12B of the heating element 12 is likewise arranged to overlap and be welded (directly) to a striplike or tab-like portion 28A of the electrically conductive terminal element 28.
As shown in Figure 3, a zone of overlap 44 is formed between the end portion 12A of the heating element 12 and the strip-like or tab-like portion 36A of the electrically conductive terminal element 36.
A plurality of weld points 46 are sequentially formed, by means of the welding electrodes 40, 42 (Figure 1), extending in a row across the zone of overlap 44. Prior to the welding operation, the zone of overlap 44 is detected either visually or by application of suitable sensing pulses. As can be seen in Figure 3, eight weld points 46 have been provided, six of which are within the zone of overlap 44. The two extreme weld points of the row 46 have been unsuccessful, in particular the lowest weld point having fallen unsuccessfully between two adjacent legs 14 of the heating element 12.
The quality of each of the weld points in its row 46 is established by measuring a value of one or more electrical parameters across each of the weld points and determining whether the measured value meets one or more predetermined limit values. Such one or more electrical parameters may comprise, for example, electrical resistance and/or electric voltage potential difference and/or electric current. In particular, electric voltage potential drop across each weld point is measured. Satisfactory quality of welding is established if a predetermined proportion of the weld points 46 within the zone of overlap 44 meet the requirements of the predetermined limit value or values. By way of example, if three out of the seven weld points 46 meet the test criteria, successful welding is considered to have taken place.
The provision of the plurality of weld points 46 is advantageous over the prior art in which only a single weld point was provided and whose quality and effectiveness could not be guaranteed, particularly if the weld point fell between two adjacent legs 14 of the end portion 12A of the heating element 12.
The plurality of weld points 46 can be provided in a random pattern or in a predetermined pattern within the zone of overlap 44.
As shown in and described with reference to Figure 3, the row of weld points 46 is provided at an angle X to a longitudinal axis 48 of the ribbon-form heating element 12.
Referring now to Figure 4, this differs from the arrangement of Figure 3 in that two rows of weld points 46A and 46B are provided across the zone of overlap 44 and intersecting one another at an angle to the longitudinal axis 48 of the ribbon-form heating element 12. It is seen that, apart from two of the weld points which have fallen between adjacent legs 14 of the heating element 12 and two which have fallen above the end portion 12A, all of the weld points have been provided within the zone of overlap 44.
Referring now to Figure 5, here the row of weld points 46 is provided substantially normal to the longitudinal axis 48 of the ribbon-form heating element 12. Apart from the extreme lower weld point which has fallen between adjacent legs 14, all of the weld points 46 in the row are fully located within the zone of overlap 44.
Figure 6 shows a modification to the arrangement of Figure 5. When the row of weld points 46 is provided in the end portion 12A of the heating element 12, there is a risk that a free end region 50 of the end portion 12A of - li the heating element 12 may not remain flat against the strip-like or tab-like portion 36A of the electrically conductive terminal element 36 and may make undesirable contact with a component adjacent thereto. To prevent this, a plurality of weld points 52 can be provided, such as by stitch welding, at the free end region 50 of the heating element 12 and suitably arranged substantially parallel to the longitudinal axis 48 of the heating element 12.
Although the provision of the multiple weld points 46, 52 has been specifically described in detail with reference to the end portion 12A of the heating element 12 and the strip-like or tab-like portion 36A of the electrically conductive terminal element 36, the other end portion 12B of the heating element 12 is likewise provided with a plurality of weld points 46, 52 where it overlaps the strip-like or tab-like portion 28A of the electrically conductive terminal element 28.
As shown in Figure 7, the present invention is also applicable where an intermediate tapping point 12C on the ribbon heating element 12 is welded to a strip-like or tab-like electrically conductive terminal element 54. As before, a plurality of weld points 46 are provided within a zone of overlap 44 of the tapping point 12C of the heating element 12 and the terminal element 54. Such plurality of weld points 46 can be formed in any desired pattern, in much the same way as described with reference to the arrangements of Figures 3 to 6.

Claims

1. An electric heater comprising at least one elongate ribbon-form electrical resistance heating element (12) supported relative to thermal and electrical insulation means (8), the at least one elongate ribbon-form electrical resistance heating element having at least one portion (12A; 12B; 12C) thereof overlapping and welded to at least one electrically conductive element (28A; 36A; 54) at a predetermined zone of overlap (44), characterised in that a plurality of weld points (46; 46A; 46B) are provided directly between the at least one portion (12A; 12B; 12C) of the at least one heating element (12) and the at least one electrically conductive element (28A; 28B; 28C) within the zone of overlap (44).
2. A heater as claimed in claim 1, characterised in that the plurality of weld points (46; 46A; 46B) are provided in a random pattern or in the form of a predetermined pattern, within the zone of overlap (44) .
3. A heater as claimed in claim 2, characterised in that one or more rows of weld points (46; 46A; 46B) is or are provided within the zone of overlap (44).
4. A heater as claimed in claim 3, characterised in that the one or more rows of weld points (46; 46A; 46B) is or are provided substantially parallel to, substantially normal to, or at any required angle relative to, a longitudinal axis of the at least one elongate ribbon-form electrical resistance heating element (12) .
5. A heater as claimed in claim 4, characterised in that two or more rows of weld points (46; 46A; 46B) are provided intersecting one another at a predetermined angle within the zone of overlap (44) .
6. A heater as claimed in any preceding claim, characterised in that the plurality of weld points (46; 46A; 46B) are provided by electrical resistance welding means (40, 42) .
7. A heater as claimed in any preceding claim, characterised in that quality of each of the weld points (46; 46A; 46B) in the plurality thereof is established on a basis of one or more measured values of one or more electrical parameters across each of the weld points meeting one or more predetermined limit values.
8. A heater as claimed in claim 7, characterised in that the one or more electrical parameters comprise (s) electrical resistance and/or electric voltage potential difference and/or electric current.
9. A heater as claimed in claim 7 or 8, characterised in that satisfactory quality of the plurality of weld points (46; 46A; 46B) is established on a basis of a predetermined proportion of the weld points within the zone of overlap (44) meeting the predetermined limit value or values.
10. A heater as claimed in any preceding claim, characterised in that the at least one elongate ribbon- form electrical resistance heating element (12) is of corrugated form.
11. A heater as claimed in any preceding claim, characterised in that the at least one elongate ribbon- form electrical resistance heating element (12) is provided with a plurality of legs (14) extending edgewise substantially along the length thereof.
12. A heater as claimed in any preceding claim, characterised in that the at least one electrically conductive element (28A; 36A; 54) is of strip or tab form.
13. A heater as claimed in claim 12, characterised in that the at least one electrically conductive element
(28A; 36A; 54) comprises steel.
14. A heater as claimed in claim 13, characterised in that the steel comprises stainless steel or is provided with a weldable metal coating.
15. A heater as claimed in any preceding claim, characterised in that the at least one electrically conductive element (28A; 36A; 54) comprises at least one terminal for the at least one elongate ribbon-form electrical resistance heating element (12) .
16. A heater as claimed in claim 15, characterised in that the at least one terminal (28A; 36A; 54) is provided in association with a terminal block (24).
17. A heater as claimed in claim 16, characterised in that the terminal block (24) forms part of a temperature- limiting device (16) .
18. A heater as claimed in any preceding claim, characterised in that the at least one portion (12A; 12B; 12C) of the at least one elongate ribbon-form electrical resistance heating element (12) comprises one or more end portions of the heating element or elements or one or more intermediate tapping points on the heating element or elements.
19. A heater as claimed in claim 18, characterised in that the at least one portion (12A) of the at least one elongate ribbon-form electrical resistance heating element (12) comprises one or more end portions thereof and additional weld points (52) are provided at a free end region (50) , or at free end regions, of the one or more end portions to secure such free end region or regions to the associated electrically conductive element or elements (28A; 36A; 54) .
20. A heater as claimed in any preceding claim, characterised in that the at least one elongate ribbon- form electrical resistance heating element (12) is supported edgewise on the thermal and electrical insulation means (8) .
21. A heater as claimed in any preceding claim, characterised in that the thermal and electrical insulation means (8) comprises microporous thermal and electrical insulation material.
22. A heater as claimed in any preceding claim, characterised in that the thermal and electrical insulation means (8) is provided in a dish-like support (6) .
23. A heater as claimed in claim 22, characterised in that the dish-like support (6) comprises metal.
24. A cooking appliance provided with an electric heater as claimed in any preceding claim.
25. A method of manufacturing an electric heater comprising: providing at least one elongate ribbon-form electrical resistance heating element (12) supported relative to thermal and electrical insulation means (8); and providing the at least one elongate ribbon-form electrical resistance heating element having at least one portion (12A; 12B; 12C) thereof overlapping at least one electrically conductive element (28A; 36A; 54) at a predetermined zone of overlap (44), characterised in that the at least one portion (12A; 12B; 12C) of the at least one heating element (12) is welded directly to the at least one electrically conductive element (28A; 36A; 54) such as to provide a plurality of weld points (46; 46A; 46B) within the zone of overlap (44) .
26. A method according to claim 25, characterised in that sensing location of the predetermined zone of overlap (44) is additionally effected, prior to providing the plurality of weld points (46; 46A; 46B) .
27. A method according to claim 26, characterised in that the sensing is effected by visual means or by use of one or more sensing pulses.
28. A method according to claim 25, 26 or 27, characterised in that the plurality of weld points (46; 46A; 46B) are provided in a random pattern or in the form of a predetermined pattern, within the zone of overlap (44).
29. A method according to claim 28, characterised in that one or more rows of weld points (46; 46A; 46B) is or are provided within the zone of overlap (44) .
30. A method according to claim 29, characterised in that the one or more rows of weld points (46; 46A; 46B) is or are provided substantially parallel to, substantially normal to, or at any required angle relative to, a longitudinal axis of the at least one elongate ribbon-form electrical resistance heating element (12) .
31. A method according to claim 30, characterised in that two or more rows of weld points (46A; 46B) are provided intersecting one another at a predetermined angle within the zone of overlap (44) .
32. A method according to any of claims 25 to 31, characterised in that the plurality of weld points (46; 46A; 46B) are provided by electrical resistance welding means (40, 42) .
33. A method according to any of claims 25 to 32, characterised in that quality of each of the weld points (46; 46A; 46B) in the plurality thereof is established on a basis of one or more measured values of one or more electrical parameters across each of the weld points meeting one or more predetermined limit values.
34. A method according to claim 33, characterised in that the one or more electrical parameters comprise (s) electrical resistance and/or electric voltage potential difference and/or electric current.
35. A method according to claim 33 or 34, characterised in that satisfactory quality of the plurality of weld points (46; 46A; 46B) is established on a basis of a predetermined proportion of the weld points within the zone of overlap (44) meeting the predetermined limit value or values.
36. A method according to any of claims 25 to 35, characterised in that the at least one elongate ribbon- form electrical resistance heating element (12) is of corrugated form.
37. A method according to any of claims 25 to 36, characterised in that the at least one elongate ribbon- form electrical resistance heating element (12) is provided with a plurality of legs (14) extending edgewise substantially along the length thereof.
38. A method according to any of claims 25 to 37, characterised in that the at least one electrically conductive element (28A; 36A; 54) is of strip or tab form.
39. A method according to claim 38, characterised in that the at least one electrically conductive element (28A; 36A; 54) comprises steel.
40. A method according to claim 39, characterised in that the steel comprises stainless steel or is provided with a weldable metal coating.
41. A method according to any of claims 25 to 40, characterised in that the at least one electrically conductive element (28A; 36A; 54) comprises at least one terminal for the at least one elongate ribbon-form electrical resistance heating element (12).
42. A method according to claim 41, characterised in that the at least one terminal is provided in association with a terminal block (24) .
43. A method according to claim 42, characterised in that the terminal block (24) forms part of a temperature- limiting device (16).
44. A method according to any of claims 25 to 43, characterised in that the at least one portion (12A; 12B; 12C) of the at least one elongate ribbon-form electrical resistance heating element (12) comprises one or more end portions of the heating element or elements or one or more intermediate tapping points on the heating element or elements.
45. A method according to claim 44, characterised in that the at least one portion (12A; 12B; 12C) of the at least one elongate ribbon-form electrical resistance heating element (12) comprises one or more end portions thereof and additional weld points (52) are provided at a free end region (50) , or at free end regions, of the one or more end portions to secure such free end region or rlegions to the associated electrically conductive element or elements (28A; 36A; 54).
46. A method according to any of claims 25 to 45, characterised in that the at least one elongate ribbon- form electrical resistance heating element (12) is supported edgewise on the thermal and electrical insulation means (8) .
47. A method according to any of claims 25 to 46, characterised in that the thermal and electrical insulation means (8) comprises microporous thermal and electrical insulation material.
48. A method according to any of claims 25 to 47, characterised in that the thermal and electrical insulation means (8) is provided in a dish-like support (6) .
49. A method according to claim 48, characterised in that the dish-like support (6) comprises metal.
PCT/GB2003/003931 2002-09-17 2003-09-10 Electric heater and method of manufacture WO2004028209A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU2003263351A AU2003263351A1 (en) 2002-09-17 2003-09-10 Electric heater and method of manufacture
GB0504799A GB2409139B (en) 2002-09-17 2003-09-10 Method of manufacturing an Electric Heater

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0221520.0 2002-09-17
GB0221520A GB0221520D0 (en) 2002-09-17 2002-09-17 Electric heater and method of manufacture

Publications (1)

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WO2004028209A1 true WO2004028209A1 (en) 2004-04-01

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Application Number Title Priority Date Filing Date
PCT/GB2003/003931 WO2004028209A1 (en) 2002-09-17 2003-09-10 Electric heater and method of manufacture

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AU (1) AU2003263351A1 (en)
GB (2) GB0221520D0 (en)
WO (1) WO2004028209A1 (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3523173A (en) * 1967-08-17 1970-08-04 Sprague Electric Co Insulated lead connection
GB1355693A (en) * 1970-08-27 1974-06-05 Ego Verwaltungs Gmbh Electrical heating elements
GB2160460A (en) * 1984-06-18 1985-12-24 Tungsram Reszvenytarsasag Method of preparing duplex-spot welded joints, especially of producing high-melt rod-foil-rod type current conductors press-sealed into hard glass or quartz glass.
EP0810814A2 (en) * 1996-05-31 1997-12-03 Emerson Electric Co. Coil termination for a radiant heater
US6207935B1 (en) * 1996-09-21 2001-03-27 Diehl Ako Stiftung & Co. Kg Radiant heating element with a metal foil heat conductor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3523173A (en) * 1967-08-17 1970-08-04 Sprague Electric Co Insulated lead connection
GB1355693A (en) * 1970-08-27 1974-06-05 Ego Verwaltungs Gmbh Electrical heating elements
GB2160460A (en) * 1984-06-18 1985-12-24 Tungsram Reszvenytarsasag Method of preparing duplex-spot welded joints, especially of producing high-melt rod-foil-rod type current conductors press-sealed into hard glass or quartz glass.
EP0810814A2 (en) * 1996-05-31 1997-12-03 Emerson Electric Co. Coil termination for a radiant heater
US6207935B1 (en) * 1996-09-21 2001-03-27 Diehl Ako Stiftung & Co. Kg Radiant heating element with a metal foil heat conductor

Also Published As

Publication number Publication date
GB2409139B (en) 2005-11-09
GB0221520D0 (en) 2002-10-23
AU2003263351A1 (en) 2004-04-08
GB2409139A (en) 2005-06-15
GB0504799D0 (en) 2005-04-13

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