GB2407747A - Wall for an electric heater and process for the production thereof - Google Patents
Wall for an electric heater and process for the production thereof Download PDFInfo
- Publication number
- GB2407747A GB2407747A GB0325416A GB0325416A GB2407747A GB 2407747 A GB2407747 A GB 2407747A GB 0325416 A GB0325416 A GB 0325416A GB 0325416 A GB0325416 A GB 0325416A GB 2407747 A GB2407747 A GB 2407747A
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- United Kingdom
- Prior art keywords
- wall
- glass
- cooking plate
- electric heater
- film
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Classifications
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- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Electric Stoves And Ranges (AREA)
- Baking, Grill, Roasting (AREA)
- Cookers (AREA)
Abstract
In a wall (14) for an electric heater (6) and a process for its production, the electric heater (6) is adapted to be located beneath a glass-ceramic cooking plate (4). The wall (14) comprises thermal insulation material incorporating at least one refractory material and is adapted to be arranged upstanding in the electric heater (6). The wall (14) has an upper surface (24) adapted for contacting a region (16) of a lower surface (18) of the glass-ceramic cooking plate (4) which is susceptible to abrasion by material of the wall, the upper surface (24) of the wall (14) being provided with a covering (26) of a material which reduces abrasion between the upper surface (24) of the wall (14) and the region (16) of the lower surface (18) of the glass-ceramic cooking plate (4).
Description
WALL FOR AN ELECTRIC HEATER AND PROCESS FOR THE
PRODUCTION THEREOF
This invention relates to a wall for an electric heater and to a process for its production, the electric heater being adapted to be located beneath a glass-ceramic cooking plate.
It is known to provide an electric heater comprising a dish-like support, such as of metal, having a base layer of thermal and electrical insulation material relative to which is supported one or more radiant electric heating elements. A wall of thermal insulation material is provided, arranged upstanding in the electric heater around a periphery thereof, the wall having an upper surface arranged to contact a lower surface of a glass- ceramic cooking plate overlying the heater. One or more similar walls may additionally be arranged within the heater, such that separate heating zones are provided in the heater.
Such a wall or walls is or are known to be provided comprising one or more refractory materials such as silica and/or vermiculite and may additionally include fibre reinforcing material, such as glass or ceramic fibre material. Such refractory materials may be - 2 - somewhat abrasive in nature with the result that the upper surface of the wall may abrasively rub against the lower surface of the glass-ceramic cooking plate if relative lateral movement is caused to occur between the heater and the cooking plate. Such movement is particularly likely to occur during manufacture and shipping of a cooking assembly, such as a bob, comprising the heater and the cooking plate. Once the assembly is installed by an end user, further such relative lateral movement is less likely to occur.
It is known to provide glass-ceramic cooking plates with a printed pattern of heat-resistant material on the lower surface thereof. Such a printed pattern is arranged to be visible through the cooking plate from the upper surface thereof and may be arranged to identify the outline of a heating zone of the cooking plate heated by the underlying heater. The printed pattern may also have aesthetic appeal.
A problem has arisen in that the upper surface of the wall of the heater makes contact with the printed pattern, which is relatively fragile in nature. When relative lateral movement occurs between the heater and the cooking plate, particularly during manufacture and shipping of the cooking assembly, the material of the upper surface of the wall tends to cause abrasive damage to the printed pattern, resulting in unacceptable visible scratches on the pattern and consequent rejection of the cooking assembly.
It is an object of the present invention to overcome or minimise this problem.
According to one aspect of the present invention there is provided a wall for an electric heater, the electric heater being adapted to be located beneath a glass- ceramic cooking plate, the wall comprising thermal insulation material incorporating at least one refractory material and adapted to be arranged upstanding in the electric heater, the wall having an upper surface adapted for contacting a region of a lower surface of the glass- ceramic cooking plate which is susceptible to abrasion by material of the wall, the upper surface of the wall being provided with a covering of a material which reduces abrasion between the upper surface of the wall and the region of the lower surface of the cooking plate.
According to another aspect of the present invention there is provided a process for the production of a wall for an electric heater, the electric heater being adapted to be located beneath a glass-ceramic cooking plate, the wall comprising thermal insulation material incorporating at least one refractory material and adapted to be arranged upstanding in the electric heater, the wall having an upper surface adapted for contacting a region of a lower surface of the glass-ceramic cooking plate which is susceptible to abrasion by material of the wall, the process comprising providing the upper surface of the wall with a covering of a material which reduces abrasion between the upper surface of the wall and the region of the lower surface of the glass-ceramic cooking plate.
The region of the lower surface of the glass-ceramic cooking plate may comprise a coating of a heat-resistant material susceptible to abrasion by material of the wall, which may be in the form of a pattern, which may be visible through the glass-ceramic cooking plate from an upper surface thereof and may be adapted to define a zone heated by the heater, the upper surface of the wall being adapted for contacting the coating, the covering of the material provided on the upper surface of the wall being substantially non-abrasive to the coating of the heat- resistant material.
The upper surface of the wall on which the covering of the material is provided may be a smoothed upper surface. - 5 -
The smoothed upper surface of the wall may also extend over edges of the upper surface of the wall.
The smoothed upper surface of the wall may be such that it is substantially free from undesirably high asperities and loose particulate material.
The smoothed upper surface of the wall may be provided by polishing the upper surface of the wall, such as by application of an abrasive means. Such abrasive means may comprise an abrasive paper of suitably fine grade.
Such abrasive paper may comprise silicon carbide.
The abrasive means may be provided in the form of a disc, which is caused to be rotated and pressed against the upper surface of the wall for a predetermined period of time, which may suitably be between about 5 and about 30 seconds. The rotated disc may be presented at a predetermined angle relative to the wall for smoothing edges of the upper surface of the wall.
Material of the upper surface of the wall removed during polishing may be dispersed and/or extracted by vacuum extraction and/or air jet means. Such air jet means may provide a high velocity jet of air and may comprise an air knife. 1 1 - 6
Alternatively, the upper surface of the wall may be blasted with mild abrasive media, such as beads of plastics material. The stream of abrasive material may be focussed on the upper surface of the wall.
As a further alternative, the entire wall may be immersed in a bed of vibrating abrasive Whippings, for example of As a further alternative, the upper surface of the wall may be burnished by urging the upper surface against a smooth plate, for example of glass or metal, which is rotated for a short time, such as 5 to 30 seconds. The wall may be heat- treated prior to burnishing or the surface of the wall may be softened by the application of a liquid, such as water.
The wall may comprise silica and/or vermiculite and may include fibre reinforcing material, such as glass or ceramic fibre material.
The covering of the material with which the upper surface of the wall is provided may be provided in the form of a film which serves as a barrier between the upper surface of the wall and the region of the lower surface of the glass-ceramic cooking plate and provides reduced coefficient of friction between the upper surface of the wall and the region of the lower surface of the glass- ceramic cooking plate.
The film may comprise a solid lubricant material, which may comprise talc (magnesium silicate), molybdenum disulphide, tungsten disulphide, graphite, yttrium oxide, finely dispersed silica, finely dispersed alumina, polytetrafluoroethylene (PTFE) or boron nitride.
The solid lubricant material may fill small irregularities or imperfections in the upper surface of the wall, to form a level surface.
The solid lubricant material may be applied to the upper surface of the wall by deposition thereto from a rotating mop means impregnated with the solid lubricant material.
Alternatively, the solid lubricant material may be provided as an emulsion or colloidal dispersion and applied as a film to the upper surface of the wall by spraying or dipping. A film of polytetrafluoroethylene (PTFE), boron nitride or graphite may particularly be applied in this way. - 8 -
The film may alternatively comprise a semi-solid or gel material of polymeric form, which may serve to fill small irregularities or imperfections in the upper surface of the wall and present a soft, compliant contact surface to the region of the lower surface of the glassceramic cooking plate.
The semi-solid or gel material may comprise polyvinyl acetate aqueous emulsion, petroleum jelly, silicone grease or a high temperature polymeric organo-silicon compound.
The high temperature polymeric organo-silicon compound may comprise a material applicable without requiring chemical transformation, such as an aqueous-based polysiloxane emulsion.
Alternatively, the high temperature polymeric organo- silicon compound may comprise a material adapted to be cured or cross- linked after application to the upper surface of the wall and may comprise RTV silicone, a polysilaxane solution, a polysilane or a silicone resin.
Such a material may be adapted to be cured or cross- linked by application of heat or ultra-violet radiation. - 9 -
The film of the semi-solid or gel material of polymeric form may be applied in the form of a liquid precursor to the upper surface of the wall by spraying, or may be applied in semi-solid or gel form directly to the upper surface of the wall by smearing.
The semi-solid or gel material of polymeric form may be such as to at least partially decompose at a subsequent normal operating temperature of the electric heater.
Alternatively or additionally, the covering of the material with which the upper surface of the wall is provided may comprise a gasket adapted to be positioned between the upper surface of the wall and the lower surface of the glass ceramic plate substantially along the entire extent of the wall. The gasket may have a thickness in the range from 0.01 to 0. 25 mm and may be made, for example, from mica, polyimide material, metal (such as stainless steel) or supported graphite. If desired, that face of the gasket to be in contact with the lower surface of the glass ceramic plate may be coated with a covering material as hereinabove described.
The gasket may be secured to the upper surface of the wall with a high temperature adhesive, such as an alkali metal silicate adhesive. -
The present invention also provides an electric heater provided with the aforementioned wall and also an assembly comprising a glass-ceramic cooking plate and a heater provided with the aforementioned wall.
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 an exploded perspective view of an assembly comprising a glass-ceramic cooking plate and an electric heater provided with an embodiment of a wall according to the present invention; Figure 2 is a cross-sectional view of the assembly of Figure 1; and Figures 3A to 3C are cross- sectional views of part of the embodiment of the wall shown in Figure 1, illustrating processing steps in the production thereof.
Referring to Figures 1 and 2, an assembly 2 is provided comprising a glass-ceramic cooking plate 4 under which is an electric heater 6. The electric heater 6 comprises a metal dish-like support 8 having a base layer 10 of l thermal and electrical insulation material relative to which is supported an electric heating element of well- known form.
A wall 14 of thermal insulation material is arranged upstanding in the heater. The wall 14 comprises one or more refractory materials, such as silica and/or vermiculite and may include reinforcing material such as glass or ceramic fibres. In particular, the wall 14 comprises bound vermiculite material.
The glass-ceramic cooking plate 4 is provided with a printed pattern 16 of heat resistant material on a lower surface 18 thereof. The printed pattern 16 is visible through the glass-ceramic cooking plate 4 from an upper surface 20 of the cooking plate 4. The printed pattern 16 may be of aesthetic appeal but, as shown in Figure 1, it is arranged to identify the outline of a heating zone 22 of the cooking plate 4 which is to be heated by the underlying heater 6.
The heater 6 is supported by well-known spring-loading means (not shown) against the lower surface 18 of the cooking plate 4, with an upper surface 24 of the wall 14 contacting the printed pattern 16 on the lower surface of the cooking plate 4. - 12
During manufacture of the assembly 2 and subsequent shipment to an end user, jolting and/or vibration may occur which causes relative lateral movement to take place between the wall 14 of the heater 6 and the cooking plate 4. The material of the wall 14 is inherently abrasive in nature and the relative lateral movement results in abrasion and harmful scratching of the relatively fragile printed pattern 16 by the upper surface 24 of the wall 14. As a result, the assembly 2 may be rejected by the end user as unsatisfactory.
This problem is overcome or minimised in the present invention by providing the upper surface 24 of the wall 14 with a covering 26 of a material which minimises or reduces abrasion between the upper surface 24 of the wall 14 and the printed pattern 16.
Figures 3A to 3C illustrate process steps involved in providing the covering 26 on the upper surface 24 of the wall 14.
Referring to Figure 3A, the upper surface 24 of the wall 14 as initially produced may be relatively rough and may include undesirably high asperities 28 and possibly some loose particulate material. The upper surface 24 of the wall 14 is therefore smoothed by polishing it with an 13 - abrasive means 30, which may comprise an abrasive paper of suitably fine grade and suitably comprising silicon carbide material. The abrasive means 30 is suitably provided as a disc, which is caused to be rotated and pressed against the upper surface 24 of the wall 14 for a predetermined period of time, which may suitably be between about 5 and about 30 seconds. The type and grade of abrasive material of the abrasive means 30 and the duration of the polishing operation is selected so as not to disturb the sub-structure of the upper surface 24 of the wall 14, thereby avoiding dislodging particulate material of the wall. This is particularly important with a wall 14 comprising vermiculite. Material of the upper surface of the wall removed during polishing is dispersed and/or extracted by vacuum extraction and/or air jet means 32. Such air jet means may provide a high velocity jet of air and may comprise an air knife.
Sharp edges 34 of the upper surface 24 of the wall 14 may be smoothed by presenting the rotated disc of the abrasive means 30 to the edge of the wall 14 at a predetermined angle to the wall.
The resulting wall 14 with its smoothed upper surface 24 is illustrated in Figure 3B. - 14
Alternatively, the upper surface 24 of the wall 14 may be blasted with mild abrasive media, such as beads of plastics material. The stream of abrasive material may be focussed on the upper surface of the wall.
As a further alternative, the entire wall 14 may be immersed in a bed of vibrating abrasive whippings, for example of wood or vermiculite.
As a further alternative, the upper surface 24 of the wall 14 may be burnished by urging the upper surface against a smooth plate, for example of glass or metal, which is rotated for a short time, such as 5 to 30 seconds. The wall 14 may be heat-treated prior to burnishing or the surface 24 of the wall 14 may be softened by the application of a liquid, such as water.
Referring now to Figure 3C, the covering 26 of the material which minimises or reduces abrasion between the upper surface 24 of the wall 14 and the printed pattern 16 (Figure 1) on the lower surface 18 of the glass- ceramic cooking plate 4 is applied to the smoothed upper surface 24 of the wall 14.
The covering 26 is provided in the form of a film and serves as a barrier between the upper surface 24 of the - 15 wall 14 and the printed pattern 16 on the lower surface of the cooking plate 4 and provides reduced coefficient of friction between the upper surface 24 of the wall 14 and the printed pattern 16.
The film-form covering 26 suitably comprises a solid lubricant material, such as talc (magnesium silicate), molybdenum disulphide, tungsten disulphide, graphite, yttrium oxide, finely dispersed silica, finely dispersed alumina, polytetrafluoroethylene (PTFE) or boron nitride.
Boron nitride is particularly advantageous because of its excellent lubricating properties, good stability at high temperatures and high chemical inertness. The solid lubricant material fills small irregularities or imperfections in the smoothed upper surface 24 of the wall 14 and forms a level surface. It also suppresses any tendency for destructive adhesion to occur between the upper surface of the wall 14 and the printed pattern 16.
The solid lubricant material forming the covering 26 is suitably applied to the upper surface 24 of the wall 14 by means of a rotating mop 36 impregnated with the solid lubricant material. Alternatively, the solid lubricant material forming the covering 26 may be provided as an emulsion or colloidal dispersion and applied as a film to - 16 - the upper surface 24 of the wall 14 by a spray gun means 38. A film-form covering 26 of polytetrafluoroethylene (PTFE), boron nitride or graphite may particularly be applied by such a spraying technique or alternatively by a dipping technique.
The film-form covering 26 may alternatively comprise a semi-solid or gel material of polymeric form, which fills small irregularities or imperfections in the smoothed upper surface 24 of the wall 14 and also presents a soft, compliant contact surface to the printed pattern 16 on the lower surface of the cooking plate 4.
The semi-solid or gel material suitably comprises polyvinyl acetate aqueous emulsion, petroleum jelly, silicone grease or a high temperature polymeric organo- silicon compound. The high temperature polymeric organosilicon compound may comprise a material applicable without requiring chemical transformation, such as an aqueous-based polysiloxane emulsion. Alternatively, the high temperature polymeric organo-silicon compound may comprise a material adapted to be cured or cross-linked after application to the upper surface 24 of the wall 14 and may comprise RTV silicone, a polysiloxane solution, a polysilane or a silicone resin. Such a material may be subsequently cured or cross-linked by application of heat 17 - or ultra-violet radiation, using well-known means (not shown).
The film-form covering 26 of the semi-solid or gel material of polymeric form can be suitably applied to the upper surface 24 of the wall 14 in the form of a liquid precursor, by spray gun means 38. Alternatively, the semi-solid or gel material can be applied directly to the upper surface 24 of the wall 14, to form the covering 26, by smearing the material onto the surface 24 such as from a suitably impregnated mop 36, which may be rotating or non-rotating.
The semi-solid or gel material of polymeric form used to provide the filmform covering 26 may be such as to at least partially decompose at a subsequent normal operating temperature of the electric heater. Siliconbased materials are advantageous in this respect in that any thermal decomposition which occurs during service in the assembly will tend to principally yield an inert residue of silica or silicon nitride, with little or no undesirable carbonaceous material.
Alternatively or additionally, the covering of the material with which the upper surface 24 of the wall 14 is provided may comprise a gasket (not shown) adapted to - 18 - be positioned between the upper surface of the wall and the lower surface 18 of the glass ceramic plate 4 substantially along the entire extent of the wall. The gasket may have a thickness in the range from 0.01 to 0.25 mm and may be made, for example, from mica, polyimide material (such as that sold under the Registered Trade Mark KAPTON), metal (such as 304 stainless steel) or supported graphite (where the graphite is bonded to a steel inner). If desired, that face of the gasket to be in contact with the lower surface 18 of the glass ceramic plate 4 may be coated with a film-form covering material as described above.
The gasket may be secured to the upper surface 24 of the wall 14 with a high temperature adhesive, such as an alkali metal silicate based adhesive.
Claims (82)
1. A wall for an electric heater, the electric heater being adapted to be located beneath a glass-ceramic cooking plate, the wall comprising thermal insulation material incorporating at least one refractory material and adapted to be arranged upstanding in the electric heater, the wall having an upper surface adapted for contacting a region of a lower surface of the glass ceramic cooking plate which is susceptible to abrasion by material of the wall, the upper surface of the wall being provided with a covering of a material which reduces abrasion between the upper surface of the wall and the region of the lower surface of the glass-ceramic cooking plate.
2. A wall as claimed in claim 1, wherein the region of the lower surface of the glass-ceramic cooking plate comprises a coating of a heatresistant material susceptible to abrasion by material of the wall, the upper surface of the wall being adapted for contacting the coating, the covering of the material provided on the upper surface of the wall being substantially non- abrasive to the coating of the heat-resistant material. - 20
3. A wall as claimed in claim 2, wherein the coating of the heatresistant material is in the form of a pattern.
4. A wall as claimed in claim 3, wherein the pattern is visible through the glass-ceramic cooking plate from an upper surface thereof.
5. A wall as claimed in claim 4, wherein the pattern is adapted to define a zone heated by the heater.
6. A wall as claimed in any preceding claim, wherein the upper surface thereof on which the covering of the material is provided is a smoothed upper surface.
7. A wall as claimed in claim 6, wherein the smoothed upper surface thereof extends over edges of the upper surface of the wall.
8. A wall as claimed in claim 6 or 7, wherein the smoothed upper surface thereof is substantially free from undesirably high asperities and loose particulate material.
9. A wall as claimed in any preceding claim, wherein the wall comprises silica and/or vermiculite. - 21
10. A wall as claimed in claim 9, wherein the wall includes fibre reinforcing material
11. A wall as claimed in claim 10, wherein the fibre reinforcing material comprises glass or ceramic fibre material.
12. A wall as claimed in any preceding claim, wherein the covering is provided in the form of a film which serves as a barrier between the upper surface of the wall and the region of the lower surface of the glass-ceramic cooking plate and provides reduced coefficient of friction between the upper surface of the wall and the region of the lower surface of the glass-ceramic cooking plate.
13. A wall as claimed in claim 12, wherein the film comprises a solid lubricant material.
14. A wall as claimed in claim 13, wherein the solid lubricant material is selected from talc (magnesium silicate), molybdenum disulphide, tungsten disulphide, graphite, yttrium oxide, finely dispersed silica, finely dispersed alumina, polytetrafluoroethylene (PTFE) and boron nitride. - 22
15. A wall as claimed in claim 13 or 14, wherein the solid lubricant material fills small irregularities or imperfections in the upper surface of the wall, to form a level surface.
16. A wall as claimed in claim 12, wherein the film is selected from a semi-solid and gel material of polymeric form.
17. A wall as claimed in claim 16, wherein the film serves to fill small irregularities or imperfections in the upper surface of the wall and present a soft, compliant contact surface to the region of the lower surface of the glass-ceramic cooking plate.
18. A wall as claimed in claim 16 or 17, wherein the material of the film is selected from polyvinyl acetate aqueous emulsion, petroleum jelly, silicone grease and a high temperature polymeric organo-silicon compound.
19. A wall as claimed in claim 18, wherein the high temperature polymeric organo-silicon compound comprises a material applicable without requiring chemical transformation. - 23
20. A wall as claimed in claim 19, wherein the material comprises an aqueous-based polysilaxane emulsion.
21. A wall as claimed in claim 18, wherein the high temperature polymeric organo-silicon compound comprises a material adapted to be cured or crosslinked after application to the upper surface of the wall.
22. A wall as claimed in claim 21, wherein the material is selected from RTV silicone, a polysiloxane solution, a polysilane and a silicone resin.
23. A wall as claimed in claim 21 or 22, wherein the material is adapted to be cured or cross-linked by application of heat or ultra-violet radiation.
24. A wall as claimed in any of claims 16 to 23, wherein the film material is such as to at least partially decompose at a subsequent normal operating temperature of the electric heater.
25. A wall as claimed in any preceding claim, wherein the covering material comprises a gasket adapted to be positioned between the upper surface of the wall and the lower surface of the glass ceramic plate substantially along the entire length of the wall. - 24
26. A wall as claimed in claim 25, wherein the gasket has a thickness from 0.01 to 0.25 mm.
27. A wall as claimed in claim 25 or 26, wherein the gasket is made of a material selected from mica, polyimide material, metal and supported graphite.
28. A wall for an electric heater substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
29. An electric heater provided with a wall as claimed in any preceding claim.
30. An assembly comprising a glass-ceramic cooking plate and an electric heater as claimed in claim 29.
31. A process for the production of a wall for an electric heater, the electric heater being adapted to be located beneath a glass-ceramic cooking plate, the wall comprising thermal insulation material incorporating at least one refractory material and adapted to be arranged upstanding in the electric heater, the wall having an upper surface adapted for contacting a region of a lower surface of the glass-ceramic cooking plate which is susceptible to abrasion by material of the wall, the t - 25 process comprising providing the upper surface of the wall with a covering of a material which reduces abrasion between the upper surface of the wall and the region of the lower surface of the glass- ceramic cooking plate.
32. A process as claimed in claim 31, wherein the region of the lower surface of the glass-ceramic cooking plate comprises a coating of a heatresistant material susceptible to abrasion by material of the wall, the upper surface of the wall being adapted for contacting the coating, the covering of the material provided on the upper surface of the wall being substantially non- abrasive to the coating of the heat-resistant material.
33. A process as claimed in claim 32, wherein the coating of the heatresistant material is in the form of a pattern.
34. A process as claimed in claim 33, wherein the pattern is visible through the glass-ceramic cooking plate from an upper surface thereof.
35. A process as claimed in claim 34, wherein the pattern is adapted to define a zone heated by the heater. - 26
36. A process as claimed in any of claims 31 to 35, wherein the upper surface of the wall on which the covering of the material is provided is a smoothed upper surface.
37. A process as claimed in claim 36, wherein the smoothed upper surface of the wall extends over edges of the upper surface of the wall.
38. A process as claimed in claim 36 or 37, wherein the smoothed upper surface of the wall is substantially free from undesirably high asperities and loose particulate material.
39. A process as claimed in claim 36, 37 or 38, wherein the smoothed upper surface of the wall is provided by polishing the upper surface of the wall.
40. A process as claimed in claim 39, wherein the polishing is effected by application of an abrasive means.
41. A process as claimed in claim 40, wherein the abrasive means comprises an abrasive paper of suitably fine grade. - 27
42. A process as claimed in claim 41, wherein the abrasive paper comprises silicon carbide.
43. A process as claimed in claim 40, 41 or 42, wherein the abrasive means is provided in the form of a disc, which is caused to be rotated and pressed against the upper surface of the wall for a predetermined period of time.
44. A process as claimed in claim 43, wherein the predetermined period of time is between about 5 and about seconds.
45. A process as claimed in claim 43 or 44, wherein the rotated disc is presented at a predetermined angle relative to the wall for smoothing edges of the upper surface of the wall.
46. A process as claimed in any of claims 39 to 45, wherein material of the upper surface of the wall removed during polishing is dispersed and/or extracted by vacuum extraction and/or air jet means.
47. A process as claimed in claim 46, wherein the air jet means provides a high velocity air jet. - 28
48. A process as claimed in claim 47, wherein the air jet means comprises an air knife.
49. A process as claimed in claim 39, wherein the upper surface of the wall is blasted with mild abrasive media.
50. A process as claimed in claim 49, wherein the mild abrasive media comprises beads of plastics material.
51. A process as claimed in claim 39, wherein the entire wall is immersed in a bed of vibrating abrasive whippings.
52. A process as claimed in claim 51, wherein the Shippings comprise wood or vermiculite.
53. A process as claimed in claim 39, wherein the upper surface of the wall is burnished by urging the upper surface against a smooth plate which is rotated for a short time.
54. A process as claimed in claim 53, wherein the smooth plate comprises glass or metal.
55. A process as claimed in claim 53 or 54, wherein the smooth plate is rotated for 5 to 30 seconds. - 29
56. A process as claimed in any of claims 31 to 55, wherein the wall comprises silica and/or vermiculite.
57. A process as claimed in claim 56, wherein the wall includes fibre reinforcing material.
58. A process as claimed in claim 57, wherein the fibre reinforcing material comprises glass or ceramic fibre material.
59. A process as claimed in any of claims 31 to 58, wherein the covering of the material with which the upper surface of the wall is provided is provided in the form of a film which serves as a barrier between the upper surface of the wall and the region of the lower surface of the glass-ceramic cooking plate and provides reduced coefficient of friction between the upper surface of the wall and the region of the lower surface of the glass- ceramic cooking plate.
60. A process as claimed in claim 59, wherein the film comprises a solid lubricant material.
61. A process as claimed in claim 60, wherein the solid lubricant material is selected from talc (magnesium silicate), molybdenum disulphide, tungsten disulphide, - 30 - graphite, yttrium oxide, finely dispersed silica, finely dispersed alumina, polytetrafluoroethylene (PTFE) and boron nitride.
62. A process as claimed in claim 60 or 61, wherein the solid lubricant material fills small irregularities or imperfections in the upper surface of the wall, to form a level surface.
63. A process as claimed in claim 60, 61 or 62, wherein the solid lubricant material is applied to the upper surface of the wall by deposition thereto from a rotating mop means impregnated with the solid lubricant material.
64. A process as claimed in claim 60, 61 or 62, wherein the solid lubricant material is provided as an emulsion or colloidal dispersion and applied as a film to the upper surface of the wall by spraying or dipping.
65. A process as claimed in claim 64, wherein the film of the solid lubricant material comprises polytetrafluoroethylene (PTFE), boron nitride or graphite.
66. A process as claimed in claim 59, wherein the film comprises a semisolid or gel material of polymeric form.
- 31 -
67. A process as claimed in claim 66, wherein the film serves to fill small irregularities or imperfections in the upper surface of the wall and present a soft, compliant contact surface to the region of the lower surface of the glass-ceramic cooking plate.
68. A process as claimed in claim 66 or 67, wherein the film material is selected from polyvinyl acetate aqueous emulsion, petroleum jelly, silicone grease and a high temperature polymeric organo-silicon compound.
69. A process as claimed in claim 68, wherein the high temperature polymeric organo-silicon compound comprises a material applicable without requiring chemical transformation.
70. A process as claimed in claim 69, wherein the material comprises an aqueous-based polysiloxane emulsion.
A process as claimed in claim 68, wherein the high temperature polymeric organo-silicon compound comprises a material adapted to be cured or crosslinked after application to the upper surface of the wall. - 32
72. A process as claimed in claim 71, wherein the material is selected from RTV silicone, a polysiloxane solution, a polysilane and a silicone resin.
73. A process as claimed in claim 71 or 72, wherein the material is adapted to be cured or cross-linked by application of heat or ultraviolet radiation.
74. A process as claimed in any of claims 66 to 73, wherein the film of the semi-solid or gel material of polymeric form is applied in the form of a liquid precursor to the upper surface of the wall by spraying.
75. A process as claimed in any of claims 66 to 73, wherein the film of the semi-solid or gel material of polymeric form is applied in that form directly to the upper surface of the wall by smearing.
76. A process as claimed in any of claims 66 to 75, wherein the semisolid or gel material of polymeric form is such as to at least partially decompose at a subsequent normal operating temperature of the electric heater.
77. A process as claimed in any one of claims 31 to 76, wherein the covering of the material with which the upper - 33 surface of the wall is provided comprises a gasket adapted to be positioned between the upper surface of the wall and the lower surface of the glass ceramic plate substantially along the entire extent of the wall.
78. A process as claimed in claim 77, wherein the gasket has a thickness in the range from 0.01 to 0.25 mm.
79. A process as claimed in claim 77 or 78, wherein the gasket is made from mica, polyimide material, metal or supported graphite.
80. A process as claimed in claim 77, 78 or 79, wherein the gasket is secured to the upper surface of the wall with a high temperature adhesive.
81. A process for the production of a wall for an electric heater substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
82. A wall for an electric heater whenever produced by a process as claimed in any of claims 31 to 81.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0325416A GB2407747A (en) | 2003-10-31 | 2003-10-31 | Wall for an electric heater and process for the production thereof |
| JP2004314938A JP4880211B2 (en) | 2003-10-31 | 2004-10-29 | Electric heater wall and glass-ceramic cookware |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0325416A GB2407747A (en) | 2003-10-31 | 2003-10-31 | Wall for an electric heater and process for the production thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0325416D0 GB0325416D0 (en) | 2003-12-03 |
| GB2407747A true GB2407747A (en) | 2005-05-04 |
Family
ID=29725691
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0325416A Withdrawn GB2407747A (en) | 2003-10-31 | 2003-10-31 | Wall for an electric heater and process for the production thereof |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JP4880211B2 (en) |
| GB (1) | GB2407747A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2113927A1 (en) | 2008-04-28 | 2009-11-04 | HEW-KABEL /CDT GmbH & Co. KG | Semiconductive winding tape comprising polytetrafluoroethylene |
| EP2447605A1 (en) * | 2010-10-27 | 2012-05-02 | Electrolux Home Products Corporation N.V. | Heating element and method of manufacturing a base body of a heating element |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5147213B2 (en) * | 2006-10-11 | 2013-02-20 | 日立オートモティブシステムズ株式会社 | Inductance type rotation angle detection device and motor drive type throttle valve control device having the same |
| CN106322457B (en) * | 2016-09-09 | 2018-10-23 | 深圳拓邦股份有限公司 | A kind of electromagnetic stove |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5223697A (en) * | 1990-12-11 | 1993-06-29 | E.G.O. Elektro-Gerate Blanc U. Fischer | Electric radiant heater |
| DE10004176A1 (en) * | 2000-02-01 | 2001-08-02 | Ego Elektro Geraetebau Gmbh | Electrical heating element has negative temperature coefficient of electrical resistance over operating temperature range; heating element contains silicon, preferably silicon carbide |
| EP1345473A2 (en) * | 2002-03-15 | 2003-09-17 | Ceramaspeed Limited | Electrical heating assembly for a cooking appliance with temperature sensing means |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0642390B2 (en) * | 1985-01-18 | 1994-06-01 | 松下電器産業株式会社 | Heating cooker |
| GB2301760B (en) * | 1995-06-01 | 1999-09-22 | Ceramaspeed Ltd | Electric heater |
| JP3436291B2 (en) * | 1996-03-05 | 2003-08-11 | 日本電気硝子株式会社 | Cooker top plate |
| GB2324694B (en) * | 1997-04-25 | 2001-03-14 | Ceramaspeed Ltd | Electric heater |
| JP2003106538A (en) * | 2001-09-27 | 2003-04-09 | Sanyo Electric Co Ltd | Heating cooker |
-
2003
- 2003-10-31 GB GB0325416A patent/GB2407747A/en not_active Withdrawn
-
2004
- 2004-10-29 JP JP2004314938A patent/JP4880211B2/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5223697A (en) * | 1990-12-11 | 1993-06-29 | E.G.O. Elektro-Gerate Blanc U. Fischer | Electric radiant heater |
| DE10004176A1 (en) * | 2000-02-01 | 2001-08-02 | Ego Elektro Geraetebau Gmbh | Electrical heating element has negative temperature coefficient of electrical resistance over operating temperature range; heating element contains silicon, preferably silicon carbide |
| EP1345473A2 (en) * | 2002-03-15 | 2003-09-17 | Ceramaspeed Limited | Electrical heating assembly for a cooking appliance with temperature sensing means |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2113927A1 (en) | 2008-04-28 | 2009-11-04 | HEW-KABEL /CDT GmbH & Co. KG | Semiconductive winding tape comprising polytetrafluoroethylene |
| EP2447605A1 (en) * | 2010-10-27 | 2012-05-02 | Electrolux Home Products Corporation N.V. | Heating element and method of manufacturing a base body of a heating element |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0325416D0 (en) | 2003-12-03 |
| JP4880211B2 (en) | 2012-02-22 |
| JP2005164223A (en) | 2005-06-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |