CA2051231A1 - Heating element and a method for manufacturing the same - Google Patents
Heating element and a method for manufacturing the sameInfo
- Publication number
- CA2051231A1 CA2051231A1 CA002051231A CA2051231A CA2051231A1 CA 2051231 A1 CA2051231 A1 CA 2051231A1 CA 002051231 A CA002051231 A CA 002051231A CA 2051231 A CA2051231 A CA 2051231A CA 2051231 A1 CA2051231 A1 CA 2051231A1
- Authority
- CA
- Canada
- Prior art keywords
- layers
- aluminium
- heating element
- nickel
- base
- Prior art date
- Legal status (The legal status 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 status listed.)
- Abandoned
Links
- 238000010438 heat treatment Methods 0.000 title claims abstract description 134
- 238000000034 method Methods 0.000 title claims abstract description 25
- 238000004519 manufacturing process Methods 0.000 title claims description 11
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 80
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 66
- 239000004411 aluminium Substances 0.000 claims abstract description 48
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 48
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 46
- 229910052751 metal Inorganic materials 0.000 claims abstract description 44
- 239000002184 metal Substances 0.000 claims abstract description 44
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 40
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 19
- 239000000956 alloy Substances 0.000 claims abstract description 19
- 229910000545 Nickel–aluminium alloy Inorganic materials 0.000 claims abstract description 14
- 230000001590 oxidative effect Effects 0.000 claims abstract description 13
- 238000005253 cladding Methods 0.000 claims description 15
- 239000005030 aluminium foil Substances 0.000 claims description 14
- 238000005520 cutting process Methods 0.000 claims description 5
- 229910000838 Al alloy Inorganic materials 0.000 claims description 4
- 239000010410 layer Substances 0.000 claims 28
- 230000007797 corrosion Effects 0.000 abstract description 28
- 238000005260 corrosion Methods 0.000 abstract description 28
- 238000010411 cooking Methods 0.000 abstract description 21
- 230000005855 radiation Effects 0.000 abstract description 20
- 235000010210 aluminium Nutrition 0.000 description 29
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 18
- 239000000377 silicon dioxide Substances 0.000 description 9
- 241000251468 Actinopterygii Species 0.000 description 6
- 239000010445 mica Substances 0.000 description 5
- 229910052618 mica group Inorganic materials 0.000 description 5
- 239000010935 stainless steel Substances 0.000 description 5
- 229910001220 stainless steel Inorganic materials 0.000 description 5
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 3
- 239000010953 base metal Substances 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 238000005507 spraying Methods 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 239000003518 caustics Substances 0.000 description 2
- 229910052729 chemical element Inorganic materials 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 238000007747 plating Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 229910001005 Ni3Al Inorganic materials 0.000 description 1
- 229910000943 NiAl Inorganic materials 0.000 description 1
- NPXOKRUENSOPAO-UHFFFAOYSA-N Raney nickel Chemical compound [Al].[Ni] NPXOKRUENSOPAO-UHFFFAOYSA-N 0.000 description 1
- -1 SUS 430 Chemical compound 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
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
- H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
- H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
- H05B3/28—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor embedded in insulating material
- H05B3/30—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor embedded in insulating material on or between metallic plates
-
- 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
- H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
-
- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47D—FURNITURE SPECIALLY ADAPTED FOR CHILDREN
- A47D13/00—Other nursery furniture
- A47D13/02—Baby-carriers; Carry-cots
- A47D13/025—Baby-carriers; Carry-cots for carrying children in seated position
-
- 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
- H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
- H05B3/12—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
Landscapes
- Resistance Heating (AREA)
- Cookers (AREA)
- Surface Heating Bodies (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A heating element for a cooking apparatus or a heating apparatus is manufactured by forming alumini-um layers on a nickel or nickel-base alloy base or forming nickel layers and then aluminium layers on a metal base, and by oxidizing the aluminium layers into an aluminium oxide layers. At the oxidizing step, nickel-aluminium alloy layers with high corrosion resistance are also produced. Only aluminium layers, not nickel layers, may be formed on a metal base and oxidized into aluminium oxide layers to obtain a heat-ing element with relatively low but practical corrosion resistance. The resultant heating element by any of the above processes which does not require a cover or other protection against corrosion is formed into a sheet and heated to provide radiation of about 800°C.
A heating element for a cooking apparatus or a heating apparatus is manufactured by forming alumini-um layers on a nickel or nickel-base alloy base or forming nickel layers and then aluminium layers on a metal base, and by oxidizing the aluminium layers into an aluminium oxide layers. At the oxidizing step, nickel-aluminium alloy layers with high corrosion resistance are also produced. Only aluminium layers, not nickel layers, may be formed on a metal base and oxidized into aluminium oxide layers to obtain a heat-ing element with relatively low but practical corrosion resistance. The resultant heating element by any of the above processes which does not require a cover or other protection against corrosion is formed into a sheet and heated to provide radiation of about 800°C.
Description
p9021 BACXGROUND OF THE INVENTION
1. Field of the Invention:
The present invention relates to a heating element used for a cooking apparatus and a heating apparatus at temperatures of around 800C, and a method for manufacturing the same.
1. Field of the Invention:
The present invention relates to a heating element used for a cooking apparatus and a heating apparatus at temperatures of around 800C, and a method for manufacturing the same.
2. Description of the Prior Art:
As a heating element for a cooking apparatus and a heating apparatus, a silica tube heater has been conventionally used. A sheath heater and a "mica heater" where a heating wire is wound around a mica strip have also been used for a cooking apparatus.
However, the above conventional heating elements have problems as follows.
In the case of the siliaa tube heater where a heating wire wound in a toroidal shape is inserted into a silica tube, when the heater is used for cooking, for example, substances such as salt spattered from an ob~ect to be cooked may attach to the surface of the silica tube. As a result, the silica tube is likely to ~e devitrified, failing to provide a sufficient amount of extreme infrared radiation required for cooking, or the silica tube may even become broken. Thus, only a temperature of 700C at highest is obtained from this heater. Further, it is difficult to form the silica tube heater into a sheet due to the structure thereof.
In the case of the sheath heater where a heating wire is covered with a thermal resistant and corrosive resistant stainless steel plate, when used for cooking, the heater utilizes secondary radiation from the stainless steel sheath. This structure re-quires a longer time until a predetermined temperature is attained. Further, in order to obtain the radiation of 800C, the temperature of the heating wire itself must be more than 800C, which will shorten the life of the heating wire. Moreover, as in the case of the silica tube heater, it is difficult to form the sheath heater into a sheet due to the structure thereof.
The mica heater can easily be formed into a sheet. However, since the heater is installed through an insulation on the outer surface of the wall of a cooking apparatus, heat conduction is not effective.
Therefore, a longer time is reguired until a predeter-mined temperature is attained on the inner surface of wall of the cooking apparatus from which heat is radi-ated for cooking, and also it is difficult to obtain the radiation of a high temperature of about 800C.
To overcome the above-described problems, a bare metal heating element made of iron-chrome-alumini-um, nickel-chrome or iron-nickel-chrome can be used to serve as a heating element which can be formed into a 8heet and which can be rapidly and easily heated to provide radiation of 800C suitable for a cooking apparatus and a heating apparatus.
The bare metal heating element is highly thermal resistant and will not be damaged when exposed in an atmosphere of high temperature. However, when used for a cooking apparatus, corrosive substances such as salt spattered from an object to be cooked may attach to the metal heating element. If such a contam-inated metal heating element is used under the condi-tion of a temperature as high as 800C, it will easily be corroded and damaged. The structures of the afore-mentioned heating elements had originally been de-veloped to prevent such corrosion.
The objective of the present invention is to provide a heating element which is not only highly corrosive resistant at high temperature, but also can be formed into a sheet, and can be rapidly and easily heated to provide heat radiation of about 800C.
SUMMARY OF THE INVENTION
The heating element of this invention, which overcomes the above-discussed and numerous other disad-vantages and deficiencies of the prior art, comprises a metal base having nickel-aluminium alloy layers formed on the top and bottom surfaces thereof.
In a preferred embodiment, the nickel-alum1nium alloy layers are covered with aluminium oxide layers.
In another preferred embodiment, the metal base is nickel or a nickel-base alloy.
In still another preferred embodiment, the nlckel content in the nickel-base alloy is at least 50%.
Alternatively, the heating element of this invention comprises a metal base having nickel layers and aluminium oxide layers formed in this order on the top and bottom surfaces thereof.
Alternatively, the heating element of this invention comprises a metal base and aluminium oxide layers, the aluminium oxide layers being obtained by first forming aluminium layers or aluminium alloy layers on the top and bottom surfaces of the metal base and by oxidizing the same.
In a preferred embodiment, the aluminium layers or the aluminium alloy layers are formed by cladding.
According to another aspect of the present invention, the method for manufacturing a heating element comprises the steps of forming aluminium layers on the top and bottom surfaces of a nickel or nickel-base alloy base, and oxidizing the aluminium layers into aluminium oxide layers.
In a preferred embodiment, the aluminium layers are formed by cladding the nickel or nickel-base alloy base with aluminium foils on both surfaces there-of, In another preferred embodiment, the method further comprises the step of cutting the nickel or nickel-base alloy base clad with the aluminium foils to a predetermined shape between the step of forming the aluminium layers and the step of oxidizing the alumini-um layers.
In still another preferred embodiment, the aluminium foils are wider than the nickel or nickel-base alloy base.
In still another preferred embodiment, the nickel content in the nickel-base alloy base is at least 50%.
Alternatively, the method of this invention comprises the steps of forming nickel layers on the top and bottom surfaces of a metal base, forming aluminium layers on the nickel layers, and oxidizing the alumini-um layers into aluminium oxide layers.
In a preferred embodiment, the nickel layers and the aluminium layers are formed by cladding.
In another preferred embodiment, the method further comprises the step of cutting the metal base clad with the nickel layers and the aluminium layers to a predetermined shape between the step of forming the aluminium layers and the step of oxidizing the alumini-um layers.
According to the structure of the present invention, the heating element is provided wlth alumin-lum oxlde layers whlch are highly corrosive resistant, and when especially high corrosion resistance is re-quired, with nickel-aluminium alloy layers on the top and bottom surfaces thereof.
~ 6 --The heating element of the present invention with high corrosion resistance at high temperature can be used in a bare form without the necessity of provid-ing a sheath, as required in the conventional heating elements, to protect against, for example, attachment of corrosive substances spattered from an ob;ect to be cooked. Further, the heating element without a sheath can easily be formed into a sheet heating element by stamping it into a desired pattern or the like. Also, since the specific heat of the heating element of the present invention can be small without an extra thick-ness for a sheath, the heating element can rapidly be heated to a high temperature of, for example, 800C, and thereby radiation of high temperature is easily obtained.
Thus, the present invention makes possible the obJective of providing a heating element which can be formed into a sheet and which can be rapidly heated 80 as to provide radiation of high temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
This invention may be better understood and its numerous obJects and advantages will become appar-ent to those skilled in the art by reference to the accompanying drawings as follows:
Figure 1 is a sectional view of a heating element of the present invention;
Figure 2 is a sectional view showing a pre-treated state of the heating element of Figure l;
Figure 3 is a chart showing the relationship between the nickel content and the corrosion resistance of the heating element of Figure 1;
Figure 4 is a schematic sectional view of a cooking apparatus using the heating element of Fig-ure l;
Figure 5 is a sheet heating element of the present invention stamped into a meander shape;
Figure 6 is a sectional view of another heating element of the present invention; and Figure 7 is a sectional view showing a pre-treated state of the heating element of Figure 6.
DESCRIPTION OF T~E PREFERRED EMBODIMENT
Example 1 Referring to Figure 1, a heating element 1 comprises a metal base 2 made of nickel or a nickel-base alloy having aluminium oxide layers 3 and nickel-aluminium alloy layers 4 formed in this order on the top and bottom surfaces thereof.
The heating element 1 of the above structure is formed by the follo~ing procedure.
As shown in Figure 2, aluminium layers 5 are formed on both surfaces of the metal base 2 by spray-ing, plating, evaporation, spattering, cladding or any other appropriate method. When spraying or cladding is employed, a thicker layer is comparatively easily obtained. ~specially, by cladding where an aluminium foil is rolled on and tightly attached to a heating element, an aluminium layer which is free from pinholes can be formed. Then, the aluminium layers 5 are oxi-dized into the aluminium oxide layers 3 with high corrosion resistance. The aluminium layers 5 can be oxidized by various methods such as anodic oxidation.
Most practically, i~ is heated at high temperature in the atmosphere. When this method is employed, the nickel-aluminium alloy layers 4 which are also highly corrosive rssistant can easily be formed between the metal base 2 and the aluminium oxide layers 3, thereby providing the resultant heating element with the property of high corrosion resistance.
A heating element of the above structure was manufactured to assess the corrosion resistance as follows.
A nickel or an alloy containing a varying content of nickel (chrome content: 21 + 2%) was used as the metal base 2. Then, the metal base 2 was clad with aluminlum foils on both surfaces thereof. The result-ant aluminlum-clad base was cut into a size required, and then heated at 900C in the atmosphere for five hours so as to produce the aluminum oxide layers 3 on both surfaces thereof. In this way, the heating ele-ment 1 having a width of 6 mm and a thickness of 50 ,u was obtained. Electricity was applied to the heating element 1 to raise the temperature of the surfaces thereof to 800C. Under this condition, a 5% saline solution was dropped by 0.5 cc to the heating element 1 _ g _ every two minutes, and the number of drops applied until the heating element 1 was corroded and cut apart was used to determine the level of the corrosion re-sistance of the heating element 1. This test was performed for ten samples, of which results are shown in Figure 3.
~ In Figure 3, each two-direction arrow shows the range of the numbers of drops counted for the samples of each nickel content, and each mark shows the average thereof. Each mark X shows a result ob-tained from a sample of the metal base without cladding of an aluminium foil. As is apparent from this figure, the corrosion resistance sharply increases when the nickel content exceeds 50%. This is because, with such a high nickel content, the corrosive resistant nickel-aluminium alloy layers 4 were further formed between the metal base 2 and the aluminium oxide layers 3.
This formation was confirmed by analyzing the heating element 1 by an X-ray diffraction method, where NiAl and Ni3Al were detected.
In the above heating element 1, the aluminium layers 5 were formed on the top and the bottom surfaces of the metal base 2, but not on the side faces thereof (in the direction of the thickness thereof). However, after the heat treatment, the formation of the nickel-aluminium alloy layer 4 was also observed on the side faces. Thls is probably because burrs of the aluminium folls produced at the aforementioned cutting process after the cladding of the aluminium foils were spread onto the side faces of the metal base 2. Further, in the corrosion resistance test, most of the sample heating elements were finally cut apart by corrosion in the portions except the cut side ends thereof, which shows that the cut side ends are not especially inferi-or in corrosion resistance.
When the base metal clad with the aluminium foils is not cut to a size of the heating element, but uséd as lt is as a heating element, the aluminium foils can be slightly wider than the metal base, so that the nickel-aluminium alloy layer can also be formed on the side faces of the base metal as in the case described above.
From the result of the aforementioned test, it is proved that the method of the present invention slgnificantly improves the corrosion resistance of the resultant heating element.
Next, an application of the above-described heating element 1 to a cooking apparatus will be de-scribed as follows.
Figure 4 shows a microwave oven 6 which has a structure of a sheet heating element 7 comprising the heatlng element 1 of the lnvention being disposed on support members 9 placed on a microwave shielding plate 8. A control panel and other components of the microwave oven 6 not directly relating to this inven-tlon are not shown in the flgure for simplicity.
The microwave shielding plate 8 is made of a corrosive resistant stainless steel plate having a number of bores of a diameter of about 3 mm so that the total area of the bores should occupy about 60~ of the total area of the plate. The microwave shielding plate 8 has two functions; shielding the sheet heating element 7 from receiving microwave radiated during m$crowave cooking and passing radiation from the heat-ing element directly onto an ob;ect to be cooked during heat cooking.
/
A nickel-chrome strip (NCHRWl) for heating was used as the metal base 2, which was clad with aluminium foils on both surfaces thereof. Then, the resultant strip was stamped into a meander shape and heated at 900C in the atmosphere for five hours to produce the sheet heating element 7 having an output of 1.2 KW. When a rated voltage of 100 V was applied to the heating element 7, the temperature of the heating element reached 700C in about one minute, and further rose to 800C in three minutes.
An ob~ect to be cooked, for example, a fish, was put in an oven chamber 10 for heat cooking. The fish was uniformly broiled under the radiation of 800C
for fifteen minutes. When a conventional sheet heating element, for example the mica heater, was employed to broil the fish, 25 minutes were required. Further, in any of the mica heater, the sheath heater and the sillca tube heater, uniform browning as attained in the heatlng element of the invention was not possible.
As described above, the sheet heating ele-ment 7 of the invention effects uniform browning over the ob~ect to be cooked, because the heating element 7 is formed as a sheet and the radiation from the sheet heating element 7 to the ob;ect is intensive. That is, since the radiation is sent in the direction vertical to the surface of the heating element 7, in the case of a strip heating element as shown in Figure 5, the radiation ls theoretically sent only to an area right below the width A of the heating element 7. (The radiation in the horizontal direction along the heating element is not counted in this case since the thickness of the heating element is negligibly small compared with the width thereof.) Actually, however, the radia-tion is somewhat diffused since the surface of the heating element is uneven, which as a result, enables the uniform browning of the object to be cooked. Thus, in the case of a strip heating element, radiation is more intensive in the direction vertical to the heating element, and therefore effective heating can be accom-plished by placing the ob~ect to be cooked in this direction.
In the case of the sheath heater or the silica heater where a heating element with a sheath is round in section, heat is radiated to every direction in the space. Therefore, the amount of radiation reaching the ob~ect to be cooked is small, that is, the heating efficiency is low when the sheath heater or the silica heater is used compared with when the strip heating element is used, under the condition that both heating elements have the same output and the same temperature of radiation.
In the above-described structure of the mlcrowave oven 6, salt or other substances spattered from an ob~ect to be cooked may attach to the surface of the heating element 7. However, this will not cause any practical problem for the heating element 7 of the invention because it is highly corrosive resistant.
The corrosion resistance of the heating element 7 was tested by repeating a cycle of alternating the micro-wave cooking of a 5~ saline solution and the heat cooking of a fish. The result was that the heating element 7 of the invention had been little damaged after 500 cycles, while a sheet heating element made of the nickel-chrome strip stamped without the treatment according to the invention had been corroded and dam-aged after 60 cycles.
From the above results, it was found that the heating element of this example had high corrosion reslstance and was little deteriorated after a long period of usage.
Example 2 Another example of the present invention will be described with reference to Figures 6 and 7 as follows.
Referring to Figure 6, a heating element 11 comprises a metal base 12 having nickel-base layers 13 and alumlnium oxide layers 14 formed in this order on the top and bottom surfaces thereof. The metal base 12 i8 made of iron-chrome, iron-chrome-aluminium or stain-less steel such as SUS 430, SUS 430A or SUS 444.
The heating element 11 of the above structure is formed in the following procedure. First nickel layers 15 and then aluminium layers 16 are formed on both surfaces of the metal base 12 by spraying, plat-ing, evaporation, spattering, cladding or any other suitable method, as described in Example 1. Then, the aluminium layers 16 are oxidized into the aluminium oxide layers 14 most practically by heating at high temperature in the atmosphere. At the same time, layers of the nickel-aluminium alloy can be formed, as described in Example 1. The nickel-aluminium alloy layers can be sufficiently formed by heating at 500 to 700C in an environment of an inactive gas, not in the atmosphere, and then heating at a temperature of 800C
or higher in the atmosphere. The nickel-base layers 13 of this example are the nickel layers 15 wholly or partly changed to the nickel-aluminium alloy. The aluminium layers 16 should be completely oxidized because, during the use of the heating element, any unoxidized aluminium which is conductive remaining in the heating element is exposed to high temperature and oxidized into aluminium oxide which is insulating, causing a gradual increase of resistance of the heating element.
The heating element of the above structure was manufactured to assess the corrosion resistance as follows.
First, the metal base 12 mad~ of iron-chrome (FCHRWl) was clad with nickel foils and then aluminium folls on both surfaces thereof. The total thickness of the clad base was 50 ,u with 42 ~ for the metal base 12, 4 ~ for the two nickel layers and 4 ,u for the two aluminium layers, and the width thereof was 6 mm. The clad base was then heated at 900C in the atmosphere for five hours so as to produce the aluminum oxide layers 14 on both surfaces. The formation of the nickel-aluminium alloy layers between the metal base 12 and the aluminium oxide layers 14 was confirmed by an X-ray diffraction method. Electricity was applied to the thus obtained heating element 11 to raise the surface temperature thereof to 800C.
/
The same corrosion resistance test as that in Example 1 was performed. As a result, the number of drops applied to the above heating element 11 until it was corroded and cut apart was 80. The same test was also performed on the following three comparative samples; a heating element made of iron-chrome and heated at 900C in the atmosphere for five hours, a heating element made of SUS 430 and SUS 444 on which the same steps of cladding of nickel and aluminium and of thermally oxidizing the aluminium as in Example 2 were performed, and a heating element made of the same material as the above on which the step of cladding of nickel and aluminium was not performed but the step of heating was performed. The results were 10, 80, and 10, respectively. These results indicate that the corrosion resistance at high temperature shown in the heating element of this invention is irrespective of the type of the base metal.
Next, an application of the above-described heating element 11 to the microwave oven 6 shown in Figure 4 will be described as follows.
An iron-chrome strip (FCHRW1) for heating was used as the metal base 12, which was clad with nickel foils and aluminium foils on both surfaces thereof.
Then, the resultant strip was stamped into a meander shape and heated at 900C in the atmosphere for five hours to produce a sheet heating element 7' having an output of 1.2 KW. When a rated voltage of 100 V was applied to the heating element 7', the temperature of the heat$ng element reached 700C in about one minute, anq further rose to 800C in three minutes. An object to be cooked, for example, a fish, was put in the oven chamber 10 for heat cooking. The fish was broiled with uniform browning under the radiation of 800C for fifteen minutes.
The same corrosion resistance test as in Example 1 was performed on the microwave oven compris-ing the sheet heating element 7' of this example, and the same favorable results as in Example 1 were ob-tained.
From the above results, it was found that the heating element of this example had high corrosion resistance and was little deteriorated after a long period of usage.
In the aforementioned examples, the strip-shaped metal base was used. However, the metal base applicable to the present invention is not limited to the strip shape, but a linear metal base can also be used to obtain the same high corrosion resistance when the structure and the method of the present invention is applied thereto.
Example 3 In this example, a metal base made of iron-chrome, iron-chrome-aluminium or stainless steel such as SUS 430, SUS 430A or SUS 444 was used. On the top 5and bottom sur$aces of the metal base were formed aluminium layers in the same manner as shown in Exam-ple 1. The aluminlum layers were then oxidized into aluminium oxide layers in the same manner as shown in Example 1. The same test as in Example 1, that is, lOdropping a 5% saline solution was performed on the resultant heating element, and the result was 20 drops until the heating element was corroded and cut apart, indicating that the corrosion resistance of the heating element of this example was about twice as high as that 15of a heating element lacking an aluminium oxide layer.
It was also found that when the aluminium layers were formed by cladding of aluminium foils on the metal base as in Examples 1 and 2, the resultant 20heating element showed stable results in the corrosion resistance test.
The heating element obtained in this example was formed into a sheet heating element in the same 25manner as in Example 1 for the application to a micro-wave oven, and the same test as in Example 1 was per-formed. After 500 cycles, some small corrosion was observed on the surface of the heating element, but such corrosion did not cause lnferiority in the cooking 30ability nor any other practical problems.
In the above examples, the aluminium layer was formed and oxidized in order to obtain the alumini-um oxide layer. It should be appreciated that an aluminium-base alloy can also be used instead of alu-minium to attain the above objective.
It is understood that various other modifica-tions will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be construed as encompassing all the features of patentable novelty that reside in the present invention, including all features that would be treated as equivalents thereof by those skilled in the art to which this invention pertains.
As a heating element for a cooking apparatus and a heating apparatus, a silica tube heater has been conventionally used. A sheath heater and a "mica heater" where a heating wire is wound around a mica strip have also been used for a cooking apparatus.
However, the above conventional heating elements have problems as follows.
In the case of the siliaa tube heater where a heating wire wound in a toroidal shape is inserted into a silica tube, when the heater is used for cooking, for example, substances such as salt spattered from an ob~ect to be cooked may attach to the surface of the silica tube. As a result, the silica tube is likely to ~e devitrified, failing to provide a sufficient amount of extreme infrared radiation required for cooking, or the silica tube may even become broken. Thus, only a temperature of 700C at highest is obtained from this heater. Further, it is difficult to form the silica tube heater into a sheet due to the structure thereof.
In the case of the sheath heater where a heating wire is covered with a thermal resistant and corrosive resistant stainless steel plate, when used for cooking, the heater utilizes secondary radiation from the stainless steel sheath. This structure re-quires a longer time until a predetermined temperature is attained. Further, in order to obtain the radiation of 800C, the temperature of the heating wire itself must be more than 800C, which will shorten the life of the heating wire. Moreover, as in the case of the silica tube heater, it is difficult to form the sheath heater into a sheet due to the structure thereof.
The mica heater can easily be formed into a sheet. However, since the heater is installed through an insulation on the outer surface of the wall of a cooking apparatus, heat conduction is not effective.
Therefore, a longer time is reguired until a predeter-mined temperature is attained on the inner surface of wall of the cooking apparatus from which heat is radi-ated for cooking, and also it is difficult to obtain the radiation of a high temperature of about 800C.
To overcome the above-described problems, a bare metal heating element made of iron-chrome-alumini-um, nickel-chrome or iron-nickel-chrome can be used to serve as a heating element which can be formed into a 8heet and which can be rapidly and easily heated to provide radiation of 800C suitable for a cooking apparatus and a heating apparatus.
The bare metal heating element is highly thermal resistant and will not be damaged when exposed in an atmosphere of high temperature. However, when used for a cooking apparatus, corrosive substances such as salt spattered from an object to be cooked may attach to the metal heating element. If such a contam-inated metal heating element is used under the condi-tion of a temperature as high as 800C, it will easily be corroded and damaged. The structures of the afore-mentioned heating elements had originally been de-veloped to prevent such corrosion.
The objective of the present invention is to provide a heating element which is not only highly corrosive resistant at high temperature, but also can be formed into a sheet, and can be rapidly and easily heated to provide heat radiation of about 800C.
SUMMARY OF THE INVENTION
The heating element of this invention, which overcomes the above-discussed and numerous other disad-vantages and deficiencies of the prior art, comprises a metal base having nickel-aluminium alloy layers formed on the top and bottom surfaces thereof.
In a preferred embodiment, the nickel-alum1nium alloy layers are covered with aluminium oxide layers.
In another preferred embodiment, the metal base is nickel or a nickel-base alloy.
In still another preferred embodiment, the nlckel content in the nickel-base alloy is at least 50%.
Alternatively, the heating element of this invention comprises a metal base having nickel layers and aluminium oxide layers formed in this order on the top and bottom surfaces thereof.
Alternatively, the heating element of this invention comprises a metal base and aluminium oxide layers, the aluminium oxide layers being obtained by first forming aluminium layers or aluminium alloy layers on the top and bottom surfaces of the metal base and by oxidizing the same.
In a preferred embodiment, the aluminium layers or the aluminium alloy layers are formed by cladding.
According to another aspect of the present invention, the method for manufacturing a heating element comprises the steps of forming aluminium layers on the top and bottom surfaces of a nickel or nickel-base alloy base, and oxidizing the aluminium layers into aluminium oxide layers.
In a preferred embodiment, the aluminium layers are formed by cladding the nickel or nickel-base alloy base with aluminium foils on both surfaces there-of, In another preferred embodiment, the method further comprises the step of cutting the nickel or nickel-base alloy base clad with the aluminium foils to a predetermined shape between the step of forming the aluminium layers and the step of oxidizing the alumini-um layers.
In still another preferred embodiment, the aluminium foils are wider than the nickel or nickel-base alloy base.
In still another preferred embodiment, the nickel content in the nickel-base alloy base is at least 50%.
Alternatively, the method of this invention comprises the steps of forming nickel layers on the top and bottom surfaces of a metal base, forming aluminium layers on the nickel layers, and oxidizing the alumini-um layers into aluminium oxide layers.
In a preferred embodiment, the nickel layers and the aluminium layers are formed by cladding.
In another preferred embodiment, the method further comprises the step of cutting the metal base clad with the nickel layers and the aluminium layers to a predetermined shape between the step of forming the aluminium layers and the step of oxidizing the alumini-um layers.
According to the structure of the present invention, the heating element is provided wlth alumin-lum oxlde layers whlch are highly corrosive resistant, and when especially high corrosion resistance is re-quired, with nickel-aluminium alloy layers on the top and bottom surfaces thereof.
~ 6 --The heating element of the present invention with high corrosion resistance at high temperature can be used in a bare form without the necessity of provid-ing a sheath, as required in the conventional heating elements, to protect against, for example, attachment of corrosive substances spattered from an ob;ect to be cooked. Further, the heating element without a sheath can easily be formed into a sheet heating element by stamping it into a desired pattern or the like. Also, since the specific heat of the heating element of the present invention can be small without an extra thick-ness for a sheath, the heating element can rapidly be heated to a high temperature of, for example, 800C, and thereby radiation of high temperature is easily obtained.
Thus, the present invention makes possible the obJective of providing a heating element which can be formed into a sheet and which can be rapidly heated 80 as to provide radiation of high temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
This invention may be better understood and its numerous obJects and advantages will become appar-ent to those skilled in the art by reference to the accompanying drawings as follows:
Figure 1 is a sectional view of a heating element of the present invention;
Figure 2 is a sectional view showing a pre-treated state of the heating element of Figure l;
Figure 3 is a chart showing the relationship between the nickel content and the corrosion resistance of the heating element of Figure 1;
Figure 4 is a schematic sectional view of a cooking apparatus using the heating element of Fig-ure l;
Figure 5 is a sheet heating element of the present invention stamped into a meander shape;
Figure 6 is a sectional view of another heating element of the present invention; and Figure 7 is a sectional view showing a pre-treated state of the heating element of Figure 6.
DESCRIPTION OF T~E PREFERRED EMBODIMENT
Example 1 Referring to Figure 1, a heating element 1 comprises a metal base 2 made of nickel or a nickel-base alloy having aluminium oxide layers 3 and nickel-aluminium alloy layers 4 formed in this order on the top and bottom surfaces thereof.
The heating element 1 of the above structure is formed by the follo~ing procedure.
As shown in Figure 2, aluminium layers 5 are formed on both surfaces of the metal base 2 by spray-ing, plating, evaporation, spattering, cladding or any other appropriate method. When spraying or cladding is employed, a thicker layer is comparatively easily obtained. ~specially, by cladding where an aluminium foil is rolled on and tightly attached to a heating element, an aluminium layer which is free from pinholes can be formed. Then, the aluminium layers 5 are oxi-dized into the aluminium oxide layers 3 with high corrosion resistance. The aluminium layers 5 can be oxidized by various methods such as anodic oxidation.
Most practically, i~ is heated at high temperature in the atmosphere. When this method is employed, the nickel-aluminium alloy layers 4 which are also highly corrosive rssistant can easily be formed between the metal base 2 and the aluminium oxide layers 3, thereby providing the resultant heating element with the property of high corrosion resistance.
A heating element of the above structure was manufactured to assess the corrosion resistance as follows.
A nickel or an alloy containing a varying content of nickel (chrome content: 21 + 2%) was used as the metal base 2. Then, the metal base 2 was clad with aluminlum foils on both surfaces thereof. The result-ant aluminlum-clad base was cut into a size required, and then heated at 900C in the atmosphere for five hours so as to produce the aluminum oxide layers 3 on both surfaces thereof. In this way, the heating ele-ment 1 having a width of 6 mm and a thickness of 50 ,u was obtained. Electricity was applied to the heating element 1 to raise the temperature of the surfaces thereof to 800C. Under this condition, a 5% saline solution was dropped by 0.5 cc to the heating element 1 _ g _ every two minutes, and the number of drops applied until the heating element 1 was corroded and cut apart was used to determine the level of the corrosion re-sistance of the heating element 1. This test was performed for ten samples, of which results are shown in Figure 3.
~ In Figure 3, each two-direction arrow shows the range of the numbers of drops counted for the samples of each nickel content, and each mark shows the average thereof. Each mark X shows a result ob-tained from a sample of the metal base without cladding of an aluminium foil. As is apparent from this figure, the corrosion resistance sharply increases when the nickel content exceeds 50%. This is because, with such a high nickel content, the corrosive resistant nickel-aluminium alloy layers 4 were further formed between the metal base 2 and the aluminium oxide layers 3.
This formation was confirmed by analyzing the heating element 1 by an X-ray diffraction method, where NiAl and Ni3Al were detected.
In the above heating element 1, the aluminium layers 5 were formed on the top and the bottom surfaces of the metal base 2, but not on the side faces thereof (in the direction of the thickness thereof). However, after the heat treatment, the formation of the nickel-aluminium alloy layer 4 was also observed on the side faces. Thls is probably because burrs of the aluminium folls produced at the aforementioned cutting process after the cladding of the aluminium foils were spread onto the side faces of the metal base 2. Further, in the corrosion resistance test, most of the sample heating elements were finally cut apart by corrosion in the portions except the cut side ends thereof, which shows that the cut side ends are not especially inferi-or in corrosion resistance.
When the base metal clad with the aluminium foils is not cut to a size of the heating element, but uséd as lt is as a heating element, the aluminium foils can be slightly wider than the metal base, so that the nickel-aluminium alloy layer can also be formed on the side faces of the base metal as in the case described above.
From the result of the aforementioned test, it is proved that the method of the present invention slgnificantly improves the corrosion resistance of the resultant heating element.
Next, an application of the above-described heating element 1 to a cooking apparatus will be de-scribed as follows.
Figure 4 shows a microwave oven 6 which has a structure of a sheet heating element 7 comprising the heatlng element 1 of the lnvention being disposed on support members 9 placed on a microwave shielding plate 8. A control panel and other components of the microwave oven 6 not directly relating to this inven-tlon are not shown in the flgure for simplicity.
The microwave shielding plate 8 is made of a corrosive resistant stainless steel plate having a number of bores of a diameter of about 3 mm so that the total area of the bores should occupy about 60~ of the total area of the plate. The microwave shielding plate 8 has two functions; shielding the sheet heating element 7 from receiving microwave radiated during m$crowave cooking and passing radiation from the heat-ing element directly onto an ob;ect to be cooked during heat cooking.
/
A nickel-chrome strip (NCHRWl) for heating was used as the metal base 2, which was clad with aluminium foils on both surfaces thereof. Then, the resultant strip was stamped into a meander shape and heated at 900C in the atmosphere for five hours to produce the sheet heating element 7 having an output of 1.2 KW. When a rated voltage of 100 V was applied to the heating element 7, the temperature of the heating element reached 700C in about one minute, and further rose to 800C in three minutes.
An ob~ect to be cooked, for example, a fish, was put in an oven chamber 10 for heat cooking. The fish was uniformly broiled under the radiation of 800C
for fifteen minutes. When a conventional sheet heating element, for example the mica heater, was employed to broil the fish, 25 minutes were required. Further, in any of the mica heater, the sheath heater and the sillca tube heater, uniform browning as attained in the heatlng element of the invention was not possible.
As described above, the sheet heating ele-ment 7 of the invention effects uniform browning over the ob~ect to be cooked, because the heating element 7 is formed as a sheet and the radiation from the sheet heating element 7 to the ob;ect is intensive. That is, since the radiation is sent in the direction vertical to the surface of the heating element 7, in the case of a strip heating element as shown in Figure 5, the radiation ls theoretically sent only to an area right below the width A of the heating element 7. (The radiation in the horizontal direction along the heating element is not counted in this case since the thickness of the heating element is negligibly small compared with the width thereof.) Actually, however, the radia-tion is somewhat diffused since the surface of the heating element is uneven, which as a result, enables the uniform browning of the object to be cooked. Thus, in the case of a strip heating element, radiation is more intensive in the direction vertical to the heating element, and therefore effective heating can be accom-plished by placing the ob~ect to be cooked in this direction.
In the case of the sheath heater or the silica heater where a heating element with a sheath is round in section, heat is radiated to every direction in the space. Therefore, the amount of radiation reaching the ob~ect to be cooked is small, that is, the heating efficiency is low when the sheath heater or the silica heater is used compared with when the strip heating element is used, under the condition that both heating elements have the same output and the same temperature of radiation.
In the above-described structure of the mlcrowave oven 6, salt or other substances spattered from an ob~ect to be cooked may attach to the surface of the heating element 7. However, this will not cause any practical problem for the heating element 7 of the invention because it is highly corrosive resistant.
The corrosion resistance of the heating element 7 was tested by repeating a cycle of alternating the micro-wave cooking of a 5~ saline solution and the heat cooking of a fish. The result was that the heating element 7 of the invention had been little damaged after 500 cycles, while a sheet heating element made of the nickel-chrome strip stamped without the treatment according to the invention had been corroded and dam-aged after 60 cycles.
From the above results, it was found that the heating element of this example had high corrosion reslstance and was little deteriorated after a long period of usage.
Example 2 Another example of the present invention will be described with reference to Figures 6 and 7 as follows.
Referring to Figure 6, a heating element 11 comprises a metal base 12 having nickel-base layers 13 and alumlnium oxide layers 14 formed in this order on the top and bottom surfaces thereof. The metal base 12 i8 made of iron-chrome, iron-chrome-aluminium or stain-less steel such as SUS 430, SUS 430A or SUS 444.
The heating element 11 of the above structure is formed in the following procedure. First nickel layers 15 and then aluminium layers 16 are formed on both surfaces of the metal base 12 by spraying, plat-ing, evaporation, spattering, cladding or any other suitable method, as described in Example 1. Then, the aluminium layers 16 are oxidized into the aluminium oxide layers 14 most practically by heating at high temperature in the atmosphere. At the same time, layers of the nickel-aluminium alloy can be formed, as described in Example 1. The nickel-aluminium alloy layers can be sufficiently formed by heating at 500 to 700C in an environment of an inactive gas, not in the atmosphere, and then heating at a temperature of 800C
or higher in the atmosphere. The nickel-base layers 13 of this example are the nickel layers 15 wholly or partly changed to the nickel-aluminium alloy. The aluminium layers 16 should be completely oxidized because, during the use of the heating element, any unoxidized aluminium which is conductive remaining in the heating element is exposed to high temperature and oxidized into aluminium oxide which is insulating, causing a gradual increase of resistance of the heating element.
The heating element of the above structure was manufactured to assess the corrosion resistance as follows.
First, the metal base 12 mad~ of iron-chrome (FCHRWl) was clad with nickel foils and then aluminium folls on both surfaces thereof. The total thickness of the clad base was 50 ,u with 42 ~ for the metal base 12, 4 ~ for the two nickel layers and 4 ,u for the two aluminium layers, and the width thereof was 6 mm. The clad base was then heated at 900C in the atmosphere for five hours so as to produce the aluminum oxide layers 14 on both surfaces. The formation of the nickel-aluminium alloy layers between the metal base 12 and the aluminium oxide layers 14 was confirmed by an X-ray diffraction method. Electricity was applied to the thus obtained heating element 11 to raise the surface temperature thereof to 800C.
/
The same corrosion resistance test as that in Example 1 was performed. As a result, the number of drops applied to the above heating element 11 until it was corroded and cut apart was 80. The same test was also performed on the following three comparative samples; a heating element made of iron-chrome and heated at 900C in the atmosphere for five hours, a heating element made of SUS 430 and SUS 444 on which the same steps of cladding of nickel and aluminium and of thermally oxidizing the aluminium as in Example 2 were performed, and a heating element made of the same material as the above on which the step of cladding of nickel and aluminium was not performed but the step of heating was performed. The results were 10, 80, and 10, respectively. These results indicate that the corrosion resistance at high temperature shown in the heating element of this invention is irrespective of the type of the base metal.
Next, an application of the above-described heating element 11 to the microwave oven 6 shown in Figure 4 will be described as follows.
An iron-chrome strip (FCHRW1) for heating was used as the metal base 12, which was clad with nickel foils and aluminium foils on both surfaces thereof.
Then, the resultant strip was stamped into a meander shape and heated at 900C in the atmosphere for five hours to produce a sheet heating element 7' having an output of 1.2 KW. When a rated voltage of 100 V was applied to the heating element 7', the temperature of the heat$ng element reached 700C in about one minute, anq further rose to 800C in three minutes. An object to be cooked, for example, a fish, was put in the oven chamber 10 for heat cooking. The fish was broiled with uniform browning under the radiation of 800C for fifteen minutes.
The same corrosion resistance test as in Example 1 was performed on the microwave oven compris-ing the sheet heating element 7' of this example, and the same favorable results as in Example 1 were ob-tained.
From the above results, it was found that the heating element of this example had high corrosion resistance and was little deteriorated after a long period of usage.
In the aforementioned examples, the strip-shaped metal base was used. However, the metal base applicable to the present invention is not limited to the strip shape, but a linear metal base can also be used to obtain the same high corrosion resistance when the structure and the method of the present invention is applied thereto.
Example 3 In this example, a metal base made of iron-chrome, iron-chrome-aluminium or stainless steel such as SUS 430, SUS 430A or SUS 444 was used. On the top 5and bottom sur$aces of the metal base were formed aluminium layers in the same manner as shown in Exam-ple 1. The aluminlum layers were then oxidized into aluminium oxide layers in the same manner as shown in Example 1. The same test as in Example 1, that is, lOdropping a 5% saline solution was performed on the resultant heating element, and the result was 20 drops until the heating element was corroded and cut apart, indicating that the corrosion resistance of the heating element of this example was about twice as high as that 15of a heating element lacking an aluminium oxide layer.
It was also found that when the aluminium layers were formed by cladding of aluminium foils on the metal base as in Examples 1 and 2, the resultant 20heating element showed stable results in the corrosion resistance test.
The heating element obtained in this example was formed into a sheet heating element in the same 25manner as in Example 1 for the application to a micro-wave oven, and the same test as in Example 1 was per-formed. After 500 cycles, some small corrosion was observed on the surface of the heating element, but such corrosion did not cause lnferiority in the cooking 30ability nor any other practical problems.
In the above examples, the aluminium layer was formed and oxidized in order to obtain the alumini-um oxide layer. It should be appreciated that an aluminium-base alloy can also be used instead of alu-minium to attain the above objective.
It is understood that various other modifica-tions will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be construed as encompassing all the features of patentable novelty that reside in the present invention, including all features that would be treated as equivalents thereof by those skilled in the art to which this invention pertains.
Claims (15)
1. A heating element comprising a metal base having nickel-aluminium alloy layers formed on the top and bottom surfaces thereof.
2. A heating element according to claim l, wherein the nickel-aluminium alloy layers are covered with alumini-um oxide layers.
3. A heating element according to claim l or 2, wherein the metal base is nickel or a nickel-base alloy.
4. A heating element according to claim 3, wherein the nickel content in the nickel-base alloy is at least 50%.
5. A method for manufacturing a heating element com-prising the steps of:
forming aluminium layers on the top and bottom surfaces of a nickel or nickel-base alloy base, and oxidizing the aluminium layers into aluminium oxide layers.
forming aluminium layers on the top and bottom surfaces of a nickel or nickel-base alloy base, and oxidizing the aluminium layers into aluminium oxide layers.
6. A method for manufacturing a heating element accord-ing to claim 5, wherein the aluminium layers are formed by cladding the nickel or nickel-base alloy base with aluminium foils.
7. A method for manufacturing a heating element accord-ing to claim 6, further comprising the step of cutting the nickel or nickel-base alloy base clad with the aluminium foils to a predetermined shape between the step of forming the aluminium layers and the step of oxidizing the aluminium layers.
8. A method for manufacturing a heating element accord-ing to claim 6, wherein the aluminium foils are wider than the nickel or nickel-base alloy base.
9. A method for manufacturing a heating element accord-ing to any of claims 5 to 8, wherein the nickel content in the nickel-base alloy base is at least 50%.
10. A heating element comprising a metal base having nickel layers and aluminium oxide layers formed in this order on the top and bottom surfaces thereof.
11. A method for manufacturing a heating element comprising the steps of:
forming nickel layers on the top and bottom surfaces of a metal base, forming aluminium layers on the nickel lay-ers, and oxidizing the aluminium layers into aluminium oxide layers.
forming nickel layers on the top and bottom surfaces of a metal base, forming aluminium layers on the nickel lay-ers, and oxidizing the aluminium layers into aluminium oxide layers.
12. A method for manufacturing a heating element ac-cording to claim 11, wherein the nickel layers and the aluminium layers are formed by cladding.
13. A method for manufacturing a heating element ac-cording to claim 12, further comprising the step of cutting the metal base clad with the nickel layers and the aluminium layers to a predetermined shape between the step of forming the aluminium layers and the step of oxidizing the aluminium layers.
14. A heating element comprising a metal base and aluminium oxide layers, the aluminium oxide layers being obtained by first forming aluminium layers or aluminium alloy layers on the top and bottom surfaces of the metal base and then by oxidizing the aluminium.
15. A heating element according to claim 14, wherein the aluminium layers or the aluminium alloy layers are formed by cladding.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2244357A JPH04123785A (en) | 1990-09-14 | 1990-09-14 | Heating body |
| JP2-244357 | 1990-09-14 | ||
| JP2259669A JPH04137385A (en) | 1990-09-27 | 1990-09-27 | Heating unit and its manufacture |
| JP2-259669 | 1990-09-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2051231A1 true CA2051231A1 (en) | 1992-03-15 |
Family
ID=26536702
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002051231A Abandoned CA2051231A1 (en) | 1990-09-14 | 1991-09-12 | Heating element and a method for manufacturing the same |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0475427B1 (en) |
| KR (1) | KR940005461B1 (en) |
| AU (1) | AU630306B2 (en) |
| BR (1) | BR9103944A (en) |
| CA (1) | CA2051231A1 (en) |
| DE (1) | DE69105419T2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5976708A (en) * | 1995-11-06 | 1999-11-02 | Isuzu Ceramics Research Institute Co., Ltd. | Heat resistant stainless steel wire |
| WO2009035241A2 (en) * | 2007-09-10 | 2009-03-19 | Amo Co., Ltd. | Drying heater, heating unit for drying laundry using the same, drying control system and control method thereof |
| KR101416170B1 (en) * | 2007-09-10 | 2014-07-11 | 주식회사 아모그린텍 | Heating Unit |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1222504A (en) * | 1967-03-03 | 1971-02-17 | Transystems Ltd | Foil thermocouples |
-
1991
- 1991-09-12 CA CA002051231A patent/CA2051231A1/en not_active Abandoned
- 1991-09-12 AU AU83843/91A patent/AU630306B2/en not_active Ceased
- 1991-09-13 EP EP91115541A patent/EP0475427B1/en not_active Expired - Lifetime
- 1991-09-13 BR BR919103944A patent/BR9103944A/en not_active IP Right Cessation
- 1991-09-13 DE DE69105419T patent/DE69105419T2/en not_active Expired - Fee Related
- 1991-09-14 KR KR1019910016044A patent/KR940005461B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| KR940005461B1 (en) | 1994-06-18 |
| KR920007494A (en) | 1992-04-28 |
| DE69105419T2 (en) | 1995-06-29 |
| BR9103944A (en) | 1992-05-26 |
| DE69105419D1 (en) | 1995-01-12 |
| AU630306B2 (en) | 1992-10-22 |
| EP0475427A1 (en) | 1992-03-18 |
| EP0475427B1 (en) | 1994-11-30 |
| AU8384391A (en) | 1992-06-11 |
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| EEER | Examination request | ||
| FZDE | Discontinued |