JPH0129036B2 - - Google Patents
Info
- Publication number
- JPH0129036B2 JPH0129036B2 JP56076231A JP7623181A JPH0129036B2 JP H0129036 B2 JPH0129036 B2 JP H0129036B2 JP 56076231 A JP56076231 A JP 56076231A JP 7623181 A JP7623181 A JP 7623181A JP H0129036 B2 JPH0129036 B2 JP H0129036B2
- Authority
- JP
- Japan
- Prior art keywords
- powder
- sheathed heater
- weight
- metal pipe
- fused
- 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.)
- Expired
Links
- 239000000843 powder Substances 0.000 claims description 50
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 44
- 239000000395 magnesium oxide Substances 0.000 claims description 22
- 229910052751 metal Inorganic materials 0.000 claims description 20
- 239000002184 metal Substances 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 claims description 12
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 11
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 6
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 6
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 5
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 5
- 239000010941 cobalt Substances 0.000 claims description 4
- 229910017052 cobalt Inorganic materials 0.000 claims description 4
- 239000005350 fused silica glass Substances 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 229910052758 niobium Inorganic materials 0.000 claims description 4
- 239000010955 niobium Substances 0.000 claims description 4
- 229910052721 tungsten Inorganic materials 0.000 claims description 4
- 239000010937 tungsten Substances 0.000 claims description 4
- 229910052727 yttrium Inorganic materials 0.000 claims description 4
- 238000009413 insulation Methods 0.000 description 11
- 238000010292 electrical insulation Methods 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 239000011521 glass Substances 0.000 description 3
- 229920006015 heat resistant resin Polymers 0.000 description 3
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910001120 nichrome Inorganic materials 0.000 description 2
- 229910052681 coesite Inorganic materials 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229910001293 incoloy Inorganic materials 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
- 229910001845 yogo sapphire Inorganic materials 0.000 description 1
Description
本発明はシーズヒータに関し、特に寿命の長い
シーズヒータを提供しようとするものである。
一般に、シーズヒータは第１図に示すように、
両端に端子棒１を備えたコイル状の電熱線２を金
属パイプ３に挿入し、この金属パイプ３に電融マ
グネシア、電融シリカ、電融アルミナ等の電気絶
縁粉末４を充填してなり、必要に応じて金属パイ
プ３の両端をガラス５や耐熱性樹脂６で封口して
なるものである。
このシーズヒータは加熱部品として、その非常
に優れた性能、品質、簡便さなどから飛躍的に多
用されてきており、家庭電化製品を初め、各種工
業用や宇宙開発、原子力などの特殊用途に至るま
で、その市場範囲は拡大してきている。その中で
も高温用シーズヒータの用途は今後さらに伸びて
いくものと思われる。
ところが、世界的視野でシーズヒータの性能お
よび品質の現状をみると、電熱線が断線するまで
の時間が短かいという欠点があつた。
本発明は上記従来のシーズヒータの欠点を解消
し、所期の目的を達成するシーズヒータを提供し
ようとするものである。
本発明者らは、電気絶縁粉末４に着目し各種検
討した結果、ニツケル、コバルト、ニオブ、タン
グステン、イツトリウムの群から選ばれる少くと
も一種の金属粉末を添加した電気絶縁粉末４を用
いてシーズヒータを構成することにより、寿命の
長いシーズヒータが得られるという結論を得た。
以下、本発明の実施例について説明する。
実施例 １
電気絶縁粉末４の主成分として電融マグネシア
粉末を用い、この電融マグネシア粉末に、ニツケ
ル粉末を1.0重量％加えて混合し、これを電気絶
縁粉末４として準備した。
なお、電融マグネシア粉末は下記第１表の組成
比のものを用いた。
第１表
MgO ……96〜97重量％
CaO ……0.2〜0.3重量％
SiO2 ……２〜３重量％
Al2O3 ……0.4〜0.5重量％
Fe2O3 ……0.14〜0.16重量％
また、電熱線２として線径0.29mmのニクロム線
第１種を用い、これを巻径２mmのコイル状とし、
両端に端子棒１を接続した。
さらに、金属パイプ３として長さ413mm、外径
８mm、肉厚0.46mmのNCF2P（商品名インコロイ
800）を用いた。
この金属パイプ３に、上記端子棒１を両端に接
続した電熱線２を挿入し、この金属パイプ３にあ
らかじめ準備しておいた上記電気絶縁粉末４を充
填し、圧延減径、焼鈍（1050℃、10分間）の各工
程を経て、金属パイプ３を長さ500mm、外径6.6mm
とし、さらに金属パイプ３の両端を低融点ガラス
５および耐熱性樹脂６で封口してシーズヒータを
完成した。
実施例 ２
実施例１と同様の電融マグネシア粉末にコバル
ト粉末を1.0重量％加えて混合し、これを電気絶
縁粉末４とした。
以下、実施例１と同様にしてシーズヒータを完
成した。
実施例 ３
実施例１と同様の電融マグネシア粉末にニオブ
粉末を1.0重量％加えて混合し、これを電気絶縁
粉末４とした。
以下、実施例１と同様にしてシーズヒータを完
成した。
実施例 ４
実施例１と同様の電融マグネシア粉末にタング
ステン粉末を1.0重量％加えて混合し、これを電
気絶縁粉末４とした。
以下、実施例１と同様にしてシーズヒータを完
成した。
実施例 ５
実施例１と同様の電融マグネシア粉末に鉄粉末
を1.0重量％加えて混合し、これを電気絶縁粉末
４とした。
以下、実施例１と同様にしてシーズヒータを完
成した。
実施例 ６
実施例１と同様の電融マグネシア粉末にイツト
リウム粉末を1.0重量％加えて混合し、これを電
気絶縁粉末４とした。
以下、実施例１と同様にしてシーズヒータを完
成した。
実施例 ７
実施例１と同様の電融マグネシア粉末に0.5重
量％のニツケル粉末と0.5重量％のコバルト粉末
を加えて混合し、これを電気絶縁粉末４とした。
以下、実施例１と同様にしてシーズヒータを完
成した。
実施例 ８
実施例１と同様の電融マグネシア粉末に0.5重
量％のニオブ粉末と0.5重量％のタングステン粉
末を加えて混合し、これを電気絶縁粉末４とし
た。
以下、実施例１と同様にしてシーズヒータを完
成した。
実施例 ９
実施例１と同様の電融マグネシア粉末に0.3重
量％のニツケル粉末と、0.4重量％のタングステ
ン粉末と、0.3重量％の鉄粉末を加えて混合し、
これを電気絶縁粉末４とした。
以下、実施例１と同様にしてシーズヒータを完
成した。
なお、比較のために従来例として、実施例１に
おける電融マグネシア粉末のみの電気絶縁粉末４
を用いて同様にシーズヒータを完成した。
上記実施例１〜９および従来例の各シーズヒー
タについて、絶縁性能および寿命性能を調べるた
めに以下の試験を行つた。
（寿命試験）
各シーズヒータについて、金属パイプ３の表面
温度が950℃に維持されるように電熱線２に通電
し、電熱線２が断線するまでの日数を調べた。
（熱時絶縁抵抗値試験）
各シーズヒータについて、金属パイプ３の表面
温度が950℃に維持されるように電熱線２に通電
し、熱時絶縁抵抗値の変化を調べた。
なお、熱時絶縁抵抗値を測定する時は金属パイ
プ３の表面温度を750℃に低下させて測定した。
上記寿命試験の結果ならびに熱時絶縁抵抗値試
験における11日後の熱時絶縁抵抗値の結果を第２
表に示す。
また、上記熱時絶縁抵抗値試験による熱時絶縁
抵抗値の変化を第２図に示す。
なお、第２図において、Ａは実施例１、Ｂは従
来例を示す。
実施例２〜９については、実施例１と同様の傾
向を示したので省略する。
The present invention relates to a sheathed heater, and particularly aims to provide a sheathed heater with a long life. Generally, sheathed heaters are as shown in Figure 1.
A coiled heating wire 2 with terminal rods 1 at both ends is inserted into a metal pipe 3, and the metal pipe 3 is filled with electrical insulating powder 4 such as fused magnesia, fused silica, fused alumina, etc. Both ends of the metal pipe 3 are sealed with glass 5 or heat-resistant resin 6 as required. This sheathed heater has been rapidly used as a heating component due to its excellent performance, quality, and simplicity, and is used in home appliances, various industrial applications, and special applications such as space exploration and nuclear power. Since then, its market scope has been expanding. Among these, the use of high-temperature sheathed heaters is expected to continue to grow in the future. However, when looking at the current performance and quality of sheathed heaters from a global perspective, one drawback is that the time it takes for the heating wire to break is short. The present invention aims to eliminate the drawbacks of the conventional sheathed heaters described above and provide a sheathed heater that achieves the intended purpose. As a result of various studies focusing on the electrical insulating powder 4, the present inventors have found that a sheathed heater can be manufactured using the electrical insulating powder 4 to which at least one metal powder selected from the group of nickel, cobalt, niobium, tungsten, and yttrium is added. It was concluded that by configuring this, a sheathed heater with a long life can be obtained. Examples of the present invention will be described below. Example 1 Electrically fused magnesia powder was used as the main component of electrically insulating powder 4, and 1.0% by weight of nickel powder was added and mixed to this fused magnesia powder to prepare electrically insulating powder 4. The fused magnesia powder used had the composition ratio shown in Table 1 below. Table 1 MgO...96-97% by weight CaO...0.2-0.3% by weight SiO2 ...2-3% by weight Al2O3 ... 0.4-0.5 % by weight Fe2O3 ...0.14-0.16% by weight In addition, a first type nichrome wire with a wire diameter of 0.29 mm was used as the heating wire 2, and this was made into a coil shape with a winding diameter of 2 mm.
Terminal bar 1 was connected to both ends. Furthermore, as the metal pipe 3, NCF2P (product name Incoloy) with length 413 mm, outer diameter 8 mm, wall thickness 0.46 mm
800) was used. The heating wire 2 with the terminal bar 1 connected to both ends is inserted into the metal pipe 3, the metal pipe 3 is filled with the electrical insulation powder 4 prepared in advance, and the metal pipe 3 is rolled to reduce its diameter and annealed at 1050°C. , 10 minutes), the metal pipe 3 is made into a metal pipe with a length of 500 mm and an outer diameter of 6.6 mm.
Then, both ends of the metal pipe 3 were sealed with low melting point glass 5 and heat resistant resin 6 to complete a sheathed heater. Example 2 1.0% by weight of cobalt powder was added to the same electrofused magnesia powder as in Example 1 and mixed, and this was used as electrical insulating powder 4. Thereafter, a sheathed heater was completed in the same manner as in Example 1. Example 3 1.0% by weight of niobium powder was added to the same electrofused magnesia powder as in Example 1 and mixed, and this was used as electrical insulating powder 4. Thereafter, a sheathed heater was completed in the same manner as in Example 1. Example 4 Electrical insulation powder 4 was prepared by adding 1.0% by weight of tungsten powder to the same electrofused magnesia powder as in Example 1 and mixing it. Thereafter, a sheathed heater was completed in the same manner as in Example 1. Example 5 Electrical insulating powder 4 was prepared by adding 1.0% by weight of iron powder to the same electrofused magnesia powder as in Example 1 and mixing it. Thereafter, a sheathed heater was completed in the same manner as in Example 1. Example 6 Electrical insulating powder 4 was prepared by adding 1.0% by weight of yttrium powder to the same electrofused magnesia powder as in Example 1 and mixing it. Thereafter, a sheathed heater was completed in the same manner as in Example 1. Example 7 Electrical insulation powder 4 was prepared by adding and mixing 0.5% by weight of nickel powder and 0.5% by weight of cobalt powder to the same electrofused magnesia powder as in Example 1. Thereafter, a sheathed heater was completed in the same manner as in Example 1. Example 8 Electrical insulation powder 4 was prepared by adding 0.5% by weight of niobium powder and 0.5% by weight of tungsten powder to the same electrofused magnesia powder as in Example 1 and mixing them. Thereafter, a sheathed heater was completed in the same manner as in Example 1. Example 9 0.3% by weight of nickel powder, 0.4% by weight of tungsten powder, and 0.3% by weight of iron powder were added to the same electrofused magnesia powder as in Example 1 and mixed.
This was designated as electrical insulating powder 4. Thereafter, a sheathed heater was completed in the same manner as in Example 1. For comparison, as a conventional example, electrical insulating powder 4 made of only electrofused magnesia powder in Example 1 was used.
A sheathed heater was also completed using the same method. The following tests were conducted to examine the insulation performance and life performance of each of the sheathed heaters of Examples 1 to 9 and the conventional example. (Lifetime test) For each sheathed heater, the heating wire 2 was energized so that the surface temperature of the metal pipe 3 was maintained at 950° C., and the number of days until the heating wire 2 broke was investigated. (Insulation resistance value test when heated) For each sheathed heater, the heating wire 2 was energized so that the surface temperature of the metal pipe 3 was maintained at 950° C., and changes in the insulation resistance value when heated were examined. In addition, when measuring the insulation resistance value under heat, the surface temperature of the metal pipe 3 was lowered to 750°C. The results of the above life test and the thermal insulation resistance value after 11 days in the thermal insulation resistance value test are
Shown in the table. Further, FIG. 2 shows the change in the insulation resistance value when heated due to the above-mentioned insulation resistance value test when heated. In FIG. 2, A shows the first embodiment and B shows the conventional example. Examples 2 to 9 showed the same tendency as Example 1, so their description will be omitted.
【表】
第２表および第２図より明らかなように、実施
例１〜９のシーズヒータは従来例のシーズヒータ
に比較して、寿命が約２〜３倍となつた。
また、11日後の熱時絶縁抵抗値についても、従
来例とほぼ同等の値を示し、劣ることはなかつ
た。
すなわち、ニツケル、コバルト、ニオブ、タン
グステン、鉄、イツトリウムの金属粉末はシーズ
ヒータの寿命を長くするように作用することが明
らかとなつた。
なお、実施例１〜９において、電気絶縁粉末の
主成分として電融マグネシア粉末を用いたが、電
融マグネシア粉末に代えて、電融アルミナ粉末、
電融シリカ粉末を用いても同様の傾向を示した。
さらに、電融マグネシア粉末を用いる場合にお
いても電融マグネシア粉末の種類により、その特
性を維持しながら本発明の効果が付加される。例
えば固有抵抗値の高い電融マグネシア粉末を用い
れば絶縁抵抗値のより高いシーズヒータを得るこ
とができ、また比較的に寿命の長い高純度電融マ
グネシア粉末を用いれば寿命のより長いシーズヒ
ータが得られる。
また、電熱線２としてニクロム線第１種を用い
たが、第３表に示す線材を用いても同様の結果が
得られ、金属パイプ３についても第４表に示すも
のを用いても同様の結果が得られた。[Table] As is clear from Table 2 and FIG. 2, the lifespan of the sheathed heaters of Examples 1 to 9 was approximately 2 to 3 times longer than that of the conventional sheathed heater. Furthermore, the thermal insulation resistance value after 11 days was almost the same as that of the conventional example, and was not inferior. That is, it has become clear that metal powders of nickel, cobalt, niobium, tungsten, iron, and yttrium act to extend the life of the sheathed heater. In Examples 1 to 9, fused magnesia powder was used as the main component of the electrical insulating powder, but instead of fused magnesia powder, fused alumina powder,
Similar trends were observed when fused silica powder was used. Furthermore, even when using electrofused magnesia powder, the effects of the present invention can be added while maintaining its characteristics depending on the type of electrofused magnesia powder. For example, if fused magnesia powder with a high specific resistance value is used, a sheathed heater with a higher insulation resistance value can be obtained, and if high-purity fused magnesia powder with a relatively long life is used, a sheathed heater with a longer life can be obtained. can get. In addition, although a type 1 nichrome wire was used as the heating wire 2, similar results were obtained using the wire shown in Table 3, and similar results were obtained using the metal pipe 3 shown in Table 4. The results were obtained.
【表】【table】
【表】【table】
【表】
また、上記実施例１〜９において、低融点ガラ
ス５、耐熱性樹脂６で封口したが、封口しない場
合にあつても同様の傾向を示した。
以上の説明から明らかなように、本発明によれ
ば、電気絶縁粉末として、電融マグネシア粉末、
電融アルミナ粉末、電融シリカ粉末のいずれか
に、ニツケル、コバルト、ニオブ、タングステ
ン、イツトリウムの群から選ばれる少なくとも一
種の金属粉末を添加したものを用いているため、
電熱線が断線するまでの時間を延ばすことがで
き、これにより、寿命の長いシーズヒータを得る
ことができるものである。
なお、本発明シーズヒータは第１図に示す形状
のものに限定されることはなく、カートリツジヒ
ータやグロープラグと称されるものをも含む。[Table] Furthermore, in Examples 1 to 9, the seals were sealed with low melting point glass 5 and heat resistant resin 6, but the same tendency was observed even when the seals were not sealed. As is clear from the above description, according to the present invention, as the electrically insulating powder, fused magnesia powder,
Because it uses either fused alumina powder or fused silica powder added with at least one metal powder selected from the group of nickel, cobalt, niobium, tungsten, and yttrium,
It is possible to extend the time until the heating wire breaks, thereby providing a sheathed heater with a long life. Note that the sheathed heater of the present invention is not limited to the shape shown in FIG. 1, but also includes what is called a cartridge heater or a glow plug.
第１図は一般的なシーズヒータの断面図、第２
図は本発明の実施例１のシーズヒータおよび従来
例のシーズヒータにおける熱時絶縁抵抗値の時間
特性図である。
２……電熱線、３……金属パイプ、４……電気
絶縁粉末。
Figure 1 is a cross-sectional view of a typical sheathed heater, Figure 2
The figure is a time characteristic diagram of the insulation resistance value at the time of heat in the sheathed heater of Example 1 of the present invention and the sheathed heater of the conventional example. 2... Heating wire, 3... Metal pipe, 4... Electrical insulation powder.
Claims (1)
絶縁粉末を充填してなるシーズヒータにおいて、
前記電気絶縁粉末として、電融マグネシア粉末、
電融アルミナ粉末、電融シリカ粉末のいずれか
に、ニツケル、コバルト、ニオブ、タングステ
ン、イツトリウムの群から選ばれる少なくとも一
種の金属粉末を添加したものを用いてなるシーズ
ヒータ。1 In a sheathed heater made by inserting a heating wire into a metal pipe and filling it with electrical insulating powder,
As the electrically insulating powder, fused magnesia powder,
A sheathed heater using fused alumina powder or fused silica powder to which at least one metal powder selected from the group of nickel, cobalt, niobium, tungsten, and yttrium is added.
Priority Applications (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7623181A JPS57191982A (en) | 1981-05-19 | 1981-05-19 | Sheathed heater |
| PCT/JP1982/000172 WO1982004172A1 (en) | 1981-05-19 | 1982-05-17 | A shielded heating element |
| EP82901435A EP0079386B1 (en) | 1981-05-19 | 1982-05-17 | A shielded heating element |
| AU83965/82A AU537836B2 (en) | 1981-05-19 | 1982-05-17 | A shielded heating element |
| US06/459,526 US4506251A (en) | 1981-05-19 | 1982-05-17 | Sheathed resistance heater |
| AT82901435T ATE21800T1 (en) | 1981-05-19 | 1982-05-17 | SHIELDED HEATING ELEMENT. |
| DE8282901435T DE3272855D1 (en) | 1981-05-19 | 1982-05-17 | A shielded heating element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7623181A JPS57191982A (en) | 1981-05-19 | 1981-05-19 | Sheathed heater |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS57191982A JPS57191982A (en) | 1982-11-25 |
| JPH0129036B2 true JPH0129036B2 (en) | 1989-06-07 |
Family
ID=13599387
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7623181A Granted JPS57191982A (en) | 1981-05-19 | 1981-05-19 | Sheathed heater |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS57191982A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016095125A (en) * | 2014-11-05 | 2016-05-26 | 日本特殊陶業株式会社 | Glow plug |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5344337B2 (en) * | 1976-02-24 | 1978-11-28 |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5344337U (en) * | 1976-09-21 | 1978-04-15 |
-
1981
- 1981-05-19 JP JP7623181A patent/JPS57191982A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5344337B2 (en) * | 1976-02-24 | 1978-11-28 |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS57191982A (en) | 1982-11-25 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| WO1982004172A1 (en) | A shielded heating element | |
| US2280257A (en) | Resistor device and method of making the same | |
| US4280932A (en) | Magnesia insulated heating elements | |
| JPH0129036B2 (en) | ||
| WO1982004171A1 (en) | A shielded heating element and a method of manufacturing the same | |
| JPS649716B2 (en) | ||
| JPH0159711B2 (en) | ||
| US1234973A (en) | Electrical heating apparatus and process of making the same. | |
| JPS6047709B2 (en) | Sea heater | |
| JPH0318318B2 (en) | ||
| JPS6362077B2 (en) | ||
| JPS647470B2 (en) | ||
| JPS6325472B2 (en) | ||
| JPH0155555B2 (en) | ||
| JPH0211992B2 (en) | ||
| JPS6322035B2 (en) | ||
| JPS6362075B2 (en) | ||
| JPH0119636B2 (en) | ||
| JPS61124087A (en) | Sheathed heater | |
| JPS648912B2 (en) | ||
| JPS5914289A (en) | Sheathed heater | |
| JPS6041809B2 (en) | sheathed heater | |
| JPH0155554B2 (en) | ||
| JPH0138360B2 (en) | ||
| JPS60208076A (en) | Sheathed heater |