JPS5844619B2 - Manufacturing method of optical fiber base material - Google Patents
Manufacturing method of optical fiber base materialInfo
- Publication number
- JPS5844619B2 JPS5844619B2 JP54123679A JP12367979A JPS5844619B2 JP S5844619 B2 JPS5844619 B2 JP S5844619B2 JP 54123679 A JP54123679 A JP 54123679A JP 12367979 A JP12367979 A JP 12367979A JP S5844619 B2 JPS5844619 B2 JP S5844619B2
- Authority
- JP
- Japan
- Prior art keywords
- optical fiber
- porous glass
- refractive index
- glass preform
- base material
- 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
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
- C03B37/01446—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/08—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant
Description
【発明の詳細な説明】
本発明は、ＶＡＤ法により光フアイバ母材を製造する方
法に関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an optical fiber preform by a VAD method.
従来より、光通信に使用される光ファイバは各種の方法
により製造されているが、ＶＡＤ法が最近注目されつつ
ある。Conventionally, optical fibers used for optical communications have been manufactured by various methods, but the VAD method has recently been attracting attention.
ＶＡＤ法（気相軸付法）は、回転しながら上方向に移動
する棒状基材の下端に煤状ガラス微粒子を付着堆積し、
棒状基材を引き上げながら煤状ガラス微粒子を軸方向に
成長させて棒状の多孔質ガラスプリフォームを形成した
後、所定の処理を施して光フアイバ母材を形成する方法
である。In the VAD method (vapor phase attachment method), soot-like glass particles are attached and deposited on the lower end of a rod-shaped base material that moves upward while rotating.
In this method, a rod-shaped porous glass preform is formed by growing soot-like glass particles in the axial direction while pulling up a rod-shaped base material, and then a predetermined process is performed to form an optical fiber preform.
そして、この光フアイバ母材を紡糸して光ファイバを形
成している。Then, this optical fiber base material is spun to form an optical fiber.
ところで、ＶＡＤ法により光ファイバを製造する場合、
種々の形の屈折率プロファイルが形成されている。By the way, when manufacturing optical fibers by the VAD method,
Various shapes of refractive index profiles are formed.
そして、屈折率プロファイルを規定するものとして火炎
内の反応状態や煤状ガラス微粒子の流れや温度分布等で
あるが、ＶＡＤ法による場合には第１図の実線で示すよ
うに外側付近ａにおける屈折率が比較的高いプロファイ
ルが得られる傾向がある。The refractive index profile is determined by the reaction state within the flame, the flow of sooty glass particles, temperature distribution, etc., but in the case of the VAD method, the refraction at the outer vicinity a is shown by the solid line in Figure 1. Profiles with relatively high rates tend to be obtained.
外側付近ａにおける屈折率が比較的高いプロファイルを
有する光ファイバは、帯域特性が良好でない。An optical fiber having a profile in which the refractive index near the outside a is relatively high does not have good band characteristics.
そこで、火炎内の反応状態や煤状ガラス微粒子の流れや
温度分布等を調整することにより屈折率分布を良好にし
ようとする試みもあるが、満足な結果は得られず、外側
付近ａにおける屈折率を低くする方法の出現が要望され
ている。Therefore, some attempts have been made to improve the refractive index distribution by adjusting the reaction state within the flame, the flow of soot-like glass particles, temperature distribution, etc., but no satisfactory results have been obtained. There is a need for a method to reduce the rate.
本発明者等は上記要望に答えるために鋭意研究を行った
結果、ＶＡＤ法により形成された多孔質ガラスプリフォ
ームをフッ素化合物の存在下で熱処理した後、所定の処
理を施すと、第１図の点線に示すように外側付近ａにお
ける屈折率が低下し、二乗分布型で帯域特性の良好な光
ファイバが得られることを知見した。As a result of intensive research in order to meet the above-mentioned needs, the present inventors have found that when a porous glass preform formed by the VAD method is heat-treated in the presence of a fluorine compound and then subjected to a predetermined treatment, as shown in FIG. As shown by the dotted line, the refractive index in the outer vicinity a decreases, and it has been found that an optical fiber having a square distribution type and good band characteristics can be obtained.
本発明はこの知見に基づいて完成されたもので、その特
徴はＶＡＤ法により形成された多孔質ガラスプリフォー
ムをフッ素化合物の存在下で熱処理して屈折率分布を調
整することにある。The present invention was completed based on this knowledge, and its feature lies in adjusting the refractive index distribution by heat-treating a porous glass preform formed by the VAD method in the presence of a fluorine compound.
以下、本発明の詳細な説明する。The present invention will be explained in detail below.
先ず、ＶＡＤ法により回転しながら上方向に移動する棒
状基材の下端に煤状ガラス微粒子を付着堆積し、棒状基
材を引き上げながら煤状ガラス微粒子を軸方向に成長さ
せて棒状の多孔質ガラスプリフォームを形成する。First, soot-like glass particles are attached and deposited on the lower end of a rod-shaped substrate that moves upward while rotating by the VAD method, and the soot-like glass particles are grown in the axial direction while pulling up the rod-shaped substrate to form a rod-shaped porous glass. Form a preform.
ついで、上記多孔質ガラスプリフォームをフッ素化合物
の存在下で熱処理する。Next, the porous glass preform is heat treated in the presence of a fluorine compound.
具体的には、例えば第２図に示すような石英パイプやア
ルミナパイプなどで形成された反応容器１内に上記多孔
質ガラスプリフォーム２を収め、反応容器１下部に設け
られたフッ素化合物ガス導入パイプ３からガス状のフッ
素化合物を供給する。Specifically, the porous glass preform 2 is placed in a reaction vessel 1 made of a quartz pipe, an alumina pipe, etc. as shown in FIG. A gaseous fluorine compound is supplied from the pipe 3.
フッ素化合物としては常温で気体であるＣＦ４、ＳＦ３
、Ｆ２などが好ましく用いられる。Fluorine compounds include CF4 and SF3, which are gases at room temperature.
, F2, etc. are preferably used.
このフッ素化合物のガスの供給量は、多孔質ガラスプリ
フォーム２の大きさ、処理温度、処理時間およびフッ素
化合物の種類等によって異るが、通常は３０〜５Ｑｃｃ
／分の程度が望ましい。The amount of this fluorine compound gas supplied varies depending on the size of the porous glass preform 2, processing temperature, processing time, type of fluorine compound, etc., but is usually 30 to 5 Qcc.
/minute is desirable.
また、反応容器１の外側には、この容器１を取り囲む加
熱ヒータ４が設げられ、この加熱ヒータ４によって反応
容器１内の多孔質ガラスプリフォーム２およびガス状の
フッ素化合物が加熱され熱処理される。Further, a heater 4 surrounding the reaction container 1 is provided outside the reaction container 1, and the porous glass preform 2 and the gaseous fluorine compound inside the reaction container 1 are heated and heat-treated by the heater 4. Ru.
処理温度は、フッ素化合物の種類、処理時間等によって
左右されるが通常の５ｉ０２系ガラスプリフオームの場
合は１０００〜１３００℃の範囲が好ましい。The treatment temperature depends on the type of fluorine compound, treatment time, etc., but is preferably in the range of 1000 to 1300°C in the case of ordinary 5i02 glass preforms.
また、処理時間は、処理温度、多孔質ガラスプリフォー
ム２の大きさ、フッ素化合物の種類等によって変動する
が一般には１〜１０時間程時間室ましい。The treatment time varies depending on the treatment temperature, the size of the porous glass preform 2, the type of fluorine compound, etc., but is generally about 1 to 10 hours.
さらに、熱処理中に多孔質ガラスプリフォーム２を回転
数１０〜３０ ｒｐｍで回転させつつ下方に送り速度２
〜１ｏｍｍ／分で移送して熱処理の均一化を計るように
する。Furthermore, during the heat treatment, the porous glass preform 2 is rotated at a rotation speed of 10 to 30 rpm and fed downward at a speed of 2.
Transfer at ~1 om/min to ensure uniform heat treatment.
このようなフッ素化合物のガス存在下での熱処理によっ
て、ガス状のフッ素化合物は活性なＦ２やＦ−に解離し
、この解離したフッ素化合物が多孔質ガラスプリフォー
ム２中に拡散してゆく。By such heat treatment of the fluorine compound in the presence of gas, the gaseous fluorine compound is dissociated into active F2 and F-, and the dissociated fluorine compound diffuses into the porous glass preform 2.
そして、多孔質ガラスプリフォーム２の外側部分におい
て、その一部は次の反応によってガラスをエツチングし
、他の一部は同時にガラスの網目構造において配位結合
する。Then, in the outer part of the porous glass preform 2, a part thereof etches the glass by the next reaction, and the other part simultaneously coordinates in the network structure of the glass.
５ｉ０２＋２Ｆ２→ＳｉＦ４＋０２
この結果、多孔質ガラスプリフォーム２の外側部分の屈
折率が低下し、第１図の点線で示すような二乗分布型の
プロファイルが得られる。5i02+2F2→SiF4+02 As a result, the refractive index of the outer portion of the porous glass preform 2 decreases, and a square distribution type profile as shown by the dotted line in FIG. 1 is obtained.
この際、フッ素化合物ガスの供給量、処理温度、処理時
間等を適宜上記範囲内で変化させることにより、多孔質
ガラスプリフォーム２の外側部分の屈折率の低下の程度
を制御することができる。At this time, the degree of decrease in the refractive index of the outer portion of the porous glass preform 2 can be controlled by appropriately changing the supply amount of the fluorine compound gas, the treatment temperature, the treatment time, etc. within the above ranges.
ついで、この熱処理が終った多孔質ガラスプリフォーム
２は、加熱されて透明ガラス化され、光フアイバ母材と
なる。Next, the porous glass preform 2 that has undergone this heat treatment is heated to become transparent vitrified and becomes an optical fiber base material.
なお、上記熱処理に伴って生成する排ガスは、反応容器
１の上部に設けられた排気パイプ５から反応容器１外に
排出される。Note that the exhaust gas generated during the heat treatment is discharged to the outside of the reaction container 1 from an exhaust pipe 5 provided at the upper part of the reaction container 1.
以下、実施例を示して本発明を具体的に説明する。Hereinafter, the present invention will be specifically explained with reference to Examples.
実施例 ■
５ｉＣ１４２０Ｑｃｃ／分、ＧｅＣｌ４５０ｃｃ／分、
ＰＯＣｌ３５ＣＣ／分、■２３０００ＣＣ／分、０２５
５００ＣＣ／分を四重管バーナに供給し、かつ棒状基材
を回転数２ Ｏｒｐｍで回転させるとともに引上げ速度
５０ｍｍ１時間で引上げて、ＶＡＤ法により外径５０１
ｒＬｍ、長さ４００７７Ｘｒ／Ｌの多孔質ガラスプリフ
ォームを形成した。Example ■ 5iC1420Qcc/min, GeCl450cc/min,
POCl35CC/min, ■23000CC/min, 025
500 CC/min was supplied to a quadruple tube burner, and the rod-shaped base material was rotated at a rotational speed of 2 orpm and pulled at a pulling speed of 50 mm for 1 hour to obtain an outer diameter of 50 mm using the VAD method.
A porous glass preform with rLm and length of 40077Xr/L was formed.
ついで、この多孔質ガラスプリフォームを第２図に示す
反応容器１に収容してＣＦ４ガス雰囲気中で以下に示す
条件で熱処理を行った。Next, this porous glass preform was placed in a reaction vessel 1 shown in FIG. 2, and heat-treated in a CF4 gas atmosphere under the conditions shown below.
ＣＦ４供給量 ３Ｑｃｃ／分熱
処理温度 １２００℃熱処理時間
２時間多孔質ガラスプリフォ
ームの ２５ ｒｐｍ回転数および
送り速度 ５關／分このよ
うにして熱処理された多孔質ガラスプリフォームを１４
００℃で透明ガラス化して光フアイバ母材とし、この光
フアイバ母材かも光ファイバを製造した。CF4 supply amount 3Qcc/min Heat treatment temperature 1200℃ Heat treatment time
2 hours Porous glass preform 25 rpm Rotation speed and feed rate 5/min Porous glass preform heat-treated in this way
The material was made into an optical fiber base material by transparent vitrification at 00° C., and an optical fiber was manufactured using this optical fiber base material.
得られた光ファイバは、第３図に示すような屈折率分布
を有していた。The obtained optical fiber had a refractive index distribution as shown in FIG.
一方、比較のため、ＣＦ４ガスで処理しない多孔質ガラ
スプリフォームから同様の方法によって光ファイバを製
造したところ、第４図に示すような屈折率分布を有する
光ファイバが得られた。On the other hand, for comparison, when an optical fiber was manufactured by the same method from a porous glass preform that was not treated with CF4 gas, an optical fiber having a refractive index distribution as shown in FIG. 4 was obtained.
第３図と第４図との屈折率分布を比較すると明らかなよ
うに、本発明の方法で処理されたもののプロファイルは
二乗分布型で外側付近における屈折率は低いのに対し、
ＣＦ、ガスで処理しない従来のもののプロファイルは完
全な二重分布型ではなく、外側付近における屈折率が比
較的高い。As is clear from comparing the refractive index distributions in FIG. 3 and FIG. 4, the profile of the one processed by the method of the present invention is a square distribution type, and the refractive index near the outside is low.
The profile of the conventional one that is not treated with CF gas is not a complete double distribution type, and the refractive index near the outside is relatively high.
このことから、本発明の方法で処理された光フアイバ母
材から形成される光ファイバは、従来のものに比べて帯
域特性が良好であることがわかる。From this, it can be seen that the optical fiber formed from the optical fiber base material treated by the method of the present invention has better band characteristics than the conventional fiber.
実施例 ２
実施例１と同様にして得られた多孔質ガラスフリフオー
ムをＳＦ６ガスの雰囲気下で熱処理した。Example 2 A porous glass friform obtained in the same manner as in Example 1 was heat-treated in an atmosphere of SF6 gas.
熱処理条件は、ＳＦ６の供給量を４０ＣＣ／分とした以
外は実施例１と同一とした。The heat treatment conditions were the same as in Example 1 except that the supply rate of SF6 was 40 cc/min.
熱処理後の多孔質ガラスプリフォームから得られた光フ
ァイバの屈折率分布は第３図に示したものとほぼ同様の
二乗分布型であった。The refractive index distribution of the optical fiber obtained from the porous glass preform after heat treatment was a square distribution type almost similar to that shown in FIG.
実施例 ３
実施例１と同様にして得られた多孔質ガラスプリフォー
ムをＦ２ガスの雰囲気下で熱処理した。Example 3 A porous glass preform obtained in the same manner as in Example 1 was heat treated in an F2 gas atmosphere.
熱処理条件はＦ２ガスの供給量を５Ｑｃｃ／分とした以
外は実施例１と同一とした。The heat treatment conditions were the same as in Example 1 except that the amount of F2 gas supplied was 5 Qcc/min.
熱処理後の多孔質ガラスプリフォームから得られた光フ
ァイバの屈折率分布は二乗分布型であった。The refractive index distribution of the optical fiber obtained from the porous glass preform after heat treatment was a square distribution type.
以上説明したように、本発明の光フアイバ母材の製造法
は、ＶＡＤ法により得られた多孔質ガラスプリフォーム
をフッ素化合物の存在下で熱処理するものである。As explained above, the method for producing an optical fiber preform of the present invention involves heat treating a porous glass preform obtained by a VAD method in the presence of a fluorine compound.
したがって、本発明によれば多孔質ガラスプリフォーム
の外側付近部分の屈折率を低下させることができ、二乗
分布型のプロファイルを確実に形成できる。Therefore, according to the present invention, it is possible to reduce the refractive index in the vicinity of the outer side of the porous glass preform, and it is possible to reliably form a square distribution type profile.
よって、本発明の方法によって処理された多孔質ガラス
プリフォームから形成された光ファイバは、二乗分布型
のプロファイルを有し、帯域特性の良好なものとなる。Therefore, an optical fiber formed from a porous glass preform treated by the method of the present invention has a square distribution type profile and good band characteristics.
第１図は本発明の方法と従来法とで得られた光ファイバ
の屈折率分布を示すグラフ、第２図は本発明の方法を実
施するに好適な装置の一例を示す概略構成図、第３図は
、実施例１で得られた光フアイバ母材から形成された光
ファイバの屈折率分布を示すグラフ、第４図は従来法で
得られた光ファイバの屈折率分布を示すグラフである。
１・・・・・・反応容器、２・・・・・・多孔質ガラス
プリフォーム、３・・・・・・フッ素化合物ガス導入パ
イプ、４・・・・・・加熱ヒータ、５・・・・・・排気
パイプ。FIG. 1 is a graph showing the refractive index distribution of optical fibers obtained by the method of the present invention and the conventional method. FIG. 2 is a schematic configuration diagram showing an example of an apparatus suitable for carrying out the method of the present invention. FIG. 3 is a graph showing the refractive index distribution of the optical fiber formed from the optical fiber base material obtained in Example 1, and FIG. 4 is a graph showing the refractive index distribution of the optical fiber obtained by the conventional method. . DESCRIPTION OF SYMBOLS 1... Reaction container, 2... Porous glass preform, 3... Fluorine compound gas introduction pipe, 4... Heater, 5... ...exhaust pipe.
Claims (1)
ムをフッ素化合物の存在下で熱処理し、上記多孔質ガラ
スプリフォームの外側部分のガラスにフッ素を結合させ
ることにより屈折率を低下させ、上記多孔質ガラスプリ
フォームの屈折率分布を二乗分布型とすることを特徴と
する光フアイバ母材の製造法。The porous glass preform obtained by the I VAD method is heat-treated in the presence of a fluorine compound, and the refractive index is lowered by bonding fluorine to the glass in the outer portion of the porous glass preform. A method for producing an optical fiber base material, characterized in that the refractive index distribution of the preform is a square distribution type.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP54123679A JPS5844619B2 (en) | 1979-09-26 | 1979-09-26 | Manufacturing method of optical fiber base material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP54123679A JPS5844619B2 (en) | 1979-09-26 | 1979-09-26 | Manufacturing method of optical fiber base material |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP21665382A Division JPS596820B2 (en) | 1982-12-10 | 1982-12-10 | Manufacturing method of optical fiber base material |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5650136A JPS5650136A (en) | 1981-05-07 |
| JPS5844619B2 true JPS5844619B2 (en) | 1983-10-04 |
Family
ID=14866615
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP54123679A Expired JPS5844619B2 (en) | 1979-09-26 | 1979-09-26 | Manufacturing method of optical fiber base material |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5844619B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6174921U (en) * | 1984-10-20 | 1986-05-21 | ||
| JPH07234738A (en) * | 1994-02-22 | 1995-09-05 | Nishiyama:Kk | Manufacture of grip incorporating switch |
Families Citing this family (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57170831A (en) * | 1981-04-13 | 1982-10-21 | Nippon Telegr & Teleph Corp <Ntt> | Manufacture of porous base material for optical fluoride fiber |
| JPS6060938A (en) * | 1983-09-10 | 1985-04-08 | Furukawa Electric Co Ltd:The | Manufacture of quartz base material for optical fiber |
| US4629485A (en) * | 1983-09-26 | 1986-12-16 | Corning Glass Works | Method of making fluorine doped optical preform and fiber and resultant articles |
| AU569757B2 (en) * | 1983-10-19 | 1988-02-18 | Nippon Telegraph & Telephone Corporation | Optical fibre preform manufacture |
| US4586943A (en) * | 1983-10-20 | 1986-05-06 | Sumitomo Electric Industries, Ltd. | Method for the production of glass preform for optical fibers |
| US4707174A (en) * | 1983-12-22 | 1987-11-17 | American Telephone And Telegraph Company, At&T Bell Laboratories | Fabrication of high-silica glass article |
| JPS60239337A (en) * | 1984-05-15 | 1985-11-28 | Sumitomo Electric Ind Ltd | Preparation of parent glass material for optical fiber |
| US5221309A (en) * | 1984-05-15 | 1993-06-22 | Sumitomo Electric Industries, Ltd. | Method for producing glass preform for optical fiber |
| JPS60260430A (en) * | 1984-06-04 | 1985-12-23 | Sumitomo Electric Ind Ltd | Manufacture of base material for optical fiber containing fluorine in clad part |
| JPS6186436A (en) * | 1984-10-05 | 1986-05-01 | Sumitomo Electric Ind Ltd | Production of parent material for optical fiber |
| US4579571A (en) * | 1984-10-09 | 1986-04-01 | Polaroid Corporation | Method for fabricating optical fiber preforms |
| CA1263807A (en) * | 1985-03-19 | 1989-12-12 | Richard James Pilon | Optical waveguide manufacture |
| JPS61247633A (en) * | 1985-04-25 | 1986-11-04 | Sumitomo Electric Ind Ltd | Production of glass base material for optical fiber |
| DE3518142A1 (en) * | 1985-05-21 | 1986-11-27 | Standard Elektrik Lorenz Ag, 7000 Stuttgart | METHOD FOR THE PRODUCTION OF AN LONG-TERM GLASS BODY, IN PARTICULAR A PREFORM FOR LIGHT WAVE GUIDES |
| US5217516A (en) * | 1985-12-27 | 1993-06-08 | Sumitomo Electric Industries, Ltd. | Method of making optical glass article |
| US4968339A (en) * | 1990-01-02 | 1990-11-06 | At&T Bell Laboratories | Method of fluorine doped modified chemical vapor deposition |
| US5039325A (en) * | 1990-01-02 | 1991-08-13 | At&T Bell Laboratories | Method for consolidating doped glass using an encapsulating structure |
| US5076824A (en) * | 1990-05-14 | 1991-12-31 | At&T Bell Laboratories | Method of making fiber optical preform with pyrolytic coated mandrel |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS54127914A (en) * | 1978-03-29 | 1979-10-04 | Nippon Telegraph & Telephone | Production of anhydrous glass material for optical fibers |
-
1979
- 1979-09-26 JP JP54123679A patent/JPS5844619B2/en not_active Expired
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS54127914A (en) * | 1978-03-29 | 1979-10-04 | Nippon Telegraph & Telephone | Production of anhydrous glass material for optical fibers |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6174921U (en) * | 1984-10-20 | 1986-05-21 | ||
| JPH07234738A (en) * | 1994-02-22 | 1995-09-05 | Nishiyama:Kk | Manufacture of grip incorporating switch |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5650136A (en) | 1981-05-07 |
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