JP3692512B2 - Crystalline glass stretch molding equipment - Google Patents

Description

【０００１】
【産業上の利用分野】
本発明は、ガラスの予備成形体を加熱すると所望しない結晶が析出する現象、所謂失透が起こり易いガラス（以下、結晶性ガラスと呼ぶ）を延伸成形する装置に関し、特に、電子部品や光学部品に用いられる断面形状が円形や矩形等の棒状スペーサ、棒状レンズ或いは薄板や毛細管等の高精度な製品を延伸して成形する装置に関するものである。
【０００２】
【従来の技術】
従来、通常のガラス材料を再成形する装置として、通称リドロー装置と呼ばれる延伸成形装置が知られている。図４に示すように、この装置は、予備成形体１１の一端を把持して予備成形体１１を一定速度で下降させる送り機構部１４と、該送り機構部１４により供給された予備成形体１１を軟化変形可能な温度に加熱する成形炉１５と、該成形炉１５内で軟化変形可能な状態になった予備成形体１１の他端より引張力を与えて再成形体１２に延伸する対をなす駆動ローラーを備えた引張り手段１６と、該引張り手段１６により延伸された再成形体１２を所定の長さの切断物１３に切断するカッターを備えた切断手段１７とを具備する。
【０００３】
ガラスが失透を生じ難い性質を有する通常のガラスである場合には、前記した従来の延伸成形装置を使用して予備成形体を単に軟化変形可能な温度に加熱し延伸して成形すれば、延伸成形中に失透が生じることなく高い寸法精度を有する再成形体が得られる。
【０００４】
【発明が解決しようとする課題】
しかしながら、失透を起こし易い性質を有する結晶性ガラスの場合には、従来の延伸成形装置を使用して予備成形体を加熱して成形すると、予備成形体の本体のガラス中に所望しない結晶が析出したり、失透物が生成して全く延びなくなったり、また、延伸途中のガラスが失透して延びないために破断して延伸成形そのものが困難となる問題が生じた。仮に、延伸はできたとしても、析出した失透物のために成形精度が悪く所望の寸法公差を逸脱したり、また、所望しない結晶の析出により熱膨張係数や硬度等の面で所望の特性が得られない等の問題が生じた。
【０００５】
そのため、従来では、結晶性ガラス材料には前記の延伸成形装置を使用することは困難とされ、高い寸法精度を有し、所望する特性を備えた結晶性ガラスからなる製品を製造する場合には、溶融ガラスから最終の寸法形状に近い形状に直接成形し、その成形体に数度の研削、研磨等の加工を施して最終の寸法形状にする方法が実施されているが、加工コストが高く、量産化に多々問題があった。
【０００６】
本発明は、上記の問題を解決した結晶性ガラスの延伸成形装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
上記の目的を達成するためになした本発明の結晶性ガラスの延伸成形装置は、結晶性ガラスからなる予備成形体の一端を把持し、一定速度で該予備成形体を成形炉に供給して加熱し、他端より引張力を与えて延伸する結晶性ガラスの延伸成形装置において、成形炉は、予備成形体を該結晶性ガラスの失透領域未満の温度に加熱する第一の加熱手段と、前記の加熱された予備成形体を失透領域未満の温度に保持する温度保持手段と、前記の失透領域未満の温度に保持された予備成形体を失透が生じない、または失透が部分的に生じても、その失透により延伸時の成形性や得られた再成形体の特性に悪影響を与えない程度の時間内で軟化変形可能な温度に加熱する第二の加熱手段と、前記の軟化変形可能に加熱され延伸された予備成形体を失透が生じない、または失透が部分的に生じても、その失透により延伸時の成形性や得られた再成形体の特性に悪影響を与えない程度の時間内で失透領域未満の温度に降温する降温手段とを具備してなることを特徴とする。
【０００８】
結晶性ガラスと呼ばれるものとして、例えば、ＳｉＯ₂ −Ａｌ₂ Ｏ₃ −Ｌｉ₂ Ｏ系の組成を有するガラスがある。この結晶性ガラスは、所定の熱処理を施されて結晶化するとβ−石英固溶体又はβ−スポジュメン固溶体を主結晶として析出し、低膨張で、且つ高い機械的強度の特性を有する結晶化ガラスとなる。本発明の装置に適用される結晶性ガラスとしては、延伸成形に際してその予備成形体が、ガラス状態にあるガラス体、および予め所定の熱処理により結晶化されたガラス体の両方のガラス体を対象とするものである。前記例示したような結晶性ガラスの場合、図１に示すように、結晶が析出して失透が生じる温度と時間の条件領域は、縦軸に温度と横軸に時間をとった同図上に斜線部で示される失透領域として表すことができる。同図でＴ１は失透領域の最高温度を、Ｔ２は失透領域の最低温度を、ｔｍは失透が生じる失透時間を示している。
【０００９】
このような結晶性ガラスを延伸成形する場合、予備成形体が延伸成形されて再成形体になるまでにたどる温度と時間の条件（以下、成形温度スケジュールと呼ぶ）が重要であり、本発明の装置は、成形炉をその結晶性ガラスが有する失透領域に入らないような成形温度スケジュールを実施できる構成にしたものである。本発明の装置により実現する成形温度スケジュールの一例を図２に示す。図１を参照して説明すると、成形炉において、結晶性ガラスの予備成形体を先ず、第一の加熱手段によりＡ点から当該結晶性ガラスの失透領域の最低温度Ｔ２未満のＢ点に予備的に昇温加熱し、そして加熱された該予備成形体を温度保持手段によりＢ点〜Ｃ点に示すように失透領域の最低温度Ｔ２未満の温度に保持し、次いで温度保持された該予備成形体を第二の加熱手段により実質的に失透が起こらない時間ｔｍ内でＣ点から軟化変形可能な温度のＤ点に急激に昇温するように加熱する。その後、延伸された予備成形体の部位を降温手段により実質的に失透が生じない時間ｔｍ内でＤ点から失透領域の最低温度Ｔ２未満のＥ点に急激に降温するようにする。本明細書において、実質的に失透が生じないとは、失透が部分的に生じても、その失透により延伸時の成形性や得られた再成形体の特性に悪影響を与えない程度の場合を含むことを意味するものである。
【００１０】
尚、図２に例示した成形温度スケジュールの場合は、失透領域の最高温度Ｔ１を超える温度まで昇温させているが、失透領域の最高温度Ｔ１を超えない場合でも、失透領域での滞留時間が失透時間ｔｍ以内の場合であれば、特性に悪影響を与える程度の失透が生じることなく十分に延伸成形が可能である。
【００１１】
【作用】
本発明の結晶性ガラスの延伸成形装置を使用すれば、成形炉は、結晶性ガラスからなる予備成形体を該結晶性ガラスの失透領域未満の温度に加熱する第一の加熱手段を具備するので、ガラス中に結晶が析出して失透する時間の制約を受けることなく予備成形体を十分且つ均一に昇温でき、前記の加熱された予備成形体を失透領域未満の温度に保持する温度保持手段を具備するので、第一の加熱手段より高温である第二の加熱手段の熱が予備成形体に伝わって予備成形体の温度が失透領域内に入ることを防止でき、前記の失透領域未満の温度に保持された予備成形体を失透が生じない、または失透が部分的に生じても、その失透により延伸時の成形性や得られた再成形体の特性に悪影響を与えない程度の時間内で軟化変形可能な温度に加熱する第二の加熱手段を具備するので、事前に予備的に昇温され温度保持された予備成形体を軟化変形可能な温度に失透時間以内の短時間で急激に加熱でき、前記の軟化変形可能に加熱され延伸された予備成形体を失透が生じない、または失透が部分的に生じても、その失透により延伸時の成形性や得られた再成形体の特性に悪影響を与えない程度の時間内で失透領域未満の温度に降温する降温手段とを具備しているので、短時間で急激な温度降下が図られて失透領域に入ることを防止でき、よって高い寸法精度を有し、且つ特性に悪影響を与える失透物のない再成形体を得ることができる。
【００１２】
【実施例】
図３は、本発明の結晶性ガラスの延伸成形装置の概略図である。同図で、１は予備成形体を、２は再成形体を、３は切断物を、４は予備成形体の送り機構部を、５は予備成形体を加熱する成形炉を、６は引張り手段を、７は切断手段を夫々示している。
【００１３】
送り機構部４は、予備成形体１の一端を把持するチャック部４ａを有し、駆動モーター（図示せず）により発生する制御された駆動力を伝達手段に伝えることにより該チャック部４ａを一定速度で下降させるようになっている。
【００１４】
成形炉５の構成について以下説明する。全体が、フレーム５ｅで囲まれた成形炉５の上部に配置された第一の加熱手段５ａは、例えば、アルミナセラミック等からなる外径φ１００ｍｍ×内径φ８０ｍｍ×高さ４００ｍｍ円筒管５ｆを中心にして、その外周に通電によりジュール熱を発生させることができるニッケル−クロム電熱線を螺旋状に巻回したヒータ５ｈをアルミナセメント５ｗで固定してあり、その外周にはセラミックファイバからなる保温材５ｉが配置してある。ヒータ５ｈのリード線は、フレーム５ｅに取り付けられた端子５ｊに接続してあり、その端子５ｊには制御された電力を供給する電源コードが接続してある。ヒータ５ｈの位置する箇所には炉内温度を監視する熱電対５ｋが設置してあり、第一の加熱手段５ａ内の温度をフィードバック制御できるＰＩＤ制御器（図示せず）に接続してある。ヒータ５ｈとしては、例えば、ニッケル−クロム電熱線や鉄−クロム電熱線等の電気抵抗の高い抵抗発熱線が適する。予備成形体１が入る円筒管５ｆの穴寸法を予備成形体１の断面形状に近い寸法に作成すると、炉内雰囲気の乱れが防止できて好ましい。第一の加熱手段５ａの上部開口部と予備成形体１との隙間を予備成形体１が移動可能な状態で密閉して炉内の空気の流出を防止することが望ましい。
【００１５】
温度保持手段５ｂは、前記の第一の加熱手段５ａの下方に設けてあり、耐熱ステンレス鋼製で冷媒として水を流す中空部を有するドーナツ状のジャケット５ｎを備えており、その寸法は外径φ２００ｍｍ×内径φ８０ｍｍ×高さ５０ｍｍであり、水流の流量を制御することにより炉内の温度調節を行えるようにしてある。ジャケット５ｎ内を通す冷媒としては、空気等の気体やその他の不活性な液体等の流体が適する。この温度保持手段５ｂは、ジャケット状以外の耐熱金属製の放熱面積の大きな板状のものであってもよい。
【００１６】
第二の加熱手段５ｃは、前記の温度保持手段５ｂの下方に設けてあり、予備成形体１の外周を囲む位置に、例えば、電気抵抗が低く大電流が流れて大量のジュール熱の発生が可能な内径φ８０ｍｍ×厚さ５ｍｍ×高さ８０ｍｍの合金製のヒータ５ｐを配置し、ヒータ５ｐの発熱量を補うためにヒータ５ｐの外周に内径φ２００ｍｍ×断面直径１２ｍｍのリング状をした補助ヒータ５ｑを配置した構造にしてある。各ヒータはフレーム５ｅに取り付けられた端子５ｕ、端子５ｓに接続してあり、各端子には制御された電力を供給する電源コードが接続してある。この第二の加熱手段５ｃの位置には炉内温度を監視する熱電対５ｒが設置してあり、ヒータ５ｐおよび補助ヒータ５ｑをフィードバック制御できるＰＩＤ制御器（図示せず）に接続してある。ヒータ５ｐおよび補助ヒータ５ｑとしては、例えば、合金製や黒鉛製、炭化珪素製等の電気抵抗が低く大電流が流れて大量のジュール熱の発生ができる発熱体や、合金製発熱部を高周波電源で加熱して発熱させるものや、反射鏡によりランプ発熱体の赤外線を集光するもの等が適する。また、成形に十分な熱量を予備成形体１に伝えるため、発熱体を予備成形体１に近づけることが望ましい。
【００１７】
降温手段５ｄは、前記の第二の加熱手段５ｃの下方に設けてあり、気孔率の高い耐熱煉瓦等からなる断熱材５ｖを配置した構造になっている。他にも降温手段５ｄの構造としては、温度保持手段５ｂと同様に、冷媒として水や空気等の流体を流す中空部を有するジャケット状の構造としてもよいし、金属製の放熱面積の大きな板状のものであってもよい。
【００１８】
引張り手段６は、前記の成形炉５の下方に設けてあり、成形炉５内で軟化変形可能な状態になった予備成形体１の他端より引張力を与えて再成形体２に延伸する対をなす駆動ローラー６ａ、６ｂを備えている。
【００１９】
切断手段７は、前記の引張り手段６下方に設けてあり、前記引張り手段６により延伸された再成形体２の下降速度と整合して当接するカッター７ａを備え、該再成形体２を所望の寸法を有する切断物３に切断するようになっている。
【００２０】
以下、結晶性ガラスの具体例として、図１および図２に例示したような失透領域の最高温度Ｔ１が１２００℃で、最低温度Ｔ２が７８０℃、失透時間ｔｍが５分である結晶性ガラスからなる予備成形体を本発明の延伸成形装置を使用して成形する場合について説明する。
【００２１】
まず、溶融ガラスを鋳込み成形して、失透物や結晶を全く含まないガラス状態の材料を準備し、このガラス材料を、断面形状が正方形で寸法が４０±０．１ｍｍ×４０±０．１ｍｍで長さ１０００ｍｍの角棒に加工して予備成形体１を作成し、これを図３に示すように、予備成形体１の上端を送り機構部４のチャック部４ａに把持し、５ｍｍ／分の一定速度で成形炉５に供給した。
【００２２】
成形炉５内で予備成形体１が延伸成形されて再成形体２となるまでの成形温度スケジュールを結晶性ガラスの失透領域の最高温度１２００℃から最低温度７８０℃の温度範囲内に、且つまた失透が生じる失透時間の５分以上滞留しないように設定した。まず、成形炉５の第一の加熱手段５ａの位置では予備成形体１を失透領域の７８０℃未満で且つそれの最も高い温度７５０℃まで序々に加熱し、温度保持手段５ｂの位置では予備成形体１を７５０℃で保持し、第二の加熱手段５ｃの位置では予備成形体１を軟化変形させ、その粘度が延伸成形に適する１×１０⁴ 〜１×１０⁶ ポイズの範囲内の１２３０℃まで昇温加熱した。その際、７８０℃から１２００℃までの温度範囲を昇温時間が５分以内になるように急加熱を行った。次に、引張り手段６の一対の駆動ローラー６ａ、６ｂを用いて、該第二の加熱手段５ｃの位置で加熱されて軟化変形状態になった予備成形体１の下端より引張力を与え引張速度２ｍ／分で延伸した。降温手段５ｄの位置では、延伸された予備成形体１を失透が生じないように失透領域の温度１２００℃から７８０℃までの降温に要する時間が５分以内になるように冷却した。以上のようにして、断面寸法が予備成形体１の１／２０である２．０ｍｍ×２．０ｍｍで、角棒状の再成形体２を成形した。
【００２３】
次いで、引張り手段６により延伸された再成形体２に切断手段７のカッター７ａを当接させて切断し、高い寸法精度を有する長さ５００ｍｍの切断物３を得た。
【００２４】
得られた切断物を調べたところ、高精度に成形されており、失透も全く観察されなかった。
【００２５】
上記したように、予備成形体１として未だガラス状態の結晶性ガラスを用いた場合には、延伸成形後において、切断物３を結晶化熱処理して所望する機械的強度及び膨張係数等の特性を有する結晶化ガラス体にした。この結晶化熱処理は、前記の延伸成形で得た切断物３を室温〜７８０℃まで昇温し、７８０℃で３０分保持し、次いで７８０〜１０００℃まで昇温し、１０００℃で３０分保持した。これにより、切断物３に平均径が０．３μｍのβ−スポジュメン固溶体からなる結晶が８０体積％析出し、ガラス質の部分が約２０体積％の結晶化ガラスを得た。この結晶化ガラスは、熱膨張係数が３５×１０^-7／℃でビッカース硬度６００であり、所望する特性を有するものであった。
【００２６】
上記の説明では、例として角棒を延伸成形する方法を挙げたが、延伸成形の対象物の形状は、丸棒、板状、管状、その他各種の形状であってもよい。
【００２７】
【発明の効果】
本発明による結晶性ガラスの延伸成形装置によれば、特性に悪影響を与える程度の失透が生じることなく所望の特性を有し、且つ高い寸法精度を有する再成形体を大量に製造できるので、実用上優れた効果を奏する。
【図面の簡単な説明】
【図１】結晶性ガラスの失透領域を示す説明図
【図２】結晶性ガラスの延伸成形温度スケジュールの一例を示す説明図
【図３】本発明の結晶性ガラスの延伸成形装置の一例を示す概念図
【図４】従来のガラスの延伸成形装置の一例を示す概念図
【符号の説明】
１ 予備成形体
２ 再成形体
３ 切断物
４ 送り機構部
５ 成形炉
５ａ 第一の加熱手段
５ｂ 温度保持手段
５ｃ 第二の加熱手段
５ｄ 降温手段
６ 引張り手段
６ａ、６ｂ 駆動ローラー
７ 切断手段
７ａ カッター[0001]
[Industrial application fields]
TECHNICAL FIELD The present invention relates to an apparatus for stretch-molding a glass (hereinafter referred to as crystalline glass) in which undesired crystals are precipitated when a glass preform is heated, and so-called devitrification occurs. The present invention relates to an apparatus for stretching and molding a highly accurate product such as a rod-shaped spacer having a circular or rectangular cross-section, a rod-shaped lens, a thin plate or a capillary tube.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a stretch molding apparatus commonly called a redraw apparatus is known as an apparatus for remolding a normal glass material. As shown in FIG. 4, this apparatus grips one end of the preform 11 and feeds the preform 11 at a constant speed, and the preform 11 supplied by the feed mechanism 14. A pair of the molding furnace 15 that heats the mold to a temperature at which it can be softened and deformed, and a pair that is stretched to the remolded body 12 by applying a tensile force from the other end of the preform 11 that has been softened and deformed in the molding furnace 15 A tensioning means 16 having a driving roller is formed, and a cutting means 17 having a cutter that cuts the reshaped body 12 stretched by the tensioning means 16 into a cut product 13 having a predetermined length.
[0003]
When the glass is a normal glass having a property that hardly causes devitrification, if the preform is simply heated and stretched to a temperature at which it can be softened and deformed using the above-described conventional stretch molding apparatus, A reshaped body having high dimensional accuracy can be obtained without devitrification during stretch molding.
[0004]
[Problems to be solved by the invention]
However, in the case of crystalline glass having the property of easily causing devitrification, when the preform is heated and molded using a conventional stretch molding apparatus, undesired crystals are formed in the glass of the preform body. There arises a problem that precipitation, devitrification matter is generated, and the glass does not extend at all, or that the glass in the middle of stretching is devitrified and does not extend, so that it becomes broken and the stretch molding itself becomes difficult. Even if the film can be stretched, the formed devitrified material has poor molding accuracy and deviates from the desired dimensional tolerance, or the desired characteristics in terms of thermal expansion coefficient and hardness due to undesired crystal precipitation. The problem that cannot be obtained occurred.
[0005]
For this reason, conventionally, it is difficult to use the above-described stretch molding apparatus for crystalline glass materials. When manufacturing a product made of crystalline glass having high dimensional accuracy and desired characteristics, The method of forming directly from the molten glass into a shape close to the final dimensional shape and subjecting the molded body to several degrees of grinding, polishing, etc. to obtain the final dimensional shape is carried out, but the processing cost is high There were many problems in mass production.
[0006]
An object of the present invention is to provide a crystalline glass stretch molding apparatus that solves the above-described problems.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the crystalline glass stretch molding apparatus of the present invention grips one end of a preform made of crystalline glass and supplies the preform to a molding furnace at a constant speed. In the crystalline glass stretch molding apparatus that heats and stretches by applying a tensile force from the other end, the molding furnace includes first heating means for heating the preform to a temperature lower than the devitrification region of the crystalline glass. , A temperature holding means for holding the heated preform at a temperature lower than the devitrification region, and the preform held at a temperature lower than the devitrification region does not cause devitrification or devitrification. A second heating means for heating to a temperature at which softening deformation is possible within a time period that does not adversely affect the formability at the time of stretching and the properties of the obtained remolded body, even if partially generated , devitrification softening deformable heated stretched preform of the Flip missing or even devitrification partially occur, lowering the temperature below the devitrification area in time as not adversely affect the properties of moldability and the resulting re-molded article at the time of stretching by the devitrification And a temperature lowering means.
[0008]
As what is called crystalline glass, for example, there is glass having a SiO ₂ —Al ₂ O ₃ —Li ₂ O-based composition. When this crystalline glass is crystallized by performing a predetermined heat treatment, β-quartz solid solution or β-spodumene solid solution is precipitated as a main crystal, and becomes a crystallized glass having low expansion and high mechanical strength characteristics. . As the crystalline glass applied to the apparatus of the present invention, the preform is a glass body in a glass state at the time of stretch molding, and both glass bodies that have been previously crystallized by a predetermined heat treatment are targeted. To do. In the case of the crystalline glass as exemplified above, as shown in FIG. 1, the temperature and time condition regions where the crystal is precipitated and devitrification occurs are shown in FIG. Can be expressed as a devitrification region indicated by hatching. In the figure, T1 indicates the maximum temperature of the devitrification region, T2 indicates the minimum temperature of the devitrification region, and tm indicates the devitrification time during which devitrification occurs.
[0009]
When such crystalline glass is stretch-molded, the temperature and time conditions (hereinafter referred to as a molding temperature schedule) that are followed until the preform is stretch-molded into a re-molded body are important. The apparatus is configured such that a molding temperature schedule can be implemented so that the molding furnace does not enter the devitrification region of the crystalline glass. An example of the molding temperature schedule realized by the apparatus of the present invention is shown in FIG. Referring to FIG. 1, in a molding furnace, a crystalline glass preform is first preliminarily moved from point A to point B less than the minimum temperature T2 in the devitrification region of the crystalline glass by the first heating means. The heated preform is maintained at a temperature lower than the minimum temperature T2 of the devitrification region as indicated by points B to C by the temperature holding means, and then the temperature-maintained preform is maintained. The molded body is heated by the second heating means so that the temperature is rapidly raised from the C point to the D point where the softening deformation is possible within a time tm in which devitrification does not occur substantially. Thereafter, the temperature of the stretched preform is rapidly lowered from point D to point E below the lowest temperature T2 of the devitrification region within a time tm when devitrification does not substantially occur by the temperature lowering means. In the present specification, substantially devitrification does not occur, even if partial devitrification occurs, the degree of devitrification does not adversely affect the formability during stretching and the properties of the obtained remolded body It is meant to include the case of.
[0010]
In the case of the molding temperature schedule illustrated in FIG. 2, the temperature is raised to a temperature exceeding the maximum temperature T1 of the devitrification region, but even in the case where it does not exceed the maximum temperature T1 of the devitrification region, If the residence time is within the devitrification time tm, the film can be sufficiently stretch-molded without devitrification to the extent that the properties are adversely affected .
[0011]
[Action]
If the crystalline glass stretch molding apparatus of the present invention is used, the molding furnace includes first heating means for heating the preform formed of the crystalline glass to a temperature lower than the devitrification region of the crystalline glass. Therefore, the preform can be heated sufficiently and uniformly without being restricted by the time during which crystals precipitate in the glass and devitrify, and the heated preform is maintained at a temperature lower than the devitrification region. Since the temperature holding means is provided, the heat of the second heating means, which is higher than the first heating means, can be prevented from being transmitted to the preform and the temperature of the preform enters the devitrification region. Even if the preformed body maintained at a temperature lower than the devitrification region does not devitrify or partially devitrifies, the devitrification causes the moldability during stretching and the characteristics of the obtained remolded body. heating to soften deformable temperature in a degree that does not adversely affect the time Since the second heating means is provided, the preform that has been preliminarily heated and held in advance can be rapidly heated to a temperature at which it can be softened and deformed within a short time within the devitrification time, and the aforementioned softening deformation is possible. The degree to which devitrification does not occur in the preform that has been heated and stretched , or even if partial devitrification occurs, the demoldability does not adversely affect the formability during stretching and the properties of the resulting remolded body. because of being and a cooling means for lowering the temperature below the devitrification area within the time, it is possible to prevent the short time by rapid temperature drop is achieved into the devitrification area, thus have a high dimensional accuracy In addition, it is possible to obtain a remolded body free from devitrification that adversely affects the properties .
[0012]
【Example】
FIG. 3 is a schematic view of the crystalline glass stretch molding apparatus of the present invention. In the figure, 1 is a preformed body, 2 is a reshaped body, 3 is a cut product , 4 is a feeding mechanism for the preform, 5 is a molding furnace for heating the preform, and 6 is a tensioner. Means 7 and cutting means 7 respectively.
[0013]
The feed mechanism section 4 has a chuck section 4a for gripping one end of the preform 1 and transmits the controlled driving force generated by a drive motor (not shown) to the transmission means to keep the chuck section 4a constant. It is designed to descend at a speed.
[0014]
The configuration of the molding furnace 5 will be described below. The first heating means 5a disposed as a whole at the upper part of the molding furnace 5 surrounded by the frame 5e is centered on a cylindrical tube 5f made of, for example, alumina ceramic or the like, outer diameter φ100 mm × inner diameter φ80 mm × height 400 mm. A heater 5h in which a nickel-chromium heating wire capable of generating Joule heat by energization is spirally wound around the outer periphery is fixed with alumina cement 5w, and a heat insulating material 5i made of ceramic fiber is provided on the outer periphery. It is arranged. The lead wire of the heater 5h is connected to a terminal 5j attached to the frame 5e, and a power cord for supplying controlled power is connected to the terminal 5j. A thermocouple 5k for monitoring the temperature in the furnace is installed at a location where the heater 5h is located, and is connected to a PID controller (not shown) capable of feedback control of the temperature in the first heating means 5a. As the heater 5h, for example, a resistance heating wire having a high electrical resistance such as a nickel-chrome heating wire or an iron-chrome heating wire is suitable. It is preferable that the hole size of the cylindrical tube 5f in which the preformed body 1 enters is made to have a dimension close to the cross-sectional shape of the preformed body 1 because the disturbance of the furnace atmosphere can be prevented. It is desirable to prevent the outflow of air in the furnace by sealing the gap between the upper opening of the first heating means 5a and the preform 1 in a state where the preform 1 can move.
[0015]
The temperature holding means 5b is provided below the first heating means 5a, and is provided with a donut-shaped jacket 5n made of heat-resistant stainless steel and having a hollow portion through which water flows as a refrigerant, and the dimensions thereof are the outer diameter. It is φ200 mm × inner diameter φ80 mm × height 50 mm, and the temperature inside the furnace can be adjusted by controlling the flow rate of the water flow. As the refrigerant passing through the jacket 5n, a fluid such as a gas such as air or other inert liquid is suitable. The temperature holding means 5b may be a plate-shaped member having a large heat dissipation area made of a heat-resistant metal other than the jacket shape.
[0016]
The second heating means 5c is provided below the temperature holding means 5b. For example, a large electric current flows at a position surrounding the outer periphery of the preform 1 to generate a large amount of Joule heat. A heater 5p made of an alloy having a possible inner diameter φ80 mm × thickness 5 mm × height 80 mm is disposed, and an auxiliary heater 5q having a ring shape with an inner diameter φ200 mm × cross-sectional diameter 12 mm on the outer periphery of the heater 5p in order to compensate for the amount of heat generated by the heater 5p. The structure is arranged. Each heater is connected to a terminal 5u and a terminal 5s attached to the frame 5e, and a power cord for supplying controlled power is connected to each terminal. A thermocouple 5r for monitoring the furnace temperature is installed at the position of the second heating means 5c, and is connected to a PID controller (not shown) capable of feedback control of the heater 5p and the auxiliary heater 5q. As the heater 5p and the auxiliary heater 5q, for example, a heating element such as an alloy, graphite, or silicon carbide that has a low electric resistance and can generate a large amount of Joule heat due to a large current flows, or an alloy heating part is a high-frequency power source. Suitable are those that generate heat by heating at, or those that condense the infrared rays of the lamp heating element with a reflector. In addition, it is desirable to bring the heating element closer to the preform 1 in order to transmit a sufficient amount of heat for molding to the preform 1.
[0017]
The temperature lowering means 5d is provided below the second heating means 5c, and has a structure in which a heat insulating material 5v made of heat-resistant brick or the like having a high porosity is disposed. In addition, the structure of the temperature lowering means 5d may be a jacket-like structure having a hollow portion for flowing a fluid such as water or air as a refrigerant, as in the temperature holding means 5b, or a metal plate having a large heat radiation area. It may be in a shape.
[0018]
The tension means 6 is provided below the molding furnace 5, and is stretched to the remolded body 2 by applying a tensile force from the other end of the preform 1 that is softened and deformable in the molding furnace 5. A pair of drive rollers 6a and 6b is provided.
[0019]
The cutting means 7 is provided below the pulling means 6 and includes a cutter 7a that is in contact with the lowering speed of the remolded body 2 stretched by the pulling means 6 and is provided with a desired shape. It cut | disconnects into the cut material 3 which has a dimension.
[0020]
Hereinafter, as a specific example of the crystalline glass, the crystallinity in which the maximum temperature T1 of the devitrification region illustrated in FIGS. 1 and 2 is 1200 ° C., the minimum temperature T2 is 780 ° C., and the devitrification time tm is 5 minutes. A case where a preform made of glass is molded using the stretch molding apparatus of the present invention will be described.
[0021]
First, molten glass is cast and formed to prepare a glassy material that does not contain devitrified substances or crystals. This glass material has a square cross-sectional shape and dimensions of 40 ± 0.1 mm × 40 ± 0.1 mm. Then, a preform 1 is prepared by processing it into a square bar having a length of 1000 mm, and as shown in FIG. 3, the upper end of the preform 1 is gripped by the chuck portion 4a of the feed mechanism 4 and 5 mm / min. Was supplied to the molding furnace 5 at a constant speed of.
[0022]
In the molding furnace 5, the molding temperature schedule until the preform 1 is stretch-molded into the re-molded body 2 is set within a temperature range from a maximum temperature of 1200 ° C. to a minimum temperature of 780 ° C. in the devitrification region of the crystalline glass, and Moreover, it set so that it may not stay for 5 minutes or more of the devitrification time when devitrification occurs. First, the preform 1 is gradually heated to a temperature lower than 780 ° C. in the devitrification region at the position of the first heating means 5a of the molding furnace 5 and 750 ° C., which is the highest temperature thereof. The molded body 1 is held at 750 ° C., the preform 1 is softened and deformed at the position of the second heating means 5c, and its viscosity is 1230 within the range of 1 × 10 ⁴ to 1 × 10 ⁶ poise suitable for stretch molding. The temperature was raised to 0 ° C. At that time, rapid heating was performed in a temperature range from 780 ° C. to 1200 ° C. so that the temperature rising time was within 5 minutes. Next, using a pair of driving rollers 6a and 6b of the pulling means 6, a tensile force is applied from the lower end of the preform 1 which is heated at the position of the second heating means 5c and is in a soft deformation state. Stretched at 2 m / min. At the position of the temperature lowering means 5d, the stretched preform 1 was cooled so that the time required for temperature decrease from 1200 ° C. to 780 ° C. in the devitrification region was within 5 minutes so as not to cause devitrification. As described above, the square bar-shaped reshaped body 2 was formed with a cross-sectional dimension of 2.0 mm × 2.0 mm which is 1/20 of the preform 1.
[0023]
Next, the cutter 7a of the cutting means 7 was brought into contact with the reshaped body 2 stretched by the pulling means 6 and cut to obtain a cut object 3 having a length of 500 mm having high dimensional accuracy.
[0024]
When the obtained cut product was examined, it was molded with high accuracy and no devitrification was observed at all.
[0025]
As described above, when crystalline glass in a glass state is still used as the preform 1, after stretch molding, the cut product 3 is crystallized by heat treatment to obtain desired characteristics such as mechanical strength and expansion coefficient. A crystallized glass body was obtained. In this crystallization heat treatment, the cut product 3 obtained by the above stretch molding is heated to room temperature to 780 ° C., held at 780 ° C. for 30 minutes, then heated to 780 to 1000 ° C. and held at 1000 ° C. for 30 minutes. did. As a result, 80% by volume of a crystal composed of a β-spodumene solid solution having an average diameter of 0.3 μm was deposited on the cut product 3, and a crystallized glass having a vitreous portion of about 20% by volume was obtained. The crystallized glass had a thermal expansion coefficient of 35 × 10 ⁻⁷ / ° C., a Vickers hardness of 600, and had desired characteristics.
[0026]
In the above description, a method of stretch-molding a square bar is given as an example, but the shape of an object to be stretch-molded may be a round bar, a plate, a tube, or other various shapes.
[0027]
【The invention's effect】
According to the stretch molding apparatus for crystalline glass according to the present invention, it is possible to produce a large number of remolded bodies having desired characteristics and high dimensional accuracy without causing devitrification to the extent that the characteristics are adversely affected . There is an excellent practical effect.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a devitrification region of a crystalline glass. FIG. 2 is an explanatory diagram showing an example of a crystalline glass stretch molding temperature schedule. FIG. 3 is an example of a crystalline glass stretch molding apparatus according to the present invention. Schematic diagram showing [FIG. 4] Schematic diagram showing an example of a conventional glass stretch molding apparatus [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Preliminary body 2 Remolded body 3 Cut object 4 Feed mechanism part 5 Molding furnace 5a 1st heating means 5b Temperature holding means 5c 2nd heating means 5d Temperature fall means 6 Pulling means 6a, 6b Drive roller 7 Cutting means 7a Cutter

Claims (1)

結晶性ガラスからなる予備成形体の一端を把持し、一定速度で該予備成形体を成形炉に供給して加熱し、他端より引張力を与えて延伸する結晶性ガラスの延伸成形装置において、
成形炉は、予備成形体を該結晶性ガラスの失透領域未満の温度に加熱する第一の加熱手段と、前記の加熱された予備成形体を失透領域未満の温度に保持する温度保持手段と、前記の失透領域未満の温度に保持された予備成形体を失透が生じない、または失透が部分的に生じても、その失透により延伸時の成形性や得られた再成形体の特性に悪影響を与えない程度の時間内で軟化変形可能な温度に加熱する第二の加熱手段と、前記の軟化変形可能に加熱され延伸された予備成形体を失透が生じない、または失透が部分的に生じても、その失透により延伸時の成形性や得られた再成形体の特性に悪影響を与えない程度の時間内で失透領域未満の温度に降温する降温手段とを具備してなることを特徴とする結晶性ガラスの延伸成形装置。In a crystalline glass stretch molding apparatus that holds one end of a preform made of crystalline glass, supplies the preform to a molding furnace at a constant speed, heats it, and stretches by applying a tensile force from the other end.
The molding furnace includes a first heating unit that heats the preform to a temperature below the devitrification region of the crystalline glass, and a temperature holding unit that maintains the heated preform at a temperature below the devitrification region. And, even if the preliminarily molded body maintained at a temperature lower than the devitrification region does not devitrify or partially devitrifies, the moldability at the time of stretching and the obtained remolding by devitrification Devitrification does not occur in the second heating means for heating to a temperature capable of being softened and deformed within a time period that does not adversely affect the properties of the body, and the preform that has been heated and stretched to be softened and deformed , or A temperature lowering means for lowering the temperature to a temperature lower than the devitrification region within a time period that does not adversely affect the formability at the time of stretching and the characteristics of the obtained remolded body due to the devitrification even if the devitrification partially occurs ; An apparatus for drawing and forming crystalline glass, comprising:

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