JP3853240B2

JP3853240B2 - Pipe inner surface grinding method and apparatus

Info

Publication number: JP3853240B2
Application number: JP2002085802A
Authority: JP
Inventors: 泰治吉永; 明義広岡; 博文奈須; 潤霜村; 裕人藤本
Original assignee: Kurimoto Ltd
Current assignee: Kurimoto Ltd
Priority date: 2002-03-26
Filing date: 2002-03-26
Publication date: 2006-12-06
Anticipated expiration: 2022-03-26
Also published as: JP2003285251A

Description

【０００１】
【発明の属する技術分野】
この発明は、鋳鉄管の内面に施したモルタルライニングのレイタンスのような薄い被削面を研削する管内面の研削方法及び装置に関する。
【０００２】
【従来の技術】
主として遠心鋳造法により製造される鋳鉄管のうち水道用の管路として使用されるものは、その腐食を防止するために外面には耐食性塗料を塗装し、内面にはセメントモルタルのライニングが施される。このライニングも遠心力によってスラリ状のモルタルを管内壁に押圧し、セメントの凝固を待つ方法により施すのが主流であるが、このスラリが凝固する際に炭化カルシウムなどを主体とした遊離物である通常レイタンスと呼ばれる（一種のセメントの垢のような）ものが滲み出る。このレイタンスは使用時に水道水に混入すると問題を引き起こす虞れがあるため、仕上げ工程で表面から完全に削り取る必要がある。
【０００３】
このようなモルタルライニング表面の析出層を研削する方法については特開平３−１８４７５４号公報（公報１）により提案された方法が公知である。この公知の研削方法は、円筒短管の外周面に管軸方向へ多数の研削紙を一定幅で植設したペーパホイルを使用するというものである。実際の例では、上記のペーパホイルを長い回転軸の先端に取付け、ローラ上で所定の速度で回転される鋳鉄管内にペーパホイルを挿入して接触させ、回転軸をモータで回転させながらモータを支持する台車を前進させて管の内面のライニング表面を均等に研削するようにしている。
【０００４】
鋳鉄管内の研削については、遠心鋳造法で製造された管の受口内に残る砂の除去のため研掃工具により研掃する装置が、例えば特開平７−１００７４６号公報（公報２）により提案されている。この公報２による研掃装置は、管の受口に挿入される研掃工具を軸端に取付けた回転軸を平行なガイド部材により水平に保持し、回転軸を取付けたユニットの重量に反発する上向きの一定力を発生させる反発駆動装置と、上記ユニットに下向きの一定力を作用させて研掃工具に所定の下向きの研掃押圧力を発生させる主駆動装置とを備えている。
【０００５】
ユニットの重量と下向きの一定力の合計から上向きの反発力を差引いた下向きの一定力を研掃押圧力とし、下向きの一定力を細かく調節して研掃工具の摩耗量が進行しても常に研掃押圧力が一定となるようにし、製品品質の安定化を図ることができるとされている。
【０００６】
【発明が解決しようとする課題】
ところで、円筒管の内面研磨のため常に均一な研削圧力を得る方法については従来より種々の提案があり、例えば特開平５−１０４４２２号公報（公報３）では鋳鉄管の全長に亘る研磨にあって均一な研削圧力を付与することを提案しており、これらが有効な手段であることは疑いのないところである。
【０００７】
しかしながら、モルタルライニングの表面を研削する場合、その表面形状は管の両端部付近で管の円周方向及び管長手方向に微小な凹凸やライニング厚みの変化が存在する。これはその施工方法に起因するものであるが、その幅や長さは管の全長を研磨する形式の研磨装置に装着する砥石やワイヤブラシなどの研掃工具の大きさに比してかなり小さいのが通常である。従って先の公報１、３に示された装置の研掃工具では、これらの微小な凹凸に対しては充分な追従ができず、摺り残しが発生する。
【０００８】
従って、微小な凹凸に追従して研削するためには少なくとも研掃工具を微小凹凸に対応できる大きさに改める必要があるが、それだけではなお次の点で不足する。上記公報１以外の従来の装置は、鋳鉄管内面の仕上げを前提としているため、そのままの押圧力や砥石回転動力ではモルタルライニング端部のレイタンス除去には過大であり、比較的柔らかなモルタルライニングにとっては過剰な研磨やライニング端面角部の欠損などの品質上の欠陥を招く虞れがある。
【０００９】
従来の公知の研削装置では一定の押圧力を作用させて研削することについて説明しているが、研掃工具の使用による摩耗で研掃押圧力が低下するのを防止するため、研掃工具を対象面に一定の押圧力で作用させる方法又は装置について開示しているのであり、対象面の表面状態によっては一定以上の押圧力が作用し得る場合に、一定の押圧力をどのように制御するのかについて説明したものはない。又、モルタルライニング層のような基本層は破砕されず、その表面の薄いレイタンスのみを研削することを目的としたものは公報１以外にはない。
【００１０】
モルタルライニング端部のレイタンス除去については微小な押圧力と動力の調節及び表面形状への追従が要求されるため、実際にはハンドグラインダを用いて手作業で行う場合が多い。しかし、手作業によるグラインダ研摩は労働安全衛生規則に一定時間毎の休憩が定められているように、その振動、粉塵が作業者の健康に影響を与え兼ねないなどの問題もあり、作業環境の改善の観点からも自動化することが急務となっている。
【００１１】
この発明は、上記の種々の問題点に留意して、鋳鉄管内面に施したモルタルライニングの管両端付近の表面のように、管全長の研削用の径の大きい研削工具では完全に除去できない程の微小なライニング表面の凹凸に追従して常に均一で安定した研削押圧力を発生し得る管内面研削方法及び装置を提供することを課題とする。
【００１２】
【課題を解決するための手段】
この発明は、上記の課題を解決する手段として、研削工具を水平に取付けた水平支持部材の一端を垂直方向に案内しながら他端を上向きの反発力で支持し、研削工具を含む水平支持部材の全自重から反発力を差引いた押圧力で研削工具の先端を水平に支持された管内面の被研削面に当接させて移動研削し、被研削面への押圧力が表面形状の変化に対応して設定値以下となるか又はこれを超えるかにより反発力を一定範囲内に保持する調整をして研削工具の先端を表面形状の変化に追従させながら押圧力を被研削面へ及ぼし、被研削面への押圧力が常に所定範囲内となるように研削する管内面研削方法としたのである。
【００１３】
この方法を実施する装置として、研削工具を水平に取付けた水平支持部材と、水平支持部材の一端を垂直方向に案内する案内機構と、水平支持部材の他端を圧縮空気の力で上向きの反発力を付与して支持する反発力付与手段とから成る研削ユニットを移動テーブル上に設け、反発力付与手段にその圧縮空気の供給圧力を調整する圧力調整手段を接続し、研削ユニットの全自重から反発力を差引いた押圧力下で、研削工具の先端を水平に支持された管内面の被研削面に当接させ、移動テーブルを移動させて移動研削する際に、被研削面への押圧力が表面形状の変化に対応して設定値以下となるか、又はこれを超えるかにより反発力を一定範囲内に保持するように圧力調整手段により供給圧力を調整して研削工具の先端を表面形状の変化に追従させながら押圧力を被研削面へ及ぼし、被研削面への押圧力が常に所定範囲内となるように研削する管内面研削装置を採用することができる。
【００１４】
上記構成の研削方法及び装置によれば、管内面の微小なうねりのような表面形状の凹凸に追従して均一で安定した押圧力で研削を行なうことができる。水平支持部材の他端を反発力で支持し、一端を垂直方向に案内してその一端に取付けた研削工具の先端を全自重から反発力を差引いた押圧力で管内面の被研削面に当接させて移動研削する。この場合、水平に支持した管を回転させながら研削工具も回転させてその先端を管端部から挿入する。
【００１５】
又、被研削面が鋳鉄管内面に施したモルタルライニングの表面において、管両端部付近に生じるレイタンスに特有の微小なうねりのような凹凸が生じている場合、その凹凸のピッチ、幅の寸法に対応する（以下の）サイズの研削工具であることが前提である。凹凸寸法より数倍以上の直径長さの研削工具では凹凸形状の上に跨がることとなり全ての表面を研削することができないからである。なお、この発明では研削という用語は研削、研磨、研掃という概念を含む意味で用いている。
【００１６】
水平支持部材は一端が垂直方向に案内されるため、常に水平を保持して昇降する。反発力は全自重より少し小さい値を選んで付与することにより、残る下向きの力が押圧力として研削工具の先端から被研削面に加えられる。この押圧力は被研削面からの反力に平衡し、これにより水平支持部材は研削工具の先端が被研削面に当接した状態で保持される。しかし、被研削面に微小な凹凸のような表面形状の変化があると水平支持部材はその凹凸に追従して降下したり、上昇したりする。
【００１７】
表面形状が凹状の場合、研削工具の先端は被研削面から離れるため研削工具に作用する上記残る下向きの力で研削工具は下降する。従って、この下降により反発力が増大するためこのときは反発力を設定値よりやや減少させる調整をし、反発力を一定範囲内に保持して水平支持部材を支持し、下降した位置で被研削面に研削工具の先端が当接すると、同じ大きさの反力と平衡し、初期状態とほぼ同じ所定範囲内の押圧力で研削が行なわれる。反対に、表面形状が凸状の場合、被研削面から作用する反力が初期状態より大きくなり、これに対応して反発力を減少させる調整をし、これにより反発力を一定範囲内に保持して少し上昇した位置で研削工具の先端が被研削面に当接し、初期状態とほぼ同じ所定範囲内の押圧力で研削が行なわれる。
【００１８】
【実施の形態】
以下、この発明の実施の形態について図面を参照して説明する。図示の管内面研削装置Ａは、水平な回転軸１ａの先端に砥石１ｂを取付け、回転軸１ａを駆動モータ１ｃにより回転駆動するように形成した研削工具１と、スライダ２ａを垂直方向に直線状のレールで案内するリニアガイドを用いた案内機構２と、この案内機構２を介して一端を案内されるＬ字形の支持フレームを用いた水平支持部材３とから成る研削ユニットを移動テーブル６上に備え、水平支持部材３はその他端を昇降シリンダ４により昇降され、又隣接して設けられた反発シリンダを用いた反発力付与手段５を最外端に連結して支持している。
【００１９】
図示の例では、Ｌ字形の支持フレームの垂直部分に研削工具１の回転軸１ａを水平に取付け、かつ垂直部分をスライダ２ａに固定することにより研削工具１を水平に保持した状態で全体を昇降自在に案内機構２により案内するように構成されている。砥石１ｂはワイヤブラシ又は研削ディスクの複数枚などでもよい。駆動モータ１ｃは圧縮空気を動力源とするエアーモータが用いられ、又昇降シリンダ４、反発シリンダ５も圧縮空気により駆動される。
【００２０】
上記水平支持部材３には、垂直上方の推力のみ作用させるように昇降シリンダ４が取付けられているが、この場合昇降シリンダ４で支持するが連結することなく接離自在に取付け、これにより研削ユニット全体が昇降する。研削を行なわないときは昇降シリンダ４が伸張して研削ユニット全体を持上げ、砥石１ｂを被研削面から引き離すように操作される。研削をするときは昇降シリンダ４を収縮させると、研削ユニットの自重により砥石が被研削面に接するまで下降する。このとき、昇降シリンダ４のピストンロッド先端が水平支持部材３と連結されていると、シリンダ４の内部摩擦抵抗が研削中の押圧力の変化に対する追従性に影響を与えるので、連結することなく切離しておく。
【００２１】
上記研削ユニットを積載した移動テーブル６は、サーボモータ７を駆動部とし、その出力軸に連結されたボールねじ７ａを回転させることにより、調整テーブル８上の２列のレール７ｂ上を所定の速度で進退動するように設けられている。調整テーブル８は、段取替えが行なわれた際に砥石１ｂの高さを調整するためのものであり、このテーブル上に２列のレール７ｂが水平かつ平行に設けられている。高さを調整するため、駆動モータ９の動力をＸ字状のジャッキにより垂直方向の昇降動に変換する機構を備えている。
【００２２】
上記管内面研削装置Ａは、図２に示すように、ダクタイル鋳鉄管内面を研削するために設置される。図示の例では、特に管内面にモルタルライニングが施されており、その表面に析出するレイタンスのうち管端部付近の所定長さ範囲（図中のｌ）のレイタンスを研削するのに用いられる。図示のように、管Ｐの受口Ｐｏ近くの平行部と挿口付近の適所に配置された管回転用の２列のローラＲで水平に支持された管Ｐの端部から回転軸１ａの先端の砥石１ｂを挿入して研削が行なわれるように配置されている。Ｍはモータであり、その回転力をローラＲに伝達して管Ｐも一定の速度で回転されながら研削が行なわれる。
【００２３】
なお、管Ｐの受口側に上記管内面研削装置Ａは配置されているが、挿口側にもほぼ同一構成、機能の研削装置Ａ’が配置されている。この研削装置Ａ’は、調整テーブル８の下に管Ｐの規格長さに起因する１ｍの移動距離を移動自在とするため、移動軸Ｓを有するだけで、その他は全く同一構成である。上記移動距離は日本ダクタイル鉄管協会規格（ＪＤＰＡ）に基づく。即ち、小口径の鉄管については７５〜１００φまでの有効長（受口を除く直管部分長さ）は４ｍ、１５０〜２５０までの有効長は５ｍと定められているからである。
【００２４】
図３に昇降シリンダ、反発シリンダへの圧縮空気の配管系を示す。（ａ）図において、１０は反発シリンダ用の精密型減圧弁、１１、１２は研削ユニットの下降上昇速度調整用の調整弁、１３は切替弁、１４は圧縮空気供給源のエアーポンプである。減圧弁１０は、圧力を調整することにより砥石１ｂによる微小な押圧力の設定を可能とするものであり、その概略構成を（ｂ）図に示す。１０ａは調圧ハンドル、１０ｂはスプリング、１０ｃはダイヤフラム、１０ｄは弁座、１０ｅはニードル、１０ｆはシートバルブ、１０ｇはスプリング、１０ｈは排気ポートである。
【００２５】
調圧ハンドル１０ａによって設定される圧力がＰ₀とする。今、Ｐ₀＞Ｐ₂であるとすると、スプリング１０ｂの押下力が２次側圧力Ｐ₂によりダイヤフラム１０ｃに及ぼす力より大となり、ダイヤフラム１０ｃと弁座１０ｄは下方へ押し下げられ、弁座１０ｄを介してニードル１０ｅを押し下げるため、シートバルブ１０ｆが開き、１次側から２次側へエアーが流れる。
【００２６】
Ｐ₀＜Ｐ₂となると、スプリング１０ｂの押下力に打ち勝ち上記と反対にダイヤフラム１０ｃが押し上げられる。このため、ニードル１０ｅと弁座１０ｄの間が開き２次側のエアー（Ｐ₂）が弁座中央の孔から排気ポート１０ｈへと流れて排気される。２次側は反発シリンダ５に接続されているため、反発シリンダ５内の圧力（Ｐ₂）が、砥石１ｂが被研削面から受ける反力によって上記設定圧Ｐ₀より小さいときは圧力Ｐ₂がＰ₀となるまでエアーが反発シリンダ５へ送られ、圧力Ｐ₂がＰ₀より大きくなると圧力Ｐ₂のエアーは減圧弁１０の排気ポート１０ｈから排出されてＰ₀へ戻る。
【００２７】
実際に減圧弁１０で設定される設定圧Ｐ₀は１．５±０．５ｋｇｆ／ｃｍ²と一定の範囲に設定され、この設定範囲を超えると減圧弁１０が供給、排気の動作状態となる。なお、前述した砥石１ｂの大きさ（直径、長さ）は、この実施形態では管端部付近の所定長さ範囲でのレイタンス形状の変化（表面のうねりによる凹凸）に対応して、管内面の鋳肌の仕上げなどのための研磨に用いられる一般的な砥石でありはるかに小さい寸法のものが使用されるが、その詳細については後で説明する。
【００２８】
上記の構成とした実施形態の管内面研削装置Ａの作用は次の通りである。なお、実際の装置では前述したように一対の管内面研削装置Ａ、Ａ’がそれぞれ管Ｐの受口側、挿口側のそれぞれから同時に並行して作動するが、以下では片側の研削装置Ａについて説明する。研削対象は、鋳鉄管Ｐの管端部付近の所定長さ範囲（図２の距離ｌ）のモルタルライニングの表面に析出されるレイタンスである。管端部付近としたのは、この付近に析出されるレイタンスの表面形状の変化（うねりによる凹凸）が管両端付近の間の大部分に析出されるレイタンスの表面形状より微小であり、特別の研削処理を必要とするからである。
【００２９】
鋳鉄管ＰをローラＲで回転させながら、受口Ｐｏ側から回転軸１ａの先端の砥石１ｂを挿入し、砥石１ｂも回転させながら管Ｐ内面のモルタルライニング表面に析出しているレイタンスに砥石１ｂを当接させる。このとき、回転軸１ａと砥石１ｂの高さを高さ調整テーブル８で大まかに設定し、昇降シリンダ４で支持した高さから昇降シリンダ４を収縮させると反発シリンダで反発力を上向きに作用させて研削ユニットの自重を減殺した残る重量が砥石１ｂから被研削面に作用する押圧力となるよう予め準備されているものとする。
【００３０】
砥石１ｂをモルタルライニングＬの表面のレイタンスに当接させながら回転させて研削する場合、図４に示すように、管端部付近ではその表面が符号Ｓで示す小さなうねり状の凹凸が形成されているため（モルタルライニング層の製造工程に起因して生じる）、これに対応する直径、長さの砥石１ｂでは小さなうねり形状部分に削り残しが生じない。図示の砥石１ｂは（ａ）図に図示のうねり長さの半ピッチ分程度の長さで、かつ（ｂ）図に示す周方向のうねり長さに砥石１ｂの全周長さ又はその半分程度が対応する寸法としている（鉄管２００φ以上）。
【００３１】
図示の例の研削装置の砥石１ｂと研削対象のモルタルライニングの具体的な寸法は次の通りである。

以上のような大きさ（寸法）の砥石１ｂを用いてレイタンスを研削する場合、図５に示すように、砥石１ｂが被研削面に当接して押圧力Ｆを及ぼし、その反力Ｆ₀を砥石１ｂが受けてこの反力Ｆ₀と反発シリンダによる反発力Ｆ₁の合計が研削ユニット全体の自重Ｗに釣合うように押圧力Ｆが作用する。但し、Ｆ＝Ｆ₀である。
｜Ｆ｜＝｜Ｗ｜−｜Ｆ₁｜
【００３２】
モルタルライニングのレイタンスの表面が平坦であれば、上記釣合い状態を保って常に一定の押圧力Ｆが作用することとなるが、レイタンスの表面がライニングの突部あるいは肉厚層上に形成されている場合、理想研削面Ｌ₀は上方の一点鎖線Ｌｕに向って変化する。このため、砥石１ｂは押圧力Ｆで釣合っていた状態から少し大きい反力Ｆ₀で押し戻されて上方の研削面Ｌｕまで上昇し、水平支持部材３に連結された反発シリンダ５のピストンロッドが同じ距離だけ上昇する。
【００３３】
従って、反発シリンダ５内の圧縮側容積Ｖがピストンの上昇分だけ大きくなり圧力が減少しようとするが、このときのシリンダ内圧力が前述した減圧弁１０の設定圧力Ｐ₀以下であれば、その内圧を上昇させて設定圧となるまで圧縮空気が供給される。これにより砥石１ｂが上方の研削面Ｌｕまで上昇した状態でも理想研削面に砥石１ｂがあったときと同じ押圧力Ｆが作用するように作動状態が回復する。但し、押圧力Ｆの回復に要する時間は反発シリンダやリニアガイドの摩擦抵抗の大きさによってそれぞれ異なり、摩擦抵抗が小さい程早く回復することは当然である。
【００３４】
なお、上記減圧時のシリンダ内圧力が設定圧力Ｐ₀より高くなっていることは、減圧弁１０により設定圧力Ｐ₀より高い２次側圧力の圧縮空気が排気ポートより排出されるから、実際には生じることはない。
【００３５】
反対に、レイタンスの表面が凹んでいたり、ライニング層が薄くなっている部分に砥石１ｂが対応した場合、砥石１ｂは研削ユニットの全自重Ｗから反発シリンダによる反発力Ｆ₁を差引いて残る重量に相当する押圧力Ｆで押し下げられ、このため反発シリンダ５のピストンが押し下げられてシリンダ内の圧力が高くなろうとするが、減圧弁１０の排気ポート１０ｈから設定圧Ｐ₀以上の圧縮空気は排出されるため、設定圧Ｐ₀に設定される。そして、砥石１ｂが低い位置の研削面Ｌ_Lに当接すると理想研削面の場合と同じ押圧力Ｆに対応する反力Ｆ₀が作用して平衡し、同じ押圧力Ｆによる研削効果が得られる。
【００３６】
上記実施形態におけるモルタルライニング表面の微小な変形については次の通りである。まず、微小な変形ができる要因については２種類あり、その各々で大きさ、形状が異なる。１つは通常の施工方法に起因して生じる変形であり、モルタルライニングを遠心力で振り付けているため、素管自体の曲がりなどの影響を受けて外周面と形成された内周面の回転軸心が一致しないために生じるものである。これらの変形は比較的緩やかであり、ライニングの口径に応じて円周長のおよそ１／２程度に亘り、軸方向には５０〜３００ｍｍの大きさで、変形深さは最大２〜３ｍｍと考えられる。
【００３７】
もう１つは手直し作業により発生する変形である。通常の方法によってモルタルライニングを施工した後、ライニング端部に「欠け」などの欠陥が見つかると、ヘラを用いて手作業で修正する場合がある。これらの作業で出来た研削面の変形は管の呼び径に拘らず、円周方向長さ５０〜６０ｍｍ、軸方向３０〜４０ｍｍ程度、高さ約２〜４ｍｍ程度となる。
【００３８】
なお、研削面の仕上がり状態については、研削粉による砥石の目詰まりなどが影響するため、研削中に発生した研削粉を除去するためのエアブロー装置及びこれらを捕捉する集塵装置を備えることが望ましい。又、上記実施形態ではダクタイル鋳鉄管のモルタルライニング内面の研削について説明したが、研削対象としては上記に限定されず、同等の性質を有する管内の被研削面であれば全て適用できることは言うまでもない。
【００３９】
上記実施形態の管内面研削装置によれば、被研削面の微小に変形した比較的軟らかくて傷つき易いモルタルライニングの表面のレイタンスに対し表面形状の変化に追従しながら完全なレイタンス除去、ライニング角部の欠損などの形状不良を発生することなく能率的かつ完全な研削面を連続作業で得ることができる。又、研削面への追従性が向上し、砥石押圧力が表面形状の変化があっても均一に負荷できるようになったため、押圧力の変動に起因する砥石の偏摩耗を防止でき、このため砥石寿命を使い切ることが可能となり、さらに砥石の摩耗によって研削中の砥石回転軸の高さが変化しても装着初期と同様の研削条件を維持できるという利点も得られる。又、作業者には長時間のグラインダ使用の重労働から解放されるという副次的な効果もある。
【００４０】
なお、上記実施形態では反発シリンダ及び研掃工具の駆動源として圧縮空気を用いるアクチュエータを使用することを前提として説明したが、上記実施形態での圧力の調整により押圧力が一定範囲内に作用するように研削に支障のない範囲で駆動源としてそれぞれ電動モータを使用してもよい。
【００４１】
【発明の効果】
以上、詳細に説明したように、この発明の管内面研削方法及び装置では研削工具を有する水平支持部材を垂直方向に案内しながらその他端を反発力で支持し、全自重から反発力を差引いた残る重量の下向きの力を押圧力として研削工具の先端から被研削面に及ぼし、被研削面の凹凸に追従するように、研削工具への押圧力を反発力を調整することにより常に所定範囲内に設定するようにしたから、被研削面に凹凸の表面形状の変化があっても過剰研削又は研削残しが発生しない均一で安定した研削押圧力を付与することができるという利点が得られる。
【図面の簡単な説明】
【図１】実施形態の管内面研削装置の概略構成図
【図２】鋳鉄管研削現場における研削装置の配置図
【図３】圧縮空気の配管系統図
【図４】モルタルライニングのレイタンス表面形状の説明図
【図５】研削装置の作用の説明図
【符号の説明】
１研削工具
１ａ回転軸
１ｂ砥石
２案内機構
２ａスライダ
３水平支持部材
４昇降シリンダ
５反発シリンダ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for grinding a pipe inner surface for grinding a thin work surface such as a mortar lining latency applied to the inner surface of a cast iron pipe.
[0002]
[Prior art]
Cast iron pipes manufactured mainly by centrifugal casting that are used as pipes for waterworks are coated with a corrosion-resistant paint on the outer surface and a cement mortar lining on the inner surface to prevent corrosion. The This lining is also mainly applied by a method in which slurry mortar is pressed against the inner wall of the pipe by centrifugal force and waits for the cement to solidify, but when this slurry solidifies, it is a free substance mainly composed of calcium carbide or the like. What is commonly called latency is oozing out (like a kind of cement plaque). Since this latency may cause problems if mixed into tap water during use, it must be completely scraped from the surface in the finishing process.
[0003]
As a method for grinding the deposited layer on the mortar lining surface, a method proposed by Japanese Patent Laid-Open No. 3-184754 (Patent Publication 1) is known. This known grinding method uses a paper foil in which a large number of grinding papers are planted at a constant width in the tube axis direction on the outer peripheral surface of a cylindrical short tube. In an actual example, the above-mentioned paper foil is attached to the tip of a long rotating shaft, the paper foil is inserted into and contacted with a cast iron tube that is rotated at a predetermined speed on a roller, and the motor is supported while the rotating shaft is rotated by the motor. The carriage is advanced so that the lining surface of the inner surface of the pipe is evenly ground.
[0004]
Regarding grinding in cast iron pipes, for example, Japanese Patent Application Laid-Open No. 7-1000074 (Patent 2) proposes an apparatus that uses a cleaning tool to remove sand remaining in a receiving port of a pipe manufactured by a centrifugal casting method. ing. The scouring device according to this publication 2 holds the rotating shaft horizontally attached to the shaft end of the scouring tool to be inserted into the receiving port of the tube by a parallel guide member, and repels the weight of the unit to which the rotating shaft is attached. A repulsion driving device that generates a constant upward force; and a main driving device that applies a downward constant force to the unit to generate a predetermined downward scouring pressing force on the polishing tool.
[0005]
Even if the amount of wear of the scouring tool progresses by finely adjusting the downward constant force, the downward constant force obtained by subtracting the upward repulsive force from the total of the unit weight and downward constant force is used as the scouring pressing force. It is said that the scouring pressure can be kept constant and the product quality can be stabilized.
[0006]
[Problems to be solved by the invention]
By the way, there have been various proposals for a method for always obtaining a uniform grinding pressure for polishing an inner surface of a cylindrical tube. For example, in Japanese Patent Laid-Open No. 5-104422 (Patent Document 3), there is polishing over the entire length of a cast iron tube. It has been proposed to apply a uniform grinding pressure, and there is no doubt that these are effective means.
[0007]
However, when the surface of the mortar lining is ground, the surface shape has minute irregularities and changes in the lining thickness in the circumferential direction and the longitudinal direction of the tube in the vicinity of both ends of the tube. This is due to the construction method, but the width and length are considerably smaller than the size of a polishing tool such as a grindstone or wire brush attached to a polishing device that polishes the entire length of the tube. It is normal. Therefore, the polishing tool of the apparatus disclosed in the

above publications

1 and 3 cannot sufficiently follow these minute irregularities, and unslidable parts are generated.
[0008]
Therefore, in order to grind following the fine irregularities, it is necessary to at least change the size of the cleaning tool to the size corresponding to the fine irregularities, but that alone is still insufficient in the following points. Since conventional apparatuses other than the above publication 1 are premised on finishing of the inner surface of the cast iron pipe, it is excessive to remove the latency at the end of the mortar lining with the same pressing force and grinding wheel rotational power, and for a relatively soft mortar lining. May cause quality defects such as excessive polishing and defects at the corners of the lining.
[0009]
In the conventional known grinding apparatus, it is explained that grinding is performed by applying a constant pressing force. However, in order to prevent the polishing pressing pressure from being lowered due to wear due to the use of the polishing tool, the polishing tool is used. A method or apparatus for applying a constant pressing force to a target surface is disclosed, and how to control a constant pressing force when a pressing force of a certain level or more can be applied depending on the surface state of the target surface. There is no explanation about it. In addition, there is no other document 1 that aims to grind only the thin latency of the basic layer such as the mortar lining layer without being crushed.
[0010]
In order to remove the latency at the end of the mortar lining, minute adjustment of the pressing force and power and follow-up to the surface shape are required, so in practice, it is often performed manually using a hand grinder. However, manual grinder grinding has problems such as vibrations and dust that can affect the health of workers, as the occupational safety and health regulations stipulate breaks at regular intervals. There is an urgent need to automate from the viewpoint of improvement.
[0011]
In consideration of the various problems described above, the present invention cannot be completely removed by a grinding tool having a large diameter for grinding the entire length of the pipe, such as the surface near the both ends of the mortar lining provided on the inner surface of the cast iron pipe. It is an object of the present invention to provide a pipe inner surface grinding method and apparatus capable of always generating a uniform and stable grinding pressing force following the unevenness of the minute lining surface.
[0012]
[Means for Solving the Problems]
As a means for solving the above-mentioned problems, the present invention provides a horizontal support member including a grinding tool, wherein one end of a horizontal support member on which a grinding tool is horizontally mounted is guided in the vertical direction while the other end is supported by an upward repulsive force. The tip of the grinding tool is brought into contact with the surface to be ground of the horizontally supported tube surface with a pressing force obtained by subtracting the repulsive force from the total weight of the workpiece, and the pressing force on the surface to be ground changes in the surface shape. Correspondingly, the repulsive force is adjusted to keep it within a certain range depending on whether it is below the set value or exceeding it, and the pressing force is applied to the surface to be ground while following the change of the surface shape of the tip of the grinding tool, In this method, the inner surface of the pipe is ground so that the pressing force on the surface to be ground is always within a predetermined range.
[0013]
As an apparatus for carrying out this method, a horizontal support member having a grinding tool mounted horizontally, a guide mechanism for guiding one end of the horizontal support member in the vertical direction, and the other end of the horizontal support member being repelled upward by the force of compressed air. A grinding unit comprising a repulsive force imparting means for applying and supporting force is provided on the moving table, and a pressure adjusting means for adjusting the supply pressure of the compressed air is connected to the repulsive force imparting means so that the total weight of the grinding unit is When pressing the grinding tool by moving the moving table with the tip of the grinding tool in contact with the ground surface of the pipe that is supported horizontally, under the pressing force minus the repulsive force, the pressing force on the ground surface The tip of the grinding tool is adjusted to the surface shape by adjusting the supply pressure with the pressure adjustment means so that the repulsive force is kept within a certain range depending on whether the value is less than or equal to the set value corresponding to the change in the surface shape. Following changes in While exerting a pressing force to the ground surface, it is possible to adopt a luminal surface grinding apparatus for grinding as the pressing force is always within a predetermined range to the ground surface.
[0014]
According to the grinding method and apparatus having the above configuration, grinding can be performed with a uniform and stable pressing force following the irregularities of the surface shape such as minute undulations on the inner surface of the tube. The other end of the horizontal support member is supported by the repulsive force, one end is guided in the vertical direction, and the tip of the grinding tool attached to the one end is applied to the surface to be ground on the inner surface of the pipe with the pressing force obtained by subtracting the repulsive force from the total weight. Move and grind in contact. In this case, the grinding tool is also rotated while rotating the horizontally supported tube, and the tip is inserted from the end of the tube.
[0015]
Also, if the surface to be ground has a mortar lining surface on the inner surface of the cast iron pipe and there are irregularities such as minute waviness specific to the latency that occurs near both ends of the pipe, the pitch and width dimensions of the irregularities It is assumed that the grinding tool has a corresponding size (below). This is because a grinding tool having a diameter length several times larger than the unevenness dimension will straddle the uneven shape and cannot grind the entire surface. In the present invention, the term “grinding” is used to include the concepts of grinding, polishing, and polishing.
[0016]
Since one end of the horizontal support member is guided in the vertical direction, the horizontal support member always moves up and down while maintaining the horizontal. When the repulsive force is selected and applied with a value slightly smaller than the total weight, the remaining downward force is applied as a pressing force from the tip of the grinding tool to the surface to be ground. This pressing force is balanced with the reaction force from the surface to be ground, whereby the horizontal support member is held with the tip of the grinding tool in contact with the surface to be ground. However, if there is a change in surface shape such as minute irregularities on the surface to be ground, the horizontal support member descends or rises following the irregularities.
[0017]
When the surface shape is concave, the tip of the grinding tool is separated from the surface to be ground, so the grinding tool is lowered by the remaining downward force acting on the grinding tool. Therefore, the repulsive force increases due to this lowering.At this time, the repulsive force is adjusted to slightly decrease from the set value, the repulsive force is kept within a certain range, the horizontal support member is supported, and the ground is ground at the lowered position When the tip of the grinding tool comes into contact with the surface, it is balanced with the reaction force of the same magnitude, and grinding is performed with a pressing force within a predetermined range substantially the same as the initial state. On the other hand, when the surface shape is convex, the reaction force acting from the surface to be ground is larger than the initial state, and the repulsive force is adjusted to decrease accordingly, so that the repulsive force is kept within a certain range. Then, the tip of the grinding tool comes into contact with the surface to be ground at a slightly elevated position, and grinding is performed with a pressing force within a predetermined range substantially the same as the initial state.
[0018]
Embodiment
Embodiments of the present invention will be described below with reference to the drawings. In the illustrated pipe inner surface grinding apparatus A, a grindstone 1b is attached to the tip of a horizontal rotary shaft 1a, and the rotary tool 1a is rotationally driven by a drive motor 1c, and a slider 2a is linearly formed in a vertical direction. A grinding unit comprising a guide mechanism 2 using a linear guide guided by a rail and a horizontal support member 3 using an L-shaped support frame guided at one end via the guide mechanism 2 is placed on a moving table 6. The other end of the horizontal support member 3 is lifted and lowered by a lifting cylinder 4 and supports a repulsive force applying means 5 using a repelling cylinder provided adjacent to the outermost end.
[0019]
In the example shown in the figure, the rotating shaft 1a of the grinding tool 1 is horizontally attached to the vertical portion of the L-shaped support frame, and the vertical portion is fixed to the slider 2a, so that the grinding tool 1 is held horizontally to move up and down. The guide mechanism 2 is configured to guide freely. The grindstone 1b may be a wire brush or a plurality of grinding disks. An air motor using compressed air as a power source is used as the drive motor 1c, and the elevating cylinder 4 and the repelling cylinder 5 are also driven by the compressed air.
[0020]
An elevating cylinder 4 is attached to the horizontal support member 3 so that only a vertically upward thrust is applied. In this case, the elevating cylinder 4 is supported by the elevating cylinder 4 but is detachably attached without being connected. The whole goes up and down. When grinding is not performed, the elevating cylinder 4 is extended to lift the entire grinding unit, and the grindstone 1b is operated away from the surface to be ground. When grinding, when the elevating cylinder 4 is contracted, the grindstone is lowered by its own weight until it comes into contact with the surface to be ground. At this time, if the tip of the piston rod of the elevating cylinder 4 is connected to the horizontal support member 3, the internal frictional resistance of the cylinder 4 affects the followability to changes in the pressing force during grinding. Keep it.
[0021]
The moving table 6 loaded with the grinding unit has a servo motor 7 as a drive unit and rotates a ball screw 7a connected to the output shaft thereof to move the rail 7b on the two rows on the adjustment table 8 at a predetermined speed. It is provided to move forward and backward. The adjustment table 8 is for adjusting the height of the grindstone 1b when the setup is changed, and two rows of rails 7b are provided horizontally and parallel on the table. In order to adjust the height, a mechanism is provided for converting the power of the drive motor 9 into vertical vertical movement using an X-shaped jack.
[0022]
As shown in FIG. 2, the pipe inner surface grinding apparatus A is installed to grind the inner surface of a ductile cast iron pipe. In the example shown in the drawing, mortar lining is applied to the inner surface of the pipe, and it is used to grind the latency of a predetermined length range (l in the figure) near the end of the pipe among the latencies deposited on the surface. As shown in the drawing, the rotating shaft 1a is connected to the rotating shaft 1a from the end of the pipe P supported horizontally by two rows of rollers R for rotating the pipe arranged in a parallel portion near the receiving port Po of the pipe P and in the appropriate position near the insertion port. It is arranged so that grinding can be performed by inserting the grindstone 1b at the tip. M is a motor, and grinding is performed while the rotational force is transmitted to the roller R and the pipe P is rotated at a constant speed.
[0023]
Although the pipe inner surface grinding apparatus A is arranged on the receiving side of the pipe P, a grinding apparatus A ′ having substantially the same configuration and function is also arranged on the insertion side. This grinding apparatus A ′ has exactly the same configuration except that it has a movement axis S in order to make the movement distance of 1 m due to the standard length of the pipe P under the adjustment table 8 freely movable. The travel distance is based on Japan Ductile Iron Pipe Association Standard (JDPA). That is, for the small-diameter iron pipe, the effective length from 75 to 100φ (straight pipe portion length excluding the receiving opening) is determined to be 4 m, and the effective length from 150 to 250 is set to 5 m.
[0024]
FIG. 3 shows a piping system for compressed air to the elevating cylinder and the repelling cylinder. (A) In the figure, 10 is a precision pressure reducing valve for a repelling cylinder, 11 and 12 are adjustment valves for adjusting the descending and raising speed of the grinding unit, 13 is a switching valve, and 14 is an air pump of a compressed air supply source. The pressure reducing valve 10 is capable of setting a minute pressing force by the grindstone 1b by adjusting the pressure, and its schematic configuration is shown in FIG. 10a is a pressure adjusting handle, 10b is a spring, 10c is a diaphragm, 10d is a valve seat, 10e is a needle, 10f is a seat valve, 10g is a spring, and 10h is an exhaust port.
[0025]
Pressure set by the pressure regulator knob 10a is a P _0. Assuming that P ₀ > P ₂ , the pressing force of the spring 10b is greater than the force exerted on the diaphragm 10c by the secondary pressure P ₂ , and the diaphragm 10c and the valve seat 10d are pushed downward, and the valve seat 10d is pushed down. Since the needle 10e is pushed down, the seat valve 10f is opened and air flows from the primary side to the secondary side.
[0026]
When P ₀ <P ₂ , the pressing force of the spring 10b is overcome and the diaphragm 10c is pushed up in the opposite direction. For this reason, the needle 10e and the valve seat 10d are opened, and secondary air (P ₂ ) flows from the hole in the center of the valve seat to the exhaust port 10h and is exhausted. Since the secondary side is connected to the repulsion cylinder 5, the pressure in the rebound cylinder 5 (P ₂₎ is a pressure P ₂ when the reaction force grindstone 1b receives from the ground surface lower than the set pressure P ₀ Air is sent to the repulsion cylinder 5 until it reaches P _0, and when the pressure P ₂ becomes higher than P ₀ , the air at the pressure P ₂ is discharged from the exhaust port 10 h of the pressure reducing valve 10 and returns to P ₀ .
[0027]
The set pressure P _{0 that} is actually set by the pressure reducing valve 10 is set to a constant range of 1.5 ± 0.5 kgf / cm ^2, and when the set pressure P ₀ is exceeded, the pressure reducing valve 10 is in supply and exhaust operation state. . In this embodiment, the size (diameter and length) of the grindstone 1b described above corresponds to the change in the latency shape (unevenness due to surface waviness) in a predetermined length range in the vicinity of the end of the tube. This is a general grindstone used for polishing for finishing the casting surface of the steel, and has a much smaller size. The details will be described later.
[0028]
The operation of the pipe inner surface grinding apparatus A of the embodiment having the above-described configuration is as follows. In the actual apparatus, as described above, the pair of pipe inner surface grinding apparatuses A and A ′ are simultaneously operated in parallel from the inlet side and the insertion side of the pipe P, respectively. Will be described. The object to be ground is the latency deposited on the surface of the mortar lining in a predetermined length range (distance 1 in FIG. 2) in the vicinity of the pipe end of the cast iron pipe P. The reason for the vicinity of the pipe end is that the change in the surface shape of the latency deposited in the vicinity (unevenness due to undulation) is finer than the surface shape of the latency that is deposited in the majority of the vicinity of both ends of the pipe. This is because a grinding process is required.
[0029]
While rotating the cast iron pipe P with the roller R, the grindstone 1b at the tip of the rotating shaft 1a is inserted from the receiving port Po side, and the grindstone 1b is deposited on the latency deposited on the mortar lining surface of the pipe P while rotating the grindstone 1b. Abut. At this time, when the height of the rotary shaft 1a and the grindstone 1b is roughly set by the height adjustment table 8, and the lifting cylinder 4 is contracted from the height supported by the lifting cylinder 4, the repulsive cylinder causes the repulsive force to act upward. Thus, it is assumed that the remaining weight after reducing the weight of the grinding unit is prepared in advance so as to be a pressing force acting on the surface to be ground from the grindstone 1b.
[0030]
When grinding is performed by rotating the grindstone 1b in contact with the latencies of the surface of the mortar lining L, as shown in FIG. Therefore, the grinding wheel 1b having a diameter and length corresponding to the mortar lining layer manufacturing process does not leave uncut portions in small waviness-shaped portions. The illustrated grindstone 1b has a length corresponding to half the pitch of the undulation length illustrated in FIG. 5A, and (b) the entire circumferential length of the grindstone 1b or about half of the undulation length in the circumferential direction illustrated in FIG. Are the corresponding dimensions (iron pipe 200φ or more).
[0031]
Specific dimensions of the grindstone 1b of the grinding apparatus of the illustrated example and the mortar lining to be ground are as follows.

When the latency is ground using the grindstone 1b having the size (dimensions) as described above, as shown in FIG. 5, the grindstone 1b abuts on the surface to be ground to exert a pressing force F, and the reaction force F ₀ is obtained. The pressing force F acts so that the total of the reaction force F ₀ received by the grindstone 1 b and the reaction force F ₁ generated by the reaction cylinder is balanced with the weight W of the entire grinding unit. However, it is F = F _0.
| F | = | W |-| F ₁ |
[0032]
If the surface of the mortar lining latencies is flat, a constant pressing force F is always applied while maintaining the above balance, but the surface of the latencies is formed on the lining protrusions or thick layers. In this case, the ideal grinding surface L ₀ changes toward the upper one-dot chain line Lu. Therefore, grinding wheel 1b is pushed back by the reaction force F ₀ slightly larger from the state which has been matched by the pressing force F rises to above the grinding surface Lu, the piston rod of the repulsive cylinder 5 connected to the horizontal support member 3 Ascend the same distance.
[0033]
Therefore, the compression side volume V in the repulsion cylinder 5 increases by the amount of the piston rise, and the pressure tends to decrease. If the pressure in the cylinder at this time is equal to or lower than the set pressure P _{0 of the} pressure reducing valve 10 described above, Compressed air is supplied until the internal pressure is raised to the set pressure. As a result, even when the grindstone 1b is raised to the upper grinding surface Lu, the operating state is recovered so that the same pressing force F as when the grindstone 1b is present on the ideal grinding surface is applied. However, the time required for recovery of the pressing force F varies depending on the magnitude of the frictional resistance of the repulsion cylinder and the linear guide, and it is natural that the smaller the frictional resistance, the faster the recovery.
[0034]
Incidentally, the cylinder pressure during the decompression is higher than the set pressure P _0, since the compressed air in the secondary pressure is higher than the set pressure P ₀ by the pressure reducing valve 10 is discharged from the exhaust port, actually Will not occur.
[0035]
Conversely, or dented surface of Reitansu, if the grinding wheel 1b is corresponding to the parts lining layer is thin, the grinding wheel 1b in weight that remains by subtracting the repulsive force F ₁ by the repulsive cylinder from the total self-weight W of the grinding unit It is pushed down by the corresponding pressing force F, and the piston of the repelling cylinder 5 is pushed down to increase the pressure in the cylinder. However, the compressed air of the set pressure P ₀ or more is discharged from the exhaust port 10h of the pressure reducing valve 10. Therefore, the set pressure P ₀ is set. Then, the grinding wheel 1b acts reaction force F ₀ corresponding to the same pressing force F and the ideal case the grinding surface when in contact with the grinding surface L _L of the low position in equilibrium, grinding effect by the same pressing force F can be obtained .
[0036]
The minute deformation of the mortar lining surface in the above embodiment is as follows. First, there are two types of factors that can cause a minute deformation, each of which has a different size and shape. One is the deformation caused by the normal construction method. Since the mortar lining is sprinkled by centrifugal force, the rotation axis of the inner peripheral surface formed with the outer peripheral surface under the influence of the bending of the raw tube itself. This is because the hearts do not agree. These deformations are relatively gradual, about half the circumference depending on the diameter of the lining, 50 to 300 mm in the axial direction, and a maximum deformation depth of 2 to 3 mm. It is done.
[0037]
The other is deformation that occurs due to rework. After a mortar lining is constructed by a normal method, if a defect such as a “chip” is found at the end of the lining, it may be manually corrected using a spatula. The deformation of the grinding surface made by these operations is about 50 to 60 mm in the circumferential direction, about 30 to 40 mm in the axial direction, and about 2 to 4 mm in height regardless of the nominal diameter of the tube.
[0038]
In addition, about the finishing state of a grinding surface, since clogging of the grindstone with grinding powder etc. influences, it is desirable to provide an air blow device for removing grinding powder generated during grinding and a dust collecting device for capturing them. . Moreover, although the said embodiment demonstrated the grinding of the mortar lining inner surface of a ductile cast iron pipe, it cannot be overemphasized that it is applicable to all the to-be-ground surfaces in a pipe | tube which has the same property as grinding object.
[0039]
According to the pipe inner surface grinding apparatus of the above embodiment, complete latency removal and lining corners follow the change in surface shape with respect to the surface latency of the surface of the mortar lining which is relatively soft and easily damaged, which is minutely deformed on the surface to be ground. An efficient and complete ground surface can be obtained in a continuous operation without causing shape defects such as chipping. In addition, the ability to follow the grinding surface has been improved, and even if there is a change in the surface shape of the grinding stone pressing force, the load can be applied uniformly, thus preventing uneven wear of the grinding stone due to fluctuations in the pressing force. It is possible to use up the life of the grindstone, and it is also possible to maintain the same grinding conditions as in the initial stage even if the height of the grindstone rotating shaft during grinding changes due to wear of the grindstone. In addition, workers have the secondary effect of being freed from heavy labor using grinders for a long time.
[0040]
Although the above embodiment has been described on the assumption that an actuator using compressed air is used as a drive source for the repulsion cylinder and the polishing tool, the pressing force acts within a certain range by adjusting the pressure in the above embodiment. As described above, an electric motor may be used as a drive source within a range that does not hinder grinding.
[0041]
【The invention's effect】
As described above in detail, in the pipe inner surface grinding method and apparatus of the present invention, the horizontal support member having the grinding tool is guided in the vertical direction while the other end is supported by the repulsive force, and the repulsive force is subtracted from the total weight. Apply the remaining downward force as the pressing force from the tip of the grinding tool to the surface to be ground, and adjust the repulsive force to the grinding tool so that it follows the unevenness of the surface to be ground. Therefore, even if there is a change in the surface shape of the unevenness on the surface to be ground, there can be obtained an advantage that a uniform and stable grinding pressing force that does not cause excessive grinding or residual grinding can be applied.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a pipe inner surface grinding apparatus according to an embodiment. FIG. 2 is a layout diagram of a grinding apparatus at a cast iron pipe grinding site. FIG. 3 is a compressed air piping system diagram. Explanatory drawing [figure 5] Explanatory drawing of action of grinding device
DESCRIPTION OF SYMBOLS 1 Grinding tool

1a Rotating shaft

1b Grinding wheel 2 Guide mechanism 2a Slider 3 Horizontal support member 4 Lifting cylinder 5 Repulsion cylinder

Claims

The other end while guiding one end of the horizontal support member 3 the grinding tool 1 mounted horizontally guiding mechanism 2 for vertically moving vertically supported by an upward repulsive force F _1, the horizontal support member 3 including the grinding tool 1 moving ground is brought into contact with the grinding surface of the horizontally supported tube inner surface the tip of the grinding tool 1 a repulsive force F ₁ by the pressing force F = W-F ₁ minus the total self-weight W, to be ground surface pressing force F by the adjustment to hold the repulsive force F ₁ within a certain range depending on whether or exceeds this in response to a change in surface shape becomes less than the set value, the grinding tool 1 tip surface shape of the A pipe inner surface grinding method in which a pressing force F is applied to a surface to be ground while following a change, and grinding is performed so that the pressing force F on the surface to be ground is always within a predetermined range.

A horizontal support member 3 with the grinding tool 1 mounted horizontally, a guide mechanism 2 for guiding one end of the horizontal support member 3 by raising and lowering it in the vertical direction, and repelling the other end of the horizontal support member 3 upward by the force of compressed air A grinding unit comprising a repulsive force applying means 5 for applying and supporting a force F ₁ is provided on the moving table 6 , and a pressure adjusting means for adjusting the supply pressure of the compressed air is connected to the repulsive force applying means 5 for grinding. Under the pressing force F = W−F _{1 obtained} by subtracting the repulsive force F ₁ from the total weight W of the horizontal support member 3 including the tool 1 , the tip of the grinding tool 1 is brought into contact with the surface to be ground of the horizontally supported pipe. When the moving table 6 is moved and brought into contact with each other and moved and ground, the repulsive force F ₁ depends on whether the pressing force F on the surface to be ground is equal to or less than the set value corresponding to the change in the surface shape. Supply pressure by pressure adjusting means to keep the pressure within a certain range While adjusting so as to follow the tip of the grinding tool 1 to a change in surface shape exerts a pressing force F to the ground surface, tube surface grinding pressing force F to the ground surface is ground to always falls within a predetermined range apparatus.

The pipe inner surface grinding apparatus according to claim 2 , further comprising lifting means for supporting the horizontal support member 3 so as to be able to come into contact with and away from the horizontal support member 3 .

The repulsive force applying means 5 is an air cylinder using compressed air as a power source, and is connected to and supported by the other end of the horizontal support member 3. A pressure reducing valve 10 is used as a pressure adjusting means, and the pressure reducing valve 10 is ground. Corresponding to the elevation of the tip of the tool 1, the compressed air is supplied to the cylinder when the pressure in the air cylinder is lower than the set pressure set by the pressure reducing valve 10 , and the compressed air in the cylinder is exhausted when the pressure is higher than the set pressure. Accordingly, the pipe inner surface grinding apparatus according to claim 2 or 3 , wherein the tip of the grinding tool 1 follows the change in the surface shape of the surface to be ground.