JP2004268278A

JP2004268278A - Ball-point pen

Info

Publication number: JP2004268278A
Application number: JP2003058289A
Authority: JP
Inventors: Tetsuhiro Kurita; 哲宏栗田
Original assignee: Pilot Ink Co Ltd
Current assignee: Pilot Ink Co Ltd
Priority date: 2003-03-05
Filing date: 2003-03-05
Publication date: 2004-09-30
Anticipated expiration: 2023-03-05
Also published as: JP4252824B2

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a handwriting from becoming blurred or disabled when a pen is used for continuous writing with a ball point facing upward. <P>SOLUTION: In this ball-point pen, a ball 3 is rotatably embraced by an inwardly facing tip edge part 21 formed at the apex of a tip main body 2 and a ball receiving seat 22 behind the tip edge part 21. In addition, ink and a follower are accommodated inside an ink accommodation cylinder, and the straight part 81 of a spring is inserted through an inner hole 5 running in the axial direction of the ball receiving seat 22. Next, an ink circulating gap 6 is formed between the internal surface of an inner hole 5 and the external surface of the straight part 81. The minimum transverse area S of the ink circulating gap 6 is set to 0.02 to 0.15 mm<SP>2</SP>. The viscosity of the ink at 20°C is set at 1 to 50 mPa s and the viscosity at a rotational frequency of 100 rpm and 20°C is 3 to 160 mPa s and also the shear-rate thinning index is 0.80 to 0.99. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、ボールペンに関する。詳細には、ペン先のボールを前方に付勢するスプリングを備えたボールペンに関する。本発明で、「前」とは、ペン先側を指し、「後」とは、その反対側を指す。
【０００２】
【従来の技術】
特許文献１には、スプリングのストレート部がペン先のボールを前方に押圧するタイプのボールペンが開示されている。また、前記特許文献１には、粘度の高い通常の油性ボールペンインキや剪断減粘性を有した中粘度インキを用いることが記載されている。また、前記特許文献１には、ペン先上向き状態でのインキの逆流を防止する、ボール弁と受け座とからなる逆流防止機構を設けることが開示されている。
【０００３】
【特許文献１】
特開平１０−３１５６７８号公報
【０００４】
【発明が解決しようとする課題】
しかし、前記特許文献１には、ペン先上向き状態でのインキの逆流を防止する逆流防止機構を備えることにより、一時的なペン先からの空気の混入は防止できたとしても、ペン先上向き状態のままで連続して筆記する場合、逆流防止機構の作用により、逆流防止機構の後方のインキ収容部からペン先へのインキ供給が遮断される。そのため、ペン先上向き状態で連続筆記すると、逆流防止機構の前方のインキが消費された後は、ペン先を下向きにしなければ、ボール後面に空気が混入し、ボール後面にインキが連続供給できなくなり、その結果、筆跡が掠れたり、筆記不能（即ちインキ吐出不能）となるおそれがあった。
【０００５】
また、この他にも、従来、ペン先上向き状態でも筆記可能にするものとして、インキの後方に高圧ガスを封入してインキを前方に押圧する構造（いわゆるガス加圧式ボールペン）が知られているが、これは、構造が複雑で、製造コストが増加し、安価に提供することが困難である。
【０００６】
本発明は前記従来の問題点を解決するものであって、ペン先上向き状態で連続筆記した場合、筆跡が掠れたり筆記不能となるおそれがなく、円滑なインキ流出性が維持できるボールペンを、安価に提供しようとするものである。
【０００７】
【課題を解決するための手段】
〔１〕本発明は、金属製筒体よりなるチップ本体２の先端部に、内向きの先端縁部２１とその後方にボール受け座２２とを設け、前記先端縁部２１と前記ボール受け座２２とによりボール３を回転可能に抱持し、前記チップ本体２をインキ収容筒７に接続し、前記インキ収容筒７の内部に、インキ７１と、該インキ７１の後端に配置され且つ該インキ７１の消費に伴い前進する追従体７２とを収容し、チップ本体２内にスプリング８のストレート部８１を挿入配置し、前記ストレート部８１の先端がボール３の後面に当接してボール３を前方に付勢し、前記ボール３を先端縁部２１の内面に密接させてなるボールペン１であって、前記ボール受け座２２の少なくとも中心部に軸方向に貫通する内孔５を設け、前記内孔５にスプリング８のストレート部８１を挿通させ、前記内孔５内面と前記ストレート部８１外面との間にインキ流通間隙６を形成し、前記インキ流通間隙６の最小横断面積Ｓを、０．０２ｍｍ^２〜０．１５ｍｍ^２の範囲に設定し、前記インキ収容筒７の内部に収容するインキ７１を、２０℃における粘度が１ｍＰａ・ｓ〜５０ｍＰａ・ｓの範囲、または２０℃における回転数１００ｒｐｍでの粘度が３ｍＰａ・ｓ〜１６０ｍＰａ・ｓの範囲且つ剪断減粘性指数が０．８０〜０．９９の範囲に設定したこと（請求項１）を要件とする。
【０００８】
前記インキ流通間隙６の最小横断面積Ｓを、０．０２ｍｍ^２〜０．１５ｍｍ^２の範囲（好ましくは０．０３ｍｍ^２〜０．１０ｍｍ^２の範囲）に設定したことにより、ボール受け座２２の内孔５内面とストレート部８１外面との間に、毛細管力の強いインキ誘導部６１を形成できる。さらに、インキ収容筒７に収容するインキ７１の粘度を、前記範囲に設定したことにより、インキ７１が従来より低粘度となり、インキ流動性に優れ、毛細管力が作用しやすくなる。
【０００９】
即ち、ボール受け座２２の内孔５内面とストレート部８１外面との間に毛細管力の強いインキ誘導部６１を形成することと、流動性に優れた低粘度のインキ７１を採用することとが相まって、ペン先上向き状態で連続筆記したとしても、潤沢なインキ７１がボール３後面に連続的に供給され、ボール３後面に空気が混入することを回避できる。その結果、筆跡掠れや筆記不能を発生させることなく、ペン先上向き状態での長時間の連続筆記が可能となるボールペンを、シンプルな構造により、安価に提供できる。
【００１０】
もし、インキ流通間隙６の最小横断面積Ｓが、０．０２ｍｍ^２より小さい場合、ボール受け座２２の内孔５内面とストレート部８１外面との間の隙間が過度に小さくなり、円滑なインキ流通性が得られないし、ストレート部８１を内孔５にスムーズに挿入できないおそれがある。また、インキ流通間隙６の最小横断面積Ｓが、０．１５ｍｍ^２より大きい場合、ボール受け座２２の内孔５内面とストレート部８１外面との間に十分な毛細管力が得られず、ペン先上向き状態で連続筆記する場合、ボール３後面まで十分にインキ７１を引き上げることができない。また、前記インキ７１の粘度が前記特定した範囲より大きい場合、インキ流動性が低下するため、ペン先上向き状態で連続筆記した際、内孔５内面とストレート部８１外面との間の強い毛細管力を有するインキ誘導部６１によっても、ボール３後面にインキ７１を十分に供給できないおそれがある。
【００１１】
尚、前記「インキ流通間隙の最小横断面積Ｓ」は、ボール受け座２２に形成される放射状の縦溝部５１がボール受け座２２に軸方向に貫通する場合は、その縦溝の横断面積を含み、一方、ボール受け座２２に形成される縦溝部５１がボール受け座２２に軸方向に貫通しない場合は、中心部に貫通した部分のみの内孔５内面とストレート部８１外面との間に形成されるインキ流通間隙の最小横断面積をいう。尚、本発明で採用するペン先ボール３の外径は０．５ｍｍ〜０．７ｍｍの範囲のものが好ましい。
【００１２】
尚、前記剪断減粘性指数は、粘度計により剪断応力値（Ｔ）及び剪断速度（ｊ）値の流動学的測定により導かれる実験式（Ｔ＝Ｋｊ^ｎ：但し、Ｋ及びｎは計算された定数である）を適用して計算されるｎ値である。尚、前記Ｅ型回転粘度計とは、具体的には、ＥＭ型回転粘度計、ＥＬ型回転粘度計、ＥＨ型回転粘度計が挙げられる。
【００１３】
〔２〕前記請求項１において、チップ本体２は、切削加工によりボール受け座２２及び内孔５を形成するタイプであってもよいが、金属製筒体の先端近傍を内方への押圧変形により複数の内方突出部４を形成し、前記内方突出部４によりボール受け座２２を構成し、前記ボール受け座２２に形成する内孔５が、前記隣り合う内方突出部４の相互間に、中心部から径方向外方に放射状に延び且つ軸方向に貫通する縦溝部５１を備え、前記縦溝部５１の溝幅をストレート部８１の外径Ａより小さく設定し、前記内方突出部４の頂面４１を凸曲面状とすること（請求項２）が好ましい。
【００１４】
ペン先上向き状態で筆記した場合、ボール３の回転により、スプリング８のストレート部８１の先端がボール３後面に接触しながら径方向外方（即ちペン先移動方向）に移動する。そして、前記ストレート部８１の先端部外面が、内方突出部４の頂面４１に接触しながら該頂面４１に沿って縦溝部５１方向に移動する。即ち、前記内方突出部４の頂面４１を凸曲面状とすることにより、筆記時、ボール３の回転により、ストレート部８１の先端が、凸曲面状の頂面４１に沿って縦溝部５１相互間を滑らかに移動する。そして、ストレート部８１の先端部外面と内方突出部４内面とが接触することにより、その接触部分に強力な毛細管力を有するインキ誘導部６１を形成できる。前記インキ誘導部６１は、回転するボール３のインキ消費側に常に形成されるため、該インキ消費側のボール３表面に有効にインキ７１を供給できる。その結果、より一層、ペン先上向き状態での連続筆記の場合において、筆跡が掠れたり筆記不能となるおそれがなくなる。
【００１５】
また、縦溝部５１の溝幅をストレート部８１の外径Ａより小さく設定したことにより、ストレート部８１の先端部が縦溝部５１に圧入されることなく、常にボール３の中心部または中心部近傍をストレート部８１で押圧でき、その結果、ボール３の回転不良やボール３と先端縁部２１との密接不良を防止できる。さらに、軸方向に貫通する縦溝部５１にストレート部８１が入り込むことを防止できることから、縦溝部５１のインキ誘導機能が阻害されることがなく、縦溝部５１を介してボール３表面のインキ消費側にインキ７１を、より一層、迅速に供給できる。尚、前記複数の内方突出部４の個数は、具体的には、製造が容易な点から、３個または４個が好ましい。
【００１６】
【発明の実施の形態】
本発明の実施の形態を図面に従って説明する。
【００１７】
図１乃至図４に本発明の一実施例を示す。
【００１８】
本実施例のボールペン１は、先端部にボール３を回転可能に抱持したチップ本体２と、該チップ本体２の後部がその前部に圧入固着されたホルダー９と、該ホルダー９の後部がその先端開口部に圧入固着されたインキ収容筒７と、該インキ収容筒７の内部に収容されるインキ７１及び追従体７２と、前記チップ本体２の内部及びホルダー９の内部に収容配置されるスプリング８と、前記インキ収容筒７の後端開口部に圧入固着される尾栓７３とからなる。
【００１９】
前記インキ収容筒７は、両端が開口された直円筒体であり、合成樹脂（例えばポリプロピレン）の押出成形により得られる。前記インキ収容筒７の先端開口部は、チップ本体２を有するホルダー９の後部が圧入固着される。前記インキ収容筒７の後端開口部には、通気孔７３ａが貫設された尾栓７３が圧入固着され、インキ収容筒７の追従体７２の後方空間と外気とが連通される。本発明では、前記インキ収容筒７の内径は、４ｍｍ〜６ｍｍのものが有効であり、本実施例では、４．４ｍｍのものが採用される。
【００２０】
前記インキ収容筒７の内部には、インキ７１（Ｂ型回転粘度計における２０℃での粘度が９ｍＰａ・ｓであり、ＥＬ型回転粘度計における２０℃での回転数１００ｒｐｍの粘度が９ｍＰａ・ｓであるとともに剪断減粘性指数が０．９７である水性インキ）が充填される。さらに、前記インキ収容筒７内には、該インキ７１の後端に配置され、且つ該インキ７１の消費に伴って前進する追従体７２（具体的には、高粘度流体７２ａと該高粘度流体７２ａ中に収容させた固形物７２ｂとからなる追従体７２）が収容される。前記追従体７２は、前記以外にも、固形物７２ｂを備えない高粘度流体７２ａのみからなる構成、またはインキ収容筒７内壁と摺動可能な固形物７２ｂのみからなる構成であってもよい。
【００２１】
前記チップ本体２は、金属（例えば、ＳＵＳ３０４、ＳＵＳ３０５、ＳＵＳ３２１等のオーステナイト系のステンレス鋼）からなる直円筒状の細管よりなる。前記チップ本体２の先端近傍内面には、内方への押圧変形により、４個の内方突出部４（即ちボール受け座２２）が周方向に等間隔に形成される。また、前記チップ本体２の先端部には、内方への押圧変形により環状の内向きの先端縁部２１が形成される。前記先端縁部２１内面と前記内方突出部４前面との間（即ちボール抱持部）にボール３（外径０．５ｍｍ）が回転可能且つ前後方向移動可能に抱持される。前記ボール３の前後方向に移動可能な量は、筆跡滲み及び筆跡掠れのない適度なインキ流出性が得られる点で、１０μｍ〜２０μｍの範囲に設定することが好ましい。
【００２２】
前記内方突出部４の頂面４１は球面状（凸曲面状）となっている。前記内方突出部４の相互間には、中心部から径方向外方の４方向に放射状に延び且つ軸方向に貫通する縦溝部５１を備えた内孔５が形成される。横断面視において、前記内孔５は、内方に膨らむ４つの円弧からなる形状であり、前記縦溝部５１は、径方向外方に向かうに従って溝幅が小さくなり、径方向外端部において溝幅がゼロとなる形状である。前記内方突出部４の頂面４１に接する仮想内接円の直径Ｂは、０．２ｍｍに設定され、ストレート部８１の外径Ａより大きく設定されるため、ストレート部８１が内孔５内に挿通可能となる。
【００２３】
前記ホルダー９は、合成樹脂（例えばポリプロピレン）の射出成形により得られる筒状体である。前記ホルダー９は、チップ本体２が取り付けられる先細状の前部と、インキ収容筒７の先端面と当接する鍔部と、インキ収容筒７の先端開口部に圧入される後部とからなる。前記ホルダー９の内部には、先端が外部に開口するチップ取付孔と、該チップ取付孔にその先端が連通し且つその後端が外部に開口するインキ流通孔とが設けられる。前記インキ流通孔の中間部内面には、周状に分散配置される複数（例えば４個）の係止突起９１が一体に形成される。
【００２４】
前記スプリング８は、線径０．１４ｍｍのステンレス鋼製線材により、前部のストレート部８１と、後部のコイル部８２とが一体に連設されてなる。前記コイル部８２の後端部には、外径が前方のコイル部８２より大きく設定された膨出部８３が形成される。前記膨出部８３は、線材間が密着した密着巻部により形成される。前記膨出部８３が、前記ホルダー９内面の係止突起９１を後方より乗り越えて、前記係止突起９１に係止され、ボール３と係止突起９１との間でスプリングが圧縮状態で保持される。尚、前記スプリング８は、前記構成以外にも、コイル部８２を備えないストレート部８１のみの構成であってもよい。
【００２５】
前記スプリング８のストレート部８１（外径Ａ：０．１４ｍｍ）は、前記内孔５の中心部に挿通され、前記ストレート部８１の先端がボール３後面に当接することにより、ボール３が、前方に付勢されて内向きの先端縁部２１の内面に密接される。それにより、非筆記時、ペン先がシールされ、ペン先下向き状態で保管したとしても、ペン先からのインキ漏出が防止され、また、ペン先上向き状態で保管したとしても、ペン先からの空気混入が防止される。尚、前記内孔５内面と前記ストレート部８１外面との間に形成されるインキ流通間隙６の最小横断面積Ｓ（図３の点線による斜線部分）は、０．０４３ｍｍ^２に設定されている。
【００２６】
図４に示すように、筆記時、スプリング８のストレート部８１の先端部は、ボール３の回転に伴ってボール３後面に接触しながら径方向外方（ペン先移動方向）に移動する。そして、前記ストレート部８１の先端部は、二つの内方突出部４の凸曲面状の頂面４１に接触し、その二つの接触部分に強い毛細管力を有するインキ誘導部６１が生じる。前記ストレート部８１先端によるインキ誘導部６１は、回転するボール３のインキ吐出側（インキ消費側）に常に形成される（図４の点線による矢印はインキの流れを表す）。そのため、ペン先上向き状態で連続筆記したとしても、ボール３後面に十分な量のインキ７１を、下方のインキ収容筒７から重力に抗して引き上げることができ、筆跡の掠れや筆記不能が生じるおそれがない。
【００２７】
【発明の効果】
請求項１により、ペン先上向き状態で連続筆記した場合、筆跡が掠れたり筆記不能となるおそれがなく、円滑なインキ流出性が維持可能なボールペンを、安価に提供できる。
【００２８】
請求項２により、ペン先上向き状態で連続筆記した場合、より一層、筆跡が掠れたり筆記不能となるおそれがない。
【００２９】
【図面の簡単な説明】
【図１】本発明の一実施例を示す縦断面図である。
【図２】図１の要部拡大縦断面図である。
【図３】（ａ）が図１のペン先部拡大縦断面図であり、（ｂ）が（ａ）のＸ−Ｘ線断面図である。
【図４】（ａ）が上向き筆記時の図１のペン先部拡大縦断面図であり、（ｂ）が（ａ）のＹ−Ｙ線断面図である。
【符号の説明】
１ボールペン
２チップ本体
２１先端縁部
２２ボール受け座
３ボール
４内方突出部
４１頂面
５内孔
５１縦溝部
６インキ流通間隙
６１インキ誘導部
７インキ収容筒
７１インキ
７２追従体
７２ａ高粘度流体
７２ｂ固形物
７３尾栓
７３ａ通気孔
８スプリング
８１ストレート部
８２コイル部
８３膨出部
９ホルダー
９１係止突起
１０被筆記面（紙面）
Ａストレート部の外径
Ｂ仮想内接円の直径
Ｓインキ流通間隙の最小横断面積[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ballpoint pen. More specifically, the present invention relates to a ballpoint pen having a spring for urging a ball at a pen tip forward. In the present invention, “front” refers to the pen tip side, and “rear” refers to the opposite side.
[0002]
[Prior art]
Patent Literature 1 discloses a ballpoint pen in which a straight portion of a spring presses a ball of a pen tip forward. Further, Patent Document 1 describes using a normal oil-based ballpoint pen ink having a high viscosity or a medium viscosity ink having a shear thinning property. Further, Patent Document 1 discloses that a backflow prevention mechanism including a ball valve and a receiving seat is provided to prevent backflow of ink when the pen tip is in an upward state.
[0003]
[Patent Document 1]
JP 10-315678 A
[Problems to be solved by the invention]
However, Patent Document 1 discloses that a backflow prevention mechanism that prevents backflow of ink in a pen tip-up state is provided. In the case of continuous writing while the ink is kept as it is, the supply of the ink from the ink storage portion behind the backflow prevention mechanism to the pen tip is shut off by the action of the backflow prevention mechanism. Therefore, when writing continuously with the pen tip upward, after the ink in front of the backflow prevention mechanism is consumed, if the pen tip is not turned downward, air will be mixed in the back of the ball and ink can not be continuously supplied to the back of the ball. As a result, there is a possibility that handwriting may be blurred or writing may be impossible (that is, ink ejection may not be possible).
[0005]
In addition to the above, there has been conventionally known a structure (so-called gas pressurized ball-point pen) in which high-pressure gas is sealed in the rear of the ink and the ink is pressed forward so that writing can be performed even when the pen tip is upward. However, this has a complicated structure, increases manufacturing costs, and is difficult to provide at low cost.
[0006]
The present invention is to solve the above-mentioned conventional problems, and when writing continuously with the pen point upward, there is no risk that handwriting will be scrambled or impossible to write, and a ballpoint pen that can maintain smooth ink outflow can be manufactured at a low cost. It is intended to provide.
[0007]
[Means for Solving the Problems]
[1] According to the present invention, an inwardly directed front edge 21 and a ball receiving seat 22 are provided at the front end of a chip main body 2 formed of a metal cylinder, and the front edge 21 and the ball receiving seat are provided. 22, the ball 3 is rotatably held, the tip body 2 is connected to the ink container 7, the ink 71 is disposed inside the ink container 7, and the ink 71 is disposed at the rear end of the ink 71. A follower 72, which advances with consumption of the ink 71, is accommodated, and a straight portion 81 of the spring 8 is inserted and arranged in the chip body 2, and the tip of the straight portion 81 contacts the rear surface of the ball 3 to hold the ball 3. A ball pen 1 urged forward to bring the ball 3 into close contact with the inner surface of the tip edge 21, wherein at least a central portion of the ball receiving seat 22 is provided with an inner hole 5 penetrating in the axial direction. The spring 8 strikes the hole 5 Is inserted over isolation portion 81, the ink flow gap 6 is formed between the bore 5 inside surface and the straight portion 81 outer surface, the minimum cross section S of the ink flow gap 6, 0.02 mm 2 ^~0. set in the range of 15 mm ^2, the ink 71 accommodated in the ink accommodating tube 7, the range viscosity at 20 ° C. is 1mPa · s~50mPa · s or 20 ° C. viscosity 3 mPa · in rotational speed 100rpm in, s to 160 mPa · s and a shear thinning index of 0.80 to 0.99 (claim 1).
[0008]
Wherein the minimum cross section S of the ink flow gaps ^6, by a range (preferably a range of ^{^{0.03mm 2 ~0.10mm 2) 0.02mm 2 ~0.15mm}} 2 is set to, among ball seat 22 An ink guide portion 61 having strong capillary force can be formed between the inner surface of the hole 5 and the outer surface of the straight portion 81. Furthermore, by setting the viscosity of the ink 71 contained in the ink containing cylinder 7 to the above range, the ink 71 has a lower viscosity than before, has excellent ink fluidity, and easily exerts a capillary force.
[0009]
That is, forming the ink guide portion 61 having strong capillary force between the inner surface of the inner hole 5 of the ball receiving seat 22 and the outer surface of the straight portion 81, and employing the low-viscosity ink 71 having excellent fluidity. As a result, even when writing is performed continuously with the pen tip facing upward, the abundant ink 71 is continuously supplied to the rear surface of the ball 3, and it is possible to prevent air from entering the rear surface of the ball 3. As a result, it is possible to provide a ballpoint pen that enables continuous writing for a long time in a pen-tip upward state without causing handwriting rubbing or writing disability, with a simple structure and at a low cost.
[0010]
If the minimum cross-sectional area S of the ink flow gap 6 is smaller than 0.02 mm ² , the gap between the inner surface of the inner hole 5 of the ball receiving seat 22 and the outer surface of the straight portion 81 becomes excessively small, and smooth ink flow is achieved. Therefore, there is a possibility that the straight portion 81 cannot be smoothly inserted into the inner hole 5. If the minimum cross-sectional area S of the ink flow gap 6 is larger than 0.15 mm ² , sufficient capillary force cannot be obtained between the inner surface of the inner hole 5 of the ball receiving seat 22 and the outer surface of the straight portion 81, and the pen tip When writing continuously in the upward state, the ink 71 cannot be sufficiently pulled up to the rear surface of the ball 3. If the viscosity of the ink 71 is larger than the specified range, the ink fluidity is reduced. Therefore, when continuous writing is performed with the pen point upward, the strong capillary force between the inner surface of the inner hole 5 and the outer surface of the straight portion 81 is obtained. There is a possibility that the ink 71 may not be able to supply the ink 71 sufficiently to the rear surface of the ball 3 even with the ink guiding portion 61 having
[0011]
The “minimum cross-sectional area S of the ink circulation gap” includes the cross-sectional area of the vertical groove when the radial vertical groove 51 formed in the ball receiving seat 22 passes through the ball receiving seat 22 in the axial direction. On the other hand, when the vertical groove portion 51 formed in the ball receiving seat 22 does not penetrate the ball receiving seat 22 in the axial direction, the vertical groove portion 51 is formed between the inner surface of the inner hole 5 having only a portion penetrating the center portion and the outer surface of the straight portion 81. The minimum cross-sectional area of the ink flow gap. The outer diameter of the pen point ball 3 employed in the present invention is preferably in the range of 0.5 mm to 0.7 mm.
[0012]
Incidentally, the shear thinning index is an empirical formula (T = Kj ⁿ : K and n are calculated by rheological measurement of a shear stress value (T) and a shear rate (j) value by a viscometer. (Which is a constant). Note that the E-type rotational viscometer specifically includes an EM-type rotational viscometer, an EL-type rotational viscometer, and an EH-type rotational viscometer.
[0013]
[2] In the first aspect, the tip body 2 may be of a type in which the ball receiving seat 22 and the inner hole 5 are formed by cutting, but the vicinity of the distal end of the metal cylindrical body is pressed and deformed inward. To form a plurality of inwardly protruding portions 4, and the inwardly protruding portions 4 constitute a ball receiving seat 22. An inner hole 5 formed in the ball receiving seat 22 is formed between the adjacent inwardly protruding portions 4. A vertical groove portion 51 extending radially outward from the center portion in the radial direction and penetrating in the axial direction is provided therebetween. The width of the vertical groove portion 51 is set to be smaller than the outer diameter A of the straight portion 81, and the inward projection is provided. It is preferable that the top surface 41 of the portion 4 has a convex curved shape (claim 2).
[0014]
When writing is performed with the pen tip facing upward, the tip of the straight portion 81 of the spring 8 moves radially outward (that is, the pen tip moving direction) while rotating in contact with the ball 3. Then, the outer surface of the tip portion of the straight portion 81 moves in the direction of the vertical groove portion 51 along the top surface 41 while contacting the top surface 41 of the inwardly projecting portion 4. That is, by making the top surface 41 of the inwardly protruding portion 4 a convex curved surface, the tip of the straight portion 81 is rotated along with the convex curved top surface 41 by the rotation of the ball 3 during writing. Move smoothly between each other. When the outer surface of the distal end portion of the straight portion 81 contacts the inner surface of the inwardly protruding portion 4, the ink guide portion 61 having strong capillary force can be formed at the contact portion. Since the ink guiding portion 61 is always formed on the ink consuming side of the rotating ball 3, the ink 71 can be effectively supplied to the surface of the ball 3 on the ink consuming side. As a result, in the case of continuous writing with the pen tip facing upward, there is no longer a possibility that the handwriting will be blurred or writing will not be possible.
[0015]
Further, by setting the groove width of the vertical groove portion 51 to be smaller than the outer diameter A of the straight portion 81, the front end portion of the straight portion 81 is not pressed into the vertical groove portion 51, and the center of the ball 3 or the vicinity of the center portion is always maintained. Can be pressed by the straight portion 81, and as a result, poor rotation of the ball 3 and poor close contact between the ball 3 and the leading edge 21 can be prevented. Further, since the straight portion 81 can be prevented from entering the longitudinal groove portion 51 penetrating in the axial direction, the ink guiding function of the longitudinal groove portion 51 is not hindered. The ink 71 can be supplied more quickly. The number of the plurality of inwardly projecting portions 4 is preferably three or four from the viewpoint of easy manufacture.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0017]
1 to 4 show one embodiment of the present invention.
[0018]
The ball-point pen 1 of the present embodiment has a tip body 2 rotatably holding a ball 3 at a tip thereof, a holder 9 having a rear portion of the tip body 2 press-fitted and fixed to a front portion thereof, and a rear portion of the holder 9 having a rear portion. The ink container 7 press-fitted into the opening at the tip thereof, the ink 71 and the follower 72 accommodated inside the ink container 7, and the ink container 7 is accommodated and arranged inside the chip body 2 and the holder 9. It comprises a spring 8 and a tail plug 73 which is press-fitted and fixed to the rear end opening of the ink container 7.
[0019]
The ink container 7 is a straight cylindrical body having both ends opened, and is obtained by extrusion molding of a synthetic resin (for example, polypropylene). The rear end of the holder 9 having the tip main body 2 is press-fitted and fixed to the opening at the tip end of the ink container 7. A tail plug 73 provided with a vent hole 73a is press-fitted and fixed to the rear end opening of the ink storage cylinder 7, and the space behind the follower 72 of the ink storage cylinder 7 communicates with the outside air. In the present invention, it is effective that the inner diameter of the ink container 7 is 4 mm to 6 mm, and in this embodiment, the inner diameter is 4.4 mm.
[0020]
Inside the ink container 7, the ink 71 (the viscosity at 20 ° C. in a B-type rotational viscometer is 9 mPa · s, and the viscosity at 20 ° C. at 100 rpm in an EL-type rotational viscometer is 9 mPa · s). And an aqueous ink having a shear thinning index of 0.97). Further, a follower 72 (specifically, a high-viscosity fluid 72a and a high-viscosity fluid 72a, which is disposed at the rear end of the ink 71 and advances with the consumption of the ink 71, is provided in the ink container 7). A follower 72) comprising a solid substance 72b accommodated in 72a is accommodated. In addition to the above, the follower 72 may be configured to include only the high-viscosity fluid 72a having no solid 72b, or may be configured to include only the solid 72b slidable with the inner wall of the ink container 7.
[0021]
The tip body 2 is a straight cylindrical thin tube made of metal (for example, austenitic stainless steel such as SUS304, SUS305, and SUS321). Four inwardly protruding portions 4 (that is, ball receiving seats 22) are formed at equal intervals in the circumferential direction on the inner surface near the distal end of the tip body 2 by inward pressing deformation. At the tip of the chip body 2, an annular inward tip edge 21 is formed by inward pressing deformation. The ball 3 (outer diameter 0.5 mm) is held between the inner surface of the distal end edge 21 and the front surface of the inwardly protruding portion 4 (ie, the ball holding portion) so as to be rotatable and movable in the front-rear direction. The amount of the ball 3 that can be moved in the front-rear direction is preferably set in the range of 10 μm to 20 μm from the viewpoint that an appropriate ink outflow property without handwriting bleeding and handwriting blur is obtained.
[0022]
The top surface 41 of the inwardly protruding portion 4 has a spherical shape (convex curved surface shape). An inner hole 5 having a vertical groove 51 extending radially outward in four directions radially outward from the center and penetrating in the axial direction is formed between the inwardly projecting portions 4. In a cross-sectional view, the inner hole 5 has a shape composed of four arcs swelling inward, and the vertical groove portion 51 has a groove width decreasing toward the radial direction outward, and a groove at a radial outer end portion. The shape has a width of zero. The diameter B of the imaginary inscribed circle in contact with the top surface 41 of the inwardly projecting portion 4 is set to 0.2 mm and is set to be larger than the outer diameter A of the straight portion 81. Can be inserted.
[0023]
The holder 9 is a cylindrical body obtained by injection molding of a synthetic resin (for example, polypropylene). The holder 9 has a tapered front portion to which the chip main body 2 is attached, a flange portion that comes into contact with the front end surface of the ink storage tube 7, and a rear portion that is pressed into the front end opening of the ink storage tube 7. The inside of the holder 9 is provided with a tip mounting hole whose tip opens to the outside, and an ink circulation hole whose tip communicates with the tip mounting hole and whose rear end opens to the outside. A plurality of (for example, four) locking projections 91 are integrally formed on the inner surface of the intermediate portion of the ink circulation hole and are arranged in a circumferentially dispersed manner.
[0024]
The spring 8 has a front straight portion 81 and a rear coil portion 82 integrally connected to each other by a stainless steel wire having a wire diameter of 0.14 mm. A bulged portion 83 having an outer diameter set to be larger than the front coil portion 82 is formed at the rear end of the coil portion 82. The bulging portion 83 is formed by a tightly wound portion in which wires are in close contact with each other. The bulging portion 83 rides over the locking projection 91 on the inner surface of the holder 9 from behind and is locked by the locking projection 91, and the spring is held between the ball 3 and the locking projection 91 in a compressed state. You. The spring 8 may have a configuration including only the straight portion 81 without the coil portion 82 in addition to the configuration described above.
[0025]
The straight portion 81 (outer diameter A: 0.14 mm) of the spring 8 is inserted into the center of the inner hole 5, and the tip of the straight portion 81 contacts the rear surface of the ball 3 so that the ball 3 moves forward. And is brought into close contact with the inner surface of the inward end edge 21. As a result, when writing is not performed, the pen tip is sealed, preventing ink leakage from the pen tip even if the pen tip is stored downward, and air from the pen tip is stored even if the pen tip is stored upward. Mixing is prevented. The minimum cross-sectional area S of the ink flow gap 6 formed between the inner surface of the inner hole 5 and the outer surface of the straight portion 81 (a hatched portion indicated by a dotted line in FIG. 3) is set to 0.043 mm ² .
[0026]
As shown in FIG. 4, during writing, the tip of the straight portion 81 of the spring 8 moves radially outward (pen tip moving direction) while contacting the rear surface of the ball 3 as the ball 3 rotates. Then, the tip of the straight portion 81 comes into contact with the convexly curved top surfaces 41 of the two inwardly projecting portions 4, and an ink guide portion 61 having strong capillary force is generated at the two contact portions. The ink guide portion 61 formed by the tip of the straight portion 81 is always formed on the ink discharge side (ink consumption side) of the rotating ball 3 (the dotted arrow in FIG. 4 indicates the flow of ink). Therefore, even if the pen tip is continuously written in the upward state, a sufficient amount of the ink 71 can be pulled up from the lower ink storage cylinder 7 against the gravity of the rear surface of the ball 3 against the gravity, and the handwriting is blurred and the writing becomes impossible. There is no fear.
[0027]
【The invention's effect】
According to the first aspect, when continuous writing is performed in a pen tip upward state, a ballpoint pen capable of maintaining a smooth ink outflow property without a risk of handwriting being scrambled or being unable to write can be provided at low cost.
[0028]
According to the second aspect, in the case where continuous writing is performed in the upward state of the pen tip, there is no further possibility that the handwriting will be blurred or writing will not be possible.
[0029]
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention.
FIG. 2 is an enlarged vertical sectional view of a main part of FIG.
3A is an enlarged vertical cross-sectional view of the pen tip portion of FIG. 1, and FIG. 3B is a cross-sectional view taken along line XX of FIG.
4A is an enlarged vertical sectional view of the pen tip portion of FIG. 1 at the time of upward writing, and FIG. 4B is a sectional view taken along line YY of FIG.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 ballpoint pen 2 tip body 21 tip edge 22 ball receiver 3 ball 4 inward protrusion 41 top surface 5 inner hole 51 vertical groove 6 ink circulation gap 61 ink guide 7 ink storage cylinder 71 ink 72 follower 72a high viscosity fluid 72b Solid substance 73 Tail plug 73a Vent hole 8 Spring 81 Straight part 82 Coil part 83 Swelling part 9 Holder 91 Locking projection 10 Writing surface (paper surface)
A Outer diameter of straight part B Diameter of virtual inscribed circle S Minimum cross-sectional area of ink flow gap

Claims

At the tip of the chip body made of a metal cylinder, an inward tip edge and a ball seat are provided behind it, and the tip edge and the ball seat rotatably hold the ball, The chip main body is connected to an ink storage cylinder, and inside the ink storage cylinder, the ink and a follower disposed at the rear end of the ink and advancing with the consumption of the ink are housed. A ball-point pen having a straight portion of a spring inserted therein, the tip of the straight portion abutting against the rear surface of the ball to urge the ball forward, and bringing the ball into close contact with the inner surface of the tip edge. At least a central portion of the receiving seat is provided with an inner hole penetrating in the axial direction, a straight portion of a spring is inserted into the inner hole, and an ink flow gap is formed between the inner surface of the inner hole and the outer surface of the straight portion. I The minimum cross section of the key distribution ^gap set in the range of 0.02mm ² ~0.15mm 2, the ink accommodated inside the ink reservoir tube, ranges viscosity at 20 ° C. is 1mPa · s~50mPa · s Or a ball-point pen having a viscosity at 20 ° C. at a rotation speed of 100 rpm in a range of 3 mPa · s to 160 mPa · s and a shear thinning index in a range of 0.80 to 0.99.

A plurality of inwardly projecting portions are formed by inwardly pressing and deforming the vicinity of the tip of the metal cylindrical body, a ball receiving seat is formed by the inwardly projecting portions, and an inner hole formed in the ball receiving seat is Between adjacent inwardly protruding portions, a vertical groove portion extending radially outward from the center portion and penetrating in the axial direction is provided, and the groove width of the vertical groove portion is set to be smaller than the outer diameter of the straight portion, The ballpoint pen according to claim 1, wherein a top surface of the inwardly protruding portion has a convex curved shape.