JP3558259B2

JP3558259B2 - Leak inspection method for empty cans, etc.

Info

Publication number: JP3558259B2
Application number: JP30032298A
Authority: JP
Inventors: 龍実池田; 行直八木; 佳三橋本
Original assignee: Daiwa Can Co Ltd
Current assignee: Daiwa Can Co Ltd
Priority date: 1998-10-08
Filing date: 1998-10-08
Publication date: 2004-08-25
Anticipated expiration: 2018-10-08
Also published as: JP2000121487A

Description

【０００１】
【発明の属する技術分野】
本発明は、被検査物品である空缶等に生じたピンホール等の有無を、加圧空気を用いてその漏洩の有無によって検査する方法に関するものである。
【０００２】
【従来の技術】
製缶工程の中で内容物を充填する前の空缶や缶蓋を閉鎖室内に置き、これに加圧空気を導入したときに、被検査物品の空缶等にピンホール等の欠陥箇所が存在すると、そこから空気が漏洩するので、その漏れの有無を感圧センサーで検知する方法や装置が実用化されている。
【０００３】
特開平７−２７６６２号公報には、缶胴と缶底を一体的に成形した状態の製品（缶蓋を取り付ける前の飲み口側が開口した空缶）の検査のため、この空缶の開口部を密封した状態で収容する密封空間部と、この空缶とほぼ同じ大きさで空気が侵入しない擬似缶体を収容した密封空間部とを設け、両密封空間部に０．８〜１．０Ｋｇｆ／ｃｍ^２の加圧空気を導入し、両密封空間部間の圧力差を測定する差圧センセーを設けた検査装置が記載されている。
【０００４】
また特公平２−５２５７号公報には、共同して一つの閉鎖室を構成する上下部品の間に缶蓋を載置して缶蓋を境として閉鎖室を２室に分割し、一方の室に加圧空気を供給したときに、他方の室へ漏洩した空気に伴う空気圧の変化を感圧センサーで検知するようにした缶蓋エアーテスターにおいて、この缶蓋エアーテスターへの缶蓋供給の中断時に、缶蓋が載置されていない状態の閉鎖室を一旦大気に開放し、次いで感圧センサーの感知下限圧力よりも僅かに高い微圧空気を供給してエアーテスターの感圧機能を検査する方法が記載されている。
【０００５】
【発明が解決しようとする課題】
上記のエアーテスターに使用される感圧センサーの圧力素子は、圧力を半導体で電圧等の電気信号に変換するものであり、通常測定範囲がゲージ圧で±０．３Ｋｇｆ／ｃｍ^２の感圧センサーが用いられる。
これに対して加圧空気圧は、検査速度を上げるため５Ｋｇｆ／ｃｍ^２前後の高い圧力が使用され、大きな漏洩箇所のある空缶や、シール不良の状態で漏洩検査を行ったときに、高い空気圧が漏洩箇所を通して感圧センサーの圧力素子に作用し、その繰返しの加圧により圧力素子の感知能力が鈍化したり、また温度に影響されて圧力感知能力が変動したりする。
【０００６】
上記特開平７−２７６６２号公報に記載された空缶の検査方法では、比較的低い０．８〜１．０Ｋｇｆ／ｃｍ^２の加圧空気を用いるので、差圧センサーの圧力感知能力の鈍化が抑制されるが、それでも差圧センサーの測定範囲より高い圧力が作用することがあり、また温度による圧力感知能力の変動に対応できず、誤作動の恐れがある。
また特公平２−５２５７号公報に記載されたエアーテスターの感圧機能検査方法では、感圧センサーの圧力素子の機能検査を各被検査品ごとに行うのではなく、缶蓋供給の中断時という不定期ごとに行うものであるから、不良感圧センサーによって合格と判定された缶蓋の中に不良品が混在する恐れが解消しない。
【０００７】
本発明は、前記の課題を解決し、感圧センサーの圧力感知能力がある程度鈍化したり変動しても、加圧空気を使用した漏洩検査による適正な合否判定が維持できる空缶等の漏洩検査方法を提供することを目的とするものである。
【０００８】
【課題を解決するための手段】
本発明は、共同して一つの閉鎖室の形成が可能な上室と下室とを相対的に移動させて閉鎖室の形成と該閉鎖室の開放を繰返す漏洩検査機の上室と下室との間に被検査品を供給載置し、前記閉鎖室を被検査品を境にして少なくとも二つの密封可能な室に分割してその一方の密封室に加圧空気を供給し、他方の密封室における圧力を感圧センサーで測定することにより、被検査品の空気漏れの有無を検査する方法において、
前記他方の室が大気に開放されている状態で前記感圧センサーで大気圧を測定してその第１測定値を記憶する工程と、
前記一方の密封室に加圧空気が供給された直後に、他方の密封室内の圧力を前記と同じ感圧センサーで測定してその第２測定値を記憶する工程と、
前記一方の密封室における加圧空気の供給が停止される直前に、他方の密封室内の圧力を前記と同じ感圧センサーで再度測定してその第３測定値を記憶する工程と、
前記の記憶した第１ないし第３の三つの測定値中の二つの測定値の差を求めてこれとそれぞれ設定した所定圧力と比較して被検査品の空気漏れの有無を判定する工程とからなる空缶等の漏洩検査方法であって、この被検査品の空気漏れの有無を判定する工程を、第２の測定値と第１の測定値との差及び第３の測定値と第２の測定値との差について重ねて行うのが好適である。
空缶の漏洩有無の判定に用いられる複数の測定値は、いずれも同じ感圧センサーによるものであるから、その感圧センサーの感圧素子が劣化したり、温度による変動が生じていても、それらの測定値の差を取ることによって、感圧素子の劣化幅や変動幅が相殺されて正確な圧力差を検知することができる。
【０００９】
【発明の実施の形態】
図２は本発明の方法を適用する漏洩検査機の概要を示す装置全体の斜視図で、この装置の概略の作動は次のとおりである。
被検査品である空缶Ｗを開口部を下にし、インフィードターレットＩでメインターレットＭに連続的に送る。メインターレットＭには多数のテストポケットＴが設けられ、この各テストポケットＴに空缶Ｗの密封機構、加圧空気の供給機構、感圧センサー、電磁弁等からなる漏洩検査機構が設置され、メインターレットＭの回転中に各空缶Ｗの漏洩検査を行い、検査済みの空缶Ｗはその検査結果の信号により、ディスチャージターレットＤで合格品Ｗｏと不良品Ｗｎとに分別される。
【００１０】
図１は、前記図２に示す漏洩検査機の各テストポケットＴに設置される漏洩検査機構の要部を示す一部断面図である。
図１において、被検査品である空缶Ｗは、円筒状の缶胴にタブ付き缶蓋を巻き締めた状態のもので、これに内容物を充填し、缶底を巻き締めて缶ジュース等として市販されるものである。すなわち、空缶Ｗはいわゆる３ピース缶の半製品であって、この空缶Ｗは開口部を下にして漏洩検査機構に供給される。
【００１１】
漏洩検査機構は、上室部１とこれに対して上下動可能な下室部２を備え、両室１，２が当接した状態では、内部に閉鎖室が形成されるようになっている。上室部１は空缶Ｗを入れる内面が円筒状のシリンダー室３と、その上部に空缶Ｗの缶蓋に当接する缶押えパット６及び密封体７を有し、缶押えパット６及び密封体７はクランプロッド１１で上下に駆動される。上室部１の上部に排気管８とその通路を開閉する電磁弁９及び感圧センサー１０が設けられている。
下室部２は内面が円筒状のシリンダー室１２を備え、その中に中子１４のピストン部が気密に摺動可能に設けられると共に、シリンダー室１２の上端にゴム製のシールリング１３が装着され、その直下の内面に加圧空気の導入路１６の開口が設けられている。中子１４は昇降ロッド１５で上下に駆動され、シリンダー室１２も図示しない駆動機構で上下に駆動されるようになっている。
【００１２】
図１に示す状態は、空缶Ｗが下室部２のシールリング１３に載置され、下室部２と中子１４とが上昇して空缶Ｗ及びシリンダー室３の開口端が下室部２のシールリング１３の上面に当接し、上下室１，２の内部に形成される閉鎖室が空缶Ｗを境として外側閉鎖室４と内側閉鎖室５の２つに分割されている。この状態で下室部２の加圧エアー導入路１６から所定圧力の加圧空気を供給すると、加圧空気は内側閉鎖室５に入る。
内側閉鎖室５は中子１４で容積を縮小されているので、内側閉鎖室５内は迅速に所定の圧力となり、この圧力が空缶Ｗの内面に作用して空缶Ｗを少し膨らませる。電磁弁９が閉じていて外側閉鎖室４が閉鎖状態にあると、外側閉鎖室４の圧力が上昇し、また空缶Ｗに漏洩箇所があって加圧空気が外側閉鎖室４に洩れたときにも外側閉鎖室４の圧力が上昇し、この圧力上昇が感圧センサー１０で検出されることになる。
【００１３】
【実施例】
図３は漏洩検査機構に空缶Ｗが供給されてから、内外閉鎖室の形成、漏洩検査、検査後の空缶Ｗの開放のための漏洩検査機構の動作を順次示すものである。
図３Ａに示すように、下室部２が下降して上室部１と離れた状態で空缶Ｗを下室部２のシールリング１３上に載置し、この上室部１内が大気に開放された状態で感圧センサー１０で大気圧を測定し、その値（ｃ）を記憶する。次に、図３Ｂに示すように、缶押えパット６が下降して空缶Ｗの蓋を押えて保持する。この状態で下室部２と中子１４とが上昇し（図３Ｃ）、上室部１と下室部２が当接して停止する（図３Ｄ）。
この状態は図１に示したのと同様であり、上下室１，２の内部に形成される閉鎖室が空缶Ｗを境として外側閉鎖室４と内側閉鎖室５の２つに分割されている。
【００１４】
次に図３Ｅの状態で、加圧エアー導入路１６から４Ｋｇｆ／ｃｍ^２の加圧空気を４００ｍｓｅｃの間内側閉鎖室５に供給する。この際、加圧空気の供給開始前１００ｍｓｅｃから排気管８の電磁弁９を開き、加圧空気の供給開始後１００ｍｓｅｃ後に閉じる。
この電磁弁９の開閉によって、空缶Ｗの膨張による外側閉鎖室４内の圧力上昇を避けて感圧センサー１０に測定誤差が発生するのを防止する。
電磁弁９が閉じて外側閉鎖室４が密閉された直後に、感圧センサー１０で外側閉鎖室４内の圧力を測定してその値（ａ）を記憶する。空缶Ｗに大きな漏洩箇所があると、この値（ａ）は、先に同じ感圧センサー１０で測定した大気圧よりかなり大きな値を示すことになる。
【００１５】
加圧空気は、なお供給されており、その供給終了の直前に再度感圧センサー１０で外側閉鎖室４内の圧力を測定してその値（ｂ）を記憶する。この値（ｂ）は、空缶Ｗに微小な漏洩箇所がある場合でも、外側閉鎖室４に漏洩空気が蓄積されて先の測定値（ａ）よりも大きくなる。
【００１６】
以上の加圧空気の供給、排気のための電磁弁９の開閉、感圧センサー１０による測定のタイミングを図４に示す。
図４のメインターレットＭには、２４箇所にテストポケットＴが設けられており、１つの空缶ＷがインフィードターレットＩでメインターレットＭの１つのそのテストポケットＴに供給されたときに、テストポケットＴは感圧センサー１０で大気圧を測定し、その値（ｃ）を記憶する。
【００１７】
メインターレットＭは右回りに回転し、その空缶ＷがセットされたテストポケットＴの漏洩検査機構が図３Ｄの状態となったときに、外側閉鎖室４内の圧力上昇を避けるため電磁弁９が開放され、この電磁弁９は２００ｍｓｅｃ後に閉じる。
電磁弁９がまだ開いている状態で加圧空気の供給が開始され、この加圧空気による加圧は４００ｍｓｅｃの間続けられる。
電磁弁９が閉じた直後に、感圧センサー１０で測定（ａ）し、加圧空気の供給終了の直前に再度感圧センサー１０で測定（ｂ）する。
【００１８】
空缶Ｗの漏洩有無の判定は、加圧空気の供給始めの圧力と大気圧の測定値の差（ａ−ｃ）が、設定値以上であった場合に不良と判定する。
前記の圧力差（ａ−ｃ）が設定値以下であっても、加圧空気の供給始めの圧力と加圧終了直前の圧力差（ｂ−ａ）が、設定値以上であった場合にも不良と判定する。
また、上記の圧力差（ｂ−ａ）に代えて、加圧空気の供給始めと大気圧との測定値の差（ａ−ｃ）を用いることができる。
空缶Ｗの漏洩有無の判定に用いられる測定値（ａ，ｂ，ｃ）は、いずれも同じ感圧センサー１０によるものであるから、その感圧センサー１０の感圧素子が劣化したり、温度による変動が生じていても、それらの測定値の差を取ることによって、感圧素子の劣化幅や変動幅が相殺されて正確な圧力差を検知することができる。
【００１９】
感圧センサー１０による測定が終了すると、図３に戻って、図３Ｆに示すように下室部２は空缶Ｗを挟持したまま下降し、次いで、図３Ｇに示すように下室部２、中子１４、缶押えパット６は下死点で停止し、続いて缶押えパット６が僅かに上昇し（図３Ｈ）て空缶Ｗの挟持が開放される。
この空缶Ｗは、前記感圧センサー１０の測定値に基づく判定に従って、図２に示すディスチャージターレットＤで合格品Ｗｏと不良品Ｗｎとに分別される。
【００２０】
上記の実施例は、空缶の漏洩検査について記載したが、被検査品は空缶に限らず類似形状の空瓶等とすることができ、また缶蓋だけの検査にも適用可能である。
缶蓋の検査に適用する場合には、特公平３−４３５７５号公報に記載されたように、漏洩検査機構を、缶蓋を境にして上下２室の密閉室とするだけでなく、一方の室を更に缶蓋中央板部密封区と缶蓋周辺部密封区とに区分するように構成することにより、それぞれの密封区の空気圧の変化を別個に測定することもできる。
感圧センサーによる大気圧の測定は、実施例に記載した時期に限らず、上室部１内が大気に開放された状態であればいつでもよいのは勿論であり、感圧センサーの測定値（ａ，ｂ，ｃ）に基づく空缶Ｗの漏洩有無の判定は、（ｂ−ａ）、（ａ−ｃ）、（ｂ−ｃ）の内の一つとすることも、これらの内の二つを組合せて、ダブルチェック方式とすることもできる。
【００２１】
【発明の効果】
本発明は、各被検査品を同一感圧センサーを用いて異なる環境のもとで測定し、得られた複数の測定値の差を求めて各被検査品の合否判定を行うようにしたので、感圧センサーの感圧素子が劣化したり、温度による変動が生じていても、判定値は劣化幅や変動幅が相殺されて正確な圧力差を検知することができ、加圧空気を使用した漏洩検査による適正な合否判定が維持できる。
【図面の簡単な説明】
【図１】本発明の方法に使用する漏洩検査機構の要部を示す一部断面図。
【図２】本発明の方法を適用する漏洩検査機の概要を示す全体の斜視図。
【図３】漏洩検査機構の動作を順次示す説明図。
【図４】本発明の測定タイミングを示す説明図。
【符号の説明】
１：上室部２：下室部３：シリンダー室４：外側閉鎖室５：内側閉鎖室６：缶押えパット７：密封体８：排気管９：電磁弁１０：感圧センサー１１：クランプロッド１２：シリンダー室１３：シールリング１４：中子１５：昇降ロッド１６：加圧エアー導入路Ｗ：空缶[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for inspecting the presence or absence of a pinhole or the like generated in an empty can or the like as an inspection object by using pressurized air to determine whether or not the leakage has occurred.
[0002]
[Prior art]
In the can-making process, place empty cans and can lids before filling with contents in a closed room, and when pressurized air is introduced into them, defects such as pinholes etc If present, air leaks therefrom, and methods and devices for detecting the presence or absence of the leak with a pressure-sensitive sensor have been put to practical use.
[0003]
Japanese Patent Application Laid-Open No. 7-27662 discloses an opening portion of a can in which a can body and a can bottom are integrally molded (an empty can having an opening on a drinking side before a can lid is attached). Are provided in a sealed state, and a sealed space part containing a pseudo can body that is substantially the same size as the empty can and does not allow air to enter is provided, and both sealed space parts are 0.8 to 1.0 kgf. An inspection apparatus is described in which pressurized air of / cm ² is introduced and a differential pressure sensor for measuring a pressure difference between both sealed spaces is provided.
[0004]
In Japanese Patent Publication No. 2-5257, a closed lid is placed between upper and lower parts which together form one closed chamber, and the closed chamber is divided into two chambers with the can lid as a boundary. When the pressurized air is supplied to the can lid air tester, the change in air pressure caused by the air leaking to the other chamber is detected by the pressure sensor, and the supply of the can lid to the can lid air tester is interrupted. Occasionally, the closed chamber where the can lid is not placed is once opened to the atmosphere, and then the pressure sensitive function of the air tester is inspected by supplying micro-pressure air slightly higher than the lower limit pressure of the pressure sensor. A method is described.
[0005]
[Problems to be solved by the invention]
The pressure sensor of the pressure sensor used in the above air tester converts pressure into an electric signal such as voltage by a semiconductor, and usually has a measurement range of ± 0.3 kgf / cm ^{2 in} gauge pressure. Is used.
On the other hand, as the pressurized air pressure, a high pressure of about 5 kgf / cm ² is used in order to increase the inspection speed, and when an air can having a large leak portion or a leak test is performed in a state of poor sealing, a high air pressure is used. Acts on the pressure element of the pressure-sensitive sensor through the leak location, and the repetitive pressurization slows down the sensing ability of the pressure element or fluctuates the pressure sensing ability due to the temperature.
[0006]
In the method for inspecting an empty can described in Japanese Patent Application Laid-Open No. Hei 7-27662, pressurized air having a relatively low pressure of 0.8 to 1.0 kgf / cm ² is used. Although suppressed, pressure higher than the measurement range of the differential pressure sensor may still act, and fluctuations in pressure sensing capability due to temperature cannot be handled, which may cause malfunction.
Further, in the method for testing the pressure-sensitive function of an air tester described in Japanese Patent Publication No. 2-5257, the function test of the pressure element of the pressure-sensitive sensor is not performed for each product to be inspected. Since the inspection is performed at irregular intervals, the possibility that defective products are mixed in the can lid determined to be acceptable by the defective pressure-sensitive sensor cannot be eliminated.
[0007]
SUMMARY OF THE INVENTION The present invention solves the above-described problems, and enables a leak inspection of an empty can or the like to maintain a proper pass / fail judgment by a leak inspection using pressurized air even if the pressure sensing capability of a pressure-sensitive sensor is somewhat slowed or fluctuated. It is intended to provide a method.
[0008]
[Means for Solving the Problems]
The present invention is directed to an upper chamber and a lower chamber of a leak inspection machine which repeatedly moves a upper chamber and a lower chamber capable of forming one closed chamber and repeats formation of the closed chamber and opening of the closed chamber. The test object is supplied and placed between the test chamber and the closed chamber is divided into at least two sealable chambers with the test object as a boundary, and pressurized air is supplied to one of the sealed chambers and the other is supplied. In the method of inspecting the inspected product for air leakage by measuring the pressure in the sealed chamber with a pressure-sensitive sensor,
A step of measuring the atmospheric pressure with the pressure-sensitive sensor in a state where the other chamber is open to the atmosphere, and storing the first measured value;
Immediately after pressurized air is supplied to the one sealed chamber, a step of measuring the pressure in the other sealed chamber with the same pressure-sensitive sensor as described above and storing the second measurement value,
Immediately before the supply of pressurized air in the one sealed chamber is stopped, the pressure in the other sealed chamber is measured again by the same pressure-sensitive sensor as described above, and a third measured value is stored,
Determining the difference between the two measured values among the stored first to third three measured values and comparing the measured value with a predetermined pressure respectively set to determine the presence or absence of air leakage of the inspected product. The method for determining whether or not there is an air leak in an inspected product includes determining a difference between the second measured value and the first measured value and the third measured value and the second measured value. It is preferable to repeat the measurement for the difference from the measured value.
Since the plurality of measurement values used to determine the presence or absence of leakage of empty cans are all based on the same pressure-sensitive sensor, even if the pressure-sensitive element of the pressure-sensitive sensor has deteriorated or has changed due to temperature, By taking the difference between the measured values, the deterioration width and the fluctuation width of the pressure-sensitive element are offset, and an accurate pressure difference can be detected.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 2 is a perspective view of the entire apparatus showing an outline of a leak inspection machine to which the method of the present invention is applied. The schematic operation of this apparatus is as follows.
The empty cans W to be inspected are successively sent to the main turret M by the infeed turret I with the opening portion down. A plurality of test pockets T are provided in the main turret M, and a leak inspection mechanism including a sealing mechanism for the empty can W, a supply mechanism of pressurized air, a pressure-sensitive sensor, a solenoid valve, and the like is installed in each test pocket T. While the main turret M is rotating, a leak inspection of each empty can W is performed, and the inspected empty cans W are separated into acceptable products Wo and defective products Wn by the discharge turret D based on a signal of the inspection result.
[0010]
FIG. 1 is a partial sectional view showing a main part of a leakage inspection mechanism installed in each test pocket T of the leakage inspection machine shown in FIG.
In FIG. 1, an empty can W to be inspected is a state in which a can lid with a tab is wrapped around a cylindrical can body. It is commercially available as That is, the empty can W is a semi-finished product of a so-called three-piece can, and the empty can W is supplied to the leak inspection mechanism with the opening portion down.
[0011]
The leak inspection mechanism includes an upper chamber 1 and a lower chamber 2 that can move up and down with respect to the upper chamber. When both chambers 1 and 2 are in contact with each other, a closed chamber is formed inside. . The upper chamber portion 1 has a cylinder chamber 3 having an inner surface in which an empty can W is placed, and a can holding pad 6 and a sealing member 7 which are in contact with a can lid of the empty can W at an upper portion thereof. The body 7 is driven up and down by a clamp rod 11. An exhaust pipe 8, a solenoid valve 9 for opening and closing the passage, and a pressure-sensitive sensor 10 are provided above the upper chamber 1.
The lower chamber 2 includes a cylinder chamber 12 having a cylindrical inner surface, in which a piston of a core 14 is slidably and slidably provided, and a rubber seal ring 13 is mounted on an upper end of the cylinder chamber 12. The opening of the pressurized air introduction passage 16 is provided on the inner surface immediately below the opening. The core 14 is driven up and down by an elevating rod 15, and the cylinder chamber 12 is also driven up and down by a drive mechanism (not shown).
[0012]
In the state shown in FIG. 1, the empty can W is placed on the seal ring 13 of the lower chamber 2, the lower chamber 2 and the core 14 rise, and the open ends of the empty can W and the cylinder chamber 3 become lower chambers. The closed chamber which abuts on the upper surface of the seal ring 13 of the part 2 and is formed inside the upper and lower chambers 1 and 2 is divided into two parts, an outer closed chamber 4 and an inner closed chamber 5 with the empty can W as a boundary. When pressurized air having a predetermined pressure is supplied from the pressurized air introduction passage 16 of the lower chamber 2 in this state, the pressurized air enters the inner closed chamber 5.
Since the volume of the inner closed chamber 5 is reduced by the core 14, the inside of the inner closed chamber 5 quickly becomes a predetermined pressure, and this pressure acts on the inner surface of the empty can W to slightly inflate the empty can W. When the solenoid valve 9 is closed and the outer closed chamber 4 is in a closed state, the pressure in the outer closed chamber 4 increases, and when there is a leak in the empty can W and pressurized air leaks into the outer closed chamber 4 The pressure in the outer closed chamber 4 also increases, and this pressure increase is detected by the pressure sensor 10.
[0013]
【Example】
FIG. 3 shows the operation of the leak inspection mechanism for forming the inner and outer closed chambers, leak inspection, and opening the empty can W after the inspection after the empty can W is supplied to the leak inspection mechanism.
As shown in FIG. 3A, the empty can W is placed on the seal ring 13 of the lower chamber 2 in a state where the lower chamber 2 descends and is separated from the upper chamber 1, and the inside of the upper chamber 1 is air. At this time, the atmospheric pressure is measured by the pressure sensor 10 and the value (c) is stored. Next, as shown in FIG. 3B, the can press pad 6 descends and presses and holds the lid of the empty can W. In this state, the lower chamber 2 and the core 14 rise (FIG. 3C), and the upper chamber 1 and the lower chamber 2 come into contact with each other and stop (FIG. 3D).
This state is the same as that shown in FIG. 1. The closed chamber formed inside the upper and lower chambers 1 and 2 is divided into two parts, an outer closed chamber 4 and an inner closed chamber 5 with the empty can W as a boundary. I have.
[0014]
Next, in the state of FIG. 3E, 4 kgf / cm ² of pressurized air is supplied from the pressurized air introduction passage 16 to the inner closed chamber 5 for 400 msec. At this time, the electromagnetic valve 9 of the exhaust pipe 8 is opened from 100 msec before the start of the supply of the pressurized air, and is closed 100 msec after the start of the supply of the pressurized air.
The opening and closing of the solenoid valve 9 prevents a pressure increase in the outer closed chamber 4 due to the expansion of the empty can W, thereby preventing a measurement error from occurring in the pressure-sensitive sensor 10.
Immediately after the solenoid valve 9 is closed and the outer closed chamber 4 is closed, the pressure in the outer closed chamber 4 is measured by the pressure sensor 10 and the value (a) is stored. If there is a large leakage point in the empty can W, this value (a) indicates a value considerably larger than the atmospheric pressure previously measured by the same pressure-sensitive sensor 10.
[0015]
The pressurized air is still supplied. Immediately before the end of the supply, the pressure in the outer closed chamber 4 is measured again by the pressure-sensitive sensor 10 and the value (b) is stored. This value (b) is larger than the previously measured value (a) even if there is a small leak location in the empty can W, because the leaked air is accumulated in the outer closed chamber 4.
[0016]
FIG. 4 shows the timing of the above-described supply and discharge of the pressurized air, opening and closing of the electromagnetic valve 9 and measurement by the pressure-sensitive sensor 10.
In the main turret M of FIG. 4, test pockets T are provided at 24 positions. When one empty can W is supplied to one of the test pockets T of the main turret M by the infeed turret I, the test is performed. The pocket T measures the atmospheric pressure with the pressure sensor 10 and stores the value (c).
[0017]
The main turret M rotates clockwise, and when the leak inspection mechanism of the test pocket T in which the empty can W is set is in the state shown in FIG. 3D, the solenoid valve 9 is used to prevent the pressure inside the outer closed chamber 4 from rising. Is opened, and the solenoid valve 9 closes after 200 msec.
The supply of pressurized air is started with the solenoid valve 9 still open, and pressurization by this pressurized air is continued for 400 msec.
Immediately after the solenoid valve 9 is closed, measurement is performed by the pressure sensor 10 (a), and immediately before the end of the supply of pressurized air, measurement is performed again by the pressure sensor 10 (b).
[0018]
The determination of the presence / absence of leakage of the empty can W is determined to be defective when the difference (ac) between the pressure at the start of supply of the pressurized air and the measured value of the atmospheric pressure is equal to or greater than the set value.
Even when the pressure difference (ac) is equal to or less than the set value, even when the pressure difference (ba) immediately before the end of pressurization and the pressure at the start of the supply of the pressurized air are equal to or greater than the set value. It is determined to be defective.
Instead of the pressure difference (ba), a difference (ac) between the measured value of the start of supply of pressurized air and the atmospheric pressure can be used.
Since the measured values (a, b, c) used for determining the presence or absence of leakage of the empty can W are from the same pressure-sensitive sensor 10, the pressure-sensitive element of the pressure-sensitive sensor 10 is deteriorated or the temperature is reduced. Even if there is a fluctuation due to the above, by taking the difference between the measured values, the deterioration width and the fluctuation width of the pressure-sensitive element can be offset, and an accurate pressure difference can be detected.
[0019]
When the measurement by the pressure-sensitive sensor 10 is completed, returning to FIG. 3, the lower chamber 2 descends while holding the empty can W as shown in FIG. 3F, and then, as shown in FIG. The core 14 and the can holding pad 6 stop at the bottom dead center, and then the can holding pad 6 slightly rises (FIG. 3H), and the holding of the empty can W is released.
The empty cans W are separated into acceptable products Wo and defective products Wn by the discharge turret D shown in FIG. 2 according to the determination based on the measurement value of the pressure-sensitive sensor 10.
[0020]
In the above embodiment, the leakage inspection of the empty can is described. However, the inspected product is not limited to the empty can, but may be an empty bottle of a similar shape or the like, and is also applicable to the inspection of the can lid alone.
When the present invention is applied to the inspection of a can lid, as described in Japanese Patent Publication No. 43575/1991, the leak inspection mechanism is not limited to a closed chamber consisting of two upper and lower chambers with the can lid as a boundary, but also one of the closed chambers. By further dividing the chamber into a can lid center plate sealed section and a can lid peripheral section sealed section, the change in air pressure in each sealed section can also be measured separately.
The measurement of the atmospheric pressure by the pressure-sensitive sensor is not limited to the time described in the embodiment, but may be any time as long as the inside of the upper chamber 1 is open to the atmosphere. The determination of the presence or absence of leakage of the empty can W based on (a, b, c) may be one of (ba), (ac), and (bc), or two of these. Can be combined to form a double check method.
[0021]
【The invention's effect】
According to the present invention, each test object is measured under different environments using the same pressure-sensitive sensor, and a pass / fail judgment of each test object is performed by obtaining a difference between a plurality of obtained measurement values. Even if the pressure-sensitive element of the pressure-sensitive sensor has deteriorated or has fluctuated due to temperature, the judgment value is offset by the deterioration width and fluctuation width, and it is possible to detect an accurate pressure difference and use pressurized air. A proper pass / fail judgment based on the leak inspection performed can be maintained.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing a main part of a leakage inspection mechanism used in the method of the present invention.
FIG. 2 is an overall perspective view showing an outline of a leak inspection machine to which the method of the present invention is applied.
FIG. 3 is an explanatory diagram sequentially showing the operation of the leak inspection mechanism.
FIG. 4 is an explanatory diagram showing measurement timing according to the present invention.
[Explanation of symbols]
1: Upper chamber 2: Lower chamber 3: Cylinder chamber 4: Outside closed chamber 5: Inside closed chamber 6: Can holding pad 7: Sealed body 8: Exhaust pipe 9: Solenoid valve 10: Pressure sensitive sensor 11: Clamp rod 12: Cylinder chamber 13: Seal ring 14: Core 15: Elevating rod 16: Pressurized air introduction path W: Empty can

Claims

The upper chamber and the lower chamber capable of forming one closed chamber are moved together to move between the upper chamber and the lower chamber of the leak inspection machine which repeatedly forms the closed chamber and opens the closed chamber. The inspection object is supplied and placed, the closed chamber is divided into at least two sealable chambers with the inspection object as a boundary, and pressurized air is supplied to one of the sealed chambers and the pressure in the other sealed chamber is increased. In the method of inspecting the product to be inspected for air leaks by measuring
A step of measuring the atmospheric pressure with the pressure-sensitive sensor in a state where the other chamber is open to the atmosphere and storing the first measured value;
Immediately after pressurized air is supplied to the one sealed chamber, a step of measuring the pressure in the other sealed chamber with the same pressure-sensitive sensor as described above and storing the second measurement value,
Immediately before the supply of pressurized air in the one sealed chamber is stopped, the pressure in the other sealed chamber is measured again by the same pressure-sensitive sensor as described above, and a third measured value is stored,
Determining the difference between the two measured values of the stored first to third measured values and comparing the difference with the predetermined pressure to determine the presence or absence of air leakage of the inspected product. A method for inspecting leakage of empty cans, etc.

Determining a difference between two measured values of the stored first to third measured values and comparing the measured value with a predetermined pressure to determine whether there is air leakage of the inspected product; 2. The leak inspection for empty cans or the like according to claim 1, wherein the difference between the second measured value and the first measured value and the difference between the third measured value and the second measured value are overlapped. Method.