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(11) | EP 0 864 385 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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| (54) |
Body-necking a wall-ironed can Querschnittsverminderung einer Dose mit gezogenen Wänden Rétreint de diamètre d'une boîte à paroi étirée |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
[0001] The invention relates to a method for manufacturing a metal, body-necked can with an ironed wall, for example one intended for being provided on one open side with an easily opening lid in order thereby to form a beverage can, comprising the stages of reducing the diameter of the can with the ironed wall by necking the wall up a considerable part of the height of the can, to be referred to as body-necking, and applying a neck rim by necking the top rim of the can.
[0002] Such a method is known. EP 0 733 415 A1 for example discloses the manufacturing of a beverage can comprising a body with zones having different diameters by drawing a cup from a blank, reducing the diameter thereof by a restraining operation and thereafter locally increasing the diameter by an expanding operation.
[0003] According to such a method the diameter of the rudimentary can body is firstly reduced. Then an expanding process is used to give the can a different shape e.g. in a shaping mould. In order to complete the beverage can subsequently a neck rim is formed at the top of the can to which the lid can be fitted.
[0004] In the known method, to (body-) neck the can it is moved into a profiled die so that the profile of the die is transferred to the can. However, if the entire body is body-necked to a smaller diameter, there is a chance of wrinkling. In order to suppress or prevent such wrinkling the can must be supported internally by a knock-out in the neck zone during body-necking. Before expanding the top rim must first be necked into a neck rim. This necking causes damage to the in-can paint and wrinkling in the neck part close to the top rim of the can. The wrinkling is connected and associated with the presence of a large gap during body-necking in the area of the body because the body is adapted to the thicker rim of the can. This gap is taken to be the gap located between the knock-out and the die. During necking the can rim fits precisely in that gap. However, the can rim is thicker than the can wall so that it has sufficient deforming reserve to be necked. However, the knock-out diameter is adapted to that thicker can rim. If the knock-out diameter were adapted to the can wall thickness, then the gap would be too small for the can rim. Therefore, adapting the knock-out diameter to the can rim thickness means that the gap is too large for the can wall, so that the chance of the can wall wrinkling increases (see Fig. 1).
[0005] Tests have shown that wrinkling can be prevented and that a simpler manufacturing method is possible if, and the invention is based essentially on this, prior to being body-necked, the can is first necked at the top rim thereof.
[0006] The neck applied for body-necking gives the can body rigidity and holds it under tension so that wrinkling is prevented during body-necking. The method in accordance with the invention makes it possible to body-neck without a knock-out. However, because of the axial loading of the can during body-necking, the body must be supported during body-necking by applying an internal overpressure. Furthermore, during body-necking a centring pin is used with a diameter equal to the internal neck diameter of the can.
[0007] In practice it is found in accordance with the invention that it is possible to form from a Ø 66 mm body a can with a circumference of less than Ø 63.5 mm or even Ø 62 mm with a 202 neck. A 202 neck is taken to be a neck with a diameter (including the flange with which the lid is applied) of 2 2/16 inch (= 53.98 mm). The internal diameter of the can neck is then approx. 52.3 mm.
[0008] The invention is also embodied in a method for manufacturing a shaped can by inflating a can which is obtained by applying the method in accordance with one of the Claims 1-4.
[0009] After pressure loads have been introduced in the material by body-necking, the material is better able to stretch and the can is able to be formed to a considerable extent, for example by inflating.
[0010] The method in accordance with the invention has been found highly suitable for cans manufactured from a packaging steel suited to wall-ironing, and manufactured from an aluminium alloy suited to wall-ironing.
[0011] The invention will now be further illustrated by reference to the drawings in which:
Fig. 1 shows schematically the successive stages of the method in accordance with the invention, and
Fig. 2 shows schematically the inflating of a necked, body-necked body in accordance with the invention.
[0012] Fig. 1 shows schematically the result of three sub-processes a, b and c of the method in accordance with the invention. Fig. la shows a wall-ironed can with a Ø 66 mm which in Fig. lb is transformed into a necked can with a 202 neck and a flange. In Fig. 1c the 202 necked can is body-necked in a die (1) into a circular cylindrical body with an outside diameter of less than Ø 63.5 mm or even less than Ø 62 mm. With a hollow centring pin (2) with an outside diameter equal to the internal neck diameter of the can, the can is placed under an internal overpressure for example by using compressed air.
1. Method for manufacturing a metal, body-necked can with an ironed wall, for example
one intended for being provided on one open side with an easily opening lid in order
thereby to form a beverage can, comprising the stages of reducing the diameter of
the can with the ironed wall by necking the wall up a considerable part of the height
of the can, to be referred to as body-necking, and applying a neck rim by necking
the top rim of the can, characterized in that prior to being body-necked it is first necked at the top rim thereof.
2. Method in accordance with Claim 1, characterized in that the body-necking is carried out with a knock-out with a circular cylindrical shape
with an outside diameter corresponding to the internal neck diameter of the neck rim.
3. Method in accordance with one of the preceding Claims, characterized in that a can of Ø 66 mm is necked to a neck with Ø 53.98 mm and then body-necked into a
circular cylindrical body with an outside diameter of less than Ø 63.5 mm.
4. Method in accordance with one of the preceding Claims, characterized in that a can of Ø 66 mm is necked to a neck with Ø 53.98 mm and then body-necked into a
circular cylindrical body with an outside diameter of less than Ø 62 mm.
5. Method for the manufacture of a shaped can by inflating a can which is obtained by
applying the method in accordance with one of the Claims 1-4.
1. Verfahren zur Herstellung einer Dose mit Querschnittsverminderung des Korpus mit gezogener
Wandung, beispielsweise einer Dose, die dazu vorgesehen ist, auf einer offenen Seite
mit einem leicht offenbaren Deckel versehen zu werden, um dadurch eine Getränkedose
zu bilden, welches die folgenden Verfahrens stufen umfasst: Vermindern des Durchmessers
der Dose mit der gezogenen Wandung durch Querschnittsverminderung der Wandung bis
zu einem beträchtlichen Teil der Höhe der Dose, was als Querschnittsverminderung des
Korpus bezeichnet wird, und Anbringen eines Randes an der Einschnürung durch Einziehen
des oberen Rande der Dose, dadurch gekennzeichnet, dass die Dose vor Bildung der Querschnittsverminderung am Korpus erst an ihrem oberen
Rand eingeschnürt wird.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass der Arbeitsgang der Einschnürung mit einem Ausschlagwerkzeug mit runder zylindrischer
Form durchgeführt wird, dessen Außendurchmesser dabei dem Innendurchmesser der Einschnürung
am Rand der Querschnittsverminderung entspricht.
3. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass eine Dose mit einem Durchmesser von 66 mm auf einen Durchmesser von 53,98 mm eingeschnürt
wird, und dass sie anschließend im Korpus zu einem runden zylindrischen Körper mit
einem Außendurchmesser von weniger als 63,5 mm eingeschnürt wird.
4. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass eine Dose mit einem Durchmesser von 66 mm auf einen Durchmesser von 53,98 mm eingeschnürt
wird, und dass sie anschließend im Korpus zu einem runden zylindrischen Körper mit
einem Außendurchmesser von weniger als 62 mm eingeschnürt wird.
5. Verfahren zur Herstellung einer geformten Dose durch Aufblasen einer Dose, die durch
Anwendung des Verfahrens nach einem der Ansprüche 1 bis 4 erhalten wird.
1. Procédé de fabrication d'une boîte en métal à corps rétreint et à paroi étirée, par
exemple destinée à être munie, sur un côté ouvert, d'un couvercle à ouverture facile
pour former de ce fait une boîte boisson, comprenant les étapes consistant à réduire
le diamètre de la boîte à paroi étirée en rétreignant la paroi sur une partie considérable
de la hauteur de la boîte, opération appelée rétreint de corps, et à appliquer un
bord de col en rétreignant le bord supérieur de la boîte, caractérisé en ce que, avant de lui faire subir le rétreint de corps, on la rétreint d'abord au niveau
de son bord supérieur.
2. Procédé selon la revendication 1, caractérisé en ce que le rétreint de corps est exécuté avec un éjecteur de forme cylindrique circulaire
et dont le diamètre extérieur correspond au diamètre intérieur du bord de col.
3. Procédé selon l'une des revendications précédentes, caractérisé en ce que l'on rétreint une boîte de 66 mm de diamètre pour former un col de 53,98 mm de diamètre,
et en ce qu'on lui fait subir ensuite un rétreint de corps pour former un corps cylindrique circulaire
dont le diamètre extérieur est inférieur à 63,5 mm.
4. Procédé selon l'une des revendications précédentes, caractérisé en ce que l'on rétreint une boîte de 66 mm de diamètre pour former un col de 53,98 mm de diamètre,
et en ce qu'on lui fait subir ensuite un rétreint de corps pour former un corps cylindrique circulaire
dont le diamètre extérieur est inférieur à 62 mm.
5. Procédé de fabrication d'une boîte façonnée, en faisant gonfler une boîte obtenue
en appliquant le procédé selon l'une des revendications 1 à 4.