EP3188855B1 - Method of manufacturing textured - smooth hybrid metal closure caps - Google Patents

Description

Field of the invention

The invention relates to the field of closure caps comprising an outer metal shell of aluminum alloy and in particular screw caps which comprise an inner insert typically made of plastic and threaded. These capsules are intended for capping containers, mainly glass bottles containing alcoholic beverages and especially wine or spirits.

The invention relates more particularly to a method of manufacturing these capsules to obtain a textured appearance on the top, or head, and smooth or shiny on the "vertical" wall or skirt of the outside of the capsule. The document WO-2005/120743 describes steps b) to e) of the method of manufacturing metal capsules according to the preamble of claim 1. It also describes all the features of step a) except that the strip or sheet is textured.

State of the art

• Une presse d'emboutissage forme des ébauches de capsules à partir d'une bande ou tôle encore appelée format, découpée en flans, vernis sur leurs deux faces, d'épaisseur typique allant de 0,15 à 0,25 mm sans prendre en compte le vernis. Selon la hauteur de la jupe (longueur de l'ébauche de capsule), une à trois passes d'emboutissage peuvent être nécessaires.
• Ces ébauches sont dégraissées en étuve à haute température, typiquement de 180 à 210°C, pendant un temps allant de 3 à 5 minutes, afin d'éliminer le lubrifiant d'emboutissage.
• Elles sont ensuite laquées sur toute leur surface extérieure et sont passées en étuve afin de cuire la laque.
• Ces ébauches laquées sont imprimées sur la jupe, typiquement en sérigraphie, procédé connu de l'homme de métier sous l'appellation d' « Offset », avec un séchage final des encres en étuve.
• Un vernis de surimpression est enfin appliqué afin de protéger l'impression, ledit vernis étant séché lors d'un passage en étuve.
• L'ébauche ainsi obtenue est dotée d'un joint et/ou d'un insert plastique intérieur fileté.

The aluminum alloy capping capsules are typically manufactured as follows:

• A stamping press forms blanks of capsules from a strip or sheet also called format, cut into blanks, varnished on both their faces, with a typical thickness ranging from 0.15 to 0.25 mm without taking into account the nailpolish. Depending on the height of the skirt (length of the capsule blank), one to three stamping passes may be required.
• These blanks are degreased in an oven at high temperature, typically 180 to 210 ° C, for a period of time ranging from 3 to 5 minutes, to eliminate the stamping lubricant.
• They are then lacquered on their entire outer surface and are put in an oven to cook the lacquer.
• These lacquered blanks are printed on the skirt, typically in screen printing, a method known to those skilled in the art under the name of "Offset", with a final drying of the inks in an oven.
• An overprint varnish is finally applied in order to protect the printing, said varnish being dried during a passage in an oven.
• The blank thus obtained is provided with a seal and / or a threaded inner plastic insert.

It will be noted that all the aluminum alloys referred to below are designated, unless otherwise indicated, according to the designations defined by the "Aluminum Association" in the "Registration Record Series" it publishes regularly.

Problem

The growing interest in aesthetic solutions led the Applicant to test the use of aluminum alloy strips known to those skilled in the art as "textured" tape or sheet, that is to say with recessed or raised patterns, typically but not exclusively lines in one or more directions, imparting a roughness Ra, measured according to standard NF EN ISO 4287, typically greater than 0.5 or even 1.0 μm, for stamping the blanks of capsules.

This type of surface is well known to the person skilled in the art and described in particular in the applications WO 9731783 A1 , WO 9508408 A1 , US 5857373 , EP 0273402 A1 or EP 0456162 A1 , CA 2412980 A1 , CA 2478648 A1 , EP 1368140 A1 etc ...

However, after stamping, if the quality of the texture remains substantially unchanged on the head of the blank, it is very degraded and unsightly on the skirt due in particular to the deformation of the (or) patterns of texture during said stamping. The valorization of the textured appearance of the initial metal (special grades made by rolling to give a textured and / or iridescent effect on the surface of the metal), is thus made impossible.

No industrially viable solution is known to date to produce textured capsules, whether in whole, or on the skirt and the top, or even partially, only on the top only, because of the aforementioned degradation of the skirt .

The invention aims to solve this problem by proposing a method that retains the initial textured appearance over the entire surface of the head of the blank, and smooth or shine over the entire height of the skirt, and this under industrially economical conditions for the bottle closure market of beverage bottles.

Object of the invention

The invention relates to a method of manufacturing metal caps for capping according to the features of claim 1. According to a preferred embodiment of the invention, the degreasing step is thermal, typically at a temperature of 180 to 210 ° C for a period of 3 to 5 minutes, or chemical in an alkaline medium. Optionally, the drawing step is chained directly with the drawing step. Typically, the blank has a thickness of 0.15 to 0.25 mm without taking into account the varnish.

According to the most common mode, the draw ratio (1- final thickness / initial thickness of the sheet or strip) is greater than or equal to 2.5%.

In a preferred embodiment, it is less than or equal to 30%.

According to a particular embodiment, only the face intended for the inside of the capsule is coated with a varnish before stamping and the face intended for the outside of the capsule is only after the degreasing step.

In another embodiment, the two faces for the inside and outside of the capsule are coated with a varnish before stamping.

Advantageously, the lubricant used for stamping is volatile and removed by heating.

The same applies to the lubricant used for the drawing, which advantageously is volatile and removed by heating, typically in a passage oven or in an oven.

Moreover, the same lubricant can be used for the two stamping and drawing steps.

Advantageously, the drawing and stretching steps are chained in two integrated steps, that is to say without any intermediate step and even more advantageously, they are carried out in one and the same press stroke.

Finally, the aluminum alloy may be, but not exclusively, AA3105 or AA8011.

Description of figures

• The figure 1 is a schematic section of the capsule used for testing. Its diameter is 33 mm, its height H is 24 mm after stamping, 20 mm after cutting the horns of anisotropy and finally 28 mm after stretching, its top or head or "top" is flat and is connected to the skirt or vertical wall A with a radius R of 5 mm.
• The figure 2 shows, from left to right, the top of a textured capsule of patterns in parallel lines after stamping and drawing according to the invention, a view of the skirt of the same capsule after stamping and finally a view of the skirt of the same capsule after stamping and drawing where the textured appearance has disappeared to give way to a smooth or shiny appearance.
• The figure 3 shows, from left to right, the top of a textured capsule of patterns in perpendicular lines and a view of the skirt of the same capsule after stamping and stretching where the textured appearance has disappeared to leave room for a smooth or gloss.
• The figure 4 represents the roughness Ra in microns, measured in the long direction from top to bottom of the wall, for:
  • The starting sheets, or formats, marked A, shiny or smooth (reference 0), and textured according to different patterns 1, 2 or 3,
  • Capsules only stamped, marked B, obtained from the formats 0, 1, 2 and 3 above, the measurement being performed on the skirt, from top to bottom of the wall,
  • The stamped and stretched capsules, marked C, also obtained from formats and capsules B marked 0, 1, 2 and 3 above, the measurement being always performed on the skirt, 15 mm from the head of the capsule.

Description of the invention

As previously mentioned, because of a growing market interest for aesthetic but economic caps, that is to say a cost compatible with the requirement of the market for beverage bottles and not that of products. cosmetics, the applicant has had the idea to test the use of aluminum alloy strips known to those skilled in the art under the name of strip or sheet "textured", that is to say having patterns hollow or reliefs, typically but not exclusively lines in one or more directions, conferring a roughness Ra, measured according to standard NF EN ISO 4287, typically greater than 0.5 or even 1.0 microns, for stamping the blanks of capsules.
However, it found that after the stamping, if the quality of the texture remained unchanged on the head or top of the blank, it was very degraded and unsightly on the skirt due to the deformation of ( or) texture patterns during said stamping in addition that it presented on the latter a more or less matte appearance. At the same time, the plaintiff had engaged in a program for reducing the thickness of said caps to minimize the amount of metal used. It has thus arrived to proceed to an additional stretching pass after the conventional stamping in one or more passes, the latter leading to a non-uniform skirt thickness which could therefore be optimized to a minimum. This type of stretching, also known as "sizing", is not used in the field of capping capsules and is used to date only in that of cans or bottles-drink.
During tests using so-called "textured" metal, it then unexpectedly found that said texture was preserved on the head, or vertex, of the capsule but completely erased, at the end of said step, on the wall or skirt, while the aforementioned "matte" appearance was improved in a smooth or shiny appearance.
The interest of the invention was therefore multiple: uniformize the thickness of the skirt over its entire height by minimizing the amount of material used, or by allowing the manufacture of higher capsules without increasing the amount of material , and finally, get an aesthetic effect with a textured appearance on the top or head and smooth or shiny on the skirt or capsule wall.
The minimum rate of stretching is justified by the fact that the latter must at least bring the thickness of the entire skirt substantially uniformly to the value of the minimum thickness locally obtained after stamping (ie 0.203 mm in the case of the figure 1 ). The latter depends on the stamping conditions (roughness of the tool, play, clamping pressure, lubrication). This minimum rate is generally considered to be 2.5 or even 3%.

The maximum draw ratio is related to the limit of stretch before rupture, intrinsic to the alloy, which must not be exceeded during the drawing, or calibration, of the bottom of the skirt, the thickest zone (of 0.236 mm according to the figure 1 ). Its " _max play" value is given by the formula (1- gmax) / (1-LIR) = e _max / e _init ) where LIR is the limit of stretchability of the metal, e _max is the maximum thickness of bottom of skirt (0.236 mm according to the figure 1 ) and einit the initial thickness of the sheet (0.210 mm in the case corresponding to the figure 1 ).
In the case of an alloy of the AA3104 or 3105 type, the industrially acceptable stretch limit is 40%. A maximum draw ratio of approximately 30% is then obtained.

In its details, the invention will be better understood with the aid of the following examples, which are however not limiting in nature.

Examples of realization Stamping step

AA8011 type alloy metal strips of known quality to those skilled in the art under the name of "textured" strip, with a Ra roughness of 0.5 μm to 2.0 μm, in a thickness of 0.210 mm (without varnish), were cut into 210 x 75 mm format.

The first stamping pass was made on these unvarnished blanks with the following features:
Diameter of the cutting ring: 64 mm, punch diameter: 33 mm, punch radius: 5 mm, a drawing ratio Re = Ø blank / punch Ø 1.94.

The diameter of the matrix was 33.68 mm and its radius 2.5 mm.

The roughness of the surface of the matrix in contact with the metal was Ra = 0.2.

The lubricant was of the type known as KLÜBERFOOD NH1 16-180. The blanking pressure was adjusted to obtain a cup without creases.

This step made it possible to manufacture cups or capsules as schematically represented in section at the figure 1 , and labeled B in figure 4 .

Drawing step

• Diamètre du poinçon : 33 mm
• Diamètre de la bague d'étirage à 28.6% : 33.30 mm

The second stretching pass was made on the cups previously stamped according to step 1 above, with the following features tools:

• Punch diameter: 33 mm
• Diameter of the drawing ring at 28.6%: 33.30 mm

jeu % étant le taux d'étirage, ici de 28.6 %, soit 0.286The diameter of the drawing rings corresponds to a negative clearance with respect to the initial thickness (here metal thickness = 0.210 mm) of metal between the diameters of the punch and the matrix and is calculated as follows: $$\varnothing \mathrm{Drawing\; ring}=\varnothing \mathrm{Punch}+\left(2\times \mathrm{thick}.\mathrm{metal}\times \left(1-\mathrm{Game}\%\right)\right)$$

gambling% being the drawing ratio, here 28.6%, ie 0.286

The same lubricant as for the stamping step, "KLÜBERFOOD NH1 16-180", has been used successfully whether it is pure or diluted with 80% water.

This step made it possible to manufacture drawn stretched capsules in accordance with the invention, referenced C figure 4 .

Results of the tests:

The surface roughness Ra has been used to quantify the criterion of brightness, the latter being all the brighter in that the surface is smooth and thus the roughness is low.

1. A : format à plat,
2. B : capsule emboutie,
3. C : capsule emboutie puis étirée selon l'invention.

The roughness of the capsule, stamped and stretched according to the invention, was compared with the roughness of the capsule only stamped (according to the prior art), and finally with the initial roughness of the metal in strip or sheet or starting format at flat, before shaping the capsule.
Roughness was measured on flat formats and on the wall or skirt of the capsules from top to bottom of the wall.
The following codes are used:

1. A: flat format,
2. B: stamped capsule,
3. C: capsule pressed then stretched according to the invention.

• 0 pour l'absence de texture, soit une surface brillante ou lisse,
• 1 et 2 des textures en lignes parallèles et 3 pour deux faisceaux de lignes parallèles croisés à 90°. La figure 2 présente une capsule emboutie au centre et deux capsules embouties puis étirées de part et d'autre, avec la texture 2.

With regard to surface conditions:

• 0 for the absence of texture, either a glossy or smooth surface,
• 1 and 2 textures in parallel lines and 3 for two parallel lines of beams crossed at 90 °. The figure 2 has a capsule pressed in the center and two capsules stamped then stretched on both sides, with the texture 2.

The figure 4 compares the roughness of the flat format A with the walls or skirts of the capsules A of the prior art and with those of the capsules C according to the invention.
It clearly shows that the invention makes it possible to divide the roughness of the wall by a factor of two to eight.
It shows just as clearly, by comparison between the capsules (A, B) and (C, D), that on the top (or top) of the capsule, the roughness is unchanged, that is to say that The invention does not change the brightness of the top of the capsule. It is greater than the initial roughness of the shiny metal, but remains less than the roughness of a rough milling metal of the type called "Mill Finish".
This point demonstrates the interest of using as a starting sheet, a shiny metal to make the most of the initial shine on the top of the capsule and obtain, by drawing, an improved shine on the whole, including the skirt or wall.
These results are also identical for all the usual criteria for 2D or 3D roughness measurement (Rz, or Sk for example).

Claims (13)

1. Method for manufacturing metal closure caps comprising:

   a) supplying a strip or sheet of aluminium alloy known to those skilled in the art as a textured strip or sheet, typically coated on at least one of its two faces, generally the face intended to be on the inside of the cap, with a coat of deep-drawing boundary lubricant,

   b) a first operation of cutting into disks known as blanks,

   c) a step of deep drawing and of cutting anisotropic earings, in one or more passes, of said metal in blank form, typically using a deep-drawing boundary lubricant, so as to form a drawn preform, comprising a head and a skirt, typically exhibiting symmetry of revolution about an axial direction,

   d) a step of degreasing said drawn preform, which step is intended typically to eliminate remains of boundary lubricant so as to form a degreased preform that can be lacquered,

   e) a possible step of applying a protective and decorative lacquer,

   and characterised in that it comprises, after the deep-drawing step, at least one draw step consisting in passing the drawn preform through drawing rings in order to stretch out and thin the metal.
2. Method according to claim 1 characterised in that the blank has a thickness of 0.15 to 0.25 mm without boundary lubricant.
3. Method according to any of claims 1 or 2 characterised in that the drawing ratio (1- final thickness/initial thickness) is greater than or equal to 2.5%.
4. Method according to any of claims 1 to 3 characterised in that the drawing ratio is less than or equal to 30%.
5. Method according to any of claims 1 to 4 characterised in that only the face intended to be on the inside of the cap is coated with a lacquer before deep-drawing and the face intended to be on the outside of the cap is coated only after the step of degreasing.
6. Method according to any of claims 1 to 4 characterised in that the faces intended to be on the inside and on the outside of the cap are coated with a lacquer before deep-drawing.
7. Method according to any of claims 1 to 6 characterised in that the lubricant used for the deep-drawing is volatile and eliminated by heating.
8. Method according to any of claims 1 to 7 characterised in that the lubricant used for the drawing is volatile and eliminated by heating.
9. Method according to any of claims 1 to 8 characterised in that the same lubricant is used for the two steps of deep-drawing and of drawing.
10. Method according to any of claims 1 to 9 characterised in that the steps of deep-drawing and of drawing are chained in two integrated steps, i.e. without another intermediate step.
11. Method according to any of claims 1 to 10 characterised in that the steps of deep-drawing and of drawing are carried out in a single and same press stroke.
12. Method according to any of claims 1 to 11 characterised in that the aluminium alloy is of the AA3105 type.
13. Method according to any of claims 1 to 11 characterised in that the aluminium alloy is of the AA8011 type.

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