EP0592461A1

EP0592461A1 - Device for drawing metallic or plastic coated metallic cans

Info

Publication number: EP0592461A1
Application number: EP92910886A
Authority: EP
Inventors: René Meneghin; Louis Trepied
Original assignee: American National Can Co
Current assignee: Rexam Beverage Can Co
Priority date: 1992-05-04
Filing date: 1992-05-04
Publication date: 1994-04-20
Also published as: WO1993022079A1; US5460024A

Abstract

L'invention concerne un dispositif d'étirage de boîtes métalliques ou métalloplastiques, notamment en Al ou ses alliages. Le dispositif selon l'invention comporte une enceinte (1) où circule un lubrifiant (9) muni d'une ouverture d'entrée (2) et d'un orifice de sortie (12) placé à l'amont d'au moins l'une des filières d'étirage (3, 3A, 3B, 3C) caractérisé en ce que, dans chacune des enceintes (1), on ménage immédiatement à l'amont de la filière une préchambre (10) annulaire cylindro-conique, longue et étroite, adjacente à la surface externe (14) de la boîte (16) en cours d'étirage. La longueur (lo) de la préchambre (10) est de préférence comprise entre 3 et 50 mm et son épaisseur (jo) comprise entre 25 et 200 mum. Ce dispositif permet une extraction aisée de la boîte formée, ainsi que l'étirage des alliages de la série 5000, et l'obtention d'épaisseurs de parois plus faibles.The invention relates to a device for drawing metal or metalloplastic cans, in particular made of Al or its alloys. The device according to the invention comprises an enclosure (1) in which a lubricant (9) circulates provided with an inlet opening (2) and an outlet orifice (12) placed upstream of at least one of the drawing dies (3, 3A, 3B, 3C) characterized in that, in each of the enclosures (1), an annular cylindrical-conical prechamber (10) is provided immediately upstream of the die, and narrow, adjacent to the outer surface (14) of the box (16) being drawn. The length (lo) of the prechamber (10) is preferably between 3 and 50 mm and its thickness (jo) between 25 and 200 mm. This device allows easy extraction of the box formed, as well as the drawing of the alloys of the 5000 series, and the obtaining of lower wall thicknesses.

Description

DEVICE FOR DRAWING METAL OR METALLOPLASTIC BOXES

The invention relates to a device for drawing metal or etalloplastic boxes.

*

When forming metallic or metalloplastic boxes by stamping - (re-stamping) - drawing, two types of difficulties are encountered.

The first is that Al alloys containing Mg (series 5000 according to the designations of the Aluminum Association) have a tendency to flu 10 ("galling" in English) on forming tools, in particular on rings or dies. stretching. It is therefore practically impossible to form boxes with bare metal; we therefore have recourse either to specific surface treatments (see FR-A-2627189) or to a coating of internal and / or external plastic.

15

The first solution is relatively complex and expensive; as for the second, it presents another difficulty, which is the appearance of a defect called "roll-back" in English, the frequency of which is all the more important as the ratio of height (H) to diameter (D) is

20 high and / or the side wall thickness (e) is lower.

This defect occurs during the extraction of the container stretched on the punch, by the extractor, and is in the form of a pleating e accordion of the body of the container or by rolling of its free edge o

25 again, in the most serious cases, by longitudinal tears in the body of the container and rolling of the intermediate tabs in the form of "petals"; it results from a hooping effect and / or adhesion of the container body on the punch during stretching. This defect is further accentuated in the case of drawing of containers coated internally with a

30 organic material such as plastic, which has an elastic return which accentuates the hooping.

We have tried to remedy this defect in various ways, however the results obtained remain insufficient and / or random: - by increasing the lubrication at the container / punch or container / die interface by any known means. However, this solution has the following limitations:

. it does not make it possible to obtain high reduction rates of thicknesses therefore the imitation of the stretching ratio (r) (for example up to a maximum value r = (Ee) / Exl00 = 20 with e <0.15 mm for aluminum boxes) and the H / D value obtained; . on the die side, the improved lubrication results in a rough, stretched outer surface with a mat appearance, rather than smooth and shiny, while this latter surface condition is the most often desired.

- using a hard metal punch (W carbide) instead of a steel punch (elastic module: 500 GPa instead of 200 GPa)

- by using a deformable hollow punch, under high hydraulic pressure during drawing and by removing the pressure before extraction from the container. However, this solution is mechanically complex, difficult to implement and costly

- by assisting the extraction by pressure of a fluid, preferably a liquid, through the punch; however, this pressure is limited by the holding of the bottom and often proves to be insufficient for correct extraction.

The plaintiff, aware of these difficulties, sought to remedy the drawbacks reported above and provided a unique solution to the two problems mentioned.

We recall that a container stretching machine essentially consists of several coaxial dies of decreasing diameters and an axial punch, generally cylindrical, the latter successively pushing the blank through the dies in which its side wall is thinned and stretched (elongated); on common industrial machines, there are generally 3 of these channels.

The device according to the invention therefore consists of at least one enclosure placed upstream of at least one of the stretching dies, semi-sealed manner, provided with a lubricant inlet opening and a discharge opening.

The main characteristic of the invention is that, in each enclosure, immediately upstream of the corresponding die, a long and narrow cylindrical-conical annular precheck adjacent to the external surface of the box being stretched is arranged. This pre-room can be delimited externally by the industry itself or by an attached mancho; it consists of an optional cylindrical annular part, extended, on the side of the die, by a conical connection part.

If lo is the total length of the prechamber, excluding the upstream connection radius, and jo its cylindrical thickness, we should preferably have:

251 jo S 200 nm 3 i lo 1 50 mm

Surprisingly, and in the case of drawing a metalloplastic container, with this device placed on the last drawing die, the drawn container can be easily removed from the punch. In this case, this tool can be used in various ways:

- It can be used on the last stretching die, which requires either a significant reduction in thickness between 20 and 45%, or a slight reduction in thickness (skin-pass) with: 1 ir% < 10.

- we can also combine the two uses and place a device on the last and penultimate drawing die which are then contiguous, the last die ensuring the skin-pass

- it can also be used on several successive channels.

In the case of drawing of Al alloys of the 5000 series, the device according to the invention must be placed on all the drawing dies. It has been observed that if:

- jo <25 nm and lo <3 mm, the seizing phenomenon appears on alloys of the 5000 naked series, and it is impossible to extract the stretched metalloplastic containers.

- jo> 200 »m, the external surfaces of the stretched container are matt, which is excluded.

- If lo> 50 mm, the efficiency is not improved whereas this leads to more expensive tools, and above all to a problem of steric bulk in existing drawing installations.

The device according to the invention will be better understood with the aid of the following examples illustrated by the following figures:

- Figure 1 shows an axial sectional view of the device, for the stretching of a metalloplastic box

- Figure 2 gives the results of Example 1

- Figure 3 shows a sectional view of the assembly used for drawing Al alloys of the 5000 series (example 3)

- Figure 4 shows a sectional view of the die and the die holder of fig. 3

- Figure 5 shows a side view of fig. 4

- Figure 6 shows in enlarged view detail A of FIG. 4.

EXAMPLE 1

The device therefore comprises an enclosure 1 provided with an opening 2 for introducing the lubricant 9, fixed upstream of the drawing die 3 by screws 4 (not shown); it is provided with a discharge opening 12. This chamber is closed upstream by a wall 13 and contains a sleeve 5 which delimits with the external surface 14 of the container 6 during drawing, located on the punch 7 , an annular space 10 of thickness j and length 1; the reference 11 shows schematically the extractor. The device is supplemented for example by an O-ring 8 located between the enclosure 1 and the wall 14 of the container 6. The wall 13 can be replaced by the guide ring (not shown) located after the upstream die, and which has a positive clearance with respect to the surface outer of the can body of a few hundredths of a mm.

The above device was used under the following conditions on a machine comprising 3 drawing dies, this device being mounted upstream of the third die.

The punch is made of tungsten carbide with a roughness Ra = 0.10 μm; l container to be stretched is a container with a composite wall formed of aluminum 3004 on the outside (initial thickness: 0.335 mm) coated with PP on the inside (initial thickness 0.040 mm) or total thickness 0.375 mm The lubricant used is demineralized water added with 0.05% of a surfactant: F0RAFAC 1110 (Company AT0CHEM) and the flow rate of which is 0.17 1 / sec.

The drawing rate was 30.6% on the first channel, 28.8% on the second and variable on the third.

The values jo and lo were set at 20 ”m and 50 mm respectively. Punch speed: 1350 m / sec. Comparative tests were carried out under the same conditions as long as the sleeve 5 had been eliminated.

The comparative results of the number of boxes (N) extracted without damage over a series of 10 tests is given in FIG. 2 for the technique according to the invention (1) and according to the prior art (2) as a function of the size of stretching of the 3rd die (r%). It can be seen that the proportion of boxes correctly extracted has more than doubled compared to the prior art.

EXAMPLE 2

Tests similar to those carried out above were repeated using a single device according to the invention on a fourth drawing die, which required a thickness reduction of 7.5% (skin-step of 10 "m) . The successive drawing rates were therefore as follows: 30.6%; 28.8%; 30%; 7.5%. All boxes can be extracted without difficulty with a punch speed of 1350 or 2250 m / sec. EXAMPLE 3

This test relates to the drawing of boxes in 5182.

The device used, shown in FIG. 3, comprises 3 stretching dies 3A, 3B, 3C made of tungsten carbide supported by the die holders 30A

30B, 30C and separated by spacers 31, 32, 33 of increasing length; during drawing, the box is still engaged with successive dies.

Each spacer has a lubricant inlet 2 9 and a lubricant outlet (not shown) 12. The punch 7 is shown in dotted lines.

The die holder 31 (or 32 or 33) comprises a ring 3 for distributing the lubricant and distribution channels 36, arranged tangentially at the opening 37 of the die 3A.

The annular prechamber, object of the invention, used for this test a cylindrical length of 12 mm (fig.) And a thickness jo (fig. 6) d

85 ”m (for 3A), 112 un- (for 3B) and 120 ι” m (for 3C).

The stretching tests were carried out on metal 5182 in the H19 state, thickness 0.3 mm, the chemical composition of which was as follows (e weight%):

and the following mechanical traction characteristics

Rm = 390 MPa R0.2 = 328 MPa A = 9.8%

The diameter of the punch was 65.760 mm and the diameter of the die respectively 66.290 mm (3A); 66.137 mm (3B) and 65.979 mm (30. The lubricant flow rate consisting of water with NALCO XL 174 at 3% vol (from Stë NALCO) at a temperature of 40 ° C is 96 liters / mi distributed in 321 / min on the 1st die, 321 / min on the 2nd die and 321 / min on the 3rd die The striking rate was 280 strokes / min on a CMB typ B4 "body maker".

Comparative tests were carried out under the same conditions, except that the conventional dies used did not include a cylindrical annular zone, but an 8 ° entry cone (| angle at the top) than 60 (fig.6).

Under these conditions, it was possible to stretch with the device selo the invention described above, more than 20,000 boxes in 3 days (with intermediate stops) without seizing, while it is not possible to stretch boxes in 5182 with conventional dies.

The device according to the invention has the advantage of being able to be easily mounted on existing drawing machines, giving them the possibility:

- either to obtain containers with higher H / D ratios and / o lower thicknesses

- or the use of more resistant and thinner-walled materials c which leads to savings in raw materials

- or the drawing of Al-Mg alloys such as 5182, deemed non-stretchable on bare metal.

Claims

1. Device allowing the stretching of metal or metal plastic boxes comprising an enclosure (1) through which circulates a lubricant (9) provided with an inlet opening (2) and an outlet orifice (12) placed upstream of at least one of the drawing dies (3.3A, 3B, 3C) characterized in that, in each of the enclosures (1), cleaning is carried out immediately upstream of the link a long, narrow cylindrical-conical pre-chamber (10) adjacent to the external surface (14) of the box (6) being drawn.

2. Device according to claim 1 characterized in that the length lo of the pre-chamber (10) is between 3 and 50 mm and its thickness jo is between 25 and 200 "m.

3. Device according to T one of claims 1 or 2 characterized in that the pre-chamber (10) is delimited externally by the die

(3.3A, 3B, 3C).

4. Device according to claim 3, characterized in that the pre-chamber is only conical.

5. Device according to one of claims 1 or 2, characterized in that the prechamber (10) is delimited externally by an attached sleeve (5).

6. Device according to claim 5 characterized in that the enclosure (1) is closed by a wall (13), provided with a seal (8) which rests on the outer surface (14) of the container (6) .

7. Device according to claim 6 characterized in that the upstream wall (13) of the enclosure (1) is constituted by the guide ring of the previous die.

8. Drawing method using the device according to one of claims 1 to 7 characterized in that the lubricant (9) is essentially aqueous.

9. Drawing method using the device according to one of claims 1 to 7, characterized in that it is placed on the last drawing die (30 where the metalloplastic container undergoes a reduction of thickness r between 20 and 45%.

10. Drawing method using the device according to any one of claims 1 to 7 characterized in that it is placed on the last drawing die where the metalloplastic container undergoes u reduction in thickness r between 1 and 10%.

11. Method of stretching using the device according to one of claims 1 to 7, in which the penultimate stretch is between 20 and 45% and the last stretch is between 1 and 10%.

12.Method of stretching using a device according to Tune d claims 1 to 7 characterized in that the penultimate die the last die are contiguous.

13. Stretching method using the di spositif according to one of claims 1 to 5, characterized in that the container (6) is an al li age of Al from the 5000 series and in that the di spositif is placed on all sectors (3A, 3B, 3C).