FR2668727A1 - Device enabling drawn containers to be easily extracted, and its use - Google Patents

Abstract

The invention relates to a device enabling drawn containers to be easily extracted after deep-drawing (stamping) or after impact extrusion, these containers being previously coated with a plastic or a metal. The device according to the invention consists of a semi-sealed (semi-impermeable) chamber (1) located upstream of at least one of the drawing dies (3) and fitted with inlets (2) and outlets (12) for the lubricant (9). It contains a sleeve (5) which delimits, together with the external surface (14) of the container being drawn (6), a long, narrow annular space. The lubricant used is preferably water. This device enables drawn containers to be easily extracted without damage ("roll-back") and/or enables greater reductions to be obtained or materials to be used which are harder than those used in the prior art.

Description

DEVICE FOR EASY EXTRACTION
OF STRETCHED CONTAINERS AND USE THEREOF
The invention relates to a device for easy extraction of drawn containers after stamping or after impact spinning, previously coated or not with a plastic or a metal.

The problem posed is the undamaged extraction after drawing of the drawn container, which is made with difficulty, particularly when the ratio height (H) to diameter (D) is high and / or the sidewall thickness ( e) is weak.

This defect called "roll-back" in English occurs during the extraction of the container stretched on the punch, by the extractor, and is in the form of an accordion pleating of the body of the container or by a rolling of its free edge or, in the most serious cases, by longitudinal tears of the body of the container and rolling intermediate tongues shaped "petals"; it results from a shrinking effect and / or adhesion of the body of the container on the punch during the drawing.

This defect is even more accentuated in the case of stretching containers coated internally with an organic material such as plastic, which has a springback 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 interface by any
known way. However this solution presents the limitations
following
It does not allow to obtain thickness reduction rates
so high limitation of the ratio r of stretching (for example up to
a maximum value r = (Ee) / Ex100 = 20 with e su, 15 mm for
aluminum boxes) and the value of H / D obtained;
In the die industry, improved lubrication results in a stretched surface
rough surface of matte appearance, rather than smooth and shiny, then
that this last surface state is most often sought; - using a hard metal punch (W carbide) instead of a
steel punch (elastic modulus: 500 GPa instead of 200 GPa); - using a deformable hollow punch under high pressure
hydraulic when stretching and removing the pressure before
extraction of the container.

However this solution is mechanically complex, difficult to implement and expensive.

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

The plaintiff aware of these difficulties has sought to remedy the disadvantages reported above.

As a reminder, a container stretching machine consists essentially 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 current industrial machines, these sectors are generally 3 in number.

The device according to the invention therefore consists of a chamber placed upstream of at least one of the drawing dies, in a semi-sealed manner, provided with a lubricant inlet opening and a an evacuation opening.

The essential feature of the invention is that this chamber contains a sleeve, contiguous to the drawing die, and which delimits with the punch surrounded by the container being drawn, a long and narrow annular space. If 1 is its length and thickness, one must have
o preferably
25 days 100 gm 3 S 1 l <50 mm
o
Surprisingly, with this device placed on the last drawing die, the drawn container can be easily extracted from the punch.

This tool can be used in various ways
It can be used on the last stretching die, which imposes either a significant reduction in thickness between 20 and 45% or a small reduction in thickness (skin-pass) with
1 S r% <10
We can also combine the two uses and place a device on the last and the last but one stretching die which are then contiguous, the last channel ensuring the skin pass.

It can also be used on several successive channels.

The device according to the invention will be better understood with the aid of the following example illustrated in FIG. 1 which represents an axial sectional view of the device, and FIG. 2 which gives the results of Example 1.

The device therefore comprises a chamber 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 an exhaust opening 12. This chamber is closed upstream by a wall 13 and contains a sleeve 5 which delimits with the outer surface 14 of the container 6 being drawn, located on the punch 7 an annular space 10 of thickness j and of length lo; 11 denotes schematically the extractor.

The device is completed for example by an O-ring 8 located between the chamber 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 presents a set positive to the outer surface of the box body by a few hundredths of a millimeter.

EXAMPLE 1
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 of tungsten carbide roughness Fa = 0.10 gm; the draw-out container is an aluminum-wall composite container 3004 on the outside (initial thickness: 0.335 mm) coated with PP inside (initial thickness 0.040 mm) or a total thickness of 0.375 mm.

The lubricant used is demineralized water containing 0.05% of a sensioactive product: FORAFAC 1110 (Atochem Co.), with a flow rate of 0.17 l / sec.

The draw ratio was 30.6% on the first die, 28.8% on the second and variable on the third.

 The values j and 1 were set at 20 gm and 50 mm respectively.

o
Punch speed: 1350 m / sec.

Comparative tests were carried out under the same conditions except that the sleeve 5 had been removed.

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 rate of stretching of the third die (r%). It is found that the proportion of correctly extracted boxes has more than doubled compared to the prior art.

EXAMPLE 2
Tests similar to those carried out above were resumed using a single device according to the invention on a 4th drawing die, which required a thickness reduction of 7.5% (skin pass of 10 μm). The successive stretching rates were as follows: 30.6%; 28.8%; 30 %; 7.5%. All boxes can be extracted without difficulty with a punching speed of 1350 or 2250 m / sec.

The device according to the invention has the advantage of being easily mounted on existing stretching machines, giving them the possibility - either to obtain containers with higher H / D ratios and / or
lower thicknesses e.

- the use of stronger and thinner-walled materials
which leads to a saving of raw material.

It is thus possible to use the alloys 3000 more loaded than the 3004, 3104 or even alloys of the 5000 series such as for example the 5182 (according to the designation of l'Aluminum Association).

Claims (10)

1. Device for extracting drawn containers having a  chamber (1) where the lubricant (9) circulates upstream of the die  drawing (3) characterized in that the sleeve (5) delimits with the  outer surface 14 of the container (6) being drawn, located on the  punch (7) a long and narrow annular space (10). 2. Device according to claim 1 characterized in that the length 1 of the annular space (10) is between 3 and 50 mm and its  o  thickness j between 25 and 100 gm. 3. Device according to claim 1 or 2 characterized in that the  chamber (1) is provided with a seal (8) which rests on the surface  exterior (14) of the container (6). 4. Device according to one of claims 1 or 2 characterized in that  the upstream wall (13) of the chamber (1) is constituted by the ring of  guidance of the previous die. 5. Use of the device according to one of claims 1 to 4  characterized in that the lubricant (9) is substantially aqueous. 6. Use of the device according to one of claims 1 to 4  characterized in that it is placed on the last ring  drawing where the container undergoes a reduction in thickness r included  between 20 and 45%.  7. Use of the device according to one of claims 1 to 4  characterized in that it is placed on the last die  drawing where the container undergoes a reduction in thickness r included  between 1 and 10%). 8. Simultaneous use of multiple devices, according to one of the  Claims 1 to 4. 8. Use of the device according to one of claims 1 to 4, on  the penultimate die according to the conditions of claim 6 and  on the last die according to the conditions of claim 7. 10. Use of a device according to one of claims 1 to 4  characterized in that the penultimate die and the last die  are contiguous.