DE2323718A1 - LID FOR PRESSURE VESSEL - Google Patents

Description

Lid for pressure vessel

The invention relates to metal lids for pressure vessels, preferably Cans for beer or other carbonated liquids.

Metal cover of this type, for example the cover described in FR-PS 1 402 391, generally have an im essential flat inner part, an edge fold and a circumferential bead that is connected to the edge fold and the inner part is. They have to withstand a relatively high internal pressure, which for beer after pasteurization reaches 6.6 kg / cm can.

However, in these conventional containers, the flat inner part with the bead is reduced by a transition zone Resistance connected, in which the metal thickness is hardly constant.

When a critical pressure is reached, a local permanent pressure is formed when the elastic limit is exceeded Deformation of the metal, which could be called a bulge. As a result, the use of such lids is minimal Safety thickness prescribed, for example 340 microns

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for an effective diameter (corresponding to the inside diameter of the container) of 65 mm or 330 microns for an effective diameter of 63 mm in the case that an alloy of aluminum with 4.5 % magnesium is used.

The calculations of the resistance of the material show that the optimal profile of the inner part of a lid should have a spherical section. But this execution brings In practice there are some disadvantages: The inner volume of the lid, which must be included in the entire packaging volume, is very important in terms of content limitations; it is no longer possible to transport the containers; the attachment an easy-to-use tear-open device with a pre-scored line on the inner part cannot be satisfactory be solved. It is therefore necessary to hold on to a substantially planar inner part.

The object of the invention is to create a metal cover which, although it contains an essentially flat inner part, but has sufficient resistance at least up to pressures of the order of 7 kg / cm, and that for a noticeably smaller thickness than that of the known cover.

This object is achieved by a cover according to the invention with an essentially flat inner part which is easy to handle Has tear-open device, with an edge fold and a circumferential bead that goes through with the edge fold and the inner part Transition pieces of substantially constant thickness is connected, solved, which is characterized in that the radius of curvature the bead is between approximately 0.5 to 1.2 mm, and the bead without discontinuity with the inner part by a straight section Section is connected, which is followed by a curved section and that the transition from the edge fold to the bead with the vertical one at the bottom level of the bead. Forms angle X of at most approximately 20 ° and forms a win-

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kel Y which is no greater than about 34 °, and the Angle X and Y are chosen so that for a larger value of the angle X the value of Y is correspondingly smaller and vice versa.

The lower limit of about 0.5 mm for the radius of curvature of the bead is due to the fact that below this value the risk of cracking gets pretty big. In practice, a lower limit of around 3 ° for the angle Y is prescribed by technological conditions.

If a critical pressure is exceeded, the lid is suddenly turned around without any significant lasting effect Deformation of the metal.

Under the effect of the pressure prevailing in the container, the transition between the fold and the bead is subjected to pressure, while tensile forces develop in the curved section. In contrast, the side wall of the bead and the straight line Section in contrast to the characteristic main Deformation zones of the conventional lid have a neutral, non-deformable zone.

For a lid with an effective diameter of 63 mm, made of a hardened alloy of aluminum with 4.5 % magnesium, a thickness of about 300 microns is sufficient to guarantee a compressive strength of at least 7 kg / cm, while for a conventional lid of the same diameter and made of the same alloy, a minimum thickness of 340 microns is required.

The invention is described, for example, with advantageous details on the basis of the following schematic drawings. Show it:

1 shows a half-sided cross section of a metal lid according to the invention for a beer can before the crimping;

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2 shows a detailed view on a larger scale of a lid assembled with a beer can;

3 shows two isobar curves (p = 7 kg / cm ² ) for X = 0 ° and 20 °, abscissa: radius of curvature r, ordinate: angle Y;

4 shows the change in the pressure ρ as a function of the angle X.

Fig. 1 shows a metal lid of generally circular shape for a beer can having a substantially planar inner part 2, an edge fold 3 and a circumferential bead 4 for reinforcement. The inner part of the lid is easy with a manageable tear-off device of conventional type provided, which is not shown.

The cover is made, for example, by pressing a sheet of hardened aluminum alloy with 4.5 % magnesium and the following characteristic values: Elasticity

2 2

strength limit = 32 kg / mm, breaking load = 36.5 kg / mm, elongation at break = 8.5 %. The effective diameter D of the container, which corresponds to the inside diameter of the can, is 63 mm.

The distance u between the floor plane of the bead. 4 and the inner part 2 is about 2.1 mm.

Fig. 2 shows that the bead 4 is continuously connected to the inner part 2 by a straight section a-b, followed by a curved section consisting of a first arcuate section b-c and a second arcuate section c-d, tangential in the inner part 2 passes over, consists; these sections essentially have same thickness.

The bead 4 has, in section, a radius of curvature r of 0.65 mm; the straight section a-b has a length L of 1 mm, the Elbow piece b-c has a radius of 1.25 mm and the elbow piece c-d a radius of 25 mm, and the connector 6 between the

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Fold 3 and the bead 4 has a substantially constant thickness and has a hook 11 which is below the plane of the inner part 2 lies and separates two sections 10 and 12 which are straight in section. The section 10 forms with the vertical at the bottom level of the bead an angle X of practically 0 ° and with the straight section a-b an angle Y of about 6 ° 30 ".

The lid is made to a remarkable thickness of only 300 microns with a tolerance of 10 microns, and can Withstand prints of the order of 8.1 kg / cm ~ whereas conventional ones Lids with a thickness of 340 microns cannot withstand more than 6.9 kg / cm of pressure.

In the following, the influence of the angles X and Y and the radius of curvature r on the properties of the lid is examined.

The angle X is set to a value of practically 0 and the radius of curvature r is 0.75 mm. Tests were carried out carried out to determine the influence of the angle Y. The results are summarized in Table I:

Y ° 7th 9 15.5 22nd 29 34 maximum pressure 7.7 7.6 7.4 7.3 7.1 7th kg / cm

The difference (Y - X) is set to 6 ° and the radius of curvature r is 0.6 mm; Attempts were made to determine the influence of changing the X angle. In Table II the results are summarized:

X ⁰ 0 14th 19.5 22nd 30th maximum
backp
kg / cm - 8th 7.9 7.7 6.8 6.4

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The angles X and Y are fixed, the first is practically O, the second is 7 °; Attempts were made to determine the influence of changing the radius of curvature r. The results are summarized in Table III:

r mm 0.475 0.55 0.60 0.65 0.70 0.75 maximum
pressure
ρ
kg / cm 7.8 7.9 8th 8.1 8.1 7.9

Beyond r = 0.75 mm, the angle Y cannot be kept at 7 and corresponding tests have shown that when r increases to 1.75 mm, Y increases to about 19 °, the pressure of 7 kg /

ρ
cm cannot be guaranteed to ground if r exceeds 1.2 mm.

The optimal tiert for r is when there is a risk of crack formation for lower values is taken into account, between about 0.6 and 0.7 mm.

The entirety of the results indicates that the angle Y must not be beyond about 34 ° when X = O and that the angle must not be greater than about 20, which corresponds to a value of Y of about 26 when a pressure of 7 kg / cra should be guaranteed.

The angles X and Y are chosen so that for a larger value of the angle X the value of Y is correspondingly smaller and vice versa. Values between 0 ° and 20 ° are preferably selected for X, between 6 ° and 34 ° for Y and between 0.5 mm and 1 mm.

In this preferred range, the pressure ρ with the angles X and Y and the radius of curvature r is given by the following formula in connection:

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= 7.0 ₊ (1-Xs ° ' ¹⁰⁴ χ (YI) - ⁰ ' ⁰ ^ _xr "0.36 72 '

Fig. 3 shows isobar curves C. and Cp which are used for X = 0 ° or 20 ° a zone in which the limit pressure ρ is greater than

7 kg / cm, separates from a zone in which this limit pressure is less than 7 kg / cm; the radius of curvature r is on the The abscissa and the angle Y are plotted on the ordinate.

The curves CL and Cp are dashed for smaller values of Y Lines are lengthened, which indicate that at values smaller than about 6 ° one enters a range of increasing technical Difficulty in making the container comes. Meanwhile, values of Y = 3 ° 30 'can be achieved with suitable tools will.

In the range of angles Y between approximately 20 ° and 7 °, the solid curve Cp is against the dash-dotted curve after shifted to the right. The experiment has shown that larger values of r are compatible with smaller values of Y if the angle X is 20 °.

Fig. 4 shows the change in the limit pressure ρ as a function of the angle X for a radius of curvature r of 0.7 mm and a Angle Y of 20 °.

The relationship between the distance (u + v) (Fig. 1) and the effective diameter D on the one hand and the ratio u / v on the other hand are chosen so that the transport conditions, the limitation of the total volume and the attachment an easy-to-use tear-off device is satisfied.

After the lid has been folded with the body 7 of a beer can (FIG. 2), the dimensions given above remain almost constant. / Q

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Under the pressure prevailing in the container, the inner part of the lid bulges slightly; the connector 6 is against the fold zone is subjected to pressure, while tensile forces are exerted from the inner part of the cover in the curved section b-c-d to develop. The point 8 of the fold 3, which is perpendicular to the can wall 7, plays the role of a hinge, because due to the fold it is essentially fixed. The arrangement formed in the side wall of the bead 4 and the rectilinear portion a-b forms a neutral, non-deformable zone.

Numerous tests have shown that in the case of a substantial If the critical pressure is exceeded, the lid suddenly turns around without significant deformation.

For a metal itself or an alloy, the reduction in the thickness of the lid and consequently the metal saving compared to the conventional lids is quite remarkable, since it is of the order of 10 to 20 % .

With the same thickness, a metal or an alloy with less good mechanical characteristics can be used. which is therefore less expensive.

For example, a lid can be produced from a hardened aluminum alloy with 2.5 % magnesium and the following characteristic data: elastic limit = 27 kg / mra "', breaking load = 32.8 kg / mm", elongation at break = 10.5 %' , or m ± t 1 % Hangan and at least 1 % magnesium and the following characteristic

see data: elastic limit = 25.5 kg / mm, breaking load = 30.5 kg / mm, elongation at break = 9%. The thickness can be effective for Diameters of 65 mm in this case vary between 320 and 340 microns.

For different steel grades, the thickness can vary from 280 to 350 microns with an effective diameter of 65 mm. You can also use normal steel or a non-oxidizing

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use steel with the following characteristic data

den: elastic limit = 21.5 or 30.5 kg / mm; Breaking load =

33.5 and 51 kg / mm, respectively; Elongation at break = 20 or 25 %, tinplate and blackplate can also be used.

Expectations;

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Claims (2)

Expectations (1 J metal lid for pressure vessels, preferably cans for Beer or other carbonated liquids with a substantially flat inner part that is easy to handle Has tear-off device, with an edge fold and a circumferential bead, which is connected to the edge fold and the inner part by transition pieces of substantially constant thickness, characterized in that the radius of curvature the bead is between approximately 0.5 to 1.2 nm and the bead (4) without discontinuity with the inner part (2) through an in section straight section (a-b) is connected, which is followed by a curved section (b-c-d) and that the transition from the edge fold (3) to Bead (4) forms an angle (X) of at most approximately 20 ° with the vertical on the floor plane of the bead (4) and with the rectilinear section (a-b) forms an angle (Y) which is not greater than approximately 34 °, and the angles (X and Y) are selected in this way are that for a larger value of the angle (X) the value (Y) is correspondingly smaller and vice versa. 2. Metal lid according to claim 1, characterized in that g e k e η / η that the radius of curvature of the bead (4) is between 0.5 mm and 1 mm, and that the value of the angle (Y) is between 6 ° and 34 °. 6724 409829/0614 Blank page