EP0480854B1 - Tin tray body and corresponding tin closed by crimping - Google Patents

Description

The invention relates to the field of metal or plastic-based cans closed by crimping, and more precisely those which have a support shoulder serving for example for adjusting the stacking with casing of identical box bodies, or when the closed box is pressed on the periphery of a positioning orifice.

In particular, there is known a body of a can of aluminum alloy of the rectangular type with rounded angles, that is to say of which the open upper end, by horizontal convention, has a contour which has four radiated portions separated by short sides and long straight sides. This box body has a side wall above its bottom which comprises, from this bottom to said upper end, a lower portion or slightly oblique skirt surmounted by a peripheral shoulder overhanging this skirt and serving to adjust the stacking with casing of successive box bodies so that there is no jamming during unstacking, then a vertical upper portion extending the outside of the shoulder, this upper portion ending at the open upper end and at an edge of horizontal peripheral crimping surrounding the opening of this end. To close the box after filling its body, place on said open upper end a cover having an end edge to be crimped slightly projecting from the crimping edge of the body and slightly folded down to facilitate the establishment and crimping. This cover has a central portion which fits into the opening of the box body.

Crimping produces an overlap with contact of the crimping edges of the cover and the box, this overlap is called "crimping overlap" and ensures sealing. It has been found that with such bodies one often obtains insufficient "crimping overlaps", and therefore risks of leakage, along the long rectilinear sides and more particularly towards the middle of these long sides, while the overlaps were satisfactory. to the right radiated portions.
The plaintiff sought to remove these defects and the corresponding risks of leakage.

STATEMENT OF THE INVENTION

The subject of the invention is a typically metallic can body comprising a bottom, a side wall and a horizontal open upper end, the opening of said end having a contour which has at least two portions of small radius, said portions being separated by rectilinear or large radius portions, said side wall comprising, from the bottom to said upper end, a lower portion then at least one bearing shoulder of said body overhanging said lower portion, then an upper portion extending the exterior of said shoulder and a crimping edge surrounding said opening of said upper end, as is already known from the prior art presented (see US-A-3221692) in which the bearing shoulder is peripheral and unique. According to the invention, said side wall comprises, to the right of each of said portions of small radius, a support shoulder, and, at least to the right of each said straight portion or of large radius of length greater than 20 mm, a surface oblique located at each said shoulder and making an angle with the vertical greater than the angle made by said lower portion with this vertical and less than 40 °, this oblique surface connecting said lower portion to said upper portion, so as to ensure the regularity of its crimping with a cover while retaining possibilities of support of said body. These oblique surfaces are typically located in the upper third of the box body, and their inclination relative to the vertical preferably exceeds that of the lower portions by at least 8 °.

• lorsqu'il y a sur la paroi latérale du corps un épaulement, une composante verticale de l'effort de sertissage du couvercle déforme l'épaulement dans les portions moins raides, c'est-à-dire au droit des portions rectilignes ou de grand rayon (typiquement plus de 50 mm) ayant typiquement plus de 20 mm de longueur individuelle. Cette déformation de l'épaulement entraîne un raccourcissement de la portion du bord de sertissage du corps qui est appliquée contre le bord d'extrémité du couvercle par l'opération de sertissage.
• il n'apparaît pas un tel défaut à l'aplomb des portions de petit rayon, typiquement compris entre 10 et 25 mm, probablement à cause du raidissement de la paroi associé à ce rayon;
• le remplacement de l'épaulement, au droit desdites portions rectilignes ou de grand rayon, par une surface ou une paroi oblique a pour effet d'éviter ou de limiter fortement une déformation telle que celle associée à l'épaulement et donc d'éviter le raccourcissement du bord de sertissage du corps de boîte.

The following interpretation is proposed for the solution given by the invention to the problem of insufficient crimping overlaps of the prior art:

• when there is a shoulder on the side wall of the body, a vertical component of the crimping force of the cover deforms the shoulder in the less stiff portions, that is to say in line with the rectilinear or large radius portions (typically more than 50 mm) typically having more than 20 mm in individual length. This deformation of the shoulder results in a shortening of the portion of the crimping edge of the body which is applied against the end edge of the cover by the crimping operation.
• such a defect does not appear directly above the portions of small radius, typically between 10 and 25 mm, probably because of the stiffening of the wall associated with this radius;
• the replacement of the shoulder, in line with said rectilinear or large radius portions, by an oblique surface or wall has the effect of avoiding or greatly limiting a deformation such as that associated with the shoulder and therefore avoiding the shortening of the crimping edge of the can body.

• avec un corps de l'art antérieur, le recouvrement de sertissage est de 1,2 mm dans les rayons et de seulement 0,6 à 0,7 mm près du milieu des portions rectilignes;
• avec un corps selon l'invention, le recouvrement est de 1,2 mm dans les rayons et de 1,1 à 1,2 mm dans les portions rectilignes.

The effect obtained is surprising. According to the following comparative tests:

• with a body of the prior art, the crimping overlap is 1.2 mm in the spokes and only 0.6 to 0.7 mm near the middle of the straight portions;
• with a body according to the invention, the overlap is 1.2 mm in the spokes and 1.1 to 1.2 mm in the straight portions.

Each oblique surface is inclined by less than 40 ° with respect to the vertical, so as to minimize the risks of deformation during crimping. Given the offset between upper and lower portions, the optimal tilt angle varies in practice between 10 and 30 °.

Each said oblique surface preferably extends to the right of the ends of the portions of small radius framing the rectilinear or large radius portion dominating said oblique surface or even less than 10 mm from each of said ends, which means that 'it then stops either at the beginning of the rounded portions which surround it or a little before.

When the cover has a central part which fits into the upper portion of the body for closing, the height of fitting is known in advance and it is ensured that each oblique surface joins this upper portion at the bottom or end. lower of this casing or less than 1 mm lower so as to minimize the possibilities of deformation during crimping, these being influenced by the inclination of the oblique surface and by the height of the upper wall not held by the casing of the cover .

When it is a box body and more precisely a lower portion of this body nestable in an identical body, the overhanging shoulders situated in line with the portions of small radius in the case of the invention are sufficient to limit and adjust this nesting so as to avoid unstacking difficulties.

The invention also relates to a closed metal can, obtainable from the previous can body, said can comprising such a body and a cover crimped on an upper portion of said body, said upper portion having a crimped horizontal outline having at at least two portions of small radius, said portions being separated by straight or large radius portions and dominating at least one shoulder which overhangs a lower portion of said body. According to the invention, this box body has such a shoulder to the right of each of said portions of small radius and, or less to the right of each said straight portion or of large radius of length greater than 20 mm, an oblique surface located at the level of each said shoulder and making an angle with the vertical greater than the angle made by said lower portion with this vertical and less than 40 °, this oblique surface connecting said lower portion to said upper portion, and probes crimped contour has an overlap of constant crimping better than 0.2 mm.

Each said oblique surface is preferably inclined from 10 to 30 ° relative to the vertical. When the cover of the box is fitted into said upper portion of the body, each said oblique surface joins this upper portion at the lower end of the fitted portion of said cover or less than 1 mm below.

The box body and the cover are typically made of aluminum or alloy or tinplate and of thickness between 0.15 and 0.30 mm, and even more typically between 0.17 and 0.26 mm. The metallic designation also applies to metallic bodies coated with plastic, the metal giving most of the mechanical resistance. The invention also applies to rigid plastic bodies having a support shoulder and a crimped metal cover. The closed can is also typically a box of the rectangular type with rounded angles, the large rectilinear portions of its outline being 30 to 100 mm long. It can also be for example an oblong box.

ADVANTAGES OF THE INVENTION

It thus makes it possible to obtain crimped cans whose crimping overlap is very regular and therefore does not present any risk of leaks.

The manufacturing modification corresponding to the invention is particularly simple.

TESTS

Figure 1 shows the side walls of two box bodies outside the invention in a stacked position, in an axial half-section.

FIG. 2 represents a box outside the invention in the crimping position.

Figures 3 and 4 show the profile of this box after the first crimping pass, respectively in the middle of a long side and in a radiated part.

FIG. 5 represents the side walls of two bodies of boxes according to the invention in the middle of a long side, the side walls of a neighboring radiated part being shown in broken lines, in two axial half-sections.

Figure 6 shows a tin can according to the invention, in half-elevation.

Figure 1 shows the profile of the side wall 1 of two identical box bodies 2, the fitting of these two bodies 2 and the adaptation of a cover 3 on one of these bodies 2 before crimping. Each body 2 comprises, above its bottom 4, a skirt or lower portion 5 here slightly inclined towards the vertical direction or direction of the axis 6 of the box body 2, then a shoulder 7 overhanging the skirt 5, then a upper portion 8 here vertical, then an outer rim or crimping edge 9 surrounding the opening 10 located at the upper end of the portion 8. As can be seen, the shoulders 7 serve to limit and adjust the nesting of the bodies box, so that unstacking on the machine is easy.
The cover 3 comprises a central portion 11 which fits into the upper portion 8 to a depth H₁ = 3 mm and a crimping edge 12 having an end portion 13 folded down a little beyond the edge 9 to serve as a primer for crimping. Here, the width or the overflow of the shoulder 7 is 1 mm, this shoulder 7 is at H = 6 mm below the upper end of the portion 8 and its opening 10 and therefore at H₂ = 3 mm below the bottom 14 of the cover 3 in the nested position. The bodies 2 and the cover 3 are made of aluminum alloy AISI 5052, or about 2.5% Mg + 0.25% Cr, 0.25 mm thick and in the semi-hard state.

Figure 2 shows a rectangular body 2 with rounded angles and a cover 3 in position for crimping, the first pass being made with two rotating rollers 15 rotating around the body 2 and the cover 3 approaching the axis 6 of the body 2. This first pass produces a pinching and tilting of the crimping edges 9 and 12 + 13. The result after tightening pass differs in the middle of a large side and in the radiated parts: the differences in "crimping overlap" are already present before tightening and they are shown diagrammatically in Figures 3 (within 10 mm from the middle of a large side) and 4 (in a radiated part). The overlap of the crimping is respectively R₁ = 0.6 to 0.7 mm and R₂ = 1.2 mm. Body 2 has an opening 10 of 104x59.8 mm with radiated corner parts of radius 20 mm. The interpretation of the poor result R₁ is that the shoulder 7 is pushed down and deforms under the effect of a vertical component of the support of the upper surface 16 of the groove 17 of the roller (s) 15, as shown in Figure 3, the portion of the edge 9 available for clamping against the edges 12 and 13 of the cover being thereby shortened. The bending of the radiated parts makes them more difficult to deform, it is observed in particular that the shoulder 7 retains its original shape there (FIG. 4), the satisfactory covering R₂ being thus maintained.

FIG. 5 shows the side walls of two box bodies 20 according to the invention, identical to bodies 2 with the exception of the following changes: in the rectilinear portions 25 60 mm long (FIG. 6), and exceeding them by 3 mm each of their ends or connections 230 with the adjacent portions of small radius 23 (radius of 20 mm), an oblique wall portion 18 has been made. This portion 18 (FIGS. 5 and 6) is inclined to the vertical 6 according to a angle 19 of 20 °, its lower end 180 is located at the lower connection 21 of the shoulders 7 with the skirt or lower portion 5, and its upper end 22 at the bottom 14 of the nested portion of the cover 3. Each flat portion 18 thus has a height H₃ = 4 mm, a width of 1 mm in horizontal projection, and is at a distance H₁ = 3 mm from the upper end 10 of the box body 20, this body 20 having a height of 30 mm.

And on each short side of the box bodies 20, there is a similar oblique wall 18 mm long between the radiated parts such as 23 of the corners of the box body.

These latter oblique walls of limited length can be removed without notable inconvenience, and replaced by a continuous shoulder, the risk of harmful deformation being small.

The shoulder 7 is kept in the radiated parts, the 4 small shoulders 7 sufficient to adjust the nesting of the box bodies 20. The crimping was carried out as described, it gave for the box closed 200 (fig. 6) a crimped bead 24 of constant height 2.8 mm.

Destructive examinations of two boxes 200 have shown that the crimp overlaps were equal to R₂ = 1.2 mm in the radiated parts 23 and on the short sides. And that the crimp overlaps on the long sides were "R₂" or very close: they varied from 1.1 to 1.2 mm.

Claims (11)

1. A body (20) of a box for conserves comprising a bottom, a side wall and a horizontal open upper end (9), the opening (10) of said end (9) having a contour which has at least two portions of small radius (23), said portions (23) being separated by rectilinear portions or portions of large radius (25), said side wall comprising from the bottom to said upper end (9) a lower portion (5) and then at least one abutment shoulder (7) of said body overhanging said bottom portion (5), then an upper portion (8) extending the end of said shoulder (7) and a crimping edge (9) surrounding said opening (10) of said upper end, characterised in that said side wall comprises one such shoulder (7) at right angles to each of said portions of small radius (23), and, at least at right angles to each of said rectilinear portions or portions of large radius (25) of length greater than 20 mm, an inclined surface (18) disposed at the level of each of said shoulders (7) and forming an angle (19) to the perpendicular (6) greater than the angle formed by said lower portion (5) to the perpendicular (6) and less than 40°, the inclined surface (18) joining said lower portion (5) to said upper portion (8) in such a way as to ensure that the crimping (R₂) thereof with the cover (3) is uniform, whilst the supporting (7) possibilities of said body (20) are maintained.
2. A box body (20) according to Claim 1, wherein said angle (19) of each of said inclined surfaces (18) to the perpendicular (6) is from 10 to 30°.
3. A box body (20) according to any of Claims 1 or 2, wherein each of said inclined surfaces (18) extends at right angles to the ends (230) of the portions of small radius (23) framing the rectilinear portion or portion of large radius (25) overlooking said inclined surface (18), or extends to less than 10 mm from each of said ends (230).
4. A box body (20) according to any of Claims 1 or 2, wherein each of said inclined surfaces (18) meets said upper portion (8) on a level with the lower end (14) of an encased lid (3), or less than 1 mm lower.
5. A box body (20) according to Claim 1, wherein said lower portion (5) is able to be encased in an identical box body, said overhanging shoulders (7) limiting and controlling this encasement operation.
6. A box body (20) according to any one of Claims 1 to 5, made of aluminium or alloy or white iron and between 0.15 and 0.30 mm in thickness.
7. A closed box (200) for conserves, said box comprising a body (20) according to any one of Claims 1 to 6, and a lid (3) which is crimped on an upper portion (8) of said body, said upper portion having a horizontal crimped contour (24) with at least two portions of small radius (23), said portions (23) being separated by rectilinear portions or portions of large radius (25), said crimped contour (24) having a constant crimp overlap (R₂) above 0.2 mm.
8. A box (200) for conserves according to Claim 7, wherein said angle (19) of each of said inclined surfaces (18) to the perpendicular (6) is from 10 to 30°.
9. A box (200) for conserves according to any one of Claims 7 or 8, said lid (3) being encased in said upper portion (8) of said body (20) and each of said inclined surfaces (18) meeting said upper portion (8) level with the lower end (14) of the encased portion of said lid (3) or less than 1 mm lower.
10. A box (200) for conserves according to any one of Claims 7 to 9, of the kind which is rectilinear and with rounded corners, the large rectilinear portions (25) of its contour being 30 to 100 mm in length, its body (20) being made of aluminium or alloy or white iron and being between 0.15 and 0.30 mm in thickness.
11. A box for conserves according to any one of Claims 7 to 9, the body of which is made of a rigid plastics material and the crimped cover of which is metal.

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