EP1121299B1 - Temporary burst stoppage in a sheet metal top - Google Patents

Abstract

A can end made of sheet metal for containers which in a closed state has an increased inner pressure compared to an ambient pressure. The can end includes a substantially flat central panel, a portion in the central panel is smaller with respect to the panel, and is adapted to be broken out of the panel by tearing. The smaller portion is defined by a score line, and a tab that is adapted for gripping and serving for opening the smaller portion. The tab is mounted at the central panel. In a longitudinally limited section of the can end, following a starting portion of the score line, at least one of a metal structure and structure lines of the sheet metal below the score line have a substantially higher density compared to a metal structure of the sheet metal below at least adjacent score line sections for temporarily blocking the opening process, which is difficult to control, after initially breaking or tearing open the score line.

Description

The invention relates to a lid made of metal with an opening system for standing in the closed state under positive or negative pressure container, for example, beverage cans, and a method for its preparation. In such cans, in particular beverage cans with carbonated content, the can before opening the lid (by means of the opening system) under an internal pressure of about 3.0 to 5.8 bar, depending on the contents, the degree of filling, of the Storage temperature and transport treatment. Upon initial opening of an opening segment, the shear-breaking score line for opening the container first tears in or out near the tensile or compressive point of a grip tab. As a result of the impulse-like action of force of the very high internal pressure, the opening causes the opening segment of the lid mirror, which is determined by the score line, to pop out uncontrollably or abruptly. This creates a risk of injury to hands, face and eyes.

In order to prevent this danger in known lids and to control the pulse-like opening process, in a predetermined limited portion of the score line, the residual wall thickness remaining below the score line is larger, ie less weakened, than the adjacent areas of the score line. By appropriate selection of the relative position of this short portion of the score line relative to the portion of the score line at which the opening process begins, it is achieved that, with the initial break, the score line can initially only travel to that predetermined blocking location and be stopped thereon a pressure equalization between container interior and exterior can take place, whereupon the opening process can be completed safely. This prevents the opening segment, opened manually by means of a grip tab, from bursting uncontrollably due to the high internal pressure or even tearing off the cover and flying out or suddenly bursting out of the opening.

Such opening locks have been used successfully in the various types of Aufreißdeckeln, so both in such covers in which the tear-open segment with the pull tab together completely detached from the lid, or in such covers, in which the tab with the tear segment on the lid also after remains open, wherein the tear segment is pivoted, for example, when opening into the container interior (SOT lid).

In order to avoid the risk of injury, the usual test guarantee for beverage cans is at 6.2 bar (90 psi or 620 kPa) as a minimum. This, initially limiting the opening or blocking (short: blocking) score line can also be used in other containers, such as low pressure containers. Used for tennis ball cans, it also provides clearance barriers in the pressure range from 1.5 bar (150 kPa) to 2.5 bar (250 kPa).

The previous system has proven itself in practice, but is subject in manufacturing various critical problem areas that require a high control effort. Due to the increased residual wall thickness in the blocking region, increased wear of the embossing scoring knife comb has disadvantages for the accuracy of the control of the further ripping process. This may result in the further tearing of the opening area after the temporary blockage of the separation process is not (more) follows the score line exactly. Another problem is that in the restricted area uncontrollable or too high tearing forces are necessary, which can lead to excessive residual wall thickness to the fact that the opening process can not be continued and completed. On the other hand, if the residual wall thickness is too small, the protective effect can be omitted since the temporary blocking of the opening process does not occur or does not occur with sufficient safety. Especially with an arrangement of the scribe line so that it tapers to a point and two Aufplatzsperren are required, both sides of a rounded tip, emanating from the two score line segments, the previous concept has not been successful.

It is an object of the invention to avoid the difficulties shown by simple means and to propose a more versatile, temporary Aufplatzsperre on a metal cover and to provide a method for its preparation.

To solve the invention provides a lid made of metal with the features of claim 1, 7 or 14 and a method according to claim 8 or 9 before.

In the predetermined limited (short) portion of the score line, the residual wall thickness substantially equals and does not significantly differ from the residual wall thickness in the adjoining, and in particular the remaining, portion of the score line. The temporary blocking of the tearing operation is achieved by deviating, in the selected, ie predetermined and limited area of the score line, the metal structure in the region of the residual wall substantially from the structure in the adjacent regions of the score line.

After the production of the score line, this metal structure is changed in a compacting manner. The compression is a relief of impressed tensile stresses. While in the rest of the score area, following its purpose, the metal sheet is weakened and tensile stresses are programmed, as it were, by inserting the score line below the score line, due to the lateral displacement of the material, thus favoring bursting, in the short area leading to temporary obstruction the time of pressure equalization is used, the programmed tension lowered, until fully compensated. This compensation provides for a reduction in shear, thus strengthening the already about 20% lower shear strength of the metal compared to its tensile strength. Although a reduction of the embossing depth in the restricted area would also be able to reduce the Schemeigung, but here it is only a theoretical optimum to achieve between the height of the remaining wall - which causes the lock - and the suitability of the remaining wall to shearing off at a tear propagation caused by the user. It may be that the optimum can be determined theoretically, but this optimum is constantly changed in the course of production, towards worse score lines, because the remaining embossing comb or the scoring comb is subject to wear and the differences between embossing line and reduced embossing depth either no longer accurate tune or change. The result is a breaking away of the shear lines when opening from the tracking of the scribe line, if the temporary opening lock was too intense, so the residual wall needed too high a shear force to be separated. If, on the other hand, the residual wall is set too low, it can not unfold its temporary blocking effect, but immediately breaks completely upon pulsed pressure escape.

It has surprisingly been found that this microstructure temporarily stops the initial opening operation reliably at the predetermined point of the score line, so that the required and desired protective effect against the dangers indicated above is reliably achieved. On the other hand, it has been found that the notching tool or a corresponding scoring knife has a longer service life. The longer service life can also be favored in that the additional embossing tool with laterally impressed line pieces is located outside the actual score line. The control of Aufbrechvorgangs is thus not achieved by the tool that introduces the score line, but by another tool that introduces additional embossing pieces that can be better controlled in their depth, length and distance from the actual score line and also easier to adjust , For example, it is possible to exchange this separate tool, the embossed pieces in their width, length or in to change their distance from the actual score line to program different Aufbrechvorgänge and pretend in the lid. Such type of controls are possible with conventional embossing tools, which have a section of a reduced height of the embossing comb, only if the entire tool is changed with its entire embossing comb. This is much more expensive, much less effective and much more complicated to make than the simple control of two additional embossing beads left and right of the actual web guide. In this case, even the placement or positioning of the short embossed pieces on both sides of the score line can be changed to allow a changed bursting behavior in the initial break-up operation and to test to a greater extent and to an optimum, than that with a variety of specifically produced embossing tools Case is.

By embossing squeezing pieces on both sides of the score line, the actual score line is reduced to rupture in width. The width defining walls left and right of the indented notch with the bottom lying below change after the second engagement of the embossing tool. Preferred values are a reduction to 30% to 70% of the original width, in particular at least 50% (claim 16). If a greater reduction is made by a stronger material displacement from the outside to the score line, and the score line reason completely disappear and stunt to an open-topped circular shape. The walls are in each case made somewhat steeper and move closer to each other, wherein the change of the slope and the reduction of the width of the depth and the width of the stamping lines on both sides of the score line is dependent.

Although it is known from US Pat. No. 3,968,899 (Jordan) to provide two adjacent notches of lesser depth adjacent to a tear line (score line), these neighboring notches are intended to relieve the main score line so that it does not break open prematurely under pressure. To accomplish this, the two minor score lines extending in the depth are provided almost completely along the entire main score line , cf. there column 3, lines 5 to 10. It is achieved to lock an early break, see. there column 3, line 32, line 36, line 41 and column 6, line 8. A comparable purpose has the GB 1,164,179 (ALCOA), cf. there on page 1, lines 19 to 27, as well as there figure 6. On the physical explanation given there, which graphically indicates the function of the three adjacent score lines, is here referenced, cf. there page 3, left column, lines 50 to 59.

Although US-A 3,406,866 (Jasper) shows no three adjacent score lines, but the two, with the local figure 3 and the associated functional explanation corresponding to the above-mentioned writings, see. there Col. 1, lines 39 to 55. None of the cited documents address the problem stated at the beginning, so that the solution given by the invention patented here can not be suggested.

The tools used to produce the microstructure change effected according to the invention with a narrower kerf line section are substantially more stable and less prone to wear, such as a normal scribing knife (also embossing comb) which is uneven in its engagement height (or depth).

The structure change is effected by acting on the cover sheet from outside the score line forth.

The action on the cover sheet outside the score line can be made from any direction, ie from the side or from below, the effect is in any case directed so that the lid material or the microstructure is compressed below the opening for opening score line, especially at strong influence of the side of a relaxed in their tensile stresses microstructure is obtained. Such a voltage-neutral zone is mechanically much more stable and achieves the same notch line depth along the entire starting portion of the opening serving score line and also beyond a temporary opening blockage or opening lock, which is able to compensate for the pulse-like escape of pressure caused by pressure difference from the environment. After balancing the pressure, the temporary lock can be overcome by the user of the grip tab in a continued opening process, so that the tear-open is exposed to the score line on the score line. The temporary blockage is therefore not a permanent blockage when the user overcomes the mechanically solidified residual wall shortly after the beginning of the opening process by a mechanically increased force.

The deformation of the microstructure is very conceivable when two short score pieces are imprinted directly next to the score line that serves to open. In the prior art, the area of the barrier has usually been that which was less solidified or had a looser structure, because here the residual wall had a greater strength and thus the incipient tearing process was temporarily interrupted. According to the invention, this area is substantially the same in thickness as the train of score lines before and after this area. Nevertheless, however, comes through a lateral squeezing of material by impressing lateral embossing pieces a mechanical solidification, which achieves a controlled opening after impulsartigem escape of overpressure or impulsartigem compensation of the negative pressure (claim 11).

The score line according to the invention may have substantially uniform depth (claim 2). The mentioned reduction of the tensile stresses below the score line can be done from one side or both sides of the opening score line (claim 3). If the temporary barrier should not be too strong mechanically, a very short length is recommended as one-sided or bilaterally displaced notched pieces, which, however, are located very close to the starting section, ie locally close to the initial break-in area of the score line.

The depth of the two short score lines next to the main score line can be controlled. By controlling the depth, the material compression under the main score line can be controlled in shape and tension relief. The greater the depth, the stronger the tension relief under the groove bottom of the main score line and the stronger the burst lock when opening the limited opening segment. Starting from a plate thickness of the order of 0.22 mm and 0.24 mm, the depth of the additional embossing line pieces can be between 0.17 mm and 0.08 mm, ie in particular have a greater depth, than the main score line for opening (claim 4).

An increased depth of the laterally displaced and limited in length bruising allows a stronger and more controlled relaxation of the structure under the opening score line (claim 14). The controlled relaxation by the additional score lines causes the flow or Gefügelinien run steeper under the locking portion of the score line, as in the remaining area, which takes place by the pushing together of the cover plate in this area (claim 6). This is accompanied by the steeper design of the wall sections of the score line, which in the blocking area anyway have a smaller distance from each other than in the at least adjacent area of the score line, up to the entire remaining area of the main score line (claim 15, claim 7, alternative (a) ).

A rounded profile at the bottom of the side crush (claim 5) has a preferential effect over a greater depth range in the direction of compaction of the whip lines or flow lines on the notch line lying under the notch area, narrowing the notch line with closer opposite walls occurs (claim 7, claim 16).

As far as the term "score line" has been used, the person skilled in the art also understands an embossing or scoring line or a weakening line introduced by other means, which allows a tear-open segment to be separated from the remaining cover mirror of the cover by shear forces for opening; such terms as tearing or tearing should be considered technically equivalent. Gearing is a densification of the poultry line of the metal.

Figur 1

zeigt in der linken Hälfte "a" in Aufsicht einen Aufreißdeckel 1 und in der rechten Hälfte "b" den zugehörigen , entlang einer Kerblinie 8 aufreissbaren Bereich 4, der an einer Grifflasche 6 vollständig vom Deckelblech gelöst wird.

Figur 2

zeigt in der linken Hälfte "a" in Aufsicht einen anderen Aufreißdeckel 9 aus Blech und in der rechten Hälfe "b" den durch eine Kerblinie 11 begrenzten Aufreißbereich 12, der zusammen mit einer Grifflasche 14 am Deckelblech auch nach dem Öffnen verbleibt.

Figur 3

zeigt im Ausschnitt und im vergrößerten Querschnitt das Deckelblech in einem kurzen Abschnitt 7,7a der Kerblinien 11 oder 8, der zum Stoppen des anfänglichen Aufreißvorganges bestimmt ist.

Figur 4

zeigt in ähnlicher Darstellung wie Figur 1b den Aufreißbereich 22 im Deckelspiegel 20 in Aufsicht, mit einer den anfänglichen Aufreißvorgang stoppenden Blockade durch kurze Prägelinien 27a,27b gemäß einem Beispiel der Erfindung.

Figur 5

zeigt entsprechend der Figur 2b den Aufreißbereich des Deckels nach Figur 2a, mit dem Aufreiß-Blockiersystem gemäß einem weiteren Beispiel.

Figur 6

ist ein ähnlicher Querschnitt wie Figur 3 durch einen Deckel nach Figur 4 oder 5 mit der Blechstärke d, vereinfacht dargestellt mit Körnern statt Fließ- oder Gefügelinien, die durch Verbinden der Mittelpunkte entstehen.

Figur 7

ist eine ähnliche Darstellung im Schnitt, wie Figur 6 zur Erläuterung weiterer Einzelheiten.

Figur 8

ist eine genauere Darstellung, ausgehend von Figur 3, bei der Gefügelinien oder "Fließlinien" des Bleches im Bereich der Kerblinie 8 dargestellt werden. Diese Kerblinie ist im Sperr- oder Blockierbereich 7 der Figur 1 geschnitten und zeigt einen trapezförmigen Kanal, der von der Oberfläche des Deckelspiegels eingeprägt ist.

Figur 8a

ist eine Ausschnittvergrößerung der Figur 8 mit einem um den Faktor 2 vergrößerten Maßstab, wobei der Kerbliniengrund 8g und die beiden Wände 16 der Kerblinie deutlicher zu erkennen sind, ebenso wie der Verlauf der Fließlinien des Metalls.

Figur 9

ist eine vergleichbare Darstellung, hier genauer dargestellt als in Figur 6, namentlich mit Fließlinien im kurzen Abschnitt 24 der Figur 4 ohne Darstellung der seitlichen Einprägungen Q1,Q2 bzw. 27a,27b von Figur 4.

Figur 9a

ist eine Ausschnittsvergrößerung mit einem um den Faktor 2 größeren Maßstab nur im Bereich des Kerblinienabschnitts 24 zwischen den beiden Einprägungen Q1,Q2, die hier nicht dargestellt sind.

The invention will be explained in more detail in the execution examples .

FIG. 1

shows in the left half "a" in supervision a Aufreißdeckel 1 and in the right half "b" the associated, along a score line 8 rupturable area 4, which is completely released at a gripping tab 6 from the cover plate.

FIG. 2

shows in the left half "a" in supervision another Aufreißdeckel 9 made of sheet metal and in the right half "b" limited by a score line 11 tear region 12, which remains together with a pull tab 14 on the cover plate even after opening.

FIG. 3

shows in section and in enlarged cross-section the cover sheet in a short section 7, 7a of the score lines 11 or 8 intended to stop the initial tearing operation.

FIG. 4

FIG. 1b shows the tear-open area 22 in the lid mirror 20 in a plan view, with a blockage interrupting the initial tearing operation through short stamping lines 27a, 27b according to an example of the invention.

FIG. 5

FIG. 2b shows the tear-open region of the cover according to FIG. 2a, with the tear-open blocking system according to a further example.

FIG. 6

is a similar cross section as Figure 3 through a lid of Figure 4 or 5 with the plate thickness d, shown in simplified form with grains instead of flow or Gefügelinien, which arise by connecting the centers.

FIG. 7

is a similar representation in section, as Figure 6 for explaining further details.

FIG. 8

is a more detailed view, starting from Figure 3, in which Gefoulinien or "flow lines" of the sheet in the area of the score line 8 are shown. This score line is cut in the blocking or blocking region 7 of Figure 1 and shows a trapezoidal channel which is impressed from the surface of the lid mirror.

FIG. 8a

FIG. 8 is a detail enlargement of FIG. 8 with a scale enlarged by a factor of 2, whereby the score line 8g and the two walls 16 of the score line are more clearly discernible, as well as the profile of the flow lines of the metal.

FIG. 9

is a comparable representation, shown here in more detail than in Figure 6, namely with flow lines in the short section 24 of Figure 4 without representation of the lateral indentations Q1, Q2 and 27a, 27b of Figure 4.

FIG. 9a

is an enlarged detail with a larger by a factor of 2 scale only in the region of the score line section 24 between the two imprints Q1, Q2, which are not shown here.

FIG. 1a shows a tear-open lid 1 with a folded edge 2 on a lid mirror 3. In the lid mirror, a tear-off region 4 is defined by a score line 8 which is opened by means of an annular grip tab 6 which is fastened to the tear-open region 4 by means of rivet 5 Container can be completely detached from the lid. By tilting the handle tab 6 relative to the lid mirror, the score line in the region of the rivet 5 is initially brought to break. By further pulling up on the pull tab 6, the opening process can then be continued by tearing along the score line 8 until the tear region 4 is completely released.

In FIG. 1b , the tear-open region 4 is shown on an enlarged scale. With 5a, the location for fixing the pull tab 6 is indicated. In the vicinity of the attachment point is provided on both sides of a narrow area 7, which serves to provisionally stop the tearing after the initial breaking of the score line, so that without risk to the user pressure equalization can take place before pulling the handle tab 6 the opening process is continued.

Figure 2a shows the same situation with a metal cover of another genus. Again, in Figure 2b on a larger scale the tear region 12 is shown. The attachment point for the grip tab lies at 13a, ie outside the tear-open area. To open a lever-grip tab 14 is raised up here as well. It tilts around its attachment point 13 and presses the tear-open area 12 into the interior of the container. The tearing process begins near the attachment point 13a. In its vicinity, in turn, similar means 7a for provisionally stopping the initial tearing operation are arranged.

Figures 1 and 2 show conventional lids made of sheet metal with a "central panel" (cover mirror) 10.3 and a seam edge. 2

Figure 3 shows the usual way of forming a block 7 or 7a for temporarily stopping the initial tearing operation. 15, the cover sheet is shown in the area of the score line 8 or 11. 17 indicates the normal residual wall thickness d2 below the score line. In the highlighted area of the block 7 or 7a, a larger residual wall thickness d3 is provided below the score line, as indicated at 18. The metal structure 19 below the score line is pinched but otherwise not substantially altered. The walls 16 of the score line 8,11 (often also called "score line" or "score line") are inclined, as a result of imprinting with an embossing punch or scoring anvil. The image shown schematically in FIG. 3 can be illustrated by means of a real section through a metal cover with a corresponding magnification, as shown in FIG. 8 and FIG. 8a . Here, the trapezoidal score line is shown in section 7, 7a of FIGS. 1, 2, wherein the residual wall thickness shown is greater than the remaining wall thickness, which is not visible in FIGS. 8, 8a, which is reduced at the lower embossed remaining score line 8.

As can be seen from FIG. 8, a drawn out flow line 19x in the metal structure 19 is below the score line. Also evident is the effect of the embossment in an area 19e farther below the score line, which reflects the image of the score line weakened. The lower surface of the metal lid is flat and not changed in the area 7 with respect to the remaining lower surface. The obliquely upward extending side walls 16 go directly into the transition points 16a, 16b in the surface of the lid mirror. Due to the imprint, the direct transitions are even slightly lowered compared to an imaginary flat plane on the lid mirror. Particularly in the enlargement of FIG. 8a, this direct transition 16a, 16b can be clearly seen in the upper edge regions of the score line 8, the groove bottom 8g of the groove 8 corresponding to that of FIG. The groove bottom 8g is narrower than the width b1 of the score line between the transition portions 16a, 16b, which is designated by b1 in FIG.

In FIGS. 4 to 7 , stopping of the initial break-in operation is differently caused by the same types of covers as in FIGS. 1 and 2. The position of the blockages with respect to the attachment points 5a, 5, 13a, 13 of the grip tabs 14, 6 is essentially the same as in FIGS. 1 and 2.

FIG. 4 shows, on a larger scale, a tear-open region 22, which corresponds to the tear-open segment 4 according to FIG. The tear-open area 22 is delimited by a continuous score line 21. In the vicinity of the narrower end of the tear-off region formed here as a drop-shaped segment, the fastening point 23 is provided for a (lever-shaped or gripping-type) grip tab. This is the "start region" S of the opening process, which continues by separating the score line along the path K. At a small distance A from this starting area S, limited areas 24 are provided on both sides of a center line M of the tear-open area, which areas serve to provisionally stop the tearing process. The mean distance 26 of these areas from the attachment point 23 is indicated by A. It may be in a specific embodiment at about 1.5 to 3.5 mm, so it is slightly further away from the point 23, as the blocks 7,7a of Figures 1,2.

The score line 21 is continuously running consistently deep with a uniform notching tool. It also has the same residual wall thickness d2 in region 24 as in the adjoining, and in particular the entire remaining score line region.

As can be seen from FIG. 6 , in the area 24 the cover plate 35 in the metal structure 38 below the score line 21 is substantially changed in such a way that in this area a microstructure freed of tensile stress is present in relation to the metal structure in the adjacent residual wall areas. This denser metallic structure provides a sufficient stopping effect for the tearing process during the initial opening, even at high pressure differences to be compensated, so that a change in the score line k2 is not required.

The denser texture is achieved not by a modified action of the scoring tool, but by the metal structure in its flow or guillotine lines being constrained by a limited length crushing or compression 27a, 27b and Q1, Q2, respectively, from one or both sides of the score line 21 is changed considerably.

It has been shown that a one-sided pinching already leads to a sufficient relaxation of the metal structure 38. However, a double-sided pinching, as shown in FIGS. 4 to 7, is preferred. For this purpose, a bead or a notch piece 27a, 27b is embossed linearly in a distance 28 which corresponds approximately or at least to the score line from the center of the score line and parallel to the limited portion 24 of the score line. The center distance of the tearing score line and the squish bead or notch may be at a concrete embodiment about 0.5 to 1 mm. The preferred length L of the notch pieces 27a, 27b in the limited area 24 may be between about 1.5 and 6 mm. Due to the short notch (s) next to the actual score line, the metal structure in the region of the residual wall (thick) of the opening to be opened score line on a roughly equal length mechanically formed. In the residual wall thickness of the adjacent or further lying away Kerbliniensegmente no deformation of the metal structure.

The notch pieces 27a, 27b may be introduced simultaneously with the creation of the score line. However, they can also be impressed later in a separate step. In the latter case, the edge slope of the opening score line changes in section 24, as shown by the solid flank 37 as compared to the dashed flank 36 in FIG.

Preferably, the notch pieces Q1, Q2 extend slightly deeper than the opening to be opened score line 21, as shown in Figure 7 can be seen. It may be useful to round the bottom contour 39 of the notch pieces, in contrast to a trapezoidal cross-sectional shape of the score line. The residual wall 42 with a thickness d2 below the score line in the section 24 is thus slightly larger than the thickness d1 of the residual wall 41 under the pieces Q1, Q2. The flank angle 40 of the additional notch pieces should be about 5 ° ≤ α ≤ 15 °.

The configuration of the score line schematically illustrated in FIG. 6 in the limited section 24 becomes clearer from the real sectional images of FIGS. 9 , 9a , which are a section and an enlargement to the scale shown there at the point 24, wherein the lateral notched pieces 27a, 27b and / or Q1, Q2 are not recognizable in the micrographs because they are outside the image area.

Going out is in the area 24, which extends perpendicular to the paper plane, of a score line 8 with a width b1, as shown in Figure 8, only slightly lower with respect to the groove bottom 8g, corresponding to the normal score line, the residual bottom height d2 Figure 3 leaves. After exposure to laterally spaced score lines Q1, Q2, as may be performed by embossing tools, the score line in section 24 of FIG. 4 is as shown in FIG . The structure is significantly changed, and the shape of the score line is changed in this particular example strongly compared to the trapezoidal shape. The change in shape depends on the depth, width and distance between the score pieces Q1, Q2 from the center of the score line 8 in the portion 24.

It can be seen in Figure 9, together with the detail of Figure 9a , that the bottom of the lid bulges 38c and 38b in the transitional portions 38c, that is material is pressed from the outside under the score line 8 in the unmodified and below the score line 21 in the modified form becomes. As a result, the poultry lines change, they become denser and the area 38e below the score line is deformed more downwardly with respect to the flow lines, corresponding to the bulge 38c with first transition section 38a and second transition section 38b to the remaining underside of the lid.

The flow lines 38y and 38x, which are specially marked out in the area 38 below the score line, run steeper below the score line 21 than in FIG. 8, in which a flow line 19x with a slight slope in the area 19 under the score line 8 is drawn out , This state 19x is also maintained in the area of the score line outside the short section 24 in the new design of the score line 21 of Figure 9, so that the flow lines from a flat slope in the remaining area to a steeper slope 38x, 38y in the blocking or Change the blocking section.

9, the initial width b1 of the score line has been so greatly reduced that the score line 8g of FIG. 8a is deformed to a circular configuration 48 in FIGS. 9 and 9a, respectively, as the walls become steeper 49a, 49b, along the inclined plane 37. Other depths and other distances of notch pieces Q1, Q2 cause less change in the score line so that the illustrated example of Figure 9 is an exaggerated example.

9a, the increase in the transition region 37a, 37b from the sloping walls 49a, 49b of the section 24 to the rest of the cover mirror 20 and 30 of Figures 4 and 5, respectively. These transitions are continuous between the wall and the remaining cover mirror, but have an increase in relation to the plane, so that here the specially deformed flow lines are also visible from the outside.

The embodiment in another form of a tear-open region 33 according to FIG. 5 is corresponding. Here, in the lid mirror 30 by a score line 31 a remaining on the lid tear segment 33 is limited, which is opened by means of a gripping tab, not shown, which is attached at 32. At the predetermined distance from the attachment point, the embossments Q1, Q2 laid laterally next to the score line are arranged to stop the opening process, which correspond to the notch pieces 27a, 27b.

The shape, size and position of the notch pieces 27a, 27b, Q1, Q2, and the residual wall thickness d1 among these pieces determine the strength of the relaxation of the structure and thus the extent of the blocking effect after initial opening. It is adjustable by changing notches outside (actually next to) the opening score line.

Claims (16)

1. Lid made from metal sheet (1; 9) for containers under an increased pressure with respect to the ambient pressure in the closed state, such as drinks cans, which lid has an essentially flatly designed surface (3, 10, 20, 30), a region (4; 11; 33; 22) in the lid surface which can be ruptured and which is smaller compared to the surface, defined by a notch line (8; 11; 21; 31), and a gripping flap (6; 14) serving to open the small region and which is attached to the lid surface;
   characterised in that after a start section (S) of the notch line (21; 31) a piece (24, 25, L) of certain length is provided, in which the metal grain (38) or the grain lines (38x, 38y) of the sheet below the notch line are considerably closer compared to a metal grain (19) below at least the notch line adjacent the piece (L), in particular the remaining notch line (21; 31), in order to temporarily block an opening step which is difficult to control after initial rupturing of the notch line (21; 31).
2. Lid according to claim 1, characterised in that a residual wall thickness (42, d2) in the defined section (24, 25) below the notch line corresponds essentially to the residual wall thickness at least in the adjacent sections of the notch line (21; 31).
3. Lid according to claim 1 or 2, characterised in that a linear piece (27a, 27b; Q1, Q2) extending over the length-defined section is incorporated, in particular embossed - on one side or on both sides - in the lid surface (20, 30) at a (slight) distance (28) from the notch line (21; 31).
4. Lid according to claim 1, wherein a length-defined embossing line (27a, 27b) provided at a lateral distance (28) from the notch line in the defined region has a greater depth (d-d1) than the notch line (21; 31) serving for opening.
5. Lid according to one of the previous claims, wherein - seen in cross-section-at least one length-defined linear piece (27a, 27b) has at its base a rounded base profile (39), which is arranged at a distance (28) from the notch line section (24) provided as barrier or blocking region.
6. Lid according to claim 1, in which a region of the grain (38) below the notch line (21, 31) in the section (24) of certain length has flow or grain lines (38x, 38y), which run more steeply than the flow or grain lines (19x) in the two sections of the notch line, which are adjacent the defined section (24) on both sides.
7. Lid made from metal sheet for containers under an increased pressure with respect to the ambient pressure in the closed state, such as drinks cans, which lid has an essentially flatly designed surface (3, 10, 20, 30), a region (4; 11; 33; 22) in the lid surface which can be ruptured and is smaller compared to the surface, defined by a notch line (8; 11; 21; 31), and a gripping flap (6; 14) serving to open the small region and which is attached to the lid surface, and in which lid the notch line (8; 11, 21, 31) has as weakening line, two side walls (49a, 49b; 16) and a linear base (8g, 48); characterised in that

   (a) at least one of the side walls (49a, 49b) in a short section (24) of the weakening line runs more steeply than in the two adjacent sections of the weakening line, and the side walls in the short section have a distance from one another, wherein

   (i) the linear base has a rounded profile cross-section, or

   (ii) the distance is shorter than in the adjacent sections, or

   (iii) the linear base (8g) has in cross-section an essentially circular shape, with a narrow point in the transition to the side walls;

   or

   (b) at least one of the side walls (49a; 49b) in a short section (24) leads into the lid surface via a projection (37a, 37b), and outside the short section (24) without such a projection leads directly (16a, 16b) into the lid surface (20, 30).
8. Process for producing a lid having a lid surface (20, 30) according to claim 1, characterised in that in a first working step, an opening notch line (21, 31) for determining an opening segment (22, 23) is embossed in the lid surface of the lid (1, 9) and a metal grain (38) of a residual wall (42) remaining below the opening notch line is compressed with respect to a grain (19) of the metal regions below the adjacent sections of the notch line (21, 31) in a (short) section (24, L) of certain length of the notch line (21, 31) serving for opening the lid.
9. Process for producing a rupture-secured notch line in a lid, characterised in that the metal sheet is squeezed, embossed or buckled (27a, 27b, Q1, Q2) in lines from at least one side of the notch line along a defined section (24, 25) of a notch line (21, 31) embossed for opening, to compress the grain below the notch line or to provide a barrier or blocking section which is relieved of tensile stresses in the defined section (24).
10. Process according to claim 8, wherein the metal grain (38), in particular flow lines (38x, 38y) in the grain of the residual wall (42) below the notch line (21, 31) serving for opening, is compressed by squeezing of the lid sheet corresponding to the first working step, but much shorter squeezing of the lid sheet on one side or on both sides in the defined section (24) of the notch line and at (slight) distance (28) from the latter and is freed of internal stresses.
11. Process according to claim 8, characterised in that at least one additional notch-like deformation (27a, 27b, Q1, Q2) is embossed in a second working step after embossing the notch line (21, 31) serving for opening.
12. Process according to one of claims 9 to 11, characterised in that the at least one additional squeezing (Q1, Q2) - leading to the change in the metal grain (38) below the notch line serving for opening - is introduced up to a second depth (d-d1) exceeding the first depth of the opening notch line (21, 31).
13. Process according to claim 10, in which compressing leads to a tension-neutral zone, which has a higher shearing strength below the notch line (21, 31) than the sections of the notch line on both sides of the zone (24); considered in notch-line direction.
14. Lid made from metal with an opening system (22, 33, 6, 14) for containers under excess or negative pressure in the closed state, such as drinks cans or the like, with a notch line (21, 31) determining a region (22, 23) of the lid which can be ruptured and a lever-like flap (6; 14) or the like serving for opening, which is arranged on the lid, wherein a means (7; 10, 7a) is provided in order to control a course of the opening step which is difficult to control during initial opening;
    characterised in that this means is a second metal grain (38; 38x, 38y) below a short section (24, 25) of the notch line (21, 31), where an inner tension of the metal is at least weaker than below the remaining sections of the notch line (21, 31), and which deviates from the first metal grain (19) in the region of a residual wall (d2) below the notch line (8; 11).
15. Lid according to claim 14, wherein the notch line in the short section (24) is narrower (b2) than in the adjacent sections with their width (b1) there.
16. Lid according to claim 15, in which a width (b2) of the notch line (21, 31) in the short section (24) is essentially 30% to 70%, in particular less than 50%, of the width (b1) of the notch line in at least the adjacent sections.