Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D51/00—Making hollow objects
  • B21D51/16—Making hollow objects characterised by the use of the objects
  • B21D51/38—Making inlet or outlet arrangements of cans, tins, baths, bottles, or other vessels; Making can ends; Making closures
  • B21D51/383—Making inlet or outlet arrangements of cans, tins, baths, bottles, or other vessels; Making can ends; Making closures scoring lines, tear strips or pulling tabs
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D17/00—Rigid or semi-rigid containers specially constructed to be opened by cutting or piercing, or by tearing of frangible members or portions
  • B65D17/28—Rigid or semi-rigid containers specially constructed to be opened by cutting or piercing, or by tearing of frangible members or portions at lines or points of weakness
  • B65D17/404—Details of the lines of weakness

Definitions

• the invention relates to the field of containers with easy opening and more particularly metal lids with easy opening.
• the easy-opening covers have a generally peripheral incision in the case of containers for food products, as shown in FIGS. 1a to 1c, FIGS. 1a and 1b corresponding to easy-opening covers with counter-bowl, or have a delimiting incision a small portion of the lid panel in the case of a lid for a beverage can.
• the incisions are defined by their profile and the residual metal thickness under the incision which is also called the "residual".
• a profile is defined by the angle alpha of the incision and by the calculated width P of the bottom of the incision.
• a typical incision is shown diagrammatically in FIG. 2 with its angle alpha and the width P, an incision where the angle alpha is 60 ° with a width P of 40 ⁇ m being symbolically designated by "60P40".
• PROBLEM POSED There is an ever greater demand for covers with easy opening, simultaneously presenting greater ease of opening and greater safety in manufacture and use.
• these requirements are to date largely contradictory insofar as the greatest ease of opening is generally obtained by reduction of the residual, a decrease which results in much less manufacturing safety (greater precision of the tools, lower safety margin), and above all very significant risks of the appearance of cracks at the bottom of the incision or under the incision, which lead to leaks, either directly or by the action of pressure during packaging, typically with sterilization, either, after conditioning, by corrosive action of the conditioned product.
• FIG. 7 represents in section an incision after crimping and sterilization, having, at the bottom of the incision, characteristic cracks which the present invention proposes if not to eliminate entirely, at least to reduce very strongly.
• FIG. 7 are also represented crack initiators under the incision.
• the problem is to find a way to manufacture, reliably and economically, easy-to-open lids with low residuals, the bottom of the incisions not being cracked at the end of manufacture, or after packaging of the product to be packaged, so as to present , despite a low residual, satisfactory resistance to mechanical stress and corrosion.
• the method of manufacturing an easy-opening metal cover (1) with central panel (3) and crimping edge (4), comprising an incision (2) on the incision strip (6), part of said panel on which said incision is formed, and a ring (8) allowing, by perforation of said incision, said opening, in which said incision (2) is formed by displacement of a punch (13) of alpha angle on said incision strip (6), supported by an anvil (21), of a blank cover, is characterized in that, so as to reduce the risks of appearance of cracks at the bottom of incision or incision, said incision (2) is formed using any means leading to an asymmetrical flow of the compressed metal between said punch (13) and said anvil (21), during said displacement.
• a first means leading to an asymmetrical flow of the metal is constituted by the use of an asymmetric punch (130) by its geometric configuration, the bisector of the angle alpha making with the direction of said displacement a non-zero gamma angle, as shown in Figure 8.
• a second means consists of the use of a blank with an incision strip cover (6) making a beta angle different from 0 relative to the horizontal plane, or different from 90 e with respect to the direction of said movement, said anvil (21), not shown in FIGS. 4a to 6b, which may have an inclination phi, as shown in FIG. 10, which may be different from said angle beta.
• a third means is constituted by the use of an asymmetrical punch by its roughness, one side of the angle alpha of the punch being rougher than the other side, this punch being able to be otherwise symmetrical or not by its geometric profile.
• a fourth possible means according to the invention consists of the use of an anvil (21) itself comprising a lower relief (210), possibly off-center by at most 500 ⁇ m relative to said punch (13,130), or asymmetrical (211) as illustrated in Figures 10 and 11. These different means can be used alone or in combination.
• These covers include a central panel (3) on which there is an incision (2) on the incision strip (6) in a horizontal plane, parallel to the mean plane (17) of the panel (3), and a crimping edge ( 4).
• the central panel is provided with a rivet (7) which fixes a ring (8) whose beak (9) is located above the incision (2) so as to ensure the opening by tilting of the ring .
• the crimping edge (4) comprises a skirt (5), strongly inclined, connecting to said central panel, possibly by a counter-cup (20).
• Figures la to le are distinguished by the presence of a counter-bowl (20) in the case of figures la and lb, and by the position of the incision (2) located in the plane of said central panel in the case of Figures la and le, and at the bottom of the bowl (20) in the case of figure lb.
• FIGS. 3a, 3b and 3c show, in axial section similar to that of FIGS. 1a to 1c, portions of the cover with easy opening (1) according to the invention having a sloping incision strip (6).
• Figures 3a and 3b illustrate the position of the incision (2) on the incision strip (6) forming the bottom of the bowl (20).
• This strip (6) has a slope of angle beta with respect to the plane (17), corresponding to the horizontal mean plane of said central panel (3).
• said strip (6) has a slope of an angle + beta, while the angle is -beta in Figure 3b.
• FIG. 3c illustrates the position of the incision (2) on the incision band (6) forming the periphery of the central area (3), externally limited by the counter-bowl
• This strip (6) has an angle slope + beta relative to the plane (17).
• Figures 3d and 3e relate to a partial opening lid of the beverage can.
• Figure 3d is a top view and Figure 3e is a section along the axis A-A of Figure 3d.
• the incision strip (6) does not form a closed strip on itself, but has the shape of a horseshoe, the open part of which remains attached to the central panel (3) of the cover.
• the ring (8) is positioned on the side of this open part, and by tilting forward tears the incision (2) and fold the tongue delimited by said incision (2) towards the inside of the box.
• FIG. 3f is a top view showing the incision strip (6) in the form of a hatched crown, the incision (2) passing through the center of this strip.
• Figure 3g is an axial section along the axis BB of Figure 3f, showing that said strip (6) has the shape of a cone portion with an angle at the top equal to 180 e - 2.
• FIGS. 4a, 5a and 6a are axial partial sections of punches, symmetrical (13) or asymmetrical (130), intended to form incisions (2) according to the invention, the two sides (14a, 14b) of the punch forming a alpha angle and connected by one end (15).
• Figure 5a shows an intermediate case where the gamma angle is zero.
• FIG. 7 similar to FIG. 2, represents a micrographic section showing the presence of cracks (12) at the bottom of the incision (10), and incipient cracks under the incision, in the case of incisions according to the art prior.
• FIG. 8 similar to FIG. 2, represents an incision obtained with an asymmetrical punch with an alpha angle equal to 50 e , and the bisector of which makes a gamma angle equal to 10 ° with the vertical.
• the delta angle is 35 ° and the rho angle is 15 °.
• FIG. 9 represents a metallographic section of an incision according to the invention, after anodic oxidation showing the fibers of the metal, that is to say the elongation of the aluminum grains represented by the lines (60).
• the intersection of the inflection lines (61) relative to the same line (60) deviates from the bisector (62) from the angle alpha, which translates the asymmetrical flow according to the invention.
• Figure 10 shows in section a sloping anvil (211) surmounted by a symmetrical punch (13).
• Figure 11 shows in section an anvil having a lower punch (210) off-center with respect to the symmetrical punch (13).
• the geometric characteristics of said asymmetric punch (130) are defined by the combination of the following conditions: - the angle alpha is between 30 and 70 e , and preferably between 40 and 60 e , - the absolute value of the difference between the angles delta and rho is at least 3 ⁇ .
• the absolute value of this difference is between 5 and 30 e .
• said beta angle is generally between 5 e and 45 e , and preferably less than 30 e .
• Said incision strip (6) with a beta angle slope is formed by stamping a metal strip in a manner known per se during the formation of the cover blank. Given the high precision of the tools for manufacturing the covers, it suffices that said strip has a width of the order of 1 mm to be assured that said incision (2) will always be well positioned on said strip (6) with a slope of 'beta angle.
• Said punch (13) can also be oriented at a gamma angle relative to said perpendicular direction (19) between two extreme values such that one of these values corresponds to a punch having one of its vertical faces (16a ), as shown in FIG. 4a, the other value corresponding to a punch having the other of its vertical faces (16b), as shown in FIG. 6a.
• the third asymmetric flow means based on the use of a differential roughness of the punch is made possible by the use of incision tools treated on the surface and of sufficient hardness to maintain said differential roughness during the lifetime. of the incision tool.
• the fourth asymmetric flow means is based on the use of a particular anvil (21) comprising: - an asymmetrical lower relief (211), typically slope and having a slope of angle phi (see FIG. 10). a lower relief (210) slightly off-center with respect to the upper punch (13) (see FIG. 11). This lower relief (210) could also be more accentuated and constitute a lower punch enabling a double incision to be obtained.
• a particular anvil (21) comprising: - an asymmetrical lower relief (211), typically slope and having a slope of angle phi (see FIG. 10).
• a lower relief (210) slightly off-center with respect to the upper punch (13) (see FIG. 11). This lower relief (210) could also be more accentuated and constitute a lower punch enabling a double incision to be obtained.
• said punch (13) can be a radiated punch, the sides of the punch (14a, 14b) connecting either to each other by the spokes, or with a possible flat end (151) of said punch.
• Said punch (13) may have a flat end (151) of length generally between 0 and 25 ⁇ m, so as to obtain an incision of width P less than 40 ⁇ m, and preferably between 10 and 30 ⁇ m.
• said anvil (21) preferably has and in particular when said anvil does not in itself constitute an asymmetrical flow means, a width L close to a theoretical width L 'defined by the intersection of the base of said incision strip with the extensions of the sides (16a , 16b) of the incision (2), and has a thickness e of at least 10 ⁇ m, and preferably less than the thickness E of said incision strip (6) - see FIG. 8.
• said anvil is positioned opposite said intersection, as illustrated in FIG. 8.
• Another object of the invention consists of the covers obtained according to the method of the invention.
• the angle alpha of the incision is between 30 and 70 e ,
• the thickness of said cover is between 0.12 and 0.30 mm (nominal thickness of the metal strip for cover),
• the residual thickness at the bottom of the incision is greater than 40 ⁇ m.
• iron alloys is meant in particular white iron, TFS, and more generally iron alloys with their surface treatments known to a person skilled in the art for their use as a material capable of forming metallic packaging, and in particular covers. .
• the angle alpha is preferably between 40 e and 60 e and the calculated width P at the bottom of the incision is between 10 and 40 ⁇ m. If an asymmetrical flow incision is made according to the invention, as shown in FIG. 9, it is easy to highlight the asymmetrical flow by considering the inflection lines (61) for the same line of metal (60) under or in the vicinity of the incision (2).
• the inflection lines are substantially symmetrical with respect to the bisector (62) of the angle alpha.
• the final cover also has an incision strip (6) making the same beta angle not zero with respect to the mean plane (17) of said central panel (3) considered to be said horizontal plane.
• Said incision strip (6) can be situated on the periphery of the central panel (3) and the inner skirt (5) of the crimping edge (4), and form an inclined plane between said central panel and said skirt, as illustrated in Figures 3a and 3b.
• the cover may have a peripheral counter-bowl (18) with a raised edge relative to the central panel (3), said incision strip (6), located between the central panel and the counter-bowl (18), forming a plane. inclined, as illustrated in Figures 3c, 3f and 3g.
• Said cover may be partially open, for example a cover for a beverage can, cover in which said incision strip (6) forms an inclined plane bordering the part of said panel intended to be opened, as illustrated in FIGS. 3d and 3e.
• said beta angle is between 5 th and 45 th and preferably between 10 and 30 th .
• All the covers with easy opening were made from aluminum strip of alloy 5052 (designation according to the Aluminum Association), nominal thickness of 230 ⁇ m, varnished on both sides, and in the corresponding metallurgical state H48 in a strongly hardened state, restored during the opening.
• Standard easy-opening covers (1) of 73 mm in diameter were manufactured, with a peripheral incision according to FIG. 3a, incision having a profile of the "60P40" type (alpha angle of 60 ° and a calculated value of dish at the bottom 40 ⁇ m incision).
• the lids obtained were crimped onto boxes which were then sterilized in a standard manner (30 min at 125 ° C).
• primer and crack are based on the fact that the risk of damage does not appear linear with the length of the cracks and that there is a threshold (2-5 ⁇ m) beyond which there is a high probability. so that the cracking gets worse instead of remaining relatively stable as in the case of crack initiation.
• Lids similar to those of the first series of tests were produced, but which differ in that the said asymmetrical flow is not obtained by means of an incision strip with a beta angle different from 0, but by the use an asymmetrical punch of type "50P25", as shown in FIG. 8 by the corresponding incision, with:
• control covers are the same as those of the first series of tests.
• the residual metallic layer under the incision is particularly sensitive to the action of corrosion due to the ingredients of the packaged products (possible presence of acids and / or salts), and the sensitivity to corrosion increases with the presence of cracks, or the presence of cracks of greater length. According to a qualitative approach, there is therefore a correlation between the damage to the incision, which can be quantified by the presence of cracks and the length of the cracks, and the resistance to corrosion.
• the improvement in corrosion resistance results in an increase in the life of the packaged products, and in the corresponding reduction in the risks of perforation of the packaging, with all the risks of contamination and soiling associated.
• the possibility of decreasing, over a wide range of values, the value of the residual thickness of metal makes it possible to modulate and decrease as desired the effort of opening of the lids with easy opening, while the lids of the 'prior art required, for the same resistance to corrosion, a significantly higher residual thickness value, and therefore involved a greater opening force.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Closures For Containers (AREA)
• Containers Opened By Tearing Frangible Portions (AREA)
• Sewage (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (2)

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• 1995
  • 1995-04-14 EP EP95420100A patent/EP0737624B1/de not_active Expired - Lifetime
• 1996
  • 1996-04-15 WO PCT/FR1996/000571 patent/WO1996032334A1/fr active IP Right Grant
  • 1996-04-15 DE DE69607337T patent/DE69607337T2/de not_active Expired - Lifetime
  • 1996-04-15 EP EP96913590A patent/EP0820409B1/de not_active Expired - Lifetime
  • 1996-04-15 ES ES96913590T patent/ES2144238T3/es not_active Expired - Lifetime
  • 1996-04-15 AU AU56525/96A patent/AU5652596A/en not_active Abandoned
  • 1996-04-15 HU HU9802582A patent/HU226349B1/hu not_active IP Right Cessation
  • 1996-04-15 US US08/930,431 patent/US6004089A/en not_active Expired - Lifetime

Non-Patent Citations (1)

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