Can Lids

Abstract

The can lid includes a metal lid surface having a first planar surface and a second planar surface facing opposite the first planar surface, the metal lid surface defining an opening closed by a closure piece bounded by a closed edge of the lid surface and separated from a surrounding lid surface by a microgap extending along the edge of the lid surface, the first lid region of the closure piece being connected to the surrounding lid surface via a pivot bearing, and further including a tear opening material disposed on the first planar surface and engaging a second lid region of the closure piece, the second lid region being opposite the pivot bearing such that pulling on the tear opening material allows the closure piece to pivot out of the reference plane in the direction of the first planar surface, the microgap being interrupted by at least one retention web between the first lid region and the second lid region. A pressure relief wave is embossed in the lid surface and extends around at least a portion of the periphery of the opening.

Description

[Technical field]

[0001] The present invention relates to a can lid, in particular for beverage cans. The can lid comprises a metal lid surface having a first flat surface and a second flat surface facing opposite the first flat surface. The lid surface has an opening bounded by a closing margin of the lid surface and closed by a closure piece of the metal lid surface. The closure piece is separated from the surrounding lid surface by a microgap that extends at least partially along the edge of the lid surface. A base plane of the closure piece is defined by the course of the microgap. A first lid region of the closure piece is connected to the surrounding lid surface via a pivot bearing. The can lid of the present invention further comprises a tear-opening member disposed on the first flat surface and engaging the second lid region of the closure piece. The second lid area is opposite the pivot bearing so that pulling the tear opening material allows the closure piece to be pivoted out of the reference plane towards the first flat surface. The microgap is interrupted between the first and second lid areas by at least one holding web, by which the closure piece and the surrounding lid surface are connected to each other in a bonded manner. [Background technology]

[0002] This type of can lid is used on a large scale in the production of beverage cans, food cans, etc. They are simple and low-cost to manufacture, allow similar cans to be stacked in a space-saving manner, and can be easily opened and, if necessary, reclosed by manually moving the closure pieces. Due to the gradual opening caused by the retaining webs and the associated venting effect, no significant spraying, popping, or foaming occurs during the initial opening.

[0003] It is generally desired that the initial opening of the can requires little force. However, this effort is countered by the need to ensure that no leaks occur or that the sealing film on the second flat surface does not stretch as pressure builds up inside the can. In practice, it is difficult to guarantee both easy initial opening and stability against pressure buildup at the same time. The pasteurization process required for many can contents, such as juices and dishes, is particularly challenging. The pasteurization process involves pressures of, for example, 6 bar, which can place considerable stresses on materials. Summary of the Invention [Problem to be solved by the invention]

[0004] It is an object of the present invention to provide a can lid which is easy to open and which furthermore has high resistance to pressure build-up in a can connected to the lid. [Means for solving the problem]

[0005] The object of the present invention is met by a can lid having the features of claim 1.

[0006] According to the invention, at least one pressure relief wave is embossed in the metal lid surface and extends around at least a part of the opening. The pressure relief wave ensures a mechanical decoupling of the inner area including the opening from the surrounding outer lid surface. When the can lid bulges upwards as a result of a pressure increase in the can or continues to bulge upwards from the curved state, the pressure relief wave is to some extent decoupled and the material is so to speak released towards the inside. In this way the connection between the closure piece and the surrounding lid surface and in particular the retaining web is relieved. It has been shown that can lids with a pressure relief wave are easy to open, on the one hand easy to open and on the other hand reliably withstand relatively high pressure values.

[0007] The pressure relief wave may include a wave trough having a curved cross section and extending across the reference plane, the curved path ensuring a degree of flexible bonding between the inner and outer lid regions, thereby contributing to the stabilization of the closed opening when the can lid bulges upwards.

[0008] It may be provided that the pressure relief wave section has a height or depth, relative to the reference plane, of at least half the thickness of the metal lid surface and at most four times the thickness of the metal lid surface. The height or depth of the pressure relief wave section is preferably at least as thick as the metal lid surface and at most twice the thickness of the metal lid surface. Here, the height or depth of the metal lid surface is to be understood as a uniform or average thickness. The height or depth of the pressure relief wave section is preferably uniform along its longitudinal direction. The height or depth as specified has proven to be very advantageous in practice.

[0009] According to an embodiment of the invention, the metal lid surface is rotationally symmetric and the radial extent of at least one pressure relief wave portion relative to the center of rotation of the metal lid surface is at least twice and at most five times the thickness of the metal lid surface. A pressure relief wave portion of suitable width performs the opening function particularly reliably.

[0010] At least one pressure relief wave preferably has a circular or arched path in the reference surface, which results in a very uniform relief effect, especially in the case of a circular lid surface.

[0011] The opening may have a geometric centre that coincides with the centre of a circle of the circular or arcuate path of the at least one pressure relief wave section, which further promotes a uniform relief effect.

[0012] According to a further embodiment of the invention, at least two, preferably at least three, particularly preferably exactly three pressure relief waves are embossed into the metal lid surface and extend parallel to one another at least partly around the periphery of the opening. This enhances the relief effect. Furthermore, the presence of multiple parallel pressure relief waves allows for a gradual relief in a customized manner.

[0013] The magnitude of the height or depth of the pressure relief wave relative to the reference plane preferably increases towards the opening, whereby the radially innermost pressure relief wave provides the greatest flexibility. Such a graduated pressure relief has proven to be particularly advantageous.

[0014] According to a specific embodiment, the arc length of the pressure relief wave increases towards the opening. In general, the further away the pressure relief wave is from the opening, the less expansion is required.

[0015] It is preferred that the pressure relief wave section located closest to the opening has a closed circular path in the reference plane, and at least one pressure relief wave section located further from the opening has an interrupted circular path. For example, an interruption can be located in the area where the opening is located closest to the edge of the lid surface. Under some circumstances, there is no space in this area to place a further circular pressure relief wave section. However, pressure relief wave sections with interrupted paths can be provided. A particularly preferred embodiment comprises one closed inner pressure relief wave section and two interrupted outer pressure relief wave sections.

[0016] According to a specific embodiment of the invention, the metal lid surface and the opening have respective geometric centers located away from each other, and at least one pressure relaxation wave portion located further from the opening has an interruption of the circular path, and a line connecting the two geometric centers extends through the interruption. For example, the metal lid surface and the opening can be rotationally symmetric, in particular circular, with the respective centers of rotation forming the geometric centers.

[0017] The present invention relates to a can lid, in particular for beverage cans. The can lid, as described above, comprises a metal lid surface having a first flat surface and a second flat surface facing away from the first flat surface. The lid surface has an opening bounded by a closing edge of the lid surface and closed by a closure piece of the metal lid surface. The closure piece is separated from the surrounding lid surface by a micro-gap extending at least partially along the edge of the lid surface. A reference plane of the closure piece is defined by the path of the micro-gap. The first lid area of ​​the closure piece is connected to the surrounding lid surface via a pivot bearing. The can lid also comprises a tear-opening member arranged on the first flat surface and engaging with the second lid area of ​​the closure piece. The second lid area is opposite the pivot bearing, so that pulling the tear-opening member makes it possible to rotate the closure piece out of the reference plane in the direction of the first flat surface. The microgap is interrupted between the first and second lid regions by at least two retention webs, via which the closure piece and the surrounding lid surface are connected to each other in a bonded manner.

[0018] The more and wider the retaining webs are, the more stable the closure pieces are accommodated in the opening. However, a stable fit of the closure pieces makes initial opening more difficult. As mentioned above, ensuring easy initial opening and sufficient stability against pressure buildup at the same time is a difficult task.

[0019] To solve this problem, according to one aspect of the present invention, an elongate elevated portion is embossed into the closure piece, the elongate elevated portion rising above the reference surface in the direction of the first flat surface and extending across a line that passes through two of the at least two retaining webs and through the elongate elevated portion.

[0020] When the can lid bulges upwards as a result of an increase in pressure inside the can, the central region of the closure piece moves upwards first. The raised portion has a stiffening effect and, due to its shape and orientation, in a lever-like manner, ensures that the upward movement of said central region is accompanied by a downward movement of the peripheral region. As a result, an imaginary axis of rotation is formed that runs parallel to or coincides with the line connecting between the two retaining webs. Thereby, the transition between the closure piece and the surrounding lid surface is softened and undesired separation of the metal edges in the micro-gap is prevented. It has been found that the effect of the elongated raised portion makes it possible to set the retaining webs back further overall from the engagement point of the tear-opening material than before. Such a setback is particularly advantageous as it improves the venting effect.

[0021] The elongated raised portion can extend from the second lid region in the direction of the first lid region. This means that the elongated raised portion can extend from the engagement point of the tear-opening material in the direction of the pivot bearing. In the case of an upwardly bulging can lid, the area of ​​the tear-opening point is particularly relieved. This is advantageous in that for the vent, the retaining web should be as far away as possible from the tear-opening point, and this area is particularly susceptible to pressure loads.

[0022] According to a further embodiment of the invention, the opening has a geometric centre and the elongated raised portion has a longitudinal axis running through the geometric centre of said opening, which ensures a particularly advantageous dampening effect.

[0023] The elongated raised portion preferably has a height relative to the reference surface that is at least as large as the thickness of the metal lid surface and at most four times the thickness of the metal lid surface. The height of the elongated raised portion is particularly preferably at least 1.5 times the thickness of the metal lid surface and at most three times the thickness of the metal lid surface. Such heights have proven to be very advantageous in typical applications.

[0024] The elongated raised portion preferably has a length of at least 5 times the thickness of the metal lid surface and at most 70 times the thickness of the metal lid surface. The length of the elongated raised portion is particularly preferably at least 20 times the thickness of the metal lid surface and at most 50 times the thickness of the metal lid surface. Such a raised portion length ensures a very good compatibility of the reinforcing effect with standard lid designs.

[0025] Provision can be made that the opening has a rounded hexagonal shape and that the elongated raised portion extends from a corner region of the opening in the direction of the opposite corner region of the opening. The elongated raised portion can in particular extend from a corner region coinciding with the second lid region. Tear-opening at the corner allows for particularly advantageous ventilation. The raised portion at the same time ensures that the closure piece does not loosen more quickly than usual at the corner. The rounded hexagonal shape of the opening is advantageous in that the installation of the retaining web in the straight section is particularly simple.

[0026] The elongated raised portions may have a club shape, which results in a particularly advantageous graduated reinforcement effect.

[0027] According to a particular embodiment, the elongated raised portion has a head close to the rim and a tail narrowing relative to the head. It has been found that a particularly pronounced increase in stability is desirable in the region of the rim.

[0028] The tail may taper, preferably continuously, in the direction opposite the head, so that the reinforcing effect decreases with distance from the tear opening point, which has proven to be particularly advantageous.

[0029] The invention also relates to a can lid, in particular for beverage cans, which can lid comprises a metal lid surface, as described above, which has a first flat surface and a second flat surface facing away from the first flat surface. The metal lid surface has an opening, which is bounded by a closing edge of the lid surface and closed by a closure piece of the metal lid surface. The closure piece is separated from the surrounding lid surface by a micro-gap that extends at least partially along the edge of the lid surface. The first lid area of ​​the closure piece is connected to the surrounding lid surface via a pivot bearing. The can lid also comprises a tear-opening material arranged on the first flat surface and engaging with a second lid area of ​​the closure piece. The second lid area is opposite the pivot bearing, so that pulling the tear-opening material makes it possible to pivot the closure piece out of the reference plane defined by the opening in the direction of the first flat surface. The micro-gap is interrupted by at least two retaining webs between the first lid area and the second lid area. The retaining webs connect the closure piece and the surrounding lid surface to each other in a bonded manner.

[0030] To solve the problem stated at the outset, according to a further aspect of the invention, a closure relief bead is embossed in the closure piece and extends at least past the at least one retaining web and along the edge of the opening.

[0031] If pressure increases within the can, the retaining webs are moved away from the central region of the closure piece by the closure relief bead and protected from unwanted overloading. Any stretching of the lid surface is compensated for by the closure relief bead so that overloading or breakage of the retaining webs does not occur.

[0032] The closure relief bead may be curved away from the edge in the region of the retaining web, in this design the closure relief bead is particularly effective in shielding the retaining web from the central region of the closure piece.

[0033] Provision can be made that a microgap is interrupted between the first and second lid regions by a plurality of retention webs, through which the closure piece and the surrounding lid surface are connected to each other in a bonded manner, and the closure relief bead extends curvedly past all retention webs and away from the edge in the region of each retention web, so that all retention webs are protected from excessive loads.

[0034] The closure relief bead preferably curves towards the edge in the area between two consecutive retaining webs, which allows the formation of a closed peripheral closure relief bead even though the curve is away from the edge in the area of ​​the retaining webs.

[0035] A further embodiment of the invention provides that the closure relief bead has a height or depth relative to the reference plane of at most 1.5 times the thickness of the metal lid surface, the height or depth of said closure relief bead being preferably at most comparable to the thickness of the metal lid surface, which has proven to be particularly advantageous for common lid designs.

[0036] The closure relief bead preferably has a first flank facing the edge of the lid surface and a second flank facing away from the edge of the lid surface, the second flank being steeper than the first flank, so that a particularly advantageous relief effect is obtained.

[0037] The combination of the pressure relief waves as described above with the elongated raised portions as described above and / or the closure relief beads has proven to be particularly advantageous. A can characterized by the above-mentioned relaxation has a graded effect. For example, in the case of a gentle pressure increase, only the pressure relief waves can start to function first, and only when a higher threshold is exceeded can the retention web be protected by the closure relief beads.

[0038] Further developments of the invention can be seen from the dependent claims, the following description and the accompanying drawings.

[0039] The invention will now be described, by way of example only, with reference to the drawings in which: [Brief description of the drawings]

[0040] [Figure 1] FIG. 1 is a plan view of a can lid according to the present invention in a closed state. [Diagram 2] FIG. 2 shows the can lid according to FIG. 1 without the closure part. [Diagram 3] FIG. 3 shows a separate representation of the closure piece of the can lid according to FIG. [Figure 4] FIG. 4 is a cross-sectional view of the closure piece of FIG. 3 taken along line AA. [Diagram 5] FIG. 5 is a cross-sectional view showing the arrangement of pressure relief waves of the can lid according to FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] 1 and 2 show a can lid 11 designed in accordance with the present invention, intended for use on beverage cans and the like, and having a metal lid surface 13. The metal lid surface 13 is The metal end face has a first, here upper (front) flat surface 16 and a second, here lower (back) flat surface 17 (FIG. 4) facing away from the first flat surface 16. The metal end face 13 is preferably formed by a sheet metal layer made of a flat plate of aluminum or tin. The metal end face 13 preferably has a uniform thickness of 0.1 mm to 0.3 mm, preferably about 0.2 mm. A coating of plastic material may be applied to the second flat surface 17 of the metal end face 13. In the illustrated embodiment, the metal end face 13 is circular in plan view and has a center 20 of the circle. The can lid 11 may be connected to the beverage container via a beaded rim 18 of the metal end face 13.

[0042] The metal lid surface 13 is provided with an opening which, in the illustrated delivery state of the can lid 11, is closed by a portion of the metal lid surface 13 as a closure piece 19. As can be seen in Fig. 2, the closure piece 19 is separated from the surrounding lid surface by a boundary line as a microgap 21. The microgap 21 extends in one plane and defines a reference plane 23 of the can lid 11 as can be seen in Fig. 4. As can be seen, the opening is offset in the metal lid surface 13, i.e. the geometric centre of the opening is away from the centre 20 of the circle.

[0043] The can lid 11 comprises a sealing frame, not shown, made of plastic material surrounding the opening and fixedly connected to the metal lid surface 13. A closure unit 29 made of plastic material and supporting the closure piece 19 is further provided and is pivotally connected to the sealing frame via a pivot bearing 30. A releasable liquid-tight connection between the sealing frame and the closure unit 29 is made possible by a latch device, not shown, formed by sealing and latching ribs and associated receiving grooves. The can lid 11 is therefore reclosable.

[0044] A tear-opening element 37, here annular and preferably also made of plastic, is connected to the closure unit 29. By pulling on the tear-opening element 37, the user can pivot the closure piece 19 upwards and out of the reference plane 23, thereby releasing the opening.

[0045] The closure piece 19 is shown separately in FIG. 3. In the illustrated embodiment, the closure piece 19 has a rounded hexagonal shape. A first lid area 61 of the closure piece 19 is connected to the surrounding lid surface via a pivot bearing 30 (FIG. 1) and a sealing frame, and an annular tear opening material 29 engages a second lid area 62 of the closure piece 19. The second lid area 62 is on the opposite side of the pivot bearing 30 via the closure unit 29. The two lid areas 61, 62 are located at opposite rounded corners of the closure piece 19. As shown, the corner of the closure piece 19 associated with the second lid area 62 is more pronounced than the other corners.

[0046] Between the first lid region 61 and the second lid region 62, the microgap 21 is interrupted by a total of six retention webs 65, via which the closure piece 19 and the surrounding lid surface are connected to one another in a bonded manner. A connecting line 67 runs through the two front retention webs 65, i.e. the retention web 65 arranged closest to the second lid region 62.

[0047] When initially opening the can, the user pulls on the tear opening member 37, thereby causing the closure unit 29 with the closure piece 19 to pivot upwards, at which point the latched connection between the closure unit 29 and the sealing frame is released.

[0048] The retaining webs 65 cause only a relatively small opening in the lid surface 13 at the beginning of the pivoting process, which extends from the second lid region 62 to the region of the two front retaining webs 65, i.e. around the connecting line 67. The retaining webs 65 prevent further opening, at least for a short period of time. The relatively small opening at the periphery of the second lid region 62 results in venting of the can. As the initial opening process proceeds further, the retaining webs 65 tear one after the other. As a result, the closure piece 19 can pivot completely upwards to open the entire opening. At this point, the gradual opening caused by the retaining webs 65 and the associated venting effect do not cause any significant spraying, blowing or foaming.

[0049] A support nub 31 includes a flat support portion 33 and is embossed into the closure piece 19. The support nub 31 on the closure piece 19 is similar in shape to three further support nubs 34, 35, 39 (FIG. 1) embossed into the area surrounding the opening in the metal lid face 13. The support nubs 34, 35, 39 have the same height 50 (FIG. 4).

[0050] The three embossed pressure relief waves 77, 78, 79 (FIG. 2) extend parallel to one another at least partially around the circumference of the opening to prevent excessive material stresses in the event of pressure buildup within the can. Specifically, the radially innermost pressure relief wave 77 has a closed circular path with the center of the circle at the geometric center of the opening. The intermediate pressure relief wave 78 and the radially outermost pressure relief wave 79 each have an arcuate path with the center of the circle at the geometric center of the opening, but are not closed at the periphery. Rather, the intermediate pressure relief wave 78 and the radially outermost pressure relief wave 79 are interrupted by an interruption 80 located closest to the bead rim 18. As shown, the interruption 80 of the radially outermost pressure relief wave 79 is preferably longer than the interruption 80 of the intermediate pressure relief wave 78. For example, the middle pressure relief wave portion 78 may extend over an angle of about 300°, and the radially outermost pressure relief wave portion 79 extends over an angle of about 250°.

[0051] A cross-sectional view of the pressure relief waves 77, 78, 79 is shown in FIG. 5. Each of the pressure relief waves 77, 78, 79 includes a wave trough 81 having a curved cross-section and extending across the reference surface 23. Between the wave troughs 81 are wave peaks 82 having a similarly curved cross-section. The depth of the wave troughs 81 relative to the reference surface 23 is at least as great as the thickness of the metal lid surface 13, and preferably at most twice the thickness of the metal lid surface 13. As shown in FIG. 5, the magnitude of the depth 85, 86, 87 of the wave troughs 81 relative to the reference surface 23 increases toward the opening, i.e., from the outside to the inside.

[0052] When the can lid 11 bulges upwards as a result of an increase in pressure inside the can, the pressure relief waves 77, 78, 79 are pulled apart to some extent, starting from the radially innermost pressure relief wave 77. The three pressure relief waves 77, 78, 79 extending around the opening thereby ensure a stepwise mechanical separation of the opening area from the surrounding outer lid surface. In this way the connection between the closure piece 19 and the surrounding lid surface is relaxed.

[0053] Further relief is achieved by an elongated raised portion 36 embossed in the closure piece 19 and presenting on the reference surface 23 in the direction of the first flat surface 16, i.e. upwards in the illustrated embodiment. The elongated raised portion 36 has a longitudinal axis 70 oriented transversely to the connecting line 67. Furthermore, the elongated raised portion 36 has a club shape and has a head 89 close to the edge and a tail 90 narrowing relative to the head 89 close to the edge. The tail 90 tapers continuously in the opposite direction to the head. The head 89 is arranged in the second lid region 62, so that the elongated raised portion 36 extends from the second lid region 62 in the direction of the first lid region 61.

[0054] When the can lid 11 bulges upwards as a result of an increase in pressure inside the can, the central region of the closure piece 19 moves upwards first. Due to the reinforcing effect of the raised portion 36, this movement of the central region is accompanied by a downward movement of the second lid region 62. That is, the part of the closure piece 19 facing the second lid region 62 pivots about the connection line 67, thereby softening the transition between the closure piece 19 and the surrounding lid surface around the periphery of the second lid region 62.

[0055] Furthermore, the closure relief bead 38 is embossed in the closure piece 19, extends along the microgap 21 and forms a recess with respect to the first flat surface 16. This means that the closure relief bead 38 is embossed in the opposite direction to the elongated raised portion 36. In the illustrated embodiment, the closure relief bead 38 is closed at the periphery and alternately curves away from the microgap 21 and towards the microgap 21. The portion 95 curved away from the microgap 21 is located next to the retention web 65 and merges with the portion 96 curved towards the microgap 21 between the retention webs 65. Thereby, a flower-like pattern of the closure relief bead 38 appears in plan view. In the second lid region 62, the closure relief bead 38 merges with the head 89 of the elongated raised portion 36.

[0056] The closure relief bead 38 preferably has a depth relative to the reference plane 23 that is at most as large as the thickness of the metal lid surface 13. The outer flank facing the edge of the closure piece 19 preferably has a smaller slope than the opposite inner flank.

[0057] In the event of an increase in pressure within the can, the retaining web 65 is pulled away from the central region of the closure piece 19 by the closure relief bead 38 and is thus protected from unwanted overloading.

[0058] The invention provides a reclosable can lid 11 which is easy to open even at the first opening and yet meets all stability requirements for pasteurisation and storage of the can. [Explanation of symbols]

[0059] 11 Can Lids 13 Metal lid surface 16 First flat surface 17 Second flat surface 18 Bead Rim 19 Closure Piece 20 Circle Center 21 Microgap 23 Reference plane 29 Closure Unit 30 Rotating bearing 31 Support Nubs 33 Flat Support 34 Support nub 35 Support nub 36 Long, narrow raised part 37 Tear-opening material 38 Closure relief bead 39 Support Nubs 50 Support nub height 61 First Lid Region 62 Second Lid Region 65 Retention Web 67 Connecting Line 70 Longitudinal axis 77 Inner pressure relaxation wave section 78 Middle pressure relaxation wave section 79 Outer pressure relaxation wave section 80 Interruption 81 Wave Valley 82 Wave Peak 85 Depth of outer wave trough 86 Depth of intermediate wave trough 87 Depth of inner wave trough 89 Head 90 Tail 95 The part that curves away from the microgap 96 The part curved toward the microgap

Claims

1. A can lid (11), in particular for beverage cans, comprising: a metal lid surface (13) having a first flat surface (16) and a second flat surface (17) facing away from the first flat surface (16), the lid surface (13) is formed with an opening bounded by a closing edge of the lid surface (13) and closed by a closure piece (19) of the metal lid surface (13), the closure piece (19) being separated from a surrounding lid surface by a microgap (21) extending at least partially along the edge of the lid surface (13), a reference surface (23) of the closure piece (19) being defined by the path of the microgap (21), a first lid region (61) of the closure piece (19) being connected to the surrounding lid surface via a pivot bearing (30); a tear-opening material (37) arranged on the first flat surface (16) and engaging with a second lid area (62) of the closure piece (19), the second lid area (62) being on the opposite side of the pivot bearing (30), such that by pulling the tear-opening material (37) the closure piece (19) can be pivoted out of the reference surface (23) in the direction of the first flat surface (16), the micro gap (21) being interrupted by at least one retaining web (65) between the first lid area (61) and the second lid area (62), via which the closure piece (19) and the surrounding lid surface are connected to each other in a bonded manner, At least one pressure relief wave (77, 78, 79) is embossed into said metal lid surface (13) and extends around at least a portion of the periphery of said opening.

2. 2. The can lid according to claim 1, The pressure relief corrugations (77, 78, 79) have a curved cross section and include wave troughs (81) extending across the reference surface (23).

3. The can lid according to claim 1 or 2, The pressure relaxation wave portions (77, 78, 79) have a height or depth (85, 86, 87) relative to the reference plane (23) that is at least half the thickness of the metal lid surface (13) and at most four times the thickness of the metal lid surface (13), and the height or depth (85, 86, 87) of the pressure relaxation wave portions (77, 78, 79) is preferably at least approximately the same as the thickness of the metal lid surface (13) and at most twice the thickness of the metal lid surface (13).

4. A can lid according to any one of claims 1 to 3, The metal end surface (13) is rotationally symmetrical, and the radial extent of the at least one pressure relaxation wave portion (77, 78, 79) relative to a center of rotation (20) of the metal end surface (13) is at least two times and at most five times the thickness of the metal end surface (13).

5. A can lid according to any one of claims 1 to 4, The at least one pressure relief wave portion (77, 78, 79) has a circular or arcuate path in the reference surface (23).

6. A can lid according to claim 5, The can lid is characterized in that the opening has a geometric center that coincides with a center of a circle of the circular or arcuate path of the at least one pressure relief wave portion (77, 78, 79).

7. A can lid according to any one of claims 1 to 6, At least two, preferably at least three, particularly preferably exactly three pressure relief waves (77, 78, 79) are embossed in the metal lid surface (13) and extend parallel to one another around at least a portion of the periphery of the opening.

8. A can lid according to claim 7, A can lid, characterized in that the height or depth (85, 86, 87) of the pressure relief wave portion (77, 78, 79) relative to the reference surface (23) increases toward the opening.

9. A can lid according to claim 7 or 8, A can lid, characterized in that the arc length of the pressure relief waves (77, 78, 79) increases toward the opening.

10. A can lid according to any one of claims 7 to 9, The pressure relief wave portion (77) located closest to the opening has a closed circular path in the reference plane (23), and at least one pressure relief wave portion (78, 79) located further from the opening has an interrupted circular path.

11. 11. A can lid according to claim 10, The metal lid surface (13) and the opening have respective geometric centers located away from each other, and the at least one pressure relief wave portion (78, 79) located farther from the opening has an interruption (80) in its circular path, and a line connecting the two geometric centers extends through the interruption.

12. A can lid (11), in particular for beverage cans, in particular a can lid according to any one of claims 1 to 11, a metal lid surface (13) having a first flat surface (16) and a second flat surface (17) facing away from the first flat surface (16), the lid surface (13) is formed with an opening bounded by a closing edge of the lid surface (13) and closed by a closure piece (19) of the metal lid surface (13), the closure piece (19) being separated from the surrounding lid surface by a microgap (21) extending at least partially along the edge of the lid surface, a reference surface (23) of the closure piece (19) being defined by the path of the microgap (21); a first lid region (61) of the closure piece (19) is connected to the surrounding lid surface via a pivot bearing (30); a tear-opening material (37) arranged on the first flat surface (16) and engaging with a second lid area (62) of the closure piece (19), the second lid area (62) being on the opposite side of the pivot bearing (30), such that by pulling the tear-opening material (37) the closure piece (19) can be pivoted out of the reference surface (23) towards the first flat surface (16), the micro gap (21) being interrupted by at least two retention webs (65) between the first lid area (61) and the second lid area (62), via which the closure piece (19) and the surrounding lid surface are connected to each other in a bonded manner, a raised elongated portion (36) is embossed on the closure piece (19), the raised elongated portion (36) extending across a line (67) that extends through two of the at least two retaining webs and through the raised elongated portion (36) and is elevated above the reference surface (23) in the direction of the first flat surface (16).

13. 13. A can lid according to claim 12, The can lid is characterized in that the elongated raised portion (36) extends in a direction from the second lid region (62) to the first lid region (61).

14. A can lid according to claim 12 or 13, The opening has a geometric center, and the elongated raised portion (36) has a longitudinal axis (70) extending through the geometric center of the opening.

15. A can lid according to any one of claims 12 to 14, The elongated raised portion (36) has a height relative to the reference plane (23) that is at least as thick as the metal lid surface (13) and at most four times the thickness of the metal lid surface (13), and the height of the elongated raised portion (36) is preferably at least 1.5 times the thickness of the metal lid surface (13) and at most three times the thickness of the metal lid surface (13).

16. A can lid according to any one of claims 12 to 15, The elongated raised portion (36) has a length that is at least 5 times the thickness of the metal lid surface (13) and at most 70 times the thickness of the metal lid surface (13), and the length of the elongated raised portion (36) is preferably at least 20 times the thickness of the metal lid surface (13) and at most 50 times the thickness of the metal lid surface (13).

17. A can lid according to any one of claims 12 to 16, The can lid is characterized in that the opening has a rounded hexagonal shape, and the elongated raised portion (36) extends from a corner region of the opening in a direction toward an opposite corner region of the opening.

18. A can lid according to any one of claims 12 to 17, The can lid is characterized in that the elongated raised portion (36) has a club shape.

19. A can lid according to any one of claims 12 to 18, The can lid is characterized in that the elongated raised portion (36) has a head portion (89) close to the rim and a tail portion (90) narrowing relative to the head portion (89).

20. 20. A can lid as claimed in claim 19, The can lid is characterized in that the tail portion (90) tapers, preferably continuously, in a direction opposite to the head portion (89).

21. A can lid (11), in particular for beverage cans, in particular a can lid according to any one of claims 1 to 11, a metal lid surface (13) having a first flat surface (16) and a second flat surface (17) facing away from the first flat surface (16), the lid surface (13) defining an opening bounded by a closing edge of the lid surface (13) and closed by a closure piece (19) of the metal lid surface (13), the closure piece (19) being separated from the surrounding lid surface by a microgap (21) extending at least partially along the edge of the lid surface; a first lid region (61) of the closure piece (19) is connected to the surrounding lid surface via a pivot bearing (30); a tear-opening material (37) arranged on said first flat surface (16) and engaging with a second lid area (62) of said closure piece (19), said second lid area (62) being on the opposite side of said pivot bearing (30), such that by pulling said tear-opening material (37) it is possible to pivot said closure piece (19) towards said first flat surface (16) and out of said reference plane (23) defined by said opening, said microgap (21) being interrupted between said first lid region (61) and said second lid region (62) by at least one retaining web (65) via which said closure piece (19) and said surrounding lid surface are connected to each other in a bonded manner; A can lid, characterized in that a closure relief bead (38) is embossed in said closure piece (19) and extends at least past said at least one retaining web and along said edge of said opening.

22. 22. A can lid according to claim 21, A can lid, characterized in that said closure relief bead (38) is curved away from said edge in the region of said retaining web (65).

23. 23. A can lid according to claim 22, The micro gap (21) is interrupted between the first lid region (61) and the second lid region (62) by a plurality of retention webs (65), through which the closure piece (19) and the surrounding lid surface are connected to each other in a bonded manner, and the closure relief bead (38) extends in a curved manner past all of the retention webs (65) and away from the edge in the region of each retention web (65).

24. 24. A can lid according to claim 23, A can lid, characterized in that the closure relief bead (38) is curved towards the edge in the area between two consecutive retention webs (65).

25. A can lid according to any one of claims 21 to 24, The closure relief bead (38) has a height or depth relative to the reference surface (23) that is at most 1.5 times the thickness of the metal lid surface (13), and the height or depth of the closure relief bead (38) is preferably at most approximately the same as the thickness of the metal lid surface (13).

26. A can lid according to any one of claims 21 to 25, The closure relief bead (38) has a first side facing the edge of the lid surface and a second side facing an opposite side of the edge of the lid surface, the second side being steeper than the first side.

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