Method for producing an easy-open lid for a container, and an easy-open lid for a container

Abstract

The invention relates to a method for producing a lid for closing a container, the lid reduces the risk of a user's injury when opening the container while being producible at relatively low costs. The method comprising the steps of providing a preform of the lid (10), wherein the preform of the lid (10) has opposing first and second sides (11, 12), wherein the first side (11) faces towards the inside of the container when the lid (10) is affixed to the container; forming a bead (20) in the preform of the lid (10), wherein the bead (20) extends out of said second side (12) in an axial direction from said first side (11) towards said second side (12), wherein the bead (20) comprises two radially spaced apart side wall portions (22, 24) and a bridge portion (26) connecting the side wall portions (22, 24); thinning the side wall portions (22, 24) of the bead (20) at least partially, thereby elongating the side wall portions (22, 24); forming a score line (30) in the bridge portion (26) of the bead (20) on said second side (12); and flattening the bead (20) such that the two thinned side wall portions (22, 24) collapse, thereby providing the lid (10).

Claims

1. A method for producing a lid for a container, the lid being adapted for closing the container, comprising: providing a preform of the lid (10), wherein the preform of the lid (10) has opposing first and second sides (11, 12), wherein the first side (11) faces towards an inside of the container when the lid (10) is affixed to the container; forming a score line bead (20) in the preform of the lid (10), wherein the score line bead (20) extends out of said second side (12) in an axial direction from said first side (11) towards said second side (12), the score line bead (20) comprising two radially spaced apart side wall portions (22, 24) and a bridge portion (26) connecting the side wall portions (22, 24) and forming a score line (30) in the bridge portion (26) of the score line bead (20) on said second side (12); at least partially thinning the two radially spaced apart side wall portions (22, 24) of the score line bead (20) resulting in elongated side wall portions (22, 24) of the score line bead; and flattening the score line bead (20) such that the two thinned side wall portions (22, 24) collapse; wherein flattening the bead (20) causes the two radially spaced apart thinned side wall portions (22, 24) to bend towards each other and form two opposite projections (32, 34), and the bridge portion (26) substantially maintains its original form and alignment with respect to said second side (12) after the score line bead (20) is flattened.

2. The method according to claim 1, wherein the two projections (32, 34) are moved towards each other substantially until they are adjacent to or abutting each other.

3. The method according to claim 1, wherein the step of thinning the two radially spaced apart side wall portions (22, 24) is performed incrementally in a plurality of separate steps.

4. The method according to claim 3, wherein the two radially spaced apart side wall portions (22, 24) are thinned by between 0.01 mm and 0.08 mm.

5. The method according to claim 1, wherein the two thinned radially spaced apart side wall portions (22, 24) have a thickness (W) of at most 0.20 mm after thinning.

6. The method according to claim 1, wherein flattening the score line bead (20) causes the score line bead (20) to bend at the score line (30) so that the bridge portion (26) does not maintain its original form and alignment with respect to said second side (12).

7. The method according to claim 1, wherein the bridge portion (26) extends outwardly from said second side (12) in a substantially convex manner after the score line bead (20) is flattened.

8. The method according to claim 1, wherein flattening the score line bead (20) causes the bridge portion (26) to move towards the two projections (32, 34) substantially until the bridge portion (26) is arranged under a distance to or is adjacent to or abuts the projections (32, 34).

9. The method according to claim 1, wherein the preform of the lid (10) has a thickness of between 0.12 mm and 0.25 mm.

10. The method according to claim 1, wherein after flattening the bead, the bridge portion (26) has a wall thickness (R) of between 0.12 mm and 0.25 mm.

11. The method according to claim 1, wherein, upon forming the score line (30) in the bridge portion (26) of the bead (20), the bridge portion (26) has a residual thickness (R) of between 0.05 mm and 0.09 mm underneath the score line (30).

12. The method according to claim 3, wherein in each of said plurality of separate steps the side wall portions (22, 24) are thinned by between 0.03 mm and 0.06 mm.

13. The method according to claim 1, wherein each of the thinned side wall portions (22, 24) have a thickness (W) of between 0.08 mm and 0.11 mm after thinning.

14. The method according to claim 1, wherein the preform of the lid (10) has a thickness of between 0.16 mm and 0.23 mm.

15. The method according to claim 1, wherein the bridge portion (26) has a residual thickness (R) of approximately 0.07 mm, underneath the score line (30) after forming the score line (30) in the bridge portion (26) of the bead (20).

Description

(1) Further details and advantages of the invention will become apparent from the following detailed description of embodiments of the invention with reference to the enclosed drawings.

(2) FIG. 1 is a cross-sectional partial view of a basic form of a lid preform (easy open end preform) for a container according to the invention.

(3) FIG. 2 is a cross-sectional partial view of a first intermediary stage in the formation of a lid for a container according to the invention.

(4) FIG. 3 is a cross-sectional partial view of a second intermediary stage in the formation of a lid for a container according to the invention.

(5) FIG. 4 is a cross-sectional partial view of a third intermediary stage in the formation of a lid for a container according to the invention.

(6) FIG. 5 is a cross-sectional partial view of a final stage in the formation of a lid for a container according to the invention.

(7) FIG. 6 is a cross-sectional partial view of the first intermediary stage in the formation of a lid similar to FIG. 2, now including tools.

(8) FIG. 7 is a cross-sectional partial view of the second intermediary stage in the formation of a lid similar to FIG. 3, now including tools.

(9) FIG. 1 shows a cross-sectional view of a part of a basic form of a preform of a lid 10 which lid 10 is adapted to close a container at one side or end thereof, such as a can containing foods or drinks (not shown). Here, the preform of the lid 10 substantially already has the extension and/or diameter that is required so that the final lid 10 can be attached to and/or seamed on the container. In practice, this basic shape is also called shell.

(10) The preform of the lid 10 has a first side 11 and an opposing second side 12, wherein the first side 11 faces towards the inside of the container when the lid 10 is affixed to the container, and wherein the second side 12 faces towards the outside of the container. FIG. 1 also shows an initial, basic form of a bead 20 in the preform of the lid 10. This bead 20 is formed and developed further in the following steps of the manufacturing process for making an easy open end for the container (lid).

(11) For the purposes of this specification, the axial direction shall be the direction extending vertically from or out of the general plane of the lid 10, whereas the radial direction shall be the direction extending parallel to or in the general plane of the lid 10 or the preform of the lid 10. In other words, the axial direction extends from the first side 11 towards the second side 12 of the (preform of the) lid 10, or vice versa, when the first and second sides 11, 12 are seen lying in the general or main plane of the overall lid 10. In FIG. 1, the axial direction is designated by the arrow A, and the radial direction is designated by the arrow B. Thus, these two directions extend perpendicularly to each other. Furthermore, this definition shall also apply in cases where the (preform of the) lid 10 does not have a round or circular form, as the present invention is applicable not only to round or circular lids but also to any other possible form of a lid, e.g. an oval or oblong or substantially rectangular form.

(12) Following the basic shape of the preform of the lid 10 as shown in FIG. 1, the material of the preform of the lid 10 is formed further in the next manufacturing steps. FIG. 2 shows a first intermediary stage in this further formation of the lid 10. As can be seen in FIG. 2, the bead 20 is formed extending already further out from the preform of the lid 10. Particularly, the bead 20 extends out of the second side 12 of the preform of the lid 10 in an axial direction with respect to the preform. This bead 20 comprises two side wall portions 22, 24 which are spaced apart from each other in a radial direction with respect to the (preform of the) lid 10. Furthermore, the bead 20 comprises an outermost or top or cover or bridge portion 26 which connects the two side wall portions 22, 24. Thus, the bead 20 substantially has a symmetrical shape in its cross-section. This form is advantageous for the following further manufacturing steps.

(13) In the next manufacturing step, the side walls 22, 24 of the bead 20 are thinned, e.g. by ironing, thereby elongating the two side wall portions 22, 24. Accordingly, the volume of material for accomplishing the axial elongation of the side wall portions 22, 24 is taken from the lid 10 as such in that the side wall portions 22, 24 are thinned. In other words, the thickness of the lid 10 is reduced from the initial thickness in the region of the side wall portions 22, 24. The result of this step is substantially shown in FIG. 3. This thinning process of the bead can be made either continuously or incrementally in separate steps. In the latter case, in each of said separate steps the thickness of the side wall portions 22, 24 can be reduced by approximately 0.05 mm.

(14) In a preferred embodiment, the thinned side wall portions 22, 24 have a thickness W of approximately 0.1 mm at the end of the process step of thinning the side walls 22, 24.

(15) In contrast to the side wall portions 22, 24, the bridge portion 26 as such substantially maintains the initial thickness of the lid 10 during and after the thinning process. Thus, in a preferred case where the preform of the lid 10 originally may have a thickness of approximately 0.16 to 0.23 mm, also the bridge portion 26 substantially has a wall thickness C of approximately 0.16 to 0.23 mm, both prior to and after the thinning step of the side wall portions 22, 24 (see FIG. 3).

(16) As the next step for manufacturing the easy open end (lid) for a container, a score line 30 is formed on the outside of the bridge portion 26 of the bead 20, i.e. on the second side 12 of the preform of the lid 10 substantially on top of the bead 20. FIG. 4 shows this third intermediary stage of the manufacturing process, partly in a cut-out enlarged view. This score line 30 is a weakened line along which the final lid 10 can be pulled-open by a user via a pull-tab, as was explained above. Accordingly, the thickness C of the bridge portion 26 is reduced at the score line 30. In a preferred case, the bridge portion 26 has a residual thickness R of approximately 0.07 mm underneath the score line 30.

(17) In a substantially final manufacturing step, the result of which is shown in FIG. 5, the bead 20, which has been extended outwardly in the preceding manufacturing step, is now flattened (compressed), i.e. in the axial direction towards the second side 12 of the lid 10. Thereby, the two thinned side wall portions 22, 24 collapse, i.e. move out of their straight axial alignment (which is shown in FIGS. 3 and 4), and are being folded or bent towards each other, preferably in a substantially symmetrical manner. Thereby, two opposite projections or shoulders 32, 34 are formed that move towards each other during the compression of the bead 20. At the end of the manufacturing step of flattening the bead 20, said projections or shoulders 32, 34 can be positioned adjacent to each other, leaving a free space between them, or can even abut each other.

(18) After this step a lid 10, e.g. an easy open end, is formed. Further steps can be performed after the above described substantially final manufacturing step. E.g. a pull-tab may be attached to the lid 10, preferably via a rivet.

(19) During the compression of the bead 20, the bridge portion 26 of the bead 20 is moved downwards and towards the two simultaneously formed projections 32, 34, substantially either until the bridge portion 26 remains arranged under a distance to the projections 32, 34 or until the bridge portion 26 is substantially lying on and abutting the projections 32, 34. This results in the double-folded arrangement of the lid 10 in the region of the bead 20 and the score line 30, as it was explained in the introduction above. In the first of said latter two cases, which substantially is shown in FIG. 5, the compressed bead 20, i.e. the bridge portion 26 together with the folded side walls 22, 24 which form the projections 32, 34, has a cross-sectional form substantially resembling the letters O or or having a substantially mushroom-like form. In the second of the above mentioned two cases, the bead 20 is substantially flattened fully to a maximum so that the lower side of the bridge portion 26 lies closely on the completely folded side walls 22, 24 or projections 32, 34, respectively, substantially leaving no or only very little free space between the stacked individual layers of the folded lid 10 formed by the bridge portion 26 and the projections 32, 34 underneath.

(20) Furthermore, during the flattening of the bead 20 in the axial direction towards the outer or second side 12 of the lid 10, the bridge portion 26 can substantially maintain its original form and alignment or orientation with respect to said second side 12. In other words, while the side walls 22, 24 are deformed in that they collapse and are folded to form the projections 32, 34, the bridge portion 26 as such is substantially not deformed but is moved as such in the downwards direction.

(21) Alternatively, during the flattening of the bead 20, the bead 20 and particularly the bridge portion 26 can be bent at the score line 30 whereby the bridge portion 26 does not maintain its original form and alignment or orientation with respect to the second side 12 of the lid 10. In this case, the bridge portion 26 can e.g. be deformed such that in the end it is rounded outwardly, i.e. extends outwardly from the second side 12 in a substantially convex manner. This form resembles the general form of the bridge portion 26 as it is shown in FIG. 5. In an alternative case, the bridge portion 26 as such can e.g. be deformed such that in the end it is depressed inwardly, i.e. forms a concave recess about the score line 30.

(22) FIG. 6 is a cross-sectional partial view of the first intermediary stage in the formation of the closure lid 10 (easy open end) similar to FIG. 2, however now additionally showing the forming tools and/or dies 40 surrounding and working on the lid 10. Similarly, FIG. 7 is a cross-sectional partial view of the second intermediary stage in the formation of the lid 10 similar to FIG. 3, again now including the forming tools and/or dies 40. Accordingly, in FIG. 6, the bead 20 is initially formed in its basic shape by drawing the bead 20 axially out of the lid 10 in the outwards direction with respect to the container, i.e. in the direction out of the second, outer side 12 of the lid 10.

(23) In FIG. 7, the side wall portions 22, 24 of the formed bead 20 are thinned (e.g. by ironing), thereby the side wall portions 22, 24 are elongated. As can be seen in FIG. 7, after this process step, the thickness of the side wall portions 22, 24 is smaller than the general thickness of the lid 10 at both radial sides of the bead 20, whereas the bridge portion 26 maintains the general thickness of the (preform of the) lid 10.