The invention relates to the provision of a positional fixing of a tab on a sheet metal lid for attaching to a body of a beverage can.
When the tab is in an attached condition to the sheet metal lid, it is known by the expert as a SOT (Stay on Tab), which is provided for opening an openable area in the surface of a lid (usually designated as “panel”). For this purpose, the tab is taken at a grip end and raised with a vertically orientated tilting motion for breaking open an openable area along a line of weakness (usually called score line) with its opening end.
Particularly with large opening ends (LOE) as openable area, difficulties are encountered in the related art with regard to fixing the positions of the tab in an attached condition to the sheet metal lid. Suggestions on this topic have already been made, for example in U.S. Pat. No. 5,799,816 (Schubert). In said document, an opening of an attaching portion of the tab is proposed, which attaching portion is usually designated as “rivet island”. Said attaching portion is secured to the panel of the sheet metal lid through a shaped rivet and overlaps a round to elongated reformed bead with an opening provided in the attaching portion, which bead may also be formed after attaching the tab, compare column 3, lines 63-67, column 5, lines 37-44, claim 3 of said document and the associated graphical illustration in FIGS. 2 and 4 thereof.
The invention addresses the technical problem of achieving such effect, but with an improved manufacture and reliability of the anti-rotation block and with an improved positional alignment of the tab in the attached condition.
According to the invention, it is suggested not to allow the projection to protrude through an opening of the attaching portion, and that the attaching portion not be provided with an opening for this purpose beforehand, but to keep the attaching portion entire and to provide a blocking means that acts on the attaching portion from an outside (one of claims 1 to 4).
In order to obtain the blocking effect, which can also be a limiting effect, which is to be understood to range from a complete prevention of a rotating movement up to a substantial limitation of said rotating movement, an outer edge of the flat attaching portion (rivet island) is stopped by abutting against the projection that is shaped to protrude out of the sheet metal lid. (claim 10). Since the projection has positional stability on the panel in all operating positions, also when starting to break open the openable area, and since the attaching portion itself is substantially coplanar with the panel of the lid, tightly surrounding the central rivet as a mounting place, none of the elements provided for preventing rotation operationally moves apart with an opening movement of the tab. Since the opening movement is a vertical tilting motion (claims 13, 14), anti-rotation is unaffected due to an outer edge of the attaching portion abutting on the panel projection.
Advantageously, a peripheral edge on a usual tab already provided during manufacturing may also be used, said edge not having to be specifically formed additionally for obtaining the rotation barrier after an attachment of the tab to the panel (“staking”). The only influencing takes place on the sheet metal lid itself, which is provided with a shape or molding, as the rivet is in a preliminary phase, which shape or molding may preferably also be pre-formed in parallel together with the formation of the rivet and subsequently be modified in shape, or more precisely “reformed”, in a further processing step of the sheet metal lid being manufactured (claim 24, claim 23, claim 44, claim 35). The projection may thus be formed integrally with the sheet metal lid, like the mounting place is formed by one-piece manufacturing for the attaching portion of the tab.
The projection can have strip shape (line shape) and be preferably orientated at least one of transversely and in parallel to a longitudinal extension of the tab (longitudinal axis or longitudinal plane), said projection engaging at a correspondingly orientated peripheral edge of the attaching portion for its blocking effect or being provided very closely adjacent thereto. In a longitudinal extension, said projection can extend over more than 30%, preferably over more than 50% to more than 80% of the width of the attaching portion (claims 5, 36).
If the projections extend parallel to the longitudinal extension of the tab, that is to say perpendicularly to the transverse direction mentioned before, the longitudinal extension is shorter than the longitudinal extension of the attaching portion (rivet island) of the tab, preferably at a position as distant as possible from the mounting place having a large distance therefrom, said distance, however, only being such large that at least one portion of the two peripheral lines abuts blockingly on the at least one projection when starting a rotating movement (claim 38).
Making the attachment as distant as possible from the mounting place allows the greatest possible force be exerted, which provides a blocking effect in opposition to inadvertent or deliberate rotation of the tab by a user (claim 22). Particularly, the projections oriented parallel to the longitudinal extension of the tab apply a great force for the blocking effect. All three may also be used in combination (claim 39).
Regarding the height or vertical extension of the at least one projection, it should be noted that said height should be at least equal to the thickness of the sheet metal of the attaching portion, (claim 20, claim 21), preferably slightly to markedly greater in order to obtain a reliable positional fixing that, however, is not impaired by operating or raising the grip portion, since the attaching portion is reliably situated on the other side of the mounting place and coplanar with the panel section surrounding the rivet (button coin area).
Several projections can be provided, not all projections having to be associated with the same outer edge portion of the attaching portion (claim 6 to 9). The projections can also be differently shaped, i.e. strip-shaped, round to oval, or a combination thereof. If a straight-lined outer edge portion of the attaching portion is provided, a straight-lined (strip-shaped) design of the projections can be advantageous. Said straight-lined or linear strip design can also be achieved by arranging at least two punctiform projections in line, which then form a group that is associated with the same outer edge portion of the attaching portion.
The attaching portion in the form of a mounting tongue is connected to the rest of the tab via a buckling portion in the form of an articulation line, i.e. integrally (claims 13, 11). It is thus provided between the opening portion (the rupture nose) and the grip portion that is preferably provided with a hole.
If the attaching portion is substantially rectangular, the substantially rectangular, flat, attaching portion is formed by using the articulation line and three edge lines (claim 12). Particularly, said flat or surface portion is square in shape, the rivet head not being central after mounting, but positioned closer to the articulation line. The distance of the outwardly directing peripheral edge is therefore larger than half the longitudinal extension of the attaching portion, so that a correspondingly improved force effect is achieved, when a projection on the panel can be assigned to the peripheral edge most distant from the mounting place.
Forming at least one projection to have an asymmetrical cross section is particularly advantageous, said projection having a steeper flank facing the attaching portion, than the flank facing away from said attaching portion (claims 17, 18, 19 and 23 or 24). Such a shape can also be selected for punctiform or oval projections.
In a subsequent reshaping, reforming, or post-forming, preferably the thickness of a top side of the (strip-shaped) projection is reduced (claim 23). Thereby, solidification of said portion as well as of the projection as a whole is achieved. This also applies to the method (claim 35). The score line may be applied simultaneously with said reforming, in the same processing step (claim 51).
The result of said reforming is optically visible in a flattened top side (claim 47). The projection thus formed has a larger width than its total height (claim 50, claims 20, 21). Even larger is the respective longitudinal extension of a projection, said longitudinal extension being considerably larger than the width of the projection. This applies to elongated strip-shaped or linear projections. When a steeper flank portion is formed (claim 44), which is markedly more pronounced than the preform, a peripheral edge may be obtained having (at least) one portion extending at an angle of substantially 90° relative to the plane of the panel (claim 49). This applies to the edge opposing the assigned peripheral edge portion of the attaching portion. An embossing process (claim 48) also helps to give a stronger or steeper shape to said flank, said embossing being responsible for the reinforcement of the reformed sheet metal on the top side (claims 47, 48, 52, 53).
When several projections are provided in the aforementioned sense, they do not have to engage at the same edge line of the attaching portion when starting a rotating movement, but instead they can be assigned to different outer edges (claim 16).
If one assumes a still unfinished sheet metal lid that is only being prepared to receive a tab (claims 30, 31), the invention claimed here includes the formation of the projection in such a position that is sufficiently distant from the intended mounting place (from the re-formed rivet or its preform), and in fact at such a distance that the outer edge in the form of an edge of the attaching surface (rivet island) facing away from the future rivet is located very close to the projection, thereby achieving the rotation stopping effect. Said location is in the outer edge portion of a rivet head zone or of the “rivet base”, which extends visibly around the formation of the rivet centre remaining from the rivet preform (claims 25 to 29, claim 46).
The projection as a line or strip lies at least partially outside the weakened rivet base portion, in which the sheet metal is thin due to the shaping of the mounting place. This addresses a peripheral portion of said rivet base zone (claim 26), preferably more than 40% of an assumed surface of a strip-shaped projection lying outside the rivet base zone (claim 27).
For a definition of the rivet base zone, reference may be made to a visible change of the surface that remains on the inside of the sheet metal lid after the rivet has been formed and the tab has been mounted (claim 28, claim 29). Due to being placed in the outer portion, i.e. as distant as possible from the weakened sheet metal or the thin sheet metal, the re-formed portion may be considerably higher before the sheet metal is damaged. The re-forming may achieve heights that are above a sheet metal thickness of the attaching portion of the tab.
When providing a strip-shaped projection, it can be designed to have a length larger than the diameter of the finished rivet head.
The attaching portion being formed from a piece of the central portion of the tab, only minor gaps are visible between the attaching portion, which is displaced downwards to a lower plane by a double buckling line, and the somewhat higher, parallel plane of the remaining tab. Accordingly, the mounting of the projections on at least one of the free peripheral edges facing outward from the attaching portion is barely or only hardly visible from the outside, so that the rotation blocking is virtually invisible to the observer. A colored tab is not changed further in its colored appearance.
Exemplary embodiments explain and supplement the invention.
a is a cross section along line C-C in
a is a sectional view through the centre plane of
a is a cross section of an embodiment of the invention corresponding to the illustration in
a is a schematic explanation of the effective torques in a projection extending parallel to the center plane 100.
b is a comparable explanation of the effective torques in a projection 20 located transversely to the center plane 100.
The sheet metal lid obtained according to FIGS. 1 to 3 has a visible edge portion 12 that is suitable for seaming to the body of a beverage can. The sheet metal lid itself is produced from thin sheet metal, typically less than 0.24 mm, and has already passed through preceding workstations before reaching the stage shown in
A mounting place 11, which will be seen more clearly lateron in the sectional enlargements, is provided approximately in the middle of the panel. An attaching portion as a sheet metal tongue 31 is associated schematically therewith, said attaching portion being part of the tab according to
For a general survey, the longitudinal midplane 100 is marked, extending in a direction to the longitudinal extension of the tab 30. A transverse plane 101 extends perpendicularly thereto.
As attached (staked end), the grip portion 32 of the tab overlaps a finger depression 13, which is provided in the panel 10, at about the same distance as the inner reinforcing bead 18a on the other side of mounting place 11. The tab is attached during the manufacture of the finished sheet metal lid, only in
The attaching tongue 31 is shown in
In
In order to ensure the rupture force and the accuracy of the breaking-open process, the tab 30 shall not be adapted to move in a rotation direction, which is designated by α in
It is obvious that the front nose end of the opening portion 33 would be moved away from the exact position that is provided to ensure the rupture force, the continued tearing and the subsequent complete opening of the opening area 17. It is therefore desirable according to
The width of the attaching portion 31 is marked with “b”, so that the minimum distance of the two projections 21b, 21a designed as beads and extending parallel to the longitudinal midplane 100 have this dimension with their inside edges 21b′ and 21a′ as distance. The longitudinal extension of the attaching portion 31 in said plane 100 extends over the rivet head as mounting place 11. It is evident that the length of the two beads 21a, 21b is shorter than half the longitudinal extension of the attaching portion 31, and that said beads are positioned as far as possible to the rear area of the attaching portion in order to apply the greatest possible force for positional fixing at an assumed rotation α.
This also results from the greatest possible distance of the projection 20—disposed in the transverse plane 101—transversely to the longitudinal mid-plane 100, said projection being longer than the two previously described parallel projections. Said projection extends over more than half, preferably even more than 80% of width b of the attaching portion 31.
According to non-illustrated embodiments, one or more of the three described strip-shaped beads may also be omitted
Thus for example, a geometry with only one projection 20 is possible, as illustrated in
The cross-section shown in
In
a also shows a cross section relating to
The asymmetry in a transverse direction to the longitudinal extension of the projection 20 (in the longitudinal plane 100 of the lid or the tab) is illustrated in
This is illustrated in
The following embodiments refer to the bottom illustration. The rivet 11 that is used for mounting the attaching portion 31 to the sheet metal lid 10 is located to the left, not in the representation. A rear end 31c of the attaching portion 31 is the peripheral edge that is assigned to a front edge 20″ of a projection 20, possibly leaving a narrow gap 20′, as is explained by
Said re-forming step comprises a designing shaping of the pre-form 20* with a coining (an embossing operation) for further flattening the top surface 20c. In said re-forming process, the tool is applied likewise from the top and from the bottom for said re-forming. The slight bend that is detectable on the left in the rising flank of the pre-form 20′ may be recognized in the bottom final form, the way in which the sharp front edge 20″ is introduced in the initially gently rising front incline of the shaped rampart 20* also being visible. To the right of the transverse plane 101, the second incline of the rampart is formed from bottom to top, for forming a flat shape 20c, starting approximately at the instep of said rampart 20* and leading gently over to the rest of the sheet metal panel 10 in portion 20b.
Additionally, in the final form, the attaching portion 31 and the tab 30 are already attached according to
In this context, a modified sequence of the two-stage re-forming may be performed besides the processing sequence according to FIGS. 1 to 3, for example the initial introduction of the pre-forms, as illustrated by the pre-form 20* in the top picture of
Further embodiments of projections are evident from the other figures. Thus,
If the at least one projection is associated with a peripheral edge 31c extending transversely to the longitudinal plane 100 of the tab 30, a rotational movement in both directions can be prevented with only one projection, if said projection extends at least on both sides of the midplane. On the other hand, if a projection is selected that is assigned to a peripheral edge extending parallel to the longitudinal plane 100, at least two projections have to be provided on two correspondingly available edges as “stop edges”, for symmetrically limiting rotational movements of the tab 30.
All the projections described are arranged outside the attaching portion 30, in order to be able to cooperate in a blocking manner with at least one of its respective outer peripheral edges (edge).
The effect of the turning moments or torques is illustrated in
Similarly, the exertion of torques may be explained for a projection 20 that extends perpendicularly to a midplane 100, said projection occupying substantially the entire width b of the attaching portion 31 near to a rear edge line 31c thereof. In this case, the (maximum) power arm is designated b1, and in a first approximation, said lever arm is not exactly but largely equal to half of the width b, marked as lever arm b1 in an assumed (hypothetical) rotational movement in a direction α as illustrated. The corresponding force via the lever arm b1 is applied by the projection 20, and the front edge 20a thereof (edge 20″ in
A more precise dimensioning of the surface areas shows that the strip-shaped projection 20 is situated at least partly outside the rivet base zone (coin area) and outside the outer peripheral portion 11b thereof. The outward displacement is equal to at least 40% of the surface portion f20, which is no longer in the periphery 11b of the rivet base 11a, but outside thereof. This position and the position and extension of the coin area are easily visible from the inside of the sheet metal lid.
Number | Date | Country | Kind |
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103 00 914.0 | Jan 2003 | DE | national |
103 19 971.3 | May 2003 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/DE03/04283 | 12/23/2003 | WO | 6/27/2006 |