OBJECT OF THE INVENTION
The present invention, an easy-open lid, applies to the field of metal containers, specifically of those containers used for food commercialization, such as tins, cans, etc., and specifically focuses on the opening means of the lid thereof, commonly called “easy-open”.
- BACKGROUND OF THE INVENTION
The invention is specifically related to the classic groove or cut which are provided on lids of this type of containers, for facilitating the opening thereof by means of a punch-tear away ring tab.
In the preferred scope of practical application of the invention, sealed food packaging, metal containers are conventionally used, the lid of which is provided with a perimetral groove or cut line, as well as a ring tab provided with a punch vertex overlapping said cut line, such that in normal conditions, the ring tab is parallel and adjacent to the lid, whereas during the opening maneuver, it swings thereon such that initially, and through its punch vertex, it causes the start of the tearing of the lid, and then it causes the complete tearing away thereof by pulling on said ring tab.
This solution, perfectly valid from the theoretical point of view, presents drawbacks in practice derived from an incorrect positioning of the ring tab. In this aspect, it happens quite frequently that, during the ring tab manufacturing process, or in the subsequent sealing, filling, sterilization, handling processes, etc., of the container, said ring tab undergoes a slight rotation, causing a modification of the theoretical position provided for its punch vertex with regard to the cut of the lid, since the ring tab rotates about the point where it is attached to the lid, noticeably eccentric with regard to the latter, whereas the cut line defines a path parallel and close to the contour of said lid, therefore more or less spacing occurs between the punch vertex of the ring tab and the cut of the lid, causing a significant increase of the force necessary to begin the opening operation, i.e. for causing the punching or breaking of the cut line, after which the lid is subsequently torn away.
This increase of force contributes to significantly increasing the number of lids in which the ring tab cannot overcome the cut and does not open the lid, even occasionally causing the ring tab to break since the hole which connects the ring tab to the lid by means of a rivet, becomes deformed, with the subsequent release of the ring tab and inability to use the container opening mechanism.
Spanish utility model number ES0152778U discloses a conventional lid, without a punch vortex, for cans that have a curled cut line to facilitate the aperture of the can. The ring tab included in said lid does not include means nor solutions that would permit the opening of the lid in case the ring tab has a slight rotation.
- DESCRIPTION OF THE INVENTION
U.S. Pat. No. 3,762,596-B discloses a can lid having means on it which prevent the rotation of the ring tab, said means consisting of respective outward projections on both sides of the ring tab. It also has a cut line the path of which in the ring tab operation area is different from that of the rest of said cut line. Specifically, the cut line in that initial breakage area is elliptical in order to space the cut line from the edge of the can and to facilitate the manufacturing process of the can. The devices used for preventing the rotation of the ring tab do not ensure that, daring the handling of the can in the different manufacturing processes thereof, it will not slightly rotate, although it does reduce said rotation. Due to the elliptical configuration of the cut line in its initial breakage area, a minimum rotation of the ring tab will prevent the punch vertex thereof from acting on said initial breakage area, therefore originating the aforementioned drawbacks in opening the can.
The improvements proposed by the invention satisfactorily solve the drawback explained above, ensuring a proper operation of the punch ring tab, even when said ring tab is significantly rotated with regard to its theoretical correct position.
Therefore more specifically, the invention entails changing the path of the cut line, specifically in the segment thereof facing the punch ring tab, such that by said cut line maintaining a general path parallel, and close to the contour of the lid, in said area facing the ring tab it undergoes two symmetrical inflections with regard to the theoretical punch point, which frame an intermediate segment in which the path of the cut is arcuate, specifically with a curvature center arranged in correspondence with the rivet of the ring tab, such that after a rotation of the ring tab, its punch vertex remains in place on said cut.
The amplitude of said arcuate segment with a curvature in the rivet of the ring tab will vary according to different constructive criteria, this amplitude necessarily being greater than 1°, although it is convenient for said arcuate segment to not exceed 80°.
Said arcuate segment will be join the rest of the cut through also rounded inflections which “smooth” the path of said cut and which, accordingly, favor tearing away the lid.
Evidently the improvements, of the invention are applicable both to circular and elliptical or rectangular lids, which are the three conventional configurations in this type of metal containers.
DESCRIPTION OF THE DRAWINGS
In any case and according to the described structure, it is achieved that, even due to a significant rotation of the ring tab, which can reach 10° to the right or left, said ring tab keeps its punch vertex on the cut line, causing the proper punching thereof with a minimum force.
To complement the description that is being made and for the purpose of aiding to better understand the features of the invention according to a preferred practical embodiment thereof, a set of drawings is attached to said description as an integral part thereof which, with an illustrative and non-limiting character, show the following:
FIG. 1 shows a schematic plan view of an easy-open lid for metal containers provided with the improvements object of the present invention.
FIG. 2 shows an enlarged detail view of the lid of the previous figure, in the area thereof in which said improvements are made.
PREFERRED EMBODIMENT OF THE INVENTION
FIG. 3 shows, according to a view similar to FIG. 1, another type of conventional easy-open lid, also provided with the improvements of the invention.
In view of the figures, and more specifically of FIG. 1, it can be seen how the improvements of the invention are applicable to a lid made of a laminar body (1), in this case having a circumferential contour, as this lid is intended for a cylindrical container, provided with a marginal strip (2) through which, by seaming or by any other means, the body (1) is attached to the opening of the container, not shown, and is provided inside said marginal strip with a cut or perimetral groove (3) which is intended for tearing away the lid (1) during the container opening maneuver, opening which is carried out with the collaboration of a ring tab (4) attached to the body (1) of the lid with the collaboration of a rivet (5), and provided with, in opposition to the ring tab (4) itself, a punch vertex (6) which must be located on the cut line (3) on which it acts when the ring tab (4) is manually swinged on the rivet (5) which fixes the ring tab to the body (1) of the lid. The lid (1) can adopt the circular configuration of FIG. 1, the rectangular configuration with rounded vertices of FIG. 3, or any other configuration conventional in this type of containers, such as an elliptical configuration, also normally being provided with deep-draws (7) which stiffen its structure.
Therefore, from this basic and conventional structure, according already to the invention, the cut line (3), in its area where it faces the ring tab (4), undergoes a variation in its path, defining a breakage segment (8) in a circumference arc shape, having a curvature center (9) arranged in correspondence with the center of the rivet (5), as can particularly be seen in FIG. 2, such that the mid-point of this arcuate breakage segment (8) is located in correspondence with the theoretical point (10) provided for operating the punch vertex (6) of the ring tab (4) when the latter is correctly located in the context of the lid (1).
As previously mentioned, this results in that, after an accidental rotation of the ring tab (4) at any time throughout the container handling process, its punch vertex (6) is kept perfectly in place facing the cut line (3), specifically along this breakage segment (8), thereby ensuring that the tearing conditions are optimal.
As was also mentioned above, the amplitude of said breakage segment (8) with a curvature center (9) coinciding with the axis of the rivet (5), can range between 1° and 80°, the amplitude of said arc preferably being 20°, 10° on each side of the theoretical point (10) provided for operating the punch vertex (6) of the ring tab (4) when the latter is correctly located in the context of the lid (1), and said breakage segment (8) will join the rest of the cut line (3) by means of double, offsetting and arcuate inflections (11-11′), which facilitate tearing away the lid (1), preventing the existence of sharp bendings in said cut line (3) which could negatively affect tearing away the lid.