EASY OPEN END

Abstract: An easy open end suitable for a food or beverage can, having a tab (60, 160) attached to a central panel (10, 130) of the end and a main score line (50, 150). A part (65, 165) of the tab overlies a protrusion (80, 180) in the end, the protrusion having an associated vent score line (90, 190). When the tab is raised, the vent score line breaks before the main score line as the tab engages the protrusion, thereby allowing venting prior to rupture of the main score line. In an alternative embodiment, a protrusion is formed in the tab instead of, or in addition to, in the central panel.

Description: EASY OPEN END This invention relates to easy open ends. In particular, but not exclusively, it relates to an easy open metal can end of the type used for connection to metal can bodies and having a dispensing aperture closed by a panel. A pull tab or ring is fixed to the end for enabling a score to be broken when the tab is raised, so as to open the panel and thereby gain access to a product within the can. Such a can end is known, for example, from GB-A-1540229, in which the panel remains attached to the can after opening. Easy opening of the can end is achieved by lifting the tab so that a forward portion of the tab engages the panel and causes the panel to be severed along the score line. The score line of the can end of GB-A-1540229 and those of other known can ends are variable in depth. Typically, can ends of the prior art have a hard spot or "hesitation point" in the score line so that the can is opened in two stages. This hesitation point is achieved by a gradual change in the depth of the score line. A first stage allows for venting by tearing along a deep score line, that is one having a low score residual, so that the pressure within the can is equalised with external pressure. The score line then becomes shallower with greater score residual so that the aperture does not open in one stage but must be opened in a second, further stage. Can ends having either a hesitation point or a hard spot pose a number of problems in manufacture and use. The production of a variable depth score line involves tooling having close tolerances and shorter tool life. Furthermore, when the can is vented by breaking the score line along its deeper region where metal to be torn is less, product may spurt out or contaminants may be sucked in according to the positive or negative pressure within the can. When a tab is used to exert pressure on the panel of an easy open end, such pressure triggering its opening along the score, one of the problems is to control the opening of the end satisfactorily. It has been found that when there is a positive pressure within the can, that is an overpressure, there is the risk that the end might explode off the can in a surprising and sometimes violent manner. Conversely, in the case of a negative pressure, such as a partial or full vacuum, there is the risk that the end might sink violently, or implode, at the moment when the end is pierced. Either of these situations may result in problems for the consumer, such as product loss, splashes or even risk of injury. According to FR-B-1590786, a vent score is made under the ring pull, in the immediate vicinity of a rivet which fixes the ring pull onto the end. The system is theoretically designed so that, when one pulls the ring upwards, the vent score opens before the principal score, allowing the venting inside the can, before the full opening of the can. In particular, it is noted that in order to achieve the opening of the vent score, the ring rests in the vicinity of the main score. This results in a large number of cases in which the main score opens before the vent score, thus rendering the whole system ineffective. One of the reasons for the high failure rate of this design undoubtedly lies in the fact that it is difficult to control the resistance of the vent incision, because the latter is made at the edge of the fixing point of the ring, where the characteristics of the metal subjected to stresses during the formation of the rivet are uncertain. This invention therefore seeks to provide an improved can end in which the opening is controlled even if the pressure which prevails within the closed can differs from that of the surrounding atmosphere, whilst preserving the ease of opening which can be found for example in a horseshoe-shape ring pull tab. According to the present invention, there is provided an easy open end comprising a central panel formed with a dispensing aperture defined by a first score line; a closure panel for closing the dispensing aperture and connected to the central panel around a major part by the first score line and around a remaining part by a bendable region; and a tab connected to the central panel and having a projection overlying the closure panel and a rear portion for lifting the tab away from the central panel; and in which either or both of the closure panel or the tab include a protrusion for engaging with the other, and the closure panel has a second score line associated with the protrusion whereby lifting of the tab initially severs this second score line. Preferably, the second or vent score line is located at least partially under the tab projection. The second score line may deviate away from the first or main score line to prevent tearing and to ensure that the vent score does not propagate into the main score. Initial severing and resultant venting or pressure equalisation of the container contents and atmosphere thus occurs under the tab. A product within the container is thus prevented from spurting out of the container over a user or drawing in contaminants. Internal pressure at which the closure panel will explode off is also greatly increased above the container burst pressure since a constant score residual thickness may be used and low score residuals avoided. The protrusion is usually located along the common longitudinal axis of the tab and panel but may alternatively be offset from this axis, or, if more than one protrusion is provided, these may be located symmetrically about this axis. The tab may be attached substantially in the centre of the central panel and the aperture may extend from the centre towards an outer edge of the central panel. The rear portion will thus extend from the centre towards an opposite point in the edge of the central panel. Preferably, the tab extends across the bendable region. It is preferred that the first score line be of uniform depth but it may alternatively vary in depth to improve ease of removal of the closure portion. Generally, this first aspect of the present invention would be preferably a beverage easy open end, which may comprise a ring pull as the tab. According to a second aspect of the present invention, there is provided an easy open end comprising a central panel for closing a dispensing aperture and connected to an outer portion of the end by a first score line; a tab connected to the central panel and having a projection overlying at least part of a protrusion in the central panel and a rear portion for lifting the tab away from the central and engaging the projection with the protrusion; and a second score line associated with the protrusion whereby initial severing of the central panel occurs along the second score line. Preferably, the second or vent score line is situated partially under the tab. The first or main score line is usually of uniform depth. This embodiment is particularly preferred for a food can. The tab may be, for example, a ring pull. In an alternative embodiment, there may be two protrusions underlying the tab projection. Each protrusion has an associated score line, which may undulate to prevent tearing. In a further aspect of the present invention, there is provided an easy open end comprising a central panel for closing a dispensing aperture and connected to an outer portion of the end by a first score line; a tab connected to the central panel, having a nose overlying a second score line in the central panel and a rear portion for lifting the tab away from the central panel and engaging the nose with the central panel in the vicinity of the first score line in order to trigger rupture of the first score; in which the tab, and/or a portion of the central panel which at least partly underlies the tab, is/are shaped such that the nose is situated at a first distance from the central panel adjacent to the first score line and that portion of the tab which is in the vicinity of the second score line is nearer to the central panel than is the nose, whereby initial severing of the central panel occurs along the second score line. Preferably, this shape comprises a protrusion on either or both of the tab or the central panel. This protrusion cna take many forms. This arrangement has the advantage that the force transmitted by the tab is first exerted on or adjacent to the second, or vent, score line, thus ensuring that the vent score opens before the nose begins to act on the central panel in the vicinity of the first, main, score. This arrangement thus ensures that pressure within the container has returned to atmospheric pressure before the main score begins to break. Preferred embodiments of easy open end will now be described, by way of example only, with reference to the drawings, in which: Figure 1 is a plan view of a first embodiment of easy open end, before a tab is fitted; Figure 2 is a fragmentary section of figure 1 along II-II with tab fitted; Figure 3 is the section of figure 2, with the tab raised to vented position; Figure 4 is the section of figure 2, with the tab raised to opened position; Figure 5a is an enlarged plan view of the region V in figure 1; Figure 5b is an enlarged cross section of score line; Figure 5c is a plot of score residuals; Figure 6 is a plan view of a second embodiment of easy open end; Figure 7 is the end of figure 6, prior to addition of the tab; 5 Figure 8 is an enlarged section of the end of figure 6 along line VIII-VIII; Figure 9 is a plan view of a third embodiment of easy open end; Figure 10 is the end of figure 9, prior to addition 10 of the tab; Figure 11 is an enlarged section of figure 9 along line XI-XI; Figure 12 is an underside perspective view of the tab of figure 9 and 11; 15 Figure 13 is an underside perspective view of an alternative form of tab; Figure 14 is a top perspective view of the tab of figure 13; Figure 15 is plan view of a fourth embodiment of easy 20 open end; Figure 16 is plan view of the end of figure 17, prior to addition of the tab; Figure 17 is an enlarged section of figure 16 along line XVII-XVII; 25 Figure 18 is a plan view of a fifth embodiment of easy open end, prior to addition of the tab; Figure 19 is a plan view of the embodiment of figure 18, with tab fitted; and Figure 20 is an enlarged section of the end of figure 30 18 along line XX-XX. In figure 1, an easy open end, typically a beverage can end, has a central panel 10 surrounded by an outer portion 20. A dispensing aperture is closed by an operable closure panel 30 connected to the central panel 35 by a bendable region 40 and a main score line 50. A tab 60 denoted by the dotted line will be joined to the central panel at 70 and a projecting part 65 of the tab overlies a part of the closure panel 30. A protrusion 80 in the closure panel 30 is arranged so as partially to underlie the tab 60. Its associated vent score line 90 is completely covered by projecting part 65. The positions of the protrusion 80 and its associated vent score line 90 under the tab 60 are better seen in figure 2. In a beverage can, the beverage may be pressurised so that pressure is exerted on the can end as indicated by the arrows. Figure 3 shows the tab in its vented position with projecting part 65 of the tab 60 bearing on protrusion 80. The can end has been broken along vent score line 90 to allow gas to be released from the can through vent 95 underneath projecting part 65. Further lifting of the tab brings it to its open position as shown in figure 4. Force on the closure portion 30 beyond that required to vent the can causes the main score line 50 to be broken progressively as shown at 55, until the closure portion 30 is only attached to the central panel 10 by bendable region 40. A drink or other product may then be dispensed from the can through the aperture thus formed. In figure 5a, the depth of the main score line 50 is uniform. The actual depth will vary according to material used but will usually be about 0.11mm (4.5 thou) for a 0.245mm thick aluminium can end, for example. In previous aluminium can ends, residual score (R in figure 5b) varied from 0.11mm (4.5 thou) at A to a hesitation point of about 0.15mm (6 thou) at B for venting, to 0.095mm (3.75 thou) at C where the forces required to break the score are greater due to the distance from the fulcrum formed by the projecting part 65 acting on the closure panel 50. A profile of residual depths for the end wall of the present invention and a prior art end wall is shown in figure 5c. It has surprisingly been found that the use of a separate vent score line 90 having a score residual less than that of main score line 50 enables the score line 50 to be of constant depth. This greatly reduces tooling costs and avoids the requirement for a hesitation spot, that is a point at which the score line changes depth. This in turn allows a wider latitude in manufacturing tolerances. It has also been found that a constant depth score line 50 can have reduced score residuals, which reduces opening loads. It is important, however, that the score residual of main score line 50 be greater than that of vent score line 90 so that venting first occurs along score line 90. It has also been found that a constant depth score line 50 can have reduced score residuals, which reduces opening loads. It is important, however, that the score residual of main score line 50 be greater than that of vent score line 90 so that venting first occurs along score line 90. Referring now to figures 6 to 8, a food can "full-aperture" end 100 of the easy open type is shown. In this embodiment, a main score line 150 spans the peripherary of the can end. The edge of this end, which here is circular, is provided with a seaming bead 110 for fixing the end to a can body. The can body is not shown here but would be of corresponding shape and dimensions. In order to allow an easy opening, without the aid of a separate tool, the can end comprises a main score line 150 around the peripherary of the end which is circular and concentric to the bead 110 in the vicinity of the bead, and a ring pull tab 160. In this embodiment, it is clear that there is no bendable region as in the beverage can end of figures 1 to 4 above, but the main score 150 allows a total opening of the can. The tab 160, which is of well-known general form, is provided with a nose 165 and is fixed by rivetting to the central oanel 130 of the end. The tab is fixed in such a way that the nose 165 can act upon the central panel 130 in the vicinity of the main score 150 in order to initiate opening of this score. A rivet head 170 is formed by a stamped piece 171 of the central panel 130. This stamped piece engages a hole 162 in the tab and is staked. The tab 160 also comprises a horseshoe shape 161 which encircles the rivet head in a known manner so as to facilitate a 90 degree pivoting of the ring away from the central panel at the moment of opening. A further score line 190, or vent score, is made in the central panel 130, under the tab. The tab 160 and/or the central panel 130 of the end is/are shaped so that the nose 165 is situated at a distance c from the central panel, opposite the main score 150. Another part of the tab which is in the vicinity of the vent score 190 is nearer to the central panel than is the nose, and may even be in contact with the nose. As is clearly seen in figure 8, this configuration is obtained by a protrusion 180 in the central panel 130 which almost contacts the inside face of the ring. In the examples of figure 6 to 8, the can end has a single vent score 190 which is arranged transversely with regard to the axis of symmetry (consistent with the cross-section of figure 8) of the tab. This vent score is at a predetermined distance from the fixing point of the tab, that is from the stamped piece 171. By providing a vent score relatively distant from the stamped piece, and therefore from the cold-forged rivet head 170, the vent score remains in a position in which the metal is not modified during the formation of the rivet. This positioning thus ensures that the characteristics of the vent score are unchanged at the time of fixing the tab. The protrusion 180 made in the central panel 130 is approximately circular in the plane of the panel and has a rounded profile. The vent score, on the other hand, has a curved part which is situated near to the edge of this protrusion (see figure 7). In order to allow the ring pull to be fixed in spite of the obstruction of the boss, the tab has two dishes of different depths which are concentric to the point of fixing of the tab to the central panel, that is concentric to a hole 162 around which the rivet will be formed. The protrusion 180 is situated below the outer dish 163 which is the least deep, while the rivetting is carried out at the centre of the deeper inner dish 164. When the ring pull is raised, the vent score 190 is first acted on due to the protrusion 180. The main score, on the other hand, is not subjected to any stress due to the distance e which separates the nose from the central panel. This arrangement therefore guarantees that the vent score is broken before the main score, so that the inside of the can is at atmospheric pressure before the main score starts to break. In figures 9 to 12, the structural components similar to those of figures 6 to 8 have the same reference numerals and will not be described further herein. In this embodiment, the protrusion is made in the ring pull tab 160. This tab comprises two concentric dishes 163, 164 having two different depths as described above with the protrusion made in the outer dish which is less deep. The protrusion 180 almost contacts the central panel 130 of the end, in the vicinity of the vent score 190. In this embodiment, two further protrusions 182 have been formed in the outer dish of the ring pull 160. These two protrusions are at 120 degrees from the protrusion 180 and enable a better application of the tab against the central panel to be achieved, thus facilitating the formation of the rivet in the central panel. Figures 13 and 14 illustrate a further embodiment of the ring pull tab, in which the tab has only a single dish 165 and the boss is in the form of a bar 166 which extends parallel to the axis of symmetry of the tab. This small bar is generally defined by the base of the single dish 165 and has itself two dish sectors 167 which extend over a 90 degree sector on either side of the bar 166. When the tab is fixed to the central panel of the easy open end, the tab is applied onto the panel by all the part of the bottom of the dish which has not been drawn and the bar 166 is in contact with the wall over the whole radial distance which extends between the panel and the vent score 190. In the embodiment of figure 15 to 17, two protrusions and two associated vent scores have been provided in the central panel of the easy open end. The two protrusions are provided one on either side of the axis of symmetry of the ring pull tab, opposite an outer curled edge of the tab (see figure 15). As in the previous embodiments, the nose is placed at a distance from the central panel of the end such that, when the tab is raised away from the central panel, the two vent scores are opened prior to any break in the main incision. The raising of the tab exerts a downward force on the two protrusions as the lower curled edge of the tab contacts these protrusions. As in the embodiment of figure 7, each vent score has a curved portion which lies nearest to its associated protrusion. In this embodiment, the tab has only a single dish at the centre of which the fixing rivet is provided. Figures 18 to 20 comprise a similar embodiment to that of figures 15 to 17, in which the invention has again been applied to a full-aperture end such as might commonly be used for closing a food can. In this embodiment, as with the other full aperture embodiments of figures 6 to 17, the whole central panel forms the closure portion 130 and score line 150 is continuous around the closure portion, surrounded by outer portion 120. The container end thus opens fully, ie it is full aperture spanning the outer portion 120 of the easy open end. Food cans are often filled with hot food and closed so that on cooling a large vacuum is drawn which on venting causes the end to implode. The embodiments of figures 6 to 20 overcome this problem by opening one or more vent scores prior to the 5 opening of the main full aperture score. In figures 18 to 20 two protrusions 180 are set back from score line 150 under the edge of the tab or ring pull 160. The tab is attached to the closure portion 130 at 170, usually by a rivet. Two protrusions are generally 10 employed to balance the forces required for removal. Undulating score lines 190 are located partially under the ring pull 160 and deviate away from the score line 150 to prevent tearing or propagating into score line 150. Their location is less important than with beverage cans since 15 there is a vacuum within the food can which tends to cause external matter such as dust to enter the can rather than for food to spurt out. Thus it is not as important for venting to occur underneath the tab as it is for beverage cans, where drink would otherwise spurt out onto the user. 20 Clearly, the positioning of the vent scores underneath the tab is preferred, however, where there is any risk of a positive pressure within the can, that is an overpressure, which could conceivably occur for either beverage or food cans. 25 Protrusions 180 are concentric to score line 150 and on the same pitch centre diameter, symmetrically about the longitudinal axis of the tab 160. One or both of the associated score lines 190 is/are ruptured to provide venting in a similar manner to all of the previously 30 described embodiments. As with the other embodiments, this venting occurs prior to the breaking of the main score line 150. The score line 150 is only broken when the tab is raised further. Score line 150 is broken by pressure of projecting part, or nose 165 of ring pull tab 35 160. It will be appreciated that the invention has been 44 -13- described above by way of example only and that changes may be made without departing from the scope of the invention as defined by the claims.

Claims: CLAIMS 1. An easy open end comprising a central panel formed with a dispensing aperture defined by a first score line; a closure panel for closing the dispensing aperture and connected to the central panel around a major part by the first score line and around a remaining part by a bendable region; and a tab connected to the central panel and having a projection overlying the closure panel and a rear portion for lifting the tab away from the central panel; and in which either or both of the closure panel or the tab include a protrusion for engaging with the other, and the closure panel has a second score line associated with the protrusion whereby lifting of the tab initially severs this second score line. 2. An easy open end comprising a central panel for closing a dispensing aperture and connected to an outer portion of the end by a first score line; a tab connected to the central panel, having a nose overlying a second score line in the central panel and a rear portion for lifting the tab away from the central panel and engaging the nose with the central panel in the vicinity of the first score line in order to trigger rupture of the first score line; in which the tab, and/or a portion of the central panel which at least partly underlies the tab, is/are shaped such that the nose is situated at a first distance from the central panel adjacent to the first score line and that portion of the tab which is in the vicinity of the second score line is nearer to the central panel than is the nose, whereby initial severing of the central panel occurs along the second score line. 3. An easy open end according to claim 2, in which the shape comprises a protrusion on either or both of the tab or the central panel. 4. An easy open end according to claim 2 or claim 3, in which the tab comprises a ring having two dishes of two different depths, concentric to the point of connection of the ring to the central panel, the outer dish being less deep than the inner dish. 5. An easy open end according to claim 4, in which the shape comprises a protrusion in the outer dish. 6. An easy open end according to claim 5, in which the protrusion comprises a bar. 7. An easy open end according to claim 4, in which the shape comprises at least one protrusion in the central panel below the outer dish. 8. An easy open end comprising a central panel for closing a dispensing aperture and connected to an outer portion of the end by a first score line; a tab connected to the central panel and having a projection overlying at least part of a protrusion in the central panel and a rear portion for lifting the tab away from the central panel and engaging the projection with the protrusion; and a second score line associated with the protrusion whereby initial severing of the central panel occurs along the second score line. 9. An easy open end according to any one of claims 1 to 8, in which the first score line is of uniform depth. 10. An easy open end according to any one of claims 1 to 9, in which the second score line deviates away from the first score line.

Inventors: CARPIER GERARD, WHITE DAVID MARTYN, CARPIER, GERARD, WHITE, DAVID, MARTYN
Applicants: CARNAUDMETALBOX SA, CARPIER GERARD, WHITE DAVID MARTYN, CARPIER, GERARD, WHITE, DAVID, MARTYN
Application year: 1993
Main classification: B65D17
IPC codes: B65D17