Tearable metal cover for cans

Abstract

 Easy-opening closure for the sheet metal lids (3) secured by seaming to a container like can (1) of the type including on the lid (3) a circular groove (5) of U-shaped section, with an outboard wall (10) and a bottom (12) on which a line of weakening (8) is placed; the said closure moreover includes a pull tab (9) connected to the lid by means of a rivet (7) positioned such that the point of the pull tab is overhanging the groove; the manual lifting and rotation of the tab cause the rotation of its tip towards the bottom to touch, with the extremity of the tip (9b) near the score line (8), the fillet between the bottom and the internal wall (11) of the groove (5) and causing by levering the breakage of the aforesaid score line (8) and the opening of the can; the ring-tab can also be provided with the point bendt towards the bottom of the groove.

Description

[0001] The present invention relates to a closure for a lid or end cover made of thin sheet metal and secured as by a seam to a container body for cans and the like or for a bottom of a drawn metal container, of the type so-called two pieces.

[0002] The aforesaid closure includes on the lid or on the bottom a circular groove and a circular line of weakening placed at the bottom of the groove and a ring-pull tab with point manufactured flat or with its point bended downwards while the remainder of it is sustantially constructively similar to the types used for the conventional easy-opening closures; the said tab is connected to the lid or bottom by means of a rivet normally formed from a protrusion obtained by drawing on the same lid or bottom then hammered on the tongue so as to have that the point faces the seam and overhangs the groove.

[0003] The ring-tab may also be fixed without the rivet using on the contrary some glue or hot melt adhesive or varnish suitably applied; in this case the tab is removable and free positionned so it will be used as opening movable tool by levering in the groove.

[0004] In the embodiment with the rivetted tab the opening is made with a finger by lifting the tab upwards so its point presses the fillet between bottom and internal wall near the line of weakening, a further tab rotation towards the outside makes possible to produce a leverage effect and to break the score line, so obtaining, by pulling off, the tearing of the metal portion included inside the line of weakening; the seam may be also used as a leverage fulcrum.

[0005] The option in wich the tab has the point very bended downwards, the opening is obtained similarly to the conventional closures, this means that the tab touches almost immediately the metal near the score line.

[0006] On the contrary in the solution with the tab connected by glue, it ts predisposed that the tab is removable and used like tool for levering one or more times inside the groove so breaking the line of weakening.

[0007] The cans with ring tab are from time of large circulation, but all these conventional closures are charactherized by the fact that are realized only on lids and not on the bottom of drawn cans, but above all, and basic element of the present invention, for that known until today, there have been no indication of manufacture of cans characterized by the contemporaneous combined presence of an evident circular groove at the bottom of wich there is the line of weakening, as well as of a ring-tab overhanging the groove as well as of the tab having the point bended downwards.

[0008] In said conventional closures the line of weakening, the point, the remainder of the tab and the rivet, lie on a common plane, that of the lid, touching and/or skimming the plate, so the tearing of the score line is obtained with a limited tab lifting from its horizontal plane in this way exerting a pressure only vertical on the metal with the tab point, in the proximity of the line of weakening.

[0009] These closures although very much spreaded are considered rather hard to open particularly if manufactured in steel while that in aluminum are less hard but their cost is very much higher; they are hard to open as to resist against mechanical shocks for the lid expansion due to the sterilization and manufacturing operations, they have to be made leaving after the incision a rather hig residual metal.

[0010] These conventional closures are also potentially dangerous as after the opening a flat portion of free metal, very sharp and dangerous, remains in the hand; other options however are possible in order to avoid this inconvenient, they consist of a double fold of the metal near the incision, but this operation causes significant extra cost.

[0011] These conventional closures are also characterized by the fact that as the ring-tab lifting engages immediately the metal near the incision, the insertion of the finger under the tab and its lifting became often a problem for the final user, the consumer .

[0012] It should also be noted that in these customary closures sometimes the tab comes off from the rivet without having beforehand obtained the opening.

[0013] The basic problem for this invention is to create an easy opening closure of the type specified with structural and functional features such as to be easy to open and not dangerous for the consumer, also free from accidental opening due to mecanical knocks during filling,sterilisation and handling, as well as producible at a lower cost.

[0014] This problem is resolved by an easy opening closure of the specified type, wich is characterized by the fact that the groove has an U or V-shaped section, with an inboard wall,a bottom and an outboard wall placed in the proximity of the seam, and then the line of weakening is provided on the bottom the groove and that the ring tab is placed horizzontally on the lid and connected to it in conventional way, that is to say with a rivet,and the point of the tab overhangs the groove until to nearly touch the external wall and that the point of the tab may be rectilinear or bended downwards;in the end the ring tab may be linked to the lid or to the bottom by means of a point of glue, or adhesive or varnish so used as an opening tool so having not limited construction features.

[0015] Further specifications and advantages of the easy opening lid according to the present invention will become more clearly apparent from the following description of a preferred embodiment thereof given by way of illustration and not of limitation with reference to the accompanyng drawings where

Figure 1 is a perspective view of a can incorporating a closure according to the invention,characterized by a substantially rectilinear tab and U-shaped groove,this is the preferred embodiment.

Figure 2 is a sectional view drawn at enlarged scale of the closure shown in Fig.1 ;and

Figure 3 is a sectional view at enlarged scale of a significative variant to the embodiment of Fig.1, that is to say substantially having the point tab very bended towards the bottom of the groove.

[0016] With reference to the accompanyng drawing views generally indicated at 1 is a can,which comprises a container-body 2 ,in this case circular shaped,with a diameter of 73 mm. and axis X-X and a lid 3 ,or bottom of drawn can, of axis Z-Z, both in steel sheet having thickness chosen between 0.17 and 0.24mm.

[0017] The lid 3 is secured,by means of a circular seam 4 with height of 2.5 mm. approx. measured from a top rim 4a, to the body 2.

[0018] In the case of a drawn can,or two pieces, the seam does not exist so the can bottom practically will simulate moreless exactly the shape of the lid with the closure.

[0019] The metal plate instead of beeing in steel can be in aluminum of a suitable thickness as quite normal for a tecnicien in this field.

[0020] In correspondance to the lid 3 the can 1 is provided with an easy-opening closure which comprises a circular groove 5 of axis X-X and at its bottom a line of weakening 8 also of axis X-X.

[0021] The groove 5 have to be engaged by a ring tab 9 ,provided with a point 9b ;the tab according to the adopted embodiment can be substantially rectilinear ,as in Fig.2, or with its point very bended downwards, as in Fig. 3 ;the said tab has to be connected to the lid 3 by means of a rivet 7 ,wich is a protrusion emerging from the plane of the lid, on wich the flat tongue 9a of the tab is strung as the tongue is provided with a hole in its final part; the said protrusion have to be hammered on the tongue,which is not specifically required for the variant of Fig. 3, so forming the rivet 7.

[0022] In the embodiment of Fig. 2 the tab 9 ,simply but representatively drawn,is applied such that its point 9b overhangs the groove 5 and faces the external wall 10,so when said ring-tab is lifted to a vertical position and then partially rotated towar ds the outside it engages the groove 5 and its point 9b presses in the bottom of the groove 5 against the base 11 a of the internal wall 11.

[0023] The horizontal axis of the tab passes through the center of the lid.

[0024] In the embodiment shown in Fig. 3, as the point of the tab 9 is bended,the tip of it is already initially positioned to touch or approaches the bottom 12 of the groove 5 near the score line,so for the breakage of said line only a limitated lifting of the tab 9 will be sufficient.

[0025] The groove 5 has a substantially U-shaped cross- sectional configuration as per Fig. 2 ,or V-shaped as per Fig. 3 ,with an annular inboard wall 11,a bottom 12 and an external annular wall 10.

[0026] Referring to the description of Fig. 2 ,wich will be now shown in detail,there is an internal wall 11 wich is set at a short limited rake angle S1 to be selected from the -5 to + 15 range and its height h1 is chosen between 1 mm and 4mm.

[0027] The outboard wall 10 of the groove has an height h 2 chosen between 4 mm. and 6.5 mm. and it is characterised by a rake angle S chosen between 2 ° and 16°.

[0028] The bottom 12 of the groove 5 is substantially flat and has width L, measured between verticals at the points in wich the bottom 12 joins the fillets arc shaped placed between the bottom 12 and the inboard wall 11 and the outboard 10, said width dimension lying within the range of 0.2 to 2.5 mm.

[0029] Between the internal wall 11 and the bottom 12 is formed a fillet 11 a with circular arc of predetermined limited radius R1 chosen between 0.25 and 0.6 mm.; it should also be noted that between the external wall 10 and the bottom 12 there is a joint 10a with predetermined radius R2 chosen between 0.4 and 2.5 mm.

[0030] The line of weakening 8 , wich is embodied by a nick formed in the sheet metal starting from its outer face, is placed in correspondence to the bottom 12 of the groove and its diameter is chosen so that it is as near as possible to the inboard wall 11 , that is to say at a predetermined distance from the tangency point between the bottom 12 and the fillet 11 a wich joins the bottom 12 with the internal wall 11, said distance lying within the range of 0.003 to 0.3 mm.

[0031] Said line can be circularly not complete, that is to say the nick is interrupted for a portion positioned in diametral opposition to the point of the ring-tab, this portion without nick permits to the tearing metal portion inside the nick to remain connected to the can after the opening; the height of the internal wall will be, if is the case, reduced in order to facilitate the vertical lifting of the tearing metal portion inside the line of weakening,making pin in its portion without nick,while the two tips of the nick are curled towards the outside.

[0032] It should be noted that the score line 8 is embodied by a V-shaped nick having its flared sides with a more acute angle if compared with the conventional ring-tab closures.

[0033] It should be noted that the tab 9, as regards its production, falls in the ambit of the various conventional types, that is to say that sustantially it consists of a perimetral part 9d semi-tubular-shaped of width L 1 chosen between 0.8 mm. and 1.5 mm., which produces the rigidity, and of an internal plane appendix 9a, the tongue, made of single flat metal plate, wich has a circular hole at its final part in wich the protrusion emerging from the plane of the lid 3 is designed to be strung, so after the rehammering this is the fixing rivet 7 wich secures the tongue on the plane of the lid and therefore the ring tab.

[0034] It should be noted that the tongue 9a has a lenght d,measured in practice between the center of the fixing hole 13 and a perpendicular passing through the two points where the tongue finishes by joining the remaining of the tab,equal to the distance between the center of the rivet 7 and a parallel to the internal wall 11 passing through the median point of the joint 11 a between the bottom and the internal wall,the said critical lenght of the tongue 9a ,chosen between 6mm and 10mm according to the rivet position,allows the lifting of the tab without stress in the direction of the arrow F until 90 °, that is to say from the horizontal position to a nearly vertical and further ,while the two curled tips 9c joining the tongue 9a with the remaining part of the tab 9,wich is the rigid portion 9d, became then pin point as well as the fulcrum of the leverage obtained by going on with the rotation F1 of the tab 9 towards the outside,the point of the tab wich have rotated downwards in the direction of the arrow G,is destined to lean with suitable pressure on the joint 11 a between the bottom and the internal wall of the groove, and so exerting powerfully on this joint a suitable force having nearly horizontal direction.

[0035] To open the can it is sufficient, by the point of the finger, to lift the tab upwards and to rotate it of about 90 _° from the horizontal position to one substantially vertical, practically as far as the tip of the point 9b, wich is originally near the point 10b and that may be partially bended downwards, goes in touch with the fillet 11 a at the bottom;a leverage is so obtained the fulcrum of wich is at 9c;now by going on towards the outside the said rotation followed by a light pressure makes possible that an horizontal force is exerted substantially directed to the joint 11 a so by virtue of the reduced value of the radius R1,it acts powerfully on the nick 8; this markedly local force overcomes the resistance offered by the residual bridge 8a and tears it open.

[0036] The partial breakage of the line of weakening 8 is so obtained and also the bending G1 of a portion of the wall 11 towards the inside.

[0037] The complete opening of the can and consequently the total tearing of the score line will be obtained by a further tab rotation F1 towards the outside leaning against the seam,possible second leverage point,and then lifting altoghether vertically, by means of the tab itself the metal portion wich lies inboard of the line of weakening. should be noted that the presence of the groove and the position of the tab give the lid a good mecanical functionality,it can so well compensate the effects of the thermic sterilization process,the filling and opening under hig level vacuum ,the knocks due to handling and transport ; also it is possible to make use, for the lid manufacturing, of metal plate at least ten per cent thinner than the conventional ring-pull closures so the container lid according to the present invention can be mass produced at a lower cost,wich is no small advantage with an article wich is intended for disposal after use.

[0038] It should be noted that the lid according to the invention has shown enhanced safety features in view of that it is virtually impossible to hurt or cut oneself on the portion of the lid internal to the nick,once removed,as its free edge is at a very short distance from the inside wall 11 ,wich acts as a protection.

[0039] A further important advantage consist in the fact that in the present lid the initial lifting of the tab, by the tip of a finger,is very much easier if compared to the conventional closures with ring-tab as,while in these ones the point of the ring must engage immediately with force the plane of the lid near the score line so obstructing the easy lifting and the insert of the finger under the tab,in the embodiment with flat ring tab and U-shaped section according to this invention the lifting is easy because only the neglectable resistance to the bending of the tongue will be in contrast with said lifting,if necessary said tongue is provided with a limitated longitudinal central bead in order to make it more stiff.

[0040] The easy-opening lid according to the present invention avoids a typical problem of some ring pull tab closures, that is to say the fact that the tab comes unhooked from the rivet without the breakage of the line of weakening,with further problems relevant to find and to use a suitable can opener ,to open the can.

[0041] The present invention solves this problem as the tongue exert on the rivet a substantially horizontal traction during the first breaking stage,this effectively prevents the fact that the metal plate of the tongue could comes out of said rivet, and if it happens during the vertical final lifting,the opening can be easily completed by using a kitchen utensil first of all a spoon but it is a quite unlikely fact.

[0042] It should finally noted that by virtue of the aforesaid facility to lift the pull tab,keeping the embodiment of Fig. 2 in wich it is substantially flat,it should be useful to prepare a limitated protrusion emerging from the lid, having an height shorter than the thikness of the tab,wich will be so partially perimetrally surrounded by this protrusion to avoid the possible fact of the hooking and stuc- king of the tabs between themselves and with the rim of the seam during the sterilization processes or other accidental lifting.

[0043] If this protrusion is predisposed the tab lifting will be well obtained by inserting the finger inside its final curved portion rather than from the outside;moreover to facilitate this unusual lifting a limitated circular concave protrusion can be predisposed,that is to say directed towards the inside of the can and made at the center of the lid,having diameter ,measured on the plane of the lid,equal to the final internal width of the tab and depth in its central point chosen between 1 mm and 3.5mm.

[0044] The detailed description of the solution of Fig. 3 now will follow,wich distinguishes itself as the tab 9 instead of to be manufactured substantially flat has the point very bended towards the bottom, beginning from a point placed at the top rim of the internal wall,so its tip approaches the bottoms. The horizontal rake angle of the point is chosen between 35 _° and 90 _° .

[0045] The groove has U or V-shaped section and when the point of the tab is around the maximum bending value the height of the internal wall is lower at least of 0.5mm if compared to the bended portion of the point,said height is chosen between 0.5 and 1.5mm,this is to facilitate the initial lifting of the tab before that the tip of its point perforate the bottom of the groove near the score line.

[0046] The tab manufacturing is different from the former solution in wich the presence of a central folding free tongue of predetermined lenght was essential,in fact it remains in the limits of the various conventional types , a part from the point bended downwards,the bended portion of wich has lenght chosen between 0.7 and 2.8mm.

[0047] Also the can opening will be like in the conventional ring pull easy open lids.

[0048] Moreover this embodiment offers the advantage to permit the use of a thinner plate,to show enhanced safety features and to allow an easier opening.

[0049] It should be noted that, particularly in the embodiment of Fig. 2 the seaming chuck M not always can touch the bottom of the groove,so that it may finish in correspondance of the tab point and consequently for blocking the lid in seaming said chuck should also press on the plane of the lid as well as on the tab and/or suitable prominences.

Claims

1. A closure for a lid or end cover made of thin sheet metal secured by seaming to a container body like can,beeing of the type wich comprises formed on the lid a circular groove of substantially U-shaped section with an outboard wall located in the proximity of the seam,an inboard wall and a bottom on wich a line of weakening is provided, said closure characterized by the fact that it also includes a metal ring pull tab with relative point appendage, connected to the lid by means of a rivet, positioned such that the point of the ring-tab overhangs the groove and that the manual lifting and rotation of said tab cause as well the rotation of its point towards the bottom as far as the extremity of the point engages,by levering, the fillet placed between the bottom and the inboard wall that is to say near the line of weakening so causing the initial breakage of the said line and, by levering on the seam and further pulling up by means of the tab, the complete opening of the can.

2. A closure according to claim 1 characterized in that the ring-tab, wich is substantially flat and horizzontally connected to the plane of the lid by means of a conventional rivet or by welding, is positioned such that its horizontal axis passes through the center of the lid and its point overhangs the groove in the direction of the external wall beginning from the top rim of the inside wall,said point leans out for a predetermined chosen portion of lenght equal to the height of the inside wall measured from the midpoint of the fillet between bottom and inside wall and the top rim of the inside wall so obtaining that at the opening the point of the tab,after the lifting and rotation of said tab as far as a substantially vertical position,engages a median point of the fillet between bottom and inside wall;the point of the tab can be partly bended downwards.

3. A closure according to Claim 2 characterized in that the tab is substantially made of a semi-tubular rigid perimetric part wich finishes point- shaped and in the interior of wich there is a tongue wich begins in the point area but directed towards the center of the ring-tab and of the lid,said tongue is also provided with a hole for fixing the tab to the rivet and is easily folding beeing flat,it has lenght measured between the center of the fixing hole and the two fillets of circular arc shape wich join its sides with the remainder of the tab and wich forms pin and fulcrum point for the leverage in the opening, equal to the distance between the center of the rivet and an ideal line,parallel to the inboard wall,passing through the median point of the fillet between bottom and inboard wall of the groove.

4. A closure according to Claim 1 characterized in that the outboard wall has an height in the range of 4 to 6.5mm measured between the top rim of the seam and the bottom of the groove and rake angle chosen between 2 _° and 16_°.

5. A closure according to Claim 4 characterized in that the inboard wall has an height in the range of 1 to 4mm,measured between the midpoint of the fillet between bottom and inside wall and the top rim of said inside wall in wich it joins the horizontal plane of the lid,said wall has also rake angle chosen limited between -5 and +15_°.

6. A closure according to Claim 5 characterized in that the bottom of the groove is substantially flat and has width chosen between 0.2 and 2.5 mm. and then it joins the outboard and the inboard walls by means of fillets circular arc shaped having limited radius value chosen respectively in the range of 0.4 to 2.5mm and 0.25 to 0.6mm.

7. A closure according to Claim 1 characterized in that on the bottom of the groove a line of weakening is provided, wich is embodied by a substantially V-shaped nick formed in the sheet metal lid starting from its external face,said line placed at a predetermined limited distance from the tangency point between the plane bottom and the fillet circular arc shaped joining bottom and inside wall chosen between 0.003 and 0.30 mm.

8. A closure according to Claim 1 characterized in that the ring-tab has, alternatively, the tip of its point very much bended towards the bottom of the groove, starting from a point placed in correspondance to the top rim of the inside wall, moreover it has horizontal rake angle in the range of 35 _° to 90 _° measured between an ideal line passing through the extremity of said tip and through the point of the lower side of the tab in wich the tab begings to bend downwards and a parallel to the horizontal axis also passing through said initial bending point, said bended portion has a lenght chosen between 0.7 and 2.8 mm.

9. A closure according to Claim 8 characterized in that in the case of the ring-tab having the terminal portion of its point very bended downwards ,that is to say with horizontal rake angle greater than 35 _° ,the said portion has its own lowest extremity very close to the bottom of the groove and the height of the inboard wall is lower, at least of 0.5 mm ,than the lenght of aforesaid bended portion,said height have to be chosen limited in the range of 0.5 to 1.5mm.

10. A closure according to Claim 1 characterized in that the tongue wich secures the pull tab to the lid has a limitated stiffening bead placed lenghtwise at its own center at the position in wich it will be bended,in order to create a light obstacle against accidental easy lifting of the tab.

11. A closure according to Claim 1 characterized in that the line of weakening is circularly not complete ,that is to say having a portion of its lenght chosen between 0.1 and 12mm lacking of nick, said portion positionned such that it is in diametral opposition to the point of the tab, the nick has its two tips circular arc shaped directed to the outside.

12. A closure according to Claim 1 characterized in that the tab is free positionned in a not definitive manner by means of a drop of glue or with tin or with varnish or with flexible material also autoadhesive like paper or other film, so it can be removed and used like an utensil for levering in the groove; in this case the groove have to be rather narrow.

13. A closure according to previous Claims characterized in that the said closure is applied on the bottom of a drawn container of the type so called two pieces.

Drawing