US 3744669 A
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United States Patent 1 [111 3,744,669 Cospen et al. July 10, 1973 1 TEAR TAB FOR EASY OPENING METAL  References Cited CANS UNITED STATES PATENTS  Inventors: Jean Cospen, Cachan; Bernard 3,295,715 1/1967 Pugh 220/902 7 Baumann Paris 83 of France LlpSkC n 3,186,582 6/1965 Henchert 220/54  Asslgneez CEBAL GP, Paris, France 3,404,799 10/ 1968 McNamara 220/54 F 14  fled Apr 1971 Primary Examiner-George T. Hall  Appl. No.: 133,819 Attorney-McDougall, Hersh & Scott  Foreign Application Priority Data  ABSTRACT A r 15 1970 France 7013593 A tear tab for easy opening metal cans in which the tab P consists of a rigid or semi-rigid plastic material formed  U S Cl 220/54 of two parts joined through an opening in the top wall  hhscll. 17/20 of the can near the tear line with the two parts being  Fieldot eiiicii fi2::121556132 48 53 27 Jbined sealing damn and'mming rigid connection with the cover to seal the opening.
11 Claims,4 Drawing Figures TEAR TAB FOR EASY OPENING METAL CANS This invention relates to metal containers having a tear tab of plastic material for easy opening.
Easy opening metal tabs for cans and containers of various types have acquired considerable significance in the packaging industry. The most widely used method comprises a grip member fixed to part of the cover which is defined by a tear line. A pulling force applied to the grip enables the detachable surface to be removed. In general, the gripping portion is in the form of a metal tab joined to the cover by a rivet which is integral with, i.e., is made of the same material as, the cover by repeated deformation.
This method of attachment involves a number of problems due to the considerable stresses which the metal undergoes during deformation of the rivet. For this reason, the covers are made of sheets of a rather expensive special purpose alloy. The machines used are expensive, complicated and cumbersome.
In addition, the grip has to be fixed a certain distance from the tear line so as not to reduce the thickness of the metal at the point where it is most vulnerable, i.e., along the tear line. This restriction prevents the formation of a genuinely easy opening closure.
The reason for this is that if the point at which the rivet is fixed is situated a certain distance from the tear line, the ratio of the two lever arms on either side of this point becomes less favorable and the force required to achieve the initial breakage of the tear line becomes greater, sometimes resulting in the rivet being torn away.
If the rivet is able to withstand the initial force, the crease that is formed during opening beyond the fixation point passes through that zone wherein the metal has undergone the greatest stress and the rivet is again in danger of being torn away during this latter opening stage.
Replacement of the integral rivet with a detachable rivet creates sealing problems which have not been resolved. The use of a plastic tab, part of which is fixed by snap engagement in the opening of the cover, has not provided a solution to the problem, especially for containers subject to internal pressure, such as with beverages containing gases or cans which have to be sterilized by heat treatment.
In all these instances, biological hermeticity is questionable.
On the other hand, these plastic tabs, which, to enable them to be engaged, are necessarily made of a relatively flexible material, can only be used for tear systems of the type which do not have any initial perforation of the line and cannot make use of this perforation to facilitate opening of the can, as in the case of metal tabs.
It is an object of this invention to overcome these disadvantages and to provide a tab of a plastic material which can be hermeticallyfixed to the cover formed of any metal or alloy without subjecting the metal to any appreciable stress in the proximity of the tear line, and with which it is impossible to cause initial breakage of this line so that the continuation of tear easily takes place.
These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, embodiments of the invention are shown in the accompanying drawings in which FIG. 1 is a sectional elevational view through a portion of the top wall of the container showing the grips embodying the features of this invention in their relative position prior to being joined;
FIG. 2 is a sectional elevational view of the element shown in FIG. 1 with the grip fixed to the top wall at the initial breakage of the tear line;
FIG. 3 is a plan view taken from the bottom side showing a modification of the two part tab embodying the features of this invention; and FIG. 4 is a sectional view through the tab shown in FIG. 3 in position of use.
Accordingly, the invention relates to a device for opening a can cover provided wih a tear line and in which the device comprises a grip formed ofa rigid or semi-rigid plastic material, one end of which is used to break the tear line and which consists of two parts joined through an opening in the cover in the proximity of the tear line, with the two parts hermetically sealing the opening and forming a rigid connection with the cover.
Attachment is preferably carried out by placing the two parts of the grip under internal mechanical tension, followed by ultrasonic heating and then by. a second internal mechanical stressing.
The distance between the opening in the cover and the tear line is selected so that the lower part of the grip, which is situated within the container, is at least tangential to the tear line. However, the edge can extend beyond the tear line.
i That end of the tab which is actually gripped may be of lesser thickness than the end portion which is joined to the cover whereby the thinner section becomes more flexible. The same result can be obtained by forming a hinge in the tab between the gripping zone and the fixing zone.
To prevent the grip from turning in the opening, the opening may be given a non-circular contour. In such instance, the upper portion of the grip is provided on its lower surface with a projection which corresponds in shape to the opening into which it penetrates.
For identification or publicity purposes, the tab can be readily colored or provided with distinctive indicia.
Referring now to the drawings, FIG. 1 diagrammatically illustrates the manner of fixing a plastic grip embodying the features of this inventionto a metal cover. The cover 1 is formed with a tear line 2 near the opening 3 and in which the opening is surrounded by a flange 4. The grip consists of a plastic material, such as a semirigid polypropylene. It is formed in two parts,
namely an upper part 5 which is placed on the top side of the cover and which includes-the actual'tab 6 and a projection 7 which extends downwardly from the underside in fitting relation through the opening 3 in the cover. The projection 7 is provided in its periphery with a screw thread 8 which cooperates with the screw threads 9 formed in the wall portion about the opening in the lower part 10 of the grip. The latter acts as a screw nut'which is dimensioned so that its outer edge will be tangible to a plane perpendicular to the cover extending through the tear line. In other words, the outer edge is preferably positioned immediately below the tear line 2. In order to obtain a hermetic seal between the two parts of the grip and the cover, an ultrasonic heating process is used in conjunction with internal mechanical stressing. This process is described in the copending application Ser. No. 1l0,964, filed Jan.
29, 1971, entitled Method and Apparatus for Hermetically Sealing a Rigid Panel.
After the tab has been fixed by this process, the three elements together form an assembly which will not be deformed in the zone where initial breakage of the tear line occurs. There can be no sliding between the different parts and, within a well defined perimeter, the elasticity of the metal is reduced to a minimum so that the force exerted by lifting of the tab 6 will be transmitted almost entirely towards the rupture zone by a type of lever action.
Since the short arm of this lever, between the fixing of the tab and the tear line, is small by comparison to the arm to which the lifting force is applied, the force applied at the former point is markedly increased and the initial rupture easily takes place, as illustrated in FIG. 2.
During breakage, the front portion of the tab rocks about a stud 11 situated behind the lower part 10 of the grip, i.e., at a distance from the fixing point equal to the distance of this point from the tear line. The crease which is formed level with the stud 11 represents the cord of an initial rupture arc, the height of which is substantially equal to the diameter of the lower part 10 of the grip.
The elongation of the height of this arc in relation to conventional systems results in a longer initial breakage, the ends of the are formed by this rupture immediately exceeding the cord which passes through the center of the fixing point of the grip. Any pull exerted on the tab tends to lift that part of the cover which has already been detached from the edge and to bring it rearward in a natural movement reducing the possibilities of inexpert handling which, with conventional systems, are often the causes of accidents during opening. Another effect of this movement is that the edge of the torn part of the cover does not penetrate too deeply into the can. Instead of being completely rigid, if the tab is made thinner, as indicated by the broken lines in FIG. 2, at that end 12 which comprises the gripping hole 13, the pull will be even more readily directed in the most favorable direction.
' Instead of making the tab thinner at 12, a hinge 14, in the form of a reduced material thickness, can be provided between the gripping hole 13 and the point where it is fixed to the cover 7.
A few other modifications can be made in accordance with the practice of this invention. For example, to prevent the grip from rotating in the circular opening 3 formed in the cover, the upper part of the screw 8 can be partially surrounded by a non-circular projection 15 equal in height to the flange 4 and which penetrates into an opening 16 of the same cross-section.
In some instances, it will be advantageous to select the diameter of the lower part 10 of the grip so that this part exceeds the tear line 2 to extend therebeyond.
The use of a plastic material in the production of the grip permits the grip to be used for identification or for publicity purposes, such as by a suitable choice of colors or by suitable printing.
In addition, the grip can have various shapes, its active portion being rounded or pointed while its passive portion is used for an effective grip. The material used is a synthetic material sufficiently rigid to cause rupture of the tear line. In addition to polypropylene, it is possible to use HP-polyethylene, LP-polyethylene, high impact polystyrene, polyvinyl chloride and the like.
It will be apparent from the disclosure that a hermetically sealed relationship is established as between the plug portions and the nut portion 10, which are joined one to the other in sealing relationship with the upper surface of the nut portion 10 engaging the underside of the can cover about the opening 3 to effect a sealing relationship therebetween, as illustrated in FIGS. 2 and 4 of the drawings.
It will be understood that changes may be made in the details of construction, arrangement, operation and materials without departing from the spirit of the inven tion, especially as defined in the following claims.
1. A means for opening metal covers for cans in which the cover is provided with a tear line that defines a removable portion and an opening within said removable portion, same means comprising a relatively rigidplastic tab positioned on the top side of the cover including a portion which projects downwardly through the opening in the cover, a grip portion to one side of said projecting portion, with the edge of the tab in the direction opposite the grip portion lying adjacent the portion of the tear line spaced from the opening in the direction opposite the grip portion, and a relatively rigid nut member adjacent the bottom side of the cover in sealing engagement with the portion of the tab which extends downwardly through the opening in the cover.
2. A means as claimed in claim 1 in which the nut is dimensioned to extend beyond the opening to at least the tear line in the cover.
3. A means as claimed inclaim 2 in which the nut is dimensioned to extend beyond the tear line.
4. A means as claimed in claim 1 in which the assembly engages the cover in sealing relation to hermetically seal the opening.
5. A means as claimed in claim 1 in which the distance between the opening in the cover and the tear line is such that the outer edge of the nut situated adjacent the bottom side of the cover is tangent to the tear line.
6. A means as claimed in claim 1 in which the distance between the opening in the cover and the tear line is such that the nut situated below the cover extends beyond the perpendicular plane through the tear line.
7. A means as claimed in claim 1 in which the opening in the cover is non-circular and in which the projection in the tab has a portion of the same configuration to prevent relative turning movement between the one part and the cover.
8. A means as claimed in claim 1 in which the grip portion of the tab is of lesser cross-section than the remainder for greater flexibility.
9. A means as claimed in claim 1 which includes a hinge in the tab separating the grip portion from the projection portion of the one part.