US3731835A

US3731835A - Easy opening container

Info

Publication number: US3731835A
Application number: US00168726A
Authority: US
Inventors: J Hawkins; H Keinanen
Original assignee: Continental Can Co Inc
Current assignee: Continental Can Co Inc
Priority date: 1971-08-03
Filing date: 1971-08-03
Publication date: 1973-05-08
Anticipated expiration: 1990-05-08

Abstract

A metal end unit for a container in which the metal end unit is formed with a pre-cut opening. A protective rim is bonded about the edge of the opening and a plastic sealing member overlies the opening and is separably bonded solely to the metal end unit by means of a thermo and pressure responsive bond promoting coating applied on the metal end unit. The plastic closure is bonded by means of R-F energy applied to induce heat in the metal end unit at the interface of said bond promoting coating and the plastic closure. Pressure is applied to form the desired bond.

Description

United States Patent [191 Hawkins et al.

541 EASY OPENING CONTAINER [75] lnventor s:Jerry D. Hawkins, Country Club Hills; Henry J. Keinanen, Hickory ,fii tbeil p qkrl t v [73] Assignee: Continental Can Company, Inc.,

New York, N.Y.

[22] Filed: Aug.3,197ll 211 Appl. No.: 168,726

Related U.S. Application Data [63] Continuation of Ser. No. 12,981, Feb. 20, 1970,

abandoned.

[5 2] U.S. Cl. ..220/53, 220/47, 220/60 [51] int. Cl. ..B65d 17/20 [58] Field of Search ..220/53, 54, 27, 60,

[5 6] References Cited UNITED STATES PATENTS Reynolds et al. ..220/53 51 May 8, 1973 3,473,692 10/1969 Moller ..220/47 Primary Examiner-George T. Hall Attorney-Fred P. Kostka, Joseph E. Kerwin and William A. Dittman [57] ABSTRACT A metal end unit for a container in which the metal end unit is formed with a pre-cut opening. A protective rim is bonded about the edge of the opening and a plastic sealing member overlies the opening and is separably bonded solely to the metal end unit by means of a thermo and pressure responsive bond promoting coating applied on the metal end unit.

The plastic closure is bonded by means of R-F energy applied to induce heat in the metal end unit at the interface of said bond promoting coating and the plastic closure. Pressure is applied to form the desired bond.

7 Claims, 6 Drawing Figures Patented May 8,1973 3,731,835

2 Sheets-Sheet 2 TO R. F.

I N VE NTORS JERRY D. HAWKINS HENRY J KE INANEN BY #4.; M

' ATT Y EASY OPENING CONTAINER This is a continuation of U.S. Pat. application Ser. No. 12,981 dated Feb. 20, 1970, now abandoned.

The present invention relates to new and useful improvements in containers and more particularly to metal containers of the easy opening type wherein a pour opening having a manually removable closure is provided at one end of the container.

Easy opening containers of the general type to which the present invention relates are made from metal and primarily intended for use in the packaging of beverages. In one type currently being marketed, the container end closure is formed with a tear portion defined by weakening or score line. The tear portion is removed by tearing along the score line upon the application of a manual force exerted on a pull tab attached thereto. Upon separation of the tear portion, a pour opening is formed so that the contents may be poured therethrough. The contents may then be emptied into another receptacle or may be directly consumed from the container.

Occasionally, when the contents are directly consumed because of the presence of the raw sharp edge about the pour opening resulting from the tearing of the tear strip therefrom, the lips of the user may be cut. This condition is of course undesirable. A further undesirable feature is the separated tear strip which also has sharp edges that may cut the user. Moreover, the tear strip is often discarded in public places such as recreation areas and thereby creates a litter problem.

Another type of easy opening container employs an end closure having a pre-cut opening which is sealed by a separately attached or external sealing strip. The sealing strips are made from metal foil or plastic in either laminated or single layer form and releasably adhered to the end closure about the marginal edges of the opening. Difficulties have been encountered with sea]- ing strips in achieving a separable seal which is capable of maintaining both a pressure type seal to withstand the pressure forces associated with beverages packaged in the containers and a seal which is easily separable upon the application of a manual force exerted by the fingersof the user. For example, in some instances the sealing strips may be manually separable from the container but not be capable of maintaining the pressure within the container so that leakage occurs to the extent that the integrity of the product is destroyed.

A further drawback in the sealing strip type of easy opening structure is that the metal edge about the precut openings may be exposed to the contents in the container. This is undesirable because the metal may react with the contents so as to have an adverse affect thereon. Also, as in the case of the tear strip type container, a raw metal edge may be exposed after removal of the sealing strip so that the injury hazard is also present.

SUMMARY OF THE INVENTION It is a principle object of the present invention to provide an easy opening container which overcomes the difficulties encountered heretofore.

It is a further object to provide a new and novel method for assembling an easy opening structure on a container end.

In accordance with the present invention, it is proposed to provide an easy opening end closure which overcomes the aforementioned problems. This is accomplished generally by a metal end unit which is formed with a pre-cut pour opening that is sealed by a plastic closure member. The plastic closure member comprises a rim which is secured about the edge of the pre-cut opening and a pull tab which overlies the rim and seals the opening. The pull tab is releasably bonded only to the metal end and not to the rim.

The plastic closure is constructed so that the rim and pull tab are disposed below the upper edge or chime of the container. Because of this thickness limitation the plastic material from which the closure is made is selected so that the components are sufficiently rigid to facilitate handling in high production processes and assembly equipment. Moreover, the plastic material is characterized by providing a closure over the opening which does not destroy the integrity of the product.

The rim of the present invention is constructed in the form of a continuous and uninterrupted band preferably made from a plastic material which is rigid and sufficiently resilient. These characteristics make it possible to snap fit the rim into position on the edge of the pre-cut opening and thereby facilitate the assembly to the end.

As mentioned above the pull tab is bonded to the end panel only and not to the underlying rim. This permits the pull tab to be attached in a manner so that it may be peeled from the end upon the application of a pulling force. Also, the plastic material is: preferably selected to have a low heat conductivity so that the rim and the pull tab may be simultaneously bonded to the metal end without bonding the pull tab to the rim.

The pull tab is bonded to the end panel so as to be separable as by peeling upon the application of a pulling force. To this end, a bond promoting coating is applied to the metal end. The pull tab is pressed against the bond promoting coating and heat is induced for a relatively short period about the opening to bond the bond promoting coating of the pull tab. The heat is controlled so that the pull tab is separable from the bond promoting coating upon the application of a pulling force.

Further objects and features will hereinafter appear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top end view of an easy opening container end unit embodying the structure of the present invention;

FIG. 2 is a top end view of the container end unit of FIG. 1 prior to the assembly of the easy-opening closure thereon;

FIG. 3 is a fragmentary cross-sectional view of a container having the end closure of FIG. I attached thereto;

F IG. 4 is an exploded cross-sectional view of the closure prior to application to the container end unit;

FIG. 5 is a fragmentary cross-sectional view of the apparatus for assembling the closure to the end unit and showing the closure and end unit disposed therein;

FIG. 6 is an enlarged fragmentary top plan view of the R-F heating coil used for bonding the closure components to the end unit; and

FIG. 7 is an enlarged fragmentary cross-sectional view of the assembly apparatus and showing the closure members disposed therein for assembly to the end unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings in particular FIGS. 1-4, there is shown a container 9 including an end closure or unit 151 incorporating the easy opening closure 11 of the present invention. The end unit is made from sheet metal such as aluminum or a ferrous metal, as for example, tin free steel, black plate or the like. The end unit 10 includes a panel 12 having a peripheral bead 13. Extending upwardly from the bead 13 is an upstanding wall 14 from the upper end of which there extends a peripheral flange. The end unit is attached to the upper end of a container body 15 by means of a double seam 14a.

The end unit 10 as shown is coated on the outer and inner surfaces thereof with an enamel coating 16 prepared from a thermosetting resin, such as epoxy resin of the polyhydic alcohol-polyfunctional halohydrin condensation type, a heat hardenable phenol/formaldehyde resin, an aminoplast, such as an urea or melamine/formaldehyde resin. In addition, certain thermoplastic resins may be employed in combination with these thermosetting resins to prepare enamel coatings having thermo-setting properties. Illustrative of these thermoplastic resins are vinyl chloride polymers, such as vinyl chloride/vinyl acetate copolymers and vinyl chloride/vinyl acetate/maleic anhydride terpolymers.

Superimposed on the enamel coating 16 is a bond promoting coating 17. The bond promoting coating 17 is selected to form a releasable bond or peelable seal with the plastic from which the closure 11 is made. 11- lustrative examples of bond promoting coatings which can be applied to the enamel coating are carboxyl containing olefin polymers, such as carboxyl modified polypropylene graft copolymers, carboxyl modified polyethylene graft copolymers, and mixtures of carboxyl modified polyethylene graft copolymers and vinyl butyral polymers, such as polyvinyl butyral. The enamel coating 16 and bond promoting coating 17 may be applied to the flat metal sheets from which the end unit 10 is formed. For a more complete description of the enamel coating 16 and the bond promoting coating 17 and the method of applying the same to the end unit 10, reference is made to pending applications of Kenneth D. Gilliam and Alfred W. Kehe, Ser. No. 858,164 filed Sept. 15, 1969 and Alfred W. Kehe filed Sept. 8, 1969, Ser. No. 855,878, both assigned to the assignee of the present invention.

As shown, the end unit 10 is made with a tear drop opening 18 extending generally radially of the panel 12 with the narrow section disposed substantially at the center thereof.

The closure 11 as shown, comprises a rim 19 and a sealing member or pull tab 20. The rim 19 is fastened about the edge of the opening 18 and pull tab 20 is positioned over the rim l9 and opening 18 and adhered to the marginal edge portions bounding the latter. It is to be noted that the rim 19 and pull tab 20 when assembled on the container 9 are entirely confined within the space defined between the upper edge of the double seam 14a and the panel 12. This limits the thickness of the rim 19 and the pull tab 20. The rim is made from a thermoplastic polymer such as an olefin homopolymer or copolymer such as polyethylene, polypropylene or ethylene/propylene copolymer and is formed by molding to a contour complementary to the pre-cut opening 18 in the end. A groove 21a defined by an upper chamfered lip 21 and a spaced lower lip 22 is formed along the periphery of the rim 19. The rim 19 is sufficiently pliable or resilient so that the groove 210 may be snap fitted into seating engagement with the edge about the pre-cut opening 18. When thus seated, the surfaces 23 and 24 of the

lips

21 and 22, respectively are in face to face engagement with the bond promoting coating 17 bounding the edge. The aforementioned materials from which the rim is made are characterized by having a low heat conductivity which is significant in bonding the pull tab 20 to the metal end as will be readily apparent from the foregoing description.

The pull tab 20 comprises a plug or closure portion 25 and an integral finger grip portion 26 which may be in the form of a ring. The plug 25 includes a continuous flange 27 depending downwardly from the underside of a web 28 and is snuggly received within the rim 19. To provide locking engagement upon reinsertion of the sealing member after initial removal from the rim, the flange 27 at the lower end thereof may be formed with a horizontal locking lip 29 which engages the underside of the lip 22.

The web 25 includes a marginal portion 30 which overlies the rim 19. A downwardly projecting flange 31 is spaced from the lip 21 of the rim 19 is formed along the outer edge of the marginal portion 30. The flange 31 terminates in a face 32 which engages the bond promoting coating 17 on the metal end 10. It is to be noted that the flange 31 is laterally spaced from and out of contact with the rim 19 so that the pull tab 20 is attached solely to the bond promoting coating 17 at the face 32 as more fully to be explained hereinafter.

The pull tab 20 comprises a plug or closure portion 25 and an integral finger grip portion 26 which may be in the form of a ring. The ring 26 is of somewhat greater thickness than the body portion so as to provide a rigid lever. In this connection, it is to be noted that the plug portion 25 extends into the ring portion 26 along the juncture therewith to define a pair of laterally spaced ends 26a which define a bend line 26b about which the ring portion bends relative to the plug portion 25. The points are further located so that the bend line 26b is substantially tangential to the inner most curved end of the pour opening 18 to facilitate the separation of the pull tab 20 from the end unit as more fully to be explained hereinafter.

The pull tab 20 is made from a thermoplastic material which may have a composition substantially similar to that of the rim 19, for example, polypropylene or polyethylene, and is formed by molding or the like. When the pull tab 20 is made from polyethylene, the bond promoting coating 16 is preferably comprised of a mixture of a carboxyl modified polyethylene resin and a vinyl butyral polymer resin. When the pull tab 20 is made from polypropylene the bond promoting coating 16 is preferably comprised of a carboxylated polypropylene resin.

The pull tab 20 is bonded to the metal end unit by heat sealing. This is accomplished by placing the end unit 10 having the rim 19 and pull tab preassembled in the opening 18in a press 35 as shown in FIGS. 5 to 7. The press 35 includes generally an anvil 36 and a vertically movable head 37.

As shown, the anvil 36 includes a support plate 38 for supporting the preassembled end closure 10 therein, Accommodated within an opening 39 in the support plate 38 and underlying the closure member 11 about the pre-cut opening 18 is an induction heating coil 41 as shown. The induction heating coil 41 is an RF coil which is connected to a suitable source of R-F energy by leads d2. The R-F coil 41 is designed to induce an energy resulting in a uniform temperature profile in the surface of the metal end unit 10 at the interface between the face 32 of the marginal edge portion and the bond promoting coating 17.

The head 37 is made from a non-metal and is of generally circular cross-section. The lower end of the head 37 is formed with a peripheral semi-circular flange 44 complementary to the curvature of the head 13 so as to be seatable therein and to clamp the end unit on the support plate 36. Fixed within an opening 43 in the head 37 is a non-conductive block 47. The non-conductive block 47 is contoured at the lower face 49 to overlie the pre-cut opening 18 and bear against the pull tab 20 to press the face 32 of the sealing member flange 31 into firm engagement with the bond promoting coating 17. A clearance cavity 51 is also provided in the head 37 to accommodate the finger grip portion 26 of the pull tab 20.

in operation, the end unit 10 having the rim 19 snap fitted in the opening 18 and the pull tab 20 assembled thereon is placed on the anvil 36. The head 37 is then brought into firm pressure engagement with the upper surface of the pull tab 20. This causes the face 32 on the flange 31 to be in intimate contact with the bond promoting coating 17.

The R-F coil a1 is energized for a relatively short period or time cycle and induces a localized surface heated area in the metal end 10 adjacent the edge of the opening 1%. This causes a heat seal to be formed at the face 32 of the pull tab and the contacting faces 23 and 24 at the rim 18. In this connection, it is to be noted that plastic material from which the rim 19 and pull tab 20 are made act as insulators and thereby prevent arcing upon introduction of the R-F energy.

The induction heat generated by R-F coil is carefully controlled so that the surface temperature at the face 32 of the pull tab 20 is maintained below that at which the bond promoting coating 17 and the pull tab form an inseparable bond. The heat and pressure at the sealing member face 32 is maintained for a sufficient length of time to produce a bond capable of being separated from the bond promoting coating 17 upon the application of a pulling force exerted by the fingers at the finger grip portion 26. At the same time, the rim 20 is bonded to the edge about the opening 18 and remains attached upon separation of the pull tab 20. The rim 19 is bonded or fused to the bond promoting coating because the induced surface heat resulting from the R-F energy is greater than that occurring at the face 32. This is not objectionable for the reason that it is desired to retain the rim 20 on the edge to coverthe raw uncut edge. Covering the raw edge prevents oxidation or corrosion by reaction with the product in the container.

It is to be noted that the pull tab 20 is attached solely to the bond promoting coating 17 and is not bonded to the rim 19 because the heat induced in the metal end unit is not conducted to the outer surface of the rim 19. In this manner, it is possible to control the bonding strength of the pull tab 20 to the end unit 10 so that it is peelable from the end and may be manually removed.

Separation of the pull tab 20 fromthe end panel 12 is accomplished by tilting the ring portion 26 upwardly so that the latter may be firmly gripped between the thumb and forefinger. During the tilting movement the bond on the face 32 on the underside of the flange 27 is separated. This separation which is in the nature of a peel occurs during the bending of the ring portion 26 relative to the closure portion 25 about the hinge line 26b.

With the ring portion 26 inclined the force to separate the locking lip 29 on the lower end of the flange 27 from the rim l9 and also the force to separate the bond between the face 32 and the bond promoting coating 17 is applied. The inclined attitude of the ring portion permits a greater force to be applied so that the peeling and separation of the closure flange lip 29 from the rim 19 and thereby the tab 20 from the panel is greatly facilitated.

What is claimed is:

1. An easy opening end unit for a container comprising a metal end having a pre-cut opening and closure therefor, said closure including a plastic rim seated on the edge defining said opening to provide a protected opening, a plastic sealing means covering said opening and disposed over said rim in non-bonding contact therewith, said sealing means having a marginal edge portion spaced outboard of said rim in intimate contact with said metal end, and a bond promoting coating on said metal end releasably bonding said plastic sealing means to said metal end whereby said sealing means is capable of being separated from said metal end upon the application of a pulling force exerted by the user.

2. The invention as defined in claim 1 wherein said bond promoting coating is thermo and pressure responsive, and wherein said sealing is releasably bonded solely to said metal end as a result of heat conducted through said metal end and the application of pressure.

3. The invention as defined in claim 2 wherein said rim is fixedly bonded to said metal end.

4. The invention as defined in claim 1 wherein said sealing means includes a plug inserted in said opening.

5. The invention as defined in claim 4 wherein said plug is defined by a flange snuggly seatable in said opening.

6. The invention as defined in claim 5 wherein said flange includes latch means co-operative with said rim for releasably latching said plug in said opening upon reinsertion into said pour opening after separation of said sealing means.

7. The invention as defined in claim 4 wherein said sealing means includes a finger grip portion extending from said plug.