US 3510022 A
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Description (OCR text may contain errors)
y 5, 1970 P. H. HELLER 3,510,022
REMOVABLE TAB HAVING A PROTECTIVE COATING Filed not. 17, 1968 INVENTOR. Q04 A1 #5415? United States Patent 3,510,022 REMOVABLE TAB HAVING A PROTECTIVE COATING Paul H. Heller, 2210 New Haven Ave., Far Rockaway, N.Y. 11691 Filed Oct. 17, 1968, Ser. No. 768,513 Int. Cl. B65d 17/24 US. Cl. 220-54 7 Claims ABSTRACT OF THE DISCLOSURE This disclosure is directed to a metal can, such as for beverages, of the type which has a removable metal tab scored in the top thereof. The improvement resides in partially coating the top and tab portion of the can with plastic. Upon removal of the tab member the plastic coating remains and prevents injury to the user from sharp metal edges at the point of former joinder of the tab and the top of the can.
Background Metal cans are widely used for beverages such as beer and soda. Several years ago cans having removable pulltabs were introduced and readily accepted by the public. The tops of these cans are scored to form a key-hole shaped tab to which a ring or tongue is attached. Upon pulling the ring or tongue the tab is lifted off the top of the can leaving a key-hole shaped opening from which the beverage may be poured or removed. Unfortunately due to the metal stamping or scoring to form the tab and the step of pulling off the tab, very sharp edges are left on the top of the can. These sharp edges pose a particular danger to consumers when drinking directly from the cans by pressing their lips against the key-hole shaped opening. The dangers have of course proven greatest for young children who might be inclined to place their lips, tongues, or fingers against these edges. A further drawback of this type of can is its greater tendency to lose carbonation through minute leaks caused by the scoring around the tab.
It is therefore an object of the present invention to provide for an improved can having a readily removable tab portion.
It is a further object of this invention to provide for such a can which can be more safely used by the consuming public.
Yet another object is to make such a can which will less readily lose carbonation.
These and other objects of the present invention may be met by providing a protective coating on the top of the metal cans as set forth in the following detailed description.
The invention This invention is directed to an improved metal can of the type having a removable member, such as a tab scored into the top of the can. A plastic film is provided on the top of the can; the film remains after opening of the can and covers the exposed metal edges left in the top of the can after removal of the tab.
FIG. 1 shows the top of a can with a plastic coating partially on and around the tab portion of the can.
FIG. 2 shows the can of FIG. 1 with the tab portion of the can removed.
The lid or top 1 of the can has a generally key-shaped removable tab portion 2, as defined by the score-line 3. In about the middle of the can a handle 4 is afiixed to the tab. This type of can is well-known and of conventional construction. The improvement of this invention resides in a plastic coating 5 which covers a portion of the lid and slightly overlaps the score-line to cover a small 3,510,022 Patented May 5, 1970 part of the tab. A transparent coating is shown to reveal the score-line underneath, for ease in depicting the construction of the can.
Upon removal of the tab by means of the handle, an opening 2' is formed as defined by the score-line edge (FIG. 2). The plastic coating 5 remains attached to the lid and the edge 6 of the plastic coating provides protection for the user of the can from the sharp edge at the score-line formed by removal of the tab.
The coating of the present invention is applied along the scoring which outlines the removable tab. A minor portion of the coating overlaps the scoring and is aflixed to the removable metal tab. The majority of the coating is firmly anchored to the top of the metal can, contiguous to the tab portion. Since the coating is coherent, and somewhat flexible, upon removal of the tab the minor portion of the coating separates from the tab and the entire coating remains on the top of the can. The aforementioned minor portion of the coating, after removal of the tab, overlaps the key-shaped hole and provides protection from the sharp metal edges. By the use of a strongly adhering coating, in the above, additional protection is provided against loss of carbonation at the scored part of the can.
Metal packages and containers are made out of steel, tin and aluminum. The most common of these is the tin can, which contains only a small portion of tin, used for the coating of the steel sheet. In the field of beverages, aluminum has now come to the fore as a packaging material. The present invention is directed to metal cans made of any of these materials which have removable portions formed therein by scoring or stamping or any similar operation whereby removal of the intended portion leaves sharp metal edges.
Many different types of coatings may be used on metal cans to provide protection against these sharp metal edges. These coatings should readily adhere to the metal cans and preferably be capable of application during the can forming process. The coatings should be tough so that they are not torn during removal of the tab from the can. The coatings should be flexible so that they present a soft plastic edge overhanging the opening in a can after removal of the tab. These properties are present in numerous commercially available coatings in the food or beverage industries.
The coatings may be applied to the can in several different ways. For example, the coatings can be applied directly during the forming or stamping operation from reservoir fed devices. The coatings may be painted onto the cans by brushes or other types of applicators. Alternatively the coating may be sprayed onto the can, or electrodeposited, or powder-pressed. Combinations of these steps may be used, in conjunction with heat and pressure sealing operations. The method of applying the coating is tailored for the particular plastic or combination of plastics which are to be used.
The important factor in choosing and applying the coating is that the minor portion of the coating should be capable of being stripped from the tab during removal of the tab from the can, and yet this minor portion should remain coherent with the remainder of the coating which remains firmly adhered to the can and which surrounds the hole formed by removal of the tab. For example the coating may be wide, wherein A of plastic is on the tab and is on the top of the can adjoining and surrounding the tab. Upon removal of the tab the & wide coating on the tab is stripped therefrom since it is coherent with the wide coating firmly adhered to the remainder of the can. The wide plastic strip therefore overhangs the opening in the can and protects the consumer from the sharp metal edges left after removal of the tab. The dimensions just set forth are of course only illustrative and may be "varied widely. It is preferable that the amount of coating which is placed on the metal tab be maintained at a minimum so that it may readily be stripped therefrom and yet will not obstruct the opening in the can. The amount of plastic or coating which surrounds the tab should be several times the amount which is on the tab itself so that the entire coating is not pulley ofl during removal of the tab. Alternatively this portion of the coating which surrounds the tab may be specially treated, by heat or pressure, to provide permanent adhesion to the metal can whereas the coating on the tab itself remains strippable.
Among the plastic coatings which may be used in the present invention are the polyvinyl acetals. Polyvinyl formal may be used as an enamel. The enamel is prepared from the formal in combination with an alkyl phenolic resin in a solvent mixture of cresylic acid or furfural and naphtha. Properties making the formal valuable in this application include toughness, adhesion, flexibility, and resistance to heat, abrasion, solvents and oils. Granular polyvinyl formal may be used on surfaces coated with a liquid phenol-formaldehyde resin after application of heat and pressure. Emulsions may also be prepared for bonding to metals such as aluminum. These polyvinyl formals mixed with phenolics, and their method of application, are well-known as food-can linings, and the technology therefrom can be adapted for the present invention.
Plasticized polyvinyl butyral, cured or cross-linked with a urea-formaldehyde, phenol-formaldehyde, or other resin, provides a flexible waterproof coating. A wash primer type of metal conditioner with polyvinyl butyral has excellent adhesion to clean metal surfaces and airdries rapidly to leave a uniform protective film. A butyral wash primer under a topcoat of polyvinyl chloride-acetate copolymer also provides corrosion resistance to metal surfaces. Thus the butyral coating may be used to improve the adhesion of other plastics to aluminum. Butyral solutions readily form cast films which are waterproof and very flexible. A small amount of phenolic around the edges of such a film will cement to almost any metal surface under heat and light pressure.
In applying coatings as powders, the pulverized material is brought in contact with the can and then fused by heat into a solid film. Among well-known polymer powders, which may also be available in solvents, are cellulose-acetate-butyrate, chlorinated polyether, fluorocarbon resins, polyesters, polyethylene, polyvinylchloride and epoxy resins. By selection of the powder, plasticizer, and sometimes primer, protective and esthetic coating can be produced. The coating can be tough, flexible, permanent or strippable, and can have a pleasant feel, luster and attractive appearance. In addition, with electrostatic powder application methods, selected areas can be coated and automation of the coating operation is greatly simplified.
Particularly strong bonds may be obtained with epoxybased resins which are commercially available for adhesion to metals such as aluminum. These resins may be cured at room temperatures or at elevated temperatures and pressures. These resins may perform the added function of a seal when added over the scoring which forms the tab member on the top of a can. This sealing function prevents the loss of carbonation which might otherwise occur due to a faulty scoring or stamping operation. The epoxy-based resin may also be used as a priming layer over which a softer plastic, such as a rubber cement, may be used. It would be the rubber cement edge which therefore hangs over the opening in the can and provides protection to the consumer.
Modifications can be made in the preferred embodiments of the invention described above without departing from the scope of the invention defined by the appended claims.
1. In a metal can for liquids having a preformed removable tab portion formed in its lid, the improvement which comprises a coherent plastic coating on the adjoining areas of said lid and a portion of said tab, said coating extending from said lid to a limited area of said tab on its periphery and said plastic adapted to adhere to said lid upon removal of said tab wherein a minor portion of said plastic coating is on the periphery of said tab and the remainder of the plastic coating is on the lid of said can substantially around the tab, wherein upon removal of said tab the plastic coating overhangs the opening formed in said can but does not substantially obstruct removal of liquid therefrom.
2. The metal can of claim 1 wherein said plastic coating comprises an epoxy-based resin securely adhered to said can.
3. The metal can of claim 1 wherein said plastic coating comprises a rubber-base resin securely adhered to said can.
4. The metal can of claim 1 wherein said minor part of said plastic coating is strippably adhered to said removable tab portion and said remainder of said plastic coating is permanently adhered to the area of said can adjoining the removable portion.
5. The metal can of claim 4 wherein said remainder of said plastic coating includes an epoxy-based resin and said minor part of said plastic coating is a rubber-based resin.
6. The can of claim 1 wherein said tab is defined by a scoreline on said lid and said plastic coating is a strip of plastic over said score-line, with the majority of said plastic on said lid and the remainder on said tab.
7. In a metal can for liquids having a preformed removable tab portion formed in its lid, said tab portion being defined by a score-line on said lid, the improvement which comprises a strip of plastic coating over said score-line, a first portion of said plastic being on the periphery of said tab and the remainder of said plastic being on the lid of said can substantially around the tab, and said remainder of said plastic being permanently adhered to the lid of said can wherein upon removal of said tab the first portion of said plastic overhangs the opening formed in said can but does not substantially obstruct removal of liquid therefrom.
References Cited UNITED STATES PATENTS 3,204,805 9/1965 May 220-24 GEORGE T. HALL, Primary Examiner U.S. Cl. X.R. 22090.6