CANS
United States Patent 3650387
A can has a metal end and a side wall of a different metal. Self-supporting sheet material which is water-impervious and electrolytically inert with respect to the metal of the side wall isolates the end from the contents of the can and serves to provide electrolytic corrosion of the end. Where the end is a tear-off end, the sheet also serves to preserve the contents from contamination if the tear-off end is damaged.
US Patent References:
Receptacle and combined quick opening means
Fried et al. - November 1965 - 3220599
Pull tab can opener
Ronci - March 1966 - 3241708
Receptacle and combined quick opening means
Fried et al. - November 1965 - 3220599
Pull tab can opener
Ronci - March 1966 - 3241708
Inventors:
Hornsby, John M. (Oakham, EN)
Wood, William G. (Melton, EN)
Wood, William G. (Melton, EN)
Application Number:
04/881542
Publication Date:
03/21/1972
Filing Date:
12/02/1969
View Patent Images:
Export Citation:
Assignee:
Petfoods Limited (Leicester, Leicestershire, EN)
Primary Class:
Other Classes:
426/127, 426/123, 206/815, 206/525, 426/126
International Classes:
B65D17/00; B65D23/02; B65D85/72; B65D23/00; B65D85/72; B65D17/20
Field of Search:
206/46R,46F 220/53,54 99/171R,171M,171C
Primary Examiner:
Dixson Jr., William T.
Claims:
What is claimed is
1. A can comprising: a tubular metal side wall having first and second ends; first and second closure means closing respectively said first and second ends; material contained in said can enclosed by said side wall and said first and second closure means; said first closure means including an imperforate readily tearable member of a metal different from that of said side wall and provided with means defining in said metal member a line of tear, and a barrier of self-supporting sheet material which is water-impervious and inert to said contained material and electrolytically inert with respect to the metal of said side wall in the presence of said contained material; said barrier being disposed inwardly of said metal member, and means maintaining said barrier in spaced relation with respect to said metal member, at least in the area thereof bearing said line-of-tear-defining means, to protect said barrier sheet against rupture by said tear-line-defining means, said barrier sheet isolating said metal member from said contained material, whereby electrolytic reaction between said side wall and said metal member is prevented.
2. A can as claimed in claim 1 wherein said side wall is tinplate and said metal member of said first closure means is aluminum.
3. A can as claimed in claim 1 wherein said sheet material is a film of thermoplastics material.
4. A can as claimed in claim 2 wherein said sheet material is tinfoil.
5. A can as claimed in claim 1 wherein said member is provided with means for tearing from said member a portion thereof defined by said line of tear.
1. A can comprising: a tubular metal side wall having first and second ends; first and second closure means closing respectively said first and second ends; material contained in said can enclosed by said side wall and said first and second closure means; said first closure means including an imperforate readily tearable member of a metal different from that of said side wall and provided with means defining in said metal member a line of tear, and a barrier of self-supporting sheet material which is water-impervious and inert to said contained material and electrolytically inert with respect to the metal of said side wall in the presence of said contained material; said barrier being disposed inwardly of said metal member, and means maintaining said barrier in spaced relation with respect to said metal member, at least in the area thereof bearing said line-of-tear-defining means, to protect said barrier sheet against rupture by said tear-line-defining means, said barrier sheet isolating said metal member from said contained material, whereby electrolytic reaction between said side wall and said metal member is prevented.
2. A can as claimed in claim 1 wherein said side wall is tinplate and said metal member of said first closure means is aluminum.
3. A can as claimed in claim 1 wherein said sheet material is a film of thermoplastics material.
4. A can as claimed in claim 2 wherein said sheet material is tinfoil.
5. A can as claimed in claim 1 wherein said member is provided with means for tearing from said member a portion thereof defined by said line of tear.
Description:
The present invention relates to improvements in cans, for example cans for containing sterilized food, and more particularly to means for isolating an end of the can from the contents of the can.
In the case of a can having a tear-off end, such ends usually being scored or otherwise deformed to facilitate opening of the end by tearing out an area thereof, it is preferred to make the tear-off end of aluminum, which can readily be torn, but the remainder of the can of a stronger and/or less expensive material, such as tinplate. However, in the presence of salts or other electrolytes in the contents of the can the aluminum end corrodes, because an electric cell is set up between the different metals, with the result that the canned product has an undesirably short shelf life The rate of corrosion can be diminished by reducing the concentration of salts in the contents but this is often undesirable, as for example in the case of canned foods, where the salts are necessary nutritional ingredients.
The use of a tearable material for the ends of such cans and the scoring also makes such cans more vulnerable to accidental damage.
The present invention enables the difficulties which are encountered in the use of such cans to be overcome.
According to the invention, there is provided a can having a metal end and a side wall of a metal different from the metal of the end, in which the end is isolated from the contents of the can by a barrier of self-supporting sheet material which is water-impervious and electrolytically inert with respect to the metal of the side wall.
Where the said end is adapted to be opened by progressively tearing out an area thereof the sheet material can serve to preserve the contents from contamination, for example contamination by entry of bacteria following mechanical damage to the end.
In the case of cans which are subjected to heat treatment before and/or after sealing the sheet material should be stable at the temperature of the heat treatment.
Examples of suitable sheet materials include thin tin foil cellulose film and films of laminates of thermoplastics materials, such as polyethylene, polypropylene, polyamide and polyester.
Thus when a tinplate can body has a tear-off end of aluminum an undesirable rate of corrosion is avoided by the use of the sheet materials mentioned above. Where, on the other hand, an end is of tinplate, and the remainder of the can of aluminum, sheet material other than tinfoil should be used, for example aluminum foil, or the plastics materials mentioned above.
It has proved difficult to provide a tear-off can end of tinplate owing to high tear strength of this material. The invention, by providing an inner sealing membrane, makes it possible to perforate a tinplate can end in order to render it more readily tearable, without loss of the possibility of maintaining the sterility of the contents of the can. The perforated end still plays an important protective role against mechanical damage, for example during processing or subsequent handling, storage and transport, and permits the use of readily tearable foils or films as the inner membrane.
The thermoplastics films mentioned, while imperforate, may exhibit a small degree of porosity to gases, e.g., water vapor, but are impermeable to micro-organisms, and thus serve to preserve the contents of the can from bacterial contamination.
The present invention will now be more fully described with the aid of examples illustrated in the accompanying drawings in which:
FIGS. 1 and 2 illustrate steps in making a can according to the invention and show a cross section through an end edge of a can in accordance with the invention before and after sealing, respectively,
FIG. 3 shows in perspective a can in accordance with the invention,
FIG. 4 shows the can of FIG. 3 partly opened by tearing the end,
FIG. 5 shows in perspective an alternative form of a can in accordance with the invention, and
FIG. 6 shows the can of FIG. 5 partly opened by tearing the end.
Conventional can-making techniques, only slightly modified, can be used to produce the cans described herein.
Referring to FIG. 1, an aluminum can end 1 is shown placed over the mouth of a tinplate can side wall 2. A layer 3 of a sealing compound, usually an organic solvent- or water-based composition, is applied to the periphery of the underside of the end 1, as in conventional can-making techniques. A piece of polyester film 4 is placed on the underside of the end 1 and adheres to the sealing compound layer 3. Optionally, a further layer 5 of the conventional sealing compound is applied to the periphery of the underside of the film 4 to provide a good seal when the edges of the end 1 and the wall 2 are rolled and crimped together as shown in FIG. 2, in the usual sealing operation. In the sealing operation, the edge of the film 4 becomes trapped between the edges of the end 1 and the wall 2. The film 4 serves to isolate the end 1 from the contents 6 of the can.
The can end 1 is scored along a line 7 around its periphery to provide a line of weakness along which the end 1 can be torn. The end 1 is also provided with a circumferential groove 8, between its peripheral edge and the score line 7, which serves to space the film 4 from underside of the can end 1 near its periphery to avoid the risk of the film 4 being punctured by the sharp edge of the end 1 if torn along the score line 7 as a result of accidental damage.
The cans shown in FIGS. 3 to 6 have aluminum tear-off ends 1, with side walls 2 and plain ends (not visible) of tinplate, and are produced by the method described above. The tear-off ends 1 are provided with ring-pull finger grips 9 including a portion having a circular aperture therein, through which protrudes a circular raised portion 10 of the aluminum can end 1 having its head riveted so as to form a circumferential shoulder securing the finger grip 9 and the can end 1 together.
The can ends 1 are scored along lines 7 to facilitate tearing when the finger grips 9 are pulled.
In the case of the can shown in FIGS. 3 and 4, the score line 7 defines a spiral-sided area which can be progressively torn out, commencing around the raised and rivetted portion 10 of the can end 1. The score line 7 continues in a circle along the edge of the end 1, enabling a circular aperture to be made in the end 1 by tearing.
In the case of the can shown in FIGS. 5 and 6 the score line 7 proceeds in a circle along the edge of the end 1, enabling a circular area to be torn out, commencing at the region nearest the raised and riveted portion 10 of the can end 1.
Each of the cans has polyester film 4 isolating the end 1 from the contents of the can. The polyester film 4 can be readily torn to give access to the contents.
In making the cans any impact adhesive or heat treatment may be used to bond the periphery of the piece of sheet material to the periphery of the can end instead of the usual sealing compound.
Instead of placing the sheet material on the can end, the sheet material can be placed over the mouth of the can before sealing.
In the case of a can having a tear-off end, such ends usually being scored or otherwise deformed to facilitate opening of the end by tearing out an area thereof, it is preferred to make the tear-off end of aluminum, which can readily be torn, but the remainder of the can of a stronger and/or less expensive material, such as tinplate. However, in the presence of salts or other electrolytes in the contents of the can the aluminum end corrodes, because an electric cell is set up between the different metals, with the result that the canned product has an undesirably short shelf life The rate of corrosion can be diminished by reducing the concentration of salts in the contents but this is often undesirable, as for example in the case of canned foods, where the salts are necessary nutritional ingredients.
The use of a tearable material for the ends of such cans and the scoring also makes such cans more vulnerable to accidental damage.
The present invention enables the difficulties which are encountered in the use of such cans to be overcome.
According to the invention, there is provided a can having a metal end and a side wall of a metal different from the metal of the end, in which the end is isolated from the contents of the can by a barrier of self-supporting sheet material which is water-impervious and electrolytically inert with respect to the metal of the side wall.
Where the said end is adapted to be opened by progressively tearing out an area thereof the sheet material can serve to preserve the contents from contamination, for example contamination by entry of bacteria following mechanical damage to the end.
In the case of cans which are subjected to heat treatment before and/or after sealing the sheet material should be stable at the temperature of the heat treatment.
Examples of suitable sheet materials include thin tin foil cellulose film and films of laminates of thermoplastics materials, such as polyethylene, polypropylene, polyamide and polyester.
Thus when a tinplate can body has a tear-off end of aluminum an undesirable rate of corrosion is avoided by the use of the sheet materials mentioned above. Where, on the other hand, an end is of tinplate, and the remainder of the can of aluminum, sheet material other than tinfoil should be used, for example aluminum foil, or the plastics materials mentioned above.
It has proved difficult to provide a tear-off can end of tinplate owing to high tear strength of this material. The invention, by providing an inner sealing membrane, makes it possible to perforate a tinplate can end in order to render it more readily tearable, without loss of the possibility of maintaining the sterility of the contents of the can. The perforated end still plays an important protective role against mechanical damage, for example during processing or subsequent handling, storage and transport, and permits the use of readily tearable foils or films as the inner membrane.
The thermoplastics films mentioned, while imperforate, may exhibit a small degree of porosity to gases, e.g., water vapor, but are impermeable to micro-organisms, and thus serve to preserve the contents of the can from bacterial contamination.
The present invention will now be more fully described with the aid of examples illustrated in the accompanying drawings in which:
FIGS. 1 and 2 illustrate steps in making a can according to the invention and show a cross section through an end edge of a can in accordance with the invention before and after sealing, respectively,
FIG. 3 shows in perspective a can in accordance with the invention,
FIG. 4 shows the can of FIG. 3 partly opened by tearing the end,
FIG. 5 shows in perspective an alternative form of a can in accordance with the invention, and
FIG. 6 shows the can of FIG. 5 partly opened by tearing the end.
Conventional can-making techniques, only slightly modified, can be used to produce the cans described herein.
Referring to FIG. 1, an aluminum can end 1 is shown placed over the mouth of a tinplate can side wall 2. A layer 3 of a sealing compound, usually an organic solvent- or water-based composition, is applied to the periphery of the underside of the end 1, as in conventional can-making techniques. A piece of polyester film 4 is placed on the underside of the end 1 and adheres to the sealing compound layer 3. Optionally, a further layer 5 of the conventional sealing compound is applied to the periphery of the underside of the film 4 to provide a good seal when the edges of the end 1 and the wall 2 are rolled and crimped together as shown in FIG. 2, in the usual sealing operation. In the sealing operation, the edge of the film 4 becomes trapped between the edges of the end 1 and the wall 2. The film 4 serves to isolate the end 1 from the contents 6 of the can.
The can end 1 is scored along a line 7 around its periphery to provide a line of weakness along which the end 1 can be torn. The end 1 is also provided with a circumferential groove 8, between its peripheral edge and the score line 7, which serves to space the film 4 from underside of the can end 1 near its periphery to avoid the risk of the film 4 being punctured by the sharp edge of the end 1 if torn along the score line 7 as a result of accidental damage.
The cans shown in FIGS. 3 to 6 have aluminum tear-off ends 1, with side walls 2 and plain ends (not visible) of tinplate, and are produced by the method described above. The tear-off ends 1 are provided with ring-pull finger grips 9 including a portion having a circular aperture therein, through which protrudes a circular raised portion 10 of the aluminum can end 1 having its head riveted so as to form a circumferential shoulder securing the finger grip 9 and the can end 1 together.
The can ends 1 are scored along lines 7 to facilitate tearing when the finger grips 9 are pulled.
In the case of the can shown in FIGS. 3 and 4, the score line 7 defines a spiral-sided area which can be progressively torn out, commencing around the raised and rivetted portion 10 of the can end 1. The score line 7 continues in a circle along the edge of the end 1, enabling a circular aperture to be made in the end 1 by tearing.
In the case of the can shown in FIGS. 5 and 6 the score line 7 proceeds in a circle along the edge of the end 1, enabling a circular area to be torn out, commencing at the region nearest the raised and riveted portion 10 of the can end 1.
Each of the cans has polyester film 4 isolating the end 1 from the contents of the can. The polyester film 4 can be readily torn to give access to the contents.
In making the cans any impact adhesive or heat treatment may be used to bond the periphery of the piece of sheet material to the periphery of the can end instead of the usual sealing compound.
Instead of placing the sheet material on the can end, the sheet material can be placed over the mouth of the can before sealing.