US 2894844 A
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Description (OCR text may contain errors)
July 14, 1959. J. G. SHAKMAN 2,894, 4
CANNING PROCESS AND PRODUCT Filed 06. :51, 1956 INVENTOR:
United States Paten CANNING PROCESS AND PRODUCT James G. Shakman, Wilmette, Ill., assignor to Pabst Brewing Company, Chicago, 111., a corporation of Delaware 1 Application October 31, 1956, Serial No. 619,518 '5 Claims. (Cl. 99-182 and improved process for canning substances which are processed during the general course of canning and which contain 'a gas, or contain vaporizable liquid, or are capable of expanding and so are capable of producing internal pressure in the can during such processing.
A more specific object of the invention is to provide a new and improved process for canning carbonated liquids, such as beer and other carbonated beverages, which are normally canned with a head space above the liquid level.
Other objects and advantages of the invention will appear from the following description in conjunction with the accompanying drawing in which:
Fig. 1 is an exploded elevational view of a can of a type suitable for use in the practice of the invention;
Fig. 2 is a vertical cross sectional view of said can after it has been filled with liquid and sealed in the initial stages of the process;
Fig. 3 is a vertical cross sectional view of the filled can of Fig. 2 after processing, and
Fig. 4 is an enlarged cross sectional view of a portion of the filled can shown in Figs. 2 and 3 illustrating the change which occurs during processing.
In accordance with the invention a material to be canned which is capable of developing internal pressure on processing, or otherwise, is sealed in a suitable container or can having concave top and bottom closures with a minimum amount of head space, said top and bottom closures being characterized by the fact that they are recessed or countersunk and have concave portions which are capable of flexing outwardly under internal pressure developed by the material in the can until they are convex but at the same time do not extend beyond the rim of the recesses or countersunk portions at the top and'bottom-of the can. If the filled can is then processed, for example, by heating or other processing, to the point where suflicient internal pressures are developed such that the concave end closures are forced outwardly in the manner just described, head space will then' be produced at the top of the filled can-but without interfering the stacking properties ofythe filled can.
One method of practicing the invention is illustrated with respect to the drawings in which the parts of the can shown in Fig. 1 comprise a cylindrical body portion 1 provided with flanges 1a and 1b, a top closure 2 and a bottom closure 3. The top closure 2 has a recessed or countersunk portion 4 and the bottom closure 3 has a recessed or countersunk portion 5.
As shown in Fig. 2 the upper closure 2 has a concave portion 6 and the lower closure 3 has a concave portion 7. In the particular embodiment shown there are annular recesses 8 and 9 within the larger recesses or countersunk portions 4 and 5, respectively. After the material to be canned 10 is placed within the can as illustrated in Fig. 2, the end closurse 2 and 3 are sealed in any suitable manner by conventional double seaming whereby the flanges 1a and 1b are interlocked with the rims of the closure members 2 and 3, for example, as shown at 11 and 12, or the bottom may be integral with the body as in an extrusion. The particular manner in which this is accomplished does not constitute a part of the inventionand therefore will not be discussed in detail.
In practicing the invention it is usually preferable to fill the can to the point where the innermost part 13 of the concave end closure 6 will be closely adjacent to the liquid level 14 as shown in Fig. 4, leaving the space 15 unfilled.
If the internal pressure of the sealed can shown in Fig. 2 is raised sufliciently the concave parts 6 and 7 of the end closures 2 and 3, respectively, pop out and assume a convex position as shown in Fig. 3. observed that the outermost parts of the convex portion in each case is within the confines of the recesses or countersunk portions 4 and 5. This inversion of the end portions 6 and 7 produces an enlarged head space as shown at 16. The conformation of the annular recesses 8 and 9 assists in maintaining the shape.
In the case of the canning of beer the change from the concave shape to the convex shape of the end closures may be accomplished during the pasteurization step when heat is the pasteurizing medium. That is to say, the beer is placed in a can as shown in Fig. 2 and is then heated in a pasteurization step at a temperature around F. thereby causing release of carbon dioxide which causes the end closure portions 6 and '7 to assume the convex shape shown in Fig. 3 and at the same time produces the head space 16.
In the case of the canning of carbonated beverages where it is conventional to carry out the canning process at a low temperature, the inversion of the end closures from a concave shape to a convex shape may take place after filling and closing the can by the expansion of carbon dioxide and water vapor when the contents of the can arrive at normal room temperature.
In some cases, substances are canned in the presence of a gas, such as nitrogen, and the expansion of the gas is sufiicient to cause the concave shape to change to the convex shape. In the case of coifee which is pressure packed in cans or packed at atmospheric pressures, there is a slow evolution of carbon dioxide which tends to produce internal pressure thereby changingthe end closures from a concave shape to the convex shape.
The invention is also applicable to the canning of tomato juice, corn, vegetables, and the like, which are pasteurized or sterilizedby processing after sealing un-.
der conditions sufiicient to generate an internal pressure that will cause the concave ends of the can to expand outwardly and assume a convex shape.
It will be understood, of course, that in the case of non-carbonated liquids including beverages Where no pressure attributable to carbon dioxide or other contained gases is present and the pressure supplied for flex ing the lids is attributable to the partial pressure of the water vapor generated, it is usually necessary to heat the contents of the can to a temperature above the boiling point of water in order to provide pressures which will cause inversion of the end closures. In processing liq- Patented July 14, 1959 It will be uids when no vapor pressure is developed, expansion of the liquid alone may invert the ends.
The invention is not limited to the employment of anyparticular temperatures in order to produce-an internal pressure necessary to cause the concaveend portions to expand to a convex shape. The temperatures generally employed will be within the range of 120 F. to 260 F. and the pressures generated within the can will vary depending upon the contents of the can. Ordinarily pressures around 50 to 90 pounds per square inch may be generated in the case of carbonated beverages.
The amount of head space provided in the can after inversion of the end closures to the convex shape is subject to variation depending upon the particular material contained in the can. Thus, for beer, ale,.and the like, a head space of around 6% of the volume is preferably provided after the end closures of the can have assumed their convex shape as shownin Fig. 3. However, by
initially using a can having concave endclosures asshown in Fig. 2 it is unnecessary to provide this head space when the can is filled and therefore smaller cans can be used to contain the same volume of liquid and still.
the fact that since the ends of the can are adapted to flex from a concave shape to a convex shape the internal pressure is reduced with the result that unusual variations in the internal pressure caused by changes in temperature or in some other manner do not strain the-cont ainer beyond practical limits.
The thickness of the sheet material used in forming the can can also vary depending upon the type of material employed, the only requirement being that the material should be rigid enough to maintain its shape but the end closure portions 6 and 7 should be flexible enough to change from a concave shape toa convex shape under the influence of the pressure generated in the can. It will be recognized that the material used in forming the can may be of the same thickness throughout but in some cases it may be desirable that the end closures be thicker than the side walls of the can. For example, in a beer can the lids or end closures can be 12 mils thick and the body mils thick. Even in such cases, however, it is not necessary that the end closures have suflicient springiness or resilience to maintain their convex shape after they have been internally expanded. The important thing is that the end closures be capable of flexing from a concave shape to a convex shape.
It will be understood that the term can is used herein in a general sense and is not limited to a metal can. The principles of the invention are applicable to the use of cans constructed of various types of materials including sheet steel, sheet aluminum and different types of plastic materials of sufficient rigidity and flexibility to serve as a container of the type described.
The invention is hereby claimed as follows:
1. A process of canning materials having gases therein, releasable upon the application of heat to said material, said process comprising sealing said material in a can having recessed ends, including initially concave end closures, in such a manner that said end closures are disposed in relatively closely confining relation to said material, and then heating said material sufficiently to release suflicient gas to build up the internal pressure in said can sufiiciently to force said end closures outwardly into convex shape within the confines of the respective recesses.
2. In a process of canning beer, the steps which comprise placing beer in an upright elongated can having a recessed bottom with a concave end closure extending substantially thereacross, thensealing the top of the can with a recessed cover member, having aconcave end closure extending substantially thereacross, in such a manner that said last mentioned closure is disposed inclosely adjacent relation to said beer, and then processing the beer in said sealed can to generate suficient pressure in said'can to cause said end closures to expand outwardly into convex shape within the confines of the recesses of said bottom and-cover member respectively.
3. In a process of canning beer, the steps which comprise placing beer in an upright elongated can having a recessed bottom with a concave end closure extending substantially thereacross, then sealingthe top of the can with a recessed cover member, having a concave end closure extending substantially thereacross, in such a manner that said last mentioned closure is disposed in closely adjacent relation to said beer, and then pasteurizing said beer, including heating said beerto a sufficiently elevated temperature to release suflicient carbon dioxide therefrom to raise the pressure in said sealed can to a pressure elfective to force said end closures outwardly into convex shape within the confines of the recesses of said bottom and cover member respectively. 7
4. A canned product comprising a sealed can having recessed ends with end closures extending substantially thereacross, said end closures being flexible between an inwardly concave position and an outwardly convex position within the confines ofsaid recesses, and a material in said can capable of developing internal pressure therein, said material being in said can in sufiicient quantity to fill said can therewith from one of said ends to a level adjacent to said end closure of the other of said ends when said can is disposed in upright position on said one end and said end closures are disposed in said concave positions, said material having pressure-developing capabilities of such a nature as to cause sufiicient pressure in said can to cause said end closures to be disposed in said outwardly convex positions within the confines of said recesses.
5. A canned product comprising a sealed can having recessed ends with end closures extending substantially thereacross, said end closures being flexible between an inwardly concave position and an outwardly'convex position within the confines of said recesses, and a carbonated liquid in said can in sufficient quantity to fill said can with liquid from one of said ends to a level adjacent to said end closure of the other of said ends when said can is disposed in upright position on said one end and said end closures are disposed in said con: cave positions, said liquid being carbonated to such an extent that the carbon dioxide in said can normally causes suflicient pressure in said can to cause said end closures to be disposed in said outwardly convex positions within the confines of said recesses.
References Cited in the file-of this patent UNITED STATES PATENTS 1,987,817 Burns Jan. 15, 1935 2,027,430 Hansen Jan. 14', 1936 2,307,043 Hothersall Jan. 5, 1943 2,503,944 Frascari Apr; 11, 1950 2,748,005 Baier May 29, 1956