Patent Application
20130320029
1. Field of the Invention
This invention relates generally to the field of plastic containers that are adapted to be heat sterilized. More specifically, the invention relates to an improved retortable container that is more dimensionally stable during the sterilization process than conventional predecessor containers.
2. Description of the Related Technology
Certain products require sterilization during the packaging process in order to inhibit the growth of bacteria. Products requiring sterilization include foods such as milk, yogurt and various sauces, as well as certain pharmaceutical products. Thermal processing, sterilization, canning and retorting are all terms referring to the process of taking a food product, already sealed in its container, and heating it to a specific temperature for a specific time. The objective is to kill spoilage organisms and pathogenic bacteria, thus preserving the food and allowing it to be stored unrefrigerated for extended lengths of time.
There are multiple designs for retorting food containers, including batch systems and continuous systems. In a batch system, containers are placed in crates or baskets, which are then loaded into a vessel into which the heating medium is introduced. This method is the oldest and most traditional and also the most versatile in the range of products and container sizes it can handle. In a continuous retort system, a conveyor is used to continuously transport the containers to be sterilized through a heating chamber that contains the heating medium. There are advantages to each method depending on individual processing operations and, just as important, the type of food being processed.
Traditionally, products that require heat sterilization have been packaged in glass containers, which are relatively stable at elevated temperatures and pressures. However, in recent years plastic retortable containers have come into use. Plastic containers tend to be less expensive than glass containers and safer in many respects because they will not shatter when dropped.
The temperatures of the retort process are elevated enough to temporarily increase the internal pressurization of the container. Plastic retortable containers accordingly have been designed to permit limited and reversible controlled flexure of one or more surfaces in order to accommodate the internal volumetric changes that are inherent to the retort sterilization process. U.S. Pat. No. 5,217,737 to Gygax et al. discloses a retortable plastic container that has a flexible bottom portion to accommodate internal volumetric changes. Other retortable containers that have been in commercial use have a champagne style bottom portion that is designed to permit a certain amount of flexure. However, when using a continuous retort process the flexure of retortable plastic containers must be limited so that it will not interfere with the process of conveying the container through the continuous retort system. Typically, such conveyors require at least two dimensionally stable points of contact on the container.
In designing such containers, the sidewall must be formed of a sufficient thickness to provide the requisite strength and stability. However, because of the significant expense of plastic resin when such containers are being produced on a commercial scale, keeping the containers as lightweighted as possible is also an important consideration. These two design factors are obviously in tension with each other. Any improvements to retortable container designs that would tend to enhance strength and stability without significantly adding to material costs would be appreciated by those skilled in this area of technology as an important advance.
A need accordingly exists for an improved retortable container that exhibits improved dimensional stability and strength during the retort process without significantly adding to material costs.
Accordingly, it is an object of the invention to provide an improved retortable container that exhibits improved dimensional stability and strength during the retort process without significantly adding a material costs.
In order to achieve the above and other objects of the invention, a retortable plastic container that is constructed according to a first aspect of the invention includes a mounting portion that is adapted to have a lid mounted thereto and a main body portion having a sidewall. The sidewall is shaped to define a curved outer surface that defines a maximum outer width of the container. The main body portion has a groove defined therein substantially at a location that defines the maximum outer width of the container.
A retortable plastic container according to a second aspect of the invention includes a main body portion having a sidewall that is fabricated from a plastic material; and a mounting portion that is adapted to have a lid mounted thereto. The mounting portion includes a substantially vertical sidewall portion that is unitary with the sidewall of the main body portion. The substantially vertical sidewall portion has a first outer radius and a mounting flange that extends upwardly and outwardly at a first angle from the substantially vertical sidewall portion. The mounting flange also has a second outer radius that is greater than the first outer radius.
These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.
Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views, and referring in particular to
The sidewall 18 is preferably fabricated from a plastic material that has the requisite characteristics for withstanding the retort process, such as a multi-layer material including polypropylene. The sidewall 18 also defines a bottom portion 20, best shown in
The lid 14 is preferably fabricated from a metallic material such as steel or aluminum, and may be an easy open type lid having a pull tab 15.
The main body portion 16 of the container 10 is preferably constructed so as to be substantially symmetrical about a longitudinal axis 26, as is best shown in
A first groove 22 is preferably defined in the sidewall 18 substantially at a location that defines the maximum outer width of the container. In addition, a second groove 24 is defined in the sidewall 18 at a location that defines the minimum outer width of the container.
Both the first groove 22 and the second groove 24 preferably extend substantially within a horizontal plane about an entire circumference of the main body portion 16. Moreover, in the preferred embodiment, the first and second grooves 22, 24 are substantially identical in size and shape as viewed in longitudinal cross-section, as shown in
The purpose of the first and second grooves 22, 24 is to provide dimensional stability to the container 10 during the retort process, and in particular to provide at least two dimensionally stable points of contact for the conveying apparatus in a continuous retort system. In the preferred embodiment, the two dimensionally stable points of contact are the location of the maximum outer width DMAX and the maximum outer width of the lid 14, which occurs at an end curl portion 42, best shown in
The angle β is preferably substantially within a range of about 20° to about 40° and more preferably substantially within a range of about 25° to about 35°. The second groove 24 also preferably has a maximum depth DG that is preferably substantially within a range of about 0.074 inch to about 0.134 inch, and more preferably substantially within a range of about 0.084 inch to about 0.124 inch. The second groove 24 further preferably has a maximum width WG it is preferably substantially within a range of about 0.078 inch to about 0.138 inch, and more preferably substantially within a range about 0.088 inch to about 0.128 inch.
Referring now to
A difference between the second outer radius R4 and the first outer radius R3, which represents the width of the mounting flange 34 as viewed in longitudinal cross-section, is preferably substantially within a range of about 0.06 inch to about 0.18 inch. More preferably, the difference between the second outer radius and the first outer radius is substantially within a range of about 0.09 inch to about 0.15 inch.
A ratio R3/R4 is preferably substantially within a range of about 0.865 to about 0.985, more preferably substantially within a range of about 0.875 to about 0.975 and most preferably substantially within a range of about 0.885 to about 0.965.
The first angle α is preferably substantially within a range of about 55° to about 85°, and more preferably substantially within a range of about 65° to about 85°.
The sidewall 18 as well as the substantially vertical sidewall portion 32 preferably has a thickness T that is substantially within a range of about 0.01 inch to about 0.05 inch, and more preferably substantially within a range of about 0.02 inch to about 0.035 inch.
As shown in
Plastic container 50 also preferably includes a main body portion 56 having a sidewall 58. The sidewall 58 is preferably fabricated from a plastic material that has the requisite characteristics for withstanding the retort process, such as polypropylene. The sidewall 58 also defines a bottom portion 60, best shown in
The main body portion 56 of the container 50 is preferably constructed so as to be substantially symmetrical about a longitudinal axis 68, as is best shown in
A first groove 62 is preferably defined in the sidewall 58 substantially at a location that defines the maximum outer width of the container 50. A second groove 64 is also defined in the sidewall 58 at a location that defines the minimum outer width of the container 50. In addition, a third groove 66 is defined in a portion of the sidewall 58 that represents a transition between the convexly curved lower portion 70 and the concavely curved upper portion 72, between the location of the first groove 62 and the second groove 64.
The first groove 62, the second groove 64 and the third groove 66 each preferably extends substantially within a horizontal plane about an entire circumference of the main body portion 56. Moreover, in the preferred embodiment, the first, second and third grooves 62, 64, 66 are substantially identical in size and shape as viewed in longitudinal cross-section, as shown in
The purpose of grooves 62, 64, 66 is to provide dimensional stability to the container 50 during the retort process, and in particular to provide at least two dimensionally stable points of contact for the conveying apparatus in a continuous retort system. In the preferred embodiment, the two dimensionally stable points of contact are the location of the maximum outer width DMAX and the maximum outer width of the lid 14 that is mounted to the mounting portion 52, which occurs at an end curl portion 42, best shown in
The container 50 provides superior dimensional stability during the retort process in comparison with the container 10, because of the additional reinforcement that is provided by the presence of the third groove 66.
Referring now to
The sidewall 84 is accordingly preferably fabricated from a plastic material that has the requisite characteristics for withstanding the retort process, such as a multi-layer material including polypropylene that can be formed using an extrusion blowmolding process. Alternatively, sidewall 84 may be fabricated from a material such as PET and formed using a stretch-reheat blowmolding process.
The bottom portion 86 is preferably constructed as described in U.S. patent application Ser. No. 13/347,261, filed Jan. 10, 2012, the entire disclosure of which is hereby incorporated by reference as if set forth fully herein. It includes defines a raised inner portion and at least one substantially flat bottom support surface. The substantially flat bottom support surface is curved and positioned near a radially outermost edge of the bottom when viewed in bottom plan. A groove is defined in the substantially flat bottom support surface. In addition, a first side wall portion that extends upwardly from the radially outermost edge of the bottom is shaped as a truncated cone, giving the bottom portion greater dimensional stability under retort conditions. The container bottom exhibits superior dimensional stability with respect to predecessor designs.
The main body portion 88 is preferably shaped so as to be substantially symmetrical about a longitudinal axis thereof.
As
Both the first and second grooves 92, 94 preferably extend about an entire circumference of the container 80, with both the first and second grooves 92, 94 being disposed within a respective substantially horizontal plane. Both the first and second grooves 92, 94 are also preferably shaped so as to be substantially symmetrical about the respective horizontal plane that bisects the groove.
Preferably, at least one of the grooves 92, 94 is provided with reinforcement structure 95 on the portion of the sidewall 84 that defines the groove. In the preferred embodiment, the reinforcement structure 95 is provided within both of the grooves 92, 94 and is configured to limit vertical expansion and contraction, i.e. a “bellows effect,” of the main body portion 88 in response to force that is applied to the sidewall 84. Such force may be the result of internal pressurization of the container 80 during the retort process, or top load force caused by stacking of containers during transport or retail display.
The reinforcement structure 95 preferably includes a plurality of flutes 100, 101 provided on the portion of the sidewall 84 that defines the respective groove 92, 94. Each of the flutes 100, 101 preferably has a vertical component, and more preferably is oriented so as to be substantially vertical. The flutes 100, 101 are also preferably spaced substantially evenly about an entire circumference of the respective groove 92, 94. In the preferred embodiment, each of the flutes 100 is of like size and shape, as are each of the flutes 101. As will be described in greater detail below with reference to
The sidewall 84 of the main body portion 88 is preferably contoured in an hourglass shape so as to have a first substantially concave portion 96 and a second substantially convex portion 98. In the preferred embodiment, the first substantially concave portion 96 is positioned above the second substantially convex portion 98. Preferably, the first substantially concave portion 96 defines a minimum lateral dimension of the main body portion 88 and the second substantially convex portion 98 defines a maximum lateral dimension DMAX of the main body portion 88.
The first upper groove sidewall 112 is preferably connected to the groove bottom 107 by a first concave fillet 116 having a third average radius of curvature R11 and to the outer portion of the sidewall 84 by a second convex fillet 118 having a fourth average radius of curvature R12. Similarly, the second lower groove sidewall 114 is connected to the groove bottom 107 by a first concave fillet that is preferably substantially symmetrical to the first concave fillet 116 and to the outer portion of the sidewall 84 by a second convex fillet that is preferably substantially symmetrical to the second convex fillet 118.
The first upper groove sidewall 122 is connected to the groove bottom 107 by a first concave fillet 126 and to an outer portion of the sidewall by a second convex fillet 128. The first concave fillet 126 has an sixth average radius of curvature R13 and the second convex fillet 128 has a fifth average radius of curvature R14.
Preferably, a ratio R13/D2 of the sixth radius R13 to the maximum depth D2 is substantially within a range of about 0.05 to about 0.6, more preferably substantially within a range of about 0.10 to about 0.5 and most preferably substantially within a range of about 0.15 to about 0.4.
A ratio R14/D2 of the fifth radius R14 to the maximum depth D2 is preferably substantially within a range of about 0.1 to about 0.6, more preferably substantially within a range of about 0.2 to about 0.5 and most preferably substantially within a range of about 0.3 to about 0.4.
Preferably, a ratio D1/D2 of the minimum depth D1 to the maximum depth D2 is substantially within a range of about 0.1 to about 0.9, more preferably substantially within a range of about 0.2 to about 0.8 and most preferably substantially within a range of about 0.35 to about 0.65.
A ratio D1/DMAX of the minimum depth D1 to the maximum lateral dimension DMAX of the container 80 is preferably substantially within a range of about 0.005 to about 0.10, more preferably substantially within a range of about 0.008 to about 0.08 and most preferably substantially within a range of about 0.010 to about 0.04.
A ratio D2/DMAX of the maximum depth D2 to the maximum lateral dimension DMAX is preferably substantially within a range of about 0.01 to about 0.20, more preferably substantially within a range of about 0.015 to about 0.16 and most preferably substantially within a range of about 0.02 to about 0.08.
Preferably, a ratio of the first concave radius R11 to the minimum depth D1 is substantially within a range of about 0.15 to about 0.65, more preferably substantially within a range of about 0.25 to about 0.55 and most preferably substantially within a range of about 0.35 to about 0.45.
In addition, a ratio of the second convex radius R12 to the minimum depth D1 is preferably substantially within a range of about 0.4 to about 1.0, more preferably substantially within a range of about 0.5 to about 0.9 and most preferably substantially within a range of about 0.6 to about 0.8.
As
In addition, a ratio R8/W1 of the average radius of curvature R8 of the substantially concave portion 104 of the flute 100 to the first width W1 is substantially within a range of about 0.02 to about 0.05, more preferably substantially within a range of about 0.025 to about 0.045 and most preferably substantially within a range of about 0.03 to about 0.04.
In the preferred embodiment, a ratio R9/W2 of the average radius of curvature R9 of the substantially convex portion 106 of the flute 101 within the second groove 94 to the second width W2 is substantially the same as the ratio R7/W1. The ratio R10/W2 of the average radius of curvature R10 of the substantially concave portion 107 of the flute 101 to the second width W2 is substantially the same as the ratio R8/W1.
It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
