Patent Application
20080041855
a) through 8(d) are a diagrammatical depiction of a characteristic of a can end that is constructed according to a preferred embodiment of the invention; and
Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views, and referring in particular to
The easy open can end that is depicted in
As may best be seen in
Preferably, the major portion 22 of the end panel 12 is curved so as to define a substantially constant radius of curvature R1 within at least one cross-sectional plane taken therethrough, such as the cross-sectional plane that is depicted in
The major portion 22 of the end panel 12 is preferably although not necessarily substantially circular in shape when viewed in top plan, as is shown in
According to one particularly advantageous aspect of the invention, the major portion 22 of the end panel 12 is constructed and arranged to facilitate a shape change of the curved major portion 22 when a predetermined pressure differential as applied between the top surface 14 and the bottom surface 16. More specifically, the curved major portion 22 is initially formed during manufacturing as shown in
In a packaging facility, a container 11 such as a metallic can will be filled with material such as food, and then the easy open end 10 will be fastened and sealed to the container 11 using the conventional double seaming process. Prior to securing the easy open end 10 to a container the packaging facility may desire to test the integrity of the easy open end 10. This can be done by using a pressure based tester such as the Borden tester discussed above. In conducting such testing, the major portion 22 of the easy open end 10 may be initially subjected to a pressure that causes the major portion 22 to revert to its as-formed shape, wherein the substantially constant radius of curvature is the initial substantially constant radius of curvature R1. The testing apparatus may then be configured so that in the event of a predetermined magnitude of leakage of the pressurized testing gas through the easy open end 10 the pressure differential between the top surface 14 and the bottom surface 16 will be equalized to an extent wherein the major portion 22 will return to the relaxed state and the radius of curvature R2. In doing so, it will generate a detectable oil canning or cricketing sound that can be detected by an operator and/or by the testing system.
After the easy open end 10 is secured to a container 11, a packaging facility will typically desire the ability to check the fill level of the container 11 as a matter of process and/or quality control. Usually, comestible items such as food are packaged in a partial vacuum or underpressure. The resulting pressure differential between the top surface 14 and the bottom surface 16 according to the preferred process will cause the major portion 22 to revert to its as-formed shape and the initial substantially constant radius of curvature R1. If the sealed container is heated, such as during a retort process, the major portion 22 may return to the relaxed state temporarily as the pressure differential between the top surface 14 and the bottom surface 16 is temporarily used by the expansion of the contents of the container 11. However, when the container 11 is cooled, the major portion 22 will return to the as-formed shape and the initial substantially constant rate use of curvature R1.
According to another advantageous feature of the invention, it is possible to detect the fill level within the container 11 by either heating the container 11 or subjecting the outside of the container 11 to an underpressure. The empty space within the container 11 between the fill level and the underside 16 of the can end 10 is known as the head space. The pressure differential between the top surface 14 and the bottom surface 16 of the end panel 12 for any given underpressure that is applied to the exterior of the container 11 or any temperature to which the container is heated will depend to a predictable extent upon the amount of head space that is present within the container 11 and accordingly on the fill level of the container 11. The major portion 22 of the can ends 10 is designed to revert to the relaxed shape and the second radius of curvature R2 at a predetermined, known pressure differential between the top surface 14 and the bottom surface 16. Since this is a known engineered characteristic of the can ends 10, the fill level of the containers 11 may be determined using a simple algorithm that will be apparent to those skilled in the art based upon the amount of underpressure that is applied to the exterior of the container or the temperature to which the container 11 has been heated.
In a first forming operation as is shown diagrammatically in
Referring now to
The curved generally concave major portion 48 of the bead die 40 is generally complementary in shape to the top surface 14 of the end panel 12 described above, while the curved generally convex major portion 42 of the bead punch 38 is generally complementary in shape to the bottom surface 16 of the end panel 12. Accordingly, the curved generally concave major portion 48 has a diameter of Dm and is preferably curved at a substantially constant radius of curvature Rd that is substantially the same as the as-formed initial radius of curvature R1 of the major portion 22 of the end panel 12. Likewise the curved generally convex major portion 42 is preferably curved at a substantially constant radius of curvature Rc that is substantially the same as the as-formed initial radius of curvature R1 of the major portion 22 of the end panel 12. In practice, there will be a slight variation between the substantially constant radius of curvature Rc and the substantially constant radius of curvature Rd as a result of the thickness of the end panel 12, with the radius of curvature Rd being slightly greater than the radius of curvature Rc. The magnitude of the difference, however, is quite small in comparison to the initial radius of curvature R1. The bead projections 44 are preferably curved at their uppermost portions at a radius Rb that is slightly greater than the radius Rc. The bead punch 38 has a major portion diameter Dp, and the bead projections have a height Hb measured from the base surface of the major portion 42. The bead die 40 has an overall working diameter Dd.
The substantially constant radius of curvature Rc and a substantially constant radius of curvature Rd are both preferably within a range of about 10 inches to about 75 inches, more preferably within a range of about 15 inches to about 50 inches and most preferably within a range of about 20 inches to about 40 inches. The convex major portion 42 of the bead punch 38 and the concave major portion 48 of the bead die 40 are both preferably spherically curved.
The ratio of the substantially constant radius of curvature Rc of the major portion 42 of the bead punch 38 to the diameter Dp of the major portion 42 is preferably within a range of about 0.05 to about 0.4, more preferably within a range of about 0.09 to about 0.25 and most preferably within a range of about 0.01 to about 0.20. Likewise, the ratio of the substantially constant radius of curvature Rd of the major portion 48 of the bead die 40 to the diameter Dm of the major portion 48 is preferably within a range of about 0.05 to about 0.4, more preferably within a range of about 0.09 to about 0.25 and most preferably within a range of about 0.01 to about 0.20.
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.
