This invention relates to containers, and more particularly to metal containers and beverages and producing markings on same.
Two piece metal beverage cans include a can body on which a can end is attached by a seam. Commercial two piece beverage cans are formed by a drawing and ironing process that forms the body sidewall integral with the base. Three piece metal cans include a cylindrical body, each end of which has a can end attached by a seam.
Two piece beverage cans are produced in vast quantities for beverages and foods use; three piece beverage cans are produced in vast quantities for food uses. Accordingly, the components of the cans must be produced at high speeds.
Conventional beverage cans and many easy open food cans have pull tabs. Pull tabs are formed from metal sheet in a tab press. Because of the quantities required, conventional tab presses form multiple tabs at once in lanes of two, three, or four tabs.
Typically, a pre-lacquered sheet of aluminum is fed from a coil into a shell press to form the can end shells. A pre-lacquered strip of aluminum is fed from a coil into a tab press to form the pull tabs. The shells and pull tabs are combined in a conversion press to form the unseamed can end.
Decoration of can ends, especially pull tabs, is known. For example, U.S. Pat. No. 6,105,806 discloses laser etching or removal of portions of a coating on a pull tab. U.S. Pat. No. 6,498,318 acknowledges difficulties in marking metal cans and discloses ablating metal pull tab stock.
U.S. Pat. No. 9,187,221 discloses marking on a can end and tab of a two dimensional code by applying a laser to the coated substrate to change an appearance of at least a portion of a photonically active component substantially without burning, etching, or ablating the lacquer, thereby forming an image. Preferably, a CO2 laser is employed that has a beam width that is less than approximately 50 microns, more preferably no more than approximately 30 microns, more preferably no more than approximately 10 microns, and preferably approximately 5 microns. Accordingly the image may be formed by dots that have a dimension of less than approximately 50 microns, preferably no more than approximately 30 microns, more preferably no more than approximately 10 microns, and preferably approximately 5 microns. Accordingly the image may be formed by dots that have a dimension of less than approximately 50 microns.
JP 2011 020701 (Taguchi) discloses marking on a flap that is separated from the structural portion of the tab by fold lines. After marking is applied to the flap, it is folded over the structural portion of the tab to form a cover.
QR codes are the most frequently used code type for applications that are read by smartphone scanning software. Conventional QR codes take in excess of 200 ms to write by conventional laser marking.
The inventors are aware of a commercial, conventional system for laser etching pull tabs that includes a CO2 laser that often operates at about 100 W. Each lane of a tab press has its own laser such that the tab press can operate at about 700 tabs per minute with a laser having a resolution or dimension of approximately 100 microns. Typically, a dark colored lacquer is removed by the laser to expose bare aluminum in the form of a simple logo or a few characters. The limitation on the process speed is also a limitation on the amount of decoration.
Laser marking of coatings is employed for flexible and card packaging for various marking applications. Typically, a thermally active pigment is loaded into a transparent or light colored lacquer, and a CO2 laser induces a color change. For example, a laser may be applied to a white lacquer label to display black text. Laser marking systems of this type are available from Sun Chemical, under the trade name Sunlase and employ a 100 micron YAG laser.
Conventional laser application to tab or other metal can substrates usually require a very high beam intensity and thus the use of high powered fibre lasers, for example 20 W or 40 W with a small focal length, for example 180 mm in order to etch a coating or metal substrate. As a result, the laser markings usually have characteristic dimensions of much less than 200 microns, typically only 50 to 150 microns.
A method for marking a code on a beverage can tab structure can include a combination of spot size (for forming an element of a two dimensional code), code area, matrix size (that is, number of elements), speed of forming the code, and code readability to achieve a commercial viable method that provides sufficient capacity of unique codes for use in the beverage can industry. The present invention is not intended to be limited by the particular combinations set out in the specification. Rather, the claims are intended to define the scope of the invention.
The method for marking a code on a beverage can tab structure includes forming a two dimensional code on a surface on a body portion of the beverage can tab structure, which encompasses both marking the tab after it is formed in a tab press and marking the tab stock before it enters the tab press. The elements of the code preferably are formed in a coating that is dark by applying an approximately round laser light forming spots. The term round is used herein to refer to approximately circular at the plane (that is, the metal surface) on which the light is projected (that is, the spots). The spots preferably are formed one at a time such that the laser remains stationary until the spot is formed. Then, after forming a spot, the laser is moved and/or the tab structure is moved to another desired location for forming another spot. More than one laser may be used to form more than one spot at a time. The process is repeated until the desired code is formed.
The laser light preferably disturbs the coating, thereby forming light-colored spots that are approximately round and have a minimum diameter of at least 200 microns. The spots form a two dimensional code, preferably a Data Matrix Code, that is readable by a wireless communication device. Preferably the code area is less than 6 mm by 6 mm.
Consumer scannable codes of less than 6 mm square are conventionally problematic and are not currently used commercially in the beverage can industry because, the inventors surmise, two dimensional codes (especially QR codes, which is the most popular version used in packaging) have a resolution that is too fine to read reliably when placed in the small available area of commercial tabs, according to the conventional wisdom that a small code requires high resolution to achieve a high number of unique combinations of elements. In some circumstance using some embodiments of the disclosure, a custom app having built-in scanning software for a smartphone may be required.
The present invention is not limited to the 6 mm by 6 mm code size limit unless the limit is expressly set out in the claims. The code is preferably read within the given process time target of approximately 50 ms.
Thus, in some embodiments, a DMC code that is scannable by conventional wireless communication devices (regardless whether using conventional or customized scanning apps) enables a quantity of possible codes that is large enough to create a unique ID for the beverage can market.
Conventional codes require a quiet zone, thus would make the available space even smaller on the tab recess. Accordingly, an inverted code (that is, forming light colored elements on a dark background) enables the use of a code using the background surrounding the code as the quiet zone.
Another embodiment of the present disclosure provides an unseamed beverage can end comprising a shell and a tab. The shell including a curl, a sidewall, a center panel, and a score in the center panel for forming a tear panel. The tab is attached to the center panel by a rivet. The tab includes a body portion that has a surface. The surface has a coating that is dark; and a marking code on the coating. The marking code is a plurality of light spots achieved by a round laser light. Each of the plurality of light spots has a minimum dimension of at least 200 microns. The plurality of light spots forms a two dimensional code that is readable by a wireless communication device.
The tab on which the code is applied includes a nose, a heel, and a structural body between the nose and the heel. The structural body has a land through which a rivet can be attached to affixed the tab 26 to a beverage can. As shown, code 28 is formed directly on the structural body of tab 26.
Code 28 can be any two dimensional code capable of being read by a scanner or wireless communication device, such as an app for a commercial smartphone. The code may be of any type such as an Aztek code, a MaxiCode, a QR code, or, as illustrated in
As illustrated in
Tab 126 includes a heel 140, a nose 142 (shown as underneath center panel 120 in the figures because tab 126 is in its actuated position after opening a tear panel), a rivet island 144, and a panel 146. Tab 126 is actuated in a conventional way by lifting heel 140 to pivot the tab about the rivet such that nose 142 presses down on the tear panel.
Panel 146 is continuous or hole-less and flat to provide a substrate that is approximately 6 mm by 6 mm or less, with a tolerance of plus/minus 0.5 mm, which is helpful for positioning code 128. Thus, panel 146 is flat, which is used herein to mean conventionally flat and sufficient for efficient reading of codes by conventional, retail wireless communication devices, such as an iPhone 6 and the like including corresponding conventional scanning software or applications.
As illustrated in
The inventors have determined that DMC codes are preferred for marking tabs because of efficiency of data storage relative to space available under the tab. Code 128 in
A DMC code type also enables, or makes more effective, reading the code 128 on tab 126, in part because of its high redundancy of about 50% and error checking associated with DMC codes. The inventors have demonstrated that a DMC code can be produced at commercial production speed (that is, commercial speed) of sufficient quality to be reliably read by conventional smartphone cameras and the associated scanning software. The inventors surmise that other code types may be possible.
As shown in the figures, DMC code 128 is a 14 by 14 two dimensional matrix of silver or light spots on a black background, which matrix is surrounded by the black coating. The spots as shown do not overlap. As best shown in
The method for forming code 128 can be applied to any tab structure. The term “tab structure” is used to refer to tab stock in a flat strip as it comes off the roll before it enters the tab press, finished tabs after exiting the tab press, and tabs after exiting the conversion press such that the tabs are affixed to commercial beverage ends.
The spots preferably are formed by disturbing the dark coating. The inventors have demonstrated that a black lacquer coating can be disturbed such that it changes color or brightness. A laser having fluence that is too low to cause vaporization, at least in the time intervals described herein, can be employed. In this regard, the black coating absorbs the 1 micron laser wavelength common to fiber lasers. Coatings other than black can be employed so long as the coating is capable of absorbing 1 micron laser wavelengths in order to change color or brightness as described here. Further, other coatings that absorb other wavelengths, for example (without limitation) 10 micron wavelengths of CO2 lasers, may also be employed.
The term “dark coating” is used herein to describe a black coating, and also encompasses other coatings that provide a sufficient change in color or brightness to appear to be a light spot relative to the coating when laser light is applied. Whether a coating constitutes a “dark coating” that can change color upon absorbing laser light of a given wavelength can be ascertained by routine experimentation in view of the present disclosure.
Code 128 is an inverted code such that it is formed by light spots on a dark background, rather than the conventional black squares on a white background. Conventional DMC codes require a 3 module wide white quiet zone around the code, but because the code is inverted the black coating itself forms the quiet zone.
Tabs 126 preferably are laser marked just prior to the conversion press during the portion of the cycle when the parts are stationary. At a tab making production speed of at least 650 ends per minute, with three lanes and one laser per lane, the stationary period is approximately 55 milliseconds (ms). Accordingly, code 128 preferably is applied in less than 75 ms, and more preferably less than 65 ms, and preferably less than 55 ms to form the two dimensional code. Providing a unique code to each of 10 billion cans, which chances of guessing a code at random is very small preferably dictates, at least a 12 by 12 module code.
The method of forming code 128 includes forming spots having an appropriate size at an appropriate speed. Code 128 is formed of spots having a diameter of at least 200 microns, preferably 250 to 400 microns, and more preferably between 250 and 350 microns. In the embodiment, the spots are approximately 330 microns. In circumstances in which the spots are not round, the diameter values may be calculated by averaging the minimum and maximum dimensions through the geometric center of the spot to produce an average spot diameter.
To aid in reading, the spots preferably have an aspect ratio, which is defined as the ratio of the maximum dimension and minimum dimension of the spot taken through its geometric center, of no more than approximately 1.5, more preferably no more than approximately 1.3, and more preferably no more than approximately 1.2.
The laser employed has a focal ratio of between approximately 40 and approximately 70, more preferably between approximately 45 and approximately 65 and even more preferably approximately 50 and approximately 60 which values the inventors believe are relatively larger than those for conventional laser marking processes and provide a relatively large diameter large spot (described above) and good tolerance to out of focus errors. The “focal ratio” is the focal distance divided by the beam diameter measured at the final lens. The focal distance preferably is greater than 225 mm, more preferably, greater than 275 mm, more preferably between 300 and 375 mm, and for the embodiment shown approximately 330 mm.
The laser employed to produce the spots of code 128 in
Alternatively, as illustrated in
The present invention is illustrated by the code and tab structure described herein. The present invention is not limited to the particular disclosure, but rather encompasses the full range of embodiments as defined by the claims.
This application is a divisional application of U.S. patent application Ser. No. 15/154,191, filed May 13, 2016, which claims the benefit of Provisional U.S. Patent Application No. 62/160,769 filed on May 13, 2015, and entitled “MARKING TABS WITH A TWO DIMENSIONAL CODE,” the contents of which are incorporated by reference herein in their entirety.
Number | Date | Country | |
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62160769 | May 2015 | US |
Number | Date | Country | |
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Parent | 15154191 | May 2016 | US |
Child | 17206573 | US |