The present invention relates to a method and apparatus for imprinting an indelible ink image upon a selected substrate. Such indelible inked images are particularly desirable for use in imprinting any informational images, such as a scanable bar code, upon selected substrates that are exposed to unusually harsh environments as in industrial applications. Although the following discussion uses scanable bar codes as an example of the particular usefulness of the present invention, it is to be understood that the method and apparatus taught herein may be used on any suitable substrate and for the imprinting of other useful indicia such a sequential numbering, operating data, warning notices, etc. where long life legibility of the imprinted material is required.
Many devices exist for reading bar codes printed on packages and other objects. Bar codes may be printed on retail merchandise for product and price identification at the point of sale, warehouse inventory control, process control, and many other applications.
The basic principle employed in bar code reading devices is the detection of contrasting reflected light. A source of illumination such as a low a powered helium neon laser, produces a beam of light which is may be moved across the bar code imprint. Dark areas (bars) absorb laser light, whereas light areas (spaces) reflect light that is detected by a scanner.
Optics are typically used to expand the laser beam into a line of laser light and to move the expanded laser beam across the area containing the bar code. Without the use of optics, the laser beam would only appear as a point of light. This process is commonly referred to as “moving-beam scanning.” As the moving beam travels across the area to be scanned for a code, commonly called the scanning zone, the light and dark transition areas are detected and converted to a digital signal known as the code. A typical bar code consists of a defined number of light and dark transition areas having given ratios between the wide and narrow intervals.
Thus a scanable bar code consists of a series of solid parallel bars separated by open spaces. The bars and spaces are printed at either a full width or half width. The bars and spaces signify a bit pattern wherein wide spaces or bars are assigned a “one” while narrow spaces and bars are assigned a “zero” (or vice versa).
Prior art U.S. Pat. No. 3,728,677 employs a mirrored wheel having a polygonal periphery. Rotation of the mirrored wheel scans a laser beam across two azimuthally spaced mirrors, which deflect the beam downwardly to trace an “X” shaped pattern.
It is also known to use prisms and mirrors, or other apparatus, to turn the scanning beam direction of an optical code scanning system. For example see U.S. Pat. Nos. 3,663,800; 3,774,014; 3,800,282; 3,902,047; and 4,064,390.
U.S. Pat. No. 3,906,203 teaches scanning a bar code and measuring its interval widths by recording the time required to traverse each interval. The successive interval widths are then multiplied by a constant such as three, five, or eight. By storing and comparing the multiplied widths of successive scans, the scanner can determine whether the latest interval is about the same size as, or much smaller, or larger, than, the prior interval.
From the above description of bar codes, their formats and how they function, it is understandable that for a bar code system to function accurately it is desirable that the bar code, printed upon the object being scanned, contain clear undistorted set of dark and light parallel lines or bars. However, in many industrial applications and uses, the imprinted bar codes may be damaged by abrasion, chemicals, solvents and/or heat to the extent that the bar code or portions thereof maybe obliterated or otherwise unreadable.
Accordingly there is a need for a method and apparatus for imprinting a durable bar code that will resist the harsh environment of the industrial workplace.
In accord with the present invention a method and apparatus is taught by which a durable bar code, and/or any other printed material, may be applied to a suitable substrate material, which may then be adhesively affixed to or fastened by means of an alternative method to any product or article.
The Sony Chemical Corporation of America has developed a proprietary radiation-curable printing ink and a method of thermally transferring such ink from an ink ribbon to a selected substrate which is the subject of U.S. Pat. Nos. 6,476,840 and 5,729,272 incorporated herein by reference.
By the present invention a substrate having printed thereon a bar code, and/or any other information bearing image, using inks curable by application of UV light is subjected to a combination of IR and UV energy whereby the ink, on the printed image, is cross-linked thereby producing a durable printed image.
Using an elliptical reflector the light energy from a UV light source is convergingly directed to a focal point. However by the present invention, the substrate having an image printed thereon, using a UV curable ink, is passed through the focused UV radiation zone above the reflected light's focal point. Thus the UV curable ink image printed upon the substrate is cured by being exposed to the combination of UV and IR energy emitted from the UV light source.
Referring to
For a more detailed description of the ink used and the process of thermally transferring an inked image from ribbon 18 to labels 16 the reader is referred to U.S. Pat. Nos. 5,729,272 and 6,476,840 both of which are incorporated herein by reference.
As carrier film 15, having ink imprinted labels 19 thereon, pass through ink curing station 14, carrier film 15 is supported upon and carried upon endless belt 30 driven by rotating drive rollers 32A and 32B by motor means not shown. A vacuum pump 31 is provided to maintain a negative pressure across tables 34A and 34B to draw carrier film 15 down upon the tables. As carrier film 15 and ink imprinted labels 19 pass through the radiation zone 32, carrier film 15 is supported upon fixed tandem tables 34A and 34B. Tables 34A and 34B act to dimensionally fix the distance between UV light source 26 and ink imprinted labels 19 as they bass through the radiation zone 32. It is to be noted that ink imprinted labels 19 are oriented to pass above the focal point 35 of the UV light reflected from elliptical reflector 26 as illustrated in
After curing of ink imprinted labels 19 within radiation zone 32, the cured labels 23 are permitted to cool prior to being wrapped upon receiving roll 36. Depending upon the exact configuration and structure of curing station 14 it may be preferred to provide covered exit and entrance conduits 38A and 38B respectively, as UV radiation shields.
Although
Ink curing station 14A generally comprises a porous web type endless belt 30 supported upon support tables 34A and 34B (similar as that illustrated in
A further embodiment of the process illustrated in
Illustrated in
Similarly
However, because of the remote location of UV energy source 52 and/or of the possibility the remote UV energy source may include an IR filter, it may be necessary to provide a preheater 59 to raise the temperature of the imprinted ink above ambient temperature to assist the curing process as described further below.
Although the above embodiment employing a remote UV energy source is described as being an alternate embodiment of the
Referring now to
Since the UV energy imparted to and absorbed by the ink imprinted label, is dependent upon many variables, such as, the UV light 25, surface area of the label, ink composition, ink color, line speed, substrate material parameters, etc., a quantitative value for the distance H above focal point 35 is not possible. The distance H must be determined qualitatively by empirical techniques for a given situation.
In the configuration illustrated in
Alternatively one may consider passing an ink imprinted substrate 19A through the extended radiation field 41 at a distance L beyond focal point 35. However since IR energy decreases more quickly than UV energy as a function of distance from its source, optimizing the level of IR and UV energy received upon imprinted substrate 19A from UV light source 25 becomes a problem without adding means for preheating the imprinted ink on substrate 19A as it approaches radiation field 41. Such a preheating device 42 is schematically illustrated in
It is to be also considered that a preheater, such as preheater 42 my also be used to preheat substrate 19 in
It is to be understood that because of the massive heat generation by the UV light source 25 within the close confines of the apparatus as schematically illustrated herein it is necessary to provide adequate circulating cooling air within the UV apparatus schematically illustrated as cooling fan 22 in
Referring now to
Having operable shutters that may be closed about UV light source 25 is particularly useful when the operator desires to stop the machine throughput but does not desire to totally turn off UV light source 25, or if the desired line speed is otherwise sensed to diminish or stop for unanticipated causes. By closing shutters 52 and 54, about UV light 25, IR and UV radiation is prevented from reaching labels 19 and possibly causing the labels to catch fire within the machine. Similarly should the operator need to stop the machine for maintenance and/or substrate change over, the operator may reduce the power to UV light 25 to a lower level without completely turning the UV light off whereby less time will be necessary for restart.
Although the invention has been described in detail with reference to the illustrated embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.
This application claims priority U.S. Provisional Patent Application Ser. No. 60/409,353 filed on Sep. 9, 2002 and is incorporated herein by reference.
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Number | Date | Country | |
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60409353 | Sep 2002 | US |