Apparatus and method for producing microperforated patches and labels applicable to modified atmosphere packaging

Abstract

An apparatus and method for producing microperforated patches for MAP includes drilling or punching microperforations through continuously advancing label stock. Holes can be drilled by at least one microperforating laser traversed across the label stock as it advances, a laser beam deflected or split using a servo-driven galvanometer, beam splitters, or a plurality of mirrors, or by drills mounted into a rotating die cylinder across which the stock passes as it is advanced. Numbers and sizes of microperforations can be adjusted by manipulation of laser control parameters, or by exchange of die cylinders. The laser can be a CO2 laser with between 10 W and 100 W output. The drills can be carbide drills. The label stock is typically 6-18 inches wide, and can include an adhesive covered by a release sheet. The stock to be microperforated can include separate rows of labels or can be suitable for die-cutting after microperforation.

Claims

1. A system for producing breathable patches or labels suitable for application to packaging materials for modified atmosphere packaging of fresh produce, the system comprising: a web comprising patch material, wherein the patch material is either pre-cut or is suitable for cutting into a plurality of patches; a web advancing system configured for continuous advancement of the web in an advancement direction of the web across a web processing region; at least one laser; and a controller configured to activate the at least one laser and to control application to the web of at least one laser beam from the at least one laser as the web is advanced in the advancement direction so as to drill microperforations in a plurality of locations distributed across the web in a transverse direction that is approximately perpendicular to the advancement direction, thereby drilling a plurality of separated rows and/or columns of microperforations in the web of patch material; wherein the system further comprises a plurality of beam splitters configured to be impacted simultaneously by one of the laser beams, each of the beam splitters being configured to direct a drilling portion of the laser beam onto the web, while allowing a transmitted portion of the laser beam to continue beyond the beam splitter; and wherein at least one of the beam splitters is rotatable, and is configured to direct the drilling portion of the laser beam onto the web in a variable direction.

2. The system of claim 1, further comprising a rotatable mirror configured to cause at least one of the laser beams to create microperforations in a plurality of the locations.

3. The system of claim 2, wherein the rotatable mirror is included in a galvanometer-based scanning head.

4. The system of claim 1, wherein the at least one laser includes at least one CO.sub.2 laser.

5. The system of claim 1, wherein the at least one laser includes a laser that has a maximum output power of between 10 W and 100 W.

6. The system of claim 1, wherein the patch material is pre-cut into a plurality of patches arranged in columns in the advancement direction of the web and in rows that are transverse to the columns.

7. The system of claim 1, wherein the web comprises a continuous sheet of the patch material and the system further comprises a label cutting cylinder configured to cut individual labels from the patch material.

8. The system of claim 1, wherein the web comprises a continuous sheet of the patch material.

9. The system of claim 1, wherein the web includes an adhesive applied to the entire underside of the patch material and protected by a release sheet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a continuous film microperforation system of the prior art;

(2) FIG. 2 is a perspective view of a stopped rigid polymer microperforation system of the prior art;

(3) FIG. 3A is an exploded view of a container and lid incorporating a MAP patch of the prior art;

(4) FIG. 3B is a perspective view of the assembled container, lid, and MAP patch of FIG. 3A;

(5) FIG. 4 is a perspective view of an embodiment in a first general aspect of the present invention, in which microperforations are drilled through patch material by a laser mounted above the patch material on a translational positioner;

(6) FIG. 5 is a perspective view of another embodiment in the first general aspect of the present invention, in which microperforations are drilled through the patch material by a plurality of fixed laser delivery heads mounted above the patch material;

(7) FIG. 6 is a perspective view of yet another embodiment in the first general aspect of the present invention, in which microperforations are drilled through the patch material by a laser beam that is translated across the patch material by a scanning galvanometer;

(8) FIG. 7 is a perspective view of still another embodiment in the first general aspect of the present invention, in which microperforations are drilled through the patch material by a laser beam that is reflected onto the patch material by a plurality of beam splitters mounted above the patch material;

(9) FIG. 8 is a perspective view of a second general aspect of the present invention, in which microperforations are punched through patch material by drills mounted into a die cylinder and;

(10) FIG. 9 is a perspective view of an embodiment similar to the embodiment of FIG. 7, but further including die-cut cylinders that cut the web into patches after they are microperforated, and an adhesive sprayer that sprays an adhesive onto the underside of the web.

DETAILED DESCRIPTION

(11) The present invention is a method for producing microperforated labels or patches with defined O2 flux rates for use in MAP packaging that reduces production costs and provides easy and precise control of the number and sizes of microperforations. The method is applicable for microperforating patches or labels arranged in a plurality of columns on a web. In embodiments, the method is applicable to patches provided on standard label stock intended for processing on conventional label presses, which are narrow web presses (web widths of 6″ to 18″).

(12) With reference to FIG. 4, the label stock 400 used in embodiments of the invention is typically between six inches and fifteen inches wide, i.e. suitable for use with narrow-web printing presses as are typically used by label manufactures, and either includes pre-cut labels 402 arranged in rows and columns, or is intended for subsequent die-cutting into rows and columns according to the desired label sizes after the microperforations are added to the material.

(13) In some embodiments, the label stock 400 is an inexpensive non-porous polyolefin material having an OTR ranging from 70 to 1000 cc O2/m2-day-atm, such as polyester or polypropylene, both of which have a CO2/O2 permeability ratio of 1. In other embodiments, the CO.sub.2 permeability of the label stock 400 is higher than the O.sub.2 permeability, i.e. the CO.sub.2/O/.sub.2 permeability ratio is greater than one. Examples of such materials include various nonwoven materials incorporating cross-linked poly(dimethyl siloxane). This approach has the advantage of slowing the metabolism of the fresh produce due to the limited oxygen supply, while at the same time limiting the build-up of CO.sub.2 within the package.

(14) Typically, but not always, an adhesive is pre-applied to the label stock 400 and is protected by a silicon release sheet (not shown) made from polyester or another suitable material coated with a silicone release agent that aids in the ease of label dispensing with automatic label dispensers. The adhesive can be applied to the entire underside of the label stock 400, or the adhesive can be applied only around the periphery of each label 402, leaving the centermost portion free of adhesive. In still other embodiments, a special coating is applied to the underside of each label 402 in the label stock 400 that “deadens” the adhesive in the center of the label 402 and allows the adhesive to remain tacky only at the periphery of the label 402. In embodiments, the labels 402 are polyolefin-based printable materials, and the adhesive is a pressure sensitive adhesive (“PSA”).

(15) In one general aspect of the present invention, one or more lasers are used to drill a desired number of microperforations in each of the patches (i.e. the labels) as the label stock moves through the apparatus. The holes are drilled in a two-dimensional array pattern, so as to produce at least one microperforation in each label of each row.

(16) In the embodiment of FIG. 4, a single laser comprising a power supply 404 and a laser head 406 is used to drill a desired number of microperforations 408 in the patches (i.e. the labels) 402 as the label stock 400 moves through the apparatus. In this embodiment, the laser head 406 is not static, but is moved transversely across the width of the label stock 400 by a translational positioner 410 controlled by a controller 412, as the label stock advances, so as to drill microperforations 408 in each of the plurality of labels 402 in each “row” of the label stock 400. The number, placement, and sizes of the perforations 408 in each label 402 are controlled simply by firmware and software control of the laser 404, laser head 406, and translational positioner 410. Unlike traditional approaches such as FIG. 1 that are applied to film in a web moving at high speed past the laser, this new approach, whereby both the label stock and the laser head are simultaneously in motion can be readily implemented because of the narrower width of the stock and the slower speeds at which typical label presses operate.

(17) FIG. 5 illustrates a similar embodiment, in which a plurality of low-power lasers 408 (for example 10 W lasers) are positioned laterally across the web so as to drill microperforations simultaneously as the web passes under them. In some embodiments, each laser is static, and drills single microperforations, or multiple microperforations in a single column, into each label, as determined by hardware or software programs, in predetermined portions of the label as the web passes by. In other embodiments the laser heads are shifted by a translational positioner 410 so as to each burn a lateral row or even a two dimensional pattern of microperforations in each label as it passes.

(18) FIG. 6 illustrates an embodiment in which the beam from a single, stationary laser 406 is deflected by a series of mirrors using a servo-controlled scanning galvanometer 600 so as to drill a plurality of microperforations as the label web passes beneath.

(19) Yet another approach is illustrated in FIG. 7, wherein one or more beam splitters 700 are used to divide a single, relatively high power laser beam into a plurality of beams that simultaneously drill one or more holes in each of the labels in each row. The beam splitters can be rotated or fixed, and each beam splitter can split its input beam into two or more than two outputs, depending on the embodiment. Note that, for clarity of illustration, the laser beam is shown to emerge from the final beam splitter 700. In similar embodiments, the row of beam splitters 700 is terminated by a mirror, so that all of the laser energy is directed to the labels.

(20) Embodiments of this general aspect use a CO.sub.2 laser with an output power of between 10 W and 100 W. This is in contrast to laser outputs of 100 W to 400 W for typical implementations in fast moving webs, such as the example shown in FIG. 1. The lower power levels of this general aspect can be used because the slower motion of the label stock 400 allows the drilling time for each hole 408 to be extended. As a result, the laser heads 406 used in this approach tend to be smaller and lighter than the laser heads 210 used in the approach of FIG. 1, which facilitates the mounting of a plurality of fixed heads 406 above the labels, movement of the laser head(s) by a translational positioner 410, or the use of a fixed, servo-driven galvanometer to move a single laser beam across a row of labels.

(21) FIG. 9 is a perspective view of an embodiment similar to the embodiment of FIG. 7, but further including die-cut cylinders 902, 904 that cut the web 400 into patches 402 after they are microperforated 408, as well as an adhesive sprayer 906 that sprays an adhesive 908 onto the underside of the web 400. Cutting cylinder 902 is positioned above the web 400, and includes die cutting blades 900 configured to press against a receiving cylinder 904 positioned below the web, thereby cutting through the web material 400 as it passes between the cylinders 902, 904.

(22) Movement of the laser head(s) 406 in embodiments across the label web is further facilitated by the narrow width of the web, which is typically between six inches and fifteen eighteen inches, as compared to widths on the order of 54-60 inches that are typically encountered when using the method illustrated in FIG. 1 to microperforate films on slitter/rewinder machines at plastic converters or collapsed blown plastic tubing on bag-making machines used by polymer film manufacturers.

(23) Typically, the applied adhesive 908 in this first general aspect covers the entire rear surface of the label 402, and will not occlude the drilled holes 408 because the adhesive 908 is ablated during the laser drilling process. Occlusion can be avoided by appropriate adjustment of the laser power and pulse duration, and/or by proper selection of the adhesive type and thickness applied to the labelstock 400 that is used for making the microperforated labels 402. As an alternative, a patterned adhesive can be applied only to the periphery of plain polyolefin film that does not have an adhesive backing, thereby leaving the center of the label free of adhesive and eliminating concerns about adhesive occlusion of the laser-drilled holes. In still other embodiments, a fully adhesive-coated labelstock 400 is used, and the adhesive in the centermost portion of each label 400 is “deadened” using a special coating and a printing plate, so that only the periphery of each finished label 402 is tacky.

(24) With reference to FIG. 8, in a second general aspect of the invention the microperforations 408 are mechanically punched through the labels 402 as they pass through the apparatus by carbide drills, pins, or some other mechanical hole-punching feature (referred to herein generically as “drills”) 800 mounted into a rotating die cylinder 802. In embodiments, the microperforations 408 are approximately 100 microns in diameter. In some of these embodiments, the die cylinder 802 can be heated by an applied heat source. As an alternative, label stock having adhesive applied in a pattern only on the peripheries of the labels can be mechanically drilled without any concerns for adhesive occlusion of the mechanical holes.

(25) In various embodiments, air or another gas is applied to the reverse side of the label stock 400 so as to remove material that is punched out of the microperforations 408. In some embodiments the stock 400 is passed over a pad, or between pads, so as to wipe such materials away from the stock. In certain embodiments where the label material 400 is continuous on the roll and is die-cut into labels, the drills 800 are included in the die cylinder that cuts the labels, so that the microperforation and die-cutting take place in a single step. In other embodiments the drills are provided on a separate microperforating die cylinder. In various embodiments, a pair of cylinders 802, 804 is provided on opposing sides of the label web in a male/female relationship, with the “female” 804 cylinder having indentations into which the drills 800 from the “male” 802 die cylinder enter as they pass through the labels, in a manner that is similar to operations used for embossing polymer materials.

(26) According to this general aspect, the numbers and/or sizes of the microperforations 408, and hence the gas permeability of the patches (i.e. the labels) 402, can be varied simply by exchanging the microperforating die cylinder in the apparatus.

(27) The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. Each and every page of this submission, and all contents thereon, however characterized, identified, or numbered, is considered a substantive part of this application for all purposes, irrespective of form or placement within the application.

(28) The invention illustratively disclosed herein suitably may be practiced in the absence of any element which is not specifically disclosed herein and is not inherently necessary. However, this specification is not intended to be exhaustive. Although the present application is shown in a limited number of forms, the scope of the invention is not limited to just these forms, but is amenable to various changes and modifications without departing from the spirit thereof. One of ordinary skill in the art should appreciate after learning the teachings related to the claimed subject matter contained in the foregoing description that many modifications and variations are possible in light of this disclosure. Accordingly, the claimed subject matter includes any combination of the above-described elements in all possible variations thereof, unless otherwise indicated herein or otherwise clearly contradicted by context. In particular, the limitations presented in dependent claims below can be combined with their corresponding independent claims in any number and in any order without departing from the scope of this disclosure, unless the dependent claims are logically incompatible with each other.