Fold inspection device for transparent overwrap film

An imaging apparatus and process for inspecting polymeric film seals and folds. Incident light is applied to the package to cause either reflected or transmitted light to reflect a pass through the poly wrap. The wrap affects the transmitted or reflected image in a manner which can be analyzed to determine the quality of the poly film application.

I. BACKGROUND OF THE INVENTION
 A. Field of the Invention
 This invention relates to inspection systems for overwrap on packaged goods
 to ensure a complete and quality overwrap, proper graphics, and pack
 construction.
 B. Description of the Prior Art
 Inspection systems for packaged goods generally are known for use as
 quality control devices, and process control for manufacturing. Consumers
 may outright reject or return defectively packaged merchandise, for a
 variety of reasons. Improperly sealed consumer goods can raise safety and
 freshness concerns and perfectly good items will routinely be returned for
 refund and disposal with concomitant losses. Inspection is one way of
 ensuring a minimum of packaging defects.
 High speed inspection systems have limited time to determine the
 acceptability of a product and are generally limited to examination of
 planar surface features; e.g. a misprint or a defect in the product
 exterior. Objects with a circular cross section; e.g. cigarettes, can be
 scanned sequentially using image scanning technology such as that in U.S.
 Pat. Nos. 5,235,649, 5,366,096, 5,414,270, 5,013,905, and 4,976,544, which
 are incorporated herein in their entireties.
 However, a transparent or partially transparent wrapper; e.g. a poly film
 wrapper, is invisible to normal optical inspection devices. A method for
 inspecting the condition of the wrap is needed to ensure the packaging is
 intact and defective goods are not shipped.
 C. Summary of the Invention
 Applicants have developed a novel imaging process to inspect polymeric film
 seals and folds. Incident light is applied to the package to cause either
 reflected or transmitted light to reflect a pass through the poly wrap.
 The wrap will affect the transmitted or reflected image in a manner which
 can be analyzed to determine the quality of the poly film application.

III. DETAILED DESCRIPTION
 Exemplary arrangements of the invention may now be seen by reference to the
 figures and this description. These examples are meant to serve as
 illustrations of the invention, and as such should not be construed as
 limiting the invention.
 The present inventive vision system is used to enhance product quality, but
 additionally is utilizable as a process inspection/control system. It
 allows an operator to see the manufacturing process dynamically as the
 cigarettes are being packaged. Therefore, a case of defectively packaged
 work is not packaged up and sent to inventory, to be discovered in a later
 quality audit, or worse, by a consumer. Thus, such a system is
 preferentially used in mainstream packaging.
 Turning now to FIG. 1, an example of a packaged item is seen. The "ideal"
 wrap would have a total of 5 lines, i.e. lines 10, 12, 14, 16, and 18 as
 closure seams, with no overlap, or minimal overlap. FIG. 2 illustrates the
 closure in an end view of the package of FIG. 1. The wrap system of FIG. 2
 illustrates that the excess wrap may be easily folded over the cut to make
 a heat sealed or glued closure.
 Lines 20, 22, 24, and 26 all originated with the same (upper or lower) edge
 of the poly film wrap. In a manner similar to wrapping any package, the
 excess film is physically folded over from side-to-side, then end-to-end,
 or vice versa. Sealing means, usually a heat treatment or the application
 of an adhesive substance, completes the wrapping procedure.
 A properly wrapped package, depending on the sequence of folds, the
 placement of the overwrap, and amount of excess material, will have a
 distinctive "fold" pattern such as may be seen in FIG. 2.
 An error in folding, placement of overwrap, or a tear in the wrap will
 drastically affect the pattern on the end. For example, in FIG. 5, the
 entire wrap is skewed to one side and the pattern is clearly visible as
 "wrong."
 Poly film, usually, is invisible when used as an overwrap--allowing
 advertising indicia or package printing to show through. Thus, standard
 inspection techniques will fail to pick up the overwrap defects, be they
 misplacement, misfolding, tearing, wrinkling, or other defects.
 Applicants novel system takes advantage of a unique property of clear or
 partially clear poly film. The film acts, for brief distances, as a light
 conductor. In many ways this is similar to fiber optic light transmission,
 when an endpoint is reached with a medium which has a different index of
 refraction, light appears to emanate from the endpoint, causing it to
 "glow."
 Thus, as may be seen in FIG. 4, light source 40 sends incident light into
 the wrap itself. The light "escapes" from the poly film wrap at edges and
 folds where it reaches a reflective boundary. The escaped light 42 is
 captured via lens 44 to camera 46 and is thence sent to an image processor
 (not shown).
 Image processing is undertaken to yield an image of the folds, or a clear
 surface image. In one embodiment, the surfaces without folds may be imaged
 for defects. By way of example, FIG. 6 illustrates such a system. Incident
 light generator 60 generates incident light 62 which is projected into
 poly film 64. Strong reflected or diverted light will be picked up at lens
 66 and focused on camera 68 for transmission to image analysis software.
 FIG. 7 illustrates a defect being detected by the novel system. Light
 source 70 generates incident light 72 which enters the poly film surface
 73. Defect 74 represents a missing portion of poly film wrap. The edges of
 the defect 75 are clearly illuminated by the light in the poly film. The
 defect is within field of vision 76 of camera 78 and lens 77. The image,
 including defect, is transmitted via cable or data transfer device 79 to
 be processed.
 The image analysis of the present invention is performed by the following
 steps The fold pattern or tear pattern is captured in the camera scan.
 Color or black & white scanning may be used, but black and white scanning
 is faster, has a higher resolution, and is more easily adapted for partial
 scanning. The image is transferred via I/O circuitry or the like to the
 computer. The computer has reference images stored which are recognized as
 acceptable images. U.S. Pat. No. 5,537,670 provides a thorough explanation
 of such a system and is incorporated herein by reference.
 A package such as that seen in FIG. 7, with its flaw in the surface, would
 be compared against a databank of acceptable reference images, then
 rejected.
 The system also may inspect for tear tape cuts and proper tear tape
 placement, as may be seen in FIG. 3.
 While edges 32 and folds 30 may be inspected, so too may be tear tape
 protrusion 34 and tear tape cuts 36, for placement and cutting
 completeness.
 The inspection system may also take advantage of the blocking
 characteristics of a poly wrap film which has printing upon it. The image
 printed upon the film will act to block light transmission in a particular
 pattern, or reduce it. The system can rapidly "learn" this light
 scattering by allowing it to store acceptable images in its database.
 Then, occluded light patterns are learned as acceptable. Other wrap
 patterns likewise may be learned in a manner similar to the system's
 initial programming with conventional packaging fold and surface images.
 Camera devices may be standard video cameras, charge-coupled-devices, or
 other optical detectors which may receive transmitted or reflected light
 from the poly film.
 The light source utilized may be fluorescent, incandescent, solid state
 generated (e.g. LED constant or "pulsed"), infrared, or other type of
 light, so long as the wavelength will be transmitted by the poly film. An
 exemplary strobe is manufactured by EG&G, Inc. of Salem, Mass. Part number
 2020 is particularly useful.
 An apparatus according to the present invention will be useful for the
 optical inspection of objects wrapped in a transparent or semi-transparent
 material.
 The transparent material is a filmic material, laminated or unlaminated,
 coated or uncoated, with or without an image on the film. The film is made
 from polypropylene, polyethylene, cellophane, or the like. Thickness may
 be in the range of from about 0.1 mil to 10 mils, preferably from the
 range of 0.5 to 3 mils, more preferably from about 1-2 mils, most
 preferably about 1.5 mils.
 The apparatus will have a light source positioned such that light enters
 the transparent wrap material at an intensity greater than ambient light
 conditions, and an optical detector which receives light from the
 transparent wrap material. A light source from 1 to 100 watts may be used,
 but it has been found most efficient to occlude the ambient light to some
 extent and use lights in the lower end of that range, from 1-25 watts, and
 preferably from 1-15 watts output.
 The apparatus will further be equipped with an image analyzer which
 receives input from the optical detector and determines the acceptability
 of that input.
 Panasonic.TM.'s GPMF702D black & white camera is particularly useful and is
 commercially available for use as the optical detector. Such a camera is
 capable of partial scanning which results in increased frame speed and
 higher inspection rates, and is easily networked into a 486 computer by a
 conventional means.
 The presently preferred controller is a 486 Pentium.TM. based processing
 unit, manufactured and designed by PPT of Eden Prairie, Minn. under the
 designation VPC 400 Vision Processing Controller. The controller
 preferably is linked to an optical image display which can display the
 images generated visually to an operator who can adjust or halt a
 packaging machine manually. An automated feedback loop may also be
 provided for correcting certain known defects, e.g. from a library of
 "defective" images, certain pre-programmed corrective steps may be
 automatically executed by the controller and inputted into the packaging
 machine.
 One of skill in the art, having regard for this disclosure, may make many
 modifications and improvements hereto without departing from the scope of
 the appended claims.