Abstract:
Apparatus and methods are provided to minimize waste and improve quality and production in web processing operations. The apparatus and methods provide defect detection both before and after application of component patches to a traveling web to create a product. Web defect detection may be provided by way of at least one visual inspection station located upstream from the patch applicator. Patch defect detection may be accomplished by way of a visual inspection station located proximate the patch applicator. If defects are detected in either the traveling web or the component patch prior to patch application, patch application may be prevented until both a satisfactory web and patch are provided. If defects are detected after patch application, the resulting product may be culled. Furthermore, the apparatus may be provided with diagnostic software to warn against extant or imminent machine complications.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention disclosed herein relates to apparatus and methods for waste reduction and improvements to the quality and production in web processing operations, such as diaper manufacturing. While the description provided relates to diaper manufacturing, the apparatus and method are easily adaptable to other applications. 
         [0002]    Generally, diapers comprise an absorbent insert or patch and a chassis, which, when the diaper is worn, supports the insert proximate a wearer&#39;s body. Additionally, diapers may include other various patches, such as tape tab patches, reusable fasteners and the like. The raw materials used in forming a representative insert are typically cellulose pulp, tissue paper, poly, nonwoven web, acquisition, and elastic, although application specific materials are sometimes utilized. Usually, most of the insert raw materials are provided in roll form, and unwound and applied in assembly line fashion. 
         [0003]    In the creation of a diaper, multiple roll-fed web processes are typically utilized. To create an absorbent insert, the cellulose pulp is unwound from the provided raw material roll and pulverized by a pulp mill. Discrete pulp cores are formed by a core forming assembly and placed on a continuous tissue web. Optionally, super-absorbent powder may be added to the pulp core. The tissue web is wrapped around the pulp core. The wrapped core is debulked by proceeding through a calendar unit, which at least partially compresses the core, thereby increasing its density and structural integrity. After debulking, the tissue-wrapped core is passed through a segregation or knife unit, where individual wrapped cores are cut. The cut cores are conveyed, at the proper pitch, or spacing, to a boundary compression unit. 
         [0004]    While the insert cores are being formed, other insert components are being prepared to be presented to the boundary compression unit. For instance, the poly sheet is prepared to receive a cut core. Like the cellulose pulp, poly sheet material is usually provided in roll form. The poly sheet is fed through a splicer and accumulator, coated with an adhesive in a predetermined pattern, and then presented to the boundary compression unit. In addition to the poly sheet, which may form the bottom of the insert, a two-ply top sheet may also be formed in parallel to the core formation. Representative plies are an acquisition web material and a nonwoven web material, both of which are fed from material rolls, through a splicer and accumulator. The plies are coated with adhesive, adhered together, cut to size, and presented to the boundary compression unit. Therefore, at the boundary compression unit, three components are provided for assembly: the poly bottom sheet, the core, and the two-ply top sheet. 
         [0005]    A representative boundary compression unit includes a die roller and a platen roller. When all three insert components are provided to the boundary compression unit, the nip of the rollers properly compresses the boundary of the insert. Thus, provided at the output of the boundary compression unit is a string of interconnected diaper inserts. The diaper inserts are then separated by an insert knife assembly and properly oriented. At this point, the completed insert is ready for placement on a diaper chassis. 
         [0006]    A representative diaper chassis comprises nonwoven web material and support structure. The diaper support structure is generally elastic and may include leg elastic, waistband elastic and belly band elastic. The support structure is usually sandwiched between layers of the nonwoven web material, which is fed from material rolls, through splicers and accumulators. The chassis may also be provided with several patches, besides the absorbent insert. Representative patches include adhesive tape tabs and resealable closures. 
         [0007]    The process utilizes two main carrier webs; a nonwoven web which forms an inner liner web, and an outer web that forms an outwardly facing layer in the finished diaper. In a representative chassis process, the nonwoven web is slit at a slitter station by rotary knives along three lines, thereby forming four webs. One of the lines is on approximately the centerline of the web and the other two lines are parallel to and spaced a short distance from the centerline. The effect of such slicing is twofold; first, to separate the nonwoven web into two inner diaper liners. One liner will become the inside of the front of the diaper, and the second liner will become the inside of the back of that garment. Second, two separate, relatively narrow strips are formed that may be subsequently used to cover and entrap portions of the leg-hole elastics. The strips can be separated physically by an angularly disposed spreader roll and aligned laterally with their downstream target positions on the inner edges of the formed liners. 
         [0008]    After the nonwoven web is sliced, an adhesive is applied to the liners in a predetermined pattern in preparation to receive leg-hole elastic. The leg-hole elastic is applied to the liners and then covered with the narrow strips previously separated from the nonwoven web. Adhesive is applied to the outer web, which is then combined with the assembled inner webs having elastic thereon, thereby forming the diaper chassis. Next, after the elastic members have been sandwiched between the inner and outer webs, an adhesive is applied to the chassis. The chassis is now ready to receive an insert. 
         [0009]    To assemble the final diaper product, the insert must be combined with the chassis. The placement of the insert onto the chassis occurs on a placement drum or at a patch applicator. The inserts are provided to the chassis on the placement drum at a desired pitch or spacing. The generally flat chassis/insert combination is then folded so that the inner webs face each other, and the combination is trimmed. A sealer bonds the webs at appropriate locations prior to individual diapers being cut from the folded and sealed webs. 
         [0010]    Roll-fed web processes typically use splicers and accumulators to assist in providing continuous webs during web processing operations. A first web is fed from a supply wheel (the expiring roll) into the manufacturing process. As the material from the expiring roll is depleted, it is necessary to splice the leading edge of a second web from a standby roll to the first web on the expiring roll in a manner that will not cause interruption of the web supply to a web consuming or utilizing device. 
         [0011]    In a splicing system, a web accumulation dancer system may be employed, in which an accumulator collects a substantial length of the first web. By using an accumulator, the material being fed into the process can continue, yet the trailing end of the material can be stopped or slowed for a short time interval so that it can be spliced to leading edge of the new supply roll. The leading portion of the expiring roll remains supplied continuously to the web-utilizing device. The accumulator continues to feed the web utilization process while the expiring roll is stopped and the new web on a standby roll can be spliced to the end of the expiring roll. 
         [0012]    In this manner, the device has a constant web supply being paid out from the accumulator, while the stopped web material in the accumulator can be spliced to the standby roll. Examples of web accumulators include that disclosed in U.S. patent application Ser. No. 11/110,616, which is commonly owned by the assignee of the present application, and incorporated herein by reference. 
         [0013]    As in many manufacturing operations, waste minimization is a goal in web processing applications, as products having spliced raw materials cannot be sold to consumers. Indeed, due to the rate at which web processing machines run, even minimal waste can cause inefficiencies of scale. In present systems, waste materials are recycled. However, the act of harvesting recyclable materials from defective product is intensive. That is, recyclable materials are harvested only after an identification of a reject product at or near the end of a process. The result is that recyclable materials are commingled, and harvesting requires the extra step of separating waste components. Therefore, the art of web processing would benefit from systems and methods that identify potentially defective product prior to product assembly, thereby eliminating effort during recyclable material harvesting. 
         [0014]    Furthermore, to improve quality and production levels by eliminating some potentially defective product, the art of web processing would benefit from systems and methods that ensure higher product yield and less machine downtime. 
       SUMMARY OF THE INVENTION 
       [0015]    Provided are method and apparatus for minimizing waste and improving quality and production in web processing operations. 
         [0016]    Importantly, the methods taught in the present application are applicable not only to diapers and the like, but in any web based operation. The waste minimization techniques taught herein can be directed any discrete component of a manufactured article, i.e., the methods taught herein are not product specific. For instance, the present methods can be applied as easily with respect to diaper components as they can for feminine hygiene products, as they can for face masks in which components such as rubber bands and nose pieces are used. 
         [0017]    For instance, by practicing the methods of the present invention, waste of staples and elastic bands can be avoided during manufacture of face masks, for instance those disclosed in U.S. Pat. No. 7,131,442. One of the objectives is simply to recognize product during manufacture that ultimately would fail quality control inspection, and avoid placing material on to that product during the manufacturing processes. 
         [0018]    As another example, the amount of adhesive applied to certain products can be reduced by not applying adhesive to products that have already been determined to be defected or assigned to rejection. For instance, in U.S. Pat. No. 6,521,320, adhesive application is shown for example in FIG. 11. By assigning or flagging product that has already been determined to end up in a scrap or recycling pile, the adhesive flow can be stopped or minimized. 
         [0019]    In yet another exemplary application of the methods of the present invention, discrete components or raw material carried on products that have already been determined to be defected or assigned to rejection can also be removed and recycled prior to commingling with other discrete components or raw material. For instance, if an absorbent pad, such as shown at reference numeral 40 of U.S. Patent No.  6 , 521 , 320  is destined for application to a product that has already been determined to be defected or assigned to rejection, the absorbent pad can be withdrawn from the product, or never introduced in the first instance. For example, during startup or shutdown of high speed diaper manufacturing operations, a certain number of products is routinely discarded into recycling. By identification of the start up or shut down routine, avoidance of introduction of absorbent pads can be achieved. Alternatively, during stand-by, the absorbent pads often degrade by accumulation of dust. By identifying which products would bear the dust, the absorbent pads can be withdrawn from further manufacture, and no additional components would be applied to such a product. 
         [0020]    In one embodiment, a method for assembling a plurality of continuous webs is provided, including defining first web inspection parameters and inspecting at least one of the plurality of continuous webs to determine whether the at least one web conforms to the first web inspection parameters. Further, the method involves providing a chassis web which is adapted to receive a patch and providing a patch web from which the patch is cut. Finally, the cut patch is applied to the chassis web if the inspected web conforms to the first web inspection parameters. In another embodiment, the method also includes steps of defining first patch inspection parameters and inspecting a cut patch to determine whether the patch conforms to the first patch inspection parameters. While the patch inspection may provide interesting diagnostic information related to a web processing machine, the application of the patch may be limited to those patches that conform to the first patch inspection parameters. 
         [0021]    Another embodiment of the method of the present invention involves defining first web inspection parameters and a product pitch. Generally in any web process, a web is provided, which is traveling at a web velocity. This embodiment involves inspecting the web to determine whether the web conforms to the first web inspection parameters and producing an inspection value as a result of the inspecting step. This value is then recorded once per sample time interval. The sample time interval may be calculated by dividing the defined product pitch by the web velocity. While the inspection value may be as simple as a bivalent value, a more informational multivalent value may be used. 
         [0022]    In addition to the web process provided, an apparatus for carrying out the process is provided. An embodiment of the apparatus includes a continuous web supply providing continuous web material from an upstream position to a downstream position and a means for providing a patch spaced from a first side of the continuous web material. A patch applicator is provided to alter the space between the patch providing means and the continuous web material and a web inspection device is positioned upstream from the patch applicator. Additionally, a programmable controller receives an input from the web inspection device and provides an output to the patch applicator. The web processing apparatus may also include a patch inspection device that provides an output to the programmable controller. A patch reject conveyor may be positioned to receive defective patches from the patch providing means. In another embodiment of a web processing apparatus, a product inspection device may be located downstream from the patch applicator to provide an output to the programmable controller. Also, a product reject conveyor could be adapted to divert defective product as indicated by the product inspection device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a schematic of a representative web processing system; 
           [0024]      FIGS. 2A-2C  are schematic representations of a web processing system incorporating principles of the present invention; 
           [0025]      FIG. 3  is an elevation view of a patch inspection; 
           [0026]      FIG. 4  is a perspective view of a patch indexer, a patch applicator and a patch reject conveyor;  FIG. 1  is a schematic of a representative web processing system; 
           [0027]      FIG. 5  is a schematic of a second embodiment of a representative web processing system; 
           [0028]      FIGS. 6A-6C  are additional schematic representations of a web processing system incorporating principles of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0029]    Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
         [0030]    It is noted that the present waste minimization techniques and apparatus are described herein with respect to products such as diapers, but as previously mentioned, can be applied to a wide variety of processes in which discrete components are applied sequentially. 
         [0031]    Referring to  FIG. 1 , a web processing operation starts with incorporating raw materials such as paper pulp and super absorbent polymer (SAP) in a pulp mill. The mixture is sent to a core forming drum, where cores are formed for retaining liquids. A core can be placed on a tissue and processed as shown. Eventually, an additional tissue layer is formed, sandwiching the core. 
         [0032]    The process continues through debulking, core cutting and spacing, optionally, compression, and application of tape and elastics. The process then proceeds with application of outer and inner non-woven layers, and waist elastic. The web can undergo folding, extraction and trimming of excess material, and application of material to tighten the diaper about the waist. Eventually, the product is folded and packaged. 
         [0033]    As seen on  FIG. 1 ,           is shown at locations of introductions of discrete components into the process. At these locations, inspection can take place to determine the presence or absence of acceptable product introduction. In addition to visual inspection, operational characteristics such as startup/ramp-up/shutdown operations can trigger waste minimization techniques as will be described later. 
         [0034]    At each of these operations shown in  FIG. 1 , diagnostics can be performed to indicate whether the product meets acceptable criteria. If so, discrete elements, such as the core, tissue layers, elastic, etc., continue to be applied in a sequence such as shown in  FIG. 1 . If not, no additional discrete elements need be applied. 
         [0035]    Referring now to  FIGS. 2   a - c,  a web processing operation incorporating the present invention is shown. 
         [0036]    Referring now to  FIG. 2 , an additional schematic of processes of the present invention is shown. As indicated, pulp rolls  200  feed raw pulp  201  into a pulp mill  204 , where the pulp is pulverized. Super absorbent polymer is added from station  206 . The SAP laced pulp is fed onto core forming roller  208 . Cores  210  from core forming roller  208  are applied to the tissue back sheet  214  which has been introduced through tissue back sheet feeder  212 . Following debulking station  216  and core cutting and spacing station  218 , an infeed of poly layer  220 , elastic layer  222  is applied to the carrier web, in addition to non woven layer  224  and two ply top sheet woven  226 . This web then is cut at cutting station  228  into discrete inserts  230 , which are then typically placed on a article transfer and placement apparatus with active puck  230 . This device is disclosed in U.S. patent application Ser. No. 11/357,546, owned by the same assignee as the present case, and which is incorporated herein by reference. 
         [0037]    The process utilizes two main carrier webs; a nonwoven web  11  which forms an inner liner web, and a web  12  that forms an outwardly facing layer in the finished diaper  50 . In this embodiment, the nonwoven web  11  is slit, at slitter station  15 , by rotary knives  14  along three lines. One of these lines is preferably on approximately the centerline of web  11  and the other two lines are parallel to and spaced a short distance from the centerline. The effect is twofold; first, to separate web  11  into two inner liners  20 . One liner will become the inside of the front of the diaper  50  and the second liner will become the inside of the back of that garment. Second, two separate, relatively narrow strips  22  and  24  are formed which are subsequently used to cover and entrap portions of leg-hole elastics  26 . Strips  22  and  24  are separated physically by an angularly disposed spreader roll  23  and aligned laterally with their downstream target positions on the inner edges of the liner webs  20 . 
         [0038]    Adhesive patterns are applied to the liner webs  20  in target areas for the leg-hole elastics  26 . A spray gun assembly  29  of a type known in the art is preferably used to apply the adhesive patterns. Two sets of leg-hole, elastic strands  26  are introduced through laydown guides  30 , which reciprocate from side to side past each other. The strands  26  are glued to the web sections  20 , their laydown patterns following a serpentine path. Given the absence of adhesive in the area separating the inner liners  20 , for some portion of each successive diaper product, the strands  26  each track parallel to the inner slit edges of the web sections  20 . Laydown guides  30  then apply the strands  26 , which form leg-hole elastics as the web sections  20  are carried along the face of a drum or roll  32 . Those parts of the elastic patterns which are near the inner slit edges of webs  20  are then covered by the introduction of an adhesive lamination thereover of the strips  22  and  24  of nonwoven web also against the drum  32 . 
         [0039]    The side-to-side excursions of the leg-hole elastic laydown guides  30  result in arcuate segments of elastic strands extending on each side of the web centerline. After the nonwoven strips  22  and  24  have been applied to cover and entrap those parts of the elastics  26  that run nearest to and parallel to the inner edges of the webs  20 , a second pair of slitter knives  34  is used to trim away a portion of the narrow nonwoven strips  22 ,  24 , along with that part of the inner liner webs  20  to which they are laminated. This also removes those portions of the elastic strands  26  which are contained within the laminations. The resultant trimmed scrap strips  36  are removed from the process for disposal elsewhere. 
         [0040]    The effect of the last-described step is to remove the cut away portions of the elastic, eliminating its corresponding unwanted gathering effect from the crotch region of the garments  50 . The remaining portions of the curved elastic strands create a gathering effect around the leg openings of the finished garments  50 . 
         [0041]    Subsequent to the combining and trimming of the inner webs  20  and the cover strips  22 ,  24 , the combining drum  32  carries the webs to a nip with a second combining drum  38 , where the web sections  20 , with their respective curved elastic patterns exposed, are transferred to and laminated adhesively against the inside face of outer liner web  12 . This process entraps the curved elastic patterns  26  between the inner liners  20  and outer web  12  thereby forming a composite web  39 . 
         [0042]    The composite web  39  is then provided with a pattern of adhesive in preparation to receive an absorbent insert or patch  46 . The patch  46  is cut from a provided patch web  40  by a cooperation of a cutter  41  and an anvil surface on a vacuum roll  42  and rotated into position for transfer to the composite web  39  by a patch applicator  105 . If the patch  46  is to be applied to the web  39 —a determination explained more fully below—the patch applicator  105  forces the web  39  against the patch  46 , thereby adhering the patch  46  to the web  39 . 
         [0043]    Leg-hole materials  48 , if not previously removed, are cut at a cutting station  47 , thereby removing the material  48  contained within an approximate perimeter defined by the curved pattern of the elastics  26 . The running composite chassis web  39  is folded, before or after cutting out of the leg holes, longitudinally along its centerline, thereby generally aligning its front waist edge with its back waist edge. The regions  53  which are to become the side seams  54  of the garments  50  are then welded by a sealing device  49  either ultrasonically or by heat. Note that the leg holes are preferably cut out before this point, leaving only a narrow zone for welding. The weld pattern is preferably wide enough to extend into both the left side seam of one garment and the right side seam of the adjacent garment. The garments  50  are then separated by passing through a cut-off knife assembly  55 , which severs the web along the transverse axis of the side seam weld  53 . 
         [0044]    In addition to the exemplary components generally found in a web processing apparatus, the present device and methods further include an advanced defect detection system. An embodiment of the defect detection system preferably comprises at least one visual inspection station  101 , but preferably a plurality of visual inspection stations  101 . Each visual inspection station  101  may include a vision sensor, such as an In-Sight Vision Sensor available from Cognex Corporation of Natick, Mass. Since each component part of a product resulting from a web process has a point of incorporation into the product, visual inspection of each component part preferably occurs prior to the point of incorporation. The results of the visual inspections that occur are relayed from each visual inspection station  101  to a programmable logic controller (PLC)  103 . Each visual inspection station  101  may provide diagnostic capability by monitoring lighting, focus and positioning. 
         [0045]    Machine vision systems typically require digital input/output devices and computer networks to control other manufacturing equipment, in this case the splicing unit. 
         [0046]    A typical machine vision system will consist of several among the following components:
       One or more digital or analog camera (black-and-white or colour) with suitable optics for acquiring images   Lighting   Camera interface for digitizing images (widely known as a “frame grabber”)   A processor (often a PC or embedded processor, such as a DSP)   Computer software to process images and detect relevant features.   A synchronizing sensor for part detection (often an optical or magnetic sensor) to trigger image acquisition and processing.   Input/Output hardware (e.g. digital I/O) or communication links (e.g. network connection or RS-232) to report results   Some form of actuators used to sort or reject defective parts.       
 
         [0055]    The sync sensor determines when a part (often moving on a conveyor) is in position to be inspected. The sensor triggers the camera to take a picture of the part as it passes by the camera and often synchronizes a lighting pulse. The lighting used to illuminate the part is designed to highlight features of interest and obscure or minimize the appearance of features that are not of interest (such as shadows or reflections). 
         [0056]    The camera&#39;s image can be captured by the framegrabber. A framegrabber is a digitizing device (within a smart camera or as a separate computer card) that converts the output of the camera to digital format (typically a two dimensional array of numbers, corresponding to the luminous intensity level of the corresponding point in the field of view, called pixel) and places the image in computer memory so that it may be processed by the machine vision software. 
         [0057]    The software will typically take several steps to process an image. In this case, the image processing will result in either detection of the indicator material, or non-detection of the indicator material. 
         [0058]    Commercial and open source machine vision software packages typically include a number of different image processing techniques such as the following:
       Pixel counting: counts the number of light or dark pixels   Thresholding: converts an image with gray tones to simply black and white   Segmentation: used to locate and/or count parts   Blob discovery &amp; manipulation: inspecting an image for discrete blobs of connected pixels (e.g. a black hole in a grey object) as image landmarks. These blobs frequently represent optical targets for machining, robotic capture, or manufacturing failure.   Recognition-by-components: extracting geons from visual input   Robust pattern recognition: location of an object that may be rotated, partially hidden by another object, or varying in size   Barcode reading: decoding of 1D and 2D codes designed to be read or scanned by machines   Optical character recognition: automated reading of text such as serial numbers   Gauging: measurement of object dimensions in inches or millimeters   Edge detection: finding object edges   Template matching: finding, matching, and/or counting specific patterns.       
 
         [0070]    In most cases, a machine vision system will use a sequential combination of these processing techniques to perform a complete inspection. A system that reads a barcode may also check a surface for scratches or tampering and measure the length and width of a machined component. 
         [0071]    Additionally, machine downtime can be minimized by the provision of systems and methods for warning a machine operator of expected machine troubles so that scheduled maintenance can occur. 
         [0072]    The PLC  103  includes software adapted to run several routines that may be initiated by some triggering event, such as an automatic detection of a defined condition or manual input by a machine operator. Some routines are run during machine setup while other routines are run during machine operation, while still other routines are run during machine diagnostics at some point during machine downtime. 
         [0073]    The PLC  103  generally receives inputs  120  from the visual inspection stations  101 , from the various machine components, or from manual input by a machine operator on an operator interface, or human machine interface (HMI)  115 . Some of the inputs can also be from stations near the pulp rolls, pulp mills, forming rollers, or elsewhere in the system where inspection is present. 
         [0074]    The HMI  115  provides an interface for user interaction with the web processing machinery and may comprise a pressure sensitive touch screen, a keyboard, a computer mouse, or even a wireless device providing such an interface. The PLC  103  preferably provides controlling outputs  121  to the patch applicator  105 , the cutter  41  and vacuum roll  42 , a patch reject conveyor  107  and a product reject conveyor  109 . 
         [0075]    The input to the PLC  103  from each inspection station  101  preferably comprises a defect indicator  111  that represents a detected web defect at a position in the process a number of patch placements from the patch applicator  105 . That is, at any given time during machine operation, between any inspection station  101  and any patch applicator  105  in a web process, there exists material sufficient to produce a determinable number of products having a patch applied thereto. Therefore, a defect may be detected and flagged as corresponding to a specific product location throughout the process. 
         [0076]    In determining whether a patch should be applied to a product by a patch applicator  105 , the PLC  103  stores a product status indicator for each product in the process, preferably for each product between the product reject conveyor  109  and most remote visual inspection station  101 . The status indicator accumulates defect indicators  111  from the inspection stations  101  to track the progress of a product through the process. 
         [0077]    A preferred product status indicator is a byte of digital data, with each bit reflecting the defect indicator  111  for the tagged product from an inspection station  101 . For example, the least significant bit in the status indicator may represent the defect indicator for the most remote visual inspection station  101 . As the bit significance increases, so does the proximity of the respective inspection station  101  to the product reject conveyor  109 . A byte of data would provide for the possibility of eight inspection stations, and specific tracking of defects at those inspection stations. To store the product status indicator, the PLC  103  preferably includes some volatile and some nonvolatile computer memory. The volatile memory may provide quicker access times during machine operation, while the nonvolatile memory could be used to store product status indicators when the machine is paused. The minimum amount of memory required by the PLC  103  is at least partly determined by the number of visual inspection stations  101  and the number of potential products in queue between the first visual inspection station  101  and the product reject conveyor  109 . For example, if a web process utilizes eight visual inspection stations  101  and two hundred products could be in queue in any given time, a volatile memory of at least two hundred bytes would be required. 
         [0078]    The visual inspection station outputs may be sampled synchronously, or the outputs may be asynchronously analyzed by the PLC  103 . If synchronous, the outputs may be sampled at a rate equal to the speed of the traveling webs divided by the product pitch, or product size. To enable use of different product sizes in a given process, the sample timing of the inspection station results may be varied, accordingly. 
         [0079]    In addition to synchronous sampling of the inspection station results, the results could be analyzed asynchronously, which may be advantageous if various materials are incorporated into the process at different rates. Asynchronous analysis of the outputs, however, may provide less visibility into the specific defects included in a completed product. 
         [0080]    Prior to operating or running a web process, the machinery must be threaded with raw patch web material. The PLC  103  may provide a software routine, such as an automatic web threading routine, for aiding such setup. An operator threads the patch web material  40  through the machine to the patch applicator  105 . The operator then initiates the automatic threading routine by using the HMI  115 . The HMI  115  is coupled to the PLC  103  and the PLC  103  controls the patch applicator  105 , patch cutter  41 , vacuum roll  42 , and patch reject conveyor  107 . A first number of patches  46  are cut by the patch cutter  41  and culled via the patch reject conveyor  107 . The culled patches  46 a may be a predetermined number from the start of the threading routine, or cut patches  46  could be inspected by a visual inspection station  101 , and culled until the patches  46  meet visual inspection parameters  108 , as seen in  FIG. 3 . 
         [0081]    Also, if the machine was shut down or paused with existing patch web material loaded through the patch cutter, but a vacuum remains drawn through the vacuum anvil drum, the patch web material on the vacuum anvil drum will act as an air filter. The longer the patch web material is on the drum, the dirtier it will get. Such soiled material may not be used in the construction of products for sale. Therefore, the PLC  103  could provide a software routine for clearing the vacuum anvil drum of soiled web material. Patches that have been on the anvil for a predetermined amount of time, and therefore may have dust built up, are culled through the reject prior to machine startup. Like the automatic threading routine, a predetermined number of patches may be culled, or the patches may be inspected for dust build-up. 
         [0082]    In addition to threading and anvil clearing, a placement accuracy routine could be provided, for use on machine startup, or when the product configuration is changed. In a representative placement accuracy routine, patches are placed to several startup reject products, and relevant dimensions are taken by a visual inspection station  101  placed downstream from the patch applicator  105 . The inspection results indicate if and when the patch placement meets specified patch placement parameters. 
         [0083]    During machine operation, the PLC  103 , through software algorithms, determines whether a patch  46  should be placed by the patch applicator  105 , whether the patch  46  should be culled, or whether the web  39  should be allowed to continue to run without patch placement. A patch  46  is placed on the moving chassis web  39  only if both the patch  46  and web  39  are in condition for satisfactory placement. 
         [0084]    After machine setup and threading of any materials, the PLC  103  begins verifying status indicators at the &lt;application&gt; position in memory. Generally, during machine operation, the PLC  103  controls whether a patch  46  is applied by a patch applicator  105 . For each product, the PLC  103  determines the action of the patch applicator  105 , the patch reject conveyor  107 , and the product reject conveyor  109 . For each product presented to a patch applicator  105 , the PLC  103  issues one of the following commands to the patch applicator  105  and patch cutter: (1) apply patch; (2) cull patch; or (3) cull web. 
         [0085]    The apply patch command is issued if no component part has been flagged as defective in the composite web  39  that is presented to the patch applicator  105  and the patch  46 , itself, satisfies inspection parameters. When the apply patch command is issued, the vacuum anvil drum  42  remains relatively stationary while the composite web  39  having a deposited adhesive is forced by the patch applicator  105  against the patch  46 . After the patch  46  is applied, the PLC awaits the arrival of the next patch attachment site or product pitch. 
         [0086]    The cull patch command is issued if a patch  46   a  does not meet inspection parameters. Representative parameters can be seen in  FIG. 4 . Culling a defective patch  46   a  involves cooperation of the vacuum roll  42  and the patch reject conveyor  107 . The vacuum roll  42  preferably has a vacuum manifold that allows a release of the vacuum draw at a certain point around the rotation path of the roll  42 . The patch reject conveyor  107  may be a simple conveyor belt positioned just below the point where the vacuum draw may be removed, such that gravity causes the unapplied patch  46   a  to fall onto the conveyor  107 . 
         [0087]    The cull web command is issued if any component part of the composite web  39  is flagged as defective. 
         [0088]    The PLC  103  may also contain a unit diagnostics program, which monitors parameters of the patch on the anvil to determine the health of the cutting knives and anvils. The unit diagnostics program involves the use of defined patch parameters measured by a vision inspection station and compared to expected values. Information that is gathered by the diagnostics program is stored and processed in a database. Where measured parameters are approaching acceptable limits, alerts are sent to the machine operator, indicating that potential problems are developing. The HMI may automatically present the Unit Diagnostics Screen for the operator to assess the situation. Furthermore, the HMI may provide graphics and charts to assist the operator by showing trend data, measured data, and comparable data. Thus, an operator is given advance notice of a problem so that any corrections can be made during the next machine downtime. Specifically, as the knives on the patch cutter age, the patches tend to skew. Furthermore, the deviation between subsequent patch cut lengths is another indicator that a knife blade may require replacement. 
         [0089]    In an effort to prolong machine run-time between service and to reduce start-up rejects, an automatic anvil adjustment program may be provided. Such adjustment allows the anvil drum and knife roll to move relative to one another. Startup and shutdown rejects can result in rejections of many products. The movements are preferably in one millimeter increments over a five millimeter range. The adjustments are made as the machine is running to prevent wear on a single spot as well as to minimize buildup of cut web material on the anvil. In addition to the automatic adjustment, a manual override adjustment may be provided for troubleshooting. 
         [0090]    If the unit diagnostics program detects a pair of patches that have parameters outside of acceptable limits, which is usually caused by a catastrophic failure of a knife or anvil, the machine operator is alerted and the HMI preferably automatically presents the Unit Diagnostics Screen for the operator to assess the situation. For every knife or anvil that fails, two patches will be affected. Therefore, if the anvil roller can accompany eight patches, twenty-five percent of the patches will fall out of acceptable limits. All patches that fall out of the acceptable limits are culled by way of the reject patch conveyor. All patches that fall within acceptable limits will continue to be placed on a composite web that is otherwise indicated as appropriate for receiving a patch. After being notified of the problem, the machine operator will observe the HMI to verify problem. In an attempt to correct the problem, the operator may try an electronic anvil shift, which, if successful, will allow the process to continue. If the electronic anvil shift does not correct the problem, the operator will request that the machine stop. To aid in repair or replacement of the failed knife or anvil, the cutter and anvil drum will stop in a position allowing easy access to the failed components. As a convenience and to enable more efficient repair of the failed components, a rapid change out (RCO) tool or kit could be provided, such as a set of hex wrenches. The operator changes the failed part and prepares the machine to restart. The routine for automatically clearing the anvil drum may then run, and the unit begins attaching patches to the composite web. The alarm that first alerted the operator of the problem is then reset, either automatically, or manually by the operator through the use of the HMI. 
         [0091]    There may arise a situation where multiple anvils or knives appear to have failed. In this situation, the operator is alerted to the problem, but no patches are culled. Rather, a visual inspection station downstream from the patch applicator is examined to determine if there truly is a problem. If the problem is verified by the placement accuracy check, the operator shuts down the machine and proper maintenance is performed. If an examination of the placement accuracy inspection station does not confirm the purported problem, the unit diagnostics program may be suspended until it can be repaired. 
         [0092]    Although the foregoing description involves the placement of an absorbent insert or patch onto a diaper chassis, it will be apparent to those skilled in the art that the apparatus and process could be used to avoid unnecessary waste in the application of any sort of patch to a moving web. Other examples of patches that may be placed are tape tab patches and reusable fasteners. 
         [0093]    Referring now to  FIGS. 5 and 6   a - c,  an additional embodiment of a representative web processing system is shown schematically and incorporating principles of the present invention. It is noted that throughout the web processing, inspection systems can be incorporated virtually anywhere, particularly at locations of raw material input into the process. 
         [0094]    The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.