Abstract:
A box inspector for detecting at an inspection station an unacceptable skew in, an item missing from, and/or an unacceptable gap in a box. The box inspector has pairs of aligned emitters and receivers generating a signal when an unacceptable skew is detected, at least two item present sensors corresponding to the number of items adapted to be located in a single row within the box and generating an item absent signal when an item is missing from the box, a gap detect sensor generating an unacceptable gap signal when the gap is larger than a predetermined gap size, and a box present sensor generating a box present signal when a box arrives at the inspection station. A controller receives signals from these components and generates indications when the box is unacceptably skewed, an item is missing from the box, and/or an unacceptable gap exists in the box.

Description:
TECHNICAL FIELD 
     The present invention relates generally to inspection equipment and, more specifically, to a completely automated system for inspecting, detecting defects in, and sorting boxes. 
     BACKGROUND OF THE INVENTION 
     In the field of industrial automation, inspection systems have long been applied to inspect, detect defects in, and sort containers such as boxes. Conveyers are often used to deliver the containers to and remove them from the inspection system. For example, U.S. Pat. No. 4,165,939 issued in 1979 and discloses an inspection system for detecting dimensional tolerances, shape, and cosmetic defects in containers. A conveyer carries the containers past an inspection point where at least one focused beam of radiant energy traverses the surface of the container at a steep angle. The pattern of the surface is detected and evaluated by optical imaging techniques to determine the acceptability of the inspected container while maintaining a capability of making allowances for manufacturing tolerances of the relative position of the area under inspection with respect to a given reference point of the container. The inspection process is initiated and terminated depending upon the translational position of the container with respect to the inspection system. 
     U.S. Pat. No. 5,802,803 discloses a case packer comprising an inspection unit, a packing unit, and a sorting unit. The inspection unit is disposed on an upstream side of a path of transportation for packaged products for inspecting each of the products being transported on the path and thereby distinguishing defective products from normal products. The packing unit is disposed on a downstream side of the path for packing a specified container simultaneously with products delivered to the container in a plurality of rows on the path. Finally, the sorting unit is disposed between the inspection unit and the packing unit along the path for discharging the defective products away from the path and arranging the normal products in the plurality of rows on the path. 
     Optoelectronic sensors for detecting and locating objects are valuable in a wide variety of fields, including industrial automation. Photoelectric sensors, which comprise a type of optoelectronic sensor, have long been used to detect and locate objects. For example, U.S. Pat. No. 3,750,877 issued in 1973 and discloses an apparatus for inspecting the walls of containers. The apparatus uses a light-emitting device, a photosensitive device, and a high-speed rotatable carrier for serially moving each of the containers between such devices to enable any undesirable opening (i.e., an edge crack) in the walls of the containers to be detected by light passing through the walls to energize the photosensitive device which in turn actuates a mechanism to reject the particular defective container. 
     U.S. Pat. No. 5,141,111 is titled “System and Method for Inspecting and Rejecting Defective Containers.” The system includes a plurality of reflective infrared sensors, an electronic logic control, and a container-removal device. The system assesses the quality of the flange of the container and senses the height of the container by sensors irradiating the flange portion of the container with narrow beams of infrared light at varying heights and receiving radiation reflected from the flange portion. The acceptability of the container is determined by the quantum of reflected radiation received by the sensors. Unacceptable containers are removed by a high-speed pneumatic cylinder. 
     U.S. Pat. No. 6,757,420 is titled “Inspection Device for Packages” and discloses an automatic inspection device. The device determines whether sealed blister packages, consisting of a blister container and a cover film, are free of defects in the blister container, the sealing seam, or the perforation. At least two light sources are arranged at a certain distance from one another and each emit a light bundle at a predetermined wavelength range, whereby the emission maxima of the two light sources are offset in relation to one another. The light sources are arranged such that the packages are vertically illuminated. The light reflected by the packages is recorded by a CCD camera and the digital images are stored in a computer, so that they are available in a computer-supported image-processing and documentation system. 
     Many entities have worked toward improving the conventional inspection systems. For example, Cognex Corporation is a manufacturer of machine vision systems, software, and sensors used in automated manufacturing to inspect and identify parts, detect defects, verify product assembly, and guide assembly robots. Cognex is headquartered in Natick, Mass. One particular Cognex system is disclosed in U.S. Patent Publication No. 2008/0310676 titled “Method and System for Optoelectronic Detection and Location of Objects.” 
     Disclosed in the patent publication is a system for optoelectronic detection and location of moving objects. The system captures one-dimensional images of a field of view through which objects may be moving, and makes measurements in those images. The system selects from among those measurements those that are likely to correspond to objects in the field of view, makes decisions responsive to various characteristics of the objects, and produces signals that indicate those decisions. The disclosed system is touted as providing excellent object discrimination, electronic setting of a reference point, no latency, and high repeatability. 
     Machine vision systems such as those of Cognex can cost many thousands of dollars and include extremely complex components such as cameras, lenses, and digital processors. Generally, machine vision systems apply computer vision to industry and manufacturing. Whereas computer vision is mainly focused on machine-based image processing, machine vision most often also requires digital input/output devices and computer networks to control other manufacturing equipment such as robotic arms. Machine vision systems combine computer science, optics, mechanical engineering, and industrial automation. 
     Defective boxes can damage on-line production machines, cause of loss of product, and result in unusable, or even dangerous, boxes. Nevertheless, no simple, cost-effective, automatic system exists to detect certain types of defects in shipping boxes. Boxes may be manually inspected, of course, for defects and proper dimensions. Manual inspection has several disadvantages. For example, modern production lines, such as container manufacturing and filling operations, typically operate at very high speeds. Manual inspection of boxes moving at such speeds is difficult. 
     Therefore, there remains a need in the art for an improved system for inspecting boxes that overcomes the shortcomings of conventional inspection systems. To overcome the shortcomings of the current solutions applied to inspect boxes, a new box inspector is provided. An object of the present invention is to inspect boxes filled with items to determine the presence of defects in the boxes or the absence of items from the boxes. Another object is to simultaneously inspect a box for one or more of dimensional conformity, gaps between flaps, and the presence of items within the box. 
     Yet another object is to decrease the cost and complexity of the machinery used to inspect boxes. A related object is to provide a system that does not scan the box under inspection. A further related object is to use fixed position beams to inspect the boxes. An additional object is to identify unacceptable boxes without disrupting production speeds or interrupting conveying equipment. It is still another object of the present invention to correlate the translational speed of the box under inspection with the inspection system. A related object is to permit adjustment of the box inspector to meet the specific requirements of a particular application. 
     BRIEF SUMMARY OF THE INVENTION 
     To achieve these and other objects, and to meet these and other needs, and in view of its purposes, the present invention provides a box inspector for detecting at an inspection station an unacceptable skew in, an item missing from, and an unacceptable gap in a box having a leading edge, a height, a width, a bottom opening closed by flaps defining the gap, and an open top. The box inspector includes at least two pairs of aligned emitters and receivers located in fixed positions at the inspection station and creating two spaced and parallel radiation beams through which the box to be inspected passes, each receiver generating a signal when the beam to be received by the receiver from the corresponding emitter is cut by the leading edge of the box. The box inspector further includes at least two item present sensors corresponding to the number of items adapted to be located in a single row within the box, the item present sensors being located in fixed positions at the inspection station, directing radiation toward the open top of the box, receiving radiation reflected from any items present in the box, and generating an item absent signal when an item is missing from the box. The box inspector still further includes a gap detect sensor located in a fixed position at the inspection station, under the box and between the flaps of the box when the box arrives at the inspection station, the gap detect sensor emitting radiation toward the box, detecting radiation reflected from the gap, and generating an unacceptable gap signal when the gap is larger than a predetermined gap size. (By “predetermined” is meant determined beforehand, so that the predetermined gap size is determined, i.e., chosen or at least known, before the box is inspected.) A box present sensor directs radiation toward the box, receives radiation reflected from the box, and generates a box present signal when the radiation indicates the presence of a box at the inspection station. Also included in the box inspector is a controller (a) receiving signals from the receivers, the item present sensors, the gap detect sensor, and the box present sensor, (b) having a skew tolerance timer with a preset value, (c) generating an indication that the box is unacceptably skewed when the signals received from the respective receivers exceed the preset value, (d) generating an indication that an item is missing from the box when the signals received indicate that an item is missing and a box is present, and (e) generating an indication that an unacceptable gap exists in the box when the signals received indicate that the gap is larger than the predetermined gap size and a box is present. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention is best understood from the following detailed description when read in connection with the accompanying drawing. It is emphasized that, according to common practice, the various features of the drawing are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawing are the following figures: 
         FIG. 1  is a top view of the conveyor system of the box inspector according to an exemplary embodiment of the present invention; 
         FIG. 2  is a top view of the conveyor system shown in  FIG. 1  with a box traveling along the conveyor; 
         FIG. 3  illustrates the components of the box inspector used to detect a box that is out-of-square or skewed; 
         FIG. 4  illustrates the components shown in  FIG. 3  with a skewed box under inspection; 
         FIG. 5  illustrates the components of the box inspector used to detect a box that should have, but is missing, a bottle or other item desired to be loaded in the box; 
         FIG. 6  illustrates the components of the box inspector used to detect a gap between the flaps used to close the bottom opening of a box, highlighting an acceptable gap; 
         FIG. 7  illustrates the components shown in  FIG. 6 , highlighting an unacceptable gap; 
         FIG. 8  illustrates the box inspector, according to another exemplary embodiment of the present invention, which combines the components used to detect skewed boxes with the components used to detect gaps; and 
         FIG. 9  is a schematic illustration depicting the components of an electrical box used to operate the box inspector and to provide a user interface according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Products such as plastic bottles manufactured by molding machines are typically shipped in containers such as rectangular cardboard boxes, each box carrying a specified number of bottles. Conveyors sequentially transport the bottles from a molding machine, and a packing mechanism automatically arranges the bottles inside a given box. The bottles are typically arranged in a plurality of rows of two or three bottles per row. 
     With general reference to the figures, the box inspector  100  of the present invention is designed to detect one or more defects in a box  98 . Specifically, and by way of example, the box inspector  100  can detect any one or more of three defects: boxes  98  that are out-of-square (i.e., skewed boxes), boxes  98  that are missing contents such as bottles  64 , and boxes  98  that have excessive gaps  96  between the flaps  94  of the boxes  98 . The problems caused by the defect of missing contents from a box  98  are perhaps obvious. 
     The problems caused by skewed boxes  98  may be less obvious, but are numerous. The shape of boxes  98  typically permits stacking, and skewed boxes  98  fail to stack properly. The items that should fit within the box  98  may not pack properly inside a skewed box  98 . Further, the items may jam upon insertion into a skewed box  98 . 
     Boxes  98  typically have four flaps  94 —one on the leading end, one on the trailing end, and one on each side—which are folded to create the bottom of the box  98 . Often, a small gap  96  exists after folding of the flaps  94 . Problems arise if the gap  96  is too wide. For example, the structural integrity of the box  98  may be compromised and, especially when the box  98  carries heavier items, the box  98  may be unable to contain the items. In addition, the boxes  98  are often manipulated or handled using suction cups; an overly large gap  96  risks a loss of suction such that the handling system may drop the box  98 . 
     The term “box” certainly includes the typical rectangular unit made of cardboard and having foldable flaps to close the top opening, the bottom opening, or both openings in the box  98 . The principles of the present invention are not limited to such a narrow definition, however, and the box inspector  100  can inspect and detect defects in similar units including packages, sachets, containers, cartons, envelopes, and others. 
     A. Conveyor and Guide Rail Setup 
     The boxes  98  to be inspected are moved in series via a transport system (e.g., on a moving belt conveyor or conveyor system  30 ) to an inspection station. The conveyor system  30  operates to move the boxes  98  in a spaced relation through the inspection station where the boxes  98  are inspected. All of the inspections performed by the box inspector  100  rely on the boxes  98  being presented to the inspection station parallel to the conveyor  32  and perpendicular to radiant energy emitted by certain components of the box inspector  100 , and being moved through the inspection station smoothly and evenly. This is an important aspect of the box inspector  100 , and the precision and repeatability of the inspections performed will be determined by how well the conveyor system  30  is set up. 
     Referring now to the drawing, in which like reference numbers refer to like elements throughout the various figures that comprise the drawing,  FIG. 1  is a top view of the conveyor system  30  of the box inspector  100  according to an exemplary embodiment of the present invention. Conventional conveyor systems are not precision pieces of equipment, but they can be modified to provide the required level of repeatability to function as a component of the box inspector  100 . Time is the variable used as the tolerance to adjust sensitivity on all of the inspections. As such, all of the rollers  34  of the conveyor  32  must turn evenly to provide a steady, smooth motion for the box  98  through the inspection station. If the pulleys that drive the rollers  34  are not fixed (i.e., they cannot spin on the shaft) to the drive shaft, it is necessary to attach them with epoxy or set screws. If set screws are used, it is recommended to use the smallest possible screws so that the screws do not protrude from the pulley and wear on the drive band. It is also recommended to use Loctite® adhesive, available from Henkel Corporation of Rocky Hill, Conn., or a similar thread-locking compound on the screws so that the screws do not back out. 
     All of the rollers  34  and roller bearings must be in good condition so they turn easily without binding. Traction between the rollers  34  and the boxes  98  is increased by the use of rubber sleeves or O-rings  36 . The increased traction allows the conveyor motor to be slowed (e.g., from a conventional 60 Hz rate to about 18 Hz by the use of a variable frequency drive) while the conveyor  32  still moves the boxes  98  in a positive and even manner. By slowing the conveyor  32 , the amount of time the boxes  98  are at the inspection station is increased. The longer it takes for boxes  98  to pass through the inspection station, the more accurate is the inspection. 
     For example, if it takes 10 milliseconds (1 millisecond= 1/1000 or 0.001 seconds) for a box  98  to pass through the skewed box detect inspection, the tolerance must be set between 1-10 milliseconds, which does not leave much room for adjustment. If it takes 100 milliseconds to pass through the inspection station, however, the tolerance can be set between 1-100 milliseconds. Ideally, the conveyor  32  should be slowed as much as possible without affecting the amount of boxes  98  that are processed. Slowing the conveyor motor also has the benefit of using less electricity, which achieves cost savings, and prolonging the life of associated moving parts such as rollers  34  and drive bands. 
     In order to present the boxes  98  to the box inspector  100  in the same position, guide rails are incorporated in the conveyor system  30 . A fixed guide rail  38  is provided on one side of the conveyor  32 . The fixed guide rail  38  is fixed with respect to, and parallel to, the conveyor  32  and the box inspector  100 . The guide rail  38  may be fixed by pins  39  or any other suitable fastener as would be known to an artisan. An adjustable guide rail  40  is provided on the opposite side of the conveyor  32 . The adjustable guide rail  40  is adjustable for different box widths, but parallel to the conveyor  32  and the box inspector  100 . One or more adjusters  42  move along a track  44  in the direction of arrow A to accommodate boxes  98  of different sizes. 
     A plurality of bearings  46 ,  48  can be provided on one or both of the guide rails  38 ,  40  to decrease friction between the guide rails  38 ,  40  and the sides of the boxes  98 . (Bearings  46 ,  48  are shown in  FIG. 1  only on the adjustable guide rail  40  for simplicity, but bearings  46 ,  48  could also by provided on the fixed guide rail  38 .) The bearings  46 ,  48  can be positioned at different heights so that they contact the boxes  98  at different locations. In the example embodiment illustrated in  FIG. 1 , lower bearings  46  alternate with upper bearings  48 . By reducing the drag on the boxes  98 , the guide rails  38 ,  40  can be set a little tighter, increasing the accuracy of inspections. If different boxes  98  are to be inspected, it is recommended to use positive stops for each setup. By doing this, changeover time is reduced and repeatability is increased. 
       FIG. 2  illustrates the conveyor system  30  of  FIG. 1  with a box  98  traveling along the conveyor  32 . The boxes  98  are kept parallel with the conveyor  32  and inspection unit using the fixed guide rail  38  and the adjustable guide rail  40 . Bearings  46 ,  48  on the adjustable guide rail  40  contact the boxes  98  as needed to assure the proper orientation and smooth, even travel along the conveyor  32 . 
     B. Out-Of-Square (Skew) Detection 
     Photoelectric sensors typically operate by emitting a beam of light and detecting light received. Such sensors are available in a variety of configurations. In one configuration, an emitter and a receiver are placed at opposite ends of a path, so that anything crossing the path that is not transparent breaks the beam of light; an object is detected when the receiver sees very little light. The placement of the emitter and receiver determines the path and thereby the location at which an object is detected. The application is constrained to insure that only desired objects cross the path, and so that determining the location of an edge of the object is all that is needed. 
     In a second configuration, an emitter and a receiver are placed in one location, with a retro-reflector placed at the opposite end of a path that reflects the beam from the emitter back to the receiver. This configuration is similar to the first configuration, but is more convenient to install because all of the required wiring is done at only one end of the path instead of at both ends. 
     In a third configuration, an emitter and a receiver are placed in one location, and the emitter emits a focused beam of light so that anything sufficiently reflective crossing in front of the beam reflects the beam back to the receiver. An object is detected when the receiver sees an amount of light above some predefined threshold. The placement of the emitter-receiver unit determines the location of the beam and thereby the location at which an object is detected. The use of a focused beam makes this location relatively precise, and reduces the chances of misdetecting objects in the background because the beam will be out of focus. The objects and their environment are constrained so that the reflected light exceeds the threshold only when desired objects are in the desired location. 
     A fourth configuration is a variation of the third in which a diffuse beam of light is used instead of a focused beam. The diffuse beam makes it easier to detect objects whose positions are not well constrained, but decreases the precision of the location at which objects are detected and increases the chances that a detection will occur when no desired object is in front of the beam. 
     Photoelectric sensors typically provide a simple signal to indicate that an object has been detected, and to indicate its location. Such a signal has two states, which might be called “present” and “absent.” In the first and second configurations, for example, the signal would be in the “present” state when little light is detected by the receiver. In the third or fourth configuration, however, the signal would be in the “present” state when light above a threshold is detected by the receiver. Usually a photoelectric sensor is used to detect specific objects and locate them at a specific position, for example to detect boxes moving down a conveyer belt and indicate the time at which the leading edge of such a box has reached a certain reference point. 
     Although the embodiments described and illustrated include fiber optics, a person of ordinary skill in the art would understand that lasers could be substituted for the fiber optics if greater accuracy is required. The terms “emitter(s)” and “receiver(s)” therefore include both lasers and fiber optics, as well as other structural equivalents as would be known to the artisan. 
       FIG. 3  illustrates the components of the box inspector  100  used to detect a box  98  that is out-of-square or skewed. Although more pairs could be used, the illustrated embodiment of the box inspector  100  has two pairs of fiber optic emitters  50  and receivers  52  to create two vertical beams  54  through which the boxes  98  must pass. One beam  54  is on the left side of the box  98  and the other beam  54  is on the right, as highlighted by the circular fields labeled “B” in  FIG. 3 . As illustrated, the emitters  50  are mounted on a top frame  56 , which is supported by a pair of legs  58 , and are adjustable from side to side. The receivers  52  are mounted on a sensor bar  60  located between the rollers  34  of the conveyor  32 . The sensor bar  60  has slots  62  to allow side-to-side adjustment of the receivers  52 . Although illustrated with the receivers  52  mounted on the sensor bar  60  below the boxes  98  and with the emitters  50  mounted on the top frame  56  above the boxes  98 , the location of the emitters  50  and receivers  52  could be reversed. 
     Ideally, the emitters  50  and receivers  52  should be mounted as close to the sides of the boxes  98  as possible, where the difference in the time the edges  92  of the boxes  98  cut the fiber optic beams  54  is the greatest. The emitters  50  must be aligned with the receivers  52  for proper operation. The emitters  50  produce a red circle that must be centered on the receiver  52 . If a box  98  is substantially square, as shown in  FIG. 3 , both beams  54  will be cut by the box  98  at approximately the same time. 
     If a box  98  is not substantially square, as shown in  FIG. 4 , one side of the box  98  will cut its beam  54  before the other side does. Upon interception of the beam  54  by the box  98 , a signal is generated by the respective one of the receivers  52  and is conveyed to a programmable logic controller (PLC)  6  (see  FIG. 9 ). The PLC  6  will start a timer when one beam  54  is cut and the other beam  54  is not. If the timer reaches its preset value (skew tolerance) before the other beam  54  is cut, the box  98  will be flagged as out of square. Therefore, when setting the skew tolerance timer, the larger the entered value (in milliseconds) the less sensitive the inspection will be and vice versa. 
     If presently available circuitry, whether analog, digital or hybrid, is used, the speed of signal generation, analysis, and comparison is extremely high. In fact, the time period required for these purposes is only a small fraction of the time required to move the box  98  past beams  54 . Therefore, it becomes evident that operation of the box inspector  100  of the present invention is relatively independent of the speed of the conveyer  32  and will accommodate most presently known speeds for such conveyers  32 . By adjustably mounting the emitters  50  and the receivers  52  (i.e., the sensors), boxes  98  of various dimensions can be inspected. 
     C. Missing Bottle Detection 
       FIG. 5  illustrates the components of the box inspector  100  used to detect a box  98  that should have, but is missing, a bottle  64  or other item desired to be loaded in the box  98 . For the embodiment illustrated, in which the box  98  should have two bottles  64  per row within the box  98 , the components include two diffused photo electric bottle present sensors  66  and a diffused photo electric box present sensor  68 . (More bottle present sensors  66  would be required if there were more bottles  64  per row.) The bottle present sensors  66  are positioned on the top frame  56  and direct radiation  67  downward toward the top of the open box  98  as highlighted by the circular fields labeled “C” and “D” in  FIG. 5 . When the radiation  67  reflects from a bottle  64  and returns to the bottle present sensor  66 , as illustrated in field “C,” the bottle present sensor  66  sends a “bottle present” signal to the PLC  6 . In contrast, when the radiation  67  is not reflected from a bottle  64  and returned to the bottle present sensor  66 , as illustrated in field “D,” the bottle present sensor  66  sends a “bottle absent” signal to the PLC  6 . 
     The bottle present sensors  66  should be adjusted as close to the bottles  64  as possible without causing any interference with the tallest box  98  to be inspected. Ideally, this height should be left in the same position for all boxes  98  to be inspected, but if the height difference between the tallest and shortest boxes  98  is too great, it may have to be adjusted on changeovers. If the height is adjusted on changeovers, it is recommended to use stops to set the height for each product. 
     The box present sensor  68  is positioned on one of the legs  58  and directs radiation  69  horizontally toward the side of the box  98  as highlighted by the circular field labeled “E” in  FIG. 5 . When the radiation  69  reflects from a box  98  and returns to the box present sensor  68 , as illustrated in field “E,” the box present sensor  68  sends a “box present” signal to the PLC  6 . In contrast, when the radiation  69  is not reflected from a box  98  and returned to the box present sensor  68 , the box present sensor  68  sends a “box absent” signal to the PLC  6  (which may be, for example, no signal at all). The sensitivity of the box present sensor  68  may be adjusted by a potentiometer on the body of the box present sensor  68 . 
     If the box present sensor  68  detects a box  98  while either or both bottle present sensors  66  do not detect a bottle  64 , the box  98  will be flagged as missing a bottle  64 . Because there may be space between the bottles  64  in the boxes  98  being inspected, a missing bottle tolerance timer is used to filter out false rejects. The missing bottle tolerance timer is the maximum amount of time that a bottle present sensor  66  can go without detecting a bottle  64  while the box present sensor  68  detects a box  98  and not flag the box  98  as missing a bottle  64 . 
     For example, if a box  98  with all bottles  64  present goes through the inspection station and one of the bottle present sensors  66  detects a gap between two of the bottles  64  for 10 milliseconds, the box  98  should not be flagged as missing a bottle  64 . If a box  98  missing a bottle  64  causes a bottle present sensor  66  to detect a gap of 100 milliseconds, however, that box  98  should be flagged as missing a bottle  64 . So, in this example case, the missing bottle tolerance timer should be set somewhere between 10 and 100 milliseconds to flag any boxes  98  missing bottles  64 , but not flag boxes  98  due to normal gaps between bottles  64 . 
     The bottle present sensors  68  can be “taught” to tell the difference between a box  98  having bottles  64  and a box  98  lacking bottles  64 . To do so, samples of each situation are provided. The teaching method is described below in Section E. 
     D. Unacceptable Gap Detection 
       FIG. 6  illustrates the components of the box inspector  100  used to detect a gap  96  between the flaps  94  used to close the bottom opening of the box  98 . The gap detect components include a diffused fiber optic gap detect sensor  70  to check for unacceptable gap size. The gap detect sensor  70  should be adjusted below the gap  96  between the bottom flaps  94  as close as possible without being contacted by any boxes  98 . As illustrated in the embodiment of the box inspector  100  shown in  FIG. 6 , the gap detect sensor  70  is mounted on the sensor bar  60  located between the rollers  34  of the conveyor  32  along with the receivers  52 . The sensor bar  60  has a channel  72  to allow side-to-side adjustment of the gap detect sensor  70 . 
     The gap detect sensor  70  emits radiation, for example light  74 , toward the box  98  and its gap  96 . An acceptable gap  96  should reflect enough light  74  back to the gap detect sensor  70  so that the gap detect sensor  70  detects that the width of the gap  96  is acceptable. This situation is illustrated in  FIG. 6 . An unacceptable gap  96  will allow more light  74  to pass through the gap  96  and less light  74  will be reflected back to the gap detect sensor  70 , so the gap detect sensor  70  detects that the gap  96  is unacceptable. This situation is illustrated in  FIG. 7 . 
     In other words, when the gap  96  is smaller, more light  74  is reflected back to the gap detect sensor  70  and vice versa. If an acceptable gap  96  is too large, the gap detect sensor  70  can be positioned so that it is hidden by one flap  94  on an acceptable gap  96 , but exposed to the gap  96  on an unacceptable gap  96 . The gap detect sensor  70  can be taught to tell the difference between an acceptable and unacceptable gap  96  if samples of each are provided. The teaching method is described below in Section E. 
     If the gap detect sensor  70  detects an unacceptable gap  96  at the same time that the box present sensor  68  detects a box  98 , the box  98  will be flagged as having an unacceptable gap  96 . The gap detect tolerance timer is the amount of time that the gap detect sensor  70  can detect an unacceptable gap  96  while the box present sensor  68  detects a box  98  before it is flagged for being defective. The higher this setting (in milliseconds) the less sensitive will be the gap detection and vice versa. 
     As mentioned above, the box inspector  100  of the present invention is designed to detect any one or more of three defects: skewed boxes  98 , boxes  98  that are missing contents such as bottles  64 , and boxes  98  that have excessive gaps  96  between flaps  94  of the boxes  98 . The components of the box inspector  100  designed to detect each of these defects are highlighted, respectively, in Sections B, C, and D above. The box inspector  100  can incorporate one, any combination of two, or all three aspects of detection. For example, as illustrated in  FIG. 8 , the box inspector  100  combines the components used to detect skewed boxes  98  with the components used to detect gaps  96 . 
     E. Operator Interface 
     As illustrated schematically in  FIG. 9 , an electrical box  20  is included to operate the box inspector  100  and to provide a user interface. The electrical box  20  may include a number of components, such as a power disconnect  1 , fuse blocks  2 , a transformer  3  (e.g., a 480 volt to 110 volt transformer), a variable frequency drive  4  (e.g., a 480 volt three-phase variable frequency drive), a power supply  5  (e.g., 24 volts), the PLC  6 , a PLC output module  7 , PLC input-output terminals  8 , amplifiers  9  (e.g., three fiber optic amplifiers to detect left-left skew, center-right skew, and right gap, respectively), terminal blocks  10 , a series of alarms or indicators  11 , a fan  12 , and a touch screen  13 . Preferably, the electrical box  20  is located proximate the conveyor system  30  (i.e., at least within visual sight of the conveyor system  30  if not adjacent to the conveyor system  30 ). The electrical box  20  may communicate with one or more of the conveyor system  30 , the adjusters  42 , the receivers  52 , the bottle present sensors  66 , the box present sensor  68 , and the gap detect sensor  70  through wires connecting the electrical box  20  to those components or wirelessly. 
     The touch screen  13  may be located, for example, on the front exterior of a door of the electrical box  20 . By providing a user interface, the touch screen  13  allows for adjustment of various settings without requiring the use of PLC software. If there is a power outage, these settings may have to be re-entered, so it is recommended to keep a setup sheet with all settings near the electrical box  20 . The touch screen  13  may display statistics such as the total number of boxes  98  inspected and rejected. 
     An “F1” button positioned below a conveyor icon serves as a reset button to restart the conveyor  32  or release the stop brake after a defective box  98  has been removed from the conveyor  32 . A remote reset button may be located on the opposite side of the conveyor  32  which serves the same purpose. An “F2” button below an alarm clock icon resets the boxes inspected and rejected counters back to zero. An “F3” button below a charts icon opens a statistics screen. The statistics screen has statistics on rejects for each individual inspection. To return to the main menu, the user presses a button under a home icon. 
     An “F4” button below a box icon opens a product selection screen. The product selection screen allows the user to select the product they will be running through the box inspector  100 . If multiple products are to be run, “recipes” with the ideal settings for each product can be set up and saved. The settings for the product to be run will automatically be loaded into the PLC  6  when that product is selected. To return to the main menu, the user presses the button below the home icon. 
     An “F5” button below a tools icon opens a tools screen. The tools screen is where the tolerances and settings may be accessed. To change a setting, the user touches the setting on the display. This action will open a numeric keypad with which to enter the new value, followed by an “ent” (enter) button. The new value should be reflected in the display below the desired parameter. 
     If desired, password protection can be assigned to various screens and different access levels can be assigned to different levels of users. For example, an operator level may view and reset counters, but could not change products or adjust tolerances. A mechanic level may view and reset counters as well as change product selection, but could not adjust inspection tolerances. A supervisor level would be able to do all of the above and adjust inspection tolerances. 
     The indicators  11  are provided to convey information from the box inspector  100  to the user. The indicators  11  may be any suitable audio-visual devices as would be know to the artisan. By way of example, the indicators  11  are illustrated in  FIG. 9  as stacked light-emitting diode (LED) indicators  11   a ,  11   b ,  11   c , and  11   d . Each stacked indicator may be assigned a different color; therefore, indicator  11   a  may be green, indicator  11   b  may be red, indicator  11   c  may be blue, and indicator  11   d  may be yellow. The indicators  11  will sound an audible alarm and turn on a colored light if a defect is detected. Each color corresponds to a different defect (red may indicate an unacceptable box skew, blue may indicate a missing bottle  64 , and yellow may indicate an unacceptable gap  96 ) and green may indicate the box inspector  100  is online and inspecting. The indicators  11  will turn off after the defective box  98  is removed and the reset button is pressed. 
     The bottle present sensors  68  (see  FIG. 5 ) can be “taught” by placing a box  98  with bottles  64  underneath the sensors  68  and pressing a teach button for 2-5 seconds. The green LED indicator  11   a  should stay on at this point when a bottle  64  is present and turn off when bottles  64  are removed (at which point, the blue LED indicator  11   c  should turn on). The sensors  68  should be taught with the area of the bottle  64  furthest away from the sensor  68  (usually the base push up/gate nub area) directly underneath the sensor  68 . The bottle present sensors  68  should be adjusted directly above the middle of the bottles  64 . This is especially important with round bottles  64 , because there is more space between the bottles  64  the farther from center the sensors  68  are located. 
     To teach the gap detect sensor  70 , the user takes the following steps. First, a box  98  with an acceptable gap  96  is placed over the gap detect sensor  70  with the gap  96  centered over the gap detect sensor  70 . Next, the user activates a “Teach  2 ” mode by pressing a “mode” key three times. Third, the user presses the “enter” key to start the first cycle. The teaching process is successful when a “status” LED lights up green. Then the box inspector  100  is ready for the second cycle. 
     In preparation for the second cycle, the user removes the sample box  98  with an acceptable gap  96  and places another box  98  with an unacceptable gap  96  directly over the gap detect sensor  70 . The user then presses the “enter” key, and the second cycle begins. The teaching process is successful when the “status” LED blinks green for five seconds. At this point, the inspector box  100  is ready for use. 
     Although illustrated and described above with reference to certain specific embodiments and examples, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention. It is expressly intended, for example, that all ranges broadly recited in this document include within their scope all narrower ranges which fall within the broader ranges.