Box inspection device and method

A quality monitoring system employing vision processing equipment to photograph at least one of the edges of every folded-over box blank as it is conveyed through a box forming machine is used to determine in-line whether the blanks, when unfolded, will produce square boxes having essentially all 90.degree. angles between adjacent sides. The folded-over blanks have a manufacturer's gap between adjacent box side panels. The electronic images are electronically digitized and the resulting data processed by computer to calculate critical parameters of the folded-over blank, including gap width, longitudinal taper of the gap width, and alignment of the lateral edges of the panels surrounding the gap in relation to the lateral edge of the gap. Comparison of these measured critical parameters with corresponding parameters for an idealized box stored in the computer indicates the quality of the formed box and whether the quality falls within acceptable parameters. Provision is made in the system to photograph the blank upstream of or downstream of a squaring and stacking station of the folding machine, or in both positions.

BACKGROUND OF THE INVENTION 
The present invention relates generally to a method and apparatus for the 
manufacture of boxes or cartons, and more specifically to a vision 
inspection or monitoring system for measuring in-line the quality of each 
finished box or carton--especially corrugated boxes. 
Boxes or cartons such as corrugated boxes are produced by the container 
industry on high-speed manufacturing machinery. The machines employed for 
this purpose are complicated assemblages of interworking parts, which 
automate the box manufacturing process, converting a simple cardboard 
blank into a box in a "folded-down" state. In a typical process, score 
lines are added to the blank at appropriate positions in order to define 
four side panels and eight end panels. A glue flap extends along one of 
the side panels. The scored blank is fed to an automated machine, which 
employs a conveyor system to move the scored blank through the machine. In 
this way, the blank undergoes controlled movement in a longitudinal 
direction while minimizing and, preferably, eliminating undesirable 
lateral movement. Glue is applied to the glue flap at a "glue station" 
within the machine, and the exterior side panels of the blank are then 
folded upon their adjacent interior side panels by means of cooperating 
deflection devices provided along the conveyor belt path so that the glue 
flaps meet the opposite exterior panels in order to produce a finished box 
in its folded-down state, as it emerges from the machine. In an embodiment 
of this invention, the seam between the panel and the glue flap may be 
pressed through press rolls. 
These boxes are manufactured at speeds in excess of 300 blanks per minute. 
Yet, at least thirty different machine variables such as feed roll 
pressure, conveyor belt speed, timing of the folding device cycle, and the 
like contribute to a properly manufactured box. For instance, if the 
folding mechanism is not timed properly in sequence with the moving blank, 
a square fold will not be obtained. Likewise, if the blank is not securely 
retained by the traveling or conveyor mechanism or is engaged too strongly 
by the folding mechanism, it could "fishtail," thereby preventing a square 
fold. Therefore, if any of these variables is not precisely coordinated 
with the other variables, the folding machine will not produce an optimal 
"square" box which, when unfolded, will have all 90.degree. angles. 
The operator of the folding machine, thus, encounters significant problems 
in controlling the production of the boxes to achieve desired optimal 
results. Because the blanks travel at speeds in excess of 300 units per 
minute, it is impractical for the operator to visually follow the folding 
and gluing steps in order to control the process to produce boxes with 
90.degree. angles. Likewise, it would be commercially unfeasible for the 
operator to cease operation of the folding machine periodically in order 
to inspect a box. Statistical processing control has been suggested to 
overcome this problem whereby selected representative samples of completed 
boxes are collected and analyzed to determine the acceptability of the 
product being produced and the desirability of adjusting the manufacturing 
process variables to overcome any detected defects. However, it is clear 
that an in-line capability of performing quality control checks of the 
product being produced without interfering with the production run would 
be highly desirable and significantly more operationally effective for 
adjustment of the process variables as opposed to analysis of already 
produced product. Also, quality control inspection of every box produced 
would be a highly desirable improvement over prior random sampling 
systems. Therefore, provision of such capability for in-line quality 
control monitoring of each box in production without interfering with the 
production run would be highly advantageous relative to prior processes 
employed in this art. 
Various video inspection systems are known in the prior art. U.S. Pat. No. 
4,344,146 issued to Davis, Jr. et al., for example, discloses such a 
scheme consisting of a television camera, which produces a digital video 
image of the subject matter, an interface with a direct memory access 
channel for structuring the digital data, high-speed random access memory 
for storing the data, a bus oriented processor for processing the data in 
the memory, a digital computer for controlling operation of the system, 
and a terminal which presents the data to the machine operator so any 
flawed work pieces may be detected and fixed. Davis indicates that such a 
system could be used to ensure that labels are correctly placed on 
bottles. U.S. Pat. No. 4,758,888 issued to Lapidot teaches an automatic 
work station for inspection of work pieces traveling along a production 
line, incorporating a television camera and a computer. The machine 
operation may retrieve the stored images to verify the detected flaws, and 
remove the applicable work pieces at a downstream sorting station. 
However, the video inspection systems disclosed by Davis and Lapidot 
merely provide a visual image of the workpiece, which then must be 
analyzed by the operator to determine whether any product flaws fall 
within acceptable ranges. Such an analysis is time consuming, prone to 
inaccuracy and subject to the skill of the operator. 
U.S. Pat. No. 4,578,052 issued to Engel et al., by contrast, provides a 
method and apparatus for detecting deviations of folds in a sheet of paper 
in which electro-optical sensors are positioned above the folding cylinder 
of a folding machine. These sensors electrically evaluate markings 
prepositioned on the sheet along the desired fold line, and a computer 
evaluates and processes the data. As illustrated in FIG. 4 of the 
reference, the system detects sheets having skewed folds, because the 
distance between each respective mark and a common reference point will 
not be the same. The operator uses the data to make necessary adjustments 
to the folding machine. The Engel system, though, is dependent upon 
prepositioning the marks along the fold lines, which requires an extra 
step in the manufacturing process, thereby increasing production costs. 
SUMMARY OF THE INVENTION 
Accordingly, it is a primary object of the present invention to provide a 
system for monitoring the quality of boxes or containers such as 
corrugated cardloard containers during the manufacturing process. 
It is a further object of the present invention to provide a video 
inspection system for evaluating fold lines of box blanks traveling at 
high speeds, and automatically determining and measuring any deviations 
from an optimal square box configuration wherein all angles of the 
unfolded, open box or carton assembly will be right angles. 
Another object of the present invention is to provide a system which will 
process in-line quality control data or information representing the 
folded configuration of each box or carton produced and indicative of the 
alignment of the resulting finished box or carton, and present it to the 
machine operator in a variety of formats, for example, in regard to the 
last box produced, the average box produced, and the boxes having maximum 
and minimum variation from acceptable product criteria. 
A still further object is to provide an apparatus for conducting quality 
control inspection of each box produced in a box forming operation in-line 
during the production process. 
These and other objects are achieved by employing vision processing 
equipment to electronically image or photograph at least one of the edges 
of every box blank as it is conveyed through a box forming machine after 
the blank has been appropriately scored, folded and glued to produce a box 
in a "folded-down" state having four interconnected, slotted panels with a 
gap or "manufacturer's joint" formed between two adjacent ones of these 
panels by a glued down "glue flap" which provides the interconnecting 
element between such panels. 
The electronic image is digitized and processed employing known vision 
processing computer equipment, and the digitized data obtained from the 
photograph of the actually produced product is employed to measure certain 
critical parameters of the produced product in order to perform quality 
control analysis thereof. The critical parameters of the formed box 
include a measurement of the gap width, any longitudinal taper of the gap 
width, and a determination of the alignment of the lateral edges of the 
two panels surrounding the gap in relation to the lateral edge of the gap. 
By comparing the results of this measurement procedure, preferably 
utilizing extrapolation techniques, with criteria stored in the computer, 
an indication is provided of the quality of the formed box and a 
determination is made as to whether the quality of the formed box is 
within acceptable parameters.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In a standard process for producing corrugated cardboard containers known 
in the trade as "RSCs" (Regular Slotted Containers), the finished box or 
carton is made from a flat blank 10 illustrated in FIG. 1, which has score 
lines 11 and slots 13 formed therein at strategic positions in order to 
accommodate production of a box having four side panels 12, 14, 16 and 18. 
The score lines 11 form the perimeter to the side panels 12, 14, 16 and 18 
of the box and slots 13 project outwardly generally along the extensions 
of the score lines 11 to form bottom panels 20a, 20b, 20c, and 20d and top 
panels 22a, 22b, 22c, and 22d on panels 12, 14, 16, and 18, respectively. 
It should be noted that panels 20a and 20c, and 22a and 22c, as well as 
panels 12 and 16 have the same general lateral width, whereas panels 20b, 
20d, 22b, 22d, 14, and 18 likewise have the same general width relative to 
one another. The bottom and top panels 20 and 22 may be folded inwardly in 
an appropriate overlapping manner to provide a bottom and a top, 
respectively, for a finished box. In addition, glue flap 24 extends 
outwardly from the longitudinally exterior edge of side panel 12. 
Accordingly, by appropriate folding of the side panels 12, 14, 16 and 18, 
the bottom panels 20, and the top panels 22 about the score lines 11 and 
gluing of the glue flap 24 to interconnect exterior side panel 12 with 
exterior side panel 18, a box is formed having a depth D and side lengths 
L.sub.1 (corresponding to the lateral width of panels 12, 16, 20a, 20c, 
22a, and 22c) and L.sub.2 (corresponding to the lateral width of panels 
14. 18, 20b, 20d, 22b, and 22d). 
FIG. 2 shows in schematic form a box manufacturing apparatus 30, for 
processing a prescored blank 10 into a finished box. In this regard, a 
leading edge 26 of the blank is fed into the machine 30 via a traveling 
means such as a conveyor belt 31. The leading edges 26a and 26d of the 
blank 10 are formed by the laterally exterior edges of the top panels 22a 
and 22d, respectively, while leading edge section 26b is being formed from 
a combination of top panels 22b and 22c of the blank 10. Trailing edges 
28a, 28b and 28d likewise are formed by the exterior edges of the bottom 
panels 20a, 20d, and combined panels 20b and 20c. 
While the blank 10 is being moved on the conveyor belt, glue is placed on 
the glue flap 24 of blank 10 at a gluing station 32, and the panels 12, 
14, 16 and 18 are folded about score lines 11 in a folder mechanism 34 of 
the machine 30. Any of a number of folding devices known in the art such 
as helical conveyor belts, helical deflection rails, or pivoting arms may 
be employed for purposes of the folder 34 to fold box side panel 12 onto 
side panel 14, and side panel 18 onto side panel 16 In so doing, glue flap 
24 comes to rest either on top of or beneath side panel 18 along its 
exterior longitudinal edge. If desired, the seam created by the 
interconnection of the glue flap 24 with panel 18 may be pressed by press 
rolls, although such pressing is not required to produce a finished box in 
a folded-down position As illustrated in FIG. 3, the finished boxes are 
squared and stacked at station 38, and then conveyed to a final storage 
position 40. 
As previously noted, in the event that proper setting and/or 
synchronization is not achieved in the blank traveling and folding 
sections of an automated folding machine used in the container industry, 
the blank may fishtail or side panels 12 and 18 may not be properly folded 
over onto panels 14 and 16, thereby producing an undesirable folded down 
box blank 50 without square edges, as shown in FIG. 4, which, when opened, 
will not provide a box with 90.degree. angular alignment between adjoining 
panels. Such a poorly folded blank 50 may exhibit manufacturer's joints 52 
and 54, which are not of equal width (unlike the manufacturer's joints 21 
and 23 of properly folded blank 10 depicted in FIG. 3), or, if the 
manufacturer's joints are equal, they may be too wide. Likewise, the 
lateral edges, which are at right angles to the direction of travel of the 
blank 10 through the machine 30, of panels 12 and 18 may not lie in proper 
alignment. Such an improperly folded blank 50, as shown in FIG. 4, causes 
severe quality control problems, especially considering the high volume in 
which these boxes are produced. 
It is, therefore, an object of the present invention to provide monitoring 
means for detecting in-line whether undesirable blanks, such as blank 50, 
are being produced, and for enabling the operator to assess and analyze 
the problem in the setting and/or synchronization of the operating 
apparatus and to adjust the critical parameters of the production process 
in order to overcome these problems, and to enable production of "square" 
boxes The term "square" box, as used herein, means a box having a 
manufacturer's joint or gap, which measures a desired width between 
adjacent interior panels, the longitudinal edges of which are parallel 
with each other and do not cause the gap to vary or taper along the 
longitudinal axis of the box as it is fed through a box forming machine, 
and which exhibits an alignment of the trailing and lead edges of the 
exterior panels such that they are parallel to each other and are 
overlappingly co-extensive with the trailing and lead edges of the 
interior panels. The portion 36 of panels 20b, 20c, 22b, and 22c, which is 
visible beneath the gaps or manufacturer' s joints 21 and 23 in FIG. 3 or 
52 and 54 in FIG. 4 has an edge 37, hereinafter referred to as the "gap 
lateral edge." 
In accordance with the present invention, therefore, a visual inspection 
system is positioned in at least one of the stations 42 and 44, 
preferably, at both 42 and 44 in order to enable evaluation of the 
condition of the folded panel prior to squaring and stacking, and after 
squaring and stacking of the finished box. Such visual inspection system 
provides a method of monitoring the quality of the boxes, using visual 
processing technology. In conjunction with a known light source, such as 
strobe light 43, a known, commercially available, high-definition video 
device 45 (such as that sold by Allen-Bradley Company under the tradename 
"CVIM System") takes an electronic image of the trailing edge 28 and/or 
lead edge 26 of every blank 10 as it exits folder 34 and approaches 
squaring and stacking station 38. It should be noted that other visible 
inspection devices may be utilized to achieve an electronic image. As 
illustrated, the photographic image, in turn, is transmitted to computer 
48, where it is electronically digitized and processed. 
FIG. 5 illustrates a computer-assisted processing method for analyzing and 
evaluating a folded-over blank 10, where it is understood that the various 
reference points and arrows depicted are not part of the blank, itself. 
Using the electronically digitized image of blank 10 produced by the video 
camera 45, a commercially available computer (such as that sold by 
Allen-Bradley Company in their "CVIM System" determines the gap width W 
between the facing longitudinal edges of panels 12 and 18 which are 
interconnected via glue flap 24. For example the gap width W may be 
measured by determining the distance Z between video reference points U 
and V, and the distances X and Y between points U and V and the exterior 
longitudinal edges of their respective side panels 12 and 18. Subtracting 
distances X and Y from distance Z yields gap width W. The resulting gap 
width W is then compared with a critical value stored in the computer for 
an idealized square box. 
As a further critical element in assuring the quality of the box being 
formed in the process, the computer also evaluates the folded-over blank 
for alignment, as, for example, by determining distances A, B, and C 
between a reference line Q visually superimposed on the blank by the 
computer, and trailing edges 28a, 28b, and 28d of blank 10. The 
folded-over blank will have square folds if the differential distance 
between distance A and distance B is substantially equivalent to the 
differential distance between distance C and distance B. However, in the 
event that a taper angle .alpha. of the longitudinal edge of panel 12 
relative to the longitudinal axis of the gap exists, then the folded-over 
blank will not have square folds. Taper angle .alpha. may be calculated as 
generally the arctangent of the ratio of the differential distance between 
distance A and distance B, as defined above, to the width of the lateral 
edge of panel 12. Likewise, a taper angle .beta. may be calculated for 
panel 18, as generally the arctangent of the ratio of the differential 
distance between distance C and distance B to the width of the lateral 
edge of panel 18. For further reference, taper angles .alpha. and .beta. 
may be combined to provide a general indication of the overall 
longitudinal taper of the edges surrounding the gap (See FIGS. 4 and 7). 
After the computer makes the required analysis, the comparative data is 
stored in a computer database. The machine operator may reference or 
recall this data at any time in order to determine whether boxes with 
squarely folded edges are being produced by the ongoing operation. 
While certain prior art box manufacturing methods rely upon statistical 
analysis of a representative sampling of the overall number of produced 
boxes to make quality measurements, the present invention allows this 
measurement to be made on every box produced, thereby freeing the 
manufacturer from the imperfections of statistical analysis. In this way, 
the manufacturer is in a position to actually certify to the customer that 
the boxes have been properly made. Without this invention, such a 
certification could only be truly made by hand inspecting every single 
box, a laborious and expensive proposition. 
Based upon the data of the video inspection system, the operator can 
optimize the machine parameters both during a box production run and for 
the next run. Moreover, he can determine whether the folding machinery has 
been properly designed. 
As shown in FIG. 2, an appropriate light source, such as a strobe light 46, 
and video device 47 may also be installed above the passing boxes at a 
position relative to stacking station 38 so that an electronic image of 
the desired lateral edge of the passing box may be obtained. In this 
regard, it should be noted that, although reference is made herein to 
analysis of the trailing edge of the box blank, the leading edge may also 
be used as an appropriate reference point. The computer analysis of the 
electronically digitized image of each blank 10 is the same as described 
above, and this allows the operator to determine whether the box has been 
squarely folded. Certification of the finished product is more accurate at 
this point in the box manufacturing process. 
However, a further problem is encountered in regard to the analysis of the 
folded box being fed to the squaring stacker station 38 by a bottom feed 
device. In such an arrangement, the pressed blank 10 is added to the 
bottom of the stack of blanks held in squaring and stacking station 38 
until a suitable number of blanks are collected at which time the complete 
stack of folded boxes is conveyed to a final storage location 40. Thus, an 
overhead video device can observe only the uppermost box blank in each of 
the stacks since the subsequently fed blanks in such stacks will all be 
hidden from view by the top box. 
The present invention, therefore provides a box "shuffler" arrangement 68, 
shown in FIG. 6. As conveyor belt 60 carries blank 10 beneath stack 38, 
the blank is urged against stationary front block 62 by a "spanker" 61, 
which reciprocates in the longitudinal direction of machine operation in 
order to square the stack 70 of box blanks 10. As each blank 10 ascends in 
the stack as a result of subsequent blanks being fed thereunder, it 
reaches a position or level suitable for an electronic image to be taken 
thereof by video device 47 which may operate in conjunction with a light 
source, such as strobe light 46, in a manner equivalent to vision device 
45 referenced above. When the blank 10 reaches the proper position for the 
electronic image to be taken, a shuffler device 68 reciprocates 
longitudinally in the machine direction under the influence of compressed 
air, and is synchronized to remove the blank next preceding the blank 10 
to be imaged from covering an edge portion of the blank 10 so that the 
necessary electronic image can be viewed by the equipment 47. After the 
image is taken, the shuffler 68 then urges the blank 10 into an 
essentially squared final stack 72 beneath preceding blanks, thus 
uncovering the necessary edge section of the next subsequent blank. Once a 
sufficient number of the blanks have been accumulated and the final stack 
72 reaches a predetermined height, armature 74 moves the stack 72 forward 
onto a conveyor belt 60, where it is baled and shipped to the customer. 
In this way the apparatus of the present invention allows a box 
manufacturer automatically to check the quality of the folded edges of 
corrugated boxes during the manufacturing process both before and after 
the squaring stage, and to certify the quality of all the boxes to a 
customer without the time consuming process of checking the boxes by hand, 
or the imperfect process of certifying quality based upon a statistical 
analysis of a random sampling of the produced boxes. 
While particular embodiments of the invention have been shown and 
described, it should be understood that the invention is not limited 
thereto, since many modifications may be made. The invention is therefore 
contemplated to cover by the present application any and all such 
modifications which fall within the true spirit and scope of the basic 
underlying principles disclosed and claimed herein.