Abstract:
A method and apparatus for preparing container board having a corrugated medium and at least one liner formed thereon for folding which comprises a tool for displacing in a non-destructive manner the corrugated medium and the liner in a portion of the board to form a curved indentation therein. The device includes a separate tool for forming a line of weakness in the liner along the curved indentation portion of the board. This arrangement increases the dimensional accuracy of the container board by substantially eliminating the occurrences of “false” score lines or rolling scores.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to a method and device for preparing container board for folding. In particular, the invention concerns providing a device for displacing in a non-destructive manner the corrugated material and the liner in a portion of the container board to form a curved indentation therein and a separate creasing tool for forming a line of weakness in the liner along the indentation. 
     BACKGROUND OF THE INVENTION 
     Container board boxes are widely used for the packaging of multiple items, such as bottles, and heavier items, such as refrigerators, televisions, and other consumer goods. Container board boxes are commonly fabricated from a web of container board which has been slotted, creased, and cut into blanks. The blanks are then folded on the crease line and glued to form flattened box blanks. The box blanks are then formed into the final box shape by the packager to receive products therein. 
     Modern value-added package design and automated filling equipment demand that the boxes be dimensionally accurate. One of the main factors affecting the dimensional accuracy of container board boxes is the size of the box panels. Presently, box panel size is determined by mechanically scoring a crease line into the container board. 
     One such existing creasing device  110  is shown in FIG.  1  and includes a pair of shafts  112 . A female ring  114  is mounted on a hub  116  located on one of the creasing/scoring shafts  112 . A male ring  118  is mounted to a hub  120  located on the other creasing/scoring shaft  112 . The female ring  114  and the male ring  118  form a nip for receiving a web of container board  124 . The male ring  118  includes a male scoring bead  122  for compressing the container board  124  into the female ring  114 . 
     The container board  124  comprises a corrugated medium  126  interposed between an inner liner board  128  and an outer liner board  130 . The male scoring bead  122  forms a crease line  132  (best seen in FIG. 2) in the inner liner  128  and the corrugated medium  126  at the nip between the male and female rings  114  and  118 . The crease line  132  separates the container board  124  into side-by-side panels, such as an inboard panel  134  and an outboard panel  136 . 
     There is a critical value of nip pressure that must be maintained in order to produce a useful crease line  132 . Too little nip pressure produces an undefined crease line, whereas too much pressure tends to cut or crack the liner paper of the liner boards  128  and  130 . 
     After the crease line  132  is formed, the outboard panel  136  is urged down around the crease line  132  either by a rotating folding rod  138  or moving belt (not shown). By nature, folding a container board sheet requires the outer liner board  130  to stretch, the inner liner board  128  to contract, and the corrugating medium  126  to compress. 
     Due to the many variables encountered in the manufacture of container board boxes, such as liner and medium paper weights, moisture content, and recycled grades, the flutes of the corrugated medium  126  adjacent to the crease line  132  may be weaker than the crease line  132  itself and frequently causes the outboard panel  136  to fold about a “false” score line  140 . These false score lines  140 , also known as “rolling scores”, change the dimension of the panels  134  and  136  on either side of the false score  140 , producing a container board box that is dimensionally not within specification. Since the dimensions of the panels are different from the design dimensions, the container blank forms a parallelogram when folded and not the intended rectangular shape. The false score lines  140  can occur at anytime during a production run of boxes and are very difficult to eliminate with normal machine set-up functions. 
     SUMMARY OF THE INVENTION 
     The present invention substantially eliminates the occurrences of “rolling scores” by displacing paper in a controlled non-destructive manner before the container board is creased to produce the necessary clearances required to permit accurate bending of the panels around the “true” crease line. 
     The present invention includes a device for displacing in a non-destructive manner the corrugated medium and at least one of the liners in a portion of the board to form a curved indentation therein. A crease or line of weakness is then formed in the liner along the curved indentation of the board. 
     It is contemplated that the device can comprise a rotatably supported backing ring and a cooperating rotatably supported forming ring with a peripheral face having a curved profile. The container board is received between the nip formed between the peripheral faces of the forming and the backing rings. The curved profile of the forming ring cooperates with the peripheral face of the backing ring to displace the corrugated medium and at least one of the liners to form the curved indentation therein. 
     It is further contemplated that the device imparts to the container board a curved indentation having a parabolic shape. 
     In one form of the invention the profile of the peripheral face of the forming ring has a radius of about six inches (15.24 cm) and a width of about one inch (2.54 cm). The peripheral face of the backing ring has a substantially flat profile and is at least about two inches (5.08 cm) wide. 
     Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiment as amplifying the best mode of carrying out the invention as presently perceived. The detailed description particularly refers to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a prior art creasing device for forming a line of weakness in a container board; 
     FIG. 2 shows,the prior art creased container board being folded about a false score line; 
     FIG. 3 shows a device for preparing a container board blank or web for folding in accordance with one form of the present invention; 
     FIG. 4 shows a partial cross-sectional view of the material displacing device of the present invention taken along line  44  of FIG. 3; 
     FIG. 5 shows a partial cross-sectional view of the creasing device of the present invention taken along line  5 — 5  of FIG. 3; 
     FIG. 6 shows a container board being compressed by the material displacing tool in accordance with the present invention; 
     FIG. 7 shows a container board being creased by the creasing tool in accordance with the present invention; and 
     FIG  8  shows the container board being folded about the score line by a folding tool in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, FIGS. 3 through 5 illustrate a device  10  for preparing container board  100  for folding. The container board  100  typically comprises a corrugated medium  102  interposed between an inner liner board  104  and an outer liner board  106 . 
     The device  10  includes a material displacing tool  12  which receives the container board  100  and displaces the corrugating medium  102  and at least the inner liner board  104  to form a curved indentation therein. The container board  100  is then transported to a creasing device  14  which forms a line of weakness or crease in the curved indentation portion of the container board  100  formed by the material displacing device  12 . The container board  100  is then transported to a folding device  16  (shown in FIG. 8) for folding the container board  100  into a box blank. U.S. Pat. No. 4,254,692 entitled  Helical Folder For Paperboard Blanks  shows such a folding device for folding container board blanks to form boxes, and is hereby incorporated by reference herein. 
     Referring now to FIGS. 3 and 4, the material displacing device  12  comprises a forming tool  18  and a cooperating backing tool  20 . The forming tool  18  and backing tool  20  are detachably secured to a respective rotatable shaft  21  and  22 . Each shaft  21  and  22  may be supported in any suitable bearing, and driven by any suitable driving device. 
     The forming tool  18  includes a collar  24  which is detachably and adjustably secured to the shaft  21 . The collar  24  comprises a hub portion  26  and a radially extending annular body portion  28 . A forming ring  30  is mounted on the hub portion  26  of the collar  24 . The forming ring  30  is secured to the annular body portion  28  of the collar  24  by a suitable fastening device, such as a set bolt  32 . As best seen in FIG. 4, the radial extent of the forming ring  30  is greater than the radial extent of the annular body portion  28  of the collar  24 . The forming ring  30  is preferably fabricated from a hard, durable material, such as steel. 
     The peripheral face  44  of the forming ring  30  has a curved profile for imparting a parabolically shaped curved indentation to the container board  100 . It has been found that the radius of curvature of the peripheral face  44  should be about 6 inches to impart a suitable parabolically curved shape to the container board  100  and to reduce any stress concentrations imparted to the container board  124  which may cut the liner during the material displacing process. 
     The backing tool  20  includes a collar  34  which is detachably and adjustably secured to the shaft  22 . The collar  34  comprises a hub portion  36  and a radially extending annular body portion  38 . A backing ring  40  is mounted on the hub portion  38  of the collar  34 . The backing ring  40  is secured to the annular body portion  38  of the collar  34  by a suitable fastening device, such as set bolt  42 . As best seen in FIG. 4, the radial extent of the backing ring  40  is greater than the radial extent of the annular body portion  38  of the collar  34 . The forming ring  30  and the backing ring  40  cooperate to form a nip for receiving the web or blank of container board  100 . The backing ring  40  is fabricated from any suitable resilient, durable material, such as urethane or steel. 
     The peripheral face  46  of the backing ring  40  has a substantially planar profile which serves as a support for the forming ring  30 . In addition, the width of the backing ring  40  is contemplated to be greater than the width of the forming ring  30  in order to support the container board  100  during the material displacing process, allowing the forming tool  30  to form the gradually extending parabolically curved indentation therein. It has been found that a suitable parabolic curve is produced when the width of the forming ring  30  is about one inch (2.54 cm) and the width of the backing ring is at least about two inches (5.08 cm). 
     Referring now to FIGS. 3 and 5, the creasing device  14 , which is substantially similar to the creasing device  110 , includes a creasing tool  52  and a cooperating supporting tool  50 . The creasing tool  52  and supporting tool  50  are detachably secured to a respective rotatable shaft  56  and  54 . 
     The creasing tool  52  includes a collar  58  which is detachably and adjustably secured to the shaft  56 . A creasing ring  60  is mounted on the hub portion of the collar  58 . The creasing ring  60  includes a male scoring bead  62  interposed between the split halves of the creasing ring  60 . The creasing ring  60  is secured to the annular body portion of the collar  58  by a suitable fastening device, such as a set bolt  64 . 
     The supporting tool  50  includes a collar  66  which is detachably and adjustably secured to the shaft  54 . A supporting ring  68  is mounted on the hub portion of the collar  66 . The supporting ring  68  is secured to the annular body portion of the collar  66  by a suitable fastening device, such as set bolt  70 . 
     The creasing ring  60  and the supporting ring  68  cooperate to form a nip for receiving the web or blank of container board  100 . 
     In operation, a container board web or blank  100  is fed into the material displacing device  12 . The container board  100  is received within the nip formed between the forming ring  30  and the backing ring  40 . The rotating forming ring  30  compresses the container board  100  into the rotating backing ring  40 . The forming ring  30  displaces in a non-destructive manner the corrugated medium  102  and the inner liner  104  in a portion of the container board  100  to form a curved parabolic indentation  107  thereon. After passing through the material displacing device  12 , the container board  100  enters the creasing device  14 . 
     The container board  100  is received in the nip formed by the creasing ring  60  and the supporting ring  68 . The male scoring bead  62  forms a line of weakness or crease line  108  (best seen in FIG. 8) in the inner liner  104  and the corrugated medium  106  at the nip between the creasing and supporting rings  60  and  68 . The crease line  108  separates the container board  100  into side-by-side panels, such as an inboard panel  101  and an outboard panel  103 . 
     As shown in FIG. 8, after the crease line  108  is formed in the container board  100 , the outboard panel  103  is urged down around the crease line  108  by a folding rod  80  or moving belt (not shown). 
     The material displacing device  12  ensures that the flutes of the corrugated medium  102  adjacent to the crease line  108  are stronger than the crease line  108  itself and prevent the formation of “rolling scores” which would otherwise change the dimensions of the panels  101  and  103  on either side of the rolling score. 
     It has been found that about a 1.25 inch (3.18 cm) parabolic curve formed in the container board  100  is sufficient to prevent the formation of rolling scores. It is believed that by controllably displacing the liner and corrugated material of the container board prior to forming the line of weakness therein, permits the crease line to be formed with greater pressure which might otherwise cut the inner liner of an “un-displaced” container board. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.