Method and apparatus for preforming and creasing container board

Information

  • Patent Grant
  • 6508751
  • Patent Number
    6,508,751
  • Date Filed
    Friday, September 12, 1997
    27 years ago
  • Date Issued
    Tuesday, January 21, 2003
    22 years ago
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.



Claims
  • 1. A device for folding corrugated container board having a corrugated medium and a liner formed thereon comprising:a tool for displacing the liner inwardly with respect to the board and compressing the corrugated medium in portion of the board to reduce the thickness of the board and to form a gradually curved indentation therein without adversely affecting the integrity of the corrugated medium; a separate tool for forming a line of weakness in the liner along the curved portion of the board, said line of weakness separating the board into side-by-side panels; a separate tool for urging one of said panels down around said line of weakness to fold said board along said line of weakness; and wherein the displacing and compressing tool comprises a rotatably supported backing ring with a peripheral face having a substantially flat profile and a cooperating rotatably supported forming ring with a peripheral face having a gradually curved profile of a width less than the width of said flat profile, a nip formed between the peripheral faces of the forming and backing rings for receiving the container board, wherein the curved profile of the forming ring cooperates with the peripheral face of the backing ring to displace the liner and compress the corrugated medium to form the curved indentation in the board and to reduce the thickness of the board.
  • 2. The device according to claim 1, wherein the material displacing tool forms a curved indentation having a parabolic shape in the liner.
  • 3. The device according to claim 2, wherein the curved profile of the peripheral face of the backing ring has a radius of about six inches.
  • 4. The device according to claim 2, wherein the peripheral face of the forming ring is at least about two inches wide.
  • 5. A method of folding corrugated container board comprising the steps of:providing a container board having a corrugated medium and a liner formed thereon; providing in a folding device a tool having a rotatably supported backing ring with a peripheral face having a substantially flat profile and a cooperating rotatably supported forming ring with a peripheral face having a gradually curved profile with a width less than the width of said flat profile, a nip formed between the peripheral faces of the forming and backing rings; receiving the container board at the nip and displacing the liner inwardly with respect to the board and compressing the corrugated medium in a portion of the board to reduce the thickness of the board and to form a gradually curved indentation in the board without adversely affecting the integrity of the corrugated medium; providing in the folding device a separate creasing tool; forming a line of weakness with the creasing tool in the liner along the curved indentation of the board, the line of weakness separating the board into side-by-side panels; providing in the folding device a separate folding tool; and urging one of the panels down around the line of weakness with the folding tool to fold the board along the line of weakness.
  • 6. A method of preparing container board according to claim 5, wherein the curved indentation has a parabolic shape.
  • 7. A method of preparing a container board according to claim 5, wherein the line of weakness is a crease or perforated crease.
  • 8. A device for folding corrugated container board having a corrugated medium between an inner liner and an outer liner comprising:a tool for displacing the inner liner inwardly with respect to the board and compressing the corrugated medium in a portion of the board to reduce the thickness of the board and to form a gradually curved indentation therein without adversely affecting the integrity of the corrugated medium and without affecting the outer liner, the displacing tool comprising a first shaft, a backing ring supported on the first shaft with a peripheral face being at least two inches wide and having a substantially flat profile, a second shaft, a forming ring supported on the second shaft with a peripheral face having a gradually curved parabolic profile with a width of about one inch and with a radius of about six inches, a nip formed between the peripheral faces of the forming and backing rings for receiving the container board; a separate creasing tool for forming a line of weakness in the inner liner along the curved portion of the board, said line of weakness separating the board into side-by-side panels; and a separate folding tool for urging one of said panels down around said line of weakness to fold said board along said line of weakness.
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Non-Patent Literature Citations (2)
Entry
The Langston Corporation's 3797 Saturn Pre-Creaser Assembly, Drawing No. 425675, which was known before the filing date of the present application.
The Langston Corporation's brochure for the Saturn III flexo folder gluer which was known before the filing date of the present application.