Method and apparatus for forming a stable container bottom

Information

  • Patent Grant
  • 6739499
  • Patent Number
    6,739,499
  • Date Filed
    Wednesday, June 11, 1997
    27 years ago
  • Date Issued
    Tuesday, May 25, 2004
    20 years ago
Abstract
An apparatus and corresponding method for contouring a container bottom to form carton legs from a standard carton blank through the use of a seal plate and a mandrel pad. The carton legs provide improved free standing stability of the carton.
Description




FIELD OF THE INVENTION




The invention relates to manufacturing containers, and in particular to an apparatus and method for contouring a stable bottom for cartons or boxes such as paperboard cartons used for holding liquids, powders and the like, and to containers so contoured.




BACKGROUND OF THE INVENTION




An example of one common and useful type of container is the paperboard carton having a square cross-section and a gabled top. Examples of such cartons include the everyday milk carton. In recent years, these cartons have been used for numerous other products, including, for example, foods, beverages and detergents. These cartons are typically coated or laminated with a heat-sealable plastic or other suitable material, which is used by manufacturers to seal the cartons.




The bottoms of such paperboard cartons, as well as other types of paperboard or cardboard containers, often are uneven, rather than perfectly flat, making them unstable. That is, rather than standing perfectly upright, the carton rests in a slightly tilted position when placed in the upright position on a flat surface. Furthermore, the carton may rock to a different tilted position if bumped or moved. This rocking and tilting is undesirable to consumers, wholesalers, transporters, grocers and other merchants and distributors of goods packaged in such cartons. This instability typically results from a natural bulge in the carton bottom due to pressure exerted by the product inside and/or discontinuities on the bottom exterior surface formed by overlapping, folded layers within the carton bottom.




Currently, there are several methods to minimize the effects of the problem of instability caused by the bulge.




A carton disclosed in Ljungstrom, U.S. Pat. No. 5,474,232, issued in 1995, provides a concave carton bottom having an arcuate cross-section such that the carton rests on the bottom end of each of two opposing side walls. Col. 7, lines 10-12. This method, however, has the disadvantage that it requires a specially designed carton blank having curved, rather than straight, side creases. Most current carton forming machines are designed to operate with certain standard carton blanks. It can be expensive and inconvenient to procure non-standard carton blanks. It would be desirable to form a concave carton bottom with standard carton blanks.




A packaging machine disclosed in Kume et al., U.S. Pat. No. 4,838,847 which issued in 1989 provides a carton bottom with a substantially pyramidal recessed central cavity. Col. 3, lines 16-20; col. 3, lines 35-40. This carton bottom is supported by end surfaces on all four sides of the carton. This specific configuration is difficult to form, and increases the likelihood of liquids spilling from the carton during transport. A need exists for a simpler stable carton bottom which does not increase the risk of spillage.




A carton bottom sealer disclosed in Mills et al., U.S. Pat. No. 5,482,204 which issued in 1996 provides a carton bottom with a lenticular profile—i.e., a “concave, stepped pyramid formed into multiple tiers of lapped layers” as the profile of the carton bottom. Col. 1, lines 57-58. This carton bottom is formed from a standard carton blank and is intended to be more stable than a traditional carton bottom. However, the structure of the foregoing carton bottom has the disadvantage of being complicated.




Another effort to provide a stable bottom for a carton is described in Fujikawa et al., U.S. Pat. No. 5,222,667 issued in 1993. The '667 patent discloses forming a recess of inverted V-shaped cross section extending across the bottom closure through the center thereof, so that the recess diminishes the bulge of the bottom closure. The recess has a width approximately equal to the width of the striplike region (31 in FIG. 5 of the Fujikawa et al. patent) having four thicknesses of the container blank. See FIG. 5; col. 3, lines 30-37; col. 2, lines 50-56. Similarly, NiMCO Corporation of Crystal Lake, Ill., had previously provided packaging machines for making cartons having a bottom configuration of the type illustrated in FIG.


1


A. In the prior art NiMCO container, the width of the recess also was limited to approximately the width of the center region having four overlapping layers, and the recess did not include the regions where there are fewer than four overlapping layers (i.e., on either side of the four-layer center region).




However, none of the foregoing bottom configurations satisfactorily solve the problem of instability resulting from a bulge in the carton bottom. Accordingly, there is a need for a more stable carton bottom than was provided by the prior art carton bottom configurations.




A need exists for an apparatus and method of forming a stable carton bottom from a standard carton blank which can be used with current carton forming machines. A need also exists for a carton bottom which is inexpensive to produce in current carton forming machines. Additionally, a need exists for providing a stable carton bottom on cartons with other than rectangular side panels, e.g., tapered cartons.




SUMMARY OF THE INVENTION




In accordance with the present invention, it has been discovered that forming the carton bottom so that selected regions of the carton bottom exterior surface extend below the surface of another region (i.e., a recessed region) of the carton bottom allows such selected regions to function as legs, thereby providing a more stable bottom structure than prior art methods. This is achieved by making the width of the recessed region wider than in certain of the prior art methods. In the preferred embodiment, the recessed region encompasses substantially the entire center portion of the bottom panel having the maximum number of overlapping layers as well as a substantial portion on either side of such center portion where there are fewer than the maximum number of overlapping layers. Providing such a wider recessed portion results in a marked improvement in carton stability over prior art methods, which had either a narrow center recess or which required either specially configured carton blanks or more complicated carton bottom configurations than the present invention.




In accordance with yet another aspect of the present invention, a stable carton with carton legs is formed from a standard carton blank. Because the present invention may be used with, among other things, a standard carton blank, current carton forming machines may be readily adapted to use the present invention.




Additionally, a standard carton blank is often less expensive and more readily available than a specially designed carton blank.




In accordance with yet another aspect of the present invention, a carton bottom is formed with a simple mechanism which can be readily incorporated into current carton forming machines. The present invention relates to a novel seal plate and mandrel pad which contour the carton bottom.




The present invention is advantageous because it easily and inexpensively can be adapted to and integrated into existing carton forming machines. For example, the sealing horn


22


and mandrel pad


40


of U.S. Pat. No. 3,971,300 or the pressure pad


118


and mandrel


120


of Hyduk, U.S. Pat. No. 5,135,463, as well as the horn and mandrel pad of other existing carton forming machines could be modified to incorporate the present invention.




In accordance with the present invention, a carton bottom is formed with improved stability. This improved stability is desirable for transportation, storage and display of the cartons to customers.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a top plan view of a lower portion of a standard paperboard carton blank suitable for use with the present invention;





FIG. 1A

is a cross-sectional view of the bottom of a sealed carton previously used by NiMCO Corporation;





FIGS. 1B

,


1


C and


1


D pictorially illustrate a typical bottom folding sequence of a paperboard container;





FIG. 2

is a perspective view of the bottom of a sealed carton with respect to which the present invention has not been used;





FIG. 3

is a cross-sectional view of the sealed carton in

FIG. 2

taken along line


3





3


of

FIG. 2

;





FIG. 3A

is a diagram illustrating layers of the sealed carton bottom in

FIG. 2

;





FIG. 4

is a cross-sectional view of a mandrel pad, seal plate and stable carton bottom;





FIG. 5

is a cross-sectional view of the stable carton bottom in

FIG. 6

taken along line


5





5


of

FIG. 6

seated on a flat surface;





FIG. 6

is a perspective view of the stable carton bottom shown in

FIG. 4

;





FIG. 7

is a perspective view of the mandrel pad and seal plate shown in

FIG. 4

; and





FIGS. 8

,


9


,


10


,


11


,


12


and


13


are cross-sectional views of alternative embodiments of the present invention.











DETAILED DESCRIPTION OF THE INVENTION




One embodiment of the present invention is suitable for use with, for example, paperboard cartons, as described in detail below. However, it should be understood that the present invention is suitable for use with cartons or containers produced from fiberboard, cardboard, or other materials of various sizes and configurations including, for example, beverage cups. Referring to the figures generally and particularly to

FIG. 1

, there is shown a top plan view of the bottom portion of a typical paperboard blank


24


. Blank


24


is conventional, and for clarity is shown before being folded. Blank


24


is a single, continuous piece which can be folded to form a sealed carton.




In the preferred embodiment, the paperboard of blank


24


is laminated with heat-sealable plastic, as is well known. One side of the blank may also be laminated with barrier material such as metal or other material. The present invention can function with blanks utilizing any top closure configuration, such as with a gable top or a flat top similar to the sealed bottom surface.




The folding sequence of blank


24


is illustrated by collective reference to

FIGS. 1B

,


1


C and


1


D. Initially blank


24


is folded, by any appropriate method, such that panels


36


,


38


,


40


and


42


form sidewalls of carton


32


, with the top and bottom ends open. Mutually facing main bottom panels


72


and


74


then are partly folded towards one another along fold lines


76


and


78


, respectively. At substantially the same time, triangular panels


44


and


46


are folded toward the center of the carton about fold lines


48


and


50


, respectively. Sealing panel or tab


81


is rotated against the surface of main bottom panel


74


, and corner panels


52


and


54


are simultaneously folded over to form partially formed carton


32


with bottom edge


66


. Referring to

FIGS. 2 and 3

, there is illustrated the bottom end of a partially formed carton


32


. The carton bottom can be sealed together by any suitable method, for example, by use of an adhesive, ultrasonic vibration, and most preferably hot fusion.




Specifically referring to

FIG. 3A

, partially formed carton


32


is divided into the five regions of varying thicknesses. A first region


33


is a striplike portion extending across the bottom of carton


32


through the center thereof and including two triangular second regions


34


at the midportion of its length, with their apexes butting against each other. Except for the second regions


34


, the first region


33


has four layers of the container blank. Second regions


34


have two layers. Carton


32


has another region having four layers of carton blank, i.e., a third region


35


including sealing panel


81


. Third region


35


partly includes a region


36


having two layers. Generally, triangular fourth regions


37


having three layers are present on opposite sides of first region


33


. The remaining portions are fifth regions


39


having one layer of the blank.




Although described in conjunction with a conventional carton having rectangular wall panels, it should be understood that the present invention also is suitable for use, for example, with containers shaped as sections of round or curved cylinders, square cylinders (i.e., prisms having square cross-sections), rectangular cylinders (i.e., prisms having rectangular cross-sections), and cones and containers having four trapezoidal shaped wall panels, as well as other container configurations having various numbers, thicknesses and shapes of overlapping layers on the container bottom. Additionally, although a particular carton bottom configuration is illustrated in

FIGS. 3 and 3A

, the present invention is also suitable for use with various other bottom configurations including, for example, fin bottoms, rex bottoms, tuck bottoms, L bottoms, J bottoms, six panel bottoms, as well as other bottom configurations. The present invention is suitable for carton bottoms which are square, rectangular or any other shape.




As illustrated in

FIG. 4

, a carton bottom


34


is contoured and formed by compressing the carton bottom between a mandrel pad


12


and a seal plate


14


. Mandrel pad


12


may be stationary and seal plate


14


pressed up against the exterior bottom surface of partially formed carton


32


by any suitable means, thereby compressing the carton bottom between mandrel pad


12


and seal plate


14


, preferably while the layers comprising the bottom wall are hot and tacky. Alternatively, seal plate


14


may be rigidly attached to the carton forming machine. Mandrel pad


12


, which partially formed carton


32


may be erected and folded around, can be pressed down to the interior top surface of the bottom of partially formed carton


32


by any suitable means, for example, by a reciprocating piston. Partially formed carton


32


is pressed between mandrel pad bottom of carton


32


into the shape of the gap between mandrel pad


12


and seal plate


14


. Subsequently, mandrel pad


12


and seal plate


14


are separated from carton bottom


34


by suitable means. After bottom sealing, the carton may be filled and finally its top opening sealed.




As illustrated in

FIGS. 5 and 6

, carton bottom


34


is contoured so as to have carton legs


56


. Carton legs


56


have an outside edge.


68


and an inside edge


70


, which may be straight, curved or any other suitable shape. Carton legs


56


enable carton bottom


34


to stand upright on flat surface


75


. Although it is preferable to form carton legs


56


parallel to bottom edge


66


to minimize the potential of leaking liquid products, carton legs


56


can be formed either perpendicular or parallel to bottom edge


66


. Alternatively, the recessed region of carton bottom


34


may be both perpendicular and parallel to bottom edge


66


, thereby forming four carton legs which are preferably of square cross-section.




In the preferred embodiment, the width of the recessed region between carton legs


56


at any position in the recessed region is greater than the sum of the widths of carton legs


56


. Alternatively, the sum of the widths of carton legs


56


is less than half the width of the entire carton bottom. Additionally, the recessed region preferably encompasses substantially the entire center region having the maximum number of overlapping layers of material (i.e., width W in

FIG. 3A

with four overlapping layers for a standard L bottom carton), as well as a substantial portion of the bottom region outside the center region predominately having less than the maximum number of overlapping layers of material. Although preferable, carton legs


56


do not necessarily need to extend the entire length of carton bottom


34


so long as their length and width are sufficient to provide a stable bottom surface.




With reference to

FIG. 7

, mandrel pad


12


and seal plate


14


are composed of steel, or any material suitable to compress and contour the bottom of carton


32


. Mandrel pad


12


contains recessed area


58


and extended areas


60


. The corners defining recessed area


58


and extended areas


60


can be about 90°, but also may be other angles, or configurations. For example, the corners can be a continuous curve (as illustrated in

FIGS. 10 and 11

) or have a 45° chamfer. The depth of recessed area


58


varies depending upon, for example, the thickness and stiffness of the paperboard or other material used for the container, the weight of the product to be packaged in the container and the particular configuration of the carton bottom. Mandrel pad


12


can be in any shape or configuration which will provide for forming a stable container bottom, including, for example, a two legged carton bottom, a three legged carton bottom or a four legged carton bottom. Similarly, the legs


56


need not be rectangular or planar, but could be curved, triangular or some other shape, or have recessed portions facing toward the interior of the carton.




Referring again to

FIG. 7

, seal plate


14


is approximately complementary to mandrel pad


12


, having a raised area


62


adapted to fit within recess


58


of mandrel pad


12


, and recessed areas


64


adapted to receive extended areas


60


of mandrel pad


12


. The surface of area


62


is preferably raised with respect to the surfaces of recessed areas


64


by approximately the same amount that recess


58


is offset from the surfaces of extended areas


60


. The size and shape of leg forming area


64


is made to correspond to mandrel pad


12


. Optionally, one or more of legs


56


may be formed with internally recessed regions. Accordingly, extended areas


60


and leg forming area


64


may have recessed and raised portions, respectively, to form such regions.




Mandrel pad


12


and seal plate


14


may contain additional recessed and raised areas to accommodate variations in the number of overlapping layers and/or their shape and/or thickness over the carton bottom, as is currently known in the art.




With reference to

FIGS. 8

,


9


,


10


,


11


,


12


and


13


, there are illustrated various alternative embodiments of the present invention. Like reference numerals correspond to reference numerals in FIG.


4


. Specifically,

FIG. 8

illustrates a tapered carton (which may be used, for example, as a beverage cup), and corresponding mandrel pad and seal plate. Referring to

FIG. 9

, there is shown a carton (and mandrel pad and seal plate) where the extended portions of carton legs


56


are not parallel to the recessed area. Although illustrated as substantially planar, carton legs


56


may be curved or any other suitable shape. Additionally, inside edge


70


may be raised more than outside edge


68


. Referring to

FIGS. 10 and 11

, there are illustrated cartons which have a curved recessed portion. The curved recessed portion is preferably concave and may encompass all or some of the carton bottom. Referring to

FIG. 12

, there is shown a carton where the width of carton legs


56


are each approximately half of the width of the carton bottom. In this embodiment, each carton leg


56


may be substantially planar. Preferably, carton legs


56


encompass substantially all of the carton bottom and come together to form an obtuse angle. Referring to

FIG. 13

, there is illustrated a carton with three carton legs


56


arranged as three roughly equally spaced strips. The three legs


56


may be arranged in a triangular configuration or other configurations which allow for standing stability.




While the invention has been described with respect to certain preferred embodiments and, as will be appreciated by those skilled in the art, it is to be understood that the invention is capable of numerous changes, modifications and rearrangements and such changes, modifications and rearrangements are intended to be covered by the following claims.



Claims
  • 1. A carton composed of foldable material having first, second, third and fourth side panels, each side panel ending at a corresponding bottom panel, the bottom panels being folded and sealed so as to form a sealed carton bottom and to define an interior region of the carton, the exterior surface of the carton bottom having first and third bottom edges on opposite sides and at the periphery of the bottom between the first and third side panels and the corresponding bottom panels, the exterior surface of the sealed carton bottom also having second and fourth bottom edges on opposite sides and at the periphery of the bottom between the second and fourth side panels and the corresponding bottom panels, the first and third bottom edges being substantially perpendicular to the second and fourth bottom edges, such that the first, second, third and fourth bottom edges form the perimeter of the carton bottom, wherein the carton is formed from a blank having substantially straight score lines adjoining the carton bottom, and wherein the exterior surface of the sealed carton bottom comprises:a first inclined surface lying substantially in a first plane; a second inclined surface lying substantially in a second plane; wherein said first and second planes intersect along a line of intersection, wherein a first end of said first inclined surface extends from substantially the entire length of said first bottom edge and a first end of said second inclined surface extends from substantially the entire length of said third bottom edge, wherein a first portion of each of said second and fourth bottom edges is located on said first inclined surface and a second portion of each of said second and fourth bottom edges is located on said second inclined surface, and wherein said line of intersection is disposed toward the interior region of the carton; further comprising a third surface lying substantially in a horizontal plane and disposed towards the interior region of the carton, wherein said third surface is disposed between said first and second inclined surfaces.
  • 2. The carton of claim 1 wherein said third surface extends from a portion of the length of said second bottom edge to a portion of the length of said fourth bottom edge and wherein said portions of said second and fourth bottom edges are located on said third surface.
  • 3. A carton composed of foldable material and having a hollow body portion and attached bottom panels folded and sealed so as to form a sealed carton bottom, thereby defining an interior region of a carton, the exterior surface of the stable sealed carton bottom having first and third bottom edge portions on opposite sides of the bottom, the exterior surface of the sealed carton bottom also having second and fourth bottom edge portions on opposite sides of the bottom, the first and third bottom edge portions being substantially perpendicular to the second and the fourth bottom edge portions, such that the first, second, third and fourth bottom edge portions lie on the perimeter of the carton bottom, wherein the exterior surface of the sealed carton bottom comprises:a first inclined surface lying substantially in a first plane; a second inclined surface lying substantially in a second plane; a third surface lying substantially in a third, horizontal plane and being disposed towards the interior region of the carton; wherein said first and second planes intersect said third, horizontal plane along first and second lines of intersection, respectively, wherein a first end of said first inclined surface extends from substantially the entire length of said first bottom edge portion and a first end of said second inclined surface extends from substantially the entire length of said third bottom edge portion, wherein said third, horizontal surface is disposed between said first and second inclined surfaces, and wherein a first portion of said second bottom edge portion and a first portion of said fourth bottom edge portion are located on said third surface.
  • 4. The carton of claim 3 wherein a second end of said first inclined surface intersects said third surface along said first line of intersection and a second end of said second inclined surface intersects said third horizontal surface along said second line of intersection.
  • 5. The carton of claim 3 wherein a second portion of said second bottom edge portion and a second portion of said fourth bottom edge portion are located on said first inclined surface, and wherein a third portion of said second bottom edge portion and a third portion of said fourth bottom edge portion are located on said second inclined surface.
US Referenced Citations (26)
Number Name Date Kind
512571 Walker Jan 1894 A
3339821 Wojcik Sep 1967 A
3586232 Scully Jun 1971 A
3712844 Ratten et al. Jan 1973 A
3971300 Bachner Jul 1976 A
4093115 Bachner et al. Jun 1978 A
4601425 Bachner Jul 1986 A
4702410 Derving Oct 1987 A
4838847 Kume et al. Jun 1989 A
4861328 Franke et al. Aug 1989 A
4991768 Kondo Feb 1991 A
5029751 Detzel Jul 1991 A
5056707 Larsen Oct 1991 A
5078315 Floberg Jan 1992 A
5135463 Hyduk Aug 1992 A
5222667 Fujikawa et al. Jun 1993 A
5324250 Janson et al. Jun 1994 A
5337538 Ljungstrom Aug 1994 A
5474232 Ljungstrom et al. Dec 1995 A
5482204 Mills et al. Jan 1996 A
5564255 Giacomelli Oct 1996 A
5725144 Stone et al. Mar 1998 A
5738272 Anchor et al. Apr 1998 A
5765746 Peasley et al. Jun 1998 A
5845840 Johansson et al. Dec 1998 A
5871144 Anchor et al. Feb 1999 A
Foreign Referenced Citations (2)
Number Date Country
0582003 Feb 1994 EP
610744 Oct 1948 GB
Non-Patent Literature Citations (2)
Entry
The Wiley Encyclopedia, p. 150, 1986.*
Webster's New World Dictionary, 3rd College edition, 1988.