Container with infolded bottom closure

This disclosure illustrates and describes a bottom closure structure for a liquid carrying, thermoplastic coated paperboard carton or container wherein the overlapped and sealed areas are formed so as to extend in an "X"-shaped configuration across the bottom, with minimal raw edge exposure on the inside. The shapes of the four main bottom panels of the blank from which the carton is formed are such that they accommodate interdigital nesting or overlapping with respect to the bottom section of an adjacent blank prior to the cutting operation on a paperboard roll, thereby resulting in a narrower roll and, hence, a substantial paperboard savings.

TECHNICAL FIELD 
This invention relates generally to liquid carrying paperboard cartons or 
containers and, more particularly, to a novel fold-in bottom closure for 
such containers. 
BACKGROUND ART 
It is well known that paperboard used for milk and juice containers can be 
economically coated with heat and pressure sensitive thermoplastic 
substances. Such substances must be inert to the substances to be 
packaged, strong and durable, inexpensive, and easy to apply in sheet form 
onto the paperboard. One example of a suitable thermoplastic substance, 
useful for packaging dairy products, is polyethylene. 
The paperboard stock for forming the containers is initially supplied in 
the form of rolls. As the stock is produced it is coated on both sides 
with layers of polyethylene of predetermined thicknesses. Blanks are then 
cut from the thus treated paperboard roll, and scored so as to be 
adaptable to being folded into a tubular shape with readily foldable and 
sealable leak-proof top and bottom closures. Generally, it has been 
desirable for the finished bottom end closure to contain at least three 
plies of stock at each bottom corner area, with a minimal length of raw 
edge exposed to the interior of the container and, hence, to the contents 
thereof. 
A very satisfactory and widely used container and infolded bottom closure 
is that shown and described in Egleston et al. U.S. Pat. No. 3,120,335. 
In view of the fact that a considerable volume of thermoplastic coated 
paperboard is used for the packaging of milk and juices on today's market 
throughout the world, it is desirable to save as much paperboard as 
possible while maintaining the current high standards for efficiently 
manufacturing a high quality, leak-proof, sanitary container. 
DISCLOSURE OF THE INVENTION 
Accordingly, a general object of the invention is to provide a liquid 
carrying, heat sealable container having an improved bottom end closure 
which remains leak-proof while containing infolded panels having 
substantially less overlapping paperboard than has heretofor been the 
case. 
Another object of the invention is to provide a container blank wherein the 
four panels thereof which serve to make up the bottom end closure are 
shaped such that the bottom end closure panels of the adjacent blank are 
internested therewith, thereby making possible the use of a narrower roll 
of paperboard for each two rows of blanks. 
A further object of the invention is to provide an improved 
paperboard-saving, bottom end closure which is adaptable to conventional 
tucking and tacking apparatus on current forming, filling and sealing 
machines with minimal modification of the latter. 
Still another object of the invention is to provide such an improved bottom 
end closure which is adaptable, after being folded flat, to being sealed 
by conventional gas heat, electrical, or ultrasonic methods. 
These and other objects and advantages of the invention will be apparent 
when reference is made to the following description and accompanying 
drawings.

BEST MODE OF CARRYING OUT THE INVENTION 
Referring now to the drawings in greater detail, FIG. 1 illustrates a 
fragmentary blank 10 suitable for being formed into a tubular body 12, as 
shown in FIGS. 2-4. One end of the body 12 is provided with a suitable top 
end closure (not shown), such as the familiar gable top configuration of 
Egleston et al. U.S. Pat. No. 3,270,940, incorporated herein by reference. 
The flat bottom end closure 14 of FIGS. 4 and 5 is shaped from the blank 10 
of FIG. 1 which is separated into two groups of panels by a staggered 
score line 16. The purpose of the score line 16 being staggered in the 
form shown is to accommodate the thickness of the sheet material as it is 
bent along the score lines when the closure is erected and thus prevent 
crowding of the material at the various corner junctions of the score 
lines. This not only enhances the strength and appearance of the finished 
container but facilitates its erection and closure by automatic machinery. 
The material above the score line 16 in FIG. 1 is the bottom closure group 
14 while the material shown below the line 16 is the body group 18. The 
latter comprises four side panels 20, 22, 24 and 26 and a side seam panel 
or flap 28. The body group is defined on the sides by edges 30 and 32, 
with the panels being separated by score lines 34, 36, 38 and 39. 
The bottom closure group 14 comprises closure panels 40, 42, 44 and 46 
adjacent the body panels 20, 22, 24 and 26, respectively, and an extension 
48 of the side seam flap 28. The closure panels 40, 42 and 46 encompass 
the same shapes and overall areas, while the panel 44 is larger in area 
and height. Each of the panels 40, 42 and 46 is gable-shaped, having short 
vertical sides and sloped outer edges terminating at an apex whose height 
is one half the width of a body panel. The short vertical sides constitute 
edges 50 and 52, and score lines 54, 56, 58 and 60 between panels 40/42, 
42/44, 44/46 and 46/48, respectively. Each of the panels 40, 42 and 46 
include identical sloped edges 62 and 64, while the panel 44 includes 
steeper sloped edges 66 and 68 terminating at an apex whose height is a 
predetermined amount greater than one half the width of a body panel. 
The two oppositely disposed end panels 42 and 46, which are joined to 
opposite sides of the largest end panel 44, are each divided by a pair of 
diagonal score lines 70 and 72, forming opposite outer triangles 74 and 76 
with the sloped edges 62 and 64, respectively. One diagonal score line 70 
extends from the juncture of the score lines 16, 34 and 54 to the apex of 
the panel 42, while the other diagonal score line 70 extends from the 
juncture of the score lines 16, 38 and 58 to the apex of the panel 46, 
respectively. One diagonal score line 72 extends from the juncture of the 
score lines 16, 36 and 56 to the apex of the panel 42, while the other 
diagonal score line 72 extends from the juncture of the score lines 16, 39 
and 60 to the apex of the panel 46, respectively. 
At this point, it should be noted that, inasmuch as the blanks 10 are cut 
from a wide roll of paperboard, an adjacent blank 10' (FIG. 1) can have 
its bottom end closure panels 40', 42', 44', 46' and 48' internested with 
the adjacent closure panels 48, 46, 44, 42 and 40, respectively. Such 
internesting saves a width of paper equal to the vertical height of the 
sloped edges 66 and 68 of the largest closure panel 44, represented in 
FIG. 1 as "A". For those applications wherein the roll of paperboard is 
wide enough for four blanks abreast, it is apparent that the width of 
paperboard saved would be twice the height "A". 
To construct the container bottom closure as shown in FIG. 4, a flat side 
seamed blank is first formed by folding the blank 10 upon itself and 
sealing the side seam flap 28 and its extension 48 to the inside faces of 
panels 20 and 40, respectively, using any of the well-known plastic 
sealing methods such as heat, sound or light. The folded blank is next 
formed into the tubular body 12 (FIG. 2) on a mandrel (not shown), with 
the bottom closure panels extending outwardly from the face of the 
mandrel. Following this, the container bottom is infolded (FIG. 3) and 
sealed (FIGS. 4 and 5). 
As indicated in FIG. 3, the inner triangular portions of the panels 42 and 
46 are urged toward each other, with the outer triangular portions 74 and 
76 thereof caused to fold-back outwardly about the score lines 70 and 72 
and toward the inner triangular portions. Upon completion of the folding 
process, the inner triangular portions 74 and 76 are confined between the 
inside panels 42/46 and the outside panels 40/44, as shown in FIG. 5, with 
the longer panel 44 overlapping the end portion of the opposite outside 
panel 40. The resultant flat end configuration is sealed by any suitable 
method, such as by gas heat or ultrasonically, in a substantially "X" 
shaped pattern, i.e., along the four diagonal, triple layered segments 
extending from each corner to the center of the bottom closure. 
In FIG. 6, it may be noted that, on the inside of the container, the apices 
of the panels 42 and 46 meet at the center of the container, while the 
apex of the panel 40 lies directly underneath. Hence, no raw edges are 
exposed on the inside of the bottom end closures. 
Referring now to FIG. 7, it may be noted that the body panels 20, 22, 24, 
26 and 28 of the blank 10" are identical to those of the FIG. 1 
embodiment, while the bottom end closure panels 40", 42", 44", 46" and 48" 
are formed so as to have 90.degree. angles between adjacent sloped edges, 
terminating at a horizontal edge located adjacent the apex formed by the 
diagonal score lines 70 and 72, and said diagonal score lines forming a 
right triangle with the horizontal score line 16. As such, cutting a roll 
of paperboard to form the sloped edges of the bottom end closure panels 
40", 42", 44", 46" and 48" will also serve to form the sloped edges of the 
bottom end closure panels of the adjacent blank, shown in phantom, 
resulting in minimal scrap therebetween. The panels 43" and 46" each have 
a height equal to approximately one-half the width of a side panel. 
As shown in FIG. 8, the blank 10" of the FIG. 7 embodiment is formed into a 
bottom end closure wherein the inner triangular portions of the panels 42" 
and 46" are first urged toward each other, with the outer trapezoidal 
portions 74" and 76" formed by the diagonal score lines 70 and 72 being 
caused to fold outwardly about the score lines 70 and 72 and onto the 
triangular portions. As such, the outer trapezoidal portions are confined 
between the inner triangular portions and the adjacent edge portions of 
the respective panels 40" and 44". The longer panel 44" extends past the 
end portion of the oppositely disposed panel 40". The resultant flat end 
configuration is sealed in a substantially "X" shaped pattern, as was the 
case with the FIG. 5 embodiment, i.e., along the four diagonal, triple 
layered segments extending from each corner to the center of the bottom 
closure. 
In this embodiment, provision may be made for obtaining an exceptionally 
tight seal of the bottom closure when finally completed. This is 
accomplished by constructing the laterally cut edges of the trapezoidal 
portions 74" and 76" such that they enter into positive abutting 
engagement with each other prior to completion of the bottom closure. More 
specifically, the panels 42" and 46" may be so proportioned that the 
combined length thereof is slightly greater than the width of each side 
panel measured along the score line 16. Thus, the paperboard is "crowded" 
together in the closing operation, thereby greatly enhancing the tightness 
of the bottom seal. 
INDUSTRIAL APPLICABILITY 
It should be apparent that the invention provides an efficient and readily 
machine formable bottom end closure for a liquid carrying paperboard 
container, which is also economical to produce insofar as the forming of 
the blanks from a paperboard roll is concerned, as compared to the 
conventional blanks heretofor in popular use. 
It should also be apparent that the container formed from the improved 
bottom closure need not expose any internal raw edges in the center or 
cross-over portion of the bottom closure. 
While but two embodiments of the invention have been shown and described, 
other modifications thereof are possible.