Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
13~?~ . R . I . F-1984
BOR-8finl6AUSl -Dll
TITLE OF THE INVENTION
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SINC7LE-PLEATED MICROWA~TE POPCORN PACKAGE
FIELD OF THE INVENTlON
This invention relates to a microwave-penetrable bag that i5
designed as a package for a product that expands when heated,
such as popcorn. The invention is al80 concerned with a process
for making the bag, and a process for popping the popcorn that is
packaged in the bag.
BACKGROUND OF THE INVENTION
The majority of microwave popcorn containers presently in use
rely on steam pressure to achieve proper package expansion.
These containers tend to be quite efficient from a distribution
standpoint since they can be shipped and displayed on a store
shelf in flattened form, thereby taking up a minimal amount of
space. Various patents disclose such packaging. Examples are
IJ.S. Patent 4,571,337 to Cage, U.S. Patent 4,548,826 to Watkins,
U . S . Patent 3, 973, 045 to Brandberg, and U . S . Patent 3, 851, 5~. 4 to
~atz .
Althou~h expandable bags are cost-effective, they are not
currently the most efficient for popcorn cooking. Two problems
are associated with such expandable bag packaging:
(1) Proper expansion of the package is not always achieved.
This reduces the space available for the popped kernels and
results in a lower yield of finished product; and
(2) Heating of the product is not always sufficient. This also
results in lower yields.
Problems associated with bag expansion occur for various
reasons. In some packagin~, venting of steam occurs prematurel~.
This has been found to he a problem with the bag of Cage et nl.,
U.S. Patent 4,571,337, which relies on a weakened seal area for
the venting function. This weskened seal area cannot be precisely
controlled due to variations in material thickness and seal
~3~D2~
strength. ~)ther packaging, such as that disclosed bv Brandbcrg
et al. in U. S. Patent 3, 973, 045, shows a vent which releases steam
throughout the entire cooking process. This system of venting is
also unreliable because of Yariations in the rate of steam generated
dùring the cooking process.
An additional cause of poor bag expansion is bag ,~eometry.
Ideallv, an expandable bag will retain its expanded form when the
internal steam pressure declines. This usually occurs in popcorn
cooking during the latter stage of the process, when fewer kernels
are being popped. Current state-of-the-art packaging relies on
bag geometry which allows the bag to collapse during the early
stages of steam ventilation, and only retain its expanded form
during the latter stage of the cooking process.
A further problem associated with current state-of-the-art
popcorn packages relates to adequately heating the popping corn
within the package. Such problems are due primarily to a transfer
of heat from the package to the oven floor. The Borek patent,
U . S . 4, 219, 573, teaches the use of a cardboard pad to solve this
problem. Although this solution is only a partial one, the
packaging materials expense is increased by this solution. Bohrer
et al., U.S. Patent 4,553,010, describes an attempted solution to
the heat transfer problem through the use of a microwave-inter-
active material such as a metallized polyester. This type of
technology could be applied to an expandable bag. However, ns
with other solutions, packaging costs are increased.
In addition to the problems relating to expansion of the
package and heating of the product, most microwsve popcorn
packages lack a convenient means for oper.ing the package. Such
convenient opening means is particularlv important in microu nve
popcorn packa~eing due to the possibilit~ of burns from escaping
steam as the package is opened.
SU~I~IARY OF THE IN~TEl\TTION
In one embodiment, the present invention comprises a flexible
package constructed of material which is penetrable b~ microwatTe
~Vf~
energy. The package is formed from roll stock or sheet stocli on
horizontal or vertical form, fill snd seal machinery. The package
is generally flat when empty, but is capable of expanding its
internal volume to accommodate an expansion of its contents. The
sheet stock used to form the package has lengthwise-extending
marginal portions opposed to each other which are folded to
confront and engage each other. Along the area of engagement,
the two marginal portions are sealed together to form R lengthwise-
extending seam. A folding of the now-seamed piece of sheet stock
provides at least one lengthwise-extending pleat and at least two
lengthwise-extending extremities that are parallel with each other.
The lengthwise-extending extremities comprise the edge~ of the
package .
The seam is disposed intermediate the two edges of the
package, and is spaced from each of them. The pleat has an inner
pleat edge that is located substantially opposite the lengthwise-
extending seam when the package is in its flattened form. The
pleat is free for movement relative to the rest of the package.
The ends of the length of sheet stock are transversely sealed
together to form a closed package.
~ hen expanded, the package is tubular, with a configuration
comprising three surfaces and three heat-sealable closures. The
package is sealed transversely at each end, and a seam extending
from one end of the package to the other comprises the third
closure .
The three-surface, single-pleated structure provides a
positive vent mechanism and a rigid structure when expanded.
When a charge of unpopped popcorn kernels is cooked in the
package, the steam released by the kernels is retained in the
package until fuil e~;pansion of the package occurs. Only after
full expansion, is there sufficient stress created to cause an
opening at the package end where a transverse sea2, the
lengthwise-extending seam and the inner pleat edge intersect to
form the venting means for the package. Even as the steam is
released, the package maintains its expanded structure, thereby
providing more space in which the kernels n-av pop. An additional
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aspect of the expanded geometrv of the three-surfsce, single-
pleated package is the minimal amount of contact between the
package and the oven floor. The minimal contact reduces the
amount of heat transferred from the package and the popcorn
product to the microwave oven floor, therefore improving the yield
of popped corn.
A further advantage of the three-surface, single-pleflted
package is its ease of opening. The lengthwise-extending seam
and the inner pleat edge are located substantially opposite each
other such that a consumer wishing to open the package need
merely grasp the pleat in one hand, grasp the seam in the other
hand, and pull in opposite directions. The package readily opens
along a transverse seal to allow access to the popped corn.
The process for forming and filling the package comprises
advancing the microwave penetrable sheet stock in a lengthwise
direction and folding at least a part of the sheet stock into a
generally tubular form which has a longitudinal axis extending
lengthwise of the sheet stock. Free, lengthwise-extending
marginal portions of the sheet stock are then folded to confront
and engage each other. The sealing of the engaged marginal end
portions to form a lengthwise-extending seam that defines the
generally tubular structure is the next step of the process
followed by the folding of the sheet stock to define the edges of
the tubular form. The sheet stock is cut and sealed transversely
to form the top closure of the package after a predetermined
amount of kernels have been dispensed into the package.
When the filled popcorn package is placed in a microwave
oven for cooking, its pleated face is adjacent the oven floor. As
microwave energ~ is applied to the package contents, the popcorn
kernels pop and release steam and Yapor which cause the pacl~.age
to expand. I)ul ing expansion, the package changes geometrv such
that onlv one surface of the package makes minimal contact with
the oven floor.
The cost of the package and the final product are below that
for most prior art products, because there are no specialized
materials or equipment necessary to produce the product.
~3~)~P~
BRIEF DESCI~IPTION OF T~E DRA~'INGS
Figure 1 is a perspective view of the three-surface, single-
pleated microwave popcorn package in an unexpanded flatterled
form .
Figure 2 is a top view of the preferred embodiment of the
three-surface, single pleated microwave popcorn package.
Figure 3 shows the three-surface, single-pleated microwave
popcorn package in an expanded form as it would be after the
popcorn had been fully cooked in a microwave oven.
Figure 4 shows the three-surface, single-pleated microwave
popcorn package in a partially expanded form as it would be after
the popcorn had begun to coolc.
Figure 5 is a top view of an alternative embodiment of the
three-surface, single-pleated microwave popcorn package, in which
the outer edge of the len~thwise-extending pleat does not extend
as far as the edges of the generally tubular structure.
Figure 6 is a top view of an alternative embodiment of the
three-surface, single pleated microwave popcorn package, in which
the lengthwise-extending seam and the inner edge of the pleat are
not ~ligned opposite each other, when the package is in a flattened
form .
Figure 7 is a top view of an alternative embodiment of the
three-surface, single-pleated microwave popcorn package, in which
the inner pleat edge and the lengthwise extending seam are not
centered with respect to the bag edges.
Figure 8 is a top view of a further alternative embodiment of
the three-surface, single-pleated microwave popcorn package, in
which the lengthuise-extending seam and the inner edge of the
pleat are not aligned opposite each other, w hen the package is in
a flattened form.
DETAILED DESCRIPTION OF TI~E INVENTION
Popcorn packages suitable for use in a microwave oven and
constructed in accordance with the present invention are shown in
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Figures 1 through 8. The popcorn package is formed from roll
stock or sheet stock on either vertical or horizontal form, fill and
seal machinery.
Figure 1 shows the generally flattened tubular structure that
is formed AS the roll stock or sheet stock materi~l proceeds
through the form, f~ll and seal machinery. A lengthwise-extending
seam 14 is disposed on 8 package face 20, intermediate two
lengthwise-extending extremities 16 and 18. The two lengthwise-
extending extremities 16 and 18 comprise the edges of the two
faces 20 and 22 of the generally tubular structure. The seam 14
is formed frorm the sheet stock by folding opposed marginal
portions of the sheet stock so that they confront and engage each
other, and then sealing the two together to form the seam 19.
The seam 14 is sealed by heat, pressure, a combination of heat
and pressure or any other suitable sealing mechanism. Joining the
opposing marginal portions of the sheet stock material to form the
seam 14 results in the formation of ~ laterally extending projection
24 from the face 20 of the package. The width of this laterally
extending projection 24 is approximatel~r 3/4 inch. The width of
the laterally extending projection 24 makes it easy to grasp, which
is important because of the projection's use in the opening of the
package. Also illustrated in ~Ygure 1 is the location of the seam
14 on the face 20 of the generally flat rectangular package.
Although the seam 14 may be disposed on the package face 20 at
any location intermediate the two edges 16 and 18, the seam 14 is
preferably disposed at the center of the package face 20 as shown
in Figure 1. This preferred embodiment produces optimal cook
performance because of the venting means opening size which is
optimized with this particular package structure.
The generaily tubular structure formed by sealing the
opposed marginal portions of the sheet stock is next fGlded such
that the two lengthwise-extending extreraities 16 and 18 comprise
the edges of the two opposing faces 20 and 22. The tubular
structure is further folded so that a lengthwise-extending pleat 27
is disposed on package face 22 intermediate the two edges 16 and
18. ~'hen the generally tubular structure is in its flattened form,
~3~29~
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the pleat 27 is folded at an inner pleat edge 26 so that it lies
against ~ace 22 of the package. If the pleat 27 were folded away
from the face 22 of the package, and the package balanced on the
outer edge 28 of the pleat, the package would have a T-shape with
the pleat 27 representing the vertical base and the seamed face 20
representing the horizontal cross-bar of the "T". Figure 1 most
clearly shows the shape of the package when it emerges from the
form, fill and seal machinery.
In a preferred embodiment, illustrated by Figure 2, the outer
pleat edge 28 will substantially align with an edge 16 of the
package when the pleat 27 is folded flat against face 22 of the
package. Also shown in Figure 2 is the location of the seam 14 in
relation to the pleat 27. When the package is in its ~lattened
form, the inner pleat edge 26, on face 22, is preferably directlv
opposite to the seam 14, on the opposite face 20 when viewed along
a transverse seal 30. The inner pleat edge 26 and the seam 14
are also preferably centered with respect to the edges 16 and 18.
The location of the pleat 27 is important for an adequate opening
mechanism for the package. An easy opening mechanism is utilized
after the contents of the package have been fully cooked. The
eas~v opening mechanism for the package involves grasping the
projection 24 of the seam 14 in one hand and grasping the pleat 27
in the other hand and then pulling apart. The pulling apart
causes the package to open along the transverse sea! 30.
The location of the inner pleat edge 26 with respect to the
seam 14 may be varied within limits. The limitations are defined
by the openability of the package. If the distance between the
seam 14 and the inner pleat edge "6 measured along the transverse
seal 30 of the package end is too large, the ease of opening the
package uill be~ lost. Ease of opening is maintained so long PS the
distance between the seam 14 and the inner pleat edge 26 meas~red
along the transverse seal 30 is about one inch or less. Also
related to the location of the pleat 27 on the package is the
position of the outer pleat edge 28. In a preferred embodiment,
the outer pleat edge 28 is aligned with an edge 16 of the package
when the package is in its flattened form shown in Figure 2.
13(~Z96D~
The width dimension of the pleat 27 may be varied
considerably without affecting the package performance, however,
a pleat width of one-half inch of less contributes to an increased
incidence of seam rupture during popp~ng of the corn kernels.
Rupture of the seam 14 ~nd the subsequent relea6e of popped corn
into the microwave oven is an undesirable result, therefore the
pleat 27 has a width dimension greater than about one inch, and
preferably about two and a half inches.
Transverse seals 30 and 32 are located at the ends of the
package and serve to seal the package from the environment. The
transverse seals 30 and 32 are formed by severing the folded sheet
stock with transverse cuts across the sheet stock's longitudinal
a~:is. The transverse cuts are made so as to sever the folded
sheet stock into a desired length for the package. The open ends
caused by the severing are then sealed closed by heat, pressure,
a combination of heat and pressure or any other suitable sealing
mechanism. The transverse seals 30 and 32 may also be formed by
a simultaneous cutting and sealing operation.
Transverse seal 30 is located at the top of the package and
transverse seal 32 is located at the bottom. The bottom seal 32 is
wider than the top seal 30 in order to insure that the package will
vent and open at the top and not at the bottom. The bottom seal
32 is about one inch wide, in contrast to the transverse seal 30,
which is approximately one-half inch wide.
Figure 3 shows the package in its expanded form after some
or all of the popcorn has been cooked. Figure 3 best illustrates a
venting means 34 which is located at a point at the end of the
package where the transverse seal 30, the seam 14 and the inner
edge 26 of the pleat 27 substantially coincide. The location of the
venting means 3i comprises a major stress po.nt at one end of the
package. The venting means 34 allows the escape of accumulated
steam from the inside of the package. As the unpopped popcorn
};ernels in the package cook, they release steam and vapor which
cause the pressure inside the package to increase and the package
to expand. As the interior pressure of the package increases, the
stress created cau~es the venting means 39 tc open in preference
~L3~)~9~
g
to a rupture of the seam 19 due to the width requirements of the
plest 27. The venting mesns 34 also opens in preference to the
bottom transverse seal 32 which is wider than the top transverse
seal 30, which comprises the venting means.
The width of the pleat 27 is greater than one inch and
preferably about two and a half inches. The width of the plent 27
allows a substantial expansion of the pack~ge before sufficient
stress to open the venting means 34 has been reached. The
venting means 34 does not open until the package is completely
expanded. The venting means opens first due to the geometry of
the package, which makes the venting means 34 the major stress
point of the e~cpanded package.
The positioning of the lengthwise-extending seam 14 and the
pleat 27, relative to esch other, also effects the opening of the
venting means 34. Table I below shows the results of bag
opensbility tests when the position of the lengthwise-extending
seam 14 is changed relative to the inner pleat edge 26. The first
column of the table indicates the position of the lengthwise-
extending seam 14 relative to the inner pleat edge 26. The
negative numbers indicate that the seam was located to the left of
the pleat edge when viewed from the top of the package, whereas
the positi~e numbers indicate the positioning of the seam to the
right of the pleat edge. The second column in the table designstes
the percentage of packages in which the venting mesns 34 opened
in preference to the seam 14. The third column in the table
indicates the number of tests conducted with the seam 19 in the
given position.
13iVZ~
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TABLE J
Position of Seam Percentage of
14 Relative to Packages Which Number of
Inner Pleat Edge Opened at Venting Tests
26 (Inches)Means 34 Conducted
- 1-1/2 0 2
- 1 0 2
- 314 0 5
- 112 85 7
0 100 7
+ 112 57 7
+ 1 50 2
+ 1-1/2 0 2
+ 2 0 2
~ 'hen expanded, as shown in Figure 3, the package has three
major surfaces. The paclcage face 20 is one surface, and has the
projection 24 disposed thereon. Projection 24 divides surface 20
into the areas designated 20a and 20b in Figure 3. Each of the
other two surfaces are comprised partly of the package face 22 and
partl,v of the pleat 27. The outer edge 28 of the pleat is the
common edge for these other two surfaces. One of the surfaces 36
consists of the sheet stock material that is bordered on its
longitudinal sides by the edge 16 and the outer pleat edge 28.
The other surface 38 consists of the sheet stock material that is
bordered on its longitudinal sides by the edge 18 and the outer
pleat edge 28. The surface 38 is the only one of the three
surfaces that comes in contact with the oven floor 40, uhen the
package is in its, expanded form.
The exp2nsion of the package, in con junction ~ith the sePded
ends of the package. represented by transverse sea]s 30 and 32,
causes the three surfaces of the package to be generallv convexlv
cvrved in a longitudinal direction, as well as in a transverse
direction. The convex curvature, in both directions, of surface
38, which is in contact with the oven floor 40, results in only a
~3~
smnll percentage of the area of surf~ce 38 being in actunl contAct
with the oven floor 40 sfter the package has expanded. This
minimal contact of the surface 38 with the oven floor 40 results in
a minim~l amount of heat being transferred from the package and
its contents to the oven floor as the popcorn cooks. As more heat
is retained in the package, the yield of popped corn increases.
The minimal contact of surface 38 with the oven floor 40 therefore
contributes to a grester yield of popped corn from the present
invention than from conventional microwave popcorn bsgs.
When forming the single pleated package, microwave
penetrable roll stock or sheet stock is advanced through form, fill
and seal machinery. The sheet stock is advanced in a direction
lengthwise of the stock and folded to produce a generally tubular
form with a longitudinal axis extending lengthwise of the stock.
The free lengthwise-extending marginal portions of the stock are
folded so that they confront and engage each other. The
confronting marginal portions are then sealed to form the
lengthwise-extending seam 14 and the projection 24. The folds
made to bring the marginal portions into engagement with one
another comprise lengthwise-extending extremities 16 and 18 which
are paraliel to each other and define the edges of opposing faces
20 and 22 of the generallv tubular structure.
The generally tubular structure is next folded to define at
least one lengthwise-extending pleat 27 which is disposed on face
22 opposed to the seam 14 on face 20. A transverse cut is then
made across the sheet stock and sealed to form the transverse seal
32 which defines the bottom end of the package. A specified
amour~t of unpopped popcorn kernels, that when fully cooked will
suhstantially fill the package, is then dispensed into the generally
tubular structure. Finally, a second transt~erse cut is made
across the sheet stock and sealed to form the top transverse seal
30. At this time, the package is completely formed and severed
from the sheet stock.
When dispensed from the form, fill and seal machinery, the
package is in a flattened form with pleat 27 folded a~ainst the
package face ~". In this flattened form, the package may be
::L3~,4P~
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folded or rolled for conVellient packagin~ of multiple package units
for consumer use.
When used in a microwsve oven, the package i8 first unfolded
or unrolled to its generally flattened form as when dispensed from
the form, fill and seal mschinery. The package i8 then placed in
the oven with the pleat 27, still folded against the face 22,
adjacent the oven floor~ Microwave energy is then applied to the
corn kernels through the package for a sufficient time to pop
substantially all the kernels.
As the popcorn kernels pop, they release steam and vapor
which cause the package to expand. The expansion of the pleat
37 creates surfaces 36 and 38. Surface 38 is the only surface that
comes into contact with the vven floor. Figure 4 shows the
package in a partially expanded form, immediately after the pleat
27 has expanded sufficiently to create surfaces 36 and 38.
When the psckage has fully expanded, it has a generally
triangular, three-surface, tubular shape with closed ends, as
shown in Figure 3. An adv&ntage of this structure is the minimel
contact between the package and its contents and the microwave
oven floor. This minimal contact feature is due to the longitudinal
convex curvature and the transverse convex curvature of surface
38 of the expanded packa~e which makes less contflct with the
oven floor than does the flat end of a conventional microwave
popcorn bag. The minimal contact between the package and the
oven floor reduces the heat transfer from the package and its
contents to the oven floor. As more heat is retained in the
packag e and its contents, more kernels are popped to increase the
yield of popcorn from the single pleated package of this invention.
An increased yield of popcorn is also realized due to the
retention, bv the package, of its expPnded structure even after
venting of accumulated steam has commenced. After the package
has fully expanded, the venting means 39 opens when sufficient
stress has been created by the steam and v apor of the popping
kernels. Even after the opening of the venting rneans 34, th
release of vapor and the subsequent reduction of the interior
pressure and stress, the package retains its expanded structure
'13~Zg~fl~
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RS shown in Figure 3. The retention of an expanded structure
permits the corn kernels more volume in which to expand after
popping. The surfaces of the package do not collapse back upon
the corn kernels and already popped corn as do the surfaces of
conventional microwave popcorn bags after ventilation of
accumulated steam. The lack of excess weight and pressure from
collapsed package surfaces on the unpopped corn allows the
popping kernels to expand to a more complete extend and therefore
produce a greater yield of a fluffier, more desirable popcorn
product .
The improved yields from the popcorn package of the
invention over conventional microwave popcorn bags is illustrated
by the following table which shows the results of a comparison of
the single pleated package of the invention with a pillow pouch bag
and a gussetted bag. Equal amounts of package material and
popcorn kernels were used for each of the three bags. An 18" x
11" sheet of suitable microwave transparent material was used to
make each bag, and 80 grams of popcorn kernels were sealed
inside each bag. Each bag was placed in a 625 watt General
Electric~ microwave oven for a five minute cook time, and the
resultant yields were as follows:
TAB LE I I
Yield Obtained
Ba~ Style in Cups
Single Pleated Bag 8.1
Pillow Pouch Bag 6. 3
Gussetted Bag 6 . 5
In general, the single pleated microwave popcorn package
produces an 8-10 cup yield of popped corn from an initial charge
of appro~imately 80 grams of popcorn kernels. This yield is
produced after cooking the popcorn kernels for about three to fi~-e
minutes in a microwave oven.
In one embodiment, the roll stock material from which the
package is made comprises fluorocarbon-treated paper laminated to
*~ k
-14--
a 48-gauge heat-sealable polyester such as Dupont's OL~. The
paper is an excellent surface for printing the identity of the
product and manufacturer and instructions for consumer use. The
fluorocarbon treatment serves to eliminate any oil stains on the
package from the internal product by resisting the penetration of
fats and oils, and the polyester is an excellent adhesive for the
package seals, as it is heat-sealable. Any commercially available
stain inhibitor may be used in place of the fluorocarbon treatment.
Any material used to form the package should be microwave-
penetrable and heat-sealable, yet able to withstand temperatures in
the range of 350F, since this temperature is the approximate cook
temperature of popcorn.
An alternative embodiment of the microwave popcorn packsge
of this invention is formed on form, fill and seal machinery from
roll stock or sheet stock material comprising a paper with a
polyvinyl acetate sealant applied in register. A heat-sealable
polyester without the paper backing is also a suitable material. A
paper without stain inhibitor treatment may be used if oils are not
used in the bag, The overall package size may also be varied
according to the amount of popcorn kernels to be added to the
package and the estimated yield of popped corn.
Figures 5, 6, 7 and 8 show alternative embodiments of the
invention in which the locations of the lengthwise-extending seam
14 and the lengthwise-extending pleat 27 are varied. Numbered
features in the alternative embodiments are in the one hundreds
series which correspond to the figure numbers, in order to clearly
distinguish the ~rariation of the features in such embodiments.
Numbered features of Figure 5 are in the five hundreds series,
those in Figure 6 are in the six hundreds series, etc.
ln Figure 5, the seam 514 and the inner pleat edge 52fi are
located opposite each other, and both the seam 514 and the inner
pleat edge 526 are positioned in the center of their respective
package faces. Additionally, the outer pleat edge 528 is not
aligned with the edge 516 in Figure 5.
Figure 6 shows a package in which the seam 614 and the
inner pleat edge 626 are not substantially opposite each other, but
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are within about one inch of each other, as measured along the
transverse seal 630. In this embodiment, the outer pleat edge 628
is in ali~rnment with the edge 616 and the seam 614 is located
substantially in the center of the package face 620.
Figure 7 shows an embodiment in which the seam 714 and the
inner pleat edge 726 are located opposite each other, but the seam
714 and the inner pleat edge 726 are not positioned in the center
of their respective package faces. The outer pleat edge 728 is in
alignment with the edge 716 in the embodiment illustrated by
Figure 7.
Figure 8 illustrates an alternative embodiment in which the
seam 814 is located off-center in relation to the package face 820
on which it is positioned. The inner pleat edge 826 is not
substantially opposite the seam 814, but is within one inch of the
seam 814 as measured along the transverse seal 830. The outer
pleat ed~e 828 is substantially aligned with the edge 816.
~ Vhile the invention has been disclosed by reference to the
details of preferred embodiments, this disclosure is intended in an
illustrative rather than in a limiting sense, as it is contemplated
that modifications will readily occur to those skilled in the art,
within the spirit of the invention and the scope of the appended
claims .
