Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The inventiDn relates to a plastic bag of a
heat sealable material including a g~sseted portion.
Methods for making bottDm and side gusseted
plastic bags are well-known in the art. The fDllowing
patents show some of the typical prior art methods for
making gusseted plastic bags and these patents are
incorporated herein by reference. These patents
include U.S. patent no. 4,046,065, U. S. patent no.
3,980,225, U. S. patent no. 3,319,540, U. S. patent no.
3,395,622, and U. S~ patent no. 3,839,128.
In the pri~r art, it was fount that the bottDm
gussetet plastic bags had two weak points, one at each
of the intersections of the center llne fold of the
gusset ant the site edges. One prlor srt solut~on to
this problem has been the use of diagonal heat seal
regions extenting from the weak points town to the bottom
of the bag at an angle to the bag bottom. The diagonal
heat seals can have two different forms. If the tiagonal
heat seal ~oins together the four layers of the bag, then
the gusset becomes restricted and the bag cannot be
opened fully 90 that the bag capacity as well as the
stant-up qualities of the bag becomes impaired.
If the diagonal heat seals are mate to seal only
the two adjacent layers of the bag rather than all fDur
layers, a separator plate must be used in the sealing
process. The use of a separator plate between the layers
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keeps the diagonal heat seal from reaching and reinforcing
the weak seal points so that the effectivenes~ of the
diagonal seal is not fully obtainable. Furthermore, the
use of a separator plate requires that the heat sealing be
separately accomplished on each side of the bag so that
an increase in equipment and manufacturing costs results.
Similarly, weak points have been found in side
gusseted bags and these have been dealt with by the use
of diagonal heat sealing also.
The instant invention can be carried out
economically and is surprisingly effective in improving
the strength of the gusseted plastic bag.
One of the embodiments of the instant invention
i8 a plsst~c bag compr~9ing two side walls of a heat
sealable material, the side walls being connected together
by an inwardly folded portion of material which is folded
along a center line fold and outer line folds to define
a gusseted portion, the side walls being heat sealed
together at least along an edge generally perpendicular
to the center line fold to define the bag, and a spot
heat sealed region spaced from the outer line
folds and located at the intersection of the center line
fold and the edge for joining together all our of the
layers of the material.
Another embodiment of the instant invention is a
plastic bag comprising two side walls of a heat sealable
material, the side walls being connected together by an
inwardly folded portion of material which is folded along
a longitudinal center line fold to define a gusseted
bottom, the side walls being heat sealed together along
opposite sides of the bag to define side edges of the
bag, and a spot heat sealed region spaced from the
bottom of the bag and located at each of the intersections
of the center line fold and the side edges for joining
together all four of the layers of the material.
Generally, each spot heat sealed region is
preferably a semi-circle positioned with a diameter
along the side edge and substantially bisected by the
center line fold. Other shapes for the heat sealed
region can be used such as rings, triangles, hexagons,
other polygons, etc.
The plastic bag can include a closure device
suitable for opening and closing the bag in accordance
with the prior art or as shown in U. S. Patent 4,212,337
issued July 15, 1980 and assigned to the assignee of the
instant application.
;Another embodiment of the invention is a metho~ of
forming a reinforced gusseted plastic bag, comprising
;the steps of supplying heat sealable material, inwardly
folding a portion of the material along a center line fold
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and outer line folds to define a gusseted portion, and
heat sealing at least along an edge generally perpendicular
to the center line fol.d to define the bag, wherein the
¦ improvement comprises spot heat sealing a region spaced
fr~m the outer line folds located at the intersection
- of the center line fold and the edge for joining together
all four of the layers of the material.
Another embodiment of the invention isa method of
forming a reinforced bottom gusseted plastic bag, compris-
, 10 ing the steps of supplying a heat sealable plastic film
web in the form of a continuous sheet having substantially
parallel sheet etges, folding the film web so that the
; sheet edges of the film web are near each other and
substantially paralle~ to each other, inwartly
folting a portion of the film web to establish a
longitutinal center line fold to define a gusset, spot
heat sealing regionsto ~oln together all four layers of
the material at spaced locations along the center
line folt, and sever-sealing the film web transversely
to intercept the heat sealet regions to tefine side etges
for the bag.
Preferably, the heat sealed regions are
spaced apart a predétermined distance equal to the
width of the bag and preferably the heat sealed regions
are circular.
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The invention accordingly comprises the features
of construction, the combination of elements and the
arrangement of parts which will be exemplified in a
construction hereinafter set forth and thè scope of the
application of which will be indicated in the cla~ms.
The invention also comprises the several steps
in the relationship of one or more of such steps with
respect to each of the others, all as exemplified in the
following detailed disclosure and the scope of the
10 application of which will be indicated in the claims.
For a fuller understanding of the nature and
ob~ects of the invention, reference should be had to the
following tetailet description, taken in connection with
the accompanying drawings, in which:
Fig. 1. ls a front elevational view of a plastic
bag in accortance with the invention;
Fig. 2 is a sectional view along the line 2-2
of Fig. l;
Fig. 3 is a perspective view of the plastic bag
of Fig. l in an open state;
Fig. 4 is a block tiagram of the apparatus for
carrying out the method of the invention; ant
Fig. 5 shows a portion of the operations
Rhown in Fig. 4, ant
Fig. 6 is a front elevational view of another
plastic bag in accordance with the invention.
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In carrying the invention into effect, certain
embodiments have been selected for illustration in the
accompanying drawings and for descrip~ion in the specifica-
tion, reference being had to Figs. 1 to 6.
A plastic bag in accordance with the instant
invention optionally includes a closure device at the
opening of the bag. Fig. 1 shows one embodiment of the
invention which includes a closure device 10. The
side walls 11 are of a heat sealable material and the
gusseted bottom 12 can be seen from Fig. 2 as being an
inwardly folded portion of the material which is folded
along a longitudinal center line fold 13 and outer line
folds 15.
In accordance with prior art practice, the
side edges 14 are formed by a sever-sealing operation.
The spot heat sealed regions 16 are located at the
intersections of the center line fold 13 and the side
edges 14 in order to provide reinforcement for the
gusseted bottom 12, particularly when the bag is
opened and loaded and the gusset bottom 12 is stressed.
The heat sealed regions 16 ~oin together the four layers
of the gusseted bottom 12 as can be appreciated by
reference to Figs. 2 and 3.
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Fig. 4 shows a block diagram of the apparatus
for carrying out the method of the invention for producing
a plastic bag in accordance with the invention. Generally,
the production of a plastic bag having a gusseted bottom
i8 known from the prior art.
Plastic film webs 17 is supplied, for example,
from a roll 18 of the heat sealable material. In its
simplest form, the pla8tic film web 17 can be a single
layer. PLastic film web 17, h~wever, could also be a
multiLayer film web,provided that both of the outsidè
layers are heat sealsble 80 that the plastic bag of
the invention can be formed. Unit 19 folds the film
web 17 in half and forms an inwardly folted portion
along a longitudinal center line to tefine a gusset
portion. Unit 19 is well-known from the prior art,such
a9 U.S. patent no. 3,059,549. Preferably the film web 17
i~ folded in half, but it may be desirable for certain
ùse~ to fold the film web 90 that the plastic bag
finally obtained will have one side wall extending
beyont the other site wsl}.
The folded film web 21 from unit 19 can have a
closure device bonded to it in unit 22 in accord-nce with
prior art mRthods, or 8 directly to unit 23 for ~pot
heat sealing regions for reinforcing the gusseted bottom.
The method of establishing spot heat sealing is well-known
in the prior art. The spot heat sealing regions 25 are
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- spaced apart a distance equal to the width of the bags
being produced. The spot heat sealed film web 24 is
thereafter sever-sealed in unit 26 to produce the plastic
bag acccrding to the lnventLon.
Fig. 5 shows the spot heat sealed film web 24
which is moved into the unit 26,and bag 27 which is eject
by the unit 26. The sever-sealing operations substant~al
bisect the spot hea~t sealed regions 25 as shown in Fig. 5
. The surprising improvement obtained by the
instant invention can be appseciated by the following
test results.
Bottom gusseted bags were made in the so-called
"5 quart size". The bags were made from low tensity
polyethylene fil~ having a thickness of 1.75 mii.
The dimensions were 10-1/2 inches wide and 11 inches dee
with a bottom gusset 2 inches deep. The bags included
interlocking closures. Of the 104 bags, half were in
accordance with the invention while the other half did n
$nclude reinforcing and were according to prior art.
Each bag was loaded with a liter of water,
se led wlth the lnterlocking closure, and dropped ln
an upright position from a heigh~ of 4 feet onto a hard
surface. Thereafter, each bag was inspected for damage
The 52 bags according to the invention had a
single bag failure while the 52 bags according to the
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prior art had 10 bag failures.
These results show that the bags according
to the invention are substantially superior to the
prior art bags without the spot heat sealing reinforcing.
Fig. 6 shows another embodiment of the invention
for a plastic bag having side gussets. The side walls 30
are of a heat sealable material. The gusseted sides 31
have been formed by inwardly folding the material along
center line folds 32 and outer line folds 33. In
accordance with prior art practice, an edge seal 34 is
formed with a skirt 36. The spot heat sealed regions 37
are located at the intersections of the center line folds
32 and the edge seal 34 in order to provide reinforcement
for the respective gusseted sides 31.
It i8 understood that the invention i9 not
limlted to the exact details of construction shown and
describet, for obvious modifications will occur to a
person skillet in the art.
Having thus tescribet the invention, what is
claimet a~ new ant desired to be secured by Letters Patent,
is as follows: ~
10.
