Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
lX84969
THERMOPLASTIC BAG, BAG PACK AND METHOD OF
MAKING THE SAME
This invention is concerned with a
thermoplastic handled sack, a plurality of said sacks
unitized into a bag pack and a method for preparing the
same.
Handled thermoplastic sacks are well known and
are finding increasing use in the grocery sack market.
Another area of use for handled bags, particularly as
the gauge of thermoplastic film reduces as the quality
of the film is improved, is the area of waste and trash
container liners. Far and away the most common type of
thermoplastic handled grocery sack is one made from a
gusseted tube sealed at the top and the bottom, with a
suitable bag mouth and handle cut-out, which yields a
double layer of film in the handled region. Bags with
double film layers in the handles ensure that
significant loads, i.e., up to 45 and more pounds, can
be safely carried without fear of the handles breaking
or tearing. There are problems associated with this
type of bag. One problem is the fact that the gusset
folds of the bag are of necessity trapped in the bottom
seal of the bag. This prevents the gusset from
extending fully as the product is loaded into the bag,
which results in a wasteful loss of volume. Another
problem is that where there are transitions from four
layers to two layers along the heat seal line of the
bottom of the bag and forces are brought to bear at
these transition points as the bag attempts to expand,
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tears develop on both sides of the bag at the transition
points. Furthermore, when bags are employed as trash or
waste container liners, e.g. office waste baskets,
extremely thin gauge film is employed, e.g. from
0.25-0.7 mils. With such thin gauge material it is
difficult to form an effective heat-seal in the bottom
of the bag. In addition, with extremely thin gauge
film, the bag tends to be pulled into the waste
container when material is thrown into the container
liner because the film does not have enough stiffness or
substance to resist the inertia of the thrown material.
It is an object of the present invention to
provide a bag and a method of making the same which bag
will have maximum volumetric efficiency without
sacrificing bag strength in the handled region of the
bag. The bag of the present invention will have a
stronger bottom seal and will be better suited for use
as a grocery sack, merchandise sack, waste or trash
container liner, and the like.
The present invention is directed to a method
for forming a thermoplastic film handled bag comprising:
(a) forming a continuous collapsed
thermoplastic film tube;
(b) forming heat-seal lines across the width
of said tube, transverse to the tube sides, at bag
length intervals, said heat-seal lines being sufficient
to seal the films of said collapsed tube together and
preweaken said line for subsequent bag separation;
(c) longitudinally folding opposite sides of
the heat-sealed tube equally toward each other until
they at least substantially meet at a common center line;
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(d) folding this structure once again along
said center line so as to bring the folded opposite
sides into face-contact;
(e) removing eight film layers in one of the
corner regions defined by a transverse heat-seal and the
spine of fold (d), the film removal being such as to
yield, on unfolding, a bag having a bag mouth opening
and single film loop handles near opposite ends of said
bag mouth opening but spaced from the bag sides; and
(f) collecting, while still folded, the
interconnected structures of (e) into a volumetrically
efficient pack of bags.
In another embodiment of the method for forming
a thermoplastic film handled sack the following steps
are utilized:
(a) forming a collapsed thermoplastic film
tube, heat-sealed transversely at each end thereof;
(b) folding opposite sides of the sealed tube
toward but spaced from each other, along lines
perpendicular to said heat-seals; and
(c) removing, from one end of the folded
structure, film regions sufficient to form a bag mouth
. opening and a pair of single layer handle loops at
opposite ends of said bag mouth opening.
- The invention is also directed to a method for
forming a unitized pack of thermoplastic film handled
sacks comprising:
(a) forming a collapsed thermoplastic film
tube, heat-sealed transversely at each end thereof;
.-. (b) folding opposite sides of the sealed tube
toward but spaced from each other, along lines
perpendicular to said heat-seals: ~
(c) stacking a plurality of such folded
structures one upon the other in registration: and
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(d) simultaneously performing a cutting,
perforating and unitizing operation at one end of the
stack that will form a pair of single-layer loop handles
with a bag mouth opening therebetween and tab members,
attached by way of film perforations to the edges of
said bag mouth opening, said tab members being unitized,
thereby forming said pack of sacks.
The invention is further directed to a
thermoplastic bag structure comprising a front and rear
bag wall, a two-film heat-seal bottom and an open-mouth
top portion, said open mouth portion being characterized
by having either one pair of single film handle loops or
two pairs of single film handle loops which are located
at opposite ends of said open mouth portion. The
handles of each pair of handle loops are disposed in a
side-by-side relationship and each handle of the bag
structure is an integral looped extension of the front
and rear bag walls. It is preferred that the open mouth
top portion of the bag have arcuate stress relief
regions at the base of the innermost handles and that
the upper edges of the mouth extend above these stress
relief regions. The bag is ungusseted along its sides
and the bottom is heat-sealed through the four or eight
layers of film.
The invention is further directed to a pack of
thermoplastic film bags comprising: a plurality of
superimposed bag structures each having a front and rear
bag wall, a two film heat-sealed bottom and an open
mouth top portion, said open mouth portion being
characterized by having one pair or two pairs of single
film handle loops located at opposite ends of said open
mouth portion, the outer side region of each bag being --
folded toward each other so that the handles of each
handle pair are in registration; tab members detachably
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attached to the upper edges of said bag mouth and said
tabs being unitized to hold said superimposed bag
structures together in a pack.
In a further embodiment of the method for
forming a thermoplastic film, handled bag, the following
steps are conducted:
(a) forming a collapsed thermoplastic tube
gusseted to a maximum, on both sides, so that the gusset
folds meet;
(b) forming a first heat-seal across the width
of said collapsed, gusseted tube, transverse to the
gusseted sides:
(c) simultaneously or subsequently forming a
second heat-seal a bag length distance spaced from said
first heat-seal across the width of said tube transverse
to the gusseted sides;
(d) folding said gusseted, heat-sealed tube
along a line coincident with the meeting line of said
gusset folds;
(e) removing from the folded structure, film
layers which will leave two, superimposed, 2-film
handled loops and a bag mouth opening; and
(f) separating the resulting bag from said
tube along the heat-seal lines.
The invention is also directed to a continuous
method for forming thermoplastic film, handled bags
comprising:
(a) forming a continuous collapsed
thermoplastic tube, gusseted to a maximum, on both sides,
so that the gusset folds meet;
~ b) forming heat-seal lines across the width
of said tube, transverse to the gusseted sides, at bag
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length intervals, said heat-seal lines being sufficient
to seal the films of said collapsed tube together and
preweaken said line for subsequent separation;
(c) folding said gusseted, heat-sealed tube
along a line coincident with the meeting line of said
gusset folds;
(d) removing from the folded structure, film
layers which will leave two, superimposed 2-film handle
loops and a bag mouth opening, said handle loops being
detachably attached by way of their heat-seals to an
adjacent folded structure and
(e) collecting said bags into a volumetrically
efficient pack of bags.
The bags can be formed in a continuous
top-to-top and bottom-to-bottom relationship or in a
top-to-bottom relationship and the resultant
interconnected bags collected in a roll for individual
dispensing.
Alternatively, the bags can be formed into
discrete, separated bags having detachable tab members
in the bag mouth region so that a plurality of stacked
bags can be unitized by way of the detachable tab. Thus
the invention is also concerned with a pack of bags.
The invention is also directed to a
thermoplastic bag structure comprising a front and rear
bag wall, a bottom and an open mouth top portion, said
open mouth portion being characterized by having loop
handles near opposite ends of the bag mouth but spaced
from the bag sides or by having double-film loop handles
at opposite ends thereof, said bag having sides gusseted
to the maximum, said bag also being folded along a line
coincident with the meeting of said gussets and
heat-sealed at said bottom through eight layers of film.
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In the drawings appended to this specification:
FIGURE 1 is a plan view of a collapsed
thermoplastic tube;
FIGURE 2 is a plan view of the sealed tube of
Figure 1 with opposite sides folded equally inwardly;
FIGURE 3 is a plan view of the structure of
Figure 2 folded again along its centerline and revealing
a handle and bag mouth region;
FIGURE 4 is a single detached bag fully
unfolded to show the handles and bag mouth regions of a
bag;
FIGURE 5 is a plan view of the tube of Figure 1
with the sides folded toward each other a predetermined
distance;
FIGURE 6 is an isometric view of a unitized
stack of bags of the type manufactured utilizing the
embodiment of Figure 5;
FIGURE 7 is a plan view of a single detached
bag in its unfolded condition;
FIGURE 8 is a plan view of the tube of Figure 1
with the sides gusseted to the maximum;
FIGURE 9 is an end view of the gusseted tube of
Figure 2 taken along the line 9-9 of Figure 8.
FIGURE 10 is a plan view of the structure of
Figure 8 folded along the gusset meeting line and
revealing a handle and bag mouth region:
FIGURE 11 is an end view taken along the lines
11-11 of Figure 10; and
FIGURE 12 is an isometric view of a single
detached bag with the handle and bag mouth region
unfolded from their position shown in Figure 10.
It is well known in the plastics film art to
continuously melt extrude a thermoplastic resin through
an annular orifice, apply internal fluid pressure, e.g.
air, to the tube thus extruded and thereby expand the
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tube and reduce the wall thickness thereof to
appropriate dimensions while cooling and solidifying the
extruded thermoplastic film. This technique and any
equivalent technique for forming a thermoplastic film
tube can be employed in providing the starting material
for the bags and bag packs of the present invention.
The contemplated thermoplastic film can be of
any type having the characteristics necessary for a
handled bag required to carry items totaling up to
45 lbs. or more. While not limited to the polyolefins,
these materials have proven in the past to be excellent,
inexpensive films from which handled bags can be made.
Preferred materials include polyethylene generically and
specifically, low density polyethylene, high density
polyethylene, including high molecular weight high
density polyethylene, linear low density ethylene
copolymerized with a C3-C8 alpha olefin and blends
and mixtures of the foregoing materials. A specific
example of a commercially available polyethylene
material suitable for use in the present invention is a
linear low density ethylene copolymerized with from
about 2 to about 7 wt.% of octene-l. This linear low
density ethylene-octene-l copolymer, i.e., LLDPE can be
melt extruded through an annular orifice and blown up to
a tube which will have a lay flat dimension of
approximately 19.5 inches. This tube is then collapsed
and can serve as an example of the starting material for
the present invention.
Referring to the drawings, a segment 10
approximately 25 inches long of such a collapsed tube is
shown in Figure 1. The sides 12 are seamless and
opposite ends 14 are heat-sealed to form a "pillow case~
type structure. In an automatic system, the
continuously advancing collapsed tube will have spaced
1~34969
heat-seal lines, such as at 14, impressed into the
tube. The distance between heat-seals will correspond
to the distance between the heat-seal at the top of the
handle loop of a finished bag to the bottom heat seal of
the bag. Obviously, this distance will vary depending
upon the size of the desired bag. The type of seal
contemplated is designed to heat weld the two films
together without severing through the films. Heat-seal
14 constitutes a thermal merging of the two-films of the
collapsed tube. The seals 14 can be made so that they
simultaneously seal and sever-through the films or the
seals may be made not to sever-through but merely weaken
the region adjacent to line 14 so that they may
subsequently be severed with comparatively little
force. Such a seal will permit the segments to remain
in linked connection through the remainder of the bag
making process and also, if desired, to link the
completed bags by way of this preweakened region while
collected in a volumetrically efficient bag pack.
Figure 2 shows the sealed tube of Figure 1 with
the sides 12 folded toward each other so that they just
contact each other at a common midline 16. As the
flattened and sealed tube of Figure 1 advances in an
automatic system, a conventional turning and folding
plate can automatically bring tube edges 12 together at
the common midline 16. In like manner, as the folded
structure of Figure 2 progresses in the automatic
system, a second folding plate will again longitudinally
fold the structure of Figure 2 upon itself so that the
common midline 16 becomes the outer spine of the fold 16
of Figure 3. The term ~spine~ is employed herein in the
same sense as that in describing the ~spine" of a book.
In this same sense the outer fold lines 18 of Figure 2
would be equivalent to the outer edges of the cover of a
book hinged at a spine.
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While in this double-folded condition with
folded opposite sides in face-contact, the handles and
bag mouth region of individual bags can be formed. In
this folded condition, the structure consists of eight
layers of film. The handles and bag mouth opening can
be formed by removing eight film layers in one of the
corner regions defined by one of the transverse heat-
seal lines 14 at its intersection with spine line or
midline 16. This region is shown in Figure 3 at region
20. The shape of the removed region 20 will dictate the
shape of the handles and the bag mouth opening. As
illustrated in Figure 3 and Figure 4, the shape of the
eight films removed resulted in straight handles 22 and
arcuate stress relief regions 24. It will be noted that
in Figure 3 two handles 22 are simultaneously formed
during the eight film cut-out procedure. Each handle 22
in Figure 3 is actually folded in two along line 18. In
Figure 4, the handles are shown in their unfolded
condition with dotted line 18 representing the midline
of the handle. Thus, by this technique double the
amount of film as is shown in Figure 3 is available in
the handle. This provides the equivalent of the same
amount of film that is employed in typical side gusseted
double film handled bags. Consequently, the bag of the
present invention can carry the same amount of weight as
a side gusseted bag.
The arcuate stress relief regions 24 located at
the base of the handles, function to transmit stress
lines that would normally be concentrated at the bag
mouth lines 26 to a position somewhat below this level.
Thus, stress forces caused either by opening the bag
during loading or after loading will, by virtue of the --
arcuate stress relief regions, be directed to broad
areas across regions 28. In this manner any preweakened
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regions in the bag mouth opening caused by perforation
tears will be avoided.
Referring again to Figure 3, the area 20
removed to form the bag mouth opening and the handles
also can form tab members 30 detachably attached by way
of perforations 32 to folded bag member 34. These tab
members can be employed to unify a plurality of
individual bags 34 stacked in registration. For
example, 50 to 100 of the bags can be stacked in
registration and an appropriate heat-seal means can fuse
the tabs together forming a unified pack. Figure 3
shows an orifice 36 pierced through tab members 30. A
hot piercing device can melt a hole through all of the
tabs, heat-seal unifying the tabs and simultaneously
forming therein orifice 36. This orifice can be
employed to suspend the resulting pack so that bags can
be torn from the pack one at a time.
Alternatively, in place of tab members 30, the
bags may remain interconnected at heat seal 14 and the
bags may be convolutely rolled into a suitable pack for
later dispensing one at a time by tearing the bags free
of the roll along lines 14. Instead of a roll the bags
can be folded back and forth one upon the other in a
zig-zag type arrangement.
While one bag member at a time can be formed by
sequential removal of regions 20 of the folded
structure, it may be found to be more expeditious to
employ a film cutting member which forms bags arranged
in a handle-to-handle and bottom-to-bottom
relationship. In Figure 3, there is shown a fragment 38
of the handle of an adjoining bag structure which would
be formed simultaneously with the formation of bag 34. -
Bag fragment 40 of Figure 3 illustrates the bottom of
another adjoining bag formed just prior to bag 34.
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As previously indicated, Figure 4 illustrates
an individual bag torn from a pack unitized by way of
tabs 30 or by way of a series of bags interconnected by
preweakened heat seal lines 14. Figure 4 shows the bag
in its fully unfolded lay flat condition. This bag is
unencumbered by trapped gussets in the bottom region
along heat-seal line 14 and thus can expand to its full
potential volume.
A cutting mechanism employed for forming the
handles and bag mouth opening can be of conventional
design which can be mounted in suitable stamping
apparatus. Such a cutting mechanism can have a
continuous or discontinuous sharp cutting edge capable
of shearing through multiple thicknesses of film. As a
part of such a cutting mechanism, piercing knives can
simultaneously form a line of perforations such as that
illustrated at 32 in Figure 3. Furthermore, as part of
this cutting and perforation action, the unitizing step
of heat piercing tabs 30 can be performed during the
same overall operation.
When extremely thin gauge film, i.e. from about
0.25-0.75 mil, is employed, the seal in the bottom of
the bag can be reinforced by providing a second heat-
seal line 42 of Pigure 2, which will seal four layers of
film together. For further reinforcing the second heat-
seal line may be line 44 coincident with line 14 of
Figure 3. In this case line 44 would be heat-sealing
eight layers of film together. Such additional heat-
seal lines can seal and sever through the structure or
merely heat-seal and preweaken it for subsequent
separation. Thin gauge bags of this type can be
conveniently employed as container liners. With such
use the handles may be draped over the container and
employed to facilitate removal of the liner from the
container and for tying the liner closed after removal.
~lX84969
In another embodiment of the method of the
present invention, the seamless sides of the tube are
folded a predetermined distance as shown at 46 of Figure
5. The folded-over region 46 can be of varying width.
The degree of foldover is related to the ultimate
thickness of the handles and width of the bag mouth
opening. Employing a lay flat tube having a
side-to-side dimension of approximately 19.5 inches, the
individual handle widths can range anywhere from about 1
to 4 inches, preferably from about 1 1/2 to 3 inches.
In forming the bags contemplated by this
embodiment of the present invention, a plurality of the
side folded structures, shown in Figure 5, are stacked
in registration and by use of a suitable cutting
mechanism the handles and bag mouth opening are formed
by removal of plastic film from one end of the stack.
If a simple bag structure is desired, where only
individual bags are formed, a cutting member defining a
broad U can strike out this configuration at one end of
the stack of bags. Simultaneously, in the upper left
and upper right-hand regions of the stack, a somewhat
- half parabolic cutter can remove plastic film of the
corresponding configuration, so as to provide
hand-access to the resulting handles.
Referring to Figure 6, there is shown a stack
of bags having handles and bag mouth opening of a more
complex design. The handles and bag mouth opening show
that at the base of the handles there are stress relief
regions 48 which function to cause stress forces which
ordinarily would be brought to bear along bag mouth line
50 (see Figure 7) to concentrate at points below this
line. The stress forces will literally extend through -
the film space between the bottom of the arc of stress
relief regions 48. Bag mouth opening 50 is the
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consequence of removing an individual bag from the bag
pack 52 of Figure 6 by tearing the same along
perforation line 54 of Figure 6. Even where the
connecting points between tab 56 and the bag proper are
few in number, in the absence of stress relief regions,
such as that illustrated at 48, tears tend to initiate
somewhere along the edge of the bag mouth opening.
As indicated above, the device which forms the
handles and bag mouth opening can also perform several
other functions simultaneously, for example, forming
detachable bag tabs. -
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It is necessary in order to accommodate thecarrying hand of the user to open the upper left and
right sides of the structures as at 58. This is
accomplished by providing for a cutting member which
will remove a hand accommodating slice from each bag
structure. As with the portion removed from the region
between handles, the portion removed can be returned for
recycle as useable resin material.
In forming a unitized pack of bags, such as is
illustrated in Figure 6, the tab member 56 can be
designed to have sufficient film area so that an orifice
60 can be formed therein. Orifice 60 functions to
permit the unitized stack of bags to be suspended from a
suitable holding member which will accommodate
dispensing of the bags.
The bag pack of Figure 6 can be utilized with a
dispenser rack by suspending the pack from orifice 60 by
placing the same around a tongue or holder member of the
rack. A plurality of individual bags of the pack of
Figure 6 are unitized together by one or more heat-
sealed regions 62 fused completely through all of the --
tabs 56 of the bag structures. Figure 6 shows three
heat fused regions 62, two above orifice 60 and one
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below. A convenient manner of forming these heat fused
regions is by employment of an ultrasonic plastic
welding device. If the bag pack is to be employed with
a dispensing rack of the type defined m U.S. Patent No. 4,062,170
of William G. Oren, dated Dec~r 13, 1976, then after ~spension
of the pack from orifice 60 the handles are unfolded and the
loops thereof are spread open and about the ears of the
rack. During this operation an individual bag is torn
free of the tab along the perforation line 54. The bag
is then conveniently in a proper position for loading
with purchased goods. It will be seen that a bag of
this structure makes maximum use of the potential volume
of the original collapsed cylinder. The ungussetted
structure does not have regions predisposed to tear in
the bottom of the bag, i.e. a trapped four-layer
gusset. At the same time, the two pairs of handles 64
(Figure 7) provide four loops of film to more than
adequately support a heavily loaded bag structure.
In a further embodiment of the method of the
present invention a bag is produced having side portions
which are gusseted to the maximum. Thus, Figure 8 shows
the tube of Figure 1 gusseted to the maximum from both
sides 12 so that the fold lines of the gusset just
contact each or are closely spaced such as shown by
ghost lines 66. While in this condition both ends of
the structure are heat-sealed along lines 68 and 70.
Figure 9 represents a cross-sectional view of
the structure of Figure 8 taken along line 9-9 of Figure
8. This view shows side gussets 72 extending in from
both sides of tube 10 and extending to a common
longitudinal meeting line 66. Thus, each longitudinal
half of the collapsed gusseted tube will have four films. ~
Figure 10 depicts the structure of Figure 8
after the portion of the collapsed and sealed tube on
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the left-hand side of gusset midline 66 has been folded
over on top of the right-hand side of gusset midline
66. This will produce a lay flat structure eight films
thick and arranged as shown in the cross-sectional end
view of Figure 11 which is taken along the line 11-11 of
Figure 10. The upper left-hand region of Figure 10
shows that film layer areas have been removed to leave
behind superimposed double film handle loops 74, two
superimposed halves of bag mouth opening 76 and an
optional unifying detachable tab 78. Tab 78 can be
employed to unitize a plurality of bag structures
together into a bag pack. Such a bag pack may be
suspended from a suitable orifice 80 fashioned in the
tab in a manner which will also unitize, for example, by
heat fusing the tabs together. At the bottom of the
structure shown in Figure 10, the eight layers of film
have been heat-sealed together along line 32 to form the
bottom of the bag structure.
Figure 12 shows the bag structure of Figure 10
unfolded to reveal the individual loop handles 74 and
the full bag mouth opening 76. At the base of the
handles 74 there are arcuate stress relief regions 84
which serve to transfer stretching stresses, down and
away from bag mouth opening 76, when the handles are
stretched in diametrically opposed directions. Gussets
72 are shown in their partially opened condition, as
heat-seal 82 securely bonds the eight layers of the bag
together at the bottom of the bag. The main body of the
bag structure as defined will have a generally square
cross-section as a result of gusseting the tube to the
maximum.
In a continuous process for forming the bags ~
and bag packs contemplated by the present invention, a
continuous tube of thermoplastic film is provided, (not
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merely a tube segment as is shown in Figure 1). This
tube is continuously collapsed and gusseted to the
maximum and positioned in a lay flat condition as shown
in Figure 8 and Figure 9. The collapsed tube is then
heat-sealed along line 68 without severing through the
four layers of film. This heat seal line will
ultimately constitute the seal lines of the handles of
the bag. Simultaneously with the forming of heat-seal
line 68 or, as a following separate step, heat-seal line
70 can be formed a bag length distance spaced from
heat-seal line 68. The character of heat-seal line 70
is the same as that of 68 in that it seals but does not
sever through the collapsed and gusseted tube. The seal
line does, however, constitute a preweakened region
which will permit ultimate severing of the bags into
individual units either by the user or by the bag
manufacturer. Next, the structure shown in Figures 8
and 9 is longitudinally folded so that the left-hand
segment of the structure of Figure 8 is folded over on
top of the right-hand longitudinal side of Figure 8
along the gusset midline 66. While the bag blank
segments are still interconnected at their respective
seal lines, a handle and bag mouth cutting means can
remove thermoplastic film regions at the bag top of each
bag blank Thus, as is shown in Figure 10 a cutting
operation removed eight area segments of thermoplastic
film so as to leave two loop handles 74 in registration
with each other, and a bag mouth opening 76. While the
cut-out of a single bag can be made sequentially, it is
preferred that the handle and bag mouth cut-out for two
bags be made at the same time leaving the bags
interconnected via the heat-seal region at 68.
Subsequent to this operation the interconnected bags can
be convolutely rolled into a volumetrically efficient
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roll-pack for ultimate bag by bag dispensing by the user
by snapping the bag free of the next adjacent bag
structure at the preweakened region along heat-seal line
68 or along preweakened heat-seal line 70. In this
version of the gusseted bag the bottom thereof will have
four films heat-sealed together and the expanded mid
body portion of the bag will approximate a square in
cross-section.
When extremely thin gauge film, i.e. from about
0.25-0.75 mil, is employed, the seal in the bottom of
the bag can be reinforced by providing a second
heat-seal line 82 which will seal the eight layers of
film together, shown in cross-section in Figure 11, at
the bottom of the bag. Such a seal can seal and sever
through the structure or merely heat-seal and preweaken
it for subsequent separation. As indicated, Figure 12
illustrates a single bag separated from either a bag
pack or a continuous string of bags. This bag has the
eight layers at the bottom of the bag sealed along line
82. Gusset regions 72 are shown in a partially unfolded
condition. Bag handle loops 74 are identical in shape
and size because they were formed in perfect
registration. This facilitates handling and ensures
handles of equal dimensions. Being of double film
loops, the handles are extremely strong. At the base of
each handle there are arcuate regions 84 formed so as to
function as stress relief regions when handles 74 are
stretched in diametrically opposed directions. These
stress relief regions will cause stresses that would
otherwise be brought to bear at the bag mouth edges 76
to be directed below the edges and extend more across
the width of the film between the lowest region of ~
stress relief arc 84.
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If desired, the bag structures shown in Figure
10 can be formed as unitary, separated bag structures
which then may be stacked one upon the other. In this
variation there is shown a tab film 78 detachably
attached by way of perforations to the bag mouth 76. A
plurality of bags can be unitized by means of this tab,
for example, by forming an orifice through all the tabs
which will heat-seal the tabs together and form a bag
pack. This operation can also leave an orifice 80
through the tabs which can serve as a support means for
the pack of bags. Thereafter, individual bags can be
torn free of the tabs along the tab perforations.
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