Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR MAKING SINGLE
SIDE FREE PLASTIC BAG
The present invention relates to thermoplastic bags useful
for packing groceries, and, in particular, to a method of providing
a convenient structure for opening such bags, one bag at a time,
from a bag pack which includes a supply of bags hung together at a
bag dispensing station.
In the past, it has been known to manufacture bags having
different configurations in order to provide convenient means of
packaging for various uses. For example, it has been known to
provide a thermoplastic bag with loop handles which are integral
with the bag and can be easily formed by cutting a T- shirt-like
formation in a stack of bags. The integral handle can be reinforced
by providing a double overlap on either edge of a thermoplastic tube
such as by gussetting the tube over folding elements provided in the
manufacturing line.
For example, U.S. Patent No. 4,597,749 to O'Brien, et al.
discloses a thermoplastic bag characterized by having a pair of
carrying handles formed integrally with the bag walls and extending
upwardly from the opposite sides of an open mouth portion of the
bag. The handle members are reinforced and comprise at least two
layers of thermoplastic material, one of the layers forming the bag,
body and handles and the other layer serving as a reinforcement
layer, the reinforcement layers being provided only in the handle
areas of the bag structure.
In U.S. Patent No. 4,588,3q2 to ~addock a plastic film sack
having gussetted sidewalls is disclosed wherein a heat-seal stripe
welding is provided in the bottom of the sack to gather four film
layers in the gussetted regions of the sack while a heat-seal stripe
welding gathers the two film layers between the gussetted regions.
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Between the heat seal stripes of the four film layers and the
heat-seal stripe of the two film layers are unsealed arcuate stress
relief regions.
In U.S. Patent No. 4,554,192 to Benoit a ba8 structure for
thermoplastic material is disclosed wherein there are front and rear
bag walls connected by sidewalls which has an open mouth top
portion. The open mouth portion is characterized by having handles
located at opposite end regions, such handles having two films as a
result of being integral extensions of the front and rear gussetted
sidewalls. The bag also has a bottom wall planarly extensible so as
- to form a rectangle with at least no substantial excess film outside
of the bulk volumetric capacity of the bottom region of the bag.
In U.S. Patent No. 4,493,419 to Prader, et al. a bag pack
of a plurality of stacked thermoplastic bag structures is disclosed
lS wherein each bag has a front~and rear bag wall and an open mouth top
portion. Handles are integral extensions of the bag walls. The
bags are bond~d together via bonding means in association with the
handles.~ ~Individual bags may have stress release curves in the
t~ handles and the bag mouth opening.
U.S. Patent No. 4,476,979 to Reimann, et al. discloses a
bag pack and individual bags characterized by having handles which
are integral extensions of the front and rear of the bags. The bags
h w a bag mouth which includes stress release curves on both sides
of an upwardly extending tab. The tab includes at least one opening
c~ 25 ~- which is positioned to create~comparatively
narrow~webs which serve~to be tear-of points severing individual
bags rom the pack. The bags~are bonded together via the tab at an
aréas~ad~acent the openings.~ -
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~,L~ See also U-S- Patent No. 4,464,157 to Benoit, et al. which
relates~to thermoplastic bag structures characterized by having a
pair of carrying handles formed integrally in the bag walls and
extending~upwardly from opposite sides of the open outh portion of
the bag.~ The handle bags are particularly characterized in having
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reinforced handle members having two layers of thermoplastic
material, one of the layers imparting tensile strength to the
individual layer and the other layer particularly employed to
provide requisite puncture and tear resistance necessary in such a
bag structure.
In U.S. Patent No. 4,604,084 to Pistner a thermoplastic bag
structure is disclosed which has a front and rear bag wall, a bottom
and an open mouth top portion, the open mouth portion having two
pairs of single film handle loops each of which are located at
opposite ends of the open mouth portion. The bag structures are
unitized by providing a detachable tab at the mouth opening and
unitizing the bag structures through this tab. The method of
forming the bags involves providing an end seal collapsed
thermoplastic film tube and removing plastic to form a bag mouth
lS opening and handles at one end thereof. The resulting bag is an
ungussetted bag which can be unitized into a pack by providing a
detachable, unitizing tab at the bag mouth opening.
In some of the most recent developments in the area of
providing thermoplastic bags at grocery counters, it is necessary to
provide an opening through the pack of bags for mounting on a tab
~ which is located on a rack generally located at the end of the
'~ grocery counter. The bags such as those shown in the Reimann, et
" ~ al. '979 patent must then be unthreaded one side at a time over the
mounting tab and expanded over arms in order to form a wide mouth
2s ~ opening for packing the plastic bags. This method generally suffers
from the drawback that the front and back sides of each of the bags
~are bonded or welded together such as by means of heat sealing or
; otherwise. In the Reimann, et al. '979 patent, the bags are bonded
together on a tab adjacent the opening. This feature reduces the
ability of the packer to separate the sides of the bag to form the
~O ~ open outh receptacle.
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Thus, it is a primary object of the present invention to
provide a method for forming a thermoplastic bag having an easily
separable bag mouth opening by providing one side of the bag
relatively free for opening from the other side of the bag.
The present invention is a method of continuously making
thermoplastic film bags having one side free for separation from an
opposite side which includes providing a continuous tube of
thermoplastic film for formation of the bags, such tube having a
continuous surface which forms opposing sides of the bag. The tube
lo is directed to a bag-forming means which continuously flattens the
tube into at least two opposing sides of such bags. The tube is
intermittently at least partially severed at one of the opposing
walls at intervals corresponding to single bag lengths such that the
severance is at a location for providing detachable separation of
one sidewall from the opposing sidewall. The tube is then subjected
to heat sealing thereacross so that seams can be formed at intervals
in order to provide bottoms to the bags. The separated bags are
then collected in a stack wherein the bags are substantially aligned
so that the stack can be fused together adjacent the point of
severance in the one side of each bag to facilitate separating one
side from the other in the stack.
Preferably the method can also include forming the
thermoplastic film into a gussetted tube before or simultaneously
while directing the tube to the bag forming means. Moreover, two
pairs of diagonal seams can be formed over the portions of the tube
corresponding to the gussets along lines diagonal to the length of
the tube, the pairs of opposite sides being at an angle to one
another, and removing the double film triangular regions bounded by
the diagonal seams so that a flat bottom gussetted bag can be formed.
Furthermore, the present method preferably includes forming
a handle and bag mouth opening at the opposite end of the sack
bottom by imposing a compound curve cutting knife on the assembled
stack of bags.
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As a result of the present invention, a stack of bags can be
provided for use in a bag packaging rack or assembly wherein the
bags can be threaded over a tab on a bag racX or assembly and
individual bags can be opened therefrom by separating them one side
. at a time away from the stack of bags.
For a better understanding of the present invention,
together with other and further objects, reference is made to the
following description, taken in conjunction with the accompanying
drawing~, and its scope will be pointed out in the appended claims.
In the drawings appended to the present specification:
Fi8. 1 is a schematic of the process of the present
invention;
Fig. 2 is a side elevation schematic view of a cutting
assembly in accordance with the present invention;
Fig. 3 is a plan view of the cutter assembly shown in Fig.
2 taken along lines 3-3;
Fig. 4 is a schematic of the cut-out portion of a double
layer loop handle bags which shows the relationship of the spacing
and arrangement of bag cuts made in accordance with the present
invention;
Fig. 5 depicts a typical plastic bag with double layer loop
handles which is not front side free;
Pig. 6 shows a similar plastic bag prepared in accordance
wlth the present lnvention which 1~ rront side-~ree7 and
Fig. 7 is a side elevation schematic view of a cutting and
welding station used in conjunction with the present invention.
Referring to Fig. 1 there can be seen a process line in
accordance with the present invention wherein a tube of
thermoplastic film 10 can be provided to a bag fabrication line via
guide rollers 12. The tube of film 10 can be separated by, for
example, a stream of air introduced to the interior o~ the bag (not
shown herein) such that at least one wall 14 thereof is exposed to a
cutting assembly 16. The cutting assembly 16 can include various
cutting means such as a series of blades to form perforations, or
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single blades which can be used to slice through the one side 14 of
the tube of film lO. As the tube of thermoplastic film is drawn
past the cutting assembly 16, the cutting means is caused to
intermittently cut into the tube either by a reciprocating force
imposed thereon or by means of a intermittent slashing action
whereby the blade is drawn across a portion of the wall 14 of film
10.
Referring to Fig. 2 and Fig. 3 one preferred cutting
assembly is depicted which includes a mounting plate 70 mounted on a
lo gusset box 80 wherein a tube of film can be guided, side gussetted,
and drawn through to downstream operation by means of rollers 82. A
gusset box can simply be provided by use of sheet metal being
inwardly oriented at either side of the bag flattening rolls 82.
Alternatively, the film need not be side gussetted thus eliminating
the requirement for the gusset box 80. In this latter case, it is
only necessary to orient the tube of film such that one side wall is
adjacent the cutting assembly. With respect to the assembly shown
herein, the mounting plate 70 can be removable so that affixing the
plate to the gusset box can be effected by a bracket 81 and holddown
clamps 71.
A motor 72 is secured to the mounting plate, and is
connected for actuating a rotatable double blade holder 77 through a
clutch assembly 73 which includes solenoid 75. The blade holder 77
can, in turn, be prorided with two blades 78 which, in a preferred
2S embodiment, can be heated for ease of cutting through thermoplastic
film. In the present preferred embodiment blades 78 pass through an
opening 74 in the mounting plate 70 to engage and slice the film
surface 14.
The cutting action of the cutting assembly 16 is imposed on
the wall 14 intermittently so that the length of thermoplastic tube
located between cuts is the length of one bag. Furthermore, the
~ ~ location of the cut on the tube 10 is such that it will be located
:~r proximal the bag bonding point and the bag opening which is to be
~ used for mounting on a bag rack system.
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In order to effect the proper cutting or slashing action,
the motor 72 can be rotating at a high RPM so that when an actuating
signal is receiYed from, for example, a printing station located
upstream which has been indexed to print at one- bag intervals, the
solenoid 75 is fired and the clutch 73 makes a 180 revolution at
high speed. Since the blade holder 77 is fixedly attached to the
clutch 73 it is also rotated at high speed causing a blade to pass
through the slot 74 and a slot in the wall of the gusset box in a
slashing action to cut the tube of film 10 at the desired location.
The width of the cut is determined by the length of the blade and
blade holder assembly. One unique advantage of the invention in
accordance with this embodiment is that the opening can be made in
one side 14 of the film tube 10 without the use of a "mouse" or
other fixed device in the inflated bubble. When the blade 78 is
heated penetration without need for a back-up plate is enhanced.
Referring to Fig. 4, there is shown the "window" SO wherein
each bag must be cut. Basically, the dimensions o~ the window are
detormined by the length of the neck "L" between the perforations 51
and the line "Z" adjoining the top of stress relief curves 52. The
dimension '~r' of this line determines the maximum width of the cut.
The neck or tab also includes the hang hole 53 which passes through
all the layers of all the bags whereby a supporting projection on a
ba8 rack can be passed therethrough for hanging the stack of bags.
Furthermore the stack of bags can be welded together such as at weld
spots S5 to facilitate handling of the bags. When the bag is to be
partially supported by the perforated attachment at the rear of the
bags during loading procedures, the perforations should be such as
to provide a strong connection, e.g., there should be sufficient
plastic to support the bag.
Tubo 10 is then flattened so that the wall 14 is directly
opposed to a second wall which will form two sides of the
thermoplastic bag. The stream of continuous thermoplastic bag
material having the timed cuts imposed thoreon is then directed to a
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subsequent processing step including a heating element 20, which can
be impressed on the bag tube to simultaneously heat-seal and sever
the bag from the continuous tube, and remove unwanted
bag-wall-separating air by means of air removal punch 21 and press
roll 23. At this stage of the process each thermoplastic bag has
been formed having a sealed bottom, open or closed top and a
suitably placed cut or perforation for providing a front side free
thermoplastic bag for use in a bag dispensing rack or system.
The stream of bags 27 formed by the heating and sealing
means 20 can then be fed along feed roll conveyer 24 to a station at
which the bags can be stacked for cutting and other processing
steps. This station is indicated generally at 26 in Fig. 1. The
stack of bags 11 are shown at station 26 underneath a cutting and
welding mechanism 9 located immediately thereabove. This station is
shown in greater detail in Fig. 7. The stack of bags shown in Fig.
7 are shown in cross-section so that the individual cuts or
perforations 6 of each bag can be more clearly seen.
The cutting and bonding device 9 can include a compound
curve cutting blade in combination with straight blades and a spot
welding device to cut the T-shirt configuration out of the tops of
the bags, and to provide the hang holes at the top of the tabs. The
spot welder heat welds the bags together to provide the unitary
stack of bag for use at the end of grocery check out lines.
A comparison of the structure and operation of plastic bags
having the T-shirt configuration at the top is depicted in Figures 5
and 6. Fig. 5 shows a plastic bag without the front side free and
Fig. 6 shows a plastic bag prepared in accordance with the present
invention wherein the front side is free to be separated from the
back of the bag. In both Figures like features bear the same
number. Thus, both bags are shown with a hang hole S3 and with weld
spots 55 by which the stack is held together. Similarlyt the bag
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shown in both Figures includes perforations 51 and provided below
the hang hole 53 and weld spots 55. However, perforations 51 in
Fig. 5 are provided in both front and back layers, whereas
perforations 51 in Fig. 6 are provided on the back wall only. The
front wall of the bag shown in Fig. 6 has been cut in accordance
with the process of the present invention so that the front side is
free to be easily
separated from the back wall by simply wiping a finger in the center
of the bag whereby it is opened as shown in Figure 6.
As mentioned previously, the front side free structure can
be provided as a straight cut or as perforations. When the free
front side is provided as perforations, the cuts are usually great
in comparison to the remaining bag web since it is desirable to
break the bag away from the tab with very little force, e.g., the
force of a finger wiping against the front surface of the bag front
side. Moreover, the cutting required to provide the free front side
can be by either reciprocating or slashing action and can include
one or several blades.
Thus, while there have been described what are presently
believed to be the preferred embodiments of the present invention,
those skilled in the art will realize that other and further changes
and modifications can be made without departing from the true spirit
of the invention, and it is intended to include all such changes and
modifications as come within the scope of the claims.
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