CA1284969C - Thermoplastic bag, bag pack and method of making the same - Google Patents
Thermoplastic bag, bag pack and method of making the sameInfo
- Publication number
- CA1284969C CA1284969C CA000495564A CA495564A CA1284969C CA 1284969 C CA1284969 C CA 1284969C CA 000495564 A CA000495564 A CA 000495564A CA 495564 A CA495564 A CA 495564A CA 1284969 C CA1284969 C CA 1284969C
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- Prior art keywords
- bag
- bags
- pack
- heat
- film
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Abstract
THERMOPLASTIC BAG, BAG PACK AND METHOD OF
MAKING THE SAME
ABSTRACT OF THE DISCLOSURE:
A thermoplastic bag structure having a gusseted and non-gusseted configuration wherein the open mouth, top portion of the bag is provided with single and two-film handle loops at opposite ends of the mouth opening. Interconnected bags can be formed into a roll pack or individually severed bags can be unitized into a bag pack. The present invention is also directed to a bag forming method utilizing a thermoplastic tube.
MAKING THE SAME
ABSTRACT OF THE DISCLOSURE:
A thermoplastic bag structure having a gusseted and non-gusseted configuration wherein the open mouth, top portion of the bag is provided with single and two-film handle loops at opposite ends of the mouth opening. Interconnected bags can be formed into a roll pack or individually severed bags can be unitized into a bag pack. The present invention is also directed to a bag forming method utilizing a thermoplastic tube.
Description
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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~%849~9 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;
(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 ~ ~84969 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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4'369 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.
' ~l~84~69 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 ~2~3~969 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.
~ ~849~9 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 '~`.
, , ~84969 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.
~.~84969 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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lX~34969 - lg -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. -~
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 . : .
- lX84969 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 ,. ~
~34969 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 ~284~9 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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~ ~84969 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.
' 1~84969 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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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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~%849~9 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;
(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 ~ ~84969 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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4'369 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.
' ~l~84~69 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 ~2~3~969 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.
~ ~849~9 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 '~`.
, , ~84969 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.
~.~84969 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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lX~34969 - lg -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. -~
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 . : .
- lX84969 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 ,. ~
~34969 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 ~284~9 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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~ ~84969 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.
' 1~84969 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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Claims (52)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for forming thermoplastic film handled bags comprising:
(a) forming a continuous collapsed thermoplastic 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 substantially meet at a common center line;
(d) folding this structure once again in the same direction along said center line;
(e) removing eight film layers in one of the corner regions defined by a transverse heat-seal line and the spine of fold (d), the film removal being such as to yield, on unfolding, a bag having a bag mouth opening and a pair of single film loop handles near opposite ends of said bag mouth opening but spaced from the sides; and (f) collecting while still folded, the interconnected structures of (e) in a volumetrically efficient pack of bags.
(a) forming a continuous collapsed thermoplastic 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 substantially meet at a common center line;
(d) folding this structure once again in the same direction along said center line;
(e) removing eight film layers in one of the corner regions defined by a transverse heat-seal line and the spine of fold (d), the film removal being such as to yield, on unfolding, a bag having a bag mouth opening and a pair of single film loop handles near opposite ends of said bag mouth opening but spaced from the sides; and (f) collecting while still folded, the interconnected structures of (e) in a volumetrically efficient pack of bags.
2. The method of claim 1, wherein during step (e) a detachable tab member is formed attached to said bag mouth opening.
3. The method of claim 2, wherein individual bag structures are separated along said heat-seal lines, a plurality of the so-separated bags are stacked in registration and unitized into a bag pack by a unitizing means through said detachable tabs.
4. The method of claim 3, wherein a pack suspending orifice is formed in said detachable tabs.
5. The method of claim 2, wherein the bottom of each bag is heat-sealed in its four-film folded condition.
6. The method of claim 2, wherein the bottom of each bag is heat-sealed in its eight film folded condition.
7. The method of claim 1, wherein said interconnected structures are collected in a convolutely rolled pack.
8. The method of claim 1, wherein said interconnected structures are reverse folded one upon the other, for subsequent individual separation along heat-seal lines.
9. A bag structure made of a thermoplastic film comprising a front and rear bag wall, a bottom and an open mouth top portion, said open mouth portion being characterized by having pair of single film loop handles near opposite ends thereof, said bag having seamless ungusseted sides, said bag being folded so that said sides meet at a common center line, the bottom of said bag being heat sealed through four layers of film, said bag being folded again along a line coincident with said center line so that said handles are in registration.
10. The bag of claim 9, wherein said open mouth top portion has arcuate stress relief regions at opposite sides of the base of each handle and the upper edges of said mouth extend above said stress relief regions.
11. A bag structure made of a thermoplastic film comprising a front and rear bag wall, a sealed bottom and an open mouth portion, said open mouth portion being characterized by having a pair of single film loop handles near opposite ends thereof; and at the base of each handle, on each side thereof there are arcuate stress relief regions and the upper edges of said mouth extend above said stress relief regions said bag having the sides equally folded toward each other to a point of contacting at a common midline, said bag being folded again along said midline so that said handles are in registration and the same relation-ship as when they were formed.
12. The bag of claim 11 having a detachable tab attached to said bag mouth opening.
13. A pack of bags comprising a stack of bags as defined in claim 12 with said tabs in registration, said stack being unitized by means fastening said tabs together.
14. The pack of bags of claim 13, each bag of which has a bottom sealed through two layers of film.
15. The pack of bags of claim 13, each bag of which has a bottom sealed through four layers of film.
16. The pack of bags of claim 13, each bag of which has a bottom sealed through eight layers of film.
17. A roll pack of bags comprising a plurality of bag structures, as defined in claim 11, said bags being inter-connected by way of preweakened heat-sealed stripes transverse of said bags, said bags being convolutely rolled into a volumetrically efficient roll pack.
18. A pack of thermoplastic bags comprising a plurality of bag structures as defined in claim 11, said bags being inter-connected by way of a preweakened heat-sealed stripes transverse of said bags, said bags being folded alternatively back and forth upon themselves to form a volumetrically efficient bag pack.
19. A method for forming a thermoplastic film handled sack 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; and (c) removing, from one end of the folded structure, sufficient film to form a bag mouth opening and a pair of single-film handle loops at opposite ends of said bag mouth opening.
(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, sufficient film to form a bag mouth opening and a pair of single-film handle loops at opposite ends of said bag mouth opening.
20. The method of claim 19, wherein the film removal is accomplished by a cutting action.
21. A method for forming a 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 (d) simultaneously performing a cutting, perforating and unitizing operation at one end of the stack that will form two pairs of single film loop handles with a bag mouth opening therebetween and tab members attached by way of film perfor-ations to said bag mouth opening, said tab members being unitized, thereby forming said pack of sacks.
(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 (d) simultaneously performing a cutting, perforating and unitizing operation at one end of the stack that will form two pairs of single film loop handles with a bag mouth opening therebetween and tab members attached by way of film perfor-ations to said bag mouth opening, said tab members being unitized, thereby forming said pack of sacks.
22. The method of claim 21, wherein said tabs are unitized by heat-sealing and a suspension orifice is also formed therein.
23. A thermoplastic bag structure comprising a front and rear bag wall, a sealed bottom and an open mouth top portion, said open mouth portion being characterized by having two pairs of single film handle loops each of which are located at opposite ends of said open mouth portion, the handles of each pair being side-by-side and each handle being an integral looped single film extension of said front and rear bag walls.
24. The bag structure of claim 23, wherein said open mouth top portion has arcuate stress relief regions at the base of the innermost handles and the upper edges of said mouth extend above said stress relief regions.
25. The bag structure of claim 24 having 2-film heat-seals at the bottom of said bag and at the tops of said handles and seamless bag sides.
26. A pack of thermoplastic bags comprising: a plurality of superimposed bag structures as defined in claim 24, the outer side regions of each bag being folded toward each other so that the handles of each handle pair are in registration; tab members detachably attached to the upper edges of said bag mouth; and said tabs being unitized to hold said bags together in a pack.
27. The pack of claim 26, wherein said tabs are unitized by heat-welding.
28. The pack of bags as in claim 27, wherein said tab also includes means accommodating physical support of said pack.
29. The pack of claim 28, wherein said support-accommodating means is at least one orifice.
30. A method for forming a thermoplastic film, handled bag comprising:
(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 layer which will leave two, superimposed, 2-film handle loops and a bag mouth opening; and (f) separating the resulting bags from said tube along the heat-seal lines.
(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 layer which will leave two, superimposed, 2-film handle loops and a bag mouth opening; and (f) separating the resulting bags from said tube along the heat-seal lines.
31. A method of continuously preparing a handled thermo-plastic film sack comprising:
(a) forming a continuous collapsed thermoplastic film 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 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; and (e) collecting said bags into a volumetrically efficient pack of bags.
(a) forming a continuous collapsed thermoplastic film 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 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; and (e) collecting said bags into a volumetrically efficient pack of bags.
32. The method of claim 31, wherein said bags are formed in a continuous top-to-top and bottom-to-bottom relationship.
33. The method of claim 31, wherein said bags are formed in a continuous top-to-bottom relationship.
34. The method of claim 31, wherein bag handles and bag mouths of two adjacent bag structures are simultaneously formed.
35. The method of claim 31, wherein said bags are collected in a convolutely rolled pack.
36. The process of claim 31, wherein said bag mouth opening is formed with a detachable tab, said bags are stacked in tab registration and unitized into a pack by way of said tab.
37. The method of claim 31, wherein the bottom of each bag is heat-sealed in its eight film folded condition.
38. The method of claim 31, wherein the resulting structures are reverse folded one upon the other for subsequent individual separation along heat-seal lines.
39. The method of claim 31, wherein said structures are separated into individual bag structures, stacked and formed into bag packs.
40. The method of claim 39, wherein said stacked bag structures are formed into bag packs by unitizing individual bag tabs extending from said bag mouth opening.
41. A bag structure made of a thermoplastic film comprising a front and rear bag wall, a bottom and an open mouth top portion, said open mouth portion being characterized by having double film loop handles at opposite ends thereof, said bag having sides gusseted to the maximum, said bag being heat-sealed at the bottom through four layers of film.
42. The bag structure of claim 41, wherein said open mouth top portion has arcuate stress-relief regions at the base of said handles and the upper edges of said bag mouth extend above said stress relief regions.
43. 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 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 line of said gussets and heat-sealed at said bottom through eight layers of film.
44. The bag structure of claim 43, wherein said open mouth top portion has arcuate stress relief regions at the base of said handles and the upper edges of said mouth extend above said stress relief regions.
45. A pack of thermoplastic bags comprising a plurality of superimposed bag structures as defined in claim 41, said bags being folded along a line coincident with the meeting line of said gussets so that the handles are in registration; tab members detachably attached to the upper edges of said bag mouth, said tabs being unitized to hold said bags together in a pack.
46. The pack of claim 45, wherein said tabs are unitized by heat-welding.
47. A pack of thermoplastic bags comprising a plurality of superimposed bag structures as defined in claim 43, said bags being folded along a line coincident with the meeting line of said gussets so that the handles are in registration; tab members detachably attached to the upper edges of said bag mouth, said tabs being unitized to hold said bags together in a pack.
48. The pack of claim 47, wherein said tabs are unitized by heat-welding.
49. A roll pack of thermoplastic bags comprising: a plurality of bag structures as defined in claim 41, said bags being interconnected at the top and bottom thereof to adjacent bag structures by way of preweakened heat-sealed stripes transverse of said bags, said bags being convolutely rolled into a volumetrically efficient roll pack.
50. A roll pack of thermoplastic bags comprising: a plurality of bag structures as defined in claim 43, said bags being interconnected at the top and bottom thereof to adjacent structures by way of preweakened heat-sealed stripes transverse of said bags, said bags being convolutely rolled into a volumetrically efficient roll pack.
51. A pack of thermoplastic bags comprising: a plurality of bag structures as defined in claim 41, said bags being inter-connected at the top and bottom thereof by way of preweakened heat-sealed stripes transverse of said bags, said bags being folded alternatively back and forth upon themselves to form a volumetrically efficient bag pack.
52. A pack of thermoplastic bags comprising: a plurality of bag structures as defined in claim 43, said bags being inter-connected at the top and bottom thereof by way of preweakened heat-sealed stripes transverse of said bags, said bags being folded alternatively back and forth upon themselves to form a volumetrically efficient bag pack.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US67275884A | 1984-11-19 | 1984-11-19 | |
| US672,756 | 1984-11-19 | ||
| US06/672,756 US4562925A (en) | 1984-11-19 | 1984-11-19 | Thermoplastic bag, bag pack and method of making the same |
| US06/675,109 US4790437A (en) | 1984-11-26 | 1984-11-26 | Thermoplastic bag, bag pack and method of making the same |
| US675,109 | 1984-11-26 | ||
| US672,758 | 1996-06-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1284969C true CA1284969C (en) | 1991-06-18 |
Family
ID=27418255
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000495564A Expired - Lifetime CA1284969C (en) | 1984-11-19 | 1985-11-18 | Thermoplastic bag, bag pack and method of making the same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1284969C (en) |
-
1985
- 1985-11-18 CA CA000495564A patent/CA1284969C/en not_active Expired - Lifetime
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| Date | Code | Title | Description |
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| MKLA | Lapsed |