US3485439A

US3485439A - Flat bottom bag

Info

Publication number: US3485439A
Application number: US687630A
Authority: US
Inventors: William E Shrum
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1967-12-04
Filing date: 1967-12-04
Publication date: 1969-12-23
Anticipated expiration: 1986-12-23

Description

w E. SHRUM 3,485,439

FLATBCTTOM BAG Filed Dec. 4, 1967 2 Sheets-Shee,t 1

' INVENTOR. AMY/1am (fish/um ETTORNEY W. E. SHRUM FLAT BOTTOM BAG Dec. 23, 1969 2 Sheets-Sheet- Filed Dec. 4, 1967 INVENTOR. lv/Y/l'am E. Shrum H 77' ORNE Y US. Cl. 229-58 8 Claims ABSTRACT OF THE DISCLOSURE This invention pertains to a flat bottom bag formed from flexible tubular material by making a pair of folds and a single seal. Specifically, the bag is formed by longitudinally folding the edge portions of a collapsed flexible tube inwardly to a superposed position on the main body portion thereof not extending beyond the longitudinal center line of the tube. A transverse seam is then formed across the width of the tube adjacent the free edges at one of its ends securing together therealong the overlying plies comprising the folded tube. This completes the structure of a basic bag element from which a flat bottom bag can be formed. Several methods are taught as suit-able for shaping the secured end of the above bag element to form the desired flat bottom structure. For example, by turning the bag element inside out and shaking out its folded edge portions a flat bottom bag is readily obtained.

DESCRIPTION OF THE INVENTION To increase the fill capacity in bag construction it has become customary to utilize a square or fiat bottom bag structure. To this end a considerable number of bag designs have been proposed in the past. One of the most popular of these comprises forming inverse folds or gussets at the opposite edge portions of a tubular body and then securely closing one of the two ends of the tube, i.e., by forming a transverse seam across the width of the tube adjacent the end to be closed. While this method often produces a satisfactory bag, fabrication can be difficult since customarily the tube must be first inflated in order for forming members to press inwardly and form the gussets. The inflating of the bag in a continuous operation wherein a continuous length of tube is employed is not entirely a simple matter. Here it is not uncommon to provide complicated and specially designed apparatus to maintain the tube in an inflated condition during the period the gussets or inverse folds are being formed along its side or edge portions.

Accordingly, it is an object of the present invention to provide an improved method for forming flat bottom bags wherein only a couple folds need be made and a single seal effected to form a bag element from which a square or flat bottom bag can be easily obtained.

Another object of the present invention is to provide a method for forming a fiat or square bottom bag from continuous flexible tubular material wherein only a minimum of equipment is required and wherein the tube can be maintained in a collapsed condition during the forming of the bag.

Another object of the present invention is to provide a bag element or article inexpensively and easily fabricated and from which a square bottom bag can be readily obtained by a single shaping step.

Yet another object of the present invention is to provide an improved square bottom bag wherein the raw or free edges adjacent the seam at the closed end of the bag are hidden within the confines thereof to provide a flat bottom bag easily fabricated and esthetically appealing for particular uses, as, for example, pouches in United States Patent O M Patented Dec. 23, 1969 which expensive articles can be more readily merchandized.

Briefly then, this invention contemplates an improved method for forming a flat bottom bag from tubular material wherein a minimum of equipment is required. Basically, only a couple of folds and a. single seam need be made to provide a basic bag element from which a square or flat bottom bag can be readily obtained. Specifically, the closed edge portions of a flexible tube are longitudinally folded inwardly, respectively, to a superposed position on the main body portion of the tube short of its longitudinal center line. A transverse seam is then effected across the width of the folded tube at one end thereof securing together therealong the overlying plies comprising the folded tube, and thereby completing the construction of the basic "bag element desired. The seamed end of the bag element can then be shaped by one of several different methods to provide a flat bottom bag. In one method, the bag element is turned inside out and the flat bottom is shaken out. Here the free or raw edges adjacent the transverse seam are placed within the confines of the bag such that its general or overall appearance is enhanced. By again turning the above obtained bag inside out, a bag with a somewhat differently formed flat bottom structure is provided. Another method of suitably shaping the bag element to provide a flat bottom includes the strategic separation of the walls of the bag element near its seamed end.

Other objects and advantages of the present invention and its details of construction will be apparent from a consideration of the following specification and accompanying drawings wherein:

FIGURE 1 is a schematic isometric view showing a method of forming, in a continuous. operation, a bag element embodying the principles of the present invention;

FIGURE 2 is an enlarged cross-sectional view taken along reference line 2-2 of FIGURE 1;

FIGURE 3 is an enlarged fragmentary view of a portion of the bag element of FIGURE 1;

FIGURE 4 is an enlarged isometric fragmentary view of the bag element of FIGURE 1 showing a method of shaping the seamed end thereof to provide a flat bottom;

FIGURE 5 is a view like FIGURE 4 onl showing a portion of the flat bottom as shaped;

FIGURE 6 is an isometric View of a bag including a flat bottom portion shaped by the method portrayed in FIGURES 3 and 4;

FIGURE 7 is an enlarged cross-sectional view taken along reference line 77 of FIGURE 6;

FIGURE 8 is an isometric view of a bag including a flat bottom portion shaped by turning the bag element of FIGURE 1 inside out and shaking out its folded edge portions; and

FIGURE 9 is an enlarged cross-sectional view taken along refernce line 9--9 of FIGURE 8.

Referring particularly to FIGURE 1, there is shown a bag element 10 formed from a continuous tube 12 of heat scalable material. Bag element 10, when properly shaped, is useful to provide a square or flat bottom bag as is explained more fully hereinafter.

Tube 12, in a generally collapsed, non-inflated condition, is fed from roll stock 14 under and edgewise upwardly about folding mandrel 16 to

nip rollers

18 and 20. Folding mandrel 16 assisted "by

nip rollers

18 and 20 longitudinally or laterally folds the

edge portions

22 and 24 of tube 12 to a position upon the main body portion 26 thereof defined between the longitudinal fold lines 23 and 30. The folded tube 12, with four overlying plies at its folded

edge portions

22 and 24, and two overlying plies at locations therebetween like that shown in FIG- URE 2, is then intermittently heat sealed in the transverse direction by sealing bar 36 to form an end seam 38 extending across the width of folded tube 12, and securing together therealong its respective overlying twoand fourply portions. A cutting means or knife 40 then parts the folded and sealed tube 12 in the transverse direction at a location remote from the end seam 38 to obtain a unit bag element 10. Actually the sealing bar 36 and knife 40 can perform their functions simultaneously with the sealing bar 36 forming the end seam 38 on an upcoming bag element 10, while knife 40 located adjacent to and downwardly therefrom separates from the folded tube 12, the previously end sealed bag element 10.

Bag element comprises a generally tubular body 42 including therein the folded

edge portions

22 and 24, and can be described as defining between its

longitudinal fold lines

28 and 30, a front wall or first wall 44 and rear wall or second wall 46 in superposed relationship with the first wall 44 and joined together therewith along the seam 38. The description of these portions as first and second walls will be seen as more aptly applied when bag element 10 is unfolded and shaped to provide a fiat bottom bag. Bag element 10 also includes a closed or secured end 48 located adjacent seam 38, and an open end 50 located remote from seam 38 opposite closed end 48, and across which the overlying plies comprising bag element 10 remain unsecured to provide a fill opening 52.

The closed end 48 of bag element 10 can be readily shaped to provide a flat or square bottom bag as illustrated in detail hereinafter. For the purposes of description it is convenient to identify strategic locations or points on the bag element 10 to better illustrate the shaping step. Points A and B comprise the terminating locations of the

inner edges

32 and 34 of the

fold edge portions

22 and 24 as they merge with the closed end 48. Point D is located on the first Wall 44 of bag element 10 adjacent the fold line 30 as best illustrated in FIGURE 2. Point F is located directly adjacent point D but is defined as being on the second wall 46. FIGURE 3 shows the distinction between points D and F with line 53 indicating the defining edge of first wall 44 hidden from view by folded edge portion 24, and on which the point D lies. Specifically, as shown in FIGURE 3, points D and -F extend inwardly from seam 38 a distance X, which distance is approximately equal to the distance X representing the width of folded edge portion 24. Points C and E differ from points D and F only in that they are located adjacent the fold line 28 of bag elemnt 10.

A method of shaping the closed end 48 of bag assemblage 10 is illustrated in FIGURES 4 and 5. Here the first wall 44 and second wall 46 are separately grasped by

d hands

54 and 56 at points D and F lying in adjacent relationship thereon, and sharply pulled apart to the position illustrated in FIGURE 5. As will be noticed in FIG- URE 4, the separating of the first wall 44 from second wall 46 in this manner results in the unfolding of the folded edge portion 24 at locations between the open end 50 and points D and F, with the points D and F comprising two adjacent corners of the flat bottom formed. What in effect has transpired in the shaping step is the shifting of inner edge 34 of the folded edge portion 24 to a position in planar alignment with the linear path of seal 38 securing closed end 48. This shifting of the location of inner edge 34 results in the partial unfolding of the folded edge portion 24 as described above, allowing the bag element 10 to bloom out into a fiat bottom structure. Folded edge portion 22 can be similarly unfolded to complete the formation of the desired flat bottom in bag element 10.

FIGURE 6 illustrates a flat bottom bag 58 formed from the bag element 10 by shaping its closed end 48 as described above. Bag 58 includes a tubular body 60 having a fill opening 62 at its end portion 64 corresponding to open end 50 of bag element 10, and a flat bottom 66 located at its other end 68 or end corresponding to the closed end 48 of bag element 10.

With fiat bottom 66 so formed, a front wall 70 and rear wall 72 are distinctly perceptible as defined wall portions of the tubular body and comprise that portion of first wall 44 and second wall 46 of bag element 10 located between its open end 50 and the previously defined corner points C, D, E and F. Joining together the front wall to the rear wall 72 are

side panels

74 and 76 formerly that part of the folded

edge portions

22 and 24 located between the open end 50 of bag element 10 and the above enumerated corner points C, D, E and F.

Flat bottom 66 of bag 58 comprises the portions of bag element located between the closed end 48 and points C, D, E, and F and in part includes

rectangular end panels

78 and 80 formerly included as portions of the first and

second walls

44 and 46.

End panels

78 and 80 merge along their

outer edges

96 and 98, defined between points C and D and E and F, with the front wall 70 and rear wall 72, and are joined together along their common

inner edges

82 and 84 by seam 38.

Flat bottom 66 additionally includes triangularly shaped

members

86 and 88 comprising the unfolded parts of the folded

edge portions

22 and 24 of bag element 10.

Triangular members

86 and 88 are of two-ply construction as shown in FIGURE 7, and each include an inner ply 94 and an outer ply 96 overlying the inner ply 94 and integrally joined together therewith along their common interiorly extending edges 98 and 100, which as shown in FIGURE 6, extend between the four corner points of flat bottom 66 and the points A and B located on seam 38. The inner plies 94 and outer plies 96 each include substantially commonly located side edges and 92 extending between points C and E and points D and F, respectively, with the outer plies 96 merging therealong with the

side panels

74 and 76, and with inner plies 94 joined together therealong with the

rectangular panels

78 and 80. The inner plies 94 of

trianguler members

86 and 88 are further joined together with

rectangular panels

78 and 80 by and along their common portions on seam 38. Actually with seam 38 dividing the inner plies 94, they can be aptly considered as each comprising two separate

triangular portions

102 and 104 abuttingly engaged and joined together along the path of seam 38.

In FIGURE 8 the bag 58 is shown turned inside out and consequently the

triangular members

86 and 88 are located within the confines of the bag 58. In this arrangement the outer plies 96 of

triangular members

86 and 88 can still correctly be termed the outer plies since even though they are now located with the confines of bag 58 they still are positioned over the inner plies 94.

Bag 58 as shown in the FIGURE 7 drawing can be formed directly from bag element 10 by turning the bag element 10 inside out and shaking out the portion of the folded

edge portions

22 and 24 located between the open end 50 and points C, D, E and F. When formed in this manner, the terminating or raw edges 106 of bag 58 located adjacent seam 38 are positioned within the confines of bag 58 as is clearly depicted in FIGURE 9, thereby enhancing the overall appearance of the bag 58 and making it suitable for containing expensive articles and the like wherein the appearance of the bag is an important aspect in the merchandising of the article. By again revising or turning inside out the bag 58 of FIG- URE 8, the bag 58 of FIGURE 6 is obtained.

For the flat bottom of bag 58 to be shaped properly it is important that the

inner edges

32 and 34 of the folded

edge portions

22 and 24 do not extend beyond the longitudinal center line 49 of the bag element 10. If the edge portions are folded to a width extending beyond the longitudinal center line 49 of the bag 10, the flat bottom 66 of bag 58 cannot form or shape properly. Also, to more perfectly form fiat bottom 66 of bag 10, further shaping by hand can be employed, as, for example, by further hand shaping the

triangular members

86 and 88.

The bags of the present invention can be made from most any flexible material which is of suflicient durability or toughness to withstand the shaping of the closed end 48 of the bag element without tearing or otherwise failing in structure. For example only, and where heat sealing is desired to form seam 38, the bag element 10 can be constructed of such heat sealable thermoplastics as polystyrene, polypropylene, polyethylene, Saran, rubber hydrochloride, and similar plastic film or sheet material fusible by the application of heat. Where sealing by heat is not an important consideration, other materials not having excellent heat scalable qualities as, for example, many of the regenerated cellulose plastic compositions can be employed to construct bag element 10. Sealing in these cases can be accomplished by suitable adhesives, solvents or other sealing substances as wopld be most appropriate for the material selected for the bag. Also contemplated as suitable materials for forming bag element 10 are sufliciently durable fabrics such as natural cloths, like cotton or wool, or synthetic materials as, for example, nylon or rayon. Here seam 38 could be formed, for example, by sewing the material together. Laminated or coated materials, as, for example, a layer of Saran laminated to or coated on a layer of polyethylene, are also suitable for bag element 10 provided the qualities as to flexibility and durability are present. Here, where a heat seal 38 is desired, it should be noted that seam 38 requires both the inner and outer surfaces of bag element 10 to have heat sealable qualities although the inner and outer surfaces need not be heat fusible or compatible to each other.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention.

Accordingly, what is claimed is:

1. A normally flatwise disposed bag element comprising a generally flattened tubular body having a closed end and an open end, the edge portions of said tubular body being folded in superposed relation therewith and extending between said closed end and said open end, said folded edge portions being short of the longitudinal center line of said tubular body, a seam included in said closed end and extending thereacross securing together therealong the overlying plies comprising the folded tubular body.

2. The bag element of claim 1 wherein said tubular body comprises a themoplastic and wherein said seam comprises a heat seal across said closed end securing together therealong the overlying plies comprising the folded tubular body.

3. The bag element of claim 1 wherein said flexible material comprises Woven fibers.

4. A normally flatwise disposed bag element which can be shaped to form a flat bottom bag, said bag element formed of flexible material and comprising a generally flattened longitudinally extending tubular body defining an imaginary longitudinal center line, said tubular body including a longitudinally extending edge por tion on each side of said longitudinal center line and first and second ends located opposite each other and extending generally transversely to said longitudinal center line, said edge portions being folded along a generally longitudinally extending line so as to be in superposed relationship with said tubular body and with each edge portion terminating short of said longitudinal center line, a seam located adjacent said first end and extending transversely across said folded tubular body, said seam securing together therealong the overlying plies comprising said folded tubular body.

5. The bag element of claim 4 wherein the terminating inner edge of each folded edge portion respectively is aligned parallel with said longitudinal center line.

6. The bag element of claim 4 wherein said seam is at right engles to said longitudinal center line.

7. The bag element of claim 4 wherein said flexible material comprises woven fibers.

8. The bag element of claim 4 wherein said flexible material comprises a thermoplastic.

References Cited UNITED STATES PATENTS 2,121,053 6/1938 Robinson 229.53 2,819,834 1/1958 Brady 22953 3,136,475 6/1964 Geimer 22957 3,143,277 8/1964 La Fleur 229 57 r DAVID M. BOCKENEK, Primary Examiner US. Cl. X.R.