US 2350132 A
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Description (OCR text may contain errors)
May 30, 1944. H, ROHDIN BAG AND METHOD OF MAKING THE SAME Filed Nov. 18, 1941 2 Sheets-Sheet l IIbwardRohdin, Mfla w I I I l I l I I I l I Gum,
May 30, 1944. H. ROHDlN BAG AND METHOD OF MAKING THE SAME 2 Sheets-Sheet 2 Filed Nov. 18, 1941 Wm W & 3% *m m w m m g ff .m R QR QMWN, \mm E @MMMQ mwwx NEW.
Patented May 30, 1944 orrlcs BAG AND METHOD OF MAKING THE SAME Howard Rolidin, Glen Ridge, N. J. Application November 18, 1941, Serial No. 419,628
It is an object of my invention to provide a bag or envelope of the double side-seam type so constructed that there will not-be exposed to the interior of thebag any edge of the material comprising it.
It is a further object of my invention to provide a bag or envelope of the class described so constructed and arranged that the strength of the seams will always approximate or surpass the strength of the material of the bag.
It is a further object of my invention to provide a bag or envelope of the class described which is particularly adapted to the use of multiple plies of heat sealable material.
It is a further object 01' my invention to provide a multi-ply bag in which each ply forms a separate, independent bag with separate, independent seams.
It is a further object oi. my invention to provide an improved method for making ilat bags or envelopes of the class described.
These and other objects 01' my invention will be made clear in the following detailed description taken in connection with the annexed drawings in which- Figure 1 shows a composite blank from which my container may be formed; V
Fig. 2 is a perspective view illustrating the manner of folding the blank shown in Fig. 1;
Fig. 3 is a perspective view of the completed Fig. 4 is a section on the line 4-4 of Fig. 3;
Fig. 5 illustrates a modified form of composite blank;
Fig. 6 is a perspective view of the bag made from the blank of Fig. 5;
Fig. '7 is a special form of composite blank;
Fig. 8 is a plan view showing a modified form of finished bag;
Fig. 9 is a plan view illustrating a method of preparing the bag shown in Fig. 8 for closure of its open end;
Fig. 10 is a plan. view of a special form of com posite blank; and
Fig. 11 is a diagrammatic illustration ofthe major steps in my improved process.
In the past few years, a great deal of work has been done in heat sealing various materials and in using such materials to form bags or envelopes 01' an extremely impervious character adapted to holding gases and liquids ,under substantial pressure differentials.
differentials in the thickness of the material to be sealed is virtually fatal to perfection-of the seal, and that a high proportion of perfect seals cannot be produced under such conditions. An example of such a condition is the collapsed mouth of a gusseted bag in which the mil erial to be gripped and sealed comprises at least four plies of. thickness in the areas 01' the gussets and only two plies of thickness intermediate the gussets. In making a heat sealable bag or envelope in which the various seals and closures must be absolutely tight, and millions of such containers are to be made, it is desirable in order to insure obtaining an efllcient percentage of commercially acceptable containers that they be designed so that the areas subjected to heat and pressure are of uniform thickness.
It is also desirable, particularly for liquid contents, that no severed edge of the sheet material composing the container shall be exposed to the liquid contents. This particular characteristic is not, perhaps, indispensable w ere the sheet So far as the accomplishment of sealing by the application of heat and pressure is concerned, it has been found that the presence 01' substantial material is perfectly homogeneous, f d completely resistant to the particular liquid. Where,
however, the material is not homogeneous, and
particularly where any portion of the material is fibrous, as paper or vegetable parchment, the avoidance of the exposure 01' a raw edge is vital, since otherwise a wicking action will occur, the liquid being drawn into the cross-section of the sheet, with resultant discoloration and unsalabillty 01' the filled package.
It is a further essential, in packages 01' this class, that the various seams be constructed and arranged so that under no circumstances can internal pressure within the package tend to separate the plies forming the seam by a peeling action. Such an action means that the seam can resist the spreading or peeling eflect only along the innermost line 01' the seal, and the entire width 01' the seam as a whole never has an opportunity to resist the load.
While the structural features of my improved bag and the steps of my improved process are applicable to a bag formed of a single ply of sheet material, they gain extraordinary advantage when used in connection withmulti-ply structures, and I have therefore directed my detailed description to the application of my'inventive principles to multi-ply bags or envelopes. Except where expressly so limited, however, the claims are to be construed as including single ply structures. Where, however, multi-vply structures are involved, it is enormously advantageous that the two plies should be, so far as possible, entirely of Cellophane 2- independent, one of the other, and that they should not be laminated so as to form substantially a single sheet.
Referring now to Fig. l, I show a composite blank composed of a base sheet l forming the outer ply of the finished container and a relatively narrower sheet I: superimposed on the base sheet I0 and adapted to form theinner ply. The sheet I2 is coextensive in length with the sheet i0 and is so located thereon as to leave approximately equal margins ll of the sheet Iii on each side of the sheet i2.
As illustrated in Fig. 2, sheets i0 and 12 are folded about a transverse median line IE to bring the inner surface l8 of the inner ply l2 into contact with itself and to bring the inner surfaces of the margins N of the outer sheet Ill into face to face contact. The margins of the inner surface i8 of the inner sheet i2 are sealed to each other along lines parallel to the margins M of the outer sheet l0, and the respective margins ll of the outer sheet are sealed throughout the areas of face to face contact. There are thus formed independent seams defining an independent bag of the inner ply I2 and an independent bag of the outer ply I. These seams are closely adjacent each other and in parallelism. The bag is completed by folding the material of each pair of seams over against one face of the bag and sealing the folded seams to that face throughout the stippled areas i9 shown in Fig. 3.
-This construction attains its greatest utility and its highest degree of imperviousness when the inner ply i2 is formed of the special sheet Nemours 8: Co. and composed substantially of polyvinyl alcohol. and the outer ply is composed of the grade known as M. S. A. T." In this grade of Cellophane," the moisture-proof coating of the basic viscous film is not only heat sealable'to itself but is positively anchored to the base film. The resultant sheet is completely waterproof. The film of polyvinyl alcohol is water soluble but is enormously resistant to penetration of oils, greases and, in general, all hydrocarbons, including all vegetable and animal fats and greases. The Cellophane" and the polyvinyl alcohol have the further peculiarity that, while each will, under heat and pressure, form a perfect bond to itself, neither, under heat and pressure, will form a bond with the other. When, therefore, a bag or envelope \as illustrated in Figs. 1, 2 and 3 is formed using Cellophane of the class described as the outer ply Ill and polyvinyl alcohol as the inner ply i2, a single, simultaneous application of heat and pressure to each of the side seams ,material produced by the E. I. du Pont de when the fold indicated in Fig. 2 is completed will result in the formation of a fused fin along each side of the inner bag formed of the ply l2 and a similar fused fin in the area of face to face contact of the margins ll of the outerply Hi. When these fins are folded to the position shown in Fig. 3, and some non-conducting or at any rate non-scalable member 20 is inserted within the inner bag formed of the ply l2, heat and pressure may then be applied to the folded fins to form a structure as illustrated in Fig. 4 in which 22 is the fused fin formed of the marginal portions of the ply I2, 24 is the fused fln formed of the marginal portions H of the ply l0. and 26 represents a fusion between the outer wall of the bag formed of the ply l2 and the surface of the fin portion of the ply II which the edges of the bag. This relationship is most important since, when the bag is fully distended, there can be no spreading or peeling effect applied either to the seam 22 or the seam 24, and such loading as is encountered by the seams must be resisted by their entire cross-section.
In Fig. 5, I show a blank similar to that shownin Fig. 1- having an outer ply 40 and an inner ply 42. In this case, the inner ply not only is narrower than the outer ply so as to leave longitudinal margins 44 on each side of the inner ply, but is also shorter than the outer ply so as to leave margins 46 at each end of the inner ply. when the blank shown in Fig. 5- is folded and sealed through the steps shown and described in connection with Figs. 1-4, inclusive, it is brought into the condition shown in Fig. 6 in which the dotted line 48 indicates the terminus of the inner ply." to leave atthe mouth of the bag the portions 46 of the outer ply 40 in face to face contact. The application of heat and pressure, therefore, to the stippled area 50 will result in the formation at the mouth of the bag of a seam which, by folding over upon and sealing to the body of the bag, will duplicate the seam illustrated in-Flg. 4.
Fig. '1 illustrates a special expedient which may usefully be resorted to when the inner ply is composed of polyvinyl alcohol. Such material is extremely limp, somewhat hydroscopic and has a tendency to stick to itself sufllciently to set up a distinct blocking" efiect which can be extremely annoying in filling and handling the bags. In Fig. 7, 60 is the outer ply, 62 the inner ply, and N a slip sheet of material which is non-blocking but which is incapable of heat sealing either to the inner ply or to'the outer ply or to itself. "Cellophane of the grade known as "P. T." is suitable for this purpose. The proportions of the inner ply 62 relative to those of the outer ply 60, while similar to Fig. 1, as shown, may, of course, be as shown in Fig. 5. For the sake of convenience, however, the slip sheet 64 should be somewhat longer than either of the other plies so that it may easily be grasped and withdrawn from the finished bag at the time of use. The width of the slip sheet 64 shouldcorrespond as accurately as possible to the width between the creases 30 (Fig. 4) of the finished bag and should be such as to underlie all or substantially all of the area of sealing 26 (Fig. 4)
In Fig. 8, I show a tapered form of bag 10 which may be formed from a blank as shown in either Fig. l or Fig. 5. If, in the bag shown in- Fig. 8, a slip sheet be used as indicated in Fig. 7, the sheet should be die-cut,so as to conform to the taper of the final bag. The bag Ill is composed of an outer ply i2 and an inner ply II and has double side seam 15 formed as previously described. In folding these side seams onto the bag Ill, the fold lines are inclined slightly toward each other so as to bring the bottom corners 18 of the folded seams 15 above the bottom fold 18 of the bag. This assures, when heat and pressure are applied to the folded seams, that these corners I6 will be caught and secured to the bottom of the bag, thus eliminating, or at any rate substantially minimizing, the danger of starting a separation of the folded seams from the bodyof the bag at the corners II. This construction also has the advantage that where the bags are formed on mandrels (as will be disunsed hereinafter) the withdrawal of the mandrel is facilitated and the same feature facilitates the withdrawal of a slip sheet where such a sheet is used.
In Fig. 9 I illustrate a bag 80 similar to the bag II shown in Fig. 8. This bag is formed from any of the blanks previously discussed, but its folded-over seams 82 are secured by heat and pressure from the bottom 24 only for a part of the length of the bag and the sealing terminates along the line as-z. The position of the line H relative to the mouth It of the bag is such that the mouth can be spread out into a single plane so as to provide the best possible opportunity for perfect heat sealing thereof. bviously, this arrangement is applicable to a bag of uniform width as illustrated in Figs. 3 and 6. No change need be made in the slip sheet, if any be used, since the sheet would be withdrawn mandrel I22, portions I22 of the blank project at each side of the mandrel I20 when the blank I22 has been folded thereabout. These projecting portions l2! are passed between opposed pairs of members I28 and III which press the projecting portions. Preferably the members of each prior to filling and therefore would not be present when the mouth is spread.
In Fig. 10 I illustrate a special form of blank OI. Upon this blank is superimposed a bag 92 of the type shown in Fig. 3, though obviously than that of the bag 2 to provide flaps I02 on each side thereof. Above the mouth I04 of the bag 92, the blank 9|! has an end flap portion "6 of a width approximately equal to that of the bag 92, and a length sufllcient to form a closing flap. A window III is cut into the intermediate portion III of the blank 90 and serves to reveal the contents through the transparent material of which the bag 92 preferablyis formed.
In forming a bag of the structure illustrated in Fig. 10, the portion 90 is folded along the line 0-4! so as to overlie the bag 92. The fiaps "2 of the portion III of the blank are then folded against the outside of the portion 98 and secured thereto by any suitable means. After filling and sealing of the bag 92 (the sealing being accomplished by heat and pressure applied through the material of the blank 90), the flap II is bent down to form an external closure and is secured to the outer surface of the por- I220. and an inner ply I22b) which is held substantially in a plane at right angles to the plane of the mandrel, and continuing advance of the mandrel folds'the blank I22 about the leading and I24 of the mandrel to form a bottom fold I2. Since the blank I22 is wider than the pair I22 and I3. are heated, though, if desired. only one member of each pair need be heated. The result is to seal the portions I23 into fins and to form two independent closures on each side; one of the material of the outer ply 2:1 and the other of the material of the inner ply I22b. These fins are, then folded (preferably during the progress of the mandrel I20) over against the rear face I 22 of the bag. When the fins are in this position, the mandrel and bag pass between additional pairs of opposed pressure members I and I38. The upper member in each pair, in contact with the folded fins I23, is heated, the lower member of each pair acting merely as a backing member. The mandrel, being substantially non-conductive and preferably somewhat yielding, prevents undesired sealing of the interior of the bag. When the bag emerges from this final pressing station, its seams will be in the condition illustrated in Fig. 4 and the mandrel may be withdrawn.
Clearly, the blank may be of the forms of Figs. 1, 5, 7 or 8, and the final pressing step may be conducted to produce a package as illustrated In Figs. 3, 6, 8 or 9. It is equally clear that the process may be carried out for any number of plies formed of any suitable material or materials.
In the design of the bag itself, it is to be noted that, if desired, the fold line which forms the bottom of the bag need not be centrally located of the blank. Moving the fold line off center results in the formation of a projecting tongue at one side of the bag, which tongue may be used as a closing flap or as a lip to facilitate opening of the bag for filling operations. This eccentricity of the fold line with respect to the blank may be established as to either of two plies or as to any selection of a few out of several plies in order to attain any desired number and selection of plies in the closing flap, and in order to provide a desired distribution of plies for sealing of the mouth.
What is claimed is:
l. The method of making bags which comprises freely superimposing on a rectangular sheet a similarly shaped sheet of lesser dimensions so as to leave exposed margins of said first-named sheet; folding both sheets about a common line to bring into face to face contact approximately equal portions of the free surface of said secondnamed sheet, and the exposed margins of said first-named sheet; then folding, upon the body of the bag, and along parallel lines spaced inwardly from the margins of said second-named sheet. the portions of the folded sheets lying outside said lines; then subjecting. in the area of said folded portions, the entire structure to heat and/or pressure while preventing the interior of that portion of the bag lying between said parallel fold lines from being sealed under the effect thereof, whereby to form sealed seams between the mutually contacting portions of the respective sheets in said area.
2. The method of making bags which comprises freely superimposing on a rectangular sheet a similarly shaped sheet of lesser dimensions so as to leave exposed margins of said first-named sheet; providing a mandrel formed of non-thermal-conductive material, said mandrel being of a width less than that of said narrower sheet:
folding said sheets about one end of said mandrel with said smaller sheet innermost, and with mangins of both sheets projecting laterally from the sides of said mandreit subjecting said projecting margins to heat and'pressure: then folding said margins about the sides of said mandrel to bring said margins into parallelism with said mandrel and within its area; and then subjecting each of said margins and the portion of the mandrel thereunder to pressure from both sides and to heat on at least the side occupied by the respective margin.
3. A bag formed of a sheet of impervious, flexible material heat sealable on both surfaces, said sheet being folded about a line intermediate the length thereof to bring the coextensive portions of a single surface thereof on each side of said line into face to face contact, the margins of said surfaces being heat-sealed in the area of such contact and said heat-sealed margins being folded against the outside of said sheet and heat-sealed thereto, the inner surfaces of the bag" walls underlying said folded margins being free of each other and the lines on which said heatseaied margins are, folded including unsecured portions of the contacting inner surfaces of the bag walls adjacent an edge of said heat-sealed margins.
4. A two-ply bag comprising a pair of superimposed sheets of flexible material, each sheet being heat-scalable on both of its surfaces, and one sheet being narrower than the other, said sheets being fblded about a common line intermediate their length, with the narrow sheet innermost to bring coextensive portions of a single surface of each sheet on each side-of said line into face to face contact, the contacting margins of each sheet being heat-sealed in the area of such contact and said heat-sealed margins being folded against the outside of the outer sheet and heatsealed thereto, the inner surfaces of the bag walls underlying said folded margins ,being free of each other and the lines on which said heat-sealed margins are folded including unsecured portions of the contacting inner surfaces of the inner sheet adjacent an edge of said heat-sealed margins.
5. A seam for a bag formed of flexible sheet material heat-sealable on both surfaces, said seam comprising a fin formed by heat-sealing contacting portions of the inner surface of the bag, said fin being folded upon and heat-sealed to the body of the bag, the inner surface of the bag walls underlying said folded fin being free of each other, and the line on whichsaid ha is folded including unsecured portions of the contacting inner surfaces of the bag walls adiaceiit an edge of said fin.
6. The method of making bags which comprises freely superimposing a relatively narrow web upon a relatively wider web so as to leave projecting margins of said wider web; each web being heat-sealable to itself on both surfaces; folding both webs about a common line to bring the free surface of said narrow web and said margins of said wider web each in contact with itself: securing. by means of heat and pressure, parallel margins of said narrow web in face to face contact; and similarly securing the margins of said wider web parallel thereto; establishing fold lines parallel to and spaced inwardly from the inner edge of the innermost'heat seal; foldmg each pair of secured margins along the lines thus established onto the body of the bag and securing them thereto by means of heat and pressure and shielding the inner surfaces of the bag against blocking during the sealing of said margins to the body of the bag.
7. The method of making bags' which comprises folding a sheet of flexible material, heatsealable on both surfaces, about a line intermediate its length to bring portions of the same surface of said sheet into face to face contact; securing, by means of heat and pressure parallel margins of said sheet in face to face contact; establishing fold lines parallel to and spaced inwardly from the inner edges of said heat-sealed areas; folding said heat-sealed margins along the lines thus established, upon thebody of the bag and securing them thereto by means of heat and pressure, and shielding the inner surfaces of the bag against blocking during the sealing of said margins to the body of the bag.
8. A method of making seams in bags formed of flexible sheet material heat-scalable on both surfaces thereof, said method comprising: bringing portions of the inner surface of a bag formed of such material into face to face contact; applying heat and pressure in the area of such contact to form a fin; establishing a fold line spaced inwardly from the innermost edge of said fln;
folding said fin about said line and against the body of the bag; applying heat and pressure to said fin to secure the same to the body of the ba and shieldingthe inner surface of-the bag against blocking during the last mentioned sealing step. HOWARD ROHDIN.