US2837979A - Production of bags - Google Patents

Description

June' 10, 1958 v Lu s 7 2,837,979

PRODUCTION OF BAGS Original Filed Feb. 28, 1955 3 Sheets-Shaet 1- 63 ji nforx [earzard d Vi'lul 1'5 65 65 Qmm Jim 10, 1958 L. J. VlLUTlS PRODUCTION OF BAGS Original Filed Feb. 28, 1955 [eonard d Vr luiz's $1z4mmd L. J. VlLUTlS PRODUCTION OF BAGS June 10, 1958 3 Sheets-Sheet 3 Original Filed Feb. 28, 1955 United States Patent PRODUCTIGN 0F BAGS Leonard J. Vilutis, Chicago, 11]., assignor to Quatrum Corporation, Chicago, Ill., a corporation of Illinois Original application February 28, 1955, Serial No. 491,104. Divided and this application January 25, 1957, Serial No. 636,438

3 Claims. (CI. 93-27) This invention relates to bags formed of flexible, heat scalable, plastic film material, preferably of a substantially transparent or translucent nature, of the class having a folded over bottom construction, and characterized by being sealed in a novel manner so as to provide the bag with a bottom that has the strength of a fold over bottom bag and the air, moisture, liquid and vacuum security of a flat bottom bag, without any wrinkles or pleats on the sealed surfaces tocause any possible weakmess.

The invention further relates to the novel method and means for providing bags of the foregoing class with adual seal for obtaining the aforesaid advantages.

It has particular relation to bags that are required for a specific use to be either gas, liquid, moisture or vacuum proof, for the protection of the product, while the bottom of the bag is required to have the same strength as the film itself, for use as a packaging bag for meat, poultry, dried fruit, cookies, liquids, metals, candy, nuts and any other type of use which requires the bottom of the bag to be of the same strength as the film itself while also having. an air, liquid, moisture and vacuum proof seal at the bottom.

Bags formed of flattened tubes offiexible, heat scalable, plastic film material formed with a flat bottom, that is where the opposed layers of the flattened tube" are sealed together without overfold, are generally air, mois tur'e, liquid and vacuum proof, but with some types of plastic film such as Saran (vinylidine chloride plus vinyl chloride) and other vinyl resin films, Pliofilm (a rubber hydrochloride), and laminates thereof, the fiat bottom seal is inherently weak, since inside weight, pressure or ,vacuum When applied directly against the seal, breaks the bottom because the seal strength is weaker than the film itself. In an attempt to overcome this deficiency it has'been customary to form such bags with fold-over bottoms, that is with two thicknesses of an overfolded endsealed to one layer of the flattened tube. This provides a strength equal'to the plastic film used since inside (and outside when vacuum is used) pressures are not applied against the line of seal, but against the film itself. since the necessary' strength at the bottom is obtained at a sacrifice of the air, moisture, liquidand vacuum proof character of the bottom seal;

For example, a: serious problem arises when the customary fold over bottom seal is used, in that it'- is not uniformly air, moisture, liquid and vacuum proof, for the following reasons: The forming plates, or fiat mandrels around which the plastic film. is wrapped and longitudinallysealed in. tubular form in conventional bag making machines, have rounded edges on the sides, while manyof the plastic films have a coating of edile dusting material for the necessary slip' required to permit the film to be passed easily through the ,bag'making machine. This causes difiiculty' in forming the film properly around the forming. plate in that it is 'not always uniformly formed around the forming plate, since many of the films This, however, is an unsatisfactory compromise following ICC are also not uniformly flat in roll stock form but tend to be baggy which in turn causes further difficulties in controlling the film about the forming plate, especially when the bag size is less than five inches fiat Width, in that it is not possible to cause the bottom seal to go completely out to the side of the bag. Another obstacle in sealing out to the edge of the fold over material is that the forming plate padding must be past the edge of the film. But since the film is formed around the plate, this cannot be done since the bag is wider than the widest part of the plate.

One attempt to solve this problem was by making the forming plate with the trailing edge in the form of a radius in order to tuck in the fold over portion of the folded over film and to bring this folded over portion of the film within the padded sealing portion of the plate, to permit the seal to extend completely over this folded over portion of the film, to' afford an air-tight and moisture-proof bag bottom. This method does bring the seal out to the edges when the bag to be formed is to be five inches or more in flat width and the machine is operating at slower speeds, with a radius end plate. This type of bag, however, with the folded over film being tucked in within the padding of the plate to permit sealing out to the edges, leaves much to be desired since the seal must take place over the tucked-in film. This causes a seal over wrinkled and uneven film, with the consequent result of sealing over pleated film, which in turn causes weak spots in the seal whenever the sealing takes place on an uneven surface. Sealing over an'uneven film area will not insure the best results for liquid, pressure or vacuum packaging due to the weak spots caused by the pleating.

it is an object of this invention to seal a flat fold over bottom bag formed with a spaced pair of transverse lines of seal with one seal in a flat even position after the customary fiat (as distinguished from a radiused .fold over seal is made, producing a flat fold over bottom bag that has the strength of the film at the bottom and is also air, moisture, liquid and vacuum proof. This is accomplished with any size bag, at any speed, with dusted or undusted film, and whether or not the film is formed firmly or loosely around the forming plate.

Other objects and advantages relate to the novel method and means for forming bags with my characterizing dual seal as will be apparent from a consideration vof the specification and accompanying drawings, wherein: s ,Fig. l is a plan view of a bag sealed in accordance with the present invention.

Fig. 2 is a section on the line 2-2 of Fig. 1.

Fig. 3 is a fragmentary side elevational view of a bag forming and sealing apparatus;

Fig. 4 is a perspective view of a fold-over blade employed in the apparatus of Fig. 3.

Figs. 5, 6, 7, 8 and 9 are end elevational views of several forms of sealing bars and electrodes optionally useful in forming my characterizing dual lines of seal.

Figs. 10 to 16 are enlarged fragmentary side elevational views of one end of the apparatus shown in Fig. 3, sequentially illustrating the steps of severing formed tubing, folding over the bottom to form a bag, and the dual sealing of the folded-over bag bottom portion.

Fig. 17 is a section on the line 17-i7 of Fig. 14.

Referring to the drawings, the reference numeral 20 generally designates a bag formed, in accordance with the present invention, from a strip of plastic film material, the longitudinal edges of which have been folded over and. sealed at the longitudinal seal line 21, and a bottom portion 22 of the resulting tube folded over and sealed in a dual manner. That is, the bottom portion 22' is pro- .vided, with two "lines of seal 23" and 24' respectively extending transversely of the bag. Seal line 23 extends substantially but not completely across, and the two thicknesses of the folded over bottom are sealed together and to the adjacent layer 25 of the twocoextensive layers of thev'bag in formed flattened condition. The seal line 24, on the other hand, extends completely across the full width of the folded over portion 22- and 'seals only the two'opposed faces of the folded end together, the line of seal 24' being disposed between and parallel to the seal line23 and the free edges 26.

As has been hereinbefore indicated, and as will be herematter more fully explained in connection with the apparatususuallyemployed in commercial production of these bags, the sealing at line 23 takes place when a flat mandrel is contained within the formed tube so that the two thicknes'ses of folded over portion 22 are sealed together and to bag face 25 by a sealing bar extending transverselyof the bag. In this arrangement it will be apparent that the width of flattened portion 22 is greater than that of face 25 while the mandrel is confined in the tube, since the opposed thickness of portion 22 becomes contiguous, whereas bag faces 25 and 27 are spaced by the forming plate or mandrel and during the sealing step are foreshortened at least by the amount taken up by the thickness of the forming plate. Thus even though the-sealing bar used extends completely across portion 22, the opposed edge portions 2828 extend over the edge of the narrowed bag face 25 as compared to its width when the mandrel is withdrawn, and thus cannot be properly sealed to each other or to the side edge portions of the bag thereat in the absence of full width bottom support or backing for the sealing 'bar.

: Although not shown, it will be understood that the present invention is equally applicable to bags of the gusset type which in formed flattened condition include opposed longitudinally extending tucks, and the folded over bottom will then have four thicknesses at the opposed'edge portions sealed together, the dual lines of seal with respect to the upper full width, excluding the tucked-in side portion's, of the bag being in the same relationship as the illustrated form. I r

Bags of the foregoing class, with the exception of my novel duallines of bottom seal, are conventionally formed in an intermittent, substantially continuous manner from a roll of film material by means of apparatus, such as for example that shown in U. S. Patent-No. 2,347,902, modified in certain respects as will hereinafter be more fully explained. In general, such process and apparatus comprises a bed over which is disposed at fiat, horizontally shiftable, elongated mandrel or forming plate about which the strip of film material, as it unwinds from the supply roll, is folded and longitudinally sealed to tubular form. 'A bottom margin of the tube, resulting from a previous cutting off operation, and projecting freely over a' transvers'e.'edge of the bed, is folded over by finger means, at a time when the forward edge of the forming plate is parallel to the edge of the bed, and with the aid of fold over guide means temporarily brought into alignment at said edge. conventionally, the fold-over guide means is then fully withdrawn from between the foldedover edge portion and heat sealing means, either electronic or thermal, disposed above the bed in the form of a bar of greater width than the bag is brought 'into pressure engagement with the folded-over end portion to fuse or heat-seal the folded-over end portions of the bag to each other and to the adjacent surface of the tube on the mandrel. After the sealing operation the mandrel is advanced to carry the folded and sealed end of the bag into engagement with a pair of feed rollers which have just ejected the previously formed bag and which thereafter grip the sealed end of the bag form and draw the form along for a distance corresponding to the selected bag length. In proper timed relation the roller drive is released, by suitable control means, so that the cut-off operation can be performed to complete the bag forming open ation. Such cycle of operation continues automatically so that the bags are successively formed and ejected from the machine. The various mechanisms for carrying out the cycle of operation are generally conventional in the art, as exemplified by the aforesaid patent, with the exception of the modifications forming a part of the present invention, as hereinafter described.

Fig. 10 illustrates the completion of one bag-forming cycle with a completed bag 20 of desired length being cut off by means of the movable upper knife 29 and the stationary lower knife 30, after having been fed to and between the draw rolls 3131 by the forming plate or mandrel 32. In this figure the forming plate has already been retracted so that its trailing or free edge is parallel to the transverse edge 33 of supporting bed 34. It will be understood that, although not shown, the opposed edge of the forming plate 32 is engaged to means for disposing it above and in spaced relationship to bed 34 so that the sheet of film material may be passed beneath the plate 32, and for moving the plate 32 horizontally for the indicated delivery of a formed bag to the rolls 31 and for subsequent retraction thereof. It will also be understood that, although not shown, means are provided for folding the sheet of film material about the plate 32 and sealing it longitudinally to tubular form in conventional manner.

7 In the practice of the present invention, the trailing or free edge of forming plate 32 is flat; that is, it is normal. to the side edges or rectangular as distinguished'from a radius or arcuate edge. This insures that the film when folded over, with the aid of the superimposed fold-over blade 35, will not have any wrinkles or unevenness when the sealing bar makes the first customary transverse seal 23.

As a further characterizing feature of the present invention, I employ a straight one-piece fold-over blade 35, as illustrated in Fig. 4, provided with padding 36, in lieu of the two customary blades or inward laterally-projecting fingers as in the aforesaid patent. This fold-over blade 35 with its padding 36 is made. of. any material that is a conductor of electricity for? use .with electronic sealing, although, thermal sealing or a combination of both may be employed. This one-piece fold-over blade permits'a straight bottom for the fold-over and aids in keepingthe fil-rnflat and even across the width of the tube or bag. This fold-over blade 35 is wider than the width of the formed bag 20, and extends across the full width of the bed 34 and has a secondary function in forming the seal line 24, as willhereinafter appear. I

This fold-over blade. 35. is reciprocable longitudinally of the bed, 34 and is secured by means of bolts '37 to the spring-urged blocks 38 slidably carried by the rods 39 mounted in recesses on the top .of bed.34.- Each of these blocks 38 carries pins. .40 engaging anassociated bell crank 41 (as shown inFig. .2) carried by a shaft 42. Shaft 42 also carries a depending arm 43 which is connected by link 44 with cam follower 45 urged against cam 46. byv spring 47 associated with link 44. Thus upon rocking of bell cranks 41, during the cutting operation, the fold-over blade 35 moves under the influence of springurged blocks 38 into substantial alignment with the edge of the bed 34, as shown in Fig. 10. This bell crank 41 also effects actuation of the movable 0r reciprocating knife element 29 which issupported between links 48 which are pivotally connected attheir upper ends to supporting arms 49 pivotally mounted on brackets 50. The links 48 are connected at their lower ends to the bell cranks41,.as at 51. i i

Fig. vlli illustrates the inception of the operation of' folding over the free end portion 22 of the tube after having been severed by the knives 29 and. 30. Thus, with the edgesof mandrel 32, blade 35 and bed edge 33 in alignment, folding blade 52, carried on block 53 with interposed'inclined blade 54, is caused to move upwardly, and then in 'su'ccession downwardly and toward the end Owens; and return-bend the end z'z ov'er the blade 3s;

as shown .in Fig. 12-. Block 53 is pivotally mounted on arms 55 of a fold-over assembly on shaft 56, and is further actuated through springs, links, and associated cam means, in conventional manner and for example more particularly described in said patent, so that it operates in timed sequence to the other operations as shown in the successive illustrations of Figs. to 16.

As further shown in Fig. 12, after the end 22 has been folded over, and as the arm 57, carrying the electrode 60, associated through the spring 58 and insulator 59, is caused to descend, in timed relationship for the purpose of effecting the sealing operation, the fold-over blade 35 is caused to recede by cam 46. It will be noted that this rearward movement is however controllably limited, through the contour of cam 46, so that although blade 35 has been moved away from the downward path of electrode 60, it still remains between folded-over end 22 and face 25, permitting electrode 60 to come down and make the customary fold-over seal 23, although the respective layers of film have not yet been compressed in this illustration.

Fig. 13 shows the beginning of compression of the layers by the further downward movement of the arm 57 which-brings the insulator 59 and electrode 60 down under spring tension. Here the bottom fold-over blade assembly carried by arm 55 has started straightening out and moving down out of the way. Fig. 13 further illustrates a characterizing feature of the present invention, in that fold-over blade 35, here by reason of the contour of its control cam 46, is permitted to move, under the action of its control spring, toward depressed electrode 60, until, as further iliustrated in Fig. 14, it compresses the trapped leading edge of portion 22 against the machined straight back side of electrode 69. As shown in the detail of Fig. 5, electrode 6!) has a fiat bottom face 61 and a back face 62 normal thereto.

When electronic sealing is employed, power from a suitable high frequency, such as a radio frequency source (not shown) is applied to electrode 60 against two grounds, one being forming plate 32 and the other foldover blade 35. This brings about the substantially simultaneous formation of the two spaced lines of seal, one line 23 and the other line 24, in the places and manner and with the respective and joint advantages previously described.

Fig. shows the withdrawal of the fold-over blade 35, upward movement of the arm 57 and spacing of the knife blades 2-3L and Fig. 16 shows the movement of the endwise sealed tube, by means of the forming plate toward the rolls 3l3l, for the start of a successive operation as shown in Fig. 10.

Figs. 6 and 7 show other suitable contours of electrodes for electronic sealing, each having a flat bottom face and a rear surface normal thereto to enable formation of the dual seal. It will be understood that the heat-sealing can be effected by thermal means, such as the bar 63 of Fig. 8 which is provided with an electric resistance wire unit 64 mounted therein. In this case also the bottom 65 is fiat and the rear face 66 is at an angle of 90 thereto. Fig. 9 illustrates a bar 67 adapted for use of a combination of the described thermal and electronic heating means.

Since these electrodes or sealingbars are wider than the bag widths, and the padding on the fold-over blade is also wider than the bag width, the seal 24 formed on the leading edge portion of the overfold is similar to that of a flat bottom bag providing the desired air, moisture,

' liquid and vacuum security of a fiat bottom bag without any wrinkles or pleats on the sealed surfaces to cause any possible weakness and Without necessity of operating the bag-forming machine at slow speeds. At the same time the customary fold-over seal 23 to a bag face is also employed to give weight strength to the bottom of the bag, to provide a novel combination and result.

Although I have found the dual sealing of fiat foldover bottom bag to be particularly effective with. respect to certain types of plastic, heat sealable, film material, it will be understood that such dual sealing may be effectively applied to a wide variety of heat-scalable plastic film materials, including cellophane, cellulose acetate, polyethylene, polystyrene, polyesters, and various combinations and laminates thereof.

This application is a division of my copending application Serial No. 491,104, filed February 28, 1955, now abandoned.

I claim:

l. in a process for making fiat rectangular fold-over bottom bags from heat-scalable plastic film material characterized by the use of a plate-like mandrel having a contour corresponding generally to the contour of the finished bag and wherein a freely projecting marginal end portion of a tube of said film material is folded into overlapping relation with a tube wall portion on said mandrel and fused thereto in a tranverse line of seal substantially coextensive with the width of the tube on the upper face of the mandrel by means of a sealing bar of greater width than said tube urged into pressure engagement thereover, the improvement which comprises further fusing together the adjacent layers only of a remaining folded-over free end portion of said tube in a second transverse line of seal fully coextensive with the width of the latter by elevating said free end portion and pressing against a surface of said scaling bar normal the base thereof.

2. In 'aprocess for making fiat rectangular fold-over bottom bags from heat-scalable plastic film material characterized by the use of a plate-like mandrel having a contour corresponding generally to the contour of the finished bag and wherein a freely projecting marginal end portion of a tube of said film material is folded into overlapping relation with a tube wall portion on said mandrel and fused thereto in a transverse line of seal substantially coextensive with the width of the tube on the upper face of the mandrel by means of a downwardly moving electronic heat sealing bar of greater width than said tube urged into pressure engagement thereover, the improvement which comprises, forming said fold with the aid of a unitary straight-edged fold-over blade of greater width than said mandrel by initially bringing it into alignment with the end of said mandrel and folding the free end of the tube thcreover, partially withdrawing said blade from the folded-over tube portion and out of the downward path of said sealing bar, urging the sealing bar into pressed engagement with the material overlying the mandrel to fuse them in a transverse line of seal, and simultaneously moving said blade toward said sealing bar to elevate an overlying free tube end portion and to press it against a surface of said sealing bar normal to the base thereof to fuse the adjacent layers of said tube end portion together in a second transverse line of seal extending completely across the latter portion.

3. In a machine for making fiat rectangular fold-over bottom bags, an elongated plate-like forming mandrel having a flat transverse edge, means for folding a freely projecting end portion of a tube of heat-sealable plastic film material embracing said mandrel into overlapping relationship with a surface of the tube overlying the mandrel, sealing means comprising a bar extending transversely of and of greater width than said mandrel disposed to move downwardly into pressed engagement with said overlapped portion to fuse it in a transverse line of seal to the said adjacent tube surface, said sealing bar being formed with a rearward face normal to the base thereof, a unitary fold-line retaining blade of greater width than said mandrel disposed thereover and transversely thereof, and means for reciprocating said blade longitudinally of said mandrel in a plane substantially parallel thereto to successively bring it forwardly into alignment with said mandrel edge during said folding,

to rearwardlypartially withdraw it from the overlapped '-Rferences' Cited in thefile of this patent portions out of the downward path of said sealing bar, UNITED STATES PATENTS and then move it forwardly into pressed engagement with said rear face of the sealing bar to thereby elevate and ggfi gi 3 3' engage therebetween a remamlng free edge of sa1d over- 5 2:494:905 Shuman Jan- 1950 lapped portion and to fuse thethicknesses thereof together in a second transverse line of seal.

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