US3381886A

US3381886A - Heat sealable bags

Info

Publication number: US3381886A
Application number: US567912A
Authority: US
Inventors: Goglio Luigi
Original assignee: Individual
Current assignee: Individual
Priority date: 1966-07-26
Filing date: 1966-07-26
Publication date: 1968-05-07
Anticipated expiration: 1985-05-07

Description

May 7, 1968 L. GOGLIO 3,381,886

HEAT SEALABLE BAG 5 Filed July 26, 1966 I B 3 Sheets-Sheet -l INVENTOR Lu /G/ 6-06 L./@

ATTORNEY y 7, 8 GOGLIO 3,381,886

HEAT SEALABLE BAGS Filed July 26, 1966 3 Sheets-Sheet 2.

INVENTOR Lu /6/ OGL/O ATTORNEY May 7, 1968 L. GOGLIO 3,381,886

HEAT SEALABLE BAGS Filed July 26, 1966 3 Sheets-Sheet 3 INVENTOR L U G/ 506L/ 0 BY JM M ATTORNEY 3,381,886 HEAT SEALABLE BAGS Lnigi Goglio, Via Solari, Milan, Italy Filed July 26, 1966, Ser. No. 567,912 7 Claims. ((11. 22957) ABSTRACT OF THE DISCLOSURE A thermoplastic bag made of a heat-scalable material such as polyethylene. The bag has front and rear substantially coextensive panels each provided with a pair of opposed side edges and a bottom edge extending transversely between the side edges, and the bag has between the front and rear panels, extending inwardly from the side edge thereof, a pair of inwardly folded gussets which are situated between the front and rear panels and which extend along the side edges thereof to the bottom edges thereof. At these bottom edges the bag is provided with a bottom seam extending all the way across the bottom end of the bag and having a substantially uniform thickness along its entire length. This uniform thickness is achieved by situating between the front and rear panels along the bottom edges thereof and between the inwardly folded gussets directly next to the latter a shim of heat-scalable material which has a thickness equal to the thickness of the gussets so that in this way the bag is provided along its entire bottom end with a uniform thickness so that when the seam is formed it will have a uniform thickness.

This invention relates to a method and related equipment for producing heat scalable, air-tight containers, having inwardly folded edges, by the use as starting material of one or more, possibly multi-ply sheets.

Heat scalable bags or containers, that can be air-tight closed, and having inwardly folded longitudinal edges, are already known. A particular type of such bags, and to which the invention is specifically referred, is formed with reinforcing welded seams all along the four edges, while the bottom is further reinforced by a cross weld seam, that extends across all plies of material; moreover, oblique weld seams may be made across the bottom corners, to allow for an easy spreading of bag, whereby a parallelepipedon shaped container, having reinforced edges, is obtained, being such container shown in the FIGS. 1 and 2 of the accompanying drawings. Same container may be made by starting either from a single sheet or from two sheets of material. Said sheet or sheets may consist of a single ply, or of two or more plies of different materials, of which at least the inner one shall be of the heat scalable type. Thus, said inner ply usually consists of a polyethylene or like plastics film. A crosssectional view, and a side elevation of such a bag, are respectively shown in the FIGS. 1 and 2 of the accompanying drawings. in particular, tWo webs are utilized as starting material for the production of bags. Two folds A and A are made on either side edges of web A, in the conventional bag-making machine, in order to obtain later the folded-in edges of the bag. The other material web, by which the bag is completed, is indicated by the letter B. In the conventional machines, the weld seams are made in the points indicated by the reference numbers 1, 2, 3 and d, i.e. all along the longitudinal edges of bag, while the bag bottom is closed by a crosswise welding seam 6. The four bottom corners of bag are possibly reinforced by oblique seams 5.

A drawback of the conventional machines consists in that a sound welding of bottom seam 6 is not always possible, due to differences in the thickness of material, whereby much material is to be scrapped, and is also impossible to Work with relatively thick webs. To explain States Patent 'ice more clearly the cause of such drawback, reference will be made to FIGS. 3 and 4, wherein the heat-sealing jaws, by which the bottom welded seam 6 in the FiG. 2 is to be made, are respectively shown in their open and closed positions. Due to the presence of the two folded-in edges, sections having different thicknesses (X in the FIG. 3), are formed by the superposition of four plies of material, while the thinner intermediate section consists of two plies only. When the welding is performed the rigid and

parallel sealing jaws

10 and 12, will exert on either end sections X a pressure higher than that exerted on the middle section. Such different thicknesses prevent the obtained welding from being uniform; indeed an unsatisfactory sealing is obtained in the most of cases, above all in the middle section, where the pressure is low.

This invention intends to obviate the above ill-effects by the provision of a method, that consists in having a strip of heat-sealable material added to the middle section of the bag bottom seam, whereby a substantially uniform thickness is encountered by the welding jaws across same seam.

In other words, the invention consists in having a strip heat-sealed, at given intervals, on the web wherefrom the bags are then formed, being the thickness of said strip such as to compensate the difference in the thickness (s in the FIG. 4) existing between the central section, and the outer sections where the folded-in edges are formed.

The equipment by which the above method is carried into practice, is an improvement and adaptation of already known machines, and is comprised of a roll, wherefrom the thickness compensating strip is unwound at intervals, a cutting device by which pro-established lengths of same strip are rhythmically cutotf, and finally a heated jaw, to which a reciprocating motion is imparted, and that is advanced for a given length along with the web with which the bag is formed, and to which said cut lengths of strip are welded.

The invention will be better understood from a consideration of the following, detailed description, taken with the accompanying drawings, wherein a number of embodiment forms thereof are shown, being both description and drawings given as not restrictive examples. In same drawings:

FIGS. 1 to 4 inclusive respectively show the bag of conventional style, and the means by which the bag bottom seam is welded.

FIG. 5 is a diagrammatic cross-section, taken in the zone of bottom welded seam of a bag, that is formed by two webs.

FIG. 6 is a diagrammatic part view of the welding jaws, while sealing a bottom seam.

FIG. 7 is a diagrammatic side elevation of the equip ment embodying the improvements according to the invention.

FIG. 8 diagrammatically shows a further part of the equipment as shown in the FIG. 7, i.e. the continuation thereof in the zone wherein the welding jaws, fitted on a carriage to which a reciprocating motion is imparted, are operating.

FIG. 9 is a diagrammatic side elevation of another embodiment form of the equipment, embodying the improvements according to the invention.

As previously stated, the invention provides for the making of bags that are wholly free from the traditional drawbacks consisting in an insufficient sealing of bottom, as a consequence of the stated differences in the thickness of material. To such a purpose, the invention proposes (see FIGS. 5 and 6) to have a strip of heat-scalable material 22 applied along the bottom seam, and namely in such a manner as to cover the section extending between the inwardly folded edges X (see FIG. 4). Said strip 22 of material is welded onto the web 23. In the considered case, the bag is completed by a second web of a plastic material 24, wherein the folded-in edges are formed, and that is superposed and welded to former web. Thus, uniform thicknesses are encountered by the heated jaws 25, while welding the bottom seam, whereby a faultless sealing of bottom is obtained.

Thus, it will be seen that the thermoplastic bag of the invention has front and rear substantially

coextensive panels

23 and 24 each provided with a pair of opposed side edges and a bottom edge, and in addition the bag has inwardly folded gussets extending inwardly from the side edges of the

panels

23 and 24 and situated between these panels, so that these gussets themselves terminate in inner side edges situated between the panels 23 and 124 inwardly of the side edges of the latter. The thicknesscompensating, heat-scalable shim 22 has a length equal to the distance between the inner side edges of the gussets, as is apparent from FIG. 5, and the thickness of the shim 22 is uniform and twice the thickness of the

sheet material

23, 24. Thus, when this heat-sealable shim 22 is situated between the

panels

23 and 24 along the bottom edges thereof and between and directly next to the inner side edges of the gussets, each of which has the width X shown in FIGS. 3 and 4, the bag will necessarily have along its entire bottom edge a uniform thickness so that the seam 6 which forms the bottom seam of the bag extending along the entire bottom end thereof will also necessarily have a uniform thickness along its entire length. The oblique scams extend obliquely across the bottom corners of the bag, at the regions of the inwardly folded gussets thereof, so as to reinforce the bag.

In the example as shown in the FIGS. 5 and 6, it has been assumed that the bag is made by two

plastics webs

23 and 24. However, it is to be understood that the invention also covers a method wherein the bag is made from a single web, as it can be seen from the FIG. 9, that shows an equipment by which such method can be carried into practice.

Referring now to FIGS. 7 and 8, 7 is the machine frame in its entirety. Revolvingly supported in said frame is the roll 27 wherefrom the strip lengths are unwound, which are to be applied onto those sections of web 23 across which the bottom beam 6 of bag shall be successively welded. By means of a ratchet gear (not shown), a pre-established length of strip, equal to required height of shim 22, is rhythmically unwound from the roll 27. Such operation is performed by a pair of unwinding rollers 28, driven by said ratchet gear. The strip 29 wherefrom the shims 22 are to be cut, is fed to a cutting machine 30, which is operated, thereby cutting the required length of strip 29, when the feed rollers 28 are at rest. The cutter blade is driven by a pneumatic piston, controlled by an electrovalve, which on turn is controlled by a microswitch. Such microswitch is operated synchronically with the bag making machine, in such a manner that a cut is made after a bag is formed. The strip 23, unwound from the roll 31also revolvingly supported by the frame 26-is led round a return roller 32, and then to drum 33, whereon the cut length 29 is laid.

Directly after the cutting station 30, a welding jaw 34 is encountered. Such jaw is designed to have the cut length of strip 29 welded onto the web 33. A to-and-from motion in respect of said out length, and thus of strip 23, is imparted to said jaw under the action of a pneumatic piston 35, that is fitted on a crank 36. Also fitted by means of suitable guides (not shown) on same crank, is the welding jaw 34. Said crank 36 is revolvingly fitted on the shaft 37 whereon the drum 33 is also fitted. Thus, an effect of the pulling action caused by the motion that is transmitted to web 23 by the driving roller 38, the welding jaw 34 is moved by a given angular amplitude while exerting its pressure against the cut length of strip 29. The pressure exerted by the roller 38 is released by an end-stroke microswitch (not shown) when the crank 36 comes into contact therewith, whereby the jaw 34 is lifted. Then, same crank 36 is brought automatically back to the position as shown in the FIG. 7 by a return spring (not shown) or by a counterweight. The above described step occurs synchronically with all other operations of machine, each time that a bag is made. In effect, the cutter piston and the piston by which the welding jaw is operated, are controlled by the electro-pneurnatic valve, which is energized by a microswitch (not shown) connected with the machine. Thus, the operation consisting in a welding of shims cut from the strip 29, onto the web 23, is rhythmically repeated. Said web 23, fitted with the shims, is then fed to driving roller 38, where the web 24, unwound from a roll 40, is superposed thereto. In more detail, the web 24, after having been unwound from the roll, is fed to a so called winding table of the conventional type, indicated in its entirety by numeral 41, and wherein either edges thereof are formed with inward folds, whereafter same web is fed to driving roller 38, where both

webs

23, 24 are joined together (see FIG. 5). Then same webs are fed by the rollers 42 to longitudinal welding jaws 43, and to transversal welding jaws 44, that are all fitted on a carriage 45 (see FIG. 8). A reciprocating motion on a base 46, in the direction of arrows Y, is imparted to same carriage. The composite web, whereon the different seams, as shown in the FIGS. 1 and 2, have been welded, is then fed by a pair of rollers 47, to a cutter, which is rhythmically operated to cut the finished bags therefrom.

The embodiment form as shown in the FIGS. 7 and 8, is comprised of devices which are for the most part of the conventional type, as e.g. the folding table 41, and the different guide and driving rollers, consisting the invention in the set made-up by the

devices

27, 28, 30 and 36. In particular, bags are made by the equipment as shown in said figures, by the use of two

webs

23 and 24 as starting material.

Conversely, by the machine shown in FIG. 9, bags are made by the use, as starting material, of a single web, that is unwound from a roll 50. The web 51 is fed to roller 33, where the shim, cut from the strip 29 that is unwound from the roll 27, is welded thereto. After said welding operation, the web 51 is fed to the conventional winding table 41, where it is converted into a fiat tubing with inwardly folded edges, and then is brought in the usual manner to conventional welding jaws. All other components of the machine are wholly similar to those of the previously described embodiment form whereby similar reference characters have been used to indicate similar or equivalent components.

While the invention has been described in detail with respect to two embodiment forms thereof only, it will be understood by those skilled in the art, after understanding the invention, that various changes and modifications may be made, without departing from the spirit and scope of the invention, and is intended, therefore, to cover all such changes and modifications in the appended claims.

What I claim is:

1. A thermoplastic bag comprising front and rear coextensive panels each having a pair of opposed side edges and a bottom edge, and a pair of inwardly folded gussets extending inwardly from said side edges of said panels and situated therebetween, said gussets extending along said side edges of said panels to said bottom edges thereof, and means situated at said bottom edges between said panels for compensating for the thickness of said gussets and providing a bottom seam of uniform thickness extending along the entire length of said bottom edges of said panels.

2. The combination of claim 1 and wherein said means is an elongated thickness-compensating shim of heatsealable material situated between said panels along said bottom edges thereof and heat-sealed to said panels.

3. The combination of claim 2 and wherein said gussets themselves have inner side edges situated between, said panels at a given distance from each other, said shim having a length substantially equal to said distance and having a pair of opposed ends respectively situated direct- 5 1y next to said edges of said gussets, said shim having a uniform thickness equal to the total thickness of each gusset.

4. The combination of claim 3 and wherein said panels and gussets are all made of a sheet material of a given thickness, and said shim having a thickness which is twice said given thickness.

5. The combination of claim 1 and wherein said bottom edges of said panels intersect said side edges thereof at a pair of opposed bottom corners of the bag, and a pair of oblique reinforcing seams extending across said bottom corners in the regions of said gussets.

6. The combination of claim 1 and wherein said gnssets are integral extensions of at least one of said panels.

UNITED STATES PATENTS 3,143,277 8/1964 La Fleur 229-57 3,145,907 8/1964 Schwinger 22953 FOREIGN PATENTS 1,055,074 10/1953 France.

DAV ID M. BOCKENEK, Primary Examiner.