Manufacturing method of a bag with a bottom gusset

Abstract

To provide a method for simultaneously manufacturing two left and right bags by using a single web-like sheet as a raw material when manufacturing a bag with a bottom gusset.SOLUTION: A method for simultaneously producing two bottom gusseted bag bodies from web-like sheets 21 simultaneously includes the following steps: a connecting process for forming a tubular sheet 22 with a central pseudo-adhesive portion 27, by bringing both overlapping portions 25 on the left and right sides of the web-like sheet 21 close to each other and heat-sealing them at their central positions while transporting the web-like sheet 21; a bottom gusset process to form bottom gazettes on both the left and right sides of the tubular sheet 22; and a central cutting process to separate the tubular sheet 22 into two pieces on the left and right at the position including the central pseudo-adhesive section 27.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a bottom gusseted bag. [Background technology]

[0002] A bag with a bottom gusset, which has a gusset at the bottom, is known as one type of bag that is commonly used today. As a manufacturing method thereof, a sheet formed in advance into a cylindrical shape is used, and the bottom gusset is formed on the left and right sides of the cylindrical sheet, which is then cut into left and right parts to simultaneously manufacture two bags, one for the left and one for the right, as disclosed in Patent Documents 1 and 2.

[0003] In these Patent Documents 1 and 2, a known bag making machine is used to send a web-like sheet to a production line that is moved by a conveyer or the like, and the left and right sides are folded inward to form a bottom gusset, and it is disclosed that, although a single sheet can be used as the web-like sheet, it is preferable to use a cylindrical one for ease of forming. However, these documents do not disclose what manufacturing method should be used when a single sheet is used as the web-like sheet. Also, Patent Document 3 discloses that a cylindrical web-like sheet is manufactured by processing a long bag-like member wound into a roll, which is a commercially available product sold by a raw material processor, but does not disclose the use of a single sheet as the web-like sheet. Patent Document 4 describes a method for manufacturing two bags, in which the left and right sides of a web-like sheet forming the bag are brought close to each other and overlapped (Fig. 6 of Patent Document 4) or butted together without overlapping (Fig. 7 of Patent Document 4), and then a bottom gusseting process is performed to form bottom gussets on the left and right sides of the tubular sheet without joining and fixing the both sides at the center. Note that although vertical seals 9, 9' are shown in Figs. 6 and 7 of Patent Document 4, these vertical seals 9, 9' are applied after the bottom gusseting process, and at the stage of the bottom gusseting process, the left and right sides of the web-like sheet brought close to each other at the center are not connected to each other, and if the web-like sheet is pulled to the left and right, they will easily move apart. However, in the bottom gusset process, a pair of left and right folding members 42, 42 are inserted from both the left and right ends in a pushing manner to fold the sheet, and in this process, a pulling force is applied to the web-like sheet from both the left and right sides. As a result of the pulling force being applied to the web-like sheet in this manner, the left and right overlapping portions of the web-like sheet, which are not joined and fixed but are merely brought close to each other by overlapping at the center, are prone to misalignment, and there is a risk that the dimensions and shape of the bag will not be stable. In response to this, the applicant of the present application applied for and obtained a patent for a manufacturing method in which a separate connecting tape is placed in the center and the left and right overlapping portions of the web-like sheet are joined and fixed together via this connecting tape, thereby smoothly carrying out the bottom gusseting process and stabilizing the dimensions and shape of the bag body, as shown in Patent Document 5. This connecting tape does not remain in the completed bag body itself because the above-mentioned center position including the connecting tape is cut away by the time the bag body is completed, but if the connecting tape or the web-like sheet meanders, there is a risk that a part of the connecting tape, such as a scrap of the connecting tape, may become mixed in with the inside of the completed bag body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5818121 [Patent Document 2] Patent No. 5784872 [Patent Document 3] Patent No. 3928949 [Patent Document 4] Japanese Patent Application Publication No. 58-102747 [Patent Document 5] Patent No. 6121039 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to provide an efficient manufacturing method that can accurately manufacture two bags with bottom gussets, one on the left and one on the right, while fundamentally eliminating the disadvantages associated with joining tape, when using a single web-like sheet as the raw material and simultaneously manufacturing two bags with bottom gussets, one on the left and one on the right. [Means for solving the problem]

[0006] The present invention includes a connecting step in which the longitudinal direction of a web-like sheet forming a bag is set as the transport direction, while both overlapping portions on the left and right sides of the web-like sheet are brought closer to each other to form a tubular sheet having a central joint portion at the center position of the web-like sheet; and a bottom gusset step in which bottom gussets are formed on both the left and right sides of the tubular sheet. The present invention relates to a method for manufacturing a bag with a bottom gusset, which produces two bags, one for the left and one for the right, by including a central cutting process of separating the tubular sheet into two pieces, one for the left and one for the right, at a position including the central joint, wherein the connecting process involves overlapping the two overlap portions of the web-like sheet one above the other, and directly contacting the outer surface of one overlap portion with the inner surface of the other overlap portion, thereby pseudo-bonding them by heat sealing to form a central pseudo-bonded portion as the central joint, and the central cutting process involves cutting the tubular sheet into two pieces, one for the left and one for the right, with a width that includes the central pseudo-bonded portion.

[0007] The web-like sheet is composed of at least two layers, an inner surface having a sealant layer and an outer surface not having the sealant layer, and the central pseudo-adhesive portion can be implemented as a pseudo-adhesive having an adhesive strength lower than that of a heat seal formed by overlapping sealant layers.

[0008] The connection process may include an overlapping step of forming an unconnected tubular sheet by overlapping the two overlap portions vertically at the central position of the web-like sheet, and a temporary sealing step of pseudo-adhering the overlap portions of the tubular sheet by heating the overlap portions of the tubular sheets in the thickness direction.

[0009] The bottom gusset process is carried out following the connection process, and is a process in which both the left and right sides of the tubular sheet are gradually folded inward using a width-alignment roller and an insertion roller arranged downstream of the width-alignment roller. The width-alignment rollers are arranged on both the left and right sides of the tubular sheet, and the distance between the left and right width-alignment rollers is set to be smaller than the left and right width of the tubular sheet in the upstream connection process. The width-alignment rollers guide the tubular sheet so that the distance between the upper and lower sheets gradually increases, and the left and right sides that become the gussets gradually rise up, thereby reducing the left and right width of the tubular sheet. The left and right gussets that have risen up are then folded inward by the insertion roller.

[0010] The insertion rollers include a first insertion roller and a second insertion roller arranged at at least two locations spaced apart along the longitudinal direction of the tubular sheet, the first insertion roller and the second insertion roller being disc-shaped rollers arranged on both the left and right sides of the tubular sheet, the first insertion roller having a greater top and bottom thickness than the second insertion roller, and the distance between the left and right first insertion rollers being greater than the distance between the second insertion rollers, so that the left and right gussets raised by the width adjustment rollers are gradually folded inward. Effect of the Invention

[0011] The present invention aims to provide an efficient manufacturing method that uses a single web-like sheet as the raw material and can accurately manufacture two bags with bottom gussets, one on the left and one on the right, while fundamentally eliminating the disadvantages caused by the joining tape. This has enabled the manufacturing process to be simplified while improving the stability of quality. [Brief description of the drawings]

[0012] [Figure 1] 1A and 1B show a bag body that can be manufactured by a manufacturing method according to an embodiment of the present invention, in which (A) is a front view and (B) is a longitudinal sectional view. [Diagram 2] 1 is a plan view of an apparatus used to carry out a manufacturing method according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a side view of an apparatus used to carry out the manufacturing method according to the embodiment of the present invention. [Figure 4] 1A and 1B are explanatory diagrams showing a side view and a plan view of a bottom gusset processing section in an apparatus used to carry out a manufacturing method according to an embodiment of the present invention, respectively. [Diagram 5] FIG. 4 is a plan view of another main part of the apparatus used to carry out the manufacturing method according to the embodiment of the present invention. [Figure 6] FIG. 1 is a first explanatory diagram of a manufacturing method according to an embodiment of the present invention. [Figure 7] FIG. 2 is a second explanatory diagram of the manufacturing method according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (About the bag) The manufacturing method of the present invention can be applied to the manufacture of bags having various types of bottom gussets, but as a typical example, a bag 11 shown in Figs. 1(A) and (B) will be described. This bag 11 is formed of a sheet 12 made of a simple thermoplastic synthetic resin or a composite of thermoplastic resin, metal foil, paper, and other materials. This bag 11 has an open top 13 and a bottom 14 on which a bottom gusset 15 is formed, and both left and right sides are closed by side seals 16. The bottom gusset 15 is formed by folding the sheet 12 inwardly along a center crease 18, and the center crease 18 is stretched during use to widen the bottom surface of the bag. A bottom seal 17 is formed along the bottom edge of the bottom 14 as necessary, and a diagonal seal 19 may be further formed to stabilize the boat-shaped shape of the widened bottom 14. Although a cup-shaped curved diagonal seal 19 is shown in Fig. 1(A), various other shapes, such as a straight line, may be used. The top portion 13 may be open, may be closed by a seal or the like, or may be provided with an openable and closable zipper.

[0014] 1(B), the sheet 12 of the bag body 11 has a sealant layer 24 disposed on the inner surface of the bag, and the outer surface is not heat-sealed at the heat-sealing temperature of the sealant layer 24. Therefore, the seals 16, 17, and 19 are formed by heat sealing between opposing sealant layers 24. The completed bag body 11 will be described with the top portion 13 at the top and the bottom portion 14 at the bottom, but in the manufacturing process described below, the top portion 13 and the bottom portion 14 will be described as being positioned on the left and right.

[0015] (Overview of the manufacturing process) The manufacturing process of this embodiment involves simultaneously producing two bag bodies 11, one on the left and one on the right, from a single web-like sheet 21, which is the raw material, and includes a connecting process, a bottom gusset process, and a center cutting process, as well as a bottom sealing process, a side sealing process, and a side cutting process.

[0016] The connecting step is performed using a web-like sheet 21 having a width sufficient to form two bags 11. The bag 11 is manufactured so that the up-down direction in Fig. 1 corresponds to the left-right direction (width direction) of the web-like sheet 21 in Fig. 2. In this joining step, the web-like sheet 21 is transported in its longitudinal direction, in the direction indicated by the downward arrow, and during this transport, a laminating step and a temporary sealing step are carried out. In the overlapping step, during this transport, the overlapping portions 25 on both the left and right sides in the transport direction are brought close to each other, and a cylindrical sheet 22 is formed in which the overlapping portions 25, 25 are overlapped vertically at the center position of the web-like sheet 21 and are not connected. Next, in the temporary sealing step, the overlap portions 25, 25 of the tubular sheet 22 are heated in the thickness direction (vertical direction) to pseudo-bond the overlap portions 25, 25 to each other, thereby forming a tubular sheet 22 having a central pseudo-bonded portion 27.

[0017] The bottom gusset process is a process in which the bottom gusset 15 is formed on both the left and right sides of the tubular sheet 22 by the bottom gusset processing section 53. The bottom sealing step is a step of forming a bottom seal 17 on the bottom edge of the bottom gusset 15, and this step can be performed as necessary.

[0018] The side sealing step is a step in which the continuous tubular sheet 22 is heat-sealed at predetermined intervals in the longitudinal direction to form side seals 16 and, if necessary, oblique seals 19 . The central cutting step is a step of dividing the tubular sheet 22 into two, left and right pieces, at the central cutting position 28 including the central pseudo-adhesive portion 27.

[0019] The side cutting step is a step of cutting the continuous tubular sheet 22 in the longitudinal direction at predetermined intervals to separate it into individual bags 11. In addition, the web-like sheet 21 refers to a sheet in a state in which both left and right overlapping portions 25 in the transport direction are brought close to each other, and the tubular sheet 22 refers to a sheet in a state in which both left and right overlapping portions 25 in the transport direction are brought close to each other, regardless of whether the overlapping portions 25 are adhered to each other or not.

[0020] (About the device overview) Next, an outline of a manufacturing apparatus for carrying out the above-mentioned manufacturing steps will be described with reference to FIGS. In this manufacturing apparatus, the longitudinal direction of the web-like sheet 21 is intermittently or continuously transported from upstream to downstream, while two bags 11, one on the left and one on the right, are simultaneously produced from a tubular sheet 22. In addition, in FIG. 2, which is a plan view, the upstream side is depicted as the upper side and the downstream side is depicted as the lower side of the figure, and in FIG. 3, which is a side view, the upstream side is depicted as the left side and the downstream side is depicted as the right side of the figure.

[0021] In this manufacturing apparatus, from upstream to downstream, a pre-processing roll 42, a first table 43, a feed adjustment section 44, and a second table 45 are arranged, with an upstream plate 47 arranged on the first table 43 and a downstream plate 48 arranged on the second table 45. Furthermore, a central heating section 52 is arranged on the second table 45 and the downstream plate 48. Downstream of the second table 45 and the downstream plate 48, a bottom gusset processing section 53, a bottom seal heating section 54, a side seal heating section 55, a central cutting section 56, and a side cutting section 57 are arranged in this order.

[0022] (About the connection process) Next, each step and the equipment therefor will be described in the order of steps. First, the connecting step is a step of connecting both overlapping portions 25 of the web-like sheet 21 to form the central pseudo-adhesive portion 27, and involves sequentially carrying out an overlapping step and a temporary sealing step. The unprocessed web-like sheet 21 is set in the device in a wound state as a pre-processed roll 42, and is unwound downstream, where a superposition step is performed on a first table 43, and a temporary sealing step is performed on a second table 45 downstream of the first table 43, sandwiched between a feed adjustment section 44.

[0023] The sheets (web-like sheet 21 and cylindrical sheet 22) are fed continuously or intermittently by the rotation of feed rollers (not shown) arranged across the sheets and sandwiching the sheets from above and below. In this example, the sheets are fed continuously upstream of the feed adjustment unit 44 and intermittently downstream, and the difference between the two feed rates is adjusted by the feed adjustment unit 44 using a dancer roller or the like. The position and number of the feed rollers can be changed in various ways depending on the length of the line and the properties of the sheets to be fed. For example, a feed roller that rotates continuously can be provided downstream of the upstream plate 47, and a feed roller that rotates intermittently can be provided at the end of the line (specifically, a position between the center cutting unit 56 and the side cutting unit 57 described later). Alternatively, a feed roller that rotates intermittently can be provided in the middle of the line, for example, in the bottom seal heating unit 54 described later.

[0024] (Layering step: Figure 2, Figure 6(A)) The overlapping step is a process of bringing both left and right overlapping margins 25 of the web-like sheet 21 closer to each other in the width direction. Through this process, the web-like sheet 21 becomes a cylindrical sheet 22, but at this stage, both overlapping margins 25 are not connected to each other. In the overlapping step, an upstream plate 47 arranged on the first table 43 is used to place the center of the web-like sheet 21 between the upper surface of the first table 43 (not shown in FIG. 6) and the lower surface of the upstream plate 47, and the left and right overlapping margins 25 of the web-like sheet 21 are folded over the upper surface of the upstream plate 47 to bring them closer to each other.

[0025] The upstream plate 47 has a generally rectangular shape in a plan view, and as the web-like sheet 21 is sent downstream with a predetermined tension, the left and right overlap margins 25 naturally bend with respect to the left and right sides of the upstream plate 47. As shown in FIG. 2, the upstream plate 47 is disposed on the table 45 so as to be suspended from above by a support member 49 on its upstream side, and while there is a small gap between its upstream end and the table 45, its downstream end is in contact with the table 45. When the web-like sheet 21 is passed through in this state, the center of the web-like sheet 21 naturally passes under the upstream plate 47. In this state, the downstream end of the upstream plate 47 is raised by the thickness of the web-like sheet 21. In this overlapping step, the adjacent left and right overlapping portions 25 of the web-like sheet 21 are overlapped vertically (in the thickness direction).

[0026] (Temporary sealing step: Figure 4, Figure 6 (B) (C)) In this state, the cylindrical sheet 22 passes through the feed adjustment unit 44 and is fed downstream thereof, where the temporary sealing step is performed on the second table 45 . Specifically, the vertically overlapping overlaps 25 are heat-sealed between the downstream plate 48 and the central heating section 52 disposed at the center of the second table 45 in the left-right direction to form the central pseudo-bonded section 27 (FIG. (C)). The relationship between the second table 45 and the downstream plate 48 is the same as the relationship between the first table 43 and the downstream plate 47 described above, and the downstream plate 48 is suspended from above by a support member 50. When passing through the support member 50, the left and right overlaps 25 open slightly (FIG. 6 (B)), but return to their original overlapped state after passing through, and the vertically overlapping overlaps 25 are heated between the downstream plate 48 and the central heating section 52 and pseudo-bonded by the central heating section 52.

[0027] As shown in FIG. 1(B), the sheet 12 of the bag body 11 is a sheet having a sealant layer 24 disposed on the inner side of the bag. When the sheet 12 is in the form of a web-like sheet 21 before being formed into a cylindrical shape, the sealant layer 24 is disposed on the upper surface of the sheet and is supplied. When the sheet 22 is formed into a cylindrical sheet 22, the sealant layer 24 is located on the inner side, but the outer side is not heat-sealed at the heat-sealing temperature of the sealant layer 24. Therefore, when the outer surface of one overlapping portion 25 and the inner surface of the other overlapping portion 25 are directly in contact with each other and heat-sealed from above and below by the central heating portion 52, a pseudo-adhesion with a smaller adhesive strength than heat-sealing with the sealant layers 24 in contact with each other is formed, and a central pseudo-adhesion portion 27 is formed as a central joint portion.

[0028] (Bottom gusset process: Fig. 4, Fig. 6(D)) Next, a bottom gusset processing section 53 performs a bottom gusset process to form a pair of left and right bottom gussets 15 on the tubular sheet 22 whose center is temporarily bonded at the central pseudo-bonding section 27 . In the manufacturing method of Patent Document 5, a freely rotatable disk-shaped insertion roller is disposed on both the left and right sides of a cylindrical sheet, and the cylindrical sheet is fed, so that both the left and right sides of the cylindrical sheet are pressed into the pair of left and right insertion rollers and folded inward to form a central crease. In this case, a considerable tension is applied to the cylindrical sheet from both the left and right sides by the insertion rollers. In this conventional manufacturing method, in order to counter the tension, the above-mentioned connection tape is used to completely heat seal the sheet, thereby obtaining sufficient adhesive strength, and even if a large tension is applied, the central joint of the connection tape is prevented from coming off, causing the sheet to shift and spread to both the left and right sides. However, in the present invention, a connection tape is not used as the central joint, and a central pseudo-adhesive portion 27 with a relatively small adhesive strength is formed. Therefore, by taking measures to reduce the tension applied to the sheet from the insertion roller, the central joint can be prevented from coming loose, causing the sheet to shift and spread to both sides.

[0029] (Methods for reducing tension: Fig. 4) A specific example of the bottom gusset processing unit 53 that employs a means for reducing the above-mentioned tension will be described with reference to FIG. 4. The bottom gusset processing unit 53 in this example includes a width-shifting roller 61 and an insertion roller (first insertion roller 62 and second insertion roller 63) disposed downstream of the width-shifting roller 61, and gradually folds both the left and right sides of the tubular sheet 22 inward to prevent a large tension from being suddenly applied to the tubular sheet 22. At that time, since the tubular sheet 22 is in a vertically expanded state, it is also preferable to arrange upper and lower rollers 64 upstream of the width-shifting roller 61 to sandwich the tubular sheet 22 from above and below, thereby stabilizing the tubular sheet 22 in the bottom gusset process. In addition, a driving upper and lower roller 65 is disposed downstream of the second insertion roller 63, and is implemented so as to rotate intermittently while sandwiching the tubular sheet 22 from above and below to feed it, but it may be implemented by a driven roller that does not rotate by its own force. The upper and lower rollers 64, the width adjustment roller 61, the first insertion roller 62 and the second insertion roller 63 are implemented as driven rollers that are simply rotatable but do not rotate under their own power, but they may also be implemented as drive rollers that rotate themselves by a drive device.

[0030] The width-shifting rollers 61 are rollers whose rotation axes are arranged vertically, and a pair are arranged on both the left and right sides of the tubular sheet 22. The distance between the left and right width-shifting rollers 61 is set to be smaller than the left and right width of the tubular sheet 22 in the upstream process (the temporary sealing step in which the central pseudo-adhesive portion 27 is formed). Between the upper and lower rollers 64 and the width-shifting rollers 61, the distance between the upper and lower sheets of the tubular sheet 22 gradually increases, and the left and right sides that become the gussets 26 gradually rise up, and the left and right width of the tubular sheet 22 decreases accordingly.

[0031] The raised left and right gussets 26 are folded inward by the insertion roller. In this example, the insertion rollers are two disk-shaped rollers, a first insertion roller 62 and a second insertion roller 63, which are arranged on both the left and right sides of the cylindrical sheet 22, and the bottom gusset 15 is gradually and smoothly folded in, thereby forming the middle crease 18 smoothly while suppressing the sudden application of tension. In this example, the first insertion roller 62, which has a relatively large thickness from top to bottom and a relatively small diameter and has a generally elliptical cross section, is arranged immediately downstream of the width adjustment roller 61, so that the raised left and right gussets 26 are folded inward slightly. This allows the folding to begin while suppressing a sudden increase in tension, and the suppression effect is further enhanced by making the outer circumferential edge of the first insertion roller 62 rounded. The second insertion roller 63 is configured as a thin plate-like disk with a relatively large diameter and a relatively small thickness from top to bottom compared to the first insertion roller 62, and its outer periphery has a clear edge so as to crease the center crease line 18 in the bottom gusset 15. The distance between the second insertion roller 63 and the first insertion roller 62 is set to be larger than the distance between the first insertion roller 62 and the width adjustment roller 61, and the distance between the left and right second insertion rollers 63 is set to be shorter than the distance between the left and right first insertion rollers 62.

[0032] (Bottom sealing process: Figure 5, Figure 7(A)) Next, a bottom seal 17 is formed on both the left and right sides of the tubular sheet 22 by a bottom sealing process. Specifically, bottom seal heating units 54 are disposed on both the left and right sides of the tubular sheet 22 to sandwich the tubular sheet 22 from above and below, thereby heating and heat sealing the tubular sheet 22. At this time, as shown in Fig. 1(B), the sealant layers 24 on the inner surfaces are welded together, but the lower ends of the bifurcated bottom gusset 15 are not sealed together.

[0033] (Side sealing process: Figure 5, Figure 7(B)) Next, a side seal 16 is formed across the tubular sheet 22 by a side sealing process. Specifically, a side seal heating unit 55 is disposed in a direction perpendicular to the longitudinal direction of the tubular sheet 22, and the tubular sheet 22 is heat-sealed by being sandwiched from above and below and heated. At this time, as shown in FIG. 1(B), the sealant layers 24 on the inner sides of the sheets 12 that form the front and back surfaces of the bag body 11 are welded together, but the lower ends of the bifurcated bottom gusset 15 are not sealed together. In addition, a diagonal heating section for forming the diagonal seal 19 can be provided together with the side seal heating section 55, but it is also possible to form the diagonal seal 19 in a separate process, or to perform the process without forming the diagonal seal 19.

[0034] Furthermore, the bifurcated bottom gussets 15 can be joined together at the side seals 16 on the left and right sides of the bag as necessary. Specifically, a bottom punch section (not shown) is formed at the position of the side seal 16 at a position upstream of the bottom gusset processing section 53 (more specifically, at a position between the bottom gusset processing section 53 and the central heating section 52). This bottom punch section (not shown) is formed in a portion corresponding to the inner sheet of the gusset sandwiching the center crease line 18. Therefore, when forming the side seal heating section 55 described later, the inner sheet of the gusset is no longer present in the bottom punch section (not shown), and the sealant layers 24 of the outer sheets come into direct contact with each other. As a result, the bifurcated bottom gussets 15 can be bonded together. Each of the above-mentioned sealing steps can be completed with a single heating step, but the reliability of the seal can be increased by performing the steps two or three times. Heat sealing can be performed according to a conventional method, and if necessary, a cooling section can be provided following each heating section to cool the heat-sealed area.

[0035] (Center cutting process: Figure 5, Figure 7(C)(D)) Next, in a central cutting step, the tubular sheet 22 is separated into two left and right pieces by cutting or the like at the central cutting position 28 including the central pseudo-adhesive portion 27. Specifically, a central cutting portion 56 is disposed in the center of the tubular sheet 22, and a pair of left and right blades provided at this central cutting portion 56 cuts the tubular sheet 22 on both the left and right sides of the central pseudo-adhesive portion 27. The distance between the pair of left and right blades may be set to a dimension that is approximately equal to or slightly larger than the width of the central pseudo-adhesive portion 27 (a dimension that does not cause cutting errors, taking into account the meandering of the tubular sheet 22).

[0036] In addition, the cylindrical sheet 22 is fed intermittently, and if it is to be cut while the feeding is stopped, it is appropriate to use a blade with a length that can cut a length of about the bottom 14 of the bag body 11. If it is to be cut during the feeding operation (movement), the length of the blade of the central cutting portion 56 is not required, and the cylindrical sheet 22 can be cut in its longitudinal direction by the movement of the cylindrical sheet 22. In addition to cutting with a blade, cutting may be performed by applying various physical energies other than a blade, such as heat. By this cutting, the cylindrical sheet 22 is separated into two parts, left and right, and each of the parts forms a bag body 11.

[0037] (Side cutting process: Figure 5, Figure 7(D)) Finally, in a side cutting process, the tubular sheet 22 is cut in the width direction at a position including the side seal 16 to separate it into individual bags 11. Specifically, a side cutting section 57 is disposed so as to cross the tubular sheet 22 which is divided into left and right halves, and a blade provided in this side cutting section 57 cuts the tubular sheet 22 above the side seal 16. Note that cutting may be performed by applying other energy such as temperature, in addition to cutting using a blade.

[0038] (Example of change) As described above, in the present invention, two bag bodies 11, one for the left and one for the right, can be continuously manufactured from a single web-like sheet 21 without using a connecting tape, and the present invention should not be understood as being limited to the above-described embodiment, but can be implemented in various modifications as long as they are not contrary to the spirit of the present invention.

[0039] For example, in the above example, the web-like sheet 21 to the bag body 11 are manufactured continuously on a single line, but the overlapping step and the steps after the temporary sealing step can be manufactured on different lines, or the product can be shipped in a processed state up to the side sealing step or center cutting step, and the center cutting step or side cutting step and after can be performed at the manufacturing site of the bag body 11. In this way, the process can be carried out on multiple lines.

[0040] In addition, when feeding intermittently, it is sufficient to feed the length of one bag body 11 as one pitch, but by providing multiple heating means and cutting means required for each processing, it is also possible to feed the length of two or more bag bodies 11 as one pitch. It should be noted that the diagrams shown in this application are conceptual diagrams for illustrating the arrangement of each process, and when implementing the present invention, the overall length of the line as well as the length of the line required for each process can be changed in various ways. Furthermore, as long as this does not go against the spirit of the present invention, the order of each process or step can be changed or some of them can be omitted. [Explanation of symbols]

[0041] 11 Bag body 12 sheets 13 Heaven 14 Bottom 15 Bottom gusset 16 Side seal 17 Bottom seal 18 Center fold 19 Diagonal Seal 21 Web-like sheet 22 Cylindrical sheet 24 Sealant Layer 25 Overlap 27 Central pseudo-adhesive section 26 Gore 28 Center cutting position 42 Unprocessed roll 43 Table 1 44 Feed adjustment section 45 Table 2 47 Upstream Plate 48 Downstream Plate 49 Support member 50 Support member 52 Central heating section 53 Bottom gusset processing section 54 Bottom seal heating section 55 Side seal heating section 56 Center cut 57 Side cut 60 Bottom gusset processing section 61 Width adjustment roller 62 First Insertion Roller 63 Second Insertion Roller 64 Upper and lower rollers 65 Drive upper and lower rollers

Claims

1. a connecting step of moving the web-like sheet forming the bag body in the longitudinal direction as a moving direction, while bringing both overlapping portions on the left and right sides of the web-like sheet closer to each other, thereby forming a tubular sheet having a central joint portion at the center position of the web-like sheet; a bottom gusset process for forming bottom gussets on both the left and right sides of the cylindrical sheet; and a center cutting step of dividing the tubular sheet into two left and right bags at a position including the center joint, thereby manufacturing two left and right bags, The connecting step includes overlapping the two overlap portions of the web-like sheet one above the other, and pseudo-bonding the overlap portions by heat sealing in a state where an outer surface of one overlap portion is in direct contact with an inner surface of the other overlap portion to form a central pseudo-bonded portion as the central joint portion, The connecting step includes a stacking step of forming an unconnected cylindrical sheet in a state where the overlapping portions are stacked vertically at the center position of the web-like sheet, and a temporary sealing step of heating the overlapping portions of the cylindrical sheet from a thickness direction of the web-like sheet to pseudo-adhere the overlapping portions, The central cutting step is a step of cutting the tubular sheet into two pieces, one at a left side and one at a right side, with a width including the central pseudo-adhesive portion, The bottom gusset process is carried out after the connection process, The bottom gusset process is a process of gradually folding inward both the left and right sides of the cylindrical sheet using a width-aligning roller and an insertion roller disposed downstream in the conveying direction, The width-adjusting rollers are disposed on both the left and right sides of the cylindrical sheet, A distance between the left and right width adjustment rollers is set to be smaller than a left and right width of the cylindrical sheet in the upstream connecting step, The width adjustment roller guides the cylindrical sheet so that the interval between the upper and lower sheets gradually increases, and the left and right sides that form the gussets gradually rise up, thereby reducing the left and right width of the cylindrical sheet, The method for manufacturing a bag with a bottom gusset is characterized in that the left and right gussets that have been raised are folded inward by the insertion roller.

2. The web-like sheet is composed of at least two layers, an inner surface having a sealant layer and an outer surface not having the sealant layer, 2. The method for manufacturing a bag with a bottom gusset according to claim 1, wherein the central pseudo-bonded portion is a pseudo-bond having a bonding strength lower than that of a heat seal formed by overlapping sealant layers.

3. The insertion rollers include a first insertion roller and a second insertion roller arranged at at least two positions spaced apart along the longitudinal direction of the cylindrical sheet, The first insertion roller and the second insertion roller are disc-shaped rollers arranged on both the left and right sides of the cylindrical sheet, The first insertion roller has a larger thickness from top to bottom than the second insertion roller, The distance between the first insertion rollers on the left and right sides is greater than the distance between the second insertion rollers, 3. The method for manufacturing a bag with a bottom gusset according to claim 1, wherein the left and right gussets raised by the width adjustment rollers are gradually folded inward. 2

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