Manufacturing method for synthetic resin film cover

Abstract

To provide a method for manufacturing a synthetic resin cover (1) that can form a weld line at a precise position, (4) does not require relatively complicated opening steps during use, and (3) has good manufacturing efficiency.SOLUTION: After folding both sides of a tubular synthetic resin film 20 inward in the width direction to form a pair of folded portions 20a and 20b, each of non-folded portions 20c-1 and 20c-2 is welded to each of the pair of folded portions 20a and 20b to form weld lines 6a and 6b, and then fold valley lines 20a-1 and 20b-1 of each of the pair of folded portions 20a and 20b are cut.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a cover made of a synthetic resin film, which has laminated portions formed by folding from the front surface to the back surface on both side portions, and has welded lines formed by welding the non-folded portion and the folded portion disposed at both longitudinal ends of such laminated portions.

Background Art

[0002] For example, as a tray for storing and transporting containers containing food products such as confectionery bread, precision instruments, industrial products such as electronic component substrates, or chemical products, a box-shaped tray having a rectangular parallelepiped shape as a whole and an open upper surface is widely used in practice. Usually, flanges projecting outward from the upper ends of both side walls and both end walls are formed on the upper surface of the tray. And, as disclosed in Patent Document 1 below, a tray cover made of a synthetic resin film for covering the upper surface of a tray containing food products or the like has also been proposed and is in practical use. This tray cover made of a synthetic resin film has laminated portions formed by folding from the front surface to the back surface on both side portions, and has welded lines formed by welding the non-folded portion and the folded portion disposed at both longitudinal ends of the laminated portions. Such a cover is attached to the tray by engaging pocket-shaped portions defined inside the welded lines disposed on both side portions of one end of the cover with the flange corners existing on both sides of one end of the upper surface of the tray, then extending the cover along the upper surface of the tray, and engaging pocket-shaped portions defined inside the welded lines disposed on both side portions of the other end of the cover with the flange corners existing on both sides of the other end of the upper surface of the tray, thereby covering the open upper surface of the tray.

[0003] As described above, the cover of the above-described form has been conventionally manufactured by folding a synthetic resin film extended in a rectangular shape from the front surface to the back surface on both side portions to form a laminated portion by laminating the non-folded portion and the folded portion, and then disposing welded lines by welding the non-folded portion and the folded portion at both longitudinal ends of the laminated portion, as also disclosed in Patent Document 1 below.

[0004] Incidentally, the applicant of the present application has previously filed an application for an invention that improves the manufacturing method of the cover as described above, and such application has already been patented (Patent Document 2 below). The manufacturing method shown in Patent Document 2 below includes a preparation step of preparing an elongated tubular synthetic resin film, and after the preparation step, a folding step of folding at least one side portion of the tubular synthetic resin film inward in the width direction to form a folded portion, and after the folding step, a cutting step of cutting the folding valley line of the folded portion to form a laminated portion, and after the folding step, a welding step of welding the folded portions at intervals in the longitudinal direction to form the welding line.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the manufacturing method shown in Patent Document 2 above, (1) since the welding step is performed after the cutting step, the posture of the film after the cutting step is not stable, and there is a risk that the position of the welding line may shift, (2) since the manufactured cover has a folded portion, it must be opened during use, and the usability is not good, (3) since only one cover is obtained by performing all the steps, the manufacturing efficiency is not good, and there are problems to be solved.

[0007] The present invention has been made in view of the above facts, and its main technical problem is to provide a novel and improved method in which the above problems existing in the conventional method of manufacturing a synthetic resin cover are solved.

Means for Solving the Problems

[0008] As a result of intensive studies, the inventors of the present invention have found that, after folding both sides of a tubular synthetic resin film inward in the width direction to form a pair of folded portions, welding lines are formed by welding, at intervals in the longitudinal direction, the non-folded portions and the respective folded portions on both longitudinal sides, and then, by cutting the fold valleys of each of the pair of folded portions, the above-described main technical problem can be achieved.

[0009] That is, according to the present invention, as a method for achieving the above-described main technical problem, there is a laminated portion in which both side portions are folded from the front surface toward the back surface and the non-folded portion and the folded portion are laminated, and welding lines obtained by welding the non-folded portion and the folded portion are disposed at both longitudinal ends of the laminated portion in the longitudinal direction, and a method for manufacturing a cover made of a synthetic resin film is provided. A preparation step of preparing an elongated tubular synthetic resin film; After the preparation step, a folding step of folding both side portions of the tubular synthetic resin film inward in the width direction to form a pair of folded portions; After the folding step, at intervals in the longitudinal direction on both longitudinal sides, the non-folded portion on the upper surface side and the upper surface side folded portion on the upper surface side of the fold valley line in each of the pair of folded portions, and the non-folded portion on the lower surface side and the lower surface side folded portion on the lower surface side of the fold valley line in each of the pair of folded portions are welded to form the welding lines, respectively, in a welding step; After the welding step, a cutting step of cutting the fold valley line of each of the pair of folded portions; A method characterized by including the above steps is provided.

[0010] Preferably, in the welding step, the upstream welding line in the cover synthetic resin film located on the downstream side and the downstream welding line in the cover synthetic resin film located on the upstream side are formed simultaneously, and after the cutting step, a separation step is included in which the tubular synthetic resin film is cut across the entire width direction between the upstream welding line and the downstream welding line. In the welding step, the upstream welding line located on the upstream side of the cover synthetic resin film and the downstream welding line located on the downstream side are formed simultaneously, and after the cutting step, it is preferable to include a separation step in which the upstream welding line in the cover synthetic resin film located on the downstream side and the downstream welding line in the cover synthetic resin film located on the upstream side are cut across the entire width direction.

Advantages of the Invention

[0011] According to the method of the present invention, the cutting step is performed after the welding step, that is, when performing the welding step, the synthetic resin film is still tubular, so the posture of the synthetic resin film when performing the welding step is stable, and the welding line can be formed at an accurate position. Furthermore, since there are two covers obtained by performing all the steps, the manufacturing efficiency is good. Also, when the manufactured cover is applied to a tray, the surface of the cover facing the food products or the like stored in the tray is defined by the inner surface rather than the outer surface exposed to the outside of the tubular synthetic resin film, so it is possible to prevent dust or the like from being adsorbed to such a surface as much as possible. Furthermore, since it is manufactured in a pre-opened state, there is no need to perform a relatively complicated opening step during use.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0013] Hereinafter, with reference to the accompanying drawings, preferred embodiments of the method of the present invention for manufacturing a synthetic resin cover will be described in more detail.

[0014] Fig. 1 shows a typical example of a synthetic resin cover manufactured by the method of the present invention. The cover, indicated as a whole by the number 2, is formed from an appropriate synthetic resin film such as a polyethylene film having a thickness of about 0.020 to 0.080 mm, and laminated portions 4a and 4b are present on both sides thereof. Each of the laminated portions 4a and 4b is formed by folding both end portions in the required width direction from the front surface to the back surface and laminating the non-folded portions 4a-1 and 4b-1 and the folded portions 4a-2 and 4b-2. The main portion 6 located between the laminated portions 4a and 4b is defined by a single-layer film.

[0015] At both longitudinal ends of each of the laminated portions 4a and 4b, there are provided welding lines 6a and 6b formed by welding the non-folded portions 4a-1 and 4b-1 and the folded portions 4a-2 and 4b-2. Each of the welding lines 6a and 6b may be a line of an appropriate form extending in the width direction of the laminated portions 4a and 4b. In the illustrated typical example, it is a form in which the inward arc-shaped lines 6a-1 and 6b-1 convex toward the inner side in the longitudinal direction and the outward arc-shaped lines 6a-2 and 6b-2 convex toward the outer side in the longitudinal direction are connected. Pocket-shaped portions 8a and 8b are defined inside the welding lines 6a and 6b in the longitudinal direction respectively.

[0016] Figure 2 shows a tray which is an example of a container to which the cover 2 shown in Figure 1 is applied. The tray, indicated as a whole by the number 10, which can be formed by an injection molding method from an appropriate synthetic resin such as polypropylene or polyethylene, is box-shaped with an overall rectangular parallelepiped shape and an open upper surface. On the open upper surface of the tray 10, rectangular flanges 16 projecting outward from the upper ends of both side walls 12 and both end walls 14 are formed. In the illustrated tray, the outer surfaces of the lower ends of both side walls 12 and both end walls 14 are set back somewhat from the outer surface of the main portion, and the outer shape of the lower end portion of the tray 10 is set somewhat smaller than the outer shape of the main portion. And on the outer surfaces of the four corners of the tray 10, L-shaped flanges 18 projecting outward from directly above the outer surface of the lower end portion with a reduced outer shape are formed. When stacking the trays 10, the lower end portion of the upper tray 10, that is, the lower end portion of both side walls 12 and both end walls 14 which is set back somewhat, is immersed in the lower tray 10, and the four flanges 18 of the upper tray 10 are placed on the upper surfaces of the corners of the rectangular flanges 16 formed on the upper surface of the lower tray 10. Since such a tray 10 itself is in a well-known form, a detailed description thereof is omitted in this specification.

[0017] When applying the cover 2 as shown in FIG. 1 to the tray 10 as shown in FIG. 2, the pocket-like portions 8a and 8b defined on both sides of one end of the cover 2 are engaged with both sides of one end of the rectangular flange 16 formed on the upper surface of the tray 10. Then, the cover 2 is extended along the upper surface of the tray 10, and the pocket-like portions 8a and 8b defined on both sides of the other end of the cover 2 are engaged with both sides of the other end of the rectangular flange 16 formed on the upper surface of the tray 10. Thus, the cover 2 is attached to the tray 10 to cover the open upper surface of the tray 10 with the cover 2. In FIG. 2, the cover 2 attached to the tray 10 in the manner described above is shown by a two-dot chain line.

[0018] Next, a preferred embodiment of the method of the present invention for manufacturing the cover 2 as described above will be described in detail.

[0019] Preparation process In the method of the present invention, a tubular synthetic resin film is prepared. Referring to FIG. 3 for explanation, in the illustrated embodiment, a sufficiently long tubular synthetic resin film 20 is flattened, wound into a roll shape, and equipped on a delivery roller 22.

[0020] Folding device The synthetic resin film 20 unwound from the delivery roller 22 is fed into the folding device 24. The folding device 24 includes a pair of loading rollers 26, a folder 28, and a pair of unloading rollers 30. In the illustrated embodiment, the pair of loading rollers 26 and the pair of unloading rollers 30 are arranged at a required distance apart in the vertical direction, and the folder 28 is disposed between the pair of loading rollers 26 and the pair of unloading rollers 30. Referring to FIG. 4 together with FIG. 3, the folder 28, which can be formed by appropriately deforming and joining a hard cardboard or a thin metal plate, is generally in the shape of a hollow box with openings at the upstream end (upper end) and the downstream end (lower end). The front wall 32 and the rear wall 34 are inclined rearward and forward, respectively, toward the downstream, and the distance between the front wall 32 and the rear wall 34 is gradually decreased toward the downstream. One side wall 36 and the other side wall 38 are flat at the upstream end, but extend with a fold line 40 that is inclined forward toward the downstream and inward in the width direction toward the downstream and a fold line 42 that is inclined rearward toward the downstream and inward in the width direction toward the downstream from the upstream end to the downstream end, and are folded. At the downstream end, a substantially X-shaped opening is defined.

[0021] Folding process The synthetic resin film 20 unwound from the delivery roller 22 is sandwiched between the pair of loading rollers 26, then passes through the folder 28 and is sandwiched between the pair of unloading rollers 30. At this time, as can be clearly understood by referring to FIG. 3, compressed air of a required pressure is filled into the synthetic resin film 20 between the pair of loading rollers 26 and the pair of unloading rollers 30 and sealed. When the synthetic resin film 20 is set in the folding device 24 in this way, the delivery roller 22, the pair of loading rollers 26 and the pair of unloading rollers 30 are rotationally driven in the directions indicated by the arrows, and the synthetic resin film 20 is conveyed through the folder 28. While the synthetic resin film 20 is being conveyed through the folder 28, the cross-sectional shape of the synthetic resin film 20 is gradually deformed into a shape corresponding to the inner cross-sectional shape of the folder 28 by the action of the compressed air. That is, both side portions of the synthetic resin film 20 are forced inward in the width direction, and the cross-sectional shape of the synthetic resin film 20 is deformed into a shape corresponding to the cross-sectional shape at the downstream end of the folder 28, and folding portions 20a and 20b (a pair of folding portions 20a and 20b) are formed on both side portions. From this, as shown in FIG. 5, non-folding portions 20c-1 and 20c-2 exist on the upper surface side and the lower surface side of the synthetic resin film 20, respectively, and in each of the pair of folding portions 20a and 20b, upper surface side folding portions 20a-2 and 20b-2 on the upper surface side of the folding valley lines 20a-1 and 20b-1 and lower surface side folding portions 20a-3 and 20b-3 below the folding valley lines 20a-1 and 20b-1 are defined. The synthetic resin film 20 unloaded from the pair of unloading rollers 30 can be wound around an appropriate take-up roller (not shown). If desired, the synthetic resin film 20 unloaded from the pair of unloading rollers 30 can also be directly conveyed to a welding / cutting / separating device described later.

[0022] Welding, cutting, and separating device As described above, the synthetic resin film 20 having the folding portions 20a and 20b formed on both sides is fed into the welding / cutting / separating device 44 shown in FIG. 6, either after being once wound around a winding roller (not shown) or directly from the carry-out roller pair 30 of the folding device 24. The illustrated welding / cutting / separating device 44 includes a carry-in roller pair 46, a welding means 48, a cutting means 50, a carry-out roller pair 52, and a separating means 54. The carry-in roller pair 46 and the carry-out roller pair 52 are intermittently rotationally driven in the directions indicated by the arrows, and repeatedly and intermittently convey the synthetic resin film 20 in the direction indicated by the arrows by the longitudinal length of the cover 2.

[0023] Welding process The illustrated welding means 48 includes a pair of upper welding blocks 56a and 56b disposed above both longitudinal sides of the synthetic resin film 20, a pair of lower welding blocks 58a and 58b (the lower welding block 58b is not shown) disposed below, and a pair of intermediate table plates 60a and 60b positioned in each of a pair of folded portions 20a and 20b of the synthetic resin film 20 (more specifically, between the upper surface side folded portion 20a-2 and the lower surface side folded portion 20a-3 in the folded portion 20a, and between the upper surface side folded portion 20b-2 and the lower surface side folded portion 20b-3 in the folded portion 20b). The upper welding block 56a and the lower welding block 58a are respectively arranged at one end in the width direction, and the upper welding block 56b and the lower welding block 58b (not shown) are respectively arranged at the other end in the width direction. In the illustrated embodiment, the pair of upper welding blocks 56a and 56b and the pair of lower welding blocks 58a and 58b are all arranged at the same position in the longitudinal direction and approach and separate simultaneously in the vertical direction. And on the lower surface of the upper welding block 56a and the upper surface of the lower welding block 58a, heating and welding ridges (not shown) corresponding to the upstream welding line 6a in the previous cover and the downstream welding line 6a in the next cover are formed. Similarly, on the lower surface of the upper welding block 56b and the upper surface of the lower welding block 58b (not shown), heating and welding ridges (not shown) corresponding to the upstream welding line 6b in the previous cover and the downstream welding line 6b in the next cover are formed.

[0024] Referring to FIG. 5 for description, while the conveyance of the synthetic resin film 20 is interrupted, a pair of upper welding blocks 56a and 56b descend and a pair of lower welding blocks 58a and 58b ascend. When the upper welding block 56a descends and presses against the upper surface of the intermediate table board 60a with the non-folded portion 20c-1 on the upper surface side and the upper surface side folded portion 20a-2 of the folded portion 20a in the synthetic resin film 20 interposed therebetween, and the lower welding block 58a ascends and presses against the lower surface of the intermediate table board 60a with the non-folded portion 20c-2 on the lower surface side and the lower surface side folded portion 20a-3 of the folded portion 20a in the synthetic resin film 20 interposed therebetween, the non-folded portion 20c-1 on the upper surface side and the upper surface side folded portion 20a-2 of the folded portion 20a in the synthetic resin film 20 are welded to form two adjacent upper surface side welding lines 6a, and also the non-folded portion 20c-2 on the lower surface side and the lower surface side folded portion 20a-3 of the folded portion 20a in the synthetic resin film 20 are welded to form two adjacent lower surface side welding lines 6a. Since the intermediate table board 60a exists in the folded portion 20a of the synthetic resin film 20, the upper surface side folded portion 20a-2 and the lower surface side folded portion 20a-3 of the folded portion 20a are not welded to each other.

[0025] Similarly, when the upper welding block 56b is lowered and pressed against the upper surface of the intermediate table board 60b with the non-folded portion 20c-1 on the upper surface side and the upper surface side folded portion 20b-2 of the folded portion 20b in the synthetic resin film 20 interposed therebetween, and the lower welding block 58b is raised and pressed against the lower surface of the intermediate table board 60b with the non-folded portion 20c-2 on the lower surface side and the lower surface side folded portion 20b-3 of the folded portion 20b in the synthetic resin film 20 interposed therebetween, the non-folded portion 20c-1 on the upper surface side in the synthetic resin film 20 and the upper surface side folded portion 20b-2 of the folded portion 20b are welded to form two adjacent welding lines 6b on the upper surface side. Also, the non-folded portion 20c-2 on the lower surface side in the synthetic resin film 20 and the lower surface side folded portion 20b-3 of the folded portion 20b are welded to form two adjacent welding lines 6b on the lower surface side. Since the intermediate table board 60b exists in the folded portion 20b of the synthetic resin film 20, the upper surface side folded portion 20b-2 and the lower surface side folded portion 20b-3 of the folded portion 20b are not welded. Next, the pair of upper welding blocks 56a and 56b are raised to their original positions and the pair of lower welding blocks 58a and 58b are lowered to their original positions, and then the intermittent conveyance of the synthetic resin film 20 is performed.

[0026] Cutting process The cutting means 50 in the illustrated embodiment includes a pair of cutting blades 62a and 62b. The pair of cutting blades 62a and 62b are respectively disposed on the rectangular bottom edges of separate plate-like pieces. Each of the pair of cutting blades 62a and 62b is positioned at the same position in the longitudinal direction and opposite to each of the pair of folded portions 20a and 20b of the synthetic resin film 20, and the pair of cutting blades 62a and 62b are respectively opposite to the folding valley lines 20a-1 and 20b-1 of each of the pair of folded portions 20a and 20b. Therefore, while the synthetic resin film 20 is conveyed in the direction indicated by the arrow, the folding valley lines 20a-1 and 20b-1 of each of the pair of folded portions 20a and 20b are cut by the pair of cutting blades 62a and 62b, whereby the synthetic resin film 20 becomes two stacked strip-like shapes from the tubular shape.

[0027] Separating process The separating means 54 disposed on the downstream side of the carry-out rollers 52 has an upper cutting blade 64 and a lower cutting blade 66 that cooperate with each other. While the conveyance of the synthetic resin film 20 is interrupted, the upper cutting blade 64 is lowered and the lower cutting blade 66 is raised, and the synthetic resin film 20 is cut across the entire width direction between the welding lines 6a and 6b for the downstream cover and the welding lines 6a and 6b for the upstream cover, and thus two completed covers 2 are simultaneously separated from the synthetic resin film 20. The separated state is shown in FIG. 7. As can be understood by referring to FIG. 7, the inner surfaces of each of the two completed covers 2 face each other. That is, in the upper cover 2, the non-folded portions 4a-1 and 4b-1 are above the folded portions 4a-2 and 4b-2, and in the lower cover 2, the non-folded portions 4a-1 and 4b-1 are below the folded portions 4a-2 and 4b-2, respectively. Next, the upper cutting blade 64 is raised and returned to its original position, and the lower cutting blade 66 is lowered and returned to its original position, and then the intermittent conveyance of the synthetic resin film 20 is performed.

[0028] According to the method of the present invention as described above, the cutting step is performed after the welding step. That is, when performing the welding step, since the synthetic resin film 20 is still in a tubular shape, the posture of the synthetic resin film 20 when performing the welding step is stable, and the welding lines 6a and 6b can be formed at accurate positions. Further, since there are two covers 2 obtained by performing all the steps, the manufacturing efficiency is good. Also, when the manufactured cover 2 is applied to the tray 10, the surface of the cover 2 facing the food products etc. stored in the tray 10 is defined by the inner surface rather than the outer surface exposed to the outside of the tubular synthetic resin film 20, so that it is possible to prevent dust etc. from being adsorbed on such a surface as much as possible. Furthermore, since it is manufactured in an open state, that is, a state immediately ready for use, it is also easy to use.

[0029] If desired, as shown in FIG. 8, the welding means 48' may include a pair of upstream upper welding blocks 56a-1' and 56b-1' disposed above the upstream sides of both longitudinal sides of the synthetic resin film 20, a pair of upstream lower welding blocks 58a-1' and 58b-1' (not shown) disposed below, a pair of downstream upper welding blocks 56a-2' and 56b-2' disposed above the downstream side, a pair of downstream lower welding blocks 58a-2' and 58b-2' (not shown) disposed below, and a pair of intermediate table plates 60a-1', 60b-1', 60a-2', and 60b-2' positioned on each of the pair of folded portions 20a and 20b of the synthetic resin film 20. In this case, heating welding ridges (not shown) corresponding to the upstream welding lines 6a of the cover are formed on the lower surfaces of the pair of upstream upper welding blocks 56a-1' and 56b-1' and the upper surfaces of the pair of upstream lower welding blocks 58a-1' and 58b-1' (not shown), respectively. Similarly, heating welding ridges (not shown) corresponding to the downstream welding lines 6a of the cover are formed on the lower surfaces of the pair of downstream upper welding blocks 56a-2' and 56b-2' and the upper surfaces of the pair of downstream lower welding blocks 58a-2' and 58b-2' (not shown), respectively. While the conveyance of the synthetic resin film 20 is interrupted, the pair of upstream upper welding blocks 56a-1' and 56b-1' and the pair of downstream upper welding blocks 56a-2' and 56b-2' descend, and the pair of upstream lower welding blocks 58a-1' and 58b-1' and the pair of downstream lower welding blocks 58a-2' and 58b-2' ascend, so that a pair of upstream welding lines 6a and 6b located on the upstream side of the synthetic resin film 20 and a pair of downstream welding lines 6a and 6b located on the downstream side are formed simultaneously. According to this modified example, since all the welding lines 6a and 6b formed on the two covers 2 laminated vertically are formed simultaneously, it is surely prevented that the longitudinal intervals between the upstream welding lines 6a and 6b and the downstream welding lines 6a and 6b vary, and the quality of the cover 2 is improved.

[0030] The preferred embodiments of the method of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to such embodiments, and various modifications and corrections can be made without departing from the scope of the present invention.

[0031] In addition, the cover manufactured by the method of the present invention is not limited to covering the upper surface of the above-described tray provided with a flange at the upper end, and can also be used to cover the upper surface of a tray in a form without a flange at the upper end, a storage container in the shape of a rectangular parallelepiped or a cube, etc. In the case of a cover applied to a tray in a form without a flange at the upper end, a storage container in the shape of a rectangular parallelepiped or a cube, instead of forming the welding lines 6a and 6b in a form connecting the convex width-direction inner arc lines 6a-1 and 6b-1 facing the inner side in the longitudinal direction and the convex width-direction outer arc lines 6a-2 and 6b-2 facing the outer side in the longitudinal direction, as shown in FIG. 9, the welding lines 6'a and 6'b are inclined outward in the width direction linearly from the longitudinal edge toward the inner side in the longitudinal direction, and the inclination angle α with respect to the longitudinal direction is preferably 45 degrees or more, particularly about 45 to 65 degrees. When the inclination angle α is 45 degrees or more, particularly about 45 to 65 degrees, when the cover is attached to the container, the laminated portions 4'a and 4'b of the cover are forced in a direction approaching the outer peripheral surface of the tray or the storage container, and it is possible to prevent as much as possible the cover from detaching from the tray or the storage container due to wind or the like.

Description of Reference Numerals

[0032] 2: Cover 4a and 4b: Laminated portion 6a and 6b: Welding line 10: Tray 20: Synthetic resin film 20a and 20b: Folded portion 20a-1 and 20b-1: Folded valley line 20a-2 and 20b-2: Upper surface side folded portion 20a-3 and 20b-3: Lower surface side folded portion 20c-1 and 20c-2: Non-folded portion 24: Folding device 28: Folder 44: Welding, cutting, and separating device 48: Welding means 50: Cutting means 54: Separating means

Claims

1. On both sides, there is a laminated portion formed by folding from the front surface to the back surface, with the non-folded portion and the folded portion laminated. Welding lines where the non-folded portion and the folded portion are welded are disposed at both longitudinal ends of the laminated portion. This is a method for manufacturing a cover made of a synthetic resin film, A preparation step of preparing an elongated tubular synthetic resin film, After the preparation step, a folding step of folding both side portions of the tubular synthetic resin film inward in the width direction to form a pair of folded portions, After the folding step, at both longitudinal side portions, with a longitudinal interval respectively, the non-folded portion on the upper surface side and the upper surface side folded portion above the folding valley line in each of the pair of folded portions, and the non-folded portion on the lower surface side and the lower surface side folded portion below the folding valley line in each of the pair of folded portions are welded respectively to form the welding lines. This is a welding step, After the welding step, a cutting step of cutting the folding valley line of each of the pair of folded portions, A method characterized by including the above steps.

2. In the welding step, the upstream welding line in the synthetic resin film for the cover located on the downstream side and the downstream welding line in the synthetic resin film for the cover located on the upstream side are formed simultaneously. After the cutting step, the method according to claim 1, including a separating step of cutting the tubular synthetic resin film across the entire width direction between the upstream welding line and the downstream welding line.

3. In the welding step, the upstream welding line located on the upstream side of the synthetic resin film for the cover and the downstream welding line located on the downstream side are formed simultaneously. After the cutting step, the method according to claim 1, including a separating step of cutting across the entire width direction between the upstream welding line in the synthetic resin film for the cover located on the downstream side and the downstream welding line in the synthetic resin film for the cover located on the upstream side.

Images