Stretchable sheet manufacturing device, and stretchable sheet manufacturing method

Abstract

A stretchable sheet manufacturing device (100) includes: a welding part formation unit (130) comprising an anvil roll (131) and an ultrasonic horn (132); and a feeding unit (120) that is provided so as to be separated from the ultrasonic horn (132) and the anvil roll (131) in the conveyance direction, and that feeds at least one from among a first sheet (11) and a second sheet (12) together with thread rubber (14) to the welding part formation unit (130). Tension greater than or equal to a prescribed magnitude is applied to the thread rubber (14) on the upstream side from the feeding unit (120), and the feeding unit (120) holds the thread rubber (14) and at least one from among the first sheet (11) and the second sheet (12) such that the thread rubber (14) which has been cut by the welding part forming unit (130) does not come loose on the upstream side from the feeding unit (120).

Description

Stretchable sheet manufacturing device and stretchable sheet manufacturing method

[0001] The present invention relates to an apparatus for manufacturing a stretchable sheet and a method for manufacturing a stretchable sheet.

[0002] A conventional technique for manufacturing a stretchable sheet member is known in which two stacked sheet members are joined by forming a plurality of welds without using an adhesive, and the welds sandwich a rubber thread between the sheet members from both sides in the width direction to regulate its position. For example, Patent Document 1 discloses a technique for attaching a wire element (corresponding to a rubber thread) to a tubular sleeve 1 without welding the wire element to the sleeve by sandwiching the wire element in a isthmus 8 formed between connecting portions 6 a and 6 b in the sleeve.

[0003] Special Publication No. 2001-504899

[0004] As disclosed in Patent Document 1, when manufacturing such a stretchable sheet, a common method is to attach the rubber thread by, for example, sandwiching two sheet members and a stretched rubber thread between an anvil and an ultrasonic horn to form a weld. However, if the rubber thread is sandwiched between the anvil and the ultrasonic horn during the manufacturing process, the rubber thread may be cut at the sandwiched position. In this case, work such as repairing the cut rubber thread is required, making it difficult to efficiently (continuously) manufacture stretchable sheets.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to efficiently manufacture an elastic sheet in which rubber thread is attached between two sheet members by multiple welds.

[0006] The main invention for achieving the above object is a manufacturing device for a stretchable sheet in which a first sheet and a second sheet are laminated together with a rubber thread therebetween, the device comprising: an anvil roll; and an ultrasonic horn disposed opposite the outer peripheral surface of the anvil roll, the welded portion forming portion forming portion that sandwiches the laminated first sheet and the second sheet together to form a plurality of welded portions and regulates the position of the rubber thread between the first sheet and the second sheet by the formed welded portions; and a welding portion forming portion disposed upstream of the ultrasonic horn and the anvil roll in a conveying direction in which the rubber thread is conveyed, the welding portion forming portion forming portion being spaced apart from the ultrasonic horn and the anvil roll. and a feed-out section that feeds out at least one of the first sheet and the second sheet together with the rubber thread to the welded portion forming section, wherein tension of a predetermined magnitude or more is applied to the rubber thread upstream of the feed-out section in the conveying direction, and the feed-out section holds at least one of the first sheet and the second sheet and the rubber thread so that even if the rubber thread is cut in the welded portion forming section, the cut rubber thread does not slip off upstream of the feed-out section in the conveying direction. Other features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[0007] According to this type of stretch sheet manufacturing device, it is possible to efficiently manufacture a stretch sheet in which rubber thread is attached between two sheet members by a plurality of welded portions.

[0008] 1 is a plan view of a stretchable sheet 10 manufactured by the manufacturing apparatus (manufacturing method) of the first embodiment. It is a schematic cross-sectional view of the stretchable sheet 10 of FIG. 1. FIG. 3A is a schematic perspective view of a pants-type disposable diaper 1 using the stretchable sheet 10. FIG. 3B is a schematic plan view of the pants-type disposable diaper 1 in an unfolded and stretched state, viewed from the skin-side surface. It is a schematic cross-sectional view of the stretchable sheet manufacturing apparatus 100 of the first embodiment. FIG. 5A is a diagram illustrating the surface configurations of an anvil roll 131 and an ultrasonic horn 132. FIG. 5B is a schematic enlarged view of the closest portions of the anvil roll 131 and the ultrasonic horn 132. FIGS. 6A and 6B are explanatory diagrams of a method for attaching the rubber thread 14 using a welded portion 50 (joint j). They are diagrams illustrating modified surface configurations of the anvil roll 131 and the ultrasonic horn 132. FIGS. 8A and 8B are diagrams illustrating a case where the position of the rubber thread 14 in the width direction is shifted when forming the welded portion 50. 9A to 9D are diagrams illustrating a mechanism for automatically restoring the rubber thread 14 when it is broken during the manufacturing process of a stretch sheet 10 using the stretch sheet manufacturing apparatus 100. A diagram illustrating how the rubber thread 14 is wound around the welded portion forming section 130. A diagram illustrating how the rubber thread 14 is wound around the welded portion forming section 130. FIGS. 12A and 12B are schematic cross-sectional views of the stretch sheet manufacturing apparatus 100 when the joining position of the second sheet 12 is changed. A schematic cross-sectional view showing the stretch sheet manufacturing apparatus 100 of the second embodiment. A schematic cross-sectional view showing how the second sheet 12 joins with the rubber thread 14 at the welded portion forming section 130. A schematic cross-sectional view showing a modified example of the stretch sheet manufacturing apparatus 100 of the second embodiment.

[0009] At least the following matters will become clear from the description of this specification and the accompanying drawings.

[0010] (Aspect 1) a weld portion forming section that sandwiches the laminated first sheet and the laminated second sheet with a rubber thread interposed therebetween, the weld portion forming section comprising: an anvil roll; and an ultrasonic horn disposed opposite the outer peripheral surface of the anvil roll. The weld portion forming section sandwiches the laminated first sheet and the laminated second sheet between them to form a plurality of welds, and the formed welds regulate the position of the rubber thread between the first sheet and the second sheet; and a feed-out section that is disposed upstream of the ultrasonic horn and the anvil roll in a conveying direction in which the rubber thread is conveyed and that feeds out at least one of the first sheet and the second sheet together with the rubber thread to the weld portion forming section, wherein tension of a predetermined magnitude or more is applied to the rubber thread upstream of the feed-out section in the conveying direction, and the feed-out section holds at least one of the first sheet and the second sheet and the rubber thread so that even if the rubber thread is cut in the weld portion forming section, the cut rubber thread will not slip off upstream of the feed-out section in the conveying direction.

[0011] According to the stretch sheet manufacturing apparatus of aspect 1, the rubber thread is held in the feed-out section while being pressed against the material sheet (at least one of the first sheet and the second sheet). Therefore, even if the rubber thread is cut in the welding section and shrinks toward the upstream side, it is prevented from slipping out upstream of the feed-out section. Furthermore, tension of a predetermined magnitude or greater is applied to the rubber thread between the tension adjustment section and the feed-out section, so that the rubber thread continues to be fed from the feed-out section toward the feed-out section together with the material sheet. Then, when the rubber thread and material sheet reach the feed-out section, the rubber thread is reattached to the material sheet via the welding section. Therefore, even if the rubber thread is cut, it is automatically restored. This allows for efficient production of stretch sheets.

[0012] (Aspect 2) An elastic sheet manufacturing apparatus as described in Aspect 1, wherein the length of the rubber thread wound around the outer peripheral surface of the anvil roll upstream of the position where the anvil roll and the ultrasonic horn face each other in the conveying direction is shorter than the length of the rubber thread from the position where the rubber thread is held together with at least one of the first sheet and the second sheet to the position where it begins to wind around the outer peripheral surface of the anvil roll.

[0013] With the stretch sheet manufacturing apparatus of Aspect 2, compared to the reverse case, the length over which the rubber thread wraps around and adheres to the outer circumferential surface of the anvil roll is short, making it less likely that frictional force will become excessively large, and the distance the rubber thread is transported from the feed section to the anvil roll is long, making it more likely that the rubber thread will shift in the cross direction (CD).This makes it easier for the rubber thread to enter the grooves formed on the outer circumferential surface of the anvil roll, making it easier to prevent the rubber thread from being cut when it is pinched between the anvil roll and the ultrasonic horn during the formation of the welded section.

[0014] (Aspect 3) The elastic sheet manufacturing apparatus according to aspect 1 or 2, wherein the rubber thread and the first and second sheets are wound around the outer peripheral surface of the anvil roll downstream in the conveying direction of the position where the anvil roll and the ultrasonic horn face each other, and the length of the rubber thread wound around the outer peripheral surface of the anvil roll upstream in the conveying direction of the opposing position is shorter than the length of the rubber thread wound around the outer peripheral surface of the anvil roll downstream in the conveying direction of the opposing position.

[0015] According to the stretch sheet manufacturing apparatus of Aspect 3, by making the length of the stretch sheet wound around the outer circumferential surface of the anvil roll as long as possible downstream of the position where the anvil roll and the ultrasonic horn face each other, the stretch sheet can be stably conveyed without wrinkles or other imperfections on the surface. On the other hand, by making the length of the rubber thread wound around the outer circumferential surface of the anvil roll as short as possible upstream of the position where the anvil roll and the ultrasonic horn face each other, the rubber thread is more likely to slip in the cross direction (CD). This makes it easier for the rubber thread to enter the grooves, making it easier to prevent the rubber thread from being cut when it is caught between the anvil roll and the ultrasonic horn during the formation of the welded portion.

[0016] (Aspect 4) A stretch sheet manufacturing apparatus according to any one of Aspects 1 to 3, wherein the delivery section has a first transport roller that transports the rubber thread in the transport direction by rotating around a rotation axis that is perpendicular to the transport direction, and the rubber thread is wound around an area that is equal to or greater than ¼ of the circumference of the first transport roller.

[0017] According to the stretch sheet manufacturing apparatus of Aspect 4, the tension of the rubber thread makes it easier for the rubber thread to be pressed against the outer circumferential surface of the conveying roller, so if the rubber thread is wrapped around at least one-quarter of the conveying roller, the rubber thread is less likely to slip on the outer circumferential surface compared to when the rubber thread is wrapped around less than one-quarter, and the holding force can be made stronger. As a result, even if the rubber thread breaks, it is less likely to slip off upstream of the feed-out section, allowing for efficient production of stretch sheets.

[0018] (Aspect 5) A stretch sheet manufacturing apparatus according to any one of Aspects 1 to 4, wherein the delivery section has a second transport roller that rotates around a rotation axis that is perpendicular to the transport direction and is spaced apart from the first transport roller, and the rubber thread is wound in an S-shape around the first transport roller and the second transport roller.

[0019] According to the stretch sheet manufacturing apparatus of Aspect 5, the rubber thread is wound around two rollers in an S-shape, which makes it easier to hold the rubber thread than when it is wound around a single roller. Therefore, even if the rubber thread breaks, it is less likely to slip off upstream of the feed-out section, allowing for efficient stretch sheet manufacturing.

[0020] (Aspect 6) The stretch sheet manufacturing apparatus according to any one of Aspects 1 to 5, wherein the delivery section has a pair of nip rollers that rotate around a rotation axis that is perpendicular to the conveyance direction, and at least one of the first sheet and the second sheet and the rubber thread are sandwiched between the nip rollers.

[0021] According to the stretch sheet manufacturing apparatus of Aspect 6, the rubber thread is easily held firmly by being sandwiched between the nip rollers. Therefore, even if the rubber thread is broken, contraction is stopped by the nip rollers, and the rubber thread is less likely to slip off upstream of the feed-out section, allowing for efficient production of a stretch sheet.

[0022] (Aspect 7) The stretch sheet manufacturing apparatus according to any one of Aspects 1 to 6, further comprising a tension adjusting section upstream of the feed-out section in the conveying direction, which feeds out the rubber thread to the feed-out section, and wherein tension equal to or greater than the predetermined magnitude is applied to the rubber thread between the tension adjusting section and the feed-out section.

[0023] According to the stretch sheet manufacturing device of aspect 7, a mechanism is provided in which a tension of a predetermined magnitude or greater is applied to the rubber thread between the tension adjusting section and the feed-out section, and the rubber thread is continuously fed out from the feed-out section to the welded section forming section in a constantly stretched state. Therefore, even if the rubber thread is cut in the welded section, the cut part of the rubber thread will not reach the upstream side of the feed-out section, and the stretched rubber thread can be continuously fed out from the feed-out section. This makes it easier for the cut rubber thread to automatically recover, allowing for efficient production of stretch sheets.

[0024] (Aspect 8) The stretch sheet manufacturing apparatus according to any one of Aspects 1 to 7, wherein the first sheet merges with the rubber thread at the feed-out section, and the second sheet merges with the rubber thread at a position between the feed-out section and the welded section forming section.

[0025] According to the stretch sheet manufacturing apparatus of Aspect 8, one sheet joins the rubber thread at the feed-out section and presses down the rubber thread, making it easier to hold the rubber thread in the feed-out section, making it less likely to slip off upstream even if the rubber thread is cut. Furthermore, another sheet joins downstream of the feed-out section, sandwiching the rubber thread between the two sheets further prevents the rubber thread from slipping off. Furthermore, if the rubber thread is cut in the welded portion forming section and shrinks upstream, the rubber thread is more likely to stop shrinking by the time the second sheet joins.

[0026] (Aspect 9) The stretch sheet manufacturing apparatus according to Aspect 8, wherein the second sheet joins with the rubber thread in the welded portion forming section.

[0027] According to the stretch sheet manufacturing apparatus of Aspect 9, after the rubber thread is fed from the feed-out section, it is conveyed while separated from the second sheet until just before the welded section forming section. Therefore, the resistance on one side in the thickness direction is reduced, and the rubber thread is more likely to slip in the cross direction (CD). This makes it easier for the rubber thread to slip into the grooves when sandwiched between the anvil roll and the ultrasonic horn in the welded section forming section, making it less likely to be cut. Therefore, stretch sheets can be efficiently manufactured.

[0028] (Aspect 10) The stretch sheet manufacturing apparatus according to any one of Aspects 1 to 9, wherein the first sheet and the second sheet join with the rubber thread in the delivery section.

[0029] According to the stretch sheet manufacturing apparatus of Aspect 10, the rubber thread is tightly held between two sheets in the feed-out section, which makes it easier to prevent the rubber thread from slipping off upstream of the feed-out section even if it is broken. Furthermore, because one of the sheets is interposed between the transport roller and the rubber thread in the feed-out section, direct contact between the rubber thread and the roller is unlikely. This reduces the risk of damage to the rubber thread due to friction between the rubber thread and the roller during transport.

[0030] (Aspect 11) The stretch sheet manufacturing apparatus according to Aspect 10, wherein either the first sheet or the second sheet has a portion between the feed-out section and the welded portion forming section where the rubber thread is spaced apart.

[0031] According to the stretch sheet manufacturing apparatus of aspect 11, after the rubber thread is fed from the feed-out section, it is conveyed while separated from the sheet member at least part of the way until it reaches the welded portion forming section. Therefore, the resistance is smaller than when the rubber thread is conveyed sandwiched between two sheet members, and the rubber thread is more likely to shift in the cross direction (CD). This makes it easier for the rubber thread to slip into the grooves when sandwiched between the anvil roll and the ultrasonic horn in the welded portion forming section, making it less likely to be cut. Therefore, stretch sheets can be efficiently manufactured.

[0032] (Aspect 12) A method for producing a stretchable sheet in which a first sheet and a second sheet are laminated together with a rubber thread interposed therebetween includes a welded portion forming step of sandwiching the laminated first sheet and the second sheet between an anvil roll and an ultrasonic horn disposed opposite to an outer peripheral surface of the anvil roll to form a plurality of welded portions, and regulating the position of the rubber thread between the first sheet and the second sheet by the formed welded portions; and a method for producing a stretchable sheet in which a first sheet and a second sheet are laminated together with a rubber thread interposed therebetween, the method including: A method for manufacturing an elastic sheet has been revealed, which is characterized by having a feeding process in which at least one of the two sheets is fed toward the anvil roll and the ultrasonic horn together with the rubber thread, wherein tension of a predetermined magnitude or more is applied to the rubber thread upstream of the feeding section in the conveying direction, and the feeding section holds at least one of the first sheet and the second sheet and the rubber thread so that even if the rubber thread is cut in the welded portion forming section, the cut rubber thread does not slip through to the upstream side of the feeding section in the conveying direction.

[0033] According to the stretch sheet manufacturing method of Aspect 12, the rubber thread is held in the feed-out section while being pressed against the first sheet, so even if the rubber thread breaks in the welded portion forming section and shrinks upstream, it is prevented from slipping out upstream of the feed-out section. Furthermore, even if the rubber thread breaks, tension is applied to the rubber thread between the tension adjusting section and the feed-out section, so the rubber thread continues to be fed from the feed-out section to the welded portion forming section while maintaining its elongated state, making it more likely to automatically recover. This allows for efficient manufacturing of stretch sheets.

[0034] First Embodiment Configuration of Stretchable Sheet 10 Fig. 1 is a plan view of a stretchable sheet 10 manufactured by a manufacturing apparatus (manufacturing method) of the first embodiment. Fig. 1 is a diagram of the stretchable sheet 10 in a stretched state without wrinkles. Fig. 2 is a schematic cross-sectional view of the stretchable sheet 10 of Fig. 1.

[0035] The stretchable sheet 10 has a stretch direction, a thickness direction, and a width direction that are perpendicular to each other. The stretchable sheet 10 also has a first sheet 11 and a second sheet 12 laminated in the thickness direction, a plurality of rubber threads 14 interposed between the first sheet 11 and the second sheet 12, and a plurality of joints j.

[0036] The multiple rubber threads 14 are arranged at intervals in the width direction while aligning with the stretch direction of the stretchable sheet 10. The rubber threads 14 are attached to the first sheet 11 and the second sheet 12 in a stretched state. Thus, the stretchable sheet 10 is provided with stretchability in the direction along which the rubber threads 14 are aligned. As the rubber threads 14 (thread-like elastic member), in addition to thread-like natural rubber, various known synthetic rubbers such as styrene-based rubber, urethane-based rubber, ester-based rubber, polyurethane, polyethylene, etc. can be used.

[0037] The multiple joints j join the first sheet 11 and the second sheet 12 to one another using a known welding method such as ultrasonic welding, and are arranged intermittently in the stretch direction and width direction of the stretchable sheet 10. Hereinafter, the "joints j" will also be referred to as "welded portions 50." The multiple joints j (welded portions 50) also regulate the position of the rubber thread 14 in the stretch direction and width direction relative to the first sheet 11 and the second sheet 12. As will be described in detail below, the position of the rubber thread 14 is regulated by pairs of joints jP formed on both sides of the rubber thread 14 in the width direction. While the planar shape of the joints j illustrated in FIG. 1 is rectangular, the planar shape of the joints j is not particularly limited, and any shape such as an ellipse, a circle, or a parallelogram can be used.

[0038] 2 is composed of two sheets, it is also possible to fold one sheet, with the folded portion being the first sheet portion and the unfolded portion being the second sheet portion. Also, the stretchable sheet 10 may be formed by layering one or more additional sheets on the first sheet 11 and the second sheet 12. In other words, the stretchable sheet 10 may be three or more layers.

[0039] <Example of use of stretchable sheet 10> Fig. 3A is a schematic perspective view of a pants-type disposable diaper 1 using the stretchable sheet 10. Fig. 3B is a schematic plan view of the pants-type disposable diaper 1 in an unfolded and stretched state, as viewed from the skin-facing side. The stretchable sheet 10 manufactured by the manufacturing apparatus (manufacturing method) of this embodiment is used, for example, as a component of an absorbent article such as a disposable diaper.

[0040] The illustrated pants-type disposable diaper 1 (hereinafter also referred to as "diaper") has an absorbent main body 2 that absorbs and retains body waste, a ventral waist section 3 that is placed against the wearer's ventral region, and a dorsal waist section 4 that is placed against the wearer's dorsal region. As shown in the unfolded state in Fig. 3B , the left-right center of the ventral waist section 3 overlaps one longitudinal end of the absorbent main body 2, and the left-right center of the dorsal waist section 4 overlaps the other longitudinal end of the absorbent main body 2. The unfolded diaper 1 is folded in half approximately at the longitudinal center, and both left and right sides of the ventral waist section 3 and both left and right sides of the dorsal waist section 4 are joined by welding or the like, thereby forming the diaper 1 into a pants-type diaper.

[0041] The ventral waist portion 3 and the back waist portion 4 are members having a generally rectangular shape in a plan view, and include a plurality of elastic threads 5 stretchable in the left-right direction of the diaper 1, arranged vertically at intervals. Thus, the ventral waist portion 3 and the back waist portion 4 are stretchable in the left-right direction of the diaper 1 to fit the waist of the wearer. A stretchable sheet 10 can be used in the ventral waist portion 3 and the back waist portion 4. The stretchable direction of the stretchable sheet 10 corresponds to the left-right direction of the diaper 1, and the width direction of the stretchable sheet 10 corresponds to the up-down direction of the diaper 1.

[0042] When the stretchable sheet 10 is used as a component of an absorbent article, the first sheet 11 and the second sheet 12 constituting the stretchable sheet 10 can be, for example, soft sheet members. For example, these can be nonwoven fabrics such as spunbond nonwoven fabrics and SMS (spunbond / meltblown / spunbond) nonwoven fabrics. Furthermore, at least one of the first sheet 11 and the second sheet 12 can be a stretchable sheet (stretchable film or stretchable nonwoven fabric) that is stretchable in the stretch direction of the stretchable sheet 10.

[0043] Furthermore, the stretchable sheet 10 is not limited to being used in the ventral waistband 3 and the dorsal waistband 4. For example, the stretchable sheet 10 can be used in leg gathers provided on both sides of the absorbent main body in the left-right direction of the diaper so that the disposable diaper fits around the legs of the wearer. Since the leg gathers stretch in the longitudinal direction of the absorbent main body, the longitudinal direction of the absorbent main body corresponds to the stretch direction of the stretchable sheet 10.

[0044] In a tape-type disposable diaper (not shown), fastening tapes (hook members) extend from the back waistband to both left and right sides. The stretchable sheet 10 can be used for the side panels that attach the fastening tapes to the back waistband. Since the side panels stretch in the left-right direction of the diaper, the left-right direction of the diaper corresponds to the stretch direction of the stretchable sheet 10.

[0045] The stretchable sheet 10 can be used not only for pants-type and tape-type disposable diapers, but also as a component of absorbent articles such as pad-type disposable diapers, sanitary napkins, and sanitary shorts-type napkins. It can also be used for other absorbent articles, such as masks and cleaning sheets.

[0046] <Stretchable Sheet Manufacturing Apparatus and Manufacturing Method> FIG. 4 is a schematic cross-sectional view of a stretchable sheet manufacturing apparatus 100 according to a first embodiment. In the first embodiment, the stretchable sheet manufacturing apparatus 100, which manufactures the stretchable sheet 10, includes a feed-out section 120, a welded section forming section 130, and a tension adjusting section 140. The stretchable sheet 10 is manufactured as a continuous body (continuous sheet) extending in the stretch direction. In the stretchable sheet manufacturing apparatus 100, the direction in which the continuous body of material is conveyed (i.e., the stretch direction of the stretchable sheet 10) is referred to as the machine direction (MD), and the direction perpendicular to the machine direction (i.e., the width direction of the stretchable sheet 10) is referred to as the cross direction (CD). Hereinafter, the continuum of the first sheet 11, the continuum of the second sheet 12, the continuum of the rubber thread 14, and the continuum of the stretchable sheet 10 will also be simply referred to as the first sheet 11, the second sheet 12, the rubber thread 14, and the stretchable sheet 10.

[0047] The feed-out section 120 is located upstream of the welded portion forming section 130 in the conveying direction (MD) and performs a feed-out process of feeding materials such as the rubber thread 14, the first sheet 11, and the second sheet 12 to the welded portion forming section 130. In FIG. 4 , the feed-out section 120 has five types of rollers, a first conveying roller 121 to a fifth conveying roller 125, which rotate around a rotation axis along the cross direction (CD). The first conveying roller 121 is rotated at a predetermined speed by a drive unit (not shown) to convey the rubber thread 14 (continuous body) and the first sheet 11 (continuous body) from the upstream side to the downstream side in the conveying direction (MD). The second conveying roller 122 and the third conveying roller 123 are rollers that convey the rubber thread 14 and the first sheet 11, respectively, and are driven to rotate in accordance with the rotation of the first conveying roller 121. The fourth transport roller 124 is provided between the first transport roller 121 and the welded portion forming unit 130 in the transport direction, and transports the second sheet 12 (continuous body) from the upstream side to the downstream side in the transport direction (MD) while merging the second sheet 12 with the rubber thread 14 and the first sheet 11 that are being transported in the transport direction. The fifth transport roller 125 is a roller that is rotated in response to the rotation of the fourth transport roller 124.

[0048] The configuration of the delivery section 120 shown in Fig. 4 is an example, and the configuration and arrangement of the rollers and the material delivery method can be changed as appropriate. For example, in Fig. 4, the first sheet 11 is delivered together with the rubber thread 14 by the first delivery roller 121, and the second sheet 12 joins with them downstream in the delivery direction (MD). However, the second sheet 12 may be delivered together with the rubber thread 14 by the first delivery roller 121, and the first sheet 11 may then join with them. Furthermore, as shown in Fig. 12B (described later), the fourth delivery roller 124 may not be provided, and the first sheet 11, the second sheet 12, and the rubber thread 14 may be delivered by the first delivery roller 121.

[0049] The weld forming unit 130 is used to perform the weld forming step of forming the weld 50 (joint j) that joins the first sheet 11 and the second sheet 12 together, and includes an anvil roll 131 and an ultrasonic horn 132. The anvil roll 131 is a rotating body that is rotated by a drive source (not shown) about a rotation axis 131c that extends along the cross direction (CD). The anvil roll 131 rotates with the stretchable sheet 10 wrapped around its outer periphery, thereby conveying the stretchable sheet 10 in the machine direction (MD). The ultrasonic horn 132 is disposed opposite the outer periphery of the anvil roll 131 and amplifies ultrasonic vibrations supplied from a vibrator (not shown) to perform ultrasonic welding at a tip 132t. 4, at position P1 where the tip 132t of the ultrasonic horn 132 faces the outer peripheral surface of the anvil roll 131, the tip 132t ultrasonically vibrates with the materials (the first sheet 11, the rubber thread 14, and the second sheet 12) sandwiched between them, thereby ultrasonically welding the materials to form a welded portion 50 (joint j). Note that it is sufficient that the anvil roll 131 and the ultrasonic horn 132 are disposed opposite each other so as to be able to come into contact with each other at position P1 via at least the materials passing therebetween.

[0050] Fig. 5A is a diagram illustrating the surface configuration of the anvil roll 131 and the ultrasonic horn 132. Fig. 5B is a schematic enlarged view of the closest portion of the anvil roll 131 and the ultrasonic horn 132.

[0051] As shown in Fig. 5A, a plurality of protrusions 311 that protrude radially outward are formed on the outer peripheral surface of the anvil roll 131. These protrusions 311, together with the tip 132t of the ultrasonic horn 132, ultrasonically weld the material to form welded portions 50 (jointed portions j). In other words, the protrusions 311 are arranged on the outer peripheral surface of the anvil roll 131 in a manner that corresponds to the arrangement pattern of the welded portions 50 (jointed portions j) on the stretchable sheet 10. In addition, a groove 312 is formed between two adjacent protrusions 311, 311 in the CD direction.

[0052] The tip 132t of the ultrasonic horn 132 has a smooth surface without any irregularities, and vibrates in a direction that expands or contracts the gap between it and the outer peripheral surface of the anvil roll 131 (i.e., in the thickness direction of the material passing therebetween). The vibration frequency is a predetermined value, for example, between 20 kHz and 40 kHz, and the amplitude is a predetermined value, for example, between 30 and 50 microns. This causes the tip 132t of the ultrasonic horn 132 to vibrate ultrasonically. Such vibration is generated, for example, by inputting an electrical signal of the above frequency to a piezoelectric element of a converter (not shown) connected to the ultrasonic horn 132.

[0053] The first sheet 11, the second sheet 12, and the rubber thread 14 are transported in the transport direction (MD) while being wound around the anvil roll 131, and pass between the anvil roll 131 and the tip 132t of the ultrasonic horn 132 at position P1. The rotational speed of the first transport roller 121 that transports the first sheet 11 and the like is approximately the same as the rotational speed of the anvil roll 131. Therefore, the first sheet 11 and the like are wound around the anvil roll 131 in a state of being taut without being stretched or loosened. On the other hand, the rubber thread 14 is transported in a stretched state in the transport direction (MD) between the tension adjustment unit 140 (described later) and the first transport roller 121. In other words, the rubber thread 14 is transported in the transport direction (MD) with a predetermined amount of tension applied. Therefore, the rubber thread 14 is wound around the anvil roll 131 in a stretched state.

[0054] To form the welded portions 50 (jointed portions j), the first sheet 11 and the second sheet 12, with the rubber thread 14 interposed therebetween, are conveyed in the machine direction (MD) and passed between the anvil roll 131 and the ultrasonic horn 132. Then, the first sheet 11 and the second sheet 12 sandwiched in the thickness direction between the outer peripheral surface of the anvil roll 131 and the tip end 132t of the ultrasonic horn 132 are ultrasonically welded to form a plurality of welded portions 50 (jointed portions j). Specifically, as shown in FIG. 5B , the first sheet 11 and the second sheet 12 are melted and joined together by ultrasonic vibrations from the ultrasonic horn 132 at positions corresponding to the convex portions 311 on the outer peripheral surface of the anvil roll 131. At this time, the rubber thread 14 is positioned in a groove 312 between two convex portions 311 adjacent in the cross direction (CD) and is not ultrasonically welded. In other words, when the welded portion 50 is formed, if the rubber thread 14 is positioned in the groove portion 312, the rubber thread 14 can be prevented from being pinched between the outer surface of the anvil roll 131 and the tip portion 132t of the ultrasonic horn 132 and being cut (see Figure 8B described below).

[0055] 1, the welded portion 50 (joint j) also serves to regulate the position of the rubber thread 14 in the stretching direction and width direction relative to the first sheet 11 and the second sheet 12, i.e., to attach the rubber thread 14 to the first sheet 11 and the second sheet 12. Figures 6A and 6B are explanatory diagrams of a method of attaching the rubber thread 14 using the welded portion 50 (joint j).

[0056] As shown in Fig. 6A , a distance D50 between a pair of welded portions 50P, each consisting of two welded portions 50, 50 located on both sides of the rubber thread 14 in the width direction (CD), is set to be equal to or larger than the width direction (CD) size D14 of the rubber thread 14 stretched when the pair of welded portions 50P is formed. Furthermore, the distance D50 is set to be smaller than the width direction (CD) size of the rubber thread 14 in its natural, unloaded state. The rubber thread 14 in its stretched state is thinner than the thickness of the rubber thread 14 in its natural state by the amount of stretch. Therefore, when the continuous rubber thread 14 is cut after the formation of the pair of welded portions 50P, for example, and the stretched state of the rubber thread 14 is relaxed, the pair of welded portions 50P can clamp the rubber thread 14, which attempts to expand in the width direction (CD) while contracting in the conveyance direction, from the width direction (CD), as shown in Fig. 6B . This restricts the position of the rubber thread 14 in the stretch direction (MD) and the cross direction (CD), and the rubber thread 14 is attached to the first sheet 11 and the second sheet 12 .

[0057] In the above example, the anvil roll 131 has a plurality of projections 311 and grooves 312 formed on its outer peripheral surface, and the tip 132t of the ultrasonic horn 132 has a smooth surface without any irregularities. However, the present invention is not limited to this. Figure 7 is a diagram illustrating a modified example of the surface configuration of the anvil roll 131 and the ultrasonic horn 132.

[0058] In the modified example shown in Fig. 7, gears 315 extending in the cross direction (CD) are provided at predetermined intervals in the circumferential direction (MD) on the outer peripheral surface of the anvil roll 131. Meanwhile, a plurality of protrusions 321 protruding from the tip 132t of the ultrasonic horn 132 on the side facing the anvil roll 131 are provided at predetermined intervals along the cross direction (CD) in the same manner as the protrusions 311 described in Fig. 5. The materials are ultrasonically welded together at the timing when the gears 315 of the anvil roll 131 and the protrusions 321 of the ultrasonic horn 132 face each other to form a welded portion 50 (joint j). That is, by ultrasonically vibrating the protrusions 321 of the ultrasonic horn 132 with the material (first sheet 11 and second sheet 12) sandwiched between the protrusions 321 and the outer peripheral surface of the anvil roll 131, a plurality of welds 50 (joints j) can be formed in the arrangement shown in FIG. 1 in accordance with the pattern of the protrusions 321 and the circumferential spacing of the gear 315. In addition, a groove 322 is provided between two adjacent protrusions 321, 321 in the width direction (CD) of the ultrasonic horn 132. If the rubber thread 14 is placed in the groove 322 when forming the welds 50 (joints j), cutting of the rubber thread 14 is suppressed, and the rubber thread 14 remains attached to the first sheet 11 and the second sheet 12.

[0059] Returning to FIG. 4 , the tension adjusting unit 140 is a mechanism that is provided upstream of the feed-out unit 120 (first feed roller 121) in the feed direction (MD) and feeds the rubber thread 14 downstream in the feed direction (MD). The tension adjusting unit 140 is configured, for example, as shown in FIG. 4 , by a pair of nip rollers that rotate while sandwiching the rubber thread 14. In this embodiment, the tension adjusting unit 140 is rotated by a drive unit (not shown) at a slower speed than the first feed roller 121 of the feed-out unit 120 to feed the rubber thread 14. As a result, the rubber thread 14 is stretched based on the difference in rotation speed (feed speed) between the tension adjusting unit 140 and the first feed roller 121 in the feed direction (MD), and is fed out downstream of the feed-out unit 120 (feed-out unit 120) in a tensioned state. As long as the tension of the rubber thread 14 can be adjusted, the tension adjusting unit 140 may be configured other than a nip roller, such as a known tension controller, or may be a combination thereof.

[0060] <Regarding Cutting of Rubber Thread When Forming Welded Portions> As described above, in the stretch sheet manufacturing apparatus 100 of this embodiment, a welded portion 50 (joint j) is formed to join the first sheet 11 and the second sheet 12, which are the materials, and the rubber thread 14 is attached to the material by clamping the rubber thread 14 from both sides in the cross direction (CD) with the pair of welds 50P. When forming the welded portion 50 (joint j), the rubber thread 14 is placed in a groove 312 (322) formed between two convex portions 311 (321) adjacent in the cross direction (CD) (see FIG. 5B ), thereby preventing the rubber thread 14 from being cut.

[0061] However, the position of the rubber thread 14 in the cross direction (CD) is not always constant due to fluctuations in the rubber thread 14 during transport and the influence of wrinkles formed in the material sheet. Figures 8A and 8B are diagrams illustrating a case where the position of the rubber thread 14 in the cross direction is shifted when forming the welded portion 50. Figures 8A and 8B schematically show a case where the rubber thread 14 is supplied (transported) with its position in the cross direction (CD) shifted relative to the welded portion forming portion 130 (anvil roll 131).

[0062] In the stretchable sheet 10 manufactured by the stretchable sheet manufacturing apparatus 100, multiple rubber threads 14 are arranged in a stretched state at intervals in the cross direction (CD) (see FIG. 1 , etc.). In FIG. 8A , of the multiple rubber threads 14 provided on the stretchable sheet 10, two rubber threads 14a and 14b are shown wound around the outer peripheral surface of the anvil roll 131. At this time, one rubber thread 14a is positioned so as to overlap with a groove 312 of the anvil roll 131, while the other rubber thread 14b is positioned so as to overlap with a protrusion 311, offset in the cross direction (CD) from the position of the groove 312. When the anvil roll 131 rotates in this state and reaches a position facing the ultrasonic horn 132 (position P1 in FIG. 4 ), one rubber thread 14a is attached between the first sheet 11 and the second sheet 12 by a pair of welds 50P formed by the protrusion 311. On the other hand, there is a risk that the other rubber thread 14b may be cut when ultrasonic vibrations are applied while it is sandwiched between the protrusion 311 and the ultrasonic horn 132 (tip 132t) as shown in Fig. 8B . In other words, if the position of the rubber thread 14 is misaligned in the cross direction (CD) when the weld 50 is formed in the weld forming unit 130, there is a risk that the rubber thread 14 may be cut.

[0063] When the rubber thread 14 is cut at the welded portion forming section 130, the cut rubber thread 14 attempts to contract from the cut position (position P1 in FIG. 4 ) toward the upstream and downstream sides in the conveying direction (MD). Here, downstream of position P1, the welded portion pair 50P has already been formed and the rubber thread 14 is sandwiched in the cross direction (CD), so the rubber thread 14 can remain attached between the first sheet 11 and the second sheet 12. On the other hand, upstream of position P1, the welded portion pair 50P has not yet been formed, so the rubber thread 14 continues to contract toward the upstream side in the conveying direction (MD) (toward the feed-out section 120).

[0064] In such a case, the rubber thread 14 must be reset to a state where it can be conveyed, sent again to the welded portion forming section 130, and attached between the first sheet 11 and the second sheet 12. Therefore, in conventional stretch sheet manufacturing devices, for example, the conveyance of materials must be temporarily stopped and the cut rubber thread must be restored so that it can be conveyed normally, resulting in labor and cost. Furthermore, such work makes it impossible to continuously manufacture stretch sheets. Thus, in conventional stretch sheet manufacturing devices, if the rubber thread is cut when forming the welded portion, there is a risk of a significant decrease in production efficiency.

[0065] Therefore, in the stretch sheet manufacturing apparatus 100 of this embodiment, even if the rubber thread 14 is cut during the manufacturing process of the stretch sheet 10, the rubber thread 14 is automatically restored, making it possible to continuously manufacture the stretch sheet 10 without stopping the apparatus. Specifically, by implementing the following measures, even if the rubber thread 14 is cut, the apparatus can be automatically restored without stopping the apparatus: (a) the rubber thread 14 is prevented from slipping out beyond the feed-out section 120 to the upstream side in the machine direction (MD), and (b) the stretched rubber thread 14 is continuously fed from the feed-out section 120.

[0066] 9A to 9D are diagrams illustrating a mechanism for automatically restoring the rubber thread 14 when it is cut during the manufacturing process of the stretch sheet 10 using the stretch sheet manufacturing apparatus 100. For the sake of simplicity, some components (e.g., the second sheet 12) are omitted from Figures 9A to 9D.

[0067] When manufacturing a stretch sheet 10 using the stretch sheet manufacturing apparatus 100, as shown in FIG. 9A , the rubber thread 14 is conveyed together with a sheet member (a material sheet such as the first sheet 11) from upstream to downstream in the conveyance direction (MD), while a weld 50 is formed in the weld forming section 130, and the rubber thread 14 is attached to the sheet member. In this embodiment, in the delivery section 120 of the stretch sheet manufacturing apparatus 100, at least one sheet member is conveyed in the conveyance direction (MD) together with the rubber thread 14 while being wound around a first conveyor roller 121. In FIG. 4 ( FIG. 9A ), the rubber thread 14 is wound around the first conveyor roller 121, and a continuous body of the first sheet 11 is also wound around the first conveyor roller 121 so as to overlap the rubber thread 14. In other words, the rubber thread 14 is held sandwiched between the outer circumferential surface of the first conveyor roller 121 and the first sheet 11. Therefore, even if the rubber thread 14 is cut at the welded portion forming portion 130 (position P1) located downstream in the conveying direction (MD) and shrinks upstream, the rubber thread 14 continues to be held by the first conveying roller 121 (feed-out portion 120) while being pressed against the first sheet 11. This prevents the rubber thread 14 from shrinking upstream of the first conveying roller 121 (feed-out portion 120). In other words, (a) the rubber thread 14 is prevented from slipping out upstream of the feed-out portion 120 (so-called slipping out).

[0068] Since the rubber thread 14 continues to be held by the first transport roller 121, the rubber thread 14 is also maintained in an elongated state in the transport direction (MD) between the first transport roller 121 (the let-off section 120) and the tension adjustment section 140. In other words, a predetermined tension of zero or more acts on the rubber thread 14 between the first transport roller 121 and the tension adjustment section 140. Therefore, (b) the rubber thread 14 continues to be sent out from the let-off section 120 to the welded portion forming section 130 downstream in the transport direction (MD) while maintaining its elongated state, and the cut portion of the rubber thread 14 is unlikely to reach an area upstream of the let-off section 120.

[0069] In this embodiment, the "tension equal to or greater than a predetermined magnitude" applied to the rubber thread 14 between the tension adjustment unit 140 and the payout unit 120 is greater than zero, preferably equal to or greater than 0.2 N. In the state shown in Fig. 9A , when the tension of the rubber thread 14 in the payout unit 120 is equal to or greater than 0.2 N, the same tension (0.2 N or greater) acts on the rubber thread 14 between the payout unit 120 and the welded portion forming unit 130. When a tension of 0.2 N or greater acts on the payout unit 120, the rubber thread 14 is more likely to be continuously supplied from the payout unit 120 to the welded portion forming unit 130, and the rubber thread 14 can be automatically restored even if it is broken.

[0070] 9B illustrates a case in which the rubber thread 14 is cut at position P1 in the welded portion forming section 130. The rubber thread 14 cut at position P1 in the welded portion forming section 130 contracts from position P1 upstream in the machine direction (MD) as shown in FIG. 9B . As described above, the stretch sheet manufacturing apparatus 100 of this embodiment prevents the cut rubber thread 14 from slipping upstream of the feed-out section 120, and the cut portion 14c of the rubber thread 14 (the end of the cut rubber thread 14) is located between the feed-out section 120 and the welded portion forming section 130. At this time, because the rubber thread 14 contracts between the feed-out section 120 and the welded portion forming section 130 (position P1), the tension of the rubber thread 14 is essentially zero. Meanwhile, the tension of the rubber thread 14 is maintained at 0.2 N or greater between the tension adjusting section 140 and the feed-out section 120.

[0071] Next, the cut portion 14c of the rubber thread 14 is placed on the first sheet 11 with substantially zero tension (i.e., in an unstretched state), and is fed toward the welded portion forming portion 130 as the first sheet 11 is fed downstream in the conveying direction (MD), as shown in FIG. 9C . In this embodiment, the rubber thread 14 is continuously fed downstream in the conveying direction (MD) together with the first sheet 11 from the feed-out portion 120. That is, even if the rubber thread 14 is cut, the rubber thread 14 and the first sheet 11 continue to be fed at a constant speed from the feed-out portion 120 toward the welded portion forming portion 130. Note that, in FIG. 9C , downstream of position P1 of the welded portion forming portion 130, the rubber thread 14 is attached to the sheet members (the first sheet 11 and the second sheet 12) via the welded portion 50, and is fed downstream in the conveying direction (MD) as the stretchable sheet 10.

[0072] Next, as shown in FIG. 9D , when the cut portion 14c of the rubber thread 14 conveyed together with the first sheet 11 reaches position P1 of the weld-forming section 130, a weld 50 is formed in the weld-forming section 130, and the rubber thread 14 is attached to the first sheet 11 (and the second sheet 12) via the weld 50. Here, when the cut portion 14c of the rubber thread 14 reaches position P1 of the weld-forming section 130 and is attached to the material sheet, the tension of the rubber thread 14 is nearly zero. However, as the rubber thread 14 is subsequently attached to the material sheet, the tension of the rubber thread 14 gradually returns to a predetermined magnitude. That is, between the delivery section 120 and the weld-forming section 130, the tension of the rubber thread 14 increases from zero to a predetermined magnitude of 0.2 N or more. As the conveyance operation continues in this manner, the cut rubber thread 14 naturally returns to its pre-cut state as shown in FIG. 9A . This allows for efficient production of the stretchable sheet 10.

[0073] In this embodiment, after the rubber thread 14 and the first sheet 11 are fed out from the feed-out section 120, the second sheet 12 (continuous body) joins them somewhere between them and the welded portion forming section 130, so that the rubber thread 14 reaches the welded portion forming section 130 sandwiched between the first sheet 11 and the second sheet 12. Therefore, the position of the rubber thread 14 in the cross direction (CD) reaches the welded portion forming section 130 and is attached to the material sheet without being significantly displaced from the position at the time of feeding out from the feed-out section 120, making it easier for the rubber thread 14 to recover naturally.

[0074] Furthermore, the stretch sheet manufacturing apparatus 100 facilitates preventing the rubber thread 14 from being cut when the welded portion 50 is formed in the welded portion forming unit 130 (see FIG. 8B ). In the case of FIG. 8B , the rubber thread 14b wound around the anvil roll 131 is positioned so as to overlap the convex portion 311 in the cross direction (CD), which poses a problem of being easily cut when it is sandwiched between the anvil roll 131 and the ultrasonic horn 132. In contrast, if the rubber thread 14b is positioned so as to overlap the groove portion 312 in the cross direction (CD) like the rubber thread 14a, the probability of the rubber thread 14b being cut can be reduced. In other words, even if the rubber thread 14 is positioned so as to overlap the convex portion 311 when it is wound around the anvil roll 131 in the cross direction (CD), cutting of the rubber thread 14 can be prevented as long as it can shift to the position of the groove portion 312 before it is sandwiched between the anvil roll 131 and the ultrasonic horn 132.

[0075] 10 and 11 are diagrams illustrating how the rubber thread 14 is wound around the weld portion forming section 130. Fig. 10 illustrates a state in which the rubber thread 14 is wound around the outer peripheral surface of the anvil roll 131 upstream in the conveying direction (MD) of the anvil roll 131 and the ultrasonic horn 132. Specifically, the rubber thread 14 is fed from the feed-out section 120 (first feed roller 121) at an angle θa toward the anvil roll 131 with respect to a tangent at position P1 where the anvil roll 131 and the ultrasonic horn 132 face each other. The rubber thread 14 begins to wind around the anvil roll 131 at position P2, which is upstream in the conveying direction (MD) of the anvil roll 131 and the ultrasonic horn 132. The rubber thread 14 then detaches from the anvil roll 131 at position P3, which is downstream in the conveying direction (MD) of the anvil roll 131 and the ultrasonic horn 132. That is, the rubber thread 14 is transported between positions P2 and P3 on the outer circumferential surface of the anvil roll 131 while being wound around the anvil roll 131.

[0076] 10 , in the section from position P2 to position P1 on the outer circumferential surface of the anvil roll 131, the welded portion 50 has not yet been formed, and therefore the position of the rubber thread 14 in the width direction (CD) is not restricted. That is, in this section, the rubber thread 14 is transported in a state in which it can move in the width direction (CD). Furthermore, because the rubber thread 14 is transported in a stretched state, a force acts on the rubber thread 14 due to the action of tension in the section from position P2 to position P1, pressing the rubber thread 14 toward the center (131c) in the radial direction of the anvil roll 131. Therefore, even if the rubber thread 14 is positioned on the convex portion 311 at position P2 where it starts to wind around the anvil roll 131, the rubber thread 14 may roll in the width direction (CD) on the outer circumferential surface of the anvil roll 131 or may be pushed aside in the width direction (CD) when it comes into contact with the tip 132t of the ultrasonic horn 132, and may enter the groove 312 at position P1 (see FIG. 5B ).

[0077] However, if the distance from position P2 to position P1 is long, the length over which the rubber thread 14 is in close contact with the outer circumferential surface of the anvil roll 131 increases, which may increase friction and make it difficult for the rubber thread 14 to move in the cross direction (CD). In contrast, in the stretch sheet manufacturing apparatus 100, the length L1 from position P4, where the rubber thread 14 is sent out from the send-out section 120 (first conveyor roller 121), to position P2, where the rubber thread 14 begins to wind around the outer circumferential surface of the anvil roll 131, is longer than the length L2 from position P2 to position P1 (L1 > L2). In other words, the length L2 over which the rubber thread 14 is wound around and in close contact with the outer circumferential surface of the anvil roll 131 is shorter than the length L1 over which the rubber thread 14 is conveyed from the send-out section 120 to the anvil roll 131. Therefore, compared to the reverse case, the rubber thread 14 is more likely to shift (move) in the cross direction (CD) during conveyance, increasing the probability that it will get caught in the groove 312 of the anvil roll 131. This makes it possible to prevent the rubber thread 14 from being cut when the welded portion forming section 130 forms the welded portion 50 .

[0078] 8A , even if the positions of the convex portion 311 and the rubber thread 14 overlap, the length L1 from the position P4 where the rubber thread 14 is unwound to the position P2 where it begins to wind around the outer circumferential surface of the anvil roll 131 is long, making the rubber thread 14 more likely to fall into the recessed portion 312. For example, if the rubber thread 14 shifts to one side in the cross direction (CD) while being conveyed the length L1, a force that shifts the rubber thread 14 to one side in the cross direction (CD) is also transmitted at position P1. In this case, the longer the distance (L1) from position P4 where the rubber thread 14 is held, the larger the moment that occurs when a shift in the cross direction (CD) occurs, making it more likely that the rubber thread 14 will move from the position of the convex portion 311 to the position of the recessed portion 312 at position P1. Therefore, the probability of the rubber thread 14 being cut can be reduced compared to when L1 is shorter than L2.

[0079] 11 shows a state in which the rubber thread 14 is wound around the tip 132t of the ultrasonic horn 132 upstream in the conveying direction (MD) of the anvil roll 131 and the ultrasonic horn 132. Specifically, the rubber thread 14 is fed from the feed-out section 120 (first feed roller 121) at an angle θb toward the ultrasonic horn 132 with respect to a tangent at position P1 where the anvil roll 131 and the ultrasonic horn 132 face each other, and begins to wind around the ultrasonic horn 132 (tip 132t) at position P2' upstream in the conveying direction (MD) of position P1. The rubber thread 14 then detaches from the anvil roll 131 at position P3 downstream in the conveying direction (MD) of position P1. That is, the rubber thread 14 is transported between the position P2' of the ultrasonic horn 132 and the position P3 of the anvil roll 131 while being wound around the ultrasonic horn 132 and the anvil roll 131.

[0080] 7 , when the outer peripheral surface of the anvil roll 131 is smooth and the protrusions 321 and grooves 322 are provided on the tip end 132t side of the ultrasonic horn 132, the shorter the length of the rubber thread 14 in close contact with the tip end 132t of the ultrasonic horn 132, the more easily the rubber thread 14 moves in the cross direction (CD) and enters the grooves 322. Therefore, it is preferable that the length L1' from position P4, where the rubber thread 14 is sent out from the send-out section 120 (first conveyor roller 121) to position P2', where the rubber thread 14 starts to wind around the ultrasonic horn 132, be longer than the length L2' from position P2' to position P1 (L1' > L2'). With this configuration, the rubber thread 14 is more likely to deviate (move) in the cross direction (CD) during conveyance than in the reverse case, and is more likely to enter the grooves 322 of the ultrasonic horn 132. This makes it possible to prevent the rubber thread 14 from being cut when the welded portion forming section 130 forms the welded portion 50 .

[0081] Furthermore, the length L3 (the length along the outer peripheral surface of the anvil roll 131 from position P1 to position P3 in Figures 10 and 11) of the rubber thread 14 wound around the peripheral surface of the anvil roll 131 downstream in the conveying direction (MD) of position P1 where the anvil roll 131 and the ultrasonic horn 132 face each other is longer than the length L2 (L2') of the rubber thread 14 wound around the peripheral surface of the anvil roll 131 or the tip 132t of the ultrasonic horn 132 upstream in the conveying direction (MD) of position P1 (L2 < L3, L2' < L3).

[0082] Downstream of position P1, where the welded portion 50 is formed by the anvil roll 131 and the ultrasonic horn 132, the rubber thread 14 is attached to the material (the first sheet 11 and the second sheet 12) by the welded portion 50. Therefore, downstream of position P1, the stretchable stretch sheet 10 is transported in a stretched state along the outer circumferential surface of the anvil roll 131. By increasing the length L3 of the stretchable sheet 10 wound around the outer circumferential surface as much as possible, the stretchable sheet 10 can be stably transported downstream in the machine direction (MD) without wrinkling or other problems occurring on the surface. Meanwhile, upstream of position P1, the welded portion 50 has not yet been formed, and the position of the rubber thread 14 in the cross direction (CD) is not restricted. Therefore, by shortening the length L2 (L2') of the rubber thread 14 wound around the circumferential surface of the anvil roll 131 as much as possible, the rubber thread can be easily moved in the cross direction (CD). This makes it easier to prevent the rubber thread 14 from being cut at position P1.

[0083] Furthermore, among the multiple transport rollers provided in the delivery section 120, the first transport roller 121 that transports the rubber thread 14 preferably has the rubber thread 14 wound around it over an area of ​​at least one-quarter of its circumference. In Fig. 10, the rubber thread 14 is wound around an area of ​​about one-third of the circumference of the first transport roller 121. As described above, the rubber thread 14 is wound around the first transport roller 121 together with at least one sheet member (first sheet 11 in Fig. 10), and is transported while being held by the first transport roller 121. Therefore, the longer the length wound around the first transport roller 121, the stronger the holding force. In this embodiment, because the rubber thread 14 in a stretched state is wound around the first transport roller 121, the tension of the rubber thread 14 itself tends to press the rubber thread 14 against the outer circumferential surface of the transport roller 121. If the rubber thread 14 is wound over a range of at least one-quarter of the circumference of the transport roller 121, the rubber thread 14 is less likely to slip on the outer circumferential surface than if it is wound over less than one-quarter, thereby increasing the holding force. Therefore, even if the rubber thread 14 is cut when forming the welded portion 50, it is easy to prevent the cut rubber thread 14 from slipping off upstream in the transport direction (MD) of the feed-out section 120 (first transport roller 121). This makes it easier to automatically restore the rubber thread 14 without stopping the stretch sheet manufacturing apparatus 100, allowing for efficient production of the stretch sheet 10.

[0084] 10, the rubber thread 14 and the first sheet 11 are wound over the rubber thread 14 over an area of ​​at least one-quarter of the circumference of the first transport roller 121. In this configuration, the rubber thread 14 is held between the outer circumferential surface of the transport roller and the first sheet 11, and the length pressed down by the first sheet 11 is increased, resulting in a stronger holding force. Therefore, even if the rubber thread 14 is broken, it is easier to prevent it from coming loose.

[0085] 4 and other drawings, in the let-off section 120, the rubber thread 14 is wound in an S-shape around a first transport roller 121 and a second transport roller 122. By winding the rubber thread 14 in an S-shape around two or more rollers, the rubber thread 14 is more easily held than when it is wound around a single roller. Therefore, even if the rubber thread 14 is cut, it is more likely that the cut rubber thread 14 will slip off upstream of the let-off section 120 in the conveying direction (MD).

[0086] Furthermore, a tension adjusting unit 140 is provided upstream of the let-off unit 120 in the conveying direction (MD), and the tension adjusting unit 140 and the let-off unit 120 (first conveyor roller 121) rotate at different peripheral speeds, thereby applying a tension of a predetermined magnitude or more (a tension of at least 0.2 N or more) to the rubber thread 14. As a result, the rubber thread 14 is constantly sent out from the let-off unit 120 to the welded portion forming unit 130 in an extended state. Therefore, even if the rubber thread 14 is cut in the welded portion forming unit 130, the rubber thread 14 in an extended state can be continuously sent out from the let-off unit 120. This makes it easier for the cut rubber thread 14 to automatically recover, allowing the stretchable sheet 10 to be produced efficiently.

[0087] 4 and other figures, in the stretch sheet manufacturing apparatus 100 of this embodiment, the rubber thread 14 and the first sheet 11 are fed from the feed-out section 120 (first transport rollers 121), and then the second sheet 12 joins them at some position in the transport direction (MD) before reaching the welded portion forming section 130. As described above, one sheet (first sheet 11) joins the rubber thread 14 in the feed-out section 120 (first transport rollers 121), and the rubber thread 14 is pressed down, making it easier for the rubber thread 14 to be held by the first transport rollers 121. As a result, even if the rubber thread 14 is broken, it is less likely to slip off upstream of the first transport rollers 121.

[0088] Furthermore, by joining another sheet (the second sheet 12) downstream of the delivery section 120 (the first transport roller 121) in the transport direction (MD), the rubber thread 14 is sandwiched between the two sheets, which further reduces the likelihood of the rubber thread 14 slipping out. Furthermore, if the rubber thread 14 is cut in the welded portion forming section 130 and shrinks toward the upstream side in the transport direction (MD), the likelihood of the shrinkage stopping by the time the second sheet joins is increased. For example, in FIG. 4 , the fourth transport roller 124 presses the rubber thread 14 and the first sheet 11 in the thickness direction to allow the second sheet 12 to join, which reduces the likelihood of the cut rubber thread 14 slipping out upstream of the fourth transport roller 124 in the transport direction (MD). This makes it easier to efficiently manufacture the stretchable sheet 10.

[0089] 12A and 12B are schematic cross-sectional views of stretch sheet manufacturing apparatus 100 in which the joining position of second sheet 12 is changed. Fig. 12A shows a case where second sheet 12 joins with rubber thread 14 and first sheet 11 in welded portion forming section 130. In Fig. 12A , the fourth transport roller 124 that joins second sheet 12 with rubber thread 14, etc. in Fig. 4 is not provided, and second sheet 12 is supplied directly to welded portion forming section 130, where second sheet 12 joins with rubber thread 14 and first sheet 11 at position P1. In this case, after being fed out from feed-out section 120, rubber thread 14 is transported while separated from second sheet 12 until just before welded portion forming section 130. Therefore, the resistance on one side in the thickness direction is smaller than when the rubber thread 14 is conveyed sandwiched between two sheets (first sheet 11 and second sheet 12) as shown in Figure 4. As a result, the rubber thread 14 is more likely to shift in the width direction (CD) while being conveyed from the feed-out section 120 to the welded section forming section 130. As a result, when the rubber thread 14 is sandwiched between the anvil roll 131 and the ultrasonic horn 132 in the welded section forming section 130 to form the welded section 50, it is more likely to enter the grooves 312 (322) and be less likely to be cut. This makes it easier to efficiently manufacture the stretchable sheet 10.

[0090] 12B illustrates a case in which the second sheet 12 joins the rubber thread 14 and the first sheet 11 at the feed-out section 120 (first transport roller 121). That is, two sheet members join the rubber thread 14 at the feed-out section 120. In FIG. 12B , the fourth transport roller 124 is not provided, and the first sheet 11 and the second sheet 12 are fed out by the first transport roller 121. That is, in FIG. 12B , the rubber thread 14 is sandwiched between the first sheet 11 and the second sheet 12, and is fed out by the first transport roller 121 toward the welded portion forming section 130. In this case, because the rubber thread 14 is sandwiched between the two sheets at the position of the first transport roller 121, it is more likely that the rubber thread 14 will slip off upstream in the transport direction (MD) from the first transport roller 121 if it is cut. Furthermore, since a sheet (the second sheet 12 in FIG. 12B ) is interposed between the rubber thread 14 and the first transport roller 121, the rubber thread 14 is less likely to come into direct contact with the roller, thereby reducing the risk of damage to the rubber thread 14 due to friction between the rubber thread 14 and the roller during transport.

[0091] Second Embodiment In the second embodiment, a stretchable sheet manufacturing apparatus 100 will be described in which the configuration of the feed-out unit 120 is different from that of the first embodiment. Note that the configuration and function of each unit other than the feed-out unit 120, and the stretchable sheet 10 to be manufactured are the same as in the first embodiment, and therefore a detailed description of each unit will be omitted.

[0092] <Configuration of the Feed-Out Unit 120> Figure 13 is a schematic cross-sectional view showing a stretchable sheet manufacturing apparatus 100 of the second embodiment. In the stretchable sheet manufacturing apparatus 100 of the second embodiment, the feed-out unit 120 has a pair of nip rollers 127 that rotate around a rotation axis in the cross direction (CD) perpendicular to the machine direction (MD). The nip rollers 127 rotate while the first sheet 11, the second sheet 12, and the rubber thread 14 (all of which are continuous bodies) are stacked in the thickness direction, thereby transporting them downstream in the machine direction (MD) at a predetermined transport speed. In Figure 13, the rubber thread 14 is held by the nip rollers 127 in a state where it is sandwiched between the first sheet 11 and the second sheet 12.

[0093] In the stretchable sheet manufacturing apparatus 100 of the second embodiment, even if the rubber thread 14 is cut when forming the welded portion 50 in the welded portion forming section 130 and contracts from the cutting position (position P1 in FIG. 13 ) toward the upstream side in the machine direction (MD), the contraction is stopped by the nip roller 127 (feed-out section 120), preventing the rubber thread 14 from slipping off toward the upstream side. Furthermore, because the rubber thread 14 is conveyed in a stretched state by the nip roller 127 (feed-out section 120) and the tension adjustment section 140 provided upstream thereof, even if the rubber thread 14 is cut, the stretched rubber thread 14 can be continuously fed from the nip roller 127. This allows the cut rubber thread 14 to naturally recover, allowing the stretchable sheet 10 to be efficiently manufactured without having to stop the stretchable sheet manufacturing apparatus 100.

[0094] 13, two sheets (the first sheet 11 and the second sheet 12) are joined to the rubber thread 14 at the nip roller 127 (the feed-out section 120), but it is sufficient if at least one sheet is joined to the rubber thread 14 at the nip roller 127. For example, as described in FIG. 4 of the first embodiment, the first sheet 11 may be joined to the rubber thread 14 at the nip roller 127 (the feed-out section 120), and the second sheet 12 may be joined at a predetermined position between the feed-out section 120 and the welded portion forming section 130.

[0095] FIG. 14 is a schematic cross-sectional view illustrating a case where the second sheet 12 meets the rubber thread 14 at the welded portion forming section 130. In FIG. 14 , similar to FIG. 12A of the first embodiment, the rubber thread 14 is fed from the feed-out section 120 and then conveyed while separated from the second sheet 12 until immediately before the welded portion forming section 130. Therefore, compared to when the rubber thread 14 is conveyed sandwiched between two sheets (the first sheet 11 and the second sheet 12) as shown in FIG. 13 , resistance is reduced, and the rubber thread 14 is more likely to slip in the cross direction (CD) while being conveyed from the feed-out section 120 to the welded portion forming section 130. This allows the rubber thread 14 to easily enter the grooves 312 (322) when sandwiched between the anvil roll 131 and the ultrasonic horn 132 at position P1 of the welded portion forming section 130, making it less likely to be cut. This facilitates efficient production of the stretchable sheet 10.

[0096] Furthermore, the transport path of the second sheet 12 may be changed to make it easier for the rubber thread 14 to shift in the cross direction (CD). Figure 15 is a schematic cross-sectional view showing a modified example of the stretchable sheet manufacturing apparatus 100 of the second embodiment. In the stretchable sheet manufacturing apparatus 100 of Figure 15, a spacing roller 128 is provided between the nip roller 127 (feed-out section 120) and the welded section forming section 130 in the transport direction (MD).

[0097] During production of the stretchable sheet 10, two sheets (first sheet 11 and second sheet 12) are joined to the rubber thread 14 by the nip rollers 127 and sent downstream in the machine direction (MD). Thereafter, one of the first sheet 11 and the second sheet 12 (the second sheet 12 in FIG. 15 ) is separated from the rubber thread 14 in the thickness direction by the separating rollers 128. The separated second sheet 12 then joins again with the rubber thread 14 (and the first sheet 11) at the welded portion forming section 130. With this configuration, the rubber thread 14 is sandwiched between the two sheet members from both sides in the thickness direction at the position of the nip rollers 127, making it easier for the nip rollers 127 to firmly hold the rubber thread 14 and less likely to come loose. Furthermore, between the nip roller 127 and the welded portion forming section 130, one sheet (the second sheet 12) is separated on one side in the thickness direction, thereby reducing resistance and making it easier for the rubber thread 14 to slip in the width direction (CD). As a result, when the rubber thread 14 is sandwiched between the anvil roll 131 and the ultrasonic horn 132 at position P1 of the welded portion forming section 130, it is easier for it to enter the grooves 312 (322), making it less likely to be cut. This makes it easier to efficiently produce the stretchable sheet 10.

[0098] ===Other= ...

[0099] DESCRIPTION OF SYMBOLS 1 Pants-type disposable diaper, 2 Absorbent body, 3 Ventral waist portion, 4 Dorsal waist portion, 5 Elastic thread, 10 Stretchable sheet, 11 First sheet, 12 Second sheet, 14 Elastic thread, 50 Welded portion (jointed portion), 50P Pair of welded portions, 100 Stretchable sheet manufacturing apparatus, 120 Feeding section, 121 First conveying roller, 122 Second conveying roller, 123 Third conveying roller, 124 Fourth conveying roller, 125 Fifth conveying roller, 127 Nip roller, 128 Separation roller, 130 Welded portion forming section, 131 Anvil roll, 311 Convex portion, 312 Groove portion, 132 Ultrasonic horn, 132t Tip portion, 321 Convex portion, 322 Groove portion, 140 Tension adjusting section, P1 Position, MD: Machine direction (stretch direction), CD: Width direction, j: Joint, jP: Joint pair

Claims

1. A manufacturing device for a stretchable sheet in which a first sheet and a second sheet are laminated together with a rubber thread therebetween, the device comprising: an anvil roll and an ultrasonic horn arranged opposite the outer peripheral surface of the anvil roll, a weld forming section which sandwiches the laminated first sheet and the second sheet to form a plurality of welds and regulates the position of the rubber thread between the first sheet and the second sheet by the formed welds; and a feed-out section which is provided upstream of the ultrasonic horn and the anvil roll in a conveying direction in which the rubber thread is conveyed and which feeds at least one of the first sheet and the second sheet together with the rubber thread to the weld forming section, wherein tension of a predetermined magnitude or more is applied to the rubber thread upstream of the feed-out section in the conveying direction, The elastic sheet manufacturing apparatus is characterized in that the feed-out section holds at least one of the first sheet and the second sheet and the rubber thread so that even if the rubber thread is cut in the welded portion forming section, the cut rubber thread does not slip out upstream of the feed-out section in the conveying direction.

2. An apparatus for manufacturing an elastic sheet as described in claim 1, characterized in that the length of the rubber thread wound around the outer surface of the anvil roll upstream in the conveying direction from the position where the anvil roll and the ultrasonic horn face each other is shorter than the length of the rubber thread from the position where the rubber thread is held together with at least one of the first sheet and the second sheet to the position where it begins to wind around the outer surface of the anvil roll.

3. An apparatus for manufacturing a stretchable sheet as described in claim 1 or 2, wherein the rubber thread, the first sheet, and the second sheet are wound around the outer peripheral surface of the anvil roll downstream in the conveying direction of the position where the anvil roll and the ultrasonic horn face each other, and the length of the rubber thread wound around the outer peripheral surface of the anvil roll upstream in the conveying direction of the opposing position is shorter than the length of the rubber thread wound around the outer peripheral surface of the anvil roll downstream in the conveying direction of the opposing position.

4. A stretchable sheet manufacturing apparatus as described in claim 1 or 2, wherein the delivery section has a first transport roller that transports the rubber thread in the transport direction by rotating around a rotation axis that is perpendicular to the transport direction, and the rubber thread is wound around an area that is at least 1 / 4 of the circumference of the first transport roller.

5. A stretchable sheet manufacturing apparatus as described in claim 4, characterized in that the delivery section has a second transport roller that rotates around a rotation axis that is perpendicular to the transport direction and is spaced apart from the first transport roller, and the rubber thread is wound in an S-shape around the first transport roller and the second transport roller.

6. A stretchable sheet manufacturing apparatus as described in claim 1 or 2, characterized in that the delivery section has a pair of nip rollers that rotate around a rotation axis that is perpendicular to the conveying direction, and at least one of the first sheet and the second sheet and the rubber thread are sandwiched between the nip rollers.

7. A stretchable sheet manufacturing device as set forth in claim 1 or 2, characterized in that it has a tension adjustment section that sends out the rubber thread to the feed section, located upstream of the feed section in the conveying direction, and a tension of at least the specified magnitude is applied to the rubber thread between the tension adjustment section and the feed section.

8. Dependent on Claim 1 or 2 - A stretchable sheet manufacturing apparatus as set forth in Claim 1 or 2, characterized in that the first sheet meets the rubber thread at the feed-out section, and the second sheet meets the rubber thread at a position between the feed-out section and the welded section forming section.

9. A stretchable sheet manufacturing apparatus according to claim 8, characterized in that the second sheet merges with the rubber thread in the welding portion forming section.

10. A stretchable sheet manufacturing apparatus according to claim 1 or 2, characterized in that the first sheet and the second sheet merge with the rubber thread in the delivery section.

11. A stretchable sheet manufacturing apparatus as set forth in claim 10, characterized in that either the first sheet or the second sheet has a portion separated from the rubber thread between the delivery section and the welding section forming section.

12. A method for producing a stretchable sheet in which a first sheet and a second sheet are laminated together with a rubber thread therebetween, the method comprising: a welded portion forming step in which the laminated first sheet and the second sheet are sandwiched between an anvil roll and an ultrasonic horn arranged opposite the outer peripheral surface of the anvil roll to form a plurality of welded portions, and the position of the rubber thread between the first sheet and the second sheet is controlled by the formed welded portions; and a feed-out step in which at least one of the first sheet and the second sheet, together with the rubber thread, is fed toward the anvil roll and the ultrasonic horn from a feed-out section provided upstream of the ultrasonic horn and the anvil roll in a feed direction in which the rubber thread is fed, the feed-out section being spaced apart from the ultrasonic horn and the anvil roll; and a tension of a predetermined magnitude or more is applied to the rubber thread upstream of the feed-out section in the feed direction. A method for manufacturing an elastic sheet, characterized in that the feed-out section holds at least one of the first sheet and the second sheet and the rubber thread so that even if the rubber thread is cut in the welded portion forming section, the cut rubber thread does not slip upstream of the feed-out section in the conveying direction.

Images