JP2025179493A - Stretchable sheet manufacturing device and stretchable sheet manufacturing method - Google Patents

Abstract

A stretchable sheet is efficiently manufactured in which rubber thread is attached between two sheet members by a plurality of welded portions.
[Solution] An elastic sheet manufacturing device (100) comprising a welded portion forming section (130) equipped with an anvil roll (131) and an ultrasonic horn (132), and a feed-out section (120) provided at a distance from the ultrasonic horn (132) and the anvil roll (131) in the conveying direction and which feeds out at least one of a first sheet (11) and a second sheet (12) together with a rubber thread (14) to the welded portion forming section (130), wherein a tension of a predetermined magnitude or more is applied to the rubber thread (14) upstream of the feed-out section (120), and the feed-out section (120) holds at least one of the first sheet (11) and the second sheet (12) and the rubber thread (14) so that the rubber thread (14) cut in the welded portion forming section (130) does not slip out upstream of the feed-out section (120).
[Selected Figure] Figure 4

Description

The present invention relates to a stretchable sheet manufacturing apparatus and a stretchable sheet manufacturing method.

A conventional technique for manufacturing stretchable sheet members involves joining two stacked sheet members together by forming multiple welds without using adhesive, and then using the welds to sandwich and position a rubber thread between the sheet members from both sides in the width direction. 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 it by sandwiching the wire element in a isthmus 8 formed between connecting portions 6a and 6b.

Special Publication No. 2001-504899

As disclosed in Patent Document 1, a common method for manufacturing such stretchable sheets is to attach the rubber thread by, for example, sandwiching two sheet members and stretched rubber thread between an anvil and an ultrasonic horn to form a weld. However, if the rubber thread becomes 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 severed rubber thread is required, making it difficult to efficiently (continuously) manufacture stretchable sheets.

The present invention was made in consideration of the above-mentioned problems, and aims to efficiently manufacture a stretchable sheet in which rubber thread is attached between two sheet members by multiple welds.

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 greater 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 out 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.

This type of stretch sheet manufacturing device can efficiently produce stretch sheets in which rubber thread is attached between two sheet members using multiple welds.

1 is a plan view of a stretchable sheet 10 manufactured by a manufacturing apparatus (manufacturing method) according to a first embodiment. 2 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 a 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 side. 1 is a schematic cross-sectional view showing a stretchable sheet manufacturing apparatus 100 according to a first embodiment. Fig. 5A is a diagram illustrating the surface configurations of the anvil roll 131 and the ultrasonic horn 132. Fig. 5B is a schematic enlarged view of the closest portions of the anvil roll 131 and the ultrasonic horn 132. 6A and 6B are explanatory diagrams of a method for attaching the rubber thread 14 by the welded portion 50 (joint j). 10A to 10C are diagrams illustrating modified examples of the surface configuration of the anvil roll 131 and the ultrasonic horn 132. 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. FIG. 9A to 9D are diagrams illustrating the mechanism by which the rubber thread 14 is automatically restored when it is broken during the manufacturing process of the stretch sheet 10 using the stretch sheet manufacturing apparatus 100. FIG. 10A and 10B are diagrams illustrating how the rubber thread 14 is wound around the welded portion forming portion 130. FIG. 10A and 10B are diagrams illustrating how the rubber thread 14 is wound around the welded portion forming portion 130. FIG. 12A and 12B are schematic cross-sectional views of the stretchable sheet manufacturing apparatus 100 when the joining position of the second sheet 12 is changed. FIG. 10 is a schematic cross-sectional view showing a stretchable sheet manufacturing apparatus 100 according to a second embodiment. 10 is a schematic cross-sectional view illustrating a case where the second sheet 12 joins with the rubber thread 14 at the welded portion forming portion 130. FIG. FIG. 10 is a schematic cross-sectional view showing a modified example of the stretchable sheet manufacturing apparatus 100 according to the second embodiment.

At least the following points become clear from the description in this specification and the accompanying drawings.

(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.

In the stretch sheet manufacturing device 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). This prevents the rubber thread from slipping off upstream of the feed-out section, even if it is cut in the welding section and shrinks toward the upstream side. 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 out from the feed-out section toward the feed-out section together with the material sheet. 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 automatically recovers. This allows for efficient production of stretch sheets.

(Aspect 2)
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.

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. Furthermore, because the distance the rubber thread travels from the delivery section to the anvil roll is long, 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 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.

(Aspect 3)
The elastic sheet manufacturing apparatus according to aspect 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 are facing 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 facing 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 facing position.

In the stretch sheet manufacturing apparatus of aspect 3, by making the length of the stretch sheet wrapped 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 wrapped 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.

(Aspect 4)
The 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 of at least ¼ of the circumference of the first transport roller.

In the stretch sheet manufacturing device 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. Therefore, 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 it is wrapped around less than one-quarter, and the holding force can be strengthened. As a result, even if the rubber thread breaks, it is less likely to slip off upstream of the feed section, allowing for efficient production of stretch sheets.

(Aspect 5)
The 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 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.

In 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 section, allowing for efficient stretch sheet production.

(Aspect 6)
A 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 conveying direction, and at least one of the first sheet and the second sheet and the rubber thread are sandwiched between the nip rollers.

With 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 breaks, the contraction is stopped by the nip rollers, making it less likely to slip off upstream of the feed section, allowing for efficient stretch sheet production.

(Aspect 7)
A stretch sheet manufacturing apparatus according to any one of aspects 1 to 6, further comprising a tension adjustment unit located upstream of the feed-out unit in the conveying direction, which feeds out the rubber thread to the feed-out unit, and wherein tension of at least the predetermined magnitude is applied to the rubber thread between the tension adjustment unit and the feed-out unit.

The stretch sheet manufacturing device of aspect 7 is equipped with a mechanism that applies a tension of a predetermined magnitude or greater to the rubber thread between the tension adjustment unit and the feed-out unit, so that the rubber thread is constantly stretched as it is fed from the feed-out unit to the welded portion forming unit. Therefore, even if the rubber thread is cut in the welded portion forming unit, the cut rubber thread will not reach the upstream side of the feed-out unit, and the stretched rubber thread can continue to be fed from the feed-out unit. This makes it easier for cut rubber threads to automatically recover, allowing for efficient production of stretch sheets.

(Aspect 8)
A 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 portion forming section.

In the stretch sheet manufacturing device of aspect 8, one sheet joins the rubber thread at the feed-out section and presses down on 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 it reaches the point where the second sheet joins.

(Aspect 9)
A stretch sheet manufacturing apparatus according to aspect 8, wherein the second sheet merges with the rubber thread in the welded portion forming section.

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

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

In the stretch sheet manufacturing apparatus of aspect 10, the rubber thread is tightly held between two sheets in the feed-out section, making it more likely that the rubber thread will slip 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 less likely. This reduces the risk of damage to the rubber thread due to friction between the roller and the thread during the transport process.

(Aspect 11)
A stretchable sheet manufacturing apparatus according to aspect 10, wherein either the first sheet or the second sheet has a portion between the delivery section and the welded portion forming section where the first sheet or the second sheet is separated from the rubber thread.

According to the stretch sheet manufacturing apparatus of aspect 11, after the rubber thread is fed from the feed section, it is transported while separated from the sheet member for at least a portion of the way until it reaches the welded portion forming section. Therefore, resistance is reduced compared to when the rubber thread is transported 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 it is 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 produced efficiently.

(Aspect 12)
Also, a method for producing a stretchable sheet in which a first sheet and a second sheet are laminated with a rubber thread interposed therebetween includes 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 to the outer peripheral surface of the anvil roll to form a plurality of welded portions, and the formed welded portions regulate the position of the rubber thread between the first sheet and the second sheet; and a method for producing a stretchable sheet in which a first sheet and a second sheet are laminated with a rubber thread interposed therebetween, the method including: 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 to the outer peripheral surface of the anvil roll to form a plurality of welded portions, and the formed welded portions regulate the position of the rubber thread between the first sheet and the second sheet. 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.

In 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. This prevents the rubber thread from slipping out upstream of the feed-out section, even if it breaks in the welded section and shrinks upstream. Furthermore, even if the rubber thread breaks, tension is applied to the rubber thread between the tension adjustment section and the feed-out section, so the rubber thread continues to be fed from the feed-out section to the welded section while maintaining its elongated state, making it more likely to automatically recover. This allows for efficient manufacturing of stretch sheets.

First Embodiment
<Configuration of stretchable sheet 10>
Fig. 1 is a plan view of a stretchable sheet 10 manufactured by the manufacturing apparatus (manufacturing method) of the first embodiment. Fig. 1 is a view 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.

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, as well as multiple rubber threads 14 and multiple joints j interposed between the first sheet 11 and the second sheet 12.

The multiple rubber threads 14 are aligned in the stretch direction of the stretchable sheet 10 and are spaced apart in the width direction. The rubber threads 14 are attached to the first sheet 11 and the second sheet 12 in a stretched state. This gives the stretchable sheet 10 stretchability in the direction along which the rubber threads 14 are aligned. The rubber threads 14 (thread-like elastic members) can be made of natural rubber threads, as well as various known synthetic rubbers such as styrene-based rubber, urethane-based rubber, ester-based rubber, polyurethane, and polyethylene.

The multiple joints j join the first sheet 11 and the second sheet 12 to one another using known welding methods such as ultrasonic welding, and are arranged intermittently in the stretch direction and width direction of the stretchable sheet 10. Hereinafter, "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 relative to the first sheet 11 and the second sheet 12 in the stretch direction and width direction. As will be described in more 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 shown in Figure 1 is rectangular, the planar shape of the joints j is not particularly limited and can be any shape, such as an ellipse, a circle, or a parallelogram.

Note that while the stretchable sheet 10 in Figure 2 is composed of two sheets, it may alternatively be, for example, a single sheet folded over, with the folded portion serving as the first sheet portion and the unfolded portion serving as the second sheet portion. The stretchable sheet 10 may also be composed of one or more additional sheets layered over the first sheet 11 and second sheet 12. In other words, the stretchable sheet 10 may be three or more layers.

<Examples of use of the stretchable sheet 10>
Fig. 3A is a schematic perspective view of a pants-type disposable diaper 1 using a 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.

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 ventral region. As shown in the unfolded state in Figure 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 in the longitudinal center, and both left-right sides of the ventral waist section 3 and both left-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.

The ventral waistband portion 3 and the back waistband portion 4 are generally rectangular in plan view, and include multiple elastic threads 5 that stretch in the left-right direction of the diaper 1, spaced apart in the vertical direction. Therefore, the ventral waistband portion 3 and the back waistband portion 4 are stretchable in the left-right direction of the diaper 1, allowing them to fit the wearer's waist. A stretchable sheet 10 can be used in the ventral waistband portion 3 and the back waistband 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.

When the stretchable sheet 10 is used as a component of an absorbent article, the first sheet 11 and second sheet 12 that make up the stretchable sheet 10 can be made of soft sheet materials. For example, they can be made of 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 made of a stretchable sheet (stretchable film or stretchable nonwoven fabric) that can stretch in the stretch direction of the stretchable sheet 10.

Furthermore, the stretchable sheet 10 is not limited to being used in the ventral waistband portion 3 and the dorsal waistband portion 4. For example, the stretchable sheet 10 can be used in the 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 wearer's legs. Because 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.

In addition, in tape-type disposable diapers (not shown), fastening tape (hook members) extend from the back waistband to both left and right sides. Stretchable sheets 10 can be used for the side panels that attach the fastening tape to the back waistband. Because 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.

The stretchable sheet 10 can also be used as a component for absorbent articles such as pad-type disposable diapers, sanitary napkins, and sanitary shorts-type napkins, in addition to pants-type and tape-type disposable diapers. It can also be used for other absorbent articles, such as masks and cleaning sheets.

<Stretch sheet manufacturing device and manufacturing method>
FIG. 4 is a schematic cross-sectional view of a stretchable sheet manufacturing apparatus 100 according to a first embodiment. The stretchable sheet manufacturing apparatus 100, which manufactures a stretchable sheet 10 according to the first embodiment, includes a feed-out unit 120, a welded portion forming unit 130, and a tension adjusting unit 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.

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, first sheet 11, and second sheet 12 to the welded portion forming section 130. In FIG. 4, the feed-out section 120 has five types of rollers, first conveying roller 121 to fifth conveying roller 125, which rotate around their axes of rotation along the cross direction (CD). The first conveying roller 121 is rotated at a predetermined speed by a drive unit (not shown), thereby conveying the rubber thread 14 (continuous body) and the first sheet 11 (continuous body) from upstream to downstream in the conveying direction (MD). The second conveying roller 122 and 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 located 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 first sheet 11 being transported in the transport direction. The fifth transport roller 125 is a roller that rotates in response to the rotation of the fourth transport roller 124.

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

The weld forming unit 130, which performs the weld forming process to form the weld 50 (joint j) that joins the first sheet 11 and the second sheet 12 together, includes an anvil roll 131 and an ultrasonic horn 132. The anvil roll 131 is a rotating body that rotates around a rotation axis 131c along the cross direction (CD) by a drive source (not shown). By rotating with the stretchable sheet 10 wrapped around its outer periphery, the stretchable sheet 10 is transported in the machine direction (MD). The ultrasonic horn 132 is positioned opposite the outer periphery of the anvil roll 131 and amplifies ultrasonic vibrations supplied from a vibrator (not shown) to perform ultrasonic welding at its tip 132t. In Figure 4, at position P1 where the tip 132t of the ultrasonic horn 132 faces the outer circumferential surface of the anvil roll 131, the tip 132t ultrasonically vibrates with the materials (first sheet 11, rubber thread 14, and second sheet 12) sandwiched between them, thereby ultrasonically welding the materials to form a welded portion 50 (joint j). Note that the anvil roll 131 and the ultrasonic horn 132 need only be positioned opposite each other so that they can come into contact at position P1 via at least the materials passing between them.

Figure 5A is a diagram explaining the surface configuration of the anvil roll 131 and the ultrasonic horn 132. Figure 5B is a schematic enlarged view of the closest portion of the anvil roll 131 and the ultrasonic horn 132.

As shown in FIG. 5A, the outer peripheral surface of the anvil roll 131 is formed with multiple protrusions 311 that protrude radially outward. 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 pattern 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.

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 surface of the anvil roll 131 (i.e., in the thickness direction of the material passing through). 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.

The first sheet 11, second sheet 12, and rubber thread 14 are transported in the transport direction (MD) while wound around the anvil roll 131, passing 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, which transports the first sheet 11, etc., is approximately the same as the rotational speed of the anvil roll 131. Therefore, the first sheet 11, etc., are wound around the anvil roll 131 in a taut state without being stretched or slackened. Meanwhile, the rubber thread 14 is transported in a stretched state in the transport direction (MD) between the tension adjustment unit 140 (described below) and the first transport roller 121. In other words, it 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.

To form the welded portions 50 (joints 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. The first sheet 11 and the second sheet 12, sandwiched in the thickness direction between the outer circumferential surface of the anvil roll 131 and the tip 132t of the ultrasonic horn 132, are then ultrasonically welded to form multiple welded portions 50 (joints j). Specifically, as shown in Figure 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 circumferential surface of the anvil roll 131. At this time, the rubber thread 14 is positioned in the groove 312 between two adjacent convex portions 311 in the cross direction (CD) and is not ultrasonically welded. In other words, if the rubber thread 14 is positioned in the groove 312 when the welded portion 50 is being formed, the rubber thread 14 can be prevented from being pinched between the outer circumferential surface of the anvil roll 131 and the tip 132t of the ultrasonic horn 132 and being cut off (see Figure 8B, described below).

As explained in Figure 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 how the rubber thread 14 is attached using the welded portion 50 (joint j).

As shown in FIG. 6A , the distance D50 between a welded portion pair 50P, 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 greater than the width direction (CD) size D14 of the rubber thread 14 stretched when the welded portion pair 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 stretched state of the rubber thread 14 is relaxed after the welded portion pair 50P is formed, for example, by cutting the continuous rubber thread 14, the welded portion pair 50P can clamp the rubber thread 14, which attempts to expand in the width direction (CD) while contracting in the conveying 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 width direction (CD), and the rubber thread 14 is attached to the first sheet 11 and second sheet 12.

In the above example, multiple convex portions 311 and grooves 312 are formed on the outer peripheral surface of the anvil roll 131, and the tip 132t of the ultrasonic horn 132 is a smooth surface without any irregularities. However, this is not limited to this. Figure 7 is a diagram illustrating modified examples of the surface configuration of the anvil roll 131 and the ultrasonic horn 132.

In the modified example shown in Figure 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, the tip 132t of the ultrasonic horn 132 is provided with multiple protrusions 321 protruding on the side facing the anvil roll 131. Similar to the protrusions 311 described in Figure 5, multiple protrusions 321 are provided at predetermined intervals along the cross direction (CD), and when the gears 315 of the anvil roll 131 and the protrusions 321 of the ultrasonic horn 132 face each other, the materials are ultrasonically welded to form a welded portion 50 (joint j). In other words, by ultrasonically vibrating the protrusions 321 of the ultrasonic horn 132 while sandwiching the material (first sheet 11 and second sheet 12) between the protrusions 321 and the outer peripheral surface of the anvil roll 131, multiple welds 50 (joints j) can be formed in the arrangement shown in FIG. 1 according to the pattern of the protrusions 321 and the circumferential spacing of the gear 315. Furthermore, grooves 322 are formed between two adjacent protrusions 321, 321 in the cross direction (CD) of the ultrasonic horn 132. If rubber thread 14 is placed in the grooves 322 when forming the welds 50 (joints j), cutting of the rubber thread 14 is prevented, and the rubber thread 14 remains attached to the first sheet 11 and the second sheet 12.

Returning to FIG. 4, the tension adjustment unit 140 is a mechanism that is provided upstream of the feed-out unit 120 (first transport roller 121) in the transport direction (MD) and transports the rubber thread 14 downstream in the transport direction (MD). The tension adjustment unit 140 is composed of a pair of nip rollers that rotate while sandwiching the rubber thread 14, as shown in FIG. 4, for example. In this embodiment, the tension adjustment unit 140 is rotated by a drive unit (not shown) at a slower speed than the first transport roller 121 of the feed-out unit 120 to transport the rubber thread 14. As a result, the rubber thread 14 is stretched based on the difference in rotational speed (transport speed) between the tension adjustment unit 140 and the first transport roller 121 in the transport direction (MD), and is sent 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 adjustment unit 140 may be configured other than a nip roller, such as a known tension controller, or a combination of these.

<About cutting the rubber thread when forming the welded part>
As described above, in the stretch sheet manufacturing apparatus 100 of this embodiment, the 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 materials by clamping the rubber thread 14 from both sides in the cross direction (CD) with the pair of welded portions 50P. When forming the welded portion 50 (joint j), the rubber thread 14 is placed in the groove portion 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.

However, due to fluctuations in the rubber thread 14 during transport and the effects of wrinkles formed in the material sheet, the position of the rubber thread 14 in the cross direction (CD) is not always constant. 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 illustrate a case where the rubber thread 14 is supplied (transported) with a shifted position in the cross direction (CD) relative to the welded portion forming portion 130 (anvil roll 131).

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 Figure 1, etc.). Figure 8A shows two of the multiple rubber threads 14 provided on the stretchable sheet 10, namely, rubber threads 14a and 14b, wound around the outer circumferential surface of the anvil roll 131. One rubber thread 14a is positioned overlapping the groove 312 of the anvil roll 131, while the other rubber thread 14b is offset in the cross direction (CD) from the position of the groove 312 and overlapping the protrusion 311. When the anvil roll 131 rotates in this state and reaches a position facing the ultrasonic horn 132 (position P1 in Figure 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. In contrast, 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 Figure 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, the rubber thread 14 may be cut.

When the rubber thread 14 is cut at the welded portion forming section 130, the cut rubber thread 14 attempts to contract upstream and downstream in the conveying direction (MD) from the cut position (position P1 in Figure 4). Here, downstream of position P1, the welded portion pair 50P has already been formed and the rubber thread 14 is clamped 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 upstream in the conveying direction (MD) (towards the feed section 120).

In such cases, 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, with conventional stretch sheet manufacturing equipment, it is necessary to, for example, temporarily stop the conveyance of materials and restore the cut rubber thread so that it can be conveyed normally, which requires time and cost. Furthermore, such work makes it impossible to continuously manufacture stretch sheets. Thus, with conventional stretch sheet manufacturing equipment, there is a risk of a significant drop in production efficiency if the rubber thread is cut when forming the welded portion.

In this embodiment, the stretchable sheet manufacturing apparatus 100 automatically restores the rubber thread 14 even if it is broken during the manufacturing process of the stretchable sheet 10, enabling continuous manufacturing of the stretchable sheet 10 without stopping the apparatus. Specifically, the following measures are implemented to automatically restore the rubber thread 14 even if it is broken, 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.

Figures 9A to 9D are diagrams illustrating the mechanism by which the rubber thread 14 automatically recovers when it is broken during the manufacturing process of the stretch sheet 10 using the stretch sheet manufacturing apparatus 100. To simplify the explanation, some components (e.g., the second sheet 12) are omitted from Figures 9A to 9D.

When manufacturing a stretch sheet 10 using the stretch sheet manufacturing apparatus 100, as shown in FIG. 9A, the rubber thread 14 is transported from upstream to downstream in the conveying direction (MD) together with a sheet member (a material sheet such as the first sheet 11), 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 transported in the conveying direction (MD) together with the rubber thread 14 while being wound around the first conveying roller 121. In FIG. 4 (FIG. 9A), the rubber thread 14 is wound around the first conveying roller 121, and a continuous first sheet 11 is also wound around the first conveying roller 121 on top of the rubber thread 14. In other words, the rubber thread 14 is held sandwiched between the outer circumferential surface of the first conveying roller 121 and the first sheet 11. Therefore, even if the rubber thread 14 were to be cut at the welded portion forming portion 130 (position P1) located downstream in the conveying direction (MD) and shrink upstream, the rubber thread 14 would continue 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 "slip-out").

And, because the rubber thread 14 continues to be held by the first transport roller 121, the stretched state of the rubber thread 14 is also maintained in the transport direction (MD) between the first transport roller 121 (feed-out 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 fed out from the feed-out section 120 to the welded portion forming section 130 downstream in the transport direction (MD) while maintaining its stretched state, and the cut portion of the rubber thread 14 is unlikely to reach upstream of the feed-out section 120.

In this embodiment, the "tension of a predetermined magnitude or greater" applied to the rubber thread 14 between the tension adjustment unit 140 and the payout unit 120 is greater than zero, preferably 0.2 N or greater. In the state shown in Figure 9A, if the tension of the rubber thread 14 in the payout unit 120 is 0.2 N or greater, the same tension (0.2 N or greater) is acting on the rubber thread 14 between the payout unit 120 and the welded portion forming unit 130. If a tension of 0.2 N or greater is acting 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 even if the rubber thread 14 is broken, it can be automatically restored.

Figure 9B shows the case where 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 Figure 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 has contracted 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 adjustment section 140 and the feed-out section 120.

Next, the cut portion 14c of the rubber thread 14 is placed on the first sheet 11 with essentially zero tension (i.e., in an unstretched state). As shown in FIG. 9C , the cut portion 14c is fed toward the welded portion forming section 130 as the first sheet 11 is fed downstream in the conveying direction (MD). In this embodiment, the rubber thread 14 continues to be fed downstream in the conveying direction (MD) together with the first sheet 11 from the feed-out section 120. In other words, even if the rubber thread 14 is cut, the rubber thread 14 and first sheet 11 continue to be fed at a constant speed from the feed-out section 120 toward the welded portion forming section 130. Note that, in FIG. 9C , downstream of position P1 of the welded portion forming section 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 a stretchable sheet 10.

Next, as shown in Figure 9D, when the cut portion 14c of the rubber thread 14, which is being transported along with the first sheet 11, reaches position P1 of the weld formation section 130, a weld 50 is formed in the weld formation section 130, and the rubber thread 14 is attached to the first sheet 11 (and the second sheet 12) via the weld 50. When the cut portion 14c of the rubber thread 14 reaches position P1 of the weld formation 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 the specified level. That is, between the delivery section 120 and the weld formation section 130, the tension of the rubber thread 14 increases from zero to a predetermined level of 0.2 N or more. As the transport operation continues in this manner, the cut rubber thread 14 naturally returns to its pre-cut state, as shown in Figure 9A. This allows for efficient production of the stretchable sheet 10.

In this embodiment, after the rubber thread 14 and 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 significantly shifting from the position at the time of feeding out from the feed-out section 120, making it easier for it to recover naturally.

The stretchable sheet manufacturing apparatus 100 also helps prevent the rubber thread 14 from being cut when the welded portion 50 is formed in the welded portion forming unit 130 (see Figure 8B). In the case of Figure 8B, the rubber thread 14b wound around the anvil roll 131 is positioned so that it overlaps the convex portion 311 in the cross direction (CD), which creates a problem of it 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 that it overlaps 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 that it overlaps the convex portion 311 in the cross direction (CD) when it is wound around the anvil roll 131, cutting of the rubber thread 14 can be prevented if it can shift to the position of the groove portion 312 before being sandwiched between the anvil roll 131 and the ultrasonic horn 132.

10 and 11 are diagrams illustrating how the rubber thread 14 is wound around the weld portion forming section 130. Figure 10 shows the rubber thread 14 wound around the outer peripheral surface of the anvil roll 131 upstream in the conveying direction (MD) of position P1, where the anvil roll 131 and the ultrasonic horn 132 face each other. Specifically, the rubber thread 14 is fed out from the feed section 120 (first feed roller 121) at an angle θa toward the anvil roll 131 relative to the 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, upstream in the conveying direction (MD) of position P1. It 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 positions P2 and P3 on the outer circumferential surface of the anvil roll 131 while being wound around the anvil roll 131.

In Figure 10, the welded portion 50 has not yet been formed in the section from position P2 to position P1 on the outer circumferential surface of the anvil roll 131, so the position of the rubber thread 14 in the cross direction (CD) is not restricted. In other words, in this section, the rubber thread 14 is transported in a state where it can move in the cross direction (CD). Furthermore, because the rubber thread 14 is transported in a stretched state, tension acts to press the rubber thread 14 toward the radial center (131c) of the anvil roll 131 in the section from position P2 to position P1. Therefore, even if the rubber thread 14 is positioned on the convex portion 311 at position P2, where it begins to wind around the anvil roll 131, the rubber thread 14 may roll in the cross direction (CD) on the outer circumferential surface of the anvil roll 131, or may be pushed aside in the cross direction (CD) upon contact with the tip 132t of the ultrasonic horn 132, potentially entering the groove 312 at position P1 (see Figure 5B).

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 delivery section 120 (first transport roller 121), to position P2, where the rubber thread 14 begins to wrap 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 transported from the delivery 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 transport, increasing the likelihood of it getting caught in the groove 312 of the anvil roll 131. This prevents the rubber thread 14 from being cut when the welded portion forming unit 130 forms the welded portion 50.

Even if the positions of the convex portion 311 and the rubber thread 14 overlap as shown in Figure 8A, the length L1 from position P4 where the rubber thread 14 is unwound to 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 width direction (CD) while being transported the length L1, a force that shifts the rubber thread 14 to one side in the width 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 greater the moment that occurs when a shift in the width direction (CD) occurs, increasing the likelihood 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.

Next, Figure 11 shows the 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 position P1, where the anvil roll 131 and the ultrasonic horn 132 face each other. Specifically, the rubber thread 14 is fed out from the feed section 120 (first feed roller 121) at an angle θb toward the ultrasonic horn 132 with respect to the 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 ultrasonic horn 132 (tip 132t) at position P2', upstream in the conveying direction (MD) of position P1. It 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 position P2' of the ultrasonic horn 132 and position P3 of the anvil roll 131 while being wound around the ultrasonic horn 132 and the anvil roll 131.

As explained in Figure 7, if the outer peripheral surface of the anvil roll 131 is smooth and the protrusions 321 and grooves 322 are provided on the tip 132t side of the ultrasonic horn 132, the shorter the length of the rubber thread 14 in contact with the tip 132t of the ultrasonic horn 132, the more likely the rubber thread 14 will move in the cross direction (CD) and enter the grooves 322. Therefore, it is preferable that the length L1' from position P4, where the rubber thread 14 is sent out from the sending section 120 (first transport roller 121), to position P2', where the rubber thread 14 begins 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 shift (move) in the cross direction (CD) during transport compared to the reverse case, increasing the probability of it entering the grooves 322 of the ultrasonic horn 132. This prevents the rubber thread 14 from being cut when the welded portion forming unit 130 forms the welded portion 50.

Furthermore, the length L3 (the length along the outer circumferential 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 circumferential 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 circumferential 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).

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 lengthening the length L3 of the stretchable sheet 10 wrapped around the outer circumferential surface as much as possible, the stretchable sheet 10 can be transported stably downstream in the machine direction (MD) without wrinkling or other surface defects. 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 wrapped around the circumferential surface of the anvil roll 131 as much as possible, the rubber thread can be more easily moved in the cross direction (CD). This helps prevent the rubber thread 14 from being cut at position P1.

Furthermore, of the multiple transport rollers provided in the delivery section 120, it is preferable that the first transport roller 121, which transports the rubber thread 14, has the rubber thread 14 wound around it over an area of at least one-quarter of its circumference. In Figure 10, the rubber thread 14 is wound around an area of approximately 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 Figure 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, the rubber thread 14 in a stretched state is wound around the first transport roller 121, so the tension of the rubber thread 14 itself presses 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 achieving a stronger holding force. Therefore, even if the rubber thread 14 is cut when forming the welded portion 50, it is easier to prevent the cut rubber thread 14 from slipping off upstream in the transport direction (MD) from the feed 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 stretch sheets 10.

In Figure 10, the rubber thread 14 is wrapped around the first transport roller 121 over an area of at least 1/4 of the circumference of the first transport roller 121, with the first sheet 11 overlapping the rubber thread 14. With this configuration, the rubber thread 14 is held between the outer surface of the transport roller and the first sheet 11, and the length pressed down by the first sheet 11 is longer, resulting in a stronger holding force. Therefore, even if the rubber thread 14 is cut, it is easier to prevent it from coming loose.

Also, as shown in Figure 4 and other figures, in the delivery section 120, the rubber thread 14 is wound in an S-shape around the first transport roller 121 and the 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 in place 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 delivery section 120 in the conveying direction (MD).

In addition, a tension adjustment unit 140 is provided upstream of the feed-out unit 120 in the conveying direction (MD). The tension adjustment unit 140 and the feed-out unit 120 (first conveyor roller 121) rotate at different peripheral speeds, applying a predetermined amount of tension (at least 0.2 N) to the rubber thread 14. As a result, the rubber thread 14 is constantly stretched when it is fed from the feed-out unit 120 to the welded portion forming unit 130. Therefore, even if the rubber thread 14 is cut in the welded portion forming unit 130, the rubber thread 14 can continue to be fed in a stretched state from the feed-out unit 120. This makes it easier for the cut rubber thread 14 to automatically recover, allowing for efficient production of the stretchable sheet 10.

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

Furthermore, by joining another sheet (second sheet 12) downstream in the conveying direction (MD) of the feed-out section 120 (first conveying roller 121), the rubber thread 14 is sandwiched between the two sheets, which further reduces the likelihood of the rubber thread 14 slipping out. Furthermore, with the rubber thread 14 sandwiched between the two sheets in this manner, when the rubber thread 14 is cut in the welded portion forming section 130 and shrinks toward the upstream side in the conveying direction (MD), the shrinkage is more likely to stop by the time the second sheet joins. For example, in Figure 4, the fourth conveying roller 124 presses the rubber thread 14 and first sheet 11 in the thickness direction to join the second sheet 12, which reduces the likelihood of the cut rubber thread 14 slipping out upstream in the conveying direction (MD) of the fourth conveying roller 124. This therefore facilitates efficient production of the stretchable sheet 10.

<Example of change of joining position of second seat 12>
12A and 12B are schematic cross-sectional views illustrating a case where the joining position of the second sheet 12 is changed in the stretch sheet manufacturing apparatus 100. FIG. 12A illustrates a case where the second sheet 12 joins the rubber thread 14 and the first sheet 11 in the welded portion forming section 130. In FIG. 12A , the fourth conveying roller 124 that joins the second sheet 12 with the rubber thread 14 in FIG. 4 is not provided. Instead, the second sheet 12 is supplied directly to the welded portion forming section 130, where it joins the rubber thread 14 and the first sheet 11 at position P1. In this case, after being fed from the feed-out section 120, the rubber thread 14 is conveyed while separated from the second sheet 12 until just before the 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 (the first sheet 11 and the second sheet 12) as shown in FIG. 4. Therefore, the rubber thread 14 is likely to shift in the cross direction (CD) while being transported from the delivery 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, the rubber thread 14 is more likely to enter the grooves 312 (322) and is less likely to be cut. This makes it easier to efficiently manufacture the stretch sheet 10.

Figure 12B shows a case where the second sheet 12 merges with the rubber thread 14 and the first sheet 11 at the feed-out section 120 (first transport roller 121). That is, two sheet members merge with the rubber thread 14 at the feed-out section 120. In Figure 12B, the fourth transport roller 124 is not provided, and the first sheet 11 and second sheet 12 are fed out by the first transport roller 121. That is, in Figure 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 easier to prevent the rubber thread 14 from slipping off upstream in the transport direction (MD) of the first transport roller 121 if it is cut. Furthermore, because a sheet (the second sheet 12 in Figure 12B) is interposed between the rubber thread 14 and the first transport roller 121, direct contact between the rubber thread 14 and the roller is unlikely. This reduces the risk of damage to the rubber thread 14 due to friction between the rubber thread 14 and the roller during transport.

Second Embodiment
In the second embodiment, a stretchable sheet manufacturing apparatus 100 will be described in which the configuration of the delivery unit 120 is different from that of the first embodiment. Note that the configuration and function of each unit other than the delivery 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.

<Configuration of delivery section 120>
Figure 13 is a schematic cross-sectional view showing a stretchable sheet manufacturing apparatus 100 of a second embodiment. In the stretchable sheet manufacturing apparatus 100 of the second embodiment, the delivery section 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 between the first sheet 11 and the second sheet 12 by the nip rollers 127.

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 unit 130 and contracts from the cutting position (position P1 in Figure 13) toward the upstream side in the conveying direction (MD), the contraction is stopped by the nip roller 127 (feed-out unit 120), preventing the rubber thread 14 from slipping off upstream. Furthermore, because the rubber thread 14 is conveyed in a stretched state by the nip roller 127 (feed-out unit 120) and the tension adjustment unit 140 located 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 for efficient production of stretchable sheets 10 without having to stop the stretchable sheet manufacturing apparatus 100.

In Figure 13, two sheets (first sheet 11 and second sheet 12) are joined to the rubber thread 14 at the nip roller 127 (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 Figure 4 of the first embodiment, the first sheet 11 may be joined to the rubber thread 14 at the nip roller 127 (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.

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

The transport path of the second sheet 12 may also 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).

During the 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 roller 127 and sent downstream in the conveying direction (MD). Then, one of the first sheet 11 and second sheet 12 (second sheet 12 in Figure 15) is separated from the rubber thread 14 in the thickness direction by the separation roller 128. The separated second sheet 12 then rejoins the rubber thread 14 (and first sheet 11) at the welded portion forming section 130. With this configuration, the rubber thread 14 is sandwiched between the two sheet members on both sides in the thickness direction at the nip roller 127, making it easier to firmly hold the rubber thread 14 by the nip roller 127 and less likely to come loose. Furthermore, between the nip roller 127 and the weld formation unit 130, one sheet (second sheet 12) is separated on one side in the thickness direction, reducing resistance and making it easier for the rubber thread 14 to shift in the cross 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 in the weld formation unit 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 manufacture the stretchable sheet 10.

===Other===
Although the embodiments of the present invention have been described above, the above embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. Furthermore, the present invention may be modified or improved without departing from the spirit thereof, and it goes without saying that the present invention includes equivalents thereof.

1. Pants-type disposable diapers,
2 absorbent body, 3 ventral waist portion, 4 dorsal waist portion, 5 elastic thread,
10 Elastic sheet,
11 First sheet, 12 Second sheet, 14 Rubber thread,
50 welded part (joint part), 50P welded part pair,
100 Stretchable sheet manufacturing apparatus,
120 sending 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 spacing roller,
130 welding part forming part,
131 anvil roll,
311 convex portion, 312 groove portion,
132 ultrasonic horn, 132t tip,
321 convex portion, 322 groove portion,
140 tension adjustment section,
P1 position,
MD: conveying direction (stretching direction), CD: width direction,
j junction, jP junction pair

Claims (12)

An apparatus for manufacturing a stretchable sheet in which a first sheet and a second sheet are laminated with rubber threads interposed therebetween,
a weld portion forming section including an anvil roll and an ultrasonic horn disposed opposite to an outer peripheral surface of the anvil roll, the weld portion forming section sandwiching the stacked first sheet and the second sheet to form a plurality of weld portions, and regulating the position of the rubber thread between the first sheet and the second sheet by the formed weld portions;
a delivery section that is provided upstream of and spaced apart from the ultrasonic horn and the anvil roll in a transport direction in which the rubber thread is transported, and that delivers at least one of the first sheet and the second sheet together with the rubber thread to the welded portion forming section;
and
a tension equal to or greater than a predetermined magnitude is applied to the rubber thread upstream of the delivery section in the transport 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. The stretchable sheet manufacturing apparatus according to claim 1,
The length of the rubber thread wound around the outer peripheral surface of the anvil roll on the upstream side in the conveying direction of the position where the anvil roll and the ultrasonic horn face each other is
An elastic sheet manufacturing apparatus characterized in that the length of the rubber thread is shorter than the length of the rubber thread from the position where it 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. The stretchable sheet manufacturing apparatus according to claim 1 or 2,
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 a position where the anvil roll and the ultrasonic horn face each other,
An elastic sheet manufacturing apparatus characterized in that the length of the rubber thread wound around the outer peripheral surface of the anvil roll upstream of the opposing position in the conveying direction is shorter than the length of the rubber thread wound around the outer peripheral surface of the anvil roll downstream of the opposing position in the conveying direction. The stretchable sheet manufacturing apparatus according to claim 1 or 2,
the delivery section includes a first transport roller that rotates about a rotation axis that is perpendicular to the transport direction to transport the rubber thread in the transport direction,
The elastic sheet manufacturing apparatus is characterized in that the rubber thread is wound around the first transport roller over an area of at least one-fourth of the circumference of the first transport roller. The stretchable sheet manufacturing apparatus according to claim 4,
the delivery unit has a second transport roller that rotates about a rotation axis in a direction perpendicular to the transport direction and is provided apart from the first transport roller;
The elastic sheet manufacturing apparatus is characterized in that the rubber thread is wound around the first transport roller and the second transport roller in an S-shape. The stretchable sheet manufacturing apparatus according to claim 1 or 2,
the delivery section has a pair of nip rollers that rotate around a rotation axis that is perpendicular to the conveyance direction,
The stretchable sheet manufacturing apparatus is characterized in that at least one of the first sheet and the second sheet and the rubber thread are sandwiched between the nip rollers. The stretchable sheet manufacturing apparatus according to claim 1 or 2,
a tension adjusting section for feeding the rubber thread to the feeding section, the tension adjusting section being located upstream of the feeding section in the conveying direction;
A stretch sheet manufacturing apparatus, characterized in that a tension equal to or greater than the predetermined magnitude is applied to the rubber thread between the tension adjusting section and the delivery section. Dependent on claim 1 or 2
The stretchable sheet manufacturing apparatus according to claim 1 or 2,
the first sheet joins with the rubber thread at the delivery section,
The stretchable sheet manufacturing apparatus is characterized in that the second sheet merges with the rubber thread at a position between the delivery section and the welded section forming section. The stretchable sheet manufacturing apparatus according to claim 8,
The stretch sheet manufacturing apparatus is characterized in that the second sheet merges with the rubber thread in the welded portion forming section. The stretchable sheet manufacturing apparatus according to claim 1 or 2,
The stretch sheet manufacturing apparatus is characterized in that the first sheet and the second sheet merge with the rubber thread in the delivery section. The stretchable sheet manufacturing apparatus according to claim 10,
a stretchable sheet manufacturing apparatus, 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 welded section forming section; A method for producing a stretchable sheet in which a first sheet and a second sheet are laminated with rubber threads interposed therebetween, comprising:
a welded portion forming step of sandwiching the stacked first sheet and the second sheet between an anvil roll and an ultrasonic horn disposed opposite to the 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;
a feeding step of feeding at least one of the first sheet and the second sheet together with the rubber thread toward the anvil roll and the ultrasonic horn from a feeding section provided upstream of the ultrasonic horn and the anvil roll in a feeding direction in which the rubber thread is fed;
and
a tension equal to or greater than a predetermined magnitude is applied to the rubber thread upstream of the delivery section in the transport 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.