Manufacturing apparatus and manufacturing method for manufacturing composite sheet associated with absorbent article

A manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, including: a producing device that produces a substrate sheet by fixing a stretchable sheet to at least low-extensible sheet, the stretchable sheet continuing along a transporting direction, the stretchable sheet being in an extended state in which the stretchable sheet is extended in the transporting direction, the producing is performed while the producing device is transporting the stretchable sheet; a reference-section forming apparatus that forms a physical reference section on the substrate sheet, the substrate sheet being in a first extended state and being transported; a contraction apparatus in which the substrate sheet that has the reference section formed on it contracts until the substrate sheet becomes in a second extended state whose extension ratio is smaller than an extension ratio of the first extended state; and a processing apparatus that performs the certain process to the substrate sheet, the substrate sheet having contracted and being in the second extended state. The contraction apparatus includes: a transport path in which the substrate sheet is transported; a sensor that detects the reference section after the contraction in the contraction apparatus and that outputs a detection signal; and an alteration device that alters a transportation state of the substrate sheet in the transport path so that a position in the substrate sheet for the certain process is located close to a target position for the certain process, the alteration being performed according to the detection signal of the sensor.

RELATED APPLICATION

The present application is a 35 U.S.C. § 371 national stage filing of International Patent Application No. PCT/JP2014/077492, filed Oct. 16, 2014, to which priority is claimed under 35 U.S.C. § 120 and through which priority is claimed under 35 U.S.C. § 119 to Japanese Priority Patent Application No. 2014-065247, filed Mar. 27, 2014, the entire disclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The invention relates to a manufacturing apparatus and a manufacturing method for manufacturing a composite sheet associated with an absorbent article such as a disposable diaper.

BACKGROUND ART

In a manufacturing line of a disposable diaper which is an example of an absorbent article, a stretchable sheet is in an extended state of a certain extension ratio and is transported in a transporting direction, and a substrate sheet is produced by stacking and joining the stretchable sheet onto a low-extensible sheet. In the general case, the substrate sheet remains in the foregoing extended state and is being transported to the downstream process. In the downstream process, the substrate sheet being in the foregoing extended state sequentially undergoes suitable processes such as attaching an absorbent main body which absorbs liquid. Then, the substrate sheet is divided into unit parts each of which corresponds to a single finished diaper. Finally, the diaper is produced.

Following the dividing, the extension of the substrate sheet is released and the substrate sheet contracts in the transporting direction. The substrate sheet is used in the exterior of a diaper, and a plurality of creases are generated in the exterior along a direction intersecting the transporting direction. Accordingly, a finished diaper is at least in a state which the diaper has contracted and is able to extend till the creases completely stretch. As a result, a diaper user such as a wearer can use a stretchable diaper.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In some cases, the foregoing processes is effectively perform after the extended state of the substrate sheet is released in a certain degree, that is, after the substrate sheet becomes in a second extended state whose extension ratio is smaller than the extension ratio of the foregoing extended state. An example thereof will be described below.

If an absorbent main body is attached to the substrate sheet which is in the extended state, when the extended state is released, creases are generated in the absorbent main body due to contraction force which is applied to the absorbent main body from the substrate sheet. This may cause deterioration of liquid absorbency of the absorbent main body because of area reduction of the surface facing wearer's skin, and may also cause leakage of urine through the creases. In this regard, before attaching the absorbent main body, if the extended state of the substrate sheet is released (e.g. by 10% of the extension ratio) as mentioned above, the contraction force which is applied to the absorbent main body from the substrate sheet is reduced by the amount of the contraction of the substrate sheet caused by the release. This allows the absorbent main body to be substantially flat and less creased. This makes it possible to enlarge the area of the surface facing wearer's skin. And, this can prevent a trouble such as deterioration of liquid absorbency of the absorbent main body, which is caused by contraction of the absorbent main body.

However, the magnitude of contraction deformation of the substrate sheet could vary depending on each part of the same sheet. This makes it difficult to perform the foregoing various processes (e.g. attaching the absorbent main body after 10% contraction) at target positions in the substrate sheet.

The invention has been made in view of the above problems, and an advantage thereof is to achieve a processing of a substrate sheet at an exact target position even if the substrate sheet has contracted from the first extended state to the second extended state.

Solution to Problem

An aspect of the invention to achieve the above advantage is a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article,

the manufacturing being performed by producing a substrate sheet and performing a certain process to the substrate sheet,the substrate sheet including a stretchable sheet and a low-extensible sheet,the low-extensible sheet having an extensibility lower than that of the stretchable sheet,

the manufacturing apparatus including:

a producing device that produces the substrate sheet by fixing the stretchable sheet to at least the low-extensible sheet,the stretchable sheet continuing along a transporting directionthe stretchable sheet being in an extended state in which the stretchable sheet is extended in the transporting direction,the producing is performed while the producing device is transporting the stretchable sheet;

a reference-section forming apparatus that forms a physical reference section on the substrate sheet,the substrate sheet being in a first extended state and being transported;

a contraction apparatus in which the substrate sheet that has the reference section formed on it contracts until the substrate sheet becomes in a second extended state whose extension ratio is smaller than an extension ratio of the first extended state; and

a processing apparatus that performs the certain process to the substrate sheet,the substrate sheet having contracted and being in the second extended state,the contraction apparatus including:a transport path in which the substrate sheet is transported;a sensorthat detects the reference section after the contraction in the contraction apparatus andthat outputs a detection signal; andan alteration device that alters a transportation state of the substrate sheet in the transport path so that a position in the substrate sheet for the certain process is located close to a target position for the certain process,the alteration being performed according to the detection signal of the sensor.

a manufacturing method for manufacturing a composite sheet associated with an absorbent article,

the manufacturing being performed by producing a substrate sheet and performing a certain process to the substrate sheet,the substrate sheet including a stretchable sheet and a low-extensible sheet,the low-extensible sheet having an extensibility lower than that of the stretchable sheet,

the manufacturing method including:

producing the substrate sheet by fixing the stretchable sheet to at least the low-extensible sheet,the stretchable sheet continuing along a transporting direction,the stretchable sheet being transported,the stretchable sheet being in an extended state in which the stretchable sheet is extended in the transporting direction;

forming a physical reference section on the substrate sheet,the substrate sheet being in a first extended state and being transported;

causing the substrate sheet to contract in a contraction apparatus until the substrate sheet becomes in a second extended state whose extension ratio is smaller than an extension ratio of the first extended state,the substrate sheet having the reference section formed on it; and

performing the certain process by a processing apparatus to the substrate sheet,the substrate sheet having contracted and being in the second extended state,

causing the substrate sheet to contract including:transporting the substrate sheet in a transport path;detecting the reference section by a sensor and outputting a detection signal by a sensor after the contraction in the contraction apparatus; andaltering a transportation state of the substrate sheet in the transport path so that a position in the substrate sheet for the certain process by the processing apparatus is located close to a target position for the certain process,the altering being performed according to the detection signal of the sensor.

Other features of this invention will become apparent from the description in this specification and the attached drawings.

Advantageous Effects of Invention

According to the invention, it is possible to achieve a processing of a substrate sheet at an exact target position even if the substrate sheet has contracted from the first extended state to the second extended state.

DESCRIPTION OF EMBODIMENTS

At least the following matters will be made clear by the description in the present specification and the accompanying drawings.

A manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article,

the manufacturing being performed by producing a substrate sheet and performing a certain process to the substrate sheet,the substrate sheet including a stretchable sheet and a low-extensible sheet,the low-extensible sheet having an extensibility lower than that of the stretchable sheet,

the manufacturing apparatus including:

a producing device that produces the substrate sheet by fixing the stretchable sheet to at least the low-extensible sheet,the stretchable sheet continuing along a transporting directionthe stretchable sheet being in an extended state in which the stretchable sheet is extended in the transporting direction,the producing is performed while the producing device is transporting the stretchable sheet;

a reference-section forming apparatus that forms a physical reference section on the substrate sheet,the substrate sheet being in a first extended state and being transported;

a contraction apparatus in which the substrate sheet that has the reference section formed on it contracts until the substrate sheet becomes in a second extended state whose extension ratio is smaller than an extension ratio of the first extended state; and

a processing apparatus that performs the certain process to the substrate sheet,the substrate sheet having contracted and being in the second extended state,the contraction apparatus including:a transport path in which the substrate sheet is transported;a sensorthat detects the reference section after the contraction in the contraction apparatus andthat outputs a detection signal; andan alteration device that alters a transportation state of the substrate sheet in the transport path so that a position in the substrate sheet for the certain process is located close to a target position for the certain process,the alteration being performed according to the detection signal of the sensor.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, when the substrate sheet is in the first extended state in which the extension ratio is large, the reference section is formed on the substrate sheet. This makes it possible to form the reference section substantially without being affected by fluctuation of the contraction. Consequently, the reference section can be formed exactly at its target position in the substrate sheet. Thus, the reference section can effectively function as a positional reference on a substrate sheet.

The sensor detects the reference section after the contraction in the contraction apparatus, and outputs the detection signal. According to the detection signal, alteration device alters the transportation state of the substrate sheet in the transport path of the contraction apparatus. Thus, the position in the substrate sheet for the certain process is adjusted so as to be located close to its target position. Consequently, concerning the substrate sheet which has contracted in the contraction apparatus till the second extended state, the processing apparatus can perform a process exactly at its target position on the substrate sheet.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

when the transport path is divided into an upstream path section and a downstream path section, the downstream path section being located downstream in the transporting direction from the upstream path section,the alteration device is arranged at a boundary position between the upstream path section and the downstream path section.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, when the transport path included in the foregoing contraction apparatus is divided into the upstream path section and the downstream path section, the alteration device is arranged at a boundary position between these two path sections. With high responsivity, the transportation state of the substrate sheet which is moving in the transport path can be therefore altered according to the detection signal.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

the alteration device includes a roll whose outer circumferential surface comes into contact with the substrate sheet and that is driven and rotated, and

the transportation state of the substrate sheet in the transport path is altered by altering a circumferential speed value of the roll.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, the transportation state of the substrate sheet in the transport path is altered by altering a circumferential speed value of the roll. This makes it possible to quickly and securely alter the transportation state.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

the alteration device includes a controller that controls the roll according to the detection signal,

when the detection signal indicates that a target position in a substrate sheet for the certain process is shifted upstream in the transporting direction from a position at which the certain process has been performed by the processing apparatus,the controller increases the circumferential speed value of the roll, and

when the detection signal indicates that the target position in the substrate sheet for the certain process is shifted downstream in the transporting direction from a position at which the certain process has been performed by the processing apparatus,the controller decreases the circumferential speed value of the roll.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, the controller increases and decreases the circumferential speed value of the roll according to the detection signal as mentioned above. Accordingly, the position in the substrate sheet for the certain process can be securely adjusted so as to be located closer to the target position for the certain process.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

the alteration device includes a roll whose outer circumferential surface comes into contact with the substrate sheet and that is capable of rotating,

the transportation state of the substrate sheet in the transport path is altered by reciprocating motion of the roll along a thickness direction of the substrate sheet.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, the transportation state of the substrate sheet in the transport path is altered by reciprocating motion of the roll along a thickness direction of the substrate sheet. This makes it possible to quickly and securely alter the transportation state.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

the alteration device includes a controller that controls the roll according to the detection signal,

when the detection signal indicates that a target position in a substrate sheet for the certain process is shifted upstream in the transporting direction from a position at which the certain process has been performed by the processing apparatus,the controller moves the roll in the thickness direction so that a loop of the substrate sheet formed by the roll becomes smaller, and

when the detection signal indicates that the target position in the substrate sheet for the certain process is shifted downstream in the transporting direction from a position at which the certain process has been performed by the processing apparatus,the controller moves the roll in the thickness direction so that a loop of the substrate sheet formed by the roll becomes larger.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, the controller adjusts the size of the loop of the substrate sheet formed by the roll, and the adjustment is performed according to the detection signal as mentioned above. Accordingly, the position in the substrate sheet for the certain process can be securely adjusted so as to be located closer to target position for the certain process.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

on the substrate sheet which is in the first extended state, parts each of which is to be the absorbent article are aligned in the transporting direction at a first pitch, and

the reference-section forming apparatus forms a leg opening of the absorbent article on the substrate sheet,the leg opening being aligned at the first pitch and serving as the reference section.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, the leg opening is used as the reference section. Accordingly, other processes necessary to manufacture the absorbent article can be performed using the leg opening as a reference. This makes it possible to manufacture an absorbent article with which a wearer is less likely to feel uncomfortable.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

the reference-section forming apparatus prints a mark on the substrate sheet as the reference section.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, the mark is printed as the reference section. This makes it possible to easily form the reference section on the substrate sheet.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

the reference-section forming apparatus prints the mark on the low-extensible sheet of the substrate sheet.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, the mark is printed as the reference section on the low-extensible sheet of the substrate sheet. Accordingly, because of low extensibility of the low-extensible sheet, the mark can serve as more precise reference section.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

on the substrate sheet which is in the first extended state, parts each of which is to be the absorbent article are aligned in the transporting direction at a first pitch, and

when a pitch obtained by reducing the first pitch at a ratio of the extension ratio in the second extended state to the extension ratio of the first extended state is defined as a second pitch,the processing apparatus performs the certain process to the substrate sheet at the second pitch.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, the substrate sheet which is in the second extended state is subject to the certain process at the foregoing second pitch. This makes it possible to securely perform the certain process for each part of the substrate sheet, the part is a part that is to be the absorbent article.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

the absorbent article includes an absorbent main body that absorbs liquid, and

the processing apparatus attaches the absorbent main body to the substrate sheet at the second pitch,the attachment being performed as the certain process.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, the absorbent main body is attached to the substrate sheet, the attachment being performed as the certain process. Accordingly, the absorbent main body can be attached to the substrate sheet precisely.

The extended state of the substrate sheet at the time of attachment of the absorbent main body is the second extended state in which the substrate sheet has contracted from the first extended state. Accordingly, in the absorbent article whose extended state has been finally released, the amount of creases which are produced on the absorbent main body is reduced by an amount corresponding to the contraction.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

concerning the substrate sheet that is in the second extended state and that is in a two-folded state in which the substrate sheet is two-folded in a width direction of the substrate sheet,in the processing apparatus, the substrate sheet is fixed in the two-folded state by forming a joined part on the substrate sheet at the second pitch,the forming of the joined part is performed by the processing apparatus as the certain process.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, the joined part is formed on the substrate sheet, and the forming of the joined part is performed as the certain process in order to fix the substrate sheet in the two-folded state. Accordingly, the joined part can be formed on the substrate sheet precisely.

The extended state of the substrate sheet at the time of forming the joined part is the second extended state in which the substrate sheet has contracted from the first extended state. Accordingly, at the time of forming the joined part, the basis weight of the substrate sheet increases by an amount corresponding to the contraction. This makes it possible to increase the joining strength of the joined part.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

concerning the substrate sheet that is in the second extended state and that is fixed in a two-folded state in which the substrate sheet is two-folded in a width direction of the substrate sheet,the processing apparatus produces the absorbent article by cutting the substrate sheet at the second pitch,the cutting is performed by the processing apparatus as the certain process.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, the substrate sheet that is in second extended state and that is fixed in the two-folded state is cut at the second pitch to produce the absorbent article. This makes it possible to produce the absorbent article with high size precision.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

an extension ratio of the substrate sheet in the first extended state remains at an extension ratio in the extended state at a time of the fixing process in the producing device in which the stretchable sheet is fixed to the low-extensible sheet,

the low-extensible sheet when is fixed to the stretchable sheet that is in the extended state is extended and tightened, and

the reference section is formed for each part of the substrate sheet, the part is a part that is to be the absorbent article.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, in the first extended state, which is an extended state for forming the reference section on the substrate sheet, the stretchable sheet remains is in the extended state at the time of the fixing process in which the stretchable sheet is fixed to the low-extensible sheet. And, at the time of the fixing, the low-extensible sheet is extended and tightened. Accordingly, the reference section can effectively function as a more precise positional reference.

The reference section is formed for each part that is to be the absorbent article. Accordingly, each part that is to be the absorbent article can be subject to the certain process precisely. This makes it possible to finish each absorbent article with higher precision.

In such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, it is desirable that

during a time period from the contraction in the contraction apparatus till the certain process,the sensor detects the reference section and outputs the detection signal.

With such a manufacturing apparatus for manufacturing a composite sheet associated with an absorbent article, the sensor detects the reference section and outputs the detection signal, during the time period from the contraction in the contraction apparatus till the certain process. This makes it possible to more quickly and more securely perform an adjustment according to the detection signal, the adjustment is performed by altering the transportation state of the substrate sheet so that the position in the substrate sheet for the certain process is located closer to a the target position in the substrate sheet for the certain process.

a manufacturing method for manufacturing a composite sheet associated with an absorbent article,

the manufacturing being performed by producing a substrate sheet and performing a certain process to the substrate sheet,the substrate sheet including a stretchable sheet and a low-extensible sheet,the low-extensible sheet having an extensibility lower than that of the stretchable sheet,

the manufacturing method including:

producing the substrate sheet by fixing the stretchable sheet to at least the low-extensible sheet,the stretchable sheet continuing along a transporting direction,the stretchable sheet being transported,the stretchable sheet being in an extended state in which the stretchable sheet is extended in the transporting direction;

forming a physical reference section on the substrate sheet,the substrate sheet being in a first extended state and being transported;

causing the substrate sheet to contract in a contraction apparatus until the substrate sheet becomes in a second extended state whose extension ratio is smaller than an extension ratio of the first extended state,the substrate sheet having the reference section formed on it; and

performing the certain process by a processing apparatus to the substrate sheet,the substrate sheet having contracted and being in the second extended state,

causing the substrate sheet to contract including:transporting the substrate sheet in a transport path;detecting the reference section by a sensor and outputting a detection signal by a sensor after the contraction in the contraction apparatus; andaltering a transportation state of the substrate sheet in the transport path so that a position in the substrate sheet for the certain process by the processing apparatus is located close to a target position for the certain process,the altering being performed according to the detection signal of the sensor.

With such a manufacturing method for manufacturing a composite sheet associated with an absorbent article, when the substrate sheet is in the first extended state in which the extension ratio is large, the reference section is formed on the substrate sheet. This makes it possible to form the reference section substantially without being affected by fluctuation of the contraction. Consequently, the reference section can be formed exactly at its target position in the substrate sheet. Thus, the reference section can effectively function as a positional reference on a substrate sheet.

The sensor detects the reference section after the contraction in the contraction apparatus, and outputs the detection signal. According to the detection signal, alteration device alters the transportation state of the substrate sheet in the transport path of the contraction apparatus. Thus, the position in the substrate sheet for the certain process is adjusted so as to be located close to its target position. Consequently, concerning the substrate sheet which has contracted in the contraction apparatus till the second extended state, the processing apparatus can perform a process exactly at its target position on the substrate sheet.

Present Embodiment

A manufacturing apparatus for a composite sheet associated with an absorbent article according to the present embodiment is used in a manufacturing line LM of pull-on disposable diapers1, which is an example of the absorbent article.

FIG. 1is a schematic perspective view of a pull-on diaper1.FIG. 2is a schematic plan view of the diaper1which is spread out, as viewed from its skin side.FIG. 3is a schematic perspective view of the diaper1which is spread out and exploded.

In the description below, the side of a diaper1which should be located at the skin side of a wearer is merely referred to as a “skin side”, and the side which should be located at the non-skin side of the wearer is merely referred to as a “non-skin side”.

As shown inFIGS. 2 and 3, the diaper1is, for example, a diaper1consisting of two pieces. That is, the diaper1includes: an absorbent main body3in a substantially rectangular shape when viewed from above, as a first component, which absorbs excretion liquid such as urine; and an exterior sheet7in a substantially hourglass shape when viewed from above, as an second component, which covers the non-skin-side surface of the absorbent main body3and serves as an exterior of a diaper1.

As shown inFIG. 3, the absorbent main body3includes an absorbent core3cwhich absorbs excretion liquid. The absorbent core3cis a body formed by shaping liquid-absorbent fiber (e.g. pulp fiber) or liquid-absorbent particles (e.g. superabsorbent polymer) into a predetermined shape (e.g. a substantially rectangular shape when viewed from above). Such an absorbent core3cmay be covered as necessary with a liquid-permeable cover sheet such as tissue paper.

On the skin-side surface of the absorbent core3c, a liquid permeable top sheet4(e.g. nonwoven fabric) is provided so as to cover the surface. Also, on the non-skin-side surface of the absorbent core3c, a liquid-impermeable leak-proof sheet5(e.g. film) is provided so as to cover the entire of the surface.

Here, in this example, both of the sheets4and5have a substantially rectangular shape when viewed from above, and extend and project outwardly from the longitudinal ends of the absorbent core3c. The projecting parts4eL of the top sheet4and the projecting parts5eL of the leak-proof sheet5are respectively joined to each other by means such as adhesion or welding. In the width direction, the leak-proof sheet5extends and projects outwardly from both ends of the absorbent core3c. These projecting parts5eW and5eW are folded back to the skin side, and are fixed by means such as adhesion or welding while covering the widthwise ends of the top sheet4. Thus, the top sheet4and the leak-proof sheet5wrap the absorbent core3cto form the absorbent main body3.

Rubber threads (not shown) may be provided, as elastic members, in both widthwise ends of the absorbent main body3along the longitudinal direction of the absorbent main body3. Such rubber threads are for providing stretchability to parts of the absorbent main body3and parts of the exterior sheet7in the vicinity of the leg openings HL. The rubber threads are placed, for example, between the top sheet4and the leak-proof sheet5, and are fixed to these sheets4and5with adhesive (e.g. hot-melt adhesive) while being extended by a predetermined ratio (two to four times of its original unstretched length).

In some cases, leakage-proof walls (not shown) for preventing side leakage of urine may be provided in the absorbent main body3. Such leakage-proof walls are so-called barrier cuffs. The barrier cuffs are configured by flexible sheets such as nonwoven fabric, and are provided, for example, on both ends of the skin-side surface of the absorbent main body3so as to stand. However, the leakage-proof wall is well known, and the description thereof will be omitted.

The exterior sheet7is a flexible sheet having a substantially hourglass shape when viewed from above in the state in which a diaper1is spread out as shownFIG. 2. The sheet7has three directions perpendicular to one another: the thickness direction; the longitudinal direction; and the width direction. The exterior sheet7is classified into three parts7f,7band7cin the longitudinal direction. That is, the exterior sheet7is classified into: a ventral part7farranged on the stomach side of a wearer; a dorsal part7barranged on the back side of a wearer; and a crotch part7carranged on the crotch of a wearer. It goes without saying that the crotch part7cis located between the ventral part7fand the dorsal part7b. In a substantially hourglass shape when viewed from above, the crotch part7cis a narrowed part7cin the width direction.

As shown inFIG. 3, the exterior sheet7is made of a so-called laminated sheet7having a two-layer structure. That is, the exterior sheet7includes an inner-layer sheet8and an outer-layer sheet9: the inner-layer sheet8faces the skin side of a wearer to serve as an inner layer; and the outer-layer sheet9faces the non-skin side of a wearer to serve as an outer layer. The inner-layer sheet8and the outer-layer sheet9are stacked in the thickness direction and are joined to each other by means such as adhesion or welding. In this example, welding is performed in a certain joining pattern (not shown) in which joined parts are discontinuously distributed.

The inner-layer sheet8is made of a stretchable sheet8having a stretchability in the width direction of a diaper1. And, the outer-layer sheet9is made of a low-extensible sheet9having a low extensibility in the width direction of a diaper1. The inner-layer sheet8having a stretchability is extended by a certain extension ratio corresponding to 2.5 times the original unstretched length in the width direction, for example (hereinafter referred to as an extended state), and the extended inner-layer sheet is stacked on the low extensible outer-layer sheet9which is stretched in the width direction. These sheets8and9are fixed to each other in the joining pattern in an integrated manner.

When the extended state is released, the inner-layer sheet8contracts in the width direction of the diaper1due to its stretchability. And, the outer-layer sheet9having a low extensibility bends in the width direction of the diaper1in the form of a plurality of creases. Thus, the outer-layer sheet9quickly follows the contraction of the inner-layer sheet8, and the entire length of the outer-layer sheet9in the width direction decreases. Consequently, in a state in which external force is not exerted on a diaper1, the entirety of the exterior sheet7shortens in the width direction, and simultaneously the outer surface of the exterior sheet7has a plurality of creases caused by the bending of the outer-layer sheet9. However, pulling external force in the width direction is exerted on the exterior sheet7, the exterior sheet7can extend almost elastically till the creases have completely stretched. That is, the exterior sheet7of a diaper1has a stretchability in the width direction.

The foregoing “stretchability” means a characteristic as follow: when pulling external force is exerted on an object, the object extends almost elastically in a direction in which the external force acts, and when the external force is released, the object contracts almost elastically. As mentioned above, a sheet having such a stretchability is the “stretchable sheet8”.

It is preferable that the stretchable sheet8satisfies the following conditions. That is, concerning a band-like sheet having a lateral length of 25 mm, while the longitudinal ends of the band-like sheet being held equally throughout the entire lateral length of 25 mm, the band-like sheet is pulled in the longitudinal direction with an external force of 1.0(N) which is applied on the longitudinal ends, and. Under this condition, it is preferable that the elongation ratio (%) of the band-like sheet is any value from 50% to 300%. Simultaneously, it is preferable that a residual elongation (%) which is elongation remaining after a sheet has contracted by releasing the external force is any value from 0% to 40%. It is more preferable that the elongation ratio is any value from 70% to 200% and simultaneously the residual elongation is any value from 0% to 30%. Here, the elongation ratio (%) is the percentage of a value (=ΔL1/L0) obtained by dividing a value ΔL1(=L1−L0) by an original unstretched length L0; the original unstretched length L0 is the length of a band-like sheet under no load which has not been pulled yet, and the value ΔL1(=L1−L0) is obtained by subtracting the original unstretched length L0 from the length L1 of a band-like sheet when the sheet is pulled with an external force of 1.0(N). The foregoing residual elongation (%) is the percentage of a value (=ΔL2/ΔL1) obtained by dividing value ΔL2 by the value ΔL1; the value ΔL2 (=L2−L0) is obtained by subtracting the original unstretched length L0 (before the pulling) from the length L2 (after the external force of 1.0(N) is released), and the value ΔL1 (=L1−L0) is obtained by subtracting the original unstretched length L0 from the length L1 when the sheet is pulled with the foregoing external force.

The “low-extensible sheet9” is a sheet having an extensibility lower than that of the stretchable sheet8. That is, the “low-extensible sheet9” is a sheet whose elongation ratio (%) when a pulling external force of a certain magnitude is exerted on the sheet is lower than the elongation ratio (%) of the stretchable sheet8. It is preferable that such a low-extensible sheet9satisfies the following conditions. That is, concerning a band-like sheet having a lateral length of 25 mm, while the longitudinal ends of the band-like sheet being held equally throughout the entire lateral length of 25 mm, the band-like sheet is pulled in the longitudinal direction with an external force of 1.0(N) which is applied on the longitudinal ends. Under this condition, it is preferable that the elongation ratio (%) of the band-like sheet is any value from 0% to 20%. It is more preferable that the elongation ratio is any value from 0% to 10%.

The stretchable sheet8and low-extensible sheet9may be made of nonwoven fabric or woven fabric or film.

A nonwoven fabric which can be used as the stretchable sheet8is exemplified by nonwoven fabric which is produced by a suitable elongation (e.g. gear elongation) of a nonwoven fabric, the nonwoven fabric including thermoplastic elastomer fibers showing substantial elasticity and thermoplastic resin fibers showing substantial inelasticity. That is, as a result of the elongation, the thermoplastic resin fibers showing substantial inelasticity and being contained in the nonwoven fabric can be subject to plastic deformation. In addition, breaking joints of the fibers makes it possible to change the structure of the nonwoven fabric to a structure which is less likely to prevent the almost elastic stretching deformation of the thermoplastic elastomer fibers. Consequently, the stretchability of the nonwoven fabric is produced and the sheet can be used as a stretchable sheet8.

As a thermoplastic elastomer showing substantial elasticity, there are polyurethane elastomer, polystyrene elastomer, polyolefin elastomer, polyamide elastomer, and the like. As a thermoplastic resin fibers showing substantial inelasticity, there is fiber containing polyolefin resin and the like. The polyolefin resin is exemplified by polyethylene (PE), polypropylene (PP), ethylene-α-olefin copolymer, and the like. In this example, the stretchable sheet8is a sheet made of nonwoven fabric produced by gear elongation, the combined nonwoven fabric containing polyurethane elastomer fiber and PP fiber.

A nonwoven fabric which can be used as the low-extensible sheet9is exemplified by spunbond nonwoven fabric, melted-blown nonwoven fabric, air-through nonwoven fabric, so-called SMS nonwoven fabric (laminating spunbond nonwoven fabric, melted-blown nonwoven fabric, and spunbond nonwoven fabric) and the like, which are composed of fiber made of PE, PP, polyester, polyamid. The configuration of fibers is not limited to the foregoing single fiber made of one thermoplastic resin. For example, composite fiber having a core-sheath structure of a PP core and a PE sheath may be employed, and other types of the foregoing fibers may also be employed. In this example, spunbond nonwoven fabric made of PP fiber is used as a low-extensible sheet9.

As shown inFIGS. 2 and 3, the foregoing absorbent main body3is attached to the skin-side surface of the exterior sheet7having the foregoing two-layer structure, that is, the body3is attached to the widthwise center on the skin-side surface of the inner-layer sheet8. And the absorbent main body3is attached to the exterior sheet7so that the longitudinal direction of the absorbent main body3is aligned to the longitudinal direction of the exterior sheet7. The attaching is made by joining at least the longitudinal ends3eand3eof the absorbent main body3to the exterior sheet7. In this example, as shown inFIG. 3, on the longitudinal ends3eand3e, substantially T-shaped joined parts j and j are formed which join the absorbent main body3and the exterior sheet7. That is, each of the joined parts j and j includes: a widthwise band-like part jW and a longitudinal band-like part jL. The widthwise band-like part jW is elongated in the width direction of the diaper1, and the longitudinal band-like part jL extends toward the crotch part7cfrom the widthwise central part of the widthwise band-like part jW. This makes it possible to effectively prevent the absorbent main body3and the exterior sheet7from unnecessarily constraining each other. However, the shape of the joined parts j is not limited thereto. For example, a spot of an additional joined part jC may be provided at a position between a pair of T-shaped joined parts j and j. Or, on each of the longitudinal ends3eand3eof the absorbent main body3, a substantially rectangular joined part (not shown) having substantially the same area as the longitudinal end3emay be formed. Or, a joined part having any other shape may be formed. In this example, forming of the joined parts j is achieved by adhesion with hot-melt adhesive. However, the invention is not limited thereto. For example, welding may be applied.

In this example, when attaching the absorbent main body3to the exterior sheet7, the exterior sheet7is in a widthwise extended state in which the exterior sheet7is loosed compared to the inner-layer sheet8which is in an extended state at the time of fixing the outer-layer sheet9to the inner-layer sheet8(corresponding to a “reference extended state” and “first extended state” to be described later). The foregoing extended state in which the exterior sheet7is loosed is referred to as a “second extended state”, and will be described later. Accordingly, when a pull-on diaper1is finally finished, the absorbent main body3is less likely to crease. This makes it possible to effectively prevent the foregoing troubles such as urine leakage and liquid-absorbency deterioration of the absorbent main body3. In the below description of the manufacturing line LM, there is described that attaching of the absorbent main body3to the exterior sheet7is made in the extended state in which the sheet7is loosed.

The exterior sheet7to which the absorbent main body3is attached as shown inFIG. 2is two-folded on its crotch part7c. And, its ventral part7fand its dorsal part7bare stacked. The ventral part7fand the dorsal part7bwhich are stacked are joined on the widthwise ends7eW, to be in a form of a pull-on diaper1, in which a waist opening HB and a pair of leg openings HL and HL are formed as shown inFIG. 1.

FIG. 4Ais a schematic side view of a manufacturing line LM which manufactures the foregoing diapers1.FIG. 4Bis a plan view showing how diapers1are manufactured inFIG. 4A.

First in this manufacturing line LM, the substrate sheet7aof diapers1is produced. The substrate sheet7ais continuously transported along a predetermined transporting direction by means such as suitable transport mechanisms CV, CV . . . . During the transportation, the substrate sheet7ais subject to various processes such as attaching components or die-cutting. After every process, the substrate sheet7ais sequentially processed, and a diaper1shown inFIG. 1is finally manufactured. In this example, as shown inFIG. 4B, the substrate sheet7ais transported basically in a so-called lateral-direction flowing. That is, the substrate sheet7ais transported in a state in which a direction corresponding to the width direction of the diapers1is aligned to the transporting direction and a state in which pieces to be diapers1are lined up in the transporting direction.

As transport mechanisms CV which are used for the foregoing transportation, there are, for example, transport rollers, suction belt conveyors whose belt surfaces (serving as placement faces) have suction-holding function, or belt conveyors having pairs of upper and lower endless belts between which the transport path of the substrate sheet7ais placed.

In the manufacturing line LM, a plurality of processing units10,20. . . are arranged in the transporting direction for the various processes. In this example, as the plurality of processing units10,20. . . , the manufacturing line LM includes: an exterior-sheet producing unit10; a leg-opening forming unit20; an exterior-sheet contraction unit30; an absorbent-main-body attaching unit40; a two-folding unit50; an end-section sealing unit60; and a dividing unit70.

The processing units10to70will be described below, and in the description below, the transporting direction defined on the manufacturing line LM is referred to as “MD direction”. One of two directions perpendicular to MD direction is referred to as “CD direction”, and the other direction is referred to as “Z direction”. CD direction is parallel to the width direction of the substrate sheet7a, and is in a direction perpendicular to the paper plane inFIG. 4A. Z direction is parallel to the thickness direction of the substrate sheet7a.

The exterior-sheet producing unit10(corresponding to the producing device), which is the first processing unit, produces a continuous sheet7aof the exterior sheet7(hereinafter merely referred to as an exterior sheet7a). The continuous sheet7ais the substrate sheet7aof the diapers1, and continues in MD direction. That is, a stretchable sheet8(serving as the inner-layer sheet8) is transported along MD direction, and a continuous sheet8aof the stretchable sheet8, which was in substantially an original unstretched length, extends in MD direction by a certain extension ratio (the continuous sheet8ais hereinafter merely referred to as a “stretchable sheet8a”). Simultaneously, the stretchable sheet8ain the extended state is stacked on and joined to a continuous sheet9aof low-extensible sheet9from the thickness direction, the continuous sheet9a(the outer-layer sheet9) being extended and tightened (the continuous sheet9ais hereinafter merely referred to as a “low-extensible sheet9a”). Consequently, the exterior sheet7ais produced as the substrate sheet7a.

For the purpose of producing the exterior sheet7a, the exterior-sheet producing unit10includes: a transport mechanism11for the stretchable sheet8a; a transport mechanism13for the low-extensible sheet9a; and an ultrasonic welding device15.

The main body of the transport mechanism11for the stretchable sheet8ais, for example, a nip-roll mechanism. That is, the mechanism11includes a pair of nip rolls11R and11R which rotate respectively about rotational axes along CD direction. The pair of nip rolls11R and11R are driven and rotated by obtaining driving force from a servo motor (serving as a power source, not shown) while the stretchable sheet8a, which is continuously transported from the upstream process, is being sandwiched between the outer circumferential surfaces of the nip rolls11R and11R. Thereby, the stretchable sheet8ais transferred to the ultrasonic welding device15.

On the other hand, the main body of the transport mechanism13for the low-extensible sheet9ais, for example, a transport roller13R which rotates about a rotational axis along CD direction. The transport roller13R is driven and rotated by obtaining driving force from a servo motor (serving as a power source, not shown) while the outer circumferential surface of the roller13R being in contact with the low-extensible sheet9a, which is continuously transported from the upstream process. Thereby, the low-extensible sheet9ais transferred to the ultrasonic welding device15.

The ultrasonic welding device15includes: a horn15hhaving a vibrating surface which vibrates ultrasonically; and an anvil roller15awhose outer circumferential surface receives ultrasonic vibration of the vibrating surface of the horn15h. The anvil roller15ais supported being capable of rotating about a rotational axis along CD direction, and is driven and rotated by obtaining driving force from a servo motor (serving as a power source, not shown). The stretchable sheet8aand the low-extensible sheet9a, which have been transferred from the transport mechanisms11and13, are wound around the outer circumferential surface of the anvil roller15aat a certain wrapping angle (45° degrees or more) with substantially no sliding relative to the outer circumferential surfaces.

Accordingly, the anvil roller15ais driven and rotated, and thereby the stretchable sheet8aand the low-extensible sheet9aare both transported, along the outer circumferential surface of the anvil roller15a, at a conveying speed which is substantially same as the circumferential speed value V15aof the anvil roller15a. The stretchable sheet8aand the low-extensible sheet9apass the position of the horn15hwhile the stretchable sheet8aand the low-extensible sheet9abeing stacked in the thickness direction on the outer circumferential surface of the anvil roller15a. At this stage, ultrasonic vibration energy is applied to these sheets8aand9afrom the vibrating surface of the horn15h, and these sheets8aand9agenerate heat and melt. Thus, the sheets8aand9aare joined to each other in a joining pattern in which a plurality of the joined parts are discontinuously distributed. And, the exterior sheet7ais consequently produced. The anvil roller15asends the exterior sheet7atoward downstream in MD direction, and then the exterior sheet7ais transported to the leg-opening forming unit20located downstream in MD direction, at a conveying speed which is substantially same as the circumferential speed value V15a.

Here, concerning the transport mechanism11of the stretchable sheet8a, the circumferential speed value V11R (m/min.) of the nip roll11R is substantially same as the conveying speed (m/min.) of the stretchable sheet8awhich is transported from the upstream process, the stretchable sheet8abeing in substantially the original unstretched length. On the other hand, the circumferential speed value V15a(m/min.) of the anvil roller15a, being located downstream thereof, is set to a value of the circumferential speed value V11R (m/min.) of the nip roll11R multiplied by the extension ratio. Accordingly, when the stretchable sheet8apasses between the nip-roll mechanism11and the anvil roller15a, the stretchable sheet8aextends from the original unstretched length till the length corresponding to the extension ratio. The stretchable sheet8apasses the position of the horn15hin the extended state. On the other hand, concerning the transport mechanism13of the low-extensible sheet9a, the circumferential speed value V13R (m/min.) of the transport roller13R is substantially same as the conveying speed (m/min.) of the low-extensible sheet9awhich is transported from the upstream process. The conveying speed (m/min.) is also substantially same as the circumferential speed value V15a(m/min.) of the anvil roller15a. Accordingly, the low-extensible sheet9aremains in a state in which the sheet9ais properly extended and tightened to substantially an extent that does not undergo plastic deformation or the like. On the anvil roller15a, the low-extensible sheet9awhich has been extended and tightened is stacked on and joined to the stretchable sheet8awhich has extended till the length corresponding to the extension ratio.

The low-extensible sheet9awhich is extended and tightened is in a so-called fully-extended state in which a sheet having a low extensibility is difficult to further extend. Accordingly, even if an unexpectedly great tension is exerted during subsequent transportation, the low-extensible sheet9acan resist the tension so that the length of the exterior sheet7ain MD direction does not change. Accordingly, the subsequent forming of the leg opening7HL in the exterior sheet7acan be made with high positioning accuracy. The foregoing “fully-extended state” can be defined as, for example, “a state in which a sheet is not damaged and cannot further extend from the current state at the elongation ratio of 5% or more with its sheet-like shape being kept”.

The foregoing “extension ratio” indicates how many times as long as the original unstretched lengths of the stretchable sheet8athe entire length of the sheet8ain an extended state is. And, the “extension ratio” defines how much the exterior sheet7(7a) of a finished diaper1can extend in the width direction from a state in which no force is exerted on the sheet7(7a). That is, in a diaper1which has been manufactured when the setting of the stretchable sheet8ais in a certain extension ratio, the exterior sheet7(7a) can extend in the width direction of a diaper1till the extended state, corresponding to the foregoing extension ratio. The extension ratio is set, for example, to any value from 1.5 times to 4 times. In this example, the extension ratio is predetermined to 2.5 times. In the description below, a state in which the stretchable sheet8aextends by the exterior-sheet producing unit10till the predetermined extension ratio is referred to as a “reference extended state”.

In the leg-opening forming unit20in the next process, the extended state of the exterior sheet7aremains in the reference extended state mentioned above. That is, the exterior sheet7ais transported in an extended state in which the exterior sheet7aextends at an extension ratio of 2.5 that is the same as the extension ratio in the reference extended state (hereinafter referred to as a first extended state). In the leg-opening forming unit20, the exterior sheet7ain the first extended state is being transported, and the leg opening7HL is cut out and formed by die-cutting the exterior sheet7aat a certain first pitch P1(corresponding to the first pitch).

Here, such a first pitch P1corresponds to the length in MD direction of a single diaper1which is in the first extended state. Accordingly, in the exterior sheet7a, a single leg opening7HL is formed for every part corresponding to a diaper1. The length of a single diaper1varies depending on an extended state of the exterior sheet7a. For example, if the exterior sheet7acontracts and is in a looser extended state, the length in MD direction of a single diaper1shortens by a length corresponding to the contraction.

The forming the leg opening7HL is performed by a die cutter device21. The die cutter device21includes a pair of upper and lower rolls21uand21dwhich rotate respectively about rotational axes along CD direction while their outer circumferential surfaces facing each other. The upper roll21uis a cutter roll21uhaving a cutter blade21con the outer circumferential surface. And, the lower roll21dis an anvil roll21dwhich receives the cutter blade21con its smooth outer circumferential surface. The cutter blade21cis a so-called annular cutting die whose shape corresponds to the shape of the leg opening7HL. The cutter blade21cis provided protruding from the outer circumferential surface21usof the cutter roll21u. Accordingly, when the exterior sheet7apasses the nip between the upper and lower rolls21uand21d, the section of the exterior sheet7awhich is located inside the annular cutter blade21cis cut out from the exterior sheet7aby die-cutting. Consequently, a leg opening7HL is formed in the exterior sheet7a.

In this example, the power source by which the upper and lower rolls21uand21dare driven and rotated is a servo motor (not shown). The upper roll21uincludes a single cutter blade21con its outer circumferential surface. Accordingly, every time when the exterior sheet7apasses the die cutter device21by the length of the first pitch P1in MD direction, the upper roll21uand the lower roll21drotate once and the leg openings7HL are thereby formed in the exterior sheet7aat the first pitch P1. Thus, the leg openings7HL are formed in the exterior sheet7aat a pitch corresponding to the length of a single diaper1which is in the first extended state.

In order to perform die-cutting with substantially no sliding relative to the exterior sheet7a, the rotation radius at the position of the cutting edge of the cutter blade21cis defined based on the first pitch P1at which the leg openings7HL are to be formed. Similarly, the rotation radius of the outer circumferential surface of the lower roll21dis defined based on the first pitch P1. That is, the rotation radius at the position of the cutting edge of the upper roll21uand the rotation radius of the outer circumferential surface of the lower roll21dare set to a value obtained by dividing the first pitch P1by 2n (two times pi). This enables the die cutter device21to form the leg openings7HL precisely at the first pitch P1, in the exterior sheet7awhich is in the first extended state. Then, the exterior sheet7awhich is in the first extended state is transferred to the exterior-sheet contraction unit30downstream in MD direction.

In the exterior-sheet contraction unit30(corresponding to the contraction apparatus) in the next process, the exterior sheet7awhich is being transported in the first extended state contracts in MD direction. Consequently, the exterior sheet7abecomes in an extended state (hereinafter referred to as a second extended state) in which the extension ratio is smaller than the extension ratio in the first extended state. In this example, the extension amount of the exterior sheet7ais reduced so that the extension ratio is 2.25 times. That is, the extension amount is reduced by 10% of 2.5 times, which is the extension ratio in the first extended state. This prevents possible creasing of the absorbent main body3, which will be subsequently attached to the exterior sheet7a. Hereinafter, the extension ratio in the first extended state is referred to as a “first extension ratio M1”, and the extension ratio in the second extended state is referred to as a “second extension ratio M2”.

The foregoing contraction of the exterior sheet7ais performed by two nip-roll mechanisms31and33provided being lined up in MD direction. That is, the upstream nip-roll mechanism31is arranged at a predetermined position in MD direction, and the downstream nip-roll mechanism33is arranged at a position downstream from the upstream nip-roll mechanism31. These nip-roll mechanisms31and33have substantially the same configuration.

That is, the upstream nip-roll mechanism31includes a pair of upper and lower nip rolls31uand31dwhich rotate respectively about rotational axes along CD direction. Also, the downstream nip-roll mechanism33includes a pair of upper and lower nip rolls33uand33dwhich rotate respectively about rotational axes along CD direction. The pair of nip rolls31uand31dof the upstream nip-roll mechanism31are driven and rotated by obtaining driving force from a servo motor (serving as a power source, not shown) while the exterior sheet7ais being sandwiched between the outer circumferential surfaces of the nip rolls31uand31d. Thereby, the exterior sheet7ais transferred downstream in MD direction. Similarly, the pair of nip rolls33uand33dof the downstream nip-roll mechanism33are driven and rotated by obtaining driving force from a servo motor (serving as a power source, not shown) while the exterior sheet7ais being sandwiched between the outer circumferential surfaces of the nip rolls33uand33d. Thereby, the exterior sheet7ais transferred further downstream in MD direction.

Here, the circumferential speed value V31(m/min.) of the nip rolls31uand31dof the upstream nip-roll mechanism31is substantially same as the circumferential speed value V15a(m/min.) of the anvil roller15aof the foregoing ultrasonic welding device15. Accordingly, the circumferential speed value V31of the nip rolls31uand31dis substantially same as the first conveying speed of the exterior sheet7a, which is the conveying speed (m/min.) of the exterior sheet7awhich is being transported in the first extended state at a position immediately upstream from the nip rolls31uand31d. On the other hand, the circumferential speed value V33(m/min.) of the nip rolls33uand33dof the downstream nip-roll mechanism33is smaller by 10% than the circumferential speed value V31of the nip rolls31uand31dof the upstream nip-roll mechanism31. Accordingly, while the exterior sheet7ais passing the transport path R30between the upstream nip-roll mechanism31and the downstream nip-roll mechanism33, the exterior sheet7acontracts to be in the second extended state; the extension ratio in the second extended state being smaller by 10% than the extension ratio in the first extended state. The exterior sheet7ain the second extended state is transported to the absorbent-main-body attaching unit40located downstream in MD direction.

In this example, when the exterior sheet7ais being transported during and after the contracting, the exterior sheet7ais basically in substantial a second extended state. During the transportation, the conveying speed of the exterior sheet7ais kept at approximately a conveying speed (hereinafter referred to as a second conveying speed) which is smaller than the first conveying speed by 10% (the ratio corresponding to the contraction). The second conveying speed can be also referred to as “a value obtained by multiplying the first conveying speed by a value obtained by dividing the second extension ratio by the first extension ratio”.

Here, the contraction ratio (%) is a value indicating the degree of the contraction of the exterior sheet7a, and is defined as follow. The contraction ratio (%) is the percentage of a divided value (=(M1−M2)/M1) obtained by dividing a subtraction value (=M1−M2) by the first extension ratio M1, the subtraction value being obtained by subtracting the second extension ratio M2 from the first extension ratio M1. In this example, as mentioned above, the contraction ratio is 10%. However, this invention is not limited thereto. That is, the contraction ratio may be set to any value as long as the exterior sheet7acan contract while being extended and tightened; for example, the contraction ratio may be any value from 2% to 80%. As a narrower example, the contraction ratio may be any value from 5% to 50%, or as a further narrower example, the contraction ratio may be any value from 7% to 30%.

In the absorbent-main-body attaching unit40(corresponding to a processing apparatus) in the next process, the exterior sheet7ais being transported in the second extended state, and the absorbent main body3is attached to the exterior sheet7aat a second pitch P2(corresponding to the second pitch) in MD direction. Here, such a second pitch P2corresponds to the length in MD direction of a single diaper1which is in the second extended state. In the second extended state, the exterior sheet7acontracts more than in the first extended state, as mentioned above. Accordingly, the second pitch P2is a smaller value than the first pitch P1by the contraction ratio. Specifically, in this example, though the first extension ratio of the first extended state is 2.5, the second extension ratio of the second extended state is reduced and is 2.25. Accordingly, the contraction ratio is 10% (=(2.5−2.25)/2.5×100%), and the second pitch P2of the absorbent-main-body attaching unit40is a smaller value than the first pitch P1by 10%.

The absorbent main body3is attached to the exterior sheet7aat a position between leg openings7HL and7HL which are adjacent in MD direction. In the present embodiment, the transportation of the exterior sheet7ain the foregoing exterior-sheet contraction unit30is adjusted so that the absorbent main body3is attached to the exterior sheet7aat a predetermined target position. The adjustment is performed by an adjustment device35, which will be described later.

The attaching of the absorbent main body3is performed by, for example, a rotating-drum device41. The rotating-drum device41includes: a rotating drum42which rotates about a rotational axis along CD direction; a servo motor (not shown) which serves as a power source and which drives and rotates the rotating drum42; and a plurality of holding pads43,43. . . provided along the rotating direction on the outer circumferential surface of the rotating drum42. Each holding pad43has a holding plane which is capable of sucking and holding the absorbent main body3, and the holding plane faces outside in the rotation radius of the rotating drum42. By the rotation of the holding pad43about the axis which is located at the plane center of its holding plane, the longitudinal direction of an absorbent main body3held by the holding plane changes from MD direction to CD direction.

Each holding pad43is configured so as to reciprocate relative to the rotating drum42within a certain range in the rotating direction. Such a reciprocating motion is produced by a suitable cam mechanism (not shown) from a rotation of the rotating drum42. Accordingly, a pitch in the rotating direction between adjacent holding pads43and43can be changed depending on the position of the rotating drum42in the rotating direction. That is, at a first position S1in the rotating direction, a space between adjacent holding pads43and43can be narrow, and at a second position S2in the rotating direction, a space between adjacent holding pads43and43can be wide.

Here, at the first position S1, a plurality of the absorbent main bodies3are supplied in the form of continuous body3awhich continues in MD direction. When each holding pad43passes the first position S1, the pad43sucks and receives the continuous body3aof the absorbent main body. And then, the cutter apparatus45located near the pad43divides the continuous body3a, and a single sheet of the absorbent main body3is produced on the holding pad43. The holding pad43, as it is, moves to the second position S2in the rotating direction by rotation of the rotating drum42. During the movement, the holding pad43rotates as mentioned above, and the longitudinal direction of the absorbent main body3is thereby changed from MD direction to CD direction. In addition thereto, the holding pad43reciprocates during the movement, and a pitch between adjacent holding pads43and43is thereby changed to the second pitch P2. Further, at the second position S2, the transport path of the exterior sheet7ais placed closely to the unit40. Accordingly, the rotating-drum device41can attach the absorbent main bodies3, at the second pitch P2in MD direction, to the exterior sheet7awhich is in the second extended state.

In the two-folding unit50in the next process, the exterior sheet7aonto which the absorbent main bodies3are attached is two-folded in CD direction at a folding position, which is substantially a central part of the exterior sheet7ain CD direction corresponding to the crotch part7cof a diaper1. Thus, in the exterior sheet7a, one end section of the sheet7ain CD direction is stacked on the other end section in the thickness direction. One end section finally becomes the ventral part7fof a diaper1, and other end section finally becomes the dorsal part7bof the diaper1.

The two-folding of the exterior sheet7ais performed by a two-fold guiding member (not shown) arranged at a predetermined position in MD direction. The two-fold guiding member is a known configuration, and is composed of a combination of a plurality of suitable bars, for example. When the exterior sheet7apasses the position of the two-fold guiding member, the guiding member folds gradually the exterior sheet7aat the folding position, which is substantially a central part of the exterior sheet7ain CD direction. When the exterior sheet7ahas completely passed the two-fold guiding member, the exterior sheet7ais two-folded.

In the two-folding unit50, the extended state of the exterior sheet7aremains the second extended state mentioned above. While the exterior sheet7aremaining in this extended state, the exterior sheet7ais transferred downstream in MD direction. That is, in the two-folding unit50, the conveying speed of the exterior sheet7ais kept substantially same as the foregoing second conveying speed.

In the next end-section sealing unit60(corresponding to the processing apparatus), the exterior sheet7aremains in the second extended state. In the end-section sealing unit60, the exterior sheet7athat has been two-folded is fixed in a state in which the exterior sheet7ais two-folded. That is, the end sections of the exterior sheet7ain CD direction, which are stacked by being two-folded in the thickness direction, are welded at a position in MD direction between adjacent absorbent main bodies3and3. And, the end sections are fixed in the state in which the exterior sheet7ais two-folded. The welded part remains on the exterior sheet7a, as a sealed end section jes (corresponding to the joined part). At a position where the sealed end section jes is to be formed, the exterior sheet7ais in the second extended state. And, the welded parts are produced at the second pitch P2in MD direction. Accordingly, the unit60forms the sealed end sections jes at the second pitch P2in the exterior sheet7a.

The forming of the sealed end section jes is performed by a heat-sealing device61. The heat-sealing device61includes a pair of upper and lower rolls61uand61dwhich are driven and rotated about rotational axes along CD direction while their outer circumferential surfaces facing each other.

The upper roll61uhas a sealing pattern section61spon its outer circumferential surface. The sealing pattern section61spis a protrusion and is heated. The lower roll61dhas a smooth outer circumferential surface, which is for receiving the sealing pattern section61sp. The sealing pattern section61spprotrudes from the outer circumferential surface of the upper roll61u, and the protruding part has a shape corresponding to a sealed end section jes. Accordingly, when the two-folded exterior sheet7apasses the nip between the upper and lower rolls61uand61d, a part of the exterior sheet7abetween the absorbent main bodies3and3which are adjacent in MD direction is heated while being pressed between a sealing pattern section61spand the outer circumferential surface of a lower roll61d. Thus, a part of the exterior sheet7awhich is to be a widthwise end of each diaper1is melted, and the sealed end section jes is formed in the melted part.

In this example, the power source by which the upper and lower rolls61uand61dare driven and rotated is a servo motor (not shown). A single sealing pattern section61spis provided on the outer circumferential surface of the upper roll61u. Every time when the exterior sheet7apasses the heat-sealing device61by the length of the second pitch P2, the upper roll61urotates once. Accordingly, the sealed end sections jes are formed at the second pitch P2. Consequently, in the exterior sheet7a, the sealed end sections jes are formed at a pitch corresponding to the length of a single diaper1which is in the second extended state.

In order to form the sealed end section jes with substantially no sliding relative to the exterior sheet7a, the rotation radius at the position of the top surface of the sealing pattern section61spis defined based on the second pitch P2at which the sealed end sections jes are to be formed. Similarly, the rotation radius of the outer circumferential surface of the lower roll61dis defined based on the second pitch P2. That is, the rotation radius at the position of the sealing pattern section61spof the upper roll61u, and the rotation radius of the outer circumferential surface of the lower roll61dare set to a value obtained by dividing the second pitch P2by 2n (two times pi). This enables the heat-sealing device61to form the sealed end sections jes precisely at the second pitch P2, in the exterior sheet7awhich is in the second extended state. Then, the exterior sheet7awhich is in the second extended state is transferred to the dividing unit70downstream in MD direction.

The extended state of the exterior sheet7aat the time of forming the sealed end section jes is the second extended state as mentioned above. The second extended state is a state in which a sheet being in the first extended state contracts. Accordingly, when forming the sealed end section jes, the basis weight (g/m2) of the exterior sheet7aincreases by an amount corresponding to the foregoing contraction. This makes it possible to increase welding strength of the sealed end section jes.

In the next dividing unit70(corresponding to the processing apparatus), the exterior sheet7aremains in the second extended state. The exterior sheet7awhich is two-folded and fixed is divided at the second pitch P2. Consequently, the downstream end part of the exterior sheet7ais cut and separated from the sheet7aat the second pitch P2to produce a diaper1.

The dividing of the exterior sheet7ais performed by a rotary cutter device71. The rotary cutter device71includes a pair of upper and lower rolls71uand71dwhich are driven and rotated about rotational axes along CD direction while their outer circumferential surfaces facing each other. The upper roll71uis a cutter roll71uhaving a cutter blade71con its outer circumferential surface, and the lower roll71dis an anvil roll71dhaving a smooth outer circumferential surface, which receives the cutter blade71c. The cutter blade71cis, for example, a flat blade extending along CD direction, and protrudes from the outer circumferential surface of the cutter roll71u. When the exterior sheet7awhich is two-folded and fixed passes a nip between these upper and lower rolls71uand71d, the exterior sheet7ais divided at the position of the sealed end section jes. Consequently, the downstream end part of the exterior sheet7ais cut and separated from the sheet7a, and the separated downstream end part becomes a diaper1.

In this example, the power source by which the upper and lower rolls71uand71dare driven and rotated is a servo motor (not shown). A single cutter blade71cis provided on the outer circumferential surface of the upper roll71u. The exterior sheet7ais transported being in the second extended state. Every time when the exterior sheet7apasses the rotary cutter device71by the length of the second pitch P2, the upper roll71uand the lower roll71deach rotate once. Accordingly, from the exterior sheet7a, a single diaper1is divided and produced. The produced diaper1is transferred downstream in MD direction by a suitable transport mechanism CV such as a belt conveyor.

In order to divide the exterior sheet7awith substantially no sliding relative to the exterior sheet7a, the rotation radius at the position of the cutting edge of the cutter blade71cis defined based on the second pitch P2at which the exterior sheet7aare to be divided. Similarly, the rotation radius of the outer circumferential surface of the lower roll71dis defined based on the second pitch P2. That is, the rotation radius at the position of the cutting edge of the upper roll71uand the rotation radius of the outer circumferential surface of the lower roll71dare set to a value obtained by dividing the second pitch P2by 2n (two times pi). This enables the rotary cutter device71to divide the exterior sheet7aprecisely at the second pitch P2, the exterior sheet7abeing in the second extended state.

The processing units10to70included in the manufacturing line LM are described above. The processing units10to70operate in conjunction with one another. There are two methods of the operation conjunction, for example. The one is a method in which the operation conjunction is achieved by controlling the positions of target apparatuses based on synchronization signals, and the other is a method in which the operation conjunction is achieved by controlling the speeds of target apparatuses.

The former method using synchronization signals is applied to the leg-opening forming unit20, the absorbent-main-body attaching unit40, the end-section sealing unit60and the dividing unit70.

The synchronization signal is a signal consisting of a unit signal which corresponds to a unit part of the exterior sheet7awhich is to be a diaper1; the unit signal is repeatedly outputted. In this example, the unit signal is a rotational angle signal having a rotational angle value of 0° to 360°. The processing units20,40,60and70each have a systematic unit operation which they should repeatedly perform for each unit part of the exterior sheet7awhich is to be a diaper1. The unit operation of each of the processing units is in one-to-one correspondence with a single unit signal.

The synchronization signal is transmitted to an amplifier of each of servo motors, which are power sources of the devices21,41,61and71of the processing units20,40,60and70. And, the positions of the servo motors are controlled based on the synchronization signal. Thus, each of the devices21,41,61and71performs its predetermined unit operation, to unit parts of the exterior sheet7a, which are to be a diaper1.

For example, in the leg-opening forming unit20, the upper and lower rolls21uand21dof the die cutter device21each rotate once as a unit operation according to position control, and this operation is performed for each unit signal of the synchronization signal. Thus, the leg openings7HL are formed on the exterior sheet7aat the first pitch P1. In the absorbent-main-body attaching unit40, the rotating drum42of the rotating-drum device41attaches, as a unit operation, the absorbent main body3to the exterior sheet7aat the second pitch P2according to position control, and this operation is performed for each unit signal. In the end-section sealing unit60, the upper and lower rolls61uand61dof the heat-sealing device each rotate once as a unit operation according to position control, and this operation is performed for each unit signal. Thus, the sealed end sections jes are formed on the exterior sheet7aat the second pitch P2. In the dividing unit70, the upper and lower rolls71uand71dof the rotary cutter device71each rotate once as a unit operation according to position control. Thus, the exterior sheet7ais divided at the second pitch P2, to produce a diaper1.

The synchronization signal is generated by a controller (not shown) which controls the processing units20,40,60and70in the manufacturing line LM, for example. The controller includes a processor and a memory, and in the memory, the program that generates the synchronization signal is stored in advance. The processor reads the program from the memory and executes it, and thereby repeatedly generates a unit signal of the synchronization signal.

For the purpose of explanation, in this example, the unit signal of the synchronization signal is a signal indicated by a rotational angle value of 0° to 360°. However, this invention is not limited thereto. For example, the unit signal of the synchronization signal may be a digital value (e.g. from 0 to 8191). Or, the synchronization signal may be generated by a suitable electric circuit, not by the processor which has read the foregoing program.

On the other hand, the latter method using speed control is applied to the exterior-sheet producing unit10, the exterior-sheet contraction unit30, and the transport mechanisms CV, CV . . . . In such a method, a reference speed value is set to the speed value (m/min.) of a core unit or the target value (m/min.) of the same. A target speed value (m/min.) is obtained by means such as multiplying the reference speed value by a suitable gain. The speed value (m/min.) of the other cooperating units is controlled so as to be close to the target speed value.

In this example, the core unit is the die cutter device21of the leg-opening forming unit20. And, the reference speed value Vs is the circumferential speed value V21(m/min.) of the lower roll21dof the die cutter device21. In the exterior-sheet producing unit10, the circumferential speed value V15aof the anvil roller15ais controlled so as to be a target speed value, which is the reference speed value Vs. In the exterior-sheet producing unit10, concerning the transport roller13R of the transport mechanism13for the low-extensible sheet9a, the circumferential speed value V13R is controlled so as to be a target speed value, which is the reference speed value. Further, in the exterior-sheet producing unit10, concerning the pair of nip rolls11R and11R of the transport mechanism11for the stretchable sheet8a, each of the circumferential speed values V11R and V11R is controlled so as to be a target speed value, which is a multiplied value obtained by multiplying the reference speed value Vs by the reciprocal of the extension ratio at the time when the sheets8and9are fixed (serving as a gain; in this example, 2.5 times).

In the exterior-sheet contraction unit30, concerning the pair of nip rolls31uand31dof the upstream nip-roll mechanism31, each of the circumferential speed values V31uand V31dis controlled so as to be a target speed value, which is the reference speed value Vs. Concerning the pair of nip rolls33uand33dof the downstream nip-roll mechanism33, each of the circumferential speed values V33uand V33dis controlled so as to be a target speed value, which is a value obtained by multiplying the reference speed value Vs by a certain gain G. The gain G is a divided value obtained by dividing a subtraction value by 100, the subtraction value being obtained by subtracting the contraction ratio (%) from 100%. In this example, the gain G is 0.9 (=(100−10)/100).

Taking into consideration the extended state of the exterior sheet7a, the target speed value of each of the transport mechanisms CV, CV . . . is obtained based on the foregoing reference speed value Vs. Concerning the transport mechanism CV, the circumferential speed value of its transport roller or its endless belt is controlled according to the target speed value. That is, concerning a transport mechanism CV transporting the exterior sheet7awhich is in the first extended state, the circumferential speed value of its transport roller or its endless belt is controlled so as to be a target speed value, which is the reference speed value Vs. On the other hand, concerning a transport mechanism transporting the exterior sheet7awhich is in the second extended state, its circumferential speed value is controlled so as to be a target speed value, which is a multiplied value obtained by multiplying the reference speed value Vs by the foregoing gain G associated with the contraction.

Under such a control for cooperation, in the exterior-sheet contraction unit30of the manufacturing line LM, the exterior sheet7acontracts in MD direction as mentioned above. But, because of variation in the stretchability of the exterior sheet7aor the like, the contraction may cause a problem that a target position for each process, which is determined on the exterior sheet7a, is shifted upstream or downstream in MD direction relative to an actual position at which a process by each of the processing units40,60and70is made according to the synchronization signal.

For example, concerning a certain part of the exterior sheet7a, its contraction is larger than expected, the exterior sheet7ais transported in which the position of the certain part is shifted toward upstream in MD direction from its transportation position which is determined according to the synchronization signal. Consequently, a process by each of the processing units40,60and70according to the synchronization signal is made at a position located downstream from the target position for the process, which is determined in the certain part of the exterior sheet7a. On the other hand, the contraction is smaller than expected, the opposite of the foregoing description will happen. That is, there is generated a shifting amount, which indicates difference between the following positions: an actual position at which a process by each of the processing units40,60and70is made according to the synchronization signal; and a target position determined on the exterior sheet7a.

In the present embodiment, the adjustment device35is provided for reducing the foregoing shifting amount.FIG. 5Ais a schematic side view of the exterior-sheet contraction unit30including the adjustment device35.FIG. 5Bis a schematic view along arrows B-B inFIG. 5A.

The adjustment device35includes a sensor36and an alteration device37. The sensor36detects a physical reference section and outputs a detection signal. The physical reference section is a section in the exterior sheet7aand is formed for each unit part of the exterior sheet7awhich is to be a diaper1. The alteration device37alters the transportation state of the exterior sheet7awhen the exterior sheet7ais in the transport path R30in the exterior-sheet contraction unit30. The alteration device37alters the transportation state of the exterior sheet7ain the exterior-sheet contraction unit30, and the alteration is performed according to the detection signal outputted from the sensor36. And, the alteration is made so that positions in the exterior sheet7afor processes made by the processing units40,60and70located downstream in MD direction (that is, positions for the processes determined according to the synchronization signal) is located close to the target position which is defined on the exterior sheet7a. The detail will be described below.

In this example, the leg opening7HL is used as the reference section. This is because it can be considered that forming of each leg opening7HL under a stable condition ensures a high positioning accuracy of the leg opening7HL and that the forming of each leg opening7HL is performed under a condition in which the 10% contraction of the exterior sheet7ahas not been made yet, that is, under a stable condition in which the exterior sheet7aextends almost as much as possible (in the first extended state). In this case, the foregoing leg-opening forming unit20corresponds to the “reference-section forming apparatus”.

On the other hand, as shown inFIG. 5A, the alteration device37includes: a nip-roll mechanism37nprovided in the exterior-sheet contraction unit30; and a controller37cwhich controls the nip-roll mechanism37n. The nip-roll mechanism37nincludes a pair of upper and lower nip rolls37nuand37ndwhich rotate respectively about rotational axes along CD direction, and the pair of nip rolls37nuand37ndare provided in the transport path R30of the exterior sheet7a, the transport path R30being formed between the upstream nip-roll mechanism31and the downstream nip-roll mechanism33of the exterior-sheet contraction unit30. The pair of nip rolls37nuand37ndare driven and rotated by obtaining driving force from a servo motor (serving as a power source) while the exterior sheet7ais sandwiched between the outer circumferential surfaces of the nip rolls37nuand37nd. Thereby, the exterior sheet7ais transferred downstream in MD direction.

The sensor36includes: an imaging device36c; and an image processing device36ipthat processes image data transmitted from the imaging device36c. The imaging device36cincludes, for example, a CCD camera, a processor and a memory. The camera36ccimages the exterior sheet7awhich is being transported between the nip-roll mechanism37nof the alteration device37and the downstream nip-roll mechanism33in the transport path R30d(corresponding to the downstream path section).

The imaging is performed according to the foregoing synchronization signal. That is, the imaging device36calways receives a synchronization signal, and the imaging device36cperforms the imaging when the device36cdetects that the rotational angle value of the synchronization signal matches a predetermined rotational angle value which is stored in the memory of the imaging device36cin advance. The predetermined rotational angle value is set to such a value that the leg opening7HL serving as the reference section is positioned within an image indicated with the image data. Every time when the rotational angle value of the synchronization signal matches the predetermined rotational angle value, the imaging device36cperforms the imaging. Accordingly, in this example, the imaging is performed for each leg opening7HL and its image data is generated. Every time when new image data is generated, the new image data is transmitted to the image processing device36ip.

The main body of the image processing device36ipis a suitable computer, and includes a processor and a memory. Every time when image data is transmitted from the imaging device36c, the image processing device36ipperforms binarization operation as an example of the image processing, according to the transmitted image data. In the binarization operation, concerning a part of the image indicated by the image data in which a leg opening7HL is imaged, positional coordinates of the pixels of the part is obtained by extracting the pixels of the part. The detail thereof is as follow.

An image indicated by image data consists of a plurality of pixels lined up two dimensionally in X direction and in Y direction. In the image, X direction is CD direction and Y direction is MD direction, for example. The image data has color information corresponding to each pixel. In this example, since image data is a grayscale image, each pixel includes only the brightness as color information. The pixels indicating a leg opening7HL each have lower brightness than those of the pixels indicating the exterior sheet7a. And, in the binarization operation, a pixel having a brightness equal to or greater than a certain threshold is assigned to white image, and a pixel having a brightness less than the certain threshold is assigned to black image. This binarization operation makes it possible to extract, as black image, a part of the image in which the leg opening7HL is imaged. The part in which the leg opening7HL is imaged is extracted as black image, and the arithmetic average values of the positional coordinates of all pixels constituting the black image can be used as representative positional coordinates, which are representative of the positional coordinates of the pixels of the part in which the leg opening7HL is imaged.

On the other hand, data of positional coordinates for comparison are stored in advance in the memory of the image processing device36ip. Here, the positional coordinates for comparison indicate positional coordinates where pixels of the leg opening7HL should be positioned in the image if the processing units40,60and70perform processes according to the synchronization signal precisely at the predetermined target position of the exterior sheet7a. Of the positional coordinates, the Y coordinate indicates the coordinate in MD direction.

Accordingly, the image processing device36ipcan calculate the shifting amount of the exterior sheet7ain MD direction based on the difference between the followings: the value of Y coordinate of the comparison positional coordinates; and the value of Y coordinate of the positional coordinates of the pixels of the part in which the leg opening7HL is imaged, the positional coordinates being obtained by extracting in the binarization operation. Every time when the shifting amount is calculated, the calculated shifting amount is transmitted to the controller37cof the alteration device37in the form of data (corresponding to a detection signal).

The controller37ccontrols the alteration device37based on the foregoing data. That is, if the data indicates “the exterior sheet7ais shifted upstream in MD direction”, the controller37ccontrols an amplifier of each of the servo motors of the nip rolls37nuand37ndof the alteration device37. And, the circumferential speed value of the nip rolls37nuand37ndis set to a larger value by a certain alteration amount ΔV than the current circumferential speed value. The alteration amount ΔV of the circumferential speed value is calculated, for example, by multiplying the shifting amount by a predetermined gain. The alteration of the circumferential speed value decreases the shifting amount by which the exterior sheet7ais shift upstream.

On the other hand, if the data indicates “the exterior sheet7ais shifted downstream in MD direction”, the controller37ccontrols an amplifier of each of the servo motors of the nip rolls37nuand37ndof the alteration device37. And, the circumferential speed value of the nip rolls37nuand37ndis set to a smaller value by a certain alteration amount ΔV than the current circumferential speed value. Also, in this case, the alteration amount ΔV of the circumferential speed value is calculated, for example, by multiplying the shifting amount by a predetermined gain. The alteration of the circumferential speed value decreases the shifting amount by which the exterior sheet7ais shift downstream.

In this example, the alteration is performed every time when the foregoing data is transmitted to the controller37c. Thus, adjustment for decreasing the shifting amount is made for all of the unit parts of the exterior sheet7aeach of which is to be a diaper1. However, this invention is not limited thereto. For example, a single alteration may be performed every time when multiple times of data transmissions are made.

In this example, the controller37cof the alteration device37includes an interlock regarding control of the rotations of the nip rolls37nuand37nd, and the interlock is in the form of a program or an electric circuit. Accordingly, the circumferential speed values of the nip rolls37nuand37ndof the alteration device37is altered between an upper limit and a lower limit; the upper limit is the circumferential speed values of the nip rolls31uand31dof the upstream nip-roll mechanism31, and the lower limit is the circumferential speed values of the nip rolls33uand33dof the downstream nip-roll mechanism33. This makes it possible to anticipate and avoid rotation being out of control.

FIG. 6is a diagram illustrating a modified example37′ of the alteration device37. In the foregoing embodiment, the alteration device37includes the nip-roll mechanism37nas shown inFIG. 5A. But, the alteration device37′ in the modified example ofFIG. 6is different in that the alteration device37′ includes a dancer-roll mechanism37dinstead of the nip-roll mechanism37n. The rest of the configuration is substantially the same as that of the foregoing embodiment. The same components as those of the foregoing embodiment will be denoted by the same reference symbols, and the description thereof is omitted.

As shown inFIG. 6, the dancer-roll mechanism37dincludes: a dancer roll37drand an actuator37da. The dancer roll37dris capable of rotating about a rotational axis along CD direction while the exterior sheet7abeing in contact with its outer circumferential surface. The actuator37dais, for example, a hydraulic cylinder, and the actuator37daallows the dancer roll37drto reciprocate in the thickness direction of the exterior sheet7a(up-and-down direction) while supporting the dancer roll37drin a rotatable manner. To the controller37dcwhich controls the actuator37da, data indicating the foregoing shifting amount is transmitted from the image processing device36ip.

Then, the controller37dccontrols the alteration device37′ based on the foregoing data. That is, if the data indicates “the exterior sheet7ais shifted upstream in MD direction”, the controller37dccontrols the actuator37daand moves the dancer roll37drupward so that a loop of the exterior sheet7abecomes smaller. This decreases the shifting amount by which the exterior sheet7ais shifted upstream. On the other hand, if the data indicates “the exterior sheet7ais shifted downstream in MD direction, the controller37dccontrols the actuator37daand moves the dancer roll37drdownward so that a loop of the exterior sheet7abecomes larger. This decreases the shifting amount by which the exterior sheet7ais shifted downstream.

In the foregoing embodiment, as shown inFIG. 4A, the exterior-sheet contraction unit30is arranged between the leg-opening forming unit20and the absorbent-main-body attaching unit40. However, the arrangement position is not limited thereto. That is, instead of the foregoing position, the exterior-sheet contraction unit30may be arranged between the absorbent-main-body attaching unit40and the two-folding unit50. Or, the unit30may be arranged between the two-folding unit50and the end-section sealing unit60, and may be arranged between the end-section sealing unit60and the dividing unit70.

In addition to the area between the leg-opening forming unit20and the absorbent-main-body attaching unit40, an additional exterior-sheet contraction unit30may be provided anywhere between the processing units40,50,60and70. For example, additional exterior-sheet contraction units30may be provided respectively to the following three areas: an area between the absorbent-main-body attaching unit40and the two-folding unit50; an area between the two-folding unit50and the end-section sealing unit60; and an area between the end-section sealing unit60and the dividing unit70. This makes it possible to adjust the exterior sheet7ato an extended state which is most appropriate to a process by each of the abovementioned four processing units40,50,60and70.

In some cases, an additional exterior-sheet contraction unit30may be provided to an area which is selected among the foregoing three areas. Or, additional exterior-sheet contraction units30may be provided respectively to two areas which are selected among the foregoing three areas.

In the foregoing manufacturing line LM, as shown inFIG. 4A, the absorbent-main-body attaching unit40is placed downstream in MD direction from the leg-opening forming unit20. However, this invention is not limited thereto. For example, as shown in the modified example LM′ of the manufacturing line LM illustrated inFIG. 7, the leg-opening forming unit20may be arranged downstream in MD direction from the absorbent-main-body attaching unit40. In this case, however, the leg opening7HL cannot be used as a reference section which the sensor36of the adjustment device35detects, and this is because the leg-opening forming unit20is located downstream from the adjustment device35of the exterior-sheet contraction unit30. Accordingly, in this case, it is necessary to provide another physical reference section with the exterior sheet7a. The detail thereof is as follow.

In the example ofFIG. 7, a printing unit80which prints a mark as a reference section (corresponding to the reference-section forming apparatus) is arranged between the exterior-sheet producing unit10and the exterior-sheet contraction unit30. The printing unit80includes a suitable printer81and a controller82which controls the printer81. The printer81is located in a transport path between the exterior-sheet producing unit10and the exterior-sheet contraction unit30, and prints a mark onto the exterior sheet7a. Here, the printing is performed according to the foregoing synchronization signal. That is, every time when the rotational angle value of the synchronization signal matches the predetermined rotational angle value, the controller82outputs a print instruction signal to the printer81so that the printer81prints a mark. Thus, the printer81prints a mark onto each unit part of the exterior sheet7awhich is to be a diaper1. Since such a mark is printed according to the synchronization signal as mentioned above, the printing is made with a high accuracy at the predetermined position of the unit part which is to be a diaper1. Accordingly, the mark can effectively serve as a reference section which indicates a specific position in the exterior sheet7a.

A type of printer applicable to the printer81is not particularly limited as long as the printer can print a mark. For example, an inkjet printer, a flexographic printer, a screen printer and the like are available. A type of the mark is not particularly limited either. For example, the mark may be a pattern, a character, a picture, a symbol or the like.

In the example ofFIG. 7, a mark is printed on the stretchable sheet8aof the exterior sheet7a. However, this invention is not limited thereto. That is, a mark may be printed on the low-extensible sheet9a. In this case, the mark can serve as a more accurate reference section. That is, even if an unexpectedly great tension is exerted during transportation after printing, the low-extensible sheet9ado not greatly deform and can resist the tension due to its low extensibility. This can prevent such a phenomenon as distortion of the mark. Consequently, the mark can effectively serve as an exact reference section.

Other Embodiments

While the embodiment according to the invention are described above, the foregoing embodiment is provided for facilitating the understanding of the invention, and is not to be interpreted as limiting the invention. As a matter of course, the invention can be altered and improved without departing from the gist thereof and the invention includes equivalent thereof. For example, the invention can be altered as described below.

In the foregoing embodiment, a configuration including the imaging device36cand the image processing device36ipis provided as an example of the sensor36that detects the reference sections. However, this invention is not limited thereto. For example, a configuration including a phototube and a suitable controller may be used as a sensor that detects the reference sections. In this case, the controller can obtain the shifting amount of the exterior sheet7ain MD direction, based on the difference between the following rotational angle values; one is the rotational angle value of a synchronization signal at the time when the phototube detects passing of the reference section, and the other one is a predetermined rotational angle value which is stored in advance for comparison in a memory of the controller.

In the foregoing embodiment, as shown inFIG. 5A, the sensor36that detects the reference sections is configured to detect the leg opening7HL (serving as the reference section) during the period when the exterior sheet7ais moving in the transport path R30d(corresponding to the downstream path section) between the nip-roll mechanism37nof the adjustment device35and the downstream nip-roll mechanism33of the exterior-sheet contraction unit30. However, this invention is not limited thereto. For example, the sensor36may detect the leg opening7HL during the period when the exterior sheet7ais moving in the transport path R30u(corresponding to the upstream path section) between the upstream nip-roll mechanism31of the exterior-sheet contraction unit30and the nip-roll mechanism37nof the adjustment device35. Or, as shown inFIG. 4A, the sensor36may detect the leg opening7HL during the period when the exterior sheet7ais moving in the transport path between the downstream nip-roll mechanism33of the exterior-sheet contraction unit30and the absorbent-main-body attaching unit40. That is, the sensor36can be used without any problem as long as the sensor36is arranged so as to detect the reference section during the time period from the contraction of the exterior sheet7ain the exterior-sheet contraction unit30till the attachment of the absorbent main body3. However, the foregoing configuration does not mean that the sensor36is not arranged so as to detect the reference section during the attachment process of the absorbent main body3or later. That is, even if the detection is performed during the attachment or later, the sensor36can be used without any serious problem. Accordingly, broadly speaking, it is sufficient that the sensor36is arranged so as to detect the reference section during the contraction in the exterior-sheet contraction unit30or later.

In the foregoing embodiment, as a mechanism in which the exterior sheet7ain the first extended state contracts, the exterior-sheet contraction unit30has a pair of nip-roll mechanisms31and33as shown inFIG. 5A. However, the invention is not limited thereto as long as a mechanism in which the exterior sheet7ais able to contract. For example, instead of the pair of nip-roll mechanisms31and33, a pair of S-shaped-winding roll mechanisms31′ and33′ shown inFIG. 8may be provided. That is, each S-shaped-winding roll mechanism31′ (33′) includes a pair of rolls31u′ and31u′ (33u′ and33d′) which are driven and rotated about rotational axes along CD direction while their outer circumferential surfaces facing each other. The exterior sheet7ais wound around the pair of rolls31u′ and31d′ (33u′ and33d′) in an S shapes. In such a configuration, the outer circumferential surfaces of the rolls31u′ and31d′ (33u′ and33d′) can hold the exterior sheet7awith substantially no relative sliding. Since these rolls31u′ and31d′ (33u′ and33d′) are driven and rotated, the exterior sheet7acan be transported at a conveying speed which is equal to the circumferential speed values of the rolls31u′ and31d′ (33u′ and33d′). The S-shaped-winding roll mechanisms31′ and33′ can therefore be used instead of the foregoing nip-roll mechanisms31and33. In the example ofFIG. 8, both of the nip-roll mechanisms31and33are replaced with the S-shaped-winding roll mechanisms31′ and33′. In some cases, either one of the nip-roll mechanisms31and33may be replaced with the S-shaped-winding roll mechanism31(or33).

In the foregoing embodiment, as shown inFIG. 4A, the stretchable sheet8aand the low-extensible sheet9aare fixed to each other in the exterior-sheet producing unit10, and the fixing is performed by the ultrasonic welding device15. However, this invention is not limited thereto. For example, as shown inFIG. 9, instead of the ultrasonic welding device15, a heat-sealing device or a compression-bonding device may be used. The heat-sealing device and the compression-bonding device have a configuration similar to each other. That is, the main difference between their configurations is whether their rolls are heated or not. Both of the devices include a pair of upper and lower rolls17uand17dwhich are driven and rotated about rotational axes along CD direction, and each of the rolls17uand17drotates at the same circumferential speed value as the circumferential speed value V15aof the anvil roller15aof the foregoing ultrasonic welding device15. In such a configuration, the stretchable sheet8aand the low-extensible sheet9awhich are stacked passes the nip between the rolls17uand17dwhile the stretchable sheet8aextending till the reference extended state and the low-extensible sheet9abeing extended and tightened. When passing the nip, both sheets8aand9aare pressed by these rolls17uand17dbetween the rolls. Thus, the sheets8aand9aare be welded or pressed, and are fixed in an integrated manner. In a case of pressing, adhesive such as hot-melt adhesive may be applied, before the pressing, onto at least either one of the stretchable sheet8aand the low-extensible sheet9ain a certain applying pattern.

In the foregoing embodiment, the die cutter device21of the leg-opening forming unit20includes the single cutter blade21con the outer circumferential surface of the upper roll21u. However, this invention is not limited thereto. That is, a plurality of the cutter blades21cmay be provided on the outer circumferential surface of the upper roll21u. In this case, it is preferable that the plurality of cutter blades21care arranged at a uniform pitch in the rotating direction of the upper roll21u. It is more preferable that the length of the circular tracks traced by the cutting edge of the cutter blade21cas a result of the rotation of the upper roll21uis an integral multiple of the first pitch P1. In such a configuration, the die-cutting by the cutter blade21ccan be stabilized. The same is also true for the heat-sealing device61of the end-section sealing unit60, and is also true for the rotary cutter device71of the dividing unit70. That is, in the foregoing embodiment, the end-section sealing unit60also includes the single sealing pattern section61spin the upper roll61u, and the dividing unit70includes the single cutter blade71cin the upper roll71u. However, this invention is not limited thereto. The sealing pattern section61spwhich traces a circular track as mentioned above may be provided in the rotating direction at a uniform pitch, and also the cutter blade71cwhich traces a circular track as mentioned above may be provided in the rotating direction at a uniform pitch.

In the foregoing embodiment, the first extended state, which is an extended state at a time of forming a leg opening7HL (serving as the reference section), remains in the reference extended state, which is the extended state of the stretchable sheet8aat the time of fixing the stretchable sheet8aand the low-extensible sheet9a. That is, the first extension ratio in the first extended state remains at the extension ratio in the reference extended state. However, this invention is not limited thereto. That is, a leg opening7HL may be formed at an extension ratio which is slightly smaller than the extension ratio in the reference extended state. In this case, a leg opening7HL can be formed at the target position in the exterior sheet7awith considerably high accuracy because the extension ratio in the first extended state, which is an extended state at the time of forming a reference section (the leg opening7HL), is larger than the extension ratio in the second extended state, which is an extended state at the time of processings.

In the foregoing embodiment, in the exterior-sheet producing unit10, the stretchable sheet8ais fixed to the low-extensible sheet9a. But, a single or a plurality of additional sheet(s) may be fixed together. The additional sheet(s) to be fixed may be a stretchable sheet, or may be a low-extensible sheet. The sheet(s) may be made of nonwoven fabric, woven fabric or film.

REFERENCE SIGNS LIST