Patent Publication Number: US-2011059666-A1

Title: Method for forming sheets with elasticized regions and sheets made by this method

Description:
TECHNICAL FIELD 
     The present invention relates to a method for forming thermoplastic polymer sheets with elasticized regions adapted to be extensible and contractible in their thickness directions and to the sheets manufactured by this method. 
     RELATED ART 
     JP2000-342625A discloses a liquid-pervious inner sheet for a bodily fluid-absorbent article wherein the sheet is formed at a desired part with an elasticized region adapted to be extensible and contractible vertically with respect to the plane defined by the sheet. This elasticized region is defined by a plurality of gathers in the form of regression lines extending from a peripheral zone toward a central zone. According to the disclosure of JP2000-342625A, undesirable fine gathers would not be formed in the elasticized region and therefore wearers would not experience any feeling of incompatibility. In addition, this sheet may advantageously used for disposable diaper since a concave space adapted to receive and retain feces is formed by the elasticized region. 
     PATENT DOCUMENT  1 : JP2000-342625A 
     DISCLOSURE OF THE INVENTION 
     Problem to be Solved by the Invention 
     The elasticized region disclosed in JP2000-342625A may be obtained by subjecting the sheet to gear-processing. However, deep-draw work using gear-process may be accompanied with problems such as so-called seizing phenomenon and sheet breakage due to interference between gears. In view of such problems, it is a principal object of the present invention to provide a method for forming sheets with elasticized regions adapted to be extensible and contractible in thickness directions of the sheets without the foregoing problems, on one hand, and the sheet manufactured by this method, on the other hand. 
     Measure to Solve the Problem 
     The object set forth above is achieved, according to the present invention, by a method for forming a thermoplastic polymer sheet at a distance from an outer peripheral edge thereof with an elasticized region adapted to be extensible and contractible in a thickness direction of the sheet using stationery mold and movable mold each having a plurality of forming blades, wherein the method is characterized in that the plurality of forming blades are configured so as to have projected cross-sectional shapes on the sheet defined by similar curved lines and/or similar flexural lines arranged around a center of similitude and to extend in the thickness direction of the sheet from the stationery mold and the movable mold so as to be engaged one with another but not to come in contact one with another, and the method comprises a step of introducing the sheet between the stationery mold and the movable mold and a step of bring the forming blades of the stationery mold and the movable mold into engagement with one another to stretch the sheet between distal ends of each pair of the adjacent forming blades. 
     The term “curved lines and/or flexural lines” used herein should be understood to include closed curved lines and/or flexural lines (i.e., curved lines and/or flexural lines having neither origins nor end points) and partially devoid curved lines and/or flexural lines (curved lines and/or flexural lines having origins and end points). 
     For the forming method according to the present invention, the forming blades are preferably maintained in engaged state for a predetermined period. Alternatively, the forming blades are preferably maintained in engaged state for a predetermined period at a temperature lower than a fusion point of the thermoplastic polymer sheet but higher than an ambient temperature (JIS K 6900, 15 to 35° C.). After the step of introducing the sheet, the sheet is preferably clamped in its thickness direction between the stationery mold and the movable mold in an outer peripheral region extending around a region in which the distal ends of the forming blades are arranged and/or a central region surrounded by the region in which the distal ends of the forming blades. Furthermore, the sheet can be formed with a partial region in which a depth of engagement is continuously changed when a plurality of forming blades are engaged one with another. 
     As the thermoplastic polymer sheet to be formed by the method according to the present invention, at least one of thermoplastic polymer film and thermoplastic polymer fibrous nonwoven fabric is used. Although “sheet” and “film” are sometimes distinguished from each other on the basis of thickness, film and sheet will not be distinguished on the basis of thickness so far as the present invention concerns and the term “sheet” is inclusive of both film and nonwoven fabric. According to the present invention, both films and nonwoven fabrics having elasticity may be used. The thermoplastic polymer sheet may comprise a laminated sheet consisting of two or more types of films and nonwoven fabrics, respectively. 
     EFFECT OF THE INVENTION 
     The method according to the present invention utilizes engagement of a plurality of forming blades one with another to form an elasticized region and therefore the inventive method is free from the interference between the gears. In addition, the engagement depth of the forming blades may be adjusted to stretch the sheet without braking the sheet. 
     The forming blades may be maintained in engaged state for a predetermined period under heating or not heating to facilitate the elasticized region to be formed. The sheet may be clamped in its thickness direction between an outer peripheral region extending around a region in which the distal ends of the forming blades are arranged and/or between a central region surrounded by the region in the distal ends of the forming blades are arranged to prevent the sheet from being dragged between each pair of the adjacent forming blades when the forming blades are engaged one with another. 
     There may be provided a partial region in which the engagement depth continuously changes to adjust a shape presented by the elasticized region when the elasticized region is stretched in the thickness direction of the sheet. When the projected cross-sectional shapes of a plurality of the forming blades on the sheet are the partially devoid closed curved lines as has previously described, the engagement depths at the origins and the end points of such shape may be adjusted to be relatively shallow to avoid sheet breakage occurring in the vicinity of these origins and end points. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  Perspective view showing a forming device as it is opened. 
         FIG. 2  Schematic diagram illustrating a step of introducing a sheet between a stationary mold and a movable mold. 
         FIG. 3  Schematic diagram illustrating a step of clamping the sheet between a pair of outer peripheral frames. 
         FIG. 4  Schematic diagram illustrating a step of forming the sheet with an elasticized region. 
         FIG. 5  Schematic diagram illustrating a part of  FIG. 4  in an enlarged scale. 
         FIG. 6  Perspective view of the sheet formed with the elasticized region. 
         FIG. 7  Schematic diagram illustrating a cross-sectional shape of the sheet formed with the elasticized region. 
         FIG. 8  Diagram exemplarily illustrating projected cross-sectional shapes of forming blades. 
         FIG. 9  Perspective view of the stationery mold in the device according to a second embodiment of the invention. 
         FIG. 10  Sectional view taken along a line X-X in  FIG. 9 . 
         FIG. 11  Schematic diagram illustrating a manner in which the forming blades used for the method according to the second of the invention are engaged one with another. 
         FIG. 12  Perspective view of the sheet for the method using the device according to the second embodiment of the invention. 
         FIG. 13  Schematic diagram illustrating a cross-sectional shape of the elasticized region formed in the sheet by the method using the device according to the second embodiment of the invention. 
         FIG. 14  Perspective view of a manufacturing equipment provided with the forming device. 
         FIG. 15  Schematic diagram illustrating operation of the manufacturing equipment. 
         FIG. 16  Schematic diagram how to control the operation of the manufacturing equipment. 
         FIG. 17  Schematic diagram how to control the operation of the manufacturing equipment. 
         FIG. 18  Schematic diagram how to control the operation of the manufacturing equipment. 
     
    
    
     IDENTIFICATION OF REFERENCE NUMERALS USED IN THE DRAWINGS 
     
         
           2  forming blade 
           3  distal end of forming blade 
           4  engagement depth 
           5  stationary mold 
           6  movable mold 
           8  movement indicating imaginary straight line (thickness direction of sheet) 
           10  thermoplastic polymer sheet 
           11  elasticized region 
           12  outer peripheral edge 
       
    
     DESCRIPTION OF THE BEST MODE FOR WORKING OF THE INVENTION 
     A method of forming a thermoplastic polymer sheet  10  (referred to hereafter simply as sheet  10 ) with an elasticized region  11  using a forming device  1  according to a first embodiment of the present invention provided with a plurality of forming blades  2  arranged in a pattern of concentric circles will be described hereinafter with reference to  FIGS. 1 through 5 .  FIG. 1  is a perspective view showing the forming device  1  in its opened state and  FIG. 2  is a sectional view taken along a line II-II in  FIG. 1 , showing a stationery mold  5  and a movable mold  6  opposed to each other. 
     As shown by  FIG. 1 , the forming device  1  generally comprises the stationery mold  5  and the movable mold  6  both provided with a plurality of the forming blades  2  which are arranged in pattern of concentric circles, respectively. In other words, these forming blades  2  are arranged so that cross-sectional shapes thereof projected on the sheet  10  describe closed curves, respectively. In addition to these forming blades  2 , the forming device  1  includes a pair of outer peripheral frames  21  and a pair of central frames  23 . When the forming device  1  is operated, the movable mold  6  is opposed to the stationery mold  5  and moved by an actuator (not shown) along a movement indicating imaginary straight line  8  closer to or apart from the stationery mold  5 , as will be appreciated from  FIG. 2 . In the course of forming, the movement indicating imaginary straight line  8  coincides with a thickness direction of the sheet  10 . 
     As will be apparent from  FIG. 2 , the forming blades  2  extend in parallel to the movement indicating imaginary straight line  8  and vertically mounted on respective pedestals  9 ,  9  provided within the stationery mold  5  and the movable mold  6 . The forming blades  2  of the stationery mold  5  and the movable mold  6  are so arranged that these forming blades  2  may be engaged one with another but never brought in contact one with another as the movable mold  6  is moved closer to the stationery mold  6  along the movement indicating imaginary straight line  8  (See  FIGS. 3 and 4 ). Distal ends  3  of the forming blades  2  in both the stationery mold  5  and the movable mold  6  are coplanar, respectively, orthogonally to the movement indicating imaginary straight line  8 . A distance between each pair of the adjacent forming blades  2  is larger than a thickness of the blade  2 . Such dimensioning ensures that the forming blades  2  of the movable mold  6  are smoothly engaged with the forming blades  2  of the stationery mold  5  without contacting. 
     The opposed surfaces  7  of the movable mold  6  and the stationery mold  5  extending orthogonally to the movement indicating imaginary straight line  8  are defined by outer peripheral close-contact surfaces  20  of a pair of rectangular outer peripheral frames  21  disposed around a region in which the distal ends  3  of the forming blades  2  are arranged and a central close-contact surfaces  22  of a pair of circular central frames  23  disposed inside the region in which the distal ends  3  of the forming blades  2  are arranged. When the forming blades  2  of the movable mold  6  and the forming blades  2  of the stationery mold  5  are not engaged each other, the distal ends  3  of the forming blades  2  do not protrude outward beyond the outer peripheral close-contact surfaces  20  and the central close-contact surfaces  22 . The outer peripheral frames  21  and the central frames  23  are mounted together with the respective pedestals  9  on foundations  41 . 
     According the embodiment shown by  FIG. 2 , the outer peripheral frame  21  and the central frame  23  of the movable mold  6  are spring-biased to move toward the outer peripheral frame  21  and the central frame  23  of the stationery mold  5  until these outer peripheral close-contact surface  20  and central close-contact surface  22  come in close contact with those  20 ,  22  of the stationery mold  5 , respectively. Alternatively, the outer peripheral frame  21  and the central frame  23  of the stationery mold  5  can be spring-biased to move toward those of the movable mold  6  or the outer peripheral frames  21  and the central frames  23  of both the stationery mold  5  and the movable mold  6  can be spring-biased to move toward those of the opposite molds  6 ,  5 , respectively. 
     Shapes of the outer peripheral frame  21  and the central frame  23  are not limited to those exemplarily illustrated and may be appropriately selected depending on a contour of the region  11  to be elasticized. For example, the outer peripheral frame  21  may have an annular shape. It is also possible to eliminate the central frame  23 . The outer peripheral close-contact surfaces  20  preferably protrude outward beyond the distal ends  3  of the forming blades  2  to prevent the sheet  10  from being unintentionally dragged into the gaps defined between each pair of the adjacent forming blades  2  engaged with each other and result in unacceptable forming, as will be described more in detail. 
     Now a process of forming the sheet  10  with the elasticized region  11  when the sheet  10  is in the form of film will be described with reference to  FIGS. 2 through 5 .  FIG. 2  illustrates a step of introducing the sheet  10  between the stationery mold  5  and the movable mold  6 ,  FIG. 3  illustrates a step of firmly sandwiching the sheet  10  between the outer peripheral frames  21 ,  21  of the stationery mold  5  and the movable mold  6 , and  FIG. 4  illustrates a step of stretching the sheet  10  wherein the forming blades  2  come in engagement and thereby forming the sheet  10  with the elasticized region  11 .  FIG. 5  is a schematic diagram illustrating a part of  FIG. 4  in an enlarged scale. Description given hereunder is on the assumption that the movable mold  6  moves along the movement indicating imaginary straight line  8  closer to and apart from the stationery mold  5 . 
     In the step of introduction, the sheet  10  is introduced between the stationery mold  5  and the movable mold  6  as will be seen in  FIG. 2 . Upon movement of the movable mold  6  toward the stationery mold  5 , the sheet  10  is firmly clamped between the outer peripheral close-contact surfaces  20 ,  20  of the outer peripheral frames  21 ,  21  of the stationery mold  5  and the movable mold  6  in the outer peripheral region extending around the region in which the distal ends  3  of the forming blades  2  are arranged, as illustrated by  FIG. 3 . In consequence, the sheet  10  is withheld from displacing in the direction orthogonal to the movement indicating imaginary straight line  8  and it is ensured that the sheet  10  is formed in a predetermined portion with the elasticized region  11 . 
     Further movement of the movable mold  6  causes the forming blades  2  to come in engagement as illustrated by  FIG. 4 . When the forming blades  2  are engaged each other, the sheet  10  is clamped between the outer peripheral close-contact surfaces  20 ,  20  and between the central close-contact surfaces  22 ,  22  under a pressure and thereby withheld from displacing in the direction orthogonal to the movement indicating imaginary straight line  8 . Consequently, the sheet  10  would not be unintentionally dragged into the gap defined between each pair of the adjacent forming blades  2  as the forming blades  2  come in engagement one with another. Specifically, the sheet  10  is stretched between each pair of the adjacent distal ends  3  of the forming blades  2  as schematically illustrated in an enlarged scale by  FIG. 5 , alternately creating high ratio-stretched zones  13  and low ratio-stretched zones  14 . In this way, the elasticized region  11  is formed. 
     The forming blades  2  are preferably maintained in engaged state for a given period. The period for which the forming blades  2  should be maintained in engaged state may be appropriately set depending on an observed configuration of the elasticized region  11  which is being formed. The forming blades  2  may be maintained in engaged state for a given period at a temperature lower than a fusing point of the thermoplastic polymer but higher than an ambient temperature to facilitate the elasticized region  11  to be formed. Such temperature is usually in a range of temperature lower than the fusing point of the thermoplastic polymer by 20 to 30° C. and may be appropriately selected taking account of on a thermal deformation temperature of the thermoplastic polymer such as a deflection temperature under load (JIS K 7191-2) or Vicat softening temperature (JIS K 7206) and depending on an observed configuration of the elasticized region  11  being formed. 
     The sheet  10  formed with the elasticized region  11  in this manner is illustrated by  FIG. 6  in perspective appearance and a cross-sectional shape thereof is schematically illustrated by  FIG. 7 . With this embodiment of the inventive device, the sheet  10  formed with the elasticized region  11  comprising a plurality of wavy undulations arranged in a concentric pattern is obtained as will be seen in  FIGS. 6 and 7 . In the elasticized region  11 , respective annular zones extending along crests of the respective wavy undulations are defined by the zones  14  stretched by the distal ends  3  of the forming blades  2  at the relatively low stretch ratio while respective belt-like zones extending along slopes of the respective wavy undulations are defined by the zones  13  stretched between each pair of the adjacent distal ends  3  of the forming blades  2  at the relatively high stretch ratio. As will be apparent from  FIG. 7 , the zones  14  stretched at the relatively low stretch ratio are correspondingly thick. In contrast with them, the high ratio-stretched zones  13  are thinner than the low ratio-stretched zones  14  and correspondingly more easily deformable than the zones  14 . 
     In the elasticized region  11 , the high ratio-stretched zones  13  and the low ratio-stretched zones  14  are alternately arranged. In response to a force exerted on the sheet  10  in the elasticized region  11  in its thickness direction, the respective high ratio-stretched zones  13  are immediately deformed in the direction of this force and the low ratio-stretched zones  14  follow the movement of the zones  13 . Consequentially, the elasticized region  11  conically deploys in the thickness direction of the sheet  10  so as to form a space  15  which is concave with respect to the plane defined by the sheet  10 , as shown in  FIG. 7  with an imaginary line. When the sheet  10  having such elasticized region  11  is used for disposable diapers, this space  15  effectively serves to retain feces therein. 
     As will be understood from the foregoing description, with the forming method using the device  1  according to this embodiment, the sheet  10  would not be broken in the course of processing since the sheet  10  is formed with the elasticized region by stretching the sheet  10  in a range of stretch ratios acceptable for the thermoplastic polymer. In addition, the method using the device  1  according to this embodiment makes it possible to form the sheet  10  with the elasticized region  11  adapted to define the space  15  without need to attach a separate member to the sheet  10 . Such sheet  10  may be used for disposable diapers adapted to retain feces to rationalize production of the diapers, for example, by decreasing the number of steps conventionally required to make the diaper. 
     While the method according to the invention has been described with respect to the case in which the sheet  10  is in the form of film, it should be appreciated that nonwoven fabrics made of thermoplastic polymer fiber may be also used as the sheet  10 . When spun bond or melt blown nonwoven fabrics are used as the sheet  10 , the high ratio-stretched zones  13  are more easily deformed than the low ratio-stretched zones  14  because heat bonds between fibers would be broken at the high ratio-stretched zones  13 . 
     In addition to the thermoplastic polymer films and the thermoplastic fibrous nonwoven fabrics, it is possible to use initially elastic sheets such as films of thermoplastic elastomer or fibrous nonwoven fabrics of thermoplastic elastomer as the sheet  10 . It is also possible to use various types of laminated sheets such as laminated sheets consisting of inelastic sheets and elastic sheets or laminated sheets comprising different types of inelastic sheets as the sheet  10 . The thermoplastic polymer may be selected from a group including polyolefins, polyesters and polyamides and the thermoplastic elastomer may be selected from a group including those made of polyurethane- and polyester-based block copolymers. 
     It should be understood that the high ratio-stretched zone  13  and the low ratio-stretched zone  14  in the elasticized region  11  formed according to the invention are not limited to those arranged in the pattern of concentric circles.  FIG. 8  exemplarily illustrates cross-sectional shapes of the forming blades  2  projected on the plane extending orthogonally to the movement indicating imaginary straight line  8 . These projected cross-sectional shapes correspond to possible patterns of the elasticized region  11  formed by the method according to the invention. More specifically, these possible patterns include a plurality of similar closed curved lines and/or flexural lines concentrically arranged in point symmetry about a center of similitude ( FIG. 8A ), a plurality of similar closed curved lines and/or flexural lines arranged concentrically and symmetrically about a straight line passing the center of similitude ( FIG. 8B ). Furthermore, the elasticized region  11  may present a pattern defined by a plurality of similar closed curved lines and/or flexural lines surrounding the center of similitude which is displaced aside insofar as these lines do not intersect one with another ( FIG. 8C ). Additionally, there may be various patterns defined by a plurality of similar closed but partially devoid curved lines surrounding the center of similitude ( FIG. 8D-8F ). 
     Now the method using the device  1  according to a second embodiment of the invention to form the elasticized region  11  comprising the high-ratio stretched zones  13  and the low-ratio stretched zones  14  alternately arranged so as to present a pattern defined by a plurality of similar closed but partially devoid curved lines surrounding the center of similitude will be described with reference to  FIGS. 9 through 18 .  FIG. 9  is a perspective view of the stationery mold  5  used in this embodiment,  FIG. 10  is a sectional view taken along a line X-X in  FIG. 9  and  FIG. 11  is a schematic diagram illustrating a manner in which the forming blades  2  are engaged one with another when the movable mold  6  is engaged with the stationery mold  5 .  FIG. 12  is a perspective view of the sheet  10  formed with the elasticized region  11  and  FIG. 13  is a diagram schematically illustrating a cross section of the elasticized region  11 . 
     Description given hereinafter is on the assumption that the forming device  1  used for the forming method has the forming blades  2  arranged so that each partially devoid closed curved line describes a rectangle having its one side devoid (referred to hereinafter as semi-rectangle) and a plurality of similar such semi-rectangles surround the center of similitude and that the sheet  10  is used in the form of film. 
       FIG. 9  shows the stationery mold  5  as an important component of the forming device  1 . Except that a plurality of forming blades  2  describe similar semi-rectangles, the stationery mold  5  used in this embodiment is similar to the stationery mold  5  used in the first embodiment and provided with the outer peripheral frame  21  and the central frame  23 . The movable mold  6  used in this embodiment is similar to the stationery mold  5  except that the outer peripheral frame  21  and the central frame  23  are spring-biased to move toward the stationery mold  5  and is not illustrated. The features similar to those of the first embodiment will not be repetitively described in details. 
     As will be seen in  FIG. 10 , the distal ends  3  of the forming blades  2  do not protrude outward beyond the outer peripheral close-contact surface  20  of the outer peripheral frame  21  as well as beyond the central close-contact surface  22  of the central frame  23 . It should be appreciated that the forming blades  2  of the stationery mold  5  extending in parallel to the movement indicating imaginary straight line  8  and are arranged so as to be engaged with the forming blades  2  of the movable mold  6  without contacting with the forming blades  2  of the movable mold  6 . 
     Engagement of the forming blades  2  according to this embodiment to create the projected cross-sectional shape defined by a plurality of the partially devoid semi-rectangles is schematically illustrated by  FIG. 11 . In  FIG. 11 , reference numeral  2   a  represents a solid line connecting the forming blades  2  extending from the stationery mold  5  and reference numeral  2   b  represents a dashed line connecting the forming blades  2  extending from the movable mold  6 . As will be seen in  FIG. 11 , the solid line connecting the distal ends  3   a  is parallel to the dashed line connecting the distal ends  3   b  in a middle segment  24  when the forming blades  2   a ,  2   b  are engaged with one another. 
     In lateral segments on both sides of the middle segment  24 , a depth  4  at which the forming blades  2   a ,  2   b  are engaged one with another continuously decreases from the middle segment  24  toward the lateral segments  25 . In consequence, the sheet  10  is prevented from being broken along corners of the forming blades  2   a ,  2   b  at the opposite end segments  25  in the course of forming the sheet  10  with the elasticized region  11  by the forming blades  2   a ,  2   b . To prevent the sheet  10  from being broken, the forming blades  2   a ,  2   b  preferably have the round corners at the opposite end segments  25 . 
     Between the movable mold  6  and the stationery mold  5  of the forming device  1  each having the forming blades  2  as have been described above, the sheet  10  is introduced and stretched between each pair of the adjacent distal ends  3  of the respective forming blades  2  to form the elasticized region  11  in a substantially same manner as in the first embodiment (See  FIGS. 2 through 5 ). As shown in  FIG. 12 , the elasticized region  11  formed by the method using the device  1  according to this embodiment presents an appearance defined by the semi-rectangles similar one to another alternately arranged around the center of similitude. 
       FIG. 13  is a schematic sectional diagram of the elasticized region  11  taken along a line XIII-XIII in  FIG. 12 . Of the elasticized region  11 , the middle zone  26  stretched by the middle segments  24  of the forming blades  2  presents a corrugated cross-sectional shape comprising a plurality of high-ratio stretched zones  13  of uniform width arranged in parallel one to another. In the lateral zones  27  on both sides of the middle zone  26 , the engagement depth  4  of the forming blades  2  gradually decreases and the width of the high-ratio stretched zones  13  formed between each pair of the adjacent forming blades  2  also gradually decreases as the forming blades  2  back away from the middle zone  26 . As a result, the elasticized region  11  may be forced in the thickness direction of the sheet  10  to form a triangular space  15  which is concave from the plane defined by the sheet  10 . In this manner, the projected cross-sectional shapes and the engagement depth  4  of the forming blades  2  may be appropriately changed to form the elasticized region  11  adapted to form the space  15  having desired shapes. 
     A manufacturing equipment  50  including the forming device  1  according to the first embodiment adapted to form the continuously fed sheet  10  with the elasticized region  11  and the method using this manufacturing equipment  50  will be described with reference to  FIGS. 14 through 18 .  FIG. 14  is a perspective view of the manufacturing equipment  50  provided with the forming device  1 ,  FIG. 15  is a schematic side view illustrating operation of the forming device  1 , and  FIGS. 16 through 18  are diagrams illustrating how to control the operation of the forming device  1  in the manufacturing equipment  50 . 
     The manufacturing equipment  50  has a horizontal base  51  and a pair of columnar supports  52  vertically extending upward from the base  51  wherein a main shaft  53  horizontally extending between a pair of the columnar supports  52  on which a rotating drum  31  is rotatably mounted. The rotating drum  31  has a peripheral surface  30  extending in parallel to a rotational axis M indicated by an imaginary line. The sheet  10  indicated by an imaginary line is guided by the inlet nip roll pair  54  into contact with the peripheral surface  30  and guided by the outlet nip roll pair  55  to be moved apart from the peripheral surface  30 . In  FIG. 14 , the equipment  50  is illustrated with one of the columnar supports  52  removed from the base  51 . 
     A plurality of revolving heads  32  are provided at regular intervals around the rotating drum  31 . The revolving heads  32  can be opposed to the peripheral surface  30  of the rotating drum  31 . The revolving heads  32  revolve together with the rotating drum  31  around the rotational axis M in the direction indicated by an arrow D in which the sheet  10  is fed. The revolving heads  32  respectively have associated arms  56  are rotatably mounted on the rotating drum  31  (See  FIG. 15 ) by the intermediary of associated spindles  57  (not shown in  FIG. 14 ) extending orthogonally to the rotational axis M. Each of the revolving heads  32  is adapted to swing around the spindle  57  apart from its position opposed to the peripheral surface  30  to its completely opened position outside the rotating drum  31  under the effect of suitable revolving head driving means (not shown) mounted on the spindle  57 . The completely opened position of the revolving head  32  is set so that the revolving head  32  is free from any interference with the sheet  10  when the revolving head  32  is revolving together with the rotating drum  31 . As the revolving head driving means, the driving means of prior art such as a servomotor may be used. 
     A plurality of the stationery molds  5  as the important components of the forming device  1  are mounted on the peripheral surface  30  of the rotating drum  31  wherein various elements such as the distal ends  3  of the respective forming blades  2  and the outer peripheral close-contact surface  20  are exposed in each of the stationery molds  5 . In association with the stationery molds  5 , a plurality of the movable molds  6  are mounted on the respective revolving heads  32  so that each of these movable molds  6  may swing to its position opposed to the associated stationery mold  5 . Both the movable mold  6  and the stationery mold  5  are similar to those having been described with respect to the first embodiment, i.e., the movement indicating imaginary straight line  8  coincides with the radial direction of the rotating drum  31  and the movable mold  6  may be brought into contact with the stationery mold  5  to engage the forming blades  2  of the movable mold  6  with the forming blades  2  of the stationery mold  5 . 
     Each of the revolving heads  32  is provided with mold driving means  34  adapted to reciprocate the movable mold  6  along the movement indicating imaginary straight line  8  and thereby to engage the forming blades  2  of the movable mold  6  with the forming blades  2  of the associated stationery mold  5 . As the mold driving means  34 , a suitable actuator of prior art such as a servomotor or a hydraulic cylinder may be used. It is possible to dispose the movable mold  6  on the peripheral surface  30  of the rotating drum  31  and to dispose the stationery mold on the revolving head  32  so that the stationery mold  5  may be reciprocated by the mold driving means  34 . 
     The inlet nip roll pair  54  and the outlet nip roll pair  55  are respectively disposed on the upstream side and the downstream side as viewed in the direction in which the sheet  10  is fed. Both the inlet nip roll pair  54  and the outlet nip roll pair  55  extend in parallel to the rotational axis M and vertically underlie the rotational axis M. The sheet  10  is guided by the inlet nip roll pair  54  into contact with the stationery mold  5  mounted on the peripheral surface  30  of the rotating drum  31  and stretched between each pair of the adjacent distal ends  3  of the forming blades  2  as the forming blades  2  of the stationery mold  5  and the movable mold  6  come in engagement in the course of counterclockwise rotation of the drum  31  as viewed in drawings and thereby formed with the elasticized region  11 . Then the sheet  10  is guided by the outlet nip roll pair  55  so as to move away from the peripheral surface  30 , in other words, from the stationery mold  5 . 
     The movable mold  6  of the forming device  1  mounted on the rotating drum  31  operates under a control as will be discussed on the basis of a position coordinate system as illustrated in  FIG. 16  wherein an optional set of the stationery mold  5  and the movable mold  6  operatively associated with each other start from 0° position defined by the highest point of the rotating drum  31  to revolve counterclockwise by 360°. It should be appreciated that detection of the rotating drum&#39;s position and the engagement depth of the forming blades  2  as well as control of operation of the revolving head driving means  33  and the mold driving means  34  are carried out by a control unit (not shown). 
     As will be apparent from  FIGS. 17 and 18 , at the 0° position, the set of the molds  5 ,  6  are completely closed and an engagement depth of the forming blades  2  is set to a target value, i.e., the depth desired to stretch the sheet  10 . In the course of revolving from 0° position toward 90° position, the mold driving means  34  nulls the engagement depth from the target value so as to release the movable mold  6  and subsequently the revolving head driving means  33  turns the movable mold  6  (the revolving head  32 ) to its completely opened position. The revolving head  32  should be completely opened before the revolving head  32  attains a position at which the outlet nip roll pair  55  is disposed (See  FIG. 16 ) in order to prevent the revolving head  32  from interfering with the sheet  10 . 
     The set of the molds  5 ,  6  revolve further beyond 180° position, passes the position of the inlet nip roll pair  54  (See  FIG. 16 ) and the sheet  10  comes in contact with the peripheral surface  30  of the rotating drum  31 . Thereupon operation to close the movable mold  6  is initiated and, after the set of the molds  5 ,  6  has passed 270° position, the movable mold  6  is completely closed with the sheet  10  clamped between the molds  5 ,  6 . Then the mold driving means  34  is initiated so that the forming blades  2  of the movable mold  6  may be engaged with the forming blades  2  of the stationery mold  5  by the desired amount of engagement which is the target value (i.e., engagement depth  4 ) at 360° position, i.e., 0° position. As described above, the engagement depth of the forming blades  2  is preferably adjusted to attain the maximum value at 0° position to avoid undesirable phenomenon of seizing possibly occurring between each pair of the adjacent forming blades  2  of the stationery mold  5  and the movable mold  6 . 
     The cycle as has been described above may be repeated to produce, in continuous fashion, the sheet formed with the elasticized regions  11  by using the manufacturing equipment  50 . It should be noted here that the positions occupied by the set of the stationery mold  5  and the movable mold  6  in the position coordinate system have exemplarily described and not limited thereto.