Patent Publication Number: US-2022211549-A1

Title: Apparatus and method for manufacturing absorbent core used in disposable wearable article

Description:
TECHNICAL FIELD 
     The present invention relates to an apparatus and a method for manufacturing an absorbent core used in a disposable wearable article. 
     BACKGROUND ART 
     For manufacturing an absorbent article such as diaper, there has been a technique in which a partial area in an absorbent core is made have different thickness from the other area in the core. In the technique, one of the two fiber stacking drums forms a first absorbent layer; another of the two fiber stacking drums forms a second absorbent layer, which has a smaller area than the first absorbent layer; and the first and second absorbent layers overlap with each other, thereby producing an absorbent core, which has a partial area thicker than the rest. 
     CITATION LIST 
     Patent Literature 
     
         
         [First patent document] JP 2,541,558 B2 ( FIG. 1 ) 
       
    
     SUMMARY OF INVENTION 
     Since the convention technique overlaps the two layers by simply putting the one on the other, the two layers are likely to be out of alignment during transporting or using the absorbent article. 
     It is an object of the present invention to provide a method and an apparatus for manufacturing an absorbent core having portions that are different in thickness, the different thickness portions being prevented from out of alignment. 
     A first method for manufacturing an absorbent core uses a feed device  3 , a first drum  1 , and a second drum  2 , 
     the feed device  3  feeds crushed fiber F, 
     the first drum  1  is provided with a first area α 1 , where the crushed fiber F is sucked and made to cling to an outer circumferential portion  10  of the first drum  1  and stacked, and 
     the second drum  2  is provided with a second area α 2 , where the crushed fiber F is sucked and made to cling to an outer circumferential portion  20  of the second drum  2  and stacked, the second area α 2  being smaller than the first area α 1 , 
     wherein the method comprises: 
     a step of forming a thick portion C 2  on the second area α 2  of the second drum  2  by stacking the fiber F fed from the feed device  3 ; 
     a step of transferring (placing) the thick portion C 2  to a predetermined position in the first area α 1 ; and 
     a step of forming a thin portion C 1  on the first area α 1  of the first drum  1  by stacking the fiber F fed from the feed device  3  around the transferred thick portion C 2 , with the transferred thick portion C 2  placed on the first area α 1 . 
     With this first method, the thick portion C 2  stacked on the second drum  2  is transferred to the first drum  1 , and then the thin portion C 1  is stacked on the first drum  1 . Thus, the thin portion C 1  is stacked around the thick portion C 2 , and the thin portion C 1  and the thick portion C 2  are unlikely to be out of alignment with each other. 
     A second method for manufacturing an absorbent core uses a feed device  3 , a first drum  1 , and a second drum  2 , 
     the feed device  3  feeds crushed fiber F, 
     the first drum  1  is provided with a first area α 1 , where the crushed fiber F is sucked and made to cling to an outer circumferential portion  10  of the first drum  1  and stacked, and 
     the second drum  2  is provided with a second area α 2 , where the crushed fiber F is sucked and made to cling to an outer circumferential portion  20  of the second drum  2  and stacked, the second area α 2  being smaller than the first area α 1 , 
     wherein the method comprises: 
     a step of forming a thick portion C 2  on the second area α 2  of the second drum  2  by stacking the fiber F fed from the feed device  3 ; 
     a step of forming a thin portion C 1  on the first drum  1 , the thin portion C 1  having a grammage lower (a thickness thinner) than a grammage (a thickness) of the thick portion C 2  on the first area α 1  other than (except) an inhibition area α 3 , the inhibition area α 3  being an area where stacking of the fiber F of the thin portion C 1  is inhibited; and 
     a step of transferring the thick portion C 2  from the second drum  2  to the inhibition area α 3  of the first drum  1  and fitting the thick portion C 2  into the thin portion C 1 . 
     With this second method, the thin portion C 1  is formed on the first drum  1 , and then the thick portion C 2  on the second drum  2  is transferred from the second drum  2  to the inhibition area α 3  (an area where the thin portion C 1  is not formed) of the first drum  1 , the thick portion C 2  and the thin portion C 1  fitting with each other. Thus, the thin portion C 1  is positioned around the thick portion C 2 . Therefore, the thin portion C 1  and the thick portion C 2  are unlikely to be out of alignment. 
     An apparatus of the present invention includes: 
     a feed device  3  that feeds crushed fiber F; 
     a first drum  1  that forms a thin portion C 1  on a first area α 1 , where the fiber F is sucked and made to cling to an outer circumferential portion  10  of the first drum  1  and stacked; 
     a second drum  2  that forms a thick portion C 2  on a second area α 2 , where the fiber F is sucked and made to cling to an outer circumferential portion  20  of the second drum  2  and stacked, the second area α 2  being smaller than the first area α 1 ; 
     a first duct portion  31  that guides the fiber F from the feed device  3  to the outer circumferential portion  10  of the first drum  1 , 
     a second duct portion  32  that guides the fiber F from the feed device  3  to the outer circumferential portion  20  of the second drum  2 ; and 
     a point P defined between the first duct portion  31  and the second duct portion  32 , 
     the first drum  1  and the second drum  2  making contact with each other, with the thick portion C 2  placed between the first drum  1  and the second drum  2  at the point P, and the thick portion C 2  stacked on the second area α 2  being passed from the second drum  2  to an area in the first drum  1  where the thin portion C 1  is not formed. 
     With this apparatus of the present invention, the thick portion C 2  formed on the second drum  2  is transferred to the first drum  1  and placed on an area where the thin portion C 1  is not formed. Thus, the thin portion C 1  is stacked so as to surround the thick portion C 2 . Therefore, the thin portion C 1  and the thick portion C 2  are unlikely to be out of alignment. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a conceptional side view showing an embodiment 1 of the present apparatus and the present method, 
         FIG. 1B  is a developed view showing an area of the drum, and 
         FIG. 1C  is a perspective view of the absorbent core. 
         FIG. 2A  is a conceptional side view showing an embodiment 2 of the present apparatus and the present method,  FIG. 2B  is a developed view showing an area of the drum, and  FIG. 2C  is a plan view of the absorbent core. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the first method of the present invention, it is preferred that the thick portion C 2  on the second drum  2  is placed in the first area α 1  of the first drum  1  by being sucked and made to cling to the first area α 1  in a state where the fiber F of the thin portion C 1  is not yet stacked in the first area α 1 . 
     In this case, the thick portion C 2  on the second drum  2  is placed on the first area α 1  of the first drum  1  and sucked in the first area α 1 , so the thick portion C 2  is more likely to be out of alignment. 
     In the second method of the present invention, it is preferred that, in the step of forming the thick portion C 2  on the second drum  2 , the thick portion C 2  is formed so as to coincide with a planar shape of the inhibition area α 3  of the first drum  1 . 
     In this case, it is possible to transfer the thick portion C 2  to the inhibition area α 3 , with the thick portion C 2  being coincided with the inhibition area α 3  in shape. 
     In the second method of the present invention, in the step of forming the thin portion C 1  on the first drum  1 , the fiber F may not be stacked in the inhibition area α 3 . 
     In the methods of the present invention, in the step of forming the thin portion C 1 , the thin portion C 1  may continuously be formed along the outer circumferential portion  10  of the first drum  1  so as to form the absorbent core C, which is continuous. 
     In this case, the continuous absorbent core C is cut in an individual wearable article unit. 
     In the methods of the present invention, the absorbent core C is formed such that a surface of the thick portion C 2  protrudes more than (higher than) a surface of the thin portion C 1 . 
     In the case where the device of the present invention is applied to the first method of the present invention, the second drum  2  makes contact with the first drum  1  at the point P, with the thick portion C 2  placed between the first drum  1  and the second drum  2 , such that the thick portion C 2  stacked on the second drum  2  is passed (transferred) from the second drum  2  to the first drum  1  in a state where the thin portion C 1  is not yet stacked on the first drum  1 . 
     On the other hand, in the case where the device of the present invention is applied to the second method of the present invention, the second drum  2  makes contact with the first drum  1  at the point P, with the thick portion C 2  placed between the first drum  1  and the second drum  2 , such that the thick portion C 2  stacked on the second drum  2  is transferred from the second drum  2  to an inhibition area α 3  of the first drum  1  in a state where the thin portion C 1  is stacked on the first drum  1  in the first area α 1  other than (except) the inhibition area α 3 , where stacking of the fiber F of the thin portion C 1  is inhibited and the fiber F of the thin portion C 1  is not stacked. 
     Any feature illustrated and/or depicted in conjunction with one of the aforementioned aspects or the following embodiments may be used in the same or similar form in one or more of the other aspects or other embodiments, and/or may be used in combination with, or in place of, any feature of the other aspects or embodiments. 
     The present invention will be understood more clearly from the following description of preferred embodiments taken in conjunction with the accompanying drawings. Note however that the embodiments and the drawings are merely illustrative and should not be taken to define the scope of the present invention. The scope of the present invention shall be defined only by the appended claims. In the accompanying drawings, like reference numerals denote like components throughout the plurality of figures. 
     EMBODIMENTS 
     Embodiments of the present invention will now be described with reference to the drawings. 
     An absorbent core manufactured by the device of the present invention is used as a core for such as disposable underwear, diapers, and incontinence pads. The core may be in hourglass shape in planar view. 
       FIG. 1  shows an embodiment 1. 
     As shown in  FIG. 1 , a manufacturing device includes a feed device  3 , a first drum  1 , and a second drum  2 . 
     The feed device  3  includes a cylindrical case  30  and a defibrating machine  33 . The defibrating machine  33  defibrates (comminutes) pulp fed from the upstream to produce fluff pulp (fiber). The fluff pulp filled in the case  30  passes through a first duct portion  31  and a second duct portion  32 , and is stacked on an outer circumferential portion  10  of the first drum  1  and an outer circumferential portion  20  of the second drum  2  due to negative pressure from respective suction chambers (not shown) of the first and second drums  1 ,  2 . The defibration and stacking described above are well-known technique in the art, and they are disclosed in JP2009-112438 A, for example. 
     Note that high molecular compound particles (super absorbent polymer particles), as it is called SAP, having high absorbing capacity may be added as a construction material for the absorbent core. 
     The first and second drums  1 ,  2  are in an approximately cylindrical shape, and are formed by plural segments (not shown) as in the well-known art. The first drum  1  and the second drum  2  are provided with the first duct portion  31  and the second duct portion  32 , respectively. These drums  1 ,  2  continuously rotate in the circumferential direction R, and suck the fiber F fed from the feed device  3  from the outer circumferential portions  10 ,  20  of these drums  1 ,  2  toward the respective inside suction chambers (not shown). Thus, the fiber F is continuously clung to and stacked on a predetermined first area α 1  in the outer circumferential portion  10  and a predetermined second area α 2  in the outer circumferential portion  20 . 
     The suction chambers are provided to the respective drums  1 ,  2  so as to correspond to a predetermined suction section T 1  along the circumferential direction R. Each suction chamber is connected to a negative pressure source (not shown) so that the chamber is in negative pressure. The suction chambers are positioned close to the inside of the outer circumferential portion  10 ,  20  of the respective drums  1 ,  2 . Thus, the fiber F is clung to and stacked on the drums  1 ,  2  during the suction section T 1 . 
     On the other hand, each drum  1 ,  2  is provided with a non-suction section T 2 , in which the outer circumferential portion  10 ,  20  of the drums does not pass by the suction chamber. 
     In the present embodiment, the first area α 1  of the first drum  1  is continuously provided in the circumferential direction R of the first drum  1 , whereas the second area α 2  of the second drum  2  is intermittently provided at regular intervals in the circumferential direction R of the second drum  2 . In general, each area α 1 , α 2  is formed in a concave drum surface. The concave surface, a basic construction and a detailed construction of a drum are well known, and they are disclosed in JP 2,541,558 B2, JP 4,312,112 B2, and JP 3,153,060 B2, for example. 
     As shown in  FIG. 1B , the second area α 2  is provided so as to be embraced in the first area α 1 . For example, in the present embodiment, the intermittently-provided second area α 2  is smaller in the circumferential direction R and the width direction D than the continuously-provided first area α 1 , and is provided so as to be embraced. In the second drum  2  of  FIG. 1A , an area in the outer circumferential portion  20  other than the second area α 2  is an inhibition area α 4 , where the stacking of the fiber F is inhibited. 
     Note that the first area α 1  may be in hourglass shape in planar developed view and may be non-continuous. 
     In the first area α 1  of  FIG. 1B , a thin portion C 1  of  FIG. 1C  is formed. In the second area α 2  of  FIG. 1B , a thick portion C 2  of  FIG. 1C  is formed. 
     The first and second duct portions  31 ,  32  of  FIG. 1A  are connected to the case  30  of the feed device  3 , and guide the fiber F from the feed device  3  to the outer circumferential portion  10  of the first drum  1  and the outer circumferential portion  20  of the second drum  20 , respectively. A part of the outer circumferential portion  10 ,  20  of each of the first and second drums  1 ,  2  faces the end of the respective first and second duct portions  31 ,  32 . 
     At least a part of the suction section T 1  of each drum  10 ,  20  faces an end opening of the respective duct portions  31 ,  32 . Note that a dome  31 D,  32 D extending along a drum may be formed at the end of each duct portion. 
     The thick portion C 2  is more bulky and thicker than the thin portion C 1 . Such thickness deference between the thin portion C 1  and the thick portion C 2  is gained by differentiating negative pressure amount in the chambers, or differentiating the suction periods, for example. 
     The first drum  1  and the second drum  2  contact with each other at a hand-over point P via the thick portion C 2  therebetween. At the point P, the first drum  1  is set in the suction section T 1 , whereas the second drum  2  is set in the non-suction section T 2 . 
     Note that the first drum  1  and the second drum  2  may be so close to each other that the second drum  2  can pass the thick portion C 2  to the first drum  1  without contacting with each other via the thick portion C 2 . 
     At the downstream of the first drum  1 , a first conveying portion  41  is provided. The first conveying portion  41  conveys a first web W 1  (a carrier web) for conveying the absorbent core C formed by the thin portion C 1  and the thick portion C 2 . At the further downstream of the first conveying portion  41 , a second conveying portion  42  is provided. The second conveying portion  42  conveys a second web W 2  that is used for sandwiching the absorbent core C in between the first web W 1  and the second web W 2 . Note that the first conveying portion  41  conveys the first web W 1  along the first drum  1  so as to sandwich the absorbent core C in between the first web W 1  and the first drum  1 . 
     Each conveying portion  41 ,  42  may include guide rollers, unwinding rollers for web, and anvil rolls that convey and cut the absorbent core C sandwiched in between a pair of webs. Note that a web may have water absorbency and water permeability. 
     The hand-over point P described above is provided between the first duct portion  31  and the second duct portion  32 . At the point P, the first drum  1  and the second drum  2  contact with each other via the thick portion C 2  therebetween, and the thick portion C 2  stacked on the second area α 2  is handed over from the second drum  2  to an area in the first drum  1 , wherein the thin portion C 1  is not formed in the area. 
     Next, a method for manufacturing the absorbent core C will be described. 
     First, when the second drum  2  faces the second duct portion  32  in the suction section T 1 , the fiber F produced by the feed device  3  is clung to and stacked on the second area α 2  to form the thick portion C 2 . The thick portion C 2  is conveyed to the hand-over point P while being sucked on the outer circumferential portion  20  of the second drum  2  at regular intervals. 
     At the hand-over point P, the thick portion C 2  is transferred from the second drum  2  to the first area α 1  of the first drum  1 . That is, at the point P, the second drum  2  is set in the non-suction section T 2 , whereas the first drum  1  is set in the suction section T 1 . 
     Thus, the thick portion C 2  on the second drum  2  is placed on the first area α 1  of the first drum  1 . 
     Note that, in the present embodiment, the thick portion C 2  is sucked and placed on (transferred to) the first area α 1  in a state where the fiber F is not stacked on the first area α 1 . 
     A part of the first drum  1 , having received the thick portion C 2 , rotates in the circumferential direction R and faces the first duct portion  31 . There the fiber F produced by the feed device  3  is clung to and stacked on the first area α 1 , thereby producing the continuous thin portion C 1  around the thick portion C 2 . At this stacking, the fiber F may be slightly stacked on the thick portion C 2  in the first area α 1 . 
     Note that, in the present embodiment, the absorbent core C, in which the thin portion C 1  is continuous along the outer circumferential portion  10  of the first drum  1 , is formed in the step of forming the thin portion C 1 . 
     As a result, the absorbent core C shown in  FIG. 1C  is formed on the outer circumferential portion  10  of the first drum  1 . The formed absorbent core C passes by the dome  31 D of the first duct portion  31 , and then transferred to the first web W 1  guided by the first conveying portion  41  in the non-suction section, and conveyed. 
     Thereafter, the absorbent core C is sandwiched in between the first web W 1  and the second web W 2  conveyed by the second conveying portion  42 . The sandwiched absorbent core C is cut in an individual wearable article unit. 
     Note that, as shown in  FIG. 1C , the absorbent core C is formed so that the surface of the thick portion C 2  protrudes more than the surface of the thin portion C 1 . 
       FIG. 2  shows an embodiment 2. 
     The embodiment 2 will be mainly described for different part from the embodiment 1. 
     In the present embodiment, an inhibition area α 3  is provided in the first drum  1  in addition to the first area α 1 . In the inhibition area α 3 , the stacking of the fiber F is inhibited (prevented). For weakening negative pressure suction, the mesh porosity in the outer circumferential portion  10  in the inhibition area α 3  may be set to be small. The first drum  1  and the second drum  2  contact with each other at the hand-over point P as follows. 
     The both drums contact at the point P so that the thick portion C 2  stacked on the second drum  2  is passed (handed over) from the second drum  2  to the inhibition area α 3  of the first drum  1 . The hand-over is performed in a state where the fiber F is clung to and stacked on the first area α 1 , except the inhibition area α 3 , of the first drum  1  while the fiber F is not stacked on the inhibition area α 3 , where stacking of the fiber F is inhibited. 
     Next, a method for manufacturing an absorbent core C will be described. 
     First, the thin portion C 1  is formed on the first drum  1  in an area other than the inhibition area α 3 , where stacking of the fiber F is inhibited. The thin portion C 1  has a smaller grammage (thinner thickness) than the thick portion C 2 . At the forming the thin portion C 1 , the fiber F may not be stacked on the inhibition area α 3 . 
     On the other hand, the thick portion C 2  is formed on the second drum  2  by stacking the fiber F fed from the feed device  3  on the second area α 2 . The thick portion C 2  is formed on the second drum  2  so as to coincide with the inhibition area α 3  of the first drum  1  in planar shape. 
     Thereafter, at the hand-over point P, the thick portion C 2  on the second drum  2  is transferred to the inhibition area α 3  of the first drum  1 , and the thick portion C 2  fits into the thin portion C 1 . As a result, the continuous absorbent core C of  FIG. 2C  is produced, being sandwiched in between a pair of the webs W 1 , W 2  as similar to the aforementioned embodiment 1. 
     Although the preferred embodiments have been described above with reference to the drawings, a person skilled in the art would easily arrive at various changes and modifications within an obvious range through this specification. 
     For example, each duct portion  31 ,  32  is connected to different defibrating machines. 
     Also, the absorbent core C is formed on the drum in an intermittent manner in the circumferential direction R. 
     Therefore, such changes and modifications are interpreted to be within the scope of the present invention determined from claims. 
     INDUSTRIAL APPLICABILITY 
     The present invention is applicable to manufacturing an absorbent core used in a disposable wearable article. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 : First drum 
               10 : Outer circumferential portion 
               2 : Second drum 
               20 : Outer circumferential portion 
               3 : Feed device 
               31 : First duct portion 
               32 : Second duct portion 
               31 D,  32 D: Dome 
               41 : First transferring portion 
               42 : Second transferring portion 
             C: Absorbent core 
             C 1 : Thin portion 
             C 2 : Thick portion 
             D: Width direction 
             F: Fiber 
             R: Circumferential direction 
             T 1 : Suction section 
             T 2 : Non-suction section 
             α 1 : First area 
             α 2 : Second area 
             α 3 : Inhibition area