Patent Publication Number: US-2023150209-A1

Title: Method for producing washable absorbent garments

Description:
FIELD OF THE INVENTION 
     The present invention relates to absorbent garment for the absorption and retention of liquids, and more particularly to washable and reusable absorbent garments. 
     More specifically, the invention relates to a method for producing washable absorbent garments. 
     PRIOR ART 
     Various washable garments having a pant-like configuration and useful as incontinence garments, menstrual garments, training garments, diapers, and the like, are commercially available, as well as being disclosed in various patents. 
     For instance, absorbent garments are commercially available which are machine washable, and thus reusable, having an absorbent pad sewn into the crotch area. 
     U.S. Pat. No. 3,489,149 discloses a menstrual panty having a pocket sewn into the crotch area, the pocket being used for receiving an absorbent disposable menstrual pad. Similarly, U.S. Pat. No. 4,352,356 discloses a urinary incontinence panty having a pouch connected in the crotch area and adapted to receive an absorbent disposable urinary incontinence pad. Another sanitary panty garment with a pocket in the crotch area is disclosed in U.S. Pat. No. 3,613,686. 
     Also, washable absorbent garments are known wherein the absorbent pad is permanently connected to the pant structure. For instance, GB2176692A discloses an absorbent sanitary garment made in the form of knitted polyester material which incorporates a non-removable pad made of brushed polyester which has the appearance of soft felt. The absorbent pad cannot be removed and is made of a material which can be frequently washed. 
     Prior art washable absorbent garments are manufactured by the same techniques uses for manufacturing textiles articles, typically by manually cutting and sewing fabric materials. In the prior art washable absorbent garments a washable absorbent core is typically sewn to a fabric layer forming a pant-structure and opposite waist sections of the pant-structure are sewn to each other. The typical production rate of prior art washable absorbent garments is in the range of 1 piece/1′. 
     Currently all washable absorbent products on the market are closed laterally by stitching, hooks or press studs. As an alternative to the above, a seamless product is proposed, made from a continuous fabric tube which does not have closures and discontinuity elements on the sides. Closure systems wherein the side edges are overlapped and connected by glued are also present on the market of traditional underwear. 
     The limits of the various solutions currently on the market essentially concern the impossibility of producing the washable absorbent garments on fully automatic machines. Therefore, all the aforementioned processes require more or less important manual actions on the part of the operators, which consequently implies increased production times. increased costs and a scarce repeatability of the finished products. 
     In addition, many of the known solutions produce an area of increased thickness on the sides due to the presence of overlapped layers and stitched folds which have undesirable aesthetic effects especially for the users who intends to wear the washable absorbent articles underneath tight clothes. 
     OBJECT AND SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a method for producing washable absorbent garment which overcomes the problems of the prior art. 
     According to the present invention, this object is achieved by a method having the features of claim  1 . 
     The claims form an integral part of the disclosure provided here in relation to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described in detail with reference to the attached drawings, given purely by way of non-limiting example, wherein: 
         FIG.  1    is a perspective view of a washable absorbent garment in an open configuration, 
         FIG.  2    is a plan view of the absorbent garment of  FIG.  1    in the open configuration, 
         FIG.  3    is a schematic cross-section taken along the line III-III of  FIG.  2   , 
         FIGS.  4  and  5    are schematic side views of an apparatus for producing the washable absorbent garments of  FIGS.  1 - 3   , 
         FIGS.  6 - 11    are schematic plan views showing intermediate steps of a method for producing washable absorbent garments, 
         FIG.  12    is a schematic perspective view showing an embodiment of the welding unit indicated by the arrow XII in  FIG.  5   , 
         FIG.  13    is a perspective view of the part indicated by the arrow XIII in  FIG.  12   , 
         FIG.  14    is a perspective view of an anvil indicated by the arrow XIV in  FIG.  13   , 
         FIG.  15    is a cross-section taken along the line XV-XV of  FIG.  14   , 
         FIG.  16    is a cross-section shoving an alternative embodiment of the anvil of  FIG.  15   , 
         FIG.  17    is a schematic view showing another embodiment of the welding unit indicated by the arrow XII in  FIG.  5   , 
         FIG.  18    is a schematic cross-section of a laser beam indicated by the arrow XVIII in  FIG.  17   , and 
         FIG.  19    is a diagram showing energy shape distribution vs. radius in the laser beam of  FIG.  18   . 
     
    
    
     It will be appreciated that the various figures may not be represented on the same scale. It will also be appreciated that in some figures certain elements or components may not be shown for a better understanding. 
     DETAILED DESCRIPTION 
     With reference to  FIGS.  1 - 3    the numeral reference  10  indicates a washable absorbent garment. 
     The washable absorbent garment  10  comprises a back layer  12  of washable fabric forming a pant structure. The back layer  12  has rear and front waist sections  14 ,  16  and a crotch section  18  intermediate between the rear and front waist sections  14 ,  16 . The rear and front waist sections  14 ,  16  are wider than the crotch section  18 , such that in the extended position of  FIGS.  1  and  2    the back layer  12  has substantially an hourglass shape. 
     The back layer  12  is a fabric formed by woven threads which is washable as ordinary textile garments, e.g. swimsuits, underwear, etc. The back layer  12  may be made of any natural or synthetic material used for producing textile articles, e.g. cotton, Lycra, nylon, polyester, polyamide, elastane, etc. and any mixture thereof. In possible embodiments, the back layer  12  may be an elastic fabric made of a mixture of cotton and elastane, e.g. 80% cotton and 20% elastane or 80% polyamide and 20% elastane. The back layer  12  may have a weight comprised between 100-250 g/m 2 , preferably between 150-200 g/m 2  and preferably between 160-190 g/m 2 . 
     The crotch section  18  of the back layer  12  has two curved side edges  22  shaped to conform to the legs of the user in the configuration in which the washable absorbent garment  10  is worn. 
     The rear and front waist sections  14 ,  16  of the back layer  12  have respective side edges  24 ,  26  which are joined to each other such that the washable absorbent garment  10  is closed in a pant-like shape and has two leg openings on opposite sides of the crotch section  18 . The side edges  24 ,  26  are joined to each other by ultrasonic welding, laser welding or glue as it will be disclosed in detail in the following. 
     The washable absorbent garment  10  may comprise a washable absorbent core  28  permanently fixed in the crotch section  18  of the back layer  12 . The washable absorbent core  28  extends only on the crotch section  18  of the back layer  12  and does not extend on the rear and front waist sections  16 ,  18  of the back layer  12 . 
     The washable absorbent core  28  includes a washable absorbent pad comprising washable superabsorbent fibers. A material suitable for producing the washable absorbent pad  30  may be that marketed by Technical Absorbents Ltd (UK) under the trade name SAE®. The washable absorbent pad may be formed by needlefelt, thermal bonded, laminated non-woven fibers, formed by polyester, polypropylene and SAE® (Sodium polyacrylate—cross-linked polymers or copolymers of carboxylic acid salts—in fibers). 
     The washable absorbent core  28  may include an acquisition and diffusion layer (ADL) and a barrier film. The washable absorbent pad may be sandwiched between the acquisition and diffusion layer and the barrier film. 
     The washable absorbent garment  10  may comprise a top layer  30  of washable fabric which covers the washable absorbent core  28 . The top layer  30  may be made of the same material as the fabric forming the back layer  12 . The top layer  30  completely covers the washable absorbent core  28  but does not extend on the rear and front waist sections  16 ,  18  of the back layer  12 . 
     The top layer  30  and the washable absorbent core  28  may be permanently joined to the back layer  12  by welding, e.g. ultrasonic welding, or glue. 
     An embodiment of an apparatus for producing the washable absorbent garment  10  of the type illustrated in  FIGS.  1 - 3    is shown in  FIGS.  4  and  5    and is indicated by the reference numeral  32 . 
     With reference to  FIG.  4   , the apparatus  32  comprises a first unwinding unit  34  configured for unwinding a first continuous fabric layer  36  from a first reel  38 . The first continuous fabric layer  36  is advanced in a machine direction MD on a conveyor  40 . 
     The apparatus  32  may comprise a second unwinding unit  42  configured for unwinding a continuous absorbent tape  44  from a second reel  46 . The apparatus  32  may comprise a first cut-and-slip unit  48  configured for transversally cutting the continuous absorbent tape  44  to form individual absorbent cores  28 . The first cut-and-slip unit  48  is configured for longitudinally spacing from each other the individual absorbent cores  28  and for applying the individual absorbent cores  28  on the first continuous fabric layer  36  in longitudinally spaced positions on the conveyor  40 . 
     The apparatus  32  may comprise a third unwinding unit  49  configured for unwinding a second continuous fabric layer  50  from a third reel  52 . The apparatus  32  may comprise a second cut-and-slip unit  54  configured for transversally cutting the second continuous fabric layer  50  to form individual top layers  30 . The second cut-and-slip unit  54  is configured for longitudinally spacing from each other the individual top layers  30  and for applying the individual top layers  30  on respective absorbent cores  28  previously applied on the first continuous fabric layer  36  on the conveyor  40 . 
     The apparatus  32  may comprise a glue dispenser  56  configured for applying a discrete pattern of glue on the first continuous fabric layer  36  for attaching the individual absorbent cores  28  and the individual top layers  30  on the first continuous fabric layer  36 . 
     The apparatus  32  may comprise a sealing press  58  located at the end of the conveyor  40 , configured for compressing the individual absorbent cores  28  and the individual top layers  30  to the first continuous fabric layer  36 . 
     After the compression, the individual absorbent cores  28  and the individual top layers  30  are permanently fixed by glue to the first continuous fabric layer  36  in longitudinally spaced positions to form a continuous garment tape  59 . Alternatively, the apparatus  32  may comprise an ultrasonic welding unit configured for permanently attaching by ultrasonic welding the individual absorbent cores  28  and the individual top layers  30  on the first continuous fabric layer  36 . 
       FIG.  6    shows a portion of the continuous garment tape  59  formed by individual absorbent cores  28  and individual top layers  30  fixed to the first continuous fabric layer  36 . 
     The apparatus  32  comprises a cutting unit  60  configured for cutting longitudinal side edges of the continuous garment tape  59  as it advances in the machine direction MD along curved profiles shaped to conform to the legs of the user. The cutting unit  60  comprises an anvil roller  62  and a cutting tool  64  cooperating with the outer surface of the anvil roller  62 . The cutting tool  64  may be a laser nozzle or an ultrasonic horn configured for carrying out a laser or ultrasonic cut of the first continuous fabric layer  36 . The cutting tool  64  may also cut simultaneously side edges of the top layer  30  and of the absorbent core  28 . 
     The cutting tool  64  may be movable transversally to the machine direction to form, in conjunction with the longitudinal movement of the continuous garment tape  59 , curved cuts which form curved side edges  22  ( FIG.  7   ) of the continuous garment tape  59 . The portions trimmed from the continuous garment tape  59  are collected in a waste collecting channel  65 . 
     The apparatus  32  comprises a transverse cutting unit  66  configured to cut the first continuous fabric layer  36  along transverse cutting lines  68  ( FIG.  7   ) to form individual blank absorbent garments  70 .  FIG.  7    shows the continuous garment tape  59  after the longitudinal and transverse cutting steps. 
     The apparatus  32  comprises a transverse folding unit  72  configured for folding the individual blank absorbent garments  70  along respective transverse folding lines, so as to overlap to each other the rear and front waist sections  14 ,  16  of each blank absorbent garment  70 .  FIG.  8    shows a blank absorbent garment  70  after the transverse folding step. 
     With reference to  FIG.  5   , the apparatus  32  comprises a welding unit  74  which receives the folded blank absorbent garments  70  from the folding unit  72 . With reference to  FIG.  9   , the welding unit  74  is configured for sealing side edges  24 ,  26  of the rear and front waist sections  14 ,  16  of the blank absorbent garments  70 , to form finished absorbent garments  10 . 
     The apparatus  32  may comprise a linear folding unit  76  configured for folding side portions of the finished absorbent garments  10  as shown in  FIG.  10   . 
     The apparatus  32  may comprise a final press unit  78  configured for pressing the folded portions of the finished absorbent garments  10 . 
     The apparatus  32  may comprise a final folding unit  80  configured for carrying out a final folding of the finished absorbent garments  10  as shown in  FIG.  11   . After the final folding unit  80  the finished absorbent garments  10  may be sent to a packaging machine. 
       FIGS.  12  and  13    show an embodiment of the welding unit  74  which carries out ultrasonic welding of the overlapped side edges  24 ,  26  of the blank absorbent garments  70 . 
     The welding unit  74  comprised a pair of ultrasonic welding devices  84 , each comprising an ultrasonic horn  86  and an anvil  88 . The anvil  88  may be a stationary element or a rotating anvil roller. 
     With reference to  FIGS.  14 ,  15 ,  16   , the anvil  88  has two inclined welding surfaces  90  converging on a sharp edge  92 . The sharp edge  92  may be parallel or slightly inclined to the moving direction X ( FIG.  12   ) of the blank absorbent garments  70 . The angle α between the two inclined welding surfaces  90  may be comprised between 90°-160°. 
     The blank absorbent garments  70  advance in the moving direction X and each of the two opposite overlapped edges  24 ,  26  passes between the ultrasonic horn  86  and the anvil  88  of a respective ultrasonic welding device  84 . The overlapped side edges  24 ,  26  are welded along respective welding lines  94  while advancing the blank absorbent garments  70  in the moving direction X. The overlapped side edges  24 ,  26  are simultaneously cut on the respective sharp edges  92  of the respective anvils  88  flush with the respective welding lines  94 . The portions of the side edges  24 ,  26  external to the welding lines  94  are disposed as scrap. Each ultrasonic welding device may comprise a suction channel  96  for aspirating the scraps. 
     In possible embodiments, to obtain an inclined cutting/sealing line on final products, the ultrasonic welding devices  84  may be moved simultaneously in cross-direction. 
     After the welding and the simultaneous cut of the side edges  24 ,  26 , finished washable absorbent garments  10  are obtained. The ultrasonic welding and simultaneous cut of the side edges  24 ,  26  provides washable absorbent garments  10  with a very smooth surface and without an increased thickness at the sides. The ultrasonic welding and simultaneous cut of the side edges  24 ,  26  also provides great flexibility when the shape and dimensions of the washable absorbent garments  10  changes. 
     With reference to  FIG.  12   , to improve the sealing quality, each ultrasonic welding device  84  may comprise two pairs of nipping rollers  98 , configured for compressing the overlapped side edges  24 ,  26  on opposite sides of the respective welding line  94 . 
       FIG.  17    shows an embodiment of the welding unit  74  which carries out laser welding of the overlapped side edges  24 ,  26  of the blank absorbent garments  70 . The welding unit  74  comprises a pair of laser welding devices  100  each of which comprises a laser resonator  102 , a focusing lens  104  and a nozzle  106 . With reference to  FIGS.  17  and  18   , the focusing lens  104  is configured for generating a laser beam  108  having a central area  110  with a first energy density and an annular area  112  with a second energy density and surrounding the central area  110 . 
     The graph of  FIG.  19    shows the energy density distribution (i.e. energy per surface unit) vs. the radius of the laser beam  108 . The first energy density of the central area  110  is configured for carrying out the cut of the two overlapped side edges  24 ,  26 . The second energy density of the annular area  112  is configured for carrying out laser welding of the two overlapped side edges  24 ,  26 . 
     In operation, the apparatus  32  implements a method for producing washable absorbent garments  10 , comprising:
         providing blank washable absorbent garments  70  each comprising a fabric back layer  12  having rear and front waist sections  14 ,  16  and a crotch section  18  intermediate between the rear and front waist sections  14 ,  16 , wherein the rear and front waist sections  14 ,  16  have respective said side edges  24 ,  26 ,   folding said blank washable absorbent garments  70  and overlapping to each other said side edges  24 ,  26  of said rear and front waist sections  14 ,  16 ,   advancing in a moving direction X said folded blank washable absorbent garments  70 , and   welding said overlapped side edges  24 ,  26  along respective welding lines  94  while advancing said folded blank washable absorbent garments  70  in said moving direction X and simultaneously cutting said side edges  24 ,  26  flush with the respective welding lines  94 .       

     The method and apparatus according to the present invention may have a production rate up to 200 pieces/ 1 ′, which is a huge progress as compared to the production rate of prior art washable absorbent products which is about 1 piece/1′. 
     A possible embodiment relates to a washable absorbent garment ( 10 ) comprising a back layer ( 12 ) of washable fabric forming a pant-like structure and having rear and front waist sections ( 14 ,  16 ) and a crotch section ( 18 ) intermediate between the rear and front waist sections ( 14 ,  16 ), wherein the rear and front waist sections ( 14 ,  16 ) have respective side edges ( 24 ,  26 ) joined to each other by welding along welding lines ( 94 ) and wherein said side edges ( 24 ,  26 ) are cut flush with said welding lines ( 94 ). 
     A possible embodiment relates to an apparatus for producing washable absorbent garments ( 10 ), comprising:
         a first unwinding unit ( 34 ) configured for unwinding a first continuous fabric layer ( 36 ) from a first reel ( 38 ) and for advancing said first continuous fabric layer ( 36 ) in a longitudinal direction,   a side cutting unit ( 60 ) configured for cutting longitudinal side edges of said first continuous fabric layer ( 36 ) along shaped profiles,   a transverse cutting unit ( 66 ) configured for cutting said first continuous fabric layer ( 36 ) along transverse cutting lines ( 68 ) to form individual blank pant-like garments ( 70 ),   a transverse folding unit ( 72 ) configured for folding the individual blank pant-like garments ( 70 ) along respective transverse folding lines, and   a welding unit ( 74 ) configured for welding overlapped side edges ( 24 ,  26 ) of said folded blank pant-like garments ( 70 ) along respective welding lines ( 94 ) while advancing said folded blank washable absorbent garments ( 70 ) in a moving direction (X) and for simultaneously cutting said side edges ( 24 ,  26 ) flush with the respective welding lines ( 94 ).       

     The welding unit ( 74 ) may comprise a pair of ultrasonic welding devices ( 84 ) each including an ultrasonic horn ( 86 ) cooperating with a respective anvil ( 88 ), wherein each anvil ( 88 ) has two inclined welding surfaces ( 90 ) converging on a sharp edge ( 92 ). 
     The welding unit ( 74 ) may comprise a pair of laser welding devices ( 100 ) configured for generating a laser beam ( 108 ) having a central area ( 110 ) configured for cutting said overlapped side edges ( 24 ,  26 ) and an annular area ( 112 ) surrounding said central area ( 110 ) configured for welding said overlapped side edges ( 24 ,  26 ). 
     Of course, without prejudice to the principle of the invention, the details of construction and the embodiments can be widely varied with respect to those described and illustrated, without thereby departing from the scope of the invention as defined by the claims that follow.