Patent Publication Number: US-2009221979-A1

Title: Topsheet for an absorbent article

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Application No. 097107029, filed on Feb. 29, 2008. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a topsheet for an absorbent article, more particularly to a topsheet including a base wall and a plurality of strip-like protrusions protruding from the base wall to form a plurality of fluid channels for spreading liquid in a desired direction. 
     2. Description of the Related Art 
     U.S. Pat. No. 6,461,339 discloses an absorbent article that includes a liquid pervious topsheet, a liquid impervious backsheet, an absorbent core disposed between the topsheet and the backsheet, and a non-woven inner layer disposed between the topsheet and the absorbent core. The topsheet has an outer layer of a non-woven fabric, and a perforated plastic film layer that is in contact with the non-woven inner layer. The outer layer may be embossed, and serves mainly for providing softness and to absorb moisture so that a sticky or sweaty feel is not experienced by the user. 
     The outer layer is formed with an opening extending from a front edge of the absorbent article to a rear edge of the absorbent article for passage of a liquid to be deposited directly onto the perforated plastic film layer so that the liquid can rapidly pass into the absorbent core through the perforated plastic film layer and the non-woven inner layer. 
     The entire disclosure of U.S. Pat. No. 6,461,339 is incorporated herein by reference. 
     By virtue of the structures of apertures formed in the perforated plastic film layer, pores formed in the outer layer, and pores formed in the non-woven inner layer, liquid deposited on the outer layer can effectively pass through the apertures and the pores in a normal direction relative to the absorbent article and into the absorbent core, but cannot effectively flow in a lengthwise direction of the absorbent article. As a consequence, liquid flow from the outer layer into the absorbent core occurs only over a limited area of the absorbent article, i.e., a wet area where the liquid is deposited. 
     It has been proposed that the fibers used for forming the non-woven inner layer be oriented in a specific direction before they are entangled together so as to permit spreading of the liquid in the lengthwise direction and so as to increase the wet area over which the liquid flows through the outer layer, the perforated plastic film layer, and the non-woven inner layer and into the absorbent core. However, the non-woven inner layer thus formed is expensive. 
     Hence, there is a need for a topsheet that is cost effective and that can effectively cause spreading of liquid in the lengthwise direction. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide a topsheet having a configuration that can effectively cause spreading of a liquid body and dispense with the aforementioned non-woven inner layer employed in the prior art. 
     According to the present invention, a topsheet for an absorbent article comprises a flexible sheet body having a flat liquid pervious base wall with first and second surfaces that are opposite to each other in a normal direction relative to the sheet body. The base wall has front and rear edges that are opposite to each other in a longitudinal direction. The sheet body further has a plurality of strip-like protrusions that are spaced apart from each other, that protrude from the first surface of the base wall, and that are distributed along the longitudinal direction as well as a widthwise direction which is transverse to the longitudinal direction. Each of the protrusions has front and rear ends that face toward the front and rear edges of the base wall, respectively, and extends lengthwise from the rear end to the front end. The protrusions are arranged in such a manner to form a plurality of strip-like open fluid channels thereamong. The fluid channels extend from the front edge to the rear edge of the base wall, and have dimensions in the normal and widthwise directions sufficient to provide capillary action, thereby promoting spreading of a liquid body on the surface of the base wall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In drawings which illustrate embodiments of the invention, 
         FIG. 1  is a fragmentary perspective view of the first preferred embodiment of a topsheet according to this invention; 
         FIG. 2  is a fragmentary sectional view of the first preferred embodiment; 
         FIG. 3  is a fragmentary perspective view of the second preferred embodiment of a topsheet according to this invention; 
         FIG. 4  is a fragmentary sectional view of the second preferred embodiment; 
         FIG. 5  is a fragmentary perspective view of the third preferred embodiment of a topsheet according to this invention; 
         FIG. 6  is a fragmentary sectional view of the third preferred embodiment; 
         FIG. 7  is a fragmentary perspective view of the fourth preferred embodiment of a topsheet according to this invention; 
         FIG. 8  is a fragmentary sectional view of the fourth preferred embodiment; and 
         FIG. 9  is a fragmentary sectional view of the fifth preferred embodiment of a topsheet according to this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before the present invention is described in greater detail with reference to the accompanying preferred embodiments, it should be noted herein that like elements are denoted by the same reference numerals throughout the disclosure. 
       FIGS. 1 and 2  illustrate the first preferred embodiment of a topsheet for an absorbent article, such as a sanitary napkin, an incontinence pad, a diaper, and the like, according to this invention. The topsheet includes a flexible sheet body  1  having a flat liquid pervious base wall  11  with first and second surfaces  111 ,  112  that are opposite to each other in a normal direction (Z) relative to the sheet body  1 . The base wall  11  has front and rear edges  113 ,  114  that are opposite to each other in a longitudinal direction (Y) that is substantially perpendicular to the normal direction (Z). 
     The sheet body  1  further has a plurality of strip-like first protrusions  12  that are spaced apart from each other. The first protrusions  12  protrude from the first surface  111  of the base wall  11  in the normal direction (Z), and are distributed along the longitudinal direction (Y), as well as along a widthwise direction (X) which is transverse to the longitudinal direction (Y). 
     In this embodiment, the sheet body  1  is made from a non-woven fabric that is formed with a plurality of open pores for passage of a liquid (not shown) therethrough in the normal direction (Z). It is noted that formation of the non-woven fabric can be conducted in a conventional manner, such as by entangling fibers together using simple mechanical techniques that do not involve orienting fibers in a specific direction. 
     Each of the first protrusions  12  has front and rear ends  121 ,  122  that face toward the front and rear edges  113 ,  114  of the base wall  11 , respectively, and extends lengthwise from the rear end  121  to the front end  122 . The first protrusions  12  are arranged in such a manner to form a plurality of strip-like open fluid channels  14  thereamong. The fluid channels  14  extend from the front edge  113  to the rear edge  114  of the base wall  11 , and have dimensions in the normal and widthwise directions (Z, X) sufficient to provide capillary action, thereby promoting spreading of a liquid body (not shown) on the first surface  111  of the base wall  11  in the longitudinal direction (Y). 
     In this embodiment, each of the first protrusions  12  is hollow and defines a recess that opens at the second surface  112  of the base wall  11 . 
     The sheet body  1  further has a plurality of strip-like second protrusions  13  that protrude from the second surface  112  of the base wall  11 , and that are distributed along the longitudinal direction (Y), as well as along the widthwise direction (X). Each of the second protrusions  13  is hollow, and defines a strip-like trough  131  that opens at the first surface Ill of the base wall  11  and that extends lengthwise in the longitudinal direction (Y). The troughs  131  defined by the second protrusions  13  are alternately disposed with the first protrusions  12 . Each of the troughs  131  is partially aligned in the widthwise direction (X) with at least one of the first protrusions  12 . That is, each of the troughs  131  has a section  131  that is aligned in the widthwise direction (X) with a portion  125  of said at least one of the first protrusions  12 . The troughs  131  have dimensions in the normal and widthwise directions (Z, X) sufficient to provide capillary action, thereby enhancing spreading of the liquid body in the longitudinal direction (Y). 
     In this embodiment, each of the first protrusions  12  extends lengthwise in the longitudinal direction (Y) so that each of the fluid channels  14  also extends in the longitudinal direction (Y). In addition, each of the fluid channels  14  is in fluid communication with an adjacent one of the fluid channels  14  so as to promote spreading of the liquid body also in the widthwise direction (X). 
       FIGS. 3 and 4  illustrate the second preferred embodiment of the topsheet according to this invention. The second preferred embodiment differs from the previous embodiment in that each of the first protrusions  12  extends lengthwise in a direction (W) that is slightly inclined relative to the longitudinal direction (Y). In some embodiments, each of the second protrusions  13  also extends lengthwise in the direction (W). 
       FIGS. 5 and 6  illustrate the third preferred embodiment of the topsheet according to this invention. The third preferred embodiment differs from the first embodiment in that each of the first protrusions  12  is curvy in shape. That is, in the third preferred embodiments, each of the first protrusions  12  extends lengthwise in a slightly meandering manner. In some embodiments, each of the second protrusions  13  is also curvy in shape. 
       FIGS. 7 and 8  illustrate the fourth preferred embodiment of the topsheet according to this invention The fourth preferred embodiment differs from the first embodiment in that the sheet body  1  is made from a perforated plastic film which is formed with apertures for passage of liquid therethrough in the normal direction (Z). It is noted that in other preferred embodiments, the apertures can be formed only in the base wall  11  of the sheet body  1 , and not in the first and second protrusions  12 ,  13  so that the first and second protrusions  12 ,  13  are liquid impervious. 
       FIG. 9  illustrates the fifth preferred embodiment of the topsheet according to this invention. The fifth preferred embodiment differs from the first embodiment in that the sheet body  1  is made from a composite material having a bi-layer structure that has a non-woven layer  101  and a perforated plastic film layer  102  bonded to the non-woven layer  101 . 
     With the inclusion of the first protrusions  12  and the troughs  131  in the sheet body  1  of the topsheet of this invention, a liquid body on the first surface  111  of the base wall  11  can rapidly spread in the longitudinal direction (Y), thereby considerably increasing the wet area of the base wall  11  over which liquid passes through both the base wall  11  as well as through walls that define the troughs  131 . Ultimately, such a configuration of the present invention promotes transport of liquid into the absorbent article. 
     With the invention thus explained, it is apparent that various modifications and variations can be made without departing from the spirit of the present invention. It is therefore intended that the invention be limited only as recited in the appended claims.