Method and apparatus for perforating a fibrous web

Abstract

A method and apparatus are disclosed for forming a pattern of low basis weight regions, such as apertures or perforations, in an unbonded fibrous web. The present apparatus includes a forming surface having a pattern of forming elements, with an unbonded web positioned in operative association with the forming surface. Differential air pressure is applied to the web so that a pattern of low basis weight regions is formed corresponding to the pattern of forming elements. The fibrous web is thereafter removed from the forming surface, and can be further processed, if desired, such as by application of binders or other finishes, and can be integrated with associated components for various end uses, including medical, industrial, and hygiene applications.

1 . A method of forming a fibrous web with a pattern of low basis weight regions, comprising the steps of: 
 providing a substantially continuous fibrous web comprising fibrous and/or filamentary material;    providing a forming surface defining a pattern of forming elements;    directing said fibrous web onto said forming surface;    applying differential air pressure to said web to displace the material thereof to form a pattern of low basis weight regions in said web corresponding to said pattern of forming elements of said forming surface; and    removing said fibrous web from said forming surface.    
   
   
       2 . A method of forming a fibrous web in accordance with  claim 1 , wherein: 
 said forming surface comprises a forming drum, wherein said pattern of forming elements comprises a pattern of openings defined by said drum.    
   
   
       3 . A method of forming a fibrous web in accordance with  claim 2 , wherein: 
 said directing step includes positioning said fibrous web on a flexible, foraminous belt, and positioning said web between said belt and said forming drum.    
   
   
       4 . A method of forming a fibrous web in accordance with  claim 3 , wherein: 
 said applying step includes drawing a vacuum from within said drum through said pattern of openings to displace fibrous material from said web to form said pattern of low basis weight regions.    
   
   
       5 . A method of forming a fibrous web in accordance with  claim 4 , wherein: 
 said applying step further includes directing pressurized air through said foraminous belt and said fibrous web, and into said pattern of openings of said forming drum.    
   
   
       6 . A method of forming a fibrous web in accordance with  claim 4 , wherein: 
 said applying step further includes directing pressurized air from within said forming drum through said pattern of openings after drawing said vacuum through said pattern of openings.    
   
   
       7 . A method of forming a fibrous web in accordance with  claim 3 , wherein: 
 said applying step includes directing pressurized air from within said drum through said pattern of openings to displace fibrous material from said web to form said pattern of low basis weight regions.    
   
   
       8 . A method of forming a fibrous web in accordance with  claim 1 , wherein: 
 said forming surface comprises a foraminous forming drum, wherein said pattern of forming elements comprises a pattern of upstanding projections on the periphery of said forming drum,    said applying step including applying differential pressure to said web of fibrous material by drawing a vacuum from within said drum so that said web inter-engages said pattern of projections to form said pattern of low basis weight regions corresponding to said pattern of projections.    
   
   
       9 . A method of forming a fibrous web in accordance with  claim 8 , including: 
 providing a cooperating female sleeve positioned in operative relationship with said forming drum and defining a pattern of recesses corresponding to said pattern of projections, so that said projections are received in said recesses with said fibrous web positioned between said forming drum and female sleeve to form said pattern of low basis weight regions.    
   
   
       10 . A method of forming a fibrous web in accordance with  claim 9 , wherein: 
 said applying step further includes directing pressurized air from within said female sleeve against said fibrous web.    
   
   
       11 . A method of forming a fibrous web in accordance with  claim 1 , wherein: 
 said forming surface comprises a foraminous belt, and said pattern of elements comprises a pattern of relatively high-flow regions defined by said belt, said applying step including directing air against said fibrous web and through said foraminous belt to form said pattern of low basis weight regions corresponding to said pattern of high-flow regions defined by said belt.    
   
   
       12 . A method of forming a fibrous web in accordance with  claim 11 , wherein: 
 said applying step includes drawing a vacuum through said foraminous belt.    
   
   
       13 . A method of forming a fibrous web in accordance with  claim 1 , wherein: 
 said forming surface comprises a foraminous belt, and said pattern of elements comprises a pattern of relatively low-flow regions defined by said belt, said applying step including directing air against said fibrous web and through said foraminous belt to form said pattern of low basis weight regions corresponding to said pattern of low-flow regions defined by said belt.    
   
   
       14 . A method of forming a fibrous web in accordance with  claim 13 , wherein: 
 said low-flow regions defined by said foraminous belt are substantially impermeable.    
   
   
       15 . A method of forming a fibrous web in accordance with  claim 13 , wherein: 
 said applying step includes drawing a vacuum through said foraminous belt.    
   
   
       16 . An apparatus for forming a fibrous web with a pattern of low basis weight regions, comprising: 
 a forming surface defining a pattern of forming elements; and    an arrangement for applying differential air pressure to a web of fibrous material, comprising fibrous and/or filamentary material, when said web is positioned on said forming surface to form a pattern of low basis weight regions corresponding to said pattern of forming elements.    
   
   
       17 . An apparatus for forming a fibrous web in accordance with  claim 16 , wherein: 
 said forming surface comprises a forming drum, wherein said pattern of forming elements comprises a pattern of openings defined by said drum.    
   
   
       18 . An apparatus for forming a fibrous web in accordance with  claim 17 , including: 
 a flexible, foraminous belt positioned in operative association with said forming drum for positioning said web of fibrous material between said foraminous belt and said forming drum.    
   
   
       19 . An apparatus for forming a fibrous web in accordance with  claim 18 , wherein: 
 said arrangement for applying differential air pressure to said web of fibrous material comprises an arrangement for drawing a vacuum from within said drum through said pattern of openings to displace fibrous material from said web to form said pattern of low basis weight regions.    
   
   
       20 . An apparatus for forming a fibrous web in accordance with  claim 19 , wherein: 
 said arrangement for applying differential fluid pressure to said web of fibrous material further comprises an arrangement for directing pressurized air through said foraminous belt and said web of fibrous material, and into said pattern of opening in said forming drum.    
   
   
       21 . An apparatus for forming a fibrous web in accordance with  claim 19 , wherein: 
 said arrangement for applying differential air pressure further includes an arrangement for directing pressurized air from within said forming drum through said pattern of openings after drawing said vacuum through said openings.    
   
   
       22 . An apparatus for forming a fibrous web in accordance with  claim 18 , wherein: 
 said arrangement for applying differential air pressure to said web of fibrous material comprises a arrangement for directing pressurized air from within said drum through said pattern of openings to displace fibrous material from said web to form said pattern of low basis weight regions.    
   
   
       23 . An apparatus for forming a fibrous web in accordance with  claim 16 , wherein: 
 said forming surface comprises a foraminous forming drum, wherein said pattern of forming elements comprises a pattern of upstanding projections on the periphery of said forming drum,    said arrangement for applying differential pressure to said web of fibrous material comprising an arrangement for drawing a vacuum from within said drum so that said web inter-engages said pattern of projections to form said pattern of low basis weight regions corresponding to said pattern of projections.    
   
   
       24 . An apparatus for forming a fibrous web in accordance with  claim 16 , including: 
 a cooperating female sleeve positioned in operative relationship with said forming drum, and defining a pattern of recesses corresponding to said pattern of projections, so that said projections are received in said recesses with said fibrous web positioned between said forming drum and female sleeve to form said pattern of low basis weight regions.    
   
   
       25 . An apparatus for forming a fibrous web in accordance with  claim 24 , wherein: 
 said forming surface comprises a foraminous belt, and said pattern of elements comprises a pattern of relatively high-flow regions defined by said belt,    said arrangement for applying differential air pressure comprising an arrangement for directing air pressure against said fibrous web and through said foraminous belt to form said pattern of low basis weight regions corresponding to said pattern of high-flow regions defined by said belt.    
   
   
       26 . An apparatus for forming a fibrous web in accordance with  claim 24 , wherein: 
 said arrangement for applying differential air pressure further comprises an arrangement for drawing a vacuum through said foraminous belt.    
   
   
       27 . An apparatus for forming a fibrous web in accordance with  claim 24 , wherein: 
 said forming surface comprises a foraminous belt, and said pattern of elements comprises a pattern of relatively low-flow regions defined by said belt,    said arrangement for applying differential air pressure including an arrangement for directing air against said fibrous web and through said foraminous belt to form said pattern of low basis weight regions corresponding to said pattern of low-flow regions defined by said belt.    
   
   
       28 . An apparatus for forming a fibrous web in accordance with  claim 27 , wherein: 
 said low-flow regions defined by said foraminous belt are substantially impermeable.    
   
   
       29 . An apparatus for forming a fibrous web in accordance with  claim 27 , wherein: 
 said arrangement for applying differential air pressure further comprises an arrangement for drawing a vacuum through said foraminous belt.