Apparatus and method for dry forming of Fibrous Tissue

Abstract

An apparatus and a method for dry forming of fibre weave ( 9 ) are disclosed. The apparatus comprises a suction box ( 4 ) and a superjacent forming head and a forming wire ( 2 ) placed in between. The weave ( 9 ) is formed on the forming wire, in that the suction box ( 4 ) has an active suction area ( 17 ) that sucks the fibres towards the forming wire ( 2 ). With the object of avoiding beaching in the formed fibre weave ( 9 ) a pressure drop regulating means ( 3 ) is mounted in the suction box in a sub-section of the suction area ( 17 ).

1 . Apparatus for dry forming of fibrous tissue, which apparatus comprises a suction box and a superjacent forming head with a forming wire fitted in between, on which the tissue is formed, in that the suction box has a suction area that sucks the fibres down towards the forming wire, wherein, a pressure drop regulating means is fitted in the suction box, in a partly across the width of the forming wire extending sub-section of the suction area, in order to regulate the air stream and hence the turbulence that appears in said sub-section of the suction area of the suction box. 
   
   
       2 . Apparatus according to  claim 1 , wherein, the means is adjustably mounted, substantially with spacious adjustment possibilities in three dimensions. 
   
   
       3 . Apparatus according to  claim 1 , wherein, the means has a roughly smooth surface in order to be self-cleaning. 
   
   
       4 . Apparatus according to  claim 1 , wherein, the means is provided with a boundary, which is tight-fitting to part of the boundary of the suction area, in that said sub-section adjoins an edge of the suction area. 
   
   
       5 . Apparatus according to  claim 1 , wherein, the means is provided as a plate, which is mounted to the suction box. 
   
   
       6 . Apparatus according to  claim 1 , wherein, the forming head has at least one perforated rotating drum, in which fibres mixed with air enter the first end of the drum, which contains agents for fluidization of the fibres, and that the means is located in the suction area at said first end of the drum. 
   
   
       7 . Apparatus according to  claim 6 , wherein, the forming head contains two or more drums and that the means is located at said first end of the drum, which drum is located at the front end, as viewed in the feeding direction of the forming wire. 
   
   
       8 . Method for dry forming of fibrous tissue and comprising a suction box and a superjacent forming head with a forming wire fitted in between, on which the tissue is formed, in that the suction box has a suction area that sucks the fibres down towards the forming wire, wherein, a pressure drop regulation is provided in a partly across the width of the forming wire extending sub-section of the suction area, in order to regulate the air stream and hence the turbulence that appears in said sub-section of the suction area of the suction box. 
   
   
       9 . Method according to  claim 8 , wherein, the pressure drop regulation varies across the said sub-section. 
   
   
       10 . Method according to  claim 8 , wherein, the pressure drop regulation is applied to change the essentially uniform pressure drop across the suction area.