forming head for dry forming a fibrous web

Abstract

The invention relates to a forming head for dry forming a fibrous web, which forming head is positioned above a forming wire opposite a suction unit. The forming head is divided into at least two independent interconnected distribution units, each of which comprises at least one revolving roller provided with protruding spikes. By dividing the forming head into a plurality of interconnected distribution units, a more efficient disintegration of agglomerates, shadows and/or lumps in the fibre material is achieved compared to the known forming heads, thereby ensuring a more homogenous final product.

1 . A forming head for dry forming a fibrous web, the forming head being positioned above a forming wire opposite a suction unit, wherein the forming head is divided into at least two distribution units detachable mounted in the forming head, the at least two distribution units are arranged one of top of the other and each distribution unit comprises at least one revolving roller provided with protruding spikes. 
     
     
         2 . A forming head according to  claim 1 , wherein the distribution units in the forming head are in communication with each other such that the upper distribution unit(s) can pass fibrous material to the underlying distribution unit(s). 
     
     
         3 . A forming head according to  claim 1 , wherein the spikes on the at least one revolving roller in at least one of the distribution units covers between about 30% to about 80%, preferably about 65% of the sectional area of the distribution units seen in relation to the forming wire. 
     
     
         4 . A forming head according to  claim 1 , wherein the spikes on the at least one revolving roller in at least one of the distribution units substantially covers the entire sectional area of the distribution units seen in relation to the forming wire. 
     
     
         5 . A forming head according to  claim 1 , wherein at least one distribution unit has the same or a smaller horizontal cross section than the underlying distribution unit. 
     
     
         6 . A forming head according to  claim 1 , wherein the at least one roller in at least one of the distribution unit is detachable mounted. 
     
     
         7 . A forming head according to  claim 1 , wherein at least one revolving roller has a different dimension and/or length than the remaining revolving rollers in a distribution step. 
     
     
         8 . A forming head according to  claim 1 , wherein the forming head is provided with a bottom having a pluralities of openings. 
     
     
         9 . A forming head according to  claim 8 , wherein the bottom is a grid having a plurality of detachable grid elements. 
     
     
         10 . A forming head according to  claim 1 , wherein the at least one roller in at least one distribution unit, is placed with the longitudinal axes oriented substantially perpendicularly to the moving direction of the forming wire. 
     
     
         11 . A forming head according to  claim 1 , wherein the rollers in at least one distribution unit, is placed with their longitudinal axes in the same or in a different orientation in relation to the rollers in one of the other distribution units. 
     
     
         12 . A forming head according to  claim 1 , wherein the rollers in each distribution unit are adapted for being rotated around their longitudinal axes with the same or different speed of rotations. 
     
     
         13 . A forming head according to  claim 1 , wherein the spikes are distributed evenly along the circumference of the roller. 
     
     
         14 . A forming head according to  claim 1 , wherein the spikes in at least one distribution unit, in the longitudinal direction of the roller, are spaced, which allow the passage in-between for corresponding spikes on an adjacent roller. 
     
     
         15 . A forming head according to  claim 1 , wherein the spikes on the rollers are made of a flexible material. 
     
     
         16 . A forming head according to  claim 1 , wherein the forming head comprises four distribution units, placed in succession starting from the distribution unit farthest from the forming wire, wherein
 the first distribution unit comprises one revolving roller,   the second distribution unit comprises two revolving rollers,   the third distribution unit comprises one revolving roller,   the fourth distribution unit comprises a plurality of revolving roller arranged in a substantially horizontal plane.   
     
     
         17 . A forming head according to  claim 16 , wherein the spikes on the revolving rollers in the first, second and fourth distribution unit substantially cover the entire sectional area of the respective distribution units when seen in a mainly horizontal plane. 
     
     
         18 . A plant for producing a fibrous web wherein the plant comprises a forming head according to  claim 1 . 
     
     
         19 . A method for dry-producing a fibrous web, using the forming head according to  claim 1 , and wherein the at least two distribution units is detachable mounted in the forming head and arranged one of top of the other, wherein
 fibrous material is added to the distribution unit farthest from the forming wire for processing in the forming head,   the fibrous material passed from one distribution unit to the underlying distribution unit(s) and   the fibrous material is laid on the forming wire for forming the fibrous web.   
     
     
         20 . A method according to  claim 19 , wherein the at least one distribution unit is removed from the forming head, and a different distribution unit is inserted instead.