Deflocculating means for use in a paper making machine

Abstract

A deflocculating mechanism for use in a paper making machine includes a support member such as a forming board or a foil blade for location beneath a forming fabric belt. The support member has an upper surface defining at least one groove that runs in a cross-machine direction, the groove being provided with retention device for holding an insert in a sliding engagement in the groove to induce micro-turbulence in pulp stock being carried by the forming fabric belt. A pressure pulse commences in the pulp stock from a single source at one side of the forming fabric as it passes over the leading edge of the insert and then travels across the fabric along the line of the insert as a single wave. This produces a more controlled agitation and deflocculation of the pulp stock.

1 . A deflocculating means for use in a paper making machine comprises: 
 a support member located beneath a forming fabric belt, the support member having an upper surface defining at least one groove that runs in a cross-machine direction, the groove being comprised of a retention means for holding an insert in a sliding engagement in the groove in order to induce micro-turbulence in pulp stock being carried by the forming fabric belt, wherein the groove has a longitudinal axis which is angled at between 0.38° and 0.77° to a transverse axis in the cross-machine direction.    
   
   
       2 . A deflocculating means as claimed in  claim 1 , wherein an upper surface of the support member defines a plurality of grooves running in a cross-machine direction.  
   
   
       3 . A deflocculating means as claimed in  claim 1 , wherein said grooves run parallel to one another across the surface of said support member.  
   
   
       4 . A deflocculating means as claimed in  claim 1 , wherein said grooves are arranged so that leading ends of the grooves with respect to the direction of travel of the belt are located on opposite sides of the support surface.  
   
   
       5 . A deflocculating means as claimed in  claim 1 , wherein the insert changes the depth of the groove.  
   
   
       6 . A deflocculating means as claimed in  claim 1 , wherein the insert projects above the level of the support surface so that if a plurality of grooves are arranged adjacent to one another across the support surface, the inserts define a series of cross-machine channels therebetween.  
   
   
       7 . A deflocculating means as claimed in  claim 1 , wherein the upper surface of the insert is flat.  
   
   
       8 . A deflocculating means as claimed in  claim 1 , wherein the upper surface of the insert has a downstream portion which diverges backwards at an angle between 0° and 5°.  
   
   
       9 . A deflocculating means as claimed in  claim 1 , wherein trailing side walls of the grooves are angled so that they slope in the direction of travel of the belt at an angle which diverges by up to 45° from the vertical.  
   
   
       10 . A deflocculating means as claimed in  claim 1 , wherein a leading edge of the support member diverges downwardly from the support surface at an angle of 30°.  
   
   
       11 . A deflocculating means as claimed in  claim 1 , wherein the retaining means is provided by the groove defining a T-shaped or dovetail-shaped transverse cross-sectional profile into which a complementary shaped insert can be slidingly engaged from one end of the groove.  
   
   
       12 . A deflocculating means as claimed in  claim 1 , wherein said support member comprises either a forming board or a foil blade.