Fiberboards 



2827 



furnish enters the box through a swing spout which distributes the fibers across 

 the width of the box and on top of a high speed rotor, which agitates the fibers 

 and creates a "snowstorm effect" in the felting chamber (Evans 1957; Robinson 

 1959). The fibers then gently settle down on the moving belt and build up a mat 

 of a density of about 2 pounds/cu ft, and 4 to 12 inches thick, depending on the 

 final thickness of the board. An equalizer or shaving roll reduces the mat to 

 uniform thickness, i.e., it controls the uniformity of the mat by controlling its 

 thickness. This volumetric metering results in uniform board density or uniform 

 board thickness only if the bulk density of the furnish does not fluctuate. Close 

 control of all process characteristics that affect bulk density, such as air velocity, 

 pulping conditions, and moisture content is therefore critical. 



Another gravity type forming machine is used by Champion International at 

 Lebanon, Ore. (Uschmann 1956). A volumetric metering device supplies the 

 furnish to a vertical chute within which it is distributed laterally across the width 

 of the forming machine by means of a number of horizontal screw conveyors. A 

 series of closely-spaced sawblade-like disks project partially into slots at the 

 bottom of the chute and transfer the furnish from the chute and through the slots 

 to moving cauls carried through the machine by a conveyor belt. The action of 

 the rotating "sawblades" prevents congregation of the furnish and deposits a 

 loose uniform mat. As the furnish falls to the cauls, a suction device creates an 

 air current which deflects the final material, depositing half of it ahead of the 

 main stream, as the bottom surface layer, while the other half is carried forward 

 and placed on top of the mat. An equalizer roll controls mat thickness before 

 application of the top surface layer. Figuire 23-57 shows a schematic of the 

 entire operation. 



Figure 23-57. — Schematic diagram of dry-process hardboard plant of Champion Inter- 

 national Corp., Lebanon, Ore. (Drawing after Sandermann and Kunnemeyer 1957). 



1. Chipper 



2. Silo 



3. Bauer mill 



4. Dryer 



5. Addition of resin 



6. Former 



7. Hot press 



8. Humidification 



