Method and device in the production of a web material

Abstract

Method for improving the formation of a web material in a wire machine, including dispersing existing flocks in stock which is transported along a transport direction from an inlet box onto a plurality of wire sections which are arranged after each other along the direction of travel, counteracting the reformation of flocks in the stock on the wire by furnishing ultrasound energy as ultrasound waves with frequencies between 15 and 75 kHz to the stock on the wire sections. The ultrasound has a higher frequency within at least one section which is closer to the inlet box than a subsequent section further away from the inlet box, within which subsequent section the ultrasound has as lower frequency.

1 . Method to improve, in the production of a web which to an essential part consists of cellulosic fibers, the formation of the web material in a one or plural wire machine by, to an essential part, dispersing existing flocks in the stock which is led from an inlet box out onto at least one wire, and to counteract the reformation of flocks in the stock on the wire, characterised i n that ultrasound energy as ultrasound waves with frequencies between 15 and 75 kHz is furnished to the stock in at least one wire section.  
     
     
         2 . Method according to  claim 1 , characterised in that the ultrasound energy is furnished to the stock on the wire within at least one cross directional section of the wire section along the transport direction of the stock on the wire.  
     
     
         3 . Method according to  claim 2 , characterised in that the ultrasound energy is furnished to the stock on the wire within a plurality of cross directional sections which are arranged after each other.  
     
     
         4 . Method according to  claim 3 , characterised in that the ultrasound energy is furnished to the stock within three to five cross directional sections which are arranged after each other.  
     
     
         5 . Method according to any of claims  1 - 4 , characterised in that the ultrasound energy is furnished to the stock within at least some section where the stock on the wire has a concentration (dry content) of between 0,2 and 6%, preferably between 0,5 and 5% or between 1 and 6%, suitably between 1,5 and 5%.  
     
     
         6 . Method according to  claim 5 , characterised in that ultrasound energy also is furnished to the stock within at least some section where the concentration of the stock is 5-15%, preferably 6-12%.  
     
     
         7 . Method according to any of claim s  1 - 5 , characterised in that the ultrasound energy is furnished to the stock within the area of the first half of the wire section.  
     
     
         8 . Method according to any of the preceding claims, characterised in that the ultrasound waves which are furnished to the stock have different frequencies within at least a couple of said sections.  
     
     
         9 . Method according to  claim 8 , characterised in that the ultrasound has a higher frequency within at least one section which is closer to the inlet box than a subsequent section further away from the inlet box, within which subsequent section the ultrasound has a lower frequency.  
     
     
         10 . Device for performance of the method according to any of claims  1 - 9 , characterised in that ultrasound elements which transmit the ultrasound energy to the stock are arranged in a wire loop in contact with the inside of the wire in the loop in the area of the distribution of the stock and thus also in contact with the liquid in the stock via the wire and via the mesh interspaces in the wire for transmission of the ultrasound energy to the stock via the wire and directly to the liquid phase via the mesh interspaces.  
     
     
         11 . Device according to  claim 10 , characterised in that ultrasound elements are arranged in a sub loop and/or in a top loop.  
     
     
         12 . Device according to  claim 11 , characterised in that ultrasound elements are arranged opposite each other in a sub wire loop and in a top wire loop.  
     
     
         13 . Device according to any of claims  10 - 12 , characterised in that the ultrasound elements and/or ultrasound generators which are connected to the ultrasound elements are adjustable in respect of power and/or frequency which is transmitted to the stock.  
     
     
         14 . Device according to any of claims  10 - 13 , characterised in that the ultrasound elements consist of separate units.  
     
     
         15 . Device according to any of claims  10 - 13 , characterised in that the ultrasound elements are integrated with one or some dewatering elements of the type which include formation tables, foils and suction boxes.  
     
     
         16 . (Amended) Method for improving the formation of a web material in a wire machine, comprising: 
 dispersing existing flocks in stock which is transported along a transport direction from an inlet box onto a plurality of wire sections which are arranged after each other along said direction of travel; and    counteracting the reformation of flocks in the stock on the wire by furnishing ultrasound energy as ultrasound waves with frequencies between  15  and 75 kHz to the stock [to] on said plurality of wire sections;    wherein the ultrasound has a higher frequency within at least one section which is closer to said inlet box than a subsequent section further away from said inlet box, within which subsequent section the ultrasound has a lower frequency.