Device for cleaning a screen in a papermaking plant

Abstract

A device for cleaning the at least one screen in a papermaking plant enables cleaning of the screen that is guided over rollers. The cleaning device has at least one vacuum chamber which bears against the screen. At least one spray nozzle is arranged in the vacuum chamber to transport a cleaning liquid, in particular water, to the screen. The at least one vacuum chamber is arranged radially outside one of the rollers and the screen, in the area of the vacuum chamber, bears on the roller at least over a major part of its length.

We claim:  
     
         1 . In a papermaking plant having at least one screen guided over a plurality of rollers, a device for cleaning the screen, comprising: 
 a vacuum device adjoining the screen;    at least one spray nozzle disposed in said vacuum device and configured to apply a cleaning liquid to the screen;    wherein said vacuum device is disposed radially outside one of the rollers, and the screen bears on the one roller in an area of said vacuum chamber at least over a major portion of a length thereof.    
     
     
         2 . The device according to  claim 1 , wherein said vacuum device comprises at least one vacuum chamber bearing against the screen.  
     
     
         3 . The device according to  claim 1 , wherein the cleaning fluid is water and said spray nozzle is one of a plurality of spray nozzles configured to spray the water onto the screen.  
     
     
         4 . The device according to  claim 2 , which comprises a plurality of sealing strips aligned transversely with respect to a direction of movement of the screen and disposed to seal said at least one vacuum chamber with respect to the screen guided over the one roller.  
     
     
         5 . The device according to  claim 2 , wherein the screen in an area of said vacuum chamber bears on the one roller over an entire length of said vacuum chamber.  
     
     
         6 . The device according to  claim 2 , wherein said spray nozzle is adjustable in terms of an angle of a jet direction in said vacuum chamber in the direction of movement of the screen.  
     
     
         7 . The device according to  claim 6 , which comprises a spray pipe supporting and communicating with said at least one spray nozzle.  
     
     
         8 . The device according to  claim 1 , wherein said vacuum device comprises at least one first vacuum chamber and at least one second vacuum chamber radially outside the one roller, and wherein said second vacuum chamber is disposed, in the direction of movement of the screen, next to said first vacuum chamber.  
     
     
         9 . The device according to  claim 8 , wherein the screen, in an area of said first vacuum chamber, bears on the one roller over an entire length of said first vacuum chamber, and wherein an area of the screen within an effective area of said at least one second vacuum chamber bears on the roller over part of a length thereof, and is lifted off the roller over a further part of the length thereof.  
     
     
         10 . The device according to  claim 8 , which comprises an extraction duct commonly connecting said at least one first vacuum chamber and said at least one second vacuum chamber to a common vacuum source.  
     
     
         11 . The device according to  claim 10 , which further comprises control devices arranged between said at least one first vacuum chamber and said at least one second vacuum chamber and said vacuum source.  
     
     
         12 . The device according to  claim 11 , wherein said control devices include flaps, pivotally disposed about respective axes aligned approximately at right angles.  
     
     
         13 . The device according to  claim 2 , wherein at least a part of said vacuum chamber is formed with a cross section increasing in size transversely to the direction of movement of the screen.  
     
     
         14 . The device according to  claim 8 , wherein at least a part of said first vacuum chamber is formed with a cross section increasing in size transversely to the direction of movement of the screen.  
     
     
         15 . The device according to  claim 14 , wherein said at least one second vacuum chamber is formed with a height increasing in size transversely to the direction of movement of the screen.  
     
     
         16 . The device according to  claim 8 , wherein said vacuum chambers are formed with edges, and a plurality of sealing strips are aligned transversely with respect to the direction of movement of the screen and disposed to seal at least some of said edges of said vacuum chambers against the screen.  
     
     
         17 . The device according to  claim 16 , wherein, on sides associated with sidewall edges of said vacuum chambers, said sealing strips are formed with profiled grooves, by way of which said sealing strips are pushed onto the sidewall edges of said vacuum chambers.  
     
     
         18 . The device according to  claim 17 , wherein said profiled grooves are T-shaped.  
     
     
         19 . The device according to  claim 16 , wherein at least some of said sealing strips are asymmetrical strips.  
     
     
         20 . The device according to  claim 1 , which comprises a spray pipe supporting and communicating with said at least one spray nozzle, and said at least one spray nozzle includes needle-jet nozzles and flat-jet nozzles.  
     
     
         21 . A papermaking plant, comprising: 
 at least one screen for forming a web from fiber pulp;    a plurality of guide rollers guiding said at least one screen, said guide rollers including a given deflection roller; and    a cleaning device for cleaning said screen, sead cleaning device including at least one vacuum chamber and at least one spray nozzle disposed in said vacuum chamber and configured to spray a cleaning liquid onto said screen;    said vacuum chamber being disposed radially outside said given deflection roller, and said screen bearing on said given deflection roller in a vicinity of said vacuum chamber at least over a major portion of a length thereof.