Up-flow rake bar screen

Abstract

The present invention relates to an up-flow rake bar screen having a multiplicity of bars which are parallel to one another and which are spaced from one another across the screen. At least a portion of each bar is curved so that, when that portion is viewed from a position at which, when the screen is in use, fluid has not yet passed through the screen, that portion of the bar appears convex.

1 . An up-flow rake bar screen assembly comprising an up-flow rake bar screen ( 10 ) having a multiplicity of bars ( 14 ) which are parallel to one another and which are spaced from one another across the screen ( 10 ), together with a rake ( 18  or  20 ) having a multiplicity of blades ( 22  or  24 ) which extend between the bars ( 14 ) of the screen ( 10 ), in which the rake ( 18  or  20 ) is provided with drive means ( 16 ) to move the blades ( 22  or  24 ) to and fro longitudinally of the bars ( 14 ), in which at least a portion of each bar ( 14 ) is curved so that, when that portion is viewed from a position at which, when the screen is in use, fluid has not yet passed through the screen ( 10 ), that portion of the bar ( 14 ) is convex, characterised in that the rake ( 18  or  20 ) is track guided, and in that the drive means ( 16 ) are arranged above the screen ( 10 ) and the rake ( 18  or  20 ) extends downwardly from the drive means ( 16 ).  
     
     
         2 . An up-flow rake bar screen assembly according to  claim 1 , characterised in that the bars ( 14 ) are each so formed as to have a rectangular cross-section.  
     
     
         3 . An up-flow rake bar screen assembly according to  claim 1 , characterised in that the bars ( 14 ) are so formed as to have a tapering cross-section.  
     
     
         4 . An up-flow rake bar screen assembly according to  claim 3 , characterised in that the tapering is in a downward direction.  
     
     
         5 . An up-flow rake bar screen assembly according to  claim 3  or  claim 4 , characterised in that the bars ( 14 ) are made of wire.  
     
     
         6 . An up-flow rake bar screen assembly according to any one of  claims 3  to  5 , characterised in that the cross-section of each bar ( 14 ) is a truncated triangle.  
     
     
         7 . An up-flow rake bar screen assembly according to any one of  claims 2  to  6 , characterised in that the corners ( 24 ( e )) of each bar ( 14 ) at the upper end of its cross section are rounded.  
     
     
         8 . An up-flow rake bar screen assembly according to any preceding claim, characterised in that each bar ( 14 ) has at least two curves spaced apart longitudinally of the bar ( 14 ) with voids or open spaces or pockets provided at the ends of the curves.  
     
     
         9 . An up-flow rake bar screen assembly according to any one of  claims 1  to  7 , characterised in that each bar ( 14 ) is curved everywhere along its length.  
     
     
         10 . An up-flow rake bar screen assembly according to any one of  claims 1  to  7 , characterized in that each bar ( 14 ) has a straight portion between two curved portions of the bar ( 14 ).  
     
     
         11 . An up-flow rake bar screen assembly according to  claim 10 , characterized in that the progress between a curved portion and the straight portion is without discontinuity, so that there is a smooth transition from the straight portion to each curved portion.  
     
     
         12 . An up-flow rake bar screen assembly according to  claim 10  or  claim 11 , characterised in that the curved portions are at the respective ends of the bar ( 14 ).  
     
     
         13 . An up-flow rake bar screen assembly according to any one of  claims 1  to  7 , characterised in that each bar ( 14 ) is curved in a central portion thereof, with its end portions being straight.  
     
     
         14 . An up-flow rake bar screen assembly according to any preceding claim, characterized in that the blades ( 22  or  24 ) are tapered in a downward direction.  
     
     
         15 . An up-flow rake bar screen assembly according to any preceding claim, characterised in that the blades ( 22  or  24 ) have rounded lowermost ends.  
     
     
         16 . A sewage system overflow installation comprising an assembly in accordance with any preceding claim.  
     
     
         17 . A method of filtering sewage during storm overflow conditions in which the sewage is passed through an up-flow rake bar screen ( 10 ) comprising a multiplicity of bars ( 14 ) which are parallel to one another and which are spaced from one another across the screen ( 10 ), at least portions of the bars ( 14 ) being curved so that those portions are convex to the approaching sewage, and moving a rake ( 18  or  20 ) having a multiplicity of blades ( 22  or  24 ) which extend between the bars ( 14 ) of the screen ( 10 ) so that the blades ( 22  or  24 ) move to and fro longitudinally of the bars ( 14 ), characterised in that the rake ( 18  or  20 ) is guided by track, and in that the rake ( 18  or  20 ) is moved by drive means ( 16 ) arranged above the screen ( 10 ) and the rake ( 18  or  20 ) extends downwardly from the drive means ( 16 ).