Screw machine

Abstract

A screw machine ( 10 ) has a rotor housing ( 12 ) defining overlapping bores ( 13, 15 ). Female rotor ( 14 ) is located in bore ( 13 ) and male rotor ( 16 ) is located in bore ( 15 ). The end faces ( 24, 26 ) of the female and male rotors, respectively, have depressions ( 44, 46, 54, 56, 64 ) formed in their surface whereby the interface area with the facing surface ( 51 ) of the outlet casing ( 53 ) is reduced.

What is claimed is:  
     
         1 . A screw machine comprising a housing defining at least one pair of parallel, overlapping bores, an outlet casing having a facing surface, and a conjugate pair of intermeshing rotors located in said at least one pair of bores, each of said rotors having an end face, said end faces of said rotors being spaced from said facing surface of the outlet casing and defining therewith an interface area; characterized by the interface area being reduced by reason of a reduction in the surface area of at least either said rotor end faces or said facing surface of the outlet casing.  
     
     
         2 . The screw machine of    claim 1    wherein at least one depression is formed in said rotor end faces.  
     
     
         3 . The screw machine of    claim 1    wherein a plurality of discrete, unconnected depressions are formed in each of said rotor end faces.  
     
     
         4 . The screw machine of    claim 1    wherein said rotor end faces comprise textured surfaces.