SCREW COMPRESSOR

PURPOSE:To maintain the gaps of a cylinder and a slide valve equal in the radial direction and prevent the slide valve from hitting on one side by forming paired cut-out sections on the slide valve which is slid in the axial direction within the cylinder while a minute gap is being maintained in a space interspaced from the outer circumferential surfaces of a male and a female rotor. CONSTITUTION:A male and a female rotor 3 and 2 which are rotated while being meshed with each other so that gas is compressed, are housed in a casing 1. And a slide valve 11 is provided, which is slid in the axial direction within a cylinder 17 while a minute gap is being maintained in a space interspaced from the outer circumferential surfaces of the male and female rotors 3 and 2. In this case, two cut-out sections 11c which make a pair, are formed in the slide valve 11 at positions which form a point of symmetry on the basis of the center of curvature 11b forming the circular arc of an outer circumferential surface in the cross sectional plane normal to the axial direction, and the two cut-out sections are faced to each other in a state that they are balanced in discharge pressure which is sucked in the respective cut-out section 11c. By this constitution, a gap in the radial direction between the slide valve 11 and the cylinder 17 can be maintained equal, and hitting on one side in the sliding surface 11a of the slide valve 11 can thereby be prevented.