JPS6128500B

PURPOSE:To provided the subject screw of high performances, capable of obtaining sufficient kneading effects and the increase of the extrusion quantity while preventing generation of excessive heat of a plastic material, which has imparted a specific deformation to the configuration of screw groove. CONSTITUTION:The space between the pitch of a screw 1 is divided into two parts, and the groove depths of divided parts 3 and 4 are repeatedly varied along a screw flight 5. The axes 6 and 7 of the root diameter part are inclined at angles of theta1 and theta2 respectively relative to the screw shaft 2, and the groove depth varies along the shaft 2 even in the same divided part. Since respective sections in the radial direction from B-B to H-H vary, the kneading of plastics and equalization of the temperature thereof are carried out exceedingly effectively by the repeated variations of sections C-C and G-G and section E-E relative to the exhaust direction a, the axial substitution operation due to sections D-D and F-F, the shearing operation at the border of respective divided parts.