| 摘要 |
PURPOSE:To reduce the wear between the inner wall of an extruder cylinder and the flight crest face of a screw by a method wherein the side wall of the flight part is made into a groove-like curved surface continuously dented at the intermediate part in the direction of the height of the flight part. CONSTITUTION:A cylinder 1 provides a plastic material feeding port 2 and an extrusion port 3. In addition, screws 4 and 4' rotate in different directions in the extruder cylinder 1 and, at the same time, engaging flight parts 5 and 5' are formed. The engaging part S of the flight parts 5 and 5' is a portion, in which pressure is developed during the conveying of molten material. Further, the side walls 51 and 51' of the flight parts 5 and 5' are made into groove-like curved surfaces continuously dented at the intermediate parts in the direction of the heights of the flight parts 5 and 5' so a to make an elongated circle-shaped gap D between the side walls 51 and 51' of the engaging part S of the flight parts 5 and 5'. Since molten material passes through the gap, which is wider at the intermediate part that the flight side walls 51 and 51' face to each other in the engaging part S of the flight parts 5 and 5' no large back flow develops and pressure is reduced, resulting in preventing the crest face of the flight part from strongly pressing against the inner wall of the extruder cylinder and accordingly the crest face of the flight of the screw from wearing. |
