PURPOSE: To easily and mechanically perform the connection and separation of a mold and an extruder by a method wherein engaging head parts, each of which is formed at the tip of an engaging pin and has an outer peripheral shape the same as or a little smaller than a through hole bored on a mold plate, are mechanically pivoted.

CONSTITUTION: Clamp main bodies 2 are arranged at an extruder side on the heat plate 11 of an extruder symmetrical to the connecting center line with a mold. To the clamp main body 2, an engaging pin 3, which pierces the head plate 11, is threabingly fitted with a nut 4 at one end. In the clamp main body 2, above and below the engaging pin, cylinder chambers 2b are formed so as to provide actuating cylinders 5 therein. The engaging pin 3 is equipped with a rectangular engaging head part 31 at the other end of the engaging pin 3 and a pivoting means 7 at its intermediate part. The engaging head parts 31 are insertingly passed through rectangular through holes 21a, which are provided on a mold plate 21. After the insertion of the engaging head parts 31 in the through holes 21a, the engaging head parts 31 and the major axes of the through holes 21a are crossed to each other by actuating the actuating cylinders 5 so as to fix a connecting ring between the plates 11 and 21. In order to release the connection between the plates, the pressurizing of the actuating cylinders 5 is released and the engaging head parts 31 and the through holes 21a are registered by the pivoting means 7. After that, the mold is taken off.