Extruder

Claim 1

An extruder comprising: a. a cylinder which has a front tubular part, rear tubular part and an intermediate part between said front tubular part and said rear tubular part and is provided with a material supplying port for supplying a material at a periphery of said rear tubular part and a material extruding outlet at said front tubular part; b. pulverizing means positioned at said material supply port, which pulverizes primary materials and feeds pulverized materials under pressure into said material supplying port, said means for pulverizing and feeding the materials comprising rotary blades which are edged at the blade ends; c. a screw which is provided with a spiral ridge on its outer periphery, rotatably housed in said cylinder, said screw having a front part, rear part and intermediate part corresponding to the parts of said cylinder; d. a material flow passage spirally formed by said spiral ridge between the outer periphery of said screw and the inner periphery of said cylinder, said passage communicating with said material supplying port and said material extruding outlet and adapted so that a capacity per turn of the spiral ridge in a front part formed by the front parts of said cylinder and screw is smaller than that of a rear part formed by the rear parts of said cylinder and screw and a capacity per turn of the spiral ridge in a passage throttle part formed by the intermediate parts of said cylinder and screw gradually decreases as said spiral ridge advances from the rear side to the front side; e. a communicating path connecting adjacent partial sections of said material flow passage which are separated by said spiral ridge in said passage throttle part; f. a rotary driving means which rotates said screw; and g. a heating means provided on said cylinder to heat said material flow passage.