| 摘要 |
PROBLEM TO BE SOLVED: To enable molding of a long-sized shaft of a rotary brush by a synthetic resin without bringing about a shrinkage or the like. SOLUTION: The synthetic resin is filled from a resin filling port 13 of an injection molding machine body 11 in a core 14a of a mold 14. Spiral grooves for the shaft are previously formed on the core 14a of the mold 14. A method for injection molding comprises the steps of moving a fourth member 14 by a moving mechanism after the filling of the synthetic resin in the core 14a of the mold 14 is completed, and bringing the axial direction of the shaft in the core 14a of the mold 14 and the axial direction of a protrusion 20 into coincidence with those of cooling cylinders 12a to 12c for constituting a cooling mechanism 12. The method further comprises the step of thereafter depressing the protrusion 20 by a hydraulic cylinder 21. The method also comprises the steps of depressing the shaft down while rotating the protrusion 20 by a key when the protrusion 20 is depressed. Thus, the shaft is pressed out from the core 14a while rotating along the spiral groove of the core 14a. Since the shaft is molded in this manner, the long-sized shaft (about 150 mm) can be molded.
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