| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a duplex writing instrument which can eliminate any problem in rotational feeding operation by devising a better parting line position to avoid any molding having an undercut. <P>SOLUTION: In the duplex writing instrument, a guide tube 30 for guiding travel in longitudinal direction of plural writing shafts 15 is stored inside the above shaft tube 20. This guide tube 30 includes a front section 31, a rear section 33 provided with the above plural gaps 34 along the longitudinal direction on outer circumference, and a boundary section 36 with guide holes 37 for inserting each of the writing shafts 15 on the boundaries of above sections. The guide tube 30 is formed by injection molding into a metal mold 40 including plural core pins 42 respectively fitted with each of the guide holes 37 and a split mold 41 forming profile. In a part forming the gaps 34, core pins 42 are directly in contact with the split mold 41. A divided face 50 as a virtual surface including two parting lines 51 formed on outer circumferential side of the guide tube 30 as a mating joint of the split mold 41 is deviated from a shaft center 60 of the above shaft tube 20. <P>COPYRIGHT: (C)2013,JPO&INPIT |
