| 摘要 |
A plunger rod for a syringe in is of integrally injection molded plastic construction having an elongated body with a coaxial end portion. An external thread extends around the end portion for threaded receipt into a plunger tip that is slidably received in a syringe barrel. A flat extends chordally across the end portion of the rod body interrupting the external thread. The plastic, of which the plunger rod is molded, is gated into the mold for the plunger rod at the flat that extends across the rod end portion, leaving a gate mark or vestige on the flat. Gating of the plastic material into the portion of the mold that forms the threaded end portion of the plunger rod achieves improved flow and improved filling of the external thread, while employing a simple and economical mold construction. The gate vestige does not interfere with threading of the plunger rod end portion into the plunger tip. The end portion of the plunger rod is cored during molding to provide a C-shaped cross section at the rod end portion, which improves dimensional stability during material shrinkage after molding.
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