Patent attributes
The present invention provides a manufacturing method for manufacturing an outer tube of an injector having a barrel portion having an excellent circularity, while preventing generation of distortion or warp. A molten resin is injected into a cavity 17 of a metal mold 11 including: a fixed mold 13 having a hole portion 12 having a shape along the outer shape of the injector outer tube 1; a movable mold 14 closing the hole portion 12; and a core 15 inserted into the hole portion 12. A cylindrical vacant portion is provided communicating with a flange forming portion 20 of the hole portion 12. The molten resin R is injected from a sprue 22 and a runner 23 via a submarine gate 24 into the cylindrical vacant portion 21 and the molten resin R is introduced into the cavity 17. The cylindrical vacant portion 21 has a push pin 25. When the molten resin has become half-molten state, the resin in the cylindrical vacant portion is introduced with pressure into the cavity 17 by the push pin 25. When the amount of the molten resin R in the cavity 17 is insufficient, a wait position of the push pin is moved in a direction apart from the connection portion of the submarine gate 24, so as to inject the molten resin R and supplement the insufficient resin in the cavity 17.
