Injection device and resin injection method

Abstract

As an injection screw 2 applies pressure, a holding pressure plunger 22 is moved backward under the pressure of a resin to flow the resin into a holding pressure path 9, and the resin in a resin path 6 is pressurized (primary holding pressure process). A shutoff plunger 12 is closed, and the resin in the resin path 6 and the holding pressure path 9 is pressurized by the holding pressure plunger 22 (secondary holding pressure process). Further, the shutoff plunger 12 is opened, and the holding pressure plunger 22 is moved forward until its tip projects into the resin path 6 to discharge all the resin in the holding pressure path 9 to the resin path 6, whereby the resin beside the injection screw 2 as compared with the shutoff plunger 12 is held with respect to the holding pressure path 9.

1 . An injection device, comprising:
 an injection nozzle, mounted on a front end of an injection cylinder, for injecting a resin, which has been charged into the injection cylinder, through a resin path using an injection screw;   shutoff means mounted in the injection nozzle and capable of shutting off the resin path;   a holding pressure path formed in the injection nozzle closer to an injection front end as compared with the shutoff means, and in fluid communication with the resin path so that the resin can freely flow thereinto; and   holding pressure means disposed reciprocatably in the holding pressure path, configured for receiving a pressing force to press the resin in the holding pressure path toward the resin path, and configured for being moved in a direction opposite to a pressing direction by the resin flowing into the holding pressure path when the pressing force is released,   wherein when a pressure of the resin path of the injection nozzle is to be maintained, shutoff of the resin path is released using the shutoff means, and the injection screw is pressurized to hold the resin in the resin path and the holding pressure path,   then the resin path is shut off by the shutoff means, and the pressing force is imparted to the holding pressure means to continue holding of the resin in the resin path and the holding pressure path by the holding pressure means, and   further, when the shutoff of the resin path is released using the shutoff means all the resin in the holding pressure path is discharged to the resin path by the holding pressure means.   
     
     
         2 . The injection device according to  claim 1 , wherein
 the holding pressure means is given the pressing force, whereby a tip site thereof is projected into the resin path, and   the tip site of the holding pressure means is projected into the resin path, whereby all the resin in the holding pressure path is discharged to the resin path.   
     
     
         3 . The injection device according to  claim 2 , wherein
 when the pressure of the resin path of the injection nozzle is to be maintained, the resin path is shut off using the shutoff means to continue the holding of the resin in the resin path and the holding pressure path,   then, with the resin path being shut off, the pressing force is exerted on the holding pressure means, an inlet path for the resin on a mold side is shut off, and the pressing force on the holding pressure means is released, and   then the shutoff of the resin path is released, and the pressing force is exerted again on the holding pressure means to discharge all the resin in the holding pressure path to the resin path.   
     
     
         4 . The injection device according to  claim 1 , wherein
 when the resin path is shut off using the shutoff means after the resin is held in the resin path and the pressure holding path by the pressurization of the injection screw, the injection screw is rotationally operated in a reverse direction to charge additional resin into the injection cylinder.   
     
     
         5 . A resin injection method for injecting a resin from an injection nozzle through a resin path and flowing the resin into a holding pressure path that is in fluid communication with the resin path to maintain a pressure of the resin in the resin path and the holding pressure path, comprising:
 pressurizing the resin in the resin path to hold the resin in the resin path and the holding pressure path;   then shutting off the resin path and pressurizing the holding pressure path to perform holding pressure of the resin path and the holding pressure path; and   further releasing shutoff of the resin path and discharging all the resin held in the holding pressure path to the resin path under pressure.   
     
     
         6 . The resin injection method according to  claim 5 , further comprising
 shutting off the resin path using the shutoff means and pressurizing the holding pressure path to hold the resin in the resin path and the holding pressure path;   shutting off an inlet path for the resin on a mold side and releasing pressurization of the holding pressure path once; and   releasing shutoff of the resin path and pressurizing the holding pressure path again to discharge all the resin in the holding pressure path to the resin path.   
     
     
         7 . The injection device according to  claim 2 , wherein
 when the pressure of the resin path of the injection nozzle is to be maintained, the resin path is shut off using the shutoff means to continue the holding of the resin in the resin path and the holding pressure path,   then, with the resin path being shut off, the pressing force is exerted on the holding pressure means, an inlet path for the resin on a mold side is shut off, and the pressing force on the holding pressure means is released, and   then the shutoff of the resin path is released, and the pressing force is exerted again on the holding pressure means to discharge all the resin in the holding pressure path to the resin path.   
     
     
         8 . The injection device according  claim 2 , wherein
 when the resin path is shut off by the shutoff means after the resin is held in the resin path and the pressure holding path using the pressurization of the injection screw, the injection screw is rotationally operated in a reverse direction to charge additional resin into the injection cylinder.   
     
     
         9 . The injection device according  claim 3 , wherein
 when the resin path is shut off by the shutoff means after the resin is held in the resin path and the pressure holding path by the pressurization of the injection screw, the injection screw is rotationally operated in a reverse direction to charge additional resin into the injection cylinder.