PURPOSE: To control the injection speed of plunger simply, rapidly, and accurately by comparing the output of a position setter to detect the moving position of a plunger with the output of a position setter to determine the speed-changing position of the plunger.
CONSTITUTION: A driver 5 is operated to make the output voltage of a position setter 9 larger than the set voltage of a position setter 10-1, and a flow control valve 6 is controlled through a comparator 11-1, an amplifier 13-1, and a control element 12 to upwardly move a plunger 3 with a low speed. Then, when the plunger 3 reaches a given position, the movement is transmitted through a moving part 8 to the setter 9, the output voltage of the detector 9 is greater than the set voltage of the position setter 10-2, and the plunger 3 is controlled to a preregulated higher speed by the control element 11-2 in the same way as mentioned above. Furthermore, when the plunger 3 is moved upwards, the output voltage of the detector 9 is made greater than the set voltage of the position setter 10-3, the plunger is likewise controlled to a slower speed by the control element 11-3, and a molten metal 4 is cast into a cavitity 2 to stop the plunger 3.
IDA HISAO
HIGUCHI FUMIO
KAIHO SHIGEO
