To control the amount of leakage of a liquid from a liquid circulating passage and the temperature of the passage by a method wherein a first on-off valve and a second on-off valve are interposed in tandem in a discharging pipe connecting with the liquid circulating passage.
An injection molding machine is put into actuation after a rod-like heater 67 is turned on. After the quality of a product is stabilized, a regular running, in which liquid is circulated through a liquid circulating passage by means of a liquid circulating pump 71. The amount of the liquid leaked from the circulating passage is automatically fed from a liquid supplying source 43 through an on-off valve 38 and a float chamber 11 so as to fill the circulating passage with the liquid at all times. By connecting a first on-off valve 54 and a second on-off valve 49 in tandem and, at the same time, guiding the pressure liquid of the liquid supplying source 43 to the outlet 54b side of the first on-off valve 54, pressures at the inlet 54a and at the outlet 54b of the first on-off valve 54 are made equal to each other, resulting in preventing the unexpected leakage at the first on-off valve 54 due to the difference between the pressures at the inlet 54a and at the outlet 54b from occurring. On the other hand, let the slight set amount of the liquid leaked between the outlet 54b of the first on-off valve 54 and the inlet 49a of a second on-off valve 49. As a result, the amount of leakage of the liquid in the circulating passage can be controlled and the first and the second on-off valves 54 and 49 can be cooled.
KOISHI YOSHITAKA
KANOU KIMIYA
MATSUI OSAMU
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