(1) Field of the Invention
This invention relates to a mold closing device of an injection molding machine. More particularly, the invention relates to a mold closing device in which the hydraulic pressure resistance in the direction of the movement of a mold closing piston is reduced so as to promote the speed of opening and closing of the injection mold.
(2) Description of the Prior Art
There are several well known mold closing devices in which oil passages are formed in the mold closing piston of a mold closing cylinder and the oil passages are opened by means of valves, thereby reducing the hydraulic pressure resistance in the oil chamber on the lower pressure side when the mold closing piston is moved.
In almost all of them, however, either the opening or closing of valves has been done by hydraulic pressure, while it has been regarded as rather disadvantages in view of structural and economic reason for both the opening and closing of valves to be carried out by hydraulic pressure. Further, even if such an invention has been already made, it has never been put into practice.