Protecting device of an injection molding machine

摘要

A protecting apparatus of an injection molding machine having an injection of cylinder 2r with a built-in double rod type piston, and a servo valve for driving and controlling the injection cylinder includes a power failure detecting circuit for detecting a power failure, and a power-failure-time signal outputting circuit Ub for outputting a neutral signal, by which the servo valve is controlled at a neutral signal, by which the servo valve is controlled at a neutral position, to an instruction signal input line for the servo valve, due to the detection of the power failure by the power failure detecting circuit. A power-failure-time shutting down circuit is connection to the oil transferring line for supplying pressurized oil to the injection cylinder. The power-failure-time shutting down circuit includes a control valve for opening the oil transferring at the time of the non-power failure, and for shutting down the oil transferring line at the time of the power failure. Thereby, even if the power failure occurs in the state when the purging cover is closed at a time of positional control in the unguarded state a problem where the resin is ejected at high speed can be presented.