20130087950 | METHOD FOR OPERATING SEVERAL NEEDLE VALVE NOZZLES OF INJECTION-MOLDING EQUIPMENT - An injection-molding equipment includes at least two cavities and at least one needle valve nozzle, each fitted with one needle, per cavity. The needles are displaceable by an electromagnetic drive into an open and a closed position to respectively release and close a gate aperture subtended in the particular related cavity. Each electromagnetic drive has at least one electromagnet with each sealing needle axially held in place in the open and in the closed position by at least one permanent magnet. A control unit generates individual power pulses of which the duration is defined and saved in said control unit. An electromagnet of an electromagnetic drive is fed a power pulse and generates an electromagnetic field to displace the sealing needle from its closed into its open position and vice-versa, with the power pulses for at least two electromagnetic drives being transmitted in time-staggered manner to the drives. | 04-11-2013 |