Patent ID: 7374418

Claim:
A valve nozzle, comprising: a main body having an internal space, a rear space, a nozzle holder, and a nozzle head attached on a front end of said nozzle holder and having a gate with an inner wall defining a circular hole; and a gate opening and closing mechanism including a torpedo in said internal space, a piston having a head portion inside said gate of said nozzle head in a closed position and retracted from said gate in an opened position, a shaft portion extending from said head portion and a rear end part connected to a rear end of said shaft portion, said head portion and said shaft portion being in said torpedo, and having a circumferential gap on an outer circumferential surface thereof providing a resin flow channel between and about said outer circumferential surface of said shaft portion and an inner circumferential surface of said torpedo, said rear end part having a tapered surface for receiving a pressure of resin in said resin flow channel, said head portion having a circular sectional portion adjacent a front end thereof in contact with said inner wall of said gate in said closed position; a coil spring disposed outside said resin flow channel on a rear side of said torpedo and pressing said rear end part toward said gate, and a coolant channel on said torpedo having a forward channel and a return channel, said forward channel extending from a coolant inlet formed on one end of said torpedo and twisting and spiraling relative to an axial direction of said torpedo toward an opposite end of said torpedo to end in a concave portion at said opposite end, said return channel extending from said concave portion and twisting and spiraling toward said one end parallel to said forward channel to end at a coolant outlet, said forward and return channels forming a duplex spiral between said coolant inlet and said coolant outlet; whereby, resin conveyed inside of said gate opening and closing mechanism fills said resin flow channel to pass between said inner wall of said gate and said head portion of said piston for injection into a mold cavity when in said open position; whereby said resin remains in said resin flow channel in said closed position; and whereby said resin in said resin flow channel applies pressure to said tapered surface until such pressure reaches or exceeds a predetermined value and overcomes a pressing force of said coil spring to remove said head portion of said piston from said gate to open said resin flow channel.