Closure nozzle for injection molding machines

Claim 1

A closure nozzle for an injection-moulding machine including a plasticizing cylinder for plasticized plastic, said nozzle comprising: a nozzle carrier having one end adapted to be connected to the plasticizing cylinder of the injection-moulding machine; a nozzle movably attached to the other end of the nozzle carrier for longitudinal displacement between an advanced and a retracted position relative to the nozzle carrier, a nozzle outlet provided in the end of the nozzle furthest from the nozzle carrier, a nozzle passage extending longitudinally through said nozzle and in communication with said outlet, a nozzle carrier passage extending longitudinally through said nozzle carrier having one end in communication with said nozzle passage and the other end adapted for communication with said plasticizing cylinder, a closure member disposed in said nozzle passage and axially displaceable relative thereto, said closure member including a differential piston having a passageway extending partially therethrough, one end of the piston passageway opening into said nozzle carrier passageway with the other end of the piston passageway terminating near the piston end adjacent the nozzle outlet and opening into the nozzle passageway, resilient means operatively associated with the piston for exerting thereon a predetermined pressure in the forward direction to urge the piston portion adjacent the outlet into sealing engagement with the outlet to sealingly close said nozzle passage from said outlet, said resilient means permitting rearward movement of said piston relative to the nozzle carrier upon discharge of plastic material from the plasticizing cylinder through the piston passageway into the nozzle passage under sufficient predetermined pressure to overcome the pressure of said resilient means on said piston and urgingly move said piston rearwardly relative to the nozzle and nozzle carrier thereby opening said outlet to said nozzle passage for discharge of the plastic material therethru, a locking assembly associated with said closure member comprising means engaging the closure member and slideable relative thereto between an advanced and retracted position; locking means on said sliding means adapted to lockingly engage said sliding means with said closure member in the advanced position and to disengage therefrom in the retracted position so as to lockingly engage said sliding means with said nozzle carrier in the retracted position; locking assembly resilient means operatively associated with said sliding means normally urging the same toward the advanced position; the advanced position pressing said piston portion of said closure member into engagement with said nozzle outlet, and the retracted position removing the pressure of the locking assembly resilient means from the closure member permitting the opening of the outlet by retracted movement of the closure member under pressure of the discharging plastic material independent from any influence of said locking assembly resilient means.