Heated injection nozzle

Claim 1

In an injection-molding machine including a hot-runner structure with a sprue channel for conveying liquefied plastic material to an injection gate of a mold plate, said sprue channel being formed in part by a nozzle with a tubular body of good thermal conductivity having a downstream extremity in engagement with said mold plate, and heater means closely surrounding said body in the vicinity of said gate, the improvement wherein said nozzle is provided with a highly heat-conductive tubular insert defining a terminal part of said sprue channel, said insert being received in an annular recess of said body and having a tip separated from said extremity by a surrounding clearance occupied by an annular heat shield; said heater means comprising an annular shell externally seated on a portion of said body adjacent said extremity and spacedly surrounded by the wall of a bore formed in a cooled supporting member, said nozzle being provided at an end remote from said extremity with a skirt separated by a substantially cylindrical air gap from said body and bearing upon said supporting member, said air gap having an outer diameter exceeding that of said shell and substantially corresponding to that of said bore whereby an annular space accommodating said shell in spaced relationship with said supporting member is formed around said body.