Patent ID: 9469062
Filing Date: 2016-10-18
CPC Classification: B29B,B29C,B29K

Claim Text:
1. A rotary joint for transferring melted plastic from at least one extruder to a plurality of molds of a rotary machine for molding preforms, the rotary joint comprising a fixed structure provided with a fixed longitudinal element therein, defining a longitudinal axis Y, wherein a first passage channel is provided within said fixed longitudinal element, a movable structure adapted to rotate about said longitudinal axis Y and adapted to be integrally fixed to the rotary machine, comprising in turn: wherein a gap is provided between the fixed structure and the movable structure, wherein a spiral seal is arranged in a part of said gap for ensuring the action of sealing the melted plastic between said fixed structure and said movable structure, wherein said spiral seal comprises a single- or multi-start spiral groove made on an inner surface of said central cylindrical through cavity facing a smooth outer surface of said fixed longitudinal element, said spiral groove being helical and defining an inclined helix so as to oppose, with its rotation motion, a natural exiting direction of a melted plastic flow into the gap, wherein the helix is inclined by an angle no greater than 45° with respect to a plane orthogonal to the longitudinal axis Y.