Rotary joint for transferring melted plastic

摘要

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 joint comprising a fixed structure (3′) provided with a fixed longitudinal element (23) therein, defining a longitudinal axis (Y), and a movable structure (3″) which can rotate about said axis (Y) and is adapted to be integrally fixed to the rotary machine; wherein a first passage channel (11) is provided within said fixed element (23); wherein a second passage channel (11′) is provided within said movable structure (3″) and coaxial to said first passage channel; said second passage channel (11′) being in communication at a first end thereof with said first passage channel (11), and being in communication at a second end thereof with a plurality of lateral radial channels (52) provided within said movable structure (3″); wherein there is provided, between the fixed structure (3′) and the movable structure (3″), a gap in which a spiral seal (24) is arranged for ensuring the action of sealing the melted plastic between said fixed structure and said movable structure.

主权项

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:
a) a first rotary element, arranged above said fixed longitudinal element and adapted to be integrally fixed to the rotary machine, said first rotary element being provided with a second passage channel coaxial to said first passage channel, said second passage channel being in communication at a first end thereof with said first passage channel, and being in communication at a second end thereof with a plurality of lateral radial channels, said lateral radial channels being provided within said first rotary element,b) a second rotary element arranged underneath the first rotary element and integrally fixed thereto, said second rotary element being provided with a central cylindrical through cavity in which a first end of said fixed longitudinal element is coaxially accommodated, 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.