Face seal for shafts of machines processing synthetic resin

Claim 1

A shaft seal for a shaft running through the wall of a housing of a chamber for the processing of plasticized resin under pressure within a resin processing machine, said shaft having an enlarged first portion housed in said chamber and a second portion extending from said chamber, said second portion positioned outside of said chamber, comprising a first heat and wear resistant sealing ring, said first sealing ring having a running face placed around said second portion of said shaft and extending outward therefrom, a second heat and wear resistant sealing ring, said second sealing ring mounted on said shaft around said second portion of said shaft, said second sealing ring positioned between said first sealing ring and said first portion of said shaft, said second sealing ring having a running face which is acted upon by the running face of said first ring, a centering ring supported on said housing and secured to said second sealing ring for radially supporting said second sealing ring, a ring-like backup body having a radially extending flange secured to said first sealing ring for radially suporting said first sealing ring, a plurality of pins circumferentially spaced around said radial flange, each pin having a stop and a spring element, said spring elements being coaxially positioned around said pins, said pins being passed through said flange and fixed to said housing such that said stops are spaced a predetermined distance from said flange and said spring elements are biased between said stops and said flange, said spring elements loading said sealing rings and urging said sealing rings towards said chamber and along said shaft, and a radial clearance between said rings and said second portion of said shaft for enabling said shaft to expand in response to increases in temperature in said resin processing machine.