Check valve arrangement for the discharge end of an extruder, plastifier or the like

Claim 1

The combination with a plastifying worm in a plastifying cylinder for plastifying a synthetic resin and displacing it in a direction past an end of said worm, of a backflow preventing valve formed on said end of said worm, said valve comprising: a valve seat formed by an upstream surface, a neck extending from said upstream surface in a downstream direction, and a tip mounted on said neck and having a downstream surface turned toward said upstream surface; a valving ring disposed between said surfaces and engageable with said seat while surrounding said neck with clearance to define a flow passage for said resin between said neck and said ring; and spacer means between said ring and said downstream surface, said downstream surface and a confronting complementary surface of said ring being shaped to enable radial removal of said spacer means upon the emergence of said valve from said sealing, said ring having an inner diameter greater than the outer diameter of said tip, said spacer means comprising a plurlaity of balls received between said downstream surface and said complementary surface of said ring, said downstream surface and said complementary surface being frustoconical and diverging outwardly from said axis to a downstream direction, said downstream surface, said neck, said complementary surface and said cylinder being so dimensioned that said balls bear radially directly against said cylinder and said downstream and complementary surfaces being substantially parallel.