US 5,629,028 AGranted

Underwater pelletizer having sealed heat transfer tubes embedded in extrusion die

AssigneeThe Conair Group, Inc.

InventorWalter Trumbull

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Abstract

An improved underwater pelletizer is provided. The improved pelletizer has sealed heat transfer tubes embedded within the extruder die to utilize the heat of the molten polymer entering the extruder die by efficiently transferring that heat to the die plate and die face of the pelletizer. Ceramic inserts and/or inserts of other insulating materials are provided adjacent the die plate to insulate the passages through which the molten polymer passes and to inhibit cooling of the polymer within the extruder die as it approaches the die plate. The insulating inserts are positioned behind, and abut, the die plate around the passages that deliver the molten polymer to the die plate. Water makeup is provided at the cutter blades of the pelletizer to prevent cavitation within the water housing so that pellets will not agglomerate within the water housing.

Claims22

Dependent claims

In an underwater pelletizer with a die face having a plurality of die orifices extending therethrough through which continuous strands of molten polymer are extruded, a cutter blade assembly abutting the die face and including blades for cutting said strands of molten polymer into pellets and a water housing enclosing the said die face and said cutter blade assembly to entrain said pellets in a flow of water, the improvement comprising:

a transition piece for receiving molten polymer at one end and for supporting a die plate at said die face at its other end;
said transition piece having longitudinal passages therethrough to permit movement of molten polymer to said die plate;
a plurality of heat transfer tubes secured longitudinally within said transition piece, said heat transfer tubes each formed as an enclosed body with heat transfer fluid entrapped within said enclosed body so that heat is transferred efficiently from one end of said heat transfer tube to the other end whereby heat from the molten plastic entering said transition piece aids in heating said die plate at said die face on the other end of said transition piece;
a plurality of annular insulating inserts fixed within said transition piece and forming the ends of said longitudinal passages closest to said die face whereby said insulating inserts inhibit cooling of said molten plastic as it progresses through said transition piece;
said cutter blade assembly having a hollow shaft through which water is introduced to a cutter blade holder holding said cutter blades against said die plate;
and
water exit nozzles formed in said cutter blade holder ahead of each cutter blade whereby water from said hollow shaft is directed into said water housing ahead of each cutter blade to prevent cavitation of the water in said water housing as said cuter blade holder turns.

4 more elements

Dependencies are inferred from the claim text.