Apparatus for making rods or tubes having a filter

Claim 1

Apparatus for making an extruded product composed of a thermoplastic material and an abrasive filler, comprising first and second extruder barrels communicating with one another so that the output of the first extruder barrel is directed into the input of the second extruder barrel, an extruder screw in each barrel, the output of said second extruder barrel being greater than the output of said first extruder barrel, motor means for rotating the screws, means for heating the extruder barrels, a first hopper communicating with the inlet end of the first barrel for introducing thermoplastic material to said first barrel, said second hopper communicating with said second barrel downstream from the inlet end of said second barrel for introducing abrasive particles to said second barrel, an extrusion die coupled to the outlet end of the second extruder barrel, whereby said thermoplastic material may be introduced into the first extruder barrel from the first hopper, melted in said barrel, and said abrasive filler may be introduced from the second hopper into the melted thermoplastic material, and the mixture extruded through at least one orifice on the die.