Apparatus for making chips of thermoplastic material
OwnerLuigi Porroinventor
Life of this patent
Estimating the term…
Abstract
A die for extruding filaments from molten plastic material such as polyethylene or polypropylene is heated until steady extrusion conditions are reached. The direct heating is then stopped, so that the die is only partially heated from the molten material while it is extruded. The extruded filaments are sheared by a blade interacting with the die. The resulting chips are cool enough for flowing to an outflow hopper without sticking to one another or to the blade. Sticking is further prevented by maintaining a strong cooling air stream within the hopper and around the blade and by making the extrusion holes in the die diverge at their output ends and by arranging them near the periphery of the die for maximum mutual distance.
Claims1
An apparatus for making chips of a thermoplastic material such as polyethylene or polypropylene, comprising:
- a die for extruding filaments and having heating means;
- a rotatable shearing tool having one shearing blade, operatively associated with the die for shearing the filaments into chips;
- an enclosure surrounding the shearing tool and the die, for leading the chips away from the shearing area and toward an outflow aperture;
- a hopper placed beneath the outflow aperture of the enclosure for collecting the chips;
- a rotatable impeller located immediately adjacent the lower outlet end of said hopper and cooperating with the hopper for generating an air stream into the hopper and the enclosure, said air stream cooling said shearing blade, and wherein the die comprises a mandrel having a flat plate-like portion and a rearwardly extending conical apex, a cylinder housing the mandrel and a breaker plate engaging the apex of the mandrel, said cylinder defining an extrusion chamber between its inner surface and the conical apex of said mandrel, said flat plate-like portion having extrusion holes in at least two coaxial circular arrays near the periphery thereof, the arrays being displaced by half an angular pitch with respect to each other, said extrusion holes extending at an angle relative to the axis of the die in a radial plane from a point near the center of said extrusion chamber to a point near the periphery of said flat plate-like portion and tapering from said extrusion chamber to said flat plate-like portion.
Dependencies are inferred from the claim text.