Extruder screw having paths within the screw, extruder, and extrusion method
An extruder screw conveying raw materials while kneading them includes a screw main body, conveyance portions, barrier portions, and paths. The conveyance portions convey the raw materials in an axial direction. The paths each include an entrance and an exit. The raw materials, the conveyance of which is limited by the barrier portions, flow in from the entrance. The raw materials flowing in from the entrance flow through the paths in an opposite direction to a conveyance direction. The exit is opened in the outer circumferential surface of the screw main body at a position outside the conveyance portions in which the entrance is opened.
1. An extruder screw configured to convey a raw material while kneading the raw material, comprising:
a screw main body having a straight axial line in a conveyance direction of the raw material, and configured to rotate on the straight axial line, the screw main body comprising cylindrical tubes and an axis of rotation supporting the cylindrical tubes;
conveyance portions provided with a space between the conveyance portions in an axial direction of the screw main body, and configured to convey the raw material in the axial direction along an outer circumferential surface extending in a circumferential direction of the screw main body with rotation of the screw main body;
barrier portions provided on the screw main body, and configured to limit conveyance of the raw material at positions adjacent to the conveyance portions; and
paths provided inside the screw main body, and in which of each, the material is allowed to flow,
wherein:
the conveyance portions and the barrier portions are each provided on the cylindrical tubes, and disposed along the axial direction of the screw main body, and
the paths each comprise:
an entrance opened in outer circumferential surfaces of the cylindrical tubes in the conveyance portions to cause the raw material, the conveyance of which is limited by the barrier portions to increase pressure on the raw material, to flow in,
an exit opened in the outer circumferential surfaces of the cylindrical tubes to allow the flowing raw material to flow out to the outer circumferential surface of the screw main body, and
a path main body provided inside the cylindrical tubes and connecting between the entrance and the exit,
inside one said barrier portion and inside said two conveyance portions adjacent to respective sides of the barrier portion,
the respective path is provided entirely through the barrier portion and entirely through the two conveyance portions adjacent to the respective sides of the barrier portion,
the entrance is provided in a downstream end of one of the two conveyance portions,
the exit is provided in an upstream end of another of the two conveyance portions, and
the raw material flowing into the entrance flows towards the exit in an opposite direction to a conveyance direction of the conveyance portions.
2. The extruder screw of claim 1 , wherein the screw main body extends in the axial direction from a basal end coupled to a rotating device to a tip,
each of the conveyance portions is provided with a flight spirally twisted along the outer circumferential surface of the screw main body, and
from a perspective of a basal end side, the flight is twisted from the basal end toward the tip of the screw main body in a same direction as a rotation direction of the screw main body.
3. The extruder screw of claim 2 , wherein each of the barrier portions is provided with a barrier annular body continuing in the circumferential direction along the outer circumferential surface of the screw main body, and
the barrier annular body is formed to have a cylindrical surface concentrically continuing in the circumferential direction with the axial line as a center.
4. The extruder screw of claim 2 , wherein each of the barrier portions is provided with a barrier flight spirally twisted along the outer circumferential surface of the screw main body, and
from the perspective of the basal end side, the barrier flight is twisted from the basal end toward the tip of the screw main body in an opposite direction to the rotation direction of the screw main body.
5. The extruder screw of claim 1 , wherein the screw main body extends in the axial direction from a basal end coupled to a rotating device to a tip,
each of the conveyance portions is provided with a flight spirally twisted along the outer circumferential surface of the screw main body, and
from a perspective of a basal end side, the flight is twisted from the basal end toward the tip of the screw main body in an opposite direction to a rotation direction of the screw main body.
6. The extruder screw of claim 5 , wherein each of the barrier portions is provided with a barrier annular body continuing in the circumferential direction along the outer circumferential surface of the screw main body, and
the barrier annular body is formed to have a cylindrical surface concentrically continuing in the circumferential direction with the axial line as a center.
7. The extruder screw of claim 5 , wherein each of the barrier portions is provided with a barrier flight spirally twisted along the outer circumferential surface of the screw main body, and
from the perspective of the basal end side, the barrier flight is twisted from the basal end toward the tip of the screw main body in a same direction as the rotation direction of the screw main body.
8. An extruder comprising the extruder screw of claim 1 and configured to knead the raw material with the extruder screw and continuously produce and extrude the kneaded material, the extruder comprising:
a barrel comprising a cylinder in which the extruder screw is rotatably inserted;
a supply port through which the raw material is supplied to the cylinder, the supply port being provided in the barrel; and
a discharge port through which the kneaded material is extruded, the discharge port being provided in the barrel.
9. An extrusion method of kneading the raw material with the extruder screw of claim 1 and continuously producing and extruding the kneaded material, the extrusion method comprising:
conveying the raw material in the axial direction by the conveyance portions of the screw main body;
limiting the conveyance of the raw material by the barrier portions of the screw main body to increase the pressure on the raw material;
causing the raw material, the pressure on which is increased, to flow into the paths provided inside the screw main body and flow through the paths in the opposite direction to the conveyance direction of the conveyance portions; and
returning the raw material flowing through the paths to the outer circumferential surface of the screw main body at the position outside the conveyance portions in which the entrance is opened.