Extruder screw having paths within the screw, extruder, and extrusion method

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 axial line;

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, in each of which the raw material flows,

wherein:

the screw main body includes hollow cylindrical members and a rotation axis supporting the cylindrical members,

the conveyance portions and the barrier portions are respectively provided in the cylindrical members and alternately arranged along the axial direction of the screw main body,

the respective path is provided entirely through the respective barrier portion and extends at least partially into the two conveyance portions adjacent to respective sides of the respective barrier portion, and comprises an entrance opened in the outer circumferential surface of the respective cylindrical member in one side of the respective conveyance portion 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 surface of the respective cylindrical member on an other side of the respective conveyance portion 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 respective cylindrical member and connecting between the entrance and the exit, and

the raw material flowing into the entrance flows towards the exit in a same 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.