Screw for extruder comprising a passage crossing over between adjacent cylindrical bodies

1. A screw for an extruder, which conveys a raw material while kneading the raw material, comprising:

a screw main body having a linear axis line along a conveyance direction of the raw material, and configured to rotate around the axis line;

a conveyance portion provided on an outer peripheral surface along a circumferential direction of the screw main body and having a flight conveying the raw material in an axial direction of the screw main body when the screw main body rotates; and

a passage comprised by the screw main body and including a first passage element into which the raw material conveyed by the flight flows, a second passage element through which the raw material flowing in from the first passage element flows, and a third passage element through which the raw material having flown through the second passage element returns to the outer peripheral surface of the screw main body,

wherein the screw main body comprises a rotating shaft provided coaxially with the axis line and a plurality of cylindrical bodies coaxially inserted into an outer peripheral surface of the rotating shaft so as to rotate following the rotating shaft and arranged in the axial direction of the rotating shaft, and a barrier portion which restricts flow of the raw material due to the flight to increase a pressure of the raw material,

at least a portion of the conveyance portion is formed on outer peripheral surfaces of the cylindrical bodies adjacent to each other on the rotating shaft, and the passage is formed in the cylindrical body so as to cross over between the adjacent cylindrical bodies, and

the first passage element is provided at a position adjacent to the barrier portion.

2. The screw for an extruder according to claim 1 , wherein the cylindrical bodies adjacent to each other on the rotating shaft have end walls adhered firmly to each other,

the second passage element of the passage includes a first portion formed in one of the cylindrical bodies adjacent to each other and a second portion formed in the other cylindrical body, the first portion and the second portion extending in the axial directions of the cylindrical bodies corresponding respectively to the first and second portions and have opening ends opened in the end surfaces of the cylindrical bodies, and the opening ends communicate with each other.

3. The screw for an extruder according to claim 2 , wherein the cylindrical bodies adjacent to each other on the rotating shaft have end walls located on the opposite side of the end surfaces, an end on the opposite side of the opening end of the first portion is closed by the end wall of one of the cylindrical bodies, and an end on the opposite side of the opening end of the second portion is closed by the end wall of the other cylindrical body.

4. The screw for an extruder according to claim 3 , wherein the first portion of the second passage element is formed by machining the one cylindrical body from the side of the end surface of the one cylindrical body, and the second portion of the second passage element is formed by machining the other cylindrical body from the side of the end surface of the other cylindrical body.

5. The screw for an extruder according to claim 1 , wherein the first passage element of the passage is opened in the outer peripheral surface of the cylindrical body and communicated with the second passage element in the cylindrical body, and the third passage element of the passage is opened in the outer peripheral surface of the cylindrical body and communicated with the second passage element in the cylindrical body.

6. The screw for an extruder according to claim 5 , wherein the first passage element and the third passage element of the passage are each formed by machining the cylindrical body from the side of the outer peripheral surface of the cylindrical body.

7. The screw for an extruder according to claim 1 , wherein a bore of the second passage element is smaller than a bore of the first passage element.

8. An extruder, which comprises the screw according to claim 1 and produces a kneaded material by kneading a raw material with the screw, comprising:

a barrel in which the screw is rotatably contained;

a supply port comprised by the barrel and supplying the raw material to the screw; and

a delivery port which is comprised by the barrel and through which the kneaded material is extruded.

9. A screw for an extruder, which conveys a raw material while kneading the raw material, comprising:

a screw main body having a linear axis line along a conveyance direction of the raw material, and configured to rotate around the axis line;

a conveyance portion provided on an outer peripheral surface along a circumferential direction of the screw main body and having a flight conveying the raw material in an axial direction of the screw main body when the screw main body rotates; and

a passage comprised by the screw main body and including a first passage element into which the raw material conveyed by the flight flows, a second passage element through which the raw material flowing in from the first passage element flows, and a third passage element through which the raw material having flown through the second passage element returns to the outer peripheral surface of the screw main body,

wherein the screw main body has a rotating shaft, provided coaxially with the axis line and a plurality of cylindrical bodies coaxially inserted into an outer peripheral surface of the rotating shaft so as to rotate following the rotating shaft and arranged in the axial direction of the rotating shaft, the rotating shaft includes a first shaft portion having a stopper portion and a second shaft portion which is coaxially extended from an end surface of the stopper portion and into which the cylindrical bodies are inserted, an end plate is fixed to an end surface on the opposite side of the stopper portion of the second shaft portion through a fastener, and a plurality of the cylindrical bodies are tightened between the end plate and the stopper portion in the axial direction of the second shaft portion, and

at least a portion of the conveyance portion is formed on outer peripheral surfaces of the cylindrical bodies adjacent to each other on the rotating shaft, and the passage is formed in the cylindrical body so as to cross over between the adjacent cylindrical bodies.

10. The screw for an extruder according to claim 9 , wherein the cylindrical bodies adjacent to each other on the rotating shaft have end walls adhered firmly to each other,

the second passage element of the passage includes a first portion formed in one of the cylindrical bodies adjacent to each other and a second portion formed in the other cylindrical body, the first portion and the second portion extending in the axial directions of the cylindrical bodies corresponding respectively to the first and second portions and have opening ends opened in the end surfaces of the cylindrical bodies, and the opening ends communicate with each other.

11. The screw for an extruder according to claim 10 , wherein the cylindrical bodies adjacent to each other on the rotating shaft have end walls located on the opposite side of the end surfaces, an end on the opposite side of the opening end of the first portion is closed by the end wall of one of the cylindrical bodies, and an end on the opposite side of the opening end of the second portion is closed by the end wall of the other cylindrical body.

12. The screw for an extruder according to claim 11 , wherein the first portion of the second passage element is formed by machining the one cylindrical body from the side of the end surface of the one cylindrical body, and the second portion of the second passage element is formed by machining the other cylindrical body from the side of the end surface of the other cylindrical body.

13. The screw for an extruder according to claim 9 , wherein the first passage element of the passage is opened in the outer peripheral surface of the cylindrical body and communicated with the second passage element in the cylindrical body, and the third passage element of the passage is opened in the outer peripheral surface of the cylindrical body and communicated with the second passage element in the cylindrical body.

14. The screw for an extruder according to claim 13 , wherein the first passage element and the third passage element of the passage are each formed by machining the cylindrical body from the side of the outer peripheral surface of the cylindrical body.

15. The screw for an extruder according to claim 9 , wherein a bore of the second passage element is smaller than a bore of the first passage element.

16. An extruder, which comprises the screw according to claim 9 and produces a kneaded material by kneading a raw material with the screw, comprising:

a barrel in which the screw is rotatably contained;

a supply port comprised by the barrel and supplying the raw material to the screw; and

a delivery port which is comprised by the barrel and through which the kneaded material is extruded.

17. A screw for an extruder, which conveys a raw material while kneading the raw material, comprising:

a screw main body having a linear axis line along a conveyance direction of the raw material, and configured to rotate around the axis line;

a conveyance portion provided on an outer peripheral surface along a circumferential direction of the screw main body and having a flight conveying the raw material in an axial direction of the screw main body when the screw main body rotates; and

a passage comprised by the screw main body and including a first passage element into which the raw material conveyed by the flight flows, a second passage element through which the raw material flowing in from the first passage element flows, and a third passage element through which the raw material having flown through the second passage element returns to the outer peripheral surface of the screw main body,

wherein the passage is provided at a position deviated from the axis line of the screw main body and configured to revolve around the axis line when the cylindrical body rotates following the rotating shaft,

the screw main body has a rotating shaft, provided coaxially with the axis line and a plurality of cylindrical bodies coaxially inserted into an outer peripheral surface of the rotating shaft so as to rotate following the rotating shaft and arranged in the axial direction of the rotating shaft, and

at least a portion of the conveyance portion is formed on outer peripheral surfaces of the cylindrical bodies adjacent to each other on the rotating shaft, and the passage is formed in the cylindrical body so as to cross over between the adjacent cylindrical bodies.

18. The screw for an extruder according to claim 17 , wherein the cylindrical bodies adjacent to each other on the rotating shaft have end walls adhered firmly to each other,

the second passage element of the passage includes a first portion formed in one of the cylindrical bodies adjacent to each other and a second portion formed in the other cylindrical body, the first portion and the second portion extending in the axial directions of the cylindrical bodies corresponding respectively to the first and second portions and have opening ends opened in the end surfaces of the cylindrical bodies, and the opening ends communicate with each other.

19. The screw for an extruder according to claim 18 , wherein the cylindrical bodies adjacent to each other on the rotating shaft have end walls located on the opposite side of the end surfaces, an end on the opposite side of the opening end of the first portion is closed by the end wall of one of the cylindrical bodies, and an end on the opposite side of the opening end of the second portion is closed by the end wall of the other cylindrical body.

20. The screw for an extruder according to claim 19 , wherein the first portion of the second passage element is formed by machining the one cylindrical body from the side of the end surface of the one cylindrical body, and the second portion of the second passage element is formed by machining the other cylindrical body from the side of the end surface of the other cylindrical body.

21. The screw for an extruder according to claim 17 , wherein the first passage element of the passage is opened in the outer peripheral surface of the cylindrical body and communicated with the second passage element in the cylindrical body, and the third passage element of the passage is opened in the outer peripheral surface of the cylindrical body and communicated with the second passage element in the cylindrical body.

22. The screw for an extruder according to claim 21 , wherein the first passage element and the third passage element of the passage are each formed by machining the cylindrical body from the side of the outer peripheral surface of the cylindrical body.

23. The screw for an extruder according to claim 17 , wherein a bore of the second passage element is smaller than a bore of the first passage element.

24. An extruder, which comprises the screw according to claim 17 and produces a kneaded material by kneading a raw material with the screw, comprising:

a barrel in which the screw is rotatably contained;

a supply port comprised by the barrel and supplying the raw material to the screw; and

a delivery port which is comprised by the barrel and through which the kneaded material is extruded.