JP2001145951A - Extrusion die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extrude even a thin-walled tubular body in such a shape that the wall thickness is uniform. SOLUTION: An extrusion die 1 is for extruding a tubular body and a resin flow path 20 is formed by fitting a head member 2 to the outside of a mandrel 10. The outer face of the mandrel 10 has a tapered and truncated conical part 11, a truncated conical flow path forming part 12 and a columnar flow path forming part 13 sequentially formed from the rear end to the forward end. In addition, the truncated conical flow path forming part 12 has a branched flow path 21 formed on the rear end and also has a diverted flow part 30 having a groove part 30a for communication formed on the outer peripheral face, provided at the downstream side. On the other hand, the head member 2 has a tapered and truncated conical hole 3 which is fitted airtightly to the truncated conical part 11 of the mandrel 10 and forms a resin flow path 20 opposite to the truncated conical flow path forming part 12. Further, the outer peripheral face of the diverted part 30 is supported in contact with the inner peripheral face of a truncated conical hole 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion die capable of extruding a tubular body having a uniform thickness.

[0002]

2. Description of the Related Art A spider type pipe die generally used for extruding a tubular body is caused by a spider because a mandrel inserted into a flow passage forming hole of a die body is supported via a spider. Spider marks appear. In particular, in an extrusion die of a multilayer tubular body,
When the spider mark occurs, there is a possibility that a trouble such as an uneven layer configuration of the extruded multilayer tubular body may occur.

The extrusion die for a tubular body to be described below is devised so that the above-mentioned spider mark does not occur.

As shown in FIG. 3, the extrusion die includes a mandrel 101 and a first head member 102 and a second head member 1 which are sequentially fitted to the outside of the mandrel 101.
03 and the third head member 104, the first flow path 105 for the inner layer, the second flow path 106 for the intermediate layer, the third flow path 107 for the outer layer, and the first flow path 105
A first merging passage 108 where the first and second merging passages 106 merge,
A second merging channel 109 is formed in which the first merging channel 108 and the third merging channel 107 merge.

[0005] The first flow path 105 has a branch flow path 120 at the upper end in the figure and a branch flow path 1.
A throttle portion 113 is provided adjacent to the downstream side of 20, and the branch channel 120 is communicated with a first resin supply channel 123 provided in the first head member 102. The second flow path 106 has a branch flow path 121 at the upper end in the figure.
And a throttle 114 is provided adjacent to the downstream side of the branch channel 121.
Is connected to a second resin supply channel 124 provided in the second head member 103. Further, the third flow path 10
7 is provided with a branch flow path 122 at the upper end in the figure and a throttle unit 115 adjacent to the downstream side of the branch flow path 122.
Are provided, and the branch flow path 122 is communicated with a third resin supply flow path 125 provided in the third head member 104.

The mandrel 101 includes a tapered frusto-conical portion 110, a frusto-conical flow path forming portion 111 following the frusto-conical portion 110, and a flow path forming portion 111. A cylindrical member 112 is provided, and a core member 113 is provided at a lower end of the cylindrical portion 112.

[0007] The first head member 102 is sequentially arranged from the upper part of the figure to the lower part in the figure.
10 is a truncated conical hole 10 which can be fitted airtightly and can face the flow path forming portion 111 of the mandrel 101.
2a and a circular hole 102b that can face the cylindrical portion 112 of the mandrel 101 following the truncated conical hole 102a, and the truncated conical hole 102a is formed in the truncated conical portion 110 of the mandrel 101. By fitting to the first
Is formed. On the outer surface of the first head member 102, a tapered frustoconical portion 102c and a frustoconical portion 102
A flow path forming portion 102d having a tapered frustoconical shape following c is provided.

The second head member 103 has the same structure as the first head member 102, and has a frusto-conical hole 103a formed in the frusto-conical portion 102 of the first head member 102.
By fitting into c, the second resin flow path 106 is formed, and the first junction flow path 108 is formed between the second resin flow path 106 and the cylindrical portion 112 of the mandrel 101.

The third head member 104 can be fitted hermetically into the frusto-conical portion 103c of the second head member 103 in order from the upper side to the lower side in the figure, and the flow path forming portion of the second head member 103. The truncated cone 104a has a truncated conical hole 104a that can oppose the truncated conical hole 104a and a circular hole 104b that can oppose the cylindrical portion 112 of the mandrel 101 following the truncated conical hole 104a. The hole 104a is formed in the frusto-conical portion 10 of the second head member 103.
3c, a third resin flow path 107 is formed, and a second merging path 109 is formed between the third resin flow path 107 and the cylindrical portion 112 of the mandrel 101.
0-235711).

[0010]

In the above prior art,
If the pressure of the molten resin flowing in the resin flow path fluctuates or the pressure distribution becomes non-uniform, the interval between the resin flow paths changes and the thickness of the extruded tubular body becomes non-uniform. In particular, when a thin-walled tubular body is extruded, that is, when the discharge amount of the molten resin is small, the molten resin is not uniformly distributed in the circumferential direction in the resin flow path, and so-called resin breakage may occur. There is a problem.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to realize an extrusion die that can extrude a thin-walled tubular body with a uniform thickness. It is assumed that.

[0012]

In order to achieve the above object, an extrusion die according to the present invention comprises a mandrel and a head member fitted outside the mandrel, and a mandrel is provided between the mandrel and the head member. In the extrusion die for extruding the tubular body from the formed resin flow path, the outer surface of the mandrel is tapered frusto-conical, tapered frusto-conical following the frusto-conical in order from the rear end to the front end. A flow path forming part, wherein the truncated conical flow path forming part is provided with a branch flow path into which a molten resin is introduced at a rear end and divides the molten resin into a plurality of flows downstream. The head member is fitted in a frusto-conical portion of the mandrel in an air-tight manner, and the truncated conical flow of the mandrel is provided. Road formation A tapered frusto-conical hole that forms the resin flow path in opposition to the outer peripheral surface of the diversion portion of the mandrel abuts and supports the inner peripheral surface of the frusto-conical hole of the head member. It is characterized by having been done.

[0013] Further, a multilayer tubular body comprising a mandrel and a plurality of head members sequentially fitted to the outside of the mandrel, and having a plurality of resin flow paths and a combined flow path sequentially formed outside the mandrel, is extruded. In the extrusion die,
The outer surface of the mandrel and the intermediate head member of the plurality of head members are sequentially tapered from the rear end to the front end, and the tapered frusto-conical portion, the tapered frusto-conical flow following the frusto-conical portion, respectively. A channel forming portion, and a branch channel into which a molten resin is introduced is provided at a rear end of the truncated conical channel forming portion. On the other hand, the plurality of the plurality of channels fitted sequentially outside the mandrel are provided. The head member is provided with a tapered frusto-conical hole that fits tightly into the frusto-conical portion and forms each resin flow path facing the frusto-conical flow path forming portion. In at least one of the head members, a communication groove for dividing the molten resin into a plurality of flows is formed on the outer peripheral surface on the downstream side of the branch flow path of the truncated conical flow path forming portion. A diverting section is provided. The outer peripheral surface of, and which is characterized in that the inner peripheral surface of the frusto-conical hole of the mated head member outside is supported in contact.

[0014]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an extrusion die according to an embodiment, in which (a) is a schematic cross-sectional view, and (b) is a schematic partial cross-sectional view along the line AA in (a).

The extrusion die 1 according to the present embodiment is for extruding a single-layer tubular body, and the resin channel 20 is formed by fitting the head member 2 to the outside of the mandrel 10. Have been.

The mandrel 10 includes a tapered frusto-conical portion 11, a tapered frusto-conical flow path forming portion 12 following the frusto-conical portion 11, and a frusto-conical flow from the rear end to the front end. A cylindrical flow path forming part 13 following the path forming part 12 is provided, and a tapered frusto-conical core member 10a is integrally provided at the tip of the cylindrical flow path forming part 13.

The frusto-conical flow path forming section 12 of the mandrel 10 has a branch flow path 21 at the rear end, and a first throttle section 22 downstream of the branch flow path 21 sequentially. , A first pressure relieving portion 23, a diversion portion 30, in which a plurality of linear communication grooves 30a are formed at intervals in the circumferential direction, a second pressure relieving portion 25, and a second throttle portion 26. Is provided.

The head member 2 can be fitted to the frusto-conical portion 11 of the mandrel 10 in an airtight manner in order from the rear end to the front end, and the frusto-conical flow path forming portion 1 of the mandrel 10 can be formed.
2 is provided with a different diameter through-hole 5 having a tapered frusto-conical hole 3 capable of forming a resin flow path 20 opposite thereto and a circular hole 4 penetrating to the tip following the frusto-conical hole 3. . A die lip 6 having a tapered frusto-conical hole 6 a communicating with the circular hole 4 is provided on the distal end surface 2 b of the head member 2.
It is mounted so as to be centerable via a holding member 7 detachably fixed by bolts 8.

The mandrel 10 inserted into the different diameter through hole 5 of the head member 2 is integrated by fixing a flange portion 14 provided at the rear end to a rear end surface 2a of the head member 2 with a bolt (not shown). Since the outer peripheral surface of the flow dividing portion 30 is supported by being in contact with the inner peripheral surface of the truncated conical hole 3 of the head member 2, positioning in the axial direction and the radial direction is performed. As a result, the resin flow path 20 is formed between the mandrel 10 and the head member 2 with high precision, and the supply flow path 9 provided in the head member 2 and the branch flow path 21 provided in the mandrel 10 are introduced. The mouth 21a communicates.

In the present embodiment, when the discharge port of the extruder (not shown) is connected to the supply flow path 9 provided in the head member 2 to supply the molten resin, the supplied molten resin is circulated by the branch flow path 21. It is split into a plurality of flows distributed in the direction and flows to the first throttle unit 22.

The molten resin pressurized in the first narrowing section 22 flows to the first pressure relaxing section 23 and the pressure is reduced, and then a plurality of linear resins provided on the outer peripheral surface of the branching section 30. Flows into the communication groove portion 30a, and flows into the second pressure relaxing portion 25 as a plurality of flows dispersed in the circumferential direction.
And the pressure distribution and the flow rate distribution in the circumferential direction are made uniform. Subsequently, the molten resin flows into the tubular resin flow path 20 through the second throttle portion 26 to be a stable flow, and is formed from the extrusion port 6b formed between the hole 6a of the die lip 6 and the core member 10a. Extruded as a tubular body of uniform thickness.

In the present embodiment, a plurality of linear communication grooves 30a are provided on the outer peripheral surface of the flow dividing section 30 at intervals in the circumferential direction. However, the present invention is not limited to this.
0 may be provided with a mesh-shaped communication groove on the outer peripheral surface, or may be provided with a spiral communication groove.

Next, an extrusion die according to another embodiment will be described.

As shown in FIG. 2, the extrusion die 51 fits a first head member 52, a second head member 53, and a third head member 54 sequentially outside the mandrel 60 and the mandrel 60. Thereby, the first resin flow path 81 for the inner layer, the second resin flow path 82 for the intermediate layer, the third resin flow path 83 for the outer layer, the first resin flow path 81 and the second resin flow path A first junction 84 where the path 82 merges, and a second junction 85 where the third resin channel 83 and the first junction 84 merge are formed, and are formed from the inner layer, the intermediate layer, and the outer layer. The three-layered tubular body can be extruded.

The outer surface of the mandrel 60 has a tapered frusto-conical portion 6 sequentially from the rear end flange portion 64 toward the front end.
1. Truncated conical channel forming section 62, cylindrical channel forming section 63
The core member 60a is provided at the front end of the columnar flow path forming portion 63.

In the truncated conical flow path forming portion 62 of the mandrel 60, a branch flow path 71 connected to the inner resin supply flow path 59a is provided at the rear end, and a branch flow path 71 downstream of the branch flow path 71 is provided. An aperture 72 is provided adjacent to the side.

The first head member 52 can be fitted to the frusto-conical portion 61 of the mandrel 60 in an airtight manner in order from the rear end to the front end, and faces the frusto-conical flow path forming portion 62 of the mandrel 60. A frusto-conical hole 52a through which a first resin flow path 81 can be formed, and a circular hole 52b penetrating to the front end following the frusto-conical hole 52a. Are sequentially tapered from the rear end flange portion 52e to the front end, the tapered frustoconical portion 52c, and the tapered frustoconical flow path forming portion 52d following the frustoconical portion 52c.
Are formed.

The frusto-conical flow path forming portion 52d of the first head member 52 has an intermediate resin supply flow path 5 at its rear end.
9b is provided with a branch flow path 73 connected thereto, and a branching section 90 in which a throttle section 74 and a mesh-like communication groove section 90a are formed on the outer peripheral surface in the downstream side of the branch flow path 73 sequentially.
Are provided adjacent to each other.

In the present embodiment, the mesh-shaped communication groove portion 90a is provided on the outer peripheral surface of the flow dividing portion 90. However, the present invention is not limited to this. A plurality of linear communication groove portions are provided on the outer peripheral surface of the flow dividing portion. May be provided at intervals in the circumferential direction, or may be provided with a spiral communication groove.

The second head member 53 is formed by sequentially forming the frusto-conical portion 52 of the first head member 52 from the rear end to the front end.
c and hermetically opposed to the frusto-conical flow path forming portion 52d of the first head member 52.
2 and a circular hole 53b penetrating to the front end following the truncated conical hole 53a, and a flange portion at the rear end on the outer surface. A tapered frustoconical portion 53c and a tapered frustoconical channel forming portion 53d following the frustoconical portion 53c are provided in order from 53e toward the front end.

The outer resin supply flow path 59 is formed at the rear end of the truncated conical flow path forming portion 53d of the second head member 53.
A branch channel 75 connected to the branch channel c is provided, and a throttle portion 76 is provided adjacent to the downstream side of the branch channel 75.

The third head member 54 is fitted airtightly into the frusto-conical portion 53c of the second head member 53 and faces the frusto-conical flow path forming portion 53d of the second head member 53. It has a truncated conical hole 54a in which the third resin flow path 83 can be formed, and a circular hole 54b penetrating to the front end following the truncated conical hole 54a.

On the front end face of the third head member 54, a die lip 56 having a frusto-conical extruded hole 56a communicating with the circular hole 54b is detachably fixed by a bolt 58. It is mounted so as to be freely aligned via a member 57.

The extrusion die 51 according to the present embodiment includes a flow dividing section 90 provided in a flow path forming section 52d of a first head member 52 forming a second resin flow path 82 for an intermediate layer.
Of the second head member 53 is a truncated conical hole 53a.
Are supported in contact with the inner peripheral surface of the. As a result, the distance between the second flow path forming portions 82 is maintained uniform, and a thin intermediate layer having a uniform thickness can be extruded without causing resin breakage.

In the present invention, the number of head members sequentially fitted to the outside of the mandrel is not limited to three as shown in FIG. 3, but may be two or four or more. It goes without saying that a plurality of head members can be provided accordingly.

[0037]

Since the present invention is configured as described above, the following effects can be obtained.

Since the interval between the resin flow paths for extruding the tubular body is kept uniform irrespective of the pressure distribution of the molten resin, a tubular body having a uniform thickness can be extruded stably.

[Brief description of the drawings]

FIG. 1 shows an extrusion die according to one embodiment, wherein (a)
Is a schematic cross-sectional view, and (b) is a schematic partial cross-sectional view along line AA of (a).

FIG. 2 is a schematic sectional view showing an extrusion die according to another embodiment.

FIG. 3 is a schematic sectional view showing an example of a conventional extrusion die.

[Explanation of symbols]

 1,51 Extrusion die 2 Head member 3,52a, 53a, 54a Truncated conical hole 4,52b, 53b, 54b Circular hole 5 Different diameter through hole 6,56 Die lip 7,57 Holding member 8,58 Bolt 10,60 Mandrel 10a, 60a Core member 11, 52c, 53c, 54c, 61 Truncated conical portion 12, 52d, 53d, 62 Truncated conical channel forming portion 13, 63 Cylindrical channel forming portion 14, 52e, 53e, 64 Flange Part 20 Resin flow path 21, 71, 73, 75 Branch flow path 22, 26, 72, 74, 76 Narrowing part 23, 25 Pressure relief part 30, 90 Dividing part 30a, 90a Communication groove part 52 First head member 53 2nd head member 54 3rd head member 81 1st resin flow path 82 2nd resin flow path 83 3rd resin flow path 84 1st merge path 85 2nd merge Channel

Claims (2)

[Claims] 1. An extrusion die, comprising: a mandrel; and a head member fitted outside the mandrel, wherein the extrusion die extrudes a tubular body from a resin flow path formed between the mandrel and the head member. The outer surface includes, in order from the rear end to the front end, a tapered frusto-conical portion, a tapered frusto-conical channel forming portion following the frusto-conical portion, and the frusto-conical channel forming portion has A branch flow path in which a molten resin is introduced at the rear end is provided, and a flow dividing portion in which a communication groove portion for dividing the molten resin into a plurality of flows is formed on the outer peripheral surface is provided on the downstream side. On the other hand, the head member is fitted in a frusto-conical portion of the mandrel in a gas-tight manner and is tapered to form the resin flow path in opposition to the frusto-conical flow path forming portion of the mandrel. With conical hole Ri, extrusion die, characterized in that the outer peripheral surface of the diverter of the mandrel is supported in contact with the inner peripheral surface of the frusto-conical hole of said head member. 2. A multi-layer tubular body comprising: a mandrel; and a plurality of head members sequentially fitted outside the mandrel, wherein a plurality of resin flow paths and a combined flow path are sequentially formed outside the mandrel. In the extrusion die, an outer surface of the mandrel and an intermediate head member among the plurality of head members are sequentially tapered from the rear end to the front end, and the tapered truncated cone portion continues from the truncated cone portion. A frusto-conical flow path forming part is provided, and a branch flow path into which the molten resin is introduced is provided at a rear end of the truncated conical flow path forming part. On the other hand, the branch flow path is fitted to the outside of the mandrel sequentially. The plurality of head members each have a tapered frusto-conical hole that fits tightly into the frusto-conical portion and forms each resin flow path facing the frusto-conical flow path forming portion. Yes, above At least one of the head members in between has a communication groove formed on an outer peripheral surface thereof for dividing the molten resin into a plurality of flows downstream of the branch flow path of the truncated conical flow path forming portion. Wherein the outer peripheral surface of the diversion portion is supported in contact with the inner peripheral surface of the truncated conical hole of the head member fitted to the outside. Die.