JPH0586737B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an extrusion nozzle used in extrusion forming plastics, and is particularly applicable to the production of plastic pellets.

<Prior Art> In the production of plastic pellets, soft string-like plastic extruded from an extrusion nozzle is immediately cut into predetermined dimensions, or after being cooled in water or with cold air, it is cut into predetermined dimensions.

<Problems to be Solved by the Invention> When cutting a string-like plastic extruded from a nozzle into pellets, it is preferable to cut it immediately after it comes out of the nozzle. However, the plastic material inside the extruder is still in a liquid state at high temperatures, and even though the nozzle has a certain thickness, it is still sticky immediately after passing through the nozzle, and even if it is cut with a cutter, it will still be sticky. However, there is a problem in that the cut pieces stick together again due to their own stickiness.

Further, when the nozzle material is worn out over many years of use, the dimensional accuracy decreases, so a wear-resistant material is required. However, although hard materials generally have excellent wear resistance, they are difficult to cut and have a high melting point or sintering temperature.

For example, although ceramic is hard, cutting it after firing is extremely difficult and requires a long time to grind. Also,
Materials with high firing or casting temperatures require high temperature resistance in their molds, and such materials are not easy to process and difficult to obtain into complex shapes.

In addition, the "core" in casting technology must be extracted after casting, and usually has a tapered draft angle, but if there is a minimum point of cross-sectional area between the two ends, it is necessary to extract it. The problem is that it is not possible.

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide an extrusion nozzle in which a plastic material is rapidly cooled while passing through the extrusion nozzle, and when it exits the nozzle, it is no longer sticky and solidifies to a state where it can be cut. It is.

A second object of the present invention is to provide a method for manufacturing an extrusion nozzle that can be manufactured easily and at low cost even when such an extrusion nozzle is made of ultra-hard material such as ceramics.

<Means for solving the problems> The configuration of the extrusion nozzle of the present invention is a device that is attached to the tip of an extruder and has a large number of through holes formed in a flat plate of a predetermined thickness. The entrance side opening of the through hole is rounded, and a valley line runs along the axis from a position offset toward the entrance side from the midpoint of the predetermined thickness to the exit side opening, and the depth of the valley is the same as the exit side. It is characterized by a plurality of radial grooves that become deeper as they get closer to the opening.

In the present invention, "the entrance side opening of the through hole is rounded" means that the circular ridgeline of the entrance side opening 3 of the through hole 2 is rounded, as shown in FIG. As a result, this means that the cross section passing through the axis of the through hole 2 is formed in a substantially arc shape. In other words, the diameter d of the through hole in the entrance side opening 3 is a constant value d at a predetermined depth or more from the entrance side surface. However, when it becomes shallower than the predetermined depth, it means a shape that increases in inverse proportion to the square of the depth.

In addition, in the present invention, "a plurality of grooves are carved radially" means that the vertical cross-sectional view is shown in FIG.
As shown in the side view seen from the exit side in Figure 2, 1
The grooves 5 are carved from the inner surface of the through hole 2 along the radial direction of the through hole, and the plurality of grooves 5, 5 are arranged almost equally along the circumferential direction of the inner surface of the through hole 2. means.

In addition, the method for manufacturing an extrusion nozzle of the present invention has a minimum point B of the cross-sectional area at a position offset from the midpoint M, and expands in a tapered manner toward the end near the minimum point B. , a plurality of protrusions are formed radially along the axial direction toward the far end from the minimum point B, and the height of the ridge line increases as it approaches the far end; A core is used that has holding parts extending outward in the axial direction from both ends and is made of a material whose melting point is higher than the temperature during molding, and this core is placed at a predetermined position in the mold in the same direction. After forming the extrusion nozzle,
The feature is that the core is removed.

As a means of removing the core, heat melting, tensile fracture,
Methods include dissolving with chemicals and splitting the core into two.

<Example> FIG. 1 shows a sectional view of an extrusion nozzle according to an example of the present invention, and FIG. 2 shows a side view as seen from the material outlet side.

The nozzle attached to the tip of the extruder is a flat plate 1 of a predetermined thickness with a large number of through holes 2 formed therein. The shape of this through hole 2 is on the material entrance side,
That is, the opening 3 on the side facing the extruder is rounded,
The minimum point A of the penetration area is located at a position deviated toward the entrance side from the midpoint M of the thickness of the flat plate, and a plurality of grooves 5, 5 are formed from the minimum point A to the opening 4 on the exit side of the material. carved in a radial pattern. The shape of the single groove 5 is such that the valley line runs along the axial direction, and the depth of the valley becomes deeper as it approaches the outlet opening 4. Further, the inner diameter of the portion where no groove is formed is also tapered so as to gradually increase as it approaches the outlet opening 4. Note that piping 6, 6 is provided for each groove of the outlet opening 4, through which cooling water or cold air can be sent into the groove.

The material entering the through hole 2 having such a shape has a rounded entrance, so the resistance when entering the through hole is small, and after passing through the minimum point A, the contact area is reduced due to the groove, and furthermore, Because the inner diameter gradually increases, the material passes through the through hole without resistance, and the material is rapidly cooled while passing through the nozzle by cooling water or cold air supplied into the groove, changing from a liquid state to a solid state. It is ejected outside the nozzle.

Next, an example of a manufacturing method when the extrusion nozzle of the present invention is made of ceramics will be described.

FIG. 3 shows a core 10 used in the manufacturing method of the present invention.
shows. This core 10 has a minimum point B of cross-sectional area at a position offset from the midpoint M, and expands in a tapered shape toward the end 11 near the minimum point B.
A taper is formed that gradually expands toward the end 12 far from the minimum point B, and a plurality of protrusions 1 are formed.
8 and 18 are formed radially. The shape of the single protrusion 18 is such that the ridge line runs along the axial direction, and the height of the protrusion increases as it approaches the end portion 12. In addition, a holding portion 1 extending outward from both ends 11 and 12 is provided.
3 and 14 are formed. This core 10 is held by a lower mold 15 and an upper mold 16 as shown in FIG.
They are arranged in parallel in the same direction to form a mold. Using this mold, alumina powder, sintering aid, organic binder,
A ceramic material mixed with a solvent is cast and formed. After the molded product is removed from the mold, the core is melted and removed by heating, and the ceramic is then sintered to obtain the product of the present invention. The melted and removed core material can be remolded and reused.

As another manufacturing method of the present invention, after the ceramic material is molded, a tensile load may be applied to both ends of the core 10 to cause tensile fracture and removal.

In addition, as yet another manufacturing method, a removable fitting portion may be provided at the minimum point B of the core to form a two-part structure, and the core may be removed non-destructively.

FIG. 5 shows a side view of another embodiment of the core.
The radial protrusions of this core consist of two protrusions 19a along one plane P passing through the axis, and two protrusions 19b perpendicular to the plane P, upper and lower. Therefore, it can be molded using a two-part mold.

The core of the present invention can be made of various materials. Above all, glass has the advantages of being easy to mold with a mold, withstanding the high pressures used when forming ceramics, having a smooth surface, being easy to regenerate after melting and removal, and having low material costs. .

The extrusion nozzle of the present invention is not limited to ceramics, but can also be made of castable metal.

<Effects of the Invention> According to the extrusion nozzle of the present invention, the material passes through the nozzle while being cooled by direct contact with the cold air, so the material is cooled in an extremely short period of time before it reaches the nozzle outlet, leading to cutting. It is solidified to a viscosity suitable for processing.

In addition, in the method of the present invention, the core is removed after molding by melting, tensile fracture, etc., so it can be manufactured easily and at low cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the extrusion nozzle of the present invention, FIG. 2 is a side view seen from the outlet side of FIG. 1,
FIG. 3 is a front view showing the core 10 used in the manufacturing method of the present invention, FIG. 4 is a sectional view showing a mold used in the manufacturing method of the present invention, and FIG. 5 is a front view showing the core 10 used in the manufacturing method of the present invention. FIG. 3 is a side view showing a modified example of the core. 1...Flat plate, 2...Through hole, 3...One end of the through hole, 4...Other end of the through hole, 5...Groove, 10... Core, 18...Protrusion, 19a, 19b...Protrusion .

Claims (1)

[Scope of Claims] 1. A device that is used by being attached to the tip of an extruder, in which a large number of through holes are formed in a flat plate of a predetermined thickness, and each of the through holes has a rounded inlet side opening, and is used by being attached to the tip of an extruder. A valley line runs along the axis from a position offset toward the inlet side from the midpoint of the predetermined thickness to the outlet side opening,
An extrusion nozzle characterized in that a plurality of grooves are radially carved, the depth of the groove becoming deeper as it approaches the outlet side opening. 2. The extrusion nozzle according to claim 1, which is made of ceramics. 3 The minimum point B of the cross-sectional area is located at a position offset from the midpoint M, and the cross-sectional area expands in a ramp-like manner toward the end near the minimum point B, and expands toward the end far from the minimum point B. A plurality of protrusions are formed radially along the axial direction, and the height of the ridge line increases as it approaches the far end, and extends outward in the axial direction from both ends. A core made of a material that has a holding part and has a melting point higher than the temperature at which the ceramic is molded is used, and the cores are placed side by side in the same direction at a predetermined position in the mold to mold the ceramic material. A method for manufacturing an extrusion nozzle, which comprises molding, removing the core, and then firing a ceramic molded product. 4. The method for manufacturing an extrusion nozzle according to claim 3, wherein the core is made of glass. 5. The method for manufacturing an extrusion nozzle according to claim 3, characterized in that after molding the ceramic material, the core is melted and removed. 6 Claim 3, characterized in that after molding the ceramic material, the core is removed by tensile destruction.
1. Method for manufacturing an extrusion nozzle as described in Section 1. 7. The method for manufacturing an extrusion nozzle according to claim 3, wherein the core is divided into two at the minimum point B. 8 The minimum point B of the cross-sectional area is located at a position deviated from the midpoint M, and the cross-sectional area expands in a ramp-like manner toward the end near the minimum point B, and at the end far from the minimum point B. A plurality of protrusions are formed radially along the axial direction, and the height of the ridge line increases as it approaches the far end, and extends outward in the axial direction from both ends. A core having a holding part is used, the cores are arranged in a predetermined position in the mold in parallel in the same direction to form a mold, metal is cast using this mold, and the core is removed after casting. , a method for manufacturing an extrusion nozzle.