JP2009220320A - Extrusion molding die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extrusion molding die for suppressing the occurrence of burrs and pinholes while securing tube-roundness, considering a technical subject to suppress burrs and pinholes caused by extruding resin in a state where the tip parts of core pins are protruded from an ejection port. <P>SOLUTION: The extrusion molding die is configured so that the pins 23a to 23d with tip parts partly protruded from the ejection port are positioned at the inside of the ejection port of the outer die, and a cylindrical extrusion molding cavity is formed by the outer die and the pins, and melted resin is extruded from the molding cavity. The protrusion amount of the pin from the ejection port is set equal to or lower than an upper limit value of little more than 2 mm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a mold, and more particularly, to an extrusion mold used for manufacturing a tube formed by extrusion.

Conventionally, as shown in FIG.
An outer mold 1 surrounding the core pin 110 with molten resin such as P (polypropylene).
A so-called extrusion molding method is known in which molding is performed by continuously extruding at a high pressure from a discharge port 130 in a molding space formed by 20. However, the tube 100 formed by the above-described extrusion molding has its outer periphery released into the atmosphere immediately after extrusion and is rapidly cooled, while the inner periphery is not rapidly cooled, so there is a temperature difference between the outer periphery and the inner periphery. Occurred, and the roundness of the cross section of the tube 100 could not be sufficiently secured. Therefore, in recent years, by slightly cooling the inner periphery of the tube 100 extruded from the discharge port 130 by slightly protruding the tip 110a of the core pin 110 from the discharge port 130 of the outer mold 120, the outer periphery of the tube 100 can be cooled. A technique for improving the roundness of the cross section of the tube 100 has been proposed in such a manner that the temperature difference between the tube 100 and the tube 100 becomes small.
JP 2006-007754 A JP2007-216580

However, when the tip 110a of the core pin 110 is protruded as described above, the tip 110a of the core pin 110 is contributed to improving the roundness of the cross section of the tube 100.
Cavitation occurs on the surface side of the tube 100, and a suction force in the inner surface direction is generated on the inner surface of the tube 100, so that a projecting deformation commonly referred to as “eyes” is formed inside the tube 100 as shown in FIG. The protrusion 160 was generated. Since this “eyes” is fixed to the inner surface of the tube 100 in a welded state, it cannot be easily removed. If the tube 100 is used as a flow path through which various fluids such as ink flow, the fluid such as ink becomes a cause of clogging. Further, due to the blending of components such as PP (polypropylene) of the molten resin, even if “eyes discoloration” does not occur, a hole 140 called “pin hole” occurs as shown in FIG. was there.

The present invention pays attention to the technical problem of suppressing the occurrence of "eyes" and "pinholes" caused by extruding the resin in a state where the tip of the core pin protrudes from the discharge port as described above.
It is an object of the present invention to provide an extrusion mold that can suppress the occurrence of “eyes” and “pinholes” while ensuring the roundness of a tube.

As a first configuration of the present invention made to achieve the above object, a pin having a tip projecting partly from the discharge port is positioned inside the discharge port of the outer mold, and the cylinder is formed by the outer mold and the pin. An extrusion mold in which a molten extrusion space is formed and molten resin is extruded from the molding space, and the protrusion amount of the pin is set to a value slightly exceeding 2 mm from the discharge port, and below that It was set as the extrusion mold characterized by having been set.
According to the extrusion molding die having this configuration, it is possible to suppress the ratio of occurrence of “eyes” and “pinholes” while sufficiently ensuring the roundness of the tube.

Further, as a second configuration, the amount of protrusion from the discharge port of the pin in the first configuration is set as follows.
It was set as the extrusion metal mold | die characterized by setting between 5 mm and 2 mm.
According to the extrusion molding die having this configuration, it is possible to extremely suppress the ratio of occurrence of “eyes” and “pinholes” while sufficiently ensuring the roundness of the tube.

Further, in the extrusion molding die having the first or second configuration as the third configuration, an extrusion molding die characterized in that means for adjusting the protruding amount of the pin is provided.
According to the extrusion molding die having this configuration, since the protruding amount of the pin from the discharge port can be varied, the optimal protruding amount can be adjusted in accordance with various characteristics such as the shape and material of the tube.
In the present invention, the “tube” includes not only an ink supply tube as an ink flow path of a so-called ink jet printer but also a medical catheter and the like and a hollow longitudinal member that can flow a fluid into the inside.

FIG. 1 is a schematic configuration diagram schematically showing a manufacturing process of the tube 100.
In the figure, a tube 100 includes PP (polypropylene) and PE (PE) that are put into a hopper 151 of an extrusion molding apparatus 150 in which an extrusion mold 1 according to the best mode is mounted at the tip.
Polyethylene), olefin plastic elastomer (TPE), styrene TPE,
Resin having flexibility after solidification such as polyamide-based TPE and urethane-based TPE, or a combination of these is melted by the heating cylinder 152 and pressed by the screw 153 from the hopper 151 toward the extrusion mold 1. Molded by extrusion.

The tube 100 extruded from the extrusion mold 1 is cooled by the cooling bath 90 in the process of being pulled with a constant tension by the puller 70, and is cut by the cutter 80 after cooling for every predetermined length.
Hereinafter, in this specification, the direction of the hopper 151 is referred to as an upstream side, and the direction of the take-up machine 70 is referred to as a downstream side.

FIG. 2 is an exploded perspective view of the extrusion mold 1 according to the best mode.
In the figure, an extrusion mold 1 includes an outer mold 2 and an inner mold 20 fitted into the outer mold 2.
And the spider 25 connected to the inner mold 20 is integrated.
The outer mold 2 includes a head die 3 and a lip 10. The head die 3 has a housing that is formed in a tubular shape that is open at both ends. On the end face 4 of the head die 3 on the downstream side, screw holes 5 of the lock bolt 7 are formed at equal intervals around the opening 6.

As shown in FIG. 2, the lip 10 has a cylindrical casing having a discharge hole 11 that communicates between a front end surface 10a where the discharge port 12 opens and an upstream rear end surface 10b. As shown in FIG. 6, the discharge port 12, which is the leading edge on the downstream side of the discharge hole 11, is edged in a wave shape in which a plurality of arcs are connected.
Around the discharge port 12 as a center, lock bolt insertion holes 13 are provided at predetermined intervals corresponding to the screw holes 5 of the head die 3.
The lip 10 is coaxial with the axis of the head die 3, and the rear end surface 10 b is the end surface 4 of the head die 3.
The lock bolt 7 is positioned at a position opposite to the lock bolt insertion hole 13 and the screw hole 5.
When the head die 3 is inserted, the head die 3 is fastened. When the lip 10 and the head die 3 are fastened, the lip 10 protrudes from the end face 4 to the downstream side, and the outer mold 2 is configured.
The internal structure of the head die 3 and the lip 10 will be described later.

The inner mold 20 includes a base 21, core pins 23a to 23d protruding from the tip of the base 21, and
And a male screw 24 protruding from the rear end of the base 21. The base portion 21 is formed by chamfering an upper and lower tapered surface 21c and a tapered surface 21d that are gradually inclined from the rear end surface 21a located on the upstream side toward the distal end surface 21b. It has a frame with a substantially trapezoidal cross section consisting of both side surfaces 21e to be connected. Further, the positioning piece 22 is formed by cutting out the both side surfaces 21e.

The core pins 23a to 23d include air holes 26 that communicate with the internal space of the base portion 21, and are formed as a plurality of tubular bodies having a perfectly circular cross section that extend horizontally downstream from the front end surface 21b. The core pins 23a to 23d are arranged in parallel in a direction that is spaced apart from each other by a predetermined distance and orthogonal to the extending direction.
In this example, a total of four pins are used as the core pins 23a to 23d. However, the number of pins is not limited to this, and by increasing or decreasing the number of pins, a single tube 100 is provided.
It is also possible to mold the tube 100 having more channels. The shape of the core pins 23a to 23d defines the shape of the inner surface of the tube 100. For example, the shape of the core pins 23a to 23d may be an ellipse other than a perfect circle in cross section.

The male screw 24 is hollow and includes an air hole 28 (see FIG. 4) that communicates with the internal space of the base portion 21, and protrudes upstream from a substantially central portion of the rear end surface 21 a of the base portion 21. Male screw 24 is Spider 2
When the spider 25 and the inner mold 20 are screwed into the female threaded portion 29 of the fifth member, the tip of the air hole 26 of the core pins 23a to 23d passes through the internal space of the base portion 21 from the exhaust hole of the air compressor (not shown). An air passage 45 (see FIG. 4) that is open to the atmosphere is formed.

The spider 25 has a housing formed in a tubular shape with openings at both ends, and the partition walls 25a to 25d extend outward in the radial direction around the female screw portion 29, so that a plurality of resin outlet paths 30 are formed.

FIG. 3 is an external view showing the extrusion mold 1 configured by assembling the spider 25 with the inner mold 20 fastened to the outer mold 2 with bolts outside the figure.
In the figure, the extrusion mold 1 is accommodated inside a holder 41 of an extrusion molding apparatus 40,
The periphery is fixed by a plurality of fixing bolts 42.

FIG. 4 is a cross-sectional view showing the internal structure when the extrusion mold 1 is accommodated in the holder 41.
In the drawing, the head die 3 includes a horizontal plane 50 and an inclined surface 51 that descends downstream from the downstream end of the horizontal plane 50. The spider 25 is fastened to the horizontal surface 50 by fixing means (not shown).
The tapered surface 21c and the tapered surface 21d of the base portion 21 are located on the side facing the inclined surface 51, and an inclined shape is formed between the inclined surface 51 and the tapered surface 21c and the tapered surface 21d that are more gently inclined than the inclined surface 51. The head die side internal space F is formed. In other words, the head die-side internal space F that gradually becomes narrower on the downstream side is formed by surrounding the tapered surface 21c and the tapered surface 21d with the inclined surface 51 of the head die 3.

4 to 6, the lip 10 includes the above-described discharge hole 11 extending in the horizontal direction. In the discharge hole 11, four core pins 23 a to 2 that are parallel to each other at equal intervals.
3d is arranged so as to protrude from the upstream side to the downstream side, and the discharge hole 11 and the core pins 23a to 2 are provided.
A linear internal space G is formed between 3d.

The internal space G (discharge hole 11) has a height corresponding to the total height H of the tube shown in FIG. 6C, and includes an upper surface L, a lower surface M, one side surface P, and the other side surface Q. .
The upper surface L and the lower surface M are surfaces formed by upper and lower inferiority centering on the central axis of the core pins 23b and 23c, and form a corrugated surface by connecting the inferior arcs to each other. The side surface P and the side surface Q are surfaces formed by grace with the central axis of the core pins 23a and 23d as the center, and are connected to the inferiority that forms the upper surface L and the lower surface M.
That is, the shape of the internal space G depends on the substantially wave-shaped outer surface shape of the tube 100 shown in FIGS. 6B and 6C, and the outer peripheral shape of the core pins 23a to 23d depends on the shape of the flow paths 101 to 104. To do.
Further, the tip portions A of the core pins 23a to 23d are attached so as to protrude, for example, 2.1 mm downstream (forward) from the discharge port 12. The protrusion amount will be described later.

FIG. 5 is a partially enlarged view showing the head die side internal space F and the internal space G. FIG.
When the resin is extruded in the direction of the extrusion mold 1 from the upstream side of the extrusion molding device 40, the extruded resin passes through the horizontal surface 50 upstream of the spider 25 as indicated by the arrow, and the resin of the spider 25 It flows into the lead-out path 30. The resin flowing into the resin outlet path 30 is formed between the tapered surface 21c and the tapered surface 21d of the base portion 21 and the inclined surface 51 of the head die 3, and gradually decreases in width toward the downstream side. To the downstream side.
When the resin led out to the head die side internal space F reaches the internal space G on the lip 10 side, it is extruded from the discharge port 12 while being formed as a tube 100 having a shape corresponding to the shape of the internal space described above.

When the resin is extruded from the discharge port 12, air is supplied from the upstream side of the air flow path 45 to the downstream side by an air compressor or the like (not shown), and from the downstream end of the air hole 26 of the core pins 23a to 23d. Air is exhausted.
As a result, the discharged air flows into the flow path 10 of the tube 100 extruded from the discharge port 12.
1 to 104, the cooling effect inside the tube 100 is enhanced, and the roundness can be improved.

FIG. 9 is an experimental result diagram showing the relationship between the core pin protrusion amount and the occurrence rate of “eyes” (foreign matter) and “pin holes” (P / H).
In addition to the configuration of the air flow path 45 described above, by setting the tip A of the core pins 23a to 23d so as to protrude downstream (forward) from the discharge port 12 which is the tip edge of the discharge hole 11, a perfect circle The ratio of occurrence of “eyes” and “pinholes” can be suppressed to about 10% or less while securing the degree. In addition, as can be seen from the figure, when the core pin protrusion amount P is in a range slightly exceeding 1 mm to 2 mm, the occurrence rate of both “eyes” and “pinholes” can be suppressed to 10% or less. Thus, it is understood that the occurrence rate of “pinholes” is significantly increased in a stepwise manner when protruding beyond a range slightly exceeding 2 mm.
Therefore, in order to suppress both “eyes” and “pinholes” while ensuring the roundness of the tube 100, it is desirable to set the protruding amount P of the core pin within a range slightly exceeding 1 mm to 2 mm. .
More preferably, by setting the intersection of straight lines, that is, about 1.75 mm,
Since both the occurrence rate of "eyes" and "pinhole" can be suppressed to 2.5% or less, a more remarkable effect can be obtained.

7 and 8 are an exploded perspective view and a cross-sectional view showing a mold 200 according to another embodiment. In addition,
The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
In the same figure, the adjustment spacer 60 includes the end face 4 of the head die 3 and the rear end face 10 of the lip 10.
It is a disk-shaped member having substantially the same diameter as b, and the wall thickness is set to 1 mm, for example. A resin outlet hole 61 having substantially the same shape as the opening 6 of the head die 3 is formed at the center of the adjustment spacer 60, and the screw hole 5 of the head die 3 and the lip 10 are locked around the resin outlet hole 61. An insertion hole 62 is provided at a position corresponding to the bolt insertion hole 13.

The adjustment spacer 60 is interposed between the lip 10 and the head die 3 and positioned coaxially with the axis of the head die 3 and the lip 10, and the lock bolt 7 is inserted into the lock bolt insertion hole 13.
When screwed into the screw hole 5 through the insertion hole 62, the adjustment spacer 60 is fastened while being sandwiched between the head die 3 and the lip 10.

As a result, the distance between the end face 4 of the head die 3 and the rear end face 10b of the lip 10 increases by the thickness of the adjustment spacer 60, and the discharge port 12 of the lip 10 and the core pin 23a.
The distance from the tip portion A to 23d, that is, the protrusion amount P can be relatively shortened.

Therefore, the protrusion amount P when the adjustment spacer 60 is not interposed as in the extrusion mold 1 according to the best mode is set to 2.1 mm, for example, and the adjustment spacer 60 is interposed between a single or a plurality of layers. Since the protrusion amount P can be gradually shortened by this, in addition to the effect produced by the extrusion mold 1 according to the best mode, the protrusion amount P from the discharge port 12 of the tip A can be easily adjusted. , Optimum protrusion amount P according to the material and shape of the tube 100
Can be obtained.

As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to embodiment, A various change or improvement is possible in the range which does not deviate from the meaning of invention. .
In addition, the present invention can be used when manufacturing a suitable tube in many other fields dealing with fluids, including an ink supply tube used in an ink jet recording apparatus.

Schematic which shows the extrusion molding process using the extrusion die 1 which concerns on the best form. The disassembled perspective view which shows the extrusion mold 1 which concerns on the best form. The perspective view which shows the external appearance which mounted | wore the extrusion molding apparatus with the extrusion die 1 which concerns on the best form. Sectional drawing which shows the state which mounted | wore the extrusion molding apparatus with the extrusion die 1 which concerns on the best form. The elements on larger scale which show the internal space of the extrusion mold 1 which concerns on the best form. The front view at the time of seeing the front-end | tip part A shown in FIG. 5 from the front, the perspective view and front view of the manufactured tube 100. FIG. The disassembled perspective view which shows the molding die 200 which concerns on another form. The elements on larger scale which show the internal space of the shaping die 200 which concerns on another form. The figure which shows the correlation with the protrusion amount of a core pin, a foreign material generation rate, and a pinhole generation rate. Sectional drawing which shows the conventional extrusion mold and a tube.

Explanation of symbols

1 extrusion mold, 2 outer mold, 3 head die, 10 lip, 11 discharge hole,
12 outlets, 20 inner molds, 23a to 23d core pins, 25 spiders,
30 resin outlet path, 40 extrusion molding device, 51 inclined surface,
100 tube, A tip, F head die side internal space, G internal space.

Claims (3)

A pin with a tip protruding partly from the discharge port is positioned inside the discharge port of the outer mold, and a cylindrical extrusion molding space is formed by the outer mold and the pin, and the molten resin is extruded from the molding space. An extrusion mold according to claim 1, wherein the protruding amount of the pin is set to a value slightly higher than a value slightly exceeding 2 mm from the discharge port. 2. The extrusion mold according to claim 1, wherein an amount of protrusion of the pin from the discharge port is set between 1.5 mm and 2 mm. The extrusion mold according to claim 1 or 2, wherein means for adjusting the protruding amount of the pin is provided.

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