JPH0452770B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a molding die for a synthetic resin nib to be included in writing implements such as markers and felt-tip pens. It is related to the molding die used to mold the nib of the pen.

(Prior Art) FIG. 7 shows a forming die in the manufacturing method proposed in Japanese Patent Publication No. 53-27973.

This molding die 50 has a large number of discharge holes 51 arranged close to each other, and when the molten synthetic resin is extruded and discharged in the form of a filament from each of these discharge holes independently, the expansion of the synthetic resin, that is, the ballast effect. This method involves partially welding the extruded synthetic resins together outside the die, leaving ink passages in the non-welded parts, and is a so-called self-adhesive molding method outside the die.

Although it is possible to mold a pen nib to a certain extent with this molding die 50, it also has the following drawbacks.

A. Machining efficiency of the die The large number of discharge holes provided in the die must be arranged with strict and accurate spacing between them. The reason for this is that the envelope of the filament-shaped molten synthetic resin extruded from these discharge holes has a similar shape to the fine voids. This makes the die extremely difficult to manufacture and is disadvantageous in terms of price.

Regarding the strength of the die: In order to deal with the large degree of irregularity and the swell ratio and surface roughness (hereinafter referred to as melt fracture phenomenon), it is necessary to shorten the length of the discharge holes and to maintain the spacing between each discharge hole. must be made narrower, which reduces the pressure resistance against the extrusion pressure of the molten resin and shortens the life of the die.

About the swell ratio In the case of independent discharge holes, in order to make the swell ratio, which is an important factor in molding, appropriate, the hole must have a certain length and a certain extrusion pressure is required. In other words, if the extrusion rate is increased, the melt fracture phenomenon occurs, so an optimum extrusion rate is required, and it is difficult to obtain the optimum swell ratio just by changing the hole length, and the control range of the swell ratio is limited. It has the disadvantage that it is very narrow and difficult to form stably.

About the melt fracture phenomenon As the extrusion speed increases, the rate of viscous deformation of the filament discharged from the discharge hole, which is an independent hole, decreases, and the rate of elastic deformation increases, and finally it becomes an elastic body. This phenomenon is caused by extremely high extrusion pressures, i.e., surface cracks similar to
Or, it occurs at extremely high drawing speeds, which is disadvantageous because it affects the capillary flow of the ink.

E. About the enlargement rate In the self-adhering method outside the die, the peripheral surface of each filament discharged from the discharge hole is exposed to air at the same time as it is discharged and is cooled, so that the solidification speed of each filament becomes faster. For this reason, the enlargement ratio is small, and there is a limit to the ability to form smaller diameter pen nibs. On the other hand, if attempts are made to reduce the diameter, cracks will inevitably occur in various parts of the pen tip cross section, making it impossible to obtain a product.

Furthermore, since the enlargement ratio is small, if the diameter of the pen tip is to be made smaller, the diameter of the die must also be made smaller, which has the disadvantage of making the processing even more difficult.

Regarding crystallinity Since each filament is attached to the outside of the die, its peripheral surface is cooled by contact with air as soon as it exits from the discharge hole, so the cooling rate is fast, and the crystallinity is low, resulting in thermal distortion (shrinkage). degree) is a big disadvantage.

About weld lines Even when each discharge hole is machined to the optimal positional relationship, weld lines, which are the seams of each filament, occur at the fused parts of each filament attached to the outside of the die. It has the disadvantage of being weak in strength and causing cracks.

H. Degree of freedom for molding materials Materials with a small swell ratio and a high melt index are unsuitable, and have the disadvantage of limiting the number of molding materials.

Regarding Cooling Each filament is individually cooled by air outside the die, and the cooling of the entire surface of the ink passage is not controlled, so there is a disadvantage that the internal ink passage gap cannot be controlled.

In order to solve the drawbacks of the die of the self-attaching method outside the die, the applicant has proposed
We have proposed an apparatus for manufacturing synthetic resin pen nibs, which is described in Publication No. 70023.

The die of this device has a shaped opening in the front part of the die in which the air hole is opened, which is composed of a generally pipe-shaped outer shaped opening and a plurality of partition shaped openings that extend from the inside of the opening independently toward the center. A plurality of melt shaping holes are formed in communication with each other, and a required number of melt speed adjustment holes are provided between the melt shaping openings and the melt passing speed of each melt shaping hole to be approximately the same. belongs to.

This die solves all of the above-mentioned problems of the self-attaching method outside the die by controlling only the diameter of the melt speed adjustment hole.

By the way, the melt passing speed of the melt shaping hole is
When controlling only by the diameter of the melt speed adjustment hole, the following problems arise.

In adjusting the melt speed, when increasing the flow rate, there is a limit to increasing the diameter of the melt speed adjustment hole. That is, the hole diameter is limited to the diameter before adjacent adjustment holes are connected, and it is impossible to increase the flow rate beyond that.

On the other hand, when adjusting the melt speed, even when reducing the flow rate, there is a limit to how small the diameter of the melt speed adjustment hole can be made. In other words, there are limits to drilling holes, and
Drilling small diameter holes can be very costly depending on the hole size. In particular, when the die is made to have a small diameter in order to reduce stretching after extrusion from the die, the shaped opening also becomes small, making it extremely difficult to drill adjustment holes.

In the case of adjustment based on the hole diameter, it is difficult to make delicate adjustments.

(Problems to be Solved by the Invention) The problems to be solved are that it is not possible to easily increase or decrease the flow rate, and that it is not possible to finely adjust the melt speed.

(Means for Solving the Problems) In order to achieve the above-mentioned problems, the present invention has a generally pipe-shaped contoured opening in the front part of the die in which the air holes are opened, and a plurality of mutually independently centered openings from the inside of the opening. The shaping opening is formed by forming a partition wall shaping opening extending in the direction of the air hole and branch wall shaping openings extending in the circumferential direction from the partition shaping opening, and forming the shaping opening with a large number of melt shaping holes communicating with each other. of each melt forming hole between all the melt forming holes and the inside of the die body.
The present invention is characterized in that melt speed adjusting holes whose lengths and diameters are appropriately set to adjust the melt passing speed to be approximately the same are provided in a 1:1 composition ratio with the melt shaping holes.

(Function) Each melt constituting each part of the cross section of the pen nib is appropriately set to the same speed by the melt speed adjustment hole which is freely adjusted from fine to large, and the ink wetted surface is enlarged by predetermined pores with a large degree of irregularity. The ink is shaped into a diametrical cross-sectional form having an ink passage of approximately 300 mm, and after being shaped, it is extruded from the opening to form a pen nib having a shape similar to that of the opening.

(Example) An example of implementation of the present invention will be described in detail below based on the drawings.

Dice A has a built-in screw (not shown),
powder falling from a hopper (not shown);
Synthetic resin in the form of particles is transferred from the melt reservoir _B1 to the flow rate control section B.

During this transfer, the die A is heated from the outside with a heater (not shown) and the synthetic resin is melted while being transferred.

In addition, the die A is provided with an air blowing pipe A ₁ and an air feeding path A ₂ that communicates with this blowing pipe, and the air feeding path is passed through the center of the flow rate control section B and the center of the injection section D. Then, air holes are formed on the injection surface.
Open A ₃ . Air blowing pipe A ₁ and air supply path A ₂
This is to prevent the synthetic resin from concentrating in the center by supplying air and blowing it out from the air hole _A3 during the stretching process during pen nib manufacturing, thus forming a nib E without a core in the center. I'll do what I do.

The die A has a shaping opening C having a shape similar to the diameter cross section of the pen tip having a desired diameter cross section to be molded, in the front part, that is, the extrusion surface, communicating with the melt reservoir _B1 at the rear via the flow rate control part B.

This shaped opening C includes a roughly pipe-shaped outer shaped opening _C2 that is concentric with the air hole _A3 , and a plurality of partition wall shaped openings _C1 that extend independently from each other in the direction of the central air hole _A3 . , and branch wall shaping openings C ₃ extending circumferentially from the left and right sides of the partition shaping opening C ₁ , and these openings C ₂ , C ₁ and C ₃ are subdivided by a large number of melt shaping holes 1 communicating with each other. to form an array.

Roughly pipe-shaped outer shaped opening C ₂ is inside,
Both the inner and outer rings are constructed by drilling 144 melt shaping holes 1, 48 in total, in communication with each other, and the opening space is subdivided into 144 blocks communicating with each other.

The bulkhead shaping opening C ₁ communicates with the inside of the outer contour shaping opening C ₂ and extends equiangularly from three sides of the inside toward the central air hole A ₃ .
_C1 is formed by drilling four melt-forming holes 1 in communication with each other, and forming subdivisions into four blocks communicating with each other.

The branch wall shaping opening C ₃ communicates with the left and right sides of the partition wall shaping opening C ₁ , extends in the circumferential direction, and is parallel to the inner branch wall shaping opening c ₁ at equal intervals in the radial direction, and the intermediate branch wall shaping opening C _{2 .} and an outer branch wall shaping opening c ₃ , and the inner branch wall shaping opening c ₁ is formed by one melt shaping hole 1 .

The intermediate branch wall shaping opening _c2 is formed by forming three melt shaping holes 1 in communication with each other and subdividing into three blocks communicating with each other.

The outer branch wall shaping opening _c3 is formed by drilling five melt shaping holes 1 in communication with each other and subdividing into five blocks communicating with each other.

The melt forming hole 1 forming the outer contour shaping opening C ₂ , the partition wall shaping opening C ₁ , and the branch wall shaping opening C ₃ has a diameter that gradually decreases toward the center in the outer contour shaping opening C ₂ and the partition wall shaping opening C ₁ . The branch wall shaping openings _C3 are made to have the same diameter, and the melt whose flow rate is controlled by the flow rate control unit B is fused into the same body and shaped into the same shape within these openings, and then extruded, and then stretched. The radial cross section of the tubular nib body to be formed has a similar shape to the radial cross section of the shaped opening C, so that the ink wetting surface has an ink passage with a preferable capillary function extended with an equal gap. .

Therefore, in principle, the diameter of the melt shaping hole 1 gradually decreases from the outside toward the center of the contour shaping opening _C2 . However, the invention is not limited to this, and depending on the diameter cross-sectional shape of the pen tip to be molded, the outer contour shaping opening C ₂ and the partition shaping opening C ₁ may be made to have the same diameter, or
It goes without saying that various modifications may be made, such as forming the middle part including the branch wall shaping opening _C3 to have a small diameter or a large diameter.

As shown in the drawing, the flow rate control part B is a melt speed adjustment hole that is interposed between all the melt shaping holes 1 and the melt pool _B1 to communicate them and control the melt flow rate. The melt shaping hole 1 in the outer shaping opening C ₂ is set as the melt speed adjustment hole B ₂ , and the partition shaping opening
The melt shaping hole 1 in C ₁ is shown as melt speed adjusting hole B ₃ , and the branch wall shaping opening C ₃ is shown as melt speed adjusting hole B ₄ .
All the melt shaping holes 1 are opened in the same number as the melt shaping holes 1, that is, in a one-to-one relationship, and the diameter relationship with all the melt shaping holes 1 is formed to be small in consideration of the melt balance phenomenon. .

And each melt speed adjustment hole B ₂ , B ₃ , B ₄
In order to be able to equally control the melt passing speed in all melt shaping holes 1 of 210 blocks on the drawing at the outline shaping opening C ₂ , partition shaping opening C ₁ , and branch wall shaping opening C ₃ , each melt is The length and diameter of the speed adjustment holes are set in relation to the diameter cross-sectional area of each melt shaping hole 1, and in consideration of the laminar flow phenomenon of the melt in the melt pool _B1 .

Specifically, melt-shaped hole 1 with a large diameter cross-sectional area
For each melt forming hole 1, the hole length and diameter are managed to be shortened and expanded, and for melt forming hole 1 with a small diameter cross section, the hole length and diameter are controlled to be expanded and reduced. The passage speed of the melt is controlled to be the same in the forming opening C, so that a tubular nib body having a diameter cross-sectional shape similar to that of the shaping opening C is extruded from the shaping opening C.

The relationship between the control of the diameter and length of each melt speed adjustment hole B ₂ , B ₃ , and B ₄ is based on a flow phenomenon in which the extrusion rate is approximately proportional to the fourth power of the hole diameter and inversely proportional to the hole length. Based on this, to greatly adjust the melt flow rate, we intensively manage the hole diameter, and to finely adjust the melt flow rate, we intensively control the hole length. Both the diameter and length are set appropriately considering the cross-sectional area ratio.

Therefore, all the melt shaping passages 1 are formed in the shape of a chain of connected circles, but this is done by dividing the shaping opening C of the pen tip E into smaller sections. ₂ , the partition wall shaping opening C ₁ and the branch wall shaping opening C ₃ and the melt ratio within each opening C ₃ , C ₂ and C ₁ to make the mass of each part of the cross section uniform. and
In addition, the cross-sectional shapes of the partition wall E ₂ and the branch wall E ₃ are determined to be faithful to the shapes of the partition wall shaping opening C ₁ and the branch wall shaping opening C ₃ so that the ink passage E ₄ is kept constant within the limit where capillary action is likely to occur. This is to preserve it.

That is, each melt speed adjustment hole B ₂ , B ₃ ,
The melt extruded at the same speed in B ₄ expands in the melt shaping hole 1... and progresses at the same speed as the melt in the adjacent passage, fusing and integrating into the outer contour shaping opening. C ₂ and bulkhead shaped opening C ₁ and branch wall shaped opening
After being shaped by C ₃ , it is extruded from the shaping opening C to form a pen nib E with a predetermined porosity. or,
The protrusion C ₄ in the outer contour shaping opening C ₂ forms an ink groove E ₅ in the outer wall E ₁ of the pen nib E so that the outer wall E ₁ is clearly colored in the same color as the ink in the ink groove E ₅ . I have to. This protrusion C ₄ can be omitted,
In this case, a pen nib E having a radial cross-sectional shape without an ink groove _E5 is formed.

_The pen nib E manufactured using the above-mentioned die has a diametric cross-sectional shape as shown in _{FIG .} extending in the centripetal direction at equal angles,
From the left and right sides of each partition wall _E2 , branch walls _E3 are formed to extend symmetrically in the circumferential direction, and the ink passage _E4 formed by the envelope of each of these walls is a circumferential passage E4a. They are configured to communicate with each other through a radial passage E4b that communicates at the center.

The advantages of this pen nib E are: a The concentric ink passages eliminate the writing directionality around the axis at a certain writing angle, while the radial ink grooves connect each of these concentric ink passages at the shortest distance, allowing them to be mutually connected. We are aiming for rapid distribution of the writing angle, which eliminates the restriction on the writing angle that changes variously during writing, and each person has different writing angles, directionality around the axis, changes in these during writing, and differences in writing speed. By dealing with this, it is possible to obtain handwriting with a constant thickness from the beginning to the end.

b All the ink passages, partition walls, and branch walls are arranged symmetrically on the left and right sides of the center line, and the strain during cooling, which is characteristic of synthetic resin during molding, is balanced on the left and right sides, and the partition walls and branch walls are arranged symmetrically. There is no irregularity phenomenon, and the ink passage exhibits an appropriate porosity similar to that of the mold, ensuring the above-mentioned handwriting. At the same time, the symmetrical partition walls and branch walls on the left and right sides of each center line have uniform bending stress in response to various writing pressures around the axis, and the symmetrical partition walls and branch walls on the left and right sides of each center line have uniform bending stress in response to various writing pressures around the axis. Due to bending stress, i.e. waist,
A consistent writing feel can be obtained on any writing surface around the axis.

c. The wall surface forming the ink passage does not occur under extremely high extrusion pressure or molding speed at extremely high drawing speed, and is a smooth wall surface that is not disadvantageous to ink flow.

d It is self-adhered within the die, has a slow cooling rate, high crystallinity, and small thermal strain.

e It is integrally molded in a die, and there are no weld lines in various parts of its diametrical cross section, and there are no cracks that could cause a decrease in strength.

f The ink passage is extruded into a tubular shape, internally cooled, and formed under controlled cooling to exhibit a desired controlled cross-sectional shape.

The above embodiment merely illustrates one embodiment of the present invention, and within the scope of the present invention, for example, each partition wall shaping opening C ₁ may be connected at the center, or each branch wall shaping opening C ₃ may be connected at one end. Place them diagonally opposite each other,
Furthermore, each branch wall shaping opening _C3 may be inserted in an intersecting manner leaving a gap for an ink passage, or the branch wall shaping opening _C3 may be arranged only on one side of the partition wall shaping opening _C1 . This can be carried out freely depending on the difference in the diameter cross-sectional shape of the pen tip to be molded.

In addition, it is assumed that the relationship between the melt shaping hole and the melt speed adjustment hole is one-to-one, and another desirable condition under this assumption is that the diameter cross section of both holes should be of similar shape. Second, the shape should be a circle, especially a perfect circle, which is least affected by the laminar flow phenomenon.

(Effect of the invention) Regarding the hole diameter and hole length of each melt speed adjustment hole, the extrusion amount is approximately proportional to the fourth power of the hole diameter,
Based on the flow phenomenon that is inversely proportional to the hole length,
By intensively controlling the pore diameter, the melt flow rate can be greatly adjusted.
By intensively controlling hole length,
The melt flow rate can be finely adjusted, the flow rate can be increased or decreased easily, and the melt speed can be finely adjusted.

The diameter of the die can be made small, and the amount of stretching after extrusion from the die can be reduced.

From simple nib cross-sectional shapes to complex nib cross-sectional shapes with enlarged ink coated surfaces and highly irregular branch walls, it is possible to extrude them into the same shape as the shaping opening. .

[Brief explanation of the drawing]

FIG. 1 is a front view showing one embodiment of the molding die of the present invention. FIG. 2 is a longitudinal sectional side view taken along the - line in FIG. 1. FIG. 3 is a longitudinal sectional side view taken along the - line in FIG. 1. FIG. 4 is a sectional view showing the radial cross-sectional shape of a synthetic resin pen nib, which is a molded product. FIGS. 5 and 6 are radial cross-sectional views showing examples of other moldable pen nibs. FIG. 7 is a front view of a conventional die. In the figure, A is a die, A ₃ is an air hole, B ₂ , B ₃ , B ₄
is the melt speed adjustment hole, C is the shaping opening, C ₁
is the partition wall shaping opening, C ₂ is the contour shaping opening, C ₃ is the branch wall shaping opening, and 1 is the melt shaping hole.

Claims (1)

[Claims] 1 In the front part of the die where the air hole is opened, there is a roughly pipe-shaped outer contour shaping opening, a plurality of partition shaping openings extending from the inside of the opening toward the center independently, and branches extending in the circumferential direction from the partition shaping opening. A shaping opening constituted by a wall shaping opening is formed with a large number of melt shaping holes communicating with each other in the radial direction, and each melt shaping opening is formed between all the melt shaping holes of the shaping opening and the inside of the die body. A molding die for a synthetic resin nib, which is provided with melt speed adjustment holes whose lengths and diameters are appropriately set so that the melt passing speed of the shaping holes can be adjusted to almost the same speed.