JP2000001083A - Mold for plastic ballpoint pen tip and manufacture of plastic ballpoint pen tip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a mold for smoothly molding a seating surface in the case of injection molding of a plastic ballpoint pen tip. SOLUTION: A core mold 50 for forming an inner surface of a ballpoint pen tip 80 is divided into a fixed side core 60 of a tip end side, and a movable side core 70 of a rear end side. The core 60 molds a ball holding part 81. A rear end of the core 60 is formed as a conical convex surface 61 for molding a seating surface 82. An end of the core 70 molds an ink hole 83 and an ink groove 84, and the end is formed in a conical recess surface 76 to be engaged with the surface 61.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold used for injection molding of a plastic ball-point pen tip.

[0002]

2. Description of the Related Art A ballpoint pen tip is usually manufactured by cutting a metal such as stainless steel, brass, bronze, and nickel silver. However, plastic ballpoint pens are also offered which are more advantageous than metals in terms of mass productivity and product unit price. The plastic ball-point pen tip has the same structure as the metal ball-point tip. Less than,
This structure will be described with reference to FIG. In addition,
In FIG. 16, A is a front view, B is a plan view excluding a ball, and C is a cc cross-sectional view shown in A.

(Structure) The external shape of the plastic ball-point pen tip 80 shown in FIG. 16A has a shell shape. That is, the tapered portion 88 extends from the middle part of the outer shape to the tip.
have. A caulking portion 87 is provided for holding the ball 90 by reducing the diameter of the tip.

On the other hand, a ballpoint pen tip 80 shown in FIG.
Is provided with a ball holding portion 81 in which a ball 90 is located at a tip portion. The bottom surface of the ball holding portion 81 is a receiving surface 82 having a concave conical shape. Also,
From the opposite side of the ball holding portion 81, a back hole 85 having the same axis as the ball holding portion 81 is provided. Back hole 85
Has a diameter substantially equal to that of the ball holding portion 81, but is not in direct contact with the receiving surface.

[0005] As shown in Figs. 16B and 16C, the ball holding portion 81 and the back hole 85 communicate with each other through an ink hole 83 provided at the same axial center as the ball holding portion 81 and the back hole 85. At the same time, the ball holding portion 81 and the back hole 85 communicate with each other by several ink grooves 84 provided radially to the ink hole 83. The plastic ball-point pen tip 80 is usually manufactured by injection molding. Conventionally, a mold as shown in FIG. 17 has been used for this injection molding.

A mold 10 shown in FIG.
The mold is divided into a cavity mold 20 for molding the outer shape of 80 and a core mold 50 for molding the inside. The cavity mold 20 further molds the outer shape on the front end side, and molds the fixed-side cavity 30 provided on the fixed-side mold plate 11 and the outer shape on the rear end side, and forms the movable-side mold provided on the movable-side mold plate 12. And a cavity 40. That is, the boundary between the fixed side cavity 30 and the movable side cavity 40 corresponds to the parting line 13 when the mold is opened.
It has become. Also, the tip side of the fixed side cavity 30 is
The tapered surface 35 for forming the tapered portion 88 of the ballpoint pen tip 80 is formed, and the leading end portion thereof is the crimped surface 34 for forming the crimped portion 87 of the ballpoint pen 80.

In the fixed cavity 30 and the movable cavity 40, a fixed mounting hole 33 into which a core mold 50 is inserted.
And a movable-side mounting hole 43 are provided. Also,
The submarine gate 14 is provided in the fixed cavity 30. Furthermore, the movable side mounting hole 43 of the movable side cavity 40
Around the periphery, a cylindrical sleeve 41 that is movable in the front-rear direction with respect to the core mold 50 is mounted. This is for projecting the molded ballpoint pen tip 80 after opening the mold, which will be described later.

On the other hand, the core mold 50 forms a ball holding portion 81 and has a fixed core 60 provided on the fixed mold plate 11.
A movable core 70 having a back hole 85 formed therein and provided in the movable mold plate 12. The tip portion of the fixed core 60 is inserted into the fixed mounting hole 33 described above. Also, ball holding part
The tip side of the part for molding 81 is the fixed side cavity
The swaging part of the ballpoint pen tip 80 together with the swaging surface 34 of 30
87 is molded, but this part is undercut. Further, the rear end of the portion where the ball holding portion 81 is molded is
A conical convex surface 61 for molding an ink hole, an ink hole portion 73 for molding an ink hole 83, and an ink groove
An ink groove 74 for molding 84 is provided.

In FIG. 17, for convenience of explanation,
Although the fixed core 60 and the movable core 70 are shown separately,
These are in contact when the ballpoint pen tip 80 is molded. Here, the core mold 50 is divided into the fixed side core 60 and the movable side core 70 because the ball holding portion 81 and the back hole 85 are filled with resin between the ink grooves 84, 84. This is because the core mold 50 can be extracted because the gaps are separated.

(Manufacturing Process) Next, the manufacturing process of the plastic ball-point pen tip 80 using the conventional mold 10 will be outlined. First, the fixed core 60 is inserted into the fixed mounting hole 33 of the fixed cavity 30. And this fixed side cavity
30 is mounted on the fixed-side template 11.

On the other hand, the movable side mounting hole of the movable side cavity 40
The movable core 70 is inserted into 43. Then, the movable side cavity 40 is mounted on the movable side mold plate 12. Next, fixed side template
After attaching 11 and movable side mold plate 12 to the mold clamping device, mold clamping,
The synthetic resin melted from the submarine gate 14 is injected and filled into the cavity 15 of the mold 10. After filling, mold
The mold is opened after the ballpoint tip 80 is solidified by cooling 10. That is, when the movable mold plate 12 is moved toward the rear end of the ball-point pen tip 80, the ball-point tip 80 is removed from the cavity 15 along with the movable-side core 70. At this time, the swaged portion 87 of the undercut ballpoint pen tip 80 is forcibly removed from the fixed core 60.

Finally, the ball-point pen tip 80 is removed from the movable-side core 70 by projecting the sleeve 41 in the distal direction.

[0013]

In the conventional mold, as described above, the ink hole and the ink groove are provided in the fixed core. More specifically, a columnar ink hole is provided at the apex of the conical convex surface that forms the receiving surface, and several plate-like ink grooves are provided radially from the ink hole. Accordingly, the conical convex surface is divided by the ink groove.

Here, the seating surface of the ball holding portion is a surface on which the ball rotates while making contact with the ball. Therefore, in order to ensure a comfortable writing feeling due to the smooth rotation of the ball, its surface is required to be as smooth and smooth as possible. However, as described above, since the conical convex surface serving as the mold of the receiving surface is divided by the ink groove portion, the processing of the conical convex surface has to rely on a sharp electric discharge machining or the like,
High-precision surface finishing equivalent to machining was not possible. Therefore, as a result, the surface roughness of the seating surface of the molded ballpoint pen tip becomes large.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mold capable of smoothly molding a seating surface in injection molding of a plastic ball-point pen tip. A second object of the invention is to facilitate the manufacture of a mold in addition to the object of the first invention.

Still another object of the present invention is to form the receiving surface of a plastic ball-point pen tip manufactured by injection molding smoothly.

[0017]

SUMMARY OF THE INVENTION In view of the above problems, the invention according to claim 1 of the present invention is a plastic having a ball holding portion 81, an ink hole 83, an ink groove 84, and a back hole 85 by injection molding. A mold 10 for manufacturing a ball-point pen tip 80, a cavity mold 20 for molding the outer shape of the ball-point pen tip 80, a ball holding portion 81, an ink hole 8
3, a core mold 50 for molding an inner surface having an ink groove 84 and a back hole 85, and a cavity mold 20 for molding the outer shape on the tip side, and a fixed cavity provided on the fixed mold plate 11. 30 and the outer shape of the rear end
And the movable side cavity 40 provided in the core mold.
50 is a fixed-side core 60 molded on the front end side, and a fixed-side core 60 provided on the fixed-side mold plate 11, and a fixed-side core 60 molded on the rear end side, and provided on the movable-side mold plate 12. Is composed of a separate movable side core 70, and the fixed side core 60 for molding the ball holding portion 81 has a seating surface serving as a bottom surface of the ball holding portion 81 at its rear end.
It has a conical convex surface 61 for molding 82 and ink holes 8
3. Movable core 70 for forming ink groove 84 and back hole 85
Is characterized in that a conical concave surface 76 that fits with the conical convex surface 61 is provided at the tip of a portion where the ink hole 83 and the ink groove 84 are formed.

That is, the fixed side mold plate 11 is provided with a fixed side cavity 30 which is the tip side of the cavity mold 20 and a core mold.
A fixed core 60, which is the distal end of the 50, is provided. on the other hand,
The movable mold plate 12 is provided with a movable cavity 40 at the rear end of the cavity mold 20 and a movable core 70 at the rear end of the core mold 50. Since the core mold 50 for molding the inside of the ballpoint pen tip 80 cannot pass through the ink groove 84, in order to open the mold, the fixed side core which is the tip side before or after the portion for molding the ink groove 84 is used. It is necessary to divide the movable core 60 into a movable core 70, which is a rear end side. here,
In the mold 10 according to the present invention, a portion for forming the ink hole 83 and the ink groove 84 is provided on the rear end side.

By doing so, the seating surface 82 of the fixed side core 60
There is no need to provide a mold for molding the ink holes 83 and the ink grooves 84 on the surface on which is molded. Therefore, since the surface on which the receiving surface 82 is formed is not divided at the portion where the ink groove 84 is formed, the conical convex surface 61 can be machined. This facilitates smooth machining of the surface on which the receiving surface 82 is molded, and also allows the receiving surface 82 to be molded by this surface.
Becomes smooth.

The reason why the tip end of the ballpoint pen tip 80 is used as the fixing portion is to protrude the product. That is, an ejector or a sleeve for ejecting a product in injection molding is usually provided on the movable side. However, since the tip of the ballpoint pen tip 80 has a fine shape, it is not appropriate to project this portion with an ejector or a sleeve. Therefore, the rear end side, which has little effect even when a force is applied by protrusion, is set as the movable portion.

Next, the assembling of the mold 10 according to the present invention will be described. First, the fixed side cavity 30 and the fixed side core 60 are mounted on the fixed side template 11. Here, the fixed-side cavity 30 and the fixed-side core 60 can be manufactured as one body, but it is desirable to manufacture them separately and combine them at the time of mounting from the viewpoint of convenience of mold manufacturing.

On the other hand, the movable side cavity 40 and the movable side core 70
Are mounted on the movable mold plate 12. Next, the fixed mold plate 11 and the movable mold plate 12 are mounted on a mold clamping device. After the mold clamping, the cavity 15 is filled with the synthetic resin melted from the submarine gate by injection. After filling, mold 10
Is cooled to sufficiently solidify the synthetic resin, and then the mold is opened. That is, when the movable mold plate 12 is moved toward the rear end of the ball-point pen tip 80, the ball-point tip 80 comes off the fixed-side cavity 30 and the fixed-side core 60 along with the movable-side core 70. At this time, the swaged portion 87 at the tip of the ballpoint pen tip 80 is undercut between the fixed side cavity 30 and the fixed side core 60, but this is to be forcibly removed.

Finally, the ballpoint pen tip 80 is removed from the movable side core 70 by protruding the ejector or sleeve provided in the movable side cavity 40 in the distal direction. As described above, by providing the portion for molding the ink holes 83 and the ink grooves 84 in the movable side core 70 on the rear end side, the conical convex surface 61 of the fixed side core 60 on the front end side can be machined smoothly. The receiving surface 82 can be molded smoothly.

According to a second aspect of the present invention, in addition to the features of the first aspect, the fixed side cavity 30 is divided at a boundary between the swaged portion 87 and the tapered portion 88 of the ballpoint pen tip 80. It is characterized by. That is, in the mold 10 according to the present invention, the fixed-side cavity 30 in the mold 10 according to the first embodiment is formed such that the surface on which the caulking portion 87 is molded and the tapered portion 88 are formed.
Are divided at the boundary with the surface to be molded.

By doing so, the mold can be divided at the place where the inclination changes, so that the manufacture of the mold is facilitated and the assembling of the mold is also facilitated. Further, according to the third aspect of the present invention, the cavity mold 20 for molding the outer shape of the ballpoint pen tip 80 and the inner surface of the ballpoint pen tip 80 having the ball holding portion 81, the ink hole 83, the ink groove 84, and the back hole 85 are molded. A method for manufacturing a plastic ball-point pen tip 80 by injection molding using a mold 10 having a core mold 50, wherein the mold 10 includes a cavity mold 20 for molding the outer shape of the ball-point pen 80, and a ball holding device. Part 81, ink hole 83,
A core mold 50 for molding an inner surface having an ink groove 84 and a back hole 85, and a cavity mold 20 for molding the outer shape on the tip side, and a fixed side cavity 30 provided on the fixed side mold plate 11, And a movable cavity 40 formed in the movable mold plate 12 by molding the outer shape of the rear end side.
The fixed-side core 60 that molds the inner surface on the front end side, and is provided on the fixed-side mold plate 11, and the fixed-side core 60 that molds the inner surface on the rear end side and is provided on the movable-side mold plate 12. The fixed-side core 60, which comprises a separate movable-side core 70 and forms the ball holding portion 81, has a seating surface 82, which is the bottom surface of the ball holding portion 81, at the rear end.
Has a conical convex surface 61 for molding the ink hole 83, ink groove 84
The movable core 70 that forms the back hole 85 has a conical concave surface 76 that fits with the conical convex surface 61 at the tip of the portion that forms the ink hole 83 and the ink groove 84, and the fixed side mold plate 11 An assembling step of mounting the fixed-side cavity 30 and the fixed-side core 60 to the movable-side mold plate 12 and the movable-side cavity 40 and the movable-side core 70, respectively, and tightening the fixed-side mold plate 11 and the movable-side A mold clamping process for clamping the mold 10,
An injection step of injecting the molten synthetic resin into the closed mold 10; a cooling step of cooling the mold 10; a mold opening step of opening the mold 10; and a ballpoint pen molded from the solidified synthetic resin. And a projecting step of projecting the chip 80.

That is, the method of manufacturing the ballpoint pen tip 80 according to the present invention is carried out using the mold 10 according to the first aspect, and the manufacturing process is described in the above description of the first aspect. Is the same as With this method, the receiving surface 82 of the molded ballpoint pen tip 80 can be molded as a smooth conical concave surface.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the drawing viewed from the front end is referred to as a plan view, the drawing viewed from the rear end is referred to as a bottom view, and the upper side of the drawing is referred to as the front end.
First, the shapes of a mold and parts thereof used in the present embodiment will be described with reference to FIGS. FIG. 1 is a front view (A) showing a mold 10 used in the present embodiment in a partial cross section, and a perspective view showing a tip section of a ballpoint pen tip 80 molded by the mold 10 in a partial cross section. FIG. FIG. 2 is a front sectional view and a bottom view of a distal end portion 31 of the fixed side cavity 30 described later. FIG. 3 is a plan view and a front sectional view of a movable side cavity 40 described later. FIG. 4 is a front view and a bottom view of a fixed core 60 described later. FIG. 5 is a front view, a plan view, and a front sectional view of a movable core 70 described later.

The mold 10 includes a cavity mold 20 for molding the outer shape of the ballpoint pen tip 80, and a core mold 50 for molding the axis portion. The cavity mold 20 has a fixed side cavity 30 formed on the fixed side mold plate 11 and a fixed side cavity 30 formed on the fixed side mold plate 11 and a movable side cavity formed on the movable side mold plate 12 and molded on the rear end side. Consists of 40. Further, the fixed side cavity 30 has a front end portion 31 for molding the front caulking portion 87.
And an intermediate portion 32 that forms the tapered portion 88 and subsequent portions. This is for convenience of mold production.

As shown in FIG. 2, on the axis of the tip 31,
A fixed-side mounting hole 33 for mounting the fixed-side core 60 is provided. Similarly, a movable mounting hole 43 for mounting the movable core 70 is provided in the axis of the movable cavity 40, as shown in FIG. Also, this movable side mounting hole 43
Around the periphery, a cylindrical sleeve 41 that can move in the front-rear direction with respect to the movable core 70 is mounted. Further, the intermediate part 32
Is provided with a submarine gate 14 (FIG. 1).
A).

The core mold 50 is formed by molding a ball holding portion 81 (FIG. 1B) having an inner surface of a caulking portion 87 and a receiving surface 82.
And the fixed core 60 provided on the fixed mold plate 11 (FIG. 1A)
And ink holes 83, ink grooves 84, and back holes 85 (FIG. 1B)
And a movable core 70 provided on the movable mold plate 12.
(FIG. 1A). In FIG. 1A, the fixed-side core 60 and the movable-side core 70 are shown separately for convenience of explanation, but they are in contact when the ball-point pen tip 80 is actually formed.

As shown in FIG. 4, the rear end of the fixed core 60 is a conical convex surface 61 for molding a seating surface 82. On the other hand, as shown in FIG. 5, the movable-side core 70 has a circular truncated cone 72 at the tip of a column 71, a columnar ink hole 73 at the tip, and a radial And four plate-shaped ink groove portions 74, 74, 74, 74 located at the same position. The tips of the ink hole 73 and the ink groove 74 form a conical concave surface 76 that fits with the conical convex surface 61 of the fixed core 60.

Since the conical convex surface 61 (FIG. 4) is not divided by the ink groove 74, its surface can be smoothed by machining. Thus, the receiving surface 82 formed by the conical convex surface 61 can be molded smoothly. Further, the surface of the movable core 70 is roughened from the inner surface of the cavity mold 20, and an undercut portion 75 having an arc-shaped cross section is provided near its rear end (FIG. 5). This is for pulling out the ballpoint pen tip 80 when opening the mold. Here, FIG. 5C is a cross-sectional view taken along a line aa in FIG. 5B to show the distal end structure of the movable core 70. Movable core in drawings referred to in the following description
The cross-sectional views 70 are all represented by those shown in FIG. 5C.

The distal end portion 31, the intermediate portion 32 and the fixed core 60 shown in FIG. 1A are provided on the fixed mold plate 11. Also,
The movable side cavity 40 and the movable side core 70 are
Is provided. That is, the intermediate portion 32 and the movable side cavity
The boundary with 40 becomes the parting line 13. Here, the reason why the fixed side cavity 30 is divided into the tip portion 31 and the intermediate portion 32 is that the mold is easily manufactured by dividing the portion at the portion where the inclination changes. In addition, these boundary portions are not portions directly in contact with the paper surface at the tip of a ballpoint pen using the ballpoint pen tip 80 finally molded by the mold 10 according to the present invention. Therefore, even if burrs are generated at the boundary portion due to the alignment of the dies, writing with a ballpoint pen as a product is not affected.

(Assembling of Mold) Next, FIGS.
The assembly of the mold 10 will be described with reference to FIG. In addition, in these drawings, it is assumed that all are shown in a front sectional view. First, the front end portion 31 is attached to the fixed mold plate 11 from the rear end side. This is the state shown in FIG. 6A. Next, the tip 31
The fixed-side core 60 is inserted into the fixed-side mounting hole 33. This is the state shown in FIG. 6B. Further, the intermediate portion 32 is mounted from the rear end side. This is the state shown in FIG.

On the other hand, a movable side cavity 40 is mounted on the movable side mold plate 12 from the front end side. This is the state shown in FIG. 8A. Then, the movable core 70 is inserted into the movable mounting hole 43 from the distal end side. This is the state shown in FIG. 8B. (Molding Step) Next, a manufacturing step of the ballpoint pen tip 80 will be described with reference to FIGS.

The fixed side mold plate 11 and the movable side mold plate 12 are
Attach to the mold clamping device and clamp the mold. That is, the intermediate part 32
The movable side cavity 40 is made to approach the fixed side cavity 30 by inserting the movable side core 70 from the rear end side. This is the state shown in FIG. When they come into contact with each other, the conical concave surface 76 of the ink groove 74 and the ink hole 73 provided at the tip of the movable core 70
Of the conical convex surface 61 forming the receiving surface 82. This is the state shown in FIG. Then, mold clamping is performed in this state.

Next, the molten synthetic resin is injected from the submarine gate 14. This is the state shown in FIG. After the resin is cooled and solidified, the mold is released and the mold is opened. At this time, the swaged portion 87 at the tip of the ballpoint pen tip 80 is undercut, but this is to be forcibly removed. Here, by retracting the movable-side cavity 12, the ball-point pen tip 80 accompanies the movable-side core. This is because the surface of the movable side core 70 has a ground surface finish to increase the frictional force with the ballpoint pen tip 80, and since the band-shaped undercut portion 75 is provided, only the movable side core 70 Is prevented from being pulled out. This is the state shown in FIG.

The ball-point pen tip 80 is fixed to the fixed side cavity 30.
After being completely pulled out of FIG. 13 (FIG. 13), the sleeve 41 is protruded in the distal direction, and the ballpoint pen tip 80 is removed. At this time, the undercut portion of the ballpoint pen tip 80 molded by the undercut portion 75 is forcibly removed by elastic deformation. This is the state shown in FIG.

Thus, as shown in FIG.
83 and radial ink grooves 84,
Is molded into a ballpoint pen tip 80 having a smooth shape.

[0040]

Since the present invention is configured as described above, the following effects can be obtained. That is, according to the first aspect of the present invention, it is possible to provide a mold capable of molding the receiving surface smoothly in injection molding of a plastic ball-point pen tip. Further, according to the second aspect of the invention, in addition to the effects of the first aspect of the invention, it is possible to facilitate the manufacture of the mold.

Further, according to the third aspect of the present invention, the receiving surface of the plastic ball-point pen tip manufactured by injection molding can be molded smoothly.

[Brief description of the drawings]

FIG. 1 is a front view (A) showing a mold according to an embodiment of the present invention in a partial cross section, and a perspective view (B) showing a tip of a ballpoint pen tip molded by the mold in a partial cross section. ).

FIG. 2 shows a front end portion of a fixed side cavity, where A is a front sectional view and B is a bottom view.

3A and 3B show a movable side cavity, where A is a plan view and B is a front sectional view.

4A and 4B show a fixed side core, where A is a front view and B is a bottom view.

FIG. 5 shows a movable side core, where A is a front view, B is a plan view,
C shows A in the aa cross section shown in B.

FIGS. 6A and 6B are front cross-sectional views showing a mold assembling process, in which A shows attachment of a distal end to a fixed mold plate, and B shows insertion of a fixed core into the distal end.

FIG. 7 is a front sectional view showing mounting of an intermediate portion to a fixed-side mold plate in a mold assembling process.

FIG. 8 is a front sectional view showing a process of assembling a mold, wherein A shows mounting of a movable-side cavity on a movable-side mold plate;
Indicates insertion of the movable core into the movable cavity.

FIG. 9 is a front cross-sectional view showing the middle of mold clamping in the manufacturing process of the ballpoint pen tip.

FIG. 10 is a front cross-sectional view showing a mold clamping state in the ballpoint pen tip manufacturing process.

FIG. 11 is a front sectional view showing injection of a synthetic resin in a manufacturing process of the ballpoint pen tip.

FIG. 12 is a front cross-sectional view showing a state in which the mold is opened in the manufacturing process of the ballpoint pen tip.

FIG. 13 is a front sectional view showing the ballpoint pen tip in a state where it is completely pulled out from the fixed side cavity.

FIG. 14 is a front cross-sectional view showing protrusion by a sleeve in the manufacturing process of the ballpoint pen tip.

FIG. 15 shows a completed ballpoint pen tip;
A is a front sectional view, and B is a bb sectional view in A.

16A and 16B show the shape of a plastic ballpoint pen tip, where A is a front view, B is a plan view excluding a ball, and C is a cross-sectional view taken along line cc in A.

FIG. 17 shows a mold of a conventional ballpoint pen tip, and is partially shown in section.

[Explanation of symbols]

 10 Mold 11 Fixed side mold plate 12 Movable side mold plate 13 Parting line 14 Submarine gate 15 Cavity 20 Cavity mold 30 Fixed side cavity 31 Tip 32 Middle part 33 Fixed side mounting hole 34 Caulking surface 35 Tapered surface 40 Moving side Cavity 41 Sleeve 43 Movable side mounting hole 50 Core mold 60 Fixed side core 61 Conical convex surface 70 Movable side core 71 Cylindrical part 72 Truncated cone 73 Ink hole 74 Ink groove 75 Undercut 76 Conical concave 80 Ballpoint pen tip 81 Ball holding Part 82 Receiving surface 83 Ink hole 84 Ink groove 85 Back hole 87 Caulking part 88 Taper part 90 Ball

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toru Kitao 2-5-112 Irie, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside the Mitsubishi Pencil R & D Center (72) Inventor Yoshihide Ishii 2, Irie 2, Kanagawa-ku, Yokohama-shi, Kanagawa No. 5-12 Mitsubishi Pencil R & D Center F-term (reference) 2C350 HA08 HA10 HA13 NC02 NC20 NE02 4F202 AH71 AH81 CA11 CB01 CK25 CK42 CK52 CK81 CM06

Claims (3)

[Claims] 1. A mold for manufacturing a plastic ball-point pen tip having a ball holding portion, an ink hole, an ink groove and a back hole by injection molding, comprising: a cavity mold for molding an outer shape of the ball-point tip;
A core mold for molding an inner surface having a ball holding portion, an ink hole, an ink groove, and a back hole; and a cavity mold for molding an outer shape on a tip side, and provided on a fixed side mold plate. And a movable-side cavity formed on the movable-side mold plate at the rear end side, and the core mold is a fixed-side core formed on the fixed-side mold plate by molding the inner surface on the front end side. And molding the inner surface on the rear end side and provided on the movable mold plate.
The fixed-side core and the movable-side core separate from the fixed-side core. The fixed-side core for molding the ball holding portion has a conical convex surface for molding a seating surface serving as a bottom surface of the ball holding portion at its rear end, and has an ink hole, The movable core for molding the ink groove and the back hole has a conical concave surface fitted with the conical convex surface at a tip of a portion where the ink hole and the ink groove are molded. . 2. The mold for a plastic ballpoint pen tip according to claim 1, wherein the fixed side cavity is divided at a boundary between the caulked portion and the tapered portion of the ballpoint pen tip. 3. Injection using a mold having a cavity mold for molding the external shape of a ballpoint pen tip and a core mold for molding the inner surface of a ballpoint pen tip having a ball holding portion, ink holes, ink grooves and back holes. A method of manufacturing a plastic ballpoint pen tip by molding, wherein the mold includes a cavity mold for molding an outer shape of the ballpoint pen tip,
A core mold for molding an inner surface having a ball holding portion, an ink hole, an ink groove, and a back hole; and a cavity mold for molding an outer shape on a tip side, and provided on a fixed side mold plate. And a movable-side cavity formed on the movable-side mold plate at the rear end side, and the core mold is a fixed-side core formed on the fixed-side mold plate by molding the inner surface on the front end side. And molding the inner surface on the rear end side and provided on the movable mold plate.
The fixed-side core and the movable-side core separate from each other. The fixed-side core for molding the ball holding portion has a conical convex surface at the rear end for molding a seating surface serving as a bottom surface of the ball holding portion. The movable core for molding the ink groove and the back hole has a conical concave surface at the tip of the portion for molding the ink hole and the ink groove, which is fitted with the conical convex surface. An assembling process of mounting the movable core and the movable core on the movable mold plate, a mold clamping process of clamping the mold by clamping the fixed mold plate and the movable mold plate, and a mold clamping process. Injection step of injecting the molten synthetic resin into the molded mold, cooling step of cooling the mold, mold opening step of opening the mold, and a protruding process that pushes out the ballpoint pen tip molded with the solidified synthetic resin Method for producing a plastic ball-point pen tip, characterized in that it comprises and.