JP7340330B2 - How to manufacture writing instrument parts - Google Patents

Description

The present invention relates to a method for manufacturing writing instrument parts. The present invention broadly relates to a method for manufacturing resin molded products. The present invention also relates to a writing instrument including parts manufactured by the manufacturing method.

2. Description of the Related Art As writing instruments equipped with a pen nib and an ink absorbing body, products having various types of configurations have been developed and sold.

In a typical configuration, the nib has sufficient rigidity that the forces applied by the user during writing do not cause substantial deformation of the nib. This type of "stiff" nib provides a solid writing feel to the user and has become a standard configuration.

On the other hand, there are also users who desire a soft writing feel like a brush. In order to meet such needs, various types of structures have been developed in which the pen tip is deformed (flexed) by the force applied by the user when writing.

For example, Patent Document 1 discloses a ballpoint pen in which a relay core and a ballpoint pen tip are elastically deformed in response to writing pressure. A rectangular window hole is formed in the ballpoint pen tip to which the relay core is attached, leaving a vertical rib, so that the ballpoint pen tip (vertical rib) is easily deformed.

Further, Patent Document 2 discloses a pen nib for a brush, which is made of a flexible porous liquid supply body made of synthetic fibers bound with a synthetic resin elastomer and has an appropriate number of annular grooves. According to the brush nib, the part having the annular groove acts as a cushion, and it is possible to freely write from thin lines to thick lines depending on the strength of writing pressure.

In a configuration in which the pen tip is deformed (flexed) by a force applied by a user when writing, the ease with which the pen tip deforms (flexibility) depends mainly on the characteristics of the material of the pen tip.

Therefore, in order to achieve a soft writing feel, the pen tip must be made of a soft (easily flexible) material.

However, materials that are soft (easily bent) tend to have a weak ability to retain their own shape, and there is a problem in that they do not return to their original shape after writing, and their life as a pen tip ends prematurely. Ta.

In view of these problems, the present applicant has developed a product that provides a soft (easy to bend) property while suppressing excessive deformation that would make it difficult to return to its original shape after writing, thereby achieving a long lifespan. We have developed a writing instrument and have applied for a patent (patent application 2018-134808).

(Configuration of the first embodiment of patent application 2018-134808)
FIG. 1 is a schematic vertical cross-sectional view of a writing instrument 1 in a first embodiment of the invention disclosed in Japanese Patent Application No. 2018-134808. FIG. 2 is a perspective view of the writing instrument 1 with the cap 60 removed.

3 is a perspective view showing the pen nib 10 of the writing instrument 1, FIG. 4 is a side view of the pen nib 10, and FIG. 5 is a cross-sectional view taken along the line AA of the pen nib 10 in FIG. 6 is a sectional view taken along the line BB of the pen tip 10 in FIG. 4.

First, as shown in FIGS. 1 to 6, the writing instrument 1 of this embodiment includes a pen nib 10 having a front core part 11, a center core part 12, and a rear core part 13, and a rear core part 13 of the pen nib 10. and an ink storage body 20 that contacts the rear core portion 13 to supply ink to the rear core portion 13. The ink storage body 20 is accommodated in a front cylinder 30 and a rear cylinder 40 that constitute a main body cylinder. The cap 60 is removably attached to the front cylinder 30 or the rear cylinder 40.

As shown in FIGS. 3 to 6, the front core 11, center core 12, and rear core 13 of the pen nib 10 of this embodiment have concentric columnar shapes (in detail, The front core 11 is thinner than the center core 12 (excluding the front end region of the front core 11 and tapered parts 12t and 13t, which will be described later). Further, the rear core portion 13 is also thinner than the center core portion 12.

A gently sloping tapered portion 13t is provided on the rear side of the rear core portion 13 to facilitate insertion into the ink storage body 20. Further, a relatively steeply inclined taper portion 12t is provided on the rear side of the central core portion 12, and continues to the rear core portion 13.

The front end of the front core part 11 has a cutting edge shape in which the upper end is located forward of the lower end in side view (see Fig. 4), and is curved in the left-right direction (see Fig. 5) and inclined in the up-down direction. It has a front end portion 11a (see FIG. 4), and acute angle forming flat portions 11b and 11c provided on both left and right sides of the front end portion 11a and making an acute angle (for example, 60 degrees) to each other (see FIG. 5). The line of intersection of the extended surfaces of the acute angle forming plane parts 11b and 11c is a straight line located further forward of the front end part 11a and extending parallel to the front end part 11a). The front end portion 11a and the acute angle forming plane portions 11b and 11c may be formed by cutting, or may be formed in advance by molding.

In addition, as shown in FIGS. 1 and 2, the writing instrument 1 of this embodiment holds the central core 12 of the nib 10, while the nib holding cylinder 50 is held in the front cylinder 30, which is the main body cylinder. It is equipped with

7 is a perspective view showing the nib holding tube 50 of the writing instrument 1, FIG. 8 is a cross-sectional perspective view of the nib holding tube 50 in FIG. 7, and FIG. 9 is a perspective view of the nib holding tube 50 in FIG. FIG. 10 is a cross-sectional view taken along the line AA of the pen tip holding cylinder 50 of FIG. 9.

Moreover, FIG. 11 is a perspective view showing the pen nib 10 and the pen nib holding cylinder 50 of the writing instrument 1, FIG. 12 is a side view showing the pen nib 10 and the pen nib holding cylinder 50, and FIG. FIG. 14 is a sectional view taken along line BB of the pen nib 10 and nib holding tube 50 of FIG. 12, and FIG. , is an enlarged view of part C of the pen tip 10 and the pen tip holding cylinder 50 in FIG. 14.

As shown in FIGS. 7 to 15, the nib holding cylinder 50 includes a holding cylinder part 52 that holds the central core part 12 of the nib 10, and a front end area (front end part 11a) of the front core part 11 of the nib 10. A spare cylinder part 51 extends around the front core part 11 except for a region including the acute angle forming plane parts 11b and 11c. The holding cylinder part 52 and the spare cylinder part 51 have concentric substantially cylindrical shapes.

In the present embodiment, the distance between the inner circumferential surface of the spare cylinder section 51 and the outer circumferential surface of the front core section 11 of the pen tip 10 (sign G1 in FIG. 15) is constant (see FIG. 16). As will be described later, it changes when force is applied to the pen tip 10 during writing).

Further, the front end of the spare cylinder part 51 also has a cutting edge shape in which the upper end is located forward of the lower end in side view (see FIG. 10), and the front end of the front core part 11 of the pen nib 10 and the spare cylinder part 51 are parallel to the front end in side view (see FIG. 12).

Further, the holding cylinder part 52 has holding protrusions 52p at four places on the inner circumferential surface, which is a cylindrical surface, in order to hold the front part of the central core part 12 of the pen nib 10 at four places spaced apart in the circumferential direction. (See FIGS. 8 and 10).

Further, in this embodiment, a flange portion 51f is provided at the rear end of the spare cylinder portion 51, and a concave air hole 51r is provided in the flange portion 51f. The inside of the main cylinder and the outside of the main cylinder can be ventilated through the air hole 51r. As a result, air is taken into the main body cylinder as ink is consumed, and appropriate ink ejection performance can be maintained. Further, the holding tube portion 52 includes a vertical rib 52r that projects radially outward for engagement with the front tube 30, and a slit for improving the ease of assembling the pen tip 10 and the pen tip holding tube 50. 52s are provided. By using the slit 52s, the rotational direction alignment of the nib 10 and the nib holding cylinder 50 with respect to the axis (making the front end 11a and the front end of the spare cylinder part 51 parallel in side view) can be performed. This can be easily done onboard.

As shown in FIG. 1, the front cylinder 30 holds the nib holding cylinder 50 using the vertical ribs 52r of the nib holding cylinder 50. Further, the length of the holding cylinder part 52 is shorter than the length of the central core part 12 (see FIGS. 11 to 13), and the front cylinder 30 has a tapered part 12t at the rear of the central core part 12 of the pen tip 10. is also held.

Note that the pen nib 10 is made of, for example, a porous body of synthetic resin having open cells, but it may be made of any material that allows ink to flow therethrough and has flexibility, and specifically, a fiber nib, a felt nib, etc. , a brush nib, a plastic nib with an axial capillary passage, etc. Further, the spare tube portion 51 of the nib holding tube 50 needs to be less deformable than the front core portion 11.

In addition, the ink storage body 20 may be any member as long as it has continuous pores that can be impregnated with ink, such as a heat-sealed fiber bundle, a resin-processed fiber bundle, a resin-processed felt, etc. Examples include needle-punched felt bodies, porous bodies (for example, open-cell bodies of synthetic resin such as sponge), and the like. Further, the ink storage body 20 may be configured to include an outer skin made of a synthetic resin film or the like on its outer peripheral surface.

(Operations and effects of the first embodiment of patent application 2018-134808)
The writing instrument 1 configured as described above can have the following effects. That is, according to the writing instrument 1 of this embodiment, since the front core part 11 of the pen nib 10 is thinner than the central core part 12 of the nib 10 held in the nib holding cylinder 50, the central core part of the nib 10 It is possible to provide sufficient flexibility of the front core portion 11 of the pen nib 10 relative to the pen tip 12.

The front end of the front core part 11 of the pen nib 10 has a cutting edge shape when viewed from the side, and the upper end length L1 (maximum length) of the front core part 11 of the nib 10 when viewed from the side is sufficiently long. In combination with this, the user can enjoy the unique writing sensation of the front core 11 of the pen nib 10 being bent by the force applied to the front end of the front core 11 of the pen nib 10.

On the other hand, according to the writing instrument 1 of the present embodiment, the spare cylinder part 51 of the nib holding cylinder 50 extends around the front core part 11 of the nib 10, except for the front end area of the front core part 11. When excessive force is applied to the front core part 11 of the pen nib 10, the spare cylinder part 51 comes into contact with the front core part 11 of the pen nib 10 to suppress further deformation of the front core part 11. do. This state is illustrated in FIG. FIG. 16 is a schematic diagram showing a state in which the pen tip 10 of the writing instrument 1 is bent.

In particular, in this embodiment, the upper end length L3 (maximum length) of the spare cylinder part 51 in side view is sufficiently long, and the distance G1 between the spare cylinder part 51 and the front core part 11 of the nib 10 during no load is Coupled with the characteristic that is constant (see Fig. 15), excessive deformation that would make it difficult for the front core 11 of the pen tip 10 to return to its original shape is effectively suppressed, and a long life can be achieved. .

Further, according to the writing instrument 1 of this embodiment, the holding protrusion 52p of the nib holding cylinder 50 holds the front part of the central core part 12 of the nib 10, and the front cylinder 30, which is the main body cylinder, holds the nib 10. The tapered portion 12t of the central core portion 12 is held. As a result, the central core portion 12 of the pen nib 10 is held at two locations in the axial direction, and more reliable retention of the central core portion 12 of the pen nib 10 is realized.

Further, according to the writing instrument 1 of this embodiment, the central core portion 12 of the pen tip 10 has a cylindrical shape. Thereby, the pen tip 10 can be given sufficient strength, and the central core 12 of the pen tip 10 can be held more reliably.

Further, according to the writing instrument 1 of the present embodiment, the holding protrusions 52p of the nib holding cylinder 50 hold the central core 12 of the nib 10 at four locations spaced apart (preferably equally spaced) in the circumferential direction. are doing. Thereby, the central core portion 12 of the pen nib 10 can be held in a well-balanced manner, and the central core portion 12 of the pen nib 10 can be held more reliably.

Further, according to the writing instrument 1 of the present embodiment, when no force is applied to the nib 10, the distance G1 between the spare cylinder part 51 and the front core part 11 of the nib 10 is constant. Thereby, the effect of suppressing excessive deformation of the front core part 11 of the pen tip 10 can be effectively provided by the spare cylinder part 51 in all directions. Further, it is possible to provide an excellent form in terms of design (beauty).

Further, according to the writing instrument 1 of the present embodiment, the front end of the spare cylinder part 51 is also shaped like a cutting blade in which the upper end is located forward of the lower end in side view (see FIG. 10), and the front end of the spare cylinder part 51 is in the shape of a cut-out blade in which the upper end is located forward of the lower end in side view (see FIG. 10). The front end of the core part 11 and the front end of the spare cylinder part 51 are parallel in side view (see FIG. 12). Thereby, the effect of suppressing excessive deformation of the front core portion 11 of the cutting edge-shaped pen tip 10 can be more effectively provided in all directions. Further, it is possible to provide an excellent form in terms of design (beauty).

(Configuration of the first embodiment of patent application 2018-134808)
Next, FIG. 17 is a schematic vertical cross-sectional view of a writing instrument 101 in a second embodiment of the invention disclosed in Japanese Patent Application No. 2018-134808. FIG. 18 is a perspective view of the writing instrument 101 with the cap 60 removed.

19 is a perspective view showing the pen nib 110 of the writing instrument 101, FIG. 20 is a side view of the pen nib 110, and FIG. 21 is a cross-sectional view taken along the line AA of the pen nib 110 in FIG. 22 is a sectional view taken along the line BB of the pen tip 110 in FIG. 20.

First, as shown in FIGS. 17 to 22, the writing instrument 101 of this embodiment includes a pen nib 110 having a front core part 111, a center core part 112, and a rear core part 113, and a rear core part 113 of the pen nib 110. and an ink storage body 20 that contacts the rear core portion 113 to supply ink to the rear core portion 113. Similar to the first embodiment, the ink storage body 20 is housed in the front cylinder 30 and the rear cylinder 40 that constitute the main body cylinder, and the cap 60 is removably attached to the front cylinder 30 or the rear cylinder 40. ing.

As shown in FIGS. 19 to 22, the central core part 112 and the rear core part 113 of the pen nib 110 of this embodiment have a concentric cylindrical shape (in detail, the tapered part 112t described later) , 113t), the rear core portion 113 is thinner than the central core portion 112.

Further, as shown in FIGS. 19 to 22, the front core portion 111 of the pen tip 110 of this embodiment has a substantially quadrangular prism shape with a rectangular cross section with rounded corners, except for a front end region to be described later. (See especially FIG. 22). The axis of the central core part 112 passes through the center (center of gravity) of the approximately rectangular cross section of the front core part 111, and the length of the diagonal line of the approximately rectangular cross section (see FIG. 22) is It is smaller than the diameter of the central core portion 112. That is, the front core portion 111 is thinner than the center core portion 112.

Further, as in the first embodiment, a gently sloped taper portion 113t is provided on the rear side of the rear core portion 113 to facilitate insertion into the ink storage body 20. Further, a relatively steeply inclined taper portion 112t is provided on the rear side of the central core portion 112, and continues to the rear core portion 113.

Also, substantially similar to the first embodiment, the front end of the front core portion 111 has a cutting edge shape in which the upper end is located forward of the lower end in side view (see FIG. 20), and an R is provided in the left-right direction. (See FIG. 21) and a front end portion 111a that is inclined in the vertical direction (see FIG. 20), and acute angle forming flat portions 111b provided on both left and right sides of the front end portion 111a and forming an acute angle (for example, 60 degrees) with each other (see FIG. 21). . The acute angle forming plane portions 111b and 111c may be formed by cutting, or may be formed in advance by molding.

Further, as in the first embodiment, the writing instrument 101 of this embodiment holds the central core 112 of the pen tip 110 while holding it in the front tube 30 which is the main body tube. The pen tip holding cylinder 150 is provided with a cylindrical shape.

23 is a perspective view showing the nib holding tube 150 of the writing instrument 101, FIG. 24 is a cross-sectional perspective view of the nib holding tube 150 in FIG. 23, and FIG. 25 is a perspective view of the nib holding tube 150 in FIG. 26 is a sectional view taken along the line AA of the pen tip holding cylinder 150 of FIG. 25.

Moreover, FIG. 27 is a perspective view showing the pen nib 110 and the pen nib holding cylinder 150 of the writing instrument 101, FIG. 28 is a side view showing the pen nib 110 and the pen nib holding cylinder 150, and FIG. FIG. 30 is a sectional view taken along line BB of the pen nib 110 and pen nib holding tube 150 of FIG. 28, and FIG. , is an enlarged view of part C of the pen tip 110 and the pen tip holding cylinder 150 in FIG. 30.

As shown in FIGS. 23 to 31, the pen tip holding cylinder 150 includes a holding cylinder part 152 that holds the central core part 112 of the pen nib 110, and a front end area (front end part 111a) of the front core part 111 of the pen nib 110. A spare cylinder part 151 extends around the front core part 111 except for a region including the acute angle forming plane parts 111b and 111c. The holding cylinder part 152 has a substantially cylindrical shape corresponding to the central core part 112, and the spare cylinder part 151 has a substantially square cylinder shape corresponding to the front core part 111.

In the present embodiment, the distance between the inner circumferential surface of the spare cylinder part 151 and the outer circumferential surface of the front core part 111 of the pen nib 110 (sign G2 in FIG. 31) is constant (during writing, (See Figure 16).

Further, the front end of the spare cylinder part 151 also has a cutting edge shape in which the upper end is located forward of the lower end in side view (see FIG. 26), and the front end of the front core part 111 of the nib 110 and the spare cylinder part 151 are parallel to the front end in side view (see FIG. 28).

Further, as in the first embodiment, the holding cylinder part 152 is arranged on the inner circumferential surface which is a cylindrical surface in order to hold the front part of the central core part 112 of the pen tip 110 at four locations spaced apart in the circumferential direction. Holding protrusions 152p are provided at four locations (see FIGS. 24 and 26).

Further, in this embodiment, a flange portion 151f is provided at the rear end of the spare cylinder portion 151, and a concave air hole 151r is provided in the flange portion 151f. The inside of the main cylinder and the outside of the main cylinder can be ventilated through the air hole 151r. As a result, air is taken into the main body cylinder as ink is consumed, and appropriate ink ejection performance can be maintained. The holding cylinder portion 152 also includes a vertical rib 152r that projects radially outward for engagement with the front cylinder 30, and a slit for improving the ease of assembling the pen tip 110 and the pen tip holding cylinder 150. 152s are provided. By using the slit 152s, the rotational direction alignment of the nib 110 and the nib holding cylinder 150 with respect to the axis (making the front end 111a and the front end of the spare cylinder part 151 parallel in side view) is achieved. This can be easily done onboard.

As shown in FIG. 17, the front cylinder 30 holds the nib holding cylinder 150 using the vertical ribs 152r of the nib holding cylinder 150. Further, the length of the holding cylinder part 152 is shorter than the length of the central core part 112 (see FIGS. 27 to 29), and the front cylinder 30 has a tapered part 112t at the rear of the central core part 112 of the nib 110. is also held.

Note that the content described above regarding the material of the pen nib 10 is also applicable to the pen nib 110.

(Operations and effects of the second embodiment of patent application 2018-134808)
The writing instrument 101 configured as described above can have the following effects. That is, also in the writing instrument 101 of this embodiment, since the front core part 111 of the pen nib 110 is thinner than the central core part 112 of the nib 110 held in the nib holding cylinder 150, the central core part 112 of the pen nib 110 It is possible to provide sufficient flexibility of the front core portion 111 of the pen tip 110 relative to the pen tip 110.

The front end of the front core 111 of the pen nib 110 has a cutting edge shape when viewed from the side, and the upper end length L11 (maximum length) of the front core 111 of the nib 110 is sufficiently long. Therefore, the user can enjoy the unique writing sensation of the front core 111 of the pen nib 110 being bent by the force applied to the front end of the front core 111 of the pen nib 110.

On the other hand, also in the writing instrument 101 of this embodiment, the spare cylinder part 151 of the nib holding cylinder 150 extends around the front core part 111 of the pen nib 110, except for the front end area of the front core part 111. Therefore, when excessive force is applied to the front core part 111 of the pen nib 110, the spare cylinder part 151 comes into contact with the front core part 111 of the pen nib 110 to suppress further deformation of the front core part 111. (This is the same as that described with reference to FIG. 16 for the first embodiment).

In particular, also in this embodiment, the maximum length (length at the upper end) of the spare cylinder part 151 is sufficiently long, and the distance G2 between the spare cylinder part 151 and the front core part 111 of the nib 110 during no load is constant. Coupled with this feature (see FIG. 31), excessive deformation that would make it difficult for the front core 111 of the pen tip 110 to return to its original shape is effectively suppressed, and a long life can be achieved.

Also, in the writing instrument 101 of this embodiment, the holding protrusion 152p of the nib holding tube 150 holds the front part of the central core part 112 of the nib 110, and the front tube 30, which is the main body tube, holds the central core part 112 of the nib 110. The tapered portion 112t of the central core portion 112 is held. Thereby, the central core portion 112 of the pen nib 110 is held at two locations in the axial direction, and more reliable retention of the central core portion 112 of the pen nib 110 is realized.

Also, in the writing instrument 101 of this embodiment, the central core portion 112 of the pen tip 110 has a cylindrical shape. Thereby, the pen tip 110 can be given sufficient strength, and the central core portion 112 of the pen tip 110 can be held more reliably.

Also, in the writing instrument 101 of this embodiment, the holding protrusions 152p of the nib holding cylinder 150 hold the central core 112 of the nib 110 at four locations spaced apart (preferably equally spaced) in the circumferential direction. ing. Thereby, the central core portion 112 of the pen nib 110 can be held in a well-balanced manner, and the central core portion 112 of the pen nib 110 can be held more reliably.

Furthermore, in the writing instrument 101 of this embodiment as well, when no force is applied to the nib 110, the distance G2 between the spare cylinder part 151 and the front core part 111 of the nib 110 is constant. Thereby, the effect of suppressing excessive deformation of the front core part 111 of the pen tip 110 can be effectively provided by the spare cylinder part 151 in all directions. Further, it is possible to provide an excellent form in terms of design (beauty).

Also, in the writing instrument 101 of this embodiment, the front end of the spare cylinder part 151 has a cutting edge shape in which the upper end is located forward of the lower end in side view (see FIG. 26), and the front core of the pen tip 110 The front end of the portion 111 and the front end of the spare cylinder portion 151 are parallel in side view (see FIG. 28). Thereby, the effect of suppressing excessive deformation of the front core portion 111 of the cutting edge-shaped pen tip 110 can be more effectively provided in all directions. Further, it is possible to provide an excellent form in terms of design (beauty).

Publication No. 59-16227 Japanese Patent Application Publication No. 3-221494 Japanese Patent Application Publication No. 11-277545

As mentioned above, the invention disclosed in Japanese Patent Application No. 2018-134808 has significantly useful effects. For this reason, the applicant has made efforts to establish a mass production system. In the process, we came to understand the following problems regarding the manufacture of the pen nib holding cylinders 50, 150.

The nib holding cylinders 50, 150 are manufactured from a resin material by injection molding. As shown in FIG. 32, the manufacturing apparatus includes a front cavity 501 having a front cavity 501c that corresponds (complementarily) to the outer peripheral contour of the front part of the pen tip holding cylinder 150, which is a resin molded product; A rear cavity 502 having a rear cavity 502c adjacent to the front cavity 501c of 501 and corresponding (complementarily) to the outer peripheral contour of the rear part of the nib holding cylinder 150; The core pin member 503 has a corresponding outer peripheral shape (complementarily) and is inserted into the front cavity 501c of the front cavity 501 and the rear cavity 502c of the rear cavity 502, and the front end shape of the nib holding cylinder 150 ( A front end defining member 504 having a rear end shape corresponding (complementarily) to the rear end shape, and an ejector member 505 having a front end shape corresponding (complementarily) to the rear end shape of the pen tip holding cylinder 150.

In the example of FIG. 32, the front cavity 501 is a fixed cavity, the rear cavity 502 is a movable cavity (moves in the axial direction of the nib holding cylinder 150 with respect to the front cavity 501), and the core pin member 503 is a movable core pin, the front end defining member 504 is a fixed pin, and the ejector member 505 is an ejector sleeve.

As shown in FIG. 33, the front end shape of the ejector member 505 has a pair of opposing extending portions 505e corresponding (complementarily) to the slit 152s of the pen tip holding cylinder 150. Each extending portion 505e extends in the axial direction and has a semicircular tip. 33(a) is a front view of the ejector member 505, FIG. 33(b) is a side view of the ejector member 505, and FIG. 33(c) is a cross section taken along line cc in FIG. 33(a). 33(d) is a sectional view taken along the line dd in FIG. 33(b), and FIG. 33(e) is a perspective view of the vicinity of the tip of the ejector member 505.

The front cavity 501c of the front cavity 501, the rear cavity 502c of the rear cavity 502, the outer peripheral shape of the core pin member 503, the rear end shape of the front end defining member 504, and the front end shape (extension) of the ejector member 505. The pen tip holding cylinder 150 is molded by injecting a resin material into the molding space defined by the portion 505e (having the portion 505e) (see FIG. 34).

Thereafter, the molded nib holding tube 150 must be removed from the manufacturing device. First, the front cavity 501 and the rear cavity 502 are separated from each other, and the front cavity 501c and the rear cavity 502c are separated from each other, so that the front part of the nib holding cylinder 150 is pulled out from the front cavity 501c. (See Figure 35).

Subsequently, the core pin member 503 is extracted from the rear cavity 502c (see FIG. 36).

Thereafter, the ejector member 505 is moved forward with respect to the rear cavity 502, so that the rear part of the pen tip holding cylinder 150 is extracted from the rear cavity 502c (see FIG. 37).

Here, after the rear part of the pen tip holding tube 150 is extracted from the rear cavity 502c, if the pen tip holding tube 150 and the ejector member 505 are separated, the pen tip holding tube 150 will fall below the manufacturing apparatus. In other words, the pen tip holding cylinder 50 can be taken out. However, the molded pen tip holding tube 150 and the ejector member 505 may adhere to each other, and the pen tip holding tube 150 may not fall down as desired. This adhesion tendency is higher when the contact area between the pen tip holding cylinder 150 and the ejector member 505 is increased due to the presence of the extending portion 505e.

As a mechanism for taking out the resin molded product that has adhered to the ejector member in this way, Patent Document 3 discloses a mechanism that locks the rear end of the resin molded product after being pulled out when returning the ejector member to the rear side. Accordingly, we are proposing the use of an additional member called a stripper bush that separates the resin molded product from the ejector member. However, employment of such additional members increases the cost of the manufacturing equipment.

The present invention has been made in view of the above findings, and its purpose is to solve the problem of a resin molded product and an ejector member adhering to each other and not being separated, while suppressing an increase in cost. It is an object of the present invention to provide a method for manufacturing parts of a writing instrument, broadly speaking, a method for manufacturing resin molded products. Another object of the present invention is to provide a writing instrument including parts manufactured by the manufacturing method.

In order to manufacture a cylindrical resin molded product, the present invention includes a front cavity having a front cavity corresponding to the outer peripheral contour of the front part of the resin molded product, and a front cavity adjacent to the front cavity of the front cavity. a rear cavity having a rear cavity corresponding to the outer peripheral contour of the rear part of the resin molded product; and a rear cavity having an outer peripheral shape corresponding to the inner peripheral contour of the resin molded product; A core pin member inserted into the rear cavity of the rear side cavity, a front end defining member having a rear end shape corresponding to the front end shape of the resin molded product, and a front end corresponding to the rear end shape of the resin molded product. an ejector member having a shape, the front cavity of the front cavity, the rear cavity of the rear cavity, the outer peripheral shape of the core pin member, and the rear end shape of the front end defining member. and the front end shape of the ejector member, molding the resin molded product by injecting a resin material into a molding space defined by the front end shape of the ejector member, and separating the front cavity and the rear cavity from each other. a front part extraction step of extracting the front part of the resin molded product from the front cavity by separating the front cavity and the rear cavity from each other; and extracting the core pin member from the front cavity and the rear cavity. a step of extracting a core pin member; and a step of extracting a rear portion of the resin molded product from the rear cavity by moving the ejector member forward with respect to the rear cavity. In the method for manufacturing a resin molded product, a protuberance that locally protrudes in the axial direction is provided on the outer peripheral contour of a rear part of the resin molded product, and the step of extracting the rear part includes removing the protuberance from the protrusion. This method includes the step of elastically deforming the material into a collapsed shape and passing it through the rear cavity of the rear cavity.

According to the method of the present invention, a protuberance that locally protrudes in the axial direction is provided on the outer peripheral contour of the rear part of a resin molded product, and in the process of extracting the rear part, the protuberance is elastically deformed into a collapsed shape. It can be passed through the rear cavity of the rear side cavity while

Thereby, the resin molded product and the ejector member can be separated from each other by the reaction force that causes the raised portion to elastically return from the collapsed shape to the raised shape immediately after being released from the rear cavity. That is, in the rear part extracting step, the resin molded product and the ejector member are separated by a reaction force that causes the raised part to elastically return from the collapsed shape to the raised shape immediately after being released from the rear cavity. The process may include a step of causing

Alternatively, even if it is not possible to separate the resin molded product and the ejector member due to such reaction force, after the rear part extraction step, the ejector is returned to move the ejector member rearward with respect to the rear cavity. By performing the process, the resin molded product and the ejector member can be separated. This is because, in the ejector return step, the raised portion that has returned to its raised shape effectively prevents the resin molded product from returning into the rear cavity. That is, after the rear part extraction process, it may further include an ejector return process of moving the ejector member to the rear side with respect to the rear side cavity, and the ejector return process includes the ejector return process that returns the raised part to the raised shape. The method may include a step of separating the resin molded product and the ejector member by preventing the resin molded product from returning into the rear cavity.

Preferably, the front end side of the raised portion is an inclined surface. In this case, it is facilitated to elastically deform the raised portion into a collapsed shape in the rear portion extraction process.

On the other hand, it is preferable that the rear end side of the raised part has a flat part perpendicular to the axial direction. In this case, since the raised portion that has returned to its raised shape is likely to interfere with the end face of the rear cavity, it is possible to enhance the effect of preventing the resin molded product from returning into the rear cavity.

Moreover, it is preferable that a plurality of raised parts be provided and arranged at the same position in the axial direction, but arranged at non-uniform positions in the circumferential direction. In this case, the reaction forces can be generated at the same time (all at once) so that they do not cancel each other out (so that the posture is tilted).

The resin molded product to be manufactured by the method of the present invention described above is particularly intended for parts of writing instruments, but at least at the time of filing of this application, it is not limited to parts of writing instruments.

Further, the present invention is a writing instrument component manufactured by the method of the present invention. In particular, the present invention provides a pen nib having a front nib, a central nib, and a rear nib, an ink storage body that contacts the rear nib of the nib and supplies ink to the rear nib; a main body cylinder that accommodates the ink storage body; and a nib holding cylinder that holds the central core of the pen nib and is held in the main body cylinder; The rear core part of the pen nib is thinner than the central core part of the pen nib, and the front core part of the nib has an upper end that is thinner than the central core part of the pen nib. The front core part of the pen tip has a cutting edge shape that is located forward of the lower end, and the maximum length in side view of the front core part of the nib is 7 mm or more. It has a spare cylinder part extending around the front core part except for the front end area of the core part, and the maximum length of the spare cylinder part in a side view is 5 mm or more, and the spare cylinder part and The distance between the nib and the front core part is 0.03 to 1.0 mm, and the outer circumferential contour of the rear part of the nib holding cylinder includes a protuberance that locally protrudes in the axial direction. The writing instrument is characterized in that the protruding portion can temporarily assume a collapsed shape due to elastic deformation.

According to the present invention, since the front core of the pen nib is thinner than the central core of the pen nib held in the nib holding tube, the front core of the pen nib can be easily bent with respect to the central core of the pen nib. It is possible to provide In particular, the front end of the front core of the pen tip has a cutting edge shape when viewed from the side, and the maximum length (length at the upper end) of the front core of the pen tip when viewed from the side is 7 mm or more. The user can enjoy the unique writing sensation of the front core of the pen tip being bent by the force applied to the front end of the front core of the pen tip.

On the other hand, according to the present invention, the spare cylinder part of the nib holding cylinder extends around the front nib except for the front end area of the front nib, and the front nib part of the nib extends around the front nib. When excessive force is applied to the pen tip, the front core portion of the pen tip comes into contact with the reserve barrel portion to suppress further deformation of the front core portion. In particular, the maximum length (length at the top end) of the spare cylinder in side view is 5 mm or more, and the distance between the spare cylinder and the front core of the nib is 0.03 to 1.0 mm. By doing so, excessive deformation that would make it difficult for the front core of the pen tip to return to its original shape is effectively suppressed, and a long life can be achieved.

According to the present invention, a protrusion that locally protrudes in the axial direction is provided on the outer circumferential contour of the rear portion of the nib holding cylinder, and the protrusion has a temporarily collapsed shape due to elastic deformation. Therefore, when manufacturing the nib holding cylinder by injection molding, there is a step of extracting the rear part of the nib holding cylinder from the rear cavity of the rear cavity, which is an injection mold, using an ejector member. In this case, the protrusion can be elastically deformed into a collapsed shape while passing through the rear cavity.

Thereby, the pen tip holding cylinder and the ejector member can be separated from each other by the reaction force that elastically returns from the collapsed shape to the raised shape immediately after the raised portion is released from the rear cavity. Alternatively, even if it is not possible to separate the pen tip holding tube and the ejector member due to such reaction force, after the process of extracting the rear part of the pen tip holding tube, the ejector member is removed from the rear cavity. By performing the ejector return step of moving the pen tip to the rear side, the pen tip holding cylinder and the ejector member can be separated. This is because, in the ejector return step, the raised portion that has returned to its raised shape effectively prevents the pen tip holding cylinder from returning into the rear cavity.

Further, in the present invention, the pen tip holding tube holds a front part of the central core part of the pen nib, and the main body cylinder holds a rear part of the central core part of the pen nib. Preferably.

According to this, the central core portion of the pen tip is held at at least two locations in the axial direction, so that the central core portion of the pen tip can be held more reliably.

Further, it is preferable that the central core portion of the pen tip has a cylindrical shape.

According to this, the pen tip can be provided with sufficient strength, and the central core portion of the pen tip can be held more reliably.

Further, it is preferable that the nib holding cylinder holds the central core portion of the nib at a plurality of locations spaced apart in the circumferential direction.

According to this, the central core portion of the pen tip can be held in a well-balanced manner, and the central core portion of the pen tip can be held more reliably.

Moreover, it is preferable that the spacing between the spare cylinder part and the front core part of the pen tip be substantially constant.

According to this, the effect of suppressing excessive deformation of the front core part of the pen tip can be effectively provided in all directions by the spare cylinder part. Further, it is possible to provide an excellent form in terms of design (beauty).

For example, the central core portion of the pen tip may be formed in a cylindrical shape except for the front end region. In this case, the reserve cylinder part may be formed in a corresponding cylindrical shape.

Alternatively, the central core portion of the pen tip may be formed into a substantially polygonal column shape, for example, a substantially quadrangular column shape, except for the front end region. In this case, the spare cylinder portion may be formed into a corresponding substantially polygonal column shape, for example, a substantially square tube shape.

Further, the front end of the spare cylinder part also has a cutting edge shape in which the upper end is located forward of the lower end in a side view, and the front end of the front core part of the pen tip and the front end of the spare cylinder part are connected to each other. are preferably parallel in side view.

According to this, the effect of suppressing excessive deformation of the front core portion of the cutting edge-shaped pen tip when viewed from the side can be more effectively provided in all directions. Further, it is possible to provide an excellent form in terms of design (beauty).

Further, it is preferable that at least a portion of the pen tip holding cylinder is made of a transparent material or a translucent material.

According to this, it becomes easier to visually recognize the color of the ink. Further, it is possible to provide an excellent form in terms of design (beauty).

Further, it is preferable that a mark indicating the angular position of the pen tip is attached to the main body cylinder and/or the pen tip holding cylinder.

According to this, the angular position (orientation) of the pen tip can be more easily grasped. The mark is not limited to a visual mark, but may be an unevenness that can be discerned by touch.

According to the method of the present invention, a protuberance that locally protrudes in the axial direction is provided on the outer peripheral contour of the rear part of a resin molded product, and in the process of extracting the rear part, the protuberance is elastically deformed into a collapsed shape. It can be passed through the rear cavity of the rear side cavity while

Thereby, the resin molded product and the ejector member can be separated from each other by the reaction force that causes the raised portion to elastically return from the collapsed shape to the raised shape immediately after being released from the rear cavity. That is, in the rear part extracting step, the resin molded product and the ejector member are separated by a reaction force that causes the raised part to elastically return from the collapsed shape to the raised shape immediately after being released from the rear cavity. The process may include a step of causing

Alternatively, even if it is not possible to separate the resin molded product and the ejector member due to such reaction force, after the rear part extraction step, the ejector is returned to move the ejector member rearward with respect to the rear cavity. By performing the process, the resin molded product and the ejector member can be separated. This is because, in the ejector return step, the raised portion that has returned to its raised shape effectively prevents the resin molded product from returning into the rear cavity. That is, after the rear part extraction process, it may further include an ejector return process of moving the ejector member to the rear side with respect to the rear side cavity, and the ejector return process includes the ejector return process that returns the raised part to the raised shape. The method may include a step of separating the resin molded product and the ejector member by preventing the resin molded product from returning into the rear cavity.

(Figures 1 to 31 are used as is, Figure 32 is used as Figure 57: Attachment omitted)
FIG. 1 is a schematic vertical cross-sectional view of a writing instrument according to a first embodiment of the invention of the applicant's earlier application. FIG. 2 is a perspective view of the writing instrument of FIG. 1 with the cap removed. FIG. 2 is a perspective view showing the pen tip of the writing instrument shown in FIG. 1. FIG. FIG. 4 is a side view of the pen tip of FIG. 3; 5 is a cross-sectional view taken along line AA of the pen tip in FIG. 4. FIG. 5 is a sectional view taken along line BB of the pen tip in FIG. 4. FIG. FIG. 2 is a perspective view showing a pen tip holding cylinder of the writing instrument shown in FIG. 1. FIG. FIG. 8 is a cross-sectional perspective view of the pen tip holding cylinder of FIG. 7; FIG. 8 is a plan view of the pen tip holding cylinder of FIG. 7; 10 is a cross-sectional view taken along line AA of the pen tip holding cylinder in FIG. 9. FIG. FIG. 2 is a perspective view showing a pen nib and a pen nib holding cylinder of the writing instrument shown in FIG. 1. FIG. FIG. 12 is a side view showing the pen tip and pen tip holding cylinder of FIG. 11; FIG. 13 is a cross-sectional view taken along line AA of the pen tip and pen tip holding cylinder of FIG. 12. 13 is a sectional view taken along line BB of the pen tip and pen tip holding cylinder of FIG. 12. FIG. FIG. 15 is an enlarged view of part C of the pen tip and pen tip holding cylinder of FIG. 14; FIG. 2 is a schematic diagram showing a state in which the pen tip of the writing instrument shown in FIG. 1 is bent. It is a schematic longitudinal cross-sectional view of the writing instrument in 2nd Embodiment of the invention of a prior application of this applicant. FIG. 18 is a perspective view of the writing instrument of FIG. 17 with the cap removed. FIG. 18 is a perspective view showing the pen tip of the writing instrument shown in FIG. 17; FIG. 20 is a side view of the pen tip of FIG. 19; 21 is a sectional view taken along line AA of the pen tip in FIG. 20. FIG. 21 is a sectional view taken along line BB of the pen tip in FIG. 20. FIG. FIG. 18 is a perspective view showing the pen tip holding cylinder of the writing instrument shown in FIG. 17; 24 is a cross-sectional perspective view of the pen tip holding cylinder of FIG. 23. FIG. FIG. 24 is a plan view of the pen tip holding cylinder of FIG. 23; FIG. 26 is a cross-sectional view taken along line AA of the pen tip holding cylinder in FIG. 25. FIG. 18 is a perspective view showing a pen nib and a pen nib holding cylinder of the writing instrument shown in FIG. 17; 28 is a side view showing the pen tip and pen tip holding cylinder of FIG. 27. FIG. FIG. 29 is a cross-sectional view taken along line AA of the pen tip and pen tip holding cylinder of FIG. 28. FIG. 29 is a sectional view taken along line BB of the pen tip and pen tip holding cylinder of FIG. 28. 31 is an enlarged view of part C of the pen tip and pen tip holding cylinder of FIG. 30. FIG. FIG. 24 is a schematic diagram of a manufacturing apparatus for manufacturing the pen nib holding cylinder of FIG. 23. FIG. 33 is a schematic diagram of the ejector member of FIG. 32; FIG. 24 is a schematic diagram for explaining the injection molding process of the manufacturing method for manufacturing the pen nib holding cylinder of FIG. 23. FIG. 24 is a schematic diagram for explaining a front part extraction step of the manufacturing method for manufacturing the pen nib holding cylinder of FIG. 23; FIG. 24 is a schematic diagram for explaining a core pin extraction step of the manufacturing method for manufacturing the pen nib holding cylinder of FIG. 23; FIG. 24 is a schematic diagram for explaining a rear part extraction step of the manufacturing method for manufacturing the pen nib holding cylinder of FIG. 23; BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic longitudinal cross-sectional view of the writing instrument in one embodiment of this invention. FIG. 39 is a perspective view of the writing instrument of FIG. 38 with the cap removed. FIG. 39 is a perspective view showing the pen tip holding cylinder of the writing instrument shown in FIG. 38; 41 is a front view of the pen tip holding cylinder of FIG. 40. FIG. 41 is a right side view of the pen tip holding cylinder of FIG. 40. FIG. FIG. 43 is a cross-sectional view taken along line AA of the pen tip holding cylinder in FIG. 42. FIG. 44 is an enlarged view of part B of the pen tip holding cylinder in FIG. 43; FIG. 42 is a sectional view taken along line CC of the pen nib holding cylinder in FIG. 41. FIG. 43 is an enlarged view of section D of the pen tip holding cylinder in FIG. 42; FIG. 41 is a schematic diagram of a manufacturing apparatus for manufacturing the pen nib holding cylinder of FIG. 40. FIG. 48 is a schematic diagram of the ejector member of FIG. 47; 41 is a schematic diagram for explaining the injection molding process of the manufacturing method for manufacturing the pen nib holding cylinder of FIG. 40. FIG. FIG. 41 is a schematic diagram for explaining the front part extraction step of the manufacturing method for manufacturing the pen nib holding cylinder of FIG. 40; 41 is a schematic diagram for explaining a core pin extraction step of the manufacturing method for manufacturing the pen nib holding cylinder of FIG. 40. FIG. FIG. 41 is a schematic diagram for explaining a rear part extraction step of the manufacturing method for manufacturing the pen nib holding cylinder of FIG. 40; 41 is a schematic diagram for explaining an ejector return step of the manufacturing method for manufacturing the pen nib holding cylinder of FIG. 40. FIG. 41 is a schematic diagram for explaining an ejector return step of the manufacturing method for manufacturing the pen nib holding cylinder of FIG. 40. FIG. FIG. 41 is a schematic diagram for explaining the ejector re-extrusion step of the manufacturing method for manufacturing the pen tip holding cylinder of FIG. 40; FIG. 41 is a schematic diagram for explaining an ejector re-return step of the manufacturing method for manufacturing the pen nib holding cylinder of FIG. 40; FIG. 29 is a diagram similar to FIG. 28 showing an example in which the tip region of the pen tip holding cylinder is colored.

(Configuration of embodiment of writing instrument)
First, an embodiment of a writing instrument having parts manufactured by the method of the present invention will be described. FIG. 38 is a schematic vertical cross-sectional view of the writing instrument 201 in this embodiment. FIG. 39 is a perspective view of the writing instrument 201 with the cap 60 removed.

The pen nib 110 is similar to the pen nib 110 of the second embodiment of the above-mentioned Japanese Patent Application No. 2018-134808. That is, FIG. 19 is also a perspective view showing the pen tip 110 of the writing instrument 201. 20 is a side view of the pen nib 110, FIG. 21 is a sectional view taken along the line AA of the pen nib 110 in FIG. 20, and FIG. 22 is a sectional view taken along the line BB of the nib 110 in FIG. FIG.

First, as shown in FIG. 38, FIG. 39, FIG. 19 to FIG. 110 and an ink storage body 20 that comes into contact with the rear core section 113 of the rear core section 110 to supply ink to the rear core section 113. Similar to each embodiment of Japanese Patent Application No. 2018-134808, the ink storage body 20 is accommodated in the front cylinder 30 and the rear cylinder 40 that constitute the main body cylinder, and the cap 60 is attached to the front cylinder 30 or the rear cylinder 40. It is removable.

As shown in FIGS. 19 to 22, the central core part 112 and the rear core part 113 of the pen nib 110 of this embodiment have a concentric cylindrical shape (in detail, the tapered part 112t described later) , 113t), the rear core portion 113 is thinner than the central core portion 112. For example, the diameter of the central core 112 is 5.1 mm, and the diameter of the rear core 113 is 3.5 mm.

Further, as shown in FIGS. 19 to 22, the front core portion 111 of the pen tip 110 of this embodiment has a substantially quadrangular prism shape with a rectangular cross section with rounded corners, except for a front end region to be described later. (See especially FIG. 22). The axis of the central core part 112 passes through the center (center of gravity) of the approximately rectangular cross section of the front core part 111, and the length of the diagonal line of the approximately rectangular cross section (see FIG. 22) is It is smaller than the diameter of the central core portion 112. That is, the front core portion 111 is thinner than the center core portion 112. More specifically, the substantially rectangular cross section of the front core portion 111 (see FIG. 22) has a long side length of 4.1 mm and a short side length of 3.2 mm.

In addition, similar to each embodiment of Japanese Patent Application No. 2018-134808, a gently sloped taper portion 113t is provided on the rear side of the rear core portion 113 to facilitate insertion into the ink storage body 20. . Further, a relatively steeply inclined taper portion 112t is provided on the rear side of the central core portion 112, and continues to the rear core portion 113. For example, the length of the rear core portion 113 (including the tapered portion 113t) is 7.7 mm, and the length of the central core portion 112 (including the tapered portion 112t) is 11.8 mm.

Also, substantially similar to each embodiment of Japanese Patent Application No. 2018-134808, the front end of the front core portion 111 has a cutting edge shape in which the upper end is located forward of the lower end in side view (see FIG. 20), and A front end portion 111a is provided with an R (see FIG. 21) and inclined in the vertical direction (see FIG. 20), and a front end portion 111a is provided on both left and right sides of the front end portion 111a and forms an acute angle (for example, 60 degrees) with each other (see FIG. 21). (The intersection line of the extended surfaces of the acute angle forming flat parts 111b and 111c is a straight line located further forward of the front end 111a and extending parallel to the front end 111a. ). For example, the upper end length L11 (maximum length) of the front core portion 111 when viewed from the side is 13.8 mm, and the lower end length L12 (minimum length) of the front core portion 111 when viewed from the side is 12.3 mm. The front end portion 111a and the acute angle forming plane portions 111b and 111c may be formed by cutting, or may be formed in advance by molding.

Further, as in each embodiment of Japanese Patent Application No. 2018-134808, the writing instrument 201 of this embodiment holds the central core portion 112 of the pen tip 110, and has a main body cylinder, as shown in FIGS. 38 and 39. A pen tip holding cylinder 250 held in the front cylinder 30 is provided. The pen tip holding tube 250 is similar to the pen tip holding tube 150 of the second embodiment of the above-mentioned Japanese Patent Application No. 2018-134808, except that it has a raised portion 255 which will be described later.

40 is a perspective view showing the nib holding tube 250 of the writing instrument 201, FIG. 41 is a front view of the nib holding tube in FIG. 40, and FIG. 42 is a right side view of the nib holding tube in FIG. 40. It is a diagram. 43 is a sectional view taken along the line AA of the pen nib holding tube in FIG. 42, FIG. 44 is an enlarged view of part B of the pen nib holding tube in FIG. 43, and FIG. 45 is a cross-sectional view of the pen nib holding tube in FIG. 41. It is a sectional view taken along the line CC of the tip holding cylinder,
FIG. 46 is an enlarged view of the D section of the pen tip holding cylinder in FIG. 42.

As shown in FIGS. 40 to 46, the pen tip holding cylinder 250 includes a holding cylinder part 252 that holds the central core part 112 of the pen nib 110, and a front end area (front end part 111a) of the front core part 111 of the pen nib 110. A spare cylinder part 251 extends around the front core part 111 except for a region including the acute angle forming plane parts 111b and 111c. The holding cylinder part 252 has a substantially cylindrical shape corresponding to the central core part 112, and the spare cylinder part 251 has a substantially square cylinder shape corresponding to the front core part 111.

For example, the upper end length L13 (maximum length) of the spare cylinder part 251 in side view is 10 mm, the lower end length L14 (minimum length) of the spare cylinder part 251 in side view is 8.3 mm, The substantially rectangular cross section of the outer peripheral surface of the portion 251 (excluding a flange portion 251f described later) (see FIG. 30) has a long side length of 5.3 mm and a short side length of 4.4 mm, The substantially rectangular cross section of the inner circumferential surface of the spare cylinder portion 251 (see FIG. 30) has a long side length of 4.5 mm and a short side length of 3.6 mm. Therefore, in the present embodiment, the distance between the inner circumferential surface of the spare cylinder section 251 and the outer circumferential surface of the front core section 111 of the pen tip 110 (represented by reference numeral G2 in FIG. 31) is constant at 0.2 mm. (It changes when force is applied to the pen tip 10 during writing: see FIG. 16). Further, an axial draft angle may be provided on at least one of the inner circumferential surface of the spare cylinder portion 251 or the outer circumferential surface of the front core portion 111 of the nib 110. This not only improves the productivity of the spare cylinder part 251 and the pen tip 110, but also provides sufficient flexibility of the front core part 111.

Further, the front end of the spare cylinder part 251 also has a cutting edge shape in which the upper end is located forward of the lower end in a side view (see FIG. 41), and the front end of the front core part 111 of the nib 110 and the spare cylinder part 251 are parallel to the front end in side view (see FIG. 28).

Further, as in each embodiment of Japanese Patent Application No. 2018-134808, the holding cylinder part 252 has a diameter of 5.5 mm in order to hold the front part of the central core part 112 of the pen nib 110 at four locations spaced apart in the circumferential direction. Holding protrusions 252p are provided at four locations on the inner peripheral surface, which is a cylindrical surface (see FIG. 43). Each holding protrusion 252p has, for example, a circumferential width of 0.6 mm and a length of 3.6 mm, and protrudes inward to a position radially distanced from the axis by 2.4 mm.

Further, in this embodiment, a flange portion 251f is provided at the rear end of the spare cylinder portion 251, and a concave air hole 251r is provided in the flange portion 251f. The inside of the main cylinder and the outside of the main cylinder can be ventilated through the air hole 251r. As a result, air is taken into the main body cylinder as ink is consumed, and appropriate ink ejection performance can be maintained. Further, the holding tube portion 252 includes a vertical rib 252r that projects radially outward for engagement with the front tube 30, and a slit for improving the ease of assembling the pen tip 110 and the pen tip holding tube 250. 252s are provided. By using the slit 252s, alignment of the pen tip 110 and the pen tip holding cylinder 250 in the rotational direction with respect to the axis (making the front end 111a and the front end of the spare cylinder part 251 parallel in side view) is performed. This can be easily done onboard.

Furthermore, in this embodiment, two raised parts 255 are provided on the outer circumferential contour of the rear part of the holding cylinder part 252, which are locally raised in the axial direction. The protrusion 255 can be temporarily collapsed due to elastic deformation (it may be accompanied by slight plastic deformation). Specifically, the holding cylinder part 252 (pen tip holding cylinder 250) including each raised part 255 is made of polycarbonate, which is an elastic material, and each raised part 255 has a height of 0.05 to 0.2 mm, preferably Height of 0.05 to 0.15 mm (height of 0.1 mm in this embodiment) and axial length of 0.5 to 5.0 mm (axial length of 1.5 mm in this embodiment) and a circumferential width of 0.5 mm or more (in this embodiment, a circumferential width of 0.7 mm), thereby defining a cavity 302c of the cavity 302, which is an injection mold, during the rear part extraction process described later. It is possible to be elastically deformed by the wall surface and temporarily take on a collapsed shape (while passing through the wall surface).

In order to facilitate such elastic deformation of each raised portion 255, the front end side of each raised portion 255 is an inclined surface 255t. The inclination angle is preferably 2 to 30 degrees with respect to the circumferential surface of the holding cylinder portion 252, and is 15 degrees in this embodiment. On the other hand, the rear end side of each raised portion 255 has a planar end portion 255e perpendicular to the axial direction of the holding cylinder portion 252.

The planar end portions 255e of each raised portion 255 are aligned at a distance of 0 to 3 mm (0.3 mm in this embodiment) from the rear end of the holding cylinder portion 252. That is, the two protrusions 255 are arranged in the same position in the axial direction.

The two raised portions 255 are provided with an interval of 60° in the circumferential direction. That is, the two raised portions 255 are arranged at non-uniform positions in the circumferential direction. Furthermore, as shown in FIGS. 42 and 46, when viewed in the axial direction, the circumferential end of each protruding portion 255 is slightly (2 ° (0.2°) in the circumferential direction from the circumferential end of the air hole 251r). A relative positional relationship is adopted in which they overlap (approximately 7 mm).

Returning to FIG. 38, the front cylinder 30 holds the nib holding cylinder 250 using the vertical ribs 252r of the nib holding cylinder 250. Further, the length of the holding cylinder part 252 is shorter than the length of the central core part 112 (see FIGS. 27 to 29), and the front cylinder 30 has a tapered part 112t at the rear of the central core part 112 of the nib 110. is also held.

Note that the material of the pen nib 110 can be the same as described above regarding the material of the nib 10 of the first embodiment of Japanese Patent Application No. 2018-134808.

(Operations and effects of one embodiment of a writing instrument)
The writing instrument 201 configured as described above can have the following effects. That is, also in the writing instrument 201 of this embodiment, since the front core part 111 of the pen nib 110 is thinner than the central core part 112 of the nib 110 held in the nib holding cylinder 250 , the central core of the nib 110 Sufficient flexibility of the front core portion 111 of the pen tip 110 relative to the portion 112 can be provided.

The front end of the front core part 111 of the pen nib 110 has a cutting edge shape in side view, and the upper end length L11 (maximum length) of the front core part 111 of the nib 110 is 13.8 mm, which is sufficient. Coupled with its long length (7 mm or more), users experience a unique writing sensation when the front core 111 of the pen nib 110 bends due to the force applied to the front end of the front core 111 of the nib 110. You can enjoy it as

On the other hand, also in the writing instrument 201 of this embodiment, the spare cylinder part 251 of the nib holding cylinder 250 extends around the front core part 111 of the pen nib 110, except for the front end area of the front core part 111 . When excessive force is applied to the front core part 111 of the pen nib 110, the spare cylinder part 251 comes into contact with the front core part 111 of the pen nib 110, and the front core part 111 is Deformation is suppressed (this is the same as that described with reference to FIG. 16 for the first embodiment of Japanese Patent Application No. 2018-134808).

In particular, also in this embodiment, the maximum length (length at the upper end) of the spare cylinder part 2 51 is 10 mm, which is sufficiently long (5 mm or more), and the distance between the spare cylinder part 2 51 and the front core part 111 of the pen tip 110 is Coupled with the feature that the interval G2 under no load is constant at 0.2 mm (see Fig. 31), excessive deformation that makes it difficult for the front core 111 of the nib 110 to return to its original shape is prevented. It is effectively suppressed and long life can be achieved.

Also, in the writing instrument 201 of this embodiment, the holding protrusion 2 52p of the nib holding cylinder 250 holds the front part of the central core part 112 of the nib 110, and the front cylinder 30, which is the main body cylinder, The tapered portion 112t of the central core portion 112 of the tip 110 is held. Thereby, the central core portion 112 of the pen nib 110 is held at two locations in the axial direction, and more reliable retention of the central core portion 112 of the pen nib 110 is realized.

Also, in the writing instrument 201 of this embodiment, the central core portion 112 of the pen tip 110 has a cylindrical shape. Thereby, the pen tip 110 can be given sufficient strength, and the central core portion 112 of the pen tip 110 can be held more reliably.

Also, in the writing instrument 201 of this embodiment, the holding protrusions 2 52p of the nib holding tube 2 50 are arranged at four locations at intervals (preferably equal intervals) in the circumferential direction of the central core 112 of the nib 110. It is held in Thereby, the central core portion 112 of the pen nib 110 can be held in a well-balanced manner, and the central core portion 112 of the pen nib 110 can be held more reliably.

Furthermore, in the writing instrument 201 of this embodiment as well, when no force is applied to the nib 110, the distance G2 between the spare cylinder part 251 and the front core part 111 of the nib 110 is constant. Thereby, the effect of suppressing excessive deformation of the front core part 111 of the pen nib 110 can be effectively provided in all directions by the spare cylinder part 251 . Further, it is possible to provide an excellent form in terms of design (beauty).

Also, in the writing instrument 201 of this embodiment, the front end of the spare cylinder part 251 has a cutting edge shape in which the upper end is located forward of the lower end in side view (see FIG. 26), and the pen tip 110 is shaped like a cutting edge. The front end of the front core part 111 and the front end of the spare cylinder part 151 are parallel in side view (see FIG. 28). Thereby, the effect of suppressing excessive deformation of the front core portion 111 of the cutting edge-shaped pen tip 110 can be more effectively provided in all directions. Further, it is possible to provide an excellent form in terms of design (beauty).

(Method for manufacturing pen nib holding tube 250)
The present invention is a method for manufacturing a resin molded product that solves the problem of the resin molded product and the ejector member adhering to each other and not being separated, without adding a structure such as a stripper bush (that is, while suppressing an increase in cost). . As one embodiment of the invention, a method for manufacturing the pen tip holding cylinder 250 of the above-mentioned writing instrument 201 as a resin molded product will be described.

The nib holding cylinder 250 is manufactured from a resin material (eg, PC, PP, PE, ABS, AS, PS, PMMA, PA, PBT, POM) by injection molding. As shown in FIG. 47, the manufacturing apparatus includes a front cavity 301 having a front cavity 301c that corresponds (complementarily) to the outer peripheral contour of the front part of the pen tip holding cylinder 250, which is a resin molded product; A rear cavity 302 having a rear cavity 302c (including a recess 302r corresponding to the raised part 255) adjacent to the front cavity 301c of 301 and corresponding (complementarily) to the outer peripheral contour of the rear part of the nib holding cylinder 250; , a core pin member 303 having an outer peripheral shape corresponding (complementarily) to the inner peripheral contour of the pen tip holding cylinder 250 and inserted into the front cavity 301c of the front cavity 301 and the rear cavity 302c of the rear cavity 302; , a front end defining member 304 having a rear end shape that corresponds (complementarily) to the front end shape of the nib holding tube 250, and a front end shape that corresponds (complementarily) to the rear end shape of the nib holding tube 250. The ejector member 305 has an ejector member 305.

In the example of FIG. 47, the front cavity 301 is a fixed cavity, the rear cavity 302 is a movable cavity (moves in the axial direction of the nib holding cylinder 250 with respect to the front cavity 301), and the core pin member 303 is a movable core pin, the front end defining member 304 is a fixed pin, and the ejector member 305 is an ejector sleeve.

As shown in FIG. 48, the front end shape of the ejector member 305 has a pair of opposing extending portions 305e corresponding (complementarily) to the slit 252s of the pen tip holding cylinder 250. Each extending portion 305e extends in the axial direction and has a semicircular tip. 48(a) is a front view of the ejector member 305, FIG. 48(b) is a side view of the ejector member 305, and FIG. 48(c) is a cross section taken along line cc in FIG. 48(a). 48(d) is a sectional view taken along the line dd in FIG. 48(b), and FIG. 48(e) is a perspective view of the vicinity of the tip of the ejector member 305.

The front cavity 301c of the front cavity 301, the rear cavity 302c of the rear cavity 302, the outer peripheral shape of the core pin member 303, the rear end shape of the front end defining member 304, and the front end shape (extension) of the ejector member 305. The pen tip holding cylinder 250 is molded by injecting a resin material into a molding space partitioned by (having a portion 305e) (injection molding process: see FIG. 49).

Thereafter, the molded nib holding tube 250 must be removed from the manufacturing device. In this manufacturing apparatus, first, the front cavity 301 and the rear cavity 302 are separated from each other, and the front cavity 301c and the rear cavity 302c are separated from each other. is extracted from the front cavity 301c (front part extraction step: see FIG. 50).

Subsequently, the core pin member 303 is extracted from the rear cavity 302c (core pin extraction process: see FIG. 51).

Thereafter, the ejector member 305 is moved forward with respect to the rear cavity 302, so that the rear part of the nib holding cylinder 250 is extracted from the rear cavity 302c (rear part extraction step).

As described above, on the outer peripheral contour of the rear portion of the holding cylinder portion 252 of the pen tip holding cylinder 250, two raised portions 255 that are locally raised in the axial direction are provided. During the rear part extraction process by the ejector member 305, the two raised parts 255 are elastically deformed by the wall surface defining the rear cavity 302c of the rear cavity 302, which is an injection mold, and temporarily (deform the wall surface). (during the passage) it takes on a collapsed shape. Thereby, despite the presence of the two protrusions, the ejector member 305 can carry out the process of extracting the rear part.

In this embodiment, the pen tip holding cylinder 250 and the ejector member are moved by the reaction force generated when the two raised parts 255 elastically return from the collapsed shape to the raised shape immediately after being released from the rear cavity 302c. 305 can be separated. As a result, many of the molded pen tip holding cylinders 250 separate from the ejector member 305 and fall during the rear part extraction process.

However, about 10% of the pen tip holding cylinder 250 is not separated from the ejector member 305 even by the above-mentioned reaction force (see FIG. 52). This adhesion tendency is higher when the contact area between the pen tip holding cylinder 250 and the ejector member 305 is increased due to the presence of the extending portion 305e. In such a case, the ejector member 305 is returned to the rear side with respect to the rear cavity 302 (ejector return step).

At this time, the raised portion 255 that has returned to its raised shape effectively prevents the pen tip holding tube 250 from returning into the rear cavity 302c (see FIG. 53), and the pen tip holding tube 250 and the ejector member 305 are separated. Ru. As a result, most of the pen tip holding tubes 250 that were not separated from the ejector member 305 even by the above-mentioned reaction force separate from the ejector member 305 and fall during the ejector return process.

Furthermore, the pen tip holding tube 250 may still not fall because the rear end of the pen tip holding tube 250 is caught in the front end of the rear cavity 302c corresponding to the flange portion 251f (see FIG. 54). In such a case, the ejector member 305 is moved forward again with respect to the rear cavity 302 (ejector re-extrusion process: see FIG. 55). As a result, the pen tip holding cylinder 250, which was caught in the rear cavity 302c and did not fall, is pushed by the ejector member 305 and falls by the ejector re-extrusion process.

Thereafter, the ejector member 305 is returned to the rear side with respect to the rear cavity 302 (ejector return step).

(Advantages of the manufacturing method of the pen nib holding cylinder 250)
According to the manufacturing method described above, when manufacturing the pen tip holding tube 250 by injection molding, the ejector member 305 is used to remove the pen tip holding tube 250 from the rear cavity 302c of the rear side cavity 302, which is an injection mold. In the step of extracting the rear part of the holder, the protruding part 255 is elastically deformed into a collapsed shape so that the ridge part 255 can be passed through the rear cavity 302c.

Immediately after the raised portion 255 is released from the rear cavity 302c, the pen tip holding cylinder 250 and the ejector member 305 can be separated by the reaction force that causes the raised portion 255 to elastically return from the collapsed shape to the raised shape.

Alternatively, even if it is not possible to separate the pen tip holding tube 250 and the ejector member 305 due to such reaction force, after the process of extracting the rear part of the pen tip holding tube 250, By performing an ejector return process in which the ejector member 305 is moved rearward, the pen tip holding cylinder 250 and the ejector member 305 can be separated. This is because, in the ejector return step, the raised portion 255 that has returned to its raised shape effectively prevents the pen tip holding cylinder 250 from returning into the rear cavity 302c.

Furthermore, even if the pen tip holding tube 250 separated from the ejector member 305 does not fall due to getting caught in the rear cavity 302c in the ejector return process, the pen tip holding tube 250 will not be able to be attached to the ejector member in the subsequent ejector re-extrusion process. Can be pushed by 305 and fall.

Further, in this embodiment, since the front end side of the raised portion 255 is the inclined surface 255t, it is facilitated to elastically deform the raised portion 255 into a collapsed shape in the step of extracting the rear portion.

On the other hand, since the rear end side of the raised portion 255 has a planar end portion 255e perpendicular to the axial direction, the raised portion 255 that has returned to its raised shape interferes with the end surface of the rear cavity 302 during the ejector return process. In other words, the effect of preventing the pen tip holding cylinder 250 from returning into the rear cavity 302c is enhanced.

Further, since the two raised portions 255 are aligned in the same position in the axial direction, the reaction force can be generated simultaneously (all at once). On the other hand, since the two raised portions 255 are arranged at non-uniform positions in the circumferential direction, the reaction forces do not cancel each other out, making it impossible to effectively tilt the posture of the pen tip holding cylinder 250. can.

Furthermore, in this embodiment, as shown in FIGS. 42 and 46, the circumferential end of each raised portion 255 slightly overlaps the circumferential end of the air hole 251r when viewed in the axial direction. During the ejector return process, each raised portion 255 is moved (rotated) in the circumferential direction while coming into contact with the wall surface of the rear cavity 302c (complementarily) corresponding to the air hole 251r. As a result, even if the pen tip holding tube 250 does not fall because it gets caught in the rear cavity 302c, the circumferential phase between the slit 252s of the pen tip holding tube 250 and the extending portion 305e of the ejector member 305 is maintained. Since the pen tip holding cylinder 250 is shifted, the pen tip holding cylinder 250 can be reliably dropped in the subsequent ejector re-extrusion process.

(Color of pen tip holding tube 250)
In the writing instrument 201, the pen tip holding cylinder 250 is preferably entirely made of a transparent material or a translucent material. In this case, it becomes easier to visually recognize the color of the ink. Further, it is possible to provide an excellent form in terms of design (beauty).

Alternatively, it is also useful that only the area near the front end of the pen tip holding cylinder 250 is colored, and the rest is made of a transparent material or a translucent material. This aspect has the effect of making it easier to grasp the relative position between the writing instrument and the writing object when the color of the writing object (for example, paper surface) and the color of the ink are similar. In particular, by forming the colored region in the shape of a parallelogram as shown in FIG. 57, an excellent form in terms of design (beauty) can be provided.

However, at least at the time of this application, an embodiment in which the pen tip holding cylinder 250 is entirely made of opaque material is not excluded from the scope of the present invention.

(Angle position mark)
Further, in the writing instrument 201, it is preferable that a mark indicating the angular position of the pen tip 110 is attached to the front tube 30 and/or the pen tip holding tube 250, which are the main body tubes. In this case, the angular position (direction of the upper end and lower end) of the pen tip 110 can be more easily grasped. The mark is not limited to a visual mark, but may be an unevenness that can be discerned by touch. The front cylinder 30 may be configured to have a polygonal shape (triangular shape, hexagonal shape, etc.), and the entire shape may function as a mark.

1, 101 Writing instrument 10, 110 Pen point 11, 111 Front core portion 11a, 111a Front end portion 11b, 111b Acute angle forming plane portion 11c, 111c Acute angle forming plane portion 12, 112 Center core portion 12t, 112t Taper portion 13, 113 Rear core Parts 13t, 113t Tapered part 20 Ink storage body 30 Front cylinder (main body cylinder)
40 Rear tube (main tube)
50, 150 Pen tip holding cylinder 51, 151 Spare cylinder part 51f, 151f Flange part 51r, 151r Air hole 52, 152 Holding cylinder part 52p, 152p Holding protrusion 52s, 152s Slit 52r, 152r Vertical rib 60 Cap G1, G2 Spacing L1 , L11 Upper end length L2, L12 in side view of the front core part Lower end length L3, L13 in side view of the front core part Upper end length L4, L14 in side view of the spare cylinder part Lower end length in side view of the spare cylinder part 201 Writing instrument 250 Pen tip holding cylinder 251 Spare cylinder part 251f Flange part 251r Air hole 252 Holding cylinder part 252p Holding protrusion 252s Slit 252r Vertical rib 255 Raised part 255t Inclined surface 255e Planar end 301 Front side cavity 301c Front cavity 302 Rear Side cavity 302c Rear cavity 302r Concave portion 303 corresponding to the raised portion Core pin member 304 Front regulation member 305 Ejector member 305e Extension portion 501 Front cavity 501c Front cavity 502 Rear cavity 502c Rear cavity 503 Core pin member 504 Front end regulation member 505 Ejector Member 505e extension part

Claims (7)

In order to manufacture cylindrical resin molded products,
a front side cavity having a front cavity corresponding to the outer peripheral contour of the front part of the resin molded product;
a rear cavity adjacent to the front cavity of the front cavity and having a rear cavity corresponding to the outer peripheral contour of the rear part of the resin molded product;
a core pin member having an outer peripheral shape corresponding to the inner peripheral contour of the resin molded product and inserted into the front cavity of the front cavity and the rear cavity of the rear cavity;
a front end defining member having a rear end shape corresponding to the front end shape of the resin molded product;
an ejector member having a front end shape corresponding to the rear end shape of the resin molded product;
Using,
the front cavity of the front cavity, the rear cavity of the rear cavity, the outer peripheral shape of the core pin member, the rear end shape of the front end defining member, and the front end shape of the ejector member; molding the resin molded product by injecting a resin material into a molding space defined by;
A front part extracting step of separating the front cavity and the rear cavity from each other and separating the front cavity and the rear cavity from each other to extract the front part of the resin molded product from the front cavity. and,
a core pin member extraction step of extracting the core pin member from the front cavity and the rear cavity;
a rear part extracting step of extracting the rear part of the resin molded product from the rear cavity by moving the ejector member forward with respect to the rear cavity;
A method for manufacturing a cylindrical resin molded product, comprising:
A protrusion that locally protrudes in the axial direction is provided on the outer peripheral contour of the rear portion of the resin molded product,
The step of extracting the rear portion includes a step of elastically deforming the protrusion into a collapsed shape and allowing it to pass through the rear cavity of the rear cavity,
A method characterized in that the rear end side of the raised part has a flat part perpendicular to the axial direction. In order to manufacture cylindrical resin molded products,
a front side cavity having a front cavity corresponding to the outer peripheral contour of the front part of the resin molded product;
a rear cavity adjacent to the front cavity of the front cavity and having a rear cavity corresponding to the outer peripheral contour of the rear part of the resin molded product;
a core pin member having an outer peripheral shape corresponding to the inner peripheral contour of the resin molded product and inserted into the front cavity of the front cavity and the rear cavity of the rear cavity;
a front end defining member having a rear end shape corresponding to the front end shape of the resin molded product;
an ejector member having a front end shape corresponding to the rear end shape of the resin molded product;
Using,
the front cavity of the front cavity, the rear cavity of the rear cavity, the outer peripheral shape of the core pin member, the rear end shape of the front end defining member, and the front end shape of the ejector member; molding the resin molded product by injecting a resin material into a molding space defined by;
A front part extracting step of separating the front cavity and the rear cavity from each other and separating the front cavity and the rear cavity from each other to extract the front part of the resin molded product from the front cavity. and,
a core pin member extraction step of extracting the core pin member from the front cavity and the rear cavity;
a rear part extracting step of extracting the rear part of the resin molded product from the rear cavity by moving the ejector member forward with respect to the rear cavity;
A method for manufacturing a cylindrical resin molded product, comprising:
A protrusion that locally protrudes in the axial direction is provided on the outer peripheral contour of the rear portion of the resin molded product,
The step of extracting the rear portion includes a step of elastically deforming the protrusion into a collapsed shape and allowing it to pass through the rear cavity of the rear cavity,
A method characterized in that a plurality of the raised portions are provided and are aligned at the same position in the axial direction, but are arranged at non-uniform positions in the circumferential direction. Further comprising an ejector return step of moving the ejector member rearward with respect to the rear cavity after the rear part extraction step,
The ejector returning step includes a step of separating the resin molded product and the ejector member by preventing the resin molded product from returning into the rear cavity by the raised portion that has returned to its raised shape. The method according to claim 1 or 2, characterized in that: 4. The manufacturing method according to claim 1, wherein the front end side of the raised portion is an inclined surface. 5. The manufacturing method according to claim 1, wherein the resin molded product is a part of a writing instrument. In order to manufacture cylindrical resin molded products,
a front side cavity having a front cavity corresponding to the outer peripheral contour of the front part of the resin molded product;
a rear cavity adjacent to the front cavity of the front cavity and having a rear cavity corresponding to the outer peripheral contour of the rear part of the resin molded product;
a core pin member having an outer peripheral shape corresponding to the inner peripheral contour of the resin molded product and inserted into the front cavity of the front cavity and the rear cavity of the rear cavity;
a front end defining member having a rear end shape corresponding to the front end shape of the resin molded product;
an ejector member having a front end shape corresponding to the rear end shape of the resin molded product;
Using,
the front cavity of the front cavity, the rear cavity of the rear cavity, the outer peripheral shape of the core pin member, the rear end shape of the front end defining member, and the front end shape of the ejector member; molding the resin molded product by injecting a resin material into a molding space defined by;
A front part extracting step of separating the front cavity and the rear cavity from each other and separating the front cavity and the rear cavity from each other to extract the front part of the resin molded product from the front cavity. and,
a core pin member extraction step of extracting the core pin member from the front cavity and the rear cavity;
a rear part extracting step of extracting the rear part of the resin molded product from the rear cavity by moving the ejector member forward with respect to the rear cavity;
A method for manufacturing a cylindrical resin molded product, comprising:
A protrusion that locally protrudes in the axial direction is provided on the outer peripheral contour of the rear portion of the resin molded product,
The step of extracting the rear portion includes a step of elastically deforming the protrusion into a collapsed shape and allowing it to pass through the rear cavity of the rear cavity,
The method characterized in that the resin molded product is a part of a writing instrument and has a slit extending in the axial direction on the rear end side. In order to manufacture cylindrical resin molded products,
a front side cavity having a front cavity corresponding to the outer peripheral contour of the front part of the resin molded product;
a rear cavity adjacent to the front cavity of the front cavity and having a rear cavity corresponding to the outer peripheral contour of the rear part of the resin molded product;
a core pin member having an outer peripheral shape corresponding to the inner peripheral contour of the resin molded product and inserted into the front cavity of the front cavity and the rear cavity of the rear cavity;
a front end defining member having a rear end shape corresponding to the front end shape of the resin molded product;
an ejector member having a front end shape corresponding to the rear end shape of the resin molded product;
Using,
the front cavity of the front cavity, the rear cavity of the rear cavity, the outer peripheral shape of the core pin member, the rear end shape of the front end defining member, and the front end shape of the ejector member; molding the resin molded product by injecting a resin material into a molding space defined by;
A front part extracting step of separating the front cavity and the rear cavity from each other and separating the front cavity and the rear cavity from each other to extract the front part of the resin molded product from the front cavity. and,
a core pin member extraction step of extracting the core pin member from the front cavity and the rear cavity;
a rear part extracting step of extracting the rear part of the resin molded product from the rear cavity by moving the ejector member forward with respect to the rear cavity;
A method for manufacturing a cylindrical resin molded product, comprising:
A protrusion that locally protrudes in the axial direction is provided on the outer peripheral contour of the rear portion of the resin molded product,
The step of extracting the rear portion includes a step of elastically deforming the protrusion into a collapsed shape and allowing it to pass through the rear cavity of the rear cavity,
The resin molded product is a part of a writing instrument, and has a longitudinal rib extending in the axial direction on the radially outer side of the rear end side,
The rear cavity of the rear cavity corresponding to the longitudinal rib reaches a front end surface of the rear cavity,
In the rear part extracting step, the vertical rib passes through the rear cavity of the rear cavity without being elastically deformed into a collapsed shape.

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