JP7492071B2 - Manufacturing method for writing implement parts - Google Patents

Description

The present invention relates to a method for manufacturing parts of a writing instrument. More broadly, it relates to a method for manufacturing a resin molded product. It also relates to a writing instrument that includes a part manufactured by the manufacturing method.

Writing instruments with a pen tip and an ink storage body have been developed and sold in a variety of configurations.

In a typical configuration, the pen tip has sufficient rigidity so that the force applied by the user when writing does not substantially deform the pen tip. Such a "rigid" pen tip is a standard configuration because it gives the user a firm writing feel.

On the other hand, there are also users who desire a soft writing feel like that of a brush. To meet such needs, various types of pens have been developed that have a pen tip that deforms (flexes) depending on the force applied by the user when writing.

For example, Patent Document 1 discloses a ballpoint pen in which the intermediate refill and ballpoint pen tip elastically deform in response to writing pressure. The ballpoint pen tip to which the intermediate refill is attached has a rectangular window hole formed therein, leaving a vertical rib, so that the ballpoint pen tip (vertical rib) can easily deform.

Patent Document 2 also discloses a calligraphy pen tip that 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. With this calligraphy pen tip, the part with the annular grooves acts as a cushion, making it possible to freely write lines ranging from thin to thick depending on the strength of the writing pressure.

In a configuration in which the pen tip deforms (flexes) due to the force applied by the user when writing, the ease with which the pen tip deforms (flexes) depends primarily on the properties of the material from which the pen tip is made.

Therefore, if you want to achieve a soft writing feel, the pen tip needs to be made from a material that is soft (flexible).

However, soft (flexible) materials tend to have poor shape retention, meaning they do not return to their original shape after writing, shortening the life of the pen tip.

In consideration of these problems, the applicant has developed a writing instrument that provides soft (easily flexible) properties while suppressing excessive deformation that makes it difficult to return to its original shape after writing, thereby realizing a long life, and has filed a patent application for this (Patent Application No. 2018-134808).

(Configuration of the first embodiment of Japanese Patent Application No. 2018-134808)
Fig. 1 is a schematic vertical cross-sectional view of a writing instrument 1 according to 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 a cap 60 removed.

In addition, FIG. 3 is a perspective view showing the pen tip 10 of the writing instrument 1, FIG. 4 is a side view of the pen tip 10, FIG. 5 is a cross-sectional view of the pen tip 10 of FIG. 4 taken along line A-A, and FIG. 6 is a cross-sectional view of the pen tip 10 of FIG. 4 taken along line B-B.

First, as shown in Figures 1 to 6, the writing instrument 1 of this embodiment includes a pen tip 10 having a front core portion 11, a central core portion 12, and a rear core portion 13, and an ink occlusion body 20 that contacts the rear core portion 13 of the pen tip 10 and supplies ink to the rear core portion 13. The ink occlusion body 20 is contained in a front tube 30 and a rear tube 40 that constitute the main body tube. A cap 60 is detachable from the front tube 30 or the rear tube 40.

As shown in Figures 3 to 6, the front core portion 11, central core portion 12, and rear core portion 13 of the pen tip 10 of this embodiment have a concentric cylindrical shape (more specifically, excluding the front end region of the front core portion 11 and tapered portions 12t and 13t, which will be described later), but the front core portion 11 is thinner than the central core portion 12. The rear core portion 13 is also thinner than the central core portion 12.

A gently sloping tapered section 13t is provided on the rear side of the rear core section 13, facilitating insertion into the ink occluder 20. A relatively steeply sloping tapered section 12t is provided on the rear side of the central core section 12, and continues to the rear core section 13.

The front end of the front core 11 is in the shape of a cutting blade with the upper end positioned forward of the lower end in side view (see FIG. 4), and has a front end 11a that is curved in the left-right direction (see FIG. 5) and inclined in the up-down direction (see FIG. 4), and acute angle forming flat parts 11b, 11c that are provided on both the left and right sides of the front end 11a and form an acute angle (e.g., 60 degrees) with each other (see FIG. 5) (the intersection line of the extended surfaces of the acute angle forming flat parts 11b, 11c is a straight line located further forward of the front end 11a and extending parallel to the front end 11a). The front end 11a and the acute angle forming flat parts 11b, 11c may be formed by cutting or may be formed in advance by molding.

As shown in Figures 1 and 2, the writing instrument 1 of this embodiment also includes a nib holding tube 50 that holds the central core 12 of the nib 10 and is held by the front tube 30, which is the main body tube.

Figure 7 is a perspective view showing the nib holding tube 50 of the writing instrument 1, Figure 8 is a cross-sectional perspective view of the nib holding tube 50 of Figure 7, Figure 9 is a plan view of the nib holding tube 50 of Figure 7, and Figure 10 is a cross-sectional view of the nib holding tube 50 of Figure 9 taken along line A-A.

In addition, FIG. 11 is a perspective view showing the pen tip 10 and pen tip holding tube 50 of the writing instrument 1, FIG. 12 is a side view showing the pen tip 10 and pen tip holding tube 50, FIG. 13 is a cross-sectional view of the pen tip 10 and pen tip holding tube 50 of FIG. 12 taken along line A-A, FIG. 14 is a cross-sectional view of the pen tip 10 and pen tip holding tube 50 of FIG. 12 taken along line B-B, and FIG. 15 is an enlarged view of part C of the pen tip 10 and pen tip holding tube 50 of FIG. 14.

As shown in Figures 7 to 15, the nib holding tube 50 has a holding tube portion 52 that holds the central core portion 12 of the nib 10, and a spare tube portion 51 that extends around the front core portion 11 of the nib 10 except for the front end region of the front core portion 11 (the region including the front end portion 11a and the acute angle forming flat portions 11b, 11c). The holding tube portion 52 and the spare tube portion 51 have a generally concentric cylindrical shape.

In this embodiment, the gap (symbol G1 in FIG. 15) between the inner circumferential surface of the spare tube portion 51 and the outer circumferential surface of the front core portion 11 of the pen tip 10 is constant (it changes when force is applied to the pen tip 10 during writing, as described later with reference to FIG. 16).

The front end of the spare tube portion 51 is also shaped like a cutting blade with its upper end positioned further forward than its lower end in side view (see FIG. 10), and the front end of the front core portion 11 of the pen tip 10 and the front end of the spare tube portion 51 are parallel in side view (see FIG. 12).

In addition, the holding tube portion 52 has four holding protrusions 52p on its inner cylindrical surface to hold the front portion of the central core portion 12 of the pen tip 10 at four points spaced apart in the circumferential direction (see Figures 8 and 10).

In this embodiment, a flange portion 51f is provided at the rear end of the spare tube portion 51, and a concave air hole 51r is provided in the flange portion 51f. The air hole 51r allows ventilation between the inside and outside of the main body tube. This allows air to be taken into the inside of the main body tube as ink is consumed, and appropriate ink ejection performance can be maintained. In addition, the retaining tube portion 52 is provided with a vertical rib 52r that protrudes radially outward for engagement with the front tube 30, and a slit 52s for improving the assembly of the nib 10 and the nib retaining tube 50. By using the slit 52s, the rotational alignment of the nib 10 and the nib retaining tube 50 with respect to the axis (the front end portion 11a and the front end of the spare tube portion 51 are made parallel in a side view) can be easily performed on the assembly machine.

As shown in Figure 1, the front tube 30 holds the nib holding tube 50 by utilizing the vertical rib 52r of the nib holding tube 50. The length of the holding tube portion 52 is shorter than the length of the central core portion 12 (see Figures 11 to 13), and the front tube 30 also holds the tapered portion 12t at the rear of the central core portion 12 of the nib 10.

The nib 10 is made of, for example, a porous synthetic resin with open bubbles, but it can be anything that allows ink to flow through it and is flexible; specifically, it can be a fiber nib, a felt nib, a calligraphy pen nib, a plastic nib with an axial capillary passage, etc. In addition, the spare tube portion 51 of the nib holding tube 50 needs to be less prone to deformation than the front core portion 11.

The ink occlusion body 20 may be made of any material having continuous pores that can be impregnated with ink, such as a heat-sealed fiber bundle, a resin-processed fiber bundle, a resin-processed felt, a needle-punched felt, or a porous body (e.g., a synthetic resin open-cell body such as a sponge). The ink occlusion body 20 may also be configured to have an outer skin made of a synthetic resin film or the like on its outer periphery.

(Effects of the first embodiment of Patent Application No. 2018-134808)
The writing instrument 1 configured as above can achieve the following effects. That is, according to the writing instrument 1 of this embodiment, since the front core portion 11 of the pen tip 10 is thinner than the central core portion 12 of the pen tip 10 held in the pen tip holding tube 50, it is possible to provide sufficient flexibility of the front core portion 11 of the pen tip 10 relative to the central core portion 12 of the pen tip 10.

The front end of the front core 11 of the pen tip 10 is shaped like a cutting blade when viewed from the side, and combined with the fact that the upper end length L1 (maximum length) of the front core 11 of the pen tip 10 when viewed from the side is sufficiently long, the user can enjoy a unique writing sensation as the front core 11 of the pen tip 10 flexes due to the force applied to the front end of the front core 11 of the pen tip 10.

On the other hand, according to the writing instrument 1 of this embodiment, the spare tube portion 51 of the nib holding tube 50 extends around the front core portion 11 of the nib 10, except for the front end region of the front core portion 11, and when excessive force is applied to the front core portion 11 of the nib 10, the spare tube portion 51 abuts against the front core portion 11 of the nib 10 to suppress further deformation of the front core portion 11. This state is shown in Figure 16. Figure 16 is a schematic diagram showing the nib 10 of the writing instrument 1 in a bent state.

In particular, in this embodiment, the length L3 (maximum length) of the top end of the spare tube portion 51 in a side view is sufficiently long, and coupled with the characteristic that the gap G1 between the spare tube portion 51 and the front core portion 11 of the pen tip 10 at no load is constant (see FIG. 15), excessive deformation that would make it difficult for the front core portion 11 of the pen tip 10 to return to its original shape is effectively suppressed, achieving a long service life.

In addition, according to the writing instrument 1 of this embodiment, the holding protrusion 52p of the nib holding tube 50 holds the front portion of the central core 12 of the nib 10, and the front tube 30, which is the main body tube, holds the tapered portion 12t of the central core 12 of the nib 10. As a result, the central core 12 of the nib 10 is held at two points in the axial direction, achieving more secure holding of the central core 12 of the nib 10.

In addition, according to the writing instrument 1 of this embodiment, the central core 12 of the pen tip 10 has a cylindrical shape. This allows the pen tip 10 to have sufficient strength, and the central core 12 of the pen tip 10 can be held more securely.

In addition, according to the writing instrument 1 of this embodiment, the holding protrusions 52p of the nib holding tube 50 hold the central core 12 of the nib 10 at four points spaced (preferably equally spaced) apart in the circumferential direction. This allows the central core 12 of the nib 10 to be held in a well-balanced manner, achieving more secure holding of the central core 12 of the nib 10.

In addition, with the writing instrument 1 of this embodiment, when no force is being applied to the pen tip 10, the gap G1 between the spare tube portion 51 and the front core portion 11 of the pen tip 10 is constant. This allows the spare tube portion 51 to effectively suppress excessive deformation of the front core portion 11 of the pen tip 10 in all directions. It also provides a form that is excellent in terms of design (aesthetics).

In addition, according to the writing instrument 1 of this embodiment, the front end of the spare tube portion 51 is also formed in a cutting blade shape with the upper end located further forward than the lower end in side view (see FIG. 10), and the front end of the front core portion 11 of the pen tip 10 and the front end of the spare tube portion 51 are parallel in side view (see FIG. 12). This makes it possible to more effectively suppress excessive deformation of the cutting blade-shaped front core portion 11 of the pen tip 10 in all directions. It also makes it possible to provide a form that is excellent in terms of design (aesthetics).

(Configuration of the first embodiment of Japanese Patent Application No. 2018-134808)
17 is a schematic vertical cross-sectional view of a writing instrument 101 according to 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.

In addition, FIG. 19 is a perspective view showing the pen tip 110 of the writing instrument 101, FIG. 20 is a side view of the pen tip 110, FIG. 21 is a cross-sectional view of the pen tip 110 of FIG. 20 taken along line A-A, and FIG. 22 is a cross-sectional view of the pen tip 110 of FIG. 20 taken along line B-B.

First, as shown in Figures 17 to 22, the writing instrument 101 of this embodiment includes a pen tip 110 having a front core portion 111, a central core portion 112, and a rear core portion 113, and an ink occlusion body 20 that contacts the rear core portion 113 of the pen tip 110 and supplies ink to the rear core portion 113. As in the first embodiment, the ink occlusion body 20 is contained by the front tube 30 and rear tube 40 that constitute the main body tube, and the cap 60 is detachable from the front tube 30 or the rear tube 40.

As shown in Figures 19 to 22, the central core 112 and rear core 113 of the pen tip 110 of this embodiment have a concentric cylindrical shape (excluding the tapered portions 112t and 113t, which will be described in detail later), but the rear core 113 is thinner than the central core 112.

As shown in Figures 19 to 22, the front core 111 of the pen tip 110 of this embodiment has a generally rectangular prism shape with rounded corners, except for the front end region described below (see Figure 22 in particular). The axis of the central core 112 passes through the center (center of gravity) of the generally rectangular cross section of the front core 111, and the length of the diagonal of the generally rectangular cross section (see Figure 22) is smaller than the diameter of the central core 112. In other words, the front core 111 is thinner than the central core 112.

As in the first embodiment, the rear core 113 has a gently sloping tapered portion 113t on the rear side thereof, facilitating insertion into the ink occlusion body 20. The central core 112 has a relatively steeply sloping tapered portion 112t on the rear side thereof, which is continuous with the rear core 113.

Also, similar to the first embodiment, the front end of the front core 111 is in the shape of a cutting blade with the upper end located forward of the lower end in side view (see FIG. 20), and has a front end 111a that is curved in the left-right direction (see FIG. 21) and inclined in the up-down direction (see FIG. 20), and acute angle forming flat parts 111b, 111c that are provided on both the left and right sides of the front end 111a and form 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, 111c is a straight line located further forward of the front end 111a and extending parallel to the front end 111a). The front end 111a and the acute angle forming flat parts 111b, 111c may be formed by cutting or may be formed in advance by molding.

As in the first embodiment, the writing instrument 101 of this embodiment has a pen tip holding tube 150 that holds the central core 112 of the pen tip 110 and is held by the front tube 30, which is the main body tube, as shown in Figures 17 and 18.

Figure 23 is a perspective view showing the pen tip holding tube 150 of the writing instrument 101, Figure 24 is a cross-sectional perspective view of the pen tip holding tube 150 of Figure 23, Figure 25 is a plan view of the pen tip holding tube 150 of Figure 23, and Figure 26 is a cross-sectional view of the pen tip holding tube 150 of Figure 25 taken along line A-A.

In addition, FIG. 27 is a perspective view showing the pen tip 110 and pen tip holding tube 150 of the writing instrument 101, FIG. 28 is a side view showing the pen tip 110 and pen tip holding tube 150, FIG. 29 is a cross-sectional view of the pen tip 110 and pen tip holding tube 150 of FIG. 28 taken along line A-A, FIG. 30 is a cross-sectional view of the pen tip 110 and pen tip holding tube 150 of FIG. 28 taken along line B-B, and FIG. 31 is an enlarged view of part C of the pen tip 110 and pen tip holding tube 150 of FIG. 30.

As shown in Figures 23 to 31, the nib holding tube 150 has a holding tube portion 152 that holds the central core portion 112 of the nib 110, and a spare tube portion 151 that extends around the front core portion 111 of the nib 110 except for the front end region of the front core portion 111 (the region including the front end portion 111a and the acute angle forming flat portions 111b, 111c). The holding tube portion 152 has a generally cylindrical shape corresponding to the central core portion 112, and the spare tube portion 151 has a generally square tube shape corresponding to the front core portion 111.

In this embodiment, the distance (symbol G2 in FIG. 31) between the inner circumferential surface of the reserve tube portion 151 and the outer circumferential surface of the front core portion 111 of the pen tip 110 is constant (it changes when force is applied to the pen tip 10 when writing: see FIG. 16).

The front end of the spare tube portion 151 is also shaped like a cutting blade with its upper end positioned further forward than its lower end in side view (see FIG. 26), and the front end of the front core portion 111 of the pen tip 110 and the front end of the spare tube portion 151 are parallel in side view (see FIG. 28).

As in the first embodiment, the holding tube portion 152 has four holding protrusions 152p on its inner cylindrical surface to hold the front portion of the central core portion 112 of the pen tip 110 at four circumferentially spaced locations (see Figures 24 and 26).

In this embodiment, a flange portion 151f is provided at the rear end of the spare tube portion 151, and a concave air hole 151r is provided in the flange portion 151f. The air hole 151r allows ventilation between the inside and outside of the main body tube. This allows air to be taken into the inside of the main body tube as ink is consumed, and appropriate ink ejection performance can be maintained. In addition, the retaining tube portion 152 is provided with a vertical rib 152r that protrudes radially outward for engagement with the front tube 30, and a slit 152s for improving the assembly of the pen tip 110 and the pen tip retaining tube 150. By using the slit 152s, the rotational alignment of the pen tip 110 and the pen tip retaining tube 150 with respect to the axis (the front end portion 111a and the front end of the spare tube portion 151 are made parallel in a side view) can be easily performed on an assembly machine.

As shown in Figure 17, the front tube 30 holds the nib holding tube 150 by utilizing the vertical rib 152r of the nib holding tube 150. The length of the holding tube portion 152 is shorter than the length of the central core portion 112 (see Figures 27 to 29), and the front tube 30 also holds the tapered portion 112t at the rear of the central core portion 112 of the nib 110.

The above-mentioned information regarding the material of the pen tip 10 can also be applied to the pen tip 110.

(Effects of the second embodiment of Patent Application No. 2018-134808)
The writing instrument 101 configured as described above can achieve the following effects. That is, with the writing instrument 101 of this embodiment, the front core portion 111 of the pen tip 110 is thinner than the central core portion 112 of the pen tip 110 held in the pen tip holding tube 150, so that the front core portion 111 of the pen tip 110 can be provided with sufficient flexibility relative to the central core portion 112 of the pen tip 110.

The front end of the front core 111 of the pen tip 110 is shaped like a cutting blade when viewed from the side, and combined with the fact that the upper end length L11 (maximum length) of the front core 111 of the pen tip 110 is sufficiently long, the user can enjoy a unique writing sensation as the front core 111 of the pen tip 110 flexes due to the force applied to the front end of the front core 111 of the pen tip 110.

On the other hand, even in the writing instrument 101 of this embodiment, the spare tube portion 151 of the nib holding tube 150 extends around the front core portion 111 of the nib 110, except for the front end region of the front core portion 111, and when excessive force is applied to the front core portion 111 of the nib 110, the spare tube portion 151 abuts against the front core portion 111 of the nib 110 to suppress further deformation of the front core portion 111 (similar to what was explained with reference to FIG. 16 for the first embodiment).

In particular, in this embodiment, the maximum length (length at the upper end) of the spare tube portion 151 is sufficiently long, and coupled with the characteristic that the gap G2 between the spare tube portion 151 and the front core portion 111 of the pen tip 110 at no load is constant (see FIG. 31), excessive deformation that would make it difficult for the front core portion 111 of the pen tip 110 to return to its original shape is effectively suppressed, achieving a long service life.

Also, with the writing instrument 101 of this embodiment, the holding protrusion 152p of the nib holding tube 150 holds the front portion of the central core 112 of the nib 110, and the front tube 30, which is the main body tube, holds the tapered portion 112t of the central core 112 of the nib 110. As a result, the central core 112 of the nib 110 is held at two points in the axial direction, realizing more secure holding of the central core 112 of the nib 110.

In addition, the writing instrument 101 of this embodiment also has a cylindrical central core 112 of the pen tip 110. This provides the pen tip 110 with sufficient strength, and ensures that the central core 112 of the pen tip 110 is held in place more securely.

Also, with the writing instrument 101 of this embodiment, the holding protrusions 152p of the nib holding tube 150 hold the central core 112 of the nib 110 at four points spaced (preferably equally spaced) apart in the circumferential direction. This allows the central core 112 of the nib 110 to be held in a well-balanced manner, achieving more secure holding of the central core 112 of the nib 110.

In addition, with the writing instrument 101 of this embodiment, when no force is being applied to the pen tip 110, the gap G2 between the spare tube portion 151 and the front core portion 111 of the pen tip 110 is constant. This allows the spare tube portion 151 to effectively suppress excessive deformation of the front core portion 111 of the pen tip 110 in all directions. It also provides a form that is excellent in terms of design (aesthetics).

Also, with the writing instrument 101 of this embodiment, the front end of the spare tube portion 151 is formed in a cutting blade shape with the upper end located further forward than the lower end in side view (see FIG. 26), and the front end of the front core portion 111 of the pen tip 110 and the front end of the spare tube portion 151 are parallel in side view (see FIG. 28). This makes it possible to more effectively suppress excessive deformation of the cutting blade-shaped front core portion 111 of the pen tip 110 in all directions. It also makes it possible to provide a form that is excellent in terms of design (aesthetics).

Japanese Utility Model Publication No. 59-16227 Japanese Patent Application Laid-Open No. 3-221494 Japanese Patent Application Laid-Open No. 11-277545

As mentioned above, the invention disclosed in Japanese Patent Application No. 2018-134808 has a remarkably useful effect. For this reason, the applicant has made efforts to establish a mass production system. In the process, the applicant has come to recognize the following problems regarding the manufacture of the pen tip holding tubes 50, 150.

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

In the example of FIG. 32, the front cavity 501 is the fixed cavity, the rear cavity 502 is the movable cavity (moves in the axial direction of the pen tip holding tube 150 relative to the front cavity 501), the core pin member 503 is the movable core pin, the front end defining member 504 is the fixed pin, and the ejector member 505 is the ejector sleeve.

As shown in FIG. 33, the front end of the ejector member 505 has a pair of opposing extensions 505e that correspond (complementarily) to the slits 152s of the pen tip holding tube 150. Each extension 505e extends in the axial direction and has a semicircular tip. FIG. 33(a) is a front view of the ejector member 505, FIG. 33(b) is a side view of the ejector member 505, FIG. 33(c) is a cross-sectional view taken along line c-c in FIG. 33(a), FIG. 33(d) is a cross-sectional view taken along line d-d in FIG. 33(b), and FIG. 33(e) is a perspective view of the vicinity of the tip of the ejector member 505.

Then, the pen tip holding tube 150 is molded by injecting a resin material into the molding space defined by the front hollow 501c of the front cavity 501, the rear hollow 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 of the ejector member 505 (which has an extension portion 505e) (see FIG. 34).

The molded nib holder 150 must then be removed from the manufacturing apparatus. 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 holder 150 is extracted from the front cavity 501c (see FIG. 35).

Next, the core pin member 503 is removed from the rear cavity 502c (see Figure 36).

Then, the ejector member 505 is moved forward relative to the rear cavity 502, causing the rear portion of the nib holding tube 150 to be extracted from the rear cavity 502c (see Figure 37).

Here, once the rear portion of the nib holding tube 150 has been extracted from the rear cavity 502c and the nib holding tube 150 and the ejector member 505 are separated, the nib holding tube 150 will fall below the manufacturing device, i.e., the nib holding tube 50 can be removed. However, there are cases where the molded nib holding tube 150 and the ejector member 505 stick to each other, and the nib holding tube 150 does not fall as desired. This tendency for adhesion is even greater when the contact area between the nib holding tube 150 and the ejector member 505 is increased by the presence of the extension 505e.

As a mechanism for removing the resin molded product that has become attached to the ejector member in this way, Patent Document 3 proposes the use of an additional member called a stripper bush, which separates the resin molded product from the ejector member by engaging the rear end of the resin molded product after it has been removed when the ejector member is returned to the rear side. However, the use of such an additional member increases the cost of the manufacturing device.

The present invention was made in light of the above findings, and its purpose is to provide a manufacturing method for a writing instrument part, or more broadly, a manufacturing method for a resin molded part, that can solve the problem of a resin molded part and an ejector member adhering to each other and not being able to be separated, while suppressing increases in cost. It is also an object of the present invention to provide a writing instrument that includes a part manufactured by this manufacturing method.

In order to manufacture a cylindrical resin molded product, the present invention provides a method for producing a cylindrical resin molded product, comprising: a front cavity having a front cavity corresponding to the outer peripheral contour of the front portion of the resin molded product; a rear cavity adjacent to the front cavity of the front cavity and corresponding to the outer peripheral contour of the rear portion 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; and an ejector member having a front end shape corresponding to the rear end shape of the resin molded product, wherein a resin material is injected into a molding space partitioned by 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. to mold the resin molded product; a front portion extraction step of extracting the front portion of the resin molded product from the front cavity by separating the front cavity and the rear cavity from each other and separating the front cavity and the rear cavity from each other; a core pin member extraction step of extracting the core pin member from the front cavity and the rear cavity; and a rear portion extraction step of extracting the rear portion of the resin molded product from the rear cavity by moving the ejector member forward relative to the rear cavity, wherein a protruding portion that protrudes locally in the axial direction is provided on the outer peripheral contour of the rear portion of the resin molded product, and the rear portion extraction step includes a step of passing the protruding portion through the rear cavity of the rear cavity while elastically deforming the protruding portion into a crushed shape.

According to the method of the present invention, a raised portion that locally rises in the axial direction is provided on the outer peripheral contour of the rear portion of the resin molded product, and during the rear portion extraction process, the raised portion can be elastically deformed into a crushed shape and passed through the rear cavity of the rear cavity.

As a result, the resin molded product and the ejector member can be separated by a reaction force that elastically returns the raised portion from a crushed shape to a raised shape immediately after the raised portion is released from the rear cavity. That is, the rear portion extraction step can include a step of separating the resin molded product and the ejector member by a reaction force that elastically returns the raised portion from a crushed shape to a raised shape immediately after the raised portion is released from the rear cavity.

Alternatively, even if the resin molded product and the ejector member cannot be separated by such a reaction force, the resin molded product and the ejector member can be separated by performing an ejector return step of moving the ejector member rearward with respect to the rear cavity after the rear portion extraction step. 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, the method can further include an ejector return step of moving the ejector member rearward with respect to the rear cavity after the rear portion extraction step, and the ejector return step can 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 by the raised portion that has returned to its raised shape.

It is preferable that the front end side of the raised portion is an inclined surface. In this case, it is easier to elastically deform the raised portion into a crushed shape during the rear portion extraction process.

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

It is also preferable that multiple raised portions are provided and aligned in the same position in the axial direction, but arranged in uneven positions in the circumferential direction. In this case, reaction forces can be generated simultaneously (all at once) without canceling each other out (so that the attitude is tilted).

The resin molded products that are the subject of manufacture by the above-mentioned method of the present invention are intended in particular to be parts of writing instruments, but at least at the time of this application, they are not limited to parts of writing instruments.

The present invention is also a part of a writing implement manufactured by the method of the present invention. In particular, the present invention is a part of a writing implement comprising a pen tip having a front core portion, a central core portion, and a rear core portion, an ink occluder that contacts the rear core portion of the pen tip to supply ink to the rear core portion, a main body tube that houses the ink occluder, and a pen tip holding tube that holds the central core portion of the pen tip and is held by the main body tube, the front core portion of the pen tip is thinner than the central core portion of the pen tip, the rear core portion of the pen tip is also thinner than the central core portion of the pen tip, the front end of the front core portion of the pen tip is in the shape of a cutting blade whose upper end is located forward of the lower end in a side view, and The maximum length of the front core portion in a side view is 7 mm or more, the nib holding tube has a reserve tube portion that extends around the front core portion except for the front end region of the front core portion of the nib, the maximum length of the reserve tube portion in a side view is 5 mm or more, the distance between the reserve tube portion and the front core portion of the nib is 0.03 to 1.0 mm, a protuberance that protrudes locally in the axial direction is provided on the outer peripheral contour of the rear portion of the nib holding tube, and the protuberance is capable of temporarily becoming crushed by elastic deformation.

According to the present invention, since the front core of the pen tip is thinner than the central core of the pen tip held in the pen tip holding tube, it is possible to provide sufficient flexibility of the front core of the pen tip relative to the central core of the pen tip. In particular, since the front end of the front core of the pen tip is shaped like a cutting blade in a side view and the maximum length (length at the upper end) of the front core of the pen tip in a side view is 7 mm or more, the user can enjoy the unique feeling of writing as the front core of the pen tip bends due to 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 tube portion of the nib holding tube extends around the front core portion of the nib, except for the front end region of the front core portion, and when excessive force is applied to the front core portion of the nib, the front core portion of the nib abuts against the spare tube portion to suppress further deformation of the front core portion. In particular, the maximum length (length at the upper end) of the spare tube portion in a side view is 5 mm or more, and the distance between the spare tube portion and the front core portion of the nib is 0.03 to 1.0 mm, which effectively suppresses excessive deformation that would make it difficult for the front core portion of the nib to return to its original shape, thereby achieving a long service life.

And according to the present invention, a raised portion that locally rises in the axial direction is provided on the outer peripheral contour of the rear part of the nib holding tube, and the raised portion can be temporarily crushed by elastic deformation. Therefore, when the nib holding tube is manufactured by injection molding, in the process of using an ejector member to extract the rear part of the nib holding tube from the rear cavity of the rear cavity, which is the injection molding die, the raised portion can be elastically deformed to a crushed shape and passed through the rear cavity.

As a result, the pen tip holding tube and the ejector member can be separated by the recoil force that elastically returns the raised portion from its crushed shape to its raised shape immediately after it is released from the rear cavity. Alternatively, even if the pen tip holding tube and the ejector member cannot be separated by such a recoil force, the pen tip holding tube and the ejector member can be separated by carrying out an ejector return process in which the ejector member is moved rearward relative to the rear cavity after the process of extracting the rear portion of the pen tip holding tube. This is because, in the ejector return process, the raised portion that has returned to its raised shape effectively prevents the pen tip holding tube from returning into the rear cavity.

In the present invention, it is preferable that the pen tip holding tube holds the front part of the central core of the pen tip, and the main body tube holds the rear part of the central core of the pen tip.

This allows the central core of the pen tip to be held in at least two places in the axial direction, making it possible to more securely hold the central core of the pen tip.

It is also preferable that the central core of the pen tip has a cylindrical shape.

This allows the pen tip to have sufficient strength and ensures more secure retention of the central core of the pen tip.

It is also preferable that the pen tip holding tube holds the central core of the pen tip at multiple locations spaced apart in the circumferential direction.

This allows the central core of the pen tip to be held in a well-balanced manner, enabling the central core of the pen tip to be held more securely.

It is also preferable that the distance between the spare tube portion and the front core portion of the pen tip be approximately constant.

This allows the spare tube section to effectively suppress excessive deformation of the front core of the pen tip in all directions. It also provides a form that is excellent in terms of design (aesthetics).

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

Alternatively, the central core of the pen tip may be formed into a substantially polygonal prism shape, such as a substantially square prism shape, excluding the front end region. In this case, the spare tube portion may be formed into a corresponding substantially polygonal prism shape, such as a substantially square tube shape.

The front end of the spare tube is also shaped like a cutting blade with its upper end positioned further forward than its lower end in a side view, and it is preferable that the front end of the front core of the pen tip and the front end of the spare tube are parallel in a side view.

This makes it possible to more effectively suppress excessive deformation of the front core of the pen tip, which is blade-shaped when viewed from the side, in all directions. It also provides a form that is excellent in terms of design (aesthetics).

It is also preferable that at least a portion of the pen tip holding tube is made of a transparent or translucent material.

This makes it easier to see the ink color. It also provides a form that is excellent in terms of design (aesthetics).

It is also preferable that the main body tube and/or the pen tip holding tube have a mark indicating the angular position of the pen tip.

This makes it easier to grasp the angular position (orientation) of the pen tip. The mark is not limited to a visual mark, but may be an uneven surface that can be sensed by touch.

According to the method of the present invention, a raised portion that locally rises in the axial direction is provided on the outer peripheral contour of the rear portion of the resin molded product, and during the rear portion extraction process, the raised portion can be elastically deformed into a crushed shape and passed through the rear cavity of the rear cavity.

As a result, the resin molded product and the ejector member can be separated by a reaction force that elastically returns the raised portion from a crushed shape to a raised shape immediately after the raised portion is released from the rear cavity. That is, the rear portion extraction step can include a step of separating the resin molded product and the ejector member by a reaction force that elastically returns the raised portion from a crushed shape to a raised shape immediately after the raised portion is released from the rear cavity.

Alternatively, even if the resin molded product and the ejector member cannot be separated by such a reaction force, the resin molded product and the ejector member can be separated by performing an ejector return step of moving the ejector member rearward with respect to the rear cavity after the rear portion extraction step. 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, the method can further include an ejector return step of moving the ejector member rearward with respect to the rear cavity after the rear portion extraction step, and the ejector return step can 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 by the raised portion that has returned to its raised shape.

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

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

The pen tip 110 is similar to the pen tip 110 of the second embodiment of the aforementioned 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. FIG. 20 is a side view of the pen tip 110, FIG. 21 is a cross-sectional view of the pen tip 110 of FIG. 20 taken along line A-A, and FIG. 22 is a cross-sectional view of the pen tip 110 of FIG. 20 taken along line B-B.

First, as shown in Figures 38, 39, 19 to 22, the writing instrument 201 of this embodiment includes a pen tip 110 having a front core portion 111, a central core portion 112, and a rear core portion 113, and an ink occlusion body 20 that contacts the rear core portion 113 of the pen tip 110 and supplies ink to the rear core portion 113. As with the embodiments of Japanese Patent Application No. 2018-134808, the ink occlusion body 20 is contained by the front tube 30 and rear tube 40 that constitute the main body tube, and the cap 60 is detachable from the front tube 30 or the rear tube 40.

As shown in Figures 19 to 22, the central core 112 and rear core 113 of the pen tip 110 of this embodiment have a concentric cylindrical shape (more specifically, excluding the tapered portions 112t and 113t described below), but the rear core 113 is thinner than the central core 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.

As shown in Figs. 19 to 22, the front core 111 of the pen tip 110 of this embodiment has a generally rectangular prism shape with rounded corners, except for the front end region described later (see Fig. 22 in particular). The axis of the central core 112 passes through the center (center of gravity) of the generally rectangular cross section of the front core 111, and the length of the diagonal of the generally rectangular cross section (see Fig. 22) is smaller than the diameter of the central core 112. In other words, the front core 111 is thinner than the central core 112. More specifically, the generally rectangular cross section of the front core 111 (see Fig. 22) has a long side length of 4.1 mm and a short side length of 3.2 mm.

Furthermore, similar to the embodiments of Patent Application No. 2018-134808, a gently sloping tapered portion 113t is provided on the rear side of the rear core portion 113, facilitating insertion into the ink occluder 20. Further, a relatively steeply sloping tapered portion 112t is provided on the rear side of the central core portion 112, and is continuous with 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, similar to each embodiment of Japanese Patent Application No. 2018-134808, the front end of the front core 111 is in the shape of a cutting blade whose upper end is located forward of the lower end in side view (see FIG. 20), and has a front end 111a that is R in the left-right direction (see FIG. 21) and inclined in the up-down direction (see FIG. 20), and acute angle forming flat parts 111b, 111c that are provided on both the left and right sides of the front end 111a and form an acute angle (for example, 60 degrees) with each other (see FIG. 21) (the intersection line of the extended planes of the acute angle forming flat parts 111b, 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 111 in side view is 13.8 mm, and the lower end length L12 (minimum length) of the front core 111 in side view is 12.3 mm. The front end 111a and the acute angle forming flat surfaces 111b and 111c may be formed by cutting or may be formed in advance by molding.

As with the embodiments of Japanese Patent Application No. 2018-134808, the writing instrument 201 of this embodiment holds the central core 112 of the pen tip 110, while also including a pen tip holding tube 250 held by the front tube 30, which is the main body tube, as shown in Figures 38 and 39. The pen tip holding tube 250 is similar to the pen tip holding tube 150 of the second embodiment of the aforementioned Japanese Patent Application No. 2018-134808, except that it has a raised portion 255, which will be described later.

Fig. 40 is a perspective view showing the pen tip holding tube 250 of the writing instrument 201, Fig. 41 is a front view of the pen tip holding tube of Fig. 40, and Fig. 42 is a right side view of the pen tip holding tube of Fig. 40. Also, Fig. 43 is a cross-sectional view of the pen tip holding tube of Fig. 42 taken along line A-A, Fig. 44 is an enlarged view of part B of the pen tip holding tube of Fig. 43, and Fig. 45 is a cross-sectional view of the pen tip holding tube of Fig. 41 taken along line C-C.
FIG. 46 is an enlarged view of portion D of the pen tip holding tube in FIG.

As shown in Figures 40 to 46, the nib holding tube 250 has a holding tube portion 252 that holds the central core portion 112 of the nib 110, and a spare tube portion 251 that extends around the front core portion 111 of the nib 110 except for the front end region of the front core portion 111 (the region including the front end portion 111a and the acute angle forming flat portions 111b, 111c). The holding tube portion 252 has a substantially cylindrical shape corresponding to the central core portion 112, and the spare tube portion 251 has a substantially square tube shape corresponding to the front core portion 111.

For example, the upper end length L13 (maximum length) of the spare tube portion 251 in a side view is 10 mm, the lower end length L14 (minimum length) of the spare tube portion 251 in a side view is 8.3 mm, the approximately rectangular cross section (see FIG. 30) of the outer circumferential surface of the spare tube portion 251 (excluding the flange portion 251f described later) has a long side length of 5.3 mm and a short side length of 4.4 mm, and the approximately rectangular cross section (see FIG. 30) of the inner circumferential surface of the spare tube portion 251 has a long side length of 4.5 mm and a short side length of 3.6 mm. Therefore, in this embodiment, the distance (symbol G2 in FIG. 31) between the inner circumferential surface of the spare tube portion 251 and the outer circumferential surface of the front core portion 111 of the nib 110 is constant at 0.2 mm (changes when force is applied to the nib 10 during writing: see FIG. 16). In addition, an axial draft angle may be provided on at least one of the inner peripheral surface of the spare tube portion 251 and the outer peripheral surface of the front core portion 111 of the pen tip 110. This not only improves the productivity of the spare tube portion 251 and the pen tip 110, but also allows the front core portion 111 to bend easily.

The front end of the spare tube portion 251 is also shaped like a cutting blade with its upper end positioned further forward than its lower end in side view (see FIG. 41), and the front end of the front core portion 111 of the pen tip 110 and the front end of the spare tube portion 251 are parallel in side view (see FIG. 28).

As in the embodiments of Patent Application No. 2018-134808, the retaining tube portion 252 has four retaining protrusions 252p on its inner circumferential surface, which is a cylindrical surface with a diameter of 5.5 mm, to retain the front portion of the central core portion 112 of the pen tip 110 at four circumferentially spaced locations (see FIG. 43). Each retaining protrusion 252p has a circumferential width of 0.6 mm, a length of 3.6 mm, and protrudes inward to a position 2.4 mm radially from the axis center, for example.

In this embodiment, a flange portion 251f is provided at the rear end of the spare tube portion 251, and a concave air hole 251r is provided in the flange portion 251f. The air hole 251r allows ventilation between the inside and outside of the main body tube. This allows air to be taken into the inside of the main body tube as ink is consumed, and appropriate ink ejection performance can be maintained. In addition, the retaining tube portion 252 is provided with a vertical rib 252r that protrudes radially outward for engagement with the front tube 30, and a slit 252s for improving the assembly of the pen tip 110 and the pen tip retaining tube 250. By using the slit 252s, the rotational alignment of the pen tip 110 and the pen tip retaining tube 250 with respect to the axis (the front end portion 111a and the front end of the spare tube portion 251 are made parallel in a side view) can be easily performed on an assembly machine.

In addition, in this embodiment, two raised portions 255 that are locally raised in the axial direction are provided on the outer peripheral contour of the rear portion of the holding tube portion 252. The raised portions 255 can be temporarily crushed by elastic deformation (may be accompanied by slight plastic deformation). Specifically, the holding tube portion 252 (pen tip holding tube 250) including each raised portion 255 is made of polycarbonate, which is an elastic material, and each raised portion 255 has a height of 0.05 to 0.2 mm, preferably a height of 0.05 to 0.15 mm (height of 0.1 mm in this embodiment), an 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 (circumferential width of 0.7 mm in this embodiment), so that it can be elastically deformed by the wall surface that defines the hollow 302c of the cavity 302, which is the injection mold, during the rear portion extraction process described later and temporarily crushed (while passing through the wall surface).

To facilitate the elastic deformation of each of the raised portions 255, the front end side of each raised portion 255 forms an inclined surface 255t. The inclination angle is preferably 2 to 30 degrees with respect to the peripheral surface of the retaining tube portion 252, and is 15 degrees in this embodiment. Meanwhile, the rear end side of each raised portion 255 has a flat end portion 255e that is perpendicular to the axial direction of the retaining tube portion 252.

The flat end 255e of each raised portion 255 is aligned at a position spaced 0 to 3 mm apart (0.3 mm apart in this embodiment) from the rear end of the retaining tube portion 252. In other words, the two raised portions 255 are aligned at the same position in the axial direction.

The two raised portions 255 are provided at 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 Figures 42 and 46, a relative positional relationship is adopted in which the circumferential end of each raised portion 255 slightly overlaps (by about 2 ° (0.7 mm) in the circumferential direction) with the circumferential end of air hole 251r when viewed in the axial direction.

Returning to Figure 38, the front tube 30 holds the nib holding tube 250 by utilizing the vertical rib 252r of the nib holding tube 250. In addition, the length of the holding tube portion 252 is shorter than the length of the central core portion 112 (see Figures 27 to 29), and the front tube 30 also holds the tapered portion 112t at the rear of the central core portion 112 of the nib 110.

The material of the pen tip 110 can be the same as that described above for the material of the pen tip 10 of the first embodiment of Japanese Patent Application No. 2018-134808.

(Effects of one embodiment of the writing instrument)
The writing instrument 201 configured as above can achieve the following effects. That is, with the writing instrument 201 of this embodiment, the front core portion 111 of the pen tip 110 is thinner than the central core portion 112 of the pen tip 110 held in the pen tip holding tube 250 , so that the front core portion 111 of the pen tip 110 can be provided with sufficient flexibility relative to the central core portion 112 of the pen tip 110.

The front end of the front core 111 of the pen tip 110 is shaped like a cutting blade when viewed from the side, and the length L11 (maximum length) of the upper end of the front core 111 of the pen tip 110 is 13.8 mm, which is sufficiently long (7 mm or more). Combined with this feature, the user can enjoy the unique writing sensation of the front core 111 of the pen tip 110 bending due to the force applied to the front end of the front core 111 of the pen tip 110.

On the other hand, in the writing instrument 201 of this embodiment, the spare tube portion 251 of the nib holding tube 250 extends around the front core portion 111 of the nib 110, except for the front end region of the front core portion 111, and when excessive force is applied to the front core portion 111 of the nib 110, the spare tube portion 251 abuts against the front core portion 111 of the nib 110 to suppress further deformation of the front core portion 111 (similar to what was explained using Figure 16 for the first embodiment of Patent Application No. 2018-134808).

In particular, also in this embodiment, the maximum length (length at the upper end) of spare tube portion 2 51 is 10 mm, which is sufficiently long (5 mm or more), and coupled with the feature that the gap G2 between spare tube portion 2 51 and the front core portion 111 of the nib 110 at no load is constant at 0.2 mm (see FIG. 31 ), excessive deformation in the front core portion 111 of the nib 110 that would make it difficult to return to its original shape is effectively suppressed, thereby achieving a long service life.

Also, with the writing instrument 201 of this embodiment, the holding protrusion 252p of the nib holding tube 250 holds the front part of the central core 112 of the nib 110, and the front tube 30, which is the main body tube, holds the tapered part 112t of the central core 112 of the nib 110. As a result, the central core 112 of the nib 110 is held at two points in the axial direction, realizing more secure holding of the central core 112 of the nib 110.

Also, in the writing instrument 201 of this embodiment, the central core 112 of the pen tip 110 has a cylindrical shape. This allows the pen tip 110 to have sufficient strength, and realizes more reliable holding of the central core 112 of the pen tip 110.

Also, in the writing instrument 201 of this embodiment, the holding protrusions 252p of the pen tip holding tube 250 hold the central core 112 of the pen tip 110 at four points spaced apart (preferably at equal intervals) in the circumferential direction. This allows the central core 112 of the pen tip 110 to be held in a well-balanced manner, realizing more reliable holding of the central core 112 of the pen tip 110.

Also, with the writing implement 201 of this embodiment, when no force is being applied to the pen tip 110, the gap G2 between the spare tube portion 251 and the front core portion 111 of the pen tip 110 is constant. This allows the spare tube portion 251 to effectively provide the effect of suppressing excessive deformation of the front core portion 111 of the pen tip 110 in all directions. Also, a form excellent in terms of design (aesthetics) can be provided.

Also, in the writing instrument 201 of this embodiment, the front end of the spare tube portion 251 is in the shape of a cutting blade with the upper end located forward of the lower end in side view (see FIG. 26), and the front end of the front core portion 111 of the pen tip 110 and the front end of the spare tube portion 151 are parallel in side view (see FIG. 28). This makes it possible to more effectively provide the effect of suppressing excessive deformation of the front core portion 111 of the pen tip 110 in the shape of a cutting blade in all directions. Also, it is possible to provide a form that is excellent in design (aesthetics).

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

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

In the example of Figure 47, the front cavity 301 is the fixed cavity, the rear cavity 302 is the movable cavity (moves in the axial direction of the pen tip holding tube 250 relative to the front cavity 301), the core pin member 303 is the movable core pin, the front end defining member 304 is the fixed pin, and the ejector member 305 is the ejector sleeve.

As shown in FIG. 48, the front end shape of the ejector member 305 has a pair of opposing extensions 305e that correspond (complementarily) to the slits 252s of the pen tip holding tube 250. Each extension 305e extends in the axial direction and has a semicircular tip. FIG. 48(a) is a front view of the ejector member 305, FIG. 48(b) is a side view of the ejector member 305, FIG. 48(c) is a cross-sectional view taken along line c-c in FIG. 48(a), FIG. 48(d) is a cross-sectional view taken along line d-d in FIG. 48(b), and FIG. 48(e) is a perspective view of the vicinity of the tip of the ejector member 305.

Then, the pen tip holding tube 250 is molded by injecting a resin material into the molding space defined by the front hollow 301c of the front cavity 301, the rear hollow 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 of the ejector member 305 (which has an extension 305e) (injection molding process: see Figure 49).

The molded nib retaining tube 250 must then be removed from the manufacturing apparatus. In this manufacturing apparatus, the front cavity 301 and the rear cavity 302 are first separated from each other, and the front cavity 301c and the rear cavity 302c are separated from each other, so that the front part of the nib retaining tube 250 is extracted from the front cavity 301c (front part extraction process: see Figure 50).

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

Then, the ejector member 305 is moved forward relative to the rear cavity 302, thereby extracting the rear portion of the nib holding tube 250 from the rear cavity 302c (rear portion extraction process).

As described above, the outer peripheral contour of the rear part of the holding tube part 252 of the nib holding tube 250 has two raised parts 255 that are locally raised in the axial direction. During the rear part extraction process by the ejector member 305, the two raised parts 255 are elastically deformed by the wall surface that defines the rear cavity 302c of the rear cavity 302, which is the injection molding die, and temporarily assume a crushed shape (while passing through the wall surface). This allows the rear part extraction process by the ejector member 305 to be performed despite the presence of the two raised parts.

In this embodiment, the pen tip holding tube 250 and the ejector member 305 can be separated by the recoil force that occurs when the two raised portions 255 elastically return from their crushed shape to their raised shape immediately after being released from the rear cavity 302c. As a result, many of the molded pen tip holding tubes 250 separate from the ejector member 305 and fall during the rear portion extraction process.

However, about 10% of the nib holding tube 250 does not separate from the ejector member 305 even due to the recoil force described above (see FIG. 52). This tendency for adhesion is higher when the contact area between the nib holding tube 250 and the ejector member 305 is increased due to the presence of the extension 305e. In such a case, the ejector member 305 is returned to the rear side relative to the rear cavity 302 (ejector return process).

At this time, the raised portion 255, which 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. As a result, most of the pen tip holding tube 250 that did not separate from the ejector member 305 even due to the recoil force described above separates from the ejector member 305 and falls during the ejector return process.

Furthermore, there are cases where the rear end of the nib holding tube 250 gets caught on the front end of the rear cavity 302c corresponding to the flange portion 251f, and the nib holding tube 250 still does not fall (see FIG. 54). In such a case, the ejector member 305 is moved forward again relative to the rear cavity 302 (ejector re-extrusion process: see FIG. 55). As a result, the nib holding tube 250 that has been caught in the rear cavity 302c and has not fallen is pushed by the ejector member 305 and falls in the ejector re-extrusion process.

Then, the ejector member 305 is returned to the rear side relative to the rear cavity 302 (ejector return process).

(Advantages of the manufacturing method of the pen tip holding tube 250)
According to the manufacturing method described above, when manufacturing the nib holding tube 250 by injection molding, in the process of using the ejector member 305 to extract the rear part of the nib holding tube 250 from the rear cavity 302c of the rear cavity 302, which is the injection molding die, the raised part 255 is elastically deformed into a crushed shape, allowing it to pass through the rear cavity 302c.

Then, immediately after the raised portion 255 is released from the rear cavity 302c, the recoil force that elastically returns the raised portion 255 from its crushed shape to its raised shape can separate the pen tip holding tube 250 and the ejector member 305.

Alternatively, even if the tip holding tube 250 and the ejector member 305 cannot be separated due to such a reaction force, the tip holding tube 250 and the ejector member 305 can be separated by performing an ejector return process in which the ejector member 305 is moved rearward relative to the rear cavity 302 after the process of extracting the rear portion of the tip holding tube 250. This is because the raised portion 255, which has returned to its raised shape during the ejector return process, effectively prevents the tip holding tube 250 from returning into the rear cavity 302c.

Furthermore, even if the pen tip holding tube 250 that has separated from the ejector member 305 during the ejector return process does not fall because it gets caught in the rear cavity 302c, the pen tip holding tube 250 can be pushed by the ejector member 305 during the subsequent ejector re-extrusion process and fall.

In addition, in this embodiment, the front end side of the raised portion 255 is an inclined surface 255t, which makes it easier to elastically deform the raised portion 255 into a flattened shape during the rear portion extraction process.

On the other hand, the rear end side of the raised portion 255 has a flat end portion 255e perpendicular to the axial direction, so that the raised portion 255 that has returned to its raised shape is more likely to interfere with the end face of the rear cavity 302 during the ejector return process, which enhances the effect of preventing the pen tip holding tube 250 from returning into the rear cavity 302c.

In addition, since the two raised portions 255 are aligned at the same position in the axial direction, the recoil forces can be generated simultaneously (all at once). On the other hand, since the two raised portions 255 are positioned at uneven positions in the circumferential direction, the recoil forces do not cancel each other out, and the attitude of the pen tip holding tube 250 can be effectively tilted.

Furthermore, in this embodiment, as shown in Figures 42 and 46, the circumferential end of each raised portion 255 slightly overlaps with the circumferential end of the air hole 251r when viewed in the axial direction, so that each raised portion 255 moves (rotates) in the circumferential direction while abutting against the wall surface of the rear cavity 302c that corresponds (complementarily) to the air hole 251r during the ejector return process. As a result, even if the pen tip holding tube 250 does not fall afterwards because it gets caught in the rear cavity 302c, the circumferential phase of the slit 252s of the pen tip holding tube 250 and the extension portion 305e of the ejector member 305 are misaligned, so that the pen tip holding tube 250 can reliably fall in the subsequent ejector re-extrusion process.

(Color of the pen tip holding tube 250)
In the writing instrument 201, it is preferable that the pen tip holding tube 250 is entirely made of a transparent or semi-transparent material. In this case, the color of the ink can be easily seen. In addition, a form excellent in terms of design (aesthetics) can be provided.

Alternatively, a useful embodiment is one in which only the area near the front end of the nib holding tube 250 is colored, with the remainder being made of a transparent or translucent material. This embodiment has the effect of making it easier to grasp the relative positions of the writing implement and the writing object when the color of the writing object (e.g., the paper surface) and the color of the ink are similar. In particular, by making the colored area a parallelogram as shown in Figure 57, a form that is also excellent in terms of design (aesthetics) can be provided.

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

(Angle position mark)
In addition, in the writing instrument 201, it is preferable that a mark indicating the angular position of the pen tip 110 is provided on the front tube 30, which is the main body tube, and/or the pen tip holding tube 250. In this case, the angular position of the pen tip 110 (the orientation of the upper end and the lower end) can be more easily grasped. The mark is not limited to a visual mark, and may be an unevenness that can be distinguished by touch. The front tube 30 may be configured in a polygonal shape (triangular, hexagonal, etc.) so that the entire shape functions as a mark.

1, 101 Writing implement 10, 110 Pen tip 11, 111 Front core portion 11a, 111a Front end portion 11b, 111b Acute angle forming flat portion 11c, 111c Acute angle forming flat portion 12, 112 Central core portion 12t, 112t Tapered portion 13, 113 Rear core portion 13t, 113t Tapered portion 20 Ink occlusion body 30 Front tube (main body tube)
40 Rear tube (main body tube)
50, 150 Pen tip holding tube 51, 151 Spare tube portion 51f, 151f Flange portion 51r, 151r Air hole 52, 152 Holding tube portion 52p, 152p Holding protrusion 52s, 152s Slit 52r, 152r Vertical rib 60 Cap G1, G2 Spacing L1, L11 Upper end length L2, L12 of front core portion in side view Lower end length L3, L13 of front core portion in side view Upper end length L4, L14 of spare tube portion in side view Lower end length 201 of spare tube portion in side view Writing instrument 250 Pen tip holding tube 251 Spare tube portion 251f Flange portion 251r Air hole 252 Holding tube portion 252p Holding protrusion 252s Slit 252r Vertical rib 255 Raised portion 255t Inclined surface 255e Flat end portion 301 Front cavity 301c Front cavity 302 Rear cavity 302c Rear cavity 302r Recess 303 corresponding to raised portion Core pin member 304 Front defining 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 defining member 505 Ejector member 505e Extension portion

Claims (4)

a pen tip having a front core, a central core, and a rear core;
an ink occlusion body that contacts the rear core portion of the pen tip and supplies ink to the rear core portion;
a main body tube that houses the ink occlusion body;
a pen tip holding tube that holds the central core portion of the pen tip and is held by the main body tube;
Equipped with
The front core of the pen tip is thinner than the central core of the pen tip,
The rear core of the pen tip is also thinner than the central core of the pen tip,
The front end of the front core of the pen tip is formed in a cutting blade shape such that an upper end is located forward of a lower end in a side view,
The maximum length of the front core of the pen tip in a side view is 7 mm or more,
the nib holding tube has a spare tube portion extending around the front core portion of the nib except for a front end region of the front core portion,
The maximum length of the spare cylinder portion in a side view is 5 mm or more,
a distance between the reserve tube portion and the front core portion of the pen tip is 0.03 to 1.0 mm;
a protruding portion that protrudes locally in an axial direction is provided on an outer peripheral contour of a rear portion of the pen tip holding tube;
A writing implement, characterized in that the raised portion is capable of being temporarily collapsed by elastic deformation. 2. The writing implement according to claim 1, wherein a front end side of the raised portion forms an inclined surface. 3. The writing implement according to claim 1, wherein the rear end side of the raised portion has a flat portion perpendicular to the axial direction. 4. The writing implement according to claim 1, wherein a plurality of the raised portions are provided, and the raised portions are aligned at the same position in the axial direction but are arranged at non-uniform positions in the circumferential direction.

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