JP4325923B2 - Writing instrument barrel - Google Patents

Description

  The present invention relates to a writing instrument shaft tube formed by injection molding a resin material, and particularly in a writing tool shaft tube having a thin wall portion and a thick wall portion, sufficient for the inside of a mold cavity at the time of molding. The present invention relates to an axial tube for a writing instrument capable of obtaining a resin filling action.

  For example, in a writing instrument typified by a ballpoint pen, most of the shaft cylinder constituting the exterior is manufactured by injection molding a resin. The prices of these writing instruments supplied at present vary, but in general, the main products that are sold in large numbers are relatively low-priced products. On the other hand, it is difficult for this type of low-priced writing instrument to achieve exceptional differentiation in terms of its function. Therefore, it is very important to provide a high-grade design for the low-priced writing instrument as described above, and this occupies a large weight when the user selects a product at a storefront or the like.

  Therefore, in recent years, when the shaft cylinder is formed by injection molding of a resin material, a thin-walled portion and a thick-walled portion are formed. Forming means such as forming the body in layers is employed. By adopting such a forming means, it is possible to give a design feeling as if the thick portion was exposed like a window to the secondary side molded body. Further, when the thick portion is formed in an annular shape so as to be orthogonal to the shaft core, it is possible to give a design feeling that a ring-shaped separate member is fitted into the shaft tube. In addition, the design effect can be further enhanced by using, for example, a transparent or translucent resin or the like, or a resin of each color as the primary side resin material.

By the way, when the resin material is injection-molded as described above, generally, as disclosed in Patent Document 1 shown below, a gate portion for resin injection is set at a substantially physical center portion of the product. The structure which does is taken.
JP 2001-122281 A (paragraphs 0010 to 0011 and FIG. 3)

  According to the injection molding means disclosed in Patent Document 1 described above, a gate portion for resin injection is set at a portion corresponding to the center of the bottom portion of the container, so that the resin injected into the mold is the bottom surface of the container. Then, it flows to the side surface portion formed with a relatively thin wall thickness, and further acts to fill the resin toward the opening edge portion of the container constituting the thick wall portion. For this reason, the flow resistance of the resin is generated in the side surface portion having a thin wall thickness, and there is a problem that the resin pressure is not sufficiently applied to the opening edge portion of the container constituted by the thick wall portion.

  In other words, in general, the injection molding is a resin material that "flows and hardens" in the mold, so in principle, the material is quickly driven into the mold before it cools. When the material cools down, the fluidity of the thin wall portion deteriorates even during flow, so that it is difficult to transmit the injection pressure to every corner of the mold. That is, when the material that has flowed through the thin wall portion flows into the thick wall portion, the flow of the material also decreases at the thick wall portion, and the thick wall portion may not be sufficiently filled with the resin material. This increases the degree of occurrence of so-called sink marks, insufficient filling, and molding defects due to bubbles or the like in the thick portion.

  In particular, as described above, a thin tube portion and a thick wall portion are formed, and the thick tube portion is exposed like a window or a ring with respect to the secondary molded body. In this case, the degree of occurrence of the above-described molding defect is increased in the thick wall portion on the primary side exposed in a window or ring shape, and the commercial value is immediately reduced.

  Therefore, as described above, the present invention can sufficiently apply a resin pressure to the thick-walled portion of the writing instrument shaft tube in which the thin-walled portion and the thick-walled portion are formed by injection molding as described above. It is an object of the present invention to provide a writing instrument shaft that can sufficiently fill a thick portion.

  The writing instrument shaft cylinder according to the present invention made to solve the above-described problems is a writing instrument having a shaft cylinder body having a thin portion and a thick portion formed by injection molding as described in claim 1. In the shaft cylinder main body, a convex portion for supplying a resin is formed on the thin wall portion in succession to the thick portion, and a gate portion for inflow of resin is formed on the convex portion. It is characterized in that it is formed.

  In this case, preferably, as described in claim 2, at least two or more thick portions are formed in the shaft cylinder body, and the convex portions are formed so as to connect the thick portions. The Further, in this case, as described in claim 3, it is desirable that the gate portion is formed at an intersection position of the convex portion.

  Moreover, in one preferable form of the axial cylinder for writing instruments concerning this invention, as the said 4th aspect, the said axial cylinder main body was made into the primary side molded object, and the secondary side molded object was formed by two-color molding. The at least part of the thick part formed in the shaft cylinder main body is not covered with the secondary side molded body, and the convex part formed on the shaft cylinder main body is formed by the secondary side molded body. It is set as the structure covered.

  Furthermore, the writing instrument shaft cylinder according to the present invention has a configuration in which a secondary side molded body is formed by two-color molding using the shaft cylinder body as a primary side molded body, as described in claim 5. The gate part in the case of forming the secondary side molded body is set at a position facing the convex part, and the resin constituting the secondary side molded body is the resin constituting the primary side molded body, It is characterized by having thermal adhesiveness.

  According to the writing instrument shaft cylinder according to claim 1, since the convex portion for resin supply is formed on the thin wall portion continuously from the thick wall portion formed in the shaft tube main body, the gate portion is Thus, the resin material supplied via the convex portion can be effectively filled into the thick portion. That is, the flow resistance of the resin material can be reduced by the presence of the convex portion, and the resin pressure can be sufficiently applied to the thick portion. Thereby, a sufficient amount of the resin material can be filled in the thick portion, and the degree of occurrence of molding defects due to so-called sink marks, insufficient filling, bubbles or the like in the thick portion can be reduced.

  Further, as described in claim 2, two or more thick portions formed in the shaft tube main body are connected by the convex portions, so that two or more portions are passed through the convex portions. It becomes possible to fill each thick material part with a resin material. Therefore, adopting the above-described configuration can contribute to reducing the number of gate portions that supply the resin material.

  In this case, as described in claim 3, by forming the gate portion at the intersection of the convex portions, the thick portions are connected to the thick portions via the convex portions connected to the thick portions. On the other hand, the resin material can be filled individually. Therefore, it is possible to efficiently fill the resin material while applying a sufficient resin pressure to each thick part.

  On the other hand, in the shaft cylinder for a writing instrument having a configuration in which the secondary cylinder is formed by two-color molding using the axial cylinder main body as the primary mold, at least one of the thick parts as described in claim 4. By having a configuration in which the portion is not covered with the secondary-side molded body, the thick-walled portion is exposed to the secondary-side molded body as if it were exposed like a window or a ring. be able to. In addition, by forming the convex portion formed on the shaft cylinder body with the secondary side molded body, the convex portion that is not necessarily preferable in terms of design can be effectively obtained by the secondary side molded body. Can be concealed.

  Furthermore, in the shaft cylinder for writing instruments of the structure which formed the secondary side molded object by the two-color molding by using the said shaft cylinder main body as the primary side molded object, the secondary side molded object as described in Claim 5 In the case where the gate portion is formed at a position facing the convex portion, the shaft cylinder body which is the primary side molded body and the molding thickness in the vicinity of the gate portion in the secondary side molding are substantially reduced. Can be made thinner. Thereby, when the gate is cut in the secondary side molding, the deformation of the secondary side molding material can be reduced, and the gate trace remaining on the secondary side can be made less noticeable.

  Further, by selecting a resin material that constitutes the secondary side molded body that has thermal adhesiveness to the resin that constitutes the primary side molded body, the secondary side molded body is peeled from the primary side molded body. In particular, it is possible to effectively prevent peeling at the time of gate cutting at the time of secondary side molding, and it is possible to provide a highly durable writing instrument barrel.

  The writing instrument according to the present invention will be described below based on the embodiments shown in the drawings. First, FIG. 1 shows the form at the time of applying the writing instrument concerning this invention to a ball-point pen with a longitudinal cross-sectional view. The shaft cylinder constituting the outline of the writing instrument (ballpoint pen) 1 includes a metal base 2 disposed at the tip, a synthetic resin front shaft 3 that supports the base 2 behind the base 2, and the front shaft. The rear shaft 4 is made of a synthetic resin rear shaft 4 detachably attached to the front shaft 3.

  A refill including a writing tip 5 and an ink storage tube 6 is accommodated in the shaft cylinder having the above-described configuration, and the tip of the writing tip 5 is projected from an opening formed at the tip of the base 2. Is configured. In this embodiment, the writing tip 5 and the ink storage tube 6 constituting the refill are connected by a joint member 7 interposed therebetween, and a tail end is provided at the rear end of the ink storage tube 6. A stopper 8 is attached. Further, as is well known, the ink 9 is accommodated in the ink accommodating tube 6 and the rear end of the ink is filled with a grease-like follower 10 that can move following the decrease of the ink.

  FIG. 2 is an enlarged longitudinal sectional view showing the configuration of the above-described front shaft 3. As shown in FIG. 2, the front end portion of the front shaft 3 is formed into a reduced diameter portion 3a whose inner diameter is slightly reduced. Then, the base 2 is configured to be locked at the reduced diameter portion 3a. Further, the secondary molded body 3b is formed in a layered manner using a two-color molding method so as to cover most of the outer surface of the front shaft 3. The secondary molded body 3b is preferably formed of a material that can prevent slipping during gripping. Furthermore, a threaded portion 3c is formed on the inner wall surface at the rear end portion of the front shaft 3, and the rear shaft 4 is screwed onto the rear end portion of the front shaft 3 using this threaded portion 3c. It is configured to be able to.

  Next, FIG. 3 is an enlarged longitudinal sectional view showing the configuration of the rear shaft 4 described above. The rear shaft 4 has a rear end formed in a cannonball shape and is closed to constitute a grip portion 4 a of the rear shaft 4. The outer end of the front end adjacent to the grip 4a is slightly reduced in diameter, and a threaded portion 4b is formed on the outer peripheral surface thereof. The rear shaft 4 is detachably attached to the rear end portion of the front shaft 3 by screwing the screw portion 4b with the screw portion 3c formed on the inner wall surface of the front shaft 3. The refill provided with the above-mentioned writing chip 5 and ink containing tube 6 can be exchanged.

  Further, the front end portion side of the screw portion 4b is formed as a cylindrical portion 4c having a relatively long axial length, and the cylindrical portion 4c is inserted along the inner peripheral surface of the front shaft 3. Therefore, in the assembled state of the ballpoint pen, the ink storage tube 6 in the refill described above is stored in the cylindrical portion 4c of the rear shaft 4 described above.

  In addition, a pair of through holes 4d are formed near the boundary between the threaded portion 4b and the cylindrical portion 4c of the rear shaft 4 at opposite positions orthogonal to the axial direction. Air exchange is enabled, and air exchange according to the reduction of ink in the refill 7 is realized.

  Next, FIG. 4 is a front view showing the shaft cylinder main body 3A constituting the front shaft 3 described above, and FIG. 5 is a side view showing the shaft body rotated by 90 degrees in the circumferential direction. 6 is a cross-sectional view as viewed in the direction of arrow AA from the center line shown in FIG. 4, and FIG. 7 is a cross-section as viewed in the direction of arrow BB from the center line shown in FIG. FIG. Further, FIG. 8 shows an enlarged cross-sectional view of the shaft cylinder body as viewed in the direction of the arrow CC from the cutting line shown in FIG.

  The shaft cylinder body 3A is not particularly shown, but a resin material is placed in a cavity formed between a core pin that molds the inner peripheral surface of the shaft cylinder and a primary molding die that molds the outer peripheral surface of the shaft cylinder. It is formed by injection (injection molding). A thin-walled portion and a thick-walled portion are formed in the shaft cylinder main body 3A by the primary molding. That is, a pair of thick portions 3e having an elliptical shape are formed so as to face each other in the circumferential direction slightly closer to the rear end portion than the center in the longitudinal direction of the shaft cylinder main body 3A. Further, a thick part 3f formed in an annular shape so as to be orthogonal to the axial center is formed slightly closer to the front end part than the elliptical thick part 3e.

  Further, although not indicated in the drawing, similar thick portions are formed in the vicinity of the front end portion and the rear end portion of the shaft cylinder main body 3A. And all the shaft cylinder main bodies 3A other than the above-mentioned thick part are comprised by the thin part. In addition, the thick part formed in the tip part vicinity of the above-mentioned axial cylinder main body 3A is formed in order to fit the cap member which is not shown so that attachment or detachment is possible.

  In addition, a convex portion for supplying a resin is formed on the thin-walled portion of the shaft cylinder main body 3A so as to be continuous with the thick-walled portion. That is, in this embodiment, the resin-projecting convex portion 3g is formed in an annular shape so as to connect between the pair of thick portions 3e having the elliptical shape. Further, a convex portion 3h for resin supply is formed so as to intersect in a T-shape at a substantially central position of the convex portion 3g connecting the pair of thick portions 3e. It is connected to the annular thick portion 3f described above. Note that the protrusions of the protrusions 3g and 3h formed so as to intersect each other in a T-shape are slightly lower than the heights of the thick portions 3e and 3f.

  As shown in FIG. 4, a resin inflow gate portion 3 i for injection molding the shaft cylinder body 3 </ b> A is formed at the intersecting position of the convex portions 3 g and 3 h intersecting in a T shape. . In addition, this gate part 3i is similarly formed in the back side of the axial cylinder main body 3A in the state shown in FIG. 4, and the axial cylinder main body 3A in this embodiment is interposed via the two gate parts 3i described above. The primary side resin material to be supplied is molded.

  According to the shaft cylinder main body 3A having the configuration shown in FIGS. 4 to 8, each of the convex portions 3g and 3h functions as a runner on the inner surface of the mold, and is a resin material supplied via the gate portion 3i. Can be effectively filled into the thick portions 3e and 3f via the convex portions 3g and 3h. That is, the flow resistance of the resin material can be reduced by the presence of the convex portions 3g and 3h, and the resin pressure can be sufficiently applied to the thick portions 3e and 3f. As a result, a sufficient amount of resin material can be filled in the thick portions 3e and 3f, and the degree of occurrence of molding defects such as so-called sink marks, insufficient filling, and bubbles in the thick portions can be reduced. .

  Further, as in the configuration of the shaft tube main body 3A shown in FIGS. 4 to 8, a configuration in which two or more thick portions 3e and 3f formed in the shaft tube main body are connected by the convex portions 3g and 3h. By doing so, it becomes possible to fill each of the resin materials into two or more thick portions via the convex portions. Therefore, by adopting the above-described configuration, it is possible to contribute to reducing the number of gate portions 3i that supply the resin material. Further, the gate portion 3i is formed at the intersecting position of the convex portions 3g and 3h formed in a T-shape, so that each of the thick portions is interposed via the convex portions connected to the respective thick portions. The resin material can be individually filled. Therefore, it is possible to efficiently fill the resin material while applying sufficient resin pressure to each thick wall part. Even with this configuration, molding defects such as sink marks, insufficient filling, and bubbles in the thick wall part are possible. It is possible to synergistically reduce the degree of generation.

  In this way, to reduce the occurrence of molding defects in the thick part, as will be described later, the thick part is exposed from the secondary side molded body by two-color molding as if it is a window or in a ring shape. In the case of such a design form, it is possible to contribute to reducing the appearance defect of the exposed portion due to molding failure, and it is possible to improve the yield of this type of writing instrument.

  Next, FIG. 9 is a cross-sectional view showing a case where the above-described shaft cylinder body 3A is used as a primary side molded body and a secondary side molded body is formed by two-color molding. FIG. 10 is a cross-sectional view further enlarging the vicinity of the gate portion where the secondary side molding is performed in the state shown in FIG. In the writing instrument 1 shown in FIGS. 1 to 3 described above, the front shaft 3 used in the writing tool 1 is a secondary side molded body by two-color molding with the shaft cylinder body as the primary side molded body as shown in FIG. 3b is formed in layers.

  In this case, a pair of elliptical thick parts 3e formed on the shaft cylinder main body 3A, an annular thick part 3f, and the vicinity of the tip of the shaft cylinder main body 3A, although not particularly indicated in the figure And the thick part formed in the rear-end part is made not to be covered with the secondary side molded body 3b. On the other hand, along with the convex portions 3g and 3h formed on the shaft cylinder main body 3A, the thin wall portion of the shaft cylinder main body 3A is covered with the secondary side molded body 3b.

  As a result, the pair of thick parts 3e formed on the shaft cylinder main body 3A in an elliptical shape is exposed from the secondary side molded body 3b formed in a layer shape by two-color molding as if it were a window. To be made. Moreover, the thick part 3f formed cyclically | annularly in 3 A of axial cylinder main bodies is also made into the form exposed to the ring shape from the secondary side molded object 3b. Thereby, the exposed part formed by the said thick part can also give the design feeling that another member was inserted with respect to the axial cylinder. On the other hand, the resin supply convex portions 3g and 3h formed on the shaft cylinder main body 3A are concealed by a secondary side molded body 3b formed in a layer shape by two-color molding.

  As described above, in forming the secondary side molded body 3b on the shaft cylinder main body 3A, as shown in FIGS. 9 and 10, the gate portion 3j for molding the secondary side molded body 3b has a primary structure. It is set at a position facing the convex portion 3h formed on the shaft cylinder main body 3A as a side molded body. By setting the gate portion 3j at such a position, it is possible to reduce the thickness of the molded body in the vicinity of the gate portion 3A that is the primary side molded body and the gate portion in the secondary side molding. Therefore, when the gate is cut during the secondary side molding, the deformation of the secondary side molding material can be reduced, and the gate trace remaining on the secondary side can be made less noticeable.

  Furthermore, as will be described in detail later, as the resin material constituting the secondary side molded body 3b, a material having thermal adhesiveness to the resin constituting the primary side molded body is selected, whereby the primary side molded body is selected. It is possible to effectively prevent peeling at the time of gate cutting in secondary-side molding, such as peeling of the secondary-side molded body against the above, and it is possible to provide a writing instrument shaft cylinder with high durability.

  As described above, when performing two-color molding, as the resin material constituting the secondary side molded body, a thermal adhesive elastomer having effective thermal adhesion to the resin constituting the primary side molded body is used. It is desirable to do. In this case, the thermal adhesive elastomer is effectively thermally bonded to the adherend resin by introducing a functional group that interacts electronically with the resin of the primary molded body that is the adherend. Can be made.

  In this embodiment, polycarbonate is adopted as the primary side molded body, and in this case, as a preferable thermal adhesive elastomer constituting the secondary side molded body, a polyester-based thermoplastic elastomer may be mentioned. Can do. In addition, in the shaft tube constituting this type of writing instrument, for example, transparent AS resin, PS resin, acrylic, ABS, etc. can be suitably used as the primary side molded body. Preferred examples of the heat-adhesive elastomer that can be obtained include urethane-based elastomers.

  As described above, by selecting a resin material that forms the secondary side molded body that has thermal adhesiveness to the resin that forms the primary side molded body, the primary side molded body is changed to the secondary side molded body. Can effectively prevent peeling and the like, and it is possible to provide a writing instrument shaft cylinder with high durability.

  Note that the writing instrument barrel according to the present invention can be molded without necessarily using the above-mentioned heat-adhesive elastomer. In this case, transparent polypropylene, AS resin, PS resin, acrylic, ABS or the like can be used as the resin for the primary side molded body, and styrene elastomer or olefin elastomer is used as the resin for the secondary side molded body. Can do.

It is a longitudinal cross-sectional view which shows the example of the writing instrument which employ | adopted the axial cylinder for writing tools concerning this invention. It is an expanded sectional view of the front axis | shaft which comprises the axial cylinder of the writing instrument shown in FIG. It is an expanded sectional view of the rear axis | shaft which comprises the same axial cylinder of the writing instrument shown in FIG. It is a front view which shows the example at the time of applying this invention to the front axis | shaft shown in FIG. It is a side view which shows the state which rotated the front axis | shaft shown in FIG. 4 90 degree | times to the circumferential direction. FIG. 5 is a cross-sectional view of the front axis when viewed in the direction of arrow AA from the center line shown in FIG. 4. FIG. 6 is a cross-sectional view of the front axis when viewed in the arrow BB direction from the center line shown in FIG. 5. It is an expanded sectional view of the front axis at the time of seeing in the arrow CC direction from the cutting line shown in FIG. It is sectional drawing which showed the mode in the case of forming a secondary side molded object in the front axis | shaft shown in FIGS. FIG. 10 is a cross-sectional view showing, in particular, the vicinity of the gate portion in an enlarged manner in the state shown in FIG. 9.

Explanation of symbols

1 Writing instrument (ballpoint pen)
2 Cap 3 Lead shaft 3A Shaft cylinder body (primary side molded body)
3b Secondary side molded body 3c Threaded portion 3e, 3f Thick portion 3g, 3h Resin supply convex portion 3i Gate portion (primary side)
3j Gate part (secondary side)
4 Rear shaft 5 Writing tip 6 Ink receiving tube

Claims (5)

A writing instrument shaft cylinder comprising a shaft cylinder body having a thin portion and a thick portion formed by injection molding,
The shaft cylinder body has a resin supply convex portion formed on the thin portion continuously from the thick portion, and a resin inflow gate portion formed on the convex portion. A writing cylinder for writing instruments.   2. The writing cylinder according to claim 1, wherein at least two thick portions are formed in the shaft main body, and the convex portions are formed so as to connect the thick portions. .   The writing instrument shaft cylinder according to claim 2, wherein the gate portion is formed at an intersection position of the convex portion. A shaft for a writing instrument having a configuration in which a secondary side molded body is formed by two-color molding, with the shaft cylinder body as a primary side molded body,
At least a part of the thick part formed on the shaft cylinder body is not covered with the secondary side molded body, and the convex part formed on the shaft cylinder body is covered with the secondary side molded body. The shaft cylinder for a writing instrument according to any one of claims 1 to 3, characterized in that: A shaft for a writing instrument having a configuration in which a secondary side molded body is formed by two-color molding, with the shaft cylinder body as a primary side molded body,
The gate part in the case of forming the secondary side molded body is set at a position facing the convex part, and the resin constituting the secondary side molded body is compared with the resin constituting the primary side molded body The shaft cylinder for a writing instrument according to any one of claims 1 to 3, which has thermal adhesiveness.

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