JP2008094004A - Manufacturing method of writing utensil cap - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a writing utensil cap which has a sheath of a simple/refined structure and can be securely fitted, without shaking, into the tail end part of a writing utensil main body, when used for writing. <P>SOLUTION: In this manufacturing method of a synthetic resin writing utensil cap, a threaded part is formed on the inner peripheral surface of a mating edge side of a sheath, and a plurality of fitting planes circumscribed, in a polygonal shape, on the outer peripheral surface of the writing utensil main body, are formed on the tail end side of the threaded part in such a way that the fitting planes jut out of the inner peripheral surface of the sheath, when the cap is fitted into the tail end part of the writing utensil main body during writing. A molding mold comprises an outer mold for molding the outer shape of the sheath, a core pin for molding the inner shape of the sheath including the fitting plane and a threaded sleeve for molding the threaded part. After coagulating a molten resin, first the cap is released from the mold by rotating the threaded sleeve, then the core pin is drawn out of the sheath to complete the release procedure. Further, the fitting plane is extended to the tail end side from a fitting surface in contact with the outer peripheral surface of the writing utensil main body in a polygonal shape. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a cap for a writing instrument made of synthetic resin, in which a threaded portion that is screwed to a writing instrument main body is formed on the inner peripheral surface of a joint at a sheath.

  When the writing instrument cap is attached to the writing instrument body, the fixing structure is such that the protrusion formed on the inner peripheral surface of the cap sheath gets over and engages the annular protrusion formed on the outer peripheral surface of the writing instrument body. There are many. Such a fixing structure has an advantage that it is easy to operate. Many are screwed onto the outward thread.

  In order to form the threaded portion in the sheath of the synthetic resin cap, the screw sleeve formed with the thread groove is released from the sheath which is the work while rotating, but at this time, it is necessary to prevent the sheath from rotating. is there. For this reason, for example, a vertical rib that does not interfere with the writing instrument body is formed in the space inside the sheath, and the vertical rib may prevent the core pin from rotating relative to the core pin that forms the inner shape of the sheath. However, this vertical rib does not function as a cap part after the cap is formed, and the structure of the sheath is simpler and clearer if no such vertical rib is provided.

  In addition, a relatively heavy object such as a fountain pen cap is often written by fitting the cap to the tail end of the writing instrument body in order to improve the balance during writing. When fitting the inner peripheral surface of the cap sheath to the slightly tapered outer peripheral surface of the part, if these roundness is not sufficient, the biting against the writing instrument body may be incomplete and rattling may occur is there.

  Therefore, the present invention has a simple and clean structure that does not require the formation of a rotation-preventing vertical rib that does not function as a cap part after molding, and the cap is fitted to the tail end of the writing instrument body. It is an object of the present invention to provide a method for manufacturing a cap for a writing instrument that fits firmly without shakiness.

In order to achieve this object, the invention of claim 1 is provided with a threaded portion that is screwed to the writing instrument main body on the inner peripheral surface of the joint, and a cap is placed on the tail end side of the threaded part at the time of writing. A method for producing a writing instrument cap made of synthetic resin, wherein a plurality of fitting planes circumscribed in a polygonal shape on the outer peripheral surface of the writing instrument body protrude from the inner peripheral surface of the sheath when fitted to the tail end of The mold includes an outer mold that molds the outer shape of the sheath, a core pin that molds the inner shape of the sheath including the fitting plane, and a screw sleeve that molds the thread portion, and a cavity formed by these molds. After the molten resin injected into the coagulum solidifies, first, the screw sleeve is rotated so that the mating plane forming portion having a different cross-sectional shape bites into the core pin to release from the non-rotatable sheath, and then the core pin is pulled out from the sheath. And release.
The invention of claim 2 is the invention according to claim 1, wherein when the fitting plane is fitted to the tail end of the writing instrument body during writing, the fitting is circumscribed in a polygonal shape on the outer peripheral surface of the writing instrument body. Extend further from the mating surface to the tail end.

Since a plurality of fitting planes circumscribing in a polygonal shape are formed on the outer peripheral surface of the writing instrument body so as to protrude from the inner peripheral surface of the sheath, there are points at several places when the cap is fitted to the tail end of the writing instrument body during writing. Since it contacts, even if the roundness of the outer peripheral surface of a writing instrument main body or the inner peripheral surface of a sheath is not enough, it can fit firmly. And since the inner surface of the sheath in which the fitting plane is formed is not a circular shape, but a substantially polygonal shape, when molding with synthetic resin, the sheath becomes non-rotatable with respect to the core pin that molds the inner surface. Thereafter, the screw sleeve for forming the threaded portion can be released while rotating without forming a rotation-preventing vertical rib that does not function as a cap portion.
Further, as in claim 2, when the fitting plane is further extended from the fitting surface circumscribing the outer peripheral surface of the writing instrument body in a polygonal shape to the tail end side, the deformed portion on which the fitting plane is formed becomes longer, and the core pin The amount of biting with respect to can be increased and the rotation can be prevented more reliably.

  The best mode for carrying out the invention will be described below with reference to the drawings. In FIG. 1, a cap sheath 1 is formed of a synthetic resin into a cylindrical shape, and a tail crown 2 is fixed to a tail end thereof. A threaded portion 4 is formed on the inner peripheral surface of the abutment side of the sheath 1. A plurality of, for example, eight fitting planes 3 are formed at equal intervals on the tail end side of the threaded portion 4. The cross section of the portion where the fitting plane 3 is formed has a shape in which regular octagonal corner portions are connected by an arc of the inner peripheral surface of the sheath 1, as shown in FIG. That is, the cross-sectional shape of this portion is not circular, but has a substantially regular octagonal shape, and the fitting plane 3 protrudes inward from the inner peripheral surface of the sheath 1. The front part of the fitting plane 3 is a fitting surface 3a that fits the tail end part of the writing instrument body when the cap is fitted to the tail end part of the writing instrument body during writing, and the rear part is the tail end of the writing instrument body. It is the extension part 3b which does not fit in a part. In the sheath 1, there are no anti-rotation vertical ribs or the like that do not function as cap portions after the molding, and the structure is simple and clean.

  The writing instrument body is, for example, a fountain pen. As shown in FIG. 2, a tip 12 is screwed to the tip of a bottomed cylindrical shaft 10 having a slightly tapered tail at the tail end, and a pen core is inserted from the tip of the tip 12. The pen tip 13 superimposed on 14 protrudes, and the ink in the ink cylinder in the shaft cylinder 10 is supplied to the pen tip 13 through the pen core 14 and used for writing. An outward threaded portion 11 is formed on the outer peripheral surface of the tip of the shaft tube 10.

  FIG. 2A shows a state in which the sheath 1 of the cap is attached to the writing instrument body and covers the pen tip 13 when not writing, but the screw portion 4 of the sheath 1 is outside the shaft tube 10 as shown in FIG. A cap is detachably fixed to the writing instrument body by being screwed onto the direction screw portion 11. At this time, the fitting plane 3 is located outside the tip 12 and does not interfere with the tip 12. Next, FIG. 2 (B) shows a state in which the cap sheath 1 is fitted to the taper portion 10a on the tail end side of the barrel 10 at the time of writing. As shown in FIG. 4, the fitting surface of the fitting plane 3 is shown. 3a is fitted into the tapered portion 10a of the shaft tube 10, but as described above, since eight fitting planes 3 are formed, the tapered portion 10a and the sheath 1 of the shaft tube 10 are not in circular contact, It is fitted by eight point contacts, and therefore the sheath 1 firmly bites into the shaft tube 10 even if the roundness of the outer peripheral surface of the shaft tube 10 and the inner peripheral surface of the sheath 1 is slightly insufficient. Can be securely fitted. Note that the extension portion 3 b of the fitting plane 3 is not fitted to the tapered portion 10 a of the shaft tube 10.

  FIG. 5 shows a mold structure for molding the sheath 1, and the mold is an outer mold M that molds the outer shape of the sheath 1 that is a workpiece, and a core pin that shapes the inner shape including the fitting plane 3 of the sheath 1. C, a screw sleeve S for forming the screw portion 3 of the sheath 1, and other auxiliary molds. The outer shape of the portion forming the fitting plane 3 of the core pin C has a shape equal to the inner shape of the sheath 1 shown in FIG. Further, a screw groove Sa for forming the screw portion 4 is formed on the outer periphery of the tip of the screw sleeve S. The molten resin is injected from the injection port Ma into the cavity formed by these molds and solidified, and then the screw sleeve S is rotated counterclockwise. At this time, since the deformed fitting plane 3 is formed by the deformed core pin C, the sheath 1 which is a workpiece does not rotate. In particular, since the extension portion 3b is provided on the fitting plane 3, the axial direction of the fitting plane 3 becomes longer, the amount of biting of the sheath 1 that is a workpiece against the core pin C increases, and the rotation can be reliably stopped. it can. Therefore, the screw sleeve S can be easily released from the sheath 1. Next, the core pin C is removed from the sheath 1 and released, and the sheath 1 is removed from the outer mold M to complete.

(A) is a longitudinal sectional view of the sheath, and (B) is a transverse sectional view. (A) is a figure which shows the state at the time of non-writing, (B) is a figure which shows the state at the time of writing. It is sectional drawing of the principal part of FIG. 2 (A). It is sectional drawing of the principal part of FIG. 2 (B). It is explanatory drawing of a shaping die.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sheath 2 Tail crown 3 Mating plane 4 Thread part 10 Shaft cylinder 11 Outward thread part 12 End 13 Pen tip 14 Pen core M Outer type C Core pin S Thread sleeve

Claims (2)

A threaded portion that is screwed to the writing instrument body is formed on the inner peripheral surface of the sheath at the joint side, and the outer periphery of the writing instrument body is fitted on the tail end side of the threaded portion when the cap is fitted to the tail end portion of the writing instrument body during writing. A method for producing a writing instrument cap made of synthetic resin, wherein a plurality of fitting planes circumscribed in a polygonal shape on the surface protrude from the inner peripheral surface of the sheath,
The molding die includes an outer mold that molds the outer shape of the sheath, a core pin that molds the inner shape of the sheath including the fitting plane, and a screw sleeve that molds the threaded portion, and is injected into a cavity formed by these molds. After the molten resin solidified, first, the screw sleeve is rotated so that the mating plane forming portion having an irregular cross-sectional shape bites into the core pin to release it from the non-rotatable sheath, and then the core pin is pulled out of the sheath and released. A method for manufacturing a cap for a writing instrument, wherein the cap is molded.   The fitting plane is further extended to the tail end side from a fitting surface circumscribed in a polygonal shape on the outer peripheral surface of the writing instrument body when the cap is fitted to the tail end part of the writing instrument body during writing. The manufacturing method of the cap for writing instruments of Claim 1 to do.

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