JP3870560B2 - Sharp pencil - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sharp pencil having a core protective tube having a uniform thickness at the tip of a tip member, and more particularly to a core protective tube of a sharp pencil that can effectively use the core without waste.
[0002]
[Prior art]
An example is Japanese Utility Model Publication No. 58-32959. The scope of the utility model registration claim of that publication is “a core protection device for a sharp core pencil for fine core comprising a core insertion tube slidably or non-slidably mounted on the tip of the main body and a core holding portion. In this case, a core protection device for a sharp pencil, in which an elastic thin film made of rubber or the like is integrally laminated on the inner surface of the core insertion tube to form a core holding portion. FIG. 4 shows an example thereof. As shown in FIG. 6, a core insertion tube is mounted in the mold, and then the core is held by introducing the resin. The core holding portion is fixed to the core insertion tube by forming a portion (thin film) or by applying an adhesive to the core insertion tube.
[0003]
[Problems to be solved by the invention]
However, in the above-described prior art, it is extremely difficult to uniformly form a core holding portion (thin wall) with a mold or the like on the inner surface of a core insertion tube having an inner diameter of less than 1 mm, and it has not been commercialized yet. Not reached. In addition, although a method of fixing the core holding part to the core insertion tube by bonding or the like has been described, this also has a risk of the adhesive being clogged in the core insertion tube due to surface tension or the like, which is not practical. It was. Further, in the method using adhesion, since the core holding portion is an elastic body, it is elastically deformed during use, so that the fixation due to the adhesion is peeled off and there is a risk that it will eventually fall out of the core insertion tube. It was.
[0004]
[Means for Solving the Problems]
The present invention has been made in view of the above problems, and is a sharp pencil having a core protective tube having a uniform thickness at the tip of a tip member, and a cylindrical elastic member is disposed in the core protective tube. In addition, a fixing ring is fixed to the front inner surface of the core protection tube, while a step portion is formed on the inner surface of the tip member, and the elastic member moves with respect to the core protection tube by the fixing ring and the step portion. The center detent member is disposed behind the step portion, and the inner diameter of the detent member is smaller than the inner diameter of the conical portion formed behind the elastic member. To do.
[0005]
【Example】
One example will be described with reference to FIGS. A core feeding mechanism 2 is disposed inside the shaft cylinder 1. The lead feeding mechanism 2 includes a lead tank 3, a chuck body 4 that is fixed in front of the lead tank 3, grips and releases the lead, a chuck ring 5 that opens and closes the chuck body 4, and the like. ing.
A tip member 7 having a core detent member 6 for preventing the core from retreating is detachably attached to the front end of the shaft tube 1 by screwing or the like. A core protection tube 8 made of a metal material formed by cutting a stainless steel pipe or the like is fixed to the tip of the tip member 7 by press-fitting or the like. It may be molded and fixed to the tip member 7.
[0006]
A cylindrical elastic member 9 having an outer diameter substantially equal to the inner diameter of the core protection tube 8 is mounted inside the core protection tube 8. In this example, the outer diameter of the elastic member 9 is slightly larger than the inner diameter of the core protection tube 8 and is reduced by the inner diameter of the core protection tube 8. The outer diameter of the elastic member 9 may be increased and be in close contact with the inner diameter of the core protection tube 8 only when the diameter is slightly reduced and the core passes through the elastic member 9.
In short, when the core passes through the elastic member 9, the elastic member 9 holds the core, preventing the core from rotating and retracting against the elastic member during writing, and the elastic member 9 protecting the core. It is only necessary to prevent the core protection tube from rotating or retracting by being closely attached to and fixed to the tube 8.
The elastic member 9 will be described in detail. The front part of the elastic member 9 has a uniform inner diameter part (straight part 10), but the rear part has a conical shape (cone part 11). The straight portion 10 serves as a holding portion 12 for holding the lead, and the conical portion 11 serves as a guide portion 13 for guiding the lead to the holding portion 12.
[0007]
A fixing ring 14 formed by cutting a long pipe member is press-fitted and fixed to the front inner surface of the core protection tube 8. It is a member that prevents the elastic member 9 from falling off from the front of the core protection tube 8. Here, it is conceivable to form this fixing ring integrally with the core protection tube, but it is difficult to obtain the processing accuracy because the core protection tube is small and elongated, and it takes processing time because it is difficult, It will also cost money. Therefore, in the present invention, the core protection tube and the fixing ring are formed by cutting a long pipe member. Since a long pipe member can be formed simply by purchasing and cutting, it can be manufactured at a very low cost.
Further, the thickness of the fixing ring 14 is about half of the thickness of the elastic member 9. Of course, the inner diameter is larger than the core to be used, but the thickness takes into account the amount of elastic expansion of the elastic member 9 when the core passes and the prevention of the core protection tube 8 from falling off. Yes.
[0008]
On the other hand, a circumferential rib 15 for preventing the elastic member 9 from falling off from the rear is formed at the front intermediate portion of the tip member 7 behind the core protection tube 8. Conical portions 16 and 17 are formed on the upper and lower surfaces of the circumferential rib 15 so that the core L2 can be easily inserted into the elastic member 9 and can be easily retracted when the core L2 is stored.
The circumferential rib 15 serves as a rear end restricting position when the core protection tube 8 is press-fitted into the tip member 7. The tip member 7 is formed by injection molding if the material is resin, but is formed by cutting or the like if the material is metal.
[0009]
A core detent member 6 made of a rubber-like elastic body is provided behind the circumferential rib 15. A first conical portion 18 having an inner diameter larger than the outer diameter of the core protection tube 8 is formed behind the core detent member 6. In front of the first conical portion 18, a second conical portion 19 and a straight portion 20 having an inner diameter smaller than the diameter of the core to be used are formed. That is, the core detent member 6 is a guide member for forcing the core that has been slightly curved and for reliably guiding the core to the elastic member 9. Since the lead held by the straight portion 20 of the lead detent 6 is further guided by the conical portion 13 of the elastic member 9, the lead can be smoothly drawn out. The inner diameter of the straight portion 20 of the core detent member 6 is smaller than the inner diameter at the rear end of the conical portion 11 (guide portion 13) of the elastic member 9.
[0010]
In this example, in order to smoothly guide the lead to the elastic member, the lead detent member is arranged. However, this is not always necessary, and the lead detent operation is performed by arranging the lead detent member. In this case, it is possible to prevent the retreating operation of the second lead L2 to follow, so that the retreating of the lead L1 can also be prevented, and the lead feeding operation and writing operation with no sense of incongruity are performed. You can continue.
[0011]
FIG. 3 shows a modification of the fixing ring. The tip of the fixing ring 21 in this example is exposed from the tip of the core protection tube 8. And the roundness 22 is formed in the front end surface. The round 22 is formed in the contact portion with the writing paper surface, thereby preventing the paper from being caught.
[0012]
【The invention's effect】
The present invention provides a sharp pencil having a core protective tube having a uniform thickness at the tip of a tip member, wherein a cylindrical elastic member is disposed in the core protective tube, and a front inner surface of the core protective tube is disposed on the front inner surface. While fixing the fixing ring, a step portion is formed on the inner surface of the tip member, and the fixing ring and the step portion restrict the movement of the elastic member with respect to the core protection tube, and at the rear of the step portion. Since the core detent member is disposed and the inner diameter of the core detent member is made smaller than the inner diameter of the conical portion formed at the rear of the elastic member, the cylindrical elastic member is easily attached to the core protective tube. In addition, it does not fall off even after being mounted.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of the present invention.
FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is a longitudinal sectional view of an essential part showing a modified example of a fixing ring.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Shaft cylinder 2 Center feeding mechanism 3 Core tank 4 Chuck body 5 Chuck ring 6 Center detent member 7 Tip member 8 Core protection tube 9 Elastic member 10 Straight part 11 Conical part 12 Holding part 13 Guide part 14 Fixed ring 15 Circumferential rib 16 Conical portion 17 Conical portion 18 First conical portion 19 Second conical portion 20 Straight portion 21 Fixing ring 22 Roundness

Claims (1)

A sharp pencil having a core protection tube with a uniform thickness at the tip of the tip member, a cylindrical elastic member is disposed in the core protection tube, and a fixing ring is fixed to the front inner surface of the core protection tube On the other hand, a step portion is formed on the inner surface of the tip member, the movement of the elastic member with respect to the core protection tube is restricted by the fixing ring and the step portion, and a core detent member is provided behind the step portion. A sharp pencil characterized in that an inner diameter of the core detent member is made smaller than an inner diameter of a conical portion formed at the rear of the elastic member .

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