JP7370590B2 - Mechanical pencil with lead breakage prevention mechanism - Google Patents

Description

The present invention relates to a mechanical pencil with a lead breakage prevention mechanism, which is provided with a lead protection pipe that covers the outer periphery of the tip end of the lead in order to prevent lead breakage.

A slider with a lead protection pipe (core holding pipe) is attached to the taper (mouthpiece) provided at the tip of the main body so that it can move back and forth, and the drawn out lead is made to protrude through the lead protection pipe to prevent the lead from breaking. A mechanical pencil in which a slider retreats through a lead protection pipe as the user writes is widely known (for example, see Patent Document 1). Normally, the core protection pipe consists of a stainless steel pipe with a narrow inner diameter through which the core passes, and the rear end of this pipe is inserted and fixed into the tip of a slider made of plastic material. An elastic breaker section is also provided to temporarily hold the. For the breaker part, you can make an elastic piece separately from an elastic material such as elastic rubber and attach it to the slider, or you can make a slit in the slider itself and use an elastic gripping piece that can hold the core. Constructed by forming. As described above, the slider has a large number of parts and is expensive to manufacture, and since the slider and the core protection pipe are structured to move together, if the remaining core becomes short, it cannot be held by the pipe, which causes the remaining core to become long.

In addition, in the conventional type, when the slider moves forward, a lead protection pipe protrudes from the tip of the taper and surrounds the outer periphery of the tip of the lead through this pipe to prevent lead breakage, but normally, visibility during writing is reduced. To ensure this, the wick is often used with its tip protruding from the pipe by about 3 to 4 mm. Therefore, depending on the angle at which you hold the mechanical pencil body when writing, the pressure applied from the writing tip of the lead will act in the lateral direction of the pipe, and the pipe will bend in the direction of bending the pipe using the part that touches the tapered tip as a fulcrum. This adds force and causes the pipe to bend. Furthermore, if this force becomes large, it becomes a resistance between the outer surface of the pipe and the tip hole of the taper, and also acts on the slider through the pipe, so the slider is pushed sideways and the smooth movement of the slider is inhibited. This may cause the core to break.

JP-A-8-72473 (Paragraphs 0010 to 0012, Figures 1 and 2)

The problem to be solved by the present invention is to provide a mechanical pencil that has a simple structure and low cost, in which a lead protection pipe is moved forward to protect the tip of the lead when the lead is fed out, and the lead protection pipe is moved back as the user writes. To provide a mechanical pencil with a lead breakage prevention mechanism in which a lead protection pipe can be smoothly retreated and moved in a stable state without bending or tilting.

According to the present invention, a main body housing a lead feeding mechanism, a breaker part that elastically temporarily holds the drawn out lead, a lead protection pipe provided in front of the breaker part and having an inner diameter through which the lead is inserted; The main body has a taper provided in the front part, and an outer pipe having an inner diameter through which the core protection pipe is inserted and protrudes from the taper, and the core protection pipe moves back and forth due to its own weight while being inserted into the outer pipe. The core protection pipe is movable, and the rear end of the core protection pipe is equipped with a contact part that comes into contact with the rear of the outer pipe to prevent it from slipping out from the outer pipe when the core protection pipe moves forward. Pencil provided. In the present invention, the direction in which the core is fed out from the taper is referred to as "front" or "tip", and the direction in which the core is stored in the main body is referred to as "rear".

Further, according to the present invention, the outer pipe is fixedly provided to the taper, or is fixed to a slider having a breaker portion so as to be movable together with the slider. provided.

The present invention is configured as described above, and the lead fed out by the lead feeding mechanism advances sequentially while being elastically temporarily held in the breaker part, enters the lead protection pipe provided in front of the breaker part, and protects the lead. The pipe falls under its own weight and moves forward inside the outer pipe, and the outer periphery of the lead protruding from the tapered tip is covered with a lead protection pipe and an outer pipe to prevent the lead from breaking, allowing writing. At this time, since the abutting portion of the core protection pipe touches the rear part of the outer pipe and the forward movement of the core protection pipe is stopped, there is no risk of the core protection pipe falling out from the taper. As you write, the lead protection pipe retreats into the main body, but at this time, the lead protection pipe moves easily against its own weight, so it moves in the axial direction within the outer pipe with almost no resistance, giving you a good writing feel. . In addition, since the core protection pipe is independent, the structure is simple and inexpensive, and it follows the core to the end, so the length of the remaining core is shorter than that of conventional pipes.

Furthermore, as mentioned above, since the lead protection pipe protrudes by passing through the outer pipe that protrudes from the taper, even if a force that bends the lead protection pipe due to writing pressure is applied, the outer pipe will not bend. It is securely supported, there is no risk of bending, and tilting movement is suppressed, ensuring straight movement of the core and preventing core breakage, and prevents the core protection pipe from bending when dropped. Therefore, core breakage can be further prevented.

FIG. 1 is a sectional view showing an embodiment of the present invention. An enlarged sectional view of the core in a retracted state. The core protection pipe is shown, (A) is a front view, and (B) is a cross-sectional view. FIG. 3 is a sectional view showing another embodiment of the present invention. An enlarged sectional view of the core in a retracted state. An enlarged sectional view of the outer pipe in a retracted state. The slider is shown, (A) is a plan view, (B) is a left side view, (C) is a front view, and (D) is a sectional view. An explanatory diagram of the tapered tip portion with the core protruding. An explanatory diagram of a mechanical pencil having a conventional lead protection pipe.

FIG. 1 shows the main parts of an embodiment of the present invention, in which a taper 3 is screwed to a small diameter portion 2 provided at the front end of a cylindrical main body 1. A core feeding mechanism is housed within the main body 1. Various mechanisms can be adopted as the lead feeding mechanism, but in the embodiment shown in the figure, a known knock-type feeding mechanism is shown. A clutch 7 is provided surrounding the outer periphery of the chuck 6 so as to tighten the chuck 6, and a flange 8 of the clutch 7 is biased rearward by a spring 9 in a direction toward the tip of the small diameter portion 2. An elastic breaker section 10 is provided inside the taper 3 to temporarily hold the drawn-out core 5. In the embodiment shown in FIG. 1, a breaker piece is formed from an elastic rubber material or an elastic plastic material, and is inserted and fixed into the taper 3.

A core protection pipe 11 having an inner diameter through which the core 5 can be inserted is provided in front of the breaker section 10. The core protection pipe 11 is preferably formed of a stainless steel pipe or the like, and as shown in FIG. The contact portion 12 is formed wider than the above.

The taper 3 has a threaded portion 13 at the rear thereof that is screwed onto the small diameter portion 2 of the main body 1, and an outer pipe 15 projects from the tip hole 14. In the embodiment shown in FIG. 1, the outer pipe 15 is press-fitted into the tip hole 14 of the taper 3 and is fixedly provided on the taper 3. The outer pipe 15 has an inner diameter through which the lead protection pipe 11 can be inserted while slidingly contacting the lead protection pipe 11 with its outer surface inscribed, and has sufficient strength to suppress the bending force acting on the lead protection pipe 11 during writing. However, it is preferably formed of a thin metal pipe material such as a stainless steel pipe with an outer diameter that does not impede visibility, but it can also be formed integrally with the taper 3. The length of the outer pipe 15 is such that when the abutment part 12 of the lead protection pipe 11 protrudes to a position corresponding to the rear part of the outer pipe 15 during writing, the tip of the outer pipe 15 is located behind the tip of the lead protection pipe 11. It is best to make the length such that the part is located.

With the above configuration, when the core 5 is fed out as shown in FIG. It protrudes, allowing you to write while protecting the lead 5. Then, as the writing is performed, the lead protection pipe 11 retreats until its tip is flush with the tip of the outer pipe 15, as shown in FIG. At this time, the core protection pipe 11 is formed to a length such that the rear end of the core protection pipe 11 does not hit the breaker part 10, or the breaker part 10 is provided at a position where the core protection pipe 11 does not hit.

In the above embodiment, an example in which the outer pipe 15 is fixedly provided on the taper 3 has been described, but the outer pipe 15 may also be provided movably. 4 to 6 show such an embodiment, in which a slider 16 is inserted into the taper 3 so as to be movable back and forth. As shown in FIG. 5, the slider 16 has a slider body 18 housed within the tapered inner surface. A breaker portion 10 is integrally formed in the slider body by an elastic gripping piece 17 having a rear portion divided by a slit 22 extending in the axial direction, and the core 5 is temporarily held by this breaker portion. A raised portion 19 is provided on the outer periphery of the gripping piece so as to come into elastic sliding contact with the inner surface of the taper 3. Inside the slider body 18, there are provided a moving space hole 20 into which the rear part of the core protection pipe 11 is freely inserted, and an outer pipe attachment hole 21 into which the rear part of the outer pipe 15 is fixedly inserted. . As the breaker section 10, a separate breaker piece as shown in the above embodiment may be provided. The core protection pipe 11 and the outer pipe 15 are formed in the same manner as in the above embodiment, but the outer pipe 15 is inscribed in the tip hole 14 of the taper 4, and when the core is fed out, the outer pipe 15 is formed outwardly from the tip hole 14. It is set up so that you can visit.

In the embodiment shown in FIG. 4, when the core is fed out by the core feeding mechanism, the slider is moved forward by the core inscribed in the breaker portion, and the outer pipe is also advanced from the tip hole of the taper. In the meantime, the core enters the free-falling core protection pipe and moves forward, and in the state shown in Figure 4, where the forward movement of the slider hits the tapered inner step and stops, the core protection pipe is attached to the rear end of the outer pipe. The abutting part of the lead protector stops the pipe from falling, and the lead protrudes beyond its tip, allowing you to write. Then, as you write, the lead protection pipe retreats against its own weight, and its tip becomes flush with the tip of the outer pipe (Figure 5).As you continue writing, it retreats with the outer pipe, and tapers. Retract until it is flush with the tip of the tip hole (Figure 6). At this time, the abutting portion provided at the rear of the core protection pipe advances within the moving space hole, and there is no risk of interfering with the retreat.

Note that depending on the angle at which the main body is held during writing, a diagonal force acts on the tip of the outer pipe via the lead protection pipe 11, and if the outer pipe easily retreats, it is necessary to sufficiently cover the lead protection pipe. There is a risk that you will not be able to. However, as described above, the elastic gripping piece 17 provided on the slider 16 is provided with a raised portion 18 on the outer periphery, and this raised portion 18 elastically slides into contact with the inner surface of the taper, thereby creating weak sliding resistance. Therefore, it is possible to provide a little resistance to the backward movement of the outer pipe, and the effect of covering the outer periphery of the core protection pipe with the outer pipe is not easily lost.

Referring to FIG. 8 and FIG. 9 showing a conventional example, the guide length in which the core protection pipe 26 of the slider 25 of the conventional example is guided by the tip hole 28 of the taper 27 is defined as A1, and the core protection pipe 26 protruding from the tip hole 28 is defined as A1. Let the base of the pipe 26 be A, and the length from the base A to the tip of the core protection pipe 26 be B1. Further, in FIG. 8 showing an embodiment of the present invention, the guide length by which the core protection pipe 11 is guided between the inner end and the tip of the outer pipe 15 is A2, and the outer pipe 15 protrudes from the tip hole 14 of the taper 3. The following description will be made assuming that the length is D, the tip of the outer pipe 15 is a fulcrum B, the length that the core protection pipe 11 protrudes from this fulcrum B is B2, and the length that the core protection pipe 11 protrudes from the taper 3 is C. .

When the protrusion length B1 of the lead protection pipe 26 of the conventional mechanical pencil shown in FIG. 9 and the length C of the lead protection pipe 11 of the present invention protruding from the taper 3 shown in FIG. 8 are the same length, the present invention Then, the length B2 of the core protection pipe 11 protruding from the tip of the outer pipe 15 is shorter than the length B1. When writing pressure is applied during writing, in the conventional case, as shown in FIG. 9, the load related to the fulcrum A is considered to be B1×load. On the other hand, in the present invention, as shown in FIG. 8, the load related to the fulcrum B is B2×load. Therefore, when the load is the same, since the length of B2 is shorter than the length of B1, it is thought that the load on fulcrum B is less than that on fulcrum A, and in the present invention, the bending force acting on the core protection pipe 11 is small. As a result, the frictional resistance during retreat is reduced, and the lateral pressing force is also reduced, ensuring straight movement of the core protection pipe.

Further, when comparing the length of guiding the core protection pipe, it is found that in the present invention, the core protection pipe 11 is guided by the outer pipe 15 compared to the guide length A1 in which the core protection pipe 26 is guided by the taper 27 in the conventional case. The guide length A2 becomes longer. Therefore, since the core protection pipe 11 can be guided for a long time, the vibration of the core protection pipe 11 is reduced, and the core protection pipe 11 can be stably moved in the axial direction. Moreover, the protruding length D of the outer pipe 15 is set to a length that allows writing while ensuring visibility, and by making the inner and outer diameters close to the outer diameter of the lead protection pipe 11, it does not interfere with visibility. Since the lead protection pipe 11 can be protected and prevented from bending when the mechanical pencil is dropped, it is possible to eliminate the situation where the lead protection pipe 11 is damaged and writing becomes impossible.

1 Main body 3 Taper 5 Core 10 Breaker portion 11 Core protection pipe 12 Contact portion 15 Outer pipe 16 Slider 17 Gripping piece 19 Protrusion 20 Moving space hole

Claims (4)

The main body houses the lead feeding mechanism,
a breaker part that elastically temporarily holds the drawn-out core;
a core protection pipe provided in front of the breaker portion and having an inner diameter through which the core is inserted;
A taper provided at the front part of the main body;
an outer pipe that protrudes from the taper and has an inner diameter that extends in the front-rear direction and is inserted through the core protection pipe while slidingly contacting the outer surface of the pipe ;
The core protection pipe is inserted into the outer pipe and is movable back and forth by its own weight,
A mechanical pencil with a lead breakage prevention mechanism, wherein the rear end of the lead protection pipe is provided with an abutment part that comes into contact with the rear part of the outer pipe so that the lead protection pipe does not slip out of the outer pipe when the lead protection pipe moves forward. The mechanical pencil with lead breakage prevention mechanism according to claim 1, wherein the outer pipe is fixedly provided on the taper. A slider is provided within the taper so that it can move back and forth,
The outer pipe is fixed to the slider and is movable together with the slider,
The mechanical pencil with lead breakage prevention mechanism according to claim 1, wherein a moving space hole is formed in the slider so that the lead protection pipe can freely fall. The slider is provided with the breaker section by an elastic gripping piece formed by dividing the rear part through a slit, and a raised part inscribed in the inner surface of the taper is provided on the outer periphery of the gripping piece. The mechanical pencil with a lead breakage prevention mechanism according to claim 3.

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