JPH09207490A - Mechanical pencil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mechanical pencil which is structurally designed so that sliding pipe member is not easily retracted, if an external impact is inflicted during writing and consequently, a lead is hardly broken. SOLUTION: A detent member 5 for a lead to be fed by a chuck 10 is installed, then a sliding pipe member 4 through which the front end part of the lead is inserted is fitted into the inner hole part 3 of a mouthpiece 2 in such a manner that the member 4 is freely sliceable back and forth, and the front end part of the member 4 is set to emerge from and retract into the front end aperture of the mouthpiece 2. Further, the mouthpiece 2 is made of a plastic material, and the sliding pipe member 4 is advanced as far as it can go, so that its front end part is protruded from the front end aperture of the mouthpiece 2. Then a projecting part 9 with a slightly smaller inner diameter or inscribed diameter than the rear end diameter of the sliding pipe member 4 is formed by undercutting on the entire periphery or at plural spots on the periphery, at almost the same position as or at a position slightly being the rear end of the sliding pipe member 4 under the state that the front end part of the member 4 is protruded from the front end part of the mouthpiece 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical pencil, and more particularly to a mechanical pencil in which a slide pipe member through which a front end portion of a lead is inserted is freely retractable at a tip opening of a cap.

[0002]

2. Description of the Related Art In a conventional mechanical pencil, a protruding pipe for guiding a core is fixed to the tip of a mouthpiece, so that the protruding pipe may be pierced by a hand or the like. Therefore, in order to eliminate such a danger, a pipe-shaped member for inserting the front end portion of the core is slidably assembled to the mouthpiece, and the slide-type pipe member can be immersed in the mouthpiece when not writing. This structure was devised, and recently, this type of mechanical pencil has become popular. However, such a slide-type pipe member is slidably fitted in the inner hole portion of the mouthpiece and only stops in the inner hole portion due to its sliding resistance. When the tip of the ruler hits an external pressure and receives an external pressure, the slide pipe member is easily retracted, and only the core projects, so that the core is easily broken.

[0003]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a mechanical pencil in which the slide pipe member does not easily retract even when an external pressure is applied to the tip portion during writing, and therefore the core does not easily break.

[0004]

In order to achieve the above object, the mechanical pencil of the present invention has a slide pipe member 4 to which a detent member 5 for a lead fed by a chuck 10 is attached and a front end portion of the lead is inserted. The slide pipe member 4 is slidably fitted in the inner hole portion 3 of the mouthpiece 2 so that the front end portion of the slide pipe member 4 can be retracted at the front end mouth of the mouthpiece 2, and the mouthpiece 2 is made of plastic. On the inner surface of the inner hole portion 3 of the slide pipe member 4, the slide pipe member 4 is advanced to the maximum extent and the front end portion of the slide pipe member 4 is projected from the front end opening of the mouthpiece 2 at substantially the same position or slightly rearward position. In addition, the inner surface convex portion 9 by undercut whose inner diameter or inscribed diameter is set slightly smaller than the diameter of the rear end of the slide pipe member 4 is provided at the entire circumference or at a plurality of positions in the circumferential direction. It is obtained by the structure according to claim.

By providing the inner surface convex portion 9,
It becomes difficult for the slide pipe member 4 to move in the front-rear direction in the inner hole portion 3 of the mouthpiece 2, but this problem is that the groove 12 is provided around the inner hole portion 3 of the mouthpiece 2 where the inner surface convex portion 9 is provided. The problem can be solved by adopting a means in which the portion provided with the inner surface convex portion 9 is formed as the thin-walled cylindrical portion 13 to facilitate elastic deformation. Also, the thin-walled tubular portion 13
Further, by further providing the slit 14, the thin-walled tubular portion 13 can be more easily elastically deformed.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. First, in FIGS. 1 to 3, reference numeral 1 is a shaft, and the shaft 1 has a base 2 screwed to a front end thereof. In addition,
In the drawing, the lower side is the front. The base 2 is made of plastic, and a slide pipe member 4 is fitted in an inner hole 3 of the base 2 so as to be slidable in the front-rear direction. The slide pipe member 4 is also made of plastic, and a core detent member 5 is attached to the rear end thereof to be integrated. In order to make it easier to fit the detent member 5 of the lead into the rear end portion and to easily get over the inner surface convex portion 9 of the mouthpiece 2 described later, the slide pipe member 4 is slit at a plurality of positions on the peripheral wall of the rear end portion. 6 (Fig. 3
Reference). The outer diameter of the latter half of the slide pipe member 4 is larger than that of the first half, and the step portion 7 of the slide pipe member 4 hooks on the same step portion 8 provided in the inner hole portion 3 of the mouthpiece 2. Although it cannot be pulled out to the front of the base 2, its front end can be projected to the front of the base 2.

A step portion 8 is formed on the inner surface of the inner hole portion 3 of the base 2.
An inner surface convex portion 9 by undercut is provided on the entire circumference at a position slightly rearward. The distance L ₁ (see FIG. 3) from the step portion 8 of the mouthpiece 2 to the inner surface convex portion 9 is the length of the latter half portion of the slide pipe member 4 having a large outer diameter, that is, the distance from the step portion 7 of the slide pipe member 4 to the rear side. The distance L ₂ to the edge is set to be substantially the same or slightly larger. In addition, the inner convex portion 9
The inner diameter of is set to be slightly smaller than the outer diameter of the rear end of the slide pipe member 4. Therefore, the slide pipe member 4 moves to the maximum extent, that is, the slide pipe member 4 moves forward until the step portion 7 of the slide pipe member 4 abuts on the step portion 8 of the mouthpiece 2, and the front end portion of the slide pipe member 4 moves toward the mouthpiece 2. In the state of projecting from the front end port (see FIG. 1), the inner surface convex portion 9 abuts on the rear end surface of the slide pipe member 4 or is located slightly rearward even if separated, so that the slide pipe member 4 is pulled rearward. Even if you try to insert it, you will not be able to easily retract due to the resistance of the inner convex portion 9.

As described above, even when the front end portion of the slide pipe member 4 projects from the front end opening of the mouthpiece 2 and the inner convex portion 9 is in contact with the rear end surface of the slide pipe member 4, the front end portion of the slide pipe member 4 is in contact. By pushing the portion a little strongly backward, the slide pipe member 4 can go over the inner surface convex portion 9 by elastic deformation and retreat, so that the entire slide pipe member 4 can be immersed in the base 2 (see FIG. 2).

Inside the shaft 1, the above-mentioned slide pipe member 4 is provided.
The chuck 10 for feeding the lead 15 forward is disposed behind the chuck. The chuck 10 is moved forward by pushing a knock member (not shown) protruding rearward of the shaft 1, and is automatically returned rearward by the force of the coil spring 11. When the entire slide pipe member 4 is immersed in the mouthpiece 2 as described above, the knock member is pushed to push the chuck 10
When is moved forward, the chuck 10 hits and pushes the slide pipe member 4, the slide pipe member 4 moves forward over the inner surface convex portion 9, and the front end portion thereof is projected from the tip end mouth of the mouthpiece 2. If you press the knock member multiple times in this state,
The lead 15 fed forward by the chuck 10 passes through the slide pipe member 4, and the front end portion thereof is projected from the front end opening of the slide pipe member 4. In this state, since the lead 15 is held and fixed by the chuck 10, it is possible to write without retreating even if a writing pressure is applied.

Since the inner surface convex portion 9 is provided in the inner hole portion 3 of the mouthpiece 2, the inner surface convex portion 9 must be overcome when the slide pipe member 4 slides in the front-rear direction in the inner hole portion. A large force is required to move the slide pipe member 4. FIG. 4 shows the base 2 which has been improved to solve this problem. That is, the groove 12 is provided around the inner hole portion 3 of the mouthpiece 2 so that the portion where the inner surface convex portion 9 is provided becomes the thin-walled cylindrical portion 13 and is easily elastically deformed. As a result, when the slide pipe member 4 slides on the inner hole portion 3 of the mouthpiece 2, the inner diameter of the portion where the inner surface convex portion 9 is provided is likely to increase due to the elastic deformation of the thin-walled tubular portion 13, so that the slide pipe member The member 4 can ride over the inner surface convex portion 9 without difficulty.

Further, as shown in FIG. 5, a thin-walled tubular portion 13 is provided inside the base 2, and the thin-walled tubular portion 13 is provided.
Further, if the slit 14 is further provided, the elastic deformation of the portion provided with the inner surface convex portion 9 is further facilitated, and the sliding of the slide pipe member 4 in the inner hole portion 3 is further smoothed.

In the above embodiment, the inner surface convex portion 9 is provided on the entire inner surface of the inner hole portion 3 of the mouthpiece 2, but the inner surface convex portion 9 is formed.
May be partially provided at a plurality of positions in the circumferential direction on the inner surface of the inner hole portion 3 of the base 2. In that case, the inscribed diameter of the portion where the inner surface convex portion 9 is provided is set to be slightly smaller than the maximum outer diameter of the slide pipe member 4.

[0013]

The mechanical pencil of the present invention is as described above, and even if the front end portion of the slide pipe member 4 protruding from the front end opening of the mouthpiece 2 receives external pressure, the slide pipe member 4
Since the rear end abuts against the inner surface convex portion 9 of the mouthpiece 2 and receives the resistance thereof, the slide pipe member 4 does not easily retract, and it is possible to solve the problem that the core breaks during writing.

Incidentally, as described in claim 2, the inner surface convex portion 9
If a groove 12 is provided around the portion where the is provided, or if a slit 14 is provided in the thin tubular portion 13 as described in claim 3,
Elastic deformation of the portion where the inner surface convex portion 9 is provided is facilitated, and the slide pipe member 4 can smoothly move over the inner surface convex portion 9 without difficulty. Therefore, it is possible to eliminate the slot 6 of the slide pipe member 4 or to make the slide pipe member 4 from metal.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a state in which a front end portion of a slide pipe member is projected from a front end opening of a mouthpiece, that is, a writing state.

FIG. 2 is a cross-sectional view of a state in which the entire slide pipe member is immersed in the mouthpiece, that is, a state when not writing.

FIG. 3 is a cross-sectional perspective view of a state in which a cap, a slide pipe member, and a detent member for a core are disassembled.

FIG. 4 is a cross-sectional perspective view of a base provided with a groove around an inner surface convex portion.

FIG. 5 is a cross-sectional perspective view of a mouthpiece provided with slits in a thin-walled tubular portion provided in an inner hole portion.

[Explanation of symbols]

 1 shaft 2 base 3 inner hole 4 slide pipe member 5 core detent member 6 slotting 7 step 8 step 9 inner convex 10 chuck 11 coil spring 12 groove 13 thin tubular section 14 slot 15 core

Claims (3)

[Claims] 1. A slide pipe member (4) for attaching a detent member (5) for a lead extended by a chuck (10) and inserting a front end portion of the lead is slidably fitted in an inner hole portion (3) of a mouthpiece (2) in a front-back direction. The front end portion of the slide pipe member 4 is freely retractable at the front end opening of the mouthpiece 2, the mouthpiece 2 is made of plastic, and the slide pipe member 4 is advanced to the maximum extent on the inner surface of the inner hole portion 3 of the mouthpiece 2. At a position substantially the same as or slightly rearward from the rear end of the slide pipe member 4 in a state in which the front end portion thereof projects from the front end opening of the mouthpiece 2,
A mechanical pencil characterized in that an inner surface convex portion 9 by undercut having an inner diameter or an inscribed diameter slightly smaller than the diameter of the rear end of the slide pipe member 4 is provided at the entire circumference or at a plurality of positions in the circumferential direction. 2. A groove 12 is provided around a portion of the inner hole portion 3 of the mouthpiece 2 where the inner surface convex portion 9 is provided, and the portion where the inner surface convex portion 9 is provided is a thin-walled cylindrical portion 13. The mechanical pencil described in 1. 3. The mechanical pencil according to claim 2, wherein the thin tubular portion 13 is provided with a slit 14.