JP7257493B2 - Mechanical pencil chuck structure - Google Patents

Description

The present invention relates to the structure of a chuck that directly participates in fixing and feeding a lead in a mechanical pencil.

A mechanical pencil is provided with a member called a chuck, which is directly involved in gripping and extending the lead during writing. The chuck is usually provided with a through hole through which the core is inserted in the axis. The tip portion of the chuck is equally divided (for example, divided into two, three, or four) by slitting with respect to the through hole. At the time of writing, the equally divided tip portion is urged to close in the axial direction, and at this time, the core is inserted into the through hole so that the ridge portion divided by the slit bites into the surface of the core. is grasped by

The following prior art documents disclose the provision of unevenness on the surface of the through hole in consideration of the gripping force of the lead in the chuck (Patent Documents 1 to 4).

JP-A-60-179299 JP-A-4-364996 JP-A-5-301493 JP-A-2005-144989

Chucks have two issues: "holding power" to firmly grip the lead when writing, and "low damage" to minimize scratches caused by gripping to prevent core breakage due to scratches on the surface of the lead. , these have been considered to be in a trade-off relationship. Here, when the chuck grips the lead, the entire surface of the through hole is not in contact with the lead surface. It is in a state of biting into the surface of the core. For this reason, if the gripping force of the chuck is too large, the ridgeline portion will bite into the surface of the lead significantly, causing large scratches on the surface of the lead. easier to do. On the other hand, if the gripping force of the chuck is reduced in an attempt to reduce the biting of the edge of the slit into the surface of the lead, the writing pressure at the time of writing causes the lead to retreat, making stable writing impossible. Such a problem becomes apparent when a color core having a bending strength lower than that of a black core is attached.

Accordingly, the present invention aims at reconciling the two problems of gripping the core of the chuck and minimizing damage by devising the shape of the ridge line of the slit.

(1) First Aspect In view of the above problems, the mechanical pencil chuck structure according to the first aspect of the present invention is the chuck 10 equally divided by the slit 20, which is positioned at the axis center of the chuck 10. Along the boundary between the gripping inner peripheral surface 31, which is the inner peripheral surface of the through hole 30, and the slit surface 21 formed by the slit 20, a roughened surface 40 is formed at least partially. It is characterized by

The "brushed surface 40" means that the ridge line 32, which is the boundary between the gripping inner peripheral surface 31 and the slit surface 21, has a certain width and is partially roughened through some process. It is formed as a surface on which It can also be said that it is a surface obtained as a result of so-called "face darashi". Here, "some process" may be a process for intentionally forming such a surface, such as a chamfering process. Moreover, although the process is not intended to form such a surface, such a surface may be formed as a result of the process.

With the above configuration, in this embodiment, one of the problems of "low damage" is solved by changing the line contact of the chuck 10 to the core at the ridge line 32 to the surface contact. This is overcome by minimizing the scratches on the surface of the core. The other "gripping force" is dealt with by roughening at least a portion of this surface to increase the frictional force with the surface of the core.

(2) Second Aspect A second aspect of the present invention is characterized in that, in addition to the features of the first aspect, the width of the rear end portion 43 of the beveled surface 40 is wider than the width of the intermediate portion 42. .

Here, the chuck 10 is formed to open forward during the knocking action. That is, in a state where there is no restraint by the fastener, the shape is such that the front portion is greatly bent outward. Since this shape is urged to close in the axial direction by the fastener during writing, the amount of deformation in the rear portion is smaller. Therefore, among the portions of the ridgeline 32 that are in direct contact with the core, the degree of contact with the core is higher toward the rear side. The portion of the ridgeline 32 is the above-mentioned chamfered surface 40, and the width of the rear end portion 43, which has a higher degree of contact with the core, is wider than that of the intermediate portion 42. and does less damage to the core.

(3) Third Aspect In the third aspect of the present invention, in addition to the features of the first or second aspect, unevenness 44 is formed on at least the side of the gripping inner peripheral surface 31 of the scouring surface 40. It is characterized by

That is, by forming the unevenness 44 on the side of the gripping inner peripheral surface 31, which has a higher degree of contact with the core, of the beveled surface 40, the gripping force due to the unevenness 44 is ensured. In addition, there is no problem even if unevenness 44 is formed on the entire surface of the brushed surface.

(4) Fourth Aspect A fourth aspect of the present invention is characterized in that, in addition to the features of the third aspect, unevenness is formed on the gripping inner peripheral surface 31 .

That is, by performing some kind of roughening process on the gripping inner peripheral surface 31 to form unevenness, as a result, the unevenness 44 is formed on the side of the gripping inner peripheral surface 31, which has a higher degree of contact with the lead, in the roughened surface 40. is to be formed.

Since the present invention is configured as described above, it is possible to achieve both the gripping force of the chuck with respect to the core and the low damage.

FIG. 4 is a perspective view showing the appearance of the chuck before opening processing; FIG. 4 is a perspective view showing a partially exploded front end portion of the chuck before opening processing. FIG. 4 is a perspective view showing the appearance of the chuck after opening processing; FIG. 4 is a perspective view showing a part of an example of a chuck after opening processing, in which the tip portion is exploded; FIG. 11 is a perspective view showing a part of an exploded tip portion of another example of the chuck after the opening process. The tip portion of the chuck shown in FIG. 5 is shown from the axial center side.

An embodiment of the present invention will be described with reference to the drawings. In the following description, the side of the writing tip attached to the mechanical pencil will be referred to as the "tip side" or "front", and the opposite side will be referred to as the "rear end side" or "rear".

FIG. 1 is a perspective view of a chuck 10 according to the present embodiment, seen from the tip side, before opening.

The chuck 10 before the opening process has a substantially cylindrical shape as a whole. A rear small-diameter columnar portion 12 with a smaller outer diameter than the rear small-diameter columnar portion 12, a rear large-diameter columnar portion 13 with an outer diameter larger than that of the rear small-diameter columnar portion 12, and a rear large-diameter columnar portion 13 with an outer diameter smaller than that of the rear large-diameter columnar portion 13, and the overall , a front tapered portion 15 tapered forward from the tip edge of the intermediate columnar portion 14, and a tip columnar portion 16 located on the tip side. there is

At the time of processing, first, by cutting a cylindrical brass material, the rear taper portion 11, the rear small diameter column portion 12, the rear large diameter column portion 13, the intermediate column portion 14, the front taper portion 15 and the tip A blank is machined to a shape having a cylindrical portion 16 is formed. First, a core insertion hole 17 (see FIGS. 2, 4 and 5) is drilled in this blank along the axis from the rear end to the vicinity of the front tapered portion 15, and then a through hole is drilled along the axis from the tip. Penetrate 30. The inner diameter of the through hole 30 is slightly larger than the outer diameter of the lead used, and the inner diameter of the lead insertion hole 17 is larger than the inner diameter of the through hole 30 (see FIGS. 2, 4 and 5). Then, a slit 20 is formed radially from the tip to the vicinity of the rear end of the intermediate cylindrical portion 14 to divide it into three parts.

FIG. 2 shows the inside of the disassembled tip portion with the slit 20 applied. A ridge line 32, which is a boundary between the slit surface 21 generated by the slit 20 and the inner peripheral surface of the through hole 30 (the gripping inner peripheral surface 31), is clearly recognized.

Then, using a conical opening tool, insert the tip of the tool into the through hole 30, rotate it in the circumferential direction, and push the chuck 10 toward the rear of the chuck 10 in three directions to perform opening processing. , is plastically deformed as shown in FIG. At this time, by rotating the opening tool, the ridge line 32 is so-called "smoothed" to form a smoothed surface 40 as shown in FIG.

Prior to the opening process, the gripping inner peripheral surface 31 of the through hole 30 may be roughened. In this case, as shown in FIG. 5, the gripping inner peripheral surface 31 is roughened.

FIG. 6 shows the state shown in FIG. 5 from the axial side.

Although it is not clearly shown in FIG. 6 because it is schematically shown, the width of the beveled surface 40 is larger at the leading end portion 41 and the trailing end portion 43 than at the intermediate portion 42. . This is because when the opening tool is inserted into the through-hole 30, the degree of contact is relatively large due to the expanding force in the initial stage of forming the tip portion 41, and the tip portion is in the middle of forming the intermediate portion 42. Since the side closer to 41 escapes outward, the resistance decreases and the degree of contact is relatively small. for it to grow.

In addition, a large number of fine irregularities are formed in the circumferential direction of the gripping inner peripheral surface 31 by roughening. This unevenness forms an unevenness 44 formed on the side of the gripping inner peripheral surface 31 of the smoothing surface 40 . The unevenness 44 is engaged with the core to secure a gripping force.

By roughening the gripping inner peripheral surface 31, the surface roughness is increased compared to before the roughening.

On the other hand, when the surface roughness of the gripping inner peripheral surface 31 is viewed in the circumferential direction, roughening as shown in FIGS. 32 became flat due to surface polishing, and along with this, the angle formed by the slit surface 21 and the tangent line at the edge of the gripping inner peripheral surface 31 became larger.

Further, when actually observing the damage to the core caused by the chuck 10, it was found that long and deep vertical scratches were generated along the longitudinal direction when the roughening process was not performed as shown in FIG. It is considered that this is because the ridgeline 32 is closer to an acute angle. On the other hand, after roughening as shown in FIGS. 5 and 6, a large number of small shallow horizontal scratches were produced instead of vertical scratches. These lateral scratches are caused by unevennesses 44 (see FIG. 6) formed on the side of the gripping inner peripheral surface 31 of the roughening surface 40 as a result of the roughening of the gripping inner peripheral surface 31 .

As described above, by roughening the gripping inner peripheral surface 31, the occurrence of core breakage can be remarkably reduced by reducing deep damage to the core while securing the core gripping force.

INDUSTRIAL APPLICABILITY The present invention can be used as a mechanical pencil chuck.

10 Chuck 11 Rear tapered part 12 Rear small diameter cylinder part
13 Rear large-diameter cylindrical part 14 Intermediate cylindrical part 15 Front tapered part
16 Cylindrical part at the tip 17 Core insertion hole
20 Slit 21 Slit side
30 Through hole 31 Gripping inner peripheral surface 32 Ridge
40 Chamfered surface 41 Tip part 42 Intermediate part
43 Rear end portion 44 Unevenness

Claims (3)

In the chuck equally divided by slitting, along the boundary between the gripping inner peripheral surface, which is the inner peripheral surface of the through hole located at the axial center of the chuck, and the slit surface formed by the slitting, A roughened surface is formed as a surface that is at least partially roughened and is a continuous flat surface as a whole ,
A chuck structure for a mechanical pencil, wherein the width of the rear end portion of the chamfered surface is wider than the width of the intermediate portion . 2. The mechanical pencil chuck structure according to claim 1, wherein irregularities are formed at least on the side of the gripping inner peripheral surface of said beveled surface. 3. The chuck structure for a mechanical pencil according to claim 2 , wherein unevenness is formed on said gripping inner peripheral surface.

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