JP2000334538A - Production of large diameter braille rivet and die used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a large diameter braille rivet, which has sufficient strength, reduces a material quantity used and has high production efficiency, and a die used therefor. SOLUTION: In a method produce a large diameter braille rivet 20 by upsetting, in which one end part 2a of a stainless steel round bar 2 is fixed and the other end part 2b is pressed in its axial direction with a die 4, As taking D for a round bar and L for a length, the round bar having a L/D of >=2.5 is used, in the region including the abutting face on the other end part 2b of the round bar 2 in the die 4, a position deviation prevention means 4a between the round bar 2 and the die 4 in upsetting is arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a large-diameter braille stud for guiding a pedestrian, particularly a visually impaired person to assist walking, and a mold used therefor.

[0002]

2. Description of the Related Art In recent years, town development friendly to persons with disabilities has been promoted, but as part of this, the installation of Braille tacks to guide visually impaired persons on the road surface or floor surface and to assist their walking has increased. are doing. The Braille tacks are composed of legs embedded on a road surface or the like and a head exposed on the ground, and are usually manufactured using various types of plastics and metal materials.

[0003] Such Braille tacks are also used in commercial facilities such as hotels and underground shopping malls, but in such cases, a sense of quality is required, so stainless steel Braille tacks with excellent metallic luster are used. There are many. By the way, when using the above-mentioned Braille tacks, the strength of the Braille tacks is improved by integrally manufacturing the head and legs so that the head exposed on the ground does not fall off from the legs due to pedestrian stepping on it. It is necessary to let Such a braille tack made of stainless steel,
It has been manufactured as an integrated product of a head and a leg by cutting a bar having a diameter substantially the same as the diameter of the head of a Braille tack for manufacturing purposes. However, since the diameter of the leg of the Braille tack is about 1/3 or less of the diameter of the head, a large amount of material is wasted at the time of cutting, a long processing time is required, and the manufacturing cost increases. There is.

[0004] Recently, braille studs have also been manufactured by forging. Specifically, it is upsetting forging of a stainless steel round bar. In this case, the processing time is greatly reduced, which is important for improving the productivity. However, for example, when a braille stud having a large diameter of the head is manufactured by forging for the purpose of ensuring the feeling of stepping on a pedestrian, the following problem occurs.

That is, as shown in FIG. 6, upsetting forging is a mold in which one end 100a of a round bar 100 is held by a fixed die 200, and the other end 100b is formed with a head-shaped space. Pressing is performed at 300, but good forging can be performed if the head diameter is about 33 mm or less, while forging becomes extremely difficult if the head diameter is about 35 mm or more (legs). About 9mm in diameter).

The following are conceivable reasons for this. That is, the head is formed by plastically deforming and filling the space S of the mold 300 with the other end 100b of the round bar. In this case, in order to increase the diameter of the head,
It is necessary to increase the amount of plastic deformation of the other end portion 100b into the internal space S. Therefore, it is necessary to increase the diameter of the round bar and increase the length of the other end portion. However,
Since the diameter of the leg is limited, it is difficult to increase the diameter of the round bar. On the other hand, if the length of the other end 100b of the round bar is increased, the round bar will When the mold and the end face of the other end of the round bar are eccentric once, the round bar immediately buckles in the mold, resulting in poor forging. In particular, when a stainless steel round bar that is hard and has poor workability is used, the above-described buckling phenomenon is likely to occur.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems when stainless steel large-diameter braille studs are manufactured by upsetting and forging, has sufficient strength and requires a small amount of material. It is an object of the present invention to provide a method of manufacturing a large-diameter braille tack that has been completed and has high production efficiency, and a mold used therefor.

[0008]

In order to achieve the above object, according to the present invention, one end of a stainless steel round bar is fixed, and the other end of the round bar is fixed in a mold in the axial direction. A method of manufacturing a large-diameter Braille tack by upsetting forging pressurized in, when the diameter of the round bar is D, and the length is L, using L / D 2.5 or more as the round bar, In the mold, a region including a contact surface with the other end of the round bar is provided with a means for preventing displacement of the round bar and the mold during the upsetting forging.

Preferably, the misalignment preventing means includes a concave portion for holding the other end portion, an uneven portion for locking the other end portion to the mold, or a projection driven into a center axis of the other end portion. It may be composed of any one of the parts (claim 2). The present invention according to claim 3 is used in the method for manufacturing a large-diameter braille stud according to claim 1, wherein the mold presses the other end of the round bar in the axial direction thereof, In a region of the mold including a contact surface with the other end of the round bar, a concave portion for holding the other end, an uneven portion for locking the other end to the mold, or the other end. Consisting of one of the projections driven into the central axis of the part,
Means for preventing displacement of the round bar and the mold during the upsetting forging are provided.

According to a fourth aspect of the present invention, there is provided a large-diameter Braille fastener manufactured by the method of manufacturing a large-diameter Braille tack according to the first or second aspect.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a large-diameter braille tack according to the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a production method according to the present invention, and a stainless steel round bar 2 is shown.
The small-diameter end 2a is fixed to the die 10, the punch 4 abutted on the large-diameter end 2b is moved downward to press the large-diameter end 2b, and upset forging is performed. On the lower surface of the punch 4 (the surface facing the large-diameter end portion 2b), a truncated conical concave space (diameter of the enlarged portion of about 36 mm) V whose diameter increases toward the lower surface
Is formed, and the material pressurized at the time of forging is plastically deformed and fills the recessed space V so that the head of the Braille tack is formed.

In this embodiment, the round bar 2 is preformed (forged) as appropriate, and a large diameter portion (having a diameter of approximately
12 mm) and a small-diameter portion (approximately 9 mm in diameter), but the invention is not limited to this, and a single-diameter round bar may be used. In this embodiment, the punch 4 moves toward the fixed die 10 to perform forging. However, the punch 4 may be fixed and the die 10 may be moved, or both may be relatively moved. Good.

The round bar 2 is connected to the small diameter portion (small diameter end portion 2).
The portion from a to the step) is held by the die 10 and provided for forging. When the diameter of the round bar 2 is D and the length of the round bar 2 is L, L / D (the ratio of length to diameter) is
2.5 or more (3.0 in this embodiment) is used.
The reason for defining L / D in this manner is that if L / D is less than 2.5, the material necessary to fill the recessed space V of the punch 4 described above is insufficient, and a large diameter head is molded. This is because the molding becomes difficult. When the round bar has a different diameter portion as described above, L / D is defined based on the diameter of the large diameter portion. The upper limit of L / D varies depending on the material of the round bar and the forging conditions, and cannot be determined unconditionally, but is, for example, 3.5 or less. Examples of stainless steel used for the round bar 2 include SUS-304 and SUS-316.

Now, the large-diameter end portion 2 of the punch 4 described above is used.
In a region including the contact surface with the large diameter portion 2b, a concave portion having a diameter slightly larger than the large diameter end portion 2b (for example, a diameter of about 12.5 mm and a depth of 0.5 mm)
Reference numeral 4a is provided concentrically with the center axis of the round bar 2 and forms a means for preventing displacement between the round bar 2 and the punch 4 (FIG. 1).
(A)). After the large-diameter end portion 2b is positioned and fitted into the concave portion 4a, the punch 4 is moved downward to perform forging. By doing so, the large-diameter end 2b is restrained by the punch 4, and the round bar 2 is not eccentric from the punch 4 at the time of forging and does not shift (slip), so that forging failure due to buckling of the round bar 2 is prevented. Generation can be suppressed. The forging temperature is not particularly limited. For example, the forging may be performed at room temperature. For example, the forging may be performed at a temperature of 200 to 700 ° C.

This forging step is completed with a gap of several mm between the punch 4 and the die 10, and the space between the punch 4 and the die 10 is filled with the plastically deformed material and Large-diameter Braille tack 20 in which leg 20b is integrated with leg 20a
(For example, the head diameter is about 36mm) (Fig. 1
(B)). On the upper surface of the large-diameter Braille tack 20, a convex portion 20c having a shape complementary to the concave portion 4a is formed.

Then, the Braille studs 20 are taken out from between the punch 4 and the die 10, and the above-mentioned projections 20c are ground and removed, and a predetermined step is formed on the leg 20a, so that the required size (for example, head 35mm diameter, head thickness 5
mm, leg length 15 mm, leg diameter 9 mm) is obtained (Fig. 1 (c)). Note that, instead of the above-described concave portion, the position shift prevention means provided on the punch can be changed to the following.

In FIG. 2, the misalignment preventing means formed on the punch 14 is constituted by an uneven portion 14a in which a plurality of indentations pressed against a square pyramid (for example, 3 mm on a side) are arranged in parallel. In this embodiment, the uneven portion 14a is provided not only on the contact surface with the large-diameter end portion 2b but also on the entire surface including the periphery (a region corresponding to the upper surface of the forged Braille tack). . Then, as shown in the cross-sectional view of FIG.
The convex portion 14b in 4a comes into contact with the end face of the large diameter end 2b.

When the punch 14 is used, a large-diameter Braille tack is manufactured as shown in FIG. First, the above-mentioned convex portion 14b is positioned so as to bite into the end face of the large-diameter end portion 2b, and forging is performed in a state where the large-diameter end portion 2b is locked by the punch 14 (FIG. 4A). In this manner, the large-diameter end 2b is restrained by the punch 4, and the displacement between the round bar 2 and the punch 14 during forging is effectively prevented. And
In the process of forging, the material also flows into the uneven portion 14a, and a large-diameter Braille tack 30 having a pattern complementary to the uneven portion 14a formed on the upper surface is obtained (FIG. 4B).

By the way, in the large-diameter braille stud 30, the pattern formed by the concave and convex portions 14a can be used as it is as a non-slip (cross hatch) 30c without removing it (FIG. 4C). ). in this case,
The step of removing the pattern and the step of separately forming a non-slip on the Braille tack become unnecessary. The uneven portion 14a may have an uneven shape, and is not limited to the above-described cross hatch, and may be, for example, a hatch pattern aligned in one direction.

Further, as shown in FIG. 5, a large diameter Braille tack can be manufactured by using another punch 24. In this embodiment, the misalignment prevention means is constituted by a conical projection 24a concentric with the center axis of the round bar 2, and the projection 24a is appropriately positioned and struck on the end face of the large diameter end 2b. Forging is performed in the inserted state (FIG. 5A). In this case as well, the large-diameter end portion 2b is restrained by the punch 24 in the same manner as described above, and forging proceeds in a state in which the displacement between the round bar 2 and the punch 4 during forging is prevented. Then, a central hole 40c having a shape complementary to the protrusion 24a is formed on the upper surface of the obtained large-diameter Braille tack 40 (FIG. 5B).

In this case, a disc-shaped recess 40d is formed on the upper surface of the large-diameter Braille stud 40 by using the center hole 40c as a guide, and various resins and rubbers are filled therein to obtain a final product. (FIG. 5 (c)). This Braille tack 4
In the case of 0, in addition to the metallic luster of stainless steel, the resin or rubber filled in the recess 40d has various color effects and anti-slip effects.

The present invention is not limited to the above-described embodiment. For example, various concave portions, uneven portions, or projecting portions may be formed as the position shift preventing means.

[0023]

As is apparent from the above description, according to the present invention, upsetting forging is performed in a state in which the end of the round bar is held and restrained in the mold by the predetermined displacement preventing means. Even if the length of the round bar is long, no misalignment (side slip) occurs between the round bar and the mold, and the round bar is less likely to buckle and to have poor forging. As a result, an integrated large-diameter braille tack can be easily manufactured, and production efficiency can be improved.

Further, compared with the conventional method of manufacturing a large-diameter braille stud by cutting, the amount of material used can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a process diagram showing an example of a method for manufacturing a large-diameter braille tack according to the present invention.

FIG. 2 is a bottom view showing the shape of the punch when viewed from below.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a process diagram showing another example of a method for manufacturing a large-diameter braille tack according to the present invention.

FIG. 5 is a process chart showing still another example of the method for manufacturing a large-diameter braille tack according to the present invention.

FIG. 6 is a process chart showing a conventional method for manufacturing a large-diameter braille tack.

[Explanation of symbols]

2 Round bar 2a Small-diameter end (one end) 2b Large-diameter end (other end) 4, 14, 24 Punch (die) 4a Concave portion (means for preventing displacement) 14a Uneven portion (means for preventing displacement) 24a Projection Part (means for preventing displacement) 10 Dies 20, 30, 40 Large diameter braille

Claims (4)

[Claims] 1. An end of a stainless steel round bar is fixed,
A method for producing a large-diameter Braille stud by upsetting forging in which the other end is pressed with a mold in the axial direction, wherein when the diameter of the round bar is D and the length is L, the round bar is L / D is 2.5 or more, in the area of the mold including the contact surface with the other end of the round bar, the displacement between the round bar and the mold during the upset forging A method for manufacturing a large-diameter braille tack, comprising a prevention means. 2. The positioning device according to claim 1, wherein the misalignment preventing means includes a concave portion for holding the other end portion, a concave and convex portion for locking the other end portion to the mold, or a protruding portion that is driven into a center axis of the other end portion. The method for manufacturing a large-diameter braille tack according to claim 1, comprising: 3. A die used in the method for manufacturing a large-diameter braille tack according to claim 1, wherein the die is configured to press the other end of the round bar in the axial direction thereof, wherein the round bar is one of the dies. In the region including the contact surface with the other end of the boss, a concave portion for holding the other end, an uneven portion for locking the other end to the mold, or a center axis of the other end is driven. A mold for manufacturing a large-diameter Braille tack, comprising: means for preventing displacement of the round bar and the mold during the upsetting forging, comprising: 4. A large diameter Braille tack made by the method for producing a large diameter Braille tack according to claim 1.