JPS599184B2 - shearing tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in shearing tools, such as hand scissors, scissors or shears, which consist of a pair of blades.

The reciprocating shearing blades of these tools often have a problem in that they are difficult to operate even if the rivet that serves as the axis of rotation of these blades is set to the correct length.

Applicant has discovered that this occurs when the surface of the shear blade catches a washer placed on or under the rivet head.

This strain occurs when the blade has a large cutting edge slope, creating a large axial pressure on the rivet head and a significant hardness difference between the blade surface and the washer or rivet head.

When the hardness of the blade surface exceeds 50 Rockwell C, this problem is observed even when using mild steel or high tensile strength steel rivets.

However, if the hardness of the lower bearing surface of the rivet head likewise exceeds 50 for Rockwell C, then considerable differences, such as the difference between 50 and 65 for Rockwell C, can be tolerated.

Therefore, the present invention provides a shearing tool having first and second blades that are mutually rotatable and capable of reciprocating around a rivet whose pointed end is enlarged and fixed by friction to the first blade. The surface hardness of the surface area of the second blade in contact with the lower bearing surface of the rivet head is 50 or more in Rockwell C, and the lower bearing of the rivet head moves relative to the surface of the second blade. The object of the present invention is to provide a shearing tool characterized in that the surface has a hardness of Rockwell C of 50 or more.

Hereinafter, the present invention will be explained in detail with reference to the accompanying drawings based on actual cases.

゛ Fig. 1 shows a front view of one embodiment of the present invention, and Fig. 2 shows a side view thereof. The blade 4 and the second blade 3 in Fig. 1 are hardened reciprocating blades, and their hardness varies. is preferably at least 50 for Rockwell C, and the thickness of the rotation shaft 5 is preferably 60 for Rockwell C.

It is preferable that the blade be chrome plated but not polished, since chrome plating has a Rockwell C rating of 60-65.

The blades are rotatably held by rivets 6, and the rivets are set to provide a desired looseness between the blades so that the blades can be opened and closed easily.

The blades are inclined to each other and the value is 7 cm in length for each blade.
Therefore, the cutting edges 7 and 9 are shifted so that they sequentially contact each other when the blade closes.

The bending or setting of the rivet point enlarges the point 10 opposite the head 11 and locks that end to the adjacent blade 4 by friction.

The bearing surface under the rivet head is connected to the second blade 3 so that the hard surface 12 of the other blade 3 which contacts the rivet head 11 and moves relative to the rivet head during opening and closing of the blade does not hit the head. (having a hardness of at least 50 in mouth well C).

According to the invention, this is easily obtained by case hardening the entire mild steel rivet or preferably a 32 ton polished drawn steel rivet, but with a rivet diameter of 5 m.
For a suitable rivet with a head diameter of 1 crIL, Rockwell C is 50 or more, preferably Rockwell C.
It has a surface hardness of 58 or more and a surface hardening depth of 0.08 mm at the point in contact with the chromium surface, preferably reaching a depth of 0.05 mm.

However, the depth of case hardening is primarily determined by the degree of cracking that can be tolerated when setting or point bending the rivet.

Point bending results in expansion of the rivet point 10, which has been hardened and loses the normal flow rate of mild steel.

Surface hardening causes cracks to appear on the cylindrical surface at the tip of the rivet.

Factors that influence the extent of cracking include case depth, degree of case hardening, rivet tip shape, length reduction due to tip bending, and rivet tip diameter.

The depth of case hardening is determined by these visible factors, which vary depending on the desired overall appearance of the tool.

Instead of surface hardening the rivet itself, the same effect can be achieved using a hardened washer under the normal mild steel rivet head.

However, the use of washers is not recommended.

Therefore, in order to obtain a good cutting effect, the set length of the rivet must be precise, usually 0.13 mm or less. This is because both the length of the rivet and the thickness of the washer must be adjusted.

To give the hardened rivet a good surface appearance, it may be galvanized.

The zinc is soft and is soon scraped from the underside of the rivet head into a powder, which mixes with the oil at the shaft and accumulates in the non-bearing area under the rivet head.

It should be appreciated that in a rivet with a head diameter ICrfL made with normal manufacturing tolerances, only a small portion of the rivet head contacts the blade.

This is because, especially if the blade is stamped from a steel plate, the axial hole will be made by punching and the blade itself will likely be surface-effected.

And because of these, the blade tends to twist in the area where it contacts the rivet head.

Thus, the zinc coating powder under the rivet head does not pose any practical problem.

Alternatively, the rivets may be soft chrome plated or finished.

(Depending on the chromium content, soft chromium becomes a thick nickel color and has a hardness of 30-35 at a temperature of 30°C.)
.

However, the barrelplatin method
Zinc is the metal to which rivets are more easily plated.

This explains why surface hardening is preferred over hard chrome plating of rivets, for example.

In fact, the hotaru plating method does not allow hard chrome to be applied to the lower part of the rivet head, and other methods are not economical for small items such as rivets.

Thus, although the present invention is easy to implement, it is extremely effective in manufacturing shearing tools such as hand scissors, scissors, and shears.

Next, specific aspects of the present invention will be described.

1. In a shearing tool having first and second blades that are mutually rotatable and capable of reciprocating around a rivet whose pointed end is enlarged and fixed by friction to the first blade, the lower part of the head of the rivet The surface hardness of the surface area of the second blade in contact with the bearing surface is set to 50 or more in Rockwell C, and the hardness of the lower bearing surface of the rivet head that contacts the surface of the second blade and moves relative to it. A shearing tool characterized by a Rockwell C rating of 50 or more.

2. The shearing tool according to item 1 above, characterized in that the rivet head is in direct contact with the surface of the second blade.

3 In the shearing tool according to the above item 1 or 2,
It is characterized by surface-hardened rivets.

4. The shearing tool according to item 3 above, characterized in that the depth of the surface hardening does not exceed 0.08 mm.

5 In the shearing tool according to any one of the above items,
The surface of the second blade is plated with hard chrome that does not wear, and its hardness exceeds 60 of Rockwell C.

6. A shearing tool according to any one of the above items, characterized in that the lower surface of the rivet head has a hardness exceeding Rockwell C 58.

7. A shearing tool according to one of the above items, characterized in that the rivet is galvanized.

9 Approximately equivalent to the above shearing tool described with reference to the attached figures.

[Brief explanation of the drawing]

FIG. 1 is a front view of an embodiment of the present invention, and FIG. 2 is a side view thereof. In the figure, 3 is a second blade, 4 is a first blade, and 6 is a side view.
is a rivet, 7 and 9 are cutting edges, 10 is a rivet tip, 1
1 is the rivet head.

Claims (1)

[Claims] 1. In a shearing tool having first and second blades that are mutually rotatable and capable of reciprocating around a rivet whose pointed end is enlarged and fixed by friction to the first blade, the lower part of the head of the rivet The surface hardness of the surface area of the second blade in contact with the bearing surface is set to 50 or more in Rockwell C, and the hardness of the lower bearing surface of the rivet head that contacts the surface of the second blade and moves relative to it. A shearing tool characterized by the fact that it is made with Rockwell C of 50 or more.