KR100189226B1 - Method of manufacturing chisel for impact tool and article made thereby - Google Patents

Abstract

The present invention relates to a method of making a durable chisel. An axial hole is formed in the cheese to open its end. Fill the nonmetallic powder in the axial hole. A core member made of hardened carbide or other material harder than the chisel body is pressed into the axial hole. By inserting the core member into the hole, the nonmetallic powder flows into and fills the space between the rear end face of the core member and the closed end of the axial hole.

Description

Chisel for impact tool and its manufacturing method

1 is a cross-sectional view of a chisel manufactured by the method according to the invention,

2 is a cross-sectional view of the chisel showing a method of assembling the chisel.

The present invention relates to a method for manufacturing a chisel for impact tool.

It is known that a type of impact tool is known to be crushed or crushed by a plaque mounted on one end of a cylinder by pulsating pistons in the cylinder to knock objects such as stone beds and concrete. One problem with this type of impact tool is that the tip of the chisel tends to wear quickly because it is repeatedly beaten against the object to be crushed.

In order to improve the durability of such a chisel, Japanese Utility Model Publication No. 59-90581 proposes a core member made of a harder material than the chisel, which is pressed into the axial hole formed in the chisel and the opening of the tip thereof.

In such a chisel, the impact is first applied to the chisel body and then transmitted to the core member.

Thus, it is essential that the rear end face of the core member is in tight contact with the closed end of the axial hole formed in the chisel body so that these two members act as one unit. Otherwise, the stress due to the impact force is concentrated in the non-contacting portion, causing hardening of the contact and non-contact surface. Such hardened surfaces tend to suffer from fatigue damage due to metal fatigue.

In order to solve this problem, Japanese Patent Laid-Open No. 3-73430 proposes to sandwich a packing made of a soft metal such as lead between the closed end of the axial hole in the chisel and the rear end of the core member.

However, this improved chisel has a problem that it is difficult to contact the rear end face of the core member tightly with the closed end face of the hole due to the inevitable dimensional error of the hole, the core member and the soft metal packing in the chisel. In addition, in the initial stage of the use of the chisel, the core member is in partial contact with the chisel body and the core member and the chisel body tend to be easily broken.

In addition, the packing tends to be displaced to one side when the core member is pressed into the hole in the chisel by the soft metal packing placed in the life preserver. This partially contacts the rear end face of the core member with the closed end face of the hole. Thus, the impact applied to the core member tends to concentrate on the partial contact portion. Therefore, the core member is easily damaged by excessively strong local force.

Moreover, in order to make the rear end face of the core member uniformly and uniformly in contact with the closed end face of the hole formed in the chisel body, both of them must be formed in hemisphere. Forming such a split surface requires a long time and a high manufacturing cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a chisel which allows the rear end surface of the core member to be in close contact with the closed end surface of the hole formed in the chisel hair once the core member is inserted into the hole.

According to the present invention there is provided a method of manufacturing a chisel for use in an impact tool, the method comprising filling a heat resistant nonmetallic powder in an axial bore formed in the chisel body and having an open end at the tip of the chisel body and the chisel Injecting a harder core member into the axial hole.

The chisel according to the present invention comprises a chisel body having an axial bore having an open end at its tip, and a core member which is pressed into the axial bore and whose wear resistance is larger than that of the chisel body, wherein the nonmetal powder is filled in the axial bore. It is characterized by.

This nonmetal powder may be graphite powder or talc powder. This powder may be used alone or after mixing the additives.

By inserting the core member into the hole, the nonmetallic powder moves in the hole to completely fill all the spaces between the rear end face of the core member and the closed end of the hole with uniform density. Thus, the rear end surface of the core member 4 is in seamless contact with the closed end of the hole through the nonmetallic powder layer.

Other features and objects of the present invention will be apparent from the following description with reference to the accompanying drawings.

An embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. The chisel body 1 has an axial hole 2 open to the tip of the chisel body. Heat-resistant nonmetal powder 3, such as graphite or talc powder, is filled in the hole 2. In addition, a core member 4 made of a wear resistant material such as hard carbide and tool steel is also pressed into the hole 2.

The edge of the closed end of the hole 2 is rounded to reduce the stress concentration. The rear end face of the core member 4 is likewise rounded for the same purpose.

In order to assemble the chisel, as shown in FIG. 2, the nonmetal powder 3 is fed into the hole 2 in the chisel body 1, and the core member 4 is press-fitted into the hole 2.

It is preferable to apply a lubricant such as molybdenum disulfide to the inner surface of the hole 2 so that the core member 4 can be easily inserted or pressed into the hole 2.

An axial groove 5 is formed in the surface of the core member 4. This functions as a vent hole, through which air in the hole 2 can escape when the core member 4 is inserted into the hole 2.

By inserting the core member 4 into the hole 2, the nonmetal powder 3 moves in the hole 2 under pressure transmitted from the rear end surface of the core member 4, All gaps between the closed ends of the holes 2 are filled with uniform density. Thus, the rear end surface of the core member 4 is in intimate contact with the closed end of the hole 25 through the nonmetal powder 3.

Since the non-metallic powder is freely movable in the hole 2, it flows into and fills a small space that can be formed between the outer circumferential surface of the core member 4 and the inner surface of the hole 2 due to the dimensional error of these members.

Thus, the impact applied to the core member 4 is applied to the entire area of the closed end face of the hole 2. That is, the stress is not locally concentrated when the impact is transmitted from the chisel body 1 to the core member 4.

According to the present invention, it is possible to contact the rear end face of the core member through the non-metallic powder layer without any contact with the closed end of the hole without merely pressing the core member into the hole formed in the chisel body.

This reduces damage to the core member and the chisel body and extends the life of the chisel.

Since the nonmetallic powder is freely movable in the hole to fill the space between the rear end face of the core member and the closed end face of the hole, the rear end face and the closed end face need not have any special shape. In addition, such nonmetallic powder fills any small gap formed between the core member and the hole of the chisel body due to the dimensional error of the eagle member, thereby preventing the core member from rattling during assembly.

Thus, since the outer surface of the core member and the inner surface of the hole do not need to be trimmed very precisely, these members can be manufactured at low cost.

Claims (4)

A method of manufacturing a chisel for impact tool, comprising: filling a heat resistant non-metal powder into an axial hole formed in the chisel body and having an open end at the tip of the chisel body and a core member having a higher wear resistance than the chisel body in the axial direction A chisel manufacturing method for an impact tool, comprising the step of press-fitting into a hole. The method of claim 1, wherein the base metal powder is graphite powder, talc powder or a mixture of graphite powder, talc powder and additives. A chisel body (1) having an axial hole (2) having an open end at its tip and a core member (4) press-fitted into the axial hole (2), the core member (4) being the chisel body An impact tool chisel having a higher wear resistance than (1), wherein the nonmetal powder (3) is filled in the axial hole (2). 4. The chisel for impact tools according to claim 3, wherein the non-metal powder (3) is a mixture of graphite powder, talc powder or graphite powder, talc powder and additives.