JPH0353801Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a plasma cutting torch for cutting mild steel, stainless steel, aluminum, copper, brass, etc.

[Conventional technology]

A plasma cutting torch uses high frequency waves to form a pilot arc between an electrode attached to the tip of a core tube and a metal chip attached to the tip of a support tube, and this pilot arc causes the metal tip to be cut between the electrode and the base material. The main arc is generated through a plasma hole formed in the core tube and the support tube. Conventionally, electrical materials such as tetrafluoroethylene resin were used between the core tube and the support tube to prevent high frequency waves from flying between them. An insulating tube made of thermoplastic resin with excellent physical properties was installed. Further, the electrodes and chips are cooled by effectively using the gas introduced from the core tube not only as a working gas but also as a cooling gas, thereby preventing the insulating cylinder from becoming overheated.

[Problem that the invention attempts to solve]

However, in a plasma cutting torch equipped with an insulating tube made of thermoplastic resin as described above, abnormal heat generation in the core tube and support tube due to consumption of the electrodes and chips or a decrease in cooling gas causes the insulating tube to partially break down. The insulating cylinder is easily deformed or burnt out due to the temperature of approximately 0.3°C. In addition, when conventional plasma cutting torches are used with a large capacity of 100A or more, problems such as deformation and burnout of the insulating cylinder as described above occur, making it impossible to handle such a large capacity. . In other words, if the insulating cylinder is deformed or burnt out, it will not be possible to obtain the necessary dielectric strength or creepage distance, and various problems will occur such as high frequency waves escaping, so it should not be used as a plasma cutting torch. It becomes unbearable. The above deformation of the insulating cylinder is thought to occur because the insulating cylinder is made of thermoplastic resin, so when abnormal heat generation occurs, the insulating cylinder collapses, and this deformation causes the insulating cylinder to form. If the resin flows to the hotter side and burns out, or if a gas flow path is formed in the deformed part, this gas flow path will be closed and the cooling effect of the gas will no longer be available. It is assumed that this will lead to burnout.

The present invention was developed in view of the above-mentioned circumstances, and it improves the shape retention of the insulating tube and suppresses the deformation of the insulating tube and the related decline in cooling effect even in the event of abnormal heat generation. An object of the present invention is to provide a plasma cutting torch whose durability can be sufficiently improved even when used in large capacity.

[Means for Solving the Problems] In order to achieve the above object, the plasma cutting torch according to the present invention has a core tube with an electrode attached to the tip, which has a continuous operating temperature of 250°C or higher and a dielectric strength.
An insulating tube made of thermosetting resin of 10KV/mm or more is fitted onto the outside, and a support tube with a chip attached to the tip is fitted onto the insulating tube, and the exposed portions of the core tube and support tube are covered with insulating material. A cooling gas flow path is formed within the insulating cylinder or in a portion in contact with the insulating cylinder to allow the gas introduced into the core tube to flow as cooling gas for the insulating cylinder.

[Function] According to the plasma cutting torch configured as described above, an insulating tube made of a thermosetting resin having a continuous operating temperature of 250°C or higher and a dielectric strength of 10 KV/mm or higher is interposed between the core tube and the support tube. Because of this, even if abnormal heat generation occurs in the electrode or chip, the insulating cylinder will not be deformed or burnt out. Furthermore, since the insulating tube does not undergo thermal deformation, the creeping distance between the core tube and the support tube will not become small, and the gas flow path formed within or in contact with the insulating tube will not be narrowed or closed.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on the drawings. Figures 1 to 5 show an embodiment of the present invention, in which reference numeral 1 denotes a plasma cutting torch and a torch body, and the torch body 1 is made of a phenolic or epoxy thermosetting resin. , covers the upper half of the core tube 2, insulating tube 3, and support tube 4.

The core tube 2 is made of brass and is provided on the central axis of the torch body 1. A through hole 2a is formed through the core tube 2 along the central axis, and a male screw 2b is screwed around the outer periphery of the tip. At the tip of the core tube 2, there is a female thread 5a on the inner periphery that is screwed into the male thread 2b.
A cap-shaped copper electrode 5 with a screw threaded thereon is attached. Reference numeral 5b denotes an electrode material of the arc generating part made of hafnium or the like embedded in the center of the tip of the electrode 5. Further, a gas supply pipe 6 is connected to one end side of the through hole 2a, and a female thread 2c is threaded onto the inner circumferential surface of the intermediate portion near the connection side of the gas supply pipe 6. The through hole 2a is formed to have a larger diameter on the electrode 5 side than the threaded portion of the female screw 2c. The internal thread 2c has a partition wall tube 7 that divides the large diameter portion of the through hole 2a into a shaft portion and an outer peripheral portion.
A male screw 7a is screwed onto the outer periphery of one end of the holder. The other end of the partition tube 7 protrudes from the other end of the core tube 2, and is set with a gap a between it and the bottom of the cap-shaped electrode 5.

The insulating tube 3 has a male screw 2d screwed on the outer periphery of the core tube 2 and a female screw 3a screwed on its inner periphery.
It is externally fitted onto the core tube 2 by screwing them together. This insulating tube 3 is made of a thermosetting resin that has high heat resistance and a dielectric strength of 10 KV/mm or more, for example, a dielectric strength of 20 KV/mm and a continuous use temperature.
Polyimide resin filled with glass fibers is used at temperatures above 250°C. Inside this insulating tube 3 is the core tube 2.
A cooling gas flow passage 9 is formed that communicates with a cooling passage 8 formed between the partition wall tube 7 and the partition wall tube 7. Although it is connected, core tube 2
In order to ensure a sufficient creepage distance between the insulating cylinder 3 and the supporting cylinder 4, the gas flow passage 9 is formed so that the cooling gas moves in the axial direction within the insulating cylinder 3, and then the gas flow passage 9 is formed so that the cooling gas moves in the axial direction within the insulating cylinder 3. It's communicating.

The support tube 4 is made of brass and includes an inner tube 4a and an outer tube 4.
It is divided into parts b, which are soldered together. The inner cylinder 4a is fitted onto the insulating cylinder 3,
A tip 11 is screwed to the lower end. Further, as described above, a cylindrical space 10 is formed between the inner cylinder 4a and the outer cylinder 4b, and communicates with the gas flow passage 9. A plasma working gas outlet 12 communicating with the vicinity of the lower part of the cylindrical space 10 is formed in the inner cylinder 4a, and an annular groove 13 is formed on the outer peripheral surface of the insulating cylinder 3 at a location facing the plasma working gas outlet 12. It is formed. A plasma working gas outlet 15 is formed from this annular groove 13 through the insulating cylinder 3 and communicating with the plasma working gas flow path 14 between the chip 11 and the electrode 5. It is substantially along the tangent line of the flow path 14. That is, these plasma working gas flow passages 14
A gas flow path communicating with the gas flow path 9 is formed by the plasma working gas ejection port 15 and the plasma working gas ejection port 15 .

On the other hand, a cooling gas outlet 16 is formed that penetrates the outer cylinder 4b and communicates with the other end of the cylindrical space 10, and the cooling gas outlet 16 extends diagonally downward from inside the cylindrical space 10 and almost along the tangent line. The seed cup 17 is screwed to the outer cylinder 4b, has a central through-hole 18 that loosely fits into the chip 11, and is provided so that the flange 11a of the chip 11 is pressed against the lower surface of the inner cylinder 4a. Flange portion 1 on the inner surface of the cup 17
Cooling gas outflow grooves 19 are formed at appropriate intervals in the circumferential direction at locations facing 1a.

In the figure, reference numeral 20 indicates a plasma hole drilled at the tip of the chip 11. Reference numeral 21 denotes a guide frame for adjusting the torch spacing, which is fitted into an annular groove formed on the outer peripheral surface of the shield cup 17. This allows the distance between the two to be kept constant. 22 is an O-ring disposed between the shield cup 17 and the outer cylinder 4b.

In the above configuration, a high-frequency discharge is led between the electrode 5 and the chip 11 to generate a pilot arc, and then the main arc is transferred between the electrode 5 and the workpiece A. Due to wear and tear, the annular groove 13 and spout 15 of the insulating cylinder 3
Even with a plasma cutting torch rated at 120A, heat of approximately 250°C may be generated in the forming part.
However, since the plasma cutting torch uses a thermosetting resin with high heat resistance, such as polyimide resin, as the constituent material of the insulating tube 3, the annular groove 13 and the spout 15 are damaged by heat generation.
is not deformed, the plasma working gas is not smoothly sent to the plasma working gas flow path 14, and the dielectric strength is not reduced due to deformation.

It should be noted that the present invention is of course not limited to the above embodiments, and the thermosetting resin used for the insulating cylinder has dielectric strength at a continuous operating temperature of 250°C or higher.
As long as it is 10KV/mm or more, other thermosetting resins such as aramid resin may be used. Further, the shape of the gas flow passage provided within the insulating cylinder or in contact with the insulating cylinder can also be arbitrarily changed in design.

[Effect of idea]

As is clear from the above explanation, according to the plasma cutting torch according to the present invention, the insulating tube inserted between the core tube and the support tube is made of a thermosetting resin with high heat resistance. Although it can be manufactured easily and inexpensively using traditional resin molding methods, it improves the shape retention of the insulating tube, and prevents the core tube and support tube from becoming overheated due to wear and tear of the electrodes and chips. Also, this insulating tube may be thermally deformed, and as a result of this deformation, the dielectric strength may decrease, and furthermore, the cooling gas flow path formed inside the insulating tube or in the area in contact with the insulating tube may become narrow. It is possible to prevent the inconvenience that the cooling effect decreases or disappears due to the cooling effect. Therefore, the occurrence of dielectric breakdown and high frequency escape can be suppressed to the utmost, and the flow rates of the cooling gas and plasma working gas can be maintained at a specified level, making it possible to maintain a stable flow rate even during long-term use or continuous use of large volumes. Also, predetermined plasma cutting can be performed reliably and stably. In particular, since the insulating tube is made of a thermosetting resin with excellent heat resistance that can be used continuously at a temperature of 250°C or higher and has a dielectric strength of 10KV/mm or higher,
It can withstand continuous use for more than 10,000 hours at 250℃, and can be used for large-capacity plasma cutting tools of more than 100A.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the present invention, in which FIG. 1 is a partially cutaway front view, and FIG.
The arrow view, Figure 3 is the - arrow view of Figure 1, Figure 4.
The figure is a view taken along the - arrow in FIG. 1, and FIG. 5 is a view taken along the - arrow in FIG. 2... core tube, 3... insulating tube, 4... support tube.

Claims (1)

[Scope of utility model registration request] The core tube with an electrode attached to the tip has a continuous operating temperature.
An insulating cylinder made of a thermosetting resin having a temperature of 250°C or more and a dielectric strength of 10 KV/mm or more is fitted onto the outside, and a support cylinder with a chip attached to the tip is fitted onto the insulating cylinder, and the core tube and support are fitted. The exposed portion of the tube is covered with an insulating material, and a cooling gas flow path is formed inside the insulating tube or in a portion in contact with the insulating tube for causing the gas introduced into the core tube to flow as cooling gas for the insulating tube. A plasma cutting torch characterized by: