JPH0353802Y2 - - 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. Conventionally, the entire space between the core tube and the support tube was made of polytetrafluoroethylene resin to prevent high frequency waves from flying between them. An insulating tube made of thermoplastic resin with excellent electrical properties was interposed. 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 entirely of thermoplastic resin as described above, abnormal heat generation in the core tube and support tube due to consumption of electrodes and chips or decrease in cooling gas causes the tip of the insulating tube to Temperatures of around 250°C are applied to the insulating cylinder, which causes troubles such as easily deforming or burning out the insulating cylinder. 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 tube is deformed or burnt out in this way, it will not be possible to obtain the necessary dielectric strength and 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 tube is thought to occur because the insulating tube is made of thermoplastic resin, so when abnormal heat generation occurs, the insulating tube collapses, and this deformation causes the insulating tube to collapse. The resin that forms the part flows to the hotter side and burns out, or if a gas passage is formed in the deformed part, this gas flow passage is closed.
It is presumed that the cooling effect of the gas is no longer available, leading 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, and a cylindrical ceramic having a dielectric strength of 10 KV/mm or more. An insulating tube provided at the electrode-side tip of the main body made of a heat-resistant resin having a dielectric strength higher than that of the ceramics is fitted onto the outside, and a support tube having a chip attached to the tip thereof is fitted onto the insulating tube, and the above-mentioned Cooling gas distribution for covering the exposed parts of the core tube and the support tube with an insulating material, and causing the gas introduced into the core tube to flow into the inside of the insulating tube or the part in contact with the insulating tube as cooling gas for the insulating tube. It formed a road.

[Function] According to the plasma cutting torch with the above configuration, the core tube with an electrode attached to the tip has a dielectric strength of 10 KV/mm.
The above cylindrical ceramic is fitted with an insulating tube provided at the electrode-side tip of the main body made of a heat-resistant resin with a dielectric strength higher than that of the ceramic, and a support tube is fitted with a chip at the tip of the insulator. By fitting the insulating tube externally, even if abnormal heat generation occurs in the electrode or chip, the electrode-side tip of the insulating tube, which is most susceptible to heat, will not be deformed or burnt out. In addition, since the tip of the insulating tube on the electrode side does not deform, the deformation of the entire insulating tube is suppressed, and the creepage distance between the core tube and the support tube is reduced, and the formation of The gas flow path is not 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. A male screw 7a screwed onto the outer periphery of one end side of a partition tube 7 that divides the large diameter portion of the through hole 2a into a shaft portion and an outer peripheral portion is screwed into the female screw 2c. 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 consists of a true cylindrical tip portion 3a located near the electrode 5 and a main body portion 3b comprising the other portion. The main body part 3b is made of, for example, polyimide resin filled with glass fiber resin with a dielectric strength of 20 KV/mm and a continuous use temperature of 250°C. It is externally fitted onto the core tube 2 by screwing together the provided female thread 3a.

On the other hand, the tip portion 3a has a dielectric strength of 10KV/
mm, and is made of alumina-based ceramics with a maximum operating temperature of 1600° C., and is fitted and fixed between a notch provided around the outer periphery of the tip of the main body portion 3b and an inner cylinder 4a of the support cylinder 4, which will be described later. A cooling passage 8 is formed between the core tube 2 and the partition wall tube 7 in the main body portion 3b.
A cooling gas flow passage 9 is formed which communicates with the core pipe 2, and this gas flow passage 9 communicates with a cylindrical space 10 formed in the support tube 4, which will be described later.
In order to provide a sufficient creepage distance between the support tube 4 and the support tube 4, the gas flow passage 9 is formed so that the cooling gas moves in the axial direction within the main body 3, and then the gas flow passage 9 is formed so that the cooling gas moves in the axial direction within the main body 3. It's communicating. In addition, the tip portion 3a
An annular groove 13 is formed on the outer circumferential surface of the inner cylinder 4a at a location opposite to a plasma working gas outlet 12 formed in the inner cylinder 4a, which will be described later. A plasma working gas outlet 15 is formed which communicates with the plasma working gas flow path 14 between the electrode 5 and the plasma working gas flow path 14 . and,
As shown in FIG. 4, this jet port 15 is substantially along a tangent to the plasma working gas flow path 14. That is, these plasma working gas flow passages 14 and plasma working gas jet ports 15 form a gas flow passage that communicates with the gas flow passage 9.

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, a cylindrical space 10 is formed between the inner cylinder 4a and the outer cylinder 4b, and communicates with the gas flow passage 9 as described above. The inner cylinder 4a has a plasma working gas outlet 12 communicating with the vicinity of the lower part of the cylindrical space 10.
is formed, and as described above, this plasma working gas outlet 1 on the outer peripheral surface of the tip 3b of the insulating cylinder 3
An annular groove 13 is formed at a location facing 2.

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 pilot arc is generated by leading a high-frequency discharge between the electrode 5 and the chip 11, 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 in a plasma cutting torch rated at 120 A, heat of about 250° C. may be generated in the forming portion, that is, the tip portion 3a. However, the plasma cutting torch has the tip portion 3a at the maximum operating temperature.
Since it is made of alumina ceramics heated to 1600°C, the annular groove 13 is heated as described above.
Therefore, the plasma working gas will not be smoothly sent to the plasma working gas flow path 14, and the dielectric strength will not decrease due to deformation.

It should be noted that the present invention is of course not limited to the above embodiments, and the ceramic used for the tip of the insulating cylinder usually has a maximum operating temperature of
Since the temperature is 800°C or higher, other ceramics may be used as long as the dielectric strength is 10 KV/mm or higher. Also,
In addition to a thermosetting resin such as the polyimide resin shown in the embodiment, a conventionally used thermoplastic resin such as tetrafluoroethylene resin may be used for the main body of the insulating cylinder. However, especially when using tetrafluoroethylene resin, which has conventionally been used as a material for insulating cylinders, for the main body, it is necessary to know the temperature distribution of each part of the insulating cylinder and decide the range of the tip to be formed of ceramics. In addition, in the present invention, 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 description, according to the plasma cutting torch of the present invention, the insulating tube inserted between the core tube and the support tube is made of cylindrical ceramics with a dielectric strength of 10 KV/mm or more. By having the structure provided at the electrode-side tip of the main body made of a resin with a heat resistance higher than that of ceramics, the insulating tube can be easily manufactured even though ceramics are used for the insulating tube, which has a complicated shape. be able to. In addition, since the insulating tube has a cylindrical ceramic at the tip of the electrode side, where heat resistance is most required, the shape retention of the insulating tube can be improved, preventing wear and tear of the electrode and chip. Even if the core tube or support tube is overheated, this insulating tube may be thermally deformed and its dielectric strength may decrease as a result of this deformation. It is possible to prevent the inconvenience that the cooling gas flow passage formed in the portion is narrowed and the cooling effect is reduced or lost. 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 the specified levels, even during long-term use and large-capacity continuous use. , predetermined plasma cutting can be performed reliably and stably.

[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 cylinder, 3a...Tip part,
3b... Body portion, 4... Support tube, 9... Cooling gas flow path (cooling gas flow path).

Claims (1)

[Scope of utility model registration request] The dielectric strength of the core tube with an electrode attached to the tip is
A cylindrical ceramic of 10 KV/mm or more is fitted with an insulating tube provided at the tip of the electrode side of the main body made of a heat-resistant resin with a dielectric strength higher than that of the ceramic, and a chip is attached to the tip of the insulating tube. A support tube is fitted onto the outside of the core tube and the exposed portions of the support tube are covered with an insulating material, and the gas introduced into the core tube is used to cool the insulating tube, and the exposed portions of the core tube and the support tube are covered with an insulating material. 1. A plasma cutting torch characterized in that a cooling gas flow path is formed for flowing a cooling gas.