WO1996025266A1

WO1996025266A1 - Plasma torch

Info

Publication number: WO1996025266A1
Application number: PCT/JP1996/000305
Authority: WO
Inventors: Masamitsu Kitahashi; Hiroyuki Tokunaga
Original assignee: Komatsu Ltd.
Priority date: 1995-02-13
Filing date: 1996-02-13
Publication date: 1996-08-22

Abstract

A plasma torch comprising a nozzle (3) through which a narrowed plasma arc extending from an electrode is emitted, wherein the torch nozzle (3) and a torch body (1) are not coaxial.

Description

Description Plasma Torch

The present invention relates to a plasma torch that requires particularly close access to a workpiece in welding or cutting.

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In plasma welding and cutting, especially when processing a workpiece with a shape that makes it difficult to approach the plasma torch, a plasma torch with an elongated tip must be used.

However, in such a plasma torch with a narrow tip, it is difficult to secure a sufficient cooling water channel to the torch nozzle's arc constrained part and the tip due to dimensional restrictions, which are easily heated by arc heat or radiation heat from the work. Therefore, if welding or cutting is performed with a large current, there is a problem that cooling is insufficient and erosion of the torch nozzle occurs.

In order to solve such a problem, as shown in Japanese Patent Publication No. 62-47063 and Japanese Patent Publication No. 63-39347, the leading end of a plasma torch is disclosed. The plasma torch has a flattened shape to improve the accessibility to the work in two directions on both sides, which are thinner in the horizontal section, and at the same time, a cooling water communication passage is provided around the torch nozzle hole to improve the cooling of the torch nozzle. Proposed.

The horizontal cross-sectional shape of the tip of this conventional plasma torch is flat and roughly It has a rectangular shape, and the torch nozzle axis is located at the center of the torch.A reciprocating passage for cooling water is provided on both sides of the torch nozzle with respect to the center of the torch, and both passages are communicated at the tip of the torch nozzle. Thereby, both sides and the tip of the torch nozzle are cooled.

As another conventional plasma torch, an electrode of a plasma torch is fitted to a power supply portion of a torch body as shown in Japanese Utility Model Laid-Open Publication No. 168073. In some cases, a torch nozzle is disposed outside the electrode through a spacer (guide tube) made of insulating material. This is because the shortest gap between the electrode and the torch nozzle is provided near the tip of the electrode, and dielectric breakdown due to high frequency that occurs at the time of ignition of the pilot arc occurs at the shortest gap (around the tip of the electrode). In this way, abnormal discharge is prevented from occurring outside the tip of the electrode inside the torch.

Further, as another conventional plasma torch, as disclosed in Japanese Patent Application Laid-Open No. Hei 5-379 and Japanese Patent Publication No. Sho 56-4351, a torch body tip is disclosed. A cap is attached to an electrical insulator attached to the outer periphery, and the cap is welded while being pressed against the workpiece, so that the stand-off is kept constant and welding or cutting is performed. There is something.

In the conventional flat-type plasma torch described above, since the outer surfaces in two directions on both sides in the thin direction of the horizontal cross section are close to the torch nozzle axis, the approach to the work is good on both sides, and the thick plate When welding the root face of the groove butted part, it is possible to insert a plasma torch even in a narrow groove and move it in the direction of thicker cross section while welding. There are advantages. However, in this configuration, the approach to the work is only good on both sides in the direction of thinner cross-sectional shape, so the applicable peaks are limited, especially when performing wire welding by mounting on a robot. There are many singularities that cannot be realized in the posture, and there is a problem in its versatility. In addition, since the torch nozzles that are consumables in these plasma torches also have a flat shape, the processing becomes complicated and the brazing process becomes very expensive. The problem is that the birds get expensive.

In the conventional plasma torch described above, in which the shortest gap between the electrode and the torch nozzle is provided near the tip of the electrode, the outer periphery except for the tip of the electrode is provided with a guide formed of an insulating material on the outer periphery. The torch nozzle is placed, and the shortest gap between the electrode and the torch nozzle is provided near the tip of the electrode. The dielectric breakdown due to high frequency that occurs when the pilot arc is ignited causes the shortest gap. It is intended to prevent discharge (abnormal discharge) in the area other than the electrode tip by causing it to occur near the electrode tip. However, since there is always a space (gap) between the guide (insulating material) and the torch body, the pilot arc is particularly necessary when the guide is leaking with cooling water. When this occurs, a so-called creeping discharge is generated on the guide surface, causing a discharge (abnormal discharge) between a portion other than the tip of the electrode and the torch nozzle, causing a problem that the torch nozzle is burned out.

Furthermore, in a conventional torch body with a cap attached to the tip of the torch body, the cap is attached to an electrical insulator attached to the outer periphery of the tip of the torch body, and the cap is not pressed against the work. Welding or cutting is performed while maintaining a constant stand-off. As a result, the arc length can be kept constant, and the welding quality or cutting quality can be stabilized. In addition, when used for welding, especially in arc spot welding, the welding point can be covered with a cap attached to the tip, improving the shielding effect and reducing the oxidation of the welding point. Can be prevented. However, in these plasma torches, the cap at the tip is directly pressed against the work, so it is heated by heat conduction from the arc or receives radiant heat from the arc, and this cap melts. There is a problem in that the torch is deformed, and the standoff cannot be kept constant, or the torch itself is melted and damaged. Among these plasma torches, a plasma torch of a plasma gas swirling flow type has a torch body and a cap even if an arc point of a work is shielded depending on a shape of a gas vent hole of the cap. There is a problem that air enters into the chamber constituted by the chips and oxidizes the welding point, and that the gas flow in the chamber is disturbed and the welding quality becomes unstable.

The present invention has been made in view of the above,

The first purpose is to make it possible to sufficiently cool the electrode and torch nozzle, especially the tip of the torch nozzle, which receives radiant heat from the arc work, and the arc restraining part or its vicinity by the cooling water. Even in the case of a torch, the dimensions from the torch nozzle axis in up to three directions around the torch nozzle axis are reduced to greatly improve the accessibility to the workpiece in these directions, and the electrodes and torch nozzle are improved. O /

It is an object of the present invention to provide a plasma torch that can be provided at a low cost because consumables such as a tool have a symmetrical shape and are easy to process. A second object of the present invention is to provide a plasma torch capable of preventing abnormal discharge inside the torch by blocking a creeping discharge path on a guide surface in the torch body and preventing burning of the torch. It is in.

In addition, the third purpose is to make it possible to cool the work contact cap attached to the tip of the plasma torch with cooling water to keep the stand-off constant. In addition to preventing the contact cap from melting and deforming, the cooled workpiece contact cap should be brought into contact with the periphery of the arc irradiation part of the workpiece. In particular, when performing lap spot welding, it is possible to reduce the melt diameter of the work on the front side, improve the appearance quality of the work, and completely eliminate the arc irradiation area from outside air. It is an object of the present invention to provide a plasma torch that can shield from gas, and at the same time, does not disturb the flow of plasma gas and can improve welding quality and stability. Disclosure of the invention

In order to achieve the first object, the plasma torch according to the present invention is

In a plasma torch in which a plasma arc extending from an electrode is squeezed and ejected by a torch nozzle, the torch nozzle axis is eccentric with respect to the center of the torch body.

Then, all or part of the medium passage provided in the torch body It is provided on one side with respect to the center of the torch body.

Further, an annular cooling water chamber is provided around the arc restraining portion of the torch nozzle or in the vicinity thereof, and the cooling water communicates with the cooling water chamber.

Furthermore, the horizontal cross-sectional shape of the electrode and the torch nozzle is symmetric.

According to the above configuration, the axis of the torch nozzle is eccentric in the longitudinal direction of the horizontal cross section with respect to the center of the flat torch body, so that the dimensions of the torch nozzle in the maximum three directions around the axis of the torch nozzle can be obtained. Therefore, work such as welding and cutting can be efficiently performed even on a work having a complicated shape.

During these operations, the electrodes and the torch nozzle are cooled with cooling water. In particular, the tip of the torch nozzle, which receives the plasma arc and radiant heat from the workpiece, and the arc restraint or its vicinity are sufficiently cooled. The life of consumables such as torch nozzles can be extended even when working with large currents.

The torch nozzle, which is a consumable part, can be made symmetrical, and at the same time, the torch body itself can secure the accessibility to the work, so that it is not necessary to make it a slender shape. Can be provided at a low cost because it can be reduced. Therefore, the running cost is superior to the conventional plasma torch.

Further, in order to achieve the second object, the plasma torch according to the present invention comprises:

Plasma arc extending from the electrode is squeezed out with a torch nozzle In the plasma torch, the electrode and the torch nozzle are arranged coaxially with an insulating member interposed therebetween, and all or a part of the space other than the vicinity of the electrode tip existing between the insulating member and the torch body. Are blocked by another insulating member in the axial direction. Further, an elastic body is used for the other insulating member.

According to the above configuration, when a pilot arc is generated, a high voltage is applied between the electrode and the torch nozzle due to dielectric breakdown. However, the electrode and the torch nozzle are coaxially arranged via the insulating member (guide tube), and at the same time, the guide is used. All or part of the space existing between the arm and the torch body is cut off in the axial direction by the insulating member, so the creeping discharge path on the guide surface is cut off and the electrode tip inside the torch is cut off. Discharge outside the vicinity, that is, abnormal discharge is eliminated, and burnout of the torch can be prevented.

Further, in order to achieve the third object, the plasma torch according to the present invention is

In a plasma torch in which a plasma arc extending from an electrode is squeezed and ejected by a torch nozzle, a cooling water passage through which cooling water passes is provided in a work contact cap detachably attached to a torch body.

According to the above configuration, the work contact cap attached to the tip of the plasma torch is cooled with the cooling water to keep the stand-off constant, so that the work contact cap melts. In particular, the deformation of the arc irradiating part of the work is prevented by being brought into contact with the cooled work abutment cap. When performing lap spot welding, The diameter of the molten metal on the side can be reduced, and the appearance quality of the workpiece can be improved.

In a plasma torch in which a plasma arc extending from an electrode is squeezed and ejected by a torch nozzle, exhaust gas from the cap is swirled into a work contact cap attached to a torch body. So that it is discharged.

According to this configuration, particularly in a plasma torch of a plasma gas swirling flow type, the arc irradiation part can be completely shielded from the outside air, and at the same time, formed by the torch body, the workpiece contact cap and the workpiece. The flow of gas in the chamber can be smoothed, and the welding quality and safety can be improved. BRIEF DESCRIPTION OF THE FIGURES

The invention will be better understood from the following detailed description and the accompanying drawings illustrating an embodiment of the invention. The embodiments shown in the accompanying drawings are not intended to specify the invention, but merely to facilitate explanation and understanding.

In the figure,

FIG. 1 is a sectional view of a first embodiment of a plasma torch according to the present invention.

FIG. 2 is a view in the direction of arrow A in FIG.

FIG. 3 is a view in the direction of arrow B in FIG.

FIG. 4 is a perspective view of another example of the cooling water chamber of the torch nozzle of the first embodiment.

FIG. 5 is a front view of another example of the work contact cap of the first embodiment. FIG.

FIG. 6 is a view in the direction of arrow C in FIG.

FIG. 7A and FIG. 7B are explanatory views of a gas vent groove formed in a conventional work contact cap.

FIGS. 8A and 8B are explanatory views of the gas vent groove formed in the work contact cap of the first embodiment.

FIG. 9 is an explanatory diagram of another example of the arrangement of the piping in the torch according to the first embodiment.

FIG. 10 is a partially cutaway perspective view of the work contact cap of the second embodiment.

FIG. 11 is a longitudinal sectional view of the torch body of the third embodiment.

FIG. 12 is a view in the direction of arrow D in FIG. 11. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a plasma torch according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of a plasma torch according to the present invention. In the drawing, reference numeral 1 denotes a torch body, and in this embodiment, only a tip portion thereof is shown. The torch body 1 is made of a synthetic resin to provide electrical insulation from the outside.The torch body 1 has an electrode 2 at the tip and an electrically conductive property at the tip of the electrode 2. The torch nozzle 3 and the torch head cover 4 are arranged concentrically with respect to the nozzle axis. The electrode 2 has an electrode base 6 supported on the torch body 1 via a guide cylinder 5 made of an insulating material, for example, ceramic or resin, and a brazing tip at the tip of the electrode base 6. And electrode pieces 7 attached by press fitting or the like. The torch nozzle 3 is in contact with the electrode via the guide cylinder 5 in an electrically insulated state. The torch cover 4 is made of a material having electrical insulation and heat resistance, for example, a ceramic.

Further, a plasma gas chamber 8 is provided outside the guide cylinder 5 supporting the electrode 2, and the plasma gas chamber 8 is provided at a front end side of the electrode piece 7 by a gas nozzle 9 provided in the guide cylinder 5 in a swirl shape. It is connected to the space so that the plasma gas blows out while turning. The plasma gas supply path 10 is connected to the plasma gas chamber 8. Further, an electrode cooling chamber 11 sealed by a seal member 20 attached to the outer periphery of the electrode table 6 is provided in the electrode table 6 of the electrode 2, and a cooling water inflow pipe 1 is provided in the electrode cooling chamber 11. 2 has been inserted. In addition, two annular cooling chambers 13a and 13b are provided around the arc restraining portion of the torch nozzle 3 so as to be displaced in the axial direction and connected to each other by a part of them. The outlet side of the electrode cooling chamber 11 of the electrode base 6 is connected to the annular cooling chamber 13 a via a torch nozzle cooling water inflow path 14.

A cooling water return path 15 is connected to another annular cooling water chamber 13b. As shown in Fig. 4, the cooling water channel of the torch nozzle is configured such that the cooling water inflow channel 14 and the cooling water return channel 15 are connected to one cooling water chamber 13c so as to be shifted from each other in the horizontal direction. However, a similar torch nozzle cooling effect can be obtained.

Further, a shield gas chamber 16 is provided around the tip of the electrode 2 and the torch nozzle 3, and the shield gas chamber 16 is a torch. Connected to shield gas nozzle 17 provided on head cover 4. The shield gas supply passage 18 is connected to the shield gas chamber 16.

As shown in FIG. 2, the torch body 1 has a substantially horizontal elliptical cross-sectional shape, and the torch nozzle axis is located at a position eccentric to one of the longitudinal directions of the cross-sectional shape of the torch body 1. The passages are arranged and connected laterally to the cooling water chamber and the gas chamber located at the torch nozzle axis, that is, the torch nozzle cooling water inflow path 14, cooling water return path 15 and plasma gas supply path 10 The shield gas supply passage 18 is disposed on the other side of the torch nozzle axis. The end of the torch body 1 on the torch nozzle axis side is formed in a semicircular shape centered on the torch nozzle axis. The semicircular portion only needs to be thick enough to hold the electrode 2, the torch nozzle 3, the torch head cover 4, etc., and the radius dimension is the minimum necessary. I'm sorry.

As a result, in the first embodiment, which is the plasma torch of the present invention, the dimensions of the torch nozzle 3 in the maximum three directions around the torch nozzle axis can be significantly reduced as compared with the conventional plasma torch. Work such as welding and cutting can be performed efficiently even for workpieces with complicated shapes due to improved accessibility to the workpieces. During these operations, the electrode 7 and the torch nozzle 3 are forcibly water-cooled with cooling water, and it is possible to sufficiently cool the tip of the torch nozzle 3 receiving the radiant heat from the arc and the work, and the vicinity of the restraint part. it can. In this case, the same cooling effect can be obtained by using alcohol, oil, or a mixture thereof in addition to water as the cooling medium. Thus, with the above configuration, the electrode 2 and the torch nozzle 3 can be sufficiently cooled even when working with a large current, so that the life of consumables can be prolonged. In addition, since the torch body 1 as a consumable is reduced in diameter itself, it is not necessary to make the consumables slender, and the amount of processing at the time of manufacturing the consumables can be reduced. In addition to the long life, running costs can be significantly reduced as compared to conventional plasma torches.

In addition, the outer periphery of the guide tube 5 fitted to the electrode base 6 axially blocks the space (gap) between the guide tube 5 and the torch body 1. Is installed.

The material of the insulating member is preferably a material having elasticity such as a 0-ring as in the first embodiment, and a material having no water absorption is also preferable.

22 is a work contact cap detachably attached to the tip of the torch with a bolt 23, so that the stand-off for welding and cutting can be set. ing. The horizontal cross-sectional shape of the work contact cap 22 is also substantially the same as the horizontal cross-sectional shape of the torch body 1, and a plasma discharge port 24 is provided at a position corresponding to the torch nozzle axis. Further, a cooling water passage 25 is provided on the other side eccentric from the plasma discharge port 24, and the cooling water passage 25 has a reciprocating water pipe 26 as shown in FIGS. a and 26 b are connected. Reference numeral 27 denotes a gas vent groove provided on the end face of the work contact cap 22, which may be a hole. Further, these gas vent grooves or holes may be configured so that the exhaust gas is discharged while turning. Next, the operation of the first embodiment will be described.

First, when an arc is generated, the insulation between the electrode 2 and the torch nozzle 3 is destroyed by the activation of high frequency (high voltage) to secure a discharge path, and then a pilot arc is formed between the electrode 2 and the torch nozzle 3. appear. The pilot arc moves to the work side, and a plasma arc is generated between the electrode piece 7 and the work, and the peak is welded or cut by the plasma arc. At this time, the plasma gas is supplied spirally (in a swirling airflow state) from the plasma gas supply path 10 and the shield gas is supplied from the shield gas supply path 18.

Since high voltage is applied between the electrode 2 and the torch nozzle 3 at the time of the above-mentioned arc-induced dielectric breakdown, the dielectric breakdown occurs near the electrode tip especially when the guide cylinder 5 is wet with cooling water. This is not carried out between the electrode 2 and the torch nozzle 3, and the insulation is broken (by creeping discharge) using the surface of the guide tube 5 as a discharge path between the rear of the electrode 2 and the rear of the torch nozzle 3. Pilot arc discharge is started through the discharge path, and the torch may burn out. This phenomenon frequently occurs when a gas that easily causes dielectric breakdown, such as argon gas, is used as the plasma gas as in plasma welding. However, in the first embodiment, the insulating member 19 causes creeping discharge on the surface of the guide cylinder 5 in the path of the abnormal discharge generated between the electrode 2 and the torch nozzle 3 inside the torch except the tip of the electrode 2. Since this path is blocked, abnormal discharge inside the torch and burnout of the torch can be prevented.

At this time, the work contact cap 22 is also cooled by the cooling water when used. This work contact cap 2 2 is cold. As a result, the portion of the workpiece that contacts the workpiece is cooled by the periphery of the arc discharge port 24. As a result, especially when performing lap spot welding, the diameter of the molten metal on the front side of the work can be reduced, the thermal strain of the work can be suppressed, and the appearance quality of the work can be improved. it can.

Further, as in the other examples shown in FIGS. 5 and 6, the exhaust gas passing through the vent hole 27 provided at the end face of the work contact cap 22 swings. While being configured to be exhausted (coinciding with the turning direction of the plasma gas), the arc irradiation part can be completely shielded from the outside air, and the torch body 1 and the work contact cap 2 2 In addition, the flow of gas in the chamber composed of the workpiece can be made smooth, and the welding quality and stability can be improved.

This principle will be described below with reference to FIGS. 7A and 7B. Fig. 7A shows the shape of the gas vent groove for the exhaust gas of the conventional workpiece contact cap.With such a structure, especially when the plasma gas is swirling, as shown in Fig. 7B At the same time, a stagnation space 27a is generated in a part of the gas vent groove, and through the stagnation space 27a, a chamber composed of the torch body 1, the workpiece contact cap 22 and the workpiece is formed. The outside air (air) enters and the arc irradiating part is oxidized, or the swirling flow of the plasma gas is irregularly reflected at the gas vent hole and the gas flow in the chamber is disturbed. Cutting quality is not stable.

On the other hand, in the workpiece abutment 22 of the first embodiment, as shown in FIG. 8A, the gas vent groove 27 faces the plasma gas flow. The gas is smoothly discharged as shown in Fig. 8B, so that the above-mentioned stagnation space is not generated and the outside air is prevented from entering the chamber. As a result, the arc irradiation part can be completely shielded, and the swirling flow of the plasma gas is not disturbed, so that the cutting quality or welding quality is stabilized.

The first embodiment is merely an embodiment of the present invention, and does not restrict the scope of the present invention. For example, as shown in Fig. 9, as in the first embodiment, the arrangement of the piping in the torch can be integrated (asymmetrically) in a part of the torch or a part of the piping can be arranged in the other. It goes without saying that a torch with improved accessibility to a workpiece in a specific direction (instead of three directions) is also included in the claims of the present invention.

FIG. 10 shows a work contact cap according to the second embodiment. In the second embodiment, a work contact cap 22 attached detachably to the tip of a work contact cap 28 attached to the torch body 1 so as to surround it is attached to the torch body 1. An annular cooling water channel 29 is formed concentrically with the arc discharge hole, and the reciprocating water pipes 26 a and 26 b are connected to the cooling water channel 29.

According to the second embodiment, the work contact cap 22 can be more reliably prevented from melting and deforming, and the temperature distribution around the arc ejection hole of the work contact cap 22 is uniform. When used in lap spot welding, the diameter of the molten metal can be reduced, so that the appearance quality of the peak can be further improved.

FIGS. 11 and 12 show the torch body of the third embodiment. This is the head cover 4 attached to the tip of the torch body 1. An annular cooling water passage 30 is formed concentrically with the arc ejection hole in the work contact cap 22 detachably attached to the tip, and the cooling water passage 30 has a cooling water inflow passage 14 and a cooling water return passage. 15 is connected. The third embodiment also provides the same effects as the second embodiment.

As described above, the present invention has the following effects.

(1) In the plasma torch of the present invention, the axis of the torch nozzle 3 is eccentric in the longitudinal direction of the horizontal cross section of the torch body 1 formed to be flat, so that the dimensions in three directions around the axis of the torch nozzle are provided. Since the method becomes smaller, the accessibility to the work is improved, and work such as welding and cutting can be performed efficiently even on a work with a complicated shape.

During these operations, the electrode 2 and the torch nozzle 3 are cooled by cooling water, and in particular, the tip of the torch nozzle 3 receiving the radiant heat from the arc and the work, and the vicinity of the arc restraining portion are sufficiently cooled. Therefore, the life of the consumable torch nozzle 3 can be extended even when working with a large current. In addition, since the torch body 1 itself is reduced in diameter, it is not necessary to make the torch nozzle 3 which is a consumable product slender, and as a result, the amount of processing required when producing the consumable product can be reduced, so that the cost of the consumable product can be reduced. it can. Therefore, the running cost can be greatly reduced as compared with the conventional plasma torch.

(2) In the plasma torch of the present invention, when a pilot arc is generated, a high voltage is applied between the electrode 2 and the torch nozzle 3 due to dielectric breakdown. However, the electrode 2 and the torch nozzle 3 are connected by an insulating member (guide tube 5). And at the same time, between guide tube 5 and torch body 1 Since all or part of the existing space is cut off by the insulating member, the creeping discharge path on the surface of the guide cylinder 5 can be cut off to prevent abnormal discharge inside the torch.

(3) In the plasma torch of the present invention, the work contact cap 22 attached to the tip of the plasma torch is cooled with cooling water to keep the stand-off constant. Cap 22 can be prevented from being melted and deformed, and the periphery of the arc irradiating section of the work can be protected by this cooled torch contact cap. The contact is cooled by the abutment, and especially when performing lap spot welding, the melt diameter on the front side of the workpiece can be reduced and the thermal strain of the workpiece can be suppressed. The external appearance quality can be improved.

In addition, the arc irradiation part was completely shielded from the outside air, and the gas flow in the chamber consisting of the torch body 1, the torch contact cap 22, and the workpiece was smoothed. The ability to improve welding or cutting quality and stability.

Although the present invention has been described with reference to exemplary embodiments, various modifications, omissions, and additions can be made to the disclosed embodiments without departing from the spirit and scope of the present invention. Is obvious to those skilled in the art. Therefore, the present invention is not limited to the above embodiments, but should be understood to include the scope defined by the elements recited in the claims and the equivalents thereof.

Claims

The scope of the claims

1. A plasma torch in which a plasma arc extending from an electrode is squeezed and ejected by a torch nozzle, wherein a torch nozzle axis is decentered with respect to the center of the torch body.

2. The plasma torch according to claim 1, wherein all or a part of the medium passage provided in the torch body is provided on one side with respect to the center of the torch body.

3. The plasma torch according to claim 1, wherein an annular cooling water chamber is provided around the arc restraining portion of the torch nozzle or in the vicinity thereof, and the cooling water communicates with the cooling water chamber.

4. The plasma torch according to claim 2, wherein an annular cooling water chamber is provided around the arc restraining portion of the torch nozzle or in the vicinity thereof, and cooling water is communicated with the cooling water chamber.

5. The plasma torch according to any one of claims 1 to 4, wherein the horizontal cross-sectional shapes of the electrode and the torch nozzle are symmetrical.

6. In a plasma torch in which a plasma arc extending from an electrode is squeezed and ejected by a torch nozzle, the electrode and the torch nozzle are coaxially arranged via an insulating member, and a gap between the insulating member and the torch body is provided. Of the space other than near the electrode tip A plasma torch characterized in that all or a part of it is cut off in the axial direction by another insulating member.

7. The plasma torch according to claim 6, wherein an elastic body is used for the another insulating member.

8. In a plasma torch in which a plasma arc extending from the electrode is squeezed and ejected by a torch nozzle, a cooling water passage through which cooling water passes through a work contact cap removably attached to the torch body. A plasma torch characterized by being provided.

9. In a plasma torch in which the plasma arc extending from the electrode is squeezed and ejected by a torch nozzle, the exhaust gas from the cap swirls to the work contact cap attached to the torch body. A plasma torch characterized by having gas vent holes that allow the gas to be exhausted.