JP3714518B2 - Plasma torch and its retainer cap - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in the structure of a retainer cap for holding a nozzle.
[0002]
[Prior art]
In general, a plasma torch is known in which a nozzle arranged to cover an electrode with a plasma gas passage is provided at the tip of a torch body, and a plasma arc is generated between the electrode and a material to be cut through the orifice of the nozzle. Yes. In this plasma torch, in order to form an atmosphere around the plasma arc, to enhance the cooling effect of the nozzle peripheral member, or to adjust the bevel angle with high accuracy, a secondary gas ( One that supplies an assist gas) is known. A conventional plasma torch for supplying a secondary gas has an inner retainer cap that is placed on the outside of the nozzle to hold the nozzle and provides a cooling water passage around the nozzle, and covers the nozzle tip to protect the nozzle tip. A shield cap and an outer retainer cap that covers the outside of the shield cap and holds the shield cap are provided, and an annular space between the inner retainer cap and the outer retainer cap serves as a passage for the secondary gas. In this configuration, when replacing the nozzle and electrode parts, it is necessary to remove the plurality of caps, which makes it difficult to replace parts. In order to solve this problem, conventionally, a plurality of caps integrated with each other has been proposed (Japanese Patent Laid-Open No. 9-285868).
[0003]
Regardless of whether a plurality of caps are integrated or not, in the conventional general plasma torch configuration, the space between the outer retainer cap and the inner retainer cap is a secondary gas passage, and the inner side of the inner retainer cap is arranged. Since the space (the space between the inner cap and the nozzle) is the cooling water passage, the outer retainer cap is separated from the cooling water passage by the secondary gas passage, and therefore the outer retainer cap is cooled by the secondary gas exclusively by air cooling. Is called. However, during cutting, the outer retainer cap is heated by the radiation of the plasma arc, but cooling of the outer retainer cap is insufficient only by air cooling with the secondary gas. There is a problem that the retainer cap cannot be touched, and it is not possible to enter the parts replacement work until the retainer cap is cooled.
[0004]
Therefore, conventionally, a device for increasing the flow rate of the secondary gas to enhance the cooling effect has been proposed (Japanese Patent Publication No. 2-504603). However, if an industrial gas such as nitrogen or oxygen is used as the secondary gas, there arises a problem that the running cost increases due to an increase in consumption. On the other hand, a structure in which the outer retainer cap is formed into a bag shape, cooling water is supplied thereto, and the outer retainer cap is cooled with water has been proposed (Japanese Patent Laid-Open No. 5-84579). However, the structure in which the outer retainer cap is water-cooled also has a plurality of caps, and there is a problem that disassembly and reassembly work at the time of parts replacement are troublesome.
[0005]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to eliminate the above-described problems of the prior art and increase the efficiency of the plasma torch component replacement work. That is, the object of the present invention is to eliminate the need to remove a plurality of caps when replacing the parts of the torch, and to allow the outer retainer cap to be cooled well during cutting so that the parts can be replaced immediately after cutting. There is in doing so.
[0006]
[Means for Solving the Problems]
A plasma torch according to a first aspect of the present invention comprises a nozzle arranged to cover an electrode with a plasma gas passage therebetween at the tip of a torch body, and a plasma arc between the electrode and a material to be cut through the nozzle orifice. And a cylindrical retainer cap that forms an outer shell of the torch, covers the outer periphery of the nozzle, holds the nozzle, and is detachably fixed to the torch body. An assist gas passage for guiding the assist gas supplied from the torch body to the vicinity of the plasma arc ejected from the orifice is provided inside the retainer cap wall or outside the retainer cap.
[0007]
According to the present invention, the retainer cap that holds the nozzle is formed with the assist gas passage that guides the assist gas supplied from the torch body to the vicinity of the plasma arc, so that the conventional assist gas passage is formed. Double retainer caps, inner retainer cap and outer retainer cap, are no longer necessary, and one retainer cap is sufficient. Therefore, it is not necessary to remove a plurality of caps when disassembling and reassembling at the time of component replacement, and work complexity is eliminated.
[0008]
A plasma torch according to a second aspect of the present invention comprises a nozzle arranged to cover an electrode with a plasma gas passage therebetween at the tip of the torch body, and a plasma arc between the electrode and the material to be cut through the nozzle orifice. A cylindrical retainer cap that forms the outer shell of the torch, covers the outer periphery of the nozzle, holds the nozzle and is detachably fixed to the torch body, and the inner periphery of the retainer cap And a space where the surface and the outer peripheral surface of the nozzle face. Then, cooling water is introduced into the space, so that the space functions as a cooling water passage for cooling the retainer cap and the nozzle at the same time.
[0009]
According to this invention, the retainer cap is also water-cooled together with the nozzle, so even if the retainer cap receives a large amount of radiant heat from the plasma arc during cutting, the heating of the retainer cap is suppressed, and thus consumable parts such as nozzles and electrodes. When it is necessary to replace the cap, the retainer cap can be removed by touching it immediately after the cutting is completed, and the replacement operation can be started immediately.
[0010]
In a preferred embodiment, a shield cap for protecting the nozzle tip is attached to the tip of the nozzle. The retainer cap holds the shield cap and the nozzle by locking the shield cap at the tip. With this configuration, the above-described cooling water passage can be formed in a space surrounded by the retainer cap, the shield cap, and the nozzle. Therefore, the three components of the retainer cap, the shield cap, and the nozzle are effectively cooled with water at once.
[0011]
The retainer cap of the plasma torch according to the third aspect of the present invention is a cylindrical part that constitutes the outer shell of the torch, covers the outer periphery of the nozzle in the torch, holds the nozzle, and is detachably fixed to the torch. An assist gas passage for guiding the assist gas to the vicinity of the plasma arc ejected from the nozzle is provided inside or outside the wall. Since the retainer cap itself has an assist gas passage, the nozzle can be held by this one retainer cap.
[0012]
In a preferred embodiment, the retainer cap is coupled to the torch body at the proximal end and supports the distal end of the nozzle at the distal end. The assist gas passage runs from the proximal end portion to the distal end portion of the retainer cap. Therefore, since this retainer cap guides the assist gas from the torch body to the tip of the nozzle, it is necessary to provide another extra part for providing an assist gas passage from the torch body to the tip of the nozzle. As a result, the torch component configuration is simplified and the torch can be easily downsized. In addition, the space inside the retainer cap can be used as a cooling water passage over a wide range from the base end portion to the tip end portion, and the cooling efficiency of the retainer cap is improved.
[0013]
The retainer cap of the plasma torch according to the fourth aspect of the present invention is a cylindrical part that constitutes the outer shell of the torch, covers the outer periphery of the nozzle in the torch, holds the nozzle, and is detachably fixed to the torch. The nozzle has an inner peripheral surface facing the outer peripheral surface of the nozzle, and a cooling water passage is formed between the inner peripheral surface and the nozzle outer peripheral surface, whereby the cooling water flowing through the cooling water passage is exposed together with the nozzle. The water is cooled.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a cross-sectional structure of a plasma torch according to an embodiment of the present invention. FIG. 2 shows an enlarged cross-sectional structure of the nozzle incorporated in the plasma torch and the tip of the retainer cap for holding the nozzle.
[0015]
In FIG. 1, reference numeral 1 denotes a torch body. The torch body 1 includes an inner sleeve 3 constituting a central member, an outer sleeve 5 fitted to the outer periphery of the inner sleeve 3, a holder 7 fitted to the outer periphery of the outer sleeve 5, and the inner sleeve 3 And a nozzle pedestal 9 fitted with a magnet ring 8 interposed therebetween. A bag-shaped electrode main body 13 is detachably fitted to the tip of the inner sleeve 3, and the tip of the electrode main body 13 that is a plasma arc generation point is made of a high melting point material that can withstand the high heat of the plasma arc. A heat resistant insert 14 (for example, hafnium, zirconium or alloys thereof in the case of oxygen plasma cutting) is provided. The consumption of the electrode occurs at the portion of the heat-resistant insert 14.
[0016]
A cylindrical guide 15 made of an insulating material is fitted to the outer periphery of the electrode body 13, and a cylindrical nozzle 17 tapered toward the tip is fitted to the outer periphery of the guide 15. The base end portion 17a of the nozzle 17 is pressed against the nozzle base 9 in a detachable state. A pilot arc current wiring (not shown) is connected to the nozzle base 9 of the torch main body 1 (this wiring is provided inside the torch main body and connected to a plasma arc power source (not shown)). When the base end portion of the nozzle 17 is pressed against the nozzle pedestal 9, the pressure contact surfaces of both become the current-carrying surfaces, and the nozzle 17 is electrically connected to the nozzle pedestal 9. In this way, a pilot arc current path for supplying current to the nozzle 17 at the time of pilot arc ignition is configured (in the past, a member constituting the outer shell of the torch body, for example, a retaining cap for holding the nozzle) Was used as the pilot arc current path, and the pilot arc current path to the nozzle was formed by the nozzle contacting the retaining cap. Furthermore, the elastic surface of the nozzle pedestal 9 is provided with several elastic electrical contact terminals 65. When the nozzle 17 is attached to the nozzle pedestal 9, the electrical contact terminal 65 bends and has a strong elastic force. The outer surface of the base end portion of the nozzle 17 is brought into contact with the nozzle 17. With this electrical contact terminal 65, the electrical connection between the nozzle 17 and the nozzle base 9 is more reliably ensured. At the tip of the nozzle 17, an orifice 18 having a sufficiently narrow diameter is formed to sufficiently squeeze the plasma arc and jet it forward.
[0017]
As shown in FIG. 2, an annular insulator 19 made of synthetic resin is fitted on the outer periphery of the tip 17 b of the nozzle 17. The outer periphery of the insulator 19 is, for example, sputtered or covered during piercing. A flanged shield cap 21 is fitted to prevent the nozzle 17 from being damaged due to the cutting material (work) 71 jumping up. The nozzle 17, the insulator 19, and the shield cap 21 are integrally formed, that is, fixedly coupled to each other, and are configured as a single part shown in FIG. 2 that is not separated by normal handling. Therefore, when the nozzle 17 is replaced, the nozzle 17, the insulator 19, and the shield cap 21 are replaced together.
[0018]
A retainer cap main body 23 for holding parts detachable from the torch main body 1 such as the nozzle 17, the guide 15, and the electrode main body 13 so as not to be detached from the torch main body 1 is put on the outside of these structures. The retainer cap body 23 has not only a role as a retainer but also a role as an outer shell of the torch. The outer periphery of the shield cap 21 is held by a hook 23 a formed at the tip of the liner cap body 23. In other words, the step 23 b on the base side of the hook 23 a is hooked on the flange 21 a of the shield cap 21 with the O-ring sandwiched, and the step 23 c on the tip side of the hook 23 a is hooked on the step 21 b of the shield cap 21. The rear end of the retainer cap body 23 covers the above-described members, extends to the holder 7 side of the torch body 1, and is connected to the holder 7 via a fixing ring 25.
[0019]
A plasma gas passage 31 is formed in the outer sleeve 5 so as to penetrate the outer sleeve 5. A plasma gas is introduced into the plasma gas passage 31 (for example, in the case of oxygen plasma cutting, it is composed of a mixed gas of 80 mol% oxygen and 20 mol% nitrogen). After passing through the plasma gas passage 31 of the outer sleeve 5, the plasma gas enters the plasma gas passage 33 that bends in a substantially U shape inside the nozzle base 9, and swirls (circumferentially in the radial direction) formed in the guide 15. A swirl flow is given through a plurality of through holes 35, which are slightly inclined in the direction and perforated in the guide 15, flow into the nozzle-electrode passage 37, is turned into plasma by the arc energy emitted from the heat-resistant insert 14, and swirls It becomes a plasma arc and is ejected to the outside through the orifice 18 of the nozzle 17.
[0020]
Further, the outer sleeve 5 is formed with a secondary gas passage 41 penetrating therethrough. The secondary gas passage 41 bends at a substantially right angle inside the outer sleeve 5 and communicates with an annular space 43 formed between the outer sleeve 5 and the retainer cap body 23. A secondary gas (for example, a mixed gas or air having an oxygen concentration lower than that of the plasma plasma gas in the case of oxygen plasma cutting) enters the annular space 43 through which the retainer cap body 23 and the secondary gas passage 41 are passed. It flows into a large number of secondary gas passages 45 surrounded by the secondary gas passage cover 24. The secondary gas passage 45 is formed, for example, in the outer periphery of the retainer cap body 23 with a groove 23b extending along the axial direction from the base end portion to the tip end portion, and the secondary gas passage 45b has a secondary gas passage. It is configured by covering the passage cover 24. As shown in an enlarged view in FIG. 2, the secondary gas that has passed through the secondary gas passage 45 is a through-hole that is formed in the inner wall of the distal end portion of the retainer cap body 23 so as to correspond to each secondary gas passage 45. 23c flows out into the annular space 47 formed between the retainer cap body 23 and the shield cap 21, and the secondary gas swirler formed in the shield cap 21 (so that the secondary gas is swung in the same direction as the plasma gas, A plurality of through holes 21c formed in the shield cap 21 with a slight inclination in the circumferential direction with respect to the radial direction) 21c enters the annular space 49 between the nozzle 17 and the shield cap 21 and enters the opening 21d of the shield cap 21. Erupts outside. As a result, a secondary gas curtain 82 rotating in the same direction is formed around the rotating plasma arc 81.
[0021]
The holder 7 of the torch body 1 is formed with a tertiary gas passage 51 penetrating through the inside thereof. The tertiary gas passage 51 communicates with an annular space 53 formed between the holder 7, the retainer cap body 23, and the fixing ring 25. A tertiary gas (for example, in the case of oxygen plasma cutting, a mixed gas or pure oxygen gas having a higher oxygen concentration than the secondary gas) enters the annular space 53 from which the retainer cap body 23 and It flows through a plurality of tertiary gas passages 55 surrounded by the tertiary gas passage cover 54. The tertiary gas passage 55 is formed, for example, on the outer periphery of the retainer cap body 23 by forming a concave groove 23d extending in the axial direction from the base end portion to the distal end portion, and covering the concave groove 23d with the tertiary gas passage cover 54. Configured.
[0022]
Then, the tertiary gas that has passed through the tertiary gas passage 55 is, as shown in an enlarged view in FIG. 2, a tertiary gas swirler (the tertiary gas in the same direction as the plasma gas and the secondary gas) formed at the tip of the retainer cap body 23. A swirling flow is given through a plurality of through holes 56 that are slightly inclined in the circumferential direction with respect to the radial direction so as to make a swivel and penetrate the distal end portion of the retainer cap body 23, and ejected so as to collide with the outer periphery of the shield cap 21. As a result, a tertiary gas curtain 83 is formed around the secondary gas 82.
[0023]
FIG. 3 is a front view of the retainer cap main body 23 as viewed from the front end side of the torch. As shown here, the secondary gas passage 45 and the tertiary gas passage 55 formed in the retainer cap main body 23 have a torch central axis. Are arranged alternately at substantially equal intervals in a radial pattern with the center at the center.
[0024]
These secondary gas passages 45 or tertiary gas passages 55 are not limited to those formed through the interior of the retainer cap body 23, and an external passage is routed to the outside of the retainer cap body 23, and the secondary passages are passed through the external passage. It is good also as a structure which guide | induces secondary gas or tertiary gas to the circumference | surroundings of a plasma arc. Further, although the secondary gas and the tertiary gas are swirl flows in the present embodiment, a radial air flow (not swirl flow) that is easy to manufacture a gas passage may be used at some sacrifice of the merit of the swirl flow.
[0025]
A cooling water passage 61 penetrating the inner sleeve 3 is formed in the inner sleeve 3. Cooling water is guided to the cooling water passage 61 from the outside of the torch body 1. After this cooling water enters the bag-shaped electrode body 13 and cools the tip of the electrode body 13, the pipe 61 a constituting the cooling water passage 61 and the inner periphery of the electrode body 13, as shown in FIG. The annular space in between flows backward, and flows out from the tip through a relay flow path in the outer sleeve 5 (not shown) to the cooling water passage 63 formed outside the nozzle 17.
[0026]
In addition to facing most of the outer peripheral surface of the nozzle 17, the flange 21 a of the shield cap 21 and most of the inner peripheral surface of the retainer cap body 23 face the cooling water passage 63 at the same time. The members 17, 21 and 23 are directly and forcibly cooled by the cooling water circulating in the cooling water passage 63. Since the highest temperature portion is in the vicinity of the tip of the nozzle 17, the insulator 19 and the shield cap 21 have the highest nozzle 17 as much as possible in design so that cooling water can be introduced to the vicinity of the tip. It is desirable to attach to the tip 17b.
[0027]
The cooling water exiting the cooling water passage 63 is discharged outside the torch body through a cooling water discharge passage in the outer sleeve 5 (not shown).
[0028]
The cooling water circulating through the cooling water passage 63 is sealed at the boundary between the parts surrounding the cooling water passage 63 by an O-ring inserted in the boundary. However, at the boundary between the nozzle 17, the insulator 19, and the shield cap 21 configured as an integral single component, the resin insulator 19 seals water as follows. That is, as shown in FIG. 2, an annular step 21e for holding the insulator 19 is provided on the inner periphery of the shield cap 21, and a ring-shaped protrusion 21f is formed on the surface of the step 21e. Has been. This protrusion 21 f bites into the lower surface of the insulator 19 and seals the boundary between the shield cap 21 and the insulator 19. Further, an annular step portion 17 c formed on the outer periphery of the nozzle 17 is fitted into an annular step portion 19 a existing on the inner periphery of the insulator 19. The cross section of the outer corner portion 17d of the step portion 17c of the nozzle 17 has a slightly sharp wedge shape, and the corner portion 17d bites into the inner corner portion of the step portion 19a of the insulator 19 so that the insulator 19 and the nozzle 17 Seal the border.
[0029]
In the above plasma torch, when the cutting of the workpiece 71 is started, first, a plasma gas having a predetermined flow rate and a predetermined pressure is caused to flow into the plasma gas passage 31, and the electrode body 13, the nozzle 17, and the workpiece 71 A high voltage is applied during this period. As described above, the energization path to the nozzle 17 at this time is a path from a plasma power source (not shown) to a nozzle 17 through a wiring (not shown) and the nozzle base 9.
[0030]
Due to the high voltage applied between the electrode body 13 and the nozzle 17, a pilot arc is formed between the electrode body 13 and the nozzle 17, and plasma gas is turned into plasma by the energy of the pilot arc and is ejected through the orifice 18 of the nozzle 17. . At the same time, the pilot arc is pushed away by the plasma gas flow, passes through the orifice 18, and is connected to the workpiece 71. At this time, energization to the nozzle 17 is turned off, a main plasma arc 81 is established between the electrode body 13 and the material 71 to be cut, and the cutting of the material 71 is performed by the main plasma arc 81. The
[0031]
While the material to be cut 71 is being cut, the electrode main body 13, the nozzle 17, the shield cap 21, and the retainer cap main body 23 are constantly exposed to high temperatures.
[0032]
In this embodiment, of course, the electrode body 13 is strongly cooled by direct water cooling, but in addition to that, most of the outer peripheral surface of the nozzle 17 faces the cooling water passage 63, and the shield cap 21 Since the flange 21a faces the cooling water passage 63, and most of the inner peripheral surface of the retainer cap body 23 also faces the cooling water passage 63, these members 17, 21, 23 are also directly and strongly strengthened by direct water cooling. To be cooled. Therefore, the nozzle 17, the shield cap 21, and the retainer cap body 23 can be sufficiently cooled.
[0033]
Since the shield cap 21 is maintained at a low temperature by direct water cooling, even if dross blows up during piercing and a high-temperature molten metal adheres to the shield cap 21, the shield cap 21 does not melt and is durable. Will improve. Moreover, since the opening 21d of the shield cap 21 does not melt, the uniformity of the gas flow of the secondary gas can be ensured, the cutting quality of the material 71 can be improved, and the material 71 having a thicker plate thickness. Piercing is possible.
[0034]
Further, most of the inner peripheral surface of the retainer cap body 23 is exposed to the cooling water and directly and strongly cooled with water. The retainer cap body 23 constitutes the outer shell of the torch, and since most of the outer peripheral surface thereof is exposed to the outside, it receives a large amount of radiant heat from the plasma arc, but the inner periphery on the back side of the externally exposed outer peripheral surface. Since most of the surface is directly and strongly water-cooled, the temperature rise of the retainer cap body 23 during cutting is effectively suppressed. Therefore, the retainer cap body 23 can be touched immediately after the end of cutting, and replacement work of consumable parts such as electrodes and nozzles can be started immediately after the end of cutting.
[0035]
In addition, since the three components of the nozzle 17, the shield cap 21 and the retainer cap main body 23 are cooled at the same time by one cooling water passage 63, each of them is dedicated to water-cooling the shield cap 21 and the retainer cap main body 23 as in the prior art. There is no need to provide a cooling water passage, and therefore the size of the torch can be designed to be smaller than in the prior art even at the same rated current.
[0036]
In addition, the electrode 13, the guide 15, the nozzle 17, the insulator 19, and the shield cap 21, which are replacement parts, are detachably connected to the torch body 1 through a fixing ring 25 by a single retainer cap body 23. . The reason that all the replacement parts can be held by the single retainer cap 23 is that the secondary gas and the tertiary gas (assist gas) supplied from the torch body 1 are guided to the vicinity of the plasma arc. Since the gas passage 45 and the tertiary gas passage 55 (assist gas passage) are formed inside (or outside) the wall of the retainer cap, the conventional double retainer cap structure of the inner retainer cap and the outer retainer cap is unnecessary. Because it became. By holding all the replacement parts with a single retainer cap in this way, when replacing the parts, the parts can be disassembled simply by removing the single retainer cap, and the replacement work is simplified.
[0037]
In the above configuration, the cooling water passage 63 is formed outside the nozzle 17, and the shield cap 21 that is electrically insulated from the nozzle 17 is fixed to the tip of the nozzle 17, so the current path of the pilot arc to the nozzle 17 is Thus, it is difficult to provide the nozzle 17 at the tip as in the prior art. Therefore, in this embodiment, a current path passing through the nozzle pedestal 9 is formed, and the nozzle 17 is electrically connected to the current path by pressing and contacting the base end portion 17a of the nozzle 17 against the nozzle pedestal 9. . Furthermore, the nozzle 17 can be easily and reliably connected to the current path by providing the nozzle base 9 with the electrical connection terminal 65 that contacts the nozzle 17 with a strong elastic force.
[0038]
As mentioned above, although this invention was demonstrated based on one Embodiment, it is clear that this invention is not limited to this.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a plasma torch according to the present invention.
FIG. 2 is an enlarged cross-sectional view of tip portions of a nozzle and a retainer cap.
FIG. 3 is a front view of the retainer cap body as viewed from the front end side of the torch.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Torch main body 3 Inner sleeve 5 Outer sleeve 7 Holder 9 Nozzle base 13 Electrode main body 15 Guide 17 Nozzle 18 Orifice 19 Insulator 21 Shield cap 21a Flange 23 Retainer cap main body 31,33 Plasma gas passage 41 Secondary gas passage 51 Tertiary gas passage 63 Cooling water passage

Claims (4)

In a plasma torch that includes a nozzle arranged to cover the electrode across the plasma gas passage at the tip of the torch body, and generates a plasma arc between the electrode and the material to be cut through the orifice of the nozzle,
A shield cap attached to the tip of the nozzle for protecting the tip of the nozzle;
It constitutes an outer shell of the torch, covering the outer periphery of the nozzle, and the cylindrical retainer cap for removably securing the shield cap and the nozzle in the torch body by holding the shield cap <br/> With
An assist gas passage that guides assist gas supplied from the torch body to the vicinity of a plasma arc that is ejected from the orifice inside the retainer cap wall or outside the retainer cap ;
A cooling water passage is formed outside the nozzle, and the nozzle, the shield cap, and the retainer cap face the cooling water passage, and the cooling water in the cooling water passage causes the nozzle, the shield cap, and the A plasma torch in which the retainer cap is cooled at the same time . The plasma torch according to claim 1, wherein the retainer cap includes a secondary gas passage and a tertiary gas passage as the assist gas passage, and the secondary gas passage and the tertiary gas passage are alternately arranged. In the cylindrical retainer cap that constitutes the outer shell of the torch of the plasma torch, covers the outer periphery of the nozzle in the torch, holds the nozzle and is detachably fixed to the torch.
An assist gas passage for guiding the assist gas to the vicinity of the plasma arc ejected from the nozzle is provided inside or outside the wall,
A shield cap that is coupled to the torch main body at the base end portion and is attached to the tip end portion of the nozzle at the tip end portion, thereby fixing the shield cap and the nozzle to the torch main body. And
An inner peripheral surface facing the outer peripheral surface of the nozzle is formed, and a cooling water passage facing the nozzle, the shield cap, and the retainer cap is formed between the inner peripheral surface and the outer peripheral surface of the nozzle. A retainer cap configured to cool the nozzle, the shield cap, and the retainer cap at the same time by the cooling water in the cooling water passage . The retainer cap according to claim 3, wherein the assist gas passage includes a secondary gas passage and a tertiary gas passage, and the secondary gas passage and the tertiary gas passage are alternately arranged.

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