JP2000326072A - Plasma torch, electrode for plasma torch and manufacture of the plasma torch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma torch with which a large cooling capacity can be exhibited with small size. SOLUTION: For a conducting tube 15 supplying cooling water to the inside of an electrode 3, its tip side part 15D is made thin. Along the tip side part 15D, a tip side part 3D surrounded by the nozzle 7 of an electrode 3, is made thin to match this. For a cooling water path 43 for sending cooling water to a nozzle 7 and a cooling water path 47 draining the cooling water after cooling the nozzle 7, their sectional shapes are the same, being short in the diametrical direction of a torch 1, long in the peripheral direction and flat. Consequently, while securing necessary cross-sectional area of the cooling water path, the diameter of the torch 1 becomes slender. A cooling water path 45 of the outer periphery of the nozzle comes into contact with a holding cap 13 as well, and the three parts which are the nozzle 7, the holding cap 13 and a nozzle protective cap 11 are cooled simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma torch used for plasma processing such as cutting or welding using a plasma arc, and more particularly to a structural improvement for reducing the size of the torch.

[0002]

2. Description of the Related Art The structure of a plasma torch is basically a combination of a plurality of cylindrical components, such as electrodes, nozzles, and nozzle protection caps, which are multiplexed and coaxial.
Between these cylindrical parts, there are a cooling water passage and passages for various gases such as working gas and assist gas.
The size of these components determines the overall size of the torch, and one of the biggest factors that determines it is the required cooling capacity. The higher the rated arc current of the torch, the greater the required cooling capacity and therefore the size. For example, in a torch with a small current of about 40 A, only the electrode can be water-cooled, and the nozzles and caps outside the nozzle can be air-cooled by an assist gas or the like, and the cooling water passage in the electrode can be narrow. On the other hand, for example, a torch with a large current of about 300 A not only has a large cooling water channel, but also has a cooling water channel in all of its components in order to water-cool not only the electrodes but also the nozzles and caps. In addition, the structure becomes complicated,
The size is large in each stage. A medium torch of, for example, about 120 A has an intermediate structure in which, for example, the electrode and the nozzle are water-cooled, and the caps are air-cooled, and has a medium size.

[0003]

The conventional plasma torch has its own structure depending on the required cooling capacity according to its rated current value, and the structure increases as the current value increases. It gets more complicated and bigger.

However, the smaller the size of the torch is, the easier the processing work, the easier the control of the torch movement, and the smaller the size of consumable nozzles and electrodes, the lower the manufacturing cost and the running cost. This is advantageous in various aspects such as a reduction in Therefore, there is a demand to further reduce the size of the large current torch. Further, it is advantageous that one kind of torch can be used for various current values for general purposes. For example, if a torch having a size comparable to a conventional medium current torch can be used not only for medium current but also for large current, it is advantageous in various aspects such as capital investment and maintenance. The biggest problem in meeting such demands is how to ensure high cooling capacity in small torches. In other words, the cooling capacity depends on the amount of cooling water, and when a large amount of cooling water flows, the cooling power is improved accordingly. An easy way to increase the amount of cooling water is to increase the discharge pressure of a pump for pumping the cooling water. However, since the resistance (pressure loss) of the water circuit is proportional to the square of the amount of water, a satisfactory increase in the amount of water cannot be expected even if the pump discharge pressure is slightly increased. For this reason, it is necessary to reduce the pressure loss of the water circuit from the viewpoint of the structure of the torch.

Accordingly, an object of the present invention is to provide a plasma torch capable of exhibiting a small pressure loss of a water circuit even with a small size and exhibiting a large cooling capacity, in order to meet the above-mentioned requirements.

[0006]

According to a first aspect of the present invention, there is provided a plasma torch having a substantially cylindrical electrode having a closed tip attached with a heat-resistant insert at which a plasma arc is generated, and a plasma torch having a closed tip. It has a nozzle with a nozzle orifice that surrounds the outside and ejects a plasma arc generated at the tip of the electrode, and a tip with a water outlet that emits cooling water.The water outlet reaches near the tip of the electrode And a water pipe inserted inside the electrode so as to perform the operation.
The water pipe has a distal portion extending a predetermined length from the water outlet, and a proximal portion located proximal to the distal portion. The thickness of the water pipe is smaller at the distal end than at the proximal end.

In this plasma torch, since the water pipe inserted into the electrode is thinner at the distal end than at the base end, the distal end of the electrode can be made thinner accordingly. Since various parts such as a nozzle are covered on the outer side of the tip of the electrode, the tip of the electrode can be made thinner, so that the entire torch can be made thinner and smaller.

[0008] In a preferred embodiment, the heat resistant insert in the electrode is exposed to the cooling water passage inside the electrode and is directly exposed to the cooling water. Thereby, the cooling efficiency of the heat-resistant insert is improved, so that it becomes easier to make the cooling water passage at the tip end side portion of the electrode thinner and to reduce the size.

A plasma torch according to a second aspect of the present invention comprises a substantially cylindrical electrode having a closed tip which is a point where a plasma arc is generated, a plasma surrounding the outside of the electrode, and a plasma generated at the tip of the electrode. A nozzle having a nozzle orifice for ejecting an arc and a tip having a water outlet for discharging cooling water, and a guide inserted inside the electrode so that the water outlet reaches near the tip of the electrode. A water pipe, a first cooling water passage formed inside the water pipe, guiding the cooling water to a water outlet of the water pipe, and formed between the water pipe and the electrode;
Second cooling water flowing from the water outlet flows along the inner peripheral surface of the electrode.
Cooling water passage. The cross-sectional areas of the first and second cooling water passages are substantially equal.

[0010] According to this plasma torch, the limited space inside the electrode is distributed to the first and second reciprocating cooling water passages, and the cooling water flows into the second cooling water passage after flowing through the first cooling water passage.
Through the cooling water channel. At this time, since the cross-sectional areas of the first and second cooling water passages are substantially equal, the resistance (pressure loss) of the cooling water passage connecting from the first to the second becomes minimum, and the maximum cooling water amount, that is, the maximum cooling water amount Ability is obtained.

A plasma torch according to a third aspect of the present invention is a plasma torch having a substantially cylindrical electrode having a closed tip serving as a plasma arc generating point, a plasma surrounding the outside of the electrode, and a plasma generated at the tip of the electrode. A nozzle having a nozzle orifice for emitting an arc, and a cooling water passage running in a direction off the center axis of the plasma torch and substantially parallel to the center axis, through which cooling water for cooling the nozzle passes.
The cross-sectional shape of the cooling water passage is a flat shape whose dimension in the circumferential direction around the torch center axis is longer than that in the radial direction.

According to this plasma torch, since the cooling water channel has a flat shape that is long in the circumferential direction instead of being short in the radial direction, it is possible to reduce the diameter of the torch while securing a necessary cross-sectional area of the cooling water channel. it can. In a preferred embodiment, the cross-sectional shape of the cooling water passage is a simple ellipse having a minor diameter in the radial direction or an ellipse curved along the circumference.

A plasma torch according to a third aspect of the present invention is a plasma torch having a substantially cylindrical electrode having a closed tip serving as a point where a plasma arc is generated, a plasma surrounding the outside of the electrode, and a plasma generated at the tip of the electrode. A nozzle having a nozzle orifice for emitting an arc, and a cooling water passage running in a direction off the center axis of the plasma torch and substantially parallel to the center axis of the torch, through which cooling water for cooling the nozzle passes. . The cooling water passage is divided into a plurality of sub passages.

[0014] Also in this torch, the diameter of the torch can be reduced while securing the necessary cross-sectional area of the cooling water channel. For the purpose of reducing the diameter of the torch, the plurality of sub-passages are preferably arranged in the circumferential direction.

A plasma torch according to a fourth aspect of the present invention is a plasma torch having a substantially cylindrical electrode having a closed tip serving as a point where a plasma arc is generated, a plasma surrounding the outside of the electrode, and a plasma generated at the tip of the electrode. A nozzle having a nozzle orifice for ejecting an arc, a cap surrounding the outside of the nozzle and functioning as an outer shell of the plasma torch, and a nozzle formed between the outer peripheral surface of the nozzle and the inner peripheral surface of the cap. A cooling water passage for simultaneous cooling and an assist gas (for example, a secondary gas or a tertiary gas) passage formed in the cap are provided.

In this torch, since the nozzle and the cap can be simultaneously cooled by the cooling water flowing through the same cooling water passage, there is no need to separately provide a cooling water passage for the nozzle and a cooling water passage for the cap. Can be

[0017] The plasma torch according to the present invention as described above can be made smaller than the conventional torch while maintaining the same cooling capacity as the conventional torch. In addition, the plasma torch according to the present invention has the same size as the conventional torch and can exhibit a larger cooling capacity, so that it can be used even with a larger current and is more versatile. In addition, the durability of the electrodes and nozzles is improved due to the larger cooling capacity. Furthermore, even when the cooling water is supplied with the same amount of water, the pressure loss of the water circuit can be reduced according to the present invention, so that the discharge pressure of the water pump can be set low, and the durability of the water pump is improved. (In general, the durability of a water pump decreases as the discharge pressure increases.)

A plasma torch electrode according to a fifth aspect of the present invention has a cylindrical electrode body having a closed distal end and a cooling water passage inside, and is embedded in the distal end of the electrode main body and has a front surface thereof. A heat-resistant insert that provides an arc generating point, wherein the heat-resistant insert is metallurgically coupled to the electrode body, and a back surface of the heat-resistant insert is exposed to a cooling water passage inside the electrode body.

In this electrode for a plasma torch, the back surface of the heat-resistant insert is exposed to the cooling water passage and directly cooled with water, so that the cooling efficiency is high. In addition, since the heat-resistant insert is metallurgically bonded to the electrode body by brazing or the like, the mechanical, electrical, and thermal connection between the heat-resistant insert and the electrode body is extremely good. For example, the depth of the heat-resistant insert embedded in the electrode can be reduced compared to the case where the heat-resistant insert is embedded in the electrode body by a method such as press fitting (that is, the length of the heat-resistant insert may be short). As a result, the heat-resistant insert can be made sufficiently short so that its water-cooled back surface can be close to the arc generation point on the front surface, and therefore, excellent cooling ability can be exhibited. Furthermore, the life of the electrode is long due to the high cooling capacity.

In a preferred embodiment, the rear surface of the heat-resistant insert has a bulging shape in order to increase the contact area with the cooling water.

According to a sixth aspect of the present invention, there is provided a method for manufacturing an electrode for a plasma torch, comprising the steps of: preparing a cylindrical electrode body having a closed end and having a cooling water passage inside; Embedding the heat-resistant insert at the tip, metallurgically joining the electrode body and the heat-resistant insert, and cutting off the portion of the electrode with the heat-resistant insert embedded facing the cooling water passage, thereby forming the heat-resistant insert. Exposing the back surface to the cooling water passage.

According to this manufacturing method, an electrode for a plasma torch having the above-described novel structure can be manufactured.

In a preferred embodiment, the following method is used for metallurgically joining the electrode body and the heat-resistant insert. First, the brazing material piece and the heat-resistant insert are inserted into the concave portion formed on the front side of the front end portion of the electrode body such that the brazing material piece is located deeper. Next, by heating the electrode body in a state where the brazing material piece and the heat-resistant insert are inserted into the recess, the brazing material piece is melted, and at the same time, the wax material melted in the recess is pressed by pushing the heat-resistant insert into the recess. Around the heat-resistant insert. Next, the electrode body is cooled in a state in which the wax material melted in the concave portion has wrapped around the heat-resistant insert, thereby completing the brazing between the outer surface of the heat-resistant insert and the inner surface of the concave portion.

This brazing method is simple and has high production efficiency, so that the manufacturing cost of the electrode can be reduced. Therefore, an electrode having a high cooling capacity and a long life can be manufactured at low cost.

[0025]

FIG. 1 shows a cross section along a central axis of a cutting plasma torch according to an embodiment of the present invention.

The plasma torch 1 is fixed to a torch moving mechanism (not shown) (hereinafter referred to as "torch main body").
) And a portion detachably attached to the torch body. The detachable parts are the electrode 3, the insulating cylinder 5, the nozzle 7, the insulating ring 9, the nozzle protection cap 11, and the holding cap 13 in order from the torch axis to the outside. Be exchanged.

A water pipe 15 having a circular cross section for introducing cooling water into the inside of the electrode 3 is arranged at the center axis position of the torch 1. A cylindrical inner sleeve 17 is fitted around the outer periphery of the base end portion of the water pipe 15 in a coaxial positional relationship therewith. The proximal end of the cylindrical electrode 3 is fitted inside the distal end of the inner sleeve 17. The electrode 3 has a closed distal end 3A, and a heat-resistant insert 4 made of hafnium or the like is attached to a central portion of the distal end 3A where an arc is generated. The back surface of the heat-resistant insert 4 is exposed to a space through which the cooling water flows inside the electrode 3.

The water pipe 15 projects forward from the front end face of the inner sleeve 17 and penetrates deep into the inside of the electrode 3. The water outlet 15 A of the water pipe 15 is located just behind the heat-resistant insert 4 at the front end 3 A of the electrode 3. Has reached. Focusing on the diameter of the water guide tube 15, the water guide tube 15 has a thick large-diameter portion 15B in the inner sleeve 17, and a thin small-diameter portion 15D extending a predetermined length from the water outlet 15A at the distal end in the electrode 3. , A tapered portion 15C connecting the large diameter portion 15B and the small diameter portion 15D. In accordance with such a change in the thickness of the water pipe 15, the thickness of the electrode 3 also changes. That is, the electrode 3 is thick at the base end portion 3B where the large-diameter portion 15B of the water pipe is contained, the inner diameter is tapered at the portion 3C where the tapered portion 15C of the water conduit is contained, and the small-diameter portion 15D of the water conduit is formed. Is thin at the tip side portion 3D that contains. And the thin tip side portion 3 of the electrode 3
The nozzle 7 is put on the outside of D. Therefore, the thin distal end portion 3D of the electrode 3 contributes to reducing the overall thickness of the torch 1. For this reason, the small diameter portion 1 of the water pipe 15
The outer diameter of 5D is preferably as narrow as possible, while the inner diameter of the water pipe 15 (that is, the cross-sectional area of the cooling water passage 19) is desirably free from a large difference between the small diameter portion 15D and the large diameter portion 15B. In order to satisfy this requirement, the thickness of the wall of the water guide pipe 15 is made thinner in the small diameter part 15D than in the large diameter part 15.

The water pipe 15 has a cooling water passage 19 therein.
Having. A cooling water passage 21 is formed between the inner peripheral surface of the electrode 3 and the outer peripheral surface of the water pipe 15. A cooling water passage 23 is formed between the inner peripheral surface of the inner sleeve 17 and the outer peripheral surface of the water pipe 15. A cooling water passage 25 is formed through the peripheral wall of the inner sleeve 17. These cooling water passages 19, 21, 23, 25 communicate in this order. The cooling water passages 19 and 21 in the electrode 3 are designed to have substantially the same cross-sectional area, so that the resistance (pressure loss) of the reciprocating cooling water passages 19 and 21 allocating the limited space inside the electrode is reduced. Be minimized. The cooling water passages 23 and 25 downstream thereof are designed to have the largest possible cross-sectional area as far as structurally possible in order to minimize the pressure loss.

A ring magnet 27 for rotating the arc generating point of the heat-resistant insert 4 of the electrode 3 is fitted around the outer periphery of the tip of the inner sleeve 17. On the outer periphery of the base end portion of the inner sleeve 17,
A cylindrical outer sleeve 29 is fitted. A short cylindrical nozzle pedestal 31 is fixed to the distal end of the outer sleeve 29, and a substantially conical cylindrical nozzle 7 tapered toward the distal end is attached to the distal end of the nozzle pedestal 31. The nozzle 7 has a coaxial positional relationship with the electrode 3 and covers the outside of the above-described thin portion 3D of the electrode 3, and narrows the plasma arc to the center axis position of the nozzle tip portion in front of the heat-resistant insert 4. It has a nozzle orifice 7A for jetting forward.

Between the nozzle 7 and the electrode 3, a cylindrical insulating tube 5 for electrically insulating the two is fitted. A working gas passage 33 is formed between the nozzle 7 and the insulating cylinder 5, and a working gas supply passage (not shown) that passes through the outer sleeve 29 and the inside of the nozzle base 31 is formed in the working gas passage 33. ) Flows into the working gas. A working gas passage 35 communicating with the nozzle orifice 7A is formed between the nozzle 7 and the tip 3A of the electrode 3. The insulating cylinder 5 is provided with a plurality of operating holes formed at regular intervals in the circumferential direction and slightly inclined in the circumferential direction with respect to the radial direction so as to communicate the working gas passage 33 and the working gas passage 35. It has a gas swirler hole 5A. The working gas enters the working gas swirler hole 5A from the working gas passage 33, and is ejected to the working gas passage 35 as a swirling flow from the working gas swirler hole 5A. The working gas swirl flows through the working gas passage 35, is turned into plasma by the energy of the arc in front of the heat-resistant insert 4, and is ejected from the nozzle orifice 7A as a plasma swirl.

A short cylindrical nozzle protection cap 11 for protecting the nozzle 7 from a work (not shown) or molten metal blown from the work is placed on the tip of the nozzle 7. Between the nozzle 7 and the nozzle protection cap 11, an insulating ring 9 that electrically insulates both is fitted. Outside the structure, a cylindrical holding cap 13 tapered toward the tip is covered. A cylindrical fixing ring 37 is fitted on the outer periphery of the base end of the outer sleeve 29, and a cylindrical rotating ring 39 is fitted on the outer periphery of the fixing ring 37. Retaining ring 3
7 is engaged with the internal thread 39A on the inner periphery of the rotating ring 39, whereby the rotating ring 3 is rotated.
Numeral 9 is rotatable about the torch center axis, and advances and retreats in a direction parallel to the torch center axis with the rotation. Then, in a state where the annular claw 19B at the distal end of the rotating ring 19 and the flange 13A on the outer periphery of the base end of the holding cap 13 are engaged, the rotating ring 19 is rotated to the most retracted position, whereby The rotating ring 19 attracts and fixes the holding cap 13 to the torch main body.
An annular claw 13B at the tip of the holding cap 13
Is the flange 1 at the base end of the nozzle protection cap 11
1A, thereby retaining the cap 13
However, a set of the nozzle protection cap 11, the insulating ring 9, the nozzle 7, the insulating cylinder 5, and the electrode 3 is attracted to the torch body and fixed. The holding cap 13 has a function as an outer shell of the torch 1 at a tip side portion of the torch 1 in addition to the function of holding the various internal parts.

The outer sleeve 29 has a cooling water passage 41 running in the radial direction, a cooling water passage 43 running in a direction parallel to the torch center axis, and a cooling water passage 43 separated from the cooling water passage 43 and also parallel to the torch center axis. And another cooling water passage 47 running in the direction. A cooling water passage 45 surrounding the outside of the nozzle 7 is formed between the outer peripheral surface of the nozzle 7, the inner peripheral surface of the holding cap 13, and the base end surface of the nozzle protection cap 11. Cooling water passage 25 in inner sleeve 17
And cooling water passages 41 and 43 in the outer sleeve 29.
The cooling water passage 45 surrounding the nozzle 3 and another cooling water passage 47 in the outer sleeve 29 are connected in this order. The cooling water passage 47 communicates with a cooling water discharge passage (not shown). Each of the cooling water passages 41, 43, and 47 in the outer sleeve 29 is designed to have a maximum cross-sectional area within a structurally possible range in order to minimize pressure loss due to the cooling water.

As shown by the arrows, the cooling water first exits the water outlet 15A through the cooling water passage 19 in the water pipe 15, and the highest temperature heat-resistant insert 4 of the tip 3A of the electrode 3
And heat-resistant insert 4 is cooled. The heat-resistant insert 4 is directly exposed to the cooling water to be effectively cooled. The front surface of the heat-resistant insert 4 is flat, but the rear surface has a curved shape that is high at the center and low at the periphery as shown in the figure, thereby securing a large area of the rear surface, that is, a contact area with the cooling water. Have been. The curved shape also has a function of smoothly turning the cooling water flowing out of the water outlet 15 </ b> A and guiding it to the cooling water passage 21. One or two or more slits 1 are provided around the water outlet 15A of the water guide pipe 15.
5E is provided. A part of the cooling water flowing through the cooling water passage 19, without touching the heat-resistant insert 4, enters the cooling water passage 21 through the slit 15 </ b> E and effectively contributes to the cooling of the nozzle 7. The cooling water guided to the cooling water passage 21 cools the electrode 3 while flowing through the cooling water passage 21 along the inner peripheral surface of the electrode 3, and then passes through the cooling water passages 23, 25, 41, and 53 in order. Nozzle 7
Into a cooling water passage 45 surrounding the cooling water passage. The cooling water entering the cooling water passage 45 is supplied to the nozzle 7 while flowing through the cooling water passage 45.
Is cooled, and the nozzle protection cap 11 and the holding cap 13 are also cooled. In this way, all the parts around the nozzle that need to be cooled, such as the nozzle 7, the nozzle protection cap 11, and the holding cap 13, are exposed in one and the same cooling water channel 45, and are simultaneously cooled by the cooling water flowing therethrough. Minimizes the number of cooling channels required (especially,
This eliminates the need to provide a cooling water passage in the holding cap or the like), thereby contributing to downsizing of the torch. The cooling water passing through the cooling water passage 45 is discharged to the outside of the torch 1 through the cooling water passage 47.

An annular secondary gas passage 51 is formed between the base end of the holding cap 13 and the outer sleeve 29. In addition, a large number of grooves 13C running from the base end to the distal end of the holding cap 13 are formed on the outer peripheral surface of the holding cap 13 at regular intervals in the circumferential direction, and the outer opening of each groove 13C is elongated. The cover 1D is completely covered with the cover 13D.
The space in the groove 13 </ b> C covered with 3D serves as a secondary gas passage 53. At the base end of each of the plurality of secondary gas passages 53 in the holding cap 13, the holding cap 13 and the outer sleeve are formed through a plurality of secondary gas introduction holes 13 </ b> E formed at the base end of the holding cap 13. It communicates with an annular secondary gas passage 51 between 29. Further, each of the plurality of secondary gas passages 51 in the holding cap 13 is connected to the holding cap 13 and the nozzle protection nozzle 13F at a tip thereof through a number of secondary gas ejection holes 13F formed at the tip of the holding cap 13. It communicates with an annular secondary gas passage 55 formed between the cap and the cap 11. This annular secondary gas passage 5
Reference numeral 5 denotes a plurality of secondary gas swirler holes 11C formed in the nozzle protection cap 11 at regular intervals in the circumferential direction and slightly inclined in the circumferential direction with respect to the radial direction.
The secondary gas swirler holes 11C communicate with a secondary gas passage 57 formed between the nozzle protection cap 11 and the tip of the nozzle 7, and the secondary gas passage 57 is formed at the tip of the nozzle protection cap 11. The formed secondary gas outlet 11B having a larger diameter than the nozzle orifice 7A communicates with the formed secondary gas outlet 11B.

The secondary gas flows from a secondary gas supply passage (not shown) formed in the outer sleeve 29 into the secondary gas passage 51, and subsequently, a large number of secondary gas passages 53 in the holding cap 13. To the secondary gas passage 55 between the tip of the holding cap 13 and the nozzle protection cap 11, and further, through a plurality of secondary gas swirler holes 11C penetrating the nozzle protection cap 11 from outside to inside, and swirling. Secondary gas passage 5 inside the nozzle protection cap 11
Squirt into 7. This secondary gas swirl flow is applied to the secondary gas passage 57.
Through the secondary gas ejection port 11B and around the plasma arc ejected from the nozzle orifice 7A. 2
The swirling direction of the secondary gas swirl flow created by the next gas swirler hole 11C is the same as the swirling direction of the plasma arc (working gas) swirl flow created by the working gas swirler hole 5A.

A tertiary gas passage 61 for supplying a tertiary gas is formed in the fixing ring 37. The tertiary gas passage 61 communicates with an annular tertiary gas passage 63 formed between the fixed ring 37 and the rotating ring 39. The holding cap 13 also has, in addition to the secondary gas passage 53 described above, a number of tertiary gas passages 65 similarly running from the base end to the tip end, each of which is formed by a groove 13G and a lid 13H. The tertiary gas passages 6 and the secondary gas passages 53 are arranged alternately. At the base end of the plurality of tertiary gas passages 65, an annular 3 between the fixing ring 37 and the rotating ring 39 is formed through a number of secondary gas introduction holes 13I formed at the base end of the holding cap 13. It communicates with the next gas passage 63. In addition, a large number of the tertiary gas passages 65 are formed at the tip thereof by a large number of
It communicates with the next gas swirler hole 13J. These tertiary gas swirler holes 13J are also inclined at a constant interval in the circumferential direction and at a slight angle in the circumferential direction with respect to the radial direction so that the tertiary gas swirls in the same direction as the secondary gas. The protective cap 11 is open to an annular tertiary gas passage 67 surrounding the distal end.

The tertiary gas is supplied from the tertiary gas passage 61 in the stationary ring 37 to the third gas between the stationary ring 37 and the rotating ring 39.
Flows into the secondary gas passage 63, and subsequently passes through a number of tertiary gas passages 65 in the retaining cap 13, and
It reaches the tertiary gas swirler hole 13J at the three leading ends, and forms a swirl flow from the tertiary gas swirler hole 13J and jets out around the secondary gas swirl flow.

As described above, since the secondary gas passage 53 and the tertiary gas passage 65 are formed inside the holding cap 13, the secondary gas and the tertiary gas are interposed between the holding cap 13 and the nozzle 7. There is no need to provide a passage. Due to this, the entire space between the nozzle 7 and the holding cap 13 can be used as the cooling water passage 45, and as a result, as described above, the nozzle 7 and the holding cap 13 and the nozzle protection cap 11 can be cooled at the same time, and there is an advantage that an unnecessary cooling water channel is unnecessary and the size can be reduced.

FIG. 2 is a cross-sectional view of the plasma torch 1 taken along the line AA in FIG. 1 (parts outside the outer sleeve 29 are not shown).

As shown in FIG. 2, the outer sleeve 29
Cooling water passages 43 and 47 running parallel to the torch central axis
Has a flat oblong shape that is long in the circumferential direction and short in the radial direction. Since the cross-sectional shape of the cooling water passages 43 and 47 is a flat shape that is short in the radial direction as described above, compared with a conventional torch having a cooling water passage whose cross section is a perfect circle,
The thickness of the torch can be made smaller while ensuring the necessary and sufficient cross-sectional area of the cooling water passage. In the example shown in FIG. 2, the cross-sectional shape of the cooling water passages 43 and 47 is an elliptical shape curved in an arc shape in accordance with the circumference. It may be oval or rectangular.

Further, the one cooling water passage 43 or 4
7 may be divided into a plurality of sub-passages and the plurality of sub-passages may be arranged in the circumferential direction instead of having a flat cross-sectional shape as described above. In this case, the diameter of each sub-passage is smaller than the one cooling water passage 43 or 77 described above, but the total cross-sectional area of the plurality of sub-passages is substantially equal to the one cooling water passage 43 or 77 described above. So that Since the narrow sub-passages are arranged in the circumferential direction, the torch can be made thin similarly to the case where one cooling water passage having a flat cross section is used. As described above, the method of distributing the cooling water passage which is originally one to a plurality of narrow sub-passages is based on the fact that one cooling water passage having a sufficiently large cross-sectional area due to the arrangement with the gas passage and other parts is required. It is effective when it is difficult to secure.

The reference numerals 71 and 73 in FIG.
1 indicates a working gas supply path not shown in FIG. 1, and reference numerals 75 and 77 indicate secondary gas supply paths not shown in FIG. The gas supply passages 71 to 75 are provided with cooling water passages 43,
Since it does not require a large cross-sectional area as compared with 47, the cross-sectional shape may be a perfect circle as shown in the figure, but of course,
As in the case of the cooling water channel, the cross section may be flat or divided into a plurality of narrower sub-passages.

FIGS. 3 and 4 show an example of a process for manufacturing an electrode used in the torch 1 shown in FIG.

As shown in FIG. 3A, a cylindrical electrode body 81 made of, for example, copper or an alloy containing copper as a main component is prepared, and a cylindrical concave portion 8 for inserting a heat-resistant insert at the tip thereof.
As shown in FIG. 3 (B), first, a small piece 83 of a wax material, for example, silver wax is put into 1A, and then a heat-resistant insert 85 made of, for example, hafnium or zirconium having a cylindrical shape slightly smaller in diameter than the concave portion 81. Insert Next, the electrode body 81 prepared as described above is held in a posture in which the tip is directed upward, and a weight 87 is placed on the heat-resistant insert 85 as shown in FIG. Vacuum furnace or inert gas furnace 89
And heated at a temperature suitable for brazing with silver wax 83 for a predetermined time. Then, the silver wax 83 in the concave portion 81A of the electrode main body 81 melts, and accordingly, the heat-resistant insert 85 sinks deeper in the concave portion 81A by the load of the weight 87,
Due to the pressure, surface tension, and the like, the molten silver wax 83 wraps around the heat-resistant insert 85.

After that, the heat-resistant insert 85 is completely buried in the concave portion 81A of the electrode main body 81 as shown in FIG.
The outer surface of the heat-resistant insert 85 is brazed to the inner surface of the concave portion 81A by the silver wax 83 (that is, the heat-resistant insert 85 is metallurgically joined by diffusion bonding).

Next, as shown in FIG. 4B, the tip of the electrode body 81 and the heat-resistant insert 85 embedded therein are formed.
Is flattened by cutting or polishing. Furthermore,
Tip of electrode body 81 and back 85 of heat-resistant insert 85
Is removed by cutting, and the rear surface 85 of the heat-resistant insert 85 is removed.
A is exposed to the space (cooling water passage) inside the electrode 81.

The heat-resistant insert 85 after cutting has a back surface 85A which is inflated as shown in the figure in order to increase the contact area with the cooling water. In addition, in order to maximize the cooling effect, as shown in Fig. 3 (F), a water-cooled surface made by cutting (the back of the heat-resistant insert)
85A is as close as possible to the hottest arcing point 85B on the front of the heat-resistant insert 85.

Conventionally, an electrode structure in which a heat-resistant insert is exposed in a cooling water passage inside an electrode is known for an electrode in which the heat-resistant insert is press-fitted into an electrode body and mechanically connected thereto (Japanese Patent Laid-Open No. Sho 60-247491). No., JP-A-61-9279
No. 6) is not known for an electrode in which a heat-resistant insert is metallurgically bonded to an electrode body by brazing (diffusion bonding) or the like.
When the heat-resistant insert is press-fitted into the electrode body, the depth of the joining surface (cylindrical surface) between the electrode body and the heat-resistant insert (that is, insertion of the heat-resistant insert, in order to secure mechanical bonding strength and water sealing properties) Depth) is quite necessary,
Usually, at least three times the diameter of the heat resistant insert is required.
Therefore, even if the back surface of the heat-resistant insert is exposed to the cooling water channel, the cooling effect is not so high because the cooling surface and the arc generating point are far apart. In contrast, FIG.
In addition, in the electrode manufactured by the method of FIG. 4, since the heat-resistant insert is brazed to the electrode body, the insertion depth of the heat-resistant insert does not need to be so long, so that the cooling surface is brought sufficiently close to the arc generating point. Therefore, it is possible to obtain a much higher cooling effect than the conventional one.

On the other hand, there is no conventional electrode in which the heat-resistant insert is soldered to the electrode body, in which the heat-resistant insert is exposed to the cooling water passage in the electrode. The reason for this is that the brazing work of the heat-resistant insert takes a considerable amount of time, and in addition to that, cutting to expose the heat-resistant insert to the cooling water passage in the electrode increases the manufacturing cost. Can be On the other hand, according to the manufacturing method shown in FIGS. 3 and 4, a very simple method of simply putting a small piece of brazing material and a heat-resistant insert into the recess of the electrode body, placing a weight thereon, and putting the weight into the furnace. Can be brazed. Moreover,
Batch processing in which a large number of electrodes are brazed all at once by one in-furnace processing is possible. Therefore, even if a cutting step for exposing the heat-resistant insert is performed thereafter, high production efficiency can be obtained, and the production cost can be suppressed to some extent.

As described above, according to the manufacturing method shown in FIGS. 3 and 4, it is possible to manufacture an electrode having a higher cooling capacity than the conventional one at a low cost. In addition, the high cooling capacity extends the life of the electrodes, reduces the frequency of electrode replacement, and reduces running costs.

The embodiment of the present invention has been described above.
These embodiments are merely examples for describing the present invention, and are not intended to limit the present invention only to these embodiments. Therefore, the present invention can be implemented in various modes other than the above-described embodiment without departing from the gist thereof.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view taken along a central axis of a cutting plasma torch according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the plasma torch 1 taken along the line AA of FIG. 1 (parts outside the outer sleeve 29 are not shown).

FIG. 3 is a sectional view showing a first half of a manufacturing process of the electrode shown in FIG. 1;

FIG. 4 is a sectional view showing the latter half of the manufacturing process of the electrode shown in FIG. 1;

[Description of Signs] 1 Plasma torch 3 Electrode 4 Heat resistant insert 3D Thin part of electrode 5 Insulation cylinder 7 Nozzle 9 Insulation ring 11 Nozzle protection cap 13 Holding cap 15 Water pipe 15B Large diameter part of water pipe 15C Tapered part of water pipe 15D Small diameter portion of water pipe 17 Inner sleeve 19, 21, 23, 25, 41, 43, 45, 47 Cooling water passage 29 Outer sleeve 53 Secondary gas passage in holding cap 65 Tertiary gas passage in holding cap

Claims (13)

[Claims] 1. A plasma torch for ejecting a plasma arc, comprising: a substantially cylindrical electrode having a closed tip with a heat-resistant insert serving as a point where the plasma arc is generated; A nozzle having a nozzle orifice for ejecting a plasma arc generated at the tip of the electrode; and a tip having a water outlet for discharging cooling water, such that the water outlet reaches near the tip of the electrode. A water conduit inserted inside the electrode, wherein the water conduit has a distal portion extending a predetermined length from the water outlet, and a proximal portion located more proximal than the distal portion. A plasma torch having a thickness of the water guide tube smaller at the distal end portion than at the base end portion. 2. The electrode according to claim 1, wherein the electrode has a distal end portion into which a distal end portion of the water pipe is inserted, and a proximal end portion located proximal to a portion near the distal end. 2. The plasma torch according to claim 1, wherein a thickness of the front end portion is smaller than that of the base end portion. 3. The plasma torch according to claim 2, wherein a distal portion of the electrode is surrounded by the nozzle, and a proximal portion of the electrode extends out of the nozzle. 4. The plasma torch of claim 1, wherein said heat resistant insert is directly exposed to cooling water inside said electrode. 5. A plasma torch for ejecting a plasma arc, comprising: a substantially cylindrical electrode having a closed tip serving as a point where the plasma arc is generated; and an electrode surrounding the electrode and being generated at the tip of the electrode. A nozzle having a nozzle orifice for ejecting the formed plasma arc, and a tip having a water outlet for discharging cooling water, inserted into the electrode so that the water outlet reaches near the tip of the electrode. A first cooling water passage formed inside the water guiding pipe and guiding cooling water to a water outlet of the water guiding pipe; and a water cooling pipe formed between the water guiding pipe and the electrode; A plasma torch, comprising: a second cooling water passage through which cooling water flowing from an outlet flows along an inner peripheral surface of the electrode, wherein the first and second cooling water passages have substantially the same cross-sectional area. 6. A plasma torch for jetting a plasma arc, comprising: a substantially cylindrical electrode having a closed tip portion serving as a point where the plasma arc is generated; and an outer electrode surrounding the electrode and being generated at the tip portion of the electrode. A nozzle having a nozzle orifice for ejecting a formed plasma arc, and a cooling water passage through which cooling water for cooling the nozzle runs in a direction off the center axis of the plasma torch and in a direction substantially parallel to the center axis. The plasma torch wherein the cross-sectional shape of the cooling water passage is a flat shape in which a dimension in a circumferential direction around the central axis is longer than a dimension in a radial direction. 7. The plasma torch according to claim 6, wherein the cross-sectional shape of the cooling water passage is a simple ellipse having a minor diameter in the direction of the radius or an ellipse curved along the circumference. 8. A plasma torch for ejecting a plasma arc, comprising: a substantially cylindrical electrode having a closed tip serving as a point where the plasma arc is generated; and an electrode surrounding the electrode and being generated at the tip of the electrode. A nozzle having a nozzle orifice for ejecting a formed plasma arc, and a cooling water passage through which cooling water for cooling the nozzle runs in a direction off the center axis of the plasma torch and in a direction substantially parallel to the center axis. Wherein the cooling water passage is divided into a plurality of sub passages. 9. A plasma torch for ejecting a plasma arc, comprising: a substantially cylindrical electrode having a closed tip serving as a point where the plasma arc is generated; and an electrode surrounding the outside of the electrode and being generated at the tip of the electrode. A nozzle having a nozzle orifice for ejecting a formed plasma arc, a cap surrounding the outside of the nozzle and functioning as an outer shell of the plasma torch, and formed between an outer peripheral surface of the nozzle and an inner peripheral surface of the cap. A plasma torch comprising: a cooling water passage for simultaneously cooling the nozzle and the cap; and an assist gas passage formed in the cap. 10. A cylindrical electrode body having a closed tip and having a cooling water passage inside, and a heat-resistant insert embedded in the tip of the electrode body and providing an arc generating point on a front surface thereof. An electrode for a plasma torch, comprising: the heat-resistant insert is metallurgically bonded to the electrode body; and a back surface of the heat-resistant insert is exposed to the cooling water passage inside the electrode body. 11. The electrode according to claim 10, wherein the back surface of the heat-resistant insert has a bulging shape. 12. A step of preparing a cylindrical electrode body having a closed tip and having a cooling water passage inside, burying a heat-resistant insert at the tip of the electrode body, and forming the electrode body and the heat-resistant insert. Metallurgically bonding, by cutting off a portion of the tip of the electrode in which the heat-resistant insert is embedded, which faces the cooling water passage,
Exposing a back surface of the heat-resistant insert to the cooling water passage. 13. The step of metallurgically joining the heat-resistant insert, wherein a recess formed on a front side of a tip end of the electrode body includes:
Inserting the brazing piece and the heat-resistant insert so that the brazing piece is located at a deeper position; and heating the electrode body in a state where the brazing piece and the heat-resistant insert are inserted into the recess. Simultaneously melting the brazing material pieces and pushing the heat-resistant insert into the interior of the recess, thereby causing the molten wax material in the recess to wrap around the heat-resistant insert; and 13. The step of cooling the electrode body in a state where the molten brazing material has wrapped around the heat-resistant insert, thereby completing the brazing between the outer surface of the heat-resistant insert and the inner surface of the concave portion. Production method.