JPH04249096A - Centering stone of plasma torch - Google Patents

Abstract

PURPOSE:To reduce the probability of misfiring of a pilot arc by furnishing No.1, No.2, and No.3 guide paths for gas, guiding the actuating gas to the top end face and the inner surfaces at the sides and in the lower part of a centering stone, and producing a convolutional gas stream. CONSTITUTION:A gas guide path 106 is provided opening at the top face and side face of a centering stone 10a, while another gas guide path 102 is furnished to guide downward the actuating gas which has passed the first named guide path 106 and been sent to the side face of the stone 10a. A circular opening 105 is provided, which is continued to a hole 103 for admitting penetration of a electrode rod 4 and opens at the bottom surface of stone 10a wider than this hole 103. A third gas guide path 107 is furnished, which penetrates the stone 10a in the tangential direction to the opening 105 and the side face of the stone 10a and which guides the actuating gas sent by the secondly named guide path 102 further to the opening 105. Thereby the actuating gas is turned into a convolutional gas stream around the electrode rod 4, which should reduce the probability of misfiring and prolong the lifetime of a plasma torch 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to plasma torches, and more particularly to the structure of a centering stone within a plasma torch.

0002

2. Description of the Related Art FIG. 4 shows the appearance of a conventional plasma torch 5 and a vertical cross-section of its tip. A centering stone 10 made of an insulated refractory is inserted into the insert chip 13, and a tungsten electrode rod 4 passes through a hole in the central axis of the centering stone 10. This centering stone 10 positions the tungsten electrode rod 4 at the central axis position of the insert chip 13.

[0003] The procedure for igniting the pilot arc is as follows:
First, a working gas (for example, Ar) is caused to flow between the tungsten rod 4 and the insert tip 13. Next, high frequency generator 1
5, the tungsten electrode rod 4 and the insert tip 1
High frequency voltage (3000~4000V, 1~2
MHz) is applied. Simultaneously with this application, a pilot current (DC 10 to 20 A) is applied between the tungsten electrode rod 4 and the insert tip 13 from the pilot arc power source
) is applied. A discharge (insulation breakdown) occurs from the tip of the tungsten electrode rod 4 due to high pressure and high frequency, and the working gas (A
r) is ionized, a pilot arc is generated by the pilot current, and the arc is emitted from the nozzle of the insert tip 13 due to the momentum (kinetic energy) of the working gas. By passing a plasma arc current between the tungsten electrode rod 4 and the workpiece 18 from the plasma arc power supply 17, an arc is generated between the tungsten electrode rod 4 and the workpiece 18, and the workpiece Plasma is ejected from the nozzle of the insert tip 13 toward the material 18.

Several conventional examples of centering stones 10 are shown in FIGS. 5, 6, and 7, respectively. In these drawings, (A) is a top view of the centering stone, (B) is a longitudinal sectional view, and (C) is a bottom view.

[0005]

[Problems to be Solved by the Invention] In order to ignite the pilot arc, as described above, a working gas is caused to flow between the tungsten electrode rod 4 and the insert tip 13, and the tungsten electrode rod 4 and the insert tip 13 At the same time, a high frequency voltage is applied between the tungsten electrode rod 4 and the insert.
Even if a voltage is applied to cause a pilot current to flow between the insert tip 13 and the centering stone 10, the arc will not reach the space 20 (
4), the arc may not come out from the nozzle of the insert chip 13 (mis-ignition). If this state continues, the insert tip 13, centering stone 10, and tungsten electrode rod 4 will overheat inside the torch 5, causing the centering stone 10 to melt and, in some cases, even the insert tip 13 to melt. There is.

The present invention aims to reduce the probability of misignition.

[0007]

[Means for Solving the Problem] Referring to FIG. 4, if there is stagnation of working gas in the space 20 near the lower end surface of the centering stone 10 during pilot arc ignition or plasma injection, Since the temperature of the working gas increases and it is in a state where it is easily ionized, discharge is likely to occur there. When electric discharge occurs, carbonization marks (
soot stains). When the pilot arc is ignited, a high-frequency electric field is usually concentrated at the tip (pointed lower end) of the tungsten electrode rod 4, causing discharge (dielectric breakdown) between that point and the nozzle edge of the insert tip 13. However, if there are carbonization marks, discharge along the marks (creeping discharge) is likely to occur.
In particular, as the tip of the tungsten electrode rod 4 wears out and becomes rounded, the electric field concentration there becomes weaker, and the electric field becomes weaker between the tungsten electrode rod 4 and the insert tip 13 along the carbonization marks on the lower end surface of the centering stone 10. Discharge (mis-ignition) is likely to occur. When welding, the flow rate of the working gas is as low as 0.2 to 1.0 liters/min, so when the pilot arc is ignited, if a leak arc occurs in a stagnant area within the torch, As a result, the pilot arc ignites incorrectly.

In the conventional centering stones shown in FIGS. 5, 6, and 7, the (
It was found that stagnation of the working gas occurred as shown by the two-dot chain line in C).

From the above considerations, in order to reduce mis-ignition of the pilot arc, it is necessary to prevent stagnation of the working gas and to remove the tungsten electrode rod 4/insert tip on the bottom surface of the centering stone. It is better to increase the creepage distance between 13 and 13.

Therefore, in the first invention of the present application, the centering stone (10a) is provided with a centering stone for blowing out the working gas supplied to the upper end surface of the centering stone (10a) to the side surface of the centering stone (10a). The first gas guide path (106) opens on the upper end surface side and the side surface of the stone (10a);
) second gas guide path (102) for guiding the working gas downward from the side surface; hole (103) through which the electrode rod (4) passes;
A circular opening (105) in the lower end surface of the centering stone (10a), which is continuous with the hole (103) and is wider than the hole (103);
A second gas guide path (102) opens on the side surface of the centering stone (10a) and the inner peripheral surface of the circular opening (105), and passes through the centering stone (10a) in the tangential direction of the circular opening (105). ) for guiding the working gas guided to the circular opening (105); a third gas guide path (107);

[0011] In the second invention, the centering stone (10b) has a circular opening (123) opened at its lower end surface and wider than the hole (122) through which the electrode rod (4) is passed; 10b) upper end surface and circular opening (123)
A first gas guide path (124) that opens to guide the working gas supplied to the upper end surface of the centering stone (10b) to the circular opening (123); and a hole (
The porous ceramic ring (125) has a central shaft portion (122) and is inserted into a circular opening (123).

In the third invention, a centering stone (10c) has a centering stone (10c) on its lower end surface with a radius R (R: a plurality of conical lower end openings (144) with a diameter R in the lower end surface, which are opened at a pitch equal to or less than the pitch shown in the cross-sectional view (B) of No. 1
A hole (14) for passing the electrode rod (4) is formed on the upper end surface of
A plurality of first gas guide passages (143) each having openings on a circumference centered at 2) and respectively connected to the plurality of lower end openings (144) are provided.

Note that symbols in parentheses indicate corresponding elements in the embodiments shown in the drawings and described later.

[0014]

[Operation] According to the first invention, the working gas passes through the first gas guide path (106) to the centering stone (10a).
), and moves downward through the second gas guide path (102), further through the third gas guide path (107), and into the circular opening (105), along the tangent to its inner peripheral surface. Blows out in the direction. The electrode rod (4) is located at the center of the circular opening (105), and the working gas blown into the circular opening (105) moves downward while going around the electrode rod (4). The insert moves in a spiral motion, and finally the insert
It is sprayed from the nozzle of the top tip (13). in this way,
Since the working gas circulates in the space (20) near the lower end face of the centering stone (10a), stagnation of the working gas does not substantially occur. As a result, the temperature of the working gas directly under the centering stone (10a) does not rise excessively, so that it is difficult to ionize. In other words, it is difficult to discharge. Therefore, since no carbonization marks are produced on the lower end surface of the centering stone (10a) due to discharge, the probability of mis-ignition of the pilot arc is reduced, and the service life of the plasma torch (5) is extended.

According to the second invention, the working gas supplied to the upper end surface of the centering stone (10b) passes through the first gas guide path (124) and enters the circular opening (123); Since there is a porous ceramic ring (125), the working gas passes through the holes of the ceramic ring (125) and exits into the space below the centering stone (10b). Since this working gas exits from every position on the exposed surface of the ceramic ring (125) in a fine stream at a substantially uniform velocity, there is virtually no partial stagnation of the working gas in the space below the centering stone (10b). It doesn't happen. As a result, the temperature of the working gas directly under the centering stone (10b) does not rise excessively, so that it is difficult to ionize. In other words, it is difficult to discharge. Furthermore, a ceramic ring (1
25) is porous, so the creeping distance of its exposed surface is much longer than that of a smooth flat surface, and creeping discharge is less likely to occur. Therefore, since no carbonization marks are produced on the lower end surface of the centering stone (10b) due to discharge, the probability of mis-ignition of the pilot arc is reduced, and the service life of the plasma torch (5) is extended.

According to the third invention, the working gas supplied to the upper end surface of the centering stone (10c) is
The gas passes through the gas guide path (143) and is blown out from the lower end opening (144) of the lower end surface of the centering stone (10c) into the space directly below the lower end surface. 10c) are formed on the circumference of the lower end surface around the hole (142) for passing the electrode rod (4) at a pitch of R or less, and each has a conical shape with a diameter R. Therefore, the working gas ejected from one lower end opening (144) below the lower end surface of the centering stone (10c) is directed in the circumferential direction and around the hole (142) for passing the electrode rod (4). As the circumference expands in the radial direction, and the opening edges of adjacent lower end openings (144) partially overlap, there is almost no area where the working gas stagnates in the space in the vicinity of the lower end surface of the centering stone (10c). This makes it difficult for discharge to occur in the space. Furthermore, the distance (creepage distance) from the electrode rod (4) to the insert tip (13) along the lower end surface of the centering stone (10c) is reduced by the pitch arrangement of the lower end opening (144) of R or less. is long, making creeping discharge less likely to occur. Therefore, since no carbonization marks are produced on the lower end surface of the centering stone (10c) due to discharge, the probability of mis-ignition of the pilot arc is reduced, and the service life of the plasma torch (5) is extended. Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0017]

[First Embodiment] FIG. 1 shows an embodiment of the first invention. This is the centering stone 1 of the working gas forced rotation type.
It is 0a. (A) in Fig. 1 shows the centering stone 10.
(B) is a cross-sectional view of the centering stone 10a shown in (A) taken along the line A1-A2, and (C) is a top view of the centering stone 10a shown in (B).
It is a sectional view taken along the A3-A4 line. A ceramic member with an alumina content of 99% is used for this stone 10a. The stone 10a is cylindrical,
It has a groove 121 in an arbitrary range from the bottom of the outer circumferential side surface, and further has a groove 102 in a part of the outer circumferential side surface (near the center). A through hole 103 for passing the tungsten electrode rod 4 of the plasma torch is provided in the central axis of the stone 10a in the direction in which the central axis extends.
03, each of the upper part 104 and the lower part 105 is a cylindrical hole having a larger diameter than the through hole. Also, a plurality of passages 106 passing through the inner surface of the upper hole 104 and the groove 102 on the outer peripheral surface of the stone, and a plurality of passages 107 passing through the inner surface of the lower hole 105 and the groove 102 on the outer peripheral surface of the stone.
There is. Note that the groove 10 on the inner surface and outer peripheral surface of the lower hole 105
Each of the plurality of passages 107 passing through the centering stone passes through the centering stone in a direction tangential to the outer peripheral surface.

FIG. 1D shows a conventional plasma torch 5.
2 shows the flow of working gas when the centering stone 10a is used. Working gas is injected from between the upper hole 104 and the tungsten electrode rod 4, passes through the passage 106, groove 102, and passage 107 of the centering stone, and is discharged between the lower hole 105 of the stone and the tungsten electrode rod 4. be done. At this time, the working gas passed through the plurality of lower passages 107 and was blown out into the circular opening around the tungsten electrode rod 4.
It moves downward while going around the electrode rod 4, that is, the electrode rod 4
Finally, the insert tip 13
It is sprayed from the nozzle. In this way, since the working gas circulates in the space near the lower end surface of the centering stone 10a, stagnation of the working gas does not substantially occur. This prevents the temperature of the working gas immediately below the centering stone 10a from rising excessively, making it difficult to ionize it. In other words, it is difficult to discharge. Therefore, since no carbonization marks are produced on the lower end surface of the centering stone 10a due to discharge, the probability of mis-ignition of the pilot arc is reduced, and the service life of the plasma torch 5 is extended. Furthermore, since the groove 101 is provided at the lower part of the outer peripheral surface of the stone, the distance (creepage distance) from the electrode rod 4 to the insert tip 13 along the lower end surface of the centering stone 10a is longer. Therefore, creeping discharge is less likely to occur.

[0019]

[Second Embodiment] FIG. 2 shows an embodiment of the second invention. This is a porous ceramic type centering stone 1
It is 0b. In FIG. 2, (A) shows a top view of the centering stone 10b, (B) is a cross-sectional view of the centering stone 10b shown in (A) cut along the line B1-B2, and (C) shows a top view of the centering stone 10b. It is a sectional view taken along the line B3-B4 of the centering stone 10a shown in (B). A ceramic member with an alumina content of 99% is used for the stone 10b. The stone 10b has a cylindrical outer shape. A tungsten electrode rod 4 of the plasma torch is attached to the central axis of the stone 10b in the direction in which the central axis extends.
There is a cylindrical through hole 122 for passing through, and the lower part of this hole is a lower hole 123 having a larger diameter than the through hole. Further, in parallel to the through hole 122, there are a plurality of through holes 124 having a circular shape centered on the through hole and passing through the upper end surface of the stone and the lower hole 123. Furthermore, the lower hole 123 is provided with a porous ceramic ring 125. The porous ceramic ring 125 is slightly longer than the lower hole 123 in the central axis direction, and a groove 121 is formed between the lower part and the outer peripheral surface of the stone. The porous ceramic ring 125 is made of porous ceramic with an alumina content of 92%, a porosity of 29.6%, an average porosity of 260 μm, and an air permeability of 8.9 (cm3 cm/sec).
c・cm2・(g/cm2)).

FIG. 2D shows a conventional plasma torch 5.
2 shows the flow of working gas when the centering stone 10b is used. Working gas is injected from the passage 124,
Enter the ceramic ring 125. The working gas passes through the holes in the ceramic ring 125 to the centering stone 10.
Exit to the space below b. This working gas exits the ceramic ring 125 in a fine stream from every position on the exposed surface at a substantially uniform velocity, so that the centering stone 1
Partial stagnation of the working gas does not substantially occur in the lower space of 0b. As a result, the temperature of the working gas directly below the centering stone 10b does not rise excessively, so that it is difficult to ionize. In other words, it is difficult to discharge. Furthermore, since the ceramic ring 125 is porous, the creepage distance of its exposed surface is much longer than if it were a smooth plane, making creeping discharge less likely to occur. Therefore, since no carbonization marks are produced on the lower end surface of the centering stone 10b due to discharge, the probability of mis-ignition of the pilot arc is reduced, and the service life of the plasma torch 5 is extended. Furthermore, the groove 121 formed between the lower part of the ceramic ring 125 and the outer peripheral surface of the stone allows the electrode rod 4 to be placed along the lower end surface of the centering stone 10b.
The distance (creeping distance) from to the insert chip 13 is long, making creeping discharge less likely to occur.

[0021]

[Third Embodiment] FIG. 3 shows an embodiment of the third invention. This is a trumpet-shaped diffused centering stone 10
It is c. In FIG. 3, (A) shows a top view of the centering stone 10c, (B) shows a cross-sectional view of the centering stone 10c shown in (A) taken along the C1-C2 line, and (C) shows a top view of the centering stone 10c. It is a bottom view of the centering stone 10c shown in (A). A ceramic member with an alumina content of 99% is used for the stone 10c. The stone 10c has a cylindrical shape and has a groove 141 in an arbitrary range from the bottom of the outer circumferential side surface, and the upper end surface has an outer shape having a circularly opened conical groove on the upper end surface side. A cylindrical through hole 142 for passing the tungsten electrode rod 4 of the plasma torch is provided in the central axis of the stone 10c in the direction in which the central axis extends. Further, a plurality of circularly opened lower end openings 144 having a diameter R are provided on the lower end surface, which are opened on the circumference centered on the hole 142 for passing the electrode rod 4 at a pitch of R or less. The centering stone 10c has openings on a circumference centered on a hole 142 provided on the upper end surface of the centering stone 10c for passing the electrode rod 4 therethrough. Further, a plurality of passages 143 are provided, each of which is connected to the plurality of lower end openings 144.

FIG. 3D shows a conventional plasma torch 5.
2 shows the flow of working gas when the centering stone 10c is used. Working gas is injected from the passage 143,
It passes through the lower end opening 144 and is discharged to the lower end surface of the stone 10c. The lower end opening 144 has a centering stone 10
The holes 142 for passing the electrode rod 4 are formed on the lower end surface of c at a pitch of R or less on the circumference, and each hole has a conical shape with a diameter R. The working gas ejected from the lower end opening 144 below the lower end surface of the centering stone 10c is transmitted through the hole 14 through which the electrode rod 4 passes.
Since the opening edges of adjacent lower end openings 144 partially overlap, the working gas stagnates in the space immediately adjacent to the lower end surface of the centering stone 10c. Almost no space left. This makes it difficult for discharge to occur in the space. Furthermore, due to the pitch arrangement of the lower end opening 144 of R or less, and the groove 141 provided at the lower part of the outer peripheral surface of the stone,
The distance from the electrode rod 4 to the insert tip 13 along the lower end surface of the centering stone 10c (creepage distance)
is long, making creeping discharge less likely to occur. Therefore, since no carbonization marks are produced on the lower end surface of the centering stone 10c due to discharge, the probability of mis-ignition of the pilot arc is reduced, and the service life of the plasma torch 5 is extended.

[0023]

As described above, according to the present invention, the working gas flow is diffused at the time of discharge, and the creepage distance on the working gas outlet side is extended, thereby preventing the occurrence of a stagnation area of the gas flow on the gas outlet side. Therefore, leakage arcs can be prevented, and mis-ignition of the pilot arc can be prevented.

[Brief explanation of the drawing]

[Fig. 1] Centering stone 1, which is the first invention
The outline of 0a is shown, (A) is the centering stone 10
(B) is a cross-sectional view of the centering stone 10a cut along the A1-A2 line shown in (A), (C) is a top view of
(B) is a cross-sectional view of the centering stone 10a taken along the line A3-A4, and (D) is a partial cross-sectional view of the conventional torch when the centering stone 10a is attached. be.

[Figure 2] Centering stone 1, which is the second invention
0b, (A) shows the centering stone 10
(B) is a cross-sectional view of the centering stone 10b cut along the B1-B2 line shown in (A), (C) is a top view of
(B) is a cross-sectional view of the centering stone 10b taken along the line B3-B4, and (D) is a partial cross-sectional view of the conventional torch when the centering stone 10b is attached. be.

[Figure 3] Centering stone 1, which is the third invention
0c, (A) shows the centering stone 10
(B) is a cross-sectional view of the centering stone 10c cut along the C1-C2 line shown in (A), (C)
1 is a bottom view of the centering stone 10a, and FIG. 2D is a partial sectional view of a conventional torch when the centering stone 10c is attached.

FIG. 4 is a block diagram showing a schematic configuration of a conventional plasma torch 5. FIG.

FIG. 5 shows an outline of a conventional centering stone 10, (A) is a top view of the centering stone 10, (A) is a top view of the centering stone 10;
B) shows a partial sectional view of the plasma torch 5 shown in FIG. 4 when the centering stone 10 is attached, and FIG. 4C shows a bottom view of the centering stone 10.

FIG. 6 shows an outline of a conventional centering stone 10d, in which (A) is a top view of the centering stone 10d, and (B) is a centering stone 10d attached to the plasma torch 5 shown in FIG. (C) shows a partial cross-sectional view of the plasma torch at this time, and (C) shows a bottom view of the centering stone 10d.

7 shows an outline of a conventional centering stone 10e, (A) is a top view of the centering stone 10e, and (B) shows the centering stone 10e attached to the plasma torch shown in FIG. 4. (C) shows a partial sectional view of the plasma torch 5, and (C) shows a bottom view of the centering stone 10e.

[Explanation of symbols]

4: Tungsten electrode rod (electrode rod) 5: Plasma torch 10, 10d, 10e: Conventional centering stone 1
3: Insert tip 1
4: Shield cap 15: High frequency generator
16: Pilot arc power supply 17: Plasma arc power supply 1
8: Workpiece material 20: Space 10 near the lower end surface of the centering stone
a: Forced turning type centering stone 101: Groove
, 102: Groove (second gas guide path) 103: Through hole (hole for passing electrode rod 4 through) 104: Upper hole 105: Lower hole (circular opening) 106: Passage (first gas guide path) 107: Passage (first gas guide path) 3 gas guide path) 10b: Porous ceramic centering stone 12
1: Groove
122: Through hole (hole for electrode rod 4 to pass through) 123: Lower hole (circular opening) 124: Passage (first gas guide path) 125: Ceramic ring (porous ceramic ring) 1
0c: Trumpet-shaped diffused centering stone 141:
Groove 14
2: Through hole (hole for passing electrode rod 4 through) 143: Passage (first gas guide path) 144: Lower end opening (multiple lower end openings)

Claims (3)

[Claims] 1. A plasma torch insert having a hole in the center shaft portion through the centering stone in the direction in which the center shaft extends, through which the electrode rod of the plasma torch is passed.
In the centering stone of the plasma torch, in which the electrode rod is positioned at the central axis position of the torch tip, a The first gas guide path opened on the upper end side and side of the centering stone;
A second gas guide path for guiding downward the working gas exiting from the side surface of the centering stone through the gas guide path; a second gas guide path that is continuous with and wider than the hole through which the electrode rod passes; a circular opening opened at the lower end surface; and a circular opening opened at the side surface of the centering stone and the inner peripheral surface of the circular opening, passing through the centering stone in the tangential direction of the circular opening, and being guided by the second gas guide path. A third gas guide path for guiding the working gas into the circular opening. 2. A plasma torch insert having a hole in the central shaft portion passing through the centering stone in the direction in which the central shaft extends, through which the electrode rod of the plasma torch is passed.
In the centering stone of a plasma torch, which positions the electrode at the center axis of the tip, a circular opening in the lower end surface of the centering stone that is wider than the hole through which the electrode is passed; a first gas guide path that opens between the upper end surface and the circular opening and guides the working gas supplied to the upper end surface of the centering stone to the circular opening;
and a porous ceramic ring having a hole in the central shaft portion through which the electrode rod is passed, and a porous ceramic ring inserted into the circular opening. 3. A plasma torch insert having a hole in the central shaft portion passing through the centering stone in the direction in which the central shaft extends, through which the electrode rod of the plasma torch is passed.
In the centering stone of the plasma torch, which positions the electrode rod at the central axis position of the torch tip, a radius R is formed on the lower end surface of the centering stone on a circumference centered on the hole for passing the electrode rod. a plurality of circularly opened conical lower end openings with a diameter R in the lower end surface, which are opened at the following pitches; and a hole for passing the electrode rod through the upper end surface of the centering stone; 1. A centering stone for a plasma torch, comprising: a plurality of first gas guide paths having respective openings on the circumference of the center, each of which is connected to the plurality of lower end openings.