JP4068232B2 - Plasma arc cutting torch - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma arc cutting torch for cutting metal with a plasma arc.
[0002]
[Prior art]
In general, a plasma arc cutting torch, mounted an electrode at the tip of the core tube provided in the torch body, fitted to the support tube via a cylindrical insulating material core tube, chip and the shield cup on the support tube The gas, such as air, oxygen, nitrogen, etc. supplied into the core tube is divided into two, and one of the gases flows into the tip and electrode to make the plasma working gas, and the other gas is for the support cylinder It is used as a cooling gas.
[0003]
Conventionally, for example, a plasma arc cutting torch shown in FIGS. 5 to 7 has been proposed.
That is, in FIGS. 5 to 7, reference numeral 51 denotes a torch body used in the plasma arc cutting apparatus, and a core tube 52 is integrally connected to the torch body 51. In the core tube 52, a through hole 521 is formed in an axial core portion, and a male screw 522 is formed in a distal end portion.
53 is a gas supply pipe connected to the core pipe 52, and the inside of the gas supply pipe 53 and the through hole 521 communicate with each other. 54 is a partition tube screwed to the middle portion of the through-hole 521 in the long axis direction, 55 is a cap-like electrode screwed to the tip of the core tube 52, and this electrode 55 is made of copper or a copper alloy. The electrode base material 56 and an insert 57 having a high melting point such as hafnium or zirconium mounted in the concave portion at the tip of the electrode base material 56 are configured.
[0004]
In a state where the electrode 55 is screwed to the distal end portion of the core tube 52, a second gas channel 59 is formed between the electrode 55, the core tube 52, and the partition wall tube 54, and the second gas channel 59 and the first gas flow path 58 communicating with the inside of the gas supply pipe 53 are communicated with each other through a gap at the tip of the partition wall pipe 54.
Reference numeral 60 denotes a cylindrical insulator disposed outside the core tube 52. A support cylinder 61 is disposed outside the insulator 60. In this case, the support cylinder 61 is separated from the divided inner cylinder 61A. The outer cylinder 61B is integrally formed by brazing. In the integrally formed support cylinder 61, a cylindrical space 62 is formed between the inner cylinder 61A and the outer cylinder 61B.
[0005]
A tip 63 having a plasma ejection hole is screwed to the support cylinder 61 at the tip of the inner cylinder 61A, and a shield cup 64 is screwed to the outside of the outer cylinder 61B.
An orifice 65 communicating with the second gas flow path 59 in the radial direction is formed in the core tube 52, and the inner surface of the insulator 60 and the outer surface of the core tube 52 are formed upward from the portion corresponding to the orifice 65. An annular passage 66 is formed. The annular passage 66 passes through the space of the intermediate step portion of the insulator 60, the gas flow hole 67, the annular passage 68 and the gas flow hole 69, and the cylindrical space 62 in the support cylinder 61. It is communicated to.
A gas flow hole 70 in the radial direction is formed in the lower part of the cylindrical space 62, and an annular groove 71 and a gas flow hole penetrating the annular groove 71 are formed in a portion corresponding to the insulator 60 facing the gas flow hole 70. 72 is formed, and as a result, the cylindrical space 62 communicates with the plasma working gas flow passage 73 between the electrode 55 and the tip 63.
Furthermore, a gas flow hole 74 is formed at the lower end of the cylindrical space 62, and the gas flowing out from the gas flow hole 74 flows out through the gap between the shield cup 64 and the chip 63.
As described above, when gas is supplied from the gas supply pipe 53, the gas is supplied from the first gas flow path 58 → the second gas flow path 59 → the annular passage 66 → the gas flow passages 67, 68, 69 → the cylindrical space. 62 is distributed.
A part of the gas circulated in the cylindrical space 62 flows into the plasma working gas flow passage 73 from the branch hole 70, and the remaining gas flows out of the gas flow hole 74. It flows out to the outside through the gap.
[0006]
In the above configuration, gas is supplied from the gas supply pipe 53 and power is supplied between the electrode 55 and the tip 63 to generate a so-called pilot arc. Thereafter, the electrode 55 and the object to be cut are Electric power is supplied between them to generate a main arc between the electrode 55 and the object to be cut, and the cutting operation is performed.
In this case, as described above, a part of the gas flowing in the cylindrical space 62 flows into the plasma working gas flow passage 73 from the branch hole 70, and the gas that has flowed into the plasma working gas flow passage 73 The cutting operation is performed while the constrained plasma jet is ejected from the through hole of the chip 63.
Of course, at the time of the cutting operation, each part is appropriately cooled by the gas flowing out from the cylindrical space 62 through the gas flow hole 74 to the outside through the gap between the shield cup 64 and the chip 63.
When the desired cutting operation is completed, the supply of power is stopped and the supply of gas is stopped simultaneously or afterwards.
Of course, it cannot be stated uniquely depending on the cutting length of the workpiece, but in general, power supply / stop is performed at each plasma arc cutting operation, that is, generation of pilot arc and main arc and extinction of main arc are repeated. Yes.
[0007]
[Problems to be solved by the invention]
By the way, in the plasma arc cutting torch having the above structure, in order to form the cylindrical space 62 inside the support cylinder 61, the divided inner cylinder 61A and outer cylinder 61B are integrally formed by brazing as the support cylinder 61. Therefore, the manufacturing cost of the support cylinder 61 including the inner cylinder 61A and the outer cylinder 61B is expensive.
[0008]
Furthermore, this is not a problem when the cutting torch is new, but generally, during plasma arc cutting, arc generation and extinguishing are repeated, but the number of repetitions of arc generation and extinguishing is very frequent in one day. Therefore, the following problems occurred.
That is, when the plasma arc cutting work was repeatedly performed with the plasma arc cutting torch having the above-described conventional structure, it was found that if the cutting work was repeated to some extent, it was difficult to obtain a desired cutting state halfway.
[0009]
When this state was verified, a part of the portions corresponding to the plurality of gas flow holes 72 formed in the insulator 60 was burned out, and the tip of the electrode 55 from the outer peripheral portion of the electrode 55 facing the gas flow hole 72. There were arc marks in the direction.
In this way, some of the portions corresponding to the plurality of gas flow holes 72 formed in the insulator 60 are burned out, particularly when the generation and extinguishing of the arc are repeated frequently, especially the electrode 55. In order to generate a pilot arc between the core 63 and the tip 63, electric power is supplied between the core tube 52 and the support cylinder 61. When this pilot arc is generated, gas is drilled in the lower part of the cylindrical space 62. The gas circulation hole 70 formed in the support cylinder 61 and the outer peripheral surface of the electrode 55 are circulated from the gas circulation hole 70 through the gas flow paths 71 and 72 of the insulator 60 to the plasma working gas flow path 73. It is considered that an undesired pilot arc is intermittently generated between the edge portion of the gas flow hole 70 and the outer peripheral surface of the electrode 55.
As described above, when a pilot arc is generated between the edge portion of the gas flow hole 70 and the outer peripheral surface of the electrode 55, the gas flow hole 72 through which the arc passes in the insulator 60 is burned out by the arc heat.
Once the gas flow holes 72 of the insulator 60 are burned out, pilot arcs are generated intermittently and repeatedly at the same location thereafter, so it is necessary to repair the burnout location of the insulator 60 at an early stage.
[0010]
By the way, in this type of plasma arc cutting torch, the electrode 55, the tip 63 and the shield cup 64 are so-called replacement parts that are detachable from the torch body 51, but other parts such as the core tube 52, insulation, etc. Since the object 60 and the support cylinder 61 are molded integrally with the torch body 51, for example, with an appropriate resin, only the insulator 60 in the above cannot be replaced with a new one.
For this reason, when the insulator 60 is burned out as described above, the entire plasma arc cutting torch must be replaced with a new one, which has become uneconomical.
[0011]
As the plasma working gas, a gas such as air, oxygen, and nitrogen is appropriately selected and used. However, compressed air is frequently used as the plasma working gas because it is easily available and inexpensive.
By the way, since the replacement period of the plasma arc cutting torch using compressed air is short for a specific user, when the old plasma arc cutting torch before the replacement was examined, it was drilled in the insulator 60 as described above. A part of the plurality of gas flow hole 72 corresponding parts was burned out, and an arc mark was generated from the outer peripheral part of the electrode 55 facing the gas flow hole 72 toward the tip of the electrode 55.
For this reason, it turned out that there was a problem in the usage method of compressed air by the cutting work situation investigation of a specific user. In other words, it is generally assumed that compressed air from which so-called oil mist such as oil and dust is removed is used, but this specific user used compressed air from which oil mist has not been removed. When the pilot arc is formed, the insulation interval between the gas flow hole 70 formed in the support cylinder 61 by the oil mist of compressed air and the outer peripheral surface of the electrode 55 is shortened, in other words, a short circuit is achieved. It is considered that an undesired pilot arc is intermittently generated between the edge portion of the flow hole 70 and the outer peripheral surface of the electrode 55.
Although the above case is careless by a specific user, even in this case, there is a demand for a plasma arc cutting torch that can avoid a failure as much as possible.
[0012]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an economical plasma arc cutting torch with low manufacturing costs.
[0013]
[Means for Solving the Problems]
The present invention relates to a plasma arc in which an electrode is attached to the tip of a core tube provided in a torch body, a support cylinder is externally fitted to the core pipe via a cylindrical insulator, and a tip and a shield cup are attached to the support cylinder. Oite the cutting torch, the cylindrical insulating material constituted from an inner cylinder and an outer cylinder disposed coaxially, downward is formed from above between the inner cylinder and the outer cylinder of the cylindrical insulator A long-axis direction cooling passage is formed, and a gas flow hole reaching the inside of the support tube is formed in an intermediate portion of the long-axis direction cooling passage, and the gas supplied into the core tube is supplied to the tip of the core tube. Led to the inside of the cylindrical insulator through a gas flow hole formed on the side, the gas is guided to the cooling passage in the longitudinal direction through a gap between the cylindrical insulator and the core tube, Forming the gas in the long axis direction in the long axis direction on the front end side of the inner cylinder of the cylindrical insulator The gas is introduced into the plasma working gas flow path between the tip and the electrode through the gas flow hole, and the gas is formed in the middle of the long-axis cooling path from the long-axis cooling path. The gas is directed to the inside of the support cylinder through a gas flow hole extending to the inside of the support cylinder, and the gas is guided between the chip and the shield cup through a gap between the support cylinder and the cylindrical insulator. A plasma arc cutting torch .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.
1 to 4, reference numeral 1 denotes a torch body, and a core tube 2 is integrally connected to the torch body 1. In the core tube 2, a through hole 201 is formed in the shaft core portion, and a screw portion for attaching the electrode 5, for example, a female screw 202, is formed at the tip portion, and at the tip side of the core tube 2. A gas flow hole 4 penetrating the outside of the through hole 201 in the radial direction is formed.
Reference numeral 3 denotes a gas supply pipe connected to the core pipe 2, and the inside of the gas supply pipe 3 communicates with the through hole 201. Reference numeral 5 denotes an electrode screwed to the distal end portion of the core tube 2, for example, a rod-shaped electrode. The electrode 5 is attached to an electrode base material 6 made of copper or a copper alloy, and a tip concave portion of the electrode base material 5. It is constituted by an insert 7 having a high melting point such as hafnium or zirconium.
[0015]
Reference numeral 8 denotes a cylindrical insulator disposed outside the core tube 2. The cylindrical insulator 8 includes an inner cylinder 8A and an outer cylinder 8B which are arranged concentrically. In the state where the cylindrical insulator 8 composed of the inner cylinder 8A and the outer cylinder 8B is disposed outside the core tube 2, an upward gap that covers the gas flow hole 4 between the inner cylinder 8A and the core tube 2 is provided. 9 is formed. For example, as shown in FIG. 1 and FIG. 2, a flange having a triangular cross section that enters the inner cylinder 8 </ b> A is formed in the upper portion of the core tube 2. A gap 9 communicating with the gas flow hole 4 communicates upward due to a gap with the inner peripheral surface of the inner cylinder 8A.
A cooling passage 10 is formed between the inner cylinder 8A and the outer cylinder 8B of the cylindrical insulator 8 in the long axis direction from the upper side to the lower side. For example, an inner cylinder is provided in the upper half of the outer cylinder 8B. A plurality of crescent-shaped grooves 101 that are loosely fitted to 8A and extend in the major axis direction are formed in the circumferential direction, and the lower portions of the crescent-shaped grooves 101 in the major axis direction are the inner cylinder 8A and the outer cylinder 8B. An annular passage 102 is communicated with each other. The crescent-shaped groove 101 and the annular passage 102 constitute a cooling passage 10 in the long axis direction from the upper side to the lower side between the inner and outer tubes 8A and 8B of the cylindrical insulator 8.
Reference numeral 11 denotes a gas flow hole which is formed in the middle portion of the cooling passage 10 in the long axis direction of the cylindrical insulator 8 and opens to the outside in the radial direction. The gas flow hole 11 is formed outside the cylindrical insulator 8. It is formed in the cylinder 8B.
[0016]
Reference numeral 12 denotes a gas flow hole communicating with the lower part of the cooling passage 10 in the major axis direction of the cylindrical insulator 8 and opening in the radial direction. The gas flow hole 12 is formed in the inner cylinder 8A of the cylindrical insulator 8. Is formed. As shown in FIG. 4, the gas flow holes 12 are spirally disposed on the circumferential portion of the inner cylinder 8A.
Reference numeral 13 denotes a cylindrical support cylinder that is externally fitted to the core tube 2 via the cylindrical insulator 8, and 14 covers the gas flow hole 11 and is formed between the support cylinder 13 and the cylindrical insulator 8. In the annular space, a plurality of cooling holes 15 in the long axis direction communicating with the annular space 14 are formed in the tip circumferential portion of the support cylinder 13.
Reference numeral 16 denotes a tip screwed to the tip of the support cylinder 13, and the tip 16 is provided with a plasma ejection hole in the shaft core portion as in the prior art. Reference numeral 17 denotes a shield cup attached to the outside of the support tube 13, and 18 denotes a plasma working gas flow passage formed between the electrode 5 and the tip 16.
As in the prior art, each part of the torch other than the electrode 5, the chip 16 and the shield cup 16 is molded integrally with the torch body 51, for example, with an appropriate resin.
[0017]
As described above, when gas is supplied from the gas supply pipe 3, the gas passes through the through hole 201 of the core pipe 2 → the gas flow hole 4 → the gap 9 between the inner cylinder 8 </ b> A of the cylindrical insulator 8 and the core pipe 2 → cylinder. It flows into the cooling passage 10 in the long axis direction of the shaped insulator 8.
A part of the gas flowing into the cooling passage 10 in the major axis direction of the cylindrical insulator 8 flows into the plasma working gas passage 18 from the gas circulation hole 12, and the remaining gas is supported from the gas circulation hole 11. After flowing into the annular space 14 formed between the cylinder 13 and the cylindrical insulator 8, it flows out of the cooling hole 15 of the support cylinder 13, and flows out to the outside through the gap between the shield cup 17 and the chip 16. Is done.
[0018]
In the above configuration, gas is supplied from the gas supply pipe 3 and electric power is supplied between the electrode 5 and the tip 16 to generate a so-called pilot arc. Thereafter, the electrode 5 and the object to be cut are Electric power is supplied between them to generate a main arc between the electrode 5 and the object to be cut, and the cutting operation is performed.
In this case, as described above, a part of the gas circulated in the cooling passage 10 in the longitudinal direction of the cylindrical insulator 8 flows into the plasma working gas flow passage 18 from the branch hole 12, and this plasma working gas flow. The cutting operation is performed while the plasma jet restrained by the gas flowing into the path 18 is ejected from the through hole of the chip 16.
[0019]
Of course, during the cutting operation, gas flows out of the cooling passage 10 in the longitudinal direction of the cylindrical insulator 8 through the gas flow hole 11, the annular space 14, and the cooling hole 15 of the support cylinder 13, and thus the shield. Each part is appropriately cooled by the gas flowing out through the gap between the cup 17 and the chip 16.
When the desired cutting operation is completed, the supply of power is stopped and the supply of gas is stopped simultaneously or afterwards.
[0020]
By the way, in order to generate a pilot arc between the electrode 5 and the tip 16, electric power is supplied between the core tube 2 and the support tube 13, and the core tube 2, the electrode 5 and the support tube 13 are as follows. As will be described below, the cylindrical insulator 8 constituted by the inner cylinder 8A and the outer cylinder 8B is reliably maintained in an electrically insulated state.
That is, in the arrangement of each part of the torch, the support cylinder 13 is formed by the gas circulation hole 11, the long-axis cooling passage 10 formed between the inner and outer cylinders 8 A and 8 B of the cylindrical insulator 8, and the gas circulation hole 12. The electrode 5 is disposed in a spatially connected state.
But,
(1) This communication distance is sufficiently long electrically.
{Circle around (2)} The gas flowing from the upper side to the lower side of the cooling passage 10 of the cylindrical insulator 8 flows into the annular space 14 formed between the support cylinder 13 and the cylindrical insulator 8 from the gas flow hole 11. In this way, the gas flow from the gas flow hole 11 toward the support cylinder 13 acts to slightly weaken the electric field from the support cylinder 13 toward the electrode 5.
For this reason, the core tube 2 and the electrode 5 and the support cylinder 13 are maintained in a state where they are reliably electrically insulated by the cylindrical insulator 8 composed of the inner cylinder 8A and the outer cylinder 8B. A burned-out state of the cylindrical insulator does not occur.
[0021]
Furthermore, even if the operator mistakenly uses compressed air mixed with oil mist, as described in (1) above, the support cylinder 13 and the electrode 5 are electrically separated by a sufficiently long distance. The conventional cylindrical insulator does not burn out. Furthermore, the gas that cools the tip 16 and the support cylinder 13 that are heated at the time of cutting passes through the annular space 14 and then flows out from the cooling hole 15 to the outside of the torch.
In other words, since the gas heated to the high temperature by cooling flows out to the outside of the torch, the temperature of the gas flowing into the plasma working gas flow passage 18 without contacting the high temperature support cylinder 13 is high as in the conventional case. Compared to the temperature of the gas when a part of the gas that has cooled the support cylinder 61 is branched and flows into the plasma working gas flow path 73, the temperature is lower.
By the way, when the plasma jet restrained by the gas flowing into the plasma working gas flow passage 18 is ejected from the through hole of the chip 16, the lower the plasma working gas, the higher the temperature of the plasma jet due to the thermal pinch effect. It is formed.
That is, as described above, since the temperature of the gas flowing into the plasma working gas flow passage 18 is lower than that in the conventional case, a plasma jet having a temperature higher than that in the conventional case is formed. Therefore, it is possible to obtain a plasma arc cutting torch capable of performing a cutting operation with a higher cutting quality than in the conventional case. Further, since the support cylinder 13 is a simple cylinder, it is easy to process and the manufacturing cost is low.
[0022]
【The invention's effect】
As is clear from the above description, the plasma arc cutting torch according to the invention is
In a plasma arc cutting torch in which an electrode is attached to the tip of a core tube provided in the torch body, a support tube is externally fitted to the core tube via a cylindrical insulator, and a tip and a shield cup are attached to the support tube. The cylindrical insulator is composed of an inner cylinder and an outer cylinder, and a long-axis cooling passage is formed between the inner and outer cylinders from the upper side to the lower side, and the cooling path between the inner and outer cylinders. A gas flow hole extending to the inside of the support tube is formed in the middle portion of the tube, and the gas supplied into the core tube is formed inside the cylindrical insulator via a gas flow hole formed on the distal end side of the core tube. Guiding the gas through the gap between the cylindrical insulator and the core tube to the cooling passage in the long axis direction of the cylindrical insulator, and the gas flowing in the long axis direction through the cooling passage in the long axis direction The chip and the electricity are connected through a gas flow hole formed on the tip side of the inner cylinder of the cylindrical insulator. To the plasma working gas flow path between the support cylinder and the cylindrical insulator through the gap between the support cylinder and the cylindrical insulator. In order to guide between the chip and the shield cup, the core tube, the electrode, and the support cylinder are maintained in an electrically insulated state by a cylindrical insulator composed of an inner cylinder and an outer cylinder. Such a burned-out state of the cylindrical insulator does not occur.
[0023]
Furthermore, even if the operator mistakenly uses compressed air mixed with oil mist, as described in (1) above, the support cylinder and the electrode are electrically separated from each other by a sufficiently long distance. Such a burned-out state of the cylindrical insulator does not occur.
[0024]
Furthermore, since the temperature of the gas flowing into the plasma working gas flow passage is lower than that of the conventional case, a plasma arc that forms a higher temperature plasma jet than the conventional case and can perform cutting work with high cutting quality. A cutting torch can be obtained.
Further, since the support cylinder is a simple cylinder, processing is easy and the manufacturing cost is low.
[0025]
As described above, according to the present invention, it is possible to obtain an economical plasma arc cutting torch with low manufacturing costs.
[Brief description of the drawings]
1 is a longitudinal sectional front view showing an embodiment of the present invention. FIG. 2 is a sectional view taken along line II-II in FIG. 1. FIG. 3 is a sectional view taken along line III-III in FIG. Fig. 5 is a partially cutaway front view showing a conventional example. Fig. 6 is a sectional view taken along line VI-VI in Fig. 5. Fig. 7 is a line VII-VII in Fig. 5. Cross-sectional arrow view [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Torch main body 2 Core pipe 3 Gas supply pipe 4 Gas flow hole 5 formed in the front end side of the core pipe 2 Electrode 8 The cylindrical insulator 9 comprised of the inner cylinder 8A and the outer cylinder 8B covers the gas flow hole 4. A gap 10 formed between the inner cylinder 8A and the core tube 2. A long-axis cooling passage 11 formed between the inner cylinder 8A and the outer cylinder 8B of the cylindrical insulator 8 from the upper side to the lower side. A gas flow hole 12 formed in the middle portion of the cooling passage 10 in the major axis direction of the insulator 8 and opened to the outside in the radial direction is communicated with a lower portion of the cooling passage 10 in the major axis direction of the cylindrical insulator 8. A gas flow hole 13 that opens in the radial direction and a cylindrical support cylinder 14 that covers the gas flow hole 11 and communicates with the annular space 15 that is formed between the support cylinder 13 and the cylindrical insulator 8. Cooling hole 15 in the longitudinal direction
16 Tip 17 Shield cup 18 Plasma working gas flow path

Claims (1)

In a plasma arc cutting torch in which an electrode is attached to the tip of a core tube provided in the torch body, a support tube is externally fitted to the core tube via a cylindrical insulator, and a tip and a shield cup are attached to the support tube. Cooling in the long axis direction formed from an inner cylinder and an outer cylinder in which the cylindrical insulator is concentrically arranged and formed between the inner cylinder and the outer cylinder of the cylindrical insulator and going downward from above to form a passage, to form a gas flow hole leading to the inside of the longitudinal direction the support tube in the middle portion of the cooling passage of the gas supplied to the core tube is formed on the distal end side of the core tube gas through the circulation hole leading to the inside of the cylindrical insulator, the gas introduced into a cooling passage of the front Sulfur butterfly axis direction via the gap between the core tube and said cylindrical insulator, the cooling of the axial direction gas the gas toward the passage in the longitudinal direction are formed on the distal end side of the inner cylinder of the cylindrical insulator Led to the plasma working gas flow path between the tip and the electrode via holes, wherein the gas is, the support tube is formed from the cooling passages of the longitudinal direction in the middle portion of the cooling passage of the long axis direction it suited to the inside of the support tube through the gas flow holes extending inwardly, characterized in that for guiding the gas between the chip and the shield cup through the gap between the cylindrical insulator and the support cylinder Plasma arc cutting torch.

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