JPH0770357B2 - Plasma torch - Google Patents

Description

TECHNICAL FIELD The present invention relates to a plasma torch for generating a transfer type plasma jet, which is mainly used for welding, cutting, melting, thermal spraying and surface processing of metals. Is.

[Prior Art] A conventional plasma torch of this type is constructed as shown in FIG. 5 which is a sectional view of an essential part in which the cooling means and the sealing means of the nozzle portion are omitted.

In the figure, a plasma torch 1 holds the entire apparatus by a known gripping part or mounting means, and a main body part 2 that supports the electrode rod 3 at its center and a known cooling means inside (not shown in the figure). Is installed in the plasma torch 1, and a nozzle portion 4 for guiding the ejected shield gas and the electrode rod 3 are arranged in the center of the plasma torch 1 and fixed thereto. It is composed of the electrode holder portion 5.

The main body 2 is made of an insulating material, and is composed of a main body 21 into which a holder base 51 constituting the electrode holder 5 inserted through the center is inserted.

The electrode rod 3 is a JIS standardized product, and is a known product.

The nozzle portion 4 is provided with a plasma injection port 45 at the tip of the central portion and a plasma gas supply port 42 for supplying a plasma gas composed of an inert gas such as argon gas.
41, and further, inside the nozzle base 41, there is provided a centering of the electrode rod 3 made of ceramics or the like and a heat shield ring 43 for preventing backflow of heat on the side of the plasma injection port 45. ing. The heat shield ring 43 is provided with a plurality of small holes 46 to allow plasma gas to flow. An insulating sleeve 44 is attached to the electrode rod 3 located at the center of the nozzle portion 4 between the end of the holder base 51 of the electrode holder portion 5 and the heat shield ring 43. Electric discharge is prevented from occurring between the inner wall and the electrode rod 3.

The electrode holder part 5 is a holder base inserted into the main body 2.
The collet chuck 52, which is inserted into the central portion of the holder base 51 and the tapered portion 54 of the holder base 51, has its other end fitted to the collet pressing screw 53. The collet pressing screw 53 is screwed into the holder base body 51, and when the collet chuck 52 is screwed into the holder base body 51, the collet chuck 52 holds the electrode rod 3 and the electrical connection between the electrode rod 3 and the holder base body 51 is made.・ Make mechanical connection.

The plasma torch 1 configured as described above applies a high frequency between the holder base 51 of the electrode holder 5 electrically and mechanically connected to the electrode rod 3 and the nozzle base 41 forming the nozzle 4. By ionizing the plasma gas such as argon gas into a plasma state,
When a voltage is applied between the electrode rod 3 and the nozzle base 41 to generate a pilot arc, and the argon gas or the like jetted by the pilot arc is ionized into a plasma state, which is transferred between the materials to be welded or the like. , The electrode rod 3 and the material to be welded are in a substantially conductive state. When a high voltage is applied between the electrode rod 3 and the material to be welded and a large current is passed in this state, a high-temperature plasma main arc is generated, and welding or welding is performed by the high-temperature plasma main arc. Depending on the application, it can be used for cutting, welding, melting, surface processing, high temperature processing and the like.

[Problems to be Solved by the Invention] This type of plasma torch is used for the purpose of being used in a relatively short cycle such as welding and cutting of metals as described above, and has a long electrode life. It has a structure that emphasizes maintainability. That is, it has a feature that it is simple and has good maintainability as compared with a plasma torch in which electrodes are directly water-cooled.

Considering that the electrode life is short, the conventional plasma torch has an insulating sleeve 44 in which an inert plasma gas such as argon gas supplied from the plasma gas supply port 42 is fitted to the electrode rod 3. The hollow space between the nozzle base 41 and the inner wall of the nozzle base 41 serves as a passage, and since the plasma gas flows to the outside of the insulating sleeve 44, the electrode rod 3 is not directly cooled, which causes a rise in the electrode temperature. Then, when the temperature of the electrode rod 3 rises, the range in which the thermoelectrons can jump out becomes wider, and a series arc, a side arc, etc. are likely to occur.

Therefore, the temperature rise of the electrode rod not only chemically shortens the service life of the electrode, but also causes the electrical service life of the electrode to be shortened.

The inert plasma gas passage extends from the plasma gas supply port 42 of the nozzle portion 4 to the plasma injection port 45, and if the insulating sleeve 44 and the electrode rod 3 are in close contact with each other during that range, The electrode rod 3 will be placed in an atmosphere of inert gas. However, when inserting the electrode rod 3, in the space formed by the holder base 51, the collet chuck 52, and the collet pressing screw 53, which form the electrode holder portion 5,
The collet pressing screw 53 is the holder base in the atmosphere.
When screwed to 51 and sealed, the atmosphere remains in the space. Therefore, the residual atmosphere is separated from the flow path of the plasma gas, and the residual atmosphere remains in the electrode holder portion 5 even when the plasma torch 1 is in use. Then, when the temperature of the electrode rod 3 rises, the surface of the electrode rod 3 is oxidized by the residual air.

Further, when the collet pressing screw 53 is used in a state where it is not sealed in the holder base 51, the plasma gas flow flowing through the nozzle portion 4 lowers the pressure in the holder base 51 according to Bernoulli's theorem, so that the atmosphere is exposed to the holder base. It penetrates from between the 51 and the collet pressing screw 53 and oxidizes the surface of the electrode rod 3 as in the former case. Even if the electrode rod 3 is held by the collet chuck 52, the electrode rod 3
The change in the temperature causes repeated contraction and expansion, and oxidation of the surface of the electrode rod 3 progresses. Oxidation of the surface of the electrode rod 3 causes poor contact in the current-carrying part, making it unusable as a plasma torch.

On the other hand, Japanese Utility Model Publication No. 57-116382 discloses a technique in which plasma gas is introduced from one end side of an electrode rod and flows around the electrode rod to reach the other end. However, no specific plasma gas flow is disclosed.

Therefore, it is an object of the present invention to maintain the features of being simple and easy to maintain, improving cooling efficiency, and extending the electrode life of the air-cooled plasma torch.

[Means for Solving Problems] A plasma torch according to the present invention is a transfer-type plasma torch in which an electrode rod is arranged in a central portion of a plasma torch body, and an electrode is provided on an inner diameter side in contact with the electrode rod. A heat shield ring having a notch groove serving as a plasma gas passage in the longitudinal direction, and a collet chuck having a notch groove serving as a plasma gas passage connected to the notch groove serving as the plasma gas passage, and the entire length of the electrode rod. A plasma gas passage is formed over the surface of the electrode rod.

[Operation] According to the present invention, a cutout groove is provided in the longitudinal direction of the electrode on the inner diameter side in contact with the electrode rod of the heat shield ring, and the collet chuck also has a plasma gas passage connected to the cutout groove that serves as the plasma gas passage. Cutout grooves are provided, and an inert plasma gas is caused to flow through these cutout grooves as a plasma gas passage.When the plasma torch is used, the electrode rod is cooled by the plasma gas flow that always flows along the electrode rod, and the temperature of the electrode rod rises. Is to suppress. Therefore, without changing the basic structure of the conventional plasma torch, the temperature rise of the electrode rod can be suppressed and the continuous use becomes possible.

[Examples] Next, examples of the present invention will be described.

FIG. 1 is a sectional view of an essential part showing an example of a plasma torch according to an embodiment of the present invention, in which a cooling means for a nozzle portion and a sealing means such as an O-ring are omitted. Needless to say, they are known means. Can be used. And FIG. 2 is A of FIG.
Fig. 3 is a sectional view taken along the line A-A, Fig. 3 is a sectional view taken along the line B-B in Fig. 1, and Fig. 4 is a sectional view taken along the line C-C in Fig. 1. In the figure, the same reference numerals and symbols as in FIG. 5 indicate the same or corresponding components of the conventional device.

In particular, the difference from the conventional plasma torch will be described. The heat shield ring 43a, which is inserted between the inner wall of the nozzle base body 41 of the nozzle portion 4 and the electrode rod 3 and also serves as the centering of the electrode rod 3.
Is the electrode rod 3 as shown in the sectional view taken along the line AA.
A notched groove 46a is engraved on the inner diameter side in contact with the. The notch groove 46a forms a plasma gas passage and has a cross-sectional area so as to be a flow passage sufficient to maintain the ignition of the plasma arc. In addition, the insulating sleeve 44a is the nozzle base 41.
Is inserted in contact with the inner wall of the electrode and forms a plasma gas passage between itself and the electrode rod 3. The function of the heat shield ring 43a and the function of the insulating sleeve 44a are not different from those of the conventional device, the heat shield ring 43a is for backflow of heat and for centering the electrode rod 3, and the insulating sleeve 44a is for the electrode rod 3 And nozzle base 4
It is to prevent discharge with 1.

As shown in the sectional view taken along the section line BB of the main body 2, a collet chuck 52a holding the electrode rod 3 is inserted into the inserted holder base 51a, and the collet chuck 52a is inserted.
Has a notch groove functioning as a collet chuck for holding the electrode rod 3, and the notch groove is formed in the plasma gas passage 52d.
I am trying. The gas passage 52d has a cross-sectional area as large as a flow passage sufficient to ignite a plasma arc.

Then, the holder base body 51a through which the electrode rod 3 is commonly inserted has a hole 51c having a diameter sufficient for allowing the outer diameter of the electrode rod 3 to pass therethrough and for the plasma gas flow to flow therethrough. Holder base 51a
A plasma gas supply port 51b communicating with a fitting hole into which the collet chuck 52a is inserted is provided in the.

Since the collet chuck 52a is in contact with the collet pressing screw 53, in order to prevent the plasma gas from being supplied from the supply port 51b and being blocked by the collet chuck 52, the collet chuck 52 is provided with a first The notch groove as shown by the cutting plane along the line CC in FIG.
52b is engraved.

The plasma torch of the present embodiment configured as described above, when an inert plasma gas such as argon gas is supplied from the plasma gas supply port 51b, the plasma gas becomes a collet chuck 52a and a collet pressing screw 53. It is led to the hollow part 52c of the collet chuck 52a through the notch groove 52b formed in the collet chuck. In the hollow portion 52c of the collet chuck 52a, the metal rod 3 that holds is present. Therefore, the plasma gas flow flows along the surface of the metal rod 3, and the plasma gas passage 52d also serves as a notch groove for use as a holding collet chuck. And through the common hole 51c of the electrode rod 3 of the holder base 51a, between the inside of the insulating sleeve 44a and the surface of the electrode rod 3, and the heat shield ring 4.
Plasma injection port 4 of nozzle base 41 through cutout groove 46a of 3a
Up to 5.

Therefore, when the plasma gas is in use, the electrode rod 3 is cooled by the plasma gas over the entire length. Then, the cavity formed in the plasma torch 1 serves as a flow path for the plasma gas that is an inert gas, and even if the collet pressing screw 53 is removed when the metal rod 3 is inserted,
The atmosphere remaining inside is discharged by the plasma gas. Therefore, the periphery of the electrode rod 3 is always placed in the atmosphere of plasma gas which is an inert gas.
Can be prevented.

As described above, in this embodiment, the surface of the electrode rod is the plasma gas flow path over the entire length of the electrode rod, and since the plasma torch does not have a space in which the atmosphere remains, the electrode rod is Since the electrode rod can be kept in the atmosphere of plasma gas which is an inert gas while being cooled by the plasma gas, the temperature rise of the electrode rod can be suppressed and the plasma torch can be continuously used. Moreover, since the electrode rod is not oxidized, the life of the electrode can be extended.

In the above embodiment, the plasma gas is supplied from the plasma gas supply port of the holder base and flows out from the end of the collet chuck toward the injection port of the nozzle part. A hole can be bored near the end and used as a plasma gas flow path.

However, in the case of implementing the present invention, a more effective plasma torch can be obtained by eliminating the cavity portion in which the gas remains except the plasma gas flow path.

[Advantages of the Invention] As described above, in the plasma torch of the present invention, a notch groove is provided in the longitudinal direction of the electrode on the inner diameter side of the heat shield ring that contacts the electrode rod, and the plasma gas passage is also provided for the collet chuck. The plasma gas passage is formed over the entire length of the electrode rod arranged in the center of the transfer type plasma torch body by providing the notch groove serving as the plasma gas passage connected to the notch groove. The surface of the electrode is an inactive plasma gas flow channel over the entire length, and the electrode rod can be cooled with plasma gas, and the electrode rod can always be placed in the atmosphere of plasma gas, which is an inert gas. The temperature rise of the rod can be suppressed and the plasma torch can be used continuously. Further, since the electrode rod is not oxidized, the life of the electrode can be extended.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an essential part of a plasma torch in which a cooling means and a sealing means of a nozzle portion of an embodiment of the present invention are omitted, and FIG. 2 is a section line AA of FIG. According to FIG. 3, FIG. 3 is a sectional view taken along the line BB of FIG. 1, FIG. 4 is a sectional view taken along the line C-C of FIG. 1, and FIG. It is a principal part sectional drawing of the conventional plasma torch which omitted the means. In the figure, 1 ... Plasma torch, 2 ... Main body 3 ... Electrode rod, 4 ... Nozzle section 5 ... Electrode holder section. In the drawings, the same reference numerals and symbols indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A transfer type plasma torch having an electrode rod arranged in the center of a plasma torch body, wherein a notch groove serving as a plasma gas passage is provided in the longitudinal direction of the electrode on the inner diameter side in contact with the electrode rod. A heat shield ring and a collet chuck provided with a notch groove serving as a plasma gas passage connected to the plasma gas passage of the heat shield ring, and forming a plasma gas passage that flows along the surface of the electrode rod over the entire length of the electrode rod. A plasma torch that is characterized.