JPH1043865A - Plasma torch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an enough shield effect with a small flow and to improve quality and working efficiency and reduce cost by installing a shield gas nozzle at a specific position against a plasma gas nozzle. SOLUTION: The retreating distance L as the difference of positions of plasma torch axial center directions of a plasma gas nozzle 5a and a shield gas nozzle 6a is arranged in the range of >=-10mm and <=50mm. Further, the shield radius R as the radius of circumference arranged with the shield gas nozzle 6a is made in >=8mm and <=50mm. The shield gas nozzles are installed at positions more than three places on the concentric circle with the plasma gas nozzle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma torch for cutting by passing a shielding gas around a plasma arc.

[0002]

2. Description of the Related Art A plasma cutting apparatus cuts using the high heat of plasma, supplies a gas to be turned into plasma (hereinafter referred to as a plasma gas) to a plasma torch, and attaches the gas to a tip of the plasma torch inside a nozzle. A high voltage is applied to the plasma gas from the applied electrode to generate a plasma arc. The plasma arc is narrowed by the nozzle, and is jetted from the nozzle tip as a high-temperature and high-speed plasma jet to cut the workpiece.

[0003] Further, in cutting metal, high efficiency cutting is possible by supplying and burning oxygen, so that a shielding gas is often jetted along the periphery of a plasma jet. Have been done.

An example of a conventional plasma torch will be described with reference to FIGS. In the plasma torch 30 shown in FIG. 3, a plasma gas nozzle 31 is arranged on the axis of the torch 30, and a shield gas passage 32 is formed around the plasma gas nozzle 31 as shown in FIG. The shield gas passage 32 is formed symmetrically with respect to the axis and over the entire circumference. Therefore, the shield gas outlet 32 which is the opening of the shield gas passage 32
3A has a ring shape concentric with the plasma gas nozzle 31 as shown in FIG. 3B.

In the plasma torch 33 shown in FIG. 4, a plasma gas nozzle 34 is arranged on the axis of the torch 33 similarly to the torch 30, and the shield gas passage is symmetrical with respect to the axis and extends over the entire circumference. Form 35. As shown in FIG. 4 (a), the shield gas passage 35 goes around the tip of the torch 33 and has an orifice 35a which is an opening at the tip of the torch 33. The orifice 35a is concentric with the plasma gas nozzle 34 as shown in FIG. 4 (b), and both the plasma gas and the shield gas are ejected from the orifice 35a.

[0006]

However, when the shield gas is ejected from the shield gas outlet having a ring shape as in the case of the plasma torch 30, the flow rate of the shield gas is low due to the large opening area, In addition, it is difficult to reach the cut site due to poor directivity. Therefore, in order to obtain a sufficient shielding effect, an enormous amount of shielding gas is required.

When the shield gas is ejected from the orifice concentric with the plasma gas nozzle, the shield gas comes into direct contact with the plasma gas.
Therefore, the shielding gas easily interferes with the plasma arc to affect the cut surface, and a part of the shielding gas is converted into a plasma, thereby limiting the usable gas.

[0008]

According to the present invention, there is provided a plasma torch for performing a cutting process by ejecting a plasma gas and a shield gas, wherein the plasma gas nozzle ejects the plasma gas. And a shield gas nozzle provided at three or more locations on a concentric circle with the nozzle to eject the shield gas, and the shield gas nozzle is in a range of −10 mm to 50 mm toward the rear of the plasma torch from the plasma gas nozzle. It is characterized by being arranged.

It is desirable that the shield gas ejection holes are arranged on a circle having a radius of 8 mm to 50 mm around the nozzle.

The jet angle of the shield gas jet hole is set at a centripetal angle of 30 ° to 0 ° with respect to the center axis of the plasma torch.
It is desirable that the range be up to.

With the above-described structure, the area of the shield gas ejection hole can be reduced without affecting the plasma gas, and the flow velocity of the shield gas can be increased and the directivity can be improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a plasma torch according to the present invention will be described with reference to the drawings. FIGS. 1A and 1B show a plasma torch according to a first embodiment, in which FIG. 1A is a sectional view of a tip, and FIG. 1B is a front view of the tip.

The tip of the plasma torch 1 shown in FIG.
As shown in FIG. 1 (a), a nozzle member 2 is provided at the distal end, and a cap 3 is further placed on the outside of the nozzle member 2. The nozzle member 2 is formed in a truncated conical shape in which the outer peripheral surface near the distal end decreases in diameter toward the distal end. Further, the inside of the nozzle member 2 and the plasma torch 1
The electrode 4 is mounted so as to coincide with the axis of, and power is supplied from a power source (not shown).

A gap is formed between the electrode 4 and the nozzle member 2 to form a plasma gas passage 5. A plasma gas nozzle 5a is formed in the nozzle member 2 so as to be continuous with the plasma gas passage 5 and coincide with the axis of the plasma torch 1. The plasma gas nozzle 5a opens at the tip of the plasma torch 1, that is, the plasma gas supplied from the plasma gas supply means (not shown) passes through the plasma gas passage 5 and is ejected from the plasma gas nozzle 5a.

The diameter of the inner peripheral surface of the cap 3 is larger than the diameter of the outer peripheral surface of the nozzle member 2 and is formed substantially in parallel.
Also, the diameter is formed small only at the tip. Therefore, when the cap 3 is fitted to the nozzle member 2, only this tip portion contacts the outer peripheral surface of the nozzle member 2, and a shield gas passage 6 is formed between the other nozzle member 2 and the cap 3.

Further, three shield gas nozzles 6a are provided in a portion having a small inner diameter formed at the tip of the cap 3. The shield gas nozzle 6a is formed on a circumference centered on the axis of the plasma torch 1, and the nozzle member 2
Is formed substantially in parallel with the outer peripheral surface of. For these reasons, the shielding gas supplied by the shielding gas supply means (not shown) passes through the shielding gas passage 6 and is ejected from the shielding gas nozzle 6a.

When the cap 3 is fitted to the nozzle member 2, the tip of the cap 3 retreats rearward of the plasma torch 1 from the tip of the nozzle member 2. Accordingly, the plasma gas nozzle 5a and the shield gas nozzle 6a are arranged at different positions in the axial direction of the plasma torch 1.

Here, as shown in FIG. 1, the end L0 of the plasma gas nozzle 5a is set to 0, and the original direction L of the plasma torch 1 is set to L.
A coordinate axis is set, where 1 is positive and the forward direction L2 is negative. When the difference between the position of the end of the plasma gas nozzle 5a and the position of the end of the shield gas nozzle 6a is the retreat distance L, the retreat distance L is set to be 50 mm or less.

When the radius of the circumference where the shield gas nozzle 6a is arranged is referred to as a shield radius R,
This shield radius R is set in the range of 8 mm to 50 mm.

A centripetal angle α, which is an angle formed between the axis of the plasma torch 1 and the central axis of the shield gas nozzle 6a.
Is set to be 30 ° or less. Temporarily
It has been experimentally found that if the angle is set to 30 ° or more, the air flow of the shielding gas affects the air flow of the plasma gas, and the cut surface is disturbed.

When cutting is performed using the plasma torch according to the present embodiment, a plasma arc is generated when a plasma gas is supplied to the plasma gas passage and a high voltage is applied to the electrode 4 to turn the electrode 4 into plasma. Is ejected from the plasma gas nozzle 5a as a high-temperature and high-speed plasma jet. At the same time, when the shielding gas is ejected from the shielding gas nozzle 6a through the shielding gas passage 6, the shielding gas is supplied to the cutting portion along with the plasma gas.

As described above, the shield gas nozzle 6
By forming a with holes, the opening area is reduced, and a high flow rate can be obtained even with a small flow rate. At the same time, the reach of the shielding gas can be extended,
The effect of the shielding gas can be efficiently obtained at the cutting site. That is, by adding the shielding gas, the purity of the gas of the plasma jet can be prevented from lowering. In the case of cutting metal, highly efficient cutting can be performed by using oxygen as the shielding gas.

Further, since strong directivity can be obtained, there is no danger of being caught in the plasma gas, and therefore there is no danger of being mixed into the plasma gas to form a plasma. From this, there is no restriction on the gas to be used.For example, when cutting a coated steel plate with oxygen plasma, the surface coating will burn with oxygen alone, but if a nonflammable gas such as nitrogen is used as the shielding gas, , Can suppress the burning of the paint.

Next, a second embodiment according to the present invention will be described with reference to FIG. 2A and 2B show a plasma torch according to a second embodiment, in which FIG. 2A is a cross-sectional view of the tip, and FIG. 2B is a front view of the tip. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The tip of the plasma torch 7 shown in FIG.
As shown in FIG. 2A, a nozzle member 8 is provided at the distal end, and a cap 9 is further placed outside the nozzle member 8.

The nozzle member 8 has a substantially cylindrical outer peripheral surface in the vicinity of the distal end, and the outer peripheral surface is substantially parallel to the axis of the plasma torch 1. In addition, a step 8a is formed on an end surface of the nozzle member 8 so as to protrude from the plasma gas nozzle 5a at a peripheral portion.

The diameter of the inner peripheral surface of the cap 9 is formed larger and parallel to the outer diameter of the nozzle member 8 so that the diameter is reduced only at the tip end so as to coincide with the outer peripheral surface of the nozzle member 8. It is configured. Further, four shield gas nozzles 10a are formed in a portion having a small inner diameter formed at the tip of the cap 3.

Therefore, when the cap 9 is fitted to the nozzle member 8, a shield gas passage 10 is formed as shown in the figure, and the shield gas supplied thereto can be ejected from the shield gas nozzle 10a.

Here, the tip of the cap 9 is fitted so as to coincide with the tip of the step 8a of the nozzle member 8, so that the shield gas nozzle 10a is disposed at a position protruding from the plasma gas nozzle 5a toward the tip of the plasma torch 1. Will be done. The retreat distance L, which is the difference between the positions of the plasma gas nozzle 5a and the shield gas nozzle 10a, is -10 mm
Set as follows. Also, shield gas nozzle 10a
The shield radius R, which is the radius of the circumference where the is arranged, is 8 mm
It is set in the range of ~ 50mm.

The shield gas nozzle 10a is formed on a circumference centered on the axis of the plasma torch 1, and the nozzle member 2
Is formed substantially in parallel with the outer peripheral surface of. That is, the axis of the plasma torch 1 is substantially parallel to the center axis of the shield gas nozzle 6a, and the centripetal angle α is 0 °.

When cutting is performed using the plasma torch according to the present embodiment, a plasma arc is supplied by supplying a plasma gas to the plasma gas passage 5 and applying a high voltage to the electrode 4 to convert the plasma gas into plasma. It is generated and ejected from the plasma gas nozzle 5a as a high-temperature and high-speed plasma jet. At the same time, shield gas passage
When the shielding gas is ejected from the shielding gas nozzle 10a through the shield gas 10, the shielding gas is supplied to the cutting portion along with the plasma gas.

As described with reference to the first and second embodiments, the centripetal angle α, which is the angle between the axis of the plasma torch and the central axis of the shield gas nozzle, is 0 ° or more and 30 ° or more.
° or less. This is because if it is less than 0 °, the shielding gas will be ejected in a direction away from the plasma gas, and the effect of the shielding gas will be diminished. This is because the cut surface may be disturbed, and the shielding gas may be mixed with the plasma gas and turned into plasma.

In order to properly obtain the effect of the shield gas, the retreat distance L, which is the difference between the positions of the plasma gas nozzle and the shield gas nozzle in the direction of the axis of the plasma torch, is -10.
It was experimentally found that the thickness is preferably not less than 50 mm and not more than 50 mm. Similarly, the shield radius R, which is the radius of the circumference where the shield gas nozzle is arranged, is preferably 8 mm or more and 50 mm or less.

In the above embodiment, three or four shield gas nozzles are provided. However, the present invention is not limited to this. For example, six to eight, or twenty-four, etc. May be provided. When only two holes are provided, the difference in the effect of the shielding gas depending on the cutting direction becomes significant, which is not appropriate.

Further, the shield gas nozzles need not be provided at equal intervals on the circumference, and the shield gas may be swirled by setting an angle with respect to the circumferential direction.

[0036]

As described above, since the shield gas injection port is formed with holes, the flow velocity of the shield gas can be increased and the directivity can be improved, and a sufficient shield effect can be obtained with a small flow rate. . Since a sufficient shielding effect can be stably obtained with such a small flow rate, both improvement in quality and working efficiency and cost reduction can be achieved.

Further, since there is almost no interference with the plasma arc, there is no danger of being mixed into the plasma gas to form a plasma.
There are no restrictions on the gas used. Therefore, for example, when cutting a coated steel plate with oxygen plasma, where oxygen alone burns the surface coating, the use of a nonflammable gas such as nitrogen for the shield can suppress the burning of the coating. . Since the shielding gas can be selected irrespective of the plasma gas in this way, the cutting application can be expanded.

[Brief description of the drawings]

FIG. 1 is a front end of a plasma torch according to a first embodiment.

FIG. 2 is a front end of a plasma torch according to a second embodiment.

FIG. 3 is a front end of a plasma torch according to a first conventional example.

FIG. 4 is a front end of a plasma torch according to a second conventional example.

[Explanation of symbols] [Explanation of symbols]

 L ... retreat distance R ... shield radius 1 ... plasma torch 2 ... nozzle member 3 ... cap 4 ... electrode 5 ... plasma gas passage 5a ... plasma gas nozzle 6 ... shield gas passage 6a ... shield gas nozzle 7 ... plasma torch 8 ... nozzle member 8a ... Step 9… Cap 10… Shield gas passage 10a… Shield gas nozzle

Claims (3)

[Claims] 1. A plasma torch for injecting a plasma gas and a shielding gas to perform cutting, comprising: a plasma gas nozzle for ejecting the plasma gas; and a plasma gas nozzle provided at three or more concentric circles with the nozzle to eject the shielding gas. A plasma gas torch, wherein the shield gas nozzle is disposed in a range of −10 mm to 50 mm rearward of the plasma torch with respect to the plasma gas nozzle. 2. The plasma torch according to claim 1, wherein the shield gas ejection holes are arranged on a circumference having a radius of 8 mm to 50 mm around the nozzle. 3. An ejection angle of the shield gas ejection hole is:
The plasma torch according to claim 1, wherein a center angle of the plasma torch is in a range of 30 ° to 0 ° with respect to a central axis of the plasma torch.