WO1994008748A1

WO1994008748A1 - Plasma torch

Info

Publication number: WO1994008748A1
Application number: PCT/JP1993/001488
Authority: WO
Inventors: Hitoshi Sato; Toshio Yoshimitsu
Original assignee: Kabushiki Kaisha Komatsu Seisakusho
Priority date: 1992-10-20
Filing date: 1993-10-18
Publication date: 1994-04-28
Also published as: JPH0639276U

Abstract

This invention relates to a plasma torch. The distal end of the torch has high approach-ability to a workpiece having a complicated shape, does not damage the torch or the workpiece even when a nozzle comes into contact with the workpiece, does not cause corrosion of a cooling water passage and can set a flowing direction and a flow rate of a plasma gas to optimum values. The nozzle (12) is equipped with an orifice (14) for controlling the flow rate and the flowing direction of the plasma gas, and an electrically insulating material (12) is deposited to a portion of the outer surface of the nozzle (12) coming into contact with atmosphere. An insulator (12) for separating an electrode (10) from the nozzle (12) is made of an aluminum nitride material. Further, the cooling water passage for cooling the electrode includes an inner cylinder (30) for supplying cooling water and an outer cylinder (6) formed around the inner cylinder (30) and discharging cooling water from a gap with the inner cylinder (30). Furthermore, the cooling water passage is molded with a resin (8) integrally with a durable member.

Description

Description Torch technology for plasma cutting machine

The present invention relates to a torch for a plasma cutting machine that cuts a material to be cut by generating a plasma arc between an electrode and the material to be cut. Background technology

The torch for the plasma cutting machine has a nozzle around the electrode to form a working gas passage, a cooling water passage to cool the electrode, and an insulator to insulate the electrode from the nozzle. It consists of a cap that fastens the nozzle to the torch main body, and narrows the plasma arc generated between the electrode and the material to be cut in front of the tip of the electrode to raise the temperature to achieve good cutting. Like that.

Regarding such a conventional technique, first, the configuration will be described with reference to FIG. 4 which is a cross-sectional view of a torch for a plasma cutting machine. An electrode 42 is press-fitted into the torch body 40 via a collar 41. A ceramic insulator 43 having a hole 44 is fitted between the electrode 42 and the torch body 40. A case 45 is provided on the outer periphery of the tip of the torch body 40. Between the case 45 and the insulator 43, a nozzle 46 having a hole 47 through which a plasma arc passes toward the material 60 to be cut is sandwiched. It is fastened to the case 45 by the stopper 50. nozzle

A gap 48 through which the working gas flows is provided between 46 and the electrode 42, and a cooling water chamber 51 is formed between the nozzle 46 and the cap 50. Further, the torch body 40 has an inlet pipe 53 and an outlet pipe for cooling water for cooling the electrode 42 and the nozzle 46.

54 are provided, and a working gas passage 52 is also provided. The inlet pipe 53 and the outlet pipe 54 communicate with the cooling water chamber 51 through passages 55 and 56 formed in the case 45, respectively. With this configuration, the working gas flows in from the arrow L, and the passage 5 2 The gas is ejected from the hole 47 at the tip of the nozzle 46 through the hole 44 of the insulator 43 and the gap 48. On the other hand, the cooling water flows in from the arrow M, cools the electrode 42, and then enters the cooling water chamber 51 from the passage 55, cools the nozzle 46, passes through the passage 56, the outlet pipe 54, and the arrow. Exhausted to N.

Next, a control system of the plasma cutting machine will be described with reference to FIGS. 5A to 5D. The electrode 42, the nozzle 46 having the hole 47, and the material 60 to be cut are the same as those in FIG. 4 described above, and 61 is a high frequency generator. First, in FIG. 5a showing the first step, a high-frequency circuit is operated to cause a high-frequency discharge to cause the gas between the electrode 42 and the nozzle 46 to be insulated. Next, in a second step shown in FIG. 5B, the high-frequency circuit is stopped, and a pilot current is caused to flow through the nozzle 46 to generate a pilot arc 62. Next, in FIG. 5c showing the third step, a pilot current is passed through the nozzle 46, and a main current is passed through the material 60 to be transferred to the main arc 63. Then, in a fourth step shown in FIG. 5d, the pilot circuit is cut off, and a main current is caused to flow through the workpiece 60 to start cutting. At this time, the main arc 64 passes through the hole 47 of the nozzle 46, and the nozzle 46 is electrically neutral.

However, such a conventional torch for a plasma cutting machine has the following problems when cutting a three-dimensionally complex molded product such as an automobile body. That is, the electrode 42 and the nozzle 46 are held by the insulator 43, but the insulator 43 is made of alumina, has a low heat transfer coefficient, and has a poor cooling ability of the nozzle 46. Therefore, in order to cool the nozzles 46, the outer periphery of the cap 50 is water-cooled, and the outer diameter of the cap 50 is increased, so that the ability to approach (adjust to) the molded product, which is the material to be cut 60, is low. May come into contact with the molded product, causing a double arc (illegal discharge) phenomenon, which may damage the torch and the molded product.

In addition, since the cooling water flows in from the cooling water inlet pipe 53 at the center of the torch, and flows out of the outlet pipe 54 through the cooling water chamber 51 on the outer periphery of the nozzle 46, the water flows through a passage having a potential difference. It will flow and electrolysis is likely to occur. Therefore, there is a risk of damaging the metal that becomes the passage and causing water clogging. Next, as another conventional technique, a metal cap is attached to the torch body via an electrical insulator, and a gas rectification chamber is formed between the cap, the insulator, and the nozzle. An arc torch that prevents a short circuit with a material to be cut and allows a stable gas flow is known (for example, see Japanese Patent Publication No. Sho 56-4351). However, the gas is allowed to flow around the outer periphery of the nozzle, and a gas shield cap is provided on the outer periphery, so that the outer diameter of the tip end of the nozzle is large and a three-dimensional molded product can be obtained. The ability to approach is low.

The present invention has been made in order to solve the disadvantages of the prior art. The outer diameter of the torch tip is small, the ability to approach a molded product is high, and the nozzle comes into contact with a material to be cut such as a molded product. It is another object of the present invention to provide a torch for a plasma cutting machine that does not damage a torch or a molded product and does not cause damage due to electrolysis of cooling water. The purpose of the present invention is to provide a torch for a plasma cutting machine that enables the optimal setting of the flow direction and the torch, and further integrates the torch's durable members to facilitate handling and management. Disclosure of the invention

A first invention according to the present invention is a torch for a plasma cutting machine, in which a nozzle has a gas outlet hole for controlling a flow direction and a flow rate of a plasma gas.

With this configuration, the gas flow direction (swirl flow or axial flow) and flow rate can be optimally set as necessary.

A second invention is the torch for a plasma cutting machine according to the first invention, wherein the insulator for insulating the electrode and the nozzle is made of an aluminum nitride material.

With this configuration, the nozzle that has a large amount of heat flowing into it due to the extremely high temperature of the plasma arc is in contact with the insulator made of aluminum nitride material with high thermal conductivity, so the heat of the nozzle is efficiently transferred to the cooling water. This prevents damage such as melting due to a rise in the temperature of the nozzle. This allows the passage of cooling water for nozzle cooling to be eliminated The tip of the torch can be made thin, and the ability to approach the material to be cut is good. In a third aspect based on the first aspect or the second aspect, the cooling water passage for cooling the electrode is provided around the inner cylinder supplying the cooling water and the inner cylinder, and cooling is performed through a gap between the inner cylinder and the inner cylinder. This is a torch for a plasma cutting machine composed of an outer cylinder that discharges water.

With such a configuration, the cooling water flows within the same electric potential and is less likely to cause electrolysis, thereby preventing corrosion mainly caused by electrolysis.

A fourth invention is the torch for a plasma cutting machine according to the first invention, wherein an electrical insulator is applied to a portion of the outer surface of the nozzle which is in contact with the atmosphere.

With this configuration, electricity does not flow even when the nozzle comes into contact with the workpiece during cutting, and there is no damage to the torch and the workpiece.

In a fifth aspect based on the first aspect, the torch has at least a case, a body, an insulator, a cooling water pipe and a gas pipe which are durable members, and the durable member is integrally formed. This is a torch for a plasma cutting machine having a resin to be molded. With this configuration, after assembling the durable members that make up the torch, except for the electrodes and nozzles that need to be replaced as consumable parts by the cutting work, and the insulators and caps that need to be removed and attached for replacement, Since it is molded with, it can be integrated and can be manufactured at low cost. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view of a torch for a plasma cutting machine according to the present invention, FIG. 2 is a cross-sectional view from a direction perpendicular to FIG. 1, and FIG. 3a and FIG. FIG. 4 is a cross-sectional view of a gas outflow hole portion of the nozzle according to the present invention (cross-section X-X in FIG. 1). FIG. 4 is a cross-sectional view of a conventional torch for a plasma cutting machine. FIG. 5B, FIG. 5C and FIG. 5D are explanatory diagrams of a control system for each step of the conventional plasma cutting machine. BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the torch for a plasma cutting machine according to the present invention will be described below in detail with reference to the accompanying drawings.

In FIG. 1, a resin case 2 is fitted into the tip of a resin cover 1, and a metal body 3 having gas holes 4 is fitted into the case 2. An electrical insulator 5 made of resin, ceramic, or the like is fitted inside the body 3, and the insulator 5 holds a metal outer cylinder 6 fitted inside. The outer cylinder 6 has one end connected to a metal block 7 disposed inside the case 2, and the other end fitted with an electrode 10. A nozzle 12 is attached to the outer periphery of the electrode 10 via an insulator 11 made of an alumina nitride material, which is an insulator, and is fastened to the body 3 by a metal cap 13. A gas outlet hole '14 is provided near the rear end of the nozzle 12, and a gas outlet 15 is provided at the front end. The gas outlet hole 14 may be in the tangential direction of the inner diameter surface of the nozzle 12 shown in Fig. 3a or the center direction of the inner diameter surface of the nozzle 12 shown in Fig. 3b. The hole diameter of 14 is also set from the required gas flow rate. An electrically insulating material 16 such as resin or ceramic is coated or adhered to the outer surface of the nozzle 12 which is in contact with the atmosphere, and is an object to be cut (not shown). Even when it comes into contact with a three-dimensional molded product, no current is supplied. A gas chamber 17 is formed between the cap 13 and the insulator 11, and a gap 18 is provided between the electrode 10 and the nozzle 12. The gas chamber 17 and the gap 18 communicate with each other through a gas outlet hole 14.

Inside the cover 1, high-frequency and high-voltage wires 19 are arranged, one end of which is connected to the body 3, and the other end of which is connected to a power supply (not shown). The gas hole 4 of the body 3 and one end of the hole 23 provided in the block 2 are connected by a pipe 20, and the other end of the hole 23 is connected to a pipe 21 having a joint 22.

In FIG. 2, a conductive inner cylinder 30 for supplying cooling water for cooling the electrodes 10 is mounted in communication with one end of a hole 33 formed in the center of the block 7, Reach inside the electrode 10. The other end of the hole 33 is connected to an inlet water pipe 31 having a joint 32. An inner cylinder 30 provided in the block 7 and an outer cylinder 6 provided around the inner cylinder 30; An outlet water pipe 34 having a joint 35 is connected to the hole 36 communicating with the gap between the case 2 and the case 3, the body 3, the insulator 5, the outer cylinder 6, the block 7, and the power supply shown in FIG. Line 19, pipes 20 and 21 and inlet water pipe 31 and outlet water pipe 34 shown in FIG. 2 are partially or entirely molded by resin 8 and integrated. . The operation of the torch for a plasma cutting machine having such a configuration is as follows. First, the flow of the plasma gas is supplied from the direction A to the joint 22, passes through the pipe 21, the hole 23, and the pipe 20, enters the gas chamber 17 from the gas hole 4, and flows through the gas outflow hole 14. Then, the gas enters the gap 18 and is ejected from the gas ejection port 15 in the direction of the material to be cut. When this gas outlet hole 14 is as shown in Fig. 3a, the plasma gas becomes a swirling flow, and the plasma arc has a small outer diameter, that is, is narrowed down, and is ejected from the gas outlet 15 and covered with a small-diameter plasma arc. Since the cutting material is cut, the cutting width is small and the processing accuracy is good. On the other hand, when the gas outlet hole 14 is as shown in Fig. 3b, the plasma gas flows axially and the plasma arc flows with a large component perpendicular to the material to be cut, so that the molten metal adheres to the material to be cut. Effective for reduction.

Next, the heat flowing into the nozzle 12 by the plasma arc mainly passes through the insulator 11, which is a sintered body of alumina nitride (A 1 N) having good heat conduction, and passes through the rear end of the electrode 10. Therefore, similarly to the cooling of the electrode 10 described later, the cooling water is efficiently cooled by the cooling water in a low temperature state. Therefore, damage such as melting due to a rise in the temperature of the nozzle 12 is prevented, so that another cooling water passage for cooling the nozzle 12 is unnecessary, and the tip of the torch can be made thin. As a result, the ability to approach the material to be cut such as a molded article having a complicated three-dimensional shape is good, the restriction on the cutting position of the molded article is improved, and the design becomes easy.

Next, the flow of cooling water is supplied from the direction B to the joint 32 (see Fig. 2), and reaches the electrode 10 through the inlet water pipe 31, the hole 33, and the inner cylinder 30. After cooling the electrode 10 with the cooling water in the state, it flows through the gap between the inner cylinder 30 and the outer cylinder 6, passes through the hole 36, the outlet water pipe 34, flows from the joint 35 in the direction C, and is discharged. You. Therefore, from direction B During the discharge from the supply to the direction C, including the conductive electrode 10 fitted to the outer cylinder 6, the members constituting the passage for the cooling water are conductive, and the metal Since it is conductively connected to the ground 7, it has the same potential. As a result, the cooling water flows through the passage having the same potential, so that it is difficult for electrolysis to occur, thereby preventing corrosion mainly caused by electrolysis.

In addition, since the insulator 16 is coated on the outer surface of the nozzle 12, even when it comes into contact with a three-dimensional molded product, which is a workpiece (not shown), there is no energization and a double arc is generated. There is no danger of damaging the torch or molded part because it does not occur.

In addition, of the main components that make up the torch, durable components that correspond to components other than those that need to be replaced due to wear due to the cutting work are molded with resin 8 and integrated, so mounting bolts etc. It is greatly reduced, the assembly structure is simplified, and it can be manufactured at low cost. In addition, handling and management become easier. Industrial applicability

The present invention has a high ability to approach a molded product with a thin torch tip and a complicated shape, and does not damage the torch or molded product even when the nozzle comes into contact with the workpiece, and does not cause corrosion of the cooling water passage. Further, it is useful as a torch for a plasma cutting machine capable of optimally setting the flow direction and flow rate of plasma gas.

Claims

The scope of the claims

1. An electrode, a plasma gas injection nozzle provided around the electrode, an insulator for insulating the electrode and the nozzle, a cap for fastening the nozzle to the torch body, and a cooling water passage for cooling the electrode A torch for a plasma cutting machine, wherein the nozzle is provided with a gas outlet hole for controlling a flow direction and a flow rate of a plasma gas.

2. The torch for a plasma cutting machine according to claim 1, wherein the insulator that insulates the electrode from the nozzle is made of an alumina nitride material.

3. The cooling water passage that cools the electrode includes an inner cylinder that supplies cooling water, and an outer cylinder that is provided around the inner cylinder and that discharges the cooling water from a gap between the inner cylinder and the inner cylinder. The torch for a plasma cutting machine according to claim 1 or 2, wherein:

4. The torch for a plasma cutting machine according to claim 1, wherein an electrical insulator is applied to a portion of the outer surface of the nozzle that comes into contact with the atmosphere.

5. The torch has a case, a body, an insulator, a cooling water pipe and a gas pipe which are at least durable members, and has a resin for integrally molding the durable members. The torch for a plasma cutting machine according to claim 1.