JP2001110592A - Electrode for plasma torch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode for plasma torch having improved cooling efficiently at the electrode, and having increased maximum flow amount transportation quantity of the electrode. SOLUTION: The electrode for a plasma torch is provided with a main body and a cooling circuit. The main body has a narrow and a long shape. The main body is provided with a electric conductive tip at the point of the body to generate arc at the outer side surface. The cooling circuit has the 1st duct, the 2nd duct, and a flow path. The 1st duct is extended along the center axis line of the electrode. The 2nd duct is extended along the axis line of the 1st duct and surrounds the 1st duct. The flow path is provided an neighbor of the inner side surface of the point, and connects the 1st and the 2nd duct. The edge of the 2nd duct surrounds and shields the edge of the 1st duct provided at neighbor of the point. The 2nd duct is provided with plural penetrating holes which the coolant enters into the duct. Each penetrating hole is formed by inclined shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to an electrode for a plasma torch. Such torches are well known to those skilled in the art for performing processes such as heating, melting, welding and cutting.

[0002]

2. Description of the Prior Art Known designs are shown in FIGS. This design was manufactured by the applicant as a 70 mm anode torch.

FIG. 1 shows a cross section of an end (hereinafter referred to as a tip) of a torch in which plasma is generated.
The torch comprises a large area of an electrode assembly 1, in which case the electrode assembly 1 is an anode surrounded by a nozzle 2 projecting beyond its tip. The nozzle 2 is provided with a coaxial cooling section for transporting the coolant to or from the tip. An annular copper brace 5 closes the ends of the two coolant paths 3, 4 and has a conductive shroud surrounding and extending beyond the electrode assembly 1.

[0004] The electrode assembly 1 is held in a nozzle 5 and fixed in place on a ring-shaped spacer 6 arranged around the electrode assembly 1. These spacers are made of an insulating material, and electrically insulate the electrode assembly 1 from the nozzle 2. The gap between the electrode assembly 1 and the nozzle 2 formed by the spacer 6 is
The tip of the electrode assembly 1 provides an annular flow path 7 for the flow of ionizable gas outside the tip of the torch.

[0005] The electrode assembly 1 is mounted on a pair of coaxial tubular members, ie, on an outer tubular member 8 and an inner tubular member 9. The inner tubular member 9 has an internal coolant passage 10 extending axially along the center of the electrode assembly 1 to carry liquid coolant axially to the tip of the electrode.
Is defined. An annular gap formed between the inner tubular member 9 and the outer tubular member 8 provides an external coolant path 11 for the return flow of liquid coolant absorbing heat at the electrode tips.
Is defined. The flow divider 12 is fixed in place at the end of the inner tubular member 9 as shown in FIGS. This is a substantially annular device having an inner bore 13 formed in communication with the internal coolant path 10. At the tip, the wall becomes thicker, forming a radially thicker end 14. The wall 15 at the tip of the flow divider 12 has a shallow taper to facilitate the flow of coolant around the radially thicker end 14.

As shown in FIGS. 2 and 3, the annular flange 16 surrounds the body of the flow divider 12 and is spaced from the tip of the flow divider 12. The annular flange 16
For the reasons described below, the circular through holes 17 are provided with an array arranged circumferentially.

[0007] The electrode tip assembly includes an electrode tip 19 and an electrode tip holder 20. The electrode tip 19 is
A cap-shaped member having a circular top 21 and a peripheral skirt 22 extending therefrom. The tip holder 20 is a single member inserted into the tip 19 and brazed.

The base end of the tip holder 20 is fitted to the end of the outer tubular member 8 and sealed by a pair of O-rings 23. The tip holder 20 has an annular structure as shown in FIGS. 4 and 5 for receiving the flow dividing section 12 shown in FIG. The inner bore 24 of the tip holder 20 has a radially inwardly projecting step 25 that provides a shoulder in which the flange 16 of the flow split 12 is located. The inner diameter of the bore is determined such that the radially thick end 14 of the flow divider 12 fits into the end of the tip holder and seals at that end. Tip holder 2
An array of a plurality of circular through holes 26 is provided around zero. These through-holes are sufficiently separated from the tip of the tip holder 20, so that the flow dividing portion 12
Is fully inserted into the tip holder 20, the thick end 14 of the tip holder 20 passes axially through the array of holes 26 so that coolant enters the tip holder 20 through these holes 26. ing.

Although the electrodes shown are anodes, the invention is equally applicable to cathodes. The cathode electrode has in most respects the same structure as described above, except that a tapered lamp of conductive material is provided on the outer surface of the electrode tip.

In operation, an ionizable gas flows through the flow path 7 and an arc is applied to the top 2 of the electrode tip 19.
It occurs first between 1 and the copper brace 5 of the nozzle 2.
The arc then moves immediately and appears between the workpiece 21 and the top 21 of the electrode assembly 1 with the end of the nozzle 2 merely acting as a gas shroud. Plasma is formed in the downstream region 27 of the electrode tip 19. In this operation, considerable heat is generated at the radially innermost portion of the tip of the copper brace. This heat is cooled by the coolant flowing through the passages 3 and 4. Considerable heat is also generated at the top 21 of the electrode tip. The liquid coolant flows along the internal coolant path 10, passes behind the top 21 of the electrode tip 19, flows through the hole 26 to the tip holder 20,
Further, it flows along the coolant outer passage 11 through the hole 17.

An object of the present invention is to improve the cooling of the electrode tip.

There is an increasing demand for a plasma torch that can provide a higher heating rate. To enable such a thing, the flow carrying capacity of the torch must be increased. Further, in low flow applications, it is necessary to extend the life of the torch, reduce electrode replacement costs, and improve operational reliability. As the flow level increases, the amount of heat generated at the electrodes increases correspondingly. Therefore, the maximum flow rate that can be supplied to the electrode is determined by the cooling efficiency at the electrode tip. The heat flux density at the electrodes is already extremely high (as high as 70 MW / m ² or more).

One way to increase the cooling of the electrodes is to increase the speed of the coolant flow. However, the high velocity water flow in the thermocritical regions of the electrodes increases the local pressure drop in those regions. To compensate for this, the coolant pump capacity can be increased. However,
The maximum pressure of a water cooling system is limited by the ratings of components of the cooling circuit, such as fittings, piping, instrumentation and fittings.

A second way to achieve a higher flow capacity is to increase the size of the electrodes. This allows
This is because the size of the electrode can reduce the heat flow density. This is effective for smaller and lower power supply electrodes, but has little significance for larger diameter electrodes. This is because as the diameter of the electrode increases, the critical flow density at which the overheating condition occurs decreases, and the maximum capacity becomes almost unchanged.

[0015]

SUMMARY OF THE INVENTION The present invention takes a different approach to this problem to improve the cooling efficiency of the electrode tip and thereby increase the maximum flow carrying capacity of the electrode.

An electrode for a plasma torch according to a first aspect of the present invention includes an elongated body formed along an axis and a cooling circuit, wherein the body generates an arc on an outer surface. A first duct having a conductive tip at the tip, wherein the cooling circuit extends along a central axis of the electrode;
A second duct extending along the axis of the first duct and surrounding the duct; and a second duct provided near the inner surface of the distal end, connecting the first duct and the second duct. A flow path, and an annular flange spaced apart from an electrode tip protruding radially outward from the first duct to support the second duct, the flange containing coolant. It has a plurality of through holes for circulation, and the size of each through hole in the circumferential direction about the electrode axis is formed larger than the size in the radial direction about the electrode axis.

Although it is not practical to redesign the structure of the coolant path in the thermal critical region of the electrode, by reducing the flow restriction and the resulting pressure drop in a portion of the non-thermal critical cooling circuit, The inventor has recognized that the cooling efficiency can be greatly improved. In this case, replacing the prior art annular hole with an elongated slit would be:
It not only increases the total flow area of the path, but also acts to reduce the throttling effect associated with smaller orifices.

The exact dimensions of the slots are designed to provide the maximum possible channel area for flow while maintaining the structural integrity of the electrodes. However, the circumferential dimensions of the individual through-holes are preferably at least twice, more preferably at least three times, and most preferably at least four times the radial dimensions. The circumferential dimension is the length of the arc from one end to the other end of the through hole.

According to a second aspect of the present invention, there is provided an electrode for a plasma torch, comprising an elongated body formed along an axis, and a cooling circuit, wherein the body has an arc on its outer surface. The cooling circuit comprises a first duct extending along a central axis of the electrode, and a first duct extending along an axis of the first duct and surrounding the duct. A second duct, provided near the inner surface of the tip, having a flow path connecting the first duct and the second duct, the end of the second duct near the tip Surrounding and sealing the end of a first duct provided, the second duct has a plurality of through-holes for coolant to enter the duct, and a circumferential direction about the electrode axis of each through-hole. The dimension is formed larger than the dimension about the electrode axis.

Although it is not practical to redesign the structure of the coolant path in the thermocritical region of the electrode, by reducing the flow restriction and consequent pressure drop in part of the non-thermal critical cooling circuit, The inventor has recognized that the cooling efficiency can be greatly improved. In this case, replacing the prior art annular hole with an elongated slit would be:
It not only increases the total flow area of the path, but also acts to reduce the throttling effect associated with smaller orifices.

The exact dimensions of the slots are designed to provide the maximum possible channel area for flow while maintaining the structural integrity of the electrodes. However, the circumferential dimensions of the individual through-holes are preferably at least twice, more preferably at least three times, and most preferably at least four times the radial dimensions. The circumferential dimension is the length of the arc from one end to the other end of the through hole.

According to a third aspect of the present invention, there is provided an electrode for a plasma torch, comprising an elongated main body formed along an axis, and a cooling circuit, wherein the main body comprises:
The cooling circuit includes a first duct extending along a central axis of the electrode, a first duct extending along the central axis of the electrode, and a cooling duct extending along the axis of the first duct. A second duct surrounding the duct, and a flow path provided near the inner side surface of the distal end and connecting the first duct and the second duct, wherein an end of the second duct is provided. The portion surrounds and seals the end of a first duct provided near the tip, and the second duct has a plurality of through holes for coolant to enter the duct, each through hole being an electrode. It is formed to be inclined radially inward from the tip.

This aspect of the invention is also based on reducing the pressure drop in the non-thermal critical region of a water cooling system. However, this aspect of the invention is not the same by increasing the surface area of the flow, but instead by directing the through hole in the second duct at an angle to smooth the flow through the through hole. To get the result.

It is preferable that the size of each through hole in the circumferential direction with respect to the electrode axis is larger than the size in the electrode axis direction. This will improve the flow through the through hole oriented in one direction.

The above three aspects of the invention may be used as is, or with various permutations.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an electrode constructed according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a sectional view of an end of a plasma torch according to the prior art;
FIG. 3 is a diagram showing the flow dividing unit of FIG. 1;
4 is a sectional view taken along line 2B-2B of FIG. 4; FIG. 4 is a view showing the electrode tip holder of FIG. 1;
FIG. 6 is a sectional view taken along the line B-3B; FIG. 6 is a view similar to FIG. 2 showing the flow splitting portion of the electrode according to the first embodiment of the present invention; FIG. 8 is a cross-sectional view taken along line 4B; FIG. 8 is a view similar to FIG. 4 showing the flow splitting portion of the electrode according to the second embodiment of the present invention; FIG. FIG. 10 is a sectional view taken along line 5B; FIG. 10 is a view similar to FIGS. 4 and 8 showing a flow splitting portion of an electrode according to the third embodiment of the present invention.

The overall structure of the plasma according to the present invention is similar in many respects to the conventional torch shown in FIGS. Therefore, the details of this torch will not be repeated here. Instead, reference is made only to the differences provided by the three aspects of the invention.

The first embodiment of the present invention is shown in FIGS. In this case, instead of the circular through-hole 17 of the prior art, there are three circumferentially arranged elongated slots 17 'arranged symmetrically with respect to the axis of the flow splitting part. The number and size of the slots 17 'can be changed. However, from a comparison of FIGS. 3 and 7, it will be appreciated that this arrangement of FIG. 7 is a significant improvement in the overall cross-sectional area through which the coolant passes. Furthermore, the flow restriction due to the relatively small size of the circular through-hole is greatly reduced by the elongated slot 17 '.

The second embodiment of the present invention is shown in FIGS. In this case, instead of the plurality of circular through holes 26, there are three elongated slots 26 'arranged symmetrically with respect to the axis of the electrode tip holder. The number and size of the slots 26 'can vary. However, from a comparison of FIGS. 4, 5, 8 and 9, it can be seen that the overall cross-sectional area of the slot 26 'is much larger than that of the circular through-hole 26 and that the flow restriction through the slot 26' is It will be appreciated that it is much smaller than the 26 case. Furthermore, the flow restriction due to the relatively small size of the circular through-hole is greatly reduced by the elongated slot 17 '.

The third embodiment of the present invention is shown in FIG. The electrode tip holder is a variation of that shown in FIGS. 8 and 9 with the circumferentially disposed slot 26 'being angled radially inward from the tip of the electrode. 10 and 1
It will be appreciated from the comparison that the slanted slots provide a fairly smooth path for coolant to enter the electrode tip holder.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an end of a plasma torch according to the related art.

FIG. 2 is a diagram illustrating a flow dividing unit of FIG. 1;

FIG. 3 is a sectional view taken along line 2B-2B in FIG.

FIG. 4 is a view showing the electrode tip holder of FIG. 1;

FIG. 5 is a sectional view taken along line 3B-3B in FIG. 4;

FIG. 6 is a view similar to FIG. 2 showing a flow splitting portion of an electrode according to the first embodiment of the present invention.

FIG. 7 is a sectional view taken along line 4B-4B in FIG.

FIG. 8 is a view similar to FIG. 4 showing a flow splitting portion of an electrode according to the second embodiment of the present invention.

FIG. 9 is a sectional view taken along the line 5B-5B in FIG.

FIG. 10 is a view similar to FIGS. 4 and 8 showing a flow splitting portion of an electrode according to the third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrode assembly 2 Nozzle 3, 4 Coolant path 5 Copper brace 7 Flow path 8 Outer tubular member 9 Inner tubular member 10 Inner coolant path 11 Outer coolant path 12 Flow division 13 Inner bore 14 Radial thick end Part 16 Flange 17 Through hole 19 Electrode tip 20 Tip holder 21 Top 26 hole

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Christopher David Chapman United Kingdom GL7.4 EU Gross Norse Fairford Kempsford Cross Tree Cottage (no address) (72) Inventor David Edward Degan UK GL54 2NP Gross Cheltenham Rissington Little Light Road 6F Term (Reference) 3K084 AA09 AA12 BA07 CA02 CB03

Claims (3)

[Claims] 1. An elongate main body formed along an axis, and a cooling circuit, wherein the main body is provided with a conductive tip at which an arc is generated on an outer surface at an end, and the cooling circuit comprises: A first duct extending along the central axis of the electrode, a second duct extending along the axis of the first duct and surrounding the duct, and provided near an inner surface of the tip And a flow path connecting the first duct and the second duct, wherein the end of the second duct surrounds and seals the end of the first duct provided near the tip. An electrode for a plasma torch, wherein the second duct has a plurality of through holes for a coolant to enter the duct, and each through hole is formed to be inclined radially inward from a tip of the electrode. 2. The electrode for a plasma torch according to claim 1, wherein a circumferential dimension of each through hole with respect to the electrode axis is formed larger than a radial dimension with respect to the electrode axis. 3. A plasma torch having an electrode according to claim 1.