EP1169889A1

EP1169889A1 - Cartridge for a plasma torch and plasma torch fitted therewith

Info

Publication number: EP1169889A1
Application number: EP00918936A
Authority: EP
Inventors: Christophe Girold
Original assignee: Commissariat a lEnergie Atomique CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 1999-04-14
Filing date: 2000-04-11
Publication date: 2002-01-09
Anticipated expiration: 2020-04-11
Also published as: FR2792493B1; EP1169889B1; JP4925510B2; CA2370462C; KR20020013848A; US6525292B1; WO2000064224A1; KR100791562B1; JP2002542602A; CA2370462A1; FR2792493A1

Abstract

A plasma torch comprising a replaceable cartridge (100) consisting of only six parts: an anode nozzle (1) made from electrolytic copper, a cathode support (2) made from electrolytic copper, a doped tungsten cathode (3), a diffusing/centralising cathode made of plastic (4), an assembler made of plastic (5) and a ceramic insert (6). The parts are press-assembled and the assembly of said parts creates volumes (71, 72, 73) that make up the cooling circuit of the anode (1) and other elements of the torch, in addition to conduits and inlet fittings for the plasmagenic gas. Liquid inlets and outlets are provided by a fitting and maintenance structure for easy assembly of the cartridge (100).

Description

CARTRIDGE FOR PLASMA TORCH AND PLASMA TORCH

EQUIPPED

DESCRIPTION

Field of the invention

The invention relates to the field of plasma torches.

State of the art

Arc plasmas are part of the family of thermal plasmas. These are partially ionized gaseous media, conductors of electricity but generally electrically neutral, at pressures of the order of atmospheric pressure. They are generated by means of a plasma torch, by passing one or more plasma gas (es) through an electric arc which is maintained between two electrodes.

To carry gases at high temperature and high mass enthalpy, blown arc torches are used. That is, the arc is confined inside the torch which contains the two electrodes and it is the high speed jet of gas at high temperature (the plasma) that is used in the process. Figure 1 illustrates very schematically the principle of such a torch. Such a torch comprises two electrodes, an anode 1 and a cathode 3, concentric with one another and providing between them a gas circulation channel 7. The two electrodes 1,3 are connected to a high voltage, high frequency generator (HT-HF) and to a direct current generator. They must Be energetically cooled (by circulation of water) to avoid their fusion.

Initially and thanks to the HT-HF generator, an electric arc 8 erupts between the two electrodes (cathode and anode) ionizing the gas introduced and making the inter electrode space conductive. The DC generator can then flow into this space and maintain the arc.

The power supplied to the torch is equal to the product of the intensity delivered (which can be regulated) by the voltage which is established between one anode and the cathode. This voltage depends on several parameters such as the nature and the flow rate of gas used, but also on the wear of the electrodes for a significant part. The power of the plasma 9 is equal to the power supplied to the torch minus the losses in the cooling water. The wear of the electrodes is therefore highly penalizing. It depends on their geometry, the efficiency of their cooling, their coaxiality, the nature and the purity of the gases.

Equipment for generating a plasma 9 of arc 8 is used for thermal spraying (surface treatment), gas heating or chemical synthesis. The energy supplied to the gas by the electric arc makes it possible to heat them to temperatures above 10,000 K.

The choice of plasma gas (es) is almost unlimited. It depends on the requirements of the process (oxidation, nitriding, high temperature in a reducing medium, etc.). The power range is very wide, ranging from a few kilowatts to several megawatts. Very often, the choice of nature and flow plasma gases dictate the range of operation possible.

A torch is therefore often designed for a given application because its technology must be compatible with the choice of plasma gas and the desired working power.

Its size, shape and simplicity can also become important if it is a question of working in a confined or hostile environment. The torches currently existing are complex assemblies, comprising at least a dozen parts (gaskets, screws and bolts, except fluids). The coaxiality of the electrodes depends on the stack of machined parts with acceptable tolerances for the seals.

The replacement of one or both electrodes is an operation which must occur regularly (in most cases after a few tens of hours of operation). This operation always requires the disassembly / reassembly of sub-assemblies and the replacement of the seals.

By way of illustration, three examples of known plasma torches are briefly discussed below. A first known torch operates with a mixture of air / argon or oxygen / argon, its power is approximately 100 k. It consists of 15 machined parts, 21 seals, 22 screws and 6 fluid fittings. The regular wearing parts are the cathode and the anode, an insulating ring and an injection nozzle. A minimum of maintenance (change of the anode) is necessary within 100 hours of operation under the best conditions of use. A second known torch has been developed for hydropyrolysis of heavy hydrocarbons. The plasmagenic gases are argon and hydrogen which are mixed with methane at the outlet of the torch. This torch is similar to a thermal spray torch. There are, except the fluid supply fittings and hardware, 10 machined parts and 7 O-rings. As a third example, it is cited as one of the simplest torches sold by the company SULZER METCO. It is the F4-MB thermal projection torch. This type of torch conventionally works with argon, helium and nitrogen alone or in mixture. The addition of hydrogen is often used to gain power (increase in arc voltage). There are still 8 machined parts, 14 O-rings, 12 fasteners and 3 fluid fittings.

The torch according to the invention aims to simplify as much as possible the mounting of the torch itself and, on the other hand, the periodic replacement of the wearing parts. It has been developed in particular for a gas heating application in a post-combustion reactor for pyrolysis gas of chlorinated radioactive waste, highly contaminated with α emitters. This reactor is intended to operate in a glove box.

In a hostile environment (radioactive, with the obligation to work in a glove box or with the manipulator), work must be simplified as much as possible. The standard exchange of sub-assemblies is often preferable to the disassembly and reassembly of individual parts in a complex assembly. The intervention time is shorter, the reliability of a new and controlled sub-assembly is much better than that of a complex assembly disassembled and reassembled.

To this end, the plasma torch according to the invention is designed in two parts, an interchangeable disposable cartridge constituting a plasma generator intended to be inserted in a connection structure and holding the cartridge. The purpose of this structure for connecting and holding the cartridge is to connect the cartridge to its supplies of plasma gas, cooling fluid and electric currents. This structure comprises for this purpose first means of connecting the cartridge.

These first means serve as intermediaries for the supply of electric currents, water and gas. These supplies are therefore completely disconnected from the plasma cartridge.

The structure comprises second means, cooperating or not with means for fixing the cartridge, in order to keep the cartridge mechanically connected to the first means for supplying electric water and gas currents.

Brief description of the invention The invention relates to a plasma generator cartridge for a plasma torch, having centered on an axis AA ', an annular anode comprising a central cavity receiving a cathode centered on AA', the anode and the cathode forming an annular space between them for the production of an arc, means for distributing a plasma-producing gas, the distributed gas circulating in the annular space between the cathode and the anode, means for cooling the anode, comprising in particular conduits for an anode cooling fluid, these conduits having an inlet and an outlet, assembly means, cartridge characterized in that the assembly means comprise a cathode support having a conductive part for bringing the electric currents necessary for the operation of the torch from a current input to the cathode, means for positioning the cathode, an assembler made of an electrically insulating material, the cathode support, the assembler and the annular anode comprising hollow parts and projecting parts all axially parallel to the axis AA ′, the projecting parts being fitted tightly into the hollow parts. In this way the mechanical assembly is carried out with a single auxiliary assembly part, the assembler, by simple operations carried out with the press to push in an axial direction the projecting parts in the hollow parts. It will be seen later that with a suitable tool, only one press operation is necessary.

In the preferred embodiment, the projecting parts comprise a first and / or a second annular ring, this first and / or second annular ring, coming to be fitted in a first and / or a second annular groove. Due to this shape offering a symmetry of revolution, the assembly is simplified since it suffices to position the parts to be assembled coaxially with the assembler, the anode and / or the cathode support, to achieve fitting without it is necessary to index them angularly. According to an advantageous characteristic of this preferred mode, an annular cooling volume formed between the assembler and the anode receives a cooling fluid through a conduit leading the fluid from an exterior surface of the cartridge but preferably from the anode at this annular volume. The tightness of the annular volume is obtained by the fact that the outside diameter of the projecting crown has a value slightly greater than that of the groove in which it is fitted. In this way the cartridge according to the invention does not require for the water supply any joint or conduit other than those produced by drilling or machining or molding in the parts necessary for the operation of the torch. In the preferred embodiment which will be described below, the assembler is a piece of electrically insulating material comprising a lower ring and a coaxial upper ring. The lower crown is fitted into a groove in the support, the upper crown is fitted into a groove of the anode. This groove of the anode is peripheral to a crown of the anode. This anode ring houses the central cavity of the anode. In this embodiment, the internal radial dimensions of the assembler are greater over at least one axially central part than that of the crown of the anode housing the central cavity. An annular volume for the circulation of an anode cooling fluid is thus formed between this crown of the anode and the assembler. This volume is in communication with conduits for supplying and evacuating the cooling fluid, by means of conduits drilled in the anode, the assembler, or even the support. Preferably also the cartridge assembled according to the invention comprises an annular gas distribution volume receiving plasmagenic gas conduits and distributing the received gas, around the cathode, by means of holes opening out either on lights or a groove gas distribution terminal. Gas tightness is obtained by the fact that the inter-electrode space comprises a part of revolution made of insulating material fitted in tight assembly around the cathode, on the one hand and inside the cavity of the anode. 'somewhere else. The annular distribution volume is constituted by a radial groove which can be located either on the anode, or on the insulating piece of revolution, or again both on the anode and on the insulating piece of revolution. In this way the cartridge according to the invention does not require for the gas supply any seal or conduit, other than those produced by drilling or machining or molding, in the parts necessary for the operation of the torch.

Other advantages and advantages of the invention will become apparent during the description of a preferred embodiment and of variant embodiments which will be made below with reference to the appended drawings.

Brief description of the drawings

- Figure 1, already discussed, illustrates the principle of a plasma torch;

- Figure 2 shows an axial section of an assembled cartridge according to the invention;

- Figure 3 shows an axial section of a cathode support and a lower part of an assembler assembled with this support; - Figure 4 shows a top view of the support shown in Figure 3;

- Figure 5 shows an axial section of a cathode centralizer and a cathode assembled with this centralizer;

- Figure 6 shows a top view of the centralizer and the cathode shown in Figure 5;

- Figure 7 shows a top view of a variant of the centralizer and the cathode shown in Figure 5;

- Figure 8 shows an axial section of an anode, an insert assembled on this anode and an upper part of an assembler assembled with this anode; - Figure 9 shows a top view of

1 anode and 1 insert shown in Figure 8;

- Figure 10 shows an axial section of an assembler;

- Figure 11 shows an axial section of a connection structure and holding a cartridge according to one invention assembled with a said cartridge shown schematically;

- Figure 12 is an axial section along a plane perpendicular to the plane of Figure 13; and - Figure 13 is a front view of the structure 80 assembled with the cartridge 100, with a partial axial section in the upper right corner.

Description of a preferred embodiment An example of cartridge 100 according to the invention will now be described in connection with FIG. 2. In this embodiment, the cartridge 100 and the parts which compose it, have shapes having a symmetry of revolution about an axis AA 'constituting the axis of the cartridge.

The parts, which assembled, together constitute a cartridge 100 according to the invention, are six in number. They are:

-an electrolytic copper anode nozzle 1

-an electrolytic copper cathode support 2

-a doped tungsten cathode 3

-a plastic cathode centering diffuser 4 -a plastic assembler 5 -a ceramic insert 6.

When they are assembled, the parts 1 to 6 form between them in a known manner and shown in FIG. 1, a gas circulation channel 7, an inter-electrode space where an arc can be created 8. The plasma 9 (not shown in the 2) is ejected through a nozzle 13 from the anode 1.

Each of these parts and their method of assembly will now be described. The cathode support 2 described below, in conjunction with FIGS. 3 and 4, is a part of cylindrical shape having a symmetry of revolution about the axis AA '. It comprises a base or lower surface 21 of circular shape located in a plane perpendicular to the axis AA '. The side opposite the base 21 has, from the center towards the periphery, a central bore 23, with a lateral surface 34 and a bottom 35, a circular groove 24 of revolution around AA ′, having two lateral edges 25, 26, a internal edge 25 and an external edge 26, as well as a bottom 27. One or more through hole (s) 28 join (join) the bottom 27 of the groove 24 at the base 21. Between the groove 24 and the bore 23, support 2 includes a crown 29, having an upper surface 30 situated in a plane parallel to the base 21. The lateral edges of this ring consist of the internal lateral edge 25 of the groove 24 and the lateral face 34 of the bore 23. In an alternative embodiment where the plasma gas is introduced through the support 2, the support comprises one or more through conduits 75, joining, through the annular ring 29 adjoining the central bore 23, the lower surface 21 to the upper surface 30 of this ring 29. Such a conduit 75 is shown in dotted lines in FIG. 3. Finally, the support 2 comprises a peripheral crown 22 having an external lateral face 36 of diameter equal to that of the base 21 and an upper face 37. The lateral edges of the crown 22 are constituted by the external lateral face 36 of the support 2 and by the external lateral face 26 of the groove 24.

From the point of view of dimensions, the diameter of the bore 23 is sufficient to receive by tightening the cathode 3 which will be described later. The adjustment is sufficiently tight to ensure good electrical contact between the cathode support 2 and the cathode 3. The contact surface between the cathode and the anode must be as large as possible to ensure the passage of a current of several hundreds of amperes practically without losses. The width of the groove 24, i.e. the difference between the radii of the outer 26 and inner edges 25 is greater than the width (i.e. the difference between the outer radius and the inner radius of the crown) of a first crown 51 of the assembler 5. On the other hand, the diameter of the external wall 26 of the groove 24 is less than the external diameter of this crown 51 of the assembler 5 so that this crown 51 of the assembler 5 can be fitted tightly into the groove 24. The assembler 5, the assembly crown 51 of which is shown in FIG. 3 are described below.

The cathode 3 and the centering device 4 will now be described with reference to FIGS. 5 and 6 in which these parts appear in the assembled position.

The cathode 3 is cylindrical in shape with a flat circular base 31 and a conical head 32. It is included in a cathode centralizer 4, shown in FIGS. 5 and 6 in position around the cathode 3.

The centering device 4 also has a circular shape of revolution around AA '. It comprises a basic cylindrical part 41, extended by a cylindrical part 42 of smaller outside diameter. The internal diameter of the centering device 4 is constant over the entire height of the centering device, with the exception, in a first embodiment, of the diameter of an upper end portion 43 situated on the side opposite the base 41, the diameter of which is slightly greater to the inside diameter of the base 41 and of the cylindrical extension 42. The centralizer 4 has through holes. In the preferred embodiment, these holes join the outer face 50 to the upper surface 49 of the centralizer 4, onto which they open at the level of lights 95 shown in FIG. 7. In this preferred embodiment, the axes of the holes are inclined on the axis AA ', but not included in a plane containing the axis AA', so as to cause a tangential injection of the gases, inducing a vortex called a vortex which will force the arc foot to rotate in the anode so as not to not stay hooked in a preferential point. In the variant with an axial annular groove 45, these through holes 44 are drilled in the part 43 of the centralizer 4, at an axial height preferably situated at the junction with the part 42. It will be seen below that these holes 44 are intended to provide a passage for plasma gas to the inter-electrode space. When the gas inlet point or points are located on the support 2, it is advantageous to provide gas passages leading from the lower surface of the centralizer 4 to the means for distributing the plasma gas, these means being as will be seen more later either an axial groove 45 or the openings 95. These passages can be formed either by axial conduits 74 or by external axial 64 or internal 68 grooves, or alternatively by combinations of conduits 74, internal grooves 68 or external grooves 64.

The flat surfaces of the centering device 4 perpendicular to the axis AA ′, are constituted by the lower 46 and upper 47 surfaces of the basic part 41 of the centering device 4. The lower surface 46 of the base 41 is delimited by two concentric circles, the diameter of the inner circle being equal to the internal diameter of the centering device 4, the external diameter of this lower surface 46 being equal to the external diameter of the basic part 41. When the plasma gas is introduced through the support 2, the lower surface 46 of the centering device 4 may include a groove into which the passages 64, 68 or 74 open. In the assembled position, this groove is in communication with the conduits 75 of the support 2. The upper surface 47 of the basic part 41 of the centralizer 4 is delimited by two circles concentric, the diameter of the outer circle is equal to the outer diameter of the basic part 41 and the diameter of the inner circle is equal to the outer diameter of the extension 42 of the centering device 4. The planar surfaces of the centering device 4 perpendicular to the axis AA 'are also constituted, in one of the variants of the centering device 4, by the bottom 48 of a groove 45 and finally by the upper surface 49 of the centering device 4.

The bottom of the groove 45 is delimited by an external circle whose diameter is equal to the internal diameter of the end portion 43 and whose internal diameter is equal to the external diameter of the cathode 3.

Finally, the axial inner surface of the centering device

4 is constituted by two cylindrical surfaces, a lower surface 39 corresponding to the parts 41 and 42 whose diameter is slightly less than the diameter of the cathode 3, and in the variant with groove 45, by an upper surface 40, corresponding to the part 43 whose diameter is greater than the diameter of the cathode 3. The exterior lateral surfaces of the centralizer 4 are 2 in number, a lower lateral surface 38 corresponding to the base 41 and an upper lateral surface 50 corresponding to the parts 42, 43. From the point in terms of dimensions, the inside diameter of the centering device 4 is, as indicated above slightly smaller than the outside diameter of the cathode 3, so that this cathode 3 can be clamped in the centering device 4. In the preferred embodiment , the diameter of the lower lateral surface 38 is equal to the diameters of the surface 25 of the support 2 and of a lateral surface 125 of a part e of anode 1, which will be discussed more far. These three surfaces 25, 38 and 125 are thus in the same alignment once the assembly has been carried out. In the variant comprising an upper groove 45, the internal diameter of the terminal part 43 is greater than the diameter of the cathode 3, so that the cathode 3 and the terminal part 43 together form the groove 45. It will be seen below that this groove 45 receives, through the through holes 44, a plasma gas. Variants of this centralizer 4 will now be described in connection with FIGS. 5 and 7. The function of the centralizer 4 is to center and electrically isolate the cathode 3 relative to the anode 1. This function is provided by the lateral surface outer 50 of the upper part 42, which as will be seen later during the description of the cartridge 100 assembled, comes to bear in tight assembly on a bore of one anode. The variants which will be described below relate to another function of the centralizer which is a function of distribution of the plasma gas in a well distributed manner in the annular volume between the anode 1 and the cathode 3. In the mode described below above, the plasma gas is brought to the holes 44 by one or more conduits 127 of the anode 1 opening facing the holes 44 or preferably in a radial groove 135 of the anode 1 situated opposite the holes 44.

According to a first alternative embodiment, the introduction of the plasma gas can be carried out differently.

In this first variant shown in plan view in FIG. 7, the internal diameter of the centering device 4 is constant, from the lower surface 46 to the surface upper 49. The distribution of the plasma gas coming from conduits 127 from anode 1 is ensured by a radial annular groove 148 of the centralizer 4 shown in dotted lines in FIG. 5. A groove is said to be radial when it is dug from a surface parallel to axis AA '. The groove is said to be axial if it is hollowed out from a surface perpendicular to the axis. According to this variant, the centralizer 4 has several holes 144 which are not necessarily through. These holes are drilled from the groove 148. They each open onto an axial slot 95 ′, in this variant joining the upper surface 49 of the centralizer 4 to the holes 144.

According to a second variant, the grooves 148 and 45 are present, the lights 95 are not necessary. The holes 144 are through and join the grooves 148 and 45.

Finally, according to a third variant, the holes 144 are drilled directly from the lateral surface 50 of the upper part 42 of the centering device 4.11 will be seen later on, the holes 144 open out at the level of a radial annular groove 135 of the anode 1 receiving one or more plasma gas lines. At the other end, the holes 144 open either on slots 95 as in the first variant or on the axial groove 45. The grooves 135 of the anode and 148 of the centering device 4 can be present simultaneously.

If, as seen above, the plasma gas is introduced through the centralizer, the junction with the gas distribution means, 45, 95, is made by axial conduits 74 or even by external external 64 or internal 68 grooves 68. is obtained by the fact that the centering device is fitted sufficiently tight in the annular cavity 10 of the anode 1, or that the cathode 3 is fitted sufficiently tight in the centralizer.

The anode 1 and its ceramic insert 6 will now be described in conjunction with FIGS. 8 and 9.

The anode 1 is also a part of revolution around the axis AA '. It has a central cavity 10 of axis AA '. This cavity is through and extends axially from an upper face 11 of the anode to a portion 134 of a lower face 12 of the anode 1. The lower face 12 of the anode 1 is located opposite of the upper face 11 and consists of several parts located axially at different levels. From the upper face 11 to the part 134 of the lower face 12, the cavity 10 comprises an upper cylindrical part 13, the diameter of which is shown in FIGS. 8 and 9 substantially equal to the diameter of the cathode 3. This arrangement is by no means mandatory. The diameter and the length of the part 13 must, in known manner, be adapted to the nature and the flow rate of the plasma gas used, the working power, and the gas speeds desired at the nozzle outlet. Next comes a frusto-conical part 14. the diameter of the upper part of the part 14 is equal to the diameter of the part 13. The diameter of the lower part of the frusto-conical part 14 is greater than that of the part 13. Finally, there is a cylindrical lower part 15 extending axially from the lower base 16 of the frustoconical part 14 to the part 134 of the lower face 12 of the anode 1. The diameter of this part 15 of the cavity 10 is greater than the largest diameter of the tapered part 14. The tapered part 14 and cylindrical 15 are connected by a flat 17. The ceramic insert 6 is housed in the cavity 10, at the top of the part 15. This simple part will now be described before continuing the description of the anode 1. The insert 6 is a ring in the shape of a torus, generated by a rectangle in rotation around the axis AA '. The width of the rectangle is equal to the width of the flat part 17. This width of the flat part 17 itself results from the difference between the radius of the lower part 15 and the radius of the lower base 16 of the frustoconical part 14.

This insert 6 is inserted in a tight fit so that its upper surface 61 comes to bear on the flat 17 of the anode 1. The external lateral surface 62 of the insert is supported on the lateral surface 18 of the part 15 of the cavity 10 of the anode 1.

The outside of the anode 1 comprises the upper face 11 delimited by two circles. The diameter of the outer circle is preferably equal to the outer diameter of the support 2, the diameter of the inner circle of the upper surface 11 is equal to the diameter of the upper part 13 of the cavity 10. The exterior of the anode 1 also includes a cylindrical outer face 19. The lower face 12 comprises several parts located axially at different levels. From the outside towards the axis AA ′, there is successively a first ring 121. The outside diameter of this ring 121 is equal to the diameter of the peripheral cylinder 19. The inside diameter of this ring 121 is preferably equal to the outside diameter of the outer wall 26 of the groove 24 of the support 2. the lower surface 133 of this ring is a flat surface perpendicular to the axis AA '. The lower surface 133 is a part of the lower surface 12 of the anode 1.

Then there is a groove 122. This groove has a groove bottom surface 124, perpendicular to the axis AA '. This surface 124 is a part of the lower surface 12 of the anode 1. This groove 122 has an external cylindrical wall 126 whose diameter is equal to the internal diameter of the first ring 121. This diameter is preferably equal to the diameter of the outer wall 26 of the groove 24 of the support 2. The inner diameter of the axial groove 122 is preferably equal to the diameter of the inner cylindrical wall 25 of the groove 24 of the support 2. Finally, there is a second ring 123. This ring 123 has a lower surface 134, perpendicular to the axis AA '. This lower surface 134 is a part of the lower surface 12 of the anode 1. The ring 123 has an external cylindrical wall 125, part of which constitutes the internal cylindrical wall of the groove 122.

The cylindrical wall 125 has a diameter preferably equal to the internal diameter of the wall 25 of the groove 24 of the support 2. One or more first conduit (s) 127 each having two ends 128, 129 drilled in the anode 1 allows (tent) a passage of fluid from one of the outer walls 11, 19 of the anode 1, to the inner wall 18 of the cavity 10. In the example shown in connection with Figures 8 and 9 , the conduit 127 leads from its first end 128, at the upper surface 11 to its second end 129 located at the wall 18 of the lower part 15 of the cavity 10. It opens into this cavity 10 at an axial level located under the insert 6. This or these first conduits 127 are provided for the distribution of the plasma gas. According to a variant mentioned above in connection with the description of the centering device 4 and its variants, this or these conduits may alternatively lead into an annular radial groove 135 hollowed out from the lateral surface 18 of the cavity 10 of the anode 1, instead of opening directly onto this surface 18. In the preferred embodiment shown in FIGS. 8 and 9 the duct (s) 127 are parallel to the axis AA ′, they are located in the crown 123 containing the central cavity 10 , and they open into the groove 135. It should be noted that, according to variants, the outer end 128, first conduits 127 or at least part of them can be located on an outer wall of the cartridge 100 without that this wall is a wall of the anode 1. It could for example be a conduit (not shown) parallel to the axis AA ′ rising from the base of the support 2 through this support and the centralizer 4. According to a variant of this m ode of embodiment a part of the duct (s) 127, could be constituted by axial grooves of the centralizer 4 parallel to the axis AA '.

One or more second conduit (s) 130 each having two ends 131, 132, lead (s) from one of the external walls 11, 19 of the anode 1, towards the groove 122. In the example shown in connection with Figures 8 and 9, the conduit 130 has its first end 131 at the peripheral cylinder 19 and its second end 132 opens into the groove 122 at the bottom 124 of this groove. It should be noted that, according to variants, the external end 131 of the second conduits or at least part of them can be located on an external wall of the cartridge 100 without this wall being a wall of the anode 1 It could for example be an external wall of the assembler 5 or of the support 2.

The method of assembly and the assembly of parts 1-6, constituting together a cartridge 100 for a plasma torch according to the invention, will now be described in conjunction with FIGS. 2, 3, 5 and 8.

First of all, the assembler 5 will be described in connection with FIGS. 3, 8 and 10.

In FIGS. 3 and 8 the lower and upper parts of the assembler 5 have been shown in order to show this assembler 5 in position relative to the support 2 (FIG. 3) and to the anode 1 (FIG.

8) respectively.

The assembler 5 is shown in axial section in FIG. 10.

The assembler 5 comprises a lower cylindrical crown 51. The diameter of the outer cylindrical surface 52 of this crown 51 is slightly greater than the diameter of the wall 26 of the groove 24 of the support 2, so that this crown 51 can be fitted in tight assembly in this groove 24. The diameter of the inner wall 53 of this ring 51 is greater, at least for the part which, in the assembled position, is fitted in this groove 24, than the diameter of the inner wall 25 of the groove 24 of the support 2. In this way an axial annular volume 77 is formed between these two walls 25, 53. The ring 51 has a lower surface 59 perpendicular to the axis AA '. In the assembled position, this surface 59 is not in contact with the surface 27 of the bottom of the groove 24. In this way an annular volume 73 is formed between these two surfaces. This crown 51 is extended by a central part 54 also in the form of a crown. The diameter of the inner wall 55 of this ring 54 is greater than the diameter of the cylindrical wall 125 of the anode 1. In this way an axial annular volume 72 is formed between these two walls 55, 125. It is recalled that the wall 125 extends axially from the bottom 124 of the groove 122 of the anode 1 to the lower surface 134 of the second ring 123 of the anode 1. This lower surface 134 constitutes the lowest surface of the anode 1.

The upper part of the assembler 5 shown in the assembled position, FIG. 8, is also in the form of a crown 56. The diameter of the external wall 57 of this crown is greater than the external diameter of the external wall 126 of the groove 122 , of the anode 1. The difference in dimension between the diameter of the outer wall 57 of the crown 56 and the diameter of the wall 126 is such that this crown 56 can be fitted in a tight assembly in the groove 122.

The diameter of the inner wall 58 of the crown 56 is greater than the diameter of the wall 125 of the anode 1. In this way an axial annular volume 76 is formed between these two walls 58, 125. It is recalled that this wall 125 from the anode 1 extends axially from the bottom 124 of the groove 122 to the part 134 of the lower surface 12 of the anode 1, which is at the lowest level of the anode. Crown 56 has a upper surface 60. In the assembled position, this surface 60 is not in contact with the surface 124 of the bottom of the groove 122. In this way an annular volume 71 is formed between these two surfaces. The central part of the assembler 5 has an upper surface 65, a lower surface 66 both perpendicular to the axis AA ′, and an external lateral surface 67.

The upper surface 65 of the central part 54 of the assembler 5 is delimited by a circle having for diameter the outside diameter of the crown 56 and a circle having for diameter the diameter of the external lateral surface 67 of the central part 54. Similarly, the lower surface 66 of the central part 54 of the assembler 5 is delimited by a circle having for diameter the outside diameter of the lower crown 51 and a circle having for diameter the diameter of the outside lateral surface 67. The circles of delimitation of the upper 65 and lower 66 surfaces are concentric. In the example shown in the figures, the internal diameter of the axial central cavity 69 is constant so that the axial internal surfaces 58, 55, 53 of this cavity form only one and the same surface. This characteristic simplifies manufacturing but it is in no way mandatory.

In summary, the assembler 5 is presented as a part of revolution having a through axial central cavity 69. It comprises a central part 54 from which spring upwards and downwards cylindrical parts 56, 51 respectively of outside diameter smaller than the outside diameter of the central portion 54. It will be seen later that, in a first embodiment of the holding structure, the shoulder forming the central portion 54 is used to accommodate through holes and tapped holes. In this embodiment, these holes form part of the means for fixing the cartridge 100 to the holding and connection structure. The other part of these means consists of tapped holes or not of the holding and connection structure and of screws or bolts or nuts. In this embodiment, the central part 54 performs another function. One of the upper 65 or lower 66 surfaces serves as an assembly stop. In the example shown in FIG. 2, the lower surface 133 of the crown 121 of the anode 1 abuts on the upper surface 65 of the central part 54. On the other hand, a functional clearance is formed between the upper surface 37 of the crown 22 of the support 2 of the cathode 3 and the lower surface 66 of the central part 54. Thanks to this stop 65 and to a suitable dimensioning of the grooves 122 and 24 and the axial lengths of the crowns 56, 51 one is sure to spare the spaces annulars 71 and 73. The same stop function could be obtained by giving the throat bottoms 122 or 24 a rounded or conical shape, the width at the bottom of the throat decreasing with the depth of penetration. The functional clearance also makes it possible to ensure contact between the surfaces 30 of the support 2 and 46 of the centralizer 4, as well as between the surfaces 134 of the anode 1 and 47 of the centralizer 4.

According to an alternative embodiment, the assembler 5 can be constituted by a straight cylinder having an axial central cavity, the inside diameters and outside of the assembler being constant from the lower surface 59 to the upper surface 60.

The assembly of the torch will now be described.

The insert 6 is placed in position as described above in the anode 1. The cathode 3 is inserted into the bore 23 of the support 2, the underside 31 of the cathode coming into contact with the bottom 35 of the bore 23 , the lateral face of the cathode being in contact thanks to a tight assembly of the lateral surface 34 of the bore 23. In this way an electrical contact between the cathode 3 and the support 2 is ensured on all the surfaces facing the support 2 and the cathode 3. The centralizer 4 is placed around the cathode 3 as described above. The lower face 46 of the centralizer 4 is in contact with the upper face 30 of the crown 29. The assembler 5 is then placed in press position, the groove 122 of the anode 1 receiving the crown 56 of the assembler 5 The upper part of the crown 56 and / or the edges of the groove 122 can be bevelled or chamfered to facilitate insertion. When the assembler 5 is in place the lower surface 133 of the crown 121 of the anode 1 is in abutment against the upper surface 65 of the central part 54 of the assembler 5. The upper surface 60 of the assembler 5 n is not at the bottom of the groove 122 which means that an annular volume 71 is, as already mentioned above, formed between the lower surface 124 of the groove 122 of the anode 1 and the upper surface 60 of the crown 56 The anode 1 and its insert 6 thus assembled with the assembler 5 is then assembled with the support assembly 2, cathode 3 and centering device 4, the crown 51 being inserted by the press into the groove 24 of the support 2. To facilitate insertion, the bottom of the crown 51 and the top of the groove 24 may be bevelled or chamfered. When the fitting operation is finished, a functional clearance remains as shown in an exaggerated manner in FIG. 2, between the lower surface 66 of the central part 54 of the assembler 5 and the upper face 37 of the ring 22 of the support 2. The lower surface 59 of the crown 51 of the assembler 5 is not in contact with the groove bottom 27 of the groove 24, an annular volume 73 is therefore, as already mentioned above, formed between the lower surfaces 59 of the crown 51 and 27 of the support 2. It will be seen later that this annular volume 73 formed between these two surfaces is intended to collect the cooling water.

The operation of the torch will now be explained. As a torch, the operation is the usual operation of a torch, however the cooling water inlet circuit and the plasma gas circuit will now be discussed. It is first of all recalled that in the example shown the interior walls 53 of the lower ring 51, 55 of the central part 54 and 58 of the upper ring 56 of the assembler 5 are aligned. It is also recalled that the internal diameter of the assembler 5 is greater than the external diameter of the crown 123 of the anode 1, the diameter of the external lateral surface 38 of the centralizer 4 and the diameter of the internal wall of the groove 24 of the support 2 so that an annular volume 72 is provided. This volume annular 72 extends axially from the upper part 60 of the crown 56 to the lower part 59 of the crown 51 of the assembler 5. In the most general case this annular volume is formed of annular volumes 76, 72 and 77 and possible annular connecting volumes between these different parts of the volume. The water is brought in through the opening 131, and through the conduit 130 on the outer surface of the anode 1, the inner end 132 of the conduit 130 opens into the annular volume 71 formed between the surfaces 124 and 60 of the groove 122 and crown 56 respectively. This water can flow along the interior wall 125 of the anode 1 through the annular volume or volumes 72 up to the annular volume 73 formed between the bottom of the annular crown 51 and the bottom 27 of the groove 24. This water flows through the conduit (s) 28 formed in the bottom of the annular groove 24. It can thus be seen that the water circuit is ensured without a seal internal to the torch, thanks to the tight assembly of the crowns 51 and 56 in the grooves 24 and 122 respectively. Naturally the water arrivals and departures could be placed differently the main thing being that a circulation of water cools a ring of the anode 1.

Similarly, the arrival of plasma gas through the opening 128 of the anode 1 is done without a gasket, the gas opening through the conduits 44 or 144 in the openings 95 arranged around the cathode 3 on the centralizer 4 , or in the groove 45, according to the variant embodiments. The torch assembled according to the invention therefore comprises only six parts, the anode 1, the support 2, the cathode 3, the centering device 4, the assembler 5 and the insert 6. The assembly of this torch can be carried out with fewer press operations if there are specialized tools for lateral support of the parts to be assembled. From the point of view of the functions of the different parts making up the assembled cartridge 100, it will be observed that if the cathode 3 is sufficiently tightened in the bore 23 of the support 2, the support 2 the cathode 3 the centering device 4, the part 42 of which is tightened in the cavity 10 of anode 1, and anode 1 form an assembled assembly. Under these conditions the assembler 5 in cooperation with the grooves 24 of the support 2 and 122 of the anode can only be considered as part of the water circuit. It will also be seen later that the assembly of the cartridge 100 can be consolidated by mounting the cartridge 100 in position in the support and connection structure.

It will also be observed that if the cartridge 100 is so simple, this is due to the overall architecture of the cartridge. Thus, the plasma gas circuit is entirely in a central part of the assembled cartridge 100. It may be a central part of the anode 1, in the form of a crown 123, this crown immediately adjoining the central cavity 10 of the anode. It may also be conduits 75 passing through the support 2 to be in communication with the passages 64, 68, 74 of the centralizer. The water circuit is located at the periphery of this same ring 123 adjoining the central cavity 10 so that there is no crossing of the water and gas circuits.

It should be noted that the assembler was presented as a separate part of the support. this is due to the fact that the assembler joining the support made of a conductive material in contact with the cathode is in contact with the anode. It is therefore made of an electrically insulating material to avoid a short circuit between the anode and the cathode. It is obviously possible to produce the support in an insulating material comprising conductive bushings to connect the cathode. In this case we can consider that the assembler is made up of the parts made of insulating material and the support is made up of the parts made of conductive material.

Some indications relating to the materials of the components of cartridge 100 will now be provided. Anode 1, and cathode support 2 which in

1 embodiment are made of electrolytic copper could be made of any material, for example metallic, conductive of electricity and allowing one evacuation of very high heat fluxes. The doped tungsten of cathode 3 could be machined in any metallic material having a low potential for extraction of electrons.

The centralizing diffuser 4 can be machined from any plastic material for assembly purposes, and having good swelling resistance to water, a high dielectric character and good mechanical resistance to radiation and to temperature.

The assembly body 5 may be machined from a plastic material for assembly purposes by simple plastic pressure.

The insulating insert 6 can be machined from a ceramic material having good impact resistance thermal, radiation and with a strong dielectric character, for example boron nitride.

It has been seen that the assemblies are of the tight fitting type produced under press, which implies a pair of suitable material: In the case of the torch presented, the assemblies are constituted by plastic couples - copper alloy or alloy of tungsten - copper alloy.

Other couples of materials can be envisaged, in particular ceramic materials could replace the plastic materials, if one interposed, in itself known manner, between the doll of pressure and the jack of press of assembly a vibrator . Two examples of connection and holding structure of the cartridge 100 will now be briefly described in connection with FIGS. 11, 12, and 13. A first connection and holding structure 80 shown in FIG. 11 in an axial section, has two parts all two of revolution around the axis AA '. A lower part 81 conceals a bore 83 whose internal diameter is equal to the external diameter of the support 2, so that this support 2 can easily be introduced into this part 81. The example shown in FIG. 11 corresponds to one of the variants of realization of the cartridge 100 in which the cooling fluid is evacuated by the conduit (s) 28 of the support 2. This is why in this example the lower part 81 comprises a water evacuation and a current inlet represented in 84. One or more O-ring (s) make it possible in known manner to ensure sealing. An upper part 82 of the holding and connection structure conceals a bore 85 whose internal diameter is equal to the external diameter of the anode 1, so that this anode 1 can easily be introduced into this part 82. This structure 82 comprises an axial central hole 91 with flared edges allowing the plasma to pass. The example shown in FIG. 11 corresponds to one of the variant embodiments of the cartridge 100 in which the arrival of the cooling fluid and the plasma gas are carried out through the conduit (s) 130 and 127 of the anode 1 for the water and gas supply respectively. This is why in this example the upper part 82 has a water inlet 86 and a gas inlet 87. One or more O-ring (s) make it possible in known manner to ensure sealing. The water inlet 86 opens opposite the conduit 130 of the anode 1. When there are several conduits 130, a radial groove 88 receiving the water inlet 86 allows distribution to the various conduits. Similarly for the gas inlet, when there are several conduits 127, an axial groove, not shown, receiving the gas inlet 87 allows distribution to the various conduits 127.

The main interest of this structure 80 is to be able to quickly exchange the cartridge 100. For mounting the upper part of the cartridge, that is to say that corresponding to the anode 1 is introduced into the upper part 82 of the structure 80. In order to facilitate a radial positioning allowing the water and gas inlets to correspond well with the orifices 128, 131 of the anode, it is possible to provide polarizing elements on the upper part 82 and on the anode 1 .When it is in place the cartridge 100 is screwed onto the upper part 82 by means of screws 89 passing through holes in the assembler 5 and screwing into tapped holes in the upper part 82. The lower part 81 is then put in place by introducing the support 2 in bore 83. Means can also be provided to facilitate correct radial positioning. Screws 90 make it possible to fix the lower part 81 to the assembler. These screws pass through holes in the assembler 5 and are screwed into tapped holes in the lower part 81.

A currently preferred embodiment of the structure 80 will now be carried out in conjunction with FIGS. 12 and 13. FIG. 13 is a front view of the structure 80 assembled with the cartridge 100, with a partial axial section in the upper right corner . FIG. 12 is an axial section along a plane perpendicular to the plane of FIG. 13.

According to this embodiment, the lower 81 and upper 82 flanges and the cartridge 100 are kept assembled by means of a bracket 92. This bracket 92 has a U shape. Two parallel arms of the U are rotatably fixed by means of screws 96 perpendicular at axis AA ′ at the upper flange 82. Insulating sleeves and washers are provided in a known manner to avoid electrical contact between the stirrup and the flange 82. The lower flange 81 is provided on its underside with a central imprint 93. In the assembled position, a screw 94 mounted in the horizontal part of the U of the bracket 92 blocks the rotation of the bracket 92 around the screws 96 and exerts pressure at the impression 93. preventing the movement of the flanges 82 and 81 in the axial direction. Insulation electrical flange 81 and the bracket is obtained by means of an insulating sleeve 95 and insulating washers. A locking lock nut 97 is provided.

The distance between the horizontal arm of the stirrup 92 and the underside of the flange 81 is sufficient to allow disengagement of the cartridge 100 from the bores 83 and 85 of the flanges 81 and 82 respectively.

The operation is as follows:

For disassembly of the cartridge 100, the lock nut 97 is released and the screw 94 unscrewed until the cartridge 100 can be extracted from one of the flanges 81 or 82. In this position the flange 82 is always secured to the bracket 92 and the flange 81 is maintained, the screw 94 still inside the cavity 93. In this position of the flanges the cartridge 100 can be extracted from the other flange by a slight rotation of the caliper 92 around the axis formed by the screws 96. This rotation frees the passage of the cartridge 100. For reassembly, the procedure is reversed.

This method of assembly is advantageous from the mechanical point of view because it makes it possible to exert an assembly pressure of the flanges 81, 82 and of the cartridge 100 which is automatically axial. There is no risk of asymmetric pressures creating a lateral deformation constraint. It is also interesting because it allows the assembly and disassembly of the cartridge 100 by means of a single screw without the need to maintain the flanges 81, 82, which is particularly advantageous when working in a glove box.

Naturally, other mechanical means for fixing the cartridge 100 to the structure 80 are within the reach of those skilled in the art. The seals are ensured by seals and by the fact that the cartridge 100 is fitted in the bores 83, 85.

The necessary adaptations of the structure 80 to make it compatible with the variants described in relation to the cartridge 100 relative to the places of arrival or departure of water or gas are within the reach of the skilled person and will not be commented on .

Claims

1. Cartridge (100) generating plasma for a plasma torch, having centered on an axis AA ', an annular anode (1) comprising a central cavity (10) formed inside a central ring (123) of the anode (1), this central cavity (10) receiving a cathode (3) centered on AA ′, the anode (1) and the cathode (3) providing between them an annular space for the production of an arc, means for distributing a plasma gas, the distributed gas circulating in the annular space between the cathode (3) and the anode (1), means for cooling the anode (1), comprising in particular conduits for an anode cooling fluid (1), these conduits having an inlet and an outlet, assembly means, cartridge characterized in that the assembly means comprise a cathode support (2) having a conductive part for bringing the electric currents necessary for the operation of the torch from a current input to the cathode (3), means (2, 23, 4) for positioning the cathode (3), an assembler (5) the support (2) of the cathode (3), the assembler (5) and the annular anode (1) having hollow parts (24, 122) and projecting parts (51, 56) all axially parallel to the axis AA ', the projecting parts (51, 56) being fitted tightly into the hollow parts (24, 122).

2. Cartridge (100) according to claim 1 characterized in that one or more hollow parts (24,

122) are formed by annular grooves (24, 122) and in that, one or more projecting parts (51, 56) are constituted by annular rings (51, 56), the outer diameter of the crowns (51, 56) being greater than the outer diameter of the grooves (24, 122) so that one or more annular crowns (51, 56) are fitted tightly in one or more annular grooves (24, 122).

3. Cartridge (100) according to claim 2 characterized in that a projecting part (51) of the assembler (5) is constituted by an annular ring (51) of lower axis AA 'having an outside diameter, a diameter interior and a lower surface, in that a hollow part (24) of the cathode support (2) (3) is constituted by an annular groove (24) centered on the axis AA ', the groove (24) having a diameter outside, an inside diameter and a bottom groove surface (27) (24), and in that the outside diameter of the lower annular ring (51) of the assembler (5) is slightly greater than the outside diameter of the groove ring (24) of the cathode support (2) (3) so that the lower annular ring (51) of the assembler (5) is fitted tightly into the annular groove (24) of the cathode support (2) ).

4. Cartridge (100) according to claim 3 characterized in that a projecting part (56) of the assembler (5) is constituted by an annular ring (56) upper axis AA 'having an outer diameter, an inner diameter and an upper surface, in that a hollow part (122) of the annular anode (1) is constituted by an annular groove (122) centered on the axis AA ', the groove (122) having an outside diameter, a inside diameter and a bottom groove surface (124), and in that the outside diameter of the annular crown (56) upper part of the assembler (5) is slightly greater than the outside diameter of the annular groove (122) of the anode (1) so that the upper annular ring (56) of the assembler (5) is fitted tightly into the annular groove (122) of the anode (1).

5. Cartridge (100) according to claim 2 characterized in that a first projecting part (51) of the assembler (5) is constituted by an annular ring (51) lower axis AA 'having an outside diameter, a diameter interior and a lower surface (59), in that a hollow part (24) of the support (2) of cathode (3) is constituted by an annular groove (24) centered on the axis AA ', the groove (24) having an outside diameter, an inside diameter and a bottom groove surface (27), and in that the outside diameter of the first annular ring (51) of the assembler (5) is slightly greater than the outside diameter of the groove ring (24) of the cathode support (2) (3) so that the lower annular ring (51) of the assembler (5) is fitted tightly into the annular groove (24) of the cathode support (2) ) and in that a second projecting part (56) of the assembler (5) is constituted by an annular ring (56) sup axis AA ′ having an outside diameter, an inside diameter and an upper surface (60), in that a hollow part (122) of the annular anode (1) is constituted by an annular groove (122) centered on axis AA ′, the groove having an outside diameter, an inside diameter and a bottom groove surface (124), and in that the outside diameter of the second annular ring (56) of the assembler (5) is slightly greater than the outside diameter of the groove annular (122) of the anode (1) so that the upper annular ring (56) of the assembler (5) is fitted tightly into the annular groove (122) of one anode (1).

6. Cartridge (100) according to claim 5 characterized in that the assembler (5) comprises a hollow central part (69) joining the crowns (51, 56) lower and upper, this central part (69) having an inner diameter , in that the groove (122) of the anode (1) receiving the upper crown (56) of the assembler (5) is peripheral to the central crown (123) of the anode (1) forming the central cavity (10) of the anode (1), the inside diameter of at least part of the assembler (5) being greater than the outside diameter of the central crown (123) of the anode (1) so that a first annular volume (72) is arranged between the assembler (5) and the central crown (123) of the anode (1), this volume (72) being in communication with the outside of the cartridge (100) through at least two conduits (130, 28), a conduit (130) for supplying a cooling fluid and a conduit (28) for discharging a cooling fluid.

7. Cartridge (100) according to claim 6 characterized in that in the assembled position the upper surface (60) of the upper crown of the assembler (5) does not abut the bottom of the groove (124) of the anode (1), so that a second annular volume (71) is formed between this upper surface (60) and the bottom of the groove (124), one (130) of the communication conduits with the outside opening into this volume (71).

8. Cartridge (100) according to one of claims 6 or 7 characterized in that in the assembled position the lower surface (59) of the lower ring (51) of the assembler (5) does not abut the bottom (27 ) of the groove (24) of the support (2), so that a third annular volume (73) is formed between this lower surface (59) and the bottom

(27) groove (24) one of the conduits (28) for communication with one exterior opening into this volume (73).

9. Cartridge (100) according to one of claims 1 to 8, characterized in that it comprises a centralizer (4) having an axial cavity centered on the cathode (3), a lower surface (46), a surface ( 38, 50) lateral exterior, an interior lateral surface (39), an upper surface (48, 49) at least an upper part (42) of the centralizer (4) being fitted inside the central cavity (10) of the anode (1), one or more passage (s) (44, 144, 95, 45, 64, 68, 74) bringing the lateral or lower external surface (50, 46) into communication with the upper surface (48, 49) of the upper part (42) of the centralizer (4).

10. Cartridge (100) according to claim 9 characterized in that passages (44, 144) are constituted by conduits (44, 144) joining the lateral outer surface (50) of the centralizer (4) or to a groove (45 ) axial annular of the centering device (4) formed between the centering device (4) and the cathode (3) by an offset of the inner lateral surface (39) of the centering device (4), that is to say holes 95 formed on the upper surface (49 ) of the centralizer (4).

11. Cartridge (100) according to claim 10, characterized in that conduits (44, 144) have an axial line not contained in an axial plane of the centralizer (4).

12. Cartridge (100) according to one of claims 10 or 11 characterized in that conduits (44, 144) have one end opening into a radial groove (148) formed on the outer lateral surface (50) of the centralizer (4 ).

13. Cartridge (100) according to one of claims 10 or 11 characterized in that the conduits (44, 144) have one end opening into a groove (135) inner radial of the inner cavity (10) of the anode ( 1).

14. Cartridge (100) according to one of claims 9 to 13 characterized in that the anode

(1) is provided with one or more conduits (127) passing axially through a central ring (123) of the anode (1) surrounding the central cavity (10) of the anode (1) and opening facing one end of the passages (44, 144) of the centralizer (4).

15. Cartridge (100) according to one of claims 9 to 13 characterized in that the support

(2) is provided with one or more conduits (75) passing through the support (2) and communicating with passages (64, 68, 74) of the centralizer (4).

16. Cartridge (100) according to one of claims 9 to 13 characterized in that the support (2) is provided with a central bore (23), this bore (23) accommodating a lower part of the cathode (3) .

17. Cartridge (100) according to claim 16 characterized in that the support (2) is provided with a central ring (29) formed around the bore (23) housing the lower part of the cathode (3), an upper surface (30) of this ring (29) being in contact with the lower surface (46) of the centralizer (4).

18. Cartridge (100) according to claim 17 characterized in that the centralizer (4) is provided with a lower shoulder (41) having a lower surface (46) and an upper surface (47), the lower surface of this shoulder constituting the lower surface (46) of the centering device (4), and the upper surface (47) of this shoulder (41) being in contact with a lower surface (134) of the central crown (123) of the anode (1 ).

19. Plasma torch characterized in that it comprises a structure (80) for connecting and holding a cartridge (100) for a plasma torch according to one of claims 1 to 18, this structure having an upper part ( 82) comprising a bore (85) for receiving the anode (1) of the cartridge, a central axial hole (91) whose diameter is at least equal to or greater than the diameter of the upper part (13) of the cavity ( 10) central anode (1), and a lower part (81) comprising a bore (83) for receiving the support (2) of the cartridge, the structure having means (89, 90, 92, 96, 97 ) of attachment to the cartridge (100) and carrying inlets (86, 87) of a cooling fluid, of plasma gas, and means (84) for evacuating the cooling fluid, these means coming, when mounting the cartridge (100) in the structure (80), position itself facing the corresponding conduits (127, 130, 75) of the cartridge (100).

20. Plasma torch according to claim 19 characterized in that the means for fixing to the cartridge (100) of the fixing and retaining structure (80) comprises a stirrup (92) rotatably fixed to the upper part (82) of the structure (80) comprising the bore (85) for receiving the anode ( 1) of the cartridge, a screw (94) mounted in the bracket (92) coming to bear on the lower part (81) of the structure (80) comprising the bore (83) for receiving the support (2) of the cartridge (100).