EP1169890B1 - Plasma torch cartridge and plasma torch adapted to be equipped therewith - Google Patents

Description

Field of the invention

The invention lies in 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, electrically conductive 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 plasmagenous gas (s) through an electric arc that 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 that contains the two electrodes and it is the high-speed gas jet at high temperature (plasma) that is used in the process.

The 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 each other and forming between them a channel 7 of gas circulation.

The two electrodes 1,3 are connected to a high voltage, high frequency generator (HT-HF) and to a DC generator. They must imperatively be energetically cooled (by circulation of water) to avoid their fusion.

Initially and thanks to the HT-HF generator, an electric arc 8 gushes between the two electrodes (cathode and anode) ionizing the introduced gas and making the interelectrode 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 that is established between the anode and the cathode. This voltage depends on several parameters such as the nature and the flow rate of gas used, but also the wear of the electrodes for a not insignificant 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 an arc plasma 8 is used for thermal spraying (surface treatment), gas heating or chemical synthesis. The energy supplied to the gas (s) by the electric arc makes it possible to heat them at temperatures above 10,000 K.

The choice of plasma gas or gases is almost unlimited. It is a function of the requirements of the process (oxidation, nitriding, high temperature in reducing medium, ....) The power range is very wide, it ranges from a few kilowatts to several megawatts. Very often, the choice of nature and Plasma gas flow dictates the possible operating range.

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 power of work.

Its size, shape and simplicity can also be important for working in small or hostile environments.

Currently existing torches are complex assemblies, comprising at least ten pieces (seals, screws and fittings fluid excepted). 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 that must take place regularly (in most cases after a few dozen hours of operation). This operation always requires the dismantling / reassembly of subassemblies and the change of the seals.

By way of illustration, three examples of known plasma torches are hereinafter briefly discussed.

A first known torch operates with a mixture of air / argon or oxygen / argon, its power is about 100 kW. It consists of 15 machined parts, 21 seals, 22 screws and 6 fluid connections. The regular wear parts are the cathode and the anode, an insulating ring and an injection nozzle. A minimum of maintenance (change of the anode) is required within 100 hours of operation under the best conditions of use.

A second known torch has been developed for hydropyrolysis of heavy hydrocarbons. The plasma gases are argon and hydrogen which are mixed with methane at the torch outlet. This torch is similar to a thermal projection torch. There are, except for fluid supply fittings and hardware, 10 machined parts and 7 O-rings.

As a third example, it is cited one of the simplest torches sold by the company SULZER METCO. This is the thermal spray torch F4-MB. This type of torch works, conventionally with argon, helium and nitrogen alone or in mixture. The addition of hydrogen is often used to gain power (increase of arc voltage). There are still 8 machined parts, 14 O-rings, 12 hardware and 3 fluid fittings.

The Japanese patent application JP 04-249,096 describes a plasma torch in which, in order to reduce the probability of creating an arc between the anode and the cathode, the plasmagenic gases follow a path that allows them to swirl. To this end, a centralizer 10a which is a part placed between the anode and the cathode has an opening 106 which goes from the top face of the centraliser to a side face. Another conduit 102 located between the anode and the centering piece 10 guides the gases from the conduit 106 down the anode.

Conduits 107 join the outside of the centralizer 10 to a central cavity 105 thereof. This feature makes it possible to create a jet swirling plasma gas. This gives a more regular wear of the cathode.

Brief description of the invention

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 wear parts. It has been developed in particular for a gas heating application in a pyrolysis gas afterburner reactor of chlorinated radioactive waste, strongly 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 glovebox or remote manipulator); the work must be simplified to the maximum. Standard exchange of subassemblies is often preferable to dismantling and reassembling isolated parts in a complex package. The intervention time is shorter, the reliability of a new and controlled subassembly 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, a disposable interchangeable cartridge constituting a plasma generator for insertion into a connecting structure and holding the cartridge. This connection structure and maintenance of the cartridge is intended to connect the cartridge to its plasma gas supplies, cooling fluid and electrical currents. This structure involves end of the first connection means of the cartridge.

These first means serve as intermediates for power supplies in electrical currents, water and gas. These power supplies are completely disassociated from the plasma cartridge.

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

The invention relates to a plasma generating cartridge for a plasma torch having the features set forth in claim 1; and a plasma torch having the features of claim 13.

In this way the plasmagenic gas circuit is produced with a single auxiliary part, the centralizer, by a simple operations performed on the press to push in an axial direction the centraliser clamped on the cathode in the axial cavity of the anode. Because of the clamping of the centering device in the anode and on the cathode, the mounting of the anode assembly cathode is achieved. This mounting of the anode on the cathode is also a part of the plasma gas distribution circuit. In the preferred embodiment, the continuity and the regularity of the gas distribution is ensured by the fact that the relay between the centralizer ducts and the gas supply ducts through the anode is provided by an annular volume of distribution. The annular distribution volume is constituted by a radial groove, which can be located either on the anode or on the centraliser, or on both the anode and the centraliser. In this way the cartridge according to the invention requires for the gas supply no seal or conduit, other than those made by drilling or machining or molding, in the parts necessary for the operation of the torch. From the assembly point of view, the use of a connection groove between the centralizer ducts and the gas supply ducts through the anode simplifies assembly since it is not necessary to index angularly the anode and the centraliser.

The plasmagene gases received at the first ends of the centralizer ducts are distributed around the cathode, through several holes opening at the upper surface of the upper part of the centralizer, either on lights or on a throat terminal gas distribution.

In the preferred embodiment, wherein the cathode is carried by a support comprising means for positioning the anode, an annular cooling volume formed between an assembler and the anode receives a cooling fluid through a conduit leading the fluid of an outer surface of the cartridge but preferably from the anode to this annular volume. The assembler, the annular anode and the support comprise hollow portions in the form of annular grooves and annular ring-shaped projections all oriented parallel to the axis AA ', the projections being fitted tightly into the hollow portions. The sealing of the annular volume is obtained by the fact that the outer diameter of each 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 requires for the water supply no seal or conduit other than those made by drilling or machining or molding in the parts necessary for the operation of the torch. The assembler or assembly body is so called because in addition to its function of forming the annular volume around the anode, in which the cooling fluid passes, it also has a mechanical assembly function of the cartridge. It contributes to the assembly of the cathode support and the anode.

In the preferred embodiment which will be described below the assembler is a piece of electrically insulating material comprising a lower crown and a coaxial upper ring. The lower crown is fitted into a groove of the support, the upper crown is fitted into a groove of the anode. This throat of the anode is peripheral to a crown of the anode. This crown of the anode houses the central cavity of the anode. In this embodiment, the inner radial dimensions of the assembler are greater on at least one portion axially central to 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 ring of the anode and the assembler. This volume is in communication with conduits for supplying and discharging the cooling fluid, via ducts pierced in the anode, the assembler, or the support.

Other advantages and interests of the invention will become apparent when describing a preferred embodiment and variants that will be made hereinafter with reference to the accompanying drawings.

Brief description of the drawings.

• The figure 1 , already commented illustrates the principle of a plasma torch.
• The figure 2 represents an axial section of an assembled cartridge according to the invention.
• The figure 3 represents an axial section of a cathode support and a lower part of an assembler assembled with this support.
• The figure 4 represents a view from above of the support represented figure 3 .
• The figure 5 represents an axial section of a cathode centering device and a cathode assembled with this centering device.
• The figure 6 represents a view from above of the centraliser and the cathode represented figure 5 .
• The figure 7 represents a view from above of a variant of the centraliser and the cathode represented figure 5 .
• The figure 8 represents an axial section of an anode, an insert assembled on this anode and a upper part of an assembler assembled with this anode.
• The figure 9 represents a top view of the anode and the insert represented figure 8 .
• The figure 10 represents an axial section of an assembler.
• The figure 11 represents an axial section along a plane perpendicular to the plane of the figure 12 a connection structure and maintenance of a cartridge according to the invention assembled with a said cartridge shown schematically.
• The figure 12 is a front view of the structure assembled with the cartridge 100, with a partial axial section in the upper right corner.

Description of a preferred embodiment

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

• d'une tuyère anode en cuivre électrolytique 1
• d'un support cathode en cuivre électrolytique 2
• d'une cathode en tungstène dopé 3
• d'un diffuseur centreur cathode en matière plastique 4
• d'un assembleur en matière plastique 5
• d'un insert céramique 6

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

• of an electrolytic copper anode nozzle 1
• of a cathode support in electrolytic copper 2
• a doped tungsten cathode 3
• of a plastic cathode center diffuser 4
• a plastic assembler 5
• a ceramic insert 6

When assembled, the parts 1 to 6 provide for each other in a known manner and represented figure 1 , a gas circulation channel 7, an inter-electrode space where an arc 8 can be created. The plasma 9 (not shown in FIG. figure 2 ) is ejected by a nozzle 13 of the anode 1.

Each of these pieces and their method of assembly will now be described.

The cathode support 2 described below, in connection with the Figures 3 and 4 , is a cylindrical piece 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 comprises, 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 inner edge 25 and an outer edge 26, and a bottom 27. One or more through hole (s) 28 seal (join) the bottom 27 of the groove 24 to the base 21. Between the groove 24 and the 23, the support 2 comprises a ring 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. Finally, the support 2 comprises a peripheral ring 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 ring 22 are constituted by the face outer side 36 of the support 2 and the outer lateral face 26 of the throat 24.

From the point of view of dimensions, the diameter of the bore 23 is sufficient to receive in tight fitting the cathode 3 which will be described later ensuring thus a good electrical contact between the cathode and the support. The width of the groove 24, i.e., the difference between the radii of the outer and inner edges 26, is greater than the width (i.e., the difference between the outer radius and the inner radius of the crown) of a first ring 51 of the assembler 5. By cons, the diameter of the outer wall 26 of the groove 24 is smaller than the outer diameter of the ring 51 of the assembler 5 so that the ring 51 of the assembler 5 can be pressed tightly in the groove 24. The assembler 5, the crown 51 of assembly is shown figure 3 is described later.

The cathode 3 and the centralizer 4 will now be described with reference to the Figures 5 and 6 in which these pieces appear in assembled position.

The cathode 3 has a cylindrical shape with a flat circular base 31 and a conical head 32. It is included in a cathode centering device 4, represented by FIG. Figures 5 and 6 in position around the cathode 3.

The centraliser 4 also has a circular shape of revolution around AA '. It comprises a basic cylindrical portion 41, extended by a cylindrical portion 42 of smaller outer diameter. The inside diameter of the centraliser 4 is constant over the entire height of the centraliser except, in one embodiment, the diameter of an upper end portion 43 located on the opposite side to the base 41, whose inner diameter is slightly greater to the inside diameter of the base 41 and the cylindrical extension 42.

The plane surfaces of the centering device 4 perpendicular to the axis AA 'are formed by the lower surface 46 and upper 47 of the basic portion 41 of the centralizer 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 centralizer 4, the outer diameter of this surface lower 46 being equal to the outer diameter of the basic portion 41. The upper surface 47 of the basic portion 41 of the centralizer 4 is delimited by two concentric circles, the diameter of the outer circle is equal to the outside diameter of the basic portion 41 and the diameter of the inner circle is equal to the outer diameter of the extension 42 of the centralizer 4. The flat surfaces of the centralizer 4 perpendicular to the axis AA 'also comprise, in the embodiment mentioned above, the bottom 48 of a groove 45 and finally the upper surface 49 of the centralizer 4.

The bottom 48 of groove 45 is delimited by an outer circle whose diameter is equal to the inside diameter of an end portion 43 and by an inner circle whose diameter is equal to the outside diameter of the cathode 3.

Finally, the axial inner surface of the centralizer 4 is constituted by a lower surface 39 corresponding to the parts 41 and 42 whose diameter is slightly smaller than the diameter of the cathode 3, and in the embodiment with groove 45 by an upper surface 40, corresponding to the portion 43 whose diameter is greater than the diameter of the cathode 3. The outer lateral surfaces of the centralizer 4 are 2 in number, a lower lateral surface 38 corresponding to the base 41 and a surface upper side 50 corresponding to the parts 42, and 43 in the version with groove 45.

From the point of view 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 press fit in the centering device 4. The internal diameter of the the end portion 43 is, in the version with groove 45 greater than the diameter of the cathode 3, so that the cathode 3 and the end portion 43 together form the groove 45.

Variations of this centralizer 4 will now be described in connection with the figures 5 and 7 . The centralizer 4 serves to center and electrically isolate the cathode 3 relative to the anode 1. This function is provided by the outer lateral surface 50 of the upper part 42, which will be seen later in the Description of the cartridge assembly 100, bears on a bore of the anode. The variants that will be described below relate to the function of the centraliser relative to the distribution of the plasmagene gas well distributed in the annular volume between the anode 1 and the cathode 3.

In a first embodiment comprising two variants shown in top view figures 6 and 7 , the centralizer 4 comprises several conduits 44. In the preferred embodiment of these conduits 44 shown figure 6 join the outer face 50 to the upper surface 49 of the centralizer 4, on which they open at the level of lights 95 represented figure 7 , or in the version with groove at the level of bottom 48 of throat 45 ( figure 6 ). In this preferred embodiment the axes of the ducts 44 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 tourbillon which will force the foot of the arc to rotate in the anode so that it does not remain attached to a preferred point. This embodiment has the advantage of distributing the wear of the cathode regularly around the cathode and thus to increase its longevity. On the other hand, it causes a vortex of the plasma which is not always desirable as a function of the use of the plasma. This is why in a second variant ducts 144 are drilled in an axial direction lying in a radial plane ( figure 7 ). They each open on a light 95, or in the version with groove 45 in the groove 45.

In the embodiments which have just been described, the ends of the ducts 44 or 144 situated on the lateral outer surface 50 of the centralizer 4 can open either directly at the level of the lateral surface 50, which is the preferred mode, either at the level of a radial groove 148 excavated from this lateral surface 50. This groove is shown in dashed lines figures 5 and 7 .

The seal is obtained by the fact that the centraliser is fitted sufficiently tightly in the central cavity 10 of the anode 1 which will now be described.

The anode 1 and its ceramic insert 6 will be described in connection with the Figures 8 and 9 .

The anode 1 is also a piece of revolution around the axis AA '. It comprises 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 portion 134 of the lower face 12, the cavity 10 has an upper cylindrical portion 13 forming a nozzle for the plasma. Next comes a frustoconical portion 14. the diameter of the upper portion of the portion 14 is equal to the diameter of the portion 13. The diameter of the lower portion of the frustoconical portion 14 is greater than that of the portion 13. Finally, there is a cylindrical lower portion extending axially from the lower base 16 of the frustoconical portion 14 to the portion 134 of the lower face 12 of the anode 1. The diameter of this portion 15 of the cavity 10 is greater than the largest diameter of the the frustoconical portion 14. The frustoconical 14 and cylindrical portions 15 are connected by a flat portion 17. The ceramic insert 6 is housed in the cavity 10, at the top of the part 15. This simple piece will now be described before continuing the description of the anode 1. The insert 6 is a torus-shaped ring, generated by a rectangle rotating about 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 such a way that its upper surface 61 bears on the flat part 17 of the anode 1. The outer lateral surface 62 of the insert bears 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 portion 13 of the cavity 10. The outside of the anode 1 also comprises a cylindrical outer face 19. The lower face 12 comprises several parts located axially at different levels. From outside to the axis AA ', there is successively a first ring 121. The outer diameter of this ring 121 is equal to the diameter of the peripheral cylinder 19. The inner diameter of this ring 121 is preferably equal to the outer 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. This surface 124 is a part of the lower surface 12 of the anode 1. This groove 122 has an outer cylindrical wall 126 whose diameter is equal to inner 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 outer cylindrical wall 125, part of which constitutes the inner cylindrical wall of the groove 122.

The cylindrical wall 125 has a diameter preferably equal to the inside diameter of the wall 25 of the groove 24 of the support 2.

One or preferably several first conduit (s) 127 each having two ends 128, 129 pierced in the anode 1 allows (tent) a fluid passage of 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 the Figures 8 and 9 each duct 127 leads from its first end 128, at the level of 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 below the insert 6. This or these first conduits 127 are provided for the distribution of plasma gas.

According to a variant mentioned above in connection with the description of the centralizer 4 and its variants, this or these conduits may alternatively lead into an annular radial groove 135 excavated from the lateral surface 18 of the cavity 10 of the anode 1, instead of directly leading to this surface 18. In the preferred embodiment shown Figures 8 and 9 the duct (s) 127 are parallel to the axis AA ', they are located in the crown 123 concealing the central cavity 10, and they open into the groove 135.

One or more second ducts 130 each having two ends 131, 132 leads from one of the outer walls 11, 19 of the anode 1 to the groove 122. In the example shown in connection with FIG. the Figures 8 and 9 , the duct 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.

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

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

On the figures 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 ( figure 3 ) and at the anode 1 ( figure 8 ) respectively.

The assembler 5 is shown in axial section figure 10 .

The assembler 5 comprises a lower cylindrical crown 51. The diameter of the outer cylindrical surface 52 of this ring 51 is slightly greater than the diameter of the wall 26 of the groove 24 of the support 2, so that the ring 51 can be fitted with assembly tight in this groove 24. The diameter of the inner wall 53 of the ring 51 is greater than the diameter of the inner wall 25 of the groove 24 of the support 2. In this way an axial annular volume is provided between these two walls 24, 53. The ring 51 has a lower surface 59. In the assembled position, this surface 59 does not come into contact with the surface 27 of the bottom of the groove 24. In this way a annular volume 73 is formed between these two surfaces.

This ring 51 is extended by a central portion 54 also in the form of a ring. 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 lower surface of the anode 1.

The upper part of the assembler 5 represented in assembled position, figure 8 is also in the form of a ring 56. The diameter of the outer wall 57 of this ring is greater than the outer diameter of the outer wall 126 of the groove 122, the anode 1. The difference in size between the diameter of the outer wall 57 of the ring 56 and the diameter of the wall 126 is such that this ring 56 can be fitted tightly in the groove 122.

The diameter of the inner wall 58 of the ring 56 is greater than the diameter of the wall 125 of the anode 1. In this way an axial annular volume is provided between these two walls 58, 125. It is recalled that this wall 125 of the anode 1 extends axially from the bottom 124 of the groove 122 to the portion 134 of the surface lower 12 of the anode 1, which is at the lowest level of the anode. The ring 56 has an 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 is formed between these two surfaces.

The central portion of the assembler 5 has an upper surface 65, a lower surface 66 both perpendicular to the axis AA ', and an outer lateral surface 67.

The upper surface 65 of the central portion 54 of the assembler 5 is delimited by a circle whose diameter is the outer diameter of the ring 56 and a circle whose diameter is the diameter of the outer lateral surface 67 of the central portion 54.

Similarly, the lower surface 66 of the central portion 54 of the assembler 5 is delimited by a circle whose diameter is the outer diameter of the lower ring 51 and a circle having the diameter of the outer lateral surface 67 as a diameter.

The delimiting circles of the upper 65 and lower 66 surfaces are concentric. In the example shown in the figures, the inner diameter of the central axial cavity 69 is constant so that the axial inner surfaces 58, 55, 53 of this cavity form a single surface.

In summary, the assembler 5 is a piece of revolution having a central axial through cavity 69. It comprises a central portion 54 from which spring upwards and downwards cylindrical portions 56, 51 respectively of diameter outer surface smaller than the outer diameter of the central portion 54. In this embodiment the upper 65 and lower 66 surfaces serve as an assembly stop. The lower surface 133 of the ring 121 of the anode 1 abuts on the upper surface 65 of the central portion 54. The upper surface 37 of the ring 22 of the support 2 of the cathode 3 abuts on the lower surface 66 of the central portion 54. Thanks to these stops and to a suitable dimensioning of the grooves 122 and 24 and the axial lengths of the rings 56, 51 it is safe to spare the annular spaces 71 and 73.

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 lower face 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 ring 29. The assembler 5 is then put in the press position, the groove 122 of the anode 1 receiving the crown 56 of the assembler 5. The upper part of the ring 56 and / or the edges of the groove 122 may be bevelled or chamfered to facilitate insertion. When the assembler 5 is in place the lower surface 133 of the ring 121 of the anode 1 is in abutment against the upper surface 65 of the central portion 54 of the assembler 5. The upper surface 60 of the assembler 5 is not at the bottom of the groove 122 so that an annular volume 71 is, as already indicated above, formed between the lower surface 124 of the groove 122 of the anode 1 and the upper surface 60 of the ring 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 centralizer 4, the ring 51 being pressed into the groove 24 of the support 2. To facilitate insertion, the bottom of the ring 51 and the top of the groove 24 may be bevelled or chamfered. When the fitting operation is completed, a functional game remains as exaggeratedly represented figure 2 between the lower surface 66 of the central portion 54 of the assembler 5 and the upper face 37 of the ring 22 of the support 2. The lower surface 59 of the ring 51 of the assembler 5 is not in contact with the bottom groove 27 of the groove 24, an annular volume 73 is therefore, as already indicated above, provided between the lower surfaces 59 of the ring 51 and 27 of the support 2. It will be seen later that the 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, against the cooling water supply circuit and the plasma gas circuit will now be commented. It is recalled that in the example shown inner walls 53 of the lower ring 51, 55 of the central portion 54 and 58 of the upper ring 56 of the assembler 5 are aligned. The outer diameter of the crown 123 of the anode 1, the diameter of the outer lateral surface 38 of the centralizer 4 and the diameter of the inner wall of the groove 24 of the support 2 are equal so that the walls 125 of the anode 1, 38 of the centralizer 4, and 25 of the support 2 are aligned. It is also recalled that the inner diameter of the assembler 5 is greater than the diameter of the walls 125, 38, and 35 so that an annular volume 72 is formed between the assembler 5 and these walls. This annular volume 72 extends axially from the upper part 60 of the ring 56 to the lower part 59 of the ring 51 of the assembler 5. The water is fed through the opening 131, and through the conduit 130 through 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 the ring 56 respectively. This water can flow along the inner wall 125 of the anode 1 through the annular volume 72 to the annular volume 73 formed between the bottom of the annular ring 51 and the bottom 27 of the groove 24. This water flows through the duct (s) 28 formed (s) in the bottom of the annular groove 24. It is thus seen, that the water circuit is provided without seal internal torch, thanks to the tight assembly of the rings 51 and 56 in the grooves 24 and 122 respectively. Naturally, the arrivals and departures of water could be placed differently, the essential being that a circulation of water cool a crown of the anode 1.

Similarly, the arrival of plasmagenic gas through the opening 128 of the anode 1 is without a seal, the gas opening through the conduits 44 or 144 in the openings 95 disposed around the cathode 3 on the centralizer 4 , or in the groove 45, according to the variant embodiments. The communication between the conduits 127 of the anode and the conduits 44 or 144 of the centralizer 4 is via the groove 135 of the anode or 148 of the centralizer 4. The radial grooves 135 and 148 may also coexist. The assembled torch according to the invention thus comprises only six parts, the anode 1, the support 2, the cathode 3, the centralizer 4, the assembler 5 and the insert 6. The assembly of this torch can be carried out with fewer press operations if specialized tooling for lateral support of the parts to be assembled is available.

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 tight in the bore 23 of the support 2, the support 2, the cathode 3, the centralizer 4, the portion 42 of which is clamped in the cavity 10 of the anode 1, and the 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 holding structure and connection.

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 cartridge 100 assembly, the central portion of the anode 1, ring-shaped 123, this crown immediately adjacent the central cavity 10 of the anode. The water circuit is located on the periphery of this same ring 123 adjacent 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 bracket. This is due to the fact that the assembler which joins 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 make the support in an insulating material having conductive vias for connecting the cathode. In this case we can consider that the assembler is constituted by the parts of insulating material and the support by the parts of conductive material.

Some indications relating to the materials of the components of the cartridge 100 will now be provided.

The anode 1 and the cathode support 2 which in the embodiment are made of electrolytic copper could be made of any material, for example metallic, electrically conductive and allowing the evacuation of very high heat fluxes.

The doped tungsten of the cathode 3 could be machined in any metallic material having a low potential for electron extraction.

The centralizer diffuser 4 can be machined in any plastic material for assembly purposes, and having good resistance to swelling with water, a strong dielectric character and good mechanical resistance to radiation and temperature.

The assembler body 5 can be machined in a plastic material for the assembly needs by simple plastic pressure.

The insulating insert 6 may be machined in a ceramic material having good resistance to thermal shock, radiation and having a strong dielectric character, for example boron nitride.

It has been seen that the assemblies are of the tight press-fit type, which implies a pair of suitable material: In the case of the torch shown, the assemblies consist of pairs of plastics-copper alloy or alloy of tungsten - copper alloy.

Other pairs of materials can be envisaged, in particular ceramic materials could replace plastic materials, if it interposed, in a manner known in itself, between the pressure headstock and the assembly press jack a vibrator .

The connection and holding structure of the cartridge 100 will now be briefly described in connection with the figures 11 and 12 . The connection and holding structure 80 comprises two flanges 81, 82, both of revolution about the axis AA '. A lower flange 81 contains a bore 83 whose inner diameter is equal to the outer diameter of the support 2, so that the support 2 can easily be introduced into the flange 81. The lower flange 81 comprises a water outlet and a water inlet. current shown in 84. One or more seal (s) toric (s) allow in known manner to ensure tightness.

The upper flange 82 of the holding and connecting structure contains a bore 85 whose inner diameter is equal to the outer diameter of the anode 1, so that this anode 1 can easily be introduced into the flange 82. This flange 82 comprises an axial central hole 91 with flared edges allowing the passage of the plasma. The lower flanges 81 and upper 82 and the cartridge 100 are held together by means of a stirrup 92. This stirrup 92 has a U shape. Two parallel arms of the U are rotatively fixed by means of screws 96 perpendicular to the axis AA 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 recess 93. In assembled position a screw 94 mounted in the horizontal part of the U of the stirrup 92 blocks the rotation of the stirrup 92 around the screws 96 and exerts a pressure on the impression 93 preventing the movement of the flanges 82 and 81 in the axial direction . The electrical insulation of the flange 81 and the stirrup is obtained by means of an insulating sleeve 95 and insulating washers. There is provided a blocking lock nut 97. The distance between the horizontal arm of the bracket 92 and the lower face of the flange 81 is sufficient to allow the disengagement of the cartridge 100 of the bores 83 and 85 of the flanges 81 and 82 respectively .

• Pour le démontage de la cartouche 100 le contre-écrou 97 est débloqué et la vis 94 dévissée jusqu'à ce que la cartouche 100 puisse être extraite de l'un des flasques 81 ou 82. Dans cette position le flasque 82 est toujours solidaire de l'étrier 92 et le flasque 81 est maintenu, la vis 94 toujours à l'intérieur de l'empreinte 93. Dans cette position des flasques la cartouche 100 peut être extraite de l'autre flasque par une légère rotation de l'étrier 92 autour de l'axe formé par les vis 96. Cette rotation libère le passage de la cartouche 100. Pour le remontage on procède inversement.

The operation is as follows:

• For disassembly of the cartridge 100, the locknut 97 is unlocked 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 integral with the stirrup 92 and the flange 81 is held, the screw 94 still inside In this position of the flanges the cartridge 100 can be extracted from the other flange by a slight rotation of the stirrup 92 around the axis formed by the screws 96. This rotation releases the passage of the cartridge. 100. For reassembly we proceed inversely.

This method of assembly is interesting from the mechanical point of view because it allows to exert an assembly pressure of the flanges 81, 82 and the cartridge 100 which is automatically axial. There is no risk of asymmetric pressures creating a strain of lateral deformation. 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 interesting when working in a glove box.

Of course, other mechanical means for fixing the cartridge 100 to the structure 80 are within the abilities of those skilled in the art.

The seals are provided by seals and the fact that the cartridge 100 is fitted into the bores 83, 85.

Claims (14)

1. A cartridge (100) generating plasma for a plasma torch, having, centred on an axis AA', an anode (1) comprising a central cavity (10) formed in an annular ring (123), said cavity (10) receiving a cathode (3) centred on AA', the anode (1) and the cathode (3) providing between them an annular space for producing an arc, plasmagene gas distribution means, the distributed gas circulating in the annular space between the cathode (3) and the anode (1), cooling means comprising particularly conduits for a cooling fluid, said conduits having an inlet and an outlet, assembly means, a centring device (4) having an axial cavity centred tightly on the cathode (3), a lower surface (46), an upper surface (49), a lateral outer surface (38, 50), a lateral inner surface (39, 40), at least one upper part (42) of the centring device (4) being fitted inside the central cavity (10) of the anode (1), plasmagene gas distribution conduits, hereinafter referred to as centring device conduits (44, 144), having a first end on the lateral outer surface (50) of the centring device (4) housed in the cavity (10) of the anode, and a second end on the upper surface (49) of the upper part (42, 43) of the centring device (4), said cartridge being characterized in that the central cavity of the centring device (4) is centred tightly on the cathode (3), and said centring device conduits (44, 144) are in communication with one or more plasmagene gas supply conduits, hereinafter referred to as conduits of the anode, said conduits of the anode (1) having two ends, a first end (128) located on an outer wall (11, 19) of the anode (1) and a second end (129), on an inner wall (18) of the cavity of the anode (1).
2. A cartridge (100) according to claim 1, characterised in that the centring device conduits (44, 144) join the outer surface (50) of the centring device (4) to an axial annular groove (45) of the centring device (4) formed between the centring device (4) and the cathode (3).
3. A cartridge (100) according to claim 1 or 2, characterised in that the centring device conduits (44, 144) have an axial line not contained in a radial plane of the centring device (4).
4. A cartridge (100) according to one of the claims 1 to 3, characterised in that the centring device conduits (44, 144) have an end emerging in a radial groove (148) formed on the lateral outer surface (50) of the centring device (4).
5. A cartridge (100) according to one of the claims 1 to 3, characterised in that the centring device conduits (44, 144) have an end emerging in a radial groove (135) of the inner cavity (10) of the anode (1).
6. A cartridge (100) according to one of the claims 1 to 3, characterised in that the centring device conduits (44, 144) have an end emerging in a radial groove (148) formed on the lateral outer surface of the centring device (4), this groove (148) being in communication with a radial groove (135) of the inner cavity (10) of the anode (1).
7. A cartridge (100) according to one of the claims 1 to 6, characterised in that the conduits (127) of the anode (1) have an axial line contained in a radial plane of the central ring (123) of the anode (1) surrounding the central cavity (10) of the anode (1).
8. A cartridge (100) according to one of claims 1 to 7, characterised in that the centring device (4) is fitted with a lower shoulder (41) of the same outer diameter as the outer diameter of the central ring (123) of the anode (1), this shoulder having a lower surface (46) and an upper surface (47), the lower surface of this shoulder constituting the lower surface (46) of the centring device (4), and the upper surface (47) of this shoulder (41) being in contact with a lower surface (134) of the central ring (123) concealing the central cavity (10) of the anode (1).
9. A cartridge (100) according to claim 8, characterised in that a base (31) of the cathode (3) is housed in a bore (23) of a ring (29) of a support (2), this ring (29) being of the same outer diameter as the outer diameter of the central ring (123) of the anode (1), and having an upper surface (30), the lower surface (46) of the centring device (4) being in contact with an upper surface (30) of the ring (29) of the support (2).
10. A cartridge (100) according to claim 9, characterised in that the anode (1) comprises an annular groove (122) formed around the annular ring (123) concealing the central cavity (10) of the anode (1), in that the support (2) comprises an annular groove (24) formed around the ring (29) concealing the bore (23) housing the base (31) of the cathode (3), the annular grooves (122) formed around the annular ring (123) and annular (24) formed around the ring (29) concealing the bore (23) housing the base (31) of the cathode (3), having the same outer diameter and in that an assembler (5) having an inner axial cavity (69) comprises a lower annular ring (51) tightly fitted in said annular groove (24) of the support (2) and an upper annular ring (56) tightly fitted in said annular groove (122) of the anode (1), the diameter of the inner axial cavity (69) of the assembler being greater than the diameter of the annular ring (123) of the anode (1) in such a way that a first annular volume (72) is provided between the anode (1) the centring device (4) and the support (2) and the assembler (5), said annular volume (72) being in comunication by means of conduits (130, 28) of the support (2), and of the anode (1), with the outer surface (21, 36, 11, 19) of the support (2) and of the anode (1).
11. A cartridge (100) according to claim 10, characterised in that, in the assembled position, an upper surface (60) of the upper ring (56) of the assembler (5) is not stopped on a bottom (124) of the annular groove (122) of the anode (1), in such a way that a second annular volume (71) is provided between this upper surface (60) and the groove bottom (124), one (130) of the conduits emerging in this volume (71).
12. A cartridge (100) according to claim 11, characterised in that, in the assembled position, a lower surface (59) of the lower ring (51) of the assembler (5) is not stopped on a bottom (27) of the annular groove (24) of the support (2), in such a way that a third annular volume (73) is provided between this lower surface (59) and the groove (24) bottom (27) one of the conduits communicating with the outside emerging in this volume (73).
13. A plasma torch, characterised in that it comprises a structure (80) for connecting and holding in place a cartridge (100) for a plasma torch according to one of the claims 1 to 12, this structure having an upper end plate (82) comprising a bore (85) for receiving the anode (1) of the cartridge, a central axial hole (91) the edges of which are flared to allow the passage of plasma, and a lower end plate (81) comprising a bore (83) for receiving a support (2) of the cartridge, the structure having means (92, 96, 94) of fixing the cartridge (100) and carrying inlets (86, 87) for a cooling fluid, plasmagene gas, and means (84) of draining the cooling fluid, these means being adapted to position themselves, when the cartridge (100) is assembled in the structure (80), opposite the corresponding conduits (127, 130) of the anode of the cartridge (100).
14. A plasma torch according to claim 13, characterised in that the means of fixing to the cartridge (100) the fixing and holding structure (80) comprises a stirrup piece (92) fixed rotationally to the upper end plate (82) of the structure (80) comprising the bore (85) for receiving the anode (1) of the cartridge, a screw (94) mounted in the stirrup piece (92) acting as support on the lower end plate (81) of the structure (80) comprising the bore (83) for receiving the support (2) of the cartridge (100).

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