EP3504943A1

EP3504943A1 - Plasma spraying device

Info

Publication number: EP3504943A1
Application number: EP17761178.7A
Authority: EP
Inventors: Silvano Keller
Original assignee: AMT AG
Current assignee: Oerlikon Metco AG
Priority date: 2016-08-26
Filing date: 2017-08-21
Publication date: 2019-07-03
Anticipated expiration: 2037-08-21
Also published as: PL3504943T3; US20190141828A1; CH712835A1; EP3504943B1; JP2019533077A; JP6963569B2; US10945330B2; WO2018035619A1; ES2953155T3

Abstract

The invention relates to a plasma spraying device, the torch head of which has a plasma channel (10) that extends between a cathode (3) and an anode (7). The plasma channel (10) is bounded by a plurality of neutrodes (4, 5, 6), which are electrically insulated from each other. A gap (26) extends between the frontmost neutrode (6) and the anode (7), which gap is divided into at least two sections (27, 29). There is a radial distance and an axial distance between the two sections (27, 29). An insulating disk (30, 31) is arranged in each of the two sections (27, 29).

Description

Plasma spray device

The invention relates to a trained according to the preamble of claim 1 plasma spraying device, an anode according to claim 16 and an educated according to claim 18 Neutrode for a generic plasma spraying device.

Plasma spraying devices are known from the prior art, the burner head of which comprises a cathode, an anode spaced therefrom and a neutron arrangement arranged therebetween, which comprises a plurality of neutrons which are mutually electrically insulated from one another. The anode is usually designed in the shape of a round nozzle. In operation, an arc is generated between the cathode and the anode. The arc is applied to the input side, i. the inside of the burner head facing region at the anode. In this area are very high temperatures, which can reach quite 0Ό00 Kelvin and more. Therefore, in addition to the anode and the adjacent to the anode parts, in particular the adjacent Neutrode, thermally highly stressed and exposed to high wear. From EP 500 492 A1 a generic plasma spraying device is known. Its burner head is provided with a cathode arrangement, an annular anode and a plurality of electrically insulated from each other Neutroden. Between the individual Neutroden in each case there is a gap, are inserted in the annular discs of insulating material. These neutrodes form the constricted plasma channel. The inner diameter of the annular discs corresponds to the inner diameter of the plasma channel. In order to cool the anode and the Neutroden, on the outside of a cooling channel (cavity) is arranged, through which cooling water is passed. The foremost of these annular discs, which is arranged between the foremost neutrode and the anode, together with the foremost neutrode is subjected to very high thermal loads and therefore subject to high wear, especially since the cooling of the anode and the foremost neutrode is effected only on the outside.

EP 1 875 785 A1 discloses an interface for a plasma gun. This includes, inter alia, a recording on the plasma gun for a nozzle attachment. The plasma channel is formed by a plurality of neutrons together with the nozzle attachment. For this purpose, both the nozzle attachment as well as the neutrodes with cylindrical Drilled holes. The nozzle attachment is fixed to the plasma gun by means of a clamping arrangement. For cooling the clamping arrangement as well as the nozzle attachment, a channel for cooling liquid from the plasma gun leads first through the clamping arrangement and then through the nozzle attachment. From the nozzle attachment the channel leads along the outside of the Neutroden back into the plasma gun. Between the foremost Neutrode and the nozzle, a sealing ring is arranged, which extends radially on the inside up to an insert of the nozzle. Outside this sealing ring, an O-ring is arranged. Finally, EP 0 289 961 A2 discloses a plasma torch designated as an adjustable cathode arc device. The plasma torch comprises three assemblies, namely a gun body group, a nozzle group provided with an anode and a cathode group. The cathode group includes a rod-shaped cathode which communicates with an axially displaceable piston. Thus, the cathode can be pushed back and forth in the axial direction. The gun body group comprises four tubular segments, the foremost of these segments being adjacent to the anode. Between the foremost segment and the anode extends a gap in which an insulating ring is arranged. The object of the invention is therefore to propose a trained according to the preamble of claim 1 plasma spraying device in which the thermally highly stressed parts of the burner head, in particular the anode together with the adjacent thereto Neutrode, is / are designed such that they have the same power rating have a longer service life or allow an increased nominal power for the same service life.

This object is achieved by a plasma spraying device, which is provided with the features listed in the characterizing part of claim 1. In that the gap of the plasma spraying device running between the foremost neutrode and the anode has at least two sections, wherein there is a radial and / or axial distance between the two sections, and in both Sections each one insulating disc is arranged, the fundamental requirement is created that the wear parts in the thermally most heavily loaded area of the plasma spraying device, in particular the anode together with the adjoining neutrode, at the same rated power have a longer life or allow increased power rating for the same life ,

In comparison with conventional plasma spraying devices, whose running between the foremost neutrode and the anode gap is usually rectilinear and is provided with an insulating, can be ensured by the inventive features in particular also a long-term stable electrical insulation between the foremost Neutrode and the anode the division of the gap into different sections and the provision of a radial and / or axial distance between the two each provided with an insulating sections, in particular the second or outer, ie The plasma channel facing away from the insulating comparatively little burden. In addition, the hydraulic seal is improved by no cooling liquid can penetrate into the plasma channel via said gap, since the seal provided for sealing the gap is thermally less stressed.

Preferred embodiments of the plasma spraying apparatus are described in the dependent claims 2 to 15.

Thus, it is proposed in a preferred development that said gap has a first inner portion, a second middle portion and a third outer portion, wherein the first portion is offset from the third portion in the radial and axial directions and wherein in the first and third portions each one insulating disc is arranged. By such an offset, the third section can be laid in a thermally less stressed area. In addition, the middle section acts as a thermal insulator. Particularly preferably, the middle section of the gap extends at an angle to the inner and / or outer section. This measure brings about an even better thermal shielding of the outer section. A further preferred embodiment provides that a sealing ring is arranged radially outside the outer section. Such a sealing ring is thus arranged in a region which is less thermally stressed.

In a further preferred development of the plasma spraying device, the foremost neutrode is provided with an annular projection facing the anode and the anode is provided with an annular recess facing the foremost neutrode, the gap extending between said projection and said recess. By these features, the divided into several sections gap can be relatively easily realized.

Preferably, the inner portion is disposed in the radial direction within the outer portion, wherein in the inner portion, an insulating disc is arranged, which is set back relative to the plasma channel in the radial direction. As a result, the said insulating disk is slightly spaced from the arc applied in the Betheb and the outer portion is thermally shielded particularly well.

A preferred development provides that the inner diameter of the foremost neutrode is at least in the end area facing the anode by at least 10%, in particular by at least 20%, preferably at least 30% greater than the inner diameter of the anode, this training ensures that the Arc does not attach to the foremost Neutrode, but only at the anode. This design also contributes to the fact that the temperature in the region of the gap between the foremost Neutrode and the anode is comparatively low, and no significant burn-off occurs at the foremost Neutrode, which ultimately contributes to an increased life, in particular the foremost Neutrode. In a preferred embodiment, the anode is annular and provided on the inside with a refractory insert, the i at least approximately reaches the direction of the longitudinal axis of the plasma channel to the gap between the foremost neutrode and the anode. With this design, the approach of the arc can be moved in the region of the gap.

Particularly preferably, the foremost Neutrode is provided with an annular collar, in which slots are recessed to form cooling fins. Such cooling fins have a large surface, so that the neutrode can be cooled very efficiently by means of a cooling liquid.

More preferably, all the neutrons are provided with an annular collar, each collar being provided with a plurality of axial slots to form a plurality of cooling fins, and wherein the cooling fins thus formed communicate with a channel or annulus in which Coolant circulates. This training allows all neutrodes to be efficiently cooled.

The said slots have particularly preferably a depth which amounts to at least 5% of the circumference of the collar, particularly preferably at least 10% of the circumference of the collar. Such trained slots form cooling fins with a particularly large surface, which is advantageous in terms of good cooling of the associated neutrode. Since the respective slot runs essentially over the entire axial length of the respective neutrode, as indicated in a preferred development, we achieve particularly good cooling of the corresponding neutrode.

Preferably, the plasma spraying device has an annular space completely surrounding the neutrons for receiving cooling liquid. Such an annulus allows the neutrodes to be cooled along their entire circumference. Particularly preferably, the annular space is arranged and designed such that the cooling liquid flows in the axial direction along the neutrodes as well as the anode. By an axial flow of Kühlflüssigkert a particularly good heat dissipation can be ensured.

In a further preferred development of the plasma spray apparatus, the cathode facing the first neutrode is provided with a conically tapered section forming part of the plasma channel. As a result, a kind of constriction is formed, by means of which the flow of the plasma jet can be influenced in the desired manner.

In claims 16 and 17, an anode for a generic plasma spraying device is also claimed, while in claims 18 to 20 a neutrode for a generic plasma spraying device is claimed.

Hereinafter, a preferred embodiment of the invention will be explained in more detail with reference to drawings. In these drawings shows:

1 shows a longitudinal section through the burner head of the plasma spraying device.

Fig. 1a is an enlarged detail of Fig. 1; FIG. 2 shows the first neutrode in perspective and sectional representation; FIG. 3 shows the second neutrode in perspective and in section; 4a shows a section through the third Neutrode

4b, the third Neutrode in perspective and sectional view;

5 shows a section through the anode;

Fig. 6 shows a first alternative embodiment of the third neutrode; Fig. 7 shows a second alternative embodiment of the third neutrode; Fig. 8 shows a third alternative embodiment of the third neutrode; Since plasma spraying devices of the generic type are known, particular reference is made below to the features and elements which are essential in connection with the invention.

FIG. 1 shows a longitudinal section through the burner head 2 of the plasma spraying device designated as a whole by 1, while FIG. 1 a shows an enlarged detail from FIG. 1. The construction of a plasma spraying device designed according to the invention or of the associated burner head 2 will be explained in more detail with reference to FIGS. 1 and 1 a. The burner head 2 has a cathode 3, an anode 7 spaced therefrom and a neutron arrangement arranged therebetween and comprising three neutrons 4, 5, 6. The neutrodes 4, 5, 6 together with the substantially hollow cylindrical anode 7 form the plasma channel 10. At the outlet end, the anode 7 has a powder feed element 44 which is provided with radially extending channels 45, via which a coating powder can be supplied. To fix the anode 7 together with the three Neutroden 4, 5, 6, a union nut 46 is provided, the clamping nose 47 presses axially in the region of the powder feed element 44 to the anode 7. The anode 7 in turn presses axially on the Neutroden 4, 5, 6 and fixes them also in the axial direction.

The first or rearmost neutron 4 has an inner space 11 with a conically narrowing portion 11 a in the flow direction towards the front. This conical section 11a forms part of the plasma channel 10. Through this conical section 11a, a constriction is formed, by means of which the flow of the plasma jet is influenced in the desired manner.

The first neutrode 4 surrounds the rod-shaped cathode 3. The middle neutrode 5 is substantially annular, the interior 12 of which widens slightly in the direction of the anode 7. The last or foremost neutrode 6 has a substantially cylindrical interior space 13 between the rearmost 4 and the middle neutrode 5, as well as between the middle 5 and the foremost neutrode 6 each an annular gap 15, 20. These two gaps 15, 20 extend substantially radially straight outward. In the two columns 15, 20, an annular insulating disk 16, 21 is inserted. The respective insulating disk 16, 21 is formed relatively thin and is limited on the outside by a flat, but also annular support ring 17, 22. In this outer support ring 17, 22 is followed in each case by an O-ring 18, 23, which serves as a seal for cooling fluid, as will be explained in more detail below.

However, this gap 26 is not rectilinear, but consists of an inner, substantially radially extending first portion 27, a central, substantially axially extending second portion 28, and a. Between the foremost Neutrode 6 and the anode outer, substantially in turn radially extending third portion 29. The first inner portion 27 is offset from the outer third portion 29 both radially and axially. The central portion 28 extends substantially at an angle of 90 ° to the first and the third section 27, 29. Of course, any other angle, for example 30 °, 45 ° or 60 ° are possible.

In the inner and the outer portion 27, 29 is an insulating disc 30, 31 each received. The two insulating discs 30, 31 are spaced and the intermediate portion of the central portion 28 acts as a thermal insulator. On the outer insulating 31 again follows an O-ring 32, which serves as a seal for cooling liquid and at the same time produces a gas-tight seal. The three insulating disks 16, 21, 30 are set back slightly relative to the plasma channel 10, which has a positive effect on their lifespan. The inner, arranged in the third gap 26 insulating 31 is set back a little further than the other two insulating discs 16, 21, to the extent that the inside of which runs outside the insert 8. The substantially hollow cylindrical anode 7 is provided on the inside with an insert 8, which consists of a refractory and conductive material such as tungsten.

The coolant used for cooling elements of the burner head is introduced into the burner head 2 via a front connecting flange 49. From this flange 49 lead oblique channels, which are not visible in the illustrations according to FIGS. 1 and 1a, in a first annular space 50. The ring cavities 50th opens into a second likewise formed as an annular space feed space 51 which extends around the three Neutroden 4, 5, 6 around and the cooling of the same serves. At the end of the flow chamber 51 opens into an oblique, embedded in the anode 7 channel 40, which leads to the region of the front end of the anode 7. The oblique channel 40 passes through an annular channel 41 embedded in the anode 7, from which the cooling liquid can flow upwards into a further return space 52 formed as an annular space which finally (not shown) extends over a plurality of channels (not shown) running inside the burner head with a rear connecting flange 53 connected is. About this rear flange 53, the coolant exits the burner head. Via a middle connection flange 55, a gas can be supplied to the burner.

By means of said O-rings 18, 23, 32, it is prevented that cooling liquid can pass from the supply space 51 via the respective gap 5, 20, 26 into the plasma channel 10. The insulating discs 16, 21, 30, 31 serve in particular as electrical but also as thermal insulation. The insulating discs 16, 21, 30, 31 are made of a non-conductive and high temperature resistant material such as silicon nitride. In addition, these insulating discs 16, 21, 30, 31 at the same time protect the existing of an elastic and temperature-resistant material such as Viton® O-rings 18, 23, 32 from thermal overload.

During operation of the plasma spraying device, an arc is present between the cathode 3 and the anode 7. This arc extends from the cathode 3 into the initial region 25 of the anode 7 or its insert 8. In this initial region 25, the insert 8 is preferably rounded, which is advantageous in terms of a long life. The arc usually travels slightly in this initial region 25. In any case, the starting region 25 of the anode 7, and thus also the region around the adjacent insulating disk 27, is the thermally most heavily loaded region of the plasma spraying device. Due to the specific design of the gap 26 between the foremost Neutrode 6 and the anode 7, and the two arranged in this gap 26 insulating 30, 31, this problem is taken into account in a special way and also arranged in the foremost gap 26 O-ring 32nd is thermally very well shielded. The middle portion 28 of the third gap 26 acts as a thermal insulator between the two insulating discs 30, 31. In addition, the inner insulating 30 is set back slightly relative to the inside of the anode 7 and the anode insert 8, which has a positive influence on their life. At the same time, the three Neutroden 5, 6, 7 as also the anode 7 cooled particularly efficient, as will be explained in more detail below. In any case, experiments have shown with such a burner head 2, that even with loss or failure or burn-off of the inner insulating 30 of the O-ring 32 remains hydraulically tight over a period of several hundred to over a thousand hours and thus works reliably and penetration of coolant prevented in the plasma channel 10. In this connection, it should be mentioned that during operation, penetration of cooling liquid into the plasma channel 10 would amount to destruction of the burner head. The three Neutroden 4, 5, 6 are provided with an annular circumferential collar (not visible). In each of these collars, a plurality of axially extending recesses -Schlitzen- is embedded to form cooling fins. The cooling liquid passes from the annular space 50 into the annular space formed as an annular space 51 and flows through it. The flow chamber 51 is arranged and designed such that the cooling liquid flows in the axial direction along the neutrodes 4, 5, 6 as well as the anode 7. The cooling liquid also flows in the axial direction through the formation of the cooling fins axial slots in the Neutroden 4, 5, 6. By the Neutroden 4, 5, 6 are provided with axially extending slots, the cooling liquid can circulate in the longitudinal direction along the Neutroden and to ensure efficient cooling. After the foremost Neutrode 6, the cooling liquid flows through the oblique holes 40 of the anode 7 in the annular channel 41 of the anode 7 a. The oblique holes 40 lead behind the annular channel 41 even further forward in the main body of the anode 7 in. From the annular channel 41, the cooling liquid enters upwards into the return chamber 52 surrounding the neutrode arrangement, from which it then flows upwards into the rear connecting flange 53 and can exit via this from the burner head 2. Possibly. The flow direction of the cooling water can also be reversed. In addition, the inner diameter of the flow chamber 51 is preferably matched to the outer diameter of the circumferential collar of the respective Neutrode 4, 5, 6, that the Neutroden 4, 5, 6 are aligned exactly when inserted into the flow chamber 51 in the radial direction.

FIG. 2 shows the first neutrode 4 in a perspective and sectional representation. In the input-side region, this neutrode 4 is provided on the outside with axially sloping recesses 56 in the form of slots, via which the coolant can flow into an annular channel 57 surrounding the neutrode 4. The annular channel 57 is on the front facing the second Neutrode bounded by an annular circumferential collar 58. In this collar 58 axially extending recesses in the form of slots 59 are recessed, so that a plurality of cooling fins 60 are formed. Such a trained collar 58 has a large surface with a correspondingly large cooling surface and allows good cooling of the first Neutrode. The respective slot 59 preferably has a depth which is at least 5% of the collar circumference, particularly preferably at least 10% of the circumference of the respective collar. The first neutrode 4 is provided on the inside facing the cathode with a conically tapered portion forming part of the plasma channel

Fig. 3 shows the second neutrode 5 in perspective and sectional view. The second Neutrode 5 in turn has an annular circumferential collar 62, in which slots 63 are recessed. The cooling fins 64 thus formed in turn allow good cooling of the second neutrode 5. Again, the slots 63 preferably have a depth which corresponds to at least 5% of the collar circumference, more preferably at least 10% of the circumference of the respective collar.

FIG. 4a shows a section through the third or foremost neutrode 6, while FIG. 4b shows the third neutrode 6 in a perspective and sectional representation. The foremost Neutrode 6 is provided on the front facing the anode with an annular projection 66, on the back of a recess 67 is formed. The annular projection 66 together with the recess 67 forms part of the third gap (Figure 2) in which the outer insulating disk 31 (Figure 2) is received. The third Neutrode 6 is provided with an annular circumferential collar 69, are inserted into the slots 70. In addition, bores 68 lead from the bottom of the respective slot 70 further into the main body of the neutrode 6 inwards. These holes 68 increase the cooling surface of this thermally most heavily loaded neutrode 6 and allow a particularly efficient cooling of this neutrode 6. On the inside of the projection 66 is preferably rounded, since in operation, the arc is very close to this area. The respective contactor 70 in turn preferably has a depth which corresponds to at least 5% of the circumference of the collar 69, particularly preferably at least 10% of the circumference of the collar 69. The inner diameter of the neutrode 6 denoted by D2 corresponds approximately to the inner diameter of the anode, as will be explained in more detail below. In the present example, fifteen slots each are embedded in the collar of the respective neutrode 4, 5, 6, and this number may well vary. Preferably, however, at least eight slots are provided. Of course, the shape and size of the slots may vary, and possibly also the number of neutrons to Neutrode may vary. The term insulating disc is also representative of any forms of insulators, which need not necessarily be designed disc-shaped.

Finally, FIG. 5 shows a section through the anode 7. The anode is provided on the rear side facing the third neutrode 6 with an annular recess 73 into which the projection 66 of the third neutrode 6 can extend. As can be seen in Fig. 2, between the said projection of the third Neutrode 6 and the annular recess 73 of the anode 7, the inner and the central portion 27, 28 of the gap 26 between the anode 7 and the third Neutrode 6 is formed. The combination of the protrusion 66 located at the third Neutrode 6 together with the annular recess of the anode 7 is formed with simple features and cost-effective manner, a multi-stage gap, which has the previously described advantages in combination with the insulating. In this embodiment, the inner diameter D1 of the insert 8 of the anode 7 corresponds approximately to the inner diameter D2 (FIG. 4a) of the frontmost Neutrode 6 adjacent thereto. However, other exemplary embodiments are also provided, as will be explained below with reference to FIGS. 6 and 7. The anode 7 is provided with axially extending projections 43, which extend in the radial direction outside the plasma channel 10. In these extensions 43, the powder feed channels 45 are inserted for supplying the coating powder. Although two powder feed channels 45 are shown in the present example, of course, three or four powder feed channels can be provided. Possibly. It is also possible to provide only a single powder feed channel. In the illustration according to FIG. 5, moreover, two of the obliquely extending bores 40 of the anode 7 can be seen, which open into the annular channel 41. Overall, the anode 7 is provided with at least ten such holes 40. In addition, it can be seen that the obliquely extending bores 40 are guided beyond the annular channel 41 into the base body of the anode 7 and thus increase the cooling area of the anode 7.

It should also be noted here that the three neutrons 4, 5, 6 as well as the anode 7 are wearing parts which after a certain period of use of the plasma spraying Device must be replaced or replaced. At the same time, usually the O-rings and the insulating discs are replaced.

FIG. 6 shows a section through a first alternative embodiment of the third or foremost neutrode 6a. This neutrode 6a is provided on the inside with a recess 75, so that its inner diameter D3 increases towards the anode. Through this recess, the inner diameter D3 is increased to a diameter D2, which is greater than the inner diameter D1 (FIG. 5) of the adjacent anode, including the use of the anode. This training is to ensure that the arc is not already attached to this foremost Neutrode 6a, but only at the anode. This design therefore also contributes to the fact that the temperature in the region of the third gap 26 (FIG. 1 a) is comparatively low, and no appreciable burn-off occurs at the foremost neutrode 6 a, which ultimately contributes to an increased service life of the foremost neutrode 6 a in particular. Preferably, the inner diameter of this third Neutrode 6a in the region adjacent to the anode by at least 10%, in particular by at least 20%, more preferably at least 30% greater than that of the anode. For example, assuming an inner diameter of the anode of 10 millimeters, the inner diameter of this third Neutrode 6a in the area adjacent to the anode is at least 1 millimeter, in particular at least 2, more preferably at least 3 millimeters larger than that of the anode. Another variant could be that the inner diameter of the third Neutrode is continuously larger than that of the anode. FIG. 7 shows a section through a second alternative embodiment of the third or foremost neutrode 6b. The inner diameter of this neutrode 6b widens continuously towards the front, so that the inner diameter D3 in the outlet area facing the anode is at least 10%, in particular at least 20%, particularly preferably at least 30% larger than the inner diameter D1 of the anode 7 (FIG. Fig. 5). By this training, in turn, it should be ensured that the arc is not already attached to this foremost neutrode 6b, but only at the anode. As can be seen in FIG. 7, the inner diameter D3 of this foremost neutrode 6b increases as it is rounded off on the outlet side. Instead of a rounding, for example, a chamfering, conical or chamfering or conical training could be provided in combination with a rounding. Finally, FIG. 8 shows a section through a third alternative embodiment of the third or foremost neutrode 6c. The inner diameter of this Neutrode 6b expands towards the front through two conical sections. The first conical section preferably includes an acute angle while the second conical section includes an acute or obtuse angle. Preferably, the first conical section encloses an angle between approximately 20 and 30 °, while the second conical section encloses an angle between approximately 80 ° and 100 °. The first conical section has at its outlet end a diameter D4 which is at least 10% larger than the inner diameter D1 of the anode 7 (FIG. 5), while the second conical section is at least 20%, in particular at least 30% larger is as the inner diameter D1 of the anode. Again, this training is sure to divide that the arc begins only at the anode and not at the foremost neutrode 6c. In summary, it can be stated that with the plasma spraying device designed according to the invention, the wear parts in the thermally most heavily loaded area of the plasma spraying device, in particular the anode 7 together with the adjacent neutrode 6, have a longer service life or allow an increased nominal power for the same service life at the same rated power , This is achieved, in particular, in that the gap 26 between the frontmost neutrode 6 and the anode 7 has at least two sections 27, 29, wherein there is a radial and / or axial spacing between the two sections 27, 29, and wherein in both sections 27, 29 each an insulating disc 30, 31 is arranged. Due to the features mentioned, in particular also in combination with the efficient cooling of the foremost neutrode and the anode causing properties, a longer service life of the wear parts or an increased nominal power is achieved with the same life compared to the known plasma spraying. As the material for the cathode, tungsten or a tungsten-based composite such as W / Cu is preferably used. The anode is preferably made of THO ₂ (thoria) while the neutrons are preferably made of copper or a copper alloy.

In the following, some advantages of the plasma spraying device designed according to the invention are summarized again:

long term electrical insulation between the foremost neutrode and the adjacent anode; reliable, long-term stable hydraulic sealing of the gap between the foremost neutrode and the adjacent anode;

particularly efficient cooling of the neutrodes, especially the foremost neutrode;

efficient cooling of the anode;

long life of the anode as well as the neutrons;

very stable arc;

In comparison with plasma spraying devices of the generic type, an increased nominal power can be achieved with a comparable service life of the wearing parts;

In comparison with generic plasma spraying devices, an increased service life of the wear parts can be achieved at a comparable rated power;

the burner head is simple and the wear parts can be replaced easily and quickly;

the burner head can be manufactured inexpensively;

the burner head has a high efficiency with respect to the supplied electrical energy; It is understood that the previous embodiment only shows a possible or preferred embodiment of the plasma spraying device or the burner head 2 and quite different from this example configurations are possible. For example, instead of three neutrons, two, four or more neutrons can be used. The design of the gap between the Neutroden or the foremost Neutrode and the anode may differ from the illustration shown. For example, the gap 26 between the foremost neutrode 6 and the anode 7 could include further stages, for example, in that the foremost neutrode has two projections and the anode is correspondingly provided with two recesses. Alternatively, to form a gap of said type between the foremost neutrode and the anode, the anode could also be provided with an annular projection facing the foremost neutrode and the foremost neutrode correspondingly provided with an annular recess facing the anode. Instead of an anode 7 with integrally formed powder feed element 44, the powder feed element could also be designed as a separate component.

Claims

claims

Plasma spraying apparatus (1) having a plasma channel (10) extending between at least one cathode (3) and an anode (7) and a plurality of neutrodes (4, 5, 6) delimiting the plasma channel (10), the neutrodes (4, 5 , 6) are electrically insulated from each other, and wherein between the foremost Neutrode (6) and the anode (7), a gap (26) extends, in which an insulating disc (30) is arranged, characterized in that the gap (26) between the foremost neutrode (6) and the anode (7) have at least two sections (27, 29), wherein there is a radial and / or axial spacing between the two sections (27, 29), and wherein in the two sections (27, 29 ) Each an insulating disc (30, 31) is arranged.

A plasma spraying apparatus according to claim 1, characterized in that said gap (26) has a first inner portion (27), a second middle portion (28) and a third outer portion (29), the first portion (27) opposite to the third Section (29) is offset in the radial and axial directions and wherein in the first and third sections (27, 29) each have an insulating disc (30, 31) is arranged.

A plasma spraying device according to claim 1 or 2, characterized in that the central portion (28) of the gap (26) extends at an angle to the inner and / or outer portion (27, 29).

Plasma spraying device according to one of the preceding claims, characterized in that radially outside the outermost portion (29) a sealing ring (32) is arranged.

Plasma spraying device according to one of the preceding claims, characterized in that the foremost neutrode (6) is provided with an annular projection (66) facing the anode (7) and the annular anode (7) facing one of the foremost neutrode (6) Well (73) provided and wherein the gap (26) extends between said projection (66) and said recess (73).

6. Plasma spraying device according to one of the preceding claims, characterized in that the inner portion (27) in the radial direction within the outer portion (29) is arranged, wherein in the inner portion (27) an insulating disc (30) is arranged opposite the plasma channel (10) is set back in the radial direction. 7. Plasma spraying device according to one of the preceding claims, characterized in that the inner diameter (D2, D3, D5) of the foremost Neutrode (6a, 6b, 6c) at least in the anode (7) to be turned end region by at least 10%, in particular by at least 20%, preferably at least 30% larger than the inner diameter (D1) of the anode (7).

8. Plasma spraying device according to one of the preceding claims, characterized in that the anode (7) is annular and is provided on the inside with a refractory insert (8) in the direction of the longitudinal axis of the plasma channel (10) at least approximately to the Gap (26) between the foremost Neutrode (6) and the anode (7) extends.

9. Plasma spraying device according to one of the preceding claims, characterized in that the foremost Neutrode (6) is provided with an annular collar (69) in which slots (70) are embedded for the formation of cooling fins. Plasma spraying apparatus according to one of the preceding claims, characterized in that all the neutrodes (4, 5, 6) are provided with an annular collar (58, 62, 69), each collar (58, 62, 69) having a multiplicity of axial slots (59, 63, 70) is provided so that a plurality of cooling fins (60, 64, 71) are formed, and wherein the cooling fins (60, 64, 71) thus formed with a channel or annulus (52) communicate in which a coolant circulates.

11. Plasma spraying device according to claim 10, characterized in that the respective slot (59, 63, 70) has a depth which is at least 5% of the circumference of the respective collar (58, 62, 69), more preferably at least 0% of the circumference of the respective collar (58, 62, 69).

12. Plasma spraying device according to one of claims 9 to 11, characterized in that the respective slot (63, 70) extends substantially over the entire axial length of the respective neutrode (5, 6).

13. Plasma spraying device according to one of the preceding claims, characterized in that the plasma spraying device (1) has a the Neutroden (4, 5, 6) completely surrounding annular space (51) for receiving coolant.

14. Plasma spraying device according to claim 13, characterized in that the annular space (51) is arranged and designed such that the cooling liquid flows in the axial direction along the Neutroden (4, 5, 6) as well as the anode (7).

15. Plasma spraying device according to one of the preceding claims, characterized in that the cathode (3) facing the first neutrode (4) with a conically tapering, a part of the plasma cornice (0) forming portion (11 a) is provided.

16. anode (7) for a plasma spraying device (1), which comprises a plasma channel (10) extending between at least one cathode (3) and an anode (7) and a plurality of neutrodes (4, 5, 6), the neutrodes (4, 5, 6) being electrically insulated from one another, and wherein a gap (26) having at least two sections (27, 29) extends between the foremost neutrode (6) and the anode (7) , and wherein in two sections (27, 29) each have an insulating disc (30, 31) is arranged, characterized in that the anode (7) is provided on the rear side facing the foremost neutrode with an annular projection or an annular recess (73) to form the gap having at least two sections.

17. anode (7) according to claim 16, characterized in that the anode (7) is provided with an annular channel (41) for introducing a coolant, wherein in the annular channel (41) has a plurality of oblique channels (40) for supply or discharge the coolant.

18. Neutrode for a plasma spraying device (1), which is provided with a between at least one cathode (3) and an anode (7) extending plasma channel (10) and part of a neutron assembly forming, adjacent to the anode neutrode (6) a gap (26) having at least two sections (27, 29) extends between this foremost neutrode (6) and the anode (7), and in each case an insulating disc (30, 31) is arranged in two sections (27, 29), characterized in that the neutrode (6) is provided with an annular projection (66) or an annular recess on the front side facing the anode for forming the gap having at least two sections.

19. Neutrode according to claim 18, characterized in that the

Inner diameter (D2, D3, D5) of the neutrode (6a, 6b, 6c) at least in the anode (7) facing end region by at least 10%, in particular by at least 20%, preferably at least 30% greater than the inner diameter (D1 ) of the anode (7).

20. Neutrode according to claim 18 or 19, characterized in that the Neutrode (6) has an annular collar (69), in which at least eight, in particular at least twelve axial slots (70) are embedded, wherein the respective slot (70) a Having depth corresponding to at least 5% of the circumference of the collar (69), more preferably at least 10% of the circumference of the collar (69).