EP3504943B1 - Plasma spray device - Google Patents

Description

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

Plasma spraying devices are known from the prior art, the torch head of which has a cathode, an anode spaced therefrom and a neutrode arrangement arranged between them, which comprises a plurality of neutrodes which are electrically insulated from one another. The anode is usually designed in the form of a round nozzle. In operation, an arc is created between the cathode and the anode. The arc is applied to the anode on the entry side, i.e. the area facing the inside of the torch head. Very high temperatures prevail in this area, which can easily reach 10,000 Kelvin and more. Therefore, in addition to the anode, the parts adjacent to the anode, in particular the adjacent neutrode, are also subject to high thermal loads and high wear.

From the EP 500 492 A1 a generic plasma spray gun is known. Its burner head is equipped with a cathode arrangement, a ring-shaped anode and several neutrodes that are electrically isolated from one another. There is a gap between the individual neutrodes, in which annular discs made of insulating material are inserted. These neutrodes form the constricted plasma channel. The inner diameter of the ring disks corresponds to the inner diameter of the plasma channel. In order to cool the anode and the neutrodes, a cooling channel (cavity) is arranged on the outside, through which cooling water is conducted. The frontmost of these annular discs, which is arranged between the frontmost neutrode and the anode, is thermally very highly stressed together with the frontmost neutrode and is therefore subject to high wear, especially since the anode and the frontmost neutrode are only surrounded by cooling water on the outside.

The EP 1 875 785 A1 discloses an interface for a plasma gun. This includes, among other things, a mount on the plasma gun for a nozzle attachment. The plasma channel is formed by a multitude of neutrodes together with the nozzle attachment. For this purpose, both the nozzle attachment and the neutrodes are equipped with cylindrical drilled. The nozzle attachment is fixed to the plasma gun by means of a clamp arrangement. To cool both the clamp assembly and the nozzle attachment, a channel for cooling liquid from the plasma gun leads first through the clamp assembly and then through the nozzle attachment. From the nozzle attachment, the channel leads along the outside of the neutrodes back into the plasma gun. A sealing ring is arranged between the foremost neutrode and the nozzle, which on the inside extends radially up to an insert of the nozzle. An O-ring is arranged outside of this sealing ring.

The WO 2006/012165 A2 discloses a conventional plasma gun having a cathode module, an intermediate module, an anode module and a feed module. The intermediate module comprises a plurality of intermediate electrodes which are separated from one another by a radially running gap. In order to insulate the intermediate electrodes from one another, ceramic insulating rings and O-rings are accommodated in the respective gap.

Finally in the EP 0 289 961 A2 discloses a plasma torch referred to as an adjustable cathode arc device. The plasma torch includes three assemblies, namely a gun body assembly, an anode-equipped nozzle assembly, and a cathode assembly. The cathode group comprises a rod-shaped cathode connected to an axially displaceable piston. The cathode can thus be pushed forwards or backwards in the axial direction. The gun body assembly includes four tubular segments. The foremost of these segments is adjacent to the anode. A gap runs between the foremost segment and the anode, in which an insulating ring is arranged.

The object of the invention is to propose a plasma spraying device designed according to the preamble of claim 1, in which the parts of the burner head that are subject to high thermal loads, in particular the anode together with the neutrode adjacent to it, is/are designed in such a way that, with the same nominal power, have a longer service life or allow an increased nominal power with 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.

Since the gap in the plasma spraying device running between the foremost neutrode and the anode has at least two sections, with a radial and/or axial distance between the two sections and with an insulating disk being arranged in each of the two sections, the basic requirement is met that the Wearing parts in the thermally most heavily loaded area of the plasma spraying device, in particular the anode together with the adjacent neutrode, have a longer service life with the same rated power or allow an increased rated power with the same service life.

In comparison with conventional plasma spraying devices, whose gap between the foremost neutrode and the anode usually runs in a straight line and is only provided with an insulating disk, the features mentioned according to the invention can also ensure long-term stable electrical insulation between the foremost neutrode and the anode. By dividing the gap into different sections and providing a radial and/or axial distance between the two sections each provided with an insulating disk, the second or outer insulating disk, i.e. the insulating disk facing away from the plasma channel, is subjected to comparatively little stress. In addition, the hydraulic seal is also improved in that no coolant can penetrate into the plasma channel via the mentioned gap, since the seal provided for sealing the gap is thermally less stressed.

Preferred embodiments of the plasma spraying device are defined in the dependent claims 2 to 15.

So it is proposed in a preferred development that said gap has a first inner section, a second middle section and a third has an outer section, the first inner section being offset in the radial and axial direction relative to the third outer section, and one of the said insulating washers being arranged in each of the first and third sections. Such an offset allows the third section to be relocated to an area that is subject to less thermal stress. In addition, the middle section acts as a thermal insulator.

The middle section of the gap particularly preferably runs at an angle to the inner and/or outer section. This measure brings about even better thermal shielding of the outer section.

A further preferred embodiment provides that a sealing ring is arranged radially outside of the outer section. Such a sealing ring is thus arranged in an area that is subjected to less thermal stress.

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 depression facing the foremost neutrode, the gap running between said projection and said depression. As a result of these features, the gap divided into several sections can be realized in a comparatively simple manner.

The inner section is preferably arranged inside the outer section in the radial direction, with an insulating disk being arranged in the inner section, which is set back in the radial direction in relation to the plasma channel. As a result, said insulating pane is somewhat spaced apart from the arc that is present during operation, and the outer section is thermally shielded particularly well.

A preferred development provides that the inside diameter of the foremost neutrode is at least 10%, in particular at least 20%, preferably at least 30% larger than the inside diameter of the anode, at least in the end region facing the anode. This training ensures that Arc does not start at 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 there is no appreciable burn-off at the foremost neutrode, which ultimately contributes to an increased service life, in particular of the foremost neutrode.

In a preferred further development, the anode is ring-shaped and is provided on the inside with a high-melting insert which, in the direction of the longitudinal axis of the plasma channel, reaches at least approximately to the gap between the foremost neutrode and the anode. With this design, the start of the arc can be relocated to the area of the gap.

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

Most preferably, all neutrodes are provided with an annular collar, each collar being provided with a plurality of axial slots so that a plurality of cooling fins are formed, and wherein the cooling fins so formed are in communication with a channel or annulus in which a coolant circulates. With this design, all neutrodes can be efficiently cooled.

The slits mentioned particularly preferably have a depth which is at least 5% of the circumference of the collar, particularly preferably at least 10% of the circumference of the collar. Slots designed in this way form cooling ribs with a particularly large surface area, which is advantageous with regard to good cooling of the associated neutrode.

Since the respective slot runs essentially over the entire axial length of the respective neutrode, as is indicated in a preferred development, particularly good cooling of the corresponding neutrode can be achieved. The plasma spraying device preferably has an annular space, which completely surrounds the neutrodes, for receiving cooling liquid. Such an annular space allows the neutrodes to be cooled along their entire circumference. The annular space is particularly preferably arranged and designed in such a way that the cooling liquid flows in the axial direction along the neutrode as well as the anode. Particularly good heat dissipation can be ensured by an axial flow of the coolant.

In a further preferred development of the plasma spraying device, the first neutrode facing the cathode is provided with a conically tapering section which forms part of the plasma channel. This forms a type of constriction, by means of which the flow of the plasma jet can be influenced in the desired manner.

Claims 16 and 17 also claim an anode for a plasma spray device according to claim 1, while claims 18 to 20 claim a neutrode for a plasma spray device according to claim 1.

Fig. 1

einen Längsschnitt durch den Brennerkopf der Plasmaspritzvorrichtung;

Fig. 1a

einen vergrösserten Ausschnitt aus der Fig. 1;

Fig. 2

die erste Neutrode in perspektivischer und geschnittener Darstellung;

Fig. 3

die zweite Neutrode in perspektivischer und geschnittener Darstellung;

Fig. 4a

einen Schnitt durch die dritte Neutrode

Fig. 4b

die dritte Neutrode in perspektivischer und geschnittener Darstellung;

Fig. 5

einen Schnitt durch die Anode;

Fig. 6

ein erstes alternatives Ausführungsbeispiel der dritten Neutrode;

Fig. 7

ein zweites alternatives Ausführungsbeispiel der dritten Neutrode;

Fig. 8

ein drittes alternatives Ausführungsbeispiel der dritten Neutrode;

A preferred exemplary embodiment of the invention is explained in more detail below with reference to drawings. In these drawings shows:

1

a longitudinal section through the torch head of the plasma spray device;

Fig. 1a

an enlarged section of the 1 ;

2

the first neutrode in perspective and section;

3

the second neutrode in perspective and section;

Figure 4a

a cut through the third neutrode

Figure 4b

the third neutrode in perspective and section;

figure 5

a cut through the anode;

6

a first alternative embodiment of the third neutrode;

7

a second alternative embodiment of the third neutrode;

8

a third alternative embodiment of the third neutrode;

Since plasma spray devices of the generic type are known, the features and elements that are essential in connection with the invention will be discussed below in particular.

The figure 1 shows a longitudinal section through the torch head 2 of the plasma spraying device, generally designated 1, while the Fig. 1a an enlarged section of the 1 shows. Based on Figures 1 and 1a the structure of a plasma spraying device designed according to the invention and of the associated torch head 2 is explained in more detail.

The burner head 2 has a cathode 3, an anode 7 spaced therefrom and a neutrode arrangement which is arranged in between and consists of three neutrodes 4, 5, 6. The neutrodes 4, 5, 6 together with the essentially 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 radial channels 45 through which a coating powder can be fed. To fix the anode 7 together with the three neutrodes 4, 5, 6, a union nut 46 is provided, the clamping lug 47 of which presses axially onto the anode 7 in the region of the powder supply element 44. The anode 7 in turn presses axially on the neutrodes 4, 5, 6 and also fixes them in the axial direction.

The first or rearmost neutrode 4 has an interior space 11 with a section 11a that narrows conically towards the front in the direction of flow. This Conical section 11a forms part of plasma channel 10. This conical section 11a forms a constriction, 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 essentially ring-shaped, with its interior 12 expanding slightly in the direction of the anode 7 . The last or foremost neutrode 6 has a substantially cylindrical interior 13. Between the rearmost 4 and the middle neutrode 5, as well as between the middle 5 and the foremost neutrode 6, there is an annular gap 15, 20. These two gaps 15, 20 run essentially radially in a straight line outwards. An annular insulating disc 16, 21 is inserted into each of the two gaps 15, 20 mentioned. The respective insulating disk 16, 21 is relatively thin and is delimited on the outside by a flat, but also annular support ring 17, 22. This outer support ring 17, 22 is followed by an O-ring 18, 23, which serves as a seal for coolant, as will be explained in more detail below.

There is also a gap 26 between the foremost neutrode 6 and the anode 7. However, this gap 26 does not run in a straight line, but consists of an inner, essentially radially running first section 27, a central, essentially axially running second section 28, and a outer third section 29, which in turn essentially runs radially. The first inner section 27 is offset both radially and axially with respect to the outer third section 29. The middle section 28 essentially runs 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°, is also possible.

In the inner as well as the outer section 27, 29 an insulating disk 30, 31 is added. The two insulating disks 30, 31 are spaced apart and the part of the middle section 28 lying between them acts as a thermal insulator. The outer insulating disk 31 is in turn followed by an O-ring 32, which serves as a seal for cooling liquid and at the same time also creates a gas-tight seal. The three insulating disks 16, 21, 30 are set back somewhat in relation to the plasma channel 10, which has a positive effect on their service life. The inner insulating disk 31 arranged in the third gap 26 is set back a little further than the other two insulating disks 16 , 21 , to the extent that its inside runs outside the insert 8 .

The essentially hollow-cylindrical anode 7 is provided on the inside with an insert 8 made of a high-melting and conductive material such as tungsten.

The cooling liquid used to cool 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 in the representations according to Figures 1 and 1a are not recognizable, into a first annular space 50. The annular space 50 opens into a second flow space 51, also designed as an annular space, which extends around the three neutrodes 4, 5, 6 and serves to cool them. At the end, the flow space 51 opens into an oblique channel 40 let into the anode 7 and leading to the area of the front end of the anode 7 . The sloping channel 40 traverses an annular channel 41 embedded in the anode 7, from which the cooling liquid can flow upwards into another return chamber 52 designed as an annular space, which finally connects via several channels (not visible) running inside the burner head with a rear connecting flange 53 connected is. The cooling liquid emerges from the burner head via this rear connecting flange 53 . A gas can be supplied to the burner via a central connecting flange 55 .

The mentioned O-rings 18, 23, 32 prevent cooling liquid from being able to get into the plasma channel 10 from the supply space 51 via the respective gap 15, 20, 26. The insulating discs 16, 21, 30, 31 serve in particular as electrical but also as thermal insulation. The insulating disks 16, 21, 30, 31 are made of a non-conductive and high-temperature-resistant material such as silicon nitride. In addition, these insulating disks 16, 21, 30, 31 also protect the O-rings 18, 23, 32, which are made of an elastic and temperature-resistant material such as ^Viton® , from thermal overload.

An arc is present between the cathode 3 and the anode 7 during operation of the plasma spraying device. This arc extends from the cathode 3 to the starting area 25 of the anode 7 or its insert 8. In this starting area 25, the insert 8 is preferably rounded, which is advantageous with regard to a long service life. The arc usually wanders around a bit in this initial area 25 . In any case, the initial area 25 of the anode 7, and thus also the area around the adjacent insulating pane 27, which is thermally at highest stressed area of the plasma spraying device. Due to the specific design of the gap 26 between the foremost neutrode 6 and the anode 7, as well as the two insulating discs 30, 31 arranged in this gap 26, this problem is taken into account in a special way, as is the O-ring 32 arranged in the foremost gap 26 is thermally particularly well shielded. The middle section 28 of the third gap 26 acts as a thermal insulator between the two insulating panes 30, 31. In addition, the inner insulating pane 30 is set back somewhat compared to the inside of the anode 7 or the anode insert 8, which has a positive effect on its service life. At the same time, the three neutrodes 5, 6, 7 and the anode 7 are cooled particularly efficiently, as will be explained in more detail below. In any case, tests with such a burner head 2 have shown that even if the inner insulating disc 30 is lost or fails or burns off, the O-ring 32 remains hydraulically tight over a period of several hundred to over a thousand hours and thus functions reliably and prevents coolant from penetrating into the plasma channel 10 is prevented. In this context, it should be mentioned that penetration of cooling liquid into the plasma channel 10 during operation would be equivalent to destroying the torch head.

The three neutrodes 4, 5, 6 are provided with an annular collar (not visible). In each of these collars, a multiplicity of axially extending recesses—slits—are let in to form cooling fins. The coolant flows from the annular space 50 into the flow space 51 designed as an annular space and flows through it. The flow space 51 is arranged and designed in such a way that the coolant 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 axial slits in the neutrodes 4, 5, 6, which serve to form the cooling ribs. By providing the neutrodes 4, 5, 6 with axially running slits, the cooling liquid can circulate in the longitudinal direction along the neutrodes and ensure efficient cooling. After the foremost neutrode 6 , the cooling liquid flows into the annular channel 41 of the anode 7 via the oblique bores 40 of the anode 7 . The oblique bores 40 lead behind the ring channel 41 even further forward into the base body of the anode 7 . From the annular channel 41, the cooling liquid enters the return space 52 surrounding the neutrode arrangement, from which it then flows upwards into the rear connection flange 53 and can exit the burner head 2 via this. If necessary, the flow direction of the cooling water can also be reversed. In addition, the inner diameter of the flow space 51 is preferably such on the The outer diameter of the circumferential collar of the respective neutrode 4, 5, 6 is adjusted so that the neutrodes 4, 5, 6 are precisely aligned in the radial direction when they are inserted into the advance chamber 51.

The figure 2 shows the first neutrode 4 in a perspective and sectional view. In the area on the input side, this neutrode 4 is provided on the outside with axially inclined recesses 56 in the form of slots, through which the coolant can flow into an annular channel 57 surrounding the neutrode 4 . The annular channel 57 is delimited by an annular peripheral collar 58 on the front side facing the second neutrode. Axially extending recesses in the form of slots 59 are embedded in this collar 58, so that a multiplicity of cooling ribs 60 are formed. A collar 58 designed in this way has a large surface area with a correspondingly large cooling surface area and enables good cooling of the first neutrode. The respective slot 59 preferably has a depth which is at least 5% of the circumference of the collar, particularly preferably at least 10% of the circumference of the respective collar. The first neutrode 4 is provided on the inner side facing the cathode with a conically tapering section forming part of the plasma channel

3 shows the second neutrode 5 in a perspective and sectional view. The second neutrode 5 in turn has an annular collar 62 in which slots 63 are embedded. The cooling ribs 64 formed in this way in turn enable good cooling of the second neutrode 5. Here, too, the slots 63 preferably have a depth that corresponds to at least 5% of the circumference of the collar, particularly preferably at least 10% of the circumference of the respective collar.

The Figure 4a shows a section through the third or foremost neutrode 6, while the Figure 4b shows the third neutrode 6 in a perspective and sectional view. The foremost neutrode 6 is provided with an annular projection 66 on the front side facing the anode, on the rear side of which a recess 67 is formed. The annular projection 66 together with the recess 67 forms part of the third gap ( 2 ), in which the outer insulating disc 31 ( 2 ) is included. The third neutrode 6 is also provided with a collar 69 running around in the form of a ring, into which slots 70 are embedded. In addition, bores 68 lead from the bottom of the respective slot 70 further inwards into the base body of the neutrode 6 . These bores 68 increase the cooling surface of this neutrode 6, which is subject to the greatest thermal stress, and enable particularly efficient cooling of this neutrode 6. The projection 66 is preferably rounded on the inside, since the arc is very close to this area during operation. The respective slot 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 are let into the collars of the respective neutrodes 4, 5, 6, although this number can vary. However, at least eight slots are preferably provided. Of course, the shape and size of the slits can also vary, with the number of neutrodes also being able to vary from neutrode to neutrode. The term insulating pane is also representative of any form of insulator that does not necessarily have to be disk-shaped.

Finally, the figure 5 a section through the anode 7. The anode is provided on the third neutrode 6 facing back with an annular recess 73 into which the projection 66 of the third neutrode 6 can extend. Like in the 2 As can be seen, the inner and central sections 27, 28 of the gap 26 between the anode 7 and the third neutrode 6 are formed between the said projection of the third neutrode 6 and the annular depression 73 of the anode 7. The combination of the projection 66 arranged on the third neutrode 6 together with the annular recess of the anode 7 forms a multi-stage gap with simple features and in a cost-effective manner, which in combination with the insulating discs has the advantages described above. In this exemplary embodiment, the inner diameter D1 of the insert 8 of the anode 7 corresponds approximately to the inner diameter D2 ( Figure 4a ) of the foremost neutrode 6 adjacent thereto. However, other exemplary embodiments are also provided, as described below with reference to FIG Figures 6 and 7 is still running. The anode 7 is provided with axially extending extensions 43 which extend outside of the plasma channel 10 in the radial direction. The powder supply channels 45 for supplying the coating powder are let into these extensions 43 . Although two powder supply ducts 45 are shown in the present example, three or four powder supply ducts can of course also be provided. If necessary, only a single powder supply duct can also be provided.

In the representation according to figure 5 two of the oblique bores 40 of the anode 7 can also be seen, which open into the annular channel 41. Overall, the anode 7 is provided with at least ten such bores 40. In addition, it can be seen that the oblique bores 40 are guided beyond the annular channel 41 into the base body of the anode 7 and thus increase the cooling surface of the anode 7 .

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

The 6 shows a section through a first alternative embodiment of the third or foremost neutrode 6a. This neutrode 6a is provided with a recess 75 on the inside, so that its inner diameter D3 increases towards the anode. Through this recess, the inner diameter D3 is enlarged to a diameter D2, which is larger than the inner diameter D1 ( figure 5 ) the adjoining anode, specifically also the use of the anode. This design is intended to ensure that the arc does not start at this foremost neutrode 6a, but only at the anode. This design therefore also contributes to the temperature in the region of the third gap 26 ( Fig. 1a ) is comparatively low, and no appreciable burn-off occurs at the foremost neutrode 6a, which ultimately contributes to an increased service life, in particular of the foremost neutrode 6a. The inner diameter of this third neutrode 6a in the area adjacent to the anode is preferably at least 10%, in particular at least 20%, particularly preferably at least 30% larger 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, particularly preferably at least 3 millimeters larger than that of the anode. Another variant could be that the inner diameter of the third neutrode is consistently larger than that of the anode.

The 7 shows a section through a second alternative embodiment of the third or foremost neutrode 6b. The inner diameter of this neutrode 6b increases 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 ( figure 5 ). This design is intended in turn to ensure that the arc does not start at this foremost neutrode 6b, but only at the anode. Like in the 7 As can be seen, the inner diameter D3 of this foremost neutrode 6b increases in that it is rounded off on the outlet side. Instead of a rounding, for example, a chamfer, a conical design or a chamfer or a conical design in combination with a rounding could also be provided.

Finally, the 8 a section through a third alternative embodiment of the third or foremost neutrode 6c. The inner diameter of this neutrode 6b widens towards the front through two conical sections. The first conical section preferably encloses an acute angle, while the second conical section encloses an acute or obtuse angle. Preferably, the first conical section encloses an angle between about 20 and 30°, while the second conical section encloses an angle between about 80° and 100°. At its outlet end, the first conical section has a diameter D4 which is at least 10% larger than the inner diameter D1 of the anode 7 ( figure 5 ), while the second conical section is at least 20%, in particular at least 30% larger than the inner diameter D1 of the anode. This design is also intended to ensure that the arc first starts 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 wearing parts in the area of the plasma spraying device that is subjected to the highest thermal stress, in particular the anode 7 together with the adjacent neutrode 6, have a longer service life with the same rated power or allow an increased rated power with the same service life . This is achieved in particular in that the gap 26 between the foremost neutrode 6 and the anode 7 has at least two sections 27, 29, there being a radial and/or axial distance between the two sections 27, 29 and in both sections 27, 29 one insulating disk 30, 31 each is arranged. The features mentioned, in particular also in combination with the features causing efficient cooling of the foremost neutrode and the anode, result in a longer service life of the wearing parts or an increased rated output with the same service life as compared to the known plasma spraying devices. Tungsten or a tungsten-based composite material such as W/Cu is preferably used as the material for the cathode. the anode is preferably made of THO ₂ (thorium dioxide), while the neutrodes are preferably made of copper or a copper alloy.

• langzeitstabile elektrische Isolation zwischen der vordersten Neutrode und der angrenzenden Anode;
• zuverlässige, langzeitstabile hydraulische Abdichtung des Spalts zwischen vordersten Neutrode und der angrenzenden Anode;
• besonders effiziente Kühlung der Neutroden insbesondere auch der vordersten Neutrode;
• effiziente Kühlung der Anode;
• hohe Lebensdauer der Anode wie auch der Neutroden;
• sehr stabiler Lichtbogen;
• im Vergleich mit gattungsgemässen Plasmaspritzvorrichtungen kann eine erhöhte Nennleistung bei vergleichbarer Lebensdauer der Verschleissteile erreicht werden;
• im Vergleich mit gattungsgemässen Plasmaspritzvorrichtungen kann eine erhöhte Lebensdauer der Verschleissteile bei vergleichbarer Nennleistung erreicht werden;
• der Brennerkopf ist einfach aufgebaut und die Verschleissteile können einfach und schnell ausgewechselt werden;
• der Brennerkopf kann kostengünstig gefertigt werden;
• der Brennerkopf besitzt in Bezug auf die zugeführte elektrische Energie einen hohen Wirkungsgrad;

Some advantages of the plasma spraying device designed according to the invention are summarized again below:

• long-term stable 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 service life of the anode as well as the neutrodes;
• very stable arc;
• in comparison with generic plasma spraying devices, an increased rated output 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 wearing parts can be achieved with a comparable nominal output;
• the torch head is simple and the wear parts can be replaced quickly and easily;
• the burner head can be manufactured inexpensively;
• the burner head has a high efficiency in relation to the electrical energy supplied;

It goes without saying that the previous exemplary embodiment only shows a possible or preferred embodiment of the plasma spraying device or of the burner head 2 and embodiments that deviate from this example are definitely possible. For example, instead of three neutrodes, two, four or more neutrodes can also be used. The design of the gap between the neutrodes or the foremost neutrode and the anode can also deviate from the illustration shown. The gap 26 between the foremost neutrode 6 and the anode 7 could, for example, contain further steps, for example by the foremost neutrode having two projections and the anode being correspondingly provided with two indentations. To form a gap of the kind mentioned between the foremost Alternatively, the anode could be provided with an annular projection facing the neutrode and the anode, and the neutrode with an annular depression facing the anode. Instead of an anode 7 with a molded powder feed element 44, the powder feed element could also be designed as a separate component.

Claims (20)

1. A plasma spraying device (1) comprising at least one cathode (3), an anode (7), a plasma channel (10) extending between the cathode (3) and the anode (7) and a plurality of neutrodes (4, 5, 6) bounding the plasma channel (10), wherein the neutrodes (4, 5, 6) are electrically insulated from one another and wherein a gap (26) extends between the frontmost neutrode (6) facing the anode (7) and the anode (7), in which a first insulating disc (30) is arranged, wherein the gap (26) between the frontmost neutrode (6) and the anode (7) has at least a first inner section (27) and a third outer section (29), and wherein a radial and/or axial distance exists between the two sections (27, 29), characterised in that the first insulating disc (30) is arranged in the first inner section (27) and a second insulating disc (31), which is separate from the first insulating disc (30), is arranged in the third outer section (29).
2. The plasma spraying device according to claim 1, characterised in that said gap (26) comprises a second middle section (28), the first inner portion (27) being offset with respect to the third outer section (29) in a radial and axial direction
3. The plasma spraying device according to claim 2, characterised in that the second middle section (28) of the gap (26) extends at an angle to the inner and/or outer section (27, 29).
4. The plasma spraying device according to any one of the preceding claims, characterised in that the plasma spraying device comprises a sealing ring (32) arranged radially outside the third outermost section (29).
5. The plasma spraying device according to one of the preceding claims, characterised in that the frontmost neutrode (6) is provided with a ring-shaped projection (66) facing the anode (7) and the anode (7) is provided with a ring-shaped indentation (73) facing the frontmost neutrode (6), and wherein the gap (26) extends between said projection (66) and said indentation (73).
6. A plasma spraying device according to any one of the preceding claims, characterised in that said first inner section (27) is arranged inside said third outer section (29) in a radial direction, and said first inner portion (27) has said first insulating disc (30) arranged therein which is set back in a radial direction from said plasma channel (10).
7. The plasma spraying device according to any one of the preceding claims, characterised in that the inner diameter (D2, D3, D5) of the frontmost neutrode (6, 6a, 6b, 6c) is larger than the inner diameter (D1) of the anode (7) by at least 10%, especially by at least 20% and preferably by at least 30%, at least in the end region facing the anode (7).
8. The plasma spraying device according to one of the preceding claims, characterised in that the anode (7) is ring-shaped and is provided with a high melting point insert (8) on the inside which, in the direction of the longitudinal axis of the plasma channel (10), reaches at least approximately as far as the gap (26) between the frontmost neutrode (6) and the anode (7).
9. The plasma spraying device according to one of the preceding claims, characterised in that the frontmost neutrode (6) is provided with a ring-shaped collar (69), in which axial slots (70) are embedded for forming cooling ribs (71).
10. The plasma spraying device according to any one of the preceding claims, characterised in that all neutrodes (4, 5, 6) are provided with an ring-shaped collar (58, 62, 69), each collar (58, 62, 69) being provided with a plurality of axial slots (59, 63, 70) so that a plurality of cooling ribs (60, 64, 71) are formed, and wherein the thus formed cooling ribs (60, 64, 71) are connected to a channel or ring-shaped space (52) in which a coolant circulates.
11. The plasma spraying device according to claim 10, characterised 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), and in a particularly preferable embodiment, at least 10% of the circumference of the respective collar (58, 62, 69).
12. The plasma spraying device according to any one of claims 9 to 11, characterised in that, with the exception of the first neutrode (4) facing the cathode (3), the respective slot (63, 70) essentially extends over the entire axial length of the respective neutrode (5, 6).
13. The plasma spraying device according to any one of the preceding claims, characterised in that the plasma spraying device (1) has an annular space (51) completely surrounding the neutrodes (4, 5, 6) for receiving coolant.
14. The plasma spraying device according to claim 13, characterised in that the annular space (51) is arranged and formed in such a way that the coolant flows in an axial direction along the neutrodes (4, 5, 6) as well as the anode (7).
15. The plasma spraying device according to any one of the preceding claims, characterised in that the first neutrode (4) facing the cathode (3) is provided with a conically tapering section (11a) forming part of the plasma channel (10).
16. An anode (7) for a plasma spraying device (1) according to claim 1, characterised in that the anode (7) is provided with a ring-shaped elevation or a ring-shaped indentation (73) on the rear side facing the frontmost neutrode (6) for forming the gap (26) having at least first inner and third outer sections (27, 29).
17. The anode (7) according to claim 16, characterised in that the anode (7) is provided with a ring-shaped channel (41) for introducing a coolant, wherein a plurality of inclined channels (40) lead into the ring-shaped channel (41) for supplying or discharging the coolant.
18. The frontmost neutrode (6) for a plasma spraying device (1) according to claim 1, characterised in that the frontmost neutrode (6) is provided with a ring-shaped projection (66) or a ring-shaped indentation on the front side facing the anode for forming the gap (26) comprising at least first inner and third outer sections (27, 29).
19. The neutrode according to claim 18, characterised in that the inner diameter (D2, D3, D5) of the frontmost neutrode (6a, 6b, 6c) is larger than the inner diameter (D1) of the anode (7) by at least 10%, especially by at least 20%, and preferably by at least 30%, at least in the end region facing the anode (7).
20. The neutrode according to claim 18 or 19, characterised in that the frontmost neutrode (6) has a ring-shaped collar (69) in which at least eight, in particular at least twelve, axial slots (70) are formed, wherein the respective slot (70) comprises a depth which corresponds to at least 5% of the circumference of the collar (69), and in a particularly preferable embodiment, at least 10% of the circumference of the collar (69).

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