EP0585203B1 - Plasma spray gun - Google Patents

Abstract

A plasma spray gun for coating especially holes, channels (ducts) or the like consists essentially of a connecting piece (1), a burner shaft (2) and a burner head (3). These three components (1, 2, 3) of the plasma spray gun are in this case constructed as replaceable modules which can be replaced quickly and easily by the user. The burner head is mounted on the burner shaft (2) by means of two screws (7), and the burner shaft (2) is mounted on the connecting piece (1) by means of three screws (6). All the lines and channels which are required for operation of the burner in this case run through the interior of the burner shaft (2). The connections (9) for the burner media and electrical power are designed radially with respect to the longitudinal axis of the plasma spray gun. <IMAGE>

Description

The invention relates to a plasma spraying device for coating cavity walls according to claim 1 and to a burner head adapted to the plasma spraying device according to claim 25.

The coating of external, easily accessible surfaces is generally not a problem with known plasma spraying devices. However, should cavity walls (internal surfaces), as e.g. in the case of bores and channels, which are coated with the known plasma sprayers, various problems and difficulties can be expected.

A major problem when coating cavity walls is the length of the bore or channel to be coated. Since the connection part of a plasma spraying device is generally much larger than the burner shaft with the burner placed at the end, it is not possible for the entire plasma spraying device to enter the bore to be coated be retracted. So that a small, handy device is available for short bores and a correspondingly long, adapted plasma spraying device is available for long bores, The length of the part of the plasma spraying device which is immersed in the bore should therefore also be able to be adapted accordingly for different bore depths.

The minimum bore or channel diameter of the inner surface to be coated (cavity wall) is determined by the outside diameter of a plasma spraying device, in particular the burner shaft with the burner head placed at the end. This means that the more compact the burner and the shaft of such a plasma spraying device, the smaller the diameter of the tube to be coated can be.

In order to achieve a homogeneous coating, especially of angled areas such as To enable sales, the plasma jet of such a plasma spraying device should emerge radially from the burner.

Another problem is the heating of the parts of the plasma spraying device that reach into the pipe or the channel, since temperatures of ten thousand degrees and more are generated by the plasma flame. This problem arises to a far greater extent if coating is to be carried out in a vacuum atmosphere, since air or CO₂ cannot be blown in for cooling purposes in a vacuum atmosphere, as is customary under atmospheric conditions. To damage the thermally highly stressed parts under atmospheric conditions and in particular under To avoid vacuum-like conditions, efficient cooling is essential.

When coating narrow pipes and the like, the further problem is the dielectric strength or the insulation of the burner. Since in the case of a transferred arc, the shortest path of which is often not identical to the desired path between the cathode and the surface to be coated, for example a pipe wall, care must be taken to ensure that the burner is insulated on all sides.

Since, with conventional plasma torches, even small shunts, caused by damage to the insulation or high dust precipitation, promote unwanted transmission of the arc to the workpiece, especially in a vacuum, the plasma spraying device should be designed in such a way that the insulation is unwanted even under extreme conditions Prevents transmission or striking of the arc.

A plasma spraying device is known for coating pipes and is marketed, for example, under the name "Type 7 MST-2" by Metco, Westbury, USA. This known plasma spraying device essentially consists of a connecting piece and an extension which can be connected to it and which has an integrated burner (plasma mat) at its end. The extension results in the supply of plasma gas and electrical current for the operation of the torch while the plasma powder is supplied outside the extension via a separate line.

To attach the extension, a sleeve is pushed over the extension, which is screwed to the connector and thereby presses the extension onto the connector.

The plasma powder line itself is fastened to this by means of flanges comprising the extension. At the end of the extension, a separate flange must be attached into which the plasma powder line is screwed. This flange has a powder guide, via which the coating material, generally plasma powder, is fed to the actual plasma flame outside the actual burner head. At the other end, the plasma powder line is screwed to a powder supply line in the area of the connector.

The plasma torch itself, which is integrated in the extension, is axially aligned with respect to the extension, so that the plasma jet also emerges axially. In order to be able to deflect the plasma jet, a deflection nozzle is also provided, through which the plasma jet is deflected by approximately 40-50 degrees with respect to the longitudinal axis of the plasma spraying device.

• Da jede Verlängerung einen integrierten Brenner aufweist, ist die Ersatzteilhaltung sehr teuer.
• Durch den achsialen Austritt des Plasmastrahls sind verwinkelte Stellen innerhalb einer Bohrung praktisch nicht zu Beschichten. Auch durch die Ablenkdüse, welche den Plasmastrahl um ca. 40-50 Grad gegenüber der Längsachse ablenkt, können Absätze und dergleichen innerhalb einer Bohrung, insbesondere wenn diese nur von einer Seite zugänglich sind, schlecht oder nur ungenügend beschichtet werden.
• Ein Austausch von einzelnen Komponenten wie beispielsweise der Anode oder Kathode durch den Benutzer ist nicht oder nur mit grossem Aufwand möglich.
• Die Kühlung, insbesondere der ausserhalb der Verlängerung geführten Pulverleitung, ist schlecht.
• Das Austauschen des Verlängerungsstücks ist aufwendig und zeitraubend.
• Zu jedem Verlängerungsstück muss eine entsprechende, korrespondierende Plasmapulverleitung vorhanden sein, welche zudem noch separat mittels Flanschen an der Verlängerung befestigt werden muss. Zudem muss die Pulverleitung auf der einen Seite noch an eine Plasmapulverzufuhrleitung und auf der anderen Seite in den vordersten Flansch eingeschraubt werden.
• Durch die aussen an der Verlängerung zur Befestigung der Pulverleitung angebrachten Befestigungsflansche können Wärmestaus der aus der Bohrung austretenden heissen Gase entstehen. Ausserdem sind diese Befestigungsflansche durch ihre exponierte Lage extrem der Verschmutzung sowie einer erhöhten Beschädigungsgefahr ausgesetzt.

The construction of this plasma spraying device has several serious disadvantages:

• Since each extension has an integrated burner, the spare parts inventory is very expensive.
• Due to the axial exit of the plasma jet, angled areas within a hole are practically impossible to coat. Even through the deflection nozzle, which deflects the plasma jet by approximately 40-50 degrees with respect to the longitudinal axis, shoulders and the like can be poorly or insufficiently coated within a bore, especially if they are only accessible from one side.
• An exchange of individual components such as the anode or cathode by the user is not possible or only possible with great effort.
• The cooling, especially of the powder line routed outside the extension, is poor.
• Replacing the extension piece is complex and time-consuming.
• A corresponding, corresponding plasma powder line must be available for each extension piece, which must also be attached to the extension separately by means of flanges. In addition, the powder line must be screwed on one side to a plasma powder supply line and on the other side into the foremost flange.
• The mounting flanges on the outside of the extension for attaching the powder line can cause heat build-up from the hot gases escaping from the bore. In addition, due to their exposed position, these mounting flanges are extremely exposed to contamination and an increased risk of damage.

From EP-A-0 079 019 a plasma torch is known, which consists of a supply part, a supply adapter, quick-release couplings and a burner part. The plasma jet emerges axially with respect to the longitudinal axis of the burner part. While the supply part is connected to the supply adapter by means of the quick-release coupling, a screw connection is provided for fastening the burner part.

A plasma spraying device is known from CH-A-647424. The tubular extension piece is cylindrical and connects the connecting part to the burner head. The connecting part is provided with a screwed-in coupling element, on which the extension piece can be connected to the burner rear part. The extension piece also has a radially arranged connecting line which opens into the interior of the extension piece via a connecting channel. This connection line can be connected to a cooling gas source for cooling the extension piece. A connection channel leads from the interior of the extension piece to the burner head.

It is therefore the object of the invention to further develop a plasma spraying device of the generic type in such a way that it can be physically easily adapted to different coating tasks and thus to coat a wide variety of cavity walls, such as those in pipes, channels and the like come with different drilling depths, that the burner head is sufficiently cooled, and that the individual components can be replaced quickly and easily.

This object is achieved by the features listed in the characterizing part of patent claim 1.

The modular structure of the plasma spraying device means that one and the same burner head can be used, but with different shafts in terms of length. This practically allows an individual adjustment of the shaft length to the bore to be coated, the channel, etc. Thus, a short shaft can be used for a short bore and a correspondingly long shaft for a deep bore. This has the advantage of being one Device has an optimal handling that corresponds to the circumstances Thanks to the burner head, which is independent of the burner, only shafts of different lengths need to be kept in stock in order to convert the plasma spraying device and thus adapt it to the different coating tasks. This can of course significantly reduce inventory costs. The modular design also reduces the changeover time to a minimum, making it much easier for the user to adapt the plasma spraying device.

Another embodiment also provides that the burner shaft has a shape deviating from a straight line. In this way, the shape of the burner shaft can be adapted to the object to be coated, so that, for example, curved tubes can also be coated. It is also conceivable to use different burner shafts for coating a complex object, so that a respectively adapted burner shaft is used for partial surfaces of the object to be coated.

In order to ensure efficient cooling, it is advantageous to apply cooling water to the entire available tube cross section of the burner shaft, because this cools the burner shaft sufficiently and uniformly and, due to the low resistance, a correspondingly large amount of water can circulate. A plasma spraying device designed in this way can therefore also be used without hesitation in a vacuum atmosphere.

An advantageous embodiment of the plasma spraying device provides that both the anode nozzle and the cathode arrangement of the burner head are accessible from the outside, so that these parts can be replaced quickly and easily by the user himself in the event of a defect or appropriate wear. The powder injector designed as a clamping jaw of the anode nozzle can also be removed or replaced by loosening a single screw. Since different powder injectors with different cross-sections are also available, the injection speed of the plasma powder can be varied by exchanging the powder injector.

The insulating body, which is attached between the anode body and the cathode body in a preferred embodiment and which has flanges partially encompassing the anode body and the cathode body on the longitudinal side, ensures good insulation between the anode and cathode bodies.

In a further preferred embodiment, in which the burner head, in addition to the insulating body, also has an attachable, ceramic protective hood, such a plasma spraying device is particularly suitable for the interior coating of narrow pipes and in particular also for coatings in a vacuum.

Another preferred embodiment of the plasma spraying device provides a series connection of the cooling water circuit in the burner head. This means that the cathode arrangement and the anode nozzle are the same Cooling water circuit are connected. This favors a compact design of the plasma spraying device and also results in a minimized number of bushings and plug connections between the individual modules. This also ensures that the same amount of water flows around the anode nozzle and the cathode arrangement.

Claim 25 claims a burner head which is adapted to a plasma spray device designed according to the invention.

Finally, preferred embodiments of the burner head are defined in claim 26.

Fig.1a und 1b

Eine schematische Darstellung des Plasmaspritzgerätes;

Fig.2a bis 2f

eine schematische Darstellung der drei Module des Plasmaspritzgerätes und deren Befestigungsart;

Fig.2g bis 2i

eine schematische Darstellung möglicher Ausführungsformen von Brennerschäften;

Fig.3a bis 3f

einen Längsschnitt durch das Plasmaspritzgerät zur Veranschaulichung der Steck- bzw. Stossverbindungen;

Fig.4, 4a und 4b

eine schematische Darstellung der drei Module des Plasmaspritzgerätes im Längsschnitt zur Veranschaulichung der Kühlung;

Fig.5a und 5b

einen Längs- und Querschnitt durch den Brennerschaft, und

Fig.6a bis 6c

einen Längs- und Querschnitt durch den Brennerkopf sowie eine Aussenansicht des Brennerkopfs.

An exemplary embodiment of a plasma spraying device according to the invention is explained in more detail below with reference to the accompanying drawings. The drawings show:

Fig.1a and 1b

A schematic representation of the plasma spraying device;

2a to 2f

is a schematic representation of the three modules of the plasma spraying device and their type of attachment;

Fig.2g to 2i

a schematic representation of possible embodiments of burner shafts;

3a to 3f

a longitudinal section through the plasma spray gun to illustrate the plug or butt connections;

Fig. 4, 4a and 4b

is a schematic representation of the three modules of the plasma spraying device in longitudinal section to illustrate the cooling;

Fig.5a and 5b

a longitudinal and cross section through the burner shaft, and

Fig.6a to 6c

a longitudinal and cross section through the burner head and an exterior view of the burner head.

1a shows a plasma spraying device in the assembled, ready-to-use state. This plasma spray device essentially consists of three modular units. These three units are a connection element 1, a burner shaft 2 and a burner head 3. The burner shaft 2 is fastened to the connection element 1 by means of screws 6 and the burner head 3 is fastened to the burner shaft 2 by means of screws 7. The media necessary for the operation of the plasma spraying device are supplied via supply lines (not shown) which are screwed or plugged onto connections 9. The connections 9 attached to the connection element 1 are arranged radially with respect to the longitudinal axis of the plasma spraying device. Furthermore, an anode nozzle 11 attached to the burner head 3, from which the plasma flame emerges radially opposite the longitudinal axis of the plasma spraying device during operation, and a protective shield 5 can be seen from this illustration. 1b also shows a ceramic cap 4 which can be attached to the burner head 3 for its thermal and electrical insulation. This ceramic cap 4 has an oval recess 8 and a bore 10. The recess 8 leaves the anode nozzle 11 free when the ceramic cap is attached. The bore 10 serves to fasten the ceramic cap 4 to the burner head 3 by inserting a fastening screw through the bore 10 and screwing it into a corresponding thread in the burner head 3. Constructive details are not apparent from these figures, since these are explained below using further figures. However, this illustration is intended to illustrate the compact design of the plasma spraying device.

2a to 2c show the parts or details essential for the attachment of the three structural units 1, 2, 3. For this purpose, the three structural units 1, 2, 3 of the plasma spraying device are each shown individually in a view from the side. 2d shows the connection element in the direction of arrow A from behind, in FIG. 2e the burner shaft 2 in arrow direction B also from behind and in FIG. 2f the burner head in arrow direction C from the front.

The connection element 1 designed for the connection of burner medium supply lines consists of a round base body 15 angled by 90 °. The burner shaft 2 is designed as a tubular extension for the supply of the burner media from the connection element 1 to the burner head 3. The burner shaft 2 is just executed in this embodiment. Further embodiments are explained below. Finally, the burner head 3 is responsible for generating a plasma flame. This burner head 3 has a cylindrical basic shape and has approximately the same outer diameter as the burner shaft 2.

In the connection element 1 there is a round opening 17 directed towards the burner shaft 2, which corresponds to the outside diameter of the burner shaft 2 and serves to fix the same. At the bottom of this opening 17, a groove 18 is made. To carry out the screws 6 necessary for fastening the burner shaft 2 to the connection element 1, the connection element 1 has three bores 19 distributed parallel to the longitudinal axis 25 of the plasma spraying device and concentrically around this longitudinal axis 25. At the lower end of the connection element 1, four connections 20, 21, 22, 23 are attached, via which the media necessary for the operation of the plasma spraying device and the power supply are supplied. The connections 20, 21 and 23 are provided with threads for fastening the supply lines and the connection 22 with a corresponding plug connection. The lines and channels for the burner media, starting from the connections 20, 21, 22, 23 and leading through the connecting element 1 and the burner shaft 2, are not shown in these representations for the sake of clarity.

The tubular burner shaft 2 has a strip 26 at the rear end directed towards the connection element 1. Furthermore, the burner shaft 2 has a collar 27 which surrounds it. The distance of this collar 27 from the rear end of the burner shaft 2 corresponds to the depth of the opening 17 present in the connecting element 1. Three internal threads 28 are distributed around the periphery of the collar 27.

At the other end facing away from the connection element 1, the burner shaft 2 has a cylindrical recess 30. A groove 31 is in turn attached to the bottom of this recess 30. Two blind threads 32 start from this groove 31. Finally, the burner head 3 has a cylindrical shoulder 36, which corresponds in shape and position to the cylindrical recess 30 of the burner shaft 2. Furthermore, a strip 34 is formed on the burner head 3, which corresponds in shape and position to the groove 31 of the burner shaft 2. At the level of this bar 34, two bores 33 run through the burner head 3 in the longitudinal direction.

In order to assemble the three structural units 1, 2, 3 into a plasma spraying device, the burner head 3 is fastened to the burner shaft 2 by passing the two screws 7 through the bores 33 of the burner head 3 and screwing them into the blind thread 31. A certain centering and alignment of the burner head 3 results on the one hand from the shoulder 36 inserted into the cylindrical recess 30 and on the other hand through the ledge 34 engaging in the groove 31. The burner shaft 2, which is designed as an extension, is then attached to the connecting element 1. For this purpose, the screws 6 are inserted through the bores 19 of the connection element 1 and screwed into the internal thread 28 of the collar 27. A certain alignment and centering of the burner shaft 2 with respect to the connection element 1 is again achieved here by the strip 26 engaging in the groove 18. The exact centering and alignment of both the burner head 3 with respect to the burner shaft 2 as well as the burner shaft 2 relative to the connection element 1 results, as will be described in detail below, from plugs engaging in sockets. The assembly of the units can of course also be done in reverse order.

2g to 2i show some further possible embodiments of burner shafts. FIG. 2g shows a cranked burner shaft 102, while a curved burner shaft 202 is shown in FIG. 2h and a rounded burner shaft 302 is shown in FIG. 2i. The burner shafts 102, 202, 302 designed in this way are fastened in the same way as was described with reference to FIGS. 2a to 2c. In the cranked burner shaft 102 shown in FIG. 2g, its burner-side end 105 runs parallel to the connection element-side end 107. The length and angle α of the angled part 117 of the burner shaft 102 can determine the parallel offset of the two ends 105, 107. The angle b between the burner-side end 105 and the angled part 117 of the burner shaft 102 corresponds to the angle a. Of course, it is also conceivable that the angle a is not equal to the angle b. As a result, the angular position with respect to the longitudinal center axis 113 of the burner head to be fastened to the end 105 on the burner side can be changed. A burner shaft 102 designed according to FIG. 2g allows, for example, a cylindrical body, which has only a small opening, to be coated on the inside. Let the burner shaft 102 with the burner head attached to it rotating into the body about the longitudinal central axis 25 of the plasma spraying device, an inner cavity that is much larger than the opening can be coated in this way.

2h shows a burner shaft 202 which is angled towards the burner head-side end 205. In this exemplary embodiment, the position of the burner shaft 202 on the burner shaft 202 can be determined by the angle c between the longitudinal center axis 25 of the plasma spraying device and the longitudinal center axis 213 of the end 205 of the burner head vary the burner head to be attached. This angle c thus has a direct influence on the exit angle of the plasma jet. The length of the angled part 211 can also influence the position of the burner head with respect to the longitudinal central axis 25 of the plasma spraying device.

A further exemplary embodiment of the burner shaft 302 can be seen in FIG. 2i, in which a part 311 of the burner shaft 302 is bent. With such a configuration, even curved pipes and the like can be coated on the inside. It is thus possible to coat a wide variety of cavity walls using differently designed burner shafts 102, 202, 302. The burner shafts 102, 202, 302 can be exchanged for coating intertwined cavities consisting of different partial surfaces, and the individual partial surfaces of a complex object can thus be coated. It goes without saying that the angles a, b, c and radii r of these burner shafts 102, 202, 302 can vary within a wide range, and that other embodiments of the burner shafts 102, 202, 302 are also conceivable.

Figures 3a to 3c show a longitudinal section through the three structural units 1, 2, 3 to illustrate the one between the cooling water lines 40, 45, 52, 53 on the one hand and between the cooling water lines 52, 53 and the cooling water channels 135, 136 and each consisting of one Plugs 39, 44, 66, 67 and a socket 49, 50, 58, 60 existing plug connections. FIGS. 3d to 3f in turn show a longitudinal section through the three structural units to illustrate the existing between the plasma gas lines 75, 76, 77 and the plasma powder lines 70, 71, 72 and each consisting of a sealing ring 84, 85; 86, 87 and a collar 79, 80; 81, 82 existing butt joints.

3b and 3e each show the burner shaft 2. This has an inserted end cap 56, 57 made of thermally highly resilient plastic at both ends. These end caps 56, 57 are used to fasten the two cooling water lines 52, 53 and the plasma gas and plasma powder line 76, 71 in the burner shaft 2.

A special feature of the plasma spraying device is that the cooling water circulates in the cooling water lines 40, 45, 52, 53 and the cooling water channels 135, 136, and in addition that the electrical power supply is provided by the metal lines Burner head 3 takes place. In the burner shaft 2, radial channels 91, 93 each lead from the bushes 49, 58 into the casing tube 92 of the burner shaft 2. As a result, the cooling water at the inlet of the burner shaft 2 can exit from the line 52 or from the bush 49 and flow through the burner shaft 2. At the end of the burner shaft 2, the cooling water can then flow into the bushing 58 via the radial channels 93 and reach the cooling channel 135 via the plug 66. The electrical connection between the two sockets 49, 58 is ensured by a rod-shaped current conductor 62. The exact functioning of this cooling water circuit is described below with reference to FIGS. 4, 4a and 4b. Since the two cooling water lines 52, 53 are at different potential, the two end caps 56, 57 also serve as an insulator between the sockets 49, 50, 58, 60. Since the cooling water lines or the cooling water channels are also connected in series via the burner head, it is of course necessary to use an electrically non-conductive or poorly conductive medium, such as high-purity water, as the cooling medium.

The plasma powder lines 70, 71, 72 shown in FIGS. 3e to 3f and the plasma gas lines 75, 76, 77 can each be connected to one another by means of a butt connection. The basic structure of the structural units has already been mentioned above, so that the following description of the figures is limited to the essential details of the plug or butt connections.

Plug connections are provided for connecting the cooling water lines 40, 45 leading through the connection element 1 to the corresponding lines 52, 53 leading through the burner shaft. These plug connections each consist of a metal plug 39, 44 and a metal socket 49, 50. The plugs 39, 44 are designed such that they have a collar 41, 46 at their rear end. If the plugs 39, 44 are now inserted into the corresponding sockets 49, 50 and the connection element 1 is screwed to the burner shaft 2, the collar 41, 46 comes to rest on the end faces 54, 55 of the sockets 49, 50 and thus arises one contact area each. The electrical current can now be transferred from one line to the other via these contact surfaces. The two strips 26, 34 engaging in the grooves 18, 31 in the area of the respective plug connections also ensure good electrical insulation between the plug connections which are at different potentials. Sealing rings 42, 43 are provided for sealing the plug connections with respect to the cooling water circulating therein.

The plug connections for the cooling water and the electrical current, which are in turn formed from plug core 66, 67 and sockets 58, 60, are also formed in the same way between the burner shaft 2 and the burner head 3. The essential difference is that an anode base body 63 made of metal and a cathode base body 64 also made of metal are present on the burner head 3. The cathode base 64 is designed such that it takes over the power supply to the cathode, while the anode base body 63 ensures the power supply to the anode. Instead of a separate line, the channels 135, 136 necessary for cooling the burner head 3 are embedded directly in these two bodies 63, 64. Since these two bodies also consist of metal, this ensures uniform cooling of the burner head 3. Furthermore, it is unnecessary that the two plugs 66, 67 must have a collar, because when the sockets 58, 60 are plugged together with the plugs 66, 67, the end faces 59, 61 on the sockets 58, 60 with the anode base body 62 and come into contact with the cathode base body 64 and thus the electrical contact is also ensured. The plugs 39, 44, 66, 67 engaging in the sockets 49, 50, 58, 60 also center the burner head 3 with respect to the burner shaft 2 and the burner shaft 2 with respect to the connecting element 1.

Sealing rings 68, 69 are in turn attached to the plugs 66, 67 as a seal for the cooling water.

The line connections between the plasma powder lines 70, 71, 72 and between the plasma gas lines 75, 76, 77 are formed as butt connections. For this purpose, the two lines 71, 76 leading through the burner shaft 2 each have a collar 79, 80, 81, 82 at their ends, which, when the plasma spraying device is screwed together, connects to a corresponding sealing ring 84, 85 that includes the line 70, 72, 75, 77 , 86, 87 in the connection element 1 and comes to rest in the burner head 3 and is sealed by this.

Since such a plasma spraying device generates a very high temperature through the plasma flame, on the one hand the burner head 3 and on the other hand also the burner shaft 2 must be cooled. This applies in particular to the coating of pipes, bores and the like, where the heat generated can only flow off poorly. This is particularly true for vacuum coatings.

The cooling water circuit in the plasma spraying device can be seen from FIG. For this purpose, the three structural units 1, 2, 3 are again shown in a longitudinal section reduced to the essential. 4a and 4b, two details are also shown in enlarged sections. Cooling in a plasma spraying device is necessary above all for the burner head 3 and the burner shaft 2.

A serial cooling circuit was chosen so that the three structural units 1, 2, 3 of the plasma spraying device have as few lines and plug connections as possible. This means that in the burner head 3, the anode nozzle 11 and the cathode arrangement 12 are connected in series in terms of cooling technology and therefore the cooling water flows through them in succession.

The cooling water is supplied at the connection 23 via a line (not shown) and enters the cooling water supply line 40 of the connection element 1 radially to the longitudinal axis of the plasma spraying device. In the connecting element 1 itself, the inflowing cooling water is first deflected by 90 °. Then the cooling water flows into the plug connection consisting of the plug 39 and the socket 49. Through the radial channels 91 present in the bushing 49, the cooling water can emerge from the line 40 and flow into the casing tube 92 of the burner shaft 2. The water can flow through the burner shaft 2 in the entire remaining cross section. At the end of the burner shaft 2, the cooling water in turn flows via radial channels 93 into the plug connection formed from the plug 66 and the socket 58. The cooling water finally flows from this plug connection into the channel 135 of the burner head 3. The sealing rings required in these plug connections are not shown for the sake of clarity. In the burner head 3, the cooling water first flows through the channel 135 present in the anode base body 63 to the anode nozzle 11 and flows around it. Thereafter, the cooling water is deflected and thereby penetrates an insulating body 65 arranged between the anode base body 63 and the cathode base body 64, in order to subsequently reach the cathode arrangement 12 and flow around it. The ring channels present on the anode nozzle 11 and on the cathode socket 13 cannot be seen from this illustration and will be explained in more detail later in the detailed description of the burner head 3.

The backflow of the cooling water from the burner head 3 takes place through a line 73 present in the burner shaft 2. This line 73 has a sheath 96 which improves the electrical insulation between the two lines 62, 73 which are at different potential and thereby reduces any leakage currents. From the line 72, the cooling water flows back into the connection element 1, where it finally exits the plasma spraying device via the connection 20.

Such a cooling water flow has the advantage that only a single cooling water circuit is necessary due to the cooling connection of the anode nozzle 11 and the cathode arrangement 12. The condition for such a cooling water course is, of course, that high-purity or ultra-pure water is used as cooling water, so that it has a correspondingly low electrical conductivity. Furthermore, the jacket tube 92 of the burner shaft 2 is flowed through in the entire available cross section and thus the entire burner shaft 2 is cooled correspondingly efficiently.

4, 4a and 4b, it should be taken into account that, for better illustration of the cooling, the plasma spraying device is shown in a section through two different planes combined in this representation. In addition, the plasma gas line and the plasma powder line have been omitted from these figures for the sake of clarity.

The burner shaft 2 can be seen in cross section in FIG. 5a, while a section of the burner shaft 2 is shown in longitudinal section in FIG. 5b. The tubular cooling water line 73, the rod-shaped current conductor 62 and the plasma powder line 71 and the plasma gas line 76 can be seen in the casing tube 92 of the burner shaft 2. The jacket 96 of the cooling water line 73, which is designed as electrical insulation, is also shown. From this representation it can be seen very well below that the jacket tube 92 of the burner shaft 2 is flowed through by the cooling water over a large area and that efficient cooling is thereby ensured. Both figures are shown enlarged compared to the previous representations for better illustration.

Figures 6a, 6b and 6c show an enlarged view of the burner head 3 in longitudinal section, in cross section and in an external view from the burner shaft. The burner head 3 serves to generate a plasma flame, by means of which the supplied plasma powder is melted and accelerated, so that the plasma powder set in motion can thereby be applied to a workpiece to be coated. Electrical energy and various media are supplied to operate the burner.

The burner head 3 has a cylindrical basic shape, which essentially consists of a cathode base body 64 with a cathode arrangement 12 mounted therein, an anode base body 63 with an anode nozzle 11 fastened therein, and an anode base body 63 Insulating body 65 electrically separating from the cathode base body 64. On its side facing the burner shank 2 there is a shoulder 36 which encompasses the entire burner head 3. The anode base body 63 consisting of metal has essentially a rectangular basic shape, the surface 98 being rounded. This upper, rounded surface 98 also forms part of the outside of the burner head 3. The cathode base body 64, which is also made of metal, has a shape which is approximately mirror-image to the anode base body 63 and in which the rounded part 99 forms a lower part of the outside of the Burner head 3 forms. The insulating body 65 is arranged between the inner surface of the cathode base body 64 and the inner surface of the anode base body 63. In order to optimize the electrical insulation between the cathode base body 64 and the anode base body 63, the insulating body 65 has a cylindrical segment-shaped flange 74 on each of its longitudinal sides, which partially encompass the anode base body 63 and the cathode base body 64 on their straight parts on the outside. At its end facing away from the burner shaft 2, the burner head 3 also has an insulating cap 101 made of ceramic.

The mechanical cohesion of the burner head 3 is ensured by screws 97, which each connect the cathode base body 64 and the anode base body 63 to the insulating body 65. In order not to impair the good insulation between the cathode base body 64 and the anode base body 63, the two bodies 63, 64 are at different locations with the insulating body 65 screwed. The cathode assembly 12 itself consists of a cylindrical cathode socket 13 with a cathode 14 which is in the form of a pin and is inserted from above. The cathode socket 13 has an external thread 103 at its rear end, by means of which it is screwed into a corresponding thread 104 of the cathode base body 64. These threads 103, 104 also ensure reliable electrical contact between the cathode base body 64 and the cathode arrangement 12. The longitudinal axis of the cathode arrangement 12 comes to lie transversely to the longitudinal axis of the burner head 3. The cathode socket 13 is enclosed at its upper end by a ceramic insulating disk 138. In order to determine the axial position of the cathode arrangement 12, the cathode socket 13 has a shoulder 106, which, by screwing in, rests with its end face on the cathode base body 64 in a defined manner. At the level of the cooling water bore 136, the cathode socket 13 has an annular groove 108 which, together with a groove 109 embedded in the cathode base body 64 and corresponding in shape and position, results in a cooling ring channel 110. In order to seal this cooling ring channel 110, a sealing ring 112 comprising the cathode socket 13 is provided above and below it. For the supply of plasma gas, the cathode socket 13 and the cathode base body 64 each have an annular groove 114, 115, which together, below the cooling ring channel 110, form an annular channel 116. A plasma gas channel 127 extending from the end face 132 opens into this ring channel 116. Longitudinal channels 118, which extend in the peripheral region of the cathode holder 13 of the cathode 14, finally emanate from this ring channel 116 run along and open at the front openings in the bore 120 of the anode nozzle 11.

The anode nozzle 11 has a cylindrical basic shape with a through bore 120, the bore 120 tapering at the beginning and at the end. The anode nozzle 11 is inserted into the anode base body 63 from the outside, so that the longitudinal axis of the anode nozzle 11 is again transverse to the longitudinal axis of the burner head 3. To define the axial position of the anode nozzle 11, it has a collar 121 designed as a stop, which comes to rest on an end face of a bore 100 in the anode base body 63 when the anode nozzle 11 is inserted. The current from the anode base body 63 is simultaneously transferred to the anode nozzle 11 via this end face. In the inserted state, the cathode 14 projects into the bore 120 of the anode nozzle 11. The anode nozzle 11 is fixed in the anode base body 63 by means of a clamping jaw 122 which is screwed onto the anode base body 63 by means of a screw (not shown). This clamping jaw 122 is designed such that it connects, via an internal bore 123, a powder channel 125 leading through the anode base body 63 to a bore 126 leading radially into the interior of the anode nozzle 11.

As already described for the cathode socket 13, the anode nozzle 11 also has an annular groove 128 which, together with a groove 129 embedded in the anode base body 63, has a cooling ring channel 130 results. Corresponding sealing rings 131 are in turn provided for sealing this cooling ring channel 130.

On the end face 132 facing the burner shaft 2, the bar 34 engaging in a corresponding groove of the burner shaft can again be seen. All connections for supply lines for the burner media also lead to plug or butt connections on this end face 132. The plug 66 is provided for the inlet of cooling water. From this plug 66, a channel 135 for cooling water leads into the anode base body 63, where it first opens into the cooling ring channel 130 leading around the anode nozzle 11. Thereafter, the cooling water channel 135 continues through the anode base body 63, is then deflected downward by 90 °, leads through the insulating body 65 into the cathode base body 64, is in turn deflected through 90 ° in order to finally open into the cooling ring channel 110 of the cathode socket 13. From the transition from the insulating body into the cathode base body 64, the cooling water channel is designated 136. Finally, the cooling water duct 136 leads out of the burner head 3 again via the plug 67.

The two tubular plugs 66, 67 are inserted into and connected to the cathode base body 64 and the anode base body 63 in such a way that good electrical contact with them is ensured.

Finally, in order to shield the burner head 3 as well as possible against heat, there is an angled heat shield 5 provided which is mounted on the side of the anode nozzle 11, flush with the surface thereof, on the burner head 3.

The operation of such a burner head 3 is well known, which is why only a few special features and advantages of the type of training described above are referred to here. An essential advantage of such a burner head 3 is that both the anode nozzle 11 and the cathode arrangement 12 are accessible from the outside and can therefore be quickly replaced by the user in a simple manner. Due to the transverse installation of the plasma cartridge, the plasma jet emerges radially from the burner head 3 with respect to the longitudinal axis. As a result, in particular when coating pipes and the like internally, any existing, angled points can also be coated uniformly and homogeneously. The plasma gas, which is passed through the channels 118 through the channels 118 in the peripheral area of the cathode socket 13 of the cathode 14, cools the cathode socket 13. Furthermore, the plasma gas is preheated by this feed, which results in an improvement in the efficiency. The metal cathode base body 64 is used for supplying the electric current to the cathode 14. As already described above, the plug 67 is designed both as a plug for connecting the cooling lines and as a contact for the electrical current. Since both the cathode socket 13 and thus the cathode 14 itself and the plug 67 are in direct contact with the cathode base body 64, the electrical current is of course also transmitted accordingly.

By connecting the cathode cooling and the anode cooling in series with respect to the cooling water circuit, the number of connecting lines can be reduced to a minimum. In order to connect the anode nozzle 11, which is at a different potential with respect to the cathode arrangement 12, via the cooling medium, it is of course assumed that a cooling liquid with a high specific electrical resistance is used as the cooling medium. As already mentioned, ultrapure or ultrapure water is ideal for this.

The connection of the plasma powder channel 125, which is designed as a clamping jaw 122, to the powder supply line 126, which opens radially into the anode nozzle 11, is interchangeable. If different clamping jaws 122 with different line cross sections are now available, the injection speed of the plasma powder which is fed to the plasma flame can be preselected or changed by exchanging this clamping jaw 122, which is designed as a powder injector.

Claims (26)

1. Plasma spray gun for the coating of cavity walls, characterized by the combination of the following features:

   - the plasma spray gun has a connecting element (1), a burner shaft (2) and a burner head (3) which are located behind each other in an axis (25) forming the longitudinal axis of the plasma spray gun;

   - the connecting element (1), the burner shaft (2) and the burner head (3) are constructed as individually exchangeable modules which are connected to each other interchangeably by the user;

   - all leads and channels (52, 53, 71, 76) necessary for the operation of the burner run right through the interior of the burner shaft (2),

   - the burner head is constructed in such a way that the plasma beam goes out radially;

   - the burner head is fitted with cooling ducts;

   - the burner shaft (2) has a sleeve pipe (92) of metal, which is equipped at both ends with connecting sections (49, 50, 58, 60, 79, 80, 81, 82) and contains in the interior conductors (62, 71, 73, 76) for the current supply and derivation for the supply and derivation of the coolant, for feeding plasma gas and for the supply of coating material;

   - the connection of all leads and channels between the connecting element (1) and the burner shaft (2) on the one hand and between the burner shaft (2) and the burner head (3) on the other hand are made through plug and/or junction connections (39, 49; 44, 50; 58, 66; 60, 67; 79, 84; 80, 85; 81, 86; 82, 87).
2. Plasma spray gun according to Claim 1, characterized in that, in the burner shaft (2) for the current feed to the burner head (3), a rod-shaped conductor (62) and for the current derivation from the burner head (3) a tubular current conductor (73) are provided, and that for the supply of the coolant, the sleeve pipe (92) with its whole remaining cross-section is used, and for the derivation of the coolant, the tubular current conductor (73) is used.
3. Plasma spray gun according to Claim 1 or Claim 2, characterized in that at least one of the two current conductors (62, 73) has a sheathing (96) designed as electrical insulation.
4. Plasma spray gun according to Claim 2 or 3, characterized in that the connecting section of the burner shaft (2) facing the burner head (3) has a closing cap (57) and two bushes (58, 60) located in it, which fit on each plug (66, 67) of the burner head (64), located on an anode-based body (63) or a cathode-based body (64) of the burner head (3), and that the one bush (58) is connected to the rod-shaped current conductor (62) and the other bush (60) to the tubular current conductor (73), the cavity of the bush (58) connected to the rod-shaped current conductor (62) is connected by radial channels (93) to the interior of the sleeve pipe (92).
5. Plasma spray gun according to Claim 1, characterized in that the burner head (3) is fixed by two screws (7) to the burner shaft (2) and the burner shaft (2) by means of three screws (6) to the connecting element (1).
6. Plasma spray gun according to Claim 1, characterized in that connections (20, 21, 22, 23) for burner-medium leads are present on the connecting element (1), which are located radially opposite the longitudinal axis (25) of the plasma spray gun.
7. Plasma spray gun according to one of the above claims, characterized in that the burner shaft has a shape differing from a straight line, especially an at least partly offset, cranked or arched shape.
8. Plasma spray gun according to one of the above claims, characterized in that the burner head has an anode-based body (63) which carries an anode nozzle (11), a cathode-based body (64) which carries a cathode (14) protruding into the anode nozzle (11), and an insulator (65) inserted between the cathode-based body (64) and the anode-based body (63), that the cathode-based body (64), the anode-based body (63) and the insulator (65) are connected to each other along planes running parallel to the longitudinal axis (25) of the plasma spray gun, with the cathode-based body (64) and the anode-based body (63) forming sections of the outside of the burner head (3), and that the cathode (14) and the anode nozzle (11) are inserted from outside transversely to the longitudinal axis (25) of the plasma spray gun into the cathode-based body (64) or anode-based body (63).
9. Plasma spray gun according to Claim 8, characterized in that the insulator (65) has flanges (74) on its longitudinal sides which partially encompass the cathode-based body (64) and the anode-based body (63) on their outer sides.
10. Plasma spray gun according to Claim 8, characterized in that connecting channels (125, 127) for the supply of plasma gas and plasma powder are provided inside the burner head (3), which run outside the insulator (65).
11. Plasma spray gun according to Claim 8, characterized in that the cathode-based body (64), the anode-based body (63) and the insulator (65) of the burner head (3) together form an essentially cylinder-shaped assembly, the longitudinal axis of which coincides with the longitudinal axis (25) of the plasma spray gun.
12. Plasma spray gun according to Claim 8, characterized in that the cathode-based body (64) and the anode-based body (63) have cooling channels (135, 136) for a liquid coolant, which are connected in series through a passage in the insulator (65) and lead to connecting elements (66, 67) which are located on the burner-shaft-side face (132) of the burner head (3).
13. Plasma spray gun according to Claims 10 and 12, characterized in that on one face side (132) of the burner head (3) all connections (66, 67, 88, 89) for connecting channls (125, 127) and also for the cooling channels (135, 136) are provided, and that the other face side (137) turned away from the burner shaft (2) are sealed off by an insulating cap (101).
14. Plasma spray gun according to Claim 8, characterized in that the burner head (3) has a cap (101) embracing the face side (137).
15. Plasma spray gun according to Claim 8, characterized in that the cathode-based body (64) on the one hand and the anode-based body (63) on the other hand are screwed to the insulator (65) at various points.
16. Plasma spray gun according to Claim 8, characterized in that a protective hood (4) of ceramic material is provided which can be pushed onto the burner head (3), leaving the anode nozzle (11) free.
17. Plasma spray gun according to one of Claims 8 to 16, characterized in that the cathode (14) is constructed in a pin shape, and that, for receiving the cathode (14), a cylindrical cathode holder (13) is provided, which is screwed into the cathode-based body (64) and passes through its coolant channel (136).
18. Plasma spray gun according to Claim 17, characterized in that the cathode-based body (64) and the cylindrical cathode holder (13) have annular grooves (114, 115) which are expanded into an annular channel (116), into which the supply pipe (127) for the plasma gas opens.
19. Plasma spray gun according to Claim 18, characterized in that there are longitudinal channels (118) in the peripheral zone of the cathode holder (13), which, starting out from the annular channel (16) lead along the cathode (14) and open out at apertures on the face side in the interior space (120) of the anode nozzle (11).
20. Plasma spray gun according to one of Claims 17 to 19, characterized in that the cathode (14) is made of doped tungsten.
21. Plasma spray gun according to Claim 8, characterized in that the anode-based body (63) has a cylindrical drilled hole into which the anode nozzle (11) is pushed, the anode nozzle (11) being fixed by a gripping die (122) acting on a collar (121) of the anode nozzle (11), screwed on the anode-based body (63).
22. Plasma spray gun according to Claim 8, characterized in that the anode nozzle (11) has a radial channel (126) situated outside the anode-based body (63), through which the supply of the plasma powder provided as coating material takes place into the interior space (120) of the anode nozzle (11).
23. Plasma spray gun according to Claims 21 and 22, characterized in that the gripping die (122) has a connecting channel (123) which joins the plasma powder channel (125) leading through the anode-based body (63) to the radial channel (126) leading into the anode nozzle (11).
24. Plasma spray gun according to Claim 8, characterized in that an offset protective screen (5) is provided on the burner head (3) on the side of the anode nozzle (11).
25. Burner head with all the features of the burner head described in Claim 8, adapted in such a manner that it can be used in a plasma spray gun according to one of Claims 1 to 7.
26. Burner head according to Claim 25, in which the burner head is provided additionally with the features of at least one burner head described in one of Claims 9 to 24.

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