POWDER ROTARY FEEDTHROUGH HAVING A PURGE CHAMBER

Abstract

A rotary feedthrough for the feedthrough of a powder-gas mixture from a stationary machine part into a rotating machine part, with a seal in the form of two flat circular-ring-shaped sliding seal surfaces arranged one on the other in a sliding manner, which sliding seal surfaces are arranged concentric to the axis of rotation of the rotating machine part and which can be moved apart from each other in the axial direction, so that they form a gap, wherein the seal is embedded in a purge chamber having at least one gas inlet and at least one gas outlet.

Claims

1. A rotary feedthrough for the feedthrough of a powder-gas mixture from a stationary machine part into a rotating machine part, with a seal in the form of two flat circular-ring-shaped sliding seal surfaces arranged one on the other in a sliding manner, which sliding seal surfaces are arranged concentric to the axis of rotation of the rotating machine part and which can be moved apart from each other in the axial direction, characterized in that the seal is embedded in a purge chamber having at least one gas inlet and at least one gas outlet.

2. A rotary feedthrough according to claim 1, characterized in that the gas inlet and the gas outlet are arranged on diametrically lying sides of the purge chamber and preferably approximately at the axial height of the sliding seal surfaces.

3. A rotary feedthrough according to claim 1, characterized in that the flat seal surfaces are resiliently pretensioned in contact with each another.

4. A rotary feedthrough according to claim 1, characterized in that the flat seal surfaces are coated with a friction-reducing coating, preferably with a PVD coating.

5. A rotary feedthrough according to claim 3, characterized in that the coating is a coating which is configured as an anti-adhesion coating for the powder material.

6. A rotary feedthrough according to claim 3, characterized in that the coating comprises a ceramic layer and/or a carbon layer, wherein the carbon layer preferably comprises internally a DLC layer and particularly preferably, starting from the DLC layer towards the surface, comprises a higher sp2 hybridized portion of carbon compounds.

7. A rotary feedthrough according to claim 1, characterized in that the sliding disks consist entirely or predominantly of ceramic or of hard metal.

8. A method for feeding a powder-gas mixture from a stationary machine part into a rotating machine part, characterized in that a rotary feedthrough is used according to claim 1 and that the purge chamber of the rotary feedthrough is flowed through by a purge gas in such a way that powder particles are removed from the space between the sliding seal surfaces by the flow of purge gas when a gap is formed between the sliding surfaces.

9. A method according to claim 8, characterized in that the purge gas flows through the purge chamber at an overpressure compared with the pressure prevailing in the transport channel.

10. A method according to claim 8, characterized in that in the presence of powder particles in the purge chamber, the purge chamber is cleaned of these by means of the flow of the purge gas.

11. A method according to claim 1, characterized in that a gas is used as purge gas, which gas is also used as carrier gas of the powder-gas mixture.

Description

[0020] The invention is now represented in detail and exemplarily with reference to the figures.

[0021] FIG. 1 shows a gun manipulator.

[0022] FIG. 2 shows a powder rotary feedthrough according to the invention.

[0023] FIG. 2 shows a powder rotary feedthrough 201 according to the invention, which comprises a powder transport channel 205 embedded in a housing 203 with an arrow with a dashed line drawn in the direction of flow of the powder-gas mixture. The small unfilled circles in the powder transport channel should schematically represent the powder particles. The powder transport channel 205 comprises a channel section 205f, which is stationary in the application and a channel section 205r, which rotates in the application. The drawn vertical dashed line shall represent the axis of rotation, which is also considered the axis of the rotary feedthrough.

[0024] If the term rotating components is used here (e.g. channel section 205r), the term essentially refers to rotatable supported components, since the component can rest if the device is not used.

[0025] Where the stationary channel section 205f and the rotating channel section 205r meet with their ends, a stationary flat circular-ring-shaped sliding disk 207f is provided on the stationary channel section 205f and a further stationary flat circular-ring-shaped sliding disk 207r is provided on the rotating channel section 205r, which, however, rotates with the channel section 205r. According to the invention, this region of the powder transport channel 205 is enclosed by a purge chamber 209 to which at least one gas supply 211 and at least one gas discharge 213 are connected.

[0026] Where the rotating channel 205r is embedded within the housing, it is embedded via rotation-permitting bearings 215, wherein these bearings 215 or further bearings also allow an axial movement relative to the rotation axis. Pressing means 217, which for example are designed as springs as shown here, press the rotating sliding disk 207r against the stationary sliding disk 207f with predefined pressure.

[0027] In the application, while the powder-gas mixture is transported through the powder transport channel, purge gas is fed into the purge chamber 209 through the gas supply 211 and drawn off again through the gas discharge 213. The purge gas flow can be fed at a higher pressure and passed through the purge chamber than it is inside the transport channel. The corresponding situation is represented schematically in FIG. 3. For reasons of clarity, the reference signs are not repeated in the display of the springs.

[0028] As soon as a small gap is formed between the two seal surfaces and powder penetrates between the two seal surfaces, the powder is sucked together with the purge gas into the rotating channel 205r or transported into the purge chamber and powder particles are thus removed from the gap between the sliding disks 207f and 207r, so that the gap closes quickly again essentially due to the spring force (FIG. 4). Due to the overpressure in the purge chamber and the superimposed rotary motion of the sliding disk 207r, the powder preferably returns into the transport channel and the gap between the sliding disks 207f and 207r is freed of powder particles.

[0029] However, if powder particles have penetrated into the purge chamber as shown in FIG. 5, they are purged out of the purge chamber with the purge gas. This means that the purge chamber has a self-cleaning mechanism.

[0030] In an embodiment, the sliding seal disks can be made of ceramic or of hard metal.

[0031] According to a preferred embodiment, the seal surfaces of the sliding disks 205f and 205r are coated with a coating, which on the one hand reduces the friction of the disks and on the other hand, preferably also acts as an anti-adhesion coating against adhesion of the powder particles on the seal surfaces.

[0032] The coating, which can be for example a PVD coating and/or a CVD coating, can be designed for example as a ceramic coating or also as a carbon coating. In the case of the carbon coating, it can be advantageous to realize an increasing sp.sup.2 hybridized portion to the surface of the seal surfaces, starting from a diamond-like coating. In this way, the layer can comprise the outer component as a run-in coating, which in use wears to a certain depth, i.e. to a certain degree of hardness.

[0033] In general, the coating permits the use of non-ceramic, more easily machinable substrate materials that are used for the sliding disks. The simpler processing of the materials allows narrower tolerances to be achieved.

[0034] According to a particularly preferred embodiment of the present invention, the mass flow of the purge gas flowing into the purge chamber through the gas inlet is continuously or regularly compared with the mass flow of the gas withdrawn from the purge chamber. If the latter is also only slightly reduced compared to the former, this means that a gap has formed through which the purge gas flows into the transport channel. If necessary, the pretension generated by the springs is then reduced to release powder particles trapped in the gap and thus accelerate the cleaning process.

[0035] The sliding seal surfaces have so far been described as flat seal surfaces. However, conical or curved seal surfaces are also conceivable. In fact, all rotationally symmetric surfaces that do not have a cylinder shell component can be used. However, the flat seal surfaces are to be preferred since they offer the least resistance to the purge gas flow and are therefore conducive to an effective purge process.

[0036] A rotary feedthrough was disclosed for the feedthrough of a powder-gas mixture from a stationary machine part into a rotating machine part, with a seal in the form of two flat circular-ring-shaped sliding seal surfaces arranged one on the other in a sliding manner, which sliding seal surfaces are arranged concentric to the axis of rotation of the rotating machine part and can be moved apart from each other in the axial direction, so that they form a gap. The rotary feedthrough is characterized in that the seal is embedded in a purge chamber having at least one gas inlet and at least one gas outlet.

[0037] The flat seal surfaces are resiliently pretensioned in contact with each another.

[0038] The flat seal surfaces can be coated with a friction-reducing coating, preferably with a PVD coating. The coating preferably is a coating which is configured as an anti-adhesion coating for the powder material.

[0039] The coating may comprise a ceramic layer and/or a carbon layer, wherein the carbon layer preferably comprises internally a DLC layer and particularly preferably, starting from the DLC layer towards the surface, comprises a higher sp.sup.2 hybridized portion of carbon compounds.

[0040] A method for feeding a powder-gas mixture from a stationary machine part into a rotating machine part was disclosed. The method is characterized in that a rotary feedthrough is used as described above and the purge chamber is flowed through by a purge gas at an overpressure compared to the pressure prevailing in the transport channel in such a way that when powder particles penetrate between the sliding surfaces through the gap thereby formed, a flow of purge gas takes place into the transport channel, which flow tears the powder particles out of the gap with it and thus cleans the gap of powder particles.

[0041] If powder particles are present in the purge chamber, it can be cleaned by means of the flow of the purge gas.