US-12618497-B2 - Powder rotary feedthrough having a purge chamber

US12618497B2US 12618497 B2US12618497 B2US 12618497B2US-12618497-B2

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.

Inventors

Alexander Michla
Martin Stoeckli
Christian Bohnheio
Dennis Hoff
Peter Stephan

Assignees

OERLIKON METCO AG, WOHLEN
MOOG GAT GMBH

Dates

Publication Date: 20260505
Application Date: 20170705
Priority Date: 20160707

Claims (20)

1 . A rotary feedthrough for the feedthrough of a non-lubricating powder-gas mixture from a stationary machine part into a rotating machine part, comprising: a housing; a stationary powder transport channel; a rotating powder transport channel; a purge chamber comprising at least one opening for the stationary powder transport channel and at least one opening for the rotating powder transport channel, in which the at least one opening for the stationary powder transport channel and the at least one opening for the rotating powder transport channel are concentrically arranged with an axis of rotation of the rotating machine part; a seal arranged within the purge chamber between facing ends of the stationary powder transport channel and of the rotating powder transport channel, the seal comprising two flat circular-ring-shaped sliding seal surfaces arranged one on the other in a sliding manner, each of the sliding seal surfaces being arranged concentric to the axis of rotation of the rotating machine part and being movable relative to each other in an axial direction along the axis of rotation of the rotating machine part; the purge chamber further comprising at least one gas inlet and at least one gas outlet, in which the at least one gas inlet and the at least one gas outlet are arranged on diametrically opposing sides of the purge chamber and are aligned transversely to the axis of rotation of the rotating machine part, and the purge chamber also comprising a purging channel connecting the at least one gas inlet and the at least one gas outlet, wherein a purging gas is suppliable from the at least one gas inlet to the at least one gas outlet through the purging channel; and bearings arranged in the housing to allow for rotational and axial movement of the rotating powder transport channel within the purge chamber, wherein the two flat circular-shaped sliding seal surfaces, which include a rotating seal surface that is axially movable within the purging chamber and relative to a stationary seal surface, the rotating seal surface and the stationary seal surface being arranged within the purging channel and within a flow path of the purge gas suppliable through the purging channel from the at least one gas inlet and the at least one gas outlet, wherein the two flat circular-shaped sliding seal surfaces are in contact with each other with a resilient pretensionable force pressing the axially movable rotating seal surface along the axis of rotation toward the stationary seal surface.
2 . The rotary feedthrough according to claim 1 , wherein the pretension force is adapted to allow the purge gas flow to release powder particles trapped in between the rotating seal surface and the stationary sliding seal surface.
3 . The rotary feedthrough according to claim 2 , wherein the flat circular ring-shaped seal surfaces are coated with an anti-adhesion coating against adhesion of the powder material on the seal surfaces.
4 . The rotary feedthrough according to claim 3 , wherein the anti-adhesion coating comprises a ceramic layer.
5 . The rotary feedthrough according to claim 4 , wherein the carbon layer comprises internally a diamond-like coating (DLC) layer.
6 . The rotary feedthrough according to claim 5 , wherein starting from the DLC layer towards the flat circular-ring-shaped seal surface, the carbon layer comprises a higher sp 2 hybridized portion of carbon compounds.
7 . The rotary feedthrough according to claim 3 , wherein the anti-adhesion coating is a PVD coating.
8 . The rotary feedthrough according to claim 3 , wherein the anti-adhesion coating comprises a ceramic layer.
9 . The rotary feedthrough according to claim 1 , wherein the sliding seal surfaces consist entirely or predominantly of ceramic or of carbide.
10 . The rotary feedthrough according to claim 1 , wherein the gas inlet and the gas outlet are approximately at an axial height of the sliding seal surfaces.
11 . The rotary feedthrough according to claim 1 , further comprising a powder-gas transport channel, which includes the stationary powder transport channel and the rotating powder transport channel, arranged concentric with the axis of rotation of the rotating machine part, wherein the stationary powder transport channel is coupled to the at least one opening for the stationary powder transport channel and the rotating powder transport channel is coupled to the at least one opening for the rotating powder transport channel, and wherein the rotating powder transport channel and the stationary powder transport channel are separated from each other by the two flat circular-ring-shaped sliding seal surfaces.
12 . The rotary feedthrough according to claim 11 , wherein the rotating powder transport channel is arranged for axial movement relative to and for rotational movement relative to the stationary powder transport channel.
13 . The rotary feedthrough according to claim 1 , further comprising a gas-powder transport channel, which includes the stationary powder transport channel and the rotating powder transport channel, extending through the purge chamber from the at least one opening for a stationary powder transport channel to the at least one opening for a rotating powder transport channel.
14 . The rotary feedthrough according to claim 13 , wherein, in the gas-powder transport channel, the stationary powder transport channel is coupled to the at least one opening for a stationary powder transport channel and the rotating powder transport channel is coupled to the at least one opening for a rotating powder transport channel.
15 . The rotary feedthrough according to claim 14 , wherein the two flat circular-ring-shaped sliding seal surfaces are arranged at facing ends of the stationary powder transport channel and the rotating powder transport channel.
16 . The rotary feedthrough according to claim 13 , wherein a mixture of gas and powder is transported through the gas-powder transport channel at a pressure lower than a pressure in the purge chamber.
17 . The rotary feedthrough according to claim 1 , wherein the resilient pretensionable force between the two flat circular-shaped sliding seal surfaces is adjustable based upon a comparison of a mass flow of the purging gas flowing into the purge chamber to a mass flow of the purging gas withdrawn from the purge chamber.
18 . A method for feeding a non-lubricating powder-gas mixture from a stationary machine part into a rotating machine part through the rotary feedthrough according to claim 1 , the method comprising: directing a flow of purge gas from the at least one gas inlet to the at least one gas outlet through the purge chamber of the rotary feedthrough in such a way that, when a gap is formed between the sliding surfaces, powder particles are removed from the space between the sliding seal surfaces by the flow of purge gas.
19 . A method according to claim 18 , wherein the purge gas flows through the purge chamber at an overpressure compared with a pressure prevailing in a transport channel through which the gas-powder mixture is fed.
20 . A method according to claim 18 , wherein, when powder particles are present in the purge chamber, the purge chamber is cleaned of the powder particles via the flow of the purge gas.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a U.S. National Stage of International Application No. PCT/EP2017/066781 filed Jul. 5, 2017, which claims priority to German Application No. 10 2016 112 470.2 filed Jul. 7, 2016. The disclosure of International Application No. PCT/EP2017/066781 is expressly incorporated by reference herein in its entirety. BACKGROUND 1. Field of the Invention The invention relates to a rotary feedthrough from a stationary medium into a rotating medium or vice versa. Among other things, a powder-gas mixture is to be fed through. 2. Discussion of Background Information Rotary feedthroughs for the feedthrough of non-lubricating media from a stationary machine part into a rotating machine part are known. In particular, the keyword “safe to run dry rotary feedthroughs” plays an important role here. While a seal in the form of two flat circular-ring-shaped sliding seal surfaces arranged one on the other in a sliding manner can also be realized for higher rotational speeds and transmission pressures up to 400 bar when feeding through lubricating media, this is only possible with non-lubricating media at lower rotational speeds and pressures. In particular, if the medium does not have to be fed continuously, the sliding surfaces should be moved apart in the axial direction from time to time in order to form a gap and to be able to cool down, whereby the rotating machine part can continue to rotate at a certain rotational speed. Otherwise, the sliding seal surfaces must remain in contact, which limits the rotational speeds and pressures accordingly. In this respect, certain leakage losses cannot be completely avoided. In DE19932355 B4, leakage losses are reduced by the fact that cylindrical axial cylinder shell surfaces are designed as seal surfaces instead of flat sliding surfaces. With such cylinder surfaces, narrow sealing gaps with much larger surfaces and gap lengths can be realized without changing the radius, i.e. without large radii and corresponding relative speeds, so that the non-lubricating medium can only pass through the cylindrical sealing gap to a small extent. However, a special case is a so-called powder-gas mixture which is used, for example, in the thermal spraying of cylinder liners and other surfaces. Such a mixture can also be referred to as a non-lubricating medium. However, a cylindrical sealing gap is not an option for this application, as the powder would settle in the sealing gap, which would very quickly lead to seizing of the rotary feedthrough. For thermal spraying of cylinder liners, coating powder must be reliably transported to a rotating injector and, accordingly, the sealing must be guaranteed at the point of the powder line where the interface between the “rigid” and “rotating” powder lines is located. To explain the application, FIG. 1 shows the gun manipulator RotaPlasma of one of the applicants. The gun manipulator 1 is shown, comprising a powder rotary feedthrough 3, means for current transmission 5, a gun holder 7, a gun connection 9 and finally the gun 11. A sealing at this interface is of essential importance for the coating process as the powder at the end of the powder line is to be injected into a plasma flame under constant conditions by means of a special powder injector. Under the constant conditions, special attention is paid to the parameters powder speed and powder quantity. These values are negatively influenced in particular by leaks in the powder line. A powder leakage, for example in the region of the powder rotary feedthrough, causes pressure variations which lead to pulsation of the powder. In addition, a leak in the powder line can cause the powder to escape to the outside due to the slight overpressure in the powder line, and thus greatly reducing the quantity of powder transported to the injector. The overpressure within the powder line is 100 to 800 mbar, depending on the parameter. According to the state of the art, a combination of Teflon bush—seal ring is used for the powder rotary feedthroughs. This was previously possible because, according to the state of the art, the gun of such a device is rotated at just under 200 revolutions per minute. At 200 rpm, however, the device already has a very limited service life, so that this process cannot be operated economically. The aim would also be to be able to operate the device at rotational speeds of up to 800 rpm and preferably more. In combination with an increased conveying rate adapted to the increased rotational speed, it is then possible to produce layers with significantly improved quality, as disclosed in a patent application already pending from one of the applicants. Such high rotational speeds can also be achieved for short periods with conventional devices. If, however, you want to produce layers beyond the laboratory scale, a new variant of the powder rotary feedthrough is required. It should be noted that the application at 800 rpm and even above is f