The present invention refers to a device according to the preamble of claim 1, and a method according to the preamble of claim 25. The invention is particularly suitable for sealing between a substantially stationary wall and a rotating shaft extending through a passage in the wall. Examples of application areas are ships and a propeller shaft extending through the hull of the ship. Also other application areas are possible.
DE-A-1955016 discloses such a device for sealing a passage through a wall between a first space, which is arranged to contain a gas, and a second space, which is arranged to contain a gas, and a second space, which is arranged to contain a liquid. A rotating turbine shaft extends in the passage through the wall and is journalled in a shaft bearing having a gap extending around the shaft between the shaft and the wall. A rotating disc is rigidly arranged on the shaft and extends outwardly from the shaft. A stationary wall in the form of a further disc is provided between the shaft bearing and the rotating disc. The stationary disc is designed in such a way that it forms a space between the two discs. Furthermore, supply conduits are provided for the supply of liquid to this space via two nozzles. The liquid forms a rotating liquid ring in the space.
DE 4212169 discloses a labyrinth sealing having a channel between a rotating part and a stationary disc. The channel may be supplied with oil via a supply channel, wherein a liquid level will be formed in the channel due to the rotation of the disc.
GB 1284596 also discloses a labyrinth sealing with feeding of liquid into a space formed by flange members from a rotating rotor. A stationary disc extends into the space and includes channels for said feeding of liquid and for discharging liquid from the space.
The object of the present invention is to provide a device enabling a sufficient sealing of a passage for a rotating shaft.
This object is achieved by the device initially defined, which is characterised in that it includes means arranged to force said liquid in the chamber to rotate at a rotary speed which substantially exceeds the rotary speed of the shaft.
By such means it is possible to ensure in an efficient manner that substantially no liquid will be transported from the second space to the first gas-filled space. The liquid, which rotates at the rotary speed which is higher than the speed of the shaft, forms a liquid body in a radially outer part of the chamber. This liquid body prevents substantially all media transport through the passage. In relation to mechanical sealings the advantage of a low friction and substantially no wear of essential sealing components is of course also achieved. Advantageously, the wall is stationary and consists, for instance, of a wall element of a ship or a stationary plant.
According to an embodiment of the invention, the chamber is arranged to permit that a part of said liquid flows into the chamber and at least partly is retained in the chamber for said sealing of the passage. Consequently, the liquid proper to be sealed off will form a sealing liquid body which prevents said media transport through the passage.
According to a further embodiment of the invention, said means are arranged to provide said rotation in the chamber between the disc and the first space. Consequently, the rotating liquid body is formed in an outer part of the chamber between the disc and the first space. The disc will thus prevent liquid from flowing straight forward from the second space to the first space. The liquid will instead be forced to the radially outer part of the chamber, i.e. to the blocking liquid body.
According to a further embodiment of the invention, said means include a blade member arranged to rotate independently of the shaft. By such a blade member the desired rotation may be achieved in an efficient manner. Advantageously, said means include a drive member, which is arranged to rotate the blade member at a rotary speed which is higher than the rotary speed of the shaft. The blade member may be rotatably carried by a bearing member which is connected to at least one of the shaft, the disc and the wall.
According to a further embodiment of the invention, the blade member includes at least one set of blades which are arranged in the chamber. Advantageously, the blade member may include a rotor member which extends outwardly in the chamber. The rotor member may include one or two such sets of blades. One such rotor member may be annular and extend around the shaft, wherein the blades are arranged on the rotor member and uniformly distributed around the shaft.
According to a further embodiment of the invention, the blade member includes a first set of blades, which are arranged on the rotor member and turned towards the first space, and a second set of blades, which are arranged on the rotor member and turned towards the disc.
According to a further embodiment of the invention, the rotor member includes a rotor of an electric motor having a stator which is provided outside the chamber. The stator and the electric connections may thus be located outside the chamber and in the first space.
According to a further embodiment of the invention, the blade member forms the chamber. The blade member may then advantageously include a first set of blades, which are arranged on a first limiting wall of the chamber and turned towards the disc, and a second set of blades, which are arranged on a second limiting wall of the chamber and turned towards the first limiting wall.
According to a further embodiment of the invention, said means are arranged to supply liquid to the chamber at such a speed and direction that the liquid in the chamber is forced to said rotation. Such means may include at least one nozzle for said liquid supply, wherein said nozzle extends in a substantially tangential direction into the chamber, and a pump for providing said liquid supply.
According to a further embodiment of the invention, the chamber includes several part chambers, which are arranged between the gap and the first space, and extend around the shaft, and two rotatable discs, which are rigidly connected to the shaft and extend outwardly from the shaft in a respective one of said part chambers, wherein each of said part chambers is arranged to contain liquid. Advantageously, said part chambers may be arranged to permit a part of said liquid to flow into the part chambers and at least partly be retained for sealing of the passage.
According to a further embodiment of the invention, the device is arranged to permit liquid to flow from the chamber to the second space. In such a way it is ensured that liquid not may flow from the chamber into the first space. The device may then include a wall portion, which partly defines the chamber and extends outwardly from the gap. The chamber may, between the disc and the wall portion, form an outlet channel, which is arranged to reduce the speed of the liquid flowing from the chamber to the second space. In such a way it is possible to regain pressure and thus reduce the energy consumption of the device. The outlet channel may extend from a radially outer position at the periphery of the disc to a radially inner position in the proximity of the shaft. In order to further increase the pressure recovering, guide vanes may be arranged in the outlet channel for conveying the liquid flowing from the chamber to the second space. Advantageously, said guide vanes are arranged on the wall portion.
The object is also achieved by the method defined in the independent claim 25.
The present invention is not to be explained more closely through a description of various embodiments, shown by way of example, and with reference to the drawings attached hereto.
The device according to the invention includes a chamber 8, which is provided between the first space 3 and the second space 4, and more precisely between the first space 3 and said gap of the passage 1. The chamber 8 is annular and extends around the shaft 5. The chamber 8 is formed of a first limiting wall 11, a second limiting wall 12 and a third limiting wall 13. The three limiting walls 11, 12, 13 thus enclose the chamber 8. The first limiting wall 11 and the second limiting wall 12 extend substantially radially outwardly and in parallel to each other. The third limiting wall 13 extends substantially coaxially with the shaft 5 and between a radially outer end of the first limiting wall 11 and a radially outer end of the second limiting wall 12. In the first embodiment, the limiting walls 11, 12, 13 are fixed in relation to the stationary wall 2.
The device also includes a rotatable disc 14, which is fixedly arranged on the shaft 5. The disc 9 extends substantially radially outwardly from the shaft 5 into the chamber 8 and divides the chamber 8 in a first part volume 8a and a second part volume 8b.
Liquid from the second space 4 may thus via the passage 1 and said gap flow from the second space 4 into the chamber 8. Consequently, the chamber 8 will contain liquid. Furthermore, the device includes different means, which are to be explained more closely in connection with the description of various embodiments and which are arranged to prevent liquid from flowing through the chamber 8 to the first space 3 by forcing the liquid in the chamber 8 to rotate at a relatively high rotary speed, i.e. a rotary speed substantially exceeding the rotary speed of the shaft 5. The rotating liquid will thus form a rotating liquid body in the first part volume 8a of the chamber 8 between the disc 14 and the first limiting wall 11.
According to the first embodiment disclosed in
The blade member 15 is according to the first embodiment rotatably carried by the shaft 5 by means of a bearing member 21, which is provided between and connected to the cylindrical support member 18 and the stationary wall 2 via a substantially cylindrical projection 22 of the first limiting wall 11. The blade member 15 is rotated independently of the shaft 5 by means of a schematically disclosed drive motor 23, which via a drive belt 24 or any other power transmission member is connected to the cylindrical support member 18. The drive motor 23 is thus arranged to rotate the blade member 15 at a rotary speed which is higher than the rotary speed of the shaft 5, and in such a way create a rotating liquid body in the radially outer part of the chamber 8. The level of the rotating liquid is marked by the arrow 25.
Furthermore, the device is arranged to permit liquid to flow from the chamber 8, and more precisely from the second part volume 8b of the chamber 8, to the second space 4. The second part volume 8b is thus located between the disc 14 and the second limiting wall 12 forming a wall portion 30 extending substantially radially outwardly from the gap mentioned above. The second part volume 8b and the gap thus form an outlet channel, which extends from a radially outer position at the periphery of the disc 14 to a radially inner position in the proximity of the shaft 5.
According to the second embodiment, the blade member 15 includes a first set of blades 17′, which are arranged on the first limiting wall 11 and turned towards the disc 13, and a second set of blades 17″, which are arranged on the second limiting wall 12 and turned towards the wall portion 30. The first set of blades 17′ and the second set of blades 17″ thus create a rotating liquid body in a radially outer part of the respective part volume 8a, so that liquid extends to the level indicated by the arrows 25.
The blade member 15 is according to the second embodiment rotatably carried by the stationary wall 2 by means of a first bearing member 21′, which is arranged between and connected to the stationary wall 2 and a substantially cylindrical projection 31 of the first limiting wall 11, and a second bearing member 21″, which is arranged between and connected to the stationary wall 2 and a substantially cylindrical projection 32 of the second limiting wall 12. A first sealing member 19′ is arranged between the first substantially cylindrical projection 31 and the shaft 5 in such a way that the first sealing member 19′ does not abut the shaft 5 when the blade member 15 rotates but only when the blade member 15 is still standing. A second sealing member 19″ is arranged between the second substantially cylindrical projection 32 and a substantially cylindrical part 33 of the stationary wall 2. The substantially cylindrical part 33 extends substantially concentrically from the wall portion 30 between the shaft 5 and the projection 32, wherein said gap is formed between the part 33 and the shaft 5. The sealing member 19″ does not abut the part 32 when the blade member 15 rotates but only when the blade member 15 is still standing.
The blade member 15 includes a first set of blades 17′, which are arranged on the rotor 40 and turned towards the first limiting wall 11, and a second set of blades 17″, which are arranged on the rotor 40 and turned towards the disc 14.
The outlet channel mentioned above, which partly is formed by the second part volume 8b of the embodiments disclosed, is arranged to reduce the speed of the liquid flowing from the chamber 8 to the second space 4. The outlet channel extends from a radially outer position at the periphery of the disc 14 to a radially inner position in the proximity of the shaft 5. By said speed reduction a pressure recovery and thus a lower energy consumption of the device is achieved. In order to further increase the pressure recovery, guide vanes 60 of the type disclosed in
The invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims.
Number | Date | Country | Kind |
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0103136-8 | Sep 2001 | SE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/SE02/01708 | 9/20/2002 | WO |