Patent Publication Number: US-2005121857-A1

Title: Device for sealing a passage through a wall

Description:
THE BACKGROUND OF THE INVENTION AND PRIOR ART  
      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.  
     SUMMARY OF THE INVENTION  
      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 . 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      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.  
       FIG. 1  discloses a device according to a first embodiment of the invention.  
       FIG. 2  discloses a device according to a second embodiment of the invention.  
       FIG. 3  discloses a device according to a third embodiment of the invention.  
       FIG. 4  discloses a set of blades of the device in  FIG. 3 .  
       FIG. 5  discloses a device according to a fourth embodiment of the invention.  
       FIG. 6  discloses a set of guide vanes of the device in  FIG. 5 .  
       FIG. 7  discloses a device according to a fifth embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION  
       FIGS. 1, 2 ,  3 ,  5  and  7  disclose different embodiments of a device for sealing a passage  1  through a wall  2  between a first space  3 , which is arranged to contain a gas, and a second space  4 , which is arranged to contain a liquid. The wall  2  may form a stationary wall element of a ship or of a stationary plant. A rotatable shaft  5 , for instance a propeller shaft of a ship, extends in the passage  1  through the wall  2  in such a way that a gap is formed, which extends around the shaft  5  between the shaft  5  and the wall  2 . The shaft  5  is rotatable around the rotary axis x.  
      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  8   a  and a second part volume  8   b.    
      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  8   a  of the chamber  8  between the disc  14  and the first limiting wall  11 .  
      According to the first embodiment disclosed in  FIG. 1 , said means include a blade member  15 , which includes a rotor member in the form of a rotatable disc  16  and two sets of blades  17 ′,  17 ″. The first set of blades  17 ′ are provided on one side of the rotatable disc  16  and the second set of blades  17 ″ are provided on the other side of the rotatable disc  16 . The rotatable disc  16  is provided on a cylindrical support member  18  of the blade member  15 . The support member  18  is substantially concentrically arranged around the shaft with regard to the rotary axis x. The rotatable disc  16  extends substantially radially outwardly in the chamber  8  from the support member  18  between the disc  14  and the first limiting wall  11  of the chamber  8  The first set of blades  17 ′ are thus turned towards the disc  14  and the second set of blades  17 ″ are turned towards the first limiting wall  11 . The blade member  15  includes also two sealing members  19 ′,  19 ″. A first such sealing member  19 ′ is turned towards the disc  14  and a second sealing member  19 ″ is turned towards the first limiting wall  11 . The sealing members  19 ′,  19 ″ are designed in such a way that they do not abut the disc  14  and the first limiting wall  11 , respectively, when the blade member  15  rotates, but will abut sealingly the disc  14  and the limiting wall  11 , respectively, when the blade member  15  is still standing and liquid flows from the second space  4  towards the first space  3 .  
      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  8   b  of the chamber  8 , to the second space  4 . The second part volume  8   b  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  8   b  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 .  
       FIG. 2  discloses a second embodiment where the blade member  15  forms the chamber  8  which thus is rotatable. It is to be noted that components having substantially the same function have been provided with the same reference signs in the various embodiments. The chamber  8  in the second embodiment thus is formed of a separate wall element  11 ,  12 ,  13 , which is rotatable around the shaft  5  independently of the rotation of the shaft  5  and which also includes a first limiting wall  11 , a second limiting wall  12  and a third limiting wall  13 . Also in this embodiment, the limiting walls  11  and  12  extend substantially radially outwardly and in parallel to each other, and the limiting wall  13  extends substantially coaxially with the shaft  5  and between a radially outer end of the limiting walls  11  and  12 . The disc  14  extends substantially radially outwardly from the shaft  5  and into the chamber  8 . A wall portion  30  extends substantially radially outwardly from said gap and substantially in parallel with the disc  14 . The wall portion  30  is rigidly connected to the stationary wall  2 . In the second embodiment, the second part volume  8   b  of the chamber  8  and thus an outlet channel for liquid from the radially outer part of the chamber  8  is formed between the disc  14  and the wall portion  30 . In the second embodiment, the first part volume  8   a  is formed partly between the first limiting wall  11  and the disc  14  and partly between the second limiting wall  12  and the wall portion  30 .  
      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  8   a,  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.  
       FIGS. 3 and 4  disclose a third embodiment where the blade member  15  includes an annular rotor  40  of an electric motor. The blade member  10  and the rotor  40  are provided in the chamber  8  and more precisely in the first part volume  8 a. Also in this embodiment, the chamber  8  is formed by a first limiting wall  11 , a second limiting wall  12  and a third limiting wall  13 , which thus enclose the chamber  8 . In the same way as in the first embodiment, the three limiting walls  11 ,  12 ,  13  are rigidly connected to the stationary wall. The electric motor also includes a stator  41 , which has a winding  42  and which is arranged outside the chamber  8 , and more precisely outside the first limiting wall  13 . The electric motor may for instance be an asynchronous motor or a so-called PMSM-motor. The blade member  15  is rotatably carried by the shaft  5  by means of a first bearing member  21 ′ and a second bearing member  22 ′. No sealing members are disclosed in  FIG. 3 , but may for instance be arranged between the shaft  5  and the substantially cylindrical projections  43 ,  44  of the limiting walls  11  and  22 , respectively.  
      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 .  
       FIG. 4  discloses schematically an example of a set of blades  17 ″ of the third embodiment. The blades  17 ″ are arranged on an annular carrier  45  which is mounted on the annular rotor  40 .  
       FIG. 5  discloses a fourth embodiment of the invention. The chamber  8  is also here formed by 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  and are fixedly connected to the stationary wall  2 . In this embodiment, said means are arranged to supply liquid to the first part volume  8   a  of the chamber  8  at such a speed and direction that the liquid in the chamber  8  is forced to rotate at a rotary speed exceeding the rotary speed of the shaft  5 . The means include a set of nozzles  50  for said liquid supply. The nozzles  50  extend in a substantially tangential direction into the chamber  8  seen in an axial section. The liquid is supplied to the nozzles  50  by means of a schematically disclosed pump  51  via conduit members  52 . A sealing member  19  is arranged between the first limiting wall  11  and the shaft  5 .  
      The outlet channel mentioned above, which partly is formed by the second part volume  8   b  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  FIG. 6  may be arranged in the outlet channel for conveying the liquid flowing from the chamber  8  to the second space  8   b.  In the fourth embodiment, the guide vanes  60  are arranged on the second limiting wall  12 , forming a wall portion  30 , and in the second embodiment on the wall portion  30 . Also the device according to the first and third embodiments may be provided with such guide vanes.  
       FIG. 7  discloses a fifth embodiment, which differs from the other embodiments by the fact that the chamber  8  includes three part chambers  8 ′,  8 ″ and  8 ′″. Except for this difference, the construction and the function of the device according to the fifth embodiment in  FIG. 7  is similar to the construction and the function of the second embodiment in  FIG. 2 . The part chambers  8 ′,  8 ″ and  8 ′″ have been formed by means of two intermedient walls  71  and  72 , which are provided with blades  17 ′″ and  17 ″″, respectively, and which extend substantially radially inwardly from the third limiting wall  13 . Furthermore, the fifth embodiment includes two rotatable discs  14 ′ and  14 ″ which extend into a respective part chamber  8 ′ and  8 ″, respectively, and two wall portions  30 ′ and  30 ″, which are provided with guide vanes  60 ′ and  60 ″, respectively, which correspond to the guide vanes  60  in  FIG. 2 . The wall portions  30 ′ and  30 ″ extend substantially radially outwardly from the cylindrical part  33  and into a respective part chamber  8 ″ and  8 ′″, respectively. The central part chamber  8 ″ includes the second part volume  8   b  and is thus substantially identical to the chamber in  FIG. 2 , whereas the part chamber  8 ′ merely receives the disc  14 ′ and the part chamber  8 ′″ merely receives the wall portion  30 ″. It is to be noted that the chamber  8  may include another number part chambers than appears from the embodiments disclosed. For instance, it may include the two part chambers  8 ′ and  8 ″, and the two rotatable discs  14 ′ and  14 ″, but merely one wall portion  30 ′. Also other configurations are possible and especially it is to be noted that the chamber  8  may include more than three part chambers disclosed.  
      The invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims.