Patent Publication Number: US-2005121905-A1

Title: Sealing device for connection of a pipe in a hole

Description:
The present invention relates to a sealing device for connection of a pipe in a hole.  
      In the art there are frequent cases in which a pipe must pass through a baffle which divides two areas.  
      Often, the connection between the pipe, and a hole which is provided in the baffle, is rigid, and for example is produced by means of welding.  
      Sometimes, on the other hand, the connection between the pipe and the hole is free, with play.  
      This situation can be required for various reasons, for example in order to permit differential movements between the pipe and the baffle, or for reasons of thermal expansion to which the pipe is subjected.  
      In particular, in gas turbines, there exist pipes for internal cooling circuits, which connect an outer case of the turbine to an inner nozzle-holder ring, by passing through a divider baffle, which is also known as the nozzle sector.  
      In these cases, it is necessary to provide sealing devices in order to prevent passage of air in the space between the pipe and the hole.  
      In the known art, in the field of gas turbines, pipes are used which are provided with washers which are welded onto the outside of the pipes.  
      The washer is thrust against a surface, which for example is precision cast, of the divider baffle, by a spring which ensures that an area above the baffle is sealed relative to an area on the opposite side of the baffle.  
      However, the level of sealing obtained is not optimal, since it is difficult to obtain perfect contact between the washer and the surface of the baffle, owing both to geometric processing tolerances and to differentiated movements which exist between the outer case to which the pipe is coupled, and the divider baffle, which is secured to the inner nozzle-holder ring.  
      The object of the present invention is thus to eliminate the disadvantage previously described, and in particular to provide a sealing device for connection of a pipe in a hole, which guarantees a high level of sealing, even in the presence of geometric differences of concentricity between the pipe and the hole.  
      Another object of the invention is to provide a sealing device for connection of a pipe in a hole, which is particularly reliable, simple and functional, and has relatively low costs.  
      These objects and others according to the present invention are achieved by providing a sealing device for connection of a pipe in a hole, as described in claim  1 .  
      Further characteristics are described in the subsequent claims.  
      Advantageously, the sealing device for connection of a pipe in a hole is used for a cooling pipe in a gas turbine, thus permitting a large saving in cooling air, but also in particular preventing blow-by which is undesirable and is difficult to assess. 
    
    
      The characteristics and advantages of a sealing device for connection of a pipe in a hole, according to the present invention, will become clearer and more apparent from the following description, provided by way of non-limiting example, with reference to the attached schematic drawings, in which:  
       FIG. 1  is a view in lateral elevation, partially in cross-section, of a sealing device according to the known art, for connection of a cooling pipe in a hole in a divider baffle in a gas turbine;  
       FIG. 2  shows an enlarged view in lateral elevation of the sealing device in  FIG. 1 ;  
       FIG. 3  is a view in lateral elevation, partially in cross-section, of a sealing device according to the present invention, for connection of a cooling pipe in a hole in a divider baffle in a gas turbine; and  
       FIG. 4  shows an enlarged view in lateral elevation of the sealing device in  FIG. 3 . 
    
    
       FIGS. 1 and 2  show a sealing device which is according to the known art, and is indicated as  10  as a whole, for connection of a cooling pipe  12  in a hole  14  in a divider baffle  16  in a gas turbine.  
      In the example illustrated, the device  10  comprises a washer  18  with an annular shape, with two flat bases and with a central hole with a diameter which is the same as the outer diameter of the pipe  12 .  
      The washer  18  is threaded onto the outside of the pipe  12 , and is joined to the latter, for example by being welded.  
      The washer  18  of the pipe  12  is thrust towards a flat surface of the baffle  16  in which the hole  14  is provided, by pressure means  20  such as a spring.  
      The spring  20  can be fitted on one end of the pipe  12  which faces the hole  14  in the baffle  16 , and pre-loaded against a wall.  
      The functioning of the sealing device  10  according to the invention is clear from the foregoing description provided with reference to  FIG. 1 , i.e. it is implemented by means of the thrust action of the pressure means  20  which brings part of a base of the washer  18  into contact with the flat surface of the baffle  16  which is disposed around the hole  14 .  
       FIG. 2  shows a situation of imperfect sealing, with consequent passage of air between the pipe  12  and the hole  14 , caused for example by imperfect co-planarity between the washer  18  and the flat surface around the hole  14 .  
      Another cause of imperfect sealing can be inaccurate squareness between the axis of the washer  18  and the flat surface of the hole  14 .  
      On the other hand,  FIGS. 3 and 4  illustrate a sealing device  110  according to the present invention, in which components which are the same as and/or equivalent to those illustrated in  FIGS. 1 and 2  have the same reference numbers increased by 100.  
      The sealing device  110  is used in the connection of a cooling pipe  112  in a hole  114  in a divider baffle  116  in a gas turbine.  
      In the example illustrated, the device  110  comprises a spherical washer  118  with an annular shape, with a central hole with a diameter which is the same as the outer diameter of the pipe  112 .  
      The washer  118  has a flat base  117 , and a base which is shaped according to an annular portion of spherical surface  119 , with convexity towards the exterior of the washer  118  itself. In practice, this shape can be obtained by extending a base of a washer of a known type  18  which does not yet have a central hole, such as to obtain a spherical cap: at this point the central hole will be provided.  
      The spherical washer  118  is threaded onto the outside of the pipe  112 , with the flat base  117  disposed on the side opposite the hole  114 . The washer  118  is joined to the pipe  112 , for example by being welded, using the flat base  117 .  
      On a flat surface of the baffle  116 , which is disposed around the hole  114 , there is provided a conical washer  122  with an annular shape, with a central hole which has a diameter slightly larger than the outer diameter of the pipe  112 , such that the pipe  112  can be inserted into it.  
      The washer  122  has a flat base and a base which is shaped according to a frusto-conical surface  123 , with the smaller base disposed on the flat base side.  
      The flat base of the conical washer  122  is supported on the flat surface which surrounds the hole  114 , such as to make the axis of the washer  122  parallel with that of the hole  114 .  
      The spherical washer  118  of the pipe  112  is thrust towards the conical washer  122 , which is applied to the baffle  116 , by pressure means  120 , such as a spring.  
      The spring  120  can be fitted on one end of the pipe  112  which faces the hole  114  in the baffle  116 , thus pre-loading the spring against one wall.  
      The functioning of the sealing device  110  according to the invention is clear from the foregoing description provided with reference to  FIGS. 3 and 4 , and briefly is as follows.  
      The thrust action of the pressure means  120  brings the annular portion of spherical surface  119  of the spherical washer  118  into contact with the frusto-conical surface  123  of the conical washer  122 . More particularly, as known from the geometry, the contact takes place around a circumference.  
      This therefore prevents the problems of imperfect sealing caused by imprecise concentricity between the axis of the washer  118  and the axis of the hole  114 .  
      Thus, even in the presence of axial movements between the pipe  112 , which for example is secured to an outer case of the gas turbine, and the divider baffle  116 , or in the presence of rotations of the pipe  112 , the sealing is guaranteed.  
      In addition, the spherical washer  118 , which is thrust by the spring  120 , tends to centre itself in the conical washer  122 , thus also centring the pipe  112 .  
      It should be noted that the figures represent pipes with a circular cross-section, and it is apparent that it would not alter anything in the sealing device according to the invention if pipes with a different cross-section were used.  
      It is also apparent that the figures illustrate pipes which pass through the divider baffle, but it is clear that it would not alter anything in the sealing device according to the invention if use were made of pipes which do not pass through the divider baffle, but simply extend as far as the start of the hole in the divider baffle itself.  
      The description provided makes apparent the characteristics of the sealing device according to the present invention, for connection of a pipe in a hole, and also makes apparent the corresponding advantages, which, it will be remembered, include: 
          optimal sealing with consequent saving of cooling air;     elimination of blow-by of air, which is undesirable and is difficult to assess;     simple and reliable use; and     low costs, compared with the known art.        

      Finally, it is apparent that the sealing device thus designed, for connection of a pipe in a hole, can be subjected to numerous modifications and variants, all of which come within the scope of the invention; in addition, all the details can be replaced by technically equivalent elements. In practice, any materials, shapes and dimensions can be used, according to the technical requirements.  
      The scope of protection of the invention is thus delimited by the attached claims.